Triaxial MEMS accelerometer with screen printed PZT thick film

Piezoelectric thick films have increasing interest due to the potential high sensitivity and actuation force for MEMS sensors and actuators. The screen printing technique is a promising deposition technique for realizing piezoelectric thick films in the thickness range from 10–100 μm. In this work integration of a screen printed piezoelectric PZT thick film with silicon MEMS technology is shown. A high bandwidth triaxial accelerometer has been designed, fabricated and characterized. The voltage sensitivity is 0.31 mV/g in the vertical direction, 0.062 mV/g in the horizontal direction and the first mode resonance frequency is 11 kHz. A Finite Element Method (FEM) model is used to validate the measured sensitivity and resonance frequency. Good agreement between the model and the measurements is seen.     

Long-Wave and Integral Boundary Layer Analysis of Falling Film Flow on Walls With Three-Dimensional Periodic Structures

Falling films exhibit very complex wavy patterns, which depend on the properties of the liquid, the Reynolds number, the wall inclination angle, and the distance from the film inlet. The film hydrodynamics governs the heat and mass transfer in the liquid films. Our vision is to control and enhance heat and mass transport by using walls with specific microscale topographies that influence the falling film flow, stability, and wavy pattern. In this work, long-wave theory and integral boundary layer approximation are used for modeling the falling film flow on walls with three-dimensional periodic microstructures. The wall topography is periodic both in the main flow direction and in the transverse direction. Examples of such microstructures are longitudinal grooves with sinusoidal path (or meandering grooves) and herringbone structures. The effects of the Reynolds number, the wall inclination angle, and the longitudinal and transverse periods of the structure on the shape of liquid–gas interface are investigated. It is shown that, as opposed to straight grooves in longitudinal direction, grooves with meandering paths may lead to significant interface deformations.     

SiC ceramic micropatterns from polycarbosilanes

Micropatterned SiC ceramics were fabricated from polycarbosilanes applying a softlithographic replication technique. A polydimethylsiloxane mould replicated from a photolithographic microstructured silicon wafer was used as master structure. The polydimethylsiloxane mould was coated with a solution containing a mixture of two different polycarbosilanes in n-octane. After treatment at 200–400 °C the cross-linked polycarbosilane films were debonded and pyrolysed at 900 °C in nitrogen and subsequently crystallised at temperatures up to 1500 °C in argon. The cross-linking and thermal degradation behaviour of the polycarbosilanes was investigated by Fourier-transform infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis. X-ray diffractrometry showed the expected development of a nanocrystalline β-SiC (3 nm) as the main phase with increasing temperature. However, traces of α-SiO₂ derived from the polycarbosilane precursors were also detected by X-ray analysis. Removal of the α-SiO₂ dioxide with hydrofluoric acid in the pyrolysed samples and subsequent increased the crystallite size to 7 nm. The Young's modulus determined by nanoindentation was increased from 3 GPa after cross-linking to 110 GPa after crystallisation. Scanning electron microscopy revealed, that the initial micropatterns were fully retained in the pyrolysed and crystallised SiC ceramics. The micropatterned cross-linked and crystallised β-SiC based substrates exhibited light scattering characteristics, which qualify them as promising candidates for diffractive optical elements in microoptical applications.     

OpenSocial

Zusammenfassung  OpenSocial definiert eine Menge von Programmierschnittstellen für Anwendungen von Drittanbietern im Kontext sozialer Netzwerke. Unter der Verwendung von Standardtechnologien wie HTML und JavaScript k?nnen Entwickler interoperable Anwendungen erstellen, die auf den sozialen Graphen des jeweiligen Netzwerks zugreifen.     

Automated generation of a progress measure for the sweep-line method

In the context of Petri nets, we propose an automated construction of a progress measure which is an important pre-requisite for a state space reduction technique called the sweep-line method. Our construction is based on linear-algebraic techniques concerning the transition vectors of the Petri net under consideration. We further discuss the possible combination of the sweep-line method with other state space reduction techniques (partial order reduction, the symmetry method).     

