Agglomeration externalities, innovation and regional growth: Theoretical perspectives and meta-analysis

Technological change and innovation and are central to the quest for regional development. In the globally-connected knowledge-driven economy, the relevance of agglomeration forces that rely on proximity continues to increase, paradoxically despite declining real costs of information, communication and transportation. Globally, the proportion of the population living in cities continues to grow and sprawling cities remain the engines of regional economic transformation. The growth of cities results from a complex chain that starts with scale, density and geography, which then combine with industrial structure characterised by its extent of specialisation, competition and diversity, to yield innovation and productivity growth that encourages employment expansion, and further urban growth through inward migration. This paper revisits the central part of this virtuous circle, namely the Marshall-Arrow-Romer externalities (specialisation), Jacobs externalities (diversity) and Porter externalities (competition) that have provided alternative explanations for innovation and urban growth. The paper evaluates the statistical robustness of evidence for such externalities presented in 31 scientific articles, all building on the seminal work of Glaeser et al. (1992). We aim to explain variation in estimation results using study characteristics by means of ordered probit analysis. Among the results, we find that the impact of diversity depends on how it is measured and that diversity is important for the high-tech sector. High population density increases the chance of finding positive effects of specialisation on growth. More recent data find more positive results for both specialization and diversity, suggesting that agglomeration externalities become more important over time. Finally, primary study results depend on whether or not the externalities are considered jointly and on other features of the regression model specification

A flashback on the dawn of the meteorite impact/extinction theory

Presented are my personal recollections on some of the major contributions by the Alvarez groups to the birth and development of the meteorite impact/extinction theory

Investigation of the Domain Wall Fermion Approach to Chiral Gauge Theories on the Lattice

We investigate a recent proposal to construct chiral gauge theories on the lattice using domain wall fermions. We restrict ourselves to the finite volume case, in which two domain walls are present, with modes of opposite chirality on each of them. We couple the chiral fermions on only one of the domain walls to a gauge field. In order to preserve gauge invariance, we have to add a scalar field, which gives rise to additional light mirror fermion and scalar modes. We argue that in an anomaly free model these extra modes would decouple if our model possesses a so-called strong coupling symmetric phase. However, our numerical results indicate that such a phase most probably does not exist. ---- Note: 9 Postscript figures are appended as uuencoded compressed tar file.Comment: 27p. Latex; UCSD/PTH 93-28, Wash. U. HEP/93-6

The self-regulation of motivation:Motivational strategies as mediator between motivational beliefs and engagement for learning

In this research we studied students´ motivational self-regulation as mediator between motivational beliefs and motivational outcomes. Dutch students in pre-vocational secondary education (N=3602, mean age 14) completed a questionnaire on five motivational strategies (Environmental Control, Interest Enhancement, Self Consequating, Performance Self-talk, Mastery Self-talk); motivational beliefs (value attached to schoolwork, competence); and motivational engagement (pleasure, effort, persistence, achievement). A validation of the self-report questionnaire on the five motivational strategies showed a good fit. Structural equation modelling indicated that strategy-use partly mediates the relation between value, and effort and pleasure. Competence showed a weak direct relation with effort an pleasure. No relations were found for achievement. Further implications of these findings for practical use and further research are discussed

A Heuristic Approach to Control the Ecovat System

The Ecovat system is a seasonal thermal storage technology developed to supply the heat demand of a neighbourhood of houses throughout the entire year. It consists of a large subterranean water tank which is divided into a number of virtual segments which can be charged or discharged independently from each other. In this work, we present a fast heuristic approach to model and control the charging (store heat) and discharging (withdraw heat) of the Ecovat system. We compare the results obtained with this approach to results obtained with a previously developed integer linear programming model (ILP) of the Ecovat system, which is too slow to be used in practice. The heuristic is found to reduce the computational time from 12+ hours for the ILP model to one second and is thereby suitable to be used in practice. The price for this reduction is an average decrease in performance of 5.2% and a maximum observed decrease of 12.5%

Factors influencing the implementation of clinical guidelines for health care professionals: A systematic meta-review

BACKGROUND: Nowadays more and more clinical guidelines for health care professionals are being developed. However, this does not automatically mean that these guidelines are actually implemented. The aim of this meta-review is twofold: firstly, to gain a better understanding of which factors affect the implementation of guidelines, and secondly, to provide insight into the "state-of-the-art" regarding research within this field. METHODS: A search of five literature databases and one website was performed to find relevant existing systematic reviews or meta-reviews. Subsequently, a two-step inclusion process was conducted: (1) screening on the basis of references and abstracts and (2) screening based on full-text papers. After that, relevant data from the included reviews were extracted and the methodological quality of the reviews was assessed by using the Quality Assessment Checklist for Reviews. RESULTS: Twelve systematic reviews met our inclusion criteria. No previous systematic meta-reviews meeting all our inclusion criteria were found. Two of the twelve reviews scored high on the checklist used, indicating only "minimal" or "minor flaws". The other ten reviews scored in the lowest of middle ranges, indicating "extensive" or "major" flaws. A substantial proportion (although not all) of the reviews indicates that effective strategies often have multiple components and that the use of one single strategy, such as reminders only or an educational intervention, is less effective. Besides, characteristics of the guidelines themselves affect actual use. For instance, guidelines that are easy to understand, can easily be tried out, and do not require specific resources, have a greater chance of implementation. In addition, characteristics of professionals - e.g., awareness of the existence of the guideline and familiarity with its content - likewise affect implementation. Furthermore, patient characteristics appear to exert influence: for instance, co-morbidity reduces the chance that guidelines are followed. Finally, environmental characteristics may influence guideline implementation. For example, a lack of support from peers or superiors, as well as insufficient staff and time, appear to be the main impediments. CONCLUSIONS: Existing reviews describe various factors that influence whether guidelines are actually used. However, the evidence base is still thin, and future sound research - for instance comparing combinations of implementation strategies versus single strategies - is needed. (aut. ref.

К определению понятий коммуникация, интеркультурная коммуникация и коммуникативистика

The Strong Electrostatic Adsorption (SEA) method was applied to the rational design of a promoted Co catalyst for Fischer–Tropsch (FT) synthesis. A series of Mn/Co/TiO2 catalysts were prepared by selective deposition of the [MnO4] anion onto the supported Co3O4 phase. Qualitative ICP-OES and XPS measurements of the prepared catalysts with increasing Mn loading displayed the preferential association of the Mn species with Co3O4 and not the TiO2 support. The SEA preparation method seemed to minimize the migration of Mn away from the Co to the TiO2 support during reduction procedures to ensure a more intimate interaction between the Mn and the Co species during FT reactivity measurements. This led to an increase in light olefins, C5+ selectivity and chain growth probability. It is anticipated that the SEA preparation method is a viable synthesis strategy for other promoted and/or bimetallic catalyst systems where intimate contact between the catalyst components is highly desired