No description available.

No description available.

Identifying potential risk factors that affect slip-induced falls is key to developing effective interventions for reduction of injuries caused by these accidents. Existing epidemiological evidence suggests that localized muscle fatigue might be considered as an intrinsic risk factor that causes lack of balance control leading to falls. The literature on the relationship between localized muscular fatigue of the lower extremity and the gait parameters affecting slip severity is scarce. The purpose of the present study was to examine how lower extremity fatigue (quadriceps) alters gait parameters and increases slip severity. Sixteen healthy young participants were recruited to walk across an unexpected slippery floor in two different sessions (Fatigue and No fatigue). Kinematic and kinetic data were collected using a three-dimensional video analysis system and force plates during both sessions. The gait parameters important in assessing slip severity were compared for the two different sessions to evaluate the effects of fatigue. A repeated measure one-way analysis of variance (ANOVA) and multivariate analysis was employed to predict statistical significance. The results indicated a substantial increase in the heel contact velocity (HCV), required coefficient of friction (RCOF), slip distance II (SDII), peak average knee joint moment during slip recovery (kneemompeak), fall frequency and, a decrease in the transitional acceleration of the whole body COM (TA) in the fatigue session further indicating higher slip severity due to fatigue. In addition, a strong positive correlation was observed between RCOF and HCV, HCV and SDII, and, SDII and kneemompeak. These findings provide new insights into the relationship between localized muscular fatigue and slip initiation/recovery process. The present study concluded that localized muscular fatigue affects the gait parameters and increases slip severity and hence can be considered as a potential risk factor for slip-induced falls. / Master of Science

Localized muscle fatigue (LMF) is a complex, multifactorial phenomenon that involves exercise-induced decrements in the ability to generate force or power. LMF can adversely affect performance and may increase the risk of work-related musculoskeletal disorders (WMSDs), and is thus of contemporary occupational relevance. Despite considerable progress in understanding and predicting muscle fatigue, there are many uncertainties and unresolved issues that are principally associated with the physiological complexity of LMF and the diverse mechanisms that underlie LMF development. This research thus aimed to address some of the theoretical and practical issues related to muscle fatigue and recovery. Regarding the theoretical aspects, two specific muscle fatigue models (MFMs) were directly compared and some important differences in their predictions were identified. These differences were used, in part, as a basis for developing testable hypotheses and designing associated experiments. Further theoretical evaluations were conducted to explore the sensitivity of these models to the model parameters and their ability to predict endurance time in both prolonged and intermittent exertions. Sensitivity to inherent model parameters was quantified, which was relatively high in conditions involving lower to moderate levels of effort. Further assessments indicated substantial variability related to model recovery parameters, which might be related to the inability of these MFMs in simulating the recovery process. From a practical viewpoint, the effect of cycle time on the development and consequences of LMF was determined during intermittent isometric exertions. A shorter cycle time led to less fatigue development as reflected by rates of change in perceived discomfort, performance, and muscle capacity. Lastly, the dependency of muscle recovery on these different histories of fatiguing muscle contractions was explored. How a muscle recovers appeared to depend only on the state from which it starts to recover, though not the exertion history that led to that state. In summary, results of these studies may help in enhancing our understanding of fatigue and recovery processes, and in improving existing models of muscle fatigue and recovery. More accurate predictions of LMF development may help in enhancing muscle performance and in reducing the risk of musculoskeletal injuries and their associated healthcare costs. / Ph. D.

In this work the interaction between a spatial localized and time periodic state (discrete breather) and small amplitude plane waves is studied.

In this work the interaction between a spatial localized and time periodic state (discrete breather) and small amplitude plane waves is studied.

When exposed to light, metal nanoparticles exhibit a phenomenon known as LSPR, Localized Surface Plasmon Resonance. The wavelengths at which LSPR occurs is very dependent on the refractive index of the surrounding medium. Binding of biomolecules to the surface of gold nanoparticles result in a change in the refractive index that can be detected spectrophotometrically by monitoring the LSPR peak shift. When functionalized with the corresponding ligand(s), gold nanoparticles can be utilized in biosensors to detect the presence and concentration of a predetermined analyte. However, the system must exhibit high specificity and give rise to a detectable shift for analytes in the desired concentration range to be of commercial interest. The aim of the diploma project was to investigate and optimize the biofunctionalization and performance of a fiber optics based LSPR biosensor.  Three ligand systems were investigated for detection of antibodies (IgG), insulin and avidin. Binding of the analyte to the ligand caused a shift of a few nanometers when using spherical gold nanoparticles. The shifts were significantly larger when using gold nanorods. When using the IgG and insulin ligands, only minor unspecific binding was observed. The setup thus shows great potential for use in a wide range of sensing applications.

