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Estimating hydraulic properties of carbonate is challenging due to its wider range of porosity and complex pore structures. To investigate the hydraulic properties of carbonate rocks, a novel approach inspired by quantum genetic optimization in this work is proposed to extract the optimal pore network model (PNM), which is applied to simulate the hydraulic properties. The pore network variables, such as porosity, pore and throat sizes, are considered as the optimal parameters, and the capillary pressure curve, breakthrough drainage pressure and permeability are calculated based on the constructed PNM. The computing time (CPU time) and memory usage (RAM usage) for the PNM extraction using the proposed approach and classical methods are compared. Results indicate that the proposed approach shows better computing efficiency than classical methods. Excellent agreements are found between the experimental and simulation results from the proposed and classical methods. The proposed approach provides promising tools to investigate the hydraulic properties of geomaterials. [ABSTRACT FROM AUTHOR]

In this paper, a nonlocal energy-informed neural network is proposed to deal with elastic solids containing discontinuities by considering the long-range interactions of material points. First, the solution to peridynamic equilibrium equation is converted to an variational energy minimization problem based on principle of virtual work, which automatically satisfies the zero-traction boundary conditions and avoids the introduction of artificial damping. Furthermore, the energetic representation of behavior of physical system can be tractable as the loss function for deep learning neural network. This allows to approximate the solution of the system by the active machine learning community. As the basic technique in deep learning, automatic differentiation is capable to evaluate derivatives for smooth functions, but it is prone to singularity due to the presence of discontinuities. To address this limitation, spatial integration is employed in the proposed neural network to evaluate the strain energy of the system rather than the spatial derivatives of displacement fields calculated by automatic differentiation. Moreover, the initial cracks can be directly introduced in the constitutive model without the explicit definition of crack surfaces. The accuracy and efficiency of the proposed neural network is validated by conducting several mechanical problems with or without discontinuities. More importantly, the proposed neural network is capable to capture the jump discontinuities at the crack surfaces, where the neural network with automatic differentiation is hard to address. Additionally, the convergence of the proposed neural network and the comparison of two widely used activation functions are investigated. [ABSTRACT FROM AUTHOR]

Understanding the dynamic failure mechanism of rocks subjected to chemical corrosion is very important. However, the previous works mainly focused on static damage rather than dynamic pulverization with chemical corrosion. In this study, Split Hopkinson Pressure Bar (SHPB) impact tests are performed to study the dynamic mechanical properties and energy evolution of granite after chemical corrosion. The XRD and SEM analyses are employed to reveal the chemical reaction processes and corrosion mechanisms. Moreover, the fractal dimension is applied to determine the failure pattern of granite. The experimental results show that the acidic environment causes muscovite, albite, and microcline to generate SiO2 (quartz), and the newly generated SiO2 has a weak pressure-bearing capacity. As corrosion progressed, micro-particles accumulate on the surface and cause stress concentrations, which implies a decrease in dynamic properties. Chemical corrosion causes internal microcracks to propagate, and more energy is absorbed when they coalesce under the dynamic impact. The chemical solution enters the inside of specimens through the surface cracks for further reaction, which causes the failure pattern to change from splitting failure to crushing failure. The findings can fill in the gap in the chemical corrosion mechanism of granite subjected to dynamic impact. Highlights: Split Hopkinson Pressure Bar tests are performed to study the dynamic mechanical properties of granite after chemical corrosion. The XRD and SEM analyses are employed to reveal the chemical reaction processes and corrosion mechanisms. The acidic environment causes muscovite, albite, and microcline to generate SiO2, and the generated SiO2 has a weak load-bearing capacity. Chemical corrosion causes microcracks to propagate, and more energy is absorbed when they coalesce under the dynamic impact. [ABSTRACT FROM AUTHOR]

The design and synthesis of artificial molecular containers for the encapsulation of hydrocarbon gases to study their host-guest chemistry are highly important for potential application in gas storage, separation, and understanding of their biological functions. In this work, we report the subcomponent self-assembly of four cubic Zn8L12Br4 (HL = N-(4-R)-1-(5-methyl-1H-imidazole-4-yl)methanimine) cages with good solubility in chloroform, which are capable of binding hydrocarbon gases including methane, ethane, and ethene in solution at ambient temperature. Two types of gas binding sites (one is in the cavity, and the other is at the window) are discovered in these cages, which are documented by nuclear magnetic resonance (NMR) spectra and density functional theory (DFT) calculations. Their performance of encapsulation of hydrocarbon gases can be tuned by carefully adjusting substituent groups. These metal-organic cages containing two types of binding sites provide new artificial models to mimic the structures and functions of biological systems in binding and transforming hydrocarbon gases. [ABSTRACT FROM AUTHOR]

