NEIGHBORHOOD PERCEPTION OF SAFETY AND THE MOBILITY GAP BETWEEN MEN AND WOMEN IN OLD AGE

Background and Objectives: Mobility limitations are a prevalent issue in older adult populations, and an important determinant of disability and mortality. Neighborhood conditions are key determinants of mobility and perception of safety may be one such determinant. Women have more mobility limitations than men, a phenomenon known as the gender mobility gap. The objective of this work was to validate a measure of perception of safety, examine the relationship between neighborhood perception of safety and mobility limitations in seniors, and explore if these effects vary by gender. Methods: This study was cross-sectional, using questionnaire data collected from community-dwelling older adults from four sites in Canada, Colombia, and Brazil. The exposure variable was the neighborhood aggregated Perception of Safety (PoS) scale, derived from the Physical and Social Disorder (PSD) scale by Sampson and Raudenbush. Its construct validity was verified using factor analyses and correlation with similar measures. The Mobility Assessment Tool – short form (MAT-sf), a video-based measure validated cross-culturally in the studied populations, was used to assess mobility limitations. Based on theoretical models, covariates were included in the analysis, both at the neighborhood level (SES, social capital, and built environment) and the individual level (age, gender, education, income, chronic illnesses, depression, cognitive function, BMI, and social participation). Multilevel modeling was used in order to account for neighborhood clustering. Gender specific analyses were carried out. SAS and M-plus were used in this study. Results: PoS was validated across all sites. It loaded in a single factor, after excluding two items, with a Cronbach α value of approximately 0.86. Mobility limitations were present in 22.08% of the sample, 16.32% among men and 27.41% among women. Neighborhood perception of safety was significantly associated with mobility limitations when controlling for all covariates, with an OR of 0.84 (CI 95%: 0.73-0.96), indicating lower odds of having mobility limitations as neighborhood perception of safety improves. Gender did not affect this relationship despite women being more likely to have mobility limitations and live in neighborhoods with poor perception of safety. Conclusion: Neighborhood perception of safety affected the prevalence of mobility limitations in older adults in the studied population.

Modeling the impact of large-scale solid mass transfers on the gravity field

The focus of this thesis is to explore and quantify the response of large-scale solid mass transfer events on satellite-based gravity observations. The gravity signature of large-scale solid mass transfers has not been deeply explored yet; mainly due to the lack of significant events during dedicated satellite gravity missions‘ lifespans. In light of the next generation of gravity missions, the feasibility of employing satellite gravity observations to detect submarine and surface mass transfers is of importance for geoscience (improves the understanding of geodynamic processes) and for geodesy (improves the understanding of the dynamic gravity field). The aim of this thesis is twofold and focuses on assessing the feasibility of using satellite gravity observations for detecting large-scale solid mass transfers and on modeling the impact on the gravity field caused by these events. A methodology that employs 3D forward modeling simulations and 2D wavelet multiresolution analysis is suggested to estimate the impact of solid mass transfers on satellite gravity observations. The gravity signature of various submarine and subaerial events that occurred in the past was estimated. Case studies were conducted to assess the sensitivity and resolvability required in order to observe gravity differences caused by solid mass transfers. Simulation studies were also employed in order to assess the expected contribution of the Next Generation of Gravity Missions for this application.