The Minimized Power Geometric model: An analytical mixing model for calculating polyphase rock viscosities consistent with experimental data

International audienceHere we introduce the Minimized Power Geometric (MPG) model which predicts the viscosity of any polyphase rocks deformed during ductile flow. The volumetric fractions and power law parameters of the constituting phases are the only model inputs required. The model is based on a minimization of the mechanical power dissipated in the rock during deformation. In contrast to existing mixing models based on minimization, we use the Lagrange multipliers method and constraints of strain rate and stress geometric averaging. This allows us to determine analytical expressions for the polyphase rock viscosity, its power law parameters, and the partitioning of strain rate and stress between the phases. The power law bulk behavior is a consequence of our model and not an assumption. Comparison of model results with 15 published experimental data sets on two-phase aggregates shows that the MPG model reproduces accurately both experimental viscosities and creep parameters, even where large viscosity contrasts are present. In detail, the ratio between experimental and MPG-predicted viscosities averages 1.6. Deviations from the experimental values are likely to be due to microstructural processes (strain localization and coeval other deformation mechanisms) that are neglected by the model. Existing models that are not based on geometric averaging show a poorer fit with the experimental data. As long as the limitations of the mixing models are kept in mind, the MPG model offers great potential for applications in structural geology and numerical modeling

Subduction interface processes recorded by eclogite-facies shear zones (Monviso, W. Alps)

International audienceThe Monviso ophiolite Lago Superiore Unit constitutes a well-preserved, almost continuous upper fragment of oceanic lithosphere subducted at c. 80 km depth, thereby providing a unique opportunity to study mechanical coupling processes and meter-scale fluid-rock interactions occurring at such depths in present-day subduction zones. It is made of (i) a variably thick (50-500 m) section of eclogitized basaltic crust (associated with minor calcschist lenses) overlying a 100-400 m thick metagabbroic body and of (ii) a c. 1 km thick serpentinite sole. We herein focus on the three major eclogite-facies shear zones found at the top of the unit, at the boundary between basalts and gabbros, and between gabbros and serpentinites, respectively. Strain localization occurred at lithological interfaces, irrespective of material strength. While ductile deformation dominates along the shear zones, local brittle behaviour is demonstrated by the existence of numerous eclogite breccias of Fe-Ti metagabbros and widespread garnet fractures, possibly linked with intermediate-depth eclogite-facies (micro)seismicity. These m- to hm-sized fragments of Fe-Ti metagabbros were later sheared and disseminated within serpentinite schists along the gabbro-serpentinite boundary (Lower Shear zone; LSZ). Pervasive and focused fluid flow is attested in the LSZ by significant alteration of bulk rock compositions, weakening of the rocks and widespread crystallization of hydrous parageneses. By contrast, the Intermediate Shear zone (ISZ) shows evidence for more restricted, short-range fluid flow. The activity of both the ISZ and LSZ ceased during early lawsonite eclogite-facies exhumation, when deformation localized deeper within the serpentinite sole, allowing for the detachment (and preservation) of this large ophiolitic fragment

Collaborative Grid Mapping for Moving Object Tracking Evaluation

Perception of other road users is a crucial task for intelligent vehicles. Perception systems can use on-board sensors only or be in cooperation with other vehicles or with roadside units. In any case, the performance of perception systems has to be evaluated against ground-truth data, which is a particularly tedious task and requires numerous manual operations. In this article, we propose a novel semi-automatic method for pseudo ground-truth estimation. The principle consists in carrying out experiments with several vehicles equipped with LiDAR sensors and with fixed perception systems located at the roadside in order to collaboratively build reference dynamic data. The method is based on grid mapping and in particular on the elaboration of a background map that holds relevant information that remains valid during a whole dataset sequence. Data from all agents is converted in time-stamped observations grids. A data fusion method that manages uncertainties combines the background map with observations to produce dynamic reference information at each instant. Several datasets have been acquired with three experimental vehicles and a roadside unit. An evaluation of this method is finally provided in comparison to a handmade ground truth

Pancreatic Serous Cystadenoma with Compression of the Main Pancreatic Duct: An Unusual Entity

Serous cystadenoma is a common benign neoplasm that can be managed without surgery in asymptomatic patients provided that the diagnosis is certain. We describe a patient, whose pancreatic cyst exhibited a radiological appearance distinct from that of typical serous cystadenoma, resulting in diagnostic difficulties. CT and MRI showed a 10 cm-polycystic tumor with upstream dilatation of the main pancreatic duct (MPD), suggestive of intraductal papillary mucinous tumor (IPMT). Ultrasonographic aspect and EUS-guided fine-needle aspiration gave arguments for serous cystadenoma. ERCP showed a communication between cysts and the dilated MPD, compatible with IPMT. The patient underwent left pancreatectomy with splenectomy. Pathological examination concluded in a serous cystadenoma, with only a ductal obstruction causing proximal dilatation

Strain localisation in mechanically layered rocks beneath detachment zones: insights from numerical modelling.

