Admissible generalizations of examples as rules

International audienc

Mesure de champs cinématiques par corrélation en coupe orthogonale : Possibilités et précision de l'imagerie double-frame avec éclairage laser pulsé

Dans le but de valider les simulations de la coupe visant à prédire l'intégrité de surface, une instrumentation basée sur une caméra double-frame et un éclairage laser pulsé a été développée. A partir des doublets d'images obtenus par ce moyen d'acquisition, les dépouillements possibles par corrélation d'images sont détaillés, accompagnés d'estimations d'incertitudes de mesure

Kinematic Field Measurements During Orthogonal Cutting Tests via DIC with Double-frame Camera and Pulsed Laser Lighting

The measurement of machined-part strain fields induced by the cutting process remains a challenge because of the presence of highly intensive and localised strains. In this study, a high-speed double-frame imaging device with pulsed laser lighting is used in order to obtain sharp and highly resolved images during orthogonal cutting tests performed in an aluminium alloy. The displacement fields are then measured using a global Q4–digital-image-correlation (DIC) method and several strategies, facilitating calculation of the total displacements due to the cut, along with the residual strains in the machined part. Numerical procedures are developed to manage the removed material that disturbs the DIC. An automatic primary shear angle detection procedure using DIC is also proposed. Five different markings, which are produced via chemical etching and micro blasting, are applied to the observed surfaces. Their effects on the kinematic fields and the uncertainties are then studied. Three surface parameters are proposed as indicators for determining the surface preparation suitability for the DIC. The repeatability of the kinematic fields induced during the cutting process is studied, because of the ease with which testing can be performed. Finally, the plastically deformed layer engendered by the cutting process is measured using the calculated residual strains

3D analysis of enamel demineralisation in human dental caries using high- resolution, large field of view synchrotron X-ray micro-computed tomography

We report major advances in the analysis of synchrotron 3D datasets acquired from human healthy and carious dental enamel. Synchrotron tomographic data for three human carious samples and a non-carious reference tooth sample were collected with the voxel size of 325 nm for a total volume of 815.4 × 815.4 × 685.4 μm3. The results were compared with conventional X-ray tomography, optical microscopy, and focused ion beam-scanning electron microscopy. Clear contrast was seen within demineralised enamel due to reduced mineral content using synchrotron tomography in comparison with conventional tomography. The features were found to correspond with the rod and inter-rod structures within prismatic enamel. 2D and 3D image segmentation allowed statistical quantification of important structural characteristics (such as the aspect ratio and the cross-sectional area of voids, as well as the demineralised volume fraction as a function of lesion depth). Whilst overall carious enamel predominantly displayed a Type 1 etching pattern (preferential demineralisation of enamel rods), a transition between Type 2 (preferential inter-rod demineralisation) and Type 1 was identified within the same lesion for the first time. This study does not provide extensive results on the different lesions studied, but illustrate a new method and its potential application

Spatial Updating Depends on Gravity

As we move through an environment the positions of surrounding objects relative to our body constantly change. Maintaining orientation requires spatial updating, the continuous monitoring of self-motion cues to update external locations. This ability critically depends on the integration of visual, proprioceptive, kinesthetic, and vestibular information. During weightlessness gravity no longer acts as an essential reference, creating a discrepancy between vestibular, visual and sensorimotor signals. Here, we explore the effects of repeated bouts of microgravity and hypergravity on spatial updating performance during parabolic flight. Ten healthy participants (four women, six men) took part in a parabolic flight campaign that comprised a total of 31 parabolas. Each parabola created about 20-25 s of 0 g, preceded and followed by about 20 s of hypergravity (1.8 g). Participants performed a visual-spatial updating task in seated position during 15 parabolas. The task included two updating conditions simulating virtual forward movements of different lengths (short and long), and a static condition with no movement that served as a control condition. Two trials were performed during each phase of the parabola, i.e., at 1 g before the start of the parabola, at 1.8 g during the acceleration phase of the parabola, and during 0 g. Our data demonstrate that 0 g and 1.8 g impaired pointing performance for long updating trials as indicated by increased variability of pointing errors compared to 1 g. In contrast, we found no support for any changes for short updating and static conditions, suggesting that a certain degree of task complexity is required to affect pointing errors. These findings are important for operational requirements during spaceflight because spatial updating is pivotal for navigation when vision is poor or unreliable and objects go out of sight, for example during extravehicular activities in space or the exploration of unfamiliar environments. Future studies should compare the effects on spatial updating during seated and free-floating conditions, and determine at which g-threshold decrements in spatial updating performance emerge

