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S Roux

Publications and source records attributed to S Roux.

At least 19 recordsLinked to original sources
PubMed2001

Specific heat of multifractal energy spectra.

Motivated by the self-similar character of energy spectra demonstrated for quasicrystals, we investigate the case of multifractal energy spectra, and compute the specific heat associated with simple archetypal forms of multifractal sets as generated by iterated maps. We considered the logistic map and the circle map at their threshold to chaos. Both examples show nontrivial structures associated with the scaling properties of their respective chaotic attractors. The specific heat displays generically log-periodic oscillations around a value that characterizes a single exponent, the "fractal dimension," of the distribution of energy levels close to the minimum value set to 0. It is shown that when the fractal dimension and the frequency of log oscillations of the density of states are large, the amplitude of the resulting log oscillation in the specific heat becomes much smaller than the log-periodic oscillation measured on the density of states.

Journal Article↗
PubMed2001

Experimental study of miscible displacement fronts in rough self-affine fractures.

Miscible fluid displacements are studied experimentally in a radial flow between two complementary replica of a self-affine rough granite fracture surface. The displacement front between a dyed fluid and a transparent (but otherwise identical) one is followed optically through one face of the cell. The evolution of its geometry is studied as a function of time, flow-rate, and normal and lateral relative displacements between the two surfaces. For a purely normal displacement, the front is globally smooth, due to the constant local distance between surfaces. For a finite lateral displacement, the front is rough due to spatial variations of this distance; its geometry is fractal and its dimension is directly related to the Hurst exponent H approximately 0.8 of the surface. The fractal regime is observed only above a lower cut-off scale that depends on the normal spacing of the surfaces and an upper one that increases with the injected volume and with the amplitude of the lateral displacement.

Journal Article↗
PubMed2001

Electroencephalographic activity during perception of motion in childhood.

The purpose of the present study was to relate observations of biological motion to cortical activity by evaluation of the association of quantified electroencephalogram (qEEG) parameters with a video film projection. Thirty right-handed healthy children (2-8-year-olds) viewed a video film showing still shots and moving shots with human movement or object movement. The EEG was recorded while children watched the video movie and was then subjected to spectral analysis; the spectral powers for theta, alpha and beta bands were matched with corresponding sequences of video film. The power values of each frequency band were analysed in a four-way repeated-measures ANOVA (Age x Hemisphere x Electrode x Sequence). Three main results were obtained: (i) younger children (2-4-year-olds) had higher power spectral values than older children (5-8-year-olds); (ii) greater EEG desynchronization of the left hemisphere was observed; (iii) observation of biological movement was related to a significant decrease in theta 1 and theta 2 power values of EEG in fronto-temporal and central regions of the left hemisphere compared with visual perception of still shots or nonhuman movement. These results indicated some support for the theory that the sensori-motor cortex and Broca's area are activated during visual observation of human motion.

Age Factors↗
PubMed2001

Brain and hippocampus fatty acid composition in phospholipid classes of aged-relative cognitive deficit rats.

The aim of this work was to study the composition of long chain fatty acids and the n-6 and n-3 fatty acid ratios in aged and young Wistar rats in brain and hippocampus, related to relative cognitive deficits. The aged animals showed cognitive deficits during acquisition of a memory task (delayed alternation). In brain, results showed a decrease in palmitoleic and palmitic acid percentages in all the studied phospholipid classes and in the phosphatidylserine and phosphatidylcholine classes, respectively, in old rats, compared to the young ones. There was also an increase in oleic and stearic acid amounts in the sphingomyelin, phosphatidylserine and phosphatidylinositol classes and in the phosphatidylserine and phosphatidylcholine classes, respectively. Arachidonic acid amount was decreased in old rats, compared to the young ones, in the phosphatidylserine and phosphatidylinositol classes. Total n-6 and n-3 fatty acid amounts were both decreased in all phospholipid classes, with a stable n-6/n-3 ratio. Our results confirm that arachidonic acid concentration is decreased in aged rats and that this reduction, more significant in phosphatidylserine and phosphatidylinositol classes, should be related to the fact that low concentrations of arachidonic acid are observed during activation of glutamate receptor.

