Testing of thin-walled steel joints fabricated by spot welding and plug welding

Selected methods of joining which can be used for manufacturing and repairing of car bodies by means of welding are presented in this article. Three kinds of 1 mm-thick steel sheets were used in the tests: deep drawing steel (DC04) and two-phase steels of increased high strength (DP600 and DP800). The comparative connections were carried out by means of resistance spot welding and with plug joints made by means of the MAG method and through braze welding. Comparative assessment of the strength and geometrical parameters of the test joints was then conducted.     

ABTS-modified multiwalled carbon nanotubes as an effective mediating system for bioelectrocatalytic reduction of oxygen

The ability of such a common redox mediator as 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) to undergo sorption on carbon surfaces is explored here to convert multiwalled carbon nanotubes (CNTs) into a stable colloidal solution of ABTS-modified carbon nanostructures, the diameters of which are approximately 10 nm (as determined by transmission electron microscopy). Subsequently, inks composed of fungal laccase (Cerrena unicolor) mixed with the dispersion of ABTS-modified CNTs and stabilized with Nafion, were deposited on glassy carbon and successfully employed to the reduction of oxygen in McIlvain buffer at pH 5.2. For comparison, the systems utilizing only ABTS-free CNTs and laccase as well as ABTS-modified CNTs did not show appreciable activity toward the oxygen reduction. The three-dimensionally distributed ABTS-modified CNTs are expected to improve the film's overall conductivity and to facilitate electrical connection between the electrode and the enzyme. The network film of ABTS-modified CNTs is rigid, and it is characterized by charge propagation capabilities comparable to the conventional redox polymers. The whole concept of utilization of CNTs modified with ultrathin films of redox mediators in the preparation of efficient bioelectrocatalytic films seems to be of general importance to electroanalytical chemistry and to the development of biosensors.     

Isolation and structure elucidation of phenolic compounds from Cyclopia subternata Vogel (honeybush) intact plant and in vitro cultures

In the presented work, an insight was made into the polyphenolic composition of intact plant material and in vitro cultures of indigenous South African plant Cyclopia subternata Vogel (honeybush). Ethyl acetate fractions of methanol extracts were separated by means of gravity column chromatography and/or semipreparative HPLC on two serially connected monolithic RP-18 columns. The structures of the isolated compounds were determined by means of 1D and 2D NMR techniques and additionally confirmed by LC-DAD-ESI-MS. Apart from the previously described honeybush components, that is mangiferin (1), scolymoside (2), hesperidin (3) and narirutin (4), three additional compounds: iriflophenone 3-C-β-glucoside (benzophenone) (5), phloretin 3′,5′-di-C-β-glucoside (dihydrochalcone) (6), and isorhoifolin (flavone) (7) were identified for the first time in the herb of C. subternata. Additionally, three isoflavone glucosides, namely calycosin 7-O-β-glucoside (8), rothindin (9) and ononin (10), which had not been previously reported in Cyclopia plants, were identified in the callus of the above species. As far as the authors are concerned, this is the first report on the presence of benzophenone and dihydrochalcone derivatives in Cyclopia genus.     

Copper oxide nanoparticle mediated DNA damage in terrestrial plant models

Engineered nanoparticles, due to their unique electrical, mechanical, and catalytic properties, are presently found in many commercial products and will be intentionally or inadvertently released at increasing concentrations into the natural environment. Metal- and metal oxide-based nanomaterials have been shown to act as mediators of DNA damage in mammalian cells, organisms, and even in bacteria, but the molecular mechanisms through which this occurs are poorly understood. For the first time, we report that copper oxide nanoparticles induce DNA damage in agricultural and grassland plants. Significant accumulation of oxidatively modified, mutagenic DNA lesions (7,8-dihydro-8-oxoguanine; 2,6-diamino-4-hydroxy-5-formamidopyrimidine; 4,6-diamino-5-formamidopyrimidine) and strong plant growth inhibition were observed for radish (Raphanus sativus), perennial ryegrass (Lolium perenne), and annual ryegrass (Lolium rigidum) under controlled laboratory conditions. Lesion accumulation levels mediated by copper ions and macroscale copper particles were measured in tandem to clarify the mechanisms of DNA damage. To our knowledge, this is the first evidence of multiple DNA lesion formation and accumulation in plants. These findings provide impetus for future investigations on nanoparticle-mediated DNA damage and repair mechanisms in plants.     

