A study of thermal and dielectric behavior of manganese malonate dihydrate single crystals

Thermal decomposition of manganese malonate dihydrate single crystals grown by gel method has been studied using the TG-DTA and DSC techniques. The presence of water molecules and the dehydration stages are discussed. Dielectric constant, dielectric loss, and AC conductivity have been estimated as a function of temperature in the range of 40–120 °C for four different frequencies. Thermal studies reveal that the material is thermally stable up to123 °C. The dielectric measurements indicate that the dielectric parameters increase with the increase in temperature. Also, the dielectric constant and dielectric loss factor values decrease whereas the electrical conductivities increase with the increase in frequency of the AC applied.     

Pulsed laser ablation of zinc selenide in nitrogen ambience: Formation of zinc nitride films

Zinc nitride (Zn₃N₂) thin films are prepared using pulsed laser deposition (PLD) from zinc selenide (ZnSe) target at different nitrogen ambient pressures viz. 1, 3, 5, 7 and 10 Pa. The films prepared with nitrogen pressures 1 and 3 Pa are amorphous in nature, whereas the films prepared at 5, 7 and 10 Pa exhibit the presence of cubic bixbyite Zn₃N₂ structure with lattice parameter very close to bulk of Zn₃N₂. The particle size calculated by Debye Scherrer's formula is in the nano regime. Surface morphology of the films is studied by SEM and AFM analysis. Optical parameters such as band gap, refractive index and porosity of the films are calculated. Moreover, the present study confers an outlook about how do various factors such as substrate temperature, reactive supplementing gas and laser-target interaction influence the film developing process during pulsed lased deposition.     

Utilization of phenylalanine and phenylacetic acid byPseudomonas solanacearum

Pseudomonas solanacearum utilized phenylalanine as sole source of carbon and nitrogen. Phenylalanine-grown cells rapidly oxidized phenylacetic acid and homogentisic acid. Gentisic and protocatechuic acids were also oxidized, after an initial lag. Phenylacetate-grown cells rapidly oxidized gentisic acid, slowly oxidizedo-hydroxyphenylacetic acid and catechol, and did not oxidizem-hydroxymandelic andm-hydroxyphenylacetic acids. Phenylalanine was degraded via phenylacetic acid-r-lactone andβ ketoadipate; Rothera’s test indicatedortho cleavage of the aromatic ring.     

Asymptotique d'un problème de positionnement optimalAsymptotic of an optimal location problem

We consider the problem of optimal location of production centres to serve a non-uniform distribution of customers. The location is required to be optimal with respect to the cost of transportation which is modeled by a weighted average of the distance function to the nearest production centre. In this Note we study the asymptotic behaviour of the problem as the number of production centres increases. This is done in connection with the theory of Monge–Kantorovich for mass transportation. To cite this article: G. Bouchitté et al., C. R. Acad. Sci. Paris, Ser. I 335 (2002) 853–858.     

Experimental study of coating flows in a partially-filled horizontally Rotating cylinder

 We describe a number of different phenomena seen in the free-surface flow inside a partially filled circular cylinder which is rotated about its horizontal axis of symmetry. At low angular velocities the flow settles into a steady two-dimensional flow with a front where the coating film coalesces with the pool at the bottom of the cylinder. This mode becomes unstable at higher angular velocities, initially to a sloshing mode on the rising side of the coating film and then to an axial instability on the front. The undulations that appear on the front grow into large-amplitude stationary patterns with cusp-like features for some parameter values. At still higher angular velocities and volume fractions, a number of different inertial instabilities and patterns appear. We present a phase diagram of the various transitions and characterize some of the more prominent instabilities and patterns in detail, along with some possible mechanisms for the observed behaviour. Received: 13 April 1996 / Accepted: 13 June 1996