<p>A high-fat diet can adversely affect bone mechanical properties, but it is unknown how these changes affect bone adaptation. Bone adaptation occurs in response to strain-related mechanisms, and strain in the bone is affected by the size and mechanical properties of the bone.The purpose of this study was to compare the strain during loading in femurs from rats fed a high-fat (HF) or normal control (NC) diet. At 3 weeks of age, male and female Wistar rats were randomly assigned to receive a NC (NC–17% fat; N=8 per gender) or HF diet (HF–41% fat; N=8 per gender) until termination (39 weeks of age). Right femurs were loaded <em>ex vivo</em> in 3-point bending to physiologic levels and mechanical strain was measured. The mechanical properties of the left femurs were determined by 3-point bend tests to failure. The dietary effects were limited in both genders. Femoral cross-sectional area properties (bone area, moment of inertia), determined from µCT scans, were significantly greater in HF femurs vs. NC for males and females. Elastic modulus was calculated from strain and deformation data and no dietary effects were seen in either gender. At the applied loads, despite significantly larger cross-sectional area properties in the HF femurs, there was no significant difference in strain between HF and NC femurs for either gender. It appears that adaptive modeling occurs during growth in the HF bones to target a predetermined level of strain to preserve bone structural integrity.</p> / Master of Applied Science (MASc)

<p>Microfluidic devices using electroosmotic flows (EOFs) in microchannels have been developed and widely applied in chemistry, biology and medicine. Advantages of using these devices include the reduction of reagent consumption and duration for analysis. Moreover the velocity profile of EOFs, in contrast to the parabolic profile found in pressure-driven flows, has a plug-like profile which contributes significantly less to solute dispersion. It also requires no valve to control the flow, which is done with the appropriate application of electrical potentials, thus becomes one of the favourite techniques for sample separation. However, high potentials of several hundred volts are usually required to generate sufficient EOF. These high potentials are not practical for general usage and could cause electrical hazard in some applications. One of the possible solutions is the introduction of zeta potential modulation. The EOF in a microchannel can be controlled by the zeta potential at the liquid/solid interface upon the application of external gate potentials across the channel walls. Combined with AC EOF, it can rectify the oscillating flows and generate pressure that can be used for microfluidic pumping applications. Since the flow induced by the alternating electric field is unsteady and periodic, it is critical to visualize the flow with high spatial and temporal resolutions in order to understand fluid dynamics. A novel method to obtain high temporal resolution for high frequency periodic electrokinetic flows using phase sampling technique in micro particle image velocimetry (PIV) measurements are first developed in order to characterize the AC electroosmotic flow. After that, the principle of zeta potential modulation is demonstrated to transport particles, cells, and other micro organisms using rectified AC EOF in open microchannels. The rectified flow is obtained by synchronous zeta-potential modulation with the driving potential in the microchannel. Subsequently, we found that PDMS might not be the best material for some pumping and biomedical applications as its hydrophobic surface property makes the priming process more difficult in small microchannels and also causes significant protein adsorption from biological samples. A more hydrophilic and biocompatible material, polyurethane (PU), was chosen to replace PDMS. A polyurethane-based soft-lithography microfabrication including its bonding, interconnect integration and in-situ surface modification was developed providing better biocompatibility and pumping performance. Finally, an electroosmotic pumping device driven by zeta potential modulation and fabricated by PU soft lithography was presented. The problem of channel priming is solved by the capillary force induced by the hydrophilic surface. Its flow rate and pressure output were found to be controllable through several parameters such as driving potential, gate potential, applied frequency, and phase lag between the driving and gate potentials.</p> / Doctor of Philosophy (PhD)

Soft material-enabled electronics can demonstrate extreme mechanical flexibility and stretchability. Such compliant, comfortable electronics allow continuous, long-term measurement of biopotentials on the skin. Manufacturing of the stretchable electronic devices is enabled by the recent development combining materials transfer printing and microfabrication. However, the existing method using inorganic materials and multi-layered polymers requires long material preparation time and expensive processing cost due to the requirement of microfabrication tools and complicated transfer printing steps. Here, this study develops a new fabrication method of soft electronics via a micro-replica-molding technique, which allows fast production, multiple use, and low cost by avoiding microfabrication and multiple transfer printing. The core materials, carbon nanomaterials integrated with soft elastomers, further reduces the entire production cost, compared to costly metals such as gold and silver, while offering mechanical compliance. Collectively, skin-wearable electrodes, designed by optimized materials and fabrication method enable a high-fidelity measurement of non-invasive electromyograms on the skin for advanced human-machine interface, targeting prosthesis.

