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Micro-/nano-indentation has become prevalent in evaluating the mechanical characteristics of biological samples, such as cells and tissues. However, the existing contact models describing conical indentation ignore the joint effects of surface energy and substrate, and consequently cannot accurately extract the Young's modulus of biological samples deposited on substrate. Through finite element methods, we examine the conical indentation of biological films on substrates while taking surface energy into account. Based on the dimensional analysis, the explicit relationship between load and indentation depth is achieved for films with their moduli varying from 0.001 to 100 times that of the substrate. If the classical Sneddon's model was employed to analyze the load-depth data, the measured modulus could reach 18 times the real modulus for films on harder substrates, but only 4% of the real modulus for films on softer substrates. Meanwhile, in micro-/nano-indentations, neglecting the contribution of surface energy would result in an overestimation of the Young's modulus of films depending on the contact size. The analytical expression provided here can be utilized to precisely deduce the mechanical characteristics of biological films deposited on substrate from the load and indentation depth data of a conical indentation. [ABSTRACT FROM AUTHOR]

Cardiac function requires appropriate proteins in each chamber. Atria requires slow myosin to act as reservoirs, while ventricles demand fast myosin for swift pumping. Myosins are thus under chamber-biased cis-regulation, with myosin gene expression imbalances leading to congenital heart dysfunction. To identify regulatory inputs leading to cardiac chamber-biased expression, we computationally and molecularly dissected the quail Slow Myosin Heavy Chain III (SMyHC III) promoter that drives preferential expression to the atria. We show that SMyHC III gene states are orchestrated by a complex Nuclear Receptor Element (cNRE) of 32 base pairs. Using transgenesis in zebrafish and mice, we demonstrate that preferential atrial expression is achieved by a combinatorial regulatory input composed of atrial activation motifs and ventricular repression motifs. Using comparative genomics, we show that the cNRE might have emerged from an endogenous viral element through infection of an ancestral host germline, revealing an evolutionary pathway to cardiac chamber-specific expression. A complex Nuclear Receptor Element (cNRE) of 32 base pairs that emerged from a viral infection drives the quail Slow Myosin Heavy Chain III (SMyHC III) promoter preferential expression to the atria. [ABSTRACT FROM AUTHOR]

Real contact area plays a critical role in tribology. However, few contact models can give accurate load-area relation at very large contact fraction due to the lack of asperity interactions. In this work, an improved Greenwood–Williamson model is advanced for elastic–plastic rough surfaces. To include the asperity interactions in a simple way, the random distribution of contacting spots is treated as hexagonal distribution, which possesses the same overall isotropic property on surface. A representative asperity is then simulated by finite element method, and the load-area relation is calculated up to almost full contact. It is found that surface morphology and material properties govern the initial linear relationship at small contact fraction, and the interactions among asperities are closely related to contact fraction and lead to a larger load than that neglecting asperity interactions. The load-area relation is further formulated for general rough surfaces by comparing with an incremental equivalent contact model at initial contact. Direct simulations on typical rough surfaces verify the accuracy of the advanced load-area relation within a large range of contact fraction. This result provides a foundation for further analysis of friction, wear and sealing in tribology. [ABSTRACT FROM AUTHOR]

Accurate relation between load and area is of great interest in tribology, especially for large contact fraction, in which the asperity interactions play an import role. The constant mean contact radius obtained in the original Greenwood–Williamson model is adopted in this work; Then, the asperity interactions are dealt with by arranging the random distributed contact spots to hexagon distribution. Finite element simulation is employed to consider only a representative unit with symmetrical boundary conditions, and the corresponding load-area relation is determined up to almost complete contact. For a given contact fraction, interactions induce larger load compared to the GW model without asperity interactions. Furthermore, by comparing with the analytical result given by an incremental contact for small contact fraction, the obtained load-area relation is extended to a general formulation, which shows good agreement with direct finite element simulations. The obtained relations are more general and applicable for a large range of contact fraction. This model provides an efficient method to predict the overall contact response of rough surfaces and reduces the computational burden greatly. [ABSTRACT FROM AUTHOR]

