Mesenchymal Stem Cells Express Low Levels of Cardiomyogenic Genes and Show Limited Plasticity towards Cardiomyogenic Phenotype

Mesenchymal stem cell differentiation towards osteogenic, chondrogenic and adipogenic lineages have been extensively described and reproduced in the literature. In contrast, cardiomyogenic differentiation still remains largely controversial. In this study the authors aim to shed new light into this unclear phenomenon and test whether BMMSC （bone marrow mesenchymal stem cells） and ATMSC （adipose tissue derived mesenchymal stem cells） are able to differentiate into functional cardiomyocytes, investigating two differentiation protocols. AT and BMMSC behaved differently when cultured in differentiation media and presented lower levels of proliferation and alkaline phosphatase production, expression of cardiomyocyte-specific transcription factors such as GATA-4, Nkx2-5 and proteins such as ct and 13 Myosin Heavy Chains. Furthermore, MSC started to express higher levels of Connexin-43 and c~ sarcomeric actinin protein. Unfortunately, though, MSC did not present cardiomyocyte-like electrophysiological properties. In order to analyze a possible explanation for such limited plasticity, the authors decided to address the issue using a quantitative approach. Gene expression was quantified by Real time PCR, and, for the first time, the authors show that a possible explanation for limited plasticity of MSC is that even though differentiated cells presented differential gene expression, the levels of key cardiomyogenic genes did not reach expression levels presented by adult cardiomyocytes, nor were maintained along differentiation, reaching peaks at 4 days of stimulation, and decaying thereafter.

Hermite WENO-based limiters for high order discontinuous Galerkin method on unstructured grids

A novel class of weighted essentially nonoscillatory （WENO） schemes based on Hermite polynomi- als, termed as HWENO schemes, is developed and applied as limiters for high order discontinuous Galerkin （DG） method on triangular grids. The developed HWENO methodology utilizes high-order derivative information to keep WENO re- construction stencils in the von Neumann neighborhood. A simple and efficient technique is also proposed to enhance the smoothness of the existing stencils, making higher-order scheme stable and simplifying the reconstruction process at the same time. The resulting HWENO-based limiters are as compact as the underlying DG schemes and therefore easy to implement. Numerical results for a wide range of flow conditions demonstrate that for DG schemes of up to fourth order of accuracy, the designed HWENO limiters can simul- taneously obtain uniform high order accuracy and sharp, es- sentially non-oscillatory shock transition.

Fractional-order visco-plastic constitutive model for uniaxial ratcheting behaviors

This paper proposes a novel unified visco-plastic constitutive model for uniaxial ratcheting behaviors. The cyclic deformation of the material presents remarkable time-dependence and history memory phenomena. The fractional(fractional-order)derivative is an efficient tool for modeling these phenomena. Therefore, we develop a cyclic fractional-order unified visco-plastic(FVP) constitutive model. Specifically, within the framework of the cyclic elasto-plastic theory, the fractional derivative is used to describe the accumulated plastic strain rate and nonlinear kinematic hardening rule based on the Ohno-Abdel-Karim model. Moreover, a new radial return method for the back stress is developed to describe the unclosed hysteresis loops of the stress-strain properly.The capacity of the FVP model used to predict the cyclic deformation of the SS304 stainless steel is verified through a comparison with the corresponding experimental data found in the literature(KANG, G. Z., KAN, Q. H., ZHANG, J., and SUN, Y. F. Timedependent ratcheting experiments of SS304 stainless steel. International Journal of Plasticity, 22(5), 858–894(2006)). The FVP model is shown to be successful in predicting the rate-dependent ratcheting behaviors of the SS304 stainless steel.

Adiabatic Shear Localization for Steels Based on Johnson-Cook Model and Second-and Fourth-Order Gradient Plasticity Models

