Petrological differentiation patterns and geomorphic distribution of ferricretes in Central Africa

Geomorphic distribution and petrological differentiation patterns of ferricretes widespread on landsurfaces were studied in the Dembia-Zemio area, southeastern Central African Republic. Four types of ferricretes are distributed on high plateaux, hillslopes and low plateaux. The main contrast corresponds to the differentiation between ferricretes of high plateaux rich in poorly hydrated minerals, hematite and kaolinite, and those covering hillslopes and low plateaux richer in hydrated minerals, goethite and gibbsite. A Principal Component Analysis of geochemical and mineralogical data was used to characterize the main differentiation patterns of ferricretes in relation with their petrographic facies and the geomorphic features of the landscape. The distribution of secondary minerals and their relationships to trace elements within and between the ferricrete types reflects differences in weathering and erosion processes. Our results document that the petrological patterns and the distribution of ferricretes are related to geomorphic features depending on hydroclimatic variations that govern the landscape evolution of many tropical shields. (Résumé d'auteur

Evolution of psychosocial factors at work in a French region

Background : Psychosocial factors at work (PFW) can be defined as all non-physicochemical occupational risks. Several epidemiological models have been proposed to measure PFW, but one of the most widely used is Karasek’s model. Aims : To determine whether psychosocial factors, evaluated by Karasek’s questionnaire, had increased in a cohort of workers. Methods : A random sample of workers in the Pays de la Loire region of France, who could be considered representative of the region’s population of salaried workers, filled in a self-administered questionnaire, including Karasek’s self-administered questionnaire, in 2002–05 and 2007–09. Karasek’s questionnaire can be used to study three psychosocial dimensions (psychological demand, decision latitude and social support in the workplace) in workers in order to define two high-risk situations for their health: ‘Job Strain’ and ‘Iso Strain’. Changes in job strain and iso strain among workers were studied according to the workers’ sociodemographic characteristics and their working conditions. Results : In this sample of 2049 workers, the proportion with iso strain increased between the two periods from 12 to 16%, P < 0.001, mainly among manual workers. Deterioration of Karasek indicators was mainly explained by an increase of the ‘low social support’ dimension (38 versus 49%, P < 0.001). Working conditions such as temporary employment of colleagues and high perceived physical exertion were associated with higher PFW. Conclusions : This study, based on a quantitative and collective model, showed deterioration of working team environments and increased risk for individual mental health in this cohort of French workers in recent years

Facteurs de risques psychosociaux de passage à la chronicité des lombalgies, repérables en soins primaires : revue de la littérature

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