Validation and interpretation of CALUX as a tool for the estimation of dioxin-like activity in marine biological matrixes

Among the different analytical tools proposed as an alternative to the very expensive gas chromatography high-resolution mass spectrometry (GC-HRMS) analyses of polychlorodibenzo-p-dioxin and polychlorodibenzofurans, Chemically Activated LUciferase gene eXpression (CALUX) in vitro cell bioassay is very promising. It allows the analyses of a high number of samples since it is relatively fast, inexpensive, and sensitive. However, this technique is not yet widely applied for screening or environmental monitoring. The main reasons are probably the lack of validation and the difficulty in interpreting the global biological response of the bioassay. In this paper, the strict quality control criteria set up for the validation of CALUX are described. The validation has shown good repeatability (relative standard deviation (RSD) = 9%) and good within-lab reproducibility (RSD = 15%) of the results. The quantification limit, in the conditions applied in this paper, is 1.25 pg CALUX-TEQ/g fat. Comparison of CALUX and GC-HRMS analysis was made forvarious marine matrixes (fishes, mussels, starfishes, sea birds, and marine mammals). Good correlations are usually observed, but there are systematic differences between the results. Attempts are made to identify the origin of the discrepancy between the two methods.     

The hide-and-seek of retrospective revaluation: Recovery from blocking is context dependent in human causal learning.

In a typical blocking procedure, pairings of a compound consisting of 2 stimuli, A and X, with the outcome are preceded by pairings of only A with the outcome (i.e., A+ then AX+). This procedure is known to diminish responding to the target cue (X) relative to a control group that does not receive the preceding training with blocking cue A. We report 2 experiments that investigated the effect of extinguishing a blocking cue on responding to the target cue in a human causal learning paradigm (i.e., A+ and AX+ training followed by A– training). The results indicate that extinguishing a blocking cue increases conditioned responding to the target cue. Moreover, this increase appears to be context dependent, such that increased responding to the target is limited to the context in which extinction of the blocking cue took place. We discuss these findings in the light of associative and propositional learning theories. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The design of distributors for gas-fluidized beds

The performance of the gas distributor often determines the success or failure of a fluidized bed and although much more is known now than 20 years ago, there are still many pitfalls for the designer.Particle and gas properties play a key role in successful design together with the critical pressure drop ratio, and hole size, geometry and spacing; these strongly influence jet penetration, dead zones, particle sifting, attrition and mixing.The current state of the art is reviewed in the light of recent research and industrial experience.     

Intra-articular kinematics of the normal glenohumeral joint in the late preparatory phase of throwing: Kaltenborn's rule revisited

A new method to quantify intra-articular relationships between articular surfaces of the glenohumeral joint during discrete poses representing the late preparatory phase of throwing is presented. This method is based on 3D bone reconstructions from medical imaging data processed into finite helical axis parameters. With the shoulder moving in the anatomical planes from 90 degrees abduction and 90 degrees external rotation into the apprehension test pose, the centre of the humeral head posteriorly translated on the glenoid and rotated about a finite helical axis, which was positioned at the joint contact. The data are contrasted with Kaltenborn's convex-concave rule explaining intra-articular kinematics of the glenohumeral joint as a ball-and-socket joint. The data show at all conditions that the glenohumeral joint does not act as a ball-and-socket joint. Consequently, the mobilization techniques used in manual therapy, which are based on this convex concave rule, should be adapted.     

