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The understanding of astrophysical phenomena requires to deal with robust numerical tools in order to handle realistic scales in terms of energy, characteristic lengths and Mach number that cannot be easily reproduced by means of laboratory experiments. In this paper, we present the 2D numerical code HADES for the simulation of realistic astrophysical phenomena in various contexts, first taking into account radiative losses. The version of HADES including a multigroup modeling of radiative transfer will be presented in a forthcoming study. Validation of HADES is performed using several benchmark tests and some realistic applications are discussed. Optically thin radiative loss is modeled by a cooling function in the conservation law of energy. Numerical methods involve the MUSCL-Hancock finite volume scheme as well as HLLC and HLLE Riemann solvers, coupled with a second-order ODE solver by means of Strang splitting algorithm that handles source terms arising from geometrical or radiative contributions, for cartesian or axisymmetric configurations. A good agreement has been observed for all benchmark tests, either in hydrodynamic cases or in radiative cases. Furthermore, an overview of the main astrophysical studies driven with this code is proposed. First, simulations of radiative shocks in accretion columns and supernova remnant dynamics at large timescales including Vishniac instability have improved the understanding of these phenomena. Finally, astrophysical jets are investigated and the influence of the cooling effect on the jet morphology is numerically demonstrated. It is also found that periodic source enables to recover pulsating jets that mimic the structure of Herbig–Haro objects. HADES code has revealed its robustness, especially for the wall-shock test and for the so-called implosion test which turns out to be a severe one since the hydrodynamic variables are self-similar and become infinite at finite time. The simulations have proved the efficiency of HADES code and the usefulness of this tool for astrophysical applications.

In this paper, we investigate the properties of solitonic structures arising in quadratic media. First, we recall the derivation of systems governing the interaction process for waves propagating in such media and we check the local and global well-posedness of the corresponding Cauchy problem. Then, we look for stationary states in the context of normal or anomalous dispersion regimes, that lead us to either elliptic or non-elliptic systems and we address the problem of orbital stability. Finally, some numerical experiments are carried out in order to compute localized states for several regimes and to study dynamic stability as well as long-time asymptotics.

This paper deals about pure hydrodynamic and radiation hydrodynamic codes developed at LUTH, dedicated to astrophysical simulations. The studied phenomena in this area are often encountered at high Mach number and in a radiation regime where no a priori assumption can be made on the radiation transfer. The radiative hydrodynamic code HADES has to can perform simulations as well as any optical depths, from smallest to highest. Validation of numerical schemes or physical assumptions will be made by laboratory astrophysical experiments. Therefore a very wide domain of initial conditions has to be accepted for computing. A succinct presentation of three codes is done, accompanied with some astrophysical applications.

In this paper, we prove a criterion to determine if a black soliton solution (which is an odd solution that does not vanish at infinity) to a one-dimensional nonlinear Schr?dinger equation is linearly stable or not. This criterion handles the sign of the limit at 0 of the Vakhitov?Kolokolov function. For some nonlinearities, we numerically compute the black soliton and the Vakhitov?Kolokolov function in order to investigate linear stability of black solitons. We then show that linearly unstable black solitons are also orbitally unstable. In the Gross?Pitaevskii case, we rigorously prove the linear stability of the black soliton. Finally, we numerically study the dynamical stability of these solutions solving both linearized and fully nonlinear equations with a finite differences algorithm.

For near the first lasing threshold, we give a detailed derivation of a real order parameter equation for the degenerate optical parametric oscillator with a saturable absorber. For this regime, we study analytically the role of the quasi-homogeneous neutral mode in the pattern formation process. We show that this effect stabilized the hexagonal patterns below the lasing threshold. More importantly, we find numerically that when Turing and Hopf bifurcations interact, a stable moving asymmetric localized structure with a constant transverse velocity is generated. The formation of the moving localized structures is analysed for both the propagation and the mean field models. A quantitative confrontation of the two models is discussed.

In this note, we numerically investigate a stochastic nonlinear Schrödinger equation derived as a perturbation of the deterministic NLS equation. The classical NLS equation with focusing nonlinearity of power law type is perturbed by a random term; it is a strong perturbation since we consider a space-time white noise. It acts either as a forcing term (additive noise) or as a potential (multiplicative noise). For simulations made on a uniform grid, we see that all trajectories blow-up in finite time, no matter how the initial data are chosen. Such a grid cannot represent a noise with zero correlation lengths, so that in these experiments, the noise is, in fact, spatially smooth. On the contrary, we simulate a noise with arbitrarily small scales using local refinement and show that in the multiplicative case, blow-up is prevented by a space-time white noise. We also present results on noise induced soliton diffusion.

