UNDERSTANDING INTERGENERATIONAL MALNUTRITION IN RURAL BANGLADESH: A SYSTEMS APPROACH

Background: Determinants of malnutrition across the lifecycle are complex. Beyond host characteristics and behavioral choices, the immediate environment and broader societal context remains a challenge to measure. The JiVitA-1 trial in rural northwest Bangladesh reveals intergenerational spatial patterns of malnutrition, based on mid-upper arm circumference (MUAC), that converge with age from early life onward, suggesting possible contextual influences. This dissertation explores these spatial patterns, and investigates interactions among biological, socioeconomic and contextual factors on trajectories of nutritional status from birth to adulthood in this typical rural South Asian population. Methods: Spatial analysis with multiple-linear regression was used to assess independent and synergistic effects of individual, household and community factors, added sequentially, on MUAC among mother-infant dyads. Explanatory improvements and spatial correlation accounted for by characteristics at each level was considered. Results: Multilevel regression models explained 13.2%, 14.5%, and 11.7% of variabilty in MUAC of infants at birth and six months and expectant mothers, respectively. Most variability in MUAC was explained by individual and household-level variables. Community influences accounted for 0.3%, 0.4%, and 0.7% of the variability in MUAC at the two infant ages and among women, respecitvely. Infant growth between birth and six months was guided by initial size (r² = 0.33), and modified further by household and community socioeconomic-status (SES) and maternal nutritional status. The full multilevel model accounted for 40% of the variance in growth rate, 1% of which was attributed to community context. Including individual- and household-level variables provided modest reductions in residual spatial autocorrelation of MUAC, compared to reductions associated with contextual factors. Promising contextual variables included neighborhood economic structure, maternal education, elevation, population density, and travel-time to markets. Many contextual variables were correlated, indicating that those living in wealthier neighborhoods enjoy healthier environments, which may reinforce benefits of greater household and neighborhood SES. Conclusions: A systems science approach revealed multi-level and age-specific influences on infant and maternal nutritional status in this rural Bangladesh setting. Contextual variables explained differences in MUAC and reduced residual spatial autocorrelation more than individual and household variables combined. Correlations between contextual variables also indicated economically-driven population sorting in this typical rural setting

Melting and differentiation of early-formed asteroids: The perspective from high precision oxygen isotope studies

A number of distinct methodologies are available for determining the oxygen isotope composition of minerals and rocks, these include laser-assisted fluorination, secondary ion mass spectrometry (SIMS)and UV laser ablation. In this review we focus on laser-assisted fluorination, which currently achieves the highest levels of precision available for oxygen isotope analysis. In particular, we examine how results using this method have furthered our understanding of early-formed differentiated meteorites. Due to its rapid reaction times and low blank levels, laser-assisted fluorination has now largely superseded the conventional externally-heated Ni “bomb” technique for bulk analysis. Unlike UV laser ablation and SIMS analysis, laser-assisted fluorination is not capable of focused spot analysis. While laser fluorination is now a mature technology, further analytical improvements are possible via refinements to the construction of sample chambers, clean-up lines and the use of ultra-high resolution mass spectrometers. High-precision oxygen isotope analysis has proved to be a particularly powerful technique for investigating the formation and evolution of early-formed differentiated asteroids and has provided unique insights into the interrelationships between various groups of achondrites. A clear example of this is seenin samples that lie close to the terrestrial fractionation line (TFL). Based on the data from conventional oxygen isotope analysis, it was suggested that the main-group pallasites, the howardite eucrite diogenite suite (HEDs) and mesosiderites could all be derived from a single common parent body. However,high precision analysis demonstrates that main-group pallasites have a Δ17O composition that is fully resolvable from that of the HEDs and mesosiderites, indicating the involvement of at least two parent bodies. The range of Δ17O values exhibited by an achondrite group provides a useful means of assessing the extent to which their parent body underwent melting and isotopic homogenization. Oxygen isotope analysis can also highlight relationships between ungrouped achondrites and the more well-populated groups. A clear example of this is the proposed link between the evolved GRA 06128/9 meteorites and the brachinites. The evidence from oxygen isotopes, in conjunction with that from other techniques, indicates that we have samples from approximately 110 asteroidal parent bodies (∼60 irons, ∼35 achondrites and stony-iron, and ∼15 chondrites) in our global meteorite collection. However, compared to the likely size of the original protoplanetary asteroid population, this is an extremely low value. In addition, almost all of the differentiated samples (achondrites, stony-iron and irons) are derived from parent bodies that were highly disrupted early in their evolution. High-precision oxygen isotope analysis of achondrites provides some important insights into the origin of mass-independent variation in the early Solar System. In particular, the evidence from various primitive achondrite groups indicates that both the slope 1 (Y&R) and CCAM lines are of primordial significance. Δ17O differences between water ice and silicate-rich solids were probably the initial source of the slope 1 anomaly. These phases most likely acquired their isotopic composition as a result of UV photo-dissociation of CO that took place either in the early solar nebula or precursor giant molecular cloud. Such small-scale isotopic heterogeneities were propagated into larger-sized bodies, such as asteroids and planets, as a result of early Solar System processes, including dehydration, aqueous alteration,melting and collisional interactions