Crystalline Amyloid Structures at Interfaces

Laying the groundwork : The interfacial self‐assembly properties of an amyloid peptide were used to develop crystalline nanostructures at air–water interfaces, which were studied by both AFM microscopy and X‐ray diffraction (see image). These structures generate regular arrays of functional groups and pave the way to controlled deposition of inorganic materials like that observed in biomineralization.

     

Überm-Bromphenole

Ohne ZusammenfassungM. Kohn und J. Wiesen, V. Mitteilung über Bromphenole.     

Sur les variétés de dimension 3 de type général dont le diviseur canonique est numériquement positif

Sans résumé     

A quadratic programming algorithm using conjugate search directions

A quadratic programming algorithm is presented, resembling Beale's 1955 quadratic programming algorithm and Wolfe's Reduced Gradient method. It uses conjugate search directions. The algorithm is conceived as being particularly appropriate for problems with a large Hessian matrix. An experimental computer program has been written to validate the concepts, and has performed adequately, although it has not been used on very large problems. An outline of the solution to the quadratic capacity-constrained transportation problem using the above method is also presented.While engaged in this research the author had a part-time post with the Manpower Services Commission.     

Flots filtrés et flots de processus a accroissements independants

Sans résumé     

Long term behavior of lithographically prepared in vitro neuronal networks

We measured the long term spontaneous electrical activity of neuronal networks with different sizes, grown on lithographically prepared substrates and recorded with multi-electrode-array technology. The time sequences of synchronized bursting events were used to characterize network dynamics. All networks exhibit scale-invariant Lévy distributions and long-range correlations. These observations suggest that different-size networks self-organize to adjust their activities over many time scales. As predictions of current models differ from our observations, this calls for revised models.     

Influence of mixing conditions on rheological behavior and electrical conductivity of polyamides filled with carbon black

The introduction of carbon black in a polyamide matrix allows one to obtain conductive materials because of the formation of a filler network. Resulting electrical properties depend, among others, on the processing conditions. In a first part, we investigate the influence of mixing conditions (rotor speed, temperature, mixing time) on electrical conductivity. Then, in a second part, we try to characterize the conducting network by rheological measurements and to establish relationships between rheological parameters and electrical properties. For that purpose, we propose to perform successive strain sweep experiments at constant frequency, from 0.5 to 100%, then from 100 to 0.5%, and finally, again, from 0.5 to 100%. Between two successive strain sweeps, we observe a drop in the moduli values that can be attributed to the breakdown of the carbon black network. A clear relationship is established between rheological and electrical properties of the compounds. Moreover, we propose a presentation of the rheological data that permits to rank the samples according to the strength of the carbon black network.