Testes biomecânicos de ossos são utilizados para determinar as propriedades mecânicas dos mesmos, e são um importante adjunto para pesquisadores desenvolverem implantes metálicos e protocolos de fixação de fraturas. O Objetivo desse foi determinar as propriedades biomecânicas do tecido ósseo de diferentes regiões do terceiro metacarpiano eqüino submetido a ensaios de compressão e flexão. Foram utilizados 30 pares de terceiro metacarpiano eqüino divididos em dois grupos com um membro de cada par. No teste de flexão em três pontos, o osso inteiro apoiado em dois suportes cilíndricos de 20 mm de diâmetro e 150 mm distantes entre si, recebeu uma carga através de um cutelo com mesmo diâmetro dos suportes e posicionado a 75 mm entre os apoios, na direção palmaro-dorsal até que ocorresse a fratura. No teste de compressão foram utilizadas amostras de diferentes regiões do osso. O corpo de prova 1 (cp1) foi composto pela diáfise média e seu comprimento foi igual a duas vezes ao diâmetro latero-medial no ponto médio do osso que coincidia com o ponto médio do corpo de prova. O grupo cp1 foi submetido a carga compressiva no sentido próximo-distal até a carga máxima de 4000 kgf. Com auxílio de trefina foram feitos corpos de prova, no sentido longitudinal, dos fragmentos de ossos restantes do corte acima descrito. Dois desses corpos de prova foram coletados do centro da porção trabecular das epífises proximal (cp2) e distal (cp3). Outros dois corpos de prova foram coletados da região cortical lateral (cp4L) e medial (cp4M) da diáfise. Esses corpos de prova foram submetidos a carga compressiva no sentido próximo-distal até fraturarem. Os resultados obtidos nos permitem concluir que na diáfise, o córtex medial resiste a uma tensão maior e apresenta um módulo de elasticidade maior que o córtex lateral; o osso trabecular na epífise distal apresenta mesmo módulo de elasticidade que na epífise próximal, contudo suporta uma tensão maior no momento da fratura. / Bone properties determined by biomechanical testing are extremely important for both metallic implants and osteosyntesis protocols development. The objective of this study was determining the biomechanical properties of some different regions of third metacarpal bone submitted to compression and bending tensions, using thirty pairs divided into two groups, each group formed by one limb of each pair. During the three points bending test the dorsal surface of the entire bone was placed upon two cylindrical bases 150 mm far from each one, and load was applied in the mid point on the palmar aspect of the bone, 75 mm far from each cylindrical base, until bones failure. For the compression test samples of different bone regions were used. The mid diaphysis was used as samples (cp1), which its height was twice its latero-lateral thickness at the mid point of the bone length. All cp1 were submitted to proximo-distal compressive loads until it reached 4000kgf. Using a trefina the others samples were obtained from the fragments of bone not used for the cp1 confection. Two of them were collected from the trabecular portion of proximal (cp2) and distal (cp3) epiphysis, and the others from lateral (cp4L) and medial (cp4m) cortex region of diaphysis. All of them were submitted to proximo-distal compressive load until their failure. By the analysis of the results obtained was concluded that the medial cortex is more resistant to tensions and has greater elastic modulus than the medial cortex, at the diaphyseal region; the trabecular bone at the distal epiphysis has the same elastic modulus than at the proximal epiphysis, however its failures occurs at greater loads.

