Olive Oil-Based Lipid Emulsions Do Not Influence Platelet Receptor Expression in Comparison to Medium and Long Chain Triglycerides In vitro

Lipid emulsions influence platelet aggregation and receptor expression. However, the effect on platelet function is not fully explained. Therefore, the aim of this study was to examine the influence of the lipids Lipofundin^®, Lipidem^® and ClinOleic^® on surface expressions of P‐selectin, GPIb and GPIIb/IIIa on platelets in vitro. Whole blood was incubated in two different concentrations (0.06 and 0.6 mg/ml) of LCT/MCT, n‐3/LCT/MCT and LCT‐MUFA for 30 min, followed by activation with TRAP‐6 or ADP for flow‐cytometric assay. Rates of P‐selectin, GPIb and GPIIb/IIIa expression were analyzed. There was a significant increase in GPIIb/IIIa‐ and P‐selectin‐expression after incubation with LCT/MCT and n‐3/LCT/MCT at the concentration of 0.6 mg/ml, without and after stimulation with TRAP‐6 and ADP. GPIb was significantly decreased. Accordingly, LCT‐MUFA had no effect on receptor expression of platelets in vitro. We demonstrated that LCT‐MUFA did not activate receptor expression of platelets whereas LCT/MCT significantly increased platelet aggregation in vitro. This finding should be noted for parenteral nutrition of intensive care patients and, in the future, might provide further insight into the pathogenic pathways of acute thromboembolic events. However, prospectively designed clinical studies are needed to support our results.     

Rational Design of Pseudozyma antarctica Lipase B Yielding a General Esterification Catalyst

Pseudozyma antarctica lipase B (CALB) shows activity in the acrylation of hydroxypropylcarbamate, a racemic mixture of enantiomers of primary and secondary alcohols. However, full conversion is hampered by the slowly reacting S enantiomer of the secondary alcohol. The same is true for a wide range of secondary alcohols, for example, octan‐2‐ and ‐3‐ol. In order to get high conversion in these reactions in a short time, the stereospecificity pocket of CALB was redesigned by using predictions from molecular modeling. Positions 278, 104, and 47 were targeted, and a library for two‐site saturation mutagenesis at positions 104 and 278 was constructed. The library was then screened for hydrolysis of acrylated hydroxypropylcarbamates. The best mutants L278A, L278V, L278A/W104F, and L278A/W104F/S47A showed an increased conversion in hydrolysis and transesterification of more than 30 %. While the wild‐type showed only 73 % conversion in the acrylation of hydroxypropylcarbamate after 6 h, 97 % conversion was achieved by L278A in this time. Besides this, L278A/W104F reached >96 % conversion in the acrylation of octan‐2‐ and ‐3‐ol within 48 h and showed a significant decrease in stereoselectivity, while the wild‐type reached only 68 and 59 % conversion, respectively. Thus the new biocatalysts can be used for efficient transformation of racemic alcohols and esters with high activity when the high stereoselectivity of the wild‐type hampers complete conversion of racemic substrates in a short time.     

Quantitative Photoelectron Spectroscopy (ESCA) of Sulfate Aerosol on Filtration Media

Photoelectron spectroscopy (ESCA) was applied to sub-micron sodium sulfate particles deposited on different filter surfaces. Only flat membrane filters were found to be suitable for aerosol analysis by ESCA. A linear dependence of ESCA signal on aerosol mass was observed for different polydisperse mass loadings on Nuclepore filters. We have also performed a systematic study of the relation between ESCA signal and particle diameter (30–220 nm). Lower detection limits range between 25 and 100 ng SO² ₄ per 0.25-cm² analyzed filter area, depending on particle radius and/or size distribution. We discuss future applications of ESCA in aerosol analysis.     

A Shock and Expansion Wave-driven Powder Disperser

The paper describes a method for dispersing small (micro- and milligram) quantities of dry powder using a shock and expansion wave technique. The batch-wise operating apparatus aerosolizes any particulate matter with primary particles down to the submicrometer size range. Depending on the initial pressure situation and on the powder mass to be dispersed, the degree of dispersion or the fraction of agglomerates can be adjusted in a wide range. For calibration purposes monodisperse aerosols can also be generated employing monosized powders. The operating characteristics of the device are presented.     

