1,979 research outputs found
Granular Rheology in Zero Gravity
We present an experimental investigation on the rheological behavior of model
granular media made of nearly elastic spherical particles. The experiments are
performed in a cylindrical Couette geometry and the experimental device is
placed inside an airplane undergoing parabolic flights to cancel the effect of
gravity. The corresponding curves, shear stress versus shear rate, are
presented and a comparison with existing theories is proposed. The quadratic
dependence on the shear rate is clearly shown and the behavior as a function of
the solid volume fraction of particles exhibits a power law function. It is
shown that theoretical predictions overestimate the experiments. We observe, at
intermediate volume fractions, the formation of rings of particles regularly
spaced along the height of the cell. The differences observed between
experimental results and theoretical predictions are discussed and related to
the structures formed in the granular medium submitted to the external shear.Comment: 10 pages, 6 figures to be published in Journal of Physics : Condensed
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Curating student learning in a virtual gallery
BACKGROUND
The development of digital and creative literacies in biology is ongoing and recent technological advances have reduced the entry barrier for students and staff to engage in the creation of digital artefacts. We have developed a platform based on the Unity game engine that allows students to create virtual galleries in which they can curate 3D exhibitions of their learning which can be viewed on either a flat screen or a virtual reality headset. As part of the instructional activities, students are introduced to Object-Based Learning pedagogy by museum curators.
THE VIRTUAL GALLERY
Following a series of workshops to learn the basics of Unity, 500 first-year human biology students (in groups of 5) used templates to create their own virtual galleries, populating them with objects from all aspects of their studies from lectures to practicals and masterclasses. These galleries demonstrated the students’ mastery of the basics of working in and navigating virtual environments. This represents a unique way to collaboratively curate evidence of their learning across the semester and to communicate that understanding to a general audience. This is a new and novel approach to developing digital literacies and a portfolio of achievement in undergraduate science students
Helium abundance in the most metal-deficient blue compact galaxies: I Zw 18 and SBS 0335-052
We present high-quality spectroscopic observations of the two most-metal
deficient blue compact galaxies known, I Zw 18 and SBS 0335-052 to determine
the helium abundance. The underlying stellar absorption strongly influences the
observed intensities of He I emission lines in the brightest NW component of I
Zw 18, and hence this component should not be used for primordial He abundance
determination. The effect of underlying stellar absorption, though present, is
much smaller in the SE component. Assuming all systematic uncertainties are
negligible, the He mass fraction derived in this component is Y =
0.243+/-0.007. The high signal-to-noise ratio spectrum (> 100 in the continuum)
of SBS 0335-052 allows us to measure the helium mass fraction with a precision
better than 2% -- 5% in nine different regions along the slit. Assuming all
systematic uncertainties are negligible, the weighted mean He mass fraction in
SBS 0335-052 is Y = 0.2437+/-0.0014 when the three He I 4471, 5876 and 6678
emission lines are used, and is 0.2463+/-0.0015 when the He I 4471 emission
line is excluded. The weighted mean helium mass fraction in the two most
metal-deficient BCGs I Zw 18 and SBS 0335-052, Y=0.2462+/-0.0015, after
correction for the stellar He production results in a primordial He mass
fraction Yp = 0.2452+/-0.0015. The derived Yp leads to a baryon-to-photon ratio
of (4.7+/-1.0) 10^{-10}, consistent with the values derived from the primordial
D and 7Li abundances, and supporting the standard big bang nucleosynthesis
theory. For the most consistent set of primordial D, 4He, and 7Li abundances we
derive an equivalent number of light neutrino species 3.0+/-0.3 (95% C.L.).Comment: 28 pages, 10 figures. To appear in Ap
The case for launch of an international DNA-based birth cohort study
The global health agenda beyond 2015 will inevitably need to broaden its focus from mortality reduction to the social determinants of deaths, growing inequities among children and mothers, and ensuring the sustainability of the progress made against the infectious diseases. New research tools, including technologies that enable high-throughput genetic and ‘-omics’ research, could be deployed for better understanding of the aetiology of maternal and child health problems. The research needed to address those challenges will require conceptually different studies than those used in the past. It should be guided by stringent ethical frameworks related to the emerging collections of biological specimens and other health related information. We will aim to establish an international birth cohort
which should assist low- and middle-income countries to use emerging genomic research technologies to address the main problems in maternal and child health, which are still major contributors to the burden of disease globally
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Risk Owners & Risk Managers: Dealing with the complexity of feeding children with neurodevelopmental disability
This paper illustrates negotiations around risk between lay people and clinicians in relation to gastrostomy interventions for disabled children. These negotiations centre on differing interpretations of what constitutes risk in relation to the safety of oral feeding and a child's need for a feeding tube between parents, carers and clinical specialties. Drawing on Heyman's distinction between risk managers and risk owners, we show that not only do clinicians act as risk managers and parents and carers as risk owners, but that these distinctions often become blurred either because of the shifting dynamics of relations of care or because of the specificity of clinical practice. Parents become risk managers in relation to carers' roles, while clinicians become risk owners in relation to particular procedures which define their practice. This has implications for lay and expert interactions as well as professional accountability for those caring for children with complex medical conditions. Although not an empirical article, we draw on empirical work in the UK. We analyse both parental and professional constructions of risk based on observations of co-ordinating a clinical trial designed to evaluate the effectiveness of gastrostomy surgery. We also examine the diverse value systems used by different groups of professionals and lay carers which inform judgements about risk and feeding. We conclude by arguing that issues of risk in contemporary health care are not just examples of ‘manufactured uncertainty’ or of ‘negotiated power’ but constitute a dialectical relationship which breaks down the essentialist dualism of lay and professional constructions of risk
Epidemiology and aetiology of maternal bacterial and viral infections in low- and middle-income countries
There have been very few systematic reviews looking at maternal infections in the developing world, even though cutting maternal mortality by three quarters is United Nation’s Millennium
Development Goal number five. This systematic review has two aims. The first is to present the prevalence of parasitic infections in the developing world over the last 30 years and the second is to evaluate the quality and distribution of research in this field
Training highly qualified health research personnel: The Pain in Child Health consortium
Background and Objectives: Pain in Child Health (PICH) is
a transdisciplinary, international research training consortium. PICH has
been funded since 2002 as a Strategic Training Initiative in Health
Research of the Canadian Institutes of Health Research, with contributions
from other funding partners and the founding participation of five
Canadian universities. The goal of PICH has been to create a community
of scholars in pediatric pain to improve child health outcomes.
