Laboratory predictors of uphill cycling performance in trained cyclists     

Arthur Henrique Bossi  Pedro Lima  Jorge Perrout de Lima  James Hopker 《Journal of sports sciences》2017,35(14):1364-1371

ABSTRACT

This study aimed to assess the relationship between an uphill time-trial (TT) performance and both aerobic and anaerobic parameters obtained from laboratory tests. Fifteen cyclists performed a Wingate anaerobic test, a graded exercise test (GXT) and a field-based 20-min TT with 2.7% mean gradient. After a 5-week non-supervised training period, 10 of them performed a second TT for analysis of pacing reproducibility. Stepwise multiple regressions demonstrated that 91% of TT mean power output variation (W kg^?1) could be explained by peak oxygen uptake (ml kg^?1.min^?1) and the respiratory compensation point (W kg^?1), with standardised beta coefficients of 0.64 and 0.39, respectively. The agreement between mean power output and power at respiratory compensation point showed a bias ± random error of 16.2 ± 51.8 W or 5.7 ± 19.7%. One-way repeated-measures analysis of variance revealed a significant effect of the time interval (123.1 ± 8.7; 97.8 ± 1.2 and 94.0 ± 7.2% of mean power output, for epochs 0–2, 2–18 and 18–20 min, respectively; P < 0.001), characterising a positive pacing profile. This study indicates that an uphill, 20-min TT-type performance is correlated to aerobic physiological GXT variables and that cyclists adopt reproducible pacing strategies when they are tested 5 weeks apart (coefficients of variation of 6.3; 1 and 4%, for 0–2, 2–18 and 18–20 min, respectively).  相似文献   

Unveiling the Colours of Cellulose Nitrate Black and White Film-based Negatives in Colonial Photography     

Élia Roldão  A. Jorge Parola  Márcia Vilarigues  Bertrand Lavédrine 《文物保护研究》2020,65(2):118-126

ABSTRACT

Aiming at contributing to the preservation of black and white (B&W) film-based negatives held by Portuguese archives, four photographic collections from the first half of the twentieth century were selected for study. During the macro assessment of the collections the preservation condition and hues found in photographic negatives from the Elmano Cunha e Costa (ECC) were noticed, distinguishing this collection from the remaining ones. Additional attention was given considering that the ECC collection was formed in a colonial context in the 1930s, while the others were formed on the Portugal mainland. The ECC collection results from an ethnographic survey of Angolan tribes recorded with B&W film-based negatives. In this collection, sets of negatives with pink, lemon yellow, greenish, orange brownish, and red brownish hues were found. To identify the origin of such hues, the image layer was analysed by microscale energy-dispersive X-ray fluorescence (μ EDXRF) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). Additionally, to assess the base decay and its effect on the formation of hues, the plastic supports were characterized by Fourier transform infrared microscopy (μ FTIR). To complement the assessment of the film-base decay, pH was measured by using combined microelectrodes. The identification of mercury, iodine, chromium, and iron by μ EDXRF allowed correlation of the hues found in the negatives with chemical corrective treatments performed to improve the image quality. SEM-EDX confirmed those results and proved that the elements found were in the photographic emulsion layer. The results obtained are relevant since the hues identified may now be used as markers to indicate the technical work performed on colonial photography. Additionally, the visual and molecular assessment of the negatives’ supports (good to fair condition) allow proposing that the original storage conditions may have had a beneficial contribution to their present condition.  相似文献   

Educational decentralization policies in Argentina and Brazil: exploring the new trends     

Jorge M. Gorostiaga Derqui 《教育政策杂志》2013,28(6):561-583

This paper compares educational decentralization policies implemented in Argentina and Brazil during the 1990s, focusing on the rationales and contexts of the policies, and through a review of secondary sources and some official documents. The paper argues that school decentralization, the movement toward transferring functions and responsibilities to schools, appears as a new and extended reform that was accompanied by more traditional forms of decentralization, but also by a process of centralization of planning and evaluation at the national level. This new form of centralization/decentralization is seen as linked to the neoliberal restructuring of the state, to pressures from globalization processes and forces, and to various internal demands for improving quality and efficiency in the delivery of education.  相似文献   

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

Sandy Taut  Maria Verónica Santelices  Carolina Araya  Jorge Manzi 《Studies in Educational Evaluation》2011,37(4):218-229

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.  相似文献   

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

Ramón Zárraga  Jorge Cervantes  Carmen Salazar-Hernandez  George Wheeler 《Journal of Cultural Heritage》2010,11(2):138-144

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.  相似文献   

Modelling adult skills in OECD countries          下载免费PDF全文

Rosario Scandurra  Jorge Calero 《British Educational Research Journal》2017,43(4):781-804

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.  相似文献   

A conceptual framework to understand student volunteerism     

Cunha  Jorge  Mensing  Rainer  Benneworth  Paul 《Tertiary Education and Management》2019,25(1):31-44

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...  相似文献   

Identifying Temporary and Permanent Gaps in Universal Service     

Jorge Reina Schement  Scott C. Forbes 《The Information Society》2000,16(2):117-126

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.  相似文献   

Reframing Policy Discourse on the School-to-Prison Pipeline     

Sun  Wei-Ling  Valenzuela  Angela 《The Urban Review》2021,53(4):708-732

The Urban Review - This work selects a political cite in which the state policy reform occurs to examine reasons and underlying ideologies for some consensus on the debates regarding the need to...  相似文献   

Influence of different sports on bone mass in growing girls     

Esther Ubago-Guisado  Alba Gómez-Cabello  Javier Sánchez-Sánchez  Jorge García-Unanue  Leonor Gallardo 《Journal of sports sciences》2015,33(16):1710-1718

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.  相似文献