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 $\beta''$ 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 $\beta''$ 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

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