Etudes en méthode de Hartree-Fock avec projection … II. La fonction d'onde exacte d'un système de deux electrons dans un etat 1S comme projection d'un déterminant de Slater

The ground state wave-function of a two electrons atom may be represented to any accuracy by a ¹S projected Slater determinant built on hypercomplex spin-orbitals.     

On the boundary conditions at the macroscopic level

We study the problem of the boundary conditions specified at the boundary of a porous domain in order to solve the macroscopic transfer equations obtained by means of the volume-averaging method. The analysis is limited to the case of conductive transport but the method can be extended to other cases. A numerical study enables us to illustrate the theoretical results in the case of a model porous medium. Roman Letters _sf interfacial area of the s-f interface contained within the macroscopic system m² - A _sf interfacial area of the s-f interface contained within the averaging volume m² - C _p mass fraction weighted heat capacity, kcal/kg/K - d _s , d _f microscopic characteristic length m - g vector that maps to _s, m - h vector that maps to _f , m - K _eff effective thermal conductivity tensor, kcal/m s K - l REV characteristic length, m - L macroscopic characteristic length, m - n _fs outwardly directed unit normal vector for the f-phase at the f-s interface - n _e outwardly directed unit normal vector at the dividing surface - T ^* macroscopic temperature field obtained by solving the macroscopic equation (3), K - V averaging volume, m³ - V _s , V _f volume of the considered phase within the averaging volume, m³ - volume of the macroscopic system, m³ - _s , _f volume of the considered phase within the volume of the macroscopic system, m³ - dividing surface, m² Greek Letters _s , _f volume fraction - ratio of thermal conductivities - _s , _f thermal conductivities, kcal/m s K - spatial average density, kg/m³ - microscopic temperature, K - ^* microscopic temperature corresponding to T ^* , K - spatial deviation temperature K - error on the temperature due to the macroscopic boundary conditions, K - spatial average - ^s , ^f intrinsic phase average     

Influence of lipidation of GBV-C/HGV NS3 (513-522) and (505-514) peptide sequences on its interaction with mono and bilayers

Two decapeptide fragments of the non-structural hepatitis G NS3 protein (GBV-C/HGV), 513-522 (RGRTGRGRSG) and 505-514 (SAELSMQRRG), as well as their palmitoylated derivatives were synthesized. The physico-chemical properties of the peptides were analyzed in both the absence and presence of the zwitterionic 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), the negative 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DPPG) and the positive 1,2-dioeloyl-3-trimethylammonium-propane (DOTAP) lipid monolayers. Based on their high hydrophilic properties, neither parent peptide presented surface activity and their incorporation into lipid monolayers was low. In contrast, their palmitoylated derivatives showed concentration-dependent surface activity and could be inserted into lipid monolayers to varying degrees depending on their sequence. Compression isotherms showed that the presence of palmitoylated peptides in the subphase resulted in a molecular arrangement less condensed than that corresponding to the pure phospholipid. In concordance with the monolayer results, differential scanning calorimetry (DSC) demonstrated that the parent peptides did not have any effect on the thermograms, while the palmitoylated derivatives affected the thermotropic properties of DPPC bilayers.     

A predictive approach of the influence of the operating parameters on the size of polymer particles synthesized in a simplified microfluidic system

Monodisperse and size-controlled spherical polymer particles were synthesized by in situ photopolymerization of O/W monomer emulsions. Monomer droplets were produced without surfactant or pretreatment at a needle tip in a simplified axisymmetric microfluidic device. The effect of the viscosity of the continuous phase on the particle size was studied. The system operated in the dripping mode, at a low Reynolds number. A dimensionless master curve describes the particle diameter as a function of the needle inner diameter as well as velocity and viscosity ratios of continuous and dispersed phases. An empirical law predicts the particle size. The normalized particle diameter depends upon the ratio of the capillary numbers of continuous and dispersed phases with an exponent equal to -0.22.     

