On the normality of Rees algebras associated to totally unimodular matrices

Let A be an integral matrix with non negative entries and let K be a field. We give a sufficient condition for the normality of the monomial subring determined by the columns of A over the field K. One of the main results proves that if A is totally unimodular, then the Rees algebra of the monomial ideal over K defined by the columns of A is a normal domain.     

Local detection of entanglement

We construct an explicit model where it can be established if a two mode pure Gaussian system is entangled or not by acting only on one of the parts that constitute the system. Measuring the dispersion in momentum and the time evolution of the dispersion in position of one particle we can tell if entanglement is present as well as the degree of entanglement of the system.     

Characterization of a Disposable Electrochemical Biosensor Based on Putrescine Oxidase from Micrococcus rubens for the Determination of Putrescine

Putrescine oxidase (PUO) from Micrococcus rubens has been characterized, as a biocatalytic component for the development of electrochemical biosensors for the determination of putrescine. PUO was immobilized by cross‐linking on screen‐printed carbon electrodes (SPCEs) containing tetrathiafulvalene (TTF) as mediator (TTF/SPCEs). Isothermal titration calorimetry was used for investigation of kinetic properties of immobilized PUO. These PUO/TTF/SPCEs showed a linear response range from 10 a 74 µM, a capability of detection of 10.1±0.6 µM (n=4, α=β=0.05) and a precision of 6.7 %. Octopus and zucchini samples have been analysed using HPLC as a reference technique.     

Common Structural Elements in the Chromophore Binding Pocket of the Pfr State of Bathy Phytochromes

Phytochromes are bimodal photoreceptors which, upon light absorption by the tetrapyrrole chromophore, can be converted between a red‐absorbing state (Pr) and far‐red‐absorbing state (Pfr). In bacterial phytochromes, either Pr or Pfr are the thermally stable states, thereby constituting the classes of prototypical and bathy phytochromes, respectively. In this work, we have employed vibrational spectroscopies to elucidate the origin of the thermal stability of the Pfr states in bathy phytochromes. Here, we present the first detailed spectroscopic analysis of RpBphP6 (Rhodopseudomas palustris), which together with results obtained for Agp2 (Agrobacterium tumefaciens) and PaBphP (Pseudomonas aeruginosa) allows identifying common structural properties of the Pfr state of bathy phytochromes, which are (1) a homogenous chromophore structure, (2) the protonated ring C propionic side chain of the chromophore and (3) a retarded H/D exchange at the ring D nitrogen. These properties are related to the unique strength of the hydrogen bonding interactions between the ring D N‐H group with the side chain of the conserved Asp194 (PaBphP numbering). As revealed by a comparative analysis of homology models and available crystal structures of Pfr states, these interactions are strengthened by an Arg residue (Arg453) only in bathy but not in prototypical phytochromes.     

Effect of a hydrotrope on the viscoelastic properties of polymer-like micellar solutions

Low-viscosity micellar aqueous solutions of cetyltrimethylammonium bromide (CTAB) undergo a major change in the presence of the hydrotrope, potassium 1-phenylmethylsulfate (KPhMS), producing a highly viscoelastic entanglement network of polymer-like micelles. The system studied here shows typical shear banding flow behavior, which tends to disappear with increasing the hydrotrope-to-surfactant concentration ratio (C _H / C _S). The linear rheological response was analyzed with the model of Granek–Cates, whereas the nonlinear behavior was reproduced with the Bautista–Manero–Puig (BMP) model. Both models introduce a kinetic equation to account for the breaking and reformation of the micelles, and they predict the linear and nonlinear rheological data very well. This paper was presented at Annual European Rheology Conference (AERC) held in Hersonisos, Crete, Greece, April 27–29, 2006.     

Seamless MESO-NH modeling over very large grids

With the computing power it brings, the new generation of massively parallel computers allows one to perform a “seamless” modeling of weather on large grids, but it requires a large parallel computing capability for the models. Due to improvements in this direction in the meteorological model of the French research community MESO-NH, a computing performance of over 4 Teraflop/s was obtained with 130 000 cores on the machine of the European computer center PRACE. This is a first in France for a weather code. A high resolution simulation, covering the Atlantic and Europe, of the tropical cyclone Helene and its interaction with a planetary wave was also conducted, for which the excellent result gives hope to an improved weather forecasting in Europe.