Analyse des Schädigungs- und Erholungsverhaltens trockenlaufender Friktionspaarungen

Forschung im Ingenieurwesen - Die Reib- und Verschleißeigenschaften trockenlaufender Friktionspaarungen werden mithilfe neuer Methoden bestimmt, um deren Schädigungs- und...     

Regulatory interaction of N-formyl peptide chemoattractant receptors with the membrane skeleton in human neutrophils

The cytoskeleton and/or membrane skeleton has been implicated in the regulation of N-formyl peptide receptors. The coupling of these chemotactic receptors to the membrane skeleton was investigated in plasma membranes from unstimulated and desensitized human neutrophils using the photoreactive agonist N-formyl-met-leu-phe-lys-N epsilon-[125I]2(p-azidosalicylamido)ethyl-1,3'- dithiopropionate (fMLFK-[125I]ASD). When membranes of unstimulated cells were solubilized in Triton-X 100, a detergent that does not disrupt actin filaments, only 50% of the photoaffinity-labeled receptors were solubilized sedimenting in sucrose density gradients at a rate consistent with previous reports. The remainder were found in the pellet fraction along with the membrane skeletal actin. Solubilization of the membranes in the presence of p-chloromercuriphenylsulfonic acid, elevated concentrations of KCl, or deoxyribonuclease I released receptors in parallel with actin. When membranes from neutrophils, desensitized by incubation with fMLFK-[125I]ASD at 15 degrees C, were solubilized, nearly all receptors were recovered in the pellet fraction. Incubation of cells with the ligand at 4 degrees C inhibited desensitization partially and prevented the conversion of a significant fraction of receptors to the form associated with the membrane skeletal pellet. In these separations the photoaffinity-labeled receptors not sedimenting to the pellet cosedimented with actin. Approximately 25% of these receptors could be immunosedimented with antiactin antibodies suggesting that N-formyl peptide receptors may interact directly with actin. These results are consistent with a regulatory role for the interaction of chemotactic N-formyl peptide receptors with actin of the membrane skeleton.     

Observation of incongruent melting in Cu10Hf7

Differential thermal analysis, scanning electron microscopy, and x-ray microanalysis are used to show that the intermetallic compound Cu₁₀Hf₇, previously reported as melting congruently at 1025 °C, melts incongruently to CuHf₂ and a Hf-Cu liquid at that temperature. A eutectic point previously reported at 43.6 at.% Hf and 980 °C does not exist.     

22—A SIMPLE METHOD FOR THE DETERMINATION OF THE K2ZrF6 CONTENT IN SOLUTION AND ON WOOL

A simple, rapid titrimetric method for the determination of zirconium is proposed. This method may be used for the determination of zirconium in the bath or on undyed and dyed wools. The zirconium content of treated wool was determined (i) by titration of the acid hydrolysate of the wool and (ii) by calculation of the difference between the initial and final bath concentrations obtained by titration. The two methods were in excellent agreement. Good correlation was found between this simple method and the determination of zirconium by atomic-absorption spectroscopy.     

The development and testing of small concentrating PV systems

Spreadsheets have been used to compare some 90 possible small PV concentrator designs that might be suitable for use at remote sites. They have apertures of about 2 m², use BP Solar LBG cells, and employ small aperture modules to reduce heat sinking and construction costs. Designs include fixed V-troughs and CPCs, single axis tracked cylindrical lens and mirror systems, and two-axis tracked spherical-symmetry systems. Performance and volume production costs were estimated. Four promising systems were constructed as prototypes:

(A) Point-focus Fresnel lenses, two-axis tracking; Cg=32×; and 69× with secondaries.

(B) Line-focus mirror parabolic troughs, one-axis tracking, Cg=20×.

(C) SMTS (‘single-mirror two-stage’), one-axis tracking, Cg=30×.

(F) Multiple line-focus mirror parabolic troughs, E–W 1/day manual tracking, Cg=6×.

The prototypes were tested at Reading, and three for up to a year’s field trial at ZSW’s test site, Widderstall, in Germany. The best system efficiencies, normalised to 25°C and excluding the end losses of linear systems, were 12.5%, 13.2%, 13.6% and 14.3% for collectors A, B, C, and F, respectively. The collectors were practical and robust, and the performances of collectors B, C and F are only 10% below the estimates in the spreadsheet calculations. The best collectors have estimated production costs between 1.5 and 1.8 US $/Wp, yielding energy costs at a good site (excluding BOS and overheads) of between 5 and 7 cents/kWh (18 and 25 cents/MJ). On the same cost basis a conventional PV array costs 4.3 $/Wp, and 18 cents/kWh (65 cents/MJ).     

The fate of forage plant DNA in farm animals: a collaborative case-study investigating cattle and chicken fed recombinant plant material

 The fate of ingested recombinant plant DNA in farm animals (cattle and chicken) being fed a diet containing conventional maize or recombinant Bacillus thuringiensis toxin-maize (Bt-maize) is described. The probability of the detection by polymerase chain reaction of chloroplast-specific gene fragments of different lengths (199 bp and 532 bp) and a Bt-maize-specific fragment [truncated version of CryIA(b)] is shown. First data indicated that only short DNA fragments (<200 bp) derived from plant chloroplasts could be detected in the blood lymphocytes of cows. In all other cattle organs investigated (muscle, liver, spleen, kidney) plant DNAs were not found, except for faint signals in milk. Furthermore, Bt-gene fragments possibly recording the uptake of recombinant maize, were not detected in any sample from cattle. However, in all chicken tissues (muscle, liver, spleen, kidney) the short maize chloroplast gene fragment was amplified. In contrast to this, no foreign plant DNA fragments were found in eggs. Bt-gene specific constructs originating from recombinant Bt-maize were not detectable in any of these poultry samples either. Received: 23 February 2000 / Revised version: 20 March 2000     

Annealing effects on defect levels of CdTe:Cl materials and the uniformity of the electrical properties

CdTe crystals grown by the traveling heater method (THM) often show a pronounced nonuniformity along the ingots due to the thermal irregularities, the Te-excess growth conditions resulting from the retrograde slope of the solidus line of the phase diagram, and from the introduced impurities. In addition, structural defects can be present that influence the electrical and optical properties. The aim of this work is to study the annealing effects of Cl-doped CdTe on the uniformity of the material, the defects, the resistivity, the /spl mu//spl tau/ product, and on the detection properties. Samples have been annealed under various pressures (vacuum, argon, CdCl/sub 2/) and include different temperature stages between 250/spl deg/C and 850/spl deg/C. An increase of the resistivity was observed after a thermal treatment of these samples under argon pressure. In this case, the highest resistivity was obtained by annealing samples at 460/spl deg/C. The presence of CdCl/sub 2/ during the annealing leads to a better uniformity of the materials. The defects present in the materials have been investigated by photo-induced transient current spectroscopy (PICTS), thermo-electric emission spectroscopy (TEES), and thermally stimulated current (TSC) methods, which allow the calculation of their activation energy, their cross section, and their concentration.