The Development and Application of Distance Learning Courses on the Internet

This paper presents the methodology, results and difficulties encountered in the development and delivery of a course through the Internet. The course, which is about the application of information technology to education, is being delivered using the AulaNet environment, which is groupware for the creation, participation and maintenance of Web-based courses. A model for group work is provided. This paper also shows how this kind of environment can be used to provide support, and to facilitate and manage cooperative learning.     

Detection of Misconceptions about Colour and an Experimentally Tested Proposal to Combat them

We study the misconceptions about colour that most people hold, determining the general phenomenological laws that govern them. Concept mapping was used to combat the misconceptions which were found in the application of a test specifically designed to determine these misconceptions, while avoiding the possible misleading inductions that could have arisen from the use of everyday language. In particular, care was taken to avoid the distorting effect that the use of the verb ‘to be’ applied to coloured objects could have on the responses. The misconceptions found were shown to have an internal consistency in the form of authentic mini-theories (implicit theories). We compared experimentally the results of two different teaching methods applied to combat these misconceptions. This study was conducted with 470 undergraduates of the University of Extremadura. We analysed the persistence over time of their learning made to overcome those misconceptions. The students were divided randomly into an experimental group (EG) and a control group (CG). To combat their misconceptions, EG were taught following a method based on the use of concept maps, and CG were taught following traditional teaching methods. The results of a pre-test and a post-test were compared for the two groups, finding statistically significant differences. The results allowed the principal working hypothesis to be accepted—concept maps are learning tools which foster conceptual change and allow misconceptions to be eradicated via meaningful learning maintained over time, i.e. EG acquired a relative long-lasting gain in learning that was superior to that acquired by CG.     

La Ola Latina: Recent Scholarship in Latina/o and Latin American Rhetorics

For generations, critics have dismissed James Forman's “Black Manifesto” as a rhetorical failure. Such judgments tend to focus on the prophetic and retributive registers of the speech and fail to account for the full range of its ironic structuration. By examining the complex interchange of prophetic, retributive, and tragic registers through which the “Manifesto” is constructed, we can more fully appreciate how Forman created a space for his auditors to reflect and redirect the vengeful and violent sociohistorical drama seemingly otherwise implied. At the same time, it helps to explain why some black auditors embraced the leadership role Forman directed them to assume, while many whites reviled the supporting role to which they were consigned. Interpreting the speech in terms of the interplay of its multiple ironic registers invites us to focus attention on the ways in which ironic protest rhetoric operates in dialogue, holding both the ironist and the audience accountable for the productivity of their encounter.     

Single cell rheometry with a microfluidic constriction: Quantitative control of friction and fluid leaks between cell and channel walls

We report how cell rheology measurements can be performed by monitoring the deformation of a cell in a microfluidic constriction, provided that friction and fluid leaks effects between the cell and the walls of the microchannels are correctly taken into account. Indeed, the mismatch between the rounded shapes of cells and the angular cross-section of standard microfluidic channels hampers efficient obstruction of the channel by an incoming cell. Moreover, friction forces between a cell and channels walls have never been characterized. Both effects impede a quantitative determination of forces experienced by cells in a constriction. Our study is based on a new microfluidic device composed of two successive constrictions, combined with optical interference microscopy measurements to characterize the contact zone between the cell and the walls of the channel. A cell squeezed in a first constriction obstructs most of the channel cross-section, which strongly limits leaks around cells. The rheological properties of the cell are subsequently probed during its entry in a second narrower constriction. The pressure force is determined from the pressure drop across the device, the cell velocity, and the width of the gutters formed between the cell and the corners of the channel. The additional friction force, which has never been analyzed for moving and constrained cells before, is found to involve both hydrodynamic lubrication and surface forces. This friction results in the existence of a threshold for moving the cells and leads to a non-linear behavior at low velocity. The friction force can nevertheless be assessed in the linear regime. Finally, an apparent viscosity of single cells can be estimated from a numerical prediction of the viscous dissipation induced by a small step in the channel. A preliminary application of our method yields an apparent loss modulus on the order of 100 Pa s for leukocytes THP-1 cells, in agreement with the literature data.     

