3D printed ultrasound phantoms for clinical training

Ultrasound is a ubiquitous, portable structural imaging technique which is used to provide visual feedback for a range of diagnostic and surgical techniques. Training for these techniques demands a range of teaching models tailored for each application. Existing anatomical models are often overly simple or prohibitively expensive, causing difficulties in obtaining patient or procedure specific models. In this study we present ultrasonic rib phantoms for clinical teaching and training purposes, fabricated by three-dimensional (3D) printing technologies. Models were produced using freely available software and data, and their effectiveness as teaching phantoms evaluated using clinical ultrasound scans of the phantoms

IIA/IIB Supergravity and Ten-forms

We perform a careful investigation of which p-form fields can be introduced consistently with the supersymmetry algebra of IIA and/or IIB ten-dimensional supergravity. In particular the ten-forms, also known as "top-forms", require a careful analysis since in this case, as we will show, closure of the supersymmetry algebra at the linear level does not imply closure at the non-linear level. Consequently, some of the (IIA and IIB) ten-form potentials introduced in earlier work of some of us are discarded. At the same time we show that new ten-form potentials, consistent with the full non-linear supersymmetry algebra can be introduced. We give a superspace explanation of our work. All of our results are precisely in line with the predictions of the E(11) algebra.Comment: 17 page

Allometric Scaling of the Active Hematopoietic Stem Cell Pool across Mammals

BACKGROUND: Many biological processes are characterized by allometric relations of the type Y = Y (0) M(b) between an observable Y and body mass M, which pervade at multiple levels of organization. In what regards the hematopoietic stem cell pool, there is experimental evidence that the size of the hematopoietic stem cell pool is conserved in mammals. However, demands for blood cell formation vary across mammals and thus the size of the active stem cell compartment could vary across species. METHODOLOGY/PRINCIPLE FINDINGS: Here we investigate the allometric scaling of the hematopoietic system in a large group of mammalian species using reticulocyte counts as a marker of the active stem cell pool. Our model predicts that the total number of active stem cells, in an adult mammal, scales with body mass with the exponent ¾. CONCLUSION/SIGNIFICANCE: The scaling predicted here provides an intuitive justification of the Hayflick hypothesis and supports the current view of a small active stem cell pool supported by a large, quiescent reserve. The present scaling shows excellent agreement with the available (indirect) data for smaller mammals. The small size of the active stem cell pool enhances the role of stochastic effects in the overall dynamics of the hematopoietic system

Metabolomics dataset of PPAR-pan treated rat liver

This article contains mass spectrometry (MS) data investigating small molecule changes as an effect of a triple peroxisome proliferator-activated receptor (PPAR-pan) agonist GW625019 in the liver as described in the manuscript (Ament et al., 2016) [1]. Samples were measured using gas chromatography-mass spectrometry (GC–MS) for total fatty acid content, and liquid chromatography-mass spectrometry (LC–MS) to measure intact lipids, carnitines and selected aqueous metabolites and eicosanoids. Data files comprise of Excel (Microsoft, WA, USA) spreadsheets of identified metabolites and their area ratio values for total fatty acids, carnitines, aqueous metabolites, and eicosanoids where the intensity of the analytes were normalised to the intensity of the internal standard. In the case of open profiling intact lipid data, the Excel file contains area ratio values of retention time and mass to charge ratio pairs; again, the area ratio values were calculated by normalising to the intensity of the internal standard. It should be noted that several metabolic changes are potentially indirect (secondary, tertiary and ensuing changes)

Factors associated with study attrition in a pilot randomised controlled trial to explore the role of exercise-assisted reduction to stop (EARS) smoking in disadvantaged groups.

BACKGROUND: Study attrition has the potential to compromise a trial's internal and external validity. The aim of the present study was to identify factors associated with participant attrition in a pilot trial of the effectiveness of a novel behavioural support intervention focused on increasing physical activity to reduce smoking, to inform the methods to reduce attrition in a definitive trial. METHODS: Disadvantaged smokers who wanted to reduce but not quit were randomised (N = 99), of whom 61 (62 %) completed follow-up assessments at 16 weeks. Univariable logistic regression was conducted to determine the effects of intervention arm, method of recruitment, and participant characteristics (sociodemographic factors, and lifestyle, behavioural and attitudinal characteristics) on attrition, followed by multivariable logistic regression on those factors found to be related to attrition. RESULTS: Participants with low confidence to quit, and who were undertaking less than 150 mins of moderate and vigorous physical activity per week at baseline were less likely to complete the 16-week follow-up assessment. Exploratory analysis revealed that those who were lost to follow-up early in the trial (i.e., by 4 weeks), compared with those completing the study, were younger, had smoked for fewer years and had lower confidence to quit in the next 6 months. Participants who recorded a higher expired air carbon monoxide reading at baseline were more likely to drop out late in the study, as were those recruited via follow-up telephone calls. Multivariable analyses showed that only completing less than 150 mins of physical activity retained any confidence in predicting attrition in the presence of other variables. CONCLUSIONS: The findings indicate that those who take more effort to be recruited, are younger, are heavier smokers, have less confidence to quit, and are less physically active are more likely to withdraw or be lost to follow-up

