Optical Bloch modeling of femtosecond-laser-induced electron dynamics in dielectrics.

A model based on optical Bloch equations is developed to describe the interaction of femtosecond laser pulses with dielectric solids, accounting for optical-cycle-resolved electron dynamics. It includes the main physical processes at play: photoionization, impact ionization, direct and collisional laser heating, and recombination. By using an electron band structure, this approach also accounts for material optical properties as nonlinear polarization response. Various studies are performed, shedding light on the contribution of various processes to the full electron dynamics depending on laser intensity and wavelength. In particular, the standard influence of the impact ionization process is retrieved.

Spectral characterization of second harmonic chi((2)) cascading phenomena.

The second harmonic generation in a thin ss-barium borate crystal is used to measure chi ((2)) cascading phenomena in the spectral domain. The harmonic generation is induced by two pulses produced by spectrally filtering a femtosecond pulse and centered at the wavelength lambda -Delta lambda and lambda +Delta lambda. New spectral components appear in spectral density of both the fundamental and harmonic pulses. High order cascading phenomena are evidenced. In good agreement with theoretical predictions, for large phase mismatch the evolution of the spectra demonstrates the competition between cascaded chi(2) and chi(3) phenomena.

Linear and nonlinear model of the human middle ear.

The measurement of the middle ear transfer function usually requires invasive methods. An equivalent analog equivalent model enables us to evaluate its characteristics without damaging any part of the ear. A linear and a nonlinear model of the middle ear have been developed to predict intracochlear pressure and the stapes volume velocity for various sound pressure levels (SPL). The linear model results have been compared with human eardrum impedance and middle ear transfer function data. The nonlinear phenomena due to the contraction of the stapedius muscle over 80 dB and to the stapes clipping displacement above 120 dB are represented by a set of variable electrical components. The model of the acoustic reflex is based on experimental observations. The study of the annular ligament behavior was performed on cats and extrapolated to humans with some hypothetical restrictions. These approximations provide information on the middle ear transfer function and enable us to better understand the nonlinear middle ear mechanisms in an intense acoustic field.

[The proper use of antimalarial drugs currently available]. / Du bon usage des médicaments antipaludiques actuellement disponibles.

French medical practitioners have at their disposal several antimalarial drugs for giving chemoprophylaxis to people travelling to a malaria endemic country or treating an imported malaria case in a patient. The choice depends on the contre-indications and indications of each drug, essentially subordinated to the presence and level of Plasmodium falciparum chemosensitivity in the visited area. For prevention, chloroquine alone can be taken in the areas where P. falciparum is absent or not chloroquine resistant; elsewhere, the choice between chloroquine/proguanil or mefloquine depends on knowing the prevalence and level of falciparum chloroquine resistance in these areas. For treatment, the only indications of chloroquine are imported malaria cases either due to P. vivax, P. ovale or P. malariae, or caused by P. falciparum contracted in one of the rare countries where the species is still sensitive to chloroquine. For uncomplicated falciparum malaria cases acquired in a chemoresistance area, mefloquine, halofantrine, sulfadoxine-pyrimethamine or oral quinine is selected, depending on the observed chemoprophylaxis, the contra-indications and the suspicion of chemoresistance type. Whatever the provenance area, P. falciparum in a patient with one or several serious symptoms or possibly profuse vomiting is treated by intravenous quinine, associated with tetracycline if the patient comes from an area known for a low quinine sensitivity of this species. The spectrum of falciparum malaria treatment has recently broadened to include new drugs such as artemisinin, artemether or atovaquone/proguanil, the latter being as yet unauthorized in France.

[Immunocompromised travelers]. / Le voyage du sujet immunodéficient.

