Some asymptotic bijections

The notion of an asymptotic bijection is introduced and used to give bijective proofs of infinite summation formulas for set partitions (Dobinski's formula) and involutions.     

Heats of formation of organic molecules by Ab Initio calculations: Carboxylic acids and esters

A bond and group equivalent scheme that allows the calculation of heats of formation for carboxylic acids and esters from ab initio 6-31G* energies has been developed. For a group of 16 compounds, the rms error for the calculated heats of formation was 0.64 kcal/mol. Heats of formation have been predicted for an additional seven compounds for which the experimental values are either unknown or suspect. © 1992 by John Wiley & Sons, Inc.     

Influence of resonant helical windings on the mirnov oscillations in a small tokamak

Summary The influence of resonant helical perturbations on the plasma confined by the small tokamak TBR-1 was experimentally investigated. Strong attenuations of the Mirnov oscillations could be easily obtained by activating different resonant helical windings. The amplitudes of these oscillations were restored as the helical perturbation ended. Partially supported by CNPq.     

Morphological and Thermal Properties of Vesicular Phospholipid Gels Studied by DSC,Rheometry and Electron Microscopy

Semisolid phospholipid preparations have been well known for several years and are still investigated as drug carrier systems, e.g. for potential cancer therapy. They may be applied parenterally as semisolid vesicular phospholipid gels suitable as implants for sustained drug release or as liposomal preparations after redisperging the stable storage form. Due to enhanced stability, mixtures of hydrated phospholipids and cholesterol are more suitable than natural unsaturated phospholipids. In order to describe characteristics of vesicular phospholipid gels, only a few techniques may be useful. Especially the structure of the semisolid preparation is not yet completely understood. We tried to get some more information about these systems by using a combination of freeze-fracture electron microscopy, differential scanning calorimetry and rheometry to elucidate, on the one hand, the inner structure or homogeneity and, on the other, the thermotropic phase transition of the three-dimensional lipid network and the temperature dependency of the fluidity/viscosity of the samples. Using freeze-fracture electron microscopy we found coexisting phospholipid domains of lamellar sheets and vesicular structures. With the help of differential scanning calorimetry the reasons for the different phase behaviour were elucidated. Rheometric measurements show increased intermediate viscosity at the thermotropic phase transition of the lipid bilayers, possibly induced by interacting membrane defects. This revised version was published online in August 2006 with corrections to the Cover Date.     

On-line monitoring of polymer deposition for tailoring the waveguide characteristics of love-wave biosensors

The Love-wave sensor is an acoustic sensing device which is particularly suitable for sensing in a liquid environment. The superior characteristics of the device are achieved by the use of an acoustic waveguide, consisting of a thin layer deposited on the surface of the substrate material. The exact thickness and material properties of the layer will not only determine sensitivity and sensing performance of the resulting device but can also be adjusted to generate higher-order Love modes. Thus, to obtain a sensing device with the desired specifications, precise control over the process of waveguide deposition is required. This has been realized by implementation of a vapor deposition polymerization system where the transmission curve (amplitude vs frequency) of one of the sensing devices is continuously monitored during deposition. As soon as the desired device specifications are reached, the deposition can be interrupted immediately. From the recorded transmission curves, information about the sensitivity of the device can be deduced, and the formation of higher-order Love modes can be visualized. The system has been used to produce biosensors based on various Love modes. It is shown that sensors operated on higher-order Love modes have a high mass sensitivity which, together with their excellent shielding properties, makes them advantageous for biosensing in conducting buffer solutions.     

Synthesis,X-ray crystal structure determination and antiinflammatory activity of the regioisomers: 5-phenyl-6-(4-pyridyl)-2,3-dihydroimidazo[2,1-b]thiazole and 6-phenyl-5-(4-pyridyl)-2,3-dihydroimidazo[2,1-b]thiazole. A structural reassignment

A regiospecific synthesis of 6-phenyl-5-(4-pyridyl)-2,3-dihydroimidazo[2,1-b]thiazole ( 2 ) was accomplished by treatment of 6-phenyl-2,3-dihydroimidazo[2,1-b]thiazole ( 10 ) with the reactive complex of pyridine and ethyl chloroformate followed by oxidation with chromium(VI) oxide. Reaction of 4-phenyl-5-(4-pyridyl)imidazole-2-thione ( 12 ) with 1,2-dibromoethane in the presence of base also gave 2 together with its regioisomer 3 . The structures of 2 and 3 were confirmed by X-ray crystallography. Evaluation, on oral administration, in a one hour arachidonic acid-induced mouse ear inflammation assay, showed the inhibition of edema by 2 (48%) and 3 (34%) to be less than that of the 6-(4-fluorophenyl) analog 1 (SK&/F 86002) (69%), a known antiinflammatory agent.