Computational fractal geometry with WFA

We define two measures of “fractalness” of gray-tone images: the degree of self-similarity and the gray-tone fractal dimension as a generalization of Minkovski dimension of compact sets. We show how to compute both these measures from the WFA-representation of a gray-tone image. Since we have developed a WFA-inference algorithm which computes a good approximation of any gray-tone image we can compute a close approximation of both our measures of fractalness for any gray-tone image. Received: 15 November 1994 / 6 October 1995     

Novel luminescent samarium(III) chelates

A series of new stable, luminescent samarium(III) chelates were synthesized and their photophysical properties were measured. The iodoacetamido activated chelate coupled to a peptide was used in a caspase-3 assay.     

Serious storytelling – a first definition and review

Multimedia Tools and Applications - In human culture, storytelling is a long-established tradition. The reasons people tell stories are manifold: to entertain, to transfer knowledge between...     

Flavonoids and other phenolic compounds in Andean indigenous grains: Quinoa (Chenopodium quinoa), kañiwa (Chenopodium pallidicaule) and kiwicha (Amaranthus caudatus)

The amount of phenolic acids, flavonoids and betalains in Andean indigenous grains, quinoa (Chenopodium quinoa), kañiwa (Chenopodium pallidicaule) and kiwicha (Amaranthus caudatus), was determined. The total amount of phenolic acids varied from 16.8 to 59.7 mg/100 g and the proportion of soluble phenolic acids varied from 7% to 61%. The phenolic acid content in Andean crops was low compared with common cereals like wheat and rye, but was similar to levels found in oat, barley, corn and rice. The flavonoid content of quinoa and kañiwa was exceptionally high, varying from 36.2 to 144.3 mg/100 g. Kiwicha did not contain quantifiable amounts of these compounds. Only one variety of kiwicha contained low amounts of betalains. These compounds were not detected in kañiwa or quinoa. Our study demonstrates that Andean indigenous crops have excellent potential as sources of health-promoting bioactive compounds such as flavonoids.     

Molecular dynamics studies on the thermostability of family 11 xylanases

Twelve members of the family 11 xylanases, including both mesophilic and thermophilic proteins, were studied using molecular dynamics (MD). Simulations of xylanases were carried out in an explicit water environment at four different temperatures, 300, 400, 500 and 600 K. A difference in thermotolerance between mesophilic and thermophilic xylanases became clear: thermophilic xylanases endured heat in higher simulation temperatures better than mesophilic ones. The unfolding pathways seemed to be similar for all simulations regardless of the protein. The unfolding initiates at the N-terminal region or alternatively from the alpha-helix region and proceeds to the 'finger region'. Unfolding of these regions led to denaturated structures within the 4.5 ns simulation at 600 K. The results are in agreement with experimental mutant studies. The results show clearly that the stability of the protein is not evenly distributed over the whole structure. The MD analysis suggests regions in the protein structure which are more unstable and thus potential targets for mutation experiments to improve thermostability.     

Block and Graft Copolymers of Poly(ethylene glycol) and Poly(dimethylsiloxane) for Blood Contacting Biomedical Materials Applications

The incorporation of both hydrophobic and hydrophilic groups into a synthetic polymer is a potent way of controlling its surface and interfacial properties. With this end result in mind, we describe herein the synthesis and characterization of poly(dimethylsiloxane-b-ethyleneoxide) block copolymers (PDMS-b-PEO) and poly(dimethylsiloxane-g-ethyleneoxide) grafted copolymers (PDMS-g-PEO). These amphiphillic copolymers were also investigated as surface modifying agents for passifying hydrophobic polymer surfaces in blood contacting applications. Specifically, the various (PDMS-b-PEO) and (PDMS-g-PEO) copolymers were coated onto poly(styrene-divinylbenzene) microspheres by their physical adsorption from solution. These surfaces were then evaluated for blood contacting applications utilizing a fibrinogen and thrombin protocol. In particular, the binding of fibrinogen and the functionality of the surface bound fibrinogen on an otherwise hydrophobic surface (polystyrene) was investigated. As the conversion of fibrinogen to fibrin is facilitated by thrombin, the aggregation of the copolymer-coated hydrophobic microspheres was followed using an optical method after the sequential exposure of the microspheres to fibrinogen and then to thrombin. We were able to determine how the adsorbed copolymers affected the functionality of the bound fibrinogen at an interface. Our hypothesis is that the hydrophobic siloxane units of the copolymers will be in close proximity to the polystyrene surface and that the PEO will extend out from the surface and therefore render the synthetic polymer system hemocompatible. Following the fibrinogen and thrombin protocol and determining the fibrinogen-dependent aggregation, the results show that the PDMS-b-PEO copolymers (having a PEO content from 4.6 to 11.5 weight %) were similar in terms of particle aggregation when compared to the pure polystyrene microspheres (blank) or to the microspheres that were coated with a linear PDMS homopolymer. By comparison, the PDMS-g-PEO copolymers (having a PEO content from 58 to 80 weight %) were seen to reduce the fibrinogen functionality on the microsphere system surface. Thus the data indicate that the PDMS-g-PEO copolymers can behave like molecular brushes that are able to pacify the surface of the hydrophobic polystyrene microspheres. A somewhat unexpected observation was that for the copolymer system having a low PEO content the fibrinogen-dependent aggregation of the otherwise hydrophobic microspheres was observed to increase relative to the pure microspheres (blank). It is clear from the findings of this investigation that the surface packing and molecular orientation of both the adsorbed copolymer and also of the fibrinogen are important factors that govern the properties and applications of blood contacting biomaterials.     

Compressibility of porous TiO2 nanoparticle coating on paperboard

Compressibility of liquid flame spray-deposited porous TiO₂ nanoparticle coating was studied on paperboard samples using a traditional calendering technique in which the paperboard is compressed between a metal and polymer roll. Surface superhydrophobicity is lost due to a smoothening effect when the number of successive calendering cycles is increased. Field emission scanning electron microscope surface and cross‒sectional images support the atomic force microscope roughness analysis that shows a significant compressibility of the deposited TiO₂ nanoparticle coating with decrease in the surface roughness and nanoscale porosity under external pressure.

PACS

61.46.-w; 68.08.Bc; 81.07.-b     

Controlled gas‐phase preparation and HDS activity of Re2(CO)10alumina catalysts

Re/Al₂O₃ catalysts were prepared from a carbonyl precursor by controlled gas‐phase deposition with all conditions accurately monitored by a computer‐programmed CVD reactor. The catalysts were made in an inert atmosphere. Growth of the rhenium concentration was studied with different preparation procedures and with different times and temperatures of deposition. Rhenium loading of the catalysts varied between 0.3 and 12.8 wt%. The activity of the catalysts was tested in thiophene hydrodesulfurization reaction and the results suggest good activity in low rhenium loading. The portion of n‐butane among the reaction products was high for the catalysts with high rhenium content. This revised version was published online in July 2006 with corrections to the Cover Date.