Remote sample characterization based on fluorescence monitoring

The possibilities and limitations of remote sample characterization using induced fluorescence are discussed. General equations for remote sensing of fluorescence are presented and discussed. The implications of different elements of a system for remote fluorescence sensing on different parameters of the equations are treated. Background light influence and signal processing are considered. Pulsed lasers, flashlamps and cw lamps as excitation sources are compared when matched to the proper detection scheme employing boxcar integration or lock-in detection. Model experiments have been performed to demonstrate different measurement strategies. Examples from remote oil-slick characterization are chosen as illustrations.     

A recyclable bifunctional acid-base organocatalyst with ionic liquid character. The role of site separation and spatial configuration on different condensation reactions

A series of bifunctional organic catalysts containing acid and basic sites with ionic liquid characteristics have been prepared and their catalytic activity and reaction coordinate for aldol and Knoevenagel condensations have been compared. While the only factor controlling catalyst activity for the Knoevenagel condensation was the distance between the acid and base sites, the spatial orientation of the organocatalyst is also key to achieve high activity and selectivity in the Claisen-Schmidt condensation. Mechanistic studies based on theoretical DFT calculations show that the acid-base bifunctional organocatalyst follows a mechanism inspired in natural aldolases for the synthesis of trans-chalcones, being able to produce a large variety of these compounds of industrial interest. The combination of the acid-base pairs within the proper geometry and the ionic liquid nature makes this catalyst active, selective and recyclable.     

Determination of nanostructure of liposomes containing two model drugs by X‐ray scattering from a synchrotron source

Small‐angle X‐ray scattering has been employed to study how the introduction of paracetamol and acetylsalicylic acid into a liposome bilayer system affects the system's nanostructure. An X‐ray scattering model, developed for multilamellar liposome systems [Pabst et al. (2000), Phys. Rev. E, 62 , 4000–4009], has been used to fit the experimental data and to extract information on how structural parameters, such as the number and thickness of the bilayers of the liposomes, thickness of the water layer in between the bilayers, size and volume of the head and tail groups, are affected by the drugs and their concentration. Even though the experimental data reveal a complicated picture of the drug–bilayer interaction, they clearly show a correlation between nanostructure, drug and concentration in some aspects. The localization of the drugs in the bilayers is discussed.     

Zur reaktion von organophosphinen mit chalkogenen und ithalogenen: Rasche übertragung von tellur und jod zwischen phosphinen

Nucleophilic attack of tertiary phosphines at tellurium in R₃PTe and at iodine in R₃PI⁺ is indicated by rapid Te (or I⁺) transfer reactions in the systems R₃PTe PR₃ and R₃PI⁺/PR₃ (R = (CH₃)₃C, (CH₃)₂N). Linear intermediates of the type R₃PYPR3 (Y = Te, I⁺) are proposed.