Monitoring of terrestrial input by massive corals

Human-induced pollution in coastal areas can significantly increase the concentration of some trace elements in the marine environment. In the tropics, scleractinian corals incorporate these trace elements in their living parts and skeleton. The potential of corals to monitor pollution through time is reviewed in this contribution. The strength and weakness of corals as pollution indicators are discussed, and a few examples are shown. Although some progress should be made in the understanding of the processes ruling the incorporation of trace elements in coralline aragonite, it is concluded that large environmental changes are well recorded by coral skeletons.     

利用微量元素分析对广西凌云生物礁成礁环境的研究

本文利用微量元素分析,探讨了广西凌云县二叠系生物礁的成礁环境,指出不同微最元素的分布与生物骨骸的固定作用和沉积环境的影响有关,利用R型因子分析对微量元系进行了分类。     

A three‐phase soil model for simulating stress wave propagation due to blast loading

A three‐phase soil model is proposed to simulate stress wave propagation in soil mass to blast loading. The soil is modelled as a three‐phase mass that includes the solid particles, water and air. It is considered as a structure that the solid particles form a skeleton and their voids are filled with water and air. The equation of state (EOS) of the soil is derived. The elastic–plastic theory is adopted to model the constitutive relation of the soil skeleton. The damage of the soil skeleton is also modelled. The Drucker–Prager strength model including the strain rate effect is used to describe the strength of the soil skeleton. The model is implemented into a hydrocode Autodyn. The recorded results obtained by explosion tests in soil are used to validate the proposed model. Copyright © 2004 John Wiley & Sons, Ltd.     

Minor and trace element incorporation into branching coral Acropora nobilis skeleton

Chemical and isotopic compositions of the Acropora nobilis skeleton were analyzed at various spatial resolutions to investigate the mechanism by which elements are incorporated into the skeleton. Chemical and isotopic profiles along growth axes of axial and radial corallites did not show seasonal variation, with the exception of the δ¹⁸O profile of the axial corallite. Detailed observations of the skeletal structure revealed that the skeletal density increased with distance from the tip because secondarily precipitated aragonite (here called the “infilling” skeleton) filled pore spaces in the “framework” skeleton. Microscale element analyses revealed that main part of the infilling skeleton had lower Mg/Ca and higher Sr/Ca and U/Ca than the framework skeleton. At microscale, Sr/Ca and U/Ca were positively correlated with each other, and negatively correlated with Mg/Ca but only weakly. The results showed that the infilling skeleton differed significantly from the adjacent framework skeleton in terms of not only formation chronology but also chemical composition, and that the bulk composition was influenced by the infilling/framework skeletal ratio. In order to use the Acropora skeleton as a paleoclimate archive, the relationship between environmental factors and the chemical composition of each skeletal component needs to be established.     

有机骨架材料充填地下溶洞的支护性能及稳定性分析

基于有机骨架材料的吸附作用,分析有机物质降低岩石矿物电解质的电导性质的作用机理,通过渗透试验、抗疲劳试验等验证了有机骨架材料良好的透水性能、抗疲劳性能、抗冲击性能及胶结泥化性能,在静载条件下对实际溶洞进行充填应用,验证了充填效果及材料性能,并建立仿真模型研究了下沉位移的变化规律。结果表明:有机复合材料能够使矿物元素活度系数变小,介电常数降低,与矿物颗粒结合后会形成稳定的晶格结构;有机骨架材料作为治理溶洞的充填材料,其结构性、耐久性都优于传统的充填材料,可满足岩溶地面塌陷治理工程中强度、稳定性与渗透性的材料要求,有效的提高了基础的抗沉降能力;实际充填施工过程中的数值分析与现场监测的位移变化规律与沉降趋势都具有较好的一致性,表明数值模拟的计算参数选取合理,得出的仿真变形规律可应用于指导工程施工。      

Pneumatization of an immature azhdarchoid pterosaur

The partial skeleton of an immature azhdarchoid pterosaur from the Santana Formation (Early Cretaceous) of NE Brazil is described, where breaks across several of the three dimensionally preserved postcranial elements have permitted the thickness of the cortex to be accurately measured. Air-space proportions (ASP) are shown to be comparable to those observed in sauropod dinosaurs. The pterosaurian pneumatic system, prevalent throughout these animals, is shown to be well developed in even non-adult animals and is inferred to have penetrated into even the smallest of bones.     