Age Factors↗
PubMed2001

Indapamide, a thiazide-like diuretic, decreases bone resorption in vitro.

We recently showed that indapamide (IDP), a thiazide-related diuretic, increases bone mass and decreases bone resorption in spontaneously hypertensive rats supplemented with sodium. In the present study, we evaluated the in vitro effects of this diuretic on bone cells, as well as those of hydrochlorothiazide (HCTZ), the reference thiazide, and acetazolamide (AZ), a carbonic anhydrase (CA) inhibitor. We showed that 10(-4) M IDP and 10(-4) M AZ, as well as 10(-5) M pamidronate (APD), decreased bone resorption in organ cultures and in cocultures of osteoblast-like cells and bone marrow cells in the presence of 10(-8) M 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. We investigated the mechanism of this antiresorptive effect of IDP; IDP decreased osteoclast differentiation as the number of osteoclasts developing in coculture of marrow and osteoblast-like cells was decreased markedly. We then investigated whether IDP affected osteoblast-like cells because these cells are involved in the osteoclast differentiation. Indeed, IDP increased osteoblast-like cell proliferation and alkaline phosphatase (ALP) expression. Nevertheless, it did not modify the colony-stimulating factor 1 (CSF-1) production by these cells. In addition, osteoblast-like cells expressed the Na+/Cl- cotransporter that is necessary for the renal action of thiazide diuretics, but IDP inhibited bone resorption in mice lacking this cotransporter, so the inhibition of bone resorption and osteoclast differentiation did not involve this pathway. Thus, we hypothesized that IDP may act directly on cells of the osteoclast lineage. We observed that resorption pits produced by spleen cells cultured in the presence of soluble osteoclast differentiation factor (sODF) and CSF-1 were decreased by 10(-4) M IDP as well as 10(-5) M APD. In conclusion, in vitro IDP increased osteoblast proliferation and decreased bone resorption at least in part by decreasing osteoclast differentiation via a direct effect on hematopoietic precursors.

Animals↗
PubMed2001

Electromagnetic wave scattering from conducting self-affine surfaces: an analytic and numerical study.

We derive an analytical expression for the scattering of an s-polarized plane wave from a perfectly conducting self-affine one-dimensional surface in the framework of the Kirchhoff approximation. We show that most of the results can be recovered by means of a scaling analysis. We identify the typical slope taken over one wavelength as the relevant parameter controlling the scattering process. We compare our predictions with direct numerical simulations performed on surfaces of varying roughness parameters and confirm the broad range of applicability of our description up to very large roughness. Finally we verify that a nonzero electrical resistivity, provided that it is small, does not invalidate our results.

Journal Article↗
PubMed2001

Inhibition of arterial thrombosis by a soluble tissue factor mutant and active site-blocked factors IXa and Xa in the guinea pig.

The substrate recognition region of tissue factor contains two residues, Lys165 and Lys166, which are important for macromolecular substrate activation by the tissue factor:factor VIIa complex. Replacement of these two residues with alanine in a soluble version of human tissue factor resulted in a mutant, hTFAA, which can bind factor VIIa but forms an enzymatically inactive complex. We found that hTFAA inhibits the activity of guinea pig factor VIIa, allowing us to evaluate hTFAA's effects on thrombosis and hemostasis in a guinea pig model of recurrent arterial thrombosis. In addition to heparin, the effects of hTFAA were compared to active site inhibited factor IXa (F.IXai) and factor Xa (F.Xai). We found that hTFAA, F.IXai and F.Xai were potent antithrombotics and may possess a decreased risk of hemorrhage when compared to unfractionated heparin. When administered at a dose that inhibited thrombosis by about 90%, hTFAA neither affected cuticle bleeding nor the activated partial thromboplastin time, and had only a modest effect on the prothrombin time. At equi-efficacious doses, F.IXai, F.Xai and heparin prolonged bleeding times by 20% (p >0.5), 50% (p <0.05) and 100% (p <0.01), respectively. In summary, our study demonstrates that, unlike heparin, specific inhibitors of factors VIIa, IXa and Xa can produce antithrombotic effects without or with only minimally disturbing normal hemostasis. The results further suggest that factor VIIa and factor IXa are especially promising targets for antithrombotic drug development.

