bluuebunny/crossref_metadata_2025_split huggingface dataset:
With a little help from our friends: How system dynamics and soft OR can learn from each other
Authors: Lane David C. 
Published: July 2007

AbstractAt its inception, the paradigm of system dynamics was deliberately made distinct from that of OR. Yet developments in soft OR now have much in common with current system dynamics modeling practice. This article briefly traces the parallel development of system dynamics and soft OR, and argues that a dialogue between the two would be mutually rewarding. To support this claim, examples of soft OR tools are described along with some of the field's philosophical grounding and current issues. Potential benefits resulting from a dialogue are explored, with particular emphasis on the methodological framework of system dynamics and the need for a comple‐mentarist approach. The article closes with some suggestions on how to begin learning from the links between the two fields.
System dynamics, systems thinking, and soft OR
Authors: Forrester Jay W. 
Published: July 2007

AbstractSystem dynamics, systems thinking, and soft operations research (soft OR) all aspire to understanding and improvement of systems. In all, the first step interprets the real world into a description used in following stages. In system dynamics, description leads to equations of a model, simulation to understand dynamic behavior, evaluation of alternative policies, education and choice of a better policy, and implementation. Case studies, systems thinking, and soft OR usually lack the discipline of explicit model creation and simulation and so rely on subjective use of unreliable intuition for evaluating the complex structures that emerge from the initial description of the real system. Nevertheless, systems thinking and soft OR, with emphasis on eliciting information from‐real‐world participants, should contribute useful insights to system dynamics. Conversely, the model creation and simulation stages of system dynamics should contribute rigor and clarity to systems thinking and soft OR.
Cognitive mapping and problem structuring for system dynamics model building
Authors: Eden Colin 
Published: July 2007

AbstractThis article discusses an approach to problem structuring that seeks to recognize the significance of multiple perspectives and the richness they provide in generating politically feasible ways of resolving problems. In particular, the method—cognitive mapping and an associated computer‐based group support system—is related to the early stages of modeling situations that are characterized by feedback dynamics. Thus, the method is argued to be particularly suitable as a visual interactive modeling method, which is mutually supportive of visual interactive system dynamics modeling methods.
Competition and complexity in spatially connected networks
Authors: Reggiani Aura , Nijkamp Peter 
Published: July 2007

AbstractMuch attention has recently been paid to the potential of using analytical tools derived from ecology and biology for analyzing competitive (or synergetic) interactions in a complex spatial network.Defining a network as a complex space‐time system, this article investigates the implications of spatial interconnections when oscillating or chaotic behavior in a certain node of a network is spread in both space and time. The main focus is on stability/ complexity in a network with a view to varying complexity in terms of the number of functional elements (e.g., nodes, competing/growing centers). Some simulation experiments involving simple‐dimensional spatial systems are described.
Teamwork in group model building
Authors: Richardson George P. , Andersen David F. 
Published: July 2007

AbstractOngoing research at the Rockefeller College of Public Affairs and Policy is focusing on strategies for efficient and effective model building in groups. The intent is to involve a relatively large client group in the business of model formulation. Recent projects have explored strategies for accelerated group model building in the context of three public policy problem areas: foster care in New York State, Medicaid costs in the state of Vermont, and homelessness policy initiatives in New York City.Five roles appear to be essential to support effective group model building: the facilitator, the modeler/ reflector, the process coach, the recorder, and the gate keeper. This article identifies the five roles, briefly discusses the problem areas, sketches the design of the group model‐building efforts, and hypothesizes principles and strategies to guide future group model building.
Mode‐locking and entrainment of endogenous economic cycles
Authors: Haxholdt Christian , Kampmann Christian , Mosekilde Erik , Sterman John D. 
Published: July 2007

