How to construct constant-round zero-knowledge proof systems for NP

Constant-round zero-knowledge proof systems for every language in are presented, assuming the existence of a collection of claw-free functions. In particular, it follows that such proof systems exist assuming the intractability of either the Discrete Logarithm Problem or the Factoring Problem for Blum integers.     

Nucleosome conformational flexibility and implications for chromatin dynamics

The active role of chromatin in the regulation of gene activity seems to imply a conformational flexibility of the basic chromatin structural unit, the nucleosome. This review is devoted to our recent results pertaining to this subject, using an original approach based on the topology of single particles reconstituted on DNA minicircles, combined with their theoretical simulation. Three types of chromatin particles have been studied so far: a subnucleosome, that is, the (H3-H4)(2) histone tetramer-containing particle, now known as the tetrasome; the nucleosome; and the linker histone H5/H1-bearing nucleosome (the chromatosome). All the particles were found to exist in two to three conformational states, which differ by their topological and mechanical properties. Our approach unveiled the molecular mechanisms of nucleosome conformational dynamics and will help to understand its functional relevance. A most surprising conclusion of the work was perhaps that DNA overall flexibility increases considerably upon particle formation, which might indeed be a requirement of genome function.     

Spontaneous Generation of Magnetic Flux in Superconductors: Testing the Model

The Kibble-Zurek scenario of the generation of topological defects, applied to superconductors, predicts the spontaneous formation of magnetic flux during a rapid quench through T^c. The predicted amount of net flux scales as the 1/8 power of the cooling rate, and as the square root of the circumference of the sample. Our experimental data is broadly consistent with the first prediction, while the second one is yet to be tested. We describe a proposed experiment to test this prediction. In addition, we describe additional observations of spontaneous flux generated through a different mechanism. PACS numbers: 05.70.Ln, 74.40.+k, 11.27.+d.     

Supporting users in finding successful matches in reciprocal recommender systems

User Modeling and User-Adapted Interaction - Online platforms which assist users in finding a suitable match, such as online-dating and job recruiting environments, have become increasingly popular...