Using delayed damping to minimize transmitted vibrations

In Mokni et al. [Mokni L, Belhaq M, Lakrad F. Effect of fast parametric viscous damping excitation on vibration isolation in sdof systems. Commun Nonlinear Sci Numer Simulat 2011;16:1720-1724], it was shown that in a single degree of freedom system a fast nonlinear parametric damping enhances vibration isolation with respect to the case where the nonlinear damping is time-independent. The present work proposes additional enhancement of vibration isolation using delayed nonlinear damping. Attention is focused on assessing the contribution of a delayed nonlinear damping over a fast parametric damping in terms of minimizing transmissibility. The results show that a nonlinear damping with delay greatly improves vibration isolation.     

Suivi de fissuration de matériaux par thermographie

The purpose of this work is to present a novel strategy for real-time monitoring crack growth of materials. The process is based on the use of thermal data extracted along the horizontal axis of symmetry of single edge notch tension (SENT) specimens, during fatigue tests. These data are exploited using an implemented program to detect in situ the growth of fatigue crack, with the critical size and propagation speed of the crack. This technique has the advantage to be applicable to a wide range of materials regardless of their electrical conductivity and their surface texture. To cite this article: D. Ait Aouit, A. Ouahabi, C. R. Mecanique 336 (2008).     

Equilibres Liquide-vapeur Isothermes De Melanges Binaires, Amine+amine

The authors have measured the vapour pressure of the binary systems, piperidine+n -butylamine, piperidine+dipropylamine, piperidine+N-methyl piperidine, piperidine+N,N-dimethyl amino butane and N-methyl piperidine+n -butylamine. The measurements were carried out using an isoteniscope built by Jose [1]. The vapour pressure, excess Gibbs free energies at 298,15, 303,15, 313,15, 323,15, 333,15, and 325,15 K, are reported for these mixtures. The excess Gibbs free energies have been fitted to Redlich-Kister equation. This revised version was published online in July 2006 with corrections to the Cover Date.     

DNA Nucleobase under Ionizing Radiation: Unexpected Proton Transfer by Thymine Cation in Water Nanodroplets

The effect of ionizing radiation on DNA constituents is a widely studied fundamental process using experimental and computational techniques. In particular, radiation effects on nucleobases are usually tackled by mass spectrometry in which the nucleobase is embedded in a water nanodroplet. Here, we present a multiscale theoretical study revealing the effects and the dynamics of water droplets towards neutral and ionized thymine. In particular, by using both hybrid quantum mechanics/molecular mechanics and full ab initio molecular dynamics, we reveal an unexpected proton transfer from thymine cation to a nearby water molecule. This leads to the formation of a neutral radical thymine and a Zundel structure, while the hydrated proton localizes at the interface between the deprotonated thymine and the water droplet. This observation opens entirely novel perspectives concerning the reactivity and further fragmentation of ionized nucleobases.     

Diastereoselective preparation of novel tetrahydrooxazinones via heterocycloaddition of N-Boc, O-Me-acetals

Under Lewis acid conditions, reaction of N-Boc, O-Me acetals with the (R)-(+)-O-vinyl-pantolactone does not lead to the expected dihydrooxazine, but to the corresponding tetrahydrooxazinone, as a result of the loss of the t-Bu group. A diastereoselective and asymmetrical way to these new heterocyclic compounds is described, together with the first evidence of their ability to undergo N-acylation.     

Lower Semicontinuous Regularization for Vector-Valued Mappings

The paper is devoted to studying the lower semicontinuity of vector-valued mappings. The main object under consideration is the lower limit. We first introduce a new definition of an adequate concept of lower and upper level sets and establish some of their topological and geometrical properties. A characterization of semicontinuity for vector-valued mappings is thereafter presented. Then, we define a concept of vector lower limit, proving its lower semicontinuity, and furnishing in this way a concept of lower semicontinuous regularization for mappings taking their values in a complete lattice. The results obtained in the present work subsume the standard ones when the target space is finite dimensional. In particular, we recapture the scalar case with a new flexible proof. In addition, extensions of usual operations of lower and upper limits for vector-valued mappings are explored. The main result is finally applied to obtain a continuous D.C. decomposition of continuous D.C. mappings. Dedicated to Alex Rubinov in honor of his 65th birthday     

Nouvelles substances d'intercomparaison proposees pour l'etalonnage en temperature et en energie d'analyseurs thermiques (ou calorimetriques) differentiels

Several organic compounds as new reference materials for temperature and energy calibration of DTA and DSC appartuses were studied in the range of temperature 300–600 K.

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Zusammenfassung Im Temperaturbereich 300–600 K wurden einige organische Verbindungen als neue Referenzsubstanzen für die Temperatur- und Energieeichung bei DTA und DSC untersucht.

     

K2CsYb(PO4)2

The crystal structure of dipotassium caesium ytterbium bis(phosphate) is built up from regular independent PO₄ tetrahedra and YbO₆ octahedra sharing corners and arranged in layers. The structure is, in many respects, similar to that of glaserite.     

Enthalpies molaires d'exces des melanges binaires thiophene et diethylsulfide avec n-alcanes

The excess molar enthalpy of thiophen and diethylsulfid with some n alkanes have been measured at 303.15 K and 1 atm. A Redlich—Kister type equation was used to represent and correlate the results. Empirical equations of group contribution model, disquac have been applied for the binaries systems.This revised version was published online in November 2005 with corrections to the Cover Date.     

Efficient Approach for the Synthesis of Novel Functionalized Isoxazolines from Limonene

New functionalized isoxazolines were effeciently and easily prepared from limonene. The procedure involves a peri‐ and regioselective 1,3‐dipolar cycloaddition of nitrile oxides on the monoterpene external double bond, followed by a highly chemoselective RuCl₃‐NaIO₄ oxidative cleavage of the internal one. All the newly prepared isoxazolyl‐ketoacids were fully characterized from their spectroscopic data.