bluuebunny/crossref_metadata_2025_split huggingface dataset:
Migration on networks and its stability consequences
Authors: Alekseeva Elena I. , Kirzhner Valery M. 
Published: July 2007

AbstractThis article reviews the authors' studies on the behavior of materially coupled dynamic systems. It discusses models of a network of a finite number of localized (pointwise) systems connected through an interaction structure involving migration, diffusion, or other forms of material exchange. On the basis of an analytical criterion for the stabilizing or destabilizing influence of the connecting structure, a classification of possible types of such structures and of the pointwise systems themselves is given.A model of a multicentric immunodependent tumor is analyzed. Tumor nodules and white blood cells are regarded as localized systems and migrating agents, respectively. We illustrate the possibility of predicting the behavior of the whole multicentric system from the internal parameters in each nodule and discuss the possibility of regulating multicentric tumor growth by controlling the intensity of migration of cells in the body.
Systems thinking/system dynamics: Let's just get on with it
Authors: Richmond Barry 
Published: July 2007

AbstractThe world has many problems. Many of these problems are approaching crisis proportions. The system dynamics community has something very powerful to contribute to addressing these problems—whether we call that something systems thinking or system dynamics. We have not been very effective in sharing what we have to offer because we have failed to truly appreciate the essence of system dynamics. As a result, we have both consciously and unwittingly diluted this essence, and in the process made more difficult the task of disseminating what we have to offer. We need to better understand and appreciate the essence of our field and then focus our energies on the real task at hand: figuring out why this essence seems to be so difficult for people to grasp, and then fixing that.
Varieties of systems thinking: The case of soft systems methodology
Authors: Checkland Peter B. , Haynes Michael G. 
Published: July 2007

AbstractA number of ways of intervening rationally in human affairs are based on systems thinking: understanding real‐world complexity via systems ideas. This article reviews the development of systems thinking and focuses on one of the systems approaches: Soft Systems Methodology (SSM). It indicates how SSM embodies systems thinking by giving an account of the crucial steps in the thinking as SSM developed. Issues in current work are reviewed by setting out a number of experientially derived generalizations. These concern: SSM as an ideal‐type process that the user suitably adapts on each occasion of use; the fact that SSM's systemicity lies primarily in the process of inquiry; the fact that its focus is the interaction between theory and practice; the implicit belief behind SSM that learning is axiomatically good; and the belief that SSM is best used participatively.
What is systemic thinking?
Authors: Espejo Raul 
Published: July 2007

AbstractThis article elaborates on the historic roots of management cybernetics and its evolving identity. The nature of this evolution is explained by presenting a theory of action in organizations, which makes visible the interplay between people's autonomous actions and their role as observers of these actions. This interplay is referred to as the process of grounding epistemology in ontology. The article then discusses complexity. The idea of distinctions is central, we make distinctions about our experiences. These distinctions define our individual complexity and also our situational complexity as we ground them in shared tasks (i.e., purposeful action). It is argued that creating situational complexity requires managing our interactions and that this management is effective if it gets the best out of us and provides our actions with direction and purpose.
I keep six honest serving men: They taught me all I knew
Authors: Flood Robert L. 
Published: July 2007

AbstractThis article explores the original holistic intent of systems science, its failure to deliver on this because of a fundamental flaw in the genetics of its conception, and the genetic reengineering that can return systems science to its original holistic intent and enter it into the mainstream of scientific theory and everyday practice. The reengineering is called critical systems thinking, and the form of it employed in practice is called total systems intervention.
Putting systems thinking into practice
Authors: Kim Daniel H. , Senge Peter M. 
Published: July 2007

AbstractThe dynamic systems perspective illuminates some of the core challenges in organizational learning. If learning occurs through experience, there are good reasons why organizations often fail to learn. In particular, large organizations face a class of systemic decision‐making situations in which learning is extremely unlikely. The systems perspective teaches us that cause and effect are often not close in time and space, that obvious interventions do not always produce obvious outcomes, and that long time delays, and systemic effects of actions can make it almost impossible to judge the effectiveness of those actions. This article presents a framework for organizational learning, outlines several breakdowns that thwart the learning process, and discusses how systems thinking can play an important role in helping organizations overcome the learning breakdowns through the design and implementation of managerial practice fields.
Learning in and about complex systems
Authors: Sterman John D. 
Published: July 2007

