Les concepts seuils des trois cours de physique principaux du programme Sciences de la nature au CÉGEP

Abstract : Threshold concepts (TC) play a crucial role in the learning sequence. They need special attention when revising the curriculum, a process currently underway with the current CEGEP Science Program revision in Quebec. The extensive literature on threshold concepts in Mechanics suggests a higher number of threshold concepts in the Mechanics course (NYA) than in other physics courses. This qualitative study analyzed the concepts present in the three physics courses of the current Science Program as well as those introduced in the new versions of the courses following the program revision. The objective was to identify the courses' threshold concepts and verify if Mechanics (NYA) has the largest number. To do so, the participants, physics teachers at an Anglophone college, engaged in a Delphi process. To be included in the list, a concept had to be considered transformative and have at least one other characteristic or known consequence usually associated with threshold concepts. The results showed that while Mechanics (NYA) and Electricity & Magnetism (NYB) have more threshold concepts than Waves & Modern Physics (NYC), there is no significant difference in the number of threshold concepts between NYA and NYB. This result was unexpected as the abundance of potential threshold concepts in NYA discussed in the literature indicated that there would be more TC in that course than in the other two. Still, there was a correlation between the thresholds identified in this study and those previously discussed in the literature. The difference in the total number of threshold concepts per course appears to be highly influenced by the grouping of the concepts. Thus, drawing a conclusion based on the total number of TC per course alone might not hold much value. However, as reported by the participants, the identification process is still worth undertaking. It can serve as the basis for discussions about the curriculum and reflection on teaching and learning the courses' concepts.Le cours de Mécanique passe pour être plus difficile que les autres cours de physique et bon nombre d’étudiants ne montrent pas d’amélioration considérable de leur compréhension conceptuelle après l’avoir suivi (Lasry et al., 2014). Il existe plusieurs explications : les différentes façons de résoudre les problèmes et les stratégies d’apprentissage entre novices et experts, la présence de conceptions alternatives, l’influence de la motivation et des attitudes, les interférences entre différents sujets et, plus récemment objet de discussions, la nature des concepts dans le cours. Les concepts seuils forment des obstacles potentiels, capables à nuire au processus d’apprentissage. Ils peuvent être intégratifs, problématiques, à sens-unique et transformer irréversiblement la pensée des étudiants (Meyer, 2010). L’utilisation continue de conceptions alternatives, l’incapacité à établir des liens entre les concepts, les difficultés dans l’apprentissage d’autres concepts (Carstensen & Bernhard, 2008), le recours à l’approche superficielle pour l’apprentissage et la résolution de problèmes (Flanagan et al., 2010), ainsi que le désengagement du processus d’apprentissage (Davies, 2006) sont les conséquences d’un manque de maîtrise des concepts seuils. En raison de leur rôle central dans le processus d’apprentissage, les concepts seuils nécessitent une attention particulière durant la révision du curriculum, un processus actuellement en cours dans le réseau collégial du Québec pour le programme des Sciences de la nature. Même si, finalement, aucune modification n’est apportée à la séquence d’apprentissage, prêter attention aux concepts seuils peut aider les enseignants à mieux comprendre les difficultés des étudiants et à améliorer leur enseignement (Loertscher et al., 2014; Perkins, 2006; Timmermans & Meyer, 2019). Au minimum, le processus d’identification des concepts seuils peut servir de point de départ à des discussions sur la manière de dispenser les cours (Brown et al., 2021). Cette étude qualitative a analysée les trois cours principaux du programme des Sciences de la nature : Mécanique (NYA), Électricité et magnétisme (NYB) et Ondes, physique moderne et enjeux environnementaux (NYC). Le but étant de répondre à deux questions de recherche: premièrement, « que sont les concepts seuils dans les cours en question? » et, deuxièmement, « le cours de mécanique (NYA) possède-t-il le nombre de concepts seuils le plus grande ? » Les participants, tous professeurs de physique d’un cégep anglophone, se sont engagés dans un processus Delphi afin de créer une liste de concepts seuils pour les trois cours du programme. Pour représenter un concept seuil, le critère utilisé devait être transformatif et présenter au moins une autre caractéristique ou une conséquence fréquemment attribuée aux concepts seuils. Les résultats montrent que le cours Ondes et physique moderne (NYC) présente le nombre de concepts seuils le plus bas des trois. En revanche, aucune différence significative n’est à observer entre NYA et NYB, les deux cours au nombre de concepts seuils plus élevé. Ce résultat est surprenant, étant donné l’abondance de la littérature concernant les concepts seuils en mécanique et compte tenu des problèmes des étudiants dans ce cours. Une analyse plus profonde suggère que le nombre total de concepts seuils dépend de la manière dont ils sont regroupés. Par exemple, “les champs” peuvent être considéré comme un concept unique ou séparés en deux catégories : “les champs magnétiques” et “les champs électriques”. Indépendamment de ce problème, les concepts identifiés dans cette étude et ceux discutés dans la littérature examinée sont étroitement corrélés. Considérer uniquement le nombre total de concepts seuils n’a que peu de valeur – c’est le processus d’identification lui-même qui doit être entrepris pour servir de base aux discussions et réflexions concernant le curriculum, l’apprentissage et l’enseignement. Il reste toujours la question de savoir ce qui rend le cours de mécanique plus difficile. Est- il possible que les étudiants soient mieux préparés à aborder les concepts seuils vers la fin du programme? La séquence fait-elle une différence? Ou bien, le premier semestre a-t-il simplement servi de filtre, décourageant ainsi ceux qui rencontrent des difficultés en mécanique à poursuivre le programme? Une étude plus approfondie des concepts seuils dans le reste du programme est nécessaire afin de pouvoir évaluer les connexions entre les cours, l’influence de la séquence et le moment auquel les concepts seuils forment un obstacle insurmontable. Enfin, compte tenu des avantages du processus d’identification des concepts seuils, il serait bon de l’étendre à d’autres cégeps et autres programmes