La formation de structures localisees intenses dans le profil transverse du faisceau signal transmis par un oscillateur parametrique degenere (DOPO), presente un regime transitoire de coalescence pendant lequel la taille des domaines correspondants a des solutions de signes opposes s'agrandit selon une loi de puissance t 1/3 .

We derive general nonlinear equations relevant to describe the propagation of powerful pump electromagnetic fields launched within a plasma (underdense or overdense). The powerful pump (such as obtained with short laser pulses) creates nonlinear-induced collective electromagnetic perturbations with matter lying in the relativistic regime. One main result is the self-consistent treatment of the coupled equations between the pump and the perturbations. In particular, the self-generated magnetic field could modify the pump propagation. We point out a mechanism due to the relativistic ponderomotive force (whose derivation is provided) to produce a magnetic field that may be stronger than those fields derived with a non-self-consistent approach. As an application we investigate the possibility of relativistic magnetic guiding of light under the combined action of the self-induced density and magnetic field.

The stresses generated in alumina scales during different oxidation stepscontrol the protective character of such scales and their lifetime. Laboratoryand industrial Fe–Cr–Al alloys, differing by their impuritycontent and preparation, and for which the oxidation kinetics werepreviously characterized, were studied here to experimentally determine ortheoretically calculate the stress level in the alumina scales. Theexperiments were performed by X-ray diffraction (XRD) at room temperature,using the sin2psi method. The oxide-stress level wascorrelated with many parameters, such as the scale microstructure andmorphology, the nature of the substrate, the substrate and oxide thickness,the oxide grain size, the cooling rate, etc. A numerical elasto-viscoplasticmodel was developed to calculate the thermal stresses and to point out theeffect of the relaxation phenomena either during cooling or duringisothermal treatment after oxidation. The results obtained by theelasto-viscoplastic model are in good agreement with the experimental ones.

Schrodinger-like equations play an essential role in the modeling of plasmas created by laser beams, and taking into account of relativistic terms yields a new kind of nonlinearity in them, as compared to the classical case. A numerical scheme involving a new handling of absorbing conditions suitable for Schrodinger-like equations is given, and several general models are studied: the classical cubic case linked to the Kerr effect for an anharmonic plasma, where numerical experiments prove the efficiency of our code applied to the computation of solitons and explosive solutions. Furthermore, new kinds of explosive solutions are computed, and we numerically show the essential role of the ground state to get approximations of the cubic explosive solution by global ones. A multiphotonic ionization model is also studied including higher-order terms in the nonlinearity. In this case, we obtain stable structures physically explained by competing saturation processes. These structures have been experimentally detected. Finally, a relativistic model involving the Lorentz kinematic factor in the evolution equations is investigated numerically; filamentary structures are found in agreement with predicted relativistic phenomena. © 1999 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 15: 672–696, 1999

Transparent boundary conditions for the Schrodinger equation iϖ t u + Δu = 0 are deduced from the solution of the Cauchy problem set in the whole space. They are established at the hypersurface { x n = 0}. Approximating the symbol of these conditions by means of rational fractions, and introducing auxiliary functions at the boundary, local absorbing conditions are derived. Then, expressing them without surfacic functions, the link between the two kinds of conditions is made.

Nonlinear equations are derived relevant to describe the propagation of powerful electromagnetic fields launched within a plasma. The nonlinear generation of self-induced collective electromagnetic perturbations are obtained with matter lying in the relativistic regime. Our main result is the self-consistent treatment of the coupled equations between the pump and its self-induced fields. In particular, a mechanism is pointed out for self-generation of quasistatic magnetic field that is due to the relativistic ponderomotive force. This process is found to be more efficient to produce quasistatic magnetic fields, as confirmed by recent experiments, as compared to known effects such as the inverse Faraday effect. As an application, we investigate conditions for relativistic magnetic guiding of light to occur under the combined action of the self-induced density and magnetic field.

Labyrinthine structures often appear as the final steady state of pattern forming systems. Being disordered, they exhibit the same kind of short range positional order as the Newell-Pomeau turbulent crystal. Labyrinths can be seen as a limit case of the texture of disordered rolls with a coherence length of the same order as the wavelength. In the various two-dimensional model equations we looked at, labyrinths and parallel rolls are steady states for the same parameters, their occurrence depending on the initial conditions. Comparing the stability of these two structures, we find that in variational models their energy is very close, rolls always being more stable than labyrinths. For the nonvariational model we propose a numerical experiment which displays a well defined bifurcation from parallel rolls to labyrinths as the more stable state.

The degenerate optical parametric oscillator may generate very high-intensity two-dimensional localized structures. A quantitative comparison of the propagation and the mean-field models is presented for different mistunings, corresponding to monostable and bistable homogeneous solutions. In both models, we study the circular domain walls as an example of localized structures. The peak intensities are comparable; the difference lies mainly in their domain of existence as a function of the pump amplitude parameter.

