Documents found
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2591.
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2593.More information
The ancient area of Villa Roma, in Nîmes (Gard), widely excavated in 1991-1992, revealed several domus and an original place where several pottery kilns succeed one another or coexist all along the 1st c. AD. However, one cluster of three kilns, in use during the years 20 to 40 AD, can be connected to a ceramic production, where we could distinguish two different fabrics whose dominant feature is limestone, and 20 vessels types. Most of them can be found in a domestic context, but a few have some features, supported by several comparisons, that engage to link them with an utilization in cult context. An overview of the global evolution of the urban area, with chronological arguments, allows us an estimation of its uniqueness – here, the residential function seems almost absent – then follows a precise description of the workshop and the vessels it produced. This example finally allows us an assessment of our knowledge on pottery craft at the scale of the town of Nemausus, the Arecomici civitas-capital.
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2594.More information
Creative spaces allow users to craft, transform and equip themselves, as well as participate, share and learn. These actions support the democratization effect of the maker movement (Hatch, 2014) as well as the development of the empowerment made possible in creative spaces (Blikstein, 2013; Davidson and Duponsel, 2021). This article presents the analysis of four creative spaces in Quebec and leads to identify the characteristics of learning spaces located outside educational institutions and supporting non-formal learning. The view on creative spaces has been guided by activity theory (Engeström, 1987). Different components (subject, tool, object, division of labor, rules and community) were analyzed through transcripts of semi-structured interviews conducted with managers of creative spaces and users. The analysis supported by activity theory makes it possible to approach in a systemic way the organization of activities in creative spaces that support non-formal learning. Our project is of interest for the advancement of knowledge, because it allows us to identify tensions related to notoriety, equipment, learning and community that could be present in other creative spaces.
Keywords: makerspace, espace créatif, creative space, makerspace, creative lab, laboratoire créatif, théorie de l’activité, activity theory, apprentissage, learning
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2595.More information
Important anthropogenic sources of fluoride to the aquatic environment include municipal waste waters and effluents from fertilizer producing plants and aluminum refineries. Many studies have demonstrated that fluoride toxicity to aquatic organisms is reduced when the toxicological test is performed in hard water rather than soft water. In principle at least three mechanisms could explain this trend: (I) a direct beneficial influence of the hardness cations (Ca2+ ; Mg2+) on the test organism (either externally, at an epithelial membrane, or internally); (II) complexation between fluoride and the hardness cations, leading to a reduction in free the fluoride concentration (F-) in the exposure media; (III) fluorite precipitation (CaF2) in the exposure media, leading to a reduction in the effective fluoride concentration. The present literature review was designed to identify which of these mechanisms might be responsible for the apparent protective effect of hardness on fluoride toxicity.An inventory of the existing literature on the toxicity of fluoride to freshwater fish, invertebrates and aquatic insects was prepared. The most complete studies were selected and the chemical data needed to model cation and anion speciation in the exposure media were extracted from the papers. Speciation at equilibrium was then modelled using as input data the total concentrations of the key constituents (calcium, magnesium, fluoride and chloride), together with the temperature and the pH.The initial speciation calculations revealed a particularity of the chemical systems studied: frequently precipitation of fluorite (CaF2) was predicted by the speciation model (MINEQL+), but the article from which the data had been extracted did not mention the appearance of a precipitate. Fluorite solubility, at a pH of 7 and at an ionic strength of 2.7 mM, is approximately 17 mg CaF2 /L (0.22 mM). When high fluoride concentrations are used in hard water, both fluoride and calcium concentrations are predicted to decrease markedly as a result of fluorite precipitation. This analysis of the published results thus suggests that the reported lower toxicity of fluoride in hard waters is likely due to the chemical precipitation of CaF2 and MgF2, resulting in a decrease in the effective fluoride concentration to which the test organisms are exposed. In other words, changes in the physical speciation of fluoride (i.e., its distribution among dissolved and particulate species) are much more important than changes in its chemical speciation in solution.Given the low solubility of fluoride in hard waters, it would seem difficult if not impossible to carry out fluoride toxicity tests in hard water. However, in a few fluoride toxicity studies the researchers checked for precipitation by monitoring fluoride and calcium concentrations throughout the toxicity test. In some of these cases, even though speciation calculations predicted fluorite formation at the exposure concentrations used, the authors did not detect any precipitation; these systems were thus apparently in a metastable, over-saturated state, where the kinetics of precipitation were slow relative to the duration of the toxicity test. The chemical equilibrium software was used to simulate fluoride speciation in these systems, by allowing the over-saturated solid phases to remain in solution. In particular, we looked for evidence that under such circumstances the hardness cations exerted a beneficial effect. However, no clear picture emerged