Showing papers by "University of British Columbia published in 1991"

Development of an Instrument to Measure the Perceptions of Adopting an Information Technology Innovation

Abstract: This paper reports on the development of an instrument designed to measure the various perceptions that an individual may have of adopting an information technology IT innovation. This instrument is intended to be a tool for the study of the initial adoption and eventual diffusion of IT innovations within organizations. While the adoption of information technologies by individuals and organizations has been an area of substantial research interest since the early days of computerization, research efforts to date have led to mixed and inconclusive outcomes. The lack of a theoretical foundation for such research and inadequate definition and measurement of constructs have been identified as major causes for such outcomes. In a recent study examining the diffusion of new end-user IT, we decided to focus on measuring the potential adopters' perceptions of the technology. Measuring such perceptions has been termed a "classic issue" in the innovation diffusion literature, and a key to integrating the various findings of diffusion research. The perceptions of adopting were initially based on the five characteristics of innovations derived by Rogers 1983 from the diffusion of innovations literature, plus two developed specifically within this study. Of the existing scales for measuring these characteristics, very few had the requisite levels of validity and reliability. For this study, both newly created and existing items were placed in a common pool and subjected to four rounds of sorting by judges to establish which items should be in the various scales. The objective was to verify the convergent and discriminant validity of the scales by examining how the items were sorted into various construct categories. Analysis of inter-judge agreement about item placement identified both bad items as well as weaknesses in some of the constructs' original definitions. These were subsequently redefined. Scales for the resulting constructs were subjected to three separate field tests. Following the final test, the scales all demonstrated acceptable levels of reliability. Their validity was further checked using factor analysis, as well as conducting discriminant analysis comparing responses between adopters and nonadopters of the innovation. The result is a parsimonious, 38-item instrument comprising eight scales which provides a useful tool for the study of the initial adoption and diffusion of innovations. A short, 25 item, version of the instrument is also suggested.

Neuronal NADPH diaphorase is a nitric oxide synthase.

Abstract: NADPH diaphorase histochemistry selectively labels a number of discrete populations of neurons throughout the nervous system. This simple and robust technique has been used in a great many experimental and neuropathological studies; however, the function of this enzyme has remained a matter of speculation. We, therefore, undertook to characterize this enzyme biochemically. With biochemical and immunochemical assays, NADPH diaphorase was purified to apparent homogeneity from rat brain by affinity chromatography and anion-exchange HPLC. Western (immunoblot) transfer and immunostaining with an antibody specific for NADPH diaphorase labeled a single protein of 150 kDa. Nitric oxide synthase was recently shown to be a 150-kDa, NADPH-dependent enzyme in brain. It is responsible for the calcium/calmodulin-dependent synthesis of the guanylyl cyclase activator nitric oxide from L-arginine. We have found that nitric oxide synthase activity and NADPH diaphorase copurify to homogeneity and that both activities could be immunoprecipitated with an antibody recognizing neuronal NADPH diaphorase. Furthermore, nitric oxide synthase was competitively inhibited by the NADPH diaphorase substrate, nitro blue tetrazolium. Thus, neuronal NADPH diaphorase is a nitric oxide synthase, and NADPH diaphorase histochemistry, therefore, provides a specific histochemical marker for neurons producing nitric oxide.

Fitting parameterized three-dimensional models to images

Abstract: Model-based recognition and motion tracking depend upon the ability to solve for projection and model parameters that will best fit a 3-D model to matching 2-D image features. The author extends current methods of parameter solving to handle objects with arbitrary curved surfaces and with any number of internal parameters representing articulation, variable dimensions, or surface deformations. Numerical stabilization methods are developed that take account of inherent inaccuracies in the image measurements and allow useful solutions to be determined even when there are fewer matches than unknown parameters. The Levenberg-Marquardt method is used to always ensure convergence of the solution. These techniques allow model-based vision to be used for a much wider class of problems than was possible with previous methods. Their application is demonstrated for tracking the motion of curved, parameterized objects. >

Universal noninteger "ground-state degeneracy" in critical quantum systems.

Abstract: One-dimensional critical quantum sytems have a universal, intensive ``ground-state degeneracy,'' g, which depends on the universality class of the boundary conditions, and is in general noninteger. This is calculated, using the conjectured boundary conditions corresponding to a multichannel Kondo impurity and shown to agree with Bethe-ansatz results. g is argued to decrease under renormalization from a less stable to a more stable critical point and plays a role in boundary critical phenomena quite analogous to that played by c, the conformal anomaly, in the bulk case.

Culture and the categorization of emotions.

