Eigenschaften und Erweiterungen der Methode CLV zum Clustern von Variablen : Anwendungen in der Sensometrie

Universität Dortmund, Fachbereich Statistik und Université Rennes II, Haute Bretagne, Laboratoire de StatistiqueIn this work, the properties of the method of clustering of variables around latent components (CLV) are investigated. A statistical model is postulated. This model is especially appropriate for sensory profiling data. It sheds more light on the method CLV. The clustering criterion can be expressed in terms of the parameters of the model. It is shown that, under weak conditions, the hierarchical algorithm of CLV finds the correct partition while the partitioning algorithm depends on the partition used as a starting point. Furthermore, the performance of CLV on the basis of a sample is investigated by means of a simulation study. It is shown that this performance is comparable to the performance of known methods such as the procedure Varclus of the software SAS. Finally, two methods for determining the number of groups are proposed and compared

Scannernoise-evoked Activation - A new Pulse Sequence simplifies fMRT of the auditory Cortex

Echo-planar Imaging (EPI) erzeugt durch schnell wechselnde Gradienten beträchtliche Schallemissionen. Dies führt nachgewiesenermaßen bei funktionellen Magnet-Resonanz-Tomographie- (fMRT-) Studien zu einer Aktivierung des auditiven Systems, insofern dieses beim jeweiligen Probanden in der Lage ist zu reagieren. Sowohl für auditive wie auch für nicht-auditive Untersuchungen wurden verschiedenste Anstrengungen unternommen, diese Interferenzen zu minimieren. Anstatt den Lärm des Scanners zu reduzieren oder die Transmission des Schalls zu behindern, war es nun das Ziel, eben diesen Schall zur Aktivierung des auditiven Kortex zu benutzen und diese mit fMRT-Untersuchungen nachzuweisen. Dieses geschieht schlicht durch das Auslassen von Read-Outs aus der Gradientenfolge der Pulssequenz. Diese Pulse sind die Hauptemissionsquellen von Schall des EPI, sie verursachen sowohl den Spitzenschallpegel als auch die Grundfrequenz, welche im umgekehrten Verhältnis zum Echo-Spacing steht. Durch eine Modell-gestützte Analyse wird gezeigt, dass das Auslassen von Read-Outs nach einem vordefinierten Schema verlässlich dazu geeignet ist, eine hämodynamische Blood-Oxygenation-Level-Dependent- (BOLD-) Signalveränderung im auditiven Kortex von normal hörenden Probanden (n=60) zu evozieren. Um den Nutzen der Technik beim auditiven fMRI zu zeigen, werden auf der Ebene der Einzelanalysen das traditionelle Family-Wise-Error-Rate- (FWER-) korrigierte Maximum Height Thresholding mit dem Spatial Mixture Modelling (SMM) verglichen. Mit Letzterem können so in 95 % der Fälle eine adäquate, bilaterale, auditive Aktivierung nachwiesen werden, wohingegen das FWER-basierte Voxel-Thresholding nur in 72 % aller Probanden eine solche Aktivierung zeigt. Um die klinische Anwendbarkeit der Technik unter pathologischen Bedingungen zu demonstrieren, wird ein Fallbericht einer Patientin vorgestellt, die an einem schweren, beidseitigen Sensorineural Hearing Loss (SNHL) aufgrund bilateraler Large Vestibular Aqueducts (LVAs) leidet. Dabei wird eben diese Modifikation benutzt, um präoperativ vor Cochlear Implantation (CI) zu zeigen, dass ein zentrales Resthörvermögen vorhanden ist. Da die Untersuchung völlig unabhängig von der Compliance des Patienten und kein zusätzliches Zubehör zum Scanner vonnöten sind, eignet sie sich hervorragend zu auditiven Untersuchungen, um so schnell das Hörvermögen zu prüfen. Dabei funktioniert die Methode unabhängig von äußerlichen Bedingungen: Bei hörgesunden Probanden ebenso wie bei Hörgeschädigten, bei Kindern, Jugendlichen und Erwachsenen aller Altersstufen sowie unabhängig von einer Sedierung während der Untersuchung. Beide benutzten Scanner zeigten unabhängig vom Gradienten oder der verwendeten Spule ein gleiches Ergebnis.Echo-planar Imaging (EPI) induces considerable sound emissions by steep gradient pulses. This leads evidentially to an activation of the auditory system, as much it is able to response in that particular subject. For auditory as well as non-auditory investigations, various efforts have been undertaken to minimize those interferences. Instead of reducing the scanner noise or cumbering its transmission, the goal was now to utilize it to activate the auditory cortex and detect it later on by functional magnetic resonance imaging (fMRI). This was achieved by simply omitting read-outs from the gradient train of an EPI pulse sequence. Those pulses are the primary noise determinant in EPI, they induce both the peak sound level and the fundamental frequency peak, which relates inversely to the echo spacing. By hypothesis-driven analyses it is demonstrated that withholding read-out gradients in a defined scheme reliably evokes hemodynamic Blood Oxygenation Level Dependent (BOLD) signal modulations in the auditory cortex of normal hearing subjects (n=60). To show the value of this new method, the first level analyses of the single subjects with the traditional Family-Wise-Error-Rate (FWER-) corrected Maximum Height Thresholding are compared with Spatial Mixture Modelling (SMM). This way in 95 % of all subjects an appropriate, bilateral auditory activation was detected with SMM, whereas the FWER-based Voxel-Thresholding revealed such activation in only 72 %. To show the clinical practicability of the new technique under pathological conditions the case report of a patient with severe, binaural Sensoneurinal Hearing Loss (SNHL) due to bilateral Large Vestibular Aqueducts (LVA) is presented. Thereby this modification is used to confirm residual audition prior to cochlear implantation (CI). As the investigation is totally independent of the patient's compliance and no additional equipment other than the scanner is necessary, it is suited well as a quick testing for central audition. At the same time the approach is absolutely independent from other conditions: It works with normal hearing subjects as well as with hearing impaired patients; with children, adolescents as well as adults of all age brackets and regardless of sedation during the test. Both scanners, that were used, showed independent from the gradient or the coil the same results

