Integrated ambient ozone evaluation by passive samplers and clover biomonitoring mini-stations

An ozone monitoring network was set up using passive samplers and biological mini-stations of two clones of white clover (Trifolium repens L. cv. Regal), NC-R (O(3)-resistant) and NC-S (O(3)-sensitive). This paper reports on a pilot study performed in the period June-October 1999 in the Rome municipal area by using five biomonitoring mini-stations and ozone passive samplers with a new nitrite based design. This combined methodology can be used to obtain information on the biological implications of the injury due to tropospheric ozone. The two techniques can integrate data for the short-medium period and can be placed in different urban and rural sites, proving to be a very useful tool for ozone concentration mapping.     

Biohydrometallurgical/UV production of ferrous sulphate heptahydrate crystals from pyrite present in coal tailings

The objective of this work was to develop a biohydrometallurgical/UV radiation route to produce ferrous sulphate heptahydrate (melanterite) from the pyrite present in coal tailings. The experimental work was carried out with a pyrite concentrate obtained from gravimetric processing of coal tailing. At laboratory scale it was performed the oxidation of pyrite in an aqueous medium in packed bed leaching columns in an oxidising environment with the presence of acidophilic bacteria (Acidithiobacillus ferrooxidans). The recirculation of the liquor allowed obtaining an iron-rich extract. The conversion of Fe³⁺ to Fe²⁺ was performed using ultraviolet irradiation (UV). Finally, the solution was evaporated allowing the formation of iron sulphate crystals. The results demonstrated that it is possible to produce high purity ferrous sulphate heptahydrate crystals using coal tailings as raw material.     

Undoped, nitrogen-doped and boron-doped multiwalled carbon nanotube/poly(vinyl alcohol) composite as active layer in simple hydrostatic pressure sensors

We report on hydrostatic pressure sensors prepared using 10 % w/w multiwalled carbon nanotube (MWCNT)/poly(vinyl alcohol) composites. Three types of carbon nanotubes were used in the composites: undoped MWCNTs, nitrogen-doped MWCNTs and boron-doped MWCNTs (B-MWCNTs). The sensor response was tested using an alternating current input, measuring the capacitance and conductance outputs. The sensors based on the three composites show a linear capacitance and conductance sensitivity pressure dependence in the range 50–120 kPa, but a higher sensitivity to pressure dependence above this interval. The highest angular coefficient of the sensitivity, which reached 0.092 kPa^?1, was observed for the capacitance sensitivity of the B-MWCNT based composite.     

Use of modified activated carbon for the oxidation of aqueous sulfide

The oxidation of aqueous sulfide promoted by activated carbon (AC) was investigated. Raman, infrared, X-ray diffraction, ultraviolet–visible spectroscopy and electron paramagnetic resonance analyses show that AC oxidizes aqueous sulfide to form a complex mixture of polysulfides and sulfur oxide species. This oxidation is strongly promoted by the presence of oxygen surface groups introduced by oxidation of the AC as shown by kinetic measurements. These results are discussed in terms of the similarities the AC have with enzymatic systems, i.e. redox surface groups (e.g. quinone) combined with an efficient electron conduction system.     

In vitro studies and preliminary in vivo evaluation of silicified concentrated collagen hydrogels

Hybrid and nanocomposite silica-collagen materials derived from concentrated collagen hydrogels were evaluated in vitro and in vivo to establish their potentialities for biological dressings. Silicification significantly improved the mechanical and thermal stability of the collagen network within the hybrid systems. Nanocomposites were found to favor the metabolic activity of immobilized human dermal fibroblasts while decreasing the hydrogel contraction. Cell adhesion experiments suggested that in vitro cell behavior was dictated by mechanical properties and surface structure of the scaffold. First-to-date in vivo implantation of bulk hydrogels in subcutaneous sites of rats was performed over the vascular inflammatory period. These materials were colonized and vascularized without inducing strong inflammatory response. These data raise reasonable hope for the future application of silica-collagen biomaterials as biological dressings.     

Toward local growth of individual nanowires on three-dimensional microstructures by using a minimally invasive catalyst templating method

We present a novel minimally invasive postprocessing method for catalyst templating based on focused charged particle beam structuring, which enables a localized vapor-liquid-solid (VLS) growth of individual nanowires on prefabricated three-dimensional micro- and nanostructures. Gas-assisted focused electron beam induced deposition (FEBID) was used to deposit a SiO(x) surface layer of about 10 × 10 μm(2) on top of a silicon atomic force microscopy cantilever. Gallium focused ion beam (FIB) milling was used to make a hole through the SiO(x) layer into the underlying silicon. The hole was locally filled with a gold catalyst via FEBID using either Me(2)Au(tfac) or Me(2)Au(acac) as precursor. Subsequent chemical vapor deposition (CVD)-induced VLS growth using a mixture of SiH(4) and Ar resulted in individual high quality crystalline nanowires. The process, its yield, and the resulting angular distribution/crystal orientation of the silicon nanowires are discussed. The presented combined FIB/FEBID/CVD-VLS process is currently the only proven method that enables the growth of individual monocrystalline Si nanowires on prestructured substrates and devices.     

Comparison of microstructural properties and Charpy impact behaviour between different plates of the Eurofer97 steel and effect of isothermal ageing

The microstructure and fracture properties of the Eurofer97 steel plates of thickness 14 mm and 25 mm were investigated in as-received state and in state after long-term thermal ageing (550 °C/5000 h). Detailed microstructure studies were carried out by means of optical light, electron and quantitative electron microscopy. Mechanical properties were evaluated by means of Charpy impact testing and hardness testing and fracture surfaces were fractographically analysed in macro and microscales. The microstructure of the Eurofer97 consisted of tempered martensite with M₂₃C₆ and MX precipitates. Microstructure of 14 mm plate was more homogenous and fine grained than 25 mm plate. Due to different microstructure the t_DBTT of thicker plate was on +10 °C higher than for 14 mm plate for which reached −60 °C. Slight microstructural changes on the level of subgrain consisting of their partial recrystallization and slight carbide coarsening were observed after applied ageing. The isothermal ageing caused evident shift in t_DBTT about +5 °C, which was most likely caused by recrystallization of subgrains.