A New ESIPT Fluorescent Dye-Doped Silica Aerogel

Summary: A silyl-functionalized benzazole dye, fluorescent by excited state intramolecular proton transfer (ESIPT) mechanism, was synthesized by reacting 2-(2′-hydroxyphenyl)benzoxazole with 3-(triethoxysilyl)propyl isocyanate. The fluorescent silica gel was prepared by the addition of a solution of 2-propanol and the fluorescent dye after the gelation time. The monolithic aerogel was obtained via supercritical CO₂ drying of the fluorescent gel. The resulting aerogel is transparent in the visible light and fluorescent in the blue-green region under UV radiation.     

Rate-equation theory of sub-Poissonian laser light

Lasers essentially consist of single-mode optical cavities containing two-level atoms with a supply of energy called the pump and a sink of energy, perhaps an optical detector. The latter converts the light energy into a sequence of electrical pulses corresponding to photo-detection events. It was predicted in 1984 on the basis of Quantum Optics and verified experimentally shortly thereafter that when the pump is non-fluctuating the emitted light does not fluctuate much. Precisely, this means that the variance of the number of photo-detection events observed over a sufficiently long period of time is much smaller than the average number of events. Light having that property is said to be'sub-Poissonian'. The theory presented rests on the concept introduced by Einstein around 1905, asserting that matter may exchange energy with a wave at angular frequency only by multiples of . The optical field energy may only vary by integral multiples of as a result of matter quantization and conservation of energy. A number of important results relating to isolated optical cavities containing two-level atoms are first established on the basis of the laws of Statistical Mechanics. Next, the laser system with a pump and an absorber of radiation is treated. The expression of the photo-current spectral density found in that manner coincides with the Quantum Optics result. The concepts employed in this paper are intuitive and the algebra is elementary. The paper supplements a previous tutorial paper (J. Arnaud, Opt. Quantum. Electron., 27 1995) in establishing a connection between the theory of laser noise and Statistical Mechanics.     

Synthesis of novel C2-aryl pyrrolobenzodiazepines (PBDs) as potential antitumour agents

Three novel C2-aryl substituted pyrrolobenzodiazepines (PBDs) have been synthesised and evaluated in a number of cell lines revealing selective cytotoxicity at the sub-nanomolar level towards melanoma and ovarian cancer cell lines.     

Radiation force on multilayer media

It is shown that the force exerted by plane electromagnetic waves on multilayer media can be evaluated in terms of the changes in momentum flow that take place at the planes of discontinuity. The expression obtained is relevant to radiation pressure experiments.     

Opérateurs linéaires gaussiens

We extend operators from the Cameron-Martin space to Gaussian Lusinian locally convex space. We then are allowed to give sense to the Mehler formula for every such bounded operator. An application is made to Hilbert-Schmidt operators. Next we show that capacities asociated to second quantizations of operators are tight on compact sets, and this is a general result even if the underlying space is not a Banach space.

Le deuxième auteur a exposé ce travail au colloque d'Amersfoort, août 1991.     

Chiral trialkanolamine-based hemicryptophanes: synthesis and oxovanadium complex

[reaction: see text] A novel class of chiral hemicryptophane hosts has been synthesized in diastereoisomerically pure form, namely, M-(R,R,R)-1a/P-(S,S,S)-1a and M-(S,S,S)-1b/P-(R,R,R)-1b. The C3-symmetrical precursor 9 was prepared, using either (R)- or (S)-glycidyl nosylate, repectively, as the chiral pool reactant and subsequently cyclized (trimerized) in the presence of Sc(OTf)3. The four stereoisomers were fully characterized and displayed two pairs of mirror-image CD spectra, which were used to determine their absolute configuration. The formation of the oxovanadium(V) complex of hemicryptophane 1a is also reported.     

Synthesis of diphenylcarbazoles as cytotoxic DNA binding agents

We report the synthesis of a series of novel diphenylcarbazoles designed to interact with DNA. The compounds bearing two or three dimethylaminoalkyloxy side chains were found to bind much more tightly to DNA, preferentially at AT-rich sites, than the corresponding hydroxy compounds. The DNA binding compounds exhibit potent cytotoxic activity toward P388 leukemia cells. The 3,6-diphenylcarbazole thus represent an interesting scaffold to develop antitumor agents interacting with nucleic acids.     

Famille de schémas implicites uniformément contrôlables pour l'équation des ondes 1-D

We present a parameterized family of finite difference schemes for the exact controllability of the 1-D wave equation. These schemes differ from the usual centered ones by additional terms of order to $h^2$, where h denotes the discretization step in space. Using a discrete version of Ingham's inequality for nonharmonic Fourier series, the spectral properties and dispersion diagrams of the schemes, we determine the parameters leading to a uniform controllability property with respect to h and an optimal stability CFL condition. To cite this article: A. Münch, C. R. Acad. Sci. Paris, Ser. I 339 (2004).     

Upper bound for the size of quadratic Siegel disks

If is an irrational number, we let {p_n/q_n}_n0, be the approximants given by its continued fraction expansion. The Bruno series B() is defined as