2,035 research outputs found
Migration as a risk factor for school dropout amongst children made vulnerable by HIV/AIDS: a prospective study in eastern Zimbabwe.
Orphans and other children made vulnerable by HIV in sub-Saharan Africa are at increased risk of moving household and of dropping out of school. However, the relationship between child migration and school enrolment has not been established. Multivariable regression models and prospective data from a cohort of children in Manicaland, Zimbabwe, were used to investigate the effect of migration on school enrolment. Children who had moved household were at increased risk of dropping out of school after adjusting for orphan status, relationship to primary caregiver, and household wealth. Interventions are needed to ensure that children who migrate are re-enrolled in school
Sources of uncertainty in future projections of the carbon cycle
This is the final version of the article. Available from the publisher via the DOI in this record.The inclusion of carbon cycle processes within CMIP5 Earth System Models provides the opportunity to explore the relative importance of differences in scenario and climate model representation
to future land and ocean carbon fluxes. A two-way ANOVA approach was used to quantify the
variability owing to differences between scenarios and between climate models at different lead
times.
For global ocean carbon fluxes, the variance attributed to differences between Representative
Concentration Pathway scenarios exceeds the variance attributed to differences between climate
models by around 2025, completely dominating by 2100. This contrasts with global land carbon
fluxes, where the variance attributed to differences between climate models continues to dominate
beyond 2100. This suggests that modelled processes that determine ocean fluxes are currently
better constrained than those of land fluxes, thus we can be more confident in linking different
future socio-economic pathways to consequences of ocean carbon uptake than for land carbon
uptake.
The apparent agreement in atmosphere-ocean carbon fluxes, globally, masks strong climate
model differences at a regional level. The North Atlantic and Southern Ocean are key regions,
where differences in modelled processes represent an important source of variability in projected
regional fluxesMOHC authors were supported by the Joint DECC / Defra Met Office Hadley Centre Cli-
mate Programme (GA01101). SY was supported by the Hong Kong Polytechnic University grant
âBayesian Modelling for Quantifying Uncertainty in Climate Predictionsâ (1-ZV9Z). We acknowl-
edge use of R software package (R Core Team 2013). We acknowledge the World Climate Re-
search Programmeâs Working Group on Coupled Modelling, which is responsible for CMIP and
we thank the climate modelling groups for providing their GCM output (listed in Table 1). Support
of this dataset was provided by the Office of Science, U.S. Department of Energy
On The Power of Tree Projections: Structural Tractability of Enumerating CSP Solutions
The problem of deciding whether CSP instances admit solutions has been deeply
studied in the literature, and several structural tractability results have
been derived so far. However, constraint satisfaction comes in practice as a
computation problem where the focus is either on finding one solution, or on
enumerating all solutions, possibly projected to some given set of output
variables. The paper investigates the structural tractability of the problem of
enumerating (possibly projected) solutions, where tractability means here
computable with polynomial delay (WPD), since in general exponentially many
solutions may be computed. A general framework based on the notion of tree
projection of hypergraphs is considered, which generalizes all known
decomposition methods. Tractability results have been obtained both for classes
of structures where output variables are part of their specification, and for
classes of structures where computability WPD must be ensured for any possible
set of output variables. These results are shown to be tight, by exhibiting
dichotomies for classes of structures having bounded arity and where the tree
decomposition method is considered
Conceptions and expectations of research collaboration in the European social sciences: Research policies, institutional contexts and the autonomy of the scientific field
