Sodium diffusion through amorphous silica surfaces: a molecular dynamics study

We have studied the diffusion inside the silica network of sodium atoms initially located outside the surfaces of an amorphous silica film. We have focused our attention on structural and dynamical quantities, and we have found that the local environment of the sodium atoms is close to the local environment of the sodium atoms inside bulk sodo-silicate glasses obtained by quench. This is in agreement with recent experimental results.     

The Mitsunobu Inversion Reaction of Sterically Hindered 17-Hydroxy Steroids

The Mitsunobu inversion reaction of 3-methoxyestra-1,3,5(10)-trien-17-ol is dramatically influenced by the acidic component. There appears to be a relationship between the dissociation constant of the electron-withdrawing substituent on the aryl acid and the overall effectiveness of the reaction, with more acidic species generally providing a higher yield of inverted product.     

Antibakterielle wirkstoffe. VIII . Die aminomethinylierung in der reihe der aminothiazole

The three-component reaction comprising the interaction of 2-amino-4-antipyrinyl-5-ethylthiazole (1) with s-triazine (2) and pyrrolidine leads to 4-anitpyrinyl-5-ethyl-2-[(4-pyrrolidinyl)methyleneamino]thiazole (5). Structure 5 is supported by ¹H- and ¹³C-NMR spectroscopy.     

On triazoles. VII Synthesis of novel tri- and tetracyclic ring systems

The ring-closure of the 5-amino-1-(2-aminophenyl)-3-methylthio-1H-1,2,4-triazole derivatives 3 and 4 with different simple and cyclic C₁ components lead to the formation of 1,2,4-triazolo[1,5-α]-1,3,5-benzotriazepines 5–6 , their 4,5-dihydro- 7 , different 5-spiro-homocyclic- 8–13 , and 5-spiro-heterocyclic- 14-15 analogues. The structure of the compounds obtained was proved with the use of their ir, uv, ¹H-nmr and ¹³C-nmr spectra.     

Chemical modification of the surface of a sulfonated membrane by formation of a sulfonamide bond

This paper describes a novel approach for the surface modification of a cation-exchange membrane, bearing sulfonate groups, by a cationic layer. The modification procedure involved the chlorosulfonation of the sulfonate groups of the base membrane with thionyl chloride, followed by a reaction with a diamine to yield a sulfonamide bond and a terminal amine. The latter could be quaternized by reaction with methyl iodide or protonated by soaking in acidic media. The membranes were characterized in detail by attenuated total reflectance Fourier transform infrared and X-ray photoelectron spectroscopies as well as elemental analysis to confirm that the above reactions occurred. The selectivity of these membranes toward the electrochemically assisted transport of protons versus Zn2+ metallic cations was determined during an electrodialysis in a two-compartment electrochemical cell. The data indicate a significant decrease of the transport of the metallic cations following modification of the membrane with the cationic layer. The later allows for the transport of protons from the catholyte to the anolyte compartment with much improved selectivity since the divalent cations are excluded from the membrane due to the electrostatic barrier of the cationic layer.     

Vitamin D: a concise synthesis of the C19 hydroxylated enyne A-ring, an interesting precursor for the preparation of C19 substituted vitamin D analogues

A new C₁₉ hydroxylated enyne 15, as potential A-ring building block of vitamin D analogues, was synthesized in enantiomerically pure form in nine steps from (−)-(S)-limonene. This short synthesis involved ozonolyzis of 1,2-limonene oxide followed by a Criegee rearrangement, epoxide trans diaxial ring opening by lithium acetylide, elimination, epoxidation and syn β-elimination of the resulting homopropargylic oxirane.     

Radionuclides in a sediment trap and bottom sediment samples from the eastern Turkish coast of the Black Sea

Summary Radionuclide (¹³⁷Cs, ²³⁸U, ²³²Th and ⁴⁰K) concentrations were determined in a sediment trap and bottom sediment samples collected from a station at the eastern Turkish coast of the Black Sea. The specific activity of the ¹³⁷Cs radionuclide in the settling particles ranged from 0.04±0.01 to 0.10±0.02 Bq^. g^-1dry weight. The calculated flux rate of the ¹³⁷Cs was between 0.37 and 2.59 Bq^. m^-2. d^-1in the sampling periods of 2002 and 2003. The ¹³⁷Cs concentration in the bottom sediment profile were between 0.039±0.013-9.083±0.017 Bq^. g^-1dry weight in the same station. The vertical profile of the radionuclides suggests that they have little mobility during the 17 years after the Chernobyl accident.     

Saturated heterocycles, 162 [1]. synthesis and steric structures of 3,4-disubstituted 1,6,7,11b-tetrahydropyrimido[6,1-a]isoquinolin-2-ones

The reaction of 1-(hydrazidomethyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline 3 with aromatic aldehydes yield hydrazones 4a,b or pyrimido[6,1-a]isoquinolines 5a-c depending upon the proportions of the reagents. With ketones, 3 gives only hydrazones 4a-d and 7 , which can be transformed to pyrimidoisoquinolines 10a-e and 11 with aldehydes. The ring closures are stereospecific; the relative configurations were determined by DNOE measurements.     

Gravity-induced convective flow in microfluidic systems: electrochemical characterization and application to enzyme-linked immunosorbent assay tests

A way of using gravity flow to induce a linear convection within a microfluidic system is presented. It is shown and mathematically supported that tilting a 1 cm long covered microchannel is enough to generate flow rates up to 1000 nL.min(-1), which represents a linear velocity of 2.4 mm.s(-1). This paper also presents a method to monitor the microfluidic events occurring in a covered microchannel when a difference of pressure is applied to force a solution to flow in said covered microchannel, thanks to electrodes inserted in the microfluidic device. Gravity-induced flow monitored electrochemically is applied to the performance of a parallel-microchannel enzyme-linked immunosorbent assay (ELISA) of the thyroid-stimulating hormone (TSH) with electrochemical detection. A simple method for generating and monitoring fluid flows is described, which can, for instance, be used for controlling parallel assays in microsystems.