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E Clement

Publications and source records attributed to E Clement.

7 recordsLinked to original sources
PubMed2000

Stresses in silos: comparison between theoretical models and new experiments

We present precise and reproducible mean pressure measurements at the bottom of a cylindrical granular column. If a constant overload is added, the pressure is linear in overload and nonmonotonic in the column height. The results are quantitatively consistent with a local, linear relation between stress components, as was recently proposed by some of us. They contradict the simplest classical (Janssen) approximation, and may rather severely test competing models.

Journal Article↗
PubMed2000

Pattern formation in a vibrated granular layer: the pattern selection issue

We present a numerical study of a surface instability occurring in a bidimensional vibrated granular layer. The driving mechanism for the formation of stationary waves is closely followed. Two regimes of wavelength selection are identified: a dispersive regime where the wavelength decreases with increasing frequency and a saturation regime where the value of the wavelength is a constant depending on the number of grains in the vertical direction. For the dispersive regime an empirical relation is proposed, based on dimensional arguments involving transport properties in the layer. A comparison is made with existing experimental results in two and three dimensions. For the saturation regime, a connection is established between the pattern formation and an intrinsic instability occurring spontaneously in dissipative gases. The observed dependence on the layer height is linked to a detailed dissipation mechanism for the collisions between grains.

Journal Article↗
PubMed1997

[A new type of headache of ocular origin: ophthalmotonic headache. Diagnosis and treatment].

INTRODUCTION: In some patients it was seen that chronic headaches disappeared after laser iridectomies had been done to prevent glaucoma, in persons with normal intra-ocular pressure (IOP). OBJECTIVE: To make a study of patients with headache, some of whom were treated with topical beta-blockers (carteolol) and others by Yag-laser iridectomies. The effect on headache and IOP was analyzed. MATERIAL AND METHODS: A survey, ophthalmological examination and headache provocation test were carried out in patients with headaches, and the changes in IOP determined by pharmacologically inducing miosis and mydriasis were recorded. Three treatment groups were formed and the results analyzed statistically. RESULTS: In the 12 patients treated pharmacologically, 62% improved and in 14% the headaches disappeared. In the 16 treated using laser 94% were cured and 6% improved. When both types of treatment were used on 9 patients, 22% improved and 78% were cured. The validity of the ocular pressure curve was checked in the diagnosis of blockage of the pupil. CONCLUSIONS: Some headaches of ocular origin (ophthalmotonic), not previously described, occur due to abrupt changes in intraocular pressure, and improve significantly when the IOP is reduced by beta-blockers or Yag-laser iridectomies are done. A valid provocation tests for diagnosis of this type of headache is described. We consider that blockage of the pupil and/or of the angle of the anterior chamber are possible etiopathogenic mechanisms.

Adrenergic beta-Antagonists↗