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Crop residue cover is vital for reducing soil erosion and improving soil fertility, which is an important way of conserving tillage to protect the black soil in Northeast China. How much the crop residue covers on cropland is of significance for black soil protection. Landsat-8 and Sentinel-2 images were used to estimate corn residue coverage (CRC) in Northeast China in this study. The estimation model of CRC was established for improving CRC estimation accuracy by the optimal combination of spectral indices and textural features, based on soil texture zoning, using the random forest regression method. Our results revealed that (1) the optimization C5 of spectral indices and textural features improves the CRC estimation accuracy after harvesting and before sowing with determination coefficients (R2) of 0.78 and 0.73, respectively; (2) the random forest improves the CRC estimation accuracy after harvesting and before sowing with R2 of 0.81 and 0.77, respectively; (3) considering the spatial heterogeneity of the soil background and the usage of soil texture zoning models increase the accuracy of CRC estimation after harvesting and before sowing with R2 of 0.84 and 0.81, respectively. In general, the CRC estimation accuracy after harvesting was better than that before sowing. The results revealed that the corn residue coverage in most of the study area was 0.3 to 0.6 and was mainly distributed in the Songnen Plain. By the estimated corn residue coverage results, the implementation of conservation tillage practices is identified, which is vital for protecting the black soil in Northeast China. [ABSTRACT FROM AUTHOR]

Efficient, fast, and accurate crop lodging monitoring is urgent for farmers, agronomists, insurance loss adjusters, and policymakers. This study aims to explore the potential of Chinese GF-1 PMS high-spatial-resolution images for corn lodging monitoring and to find a robust and efficient way to identify corn lodging accurately and efficiently. Three groups of image features and five machine-learning approaches are used for classifying non-lodged, moderately lodged, and severely lodged areas. Our results reveal that (1) the combination of spectral bands, optimized vegetation indexes, and texture features classify corn lodging with an overall accuracy of 93.81% and a Kappa coefficient of 0.91. (2) The random forest is an efficient, robust, and easy classifier to identify corn lodging with the F1-score of 0.95, 0.92, and 0.95 for non-lodged, moderately lodged, and severely lodged areas, respectively. (3) The GF-1 PMS image has great potential for identifying corn lodging on a regional scale. [ABSTRACT FROM AUTHOR]

BACKGROUND: Septic cardiomyopathy (SCM) occurs in the early stage of sepsis and septic shock, which has implications for treatment strategies and prognosis. Additionally, myocardial involvement in the early stages of sepsis is difficult to identify. Here, we assess subclinical myocardial function using laboratory tests and speckle-tracking echocardiography (STE). METHODS: Emergency department patients diagnosed with sepsis or septic shock were included for analysis. Those with other causes of acute or pre-existing cardiac dysfunction were excluded. Transthoracic echocardiography (TTE), including conventional echocardiography and STE, were performed for all patients three hours after initial resuscitation. Samples for laboratory tests were taken around the time of TTE. RESULTS: Left ventricular functions of 60 patients were analyzed, including 21 septic shock patients and 39 sepsis patients. There was no significant difference in global longitudinal strain (GLS), global circumferential strain (GCS), or global radical strain (GRS) between patients with sepsis and septic shock (all with P>0.05). However, GLS and GCS were significantly less negative in patients with abnormal troponin levels or in patients with abnormal left ventricular ejection fraction (LVEF) values (all with P<0.05). There were also moderate correlations between GLS and levels of cTnl (r=0A0, P=0.002) or N-terminal pro-B-type natriuretic peptide (NT-proBNP) (r=0.44, P=0.001) in sepsis and septic shock patients. CONCLUSION: Myocardial dysfunction, e.g., lower LVEF or less negative GLS in patients with sepsis or septic shock, is more affected by myocardial injury. GLS could be incorporated into mainstream clinical practice as a supplementary LVEF parameter, especially for those with elevated troponin levels. [ABSTRACT FROM AUTHOR]

Cocoa tree (Theobroma cacao L.) is a recently planted crop in Taiwan, a country located in East Asia. Taiwanese cocoa beans are appreciated globally because of their distinctive flavor and aroma. The effects of the water extracts of unfermented Taiwan cocoa beans (WUFCB) and fermented and roasted Taiwan cocoa beans (WFRCB) on the anti-oxidation, vascular protection, and variation in phytochemical components were investigated. Variations in the catechins components of WUFCB and WFRCB were examined by high performance liquid chromatography. The values of catechin compounds in WUFCB (epicatechin [EC]: 52.32 ± 0.56 mg/g, and catechin (C): 15.14 ± 0.26 mg/g) were approximately two times higher than those found in WFRCB (EC: 26.22 ± 0.48 mg/g, and C: 4.56 ± 0.10 mg/g), indicating that the fermentation and roasting steps caused decline in catechins compounds of WFRCB. In the range of 50–300 µg mL-1, both WUFCB and WFRCB depict noncytotoxicity in endothelial cells; they protect cells from H2O2 -induced cytotoxicity as established by MTT assay. Meanwhile, nitric oxide (NO) levels in endothelial cells were elevated by WUFCB. In addition, WUFCB displayed radical scavenging in the acellular model and inhibited increase in reactive oxygen species (ROS) noted in endothelial cell induced by H2O2 . Overall, the significant vascular protection of WUFCB is associated with increased NO formation. The decreased ROS generation against oxidative damage was attributed to abundant catechin compounds. This study establishes Taiwan cocoa polyphenol as an effective and complementary tool for preventing endothelial dysfunction and cardiovascular disease. [ABSTRACT FROM AUTHOR]

The physical phenomenon of residual stress relaxation and redistribution in the film/substrate systems due to creep deformation is focused in this work. A new analysis model to elucidate either the film or the substrate subjected to creeping deformation is developed. Specific analyses are made on the NiCrAlY coating-based system and silicon-epoxy bilayer structure. Results reveal that the proposed model can lead to an excellent agreement with the simulated results of finite element method. Furthermore, comparisons among FE results, the present model, and Zhang’s creep solution [J. Appl. Phys. 101, 083530 (2007)] have been carried out. Meanwhile, comparisons between Hsueh’s viscoelastic solution [J. Appl. Phys. 91, 2760 (2002)] and our current model in the case of creep exponent n=1 have also been conducted. Effects of thickness ratio of the film to the substrate on the stress distribution and the evolution of the accumulated creep strain have also been discussed in this paper. [ABSTRACT FROM AUTHOR]

Highlights • Heterogeneous coarsening of nanolath structure is characterized under the low plastic strain level condition. • Two regions in CSS curve are classified based on the cyclic softening behavior and the homogeneity of microstructural coarsening. • A dislocation-based viscoplastic constitutive model is developed by introducing an intergranular back-stress related to the heterogeneous coarsening. • The macroscopic mechanical behaviors and microstructural evolution of a nanolath strengthened steel at high/low plastic strain levels are reasonably reproduced. Abstract Cyclic softening behavior at elevated temperature of nanolath strengthened steel was rationalized under different strain amplitudes. Results indicated that the evolution of internal stress components and the coarsening of subgrains are significantly depending on the plastic strain level. This paper proposes a dislocation-based viscoplastic constitutive model to represent the cyclic deformation response especially at low plastic strain level. The heterogeneous coarsening of subgrains is explicitly formulated via employing different evolution laws for multiple dislocation populations. An additional back-stress hardening component is introduced to account for the retarded cyclic softening. The cyclic deformation response and microstructural evolution of a nanolath strengthened steel at high/low plastic strain levels are perfectly reproduced. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract The evolution of grain size and structure morphology across the CrMoV welded joint were investigated. The tensile properties of subzones in the weldment were measured by miniature specimens. And the measured results were compared to the results acquired from the standard round bar specimen. It is found that the strength characterized by miniature specimen is lower than that obtained by standard specimen. The deviation of strength is acceptable. However, the measured Young's modulus is not consistent with the elastic modulus of standard specimen, due to the jig deformation and clamped effects of the miniature specimen. Although HAZ is the weakest location due to the deteriorated microstructure and the reduced strength, the failure pattern is different comparing the measured results of the miniature specimen and that of the standard round bar cross-weld specimen. For the miniature specimen, fracture occurred at the HAZ region close to the base metal (BM). However, the fracture of the standard specimen occurred in the BM instead of the HAZ region. The difference is ascribed to the different constraints of specimens with various geometric dimension. [ABSTRACT FROM AUTHOR]

Abstract Developing the fiber/matrix interface with combined structural and functional performances is of tremendous importance in ensuring the service safety of fiber reinforced plastic composites (FRPs) and expanding the capabilities of FRPs to perform multiple parallel tasks. Herein, a multi-functional interface sensor that can improve the interfacial shear strength, and simultaneously monitor and heal the interfacial damage between glass fiber yarn and thermoplastic ethylene-vinyl acetate copolymer resin (GF/EVA) is reported. The basic idea is introducing multi-walled carbon nanotube into GF/EVA interface. By this proposed method, the interfacial shear strength (IFSS) of GF/EVA composites is enhanced by 48.9%. The resistance of the interface sensor is recorded during the pull-out tests, and results show that the relative resistivity change could reflect the interfacial damage information very well. Electric heating of the sensor is adopted to heal the interfacial damage. The applied electrical power is discussed to evaluate the self-healing efficiency of the interfaces at different damage degrees. Successful interfacial self-healing ability is achieved and confirmed using different characterization techniques. Moreover, to verify the feasibility of our method in GF/EVA composite laminates, in-situ monitoring of the laminates under complicated stress and healing of delamination are performed. The results show that the developed sensor could monitor and heal the GF/EVA composite laminates with high sensing/healing ability. The proposed method and the obtained results could help to get a multi-functional sensor to ensure the service safety of composite structures. [ABSTRACT FROM AUTHOR]

A micro-mechanism based void growth model involving the void shape change during the creep deformation is proposed, referring to the traditional Cocks–Ashby (C–A) model framework, for multiaxial power-law creep rupture prediction. Accordingly, an improved prediction for creep lifetime and multiaxial creep ductility are derived. Results indicate that the creep life and creep ductility are significantly affected by the void shape evolution in the low stress triaxiality range. By contrast, such an effect could be neglected under the situation of high stress triaxiality. In addition, a large fraction of creep ductility is consumed during the tertiary creep stage. A good agreement has been achieved between the proposed model and the collected experimental data. [ABSTRACT FROM AUTHOR]

