Secondary students’ modelling conceptualisation in situations related to particle dynamics: a clinical perspective

This study investigates the modelling conceptualisation of secondary school students in two situations related to particle dynamics: pendulum’s motion and horizontal motion. We performed in-depth clinical interviews with secondary school students (N?=?10). Participants’ ideas about properties which are not ‘given’ in empirical observations were explored in order to investigate signs of abstractions and idealisations in their reasoning processes. We proposed contributions to modelling in science education based on Mario Bunge’s epistemology and we employed his basic concepts as the axis to analyse our results: (1) abstractions and idealisations, considered as thought processes required to build conceptual counterparts of concrete objects; (2) theoretical models, meaning hypothetico-deductive systems concerning those conceptual objects; and (3) general theoretical frameworks that allow us to derive those theoretical models. We developed our analysis viewing the ideas presented by participants as concepts-in-action and theorems-in-action as regarded by Gérard Vergnaud’s Theory of Conceptual Fields. Results indicated a gradation in the concepts-in-action mobilised in terms of levels of idealisation and showed that participants do not spontaneously recognise the use of a general theory as a possible way to obtain a theoretical model. These results suggest that science education practices must pay better attention to make abstractions and idealisations explicit in scientific concepts formation, as well as to the heuristic role of theories in model construction.     

Consolidating properties of Regalrez 1126 and Paraloid B72 applied to wood

This study is aimed at an assessment of the properties of two polymeric products applied to Norway spruce (Picea abies) and White poplar (Populus alba) wood species. It contributes to ongoing research experiments on the consolidating properties of two synthetic resins and their potential synergic action on wood, resulting from their different interaction with the substrate: Paraloid B72 and Regalrez 1126. Experiments were carried out on a series of samples of the two wood varieties. The consolidants were applied alone and one after the other, with one coat of Regalrez and then one of Paraloid. Porosity and variations in pore size distribution were ascertained by mercury intrusion porosimetry (MIP). Colorimetric and IR spectroscopic measurements were also taken before and after aging by solar radiation and freeze/thaw cycles, to verify the possible slowing of photodegradation of the treated wood and the consolidating resistance. Results confirm that both products penetrate the wood with a different behaviour. After double treatment with Regalrez + Paraloid, a significant advantage was observed in terms of mechanical resistance and pore size distribution, although no advantages as regards resistance to photo-oxidizing processes or colour changes were observed.     

Cultural goods, cultivation of taste, satisfaction and increasing marginal utility during vacations

This paper analyzes the link between cultivation of taste and tourist satisfaction during vacations. A simple model shows that, when cultural capital accumulation matters, customers are ready to sacrifice some of their current utility in order to get higher returns in future, and therefore, the relation between satisfaction and the demand for cultural goods may be convex. On the contrary, when cultivation of taste comes from learning by consuming behavior, the relation is concave. An analysis based on 1,749 interviews in Aosta Valley in Summer 2008 provides some evidence in favor of the cultural capital accumulation hypothesis.     

Development,construct validity and test–retest reliability of a field-based wheelchair mobility performance test for wheelchair basketball

The aim of this study was to develop and describe a wheelchair mobility performance test in wheelchair basketball and to assess its construct validity and reliability. To mimic mobility performance of wheelchair basketball matches in a standardised manner, a test was designed based on observation of wheelchair basketball matches and expert judgement.

Forty-six players performed the test to determine its validity and 23 players performed the test twice for reliability. Independent-samples t-tests were used to assess whether the times needed to complete the test were different for classifications, playing standards and sex. Intraclass correlation coefficients (ICC) were calculated to quantify reliability of performance times.

Males performed better than females (P < 0.001, effect size [ES] = ?1.26) and international men performed better than national men (P < 0.001, ES = ?1.62). Performance time of low (≤2.5) and high (≥3.0) classification players was borderline not significant with a moderate ES (P = 0.06, ES = 0.58). The reliability was excellent for overall performance time (ICC = 0.95).

These results show that the test can be used as a standardised mobility performance test to validly and reliably assess the capacity in mobility performance of elite wheelchair basketball athletes. Furthermore, the described methodology of development is recommended for use in other sports to develop sport-specific tests.     

Ammonium oxalate treatment: Evaluation by μ-Raman mapping of the penetration depth in different plasters

This study is focused on the evaluation by μRaman mapping of the penetration depth achieved by ammonium oxalate treatment in different plaster specimens, a hot issue in the conservation field. The role of the carbonatic aggregate particles and the influence of the different variables of the treatment on the penetration depth and on the distribution of the newly-formed phase (whewellite) have been ascertained. Based on the results of μRaman mapping, analyses with Field Emission Scanning Electron Microscopy have been carried out in order to observe the whewellite crystals and the carbonatic aggregate particles involved in the reaction with ammonium oxalate.     

中国未来原油进口的多元化分析

本文从降低供应风险的角度,对2020年前我国原油进口结构的优化路径进行了定量分析。并且为应对伊朗原油出口的减少提出了数量化的政策建议。研究结论显示,由于我国对世界原油的需求将会持续旺盛,在未来几年内,我国需要大量增加从俄罗斯、科威特、阿联酋、卡塔尔、墨西哥及阿尔及利亚等传统产油国的进口,同时减少对沙特阿拉伯、安哥拉、苏丹和伊朗的原油依赖。从未来原油进口的地区分布上看,中东地区依然是我国原油进口的主要来源地,同时也是供应风险最大的地区。为应对伊朗石油禁运,我国应该增加从加拿大、墨西哥、尼日利亚和卡塔尔等国的原油进口来弥补供应缺口,并满足国内快速增长的原油消费需求。