Showing papers by "University of Waterloo published in 2003"

Multi-Agent Systems for the Simulation of Land-Use and Land-Cover Change: A Review

Abstract: This paper presents an overview of multi-agent system models of land-use/cover change (MAS/LUCC models). This special class of LUCC models combines a cellular landscape model with agent-based representations of decisionmaking, integrating the two components through specification of interdependencies and feedbacks between agents and their environment. The authors review alternative LUCC modeling techniques and discuss the ways in which MAS/LUCC models may overcome some important limitations of existing techniques. We briefly review ongoing MAS/LUCC modeling efforts in four research areas. We discuss the potential strengths of MAS/LUCC models and suggest that these strengths guide researchers in assessing the appropriate choice of model for their particular research question. We find that MAS/LUCC models are particularly well suited for representing complex spatial interactions under heterogeneous conditions and for modeling decentralized, autonomous decision making. We discuss a range of possible roles for MAS/LUCC models, from abstract models designed to derive stylized hypotheses to empirically detailed simulation models appropriate for scenario and policy analysis. We also discuss the challenge of validation and verification for MAS/LUCC models. Finally, we outline important challenges and open research questions in this new field. We conclude that, while significant challenges exist, these models offer a promising new tool for researchers whose goal is to create fine-scale models of LUCC phenomena that focus on human-environment interactions.

Recent Advances in Petroleum Microbiology

Abstract: Recent advances in molecular biology have extended our understanding of the metabolic processes related to microbial transformation of petroleum hydrocarbons. The physiological responses of microorganisms to the presence of hydrocarbons, including cell surface alterations and adaptive mechanisms for uptake and efflux of these substrates, have been characterized. New molecular techniques have enhanced our ability to investigate the dynamics of microbial communities in petroleum-impacted ecosystems. By establishing conditions which maximize rates and extents of microbial growth, hydrocarbon access, and transformation, highly accelerated and bioreactor-based petroleum waste degradation processes have been implemented. Biofilters capable of removing and biodegrading volatile petroleum contaminants in air streams with short substrate-microbe contact times ( 2 S and sulfoxides from petrochemical waste streams. Microbes also have potential for use in removal of nitrogen from crude oil leading to reduced nitric oxide emissions provided that technical problems similar to those experienced in biodesulfurization can be solved. Enzymes are being exploited to produce added-value products from petroleum substrates, and bacterial biosensors are being used to analyze petroleum-contaminated environments.

Methods for isolating and characterizing ACC deaminase-containing plant growth-promoting rhizobacteria.

Abstract: One of the major mechanisms utilized by plant growth-promoting rhizobacteria (PGPR) to facilitate plant growth and development is the lowering of ethylene levels by deamination of 1-aminocyclopropane-1-carboxylic acid (ACC) the immediate precursor of ethylene in plants. The enzyme catalysing this reaction, ACC deaminase, hydrolyses ACC to α-ketobutyrate and ammonia. Several bacterial strains that can utilize ACC as a sole source of nitrogen have been isolated from rhizosphere soil samples. All of these strains are considered to be PGPR based on the ability to promote canola seedling root elongation under gnotobiotic conditions. The treatment of plant seeds or roots with these bacteria reduces the amount of ACC in plants, thereby lowering the concentration of ethylene. Here, a rapid procedure for the isolation of ACC deaminase-containing bacteria, a root elongation assay for evaluating the effects of selected bacteria on root growth, and a method of assessing bacterial ACC deaminase activity are described in detail. This should allow researchers to readily isolate new PGPR strains adapted to specific environments.

