Investigation of pollutants dispersion from power stations

Theoretical investigations were conducted of pollutants dispersion, NO_x, SO₂ and Particulate Matter (PM), from stacks of arbitrary four power plants in Libya, e.g. North Benghazi, South Tripoli, Zweitina, Khoms. The first four stations are gas power plants, while the last one is gas and steam station. Gaussian plume model has been used to identify ground‐level NO_x concentrations profile downwind and crosswind of the chimneys through urban regions and also the location of maximum pollutant concentrations. The study is based on the worst‐case emission conditions of Pasquill stability categories (class D). Results indicate that maximum ground‐level NO_x impacts for all plants locate at a distance of approximately 1.0–2.5 km from stacks. The site most critical to ambient air NO_x impact is Zweitina, where the plant site is in direct vicinity to residential areas. Khoms electric station exhibits the maximum emitted NO_x, SO₂, and PM intensity, about 305, 48, and 0.7 µg/m³, respectively, that is lower than allowable concentrations recommended by World Health Organization. Copyright © 2006 John Wiley & Sons, Ltd.     

Experimental studies and analysis of the draping of woven fabrics

This study investigates and compares the draping and forming of four types of woven fabrics, namely a loose plain weave (basket weave), a tight plain weave, a satin and a twill weave. The fabrics were draped over a hat mould consisting of a hemispherical dome surrounded by a flat base. The draping of each fabric was examined in terms of wrinkle formation, boundary profile of the draped fabric, distribution of fibre orientation and local shear angles. A theoretical analysis of the experimental results involved the calculation of the distributions of the fibre volume fraction and mechanical properties, in terms of components of the reduced stiffness matrix, from the experimental data of local shear angles.     

Combining Biocompatible and Biodegradable Scaffolds and Cold Atmospheric Plasma for Chronic Wound Regeneration

Skin regeneration is a quite complex process. Epidermal differentiation alone takes about 30 days and is highly regulated. Wounds, especially chronic wounds, affect 2% to 3% of the elderly population and comprise a heterogeneous group of diseases. The prevailing reasons to develop skin wounds include venous and/or arterial circulatory disorders, diabetes, or constant pressure to the skin (decubitus). The hallmarks of modern wound treatment include debridement of dead tissue, disinfection, wound dressings that keep the wound moist but still allow air exchange, and compression bandages. Despite all these efforts there is still a huge treatment resistance and wounds will not heal. This calls for new and more efficient treatment options in combination with novel biocompatible skin scaffolds. Cold atmospheric pressure plasma (CAP) is such an innovative addition to the treatment armamentarium. In one CAP application, antimicrobial effects, wound acidification, enhanced microcirculations and cell stimulation can be achieved. It is evident that CAP treatment, in combination with novel bioengineered, biocompatible and biodegradable electrospun scaffolds, has the potential of fostering wound healing by promoting remodeling and epithelialization along such temporarily applied skin replacement scaffolds.     

Measuring bone cell adhesion on implant surfaces using a spinning disc device

The adhesion behaviour of osteoblastic cells on implant surfaces is a main focus during the development of osteoconductive implant surfaces. Therefore, besides cell spreading and proliferation on surfaces the adhesion strength of cells to the substrate is of high interest. There are different approaches to determine cell adhesion but only few quantitative methods. For this purpose, we have developed an adhesion device based on the spinning disc principle in conjunction with an inverse confocal laser scanning microscope (LSM). Mirror polished disc‐shaped test samples made of titanium‐ (Ti6Al4V) and cobalt‐alloys (Co28Cr6Mo), as well as stainless steel (316L), were seeded with osteoblasts, stained with a fluorescent dye, at defined radial positions and were incubated for 18 h in cell culture medium (DMEM). After incubation the test samples were placed into the adhesion chamber filled with DMEM. By means of a computer controlled motor the test samples were rotated for 3 min. Using the LSM the detachment of the cells at defined radial positions was determined and the cell count was recorded before and after rotation with the help of imaging software. An average shear stress of 47.1 N/m², 53.2 N/m² and 49.4 N/m² was assessed for the mirror polished Ti6Al4V, Co28Cr6Mo and 316L surfaces respectively. The technique is suitable for studying bone cell adhesion strength on orthopaedic implant materials. Future investigations will focus on different bioactive and anti‐infectious implant surfaces, as well as soluble bioactive factors.     

Mechanical characterization of anti-infectious,anti-allergic,and bioactive coatings on orthopedic implant surfaces

In total joint replacement much effort has been made to reduce implant loosening. We investigated different implant coatings (copper integrated titanium dioxide (TiO₂–Cu), titanium nitride (TiN), plasma polymerized allylamine (PPAAm), and calcium phosphate (CaP)) regarding the adhesion strength and wear resistance. Standardized scratch and adhesive tests were applied. Abrasive wear was measured with artificial bone and bone cement using a special testing machine. All tested coatings have higher bonding strengths than the 22 N/mm² required for medical implant surface coatings by ASTM standard 4711-F. Using bone cement, wear testing revealed higher wear rates in most cases. Polished surfaces reduce the amount of wear, whereas rough surfaces highly increase the wear rate due to three-body wear, especially ceramic surfaces. In general, the application of bone cement in conjunction with modified implant surfaces can lead to an increase in wear rate.     