AbstractChange is accelerating, and as the complexity of the systems in which we live grows, so do the unanticipated side effects of human actions, further increasing complexity. Many scholars call for the development of systems thinking to improve our ability to manage wisely. But how do people learn in and about complex dynamic systems? Learning is a feedback process in which our decisions alter the real world, we receive information feedback about the world and revise the decisions we make and the mental models that motivate those decisions. Unfortunately, in the world of social action various impediments slow or prevent these learning feedbacks from functioning, allowing erroneous and harmful behaviors and beliefs to persist. The barriers to learning include the dynamic complexity of the systems themselves; inadequate and ambiguous outcome feedback; systematic mispercep‐tions of feedback; inability to simulate mentally the dynamics of our cognitive maps; poor interpersonal and organizational inquiry skills; and poor scientific reasoning skills. To be successful, methods to enhance learning about complex systems must address all these impediments. Effective methods for learning in and about complex dynamic systems must include (1) tools to elicit participant knowledge, articulate and reframe perceptions, and create maps of the feedback structure of a problem from those perceptions; (2) simulation tools and management flight simulators to assess the dynamics of those maps and test new policies; and (3) methods to improve scientific reasoning skills, strengthen group process, and overcome defensive routines for individuals and teams.
Pictorial modeling of dynamic systems
Authors: Camara António S. , Ferreira Francisco C. , Nobre Edmundo , Fialho José E. 
Published: July 2007

AbstractThe world may be considered to consist of interacting objects. An object‐oriented view is missing, however, in traditional system dynamics models. An attempt to develop a simulation methodology based on this view and using extended cellular automata principles is documented in this article. This methodology relies on pictorial entities representing real or abstract objects and a set of intuitive behavior and interaction rules. A simple predator‐prey model shows how such a pictorial simulation approach compares with traditional system dynamics models.
Modeling spatial dynamics of sea‐level rise in a coastal area
Authors: Ruth Matthias , Pieper Frederick 
Published: July 2007

AbstractThis article illustrates the development and functioning of a dynamic spatial model that simulates the effects of gradual sea‐level rise on coastal areas. Emphasis is given to identifying the dynamics of coastal systems and translating them into a spatially explicit dynamic simulation model. The model is designed to be flexible enough to serve as a base model for interdisciplinary research on sea‐level rise and coastal dynamics. An application is provided for a coastal area on Cape Cod, Massachusetts.
Exemplary urban model for Fernbank Museum of Natural History
Authors: Braden Charles H. 
Published: July 2007

AbstractNotes and Insights is a forum for discussion and debate about current issues in the philosophy and application of the system dynamics approach, and a marketplace for the exchange of information about current research, policy issues, and teaching experiences. Manuscripts treating material particularly suited to presentation in short form (less than 2,000 words) should be sent to Erich Zahn, Betriebswirtschaft‐liches Institut, Abt. IV, Universität Stuttgart, Keplerstr. 17, D‐7000 Stuttgart 1, Germany.
Efficient methods for sensitivity analysis
Authors: Clemson Barry , Tang Yongming , Pyne James , Unal Resit 
Published: July 2007

AbstractSensitivity analysis is usually difficult because to test exhaustively too many trials are required for the available time, money, or patience. This article discusses Latin hyper‐cube sampling and Taguchi methods, both of which are methods for experimental design that allow testing of all combinations of parameter values with a manageable number of trials. The procedures for use of the Taguchi methods are presented in some detail.
Benchmarking the system dynamics community: Research results
Authors: Scholl Greg J. 
Published: July 2007

AbstractThis article reports on the findings of a wide‐ranging study designed to ‘benchmark’ the system dynamics community. The study captured information about individual practitioners across a number of dimensions, including background, approach to and practice of model building, use of hardware and software and knowledge of the history and development of the field. Circulated to all members of the System Dynamics Society, the study attracted responses from 163 members (over 35 percent). The following pages present research results and discuss their possible implications. In particular, important conclusions highlight a potential quality gap in the model base, postulate a relationship between pedagogy and practice and begin a dialog concerning the dynamics of supply and demand in the field.
Projecting dynamic behavior in the absence of a model: An experiment
Authors: Dangerfield Brian , Roberts Carole 
Published: July 2007