Halocarbon emissions and sources in the equatorial Atlantic Cold Tongue

Halocarbons from oceanic sources contribute to halogens in the troposphere, and can be transported into the stratosphere where they take part in ozone depletion. This paper presents distribution and sources in the equatorial Atlantic from June and July 2011 of the four compounds bromoform (CHBr3), dibromomethane (CH2Br2), methyl iodide (CH3I) and diiodomethane (CH2I2). Enhanced biological production during the Atlantic Cold Tongue (ACT) season, indicated by phytoplankton pigment concentrations, led to elevated concentrations of CHBr3 of up to 44.7 and up to 9.2 pmol L−1 for CH2Br2 in surface water, which is comparable to other tropical upwelling systems. While both compounds correlated very well with each other in the surface water, CH2Br2 was often more elevated in greater depth than CHBr3, which showed maxima in the vicinity of the deep chlorophyll maximum. The deeper maximum of CH2Br2 indicates an additional source in comparison to CHBr3 or a slower degradation of CH2Br2. Concentrations of CH3I of up to 12.8 pmol L−1 in the surface water were measured. In contrary to expectations of a predominantly photochemical source in the tropical ocean, its distribution was mostly in agreement with biological parameters, indicating a biological source. CH2I2 was very low in the near surface water with maximum concentrations of only 3.7 pmol L−1. CH2I2 showed distinct maxima in deeper waters similar to CH2Br2. For the first time, diapycnal fluxes of the four halocarbons from the upper thermocline into and out of the mixed layer were determined. These fluxes were low in comparison to the halocarbon sea-to-air fluxes. This indicates that despite the observed maximum concentrations at depth, production in the surface mixed layer is the main oceanic source for all four compounds and one of the main driving factors of their emissions into the atmosphere in the ACT-region. The calculated production rates of the compounds in the mixed layer are 34 ± 65 pmol m−3 h−1 for CHBr3, 10 ± 12 pmol m−3 h−1 for CH2Br2, 21 ± 24 pmol m−3 h−1 for CH3I and 384 ± 318 pmol m−3 h−1 for CH2I2 determined from 13 depth profiles

Antifungal defense of probiotic Lactobacillus rhamnosus GG is mediated by blocking adhesion and nutrient depletion

Data Availability: All relevant data are available from the Gene Expression Omnibus at the following accession number: GSE97755. Funding: This work was funded by the German Research Council (DFG) Graduation College 685, Dr. Jekyll and Mr. Hyde: A systems approach to the therapy of nosocomial infections caused by Candida albicans: a commensal organism switches to a deadly pathogen/ PTJ (FKZ: 0315409BBMBF), the Dr. Manfred Plempel-foundation, the Dr. Siegried Stettendorf-Foundation, the InfectERA Program (FunComPath; BMBF FKZ 031L0001A), the Integrated Research and Treatment Center for Sepsis Control and Care (CSCC) project CanBac (BMBF, FKZ: 01EO1002), and the German Research Council (DFG) GZ:HE7565/1-1. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Textile Design of an Intervertebral Disc Replacement Device from Silk Yarn

