Effect of blend composition on the morphology and mechanical properties of microfibrillar composites

Various blend compositions of polyethyleneterphthalate (PET) and polyamide 6 (PA 6) were used to prepare microfibrillar composites (MFC's) in form of thin ribbons. Steps for preparation were: (1) blending, (2) extrusion, (3) fibrillation, and (4) isotropization. The latter step was performed at a temperature condition above the melting temperature of PA 6, but below that of PET. In this way PET microfibrils remained as reinforcing elements in the PA 6-matrix. Depending on the actual PET/PA 6 ratio, various fibril arrangements in terms of fibril length and uniformity of fibril distribution could be achieved. A reasonable improvement in mechanical properties was reached already at 30 wt. % PET in PA 6 which was in terms of tensile strength higher than a 30 wt. % short glass fiber filled PA 6 system.     

Fretting fatigue failure of polyester resin and its glass fibre mat composites

When relative movement can arise between mating parts and one is subjected to cyclic stresses, then the fatigue life can be very much reduced. Such a phenomenon is referred to as fretting fatigue. In this paper, results of fretting fatigue experiments obtained with unsaturated polyester and its glass fibre mat composites are reported. In addition, some fracture and wear properties of the materials are discussed.     

Reibung und Verschleiß von Polymer-Verbundwerkstoffen

Friction and Wear of Polymer Composites Polymer composites are more and more used as structural components which are very often subjected to friction and wear loadings under use. This paper describes the principle microstructure in polymer composites and their friction and wear properties as a function of microstructural composition. Special attention is focussed on the behavior of these materials under sliding situations against steel and under severe abrasive loading (wear by rough abrasive paper). Models to describe the tribological properties of composites by modified rules of mixtures and/or by terms combining mechanical and microstructural parameters of the partners in contact are introduced.     

Probleme beim Pelletieren von Mischfutter mit hohen Fettanteilen

In the steam conditioning with subsequent pressing mixed feed passes considerable temperature ranges, which depend on the processing abilities. By maturation or sweating during long term conditioning up to 30 min cohesion and absorption of fats and molasses can be improved. Free added fats lower the friction and reduce the pellet firmness. Here technical limits are set especially with broiler feed. Trials with various lengths of the press canal indicate the influence on firmness and energy consumption. The fat is extracted from meal and pellets after the processing steps and investigated by its characteristic values w. r. t alterations by the process. A subsequent storage makes the influence of the fat alterations by the press process more obviously.     

Technological aspects of flexible CIGS solar cells and modules

This paper describes the technological status of and some challenges in the manufacturing of Cu(In,Ga)Se₂ (CIGS)-based solar cells on flexible polymer and metal substrates. Substrate characteristics such as thermal expansion properties and stability, surface roughness, or substrate composition, strongly influence growth and properties of the following layers. For example, adhesion failure, cracking, or contamination by diffusion of impurities from the substrate may occur with some substrates. Aspects of (external) sodium incorporation into CIGS are discussed for high and low CIGS deposition temperature. Low-temperature deposition processes are particularly important when polyimide substrates are used. The electrical insulation of metal foils by dielectric barriers (e.g. SiO_x or Al₂O₃) allows the fabrication of monolithically integrated modules. A soft and selective patterning technique based on laser scribing and mask-free photolithography is described. Working modules as large as 20 cm × 30 cm were achieved with these methods.     

DNA origami-based nanoribbons: assembly, length distribution, and twist

A variety of polymerization methods for the assembly of elongated nanoribbons from rectangular DNA origami structures are investigated. The most efficient method utilizes single-stranded DNA oligonucleotides to bridge an intermolecular scaffold seam between origami monomers. This approach allows the fabrication of origami ribbons with lengths of several micrometers, which can be used for long-range ordered arrangement of proteins. It is quantitatively shown that the length distribution of origami ribbons obtained with this technique follows the theoretical prediction for a simple linear polymerization reaction. The design of flat single layer origami structures with constant crossover spacing inevitably results in local underwinding of the DNA helix, which leads to a global twist of the origami structures that also translates to the nanoribbons.     

Microphotoluminescence and perfect ordering of SiGe islands on pit-patterned Si(001) substrates

We show that both the morphology and the optoelectronic properties of SiGe islands growing in the pits of periodically pre-patterned Si(001) substrates are determined by the amount of Ge deposited per unit cell of the pattern. Pit-periods (p) ranging from 300 to 900 nm were investigated, and Ge growth was performed by molecular beam epitaxy (MBE) at temperatures of 690 and 760?°C. The ordered SiGe islands show photoluminescence (PL) emission, which becomes almost completely quenched, once a critical island volume is exceeded. By atomic force and transmission electron microscope images we identify the transition from pyramid-shaped to dome-shaped islands with increasing p. Eventually, the nucleation of dislocations in the islands leads to PL quenching. Below a critical Ge coverage a narrowing and a blue shift of the PL emission is observed, as compared to islands grown on a planar reference area of the same sample.     

迈丹商业综合体

迈丹商业中心本身作为高效的商业综合体项目,还成为了伊斯坦布尔飞速发展区之一的真正核心。它坐落在城市亚洲区的近郊,基地包括宜家家居中心,不久后还将在此开发新的住宅区。通过其几何形体与交通策略,综合体与老城肌理融合,为传统的城外商业地产项目开辟了新的模式。合理组织不同的业态空间,将停车场置     

Formation of cadaverine, histamine, putrescine and tyramine by bacteria isolated from meat, fermented sausages and cheeses

Enterobacteriaceae (EB, n = 149), Lactobacillus (LB, n = 162) and Leuconostoc sp. (LC, n = 89) and enterococci (EC, n = 137), isolated from raw meat (n = 65), fermented sausages (n = 50) and cheese (n = 55) samples, were cultivated in a broth containing precursor amino acids (each 3 g/l). After incubation, the liquid culture was chemically analysed for cadaverine (CAD), putrescine (PUT), histamine (HIS) and tyramine (TYR) formation at pH 5.2 and at pH 6.7. The majority of EB isolates (147 of 149) was capable of forming >100 mg/l of either CAD or PUT. Among the most frequently isolated species Hafnia alvei and Serratia liquefaciens, formation of >100 mg/l HIS occurred, but with low prevalence (1.6 and 6.5%, respectively). Twelve of 149 isolates (8%) were able to produce more than 10 mg/l HIS. One hundred forty-two isolates (95.3%) produced less than 10 mg/l TYR, and 7 isolates (4.7%) 10 mg/l to a maximum of 35.3 mg/l TYR. For LB + LC, one isolate (Leuconostoc mesenteroides ssp. mesenteroides) formed >100 mg/l PUT and one >100 mg/l CAD (of all 251 LB + LC isolates 0.4% each). Formation of >100 mg/l HIS and TYR was detected in 3.6 and 19% of the LB + LC isolates, respectively. For the EC isolates, maximum levels for PUT, CAD and HIS were 25.4 mg/l, 6.0 mg/l and 15.7 mg/l, respectively. TYR was formed in quantities of 100–1000 mg/l by 47.9% of EC faecalis (n = 75), and 59.7% of EC faecium (n = 62) isolates. More than 1000 mg/l TYR were formed by 50.7 and 35.5% of the isolates, respectively. A low initial pH of 5.2 compared to the initial pH of 6.7 favoured tyramine production by lactic acid bacteria, but was associated with lower CAD yield by EB. A considerable intra-species variability in amine formation was observed.