PEAKS: powerful software for peptide de novo sequencing by tandem mass spectrometry

Abstract: A number of different approaches have been described to identify proteins from tandem mass spectrometry (MS/MS) data. The most common approaches rely on the available databases to match experimental MS/MS data. These methods suffer from several drawbacks and cannot be used for the identification of proteins from unknown genomes. In this communication, we describe a new de novo sequencing software package, PEAKS, to extract amino acid sequence information without the use of databases. PEAKS uses a new model and a new algorithm to efficiently compute the best peptide sequences whose fragment ions can best interpret the peaks in the MS/MS spectrum. The output of the software gives amino acid sequences with confidence scores for the entire sequences, as well as an additional novel positional scoring scheme for portions of the sequences. The performance of PEAKS is compared with Lutefisk, a well-known de novo sequencing software, using quadrupole-time-of-flight (Q-TOF) data obtained for several tryptic peptides from standard proteins.

Issues in data stream management

Abstract: Traditional databases store sets of relatively static records with no pre-defined notion of time, unless timestamp attributes are explicitly added. While this model adequately represents commercial catalogues or repositories of personal information, many current and emerging applications require support for on-line analysis of rapidly changing data streams. Limitations of traditional DBMSs in supporting streaming applications have been recognized, prompting research to augment existing technologies and build new systems to manage streaming data. The purpose of this paper is to review recent work in data stream management systems, with an emphasis on application requirements, data models, continuous query languages, and query evaluation.

Automatic Sequences: Theory, Applications, Generalizations

Abstract: Preface 1. Stringology 2. Number theory and algebra 3. Numeration systems 4. Finite automata and other models of computation 5. Automatic sequences 6. Uniform morphisms and automatic sequences 7. Morphic sequences 8. Frequency of letters 9. Characteristic words 10. Subwords 11. Cobham's theorem 12. Formal power series 13. Automatic real numbers 14. Multidimensional automatic sequences 15. Automaticity 16. k-regular sequences 17. Physics Appendix. Hints, references and solutions for selected exercises Bibliography Index.

Towards an Integrative Model of Small Firm Internationalisation

Abstract: Firm internationalisation has long been regarded as an incremental process, wherein firms gravitate towards ‘psychologically close’ markets and increase commitment to international markets in a gradual, step-wise, manner through a series of evolutionary ‘stages’ However, much of the recent literature provides clear evidence of rapid and dedicated internationalisation by ‘born global firms’ Typically, these are smaller entrepreneurial firms that internationalise from inception, or start to shortly thereafter Their main source of competitive advantage is often related to a more sophisticated knowledge base In addition, the authors have found evidence of firms supporting this ‘born global’ pattern of behaviour but also evidence of firms that suddenly internationalise after a long period of focusing on the domestic market These ‘born-again’ globals appear to be influenced by critical events that provide them with additional human or financial resources, such as changes in ownership/management, being taken over by another company with international networks, or themselves acquiring such a firm Based upon the extant literature and our own research, we propose an integrative model that recognises the existence of different internationalisation ‘pathways’ We then explore differences in behaviour due to the firm's internationalisation trajectory and discuss the strategic and public policy implications

Generalized Lorentz invariance with an invariant energy scale

Abstract: The hypothesis that the Lorentz transformations may be modified at Planck scale energies is further explored. We present a general formalism for theories which preserve the relativity of inertial frames with a nonlinear action of the Lorentz transformations on momentum space. Several examples are discussed in which the speed of light varies with energy and elementary particles have a maximum momenta and/or energy. Energy and momentum conservation are suitably generalized and a proposal is made for how the new transformation laws apply to composite systems. We then use these results to explain the ultrahigh-energy cosmic ray anomaly and we find a form of the theory that explains the anomaly, and leads also to a maximum momentum and a speed of light that diverges with energy. We finally propose that the spatial coordinates be identified as the generators of translation in Minkowski spacetime. In some examples this leads to a commutative geometry, but with an energy dependent Planck constant.

A central capacity sharing model of dual-task performance.

