Nouvelles tendances dans la Didactique de la Chimie et rôle du Comité pour l'Enseignement de la Chimie de l'IUPAC

We call attention to the enormous spreading undergone by the didactic of chemistry in the last few years and comment on some of the trends that are significant in this field from the point of view of the author. We also comment on some of the projects developed by the committee for teaching chemistry in the IUPAC

A sensory 3-D map of the odor description space derived from a comparison of numeric odor profile databases

Many authors have proposed different schemes of odor classification, which are useful to aid the complex task of describing smells. However, reaching a consensus on a particular classification seems difficult because our psychophysical space of odor description is a continuum and is not clustered into well-defined categories. An alternative approach is to describe the perceptual space of odors as a low-dimensional coordinate system. This idea was first proposed by Crocker and Henderson in 1927, who suggested using numeric profiles based on 4 dimensions: fragrant, acid, burnt, and caprylic. In the present work, the odor profiles of 144 aroma chemicals were compared by means of statistical regression with comparable numeric odor profiles obtained from 2 databases, enabling a plausible interpretation of the 4 dimensions. Based on the results and taking into account comparable 2D sensory maps of odor descriptors from the literature, a 3D sensory map (odor cube) has been drawn up to improve understanding of the similarities and dissimilarities of the odor descriptors most frequently used in fragrance chemistry.Zarzo Castelló, M. (2015). A sensory 3-D map of the odor description space derived from a comparison of numeric odor profile databases. Chemical Senses. 40(5):305-313. doi:10.1093/chemse/bjv012S30531340

La reacción química : descripciones e interpretaciones de los alumnos de liceo

We have carried out a piece of research about the assimilation of the chemical reaction by secondary students, based on the study of their spontaneous descriptions of the process, their ability to explain it in corpuscular terms and of correctly applying the law of matter preservation. The experimental sample were 19 students between 13 and 14 years of age who had been introduced to the subject the previous year. We have introduced a variant in the technique of interviews

A multidimensional statistical study of similarities between 74 notes used in perfumery

From a data bank of 2467 odoriferous products, the similarities between 74 notes used in perfumery were calculated. The similarity matrix (74,74) contains - 63% of zero values and shows that only a few pairs of notes present high similarity coefficients. A fine analysis using ascending hierarchical taxonomy with the complete linkage procedure shows that 14 notes are isolated while 60 notes are regrouped in 27 groups containing two to four notes. The isolated notes correspond to well-defined structural particularities. Some pairs of notes or groups present similarities in their chemical structures but some groups are built on the basis of semantic processes. This study shows that the notes are generally independent, with no strict hierarchy among them, and rules out the existence of primary odor

Combining Model-Based Design (MBD) and Model-Based Testing (MBT) for early validation of embedded real-time systems

International audienceThis paper describes an approach combining Model-Based Engineering (MBE) and Model-Based Testing, and its application to requirements validation for an embedded Instrumentation & Control (I&C) system. Many aspects of the embedded system can thus be validated early in the lifecycle, long before an actual implementation is developed, and, most importantly, requirements can be validated before the system is implemented. A flexible integration environment makes it possible to reuse the test cases throughout the lifecycle. This approach is being implemented in the CONNEXION R&D project, using Esterel Technologies’ SCADE Suite and All4tec’s MaTeLo, with Corys’ ALICES as an integration environment

On the role of chirality in structure-odor relationships

The influence of chirality on odors was studied on 16 enantiomeric pairs according to the dispersion/hydrogen bonding theory of receptor-odorant interaction. Comparisons of molecular structures were made by superimposition of optimized conformations, using the Alchemy II package. The quality of fit was assessed using the RMS parameter included in Alchemy II and a new index for hydrogen bonding: the angle between H-bonds in the two molecules. In the case of camphoraceous odorants where an interaction model was already known superimposition according to the model led to correct predictions of the high similarity of odors observed in enantiomeric pairs. For several urinous odorants comparisons were made using d-androstenone as a reference compound for the urinous odor. Correct predictions were obtained for l-androstenone, both enantiomers of androsta-4, 16-dienone, and (+)-2-methyl-4-(5,5,6-exo-trimethy1-2-exonorbornyl)-cyclobexane. The (−) enantiomer of the latter compound was correctly predicted only if it was assumed that its weak intensity is due to a partial interaction with the hydrophobic zone of the receptor. For ambergris odorants which have a complex odor (−)-Ambrox was selected as the reference compound. The odors of (+)-Ambrox and enantiomers of four other compounds (ambergris or woody) were correctly predicted by superimposition. For nootkatone and three derivatives which have a grapefruit note for one enantiomer and a woody note for the other no models or reference compounds were available. The superimpositions were made between grapefruit enantiomers, on the one hand, and woody enantiomers on the other hand. Woody and grapefruit characters were correctly predicted in all cases. The limits of this approach based on molecular modelling are discusse

Analysis of a system of description of odors by means of four different multivariate statistical methods

In order to analyze the relationships among 32 descriptors of odors (notes), similarity coefficients were calculated using a data bank of 628 odoriferous products. The simple examination of the similarity matrix (32,32) has shown notes selectively and strongly associated (e.g. camphoraceous-piney and musky-powdery) and others less selectively associated (e.g. floral, green and herbaceous). This analysis was completed by four multivariate statistical methods. Non-linear mapping (NLM) proved to be more efficient than principal coordinates analysis for planar representation of olfactory notes, and has given results similar to those previously obtained using other data and other methods (similar disposition of notes around the central note ‘floral'). Furthermore, the ascending hierarchical taxonomy and the minimal spanning tree were coherent with the NLM representation. These three methods complete each other and constitute a convenient system to analyze odor description

Conceptions of French and Tunisian students on conduction in electrochemical cells

Cet article présente les conceptions sur la conduction électrique dans les piles électrochimiques repérées chez des élèves et des étudiants français ou tunisiens. Cinquante-cinq lycéens (de 16-17ans ) et soixante-quatre étudiants ont participé à cette étude. La démarche mise en place associe un questionnaire et des entretiens semi-directifs basés sur l'observation de dispositifs expérimentaux. L'omniprésence des conceptions relatives à la présence des électrons en solution est essentiellement due à l'assimilation du courant électrique à un déplacement d'électrons, même dans les électrolytes. L'absence de liaison entre le mouvement des ions et le courant électrique constitue un obstacle à la construction des concepts nécessaires à la compréhension du fonctionnement des piles électrochimiques. Quelques facteurs de persistance des conceptions repérées sont brièvement analysés

Relations structure-odeur soufrée pour une série de composés organiques

Les relations structure-odeur soufrée sont établies en choisisant les fragments de molécules comme descripteurs selon les principes de la méthode GESDEM (Genération et Sélection de Descripteurs et Elaboration de Motifs). La série étudiée comporte 48 molécules soufrées et 34 non-soufrées. 96 % des molécules ont été classées en tant que telles par un modèle obtenu en utilisant un réseau neuronal (RN) de configuration 8-5-1