6,784 research outputs found
[Grußwort zur Eröffnung der Tagung: 6th Frankfurt Scientific Symposium, GNARP und wie sie die Welt sieht: Aussichten transatlantischer Partnerschaft im digitalen Zeitalter: 5.10.2006 - 7.10.2006]
... This year's Scientific Symposium of the University Library is already number six in the row. It was again prepared and organised like some of the previous conferences together with our North American partners. This means that a continuous specialists’ discussion and a professional partnership have been already installed. All librarians and information managers are invited to learn more about the results of this coÂoperation every year when it's time for the next Symposium during Frankfurt Book Fair. ..
A Complexity Preserving Transformation from Jinja Bytecode to Rewrite Systems
We revisit known transformations from Jinja bytecode to rewrite systems from
the viewpoint of runtime complexity. Suitably generalising the constructions
proposed in the literature, we define an alternative representation of Jinja
bytecode (JBC) executions as "computation graphs" from which we obtain a novel
representation of JBC executions as "constrained rewrite systems". We prove
non-termination and complexity preservation of the transformation. We restrict
to well-formed JBC programs that only make use of non-recursive methods and
expect tree-shaped objects as input. Our approach allows for simplified
correctness proofs and provides a framework for the combination of the
computation graph method with standard techniques from static program analysis
like for example "reachability analysis".Comment: 36 page
The arrival of the frequent: how bias in genotype-phenotype maps can steer populations to local optima
Genotype-phenotype (GP) maps specify how the random mutations that change
genotypes generate variation by altering phenotypes, which, in turn, can
trigger selection. Many GP maps share the following general properties: 1) The
number of genotypes is much larger than the number of selectable
phenotypes; 2) Neutral exploration changes the variation that is accessible to
the population; 3) The distribution of phenotype frequencies ,
with the number of genotypes mapping onto phenotype , is highly
biased: the majority of genotypes map to only a small minority of the
phenotypes. Here we explore how these properties affect the evolutionary
dynamics of haploid Wright-Fisher models that are coupled to a simplified and
general random GP map or to a more complex RNA sequence to secondary structure
map. For both maps the probability of a mutation leading to a phenotype
scales to first order as , although for the RNA map there are further
correlations as well. By using mean-field theory, supported by computer
simulations, we show that the discovery time of a phenotype similarly
scales to first order as for a wide range of population sizes and
mutation rates in both the monomorphic and polymorphic regimes. These
differences in the rate at which variation arises can vary over many orders of
magnitude. Phenotypic variation with a larger is therefore be much more
likely to arise than variation with a small . We show, using the RNA
model, that frequent phenotypes (with larger ) can fix in a population
even when alternative, but less frequent, phenotypes with much higher fitness
are potentially accessible. In other words, if the fittest never `arrive' on
the timescales of evolutionary change, then they can't fix. We call this highly
non-ergodic effect the `arrival of the frequent'.Comment: full paper plus supplementary material
Arteriogenesis versus angiogenesis: similarities and differences
Cardiovascular diseases account for more than half of total mortality before the age of 75 in industrialized countries. To develop therapies promoting the compensatory growth of blood vessels could be superior to palliative surgical surgical interventions. Therefore, much effort has been put into investigating underlying mechanisms. Depending on the initial trigger, growth of blood vessels in adult organisms proceeds via two major processes, angiogenesis and arteriogenesis. While angiogenesis is induced by hypoxia and results in new capillaries, arteriogenesis is induced by physical forces, most importantly fluid shear stress. Consequently, chronically elevated fluid shear stress was found to be the strongest trigger under experimental conditions. Arteriogenesis describes the remodelling of pre-existing arterio-arteriolar anastomoses to completely developed and functional arteries. In both growth processes, enlargement of vascular wall structures was proposed to be covered by proliferation of existing wall cells. Recently, increasing evidence emerges, implicating a pivotal role for circulating cells, above all blood monocytes, in vascular growth processes. Since it has been shown that monocytes/macrophage release a cocktail of chemokines, growth factors and proteases involved in vascular growth, their contribution seems to be of a paracrine fashion. A similar role is currently discussed for various populations of bone-marrow derived stem cells and endothelial progenitors. In contrast, the initial hypothesis that these cells -after undergoing a (trans-)differentiation- contribute by a structural integration into the growing vessel wall, is increasingly challenged
Book Review: Body by Weimar: Athletes, Gender, and German Modernity (By Erik N. Jensen. New York, NY: Oxford University Press. 2010. S. 184)
For a long time, the history of sports has tended to limit its interest to
sport’s inherent structures and developments. It has failed, and often
continues to fail, to analyse sport in a broader context. In the last few
years, however, there have been efforts to examine the significance of sport
in relation to social, cultural and political developments. Jensen ties in
with these approaches, which, in the case of Weimar history, have started
examining boxing, football and other competitive sports in general to explore
the culture and society of Germany in the 1920s and early 1930s..
Stärkung der internationalen Zusammenarbeit. Internationales Kolloquium mit VertreterInnen kunstbibliothekarischer Vereinigungen
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