Infection dynamics: from organ to host population

A symposium discussing collaborative research work on infectious diseases dynamics was held at Queens' College, University of Cambridge on 25 October 2006

One Fish, Two Fish, Red Fish, Blue Fish: Effects of Price Frames, Brand Names, and Choice Set Size in Medicare Part D Insurance Plan Decisions

Because many seniors choose Medicare Part D plans offering poorer coverage at greater cost, the authors examined the effect of price frames, brand names, and choice set size on participants\u27 ability to choose the lowest cost plan. A 2×2×2 within-subjects design was used with 126 participants aged 18 to 91 years old. Mouselab, a web-based program, allowed participants to choose drug plans across eight trials that varied using numeric or symbolic prices, real or fictitious drug plan names, and three or nine drug plan options. Results from the multilevel models suggest numeric versus symbolic prices decreased the likelihood of choosing the lowest cost plan (-8.0 percentage points, 95% confidence interval=-14.7 to -0.9). The likelihood of choosing the lowest cost plan decreased as the amount of information increased suggesting that decision cues operated independently and collectively when selecting a drug plan. Redesigning the current Medicare Part D plan decision environment could improve seniors\u27 drug plan choices

Risky choice in younger versus older adults: Affective context matters

Earlier frameworks have indicated that older adults tend to experience decline in their deliberative decisional capacity, while their affective abilities tend to remain intact (Peters, Hess, Västfjäll, & Auman, 2007). The present study applied this framework to the study of risky decision-making across the lifespan. Two versions of the Columbia Card Task (CCT) were used to trigger either affective decision-making (i.e., the “warm” CCT) or deliberative decision-making (i.e., the “cold” CCT) in a sample of 158 individuals across the lifespan. Overall there were no age differences in risk seeking. However, there was a significant interaction between age and condition, such that older adults were relatively more risk seeking in the cold condition only. In terms of everyday decision-making, context matters and risk propensity may shift within older adults depending upon the context

Brain activation during memory encoding in type 2 diabetes mellitus:a discordant twin pair study

Type 2 diabetes mellitus increases the risk of dementia and neuronal dysfunction may occur years before perceptible cognitive decline. We aimed to study the impact of type 2 diabetes on brain activation during memory encoding in middle-aged people, controlling for age, sex, genes, and early-shared environment. Twenty-two twin pairs discordant for type 2 diabetes mellitus (mean age 60.9 years) without neurological disease were recruited from the Australian Twin Registry (ATR) and underwent functional magnetic resonance imaging (fMRI) during a memory encoding task, cognitive tests, and structural MRI. Type 2 diabetes was associated with significantly reduced activation in left hemisphere temporoparietal regions including angular gyrus, supramarginal gyrus, and middle temporal gyrus and significantly increased activation in bilateral posteriorly distributed regions. These findings were present in the absence of within-pair differences in standard cognitive test scores, brain volumes, or vascular lesion load. Differences in activation were more pronounced among monozygotic (MZ) pairs, with MZ individuals with diabetes also displaying greater frontal activation. These results provide evidence for preclinical memory-related neuronal dysfunction in type 2 diabetes. They support the search for modifiable later-life environmental factors or epigenetic mechanisms linking type 2 diabetes and cognitive decline

Human cloning in film: horror, ambivalence, hope

Fictional filmic representations of human cloning have shifted in relation to the 1997 announcement of the birth of Dolly the cloned sheep, and since therapeutic human cloning became a scientific practice in the early twentieth century. The operation and detail of these shifts can be seen through an analysis of the films The Island (2005) and Aeon Flux (2005). These films provide a site for the examination of how these changes in human cloning from fiction to practice, and from horror to hope, have been represented and imagined, and how these distinctions have operated visually in fiction, and in relation to genre

The influence of thermal evolution in the magnetic protection of terrestrial planets

Magnetic protection of potentially habitable planets plays a central role in determining their actual habitability and/or the chances of detecting atmospheric biosignatures. Here we develop a thermal evolution model of potentially habitable Earth-like planets and super-Earths (SEs). Using up-to-date dynamo-scaling laws, we predict the properties of core dynamo magnetic fields and study the influence of thermal evolution on their properties. The level of magnetic protection of tidally locked and unlocked planets is estimated by combining simplified models of the planetary magnetosphere and a phenomenological description of the stellar wind. Thermal evolution introduces a strong dependence of magnetic protection on planetary mass and rotation rate. Tidally locked terrestrial planets with an Earth-like composition would have early dayside magnetopause distances between 1.5 and 4.0 Rp , larger than previously estimated. Unlocked planets with periods of rotation ~1 day are protected by magnetospheres extending between 3 and 8 Rp . Our results are robust in comparison with variations in planetary bulk composition and uncertainties in other critical model parameters. For illustration purposes, the thermal evolution and magnetic protection of the potentially habitable SEs GL 581d, GJ 667Cc, and HD 40307g were also studied. Assuming an Earth-like composition, we found that the dynamos of these planets are already extinct or close to being shut down. While GL 581d is the best protected, the protection of HD 40307g cannot be reliably estimated. GJ 667Cc, even under optimistic conditions, seems to be severely exposed to the stellar wind, and, under the conditions of our model, has probably suffered massive atmospheric losses

On the relative importance of thermal and chemical buoyancy in regular and impact-induced melting in a Mars-like planet

We ran several series of two-dimensional numerical mantle convection simulations representing in idealized form the thermochemical evolution of a Mars-like planet. In order to study the importance of compositional buoyancy of melting mantle, the models were set up in pairs of one including all thermal and compositional contributions to buoyancy and one accounting only for the thermal contributions. In several of the model pairs, single large impacts were introduced as causes of additional strong local anomalies, and their evolution in the framework of the convecting mantle was tracked. The models confirm that the additional buoyancy provided by the depletion of the mantle by regular melting can establish a global stable stratification of the convecting mantle and throttle crust production. Furthermore, the compositional buoyancy is essential in the stabilization and preservation of local compositional anomalies directly beneath the lithosphere and offers a possible explanation for the existence of distinct, long-lived reservoirs in the martian mantle. The detection of such anomalies by geophysical means is probably difficult, however; they are expected to be detected by gravimetry rather than by seismic or heat flow measurements. The results further suggest that the crustal thickness can be locally overestimated by up to ~20 km if impact-induced density anomalies in the mantle are neglected.Comment: 29 pages, 10 figure

Artificial insect wings of diverse morphology for flapping-wing micro air vehicles

The development of flapping-wing micro air vehicles (MAVs) demands a systematic exploration of the available design space to identify ways in which the unsteady mechanisms governing flapping-wing flight can best be utilized for producing optimal thrust or maneuverability. Mimicking the wing kinematics of biological flight requires examining the potential effects of wing morphology on flight performance, as wings may be specially adapted for flapping flight. For example, insect wings passively deform during flight, leading to instantaneous and potentially unpredictable changes in aerodynamic behavior. Previous studies have postulated various explanations for insect wing complexity, but there lacks a systematic approach for experimentally examining the functional significance of components of wing morphology, and for determining whether or not natural design principles can or should be used for MAVs. In this work, a novel fabrication process to create centimeter-scale wings of great complexity is introduced; via this process, a wing can be fabricated with a large range of desired mechanical and geometric characteristics. We demonstrate the versatility of the process through the creation of planar, insect-like wings with biomimetic venation patterns that approximate the mechanical properties of their natural counterparts under static loads. This process will provide a platform for studies investigating the effects of wing morphology on flight dynamics, which may lead to the design of highly maneuverable and efficient MAVs and insight into the functional morphology of natural wings.Organismic and Evolutionary Biolog