Abstract: The authors present the central capacity sharing (CCS) model and derive equations describing its behaviors to explain results from dual-task situations. The predictions of the CCS model are contrasted with those of the central bottleneck model. The CCS model predicts all of the hallmark effects of the psychological refractory period (PRP) pardigm: -1 slope of the PRP effect at short stimulus onset asynchronies (SOAs), underadditivity of precentral Task 2 manipulations, additivity of central or postcentral Task 2 manipulations with SOA, and carry forward to Task 2 of Task 1 precentral or central manipulations at short SOAs. The CCS model also predicts that Task 1 response times increase with decreasing SOA. The model is a viable alternative to the central bottleneck model.

The identity function of autobiographical memory: Time is on our side

Abstract: Autobiographical memory plays an important role in the construction of personal identity. We review evidence of the bi-directional link between memory and identity. Individuals' current self-views, beliefs, and goals influence their recollections and appraisals of former selves. In turn, people's current self-views are influenced by what they remember about their personal past, as well as how they recall earlier selves and episodes. People's reconstructed evaluations of memories, their perceived distance from past experiences, and the point of view of their recollections have implications for how the past affects the present. We focus on how people's constructions of themselves through time serve the function of creating a coherent--and largely favourable--view of their present selves and circumstances.

An Efficient Protocol for Authenticated Key Agreement

Abstract: This paper proposes an efficient two-pass protocol for authenticated key agreement in the asymmetric (public-key) setting. The protocol is based on Diffie-Hellman key agreement and can be modified to work in an arbitrary finite group and, in particular, elliptic curve groups. Two modifications of this protocol are also presented: a one-pass authenticated key agreement protocol suitable for environments where only one entity is on-line, and a three-pass protocol in which key confirmation is additionally provided. Variants of these protocols have been standardized in IEEE P1363 [17], ANSI X9.42 [2], ANSI X9.63 [4] and ISO 15496-3 [18], and are currently under consideration for standardization and by the U.S. government's National Institute for Standards and Technology [30].

Topology control for wireless sensor networks

Abstract: We consider a two-tiered Wireless Sensor Network (WSN) consisting of sensor clusters deployed around strategic locations and base-stations (BSs) whose locations are relatively flexible. Within a sensor cluster, there are many small sensor nodes (SNs) that capture, encode and transmit relevant information from the designated area, and there is at least one application node (AN) that receives raw data from these SNs, creates a comprehensive local-view, and forwards the composite bit-stream toward a BS. In practice, both SN and AN are battery-powered and energy-constrained, and their node lifetimes directly affect the network lifetime of WSNs. In this paper, we focus on the topology control process for ANs and BSs, which constitute the upper tier of a two-tiered WSN. We propose approaches to maximize the topological network lifetime of the WSN, by arranging BS location and inter-AN relaying optimally. Based on an algorithm in Computational Geometry, we derive the optimal BS locations under three topological lifetime definitions according to mission criticality. In addition, by studying the intrinsic properties of WSNs, we establish the upper and lower bounds of their maximal topological lifetime. When inter-AN relaying becomes feasible and favorable, we continue to develop an optimal parallel relay allocation to further prolong the topological lifetime of the WSN. An equivalent serialized relay schedule is also obtained, so that each AN only needs to have one relay destination at any time throughout the mission. The experimental performance evaluation demonstrates the efficacy of topology control as a vital process to maximize the network lifetime of WSNs.