The local creep properties of a CrMoV weldment were acquired by using miniature specimens of in-situ creep test. The creep performances of heat-affected zone (HAZ), weld pass metal in the welding direction (WP) and multiple weld passes through the thickness direction (MWP) were compared with each other. It is shown that the magnitudes of creep strength order satisfy WP > MWP > HAZ, while the creep ductility of these three samples exhibit an inverse order: WP < MWP < HAZ. In addition, the typical three-stage creep deformation curves are observed in both WP and MWP samples. However, no significant difference between the primary and the secondary stages is detected for HAZ sample. [ABSTRACT FROM AUTHOR]

Strain controlled fatigue of P92 steel with various strain hold dwells introduced at the peak loading point were conducted at 625 °C. Two features which depend on the cycle and strain range level were observed under the fatigue-creep condition for the viscous and cyclic softening material. The first one is the accelerated cyclic softening response which is ascribed to the accumulated inelastic strain transformation from the creep mechanism during the strain dwell period and becomes more significant with the decrease of strain ranges. The second one is the decelerated stress relaxation behavior which is caused by the reduced viscous stress related to the continuous cyclic softening and fades with the decrease of cyclic strain ranges. Accordingly, a new unified viscoplastic constitutive model within the framework of Chaboche model was developed by improving the nonlinear isotropic hardening rule and the kinematic hardening rule with a cyclic softening parameter. As a result, the accelerated cyclic softening and decelerated stress relaxation response of fatigue-creep interaction was finely reproduced by the proposed model. [ABSTRACT FROM AUTHOR]

Cyclic softening behavior of modified 9–12%Cr steel was investigated at 873 K under different loading modes and stress levels. Results indicated that two domains were identified depending on the plastic strain level, in which cyclic deformations and control modes were different. Significant different cyclic softening was only observed in the macroplasticity domain at high loading levels between stress and strain controlled fatigue, companied with a relatively homogenous coarsening of subgrain. By contrast, in the microplasticity domain at low loading levels, slight cyclic softening was attributed to the fact that back stress remained a relative stable value (or decreased very slightly). An additional back stress component was produced due to the heterogeneous subgrain coarsening at the inter-packet scale. As a result, the cyclic softening was retarded due to the competition between the hardening of inter-packet back stress and the softening of intragranular back stress. [ABSTRACT FROM AUTHOR]

Effect of inhomogeneous microstructure of a CrMoV multi-pass weld metal on creep behavior was investigated experimentally. Four subzones in the multi-pass weld metal were identified in terms of the grain size and morphology. Compared to the micro-hardness and tensile strength, a remarkable different creep behavior was achieved for different subzones. Especially, the heterogeneous creep deformation was observed during the tertiary creep stage. Such a heterogeneous creep behavior of multi-pass weld metal was ascribed to the coupling effect of inhomogeneous microstructure and loading direction. [ABSTRACT FROM AUTHOR]

Lamb wave propagating behavior in woven glass fiber reinforced epoxy (WGF/epoxy) composite laminates was studied by simulation and experiment. A 3D finite element (FE) model was built in Abaqus/Explicit software with the help of user material subroutine to capture the wave propagating features in WGF/epoxy composite plate. The Lamb wave tests were carried out by a non-circular array with 8 piezoelectric (PZT) wafers. A defect imaging algorithm was developed using MATLAB based on the ellipse theory in time-dependent domains. Two defect imaging cases were carried out in the WGF/epoxy composite plate to verify the feasibility of the proposed algorithm. A good agreement between the simulated waveforms and experimental data was achieved. This indicates a great potential of the proposed algorithm in the field of damage localization and identification for WGF/epoxy thin-walled laminates. [ABSTRACT FROM AUTHOR]

Fatigue tests of 9–12% Cr ferrite steel with various hold times at both peak and valley points were conducted under stress control at 898 K. The role of anelastic recovery in the creep-fatigue interaction was discussed systematically. Results indicate that anelastic strain increases primarily with the cycle increase and then decreases slowly until the specimen failed during the unloading process. By contrast, the kinetics of anelastic recovery decreases during the unloading process while is insensitive to the peak stress and hold time at the early stage. In addition, the creep-fatigue (cyclic creep) interaction is much decelerated due to the anelastic recovery compared to the static creep state. A modified life prediction model is developed accordingly under the frame of ductility exhaustion concept by incorporating the effect of anelastic recovery. A good agreement with the experimental data is achieved and thus provides us confidence in the use of the modified model in practice. [ABSTRACT FROM AUTHOR]

Axially loaded push-pull tests of a low strength Cr−Ni−Mo−V steel welds using cross-weld specimens with different sizes were conducted up to the very high cycle fatigue regime under ultrasonic frequency. Results showed that smaller samples had higher fatigue strength with interior cracking predominant at the weld metal. Fine granular area characteristic of polycrystalline features close to micro-defects was indicative of higher fatigue strength with implications of cyclic hardening, and was related to localization of plastic deformation. A physical criterion for formation of fine granular area was proposed as the ratio of accumulation to release rates of cyclic plastic energy was higher than one. It was found that the size effect on fatigue strength of the low strength welds was coupled with frequency effect, an issue that both current deterministic and probabilistic approaches were unable to rationalize, was actually dependent on tensile strength as well as extrinsic factors such as cyclic hardening and micro-defect distribution. [ABSTRACT FROM AUTHOR]