To consider the effects of the interactions and interplay among microstructures, gradient-dependent models of second- and fourth-order are included in the widely used phenomenological Johnson-Cook model where the effects of strain-hardening, strain rate sensitivity, and thermal-softening are successfully described. The various parameters for 1006 steel, 4340 steel and S-7 tool steel are assigned. The distributions and evolutions of the local plastic shear strain and deformation in adiabatic shear band （ASB） are predicted. The calculated results of the second- and fourth- order gradient plasticity models are compared. S-7 tool steel possesses the steepest profile of local plastic shear strain in ASB, whereas 1006 steel has the least profile. The peak local plastic shear strain in ASB for S-7 tool steel is slightly higher than that for 4340 steel and is higher than that for 1006 steel. The extent of the nonlinear distribution of the local plastic shear deformation in ASB is more apparent for the S-7 tool steel, whereas it is the least apparent for 1006 steel. In fourth-order gradient plasticity model, the profile of the local plastic shear strain in the middle of ASB has a pronounced plateau whose width decreases with increasing average plastic shear strain, leading to a shrink of the portion of linear distribution of the profile of the local plastic shear deformation. When compared with the sec- ond-order gradient plasticity model, the fourth-order gradient plasticity model shows a lower peak local plastic shear strain in ASB and a higher magnitude of plastic shear deformation at the top or base of ASB, which is due to wider ASB. The present numerical results of the second- and fourth-order gradient plasticity models are consistent with the previous numerical and experimental results at least qualitatively.

NONSMOOTH MODEL FOR PLASTIC LIMIT ANALYSIS AND ITS SMOOTHING ALGORITHM

By means of Lagrange duality of Hill＇s maximum plastic work principle theory of the convex program, a dual problem under Mises＇ yield condition has been derived and whereby a non-differentiable convex optimization model for the limit analysis is developed. With this model, it is not necessary to linearize the yield condition and its discrete form becomes a minimization problem of the sum of Euclidean norms subject to linear constraints. Aimed at resolving the non-differentiability of Euclidean norms, a smoothing algorithm for the limit analysis of perfect-plastic continuum media is proposed. Its efficiency is demonstrated by computing the limit load factor and the collapse state for some plane stress and plain strain problems.

PLASTIC LIMIT ANALYSIS OF INCOMPATIBLE FINITE ELEMENT METHOD

This paper describes an incompatible finite element model satisfying the consistency condition of energy to solve the numerical precision problem of finite element solution in perfectly plastic analysis. In this paper the reason and criterion of the application of the model to plastic limit analysis are discussed, and an algorithm of computing plastic limit load is given.

An empirical behavioral order‑driven model with price limit rules

We propose an empirical behavioral order-driven(EBOD)model with price limit rules,which consists of an order placement process and an order cancellation process.All the ingredients of the model are determined based on the empirical microscopic regularities in the order flows of stocks traded on the Shenzhen Stock Exchange.The model can reproduce the main stylized facts in real markets.Computational experiments unveil that asymmetric setting of price limits will cause the stock price to diverge exponentially when the up price limit is higher than the down price limit and to vanish vice versa.We also find that asymmetric price limits have little influence on the correlation structure of the return series and the volatility series,but cause remarkable changes in the average returns and the tail exponents of returns.Our EBOD model provides a suitable computational experiment platform for academics,market participants,and policy makers.

PLASTIC LIMIT ANALYSIS OF DISCONTINUOUS LINING UNDERGROUND PRESSURE

Discontinuous lining is a special form of support in underground excavation. Based on the method of plastic limit analysis, it is found the upper and the lower bound solution of the pressure of circular discontinuous lining and discussed support parameter of discontinuous lining and its applicable conditions , which provides theoretical basis for the design and calculation of discontinuous lining.

Anisotropic plastic deformation behavior of B2-ordered Fe_3Al single crystals at room temperature

The tensile plastic deformation behavior of B2 ordered Fe 3Al single crystals at room temperature was systematically investigated. The results show that the mechanical properties are strongly orientation dependent. The plastic elongation of crystals with orientation near is as high as 42%. Slip trace analysis shows that although slip planes are found to change among {110} , {112} and {123} with the change in orientations, the initial slip planes in all cases are {110}. Five stage work hardening curve including four linear stages and one parabolic stage is obtained; but not all stages are observed in the actual deformation of each crystal. In combination with investigations of dislocation substructure, it is found that deformations in stage Ⅰ～Ⅲ are corresponding to the motion of two fold superdislocations. The higher work hardening rate of stage Ⅱ is mainly due to the stronger interactions between primary dislocations and secondary dislocations than those in stage Ⅲ. Deformation in stage Ⅳ involved is not only the motion of two fold superdislocations but also the slip of dissociated superpartials with APB traps and the formation of APB tube, both of which are attributed to the hardening. Deformation in stage Ⅴ is controlled by the cross slip of dissociated superpartials. The dominated softening effect of cross slip reduces the hardening rate and leads to the formation of parabolic stage.