An Atlas of Interpersonal Situations

Abstract: Foreword Part I. Introduction and Theory: 1. Interpersonal situations: the context of social behavior 2. Outcome interdependence 3. Interaction conditions and person factors 4. Exploring the geography of the outcome patterns Part II The Situations: Preface to the Entries for the Situations Single Component Patterns: 1. Independence: we go our separate ways 2. Mutual partner control: I scratch your back, you scratch mine 3. Corresponding mutual joint control: getting in sync 4. Conflicting mutual joint control: match or mismatch Two- and three-component patterns: 5. The prisoner's dilemma: me versus we 6. Threat: trading loyalty for justice 7. Chicken: death before dishonor 8. Hero: let's do it your way 9. Conjunctive problems: together we can do it 10. Disjunctive problems: either of us can do it 11. Asymmetric dependence: you're the boss Time-extended patterns: 12. Iterated prisoner's dilemma: united we stand, divided we fall 13. Investment: building for the future 14. Delay of gratification: resisting temptation Incomplete information situations 15. Negotiation: can we agree on a deal? 16. Encounters with strangers: lack of information about a partner 17. Joint decisions under uncertainty: bird in the hand 18. Twists of fate: coping with an uncertain future N-person Situations 19. Third parties: effects of an outsider 20. N-person prisoner's dilemma: tragedy of the commons Movement from one situation to another 21. Movement among situations: where do we go from here? Part III. Epilogue.

Electrochemical Property: Structure Relationships in Monoclinic Li3-yV2(PO4)3

Abstract: Monoclinic lithium vanadium phosphate, alpha-Li(3)V(2)(PO(4))(3), is a highly promising material proposed as a cathode for lithium-ion batteries. It possesses both good ion mobility and high lithium capacity because of its ability to reversibly extract all three lithium ions from the lattice. Here, using a combination of neutron diffraction and (7)Li MAS NMR studies, we are able to correlate the structural features in the series of single-phase materials Li(3-y)V(2)(PO(4))(3) with the electrochemical voltage-composition profile. A combination of charge ordering on the vanadium sites and lithium ordering/disordering among lattice sites is responsible for the features in the electrochemical curve, including the observed hysteresis. Importantly, this work highlights the importance of ion-ion interactions in determining phase transitions in these materials.

Combinatorial Designs: Constructions and Analysis

Abstract: Introduction to BIBDs.- Symmetric BIBDs.- Difference sets and automorphisms.- Hadamard matrices and designs.- Resolvable BIBDs.- Steiner triple systems.- Mutually orthogonal Latin squares.- Pairwise balanced designs.- t-designs.- Orthogonal arrays and codes.- Index.

When do stereotypes come to mind and when do they color judgment? A goal-based theoretical framework for stereotype activation and application.

Abstract: The authors describe a theoretical framework for understanding when people interacting with a member of a stereotyped group activate that group's stereotype and apply it to that person. It is proposed that both stereotype activation and stereotype application during interaction depend on the strength of comprehension and self-enhancement goals that can be satisfied by stereotyping one's interaction partner and on the strength of one's motivation to avoid prejudice. The authors explain how these goals can promote and inhibit stereotype activation and application, and describe diverse chronic and situational factors that can influence the intensity of these goals during interaction and, thereby, influence stereotype activation and application. This approach permits integration of a broad range of findings on stereotype activation and application.

Comparison of PSS, SVC, and STATCOM controllers for damping power system oscillations

Abstract: This paper discusses and compares different control techniques for damping undesirable interarea oscillation in power systems by means of power system stabilizers (PSS), static VAr compensators (SVCs), and shunt static synchronous compensators (STATCOMs). The oscillation problem is analyzed from the point of view of Hopf bifurcations, an "extended" eigenanalysis to study different controllers, their locations, and the use of various control signals for the effective damping of these oscillations. The comparisons are based on the results obtained for the IEEE 50-machine, 145-bus test system, which is a benchmark for stability analysis.

The relationship between habitual patient-reported symptoms and clinical signs among patients with dry eye of varying severity.

