Modelling the viscoplastic behaviour of Callovo-Oxfordian claystone with consideration of damage effect

In order to evaluate the performance of deep geological disposal of radioactive waste,an underground research laboratory(URL)was constructed by Andra in the Callovo-Oxfordian(COx)claystone formation at the Meuse/Haute-Marne(MHM).The construction of URL induced the excavation damage of host formations,and the ventilation in the galleries desaturated the host formation close to the gallery wall.Moreover,it is expected that the mechanical behaviour of COx claystone is time-dependent.This study presents a constitutive model developed to describe the viscoplastic behaviour of unsaturated and damaged COx claystone.In this model,the unsaturation effect is considered by adopting the Bishop effective stress and the van Genuchten(VG)water retention model.In terms of the viscoplastic behaviour,the nonstationary flow surface(NSFS)theory for unsaturated soils is used with consideration of the coupled effects of strain rate and suction on the yield stress.A progressive hardening law is adopted.Meanwhile,a non-associated flow rule is used,which is similar to that in Barcelona basic model(BBM).In addition,to describe the damage effect induced by suction change and viscoplastic loading,a damage function is defined based on the crack volume proportion.This damage function contains two variables:unsaturated effective stress and viscoplastic volumetric strain,with the related parameters determined based on the mercury intrusion porosimetry(MIP)tests.For the model validation,different tests on COx claystone under different loading paths are simulated.Comparisons between experimental and simulated results indicated that the present model is able to well describe the viscoplastic behaviour of damaged COx claystone,including swelling/shrinkage,triaxial extension and compression,and triaxial creep.

Extension of Chemoprevention of Seasonal Malaria to Five Cycles and to Children from the Age of 6 to 9 Years in Africa: Analysis of Its Acceptability, Feasibility, Cost and Impact A Systematic Review

Introduction: Seasonal Malaria Chemoprevention (SMC) aims at preventing malaria in children during the high transmission season. It has been recommended by the WHO since 2013 for children from the age of 3-59 months. However, despite the impact of this intervention, a peak in the prevalence and incidence of malaria is observed in children from the age of 5-9 years. The aim of this study is to determine from the current literature the feasibility, impact and cost-effectiveness of extending SMC to five cycles and to older children. Methods: A litterature search of PubMed/Medline, NCBI and Google scholar identified 1333 articles. After reading the titles and abstracts by two authors, 24 articles were selected and submitted for full reading. Random control studies on the extension of SMC, malaria, feasibility of SMC, impact of SMC and cost-effectiveness of SMC were selected. A total of 16 articles were included for the qualitative synthesis after excluding 8 studies. Results: Following the summary of the evidence, we conclude that the extension is feasible but will be confronted with the unavailability of older children. The intervention period coincides with field work. SMC is effective in reducing the prevalence and incidence of malaria and the parasite density in children. The financial cost of administering SMC is lower than that of treating a child suffering from malaria. Conclusion: After analysing the information, it was found that the majority of the African population supports the extension of the SMC to the number of cycles and the age group in order to alleviate the high mortality and morbidity rates among children due to malaria.

Calibration of an elastoplastic model of sand liquefaction using the swarm intelligence with a multi-objective function

According to post-seismic observations,spectacular examples of engineering failures can be ascribed to the occurrence of sand liquefaction,where a sandy soil stratum could undergo a transient loss of shear strength and even behave as a“liquid”.Therefore,correct simulation of liquefaction response has become a challenging issue in geotechnical engineering field.In advanced elastoplastic models of sand liquefaction,certain fitting parameters have a remarkable effect on the computed results.However,the identification of these parameters,based on the experimental data,is usually intractable and sometimes follows a subjective trial-and-error procedure.For this,this paper presented a novel calibration methodology based on an optimization algorithm(particle swarm optimization(PSO))for an advanced elastoplastic constitutive model.A multi-objective function was designed to adjust the global quality for both monotonic and cyclic triaxial simulations.To overcome computational problem probably appearing in simulation of the cyclic triaxial test,two interrupt mechanisms were designed to prevent the particles from wasting time in searching the unreasonable space of candidate solutions.The Dafalias model has been used as an example to demonstrate the main programme.With the calibrated parameters for the HN31 sand,the computed results were highly consistent with the laboratory experiments(including monotonic triaxial tests under different confining pressures and cyclic triaxial tests in two loading modes).Finally,an extension example is given for Ottawa sand F65,suggesting that the proposed platform is versatile and can be easily customized to meet different practical needs.

