Current practice in the modelling of Age, Period and Cohort effects with panel data: a commentary

This comment assesses how age, period and cohort (APC) effects are modelled with panel data in the social sciences. It considers variations on a 2-level multilevel model which has been used to show apparent evidence for simultaneous APC effects. We show that such an interpretation is often misleading, and that the formulation and interpretation of these models requires a better understanding of APC effects and the exact collinearity present between them. This interpretation must draw on theory to justify the claims that are made. By comparing two papers which over-interpret such a model, and another that in our view interprets it appropriately, we outline best practice for researchers aiming to use panel datasets to find APC effects, with an understanding that it is impossible for any statistical model to find and separate all three effects

Dynamo action in the ABC flows using symmetries

This is an Accepted Manuscript of an article published by Taylor & Francis in Geophysical and Astrophysical Fluid Dynamics, Volume 108, Issue 1, 2014 available online 25 Sep 2013: http://wwww.tandfonline.com/10.1080/03091929.2013.832762.This paper concerns kinematic dynamo action by the 1:1:1 ABC flow, in the highly conducting limit of large magnetic Reynolds number Rm. The flow possesses 24 symmetries, with a symmetry group isomorphic to the group O24 of orientation preserving transformations of a cube. This can be exploited to break up the linear eigenvalue problem into five distinct symmetry classes, or irreducible representations, which we label I–V. The paper discusses how to reduce the scale of the numerical problem to a subset of Fourier modes for a magnetic field in each representation, which then may be solved independently to obtain distinct branches of eigenvalues and magnetic field eigenfunctions. Two numerical methods are employed: the first is to time step a magnetic field in a given symmetry class and obtain the growth rate and frequency by measuring the magnetic energy as a function of time. The second method involves a more direct determination of the eigenvalue using the eigenvalue solver ARPACK for sparse matrix systems, which employs an implicitly restarted Arnoldi method. The two methods are checked against each other, and compared for efficiency and reliability. Eigenvalue branches for each symmetry class are obtained for magnetic Reynolds numbers Rm up to 104 together with spectra and magnetic field visualisations. A sequence of branches emerges as Rm increases and the magnetic field structures in the different branches are discussed and compared. In a parallel development,results are presented for the corresponding fluid stability problem as a function of the Reynolds number Re.Leverhulme Trus

Restrictive antibiotic stewardship associated with reduced hospital mortality in gram-negative infection

Introduction: Antimicrobial stewardship has an important role in the control of Clostridium difficile infection (CDI) and antibiotic resistance. An important component of UK stewardship interventions is the restriction of broad-spectrum beta-lactam antibiotics and promotion of agents associated with a lower risk of CDI such as gentamicin. Whilst the introduction of restrictive antibiotic guidance has been associated with improvements in CDI and antimicrobial resistance evidence of the effect on outcome following severe infection is lacking. Methods: In 2008, Glasgow hospitals introduced a restrictive antibiotic guideline. A retrospective before/after study assessed outcome following gram-negative bacteraemia in the 2-year period around implementation. Results: Introduction of restrictive antibiotic guidelines was associated with a reduction in utilisation of ceftriaxone and co-amoxiclav and an increase in amoxicillin and gentamicin. 1593 episodes of bacteraemia were included in the study. The mortality over 1 year following gram-negative bacteraemia was lower in the period following guideline implementation (RR 0.852, P = 0.045). There was no evidence of a difference in secondary outcomes including ITU admission, length of stay, readmission, recurrence of bacteraemia and need for renal replacement therapy. There was a fall in CDI (RR 0.571, P = 0.014) and a reduction in bacterial resistance to ceftriaxone and co-amoxiclav but no evidence of an increase in gentamicin resistance after guideline implementation. Conclusion: Restrictive antibiotic guidelines were associated with a reduction in CDI and bacterial resistance but no evidence of adverse outcomes following gram-negative bacteraemia. There was a small reduction in one year mortality

The Joint European Compound Library:boosting precompetitive research

The Joint European Compound Library (JECL) is a new high-throughput screening collection aimed at driving precompetitive drug discovery and target validation. The JECL has been established with a core of over 321000 compounds from the proprietary collections of seven pharmaceutical companies and will expand to around 500000 compounds. Here, we analyse the physicochemical profile and chemical diversity of the core collection, showing that the collection is diverse and has a broad spectrum of predicted biological activity. We also describe a model for sharing compound information from multiple proprietary collections, enabling diversity and quality analysis without disclosing structures. The JECL is available for screening at no cost to European academic laboratories and SMEs through the IMI European Lead Factory (http://www.europeanleadfactory.eu/)

Experimental Combat-Stress Model in Rats: Histological Examination of Effects of Amelogenesis-A Possible Measure of Diminished Vagal Tone Episodes

Developmental defects of enamel-stress histomarker rings (accentuated striae) may be a potential measure of diminished vagal tone in research on extreme stress such as exposure to combat. To develop an animal model of this measure, we examined the enamel of rat incisors which erupt continuously. We examined incisors from 15 stressed-colony rats and 7 control-rats for these histomarkers using the Visible Burrow System (VBS). VBS was developed to study combat stress in rats. No stress rings were found in any of the rat incisors examined. In contrast to humans, rats have likely evolved to prioritize incisor strength during combat stress. Studies of amelogenesis during combat stress in other rodents with continuously growing incisors are warranted. Laboratory animals such as rabbits or marmosets may be especially suitable, since they less frequently use their incisors for self defense