Theoretical Models for Surface Forces and Adhesion and Their Measurement Using Atomic Force Microscopy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effective swimmer’s action during the grab start technique

The external forces applied in swimming starts have been often studied, but using direct analysis and simple interpretation data processes. This study aimed to develop a tool for vertical and horizontal force assessment based on the swimmers' propulsive and structural forces (passive forces due to dead weight) applied during the block phase. Four methodological pathways were followed: the experimented fall of a rigid body, the swimmers' inertia effect, the development of a mathematical model to describe the outcome of the rigid body fall and its generalization to include the effects of the inertia, and the experimental swimmers' starting protocol analysed with the inclusion of the developed mathematical tool. The first three methodological steps resulted in the description and computation of the passive force components. At the fourth step, six well-trained swimmers performed three 15 m maximal grab start trials and three-dimensional (3D) kinetic data were obtained using a six degrees of freedom force plate. The passive force contribution to the start performance obtained from the model was subtracted from the experimental force due to the swimmers resulting in the swimmers' active forces. As expected, the swimmers' vertical and horizontal active forces accounted for the maximum variability contribution of the experimental forces. It was found that the active force profile for the vertical and horizontal components resembled one another. These findings should be considered in clarifying the active swimmers' force variability and the respective geometrical profile as indicators to redefine steering strategies.

Associação entre as narrativas em saúde bucal e condições socioeconômico-culturais: a dentição como reflexo da desigualdade social

This anthropological study investigates the lived-experience of oral diseases in the context of poverty in Northeast Brazil. During six months in 2004???, ethnographic interviews, narratives and participant-observation with 31 residents of the low-income community, Dendê, located in Fortaleza, Ceará were conducted and analyzed utilizing a hermeneutic-dialetic method. It is revealed that precarious life conditions make prioritizing caretaking a difficult task. Despite suffering tooth pain, seeking a dentist's care is perceived as "a luxury" not a citzens' right. Difficulties in accessing services and poor quality restorations, favor tooth extractions as the most effective intervention. The deterioration of one's oral health is lamented by community members who seek help from popular clinics, politicians and traditional healers. The experience of dental disease differs according to social class, leaves oral scars of inequity, harms self-esteem and inhibits social inclusion. In this context, "treating" the Teeth of Inequity demands that we deepen our comprehension of the social determinants of health, reduce injustice in the access to quality care, remove demoralizing stigmas and empower the community to confront structural forces which affect its life

Latin Americans in London:language, integration and ethnic identity

This thesis studies the links between language, migration and integration in the context of the 'new migrant' group of Latin Americans in London. It reviews the many ways in which language impacts the integration processes of migrants by influencing people's access to jobs, services, social contacts and information. By focusing on migrants' experiences this research also investigates the ways in which language and identity articulate, as well as the affective variables that are at play in the acquisition of the local language. With a large sector trapped in a cycle of poor command of English and labour market disadvantage, many Latin Americans experience exclusion and poverty. In reaction to this, a sector of the community is campaigning for ethnic minority recognition. This work reviews the debates for recognition and the strategy of organising around ethnicity, paying special attention to the role language plays in the process. The study is based on over two and half years of qualitative research, which included interviews, surveys, and long-term participant observation within a community organisation and a recognition campaign. Its interdisciplinary perspective allows the recognition of both the intimate links between language and identity, as well as the social and structural forces that influence migrants' linguistic integration. It unveils the practical and symbolic value that the mother tongue has for Latin American migrants and provides a broader account of their experiences. This research calls attention to the need for a more comprehensive approach to the study of language and migration in order to acknowledge the affective and social factors involved in the linguistic practices of migrants. By studying the community's struggles for recognition, this work evidences both the importance of visibility for minority groups in London and the intrinsic methodological limitations of monitoring through ethnic categorisation.

Armenia's foreign policy, 1991–2004: Between history and geopolitics

This dissertation is the first systematic study of Armenia’s foreign policy during the post-independence period, between 1991 and 2004. It argues that a small state’s foreign policy is best understood when looking at the regional level. Armenia’s geographic proximity to Iran, Russia and Turkey, places it in an area of heightened geopolitical interest by various great powers. This dissertation explores four sets of relationships with Armenia’s major historical ‘partners’: Russia, Iran, Turkey and the West (Europe and the United States). Each relationship reveals a complex reality of a continuous negotiation between ideas of history, collective memory, nationalism and geopolitics. A detailed study of Armenia’s relations with these powers demonstrates how actors’ relations of amity and enmity are formed to constitute a regional security complex. Turkey represents the ultimate “other”, while both Europe and Iran are seen as ideational “others”, whose role in Armenia’s foreign policy, aside from pragmatic policy considerations, reflects a normative quest. Russia and the United States, on the other hand, represent the powerful structural forces that define the regional security complex, in which Armenia operates. This dissertation argues that although Armenia has been severely constrained in certain foreign policy choices, it was adept at carving a space for action that privileged the issue of Nagorno-Karabakh over other geopolitical imperatives.

