Grundlagen des Burrows-Wheeler-Kompressionsalgorithmus

Zusammenfassung. Der Burrows-Wheeler-Kompressionsalgorithmus hat als ein universelles Kompressionsverfahren in den letzten Jahren aufgrund seiner hervorragenden Kompressionsraten und hohen Verarbeitungsgeschwindigkeiten eine bemerkenswerte Beachtung erfahren. Das Herzstück des Algorithmus stellt die sogenannte Burrows-Wheeler-Transformation dar. Es handelt sich bei dieser Transformation um eine Permutation der Eingabedaten, welche Zeichen mit ähnlichem Kontext nahe beieinander anordnet. Die Transformation sowie die zugehörige Rücktransformation werden zusammen mit den weiteren Stufen des Algorithmus in einer gegenüber der Standardversion verbesserten Variante vorgestellt und die Ergebnisse mit denen anderer Datenkompressionsalgorithmen verglichen. Eingegangen am 12. April 2003, Angenommen am 7. November 2003CR Subject Calssification: E4, H1.1     

Innovation and isomorphism: A case-study of university identity struggle 1969–1999

Higher education institutions face today strongpressure from institutional environments toadopt certain structures and management systemsfor reasons of legitimacy and survival.However, the external pressure is multifaceted, demanding organisational and educationalinnovations on one side and adjustments todeveloping national and international standardson the other. By studying a Norwegianuniversity from its establishment in 1969 to1999, and by extensive triangulation of morequalitative studies on this university in thisperiod, the paper concludes that highereducation institutions may handle this dilemmaby relating it to the continuous struggle fororganisational identity.     

Dyslexia and hormone deficiences

From a group of 75 children, originally selected as dyslectic on the basis of their reading and/or spelling problems relative to a total group of 1000 4.th grade children in the city of Trondheim, blood tests were obtained on 35 children. A control group of 45 children was drawn among the 1000 children. Among the 12 different hormones measured, significant differences came out on cortisol, triiodothyronine (T. 3), prolactin, and human growth hormone (HGH, somatotrophin) in boys and girls separately. A follow-up study of 22 dyslectic children from the same cohort gave results consistent with those obtained in the original study. The higher values of the dyslectic group on cortisol and prolactin may suggest the dyslectics to be in a stressful situation, possibly due to their language problems in school. The most striking difference, however, was the very low levels of HGH in the dyslectic group—to the extent that there was little overlap in the two distributions. This result was totally unexpected and is, in fact, opposite of what to be expected on the basis of at least short — time stress events. The results holds up when age and pubery development are controlled for.