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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.
61

WHOLE-BODY PROTEIN METABOLISM IN MATURE AND GROWING HORSES RECEIVING PREDOMINANTLY FORAGE DIETS

Stratton, Sophie A. 01 January 2018 (has links)
There has been limited investigation as to whether a predominantly forage-based diet can provide adequate amounts of limiting amino acids (AA) to horses. The first objective was to determine if AA supplementation of AA believed to be limiting to protein synthesis in forage-based diets would affect measures of whole-body protein metabolism in sedentary mature horses. The effect of forage type (timothy or alfalfa) and AA supplementation (lysine, threonine or histidine) on plasma urea nitrogen (PUN) and AA concentrations and measures of whole-body phenylalanine kinetics were evaluated. There was no effect of either forage type or AA supplement on rates of whole-body protein synthesis (P > 0.05). The second objective was to determine the effects of either timothy or alfalfa hay supplemented with either a high or low protein ration balancer on measures of whole-body protein metabolism in yearling horses. The effect of forage type and the ration balancer protein level on concentrations of PUN, plasma AA and measures of wholebody phenylalanine kinetics were evaluated. There was no effect of treatment on average daily gain (P = 0.18). When horses consumed the alfalfa-based diets, rates of phenylalanine flux, oxidation and use for protein synthesis were greater than when they consumed timothy-based diets (P < 0.05). Phenylalanine use for protein synthesis was not affected by the protein level of the ration balancer (P = 0.3). Yearling horses achieve greater rates of protein synthesis when fed alfalfa-based diets, compared to timothy-based diets, supplemented with a low protein ration balancer.
62

An Integrated Multi-modal Registration Technique for Medical Imaging

Wang, Xue 17 November 2017 (has links)
Registration of medical imaging is essential for aligning in time and space different modalities and hence consolidating their strengths for enhanced diagnosis and for the effective planning of treatment or therapeutic interventions. The primary objective of this study is to develop an integrated registration method that is effective for registering both brain and whole-body images. We seek in the proposed method to combine in one setting the excellent registration results that FMRIB Software Library (FSL) produces with brain images and the excellent results of Statistical Parametric Mapping (SPM) when registering whole-body images. To assess attainment of these objectives, the following registration tasks were performed: (1) FDG_CT with FLT_CT images, (2) pre-operation MRI with intra-operation CT images, (3) brain only MRI with corresponding PET images, and (4) MRI T1 with T2, T1 with FLAIR, and T1 with GE images. Then, the results of the proposed method will be compared to those obtained using existing state-of-the-art registration methods such as SPM and FSL. Initially, three slices were chosen from the reference image, and the normalized mutual information (NMI) was calculated between each of them for every slice in the moving image. The three pairs with the highest NMI values were chosen. The wavelet decomposition method is applied to minimize the computational requirements. An initial search applying a genetic algorithm is conducted on the three pairs to obtain three sets of registration parameters. The Powell method is applied to reference and moving images to validate the three sets of registration parameters. A linear interpolation method is then used to obtain the registration parameters for all remaining slices. Finally, the aligned registered image with the reference image were displayed to show the different performances of the 3 methods, namely the proposed method, SPM and FSL by gauging the average NMI values obtained in the registration results. Visual observations are also provided in support of these NMI values. For comparative purposes, tests using different multi-modal imaging platforms are performed.
63

Passive and muscle-based predictive computer models of seated and supine humans in whole-body vibration

