Perceived effects and uses of the national teacher evaluation system in Chilean elementary schools

This paper addresses the perceived consequences of the Chilean national teacher evaluation system. We interviewed 57 school leaders in 30 schools across 10 municipalities about effects and uses of the assessment in their schools. Results show that in the large majority of schools our interviewees observe positive effects such as increased teamwork and internal reflection processes based on the assessment results. Reports about effects at teacher level far outnumber institutional effects, and are mixed. In all schools our interviewees report on teachers’ negative emotions and work overload due to the assessment process, but also about their internalization of the underlying professional standards. The paper analyzes differences among schools and offers suggestions for the development of large-scale standardized teacher evaluation systems.     

Modelling adult skills in OECD countries

Research in the social sciences has focused extensively on the relationship between family background, educational attainment and social destination, on the one hand, and on the processes of skills creation and skills use, on the other. This paper brings these two branches of the literature together by examining the correlation between a range of social factors. The methodology we adopt provides a comprehensive approach to the study of the channels through which literacy skills are acquired, taking into account the interrelation of family background, educational attainment, and the use of skills at work and at home. We use the Programme of International Assessment of Adult Competences (PIAAC) dataset and apply a structural equation model (SEM). Our results show that family background and education play an important role in the configuration of adult skills and skill practices. Unequal family access to resources has a strong impact at later stages in life and strongly affects educational attainment and skills outcomes. Additionally, skills use has a positive and direct impact on adult skills.     

A conceptual framework to understand student volunteerism

Tertiary Education and Management - This paper develops a conceptual framework to understand the value of an increasing number of university study programmes that send students to the global south...     

An analysis of question asking on scientific texts explaining natural phenomena

This article relays results of a study focused on questions invoked to correct declarative knowledge deficits while readers process science texts explaining natural phenomena. Firstly, the authors focused on finding out what kind of questions are asked by students who read these texts and, secondly how task demand influences quantity and quality of formulated questions. Two hundred and eighty nine Portuguese students from 8th, 10th, and 12th grade participated in the study. The students were instructed to ask questions on two short science paragraphs that explained natural phenomena. Three task conditions were chosen. Thus, in the “Class” condition, the task was introduced as an activity aimed at developing the capacity to ask questions. In the “Examination” condition, the task was presented as a test on question generation. Finally, in the “Extra‐academic” condition the questioning task was camouflaged as a participation in a research project sponsored by the Ministry of Education and geared at the improvement of science textbooks. The results have shown that students are able to ask many questions when given an opportunity to do so. The study has also proven that students are capable of generating a large volume of causal‐antecedent questions relative to this kind of texts. Finally, no clear effects were found between grade level and/or task demand as defined in the conducted study. © 2000 John Wiley & Sons, Inc. J Res Sci Teach 37: 602–614, 2000     

Effect of the addition of hydroxyl-terminated polydimethylsiloxane to TEOS-based stone consolidants

Hybrid stone consolidants prepared from tetraethoxysilane (TEOS) and α,ω-hydroxyl-terminated polydimethylsiloxane (PDMS-OH) have been considered as one of the most promising approaches to improve the effectiveness of traditional alkoxysilane-based formulations. They have emerged as response to the negative reports commonly found in the literature: the resulting silica gel phase (SiO₂) tends to develop fractures and fissures inside the stone as the gel shrinks during the drying stage. In this work, we employed SEM, solid-state ²⁹Si NMR spectroscopy and compressive tests to characterize SiO₂-PDMS hybrid gels. We report the morphological characteristics exhibited by gels prepared in vitro and in situ. It was found an appreciable reduction of gel fracture for hybrids prepared from 5% w/w of PDMS. As TEOS polycondenses, PDMS-OH is chemically incorporated into the gel matrix via Si-O-Si bonds. The inclusion of these elastic chains provides the necessary flexibility to resist the stress imposed by capillary pressure. Additionally, an important hydrophobic character is imparted to the stone.     

