This is a preprint of a paper published (with a slightly different title: Spatial semantics and individual differences in the perception of shape in information space) in the Journal of the American Society for Information Science, 51(6), 521-528. Abstract: User problems with large information spaces multiply in complexity when we enter the digital domain. Virtual information environments can offer 3-D representations, reconfigurations and access to large databases that can overwhelm many usersâ abilities to filter and represent. As a result, users frequently experience disorientation in navigating large digital spaces to locate and use information. To date, the research response has been predominantly based on the analysis of visual navigational aids that might support users' bottom-up processing of the spatial display. In the present paper an emerging alternative is considered that places greater emphasis on the top-down application of semantic knowledge by the user gleaned from their experiences within the socio-cognitive context of information production and consumption. A distinction between spatial and semantic cues is introduced and existing empirical data are reviewed that highlight the differential reliance on spatial or semantic information as domain expertise of the user increases. The conclusion is reached that interfaces for shaping information should be built on an increasing analysis of users' semantic processing.

Artificial Intelligence Lab, Department of MIS, University of Arizona / Can on-line information retrieval systems negotiate the diverse vocabularies of different users? This article suggests a robust algorithmic solution to the vocabulary problem in collaborative systems.

The present paper reviews the general usability framework that has dominated discussion in the field of human-computer interaction (HCI) and finds it wanting. An alternative view of the important determinants of user experience of interactive devices is presented with examples.

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No description available.

Using concepts derived from Social Identity theory, this study investigated the impact of status, perceived legitimacy/illegitimacy and perceived stabiliity/instability on intergroup bias in a real-life intergroup situation between blacks and whites in South Africa. The sample consisted of 369 students registered at the University of Natal, Durban. Of the total, 208 subjects were used exclusively in preliminary testing necessary for the development of the questionnaire. The independent variables, status, perceived legitimacy/illegitimacy and perceived stability/instability, were assessed by means of the group perception ladder; this being an adapted version of Cantril's (1965) Self-Anchoring Striving Scale. An attitude scale for black-white relations was also constructed and administered as a check on the validity of the group perception ladder. The dependent measure was the degree of ingroup bias displayed in (i.) voting preferences among four candidates (2 whites and 2 blacks) standing in a mock faculty council election, (ii) evaluation of these candidates .on a list of trait scales, (iii) number of student residence rooms allocated to ingroup and outgroup, (iv) relative desirability of the rooms allocated to each group and (v) the degree of integration shown in the allocation of rooms to each group. Both the independent and dependent measures were compiled into a questionnaire, carefully randomized according to a Latin-square arrangement. This questionnaire was then administered to a group of 161 paid student volunteers of all races. Participants were unaware that race was a subject of interest. A system of colour coding was used to identify the race of the subject . The data' from Indian and 'coloured' volunteers was discarded from the analysis, Since blacks and whites formed the racial categorizations selected for investigation.. The data from 70 blacks and 70 whites was analysed using the statistical technique of multiple linear regression. A statistically significant pattern of results was found on two of the dependent measures, namely, ingroup bias in voting preferences and degree of integration. The findings provided partial support for the predictions of Soc i a I I dentity theory. Under conditions where stability / instability was found to have a significant effect, the perception of instability generally resulted in an enhancement of ingroup bias. A significant effect for status was only found when the status relations were perceived as legitimate. Perceived legitimacy was found to be more salient in the low status group; eliciting a stronger reaction from its members. In both the high and low status groups those who perceived the social stratification as illegitimate were found to display lesser ingroup bias than comparable others who believed that the status system is legitimate. While social Identity theory predicts such a trend for high status groups, the similar findings in the low status group is contrary to the theory. These results were evaluated against the backdrop of several methodological and practical problems associated with the research. / Thesis (M.A.)-University of Natal, Durban, 1986.

Pseudomonas is the most common cause of chronic lung infections leading to death in cystic fibrosis patients. While chronic infection is extremely difficult to eradicate, the initial bacterial-host interactions prior to biofilm formation and establishment of chronic infections represents an attractive therapeutic target. It is clear that interaction between pathogens and the host is a very complex process and successful adaptation requires tight control of virulence factor expression. The aim of this project was to look for early changes in P. aeruginosa global gene expression in response to attachment to epithelial cells. P. aeruginosa PA01 was incubated with polarized HBE cells at a MOI of 100 for 4 hours and bacteria attached to epithelial cells (interacting) were collected separately from those in the supernatant (non-interacting). To minimize media effects observed by others, iron and phosphate were supplemented at appropriate levels to avoid expression changes due to limitation of these nutrients, as confirmed in our microarray experiments. Analysis of 3 independent experiments demonstrated that 766 genes were up or down regulated by more than 1.5 fold during attachment. Among these, 371 genes, including ion, oprC, as well as 3 genes in quorum-sensing systems and 9 genes involved in the pmrAB and phoPQ two-component regulatory systems were found to be induced in the interacting bacteria. On the other hand, 395 genes, including oprG outer membrane porin and pscP involved in type III secretion system were down regulated. To understand the roles of these differentially expressed genes, a cytotoxicity (LDH release) assay was performed and demonstrated that oprG and ion mutants were less capable than the wild type of killing HBE epithelial cells. These findings suggest that, under these interaction assay conditions, regulation of the expression of certain virulence factors provides a potential advantage for successful adaptation. In addition, a mutant lacking a filamentous hemagglutinin like protein was found to be less cytotoxic to HBE cells and also deficient in A549 epithelial cell binding, indicating that this probable non-pilin adhesin has multiple functions in P. aeruginosa.