Investigation on the properties of compacted silty clay subjected to electro-osmosis using bender element

The moisture content of subgrade soil in seasonally frozen regions is often higher than its optimum value,leading to a decline in mechanical properties and a reduction in subgrade bearing capacity.Electro-osmosis has shown promise as a technology for controlling subgrade moisture,but significant heterogeneity has also been observed in treated soil.This study investigates the impact of electro-osmosis on soil stiffness through a series of bender element tests of compacted clay.The effects of dry density and supply voltage on the performance of electroosmosis treatment and the layered structure and anisotropy of the soil were analyzed.The results show that electro-osmosis treatment increased the shear wave velocity of the soil by 140% compared to untreated saturated soil and by 70% compared to soil with optimum water content.It has also been found that layered compaction of soil resulted in a layered structure,with electro-osmosis having a more prominent impact on soil near the cathode,resulting in a more pronounced layered structure.Besides,electro-osmosis was found to enhance soil anisotropy,particularly near the anode.Increasing the dry density and voltage levels can help improve soil uniformity.These findings provide insights into the potential use of electro-osmosis in improving soil stiffness,which could benefit various engineering applications.

选择离子流动管质谱对汽车尾气成分的分析

运用选择离子流动管质谱 (SIFT/MS)装置 ,以H3 O+ 、NO+ 、O+ 2 为初始离子对安装有催化转换装置的汽油车引擎启动 5min后的尾气进行了取样分析 ,结果表明 ,尾气中含有大量的 CH 化合物 (包括烷烃、烯烃、炔烃、二烯烃以及芳香烃 ) ,含氧有机物 (包括醛、酮、醇 )以及NH3 和NOx 等污染成分。其中 ,NO的含量最高 ,它的浓度比其它所有SIFT/MS装置所能测量到的各种物质的总和还多 ;在CH化合物中以芳香烃的含量最高 ,约占整个CH化合物含量的一半以上 ;在含氧有机物中以醛类物质的含量最高。初步讨论了这些成分的形成动力学过程 ,对引擎冷启动和热启动时的尾气成分进行了分析 ,结果表明 :冷启动尾气中CH化合物和NOx 的含量是热启动的 3～ 5倍 ,而含氧有机物的含量没有很大的变化 ,此结果也证明了尾气的催化转化装置是一种减少尾气中CH化合物和NOx 污染物的一种有效的控制方法。

循环荷载下非饱和结构性黄土的损伤模型

在边界面弹塑性模型基础上,借助胶结体损伤理论与非饱和土力学,提出一个可以描述循环荷载作用下非饱和黄土力学特性的弹塑性本构模型。在损伤模型中,定义胶结体弹性衰减规律,将结构损伤与应变增量的绝对累计值联系起来;并利用土的持水曲线建立常含水量下吸力与土体应力之间的耦合作用关系。通过与循环三轴试验结果的比较,表明该模型能够较好地模拟非饱和黄土在循环荷载作用下的力学特性。

循环荷载下非饱和结构性土的边界面模型

基于结构体损伤概念和非饱和土力学,利用边界面塑性理论,提出了一个可以描述循环荷载作用下非饱和土力学特性的弹塑性本构模型。在BBM(Barcelona Basic Model)模型的基础上,利用土的持水曲线建立了常含水率下吸力与土体应力之间的耦合作用关系;通过屈服面的大小的改变来反映土体结构性的变化,建立了与累积塑性应变相关的损伤规律。同时,修正了常用边界面理论中映射准则,引入可移动映射中心的概念,将加载、卸载过程的映射准则进行统一,以反映循环荷载下土体产生的滞回特性。通过与相关文献以及本文的循环三轴试验结果的比较,表明本文模型能够较好地模拟非饱和黄土在循环荷载作用下的力学特性。

非饱和土热力学参数确定的探讨

研究非饱和土热力学的力学性质,必须建立能量守恒方程,表征能量的两个基本物理力学参数(体积比热系数和热传导系数)的确定是求解能量守恒方程的重要因素。对于不同颗粒组成的土体,对其干燥颗粒有效热力学参数进行了分析,对固体、液体和气体三相共存的热力学参数进行了研究,并对计算结果进行了对比分析,在此基础上,提出了较适合计算热传导系数的方法,并将此方法和体积平均法、自洽法及Hashin-Strikman方法进行了比较。经与试验结果对比表明:提出的方法能较好地描述非饱和土的热力学参数特性。

