Morphological analysis of stylolites for paleostress estimation in limestones surrounding the Andra Underground Research Laboratory site

We develop and test a methodology to infer paleostress from the morphology of stylolites within borehole cores. This non-destructive method is based on the analysis of the stylolite trace along the outer cylindrical surface of the cores. It relies on an automatic digitization of high-resolution photographs and on the spatial Fourier spectrum analysis of the stylolite traces. We test and show, on both synthetic and natural examples, that the information from this outer cylindrical surface is equivalent to the one obtained from the destructive planar sections traditionally used. The assessment of paleostress from the stylolite morphology analysis is made using a recent theoretical model, which links the morphological properties to the physical processes acting during stylolite evolution. This model shows that two scaling regimes are to be expected for the stylolite height power spectrum, separated by a cross-over length that depends on the magnitude of the paleostress during formation. We develop a non linear fit method to automatically extract the cross-over lengths from the digitized stylolite profiles. Results on cores from boreholes drilled in the surroundings of the Andra Underground Research Laboratory located at Bure, France, show that different groups of sedimentary stylolites can be distinguished, and correspond to different estimated vertical paleostress values. For the Oxfordian formation, one group of stylolites indicate a paleostress of around 10 MPa, while another group yields 15 MPa. For the Dogger formation, two stylolites indicate a paleostress of around 10 MPa, while others appear to have stopped growing at paleostresses between 30 and 22 MPa, starting at an erosion phase that initiated in the late Cretaceous and continues today. This method has a high potential for further applications on reservoirs or other geological contexts where stylolites are present.Comment: International Journal of Rock Mechanics and Mining Sciences (2013) online firs

A structured annotation frame for the transposable phages: A new proposed family “Saltoviridae” within the Caudovirales

AbstractEnterobacteriophage Mu is the best studied and paradigm member of the transposable phages. Mu-encoded proteins have been annotated in detail in UniProtKB and linked to a controlled vocabulary describing the various steps involved in the phage lytic and lysogenic cycles.Transposable phages are ubiquitous temperate bacterial viruses with a dsDNA linear genome. Twenty-six of them, that infect α, β and γ-proteobacteria, have been sequenced. Their conserved properties are described. Based on these characteristics, we propose a reorganization of the Caudovirales, to allow for the inclusion of a “Saltoviridae” family and two newly proposed subfamilies, the “Myosaltovirinae” and “Siphosaltovirinae”. The latter could temporarily be included in the existing Myoviridae and Siphoviridae families

Phenoloxidase and peroxidase activities in Sphagnum-dominated peatland in a warming climate

International audiencePeatlands still suffer from the scarcity of available data about the characterization and the response to climate forcing of the main oxidative enzymes that occur over the seasons. In the present study, phenoloxidase and peroxidase activities were examined in Sphagnum lawns along a narrow fen-bog gradient under experimental elevated temperatures. We showed that peroxidase activities from Sphagnum mosses were 1000-fold higher than those of phenoloxidases irrespective of seasons and sampling areas. Peroxidase activities increased (+30%) with the rise of air temperatures (an average of 1 °C), while warming did not alter phenoloxidase activities. These results suggest that the monitoring of peroxidase activities in peatlands may represent a suitable and forward indicator of the impact of climate warming on carbon cycle in peatlands

Effect of a temperature gradient on Sphagnum fallax and its associated living microbial communities: a study under controlled conditions.

International audienceMicrobial communities living in Sphagnum are known to constitute early indicators of ecosystem disturbances, but little is known about their response (including their trophic relationships) to climate change. A microcosm experiment was designed to test the effects of a temperature gradient (15, 20, and 25°C) on microbial communities including different trophic groups (primary producers, decomposers, and unicellular predators) in Sphagnum segments (0-3 cm and 3-6 cm of the capitulum). Relationships between microbial communities and abiotic factors (pH, conductivity, temperature, and polyphenols) were also studied. The density and the biomass of testate amoebae in Sphagnum upper segments increased and their community structure changed in heated treatments. The biomass of testate amoebae was linked to the biomass of bacteria and to the total biomass of other groups added and, thus, suggests that indirect effects on the food web structure occurred. Redundancy analysis revealed that microbial assemblages differed strongly in Sphagnum upper segments along a temperature gradient in relation to abiotic factors. The sensitivity of these assemblages made them interesting indicators of climate change. Phenolic compounds represented an important explicative factor in microbial assemblages and outlined the potential direct and (or) indirect effects of phenolics on microbial communities

Prediction of one-repetition maximum from submaximal ratings of perceived exertion in older adults pre-and post-training

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Experimental climate effect on seasonal variability of polyphenol/phenoloxidase interplay along a narrow fen-bog ecological gradient in Sphagnum fallax

International audienceExtracellular phenoloxidase enzymes play an important role in the stability of soil carbon storage by contributing to the cycling of complex recalcitrant phenolic compounds. Climate warming could affect peatland functioning through an alteration of polyphenol/phenoloxidase interplay, which could lead them to becoming weaker sinks of carbon. Here, we assessed the seasonal variability of total phenolics and phenoloxidases subjected to 2-3 °C increase in air temperature using open-top chambers. The measurements were performed along a narrow fen-bog ecological gradient over one growing season. Climate warming had a weak effect on phenoloxidases, but reduced phenolics in both fen and bog areas. Multivariate analyses revealed a split between the areas and also showed that climate warming exacerbated the seasonal variability of polyphenols, culminating in a destabilization of the carbon cycle. A negative relationship between polyphenols and phenoloxidases was recorded in controls and climate treatments suggesting an inhibitory effect of phenolics on phenoloxidases. Any significant decrease of phenolics through repeatedly elevated temperature would greatly impact the ecosystem functioning and carbon cycle through an alteration of the interaction of polyphenols with microbial communities and the production of extracellular enzymes. Our climate treatments did not have the same impact along the fen-bog gradient and suggested that not all the peatland habitats would respond similarly to climate forcing

Correlation of multi-temporal ground-based optical images for landslide monitoring

The objective of this work is to present a low-cost methodology to monitor the displacement of continuously active landslides from ground-based optical images analyzed with a normalized image correlation technique. The performance of the method is evaluated on a series of images acquired on the Super-Sauze landslide (South French Alps) over the period 2008-2009. The image monitoring system consists of a high resolution optical camera installed on a concrete pillar located on a stable crest in front of the landslide and controlled by a datalogger. The data are processed with a cross-correlation algorithm applied to the full resolution images in the acquisition geometry. Then, the calculated 2D displacement field is orthorectified with a back projection technique using a high resolution DEM interpolated from Airborne Laser Scanning (ALS) data. The heterogeneous displacement field of the landslide is thus characterized in time and space. The performance of the technique is assessed using differential GPS surveys as reference. The sources of error affecting the results are then discussed. The strongest limitations for the application of the technique are related to the meteorological, illumination and ground surface conditions inducing partial or complete loss of coherence among the images. Small movements of the camera and the use of a mono-temporal DEM are the most important factors affecting the accuracy of the ortho-rectification of the displacement field. As the proposed methodology can be routinely and automatically applied, it offers promising perspectives for operational applications like, for instance, in early warning systems. © 2012 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS)