Thermal stability of CrN<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> nanometric coatings deposited on stainless steel

Thin CrN _x coatings are often used as protective coatings for steel. In these applications, coated parts might be subjected to high temperatures that can alter the coatings structural and mechanical properties. In this work, the properties of nanometric CrN _x coatings deposited by reactive magnetron sputtering on AISI 304L stainless steel were studied by transmission electron microscopy, glazing incident X-ray diffraction, Atomic Force Microscopy, and nanoindentation. The effect of annealing, both in air and vacuum, on the coating crystal structure, surface morphology and hardness were also investigated. It was found that annealing in vacuum-induced phase transformation from CrN to Cr₂N, while after annealing in air only Cr₂O₃ phase was present. Surface roughness did not increase for annealing in vacuum. CrN _x coatings with higher Cr₂N phase content showed lower roughness increase for annealing in air. Measured hardness was >10 GPa for as-deposited CrN _x samples. An increase in hardness up to >20 GPa was found for vacuum-annealed samples.     

Geochemical modelling of arsenic and selenium leaching in alkaline water treatment sludge from the production of non-ferrous metals

Geochemical modelling of leaching of oxyanion forming elements such as arsenic (As) and selenium (Se) is frequently not successful. A consistent thermodynamic dataset of As and Se was therefore composed, not only including precipitation, but also adsorption and solid solution, and was applied to the pH-dependent leaching behaviour of As and Se in an alkaline residue with a pH 11.1 from the lime treatment of sulphuric acid wastewaters from the production of non-ferrous metals. The As and Se content ranged up to 6.7 wt% and 0.29 wt%, respectively and speciation analysis showed that 96.3% of As occured as arsenate whereas Se speciation comprised 79% selenate and 21.0% selenite. XRD and SEM/EDX analysis showed that arsenate occurred as rauenthalite (Ca(3)(AsO(4))(2).10H(2)O), associated with gypsum, the most important mineral. Arsenate and arsenite concentrations were only slightly below equilibrium with rauenthalite and calciumarsenite (CaHAsO(3)), respectively and consideration of adsorption and solid solution only marginally improved model predictions. Selenate (Se(VI)) and selenite (Se(IV)), on the other hand, were far from equilibrium with their corresponding calcium metalate. The application of solid solutions and adsorption of Se(VI) and Se(IV) oxyanions with gypsum, calcite and ettringite significantly improved model predictions but missing thermodynamic data and especially the lack of a comprehensive model for solid solution and surface exchange with calcite and ettringite still hampered efficient modelling.     

Assessment of Pb-slag, MSWI bottom ash and boiler and fly ash for using as a fine aggregate in cement mortar

Three types of wastes, metallurgical slag from Pb production (SLG), the sand-sized (0.1-2 mm) fraction of MSWI bottom ash from a grate furnace (SF), and boiler and fly ash from a fluidised bed incinerator (BFA), were characterized and used to replace the fine aggregate during preparation of cement mortar. The chemical and mineralogical behaviour of these wastes along with the reactivities of the wastes with lime and the hydration behaviour of ordinary Portland cement paste with and without these wastes added were evaluated by various chemical and instrumental techniques. The compressive strengths of the cement mortars containing waste as a partial substitution of fine aggregates were also assessed. Finally, leaching studies of the wastes and waste containing cement mortars were conducted. SLG addition does not show any adverse affect during the hydration of cement, or on the compressive strengths behaviours of mortars. Formation of expansive products like ettringite, aluminium hydroxide and H2 gas due to the reaction of some constituents of BFA and SF with alkali creates some cracks in the paste as well as in the cement mortars, which lower the compressive strength of the cement mortars. However, utilization of all materials in cement-based application significantly improves the leaching behaviour of the majority of the toxic elements compared to the waste as such.     

In vivo mutational analysis of the mupirocin gene cluster reveals labile points in the biosynthetic pathway: the "leaky hosepipe" mechanism

A common feature of the mupirocin and other gene clusters of the AT-less polyketide synthase (PKS) family of metabolites is the introduction of carbon branches by a gene cassette that contains a beta-hydroxy-beta-methylglutaryl CoA synthase (HMC) homologue and acyl carrier protein (ACP), ketosynthase (KS) and two crotonase superfamily homologues. In vivo studies of Pseudomonas fluorescens strains in which any of these components have been mutated reveal a common phenotype in which the two major isolable metabolites are the truncated hexaketide mupirocin H and the tetraketide mupiric acid. The structure of the latter has been confirmed by stereoselective synthesis. Mupiric acid is also the major metabolite arising from inactivation of the ketoreductase (KR) domain of module 4 of the modular PKS. A number of other mutations in the tailoring region of the mupirocin gene cluster also result in production of both mupirocin H and mupiric acid. To explain this common phenotype we propose a mechanistic rationale in which both mupirocin H and mupiric acid represent the products of selective and spontaneous release from labile points in the pathway that occur at significant levels when mutations block the pathway either close to or distant from the labile points.     

Prospective memory impairment in individuals with Parkinson's disease.