Layered composite rocks (LCRs) are often encountered in underground excavation in which extensive deformation, buckling and local collapse near the layer interface frequently occur. However, there is limited advance knowledge of the failure mechanisms of LCRs to interpret the field observations due to the relative scarcity of polyaxial compression testing. To that end, this study conducts the true-triaxial experiments with the acoustic emission (AE) monitoring on the LCR specimens, with the emphases being on the effects of mechanical contrast (MC) between the layers on the fracture behaviors under true-triaxial stresses. First, the strength of LCRs is controlled by the weaker layer. Second, at the unstable fracturing phase, high AE event rate is faithfully recorded but intermittently interrupted by macrofracturing in granite but not in sandstone. Third, main failure planes of LCRs appear sub-orthogonally to σ3 (minimum principal stress), taken the form of delamination fracture and exhibited the mode of σ3-transverse-symmetric fracturing. As the distance from the unloaded surface increases, the fracturing transitions from σ3-transverse-symmetric spalling to σ3-transverse-symmetric shearing. Depending on the MC, both the fracture propagation through the interface and the fracture containment within sandstone are registered. Moreover, the interface effect is numerically revealed through a 3D finite-element modeling. This study gets insights into the failure mechanisms of LCRs with a changing mechanical property in individual layers under true-triaxial stresses. Highlights: True-triaxial experiment investigations of layered composite rocks in a brittle-brittle sequence. Quantitative interpretations of acousto-mechanical properties and fracturing behaviors in layered composite rocks. The fracture propagation through the interface is registered, as well as the fracture containment within the sandstone. The delamination fracture along σ3-unloading direction dominates the feature of σ3-transverse-symmetric fracturing. The interface effect is revealed by a 3D finite-element modelling. [ABSTRACT FROM AUTHOR]

This paper aims at studying spatial variations and voxel scale effects on digital-permeability of sandstone reservoirs at small-scale. X-ray μ-CT imaging is applied to capture various pore-structures. Digital pore-scale analysis is employed to quantitatively analyze voxel scale effects on microstructures with connective pore space and invalid pores. The coupling multipoint statistics-marching cube (MPS-MC) three-dimensional (3D) reconstruction is used to construct 3D virtual micro-channel models with connective seepage channels. Pore network numerical simulations with valid realistic geometries are conducted to deeply understand voxel scale effects on microscopic hydraulic properties of sandstone reservoirs. The results show that digital porosity, micro-pore and micro-grain size gradually become stable with a voxel scale larger than 3003. The spatial variation of permeability and voxel scale effects relates extremely to the seepage index and digital porosity. As digital porosity is less than 30%, the seepage index increases with an exponential manner, and as digital porosity is larger than 30%, it decreases with a logarithm manner. The permeability is easy to evaluate by the established logarithm relation between the permeability and seepage index with relative errors all less than 5%. The proposed permeability-seepage index in the digital analysis framework provides excellent approaches to effectively evaluate the hydraulic properties of rock reservoirs. [ABSTRACT FROM AUTHOR]

True triaxial experiment with a synchronous acoustic emission (AE) monitoring system is a popular measure for the assessment of strength and cracking behaviors of brittle flawed rocks under anisotropic stress circumstances. This measure was employed to investigate the laboratory-scale brittle failure of flawed sandstone containing two different en echelon flaw configurations. Quantitative interpretations and comparisons of acousto-mechanical properties and cracking behaviors in intact and flawed sandstone have become available. Observations first revealed that en echelon flaws considerably weakened rock strength and deformability, and strongly affected the damage and failure processes. Second, intact specimen showed a quasi-2D spallation failure, while the failure of flawed specimens was dominated by the induced cracks initiated from en echelon flaws. Third, the two fundamental failure types of rock bridge including tensile-dominated failure and shear-dominated failure were registered. Whatever the failure type, micro-shear failure mechanism co-existed with micro-tensile failure mechanism. Moreover, AE amplitude distributions at the stable and unstable cracking phases follow a power law. The current findings provide insights into the brittle failure mechanisms of flawed rocks and have significant implications at scales relevant to seismicity and engineering applications. Highlights: True triaxial experiment investigations of brittle failure in flawed sandstone Quantitative interpretations and comparisons of acousto-mechanical properties and cracking behaviors in intact and flawed sandstone Quasi-2D spallation failure occurs in intact specimen, while the shear cracks initiated from the flaw tips dominate the failure in flawed specimens Co-existences of micro-shear failure mechanism with micro-tensile failure mechanism at the triggering processes of rock fracture AE amplitude distributions at the stable and unstable cracking stages follow a power law [ABSTRACT FROM AUTHOR]

Understanding the 3D spatial cracking behavior plays significant role in evaluating the mechanical properties of rocks. This work studied the spatial propagations of 3D cracks and its effects on the mechanical properties during the failure process of sandstone under uniaxial compression using X-ray CT imaging and 3D reconstruction techniques. Results show that five cracking stages can be identified including the initial flaw compaction stage, linear elastic deformation stage, microcrack propagation and coalescence to macrocrack formation stage, stable propagation stage of macrocracks and the sample failure stage. As cracking direction increases from 0° to 90°, peak stress decreases, microcrack initiation stress increases for sample S1 and decreases for samples S2–S3, which is opposite to macrocrack initiation stress of cracks. However, these variations of microcrack initiation stress, macrocrack initiation stress and peak stress are opposite as cracking direction increases from 180° to 270°. The proposed relation between the stress and normalized damage volume is effective to evaluate the stress during the failure process of sandstone. Highlights: Digital framework is proposed to characterize real-time 3D spatial crack characteristics. 3D cracking behavior is studied by digital damage ratio and normalized damage volume. A stress-damage volume relation is established to evaluate the stress during the failure process of rocks. Effects of spatial cracking direction on the failure process and mechanical properties are analyzed. [ABSTRACT FROM AUTHOR]