AbstractNotes and Insights is a forum for discussion and debate about current issues in the philosophy and application of the system dynamics approach, and a marketplace for the exchange of information about current research, policy issues, and teaching experiences. Manuscripts treating material particularly suited to presentation in short form (less than 2,000 words) should be sent to Erich Zahn, Betriebswirtschaft‐liches Institut, Abt. IV, Universitát Stuttgart, Keplerstr. 17, D‐7000 Stuttgart 1, Germany or to Yaman Barlas, Dept. of Industrial Engineering, Bogazici University, 80815 Bebek, Istanbul, Turkey.
Urban dynamics—the first fifty years
Authors: Alfeld Louis Edward 
Published: July 2007

AbstractTwenty‐five years have passed since the publication of Jay W. Forrester's Urban Dynamics. Any assessment of the condition of America's cities today raises the question of what might have been had the model and the methodology been accepted as a central urban planning and policy tool. Instead of looking backward at what might have been, however, it seems more useful to look ahead at what still may be. Urban dynamics still has a role to play in our urban future; this article provides a backdrop for how that role might best be shaped.
Designing corporate strategy with system dynamics: A case study in the pulp and paper industry
Authors: Risch Jonathan D. , Sterman John D. , Troyano‐Bermúdez Luis 
Published: July 2007

AbstractWe describe the use of system dynamics tools and processes to assist a major integrated forest products company develop its strategy. The firm had recently acquired a major pulp and paper mill and had entered a new market, the specialty paper business. However, despite substantial investment, the mill was losing money, contrary to expectations. We drew on established strategic frameworks, using system dynamics to integrate the data generated by traditional analyses. Through internal and external interviews, archival data, site visits, and analysis of the market place, we develop a representation of management's collective mental model, showing the feedback processes they believed would lead to success in the specialty market. We then develop a dynamic hypothesis, explicated in the form of causal loop diagrams, to explain the failure of the firm's strategy to yield profitable operation for the mill. We show how management underestimated a variety of side effects of the new strategy, both at the market level and in the mill. These side effect feedbacks undercut the intended effect of the new strategy. We describe the theory, data, and process, including current steps the firm is undertaking to implement the results emerging from the study.
Sensitivity analysis and optimization of system dynamics models: Regression analysis and statistical design of experiments
Authors: Kleijnen Jack P. C. 
Published: July 2007

AbstractThis paper discusses what‐if analysis and optimization of system dynamics models. These problems are solved, using the statistical techniques of regression analysis and Design of Experiments (DOE). These issues are illustrated by applying the statistical techniques to a system dynamics model for coal transportation, taken from Wolstenholme's book System Enquiry: a System Dynamics Approach (1990). The regression analysis uses the least‐squares algorithm. DOE uses classic designs, namely, factorials and central composite designs. Compared with intuitive approaches, DOE is more efficient: DOE gives more accurate estimators of input effects. Moreover DOE is more effective: interactions among inputs are estimable too. The system dynamics model is also optimized, using a heuristic that is inspired by Response Surface Methodology (RSM) but that also accounts for constraints. Conclusions are presented for the case study, and general principles are derived. References are given for further study.
Edutainment, learning and system dynamics
Authors: Langley Paul A. , Larsen Erik R. 
Published: July 2007

AbstractNotes and Insights is a forum for discussion and debate about current issues in the philosophy and application of the system dynamics approach, and a marketplace for the exchange of information about current research, policy issues and teaching experiences. Manuscripts treating material particularly suited to presentation in short form (less than 2,000 words) should be sent to Erich Zahn, Betriebswirtschaftlic hes Institut, Abt. IV, Universität Stuttgart, Keplerstr. 17, D‐7000 Stuttgart 1, Germany or to Yaman Barlas, Dept. of Industrial Engineering, Bogazici University, 80815 Bebek, Istanbul, Turkey.
Dietary zinc deficiency lowers the proportions of splenic CD90+(Thy-1+) B-cells and late thymic emigrant T-cells in growing rats
Authors: Hosea Heather J. , Rector Edward S. , Taylor Carla G. 
Published: July 2007