Integrated microfluidic electrophoresis system for analysis of genetic materials using signal amplification methods

An isothermal signal amplification technique for specific DNA sequences, known as cycling probe technology (CPT), was performed within a microfluidic chip. The presence of DNA from methicillin-resistant Staphylococcus aureus was determined by signal amplification of a specific DNA sequence. The microfluidic device consisted of four channels intersecting to mix the sample and reagents within 55 s, as they were directed toward the reactor coil by electrokinetic pumping. The 160-nL CPT reactor occupied approximately 220 mm2. Gel-free capillary electrophoresis separation of the biotin- and fluorescein-labeled probe from the probe fragments was performed on-chip following the on-chip reaction. An off-chip CPT reaction, with on-chip separation gave a detection limit of 2 fM (0.03 amol) target DNA and an amplification factor of 85,000. Calibration curves, linear at <5% probe fragmentation, obeyed a power law relationship with an argument of 0.5 [target] at higher target DNA concentrations for both on-chip and off-chip CPT reaction and analysis. An amplification factor of 42,000 at 250 fM target (25,000 target molecules) was observed on-chip, but the reaction was approximately 4 times less sensitive than off-chip under the conditions used. Relative SD values for on-chip CPT were 0.8% for the peak migration times, 9% for the area of intact probe peak, and 8% for the fragment/probe peak area ratio.     

Failure micromechanisms in continuous carbon-fibre/epoxy-resin composites

This study is concerned with the influence of the strength of the fibre/matrix interface on the strength and failure process in uniaxial arrays of carbon fibres in an epoxy resin. A batch of high-strength carbon fibres has been supplied with several levels of an oxidative surface treatment to produce composites with various interface strengths. Tensile tests have been conducted on single fibres, on loose bundles and on tows impregnated with an epoxy resin. Further tests have been conducted to estimate the interface strength. A hybrid-tow test configuration has then been used to follow the sequence of failure within a single tow of the carbon fibre in a uniaxial composite. The results indicate that the fibre strength is affected only slightly by the surface treatment, the strength of impregnated tows is reduced, and their mode of failure and that of the hybrid tows is affected significantly.     

Das topologische Problem der gedruckten Schaltung und seine Lösung

Übersicht Die gedruckte Schaltung erlaubt keine Kreuzung von Zweigen. Es wird gezeigt, wie man in einem systematischen Verfahren zur kreuzungsfreien Darstellung eines Graphen gelangt, falls er vom Geschlecht Null ist, und wie man gegebenenfalls durch Entfernung von Zweigen die Kreuzungsfreiheit erzielt.Gliederung: 1. Die Aufgabe; 2. Vorbereitende Sätze; 3. Kriterium der Ebenheit und Konstruktion des kreuzungsfreien Graphen bei Kenntnis einer Hamilton-Linie; 4. Kriterien der Ebenheit und Konstruktion des kreuzungsfreien Graphen, falls eine Hamilton-Linie nicht bekannt ist; 5. Ergänzungen.

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Summary Printed cards do not admit branch crossings. For a graph it is shown how by a systematic method a representation containing no crossings is achieved, if need be by removing branches.Contents: 1. Problem; 2. Preparing Theorems; 3. Criterion for planarity and construction of the graph containing no crossings if a Hamiltonian circuit is known; 4. Criteria for planarity and construction of the graph containing no crossings if a Hamiltonian circuit is not known; 5. Supplement.

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Mit 7 Textabbildungen

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Der Verfasser hat über diesen Gegenstand im Elektrotechnischen Kolloquium der Technischen Hochschule Stuttgart am 11. 6. 1963 vorgetragen.     

Influence of a new chemical crosslink system on the morphology and crystallite size of nylon-12

Special polyamide chains of desirable structure were polymerized such that they already contained reactive sites at the chain ends. The degree of crosslinking is determined by the chain structure and the amount of a specific epoxide silane, which causes crosslinking by formation of condensed silicon centres. The influence of the chain structure and the amount of epoxide silane on the morphology and the crystallite size were investigated by transmission electron microscopy using electron spectroscopic imaging and differential scanning calorimetry. A three-component structure was observed, consisting of crystalline and amorphous regions with a transition region between them. The lamellar thickness of the crystallites (5–7 nm) was independent of the chain structure and of the amount of epoxide silane, i.e. independent of the degree of crosslinking. Conversely, the lamellar length of the crystallites was dependent on the chain structure. For the material containing linear chains it was usually greater than 100 nm; for the material containing highly branched chains it varied from about 100 nm down to a block-like structure. The width of the transition region, in which the chains are under stress, was about 2 nm. The condensed silicon centres (crosslink points) were randomly distributed with respect to the resolution of the transmission electron microscope. RuO₄ is a good staining agent for nylon-12.