增湿情况重塑黄土非饱和渗透系数的测定方法研究

对浸润锋前进法、Boltzmann变换法和瞬态剖面法3种直接方法在确定增湿情况下重塑黄土非饱和渗透系数的适宜性进行了研究,并对其进行了改进。首先应用重塑黄土进行了一维水平入渗试验,对前2种方法进行了改进,检验了改进后的效果,比较了这2种改进方法、瞬态剖面法和间接法所得非饱和渗透系数的差异,然后应用Hydrus软件对一维入渗试验进行了数值模拟,获得了采用不同方法所得非饱和渗透参数时预测浸润锋迁移距离和时间关系的准确性,分析了前2种方法所采用假定的合理性并对瞬态剖面法测点布置进行了改进和效果检验。室内试验结果表明浸润锋前进法采用改进的水力梯度计算公式后,不同吸力下渗透系数波动的现象减少;Boltzmann变换法采用新的变量λ*后,各测点λ*-θ关系的统一性增加;由于测点间距较大,瞬态剖面法偏离其他方法所得渗透系数很大。数值模拟结果表明采用2种改进方法所得的非饱和渗透参数均能较好地预测浸润锋迁移距离和时间的关系;浸润锋前进法采用的水分剖面平行移动假定以及Boltzmann变换方法采用的Boltzmann变量与体积含水率关系唯一假定,均需要在入渗一定距离后才能得到基本满足;采用改进后的测点布置位置和间距后,瞬态剖面法所得不同吸力下的非饱和渗透系数与前2种改进方法所得的差距减少,但仍不如前2种改进方法更接近于输入值。

Bone metastases:When and how lung cancer interacts with bone

Bone metastasis is a common and debilitating consequence of lung cancer:30%-40% of patients with nonsmall cell lung cancer develop bone metastases during the course of their disease. Lung cancer cells find a favorable soil in the bone microenvironment due to factors released by the bone matrix, the immune system cells, and the same cancer cells. Many aspects of the cross-talk among lung tumor cells, the immune system,and bone cells are not clear, but this review aims to summarize the recent findings in this field, with particular attention to studies conducted to identify biomarkers for early detection of lung cancer bone metastases.

On the chemo-thermo-hydro-mechanical behaviour of geological and engineered barriers

An overview of the recent findings about the chemo-hydro-mechanical behaviour of materials used for both geological and engineered barriers in nuclear waste disposal is presented, through some examples about the natural Boom Clay （BC） and compacted bentonite-based materials. For the natural BC, it was found that compression index identified from both oedometer and isotropic compression tests is sim- ilar and the compressibility of BC from the Mol site is higher than that of BC from the Essen site： the shear strength of Mol BC is also higher than that of the Essen BC, suggesting a significant effect of carbo- nates content; the thermal volume change is strongly overconsolidation ratio （OCR） dependent-low OCR values promote thermal contraction while high OCR values favour thermal dilation; the volume change behaviour is also strongly time dependent and this time dependent behaviour is governed by the stress level and temperature; the effect of pore-water salinity on the volume change behaviour can be signif- icant when the smectite content is relatively high. For the bentonite-based materials, it was found that thermal contraction also occurs at low OCR values, but this is suction dependent--suction promotes ther- mal dilation. Under constant volume conditions, wetting results in a decrease of hydraulic conductivity, followed by an increase. This is found to be related to changes in macro-pores size-wetting induces a decrease of macro-pores size, followed by an increase due to the aggregates fissuring. The presence of technological voids can increase the hydraulic conductivity but does not influence the swelling pressure.

Clays in radioactive waste disposal

Clays and argillites are considered in some countries as possible host rocks for nuclear waste disposal at great depth.The use of compacted swelling clays as engineered barriers is also considered within the framework of the multi-barrier concept.In relation to these concepts,various research programs have been conducted to assess the thermo-hydro-mechanical properties of radioactive waste disposal at great depth.After introducing the concepts of waste isolation developed in Belgium,France and Switzerland,the paper describes the retention and transfer properties of engineered barriers made up of compacted swelling clays in relation to microstructure features.Some features of the thermo-mechanical behaviors of three possible geological barriers,namely Boom clay（Belgium）,Callovo-Oxfordian clay（France） and Opalinus clay（Switzerland）,are then described,including the retention and transfer properties,volume change behavior,shear strength and thermal aspects.