This paper investigates the interactions between policy drivers and academic practice in international research collaboration. It draws on the case of the Open Research Area (ORA), a funding scheme in the social sciences across four national research agencies, seeking to boost collaboration by supporting âintegratedâ projects. The paper discusses the schemeâs governance and its place within the European policy space before turning to awarded researchersâ perceptions of its originality and impact on their projectâs emergence and development. Drawing on Bourdieuâs field theory, we analyse the schemeâs capacity to challenge researchersâ habitual collaborative practice as well as the hierarchical foundations of the social science field. We relate the discourses of researchers, located in France, Germany, the Netherlands and the United Kingdom, to such structural dimensions of the academic profession as, disciplinary cultures, institutional environments and national performance management of research careers. The paper argues that the ORA introduces novel mechanisms of power sharing and answerability in social sciences research capable of unsettling the autonomy of the scientific field. This analysis offers a new perspective on the often unquestioned superiority of the model of international collaboration induced by schemes such as ORA
Is telomere length socially patterned? Evidence from the West of Scotland Twenty-07 study
Lower socioeconomic status (SES) is strongly associated with an increased risk of morbidity and premature mortality, but it is not known if the same is true for telomere length, a marker often used to assess biological ageing. The West of Scotland Twenty-07 Study was used to investigate this and consists of three cohorts aged approximately 35 (N = 775), 55 (N = 866) and 75 years (N = 544) at the time of telomere length measurement. Four sets of measurements of SES were investigated: those collected contemporaneously with telomere length assessment, educational markers, SES in childhood and SES over the preceding twenty years. We found mixed evidence for an association between SES and telomere length. In 35-year-olds, many of the education and childhood SES measures were associated with telomere length, i.e. those in poorer circumstances had shorter telomeres, as was intergenerational social mobility, but not accumulated disadvantage. A crude estimate showed that, at the same chronological age, social renters, for example, were nine years (biologically) older than home owners. No consistent associations were apparent in those aged 55 or 75. There is evidence of an association between SES and telomere length, but only in younger adults and most strongly using education and childhood SES measures. These results may reflect that childhood is a sensitive period for telomere attrition. The cohort differences are possibly the result of survival bias suppressing the SES-telomere association; cohort effects with regard different experiences of SES; or telomere possibly being a less effective marker of biological ageing at older ages
Optical detection of single non-absorbing molecules using the surface plasmon of a gold nanorod
Current optical detection schemes for single molecules require light
absorption, either to produce fluorescence or direct absorption signals. This
severely limits the range of molecules that can be detected, because most
molecules are purely refractive. Metal nanoparticles or dielectric resonators
detect non-absorbing molecules by a resonance shift in response to a local
perturbation of the refractive index, but neither has reached single-protein
sensitivity. The most sensitive plasmon sensors to date detect single molecules
only when the plasmon shift is amplified by a highly polarizable label or by a
localized precipitation reaction on the particle's surface. Without
amplification, the sensitivity only allows for the statistical detection of
single molecules. Here we demonstrate plasmonic detection of single molecules
in realtime, without the need for labeling or amplification. We monitor the
plasmon resonance of a single gold nanorod with a sensitive photothermal assay
and achieve a ~ 700-fold increase in sensitivity compared to state-of-the-art
plasmon sensors. We find that the sensitivity of the sensor is intrinsically
limited due to spectral diffusion of the SPR. We believe this is the first
optical technique that detects single molecules purely by their refractive
index, without any need for photon absorption by the molecule. The small size,
bio-compatibility and straightforward surface chemistry of gold nanorods may
open the way to the selective and local detection of purely refractive proteins
in live cells
Upper- and mid-mantle interaction between the Samoan plume and the Tonga-Kermadec slabs
Mantle plumes are thought to play a key role in transferring heat from the core\u2013mantle
boundary to the lithosphere, where it can significantly influence plate tectonics. On impinging
on the lithosphere at spreading ridges or in intra-plate settings, mantle plumes may generate
hotspots, large igneous provinces and hence considerable dynamic topography. However, the
active role of mantle plumes on subducting slabs remains poorly understood. Here we show
that the stagnation at 660 km and fastest trench retreat of the Tonga slab in Southwestern
Pacific are consistent with an interaction with the Samoan plume and the Hikurangi plateau.
