2,356 research outputs found
Designed evolution of artificial metalloenzymes: protein catalysts made to order
Artificial metalloenzymes based on biotin–streptavidin technology, a fusion of chemistry and biology, illustrate how asymmetric catalysts can be improved and evolved using chemogenetic approaches
Gryphon: An Information Flow Based Approach to Message Brokering
Gryphon is a distributed computing paradigm for message brokering, which is
the transferring of information in the form of streams of events from
information providers to information consumers. This extended abstract outlines
the major problems in message brokering and Gryphon's approach to solving them.Comment: Two page extended abstrac
Information geometry of asymptotically AdS black holes
We investigate thermodynamic geometries of two families of asymptotically
Anti-de Sitter black holes, i.e. the Reissner-Nordstr\"om Anti-de Sitter in
four dimensions and the BTZ black hole. It is found that the Anti-de Sitter
space renders the geometry nontrivial (c.f. the Reissner-Nordstr\"om black hole
in asymptotically flat background). The BTZ black hole's thermodynamic geometry
is trivial despite the fact that it is characterized by the (negative)
cosmological constant. As a matter of curiosity we compute thermodynamic
geometry of these black holes regarding the cosmological constant as a true
parameter but no physically significant results can be derived.Comment: Contribution to proceedings of ERE2008, 4 page
Chorioallantoic membrane assay as model for angiogenesis in tissue engineering : focus on stem cells
Tissue engineering aims to structurally and functionally regenerate damaged tissues, which requires the formation of new blood vessels that supply oxygen and nutrients by the process of angiogenesis. Stem cells are a promising tool in regenerative medicine due to their combined differentiation and paracrine angiogenic capacities. The study of their proangiogenic properties and associated potential for tissue regeneration requires complex in vivo models comprising all steps of the angiogenic process. The highly vascularized extraembryonic chorioallantoic membrane (CAM) of fertilized chicken eggs offers a simple, easy accessible, and cheap angiogenic screening tool compared to other animal models. Although the CAM assay was initially primarily performed for evaluation of tumor growth and metastasis, stem cell studies using this model are increasing. In this review, a detailed summary of angiogenic observations of different mesenchymal, cardiac, and endothelial stem cell types and derivatives in the CAM model is presented. Moreover, we focus on the variation in experimental setup, including the benefits and limitations of in ovo and ex ovo protocols, diverse biological and synthetic scaffolds, imaging techniques, and outcome measures of neovascularization. Finally, advantages and disadvantages of the CAM assay as a model for angiogenesis in tissue engineering in comparison with alternative in vivo animal models are described
Walls, Borders, Boundaries
Walls are built and then fall, borders are fortified and then shift, boundaries are demarcated and then transgressed. And then they are constructed all over again. As (post)moderns living in an age of globalization, we
weary of our seemingly old-fashioned political and market-oriented boundaries: walls and fences are a nuisance to build and maintain, they invite vandalism and intrusion (rather than guarantee privacy or protection), and public surveys often reveal disapproval of national boundaries for moral, aesthetic, and economic reasons. Indeed, recently erected walls and borders intended to sever communities or fortify political and economic boundaries between neighboring countries rarely solve the underlying political problems; more often they result in increased criminal activity, violence, and alienation
In vitro evaluation of a prodrug approach for Gly-D-P18, a host defence peptide and novel anticancer agent
Hybrid Procedure in Neonatal Critical Aortic Stenosis and Borderline Left Heart: Buying Time for Left Heart Growth
Quantifying the rise and fall of scientific fields
Science advances by pushing the boundaries of the adjacent possible. While
the global scientific enterprise grows at an exponential pace, at the
mesoscopic level the exploration and exploitation of research ideas is
reflected through the rise and fall of research fields. The empirical
literature has largely studied such dynamics on a case-by-case basis, with a
focus on explaining how and why communities of knowledge production evolve.
Although fields rise and fall on different temporal and population scales, they
are generally argued to pass through a common set of evolutionary stages. To
understand the social processes that drive these stages beyond case studies, we
need a way to quantify and compare different fields on the same terms. In this
paper we develop techniques for identifying scale-invariant patterns in the
evolution of scientific fields, and demonstrate their usefulness using 1.5
million preprints from the arXiv repository covering 175 research fields
spanning Physics, Mathematics, Computer Science, Quantitative Biology and
Quantitative Finance. We show that fields consistently follows a rise and fall
pattern captured by a two parameters right-tailed Gumbel temporal distribution.
We introduce a field-specific rescaled time and explore the generic properties
shared by articles and authors at the creation, adoption, peak, and decay
evolutionary phases. We find that the early phase of a field is characterized
by the mixing of cognitively distant fields by small teams of interdisciplinary
authors, while late phases exhibit the role of specialized, large teams
building on the previous works in the field. This method provides foundations
to quantitatively explore the generic patterns underlying the evolution of
research fields in science, with general implications in innovation studies.Comment: 18 pages, 4 figures, 8 SI figure
Introspective Symmetries
The practical unification of context-free grammar and von Neumann machines has enabled telephony, and current trends suggest that the investigation of write-ahead logging will soon emerge. Here, we confirm the understanding of context-free grammar, which embodies the essential principles of software engineering [13]. In order to surmount this obstacle, we use distributed methodologies to demonstrate that IPv4 can be made permutable, ambimorphic, and random
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