Sur une variante de la méthode des boites pour la détermination numérique de la dimension fractale d'un sous-ensemble du plan

In this work, we propose a particular discretization of the size of the grids in order to compute numerically, by the box-counting algorithm, the fractal dimension of a subset in two-dimensional space. The efficiency of the associated method is successfully tested on various examples of fractal sets which are derived from discret dynamical systems. To cite this article: N. Akroune, C. R. Acad. Sci. Paris, Ser. I 338 (2004).     

New adsorbents from oil shales: Preparation, characterization and U, Th isotope adsorption tests

New activated adsorbents for radionuclides have been produced from Moroccan oil shales by pyrolysis of the natural material at 550 °C flowed by a KMnO₄ activation. The texture and composition of the native rock and the adsorbents were studied before their use in tests for adsorption of radionuclides from standard solutions prepared from uranylnitrate and thorium nitrate in equilibrium with their daughters. The distribution coefficients between solutions containing U, Th and Ra and the adsorbents were evaluated by means of specific activities, measured by g-ray spectrometry. The adsorbents were observed to eliminate U, Th, Ra, Ac and Tl from aqueous solutions. This revised version was published online in August 2006 with corrections to the Cover Date.     

A comparative study of two polymorphs of L‐aspartic acid hydrochloride

Two polymorphs of L‐aspartic acid hydrochloride, C₄H₈NO₄⁺·Cl⁻, were obtained from the same aqueous solution. Their crystal structures have been determined from single‐crystal data collected at 100 K. The crystal structures revealed three‐ and two‐dimensional hydrogen‐bonding networks for the triclinic and orthorhombic polymorphs, respectively. The cations and anions are connected to one another via N—H...Cl and O—H...Cl interactions and form alternating cation–anion layer‐like structures. The two polymorphs share common structural features; however, the conformations of the L‐aspartate cations and the crystal packings are different. Furthermore, the molecular packing of the orthorhombic polymorph contains more interesting interactions which seems to be a favourable factor for more efficient charge transfer within the crystal.     

A serendipitous conversion of enaminolactone nitriles with primary amines: a new synthesis of substituted 2-aminopyridine derivatives

In the course of our studies on Cerpegin analogues synthesis, a serendipitous reactivity of enaminolactone nitrile has been observed. Instead of expecting iminocerpegins, we have gained new class of substituted 2-aminopyridines. The methodology has been applied on a wide range of primary amines, as aliphatic, aromatic, heteroaromatic and also, diamines, hydrazines and chiral amines.     

Distances on Lie groups of polynomial volume growth

For any simply connected solvable Lie group Q of polynomial volume growth, we introduce the notion of nil-shadow of Q. We shall give an explicit formula for the distance to the origin of an element q ∈ Q in terms of its exponential coordinates of the second kind taken in an appropriate basis. This result extends a previous result for nilpotent Lie groups [6, Theorem DN] and [7, Theorem 1].     

Electrical properties of elastomer-based composites reinforced with carbon nanotubes—A review

Even though carbon nanotubes offer an excellent solution for the design of strain sensors, their widespread commercial utilization has been hampered by the unavailability of design rules, inconsistencies in their macro-scale properties, and lack of understanding of the effects of various parameters on their characteristics. Nevertheless, many researches have been carried out to characterize elastomeric nanocomposites filled with carbon nanotubes in order to optimize their properties such as electrical conductivity and strain sensitivity range. This article reviews the effect of different parameters on the electrical properties of such nanocomposites, followed by the analysis of performances of elastomer strain sensors.