This study investigated prospective memory and its relationship to executive and memory functions in persons with Parkinson's disease (PD). Twenty-three individuals with PD and 25 healthy comparison participants participated in the study. In the prospective memory tasks, participants were asked to execute 3 actions after 20 min (time-based condition) or after a timer ring (event-based condition). A score was computed for the correct recall of the intention to perform the actions (prospective component) and for the correct execution of the actions (retrospective component). Participants with PD also received an extensive neuropsychological test battery. PD participants were less accurate than comparison participants in the prospective component of the time-based but not the event-based task. Individuals with PD were also impaired on the retrospective component of both tasks. In the PD group, a general trend toward significant correlations was found between performance level on the prospective memory component of the time-based task and scores on executive and working memory measures. These results document that prospective memory is impaired in PD possibly in relation to a dysregulation of cognitive functions associated with frontal systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fetal magnetocardiographic signals extracted by 'signal subspace' blind source separation

In this paper, we apply independent component analysis to fetal magnetocardiographic data. In particular, we propose an extension of the "cumulant-based iterative inversion" algorithm to include a two-step "signal subspace" subdivision, which allows the user to control the number of components to be estimated by analyzing the eigenvalues distribution in an interactive way. Our results show that this method is a powerful means not only for the extraction of the cardiac signals from the background noise but also for a sharp separation of the baby's heart from the mother's.     

Reuse of a treated red mud bauxite waste: studies on environmental compatibility

Red mud is the major solid waste produced in the process of alumina extraction from bauxite (Bayer process). Environmental "compatibility" of a treated red mud was studied in order to evaluate its possible recycling in environmental compartments. The leaching test requested by the Italian law on treated solid waste to be "re-introduced in the environment" was performed on this material. Moreover, in order to better evaluate the environmental compatibility, three different types of eco-toxicological tests were applied (Microtox test, ASTM microalgae toxicity test and sea urchin embryo toxicity test). These "chemical" and eco-toxicological tests gave encouraging results. The possibility to use this material for treating contaminated waters and soils was evaluated, again with particular attention to the Italian regulatory system, through experiments on the treated red mud metal trapping ability and on the subsequent release of trapped metals, at low pH conditions. The treated red mud showed a general high metal trapping capacity and the release at low pH was generally low.     

Photo-induced proton gradients and ATP biosynthesis produced by vesicles encapsulated in a silica matrix

Sol-gel immobilization of soluble proteins has proven to be a viable method for stabilizing a wide variety of proteins in transparent inorganic matrices. The encapsulation of membrane-bound proteins has received much less attention, although work in this area suggests potential opportunities in microarray technology and high-throughput drug screening. The present paper describes a liposome/sol-gel architecture in which the liposome provides membrane structure and protein orientation to two transmembrane proteins, bacteriorhodopsin (bR) and F(0)F(1)-ATP synthase; the sol-gel encapsulation converts the liposomal solution into a robust material without compromising the intrinsic activity of the incorporated proteins. Here we report on two different proteoliposome-doped gels (proteogels) whose properties are determined by the transmembrane proteins. Proteogels containing bR proteoliposomes exhibit a stable proton gradient when irradiated with visible light, whereas proteogels containing proteoliposomes with both bR and F(0)F(1)-ATP synthase couple the photo-induced proton gradient to the production of ATP. These results demonstrate that materials based on the liposome/sol-gel architecture are able to harness the properties of transmembrane proteins and enable a variety of applications, from power generation and energy storage to the powering of molecular motors, and represent a new technology for performing complex chemical synthesis in a solid-state matrix.     

A new ligand for immunoglobulin g subdomains by screening of a synthetic peptide library

By screening a synthetic peptide library of general formula (NH(2)-Cys1-X2-X3-X4)(2)-Lys-Gly-OH, a disulfide-bridged cyclic peptide, where X2-X3-X4 is the tripeptide Phe-His-His, has been selected as a ligand for immunoglobulin G (IgG). The peptide, after a preliminary chromatographic characterization, has proved useful as a new affinity ligand for the purification of polyclonal as well as monoclonal antibodies from biological fluids, with recovery yields of up to 90% (90% purity). The ligand is able to bind antibody fragments containing both Fab and Fc from different antibody isotypes, a fact suggesting the presence of at least two different antibody-binding sites. While the recognition site on Fab is unknown, comparative binding studies with Fc, in association with the striking similarities of the peptide (named Fc-receptor mimetic, FcRM) with a region of the human FcgammaRIII receptor, strongly indicate that the peptide could recognize a short amino acid stretch of the lower hinge region, which has a key role in autoimmune disease triggering. The unique properties make the ligand attractive for both the purification of antibody fragments and as a lead for the generation of Fc-receptor antagonists.     

Bacteria enclosure between silica-coated membranes for the degradation of organic compounds in contaminated water

A non-conventional technique is proposed for the enclosure of either pure bacterial cultures or entire biocoenoses, for a possible utilization in the treatment of contaminated water. Biological components have been enclosed between polyester membranes coated by silica films consisting of: (a) SiO2 and nitrocellulose, (b) SiO2, ZnS crystals and nitrocellulose, (c) SiO2, TiO2 crystals and nitrocellulose, (d) SiO2, ZnS and TiO2 crystals and nitrocellulose. Morphological, structural and mechanical features of membranes were investigated by means of optical and electron microscopy, mercury porosimetry and wear resistance tests. Degradation kinetics have been finally studied by dipping the entrapped biomass into aqueous solutions of three different model organic compounds (alpha-d-glucose, ethyl alcohol and peptone). Results are very promising: in fact, no metabolic inhibition mechanisms of microorganisms have been evidenced. The porosity of the system allows mass transfer through the membranes, hence bacteria can grow and degrade pollutants. Besides, by this system, cells are constrained, avoiding they to spread across the retainment scaffold.