谈新世纪版实验教材对"方程"的处理

方程是初中代数中非常重要的内容 ,新世纪版教材在处理方程的内容时 ,突出了方程是表示现实世界中一类具有相等关系问题的数学模型、方程的一般性解法、方程的近似解、方程的应用以及方程与函数的联系等方面 ,强调发展学生的符号意识     

Looking back: reasoning and metacognition with narrative texts

This study explored the abilities of 5th, 8th, and 10th graders, and College students to reason logically about what they read. Both students’ metacognitive behavior (looking back at previously read text) and their performance on logical deduction questions were recorded and analyzed in a reading task. Conditional logic premises and deductive questions were embedded in three narratives containing premise information that was factual (True Story), contrary to fact (False Story), or unverifiable via common world knowledge (Neutral Story). The texts and questions were presented one sentence at a time on a computer screen; participants controlled the presentation of sentences. For answering the questions, three response tasks were devised. One task (labeled Generate) required readers to generate their own logical conclusions in response to deduction questions. Two tasks (labeled Valid and Invalid) required readers to evaluate logically valid or logically invalid conclusions drawn by story characters in the texts. Students in early and late adolescence looked back more when asked to evaluate logical conclusions than when asked to generate conclusions on their own; College students’ lookback frequencies were not significantly affected by response task, but were greater overall than those of younger students. With conditional forms requiring an uncertainty response (Affirmed Consequent and Denied Antecedent), readers looked back more when evaluating logically invalid conclusions than when evaluating logically valid ones. Readers of all ages were more likely to agree with story characters’ (valid) uncertain conclusions with the AC and DA forms than they were to disagree with story characters’ (invalid) certain conclusions to these forms. Both lookback frequency and performance on logic questions were lowest when readers were required to reason from contrary to fact premises.     

Effects of Exercise and Milk Consumption on Blood Serum Cholesterol in Rats

Abstract

This study investigated the effects of exercise on blood cholesterol and correlated those effects with estimates of body fat through experiments with 45 albino weanling rats (15 litter mate trios). The rats were confined to individual cages in a temperature-controlled room and fed a stock diet until they were 11 weeks old. At this time the trios were divided. Group A was continued on a stock diet and exercised for an hour in the morning and an hour in the afternoon by forced swimming. Group B was subjected to the same exercise but a portion of the stock diet was replaced with powdered whole milk, so that 30 percent of the caloric intake was derived from the whole milk supplement. Group C was fed the stock diet but activity was restricted. After 15 weeks blood samples were taken, the animals sacrificed, and the heart and adrenals weighed. The specific gravity of the carcass was also determined. Exercise resulted in a statistically significant decrease in total and free blood serum cholesterol concentration. These animals were also leaner and had larger hearts and adrenal glands. Serum cholesterol was negatively related to carcass specific gravity. The milk supplement had no significant effect on any of these measures. Several possible explanations for the effects of exercise on blood cholesterol are discussed.     

LENGTH OF SCHOOLING AND ITS EFFECT ON PERFORMANCE IN THE JUNIOR SCHOOL

Friendship patterns in an urban girls’ secondary comprehensive school with nearly 30 per cent immigrant pupils were studied by a sociometric technique. Pupils were found to choose their friends most frequently from their own ethnic groups, but this was more marked in the lower streams and older age groups than in the upper streams and younger age groups. In the upper streams and the sixth form some preference was found, but immigrant pupils tended to be well integrated with British girls in complex friendship groups.