Effective nuclear temperature in a fluctuating spin system

We report on very low temperature (27 mK) Mossbauer absorption spectra on Gd 155 in the Heisenberg frustrated antiferromagnets Gd2 Sn2 O7 (GdSn) and Gd2 Ti2 O7. We show that electronic fluctuations of correlated Gd3+ moments are present near T=0 in GdSn by observing that the hyperfine levels are out of equilibrium. Using a model spin 1/2 system, submitted to a magnetic (hyperfine) field reversing randomly in time, we find an analytical expression for the stationary probability distribution of the level populations (or magnetization). This quantity is a simple function of the ratio of the nuclear relaxation time to the average electronic flip time. These two time scales are found to be of the same magnitude in GdSn, and we discuss a relevant mechanism for nuclear relaxation and the influence of electronic fluctuations on the nuclear specific heat.Comment: 8 pages, 4 .eps figures. submitted to E.P.J.

3H-thymidine labelling pattern of preleptotene chromosome condensation stages in the fœtal sheep ovary

International audienc

THE PRELEPTOTENE CHROMOSOME CONDENSATION AND DECONDENSATION IN THE OVARY OF THE SHEEP EMBRYO

International audienc

Epidemiological experience in the mission of the United Nations Transition Assistance Group (UNTAG) in Namibia.

Epidemiological data have rarely been generated during United Nations (UN) missions to Third World countries, even in situations where there is hardly any combat involvement. Continuous surveillance was therefore carried out during the 12-month stay of UN personnel in Namibia in 1989-90. In this population of 7114 persons, mostly young men, the mortality rate was 255 per 100,000; death was mainly due to traffic accidents. Hospitalization was chiefly because of fever of unknown origin or trauma. Repatriation to the country of origin was necessary in 46 patients, frequently for psychiatric reasons including alcoholism. Over this one-year period there were, on average, 2.7 new consultations per person for treatment (mostly for dental problems), and 0.8 per person for prophylactic measures. The extremely high mortality due to traffic accidents indicates a need for prevention. In the selection process for future missions, more emphasis should be given to the psychological and dental health of volunteers. All military contingents and civilian groups should learn about effective preventive measures prior to their arrival, and adhere to them

Building resilient and sustainable: a need to decompartementalise the researches

International audienc

Vulnerability and social resilience: comparison of two neighborhoods in New Orleans after Hurricane Katrina

International audienc

Incertitude et jugement expert pour l'aide à l'évaluation de la résilience des réseaux techniques urbains

National audienceProper functioning of levees and roadway networks is a major challenge for the management of risks and the resilience territories. The general lack of data allowing describing their behaviour for the feared rare events leads to exploit mainly the expert opinion to estimate their levels of functioning. In this context, the Incertu project proposes a method for the functional modelling of the mechanisms of infrastructure failure in a systemic context, taking into account the uncertainties linked to the expert evaluation of their mechanisms of failure and the reduction of biases using a model of calibration.Le bon fonctionnement des réseaux de digues et de voiries constitue un enjeu majeur pour la gestion des risques et la résilience des territoires. Le manque général de données permettant de décrire leurs comportements pour les événements rares redoutés conduit à exploiter principalement les dires experts pour estimer leurs niveaux de fonctionnement. Le projet Incertu propose une démarche méthodologique pour la modélisation fonctionnelle des mécanismes de défaillance des infrastructures en contexte systémique, la prise en compte des incertitudes liées à l'évaluation experte de leurs mécanismes de défaillance et la réduction des biais via un modèle de calibration