Two phase residence time distribution in a modified twin screw extruder

Biomass fractionation is performed with a modified Clextral twin-screw extruder used as a thermo-mechano-chemical reactor. This new process is firstly analyzed. Visual observations, residence time distributions, and global mass balances are used to obtain information about the process phenomena and their coupling. Residence time distributions (RTD) classical models are adopted to represent the experimental plots. The influence of continuous and discrete process parameters upon the RTD of the solid and liquid phases is analyzed

Prospectives

Tiré de: Prospectives, vol. 12, no 1, février 1976Titre de l'écran-titre (visionné le 24 janv. 2013

Assessment of Aging of the Human Skin by In Vivo Ultrasonic Imaging

The ultrasonic imaging technique that we have developed provides cross-sectional images of human skin in vivo with a resolution of about 80 μm axially (i.e., deep into the skin) and 250 μm lateral (parallel to the surface). In order to study aging skin, we obtained ultrasonic images from the mid-fore-arm (volar and dorsal sides) of 142 women. Ultrasonically, on the images, the dermis appears composed of two bands: a dark superficial one where the ultrasonic waves are propagated in a relatively homogeneous or non-echogenic medium, and a deeper one, which is lighter in color, suggesting a heterogeneous medium. Our results show that skin is thicker on the dorsal than on the volar forearm. In contrast to previously published results, skin thickness remains constant until the seventh decade of life, diminishing thereafter. The relative thicknesses of the two bands show marked variations with age: a progressive thickening of the dark band, from zero in infants to approximately 75% of total skin thickness in aged subjects, while the light band shows the inverse trend. Comparing the amplitude of the bands on the volar and dorsal forearm, the relative thickness of the dark band is larger on the dorsal (exposed) side and increases with age. These findings and the analysis of variously stained biopsies taken in some of our patients lead us to assign this dark band to a zone in the upper dermis where the collagen network is delicate, dense, and well organized. This is supported by some data in the literature. The thickness of this subepidermal non-echogenic band appears to be a far more sensitive marker of skin aging at the dermal level than is the measurement of skin thickness

Spatial Scaling Patterns of Functional Diversity

Ecology, biogeography and conservation biology, among other disciplines, often rely on species identity, distribution and abundance to perceive and explain patterns in space and time. Yet, species are not independent units in the way they interact with their environment. Species often perform similar roles in networks and their ecosystems, and at least partial redundancy or difference of roles might explain co-existence, competitive exclusion or other patterns reflected at the community level. Therefore, considering species traits, that is, the organisms' functional properties that interact with the environment, might be of utmost importance in the study of species relative abundances. Several descriptive measures of diversity, such as the species-area relationship (SAR) and the species abundance distribution (SAD), have been used extensively to characterize the communities and as a possible window to gain insight into underlying processes shaping and maintaining biodiversity. However, if the role of species in a community is better assessed by their functional attributes, then one should also study the SAR and the SAD by using trait-based approaches, and not only taxonomic species. Here we merged species according to their similarity in a number of traits, creating functional units, and used these new units to study the equivalent patterns of the SAR and of the SAD (functional units abundance distributions - FUADs), with emphasis on their spatial scaling characteristics. This idea was tested using data on arthropods collected in Terceira island, in the Azorean archipelago. Our results showed that diversity scales differently depending on whether we use species or functional units. If what determines species communities' dynamics is their functional diversity, then our results suggest that we may need to revaluate the commonly assumed patterns of species diversity and, concomitantly, the role of the underlying processes.Peer reviewe

Arthropod co-occurrence networks indicate environmental differences between islands and signal introduced species in Azorean native forest remnants