Indentation has become a promising tool to characterize the mechanical parameters of materials. In this work, herein, spherical indentations on elastic‐perfectly plastic materials and strain‐hardening materials are investigated through finite‐element method (FEM) simulations. A new method to extract the yield strength and strain‐hardening exponent from spherical indentation is proposed. The deviation of nominal contact pressure from Hertzian prediction is used as an indicator to determine the plastic parameters. The difference between Hertzian contact pressure and real contact pressure is also investigated for the estimation of contact radius during indentation process. Herein, a more convenient approach is provided in this analysis to directly determine the mechanical parameters of elastic–plastic materials from spherical indentation tests. Validation of this method is presented in the form of a comparison between analytical stress–strain relationships and corresponding curves obtained via iterative FEM simulations of the indentation process. No experimental data are involved in this validation. [ABSTRACT FROM AUTHOR]

HLA‐C*17:69 differs from HLA‐C*17:01:01:02 by one nucleotide in exon 4. [ABSTRACT FROM AUTHOR]

Carbohydrate-binding malectin/malectin-like domain-containing proteins (CBMs) are a recently identified protein subfamily of lectins that participates various functional bioprocesses in the animal, bacterial, and plant kingdoms. However, little is known the roles of CBMs in rice development and stress response. In this study, OsCBM1, which encodes a protein containing only one malectin-like domain, was cloned and characterized. OsCBM1 is localized in both the endoplasmic reticulum and plasma membrane. Its transcripts are dominantly expressed in leaves and could be significantly stimulated by a number of phytohormone applications and abiotic stress treatments. Overexpression of OsCBM1 increased drought tolerance and reactive oxygen species production in rice, whereas the knockdown of the gene decreased them. OsCBM1 physically interacts with OsRbohA, a NADPH oxidase, and the expression of OsCBM1 in osrbohA, an OsRbohA-knockout mutant, is significantly downregulated under both normal growth and drought stress conditions. Meanwhile, OsCBM1 can also physically interacts with OsRacGEF1, a specific guanine nucleotide exchange factor for the Rop/Rac GTPase OsRac1, and transient coexpression of OsCBM1 with OaRacGEF1 significantly enhanced ROS production. Further transcriptome analysis showed that multiple signaling regulatory mechanisms are involved in the OsCBM1-mediated processes. All these results suggest that OsCBM1 participates in NADPH oxidase-mediated ROS production by interacting with OsRbohA and OsRacGEF1, contributing to drought stress tolerance of rice. Multiple signaling pathways are likely involved in the OsCBM1-mediated stress tolerance in rice. [ABSTRACT FROM AUTHOR]

Mixture production equipment is widely employed in road construction, and the quality of the produced mixture is the essential factor to ensure the quality of road construction. To detect the quality of the real-time produced mixture and solve the shortcomings of laboratory detection lag, a new fault detection method in the mixture production process is proposed, which is based on wavelet packet decomposition (WPD) and support vector machine (SVM). The proposed scheme includes feature extraction, feature selection, SVM classification, and optimization algorithm. During feature extraction, wavelet basis function is utilized to 4-layer decompose the aggregate and asphalt data mixed in real-time. The energy value calculated by wavelet packet coefficient is the extracted feature. During feature selection, a method combining the chi-square test and wrapper (CSW) is conducted to select the optimal feature subset from WPD features. Eventually, by adopting the optimal feature subset, SVM has been developed to classify various faults. Its parameters are optimized by differential evolution (DE) algorithm. In the test stage, multiple faults of different specifications of aggregates and asphalt are detected in the mixture production process. The results demonstrate that (1) accuracy produced by the CSW method with WPD features is 4.33% higher than the PCA method with statistical features; (2) SVM classification method optimized by DE algorithm brings an increase in recognition accuracy of identifying different types of mixture production faults produced by different equipment. Compared to other available methods, the proposed algorithm has a very outstanding detection performance. [ABSTRACT FROM AUTHOR]

Xiu-Qing Jing, Wen-Qiang Li and Meng-Ru Zhou have contributed equally to this work Correction to: Rice (2021) 14:100 https://doi.org/10.1186/s12284-021-00541-5 Unfortunately in the original version of the article, the Figure 5D was published incorrectly. The 3,3'-diaminobenzidine (DAB)-stained N. benthamiana leaves were transiently transformed with cMyc (P35S-cMyc), OsCBM1 (P35S-OsCBM1), OsRacGEF1 (P35S-OsRacGEF1), and their combination, respectively. Correction to: Rice Carbohydrate-Binding Malectin-Like Protein, OsCBM1, Contributes to Drought-Stress Tolerance by Participating in NADPH Oxidase-Mediated ROS Production. [Extracted from the article]

Microcantilever-based techniques can be used to explore the autonomy and property of biomolecules (e.g., DNA and single actin filaments) which, in measurement, are adsorbed on the cantilever surface. Here, an energy method is presented to predict the cantilever deflection induced by adsorbed atoms/molecules. The cantilever is modeled as a sandwich beam containing two surface layers of a finite thickness and a bulk layer between them. The adsorptions of O atoms on Si(100) and Hg atoms on Au(100) are taken as two representative examples. We demonstrate that physisorption can induce distinctly different deformation behaviors of cantilevers, which depend not only on the adatoms but also on the substrate material. These results are consistent with relevant experimental observations. This study is helpful for optimal design of microcantilever-based measurement techniques. [ABSTRACT FROM AUTHOR]

We analyze the contribution of couple stresses to the interaction between a screw dislocation and a bi-material interface. Using Fourier integral transforms, we develop analytical representations for the stress distributions in each of the adjoining materials as well as the interaction force acting on the dislocation. Our results are illustrated with several numerical examples, which indicate that couple stresses significantly influence the corresponding stress distributions and the mobility of the dislocation when the distance between the dislocation and the material interface remains below or near the characteristic length of the materials. [ABSTRACT FROM AUTHOR]

Leaf rolling is considered as one of the most important agronomic traits in rice breeding. It has been previously reported that SEMI- ROLLED LEAF 1 ( SRL1) modulates leaf rolling by regulating the formation of bulliform cells in rice (Oryza sativa); however, the regulatory mechanism underlying SRL1 has yet to be further elucidated. Here, we report the functional characterization of a novel leaf-rolling mutant, curled leaf and dwarf 1 ( cld1), with multiple morphological defects. Map-based cloning revealed that CLD1 is allelic with SRL1, and loses function in cld1 through DNA methylation. CLD1/ SRL1 encodes a glycophosphatidylinositol ( GPI)-anchored membrane protein that modulates leaf rolling and other aspects of rice growth and development. The cld1 mutant exhibits significant decreases in cellulose and lignin contents in secondary cell walls of leaves, indicating that the loss of function of CLD1/ SRL1 affects cell wall formation. Furthermore, the loss of CLD1/ SRL1 function leads to defective leaf epidermis such as bulliform-like epidermal cells. The defects in leaf epidermis decrease the water-retaining capacity and lead to water deficits in cld1 leaves, which contribute to the main cause of leaf rolling. As a result of the more rapid water loss and lower water content in leaves, cld1 exhibits reduced drought tolerance. Accordingly, the loss of CLD1/ SRL1 function causes abnormal expression of genes and proteins associated with cell wall formation, cuticle development and water stress. Taken together, these findings suggest that the functional roles of CLD1/ SRL1 in leaf-rolling regulation are closely related to the maintenance of cell wall formation, epidermal integrity and water homeostasis. [ABSTRACT FROM AUTHOR]

Soft membranous materials widely exist in engineering and nature, and the determination of their constitutive parameters is of both scientific and engineering significance. In this paper, the bulge test method is extended to determine the hyperelastic parameters of soft membranes with or without initial stresses. Two extensively applied models-neo-Hookean model and Arruda-Boyce model-are employed to characterize the nonlinear behavior of the membrane under test. The hyperelastic parameters are then extracted from the pressure-deflection curve of the membrane recorded in the bulge tests. Our method is finally validated by both finite element simulations and uniaxial tension experiments. The proposed method can be used to evaluate various soft membranes and tissues and hold promise for numerous applications in such fields as biomedical engineering and bionic engineering. [ABSTRACT FROM AUTHOR]

In this paper, the compression of an isolated cell by two rigid indenters is analyzed. The neo-Hookean model is employed to characterize the hyperelastic behavior of biological cells. Owing to the greatly increased ratio between surface energy density and elastic modulus, surface energy plays important roles in the mechanical performance of biological cells. Using the dimensional analysis method and a finite element approach incorporating surface energy, we study the elastic compression of hyperelastic cells at finite deformation and give the explicit relations of contact radius and indent depth depending on compressive load. Our results reveal that surface energy obviously influences both the local deformation and the overall responses of hyperelastic cells at finite deformation. The obtained results are useful to determine the elastic properties of biological cells from indent-depth curves accurately. [ABSTRACT FROM AUTHOR]