Methods: Quantitative analyses enumerated PICH faculty, trainees,
training activities and scientific outputs. Interviews with PICH stakeholders
were analyzed using qualitative methods capturing perceptions of the
program’s strengths, limitations, and opportunities for development and
sustainability.
Results : PICH has supported 218 trainee members from 2002 through
2013, from 14 countries and more than 16 disciplines. The faculty at the
end of 2013 comprised nine co-principal investigators, 14 Canadian
coinvestigators, and 28 Canadian and international collaborators. Trainee
members published 697 peer-reviewed journal articles on pediatric pain
through 2013, among other research dissemination activities including
conference presentations and webinars. Networks have been established
between new and established researchers across Canada and in 13 other
countries. Perceptions from stakeholders commended PICH for its positive
impact on the development of pediatric pain researchers. Stakeholders
emphasized skills and abilities gained through PICH, the perceived impact
of PICH training on this research field, and considerations for future training
in developing researchers in pediatric pain.
Conclusions: PICH has been successfully developing highly qualified
health research personnel within a Canadian and international community
of pediatric pain scholarship
Rheophysics of dense granular materials : Discrete simulation of plane shear flows
We study the steady plane shear flow of a dense assembly of frictional,
inelastic disks using discrete simulation and prescribing the pressure and the
shear rate. We show that, in the limit of rigid grains, the shear state is
determined by a single dimensionless number, called inertial number I, which
describes the ratio of inertial to pressure forces. Small values of I
correspond to the quasi-static regime of soil mechanics, while large values of
I correspond to the collisional regime of the kinetic theory. Those shear
states are homogeneous, and become intermittent in the quasi-static regime.
When I increases in the intermediate regime, we measure an approximately linear
decrease of the solid fraction from the maximum packing value, and an
approximately linear increase of the effective friction coefficient from the
static internal friction value. From those dilatancy and friction laws, we
deduce the constitutive law for dense granular flows, with a plastic Coulomb
term and a viscous Bagnold term. We also show that the relative velocity
fluctuations follow a scaling law as a function of I. The mechanical
characteristics of the grains (restitution, friction and elasticity) have a
very small influence in this intermediate regime. Then, we explain how the
friction law is related to the angular distribution of contact forces, and why
the local frictional forces have a small contribution to the macroscopic
friction. At the end, as an example of heterogeneous stress distribution, we
describe the shear localization when gravity is added.Comment: 24 pages, 19 figure
A Stealth Supersymmetry Sampler
The LHC has strongly constrained models of supersymmetry with traditional
missing energy signatures. We present a variety of models that realize the
concept of Stealth Supersymmetry, i.e. models with R-parity in which one or
more nearly-supersymmetric particles (a "stealth sector") lead to collider
signatures with only a small amount of missing energy. The simplest realization
involves low-scale supersymmetry breaking, with an R-odd particle decaying to
its superpartner and a soft gravitino. We clarify the stealth mechanism and its
differences from compressed supersymmetry and explain the requirements for
stealth models with high-scale supersymmetry breaking, in which the soft
invisible particle is not a gravitino. We also discuss new and distinctive
classes of stealth models that couple through a baryon portal or Z' gauge
interactions. Finally, we present updated limits on stealth supersymmetry in
light of current LHC searches.Comment: 45 pages, 16 figure
Willingness to participate in future HIV prevention studies among gay and bisexual men in Scotland, UK: a challenge for intervention trials
This article examines willingness to participate in future HIV prevention research among gay and bisexual men in Scotland, UK. Anonymous, self-complete questionnaires and Orasure Gäó oral fluid samples were collected in commercial gay venues. 1,320 men were eligible for inclusion. 78.2% reported willingness to participate in future HIV prevention research; 64.6% for an HIV vaccine, 57.4% for a behaviour change study, and 53.0% for a rectal microbicide. In multivariate analysis, for HIV vaccine research, greater age, minority ethnicity, and not providing an oral fluid sample were associated with lower willingness; heterosexual orientation and not providing an oral fluid sample were for microbicides; higher education and greater HIV treatment optimism were for behaviour change. STI testing remained associated with being more willing to participate in microbicide research and frequent gay scene use remained associated with being more willing to participate in behaviour change research. Having an STI in the past 12 months remained significantly associated with being willing to participate in all three study types. There were no associations between sexual risk behaviour and willingness. Although most men expressed willingness to participate in future research, recruitment of high-risk men, who have the potential to benefit most, is likely to be more challenging
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