245 research outputs found
How to achieve sustainable water ecosystems management connecting research, people and policy makers in Europe (AWARE). Deliverable D 1.2: The North Sea-3S* case Study (* 3S for Seine, Somme, Scheldt watersheds)
How to achieve sustainable water ecosystems management connecting research, people and policy makers in Europe (AWARE). Deliverable D 2.2 North Sea case study content and process design report
How to achieve sustainable water ecosystems management connecting research, people and policy makers in Europe (AWARE). Deliverable D 2.5: 3S-North Sea case study report: results of the local events, on-line survey and interviews
Mass Transfer by Stellar Wind
I review the process of mass transfer in a binary system through a stellar
wind, with an emphasis on systems containing a red giant. I show how wind
accretion in a binary system is different from the usually assumed Bondi-Hoyle
approximation, first as far as the flow's structure is concerned, but most
importantly, also for the mass accretion and specific angular momentum loss.
This has important implications on the evolution of the orbital parameters. I
also discuss the impact of wind accretion, on the chemical pollution and change
in spin of the accreting star. The last section deals with observations and
covers systems that most likely went through wind mass transfer: barium and
related stars, symbiotic stars and central stars of planetary nebulae (CSPN).
The most recent observations of cool CSPN progenitors of barium stars, as well
as of carbon-rich post-common envelope systems, are providing unique
constraints on the mass transfer processes.Comment: Chapter 7, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
Estimating the binary fraction of planetary nebulae central stars
During the past 20 years, the idea that non-spherical planetary nebulae (PN)
may need a binary or planetary interaction to be shaped was discussed by
various authors. It is now generally agreed that the varied morphologies of PN
cannot be fully explained solely by single star evolution. Observationally,
more binary central stars of planetary nebulae (CSPN) have been discovered,
opening new possibilities to understand the connections between binarity and
morphology. So far, \simeq 45 binary CSPN have been detected, most being close
systems detected via flux variability. To determine the PN binary fraction, one
needs a method to detect wider binaries. We present here recent results
obtained with the various techniques described, concentrating on binary
infrared excess observations aimed at detecting binaries of any separation.Comment: 2 pages, IAU 283: An Eye To The Future proceeding
Binary orbits as the driver of Ī³-ray emission and mass ejection in classical novae
Classical novae are the most common astrophysical thermonuclear explosions, occurring on the surfaces of white dwarf stars accreting gas from companions in binary star systems. Novae typically expel ļæ½10,000 solar masses of material at velocities exceeding 1,000 km/s. However, the mechanism of mass ejection in novae is poorly understood, and could be dominated by the impulsive flash of the thermonuclear runaway, prolonged optically thick winds, or binary interaction with the nova envelope. Classical novae are now routinely detected in GeV gamma-rays, suggesting that relativistic particles are accelerated by strong shocks in nova ejecta. Here we present high-resolution imaging of the gamma-ray-emitting nova V959 Mon at radio wavelengths, showing that its ejecta were shaped by binary motion: some gas was expelled rapidly along the poles as a wind from the white dwarf, while denser material drifted out along the equatorial plane, propelled by orbital motion. At the interface between the equatorial and polar regions, we observe synchrotron emission indicative of shocks and relativistic particle acceleration, thereby pinpointing the location of gamma-ray production. Binary shaping of the nova ejecta and associated internal shocks are expected to be widespread among novae, explaining why many novae are gamma-ray emitters
Evaluation of the impact of a school gardening intervention on children's fruit and vegetable intake: a randomised controlled trial.
Background: Current academic literature suggests that school gardening programmes can provide an interactive environment with the potential to change childrenās fruit and vegetable intake. This is the first cluster randomised controlled trial (RCT) designed to evaluate whether a school gardening programme can have an effect on childrenās fruit and vegetable intake.
Methods: The trial included children from 23 schools; these schools were randomised into two groups, one to receive the Royal Horticultural Society (RHS)-led intervention and the other to receive the less involved Teacher-led intervention. A 24-hour food diary (CADET) was used to collect baseline and follow-up dietary intake 18 months apart. Questionnaires were also administered to evaluate the intervention implementation.
Results: A total of 641 children completed the trial with a mean age of 8.1 years (95% CI: 8.0, 8.4). The unadjusted results from multilevel regression analysis revealed that for combined daily fruit and vegetable intake the Teacher-led group had a higher daily mean change of 8 g (95% CI: ā19, 36) compared to the RHS-led group -32 g (95% CI: ā60, ā3). However, after adjusting for possible confounders this difference was not significant (intervention effect: ā40 g, 95% CI: ā88, 1; pā=ā0.06). The adjusted analysis of process measures identified that if schools improved their gardening score by 3 levels (a measure of school gardening involvement - the scale has 6 levels from 0 āno gardenā to 5 ācommunity involvementā), irrespective of group allocation, children had, on average, a daily increase of 81 g of fruit and vegetable intake (95% CI: 0, 163; pā=ā0.05) compared to schools that had no change in gardening score.
