bluuebunny/crossref_metadata_2025_split huggingface dataset:
Systems analysis of an acarine predator‐prey system II: Interactions in discontinuous environment
Authors: Fujita Kazuyuki 
Published: October 2006

SummaryAn acarine predator‐prey system in a circular stepping‐stone environment was described with a simulation model to elucidate the factors responsible for persistence of the system. The main assumptions in this model are: (1) The prey are inevitably eliminated in patches in which predators exist. (2) The density of prey declines and becomes extinct by plant defoliation due to feeding by prey. In this regard this model is different from the models which mimickedHuffaker's (1958) experiments and assumed stable plant‐prey relations.Analyses showed that the critical factor in persistence of the predator‐prey system was the plant‐prey relations, at any combination of other parameters involved in the model. The predator‐prey system did not persist long under the unstable relationship of prey and plant. Otherwise the system persisted longer especially when I used a larger number of patches, a larger amount of plant in each patch, and long‐distance‐migrations of the prey. In particular, frequent emigration of the prey regardless of plant conditions was most effective.
Estimating developmental and mortality rates and stage recruitment from insect stage‐frequency data
Authors: Bellows T. S. , Birley M. H. 
Published: October 2006

SummaryA model for the analysis of insect stage‐frequency data is developed which includes stage‐specific variable developmental periods and stage‐specific daily survival rates. The model can predict the development of an insect population through its developmental stages and consequently may form the basis for a simulation model of the population.
The structure and behavior of defoliating insect/forest systems
Authors: McNamee P. J. , McLeod J. M. , Holling C. S. 
Published: October 2006

SummaryUsing four detailed and complex simulation models we derive a framework for predicting behavior of any defoliating insect/forest system. The framework uses simple and easily gathered biological information on four sets of state variables, each with a characteristic temporal scale, to predict presence, absence or form of key ecological processes acting on or between the variables. The combination of these key processes enables prediction of system equilibrium structure and this structure can be used to derive the temporal behavior of the system. Four qualitatively different classes of system behavior arise from the equilibrium structures.The framework is tested against twelve other systems and field invalidation experiments are outlined. Forest defoliator research and management implications are discussed.
Spatial relationships between mate acquisition probability and aggregation size in a gregarious coreid bug, (Colpula lativentris): A case of the ideal free distribution under perceptual constraints
Authors: Nishida Takayoshi 
Published: October 2006

SummarySpatial relationships of mate acquisition probability for individuals of both sexes of a gregariously‐mating coreid bug, Colpula lativentris, were studied in relation to aggregation size. Operational sex ratio was always strongly male biased. Mate acquisition probability of females was rather constant and independent of aggregation size, as predicted by an ideal free distribution. Moreover laboratory experiments showed that both multiple mating and rearing density little affected female fecundity, suggesting ideal free distribution of females in terms of reproductive success. On the other hand, mate acquisition probability of males was higher in larger aggregations, where more receptive females were available. This male discrepancy from an ideal free distribution was similar to the patterns predicted by an ideal free distribution under perceptual constraints (Abrahams, 1986), but not by that under unequal competitive ability.
Automated Solutions for Total RNA Isolation from Diverse Sample Types
Authors: Selley Paula , Bruner Jimmy , Kelly Fiona , Maurio Frank , Waters Michelle , Strum Jay 
Published: October 2006

In response to the increasing demands to generate larger amounts of quality data faster, specifically in the area of RNA isolation to support gene expression assays, we have adopted several automated solutions for isolating total RNA from a variety of sample types, e.g., blood, cells, and tissue. For isolation from blood, collected in PAXgene (PreAnalytiX, Hombrechtickon, CH) tubes, we use a Qiagen BioRobot Universal System (Qiagen Inc-USA, Valencia, CA). For total RNA from cells, we have adapted a 96-well plate solid-phase extraction method using Promega SV96 (Promega, Inc., Madison, WI) reagents. Finally, if starting from tissues, we use the AutoGenPrep 245 (AutoGen Inc, Holliston, MA) robot to perform a modified acid guanidine phenol chloroform isolation. The use of the AutoGenPrep 245 is preceded by tissue homogenization, usually performed on the Qiagen TissueLyser. Following total RNA isolation the RNA is quantified by QuantiT (Invitrogen Corporation, Carlsbad, CA) using a Biomek FX method that performs whole plate serial dilutions, and then creates a reaction plate with samples in duplicate. Finally, to check for genomic DNA contamination in the total RNA sample, a minus reverse transcription PCR assay is performed. In using these methods, we are able to increase our throughput without compromising data integrity.
Independent contributions of neural and “higher‐order” deficits to symptoms in Alzheimer's disease: A latent variable modeling approach
Authors: Tractenberg Rochelle E. , Aisen Paul S. , Weiner Myron F. , Cummings Jeffrey L. , Hancock Gregory R. 
Published: October 2006

