Documents found
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2953.More information
AbstractThis article presents the results of a study of the way teachers of French conceptualize instructional content as related to classroom interaction. Specifically, teacher's perceptions of the management of their interactions was mediated through a verbal report on planning. Improvisation is reported to be a frequent behavior adopted by teachers in their responses to students' reactions. Instructional planning is mostly mental and emphasizes functional connections: content aspects are related to each other according to the needs of students. At the cognitive level, teacher planning seems to be the result of an accomodation between the instructional organizers and the potentially disorganizing aspects of the context. These descriptive results, supported by numerous excerpts, corroborate results noted in other disciplines and thus attain a certain level of generalisability.
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2954.More information
The multiple conceptualizations of learning assessment have led to a wide variety of practices, and it is difficult to determine which ones promote student learning. The purpose of this research is to attempt to identify best practices in formative assessment in the context of elementary and secondary education. A systematic review, which identified and analyzed 35 articles, revealed five practices that are recognized as being effective in promoting student learning in the classroom. Two other practices appear promising but require further research. Implications for policies, practices and research are discussed.
Keywords: pratiques évaluatives, évaluation des apprentissages, évaluation formative, données probantes, enseignement primaire et secondaire, assessment practices, assessment of learning, formative assessment, evidence, elementary and secondary education, prácticas evaluativas, evaluación de los aprendizajes, evaluación formativa, datos probatorios, enseñanza primaria y secundaria
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2955.More information
The rotifer and cladoceran communities of a small tropical eutrophic lake (the municipal lake of Yaoundé, Cameroon) were examined from November 1996 to December 1997, in relation to some physical and chemical variables. Using a Van Dorn bottle, water samples were collected weekly from 5 depths (0 m, 0.5 m, 1 m, 1.5 m and 2.5 m) at three stations (I, II and III) representing the upper, middle and lower parts of the lake, respectively. Water temperature was measured with a thermometer placed in the sampling bottle and pH was measured in the field with a portable pH-meter. Oxygen concentrations were determined according to the Winkler method. Water colour, suspended solids, and ammonium-nitrogen (NH4 -N) were analyzed spectrophotometrically using standard methods. The transparency of the water column was determined with a Secchi disk. Zooplankton species were identified alive under a phase contrast microscope using several manuals, and rotifers and cladocerans were counted in a Dolfuss chamberThroughout the study, temperature and pH values of the water remained around 25°C and 7, respectively. The Secchi disk transparency did not exceed 1 m and the dissolved oxygen concentration decreased with depth to almost zero in the bottom waters. Spatial and temporal variations of these variables indicated that the middle zone (0.5 and 1.5 m) was the stratum with a critical role in the functioning of the lake. Indeed, it represented the transition zone between the trophogenic upper water layer (0 to 0.5 m) where photosynthetic activity occurred and the bottom water layer (1.5 to 2.5 m) formed by the microaerophilic to anaerobic tropholitic layer where reducing processes were important.The rotifer and cladoceran communities were relatively diverse, with 41 species collected during the study year (i.e., 26 species of Brachionidae and Trichocercidae and 15 species of Cladocera), of which 16 are reported for the first time in Cameroon. These organisms filter small organic particles (fresh algal detritus and bacteria) and their presence in the lake could be related to the relatively high algal biomass found there. In terms of relative abundance, rotifers appear to be more important than cladocerans. Among the quantitatively dominant species, the most frequent ones were the Brachionidae (Brachionus angularis angularis, B. falcatus falcatus, B. calyciflorus), the Trichocercidae (Trichocerca elongata elongata and T. bicristata bicristata) and the Cladocera (Ceriodaphnia cornuta and Chydorus eurynotus).Brachionus angularis was the most abundant and frequent rotifer observed during this study. According to several authors, a high abundance of Brachionus can be considered as a biological indicator of more eutrophic waters. This corroborates the hypereutrophic status assigned to the lake through previous studies dealing with bacterioplankton and phytoplankton in this system. Among Cladocera, Daphnia, an important bacterivore, was absent despite the high density of bacteria (~108 cell mL-1) in the lake. Previous studies in other Cameroonian aquatic systems reported the scarcity of Daphnia and these earlier authors argued that it was probably replaced by smaller sized species, which in the case of the present study would be Ceriodaphnia cornuta and Moina micrura, the only representatives of Daphniidae encountered. Up to 75% of the number of species identified were periphytic species that generally develop in the littoral zone. The massive occurrence of these species in the plankton sample of the lake was related to the high particle content. Abundance generally peaked in the middle zone of the water column, likely due to the availability of resources and the general potential for such zones to provide a refuge from predation.However, there did not appear to be any correlation between the rotifer and cladoceran communities and physico-chemical variables when the data set was examined as whole, or grouped by seasons. This suggests that the heterogeneity in species abundances was controlled by other factors, among them sampling points, depths and time of sampling. A multivariate test using canonical correspondence analysis suggested that about 3% and 5% of the variance associated with the species abundance heterogeneity could be explained by sampling point and depth, respectively. Up to 36% of this variance was attributed to the sampling months. We therefore hypothesize that the environmental conditions affecting the development and biological cycles of the studied species are highly dependent on the prevalent seasons found in a tropical zone, i.e. the rainy and the dry seasons.