Our findings are based on comparisons between 3D anisotropic tomography images and 3D
petrological-thermo-mechanical models, which self-consistently explain several unique
features of the Fiji\u2013Tonga region. We identify four possible slip systems of bridgmanite in the
lower mantle that reconcile the observed seismic anisotropy beneath the Tonga slab
(VSH4VSV) with thermo-mechanical calculations
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âFreeâ inhibin α subunit is expressed by bovine ovarian theca cells and its knockdown suppresses androgen production
Inhibins are ovarian dimeric glycoprotein hormones that suppress pituitary FSH production. They are synthesised by follicular granulosa cells as α plus ÎČA/ÎČB subunits (encoded by INHA, INHBA, INHBB, respectively). Inhibin concentrations are high in follicular fluid (FF) which is also abundant in âfreeâ α subunit, presumed to be of granulosal origin, but its role(s) remains obscure. Here, we report the unexpected finding that bovine theca cells show abundant INHA expression and âfreeâ inhibin α production. Thus, theca cells may contribute significantly to the inhibin α content of FF and peripheral blood. In vitro, knockdown of thecal INHA inhibited INSL3 and CYP17A1 expression and androgen production while INSL3 knockdown reduced INHA and inhibin α secretion. These findings suggest a positive role of thecal inhibin α on androgen production. However, exogenous inhibin α did not raise androgen production. We hypothesised that inhibin α may modulate the opposing effects of BMP and inhibin on androgen production. However, this was not supported experimentally. Furthermore, neither circulating nor intrafollicular androgen concentrations differed between control and inhibin α-immunized heifers, casting further doubt on thecal inhibin α subunit having a significant role in modulating androgen production. Role(s), if any, played by thecal inhibin α remain elusive
Thermal Properties of Graphene, Carbon Nanotubes and Nanostructured Carbon Materials
Recent years witnessed a rapid growth of interest of scientific and
engineering communities to thermal properties of materials. Carbon allotropes
and derivatives occupy a unique place in terms of their ability to conduct
heat. The room-temperature thermal conductivity of carbon materials span an
extraordinary large range - of over five orders of magnitude - from the lowest
in amorphous carbons to the highest in graphene and carbon nanotubes. I review
thermal and thermoelectric properties of carbon materials focusing on recent
results for graphene, carbon nanotubes and nanostructured carbon materials with
different degrees of disorder. A special attention is given to the unusual size
dependence of heat conduction in two-dimensional crystals and, specifically, in
graphene. I also describe prospects of applications of graphene and carbon
materials for thermal management of electronics.Comment: Review Paper; 37 manuscript pages; 4 figures and 2 boxe
Normal X-inactivation mosaicism in corneas of heterozygous FlnaDilp2/+ female mice--a model of human Filamin A (FLNA) diseases
<p>Abstract</p> <p>Background</p> <p>Some abnormalities of mouse corneal epithelial maintenance can be identified by the atypical mosaic patterns they produce in X-chromosome inactivation mosaics and chimeras. Human <it>FLNA</it>/+ females, heterozygous for X-linked, filamin A gene (<it>FLNA</it>) mutations, display a range of disorders and X-inactivation mosaicism is sometimes quantitatively unbalanced. <it>Flna</it><sup><it>Dilp2/+ </it></sup>mice, heterozygous for an X-linked filamin A (<it>Flna</it>) nonsense mutation have variable eye, skeletal and other abnormalities, but X-inactivation mosaicism has not been investigated. The aim of this study was to determine whether X-inactivation mosaicism in the corneal epithelia of <it>Flna</it><sup><it>Dilp2/+ </it></sup>mice was affected in any way that might predict abnormal corneal epithelial maintenance.</p> <p>Results</p> <p>X-chromosome inactivation mosaicism was studied in the corneal epithelium and a control tissue (liver) of <it>Flna</it><sup><it>Dilp2/+ </it></sup>and wild-type (WT) female X-inactivation mosaics, hemizygous for the X-linked, <it>LacZ </it>reporter H253 transgene, using ÎČ-galactosidase histochemical staining. The corneal epithelia of <it>Flna</it><sup><it>Dilp2/+ </it></sup>and WT X-inactivation mosaics showed similar radial, striped patterns, implying epithelial cell movement was not disrupted in <it>Flna</it><sup><it>Dilp2/+ </it></sup>corneas. Corrected stripe numbers declined with age overall (but not significantly for either genotype individually), consistent with previous reports suggesting an age-related reduction in stem cell function. Corrected stripe numbers were not reduced in <it>Flna</it><sup><it>Dilp2/+ </it></sup>compared with WT X-inactivation mosaics and mosaicism was not significantly more unbalanced in the corneal epithelia or livers of <it>Flna</it><sup><it>Dilp2/+ </it></sup>than wild-type <it>Flna<sup>+/+ </sup></it>X-inactivation mosaics.</p> <p>Conclusions</p> <p>Mosaic analysis identified no major effect of the mouse <it>Flna<sup>Dilp2 </sup></it>mutation on corneal epithelial maintenance or the balance of X-inactivation mosaicism in the corneal epithelium or liver.</p
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