BackgroundAnalytic models of Alzheimer's disease (AD) tend to focus on one type of symptom and assume implicitly that no measurement error is present. These tendencies render changes in symptom domains difficult to model mathematically, although latent variable methods can accommodate both multiple symptom domains and error. This study formulated and compared underlying (latent) factor structures representing previously reported dependence and independence of symptoms of cognitive decline, functional impairment, and behavioral disturbance in AD.MethodsIn confirmatory factor analyses of data from 2 cohorts of AD patients, 2 levels of latent variables were conceptualized. One general neurologic factor represented disease, and symptom factors represented cognition, function, and behavior. Two “null” models had either a single factor or 3 symptom factors. Two 2‐level models treated the general factor as underlying both the observed variables and the symptom factors or treated the symptom factors as explaining variability in the observed variables after taking the general factor into account (“residualized”).Results/ConclusionsThe residualized model fit the data in both cohorts significantly better than the other models, and relations in this model between some observed and latent variables were different across cohorts. Neither cohort supported a single factor model; both cohorts independently supported a residualized model that may permit differentiation of symptom‐ from disease‐modifying effects of treatment.
Dynamic market entry and the value of flexibility in transitional international joint ventures
Authors: Lukas Elmar 
Published: October 2006

AbstractThe purpose of this study is to formalize the optimal choice of market entry strategy for an individual multinational enterprise (MNE) from a dynamic perspective. It is argued that incorporating a suitable treatment of irreversibility, uncertainty and flexibility related to an MNE's investment decision gives further insights into the expansion, dissolvement, and optimal timing of international joint ventures (IJVs). In most cases, the initial entry strategy serves as a platform allowing the firm to make subsequent investments to exploit host‐country advantages and capabilities. We allow for this by taking a three‐step expansion strategy explicitly into account. The evolutionary process of the value of the foreign direct investment can be interpreted as a compound complex chooser option. The results suggest that uncertainty, size of equity share and future investment/divestment opportunities play an important role when it comes to transit from export to the first phase of the foreign direct investment commitment. The paper underscores the importance of modeling the dynamics of market entry and helps to refine the application of real options in the alliance context by providing a closed‐form solution in continuous time to value the overall strategic flexibility.
Urban Acquaintance Fields: An Evaluation of a Spatial Model
Authors: Moore E G , Brown L A 
Published: October 2006

The present paper is concerned with examination of the spatial characteristics of empirical data relating to contact fields for a sample of residents in Cedar Rapids, Iowa. It is shown that a model of individual urban contact fields described in an earlier paper (Moore, 1970) provides interesting insights into the spatial characteristics of the empirical contact fields. The model is briefly presented, its aggregate form is derived, and the data are then examined with reference to the aggregate-level model. Analysis of person-to-person contacts may be regarded as the first step towards identification of spatial regularities in information flows(1). Most studies of contact fields have been quite restrictive in their spatial representation, having adopted distance-decay functions as the prime means of description (Hägerstrand, 1957; Marble and Nystuen, 1963; Morrill and Pitts, 1967; Marble and Bowlby, 1968). If the distribution of opportunities for contact is neither uniform nor possesses a symmetrical decline in frequency with increasing distance from the respondent, fitting distance-decay functions to observed contacts tends to hide interesting spatial properties of contact fields. This paper is concerned, therefore, with examining the validity and implications of the aggregated form of a model of individual urban contact fields in an empirical situation.
Factorial Ecologies: Oblique and Orthogonal Solutions. A Case Study of the New York SMSA
Authors: Hughes J W , Carey G W 
Published: October 2006

The utilization of factor analytic methods in the investigation of the spatial structure of urban areas has raised several methodological concerns. Two of these issues are examined in this study: the validity of the orthogonal model, and the possibility of bias through boundary drawing. This paper thus focuses on the effect of the choice of rotational technique upon the derived factor structures at three levels of metropolitan delineation—metropolitan area, city, and inner city sub-area. The rotational techniques are examined specifically in regard to dimensional interpretation and dimensional interrelationships at the three scales of observation. The findings have important methodological implication for the investigation of microregion structural variations.
Migration and the Dynamics of Multiregional Population Systems
Authors: Cordey-Hayes M 
Published: October 2006