Na atualidade, vários são os métodos de osteossíntese utilizados na reparação de fraturas de fêmur em cães, porém alguns apresentam complicações na técnica, e outros não encontram-se disponíveis na atividade profissional diária de alguns médicos veterinários da América Latina. O presente trabalho teve como objetivo desenvolver um novo modelo simples de osteossíntese, baseado na utilização de pinos de Steinmann e Schanz denominado pinos intramedulares múltiplos bloqueados (PIMB), e testar biomecanicamente a resistência as forças de flexão em comparação com a técnica de pino intramedular único (PIU). Para tanto foram utilizados fêmures bilaterais de oito cadáveres de cães com peso entre 15 a 25 quilos que foram divididos em dois grupos, o primeiro grupo composto por oito fêmures utilizou os pinos intramedulares múltiplos bloqueados e o segundo grupo composto por oito fêmures utilizou pino intramedular único, ocupando entre 40 - 42 % do canal medular como controle do Grupo 1. Os dois grupos de fêmures foram submetidos a ensaios não destrutivos para avaliar a resistência as forças de flexão, com forças entre 0 e 50 Kg, e velocidade de deslocamento de 5mm/minuto, num dispositivo de quatro pontos. Os resultados encontrados nas condições apresentadas neste estudo mostraram que a técnica de pinos intramedulares múltiplos bloqueados apresenta uma menor resistência as forças de flexão comparada com a técnica de pino intramedular único / Currently, there are several methods of fixation used in the repair of femoral fractures in dogs, but some show complications in the technique, and others are not available daily in the professional activity of some veterinarians from Latin America. This study aimed the development of a new, simple model for bone fixation, based on the use of Steinmann and threaded pins, used as multiple locked intramedullary pins (MLIP), and biomechanically test the implants resistance to bending forces. Therefore, we used bilateral femurs of eight cadaveric dogs weighing between 15-25 kg, divided into two groups; in the first group multiple locked intramedullary pins were used in eight femurs, and in the second group, the control group, we used a single intramedullary pin (SIP) occupying between 40-42% of the intramedullary canal, of eight femurs. Both groups were subjected, in a four point device, to nondestructive testing to evaluate the resistance to flexion forces, with forces varying between 0 and 50 kg, and a speed of 5mm/minute. The results under the conditions presented in this study showed that technique locked multiple pins has a lower resistance to bending forces compared with the technique of single intramedullary pin.

Magister Sport, Recreation and Exercise Science - MSRES / Cricket is a highly technically skilled-based game, which consists of four distinct disciplines (batting, bowling, fielding, and wicket keeping) with varying physiological and biomechanical demands. There are three standardized professional versions of the game, namely, test match or multi-day cricket, limited overs or one-day cricket and Twenty-20 or T20 cricket. One-day games consist of two innings with each team getting a chance to bat and bowl. One innings encompasses fifty overs and the game generally lasts for approximately 6 hours. Although research has been conducted on the physical demands of cricket, not many studies compare the differences of these demands between different playing positions. Furthermore, there is a lack of research around the differences between professional and amateur level cricket players.

Foram estudados os efeitos da metilprednisolona na traquéia de coelhas albinas adultas da raça Nova Zelândia. O objetivo deste estudo foi investigar os efeitos potenciais desta substância nas propriedades biomecânicas da traquéia de coelhas por meio de ensaio de tração axial. Os animais foram divididos em dois grupos. Dez coelhas do grupo controle receberam por via subcutânea 2 mg/Kg/dia de metilprednisolona diluída em solução salina. As dez coelhas do grupo controle receberam também de modo subcutâneo volumes proporcionais de solução salina. Após 21 dias, os animais foram sacrificados e suas traquéias submetidas a ensaio de tração e estudo histopatológico. Os animais do grupo experimental apresentaram peso significantemente inferior ao do grupo controle no final do tratamento (C = 3996 ± 314 g x E = 3555 ± 373 g). Os grupos não diferiram do ponto de vista estatístico quanto as seguintes variáveis: carga no limite de proporcionalidade (C = 8,94 ± 1,68 N x E = 8,93 ± 1,52 N); carga máxima (C = 9,12 ± 2,2 N x E = 9,57 ± 1,90 N); alongamento no limite de proporcionalidade (C = (683 ± 2,08) x '10 POT.-3' m x E = (6,05 ± 1,50) x '10 POT.-3' m); alongamento máximo (C = (7,44 ± 2,60) x '10 POT.-3' m x E = (6,85 ± 1,55) x '10 POT.-3' m); energia absorvida na fase elástica (C = (28,70 ± 14,43) x '10 POT.-3' J x E = (27,75 ± 11,06) x '10 POT.-3' J); rigidez (C = (1,08 ± 0,41) x '10 POT.-3' N/m x E = (1,2 ± 0,37) x '10 POT.-3' N/m). Concluiu-se ao término deste estudo que não houve alterações morfológicas e biomecânicas das traquéias estudadas, no entanto, os animais do grupo experimental sofreram significante emagrecimento ao final do tratamento, quando comparado ao grupo experimental / The effects of methilprednisolona in the adult’s trachea albinos female rabbits were studied. The goal of this study was examine the potential effects of this armorial traction. The animals were divided in two groups. Ten female rabbits of control group received by way of subcutaneous 2mg/kg/day of salt bed diluted solution. These ten female rabbits of the control group also received by way of subcutaneous proportional volumes of salt bed solution. After 21 days, the animals were sacrificed and their trachea were subjected to traction tests and anatomical pathological studies. Animals of the experimental group presented inferior weight significant from the control group in the end of the treatment (C = 8,94 ± 314g X E = 3555 ± 373g). The groups didn’t differ from the statistic point of view as regards of the following variables: limit load of proportionality (C = 8,94 ± 1,68 N X E = 8,93 ± 1,52 N); maxim load (C = 9,12 ± 2,2 N X E = 9,57 ± 1,90 N); stretch out on the limit of proportionality (C = (683 ± 2,08) x '10 POT.-3' m X E = (6,05 ± 1,50) x '10 POT.-3' m); maxim stretch out (C = (7,44 ± 2,60) x '10 POT.-3' J X E = (6,85 ± 1,55) x '10 POT.-3' J); absorbed energy in the elastic phase (C = 28,70 ± 14,43) x '10 POT.-3' m J X E = (27,75 ± 11,06) x '10 POT.-3' J); rigidity (C = 1,08 ± 0,41) x '10 POT.-3' N/m X E = (1,2 + 0,37) x '10 POT.-3' N/m). It was concluded in the end of the treatment that there weren’t any morphological and biomechanical alterations of the trachea studied, although, the animals of the experimental group suffered a significant slimming in the end of the treatment when compared with the experimental group

