The calculation of the distance to a nearby defective matrix

In this paper a new fast algorithm for the computation of the distance of a matrix to a nearby defective matrix is presented. The problem is formulated following Alam & Bora (Linear Algebra Appl., 396 (2005), pp.~273--301) and reduces to finding when a parameter-dependent matrix is singular subject to a constraint. The solution is achieved by an extension of the Implicit Determinant Method introduced by Spence & Poulton (J. Comput. Phys., 204 (2005), pp.~65--81). Numerical results for several examples illustrate the performance of the algorithm.Comment: 12 page

Separation of spatial and temporal structure of auroral particle precipitation

[1] Knowledge of the dominant temporal and spatial scales of auroral features is instrumental in understanding the various mechanisms responsible for auroral particle precipitation. Single spacecraft data always suffer from temporal/spatial ambiguity. In an effort to separate the temporal and spatial variations of the aurora, we use electron and ion precipitation data from two co-orbiting satellites, F6 and F8 of the Defense Meteorological Satellite Program (DMSP). The two spacecraft have almost identical polar orbits with a small difference in period. As a result the time difference between the two measurements varies with time. We use two statistical tools in order to determine the most probable lifetimes and spatial dimensions of the prevalent auroral features. The first tool is cross-correlation analysis between the magnetic latitude series of electron and ion, number and energy fluxes measured by the two DMSP spacecraft. As one spacecraft overtakes the other, the variable time lag between the two measurements results in different cross-correlation of the two series. We explore the dependence of this variation on the time lag between the satellites. We find that the electron precipitation exhibits a decreasing correlation between the two spacecraft with increasing time lag, whereas there is only a small similar effect for the ion precipitation data. The second statistical tool is cross-spectral analysis, for which we compute the so-called coherence function as a function of frequency (or inverse wavelength) and hence size of the auroral features. The coherence function is a measure of the stability of auroral features of different sizes. We investigate its variation as a function of the time separation between the two measurements. We show that the coherence function of both electrons and ions remains high for up to 1.5 min spacecraft separations for all features larger than about 100 km in width. For smaller features the coherence is lower even for time lags of a few seconds. The results are discussed in the context of characteristic temporal and spatial auroral scales deduced from complementary studies and expected from theory

Social Capital: A review from an ethics perspective

In this paper we extend previous reviews of the social capital literature to encompass an ethics perspective. First, we update previous reviews of social capital. Social capital continues to gain currency in both academic and practical circles, despite relatively little critical reflection on the implications of promoting this popular concept. Our work goes some way to rectifying this paucity in understanding what has been termed the ‘dark side’ of social capital. In particular, we review the social capital concept from the perspective of three theories of business ethics: utilitarianism, justice and ethic of care. While the utilitarian perspective closely parallels accounts of social capital’s rationale, the concept’s operation is mirrored very closely by the assumptions underpinning the ethic of care, while the dark side of social capital is commonly given voice in justice-based critiques. We conclude by considering the implications of our analysis

Capital and labour productivity convergence of manufacturing industry in the regions of Greece

Given that spatially uneven industrial growth is a prime topic in economic geography, it is surprising that changing regional productivity is a relatively understudied area. However, there are clear signs that this situation has started to change lately. Recent findings in the field of international economics regarding productivity convergence have led to a proliferation of studies focused on the sources of this phenomenon at the regional scale, with structural change and technological diffusion prominent. This paper explores the process of manufacturing productivity convergence in the regions of Greece. The first issue to be addressed is methodological and concerns the evolution of current thinking about productivity in regional analysis. Why is it the case that more attention seems to have been paid to the input factors of production, especially labour, rather than their productive use? Definitional issues in the measurement of productivity follow next. The main aim of the research is to estimate and understand the evolution of regional manufacturing productivity in Greece during the period 1984-1993. Detailed econometric analysis in this case is precluded by inadequate data, but rather more straightforward comparative analysis of labour and capital productivity clearly points to a significant convergence. A variety of approaches are then employed in an attempt to isolate and account for the forces behind regional productivity dynamics in Greece. Key words: capital productivity, convergence, labour productivity, regional disparities, uneven growth, Greek regions.