La spectroscopie localisée par Résonance Magnétique Nucléaire (RMN) a de nombreuses applications in vivo, car cette technique permet l'étude des métabolites endogènes. Cette thèse explore dans ce contexte diverses voies d'amélioration des données de spectroscopie. La première méthode présentée, est une méthode de correction de spectre mono-voxel. Une méthode de reconstruction pour l'imagerie spectroscopique s'appuyant sur la résolution d'un système d'équations linéaires au lieu de la transformation inverse de Fourier utilisée habituellement est ensuite proposée. Cette modification permet notamment la prise en compte des défauts du champ magnétique local. Enfin, une dernière méthode qui trouve son utilité lorsque le signal est trop faible pour permettre la quantification des signaux des métabolites ou lorsque les défauts du champ magnétique sont trop importants est développée puis validée par simulation et expérimentalement. / The selection a small region within the body is a critical requirement for in vivo NMR spectroscopy. This thesis presents different methods to optimize this selection and avoid contamination with extraneous signals even in presence of static magnetic field inhomogeneities and radiofrequency pulses imperfections.The first method presented allows for correcting single-voxel spectrum.The second reconstruction method for spectroscopic imaging is based on solving a system of linear equations instead of the inverse Fourier transform usually used.This particular modification allows taking into account defects in the local magnetic field.The last method developedallows metabolites quantificationeven when the signal is weak or when themagnetic field defects are large.

In the rapidly growing field of CFD-calculations (Computational Fluid Dynamics), companies and organizations are bringing forth new tools, tools that display an image of a given fire scenario. These tools are developed because they provide time efficiency as well as a sustainable economic approach. Another useful tool is analytical solutions, these analytical solutions serve the same purpose as CFD-modeling, providing results of a given scenario. The purpose of this thesis was to simulate a fire plume with two different CFDprograms and compare the gas temperature from each simulation with a full-scale test. Also, analytical solutions were used to perform the same comparisons. Four different calculation models were utilized to obtain results. The CFD-programs were FDS (Fire Dynamics Simulator) and FireFOAM. The analytical solutions were performed using McCaffrey´s plume equation and Eurocode solutions for localized fire temperatures. FDS is a very well documented program, due to this, problems that arose were easily fixed. The structure of FDS enables the user to maneuver the program easily. SmokeView was used to visualize the simulation. FireFOAM is written in C++ and is operated through the command prompt. The structure of the program was time-consuming to understand mainly because of two reasons, primarily because the authors lack of knowledge in coding in C++, and second because of the LINUX environment. Moreover, the process of working in FireFOAM was mostly through trial and error. On some occasions, issues arose that could be solved by communication with other CFD users at CFD-Online. When major problems occurred, regarding the code or other CFD issues, Johan Anderson at RISE Research Institutes of Sweden guided us through most of these problems and enabled us to move forward with the work. ParaView was used to visualize the simulation, and Excel was used to evaluate the temperature data from the FDS- and FireFOAM simulations. For the calculations in FDS and FireFOAM, a sensitivity analysis was performed to see which grid size presented best results in each program. A grid size of 5 cm, 10 cm, and 20 cm were applied in FDS, and in FireFOAM the grid dimensions were set to 5 cm and 10 cm. The results showed that 5 cm was the most appropriate grid size for both programs. It would have been more favorably to simulate with several different grid sizes, to further strengthen the grid analysis. Though, due to the time frame of the thesis, further simulations were not performed. Calculations were repeated for the same scenario only with a lower HRR (Heat release rate). An extensive sensitivity analysis was conducted for FDS in the form of two different simulations. One simulation where HRR was the same as the full-scale test but with twice the area of the burner. In the second simulation, the same area was used on the burner as the fullscale test, but with half the HRR. Results from the analytical solutions were easy to achieve; however, the model has some limitations regarding calculations within the flame region. The estimated gas temperature, using FDS, aligns well with the full-scale test. The temperatures analyzed from FireFOAM deviated in general through the flame region and reached unreasonable high temperatures close to the ceiling. Since the analytical solutions were based on different conditions compared to those applied in the full-scale test, it was expected that the results should deviate. However, McCaffrey plume equations can still be used to give an approximate picture of scenarios similar to that of the full-scale test, and the same applies to Eurocode solutions for localized fire temperatures. Analysis of the results shows that FDS can be used to simulate similar scenarios. FireFOAM simulates a gas temperature that is overestimated within the flame region. One of the reasons for this was due to the grid size since the sensitivity analysis III showed that a refined grid size resulted in more correct temperature value, the reason for not simulating with a more refined grid size was due to the restricted time frame of this thesis. FireFOAM is, at present, recommended for researchers who wish to use the code for specific purposes. Therefore, given the same premises, FireFOAM is not recommended for the standard fire safety analysis.

