Guest Editors' Introduction

Journal of Signal Processing Systems -     

Pervaporation of water-alcohol mixtures and acetic acid-water mixtures

In this study, pervaporation experiments were performed with methanol-water mixtures, ethanol-water mixtures, IPA (isopropyl alcohol)-water mixtures, and acetic acid-water mixtures, over the complete concentration range allowed by the membrane (Pervap 2201, Sulzer). The results of the three water-alcohol mixtures are compared to investigate the influence of molecular weight and polarity on the permeation behavior. The results show that ethanol and IPA have a similar permeation behavior, whereas methanol shows a different behavior. This can be explained by the relatively high polarity of methanol, which makes methanol sorption competitive with water sorption. The IPA-water mixtures are compared with the acetic acid-water mixtures. IPA and acetic acid have approximately the same molecular weight, but contain a different functional group. The acetic acid-water mixtures have a higher total flux than the IPA-water mixtures. Moreover, the partial acetic acid flux is higher than the partial IPA flux. Acetic acid contains a carbonyl group, which has a high capacity of forming hydrogen bonds with the alcohol groups of the PVA (polyvinyl alcohol) top layer. Moreover, it is a large molecule, causing high swelling resulting in a high permeation flux and a low separation factor. The behavior of the acetic acid-water mixtures shows more resemblance to the methanol-water mixtures than to the IPA-water mixtures. This suggests that the polarity and functional group of the different feed components is more important than the molecular size.     

Right Hemisphere Sensitivity to Word- and Sentence-Level Context: Evidence From Event-Related Brain Potentials.

Researchers using lateralized stimuli have suggested that the left hemisphere is sensitive to sentence-level context, whereas the right hemisphere (RH) primarily processes word-level meaning. The authors investigated this message-blind RH model by measuring associative priming with event-related brain potentials (ERPs). For word pairs in isolation, associated words elicited more positive ERPs than unassociated words with similar magnitudes and onset latencies in both visual fields. Embedded in sentences, these same pairs showed large sentential context effects in both fields. Small effects of association were observed, confined to incongruous sentences after right visual hemifield presentation but present for both congruous and incongruous sentences after left visual hemifield presentation. Results do not support the message-blind RH model but do suggest hemispheric asymmetries in the use of word and sentence context during real-time processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the assessment of economic risk: factorial design versus Monte Carlo methods

The feasibility of large investment projects (such as gas transmission and power system projects) has many aspects. Usually, this problem cannot be modeled as a single optimization problem; instead, the multiple aspects (demand, supply, prices, investment costs) are modeled separately. Each aspect may require a large, nonlinear submodel. The results of such a submodel can often be summarized by one or a few variables, which combine all the submodel's information; for example, total demand is the sum of the demand per customer type, each type being modeled separately. Traditionally, the feasibility of the investment project is then judged by combining the results of the various submodels for the ‘base case’ values of all model inputs.This base case information, however, is not sufficient for the decision makers; they also like to know the economic risk they are taking. To assess this risk on the project level (Hertz, D. B., Risk analysis in capital investment. Harvard Business Review, 1964, 95–106) developed a method known as risk analysis. This method is based on the estimated probability distribution of a project's net present value (NPV). This distribution is obtained by introducing distributions for the model inputs. The project's economic risk is then. expressed as the probability of a negative NPV exceeding a critical value (say) α. Nowadays this approach is becoming popular, because many software packages (such as @RISK and Crystal Ball) facilitate such a risk analysis. Although Hertz's risk analysis is appealing, it has a number of theoretical and practical flaws, which may lead to wrong conclusions. These flaws are discussed in this paper.From a modelling point of view, Hertz's risk analysis is similar to analysing the technological or operational risk of an investment. However, economic risk and technological risk are different concepts that require different analyses. In this paper these differences are discussed and it is shown that Hertz's risk analysis does not measure what is normally meant by a project's economic risk. Furthermore, the information requirements for the application of risk analysis to large investment projects are formidable; this makes the results of Hertz's investment analysis unreliable. Less information is required by sensitivity analysis based on the statistical design of experiments (such as 2^k−P designs); this analysis is more robust, and leads to results that better satisfy the information needs of decision makers.     

Current situation on regulations for mycotoxins. Overview of tolerances and status of standard methods of sampling and analysis

A worldwide enquiry was undertaken in 1986-1987 to obtain up-to-date information about mycotoxin legislation in as many countries of the world as possible. Together with some additional data collected in 1981, information is now available about planned, proposed, existing or absence of legislation in 66 countries. Details about tolerances, legal bases, responsible authorities, prescribed methods of sampling and analysis and disposition of commodities containing inadmissible amounts of mycotoxins, are given. The information concerns aflatoxins in foodstuffs, aflatoxin M1 in dairy products, aflatoxins in animal feedstuffs, and other mycotoxins in food- and feedstuffs. In comparison with the situation in 1981, limits and regulations for mycotoxins have been expanded in 1987 with more countries having legislation (proposed or passed) on the subject, more products, and more mycotoxins covered by this legislation. The differences between tolerances in the various countries are sometimes quite large, which makes harmonization of mycotoxin regulations highly desirable.     

Comparison of the critical liquid volume fraction to rectilinear-diameter methods for prediction of the critical density of ethylene and oxygen

A comparison of the prediction of the critical density for ethylene and oxygen from available coexistence density values using three methods is presented. The conventional rectilinear diameter, the rectilinear diameter with an additional term to represent the postulated curvature near the critical point, and the critical liquid volume fraction were each utilized to predict critical density values for ethylene and oxygen. The correlating functions and fitted constants for the three techniques are given for different ranges of saturation density values. The accepted saturation lines for ethylene and oxygen calculated from new correlations of thermodynamic properties for these fluids were used in this study. The critical density of ethylene was predicted using coexistence density values from 220 to 230 K and from 220 to 282.34 K. Similarly, the critical density for oxygen was predicted using coexistence densities from 100 to 116 K, from 100 to 154.004 K, and from 100 to 154.571 K. Values of the critical density predicted using the three methods are compared with the accepted critical density values for these fluids. The ability of the three methods to predict accurate critical density values using saturation densities at temperatures removed from the critical point is assessed.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Polychlorinated biphenyl equilibria in an estuarine system

The stability of the partition of polychlorinated biphenyl (PCB) congeners between water and the compartments of particulate matter (seston), surface sediment, net-plankton and mussels has been investigated for 1.5 years. Samples were regularly obtained from four stations, representing River Rhine, brackish and saline estuarine and stagnant saline conditions. In spite of the PCB gradients, from freshwater to seawater, and time variations in concentrations, the partition coefficients Kd (distribution coefficients) were very stable for each of the congeners. This demonstrates that the partition between water and the other compartments is due to processes which reach their equilibrium within weeks, independent of the local variations in concentrations. This confirms the non-foodchain accumulation concept of Schneider [1] for aquatic organisms.     

Corrections for range restriction in structured interview ethnic group differences: The values may be larger than researchers thought.

Previous studies of standardized ethnic group differences in the employment interview have shown differences to be relatively small. Unfortunately, many researchers conducting interview studies have not considered the issue of range restriction in research design. This omission is likely to lead to underestimates of standardized ethnic group differences (d) when the interview is considered as an initial screening device or used in combination with other initial screening devices. The authors found that 2 forms of a behavioral interview were associated with standardized ethnic group differences of .36 and .56 when corrected for range restriction. These differences are substantially larger than previously thought and demonstrate the importance of considering a variety of study design characteristics in obtaining the appropriate parameter estimates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)