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Microstructure and anisotropic swelling behaviour of compacted bentonite/sand mixture

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Journal of Rock Mechanics and Geotechnical Engineering 2014年第2期6卷 126-132页

作者： Simona Saba Jean-Dominique Barnichon Yu-Jun Cui Anh Minh Tang Pierre delage ecole des Ponts parisTech Laboratoire Navier Institut de Radioprotection et de Surete Nucleaire(IRSN)

Pre-compacted elements （disks, tutus） of bentonite/sand mixture are candidate materials for sealing plugs of radioactive waste disposal. Choice of this material is mainly based on its swelling capacity allowing all gaps in the system to be sealed, and on its low permeability. When emplaced in the gallery, these elements will start to absorb water from the host rock and swell. Thereby, a swelling pressure will develop in the radial direction against the host rock and in the axial direction against the support structure. In this work, the swelling pressure of a small scale compacted disk of bentonite and sand was experimentally studied in both radial and axial directions. Different swelling kinetics were identified for different dry densities and along different directions. As a rule, the swelling pressure starts increasing quickly, reaches a peak value, decreases a little and finally stabilises. For some dry densities, higher peaks were observed in the radial direction than in the axial direction. The presence of peaks is related to the microstructure change and to the collapse of macro- pores. In parallel to the mechanical tests, microstructure investigation at the sample scale was conducted using microfocus X-ray computed tomography （BCT）. Image observation showed a denser structure in the centre and a looser one in the border, which was also confirmed by image analysis. This structure heterogeneity in the radial direction and the occurrence of macro-pores close to the radial boundary of the sample can explain the large peaks observed in the radial swelling pressure evolution. Another interesting result is the higher anisotropy found at lower bentonite dry densities, which was also analysed by means ofμCT observation of a sample at low bentonite dry density after the end of test. It was found that the macro-pores, especially those between sand grains, were not filled by swelled bentonite, which preserved the anisotropic microstructure caused by uniaxial compression

关键词： Bentonite/sand mixture Nuclear waste disposal Anisotropy Swelling pressure Microstructure Microfocus X-ray computed tomography(μCT)

Unveiling the lamellar structure of the human cornea over its full thickness using polarization-resolved SHG microscopy

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Light(Science & Applications) 2023年第9期12卷 1782-1794页

作者： Clothilde Raoux Anatole Chessel Pierre Mahou Gaël Latour Marie-Claire Schanne-Klein Laboratory for Optics and Biosciences Ecole PolytechniqueCNRSINSERMInstitut Polytechnique de Paris91128 PalaiseauFrance Universitéparis-Saclay 91190 Gif-sur-YvetteFrance

A key property of the human cornea is to maintain its curvature and consequently its refraction capability despite daily changes in intraocular *** is closely related to the multiscale structure of the corneal stroma,which consists of 1-3µm-thick stacked lamellae made of thin collagen ***,the distribution,size,and orientation of these lamellae along the depth of the cornea are poorly characterized up to *** this study,we use second harmonic generation(SHG)microscopy to visualize the collagen distribution over the full depth of 10 intact and unstained human corneas(500-600µm thick).We take advantage of the small coherence length in epi-detection to axially resolve the lamellae while maintaining the corneal physiological ***,as raw epi-detected SHG images are spatially homogenous because of the sub-wavelength size of stromal collagen fibrils,we use a polarimetric approach to measure the collagen orientation in every *** a careful validation of this approach,we show that the collagen lamellae(i)are mostly oriented along the inferior-superior axis in the anterior stroma and along the nasal-temporal axis in the posterior stroma,with a gradual shift in between and(ii)exhibit more disorder in the anterior *** results represent the first quantitative characterization of the lamellar structure of the human cornea continuously along its entire thickness with micrometric *** also shows the unique potential of P-SHG microscopy for imaging of collagen distribution in thick dense tissues.

