Mixtures of stochastic differential equations with random effects: Application to data clustering

International audienceWe consider N independent stochastic processes (Xi(t), t ∈ [0, Ti]), i = 1,. .. , N , defined by a stochastic differential equation with drift term depending on a random variable φi. The distribution of the random effect φi is a Gaussian mixture distribution, depending on unknown parameters which are to be estimated from the continuous observation of the processes Xi. The likelihood of the observation is explicit. When the number of components is known, we prove the consistency of the exact maximum likelihood estimators and use the EM algorithm to compute it. When the number of components is unknown, BIC (Bayesian Information Criterion) is applied to select it. To assign each individual to a class, we define a classification rule based on estimated posterior probabilities. A simulation study illustrates our estimation and classification method on various models. A real data analysis is performed on growth curves with convincing results

HIV/AIDS/STI Surveillance Report:Report Number 21

Since the first cases of Acquired Immunodeficiency Syndrome (AIDS) in Tanzania were reported in 1983, the epidemic has evolved from being a rare and new disease to a common household problem, which has affected most Tanzania families. The mainland Tanzania faces a generalized human immunodeficiency virus (HIV) and AIDS epidemic, with an estimated 6.5% of the mainland population infected with HIV (7.7% of adult women and 6.3% of adult men). Overall, 1.4 million Tanzanians (1,300,000 adults and 110,000 children) are living with HIV infection, in a total population of 41 million. The social, economic, and environmental impact of the pandemic is sorely felt as an estimated 140,000 Tanzanians have perished, leaving behind as estimated 2.5 million orphans and vulnerable children, representing approximately 10-12% of all Tanzanian children. As elsewhere in sub-Saharan African, the underlying factors of poverty, migration, marginalization, lack of information and skills, disempowerment, and poor access to services raise the risk of HIV and have an impact on the course and spread of the pandemic. Close to 85% of HIV transmission in Tanzania occurs through heterosexual contact, less than 6% through mother-to-child transmission, and less than 1% through blood transfusion. There continues to be a significant difference in the prevalence among urban (10.9%) and rural (5.3%) areas of the country. The National AIDS Control Programme (NACP) of Tanzania was founded in 1987 to champion the health sector response to the HIV epidemic. The primary objectives of the program were to reduce spread of HIV infection, screen blood supplies, enhance clinical services for HIV/AIDS patients and improve STI treatment, prevention of mother-to-child transmission (PMTCT), advocate behavioral change and conduct epidemiologic surveillance and other research. The program phases started with a two-year phase called Short Term Plan\ud (1985-1986). Subsequent phases were termed Medium Term Plans lasting for five-year periods. Through these program phases successful national responses have been identified, the most effective ones being those touching on the major determinants of the epidemic and addressing priority areas that make people vulnerable to HIV infection. These include the following; Since early eighties great efforts have been made to reduce spread of HIV infection through screening of donor blood, advocating behavioral change, condom promotion and improvement of STI treatment. In addition a number of epidemiologic surveillance have been conducted to monitor the trend of HIV infection among different subpopulations e.g. blood donors and pregnant women attending antenatal clinics. In 2004, the National Blood Transfusions Services (NBTS), which is a centralized system of coordinated blood transfusion services, was established. The NBTS is responsible for collection, processing, storage and distribution of safe blood and blood products to health facilities. At the moment NBTS coordinates eight zonal blood transfusion centers, namely Lake Zone-(LZBTC) in Mwanza region, Western-(WZBTC) in Tabora, Northern (NZBTC) in Kilimanjaro region, Eastern (EZBTC) in Dar es Salaam, Southern highlands (SHZBTC) in Mbeya, Southern (SZBTC) in Mtwara and Zanzibar and a military zone –Tanzania People’s Defence Force (TPDF). Since the establishment of NBTS, donated blood in the eight zones is systematically screened for HIV, hepatitis B virus (HBV), hepatitis C virus (HCV) and syphilis. The National HIV Care and Treatment Plan (NCTP) was launched in October 2004, with the main focus of a rapid scaling up of HIV care and treatment services, aimed at having more than 400,000 patients on care and treatment by the end of 2008 and, at the same time, follow up disease progression in 1.2 million HIV+ persons who are not eligible for ntiretroviral therapy (ART). Prevention of Mother to Child Transmission of HIV (PMTCT) services were established in 2002 , providing a package of services that include: counseling and testing for pregnant women; short-course preventive ARV regimens to prevent mother-to-child transmission; counseling and support for safe\ud infant feeding practices; family planning counseling or referral; and referral for long-term ART for the\ud child. This report which covers the NACP activities through December 2008 has been arranged in five chapters and is intended for various stakeholders, primarily those working within the health sector.\u