This paper gives a personal perspective on some models of national settlement systems, and draws attention to the importance of population migration within these models. It includes a discussion of the inadequacies of current models of interurban migration for the analysis of the dynamic interaction between the demographic and economic growth sectors of a system of postindustrìal cities. The paper is not, however, a review; instead, the aim is to obtain insights on how to progress towards a framework and a strategy for research that will usefully contribute to the analysis of national settlement policy. Section 2 considers recent developments in multiregional demographic analysis and argues that these are of limited usefulness unless they are integrated with models of regional economic growth. Results are presented which show that multiregional demographic analyses are extremely sensitive to the assumptions about migration movements. Section 3 outlines three models which interrelate demographic and economic growth, and stresses the links between the two sectors. Each model considers population migration a key link, and two of them assume that the movement of workers provides an equilibrating mechanism between labour supply and demand. Section 4 questions the validity of this traditional approach to migration and argues that, for a system of postindustrial cities, a new approach is required (Morrison, 1973; Renshaw, 1972; Cordey-Hayes and Gleave, 1973; 1974). A conceptual framework, which emphasizes information flows, differential mobility, and inhomogeneity of labour, is sketched. The final section concludes that no single model or approach provides a royal road to models of national settlement systems, owing to gaps in our understanding of the dynamics of interactions amongst cities. It is suggested that a hierarchy of models should be developed at varying levels of approximation.
On the Inefficiency of Being Efficient
Authors: Goldberg M A 
Published: October 2006

Decisionmaking in the industrialized nations of the western world increasingly can be characterized by its scale and speed of implementation. Another facet of decisionmaking is the narrowness with which problems are defined and the equally narrow range of alternatives sought for solution. This paper documents these elements of decisions and also sketches out a number of scenarios where such an approach has led to unexpected, and often undesirable, consequences. An alternative view of complex decisions, based on these scenarios, is developed. It relies heavily not on optimization as its pivotal criterion but rather upon the persistence of the decisionmaking unit, which is ultimately our society. Examples are presented which illustrate the counterproductive nature of many optimizing solutions. The argument is made that in an uncertain world, such as the one in which we live, optimizing approaches to decisions cannot succeed in the longer run because their assumptions about the constancy of our world do not hold up. Accordingly, a more flexible framework is suggested which values the complexity and uncertainty of the socioecological systems within which we must operate. The stability of these systems is seen to be a critical consideration of decisions, and several aspects of stability are presented which have been overlooked in the past. The paper is concluded with a number of points which it is argued should be explicitly accounted for in future decisionmaking frameworks. Among the points stressed are: the desirability of making small scale decisions and implementing them slowly; the need to acknowledge the limits of what is knowable and thus the role of uncertainty; the virtues of maintaining a diversity of components in our socioecological systems; and finally the need to keep decision options open.
Mode Choice, Transport Pricing, and Urban Form
Authors: Dendrinos D S 
Published: October 2006

The paper examines, within the framework of the standard von Thünen type model with no congestion, the market equilibrium urban form under a regime of commuters who use both the auto and the transit modes, but with no transfers, for their journey to work. There is an extension, however, in that households are assumed to be operating under both an income constraint and a time constraint. The rent and density gradients are obtained in closed forms. Comparative statics are performed, and some policies regarding parking fees, pricing, and investment in the two modes are tested. It is shown that the city may consist of three rings, where the residential location of the user of one mode is split by the residences of the users of the second mode.
Place Attributes in a Migration Decision Context
Authors: Gustavus Susan O , Brown L A 
Published: October 2006

The research reported in this paper used four different survey methods to elucidate the importance of thirteen place attributes in the decision to migrate to Columbus, Ohio; (1) a Likert-type assessment of the general importance of each attribute; (2) a paired-comparison technique for ascertaining attribute trade-off possibilities; (3) measures of saliency and satisfaction with each attribute in the former place of residence, in the town that was the second choice for migration, and in Columbus, the migration destination; and (4) open-ended self-reports of reasons for moving. Use of these varying methodological approaches allows observations both on research strategies for migration studies and on substantive findings concerning place attributes. Relative to the latter, a two-step process is proposed. The first stage of the migration process is identifying a set of alternative destinations in comparison with the former place of residence. Although all thirteen attributes are important in the abstract, housing, jobs, schools, and health care facilities are particularly critical should trade-offs be necessary. Nearness to home and shopping would be traded off most readily, as would ‘city lights’ amenities, which are generally regarded as important in migration literature. In the second stage, a destination is chosen. Attributes appear to function primarily as threshold conditions in this process. Thus, Columbus and the second choice were both perceived as dramatically different from the former place of residence, but were nearly identical to one another. In this context personal contacts in a potential migration destination are apparently crucial in confirming for the migrant that perceptions of attributes are correct and in easing assimilation and adjustment problems.
Trade-off Surveys in Planning: Theory and Application
Authors: Dowall D E , Juhasz J B 
Published: October 2006