Modelling of boron nitride: Atomic scale simulations on thin film growth

Molecular-dynamics simulations on ion-beam deposition of boron nitride are presented. A realistic Tersoff-like potential energy functional for boron nitride, which was specially fitted to ab initio-data, has been used. The impact of energetic boron and nitrogen atoms on a c-BN target is simulated with energies ranging from 10 to 600 eV. The structural analysis of the grown films shows that a loose, dominantly sp²-bonded structure arises at high ion flux. In no case the formation of a sp³-bonded phase is observed, but the obtained films partially reveal textured basal planes as found in experiment. Two different growth regimes are identified for ion energies above and below 100 eV.     

Growth of Salmonella enteritidis in yolk from eggs laid by immunized hens

After hyperimmunization of laying hens with Salmonella enteritidis, antibodies can be found in egg yolks. This study was conducted to ascertain whether the growth of S. enteritidis would be suppressed in the presence of antibodies contained in egg yolk. Specifically pathogen-free (SPF)-laying hens were immunized with S. enteritidis; eggs were collected, the yolk was separated and the concentration of S. enteritidis antibodies was determined quantitatively by using the enzyme-linked immunosorbent assay (ELISA), the radial immunodiffusion and the bicinchoninic acid protein assay. Then, the yolk was inoculated with approximately 10, 100 or 1000 S. enteritidis cells/ml and incubated at 15, 20 and 30 degrees C for 0, 2, 6 and 24 h. The growth of organisms in each yolk was examined, and the generation times were calculated. The egg yolk from nonimmunized hens served as negative control. The highest level of antibody concentration was found in the hyperimmunized group. There was no difference in the generation times of S. enteritidis between the antibody-positive yolk and the negative yolk at the three different incubation temperatures. The results suggest that antibodies in the yolk do not influence the growth of S. enteritidis, even if the hens are highly immunized.     

Two software tools for plane-wave scattering on nonspherical particles in the German Aerospace Center's Virtual Laboratory

We present the methodological background, the range of applicability, and the on-line usage of two software packages, MIESCHKA and CYL, which we have developed for light-scattering analysis on nonspherical particles. MIESCHKA solves Maxwell's equations in a rigorous way but is restricted to axisymmetric geometries, whereas CYL is an approximation for finite columns with nonspherical cross sections. We have established an easy on-line access to both of these programs through the Virtual Laboratory. Its generic software infrastructure was designed to simplify the web-based usage and to support the intercomparability of scientific software.     

Surface chemical heterogeneity of bacteriogenic iron oxides from a subterranean environment

This study quantifies the surface chemical heterogeneity of bacteriogenic iron oxides (BIOS) and its end-members (2-line ferrihydrite and intermixed intact and fragmented bacteria). On a dry weight basis, BIOS consisted of 64.5 +/- 1.8% ferrihydrite and 34.5 +/- 1.8% organic matter. Enrichment of Al, Cu, Cr, Mn, Sr, and Zn was shown in the solid versus the aqueous phase (1.9 < log Kd < 4.2). Within the solid-phase Al (69.5%), Cu (78.7%), and Zn (77.9%) were associated with the bacteria, whereas Cr (59.8%), Mn (99.8%), and Sr (79.4%) preferred ferrihydrite. Acid-base titration data from the BIOS and bacteria were fitted using FOCUS pKa spectroscopy. The bacteria spectrum with pKa's of 4.18 +/- 0.37, 4.80 +/- 0.54, 6.98 +/- 0.45, and 9.75 +/- 0.68 was similar to discrete and continuous spectra for intact and fragmented bacteria. The BIOS spectrum recorded pKa's of 4.27 +/- 0.51, 6.61 +/- 0.51, 7.89 +/- 1.10, and 9.65 +/- 0.66 and was deconvoluted to remove overlapping binding site contributions from the bacteria. The resulting residual iron oxide spectrum coincided with discrete MUSIC spectra for goethite and lepidocrocite with pKa values of 4.10 +/- 0.43, 6.53 +/- 0.45, 7.81 +/- 0.76, and 9.51 +/- 0.68. Surface site density analysis showed that acidic sites (pKa < 6) were contributed by the bacteria (37%), whereas neutral sites (6 < pKa < 8) were characteristic of the iron oxide fraction (35%). Basic sites (8 < pKa) were higher in the bacteria (57%), than in the BIOS (44%) or iron oxide fractions (47%). This analysis suggested a high degree of bacterial group masking and a similarity between the BIOS and goethite surface reactivity. An understanding of the BIOS surface chemical heterogeneity and inherent proton and metal binding capacity was obtained through the use of FOCUS apparent pKa spectroscopy.