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

Comparaison de groupes de variables. 2eme partie: Un exemple d'applications

SIGLECNRS-CDST / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Modelling cyanobacteria blooms in urban lakes. Application to Lake of Enghien-les-Bains.

The ecosystems in urban lakes are very vulnerable to human pressure because of their specific physical functioning, characterized by intermittent thermal stratification and low flow speeds. Furthermore, the high intake of nutrients in these environments encourages blooms of phytoplankton, including toxic cyanobacteria, disrupting their use and causing health problems (Catherine et al., 2008). This work focuses on the implementation of a predictive model of cyanobacteria blooms in urban lakes. It is part of a project whose objective is to develop a monitoring and warning system, in real-time, of phytoplankton blooms in freshwater ecosystems

Acquisition des mesures sur les sites d'application

Acquisition des mesures sur les sites d'applicatio

Modelling cyanobacteria blooms in urban lakes. Application to Lake of Enghien-les-Bains.

The ecosystems in urban lakes are very vulnerable to human pressure because of their specific physical functioning, characterized by intermittent thermal stratification and low flow speeds. Furthermore, the high intake of nutrients in these environments encourages blooms of phytoplankton, including toxic cyanobacteria, disrupting their use and causing health problems (Catherine et al., 2008). This work focuses on the implementation of a predictive model of cyanobacteria blooms in urban lakes. It is part of a project whose objective is to develop a monitoring and warning system, in real-time, of phytoplankton blooms in freshwater ecosystems

Transport properties of disordered CVD graphene in the strong localized regime

The Chemical Vapor Deposition (CVD) of graphene is nowadays one of the most promising methods for the production of large scale graphene films [1]. The growth is first initiated onto transition metal substrates (Cu, Pt.) before being transferred onto an insulating wafer. High quality and homogeneous graphene films can be obtained this way, displaying amazing electronic properties such as the anomalous Quantum Hall Effect at low temperature and high magnetic field [2]. On the other hand, achieving high quality graphene films requires states-of-the art techniques and when the ideal set of parameters is not fulfilled, one may end up with a variety of disordered graphene devices with interesting electronic properties. We investigated the extreme limit of a highly disrupted multi-layer graphene film showing high electrical resistance. We demonstrate that electronic conduction occurs through hopping between localized sites, provided the drain-source voltage remains higher than a temperature-dependent threshold value. An exhaustive data analysis concludes that the sample can be assimilated as an array of very tiny graphene dots (~6nm in diameter) weakly interacting each other. The presence of such few-layer graphene islands is confirmed thanks to Raman spectroscopy [3]. In the strongly localized regime, the magneto-conductance (MC) happened to be unusual, being first positive up to 6T and then negative by about 50% up to the maximum experimental magnetic field (55T)

Magneto-transport properties of a random distribution of few-layer graphene patches.

International audienceIn this study, we address the electronic properties of conducting films constituted of an array of randomly distributed few layer graphene patches and investigate on their most salient galvanometric features in the moderate and extreme disordered limit. We demonstrate that, in annealed devices, the ambipolar behaviour and the onset of Landau level quantization in high magnetic field constitute robust hallmarks of few-layer graphene films. In the strong disorder limit, however, the magnetotransport properties are best described by a variable-range hopping behaviour. A large negative magneto-conductance is observed at the charge neutrality point, in consistency with localized transport regime

High-frequency monitoring of phytoplankton dynamics within the European water framework directive: application to metalimnetic cyanobacteria

Large, sub-alpine, stratified lakes are directly within the scope of the European Water Framework Directive (WFD) and need adapted monitoring systems. Moreover, anthropogenic eutrophication was frequently the main cause of their water quality degradation in the 20th century. This paper is primarily aimed at demonstrating how in situ sensor-equipped buoys could be the base of monitoring designs to support the WFD objectives. The core of this paper, mainly methodological, focuses on single-depth, high frequency (4 per hour) fluorescence measurements. It shows that the internal wave pattern provides additional information to the single-depth time series to assess phytoplankton dynamics in a stratified water column displaying strong, vertical biomass heterogeneity. The paper deals with the following three aspects: (1) definition of an indicator to determine whether or not the sensor actually detects the metalimnetic fluorescence peak, (2) vertical representation of chlorophyll distribution from single-depth series; (3) time evolution of the fluorescence peak (maximum value, depth and associated temperature, peak width)