Navigating racial boundaries: The one-drop rule and mixed-race Jamaicans in South Florida

Like many West Indians, mixed-race Jamaican immigrants enter the United States with fluid notions about race and racial identifications that reflect socio-political events in their home country and that conflict with the more rigid constructions of race they encounter in the U.S. This dissertation explores the experiences of racially mixed Jamaicans in South Florida and the impact of those experiences on their racial self-characterizations through the boundary-work theoretical framework. Specifically, the study examines the impact of participants’ exposure to the one-drop rule in the U.S., by which racial identification has been historically determined by the existence or non-existence of black forebears. Employing qualitative data collected through both focus group and face-to-face semi-structured interviews, the study analyzes mixed-race Jamaicans’ encounters in the U.S. with racial boundaries, and the boundary-work that reinforces them, as well their response to these encounters. Through their stories, the dissertation examines participants’ efforts to navigate racial boundaries through choices of various racial identifications. Further, it discusses the ways in which structural forces and individual agency have interacted in the formation of these identifications. The study finds that in spite of participants’ expressed preference for non-racialism, and despite their objections to rigid racial categories, in seeking to carve out alternative identities, they are participating in the boundary-making of which they are so critical.^

Un -equal opportunity: Sex and school among first and second generation Mexican immigrant adolescent girls

The purpose of this dissertation was to determine the interactions of sexuality and education among low socioeconomic status first and second generation Mexican immigrant adolescent girls. Much of the existing research differentiates between immigrant generations with little examination of the differences within a particular immigrant generation. This study utilized qualitative methods to examine how various social institutions intersected to influence the young women's decisions about education and sexuality. The methodology included more than three years of participant observation in a South Florida high school and surrounding community; structured and unstructured interviews with twenty young women, their family members, school personnel, and community activists; and surveys conducted with the young women and their parent or guardian. ^ Moving beyond the limits of essentialist immigration theories, this project revealed within group (i.e. immigrant generation) complexities as well as between group similarities. The data included in this dissertation delineate how relationships of power and control permeated the lives of first and second generation Mexican immigrant adolescent girls. The lens of this dissertation is focused on the salient issues of sexuality and education: two dominant forces in many adolescent lives. ^ I found the young women represented a variety of positions on the academic orientation and sexuality continuums and engaged in activities that both reinforced and countered their stated positions on each of these issues. Specifically, first and second generation immigrants are often viewed as maintaining opposing viewpoints about both education and female sexuality however, for these young women the within group variation was larger than the between group variation. While all the young women in this study expressed a belief in the value of education, they engaged in activities that both fortified and contradicted that expressed position. Additionally, although acculturation can lead to increased sexual activity and decreased engagement with education, the first generation immigrant young women in this study became pregnant and/or withdrew from school in equal proportions to their second generation counterparts. In summary, structural forces combined, often inadvertently, and contributed to these young women's spiraling negative academic orientation and/or rational choice of motherhood. Finally, the findings are linked to policy implications. ^

Syndemic health disparities and resilience processes related to HIV transmission risk among African American/Black men in south Florida

Rates of HIV infection continue to climb among minority populations and men who have sex with men (MSM), with African American/Black MSM being especially impacted. Numerous studies have found HIV transmission risk to be associated with many health and social disparities resulting from larger environmental and structural forces. Using anthropological and social environment-based theories of resilience that focus on individual agency and larger social and environmental structures, this dissertation employed a mixed methods design to investigate resilience processes among African American/Black MSM.^ Quantitative analyses compared African American/Black (N=108) and Caucasian/White (N=250) MSM who participated in a previously conducted randomized controlled trial (RCT) of sexual and substance use risk reduction interventions. At RCT study entry, using past 90 day recall periods, there were no differences in unprotected sex frequency, however African American/Black MSM reported higher frequencies of days high (P<0.000), and drugs and sex used in combination (P<0.000), and substance dependence (P<0.000) and lower levels of social support (P<0.024) compared to Caucasian/White MSM. At 12- month follow-up, multi-level statistical models found that African American/Black MSM reduced their frequencies of days high and unprotected sex at greater rates than Caucasian/White MSM (P<0.001).^ Qualitative data collected among a sub-sample of African American/Black MSM from the RCT (N=21) described the men's experiences of living with multiple health and social disparities and the importance of RCT study assessments in facilitating reductions in risk behaviors. A cross-case analysis showed different resilience processes undertaken by men who experienced low socioeconomic status, little family support, and homophobia (N=16) compared to those who did not (N=5).^ The dissertation concludes that resilience processes to HIV transmission risk and related health and social disparities among African American/Black MSM varies and are dependent on specific social environmental factors, including social relationships, structural homophobia, and access to social, economic, and cultural capital. Men define for themselves what it means to be resilient within their social environment. These conclusions suggest that both individual and structural-level resilience-based HIV prevention interventions are needed.^