AbstractWe explore the robustness of aggregation in Sterman's model of the economic long wave. The original model aggregates all capital‐producing firms into a single sector and generates a large‐amplitude self‐sustained oscillation with a period of roughly 50 years. We disaggregate the model into two coupled industries, one representing production of plant and long‐lived infrastructure and the other representing short‐lived equipment and machinery. While holding the aggregate equilibrium characteristics of the model constant, we investigate how mode‐locking occurs as a function of the difference in capital lifetimes and the strength of the coupling between the sectors. Disaggregation allows new modes of behavior to arise: In addition to mode‐locking, we observe cascades of period‐doubling bifurcations, chaos, intermittency, and quasi‐periodic behavior. Despite the introduction of these additional modes, the basic behavior of the model is robust to the aggregation assumption. We consider the likely effects of finer disaggregation, the introduction of additional coupling mechanisms, such as prices, and other avenues for the exploration of aggregation in system dynamics models.
A system dynamics approach to modeling fisheries management issues: Implications for spatial dynamics and resolution
Authors: Ruth Matthias 
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, Universitat Stuttgart, Keplerstr. 17, D‐7000 Stuttgart 1, Germany or to Yaman Barlas, Dept. of Industrial Engineering, Bogazici University, 80815 Bebek, Istanbul, Turkey.
Association of fast food consumption with energy intake, diet quality, body mass index and the risk of obesity in a representative Mediterranean population
Authors: Schröder Helmut , Fïto Montserrat , Covas Maria Isabel 
Published: July 2007

The aim of the present study was to describe the association of fast food consumption with BMI, energy intake and diet quality in a Mediterranean population. The subjects were Spanish men (n 1491) and women (n 1563) aged 25–74 years who were examined in 1999–2000, in a population-based cross-sectional survey in northeast Spain (Girona). Dietary intake was assessed using a FFQ that included four typical fast food items. Two dietary-quality indices, the Mediterranean diet score and the healthy eating index, were created. Height and weight were measured. Within the population studied, 10·1 % reported eating fast food at least once per month. Dietary energy intake and energy density were directly associated with frequency of fast food consumption. Multivariate logistic regression analysis adjusted for lifestyle and educational level showed an inverse association of frequency of fast food consumption with meeting the dietary reference intake (DRI) for energy (P = 0·001). The consumption of fast food more than once per week increased the risk of overall low diet quality (P < 0·001). BMI was directly associated with fast food consumption expressed in g/d (P = 0·025) and in kJ/d (P = 0·017). The risk of being obese increased with the frequency of fast food consumption (P = 0·046). Fast food consumption was associated with higher energy intakes, poor diet quality and higher BMI. The likelihood of not meeting the DRI for energy, and of being obese, increased with the frequency of fast food consumption.
Tubercular and chronic pyogenic osteomyelitis of cranio-facial bones: a retrospective analysis
Authors: Sethi A , Sethi D , Agarwal A K , Nigam S , Gupta A 
Published: July 2007

AbstractAim:To analyse current trends in our population with respect to the presentation, diagnosis and management of tubercular and chronic pyogenic osteomyelitis of the cranio-facial bones.Design:Retrospective study.Setting:Tertiary healthcare centre.Patients and methods:The study population comprised 14 patients with tubercular and chronic pyogenic osteomyelitis who were managed in the otorhinolaryngology department between May 2002 and December 2005.Results:Odontogenic infections, sinus infections and aural infections were the most commonly identified aetiological factors. Most of the patients presented with swelling, pain and discharging sinus. The diagnosis was established on the basis of clinical evaluation, radiological investigations and histopathological analysis, with six cases diagnosed with tubercular osteomyelitis and eight cases with chronic pyogenic osteomyelitis. All the patients were initially commenced on oral antibiotics, which were continued for two weeks in all cases with chronic pyogenic osteomyelitis. All the patients with pyogenic osteomyelitis underwent surgical management, with one patient requiring repeated surgical interventions. All the patients with tubercular osteomyelitis received anti-tubercular chemotherapy, with complete cure.Conclusions:Osteomyelitis of the cranio-facial bones is an uncommon entity which requires a high index of clinical suspicion along with radiological and histopathological investigations in order to establish the diagnosis. Tubercular osteomyelitis is clinically and radiologically indistinguishable from pyogenic osteomyelitis, and the two conditions can be differentiated only on the basis of histopathological evaluation of involved tissue.
Bone changes after maxillary sinus surgery: an experimental scanning electron microscopy study
Authors: Moreno P M , Meseguer D H 
Published: July 2007

