Data storage in optical fibers and reconstruction by use of low-coherence spectral interferometry

We demonstrate optical data storage in optical fibers and reconstruction by use of low-coherence spectral interferometry. The information was stored by means of writing fiber Bragg gratings with different central wavelengths at different locations of the fiber. We need only a single short pulse is needed to read all the stored data. The maximum theoretical reconstruction rate that can be obtained with our technique is 10 Tbits/s. Our storage technique can be useful for identifying users in optical communication networks.     

Dephasing times in closed quantum dots

Dephasing of one-particle states in closed quantum dots is analyzed within the framework of random matrix theory and the master equation. The combination of this analysis with recent experiments on the magnetoconductance allows, for the first time, the evaluation of the dephasing times of closed quantum dots. These dephasing times turn out to be dependent on the mean level spacing and significantly enhanced as compared with the case of open dots. Moreover, the experimental data available are consistent with the prediction that the dephasing of one-particle states in finite closed systems disappears at low enough energies and temperatures.     

Syntheses of 2,4‐diaryl‐2,3‐dihydro‐1,5‐benzothiazepines

The condensation of α,β‐unsaturated ketones with substituted o‐aminothiophenols, obtained by reductive cleavage of the corresponding disulfides in the presence of triphenylphosphine, is an effective method for the synthesis of 2,4‐diaryl‐2,3‐dihydro‐1,5‐benzothiazepines under neutral conditions.     

Stability of a hypersonic shock layer on a flat plateStabilité d'une couche de choc hypersonique sur une plaque plane.

Stability of a hypersonic shock layer on a flat plate is examined with allowance for disturbances conditions on the shock wave within the framework of the linear stability theory. The characteristics of the main flow are calculated on the basis of the Full Viscous Shock Layer model. Conditions for velocity, pressure, and temperature perturbations are derived from steady Rankine–Hugoniot relation on the shock wave. These conditions are used as boundary conditions on the shock wave for linear stability equations. The growth rates of disturbances and density fluctuations are compared with experimental data obtained at ITAM by the method of electron-beam fluorescence and with theoretical data of other authors. To cite this article: A.A. Maslov et al., C. R. Mecanique 332 (2004).     

A mixed integer linear programming approach to minimize the number of late jobs with and without machine availability constraints

This study investigates scheduling problems that occur when the weighted number of late jobs that are subject to deterministic machine availability constraints have to be minimized. These problems can be modeled as a more general job selection problem. Cases with resumable, non-resumable, and semi-resumable jobs as well as cases without availability constraints are investigated. The proposed efficient mixed integer linear programming approach includes possible improvements to the model, notably specialized lifted knapsack cover cuts. The method proves to be competitive compared with existing dedicated methods: numerical experiments on randomly generated instances show that all 350-job instances of the test bed are closed for the well-known problem 1|_ri|∑_wiUi$1|r_i|\sum w_i{U}_i$. For all investigated problem types, 98.4% of 500-job instances can be solved to optimality within 1 hour.     

Convex equipartitions: the spicy chicken theorem

We show that, for any prime power $n$ and any convex body $K$ (i.e., a compact convex set with interior) in $\mathbb{R }^d$ , there exists a partition of $K$ into $n$ convex sets with equal volumes and equal surface areas. Similar results regarding equipartitions with respect to continuous functionals and absolutely continuous measures on convex bodies are also proven. These include a generalization of the ham-sandwich theorem to arbitrary number of convex pieces confirming a conjecture of Kaneko and Kano, a similar generalization of perfect partitions of a cake and its icing, and a generalization of the Gromov–Borsuk–Ulam theorem for convex sets in the model spaces of constant curvature.     

Expedient Access to Functionalized Furan/3(2H)-furanone Ensembles via Microwave-Assisted Domino Reactions

A one-pot linkage between furan and 3(2H)-furanone rings has been effected via the microwave-assisted Et₃N-catalyzed domino condensation of the furan and benzofuran carboxylic acids with available cyanopropargylic alcohols (MeCN, 100 °C, 1.2 atm, 2–17 h). Despite involving a number of C-H-forming/breaking steps, the assembly is chemoselective and the final products, 5-(2-furyl)-3(2H)-furanones, are formed in 59–96% yields.     

Two-state and continuous phase transitions in lipid bilayers A time-resolved X-ray diffraction study

Structural changes associated with transition from one phase to another have been examined in several lipid-water systems using time-resolved X-ray diffraction methods. Two types of transition mechanism can be recognized on the basis of scattering originating from the packing of the hydrocarbon chains. Two-state transitions are characterized by coexistence of the wide-angle scattering patterns of the initial and final phases throughout the transition region. Continuous transitions, on the other hand, take place through a series of intermediate states that are believed to arise from deformation of the hydrocarbon chain lattice as one phase transforms into another. Two-state processes are observed as subgel to liquid crystal transitions, and continuous transformations are typical of subgel to gel phase transitions. Examples of these transition types are presented and other transitions that do not appear to conform to either of these mechanisms are described.     

Reactions of 3-Thia(Selena)Pentane-1,5-Diones with Lewis Acids

3-Thia(selena)pentane-1,5-diones react with Lewis acids by heteroatom. In these reactions soft Lewis acids such as tin tetrachloride and antimony pentachloride form adducts but hard Lewis acid such as phosphorus pentachloride oxidizes chalcogen atom of 3-thia(selena)-pentane-1,5-dione. Carbon analogues of these diketones form pyrylium salts in the reactions with these Lewis acids.