Controlling epidemic spread by social distancing: Do it well or not at all

BACKGROUND: Existing epidemiological models have largely tended to neglect the impact of individual behaviour on the dynamics of diseases. However, awareness of the presence of illness can cause people to change their behaviour by, for example, staying at home and avoiding social contacts. Such changes can be used to control epidemics but they exact an economic cost. Our aim is to study the costs and benefits of using individual-based social distancing undertaken by healthy individuals as a form of control.METHODS: Our model is a standard SIR model superimposed on a spatial network, without and with addition of small-world interactions. Disease spread is controlled by allowing susceptible individuals to temporarily reduce their social contacts in response to the presence of infection within their local neighbourhood. We ascribe an economic cost to the loss of social contacts, and weigh this against the economic benefit gained by reducing the impact of the epidemic. We study the sensitivity of the results to two key parameters, the individuals' attitude to risk and the size of the awareness neighbourhood.RESULTS: Depending on the characteristics of the epidemic and on the relative economic importance of making contacts versus avoiding infection, the optimal control is one of two extremes: either to adopt a highly cautious control, thereby suppressing the epidemic quickly by drastically reducing contacts as soon as disease is detected; or else to forego control and allow the epidemic to run its course. The worst outcome arises when control is attempted, but not cautiously enough to cause the epidemic to be suppressed. The next main result comes from comparing the size of the neighbourhood of which individuals are aware to that of the neighbourhood within which transmission can occur. The control works best when these sizes match and is particularly ineffective when the awareness neighbourhood is smaller than the infection neighbourhood. The results are robust with respect to inclusion of long-range, small-world links which destroy the spatial structure, regardless of whether individuals can or cannot control them. However, addition of many non-local links eventually makes control ineffective.CONCLUSIONS: These results have implications for the design of control strategies using social distancing: a control that is too weak or based upon inaccurate knowledge, may give a worse outcome than doing nothing

Metal halide perovskites for energy applications

Exploring prospective materials for energy production and storage is one of the biggest challenges of this century. Solar energy is one of the most important renewable energy resources, due to its wide availability and low environmental impact. Metal halide perovskites have emerged as a class of semiconductor materials with unique properties, including tunable bandgap, high absorption coefficient, broad absorption spectrum, high charge carrier mobility and long charge diffusion lengths, which enable a broad range of photovoltaic and optoelectronic applications. Since the first embodiment of perovskite solar cells showing a power conversion efficiency of 3.8%, the device performance has been boosted up to a certified 22.1% within a few years. In this Perspective, we discuss differing forms of perovskite materials produced via various deposition procedures. We focus on their energy-related applications and discuss current challenges and possible solutions, with the aim of stimulating potential new applications

A Universal Trend of Reduced mRNA Stability near the Translation-Initiation Site in Prokaryotes and Eukaryotes

Recent studies have suggested that the thermodynamic stability of mRNA secondary structure near the start codon can regulate translation efficiency in Escherichia coli, and that translation is more efficient the less stable the secondary structure. We survey the complete genomes of 340 species for signals of reduced mRNA secondary structure near the start codon. Our analysis includes bacteria, archaea, fungi, plants, insects, fishes, birds, and mammals. We find that nearly all species show evidence for reduced mRNA stability near the start codon. The reduction in stability generally increases with increasing genomic GC content. In prokaryotes, the reduction also increases with decreasing optimal growth temperature. Within genomes, there is variation in the stability among genes, and this variation correlates with gene GC content, codon bias, and gene expression level. For birds and mammals, however, we do not find a genome-wide trend of reduced mRNA stability near the start codon. Yet the most GC rich genes in these organisms do show such a signal. We conclude that reduced stability of the mRNA secondary structure near the start codon is a universal feature of all cellular life. We suggest that the origin of this reduction is selection for efficient recognition of the start codon by initiator-tRNA

Early effects of parathyroid hormone on bisphosphonate/steroid-associated compromised osseous wound healing

Summary: Administration of intermittent parathyroid hormone (PTH) promoted healing of tibial osseous defects and tooth extraction wounds and prevented the development of necrotic lesions in rats on a combined bisphosphonate and steroid regimen. Introduction: Osteonecrosis of the jaw (ONJ) has emerged in association with antiresorptive therapies. The pathophysiology of ONJ is unknown and no established cure currently exists. Our objective was to determine the effect of intermittent PTH administration on early osseous healing in the jaw and long bones of rats receiving bisphosphonate and steroid treatment. Methods: Ovariectomized rats received the combination therapy of alendronate and dexamethasone (ALN/DEX) for 12 weeks. Osseous wounds were created in the jaw and tibia. PTH was administered intermittently and healing at 2 weeks post-op was compared between the jaw and tibia by microcomputed tomography and histomorphometric analyses. Results: ALN/DEX treatment was associated with necrotic open wounds in the jaw but had no negative effects on healing and promoted bone fill in tibial defects. PTH therapy prevented the development of necrotic lesions in the jaw and promoted healing of the tibial defects. PTH therapy was associated with the promotion of osteocyte survival in osseous wounds both in the jaw and tibia. Conclusions: Wound healing was impaired in the jaw in rats on a combined bisphosphonate and steroid regimen, and PTH therapy rescued necrotic lesions. These findings suggest that PTH therapy could be utilized to prevent ONJ from occurring in patients on combination antiresorptive and steroid therapy

Vaginal birth after classical Caesarean section

Current belief in obstetric practice is that the scar of a classical Caesarean section is more prone to rupture than that of a lower segment Caesarean section and that for this reason elective repeat Caesarean should always be undertaken in subsequent pregnancies