Exit problems related to the persistence of solitons for the Korteweg-de Vries equation with small noise

We consider two exit problems for the Korteweg-de Vries equation perturbed by an additive white in time and colored in space noise of amplitude a. The initial datum gives rise to a soliton when a=0. It has been proved recently that the solution remains in a neighborhood of a randomly modulated soliton for times at least of the order of a^{-2}. We prove exponential upper and lower bounds for the small noise limit of the probability that the exit time from a neighborhood of this randomly modulated soliton is less than T, of the same order in a and T. We obtain that the time scale is exactly the right one. We also study the similar probability for the exit from a neighborhood of the deterministic soliton solution. We are able to quantify the gain of eliminating the secular modes to better describe the persistence of the soliton

Contract renewal as an incentive device. An application to the French urban public transport sector

In the French urban public transport industry, services are often delegated to a private firm by the mean of a fixed-term regulatory contract. This contract specifies the duties of the firm and a financial compensation. When it expires, a new contract is awarded, possibly to a different operator. Cost-plus and fixed-price (gross cost or net cost) contracts are commonly used to regulate the operators in the transport industry. In this paper, we analyse the incentives for the operator to reduce its cost. These incentives come from both the profit maximization during the current contract and the perspective of contract renewal. In our model, the amount of cost-reducing effort depends on the contract type and the time remaining till contract expiration. We use a sample of 124 French urban public transport networks covering the period 1995-2002 to test our predictions. Our proxy for the cost reducing effort is technical efficiency. The data largely confirm the importance of contract type on performances and the incentive effect of contract renewal.incentive regulation, urban transport, stochastic frontier analysis.

Contract Renewal as an Incentive Device. An Application to the French Urban Public Transport Sector

In the French urban public transport industry, services are often delegated to a private firm by the mean of a fixed-term regulatory contract. This contract specifies the duties of the firm and a financial compensation. When it expires, a new contract is awarded, possibly to a different operator. Cost-plus and fixed-price (gross cost or net cost) contracts are commonly used to regulate the operators in the transport industry. In this paper, we analyse the incentives for the operator to reduce its cost. These incentives come from both the profit maximization during the current contract and the perspective of contract renewal. In our model, the amount of cost-reducing effort depends on the contract type and the time remaining till contract expiration. We use a sample of 124 French urban public transport networks covering the period 1995-2002 to test our predictions. Our proxy for the cost reducing effort is technical efficiency. The data largely confirm the importance of contract type on performances and the incentive effect of contract renewal.

Étude de la propagation des ondes radio dans les environnements planétaires

In the Solar System, the study of the radio emissions at very low frequencies (from few kHz up to few MHz) is a source of information about the processes of acceleration of electrons in the planetary environment and in the Solar Wind. The understanding of the emission mechanisms and the knowledge of the methods of detection enable to probe the physical conditions of the plasma sources. This dissertation deals with the propagation of the radio waves in the planetary environment. Their inhomogeneous characteristics could induce a non-linear path of rays in addition to the anisotropy of the plasma caused by the presence of magnetic fields. The study of wave propagation effects permits to relax the hypothesis of rectilinear propagation between the source and the detectors, to track the evolution of the wave characteristics and to probe the propagating medium. The theoretical study of the propagation of electromagnetic waves in magnetized and anisotropic plasma led to the development of a generalized ray tracing code, that includes the calculation of the polarization state of the wave along the rays: ARTEMIS-P (Anisotropic Ray Tracer for Electromagnetism in Magnetosphere, Ionosphere and Solar wind, including Polarization). This code led to two studies: on the one hand, the modeling of the "Over-the-Horizon" effect consisting of the detection of guided radio signatures associated with lightning bursts in Saturn atmosphere, and on the other hand, the characterization of the influence of the auroral cavities profile on the beaming of the Auroral Kilometric Radiation (AKR) at the Earth.Dans le système solaire, l’étude des rayonnements radio très basse fréquence (de quelques kHz à quelques MHz) permet d’obtenir des informations sur les proces- sus d’accélération des électrons dans les environnements planétaires et dans le vent solaire. La compréhension des mécanismes d’émission et la maîtrise des moyens de détection permettent de sonder les conditions physiques dans les plasmas sources. Cette thèse porte sur l’étude de la propagation des ondes radio dans les environne- ments planétaires. Leur caractère inhomogène implique que la propagation n’est pas obligatoirement rectiligne, et la présence des champs magnétiques ambiants rend le plasma anisotrope. L’étude des phénomènes de propagation permet de s’affranchir d’une hypothèse de propagation en ligne droite entre les sources du rayonnement et les détecteurs, de suivre l’évolution des caractéristiques des ondes et de sonder le milieu de propagation. L’étude théorique de la propagation des ondes électroma- gnétiques dans les plasmas magnétisés a mené au développement d’un code général de tracé de rayons, calculant également l’état de polarisation de l’onde le long des rayons : ARTEMIS-P (Anisotropic Ray Tracer for Electromagnetism in Magnetosphere, Ionosphere and Solar wind, including Polarization). Ce code nous a permis de me- ner deux études : l’effet de détection au-delà de l’horizon des signatures radio des éclairs d’orages de Saturne et l’influence de l’ionosphère sur la propagation des ondes radio produites dans l’atmosphère de Saturne, et l’influence du profil des cavités auro- rales sur le diagramme de rayonnement des sources de l’émission kilométrique terrestre