Conclusions: This study is the first cluster randomised controlled trial designed to evaluate a school gardening intervention. The results have found very little evidence to support the claims that school gardening alone can improve childrenās daily fruit and vegetable intake. However, when a gardening intervention is implemented at a high level within the school it may improve childrenās daily fruit and vegetable intake by a portion. Improving childrenās fruit and vegetable intake remains a challenging task
Hybridization of institutions
Extended version including all proofsModal logics are successfully used as specification logics for reactive systems. However, they are not expressive enough to refer to individual states and reason about the local behaviour of such systems. This limitation is overcome in hybrid logics which introduce special symbols for naming states in models. Actually, hybrid logics have recently regained interest, resulting in a number of new results and techniques as well as applications to software specification.
In this context, the first contribution of this paper is an attempt to āuniversalizeā the hybridization idea. Following the lines of [DS07], where a method to modalize arbitrary institutions is presented, the paper introduces a method to hybridize logics at the same institution-independent level. The method extends arbitrary institutions with Kripke semantics (for multi-modalities with arbitrary arities) and hybrid features. This paves the ground for a general result: any encoding (expressed as comorphism) from an arbitrary institution to first order logic (FOL) deter- mines a comorphism from its hybridization to FOL. This second contribution opens the possibility of effective tool support to specification languages based upon logics with hybrid features.FundaĆ§Ć£o para a CiĆŖncia e a Tecnologia (FCT
The chemical evolution of the solar neighbourhood for planet-hosting stars
Theoretical physical-chemical models for the formation of planetary systems
depend on data quality for the Sun's composition, that of stars in the solar
neighbourhood, and of the estimated "pristine" compositions for stellar
systems. The effective scatter and the observational uncertainties of elements
within a few hundred parsecs from the Sun, even for the most abundant metals
like carbon, oxygen and silicon, are still controversial. Here we analyse the
stellar production and the chemical evolution of key elements that underpin the
formation of rocky (C, O, Mg, Si) and gas/ice giant planets (C, N, O, S). We
calculate 198 galactic chemical evolution (GCE) models of the solar
neighbourhood to analyse the impact of different sets of stellar yields, of the
upper mass limit for massive stars contributing to GCE () and of
supernovae from massive-star progenitors which do not eject the bulk of the
iron-peak elements (faint supernovae). Even considering the GCE variation
produced via different sets of stellar yields, the observed dispersion of
elements reported for stars in the Milky Way disk is not reproduced. Among
others, the observed range of super-solar [Mg/Si] ratios, sub-solar [S/N], and
the dispersion of up to 0.5 dex for [S/Si] challenge our models. The impact of
varying depends on the adopted supernova yields. Thus,
observations do not provide a constraint on the M parametrization.
When including the impact of faint supernova models in GCE calculations,
elemental ratios vary by up to 0.1-0.2 dex in the Milky Way disk; this
modification better reproduces observations.Comment: 36 pages, 26 figures, 1 Table, 1 Appendix, Accepted for publication
in MNRA
The Blue Stragglers of the Old Open Cluster NGC 188
The old (7 Gyr) open cluster NGC 188 has yielded a wealth of astrophysical
insight into its rich blue straggler population. Specifically, the NGC 188 blue
stragglers are characterized by: A binary frequency of 80% for orbital periods
less than days;Typical orbital periods around 1000 days;Typical
secondary star masses of 0.5 M; At least some white dwarf companion
stars; Modestly rapid rotation; A bimodal radial spatial distribution;
Dynamical masses greater than standard stellar evolution masses (based on
short-period binaries); Under-luminosity for dynamical masses (short-period
binaries). Extensive -body modeling of NGC 188 with empirical initial
conditions reproduces the properties of the cluster, and in particular the
main-sequence solar-type binary population. The current models also reproduce
well the binary orbital properties of the blue stragglers, but fall well short
of producing the observed number of blue stragglers. This deficit could be
resolved by reducing the frequency of common-envelope evolution during Roche
lobe overflow. Both the observations and the -body models strongly indicate
that the long-period blue-straggler binaries - which dominate the NGC 188 blue
straggler population - are formed by asymptotic-giant (primarily) and red-giant
mass transfer onto main sequence stars. The models suggest that the few
non-velocity-variable blue stragglers formed from mergers or collisions.
Several remarkable short-period double-lined binaries point to the importance
of subsequent dynamical exchange encounters, and provide at least one example
of a likely collisional origin for a blue straggler.Comment: Chapter 3, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G.
Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe
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