Propriétés et extensions de la classification de variables autour de composantes latentes. Application en évaluation sensorielle

In this work, the properties of the method of clustering of variables around latent components (CLV) are investigated. A statistical model is postulated. This model is especially appropriate for sensory profiling data. It sheds more light on the method CLV. The clustering criterion can be expressed in terms of the parameters of the model. It is shown that, under weak conditions, the hierarchical algorithm of CLV finds the correct partition while the partitioning algorithm depends on the partition used as a starting point. Furthermore, the performance of CLV on the basis of a sample is investigated by means of a simulation study. It is shown that this performance is comparable to the performance of known methods such as the procedure Varclus of the software SAS. Finally, two methods for determining the number of groups are proposed and compared.Dans ce travail, les propriétés de la méthode de classification de variables autour de composantes latentes (CLV) sont étudiées. Un modèle statistique pour cette méthode est formulé. Ce modèle est particulièrement adapté aux données issues d'un profil sensoriel. Il permet de jeter un nouvel éclairage sur la méthode CLV. Le critère de classification s'écrit en fonction des paramètres du modèle. Il est démontré que, sous des conditions peu contraignantes, l'algorithme hiérarchique retrouve correctement les groupes de variables tandis que l'algorithme de partitionnement dépend de l'initialisation. Le comportement de la méthode CLV lors de la classification sur la base d'un échantillon est analysé à l'aide d'une étude de simulations. Il s'avère que la performance de CLV est comparable à celle de méthodes connues telles que la méthode Varclus du logiciel SAS. Finalement, deux procédures automatiques pour la détermination du nombre de groupes sont proposées et comparées

Propriétés et extensions de la classification de variables autour de composantes latentes (application en évaluation sensorielle)

Dans ce travail, les propriétés de la méthode de classification de variables autour de composantes latentes (CLV) sont étudiées. Un modèle statistique pour cette méthode est formulé. Ce modèle est particulièrement adapté aux données issues d'un profil sensoriel. Il permet de jeter un nouvel éclairage sur la méthode CLV. Le critère de classification s'écrit en fonction des paramètres du modèle. Il est démontré que, sous des conditions peu contraignantes, l'algorithme hiérarchique retrouve correctement les groupes de variables tandis que l'algorithme de partitionnement dépend de l'initialisation. Le comportement de la méthode CLV lors de la classification sur la base d'un échantillon est analysé à l'aide d'une étude de simulations. Il s'avère que la performance de CLV est comparable à celle de méthodes connues telles que la méthode Varclus du logiciel SAS. Finalement, deux procédures automatiques pour la détermination du nombre de groupes sont proposées et comparéesIn this work, the properties of the method of clustering of variables around latent components (CLV) are investigated. A statistical model is postulated. This model is especially appropriate for sensory profiling data. It sheds more light on the method CLV. The clustering criterion can be expressed in terms of the parameters of the model. It is shown that, under weak conditions, the hierarchical algorithm of CLV finds the correct partition while the partitioning algorithm depends on the partition used as a starting point. Furthermore, the performance of CLV on the basis of a sample is investigated by means of a simulation study. It is shown that this performance is comparable to the performance of known methods such as the procedure Varclus of the software SAS. Finally, two methods for determining the number of groups are proposed and comparedRENNES2-BU Centrale (352382101) / SudocSudocFranceF

Anti-oomycete activities from essential oils and their major compounds on Phytophthora infestans

