The Simultaneous Effects of Spatial and Social Networks on Cholera Transmission

This study uses social network and spatial analytical methods simultaneously to understand cholera transmission in rural Bangladesh. Both have been used separately to incorporate context into health studies, but using them together is a new and recent approach. Data include a spatially referenced longitudinal demographic database consisting of approximately 200,000 people and a database of all laboratory-confirmed cholera cases from 1983 to 2003. A complete kinship-based network linking households is created, and distance matrices are also constructed to model spatial relationships. A spatial error-social effects model tested for cholera clustering in socially linked households while accounting for spatial factors. Results show that there was social clustering in five out of twenty-one years while accounting for both known and unknown environmental variables. This suggests that environmental cholera transmission is significant and social networks also influence transmission, but not as consistently. Simultaneous spatial and social network analysis may improve understanding of disease transmission

Interlayer Exchange Coupling in (Ga,Mn)As-based Superlattices

The interlayer coupling between (Ga,Mn)As ferromagnetic layers in all-semiconductor superlattices is studied theoretically within a tight-binding model, which takes into account the crystal, band and magnetic structure of the constituent superlattice components. It is shown that the mechanism originally introduced to describe the spin correlations in antiferromagnetic EuTe/PbTe superlattices, explains the experimental results observed in ferromagnetic semiconductor structures, i.e., both the antiferromagnetic coupling between ferromagnetic layers in IV-VI (EuS/PbS and EuS/YbSe) superlattices as well as the ferromagnetic interlayer coupling in III-V ((Ga,Mn)As/GaAs) multilayer structures. The model allows also to predict (Ga,Mn)As-based structures, in which an antiferromagnetic interlayer coupling could be expected.Comment: 4 pages, 3 figure

Cholera Transmission in Bangladesh: Social Networks and Neighborhoods

Transmission of infectious pathogens across networks is well-documented, yet remains primarily focused on diseases spread by sexual contact. Such analytical tools, however, may also facilitate understanding of how other types of health outcomes are related to physical and social contacts. This research examines the relationship between cholera incidence and the social network that links households in rural Bangladesh. Using twenty-one years of longitudinal demographic and health data, clustering of similar disease rates in the network was measured and compared to spatial autocorrelation of cholera at the neighborhood level. Results indicate that rates are significantly concentrated amongst households within the same local environment, and that social clustering is only evident during certain years examined. These outcomes suggest that intervention efforts should place priority on identifying local-level environmental factors, but also consider the potential of networks as they assist transmission, as well as their role in interactions within a defined neighborhood

Does temperature preference change in aging flies?

Aging is known to be affected by many factors such as nutrition and exercise, and more studies are needed to understand the mechanisms of aging. Aging in flies shows many similarities with humans; therefore we study mechanisms of aging in flies as a model organism. Studying aging in flies requires knowledge of meaningful bio markers to measure quantitatively the rate of aging. In this study, I addressed the question of whether flies would change their temperatures preferences as they age. In a series of experiments, we sought out to compare if young flies showed the expected temperature preference rhythm (TPR).We then investigated whether the temperature preference is altered with age. We observed a trend for aging flies to lose the temperature preference rhythm. In addition, older flies preferred lower evening temperature compared to the young ones. While we were able to see a loss of temperature preference rhythm, we believe this is not a reliable or easy biomarker in the search for the measurable signs of aging.We set out to see if a biomarker of aging in could be found in temperance preference since it was found previously to be a predictable circadian rhythm in young flies. Since flies live 70 days it can be said that a day in the life of a fly is like a year in the life of a human. This is important because in our lab we use flies as a model organism for studying aging as to then apply to our understanding of human health and longevity. Currently most labs use over all lifespan as their biomarker of aging, but we need something that can be seen throughout the lifespan, not just at the end of it. We are always on the lookout for ways to see how aging effects the different conditions and genetic mutations we use. First we chose both wild types and genetic mutations to test for variation in results. We aged these flies at different intervals so as to have different ages to compare together. We further put these flies in alternating light-dark conditions to test together at different time points along the circadian 24 hour clock. The flies were tested in an apparatus that had a hot and cold side, with room temperature estimated in the middle along a temperature gradient that was established. There were 4 channels that separated the different groups of 50 individuals which labeled by their time of time, age, gender and genotype. After 30 minutes, a picture was taken to determine each of their temperature preference. No fly was retested and instead many bio repeats were used to establish a trend. Each fly was given a xy coordinate which a formula and computer program assigned a temperature to each. This data was averaged using statistical test and used to plot graphs of how the rhythm of temperature preference changed from young and old, and compared to the previously reported data

Half-metallic ferrimagnet formed by substituting Fe for Mn in semiconductor MnTe

A ternary ferrimagnetic half-metal, constructed through substituting 25% Fe for Mn in zincblende semiconductor MnTe, is predicted in terms of accurate first-principles calculations. It has a large half-metallic (HM) gap of 0.54eV and its ferrimagnetic order is very stable against other magnetic fluctuations. The HM ferrimagnetism is formed because the complete moment compensation in the antiferromagnetic MnTe is replaced by an uncomplete one in the Fe-substituted MnTe. This should make a novel approach to new HM materials. The half-metal could be fabricated because Fe has good affinity with Mn, and useful for spintronics.Comment: 5 pages with figures include

Circadian deep sequencing reveals stress-response genes that adopt robust rhythmic expression during aging

Disruption of the circadian clock, which directs rhythmic expression of numerous output genes, accelerates aging. To enquire how the circadian system protects aging organisms, here we compare circadian transcriptomes in heads of young and old Drosophila melanogaster. The core clock and most output genes remained robustly rhythmic in old flies, while others lost rhythmicity with age, resulting in constitutive over- or under-expression. Unexpectedly, we identify a subset of genes that adopted increased or de novo rhythmicity during aging, enriched for stress-response functions. These genes, termed late-life cyclers, were also rhythmically induced in young flies by constant exposure to exogenous oxidative stress, and this upregulation is CLOCK-dependent. We also identify age-onset rhythmicity in several putative primary piRNA transcripts overlapping antisense transposons. Our results suggest that, as organisms age, the circadian system shifts greater regulatory priority to the mitigation of accumulating cellular stress