AbstractAims:The purpose of this study was to explore the pathogenic role of bone in sinus surgery, and to determine whether mucosal disease after sinus surgery may be induced by underlying disease within the bone.Material and methods:Twenty-five rabbits were divided into five groups. In group one, wide surgical removal of the maxillary sinus mucosa and creation of a nasoantral window were undertaken. In group two, only nasoantral window creation was undertaken. In group three, the mucosa of the anterior maxillary sinus was removed. In group four, a strip of mucosa around the ostium was removed. Group five was used as a control.Results:After three months, in the groups which had undergone wide surgical removal, the medial sinus walls were observed to be retracted and the inner curtain of the bone disturbed, with alteration of the haversian canal system and osteoclastic bone resorption.Conclusions:After radical sinus surgery, electron microscopic changes were observed in the bony walls, similar to those changes seen in osteomyelitis.
On a class of elliptic problems in R2: symmetry and uniqueness results
Authors: Prajapat J. , Tarantello G. 
Published: July 2007

In the plane R2, we classify all solutions for an elliptic problem of Liouville type involving a (radial) weight function. As a consequence, we clarify the origin of the non-radially symmetric solutions for the given problem, as established by Chanillo and Kiessling.For a more general class of Liouville-type problems, we show that, rather than radial symmetry, the solutions always inherit the invariance of the problem under inversion with respect to suitable circles. This symmetry result is derived with the help of a 'shrinking-sphere' method.
Overview of Multiple–Aperture Interferometry Binary Star Results from the Northern Hemisphere
Authors: McAlister Harold A. 
Published: July 2007

AbstractLong-baseline optical interferometry (LBI) can nearly close the gap in selection space between astrometric and spectroscopic detection of binary star systems, bringing the complementary powers of astrometry and spectroscopy to bear on a complete dynamical understanding of such systems, particularly including the determination of the masses of the individual stellar components. In the case of double-lined spectroscopic systems, their resolution by long-baseline interferometry also yields the orbital parallax and hence the luminosities of the individual stars. In some of these cases, the angular diameters of one or more components are accessible, and so a complete specification of a star in terms of its mass, radius and luminosity is made.The northern hemisphere is now equipped with several interferometers of unprecedented capability in terms of their baseline sizes, numbers of telescopes and telescope apertures. These instruments, most notably the Palomar Testbed Interferometer at Mt. Palomar Observatory, have produced very significant results of a number of interesting systems fulfilling interferometry's promise to produce fundamental astrophysical data at levels of accuracy that challenge or confirm astrophysical theory.This paper presents basic principles of long-baseline interferometric study of binary stars and summarizes results from northern interferometers with specific examples of their broad impact on binary star astronomy.
Doppler Tomography of Accretion Disks and Streams in Close Binaries
Authors: Richards Mercedes T. 
Published: July 2007

AbstractThe application of tomography to the study of gas flows in interacting binaries has led to fascinating images of the Cataclysmic Variables and Algol-type binaries. Such detailed images are currently unachievable using direct-imaging techniques. Numerous images of accretion flows have now been derived from optical and ultraviolet spectra and they have been used to identify multiple emission sources including the gas stream, accretion disk, accretion annulus, shock regions, and the chromosphere of the mass loser. It was difficult to distinguish between the separate sources of emission since these sources have overlapping velocities in the Doppler tomogram. However, with the aid of a new spectral synthesis code, we can now systematically extract the individual emission sources to sequentially isolate the images of the disk and gas stream. With these new tools, we have begun to extract the critical properties of the disk and gas stream more accurately than previously possible.
Reducing Binary Star Data from Long-Baseline Interferometers
Authors: ten Brummelaar Theo A. 
Published: July 2007

