Texture Gradient Research Articles

Soil properties governing phosphorus adsorption in soils of Southern Brazil

Southern Brazil is carachterized by soil classes with contrasting mineralogical composition and chemical behavior that directly affect the P adsortion capacity. This study is a first detailed regional assessment of the main factors (including mineralogical composition, total organic C, and specific surface area) that determine P adsorption in 60 representative soils of southern Brazil under natural vegetation. Most soils showed medium to clay texture. Organic C increased with increasing altitude and rainfall but decreasing temperature. Kaolinite, goethite and hematite were the dominant minerals in the highly weathered soils (Ferralsols and Nitisols), associated with smaller amounts of 2:1 clay minerals, quartz and gibbsite. In soils with a textural gradient (Acrisols, Alisols and one Plinthosol), minerals in the clay fraction consisted of kaolinite and quartz together with lower proportions of Fe oxides, 2:1 clay minerals and mica. The less weathered soils (Cambisols, Chernozems, Vertisols and Luvisols) abounded with kaolinite and 2:1 clay minerals in addition to goethite, ferrihydrite and quartz. P adsorption was positively correlated with clay and organic C content and specific soil surface area. The mineral most strongly influencing P adsorption was gothite, and hematite and gibbsite to a lesser extent.

Radiomic Texture and Shape Descriptors of the Rectal Environment on Post-Chemoradiation T2-Weighted MRI are Associated with Pathologic Tumor Stage Regression in Rectal Cancers: A Retrospective, Multi-Institution Study.

(1) Background: The relatively poor expert restaging accuracy of MRI in rectal cancer after neoadjuvant chemoradiation may be due to the difficulties in visual assessment of residual tumor on post-treatment MRI. In order to capture underlying tissue alterations and morphologic changes in rectal structures occurring due to the treatment, we hypothesized that radiomics texture and shape descriptors of the rectal environment (e.g., wall, lumen) on post-chemoradiation T2-weighted (T2w) MRI may be associated with tumor regression after neoadjuvant chemoradiation therapy (nCRT). (2) Methods: A total of 94 rectal cancer patients were retrospectively identified from three collaborating institutions, for whom a 1.5 or 3T T2w MRI was available after nCRT and prior to surgical resection. The rectal wall and the lumen were annotated by an expert radiologist on all MRIs, based on which 191 texture descriptors and 198 shape descriptors were extracted for each patient. (3) Results: Top-ranked features associated with pathologic tumor-stage regression were identified via cross-validation on a discovery set (n = 52, 1 institution) and evaluated via discriminant analysis in hold-out validation (n = 42, 2 institutions). The best performing features for distinguishing low (ypT0-2) and high (ypT3–4) pathologic tumor stages after nCRT comprised directional gradient texture expression and morphologic shape differences in the entire rectal wall and lumen. Not only were these radiomic features found to be resilient to variations in magnetic field strength and expert segmentations, a quadratic discriminant model combining them yielded consistent performance across multiple institutions (hold-out AUC of 0.73). (4) Conclusions: Radiomic texture and shape descriptors of the rectal wall from post-treatment T2w MRIs may be associated with low and high pathologic tumor stage after neoadjuvant chemoradiation therapy and generalized across variations between scanners and institutions.

Particle size distribution of sediment detached from rills under raindrop impact in semi-arid soils

