Polarization stabilization in vertical-cavity surface-emitting lasers through asymmetric current injection

We present experimental evidence that asymmetric current injection in intracavity contacted vertical-cavity surface-emitting lasers (VCSELs) stabilizes the polarization of the emitted light. Anisotropies in the gain and loss mechanisms introduced by asymmetric current injection are considered to explain this effect. The design scheme opens perspectives to obtain actual polarization control in VCSEL

Estimating the number needed to treat from continuous outcomes in randomised controlled trials: methodological challenges and worked example using data from the UK Back Pain Exercise and Manipulation (BEAM) trial

Background Reporting numbers needed to treat (NNT) improves interpretability of trial results. It is unusual that continuous outcomes are converted to numbers of individual responders to treatment (i.e., those who reach a particular threshold of change); and deteriorations prevented are only rarely considered. We consider how numbers needed to treat can be derived from continuous outcomes; illustrated with a worked example showing the methods and challenges. Methods We used data from the UK BEAM trial (n = 1, 334) of physical treatments for back pain; originally reported as showing, at best, small to moderate benefits. Participants were randomised to receive 'best care' in general practice, the comparator treatment, or one of three manual and/or exercise treatments: 'best care' plus manipulation, exercise, or manipulation followed by exercise. We used established consensus thresholds for improvement in Roland-Morris disability questionnaire scores at three and twelve months to derive NNTs for improvements and for benefits (improvements gained+deteriorations prevented). Results At three months, NNT estimates ranged from 5.1 (95% CI 3.4 to 10.7) to 9.0 (5.0 to 45.5) for exercise, 5.0 (3.4 to 9.8) to 5.4 (3.8 to 9.9) for manipulation, and 3.3 (2.5 to 4.9) to 4.8 (3.5 to 7.8) for manipulation followed by exercise. Corresponding between-group mean differences in the Roland-Morris disability questionnaire were 1.6 (0.8 to 2.3), 1.4 (0.6 to 2.1), and 1.9 (1.2 to 2.6) points. Conclusion In contrast to small mean differences originally reported, NNTs were small and could be attractive to clinicians, patients, and purchasers. NNTs can aid the interpretation of results of trials using continuous outcomes. Where possible, these should be reported alongside mean differences. Challenges remain in calculating NNTs for some continuous outcomes

A role for ColV plasmids in the evolution of pathogenic Escherichia coli ST58.

Escherichia coli ST58 has recently emerged as a globally disseminated uropathogen that often progresses to sepsis. Unlike most pandemic extra-intestinal pathogenic E. coli (ExPEC), which belong to pathogenic phylogroup B2, ST58 belongs to the environmental/commensal phylogroup B1. Here, we present a pan-genomic analysis of a global collection of 752 ST58 isolates from diverse sources. We identify a large ST58 sub-lineage characterized by near ubiquitous carriage of ColV plasmids, which carry genes encoding virulence factors, and by a distinct accessory genome including genes typical of the Yersiniabactin High Pathogenicity Island. This sub-lineage includes three-quarters of all ExPEC sequences in our study and has a broad host range, although poultry and porcine sources predominate. By contrast, strains isolated from cattle often lack ColV plasmids. Our data indicate that ColV plasmid acquisition contributed to the divergence of the major ST58 sub-lineage, and different sub-lineages inhabit poultry, swine and cattle

Phenology of the avian spring migratory passage in Europe and North America : Asymmetric advancement in time and increase in duration

Climate change has been shown to shift the seasonal timing (i.e. phenology) and distribution of species. The phenological effects of climate change on living organisms have often been tested using first occurrence dates, which may be uninformative and biased. More rarely investigated is how different phases of a phenological sequence (e.g. beginning, central tendency and end) or its duration have changed over time. This type of analysis requires continuous observation throughout the phenological event over multiple years, and such data sets are rare. In this study we examined the impact of temperature on long-term change of passage timing and duration of the spring migration period in birds, and which species' traits explain species-specific variation. Data used covered 195 species from 21 European and Canadian bird observatories from which systematic daily sampling protocols were available. Migration dates were negatively associated with early spring temperature and timings had in general advanced in 57 years. Short-distance migrants advanced the beginning of their migration more than long-distance migrants when corrected for phylogenic relatedness, but such a difference was not found in other phases of migration. The advancement of migration has generally been greater for the beginning and median phases of migration relative to the end, leading to extended spring migration seasons. Duration of the migration season increased with increasing temperature. Phenological changes have also been less noticeable in Canada even when corrected for rate of change in temperature. To visualize long-term changes in phenology, we constructed the first multi-species spring migration phenology indicator to describe general changes in median migration dates in the northern hemisphere. The indicator showed an average advancement of one week during five decades across the continents (period 1959-2015). The indicator is easy to update with new data and we therefore encourage future research to investigate whether the trend towards longer periods of occurrence or emergence in spring is also evident in other migratory populations. Such phenological changes may influence detectability in monitoring schemes, and may have broader implications on population and community dynamics.Peer reviewe

