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L Raynaud

Publications and source records attributed to L Raynaud.

6 recordsLinked to original sources
PubMed1999

Large-Scale Bundle Ordering in Sterically Stabilized Latices.

Time-resolved small-angle light scattering and linear conservative dichroism measurements are presented for concentrated, sterically stabilized, aqueous latices under simple shear flow. At low stress levels, flow causes a mild distortion of the liquid-like structure in colloidally stable dispersions, which is quite well understood. In this paper flow-induced structures are investigated in concentrated dispersions when the system is brought far from equilibrium by means of hydrodynamic forces. At high stress levels various structural changes have been predicted by numerical simulation, among others string phases oriented in the flow direction. Here, experimental results are reported on a bundle-like ordering in very dense systems, which involves a length scale much larger than that of a single string of particles. Two latices, with different particle sizes and different thicknesses of the stabilizing layer, are compared. The occurrence of the bundle-like ordering is related to the rheological behavior: it causes a significant decrease in viscosity. It is shown that the presence of this phase results in a structural hysteresis, which explains a thixotropic behavior that is encountered in some stable colloidal suspensions. Also the relaxation behavior of the bundle-like phases has been studied. Interparticle forces are found to have a very strong effect on the relaxation time scales. Copyright 1999 Academic Press.

Journal Article↗
PubMed1998

Identification of Encephalitozoon intestinalis in travelers with chronic diarrhea by specific PCR amplification.

With the use of Weber's modified trichrome and Uvitex 2B techniques, spores of microsporidia were detected in the stools of four travelers presenting clinically with chronic diarrhea. The general health of these patients was not impaired, and human immunodeficiency virus screening was negative. Immune evaluation, including the study of lymphocytic subpopulations, assay of serum immunoglobulins, and an intradermal multitest, showed normal results. Molecular identification of microsporidian species was based on the PCR amplification of a small-subunit rRNA sequence followed by HinfI endonuclease restriction. Encephalitozoon intestinalis microsporidiosis was thus shown in two of the four patients examined. In two patients, therapy based on albendazole made stools devoid of microsporidian spores without influence on the intestinal disorders. The pathogenic role of E. intestinalis in immunocompetent individuals remains to be demonstrated.

Animals↗
PubMed1996

Cerebral activations during number multiplication and comparison: a PET study.

Positron emission tomography was used to examine the cerebral networks underlying number comparison and multiplication in eight normal volunteers. Cerebral blood flow was measured within anatomical regions of interest defined in each subject using magnetic resonance imaging. Three conditions were used: rest with eyes closed, mental multiplication of pairs of arabic digits and larger-smaller comparison of the same pairs. Both multiplication and comparison activated the left and right lateral occipital cortices, the left precentral gyrus, and the supplementary motor area. Beyond these common activations, multiplication activated also the left and right inferior parietal gyri, the left fusiform and lingual gyri, and the right cuneus. Relative to comparison, multiplication also yielded superior activity in the left lenticular nucleus and in Brodmann's area 8, and induced a hemispheric asymmetry in the activation of the precentral and inferior frontal gyri. Conversely, relative to multiplication, comparison yielded superior activity in the right superior temporal gyrus, the left and right middle temporal gyri, the right superior frontal gyrus, and the right inferior frontal gyrus. These results underline the role of bilateral inferior parietal regions in number processing and suggest that multiplication and comparison may rest on partially distinct networks.

Adult↗
PubMed1985

Carpipramine metabolism in the rat, rabbit and dog and in man after oral administration.

Carpipramine administered orally is excreted via the urine and faeces in rat, rabbit, dog and man. Many metabolites are formed, including several conjugates in the urine. A total of 20-25 metabolites was detected by t.l.c. and h.p.l.c., 16 of which were isolated and identified. Three metabolic pathways were observed: hydroxylation of the iminodibenzyl ring to a phenol or alcohol without modification of the side-chain, hydroxylation of the terminal piperidine of the 2-piperidinol side-chain, and cyclization and dehydrogenation of the same 2-piperidinol group.

Animals↗
PubMed1983

Comparison of the metabolism of oltipraz in the mouse, rat and monkey and in man. Distribution of the metabolites in each species.

4-Methyl-5-(2-pyrazinyl)-1,2-dithiole-3-thione (35 972 R.P., oltipraz) and its metabolites were extracted from human urine and from mouse, rat and monkey urine using Amberlite XAD4 resin. The metabolites were identified by GLC, TLC and HPLC and isolated by preparative TLC or HPLC. The structures of 11 compounds were determined by spectroscopic examination (MS, IR, NMR). Six of the principal metabolites isolated in sufficient quantity from human urine were administered to the mouse, confirming the metabolic pathways of oltipraz.

Acetylation↗