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Showing papers by "University of Alberta published in 1990"


Book
01 Aug 1990
TL;DR: This third edition of a classic textbook can be used to teach at the senior undergraduate and graduate levels and concentrates on fundamental theories as well as techniques and algorithms in distributed data management.
Abstract: This third edition of a classic textbook can be used to teach at the senior undergraduate and graduate levels. The material concentrates on fundamental theories as well as techniques and algorithms. The advent of the Internet and the World Wide Web, and, more recently, the emergence of cloud computing and streaming data applications, has forced a renewal of interest in distributed and parallel data management, while, at the same time, requiring a rethinking of some of the traditional techniques. This book covers the breadth and depth of this re-emerging field. The coverage consists of two parts. The first part discusses the fundamental principles of distributed data management and includes distribution design, data integration, distributed query processing and optimization, distributed transaction management, and replication. The second part focuses on more advanced topics and includes discussion of parallel database systems, distributed object management, peer-to-peer data management, web data management, data stream systems, and cloud computing. New in this Edition: New chapters, covering database replication, database integration, multidatabase query processing, peer-to-peer data management, and web data management. Coverage of emerging topics such as data streams and cloud computing Extensive revisions and updates based on years of class testing and feedback Ancillary teaching materials are available.

2,395 citations


Journal ArticleDOI
TL;DR: Fraction X in combination with mitochondria might be responsible for the observed compartmentalization of a serine-labeled pool of phospholipids previously identified and might be involved in the transfer of lipids between the endoplasmic reticulum and mitochondria.

1,012 citations


Journal ArticleDOI
TL;DR: In this paper, three small-area models, of Battese, Harter, and Fuller (1988), Dempster, Rubin, and Tsutakawa (1981), and Fay and Herriot (1979), are investigated.
Abstract: Small-area estimation has received considerable attention in recent years because of a growing demand for reliable small-area statistics. The direct-survey estimators, based only on the data from a given small area (or small domain), are likely to yield unacceptably large standard errors because of small sample size in the domain. Therefore, alternative estimators that borrow strength from other related small areas have been proposed in the literature to improve the efficiency. These estimators use models, either implicitly or explicitly, that connect the small areas through supplementary (e.g., census and administrative) data. For example, simple synthetic estimators are based on implicit modeling. In this article, three small-area models, of Battese, Harter, and Fuller (1988), Dempster, Rubin, and Tsutakawa (1981), and Fay and Herriot (1979), are investigated. These models are all special cases of a general mixed linear model involving fixed and random effects, and a small-area mean can be expr...

690 citations


Journal ArticleDOI
TL;DR: In this paper, the authors provided a thorough economic analysis of the simplest bottleneck model of road congestion with peak-load demand, where a fixed number of identical individuals, one per car, must travel from home to work, between which is a bottleneck of given capacity.

616 citations


Journal ArticleDOI
01 Jul 1990
TL;DR: These general guidelines will be of assistance to standardize the assessment of islet isolations, making it possible to better interpret and compare procedures from different centers.
Abstract: Recent progress in islet isolation from the pancreas of large mammals including man, accentuated the need for the development of precise and reproducible techniques to assess islet yield. In this report both quantitative and qualitative criteria for islet isolation assessment were discussed, the main topics being the determination of number, volume, purity, morphologic integrity andin vitro andin vivo function tests of the final islet preparations. It has been recommended that dithizone should be used as a specific stain for immediate detection of islet tissue making it possible to estimate both the total number of islets (dividing them into classes of 50 µ diameter range increments) and the purity of the final preparation. Appropriate morphological assessment should include confirmation of islet identification, assessment of the morphological integrity and of the purity of the islet preparation. The use of fluorometric inclusion and exclusion dyes together have been suggested as a viability assay to simultaneously quantitate the proportion of cells that are intact or damaged. Perifusion of islets with glucose provides a dynamic profile of glucose-mediated insulin release and of the ability of the cells to down regulate insulin secretion after the glycemic challenge is interrupted. Although perifusion data provides a useful guide to islet viability the quantity and kinetics of insulin release do not necessarily predict islet performance after implantation. Therefore, the ultimate test of islet viability is their function after transplantation into a diabetic recipient. For this reason,in vivo models of transplantation of an aliquot of the final islet preparation into diabetic nude (athymic) rodents have been suggested. We hope that these general guidelines will be of assistance to standardize the assessment of islet isolations, making it possible to better interpret and compare procedures from different centers.