We report on two innovations in survey methodology for land-use planning: The use of trade-off choices and the application of cluster analysis to the data. Cluster analysis is used to reduce the attitudinal items to significant dimensions. Cluster-score patterns can then provide empirical typologies of residents according to meaningful data-based distinctions. These subgroups of citizens can be found in homogeneous or heterogeneous subregions with differing consequences for the regional plan. We report on an initial application of this methodology to the mountain area of Jefferson County, Colorado. A questionnaire utilizing the trade-off approach was administered to 316 citizens. The analysis of the citizens' responses yielded eight clusters, four general and four local in orientation. On the basis of the patterns of cluster scores, thirteen subgroups were identified, which were then arranged on a continuum of convenience-versus-environment orientation. The subgroups were found to occupy heterogeneous and homogeneous subregions of the mountain area. We discuss possible implications of these findings for a comprehensive plan, and argue that the findings, although of tentative substance, provide a confirmation of the methodology.
Dynamic Properties of the 1966–1971 Canadian Spatial Population System
Authors: Liaw Kao-Lee 
Published: October 2006

This paper uses an extended Rogers model of multiregional demographic growth to characterize the 1966–1971 Canadian spatial population system, which is disaggregated simultaneously into two sexes, fourteen age groups, and eight regions. It is assumed that much foresight about the future of a spatial population system can be gained by studying the dynamic implications of a fixed matrix of empirically estimated demographic rates. The analysis reveals that during the period 1966–1971 the Canadian spatial population system had very strong growth potential, over 40% of which was due to foreign net immigration, and that the system's long-run redistributional trend is: (1) a continued dominance by Ontario; (2) a strong westward-shifting potential; (3) a drastic reduction in Quebec's competitiveness; (4) a substantial increase in the mean age of every regional subpopulation, except in the North; and (5) a switch from male to female dominance. It is also shown that the convergence toward the long-run distribution can be divided into two stages: First a quick convergence toward relatively smooth regional age profiles, and then a slow but persistent spatial convergence.
Corporate Organisation and Regional Office Employment
Authors: Marshall J N 
Published: October 2006

Research in the United Kingdom focussed on large multisite organisations has suggested that they play an important role in accounting for the distribution of office employment. It is generally suggested that deficits in peripheral-region office employment may be related to the increasing concentration of office employment in manufacturing industry close to corporate headquarters, usually in the Southeast of England. This paper argues that such a view of ownership and in particular of external control as an explanation for variations in office employment is oversimplistic. By use of empirical evidence from an establishment survey conducted in the Northern Region of England it is argued that the role of independent (not externally owned) establishments in explaining variations in office employment has been underestimated. Further, by use of concepts derived from the organisational-science literature, a more complex explanation for variations in office employment is presented.
A Theory of Displaced Ideals: An Analysis of Interdependent Decisions via Nonlinear Multiobjective Optimization
Authors: Nijkamp P 
Published: October 2006

This paper is devoted to a discussion of the use of nonlinear multiobjective models for the analysis of environmental policy. The central focus of the paper is on an interactive procedure by way of a so-called displaced ideal approach. The conflicting nature of multiple objectives in a spatial and environmental system is analyzed by means of a spatial variant of the ‘keeping up with the Joneses' effect. Geometric programming appears to be a useful tool to solve these nonlinear spatial—environmental multiobjective models.
On the Impact of Geographic Distance on the Interregional Patterns of Production and Trade
Authors: Peschel Karin 
Published: October 2006

The paper questions the ‘classical’ concept of distance on which interregional interaction models of the linear programming and the gravitation type are based. In contrast to the conclusions drawn from several econometric studies by Gordon inter alia the following hypotheses are suggested: There is no spatial stability in the relationship between flow levels and geographic distance with respect to particular commodity groups because of historical and geographical particularities in connection with product heterogeneity and oligopolistic market structure. If at all, a distance variable may explain the patterns of production and trade on an aggregate level. This factor of distance is neither equivalent to the transportation costs of today, nor does it fully represent the communication costs of today. It rather reflects the influence of the past on the contemporary spatial pattern of production and trade. With respect to international trade the impact of distance is of minor importance compared to the influence of cultural and linguistic affinity of spatial association and political relationship. These hypotheses are supported by quoting the results of several studies of the Institut für Regionalforschung der Universität Kiel arrived at in the past few years. All this research work centred on the question of how the spatial pattern of production and trade was influenced by national borders and geographic distance in the course of the European economic integration process. The final conclusion of the paper is the need for a theoretical reorientation.