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Université de Fribourg

A unilateral section of the corticospinal tract at cervical level in Primate does not lead to measurable cell loss in Motor cortex

Wannier, Thierry. ; Schmidlin, Eric ; Bloch, Jocelyne ; Rouiller, Eric M.

In: Journal of Neurotrauma, 2005, vol. 22(6), p. 703

The effects of a unilateral interruption of the dorsolateral funiculus at cervical level on the survival of neurons in the motor cortex were investigated in macaque monkeys. The lesion was made on the left side at the transition region between the 7th and 8th cervical segments, above the motoneurons controlling hand muscles. As a result, the homolateral hand became paretic,...

Université de Neuchâtel

Multi-scale analysis of shell growth increments using wavelet transform

Toubin, M. ; Dumont, C. ; Verrecchia, Eric P. ; Laligant, O. ; Diou, A. ; Truchetet, F. ; Abidi, M. A.

In: Computers & Geosciences, 1999, vol. 25, no. 8, p. 877-885

Shell increments contain information related to the evolution of the environment in which the organism grew during its biomineralization. To extract the information from variations in shell topography, a new and promising technique is presented, involving multi-scale analysis of the shell topography using a B-spline wavelet transform. An accurate non-contact optical system, based on laser...

Université de Neuchâtel

La classification des premiers organismes vivants

Verrecchia, Eric P. ; Dupraz, Christophe ; Pattisina, Ronny

In: Pour la Science (Dossier), 2004, vol. 44, p. 84-89

Les stromatolithes fossiles sont les témoins des plus anciens organismes de la planète. Leur nomenclature était fondée, à tort, sur des différences de formes qui pouvaient résulter, l’analyse moderne le montre, d’une même espèce.

Université de Neuchâtel

Monitoring organic matter dynamics in soil profiles by 'Rock-Eval pyrolysis' : bulk characterization and quantification of degradation

Sebag, D. ; Disnar, J. R. ; Guillet, B. ; Di Giovanni, C. ; Verrecchia, Eric P. ; Durand, A.

In: European Journal of Soil Science, 2005, vol. 57, no. 3, p. 334-355

Rock-Eval pyrolysis was designed for petroleum exploration to determine the type and quality of organic matter in rock samples. Nevertheless, this technique can be used for bulk characterization of the immature organic matter in soil samples and recent sediments. We studied 76 samples from seven soil classes and showed that their pyrograms can be described by a combination of four elementary...

Université de Neuchâtel

Lacustrine and palustrine carbonate petrography : an overview

Freytet, Pierre ; Verrecchia, Eric P.

In: Journal of Paleolimnology, 2002, vol. 27, p. 221-237

Lacustrine limestones were formerly identified by their faunistic (limnea, planorbis) and floristic (Charophytes) content. For 30 years, indications of pedogenesis have been found in many lacustrine deposits, and consequently the concept of palustrine limestone was defined. Lacustrine fabrics are not that numerous: varved, laminated, homogeneous, peloidal, brecciated, gravelly, bioturbated...

Université de Neuchâtel

Biomineralization in plants as a long-term carbon sink

Cailleau, Guillaume ; Braissant, Olivier ; Verrecchia, Eric P.

In: Naturwissenschaften, 2004, vol. 91, p. 191-194

Carbon sequestration in the global carbon cycle is almost always attributed to organic carbon storage alone, while soil mineral carbon is generally neglected. However, due to the longer residence time of mineral carbon in soils (102–106 years), if stored in large quantities it represents a potentially more efficient sink. The aim of this study is to estimate the mineral carbon accumulation due...

Université de Neuchâtel

Is the contribution of bacteria to terrestrial carbon budget greatly underestimated ?

Braissant, Olivier ; Verrecchia, Eric P. ; Aragno, Michel

In: Naturwissenschaften, 2002, vol. 89, no. 8, p. 366-370

Some commonly found species of soil bacteria use low molecular weight organic acids as their sole source of carbon and energy. This study shows that acids such as citrate and oxalate (produced in large amounts by fungi and plants) can rapidly be consumed by these bacteria. Two strains, Ralstonia eutropha and Xanthobacter autotrophicus, were cultured on acetate- and citrate-rich media. The...

Université de Neuchâtel

The natural hydrous sodium silicates from the northern bank of Lake Chad : occurrence, petrology and genesis

Sebag, D. ; Verrecchia, Eric P. ; Lee, Seong-Joo ; Durand, A.

In: Sedimentary Geology, 2001, vol. 139, p. 15-31

Hydrous sodium silicates sometimes associated with zeolites, form in an alkaline environment, in which there is a high concentration of dissolved silica. Such an environment existed during the Holocene in N'Guigmi interdunal depressions (Lake Chad), which led to the precipitation of various types of hydrous sodium silicates, including magadiite, kenyaite, and zeolites. Scanning electron and...

Université de Neuchâtel

Biologically induced mineralization in the tree Milicia excelsa (Moraceae) : its causes and consequences to the environment

Braissant, Olivier ; Cailleau, Guillaume ; Aragno, Michel ; Verrecchia, Eric P.

In: Geobiology, 2004, vol. 2, p. 59-66

Iroko trees (Milicia excelsa) in Ivory Coast and Cameroon are unusual because of their highly biomineralized tissues, which can virtually transform the trunk into stone. Oxalic acid (C2O4H2) and metal-oxalate play important roles in their ecosystems. In this study, the various forms of oxalate and carbonate mineralization reactions are investigated by using scanning electron microscopy and X-ray...