Wang, Yang 01 December 2012 (has links)
Studies of human response to whole-body vibration, such those encountered in heavy machinery and ground and aerial transportation, have highlighted the critical role of the head-neck posture of seated human occupants and the role of the transport system of a supine human on the severity of the transmitted vibration to the human body. Novel passive and muscle-based models are introduced in this work to predict the biodynamical response of the human under whole-body vibration in seated and supine postures. Planar and three-dimensional models representing the human head-neck system under different seated postures and fore-aft and multiple-axis whole-body vibration are first introduced. In these models, the head-neck system is represented by rigid links connected via spring-damper components representing the soft-tissue and connecting elements between the bones. Additional muscle components are added to some models. The muscle components comprise additional mass, spring, and damper elements arranged in a special order to capture the effect of changes in the displacement, velocity, acceleration, and jerk. The results show that the proposed models are able to predict the displacement and acceleration of the head under different vibration files, with the muscle-based models showing better performance than the passive models. The second set of models is introduced in this work to investigate the effect of the underlying transport system conditions on the response of supine humans under vertical and multiple-axis whole-body vibration. In these models, the supine human body is represented by three rigid links representing the head, torso/arms, and legs. The links are connected via rotational and translational joints, and therefore, it is expected that the models can capture the coupling effects between adjacent segments. The joints comprise translational and rotational spring-damper components that represent the soft tissue and the connecting elements between the segments. The contact surfaces between the supine human and the underlying transport system were modeled using spring-damper elements. Two underlying transport systems were considered, including a rigid support and a long spinal board attached to a military litter. The results showed that the proposed models were able to predict the effect of the transport systems on the human response under different vibration conditions.
64

Estudo da vibração ocupacional de corpo inteiro em pedreiras na região metropolitana de São Paulo. / Study of the occupational whole body vibration on quarries in the metropolitan region of São Paulo.

Carvalho, Felipe Baffi de 06 June 2019 (has links)
O setor de mineração registrou de 2011 até 2013 o maior número de acidentes entre as indústrias extrativas, evidenciando a relevância da preocupação com os controles dos riscos e doenças ocupacionais. Atividades intrínsecas do setor, como perfuração manual, transporte de minério e estéril com caminhões ou carregadeiras, locomoção com veículos dentro do site, manutenção e amostragem com o uso de serras circulares, entre outros, são caracterizadas por presença e alta intensidade de vibração. O objetivo do trabalho consiste em avaliar a exposição ocupacional à vibração de corpo inteiro em operadores de equipamentos frequentes em minerações a céu aberto, além de comparar os resultados obtidos com a legislação brasileira vigente e apresentar sugestões para a redução dos valores de vibração de corpo inteiro (VCI) encontrados. O autor pesquisou artigos sobre vibração de corpo inteiro na mineração e em outros setores, números de casos de doenças ocupacionais associadas ao agente em território nacional, tipos de assento disponíveis no mercado e legislações nacionais e internacionais europeias e norte-americanas. Foram visitadas três pedreiras na região metropolitana de São Paulo, onde realizaram-se avaliações preliminares da exposição seguidas de levantamento quantitativo de parâmetros aren (aceleração resultante da exposição normalizada) e VDVR (valor dose de vibração resultante). Ao todo, foram analisados 22 equipamentos envolvendo caminhões fora-de-estrada, escavadeiras, pás-carregadeiras, perfuratrizes, rompedores pneumáticos e caminhões pipa. Os equipamentos estudados em sua maioria ficaram acima do nível de ação estabelecido pela NHO-09 (norma de higiene ocupacional) e alguns acima do limite de exposição. Os equipamentos com os maiores índices de Vibração de Corpo Inteiro encontrados foram as pás-carregadeiras e os menores, perfuratrizes. / The mining sector registered the greatest number of accidents among the extractive industries from 2011 to 2013, highlighting the relevance of the concern with occupational risks and diseases control. Intrinsic activities of it such as manual drilling, ore and / or waste transportation with truck or loaders, locomotion with vehicles inside the mine site, maintenance and sampling with the use of circular saws are characterized by presence and high intensity of vibration. The objective of this study is to evaluate the whole-body vibration in common open pit machinery operators, comparing values obtained with current Brazilian legislation and to suggest improvements to reduce whole-body vibration (WBV) in the studied sites. The author researched articles on whole body vibration in and out of mining, numbers of occupational diseases associated with the agent in the national territory, types of seats available in the market and international laws in Europe and the United States. Three quarries were visited in the metropolitan region of São Paulo, where preliminary exposure assessments were performed followed by a quantitative survey of aren factors (acceleration resulting from normalized exposure) and VDVR (resulting dose of vibration). Altogether, it was analyzed 22 equipment involving off-road trucks, excavators, shovel loaders, drills, breakers and water trucks. Most of the equipment studied was above the action level established by the NHO-09 (occupational hygiene standard) and some even above the exposure limit. The equipment with the highest indexes of Whole-Body Vibration found were the loader and the lowest, drills.
65

The transmission of vibration at the lower lumbar spine due to whole-body vibration: a numerical human model study

Pang, Toh Yen, tohyen_pang@yahoo.com January 2006 (has links)
Lower back disorders due to whole-body vibration (WBV) are the most common injuries reported by professional drivers. Such injuries often have long-term complications leading to significant personal and societal costs. An improved mathematical model of the whole human body would contribute to a better understanding of the mechanisms of lower back injury and be valuable in injury prevention research. Current biodynamic human models reported in the literature lack detailed information for predicting the non-linearity due to vibration amplitude of transmission of vibration from seat to a human. Therefore, one of the primary objectives of this research has been to develop and validate a detailed threedimensional biodynamic human model, with special attention given to the incorporation of active trunk muscles with non-linear stiffness properties. These muscles have been incorporated into an existing spine and neck model of a MADYMO 50th percentile male occupant model. A detailed multi-body human model has been developed, called MODEL ONE. This thesis shows that incorporating non-linear stiffness functions and energy dissipation using hysteresis or damping into a human model is appropriate for predicting non-linear biodynamic responses in arbitrary excitation functions. A major advantage of MODEL ONE compared to other multi-body models and lumped mass models is its ability to predict nonlinear seat-to-human transmissibility. However MADYMO 50th male occupant models use simplified geometry and rigid bodies to represent the lower lumbar spine. These simplified spinal models have no ability to simulate the internal stresses and deformations of soft tissues, even if these are the apparent cause of lower back pain (LBP). Therefore a detailed finite element human lower lumbar spine model - with appropriate material properties and capable of simulating internal stresses⎯is necessary, in order to better understand spinal injuries under WBV. A three-dimensional finite element model of a lower lumbar spine motion segment - called MODEL TWO - has thus been developed for the present study. MODEL TWO comprises a detailed geometric description of vertebrae, nucleus pulposus, endplates, and intervertebral discs. The intervertebral discs lump together the annulus fibrosus, ground substance and ligaments. The vertebrae have been assumed to be rigid. The material properties of the intervertebral discs of MODEL TWO were obtained from test matrices and from various parameter data reported in the literature. MODEL TWO has been validated against cadaveric experiments reported in the literature. The mechanical behaviour and stress distribution within the MODEL TWO intervertebral disc agree reasonably well with the cadaveric experiments. MODEL TWO was integrated into MODEL ONE to form a new human model, called MODEL THREE, which was subsequently dynamically validated against volunteers� responses to WBV reported in the literature. MODEL THREE, as presented in this thesis, consists of a multi-body human model with detailed representation of a finite element (FE) lower lumbar spine. As far as the author is aware, MODEL THREE is the first model with detailed representation of a FE lower lumbar spine to successfully demonstrate that it is capable of simulating the stress profile of the entire intervertebral disc and endplate region due to WBV. The simulated results revealed abnormal stress concentrations in both the posterior and xviii the posterolateral annulus. The stresses increased most in the posterolateral intervertebral discs region during WBV, suggesting a possible mechanism for disc mechanical overload leading to fatigue fracture and degeneration. The results from MODEL THREE are promising and lead to a more comprehensive understanding of the behaviour of the intervertebral disc under WBV. MODEL THREE has also provided a good foundation for the development of a bio-fidelity human model. However, implementation of currently unavailable and/or inadequate in vitro and in vivo experimental studies is needed to further validate and develop MODEL THREE. A better understanding of injury mechanisms and the clinical significance of LBP will ultimately be arrived at using a combination of analytical models with in vitro and in vivo experimental data.
66

Optimization of plastic scintillator thicknesses for online beta detection in mixed fields

