Influences d’un stage muséal sur le sentiment d’autoefficacité en sciences de futurs enseignants

Résumé

Cette étude qualitative, ancrée dans l’approche sociale-cognitive de la théorie de l’autoefficacité de Bandura, s’intéresse à quatre stagiaires dont le stage d’enseignement s’est déroulé au Musée canadien de la nature. Les données du questionnaire STEBI, combinées aux entrevues semi-dirigées ont permis d’analyser l’évolution du sentiment d’autoefficacité en sciences chez les stagiaires. Les résultats révèlent un accroissement du score STEBI, alors que l’apprentissage vicariant et la possibilité de répétition favorisent une meilleure connaissance de soi et une pratique réflexive chez les stagiaires du palier élémentaire. Les résultats témoignent du potentiel d’un tel stage pour rehausser le sentiment d’autoefficacité en sciences.     

Statistical analysis of a database of absorption spectra of phytoplankton and pigment concentrations using self-organizing maps

We present a statistical analysis of a large set of absorption spectra of phytoplankton, measured in natural samples collected from ocean water, in conjunction with detailed pigment concentrations. We processed the absorption spectra with a sophisticated neural network method suitable for classifying complex phenomena, the so-called self-organizing maps (SOM) proposed by Kohonen [Kohonen, Self Organizing Maps (Springer-Verlag, 1984)]. The aim was to compress the information embedded in the data set into a reduced number of classes characterizing the data set, which facilitates the analysis. By processing the absorption spectra, we were able to retrieve well-known relationships among pigment concentrations and to display them on maps to facilitate their interpretation. We then showed that the SOM enabled us to extract pertinent information about pigment concentrations normalized to chlorophyll a. We were able to propose new relationships between the fucoxanthin/Tchl-a ratio and the derivative of the absorption spectrum at 510 nm and between the Tchl-b/Tchl-a ratio and the derivative at 640 nm. Finally, we demonstrate the possibility of inverting the absorption spectrum to retrieve the pigment concentrations with better accuracy than a regression analysis using the Tchl-a concentration derived from the absorption at 440 nm. We also discuss the data coding used to build the self-organizing map. This methodology is very general and can be used to analyze a large class of complex data.     

Transmission Electron Microscopy and UV–vis–IR Spectroscopy Analysis of the Diameter Sorting of Carbon Nanotubes by Gradient Density Ultracentrifugation

Diameter separation of single‐walled carbon nanotubes is achieved via the density gradient ultracentrifugation process. Statistical analysis of the separated samples is performed using high‐resolution transmission electron microscopy (HRTEM). The evolution of the diameter distribution with respect to the gradient density is extracted by analyzing hundreds of HRTEM images, and the results are found to be consistent with those estimated by UV–vis–IR spectroscopy. The efficiency of the separation process can be quantitatively characterized by the standard deviation of the diameter distribution, which is determined from the TEM analyses. This particular study indicated that for electric arc nanotubes dispersed in sodium cholate, diameter sorting is more efficient in the upper part of the gradient.     

Optimal separable algorithms to compute the reverse euclidean distance transformation and discrete medial axis in arbitrary dimension

In binary images, the distance transformation (DT) and the geometrical skeleton extraction are classic tools for shape analysis. In this paper, we present time optimal algorithms to solve the reverse Euclidean distance transformation and the reversible medial axis extraction problems for d-dimensional images. We also present a d-dimensional medial axis filtering process that allows us to control the quality of the reconstructed shape     

Ab initio derivation of the electronic structure properties across the Cu-Cu2O interface

The interface between the Cu and Cu₂O is investigated by means of the density functional theory. Several parameters representing the effects of the electronic structure of the boundary are derived. They show that there exist a continuous chemical bonding across the Cu-Cu₂O system. This is not compatible with the usual Schottky barrier model and because of that a new qualitative scheme of the band alignment is proposed. A possible way for a quantitative interpretation of the experimental current-potential data in the framework of the electronic structure concept is considered.     

Spectral code index (SPECOIND): a general infrared spectral database search method

A new spectral code that can be used by Relational Database Management Systems (RDBMS) as an index for infrared (IR) spectra searches in Relational Database (RDB) is presented and its suitability is evaluated. Spectral codes are constructed for all spectra in the database as the spectral indexes and three query strings are created with the same theory used for the creation of the index code for the query spectrum. Some effects of parameters used to create index strings and query strings are discussed. All spectral searches are accomplished in structured query language (SQL) approach and the utilization examples of SQL have been shown. The sequential application of this procedure can reduce the original library of about 18000 spectra to a few spectra that can be used as references for subsequent detailed comparison. The software developed for the proposed system is particularly suitable for spectral search and structure interpretation.     

FCPAC: Fast calculation of partial atomic charges using strictly localized molecular orbitals

Most force fields of molecular mechanics use constant partial atomic charges whereas it is now admitted that those charges strongly vary with the environment. Charge variations are particularly important in hydrogen bonds where polar entities come close together. Moreover, organizing H-bonds in networks, like in secondary structures of proteins, go with cooperative effects which lead to an overall electrostatic stabilization of the system. This is why variable atomic charges are required to correctly mimic these effects. Different methods of charge calculation were developed, most use polarizable dipole or electronegativity equalization. In this work, we propose a semi-empirical method (fast calculation of partial atomic charges (FCPAC)) which derives partial atomic charges from strictly localized molecular orbitals. The approximations enable to treat molecular systems with hundreds of atoms within reasonable delays. Results reported here show that charges calculated with FCPAC are similar to charges derived from Mulliken’s population analysis of a restricted Hartree–Fock wave function using the split valence basis set 6-31G and including polarization orbitals p and d respectively for hydrogen and heavy atoms, RHF/6-31G(d,p). Comparison with ab initio calculation was also performed on a system composed of five formamide molecules disposed in the same geometry as peptide bonds in an helix. Charges variations are similar and suggest that FCPAC is suitable for quantitative estimation of cooperative effects.     

Occurrence of the tdh and trh genes in Vibrio parahaemolyticus isolates from waters and raw shellfish collected in two French coastal areas and from seafood imported into France

The occurrence of the hemolysin genes, tdh and trh, in Vibrio parahaemolyticus strains isolated from environmental samples collected in two French coastal areas, clinical samples, and seafood products imported into France was studied. Polymerase chain reaction (PCR) with two sets of primers was used to detect the hemolysin genes. Most of the clinical isolates (91%) and 1.5% of the isolates from seafood possessed the hemolysin genes. Three and fifteen percent, respectively, of the two groups of environmental strains carried the hemolysin genes depending on the geographic site. The tdh and trh genes play important roles in virulence. Thus, our results indicate that pathogenic V. parahaemolyticus isolates are present in French coastal areas and in seafood imported into France. Furthermore, they may also be present in French seafood products.