Théorie des effets rhéo-optiques dans un continu polarisable et magnétisable

Summary The total momentum-energy tensor describing the interaction of a polarizable and magnetizable continuum with an electromagnetic field is constructed on the basis ofLorentz invariance. The equations of balance of energy and momentum are deduced and applied to the study of the magnetooptical, electrooptical and photoelastic behavior of an elastic polarizable and magnetizable isotropic continuum. This model exhibits theCotton-Mouton andKerr effects but thePockels andFaraday rotations don't appear.     

Methodology for the validation of analytical methods involved in uniformity of dosage units tests

Validation of analytical methods is required prior to their routine use. In addition, the current implementation of the Quality by Design (QbD) framework in the pharmaceutical industries aims at improving the quality of the end products starting from its early design stage. However, no regulatory guideline or none of the published methodologies to assess method validation propose decision methodologies that effectively take into account the final purpose of developed analytical methods. In this work a solution is proposed for the specific case of validating analytical methods involved in the assessment of the content uniformity or uniformity of dosage units of a batch of pharmaceutical drug products as proposed in the European or US pharmacopoeias. This methodology uses statistical tolerance intervals as decision tools. Moreover it adequately defines the Analytical Target Profile of analytical methods in order to obtain analytical methods that allow to make correct decisions about Content uniformity or uniformity of dosage units with high probability. The applicability of the proposed methodology is further illustrated using an HPLC-UV assay as well as a near infra-red spectrophotometric method.     

Modelling the flow of power law fluids in a packed bed using a volume-averaged equation of motion

The development of a theoretical model for the prediction of velocity and pressure drop for the flow of a viscous power law fluid through a bed packed with uniform spherical particles is presented. The model is developed by volume averaging the equation of motion. A porous microstructure model based on a cell model is used. Numerical solution of the resulting equation is effected using a penalty Galerkin finite element method. Experimental pressure drop values for dilute solutions of carboxymethylcellulose flowing in narrow tubes packed with uniformly sized spherical particles are compared to theoretical predictions over a range of operating conditions. Overall agreement between experimental and theoretical values is within 15%. The extra pressure drop due to the presence of the wall is incorporated directly into the model through the application of the no-slip boundary condition at the container wall. The extra pressure drop reaches a maximum of about 10% of the bed pressure drop without wall effect. The wall effect increases as the ratio of tube diameter to particle diameter decreases, as the Reynolds number decreases and as the power law index increases.     

Numerical developments for short-pulsed Near Infra-Red laser spectroscopy. Part I: direct treatment

This two part study is devoted to the numerical treatment of short-pulsed laser near infra-red spectroscopy. The overall goal is to address the possibility of numerical inverse treatment based on a recently developed direct model to solve the transient radiative transfer equation. This model has been constructed in order to incorporate the last improvements in short-pulsed laser interaction with semi-transparent media and combine a discrete ordinates computing of the implicit source term appearing in the radiative transfer equation with an explicit treatment of the transport of the light intensity using advection schemes, a method encountered in reactive flow dynamics. The incident collimated beam is analytically solved through Bouger-Beer-Lambert extinction law.In this first part, the direct model is extended to fully non-homogeneous materials and tested with two different spatial schemes in order to be adapted to the inversion methods presented in the following second part. As a first point, fundamental methods and schemes used in the direct model are presented. Then, tests are conducted by comparison with numerical simulations given as references. In a third and last part, multi-dimensional extensions of the code are provided. This allows presentation of numerical results of short pulses propagation in 1, 2 and 3D homogeneous and non-homogeneous materials given some parametrical studies on medium properties and pulse shape. For comparison, an integral method adapted to non-homogeneous media irradiated by a pulsed laser beam is also developed for the 3D case.     

Bilans d'energie et de quantité de mouvement pour un continu deformable,polarisable et magnétisable

In this paper, it is shown that the different electromagnetic energy-momentum tensors proposed by various authors for a continuum interacting with an electromagnetic field all lead to the same equations of balance for energy and momentum provided the definitions of stress and internal energy are suitably related. These various tensors come out from different partitions of the total energy-momentum tensor. From a particular partition, we derive an expression of the balance of energy suitable for application to continuum thermodynamics. In the classical approximation, the corresponding equation of balance of momentum gives rise to an expression for the electromagnetic force in a polarizable and magnetizable continuum.     

