728 research outputs found
Jump Rope Vortex in Liquid Metal Convection
Understanding large scale circulations (LSCs) in turbulent convective systems
is important for the study of stars, planets and in many industrial
applications. The canonical model of the LSC is quasi-planar with additional
horizontal sloshing and torsional modes [Brown E, Ahlers G (2009) J. Fluid
Mech. 638:383--400; Funfschilling D, Ahlers G (2004) Phys. Rev. Lett.
92(19):194502; Xi HD et al. (2009) Phys. Rev. Lett. 102(4):044503; Zhou Q et
al. (2009) J. Fluid Mech. 630:367--390]. Using liquid gallium as the working
fluid, we show via coupled laboratory-numerical experiments that the LSC in a
tank with aspect ratios greater than unity takes instead the form of a "jump
rope vortex", a strongly three-dimensional mode that periodically orbits around
the tank following a motion much like a jump rope on a playground. Further
experiments show that this jump rope flow also exists in more viscous fluids
such as water, albeit with a far smaller signal. Thus, this new jump rope mode
is an essential component of the turbulent convection that underlies our
observations of natural systems
RÀumliche Charakterisierung der hydraulischen LeitfÀhigkeit inalluvialen Schotter-Grundwasserleitern: EinMethodenvergleich
Zusammenfassung: FĂŒr die Modellierung des Stofftransportes im Grundwasser im MaĂstabsbereich von 10-100m sind detaillierte Kenntnisse der rĂ€umlichen Verteilung der hydraulischen LeitfĂ€higkeit unabdingbar. Bei einem Testfeld (10Ă20m) im alluvialen Schotter-Grundwasserleiter des voralpinen Thurtals (Schweiz) wurden vier unterschiedliche Methoden, wirksam auf verschiedenen Messskalen, angewandt, um diesen Parameter zu bestimmen. Der Vergleich der Ergebnisse zeigte, dass tiefenaufgelöste Slugtests verlĂ€ssliche Resultate fĂŒr den gefragten MaĂstab liefern. FĂŒr deren Auswertung ist ein plausibler Wert fĂŒr das AnisotropieverhĂ€ltnis der hydraulischen LeitfĂ€higkeit (K v/K h) nötig, welches aus einem entsprechend ausgewerteten Pumpversuch erfasst werden konnte. Die integralen Resultate von Pumpversuchen entsprechen tendenziell der oberen Grenze des natĂŒrlichen Spektrums der hydraulischen LeitfĂ€higkeit auf dem MaĂstab des Testfeldes. Flowmetermessungen sind zu empfehlen, wenn primĂ€r die relative Verteilung der hydraulischen LeitfĂ€higkeit interessiert, und Siebanalysen, wenn eine grobe AbschĂ€tzung der hydraulischen LeitfĂ€higkeit ausreich
Intergenerational resource sharing and mortality in a global perspective
Resource sharing has always been a central component of human sociality. Children require heavy investments in human capital; during working years, help is needed due to illness, disability, or bad luck. While hunter-gatherer elders assisted their descendants, more recently, elderly withdraw from work and require assistance as well. Willingness to share has been critically important for our past evolutionary success and our present daily lives. Here, we document a strong linear relationship between the public and private sharing generosity of a society and the average length of life of its members. Our findings from 34 countries on six continents suggest that survival is higher in societies that provide more support and care for one another. We suggest that this support reduces mortality by meeting urgent material needs, but also that sharing generosity may reflect the strength of social connectedness, which itself benefits human health and wellbeing and indirectly raises survival
Intergenerational Family Support and the Health and Well-Being of Older Adults in Sub-Saharan Africa:A systematic review
Many countries in sub Saharan Africa (SSA) have experienced an ageing of their population and this is projected to increase in the future. Family support is the main source of support for most older adults in SSA. Yet, relatively little is known about intergenerational family support provided to older adults in SSA and its effects on their health and well-being. This review adds to the scientific discussion synthesizing the health and well-being effects of family support provided to older adults in SSA. A systematic literature review was conducted to identify and analyze studies that focus on the provision of family support to older adults and its effects on their health and well-being. Eight (8) databases and other sources were searched for English Language publications between January 2000 and May 2020. Narrative synthesis was used to summarize the findings of the studies included. Out of 2426 records screened and 26 full-text publications retrieved and assessed, 8 studies were included in the review. The results suggest that receiving social and financial support from family as well as having frequent contact with family were positively related to better psychological well-being, self-rated health, and quality of life of older adults in SSA
The progression of the tobacco epidemic in India on the national and regional level, 1998-2016
BACKGROUND: Evidence regarding the progression of the tobacco epidemic remains fragmented in low- and middle-income countries. In India, most of the studies that examined tobacco consumption focused on one time point, on the country as a whole, and on men. Despite important gender differences in tobacco consumption, vast economic and cultural differences exist within India. We, therefore, assessed the progression of the tobacco epidemic in India on both the national and the regional level, by gender. METHODS: We use information on current tobacco use among Indians aged 15â49 from three rounds of the National Family Health Survey (NFHS) (1998-99, 2005-06, 2015-16) to estimate the age-standardized sex specific smoking and smokeless tobacco prevalence across India and its states. RESULTS: Age-standardized tobacco use prevalence in India increased between 1998-1999 and 2005-2006, and declined from 2005-2006 to 2015â2016, simultaneously for men and women. There are substantial spatial differences in the progression of the tobacco epidemic in India. While tobacco use declined in the majority of states, we observe high and increasing use for men in the north-eastern states of Manipur, Mizoram and Nagaland, and for women in the western state of Gujarat and north-eastern state of Manipur. We observed even more states with a recent increasing prevalence in either tobacco smoking or smokeless tobacco. Throughout, prevalence of tobacco use has been higher among men than women for all Indian regions, and remained higher than the national average in the north-eastern states. CONCLUSIONS: Our results suggest that India and the majority of its states experienced a âcompressed tobacco epidemicâ in which the prevalence of tobacco consumption increased and decreased simultaneously for women and men over a comparatively short period of time. Despite the overall progress India made in reducing tobacco use, further lowering tobacco consumption remains a public health priority, as the prevalence of smoking and/or smokeless tobacco use remains high in a number of states. We therefore conclude that tobacco regulations should be expanded with the aim of reducing the overall health burden associated with tobacco consumption across India. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12889-021-12261-y
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Semantic units: organizing knowledge graphs into semantically meaningful units of representation
Background
In todayâs landscape of data management, the importance of knowledge graphs and ontologies is escalating as critical mechanisms aligned with the FAIR Guiding Principlesâensuring data and metadata are Findable, Accessible, Interoperable, and Reusable. We discuss three challenges that may hinder the effective exploitation of the full potential of FAIR knowledge graphs.