Armenia's Foreign Policy, 1991-2004: Between History and Geopolitics

This dissertation is the first systematic study of Armenia’s foreign policy during the post-independence period, between 1991 and 2004. It argues that a small state’s foreign policy is best understood when looking at the regional level. Armenia’s geographic proximity to Iran, Russia and Turkey, places it in an area of heightened geopolitical interest by various great powers. This dissertation explores four sets of relationships with Armenia’s major historical ‘partners’: Russia, Iran, Turkey and the West (Europe and the United States). Each relationship reveals a complex reality of a continuous negotiation between ideas of history, collective memory, nationalism and geopolitics. A detailed study of Armenia’s relations with these powers demonstrates how actors’ relations of amity and enmity are formed to constitute a regional security complex. Turkey represents the ultimate “other”, while both Europe and Iran are seen as ideational “others”, whose role in Armenia’s foreign policy, aside from pragmatic policy considerations, reflects a normative quest. Russia and the United States, on the other hand, represent the powerful structural forces that define the regional security complex, in which Armenia operates. This dissertation argues that although Armenia has been severely constrained in certain foreign policy choices, it was adept at carving a space for action that privileged the issue of Nagorno-Karabakh over other geopolitical imperatives.

Food Swamps, Obesity & Health Zoning Restrictions on Fast Food Restaurants

Protecting public health is the most legitimate use of zoning, and yet there is minimal progress in applying it to the obesity problem. Zoning could potentially be used to address both unhealthy and healthy food retailers, but lack of evidence regarding the impact of zoning and public opinion on zoning changes are barriers to implementing zoning restrictions on fast food on a larger scale. My dissertation addresses these gaps in our understanding of health zoning as a policy option for altering built, food environments.

Chapter 1 examines the relationship between food swamps and obesity and whether spatial mapping might be useful in identifying priority geographic areas for zoning interventions. I employ an instrumental variables (IV) strategy to correct for the endogeneity problems associated with food environments, namely that individuals may self-select into certain neighborhoods and may consider food availability in their decision process. I utilize highway exits as a source of exogenous variation .Using secondary data from the USDA Food Environment Atlas, ordinary least squares (OLS) and IV regression models were employed to analyze cross-sectional associations between local food environments and the prevalence of obesity. I find even after controlling for food desert effects, food swamps have a positive, statistically significant effect on adult obesity rates.

Chapter 2 applies theories of message framing and prospect theory to the emerging discussion around health zoning policies targeting food environments and to explore public opinion toward a list of potential zoning restrictions on fast-food restaurants (beyond moratoriums on new establishments). In order to explore causality, I employ an online survey experiment manipulating exposure to vignettes with different message frames about health zoning restrictions with two national samples of adult Americans age 18 and over (N1=2,768 and N2=3,236). The second sample oversamples Black Americans (N=1,000) and individuals with high school as their highest level of education. Respondents were randomly assigned to one of six conditions where they were primed with different message frames about the benefits of zoning restrictions on fast food retailers. Participants were then asked to indicate their support for six zoning policies on a Likert scale. Subjects also answered questions about their food store access, eating behaviors, health status and perceptions of food stores by type.

I find that a message frame about Nutrition and increasing Equity in the food system was particularly effective at increasing support for health zoning policies targeting fast food outlets across policy categories (Conditional, Youth-related, Performance and Incentive) and across racial groups. This finding is consistent with an influential environmental justice scholar’s description of “injustice frames” as effective in mobilizing supporters around environmental issues (Taylor 2000). I extend this rationale to food environment obesity prevention efforts and identify Nutrition combined with Equity frames as an arguably universal campaign strategy for bolstering public support of zoning restrictions on fast food retailers.

Bridging my findings from both Chapters 1 and 2, using food swamps as a spatial metaphor may work to identify priority areas for policy intervention, but only if there is an equitable distribution of resources and mobilization efforts to improve consumer food environments. If the structural forces which ration access to land-use planning persist (arguably including the media as gatekeepers to information and producers of message frames) disparities in obesity are likely to widen.

