Program verification with interacting analysis plugins

In this paper we propose and argue for a modular framework for interprocedural program analysis, where multiple program analysis tools are combined in order to exploit the particular advantages of each. This allows for “plugging together” such tools as required by each verification task and makes it easy to integrate new analyses. Our framework automates the sharing of information between plugins using a first order logic with transitive closure, in a way inspired by the open product of Cortesi et al.. We describe a prototype implementation of our framework, which performs static assertion checking on a simple language for heap-manipulating programs. This implementation includes plugins for three existing approaches — predicate abstraction, 3-valued shape analysis and a decidable pointer analysis — and for a simple type system. We demonstrate through a detailed example the increase in precision that our approach can provide. Finally we discuss the design decisions we have taken, in particular the tradeoffs involved in the choice of language by which the plugins communicate, and identify some future directions for our work

Cleanly combining specialised program analysers

Automatically proving that (infinite-state) software programs satisfy a specification is an important task, but has proved very difficult. Thus, in order to obtain techniques that work with reasonable speed and without user guidance, researchers have typically targeted restricted classes of language features, programming idioms and properties. We have designed a system in which several of these specialised techniques can be used together in proving that a program is correct; this is done without breaking modularity by propagating information between the analyses, expressed as formulae of an expressive common logic. In this way, we can verify programs which, because they use diverse language features and idioms, are difficult or impossible to prove using any one individual technique. Our system is implemented in the experimental tool HECTOR

Simulations of slow positron production using a low energy electron accelerator

Monte Carlo simulations of slow positron production via energetic electron interaction with a solid target have been performed. The aim of the simulations was to determine the expected slow positron beam intensity from a low energy, high current electron accelerator. By simulating (a) the fast positron production from a tantalum electron-positron converter and (b) the positron depth deposition profile in a tungsten moderator, the slow positron production probability per incident electron was estimated. Normalizing the calculated result to the measured slow positron yield at the present AIST LINAC the expected slow positron yield as a function of energy was determined. For an electron beam energy of 5 MeV (10 MeV) and current 240 $\mu$A (30 $\mu$A) production of a slow positron beam of intensity 5 $\times$ 10$^{6}$ s$^{-1}$ is predicted. The simulation also calculates the average energy deposited in the converter per electron, allowing an estimate of the beam heating at a given electron energy and current. For low energy, high-current operation the maximum obtainable positron beam intensity will be limited by this beam heating.Comment: 11 pages, 15 figures, submitted to Review of Scientific Instrument

Do red deer stags (Cervus elaphus) use roar fundamental frequency (F0) to assess rivals?

It is well established that in humans, male voices are disproportionately lower pitched than female voices, and recent studies suggest that this dimorphism in fundamental frequency (F0) results from both intrasexual (male competition) and intersexual (female mate choice) selection for lower pitched voices in men. However, comparative investigations indicate that sexual dimorphism in F0 is not universal in terrestrial mammals. In the highly polygynous and sexually dimorphic Scottish red deer Cervus elaphus scoticus, more successful males give sexually-selected calls (roars) with higher minimum F0s, suggesting that high, rather than low F0s advertise quality in this subspecies. While playback experiments demonstrated that oestrous females prefer higher pitched roars, the potential role of roar F0 in male competition remains untested. Here we examined the response of rutting red deer stags to playbacks of re-synthesized male roars with different median F0s. Our results show that stags’ responses (latencies and durations of attention, vocal and approach responses) were not affected by the F0 of the roar. This suggests that intrasexual selection is unlikely to strongly influence the evolution of roar F0 in Scottish red deer stags, and illustrates how the F0 of terrestrial mammal vocal sexual signals may be subject to different selection pressures across species. Further investigations on species characterized by different F0 profiles are needed to provide a comparative background for evolutionary interpretations of sex differences in mammalian vocalizations

Circadian Entrainment Triggers Maturation of Human In Vitro Islets

Stem-cell-derived tissues could transform disease research and therapy, yet most methods generate functionally immature products. We investigate how human pluripotent stem cells (hPSCs) differentiate into pancreatic islets in vitro by profiling DNA methylation, chromatin accessibility, and histone modification changes. We find that enhancer potential is reset upon lineage commitment and show how pervasive epigenetic priming steers endocrine cell fates. Modeling islet differentiation and maturation regulatory circuits reveals genes critical for generating endocrine cells and identifies circadian control as limiting for in vitro islet function. Entrainment to circadian feeding/fasting cycles triggers islet metabolic maturation by inducing cyclic synthesis of energy metabolism and insulin secretion effectors, including antiphasic insulin and glucagon pulses. Following entrainment, hPSC-derived islets gain persistent chromatin changes and rhythmic insulin responses with a raised glucose threshold, a hallmark of functional maturity, and function within days of transplantation. Thus, hPSC-derived tissues are amenable to functional improvement by circadian modulation

From research to policy in chronic disease prevention: mandatory salt reduction in South Africa

Abstract of a poster that presented at 20th International Congress of Nutrition, Granada, Spain, September 15-20, 2013

Knowledge of iodine nutrition in the South African adult population

OBJECTIVES: To determine the level of knowledge regarding iodine nutrition and its relationship with socio-economic status in the South African population. DESIGN: A cross-sectional population survey collecting questionnaire information on knowledge of iodine nutrition and sociodemographic variables in a multistage, stratified, cluster study sample, representative of the adult South African population. SETTING: Home visits and personal interviews in the language of the respondent. SUBJECTS: Data were collected from one adult in each of the selected 2164 households, and the participation rate was 98%. RESULTS: Only 15.4% of respondents correctly identified iodised salt as the primary dietary source of iodine, 16.2% knew the thyroid gland needs iodine for its functioning, and a mere 3.9% considered brain damage, and 0.8% considered cretinism, as the most important health consequence of iodine deficiency. Compared with respondents from high socio-economic households, respondents from low socio-economic households were considerably less informed about aspects of iodine nutrition covered in this study. CONCLUSIONS: The knowledge level of iodine nutrition is low among South Africans, particularly among the low socio-economic groups. These data suggest that the international emphasis on brain damage resulting from iodine deficiency has not been conveyed successfully to the consumer level in this country