Mechanochemical Treatment of CaC03 for Reducing Hyprophylicity

The article discusses the modification of CaCO₃ hydrophylicity by mechanochemical methods, in view of its compatibilization with hydrophobic polymeric matrices. The observation was made that by ultrahigh-speed stirring of the solutions of polybutadiene and acrylic acid—in which CaCO₃ powder has been suspended—as well as by vibratory milling of CaCO₃ in the presence of isoprene, modifications in the hydrophylicity of the anorganic particles occur. The treatment's efficiency depends on two process parameters: duration and monomer/charge ratio.     

Grid-Computing — Science oder Fiction?

Ohne Zusammenfassung     

Trisodium trimetaphosphate crosslinked xanthan networks: synthesis,swelling, loading and releasing behaviour

Xanthan (Xan) is a biocompatible and biodegradable polysaccharide with a promising potential as substrate for controlled drug delivery applications. Xan based hydrogels were synthesized in alkaline medium using trisodium trimetaphosphate (STMP) as crosslinking agent. Hydrogels with various crosslinking agent/polymer ratios were synthesized and subsequently characterized by the means of elemental analysis and dynamic swelling degree, model compound loading and releasing behaviour. Two physical parameters (crosslinking density and phosphate charge) are manifesting antagonistic actions by stiffening or disrupting the three-dimensional macromolecular ensemble. The highest swelling degree was obtained using an intermediate STMP:Xan ratio in which case the opposing effects of the two forces are well balanced. The synthesized networks are pH sensitive. In acid and alkaline media the swelling degrees are lower by comparison to neutral pH. The entrapping and releasing behaviour of the newly synthesized xanthan networks were studied using methylene blue as a cationic model molecule. The releasing kinetics present a first-order model.     

In vitro and in vivo behavior of ketoprofen intercalated into layered double hydroxides

Ketoprofen (Ket) was intercalated into layered double hydroxides (ZnAlLDH and MgAlLDH) using the ionic exchange method. The drug intercalation was confirmed by X-ray diffraction (XRD) and FTIR spectroscopy. Ket release from the inorganic matrix was studied at pH 7.4 in continuous regime with a flow rate of 0.5 and respectively 1.0 ml/min. The kinetical data were interpreted using the Ritger and Peppas model. The data prove that the release kinetics and mechanism depend on the eluent flow rate. Quantification of gastric tolerance shows that the ulcerogenic effect of the intercalated drug is lower than the one of the raw Ket. The antinociceptive effect of both formulations was studied by the hot-plate method performed on mice. The MgAlLDH_Ket formulation shows a tendency towards a stronger antinociceptive effect than its ZnAlLDH_Ket counterpart during the 210 min recorded period.     

Microstructural and compositional evolution of compound layers during gaseous nitrocarburizing

Compound layers developed at 848 K during gaseous nitrocarburizing of iron and iron-carbon specimens were investigated for several combinations of N and C activities imposed at the specimen surface by gas mixtures of NH₃, N₂, CO₂, and CO. The microstructural evolution of the compound layer was studied by light microscopy and by X-ray diffraction analysis. Composition-depth profiles were determined by electron probe (X-ray) microanalysis. Layer growth kinetics was investigated by layer thickness measurements. The influence of the N and C activities on the microstructural and compositional evolution and the growth kinetics of the compound layers formed is discussed for the iron substrate. The results indicate that the microstructure is governed by a fast C and a slow N absorption at the surface in an early stage of gaseous nitrocarburizing. The influence of carbon in the substrate on the microstructural and compositional evolutions and on the growth kinetics was evaluated from comparing the results obtained for a normalized Fe-0.8C alloy with those for iron under identical nitrocarburizing conditions. An erratum to this article is available at .     

Simultaneous scheduling and location (ScheLoc): the planar ScheLoc makespan problem

While in classical scheduling theory the locations of machines are assumed to be fixed we will show how to tackle location and scheduling problems simultaneously. Obviously, this integrated approach enhances the modeling power of scheduling for various real-life problems. In this paper, we introduce in an exemplary way theory and three polynomial solution algorithms for the planar ScheLoc makespan problem, which includes a specific type of a scheduling and a rather general, planar location problem, respectively. Finally, a report on numerical tests as well as a generalization of this specific ScheLoc problem is presented.     