Impact of powder morphology on quality of low-pressure injection moulded reaction-bonded net shape oxide ceramics

Low-pressure injection moulding is a very efficient process for net shape manufacturing of ceramic micro parts. In order to obtain sintered ceramic specimens without shape distortion or damages, density gradients in the green bodies have to be avoided. Especially feedstocks with a solid loading near the critical powder volume content often tend to segregate the binder while flowing. However, the value of critical powder content can be significantly influenced by particle size, particle size distribution and particle morphology. This paper compares two powder mixtures of identical chemical compositions with different specific surfaces and morphology and evaluates their workability for low-pressure injection moulding. The aim of this paper is to identify the influence of morphology on feedstock rheology as well as on accuracy, mechanical properties and microstructure of net shape manufactured reaction-bonded zircon ceramics.     

Resistance degradation in donor-doped PZT ceramic stacks with Ag/Pd electrodes: II. Distribution of conduction paths

Neodymium-doped PZT layers with Ag/Pd inner electrodes showed a metal-like conductive behaviour after degradation under electric fields of 250–1250 V/cm at 420–520 °C. This conductive state was studied by means of impedance spectroscopy. Depth profiling by mechanical removal of material revealed a strongly inhomogeneous distribution of conduction paths within a degradation zone located in the interior of the ceramic layers, probably along grain boundaries. The thickness of the degradation zone (several tens to hundreds of micrometres) increased with degradation time and DC load. After complete mechanical removal of the degradation zone, virgin PZT was again found. Spatially resolved conductivity measurements (microelectrodes) and conductive atomic force microscopy (C-AFM) investigations gave further information on inhomogeneities in conductivity and the connectivity of surface precipitates. A mechanistic model is provided suggesting formation of silver paths along grain boundaries according to a mechanism which strongly differs from conventional electrochemical dendrite formation.     

Influence of dispersant,storage time and temperature on the rheological properties of zirconia–paraffin feedstocks for LPIM

The dependence of the rheological properties of zirconia–paraffin feedstocks for low-pressure injection moulding (LPIM) on binder composition, storage time and temperature was investigated. Feedstocks with varying amounts of dispersant were fabricated to work out the required quantity for a monolayer of dispersant molecules on zirconia particles. Experimental results revealed that a shear rate dependent characteristic of the viscosity against the amount of dispersant exists. The observations were compared with calculated values according to an adsorption model, which overestimated the required quantity of dispersant to form a monolayer. Feedstocks stored at elevated temperature for several days exhibited a time-dependent decrease of the yield stress and viscosity, which is supposed to be caused by physical or chemical interactions among zirconia and the dispersant. Increasing working temperature and decreasing solids loading were found to significantly decrease the yield stress as well as the viscosity. Flow activation energies and flow indices were calculated and compared with literature. This study shows that the dispersant used in this investigation has a remarkable influence especially on the time-dependent flow behaviour of zirconia–paraffin feedstocks that affects further processing and reproducibility.     

Fabrication of particle and composition gradients by systematic interaction of sedimentation and electrical field in electrophoretic deposition

The systematic interaction of sedimentation and electrical field in electrophoretic deposition allows the tailoring of specific properties of deposited green bodies. This technique permits a selective deposition of the nanosized fraction of conventional powders with broad or non-monomodal particle size distribution, thus making preceding classification obsolete. Potential applications are coatings with a very smooth surface or the replication of microstructures or moulds which are filled with nanosized particles and subsequently with coarser particles as support in one process step. Also, graded structures can be fabricated with regard to particle size distribution, porosity and composition (e.g. zirconia toughened alumina). In this paper, the interaction of sedimentation and electrical field in electrophoretic deposition is described. In addition the effectiveness of the combined process will be shown.     

Fabrication of CNT-SiC/SiC composites by electrophoretic deposition

Due to the outstanding mechanical and thermal properties of carbon nanotubes (CNTs), they are considered suitable reinforcement for structural materials. In this study, for the first time, electrophoretic deposition (EPD) was used to deposit (multi-walled) CNTs onto SiC fibres (SiC_f) to form an effective CNT interphase layer for SiC_f/SiC composites. This deposition was followed by electrophoretic infiltration of the CNT-coated SiC fibre mats with SiC powder to fabricate a new CNT-SiC-fibre-reinforced SiC-matrix (SiC_f/SiC) composite for fusion applications. In these EPD experiments, a commercial aqueous suspension of negatively charged CNTs and an optimized aqueous suspension of negatively charged SiC particles were used. The CNT-coatings on the SiC fibres were firm and homogenous, and uniformly distributed nanotubes were observed on the fibre surfaces. In a following step of EPD, a thick SiC layer was formed on the fibre mat when the CNT-coated SiC fibres were in contact with the positive electrode of the EPD cell; however, spaces between the fibres were not fully filled with SiC. Conversely, when CNT-coated SiC fibres were isolated from the electrode, the SiC particles were able to gradually fill the fibre mat resulting in relatively high infiltration, which leads to dense composites.