19,817 research outputs found
Anelastic dynamo models with variable electrical conductivity: an application to gas giants
The observed surface dynamics of Jupiter and Saturn is dominated by a banded
system of zonal winds. Their depth remains unclear but they are thought to be
confined to the very outer envelopes where hydrogen remains molecular and the
electrical conductivity is small. The dynamo maintaining the dipole-dominated
magnetic fields of both gas giants likely operates in the deeper interior where
hydrogen assumes a metallic state. Here, we present numerical simulations that
attempt to model both the zonal winds and the interior dynamo action in an
integrated approach. Using the anelastic version of the MHD code MagIC, we
explore the effects of density stratification and radial electrical
conductivity variation. The electrical conductivity is mostly assumed to remain
constant in the thicker inner metallic region and it decays exponentially
towards the outer boundary throughout the molecular envelope. Our results show
that the combination of stronger density stratification and weaker conducting
outer layer is essential for reconciling dipole dominated dynamo action and a
fierce equatorial zonal jet. Previous simulations with homogeneous electrical
conductivity show that both are merely exclusive, with solutions either having
strong zonal winds and multipolar magnetic fields or weak zonal winds and
dipole-dominated magnetic fields. All jets tend to be geostrophic and therefore
reach right through the convective shell in our simulations. The particular
setup explored here allows a strong equatorial jet to remain confined to the
weaker conducting outer region where it does not interfere with the deeper
seated dynamo action. The flanking mid to high latitude jets, on the other
hand, have to remain faint to yield a strongly dipolar magnetic field. The
fiercer jets on Jupiter and Saturn only seem compatible with the observed
dipolar fields when they remain confined to a weaker conducting outer layer.Comment: 16 pages, 11 figures, 2 tables, submitted to PEP
Investigating Fatigue Performance on the Foamed Asphalt Specimens Generated Using Different Foam Properties
An evaluation of fatigue resistance for foamed asphalt mixture is very demanding since the binder is not continuously distributed on the aggregate surface and this mixtures contains water, the content of which dramatically affects the mechanical properties. This paper discusses the results of laboratory fatigue testingon the foamed asphalt mixtures in which the specimens are generated using three different foamed bitumen properties. Foamed bitumen as the binder was produced at three different foaming water content (FWC) at a temperature of 180oC using a 70/100 pen. The aggregates were mechanically mixed with foamed bitumen using a Hobart mixer. The resulting mixtures were then compacted using a gyratory compactor to generatespecimen with diameter of 100 mm. The specimens were fatigue tested at various stress levels at a temperature of 20oC following a curing period of 3 days at 40oC. Overall, fatigue performance of foamed asphalt can be identified based upon both stress and strain for mixtures produced at FWC 1%, 5%, and 10%
Filamentary fragmentation in a turbulent medium
We present the results of smoothed particle hydrodynamic simulations
investigating the evolution and fragmentation of filaments that are accreting
from a turbulent medium. We show that the presence of turbulence, and the
resulting inhomogeneities in the accretion flow, play a significant role in the
fragmentation process. Filaments which experience a weakly turbulent accretion
flow fragment in a two-tier hierarchical fashion, similar to the fragmentation
pattern seen in the Orion Integral Shaped Filament. Increasing the energy in
the turbulent velocity field results in more sub-structure within the
filaments, and one sees a shift from gravity-dominated fragmentation to
turbulence-dominated fragmentation. The sub-structure formed in the filaments
is elongated and roughly parallel to the longitudinal axis of the filament,
similar to the fibres seen in observations of Taurus, and suggests that the
fray and fragment scenario is a possible mechanism for the production of
fibres. We show that the formation of these fibre-like structures is linked to
the vorticity of the velocity field inside the filament and the filament's
accretion from an inhomogeneous medium. Moreover, we find that accretion is
able to drive and sustain roughly sonic levels of turbulence inside the
filaments, but is not able to prevent radial collapse once the filaments become
supercritical. However, the supercritical filaments which contain fibre-like
structures do not collapse radially, suggesting that fibrous filaments may not
necessarily become radially unstable once they reach the critical line-density.Comment: (Accepted for publication in MNRAS
Gluon and Ghost Dynamics from Lattice QCD
The two point gluon and ghost correlation functions and the three gluon
vertex are investigated, in the Landau gauge, using lattice simulations. For
the two point functions, we discuss the approach to the continuum limit looking
at the dependence on the lattice spacing and volume. The analytical structure
of the propagators is also investigated by computing the corresponding spectral
functions using an implementation of the Tikhonov regularisation to solve the
integral equation. For the three point function we report results when the
momentum of one of the gluon lines is set to zero and discuss its implications.Comment: Proceedings of Light Cone 2016, held in Lisbon, September 2016. Minor
changes in text. To appear in Few B Sy
The role of human resources on the economy: a study of the Balkan eu member states
In this paper we analyze the impact of the quality of human capital on the main economic indicators of South-Eastern Europe countries [SEE] at the NUTS 2 level. The subjects of this research are the human capital indicators of regional competitiveness. The quality of human capital depends largely on the age structure of the population and the quality of education. Those regions, which have the highest percentage of the working-age population and highly educated people, are able to achieve higher productivity and gain a competitive advantage over other regions. As main indicators of the quality of human capital we identified: population; persons aged 25-64 with tertiary education attainment; students in tertiary education and participation of adults aged 25-64 in education and training and human resources in science and technology. As main economic indicators, we identified: regional gross domestic product; employment and income of households. The aim of this paper is to determine whether there is a correlation between the indicators of the quality of human capital and economic indicators. As a main methodology we have used the correlation coefficient which shows interdependence of the analyzed indicators. As part of our analysis, we consider only EU member states that belong to the SEE countries: Slovenia, Croatia, Romania, Bulgaria and Greece. We conclude that in all countries there is a high multiple correlation coefficient between the indicators human resources in science and technology, number of students and employment.This paper is the result of the project No. 47007 III funded by the Ministry for Education, Science and Technological Development of Republic of Serbia
Living on a trophic subsidy: Algal quality drives an upper-shore herbivore’s consumption, preference and absorption but not growth rates
Indexación: Scopus.The transfer of seaweeds from subtidal bottoms to nearby intertidal rocky shores is a common but often overlooked phenomenon. Freshly detached seaweeds often represent critical trophic subsidies for herbivores living in upper-shore rocky intertidal areas, such as the marine snail Diloma nigerrima. This species relies on three species of seaweeds for food and displays feeding strategies to deal with a resource that is scarce and at times unpredictable. This study focused on the nutritional quality of freshly detached algae (Durvillaea antarctica, Lessonia spicata and Lessonia trabeculata) and measured Diloma nigerrima’s algal consumption rates in trials with and without choice. Absorption efficiency and growth of individual snails fed on each alga were also measured. Durvillaea antarctica had the highest nutritional quality and was the most consumed algae in both single and multiple-choice trials. Absorption efficiency was also highest for D. antarctica but growth rates of snails fed with this species were similar to those fed with the other algae. Combined, these results suggest that D. nigerrima has the ability to discriminate among seaweeds based on their nutritional quality. A potential increase in oxygen uptake when D. nigerrima is consuming the preferred food item is also proposed as a plausible hypothesis to explain the mismatch between snails’ preference and growth rate. These results aim to guide further studies on trophic subsidies and their role in coastal systems. © 2018 Quintanilla-Ahumada et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.https://journals.plos.org/plosone/article?id=10.1371/journal.pone.019612
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