Clones identification of Sequoia sempervirens (D. Don) Endl. in Chile by using PCR-RAPDs technique

A protocol of polymerase chain reaction-random amplified polymorphic DNAs (PCR-RAPDs) was established to analyse the gene diversity and genotype identification for clones of Sequoia sempervirens (D. Don) Endl. in Chile. Ten (out of 34) clones from introduction trial located in Voipir-Villarrica, Chile, were studied. The PCR-RAPDs technique and a modified hexadecyltrimethylammonium bromide (CTAB) protocol were used for genomic DNA extraction. The PCR tests were carried out employing 10-mer random primers. The amplification products were detected by electrophoresis in agarose gels. Forty nine polymorphic bands were obtained with the selected primers (BG04, BF07, BF12, BF13, and BF14) and were ordered according to their molecular size. The genetic similarity between samples was calculated by the Jaccard index and a dendrogram was constructed using a cluster analysis of unweighted pair group method using arithmetic averages (UPGMA). Of the primers tested, 5 (out of 60) RAPD primers were selected for their reproducibility and high polymorphism. A total of 49 polymorphic RAPD bands were detected out of 252 bands. The genetic similarity analysis demonstrates an extensive genetic variability between the tested clones and the dendrogram depicts the genetic relationships among the clones, suggesting a geographic relationship. The results indicate that the RAPD markers permitted the identification of the assayed clones, although they are derived from the same geographic origin. Project (No. CONICYT-FONDEF PROYECT D01 I 1008) supported by the National Commission of Science and Research of Chile     

Acute intraocular pressure changes during isometric exercise and recovery: The influence of exercise type and intensity,and participant´s sex

ABSTRACT

We assessed the intraocular pressure (IOP) behaviour during a 1-minute period of isometric physical effort and the immediate 1-minute of recovery in the mid-thigh clean pull and squat exercises at three different intensities. Twenty physically active individuals performed the isometric mid-thigh clean pull and squat exercises at three intensities (0% [low-intensity], 25% [medium-intensity] and 50% [high-intensity] of the maximum isometric force). IOP was semi-continuously measured by rebound tonometry. There was a statistically significant effect of exercise intensity on IOP (p < 0.001, ?_p² = 0.416), observing that IOP increments were positively associated with exercise intensity. The mid-thigh clean pull and squat exercises did not demonstrate differences (p = 0.510), and also, no differences were observed between men and women (p = 0.683). The IOP changes during the isometric physical effort showed a positive linear behaviour in all conditions (r = 0.70 to 0.96). IOP returned to baseline levels after 8 seconds of recovery. Our data showed a progressive and instantaneous IOP increment during isometric exercise, which was positively associated with exercise intensity. IOP changes were independent on the type of exercise and participant´s sex. After exercise, IOP rapidly (≈ 8 seconds) returned to baseline levels.     

Preservice Science Teachers' Beliefs About Teaching and Learning: The Influence of K-12 Field Experiences

Teaching is a complex task shaped by many external and internal influences, including the beliefs held by individual teachers. This study sought an understanding of the impact of field experiences on the beliefs developed by preservice science teachers. The participants were students in an undergraduate science education methods course that involved observation and teaching experiences in K-12 classrooms. The data used in this qualitative study included drawings representing beliefs and in-depth interviews with selected participants. The findings indicate that beliefs focused on two key dualities: learning through experience and transmission and student-centered and teacher-centered instruction. The findings also suggest that field experiences both reinforce and challenge the beliefs held by preservice science teachers.     

Two teacher quality measures and the role of context: evidence from Chile

This research examines empirically the relationship between two measures of teacher quality: one based on professional standards and a second one using teacher value-added estimates. It also studies the extent to which teacher observable characteristics, such as teacher training variables, are associated to better performance on either of these measures and whether any of these two assessments is able to effectively measure teacher quality isolated from the effect of the context where teachers work. Context in this article is defined as any variable that is not under the direct control of the teacher but plays an important role on student learning and we believe is captured by school and municipal variables. The study uses hierarchical linear models and information from national and standardized assessments from Chile, specifically from the municipal education sector. Results show a small correlation between the two measures of teacher quality, in the lower end of results from previous studies conducted in the USA, and suggest that there is only a limited relationship between both measures of teacher quality. Teacher initial education type and professional development were statistically associated only to the standard-based measure of teacher quality. Context (both the school and municipal levels) plays an important role in the teacher effect measure, and in the standard-based measures, therefore, we conclude that neither of these measures are context-free. We expect that these results will contribute to the discussion about how to best measure teacher quality and how to evaluate teacher performance both in Chile and other parts of the world.     