Island biotas are in imminent threat from anthropogenic impacts. Of these impacts, the negative effects of exotic species on the taxonomic and functional diversity of the local fauna are of major concern. Exotics may also have a detrimental effect on interspecific interactions which, in turn, can destabilize ecological networks. Species co-occurrence networks can detect species-to-species associations and are used to predict ecological interaction networks and utilized as tools to assess environmental impacts on community structure. Here, we aim to investigate whether or not topological differences of the arthropod co-occurrence networks among native forest fragments from seven Azorean islands can reveal the influence of the abiotic environment and exotic species on these networks. Co-occurrence networks were sensitive to environmental and community dissimilarities, showing a clear separation between islands and pinpointed differences between indigenous and exotic networks. Most exotics were little connected and exotic networks had a large proportion of unconnected species. The resulting decreased connectance and the increased modularity with the increase of the proportions of exotics in the networks suggest that most exotics have too low prevalence to show associations with other species, and only a few dominants drive co-occurrences. The proportion of negative links, as indicators of competition, did not increase with the increase of exotics in the habitats, suggesting that exotics provided new functional roles when they colonized native forest remnants. However, when the theoretical networks consisting of only indigenous species were investigated, connectance decreased and closeness increased with the increase of exotics, suggesting processes of network degradation. Since our study provides ample evidence for the usefulness of co-occurrence network analysis in studying island ecosystems, we recommend the use of this tool for ecosystem assessments, early warning systems and decision-making in island biodiversity conservation.info:eu-repo/semantics/publishedVersio

Early determinants of food liking among 5y-old children: a longitudinal study from the EDEN mother-child cohort

International audienceAbstractBackgroundIdentifying the determinants of child’s liking for different foods may help to prevent future choices of unhealthy food.ObjectiveTo study early-life food-related characteristics associated with child’s liking for different foods at 5y with a longitudinal study.Design1142 5y- old children completed a liking test for “fruit and vegetables”, “meat, fish and eggs”, desserts and cheese. Data related to maternal food intake before pregnancy, infant feeding during the first year of life, maternal feeding practices at 2y, child’s food intake at 3y, and child’s food neophobia from 1 to 4y were collected prospectively from the mother. The associations between these factors and child‘s liking for each category of foods were analyzed using structural equation modelling.ResultsHigh food neophobia at 4 y was related to lower child’s liking for all food groups. Maternal feeding practices at 2y were associated with liking for dessert: negatively for the practices allowing child to control his/her own food intake, positively for restriction of child’s food intake for weight reasons. Moreover, child’s food intake at 3y was positively associated with child’s liking for “fruit and vegetables” as well as for cheese. Finally, adherence to the infant feeding pattern “long breastfeeding, later introduction of main meal components and use of home-made products” was positively associated with child’s liking for meat/fish/eggs.ConclusionsFor all food groups, food neophobia was a common determinant of child’s liking for food at 5y, whereas other factors were associated with food liking for specific food groups

Blunted muscle angiogenic training-response in COPD patients versus sedentary controls

International audienceThe impaired skeletal muscle of chronic obstructive pulmonary disease (COPD) patients reduces exercise capacity. Similar to the oxidative muscle fibres, the angio-adaptation of muscle to training may be blunted in these patients, as in other chronic conditions. We therefore compared muscle functional responses and angio-adaptations after training in COPD patients and sedentary healthy subjects (SHS). 24 COPD patients (forced expiratory volume in 1 s 45.6¡17.5% predicted) and 23 SHS (,150 min?week-1 of moderate-to-vigorous exercise) completed a 6-week rehabilitation programme based on individualised moderate-intensity endurance training. Histomorphological muscle analysis and measurements of pro-angiogenic vascular endothelial growth factor (VEGF)-A and anti-angiogenic thrombospondin (TSP)-1 were conducted before and after training. COPD patients and SHS showed improved symptom-limited oxygen consumption and muscle endurance, although improvements were lower in COPD patients (+0.96¡2.4 versus +2.9¡2.6 mL?kg-1 ?min-1 , p,0.05, and +65% versus +108%, p50.06, respectively). The capillary-to-fibre (C/F) ratio increased less in COPD patients than SHS (+16¡10% versus +37¡20%, p,0.05) and no fibre type switch occurred in COPD patients. The VEGF-A/TSP-1 ratio increased in COPD patients and SHS (+65% versus +35%, p,0.05). Changes in C/F and symptom-limited oxygen consumption were correlated (r50.51, p,0.05). In addition to a lack of fibre switch, COPD patients displayed a blunted angiogenic response to training

Dispersal ability determines the scaling properties of species abundance distributions: a case study using arthropods from the Azores.

Peer reviewe