Keywords: Brachionidae, Trichocercidae, cladocères, diversité spécifique, lacs tropicaux, dynamique saisonnière, Brachionidae, Trichocercidae, Cladocera, species diversity, tropical lakes, seasonal dynamics
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2956.More information
Metallothionein (MT), an intracellular metal binding protein, is recognized for its role in the regulation of essential and non-essential trace metals. The mechanisms of synthesis of this protein have been studied in the laboratory but much less work has been carried out in the field, particularly in lotic environments. According to the literature, metallothionein protects tissues from metal damage, and may be used as a direct measure of the biochemical state of the affected tissue. Metallothionein shows high affinity for group IB and IIB metals ions (e.g. Cd, Cu, Zn), and consequently can sequester and detoxify metals. The use of MT as a biomarker for elevated levels of trace metals in aquatic environments has therefore been proposed as a tool in ecotoxicological studies. Changes at the biochemical level offer distinct advantages as biomarkers, since molecular alterations are normally the first detectable responses to environmental changes.The present study focused on two objectives, the first of which was to identify which trace metals (silver "Ag", cadmium "Cd", copper "Cu", nickel "Ni", lead "Pb" and zinc "Zn") may induce MT synthesis in three sentinel species collected in two northern Quebec rivers (Colombière River, close to Val d'Or, and Matagami River close to the town of Matagami) in a mining region (Abitibi, Québec). The three sentinel species were the adult bivalve Pyganodon grandis, the larval mayfly Hexagenia limbata, and the adult great northern pike Esox lucius. The second objective was to define variables that could influence the uptake of these trace metals and consequently the concentrations of MT in the sentinel species. The selection of these sentinel species was based on the following criteria: their relative abundance in the aquatic systems studied; their relative immobility; the ease of sampling; metal tolerance; metal bioaccumulation capacity; dynamics of metal accumulation; capacity to synthesize metallothionein; and availability of physiological and behavioural data.In 2001, physico-chemical conditions (e.g.: temperature, oxygen, transparency, phosphorus, chlorophyll a, etc.) were monitored during two sampling campaigns at 21 stations. Trace metals were measured in water and sediment in all stations, and in tissues of the sentinel species that were collected when present at the station (P. grandis - gills; H. limbata - whole body; E. lucius - kidney). Dialysis cells were used to collect water samples for the determination of concentrations of total dissolved metals, major anions and cations, humic and fulvic acids, and dissolved organic carbon. At each sampling site, divers collected three replicate sub-samples from two sediment cores for metal analyses. The cores were extruded in the boat and samples taken from the uppermost 0.5 cm, i.e. from the oxidized layer.The two rivers differ in their morphometry, their physico-chemistry, and their biology. The Allard River is larger (200 m vs. 7 m) and deeper (30 m vs. 3 m) than the Colombière River. The Colombière River is slightly more acid (pH: 6.2 - 6.7) and less productive (14 - 32 µg total P L-1) than the Allard River (pH: 6.7 - 7.4; 24 - 45 µg total P L-1). However, the rivers present some similarities such as slow current conditions and limited water transparencies. The range of Ag, Cu and Ni concentrations in water and sediment was greater in the Colombière River, whereas Pb concentrations were higher in the Allard River and Cd concentrations were similar in the two rivers. Zinc was the dominant metal in both rivers, but variations were more significant in water in the Colombière River. Although trace metal and MT concentrations were highly variable among species, stations and rivers, no consistent spatial gradients were detected in animals collected downstream from mining activities.As was the case for the ambient environment, Zn was also the dominant metal in organisms of both rivers. Zinc concentrations were similar in mayflies from the two rivers, but higher in molluscs and lower in pike collected from the Colombière River than in comparable animals from the Allard River. Following Zn, Cu was the second metal in importance in species from the two rivers, whereas the concentrations of Ag were low in all organisms and were undetectable in pike. Cadmium was more concentrated in mayflies and molluscs from the Colombière River than in those from Allard River, and also higher in the pike collected in the contaminated zone of the Colombière River. The concentrations of Ni in all species were comparable between rivers, but were more elevated in mayflies than in the other sentinel species.The range of Pb concentrations was comparable between rivers for all species, but concentrations were lower in the pike (kidney). The concentration of MT was higher in the pike than in the two other species. Mayflies had higher MT levels in the Allard River, while MT concentrations were higher in molluscs of the Colombière River. The relationships between metals and MT were