A Discusion on Limited Load-Carrying Capacity of Rectangular Plates

The elastic-plastic method is often used in designing the inner flat bulkhead plates of submarines, and the upper structure of ships and drilling platforms. Such bulkhead plates can bear the load only once. For the improvement of the load-carrying capacity or the reduction of the weight of plates, the yield line analytical method is employed in this paper to design the bulkhead plate to improve economy and increase the effiective load. Besides, a further sutdy of this method has been made theoretically and experimentally, and the data of the limited load-carrying capacity of the plate have been obtained. Furthermore, the safety coefficients for such a method are presented, which can be used as reference for related departments and staffs.

ENTIRE SOLUTIONS OF HIGHER ORDER DIFFERENTIAL EQUATIONS WITH ENTIRE COEFFICIENTS HAVING THE SAME ORDER

In this paper,we consider entire solutions of higher order homogeneous differential equations with the entire coefficients having the same order,and prove that the entire solutions are of infinite lower order.The properties on the radial distribution,the limit direction of the Julia set and the existence of a Baker wandering domain of the entire solutions are also discussed.

Finite element analyses of slope stability problems using non-associated plasticity

In recent years, finite element analyses have increasingly been utilized for slope stability problems. In comparison to limit equilibrium methods, numerical analyses do not require any definition of the failure mechanism a priori and enable the determination of the safety level more accurately. The paper compares the performances of strength reduction finite element analysis(SRFEA) with finite element limit analysis(FELA), whereby the focus is related to non-associated plasticity. Displacement-based finite element analyses using a strength reduction technique suffer from numerical instabilities when using non-associated plasticity, especially when dealing with high friction angles but moderate dilatancy angles. The FELA on the other hand provides rigorous upper and lower bounds of the factor of safety(FoS) but is restricted to associated flow rules. Suggestions to overcome this problem, proposed by Davis(1968), lead to conservative FoSs; therefore, an enhanced procedure has been investigated. When using the modified approach, both the SRFEA and the FELA provide very similar results. Further studies highlight the advantages of using an adaptive mesh refinement to determine FoSs. Additionally, it is shown that the initial stress field does not affect the FoS when using a Mohr-Coulomb failure criterion.

RIGID FINITE ELEMENT AND LIMIT ANALYSIS

According to the lower-bound theorem of limit analysis the Rigid Finite Element Meth-od(RFEM)is applied to structural limit analysis and the linear programmings for limit analysis are deducedin this paper.Moreover,the Thermo-Parameter Method(TPM)and Parametric Variational principles(PVP)are used to reduce the computational effort while maintaining the accuracy of solutions.A better solution isalso obtained in this paper.

Test study of high liquid limit clay modified by quick lime used as sub-grade material

Through laboratory test, the relationships among change of compactibility, liquid/plastic limit, free swell, swell ratio without load, california bearing ratio (CBR) and soakage (after being soaked in water), and mix-ratio of quick lime and time were studied. The results show that optimum water content, plastic limit and CBR of high liquid limit clay improved by quick lime increase with the increase of mix-ratio of quick lime, while the maximum dry density, liquid limit, plasticity index, soakage (after being immersed in water), free swell, and swell ratio without load decrease with the increase of mix-ratio of quick lime. Plastic limit of high liquid clay improved by quick lime gradually increases with time, while the liquid limit, plasticity index, free swell and swell ratio without load gradually decrease with time. When the mix-ratio of quick lime exceeds 2%, after 14 d, swell ratio without load of the improved clay is zero, its free swell is about 30% of that of untreated soil, and its plasticity index is less than 26 for sub-grade material, satisfying the requirement by 'Specifications for Design of Highway Subgrade'.

Fall cone tests considering water content, cone penetration index, and plasticity angle of fine-grained soils

This paper analyzed the consistency of some parameters of soils in the literature and experimental results from fall cone test and its application to soil plasticity classification.Over 500 data from both literatures and experiments using fall cone and Casagrande methods were compiled to assess the relationships among specified water content,cone penetration index ebT,and plasticity angle eaT of finegrained soils.The results indicate that no unique correlation exists among b,liquid limit of the fall cone test(LLc)and a.The water content at 1 mm cone penetration eC0T correlates well with b,plasticity ratio eRpT(i.e.the ratio of plastic limit to liquid limit),and a.Finally,the potential of using the btan a diagram to classify soil plasticity was also discussed.

