Base‐Stabilized Phosphinidene Boranes by Silylium‐Ion Abstraction

We report the preparation of N‐heterocyclic carbene (NHC)‐stabilized compounds containing P=B double bonds. The reaction of the highly functionalized phosphinoborane Mes*(SiMe₃)P?B(Cl)Cp* with Lewis bases allows access to base‐stabilized phosphinidene boranes Mes*P=B(L)Cp* (L=4‐dimethylaminopyridine (DMAP), NHC) by Me₃SiCl elimination. The formation of these species is shown to proceed through transient borylphosphide anions generated by Me₃Si abstraction.     

An anti‐diffusive volume of fluid method for interfacial fluid flows

A volume of fluid (VOF) method is developed combining a first‐order limited downwind scheme with higher order accurate schemes. The method is characterized by retaining a sharp fluid interface and a reduction in numerical diffusion near the interface, but avoids complicated geometrical reconstruction as occurs in most volume tracing algorithms. To demonstrate the accuracy and robustness of the method, a selection of numerical experiments are presented involving a pure advection problem, a water wave impact caused by a dam breaking and liquid sloshing in a partially filled tank. Copyright © 2011 John Wiley & Sons, Ltd.     

Complexation of gadolinium(III) ions on top of nanometre-sized magnetoliposomes

The complex of diethylenetriaminepentaacetate (DTPA) with the paramagnetic gadolinium ion [Gd(III)] is a well-known blood pool contrast agent for magnetic resonance imaging (MRI). To obtain MRI pictures from other anatomical structures, for instance from tissues containing cells with phagocytic activity, larger colloidal complexes have to be constructed. Therefore, in view of modifying the physiological behaviour, the DTPA chelate was first hydrophobized by covalently linking it to phosphatidylethanolamine (PE), and the resulting conjugate was then incorporated into nanometre-sized, sonicated phospholipid vesicles. Qualitative information on the affinity of the PE–DTPA derivative for Gd(III) ions was derived from competition experiments using the dye Arsenazo. Furthermore, it was found that only the membranotropic adducts residing in the outer shell of the vesicle bilayer are accessible to the lanthanide ion. The vesicular particulate was also used as a vehicle to transport PE–DTPA into the coating of so-called magnetoliposomes which consist of nanometre-sized iron oxide cores onto which a phospholipid bilayer is strongly chemisorbed. After loading the resulting structures with Gd(III), this new type of magnetoliposome may offer unique potentialities as a novel bi-label MRI contrast medium.     

Solvent-Free Condensation of Methyl Pyridinium and Quinolinium Salts with Aldehydes Catalyzed by DBU

Methylpyridinium and methylquinolinium salts were condensed under solvent-free conditions with aromatic aldehydes in the presence of 1,8-diazabicyclo[5.4.]undec-7-ene (DBU) as catalyst, by grinding at room temperature. The products are dyes or useful intermediates. The DBU can be easily recycled and reused.     

WATER UPTAKE INTO STRATUM CORNEUM; PARTITION BETWEEN LIPIDS AND PROTEINS

Water uptake in natural and reaggregated stratum corneum was determined by weight difference after storage in an atmosphere of controlled relative humidity.

Interlayer spacing in separated lipids as a function of their water content was determined by low-angle X-ray diffractometry. These values were used as a calibration curve to determine the water content of the lipid bilayers in reaggregated stratum corneum.

The results revealed different behavior of the lipid models compared to natural lipids of the stratum corneum. The additional water taken up after reaggregation of equilibrated lipids and proteins, was equally partitioned between the protein and the natural lipid fraction, while the models gave a proportionally higher water uptake into the lipids at high relative humidity. It is obvious that the models, so far, do not mimic all the properties of the natural stratum corneum lipids.     

Use of peat-based sorbents for removal of arsenic compounds

It is important to apply sorbent materials for purification of water from arsenic contamination due to serious arsenic pollution worldwide. We have developed new sorbents based on natural materials that provide a cheap and environmentally friendly alternative. For the first time, peat modified with iron compounds and iron humates were tested for sorption of arsenic compounds. The highest sorption capacity was found in peat modified with iron compounds. We have found that sorption of different arsenic speciation forms was strongly dependent on solution pH, reaction time and temperature. Calculations of the sorption process using thermodynamic parameters indicate the spontaneity of sorption process and its endothermic nature. Sorption kinetics showed that most arsenates are removed within 2 hours, and the kinetics of arsenate sorption on modified peat can be described by the pseudo-second order mechanism.      

N-Cyanoimides via the Cyanation of Imides

The conversion of cyclic imides to the corresponding N-cyanoimides has been carried out using cyanogen bromide as the nitrile source. This methodology provides a convenient route for the preparation of both aromatic and aliphatic N-cyanoimides.     

The effects of fluorescent probes on model membrane organization: photo-induced lipid sorting and soft structure formation

Liquid crystalline phase behaviour in model cell membranes prepared in-vitro has generated an enormous amount of interest in recent years and the phase diagrams of various bio-mimetic mixtures explored. Most recently photo-induced oxidation in fluorescently labelled membranes has been shown to influence these phase diagrams and can be used to generate interesting membrane-based geometries based on differences in membrane composition. In this article the different phases observed in model membranes will be discussed. Methods used to study these systems and recent developments in photo-stimulated phase changes are described along with areas for future investigation.