Limited information is available on the role of raindrop impact (RI) in the particle size distribution of sediment (PSDs) and the homogeneous of sediment particles eroded in rills under slope gradients particularly in semi-arid soils. Toward this, a laboratory experiment was designed with three dominant semi-arid soils consist of loamy sand, clay and sandy clay, at four slope gradients (5, 10, 15, and 20%) under two soil surface conditions (SSC) i.e, with raindrop impact (RI) and without RI using a rainfall simulator with 90 mm h−1 in intensity for 30 min. Forty eight rainfall events were setted up to soil samples packed into the flumes with 0.4 m width by 4 m length. Runoff and sediment ratio for the two SSC was computed using the ratio of values with RI to their values without RI in each time interval from starting runoff. Based on the results, the soils appeared different behavior in runoff and sediment ratio during runoff generation time. In clay and sandy clay, contribution of RI in runoff and sediment increased during runoff generation in the rills which was associated to higher percentage of water-stable aggregates. The two soils produced higher runoff and sediment under RI with increasing slope gradient. The sediment selectivity by concentrated flow was determined using the comparison between PSDs in steady-state runoff and the PSD of original soil (PSDo). The PSDs curves of loamy sand were similar for the two SSC at slope gradients and overlapped almost with the PSDo, indicating lower importance of RI in the sediment transport selectivity in the soil with lower water-stable aggregates. Enrichment ratio of particles in sediment (ERs) varied with both soil texture and slope gradient. The contribution of RI in variation of ERs was more obvious in sand, indicating lower selectivity of sand to detachment by concentrated flow. The geometric mean diameter (dg) and standard deviation (δg) of the sediment particles were defined as a measure to determination of the homogeneity of sediment. Values of these indices increased under RI, indicating the contribution of RI in the transportability of all soil particles especially coarse particles. This study revealed that the RI is the major factor controlling runoff, sediment, the selectivity of soil particle by concentrated flow and sediment homogeneity in semi-arid soils. These variables can be quantified by PSDs, ERs, dg and δg for the two soil surface conditions and compared with the original soil.

Crystal Plasticity Analysis of the Relation between Micro‐Texture and Surface Ridging for a 21%Cr Ferritic Stainless Steel

The micro‐texture of ferritic stainless steel generated by rolling and annealing processes is supposed to behave plastic anisotropy and heterogeneous strain response during forming, especially for the high Cr content ferritic stainless steel with single ferrite phase. The relation between crystallographic orientations and their strain responses during loading are analyzed for a 21% Cr ferritic stainless steel sheet. The crystallographic orientation distributions in surface and center layers as well as in cross section are characterized by an electron backscatter diffraction (EBSD) method. It indicates that texture gradients along thickness with center layer having a higher density of <111>//ND texture are formed. Some grain clusters with similar oriented grains gathering together to be parallel to the rolling direction are observed. Then, the experimental orientation distributions are condensed and incorporated into a developed crystal plasticity finite‐element model (CPFEM), in which the multiple slip systems and the interaction between neighbor grains are considered. The simulation results confirm that the heterogeneous distributions of normal strain and shear strain preserved for the different crystal orientation grains result in the surface ridging. The texture gradients can help to decrease the tendency of surface ridging. The simulation results show a reasonable agreement with the tensile test results.

Experimental verification of a crystal plasticity-based simulation framework for predicting microstructure and geometric shape changes: Application to bending and Taylor impact testing of Zr

This paper is concerned with experimental verification of a recently developed multi-scale simulation framework for plastic deformation of metallic materials from quasi-static to impact deformation conditions. The framework is a visco-plastic self-consistent (VPSC) polycrystalline model embedded in an implicit finite element method (FE-VPSC) to provide a microstructure-sensitive constitutive response at each material point. Each material point of the FEM model is a polycrystalline aggregate with crystallographic deformation mechanisms operating at the single crystal scale with their evolving activity based on a dislocation density-based hardening law and texture. Four beams and three cylinders machined in different orientations from a textured plate of high-purity zirconium are tested quasi-statically in 4-point bending and at speeds of 100 m/s, 170 m/s and 243 m/s during Taylor impact tests, respectively. The variation in dimensional changes resulting from different sample orientations in the plate with respect to loading directions is measured for each sample. Moreover, texture and twinning characterization is performed using electron backscattered diffraction (EBSD). The deformation processes and underlying evolution of microstructure are successfully simulated using the FE-VPSC framework. In doing so, the model parameters are optimized and validated across a broad range of strain rates and temperatures. Simulation results in terms of geometrical changes and microstructural evolution are compared with the experimental measurements. The model predicts anisotropic material flow resulting from the hard-to-deform crystallographic directions, the development of gradients in texture and twinning through the geometries, tension–compression asymmetry, as well as the extent of plasticity under impact.

