11,759 research outputs found
Read Operators and their Expressiveness in Process Algebras
We study two different ways to enhance PAFAS, a process algebra for modelling
asynchronous timed concurrent systems, with non-blocking reading actions. We
first add reading in the form of a read-action prefix operator. This operator
is very flexible, but its somewhat complex semantics requires two types of
transition relations. We also present a read-set prefix operator with a simpler
semantics, but with syntactic restrictions. We discuss the expressiveness of
read prefixes; in particular, we compare them to read-arcs in Petri nets and
justify the simple semantics of the second variant by showing that its
processes can be translated into processes of the first with timed-bisimilar
behaviour. It is still an open problem whether the first algebra is more
expressive than the second; we give a number of laws that are interesting in
their own right, and can help to find a backward translation.Comment: In Proceedings EXPRESS 2011, arXiv:1108.407
The area-angular momentum inequality for black holes in cosmological spacetimes
For a stable marginally outer trapped surface (MOTS) in an axially symmetric
spacetime with cosmological constant and with matter satisfying
the dominant energy condition, we prove that the area and the angular
momentum satisfy the inequality which is saturated precisely for the extreme
Kerr-deSitter family of metrics. This result entails a universal upper bound
for such MOTS, which is saturated for
one particular extreme configuration. Our result sharpens the inequality , [7,14] and we follow the overall strategy of its proof in the sense
that we estimate the area from below in terms of the energy corresponding to a
"mass functional", which is basically a suitably regularised harmonic map
. However, in the cosmological case
this mass functional acquires an additional potential term which itself depends
on the area. To estimate the corresponding energy in terms of the angular
momentum and the cosmological constant we use a subtle scaling argument, a
generalised "Carter-identity", and various techniques from variational
calculus, including the mountain pass theorem.Comment: 24p; minor corrections to v
Precursors and post-translational transport of proteins in the assembly of the mitochondrial inner membrane
Assembly of mitochondria
The majority of mitochondrial proteins are synthesized on cytoplasmic ribosomes and transferred to the mitochondria where they are assembled to supramolecular structures. The intracellular transfer of these proteins appears to occur by a post-translational mechanism, i.e., it involves extramitochondrial precursor forms which are translocated in a step independent from translation. The synthesis and transfer of individual proteins was investigated in vivo, or in vitro employing homologous and heterologous cell free systems for protein synthesis. Cytochrome c was initially made as the apoprotein. This precursor protein was converted to the holoprotein on uptake by mitochondria in reconstituted systems. Integrity of mitochondria was essential for the apo to holo conversion. In the case of the ADP/ATP carrier protein, an integral transmembrane protein of the inner mitochondrial membrane, the initial translation product had the same apparent molecular weight as the mature protein. It was found in soluble form in the post-ribosomal supernatant. Citrate synthase, a matrix protein, was synthesized as a precursor with an apparent molecular weight of 47 000. Transfer to the mitochondria was accompanied by cleavage to yield a molecular weight of 45 000. The significance of these results in relation to the mechanisms of intracellular transfer and of assembly of the individual proteins is discussed
Influence of weaning age (28 vs. 63 d) on quantitative and qualitative carcass traits of rabbits
Nowadays there is an increasing interest towards breeding systems, also for rabbit meat production, that are more mindful of animal welfare through an attenuation of the productive cycles intensity. These particular rearing techniques provide a delaying of the weaning age to reduce young rabbits stress. The present experiment is part of a wider research (Pinna et al., 2004; Marongiu et al., 2004) conducted in a sardinian farm in which rabbits are usually weaned at about 60 days of age. Surely this managerial choice could be considered rather questionable but from a scientific point of view could also represent the occasion to examine the productive performance of rabbits submitted to such a late weaning. The final part of the survey, regarding the carcass composition and the meat chemical-nutritional characteristics, was carried out through the comparison of two groups of rabbits weaned at 28 and at 63 days of age respectively
Changing Gilgit-Baltistan: perceptions of the recent history and the role of community activism
Changing Gilgit-Baltistan: Perceptions of the recent history and the role of community activis
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