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Evidence regarding the benefits of an instructor's deictic gestures in video lectures on adults' learning may not necessarily be reflective of their effect on children's learning. Furthermore, there is a lack evidence regarding how deictic gestures specifically affect learners' learning process. Based in cognitive load theory, with consideration of the signaling principle and embodiment principle in multimedia learning, the present study sought to determine whether an instructor's deictic gestures affected young adults' and children's learning from video lectures differently. Participants consisted of 60 college students as the young adults sample and 63 pupils as the children sample. Each participant viewed one of two video lectures, either with or without the instructor using deictic gestures. During the experiment, participants' eye movements, prior knowledge, learning process, and learning performance were recorded and measured. The results of nonparametric tests showed that when the instructor used deictic gestures, the children paid more attention to the video content while the young adults reported a higher learning experience. Both groups demonstrated improved learning performance, regardless of age. Our findings highlight the fact that young adults and children do learn differently from video lectures with an instructor using deictic gestures. Furthermore, our findings contribute to understandings regarding the design of video lectures and video-based learning, specifically, that if an instructor is presenting the content in video lectures, they should be encouraged to use deictic gestures to improve students' learning. [ABSTRACT FROM AUTHOR]

High concentrations of heavy metals (HMs) in water (e.g., As, Cr, and Cd) are harmful to human health, especially to children. HMs' (As, Cd, Mn, Fe, Cu, Hg, Zn, Cr, and Se) values have been determined from the water of the Guenniche plain (Tunisia); then the carcinogenic risk (CR) and non-carcinogenic Risk (N-CR) were estimated through ingestion and dermal contact for adults and children. The analysis results show that the Hg, As, and Cd in 50% of the ephemeral streams (ESs) exceeded one of the WHO and NT guidelines for safe water, as is the case with Hg and Cd in 25% of the shallow groundwater wells (SGW). In all samples, the N-CR of all HMs, and the CR due to the dermal contact controlled by As, for both age brackets, are deemed to fall far short of the threshold set by USEPA. The CR due to the ingestion pathway caused by As, Cr, and Cd contamination indicates a "high" to "very high" risk on its users in roughly 50% of all the samples (ESs and SGW) for both age brackets by exceeding 10−5. Overall, the SGW samples close to the floodplain area of the ESs pose a real CR to both age groups, which is more serious for children. Therefore, the SGW are not recommended for drinking use, with an urgent call for a solution by the policy-makers to improve the water quality of the region. [ABSTRACT FROM AUTHOR]

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