Amino Acid Substitution↗
PubMed2000

Maturation of frontal and temporal components of mismatch negativity (MMN) in children.

The mismatch negativity (MMN) response of auditory ERPs in adults appears to result from several overlapping components involving both frontal and temporal brain areas. Our aim was to test whether a similar configuration could be observed in children, and to examine the maturation rates of the different components. MMN (standard tones: 1000 Hz, deviants: 1100 Hz) was recorded from 28 scalp electrodes in 24 healthy children aged from 5 to 10 and in eight adults for comparison. Scalp current density analysis revealed both temporal and frontal components in children of all ages as well as in adults. Moreover the amplitudes of the temporal components were significantly greater in children than in adults, whereas the frontal components were similar at all ages. The results strongly suggest that MMN is mediated by at least two separate neural systems, and that the frontal system matures earlier than the sensory-specific system.

Acoustic Stimulation↗
PubMed2000

Bone loss. Factors that regulate osteoclast differentiation: an update.

Osteoclast activation is a critical cellular process for pathological bone resorption, such as erosions in rheumatoid arthritis (RA) or generalized bone loss. Among many factors triggering excessive osteoclast activity, cytokines such as IL-1 or tumour necrosis factor (TNF)-alpha play a central role. New members of the TNF receptor ligand family (namely receptor activator of nuclear factor-kappa B [RANK] and RANK ligand [RANKL]) have been discovered whose cross-interaction is mandatory for the differentiation of osteoclasts from hemopoietic precursors, in both physiological and pathological situations. Osteoprotegerin, a decoy receptor which blocks this interaction, decreases osteoclast activity and could have a fascinating therapeutic potential in conditions associated with upregulated bone resorption.

Cell Differentiation↗
PubMed2000

Self-organization, localization of shear bands, and aging in loose granular materials

We introduce a mesoscopic model for the formation and evolution of shear bands in loose granular media. Numerical simulations reveal that the system undergoes a nontrivial self-organization process which is governed by the motion of the shear band and the consequent restructuring of the material along it. High density regions are built up, progressively confining the shear bands in localized regions. This results in an inhomogeneous aging of the material with a very slow increase in the mean density, displaying an unusual glassylike system-size dependence.

Journal Article↗
PubMed2000

Bubbling and large-scale structures in avalanche dynamics.

Using a simple lattice model for granular media, we present a scenario of self-organization that we term self-organized structuring where the steady state has several unusual features: (1) large-scale spatial and/or temporal inhomogeneities and (2) the occurrence of a nontrivial peaked distribution of large events which propagate like "bubbles" and have a well-defined frequency of occurrence. We discuss the applicability of such a scenario for other models introduced in the framework of self-organized criticality.

Journal Article↗
PubMed2000

Evaluation of a ginkgo biloba extract (EGb 761) in functional tests for monoamine oxidase inhibition.

A standardized extract of ginkgo biloba (EGb 761) was evaluated in functional tests for monoamine oxidase (MAO) inhibition in mice: l-dihydroxyphenylalanine (CAS 59-92-7,1-DOPA) potentiation, tryptamine (CAS 61-54-1) potentiation, 5-hydroxytryptophan (CAS 4350-07-6,5-HTP) potentiation and phenylethylamine (CAS 64-04-0) potentiation. The doses investigated (25, 50 and 100 mg/kg p.o once daily for 5 days) were those known to possess anti-stress properties in other animal models. In contrast to the reference substances investigated (nialamide (CAS 51-12-7), clorgyline (CAS 17780-75-5) and 1-deprenyl (CAS 14611-52-01), EGb 761 did not exhibit any activity indicative of MAO inhibition. It was concluded that MAO inhibition was not the mechanism primarily responsible for EGb 761's anti-stress activity.