from this second analysis: two of the studies designed particularly to test the effect of calcium on fluoride toxicity showed a protective effect, whereas one study indicated the opposite effect, i.e. an increase in fluoride toxicity as the calcium concentration was raised. All fish studies for which calcium concentrations were available (N=20 studies; 58 toxicity tests) were pooled and tested for a possible calcium effect on fluoride toxicity. No relationship was observed between fluoride ion toxicity (LC50, expressed as calculated free [F-]) and calculated dissolved calcium concentrations for these pooled data (Fig. 2). Fluorite solubility was the most important factor influencing the data point distribution in the relationship. The same exercise was performed for all the invertebrate studies (N=11 studies; 22 toxicity tests) but again no relationship was found (Fig. 3).Several factors other than hardness affect fluoride toxicity to aquatic organisms. Fluoride toxicity to fish increased with exposure duration up to 200 h, where it reached a threshold LC50 level around 100 mg/L (5.3 mM) expressed as free fluoride (Fig. 4). Fish life stage (Fig. 5), the temperature of the exposure media (Fig. 6) and the chloride concentration also affected fluoride toxicity in fish. For invertebrates, fluoride toxicity increased with exposure duration but to a lesser extent than for fish.In summary, water hardness clearly reduces fluoride toxicity to aquatic organisms by limiting the equilibrium solubility of the fluoride ion. However, in those cases where the precipitation of CaF2 (s) and MgF2 (s) is slow, and where the hardness cations and fluoride co-exist in the dissolved state in the exposure medium, the experimental evidence for a protective effect of hardness on fluoride toxicity is equivocal. To answer the question, new experiments should be performed under conditions that take into account the behaviour of calcium and fluoride in the natural environment. Metastable environments where fluoride concentrations exceed the solubility limit imposed by CaF2 or MgF2 could be reproduced in laboratory toxicity tests by using continuous flow systems. For tests below the solubility limit, toxicity tests with varying levels of Ca or Mg could be designed to stay within the solubility range of CaF2 or MgF2. In both cases, dissolved calcium, magnesium and fluoride concentrations should be monitored throughout the toxicity tests.
Keywords: Poisson, invertébrés, dureté, fluorure, spéciation, toxicité, Fish, invertebrates, hardness, fluoride, speciation, toxicity
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2597.More information
This article reports on the revival of the use of digital resources in Ivorian higher education since the first recorded case of coronavirus in March 2020. It first provides a reminder of the institutionalization of the policy development in Ivorian higher education. Then, it notes the possible impacts of the massive diffusion of digital university education in Côte d'Ivoire.
Keywords: Politique numérique, impacts anticipés, coronavirus, enseignement supérieur, Côte d'Ivoire, Digital policy, anticipated impacts, coronavirus, higher education, Côte d'Ivoire
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2598.More information
Around the world, confinement measures imposed during the COVID‑19 pandemic have forced universities to shut down their campuses. Graduate students opted for online modalities to progress their academic writing projects, including theses and dissertations. In Canada, a non-profit organization named Thèsez‑vous implemented innovative digital strategies to support students in times of crisis. This article presents qualitative results obtained from 33 PhD students who have used said tools to continue their studies. A follow-on discussion focuses on existing digital learning environments and considerations for subsequent research.
Keywords: Pandémie, outils numériques, modalités virtuelles, cycles supérieurs, étudiants, rédaction académique, enseignement et apprentissage, Pandemic, digital tools, virtual modalities, higher studies, graduate students, academic writing, teaching and learning
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2599.More information
This paper discusses the role of the DOBIS system at the National Library of Canada in the evolving library and information network in Canada. DOBIS is an on-line integrated library management system which has been developed by the National Library of Canada and the Canada Institute for Scientific and Technical Information, and is operated and maintained by the National Library of Canada. This system is used in a shared system/network mode by the National Library of Canada and the Canada Institute for Scientific and Technical Information to support their national services and also by the Library of Parliament and a growing number of Canadian federal government libraries to support their library operations. DOBIS has been operational since the fall of 1979. The DOBIS data base now contains over 2.3 million bibliographic records. Two of the major objectives of the National Library of Canada when it undertook the development of the DOBIS system were to facilitate library resources sharing across Canada, and to make the nation's information resources more readily accessible to all Canadians. In order to further fulfill these objectives, the National Library is now planning to use the DOBIS system and data base in its participation in the development of a decentralized Canadian library and information network, the goal of which is to get the right information where it is needed and when it is needed. The latest computer/communications technologies are being employed in this development. The basic development strategy involves linking together existing independently operating systems, one example being DOBIS, so that users of one system can have access to the services of the other interconnected systems. This strategy is called "open systems interconnection", or OSI, because the services of all the interconnected systems are open to one another.
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