Ward's Hierarchical Clustering Method: Clustering Criterion and Agglomerative Algorithm

The Ward error sum of squares hierarchical clustering method has been very widely used since its first description by Ward in a 1963 publication. It has also been generalized in various ways. However there are different interpretations in the literature and there are different implementations of the Ward agglomerative algorithm in commonly used software systems, including differing expressions of the agglomerative criterion. Our survey work and case studies will be useful for all those involved in developing software for data analysis using Ward's hierarchical clustering method.Comment: 20 pages, 21 citations, 4 figure

Identifying Prototypical Components in Behaviour Using Clustering Algorithms

Quantitative analysis of animal behaviour is a requirement to understand the task solving strategies of animals and the underlying control mechanisms. The identification of repeatedly occurring behavioural components is thereby a key element of a structured quantitative description. However, the complexity of most behaviours makes the identification of such behavioural components a challenging problem. We propose an automatic and objective approach for determining and evaluating prototypical behavioural components. Behavioural prototypes are identified using clustering algorithms and finally evaluated with respect to their ability to represent the whole behavioural data set. The prototypes allow for a meaningful segmentation of behavioural sequences. We applied our clustering approach to identify prototypical movements of the head of blowflies during cruising flight. The results confirm the previously established saccadic gaze strategy by the set of prototypes being divided into either predominantly translational or rotational movements, respectively. The prototypes reveal additional details about the saccadic and intersaccadic flight sections that could not be unravelled so far. Successful application of the proposed approach to behavioural data shows its ability to automatically identify prototypical behavioural components within a large and noisy database and to evaluate these with respect to their quality and stability. Hence, this approach might be applied to a broad range of behavioural and neural data obtained from different animals and in different contexts

Micromorphological and chemical investigation of late-Viking age grave fills at Hofstaðir, Iceland

Grave fills from seven human burials from a late-Viking age - early medieval cemetery at Hofstaðir, Mývatnssveit (Iceland) were examined by soil micromorphology and organic chemical analysis. Detailed analysis of the weathering of the mineral constituents of the grave fills demonstrates a relationship between the extent of weathering of volcanic silicates within the fills and the presence of buried human remains. Gas chromatography-mass spectrometry (GC–MS) of extracts from the fills and controls of two graves revealed organic signatures dominated by plant-derived organic matter, with no evidence of degradation products of the body tissues. Transformation of n-alkanes into n-alkan-2-ones provides evidence for microbial activity within the fills. GC–MS analysis of the organic extract from under one of the skulls and pyrolysis gas chromatography of wood fragments found in that grave provide compelling evidence for the former presence of a conifer wood coffin. The use of this non-native wood in the burial provides evidence for either the import of foreign lumber or the utilisation of driftwood, most likely originating from Russia/Siberia

Sols et paysages forestiers du Poitou oriental

Dupuis J., Jambu P. Sols et paysages forestiers du Poitou oriental . In: Norois, n°42, Avril-Juin 1964. pp. 201-205

Contribution à l'étude des sols de la partie orientale du Marais Poitevin (Marais mouillé)

