Adaptive modelling of plates in bending and shear

As an alternative to a direct finite element approximation of the Reissner–Mindlin plate equations we propose an adaptive modeling starting with a finite element solution according to the Germain–Kirchhofff equation and in an adaptive manner adding shear deformations calculated from the Germain–Kirchhoff shear forces. The system matrix need not be changed, so the extra cost, compared to the first solution, can be kept small.     

Analysis of local composition gradients in the hard-phase grains of cermets using a combination of X-ray diffraction and electron microscopy

Combination of X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used for investigation of local composition gradients in the hard-phases of cermets. XRD revealed distribution of lattice parameters in hard-phase grains, from which the composition gradients in the hard-phases were estimated using an appropriate microstructure model. This microstructure model was build with the aid of SEM micrographs, which were taken with back-scattered electrons (BSE) and completed by the registration of the electron back-scatter diffraction (EBSD) patterns and characteristic X-ray spectra. SEM/BSE yielded the first information about the spatial distribution of elements in individual hard-phase grains, SEM/EBSD about the morphology, the size and the size distribution of these grains. The final interpretation of the distribution of lattice parameters, which was obtained from the X-ray line profile analysis, was done with the aid of the local elemental analysis that was performed using SEM with the energy dispersive analysis of the characteristic X-ray spectra (EDX) and the known dependence of the lattice parameters on concentration.     

Fibre reinforced glasses

A new method of preparing fibre reinforced glasses is put forward, which is based on further developments of the known slurry method and the sol-gel technique. This method combines the advantages of the two procedures. The prepregs are hot-pressed and the influence of preparation parameters on the bending strength are investigated. The pressure, temperature, time of pressing, granulation of the glass powder, the type of sol-gel solution and the gas atmosphere during the hot-pressing were all studied.     

OPTIMA

Zusammenfassung Im Rahmen der Reorganisation des Landesbetriebes Hamburger Stadtreinigung wurden zur Erhöhung der Effizienz und Wirtschaftlichkeit verschiedene Planungs- und Steuerungsinstrumente eingeführt. Eines dieser Instrumente stellt das EDV-gestützte Planungssystem OPTIMA, zur täglichen Planung der Abfallentsorgung des Stadtgebietes der Freien und Hansestadt Hamburg dar.Die Abfallentsorgung wird mit einem hierarchischen System, bestehend aus vier Ebenen, geplant. Für eine der Ebenen — die tägliche Abfuhrplanung — wurde die Unterstützung durch ein Netzwerkflußmodell vorgeschlagen und auf einem Personal Computer implementiert.Neben dem Aufbau und der Funktionsweise werden auch weiterführende Einsatzmöglichkeiten des Planungssystems beschrieben und eine erste Beurteilung des Einsatzes vorgenommen.Dem Aufsatz liegt ein Projekt zugrunde, das der Autor während seiner Tätigkeit bei der Fa. SCS Informationstechnik GmbH, Hamburg durchgeführt hat.     

Small‐Molecule Inhibitors of AF6 PDZ‐Mediated Protein–Protein Interactions

PDZ (PSD‐95, Dlg, ZO‐1) domains are ubiquitous interaction modules that are involved in many cellular signal transduction pathways. Interference with PDZ‐mediated protein–protein interactions has important implications in disease‐related signaling processes. For this reason, PDZ domains have gained attention as potential targets for inhibitor design and, in the long run, drug development. Herein we report the development of small molecules to probe the function of the PDZ domain from human AF6 (ALL1‐fused gene from chromosome 6), which is an essential component of cell–cell junctions. These compounds bind to AF6 PDZ with substantially higher affinity than the peptide (Ile‐Gln‐Ser‐Val‐Glu‐Val) derived from its natural ligand, EphB2. In intact cells, the compounds inhibit the AF6–Bcr interaction and interfere with epidermal growth factor (EGF)‐dependent signaling.     

Measurement and modeling of dielectric properties of Pb(Zr,Ti)O3 ferroelectric thin films

In this study, the real and imaginary parts of the complex permittivity of lead zirconate titanate ferroelectric thin films are studied in the frequency range of 100 Hz to 100 MHz. The permittivity is well fitted by the Cole-Cole model. The variation of the relaxation time with the temperature is described by the Arrhenius law and an activation energy of 0.38 eV is found. Because of its nonlinear character, the dielectric response of the ferroelectric sample depends on the amplitude of the applied ac electric field. The permittivity is composed of three different contributions: the first is due to intrinsic lattice, the second is due to domain wall vibrations, and the third is due to domain wall jumps between pinning centers. This last contribution depends on the electric field, so it is important to control the field amplitude to obtain the desired values of permittivity and tunability.     

Freestanding silicon quantum dots: origin of red and blue luminescence

In this paper, we studied the behavior of silicon quantum dots (Si-QDs) after etching and surface oxidation by means of photoluminescence (PL) measurements, Fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance spectroscopy (EPR). We observed that etching of red luminescing Si-QDs with HF acid drastically reduces the concentration of defects and significantly enhances their PL intensity together with a small shift in the emission spectrum. Additionally, we observed the emergence of blue luminescence from Si-QDs during the re-oxidation of freshly etched particles. Our results indicate that the red emission is related to the quantum confinement effect, while the blue emission from Si-QDs is related to defect states at the newly formed silicon oxide surface.