Variable density flow in porous media. A study by means of pore level numerical simulations

This paper is devoted to the modelling of isothermal low Reynolds and Mach numbers transient compressible flow through porous media. Traditionally, this type of flow at the macroscopic level is described by the classical Darcy's law combined with a mass balance that includes the transient term. This model is called the ‘classic model’. The aim of this paper is to explore the validity of this classic model. To this end, the flow of an ideal gas is considered within two‐dimensional model porous media. The flow is due to the imposed pressure variations at the outlet of the fluid domain. At the microscopic level, the flow is computed by solving the full compressible Navier–Stokes equations in two dimensions. Special attention is given to the outlet boundary conditions. The analysis is based on the comparison between the macroscopic data, obtained on the one hand by spatially averaging the microscopic results, and on the other hand by solving the problem directly at the macroscopic level. Situations for which a good agreement is found between the two series of data and situations for which discrepancies are observed are exhibited. These various behaviours are discussed in terms of the various time scales controlling the flow and are explained by analysing the flow structure at pore level. Copyright © 1999 John Wiley & Sons, Ltd.     

New Synthetic Analogs of Retinoids: Synthesis of Aromatic Analogs of 9‐Methylidene‐ and 13‐Demethyl‐9‐methylidene‐retinol, ‐retinal,and Ethyl 13‐Demethyl‐9‐methylideneretinoate

Aromatic analogs of 9‐methylidene and 13‐demethyl‐9‐methylideneretinol, ‐retinal, and ethyl 13‐demethyl‐9‐methylideneretinoate were synthesized via a new β‐methylidene‐aldehyde synthon.     

Determination of butyltin and phenyltin species by reversed-phase liquid chromatography and fluorimetric detection

Chromatographic separation of monobutyltin (MBT), monophenyltin (MPhT), dibutyltin (DBT), diphenyltin (DPhT), tributyltin (TBT) and triphenyltin (TPhT) was studied using end-capped reversed-phases (RP) and methanol-acetic acid-water or acetronitrile-acetic acid-water mixtures as mobile phases. Several RP columns were evaluated, and the effect of acetic acid, oxalic acid, triethylamine, and organic modifier on peak shape and retention was examined. A method based on gradient elution RPLC and fluorimetric detection is proposed for the determination of DBT, DPhT, TBT and TPhT. The sensitivity of the method makes it suitable for environmental analysis.     

Synthesis of N‐methyl‐4‐pyridyl‐1,2,3,4‐tetrahydroisoquinolines via a pictet‐spengler cyclisation

The synthesis of N‐methyl‐4‐pyridyl‐1,2,3,4‐tetrahydroisoquinolines (6a,b,c) was achieved via a Pictet‐Spengler cyclization of an activated amino group derivatized in a carbamate form. The obtained compounds have been designed as potential serotonin analogs.     

Analysis of flumequine and oxolinic acid in edible animal tissues by LC with fluorimetric detection

Summary A simple rapid method has been developed for the determination of flumequine and oxolinic acid in edible animal tissues. Analytes are extracted from the sample matrix using dichloromethane in neutral conditions, then back-extracted in 0.01 M sodium hydroxide and determined by reversed-phase liquid chromatography with fluorimetric detection. The method has been applied to pork, salmon and chicken muscle with recoveries higher than 77% in all matrices. The detection limits achieved (<1 μg kg⁻¹) allow the determination of these drugs at a residue level far below their MRL Moreover, some variables that may affect the spiking process have been studied.     

Separation of butyltin and phenyltin species by ion-exchange chromatography with complexing mobile phases

Summary Butyltin and phenyltin species have been separated by ion-exchange chromatography using silica-based and polymer-based columns. Mobile phases consisted of methanol-water mixtures containing polyfunctional carboxylic acids, which can act as complexing agents for organotin species. The best results were achieved with a system based on a methanol mobile phase containing malic and oxalic acids and a polymer-based column, which allowed the separation of tri- and diorganotin compounds and some resolution between monobutyltin and monophenyltin.