1,507 research outputs found
Ab initio Modelling of the Early Stages of Precipitation in Al-6000 Alloys
Age hardening induced by the formation of (semi)-coherent precipitate phases
is crucial for the processing and final properties of the widely used Al-6000
alloys. Early stages of precipitation are particularly important from the
fundamental and technological side, but are still far from being fully
understood. Here, an analysis of the energetics of nanometric precipitates of
the meta-stable phases is performed, identifying the bulk, elastic
strain and interface energies that contribute to the stability of a nucleating
cluster. Results show that needle-shape precipitates are unstable to growth
even at the smallest size formula unit, i.e. there is no energy
barrier to growth. The small differences between different compositions points
toward the need for the study of possible precipitate/matrix interface
reconstruction. A classical semi-quantitative nucleation theory approach
including elastic strain energy captures the trends in precipitate energy
versus size and composition. This validates the use of mesoscale models to
assess stability and interactions of precipitates. Studies of smaller 3d
clusters also show stability relative to the solid solution state, indicating
that the early stages of precipitation may be diffusion-limited. Overall, these
results demonstrate the important interplay among composition-dependent bulk,
interface, and elastic strain energies in determining nanoscale precipitate
stability and growth
Fragmentation of chloroplast coupling factor in dependence of bound nucleotides Preparation of a reconstitutionally active form of subunit δ
AbstractPrevious studies on the ability of CF1, fragments to reconstitute photophosphorylation in CF1,-depleted thylakoids have shown that the degree of reconstitution was correlated with the presence of subunit δ in the fragment. This was taken as evidence that subunit δ was necessary for plugging the active proton channel CF0 [(1986) Eur. J. Biochem. 160, 635–643]. We questioned whether or not δ alone had this ability. In order to obtain δ we investigated the role of bound nucleotides in the stability of CF1. Starting from ammonium sulfate-precipitated CF1, we found that a low content of bound ADP (1 mol ADP/mol CF1) seemed to stabilize the β—δ interaction, while loosening the interaction between α,β and γ. By elution from an anion-exchange column in the presence of the nonionic surfactant Mega 9 we obtained β3δ and CF1(—δ) (both containing one ADP) or, after washing with alcohol/glycerol mixtures, β (nucleotide-free) and CF1/CF1(—ϵ). On the other hand, with a further 2 ADP and 2 ATP bound to CF1, (after incubation with excess ATP) the α-β-γ interaction was stabilized in such a way that subunit δ alone could be isolated from the complex. Subunit δ, when isolated by this procedure and added back to CF1-depleted thylakoids, reconstituted a high rate of photophosphorylation
Transport of Mars-Crossing Asteroids from the Quasi-Hilda Region
We employ set oriented methods in combination with graph partitioning algorithms to identify key dynamical regions in the Sun-Jupiter-particle three-body system. Transport rates from a region near the 3:2 Hilda resonance into the realm of orbits crossing Mars' orbit are computed. In contrast to common numerical approaches, our technique does not depend on single long term simulations of the underlying model. Thus, our statistical results are particularly reliable since they are not affected by a dynamical behavior which is almost nonergodic (i.e., dominated by strongly almost invariant sets)
Planning and implementing a nationwide football-based health-education programme
Communicable and non-communicable diseases place enormous social and economic burdens on developed and developing countries. Health education leading to changes in people's attitudes and behaviours remains the best approach for reducing the problem of communicable diseases while there is evidence that programmes providing regular physical exercise and advocating a controlled diet can reduce the prevalence of many non-communicable diseases. Hence, the delivery of health education and physical activity within a single coherent programme offers great potential for simultaneously addressing both health issues. Since 2006, FIFA has developed and tested a novel football-based health-education programme for children entitled ‘11 for Health’, which is aimed at increasing children's levels of physical activity while also delivering 11 simple health messages. When new interventions of this type are published in the scientific literature, it is often not possible to describe important background information about the project that could assist other researchers in developing and implementing similar programmes. This paper attempts to bridge this gap by describing the aims and objectives, organisation, planning, implementation and monitoring requirements needed to deliver FIFA's ‘11 for Health’ programme, first as a pilot project and subsequently as a nationwide project, through a tripartite arrangement between FIFA, the national Football Association and the Government Ministries in Mauritius
Schätze aus Vulkanen: Eine Zeitreise durch 300 Millionen Jahre Erdgeschichte
Wir müssen nicht glauben, daß alle Wunder der Natur in anderen Ländern und Weltteilen seien. Sie sind überall. Aber diejenigen, die uns umgeben, achten wir nicht, weil wir sie von Kindheit an und täglich sehen
‘11 for Health’, a football-based health education programme for children: a two-cohort study in Mauritius and Zimbabwe
The Role of the Kidney in the Elimination of Pancreatic Lipase and Amylase from Blood
Peer Reviewe
Analytical model of brittle destruction based on hypothesis of scale similarity
The size distribution of dust particles in nuclear fusion devices is close to
the power function. A function of this kind can be the result of brittle
destruction. From the similarity assumption it follows that the size
distribution obeys the power law with the exponent between -4 and -1. The model
of destruction has much in common with the fractal theory. The power exponent
can be expressed in terms of the fractal dimension. Reasonable assumptions on
the shape of fragments concretize the power exponent, and vice versa possible
destruction laws can be inferred on the basis of measured size distributions.Comment: 10 pages, 3 figure
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