In this work, the geometry-constraint-based non-ordinary state-based peridynamic (GC-NOSBPD) model is further generalized to study the mechanical responses and rate-dependent fracture behaviors of viscoelastic materials. The viscoelasticity is generated by directly incorporating the classical viscoelastic constitutive relation in the form of the Generalized Maxwell Model, which is expressed as Prony-series type expansion, into the GC-NOSBPD framework. A strain-based scalar damage variable only driven by elastic energy, whose evolution follows a rate-independent law, is proposed to describe the progressive growth of the mode-I crack. Combining the rate-independent damage variable and viscoelasticity results in a rate-dependent damage model in the hypothesis that the fracture of viscoelastic material is driven by both elastic and viscous components of the energy. The fidelity of this model is established in the absence of damage by comparison with the benchmark solution for the viscoelastic response of a 3D bar subjected to various load histories. Further, the proposed model is employed to simulate two quasi-static fracture tests under various loading rates: a three-point bend fracture test for concrete and a double-cantilever-beam delamination test for rubber interface. These numerical results agree well with experimental tests, showing that the proposed model can effectively capture rate-dependent crack propagation. [ABSTRACT FROM AUTHOR]

Charged metal-organic cages generally produce aggregates with various morphologies and different properties through the multiple supramolecular interactions in solution. Herein, a luminescent hexahedral metal-organic cage containing pyrene chromophores is successfully constructed through coordination-driven subcomponent self-assembly. The cage exhibits novel spontaneous aggregation in a dilute solution and time-dependent luminescence enhancement behavior during the subsequent incubation process. Dynamic light scatter (DLS) and transmission electron microscopy (TEM) results prove that the metal-organic cages can form blackberry-like aggregates in methanol dilute solution. Unexpectedly, the luminescent intensity of this system shows a linear increase with the extension of the incubation time in methanol, and this process is also reflected in the change in the quantum yield of the system (2% to over 80% after 5 days incubation time). Ultraviolet-visible (UV-vis), 1H nuclear magnetic resonance (1H NMR) and mass spectra show that metal-organic cages can stably exist in dilute solution. Time-depended DLS and TEM data reveal that the aggregates of metal-organic cages are gradually changed from the dense state to the loose one, which may involve the transition of the system from an energy unstable state to a stable one, probably leading to the unusual time-dependent luminescent property. This unique time-dependent luminescent cage aggregate can be potentially applied as a "supramolecular time meter". [ABSTRACT FROM AUTHOR]

In this paper, a 3D non-local lattice bond model is proposed to model fracturing behaviors of materials. First, the formulations and detailed derivation for three-dimensional non-local lattice bond models are obtained by comparing the strain energy stored in a discrete lattice with the classical continuum strain energy. Then, the capabilities of three-dimensional non-local lattice bond models are verified using benchmarks. To further assess the performance of the non-local lattice bond model, fracturing behaviors in brittle solids are predicted. Compared with the previous numerical results, the proposed model demonstrates better performances, which are more consistent with the experimental observations. [ABSTRACT FROM AUTHOR]

Multiphase heterogeneity significantly affects mechanical and micro-cracking properties of geomaterials. Heterogeneity representations of geomaterials, however, can bring out fatal errors for cracking behavior investigations due to inaccurate characterizations of multiphase matrixes. This work aims to deeply characterize microscopic heterogeneity in rocks represented by digital multiphase matrixes, and to study their effects on cracking properties of geomaterials. X-ray μ-Computed Tomography (μCT) imaging under the same physical field of view is employed to obtain multiphase microstructures of sandstone with different resolutions. Digital colour difference segmentation (DCDS) and the coupling multiple point statistics-marching cube (MPS-MC) algorithms are applied to accurately characterize three-dimensional (3D) multiphase heterogeneity of rocks. Digital simulations coupled with uniaxial compression are conducted to study multiphase heterogeneity effects on micromechanics and cracking behaviors. Results show that with increasing resolution and voxel scale, heterogeneity index increases. Peak stress and crack ratio increase with increasing heterogeneity index, and the relative errors between experimental and numerical stresses are all less than 5% when the voxel is larger than 3003. Micro-pores extremely improve damage of multiphase microstructures, and the transgranular cracks initiate first, and then intergranular cracks initiate due to large heterogeneity of microscopic elements between micro-pores and microscopic interfacial transition zones (ITZs) and similar strength heterogeneity of microscopic elements in micro-grains. The proposed digital-analysis framework is effective to evaluate multiphase heterogeneity effects on mechanical and cracking responses in various engineering projects. [ABSTRACT FROM AUTHOR]

This paper discusses the relationship between statistical mechanics and nonlocal mechanical theories. Specifically, the relationship among statistical mechanics, nonlocal vector calculus, smoothed particle hydrodynamics (SPH), and peridynamics is established. Furthermore, a general particle dynamics method is proposed to solve the solid mechanics problem based on the nonlocal vector calculus and peridynamic bond constitutive model. The proposed method is a successful nonlocal mechanics theory; the convergence of the nonlocal property is verified by numerical experiments. [ABSTRACT FROM AUTHOR]

Water existing in micro-pores has tremendous influences on the mechanical and damage characteristics of rocks. This study aims to investigate the micro-pore water effects on the mechanical and damage characteristics of sandstone subjected to different loading configurations, in which four groups of sandstone specimens with different water contents were applied in the conventional uniaxial compression, cyclic loading and unloading experiments. X-ray CT imaging and 3D reconstruction techniques are applied to capture the cracking behaviors under uniaxial compression and cyclic loading–unloading. The digital microstructural variables are defined to describe the characteristics of microstructures and evolution of micro-pore water in rocks. Numerical simulation is applied to study the micro-pore effects on the mechanical properties of rocks. Results show that the specimens are mainly failed by the mixture modes of primary shear cracks and secondary tensile cracks. With increasing mass water content, the uniaxial compressive strength (UCS) decreases and the pore size first decreases, then increases, and finally decreases due to the infiltration of water phase in microstructures. The water content has a negative effect on the mechanical properties, in which the digital porosity and volumetric water content and the micro-pore water saturation have a negative effect on the UCS. In addition, the damage becomes easier near the pores with larger sizes. [ABSTRACT FROM AUTHOR]