555 citations


Journal ArticleDOI
TL;DR: It is shown that under suitable hypotheses there exists a globally asymptotically stable positive equilibrium and questions concerning oscillation and nonoscillation of solutions are addressed analytically and numerically.
Abstract: A single-species growth model with stage structure consisting of immature and mature stages is developed using a discrete time delay. It is shown that under suitable hypotheses there exists a globally asymptotically stable positive equilibrium. Questions concerning oscillation and nonoscillation of solutions are addressed analytically and numerically. The effect of the delay on the populations at equilibrium is also considered.

535 citations


Journal ArticleDOI
TL;DR: The authors proposed that gender stereotypes arise to rationalize the distribution of the sexes into social roles, and they read descriptions of members of two fictional categories, one having 80% city workers and 20% child raisers, the other with the percentages reversed.
Abstract: It is proposed that gender stereotypes arise to rationalize the distribution of the sexes into social roles. Ss read descriptions of members of two fictional categories, one having 80% «city workers» and 20% «child raisers», the other with the percentages reversed. They late made personality ratings of each category and of the category subgroups occupying each role

488 citations


Journal ArticleDOI
TL;DR: This paper examined the effects of foveal processing difficulty on the perceptual span in reading and found that less parafoveal information was acquired when processing in the fovea was difficult.
Abstract: Two experiments were conducted to examine the effects of foveal processing difficulty on the perceptual span in reading. Subjects read sentences while their eye movements were recorded. By changing the text contingent on the reader's current point of fixation, foveal processing difficulty and the availability of parafoveal word information were independently manipulated. In Experiment 1, foveal processing difficulty was manipulated by lexical frequency, and in Experiment 2 foveal difficulty was manipulated by syntactic complexity. In both experiments, less parafoveal information was acquired when processing in the fovea was difficult. We conclude that the perceptual span is variable and attentionally constrained. We also discuss the implications of the results for current models of the relation between covert visual-spatial attention and eye movement control in reading.

475 citations


Journal ArticleDOI
TL;DR: In this paper, the authors compare several simple models of nonadditive, interactive relationships between heredity and environment and reveal that ANOVA often fails to detect non-additivity because it has less power in tests of interaction than in test of main effects.
Abstract: It makes sense to attribute a definite percentage of variation in some measure of behavior to variation in heredity only if the effects of heredity and environment are truly additive Additivity is often tested by examining the interaction effect in a two-way analysis of variance (ANOVA) or its equivalent multiple regression model If this effect is not statistically significant at the a = 005 level, it is common practice in certain fields (eg, human behavior genetics) to conclude that the two factors really are additive and then to use linear models, which assume additivity Comparing several simple models of nonadditive, interactive relationships between heredity and environment, however, reveals that ANOVA often fails to detect nonadditivity because it has mueh less power in tests of interaction than in tests of main effects Likewise, the sample sizes needed to detect real interactions are substantially greater than those needed to detect main effects Data transformations that reduce interaction effects also change drastically the properties of the causal model and may conceal theoretically interesting and practically useful relationships Ifthe goal of partitioning variance among mutually exclusive causes and calculating "heritability" coefficients is abandoned, interactive relationships can be examined more seriously and can enhance our understanding of the ways living things develop

429 citations


Journal ArticleDOI
TL;DR: In this article, the authors examined that the appropriate relationship between a corporate center and its principal business units in complex organizations involves understanding the appropriate relationships between the center and the business units.
Abstract: Strategic management in complex organizations involves understanding the appropriate relationship between a corporate center and its principal business units. The reported study examined that relat...