A New Non‐Pterodactyloid Pterosaur from Qinglong County,Hebei Province of China

A new basal non-pterodactyloid pterosaur, Changchengopterus pani gen. et sp. nov., is erected, on the basis of a nearly complete postcranial skeleton. The new taxon is distinguished by relatively short extensions of the prezygapophyses, postzygapophyses and haemal arches of the caudal vertebrae; a humerus that has a subtriangular deltopectoral crest; limb elements that decrease in length in the following order: ulna> wing-phalange 2 > wing-phalange 3 = wing-phalange 1>humerus >tibia>femur>wing-metacarpal. Phylogenetic analysis suggests that Changchengopterus is a basal member of rhamphorhynchoids, and more closely related to Dorygnathus than to other rhamphorhychoids. The geological age of the Changchengopterus -bearing sediments is no latter than the end of the Late Jurassic and it is possible Middle Jurassic.     

A discretized analytical solution for fully coupled non‐linear simulation of heat and mass transfer in poroelastic unsaturated media

Mathematical simulation of non‐isothermal multiphase flow in deformable unsaturated porous media is a complicated issue because of the need to employ multiple partial differential equations, the need to take into account mass and energy transfer between phases and because of the non‐linear nature of the governing partial differential equations. In this paper, an analytical solution for analyzing a fully coupled problem is presented for the one‐dimensional case where the coefficients of the system of equations are assumed to be constant for the entire domain. A major issue is the non‐linearity of the governing equations, which is not considered in the analytical solution. In order to introduce the non‐linearity of the equations, an iterative discretized procedure is used. The domain of the problem is divided into identical time–space elements that cover the time–space domain. A separate system of equations is defined for each element in the local coordinate system, the initial and boundary conditions for each element are obtained from the adjacent elements and the coefficients of the system of equations are considered to be constant in each step. There are seven governing differential equations that should be solved simultaneously: the equilibrium of the solid skeleton, mass conservation of fluids (water, water vapor and gas) and energy conservation of phases (solid, liquid and gas). The water vapor is not in equilibrium with water and different phases do not have the same temperature. The governing equations that have been solved seem to be the most comprehensive in this field. Three examples are presented for analyzing heat and mass transfer in a semi‐infinite column of unsaturated soil. Copyright © 2009 John Wiley & Sons, Ltd.     

大骨节病低氟说的诠释

提出环境低氟是大骨节病原始病因,探索氟元素如何滋养和损伤骨骼系统,寻求有效防治措施。指出地质环境和饮水低氟促成大骨节病发生;在无其他氟源情况下,饮水氟质量浓度小于0.2 m g/L患轻度大骨节病,小于0.1 m g/L患重度大骨节病。人体发生以低氟为中心代谢紊乱,骨基质和骨盐合成不足,阻碍骨生长发育;提出防治大骨节病向人体补氟的具体方法。(6000)     

泸定大渡河桥冰碛土的结构及现场剪切试验研究

泸定大渡河桥康定岸分布巨厚层冰碛土,为研究土的抗剪强度特性,在不同位置和深度进行了6组现场剪切试验,基于地质勘察和试验结果分析土的结构特征、剪切强度和变形特性及其与土的结构的关系。研究表明:冰碛土的颗粒以粗粒、巨粒粒组为主,骨架颗粒呈悬浮状,混杂、无序堆积,骨架间充填杂基,形成骨架悬浮密实结构。根据颗粒组成和骨架风化程度,划分为骨架悬浮密实结构、软化骨架悬浮密实结构、砂砾土富集结构、大块石包绕结构等4种细观结构类型。冰碛土剪切破坏主要有剪切破碎带、包绕块石边界、锯齿状剪切和切穿软化骨架等4种模式,剪切荷载作用下线弹性变形阶段明显,剪切刚度大,初始屈服历时短。颗粒骨架和杂基形成的悬浮密实结构,是冰碛土强度与变形特性的内在控制因素,剪切荷载作用下骨架颗粒与具有一定胶结的基质间相互作用,剪切破坏时表现为基质的压碎与骨架的变位。骨架颗粒强度、大骨架颗粒分布、基质胶结程度的不同,对冰碛土强度和变形特性都构成一定的影响。土的抗剪强度、剪切刚度和剪胀性随骨架强度和基质胶结程度的提高而增大,而延性随之变差。     

Hybrid time integration and coupled solution methods for nonlinear finite element analysis of partially saturated deformable porous media at small strain

