521 research outputs found
Mechanics and force transmission in soft composites of rods in elastic gels
We report detailed theoretical investigations of the micro-mechanics and bulk
elastic properties of composites consisting of randomly distributed stiff
fibers embedded in an elastic matrix in two and three dimensions. Recent
experiments published in Physical Review Letters [102, 188303 (2009)] have
suggested that the inclusion of stiff microtubules in a softer, nearly
incompressible biopolymer matrix can lead to emergent compressibility. This can
be understood in terms of the enhancement of the compressibility of the
composite relative to its shear compliance as a result of the addition of stiff
rod-like inclusions. We show that the Poisson's ratio of such a composite
evolves with increasing rod density towards a particular value, or {\em fixed
point}, independent of the material properties of the matrix, so long as it has
a finite initial compressibility. This fixed point is in three
dimensions and in two dimensions. Our results suggest an important
role for stiff filaments such as microtubules and stress fibers in cell
mechanics. At the same time, our work has a wider elasticity context, with
potential applications to composite elastic media with a wide separation of
scales in stiffness of its constituents such as carbon nanotube-polymer
composites, which have been shown to have highly tunable mechanics.Comment: 10 pages, 8 figure
Emerging coordination mechanisms for multi-party IPR holders: linking research with standardization
The standards setting process relies to an increasing degree on successfully integrating up-to-date research and development results (R&D). The successful interaction between research and standards can provide important social benefits. But, to do so, a number of challenges need to be faced. One key and persistent challenge is to provide the conditions in which the cross-purposes of formal standards-setting bodies and intellectual property rights can equitably be accommodated. This means balancing the collective gains to be reaped from the elaboration of a common standard against the individual gains to be allocated to relevant individual rights-holders. This discussion paper focuses on approaches to the reemerging tension between intellectual-property-rights and standards. It points to the importance that successful approaches can have to improve the interaction the between research and standardization activities. It then goes on to consider the (re)emergence of two approaches that are indicative of the changing relationship between intellectual property rights and standards-setting bodies
Reconstructing a Simple Polytope from its Graph
Blind and Mani (1987) proved that the entire combinatorial structure (the
vertex-facet incidences) of a simple convex polytope is determined by its
abstract graph. Their proof is not constructive. Kalai (1988) found a short,
elegant, and algorithmic proof of that result. However, his algorithm has
always exponential running time. We show that the problem to reconstruct the
vertex-facet incidences of a simple polytope P from its graph can be formulated
as a combinatorial optimization problem that is strongly dual to the problem of
finding an abstract objective function on P (i.e., a shelling order of the
facets of the dual polytope of P). Thereby, we derive polynomial certificates
for both the vertex-facet incidences as well as for the abstract objective
functions in terms of the graph of P. The paper is a variation on joint work
with Michael Joswig and Friederike Koerner (2001).Comment: 14 page
Remarks on the classification of quasitoric manifolds up to equivariant homeomorphism
We give three sufficient criteria for two quasitoric manifolds (M,M') to be
(weakly) equivariantly homeomorphic.
We apply these criteria to count the weakly equivariant homeomorphism types
of quasitoric manifolds with a given cohomology ring.Comment: 11 page
Current Results of the EC-sponsored Catchment Modelling (CatchMod) Cluster
To support the Water Framework Directive implementation, much research has been commissioned at both national and European levels. CatchMod is a cluster of these projects, which is focusing on the development of computational catchment models and related tools. This paper presents an overview of the results of the CatchMod cluster to dat
Web-based multimodal graphs for visually impaired people
This paper describes the development and evaluation of Web-based multimodal graphs designed for visually impaired and blind people. The information in the graphs is conveyed to visually impaired people through haptic and audio channels. The motivation of this work is to address problems faced by visually impaired people in accessing graphical information on the Internet, particularly the common types of graphs for data visualization. In our work, line graphs, bar charts and pie charts are accessible through a force feedback device, the Logitech WingMan Force Feedback Mouse. Pre-recorded sound files are used to represent graph contents to users. In order to test the usability of the developed Web graphs, an evaluation was conducted with bar charts as the experimental platform. The results showed that the participants could successfully use the haptic and audio features to extract information from the Web graphs
Polytopality and Cartesian products of graphs
We study the question of polytopality of graphs: when is a given graph the
graph of a polytope? We first review the known necessary conditions for a graph
to be polytopal, and we provide several families of graphs which satisfy all
these conditions, but which nonetheless are not graphs of polytopes. Our main
contribution concerns the polytopality of Cartesian products of non-polytopal
graphs. On the one hand, we show that products of simple polytopes are the only
simple polytopes whose graph is a product. On the other hand, we provide a
general method to construct (non-simple) polytopal products whose factors are
not polytopal.Comment: 21 pages, 10 figure
The Influence of Strategic Patenting on Companies’ Patent Portfolios
This paper analyses whether strategic motives for patenting influence the characteristics of companies’ patent portfolios. We use the number of citations and oppositions to represent these characteristics. The investigation is based on survey and patent data from German companies. We find clear evidence that the companies’ patenting strategies explain the characteristics of their patent portfolios. First, companies using patents to protect their technological knowledge base receive a higher number of citations for their patents. Second, the motive of offensive – but not of defensive – blocking is related to a higher incidence of oppositions, whereas companies using patents as bartering chips in collaborations receive fewer oppositions to their patents
Cytotoxic activity of the sub-fraction 2125 from Vernonia scorpioides against Sarcoma 180 tumor cells in mice
The effect of the selected sub-fraction SF-2125 of the Vernonia scorpioides leaf extract on Sarcoma 180 (S180) ascitic tumor-bearing mice was investigated. The animals were treated with SF-2125 at a concentration of 5 mg/kg, administered intraperitoneally and intravenous during the development of the tumor. Treatment with SF-2125 5 mg/kg i.p. increased the lifespan of the animals, maintained their body and the ascitic tumor showed no development. Intravenous treatment did not reduce the tumor volume
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