Abstract: PURPOSE. To investigate symptom profiles and clinical signs in subjects with dry eye and normal subjects in a cross-sectional multicenter study. METHODS. Subjects aged 35 to 65 were recruited according to dry eye diagnostic codes and telephone interview and completed the Dry Eye Questionnaire 2001, among others, and underwent dry eye clinical tests. RESULTS. Subjects (122) included 28 control subjects (C), 73 with non-Sjogren's keratoconjunctivitis sicca (non-SS KCS) and 21 with Sjogren's syndrome (SS). Subjects with SS or non-SS KCS reported discomfort and dryness most frequently and that many symptoms worsened over the day and were quite bothersome. Groups were significantly different in corneal fluorescein staining, conjunctival lissamine green staining, Schirmer 1 tear test, and tear break-up time (TBUT; X 2 and Kruskal-Wallis, P < 0.0001). Statistically significant, but moderate, correlations were found between the frequency and evening intensity of dryness and discomfort and TBUT, Schirmer's tear test, overall corneal fluorescein staining, and temporal lissamine green conjunctival staining (Spearman r = 0.31-0.45, P < 0.01). Symptoms were moderately to highly correlated with the clinician's global grading of severity and highly correlated to patient's self-assessment of severity (r = 0.46-0.86, P < 0.0001), whereas signs showed lower correlations (r = 0.22-0.46, P < 0.0001). CONCLUSIONS. Subjects with SS or non-SS KCS reported frequent and intense ocular surface symptoms in the evening, some of which correlated moderately with clinical test results. The global clinician grade of dry eye correlated more highly with patient symptoms than did clinical signs, suggesting that patient symptoms influence dry eye diagnosis and grading of dry eye more than clinical test results.

The MDS‐CHESS Scale: A New Measure to Predict Mortality in Institutionalized Older People

Abstract: OBJECTIVES: To develop a scale predicting mortality and other adverse outcomes associated with frailty. DESIGN: Observational study based on Minimum Data Set (MDS) 2.0 and mortality data. SETTING: Ontario chronic hospitals. PARTICIPANTS: All chronic hospital patients (N = 28,495) assessed with the MDS 2.0 after mandatory implementation in July 1996 followed until May 1999. MEASUREMENTS: MDS 2.0 assessments done as part of normal practice mainly by registered nurses or multidisciplinary teams in a chronic hospital. Mortality data are available from the accompanying discharge tracking form. RESULTS: The MDS-Changes in Health, End-stage disease and Symptoms and Signs (CHESS) score is a composite measure addressing changes in health, end-stage disease, and symptoms and signs of medical problems. It is a strong predictor of mortality (P < .0001) independent of the effects of age, sex, activities of daily living impairment, cognition, and do-not-resuscitate orders. It is also strongly associated with physician activity, complex medical procedures, and pain (P < .001 for each dependent variable). CONCLUSIONS: The CHESS score provides a useful new MDS-based test to predict mortality and to measure instability in health as a clinical outcome.

Ecological Consequences of a Century of Warming in Lake Tanganyika

Abstract: Deep tropical lakes are excellent climate monitors because annual mixing is shallow and flushing rates are low, allowing heat to accumulate during climatic warming. We describe effects of warming on Lake Tanganyika: A sharpened density gradient has slowed vertical mixing and reduced primary production. Increased warming rates during the coming century may continue to slow mixing and further reduce productivity in Lake Tanganyika and other deep tropical lakes.

Impact of the graphic Canadian warning labels on adult smoking behaviour

Abstract: Objective: To assess the impact of graphic Canadian cigarette warning labels on current adult smokers. Design: A random-digit-dial telephone survey was conducted with 616 adult smokers in south western Ontario, Canada in October/November 2001, with three month follow up. Main outcome measures: Smoking behaviour (quitting, quit attempts, and reduced smoking), intentions to quit, and salience of the warning labels. Results: Virtually all smokers (91%) reported having read the warning labels and smokers demonstrated a thorough knowledge of their content. A strong positive relation was observed between a measure of cognitive processing—the extent to which smokers reported reading, thinking about, and discussing the new labels—and smokers’ intentions to quit (odds ratio (OR) 1.11, 95% confidence interval (CI) 1.07 to 1.16; p Conclusions: Graphic cigarette warning labels serve as an effective population based smoking cessation intervention. The findings add to the growing literature on health warnings and provide strong support for the effectiveness of Canada’s tobacco labelling policy.