Shoe soles for the gripping robot: Searching for polymer-based materials maximising friction

The development of light-weight climbing robots capable of operating in various environments is a growing area in robotics. That is why there is a strong need for new tribologically-optimised materials at their gripping devices that may lead to the enhancement of the attachment force while reducing energy expenditure. Since insects are equipped with a set of very efficient attachment systems, enabling them to grip a variety of substrates, they may provide approaches for the innovation of climbing robots’ grippers. The goal of our study was a broad screening of polymeric materials to find out those with similar structure and functional principles to biological examples known from insect smooth attachment systems. Friction, adhesion and stiffness measurements were carried out. Rubber foamy materials covered with thin polymeric films and sandwich-like materials provided excellent compliant properties and the best performance in experiments (friction coefficients up to 3.2).     

Über die Bestimmung des Zirkoniums in hochlegierten Stählen

Übersicht über die im Schrifttum aufgeführten Verfahren zur Zirkoniumbestimmung und deren Schwierigkeiten. Nacharbeitung der photometrischen Bestimmung mit Arsenazo III und Einsatz bei hohen Legierungsgehalten. Anwendung des Verfahrens auf geringere Zirkoniumgehalte ohne Vortrennung.     

Critical Review of Deflection Formulas for FRP-RC Members

The design of fiber-reinforced polymer reinforced concrete (FRP-RC) is typically governed by serviceability limit state requirements rather than ultimate limit state requirements as conventional reinforced concrete is. Thus, a method is needed that can predict the expected service load deflections of fiber-reinforced polymer (FRP) reinforced members with a reasonably high degree of accuracy. Nine methods of deflection calculation, including methods used in ACI 440.1R-03, and a proposed new formula in the next issue of this design guide, CSA S806-02 and ISIS M03-01, are compared to the experimental deflection of 197 beams and slabs tested by other investigators. These members are reinforced with aramid FRP, glass FRP, or carbon FRP bars, have different reinforcement ratios, geometric and material properties. All members were tested under monotonically applied load in four point bending configuration. The objective of the analysis in this paper is to determine a method of deflection calculation for FRP RC members, which is the most suitable for serviceability criteria. The analysis revealed that both the modulus of elasticity of FRP and the relative reinforcement ratio play an important role in the accuracy of the formulas.     

CFRP Prestressed High-Strength Concrete Prisms Subjected to Direct Tension

This paper describes the behavior of carbon fiber-reinforced polymer (CFRP) prestressed high-strength concrete prisms under direct tension. Seven prestressed concrete prisms with different levels of prestressing were cast and tested. Prisms were 50×50?mm in cross section and their lengths varied between 1,400 and 2,000?mm. Concrete compressive strength was as high as 147?MPa. Tension stiffening, crack width, and crack spacing in prisms were investigated. Concrete properties, such as the stress–strain relationship under direct tension and bond strength, were also determined. Test results revealed that tension stiffening in CFRP prestressed high-strength concrete is significant when higher concrete strength and higher prestressing level are applied. Tension stiffening factors are proposed based on the postcracking behavior of concrete. Experimental results also showed that increasing the prestressing level increases the amount of tension stiffening and reduces the number of cracks, which delays their appearance. However, cracks widened at a faster rate in the prisms with higher prestressing levels. Experimental results were compared with Comite Euro-International du Beton and American Concrete Institute proposed equations. Modifications were suggested for the above-mentioned equations to account for use of CFRP bars in prestressed sections.     

Effects of peroxidative stress and age on the concentration of a deoxyguanosine-malondialdehyde adduct in rat DNA

The effect of age and peroxidative stress on the concentration of a deoxyguanosine malondialdehyde adduct (dG-MDA) in rat tissues was investigated. Vitamin E deficiency had not effect on the dG-MDA content of liver DNA in rats fed a diet containing 10% corn oil. When 2% cod liver oil was added to this diet, the dG-MDA content of liver DNA doubled in the positive controls fed a high level of vitamin E (100 ppm dl-α-tocopherol), and there was a further increase when vitamin E was deleted. Neither iron nitrilotriacetate administration nor choline deficiency had any effect on the dG-MDA content of liver DNA. Carbon tetrachloride had a lowering effect. The failure of iron or carbon tetrachloride administration and of vitamin E deficiency to increase liver dG-MDA is consistent with their failure in previous experiments to affect the urinary excretion of dG-MDA. In contrast, these forms of peroxidative stress produce large increments in the urinary excretion of MDA adducts with lysine, reflecting increased formation and degradation of MDA-modified proteins. DNA appears to be protected from modification by MDA produced at extranuclear sites. The frequency of dG-MDA in different tissues of 4-month-old rats varied markedly: brain ≫ liver > kidneys and testes. Higher concentrations of dG-MDA were found in the liver and kidneys, but not the testes, of 25-month-old rats. The determinants of the concentration of dG-MDA in DNA merit further investigation.