The targeted concentration of acoustic waves has significant implications for industrial nondestructive testing, ultrasound diagnosis, and medical treatment. Most conventional sound-focusing metasurfaces suffer from an untunable focus, narrow bandwidth, and fixed geometric configurations, which severely constrain their practical utility. In this paper, we propose a reconfigurable acoustic coding metasurface composed of two coding units with high transmittance and transmitted phases of 0 and π for realizing tunable and broadband sound focusing. Through the straightforward manipulation of each unit structure and alterations in the coding sequences, precise control of the focus position across the entire working plane is attainable, enabling both tunable axial-axis and off-axis sound-focusing effects. Moreover, the sound-focusing performance of the proposed metasurface is excellent within a broad frequency range from 3000 to 5500 Hz. The experimental results are consistent with theoretical expectations and numerical simulations. This work lays a practical foundation for the design of acoustic devices for tunable and broadband sound focusing. [ABSTRACT FROM AUTHOR]

This study presents a compact disk (CD) microfluidic platform for separating human blood plasma from a whole blood sample and then mixing the plasma with a suitable reagent for further analysis purposes. It is shown that the volume of plasma decanted into the plasma reservoir can be precisely controlled through an appropriate control of the disk rotation speed. For example, 0.5 μL of plasma can be deposited in the plasma reservoir by rotating the disk at a speed of 2,600 rpm for 5 s. The performance of three microfluidic CD platforms incorporating square-wave mixing channels with different corner shapes is evaluated both numerically and experimentally. The results show that given the use of a rectangular corner feature and a CD rotation speed of 3,400 rpm, a mixing efficiency of more than 97 % can be obtained within 5 s. The practical feasibility of the proposed platform is demonstrated by performing prothrombin time (PT) tests using whole blood samples acquired from 20 healthy male donors. It is shown that the mean time required to complete the entire PT test (including separation, decanting, mixing and coagulation) is less than 4 min. [ABSTRACT FROM AUTHOR]

The overexpression or abnormal activation of cyclo-oxygenase-2 (COX-2) has been reported in pancreatic cancer cells. NS-398, a selective inhibitor of COX-2, is unable to inhibit pancreatic cancer cell proliferation, as determined by a Cell Counting Kit 8 assay. However, it does increase cancer cell invasiveness, and therefore the invasiveness of the PANC-1 cells was determined, along with the activation of P38, which was assessed by western blotting. In the present study, to evaluate the mechanisms underlying the action of NS-398 in pancreatic cancer cells, PANC-1 cells were treated with NS-398, and the invasion signaling pathways of cluster of differentiation (CD)147-matrix metalloproteinase (MMP)-2 and mitogen-activated protein kinases were evaluated. The results showed that NS-398-induced the expression of CD147 and MMP-2 via the activation of P38, which was involved in antiproliferative activity and induced pancreatic cancer cell invasiveness. The PANC-1 cells were also co-treated with CD147 small interfering (si)RNA and NS-398, and it was found that the NS-398-induced activation of P38 was not inhibited by CD147 siRNA, however, the expression of MMP-2 was inhibited. CD147 siRNA inhibited the invasiveness of the pancreatic cancer cells induced by NS-398, but also restored NS-398-induced antiproliferative activity. These data indicated that P38 in the pancreatic cancer cells was non-specifically activated by NS-398. This activation induced the expression of CD147-MMP-2, opposed the antiproliferative activity of NS-398 and increased the invasiveness of the PANC-1 cells. [ABSTRACT FROM AUTHOR]

Using the reactive molecular dynamic simulation, the surface roughness and oxide layer morphology are studied during the early oxidation of polycrystalline copper under applied tensile strains at 900 K. We find that the surface roughness of oxide layer increases with the formation and growth of oxide islands. The transformation of oxide wetting layer to the island structure occurs as a result of atom diffusion triggered by the oxidation-induced growth stress. Such a transformation process is enhanced by promoting the free energy of copper atoms, especially along the grain boundary when the external tensile strain is applied. This new insight provides a fundamental interpretation of the instability of oxide layer and the origin of surface defects under applied tensile loadings. [ABSTRACT FROM AUTHOR]

Symmetrical and asymmetrical strain cycling tests of X12CrMoWVNbN10-1-1 steel were conducted at 873 K. Significant rate dependence, mean stress relaxation and continuously cyclic softening behavior were observed during the fatigue process. In addition, a strain-amplitude dependent competition between cyclic softening and mean stress relaxation was revealed. When the strain amplitudes were larger than the initial plastic point, the cyclic softening was dominated with a rapidly relaxed mean stress and a significantly altered hysteresis loop during the primary cycles. Whilst for the strain amplitudes being less than the initial plastic point, the continuously relaxed mean stress with unclearly altered hysteresis loops was observed during the whole lifetime. Accordingly, a new cyclic viscoplastic constitutive is proposed through the combination of a new nonlinear kinematic hardening rule and the Abdel-Karim–Ohno model. The strain-amplitude dependent cyclic softening and mean stress relaxation behavior were finely reproduced by the proposed model, which was achieved by introducing a mean stress relaxation parameter as a function of the maximum plastic strain and the accumulated cyclic plastic strain. [ABSTRACT FROM AUTHOR]

Welding residual stress relaxation and migration behavior in the welded turbine rotor was studied by using thermal elastic–plastic finite element method under the fatigue and creep loadings. The effect of solid-state phase transformation on the generation of residual stress during welding process was involved. Results reveal that the increase of welding pass number will reduce the peak of residual stress and the width of heat affected zone (HAZ). Under the repeated loadings, the welding residual stress is largely released after the first cycle of start-up and shut-down with a residence time. In addition, such a relaxation mainly depends on the temperature, the initial level of residual stress and the residence time of steady operation. Compared to the contribution of alternating load induced during the start-up and shut-down operation, the relaxation of residual stress is mainly ascribed to the creep mechanism. [ABSTRACT FROM AUTHOR]

