Effect of ultrasonic treatment on zinc removal from hydroxide precipitates by dissolved air flotation

The effect of ultrasonication on the precipitation of zinc hydroxide, as well as the separation of zinc hydroxide and gypsum precipitates by use of dissolved air flotation are considered in this paper. Both ultrasonic treatment and the addition of carboxy-methyl cellulose (CMC) resulted in flocculation of the zinc hydroxide formed during precipitation. The best flotation results could be obtained by using the CMC during precipitation of the hydroxides, followed by ultrasonic conditioning prior to flotation. Apart from flocculating the zinc hydroxide particles, expediting precipitation and enhancing reagent adsorption, ultrasonic treatment also promoted the mechanical removal of the zinc hydroxide from the surfaces of the gypsum particles.Articl

Analysis of electrochemical noise data with phase space methods

Analysis of the apparently random fluctuations in the current and potential of freely corroding systems has long been seen as a promising approach to the development of better corrosion sensors. Apart from the rate of corrosion, electrochemical noise signals also contain information on the nature of the corrosion system. This is crucially important in the monitoring of localized corrosion, where the rate of corrosion can be a poor predictor of the potential damage to structures. Unfortunately, assessment of the typically complex corrosion dynamics from electrochemical noise can be difficult, and has met with partial success only over the last three decades or so. In this paper, the use of phase space methods as a basis for monitoring corrosion systems is considered. The correlation dimensions of the corroding systems are used as a discriminating statistics and preliminary experiments are discussed. © 2006 Elsevier Ltd. All rights reserved.Articl

Methanogenic digestion of lignocellulose residues under conditions of high-rate acidogenic fermentation

A semicontinuous module reactor was operated under methanophilic conditions to effect rapid solid anaerobic digestion of lignocellulose substances for waste utilization and stabilization. This was achieved by recovering the methanogenic phase from the high-rate acidogenic fermentation phase. The influence of a total carbon to nitrate ratio (C/N(NO3)) of the lignocellulose feed on the development of methanogens from a high-rate acidification fermentation phase was first investigated. The effects of Ph adjustment and dilution of the high-rate acidification fermentation phase using the two-phase anaerobic digestion configuration were subsequently evaluated. The results showed that an increase in the C/N(NO3) ratio of the feed substrate could promote the development of methanogens as a result of the restraint of denitrification during or after the acidification fermentation phase. In-process neutralization of the digestion pH and dilution of the digestion intermediate products could reduce the inhibition from the high-rate acidification fermentation phase. The integrated digestion process promoted the biotransformation of lignocellulose residues from the high-rate acidification phase to the methanogenic phase and ultimately stabilized digestion.Articl

Degradation of humic acids in a microbial film consortium from landfill compost

Bacterial biofilms are ubiquitous in nature and industrial settings. In this study, a biofilm consortium was enriched in a continuous-flow-cell system using humic acid as the sole carbon and energy source. The degradation of the humic acids by the consortium under two supplementary carbon sources was investigated by ultraviolet (UV) absorbency, Fourier transform infrared (FTIR) spectroscopy, and electrospray mass spectrometry (ES-MS). The morphological characteristics of the biofilm consortium and the isolated cultures from the biofilm were observed under an epifluorescence microscope. The metabolic diversity of the selected cultures from the degradative consortium, based on substrate usage pattern, was examined using Biolog EcoPlates. Microscopic analysis revealed that the biofilm was formed by various morphotypes of bacteria, fungi, and yeasts, as well as amoebas. The substrate usage profiles of the bacteria confirmed that, in addition to yeasts and fungi, two groups of bacterial consortia were developed in the biofilm to degrade the humic acids. The degradation of humic acid in the biofilm was mostly carried out in a secondary or a cometabolic path. Addition of the readily digestible external carbon source enhanced the growth of the biofilm consortium. The FTIR and ES-MS spectra confirmed the changes in chemical structure of the humic acid by the biofilm community.Articl

Degradation of humic acids in a microbial film consortium from landfill compost

Bacterial biofilms are ubiquitous in nature and industrial settings. In this study, a biofilm consortium was enriched in a continuous-flow-cell system using humic acid as the sole carbon and energy source. The degradation of the humic acids by the consortium under two supplementary carbon sources was investigated by ultraviolet (UV) absorbency, Fourier transform infrared (FTIR) spectroscopy, and electrospray mass spectrometry (ES-MS). The morphological characteristics of the biofilm consortium and the isolated cultures from the biofilm were observed under an epifluorescence microscope. The metabolic diversity of the selected cultures from the degradative consortium, based on substrate usage pattern, was examined using Biolog EcoPlates. Microscopic analysis revealed that the biofilm was formed by various morphotypes of bacteria, fungi, and yeasts, as well as amoebas. The substrate usage profiles of the bacteria confirmed that, in addition to yeasts and fungi, two groups of bacterial consortia were developed in the biofilm to degrade the humic acids. The degradation of humic acid in the biofilm was mostly carried out in a secondary or a cometabolic path. Addition of the readily digestible external carbon source enhanced the growth of the biofilm consortium. The FTIR and ES-MS spectra confirmed the changes in chemical structure of the humic acid by the biofilm community.Articl

Structural analysis of inhibitors of the Mycobacterium tuberculosis biotin-protein ligase BirA.

Biotin is an essential cofactor that is necessary for the synthesis of essential membrane phospholipids, cell-wall mycolic acids, and important virulence factors in Mycobacterium tuberculosis (Mtb). The first committed step of fatty acid biosynthesis is catalyzed by Acetyl-Coenzyme A Carboxylase, a multimeric complex that requires the covalent ligation of biotin to the Biotin Carboxyl Carrier Protein (BCCP) domain in order to become functionally active. In Mtb, this step is catalyzed by the biotin protein ligase BirA. Biotinylation proceeds through a two-step reaction wherein biotin is first activated to 5'-biotinyl-AMP before transfer to the e-amino group of a target lysine residue of the BCCP domain. BirA is the only biotin protein ligase detected in the Mtb genome and has been shown to be essential for fatty acid biosynthesis in Mycobacterium smegmatis. Inhibitors of BirA are under investigation as potential novel antibacterial agents for the treatment of tuberculosis and other pathogenic microorganism

Gradual Ownership Types

Gradual Ownership Types are a framework allowing programs to be partially annotated with ownership types, while providing the same encapsulation guarantees. The formalism provides a static guarantee of the desired encapsulation property for fully annotated programs, and dynamic guarantees for partially annotated programs via dynamic checks inserted by the compiler. This enables a smooth migration from ownership-unaware to ownership-typed code. The paper provides a formal account of gradual ownership types. The theoretical novelty of this work is in adapting the notion of gradual type system with respect to program heap properties, which, unlike types in functional languages or object calculi, impose restrictions not only on data, but also on the environment the data is being processed in. From the practical side, we evaluate applicability of Gradual Ownership Types for Java 1.4 in the context of the Java Collection Framework and measure the necessary amount of annotations for ensuring the owners-as-dominators invariant.status: publishe