Principles and potential of the anaerobic digestion of waste-activated sludge

When treating municipal wastewater, the disposal of sludge is a problem of growing importance, representing up to 50% of the current operating costs of a wastewater treatment plant. Although different disposal routes are possible, anaerobic digestion plays an important role for its abilities to further transform organic matter into biogas (60–70 vol% of methane, CH₄), as thereby it also reduces the amount of final sludge solids for disposal whilst destroying most of the pathogens present in the sludge and limiting odour problems associated with residual putrescible matter. Anaerobic digestion thus optimises WWTP costs, its environmental footprint and is considered a major and essential part of a modern WWTP. The potential of using the biogas as energy source has long been widely recognised and current techniques are being developed to upgrade quality and to enhance energy use. The present paper extensively reviews the principles of anaerobic digestion, the process parameters and their interaction, the design methods, the biogas utilisation, the possible problems and potential pro-active cures, and the recent developments to reduce the impact of the problems. After having reviewed the basic principles and techniques of the anaerobic digestion process, modelling concepts will be assessed to delineate the dominant parameters. Hydrolysis is recognised as rate-limiting step in the complex digestion process. The microbiology of anaerobic digestion is complex and delicate, involving several bacterial groups, each of them having their own optimum working conditions. As will be shown, these groups are sensitive to and possibly inhibited by several process parameters such as pH, alkalinity, concentration of free ammonia, hydrogen, sodium, potassium, heavy metals, volatile fatty acids and others. To accelerate the digestion and enhance the production of biogas, various pre-treatments can be used to improve the rate-limiting hydrolysis. These treatments include mechanical, thermal, chemical and biological interventions to the feedstock. All pre-treatments result in a lysis or disintegration of sludge cells, thus releasing and solubilising intracellular material into the water phase and transforming refractory organic material into biodegradable species. Possible techniques to upgrade the biogas formed by removing CO₂, H₂S and excess moisture will be summarised. Special attention will be paid to the problems associated with siloxanes (SX) possibly present in the sludge and biogas, together with the techniques to either reduce their concentration in sludge by preventive actions such as peroxidation, or eliminate the SX from the biogas by adsorption or other techniques. The reader will finally be guided to extensive publications concerning the operation, control, maintenance and troubleshooting of anaerobic digestion plants.     

S-parameter measurement based quasistatic large-signal cold HEMT model for resistive mixer design

The nonlinear cold HEMT model generation procedure is described. It starts with the determination of the corresponding small-signal model by adapting the cold FET extraction approach for HEMTs. Then, the small-signal model is transformed to obtain a straightforward implementable, consistent small-signal cold HEMT model, suitable for resistive mixer design. © 1996 John Wiley & Sons, Inc.     

The hide-and-seek of hidden covariation detection: Reply to Lewicki, Hill, and Czyzewska (1997).

P. Lewicki, M. Czyzewska, and H. Hoffman (see record 1997-02349-013) argued that H. Hendrickx, J. De Houwer, F. Baeyens, P. Eelen, and E. Van Avermaet's (see record 1997-02349-012) failures to replicate hidden covariation detection (HCD) were due to procedural weaknesses. They also discuss theoretical arguments and evidence supposedly supportive of the generality and robustness of the phenomenon. In the current article, the authors argue that the boundary conditions Lewicki et al. proposed are not based on experimental evidence, that they are too vague, and that the criteria they give for obtaining HCD are applied in a highly selective way. Further, Lewicki et al. did not take alternative explanations of the null results into account. The authors conclude that HCD is not as general and robust as previously suggested and that research efforts must be directed at identifying its boundary conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Catalytic combustion of volatile organic compounds