Inability of Proteus mirabilis mutants to reduce N-oxides and sulfoxide

Bibliography: pages [44]-47.Proteus mirabilis strain PM5006 can grow anaerobically on oxidizable substrates such as glycerol or fermentable substrates such as glucose using a number of electron acceptors. It was found that dimethyl sulfoxide (DMSO)/ trimethylamine-N-oxide (TMAO)/ nicotinamide-N-oxide (NAMO), and nitrate (N0₃) can serve as electron acceptors. Cell-free extracts of P. mirabilis were found to reduce these compounds to dimethyl sulfide (DMS), trimethylamine (TMA)/ nicotinamide (NAM), and nitrite (NO₂)/ in the presence of various electron donors such as NADH, formate, lactate, reduced benzyl viologen and sodium dithionite. In order to determine whether the same or different terminal reductase(s) are involved in the reduction of these compounds, the plasmid pJB4JI (cointegrate pPH1::Mu::Tn5), harbored in E. coli 1830, was conjugated into P. mirabilis and transconjugants selected for kanamycin resistance. The Kanamycin-resistant mutants were subsequently screened for their inability to grow anaerobically on glycerol/DMSO medium. When these mutants were tested for anaerobic growth on glycerol medium containing TMAO, NAMO and N0₃ as electron acceptors, it was found that there were two groups. Group I mutants were unable to grow using DMSO, TMAO and NAMO as electron acceptors while their growth was unaffected on NO₃. In contrast, group II mutants were unable to grow on all the electron acceptors including NO₃. Enzyme assays with dithionite-reduced benzyl viologen as electron donor showed that group I mutants were unable to reduce the various electron acceptors except NO₃. The group II mutants lost the ability to reduce all the electron acceptors including NO₃. On the basis of these results we conclude that the same terminal reductase is involved in the reduction of DMSO, TMAO, and NAMO (group I). On the other hand, the group II mutants also lost the NO₃ reductase activity. Thus, group II mutants must be defective in the synthesis or insertion of molybdenum cofactor (MOCO) which is in agreement with previous studies.M.S. (Master of Science

Estimation of population parameters in stochastic differential equations with random effects in the diffusion coefficient

We consider N independent stochastic processes (Xi(t), t ∈ [0, T]), i = 1,...,N, defined by a stochastic differential equation with diffusion coefficients depending linearly on a random variable φi. The distribution of the random effect φi depends on unknown population parameters which are to be estimated from a discrete observation of the processes (Xi). The likelihood generally does not have any closed form expression. Two estimation methods are proposed: one based on the Euler approximation of the likelihood and another based on estimations of the random effects. When the distribution of the random effects is Gamma, the asymptotic properties of the estimators are derived when both N and the number of observations per component Xi tend to infinity. The estimators are computed on simulated data for several models and show good performances

Maximum likelihood estimation for stochastic differential equations with random effects

We consider N independent stochastic processes (Xi (t), t [0,Ti]), i=1,..., N, defined by a stochastic differential equation with drift term depending on a random variable phi i. The distribution of the random effect phi i depends on unknown parameters which are to be estimated from the continuous observation of the processes Xi. We give the expression of the exact likelihood. When the drift term depends linearly on the random effect phi i and phi i has Gaussian distribution, an explicit formula for the likelihood is obtained. We prove that the maximum likelihood estimator is consistent and asymptotically Gaussian, when Ti=T for all i and N tends to infinity. We discuss the case of discrete observations. Estimators are computed on simulated data for several models and show good performances even when the length time interval of observations is not very large

Double deletion of a chromosome 21 inserted in a chromosome 22 in an azoospermic patient

We report on a phenotypically normal 41-year-old azoospermic man with a 45 chromosomes karyotype including one normal chromosome 21, one normal chromosome 22, and a der(22)ins(22;21). Array CGH showed a 1.8 Mb terminal deletion of bands 21pter to 21q21.1 and a 341 kb terminal deletion on band 21q22.3

Innovations 2022 en psychiatrie infanto-juvénile

Deux volets cliniques sont évoqués cette année pour le Service de Psychiatrie Infanto-Juvénile des Cliniques universitaires Saint-Luc. Ils traduisent les offres d’aide et de soins mises en place au regard de l’augmentation des situations de détresse psychique des enfants, des adolescents et de leur entourage. Le premier volet concerne le déploiement des activités du centre de référence des troubles du spectre de l’autisme, à savoir la mise en place d’un groupe de stimulation précoce pour les jeunes enfants en attente de diagnostic ainsi qu’un groupe de formation « parents » après le diagnostic. Le second est constitué par la consolidation du temps juridique au sein de l’équipe SOS-Enfants des Cliniques ; nous montrerons le bien-fondé et les apports de cette fonction spécifique dans les cas complexes de maltraitance infanto-juvénile

Matérialités soignantes : les technologies du care en santé

Quelle est la place des technologies de santé dans le soin ? Faut-il opposer la froideur distante des médiations instrumentales du cure à la proximité chaleureuse des relations humaines du care ? En quels sens peut-on dire que les dispositifs sociotechniques de plus en plus complexes, omniprésents dans le domaine sanitaire, contribuent à redéfinir les relations de soin (soin de soi et d’autrui) ? En se positionnant au croisement de l’anthropologie de la santé et de l’anthropologie et de la sociologie des sciences et des techniques, ce numéro vise à montrer de quelle manière l’étude des équipements et des pratiques matérielles constitue une entrée féconde pour comprendre les sens du soin dans les mondes contemporains de la santé. Abordant des contextes sanitaires diversifiés, les contributions réunies ici mettent en lumière non seulement le fait que les technologies peuvent être intégrées à des relations et des pratiques soignantes, attentives et singularisées, qui passent par elles, mais aussi que le soin vient aux technologies par un travail collectif, fait d’ajustements, de négociations, d’appropriations, non dépourvu de tensions et d’ambivalences, qui les produit comme autant de matérialités soignantes. What is the place of health technologies in care? Should the distant coldness of the instrumental means of cure be strictly opposed to the warm proximity of human relations of care? How do the increasingly complex socio-technical devices, omnipresent nowadays in the healthcare field, contribute to redefining the relations of care (care of oneself and care of others)? This issue, positioned at the crossroads of the anthropology of health and the anthropology and sociology of science and technology, aims to show that studying equipment and material practices constitutes a rich entry point to understanding the meanings of care in contemporary health worlds. Addressing various health contexts, the contributions gathered here highlight not only the fact that technologiesusedcan be fully integrated into attentive and personalized care relationships and practices, but also that the care comes to technologies through collective work, made of adjustments, negotiations, appropriations, not devoid of tensions and ambivalences, which gives rise to many material dimensions of care