First Triassic palaeomagnetic constraints from Junggar (NW China) and their implications for the Mesozoic tectonics in Central Asia

International audienceNorthwestern China belts result from the Palaeozoic collage of Central Asia and the subsequent reactivations due to far-field effects of the Mesozoic Tibetan and the Cenozoic Himalayan collisions. Triassic is a crucial period to understand and decipher the tectonics related to these two episodes. About 250 oriented palaeomagnetic cores from 43 sites were collected from six sections of Upper Permian to Late Triassic sandstone, in South and West Junggar, Northwestern China. Thermomagnetic, IRM and hysteresis measurements reveal magnetite as the main carrier of the magnetic remanence with minor hematite and maghemite. Stepwise thermal demagnetisation has generally isolated two components. The low temperature component, up to 300-350 °C, displays a direction consistent with the present-day geomagnetic field. The locality-mean directions related to the high temperature component (above 350 °C) were also calculated. Two out of six sections display intense viscous magnetisation and the occurrence of maghemite reveals a possible Cenozoic chemical remagnetisation for these two localities. For the other four localities, we assume that the magnetisation is primary because: (1) AMS measurements reveal a primary fabric, (2) there are local occurrences of antipodal polarities, and (3) palaeolatitudes of tilt-corrected poles are compatible with previous studies. The consistency between the Early Triassic poles of West and South Junggar indicates that Junggar evolved as a rigid block only since Early Mesozoic. The comparison of the Late Palaeozoic and the Early Mesozoic poles of Junggar and those of Siberia and Tarim shows major rotations between the Late Permian and the Late Jurassic-Early Cretaceous. These periods of discrete rotations are characterized by strike-slip faulting in Tianshan and Altai and they may correlate with the major episodes of coarse-grained detrital sedimentation and uplift of the range. Especially, the counter-clockwise rotations of Junggar relative to Tarim and Siberia, which occurred between the Early and the Late Triassic and between the Late Triassic and the Late Jurassic, are accommodated by transpressive tectonics in the Tianshan and the Altai belts. This reactivation is a far-field effect of Tibetan blocks diachronous collisions. Therefore, these first Triassic palaeomagnetic results from Junggar infer that post-Carboniferous rotations were due to the combined effect of the post-orogenic transcurrent movement and the Mesozoic oblique reactivation

Modeling E. coli Tumbles by Rotational Diffusion. Implications for Chemotaxis

The bacterium Escherichia coli in suspension in a liquid medium swims by a succession of runs and tumbles, effectively describing a random walk. The tumbles randomize incompletely, i.e. with a directional persistence, the orientation taken by the bacterium. Here, we model these tumbles by an active rotational diffusion process characterized by a diffusion coefficient and a diffusion time. In homogeneous media, this description accounts well for the experimental reorientations. In shallow gradients of nutrients, tumbles are still described by a unique rotational diffusion coefficient. Together with an increase in the run length, these tumbles significantly contribute to the net chemotactic drift via a modulation of their duration as a function of the direction of the preceding run. Finally, we discuss the limits of this model in propagating concentration waves characterized by steep gradients. In that case, the effective rotational diffusion coefficient itself varies with the direction of the preceding run. We propose that this effect is related to the number of flagella involved in the reorientation process

“Liaisons dangereuses”: The invasive red-vented bulbul ( Pycnonotus cafer ), a disperser of exotic plant species in New Caledonia

International audienceThe biodiversity hotspot of New Caledonia hosts high levels of endemism (74% of flora) that is threatened increasingly by climate change, habitat reduction, and inva-sive species. The fruit-eating red-vented bulbul (Pycnonotus cafer) is currently invading the main island of the archipelago, and its recent dispersal out of urbanized habitats raises questions about its potential to disperse noxious plant seeds along urban corridors and beyond. Indeed, the red-vented bulbul is considered a vector of several introduced plant species in its alien range including Miconia calvescens, Lantana camara, and Schinus terebinthifolius. We conducted a quantitative assessment of the bulbul's fruits consumption by analyzing the gut contents of shot birds. We estimated gut passage times for four species of fruit found in gut contents (S. terebin-thifolius, Myrtastrum rufopunctatum, Passiflora suberosa, and Ficus prolixa) and tested the effects of bird digestion on seed germination rates for two species. Finally, we monitored the movements of individual VHF radio-tagged red-vented bulbuls. All of the consumed fruit species we identified here have red fleshy diaspore, including fruit of the shrub M. rufopunctatum that occurred frequently (9.6%) in bulbul gut samples. Median gut passage times were short (15-41 min), corresponding to short-distance seed transportation (77-92 m). The effect of gut passage was positive for the germination of the invasive S. terebinthifolius and negative for the endemic M. ru-fopunctatum, suggesting a potential bias in the contribution to the dispersal toward alien species. This study provides the first integrated assessment of mechanisms involved in the seed dispersal effectiveness of this high-concern invasive bird species that is expected to face similar plant communities in most of its alien range in tropical islands. More generally, our results enhance knowledge of synergies between non-native frugivores and plant species dispersal