Pourtangestani, Khadijeh 01 December 2010 (has links)
For efficient beta detection in a mixed beta gamma field, Monte Carlo simulation models have been built to optimize the thickness of a plastic scintillator, used in whole body monitor. The simulation has been performed using MCNP/X code and different thicknesses of plastic scintillators ranging from 150 to 600 um have been used. The relationship between the thickness of the scintillator and the efficiency of the detector has been analyzed. For 150 m thickness, an experimental investigation has been conducted with different beta sources at different positions on the scintillator and the counting efficiency of the unit has been measured. Evaluated data along with experimental ones have been discussed. A thickness of 300 um to 500 um has been found to be an optimum thickness for better beta detection efficiency in the presence of low energy gamma ray. / UOIT
67

Cellular and Molecular Mechanism Underlying the Effect of Low-magnitude, High-frequency Vibration on Bone

Lau, Esther Yee Tak 27 July 2010 (has links)
An emerging non-pharmacological treatment for bone degenerative diseases is whole body vibration (WBV), a mechanical signal composed of low-magnitude, high-frequency (LMHF) vibrations that when applied to bone, have osteogenic and anti-resorptive effects. Currently, the cellular and molecular mechanism underlying the effect of WBV on bone is unclear. In this study, we investigated the response of osteocytes, the putative mechanosensor in bone, under LMHF vibration. As bone cells differentiate from mesenchymal stromal cells (MSCs), we also studied the osteogenic differentiation of rat MSCs in the presence of vibration loading. We found that vibrated osteocytes show gene and protein expression changes suggestive of an anti-osteoclastogenic response, and secrete soluble factors that inhibit osteoclast formation and activity. In contrast, rat MSCs showed moderate to no response to LMHF vibration during osteogenic differentiation. Our data suggest that in vivo effects of LMHF vibration are mediated through mechanosensing and biochemical responses by osteocytes.
68

Cellular and Molecular Mechanism Underlying the Effect of Low-magnitude, High-frequency Vibration on Bone

Lau, Esther Yee Tak 27 July 2010 (has links)
An emerging non-pharmacological treatment for bone degenerative diseases is whole body vibration (WBV), a mechanical signal composed of low-magnitude, high-frequency (LMHF) vibrations that when applied to bone, have osteogenic and anti-resorptive effects. Currently, the cellular and molecular mechanism underlying the effect of WBV on bone is unclear. In this study, we investigated the response of osteocytes, the putative mechanosensor in bone, under LMHF vibration. As bone cells differentiate from mesenchymal stromal cells (MSCs), we also studied the osteogenic differentiation of rat MSCs in the presence of vibration loading. We found that vibrated osteocytes show gene and protein expression changes suggestive of an anti-osteoclastogenic response, and secrete soluble factors that inhibit osteoclast formation and activity. In contrast, rat MSCs showed moderate to no response to LMHF vibration during osteogenic differentiation. Our data suggest that in vivo effects of LMHF vibration are mediated through mechanosensing and biochemical responses by osteocytes.
69