Infrared and visible image fusion via gradientlet filter

In this paper, we propose an image filter based on fuzzy gradient threshold function and global optimization, termed as gradientlet filter, from the perspective of luminance and gradient separation. It can remove small gradient textures and noise while maintaining the overall brightness and edge gradients of an image. Based on gradientlet filter and image saliency, we further put forward a new method for infrared and visible image fusion, which can overcome the challenges of low contrast, edge blurring and noise existing in traditional fused images. First, the gradientlet filter is used to decompose source images into approximate layers and residual layers, where the former reflects the overall brightness of source images without edge blurring and noise, and the latter reflects the small gradient texture and noise of source images. Second, according to the characteristics of the approximate and residual layers, we propose contrast and gradient saliency maps and construct corresponding weight matrices. Finally, the fused image is obtained by fusion and reconstruction based on previously obtained sub-images and weight matrices. Extensive experiments on publicly available databases demonstrate the advantages of our method over state-of-the-art methods in terms of maintaining image contrast, improving target saliency, preventing edge blurring, and reducing noise.

Rooting depth as a key woody functional trait in savannas.

Dimensions of tree root systems in savannas are poorly understood, despite being essential in resource acquisition and post-disturbance recovery. We studied tree rooting patterns in Southern African savannas to ask: how tree rooting strategies affected species responses to severe drought; and how potential rooting depths varied across gradients in soil texture and rainfall. First, detailed excavations of eight species in Kruger National Park suggest that the ratio of deep to shallow taproot diameters provides a reasonable proxy for potential rooting depth, facilitating extensive interspecific comparison. Detailed excavations also suggest that allocation to deep roots traded off with shallow lateral root investment, and that drought-sensitive species rooted more shallowly than drought-resistant ones. More broadly across 57 species in Southern Africa, potential rooting depths were phylogenetically constrained, with investment to deep roots evident among miombo Detarioids, consistent with results suggesting they green up before onset of seasonal rains. Soil substrate explained variation, with deeper roots on sandy, nutrient-poor soils relative to clayey, nutrient-rich ones. Although potential rooting depth decreased with increasing wet season length, mean annual rainfall had no systematic effect on rooting depth. Overall, our results suggest that rooting depth systematically structures the ecology of savanna trees. Further work examining other anatomical and physiological root traits should be a priority for understanding savanna responses to changing climate and disturbances.

Design and Implementation of Shape and Texture Based Image Segmentation on Morphological Gradient Approach

Identifying and separating objects within an image is a significant challenge due to high object and background variability. This can be obtained through feature extraction approach. There are different ways of extracting the image features. It is based on texture, shape and colour. The present paper aims to study and analyse the various approaches for feature extraction and object recognition. This study proposed a hybrid approach, which is a combination of enhanced Fractal Texture Analysis with Layout Descriptor to overcome the obstacles in image segmentation. It is used to lessen the boundary complexity of the segmented image. First, the image is preprocessed to discard the noise and to retain the adequate details of the image in a perfect way through Adaptive Switching Median Filter. Secondly, it improves the power of the edges detected through a noise-protected edge detector. Finally, it is applied with morphological gradient technique that is a twin function of both shape and texture gradient removal for extorting the qualities of the image. In this way, the proposed methodology directly performs on the colour image which supports to enhance prediction accuracy of the object in terms of colour characteristics that offers better results than the grayscale conversion approach. Moreover, the shape feature is extracted from the preprocessed image depending on the details like compactness, rectangularity, eccentricity and moment invariants.

