The behaviour of aged three‐way catalytic converters in the different modes of legislated cycles

Automotive three‐way catalytic converters are routinely applied today in the elimination of carbon monoxide, urburned or partially burned hydrocarbons and nitrogen oxides from gasoline engine exhaust gas. Catalyst activity in this case is only indirectly assessed by means of the measurement of overall emissions during a legislated driving cycle. The specific structure of the driving cycles embodied in a legislated emissions test procedure, significantly affects catalyst performance. In addition, catalyst behaviour is affected by the levels of raw engine emissions and catalyst inlet temperatures. The latter are strongly influenced by exhaust system design. The above explain easily the difficulties arising when one wants to discriminate between the behaviour of different catalysts in a specific test procedure. The advent of reliable mathematical models of three‐way catalytic converter operation allows for a detailed analysis of catalyst performance over the full legislated cycle, which gives more insight into the catalytic activity itself. In this paper, a specific experimental and computational case study is employed to demonstrate the role of mathematical modelling in the detailed analysis of aged catalyst performance during the US and EU legislated test procedures. Copyright © 2000 John Wiley & Sons, Ltd.     

Directed Evolution of Phi Class Glutathione Transferases Involved in Multiple-Herbicide Resistance of Grass Weeds and Crops

The extensive application of herbicides in crop cultivation has indisputably led to the emergence of weed populations characterized by multiple herbicide resistance (MHR). This phenomenon is associated with the enhanced metabolism and detoxifying ability of endogenous enzymes, such as phi class glutathione transferases (GSTFs). In the present work, a library of mutant GSTFs was created by in vitro directed evolution via DNA shuffling. Selected gstf genes from the weeds Alopecurus myosuroides and Lolium rigidum, and the cereal crops Triticum durum and Hordeum vulgare were recombined to forge a library of novel chimeric GSTFs. The library was activity screened and the best-performing enzyme variants were purified and characterized. The work allowed the identification of enzyme variants that exhibit an eight-fold improvement in their catalytic efficiency, higher thermal stability (8.3 °C) and three-times higher inhibition sensitivity towards the herbicide butachlor. The crystal structures of the best-performing enzyme variants were determined by X-ray crystallography. Structural analysis allowed the identification of specific structural elements that are responsible for k_cat regulation, thermal stability and inhibition potency. These improved novel enzymes hold the potential for utilization in biocatalysis and green biotechnology applications. The results of the present work contribute significantly to our knowledge of the structure and function of phi class plant GSTs and shed light on their involvement in the mechanisms of MHR.     

The future cost of uranium enrichment: Technology and economics

The cost of uranium enrichment is the most important factor determining the fuel cost of nuclear energy. This paper attempts to forecast the future direction of the price of separative work by examining the forces that determine it. It is argued that the interplay among the characteristics of enrichment technologies, the structure of the international market, and the balance of supply and demand determine the enrichment price. The analysis indicates that all forces point towards a price much lower than the current one. It is predicted that, depending on the technological advances, the price of separative work unit for uranium enrichment will range between $40 and $90 by the year 2000.     

A PET study of Turner's syndrome: effects of sex steroids and the X chromosome on brain

Women with Turner's syndrome (TS) allow us to study the neurobiological associates of cognitive and behavioral abnormalities because they lack one/part of one X chromosome, and endogenous estrogen. We studied 13 healthy controls (mean age +/- SD, 28 +/- 6 years) and 16 TS subjects (mean age +/- SD, 26 +/- 6 years). We measured cognitive abilities using neuropsychological tests, and cerebral metabolic rates for glucose with positron emission tomography. Compared to controls, TS subjects had significant absolute hypermetabolism in most brain areas; however, normalized metabolism was significantly lower in TS subjects than controls in the insula and association neocortices bilaterally, and there were significant differences in functional metabolic associations of brain region pairs originating in occipital cortex bilaterally, and within the right hemisphere. There were significant correlations between right-left cognitive and metabolic asymmetries in the TS group. Also, within TS a preliminary analysis demonstrated "X chromosome dosage" effects in language ability and left temporal metabolism, asymmetry of right-left test scores, and parietal metabolism. We hypothesize that within TS: i) generalized brain hypermetabolism reflects global abnormalities in neuron packing; ii) neuronal abnormalities occur in association neocortex that differ in nature or extent from whole brain and are associated with significant differences in normalized metabolism; iii) cognitive deficits are related to brain metabolic abnormalities; and iv) social-behavioral problems may be related to abnormalities of brain metabolism. Moreover, in human brain the X chromosome involved in development of the association neocortices.     