Results
We introduce âsemantic unitsâ as a conceptual solution, although currently exemplified only in a limited prototype. Semantic units structure a knowledge graph into identifiable and semantically meaningful subgraphs by adding another layer of triples on top of the conventional data layer. Semantic units and their subgraphs are represented by their own resource that instantiates a corresponding semantic unit class. We distinguish statement and compound units as basic categories of semantic units. A statement unit is the smallest, independent proposition that is semantically meaningful for a human reader. Depending on the relation of its underlying proposition, it consists of one or more triples. Organizing a knowledge graph into statement units results in a partition of the graph, with each triple belonging to exactly one statement unit. A compound unit, on the other hand, is a semantically meaningful collection of statement and compound units that form larger subgraphs. Some semantic units organize the graph into different levels of representational granularity, others orthogonally into different types of granularity trees or different frames of reference, structuring and organizing the knowledge graph into partially overlapping, partially enclosed subgraphs, each of which can be referenced by its own resource.
Conclusions
Semantic units, applicable in RDF/OWL and labeled property graphs, offer support for making statements about statements and facilitate graph-alignment, subgraph-matching, knowledge graph profiling, and for management of access restrictions to sensitive data. Additionally, we argue that organizing the graph into semantic units promotes the differentiation of ontological and discursive information, and that it also supports the differentiation of multiple frames of reference within the graph
Oscillatory thermal-inertial flows in liquid metal rotating convection
We present the first detailed thermal and velocity field characterization of
convection in a rotating cylindrical tank of liquid gallium, which has
thermophysical properties similar to those of planetary core fluids. Our
laboratory experiments, and a closely associated direct numerical simulation,
are all carried out in the regime prior to the onset of steady convective
modes. This allows us to study the oscillatory convective modes, sidewall modes
and broadband turbulent flow that develop in liquid metals before the advent of
steady columnar modes. Our thermo-velocimetric measurements show that strongly
inertial, thermal wind flows develop, with velocities reaching those of
comparable non-rotating cases. Oscillatory bulk convection and wall modes
coexist across a wide range of our experiments, along with strong zonal flows
that peak in the Stewartson layer, but that extend deep into the fluid bulk in
the higher supercriticality cases. The flows contain significant time-mean
helicity that is anti-symmetric across the midplane, demonstrating that
oscillatory liquid metal convection contains the kinematic components to
sustain system-scale dynamo generation.Comment: 29 pages, 12 figure
Mortality convergence in the enlarged European Union:a systematic literature review
BACKGROUND: The high mortality rates in the European Union (EU) Member States that acceded in 2004 sparked political interest in mortality convergence. Whether mortality is converging in the EU remains unclear. We reviewed the literature on mortality convergence in the post-2004 EU territory as a whole. We also explored whether the study designs influenced the results and whether any determinants of mortality convergence had been empirically examined. METHODS: A systematic literature review was performed. Our search included scientific databases and the websites of international governmental institutions and European demographic research institutes. RESULTS: We uncovered 94 unique records and included seven studies that reported on 36 analyses. There was marked methodological heterogeneity, including in the convergence measures (beta and sigma convergence). All of the beta convergence analyses found narrowing mortality differentials, whereas most of the sigma convergence analyses found widening mortality differentials. The results are robust to the units of analysis and mortality and dispersion measures. Our results also suggest that there is a lack of evidence on the determinants of mortality convergence in the EU. CONCLUSIONS: There is general agreement that the EU regions and the Member States with high initial mortality rates improved the fastest, but this trend did not lead to overall mortality convergence in the EU. The harmonization of mortality convergence measures and research into determinants of mortality convergence are needed to support future EU cohesion policy. Policy-makers should consider supporting areas that have moderate but stagnant mortality rates, in addition to those with high mortality rates
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