The present study proposes a simple lab-on-CD device in which the plasma is first separated from the whole human blood, then divided into two samples of equal volume, and finally decanted into a detection chamber for analysis purposes. The performance of the proposed device is then evaluated using blood samples with hematrocrit concentrations ranging from 6 to 48 %. The results show that for a blood sample with a hematocrit concentration of 6 %, a separation efficiency of 96 % can be achieved within 5-6 s. Moreover, the two plasma samples collected from the left and right branches of the optimized Y-shaped splitter network differ in volume by no more than 0.5 nL. It is shown that the volume of plasma decanted into the detection chamber can be precisely controlled through an appropriate manipulation of the disk rotation speed. Finally, the practical feasibility of the proposed device is demonstrated by performing a creatinine test, the linear dynamic range show that it can be used for creatinine detection in blood assay. In this study, systematical evaluation on the functionality and performance of such a device has been done. The merits of this device are its low cost, straightforward fabrication process, low sample consumption, and high portability. [ABSTRACT FROM AUTHOR]

Cyclic microindentations were performed on the occlusal surface and axial section of tooth enamel, using the Berkovich indenter. Under the action of a cyclic indentation load, the indenter continuously penetrated into the tooth enamel and reached a quasi-steady state at which the penetration depth per cycle was a constant. At the quasi-steady state, both the amplitude of the indentation depth and the penetration depth per cycle for the cyclic indentation of the axial section are larger than those for the indentation of the occlusal section under the same loading condition. The energy dissipation per cycle consists of two contributions; one is the plastic energy dissipated per cycle due to the propagation of the plastic zone underneath the indentation and the other is the energy dissipation due to the viscous flow during the cyclic indentation. Both the penetration depth and the plastic energy dissipated per cycle at the quasi-steady state are independent of the maximum applied load and increase with increasing the amplitude of the cyclic indentation load. [ABSTRACT FROM AUTHOR]

The current state of influence of load ratio, R , on fatigue crack growth (FCG) behavior is thoroughly reviewed. Two main approaches, including crack closure concept and driving force parameter method, when used independently, are found to be short of accuracy during load-shedding procedure in the near-threshold regime. By combining an equivalent driving force model and crack closure approach, a new crack opening equation and a general FCG law is established for the load-shedding technique. This merging method does not involve crack closure measurement, and is capable to predict R dependence of FCG curves and fatigue thresholds fairly well. [ABSTRACT FROM AUTHOR]

Using reactive molecular dynamic simulation, the diffusion behavior of oxygen ions is studied during the oxidation of Fe (1 0 0) under applied tensile strains at room temperature. We find that the strain induced changes of the oxide structure lead to the change of the oxygen diffusion coefficient. This is supported by the comparative analysis of diffusion energy barrier in the corresponding oxide structure. Compared with the effect of the diffusant concentration (composition) and oxidation growth stresses, the evolution of oxide structure plays a dominant role on the change of diffusion coefficient in the strain-reaction engineering. [ABSTRACT FROM AUTHOR]

Micro-tensile tests based on small-scale specimens were carried out to investigate the microstructure dependence of strain hardening behavior along a Ni–Cr–Mo–V steel welded joint. Results indicated the weld metal (WM) had higher tensile strength but lower strain hardening exponent than base metal (BM), whereas a gradient distribution of strain hardening exponents was observed within the heat-affected zone (HAZ). Bainitic microstructures showed weaker strain hardening capacity than lathy martensites. A Kocks–Mecking type plot of strain hardening rate versus true stress presented at least two hardening stages (stages III and IV) with varied duration along the whole welds. Larger grain size and more lathy martensites were beneficial to prolong the hardening period. A new strength prediction model was developed by considering the size effect on tensile strength. The predicted strength distributions along the welds were in good agreement with experimental data. [ABSTRACT FROM AUTHOR]

Crack closure and opening behavior of physically short fatigue crack tip was investigated in microstructures with different grain sizes by using the in-situ SEM fatigue test. A gradually decreased crack closure zone near the crack tip was observed which depended on the microstructures, crack size and stress levels. A new parameter involving the load level, grain size, specimen dimensions and crack length was proposed to interpret the physically short crack closure development. The contribution of the gradient crack closure zone on the physically short fatigue crack growth behavior was evaluated by using the modified partial crack closure model. A generalized fatigue crack growth driving force was finally determined and correlated well with the physically short crack growth rate. [ABSTRACT FROM AUTHOR]

An efficient enantioselective [3+2] cycloaddition of alkynes with oxiranes via selective C-C bond cleavage of epoxides was developed. A number of optically active 2,5-dihydrofurans were obtained in excellent yields (up to 99%) and enantioselectivities (up to 95% ee) under mild reaction conditions. Moreover, chiral tetrahydrofuran could also be obtained by cycloaddition of alkene and oxirane or hydrogenation of chiral 2,5-dihydrofuran. [ABSTRACT FROM AUTHOR]