Despite the success of adsorption and thermal incineration of (C)VOC emissions, there is still a need for research on techniques which are both economically more favorable and actually destroy the pollutants rather than merely remove them for recycling elsewhere in the biosphere. The catalytic destruction of (C)VOC to CO2, H2O and HCl/Cl2 appears very promising in this context and is the subject of the present paper. The experiments mainly investigate the catalytic combustion of eight target compounds, all of which are commonly encountered in (C)VOC emissions and/or act as precursors for the formation of PCDD/F. Available literature on the different catalysts active in the oxidation of (C)VOC is reviewed and the transition metal oxide complex V2O5-WO3/TiO2 appears most suitable for the current application. Different reactor geometries (e.g. fixed pellet beds, honeycombs, etc.) are also described. In this research a novel catalyst type is introduced, consisting of a V2O5-WO3/TiO2 coated metal fiber fleece. The conversion of (C)VOC by thermo-catalytic reactions is governed by both reaction kinetics and reaction equilibrium. Full conversion of all investigated VOC to CO2, Cl2, HCl and H2O is thermodynamically feasible within the range of experimental conditions used in this work (260-340 degrees C, feed concentrations 30-60 ppm). A first-order rate equation is proposed for the (C)VOC oxidation reactions. The apparent rate constant is a combination of reaction kinetics and mass transfer effects. The oxidation efficiencies were measured with various (C)VOC in the temperature range of 260-340 degrees C. Literature data for oxidation reactions in fixed beds and honeycomb reactors are included in the assessment. Mass transfer resistances are calculated and are generally negligible for fleece reactors and fixed pellet beds, but can be of importance for honeycomb monoliths. The experimental investigations demonstrate: (i) that the conversion of the hydrocarbons is independent of the oxygen concentration, corresponding to a zero-order dependency of the reaction rate; (ii) that the conversion of the hydrocarbons is a first-order reaction in the (C)VOC; (iii) that the oxidation of the (C)VOC proceeds to a higher extent with increasing temperature, with multiple chlorine substitution enhancing the reactivity; (iv) that the reaction rate constant follows an Arrhenius dependency. The reaction rate constant kr (s(-1)) and the activation energy E (kJ/mol) are determined from the experimental results. The activation energy is related to the characteristics of the (C)VOC under scrutiny and correlated in terms of the molecular weight. The kr-values are system-dependent and hence limited in design application to the specific VOC-catalyst combination being studied. To achieve system-independency, kr-values are transformed into an alternative kinetic constant K (m3/(m2u)) expressed per unit of catalyst surface and thus independent of the amount of catalyst present in the reactor. Largely different experimental data can be fitted in terms of this approach. Results are thereafter used to define the Arrhenius pre-exponential factor A*, itself expressed in terms of the activation entropy. Destruction efficiencies for any given reactor set-up can be predicted from E- and A*-correlations. The excellent comparison of predicted and measured destruction efficiencies for a group of chlorinated aromatics stresses the validity of the design approach. Since laboratory-scale experiments using PCDD/F are impossible, pilot and full-scale tests of PCDD/F oxidation undertaken in Flemish MSWIs and obtained from literature are reported. From the data it is clear that: (i) destruction efficiencies are normally excellent; (ii) the efficiencies increase with increasing operating temperature; (iii) the higher degree of chlorination does not markedly affect the destruction efficiency. Finally, all experimental findings are used in design recommendations for the catalytic oxidation of (C)VOC and PCDD/F. Predicted values of the a)VOC and PCDD/F. Predicted values of the acceptable space velocity correspond with the cited industrial values, thus stressing the validity of the design strategy and equations developed in the present paper.     

The valorization of plastic solid waste (PSW) by primary to quaternary routes: From re-use to energy and chemicals

Polymers are the most versatile material in our modern day and age. With certain chemicals and additives (pigments, concentrates, anti-blockers, light transformers (LTs), UV-stabilizers, etc.), they become what we know as plastics. The aim of this review is to provide the reader with an in depth analysis regarding the recovery, treatment and recycling routes of plastic solid waste (PSW), as well as the main advantages and disadvantages associated with every route. Recovery and recycling of PSW can be categorized by four main routes, i.e. re-extrusion, mechanical, chemical and energy recovery. Re-extrusion (primary recycling) utilizes scrap plastics by re-introducing the reminder of certain extruded thermoplastics (mainly poly-α-olefins) into heat cycles within a processing line. When plastic articles are discarded after a number of life cycles, mechanical recycling techniques present themselves as a candidate for utilizing a percentage of the waste as recyclate and/or fillers. Collectively, all technologies that convert polymers to either monomers (monomer recycling) or petrochemicals (feedstock recycling) are referred to as chemical recycling. The technology behind its success is the depolymerization processes (e.g. thermolysis) that can result in a very profitable and sustainable industrial scheme, providing a high product yield and a minimal waste. Nevertheless, due to their high calorific value and embodied energy, plastics are being incinerated solely or in combination with municipal solid waste (MSW) in many developed countries. This review also presents a number of application and technologies currently being used to incinerate plastics. Cement kilns and fluidized beds are the two most common units used to recover energy from PSW or MSW with high PSW content. It is concluded that, tertiary (chemical methods) and quaternary (energy recovery) are robust enough to be investigated and researched in the near future, for they provide a very sustainable solution to the PSW cycle.