Agroecosystem patterns and land management co‐develop through environment, management, and land‐use interactions

AbstractA poor understanding of the interactions between biophysical and social elements within rural mountainous landscapes can lead to suboptimal management and recommendations. The objective of this study was to contribute to more contextualized natural resource management in a rural landscape in the Ecuadorian Andes by (1) identifying biophysical patterns in soil properties, biodiversity, and C stocks that emerge from natural landscape pedogenic processes, resulting from elevation‐induced climate gradients, erosion and soil textural patterns, and (2) assessing farm management and land‐use effects on and their interactions with these biophysical patterns. Our findings revealed that the climate and soil texture gradients within the landscape led to an exponential increase in SOC with elevation moderated by slope gradient, indicating significant erosion processes. Farmers adapted their farm management according to the observed environmental patterns creating three distinct management zones. Differentiated agricultural management in these zones and asymmetrical distribution of land‐uses in turn were observed to significantly influence soil and agroecosystem properties. For example, available P was found to be significantly higher in the upper and middle agricultural management zones (24.0 and 28.7 mg/kg, respectively), where agricultural inputs were higher compared to the lower agricultural management zone (8.9 mg/kg, P < 0.001). Mixed hedgerows, on the other hand, displayed significantly higher Shannon index scores for ground vegetation (1.8) and soil macrofauna (2.0) compared to agricultural land‐uses (1.0 and 1.7). Our results provide important insights into how agroecosystem patterns and land management co‐developed through complex environment, management, and land‐use interactions.

Dependence of mechanical properties on microstructure of high-textured pyrocarbon prepared via isothermal and thermal gradient chemical vapor infiltration

In order to explore the dependence of mechanical properties on the microstructure of high-textured (HT) pyrolytic carbon (PyC), the microstructure and properties of HT PyC specimens prepared by isothermal isobaric chemical vapor infiltration (ICVI) and thermal gradient chemical vapor infiltration (TCVI) processes were investigated. The HT PyC of ICVI was uniform and exhibited a more distinct long-range order compared to that of TCVI. Besides, a spatial gradient in texture existed within the HT PyC of TCVI, demonstrating the micro-nonuniformity of the whole matrix. The orientation angle (OA) of HT layers in TCVI increased gradually from the fiber surface to outside, whereas the OA of HT layers in ICVI with better microcrystalline was nearly similar. According to the results of three-point bending and micro-indentation, the flexural strength, interfacial fracture strength, and micro-hardness of TCVI specimens were slightly higher than those of ICVI specimens. Furthermore, the residual thermal stress distribution of TCVI specimens was complex owing to the spatial gradient in temperature of TCVI process, while the residual thermal stress distribution of ICVI specimens was relatively uniform. This work provides meaningful guidance for the process selection and industrial applications of C/C composites.

Syn-deformational melt percolation through a high-pressure orthogneiss and the exhumation of a subducted continental wedge (Orlica-Śnieżnik Dome, NE Bohemian Massif)

High-pressure granitic orthogneiss of the south-eastern Orlica–Śnieznik Dome (NE Bohemian Massif) shows relics of a shallow-dipping foliation, reworked by upright folds and a mostly pervasive N–S trending subvertical axial planar foliation. Based on macroscopic observations, a gradual transition from banded to schlieren and nebulitic orthogneiss was distinguished. All rock types comprise plagioclase, K-feldspar, quartz, white mica, biotite and garnet. The transition is characterized by increasing presence of interstitial phases along like-like grain boundaries and by progressive replacement of recrystallized K-feldspar grains by fine-grained myrmekite. These textural changes are characteristic for syn-deformational grain-scale melt percolation, which is in line with the observed enrichment of the rocks in incompatible elements such as REEs, Ba, Sr and K suggesting open-system behaviour with melt passing through the rocks. The P–T path deduced from the thermodynamic modelling indicates decompression from ~ 15−16 kbar and ~ 650–740 oC to ~ 6 kbar and ~ 640 oC. Melt was already present at the P–T peak conditions as indicated by the albitic composition of plagioclase in films, interstitial grains and in myrmekite. The variably re-equilibrated garnet suggests that melt content may have varied along the decompression path, involving successively both melt gain and loss. The ~ 6–8 km wide zone of vertical foliation and migmatite textural gradients is interpreted as vertical crustal-scale channel where the grain-scale melt percolation was associated with horizontal shortening and vertical flow of partially molten crustal wedge en masse.