Zn-deficient (ZD) rats have a lower proportion of splenic CD90+T-cells which could be due to fewer new T-cells exiting the thymus, defective post-thymic maturation or increased cell death. Post-thymic maturation of splenic lymphocytes and their viability were determined by flow cytometry in weanling rats assigned to ZD ( < 1 mg Zn/kg;ad libitum), diet-restricted (DR; 30 mg Zn/kg; limited to the amount of feed as consumed by ZD rats), marginally Zn-deficient (MZD; 10 mg Zn/kg;ad libitum) or control (30 mg Zn/kg;ad libitum) groups for 3 weeks. ZD rats had a 29 % lower percentage of splenic CD90+T-cells and both ZD and DR rats had a 30 % lower proportion of splenic CD90+B-cells compared with control rats. When the splenic CD90+T-cells were characterised further, there was no difference among the groups in the first two stages of post-thymic development; however, ZD, DR and MZD rats had a 42 % lower proportion of late thymic emigrants (TCRαβ+CD90+CD45RC+RT6.1+) compared with control rats. There was no difference among groups in the proportion of splenic CD90+T-cells in the non-viable region; however, ZD rats had a higher proportion of CD90+B-cells in the non-viable region compared with MZD and control animals, suggesting that this phenotype was more susceptible to cell death during deficiency. The lower proportion of splenic CD90+T-cells in ZD rats does not appear to be due to a defect in thymic production or increased cell death in the spleen. Future studies should determine if late thymic emigrants have homed to other peripheral organs.
Intestinal, hepatic, splanchnic and hindquarter amino acid and metabolite partitioning during an establishedTrichostrongylus colubriformisinfection in the small intestine of lambs fed fresh Sulla (Hedysarum coronarium)
Authors: Bermingham Emma N. , McNabb Warren C. , Sutherland Ian A. , Sinclair Bruce R. , Treloar Bryan P. , Roy Nicole C. 
Published: July 2007

Increased partitioning of amino acids (AA) from skeletal muscle to the intestine and immune system during parasitic infection may be the cause of poor growth in parasitised animals. The effect of an establishedTrichostrongylus colubriformisinfection (6000 L3T. colubriformislarvae for 6 d (n5) or kept as parasite-free controls (n6)) on AA fluxes across the mesenteric-drained viscera, portal-drained viscera (PDV), liver, total splanchnic tissues (TSP) and hindquarters were determined in lambs fed fresh Sulla (Hedysarum coronarium; 800 g DM/d) 48 d post-infection. The lambs were infused with ρ-aminohippuric acid (PAH; 723 mg/h) into the mesenteric vein for 8 h to measure TSP plasma flow. Concurrently, indocyanine green (ICG; 14·6 mg/h) was infused into the abdominal aorta to measure plasma flow across the hindquarters. Blood was continuously collected from the mesenteric, portal and hepatic veins, vena cava and the mesenteric artery and plasma harvested. PAH, ICG, AA, metabolite and insulin concentrations were measured. Intestinal worm burdens on day 48 post-infection were higher in the infected lambs (P < 0·05). Plasma flows across the tissue beds were unaffected by parasitic infection (P>0·10). There was a 28 % reduction in the release of AA from the PDV of infected lambs (P < 0·05). The uptakes of most AA were similar in the liver; however, there was increased uptake (P < 0·10) of AA by the TSP of infected lambs. Despite this reduction in AA availability at the liver, there was no effect of parasitic infection on AA uptake across the hindquarters (P < 0·05).
Effectiveness of transmeatal low power laser irradiation for chronic tinnitus
Authors: Gungor A , Dogru S , Cincik H , Erkul E , Poyrazoglu E 
Published: July 2007