The goal of the paper is to determine the most efficient, yet accurate and stable, finite element nonlinear solution method for analysis of partially saturated deformable porous media at small strain. This involves a comparison between fully implicit, semi‐implicit, and explicit time integration schemes, with monolithically coupled and staggered‐coupled nonlinear solution methods and the hybrid combination thereof. The pore air pressure p_a is assumed atmospheric, that is, p_a=0 at reference pressure. The solid skeleton is assumed to be pressure‐sensitive nonlinear isotropic elastic. Coupled partially saturated ‘consolidation’ in the presence of surface infiltration and traction is simulated for a simple one‐dimensional uniaxial strain example and a more complicated plane strain slope example with gravity loading. Three mixed plane strain quadrilateral elements are considered: (i) Q4P4; (ii) stabilized Q4P4S; and (iii) Q9P4; “Q” refers to the number of solid skeleton displacement nodes, and “P” refers to the number of pore fluid pressure nodes. The verification of the implementation against an analytical solution for partially saturated pore water flow (no solid skeleton deformation) and comparison between the three time integration schemes (fully implicit, semi‐implicit, and explicit) are presented. It is observed that one of the staggered‐coupled semi‐implicit schemes (SIS(b)), combined with the fully implicit monolithically coupled scheme to resolve sharp transients, is the most efficient computationally. Copyright © 2015 John Wiley & Sons, Ltd.     

Suitability of monosaccharides as markers for particle identification in carbonate sediments*†

The identification of the remains of organisms contributing to carbonate sediments by means of scanning electron-microscopy is limited to particles of the 2–20 μm size class. Mineralogy and the content of Mg, Sr and trace elements alone are usually insufficient to solve the problem of identification, especially in the differentiation between algal and coral aragonite. The organic matrix of calcareous organisms consists of stable biopolymers such as polysaccharides and glycoproteins which are intimately associated with the carbonate skeleton. Analysis of these hydrolysed compounds gives rise to characteristic arrays of monosaccharides which provide independent criteria for producer identification. The calcareous green algae Halimeda, Penicillus and Udotea show high xylose and low fucose levels. Xylose and fucose levels are elevated in the red algae Amphiroa but only fucose is prominent in the brown algae Padina. The corals Oculina, Porites, Millipora and Montastrea are relatively rich in fucose and show little or no xylose. In the bivalves Arca, Codakia and in Argopecten mannose may be characteristic. Analysis of artificial and natural sediments demonstrates that coral and algal aragonite can be distinguished on the basis of the total sugar concentration and respective xylose and fucose levels. The applicability of the technique in comparison to geochemical and mineralogical methods has been demonstrated for surface sediments from varying water depths of Harrington Sound, Bermuda.     

Hydro‐mechanical modeling of cohesive crack propagation in multiphase porous media using the extended finite element method

In this paper, a numerical model is developed for the fully coupled hydro‐mechanical analysis of deformable, progressively fracturing porous media interacting with the flow of two immiscible, compressible wetting and non‐wetting pore fluids, in which the coupling between various processes is taken into account. The governing equations involving the coupled solid skeleton deformation and two‐phase fluid flow in partially saturated porous media including cohesive cracks are derived within the framework of the generalized Biot theory. The fluid flow within the crack is simulated using the Darcy law in which the permeability variation with porosity because of the cracking of the solid skeleton is accounted. The cohesive crack model is integrated into the numerical modeling by means of which the nonlinear fracture processes occurring along the fracture process zone are simulated. The solid phase displacement, the wetting phase pressure and the capillary pressure are taken as the primary variables of the three‐phase formulation. The other variables are incorporated into the model via the experimentally determined functions, which specify the relationship between the hydraulic properties of the fracturing porous medium, that is saturation, permeability and capillary pressure. The spatial discretization is implemented by employing the extended finite element method, and the time domain discretization is performed using the generalized Newmark scheme to derive the final system of fully coupled nonlinear equations of the hydro‐mechanical problem. It is illustrated that by allowing for the interaction between various processes, that is the solid skeleton deformation, the wetting and the non‐wetting pore fluid flow and the cohesive crack propagation, the effect of the presence of the geomechanical discontinuity can be completely captured. Copyright © 2012 John Wiley & Sons, Ltd.     

Interaction between different internal length scales in strain localization analysis of fully and partially saturated porous media—the 1‐D case

The paper analyses the interaction between two internal length scales during dynamic strain localization in multiphase porous materials. The first internal length is introduced in the mathematical model by the gradient‐dependent plasticity for the solid skeleton, while the second one is naturally contained in the multiphase model and is due to the seepage process of the water via Darcy's law, which induces a rate‐dependent behaviour of the solid skeleton. Numerical results of a one‐dimensional example of water saturated porous medium demonstrate the competing effect between these two length scales. The porous medium is here treated as a multiphase continuum, with the pores filled by water and air, the last one at constant atmospheric pressure. Copyright © 2005 John Wiley & Sons, Ltd.     

