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P Gaspard

Publications and source records attributed to P Gaspard.

At least 19 recordsLinked to original sources
PubMed2000

Entropy production, fractals, and relaxation to equilibrium

The theory of entropy production in nonequilibrium, Hamiltonian systems, previously described for steady states using partitions of phase space, is here extended to time dependent systems relaxing to equilibrium. We illustrate the main ideas by using a simple multibaker model, with some nonequilibrium initial state, and we study its progress toward equilibrium. The central results are (i) the entropy production is governed by an underlying, exponentially decaying fractal structure in phase space, (ii) the rate of entropy production is largely independent of the scale of resolution used in the partitions, and (iii) the rate of entropy production is in agreement with the predictions of nonequilibrium thermodynamics.

Journal Article↗
PubMed2000

Nonlinear Schrodinger flow in a periodic potential

We report a study of solutions of the defocusing nonlinear Schrodinger equation in a spatially periodic potential. The ground-state solution and the steady flows of the system are studied analytically. Above a critical current, a steady state no longer exists and time-dependent solutions are generated, which are numerically simulated and described.

Journal Article↗
PubMed1997

[Treatment of sludge from purification stations with the purpose of ameliorating soils intended for agriculture: parasitic contamination and model development with a view to managing the sanitation risk].

Helminth eggs (Ascaris, Taenia...) present in urban sludge constitute a sanitary risk when used for the enrichment of agricultural soil. These eggs are very resistant in the environment and their survival could reach 6 months to one year in soils. To control the risks for the public health, we have to determine parameters leading to the eggs destruction in soils. Then the aim of the work is to study several conditions (humidity, temperature, texture,...) that could influence the survival of intestinal nematode eggs in various types of soil. Survival experiments were carried out in clayey soil, silty-loam soil and sandy soils with humidity levels corresponding to: field capacities, wilting point and variation between this 2 limit point (storage temperatures 4 degrees C, 19 degrees C and 30 degrees C). The result of this study has shown that the temperature conditioned for a great part the survival of the eggs in all types of soils with survival times superior at two year with a temperature of 4 degrees C. Between survivals at 20 degrees C and 30 degrees C, no difference has been observed. The humidity is the second parameter that condition the egg survival with a good viability preservation at the wilting point. This study also shows better survival in the conditions of deep soil with the protection of the egg from drying. With these data and with the simulation of continental temperate conditions, a contamination rate of 0.35% could be found on the surface soil after one year and a more important rate in the deep soil with 10.6%. The last step is the validation of this model and calculated values seem to be a good evaluation of the results found on fields. All these data must be take into account for the establishment of the regulation about the urban sludge reused for agricultural purpose.

Agriculture↗
PubMed1995

Intracoronary stenting without coumadin: one month results of a French multicenter study.

In order to simplify post-coronary stenting treatment and to obtain a lower rate of complications, especially in bailout situations, seven French institutions treated 246 stented patients with 0.25 g/day of ticlopidine, 0.1 g/day of IV aspirin, and 2 days of heparin followed by low-molecular-weight heparin for 1 month. Fifty percent of patients had a planned stenting procedure, and 50% had an unplanned procedure, including 29 (11.8%) in bailout situations. Subacute occlusion occurred in three (1.2%) patients (one death, two non-Q-wave infarctions). During the 1 month follow-up period, another death was reported (non-stent-related), two elective coronary artery bypass grafts were performed, and three additional patients presented with non-Q-wave myocardial infarctions. Nine (3.7%) patients had a groin complication that required blood transfusion or surgical repair. These results suggest that while waiting for the technological advancements of stents, postprocedural treatment that includes a low dosage of ticlopidine, aspirin, and low-molecular-weight heparin is a very effective alternative to conventional poststenting therapy.

Adult↗
PubMed1993

Cardioprotective effect of intracoronary nifedipine during percutaneous transluminal coronary angioplasty. A French double-blind cross-over multicentre study.

The aim of this double-blind, placebo-controlled, cross-over study was to assess the cardioprotective effect of intracoronary nifedipine during percutaneous transluminal coronary angioplasty balloon occlusion. A balloon inflation without drug injection was initially made to ascertain that a shift of the ST segment (> or = 2 mm, 0.08 s after the J point) appeared (inclusion criterion). Two other balloon inflations were preceded by intracoronary injection of either 0.2 mg nifedipine or placebo, distal to the stenosis through the balloon catheter. The evaluation criteria were (1) time to ST segment shift, and (2) maximal amplitude of ST segment shift caused by balloon occlusion. Comparison of the data used an analysis of variance. Sixty-seven patients (mean age 54 +/- 8 years; 54 male, 13 female) were studied; 50 patients had 1-, 16 patients 2- and 1 patient 3-vessel disease. The dilated vessel was the left anterior descending coronary artery (n = 51), the right coronary artery (n = 12) and the left circumflex coronary artery (n = 4). Balloon inflation time was 100 +/- 31 s in the nifedipine group and 93 +/- 29 s in the placebo group. Five patients were excluded (procedure stopped after the first inflation in 1 and ST segment shift < 2 mm during the first inflation in 4). The time to 2-mm ST segment shift was longer in the nifedipine group than in the placebo group (62 +/- 40 s versus 51 +/- 40 s, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Irrigation with waste water: parasitological analysis of soil.

In third world countries, the agricultural use of treated wastewater represents an interesting solution. A recent report of W.H.O. shows the importance of strict parasitological criteria for such reuse. The aim of this paper is to study the conditions under which Ascaris eggs have been recovered from artificially contaminated soils (sandy, clay or loamy soil, mould garden). The eggs elution has been carried out from soil particles using various solutions (detergents, distilled water, formaldehyde, sodium hydroxide, sodium hypochlorite). The recovery percentage analysis showed the superiority of the sodium hypochlorite solution titrating 10 chlorometric degrees, whatever the soil type. The eggs concentration in the eluates has been carried out through the flotation technique by testing various reagents with densities ranging from 1.16 to 1.44. The zinc sulphate solution at 50%, 55% and 66% prove to be flotation agents that are well adapted to this sampling type. By carrying out the elution with a sodium hypochlorite solution titrating 10 chlorometric degrees and the concentration by flotation with a zinc sulphate solution at 55% the recovery percentages, which are independent of the parasitic load, vary from 66 to 78%.

Agriculture↗