International audienceAbstract Botanicals are various plant-based products like plant extracts or essential oils. Anti-fungal activities of selected essential oils were tested on the pathogen causing potato and tomato late blight ( Phytophthora infestans ). Tests to evaluate anti-oomycete activities of commercial essential oils and their major compounds were carried out in vitro in microplate in liquid media. Anti-oomycete activities on Phytophthora infestans strain were obtained from essential oils/major compounds: Eucalyptus citriodora /citronellal; Syzygium aromaticum (clove)/eugenol; Mentha spicata /D-Carvone, L-Carvone; Origanum compactum /carvacrol; Satureja montana (savory)/carvacrol; Melaleuca alternifolia (tea tree)/terpinen-4-ol, and Thymus vulgaris /thymol. As an active substance of mineral origin, copper sulfate was chosen as a control. All selected essential oils showed an anti-oomycete activity calculated with IC 50 indicator. The essential oils of clove, savory, and thyme showed the best anti-oomycete activities similar to copper sulfate, while oregano, eucalyptus, mint, and tea tree essential oils exhibited significantly weaker activities than copper sulfate. Clove essential oil showed the best activity (IC 50 = 28 mg/L), while tea tree essential oil showed the worst activity (IC 50 = 476 mg/L). For major compounds, three results were obtained: they were statistically more active than their essential oils (carvacrol for oregano, D- and L-Carvone for mint) or as active as their essential oils sources (thymol for thyme, carvacrol for savory, terpinen-4-ol for tea tree) or less active than their original essential oils (eugenol for clove, citronellal for eucalyptus). Microscopical observations carried out with the seven essential oils showed that they were all responsible for a modification of the morphology of the mycelium. The results demonstrated that various essential oils show different anti-oomycete activities, sometimes related to a major compound and sometimes unrelated, indicating that other compounds must play a role in total anti-oomycete activity

Proposition d’un test de permutation dans le cadre d’une régression non linéaire pour l’évaluation de néo-fongicides

COMInternational audienceLes plantes cultivées sont régulièrement impactées par des champignons phytopathogènes qui peuvent causer des pertes quantitatives et qualitatives. Si l’utilisation de fongicides chimiques reste la réponse principale, de nouveaux fongicides bio-sourcés apparaissent sur le marché du biocontrôle ou sont en cours de développement grâce à une profonde attente sociétale (respect de l’environnement, développement de l’agriculture biologique, ...) et politique (plan Ecophyto2025, rapport agriculture innovations 2025, ...). L’évaluation de ces bio-fongicides nécessite d’optimiser les méthodes d’évaluations biologiques et statistiques. Ainsi, pour estimer et comparer au laboratoire l’efficacité de bio-fongicides, des essais en microplaques ou en boîtes de Pétri sont réalisés in vitro sur des champignons pathogènes de plantes. L’efficacité des bio-fongicides est évaluée par le calcul d’un indicateur de type CI 50 (la concentration d’inhibition à 50%) grâce à une régression non linéaire dans laquelle la CI 50 est un des paramètres estimés. Pour comparer les CI 50 , deux modèles sont ajustés, l’un avec des CI 50 dépendant du bio-fongicide, l’autre avec la même CI 50 pour tous les bio-fongicides. Un test F est utilisé pour comparer ces modèles. Les conditions d’application de ce test étant questionnables, une procédure de permutation adaptée au modèle est proposée pour le calcul de la p-value ainsi qu’une procédure bootstrap pour le calcul d’intervalles de confiance

Antifungal activity of essential oils on two Venturia inaequalis strains with different sensitivities to tebuconazole

International audienceThe antifungal activity of seven essential oils (eucalyptus, clove, mint, oregano, savory, tea tree, and thyme) was studied on Venturia inaequalis, the fungus responsible for apple scab. The composition of the essential oils was checked by gas chromatography-mass spectrometry. Each essential oil had its main compound. Liquid tests were performed to calculate the IC50 of essential oils as well as their majority compounds. The tests were made on two strains with different sensitivities to tebuconazole: S755, the sensitive strain, and rs552, the strain with reduced sensitivity. Copper sulfate was selected as the reference mineral fungicidal substance. IC50 with confidence intervals were calculated after three independent experiments. The results showed that all essential oils and all major compounds had in vitro antifungal activities. Moreover, it was highlighted that the effectiveness of four essential oils (clove, eucalyptus, mint, and savory) was higher than copper sulfate on both strains. For each strain, the best activity was obtained using clove and eucalyptus essential oils. For clove, the IC50 obtained on the sensitive strain (5.2 mg/L [4.0–6.7 mg/L]) was statistically lower than the IC50 of reduced sensitivity strain (14 mg/L [11.1–17.5 mg/L]). In contrast, for eucalyptus essential oil, the IC50 were not different with respectively 9.4–13.0 and 12.2–17.9 mg/L for S755 and rs552 strains. For mint, origano, savory, tea tree, and thyme, IC50 were always the best on rs552 strain. The majority compounds were not necessarily more efficient than their corresponding oils; only eugenol (for clove) and carvacrol (for oregano and savory) seemed to be more effective on S755 strain. On the other hand, rs552 strain seemed to be more sensitive to essential oils than S755 strain. In overall, it was shown that essential oils have different antifungal activities but do not have the same antifungal activities depending on the fungus strain used

Modélisation de l’accumulation du cadmium dans des légumes en fonction des concentrations extractibles des sols

AFFInternational audienc