Can educational engagement prevent Early School Leaving? Unpacking the school’s effect on educational success

There is growing evidence that school engagement, or more specifically disengagement, is a key indicator for predicting Early School Leaving. The aim of this article is to explore the impact of secondary schools in student (dis)engagement and subsequent opportunities to succeed in school. Drawing on data from a qualitative study in five secondary schools in Barcelona, the article discusses the role of school context in inhibiting or facilitating school engagement by exploring compositional effects, organisational and pedagogical practices, and teachers’ expectations. To do so a twofold perspective is adopted: firstly, we look at the main school features and their impact on students’ educational opportunities; and secondly, a systematic analysis of the dimensions of school engagement (behavioural, emotional and cognitive) is carried out. As a result, the article contributes to the identification of the most significant variables at school level that influence student engagement and their opportunities for school success.     

Assessing the effects of school‐wide Second Step implementation in a predominately English language learner,low SES,Latino sample

Because school violence is widespread, social and emotional competence must be targeted. Second Step is a social and emotional violence‐prevention curriculum that teaches prosocial skills and reduces aggressive behavior. The purpose of this study was to examine the effects of Second Step implementation on students (N = 403) in preschool through fourth grade who were predominately Latino, English language learners, and from families with low socioeconomic status. The data of 165 out of the 403 students were included in the present study. Analyses consisted of paired‐samples t‐tests to identify changes in social and emotional knowledge and behavioral and emotional risk. Results showed that there was a significant increase in both social and emotional knowledge and behavioral and emotional risk following the implementation of Second Step. These results are discussed with regard to previous and future research, limitations, and implications for school practice.     

Students’ conception of infinite series

This is a report of a study of students’ understanding of infinite series. It has a three-fold purpose: to show that students may construct two essentially different notions of infinite series, to show that one of the constructions is particularly difficult for students, and to examine the way in which these two different constructions may be built so that we may uncover ways to help students improve their understanding. The theoretical framework consists of action–process–object–schema theory and the specific model of conceptions in Balacheff’s theory of conception, knowing, and concept. Approaching the problem from these two different theoretical perspectives allows us to provide different and at the same time complementary explanations of observed phenomena. The two different infinite series constructions are, briefly stated, series as an infinite unending process of addition and series as a sequence of partial sums. Students are found to have difficulty building an understanding of series as a sequence of partial sums and thus tend to have difficulty in problem situations that require this interpretation. The study uses semi-structured interviews with 10 graduate students. The interviews explore situations that might give insight into students’ notion of the sequence of partial sums.     

Enhancing preschool children's vocabulary: Effects of teacher talk before,during and after shared reading

This observational study analyzed patterns of teacher extratextual talk as it occurs before, during, and after reading books to children, and the frequency and duration of teacher questioning by type (label, define, associate) on preschoolers’ receptive and expressive vocabulary knowledge. Over the course of 18 weeks, 13 teachers and 100 children participated in ninety 20-min small-group sessions of teacher-guided shared reading instruction. Teachers’ reading instruction was examined through videotaped observations using the Multi-Option Observation System for Experimental Studies (MOOSES™; Tapp, Wehby, & Ellis, 1995). Two findings, in particular, yielded relevant educational and theoretical implications. First, time spent after reading was significantly related to expressive vocabulary. However, question timing did not seem to matter in terms of receptive vocabulary outcomes. Second, duration of teacher association questioning was significantly related to receptive vocabulary outcomes while both frequency and duration of teacher vocabulary-related association-level questioning were related to expressive vocabulary. For receptive vocabulary, both vocabulary- and comprehension-related association-level questioning mattered. These findings complement the body of work demonstrating that engaging children in interactive shared reading that elicits their active participation is related to meaningful gains in children's language and literacy growth. Limitations of the study and directions for future research are discussed.     

Evaluating Continuing Resources: Perspectives and Methods from Science Librarians

Five science librarians share their experiences with the evaluation of continuing resources at an academic university and discuss implications caused by the evaluation process. Four of the authors were new to collection evaluations at the time of the Serial Evaluation Project. These new librarians faced many challenges, both personally and professionally, in dealing with the cancellation process. Although the differences in approaches to collection analysis are discussed somewhat, they are not a focus of the article.     

Planning as action research

Planning contains so much more than the written plan. Early in 2000, an invitation came from the Collaborative Action Research Network (CARN), to people experienced in action research who might want to help plan and present an action research event for elementary school science teachers in Venezuela, South America, in Autumn 2000. This article analyses the outcomes from planning and enacting the resulting workshop to show how planning can be the subject of action research. It goes on to show how planning and teaching interact in a multifaceted way towards technical, practical and emancipatory ends. Planning and teaching are best seen as conversation, a conversation that is both synchronous and asynchronous.