Holographic construction of open structure,dispersion transmission gratings

A method of fabricating free-standing transmission gratings with line densities of the order of 1000 $\text{e}$/nm is described. The technique involves a combination of two well-known procedures: application of photoresist and electroplating for the production of fine metal grids, and holographic (interferographic) manufacturing of dispersion gratings. Results of preliminary tests are mentioned.     

k-dimensional skeletoids in Rn and the Hilbert cube

In their paper on pseudo-boundaries and pseudo-interiors R. Geoghegan and R.R. Summerhill construct k-dimensional pseudo-boundaries in $\text{R}$ⁿ, where they used West's notion of a pseudo-boundary, rather than Toruńczyk's. In this paper we construct pseudo-boundaries in the sense of Toruńczyk (skeletoids) in $\text{R}$ⁿ and use this result to find k-dimensional skeletoids in the Hilbert cube.     

SCS-pincer palladium-catalyzed auto-tandem catalysis using dendritic catalysts in semi-permeable compartments

Novel monometallic and dendritic SCS-pincer palladium complexes 2, 3 and 4 have been synthesized in good yields (60-89%) and high purity (palladium loading >97%). These complexes were successfully used as catalysts in the stannylation of cinnamyl chloride with hexamethylditin and in the catalytic auto-tandem reaction consisting of this stannylation followed by an electrophilic addition with 4-nitrobenzaldehyde, showing similar reaction rates and selectivities for all complexes. Dendritic complex 4 has furthermore been used in the compartmentalized catalysis of single and auto-tandem reactions, allowing catalyst reuse for four consecutive runs.     

On the rapid evaluation of cofactors in the calculation of nonorthogonal matrix elements

The calculation of matrix elements involving nonorthogonal orbitals is speeded up by recognizing the orthogonalities between orbitals, leading to generalized Slater rules. The block structure present in the overlap matrix makes an efficient evaluation of its cofactors possible. These cofactors are calculated per subblock, each with its own parity sign. An adjustment parity sign has to be evaluated, which is added to the combined local signs, to give the correct total sign for the matrix element. An algorithm for the evaluation of this adjustment sign has been developed, making an easy and correct evaluation possible. The current scheme is shown to be very efficient, but possibilities for further improvement remain. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 77–83, 1998     

A morphological study of membranes obtained from the systems polylactide-dioxane-methanol,polylactide-dioxane-water and polylactide-N-methyl pyrrolidone-water

The influence of liquid–liquid demixing, solid–liquid demixing, and vitrification on the membrane morphologies obtained from several polylactide-solvent-nonsolvent systems has been investigated. The polymers investigated were the semicrystalline poly-L-lactide (PLLA) and the amorphous poly-DL-lactide (PDLLA). The solvent-nonsolvent systems used were dioxane-water, N-methyl pyrrolidone-water and dioxane-methanol. For each of these systems it was attempted to relate the membrane morphology to the ternary phase diagram at 25°C. It was demonstrated that for the amorphous poly-DL-lactide the intersection of a glass transition and a liquid–liquid miscibility gap in the phase diagram was a prerequisite for the formation of stable membrane structures. For the semicrystalline PLLA a wide variety of morphologies could be obtained ranging from cellular to spherulitical structures. For membrane-forming combinations that show delayed demixing, trends expected on the basis of phase diagrams were in reasonable agreement with the observed membrane morphologies. Only for the rapidly precipitating system PLLA-N-methyl pyrrolidone-water were structures due to liquid–liquid demixing obtained when structures due to solid–liquid demixing were expected. Probably, rapid precipitation conditions promote solid–liquid demixing over liquid–liquid demixing, because the activation energy necessary for liquid–liquid demixing is lower than that for crystallization. © 1996 John Wiley & Sons, Inc.     

Phase behavior of polylactides in solvent–nonsolvent mixtures

Isothermal phase diagrams for the semicrystalline poly-L-lactide (PLLA) and the amorphous poly-DL-lactide (PDLLA) in combination with several solvent–nonsolvent combinations (dioxane/water, dioxane/methanol, chloroform/methanol, and NMP/water) have been determined. The locations of the liquid–liquid miscibility gap, the solid–liquid miscibility gap and the vitrification boundary in the isothermal phase diagrams at 25°C were identified. The liquid–liquid miscibility gap for the systems with PLLA was located in the same composition range as the corresponding systems with PDLLA. For the systems containing PLLA solid–liquid demixing was thermodynamically preferred over liquid–liquid demixing. Attempts were made to correlate the experimental findings with predictions on the basis of the Flory-Huggins theory for ternary solutions using interaction parameters derived from independent experiments. Qualitative agreement was found between the theoretical predictions and the experimentally obtained liquid–liquid miscibility gap. No good agreement was found for the solid–liquid miscibility gap. © 1996 John Wiley & Sons, Inc.     

Crosslinking of porcine aortic leaflets with butane‐1,4‐diol diglycidyl ether

Currently, efforts are being made to reduce xenograft calcification and to optimize biomechanical properties by applying different crosslinking methods and techniques. Porcine aortic leaflets could be stabilized with a bisepoxy compound, butane‐1,4‐diol diglycidyl ether (BDDGE), under acidic (pH 4.5) or alkaline conditions (pH > 8.5). Maximum values of the shrinkage temperature (83°C), which are comparable to glutaraldehyde‐crosslinked materials, are achieved at pH 9.0 and 10.0 within 48 h with a BDDGE concentration of 4 wt6percnt;. The crosslinking efficacy decreased at higher pH values or at prolonged reaction times due to a higher proportion of one‐side or masking reactions. Crosslinking of aortic leaflets at pH 4.5, which consisted in a reaction between the epoxide groups of BDDGE and the carboxylic acid groups of the tissue, afforded crosslinked material with a shrinkage temperature of 76°C after 7 days of reaction.