Regional science at the turn of the century: Reflections on its epistemological status

As a contribution to the current debate on the state-of-the art of regional science, this paper presents some reflections on the epistemological and methodological status of the discipline as we approach the turn of the century. First of all, and contrary to the widely held view that quantitative approach is seriously 'in crisis', it is argued that the discipline is going through a period of intensive, but constructive, theoretical development. To support this assertion, the authors suggest that it is important to abandon a hidden source of prejudice: the tendency to evaluate the present situation in terms of an outdated conception of the discipline. Modern quantitative geography and regional science is a vast and varied scientific field, which has radically evolved under the pressure of changing theoretical paradigms and technological advance. It has little to do with the old regional science of the 60s. The first part of the paper reviews this evolution: 1. from the original goal of applying to geography the tools of classical science, such as statistics, optimization and modelling (whose use was made possible in the 60s by the availability of the new "number crunching" computers) 2. to the present informatization (and hence quantification) of all branches of regional science, based on PCs and the Net, used as tools not just for computation, but for data handling, representation, visualization and communication). An attempt is made to fit all of these efforts, those with a long tradition (modelling, O.R., gaming simulation, statistics etc.), as well as the more recent approaches (expert systems, G.I.S., hypermedia, virtual reality, A.I.) into a single framework, stressing the specific aims of each and identifying existing - or potential - interconnections. In the second part of the paper we focus on the new frontiers of regional science and quantitative geography with particular reference to the processes of analysis and planning. It is suggested that: 1. the goal of analysis is shifting from simulation (the explicitation in terms of the "scientific method") of the mental processes involved in problem-solving, to the replication of the human ability to "formulate problems". This implies that creativity, and related aspects such as learning, and expertise, will come increasingly within the scope of research in regional science 2. progress in planning will be limited unless we will be able to go beyond the misleading counterposition between the formalised "rational" approach and the intuitive design approach. A fruitful way to cope with planning in a complex world is to integrate the two strategies and, in doing so, to tap into wider sources of knowledge. In other words, it is important to learn the 'art' of using the tools of geographical science.

TOWARDS INSTITUTIONAL INFRASTRUCTURES FOR E-SCIENCE: The Scope of the Challenge

The three-fold purpose of this Report to the Joint Information Systems Committee (JISC) of the Research Councils (UK) is to: • articulate the nature and significance of the non-technological issues that will bear on the practical effectiveness of the hardware and software infrastructures that are being created to enable collaborations in e- Science; • characterise succinctly the fundamental sources of the organisational and institutional challenges that need to be addressed in regard to defining terms, rights and responsibilities of the collaborating parties, and to illustrate these by reference to the limited experience gained to date in regard to intellectual property, liability, privacy, and security and competition policy issues affecting scientific research organisations; and • propose approaches for arriving at institutional mechanisms whose establishment would generate workable, specific arrangements facilitating collaboration in e-Science; and, that also might serve to meet similar needs in other spheres such as e- Learning, e-Government, e-Commerce, e-Healthcare. In carrying out these tasks, the report examines developments in enhanced computer-mediated telecommunication networks and digital information technologies, and recent advances in technologies of collaboration. It considers the economic and legal aspects of scientific collaboration, with attention to interactions between formal contracting and 'private ordering' arrangements that rest upon research community norms. It offers definitions of e-Science, virtual laboratories, collaboratories, and develops a taxonomy of collaborative e-Science activities which is implemented to classify British e-Science pilot projects and contrast these with US collaboratory projects funded during the 1990s. The approach to facilitating inter-organizational participation in collaborative projects rests upon the development of a modular structure of contractual clauses that permit flexibility and experience-based learning.