NMR imaging of fluid pathways during drainage of softwood in a pressure membrane chamber

An experiment was implemented to study fluid flow in a pressure media. This procedure successfully combines nuclear magnetic resonance imaging with a pressure membrane chamber in order to visualize the non-wetting and wetting fluid flows with controlled boundary conditions. A specially designed pressure membrane chamber, made of non-magnetic materials and able to withstand 4 MPa, was designed and built for this purpose. These two techniques were applied to the drainage of Douglas fir sapwood. In the study of the longitudinal flow, narrow drainage fingers are formed in the latewood zones. They follow the longitudinal direction of wood and spread throughout the sample length. These fingers then enlarge in the cross-section plane and coalesce until drainage reaches the whole latewood part. At the end of the experiments, when the drainage of liquid water in latewood is completed, just a few sites of percolation appear in earlywood zones. This difference is a result of the wood anatomical structure, where pits, the apertures that allow the sap to flow between wood cells, are more easily aspirated in earlywood than in latewood.     

A formal finite element approach for open boundaries in transport and diffusion ground-water problems

In the application of the finite element method to diffusion and convection-dispersion equations over a ground-water domain, the Galerkin technique was used to incorporate Neumann (or second-type) and Cauchy (or third-type) boundary conditions. While mass movement through open boundaries is a priori unknown, these boundaries are usually treated as a zero Neumann condition at some far distance from the domain of interest. Nevertheless, cheaper and better solutions can be obtained if these unknown conditions are adequately incorporated in the weak formulation and in the transient solution schemes (open boundary condition). Theoretical and numerical proofs are given of the equivalences between this approach and a ‘well-posed’ problem in a semi-infinite domain with a zero Neumann condition at a boundary placed at infinity. Transport and diffusion equations were applied in one dimension to show the numerical performances and limitations of this procedure for some linear and non-linear problems. No a priori limitations are foreseen in order to find similar solutions in two or three dimensions. Thus the spatial discretization in the proximity of open boundaries could be drastically reduced to the domain of interest.     

Arbres et dimension des ordres

Nous montrons que la dimension d'un ordre partiel est au plus égale à n si et seulement si cet ordre est isomorphe à l'inclusion sur une famille de sous-arbres d'un arbre àn sommets pendants. La dimension de deux classes voisines de treillis est établie.     

Configuration interaction study of H2 using a modified slater-type orbital

A non-standard 1s basis function, χ = (1 + ar²) exp(?ζr), is used to approximate the ground state of the hydrogen molecule in a configuration interaction framework and using numerical integration over MO's. Results are compared to the traditional 1s STO.     

Emission energies and photophysical properties of ladder oligo(p-aniline)s

Emission properties and the photophysics of three ladder oligo(p-aniline)s; namely 5,11-diethyl-6,12-dimethylindolo[3,2-b]carbazole (DIMER 2P), 14-ethyl-5,8-dihydro-diindolo[3,2-b:2′,3′-h]carbazole (TRIMER 2P), and 5,8,14-triethyl-diindolo[3,2-b:2′,3′-h]carbazole (TRIMER 3P) are presented. The optimization (relaxation) of the first singlet excited electronic state (S₁) has been done using the restricted configuration interaction (singles) (RCIS/6-31G*) approach. The excitation to the S₁ state does not cause important changes in the geometrical parameters of the compounds, as is experimentally corroborated by the small Stokes shifts. Emission energies from the relaxed excited states have been obtained from TDDFT calculations performed on the S₁ optimized geometries and have been correlated with the corresponding fluorescence spectra of the derivatives dissolved in dichloromethane. A good agreement has been found between TDDFT emission energies and the (0,0) fluorescence bands. As predicted from theoretical calculations, all compounds exhibit small Stokes shift, which testify the rigidity of these ladder compounds. Moreover, this theoretical approach provides a good evaluation of the bathochromic shifts caused by the increase in the conjugation length or by the presence of alkyl chains on the nitrogen atoms. Finally, the fluorescence quantum yield and lifetime of the compounds in dichloromethane have been obtained. From these data, the radiative and nonradiative rate constants of the deactivation of the S₁ state have been determined.     

Diastereoselective aldolization of alpha-aminonitriles. Diastereoselective synthesis of beta-amino alcohols and beta,gamma-diamino alcohols

Aldolization performed by addition of lithiated N-benzyl-N-tert-butylaminoacetonitrile to aldehydes provides diastereomerically pure anti-beta-hydroxy-alpha-aminonitriles. They are transformed into syn,anti-protected beta,gamma-diamino alcohols by a two-step procedure, involving addition of a Grignard reagent and reduction. The cleavage of the N-tert-butyl group is achieved by a simple acidic treatment. The application of this methodology to chiral, nonracemic aldehydes is studied. Starting from D-isopropylideneglyceraldehyde, an anti, anti, syn, anti-(2R,3S,4S,5R,6R)-diaminotriol is prepared in acceptable yield and with a good level of diastereoselectivity.     

Synthesis of diindolocarbazoles by Ullmann reaction: a rapid route to ladder oligo(p-aniline)s

[structure: see text] New and facile synthesis of symmetric diindolocarbazoles was developed using the copper-catalyzed Ullmann reaction. The key step is a double-intramolecular cyclization reaction realized on N-alkyl-3,6-dibromo-2,7-bis(2'aminophenyl)carbazole derivatives which offers the desired symmetric ladder oligo(p-aniline)s. Depending upon the nature of the side- and/or end-groups, well-defined thin films and/or semiladder polymers could be obtained. These electroactive ladder oligomers may have great potential in organic electronics.     

Determination of falintolol, a new aliphatic beta-adrenergic antagonist, in whole blood by gas chromatography with electron-capture detection: geometric isomers resolution

Falintolol oxalate, a new beta-adrenergic antagonist, is characterized by the presence of an oxime function and exists in a racemic form as a mixture of syn- and anti- isomers in a ratio of about 8:2. This article describes a selective gas chromatographic method for the resolution of the geometric isomers and the quantitation of the drug. The unchanged falintolol and internal standard, a related compound, are separated from blood by a solvent extraction under alkaline conditions, and then the drug is derivatized. The heptafluorobutyric derivatives are chromatographed on an SE-30 capillary quartz column and detected with a nickel-63 electron-capture detector. Because the syn- and anti- isomers of falintolol display comparable chromatographic responses, the sum of the two geometrical isomers is used for the quantitation of falintolol in blood. This method allows small serial blood samples in conscious rats, and 0.05 microgram of falintolol/0.1 mL of blood can be routinely determined. A calibration curve is prepared for the blood extracts. Linearity is observed in the study range (0.05 to 1 microgram/0.1 mL of blood). No interference by endogenous substances is observed. The procedure is applied successfully to drug absorption in rats when repeated oral doses are administered.