420 citations


Journal Article
TL;DR: Two lines of evidence are presented for the existence of additional Th differentiation states and the commitment of Th cells to the Th1 or Th2 phenotypes occurred mainly in vivo.
Abstract: Many long term mouse Th clones express either the type 1 or type 2 Th cell (Th1 or Th2) cytokine secretion phenotype. In this report we present two lines of evidence for the existence of additional Th differentiation states. Lectin-stimulated spleen cells secreted moderate levels of IL-2 compared with long term Th1 clones, whereas the levels of other cytokines were more than 100-fold lower than those produced by either Th1 or Th2 clones. This suggests that many spleen cells produce substantial amounts of IL-2 but little or no IL-4, IL-5, IFN-gamma, IL-3, and granulocyte/macrophage-CSF. In contrast to long term Th clones, many short term alloreactive clones displayed cytokine secretion phenotypes intermediate between the Th1 and Th2 patterns. The proportion of recognizable Th1 and Th2 clones at early times in culture was greatly increased by immunization of the mice from which the responder and stimulator cells were derived; Brucella abortus immunization resulted in the isolation of exclusively Th1 clones, whereas infection with Nippostrongylus brasiliensis resulted in a strong trend toward the isolation of Th2 clones. The immunization of mice from which responder cells were derived strongly affected the type of Th clone obtained, whereas the source of stimulator cells had much less effect, suggesting that the commitment of Th cells to the Th1 or Th2 phenotypes occurred mainly in vivo. A model for the possible relationships of the various Th cells is presented.

Journal ArticleDOI
TL;DR: The relationship between vegetation components, surface water chemistry and peat chemistry from 23 fens in boreal Alberta, Canada, substantiate important differences along the poor to rich fen gradient as mentioned in this paper.
Abstract: The relationships between vegetation components, surface water chemistry and peat chemistry from 23 fens in boreal Alberta, Canada, substantiate important differences along the poor to rich fen gradient. Each of the three fen types have their own characteristic species. The extreme-rich fens are characterized by Calliergon trifarium, Drepanocladus revolvens, Scirpus hudsonianus, S. cespitosus, Scorpidium scorpioides, and Tofieldia glutinosa. Moderate-rich fens are characterized by Brachythecium mildeanum, Carex diandra, Drepanocladus vernicosus, D. aduncus, and D. polycarpus. Poor fens are characterized by Carex pauciflora, Drepanocladus exannulatus, Sphagnum angustifolium, S. jensenii, and S. majus. Moderate-rich fens have fewer species in common with poor fens than with extreme-rich fens, while species richness is highest in the moderate-rich fens and lowest in poor fens. Variation in vascular plant occurrence appears to be more associated with nutrient levels, while bryophytes are more affected by changes in acidity and mineral elements. Based on chemical criteria, the three fen types are clearly separated by surface water pH, calcium, magnesium, and conductivity, but are less clearly differentiated by the nitrogen and phosphorus components of the surface waters. Moderate-rich fens are chemically variable both temporally and spatially, whereas poor fens and extreme-rich fens are more stable ecosystems. Whereas components of alkalinity-acidity are the most important factors that distinguish the three fen types in western Canada, nutrient concentrations in the surface waters generally do not differ appreciably in the three fen types.

Journal ArticleDOI
TL;DR: The responses elicited during standing resembled those during the stance phase of walking and appeared to make use of similar reflex pathways, which closely resembled the responses to stimulation of a purely cutaneous nerve, the sural nerve.
Abstract: 1. Reflex responses during walking were elicited in humans by stimulation of the tibial nerve at the ankle. The stimulus intensity was controlled by monitoring the M-wave from an intrinsic foot mus...

Journal ArticleDOI
01 Dec 1990-Spine
TL;DR: Cumulative compression and shear were significantly higher in institutional aides with pain compared with those without pain (P < 0.01), and the pain group was similar to the no-pain group in age, weight, and height.
Abstract: The association between cumulative load (biomechanic load and exposure time integral over the entire work experience) and back pain was investigated in a group of institutional aides with physically stressful jobs. A questionnaire/interview was conducted with 161 of these institutional aides. The point prevalence of back pain in this sample was 62%. Men had worked a mean duration of 14.3 years and women 11.6 years at the time of the onset of the first pain episode. Every job performed was analyzed by the use of a two-dimensional static mathematical model. The compression and shear at the thoracolumbar and lumbosacral discs were computed by the use of a biomechanic model. Cumulative compression and shear were significantly higher in institutional aides with pain compared with those without pain (P less than 0.05-0.01). The pain group was similar to the no-pain group in age, weight, and height.

