Snap-through is a striking instability in which an elastic object rapidly jumps from one state to another. It is seen in the leaves of the Venus flytrap plant and umbrellas flipping on a windy day among many other examples. Similar structures that snap-through are used to generate fast motions in soft robotics, switches in micro-scale electronics and artificial heart valves. Despite the ubiquity of snap-through in nature and engineering, its dynamics is usually only understood qualitatively. In this thesis we develop analytical understanding of this dynamics, focussing on how the mathematical structure underlying the snap-through transition controls the timescale of instability. We begin by considering the dynamics of 'pull-in' instabilities in microelectromechanical systems (MEMS) - a type of snap-through caused by electrostatic forces in which the motions are dominated by fluid damping. Using a lumped-parameter model, we show that the observed time delay near the pull-in transition is a type of critical slowing down - a so-called 'bottleneck' due to the 'ghost' of a saddle-node bifurcation. We obtain a scaling law describing this slowing down, and, in the process, unify a large range of experiments and simulations that exhibit delay phenomena during pull-in. We also investigate the pull-in dynamics of MEMS microbeams, extending the lumped-parameter approach to incorporate the details of the beam geometry. This provides a model system in which to understand snap-through of a continuous elastic structure due to external loading. We develop a perturbation method that systematically exploits the proximity to pull-in to reduce the governing equations to a simpler evolution equation, with a structure that highlights the saddle-node bifurcation. This allows us to analyse the bottleneck dynamics in detail, which we compare with previous experimental and numerical data. The remainder of the thesis is concerned with the dynamics of snap-through in macroscopic systems. In particular, we explore the extent to which dissipation is required to explain anomalously slow snap-through. Considering an elastic arch as an archetype of a snapping system, we use the perturbation method developed earlier to show that two bottleneck regimes are possible, depending delicately on the relative importance of external damping. In particular, we show that critical slowing down occurs even in the absence of damping, leading to a new scaling law for the snap-through time that is confirmed by elastica simulations and experiments. In many real systems material viscoelasticity is present to some degree. Finally, we examine how this influences the snap-through dynamics of a simple truss-like structure. We present a regime diagram that characterises when the timescale of snap-through is controlled by viscous, elastic or viscoelastic effects.