DECADIESE: a new method to assess buildings’ sustainable value through functional performance and externalities integration

International audienceAmbitious building retrofits to improve energy performance are often hardly justified by energy savings only. Indeed the return on investment to divide energy consumption of a building by two is more than 25 years, which often discourage investors. Energy efficiency thus needs to be considered differently to be economically justified. That is why a new methodology called DECADIESE has been developed by a consortium of major companies from the French building sector and academic partners. Broader than an energy efficiency focus only, DECADIESE aims at capturing the sustainable value of a building with an original focus beyond the scope of classical analytic methods, by extending the perimeter of associated stakeholders in order to allow ambitious building projects. DECADIESE considers an extended value of a building by incorporating economic, social and environmental aspects through externalities elicitation and integration with a multi-stakeholders point of view, but also by recentering the value created by a building around the benefits brought to its users through a functional approach. The methodology is built around a structured process involving multiple stakeholders (such as building owner, building owner assistant, engineering contractor, potential users and neighbours…) that contribute to feed the different modules of an experimental tool, finally aggregated in cost-benefits indicators. This paper focuses on the functional part of this model. On the one hand, buildings costs are first broken down into usage functions following a process inspired from value engineering standards. Usage functions costs offer a new vision of costs breakdown for a building, which highlights possible mismatches between functional objectives for users and associated amounts of money. On the other hand, the functional performance of the building is assessed thanks to a grid composed of 95 qualitative and quantitative criteria. Those elementary scores are then aggregated in 7 usage functions scores thanks to a fuzzy logic model based on building experts rules. Once those elements identified, DECADIESE proposes to a project owner a new vision of its project and the ability to compare building variants. DECADIESE has been experimentally applied on several case studies. Results show a good relevance of results and reveal a high interest of building sector actors. Next steps are underway to make the methodology more reliable and usable by building sector actors

The DECADIESE methodology: Extending usage and value creation perspectives of a building by value and externalities management

International audienceAmbitious building retrofits are often hardly justified by energy savings only. A previous research project has shown that dividing by two the energy consumption of a building (like a school) may lead to a return on investment superior to 25 years [RS4E, 2010]. In this configuration, decision-makers are often not inclined to invest. Thus there is a need to investigate in more details and highlight the benefits of such retrofits or new buildings with a broader point of view. That is why the DECADIESE methodology has been developed by a consortium of major construction and energy companies (EDF R&D, Bouygues Construction, Vinci Construction, Foncière des Régions) and academic partners (CentraleSupélec, Université Paris Diderot – Paris VII, Mines ParisTech) in the frame of a French research agency-supported research project (2012-2014).DECADIESE considers an extended value of a building by incorporating sustainable dimensions through externalities integration, but also by recentering the value created by a building around the benefits for its users. This paper focuses on the latter. On one hand, costs are broken down into seven usage functions, which highlights possible mismatches between functional objectives and associated amounts of money. On the other hand, the functional performance of the building is assessed thanks to 95 criteria that are then aggregated into seven usage functions scores. Once those elements identified, DECADIESE gives to a project owner the ability to compare building variants.A complete overview of the methodology is given in section 2, and the functional aspects are explained in more details. Section 3 presents the first results and a short discussion. Finally, section 4 highlights the main conclusions and perspectives

Pontage aortocoronarien, hémodialyse et vol thoracique interne

International audienceThe dramatic occurrence, during haemodialysis sessions, of hemodynamic and cerebral symptoms in a 53-year-old haemodialysed woman with a history of aortocoronary bypass leads to discovery and treatment by percutaneous angioplasty and stenting of a significant stenosis of proximal subclavian artery, ipsilateral to the arteriovenous fistula, with retrograde flow in internal mammary artery graft and vertebral artery. All symptoms resume after interventional radiology. Analysis of literature confirms possibility of coronary artery steal induced by use of the arteriovenous fistula in haemodialysed patients with ipsilateral internal mammary bypass, especially if there is concomitant subclavian artery stenosis, and leading us to discuss the diagnostic and therapeutic implications