关键词： structure curvature resolved

Effects of lime treatment on the microstructure and hydraulic conductivity of Héricourt clay

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Journal of Rock Mechanics and Geotechnical Engineering 2014年第5期6卷 399-404页

作者： Thanh Danh Tran Yu-Jun Cui Anh Minh Tang Martine Audiguier Roger Cojean mines parisTech-Centre de Géosciences FontainebleauFrance Laboratoire Navier/CERMES Ecole des Ponts ParisTech6 et 8 Avenue Blaise Pascal77455 Marne-la-Vallée Cedex 2France mines parisTeche-Centre de Géosciences FontainebleauFrance

This study aims at evidencing the effects of lime treatment on the microstructure and hydraulic conductivityof a compacted expansive clay, with emphasis put on the effect of lime hydration and *** this purpose, evolutions of hydraulic conductivity were investigated for both lime-treatedand untreated soil specimens over 7 d after full saturation of the specimens and their microstructureswere observed at the end. Note that for the treated specimen, dry clay powder was mixed with quicklimeprior to compaction in order to study the effect of lime hydration. It is observed that lime hydration andmodification did not affect the intra-aggregate pores but increased the inter-aggregates pores size. Thisincrease gave rise to an increase of hydraulic conductivity. More precisely, the hydraulic conductivity oflime-treated specimen increased progressively during the first 3 d of modification phase and stabilisedduring the next 4 d which correspond to a short period prior to the stabilisation phase. The microstructureobservation showed that stabilisation reactions took place after 7 d. Under the effect of stabilisation,a decreasing hydraulic conductivity can be expected in longer time due to the formation ofcementitious compounds. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

关键词： Clays Lime hydration Hydraulic conductivity Microstructure Temperature effect

V_p/V_s Anisotropy and Implications for Crustal Composition Identification and Earthquake Prediction

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Acta Geologica Sinica(English Edition) 2009年第4期83卷 801-815页

作者： WANG Qian JI Shaocheng XU Zhiqin departement des Genies Civil Geologique et des Mines Ecole Polytechnique de Montreal Montreal H3C 3A7 Canada Key Laboratory of Continental Dynamics Ministry of Land and Resources Chinese Academy of Geological Sciences 10037 Beijing China

The ratio of P- to S-wave velocities （Vp/Vs） is regarded as one of the most diagnostic properties of natural rocks. It has been used as a discriminant of composition for the continental crust and provides valuable constraints on its formation and evolution processes. Furthermore, the spatial and temporal changes in Vp/Vs before and after earthquakes are probably the most promising avenue to understanding the source mechanics and possibly predicting earthquakes. Here we calibrate the variations in Vp/Vs in dry, anisotropic crustal rocks and provide a set of basic information for the interpretation of future seismic data from the Wenchuan earthquake Fault zone Scientific Drilling （WFSD） project and other surveys. Vp/Vs is a constant （Ф0） for an isotropic rock. However, most of crustal rocks are anisotropic due to lattice-preferred orientations of anisotropic minerals （e.g., mica, amphibole, plagioclase and pyroxene） and cracks as well as thin compositional layering. The Vp/Vs ratio of an anisotropic rock measured along a selected pair of propagation-vibration directions is an apparent value （Фy） that is significantly different from the value for its isotropic counterpart （Ф0）. The usefulness of apparent Vp/Vs ratios as a diagnostic of crustal composition depends largely on rock seismic anisotropy. A 5% of P- and S-wave velocity anisotropy is sufficient to make it impossible to determine the crustal composition using the conventional criteria （Vp/Vs≤1.756 for felsic rocks, 1.756〈Vp/Vs≤1.809 for intermediate rocks, 1.809〈Vp/Vs≤1.944 for mafic rocks, and Vp/V2〉1.944 fluidfilled porous/fractured or partially molten rocks） if the information about the wave propagation-polarization directions with respect to the tectonic framework is unknown. However, the variations in Vp/Vs measured from borehole seismic experiments can be readily interpreted according to the orientations of the ray path and the polarization of the shear waves with respect to the present-day principal stre

