1,832 research outputs found
Experimental study of the compaction dynamics for 2D anisotropic granular materials
We present an experimental study of the compaction dynamics for
two-dimensional anisotropic granular systems. Compaction dynamics is measured
at three different scales : (i) the macroscopic scale through the packing
fraction , (ii) the mesoscopic scale through both fractions of aligned
grains and ideally ordered grains , and (iii) the
microscopic scale through both rotational and translational grain mobilities
. The effect of the grain rotations on the compaction dynamics has
been measured. At the macroscopic scale, we have observed a discontinuity in
the late stages of the compaction curve. At the mesoscopic scale, we have
observed the formation and the growth of domains made of aligned grains. From a
microscopic point of view, measurements reveal that the beginning of the
compaction process is essentially related to translational motion of the
grains. The grains rotations drive mainly the process during the latest stages
of compaction.Comment: 8pages, 11 figure
Ripple and kink dynamics
We propose a relevant modification of the Nishimori-Ouchi model [{\em Phys.
Rev. Lett.} {\bf 71}, 197 (1993)] for granular landscape erosion. We explicitly
introduce a new parameter: the angle of repose , and a new process:
avalanches. We show that the parameter leads to an asymmetry of the
ripples, as observed in natural patterns. The temporal evolution of the maximum
ripple height is limited and not linear, according to recent
observations. The ripple symmetry and the kink dynamics are studied and
discussed.Comment: 7 pages, 10 figure, RevTe
Identification of tenuis of four French Polynesian <i>Carapini</i> (Carapidae: Teleostei)
Four species of adult Carapini (Carapidae) occur on Polynesian coral reefs: Encheliophis gracilis, Carapus boraborensis, C. homei and C. mourlani. Samples collected in Rangiroa and Moorea allowed us to obtain different tenuis (larvae) during their settlement phases or directly inside their hosts. These were separated into four lots on the basis of a combination of pigmentation, meristic, morphological, dental and otolith (sagittae) features. Comparison of these characters with those of the adults allows, for the first time, taxonomic identification of these tenuis-stage larvae
Scaling in the Bombay Stock Exchange Index
In this paper we study BSE Index financial time series for fractal and
multifractal behaviour. We show that Bombay stock Exchange (BSE)Index time
series is mono-fractal and can be represented by a fractional Brownian motion.Comment: 11 pages,3 figure
Dimer percolation and jamming on simple cubic lattice
We consider site percolation of dimers (``neadles'') on simple cubic lattice.
The percolation threshold is estimated as . The jamming threshold is estimated as .Comment: 3 pages, 4 figures, submitted to EPJ
Intraocular Pressure Correlates with Optic Nerve Sheath Diameter in Patients with Normal Tension Glaucoma
PURPOSE: 1. Identify differences in optic nerve sheath diameter (ONSD) as an indirect measure of intracranial pressure (ICP) in glaucoma patients and a healthy population. 2. Identify variables that may correlate with ONSD in primary open-angle glaucoma (POAG) and normal tension glaucoma (NTG) patients.
METHODS: Patients with NTG (n = 46) and POAG (n = 61), and healthy controls (n = 42) underwent B-scan ultrasound measurement of ONSD by an observer masked to the patient diagnosis. Intraocular pressure (IOP) was measured in all groups, with additional central corneal thickness (CCT) and visual field defect measurements in glaucomatous patients. Only one eye per patient was selected. Kruskal-Wallis or Mann-Whitney were used to compare the different variables between the diagnostic groups. Spearman correlations were used to explore relationships among these variables.
RESULTS: ONSD was not significantly different between healthy, NTG and POAG patients (6.09 ± 0.78, 6.03 ± 0.69, and 5.71 ± 0.83 respectively; p = 0.08). Visual field damage and CCT were not correlated with ONSD in either of the glaucoma groups (POAG, p = 0.31 and 0.44; NTG, p = 0.48 and 0.90 respectively). However, ONSD did correlate with IOP in NTG patients (r = 0.53, p 0.25 in all groups).
CONCLUSIONS: Indirect measurements of ICP by ultrasound assessment of the ONSD may provide further insights into the retrolaminar pressure component in glaucoma. The correlation of ONSD with IOP solely in NTG patients suggests that the translaminar pressure gradient may be of particular importance in this type of glaucoma
Tailles de première maturité et de capture de six espèces de poisson-chat dans le delta de l’Ouémé au Bénin (Afrique de l’Ouest)
Dans le moyen delta de l’Ouémé au Bénin, les tailles de première maturité et de capture des populations de six espèces de poisson-chat ont été étudiées. Il s’agit de Clarias gariepinus, de C. ebriensis, de Schilbe intermedius, de S. mystus, de Synodontis schall et de S. nigrita. La relation de type sigmoïde entre le pourcentage de maturité sexuelle (P) et la taille (Lt) des poissons a été déterminée d’après le modèle logistique de Dagnelie (1973). L’équation générale de Von Bertalanffy (1938) incorporée au logiciel FISAT II a permis de déterminer les tailles de première capture (Lc50). En général, les mâles maturent à une taille inférieure à celle des femelles. Les tailles à la première maturité (L50) sont supérieures aux tailles de première capture (Lc50). On en déduit une surexploitation des six populations de poissons étudiées qui sont en général pêchées avant la première reproduction. Il serait intéressant que les poissons soient capturés à une plus grande taille (Lc50 > L50)Keywords: Poissons-chats, maturité sexuelle, exploitation, delta de l’Ouémé
- …