Synthesis and first characterization of N-alkyldiaminoresorcinols

We report the synthesis and first characterization of N-alkyldiaminoresorcinols (or 4,6-bis-dialkylaminobenzene-1,3-diols C₆H₂(NHR)₂(OH)₂) (10a, R = CH₂-2-Py; 10b, R = CH₂-3-Py; 10c, R = CH₂-4-Py) which result from one-pot stepwise reactions: (i) air-oxidation of diaminoresorcinol 3, (ii) transamination reaction leading to the corresponding functional 6π+6π quinonemonoimine zwitterions C₆H₂(NHR)₂(O)₂ (9a, R = CH₂-2-Py; 9b, R = CH₂-3-Py; 9c, R = CH₂-4-Py), (iii) reduction and re-aromatization in the presence of the corresponding primary amine bearing a pyridine moiety.     

Massively parallel mesh adaptation and linear system solution for multiphase flows

ABSTRACT

In this paper, a work performed to allow massively parallel finite element flow computations is presented. It includes the development and optimisation of two particular features of a finite element multiphase computational fluid dynamics software, which are mesh generation and linear system solution, using anisotropic adaptation and multigrid preconditioning. Parallel performances on supercomputers are shown, where the largest generated mesh (on 65 536 Intel Xeon or 261 144 Power PC cores) had 33.4 billions of nodes, leading to a 100 billion of unknowns linear system solution. Final applications concern, between others, image-based flow simulations.     

Benzo[1,2‐d:4,5‐d′]bisimidazoles as a Convenient Platform Towards Dyes that are Capable of Excited‐State Intramolecular Proton Transfer and of Two‐Photon Absorption

New, strongly fluorescent benzo[1,2‐d:4,5‐d′]bisimidazoles have been prepared by the reaction of Bandrowski′s base with various aldehydes. Their structures were carefully designed to achieve efficient excited‐state intramolecular proton transfer and good two‐photon‐absorption (2PA) cross‐sections. Functional dyes that possessed both high fluorescence quantum yields and large Stokes shifts were prepared. A π‐expanded D‐A‐D derivative that possessed Φ_fl=50 % and σ₂=230 GM in the spectroscopic area of interest for biological imaging is an excellent candidate as a fluorescent probe. Thanks to the presence of two reactive amino groups, such compounds can be easily transformed into probes for bioconjugation. All of these benzo[1,2‐d:4,5‐d′]bisimidazoles were also strongly fluorescent in the solid state.     

Raman and FTIR spectroscopy applied to the conservation report of paleontological collections: identification of Raman and FTIR signatures of several iron sulfate species such as ferrinatrite and sideronatrite

Fossil materials that contain iron sulfide are well known for their instability when exposed to oxygen and humidity. This term however combines a great variety of materials showing different types of damages. Most of them consist of crystal efflorescence appearing on the surface and inside the matrix. In this work, a methodology was determined for the analysis of these damages by the use of Raman and infrared spectroscopy. The infrared and Raman signatures of a large set of iron sulfates were characterized. Specific attention was paid to sideronatrite and ferrinatrite, which are two associated sodium/iron(III) sulfates, and their infrared and Raman bands were partially assigned. Analysis performed on a selection of 11 damaged fossils showed a great variety of degradation products: besides one case that appeared to be a synthetic resin close to polyvinylchloride acetate, which was applied with a brush on the fossil surface, all degradation products belong to the sulfate group. However, many iron‐free sulfates, such as gypsum, halotrichite, epsomite, or pentahydrite were found, often in association with iron sulfates. In one case, despite the presence of iron in the matrix, no iron sulfate could be detected. This shows that the term ‘pyritic fossil’, commonly used by collection managers, is not appropriate as it oversimplifies the reality. A name such as ‘sulfide‐containing fossil’ would be more suitable. Copyright © 2012 John Wiley & Sons, Ltd.     

Toward n-channel organic thin film transistors based on a distyryl-bithiophene derivatives

Solution and solid-state properties of two new perfluoroalkyl end-substituted analogues of distyryl-bithiophene (CF₃-DS2T and diCF₃-DS2T) are presented. Vacuum deposited thin films were investigated by atomic force microscopy, X-ray diffraction, and implemented as active layers into organic thin film transistors. While physicochemical measurements in solution suggest a preferential hole injection and transport inside CF₃-DS2T and diCF₃-DS2T films, electrical measurements performed under high vacuum show that CF₃-DS2T behaves as n-type semiconductor while no charge transport was measured in diCF₃-DS2T. The results highlighted the importance of substituents on conjugated backbone and on the resulting fine ordering in solid state to control the charge transport.     

A synthetic heparan sulfate-mimetic peptide conjugated to a mini CD4 displays very high anti- HIV-1 activity independently of coreceptor usage

The HIV-1 envelope gp120, which features both the virus receptor (CD4) and coreceptor (CCR5/CXCR4) binding sites, offers multiple sites for therapeutic intervention. However, the latter becomes exposed, thus vulnerable to inhibition, only transiently when the virus has already bound cellular CD4. To pierce this defense mechanism, we engineered a series of heparan sulfate mimicking tridecapeptides and showed that one of them target the gp120 coreceptor binding site with μM affinity. Covalently linked to a CD4-mimetic that binds to gp120 and renders the coreceptor binding domain available to be targeted, the conjugated tridecapeptide now displays nanomolar affinity for its target. Using solubilized coreceptors captured on top of sensorchip we show that it inhibits gp120 binding to both CCR5 and CXCR4 and in peripheral blood mononuclear cells broadly inhibits HIV-1 replication with an IC(50) of 1 nM.     

Analysis of Path Integrals at Low Temperature: Box Formula,Occupation Time and Ergodic Approximation

We study the low temperature behavior of path integrals for a simple one-dimensional model. Starting from the Feynman–Kac formula, we derive a new functional representation of the density matrix at finite temperature, in terms of the occupation times for Brownian motions constrained to stay within boxes with finite sizes. From that representation, we infer a kind of ergodic approximation, which only involves double ordinary integrals. As shown by its applications to different potentials, the ergodic approximation turns out to be quite efficient, especially in the low-temperature regime where other usual approximations fail.     

A simple criterion for the m-cyclicity of the group of rational points on an elliptic curve defined over a finite field

We give a simple criterion for the cyclicity of the m-torsion subgroup of the group of rational points on an elliptic curve defined over a finite field of characteristic larger than 3 for m = 2, 3, 4, 6, 12. Received: 25 January 2005     

Constructions arborescentes d'immeubles

 We prove that, contrarily to the case of spherical and euclidean buidings, the set of (isomorphism classes of) locally finite 3-dimensional hyperbolic buildings is uncountable. The proof uses on one hand a classification of 3-dimensional Coxeter polytops satisfying some local properties of irreducibility and symmetry, and on another hand, an arborescent construction of buildings for splitable Coxeter systems. Received: 20 September 2001 / Revised version: 22 May 2002 / Published online: 2 December 2002 Mathematics Subject Classification (2000): 51E24, 51M10, 51F15