AbstractProcessing long-baseline interferometry data presents a unique set of complications: How does one derive relative astrometry from interferometric data? How can 1-D interferometric results be used to solve a 2-D orbit? How can baseline-only solutions be combined with historical data and how should interferometric data be published so that they can be combined with archived data? What new techniques for interferometers are coming on line? This paper contains a brief review of interferometric data analysis in the context of binary star astrometry.
Line-Profile Variations on Massive Binary Systems: Determining η Carinae Orbital Parameters
Authors: Falceta-Gonçalves D. , Abraham Z. , Jatenco-Pereira V. 
Published: July 2007

AbstractWhen the winds of two massive stars orbiting each other collide, an interaction zone is created consisting of two shock fronts at both sides of a contact surface. During the cooling process, elements may recombine generating spectral lines. These lines may be Doppler shifted, as the gas stream flows over the interaction zone. To calculate the stream velocity projected into the line of sight we use a simplified conical geometry for the shock fronts and, to determine the synthetic line profile, we have to sum the amount of emitting gas elements with the same Doppler shifted velocity. We show that the stellar mass loss rates and wind velocities, and the orbital inclination and eccentricity, are the main parameters on this physical process. By comparing observational data to the synthetic line profiles it is possible to determine these parameters. We tested this process to Brey 22 WR binary system, and applied to the enigmatic object of η Carinae.
Pipeline Reduction of Binary Light Curves from Large–Scale Surveys
Authors: Prša Andrej , Zwitter Tomaž 
Published: July 2007

AbstractOne of the most important changes in observational astronomy of the 21stCentury is a rapid shift from classical object-by-object observations to extensive automatic surveys. As CCD detectors are getting better and their prices are getting lower, more and more small and medium-size observatories are refocusing their attention to detection of stellar variability through systematic sky-scanning missions. This trend is aditionally powered by the success of pioneering surveys such as ASAS, DENIS, OGLE, TASS, their space counterpart Hipparcos and others. Such surveys produce massive amounts of data and it is not at all clear how these data are to be reduced and analysed. This is especially striking in the eclipsing binary (EB) field, where most frequently used tools are optimized for object-by-object analysis. A clear need for thorough, reliable and fully automated approaches to modeling and analysis of EB data is thus obvious. This task is very difficult because of limited data quality, non-uniform phase coverage and solution degeneracy. This paper reviews recent advancements in putting together semi-automatic and fully automatic pipelines for EB data processing. Automatic procedures have already been used to process Hipparcos data, LMC/SMC observations, OGLE and ASAS catalogs etc. We discuss the advantages and shortcomings of these procedures.
The Incidence of Multiplicity Among Bright Stellar Systems
Authors: Eggleton Peter P. , Kisseleva-Eggleton Ludmila , Dearborn Xander 
Published: July 2007

AbstractWe consider the multiplicity of stellar systems with (combined) magnitude brighter than 6.00 in Hipparcos magnitudes. We identify 4555 such bright systems, and the frequencies of multiplicities 1, 2, . . , 7 are found to be 2722, 1412, 299, 86, 22, 12 and 2. We also consider the distributions of periods of orbits and sub-orbits. For the even more restricted set of 474 systems with VH ≤ 4.00 the proportions of higher multiples up to sextuple are progressively larger, suggesting incompleteness in even the relatively well-studied larger sample.We construct a Monte-Carlo algorithm that will generate systems with roughly the observed multiplicities and orbital parameters, taking account of selection effects.
The Frequency Distribution of Semimajor Axes of Wide Binaries: Cosmogony and Dynamical Evolution
Authors: Poveda Arcadio , Allen Christine , Hernández-Alcántara A. 
Published: July 2007