A causa mais frequente de surdez de herança autossômica recessiva são as mutações no lócus DFNB1, onde estão os genes GJB2 e GJB6. Dentre os indivíduos com deficiência auditiva associada a esse lócus, 10% a 50% apresentam uma única mutação recessiva no gene GJB2, frequência muito superior à esperada em função da frequência de heterozigotos na população geral. Apesar de alguns desses casos terem sido elucidados após a identificação de grandes deleções no gene GJB6 ou nas suas proximidades, a existência de muitos indivíduos com uma única mutação patogênica no gene GJB2 sugere que a haplo-insuficiência nesse gene possa interagir com outras mutações no mesmo gene, no gene GJB6 vizinho, ou até em outros genes. O objetivo desse estudo foi identificar novos alelos patogênicos, novas proteínas e novos genes que interagem com o lócus DFNB1, do ponto de vista molecular e celular, e que possam ser responsáveis por surdez de herança autossômica recessiva. Desse modo, pretendemos contribuir para o esclarecimento da patogênese da surdez de herança autossômica recessiva. Nesse trabalho, três tipos de estudos foram realizados, com metodologias próprias. Na primeira parte, buscamos identificar novos alelos patogênicos no lócus DFNB1 que poderiam ser responsáveis por surdez quando presentes em heterozigose composta com outros alelos patogênicos nos genes GJB2 e GJB6. Foi realizada a análise do DNA de 16 pacientes surdos portadores de uma única mutação patogênica em um desses dois genes por meio: (i) do sequenciamento das regiões codificadora, promotora e doadora de splicing (intron 1) do gene GJB2, (ii) da triagem de uma deleção de 200 kb localizada a 130 kb da proximidade distal da região 5\' do gene GJB6 e (iii) da pesquisa de variações no número de cópias de um ou mais exons dos genes GJB2, GJB6, GJB3 e WFS1 por MLPA (Multiplex Ligation-dependent Probe Amplification). Detectamos uma segunda mutação provavelmente patogênica em dois dos 16 pacientes heterozigotos: em um deles, a mutação p.L76P (c.C227T) foi identificada na região de código do gene GJB2 e foi por nós descrita pela primeira vez; no segundo caso, uma duplicação (0,4-1,2Kb) que inclui a região de código do gene GJB2 foi detectada, também inédita na literatura. Na segunda parte, tivemos como objetivo obter um modelo experimental para estudos funcionais in vitro da proteína codificada pelo gene GJB2, a conexina 26, em seu local de expressão que são as células de suporte do órgão de Corti. Padronizamos o cultivo in vitro de células progenitoras do órgão de Corti de camundongos e de cobaias e conseguimos obter a diferenciação in vitro das otoesferas dos camundongos em células que expressam marcadores de células ciliadas (Miosina VIIa e Jagged2) e de células de suporte (p27kip e Jagged1). Por fim, na terceira parte, buscamos por proteínas que interagem com a conexina 26 por meio de ensaios de precipitação por afinidade. Para isso, produzimos clones recombinantes de uma proteína de fusão GST-Cx26 e de uma proteína controle (GST), e realizamos sua expressão in vitro em bactérias E.coli B21. Ensaios de precipitação por afinidade entre a proteína de fusão GST-Cx26 ou GST sozinha e proteínas extraídas de cérebro ou fígado de camundongos foram realizados em diferentes condições. A identificação e a análise das proteínas presentes em bandas de SDS-PAGE, obtidas no ensaio de precipitação com a proteína de fusão GST-Cx26 e ausentes no ensaio com a GST, foram realizadas por espectrometria de massas. Identificamos um total de 49 proteínas candidatas a interagirem com a região C-terminal da Cx26. Realizamos diversas análises in silico e em literatura específica e após exclusão de candidatas por: (i) redundância de representação no ensaio GST-Cx26, (ii) diferença entre a massa molecular esperada e a obtida, (iii) precipitação inespecífica e (iv) localização subcelular incompatível com a conexina 26, selecionamos um total de 22 proteínas candidatas a interagirem com a região C-terminal da conexina 26, para estudos futuros. A confimação da interação entre essas 22 proteínas e a conexina 26 é desejável por meio de estudos de co-localização e imuno-coprecipitação / The most frequent causes of nonsyndromic recessive hearing loss are mutations in locus DFNB1, in the GJB2 and GJB6 genes. Among the individuals with hearing loss with mutations in this locus, 10% to 50% present a single recessive mutation in the GJB2 gene, frequency much higher than expected taking into account the frequency of heterozygotes in the general population. Although some of these cases have been elucidated after the identification of large deletions in GJB6 or its surrounding regions, the existence of many individuals with a single pathogenic mutation in the GJB2 gene suggests that haplo-insufficiency of this gene may interact with other types of mutations in the same gene, in the neighbor gene GJB6, or even in other genes. The aim of this study was to identify new pathogenic alleles, proteins and genes that interact with the locus DFNB1, from the molecular and cellular perspective, and that may be responsible for autosomal recessive deafness. Thus, we aimed to contribute to the understanding of the pathogenesis of autosomal recessive deafness. In this work, three different types of studies were performed, each one with a particular methodology. In the first part, we searched for new pathogenic alleles in the locus DFNB1 that could be responsible for deafness, when present in compound heterozygosis with other pathogenic alleles in GJB2 and GJB6 genes. We performed DNA analysis in samples from 16 deaf patients, carriers of a single pathogenic mutation in one of these two genes by: (i) sequencing the coding, promoter and splice donor (intron 1) regions of the GJB2 gene, (ii) screening for a deletion of 200 kb located 130 kb upstream from GJB6 gene and (iii) investigating copy number variations in of one or more exons of the genes GJB2, GJB6, GJB3 and WFS1 by MLPA (Multiplex Ligation-dependent Probe Amplification). We detected a second mutation, probably pathogenic, in two of the 16 heterozygous patients: in one case, the p.L76P (c.C227T) mutation was identified in the coding region of the GJB2 gene and was firstly described by us; in the second case, a novel duplication (0.4 - 1.2 Mb) that includes the coding region of the GJB2 gene was detected. In the second part, our objective was to obtain an experimental model for in vitro functional studies of the protein encoded by the GJB2 gene, connexin 26, in its site of expression, that is, in the supporting cells of the organ of Corti. We standardized the culturing of guinea pigs and mice progenitor cells of organ of Corti. We were also able to induce differentiation of mice\'s otospheres into cells that express markers of hair (myosin VIIa and Jagged2) and supporting cells (p27kip and Jagged1). Finally, we searched for connexin 26 interacting proteins by pull-down assays. Recombinant clones expressing a fusion protein GST-Cx26 and a control protein (GST) were produced, so that in vitro expression in E. coli B21 could be performed. Pull-down experiments, perfomed with fusion protein GST-Cx26 or GST alone, and with proteins from mice brain or liver extracts were done under several different conditions. The identification and analysis of proteins present in SDS-PAGE bands in experiments performed with the fusion protein GST-Cx26, and absent in the GST assay, were performed by mass spectrometry. We identified a total of 49 candidate proteins for interaction with the C-terminal region of Cx26. In silico analyses performed in several databases and search in the literature allowed exclusion of candidates by: (i) redundancy of representation in the GST-Cx26 experiments; (ii) discrepancy between the expected and the obtained molecular weight; (iii) nonspecific precipitation and (iv) subcellular localization incompatible with connexin 26 localization. Summing up, we selected a total of 22 candidate proteins to interact with the C-terminal region of connexin 26. Confirmation of the interaction between these proteins and connexin 26 is planned to be performed by co-localization studies and by immuno-coprecipitation

