Intercalation of Toluidines into α-Zirconium Hydrogenphosphate

Intercalates of o-, m-, and p-toluidine into α-Zr(HPO₄)₂ · H₂O were prepared and characterized by powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. As follows from IR, toludine molecules are protonated in the interlayer space. Toluidine molecules are arranged in a bimolecular way in the intercalates containing more than 1.5 toluidine molecules per Zr atom. On the other hand, a monolayer of the toluidine molecules is supposed in the intercalates with less than one toluidine molecule per Zr atom.     

Absolute Asymmetric Synthesis: The Origin, Control, and Amplification of Chirality

Biomolecular homochirality, the origin of which is still a puzzle, has challenged scientists to design chemical systems that provide chiral molecules through absolute asymmetric synthesis and to amplify a small stereochemical bias in such systems. The photoresolution of the enantiomers of helical-shaped, sterically overcrowded alkene 1 with circularly polarized light and the transduction of the stereochemical information by triggering the helical arrangement of a large collection of achiral molecules in a twisted nematic liquid crystalline phase (2) are examples of control and amplification of chirality.     

Polymers from intermediates obtained from hydrogen cyanide

The recent demonstration of an easy synthesis of diiminosuccinonitrile (DISN) from hydrogen cyanide and cyanogen, the reduction of DISN to diaminomaleonitrile (DAMN), and the use of these compounds to form difunctional heterocycles has made several new polyamide intermediates accessible. The 1- and 2-methyl-1,2,3-triazole-4,5-dicarbonyl chlorides have been polymerized interfacially to form high-melting polyamides of good heat stability. Interfacial polymerization of 1-methylimidazole-4,5-dicarbonyl chloride and trans-2,5-dimethylpiperazine has given a polyamide that is water-soluble. The 2,6- and 2,3-pyrazinedicarbonyl chlorides have been similarly converted to high-melting polyamides. 2,6-Dicyano-3,5-dipiperazinylpyrazine has been prepared from tetracyanopyrazine and piperazine and reacted with toluene diisocyanate to form a strong, stiff polyurea. Polyamides were also made from 2,3-diaminoquinoxaline, 1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarbonitrile, and DAMN.     

Static wetting on flexible substrates: a finite element formulation

In static wetting on an elastic substrate, force exerted by the liquid–vapour surface tension on a solid surface deforms the substrate, producing a capillary ridge along the contact line. This paper presents a finite element formulation for predicting elastic deformation, close to the static wetting line (with angle of contact=90o and σSV=σSL).The substrate deformation is modelled with the Mooney–Rivlin constitutive law for incompressible rubber‐like solids. At the contact line, a stress singularity is known to arise, due to the surface tension acting on a line of infinitesimal thickness. To relive the stress singularity, either (i) the surface tension is applied over a finite contact region (of macroscopic thickness), or (ii) the solid crease angle is fixed. These two options suggest that normal component of Neumann's triangle law of forces, for the three surface tensions, is not applicable for elastic substrates (as for rigid ones). The vertical displacement of the contact line is a strong function of liquid/vapour surface tension and shear modulus of the solid. Copyright 2004 John Wiley & Sons, Ltd.     

Standardization for oxygen isotope ratio measurement - still an unsolved problem

Numerous organic and inorganic laboratory standards were gathered from nine European and North American laboratories and were analyzed for their delta(18)O values with a new on-line high temperature pyrolysis system that was calibrated using Vienna standard mean ocean water (VSMOW) and standard light Antartic precipitation (SLAP) internationally distributed reference water samples. Especially for organic materials, discrepancies between reported and measured values were high, ranging up to 2 per thousand. The reasons for these discrepancies are discussed and the need for an exact and reliable calibration of existing reference materials, as well as for the establishment of additional organic and inorganic reference materials is stressed. Copyright 1999 John Wiley & Sons, Ltd.     

Ab initio calculations of the photoionization of diatomic molecules

A review is presented of the calculation of photoionization spectra, particularly in the spectral range where electron autoionization of diatomic molecules takes place. In addition to some interesting results obtained over years that compare favourably with experiment, the emphasis here is put on the relation between the methods developed for the calculation of observables associated with the continuum energy spectrum of the electrons and the Alchemy system of programs. This system of programs serves as a basis for initial and intermediate calculations. The examples presented show that diatomic molecules not only in gas phase but also oriented in space or physisorbed at surfaces may be studied readily.     

Diffusion in multi-component polymeric systems: Diffusion of non-volatile species in thin films

Polymeric films for high-tech products like LCD-panels, transdermal patches or medical test strips typically consist of a polymer and one or more non-volatile additives. If during the production process a multi-component solution is coated and subsequently dried, the diffusion of solvents and non-volatile species in the polymeric systems plays an important role. Recent experiments revealed that the drying conditions can have a significant influence on the formation of inhomogeneous distribution of the non-volatile components in the final foil and therefore affects desired product properties. The distribution of the non-volatile components in the final film has an important impact on the physical and chemical properties, including mechanical and optical properties, wetting behavior or drug release rates i.e. the product quality of the polymeric system. To be able to describe the diffusion of non-volatile species in a multi-component polymeric system during drying correctly, reliable information about the influence of the solvent concentration on the mobility of the additive are essential. To obtain information about the mobility of the additive in the polymeric solution new experiments were performed and observed by means of Inverse-Micro-Raman-Spectroscopy (IMRS). By fitting simulated concentration profiles to the experimental data, the temperature and concentration dependent diffusion coefficient of the non-volatile additive in the polymer solution was determined. The investigations are part of a bilateral funding of NFG in the US and DFG in Germany. Diffusion of volatile species in multicomponent polymeric systems are investigated by the group of Richard Cairncross.     

A finite element method for free surface flows of incompressible fluids in three dimensions. Part II. Dynamic wetting lines

To date, few researchers have solved three‐dimensional free surface problems with dynamic wetting lines. This paper extends the free surface finite element method (FEM) described in a companion paper [Cairncross RA, Schunk PR, Baer TA, Sackinger PA, Rao RR. A finite element method for free surface flows of incompressible fluid in three dimensions. Part I. Boundary fitted mesh motion. International Journal for Numerical Methods in Fluids 2000; 33 : 375–403] to handle dynamic wetting. A generalization of the technique used in two‐dimensional modeling to circumvent double‐valued velocities at the wetting line, the so‐called kinematic paradox, is presented for a wetting line in three dimensions. This approach requires the fluid velocity normal to the contact line to be zero, the fluid velocity tangent to the contact line to be equal to the tangential component of web velocity, and the fluid velocity into the web to be zero. In addition, slip is allowed in a narrow strip along the substrate surface near the dynamic contact line. For realistic wetting line motion, a contact angle that varies with wetting speed is required because contact lines in three dimensions typically advance or recede at different rates depending upon location and/or have both advancing and receding portions. The theory is applied to capillary rise of static fluid in a corner, the initial motion of a Newtonian droplet down an inclined plane, and extrusion of a Newtonian fluid from a nozzle onto a moving substrate. The extrusion results are compared with experimental visualization. Copyright © 2000 John Wiley & Sons, Ltd.