Grundlagen des Burrows-Wheeler-Kompressionsalgorithmus

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.     

Factors associated with exclusive breastfeeding 2 to 4 weeks following discharge from a large, urban, academic medical center striving for baby-friendly designation

Substantial evidence documents the superiority of breastfeeding for mothers and breastmilk for babies. Although the American Academy of Pediatrics and the U.S. Healthy People 2010 initiative promote breastfeeding, current breastfeeding rates often fall short of recommendations. This study determined factors associated with exclusive breastfeeding 2 to 4 weeks following discharge from a large, urban, academic medical center striving for Baby-Friendly designation. Results indicated that mothers who breastfed within the first hour of birth (61%) were significantly more likely to be exclusively breastfeeding 2 to 4 weeks after discharge. Incorporating care practices that include a number of the "Ten Steps to Successful Breastfeeding," as recommended by the Baby-Friendly Hospital Initiative, may increase the duration of exclusive breastfeeding after discharge.     

Choice behavior in transition: Development of preference in a free-operant procedure

Twenty acquisition curves were obtained from each of 8 pigeons in a free-operant choice procedure. Every condition began with a phase in which two response keys had equal probabilities of reinforcement, and, as a result, subjects’ responses were divided fairly evenly between the two keys. This was followed by a phase in which one key had a higher probability of reinforcement than the other, and the development of preference was observed. In all but a few cases, response proportions increased for the key with the higher probability of reinforcement. In most conditions, the two probabilities differed by .06, but the actual probabilities varied (from .16 and .10 in one condition to .07 and .01 in another). Development of preference for the key with the higher probability of reinforcement was slower when the ratio of the two reinforcement probabilities was small (.16/.10) than when it was large (.07/.01). This finding is inconsistent with the predictions of several different quantitative models of acquisition, including the kinetic model (Myerson & Miezin, 1980) and the ratio-invariance model (Horner & Staddon, 1987). However, the finding is consistent with a hypothesis based on Weber’s law, which states that the two alternatives are more discriminable when the ratio of their reinforcement probabilities is larger, and, as a result, the acquisition of preference is faster.     

Drawing Parallels in Search of Educational Equity: A Multicultural Education Delegation to China Looks Outside to See Within

In 2004, a professional delegation of multicultural educators visited the People's Republic of China to explore how diversity issues are addressed and how students are prepared for entry into the international workforce. The delegation, sponsored by the People to People Ambassador Programs, observed numerous parallels to the American system of education, including the challenge of providing equity for students of minority cultures, especially those in poor rural areas, and the conflict between modernization and preservation of cultural heritage.