The collision efficiency in a shear flow

Fluid flows with cohesive particles are present in oil industry (e.g. natural gas/oil with hydrates, wax or asphaltenes), medicine (e.g. blood cells), nano- and ferro-fluidic applications (e.g. fluids with nanoparticles subject to the van der Waals and electrostatic interactions) and even in astrophysics (e.g. grains in planetary rings). Such flows may lead to formation of agglomerates that, for example in pipelines, may result in unwanted phenomena such as formation of deposits. The main process parameter governing this is the “collision efficiency”, which is the ratio of the number of collisions resulting in agglomeration to the total number of collisions. This is commonly considered to depend on the relativemagnitudes of attractive and repulsive interactions during a collision. The effect of the particles' mechanical properties on the agglomeration efficiency has, however, not yet been studied. In this paper the agglomeration efficiency is studied as a function of inter-particle friction, stiffness, density and volume fraction by numerical simulation. By running direct numerical simulations (DNS) with Lagrangian particle tracking of a shear flow laden with solid particles, the parameters influencing the agglomeration efficiency are demonstrated and their effects quantified. Finally, an expression that relates the collision efficiency to the salient dimensionless physical parameters is proposed.     

Different Aspects of the Elemental Analysis of Honey by Flame Atomic Absorption and Emission Spectrometry: A Review

The elemental composition of honey is correlated with the botanical provenience of nectar, pollen, and honeydew that are collected and ripened by bees. In addition to this, the geographical origin related to the locality of an apiary, the soil composition, and climatic conditions may contribute to the origin of elements in honey. The environmental pollution or other anthropogenic processes and activities also have an effect on the quality and the safety of honey since they may be accompanying sources that lead to its contamination and the presence of various trace elements (Cd, Cr, Cu, Fe, Ni, Pb, and Zn). This review article covers the literature devoted to the analysis of honey carried out by the most popular and commonly utilized flame atomic absorption and emission spectrometry, which was published from 1999 to 2011. Various aspects of such analysis are treated in detail, including ways of the sample preparation, the calibration, and the quality assurance of results. In addition, methods and results related to the fractionation analysis of elements in honey by means of chromatographic and non-chromatographic approaches are described.     

Bewertung der Umweltverträglichkeit von Bauprodukten im Rahmen von bauaufsichtlichen Zulassungen

Nachdem in den letzten Jahren die Auswirkungen von Baumaßnahmen auf das Grundwasser stärker in den Fokus der Öffentlichkeit gerückt sind, wird mittlerweile bei der Erteilung von allgemeinen bauaufsichtlichen Zulassungen für spezielle Bauprodukte eine Bewertung der Umweltverträglichkeit vorgenommen. Da Umweltschutz eine wesentliche Anforderung an Bauprodukte im Rahmen der europäischen Bauproduktenrichtlinie ist, werden auch genormte Bauprodukte zukünftig in dieser Hinsicht stärker überprüft werden müssen. In dem Artikel wird vorgestellt, nach welchem Bewertungsschema das DIBt die Beurteilung der Auswirkungen auf Boden und Grundwasser für welche Bauprodukte vornimmt und welche zukünftige Entwicklung sich bei genormten Bauprodukten abzeichnet. Assessment of the environmental compatibility of constructions products within the scope of technical approvals. During the last years the effects of construction works on groundwater have moved more and more into the public spotlight. An assessment of the environmental compatibility has since then been carried out when granting technical approvals for specific construction products. Since environmental protection is an essential requirement for construction products within the scope of the European Construction Products Directive, in future also standardized construction products will have to be checked much stronger in this respect. This article introduces the assessment scheme according to which DIBt performs the evaluation of the effects on soil and groundwater for which construction products and which future development begins to emerge on standardized construction products.