High-temperature oxidation of titanium-aluminum alloys and development of a method of increasing their heat resistance

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 25, No. 3, pp. 49–53, May–June, 1989.     

Sensory and rheological properties of Polish commercial mayonnaise

Sensory and rheological analyses were performed to compare seven commercial mayonnaises having various fat contents and containing, or not, thickening and stabilizing agents. It was found that mayonnaise samples differed in their sensory and rheological properties. The samples with a higher fat content scored higher in sensory analysis than the low-fat ones. The mayonnaises studied showed non-Newtonian, pseudoplastic flow with yield stress and thixotropy. All mayonnaises, although to a different degree, exhibited a decrease in the apparent viscosity at constant shear. The mayonnaise samples which contained thickeners and stabilizers had a greater rheological stability.     

Functionalized Peptide Fibrils as a Scaffold for Active Substances in Wound Healing

Technological developments in the field of biologically active peptide applications in medicine have increased the need for new methods for peptide delivery. The disadvantage of peptides as drugs is their low biological stability. Recently, great attention has been paid to self-assembling peptides that can form fibrils. Such a formulation makes bioactive peptides more resistant to enzymatic degradation and druggable. Peptide fibrils can be carriers for peptides with interesting biological activities. These features open up prospects for using the peptide fibrils as long-acting drugs and are a valid alternative to conventional peptidic therapies. In our study, we designed new peptide scaffolds that are a hybrid of three interconnected amino acid sequences and are: pro-regenerative, cleavable by neutrophilic elastase, and fibril-forming. We intended to obtain peptides that are stable in the wound environment and that, when applied, would release a biologically active sequence. Our studies showed that the designed hybrid peptides show a high tendency toward regular fibril formation and are able to release the pro-regenerative sequence. Cytotoxicity studies showed that all the designed peptides were safe, did not cause cytotoxic effects and revealed a pro-regenerative potential in human fibroblast and keratinocyte cell lines. In vivo experiments in a dorsal skin injury model in mice indicated that two tested peptides moderately promote tissue repair in their free form. Our research proves that peptide fibrils can be a druggable form and a scaffold for active peptides.     

Protective ceramic multilayer coatings for carbon fibers

Uniform, adherent, crack-free and non-bridging HfC and HfC/SiC coatings on carbon fibers have been synthesized by a reactive CVD (RCVD) process at low temperatures. To fabricate SiC coating on HfC-coated carbon fiber, an alternative approach using unsaturated organosilicon polymer solution was also proposed. The schemes describing the formation of carbide coatings on carbon fibers by RCVD and transformation of unsaturated organosilicon polymers into silicon carbide are discussed. The HfC and HfC/SiC coatings were studied by SEM, EDS and XPS techniques. Coatings are composed of hafnium, silicon and carbon as the main constituents and oxygen and fluorine as contaminants. As was proposed, the composition of the coatings is affected by several factors, among them a chemical attack of coated fibers by gaseous oxygen- and fluorine-containing by-products can be considered as dominant ones. The duplex HfC/SiC-coated carbon fibers exhibit more oxidation resistance at elevated temperatures than the initial and HfC-coated carbon fibers.     

Fatigue limit of induction hardened railway axles

A new surface induction hardening technology was designed for the purpose of increasing the resistance of railway wheelsets to fatigue damage. This paper gives a detailed presentation of the technological aspects of induction hardening of axles. The increased fatigue resistance in hardened surfaces compared with standard heat treatment of EA4T steel was verified using tensile test specimens, press‐fitted wheel seat/axle joints at 1:3 scale and press‐fitted wheel/axle joints at actual size. The 70% increase in the fatigue limit of induction hardened EA4T steel specimens compared with material subjected to standard heat treatment clearly demonstrates the effectiveness of this technology.     

Metamaterials based on polymer dispersions of nanoparticles and particles of copper obtained by cathodic current pulse electrolysis

In the present paper a novel group of electromagnetic metamaterials as well as the method of their fabrication is presented. The studied metamaterials are polymer composites and nanocomposites made of polymer matrix/host (ethylene-vinyl acetate (EVA), polyethylene, polypropylene etc.) filled with copper flakes, of micrometer and/or nanometer size, as the conducting inclusions. The copper filler flakes were obtained by cathodic current pulse electrolysis from copper sulfate electrolytes at the stainless steel electrodes. SEM analysis showed that the morphology and structure of the copper deposit can be precisely controlled by applying different kind of current pulse and reversed current pulsed electrolysis. The polymer composite metamaterials formed by extrusion of small beads of polymer mixed with the copper flakes consisted of polymer matrix and copper flakes, ranging in length from 1 to 500 micrometers, and ranging in thickness from 80 nm to 2000 nm. The concentration of the copper flakes ranged from 0.5 wt% to 40 wt%, depending on the applications and required electromagnetic and mechanical properties. The studied materials were found to exhibit effective magnetic permeability that was smaller than unity, which is indicative of the typical properties of metamaterials. Present development solves technological and economical problems related to modern microelectronics methods which are currently mainly used for metamaterial fabrication.     

Vascular active contour for vessel tree segmentation

In this paper, a novel active contour model is proposed for vessel tree segmentation. First, we introduce a region competition-based active contour model exploiting the gaussian mixture model, which mainly segments thick vessels. Second, we define a vascular vector field to evolve the active contour along its center line into the thin and weak vessels. The vector field is derived from the eigenanalysis of the Hessian matrix of the image intensity in a multiscale framework. Finally, a dual curvature strategy, which uses a vesselness measure-dependent function selecting between a minimal principal curvature and a mean curvature criterion, is added to smoothen the surface of the vessel without changing its shape. The developed model is used to extract the liver and lung vessel tree as well as the coronary artery from high-resolution volumetric computed tomography images. Comparisons are made with several classical active contour models and manual extraction. The experiments show that our model is more accurate and robust than these classical models and is, therefore, more suited for automatic vessel tree extraction.     

Stahlleichtbau mit Verbundelementen

Der folgende Beitrag gibt einen Überblick über den Stahlleichtbau mit Verbundelementen. Im Vordergrund stehen hierbei Bauteile mit Blechdicken < 3 mm, die im Verbund mit OSB‐ oder Gipskartonplatten wirken. Durch die Verbundwirkung ergeben sich nennenswerte Verbesserungen der Tragfähigkeit und der Gebrauchstauglichkeit sowie der bauphysikalischen Eigenschaften. Weiterhin werden Sandwichelemente behandelt. Lightweight steel construction with composite elements. This paper contains an overview of lightweight steel structures acting compositely with other materials. Primarily members with wall thicknesses below 3 mm are covered. They act together with OSB‐ or gypsum‐boards. This leads to a significant improvement of the ultimate load as well as of the serviceability and building physics aspects. Furthermore sandwich panels are discussed.