A Polly Cracker system based on Satisfiability

This paper presents a public-key cryptosystem based on a subclass of the well-known satisfiability problem from propositional logic, namely the doubly-balanced 3-sat problem. We first describe the construction of an instance of our system starting from such a 3-sat formula. Then we discuss security issues: this is achieved on the one hand by exploring best methods to date for solving this particular problem, and on the other hand by studying (systems of multivariate) polynomial equation solving algorithms in this particular setting. The result of our investigations is that both types of method fail to break our instances. We end the paper with some complexity considerations and implementation results

The Carbon Assimilation Network in Escherichia coli Is Densely Connected and Largely Sign-Determined by Directions of Metabolic Fluxes

Gene regulatory networks consist of direct interactions but also include indirect interactions mediated by metabolites and signaling molecules. We describe how these indirect interactions can be derived from a model of the underlying biochemical reaction network, using weak time-scale assumptions in combination with sensitivity criteria from metabolic control analysis. We apply this approach to a model of the carbon assimilation network in Escherichia coli. Our results show that the derived gene regulatory network is densely connected, contrary to what is usually assumed. Moreover, the network is largely sign-determined, meaning that the signs of the indirect interactions are fixed by the flux directions of biochemical reactions, independently of specific parameter values and rate laws. An inversion of the fluxes following a change in growth conditions may affect the signs of the indirect interactions though. This leads to a feedback structure that is at the same time robust to changes in the kinetic properties of enzymes and that has the flexibility to accommodate radical changes in the environment

Plasmonic Control of Radiative Properties of Semiconductor Quantum Dots Coupled to Plasmonic Ring Cavities

In recent years, a lot of effort has been made to achieve controlled delivery of target particles to the hotspots of plasmonic nanoantennas, in order to probe and/or exploit the extremely large field enhancements produced by such structures. While in many cases such high fields are advantageous, there are instances where they should be avoided. In this work, we consider the implications of using the standard nanoantenna geometries when colloidal quantum dots are employed as target entities. We show that in this case, and for various reasons, dimer antennas are not the optimum choice. Plasmonic ring cavities are a better option despite low field enhancements, as they allow collective coupling of many quantum dots in a reproducible and predictable manner. In cases where larger field enhancements are required, or for larger quantum dots, nonconcentric ring-disk cavities can be employed instead

Viral nanomotors for packaging of dsDNA and dsRNA

While capsid proteins are assembled around single-stranded genomic DNA or RNA in rod-shaped viruses, the lengthy double-stranded genome of other viruses is packaged forcefully within a preformed protein shell. This entropically unfavourable DNA or RNA packaging is accomplished by an ATP-driven viral nanomotor, which is mainly composed of two components, the oligomerized channel and the packaging enzymes. This intriguing DNA or RNA packaging process has provoked interest among virologists, bacteriologists, biochemists, biophysicists, chemists, structural biologists and computational scientists alike, especially those interested in nanotechnology, nanomedicine, AAA+ family proteins, energy conversion, cell membrane transport, DNA or RNA replication and antiviral therapy. This review mainly focuses on the motors of double-stranded DNA viruses, but double-stranded RNA viral motors are also discussed due to interesting similarities. The novel and ingenious configuration of these nanomotors has inspired the development of biomimetics for nanodevices. Advances in structural and functional studies have increased our understanding of the molecular basis of biological movement to the point where we can begin thinking about possible applications of the viral DNA packaging motor in nanotechnology and medical applications

V. Les variations de la définition de l'Église chez Joh. Adam Möhler, particulièrement en ce qui concerne la relation entre l'Épiscopat et le Primat

Le Professeur J. R. Geiselmann, Doyen honoraire de la Faculté de Théologie catholique de Tübingen, analyse l'évolution des idées ecclésiologiques de J. A. Möhler, le plus grand théologien de l'Ecole catholique de Tübingue au XIXe s. Dans son cours de Droit canonique, Möhler juxtaposait deux notions d'Église : celle de société hiérarchisée, qui a dominé la théologie issue de la Contre-Réforme, et celle d'une communauté habitée et gouvernée par le Saint-Esprit. Dans L'Unité dans l'Église (1825), Möhler tente d'unifier ces deux représentations en faisant, de la structure organisée et juridique de l'Église, une expression, presque un produit, de l'Esprit d'amour qui forme les communautés aux différents échelons de l'Église locale, de l'Église métropolitaine et de l'Église universelle. Mais, dans la Symbolique, œuvre de sa pleine maturité, Möhler a opéré une synthèse beaucoup plus satisfaisante, en rattachant la structure, à la fois extérieure (visible) et spirituelle, de l'Église, à l'Incarnation. La primauté romaine, tenue et justifiée dans L'Unité, mais de façon insatisfaisante, est fondée, dans la Symbolique, à partir de l'institution d'un organisme ecclésial divino-humain, par Jésus-Christ. — Le Professeur Geiselmann utilise un certain nombre de documents inédits ou d'exemplaires originaux et annotés d'ouvrages qui lui permettent de critiquer plusieurs interprétations proposées avant lui.Geiselmann J. R., Steinhauser M. L. V. Les variations de la définition de l'Église chez Joh. Adam Möhler, particulièrement en ce qui concerne la relation entre l'Épiscopat et le Primat. In: Revue des Sciences Religieuses, tome 34, fascicule 2-4, 1960. L'ecclésiologie au XIXe siècle. pp. 141-195