Journal ArticleDOI
TL;DR: This article found that personal crime is contingent on the exposure that comes from following certain lifestyles, particularly for certain demographic groups, particularly young males, and the importance of the resulting conflict styles in promoting or reducing the opportunity for crime in certain settings and conditions.
Abstract: From Kennedy, L.W., and Forde, D.R. (1990). Routine activities and crime: An analysis of victimization in Canada. Criminology, 28, 137-152.Miethe, Stafford, and Long (1987) have suggested that there are strong interaction effects between demographic characteristics of victims and certain routine activities that occur at night and away from home, but only for victims of property crime. This same pattern does not appear for victims of violent crime, they maintain, because unlike property crime, violent crime often involves interpersonal conflict and disagreement and is therefore spontaneous. Using data from the Canadian Urban Victimization Survey, which contains detailed measures of routine activities not available in the9.1 Abstract 217 9.2 Introduction 218 9.3 Review of Literature 218 9.4 The Study 220 9.5 Measures of Crime 220 9.6 Individual Characteristics 221 9.7 Group Characteristics 222 9.8 Findings 2229.8.1 Impact of Individual-Level Characteristics and Routine Activities on Victimization 2229.8.2 Impact of Urban Structure on Routine Activities and Victimization 2259.9 Discussion and Conclusions 229U.S. study by Miethe and colleagues, this study finds contrary evidence that suggests that personal crime is contingent on the exposure that comes from following certain lifestyles. This is particularly true for certain demographic groups, particularly young males. The findings are considered in the light of the literature focusing on the interaction between situation and personality and the importance of the resulting conflict styles in promoting or reducing the opportunity for crime in certain settings and under certain conditions.

Book ChapterDOI
TL;DR: The structure and function of major groups of hemolymph proteins that are common to all insects, storage proteins, lipoproteins, vitellogenins, and inducible antibacterial proteins are discussed.
Abstract: Publisher Summary This chapter discusses the structure and function of major groups of hemolymph proteins that are common to all insects, storage proteins, lipoproteins, vitellogenins, and inducible antibacterial proteins. It also discusses some proteins and peptides that are present in smaller amounts, sometimes occurring only in a few insect species. With the development of microsequencing techniques that can provide information about the sequence of amino acids at the N-terminal end of an intact protein on a sample of less than 20 picomoles, it has become feasible to use one- or two-dimensional polyacrylamide gel electrophoresis (PAGE) a the protein purification method of choice. In many cases, proteins can be transferred directly from gels to derivatized paper or other media and spots cut from the medium can be inserted directly into the sequencer. If necessary, proteins on the medium can be cleaved to peptides, which can be separated by high-pressure liquid chromatography (HPLC) or by PAGE.

Journal ArticleDOI
TL;DR: Growing cells of Campylobacter coli and C. jejuni were naturally transformed by naked DNA without the requirement for any special treatment, and transformation into plasmid-free cells was very rare.
Abstract: Growing cells of Campylobacter coli and C. jejuni were naturally transformed by naked DNA without the requirement for any special treatment. Transformation frequencies for homologous chromosomal DNA were approximately 10(-3) transformants per recipient cell in C. coli and 10(-4) in C. jejuni. Maximum competence was found in the early log phase of growth. Campylobacters preferentially took up their own DNA in comparison with Escherichia coli chromosomal DNA, which was taken up very poorly. Three new Campylobacter spp.-to-E. coli shuttle plasmids, which contained additional cloning sites and selectable markers, were constructed from the shuttle vector pILL550A. These plasmid DNAs were taken up by campylobacters much less efficiently than was homologous chromosomal DNA, and transformation into plasmid-free cells was very rare. However, with the use of recipients containing a homologous plasmid, approximately 10(-4) transformants per cell were obtained. The tetM determinant, originally obtained from Streptococcus spp. and not heretofore reported in Campylobacter spp., was isolated from an E. coli plasmid and was introduced, selecting for tetracycline resistance, by natural transformation into C. coli.