In this paper, the creep behavior of sandstone under the different confining pressures is investigated. The nuclear magnetic resonance (NMR) measurements are carried out to detect the micro-pore characteristics of sandstones before and after compression tests and creep tests. The variations of the parameters, including transverse relaxation time (T2) spectra distribution, percentage of the pore distribution and the changes of porosity are analyzed quantificationally. The experimental results show that creep behavior can be regarded as a process of gradual accumulation of damage to rocks. The confining pressure can limit the increase in porosity during the creep stage, and the effect of confining pressure on the incremental value of porosity is more obvious under high-stress conditions than under low-stress conditions. Moreover, the relationship between the creep stain and the incremental value of porosity is established to reveal the relationship between micro-crack expansion of rocks and macro-creep characteristics of sandstone. It is found that, as the loading ratio or confining pressure increases, the variation of the creep strain is similar to the variation of the incremental value of porosity. The larger the confining pressure, the smaller the effects of creep strain on the incremental value of porosity. However, the greater the loading ratio is, the faster the incremental value of porosity increases. The present study can provide a theoretical basis for the deep mining of mineral resources and the structural stability analysis of deep-buried underground engineering. [ABSTRACT FROM AUTHOR]

In this paper, a compressive-shear fracture model of the phase-field method is proposed to simulate the compressive-shear failure behaviours of pre-cracked rock materials and investigate their fracture mechanisms. In the proposed model, a modified Hoek–Brown criterion is incorporated into the driving term in the evolution equation of the phase field to control the crack phase field. Rock-like specimens containing single flaw and double flaws were used to validate the performance of the proposed numerical model in capturing compressive-shear fractures. The numerical results were in good agreement with the experimental observations. Subsequently the effects of flaw geometries, i.e. flaw inclination angle, spacing and continuity, on the cracking behaviours and mechanical properties of rock-like specimens containing double parallel flaws were investigated. Typical shear cracks, such as coplanar or quasi-coplanar secondary cracks and oblique secondary cracks as well as coalescence types of different shear cracks, were captured. The mechanical properties were also strongly related to the flaw geometry. These performances indicated that the proposed numerical model has ability to simulate compressive-shear cracks. [ABSTRACT FROM AUTHOR]

Understanding the mechanical properties plays pivotal roles in rock engineering. This work aims to establish novel relations linking the porosity, ultrasonic wave and fluid saturation to estimate the uniaxial compressive strength (UCS) fast and simply. The uniaxial compressive coupled with ultrasonic wave tests on sandstone samples are carried out to obtain the datasets of the UCS, P-wave and S-wave velocities. X-ray CT imaging technique is employed to capture the microstructure information. The color difference phase separation approach to segment the pore, water and solid phases is proposed, and pore-scale variables to describe the microstructure characteristics are defined. Novel relations to determine the micro velocities of P-wave and S-wave are established, and the modulus of deformation and the physical properties of rocks are evaluated. Novel relation to determine the UCS is established and validated by the real and virtual experiment datasets. Results show that the UCS, P-wave and S-wave velocities computed by the proposed method decrease with increasing fluid saturation. The errors between the calculated and experimental UCS, P-wave and S-wave velocities are all < 5%, showing excellent consistency with each other. The proposed method is effective to estimate the mechanical properties fast and accurately, simplifying the estimation of the UCS in rock engineering. [ABSTRACT FROM AUTHOR]

Pore scale variables (e.g., porosity, grain size) are important indexes to predict the hydraulic properties of porous geomaterials. X-ray images from ten types of intact sandstones and another type of sandstone samples subjected to triaxial compression are used to investigate the permeability and fracture characteristics. A novel double threshold segmentation algorithm is proposed to segment cracks, pores and grains, and pore scale variables are defined and extracted from these X-ray CT images to study the geometric characteristics of microstructures of porous geomaterials. Moreover, novel relations among these pore scale variables for permeability prediction are established, and the evolution process of cracks is investigated. The results indicate that the pore-scale permeability is prominently improved by cracks. In addition, excellent agreements are found between the measured and the estimated pore scale variables and permeability. The established correlations can be employed to effectively identify the hydraulic properties of porous geomaterials. [ABSTRACT FROM AUTHOR]

A 3-D conjugated bond-pair-based peridynamic model is developed to comprehensively investigate failure characteristics of rock-like materials with intermittent fissures in the compressive-shear loading tests. Rock-like specimens containing one single central fissure are first simulated. Numerical results indicate that the 3-D conjugated bond-pair-based peridynamic model can faithfully reproduce failure characteristics of rock-like materials under compressive-shear loads. Then, the failure characteristics of rock-like specimens containing two parallel central intermittent fissures are numerically investigated. Effects of fissure inclination angle, fissure ligament length and rock bridge angle on fracturing behaviors, such as crack coalescence patterns, are also studied as well as crack initiation stress and coalescence stress. [ABSTRACT FROM AUTHOR]

This paper details a method for investigating the stability of a layered slope that combines random field theory with horizontal integration. Both the cohesion and friction coefficient are treated as a Gaussian random field. The closed-form solution of the factor of safety and the probability of failure of the layered slope are derived, in which the effects of spatial correlation lengths and spatial correlation parameters on the stability of the layered slope are considered. The derived probability of failure is greatly affected by the input spatial correlation length of the soil parameters. The effectiveness of this proposed method is validated with the results of the Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