Tooth enamel is often subjected to repeated contact and often experiences contact deformation in daily life. The mechanical strength of the enamel determines the biofunctionality of the tooth. Considering the variation of the rod arrangement in outer and inner enamel, we approximate enamel as a bilayer structure and perform finite element analysis of the cyclic indentation of the bilayer structure, to mimic the repeated contact of enamel during mastication. The dynamic deformation behaviour of both the inner enamel and the bilayer enamel is examined. The material parameters of the inner and outer enamel used in the analysis are obtained by fitting the finite element results with the experimental nanoindentation results. The penetration depth per cycle at the quasi-steady state is used to describe the depth propagation speed, which exhibits a two-stage power-law dependence on the maximum indentation load and the amplitude of the cyclic load, respectively. The continuous penetration of the indenter reflects the propagation of the plastic zone during cyclic indentation, which is related to the energy dissipation. The outer enamel serves as a protective layer due to its great resistance to contact deformation in comparison to the inner enamel. The larger equivalent plastic strain and lower stresses in the inner enamel during cyclic indentation, as calculated from the finite element analysis, indicate better crack/fracture resistance of the inner enamel. [ABSTRACT FROM AUTHOR]

Abstract: Tooth enamel is a complex structure, consisting of numerous enamel rods surrounded by a protein-rich sheath. Considering the possible effect of the protein-rich sheath on the indentation deformation of an enamel rod and the limitation of the Oliver–Pharr method in measuring the elastic modulus of the enamel rod, we used a finite element method to analyze the indentation deformation of an elastic-perfectly plastic cylinder surrounded by an elastic-perfectly plastic film. A concept of the threshold indentation depth was proposed, at which the percentage error of the measured modulus of the cylinder is ±10%. For the indentation depth less than the threshold indentation depth, the elastic modulus measured from the indentation test can be approximated as the intrinsic elastic modulus of the cylinder. The normalized threshold indentation depth strongly depends on the modulus ratio of the film to the cylinder and the ratio of the film thickness to the cylinder radius. The results can be used to guide the use of the Oliver–Pharr method in characterizing the mechanical properties of tooth enamel and bio-composites with core-shell structures. [Copyright &y& Elsevier]

Abstract: Using nonlinear Rayleigh waves, the effect of surface scratches on the propagation of nonlinear ultrasonic waves in a glass plate was investigated. The results showed that the amplitudes of the fundamental and second harmonics of the nonlinear Rayleigh waves decreased with increasing average width of surface scratches due to the interaction between scratch-induced cracks and wave propagation. The increase of the nonlinearity with the average scratch width suggests that the surface scratches caused the decrease of apparent Young's modulus near the glass surface. Nonlinear Rayleigh surface waves could be a potential method for the quantitative and rapid measurement of surface and subsurface damage in brittle materials. [Copyright &y& Elsevier]

Abstract: It was still short of generalized fatigue crack growth (FCG) models in the near-threshold regime due to its complex influencing factors. The near-threshold FCG behaviour of a rotor steel 25Cr2Ni2MoV at different load ratios was investigated experimentally, and the FCG driving mechanism was theoretically analysed based on equivalent driving force model. It was found that the crack growth process was determined by combined effects of equivalent driving force at constant amplitude loading and crack closure. A new crack closure model was proposed by considering the influences of load ratio and FCG rate, which could successfully interpret the effect of load ratio on FCG. The correlation of the crack closure model with the transition of driving forces in crack advance was beneficial to unify crack closure theory and crack growth driving parameters in the near-threshold regime. [Copyright &y& Elsevier]

Abstract: Shakedown behavior of multilayered beams under cyclic thermo-mechanical loadings was analyzed based on Armstrong–Fredrick nonlinear kinematic hardening model coupled with ductile damage. The shakedown limit loads were determined by the accumulation of plastic straining after enough cycles under various loading combinations and presented by the Bree-like diagram. The effects of the thickness ratio of film/substrate as well as damage parameters on shakedown behavior were also addressed. The calculated results indicated that the twice yield stress limit for shakedown evaluation is considerable conservative compared with the shakedown domain obtained by nonlinear kinematic hardening model. However, shakedown limit loads decreases remarkably considering the ductile damage and the twice yield stress limit for shakedown estimation may be unsafe for engineering designs, especially when the thermal load is prominent. [Copyright &y& Elsevier]

It is known that fine granular area morphology is often formed around interior micro‐defect in the case of very high cycle fatigue failure of high strength steel. The mechanism of "fragmentation of martensitic laths and formation of dislocation cells" (Zhu's model), which revealed a microstructure‐dependent crack initiation and early growth for micro‐defect induced internal fatigue cracking, was discussed in several lathy martensitic or similar steels, verified under environmental fatigue, and applicable to white etching crack in rotating contact fatigue. A machine learning‐Z parameter integrated approach was developed for fatigue life, which is promising for design against fatigue of engineering structures for long life. Highlights: The FGA model of martensitic steels in air (Zhu's model) was illustrated.Zhu's model was confirmed in environmental media and similar steels.Zhu's model was applicable to white etching crack in rotating contact fatigue.Machine learning‐Z parameter was integrated for fatigue life prediction. [ABSTRACT FROM AUTHOR]

Abstract: Very high cycle fatigue (VHCF) behavior of a low strength weldment was investigated by fully reversed axial tests in air at room temperature and 370°C. The role of non-metallic inclusions in the VHCF was addressed in terms of experimental results and finite element simulations. The higher potential for interior crack nucleation at higher temperature was ascribed to matrix softening, surface oxidation and surface compressive residual stress. A new model for interpretation of the role of inclusion in the transition of crack initiation modes was developed. [Copyright &y& Elsevier]

