Fluctuation symmetries for work and heat

We consider a particle dragged through a medium at constant temperature as described by a Langevin equation with a time-dependent potential. The time-dependence is specified by an external protocol. We give conditions on potential and protocol under which the dissipative work satisfies an exact symmetry in its fluctuations for all times. We also present counter examples to that exact fluctuation symmetry when our conditions are not satisfied. Finally, we consider the dissipated heat which differs from the work by a temporal boundary term. We explain when and why there can be a correction to the standard fluctuation theorem due to the unboundedness of that temporal boundary. However, the corrected fluctuation symmetry has again a general validity.Comment: 10 pages, 4 figures (v2: minor typographic corrections

Household food security status in South Africa

The Human Sciences Research Council has established a policy research initiative to monitor household food security and to identify and evaluate policy options. In this special edition, a selection of articles from this project is assembled. While deep chronic hunger has fallen with the expansion of the social grants, under-nutrition is a very serious and widespread challenge. This special edition draws together the best available evidence on household food security with the aim of stimulating wider debate.food security, social grants, smallholder and subsistence production, poverty, Consumer/Household Economics,

Current and future directions in frailty research.

The concept of frailty has been evolving dramatically for the past 30 years. Through its evolution, a variety of single and multidimensional models have been used to describe frailty. This article reviews the current literature related to the defining dimensions of frailty and identifies the gaps in the literature requiring additional research. A detailed literature review was performed to identify key dimensions and models currently being used to define frailty, classify interventions that have been developed to reverse frailty, and identify potential areas for future research within this field. Despite the large body of research defining the dimensions of frailty, no consensus exists on a comprehensive, operational definition. A standardized definition will be critical to design effective interventions at earlier stages along the continuum of frailty and interpret findings from evaluation studies. Identified gaps in the literature include studies supporting the utility of expanding the definition of frailty to incorporate social determinants, studies evaluating the role of obesity in the development of frailty, and the need for longitudinal studies for defining the pathways to developing frailty. This review highlights the need for an accurate definition of frailty and for longitudinal research to explore the development of frailty and evaluate the effectiveness of the frailty reversal interventions that may avert or delay adverse outcomes within this susceptible population. These future research needs are discussed within the context of the growing pressures to bring down health care costs, and the role of comparative effectiveness research and cost-effectiveness research in identifying interventions with the potential to help slow the growth of health care spending among the elderly

Stochastic Analysis of a Churn-Tolerant Structured Peer-to-Peer Scheme

We present and analyze a simple and general scheme to build a churn (fault)-tolerant structured Peer-to-Peer (P2P) network. Our scheme shows how to "convert" a static network into a dynamic distributed hash table(DHT)-based P2P network such that all the good properties of the static network are guaranteed with high probability (w.h.p). Applying our scheme to a cube-connected cycles network, for example, yields a $O(\log N)$ degree connected network, in which every search succeeds in $O(\log N)$ hops w.h.p., using $O(\log N)$ messages, where $N$ is the expected stable network size. Our scheme has an constant storage overhead (the number of nodes responsible for servicing a data item) and an $O(\log N)$ overhead (messages and time) per insertion and essentially no overhead for deletions. All these bounds are essentially optimal. While DHT schemes with similar guarantees are already known in the literature, this work is new in the following aspects: (1) It presents a rigorous mathematical analysis of the scheme under a general stochastic model of churn and shows the above guarantees; (2) The theoretical analysis is complemented by a simulation-based analysis that validates the asymptotic bounds even in moderately sized networks and also studies performance under changing stable network size; (3) The presented scheme seems especially suitable for maintaining dynamic structures under churn efficiently. In particular, we show that a spanning tree of low diameter can be efficiently maintained in constant time and logarithmic number of messages per insertion or deletion w.h.p. Keywords: P2P Network, DHT Scheme, Churn, Dynamic Spanning Tree, Stochastic Analysis

Identification of long non-coding RNAs involved in neuronal development and intellectual disability

Recently, exome sequencing led to the identification of causal mutations in 16–31% of patients with intellectual disability (ID), leaving the underlying cause for many patients unidentified. In this context, the noncoding part of the human genome remains largely unexplored. For many long non-coding RNAs (lncRNAs) a crucial role in neurodevelopment and hence the human brain is anticipated. Here we aimed at identifying lncRNAs associated with neuronal development and ID. Therefore, we applied an integrated genomics approach, harnessing several public epigenetic datasets. We found that the presence of neuron-specific H3K4me3 confers the highest specificity for genes involved in neurodevelopment and ID. Based on the presence of this feature and GWAS hits for CNS disorders, we identified 53 candidate lncRNA genes. Extensive expression profiling on human brain samples and other tissues, followed by Gene Set Enrichment Analysis indicates that at least 24 of these lncRNAs are indeed implicated in processes such as synaptic transmission, nervous system development and neurogenesis. The bidirectional or antisense overlapping orientation relative to multiple coding genes involved in neuronal processes supports these results. In conclusion, we identified several lncRNA genes putatively involved in neurodevelopment and CNS disorders, providing a resource for functional studies

Contributions of X-ray CT to the characterization of natural building stones and their disintegration

This paper highlights the use of the high resolution scanner at the Centre for X-ray Tomography in Ghent, Belgium (UGCT), for the 3D quantitative evaluation of the disintegration of some French natural building stones. Rocks deteriorate when they are exposed to extreme weathering factors such as a combination of water and freeze-thaw cycles or high pressure. The results of those processes can be very diverse: from element migration to crust formation to the origination of micro-cracks. Thanks to its non-destructive character, high resolution computed tomography (CT) turned out to be an excellent monitoring tool as it contributes to the characterization of the internal structure of the natural building stone. X-ray CT also provides a better insight into the micro-structural durability properties of the building stone

Super-orbital re-entry in Australia - laboratory measurement, simulation and flight observation

There are large uncertainties in the aerothermodynamic modelling of super-orbital re-entry which impact the design of spacecraft thermal protection systems (TPS). Aspects of the thermal environment of super-orbital re-entry flows can be simulated in the laboratory using arc- and plasma jet facilities and these devices are regularly used for TPS certification work [5]. Another laboratory device which is capable of simulating certain critical features of both the aero and thermal environment of super-orbital re-entry is the expansion tube, and three such facilities have been operating at the University of Queensland in recent years[10]. Despite some success, wind tunnel tests do not achieve full simulation, however, a virtually complete physical simulation of particular re-entry conditions can be obtained from dedicated flight testing, and the Apollo era FIRE II flight experiment [2] is the premier example which still forms an important benchmark for modern simulations. Dedicated super-orbital flight testing is generally considered too expensive today, and there is a reluctance to incorporate substantial instrumentation for aerothermal diagnostics into existing missions since it may compromise primary mission objectives. An alternative approach to on-board flight measurements, with demonstrated success particularly in the ‘Stardust’ sample return mission, is remote observation of spectral emissions from the capsule and shock layer [8]. JAXA’s ‘Hayabusa’ sample return capsule provides a recent super-orbital reentry example through which we illustrate contributions in three areas: (1) physical simulation of super-orbital re-entry conditions in the laboratory; (2) computational simulation of such flows; and (3) remote acquisition of optical emissions from a super-orbital re entry event