International audienceFully dynamic numerical simulations have been designed in order to asses how the orientation of mechanical layering in rocks controls the orientation of shear bands and the depth of penetration of strain in the footwall of detachment zones. Two parametric studies are presented. In the first one, the influence of stratification orientation on the occurrence and mode of strain localisation is tested. The second parametric study shows that results are length-scale independent and that orientation of shear bands is not sensitive to the viscosity contrast or the strain rate. Based on the results, a conceptual model for strain localisation under detachment faults is presented. In the early stages, strain localisation occurs at slow rates by viscous shear instabilities but as the layered media is exhumed, the temperature drops and the strong layers start yielding plastically, forming shear bands and localising strain at the top of the shear zone. Once strain localisation has occured, the deformation in the shear band becomes extremely penetrative but the strength cannot drop since the shear zone has a finite thickness

Long term virological, immunological and mortality outcomes in a cohort of HIV-infected female sex workers treated with highly active antiretroviral therapy in Africa

BACKGROUND: Concerns have been raised that marginalised populations may not achieve adequate compliance to antiretroviral therapy. Our objective was to describe the long-term virological, immunological and mortality outcomes of providing highly active antiretroviral therapy (HAART) with strong adherence support to HIV-infected female sex workers (FSWs) in Burkina Faso and contrast outcomes with those obtained in a cohort of regular HIV-infected women. METHODS: Prospective study of FSWs and non-FSWs initiated on HAART between August 2004 and October 2007. Patients were followed monthly for drug adherence (interview and pill count), and at 6-monthly intervals for monitoring CD4 counts and HIV-1 plasma viral loads (PVLs) and clinical events. RESULTS: 95 women, including 47 FSWs, were followed for a median of 32 months (interquartile range [IQR], 20-41). At HAART initiation, the median CD4 count was 147 cells/μl (IQR, 79-183) and 144 cells/μl (100-197), and the mean PVLs were 4.94 log10 copies/ml (95% confidence interval [CI], 4.70-5.18) and 5.15 log10 copies/ml (4.97-5.33), in FSWs and non-FSWs, respectively. Four FSWs died during follow-up (mortality rate: 1.7 per 100 person-years) and none among other women. At 36 months, the median CD4 count increase was 230 cells/μl (IQR, 90-400) in FSWs vs. 284 cells/μl (193-420) in non-FSWs; PVL was undetectable in 81.8% (95% CI, 59.7-94.8) of FSWs vs. 100% (83.9-100) of non-FSWs; and high adherence to HAART (> 95% pills taken) was reported by 83.3% (95% CI, 67.2-93.6), 92.1% (95% CI, 78.6-98.3), and 100% (95% CI, 54.1-100) of FSWs at 6, 12, and 36 months after HAART initiation, respectively, with no statistical difference compared to the pattern observed among non-FSWs. CONCLUSIONS: Clinical and biological benefits of HAART can be maintained over the long-term among FSWs in Africa and could also lead to important public health benefits

Randomised controlled trial demonstrates that fermented infant formula with short-chain galacto-oligosaccharides and long-chain fructo-oligosaccharides reduces the incidence of infantile colic

Aim: We examined the effects on gastrointestinal (GI) tolerance of a novel infant formula that combined specific fermented formula (FERM) with short-chain galacto-oligosaccharides and long-chain fructo-oligosaccharides (scGOS/lcFOS), with a 9:1 ratio and concentration of 0.8 g/100 mL. Methods: This prospective, double-blind, randomised, controlled trial comprised 432 healthy, term infants aged 0–28 days whose parents decided to not start, or discontinued, breastfeeding. Infant formula with scGOS/lcFOS+50%FERM, scGOS/lcFOS+15%FERM, 50%FERM and scGOS/lcFOS were tested. Parents completed standardised seven-day diaries on GI symptoms, crying, sleeping and stool characteristics each month until the infants were 17 weeks. Results: All the formulas were well tolerated. At four weeks, the overall incidence of infantile colic was significantly lower (8%) with scGOS/lcFOS+50%FERM than scGOS/lcFOS (20%, p = 0.034) or 50%FERM (20%, p = 0.036). Longitudinal modelling showed that scGOS/lcFOS+50%FERM-fed infants also displayed a persistently lower daily crying duration and showed a consistent stool-softening effect than infants who received formula without scGOS/lcFOS. Conclusion: The combination of fermented formula with scGOS/lcFOS was well tolerated and showed a lower overall crying time, a lower incidence of infantile colic and a stool-softening effect in healthy term infants. These findings suggest for the first time that a specific infant formula has a preventive effect on infantile colic in formula-fed infants