Gastric cancer:The times they are a-changin'

Gastric cancer is the third leading cause of cancer death worldwide.Even though during these last decades gastric cancer incidence decreased in Western countries,it remains endemic and with a high incidence in Eastern countries.The survival in advanced and metastatic stage of gastric cancer is still very poor.Recently the Cancer Genoma Atlas Research Network identified four subtypes with different molecular profiles to classify gastric cancer in order to offer the optimal targeted therapies for pre-selected patients.Indeed,the key point is still the selection of patients for the right treatment,on basis of molecular tumor characterization.Since chemotherapy reached a plateau of efficacy for gastric cancer,the combination between cytotoxic therapy and biological agents gets a better prognosis and decreases chemotherapeutic toxicity.Currently,Trastuzumab in combination with platinum and fluorouracil is the only approved targeted therapy in the first line for c-erb B2 positive patients,whereas Ramucirumab is the only approved targeted agent for patients with metastatic gastric cancer.New perspectives for an effective treatment derived from the immunotherapeutic strategies.Here,we report an overview on gastric cancer treatments,with particular attention to recent advances in targeted therapies and in immunotherapeutic approach.

On the hydro-mechanical behaviour of MX80 bentonite-based materials

Bentonite-based materials have been considered in many countries as engineered barrier/backfilling materials in deep geological disposal of high-level radioactive waste.During the long period of waste storage,these materials will play an essential role in ensuring the integrity of the storage system that consists of the waste canisters,the engineered barrier/backfill,the retaining structures as well as the geological barrier.Thus,it is essential to well understand the hydro-mechanical behaviours of these bentonite-based materials.This review paper presents the recent advances of knowledge on MX80 bentonite-based materials,in terms of water retention properties,hydraulic behaviour and mechanical behaviour.Emphasis is put on the effect of technological voids and the role of the dry density of bentonite.The swelling anisotropy is also discussed based on the results from swelling tests with measurements of both axial and radial swelling pressures on a sand-bentonite mixture compacted at different densities.Microstructure observation was used to help the interpretation of macroscopic hydromechanical behaviour.Also,the evolution of soil microstructure thus the soil density over time is discussed based on the results from mock-up tests.This evolution is essential for understanding the longterm hydro-mechanical behaviour of the engineered barrier/backfill.

Experimental study on hydro-mechanical coupling behaviours of highly compacted expansive clay

Highly compacted expansive clays have been usually considered as a possible material for sealing and backfill in deep geological disposal of radioactive waste. In this condition, the material is simultaneously subjected to water infiltration from the geological barrier and stresses generated by the swelling of engineered barriers in confined conditions. Its behaviour under hydro-mechanical loading is essential to the safe design of the whole storage system. In the present work, MX80 bentonite, a kind of expansive clay from Wyoming, USA, was studied. After compaction, its dry density was 1.8 Mg/m^3 and its initial suction was 110 MPa. Firstly, the soil was humidified under controlled suction and free-swelling conditions. Significant swelling was observed. Secondly, four values of suction of 110, 39, 9 and 0 MPa were employed to perform isotropic compressive tests at constant suction conditions. That allowed studying the effect of suction on the yield pressure, elastic and plastic compressibility parameters. The results show that the elastic and plastic compressibility parameters increase when the suction decreases. The relationship between these parameters and the logarithm of suction can be linearly correlated. The yield stress drastically decreases upon wetting under free-swelling conditions, from 12 - 18 MPa （at an initial suction of 110 MPa） to 0.2 MPa at saturated state.

Metabolomics profile in gastrointestinal cancers:Update and future perspectives

Despite recent progress in diagnosis and therapy,gastrointestinal(GI)cancers remain one of the most important causes of death with a poor prognosis due to late diagnosis.Serum tumor markers and detection of occult blood in the stool are the current tests used in the clinic of GI cancers;however,these tests are not useful as diagnostic screening since they have low specificity and low sensitivity.Considering that one of the hallmarks of cancer is dysregulated metabolism and metabolomics is an optimal approach to illustrate the metabolic mechanisms that belong to living systems,is now clear that this-omics could open a new way to study cancer.In the last years,nuclear magnetic resonance(NMR)metabolomics has demonstrated to be an optimal approach for diseases’diagnosis nevertheless a few studies focus on the NMR capability to find new biomarkers for early diagnosis of GI cancers.For these reasons in this review,we will give an update on the status of NMR metabolomic studies for the diagnosis and development of GI cancers using biological fluids.