The root-knot nematode (RKN) is one of the most damaging agricultural pests.Effective biological control is need for controlling this destructive pathogen in organic farming system. During October 2010 to 2011, the nematicidal effects of the Syncephalastrum racemosum fungus and the nematicide, avermectin, alone or combined were tested against the RKN (Meloidogyne incognita) on cucumber under pot and field condition in China. Under pot conditions, the application of S. racemosum alone or combined with avermectin significantly increased the plant vigor index by 31.4% and 10.9%, respectively compared to the M. incognita-inoculated control. However, treatment with avermectin alone did not significantly affect the plant vigor index. All treatments reduced the number of root galls and juvenile nematodes compared to the untreated control. Under greenhouse conditions, all treatments reduced the disease severity and enhanced fruit yield compared to the untreated control. Fewer nematodes infecting plant roots were observed after treatment with avermectin alone, S. racemosum alone or their combination compared to the M. incognita-inoculated control. Among all the treatments, application of avermectin or S. racemosum combined with avermectin was more effective than the S. racemosum treatment. Our results showed that application of S. racemosum combined with avermectin not only reduced the nematode number and plant disease severity but also enhanced plant vigor and yield. The results indicated that the combination of S. racemosum with avermectin could be an effective biological component in integrated management of RKN on cucumber. [ABSTRACT FROM AUTHOR]

Due to their superior optical, elastic and electrical properties, chiral nanowires have many applications as sensors, probes, and building blocks of nanoelectromechanical systems. In this paper, we develop a refined Euler–Bernoulli beam model for chiral nanowires with surface effects and material chirality incorporated. This refined model is employed to investigate the bending and buckling of chiral nanowires. It is found that surface effects and material chirality significantly affect the elastic behaviour of chiral nanowires. This study is helpful not only for understanding the size-dependent behaviour of chiral nanowires, but also for characterizing their mechanical properties. [ABSTRACT FROM AUTHOR]

When the cross-sectional size of structural elements reduces to nanometers, surface effects become quite important in their mechanical behaviors. In this letter, a theoretical model is proposed to account for surface effects through both surface energy and core-shell model. Through the principle of minimum potential energy, a refined analytical solution is derived for the stiffness of nanosprings. It is shown that surface energy evidently affects the stiffness of nanosprings. The present model provides an efficient tool to analyze the mechanical performance of various nanosized helixes and is also helpful to design nanospring-based devices. [ABSTRACT FROM AUTHOR]

Based on the conventional Euler buckling model, uniaxial compression tests have been utilized recently to measure the mechanical properties of nanowires. However, owing to the increasing ratio of surface area to bulk at nanoscale, the influence of surface energy becomes prominent and should be taken into consideration. In this letter, an analytical relation is given for the critical force of axial buckling of a nanowire by accounting for both the effects of surface elasticity and residual surface tension. This study might be helpful to characterize the mechanical properties of nanowires or design nanobeam-based devices in a wide range of applications. [ABSTRACT FROM AUTHOR]

Surface effects often play a significant role in the physical properties of micro- and nanosized materials and structures. In this letter, the authors presented a theoretical model directed towards investigation of the effects of both surface elasticity and residual surface tension on the natural frequency of microbeams. A thin surface layer was introduced on the upper and lower surfaces to rationalize the near-surface material properties that are different from the bulk material. An explicit solution is derived for the natural frequency of microbeams with surface effects. This study might be helpful for the design of microbeam-based sensors and some related measurement techniques. [ABSTRACT FROM AUTHOR]

The atomic force microscopy (AFM) has been widely used to measure the mechanical properties of biological cells through indentations. In most of existing studies, the cell is supposed to be linear elastic within the small strain regime when analyzing the AFM indentation data. However, in experimental situations, the roles of large deformation and surface tension of cells should be taken into consideration. Here, we use the neo-Hookean model to describe the hyperelastic behavior of cells and investigate the influence of surface tension through finite element simulations. At large deformation, a correction factor, depending on the geometric ratio of indenter radius to cell radius, is introduced to modify the force-indent depth relation of classical Hertzian model. Moreover, when the indent depth is comparable with an intrinsic length defined as the ratio of surface tension to elastic modulus, the surface tension evidently affects the indentation response, indicating an overestimation of elastic modulus by the Hertzian model. The dimensionless-analysis-based theoretical predictions, which include both large deformation and surface tension, are in good agreement with our finite element simulation data. This study provides a novel method to more accurately measure the mechanical properties of biological cells and soft materials in AFM indentation experiments. [ABSTRACT FROM AUTHOR]