Chiral Hall Effect in Noncollinear Magnets from a Cyclic Cohomology Approach.

We demonstrate the emergence of an anomalous Hall effect in chiral magnetic textures which is neither proportional to the net magnetization nor to the well-known emergent magnetic field that is responsible for the topological Hall effect. Instead, it appears already at linear order in the gradients of the magnetization texture and exists for one-dimensional magnetic textures such as domain walls and spin spirals. It receives a natural interpretation in the language of Alain Connes' noncommutative geometry. We show that this chiral Hall effect resembles the familiar topological Hall effect in essential properties while its phenomenology is distinctly different. Our findings make the reinterpretation of experimental data necessary, and offer an exciting twist in engineering the electrical transport through magnetic skyrmions.

Soil properties explain tree growth and mortality, but not biomass, across phosphorus-depleted tropical forests

We observed strong positive relationships between soil properties and forest dynamics of growth and mortality across twelve primary lowland tropical forests in a phosphorus-poor region of the Guiana Shield. Average tree growth (diameter at breast height) increased from 0.81 to 2.1 mm yr−1 along a soil texture gradient from 0 to 67% clay, and increasing metal-oxide content. Soil organic carbon stocks in the top 30 cm ranged from 30 to 118 tons C ha−1, phosphorus content ranged from 7 to 600 mg kg−1 soil, and the relative abundance of arbuscular mycorrhizal fungi ranged from 0 to 50%, all positively correlating with soil clay, and iron and aluminum oxide and hydroxide content. In contrast, already low extractable phosphorus (Bray P) content decreased from 4.4 to <0.02 mg kg−1 in soil with increasing clay content. A greater prevalence of arbuscular mycorrhizal fungi in more clayey forests that had higher tree growth and mortality, but not biomass, indicates that despite the greater investment in nutrient uptake required, soils with higher clay content may actually serve to sustain high tree growth in tropical forests by avoiding phosphorus losses from the ecosystem. Our study demonstrates how variation in soil properties that retain carbon and nutrients can help to explain variation in tropical forest growth and mortality, but not biomass, by requiring niche specialization and contributing to biogeochemical diversification across this region.

The Influence of a Novel Inorganic-Polymer Lubricant on the Microstructure of Interstitial-Free Steel during Ferrite Rolling

A novel polyphosphate lubricant was used and evaluated during hot (ferrite) rolling of an interstitial-free (IF) steel. The texture evolution of these rolled IF steels have been examined by means of X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) measurements. The polyphosphate lubricant shows an improved lubrication performance in terms of the texture optimization compared with lubricating oil and with unlubricated conditions. The γ-fiber texture is enhanced, and less shear texture is produced. This microstructure is responsible for enhanced drawability of ferrite rolled IF steels. The very high thermal stability of the polyphosphate enabled its use at very high temperatures (from 700 to 800 °C). Rolling temperature exerted limited influence on the resulting rolling texture evolution. The polyphosphate lubricant stabilizes the surface texture and reduces the gradient of shear texture through the thickness. The in-grain shear bands are reduced significantly (48.5%) compared with the unlubricated condition. Measured grain orientations indicate that the favorable texture of {111}&lt;112&gt; along the γ-fiber is developed while the undesired α-fiber texture of {001}&lt;110&gt; is effectively suppressed.

