Mechanical behaviour of fluid-lubricated faults.

Fluids are pervasive in fault zones cutting the Earth's crust; however, the effect of fluid viscosity on fault mechanics is mainly conjectured by theoretical models. We present friction experiments performed on both dry and fluid-permeated silicate and carbonate bearing-rocks, at normal effective stresses up to 20 MPa, with a slip-rate ranging between 10 µm/s and 1 m/s. Four different fluid viscosities were tested. We show that both static and dynamic friction coefficients decrease with viscosity and that dynamic friction depends on the dimensionless Sommerfeld number (S) as predicted by the elastohydrodynamic-lubrication theory (EHD).Under favourable conditions (depending on the fluid viscosity (η), co-seismic slip-rate (V), fault geometry (L/H02) and earthquake nucleation depth (∝σeff)), EHD might be an effective weakening mechanism during natural and induced earthquakes. However, at seismic slip-rate, the slip weakening distance (Dc) increases markedly for a range of fluid viscosities expected in the Earth, potentially favouring slow-slip rather than rupture propagation for small to moderate earthquakes.

Changes in leisure time and occupational physical activity over 8 years: the Cornellè Health Interview Survey Follow-Up Study.

AIM: To describe changes in leisure time and occupational physical activity status in an urban Mediterranean population-based cohort, and to evaluate sociodemographic, health-related and lifestyle correlates of such changes. METHODS: Data for this study come from the Cornellè Health Interview Survey Follow-Up Study, a prospective cohort study of a representative sample (n = 2500) of the population. Participants in the analysis reported here include 1246 subjects (567 men and 679 women) who had complete data on physical activity at the 1994 baseline survey and at the 2002 follow-up. We fitted Breslow-Cox regression models to assess the association between correlates of interest and changes in physical activity. RESULTS: Regarding leisure time physical activity, 61.6% of cohort members with "sedentary" habits in 1994 changed their status to "light/moderate" physical activity in 2002, and 70% who had "light/moderate" habits in 1994 did not change their activity level. Regarding occupational physical activity, 74.4% of cohort members who were "active" did not change their level of activity, and 64.3% of participants with "sedentary" habits in 1994 changed to "active" occupational physical activity. No clear correlates of change in physical activity were identified in multivariate analyses. CONCLUSION: While changes in physical activity are evident in this population-based cohort, no clear determinants of such changes were recognised. Further longitudinal studies including other potential individual and contextual determinants are needed to better understand determinants of changes in physical activity at the population level.

Avances en hemocromatosis hereditaria / Advances in hereditary hemochromatosis

Hereditary hemocromatosis (HH) is a genetic disease with a recessive autosomic pattern, in which inadequate iron (Fe) absorption is made by the intestinal cell. As consequence of that process, takes place a progressive accumulation of metal in different organs, predominantly in the liver. This leads to an alteration of liver structure and function: cirrhosis and hepatocarcinoma (1). The gene implied in this pathology was identified (HFE) in 1996. This codes a similar molecule to the mayor histocompatibility complex type 1(MHC-T1 like) that can modulate the transport of PE binding the transferrin receptor. This progress allows a deep understanding of the molecular and cellular biology of the homeostasis of the Fe and its alterations in the NH. The diagnosis of disease by means of a genetic test let to carry out a familiar screening and to detect asymptomatic carriers. This makes possible to begin the appropriate treatment at early stages of the disease in order to avoid its consequences and offering a better quality of life to these patients.

Avances en hemocromatosis hereditaria / Advances in hereditary hemochromatosis

Hereditary hemocromatosis (HH) is a genetic disease with a recessive autosomic pattern, in which inadequate iron (Fe) absorption is made by the intestinal cell. As consequence of that process, takes place a progressive accumulation of metal in different organs, predominantly in the liver. This leads to an alteration of liver structure and function: cirrhosis and hepatocarcinoma (1). The gene implied in this pathology was identified (HFE) in 1996. This codes a similar molecule to the mayor histocompatibility complex type 1(MHC-T1 like) that can modulate the transport of PE binding the transferrin receptor. This progress allows a deep understanding of the molecular and cellular biology of the homeostasis of the Fe and its alterations in the NH. The diagnosis of disease by means of a genetic test let to carry out a familiar screening and to detect asymptomatic carriers. This makes possible to begin the appropriate treatment at early stages of the disease in order to avoid its consequences and offering a better quality of life to these patients. (AU)