Designing exploratory partnerships in Southeast Asia: The challenge of building a sustainable ecosystem to address chronic malnutrition

International audienceMalnutrition linked to under nutrition is a cause of 3.1 million child deaths annually. Stakeholders from all over the word, gathered within various organizations, from public to private sector, tend to work together to fight against this disease that affects very vulnerable people. However, these stakeholders are generally highly dependent on numerous geopolitical issues and form together a highly fragmented ecosystem, which appears to be not efficient enough to provide nutrition solutions to all affected children. At the same time, researchers have identified for decades that other forms of malnutrition, such as chronic malnutrition, could also result from dietary habits that are linked to specific sociocultural contexts, which require a radically different approach: instead of treating an easily diagnosable patient, the aim is to prevent and change nutritional habits, and the mass of affected children is much larger. Thus, innovative partnerships beyond NGOs, local actors and public agencies need to be explored, for instance with private actors, to consider new ways to structure such a sustainable ecosystem. And the shift in the understanding of how to treat the disease entails necessarily deep changes in the structuration of an appropriate ecosystem to deal with it, which also highlights the need for a collective capability for innovation.In this paper, we tackle the organizational issue of building a sustainable ecosystem, both robust and innovative, to prevent chronic malnutrition in Southeast Asia. In particular, we study the building of innovative partnerships that contribute to long-term nutrition transition in this area where there international funds alone are not sufficient to support the stunting prevention, and thus private and public actors must work to develop hybrids models

Cerebral and Peripheral Changes Occurring in Nitric Oxide (NO) Synthesis in a Rat Model of Sleeping Sickness: Identification of Brain iNOS Expressing Cells

International audienceBACKGROUND: The implication of nitric oxide (NO) in the development of human African trypanosomiasis (HAT) using an animal model, was examined. The manner by which the trypanocidal activity of NO is impaired in the periphery and in the brain of rats infected with Trypanosoma brucei brucei (T. b. brucei) was analyzed through: (i) the changes occurring in NO concentration in both peripheral (blood) and cerebral compartments; (ii) the activity of nNOS and iNOS enzymes; (iii) identification of the brain cell types in which the NO-pathways are particularly active during the time-course of the infection. METHODOLOGY/PRINCIPAL FINDINGS: NO concentration (direct measures by voltammetry) was determined in central (brain) and peripheral (blood) compartments in healthy and infected animals at various days post-infection: D5, D10, D16 and D22. Opposite changes were observed in the two compartments. NO production increased in the brain (hypothalamus) from D10 (+32%) to D16 (+71%), but decreased in the blood from D10 (-22%) to D16 (-46%) and D22 (-60%). In parallel with NO measures, cerebral iNOS activity increased and peaked significantly at D16 (up to +700%). However, nNOS activity did not vary. Immunohistochemical staining confirmed iNOS activation in several brain regions, particularly in the hypothalamus. In peritoneal macrophages, iNOS activity decreased from D10 (-83%) to D16 (-65%) and D22 (-74%) similarly to circulating NO. CONCLUSION/SIGNIFICANCE: The NO changes observed in our rat model were dependent on iNOS activity in both peripheral and central compartments. In the periphery, the NO production decrease may reflect an arginase-mediated synthesis of polyamines necessary to trypanosome growth. In the brain, the increased NO concentration may result from an enhanced activity of iNOS present in neurons and glial cells. It may be regarded as a marker of deleterious inflammatory reactions

Is There a Relationship between Ovarian Epithelial Dysplasia and Infertility?

