No description available.

Wobble, also known as speed wobble or shimmy, and the hazard it can cause to cyclists, is a well-known behavior of some bicycles. lt is a relatively high-frequency oscillation, 4-10 Hz. of the front fork and wheel assembly about the steering axis, and it can result in loss of control if left unaddressed. The importance of tyre mechanical properties, specifically conering stiffness, to the wobble motion of bicycles has been shown. Some tyres can make a bicycle more likely to wobble, while others can make the same bicycle less likely to wobble. There are only a few facilities in the world, however, capable of measuring these properties of bicycle tyres, and facilities for testing motorcycle and automobile tyres are not designed to work with bicycle wheels and/or are prohibitively expensive to use. We introduce and characterize an inexpensive, table-top device for measuring the necessary mechanical properties of bicycle tyres.

Bakgrund: Tio till tjugo procent av akuta skador på ligamenten kring fotleden resulterar ikronisk fotledsinstabilitet, vilket innebär en instabilitetskänsla, stukningstendens, smärta ochsvullnad i fotleden. Det är värdefullt att som fysioterapeut ha kunskap om vilkenrehabiliteringsmetod som förbättrar balans i syfte att öka stabiliteten i foten. Syfte: Sammanställa litteraturen och bedöma det vetenskapliga underlaget gällande effektenpå balansen hos individer med kronisk fotledsinstabilitet genom träning med balansbräda.Detta ställs upp i två sammanvägningar: balansbräda jämfört med styrketräning, ochbalansbräda jämfört med ingen behandling. Metod: En systematisk litteratursökning efter randomiserade kontrollerade studier utfördes idatabaserna PubMed, Uppsala universitetsbibliotek, samt Cochrane Library. Totaltinkluderades åtta studier med sammanlagt 286 deltagare. Samtliga studier kvalitetsgranskadesenligt PEDro-skalan, och GRADEstud användes för bedömning av det sammanvägdaresultatets tillförlitlighet. Resultat: Signifikant förbättring av balans kopplat till styrketräning samt balansträning medbalansbräda, men liten fördel för en kombination för de båda kopplat till statisk balans. Kvalitetsgranskning enligt PEDro visade på att sex studier hade en måttlig kvalité och tvåstudier hade hög kvalité. Utifrån evidensbedömningen anses det föreligga en lågtillförlitlighet till det vetenskapliga underlaget för styrketräning med motståndsband förfotleden samt balansträning med balansbräda. Konklusion: Både styrketräning för relevant muskulatur och balansträning med balansbrädaförbättrar balansen efter ett ≥4 veckor långt protokoll med ≥3 träningssessioner/vecka.Evidensen talar för att båda rehabiliteringsmetoder ger liknande utfall, men fler studierbehövs för att bekräfta resultatet då de sammanvägda resultaten har låg tillförlitlighet. / Background: Ten to twenty percent of acute ankle injuries result in chronic ankle instability,which results in instability in the foot, distorsion tendency, and pain and swelling around theankle. Thus it´s valuable for physiotherapists to have knowledge regarding whichrehabilitation methods yield the most positive effect on balance in order to increase stabilityin the foot. Purpose: To compile the literature and assess the evidence regarding the effects on balanceof people diagnosed with chronic ankle instability through rehabilitation with awobble-board. This is set up in two comparisons: wobble-board compared tostrength-training, and wobble-board compared to no treatment. Method: A systematic literature search for randomized controlled trials was done inPubMed, Uppsala University Library, and CochraneLibrary. A total of eight studies wereincluded in this review, with a total of 286 participants. Study quality was judged by using the PEDro-scale, and GRADEstud was used to assess the reliability of the combined results. Results: Significant improvement in balance related to resistance training and balancetraining with wobble-board, with a small advantage to training with a combination of the twowhen measuring static balance. Quality according to PEDro showed six studies of moderatequality and two studies of high quality. Grading of the evidence is deemed insufficient whenit comes to training with resistance bands and training with a wobble-board. Conclusion: Both strength-training for the relevant muscles and balance-training using thewobble-board improves the balance after a ≥4 week-long protocol with ≥3 sessions/week.The evidence shows that both methods give similar results, however further research isrequired to confirm the results because the reliability of the combined results was deemedinsufficient.