This study applied dual processing theory, the theory of working memory, and the theory of cue summation to examine how the video and audio in a television news story interact with or against each other when the story uses pull quote graphics to convey key information to viewers. Using eye-tracking, the study produced visual depictions of exactly what viewers look at on the screen when the words in the reporter's voice track match the text in the pull quote graphic verbatim, when the reporter summarizes the text in the graphic, and when the reporter's voice track ignores the text in the pull quote. The study tested the effect on recall when viewers were presented with these three story conditions—high redundancy, medium redundancy, and low redundancy, respectively. Key findings included the following: first, that stories with low redundancy resulted in lower recall and memory sensitivity scores (a measure of memory strength) than pull quotes that the reporter either summarized or read verbatim on the air. Second, it was found that neither high-redundancy nor medium-redundancy stories were superior or inferior to the other when looking at the effect on recall and memory sensitivity. And finally, in high-, medium-, and low-redundancy conditions, subjects stated that they relied more on the reporter's narration than the pull quote to get information. The study states possible implications for news producers and reporters and suggests future research in the broadcast television news industry.

No description available.

The purpose of this study was to determine the reliability of two new alternative portable methods for measuring maximal isometric force measures while performing the standard mid-thigh pull. One method, the bar grip method, required the use of the trunk and upper extremity muscles, while the second method, the pelvic belt method, did not. Both methods demonstrated good test-retest reliability via randomized repeated measures over 24-36 hours. Interestingly, the pelvic belt method generally demonstrated average maximal forces up to 65% higher than the bar method. There was a good relationship between both methods. These new alternative methods could provide strength coaches an option for a more efficient, cost-effective, portable means for the mid-thigh pull test.

This study applied dual processing theory, the theory of working memory, and the theory of cue summation to examine how the video and audio in a television news story interact with or against each other when the story uses pull quote graphics to convey key information to viewers. Using eye-tracking, the study produced visual depictions of exactly what viewers look at on the screen when the words in the reporter's voice track match the text in the pull quote graphic verbatim, when the reporter summarizes the text in the graphic, and when the reporter's voice track ignores the text in the pull quote. The study tested the effect on recall when viewers were presented with these three story conditions—high redundancy, medium redundancy, and low redundancy, respectively. Key findings included the following: first, that stories with low redundancy resulted in lower recall and memory sensitivity scores (a measure of memory strength) than pull quotes that the reporter either summarized or read verbatim on the air. Second, it was found that neither high-redundancy nor medium-redundancy stories were superior or inferior to the other when looking at the effect on recall and memory sensitivity. And finally, in high-, medium-, and low-redundancy conditions, subjects stated that they relied more on the reporter's narration than the pull quote to get information. The study states possible implications for news producers and reporters and suggests future research in the broadcast television news industry.