More and more immunocompromised people travel abroad especially in tropical countries where infectious risks are high. Before leaving, these subjects must consult their general practitioner who will determine their fitness in function of type of immunodeficiency, travel destination, availability of medical care at the destination, and possibility of medical evacuation. Counseling should also be provided concerning the precautions necessary to avoid the hazards of exposure to fecal material, venereal disease, insect bites, and sun. Antimalarial drug prophylaxis is the same as for uncompromised subjects. Advising immunocompromised subjects about vaccinations is difficult since there is no consensus on the subject. Administration of inert vaccines is usually recommended but their effectiveness is often diminished and harmful effects have been observed in HIV-infected subjects. Administration of live vaccines is always contraindicated in severely immunocompromised subjects but some live vaccines can be used in moderately immunocompromised subjects. The guidelines for vaccination differ depending on the underlying cause of immunodeficiency: congenital defects, cancer, hemopathy, treatment with immunosuppressors or corticosteroids (transplant patients and patients with systemic disease), HIV-infection, or spleen dysfunction. If there is a high risk of contracting a disease for which vaccination is contraindicated, drug prophylaxis or administration of immunoglobulins can be an alternative. If not, travel should either be postponed or the destination should be changed.

Lymphocytic choriomeningitis virus in southern France: four case reports and a review of the literature.

Infections due to choriomeningitis virus have been only infrequently reported in humans. Most cases have been diagnosed during laboratory outbreaks in the USA and Germany. In this report, we describe 4 cases of acute meningitis due to choriomeningitis virus occurring after close contact with domestic syrian hamsters. Although the disease is usually mild, some fatal cases have been described. The purpose of this report is to alert physicians to the possibility of lymphocytic choriomeningitis in patients who have had close contact with Syrian hamsters.

[Apropos of 2 cases of severe malaria contracted in the port of Marseille]. / A propos de deux cas de paludisme grave contractés sur le port de Marseille.

Acute Plasmodium falciparum malaria occurred during summer 1993 in two inhabitants living close to Marseille harbour. History of blood transfusion and travel outside France were excluded as was also discarded airport malaria. Entomological investigations confirmed the absence of Anopheles breeding sites in the port area. An hypothesis is a vectorial transmission following introduction of one or several anopheles arrived on a ship coming from tropical Africa. During this season, the weather conditions were favourable to the survival of anopheles and the completion of P. falciparum sporogonic cycle. Physicians were advised to take into consideration malaria in the differential diagnosis of fever from unknown origin in any patient working or living inside or around the harbour area regardless history of previous travel in malaria endemic region.

[Necrotizing hepatic granuloma of brucellosis origin. Apropos of a case]. / Granulome nécrosant hépatique d'origine brucellienne. A propos d'un cas.

The authors report on a case of febrile necrotizing brucellosis hepatic granulomatosis in a patient living in brucellosis endemia areas. This hepatic localization of brucellosis is rare: to our knowledge only 28 cases have been described in the literature. The bacteriological diagnosis was not established by blood or abscess pus cultures, but by Brucella serology only. Surgery completed by biantibiotherapy have permitted a complete recovery.

[Eosinophilic meningitis. Review of the literature and a new case originating from Reunion Island]. / Méningite à éosinophiles. Revue de la littérature à propos d'un nouveau cas en provenance de la Réunion.

We report a case of eosinophilic meningitis occurring in a European patient living in the Reunion Island. We review the literature and discuss the diagnosis of angiostrongylosis.

Spotless boutonneuse fever.

Mediterranean spotted fever is endemic in southern France, especially during summer. Clinical diagnosis is generally based upon the presence of a febrile eruption with or without the typical tache noire. Usual laboratory findings, which include thrombocytopenia, elevated levels of hepatic enzymes, and hyponatremia, are not specific to the disease. The diagnosis may be confirmed serologically by obtaining specific western immunoblot results and by isolation of Rickettsia conorii from blood culture with use of the shell vial cell culture technique. We report here the first documented case of spotless boutonneuse fever.

[Current status of knowledge on the epidemiology of rickettsiosis in Africa]. / Etat actuel des connaissances sur l'épidémiologie des rickettsioses en Afrique.

Rickettsioses have been reported all over Africa. Serologic investigations have been driven using non specific methods as Giroud microagglutination and Weil-Felix test which led to numerous false positive. This explains the difficulties encountered in the evaluation of the prevalence of such diseases in Africa. However, three recent studies made in Tunisia, Central Africa and Zimbabwe show that seroprevalence of spotted fever group rickettsiae infections is close to 45% using MIF as reference method. New technics as Western and Line immunoblotting and RFLP PCR should allowed to new studies and revision of epidemiologic data on rickettsioses in Africa.