Aim. Ovarian epithelial dysplasia was initially described in material from prophylactic oophorectomies performed in patients at genetic risk of ovarian cancer. Similar histopathological abnormalities have been revealed after ovulation stimulation. Since infertility is also a risk factor for ovarian neoplasia, the aim of this study was to study the relationship between infertility and ovarian dysplasia. Methods. We blindly reviewed 127 histopathological slides of adnexectomies or ovarian cystectomies according to three groups—an exposed group to ovulation induction (n = 30), an infertile group without stimulation (n = 35), and a spontaneously fertile control group (n = 62)—in order to design an eleven histopathological criteria scoring system. Results. The ovarian dysplasia score was significantly higher in exposed group whereas dysplasia score was low in infertile and control groups (resp., 8.21 in exposed group, 3.69 for infertile patients, and 3.62 for the controls). In the subgroup with refractory infertility there was a trend towards a more severe dysplasia score (8.53 in ovulation induction group and 5.1 in infertile group). Conclusion. These results raise questions as to the responsibility of drugs used to induce ovulation and/or infertility itself in the genesis of ovarian epithelial dysplasia

Acetabular Peri-Prosthetic Fractures-A Narrative Review.

Acetabular peri-prosthetic fractures are rare but their incidence is rising due to the increased prevalence of total hip arthroplasty, the increasing life expectancy and the growing functional demand of an ageing population, the incidence of primary total hip arthroplasty is increasing. They are either intra-operative or post-operative and have various aetiologies. Several factors such as implant stability, bone loss, remaining bone stock, fracture pattern, timing, age and co-morbidities of the patients must be considered for adequate treatment. To date, the literature on this subject has been sparse and no universally recognized treatment algorithm exists. Their rarity makes them a little-known entity and their surgical management represents a challenge for most orthopaedic surgeons. This review aims to present an update on epidemiology, the diagnostic work up, existing classification systems, surgical approaches and therapeutic options for acetabular peri-prosthetic fractures

Identification of the bacteria and their metabolic activities associated with the microbial spoilage of custard cream desserts

The famous French dessert “ile flottante” consists of a sweet egg white foam floating on a vanilla custard cream,which contains highly nutritive raw materials, including milk, sugar and egg. Spoilage issues are therefore a keyconcern for the manufacturers. This study explored the bacterial diversity of 64 spoiled custard cream dessertsmanufactured by 2 French companies. B. cereus group bacteria, coagulase negative Staphylococcus, Enterococcus and Leuconostoc spp. were isolated from spoiled products. Thirty-one bacterial isolates representative of the main spoilage species were tested for their spoilage abilities. Significant growth and pH decrease were observed regardless of species. While off-odours were detected with B. cereus group and staphylococci, yoghurt odours were detected with Enterococcus spp. and Leuconostoc spp. B. cereus group bacteria produced various esters and several compounds derived from amino acid and sugar metabolism. Most Staphylococci produced phenolic compounds. Enterococcus spp. and Leuconostoc spp. isolates produced high levels of compounds derived from sugar metabolism. Each type of spoilage bacteria was associated with a specific volatile profile and lactic acid was identified as a potential marker of spoilage of custard cream-based desserts. These findings provide valuable information for manufacturers to improve food spoilage detection and prevention of chilled desserts made with milk and egg

Design and characterization of extreme-ultraviolet broadband mirrors for attosecond science

International audienceA novel multilayer mirror was designed and fabricated based on a recently developed three-material technology aimed both at reaching reflectivities of about 20% and at controlling dispersion over a bandwidth covering photon energies between 35 and 50 eV. The spectral phase upon reflection was retrieved by measuring interferences in a two-color ionization process using high-order harmonics produced from a titanium: sapphire laser. We demonstrate the feasibility of designing and characterizing phase-controlled broadband optics in the extreme-ultraviolet domain, which should facilitate the manipulation of attosecond pulses for applications