Novas seqüências para supressão de contribuições indesejadas em Imagens e Espectroscopia por Ressonância Magnética Nuclear, tais como as provenientes da água, um solvente que sempre resulta num sinal muito intenso em sistemas biológicos, são motivos de estudo e desenvolvimento com diversas aplicações atuais. O método que estamos propondo aqui, uma versão adiabática de MEGA incorporada nas seqüências PRESS e STEAM, visa a supressão do sinal da água presente no espectro de um volume localizado em uma amostra intacta. Para o campo magnético desse estudo (2.0 Tesla) e pelas características do magneto usado nesses experimentos, o pico do solvente tem o inconveniente de apresentar uma linha espectral muito larga quando comparado com a extensão do deslocamento químico das fiações de açúcar. O resultado indesejado é a sobreposição pelas suas vertentes, das diversas outras linhas espectrais, cujo interesse é de extrema importância, como a de alguns sólidos solúveis de açúcares. O principal problema encontrado é que a separação entre os picos da água e dos açúcares próximos é da ordem de 1 ppm. A metodologia proposta consiste na aplicação de pulsos de gradiente de campo magnético intensos em conjunto com uma seqüência de pulsos de RF adiabáticos e convencionais, seletivos em freqüência e espacialmente, para suprimir o pico da água em uma região espectral muito específica, sem nenhum dano a linearidade de fase do espectro restante. Esse procedimento, aliado a uma localização espacial muito eficiente, aumenta ainda mais o poder de análise desta ferramenta, a 1H MRS. Os resultados obtidos em campo de 2.0Tesla (85 Hz/ppm) mostraram que as seqüências híbridas adiabáticas MEGA-PRESS e MEGA-STEAM são bem eficazes na supressão do pico da água, como era esperado. Além disso, sua aplicação no monitoramento do grau de maturação de frutas intactas através do seu teor de açúcar, se mostrou muito bom dadas as condições experimentais extremamente limiares apresentadas pelo espectrômetro / New sequences for suppression of undesirable contributions in Magnetic Resonance Imaging and Spectroscopy, such as water, a solvent that always represent a very strong peak in biological systems, are object of recent development for several different applications. The method proposed here, an adiabatic version of MEGA incorporated within PRESS and STEAM, aims the suppression of the water peak present on volume selected spectra of intact specimens. For the magnetic field of this study (2.0 Tesla) and for the characteristics of the magnet used in the experiments, the solvent peak has the inconvenience of having a large width as compared to the spread in chemical shift of the sugar fractions. The undesirable result is the superposition on its tail with severa1 spectral lines, whose interest is of extreme importance, such as some sugar solid solutes. The main problem encountered is that the separation between the water peak and the nearest sugar peaks is of the order of 1 ppm. The proposed methodology consists on the application of intense gradient pulses along with a sequence of adiabatic and conventional RF pulses, both frequency and spatially selective, to suppress the water peak in a very specific spectral region, without any disturbance of the phase linearity of the remaining part of the spectrum. This procedure, allied to a very efficient spatial localization, enhances the power of the very well-known tool, the 1H MRS. Results obtained at 2.0Tesla (85 Hz/ppm) show that the hybrid adiabatic sequences MEGA-PRESS and MEGA-STEAM are efficient on suppressing the water peak, as expected. Also, their application on monitoring the degree of ripeness of intact fruits through their sugar content, has shown very good results, considering the extremely limiar experimental conditions presented by the spectrometer