Brittleness has significant effects on the fracturing behaviors of preflawed rock-like materials. In this study, uniaxial compressive experiments are conducted on rock-like specimens containing three flaws, and a three-dimensional digital image correlation technique is applied to capture the real-time displacement and strain fields on the rock-like specimens' surface. The present experimental study focuses on the effects of the brittleness of rock-like materials on crack initiation, propagation, and coalescence behaviors in three flaw-contained specimens. The experimental results show that the crack initiation mode transforms from the tensile mode to the shear mode with a decrease in the brittleness index of rock-like materials. Meanwhile, crack coalescence modes transform from the tensile crack coalescence mode to the mixed tension-shear coalescence mode, then to the shear coalescence mode as the brittleness index of rock-like materials decreases. Moreover, the ratio of the crack initiation stress to the peak stress increases, while the ratio of the crack coalescence stress to the peak stress decreases as the brittleness index decreases. This paper also addresses the influences of the rock bridge angle on the mechanical and cracking behaviors of three flaw-contained specimens. For specimens with the lower brittleness index, the ratio of the crack initiation stress to the peak stress decreases, while the ratio of the crack coalescence stress to the peak stress increases as the rock bridge angle increases. However, for specimens with the higher brittleness index, the ratio of the crack initiation stress to the peak stress and the ratio of the crack coalescence stress to the peak stress decrease with increasing the rock bridge angle. The experimental results provide a better understanding of the sensitivity of mechanical and cracking behaviors of three flaw-contained specimens to the brittleness of rock-like materials under uniaxial compression. [ABSTRACT FROM AUTHOR]

In this paper, a 3D numerical reconstruction method is proposed based on improved simulated annealing algorithms and limited morphological information from experiments. Firstly, X-ray micro-CT experimental tests are applied to obtain the CT images and the mechanical parameters of Xingluokeng sandstone. Then, the voxel block exchanging algorithm is introduced to accelerate the preliminary reconstruction stage of the porous sandstone model. Two-point probability control function, lineal-path control function and fractal control function are employed to characterize complex pore morphologies. The system updating algorithm is improved to avoid wasting time on the unnecessary and unsuccessful position exchange. Finally, to verify the proposed method, the topological and mechanical properties of the reconstructed porous sandstone model are analyzed by a distance-ordered homotopic thinning algorithm as well as the numerical compression. Moreover, the numerical results of the reconstructed model are compared with the experimental data. It is found that the proposed method in this paper has a good ability to predict the properties of the rocks for engineering purposes. [ABSTRACT FROM AUTHOR]

Mechanical properties and cracking behaviors of flaw-weakened rock mass are distinguishably influenced by the quasi-static strain rate. Such advanced knowledge is mainly obtained through the numerical simulations, which are rarely verified experimentally. This paper carries out a coupled experimental-numerical investigation on double-flawed rock-like specimens at different quasi-static strain rates, with consideration given to the macro-mechanical properties, the quasi-static cracking behaviors and the underlying fracture mechanism. Three ordinary arrays of double pre-existing flaws, namely, the coplanar array, the vertical non-overlapping array and the vertical aligning array, are analyzed experimentally. The obtained results show that the crack initiation stress and the peak stress of double flaw-contained specimens generally increase with increasing the strain rate. The extension length of the first macroscopic crack, the crack initiation mode, the amount of far-field cracks, and the degree of ultimate fragmentation in double flaw-contained specimens are closely related to the strain rate. Furthermore, the vertical non-overlapping array of double pre-existing flaws is studied numerically by using peridynamics. The quasi-static fracture behaviors obtained by peridynamics are in good agreement with the experimental observations. The stress concentrates around the tips of flaws when the strain rate is relatively low, while apart from around the tips of flaws, the stress concentration also occurs in the interior of specimens when the strain rate is relatively high. This study provides the better understanding of the quasi-static strain rate effects on mechanical properties and fracture behaviors of rock mass, in particular those containing natural flaws that appear in sets or groups with similar orientation and characteristics. [ABSTRACT FROM AUTHOR]

The crack initiation, growth, wrapping and coalescence of two 3D pre-existing cross-embedded flaws in PMMA specimens under uniaxial compression are investigated. The stress-strain curves of PMMA specimens with 3D cross-embedded flaws are obtained. The tested PMMA specimens exhibit dominant elastic deformation and eventual brittle failure. The experimental results show that four modes of crack initiation and five modes of crack coalescence are observed. The initiations of oblique secondary crack and anti-wing crack in 3D cracking behaviors are first reported as well as the coalescence of anti-wing cracks. Moreover, two types of crack wrapping are found. Substantial wrapping of petal cracks, which includes open and closed modes of wrapping, appears to be the major difference between 2D and 3D cracking behaviors of pre-existing flaws, which are also first reported. Petal crack wraps symmetrically from either the propagated wing cracks or the coalesced wing cracks. Besides, only limited growth of petal cracks is observed, and ultimate failure of specimens is induced by the further growth of the propagated wing crack. The fracture mechanism of the tested PMMA specimens is finally revealed. In addition, the initiation stress and the peak stress versus the geometry of two 3D pre-existing cross-embedded flaws are also investigated in detail. [ABSTRACT FROM AUTHOR]

