322 research outputs found
Younger but sicker? : Cohort trends in disease accumulation among middle-aged and older adults in Scotland using health-linked data from the Scottish Longitudinal Study
This research was supported by the Economic and Social Research Council (ESRC) Centre for Population Change Connecting Generations research programme, grant number ES/W002116/1. This work was supported by the Academy of Medical Sciences, the Wellcome Trust, the Government Department of Business, Energy and Industrial Strategy, the British Heart Foundation Diabetes UK, and the Global Challenges Research Fund [Grant number SBF004\1093 awarded to Katherine Keenan]. The contribution from AM is funded by the National Institute for Health and Care Research (grant number NIHR202639).Background In the United Kingdom, rising prevalence of multimorbidity—the co-occurrence of two or more chronic conditions- is coinciding with stagnation in life expectancy. We investigate patterns of disease accumulation and how they vary by birth cohort, social and environmental inequalities in Scotland, a country which has long suffered from excess mortality and poorer health outcomes relative to its neighbours. Methods Using a dataset which links census data from 1991, 2001 and 2011 to disease registers and hospitalization data, we follow cohorts of adults aged 30–69 years for 18 years. We model physical and mental disease accumulation using linear mixed-effects models. Results Recent cohorts experience higher levels of chronic disease accumulation compared to their predecessors at the same ages. Moreover, in more recently born cohorts we observe socioeconomic status disparities emerging earlier in the life course, which widen over time and with every successive cohort. Patterns of chronic conditions are also changing, and the most common diseases suffered by later born cohorts are cancer, hypertension, asthma, drug and alcohol problems and depression. Conclusion We recommend policies which target prevention of chronic disease in working age adults, considering how and why certain conditions are becoming more prevalent across time and space.Peer reviewe
Channelized melt flow in downwelling mantle: Implications for 226Ra-210Pb disequilibria in arc magmas
We present the results of an analytical model of porous flow of viscous melt into a steadily dilating ‘‘channel’’ (defined as a cluster of smaller veins) in downwelling subarc mantle. The model predicts the pressure drop in the mantle wedge matrix surrounding the channel needed to drive melt flow as a function of position and time. Melt is sucked toward the dilatant region at a near-constant velocity (105 s1) until veins comprising the channel stop opening (t = t). Fluid elements that complete their journey within the time span t < t arrive at a channel. Our results make it possible to calculate the region of influence sampled by melt that surrounds the channel. This region is large compared to the model size of the channelized region driving flow. For a baseline dilation time of 1 year and channel half width of 2 m, melt can be sampled over an 80-m radius and has the opportunity to sample matrix material with potentially contrasting chemistry on geologically short timescales. Our mechanical results are consistent with a downgoing arc mantle wedge source region where melting and melt extraction by porous flow to a channel network are sufficiently rapid to preserve source-derived 238U-230Th-226Ra, and potentially also 226 Ra-210Pb, disequilibria, prior to magma ascent to the surface. Since this is the rate-determining step in the overall process, it allows the possibility that such short-lived disequilibria measured in arc rocks at the surface are derived from deep in the mantle wedge. Stresses due to partial melting do not appear capable of producing the desired sucking effect, while the order of magnitude rate of shear required to drive dilation of 107 s1 is much larger than values resulting from steady state subduction. We conclude that local deformation rates in excess of background plate tectonic rates are needed to ‘‘switch on’’ the dilatant channel network and to initiate the sucking effect
Delayed Capillary Breakup of Falling Viscous Jets
Thin jets of viscous fluid like honey falling from capillary nozzles can attain lengths exceeding 10 m before breaking up into droplets via the Rayleigh-Plateau (surface tension) instability. Using a combination of laboratory experiments and WKB analysis of the growth of shape perturbations on a jet being stretched by gravity, we determine how the jet's intact length lb depends on the flow rate Q, the viscosity η, and the surface tension coefficient γ. In the asymptotic limit of a high-viscosity jet, lb∼(gQ2η4/γ4)1/3, where g is the gravitational acceleration. The agreement between theory and experiment is good, except for very long jets.</p
Numerical and experimental investigations of three-dimensional container filling with Newtonian viscous fluids
This work employs numerical and experimental approaches to investigate three-dimensional container
filling with Newtonian viscous fluids. For this purpose, a computer code developed for simulating
three-dimensional free surface flows has been used. The CFD Freeflow3D code was specifically designed
