Caractérisation rhéologique de la bentonite de maghnia en suspension aqueuse sans et avec additifs anioniques

L'objectif de ce travail est l’étude de l'effet de l’ajout de deux polymères anioniques sur les caractéristiques rhéologiques d'une suspension aqueuse de bentonite algérienne de forage (de Maghnia, Ouest de l’Algérie). Les additifs sont la gomme de xanthane et le carboxymethylcellulose, CMC, utilisés souvent dans la formulation des boues de forage. Dans cet article, nous présentons et discutons des mesures rhéologiques réalisés sur : 1) une suspension aqueuse de bentonite (3%), 2) des polymères en solution aqueuse (le xanthane et le CMC à trois poids moléculaires différentes) et 3) des mélanges eau-bentonite-(xanthane ou CMC) à différentes concentrations de polymère. Ce travail a permis, notamment, de renforcer la conclusion rapportée dans des travaux conduits antérieurement sur la base d’une bentonite de laboratoire, montrant la dominance du comportement rhéologique du CMC et de xanthane sur celui de la suspension de bentonit

Convergence of vector bundles with metrics of Sasaki-type

If a sequence of Riemannian manifolds, $X_i$, converges in the pointed Gromov-Hausdorff sense to a limit space, $X_\infty$, and if $E_i$ are vector bundles over $X_i$ endowed with metrics of Sasaki-type with a uniform upper bound on rank, then a subsequence of the $E_i$ converges in the pointed Gromov-Hausdorff sense to a metric space, $E_\infty$. The projection maps $\pi_i$ converge to a limit submetry $\pi_\infty$ and the fibers converge to its fibers; the latter may no longer be vector spaces but are homeomorphic to $\R^k/G$, where $G$ is a closed subgroup of $O(k)$ ---called the {\em wane group}--- that depends on the basepoint and that is defined using the holonomy groups on the vector bundles. The norms $\mu_i=\|\cdot\|_i$ converges to a map $\mu_{\infty}$ compatible with the re-scaling in $\R^k/G$ and the $\R$-action on $E_i$ converges to an $\R-$action on $E_{\infty}$ compatible with the limiting norm. In the special case when the sequence of vector bundles has a uniform lower bound on holonomy radius (as in a sequence of collapsing flat tori to a circle), the limit fibers are vector spaces. Under the opposite extreme, e.g. when a single compact $n$-dimensional manifold is re-scaled to a point, the limit fiber is $\R^n/H$ where $H$ is the closure of the holonomy group of the compact manifold considered. An appropriate notion of parallelism is given to the limiting spaces by considering curves whose length is unchanged under the projection. The class of such curves is invariant under the $\R$-action and each such curve preserves norms. The existence of parallel translation along rectifiable curves with arbitrary initial conditions is also exhibited. Uniqueness is not true in general, but a necessary condition is given in terms of the aforementioned wane groups $G$.Comment: 44 pages, 1 figure, in V.2 added Theorem E and Section 4 on parallelism in the limit space

Rheological and electrokinetic properties of carboxymethylcellulose-water dispersions in the presence of salts

The purpose of this work is to investigate the effect of the addition of salts in the form of calcium chloride, sodium chloride and potassium chloride on the rheological and electrokinetic properties of diluted sodium carboxymethylcellulose (Na-CMC) dispersions (0.50%). The rheological data of a water-CMC-salt system were obtained using coaxial cylinder viscometer covering a wide range of shear rate (0 to 600 s-1). Ostwald–de Waele power law was used for fitting flow curves of various samples. The presence of salts in CMC aqueous solutions leads to the reduction of the consistency index and the increase of flow index as salinity increases. When the concentration of salts is greater than 3%, the rheological parameters of CMC solutions in saline medium are quasi stable. The electrokinetic measurements show an increase of the zeta potential of CMC dispersions when the concentration of salts in solution increases. Calcium chloride caused the greatest increase in zeta potential. Excluding the monovalent cations, the divalent cation is able to reverse the sign of the zeta potential from negative to positiv

Physicochemical Profile of Essential Oil of Daucus carota

Essential oils have a significant antimicrobial activity. These oils can successfully replace the antibiotics. So, the microorganisms show their inefficiencies resistant for the antibiotics. For this reason, we study the physicochemical analysis and antimicrobial activity of the essential oil of Daucus carota. The extraction is done by steam distillation of water which brought us a very significant return of 4.65%. The analysis of the essential oil is performed by GC / MS and has allowed us to identify 32 compounds in the oil of D. carota flowering tops of Bouira. Three of which are in the majority are the α-Pinene (22.3%), the carotol (21.7%) and the limonene (15.8%