Tribologische Untersuchungen an Gleitpaarungen aus ZrO2, POM und Stahl für den Einsatz als wassergeschmierte mikromechanische Bauteile

Tribological studies on sliding pairs of ZrO₂, POM and steel for applications as water‐lubricated micro‐mechanical components Micro‐tribological tests were carried out on varying mated sliding pairs of TZP‐ZrO₂, polyoxymethylene (POM) and steel 17‐4PH in air and distilled water using a laboratory tribometer (system: flattened ball‐on‐disc) under unidirectional sliding. The effects of relative humidity in air or water lubrication, respectively, the surface pressure and the sliding speed were studied with the self‐mated zirconia. The results show that zirconia can be a favourable material for tribologically high‐loaded micro‐mechanical components at water lubrication, particularly, in comparision with already used polymeric materials. Self‐mated zirconia resulted also during unlubricated sliding in air in lower friction and wear than the steel/steel, POM/steel or POM/ZrO₂ pairs, respectively. Keywords: precision engineering, micromechanical components, sliding wear, friction, water lubrication, zirconia, polyoxymethylene, steel 17‐4 PH.     

Supersensitivity of cortical neurones of the rat to acetylcholine and L-glutamate following chronic morphine treatment

Report about 4 operations using Hohmann's procedure in therapy-resistent epicondylitis humeri ulnaris. The ulnar nerve was not seen during operation. The intervention is as simple as on the radial side. It can be recommended.     

Simulation von Schädigungs‐ und Kriechvorgängen im Asphalt

Simulation of damage and creep processes in asphalt There is an increasing need for the use of numerical methods in road design. Here, the main difficulty lies in modeling the highly complex, nonlinear material behaviour of asphalt. The present paper deals with this problem and proposes a continuum mechanics model serving to simulate the main nonlinear mechanical processes taking place in asphalt. Plastic deformation, damage and crack development as well as viscous processes are treated. The model is implemented into the finite element program Abaqus and is used to simulate tests on asphalt specimens.     

Comparative Anti-Inflammatory Effects of Salix Cortex Extracts and Acetylsalicylic Acid in SARS-CoV-2 Peptide and LPS-Activated Human In Vitro Systems

The usefulness of anti-inflammatory drugs as an adjunct therapy to improve outcomes in COVID-19 patients is intensely discussed in this paper. Willow bark (Salix cortex) has been used for centuries to relieve pain, inflammation, and fever. Its main active ingredient, salicin, is metabolized in the human body into salicylic acid, the precursor of the commonly used pain drug acetylsalicylic acid (ASA). Here, we report on the in vitro anti-inflammatory efficacy of two methanolic Salix extracts, standardized to phenolic compounds, in comparison to ASA in the context of a SARS-CoV-2 peptide challenge. Using SARS-CoV-2 peptide/IL-1β- or LPS-activated human PBMCs and an inflammatory intestinal Caco-2/HT29-MTX co-culture, Salix extracts, and ASA concentration-dependently suppressed prostaglandin E2 (PGE₂), a principal mediator of inflammation. The inhibition of COX-2 enzyme activity, but not protein expression was observed for ASA and one Salix extract. In activated PBMCs, the suppression of relevant cytokines (i.e., IL-6, IL-1β, and IL-10) was seen for both Salix extracts. The anti-inflammatory capacity of Salix extracts was still retained after transepithelial passage and liver cell metabolism in an advanced co-culture model system consisting of intestinal Caco-2/HT29-MTX cells and differentiated hepatocyte-like HepaRG cells. Taken together, our in vitro data suggest that Salix extracts might present an additional anti-inflammatory treatment option in the context of SARS-CoV-2 peptides challenge; however, more confirmatory data are needed.     

Dependence of Dye Regeneration and Charge Collection on the Pore‐Filling Fraction in Solid‐State Dye‐Sensitized Solar Cells

Solid‐state dye‐sensitized solar cells rely on effective infiltration of a solid‐state hole‐transporting material into the pores of a nanoporous TiO₂ network to allow for dye regeneration and hole extraction. Using microsecond transient absorption spectroscopy and femtosecond photoluminescence upconversion spectroscopy, the hole‐transfer yield from the dye to the hole‐transporting material 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9'‐spirobifluorene (spiro‐OMeTAD) is shown to rise rapidly with higher pore‐filling fractions as the dye‐coated pore surface is increasingly covered with hole‐transporting material. Once a pore‐filling fraction of ≈30% is reached, further increases do not significantly change the hole‐transfer yield. Using simple models of infiltration of spiro‐OMeTAD into the TiO₂ porous network, it is shown that this pore‐filling fraction is less than the amount required to cover the dye surface with at least a single layer of hole‐transporting material, suggesting that charge diffusion through the dye monolayer network precedes transfer to the hole‐transporting material. Comparison of these results with device parameters shows that improvements of the power‐conversion efficiency beyond ≈30% pore filling are not caused by a higher hole‐transfer yield, but by a higher charge‐collection efficiency, which is found to occur in steps. The observed sharp onsets in photocurrent and power‐conversion efficiencies with increasing pore‐filling fraction correlate well with percolation theory, predicting the points of cohesive pathway formation in successive spiro‐OMeTAD layers adhered to the pore walls. From percolation theory it is predicted that, for standard mesoporous TiO₂ with 20 nm pore size, the photocurrent should show no further improvement beyond an ≈83% pore‐filling fraction.     

Comparison of methods for the synchronization of estrous cycles in dairy cows. 2. Effects of progesterone and parity on conception

Three experiments with 571 dairy cows indicated that significantly more primiparous cows given two prostaglandin F2 alpha injections 14 d apart conceived within 30 d of first AI than did cows given two injections 11 d apart (84 vs. 62%). Fewer multiparous cows given two injections 14 d apart and inseminated after estrus conceived than did cows given two injections and a progesterone intravaginal coil inserted 8 d after the first injection (42 vs. 66%). Fewer cows given one injection of prostaglandin and inseminated at estrus conceived than did cows given two injections 14 d apart and a progesterone coil (39 vs. 66%). Conception rates of cows given two prostaglandin injections were positively related to plasma progesterone concentrations 2 and 4 d before the second injection (r = .81 and .86). Cows with progesterone concentrations below 5 ng/ml, 2 d before the second prostaglandin injection, and synchronized by two prostaglandin injections or by two injections and a progesterone coil had conception rates of 36 and 63%, respectively. Cows with progesterone concentrations above 5 ng/ml had a conception rate of 75 and 46% in the two treatments, respectively. Conception after estrus synchronization depends on the method and on the plasma concentrations of progesterone. Progesterone coils may be used before AI to enhance fertility in cows with low progesterone concentrations.     

Synthesis of statistical polydiene networks by reaction of liquid polyenes with telechelic siloxanes

The present investigation concerns the synthesis of statistical networks similar to vulcanized rubber. We have used liquid precursor polymers: polybutadiene (PB) and polyisoprene (PI) with telechelic siloxanes. The reactivity of the polydienes can be classified as follows: PB units 1,2 PI units 3,4 PI units 1,4 0. The network formation is a function of the ratio R = nb, of pendent double bonds/nb. of SiH. For R 1 the networks are rather hard and brittle, for 8 R 10 they are soft and elastic, whereas for R 16 the gels obtained are very soft and sticky.