AbstractObjective:To evaluate effectiveness of 5 mW laser irradiation in the treatment of chronic tinnitus.Study design:Prospective, randomised, double-blind study.Methods:This investigation included 66 ears in 45 patients with chronic unilateral or bilateral tinnitus. A 5 mW laser with a wavelength of 650 nm, or placebo laser, was applied transmeatally for 15 minutes, once daily for a week. A questionnaire was administered which asked patients to score their symptoms on a five-point scale, before and two weeks after laser irradiation. A decrease of one scale point, regarding the loudness, duration and degree of annoyance of tinnitus, was accepted to represent an improvement.Results:The loudness, duration and degree of annoyance of tinnitus were improved, respectively, in up to 48.8, 57.7 and 55.5 per cent of the patients in the active laser group. No significant improvement was observed in the placebo laser group.Conclusion:Transmeatal, low power (5 mW) laser irradiation was found to be useful for the treatment of chronic tinnitus.
Serum leptin levels in patients with nasal polyposis
Authors: Guven M , Bulut Y , Aladag I , Yelken K , Erdoğan H 
Published: July 2007

AbstractBackground:Nasal polyposis is one of the most common inflammatory pathologies of the nasal cavity. The aetiopathogenetic mechanisms of nasal polyp formation are still unclear.Objectives:The aim of this study was to investigate the serum leptin levels in patients with nasal polyposis.Design:A randomised, prospective study was performed of 28 adult patients with nasal polyposis and 22 control subjects of a similar age, sex and body mass index.Results:Serum leptin levels were 12.10 ± 9.39 ng/ml in the nasal polyposis patients and 6.17 ± 7.68 ng/ml in the controls. A significant difference (p = 0.021) was observed in the mean serum leptin levels between nasal polyposis patients and controls.Conclusion:Serum leptin levels were found to be significantly higher in patients with nasal polyposis. Leptin, apart from its primary role in the regulation of body weight and energy expenditure, may have a role in the inflammatory response of nasal polyposis.
Minimal blow-up asymptotics of quasilinear heat equations
Authors: Chaves M. , Galaktionov Victor A. 
Published: July 2007

We study the asymptotic properties of blow-up solutions u = u(x, t) ≥ 0 of the quasilinear heat equation
,
where k(u) is a smooth non-negative function, with a given blowing up regime on the boundary u(0, t) = ψ(t) > 0 for t ∈ (0, 1), where ψ(t) → ∞ as t → 1−, and bounded initial data u(x, 0) ≥ 0. We classify the asymptotic properties of the solutions near the blow-up time, t → 1−, in terms of the heat conductivity coefficient k(u) and of boundary data ψ(t); both are assumed to be monotone. We describe a domain, denoted by , of minimal asymptotics corresponding to the data ψ(t) with a slow growth as t → 1− and a class of nonlinear coefficients k(u).We prove that for any problem in S11−, such a blow-up singularity is asymptotically structurally equivalent to a singularity of the heat equation ut = uxx described by its self-similar solution of the form u*(x, t) = −ln(1 − t) + g(ξ), ξ = x/(1 − t)1/2, where g solves a linear ordinary differential equation. This particular self-similar solution is structurally stable upon perturbations of the boundary function and also upon nonlinear perturbations of the heat equation with the basin of attraction .
A Cauchy problem for the Tartar equation
Authors: Sazhenkov Sergey 
Published: July 2007

In order to study weak limits of quadratic expressions of oscillatory solutions of partial differential equations, there was proposed a construction of H-measures defined on the space of positions and frequencies. The present paper is devoted to the investigation of the Tartar equation
which describes the evolution of the H-measure μt associated with a sequence of oscillatory solutions of the linear transport equation

in cases when a given solenoidal velocity field v(x, t) is sufficiently smooth. Here, (t, x, y) ∈ (0, T) × Ω × S1, 0 < T < +∞, Ω is a bounded open subset of R2 and S1 is the unit circle in R2, given coefficients Yij = Yij(y) are infinitely smooth.Assuming that v belongs to , we establish the well posedness of Cauchy problem for the Tartar equation in the same measure class as the H-measures are in. For this purpose, we develop and use an extension of the theory of Lagrange coordinates for a case of non-smooth solenoidal velocity fields.