Quasi-static and dynamic response, and texture evolution of two overaged Al 7056 alloy plates in T761 and T721 tempers: Experiments and modeling

The thermo-mechanical behavior and texture evolution of two overaged Al 7056 alloy plates, in T761 and T721 tempers, are measured over a wide range of strain rates (10−4 – 3 × 103 s−1) and temperatures (22–300 °C) under uniaxial tension and compression along the thickness direction, i.e. normal to the plate surface. A detailed study of the initial microstructure reveals an increase in precipitate size and decrease in density of precipitates, as the alloy is aged from the T761 to T721 temper; which in turn affects the flow stress and strain hardening behavior. Differences in flow strength and strain hardening rate, as well as tension-compression asymmetry in the two tempers, are apparent at the lower temperatures (22 °C & 100 °C) and decrease significantly at the higher temperatures (200 °C & 300 °C). Furthermore, initial texture measurements show a strong texture gradient along the normal direction (ND) of the plate. This texture gradient affects the ultimate stress insignificantly. However, it does have a considerable effect on the failure strains of specimens taken from different locations through the thickness. A transition from shear fracture at and below 200 °C to cup and cone fracture mode above 200 °C is observed in tension. Both tempers exhibit a positive strain rate sensitivity (SRS) that is dependent on temperature and strain rate. A sharp decrease in flow stress is found at 300 °C. The Khan-Liu (KL) model is modified to correlate with the measured thermo-mechanical responses of the two tempers over the studied, wide range of strain rates and temperatures. There is a close correlation between simulated and observed results.

Microstructural evolution of AZ31 Mg alloy with surface mechanical attrition treatment: Grain and texture gradient

Nanocrystalline surface layers and gradient nanostructures are produced in AZ31 Mg alloy through surface mechanical attrition treatment (SMAT). The grain sizes in the surface layer of the alloy are significantly refined to a nanoscale after SMAT. A gradient nanostructure is formed in which the grain size increases gradually from surface to matrix. The microhardness of the surface layer and the tensile strength of the alloy are significantly improved, but with a certain loss of fracture elongation. SEM photographs of tensile fracture of samples after SMAT show that the fractures of the GNS layer are brittle fractures with poor toughness, while the plasticity of the matrix is better, and the fractures exhibit typical ductile features. To investigate the effect of SMAT on the textural evolution of AZ31 Mg alloy, electron backscatter diffraction is used to analyze the as-received sample and samples after SMAT. The non-basal plane orientation is increased and the basal texture is significantly weakened in the fine-grained layer after SMAT. The weakening of the basal texture reduces the anisotropy of the mechanical properties of Mg alloys, which is beneficial for their industrial application.

Preparation of chemically etched surface texture and its friction characteristics in sheet forming

The surface texture of die can reduce friction, and the reasonable texture type can also form oil film on the die surface to save the use of lubricant. In this paper, a method of preparing surface texture on the die by chemical etching is proposed. This paper mainly studies the law of preparation of surface texture by chemical etching and the effect of chemically etched surface texture on die friction. In the experiments, the surface of samples of Cr12 were treated by chemical etching to obtain several groups of surface texture, and the morphology of the chemically etched surface was observed by laser confocal microscope to obtain the characteristics of the surface. Then, four gradients of surface texture with different etching time are selected according to the three-dimensional parameters to obtain the frictional property of samples with chemically etched surface texture using the home-made friction testing machine. Finally, the mechanical rheological model is used to analyze the lubrication state and load-bearing mechanism to prove the results. The results show that the chemically etched surface texture was composed of asperities and pits. The characteristics of surface texture with different etching time show a certain pattern, and the surface of the die had certain hydrophilicity. In addition, the chemically etched surface texture can effectively reduce the friction coefficient between the die and the plate under high load condition (nominal pressure ≥ 32MPa), with an average reduction of 35.6%, a maximum reduction of 49.5% (nominal pressure = 72 MPa, arithmetical mean height of the scale limited surface Sn=1.3.And the analysis results show that the friction coefficient is mainly determined by the area ratio of closed oil pit which was obtained using the image processing technology of MATLAB to verification experiment results. The calculation data and the experiment results are consistent which proves the conclusion.

