Photoinduced morphism of gemini surfactant aggregates

The photochemical behaviour of an azobenzene chromophore inserted in a gemini surfactant imparts photocontrol to the resulting amphiphile assemblies, including the collapse, upon irradiation, of the multi lamellar vesicles formed in aqueous solution.     

Phosphonated Near‐Infrared Fluorophores for Biomedical Imaging of Bone

The conventional method for creating targeted contrast agents is to conjugate separate targeting and fluorophore domains. A new strategy is based on the incorporation of targeting moieties into the non‐delocalized structure of pentamethine and heptamethine indocyanines. Using the known affinity of phosphonates for bone minerals in a model system, two families of bifunctional molecules that target bone without requiring a traditional bisphosphonate are synthesized. With peak fluorescence emissions at approximately 700 or 800 nm, these molecules can be used for fluorescence‐assisted resection and exploration (FLARE) dual‐channel imaging. Longitudinal FLARE studies in mice demonstrate that phosphonated near‐infrared fluorophores remain stable in bone for over five weeks, and histological analysis confirms their incorporation into the bone matrix. Taken together, a new strategy for creating ultra‐compact, targeted near‐infrared fluorophores for various bioimaging applications is described.     

Limiter Biasing Experiments in TEXTOR-94

Particle collection by the ALT-II belt limiter in the TEXTOR-94 tokamak is exclusively limited to the parallel outflux because the scoop walls that are oriented parallel to the field lines obstruct the poloidal E×B mass flow. With normal B _tor direction (E×B towards the scoops), a threefold decrease of plenum pressure is measured during negative biasing, while with reversed B _tor (E×B away from the scoops), a 60% pressure increase is observed. This behaviour is exactly opposite to that observed in X-point divertors. A simple fluid model explains this apparent contradiction, and gives good quantitative agreement with measurements of the parallel Mach number in the SOL. The essential physics is governed by the Bohm-Chodura criterion.     

Carbon-13 nuclear magnetic resonance spectra of 1,2,3,4-tetrahydroquinazoline and some 3-benzyl derivatives

The concerted use of the ¹H/¹³C shift correlation with full ¹H/¹H decoupling and the modified COLOC sequence for long-range X/H correlation 2D nmr spectroscopy allows the total assignment of the ¹³C nmr resonances of 1,2,3,4-tetrahydroquinazoline and 3-benzyl-1,2,3,4-tetrahydroquinazoline. From these data, the ¹³C nmr chemical shifts of a series of 3-benzylsubstituted-1,2,3,4-tetrahydroquinazolines are deduced.     

Optical absorption of molybdenum thin films between 0.32 and 5.50 eV: Interpretation in terms of energy band transitions

We report, between 0.32 and 5.50 eV, the optical conductivity of polycrystalline thin films of molybdenum. The films have been deposited in ultra high vacuum and the measurements have been carried out in situ. We observe two maxima at 2.75 and 4.0 eV and two shoulders at 1.85 and 5.1 eV. The structure is understood in terms of interband transitions, the conductivity is compared to a joint density of states histogram deduced from Petroff and Viswanathan energy bands.     

Fluorescent nanoprobes dedicated to in vivo imaging: from preclinical validations to clinical translation

With the fast development, in the last ten years, of a large choice of set-ups dedicated to routine in vivo measurements in rodents, fluorescence imaging techniques are becoming essential tools in preclinical studies. Human clinical uses for diagnostic and image-guided surgery are also emerging. In comparison to low-molecular weight organic dyes, the use of fluorescent nanoprobes can improve both the signal sensitivity (better in vivo optical properties) and the fluorescence biodistribution (passive "nano" uptake in tumours for instance). A wide range of fluorescent nanoprobes have been designed and tested in preclinical studies for the last few years. They will be reviewed and discussed considering the obstacles that need to be overcome for their potential everyday use in clinics. The conjugation of fluorescence imaging with the benefits of nanotechnology should open the way to new medical applications in the near future.     

On the Pentomino Exclusion Problem

In this paper we are interested in the Pentomino Exclusion Problem due to Golomb: Find the minimum number of unit squares to be placed on a k\times n chessboard so as to exclude all pentominoes . Using an appropriate definition of density of a tiling, we obtain the asymptotic value of this number, and we establish this number for the k\times n chessboard when k≤ 4 . Received June 7, 1999, and in revised form March 1, 2001. Online publication August 9, 2001.     

Synthese D' α-hydroxy-aldehydes chiraux a partir du D-mannitol. Intermediaires pour la synthese de metabolites de l'acide arachidonique.

Enantiomerically pure α-hydroxy-aldehydes, key intermediates for the synthesis of arachidonic acid metabolites, are prepared from D-mannitol by nucleophilic opening of diastereoisomeric diepoxides.