A design matrix in response surface method (RSM) that satisfies the orthogonality is very useful because the mean square error can be minimized, so that the response surface is more precise. But the orthogonality of a second-order design matrix in conventional RSM cannot be satisfied. In this paper, a second-order orthogonal experimental design (SOED)-based RSM is proposed by considering the orthogonality of high-order design matrix. The SOED is constructed by changing the length of star points, and the main characteristic of SOED is that the design matrix is diagonal. When the high-order terms are considered in the SOED-based RSM, a globe optimal solution can be found. As the regression equation is determined, the reliability index can be analyzed by the normalized distance between the mean value of the performance function and the critical limit state of the safety factor. A practical large-scale landslide with two slip surfaces is taken to verify the applicability and precision of the proposed method in detail. It is found that the SOED-based response surface is more rigorous than the conventional RSM. [ABSTRACT FROM AUTHOR]

A new copper(II) complex [Cu(bmbp)Cl]·DMF, where bmbp is 4-butyloxy-2,6-bis(1-methyl-2-benzimidazolyl)pyridine, was synthesized and characterized by X-ray single-crystal structure analysis. The complex crystallizes in triclinic, space group P-1 with a = 8.4551(3) Å, b = 12.8262(4) Å, c = 14.7111(5) Å, α = 64.335(3)°, β = 75.314(3)°, γ = 86.749(2)°, V = 1388.42(8) Å, Z = 2. The Cu(II) ion adopts a distorted trigonal bipyramidal geometry coordinated by three nitrogen atoms of the ligand and two chloride atoms. TG analysis showed that the complex has high thermal stability. Electrochemical measuring exhibited an irreversible one-electron transfer process. DPPH radical scavenging assay showed that the ligand and its Cu(II) complex exhibited much lower antioxidant activity than that of ascorbic acid. Graphical abstract: [ABSTRACT FROM AUTHOR]

This paper analyzes the bearing capacity of shallow foundations resting on rock masses subjected to seismic loads based on limit analysis theory. The non-linear twin shear strength criterion is used to consider the effects of intermediate principal stress on the bearing capacity of shallow foundations. The pseudo-dynamic approach is applied to account for the effects of seismic loads on the bearing capacity of shallow foundations. Both the horizontal and vertical seismic acceleration coefficients and the effects of an amplification factor on the upper bound evaluations of the foundation's bearing capacity are investigated. The ?-functions are then applied to derive the upper bound solution of the load-bearing capacity. A numerical computation is performed and indicates that the seismic acceleration coefficients, amplification factor and the intermediate principal stress parameter significantly affect the bearing capacity of shallow foundations. [ABSTRACT FROM AUTHOR]

In order to resolve grid distortions in finite element method (FEM), the meshless numerical method which is called general particle dynamics (GPD) was presented to simulate the large deformation and failure of geomaterials. The Mohr-Coulomb strength criterion was implemented into the code to describe the elasto-brittle behaviours of geomaterials while the solid-structure (reinforcing pile) interaction was simulated as an elasto-brittle material. The Weibull statistical approach was applied to describing the heterogeneity of geomaterials. As an application of general particle dynamics to slopes, the interaction between the slopes and the reinforcing pile was modelled. The contact between the geomaterials and the reinforcing pile was modelled by using the coupling condition associated with a Lennard-Jones repulsive force. The safety factor, corresponding to the minimum shear strength reduction factor ' R', was obtained, and the slip surface of the slope was determined. The numerical results are in good agreement with those obtained from limit equilibrium method and finite element method. It indicates that the proposed geomaterial-structure interaction algorithm works well in the GPD framework. [ABSTRACT FROM AUTHOR]

Increased autophagic vacuoles (AVs) occur in injured or degenerating neurons, under both developmental and pathological situations. Although an induced autophagy has been shown in inflammation response to cell factors, the underlying mechanism(s) remain(s) unknown. Here, we show that both cell factor IL-6 and environmental toxin MPP promote the formation of vacuolation in SHSY5Y cells. By electron and immunofluorescent microscopy analyses, we showed that these structures are acid autolysosomes, containing cellular debris, and labeled by LC3 or LAMP1, markers of autophagosomes or lysosomes, respectively. Combining MPP and IL-6 do not further increase vacuolation of SHSY5Y cells, and the vacuolation is less than that in the MPP-treated group. MPP-induced vacuolation results from significant increase in autophagy formation and delay in autophagy degradation, in relation to a decline of the lysosomal activity of arylsulfatase A. At molecular level, we show that this defect in autolysosomal maturation is independent of mammalian target of rapamycin and p38 inhibitions. Most importantly, we provide the first evidence that activation of ERK pathway is sufficient to commit cell to autophagic vacuolation. The sustained activation is required for MPP to disrupt the autophagic pathway. IL-6 also induces a temporary and significant activation of ERK, but not sustained activation, and change sustained activation in MPP-treated group into temporary activation. Taken together, these findings strongly support that IL-6 promotes the maturation of autophagosomes into functional autolysosomes by regulating ERK. [ABSTRACT FROM AUTHOR]