Syndemic Health Disparities and Resilience Processes Related to HIV Transmission Risk among African American/Black Men in South Florida

Rates of HIV infection continue to climb among minority populations and men who have sex with men (MSM), with African American/Black MSM being especially impacted. Numerous studies have found HIV transmission risk to be associated with many health and social disparities resulting from larger environmental and structural forces. Using anthropological and social environment-based theories of resilience that focus on individual agency and larger social and environmental structures, this dissertation employed a mixed methods design to investigate resilience processes among African American/Black MSM. Quantitative analyses compared African American/Black (N=108) and Caucasian/White (N=250) MSM who participated in a previously conducted randomized controlled trial (RCT) of sexual and substance use risk reduction interventions. At RCT study entry, using past 90 day recall periods, there were no differences in unprotected sex frequency, however African American/Black MSM reported higher frequencies of days high (P Qualitative data collected among a sub-sample of African American/Black MSM from the RCT (N=21) described the men’s experiences of living with multiple health and social disparities and the importance of RCT study assessments in facilitating reductions in risk behaviors. A cross-case analysis showed different resilience processes undertaken by men who experienced low socioeconomic status, little family support, and homophobia (N=16) compared to those who did not (N=5). The dissertation concludes that resilience processes to HIV transmission risk and related health and social disparities among African American/Black MSM varies and are dependent on specific social environmental factors, including social relationships, structural homophobia, and access to social, economic, and cultural capital. Men define for themselves what it means to be resilient within their social environment. These conclusions suggest that both individual and structural-level resilience-based HIV prevention interventions are needed.

Influence of optimized lubrication-cooling and minimum quantity lubrication on the cutting forces, on the geometric quality of the surfaces and on the micro-structural integrity of hardened steel parts

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A large displacement structural analysis of a pipeline subjected to gravity and buoyancy forces

A nonlinear analysis of an elastic tube subjected to gravity forces and buoyancy pressure is carried out. An update lagrangian formulation is used. The structural analysis efficiency in terms of computer time and accuracy, has been improved when load stiffness matrices have been introduced. In this way the follower forces characteristics such as their intensity and direction changes can be well represented. A sensitivity study of different involved variables on the final deformed pipeline shape is carried out.

Optimal design of a beam subjected to compression forces in the framework of different structural models

The optimal design of a vertical cantilever beam is presented in this paper. The beam is assumed immersed in an elastic Winkler soil and subjected to several loads: a point force at the tip section, its self weight and a uniform distributed load along its length. lbe optimal design problem is to find the beam of a given length and minimum volume, such that the resultant compressive stresses are admisible. This prohlem is analyzed according to linear elasticity theory and within different alternative structural models: column, Navier-Bernoulli beam-column, Timoshenko beamcolumn (i.e. with shear strain) under conservative loads, typically, constant direction loads. Results obtained in each case are compared, in order to evaluate the sensitivity of model on the numerical results. The beam optimal design is described by the section distribution layout (area, second moment, shear area etc.) along the beam span and the corresponding beam total volume. Other situations, some of them very interesting from a theoretical point of view, with follower loads (Beck and Leipholz problems) are also discussed, leaving for future work numerical details and results.

A partial velocity approach to subcycling structural dynamics

Subcycling, or the use of different timesteps at different nodes, can be an effective way of improving the computational efficiency of explicit transient dynamic structural solutions. The method that has been most widely adopted uses a nodal partition. extending the central difference method, in which small timestep updates are performed interpolating on the displacement at neighbouring large timestep nodes. This approach leads to narrow bands of unstable timesteps or statistical stability. It also can be in error due to lack of momentum conservation on the timestep interface. The author has previously proposed energy conserving algorithms that avoid the first problem of statistical stability. However, these sacrifice accuracy to achieve stability. An approach to conserve momentum on an element interface by adding partial velocities is considered here. Applied to extend the central difference method. this approach is simple. and has accuracy advantages. The method can be programmed by summing impulses of internal forces, evaluated using local element timesteps, in order to predict a velocity change at a node. However, it is still only statistically stable, so an adaptive timestep size is needed to monitor accuracy and to be adjusted if necessary. By replacing the central difference method with the explicit generalized alpha method. it is possible to gain stability by dissipating the high frequency response that leads to stability problems. However. coding the algorithm is less elegant, as the response depends on previous partial accelerations. Extension to implicit integration, is shown to be impractical due to the neglect of remote effects of internal forces acting across a timestep interface. (C) 2002 Elsevier Science B.V. All rights reserved.