Assessment of a two-surface plasticity model for hexagonal materials

A computationally efficient two-surface plasticity model is assessed against crystal plasticity. Focus is laid on the mechanical behavior of magnesium alloys in the presence of ductility-limiting defects, such as voids. The two surfaces separately account for slip and twinning such that the constitutive formulation captures the evolving plastic anisotropy and evolving tension-compression asymmetry. For model identification, a procedure is proposed whereby the initial guess is based on a combination of experimental data and computationally intensive polycrystal calculations from the literature. In drawing direct comparisons with crystal plasticity, of which the proposed model constitutes a heuristically derived reduced-order model, the available crystal plasticity simulations are grouped in two datasets. A calibration set contains minimal data for both pristine and porous material subjected to one loading path. Then the two-surface model is assessed against a broader set of crystal plasticity simulations for voided unit cells under various stress states and two loading orientations. The assessment also includes microstructure evolution(rate of growth of porosity and void distortion). The ability of the two-surface model to capture essential features of crystal plasticity is analyzed along with an evaluation of computational cost. The prospects of using the model in guiding the development of physically sound damage models in Mg alloys are put forth in the context of high-throughput simulations.

Analysis of complete plasticity assumption for solid circular shaft under pure torsion and calculation of shear stress

The distribution of shear stress on the cross-section of plastic metal solid circular shaft under pure torsion yielding, the applicability of complete plastic model assumption and the shear stress formula were researched. Based on the shear stress formula of circular shaft under pure torsion in elastic stage, the formula of torque in elastic stage and the definition of yield, it is obtained that the yielding stage of plastic metal shaft under pure torsion is only a surface phenomenon of torque-torsion angle relationship, and the distribution of shear stress is essentially different from that of tensile stress when yielding under uniaxial tension. The pure torsion platform-torsion angle and the shape of torque-torsion angle curve cannot change the distribution of shear stress on the shaft cross-section. The distribution of shear stress is still linear with the maximum shear stress ts. The complete plasticity model assumption is not in accordance with the actual situation of shaft under torsion. The experimental strength data of nine plastic metals are consistent with the calculated results of the new limiting strain energy strength theory （LSEST）. The traditional yield stress formula for plastic shaft under torsion is reasonable. The shear stress formula based on the plane assumption in material mechanics is applicable for all loaded stages of torsion shaft.

Target reliability index for serviceability limit state of single piles

The objective is to develop an approach for the determination of the target reliability index for serviceability limit state(SLS) of single piles. This contributes to conducting the SLS reliability-based design(RBD) of piles. Based on a two-parameter,hyperbolic curve-fitting equation describing the load-settlement relation of piles, the SLS model factor is defined. Then, taking into account the uncertainties of load-settlement model, load and bearing capacity of piles, the formula for computing the SLS reliability index(βsls) is obtained using the mean value first order second moment(MVFOSM) method. Meanwhile, the limit state function for conducting the SLS reliability analysis by the Monte Carlo simulation(MCS) method is established. These two methods are finally applied to determine the SLS target reliability index. Herein, the limiting tolerable settlement(slt) is treated as a random variable. For illustration, four load test databases from South Africa are compiled again to conduct reliability analysis and present the recommended target reliability indices. The results indicate that the MVFOSM method overestimates βsls compared to that computed by the MCS method. Besides, both factor of safety(FS) and slt are key factors influencing βsls, so the combination of FS and βsls is welcome to be used for the SLS reliability analysis of piles when slt is determined. For smaller slt, pile types and soils conditions have significant influence on the SLS target reliability indices; for larger slt, slt is the major factor having influence on the SLS target reliability indices. This proves that slt is the most key parameter for the determination of the SLS target reliability index.

Limit Cycle Containing Nine Critical Points in its Interior for a Class of Cubic Systems

Discuss a class of real planar cubic systems with a critical point O (0,0) of nine orders and obtain the conditions for its limit cycle surrounding the origin, and prove that when small pertubations of coefficients are made, the critical point O (0,0) of nine orders is split into nine real simple critical points and the limit cycle surrounding the origin becomes the limit cycle containing nine critical points in its interior.

Analytic Solution of Elasto-Plastic Stress in Infinite Slope under Uniform Load

According to the Mohr-Coulomb yield criterion, the stress field of the infinite slope is derived under a vertical uniform load q on the top of the slope. It is indicated that elastic and elasto-plastic states would occur in the slope. When q is smaller than the critical load, q(p), the slope is in the elastic state. If q equals q(p), the slope is in the critical state, and the plastic deformation would occur along the critical angle. With the increase of q, the plastic zone would extend, and the slope is in the elasto-plastic State. If q equals limit load, the slope is in the limit equilibrium state. The slope may be divided into three zones. Some charts of the critical angle, the critical and limit load coefficients are presented in this paper.