5-Hydroxytryptophan↗
PubMed2000

Wave scattering from self-affine surfaces

Electromagnetic wave scattering from a perfectly reflecting self-affine surface is considered. Within the framework of the Kirchhoff approximation, we show that the scattering cross section can be exactly written as a function of the scattering angle via a centered symmetric Levy distribution for the general roughness amplitude, Hurst exponent and wavelength of the incident wave. Our prediction is supported by direct numerical simulations.

Journal Article↗
PubMed2000

Thermally activated breakdown in the fiber-bundle model

Guarino et al., (cond-Mat/9908329) have recently introduced a fiber bundle model where fiber fracture can be thermally activated. Under a fixed (subcritical) loading, the mean failure time of the bundle is studied. An analytical expression for the latter is obtained as a function of the load. The effect of a (narrow) quenched disorder in the fracture stress of the fibers with a Gaussian distribution is shown to lead to an effective temperature simply translated with respect to the actual one. Finally, some "critical" properties of fracture precursors which have been proposed are investigated within the present model.

Journal Article↗
PubMed2000

A new model of chronic cardiac ischemia in rabbits.

Chronic cardiac ischemia has mainly been studied in large species such as pigs or dogs. Little research has been performed using small species such as rabbits. In the present study, 1-3 wk after implantation of a novel device (ameroid) on the circumflex coronary artery of New Zealand White rabbits, vessel patency was evaluated by coronary angiography, corrosion cast, and radiolabeled microspheres. Coronary angiograms showed, after 21 days, either total occlusion or severe stenosis in seven of eight arteries, which was confirmed by corrosion casts. The ameroid group had less blood flow in the epicardial (-62%) and endocardial (-54%) layers of the ischemic area compared with sham-operated rabbits (P < 0.05). Blood flow increased in the ischemic area compared with day 0 during acute occlusion, suggesting that progressive coronary occlusion initiated the growth of de novo collateral vessels. Thus we have developed a new model of chronic cardiac ischemia in rabbits with documented progressive coronary stenosis and occlusion that is suitable to test various therapeutic angiogenesis strategies.

Animals↗
PubMed2000

The family history of patients with primary or secondary antiphospholipid syndrome (APS).

OBJECTIVE: To evaluate familial history for evidence of antiphospholipid syndrome (APS) and autoimmune disease in rheumatology department patients with primary or secondary APS. METHODS: We retrospectively studied patients with APS and systemic lupus erythematosus (SLE) managed at the Rheumatology Department of the Bichat University Hospital, Paris, between 1987 and 1996. Data were collected by chart review and by a 1997 standardized telephone interview. RESULTS: We identified 108 patients with APS managed during the ten-year study period. According to classical classification criteria, 39 patients had primary antiphospholipid syndrome (PAPS) and 69 secondary antiphospholipid syndrome (SAPS). Family history data were obtained for 29 (74%) and 55 (80%) PAPS and SAPS patients. respectively (78% of the 108 patients). Twelve PAPS (41% and 19 SAPS (35%) patients had one or more relatives with evidence of at least one clinical feature of APS such as thrombosis or recurrent fetal loss; of these patients, seven in the PAPS (24%) and 11 in the SAPS (20%) group had two or more relatives with evidence of a clinical feature of APS. Three PAPS (10%) and 14 SAPS (25%) patients had one or more family members with an autoimmune disease. CONCLUSION: A positive family history for autoimmune disease and/or antiphospholipid syndrome is common in patients with PAPS or SAPS. This finding supports a genetic contribution to APS. The percentage of a positive family history for autoimmune disease tend to be higher in patients with SAPS than in those with PAPS.

Abortion, Habitual↗
PubMed2000

Private practice interdisciplinary breast centers: their rationale and impact on patients, physicians, and the health care industry: a bicoastal perspective.

This article reports on the experience of two private practice breast centers in New York and California. It demonstrates that comprehensive breast centers directed by full-time breast imagers have a significant impact on medical care from the perspective of the patient, her physicians, and the health care system. These two centers, separated by a continent, disparate in their formation and founding philosophies, yield very similar results in breast cancer diagnosis, reduction of the benign biopsies, and improving the cost of breast biopsies.

Biopsy↗