Showing papers by "University of British Columbia published in 1998"

Fishing Down Marine Food Webs

Abstract: The mean trophic level of the species groups reported in Food and Agricultural Organization global fisheries statistics declined from 1950 to 1994. This reflects a gradual transition in landings from long-lived, high trophic level, piscivorous bottom fish toward short-lived, low trophic level invertebrates and planktivorous pelagic fish. This effect, also found to be occurring in inland fisheries, is most pronounced in the Northern Hemisphere. Fishing down food webs (that is, at lower trophic levels) leads at first to increasing catches, then to a phase transition associated with stagnating or declining catches. These results indicate that present exploitation patterns are unsustainable.

Corporate Disclosure Policy and Analyst Behavior

Abstract: This paper examines the relation between the disclosure practices of firms, the number of analysts following each firm, and properties of the analysts' earnings forecasts. Using data from the Financial Analysts Federation Corporate Information Committee Report (FAF Report), we provide evidence that firms with more informative disclosure policies have a larger analyst following, more accurate analyst earnings forecasts, less dispersion among individual analyst forecasts and less volatility in forecast revisions. The results enhance our understanding of the role of analysts in capital markets. Further, they suggest that potential benefits to disclosure include increased investor following, reduced estimation risk and reduced information asymmetry, each of which have been shown to reduce a firm's cost of capital in theoretical research.

Interpreting the significance of changes in health-related quality-of-life scores.

Abstract: PURPOSETo determine the significance to patients of changes in health-related quality-of-life (HLQ) scores assessed by the European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire (QLQ-C30).PATIENTS AND METHODSA subjective significance questionnaire (SSQ), which asks patients about perceived changes in physical, emotional, and social functioning and in global quality of life (global QL) and the QLQ-C30 were completed by patients who received chemotherapy for either breast cancer or small-cell lung cancer (SCLC). In the SSQ, patients rated their perception of change since the last time they completed the QLQ-C30 using a 7-category scale that ranged from "much worse" through "no change" to "much better." For each category of change in the SSQ, the corresponding differences were calculated in QLQ-C30 mean scores and effect sizes were determined.RESULTSFor patients who indicated "no change" in the SSQ, the mean change in scores in the corresponding QLQ-C30 domains was n...

Algorithms for Mining Distance-Based Outliers in Large Datasets

Abstract: This paper deals with finding outliers (exceptions) in large, multidimensional datasets. The identification of outliers can lead to the discovery of truly unexpected knowledge in areas such as electronic commerce, credit card fraud, and even the analysis of performance statistics of professional athletes. Existing methods that we have seen for finding outliers in large datasets can only deal efficiently with two dimensions/attributes of a dataset. Here, we study the notion of DB- (DistanceBased) outliers. While we provide formal and empirical evidence showing the usefulness of DB-outliers, we focus on the development of algorithms for computing such outliers. First, we present two simple algorithms, both having a complexity of O(k N’), k being the dimensionality and N being the number of objects in the dataset. These algorithms readily support datasets with many more than two attributes. Second, we present an optimized cell-based algorithm that has a complexity that is linear wrt N, but exponential wrt k. Third, for datasets that are mainly disk-resident, we present another version of the cell-based algorithm that guarantees at most 3 passes over a dataset. We provide

Demographic Diversity and Faultlines: The Compositional DYnamics of Organizational Groups

Abstract: In this article we address issues of diversity within organizational groups by discussing and summarizing previous approaches and by introducing a new variable—faultlines—which depends on the alignment of individual member characteristics. By analyzing a group's faultlines, we focus attention on the underlying patterns of group member characteristics, which can be an important determinant of subgroup conflict, particularly when the group's task is related to one of its faultlines. We discuss the dynamics of faultlines from the early to later stages of a group's development and show how they may be strongest and most likely when diversity of individual member characteristics is moderate.

The dynamics of reinforcement learning in cooperative multiagent systems

Abstract: Reinforcement learning can provide a robust and natural means for agents to learn how to coordinate their action choices in multi agent systems. We examine some of the factors that can influence the dynamics of the learning process in such a setting. We first distinguish reinforcement learners that are unaware of (or ignore) the presence of other agents from those that explicitly attempt to learn the value of joint actions and the strategies of their counterparts. We study (a simple form of) Q-leaming in cooperative multi agent systems under these two perspectives, focusing on the influence of that game structure and exploration strategies on convergence to (optimal and suboptimal) Nash equilibria. We then propose alternative optimistic exploration strategies that increase the likelihood of convergence to an optimal equilibrium.