AIMS: To investigate the effects of Yoga on improving low back stability (threshold of stability, and mean total velocity of center of pressure), trunk strength (isometric strength in extension and flexion), and back endurance (isometric endurance in extension, flexion, and side laterals). METHODS: A pretest posttest control group experimental design was used. Sixteen participants, 10 females and 6 males, without a history of low back pain, and no prior experience of Yoga, were recruited. Yoga participants were recruited following registration in a yoga class; the control subjects were selected and recruited selectively in order to match the stature and body mass of the Yoga participant pool. Performance was measured prior to the beginning of Yoga exercises and 7 weeks later for both the groups. RESULTS: Contrary to the control group, the Yoga group significantly improved in terms of low back stability (decrease in threshold of stability by ~19%) and sway parameters (decrease in mean total velocity of COP by ~17%). CONCLUSIONS: The outcomes of this study illustrate the potential of Yoga as a low-impact exercise regime for improving low back stability via neuromuscular control and proprioception. There was no significant difference in trunk strength and endurance when comparing the two groups; therefore, the Yoga exercise was equally effective as the regular exercises. / Master of Science

Low back pain (LBP) is a common ailment in the United States, affecting up to 80% of adults at least once in their lifetime. Although 90% of LBP cases are considered nonspecific, recent studies show that abnormal mechanics of the lower back can be a major factor. One method of assessing the lower back mechanical environment is through perturbation experiments. An intensive literature review of perturbation systems was used to select and develop a system for the Human Musculoskeletal Biomechanics Lab (HMBL). Following construction, individuals with high/low exposure to day-long physical activity were assessed to quantify daily changes in their lower back mechanics and determine whether complete recovery occurs during overnight rest. Despite significant decrease in maximum voluntary contractions (MVC), intrinsic stiffness of the high exposure group remained constant following day-long physical activity. The final component of this Master’s project is devoted to the design of a wobble chair system for study of trunk stability. Development of the perturbation system and wobble chair are hoped to facilitate future research aimed at a better understanding of trunk mechanical and neuromuscular behaviors to prevent and treat LBP in the future.

This thesis describes a computational investigation of the mutagenicity of 5-bromouracil (BrU). In Chapter 1, three models of spontaneous and BrU-induced base mispairing (rare tautomer, wobble pair, and ion) are reviewed. Chapter 2 presents the computational techniques used: electronic structure methods (Hartree–Fock-based and density functional theory) and molecular dynamics. Chapter 3 presents optimisations of the keto and enol tautomers of BrU and uracil (U) in water clusters. The enol tautomer of BrU is found to be more stable than that of U. Chapter 4 is a molecular dynamics study of the keto-enol tautomerism of BrU and U in a periodic water box. The pKₐ of BrU at N3 is found to be lower than that of U. Chapter 5 is a study of stacked base dimers containing BrU, U, or thymine (T) stacking with natural bases. Some structures were taken from the Protein Data Bank, while others were generated using an in-house methodology. BrU is found to stack more strongly than T in vacuo, but solvation and thermal effects nullify this difference. Chapter 6 discusses the significance of the results in Chapters 3–5 in terms of BrU-induced mutagenesis. Appendices A and B–D provide supplementary material to Chapters 2 and 5, respectively. Appendix E is an investigation of the “base flipping” pathway of 2-aminopurine (2AP). Both 2AP/N and A/N dinucleosides (N = thymine or guanine) are found to adopt a wide range of energy-minimum conformations – not only stacked and “flipped”, but also intermediate – and the stacked are not the most favourable by free energy. Appendix F is a list of publications and papers in preparation. One publication concerns BrU stacking. The other is a conformational study of the dipeptide tyrosine-glycine: the theoretical results are shown to be consistent with experiment (R2PI spectra) if thermal effects are taken into account.

No description available.