Cloning, expression, and biochemical characterization of Streptomyces rubellomurinus genes required for biosynthesis of antimalarial compound FR900098

The antibiotics fosmidomycin and FR900098 are members of a unique class of phosphonic acid natural products that inhibit the nonmevalonate pathway for isoprenoid biosynthesis. Both are potent antibacterial and antimalarial compounds, but despite their efficacy, little is known regarding their biosynthesis. Here we report the identification of the Streptomyces rubellomurinus genes required for the biosynthesis of FR900098. Expression of these genes in Streptomyces lividans results in production of FR900098, demonstrating their role in synthesis of the antibiotic. Analysis of the putative gene products suggests that FR900098 is synthesized by metabolic reactions analogous to portions of the tricarboxylic acid cycle. These data greatly expand our knowledge of phosphonate biosynthesis and enable efforts to overproduce this highly useful therapeutic agent.     

Characterisation of electroplated Bi<Subscript>2</Subscript>(Te<Subscript>1−x</Subscript>Se<Subscript>x</Subscript>)<Subscript>3</Subscript> alloys

Composition modulated Bi₂(Te_1−xSe_x)₃ thin films were prepared on stainless steel substrates by cathodic electrodeposition. The composition was dependent on the deposition conditions. It was possible to obtain, in the same electrolyte, films with either an excess or a deficiency of bismuth in relation to stoichiometric Bi₂(Te_0.9Se_0.1)₃ by changing the deposition potential or the applied current density. The excess of bismuth was reached at the highest cathodic conditions. The variation of the crystallographic axis and the morphology with a granular structure were correlated with the presence of the Bi enrichment in the ternary. The crystallographic texture of bismuth telluride films was studied according to the electrodeposition conditions. The films presented a fibre texture, and a main orientation {11.0} was observed. Electrical and thermoelectric properties of a Bi_1.98Te_2.67Se_0.39 film were measured and showed an n-type behaviour.     

Interaction between a disclination and a uniaxial-isotropic phase interface in a nematic liquid crystal

We consider the interaction between a disclination line of strength +/-1/2 and an interface between the uniaxial and isotropic phases of a nematic liquid crystal. We apply a recently developed set of interface conditions including a configurational force balance which generalizes the Gibbs-Thomson equation to account for the curvature elasticity of the uniaxial phase and the orientation dependence of the interfacial free-energy density. We consider a rectangular vessel containing both phases and a disclination. We formulate a relevant free-boundary problem and use numerical methods to determine equilibrium shapes of the interface. When the interfacial free-energy is constant, the shape of the interface is insensitive to whether the strength of the defect is +1/2 or -1/2 and to rotations of the director field consistent with the boundary conditions. Accounting for the dependence of the interfacial free-energy density on the angle between the interfacial unit normal field and the director field eliminates these degeneracies. In particular, when such dependence is taken into account, different solution branches are found, indicating the presence of a bifurcation. We find also that, depending on the magnitude of the anisotropic contribution to the interfacial free-energy density, the interaction between the disclination and the interface may be repulsive or attractive. When the interaction is repulsive, the disclination line positions itself at an energetically optimal distance adjacent to the interface. Otherwise, the uniaxial phase expels the disclination to the interface where a cusp forms.     

Laser operation of Yb3+ in the acentric RbTiOPO4 codoped with Nb5+

We report on continuous-wave lasing of Yb(3+) at room temperature in the noncentrosymmetric RbTiOPO(4) crystal, codoped with Nb(5+), for all three possible polarizations. A maximum output power of 154 mW at 1050 nm was obtained for an absorbed power of 386 mW. The highest slope efficiency reached approximately 60% and the lowest threshold (with respect to the absorbed power) was 18 mW. The laser was tunable from 1009 to 1081 nm.