Age-related differences in repeated-sprint ability in highly trained youth football players

Abstract

In this study, we investigated the age-related differences in repeated-sprint ability and blood lactate responses in 134 youth football players. Players from the development programme of a professional club were grouped according to their respective under-age team (U-11 to U-18). Following familiarization, the participants performed a repeated-sprint ability test [6 × 30-m sprints 30 s apart, with active recovery (2.0–2.2 m · s^?1) between sprints]. The test variables were total time, percent sprint decrement, and post-test peak lactate concentration. Total time improved from the U-11 to U-15 age groups (range 33.15 ± 1.84 vs. 27.25 ± 0.82 s), whereas no further significant improvements were evident from U-15 to U-18. No significant differences in percent sprint decrement were reported among groups (range 4.0 ± 1.0% to 5.5 ± 2.1%). Post-test peak lactate increased from one age group to the next (range 7.3 ± 1.8 to 12.6 ± 1.6 mmol · l^?1), but remained constant when adjusted for age-related difference in body mass. Peak lactate concentration was moderately correlated with sprint time (r = 0.70, P > 0.001). Our results suggest that performance in repeated-sprint ability improves during maturation of highly trained youth football players, although a plateau occurs from 15 years of age. In contrast to expectations based on previous suggestions, percent sprint decrement during repeated sprints did not deteriorate with age.     

Prediction of adult height in girls: The Beunen-Malina-Freitas method

Abstract

The purpose of this study was to validate and cross-validate the Beunen-Malina-Freitas method for non-invasive prediction of adult height in girls. A sample of 420 girls aged 10–15 years from the Madeira Growth Study were measured at yearly intervals and then 8 years later. Anthropometric dimensions (lengths, breadths, circumferences, and skinfolds) were measured; skeletal age was assessed using the Tanner-Whitehouse 3 method and menarcheal status (present or absent) was recorded. Adult height was measured and predicted using stepwise, forward, and maximum R ² regression techniques. Multiple correlations, mean differences, standard errors of prediction, and error boundaries were calculated. A sample of the Leuven Longitudinal Twin Study was used to cross-validate the regressions. Age-specific coefficients of determination (R ²) between predicted and measured adult height varied between 0.57 and 0.96, while standard errors of prediction varied between 1.1 and 3.9 cm. The cross-validation confirmed the validity of the Beunen-Malina-Freitas method in girls aged 12–15 years, but at lower ages the cross-validation was less consistent. We conclude that the Beunen-Malina-Freitas method is valid for the prediction of adult height in girls aged 12–15 years. It is applicable to European populations or populations of European ancestry.     

Effect of different inter-repetition rest intervals across four load intensities on velocity loss and blood lactate concentration during full squat exercise

ABSTRACT

This study aimed to analyze the acute effect of inter-repetition rest (IRR) intervals on mechanical and metabolic response during four resistance exercise protocols (REPs). Thirty resistance-trained men were randomly assigned to: continuous repetitions (CR), 10 s (IRR10) or 20 s (IRR20) inter-repetition rest. The REPs consisted of 3 sets of 6, 5, 4 and 3 repetitions against 60, 70, 75 and 80% 1RM, respectively, in the full squat exercise. Muscle fatigue was assessed using: percentage of velocity loss over three sets, percentage of velocity loss against the ~1 m·s^?1 load (V1 m·s^?1), and loss of countermovement jump (CMJ) height pre-post exercise. Blood lactate was measured before and after exercise. The percentage of velocity loss over three sets and lactate concentration were significantly lower (P < 0.05) for IRR groups compared to CR in all REPs. The CR group showed a significantly higher (P < 0.05) velocity loss against V1 m·s^?1 load and loss of CMJ height pre-post exercise than IRR groups in REP against 60% 1RM. In conclusion, both IRR groups produced a significant lower degree of fatigue compared to CR group. However, no significant differences were found in any measured variables between IRR configurations.