L’objectif principal de ce travail est d’améliorer notre compréhension de la rhéologie terrestre et du mouvement de Chandler qui en dépend. Nous calculons le facteur gravimétrique complexe à la période de Chandler par une analyse conjointe de séries temporelles gravimétriques et du mouvement du pôle. Nous montrons l’importance et les limites des corrections gravimétriques dans les analyses locales et l’intérêt d’une combinaison des données de différentes stations. Suivant une approche plus théorique, nous menons une étude analytique puis numérique afin de déterminer les solutions du problème des petites déformations d’une Terre homogène anélastique en rotation. L’influence de l’anélasticité sur la période et le facteur de qualité de Chandler est étudiée, et nous montrons que ce dernier est plus sensible que la période aux paramètres rhéologiques, notamment à la viscosité de Kelvin. Enfin, nous étudions, en domaine de Laplace, l’influence de la fréquence de forçage par une surcharge. / The main goal of this work is to improve our understanding of the Earth’s rheology and of the Chandler wobble which depends on it. We compute the complex gravimetric factor at the Chandler frequency by a joint analysis of gravimetric and polar motion time series. We show the importance and the limits of gravimetric corrections for local analyses and the effectiveness of the combination of data from different stations. Using a more theoretical approach, we carry out an analytical and numerical study to determine the solutions of the small deformations of an anelastic homogeneous rotating Earth model. The influence of anelasticity on the Chandler wobble period and quality factoris studied and we show that the latter is more sensitive than the period to the rheological parameters, especially to the Kelvin’s viscosity. Finally, we study in Laplace domain the influence of the forcing frequency for the loading problem.

Two and three-wheeled vehicles are being used in increasing numbers in many emerging countries. The dynamics of such vehicles are very different from those of cars and other means of transportation. This thesis deals with a study of the dynamics of a motorcycle and an extensively used three-wheeled vehicle, called an “auto-rickshaw” in India. The commercially available multi-body dynamics (MBD) software, ADAMS, is used to model both the vehicles and simulations are performed to obtain insight into their dynamics. In the first part of the thesis, a study of the two wheeler dynamics is presented. A fairly detailed model of a light motorcycle with all the main sub-systems, such as the frame, front fork, shock absorbers , power train, brakes, front and rear wheel including tire slips and the rider is created in ADAMS-Motorcycle. The simulation results dealing with steering torques and angles for steady turns on a circular path are presented. From the simulation results and analytical models, it is shown that for path radius much greater than motorcycle wheel base, the steering torque and angle can be described by only two functions for each of the two variables. The first function is related to the lateral acceleration and can be determined numerically and the second function, in terms of the inverse of the path radius, is derived as an analytical approximation. Various tire and geometric parameters are varied in the ADAMS simulations and it is clearly shown that steady circular motion of a motorcycle can be reasonably approximated by only two curves–one for steering torque and one for steering angle. In the second part of the thesis, a stability analysis of the three-wheeled “autorickshaw” is presented. The steering instability is one of the major problems of the “auto-rickshaw” and this is studied using a MBD model created in ADAMS-CAR .In an Initial model the frame ,steering column and rear-forks (trailing arms) are assumed to be rigid. A linear eigenvalue analysis, at different speeds, reveals a predominantly steering oscillation, called a “wobble” mode, with a frequency in the range of 5 to 6Hz. The analysis results show that the damping of this mode is small but positive up to the maximum speed(14m/s) of the three-wheeled vehicle. Experiments performed on the three-wheeled vehicle show that the mode is unstable at speeds below 8.33m/s and thus the experimental results do not agree with the model. Next, this wobble instability is studied with an analytical model, similar to the model proposed for wheel shimmy problem in aircrafts. The results of this model show that the wobble is stable at low speeds regardless of the magnitude of torsional stiffness of steering column. This is also not matching with the experimental result. A more refined MBD model with flexibility incorporated in the frame, steering column and the trailing arm is constructed. Simulation results with the refined model show three modes of steering oscillations. Two of these are found to be well damped and the third is found to be lightly damped with negative damping at low speeds, and the results of the model with the flexibility is shown to be matching reasonably well with the experimental results. Detailed simulations with flexibility of each body incorporated, one at a time, show that the flexibility in the steering column is the main contributor of the steering instability and the instability is similar to the wheel shimmy problem in aircrafts. Finally, studies of modal interaction on steering instabilities and parametric studies with payload and trail are presented.