Abstract: Some writers assume--and others deny--that all human beings distinguish emotions from nonemotions and divide the emotions into happiness, anger, fear, and so on. A review of ethnographic and cross-cultural studies on (a) emotion lexicons, (b) the emotions inferred from facial expressions, and (c) dimensions implicit in comparative judgments of emotions indicated both similarities and differences in how the emotions are categorized in different languages and cultures. Five hypotheses are reviewed: (a) Basic categories of emotion are pancultural, subordinate categories culture specific; (b) emotional focal points are pancultural, boundaries culture specific; (c) emotion categories evolved from a single primitive category of physiological arousal; (d) most emotion categories are culture specific but can be defined by pancultural semantic primitives; and (e) an emotion category is a script with both culture-specific and pancultural components.

Psychopathy and the DSM-IV Criteria for Antisocial Personality Disorder

Abstract: The Axis II Work Group of the Task Force on DSM—IV has expressed concern that antisocial personality disorder (APD) criteria are too long and cumbersome and that they focus on antisocial behaviors rather than personality traits central to traditional conceptions of psychopathy and to international criteria. We describe an alternative to the approach taken in the rev. 3rd ed. of the Diagnostic and Statistical Manual of Mental Disorders ( DSM—III—R ; American Psychiatric Association, 1987 ), namely, the revised Psychopathy Checklist. We also discuss the multisite APD field trials designed to evaluate and compare four criteria sets: the DSM—III—R criteria, a shortened list of these criteria, the criteria for dyssocial personality disorder from the 10th ed. of the International Classification of Diseases ( World Health Organization, 1990 ), and a 10-item criteria set for psychopathic personality disorder derived from the revised Psychopathy Checklist.

Physical properties of the fluid lipid-bilayer component of cell membranes: a perspective.

Abstract: The motivation for this review arises from the conviction that, as a result of the mass of experimental data and observations collected in recent years, the study of the physical properties of membranes is now entering a new stage of development. More and more, experiments are being designed to answer specific, detailed questions about membranes which will lead to a quantitative understanding of the way in which the physical properties of membranes are related to and influence their biological function.

Enhancement and Denial in Socially Desirable Responding

Abstract: One research tradition has distinguished self-deception, the tendency to give favorably biased but honestly held self-descriptions impression management, the tendency to give favorable selfdescriptions to others. A 2nd tradition has distinguished enhancement, the claiming of positive attributes, from denial, the repudiation of negative attributes. The 2 distinctions were evaluated jointly in 3 studies. Factor analyses showed that impression management items (both enhancement and denial) loaded together. Self-deception items split up: Enhancement items formed a 2nd factor, whereas denial items fell closer to the impression management factor. Of the 4 types, self-deceptive enhancement best predicted adjustment. These results clarify the constructs of enhancement and denial: The critical distinction is not simply one of keying direction but whether the item content refers to a positive or negative attribute.

Simulation of surface urban heat islands under `ideal' conditions at night part 2: Diagnosis of causation

Abstract: A simple energy balance model which simulates the thermal regime of urban and rural surfaces under calm, cloudless conditions at night is used to assess the relative importance of the commonly stated causes of urban heat islands. Results show that the effects of street canyon geometry on radiation and of thermal properties on heat storage release, are the primary and almost equal causes on most occasions. In very cold conditions, space heating of buildings can become a dominant cause but this depends on wall insulation. The effects of the urban ‘greenhouse’ and surface emissivity are relatively minor. The model confirms the importance of local control especially the relation between street geometry and the heat island and highlights the importance of rural thermal properties and their ability to produce seasonal variation in the heat island. A possible explanation for the small heat

Financial Policy and Reputation for Product Quality

Abstract: The effect of financial policy on a firm's incentives to maintain its reputation for producing a high-quality product is analyzed. It is demonstrated that in certain situations debt will reduce a firm's ability to credibly offer high-quality products and, as a consequence, will reduce its value. However, for firms with assets that have high salvage values in liquidation, debt may increase their ability to credibly offer high-quality products and, therefore, increase their values. Article published by Oxford University Press on behalf of the Society for Financial Studies in its journal, The Review of Financial Studies.

Solitary pulmonary nodule: high-resolution CT and radiologic-pathologic correlation.

Abstract: Edge and internal characteristics of pulmonary nodules evaluated with high-resolution computed tomography (HRCT) were correlated with the pathologic specimens in 93 patients. Speculation correlated pathologically with irregular fibrosis, localized lymphatic spread of tumor, or an infiltrative tumor growth pattern and was observed in six of 11 benign nodules (55%) and 74 of 85 malignant nodules (87%). Pleural tags were observed in three benign nodules (27%) and 49 malignant lesions (58%); pathologically, these represented fibrotic bands usually associated with juxta-cicatricial pleural retraction. Bubblelike areas of low attenuation within the nodule were observed in 21 malignant lesions (25%) and only one benign nodule (9%). They were observed most commonly in bronchioloalveolar carcinomas (seven of 14) and were due either to patent small bronchi or small, cystic spaces within neoplastic glands. Malignant nodules as a group were larger than benign lesions (P = .02) and more commonly demonstrated a spiculated contour (P less than .05), lobulation (P less than .001), and inhomogeneous attenuation (P less than .05).