Abstract: In-situ nanoscratch experiments were carried out on occlusal surface and axial section (on which axis is perpendicular to rods and axis parallels to rods, respectively) of human enamel using a sphero-conical indenter (∼1μm tip radius) at different normal loads. The elastic recovery and inelastic deformation during scratching process was evaluated in terms of three curves along the track: surface roughness, scratch depth, and post depth. Coefficient of friction (COF) and wear rate was addressed for the single rod. Results reveal that the amount of elastic recovery and inelastic deformation of a single rod on the axial section is more than that on the occlusal surface. At the enamel rod scale, COF depends on loads and locations. The wear resistance of a single rod on the occlusal surface is greater than that at direction of axis perpendicular to rods and axis parallel to rods. The load-dependence is attributed to the ploughing and pile-up. The location-dependence is ascribed to the angle change of normal loading direction, hydroxyapatite crystals orientation and the scratching direction. In addition, viscoelastic protein layers between the apatite crystals play an important role in the anisotropic wear behavior at microscale. [Copyright &y& Elsevier]

Abstract: Very high cycle fatigue (VHCF) tests at 370°C were carried out for a Cr–Mo–V steel to investigate the influence of microstructure and microdefects on fatigue behavior. Duplex S–N curves were obtained with the crack initiation switched from specimen surface to interior. A new elliptical type of fish-eye pattern originated from microstructure heterogeneities was observed. In the high cycle fatigue regime, the influence of microstructures on fatigue performance was greater than that of microdefects. In the VHCF regime, by contrast, the fatigue performance was dominated by inclusions and could be interpreted by using the proposed life controlling parameter Z. [Copyright &y& Elsevier]

RhoA has been shown to play a major role in vascular processes and acetylsalicylic acid (aspirin) is known to exert a cytoprotective effect via multiple mechanisms. In the present study, we aimed at investigating the effect of aspirin on RhoA expression under a stress state in rat VSMCs (vascular smooth muscle cells) and the underlying mechanisms. The expression of iNOS (inducible nitric oxide synthase) and iNOS activity as well as NO concentration was significantly promoted by LPS (lipopolysaccharide) accompanying the elevation of RhoA expression, which was blocked by the addition of the iNOS inhibitor L-NIL [L-N6-(1-iminoethyl)lysine dihydrochloride]. Aspirin (30 μM) significantly attenuated the elevation of RhoA, while indomethacin and salicylate had no similar effect. The sGC (soluble guanylate cyclase) inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one) showed the same effect as aspirin in down-regulating RhoA but was reversed by the addition of the cGMP analogue 8-Br-PET-cGMP (β-phenyl-1,N²-ethano-8-bromoguanosine 3',5'-cyclic monophosphorothioate). 8-Br-PET-cGMP solely enhanced the RhoA expression that was abrogated by preincubation with aspirin. Degradation analysis indicated that aspirin enhanced the protein degradation rate of RhoA and GDP-bound RhoA seemed to be more susceptible to aspirin-enhanced degradation compared with the GTP-bound form. Our results indicate that aspirin attenuates the LPS-induced overexpression of RhoA both by inhibiting new synthesis and accelerating protein degradation, which may help elucidate the multiple beneficial effects of aspirin. [ABSTRACT FROM AUTHOR]

Abstract: In order to reveal the physical mechanisms of ratchetting process under creep–fatigue loadings, following ratchetting tests in advanced 9–12% chromium ferrite steel, a study of associated fracture modes and dislocation patterns explored by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations is presented in this paper. Two main domains were observed depending both on the peak hold time and on the stress ratio, in which the ratchetting deformation and failure mechanisms were different. These two damage domains correspond to two distinct creep–ratchetting interaction mechanisms. Particular attention was paid to the dependence of ratchetting damage behavior on the stability of dislocation substructure. In addition, an attempt is made to correlate the results of the microstructural investigations with the variations of internal stress. [Copyright &y& Elsevier]

Enterotoxigenic Escherichia coli (ETEC) expressing F4 fimbria is the major pathogenic bacteria causing diarrhoea in neonatal and post-weaning piglets. Previous studies have revealed that the susceptibility to ETEC F4ab/F4ac is an autosomal Mendelian dominant trait and the loci controlling the F4ab/F4ac receptor are located on SSC13q41, between markers SW207 and S0283. To pinpoint these loci and further validate previous findings, we performed a genome-wide association study (GWAS) using a two generation family-based population, consisting of 301 piglets with phenotypes of susceptibility to ETEC F4ab/F4ac by the vitro adhesion test. The DNA of all piglets and their parents was genotyped using the Illumina PorcineSNP60 BeadChip, and 50,972 and 50,483 SNPs were available for F4ab and F4ac susceptibility, respectively, in the association analysis after quality control. In summary, 28 and 18 significant SNPs (p<0.05) were detected associated with F4ab and F4ac susceptibility respectively at genome-wide significance level. From these significant findings, two novel candidate genes, HEG1 and ITGB5, were firstly identified as the most promising genes underlying F4ab/F4ac susceptibility in swine according to their functions and positions. Our findings herein provide a novel evidence for unravelling genetic mechanism of diarrhoea risk in piglets. [ABSTRACT FROM AUTHOR]