High‐resolution synchrotron X‐ray fluorescence investigation of calcite coralloid speleothems: Elemental incorporation and their potential as environmental archives

Synchrotron high‐resolution and micro‐X‐ray fluorescence elemental mapping of two coeval coralloid speleothems from Lamalunga Cave (Italy) are complemented with petrographic, morphological and microstratigraphic studies. The importance of these speleothems relies on their direct and indirect association with a complete Neanderthal skeleton (‘Altamura Man’) found inside the cave. The coralloids grew discontinuously between 64·6 ka and the Holocene and reveal exceptionally high concentrations of Mg, Sr and Si, particularly on convex surfaces, where evaporation is more intense. The incorporation of trace elements depends on several factors including location, shape and geometrical evolution during their growth, as well as climate and environmental parameters. This resulted in calcite precipitation with Sr compositions from 100 to 1200 ppm and an average concentration of 7000 ppm Mg. An unusually high Si content (up to 16%) is possibly derived from volcanic ash transported as particulate and in solution inside the cave. The most common fabrics observed consist of non‐fluorescent elongated columnar calcite forming clean isopachous bands and fluorescent fibre‐like crystals associated with laminated, lenticular bands high in Sr, Mg and Si. Variability in Sr, Mg and Si concentrations appears to induce fabric changes in the coralloids. Elongation and lattice distortion of the crystals was found to coincide with high Mg concentrations. The transition from compact elongated to open to fibre‐like, is here interpreted as due to high concentrations of Si and Sr, which are preferentially incorporated in the speleothem at crystal boundaries and intra‐laminae. It is here inferred that coralloid fabric changes and their elemental content potentially record local rainfall variations through time, with the clean compact calcite marking high infiltration and open fibre‐like and micrite fabrics recording dry periods.     

颗粒体系中的骨架及力链网络

颗粒物质是大量离散的固体颗粒相互作用而组成的复杂体系,具有非连续和接触耗散等基本特征,其物理机制研究是近20年科学前沿之一。砂土就是典型的颗粒物质,土体中的有效应力是作用在土体骨架上的平均应力,土体变形主要来源于骨架上的颗粒位置,但对土体骨架并没有一个清晰的物理描述。近期颗粒物质力学研究认为,体系中颗粒相互接触形成的网络结构是外荷载传递路径的物理基础,可能就是土力学所指的骨架。同时还发现,较大的力通常沿着准直线的路径传递,人们常把传递较大力、与该准直线路径对应的若干颗粒组成的链状结构,称为强力链;弱力链则传递较小力。力链结构及其演变规律的描述是颗粒物质研究的核心之一。以单轴侧限压缩数值模拟为例,对比说明了土体颗粒骨架与力链结构的关系,明确提出强力链网络决定颗粒体系的宏观力学行为。     

A FORMULATION OF FULLY COUPLED THERMAL–HYDRAULIC–MECHANICAL BEHAVIOUR OF SATURATED POROUS MEDIA—NUMERICAL APPROACH

The theoretical aspects of fully coupled thermohydromechanical behaviour of saturated porous media are presented. The non-linear behaviour of soil skeleton is assumed. A new concept called ‘thermal void ratio state surface’ is introduced to include thermal effects, and the stress state level influence on volume changes. The fluid phase flows according to Darcy's law and energy transport is assumed to follow Fourier's law classically. Variation of water permeability, water and solid unit weight due to thermal effects and pore pressure changes are included. A finite element package is developed based on final matrix form obtained from discretization of integral form of field equations by finite element method and integration in time. A very good agreement between the theoretical predictions and the experimental results was obtained for the several simple problems proposed by other authors. © 1997 by John Wiley & Sons, Ltd.     

四射珊瑚AuloPhyllum fungites骨骼微细构造的电镜研究

本文对Aulophyllum fungires （Fleming）,1828的骨骼微细构造进行了扫描电镜研究.结果表明,其骨骼纵列构造和横列构造全由纤状骨骼方解石晶针构成.晶针大小可分两级:大者在隔壁和横板中,大小近相等,其平均长度为32μm,平均直径为4μm;小者在鳞板,内斜板和柱隔壁中,其平均长度为10μm,平均直径2μm.晶针只在隔壁中沿轴部组成一排晶（?）,其平均直径为30—60μm,晶（?）两侧晶针组成晶束几近垂直,并间歇生长.在纵切面上,横板与隔壁相接处,间歇生长线是连续的,说明两者同步增长和形成过程相同.