Identifying Temporary and Permanent Gaps in Universal Service

This article examines the nature of the gap in household telephone penetration among Whites, Blacks, and Hispanics. By analyzing historic and current penetration levels of the radio, television, and telephone, it suggests that most information technology gaps are amalgamations of smaller socioeconomic trends and can be discerned and reduced only with careful historical analysis of both technology choices and living patterns. It proposes localized universal service strategies, since the penetration gaps are affected by a complex array of factors more particular to localities than to the country as a whole and as such must be investigated with rigor and caution if progress toward the elimination of penetration gaps is to occur.     

Influence of different sports on bone mass in growing girls

The aim of this study was to analyse whether there are differences in bone mass in girls playing different sports. Two hundred girls (10.6 ± 1.5 years old, Tanner stages I–III) participated in the study and were divided into groups of 40 (swimmers, soccer players, basketball players, handball players and controls). Bone mineral content and bone mineral density (BMD) (whole body and hip) were measured using dual-energy X-ray absorptiometry. The degree of sexual development was determined using Tanner test, and physical activity habits were recorded through a questionnaire designed ad hoc for this research. Girls were divided by pubertal stage and the type of sport. In the prepubertal group, intertrochanteric BMD was significantly higher in both handball and soccer players compared with the control group (P < 0.05). Furthermore, in the pubertal group, total BMD, mean arms BMD, pelvis BMD, femoral neck BMD, intertrochanteric BMD and Ward’s triangle BMD were significantly higher in soccer and handball players compared with the control group (P < 0.05), and the swimmers showed significantly higher values in the mean arms BMD compared with the control group (P < 0.01). Our data suggest that sport practice during puberty, especially in activities that support the body weight, may be an important factor in achieving a high peak bone mass and improving bone health in girls.     

随机扩增多态性DNA技术研究发现二氧化钛纳米颗粒对西葫芦具有基因毒性

研究目的：二氧化钛（TiO2）纳米颗粒已经广泛应用于化妆品、防晒霜、涂料和牙膏等。这些纳米颗粒性质非常稳定,能在废水和生物固体中转移和分散。现有研究表明,TiO2纳米颗粒对动物正常生理活动具有毒性等负面作用。但是,它们对植物是否具有毒性特别是是否会产生植物基因毒性至今尚不清楚。因此,本文使用随机扩增多态性DNA技术研究TiO2纳米颗粒是否对西葫芦具有基因毒性,为TiO2纳米颗粒排放进入环境后的潜在植物毒性风险评价提供依据。 创新要点：首次发现了TiO2纳米颗粒对西葫芦具有基因毒性。 重要结论：采用随机扩增多态性DNA技术,发现TiO2纳米颗粒污染处理的西葫芦样品与未处理样品的基因组DNA图谱相比,不仅在谱带强度有明显差异,而且存在谱带消失和新谱带产生现象,表明TiO2纳米颗粒对西葫芦具有基因毒性。     

An empirical investigation of mobile government adoption in rural China: A case study in Zhejiang province

This study is among the first attempts to empirically investigate the adoption of mobile government by rural populations in developing economies. Based on 409 validated questionnaires collected from families living in rural China, the study examines the interdependences among rural inhabitants' demographic attributes, their access to and perceptions of mobile government, and quantifies how their intention to use mobile government is influenced by technology attributes, social factors and trust beliefs. The results indicate that young males, who live far from a village center or market, and have some knowledge of recent government policies, tend to have a more positive perception of mobile government, and therefore become potential adopters of the service. Perceived ease of use, near-term usefulness, long-term usefulness, integrity, benevolence, image and social influence have significant and positive influences on the intention to use mobile government. Specifically, perceived ease of use, long-term usefulness and social influence have a direct influence on intention to use, while perceived near-term usefulness, integrity, benevolence and image have an indirect influence.     

Discrete-time modeling and control of a boost converter by means of a variational integrator and sliding modes

This work deals with the discrete-time modeling of a boost DC-to-DC power converter by means of a discrete Lagrangian formulation based on the midpoint rule integration method. Then in the basis of this model, a discrete-time sliding mode regulator is designed in order to force the boost circuit to track a DC-biased sinusoidal signal. Simulations and experimental tests are carried on where the great performance of the proposed methodology is verified.