As lesões ligamentares são provavelmente a causa mais comum de claudicação em membros pélvicos e de afecção degenerativa da cartilagem na articulação femoro-tíbio-patelar, vistas em cães. Objetivou-se avaliar a função biomecânica da articulação do joelho em cães, comparando a medida de deslocamento cranial e a rigidez articular da tíbia em relação ao fêmur com o ligamento cruzado cranial íntegro, seccionado e reparado cirurgicamente. Utilizou-se a máquina Kratos 5002, que permite gravar em tempo real os parâmetros força (N) e deslocamento/deformação em mm. O ensaio consitiu em aplicar força de (N) registrando assim a gaveta cranial. Para o joelho íntegro, a média de deslocamento em milímetros encontrada para três repetições foram de 3,39 ; 3,47; 3,53. Para o joelho lesado foram de 12,96; 13,24; 13,34. Para o joelho reparado foram de 4,05; 4,61; 4,42. Este estudo permite-nos concluir que após lesão a translação cranial do joelho lesado é acrescida em quatro vezes e a rigidez articular é diminuída em uma vez e meia. A análise estatística revelou diferença significante entre os dados do grupo íntegro e lesado, tanto para deslocamento quanto para rigidez (p&lt;0,05). Para o joelho reparado a translação cranial não apresenta diferença estatística significante entretanto mostra que a rigidez articular não volta a normalidade. / Ligamentary lesions are probaly the most comum cause of hind limb lamness and the degenerative disease of the knee joint seem in dogs. The biomechanical function of the knee joint in dogs was made, comparing the cranial translation degree and articular stiffness of the tibia in relation to the femur, in normal joints, joints with rupture of cranial crucial ligament and cirurgicaly repared. Mechanical assays was realized by Kratos 5002 machine, and recorded in real time the parameters of force (N) and translation/deformation, in mm. The assay had consisted in to use a force(N) registering the cranial translation. To the normal knee, the deslocation media founded after 3 repetitions was 3,39 ; 3,47; 3,53. To the knee with surgical section was 12,96; 13,24; 13,34. To the repared knee was 4,05; 4,61; 4,42These study allows to conclude that the cranial translation is added in four times and the articular stiffness is reduced one and a half times when statistically compared. The statistical analysis reveled significant diference between groups to the cranial tranlation e articular stiffness (p&lt;0,05). To the repared knee the cranial translation don?t reveled significant diference but the articular stiffiness seens anormal.

