Cerebellar Zones: A Personal History

Cerebellar zones were there, of course, before anyone noticed them. Their history is that of young people, unhindered by preconceived ideas, who followed up their observations with available or new techniques. In the 1960s of the last century, the circumstances were fortunate because three groups, in Leiden, Lund, and Bristol, using different approaches, stumbled on the same zonal pattern in the cerebellum of the cat. In Leiden, the Häggqvist myelin stain divulged the compartments in the cerebellar white matter that channel the afferent and efferent connections of the zones. In Lund, the spino-olivocerebellar pathways activated from individual spinal funiculi revealed the zonal pattern. In Bristol, charting the axon reflex of olivocerebellar climbing fibers on the surface of the cerebellum resulted in a very similar zonal map. The history of the zones is one of accidents and purposeful pursuit. The technicians, librarians, animal caretakers, students, secretaries, and medical illustrators who made it possible remain unnamed, but their contributions certainly should be acknowledged

An Occurrence of Interstratified Kaolinite-smectite Minerals in a Red-black Soil Toposequence

ABSTRACT: Interstratified kaolinite-smectite minerals form the major part of a pedon transitional between 'red ' kaolinitic and black smectitic soils in a soil toposequence derived from basalt in Burundi, Central Africa. These interstratified kaolinite-smectites have many X-ray, morphological and chemical features incommon with 'tabular halloysite'. Modifications tothe 001 spacings of these minerals brought about by thermal nd chemical treatments, however, show that they are not halloysite but consist of a mixture of ~ 70~o kaolinite and 30~o smectite randomly interstratified. Field evidence indicates that hese clays can be considered asa transient stage in the overall reaction smectite--,kaolinite + ron oxides, which takes place in this landscape whenever the slope gradients give rise to better drainage conditions. When Wilson & Cradwick (1972) reported the first occurrence of interstratified kaolinite-smectite n soils, they suggested that, as X-ray criteria for identifying such clays had now been made available, further accounts of such occurrences could be expected. Although several subsequent papers described similar minerals occurring in sediment

Formation de radicaux libres sur la surface des montmorillonites

Recent contributions from Ducros, Chaussidon and Fripiat' s laboratories have shown that residual water molecules firmly held in interlayer position between montmorillonite sheets have a degree of dissociation higher than usual. Interesting physical and chemical properties due to this dissociation phenomenon have been reported elsewhere. The present paper aims to describe the deep modifications undergone by cyclic and polycyclic derivatives adsorbed by montmorillonites . Triphenyl carbinol is transformed into triphénylcarbonium by reaction with the protons produced by the dissociation of residual water. Coronene and ovalene are also deeply modified but the nature of this reaction is still hypothetical. U.V. spectroscopy ans X-Ray diffraction were the main analytical tools used in this work.Des recherches récentes menées dans les laboratoires de Ducros, de Chaussidon et de Fripiat ont montré que l'eau résiduelle fortement adsorbée par les surfaces internes de la mont-morillonite était caractérisée par un degré de dissociation particulièrement élevé. Il en découle diverses conséquences tant dans le domaine des propriétés physiques que chimiques. Le but de cette contribution est de montrer que des dérivés polycycliques adsorbés par la montmorillonite subissent de profondes modifications de structure. Le triphénylcarbinol forme l'ion triphénylcarbonium par réaction avec les ions hydrogène provenant de la décomposition de l'eau résiduelle. Le coronène et l'ovalène adsorbés par les montmorillonites subissent des modifications dont la nature est encore hypothétique. La spectroscopic dans l'ultraviolet a été la technique principalement utilisée mais la diffraction des rayons X a également fourni des indications intéressantes .Fripiat José Jean, Helsen J., Vielvoye L. Formation de radicaux libres sur la surface des montmorillonites. In: Bulletin du Groupe français des argiles. Tome 15, nouvelle série n°10, 1964. pp. 3-10