The authors present the results of an investigation conducted, under the aegis of the PETRI association, on 701 patients living in the Paris region who, over a 1-year period, had asked the medical advisers of the Social Security Sickness Benefits department to dispense them from paying their portion of the cost of treatment on the ground that they had cancer of the bladder*. The purposes of the investigation were to obtain accurate data concerning the role played by tobacco and alcohol abuse in bladder cancer and to look for possible occupational exposures. The smoking and drinking habits of 636 patients could be analyzed: 89 percent of the men were, or had been, smokers with an average consumption of 33 packs per annum, and with a frequent overconsumption of alcoholic drinks. The professional cursus of 665 patients (31 percent active, 64 percent retired) could be established. The study confirmed that tobacco smoking and alcohol abuse, as well as certain occupational factors, play a role in the development of bladder cancer. Some professional sectors, such as the plastic industry or the hide and leather work, were better represented among these patients than would have been expected from their distribution in the active population. Surveillance of the population exposed by industrial doctors, and follow-up of people who have retired from some sectors of activity are as essential as anti-smoking campaigns.

We study the dynamics of the formation of circular domain walls, which are large-intensity structures, in a degenerate optical parametric oscillator. We show that the mean-field and the propagation models predict the same increase in the domain size proportional to t(1/3) ., Journal Article, info:eu-repo/semantics/published

A total of 197 definite cases of mesothelioma (mainly of the pleura) have been reported by pathologists to the French Mesothelioma Register for the period 1965--78. A moderate linear increase in the annual incidence of mesothelioma cases since 1965 was noted. In men and women over the ages of 47 and 41 years, respectively, the annual death rate was higher in those with mesothelioma than in those of the general population. The proportions of mesothelioma patients who had experienced occupational, para-occupational, and unknown asbestos exposures were 77%, 3%, and 20% respectively. The number of cases reported to the register is obviously an underestimate of the true number of mesothelima cases in France, because such cases are not reported to the register systematically. Mesothelioma registers cannot provide information about dose-response relationships; however, with good management of the register, such relationships could be obtained, since a good assessment of dose can be accomplished by biologic monitoring.

A mesothelioma register was initiated in France in 1975 to record pathologists, cases diagnosed since 1965. These cases have been accepted as definite mesothelioma after histological reexamination by the mesothelioma panel. Histories of asbestos exposure have been recorded using a standardized questionnaire. Among 699 cases reported, 296 were confirmed and 79 excluded by the panel. Twenty per cent of cases were females. Tumour was located in the pleura in 96% of cases. Age at death was lower for the mesothelioma group than for the general population. A linear increase of annual incidence since 1965 has been observed. Mapping of cases showed irregular distribution with areas without any case. Distribution of cases according to asbestos exposure was the following: definite occupational history 50%, definite non-occupational 3%, possible occupational 31%, undiscovered 16%. Distribution of cases according to the latency period showed a two peaks-curve, median being 36 years. The obvious under-reporting of cases and the absence of control group greatly affected the validity of some results.

Three groups of people working in buildings with insufficient protection against sources of asbestos (ceilings, lagging, cupboards, etc.) have been compared by clinical and radiological examinations. The first group, G1 (n = 160), comprised people working in direct contact with sources of asbestos; the second one, G2 (n = 277), comprised people who had worked for at least 10 years in buildings with little protection; and the third one, G3 (n = 157), may be considered a control group, since the only period of exposure was while the buildings were being constructed. The prevalence of lung abnormalities (clinical, functional and radiological) was higher in G1 than in G3; G2 was closer to G1 for some signs, but closer to G3 for most. These differences are no explained by obvious possible confounding factors (such as age, sex or tobacco consumption). They were analysed taking the number of years of presence in the buildings into account.

Two different methods have been tested for assessing retrospectively occupational exposure to asbestos dust in 80 cases with suspected asbestos-related thoracic diseases: 1) Occupational history was recorded by an interviewer using a standardized questionnaire. The patients were divided into three groups: those obviously exposed (E), those obviously not exposed (NE) and those with an inconclusive questionnaire (IQ). 2) Ferruginous bodies were isolated from lung washing fluid and counted under the light microscope. In the questionnaire groups, the proportions positive for ferruginous bodies in lung washing fluid were as follows: E, 29/33; NE, 1/7; IQ, 17/40. In cases positive for ferruginous bodies in lung washing fluid, the median numbers of bodies per ml of fluid were: E, 11.7 (range, 0.05-31,250); NE, 0.06; IQ, 1.1 (range, 0.06-350) Since the data provided by the two methods were in good agreement (P less than 0.001) for the E and NE questionnaire groups, the presence of ferruginous bodies in lung washing fluid is considered to be a good indicator of past exposure. In the IQ group, the monitoring of ferruginous bodies in lung washing fluid demonstrated exposure to asbestos in 43% of cases.