Vegetation stabilises slopes via both mechanical reinforcement (through root anchorage) and hydrologic reinforcement (through transpiration-induced soil matric suction). However, relatively little is known about the effectiveness of different plant species in stabilising soil slopes via the two reinforcing mechanisms, and so decisions on species selection are seldom made with optimisation of slope reinforcement in mind. In this thesis, a comprehensive testing programme including laboratory, glasshouse and field experiments is designed and implemented, with the aim to quantify and investigate the transpiration-induced hydrologic reinforcement and root biomechanical properties during the early plant establishment of selected woody species, widespread under European temperate climate. Ten species native to Europe (Buxus sempervirens L.; Corylus avellana L.; Crataegus monogyna Jacq.; Cytisus scoparius (L.) Link; Euonymus europaeus L.; Ilex aquifolium L.; Ligustrum vulgare L.; Prunus spinosa L.; Salix viminalis L. and Ulex europaeus L.) were investigated in a glasshouse experiment to understand any relation of transpiration induced hydrologic reinforcement with above- and below-ground plant traits (e.g. specific leaf area; root length density). The ten species showed large differences in terms of water uptake, which translated to significant differences in matric suction and soil strength. Species with the largest water uptake increased soil strength more than ten times that in fallow soil. Specific leaf area, root length density and root:shoot ratio were best correlated with the induced hydrologic reinforcement provided by the ten tested species. These results supplied essential species information for designing the subsequent experiments. Based on the previous findings, three representative yet contrasting species (Corylus avellana, Ilex aquifolim and Ulex europaeus) were selected and planted in 1-m soil columns to investigate the effects of season (i.e. summer vs winter), plant functional type (i.e. deciduous vs evergreen) and soil depth on the magnitude and distribution of transpiration-induced matric suction and the associated soil strength gain. Evergreens could slowly induce matric suction and hence potentially stabilise soil during winter. However, there were very large differences between the tested evergreens (I. aquifolium and U. europaeus). Indeed, only U. europaeus provided matric suction and soil strength gain along the entire depth-profile because of its fast growth (above- and below-ground). A full-scale field experiment was also performed to provide ground-truth data on the extent of variation in hydrologic reinforcement among species, hence validating the glasshouse results obtained in the first two studies. The two-year field experiment yielded a similar ranking to the glasshouse experiments in terms of the species ability to rapidly develop matric suction and soil strength. In particular, the evergreen U. europaeus induced large matric suction (e.g. ≥ 70 kPa at 0.5 m depth) even during the early establishment period. Furthermore, this field research highlighted the greater (compared to other tested species) temporal effectiveness of U. europaeus, which was able to provide matric suction on the slope from early spring to late autumn. The greater ability of U. europaeus in inducing and preserving matric suction can be attributed to its large water uptake, which supports its fast growth, as well as to the notable interception loss provided by its canopy. Therefore, U. europaeus can represent a very suitable species for slope stabilisation under the temperate climate context. Root biomechanical properties, including tensile strength and Young's modulus, were investigated in the laboratory for the same ten species. The results highlighted a large variability in the tensile strength-diameter relations during the early stage establishment of plants, especially in thin roots with diameter ranging from 0.4 to 2.0 mm. The root tensile strength-diameter relationships highlighted three different trends. The common negative power relation between root tensile strength and diameter existed only for two out of the ten tested species (i.e. E. europaeus and U. europaeus). B. sempervirens, I. aquifolium and P. spinosa showed a slight increase in tensile strength with increasing root diameter. C. avellana, C. monogyna and L. vulgare consistently showed an initial increase in root tensile strength with increasing root diameter, reaching peak strength between 1.0 and 2.5 mm diameter. Beyond the peak strength, a reduction in strength was observed with increasing root dimeter. These bimodal trends might be partially explained by the differences in the development stage of root primary and secondary structures. Root moisture content can be one of the factors inducing the observed large variability in root tensile strength. Therefore, the last part of this thesis assessed the effects of root drying on the root biomechanical properties of U. europaeus. Root strength and stiffness showed an abrupt increase when root water content dropped below 0.5 g g-1. The strength increase can be explained by the reduction in root diameter and by changes in root properties induced by the root water potential drop. Moreover, root water loss and root strength gain were diameter-dependent because of the relatively larger evaporative surface per volume of thin roots.

by Lanyi Xu. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (p. [175]-186). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.