AbstractThe frequency distribution f(a) of semimajor axes of double and multiple systems, and their eccentricities and mass ratios, contain valuable fossil information about the process of star formation and the dynamical history of the systems. In order to advance in the understanding of these questions, we made an extensive analysis of the frequency distribution f(a) for wide binaries (a > 25 AU) in various published catalogues, as well as in our own (Poveda et al 1994; Allen et al 2000; (Poveda & Hernández–Alcántara 2003). Based upon all these studies we have established that the frequency distribution f(a) is a function of the age of the system and follows Öpik's distribution f(a) ∼ 1/a in the range of 100 AU < a < ac(t), where ac (t) are the critical semimajor axes beyond which binaries have been dissociated by encounters with massive objects. We argue that the physics behind the distribution f(a) ∼ 1/a is a process of energy relaxation, analogous to those present in stellar clusters (secular relaxation) or in the early stages of spherical galaxies (violent relaxation). The existence of runaway stars indicates that both types of relaxation are important in the process of binary and multiple star dynamical evolution.
Experimental demonstration of chaotic instability in biological nitrification
Authors: Graham David W , Knapp Charles W , Van Vleck Erik S , Bloor Katie , Lane Teresa B , Graham Christopher E 
Published: July 2007

Abstract
Biological nitrification (that is, NH3 → NO2− → NO3−) is a key reaction in the global nitrogen cycle (N-cycle); however, it is also known anecdotally to be unpredictable and sometimes fails inexplicably. Understanding the basis of unpredictability in nitrification is critical because the loss or impairment of this function might influence the balance of nitrogen in the environment and also has biotechnological implications. One explanation for unpredictability is the presence of chaotic behavior; however, proving such behavior from experimental data is not trivial, especially in a complex microbial community. Here, we show that chaotic behavior is central to stability in nitrification because of a fragile mutualistic relationship between ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), the two major guilds in nitrification. Three parallel chemostats containing mixed microbial communities were fed complex media for 207 days, and nitrification performance, and abundances of AOB, NOB, total bacteria and protozoa were quantified over time. Lyapunov exponent calculations, supported by surrogate data and other tests, showed that all guilds were sensitive to initial conditions, suggesting broad chaotic behavior. However, NOB were most unstable among guilds and displayed a different general pattern of instability. Further, NOB variability was maximized when AOB were most unstable, which resulted in erratic nitrification including significant NO2− accumulation. We conclude that nitrification is prone to chaotic behavior because of a fragile AOB–NOB mutualism, which must be considered in all systems that depend on this critical reaction.
Looking at the Beginnings: Enquiries about Emergence of Cognition in Evolution
Authors: Riofrio Walter 
Published: July 2007

AbstractTrying to understand when and how the cognitive phenomena arise in evolution continues being a hard problem of confronting. One important task is to find the ways in which we will be able to arrive at those explanations that will enable us to understand how living beings put together perceived sensory information as well as how they represent it. In this presentation, we address some conceptual questions involved in the relationships between sensorial information perceived by brains and its representational capacities.
Chronic Daily Bilateral Headache Responsive to Indomethacin
Authors: Solomon Seymour , Newman Lawrence C. 
Published: July 2007

Indomethacin is known to be specifically effective for chronic paroxysmal hemicrania, episodic paroxysmal hemicrania, and hemicrania continua. Different forms of idiopathic stabbing headaches have also been responsive to indomethacin, but less consistently than the others.Two cases of indomethacin‐responsive headache are reported. One patient presented with what appeared to be new‐onset, chronic, daily, bilateral headache aggravated by coughing. Both the chronic daily headache and the exacerbations induced by coughing were suppressed with indomethacin therapy. The second patient experienced hemicrania continua responsive to indomethacin, and the response persisted even when the headache evolved into bilateral continuous pain.There may be other idiopathic primary headache disorders that are peculiarly responsive to indomethacin. When any primary headache disorder does not respond to standard therapy, a brief therapeutic trial of indomethacin is warranted.