Different lung function tests have been studied in a group of 39 spray workers, with exposure of a few months to 20 years, in order to determine early impairments in ventilatory or gaseous exchange parameters. Lung function was assessed by conventional spirometric tests, plethysmographic measurement of lung volume, determination of arterial oxygen tension at rest and on exercise and measurement of single-breath diffusion of carbon monoxide. Asbestos exposure was assessed using a standardized questionnaire administered by an interviewer to determine length of exposure, and light microscopic examination to ascertain the number of ferruginous bodies in one sputum sample or in lung washing fluid. The results of the functional tests are expressed with respect either to duration of working exposure or to the number of ferruginous bodies. Restrictive ventilatory impairment with decrease in diffusion of carbon monoxide and increase in the oxygen alveolar-arterial difference on exercise was observed both in the group with 1-50 ferruginous bodies and in workers exposed for more than five years. The decrease in lung volume was approximately 10% when the length of asbestos exposure varied from 0-5 to 10-15 years, and 15% between those with no ferruginous bodies and those with more than 50. No obstructive profile was observed, even in heavy smokers. All function tests were altered equally. Plethysmography therefore appears to be a suitable technique for the follow-up of asbestos workers.

A matched survey of 55 full-time workers probably exposed to asbestos in an electricity-generating power station (exposed group) and of 53 unexposed workers in an automobile plant has been conducted. The asbestos risk in the power station was confirmed by the presence of airborne fibers in the range 0.1--6000 X 10(-9) g/m3 in the air sampled during the survey period and by the presence of FB in the sputa of 32.7% of the workers. The following parameters were significantly related to asbestos exposure in the study group: FB in the sputa, localized rectitude of the diaphragm, pleural thickening, pleural calcification, and the chest pain. Moreover, for all persons studied, gastrointestinal symptoms and recent hoarsening of the voice were significantly related to the number of FB in the sputa.

The object of the ILO/UC International Classification of Pneumoconioses and the general instructions for its use in asbestos respiratory diseases have been set forth. The ILO 1979 classification has been used in four groups of asbestos exposed subjects : two groups were hospitalized and two groups were at work. All the subjects have been investigated by a hospitalized and two groups were at work. All the subjects have been investigated by a standardized questionnaire on occupational history, PA and lateral chest X-rays and, for most them, by ferruginous bodies counting either in sputum or in bronchoalveolar lavage. The most frequent radiological signs were parenchymal fibrosis, pleural thickening, pleural calcification and diaphragmatic straightness. The fibrosis and the diaphragmatic straightness were related to the length of the exposure. Up to 20-29 years since the onset of exposure, the frequency of radiological signs was : diaphragmatic straightness more frequent than fibrosis which was more frequent than pleural thickening, which was more frequent than calcification. But the frequency of only two signs, pleural straightness and fibrosis, appeared significant after 10 years of exposure. The value of these four radiological signs as biological indicators of asbestos exposure is discussed.

Typically, the functional abnormalities in individuals exposed to asbestos dust take the form of a pulmonary fibrosis. Recently, several authors have stressed the early existence of small airways obstruction. In the present study, by measurement of closing volume, we have confirmed an obstructive factor in a certain number of exposed subjects, even if they were non-smokers, i.e. had no other apparent reason for small airways disease.

Thirty-six histologically confirmed cases of pleural and peritoneal mesothelioma have been observed in a chest unit over a period of 53 months. The past asbestos exposure was assessed by a standardized questionnaire in all cases and the asbestos lung burden was determined by means of mineralogical analysis of lung-related biological specimens (sputum, bronchoalveolar lavage fluid, lung tissues) in 28 cases. The results of these two methods were found in good agreement. Past asbestos exposure has been definitely implicated in 17 cases and definitely eliminated in 10 cases. The results were inconclusive in other cases. The group with definite past asbestos exposure was different from the nonasbestos-exposed group by clinical, biological, pathological, and prognosis features that were analyzed. In cases without past asbestos exposure there were no other possible causative agents. Younger age and similar incidence in men and women suggest an environmental or natural disease.

The relationship was studied between the presence in X-rays of one or several regions of straightness on the diaphragm, which interrupt or replace its normal curve, and the intensity, length and latency of asbestos exposure. Subjects were four groups in whom intensity of exposure, assessed by questionnaire and by ferruginous body counts, increased progressively. Diaphragmatic straightness increased with increasing intensity but not with length or latency of asbestos exposure.