Antiretroviral Therapy for HIV Infection in 1998: Updated Recommendations of the International AIDS Society–USA Panel

Abstract: Objective.—To provide recommendations for antiretroviral therapy based on information available in mid-1998.Participants.—An international panel of physicians with expertise in antiretroviral research and care of patients with human immunodeficiency virus (HIV) infection, first convened by the International AIDS Society–USA in December 1995.Evidence.—The panel reviewed available clinical and basic science study results (including phase 3 controlled trials; clinical, virologic, and immunologic end point data; data presented at research conferences; and studies of HIV pathophysiology); opinions of panel members were also considered. Recommendations were limited to drugs available in mid-1998.Consensus Process.—Panel members monitor new clinical research reports and interim results. The full panel meets regularly to discuss how the new information may change treatment recommendations. Updated recommendations are developed through consensus of the entire panel at each stage of development.Conclusions.—Accumulating data from clinical and pathogenesis studies continue to support early institution of potent antiretroviral therapy in patients with HIV infection. A variety of combination regimens show potency, expanding choices for initial regimens for individual patients. Plasma HIV RNA assays with increased sensitivity are important in monitoring therapeutic response; however, more data are needed to determine precisely the HIV RNA levels that define treatment failure. Long-term adverse drug effects are beginning to emerge, requiring ongoing attention. Some issues regarding optimal long-term approaches to antiretroviral management are unresolved. The increased complexity in HIV management requires ongoing monitoring of new data for optimal treatment of HIV infection.

Biodiversity inventories, indicator taxa and effects of habitat modification in tropical forest

Abstract: Despite concern about the effects of tropical forest disturbance and clearance on biodiversity1,2, data on impacts, particularly on invertebrates, remain scarce3,4,5,6,7,8. Here we report a taxonomically diverse inventory on the impacts of tropical forest modification at one locality. We examined a gradient from near-primary, through old-growth secondary and plantation forests to complete clearance, for eight animal groups (birds, butterflies, flying beetles, canopy beetles, canopy ants, leaf-litter ants, termites and soil nematodes) in the Mbalmayo Forest Reserve, south-central Cameroon. Although species richness generally declined with increasing disturbance, no one group serves as a good indicator taxon9,10,11,12 for changes in the species richness of other groups. Species replacement from site to site (turnover) along the gradient also differs between taxonomic groups. The proportion of ‘morphospecies’ that cannot be assigned to named species and the number of ‘scientist-hours’ required to process samples both increase dramatically for smaller-bodied taxa. Data from these eight groups indicate the huge scale of the biological effort required to provide inventories of tropical diversity, and to measure the impacts of tropical forest modification and clearance.

Cultural Continuity as a Hedge against Suicide in Canada's First Nations

Abstract: This research report examines self-continuity and its role as a protective factor against suicide. First, we review the notions of personal and cultural continuity and their relevance to understanding suicide among First Nations youth. The central theoretical idea developed here is that, because it is constitutive of what it means to have or be a self to somehow count oneself as continuous in time, anyone whose identity is undermined by radical personal and cultural change is put at special risk of suicide for the reason that they lose those future commitments that are necessary to guarantee appropriate care and concern for their own well-being. It is for just such reasons that adolescents and young adults - who are living through moments of especially dramatic change - constitute such a high-risk group. This generalized period of increased risk during adolescence can be made even more acute within communities that lack a concomitant sense of cultural continuity which might otherwise support the efforts o...