Corrosion protection of a thin aluminium layer deposited on polyester

Organosilicon plasma polymer layers were deposited by surface dielectric barrier discharge (DBD) at atmospheric pressure, in an attempt to enhance the corrosion protection of a reflective aluminium (Al) layer applied on a polyester (PET) fabric. A number of tests were carried out to characterize the improvement of corrosion resistance - namely sodium carbonate (Na₂CO₃), water vapor and Kesternich tests - as a function of plasma treatment time, type of carrier gas, admixture of oxygen, amount of hexamethyldisiloxane (HMDSO) precursor supplied to plasma and post-plasma-treatment heating. Moreover, plasma-deposited protective films were characterized by the scanning electron microscopy (SEM), infrared spectroscopy (DRIFT FTIR), and X-ray photoelectron spectroscopy (XPS). While aluminium was consumed in the Na₂CO₃ corrosive solution within a few minutes for the untreated surface, the optimally performing plasma polymerized layers revealed an extraordinary corrosion resistance. Furthermore, the best protective organosilicon coatings showed only a 1-2% absolute reduction of reflection compared to the untreated fabric, over the complete solar spectrum (250-2500 nm).     

Effect of strain gradients on the size effect of concrete in uniaxial tension

A series of uniaxial tension experiments has been conducted to investigate the size effect on strength and fracture energy of quasi brittle materials like concrete and sandstone. This paper focuses on the results of the concrete tests, and specifically deals with the variation of the nominal strength for specimens of six different sizes in a scale range of 1:32. It was found that under given experimental conditions, the nominal strength strongly depended on the specimen size. More important however, is the fact that most of this size effect could be attributed to strain gradients which were present in the cross section of the specimens. These strain gradients were caused by the specimen shape, load eccentricity and material inhomogeneity. Through a combination of experimental data and a simple linear elastic analysis, the importance of strain gradients with respect to the ultimate load level could be visualized. This leads to the conclusion that studying a material size effect is not possible without taking into account structural stress/strain gradients. This revised version was published online in July 2006 with corrections to the Cover Date.     

Novel process for low temperature crystallization of a-SiC:H for optoelectronic applications

Metal-induced crystallization (MIC) process was employed to crystallize hydrogenated amorphous silicon carbide (a-SiC:H) films deposited by PECVD on n-type Si substrate. To optimize the crystallization process, Aluminum thin films of different thicknesses were deposited on a-SiC:H films which were then annealed at 600 °C in N₂ environment for 1 h. UV–visible spectrophotometer, atomic force microscopy (AFM) and hall measurement system were used to characterize the films. It was observed from the UV–visible spectrum that the films crystallized using higher Al thickness show absorption in the visible range whereas the samples crystallized with lower Al thickness did not show absorption in the visible range but shows large absorption above the bandgap of the material. Considering UV–visible and Hall measurement data it can be concluded that the sample crystallized with 50 nm of Al can be a good candidate for SiC–Si hetero-junction solar cells.     

Geschiebemessung in Österreich

Bedload transport is an important aspect in the fields of river engineering, flood protection, torrent and avalanche control and ecology, as well as in the context of hydropower and waterway management. In addition to providing us with a better understanding of the process itself, bedload monitoring allows us to determine the initiation of motion of bedload particles, bedload transport rates and bedload yields – important variables for planning enhanced management strategies and implementing sustainable measures. Further, this monitoring data serves as the basis for selecting, applying, calibrating and validating bedload transport formulae and numerical models. As the bedload transport process is characterized by significant spatial and temporal variability and the specific conditions vary between monitoring stations, determining the most suitable measuring system is of great importance, as are standardization and quality assurance. This article provides an overview of bedload monitoring in Austria, introduces the methodology used to assess the bedload transport process, and presents selected results.