Mechanisms of Bacterial Extracellular Electron Exchange.

The biochemical mechanisms by which microbes interact with extracellular soluble metal ions and insoluble redox-active minerals have been the focus of intense research over the last three decades. The process presents two challenges to the microorganism; firstly electrons have to be transported at the cell surface, which in Gram negative bacteria presents an additional problem of electron transfer across the ~ 6 nm of the outer membrane. Secondly the electrons must be transferred to or from the terminal electron acceptors or donors. This review covers the known mechanisms that bacteria use to transport electrons across the cell envelope to external electron donors/acceptors. In Gram negative bacteria electron transfer across the outer membrane involves the use of an outer membrane β-barrel and cytochrome. These can be in the form of a porin-cytochrome protein, such as Cyc2 of Acidothiobacillus ferrioxydans, or a multiprotein porin-cytochrome complex like MtrCAB of Shewanella oneidensis MR-1. For mineral respiring organisms there is the additional challenge of transferring the electrons from the cell to mineral surface. For the strict anaerobe Geobacter sulfurreducens this requires electron transfer through conductive pili to associated cytochrome OmcS that directly reduces Fe(III)oxides, while the facultative anaerobe S. oneidensis MR-1 accomplishes mineral reduction through direct membrane contact, contact through filamentous extentions and soluble flavin shuttles, all of which require the outer membrane cytochromes MtrC and OmcA in addition to secreted flavin

Corrosion studies of different ferrous alloys for rolling cylinders

peer reviewedThe aim of this work is to study the corrosion behaviour in chloride media of a high chromium iron alloy. The influence of the surface finishing as well as the heat treatment was analysed. The technique employed for measuring the corrosion behaviour was the Electrochemical Impedance Spectroscopy, an electrochemical technique that allows the observation not only of the corrosion rates but also the changes on the corrosion mechanism of the alloy. The results showed that it is worth performing a double tempering and a having smoother surface finishing only for long exposure periods. A comparison between different oxidising conditions was also performed simulating the life in service of the hot rolling cylinders and revealed an increase in the protective properties as the oxidising time increased due to the chromium present on the alloy (18%). (c) 2005 Elsevier Ltd. All rights reserved

Oil film bearings applied to heavy duty rolling mill drive couplings.

The present work describes an investigation related to rolling mill drive-lines in the Steel Industry with special reference to Hookes joint couplings. This coupling transmits the torque and the rotational motion, required for the rolling process, and contains four hearings which are under oscillating motion. Together with the impact loads often found in rolling mills this provides a severe operating environment which has been simulated to permit an experimental investigation of the suitability of oil film bearings for such applications. In the rig, displacements of the shaft centre, i.e. locus path or eccentricity, have been recorded versus load levels and frequencies of oscillation or rotational speeds for constant oil inlet pressure. Three different types of oil lubricant bearings have been tested under the adverse conditions of dynamic load and oscillating motion, but less severe tests for conditions of continuous motion and static load were also carried out to give reference of the behaviour of such bearings. Comparisons have been obtained between hydrodynamic bearings with axial and circumferential grooving and slot entry hybrid bearings, showing the latter to be suited to the particular application considered. Results have been compared with existing design procedures suitably modified to take account of the adverse operating conditions

Anisotropic spin-orbit induced splitting of intersubband spin plasmons

The anisotropic splitting of intersubband spin plasmons, resulting from spin-orbit coupling, is studied by angle-resolved inelastic light scattering on a [001]-oriented GaAs/AlGaAs quantum well. Confirming theoretical predictions made in [C. A. Ullrich and M. A. Flatte, Phys. Rev. B ´ 68, 235310 (2003)], this splitting is proven to exhibit a characteristic two-fold symmetry with the in-plane orientation, and to increase with increasing modulus of the excitation momentum. This opens the way to a more complete investigation, aiming at evidencing the existence of a collective spin-orbit field driving these excitations.Fil: Baboux, F.. Universite de Paris Vi. Institut Des Nanosciences de Paris; Francia. Centre National de la Recherche Scientifique; FranciaFil: Perez, F. Universite de Paris Vi. Institut Des Nanosciences de Paris; Francia. Centre National de la Recherche Scientifique; FranciaFil: Ullrich, C. A. . University Of Missouri; Estados UnidosFil: D'Amico, I. . University Of York; Reino UnidoFil: Gomez, Javier Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centre National de la Recherche Scientifique; Francia. Universite de Paris Vi. Institut Des Nanosciences de Paris; FranciaFil: Bernard, M.. Universite de Paris Vi. Institut Des Nanosciences de Paris; Franci

Characterization of Sex-Based Dna Methylation Signatures in the Airways During Early Life.

Human respiratory conditions are largely influenced by the individual\u27s sex resulting in overall higher risk for males. Sex-based respiratory differences are present at birth suggesting a strong genetic component. Our objective was to characterize early life sex-based genomic signatures determined by variable X-chromosome methylation in the airways. We compared male versus female genome-wide DNA methylation in nasal airway samples from newborns and infants aged 1-6 months (N = 12). We analyzed methylation signals across CpG sites mapped to each X-linked gene using an unsupervised classifier (principal components) followed by an internal evaluation and an exhaustive cross-validation. Results were validated in an independent population of children (N = 72) following the same algorithm. X-linked genes with significant sex-based differential methylation in the nasal airway of infants represented only about 50% of the unique protein coding transcripts. X-linked genes without significant sex-based differential methylation included genes with evidence of escaping X-inactivation and female-biased airway expression. These genes showed similar methylation patterns in males and females suggesting unbalanced X-chromosome dosage. In conclusion, we identified that the human airways have already sex-based DNA methylation signatures at birth. These early airway epigenomic marks may determine sex-based respiratory phenotypes and overall predisposition to develop respiratory disorders later in life

Serum levels and removal by haemodialysis and haemodiafiltration of tryptophan-derived uremic toxins in ESKD patients

Tryptophan is an essential dietary amino acid that originates uremic toxins that contribute to end-stage kidney disease (ESKD) patient outcomes. We evaluated serum levels and removal during haemodialysis and haemodiafiltration of tryptophan and tryptophan-derived uremic toxins, indoxyl sulfate (IS) and indole acetic acid (IAA), in ESKD patients in different dialysis treatment settings. This prospective multicentre study in four European dialysis centres enrolled 78 patients with ESKD. Blood and spent dialysate samples obtained during dialysis were analysed with high-performance liquid chromatography to assess uremic solutes, their reduction ratio (RR) and total removed solute (TRS). Mean free serum tryptophan and IS concentrations increased, and concentration of IAA decreased over pre-dialysis levels (67%, 49%, -0.8%, respectively) during the first hour of dialysis. While mean serum total urea, IS and IAA concentrations decreased during dialysis (-72%, -39%, -43%, respectively), serum tryptophan levels increased, resulting in negative RR (-8%) towards the end of the dialysis session (p < 0.001), despite remarkable Trp losses in dialysate. RR and TRS values based on serum (total, free) and dialysate solute concentrations were lower for conventional low-flux dialysis (p < 0.001). High-efficiency haemodiafiltration resulted in 80% higher Trp losses than conventional low-flux dialysis, despite similar neutral Trp RR values. In conclusion, serum Trp concentrations and RR behave differently from uremic solutes IS, IAA and urea and Trp RR did not reflect dialysis Trp losses. Conventional low-flux dialysis may not adequately clear Trp-related uremic toxins while high efficiency haemodiafiltration increased Trp losses