Low back pain in general practice: cost-effectiveness of a minimal psychosocial intervention versus usual care

An intervention that can prevent low back pain (LBP) becoming chronic, may not only prevent great discomfort for patients, but also save substantial costs for the society. Psychosocial factors appear to be of importance in the transition of acute to chronic LBP. The aim of this study was to compare the cost-effectiveness of an intervention aimed at psychosocial factors to usual care in patients with (sub)acute LBP. The study design was an economic evaluation alongside a cluster-randomized controlled trial, conducted from a societal perspective with a follow-up of 1 year. Sixty general practitioners in 41 general practices recruited 314 patients with non-specific LBP of less than 12 weeks’ duration. General practitioners in the minimal intervention strategy (MIS) group explored and discussed psychosocial prognostic factors. Usual care (UC) was not protocolized. Clinical outcomes were functional disability (Roland–Morris Disability Questionnaire), perceived recovery and health-related quality of life (EuroQol). Cost data consisted of direct and indirect costs and were measured by patient cost diaries and general practitioner registration forms. Complete cost data were available for 80% of the patients. Differences in clinical outcomes between both the groups were small and not statistically significant. Differences in cost data were in favor of MIS. However, the complete case analysis and the sensitivity analyses with imputed cost data were inconsistent with regard to the statistical significance of this difference in cost data. This study presents conflicting points of view regarding the cost-effectiveness of MIS. We conclude that (Dutch) general practitioners, as yet, should not replace their usual care by this new intervention

Controls on gut phosphatisation : the trilobites from the Weeks Formation Lagerstätte (Cambrian; Utah)

Despite being internal organs, digestive structures are frequently preserved in Cambrian Lagerstätten. However, the reasons for their fossilisation and their biological implications remain to be thoroughly explored. This is particularly true with arthropods--typically the most diverse fossilised organisms in Cambrian ecosystems--where digestive structures represent an as-yet underexploited alternative to appendage morphology for inferences on their biology. Here we describe the phosphatised digestive structures of three trilobite species from the Cambrian Weeks Formation Lagerstätte (Utah). Their exquisite, three-dimensional preservation reveals unique details on trilobite internal anatomy, such as the position of the mouth and the absence of a differentiated crop. In addition, the presence of paired pygidial organs of an unknown function is reported for the first time. This exceptional material enables exploration of the relationships between gut phosphatisation and the biology of organisms. Indeed, soft-tissue preservation is unusual in these fossils as it is restricted to the digestive structures, which indicates that the gut played a central role in its own phosphatisation. We hypothesize that the gut provided a microenvironment where special conditions could develop and harboured a source of phosphorus. The fact that gut phosphatization has almost exclusively been observed in arthropods could be explained by their uncommon ability to store ions (including phosphorous) in their digestive tissues. However, in some specimens from the Weeks Formation, the phosphatisation extends to the entire digestive system, suggesting that trilobites might have had some biological particularities not observed in modern arthropods. We speculate that one of them might have been an increased capacity for ion storage in the gut tissues, related to the moulting of their heavily-mineralised carapace

Shot Noise in Mesoscopic Conductors

Theoretical and experimental work concerned with dynamic fluctuations has developed into a very active and fascinating subfield of mesoscopic physics. We present a review of this development focusing on shot noise in small electric conductors. Shot noise is a consequence of the quantization of charge. It can be used to obtain information on a system which is not available through conductance measurements. In particular, shot noise experiments can determine the charge and statistics of the quasiparticles relevant for transport, and reveal information on the potential profile and internal energy scales of mesoscopic systems. Shot noise is generally more sensitive to the effects of electron-electron interactions than the average conductance. We present a discussion based on the conceptually transparent scattering approach and on the classical Langevin and Boltzmann-Langevin methods; in addition a discussion of results which cannot be obtained by these methods is provided. We conclude the review by pointing out a number of unsolved problems and an outlook on the likely future development of the field.Comment: 99 two-column pages; 38 .eps figures included. Submitted to Physics Reports. Many minor improvements; typos corrected; references added and update