Described in this paper are the synthesis, characterization and catalytic application of H-ZSM-5 zeolites for the conversion of CHBr into aromatics. The H-ZSM-5 zeolites were fabricated by hydrothermal crystallization using n-butylamine (BTA) as a template and characterized by XRD, SEM and NH-TPD techniques. The effects of batch SiO/AlO ratio, alkalinity, NaCl/AlO ratio, seed crystals, and crystallization time on the yield, structure/texture and catalytic performance were systematically studied. Adopting the optimum sol (SiO/AlO = 70, BTA/SiO = 0.2847, NaO/SiO = 0.1237, HO/SiO = 37.4, NaCl/AlO = 60, and seed/SiO = 5 wt%) and under the most preferable crystallization conditions of 100 °C/24 h-170 °C/24 h, H-ZSM-5 zeolites of high crystallinity and small size (300-700 nm) were obtained. Good catalytic performance was observed over the H-ZSM-5 zeolites (aromatic yield up to 44.2%). However, unlike the modification of large commercial HZSM-5, the use of MoO or PbO as modifying agents for the small-size H-ZSM-5 zeolites results in a decline of catalytic performance. The relationship between the structure and the catalytic efficiency of as-synthesized H-ZSM-5 samples were investigated. It was found that with crystallinity enhancement and/or decline in crystal size, there is improvement of catalytic performance. [ABSTRACT FROM AUTHOR]

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The three-point bending experiments were applied to investigating effects of loading rates on fracture toughness of Huanglong limestone. The fracture toughness of Huanglong limestone was measured over a wide range of loading rates from 9×10−4 to 1.537 MPa·m1/2/s. According to the approximate relationship between static and dynamic fracture toughness of Huanglong limestone, relationship between the growth velocity of crack and dynamic fracture toughness was obtained. The main conclusions are summarized as follows. (1) When the loading rate is higher than 0.027 MPa·m1/2/s, the fracture toughness of Huanglong limestone increases markedly with increasing loading rate. However, when loading rate is lower than 0.027 MPa·m1/2/s, fracture toughness slightly increases with an increase in loading rate. (2) It is found from experimental results that fracture toughness is linearly proportional to the logarithmic expression of loading rate. (3) For Huanglong limestone, when the growth velocity of crack is lower than 100 m/s, the energy release rate slightly decreases with increasing the growth velocity of crack. However, when the growth velocity of crack is higher than 1 000 m/s, the energy release rate dramatically decreases with an increase in the crack growth velocity. [ABSTRACT FROM AUTHOR]

A new reaction system was designed to economically convert glucose to lactic acid environment-friendly. Hydrophobic ionic liquids were chosen as solvent that can promote the decomposition reaction of glucose, and the catalytic performance of the solid bases was evaluated. Both the reaction temperature and time can affect the yield of lactic acid. A high yield (97%) of lactic acid was achieved under the optimal reaction condition. The 1H NMR spectra and HPLC-MS were used to identify the formation of the lactic acid and variations of ionic liquid. It is found that ionic-liquids have a unique solvent effect for glucose and bases. Water can be used as solvent to extract calcium lactate. This shows a great potential of hydrophobic ionic liquids in the solid bases catalyzed reaction that is limited by the weak solubility of solid bases in organic and water solution. [ABSTRACT FROM AUTHOR]

The near crack line analysis method was used to investigate a crack loaded by two pairs of point shear forces in an infinite plate in an elastic-perfectly plastic solid, and the analytical solution was obtained. The solutions include: the unit normal vector of the elastic-plastic boundary near the crack line, the elastic-plastic stress fields near crack line, law that the length of the plastic zone along the crack line is varied with an external loads, and the bearing capacity of an infinite plate with a center crack loaded by two pairs of point shear forces. The results are sufficiently precise near the crack line because the assumptions of the small scale yielding theory have not been made and no other assumption have been taken. [ABSTRACT FROM AUTHOR]

A 62-yr-old man was referred for management of GI polyposis. Large bowel polyps were initially diagnosed >25 yr ago, and the patient had undergone multiple colonoscopies and polypectomies. Personal and family history were notable for thyroid goiter and hypothyroidism. Physical examination was notable for lingular papillomatosis. No cutaneous lesions were seen. Upper endoscopy revealed esophageal glycogen acanthosis. There were multiple polyps throughout the stomach and the small and large intestines. Histology of these polyps showed multiple cell types including juvenile polyps, inflammatory polyps with fibromuscular proliferation and lamina propria ganglion cells, and focal adenomatous change. A clinical diagnosis of Cowden syndrome was made. Mutation analysis revealed a variant in exon 8 of the PTEN gene. Direct sequencing revealed a germline heterozygous C.892–895InsA, which is predicted to result in a truncated PTEN protein. Cowden syndrome is an underdiagnosed, underrecognized, autosomal dominant, inherited syndrome. For the gastroenterologist, esophageal acanthosis and multiple hamartomatous polyps should suggest the diagnosis. Sensitive molecular diagnostic tests looking for mutations in the appropriate genes are clinically available. Together with genetic counseling, molecular diagnostic testing will allow more accurate risk assessment and surveillance for cancer for both the patient and family members. [Copyright &y& Elsevier]

A number of genetic alterations have been described in colorectal cancers. They include allelic losses on specific chromosomal arms, mutations of oncogenes, tumor suppressor genes and mismatch repair genes, microsatellite instability in coding repeat sequences of target genes and methylation defects in gene promoters. Since these alterations have been reported by different groups on different tumors and cell lines, the complete repertoire of genetic alterations for any given tumor sample remains unknown. In the present study, we analysed a series of 22 colorectal cancer cell lines for 31 different genetic alterations. We found significant correlations between mutational profiles in these colorectal cell lines associated with differences in mismatch repair status. This panel of colon cancer cell lines is representative of the genetic heterogeneity occurring in sporadic colorectal carcinoma. Our results may prove to be very useful for understanding the different biological pathways involved in the development of colon cancer, and for groups studying cellular biology and pharmacology on the same cell lines. Oncogene (2001) 20, 5025–5032. [ABSTRACT FROM AUTHOR]