On the low heritability of life-history traits.

Abstract: Life-history traits such as longevity and fecundity often show low heritability. This is usually interpreted in terms of Fisher's fundamental theorem to mean that populations are near evolutionary equilibrium and genetic variance in total fitness is low. We develop the causal relationship between metric traits and life-history traits to show that a life-history trait is expected to have a low heritability whether or not the population is at equilibrium. This is because it is subject to all the environmental variation in the metric traits that affect it plus additional environmental variation. There is no simple prediction regarding levels of additive genetic variance in life-history traits, which may be high at equilibrium. Several other patterns in the inheritance of life-history traits are readily predicted from the causal model. These include the strength of genetic correlations between life-history traits, levels of nonadditive genetic variance, and the inevitability of genotype-environment interaction.

Abnormal processing of affective words by psychopaths.

Abstract: We tested the hypothesis that psychopathy is associated with abnormal processing of affective verbal material. Criminal psychopaths and nonpsychopaths, defined by the Psychopathy Checklist, performed a lexical decision task ("Is it a word or not?") while we recorded reaction time and event-related potentials in response to letter-strings consisting of affective and neutral words and pronounceable nonwords. On the assumption that they do not make efficient use of affective information, our primary prediction was that psychopaths would show less behavioral and event-related potential differentiation between affective and neutral words than would nonpsychopaths. The results were in accordance with this prediction. The lexical decisions of nonpsychopaths were significantly faster, and relevant event-related potential components were significantly larger, to affective words than to neutral words. In sharp contrast, psychopaths failed to show reaction time facilitation or larger amplitude event-related potentials to affective words. We suggest that psychopaths extract less information from affective words than do other individuals. Possible implications of these and related findings for understanding the behavior of psychopaths are discussed.

Cytoskeletal rearrangements accompanying salmonella entry into epithelial cells.

Abstract: Salmonella bacteria can enter (invade) eukaryotic cells, and exist as intracellular parasites. Confocal, light immunofluorescence and electron microscopy were used to examine various cytoskeletal components of cultured Madin Darby canine kidney (MDCK) and HeLa epithelial cells after infection with Salmonella typhimurium. These bacteria entered and remained within membrane-bound vacuoles and were surrounded by large (5–10 microns) dense structures composed of various cytoskeletal components. These structures consisted of extensive aggregations of polymerized actin, alpha-actinin and tropomyosin above and beside the invading bacterium in both epithelial cell lines. These structures were evident soon after bacterial addition (maximal at 20 min for HeLa cells, 60 min for MDCK cells), and disappeared later in the infection as the cytoskeletal components returned to a more normal distribution after bacterial internalization. Surprisingly, tubulin also aggregated above internalized Salmonella although bacterial entry or penetration through polarized monolayers was not disrupted by the microtubule-inhibiting agent nocadazole (this treatment actually enhanced tubulin accumulation around these organisms). There were little if any rearrangements in intermediate filaments composed of keratin or vimentin. Large amounts of talin also accumulated above and around invading Salmonella, but there was only a minor accumulation of vinculin around a few organisms. Pretreatment of epithelial cells with the microfilament inhibitor cytochalasin D blocked bacterial internalization but did not prevent accumulation of polymerized actin and alpha-actinin directly beneath uninternalized bacteria, yet prevented accumulation of the other cytoskeletal components. These results suggest that Salmonella bind to the surface and trigger a signal in epithelial cells that causes marked rearrangements in various cytoskeletal components, including recruitment of actin filaments and alpha-actinin, which then generates the force necessary for bacterial uptake.

Conflicting Selection Pressures and Life History Trade-Offs

Abstract: We review studies of natural selection in wild populations in which selection has acted in opposite directions at different stages of the life history. For example, the phenotype with highest probability of survival may have the lowest reproductive success. We discuss two important implications of these findings. First, measurements of opposing selection confirm that evolution of traits is governed by a balance of conflicting fitness advantages. Second, studies of opposing selection are informative about mechanisms underlying life history trade-offs. We outline difficulties in measuring opposing selection, particularly the problem that patterns of selection may be masked by the positive effects of nutrition on size of metric traits and fitness components. We discuss some solutions to these problems, and present a statistical technique to help disentangle direct selection from nutritional effects. Finally, we show how fluctuations in selection pressures lead to norms of reaction for life history traits in the absence of developmental plasticity.