Genesis and classification of soils from granitic hills in southern Brazil

Southern Brazil abounds with granitic hills capped by intricately distributed soils most of which have been classified as Entisols or Inceptisols in medium- and small-scale soil surveys. However, field observations have revealed substantial texture gradients that are consistent with better-developed soils; also, the physical, chemical and mineralogical properties of the soils suggest that they are only slightly to moderately weathered. In this work, we examined the influence of formation-related factors and processes in soils from two granite toposequences. The eight soil profiles studied for this purpose were shallow, their C horizons occurring at depths of less than 100 cm. The low degree of flocculation and the fine/total clay ratio of the soils suggest that lessivage, which contributed to the development of the texture gradient in six of the profiles, was the main pedogenic process responsible for the formation of these soils. The soils at topographically high points were dystrophic or allitic, whereas those at low points were eutrophic. Based on their Ki values, the soils were weathered to a medium extent, which is in conflict with their low clay activity and cation exchange capacity. On the other hand, the Fed/Fes ratios of the soils were consistent with strong weathering, which in turn was consistent with their pH and exchangeable Al values. The iron oxides contents increased with increasing depth in the profiles as a result of lessivage. Feo/Fed ratios were suggestive of a prevalence of crystalline iron oxides. Increased substitution of Al in Fe oxides in the topographically higher soils further confirmed their increased weathering. Based on the foregoing, the soils were classified as Ultisols/Alfisols, Entisols and Inceptisols, the last series being less frequent than suggested by existing soil surveys. The transitional nature of these soil classes reflected in the presence of Ultisols/Alfisols with a thin B horizon, and also of argilluvic Inceptisols.

The effect of tungsten content on the rolling texture and microstructure of Ta-W alloys

The effect of tungsten content on deformation texture and microstructure of Ta-W alloy is studied. It is found that the increase of tungsten content results in the strengthening of α-fiber and the weakening of γ-fiber in Ta-W alloys. The volume fraction of γ-fiber developed in Ta-10W alloy is lower than that in Ta-2.5W alloys. Meanwhile, a more significant through-thickness texture gradient is formed in Ta-10W alloy. The addition of tungsten has an important effect on the ability cross-slip of dislocations. Therefore, more dislocation loops and activated slip systems can be seen in Ta-2.5W alloy. The size of the dislocation cells in Ta-2.5W alloy is larger than that in Ta-10W alloy. As shear bands tends to appear in γ-fiber, the density of shear bands in the Ta-2.5W alloy is much higher than that of Ta-10W alloy at the same reduction strain. Meanwhile, the wavelength of the wavy shear bands in Ta-10W alloy is smaller than that in Ta-2.5W alloy. In Ta-10W alloy, new grains with Goss orientation can be seen in periodic shear bands developed in {111}<112> orientations, which is different from that in Ta-2.5W alloy.

Responses of soil aggregate stability, erodibility and nutrient enrichment to simulated extreme heavy rainfall

Extreme precipitation regime under global change context is estimated to cause heavy rainstorms and longer drought intervals. Temporal variations of soil structure and erosion characteristics during and after heavy rainstorms were less investigated, particularly across a wide soil texture gradient. In this study, 15 soils were selected with clay content ranging in 12.9–38.2%. Soil erosion characteristics and enrichment ratios of organic carbon (EROC) and nitrogen (ERN) were measured during 3 successive rainfall simulations at slope of 15° and intensity of 120 mm h−1. The water-stable aggregate distribution was measured for soils before and after rainfall and drying. The mean weight diameter (MWD) of water-stable aggregate remained unchanged before (1.476 ± 0.182) and after rainfall and drying (1.406 ± 0.135 mm), but decreased for soils with higher organic carbon contents. Soil erodibility (K factor) averaged in 0.018 ± 0.003, 0.011 ± 0.001 and 0.008 ± 0.001 in 3 successive rainfall events, with 42% and 27% decreases after each event, respectively (P < 0.05); and the decreases were greater for less aggregated soils or coarser textured soils. Stepwise regression showed that the <0.25 mm water-stable aggregate explained most variations of K and its dynamics. The EROC and ERN were close to 1 and were not correlated with clay content or MWD (P > 0.05). The ERN decreased first and then remained stable, and EROC was unchanged during successive rainfalls. These results indicated that soil texture or aggregation status affected soil erodibility and its temporal changes in successive rainstorms.