Willem A. van der Kloot

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Acute tryptophan depletion (ATD) induces depressive symptoms in 50-60% of selective serotonin reuptake inhibitor (SSRI) treated, recovered depressed patients. However, no reliable predictors of mood response to ATD have been established. In the present study, individual subject data of six ATD studies were pooled ('mega-analysis') in order to investigate(More)
Dissimilarity measures (D) derived from sortings of stimuli can be submitted to multidimensional scaling (MDS) either directly, or after transforming them to profile distances (Δ) computed on the rows of the D matrix. The latter procedure was criticized by Drasgow and Jones (1979) who performed two simulation studies, which are criticized here in turn. In(More)
Hierarchical agglomerative cluster analysis (HACA) may yield different solutions under permutations of the input order of the data. This instability is caused by ties, either in the initial proximity matrix or arising during agglomeration. The authors recommend to repeat the analysis on a large number of random permutations of the rows and columns of the(More)
The semantic structure and the underlying dimensions of 176 common Dutch words used to describe various kinds of pain were studied. Seventy-seven subjects rated the intensity of the pain described by each of these words; another 53 subjects sorted the words with regard to their similarity in meaning. A unidimensional solution adequately represented the(More)
Five groups of 19 subjects made ratings on 11 personality trait scales of overlapping subsets of 59 artificial stimulus persons who were described by one to five personality trait adjectives. The data were analyzed per group of subjects (blockwise) and per type of stimulus person (questionnaire-wise) by means of three-mode principal component analyses. This(More)
Data produced by 60 subjects rating 31 artificial persons on 11 personality trait scales were analyzed by three-mode principal component analysis. The subjects shared a circular configuration of stimuli and scales. Individuals tended to depart from this pattern in extremity of judgement rather than configuration, suggesting the operation of a response(More)
Knowledge on cross-cultural quality of life (QOL) and illness perceptions may help women with breast cancer cope more effectively. The self regulation model (SRM) guided the current exploratory longitudinal pilot-study. Central to SRM is the perception of health threats and their effects on QOL. Illness perceptions and QOL were assessed in 22 Dutch and 21(More)
The intercorrelations among the 15 scales of the 30-item Core version of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire suggest that one may combine (1) the physical functioning and role functioning scales, (2) the emotional functioning and cognitive functioning scales, and (3) the nine symptom scales. Together(More)
BACKGROUND Sternocostoclavicular hyperostosis (SCCH) is a rare, debilitating, chronic inflammatory disorder of the anterior chest wall due to a chronic sterile osteomyelitis of unknown origin. SCCH is largely underdiagnosed and often misdiagnosed. In individual cases it can remain unrecognized for years. The purpose of this study is twofold. Firstly, to(More)
AIM The new budget system for Dutch hospitals makes use of patient groups that are highly homogeneous in terms of diagnosis and treatment combinations (diagnose behandeling combinaties (DBC)). These DBCs are the Dutch DRG variants. The DBC mainly concerns medical care; nursing care is almost regarded as a constant factor. In this study the DBC is linked to(More)
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