to deal with unsteady three-dimensional flows possessing multiple moving free surfaces. An experimental
apparatus that allows the visualization of the various phenomena that can occur during the filling of
containers has been constructed and employed. Experiments on container filling were carried out by
varying the fluid velocity at the injection nozzle. This paper presents a computational study on container
filling with Newtonian viscous fluids and employs the experimental results to validate the software. The
experimental observations were compared with the predictions from the Freeflow3D code and good
agreement between the two sets of results is observed. Moreover, the code predictions showed that it
is capable of capturing the most relevant phenomena observed in the experiments.The Brazilian authors would like to acknowledge the financial support given by the funding agencies: CNPq - Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (Grant Nos. 302631/2010-0, 301408/2009-2, 472514/2011-3), FAPESP - Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (Grant No. 2011/13930-0) and CAPES Grant Nos. BEX 2844/10-9 and 226/09 (CAPES-FCT). This work is part of the activities developed within the CEPID-CeMEAI FAPESP project Grant No. 2013/07375 - 0 and also benefits from the early collaboration within the framework of the University of Sao Paulo (Brazil) and University of Porto (Portugal) research agreements. The Portuguese authors gratefully acknowledge funding from Fundacao para a Ciencia e Tecnologia (FCT) under the project PEst-C/CTM/LA0025/2013 (Strategic Project - LA 25-2013-2014), project PTDC/MAT/121185/2010 and FEDER, via FCT
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REFERENCE THETA PINCH REACTOR (RTPR): A STUDY OF A PULSED HIGH-BETA FUSION REACTOR BASED ON THE THETA PINCH.
Random field sampling for a simplified model of melt-blowing considering turbulent velocity fluctuations
In melt-blowing very thin liquid fiber jets are spun due to high-velocity air
streams. In literature there is a clear, unsolved discrepancy between the
measured and computed jet attenuation. In this paper we will verify numerically
that the turbulent velocity fluctuations causing a random aerodynamic drag on
the fiber jets -- that has been neglected so far -- are the crucial effect to
close this gap. For this purpose, we model the velocity fluctuations as vector
Gaussian random fields on top of a k-epsilon turbulence description and develop
an efficient sampling procedure. Taking advantage of the special covariance
structure the effort of the sampling is linear in the discretization and makes
the realization possible
The meandering instability of a viscous thread
A viscous thread falling from a nozzle onto a surface exhibits the famous
rope-coiling effect, in which the thread buckles to form loops. If the surface
is replaced by a belt moving with speed , the rotational symmetry of the
buckling instability is broken and a wealth of interesting states are observed
[See S. Chiu-Webster and J. R. Lister, J. Fluid Mech., {\bf 569}, 89 (2006)].
We experimentally studied this "fluid mechanical sewing machine" in a new, more
precise apparatus. As is reduced, the steady catenary thread bifurcates
into a meandering state in which the thread displacements are only transverse
to the motion of the belt. We measured the amplitude and frequency of
the meandering close to the bifurcation. For smaller , single-frequency
meandering bifurcates to a two-frequency "figure eight" state, which contains a
significant component and parallel as well as transverse
displacements. This eventually reverts to single-frequency coiling at still
smaller . More complex, highly hysteretic states with additional frequencies
are observed for larger nozzle heights. We propose to understand this zoology
in terms of the generic amplitude equations appropriate for resonant
interactions between two oscillatory modes with frequencies and
. The form of the amplitude equations captures both the axisymmetry of
the U=0 coiling state and the symmetry-breaking effects induced by the moving
belt.Comment: 12 pages, 9 figures, revised, resubmitted to Physical Review
Thermal convection with non-Newtonian plates
The coupling between plate motions and mantle convection is investigated using a fully dynamic numerical model consisting of a thin non-Newtonian layer which is dynamically coupled to a thick Newtonian viscous layer. The non-Newtonian layer has a simple power-law rheology characterized by power-law index n and stiffness constant Μ p. A systematic investigation of steady, single cell configurations demonstrates that under certain conditions ( n > 7 being one of them) the non-Newtonian layer behaves like a mobile tectonic plate. Time-dependent calculations with multicellular configurations show the ability of the plate-mantle coupling model to adjust the number of plates and their sizes in accordance with the flow in the Newtonian layer. These calculations show that the geometry and number of plates do not necessarily resemble the planform of convection below.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72550/1/j.1365-246X.1992.tb02109.x.pd
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