Improved Survival Among HIV-Infected Individuals Following Initiation of Antiretroviral Therapy

Abstract: Context.—Clinical trials have established the efficacy of antiretroviral therapy with double- and triple-drug regimens for individuals infected with the human immunodeficiency virus (HIV), but the effectiveness of these regimens in the population of patients not enrolled in clinical trials is unknown.Objective.—To characterize survival following the initiation of antiretroviral therapy among HIV-infected individuals in the province of British Columbia.Design.—Prospective, population-based cohort study of patients with antiretroviral therapy available free of charge (median follow-up, 21 months).Setting.—Province of British Columbia, Canada.Patients.—All HIV-positive men and women 18 years of age or older in the province who were first prescribed any antiretroviral therapy between October 1992 and June 1996 and whose CD4+ cell counts were less than 0.350×109/L.Main Outcome Measures.—Rates of progression from initiation of antiretroviral therapy to death or a primary acquired immunodeficiency syndrome (AIDS) diagnosis for subjects who initially received zidovudine-, didanosine-, or zalcitabine-based therapy (ERA-I) and for those who initially received therapy regimens including lamivudine or stavudine (ERA-II).Results.—A total of 1178 patients (951 ERA-I, 227 ERA-II) were eligible. A total of 390 patients died (367 ERA-I, 23 ERA-II), yielding a crude mortality rate of 33.1%. ERA-I group subjects were almost twice as likely to die as ERA-II group subjects, with a mortality risk ratio of 1.86 (95% confidence interval [CI], 1.21-2.86; P=.005). After adjusting for Pneumocystis carinii and Mycobacterium avium prophylaxis use, AIDS diagnosis, CD4+ cell count, sex, and age, ERA-I participants were 1.93 times (95% CI, 1.25-2.97; P=.003) more likely to die than ERA-II participants. Among patients without AIDS when treatment was started, ERA-I participants were 2.50 times (95% CI, 1.59-3.93; P<.001) more likely to progress to AIDS or death than ERA-II participants.Conclusion.—The HIV-infected individuals who received initial therapy with regimens including stavudine or lamivudine had significantly lower mortality and longer AIDS-free survival than those who received initial therapy with regimens limited to zidovudine, didanosine, and zalcitabine.

Engraftable human neural stem cells respond to development cues, replaceneurons, and express foreign genes

Abstract: Stable clones of neural stem cells (NSCs) have been isolated from the human fetal telencephalon. These self-renewing clones give rise to all fundamental neural lineages in vitro. Following transplantation into germinal zones of the newborn mouse brain they participate in aspects of normal development, including migration along established migratory pathways to disseminated central nervous system regions, differentiation into multiple developmentally and regionally appropriate cell types, and nondisruptive interspersion with host progenitors and their progeny. These human NSCs can be genetically engineered and are capable of expressing foreign transgenes in vivo. Supporting their gene therapy potential, secretory products from NSCs can correct a prototypical genetic metabolic defect in neurons and glia in vitro. The human NSCs can also replace specific deficient neuronal populations. Cryopreservable human NSCs may be propagated by both epigenetic and genetic means that are comparably safe and effective. By analogy to rodent NSCs, these observations may allow the development of NSC transplantation for a range of disorders.

Interpersonal and intrapsychic adaptiveness of trait self-enhancement: a mixed blessing?

Abstract: Reactions to trait self-enhancers were investigated in 2 longitudinal studies of personperception in discussion groups Groups of 4-6 participants met 7 times for 20 rain After Meetings 1 and 7, group members rated their perceptions of one another In Study 1, trait self-enhancement was indexed by measures of narcissism and self-deceptive enhancement At the first meeting, self-enhancers made positive impressions: They were seen as agreeable, well adjusted, and competent After 7 weeks, however, they were rated negatively and gave self-evaluations discrepant with peer evaluations they received In Study 2, an independent sample of observers (close acquaintances) enabled a pretest index of discrepancy self-enhancement: It predicted the same deteriorating pattern of interpersonal perceptions as the other three trait measures Nonetheless, all self-enhancement measures correlated positively with self-esteem

Monkey See, Monkey Do: The Influence of Work Groups on the Antisocial Behavior of Employees

Abstract: This cross-level field study, involving 187 employees from 35 groups in 20 organizations, examined how individuals' antisocial behaviors at work are shaped by the antisocial behavior of their cowor...

3-D inversion of gravity data

Abstract: We present two methods for inverting surface gravity data to recover a 3-D distribution of density contrast. In the first method, we transform the gravity data into pseudomagnetic data via Poisson's relation and carry out the inversion using a 3-D magnetic inversion algorithm. In the second, we invert the gravity data directly to recover a minimum structure model. In both approaches, the earth is modeled by using a large number of rectangular cells of constant density, and the final density distribution is obtained by minimizing a model objective function subject to fitting the observed data. The model objective function has the flexibility to incorporate prior information and thus the constructed model not only fits the data but also agrees with additional geophysical and geological constraints. We apply a depth weighting in the objective function to counteract the natural decay of the kernels so that the inversion yields depth information. Applications of the algorithms to synthetic and field data produce density models representative of true structures. Our results have shown that the inversion of gravity data with a properly designed objective function can yield geologically meaningful information.