Four-probe measurements of the in-plane thermoelectric properties of nanofilms

Measuring in-plane thermoelectric properties of submicron thin films has remained a challenging task. Here we report a method based on a suspended microdevice for four-probe measurements of the Seebeck coefficient, thermal conductivity, electrical conductivity, and thermoelectric figure of merit of patterned indium arsenide (InAs) nanofilms assembled on the microdevice. The contact thermal resistance and intrinsic thermal resistance of the 40 nm thick InAs nanofilm sample were measured by using the nanofilm itself as a differential thermocouple to determine the temperature drops at the contacts. The microdevice was also used to measure a 190 nm thick silicon dioxide (SiO(2)) film and the results were compared with those reported in the literature. A through-substrate hole under the suspended microdevice allows for transmission electron microscopy characterization of the nanofilm sample assembled on the device. This capability enables one to correlate the measured thermoelectric properties with the crystal structures of the nanofilm.     

Integrating positive emotions into theory, research, and practice: A new challenge for psychotherapy.

This article elaborates on the themes and directions that emerged from a dialogue on the potential usefulness of positive emotions in psychotherapy. In defining a positive emotion, the authors propose that there are two intersecting axes of interest. The axes are emotional experience--whether something feels good or bad to the client--and therapeutic value--how helpful the emotion is to the therapeutic process. Three of the four quadrants formed by the intersection of these axes potentially contain positive emotions. Special consideration is given to the quadrant of positive experience/positive value, which has been relatively neglected until now. In this quadrant, positive emotions generate change either in their facilitating role--often in the therapeutic relationship--or as central agents of the change process. The authors conclude by considering how positive and negative emotions interact and call for careful theorizing and research to clearly understand positive emotions in psychotherapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thermal analysis and optimization of an anaerobic treatment system of whey

The whey produced during cheese and cream cheese making process is one of the most important environmental problems dairy industries are facing, due to its high organic load. Anaerobic treatment seems to be a promising solution for this problem, since it not only reduces greatly the organic load but it also produces biogas, which can be then burnt. It is the scope of this study to perform an exergetic and economic analysis of an anaerobic treatment system of whey accompanied by the production of steam resulting from the burning of biogas. The system analyzed extends from the storage of whey, up to the disposal of the treated effluent from the anaerobic reactor, and the exit of the steam to be used in the plant. The exergy analysis is performed treating the system as a steam production plant, while the economic analysis, which is performed using the Net Present Value (NPV) method, is performed treating the system as a natural gas production plant. The exergy efficiency and NPV calculations are followed by a sensitivity analysis and an optimization with respect to some of the parameters used. Moreover, the exergy efficiency and NPV are calculated for three scenarios. The results indicate that the anaerobic treatment of high strength waste such as whey is a sustainable investment, at least for a substantial volume of whey.     

Is patenting activity impeding the academic performance of South African University researchers?

The present study investigates whether activities related to the patenting of inventions impede or are in conflict with the academic performance of university professors, particularly the publication or the production of public knowledge. The Poisson regression model is used taking into account the confounding effects of other variables deemed to affect the publication productivity, viz.; research/faculty orientation, collaboration, etc. The study is conducted in South Africa, where university R&D is highly funded by the private sector, compared to other countries, viz. USA, UK, Germany, etc. Furthermore, within the South African institutions of learning, there are more incentives to publish than to invent. It is found that: (i) inventiveness and academic performance can co-exist and re-enforce each other, (ii) professors who are inventive have a broader network of researchers-collaborators and (iii) perform highly academically (from the NRF-rating perspective) and publish more than those who do not invent at all.     

Production and properties of nanoelectrospray emitters used in Fourier transform ion cyclotron resonance mass spectrometry: implications for determination of association constants for noncovalent complexes

Electrospray ionization (ESI) is extensively used in the analysis of biological compounds; yet some fundamental properties of this technique are not completely understood. It is widely recognized that care should be exercised when noncovalent complexes are being studied by ESI, since weak noncovalent binding can be broken or formed during the desolvation process. In the present work, spectra from the noncovalent complex, vancomycin/diacetyl-L-lysyl-D-alanyl-D-alanine, obtained from ESI and from nanoelectrospray ionization (nanoESI), have been compared. The results indicated that the milder desolvation conditions arising as a result of the smaller sizes of droplets produced in the nanoESI source attenuated effects upon weak bonds in the desolvation process. The association constant values calculated from the relative peak intensities suggest that, when using ESI, the analyzed noncovalent complex dissociated in the condensed phase during the spraying process. The influences of experimental parameters such as tip diameter and coating for nanoESI needles were investigated. Principal component analysis, a multivariate analysis method, was applied to achieve a better evaluation of the spectra obtained using different needle diameters and coatings for the analysis of the noncovalent complex vancomycin/diacetyl-L-lysyl-D-alanyl-D-alanine. It was found that 2-microm tip diameter resulted in more reproducible spectra than the larger tip diameters tested (6-20 microm).