Matrix Convex Sets Without Absolute Extreme Points

This article shows the existence of a class of closed bounded matrix convex sets which do not have absolute extreme points. The sets we consider are noncommutative sets, $K_X$, formed by taking matrix convex combinations of a single tuple $X$. In the case that $X$ is a tuple of compact operators with no nontrivial finite dimensional reducing subspaces, $K_X$ is a closed bounded matrix convex set with no absolute extreme points. A central goal in the theory of matrix convexity is to find a natural notion of an extreme point in the dimension free setting which is minimal with respect to spanning. Matrix extreme points are the strongest type of extreme point known to span matrix convex sets; however, they are not necessarily the smallest set which does so. Absolute extreme points, a more restricted type of extreme points that are closely related to Arveson's boundary, enjoy a strong notion of minimality should they span. This result shows that matrix convex sets may fail to be spanned by their absolute extreme points.Comment: 18 page

Safe and smooth through a shallow fairway

Since the ever growing dimensions of all vessel types coming to the Flemish harbours which started in the mid 80’s of last century, the research at Flanders Hydraulics Research, a laboratory belonging to the Flemish Government, concerning harbour infrastructure and fairways was shifting from structural based examinations to ship related examinations. The key question was and is: how can an existing or new-built ship access the shallow water areas in Belgium safely and smoothly? With the installation of the first ship manoeuvring simulator in 1989 and the Towing Tank for Manoeuvres in Shallow water (co-operation Flanders Hydraulics Research- Ghent University) in 1992 fundamental and applied research studies followed successively. In May 2008 this joint work resulted in the Knowledge Centre Manoeuvring in Shallow and Confined Water (www.shallowwater.be) established to fix, extend and provide the scientific know-how on the behaviour of vessels in shallow and confined navigation areas. The presentation will give an overview of the latest fundamental researches executed at FHR and UGent concerning the influence of shallow water manoeuvring, bank effects and ship-ship interaction. Based on model tests with scale models of about 4 m length forces have been measured and the influence of different test parameters have been examined. Combining these measurements with mathematical models incorporated in the simulators gives the opportunity to evaluate new situations together with the pilots of the Flemish Pilotage. This research has been used to evaluate the accessibility of the largest containerships (the E-type vessel of Maersk Sealand and the 366 m vessels of other shipping companies as MSC and CMA-CGM) to the port of Antwerp and the port of Zeebrugge and the largest LNG carriers to the LNG terminal in Zeebrugge. New limits have been examined for the West lock in Terneuzen for Kamsarmax vessels where the useful width of 38 m for the lock is compared with the vessel’s beam of 37 m. This high blockage introduces lock effects that determines the behaviour entering the lock

A critical analysis of the X.400 model of message handling systems

The CCITT X.400 model of store and forward Message Handling Systems (MHS) serves as a common basis for the definition of electronic mail services and protocols both within CCITT and ISO. This paper presents an analysis of this model and its related recommendations from two perspectives. First the concepts of service, protocol and interface are discussed together with their application to this model; second the positioning within ISO's reference model for Open Systems Interconnection (OSI) is commented on

On the impossibility of inferring cohort fertility measures from period fertility measures

A particularly important struggle faced by demographic analysts is, how to arrive at statements about family formation processes from a cohort perspective from data that are essentially collected on an annual basis. The present paper is concerned with this struggle, mostly restricted to the case of fertility. The central question investigated here is: given observed period data, what can we conclude about the completed family size of real women? I review several existing methods to infer cohort fertility from period fertility measures. The conclusion is that, for each method, its justifiability can be verified only empirically: by looking at cohort fertility directly. To illustrate how this can be done, the paper analyses fertility data from a cohort perspective for two countries, Italy and the Netherlands.cohort fertility, demographic transition, fertility, Italy, Netherlands, period adjustment, tempo and quantum, total fertility rate

Film documentary : nodding syndrome: an illness in the making

This film documentary is based on fifteen months of anthropological fieldwork in northern Uganda and shows the complexity of nodding syndrome and the many different narratives, explanatory models and coping styles regarding this affliction. In attempting to understand what nodding syndrome is and how it is experienced, we should look at the context in which meaning making takes place

Polycentric Development to Combat Regional Disparities? the Relation Between Polycentricity and Regional Disparities in European Countries

Trends in regional disparities have been a major issue in regional science for many decades and knowledge of ways to overcome such disparities has great importance for regional policy-making. Strong initial differences between regions affect the capacity of each region to grow and their ability to respond to challenges imposed externally, for instance globalisation and growing international competition and trade (Cuadrado-Roura, 2001). Initial differences can relate to a wide variety of factors, for instance the availability of human resources, the accessibility of a region and the presence of advanced production services. A factor that gets increasing attention is the city system. Flourishing regions can often count on a large, well-accessible and internationally known city or regional clusters of cities. Concentration of support to dynamic growth poles would be an engine for growth of the whole country (or regions) through regional spillovers (Perroux 1955 and Kaldor 1970) Particularly also in regional and spatial policies addressing regional disparities attention is paid to the city system. It has been suggested that polycentric development can be instrumental to reducing regional disparities, see for instance in the European Spatial Development Perspective (CEC, 1999) and the Second Cohesion Report (CEC, 2001). In the Third Cohesion Report the main emphasis is territorial cohesion, which is placed on an equal footing as economic and social cohesion in the (unratified) Constitutional Treaty. Within the discussion on territorial cohesion polycentricity gets much emphasis (Faludi, 2005). Also many European countries pursue a polycentric development, often addressing the dominance of their prime city to diminish regional disparities. Apparently, policy makers assume a strong relationship between the urban system and the persistence of regional disparities. However, this assumption lacks empirical justification. The aim of this paper is to test the hypothesis that a polycentric city system leads to less regional disparities. The paper presents measures of the extent of polycentricity of the national urban systems of 26 European countries. This data is linked with calculations of regional disparities within these 26 countries. Are countries with a relatively polycentric urban system characterised by less regional disparities than more monocentric countries? And, what are the consequences of our findings for regional development policies?

Attention deficit hyperactivity disorder (ADHD) in the schools: alternative interventions for school counselors

Includes bibliographical references