零度以下融化

今年第一次天气预报提醒人们由于寒潮将至，每一个家庭应注意防护最容易受到损坏的水管。人们知道防止水管中的水冷凝可以避免水由液态转变为固态的过程中膨胀造成的破坏。但是许多人并不知道他们同时也防止了因为冰的表面仍保持液态而产生的一种更大的压力。     

Student use of out-of-class study groups in an introductory undergraduate biology course

Self-formed out-of-class study groups may benefit student learning; however, few researchers have quantified the relationship between study group use and achievement or described changes in study group usage patterns over a semester. We related study group use to performance on content exams, explored patterns of study group use, and qualitatively described student perceptions of study groups. A pre- and posttest were used to measure student content knowledge. Internet-based surveys were used to collect quantitative data on exam performance and qualitative data on study group usage trends and student perceptions of study groups. No relationship was found between gains in content knowledge and study group use. Students who participated in study groups did, however, believe they were beneficial. Four patterns of study group use were identified: students either always (14%) or never (55%) used study groups, tried but quit using them (22%), or utilized study groups only late in the semester (9%). Thematic analysis revealed preconceptions and in-class experiences influence student decisions to utilize study groups. We conclude that students require guidance in the successful use of study groups. Instructors can help students maximize study group success by making students aware of potential group composition problems, helping students choose group members who are compatible, and providing students materials on which to focus their study efforts.