Low back pain is often due to degeneration of the intervertebral discs (IVD). It is one of the most common age- and work-related problems in today’s society. Current treatments are not able to efficiently restore the full function of the IVD. Therefore, the aim of the present work was to reconstruct the two parts of the intervertebral disc—the annulus fibrosus (AF) and the nucleus pulposus (NP)—in such a way that the natural structural features were mimicked by a textile design. Silk was selected as the biomaterial for realization of a textile IVD because of its cytocompatibility, biodegradability, high strength, stiffness, and toughness, both in tension and compression. Therefore, an embroidered structure made of silk yarn was developed that reproduces the alternating fiber structure of +30° and −30° fiber orientation found in the AF and mimics its lamellar structure. The developed embroidered ribbons showed a tensile strength that corresponded to that of the natural AF. Fiber additive manufacturing with 1 mm silk staple fibers was used to replicate the fiber network of the NP and generate an open porous textile 3D structure that may serve as a reinforcement structure for the gel-like NP

Unprecedented insights into extents of biological responses to physical forcing in an Arctic sub-mesoscale filament by combining high-resolution measurement approaches

In Fram Strait, we combined underway-sampling using the remote-controlled Automated Filtration System for Marine Microbes (AUTOFIM) with CTD-sampling for eDNA analyses, and with high-resolution optical measurements in an unprecedented approach to determine variability in plankton composition in response to physical forcing in a sub-mesoscale filament. We determined plankton composition and biomass near the surface with a horizontal resolution of ~ 2 km, and addressed vertical variability at five selected sites. Inside and near the filament, plankton composition was tightly linked to the hydrological dynamics related to the presence of sea ice. The comprehensive data set indicates that sea-ice melt related stratification near the surface inside the sub-mesoscale filament resulted in increased sequence abundances of sea ice-associated diatoms and zooplankton near the surface. In analogy to the physical data set, the underway eDNA data, complemented with highly sampled phytoplankton pigment data suggest a corridor of 7 km along the filament with enhanced photosynthetic biomass and sequence abundances of sea-ice associated plankton. Thus, based on our data we extrapolated an area of 350 km2 in Fram Strait with enhanced plankton abundances, possibly leading to enhanced POC export in an area that is around a magnitude larger than the visible streak of sea-ice

Why are different estimates of the effective reproductive number so different? A case study on COVID-19 in Germany

The effective reproductive number R$_t$ has taken a central role in the scientific, political, and public discussion during the COVID-19 pandemic, with numerous real-time estimates of this quantity routinely published. Disagreement between estimates can be substantial and may lead to confusion among decision-makers and the general public. In this work, we compare different estimates of the national-level effective reproductive number of COVID-19 in Germany in 2020 and 2021. We consider the agreement between estimates from the same method but published at different time points (within-method agreement) as well as retrospective agreement across eight different approaches (between-method agreement). Concerning the former, estimates from some methods are very stable over time and hardly subject to revisions, while others display considerable fluctuations. To evaluate between-method agreement, we reproduce the estimates generated by different groups using a variety of statistical approaches, standardizing analytical choices to assess how they contribute to the observed disagreement. These analytical choices include the data source, data pre-processing, assumed generation time distribution, statistical tuning parameters, and various delay distributions. We find that in practice, these auxiliary choices in the estimation of R$_t$ may affect results at least as strongly as the selection of the statistical approach. They should thus be communicated transparently along with the estimates

Collaborative nowcasting of COVID-19 hospitalization incidences in Germany

Real-time surveillance is a crucial element in the response to infectious disease outbreaks. However, the interpretation of incidence data is often hampered by delays occurring at various stages of data gathering and reporting. As a result, recent values are biased downward, which obscures current trends. Statistical nowcasting techniques can be employed to correct these biases, allowing for accurate characterization of recent developments and thus enhancing situational awareness. In this paper, we present a preregistered real-time assessment of eight nowcasting approaches, applied by independent research teams to German 7-day hospitalization incidences during the COVID-19 pandemic. This indicator played an important role in the management of the outbreak in Germany and was linked to levels of non-pharmaceutical interventions via certain thresholds. Due to its definition, in which hospitalization counts are aggregated by the date of case report rather than admission, German hospitalization incidences are particularly affected by delays and can take several weeks or months to fully stabilize. For this study, all methods were applied from 22 November 2021 to 29 April 2022, with probabilistic nowcasts produced each day for the current and 28 preceding days. Nowcasts at the national, state, and age-group levels were collected in the form of quantiles in a public repository and displayed in a dashboard. Moreover, a mean and a median ensemble nowcast were generated. We find that overall, the compared methods were able to remove a large part of the biases introduced by delays. Most participating teams underestimated the importance of very long delays, though, resulting in nowcasts with a slight downward bias. The accompanying prediction intervals were also too narrow for almost all methods. Averaged over all nowcast horizons, the best performance was achieved by a model using case incidences as a covariate and taking into account longer delays than the other approaches. For the most recent days, which are often considered the most relevant in practice, a mean ensemble of the submitted nowcasts performed best. We conclude by providing some lessons learned on the definition of nowcasting targets and practical challenges