Exploratory mining and pruning optimizations of constrained associations rules

Abstract: From the standpoint of supporting human-centered discovery of knowledge, the present-day model of mining association rules suffers from the following serious shortcomings: (i) lack of user exploration and control, (ii) lack of focus, and (iii) rigid notion of relationships. In effect, this model functions as a black-box, admitting little user interaction in between. We propose, in this paper, an architecture that opens up the black-box, and supports constraint-based, human-centered exploratory mining of associations. The foundation of this architecture is a rich set of constraint constructs, including domain, class, and SQL-style aggregate constraints, which enable users to clearly specify what associations are to be mined. We propose constrained association queries as a means of specifying the constraints to be satisfied by the antecedent and consequent of a mined association.In this paper, we mainly focus on the technical challenges in guaranteeing a level of performance that is commensurate with the selectivities of the constraints in an association query. To this end, we introduce and analyze two properties of constraints that are critical to pruning: anti-monotonicity and succinctness. We then develop characterizations of various constraints into four categories, according to these properties. Finally, we describe a mining algorithm called CAP, which achieves a maximized degree of pruning for all categories of constraints. Experimental results indicate that CAP can run much faster, in some cases as much as 80 times, than several basic algorithms. This demonstrates how important the succinctness and anti-monotonicity properties are, in delivering the performance guarantee.

B Cell–attracting Chemokine 1, a Human CXC Chemokine Expressed in Lymphoid Tissues, Selectively Attracts B Lymphocytes via BLR1/CXCR5

Abstract: Although most leukocytes, T lymphocytes in particular, respond to several different chemokines, there is virtually no information on chemokine activities and chemokine receptors in B lymphocytes. A putative chemokine receptor, BLR1, that is expressed in Burkitt's lymphoma cells and B lymphocytes was cloned a few years ago. Deletion of the gene for BLR1 yielded mice with abnormal primary follicles and germinal centers of the spleen and Peyer's patches, reflecting the inability of B lymphocytes to migrate into B cell areas. By screening expressed sequence tag DNA sequences, we have identified a CXC chemokine, termed B cell–attracting chemokine 1 (BCA-1), that is chemotactic for human B lymphocytes. BCA-1 cDNA encodes a protein of 109 amino acids with a leader sequence of 22 residues. The mature protein shares 23–34% identical amino acids with known CXC chemokines and is constitutively expressed in secondary lymphoid organs. BCA-1 was chemically synthesized and tested for activity on murine pre–B cells 300-19 transfected with BLR1 and on human blood B lymphocytes. In transfected cells, BCA-1 induced chemotaxis and Ca2+ mobilization demonstrating that it acts via BLR1. Under the same conditions, no activity was obtained with 10 CXC and 19 CC chemokines, lymphotactin, neurotactin/fractalkine and several other peptide ligands. BCA-1 was also a highly effective attractant for human blood B lymphocytes (which express BLR1), but was inactive on freshly isolated or IL-2–stimulated T lymphocytes, monocytes, and neutrophils. In agreement with the nomenclature rules for chemokine receptors, we propose the term CXCR5 for BLR1. Together with the observed disturbance of B cell colonization in BLR1/ CXCR5-deficient mice, the present results indicate that chemotactic recruitment by locally produced BCA-1 is important for the development of B cell areas of secondary lymphoid tissues.

Egoistic and Moralistic Biases in Self-Perception: The Interplay of Self-Deceptive Styles With Basic Traits and Motives

Abstract: The literature on personality traits and defense mechanisms suggests individual differences in two self-favoring tendencies, which we label "egoistic bias" and "moralistic bias." The two biases are self-deceptive in nature and can be traced to two fundamental values, agency and communion, that impel two corresponding motives, nPower and nApproval. The two sequences of values, motives, and biases form two personality constellations, Alpha and Gamma.Associated with Alpha is an egoistic bias, a self-deceptive tendency to exaggerate one's social and intellectual status. This tendency leads to

A randomized, double-blind trial comparing combinations of nevirapine, didanosine, and zidovudine for HIV-infected patients: the INCAS Trial. Italy, The Netherlands, Canada and Australia Study.