Background: The mixed model based single locus regression analysis (MMRA) method was used to analyse the common simulated dataset of the 15th QTL-MAS workshop to detect potential significant association between single nucleotide polymorphisms (SNPs) and the simulated trait. A Wald chi-squared statistic with df =1 was employed as test statistic and the permutation test was performed. For adjusting multiple testing, phenotypic observations were permutated 10,000 times against the genotype and pedigree data to obtain the threshold for declaring genome-wide significant SNPs. Linkage disequilibrium (LD) in term of D’ between significant SNPs was quantified and LD blocks were defined to indicate quantitative trait loci (QTL) regions. Results: The estimated heritability of the simulated trait is approximately 0.30. 82 genome-wide significant SNPs (P < 0.05) on chromosomes 1, 2 and 3 were detected. Through the LD blocks of the significant SNPs, we confirmed 5 and 1 QTL regions on chromosomes 1 and 3, respectively. No block was detected on chromosome 2, and no significant SNP was detected on chromosomes 4 and 5. Conclusion: MMRA is a suitable method for detecting additive QTL and a fast method with feasibility of performing permutation test. Using LD blocks can effectively detect QTL regions. [ABSTRACT FROM AUTHOR]

Background: Lymphocytes act as a major component of the adaptive immune system, taking very crucialresponsibility for immunity. Differences in proportions of T-cell subpopulations in peripheral blood among individuals under same conditions provide evidence of genetic control on these traits, but little is known about the genetic mechanism of them, especially in swine. Identification of the genetic control on these variants may help the genetic improvement of immune capacity through selection. Results: To identify genomic regions responsible for these immune traits in swine, a genome-wide association study was conducted. A total of 675 pigs of three breeds were involved in the study. At 21 days of age, all individuals were vaccinated with modified live classical swine fever vaccine. Blood samples were collected when the piglets were 20 and 35 days of age, respectively. Seven traits, including the proportions of CD4+, CD8+, CD4+CD8+, CD4+CD8-, CD4-CD8+, CD4-CD8- and the ratio of CD4+ to CD8+ T cells were measured at the two ages. All the samples were genotyped for 62,163 single nucleotide polymorphisms (SNP) using the Illumina porcineSNP60k BeadChip. 40833 SNPs were selected after quality control for association tests between SNPs and each immune trait considered based on a single-locus regression model. To tackle the issue of multiple testing in GWAS, 10,000 permutations were performed to determine the chromosome-wise and genome-wise significance levels of association tests. In total, 61 SNPs with chromosome-wise significance level and 3 SNPs with genome-wise significance level were identified. 27 significant SNPs were located within the immune-related QTL regions reported in previous studies. Furthermore, several significant SNPs fell into the regions harboring known immunity-related genes, 14 of them fell into the regions which harbor some known T cell-related genes. Conclusions: Our study demonstrated that genome-wide association studies would be a feasible way for revealing the potential genetics variants affecting T-cell subpopulations. Results herein lay a preliminary foundation for further identifying the causal mutations underlying swine immune capacity in follow-up studies. [ABSTRACT FROM AUTHOR]

Abstract: Synthesis creep test of Sn63Pb37 alloy was conducted under the combination of tensile stress and direct electric current. Results indicate that the steady-state creep strain rate of Sn63Pb37 alloy increases with increasing the electric current and changes more drastically at low stress level than that at high stress level. The stress exponent in power law decreases linearly with increasing the electric current, while the creep activation energy increases with the square of electric current. To illuminate the electromechanical interaction in creep behavior, a modified Arrhenius type model involving the current effect was proposed. [Copyright &y& Elsevier]

Abstract: The closed-form solutions of bending curvature and stress distribution in film/substrate system with the synthesis surface effect are proposed by minimizing the total potential energy. Effects of the roughness and the residual surface stress on stress in film are addressed. Results reveal that, at a given thickness of the substrate, effects of roughness and residual surface stress on the bending curvature become significant with decreasing the film thickness. The roughing surface will enlarge the magnitudes of bending curvature and film stress. The direction change of residual surface stresses can lead to a reversed bending of film/substrate system. [Copyright &y& Elsevier]

Abstract: The ratcheting-creep interaction of advanced 9–12% chromium ferrite steel was tested and simulated under various hold times at 600°C. A constitutive model involving the influence of anelastic relaxation was proposed and agreed very well with the experimental data. Results indicated that when the dwell time at peak load was less than 5-min, the total strain was mainly produced by the ratcheting strain due to the anelastic creep recovery and eventually failed due to ductile-fatigue damage, while for a longer holding time the accumulated creep strain and the fatigue-creep damage were the controlling mechanism of deformation and failure. [Copyright &y& Elsevier]

Abstract: The ratchetting behavior of advanced 9–12% chromium ferrite steel was investigated by cyclic loading tests with various hold times and stress ratios at elevated temperature of 873K. Particular attention was paid to the effect of hold time on the whole-life ratchetting deformation and failure mechanism. Results indicate that the total ratchetting strains under creep-fatigue loading can be decomposed into two parts, i.e., cyclic accumulated creep strain produced during the peak stress hold time , cyclic accumulated inelastic strain produced during the stress change process (). A transition in ratchetting components and rupture behavior with the increase of hold time was observed. In the long hold time domain, a quick shakedown of ratchetting strain occurs after the very first few cycles and the rupture behavior is fully controlled by the time-dependent creep damage. In the short hold time domain, ratchetting strain increases till the specimens fails and a mixed damage mode is responsible for the failure. An attempt is made to explain the existence of these two domains in terms of the evolutions of three internal stress components (back stress, isotropic stress and viscous stress) measured at the end of the holding period. [Copyright &y& Elsevier]