Journal ArticleDOI
TL;DR: It is concluded from this preliminary study that aerosolized amiloride can be safely administered to adults with cystic fibrosis and the slowing of the loss of FVC and the improvement in sputum viscosity and elasticity suggest a beneficial clinical effect.
Abstract: Excessive active absorption of sodium is a unique abnormality of the airway epithelium in patients with cystic fibrosis. This defect is associated with thickened mucus and poor clearance of airway secretions and may contribute to the pulmonary disease in these patients. To study whether the inhibition of excessive absorption of sodium might affect the course of lung disease in cystic fibrosis, we performed a double-blind, crossover trial comparing aerosolized amiloride (5 mmol per liter; 3.5 ml four times daily), a sodium-channel blocker, with vehicle alone. Fourteen of the 18 adult patients initially enrolled in the study completed the one-year trial (25 weeks for each treatment). The mean (±SEM) loss of forced vital capacity (FVC) was reduced from 3.39±1.13 ml per day during treatment with vehicle alone to 1.44±0.67 ml per day during treatment with amiloride (P<0.04). A measured index of sputum viscosity and elasticity was abnormal during treatment with vehicle alone and improved during treatme...

Journal ArticleDOI
TL;DR: This paper is the first to analyze systematically user equilibrium, system optimum, and various pricing regimes for a simple network of routes in parallel for traffic congestion during the morning commute.
Abstract: Most theoretical studies of traffic congestion during the morning commute have been limited to one origin, one destination, and one route. This paper is the first to analyze systematically user equilibrium, system optimum, and various pricing regimes for a simple network of routes in parallel. Departure time and route decisions of commuters are assumed to be governed by the tradeoff between travel time and schedule delay (the difference between actual and desired arrival time). In equilibrium without tolls wasteful queuing occurs, although the numbers of drivers on each route is the same as in the system optimum. An optimal time-varying toll eliminates queuing without affecting route usage. Uniform and step tolls alter route usage, but only slightly. Step tolls generally yield much greater efficiency gains than uniform tolls because they reduce queuing by altering departure times.

Journal ArticleDOI
TL;DR: A method is described which can be used to extract common spatial patterns underlying the EEGs from two human populations and it is suggested that the problems associated with the more common approach to discriminating EEGs, significance probability mapping, can be avoided.
Abstract: A method is described which can be used to extract common spatial patterns underlying the EEGs from two human populations. These spatial patterns account, in the least-squares sense, maximally for the variance in the EEGs from one population and minimally for the variance in the other population and therefore would seem to be optimal for quantitatively discriminating between the individual EEGs in the two populations. By using this method, it is suggested that the problems associated with the more common approach to discriminating EEGs, significance probability mapping, can be avoided. The method is tested using EEGs from a population of normal subjects and using the EEGs from a population of patients with neurologic disorders. The results in most cases are excellent and the misclassification which occurs in some cases is attributed to the nonhomogeneity of the patient population particularly. The advantages of the method for feature selection, for automatically classifying the clinical EEG, and with respect to the reference-free nature of the selected features are discussed.

Journal ArticleDOI
TL;DR: This minireview discusses the parameters that should be considered in the development of experimental protocols for study of the efficacy of antibacterial agents against pathogenic bacteria in biofilm.
Abstract: In this minireview, we summarize recent studies of the interaction of bacteria in biofilms with antibacterial agents and we discuss the parameters that should be considered in the development of experimental protocols for study of the efficacy of antibacterial agents against pathogenic bacteria in biofilm.

