Real-time X-Ray diffraction measurements of the phase transition in KCl shocked along

We have directly imaged subcritical fluctuations during the nucleation phase of three-dimensional islands in strained layer epitaxy. The fluctuations are defect mediated and are found to be large even at low growth temperatures. We attribute the existence of large fluctuations to the time dependence of the supersaturation. This indicates classical nucleation concepts are relevant, even at low growth temperatures.     

Preuve ≪Elementaire≫ du theoreme de Grothendieck-Lefschetz pour les hypersurfaces

Sans résumé     

The influence of the amount of hardener on the tensile mechanical behavior of an epoxy system

The tensile mechanical behavior of an epoxy/amine system, with varying amounts of hardener, was evaluated. The results showed that a brittle to ductile transition occurs as the amount of hardener is increased. This behavior was associated with the change in the number of molecular segments that present mobility in the macromolecular network. The epoxy-rich formulations are brittle due to the total consumption of the functional groups on the hardener molecule. On the other hand, the amine-rich formulations showed a fracture behavior characteristic of materials with large deformation capacity. This behavior was associated with the presence of unreacted points on the hardener molecule which introduce a new mobile molecular segment in the macromolecular network formed. © 1998 John Wiley & Sons, Ltd.     

Spectral computations: from operators to matrices

In this work we will address the problem of finding spectral values and bases for the corresponding spectral subspaces for a bounded operator on a Banach space. We will make a bridge between the spectral problem for the continuous operator and the computation of the eigenpairs of a matrix. This approximate problem results first from an approximation by a sequence of continuous operators with finite rank, followed by the reduction to a spectral problem for an operator whose domain as well as range are finite dimensional. Some discussion on defect correction procedures will be also presented. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermodynamique des mélanges liquides binaires. Chaleurs de mélange des cycloalcanes

Heats of mixing were measured between 10° and 80°C for all binary systems formed with cycloalcanes C_nH_2n, n = 5, 6, 7, 8.     

Aging of polyamide 12 in oil at different temperatures and pressures

Polyamide 12 (PA 12) is an alternative to steel in the manufacture of pipes for transporting oil and gas. However, polyamide pipes suffer degradation, triggered by factors such as temperature and exposure to chemicals. In this research, the authors studied the variation of mechanical and thermal properties and of structural characteristics of a PA 12 grade after aging in oil. The aging process lasted 3360 h. It was made at ambient temperature and at 70 °C, under pressures of 1 and 17 atm. At ambient temperature and atmospheric pressure, PA 12 increased in volume, weight and rigidity, and decreased in damping. At 70 °C and atmospheric pressure, there was a smaller increase in volume and weight. PA 12 samples also darkened, showed an increase in crystallinity and damping, and a decrease in rigidity. At 70 °C and 17 atm, a decrease in volume and weight was observed; the samples also darkened, increased in crystallinity and rigidity, and decreased in damping. In all aging conditions, the results of the thermal analysis and the analysis of functional groups showed that the chemical structure of the material was not significantly changed. According to the results, PA 12 has a good resistance to aging under these conditions. Copyright © 2017 John Wiley & Sons, Ltd.     

Interaction of low-energy electrons with the pyrimidine bases and nucleosides of DNA

We report computed cross sections for the elastic scattering of slow electrons by the pyrimidine bases of DNA, thymine and cytosine, and by the associated nucleosides, deoxythymidine and deoxycytidine. For the isolated bases, we carried out calculations both with and without the inclusion of polarization effects. For the nucleosides, we neglect polarization effects but estimate their influence on resonance positions by comparison with the results for the corresponding bases. Where possible, we compare our results with experiment and previous calculations.     

Ru-OSO coordination photogenerated at 100 K in tetraammineaqua(sulfur dioxide)ruthenium(II) (±)-camphorsulfonate

The photoinduced O-bound coordination mode in RuSO(2) complexes, previously observed only at 13 K, has been generated at 100 K in tetraammineaqua(sulfur dioxide)ruthenium(II) (±)-camphorsulfonate. This coordination state, often denoted MS1, decays to the η(2)-bound MS2 state, with an estimated half-life of 3.4(8) h and a long-lived population of 2.9(4)% at 120 K.     

Transition of unsteady flows of evaporation to steady state

We investigate the half-space problem of evaporation and condensation in the scope of discrete kinetic theory. Exact solutions are found to the boundary value problem and the initial boundary value problems of the flow in the half space for a discrete velocity model. The results are used to analyze the transition of the unsteady solutions towards steady states. To cite this article: A. d'Almeida, C. R. Mecanique 336 (2008).