very variable between rivers and species. Nevertheless, MT concentrations were most strongly related to those of accumulated Cd in the three sentinel species. The relationships between MT and Cd for all three species were stronger in the Allard River than in the Colombière River. In the case of P. grandis, because the number of stations where the bivalves could be collected from the Colombière River was low (n=4), no statistically significant relationship was observed between MT and Cd in the tissues, in spite of the high correlation coefficient (r=0.98). For the bivalves, manganese (Mn) concentrations in the sediment were negatively correlated with accumulated Cd concentrations and with MT levels. In H. limbata, in addition to Cd, other metals such as Cu (-) and Zn (+) also exhibited weak relationships with MT. Finally, in bivariate analyses, Pb concentrations in pike liver were significantly correlated with those of MT in this species, but based on multiple regression models, no variable other than Cd affected the level of MT in E. lucius.
Keywords: Métaux traces, cadmium, métallothionéine, éphémère, mollusque, bivalve, brochet, Trace metals, cadmium, metallothionein, mayfly, bivalve mollusc, pike
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2957.More information
Very few studies have ever focused on the thermal balance of a wastewater treatment process, despite its major impact on various aspects of sanitary engineering, such as biological growth, oxygen transfer and, most importantly, purification kinetics. This lack of knowledge is particularly worrying for the design of aerated lagoons and waste stabilization ponds, since these two extensive treatment technologies are extremely dependent on climatic conditions and subject to high thermal variations. In temperate regions, a pond annual temperature range can even exceed 20 °C, while a 10 °C variation will induce a more than 60% drop or increase in its removal yield. Our paper intends to present a comprehensive temperature prediction model which accounts for the main heat loss and gain terms exchanged through the pond surface and walls.Our approach includes six different energy inputs and outputs, namely: solar radiation, air-water surface convection, atmospheric radiation, back surface radiation, evaporation and ground-water-walls convection. Each of these components was described extensively by means of a literature review of all previous efforts made to predict equilibrium temperature in lakes, rivers, salt-gradient solar ponds, cooling tanks, even outdoor pools. The best aspects of each prediction model were then incorporated into a new computer model developed as two different but complementary variants: one for steady-state conditions and the other for continuous and therefore also transient simulations. The main difference between these two approaches is that the first one neglects enthalpy variation while the second one takes the form of a differential equation, with basin temperatures being estimated by an iterative calculation procedure and a numerical integration method, respectively.Two hypotheses were necessary to develop this model. The first one posits that pond hydrodynamics correspond to completely mixed conditions. Such hydraulic behavior is extremely frequent in aerated lagoons and waste stabilization ponds in temperate climates, but less so in tropical or Mediterranean regions, where thermal balances appear much more complex since stabilization ponds are often thermally stratified. The second hypothesis is that all radiation fluxes received by the ponds are completely absorbed by the pond's contents and are never reflected, even partially, by their bottoms or walls.This model, which is in fact the thermal balance of the basins, relies mainly on meteorological factors and pond characteristics. Only two out of the six estimated fluxes - evaporation rates and solar radiation - are measured directly in situ. It seemed too difficult to estimate them, since predictive equations found in literature constantly gave unsatisfactory results.To establish the validity of this model, experimental data were collected at a wastewater treatment plant located in the southern part of Belgium. This plant consists of a series of two aerated lagoons and four waste stabilization ponds, designed for a nominal capacity of 7,500 inhabitant-equivalents. Five rounds of measurements, each lasting from five to twenty days, were conducted at different periods of the year. Meteorological factors were continuously monitored by a data acquisition unit while the pond water temperatures and hydraulic flows were measured hourly. Evaporation rates were determined daily with several floating evaporation pans set at the pond surfaces. Vertical temperature and illumination profiles were also measured in order to verify the strict applicability of the two previous hypotheses.Ninety-three experimental data sets were collected on this particular facility. Predicted temperatures were compared with measured temperatures as well as with the results of three other models previously developed for waste stabilization ponds. Our new model systematically proved more reliable and accurate than previous approaches, since equilibrium temperatures were predicted with a mean absolute