Recently, an algorithm to detect groups in a dataset that follow different linear patterns was proposed in [VWZ06]. The algorithm is flexible in the sense that it does not require the specification of a response variable. On the other hand, the algorithm requires that each observation follows one of the linear patterns in the data. However, it often occurs in practice that part of the data does not follow any of the linear patterns. Therefore, we introduce a robust linear grouping algorithm based on trimming that can still find the linear structures even if part of the data does not belong to any of the groups.

Hypothesis tests and confidence intervals based on the classical Hotelling T-2 statistic can be adversely affected by outliers. Therefore, we construct an alternative inference technique based on a statistic which uses the highly robust MCD estimator of Rousseeuw (1984) instead of the classical mean and covariance matrix. the distribution of this new statistic differs from the classical one. Similarly to the classical T-2 distribution, we obtain a multiple of a certain F-distribution. It is shown through a Monte Carlo study that this approximation is very accurate, both at the normal model and at contamination models.

Principal Component Analysis, Canonical Correlation Analysis and Factor Analysis (Johnson and Wichern 1998) are three different methods for analyzing multivariate data. Recently robust versions of these methods have been proposed by Croux and Haesbroeck (2000), Croux and Dehon (2001) and Pison et al. (2002) which are able to resist the effect of outliers. Influence functions for these methods are also present. However, there does not yet exist a graphical tool to display the results of the robust data analysis in a fast way. Therefore we now construct such a diagnostic tool based on empirical influence functions. These graphics will not only allow us to detect the influential points for the multivariate statistical method but also classify the observations according to their robust distances. In this way we can identify regular points, good (non-outlying) influential points, influential outliers, and non-influential outliers. We can downweigh the influential outliers in the classical estimation method to obtain reliable and efficient estimates of the model parameters. Some generated data examples will be given to show how these plots can be used in practice.

Declining captive markets and increasing competition are making formal strategic analysis important for seaport authorities and port operators. This paper develops a new conceptual framework, based on the resource-based view of complex organizations, that allows the identification of the key determinants of a port cluster's competitiveness. The empirical application to the Antwerp port cluster suggests that non-cost related and qualitative elements largely explain the strong competitive position of this cluster for general cargo and containers. The analysis suggests that measuring realized competitive advantage remains important, but that insights into the underlying sources of competitive advantage are equally critical.

Some studies have suggested that disorders in the peripheral and central metabolism of serotonin (5-HT) and noradrenaline may play a role in the pathophysiology of autistic disorder. This study examines serotonergic and noradrenergic markers in a study group of 13 male, post-pubertal, caucasian autistic patients (age 12–18 y; I.Q. > 55) and 13 matched volunteers. [3H]-paroxetine binding Kd values were significantly higher in patients with autism than in healthy volunteers. Plasma concentrations of tryptophan, the precursor of 5-HT, were significantly lower in autistic patients than in healthy volunteers. There were no significant differences between autistic and normal children in the serum concentrations of 5-HT, or the 24-hr urinary excretion of 5-hydroxy-indoleacetic acid (5-HIAA), adrenaline, noradrenaline, and dopamine. There were no significant differences in [3H]-rauwolscine binding Bmax or Kd values, or in the serum concentrations of tyrosine, the precursor of noradrenaline, between both study groups. There were highly significant positive correlations between age and 24-hr urinary excretion of 5-HIAA and serum tryptophan. The results suggest that: 1) serotonergic disturbances, such as defects in the 5-HT transporter system and lowered plasma tryptophan, may play a role in the pathophysiology of autism; 2) autism is not associated with alterations in the noradrenergic system; and 3) the metabolism of serotonin in humans undergoes significant changes between the ages of 12 and 18 years.

This article aims to identify empirically the most important location advantages determining the port of Antwerp's competitive position for containers and conventional cargo as compared to its main rivals in the Hamburg-Le Havre range. A conceptual framework is developed for analysing the competitiveness of seaports, based on an extended version of Porter's ‘diamond’ approach. This framework is tested through a large scale survey with port operators and experts. This article suggests that the port of Antwerp largely benefits from the superstructure used by forwarders, the flexibility and the productivity of its dockworkers and its forwarders. The analysis also identifies three key disadvantages, namely the weak competitiveness of pilotage and inland navigation service providers in the port of Antwerp, and the limited maritime accessibility of the port. The introduction of the extended ‘diamond’ framework allows the identification of a set of strengths and weaknesses characterising a specific port cluster and can thus contribute substantially to the development of port policy and management.