Plasma Nitriding of CrMoV Steel for the Enhancement of Hardness and Corrosion Resistance

In the plasma ionic environment of nitrogen and hydrogen at 4:1 ratio, nitriding had been realized in the plasma laboratory. Nitriding of steel samples was followed at the lower temperature of 450 °C and also at the higher temperature of 550 °C while the sample was biased at the fixed - 250 V. Steel nitrided at 550 °C had shown a significantly enhanced resistance to corrosion in comparison to that of steel nitrided at 450 °C. X-ray diffraction studies of nitrided steels had shown the presence of nitrides of iron (FexN). Scanning electron microscopic and the electron dispersive spectroscopic analyses (SEM + EDS) of the cross section of the nitrided steels had shown the nitrided layer and the elemental distribution from top to the core. Following structural analysis, microhardness and the potentiodynamic polarization tests were performed. A significant improvement in hardness (around 1180 Hv) and the case depth around 150 lm was obtained after nitriding at the higher temperature. Corrosion resistance was also found to be significantly improved. These achievements might be attributed to the presence of FexN, CrN phases and also to the nitrogen solid solution

Extension of the life span of pressure ulcer fibroblasts with recombinant human interleukin-1 beta.

Recombinant human interleukin-1 beta (rhuIL-1 beta) was investigated in a randomized, blinded placebo-controlled trial to evaluate its effect on the healing of chronic pressure ulcers. The influence of this topically applied cytokine to 26 pressure ulcer patients was correlated with tissue culture and electron microscopic evaluation. Cellular replication studies showed that low (0.01 micrograms/cm2/day) and medium (0.1 micrograms/cm2/day) concentrations of rhuIL-1 beta were not effective in extending replication in pressure ulcer fibroblasts, in vitro. Tissue culture measurements from pressure ulcer biopsies demonstrated that, after 29 days of a high level of rhuIL-1 beta treatment (1.0 micrograms/cm2/day), the cytokine was effective in extending the ability of pressure ulcer fibroblasts to replicate. Tissue culture and electron microscopy suggested that, although rhuIL-1 beta promoted increases in fibroblast numbers, the primary effect appeared to be development of the extracellular matrix. The possible direct and indirect influences of rhuIL-1 beta therapy on pressure ulcers are discussed

Experimental and theoretical methods to evaluate the pressure losses in air distribution lines

Modern pipes for compressed air distribution lines are made of aluminium alloy and built by means of manufacturing extrusion process. This kind of pipes needs of suitable mathematical formulation providing performances, in terms of pressure drop and flow-rate. To this aim in this work a methodology based both on experimental tests and on theoretical approach was carried out. Analytical formulations were performed providing best experimental data fitting and range of applicability. Performances of most common line components (straight pipes, elbows, straight fittings and tees) made of different commercial sizes were evaluated carrying out experimental tests by means of a properly instrumented test bench. Experimental and theoretical results were in good agreement, thus validating the proposed formulation

Iron limitation effects on nitrogen-fixing organisms with possible implications for cyanobacterial blooms

Cyanobacteria-dominated harmful algal blooms are increasing in occurrence. Many of the taxa contributing to these blooms are capable of fixing atmospheric nitrogen and should be favored under conditions of low nitrogen availability. Yet, synthesizing nitrogenase, the enzyme responsible for nitrogen fixation, is energetically expensive and requires substantial concentrations of iron. Phosphorus addition to nitrogen poor streams should promote nitrogen fixation, but experimental results so far have been inconclusive, suggesting that other factors may be involved in controlling this process. With iron potentially limited in many streams, we examined the influence of phosphorus-iron colimitation on the community structure of nitrogen-fixing organisms. In stream microcosms, using microscopic and molecular sequence data, we observed: (i) the greatest abundance of heterocyst forming nitrogen-fixing cyanobacteria in low nitrogen treatments with high phosphorus and iron and (ii) greater abundance of non-photosynthetic nitrogen-fixing bacteria in treatments with nitrogen compared to those without it. We also found that comparisons between molecular results and those obtained from microscopic identification provided complementary information about cyanobacterial communities. Our investigation indicates the potential for phosphorus-iron colimitation of stream nitrogen-fixing organisms