SUMMARY The « Marais Poitevin » is an ancient marine gulf, filled with recent alluvions. Dike-building has occasioned the differentiation of two areas : the « dried-up marsh » near the sea and the « wet marsh » in the inner part of the ancient gulf where several rivers couring from the environing plateaus converge. This wet marsh is affected every winter by scattering of floods. The marine deposits that have filled up the gulf almost exclusively consist of heavy clay (scrobicularia-clay). Upstream, after the retirement of the sea, a marshy vegetation of soft water has covered the heavy clay with a peat-layer of variable thickness. This peat disappears under fluvialile clays along the rivers, or under colluvial deposits in the valley of the river Mignon. All these deposits date from the Holocène. The soils are monophasic and they have only be influenced by the actual climate. They are too recent to show an important profile-development. Hydromorphism is a general characteristic of all the soils ; its intensity is more or less a function of artificial drainage-works.RÉSUMÉ Le Marais Poitevin est un ancien golfe marin comblé par des alluvions récentes. La construction de digues a conduit à la différenciation de deux terroirs : le « Marais Desséché » en bordure de la mer et le « Marais Mouillé » au fond de l'ancien golfe au débouché des rivières venues du Bocage qui constitue une zone d'épandage des crues. Les apports marins qui ont comblé le golfe sont presque exclusivement constitués d'une argile lourde : le bri (argile à scrobiculaires). En amont, après le recul de la mer, une végétation marécageuse d'eau douce a recouvert le bri sous une couche variable de tourbe plus ou moins épaisse. Les tourbes disparaissent elles-mêmes sous des argiles fluviatiles le long des rivières, ou sous des colluvions dans la vallée du Mignon. Tous ces dépôts sont d'âge Holocène. Les sols sont monophasés et n'ont subi que l'empreinte du climat actuel. Ils sont trop récents pour être différenciés. L'hydromorphie est générale mais variable, commandée par le réseau des canaux artificiels.Jambu P., Nijs R. Contribution à l'étude des sols de la partie orientale du Marais Poitevin (Marais mouillé). In: Norois, n°52, Octobre-Décembre 1966. pp. 565-593

Effects of addition of clay minerals on the fatty acid fraction of a podzol soil

International audienceThe Al horizon of a sandy podzol soil, with a very small proportion of clay-sized material, was sampled and homogenized. Samples, both with and without supplementation with 150 g clay minerals kg-1, natural heteroionic bentonite (saturated with Na, Ca, Mg, K), Mg-bentonite or Fe-kaolinite, were moistened to two-thirds of water-holding capacity and incubated at 28°C for 16 weeks. After incubation, lipids were extracted with 3:1 light petroleum: ethylacetate mixture in a Soxhlet apparatus as unbound components (directly extractable by organic solvents) and bound components (only extractable after treatment with acids). Monoacids (free and esterified), diacids, ketoacids and hydroxyacids were isolated from the two lipidic fractions (unbound and bound) by column chromatography. The different components of each family were analyzed by gas chromatography (GC) or gas chromatography-mass spectrometry (GC-MS). Incubation without supplementation generated a selective decrease in abundance of free mono-acids in unbound and bound fractions. The decrease was in inverse proportion to the chain-length of components. Soil supplementation with bentonite (homoionic or heteroionic) did not induce an overall quantitative change, but promoted a transfer of fatty acids from the unbound to the bound fraction, increased the exchange between free and esterified monoacids (transesterification) and stimulated hydrolysis of glycerides. In contrast, soil supplementation with Fe-kaolinite caused much decomposition or biotransformation of monoacids but it did not induce change either in the intensity of transesterification in the wax ester fraction or in the intensity of hydrolysis in the glyceride fraction. Copyright \textcopyright 1995, Wiley Blackwell. All rights reserve

Rôle des acides fulviques dans la mobilisation du fer et de l'aluminium

Dupuis Jacques, Dupuis Thérèse, Jambu Pierre, Righi Dominique. Rôle des acides fulviques dans la mobilisation du fer et de l'aluminium. In: Phénomènes de transport de matière dans l'écorce terrestre. ATP - CNRS. Action thématique Programmée du Centre National de la Recherche Scientifique. Résultats scientifiques. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1979. pp. 7-11. (Sciences Géologiques. Mémoire, 53

Les rendzines historiques des buttes coquillères de Saint-Michel-en-l'Herm (Vendée)

National audienc

Rôle des acides fulviques dans la mobilisation du fer et de l'aluminium

Dupuis Jacques, Dupuis Thérèse, Jambu Pierre, Righi Dominique. Rôle des acides fulviques dans la mobilisation du fer et de l'aluminium. In: Phénomènes de transport de matière dans l'écorce terrestre. ATP - CNRS. Action thématique Programmée du Centre National de la Recherche Scientifique. Résultats scientifiques. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1979. pp. 7-11. (Sciences Géologiques. Mémoire, 53