error of only 0.7 °C. More than 52% of the deviations between calculated and observed temperatures were even below 0.5 °C, which indicates their relatively low dispersion.Continuous simulations were also conducted during a one-day period to demonstrate the importance of the ponds' large thermal capacities. The steady-state approach, which does not account for this latter phenomenon, failed to give consistent results, unlike our dynamic heat balance approach, which yielded extremely good fits with experimental data.A sensitivity analysis allowed us to show the influence of the various meteorological factors on the basins' equilibrium temperatures. In decreasing order, the fits seemed particularly sensitive to inlet temperature, solar radiation, air temperature and evaporation. Surprisingly, wind speed made only a small contribution to the total heat balance. However, this must be seen as a direct consequence of the fact that in our model this latter parameter is no longer used to calculate the predominant evaporation rates but only to estimate the much smaller convection term.Whatever the season considered, more than 90% of the ponds' energy inputs come from solar radiation while the dominating loss mechanisms are represented by the balance of the two infrared radiation fluxes (46%) and evaporation (42%). The sign of the air-water convection term varies according to the period of the year but never accounts for more than 10% of the total heat balance. Heat losses or gains from basin walls always remain insignificant and could therefore easily be neglected in order to simplify our approach to basin equilibrium temperatures.
Keywords: Lagunage aéré, lagunage naturel, bilan thermique, température d'équilibre, transfert de chaleur, Aerated lagoon, waste stabilization pond, thermal balance, equilibrium temperature, heat transfer
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2958.More information
This article contributes to reflections on students' relationship to writing (RW) in the second-language context of Allophone immigrants, for which it proposes the designation RW+. The text is based on a Quebec study regarding the effects of producing plurilingual identity texts on the RW+ of eight Allophone immigrant students with severe educational delays in a secondary-school reception class (experimental group: n=4; control group: n=4). Individual interviews and participant observation are used to describe the participants' RW+ and to determine the effects of the new approach, which, in contrast with the traditional educational practices observed in the control group, is associated with the development of a more positively connoted RW+. This results, among other things, in the students' greater engagement.
Keywords: français langue seconde, élèves immigrants allophones, rapport à l'écrit, littératie, textes identitaires plurilingues, french as a second language, allophone immigrant students, relationship to writing, literacy, plurilingual identity texts, francés como segunda lengua, estudiantes inmigrantes alófonos, relación con la escritura, alfabetización, textos de identidad plurilingües
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2959.More information
Students experiencing some difficulties in their studies and registered in the program Tremplin DEC at the CEGEP of Sherbrooke had participated to the « Personal Goal Management » intervention. Many aspects of the global well-being of the students were evaluated before and after the intervention in the frame of a quasi-experimental device with control group and with pretest and post-test. In spite of the small number of participants, the quantitative and qualitative results show that students experience many benefits in terms of learning and well-being from this participation to the goal-oriented program. These results support those of the many others studies in the domain.
Keywords: buts personnels, gestion des buts, bien-être global, personal goals, goal management, global well-being
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2960.More information
In Quebec, school reforms instituted between 1986 and 2004 at the various levels of education are mainly aimed at developing competencies. Knowledge of instructional practices and, in fact, the practices of assessment of learning, could lead to a better understanding of the results of the reality in the classroom. Proposed by Raîche (2006), the PIEA framework sets out the following characteristics of classroom learning assessment practices: planning, integration, equity and authenticity. A sample of 1975 students enrolled in Quebec's technical and pre-university college programs responded to a questionnaire consisting of 24 items. The analyzes carried out to determine the number of dimensions to be retained and to explore the various factor solutions identified a four-factor model associated with the characteristics proposed by the PIEA model, but not exactly the same.
Keywords: évaluation des apprentissages, approche par compétences, analyse factorielle exploratoire, validation d'échelle, assessment of learning, competency-based approach, exploratory factor analysis, scale validation, evaluación de aprendizajes, enfoque por competencias, análisis factorial exploratorio, validación de escala