Abstract: Context.—Current guidelines recommend that individuals infected with the human immunodeficiency virus type 1 (HIV-1) be treated using combinations of antiretroviral agents to achieve sustained suppression of viral replication as measured by the plasma HIV-1 RNA assay, in the hopes of achieving prolonged remission of the disease. However, until recently, many drug combinations have not led to sustained suppression of HIV-1 RNA.Objective.—To compare the virologic effects of various combinations of nevirapine, didanosine, and zidovudine.Design.—Double-blind, controlled, randomized trial.Setting.—University-affiliated ambulatory research clinics in Italy, the Netherlands, Canada, and Australia (INCAS).Patients.—Antiretroviral therapy–naive adults free of the acquired immunodeficiency syndrome with CD4 cell counts between 0.20 and 0.60×109/L (200-600/µL).Intervention.—Patients received zidovudine plus nevirapine (plus didanosine placebo), zidovudine plus didanosine (plus nevirapine placebo), or zidovudine plus didanosine plus nevirapine.Main Outcome Measure.—Plasma HIV-1 RNA.Results.—Of the 153 enrolled patients, 151 were evaluable. At week 8, plasma HIV-1 RNA levels had decreased by log 2.18, 1.55, and 0.90 in the triple drug therapy, zidovudine plus didanosine, and zidovudine plus nevirapine groups, respectively (P<.05). The proportions of patients with plasma HIV-1 RNA levels below 20 copies per milliliter at week 52 were 51%, 12%, and 0% in the triple drug therapy, zidovudine plus didanosine, and zidovudine plus nevirapine groups, respectively (P<.001). Viral amplification was attempted in 59 patients at 6 months. Viral isolation was unsuccessful in 19 (79%) of 24, 10 (53%) of 19, and 5 (31%) of 16 patients in the triple drug therapy, zidovudine plus didanosine, and zidovudine plus nevirapine groups, respectively. Among patients from whom virus could be amplified, resistance to nevirapine was found in all 11 patients receiving zidovudine plus nevirapine and in all 5 patients receiving triple drug therapy. Rates of disease progression or death were 23% (11/47), 25% (13/53), and 12% (6/51) for the zidovudine plus nevirapine, zidovudine plus didanosine, and triple drug therapy groups, respectively (P=.08).Conclusions.—Triple drug therapy with zidovudine, didanosine, and nevirapine led to a substantially greater and sustained decrease in plasma viral load than the 2-drug regimens studied. Our results also suggest that suppression of viral replication, as demonstrated by a decrease in the plasma HIV-1 RNA load below the level of quantitation of the most sensitive test available, may at least forestall the development of resistance.

Psychopathy and recidivism: A review

Abstract: Psychopathy is defined by a constellation of interpersonal, affective and behavioural characteristics that should, in principle, be strongly related to risk for recidivism and violence. We reviewed the literature on The Hare Psychopathy Checklist-Revised scales (PCL-R; Hare, 1980, 1991) and recidivism. We found that the PCL-R consistently was an important predictor across inmate samples and was consistently among the best predictors of recidivism. Average correlations between the PCL-R and recidivism, weighted by their degrees of freedom, were .27 for general recidivism, .27 for violent recidivism, and .23 for sexual recidivism. Relative risk statistics at one year indicated that psychopaths were approximately three times more likely to recidivate—or four times more likely to violently recidivate—than were non-psychopaths. The correlation between general recidivism and PCL-R Factor 2 (a measure of the social deviance facet of psychopathy) was stronger than the correlation between general recidivism and PCL-R Factor 1 (a measure of the interpersonal/affective facet of psychopathy). Both PCL-R factors contributed equally to the prediction of violent recidivism. The PCL-R routinely made a significant contribution towards predicting recidivism beyond that made by key demographic variables, criminal history, and personality disorder diagnoses. Across studies, PCL-R scores were as strongly associated with general recidivism, and were more strongly associated with violent recidivism, than were actuarial risk scales designed specifically to predict reoffending. Taken together, these findings indicate that the PCL-R should be considered a primary instrument for guiding clinical assessments of risk for criminal recidivism and dangerousness.