Peroxisome proliferator activated receptor γ (PPARγ) is a nuclear hormone receptor that has been shown to regulate differentiation and cell growth. Studies of the differentiative effects of PPARγ agonists on several cancer cell lines led to the hypothesis that dysfunction of PPARγ contributes to tumorigenesis. These functional observations were strengthened by genetic evidence: somatic loss-of-function mutations in PPARG, encoding PPARγ, in sporadic colorectal carcinomas and somatic translocation of PAX8 and PPARG in follicular thyroid carcinoma. Recently overrepresentation of the H449H variant was found in a cohort of American patients with glioblastoma multiforme. The glioblastoma multiforme data suggest that PPARG contributes common, low-penetrance alleles for cancer susceptibility. To test this hypothesis in a broader range of cancers we examined a series of carcinomas of the cervix, endometrium, ovary, prostate, and kidney for germline sequence variation in PPARG. In addition to the two common sequence variants, P12A and H449H, there were five other sequence variants. P12A alleles were underrepresented in renal cell carcinoma patients compared to country-of-origin race-matched controls (3.75% vs. 12.1%, P<0.04). In contrast, the H449H variant was overrepresented in individuals with endometrial carcinoma compared to controls (14.4% vs. 6.25%, P<0.02). These observations lend genetic evidence consistent with our hypothesis that PPARG serves as a common, low-penetrance susceptibility gene for cancers of several types, especially those epidemiologically associated with obesity and fat intake. [ABSTRACT FROM AUTHOR]

The p21 gene encodes a cyclin dependent kinase inhibitor protein (p21) which has a tumor suppressive activity in a variety of tumor cell lines. Since, the p21 gene is up-regulated by the p53 tumor suppressor gene, which is frequently mutated in gliomas, acting therefore in the same control pathway, it constitutes a good candidate gene to be also inactivated in these tumors. To test this hypothesis, DNAs from 81 gliomas (48 glioblastomas, 11 anaplastic astrocytomas, 10 low-grade astrocytomas, 12 oligodendrogliomas and mixed gliomas), were investigated for mutations in the p21 coding sequence by denaturant gradient gel electrophoresis followed by sequencing. All these tumors have been previously screened for p53 mutations. Three different DNA variants were identified on codon 31 (17 cases), 27 (1 case) and 117 (1 case) and shown to be also present in matching constitutional DNA, suggesting they were polymorphisms. None of the tumors demonstrated a somatic mutation. No significant correlation between the presence of a p21 variant and the p53 mutation tumor status was observed. In conclusion, mutation in the p21 gene unlikely contributes to the development of gliomas. [ABSTRACT FROM AUTHOR]

We have recently shown that analysis of BAT-26, was sufficient to establish the Replication Error status of colorectal tumors and cell lines without the need for matching normal DNA. BAT-26, a poly(A) tract in the 5th intron of the hMSH2 gene, does not present significant size variation either between the allleles of one individual or between alleles of different individuals. In colorectal tumors without defects in the replication error system (RER- phenotype), BAT-26 is also quasi-monomorphic. On the contrary, in RER+ colorectal tumors, BAT-26 shows unstable shortened alleles. In order to see whether this behaviour was specific for BAT-26, or was a more general phenomenon for mononucleotide repeat microsatellites, we analysed eight other mononucleotide repeats. In control individuals (72 samples) and in RER- colorectal tumors and cell lines (55 samples), these microsatellites were polymorphic, dimorphic, quasi-monomorphic or monomorphic, indicating that the quasi-monomorphic nature of BAT-26 was not a general rule. All of them showed a tendency to be shorter in RER+ colorectal tumors and cell lines (19 samples), but only quasi-monomorphic and monomorphic mononucleotide repeats could be used to determine the RER status of tumors without matching normal DNA, although with a lower efficiency than BAT-26 due to either a smaller range of shortening in RER+ tumors or to a larger number of false negative cases. [ABSTRACT FROM AUTHOR]

We have recently shown that loss of heterozygosity of specific markers, including those at 10q23, 17p13-p15 and 16q24, can occur in the stromal and epithelial compartments of primary invasive breast carcinomas. Here, we demonstrate high frequencies of somatic mutations in TP53 (encoding tumor protein p53) and PTEN (encoding phosphate and tensin homolog) in breast neoplastic epithelium and stroma. Mutations in TP53 and PTEN are mutually exclusive in either compartment. In contrast, mutations in WFDC1 (16q24, encoding WAP four-disulfide core domain 1) occur with low frequency in the stroma. [ABSTRACT FROM AUTHOR]

Pioneered by Lehn, Cram, Peterson and Breslow, supramolecular chemistry concepts have evolved providing fundamental knowledge of the relationships between the structures and reactivities of organized molecules. A particular fascinating class of metallo-supramolecular molecules are hollow coordination cages that provide cavities of molecular dimensions promoting applications in diverse areas including catalysis, enzyme mimetics and material science. Here we report the synthesis of coordination cages with exceptional cross-sectional diameters that are composed of multiple sub-cages providing numerous distinctive binding sites through labile coordination solvent molecules. The building principles, involving Archimedean and Platonic bodies, renders these supramolecular keplerates as a class of cages whose composition and topological aspects compare to characteristics of edge-transitive {Cu2} MOFs with A3X4 stoichiometry. The nature of the cavities in these double-shell metal-organic polyhedra and their inner/outer binding sites provide perspectives for post-synthetic functionalizations, separations and catalysis. Transmission electron microscopy studies demonstrate that single molecules are experimentally accessible. [ABSTRACT FROM AUTHOR]