Iron homeostasis is essential for maintaining the physiological requirement for iron while preventing iron overload. Multicopper ferroxidases regulate the oxidation of Fe(II) to Fe(III), circumventing the generation of harmful hydroxyl-free radicals. Ceruloplasmin is the major multicopper ferroxidase in blood; however, hephaestin, a membrane-bound ceruloplasmin homolog, has been implicated in the export of iron from duodenal enterocytes into blood. These ferroxidases supply transferrin, the iron-carrier protein in plasma, with Fe(III). Transferrin circulates through blood and delivers iron to cells via the transferrin receptor pathway. Due to the insoluble and reactive nature of free Fe(III), the oxidation of Fe(II) upon exiting the duodenal enterocyte may require an interaction between the ferroxidase and transferrin. In Chapter 3, the putative interaction of transferrin with ceruloplasmin and a soluble form of recombinant hephaestin was investigated. Utilizing native polyacrylamide gel electrophoresis, covalent cross-linking and surface plasmon resonance, a stable interaction between the two proteins was not detected. The lack of interaction between hephaestin and transferrin prompted the investigation into the localization of hephaestin in the human small intestine. Hephaestin has been reported to have both intracellular and extracellular locations in murine tissue. In the Appendix, the location of hephaestin in human tissue was investigated using a novel polyclonal antibody. Hephaestin was localized to the basolateral membrane and an intracellular location of the enterocyte, as well as a novel location in the myenteric plexus of the duodenum. The delivery of iron to cells via the transferrin receptor pathway is well established; however, little is known about the interaction of transferrin with the transferrin receptor at the molecular level. In Chapters 4 and 5, surface plasmon resonance was employed to further characterize the binding event between transferrin and the transferrin receptor. It was found that mutations affecting iron release in transferrin did not impact receptor binding. However, when N-lobe residues predicted to form contacts with the transferrin receptor were targeted, significant changes in the transferrin receptor binding kinetics and affinity were observed.

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Multidrug resistance protein 1 (MRP1) is an integral membrane protein belonging to the ATP-binding cassette (ABC) superfamily that utilizes ATP binding and hydrolysis to transport various endogenous substrates and/or xenobiotics across membranes against a concentration gradient. The overall goal of my research was to examine the nucleotide and protein interactions of MRP1 using various biochemical methods. In the first study, Cu2+(Ph)3 which promotes cross-linking of two nearby Cys residues and limited proteolysis were used to study conformational changes of MRP1 at different stages of ATP binding and hydrolysis at the nucleotide binding domains (NBDs). The limited trypsin digestion patterns indicated that some Cys residues of MRP1 could be cross-linked in the nucleotide-free state and that the Cys cross-linked MRP1 was more susceptible to trypsinolysis. Furthermore, binding of ATP, AMP-PNP, and trapping of ADP by MRP1 prevented the cross-linking events from occurring, but binding of ATPγS did not. However, the ATPγS-bound MRP1, like nucleotide-free MRP1, showed enhanced sensitivity towards trypsinolysis. These studies show that the two ATP analogs, AMP-PNP and ATPγS, interact with MRP1 in different ways. In the second study, the interaction of MRP1 with other cellular proteins was examined. An in vivo chemical cross-linking approach combined with affinity purification and MS analysis was initially used to identify protein partners directly interacting with MRP1. When this approach proved unsuccessful, a second approach involving immunoaffinity purification of MRP1-containing complexes followed by MS analysis was adopted. Six potential candidate interacting protein partners of MRP1 were identified via this approach and two of them, FUS and drebrin, were further characterized by co-immunoprecipitation and colocalization experiments. FUS seems unlikely to be an important binding partner of MRP1 since confocal and subcellular fractionation studies showed it to be exclusively localized in the nucleus. On the other hand, drebrin depletion by siRNA knock-down resulted in a moderate decrease in MRP1 overall expression levels although the membrane localization of MRP1 remained unchanged. / Thesis (Master, Pathology & Molecular Medicine) -- Queen's University, 2008-12-08 17:44:52.767