Objectives: To determine if force differences exist between isometric pulling positions corresponding to key positions of the deadlift. Design: Cross-sectional evaluation of isometric strength Methods: 14 powerlifters performed isometric pulls on a force plate at 3 key positions related to the deadlift (at the floor, just above the patella, and 5-6 cm short of lockout) and in the mid thigh pull position (MTP). A 1x4 repeated measures ANOVA was used to ascertain differences between the various pulling positions tested. Bonferroni-adjusted paired samples t-tests were used post-hoc. Results: Forces generated at each bar height were significantly different (F(3,39) = 51.058, p2=0.80). Paired samples t-tests showed significant differences between positions, revealing a trend of greater force generation at increasing heights for positions corresponding to the deadlift. Force generated in the mid thigh pull position was significantly higher than any other position. Conclusion: In positions corresponding to the deadlift, force generation increases at higher bar heights.

La faible densité et les propriétés mécaniques remarquables des composites polymères en font des matériaux de choix pour remplacer les métaux. Cependant, leurs propriétés physicochimiques rendent leurs surfaces peu adhésives pour divers types de revêtements. Pour améliorer l’adhérence de revêtements métalliques sur des substrats de PEEK, et pour mieux comprendre les mécanismes de l’adhésion, les propriétés de surface du matériau ont été modifiées par des procédés physiques en voie sèche.D’une part, cette étude montre que les traitements par plasma oxydants (à basse pression, ou à pression atmosphérique) permettent d’améliorer la mouillabilité de la surface et l’adhérence de revêtements métalliques, par l’augmentation de la polarité de la surface, quantifiée par XPS. D’autre part, cette étude montre que l’ablation laser infrarouge à impulsion femtoseconde permet la gravure d’un motif dense, induisant de meilleures tenues mécaniques de l’assemblage. Enfin, cette étude montre que la modification de la chimie et de la topographie combinées améliore davantage ce potentiel d’adhérence.Le but de cette étude est d’ouvrir une voie vers un modèle décrivant les mécanismes de l’adhésion, influencés par la chimie de surface et la géométrie d’un motif, en s’appuyant sur un modèle mécanique permettant de décrire la dynamique des contraintes se propageant au travers de l’interface, en tenant compte des propriétés mécaniques des matériaux. / Thanks to their low densities and good mechanical properties, polymer composites are good candidates for metal alloys substitutes. However, their physicochemical properties limit their adhesion potential towards several types of coatings. In order to improve metallic thin films adhesion on PEEK substrates, and to better comprehend adhesion mechanisms, dry-phase methods have been used to alter the surface properties of the material.First, this study shows that oxidative plasma treatments (at low or at atmospheric pressure) improve the wettability and the practical adhesion of metallic coatings, by an increase of the polar component of the surface, as measured by XPS. Second, this study shows that dense patterns etched by an infrared femtosecond laser allow good practical adhesion of the metallic thin films on the substrate. Finally, this study shows that the modification of both surface chemistry and the surface topography at the same time further improves the practical adhesion of the metallic thin films.The goal of this study is to propose a route towards a model describing the combined influence of surface texture and chemistry, with the support of a mechanical model describing the dynamics of the stress dissipation through the interface while taking into account the mechanicals properties of the interfacial materials.

Computers have been assisting in recording, sound synthesis and other fields of music production for quite some time. The actual performance of music continues to be an area in which human players are chosen over computer performers. Musical performance is an area in which personalization is more important than consistency. Human players play with each other, reacting to phrases and ideas created by the players that they are playing with. Computer performers lack the ability to react to the changes in the performance that humans perceive naturally, giving the human players an advantage over the computer performers. This thesis creates a framework for describing unique musical performers that can play along in realtime with human players. FrTime, a reactive programming language, is used to constantly create new musical phrases. Musical phrases are constructed by unique user programmed performers and by chord changes that the framework provides. The reactive language creates multiple musical phrases for each point in time. A simple module which chooses musical phrases to be performed at the time of performance is created.

In the autumn of 2015 one of the largest waves of refugees ever occurred in Europe. Sweden was the country that received the second highest number of refugees, which led to significant changes in Swedish refugee policy as an effort to reduce the number. This highlighted an issue; Has Sweden become less attractive as a country to immigrate to? The thesis analyses whether Sweden has potentially become less attractive as a country to seek refuge in after the implementation of the stricter refugee policy in 2015. This case study uses a theory-consuming research design and a qualitative content analysis as a method. The analytical model used in the study is the push and pull model, as this model in connection with the empirical material deals with how Sweden's changed refugee policy influences the Swedish pull factors. This qualitative study shows that the changes in the refugee policy does not affect the incentive structure much as only two pull factors, social rights and political stability, are affected by the changes in refugee policy.