University of Amsterdam

About: University of Amsterdam is a education organization based out in Amsterdam, Noord-Holland, Netherlands. It is known for research contribution in the topics: Population & Randomized controlled trial. The organization has 59309 authors who have published 140894 publications receiving 5984137 citations. The organization is also known as: UvA & Universiteit van Amsterdam.

Empirical tests of the Gradual Learning Algorithm

Abstract: The Gradual Learning Algorithm (Boersma 1997) is a constraint-ranking algorithm for learning optimality-theoretic grammars. The purpose of this article is to assess the capabilities of the Gradual Learning Algorithm, particularly in comparison with the Constraint Demotion algorithm of Tesar and Smolensky (1993, 1996, 1998, 2000), which initiated the learnability research program for Optimality Theory. We argue that the Gradual Learning Algorithm has a number of special advantages: it can learn free variation, deal effectively with noisy learning data, and account for gradient well-formedness judgments. The case studies we examine involve Ilokano reduplication and metathesis, Finnish genitive plurals, and the distribution of English light and dark /l/.

Social Consequences of the Internet for Adolescents: A Decade of Research

Abstract: Adolescents are currently the defining users of the Internet. They spend more time online than adults do, and they use the Internet for social interaction more often than adults do. This article discusses the state of the literature on the consequences of online communication technologies (e.g., instant messaging) for adolescents' social connectedness and well-being. Whereas several studies in the 1990s suggested that Internet use is detrimental, recent studies tend to report opposite effects. We first explain why the results of more recent studies diverge from those of earlier studies. Then, we discuss a viable hypothesis to explain the recent findings: the Internet-enhanced self-disclosure hypothesis. Finally, we discuss some contingent factors that may deserve special attention in future research.

Pneumatic dilation versus laparoscopic Heller's myotomy for idiopathic achalasia.

Abstract: BACKGROUND Many experts consider laparoscopic Heller's myotomy (LHM) to be superior to pneumatic dilation for the treatment of achalasia, and LHM is increasingly considered to be the treatment of choice for this disorder. METHODS We randomly assigned patients with newly diagnosed achalasia to pneumatic dilation or LHM with Dor's fundoplication. Symptoms, including weight loss, dysphagia, retrosternal pain, and regurgitation, were assessed with the use of the Eckardt score (which ranges from 0 to 12, with higher scores indicating more pronounced symptoms). The primary outcome was therapeutic success (a drop in the Eckardt score to ≤3) at the yearly follow-up assessment. The secondary outcomes included the need for retreatment, pressure at the lower esophageal sphincter, esophageal emptying on a timed barium esophagogram, quality of life, and the rate of complications. RESULTS A total of 201 patients were randomly assigned to pneumatic dilation (95 patients) or LHM (106). The mean follow-up time was 43 months (95% confidence interval [CI], 40 to 47). In an intention-to-treat analysis, there was no significant difference between the two groups in the primary outcome; the rate of therapeutic success with pneumatic dilation was 90% after 1 year of follow-up and 86% after 2 years, as compared with a rate with LHM of 93% after 1 year and 90% after 2 years (P=0.46). After 2 years of follow-up, there was no significant between-group difference in the pressure at the lower esophageal sphincter (LHM, 10 mm Hg [95% CI, 8.7 to 12]; pneumatic dilation, 12 mm Hg [95% CI, 9.7 to 14]; P=0.27); esophageal emptying, as assessed by the height of barium-contrast column (LHM, 1.9 cm [95% CI, 0 to 6.8]; pneumatic dilation, 3.7 cm [95% CI, 0 to 8.8]; P=0.21); or quality of life. Similar results were obtained in the per-protocol analysis. Perforation of the esophagus occurred in 4% of the patients during pneumatic dilation, whereas mucosal tears occurred in 12% during LHM. Abnormal exposure to esophageal acid was observed in 15% and 23% of the patients in the pneumatic-dilation and LHM groups, respectively (P=0.28). CONCLUSIONS After 2 years of follow-up, LHM, as compared with pneumatic dilation, was not associated with superior rates of therapeutic success. (European Achalasia Trial Netherlands Trial Register number, NTR37, and Current Controlled Trials number, ISRCTN56304564.).