Population Dynamics Constrain the Cooperative Evolution of Cross-Feeding

Cross-feeding is the exchange of nutrients among species of microbes. It has two potential evolutionary origins, one as an exchange of metabolic wastes or byproducts among species, the other as a form of cooperation known as reciprocal altruism. This paper explores the conditions favoring the origin of cooperative cross-feeding between two species. There is an extensive literature on the evolution of cooperation, and some of the requirements for the evolution of cooperative cross-feeding follow from this prior work–specifically the requirement that interactions be limited to small groups of individuals, such as colonies in a spatially structured environment. Evolution of cooperative cross-feeding by a species also requires that cross-feeding from the partner species already exists, so that the cooperating mutant will automatically be reciprocated for its actions. Beyond these considerations, some unintuitive dynamical constraints apply. In particular, the benefit of cooperative cross-feeding applies only in the range of intermediate cell densities. At low density, resource concentrations are too low to offset the cost of cooperation. At high density, resources shared by both species become limiting, and the two species become competitors. These considerations suggest that the evolution of cooperative cross-feeding in nature may be more challenging than for other types of cooperation. However, the principles identified here may enable the experimental evolution of cross-feeding, as born out by a recent study

What traits are carried on mobile genetic elements, and why?

Although similar to any other organism, prokaryotes can transfer genes vertically from mother cell to daughter cell, they can also exchange certain genes horizontally. Genes can move within and between genomes at fast rates because of mobile genetic elements (MGEs). Although mobile elements are fundamentally self-interested entities, and thus replicate for their own gain, they frequently carry genes beneficial for their hosts and/or the neighbours of their hosts. Many genes that are carried by mobile elements code for traits that are expressed outside of the cell. Such traits are involved in bacterial sociality, such as the production of public goods, which benefit a cell's neighbours, or the production of bacteriocins, which harm a cell's neighbours. In this study we review the patterns that are emerging in the types of genes carried by mobile elements, and discuss the evolutionary and ecological conditions under which mobile elements evolve to carry their peculiar mix of parasitic, beneficial and cooperative genes

An Exploratory Analysis of the Smoking and Physical Activity Outcomes From a Pilot Randomized Controlled Trial of an Exercise Assisted Reduction to Stop Smoking Intervention in Disadvantaged Groups.

INTRODUCTION: Economically disadvantaged smokers not intending to stop may benefit from interventions aimed at reducing their smoking. This study assessed the effects of a behavioral intervention promoting an increase in physical activity versus usual care in a pilot randomized controlled trial. METHODS: Disadvantaged smokers who wanted to reduce but not quit were randomized to either a counseling intervention of up to 12 weeks to support smoking reduction and increased physical activity (n = 49) or usual care (n = 50). Data at 16 weeks were collected for various smoking and physical activity outcomes. Primary analyses consisted of an intention to treat analysis based on complete case data. Secondary analyses explored the impact of handling missing data. RESULTS: Compared with controls, intervention smokers were more likely to initiate a quit attempt (36 vs. 10%; odds ratio 5.05, [95% CI: 1.10; 23.15]), and a greater proportion achieved at least 50% reduction in cigarettes smoked (63 vs. 32%; 4.21 [1.32; 13.39]). Postquit abstinence measured by exhaled carbon monoxide at 4-week follow-up showed promising differences between groups (23% vs. 6%; 4.91 [0.80; 30.24]). No benefit of intervention on physical activity was found. Secondary analyses suggested that the standard missing data assumption of "missing" being equivalent to "smoking" may be conservative resulting in a reduced intervention effect. CONCLUSIONS: A smoking reduction intervention for economically disadvantaged smokers which involved personal support to increase physical activity appears to be more effective than usual care in achieving reduction and may promote cessation. The effect does not appear to be influenced by an increase in physical activity