Stimulus sampling theory (SST: Estes, 1950, 1955a,b, 1959) was the first rigorous mathematical model of learning that posited a central role for an abstract cognitive representation distinct from the stimulus or the response. SST posited that (a) conditioning takes place not on the nominal stimulus presented to the learner, but on a cognitive representation caused by the nominal stimulus, and (...

A new tendency is emerging in cognitive science that pays attention to the possible commonalities between elementary processes of learning (such as classical or instrumental conditioning) and more complex inductive processes (like categorization or causality judgements) (see, e.g., Estes, 1985; Gluck & Bower, 1988; Holland et al., 1986; Pearce, 1988; Shanks & Dickinson, 1987; Schlimmer & Grange...

Um novo alcalóide denominado Helindicina (1), e o conhecido licopsamina (2) foram isolados das raízes de Heliotropium indicum (Boraginaceae). As estruturas foram estabelecidas tendo como base um amplo estudo de 1D e 2D RMN (COSY, HMBC, HMQC, NOESY) e HREIMS. Este representa o primeiro relato de um alcalóide contendo um anel lacônico no gênero Heliotropium. Estes alcalóides mostraram moderada at...

Do extrato etéreo das folhas de Vellozia candida Mikan (Velloziaceae) foram isolados os flavonóis 3',4',5,7-tetraidroxi-3,6-dimetoxi-8-metilflavona e 3’,4’,5-triidroxi-3,6,7-trimetoxi-8-metilflavona. Estes compostos foram identificados através de seus dados espectrais, incluindo RMN 2D e EMEM. O derivado 5-hidroxi-3,3’,4’,6,7-pentametoxi-8-metilflavona foi obtido por metilação usando diazometano.

old Dylan Salmon dropped him off at the house of Maryann Constantino. Dylan’s mother had located the provider, a 36-year-old mother, after an extensive search for child care. Her older daughter, Rachel, had been in Constantino’s care for 2 years before starting school. “This isn’t someone I just found in the phone book,” Salmon said. “I was careful to find someone I trusted and came recommended...

OBJECTIVE To review the accuracy of electrocardiography in screening for left ventricular hypertrophy in patients with hypertension. DESIGN Systematic review of studies of test accuracy of six electrocardiographic indexes: the Sokolow-Lyon index, Cornell voltage index, Cornell product index, Gubner index, and Romhilt-Estes scores with thresholds for a positive test of > or =4 points or > or =...