Mechanical properties of friction induced nanocrystalline pearlitic steel.

Nanocrystalline structured variants of commercially available alloys have shown potential for boosting the mechanical properties of these materials, leading to a reduction in waste and thereby retaining feasible supply chains. One approach towards achieving these nanostructures resides in frictional treatments on manufactured parts, leading to differential refinement of the surface structure as compared to the bulk material. In this work the machining method is considered to be a testing platform for the formation and study of frictional nanostructured steel, assembly of which is stabilized by fast cooling of the produced chip. Analysis of the mechanical properties has shown extraordinary results at the surface, over 2000 MPa of strength on AISI1045 steel, more than three times the strength of the base material, demonstrating at the same time a reduction of 15% in the elastic modulus. The microscopic analysis suggests a reassembly of the elements in a new lattice of carbon supersaturated nano-ferrite.

Structural evolution and strain induced mixing in Cu-Co composites studied by transmission electron microscopy and atom probe tomography.

A Cu-Co composite material is chosen as a model system to study structural evolution and phase formations during severe plastic deformation. The evolving microstructures as a function of the applied strain were characterized at the micro-, nano-, and atomic scale-levels by combining scanning electron microscopy and transmission electron microscopy including energy-filtered transmission electron microscopy and electron energy-loss spectroscopy. The amount of intermixing between the two phases at different strains was examined at the atomic scale using atom probe tomography as complimentary method. It is shown that Co particles are dissolved in the Cu matrix during severe plastic deformation to a remarkable extent and their size, number, and volume fraction were quantitatively determined during the deformation process. From the results, it can be concluded that supersaturated solid solutions up to 26 at.% Co in a fcc Cu-26 at.% Co alloy are obtained during deformation. However, the distribution of Co was found to be inhomogeneous even at the highest degree of investigated strain.

On the remarkable thermal stability of nanocrystalline cobalt via alloying.

Nanostructured Co materials are produced by severe plastic deformation via alloying with small amounts of C and larger amounts of Cu. The thermal stability of the different nanostructured Co materials is studied through isothermal annealing at different temperatures for various times and compared to the stability of severe plastically deformed high-purity nanocrystalline Co. The microstructural changes taking place during annealing are evaluated by scanning electron microscopy, transmission electron microscopy and microhardness measurements. In the present work it is shown that the least stable nanostructured material is the single-phase high purity Co. Alloying with C improves the thermal stability to a certain extent. A remarkable thermal stability is achieved by alloying Co with Cu resulting in stabilized nanostructures even after annealing for long times at high temperatures. The essential reason for the enhanced thermal stability is to be found in the immiscibility of both components of the alloy.

Novel temperature dependent tensile test of freestanding copper thin film structures.

The temperature dependent mechanical properties of the metallization of electronic power devices are studied in tensile tests on micron-sized freestanding copper beams at temperatures up to 400 °C. The experiments are performed in situ in a scanning electron microscope. This allows studying the micromechanical processes during the deformation and failure of the sample at different temperatures.

Bioabsorbable implants in orthopaedics: new developments and clinical applications.

The use of bioabsorbable implants in orthopaedic surgical procedures is becoming more frequent. Advances in polymer science have allowed the production of implants with the mechanical strength necessary for such procedures. Bioabsorbable materials have been utilized for the fixation of fractures as well as for soft-tissue fixation. These implants offer the advantages of gradual load transfer to the healing tissue, reduced need for hardware removal, and radiolucency, which facilitates postoperative radiographic evaluation. Reported complications with the use of these materials include sterile sinus tract formation, osteolysis, synovitis, and hypertrophic fibrous encapsulation. Further study is required to determine the clinical situations in which these materials are of most benefit.

Influence of dietary amiloride supplement on the zinc status of growing rats with marginal zinc supply.

We divided 36 male pathogen-free Sprague-Dawley rats with an average live mass (LM) of 51 g into four treatment groups of nine animals each. They received for a period of 28 trial days a semisynthetic purified diet based on casein for ad libitum consumption, supplemented with 5 ppm zinc (groups 1-3) or 57 ppm zinc (group 4) as zinc sulfate. In addition to the diet, groups 2 and 3 were given a diuretic supplement of amiloride at the therapeutic dose rate (0.4 mg amiloride/kg LM0.75 per day) or in a dosage corresponding to the chronic toxicity level (maximum tolerated dose; 0.8 mg amiloride/kg LM0.75 per day). The supplementation with amiloride, acting as a potential Zn-binding ligand at the selected dosage levels, had no influence on the animals' live weight during the 28-day trial period; weight gain was determined solely by the dietary Zn concentration. Amiloride administered at the therapeutic or the maximum tolerated dose produced no evidence of a diminished Zn status in terms of the alkaline phosphatase activity in the serum or the Zn concentration in the serum, femur and testes. Medication with amiloride at the maximum tolerated dose even exerted a positive effect on the zinc supply status as demonstrated by the raised Zn concentration in the serum. This suggests that zinc supplementation may not be required during medication with amiloride in human medicine.

BQ-153, a novel endothelin (ET)A antagonist, attenuates the renal vascular effects of endothelin-1.

Endothelin (ET)-1, leukotriene D4 and the thromboxane analogue, U-44069, were all shown to produce dose-dependent reductions in renal blood flow after direct injection into the renal artery of anaesthetized pigs. The effects of ET-1 differed from the other two mediators in that ET-1 caused a transient vasodilator followed by a prolonged vasoconstrictor response. The pressor response was not mediated by the secondary release of either leukotriene D4 or thromboxane A2 as evidenced by the lack of effect of appropriate receptor antagonist MK571 (3-[-2(7-chloro-2 quinolinyl) ethenyl]phenyl[3-(dimethylamino-3-oxopropyl)thio]methyl thio propionic acid) and L-670,596 respectively. This response, however, could be inhibited in a dose-dependent fashion by the selective ETA antagonist, BQ-153 (cyclo-D-sulphalanine-L-Pro-D-Val-L-Leu-D-Trp-). Following blockade by BQ-153 the vasodilator response was unaffected and a residual pressor response remained, suggesting that either or both of these effects were mediated either through an ETB or a novel, as yet undefined, endothelin receptor.