Context effects and decompositional choice modeling

This paper describes the application of the extended or universal logit model to decompositional or "stated" choice modeling in order to increase the scope and validity of such choice models. In this approach, choice experiments are designed that permit the estimation of utility functions that include the effects of context variables like choice set composition and decision background. The approach is illustrated with some simple calculated examples concerning consumer choice of shopping center, housing, and transportation mode.An earlier version of this paper was presented at the 30th European Congress, Istanbul, August 1990.     

Introduction

Photonic Network Communications -     

Analyzing heterogeneity in conjoint estimates of residential preferences

Conjoint estimates of residential preferencesare typically based on aggregate responses. Forreasons of segmentation or to differentiatebetween non-significant housing attributes andattributes that are characterized byconflicting preferences, further analysis isrequired. In this paper, the heterogeneity inthe conjoint estimates of residentialpreferences of families is analyzed. It isexamined how the estimated part-worth utilitiesof the housing attributes are related to thesocio-economic variables and current housingattributes by applying regression analysis.Although the explained variance was rather low,suggesting that residential preferences offamilies are highly idiosyncratic, therelationships that were significant could beinterpreted well.     

Breitbandkommunikation

Ohne Zusammenfassung     

Towards Attributed Graphs in Groove: Work in Progress

Graphs are a very expressive formalism for system modeling, especially when attributes are allowed. Our research is mainly focused on the use of graphs for system verification.Up to now, there are two main different approaches of modeling (typed) attributed graphs and specifying their transformation. Here we report preliminary results of our investigation on a third approach. In our approach we couple a graph to a data signature that consists of unary operations only. Therefore, we transform arbitrary signatures into a structure comparable to what is called a graph structure signature in the literature, and arbitrary algebras into the corresponding algebra graph.     

<Superscript>1</Superscript>H-MRS of brain metabolites in migraine without aura: absolute quantification using the phantom replacement technique

Objective   

Several studies have demonstrated differences in migraine patients when performing ¹H-MRS; however, no studies have performed ¹H-MRS in migraine without aura (MwoA), the most common migraine subtype. The aim of this ¹H-MRS study was to elucidate whether any differences could be found between MwoA patients and controls by performing absolute quantification.     

Controlling the aggregation propensity and thereby digestibility of allergens by Maillardation as illustrated for cod fish parvalbumin

The aggregation propensity of heat-treated codfish parvalbumin is investigated upon Maillardation of the protein under food-relevant conditions. About twelve of the fourteen lysine residues had reacted with glucose under these conditions. It is shown using circular dichroism and fluorescence that extensive coupling of glucose moieties on the protein surface does not affect the secondary and tertiary structural fold nor severely impair calcium-binding under ambient conditions. The glucosylated protein has a 3 °C higher denaturation temperature, while the free energy change involved with denaturation is reduced by 5-10%. It is shown by establishing insight in the change in heat capacity involved in the denaturation process that glucosylation of the protein is likely to result in a lower exposed hydrophobicity in the unfolded state. Aggregation kinetics, as monitored using light scattering techniques, shows that this lower exposed hydrophobicity of the denatured state slows down the aggregation process, while the shape and size of formed aggregates are comparable to those formed by non-glucosylated protein. This lower aggregation propensity allows a significantly faster digestion of heat-treated materials by pepsin. This work demonstrates that (pre-)processing of ingredients containing potential allergens, like cod fish parvalbumin, using food-relevant conditions may provide an effective tool to minimize risks of provoked allergic responses during food consumption.     

Modelling lung cancer due to radon and smoking in WISMUT miners: preliminary results

A mechanistic two-stage carcinogenesis model has been applied to model lung-cancer mortality in the largest uranium-miner cohort available. Models with and without smoking action both fit the data well. As smoking information is largely missing from the cohort data, a method has been devised to project this information from a case-control study onto the cohort. Model calculations using 256 projections show that the method works well. Preliminary results show that if an explicit smoking action is absent in the model, this is compensated by the values of the baseline parameters. This indicates that in earlier studies performed without smoking information, the results obtained for the radiation parameters are still valid. More importantly, the inclusion of smoking-related parameters shows that these mainly influence the later stages of lung-cancer development.     

Fermentation characteristics of polysaccharide fractions extracted from the cell walls of maize endosperm

Cell walls were extracted from maize endosperm and separated into different polysaccharide fractions by sequential extraction with solutions of saturated Ba(OH)₂, demineralised water and 1 and 4 M KOH. Solubilised polysaccharides were collected after each extraction. Residues were collected following the extractions with demineralised water and 1 and 4 M KOH. The original cell wall (CW) material, extracts and residues were analysed for their fermentation characteristics using an in vitro cumulative gas production technique. The rate of fermentation of the alkali‐treated residues was faster than that of the original CW material, except for the 4 M KOH residue, which had a similar rate of degradation to the original CW material. The polysaccharides solubilised from the cell wall (extracts) were all rapidly fermented, more rapidly than both CW and residues. A division of the gas production profile into two phases using curve fitting was in good agreement with a division of the cell wall fermentation into the fermentation of arabinoxylans and cellulose. Therefore the likelihood of preferential degradation of arabinoxylans from the maize cell wall was discussed. The volatile fatty acid production pattern was fairly well explained by the fermentation rate and composition of the substrates. It was concluded that breaking the interactions of polysaccharides in the maize cell wall by mild alkali extraction increases the fermentability of maize cell walls in the gastrointestinal tract of farm animals. Contrarily, more severe alkali extractions will reduce the fermentability of maize cell walls. © 2002 Society of Chemical Industry