Formation and properties of magnesium–ammonium–phosphate hexahydrate biocements in the Ca–Mg–PO<Subscript>4</Subscript> system

Calcium substituted trimagnesium phosphate with the general formula Ca_xMg_(3−x)(PO₄)₂ (0 < x < 1.5) was synthesized by calcination of powder mixtures with the appropriate stoichiometry and reacted with 3.5 M diammonium hydrogenphosphate solution to form a cementitious matrix of magnesium ammonium phosphate hexahydrate (struvite). The degree of ionic substitution was shown to influence physical cement properties; clinically suitable cement formulations with setting times in the range 5–15 min and compressive strengths of >50 MPa were obtained for x ≤ 0.75 together with a grinding time ≥1 h and a powder to liquid ratio ≥2.5 g/ml. The cement cytocompatibility was investigated by culturing human osteoblast cell line MG63 on cement surfaces demonstrating pronounced cell growth during 13 days cultivation.     

Theoretical principles for the indirect determination of the total glucosinolate content in rapeseed and meal quantifying the sulphur concentration via X-ray fluorescence (X-RF method)

The introduction of double low oilseed rape cultivars into common crop production will require the development of methods for a precise, rapid and simple determination of the total glucosinolate content in rapeseed. Recent methods are often inappropriate for plant breeding work, and also for the trade and oil mills in separating parcels of seed according to their glucosinolate contents. In contrast to the methods commonly used (chromatography, enzymic and colorimetric tests) an indirect method is described here which is based on the very close correlation between the total sulphur and glucosinolate content in rapeseed. The sulphur content of the samples can be determined precisely and non-destructively by means of X-ray fluorescence spectroscopy (X-RF). This new method, which is suitable for rapeseed and meal, requires simple preparation of the seed samples by grinding and compressing. The whole analytical procedure (sample preparation and measurement) takes 2-4 min. If necessary, moist seed samples can be quickly dried by microwave heating, because the method does not require intact glucosinolates. The steps of the X-RF method are fairly insensitive to errors. The method shows an excellent repeatability (r = 1.9 μmol g^?1) and reproducibility (R = 3.8 μmol g^?1). The results obtained with this X-RF method correlate closely with the conventional reference methods (r² = 96-99%).     

C60Con complexes as hydrogen adsorbing materials

An active line of contemporary research is dedicated to the adsorption and storage of hydrogen on metal-doped carbon materials. Using density functional theory and van der Waals corrections we have studied molecular and dissociative adsorption of H₂ on neutral and cationic C₆₀Co_n complexes with n = 1–8. The Co atoms form compact clusters on the surface of the fullerene. Dissociative chemisorption of one H₂ molecule is more stable than molecular adsorption on neutral C₆₀Co_n, with the only exception of C₆₀Co. When C₆₀Co_n is ionized, the electronic charge deficit remains localized in the cobalt cluster. The molecular and dissociative adsorption features on cationic C₆₀Co_n⁺ and neutral C₆₀Co_n complexes are in general similar, but some differences can be highlighted. Molecular and dissociative H₂ adsorption on C₆₀Co₂⁺ are competitive; in fact, molecular adsorption is slightly more stable as a result of the localized electronic charge deficit on the Co dimer. Another difference is that the dissociative adsorption energies on some of the neutral C₆₀Co_n complexes are substantially larger than the dissociative adsorption energies on the corresponding C₆₀Co_n⁺ cationic complexes by amounts between 0.2 and 0.5 eV. Activation barriers for dissociation of the adsorbed H₂ molecule strongly depend on the charge state and cluster size. These barriers help to interpret the adsorption state (molecular or dissociated) of experimentally produced hydrogenated C₆₀Co_n⁺ complexes. Hydrogen saturation has been studied in two cases. C₆₀Co adsorbs three H₂ units in molecular form, and C₆₀Co_n adsorbs up to thirteen H₂ units, four dissociated and nine in molecular form.     

Regelung eines redundant aktuierten Steer-by-Wire-Systems

Forschung im Ingenieurwesen - Im Rahmen des autonomen Fahrens gewinnen Steer-by-Wire (SbW) Systeme wieder an Bedeutung, da ein permanent mitdrehendes Lenkrad im Fahrzeug unerwünscht ist. Zudem...     

Hochtemperatur-Verschleißverhalten von Ein- und Mehrphasenwerkstoffen

In many industries combined erosion, impact and abrasive wear at high temperatures play a dominating role regarding lifetime of tools and wearing parts. In view of the above an austenite, a high speed steel (HSS) and a Fe-Cr-C-B complex alloy were investigated at different temperatures and loading situations to examine their wear resistance. The dependence of hardness of these materials on temperature was investigated by an especially designed hot hardness test rig (HHT) from room temperature up to 800 °C. 2-body particle erosion and 3-body impact/abrasion were investigated at elevated temperatures, and wear results were correlated with the hot hardness results. The austenite shows ductile behaviour in all tests and a formation of a mechanically mixed layer (MML) at higher temperature entailing a wear decreasing effect. The tool steel reveals a significant drop in hardness at 500 °C which leads to increased wear rate and the formation of a MML due to ductile surface regions. The complex alloy shows brittle wear behaviour. Softening of the matrix above 500 °C leads to significant fracture of the hard phases.     

Polarization and phase control of remote surface-plasmon-mediated two-photon-induced emission and waveguiding

We report here on the control of remote surface-plasmon-mediated two-photon-induced luminescence of dendritic silver nanoparticle aggregates as observed by femtosecond laser microscopy. With a focal spot diameter approximately 1 microm, polarized remote emission has been observed 99 microm from the focal spot. We show control over the regions of emission by changing the polarization of the incident beam and by changing the spectral phase of the laser pulse.     

Simulating plant conditions in the laboratory – Principles and limitations

Before corrosion tests are carried out, one must realise the scale to be selected. As in chemical engineering the problem of “scaling down” and “scaling up” arises if plant conditions are to be simulated on a laboratory scale. As a consequence of the multiplicity of corrosion phenomena, parameters and mechanisms the number of corrosion testing methods is large and test procedures have carefully to be adjusted to the particular practical problem. Simulation principles are illustrated by a number of examples.     

Present quality level of large heat resistant rotor forgings made of 1% CrMoV steel – Part II

While in part I mainly mechanical and toughness properties together with structural aspects have been dealt with now design properties are described. The basic properties for heat resistant rotor materials are traditionally the creep properties. So they are here investigated more in detail and it is shown that modern 1% CrMoV rotor steels have a quite similar creep behaviour both oil and air quenched. Long term high temperature exposure and its influence on the properties are as well mentioned as heat stability behaviour.     

Fluorescence correlation spectroscopy assay for gliadin in food

Gliadin proteins are primarily responsible for celiac disease. As gliadin is a complex mixture of proteins difficult to solubilize and to extract from food, it is difficult to develop an assay capable of accurate quantization of gliadin in food for celiac patients. In this work, we present an advanced fluorescence assay for the detection of traces of gliadin in food. The described assay is based on measurement of the fluctuations of fluorescein-labeled gliadin peptides (GP) in a focused laser beam in the absence and in the presence of anti-GP antibodies. A competitive assay based on the utilization of unlabeled GP was developed. The obtained results indicate that the combination of high-avidity IgG antibodies together with the innovative fluorescence immunoassay strategy resulted in a gluten detection limit of 0.006 ppm, which it is much lower than the values reported in the literature.