Segmental and whole body electrical impedance measurements in dialysis patients

Nescolarde Selva, Lexa 20 July 2006 (has links)
The main objective of this thesis is to contribute to the prevention and control of the cardiovascular risk, hydration state and nutritional state in dialysis patients using non-invasive electrical impedance measurements. The thesis is structured in three parts with the following objectives: 1) to establish electrical impedance reference data for healthy Cuban population, 2)to improve the diagnostic based on impedance methods in Cuban hemodialysis (HD)patients and 3) to develop the impedance methods for continuous ambulatory peritoneal dialysis patients (CAPD).Healthy population: We analyzed the impedance vector distribution using the Bioimpedance Vector Analysis (BIVA) for the three more representative race-ethnicities in Cuba. We measured 1196 healthy adult (689 M, 507 W, 18-70 yr). The 95% confidence ellipses were drawn using specific BIVA software for mean vectors of different races. Due to the close distribution of mean vectors that we found for the three race-ethnicities, we concluded that only one set of sex-specific tolerance ellipses can be used for the Cuban population.HD patients: The BIVA method was used in a sample of 74 HD patients in stable (without edema) and critical (hyper-hydrated and malnutrition) states in order to establish the relation between hyper-hydration and mortality. Stable group include 48 patients (28 M and 18 W), and critical group include 28 critical patients (16 M and 12 W). Student's t test and Hotelling's T2 test were used to analyse the separation of groups obtained by means of clinical diagnosis and those obtained by BIVA. A statistically significant difference was obtained (P < 0.05) in R/H, Xc/H and phase angle, PA. Critical patients (hyper-hydrated and malnutrition) were located below the inferior pole of the 75% tolerance ellipse, with PA lower than 4º. In conclusion, the BIVA method could be used to detect hyper-hydration state before edema appears, and to predict survival through PA. Advantages of the method are its simplicity, objectivity and that it does not require the definition of a patient dry weight.CAPD patients: Segmental impedance measurements were obtained using 9 configurations (7 longitudinal and 2 transversal) in 25 CAPD male patients.In a first study we analyzed Z, Z/H and ZBMI indexes. 23 male patients were classified according to the hydration state as normo-hydrated, group 0 (10 M) or hyper-hydrated, group 1 (13 M). Wilcoxon test was used to analyze the change in impedance produced by a PD session. Mann-Whitney U test was used to analyse the separation between groups obtained by means of clinical diagnosis and those obtained by Z, Z/H or ZBMI. Spearman correlation was used to study the correlation between impedance vectors in each segment and clinical assessment. Statistical significance was set at P < 0.05. Results show that ZBMI gives information about the specific resistivity of tissues and not about fluid and fat mass changes. BIVA separate hyper-hydrated and normo-hydrated patients. Transversal measurements in the leg region and longitudinal in the thorax region are useful to corroborate the hydration and nutritional state in CAPD patients.In a second study a new classification was performed. Group 0 has normo-hydrated patients (10 M) and group 1 includes patients (15 M) with varying degrees of hypertension, overhydration and high score on cardiovascular risk factors. Mann-Whitney U-test was used to compare the differences in clinical measurements, laboratory test, and bioimpedance measurements between groups. The Mahalanobis Distance (dM2) was calculated using a bidimensional space, using the resistance measurement, right-side (RRS/H) or thorax segment (RTH/H) and the BPmean. Hotelling's T2 test was used to analyzed difference between groups through (RTH/H, BPmean) and (RRS/H, BPmean) vectors. A statistically significant difference was obtained (P < 0.05) in both vectors. Group 1 showed a small dM2 with respect to a reference patient (a critical patient with acute lung oedema) with high BPmean and low values of RTH/H and RRS/H. Moreover, Group 0 showed a larger dM2 with respect to the reference patient with lower BPmean and higher values of RTH/H and RRS/H. All patients classified as hyper-hydrated leading to hypertension by clinical assessment were correctly classified using dM2(RTH/H, BPmean). We conclude that segmental bioimpedance of the thoracic region could be a simple, objective, non-invasive method of support to facilitate the clinical assessment in CAPD.
70

Bandwidth Enhancement of WWAN Laptop Computer Antenna Using a Parasitic Open Slot

Chen, Wei-Ji 09 June 2010 (has links)
In this thesis, we propose a new bandwidth-enhancement method of using a parasitic open slot to achieve a wide lower band for the internal laptop computer antenna with a small size to cover the GSM850/900 operation and a wide upper band to cover the GSM1800/1900/UMTS operation as well. The occupied antenna volume is only 48 ¡Ñ 10 ¡Ñ 3.5 mm^3 above the top edge of the display ground. For practical application, we analyze the effects of the antenna position, nearby metal plate, shielding metal plate, keyboard ground, FR4 substrate, and the size of display ground on the performance of the WWAN antenna. In addition, effects of the user¡¦s whole-body on the proposed antenna are also analyzed. Owing to the user¡¦s whole-body being mainly lossy materials, a decrease in the antenna¡¦s radiation efficiency is observed when the user¡¦s whole-body is in close proximity to the WWAN laptop computer antenna.

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