Journal ArticleDOI
TL;DR: The pathologic features suggest that anti-class I antibody appearing or persisting in the early posttransplant period injures the endothelium of the microvasculature, with the clinical presentation different from that of hyperacute rejection.
Abstract: In renal transplantation, preformed cytotoxic antibody against donor HLA class I antigens causes hyperacute rejection of renal allografts, but its pathogenic significance when it develops in the posttransplant period is unknown. In the present studies we describe the clinical and pathologic features of patients with rejection associated with anti-class I. In the course of 400 consecutive cadaveric renal transplants, 7 patients were identified who had antibody against donor class I HLA antigens in association with atypical but distinctive patterns of rejection. All 7 were presensitized. In 3 patients, the transplant had been inadvertently performed with a positive donor-specific T cell crossmatch. In the remaining 4, the T cell crossmatch on current sera was negative but became positive posttransplant. The clinical picture was deterioration of graft function with rapid onset of oliguria, apparently due to acute tubular necrosis, but with persistence of blood flow demonstrable by radioisotope scan studies. Renal histology showed that the typical lesions observed in cell-mediated rejection, such as tubulitis and interstitial infiltration, were absent. Granular complement deposition (6), polymorphonuclear infiltration (6), and endothelial injury in the microvasculature (6) were common, and mononuclear infiltrates were absent (2) or not prominent (4). In 3 patients the glomerular changes resembled a picture of hemolytic uremic syndrome, with capillary fibrin thrombi and widening of the subendothelial space. IgG staining was negative. The pathologic features suggest that anti-class I antibody appearing or persisting in the early posttransplant period injures the endothelium of the microvasculature, with the clinical presentation different from that of hyperacute rejection. Particularly in sensitized patients, rapid deterioration in function, leading to a picture of acute tubular necrosis, with pathologic features of endothelial injury in the microcirculation, should suggest the diagnosis of anti-class I-mediated rejection.

Journal ArticleDOI
TL;DR: It is concluded that verb information is not used by the parser to modify its initial parsing strategies, although it may be used to guide subsequent reanalysis.
Abstract: We investigated whether readers use verb information to aid in their initial parsing of temporarily ambiguous sentences. In the first experiment, subjects' eye movements were recorded. In the second and third experiments, subjects read sentences by using a noncumulative and cumulative word-by-word self-paced paradigm, respectively. The results of the first two experiments supported Frazier and Rayner's (1982) garden-path model of sentence comprehension: Verb information did not influence the initial operation of the parser. The third experiment indicated that the cumulative version of the self-paced paradigm is not appropriate for studying on-line parsing. We conclude that verb information is not used by the parser to modify its initial parsing strategies, although it may be used to guide subsequent reanalysis.

Journal ArticleDOI
TL;DR: In this paper, a general theory of the tension field is developed for application to the analysis of wrinkling in isotropic elastic membranes undergoing finite deformations, where the principal contribution is a partial differential equation describing a geometrical property of tension trajectories.
Abstract: A general theory of the tension field is developed for application to the analysis of wrinkling in isotropic elastic membranes undergoing finite deformations. The principal contribution is a partial differential equation describing a geometrical property of tension trajectories. This is one of a system of two equations which describes the state of stress independently of the deformation. This system is strongly elliptic at any stable solution, whereas the deformation is described by a system of parabolic type. Controllable solutions, i.e. those states that can be maintained in any isotropic elastic material by application of edge tractions and lateral pressure alone, are obtained. The general axisymmetric problem is solved implicitly and the theory is applied to the solution of two representative examples. Existing small strain theories are shown to correspond to a singular limit of the general theory, at which the underlying system changes from elliptic to parabolic type.