关键词： Vp/Vs ratio Seismic anisotropy Crustal composition Earthquake prediction

Spallation Process of Thermally Grown Oxides by In-Situ CCD Monitoring Technique

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Journal of Iron and Steel Research International 2009年第6期16卷 90-94页

作者： QI Yu-hong Philippe Lours Yannick Le Maoult Materials Science and Engineering department Dalian Maritime University Dalian 116026 Liaoning China Research Centre on Tools Materials and Processes Ecole des Mines 81013 Albi France

In cooling process of Fe-Cr-Al alloy oxidized at 1 300 ℃, the effect of cooling speed and exposure time on oxide spalled area fraction and successive variety of the spalled region were studied by investigating evolvement of the thermally grown oxide using in-situ CCD monitoring technique. The results showed that oxide spallation can be restrained by controlling cooling speed and the critical temperature drop of spallation initiation which is closely related to the oxide thickness or exposure time, and the spallation process of a little region may be described in more detail as two routes： from the oxide/substrate interface micro-decohesion, micro-buckles, buckle spreading, buckle crack to spallation and from the interface micro-decohesion, micro-buckles, buckle crack and spallation to the residual oxide decohesion and spallation.

关键词： in-situ CCD monitoring technique spallation thermally grown oxide Fe-Cr-AI

Immature and mature antibodies as defenders against cancer

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Cellular & Molecular Immunology 2023年第1期20卷 3-5页

作者： Robin V.Lacombe Sophie Sibéril Jordan D.Dimitrov Centre de Recherche des Cordeliers INSERMCNRSSorbonne UniversitéUniversitéParis CitéParisFrance

Antibodies(Abs)are glycoprotein molecules that represent an essential component of the adaptative immune *** are secreted in body fluids and act as a critical part of immune *** recognition of self-antigens by Abs is normally selected against during B-cell development,autoreactive Abs can be generated as a result of pathological immune responses,as observed in autoimmune *** can also be produced in cancer patients,where they may have beneficial roles[1].Indeed,the presence of intratumoral antibody-secreting cells(ASCs)and B-cell-rich tertiary lymphoid structures(TLSs)has been observed in many cancer types and generally correlates with a favorable clinical prognosis[2,3,4,5,6].The existence of specific antitumor antibody responses suggests that tumor cells express molecules that are recognized as nonself antigens by the immune system or that tolerance of self-antigens expressed on cancer cells is lost[1,4].The study of the origin of tumor-reactive Abs and their specificity and functions is of paramount importance for understanding the development of adaptive antitumor immune responses and for revealing novel therapeutic avenues.A recent publication in Cell by Mazor et al.[7]has provided an important advance in our understanding of antibody responses in *** particular,this work paves the way for the distinction between antibody-reactive tumors and antibody-nonreactive tumors,which is reminiscent of the dichotomy of the noninfiltrated“cold”tumor microenvironment(TME)in contrast with the highly infiltrated with immune cells“hot”TME[8].Moreover,an important finding of the study was the demonstration that tumor-directed autoreactivity may be either preexisting or induced by somatic hypermutations,a mechanism related to the chronicity of cancer.

关键词： cancer antibodies specificity

Experimental Study of Corner Stall in a Linear Compressor Cascade

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Chinese Journal of Aeronautics 2011年第3期24卷 235-242页

作者： MA Wei OTTAVY Xavier LU Lipeng LEBOEUF Francis GAO Feng Laboratoire de Mecanique des Fluides et d'Acoustique Ecole Centrale de Lyon Ecully 69134 France School of Jet Propulsion Beihang University Beijing 100191 China

In order to gain a better knowledge of the mechanisms and to calibrate computational fluid dynamics （CFD） tools including both Reynolds-averaged Navier-Stokes （RANS） and large eddy simulation （LES）, a detailed and accurate experimental study of comer stall in a linear compressor cascade has been carried out. Data are taken at a Reynolds number of 382 000 based on blade chord and inlet velocity. At first, inlet flow boundary layer is surveyed using hot-wire anemometry. Then in order to investigate the effects of incidence, measurements are acquired at five incidences, including static pressures on both blade and endwall sur- faces measured by pressure taps and the total pressure losses of outlet flow measured by a five-hole pressure probe. The maxi- mum losses as well as the extent of losses of the comer stall are presented as a function of the investigated incidences.

关键词： comer separation compressor cascades incidence hot-wire anemometry computational fluid dynamics

Loaded Rubber-Like Materials Subjected to Small-Amplitude Vibrations

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Chinese Journal of Polymer Science 2014年第5期32卷 620-632页

作者： T.Beda J.B.Casimir K.E.Atcholi Y.Chevalier Industrial and Mechanical Engineering department Ecole Nationale Supérieure Polytechnique (ENSP) Département de Physique Faculté des Sciences Université de NGaoundéré Laboratoire d’Ingénierie des Structures Mécanique et des Matériaux (LISMMA) SUPMECA de Paris Institut de Recherche sur les Transports l’Energie et la Société (IRTES EA7274) Laboratoire Systèmes et Transport (SeT EA 3317) Université de Technologie de Belfort-Montbéliard (UTBM)

This paper proposes a constitutive law and a method for characterizing highly preloaded viscoelastic materials subjected to linear （small-amplitude） vibrations. A multiplicative non-separable variables law has been suggested to model the behavior that depends on both stretch and time/frequency. This approach allows splitting the intricate combined test performed simultaneously on both stretch and frequency, generally in a limited experimental domain up to 100 Hz, into two independent tests. Thus, on one hand, the dynamic complex modulus dependent on frequency alone is evaluated on the basis of vibration tests in a large experimental domain up to 100 kHz. On the other hand, energetic parameters are determined from a quasi-static hyperelastic tensile test. The complex modulus, dependent on both stretch and frequency, is then deduced from the results acquired from uncoupled investigations. This work shows that, in extension, the elastic modulus increases with increasing stretch, and the loss factor decreases with increasing stretch; while, in compression, around the material undeformed state, the modulus increases as the stretch increases till a certain value of compression stretch （upturn point depending on material characteristics）, and then the modulus decreases as the stretch increases. Globally, preload rigidifies materials but reduces their damping property. These results closely match a well-known observation in solid mechanics.

关键词： Elastomers Viscoelasticity Hyperelasticity Vibrations Modeling Characterization Combined modulus.

Surface complexation modeling of Eu(Ⅲ) adsorption on silica in the presence of fulvic acid

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Science China Chemistry 2014年第9期57卷 1276-1282页

作者： YE YuanLv CHEN ZongYuan MONTAVON Gilles JIN Qiang GUO ZhiJun WU WangSuo Radiochemistry Laboratory School of Nuclear Science and TechnologyLanzhou University Laboratoire SUBATECH UMR 6457 CNRS-IN2P3/Ecole des Mines de Nantes/PRES UNAM4 rue A. Kastler 44307 Nantes CedexFrance

Humic substances （HS） substantially affect heavy metal （M） adsorption on mineral surfaces. However, quantitative descriptions of ternary systems involving M, HS and mineral surfaces remain unclear. This study examines adsorption in a model ternary system including Eu（III）, fulvic acid （FA） and silica, and describes the adsorption of Eu（III） and FA by combining a double-layer model （DLM） and the Stockholm humic model （SHM）. SHM explains the binding of H＋ and Eu^3＋ to EA and the DLM for FA and Eu（Ill） adsorption on silica. Experimental results showed that the presence of FA promotes Eu（III） adsorp- tion at acidic pH values, but decreases it at basic pH values, which indicates the formation of ternary surface complexes. Modeling calculations have shown that two ternary surface complexes are required to describe the experimental results in which Eu^3＋ acts as a bridge between the surface site and FA. The present study suggests that the discrete-site approach to HS is a promising method for interpreting the adsorption data for M, HS and mineral ternary systems.

关键词： Eu(III) fuivic acid adsorption silica Stockholm humic model