Environment-sensitivity functions for gross primary productivity in light use efficiency models

The sensitivity of photosynthesis to environmental changes is essential for understanding carbon cycle responses to global climate change and for the development of modeling approaches that explains its spatial and temporal variability. We collected a large variety of published sensitivity functions of gross primary productivity (GPP) to different forcing variables to assess the response of GPP to environmental factors. These include the responses of GPP to temperature; vapor pressure deficit, some of which include the response to atmospheric CO2 concentrations; soil water availability (W); light intensity; and cloudiness. These functions were combined in a full factorial light use efficiency (LUE) model structure, leading to a collection of 5600 distinct LUE models. Each model was optimized against daily GPP and evapotranspiration fluxes from 196 FLUXNET sites and ranked across sites based on a bootstrap approach. The GPP sensitivity to each environmental factor, including CO2 fertilization, was shown to be significant, and that none of the previously published model structures performed as well as the best model selected. From daily and weekly to monthly scales, the best model's median Nash-Sutcliffe model efficiency across sites was 0.73, 0.79 and 0.82, respectively, but poorer at annual scales (0.23), emphasizing the common limitation of current models in describing the interannual variability of GPP. Although the best global model did not match the local best model at each site, the selection was robust across ecosystem types. The contribution of light saturation and cloudiness to GPP was observed across all biomes (from 23% to 43%). Temperature and W dominates GPP and LUE but responses of GPP to temperature and W are lagged in cold and arid ecosystems, respectively. The findings of this study provide a foundation towards more robust LUE-based estimates of global GPP and may provide a benchmark for other empirical GPP products.publishersversionpublishe

IL-33 delivery induces serous cavity macrophage proliferation independent of interleukin-4 receptor alpha

IL-33 plays an important role in the initiation of type-2 immune responses, as well as the enhancement of type 2 effector functions. Engagement of the IL-33 receptor on macrophages facilitates polarization to an alternative activation state by amplifying IL-4 and IL-13 signaling to IL-4Rα. IL-4 and IL-13 also induce macrophage proliferation but IL-33 involvement in this process has not been rigorously evaluated. As expected, in vivo delivery of IL-33 induced IL-4Rα-dependent alternative macrophage activation in the serous cavities. IL-33 delivery also induced macrophages to proliferate but, unexpectedly, this was independent of IL-4Rα signaling. In a filarial nematode infection model in which IL-4Rα-dependent alternative activation and proliferation in the pleural cavity is well described, IL-33R was essential for alternative activation but not macrophage proliferation. Similarly, during Alternaria alternata induced airway inflammation, which provokes strong IL-33 responses, we observed that both IL-4Rα and IL-33R were required for alternative activation, while macrophage proliferation in the pleural cavity was still evident in the absence of either receptor alone. Our data show that IL-33R and IL-4Rα promote macrophage proliferation independently of each other, but both are essential for induction of alternative activation

Anthropogenic N deposition increases soil organic matter accumulation without altering its biochemical composition

Accumulating evidence indicates that future rates of atmospheric N deposition have the potential to increase soil C storage by reducing the decay of plant litter and soil organic matter (SOM). Although the microbial mechanism underlying this response is not well understood, a decline in decay could alter the amount, as well as biochemical composition of SOM. Here, we used sizeâ density fractionation and solidâ state 13Câ NMR spectroscopy to explore the extent to which declines in microbial decay in a longâ term (ca. 20 yrs.) N deposition experiment have altered the biochemical composition of forest floor, bulk mineral soil, as well as free and occluded particulate organic matter. Significant amounts of organic matter have accumulated in occluded particulate organic matter (~20%; oPOM); however, experimental N deposition had not altered the abundance of carboxyl, aryl, alkyl, or O/Nâ alkyl C in forest floor, bulk mineral soil, or any soil fraction. These observations suggest that biochemically equivalent organic matter has accumulated in oPOM at a greater rate under experimental N deposition, relative to the ambient treatment. Although we do not understand the process by which experimental N deposition has fostered the occlusion of organic matter by mineral soil particles, our results highlight the importance of interactions among the products of microbial decay and the chemical and physical properties of silt and clay particles that occlude organic matter from microbial attack. Because oPOM can reside in soils for decades to centuries, organic matter accumulating under future rates of anthropogenic N deposition could remain in soil for long periods of time. If temperate forest soils in the Northern Hemisphere respond like those in our experiment, then unabated deposition of anthropogenic N from the atmosphere has the potential to foster greater soil C storage, especially in fineâ texture forest soils.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/136051/1/gcb13480_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/136051/2/gcb13480.pd