A novel ETV6-NTRK3 gene fusion in congenital fibrosarcoma

Abstract: Congenital (or infantile) fibrosarcoma (CFS) is a malignant tumour of f ibroblasts that occurs in patients aged two years or younger. CFS is unique among human sarcomas in that it has an excellent prognosis and very low metastatic rate1,2. CFS is histologi-cally identical to adult-type f ibrosarcoma (ATFS); however, ATFS is an aggressive malignancy of adults and older children that has a poor prognosis3. We report a novel recurrent t(12;15)(p13;q25) rearrangement in CFS that may underlie the distinctive biological properties of this tumour. By cloning the chromosome breakpoints, we show that the rearrangement fuses the ETV6 (also known as TEL) gene from 12p13 with the 15q25 NTRK3 neurotrophin-3 receptor gene (also known as TRKQ. Analysis of mRNA revealed the expression of ETV6-NTRK3 chimaeric transcripts in all three CFS tumours analysed. These were not detected in ATFS or infantile fibromatosis (IFB), a histologically similar but benign fibroblastic proliferation occurring in the same age-group as CFS. ETV6-NTRK3 fusion transcripts encode the helix-loop-helix (HLH) protein dimerization domain of ETV6 fused to the protein tyrosine kinase (PTK) domain of NTRK3. Our studies indicate that a chimaeric PTK is expressed in CFS and this may contribute to onco-genesis by dysregulation of NTRK3 signal transduction pathways. Moreover, ETV6-NTRK3 gene fusions provide a potential diagnostic marker for CFS.

Dendritic Cell Survival and Maturation Are Regulated by Different Signaling Pathways

Abstract: Although dendritic cell (DC) activation is a critical event for the induction of immune responses, the signaling pathways involved in this process have not been characterized. In this report, we show that DC activation induced by lipopolysaccharide (LPS) can be separated into two distinct processes: first, maturation, leading to upregulation of MHC and costimulatory molecules, and second, rescue from immediate apoptosis after withdrawal of growth factors (survival). Using a DC culture system that allowed us to propagate immature growth factor–dependent DCs, we have investigated the signaling pathways activated by LPS. We found that LPS induced nuclear translocation of the nuclear factor (NF)-κB transcription factor. Inhibition of NF-κB activation blocked maturation of DCs in terms of upregulation of major histocompatibility complex and costimulatory molecules. In addition, we found that LPS activated the extracellular signal–regulated kinase (ERK), and that specific inhibition of MEK1, the kinase which activates ERK, abrogated the ability of LPS to prevent apoptosis but did not inhibit DC maturation or NF-κB nuclear translocation. These results indicate that ERK and NF-κB regulate different aspects of LPS-induced DC activation: ERK regulates DC survival whereas NF-κB is responsible for DC maturation.

Comparative efficacy of treatments for post-traumatic stress disorder: a meta-analysis

Abstract: A meta-analysis was conducted on 61 treatment outcome trials for post-traumatic stress disorder (PTSD). Conditions included drug therapies (TCAs, carbamazepine, MAOIs, SSRIs, and BDZs), psychological therapies (behaviour therapy, Eye-Movement Desensitization and Reprocessing (EMDR), relaxation training, hypnotherapy, and dynamic therapy), and control conditions (pill placebo, wait-list controls, supportive psychotherapies, and non-saccade EMDR control). Psychological therapies had significantly lower drop-out rates than pharmacotherapies (14% versus 32%), with attrition being uniformly low across all psychological therapies. In terms of symptom reduction, psychological therapies were more effective than drug therapies, and both were more effective than controls. Among the drug therapies, the SSRIs and carbamazepine had the greatest effect sizes, although the latter was based upon a single trial. Among the psychological therapies, behaviour therapy and EMDR were most effective, and generally equally so. The most effective psychological therapies and drug therapies were generally equally effective. Differences across treatment conditions were generally evident across symptom domains, with little matching of symptom domain to treatment type. However, SSRIs had some advantage over psychological therapies in treating depression. Follow-up results were not available for most treatments, but available data indicates that treatment effects for behaviour therapy and EMDR are maintained at 15-week follow-up. © 1998 John Wiley & Sons, Ltd.