Effects of mineralogy on thermo-hydro-mechanical parameters of MX80 bentonite

Thermal conductivity, water retention curve and swelling behavior of two MX80 bentonite samples were studied in the present work. The difference obtained from these two MX80 bentonite samples was then analyzed in terms of mineralogical effects （effects of the proportion of quartz and montmorillonite）. It was concluded that the mineralogical effect was significant on the thermal conductivity and the swelling capacity; on the contrary, it was negligible on the water retention property.

Metallogeny of the Lannigou Sedimentary Rock-hosted Disseminated Gold Deposit in Southwestern Guizhou Province,China

The Lannigou deposit is a large-sized sedimentary rock-hosted disseminated gold （SRHDG） deposit located in the Youjiang Basin. It is hosted by the Middle Triassic turbidite. Wall rock alterations, including silicification, pyritization, arsenopyritization, carbonatization and argillization, commonly occur along fractures. PGE study demonstrates that either Permian basalts or Triassic ultrabasic intrnsives are unlikely to be the main source of gold mineralization. Coupled with the lack of other nmgmatic activity in the vicinity of the mining area, an amagmatic origin is proposed. Organic matter compositions and GC-MS analysis of the ores and host rocks show that the organics in the ores and the host rocks have a common source; the organic matter in the ores was mainly indigenous. The positive correlation between S2 and Au contents, along with the common occurrence of organic inclusions, suggest involvement of organic matter in the ore-forming process in terms of promoting Au leaching from the source rocks, making colloidal Au migration possible, as well as hydrocarbon reduction of sulphate. Geological and geochemical characteristics of the Lannigou deposit suggest that it was formed through circulation of meteoric water and probably less importantly organic bearing formation water driven by high geothermal gradient caused by late Yanshanian extension, which leached Au from the source bed, and then migrated as Au-bisnlfides and colloidal Au, culminating in deposition by reduction-adsorption and surface complexation of gold onto the growth surface of arsenlan pyrite.

First-Principles Study of Orthorhombic Perovskites MgSiO3 up to 120 GPa and Its Geophysical Implications

High-pressure behaviour of orthorhombic MgSiO3 perovskite crystal is simulated by using the density functional theory and plane-wave pseudopotentials approach up to 120 GPa pressure at zero temperature. The lattice constants and mass density of the MgSiO3 crystal as functions of pressure are computed, and the corresponding bulk modulus and bulk velocity are evaluated. Our theoretical results agree well with the high-pressure experimental data. A thermodynamic method is introduced to correct the temperature effect on the O-K first-principles results of bulk wave velocity, bulk modulus and mass density in lower mantle PIT range. Taking into account the temperature corrections, the corrected mass density, bulk modulus and bulk wave velocity of MgSiO3-perovskite are estimated from the first-principles results to be 2%, 4%, and 1% lower than the preliminary reference Earth model （PREM） profile, respectively, supporting the possibility of a pure perovskite lower mantle model.

Effect of water chemistry on the hydro-mechanical behaviour of compacted mixtures of claystone and Na/Ca-bentonites for deep geological repositories

In the French deep geological disposal for radioactive wastes,compacted bentonite/claystone mixtures have been considered as possible sealing materials.After emplacement in place,such mixtures are hydrated by the site solution as well as the cement solution produced by the degradation of concrete.In this study,the effects of synthetic site solution and cement solution on the hydro-mechanical behaviour of compacted mixtures of claystone and two types of bentonites(MX80 Na-bentonite and Sardinia Cabentonite)were investigated by carrying out a series of swelling pressure,hydraulic conductivity and mercury intrusion porosimetry(MIP)tests.It was found that for the MX80 bentonite/claystone mixture hydrated with synthetic site solution,the swelling capacity was reduced compared to the case with deionised water owing to the transformation of Na-montmorillonite to multi-cation dominant montmorillonite by cation exchanges.For the Sardinia bentonite/claystone mixture,the similar increasing rate of swelling pressure was observed during the crystalline swelling process for different solutions,suggesting insignificant cation exchanges.Additionally,the cations in the synthetic site solution could reduce the thickness of diffuse double layer and the osmotic swelling for both MX80 bentonite/claystone and Sardinia bentonite/claystone mixtures.The large-pore volume increased consequently and enhanced water flow.In the cement solution,the hydroxide could also dissolve the montmorillonite,reducing the swelling pressure,and increase the large-pore volume,facilitating the water flow.Furthermore,the decrease of swelling pressure and the increase of hydraulic conductivity were more significant in the case of low dry density because of more intensive interaction between montmorillonite and hydroxide due to the high permeability.