Simple optoelectronic method for analysis of transverse mode structure of lasers

Laser beam quality evaluation is generally carried out through the measurement of the M² second-moment. This standard procedure is time consuming and is difficult to be implemented for checking, for instance, each VCSEL diode moving out of the assembly line of a high volume production factory. In this paper, we propose an alternative fast method allowing to distinguish easily a single transverse mode from a multiple transverse mode behaviour. This method is based on an electronic analysis (locking amplifier) of the local slope of the output laser characteristic, i.e. laser output power versus pumping.     

Mechanical relaxations in polypropylene: A new experimental and theoretical approach

Accurate dynamic mechanical measurements have been performed on semicrystalline isotactic polypropylene over wide ranges of temperature and frequency. A mechanical model has been used to analyze experimental results in order to separate the behavior of amorphous and crystalline phases. The two main α and β relaxation processes have been analyzed. The β relaxation, related to the glass-rubber transition of the amorphous fraction, has been studied with the help of a physical model. The behavior is similar to that of a wholly amorphous polymer, with two characteristics: a high rubbery plateau, indicating a crosslinking effect by the crystalline phase, and a strong effect of interfaces in shear strain. Experimental data suggest the α relaxation originates within the crystalline phase and that it can be attributed to diffusion of defects. The amorphous phase plays an important role in this process, because it has to adapt itself by cooperative movements to respect the compatibility of deformations of the two phases. The formalism developed here rationalizes experimental results obtained with samples having different thermal histories.     

Low-temperature solubility of copper in iron: experimental study using thermoelectric power,small angle X-ray scattering and tomographic atom probe

Measuring the solubility limit of copper in iron at temperature lower than 700°C is problematic because copper diffusion is too slow in this temperature range. To overcome this difficulty, fine precipitation of copper is studied. The solubility limit of copper is measured after complete precipitation using two complementary techniques: thermoelectric power and small angle X-ray scattering. Values obtained are confirmed by tomographic atom probe and give results much higher than what is usually extrapolated from high-temperature experiments.     

A heuristic for the multi-period petrol station replenishment problem

In the multi-period petrol station replenishment problem (MPSRP) the aim is to optimize the delivery of several petroleum products to a set of petrol stations over a given planning horizon. One must determine, for each day of the planning horizon, how much of each product should be delivered to each station, how to load these products into vehicle compartments, and how to plan vehicle routes. The objective is to maximize the total profit equal to the revenue, minus the sum of routing costs and of regular and overtime costs. This article describes a heuristic for the MPSRP. It contains a route construction and truck loading procedures, a route packing procedure, and two procedures enabling the anticipation or the postponement of deliveries. The heuristic was extensively tested on randomly generated data and compared to a previously published algorithm. Computational results confirm the efficiency of the proposed methodology.     

A Novel Allenic Epoxycyclohexane and Related Compounds from Eutypa lata (Pers: F.) Tul

The novel allenic epoxycyclohexanes 1 , and related compounds 2 and 3 have been isolated from the culture medium of Eutypa lata. Their structures were established by combination of spectroscopic and chemical techniques. Biogenetic origin and biological activity of these compounds are also discussed.     

Study of the electron transfer reaction between [Co(EDTA)]− and [Ru(NH3)5py]2+ in methanol–water mixtures

The title reaction was studied in different water–cosolvent (methanol) mixtures. The results have been rationalized employing the Marcus–Hush treatment. To apply this treatment, the true, unimolecular, electron‐transfer rate constants (k_et) were obtained from the experimentally measured rate constants after calculation of the equilibrium constant for the processes of formation of the encounter complex. This calculation was carried out using Eigen–Fuoss (EF) and exponential mean spherical (EMSA) approaches employing effective values of the solvent dielectric constant. These effective values were obtained from the measured association constants corresponding to other ion pairs. The results reveal that in these media there is an additional component of reorganization energy, absent in neat solvents. An explanation of the origin of this component is given. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 658–666, 2009     

Analyse par simulation numérique du développement de l'instabilité électro-convective d'une couche de liquide diélectrique infinie soumise à une injection unipolaire

In this article electroconvective phenomenon, which take place in a dielectric liquid layer submitted to an unipolar injection, are studied by numerical simulations means. For the first time the full and coupled resolution of the Electro-Hydro-Dynamic equations are achieved. The results are compared with those coming from stability analysis especially for the linear and non-linear criteria in strong and weak injection cases. The hysterical behavior of the development of this instability is accurately reproduced. To cite this article: P. Traoré et al., C. R. Mecanique 337 (2009).     

InGaAs/Si3N4 interface obtained in ultrahigh vacuum multipolar plasma: In-situ control by ellipsometry and electrical characterization

A multipolar plasma passivation scheme controlled by in-situ ellipsometry has been developed to produce a high electrical quality InGaAs/Si₃N₄ interface. We have demonstrated the possibility to remove all native oxides at the InGaAs surface by heating the sample at 240°C, then using the action of a multipolar H₂ plasma at 185°C, without optical degradation of the surface. The passivation by a native nitride layer is then performed using a N₂ plasma, and Si₃N₄ is deposited. The treatment induces a reduction of the density of interface states N_ss(E), and also a change of the nature of these interface states as shown by a reduction in the capture cross section σ_n(E).     

Dihydroquinoline derivative as a potential anticancer agent: synthesis,crystal structure,and molecular modeling studies

Molecular Diversity - Cancer is one of the leading causes of death worldwide and requires intense and growing research investments from the public and private sectors. This is expected to lead to...