Journal ArticleDOI
01 May 1990-Diabetes
TL;DR: The results suggest that early nonspecific immunotherapy of genetically predisposed individuals could prevent the development of autoimmune diabetes and lend support to a relationship between the boosting of endogenous NS activity and the establishment of tolerance to self in the context of autoimmunity.
Abstract: The nonobese diabetic (NOD) mouse is an excellent model of insulin-dependent (type I) human diabetes mellitus. We report that a single injection of complete Freund's adjuvant (CFA) given at an early age (5 wk) prevented the appearance of diabetes and greatly increased the life span of NOD mice without additional therapy. No treated mouse developed hyperglycemia by the age of 12 mo (n = 13), whereas all untreated mice died of diabetes before 8 mo of age (n = 38). All CFA-treated mice were alive and healthy at 12 mo of age. Some CFA-treated NOD mice that were monitored for long-term survival are still alive with no sign of disease at 18 mo of age (n = 5). Administration of CFA resulted in decreased in vitro splenic lymphocyte proliferative responses to alloantigen and mitogen. Cell-mixing experiments indicated that antigen-nonspecific inhibitory cells were elicited in the spleen and increased in the bone marrow. These regulatory cells were Thy-1- and nonadherent to nylon wool, as has been described for natural suppressor (NS) cells. These data lend support to a relationship between the boosting of endogenous NS activity and the establishment of tolerance to self in the context of autoimmunity. Our results suggest that early nonspecific immunotherapy of genetically predisposed individuals could prevent the development of autoimmune diabetes.

Journal ArticleDOI
TL;DR: This article presented a conceptual framework that views fish assemblages as products of a series of filters, operating at different spatial and temporal scales, through which an assemblage's component species must pass.
Abstract: Many autecological effects of temperature on fish are known, and fishery biologists have begun to incorporate this knowledge into population-level relations that can be used to assess possible effects of climatic warming on fishes and their habitats. However, the problem of extrapolating these or other relations to multispecies assemblages is not straightforward, given the complexity of community-level phenomena. I present a conceptual framework that views fish assemblages as products of a series of filters, operating at different spatial and temporal scales, through which an assemblage's component species must pass. This framework can facilitate an understanding of the processes that organize fish assemblages and suggest ways in which the complex problem can be divided into manageable pieces. I apply this framework in an examination of small-lake fish assemblages in three regions on two continents. The procedure reveals local and regional relations of richness and composition and highlights the ...

Journal ArticleDOI
28 Sep 1990-Gene
TL;DR: Although expression of the cat gene was constitutive in both C. coli and Escherichia coli, results of primer extension experiments indicated that transcription was initiated at different sites in these two species, suggesting that the codon usage bias is not one of the obstacles which affects Campylobacter spp.

Journal ArticleDOI
TL;DR: The theory of toroidal Lie algebras has been studied in this paper, where the authors describe the universal central extension t of this algebra and give an abstract presentation for it in terms of generators and relations involving the extended Cartan matrix.
Abstract: The paper describes the theory of the toroidal Lie algebra, i.e. the Lie algebra of polynomial maps of a complex torus ℂ××ℂ× into a finite-dimensional simple Lie algebra g. We describe the universal central extension t of this algebra and give an abstract presentation for it in terms of generators and relations involving the extended Cartan matrix of g. Using this presentation and vertex operators we obtain a large class of integrable indecomposable representations of t in the case that g is of type A, D, or E. The submodule structure of these indecomposable modules is described in terms of the ideal structure of a suitable commutative associative algebra.

Journal ArticleDOI
TL;DR: The heuristic, developed to get an initial lower bound, finds an optimal solution for most of the random test problems, and an extension to the basic problem that allows for preselected points, which may correspond to existing facility locations.

Journal ArticleDOI
TL;DR: The authors concluded that knowledge development related to caring in nursing is limited by the lack of refinement of caring theory, the Lack of definitions of caring attributes, the neglect to examine caring from the dialectic perspective, and the focus of theorists and researchers on the nurse to the exclusion of the patient.
Abstract: If caring is to be retained as the "essence" of nursing, and if research in this area is to advance, then the various perspectives of caring must be clarified, the strengths and the limitations of these conceptualizations examined, and the applicability of caring as a concept and theory to the practice of nursing identified. Examination of the concept of caring resulted in the identification of five epistemological perspectives: caring as a human state, caring as a moral imperative or ideal, caring as an affect, caring as an interpersonal relationship, and caring as a nursing intervention. Two outcomes of caring were identified: caring as the subjective experience and as the physiologic responses in patients. The authors concluded that knowledge development related to caring in nursing is limited by the lack of refinement of caring theory, the lack of definitions of caring attributes, the neglect to examine caring from the dialectic perspective, and the focus of theorists and researchers on the nurse to the exclusion of the patient.