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In order to grasp the variation law of secondary flow in helical tube, the local intensity and development law of secondary flow in helical tube were studied, and the dimensionless helical intensity H was proposed as the local secondary flow intensity index. By means of numerical simulation, the average volume of H Hm was taken and compared with the Dean number describing the overall secondary flow intensity. The results showed that with different Reynolds number, curvature and pitch, the correlation coefficient between Hm and Dean number was about 1, and there was a good proportional relationship, indicating that H could accurately measure the intensity of local secondary flow. At the same time, the influence of geometric parameters on the development law of secondary flow in the helical tube was explored. According to the intensity of secondary flow, the flow in the helical tube could be divided into development stage, transition stage and stable stage. The secondary flow increased rapidly in the development stage, reached its maximum value in the transition stage, and fluctuated periodically in the stable stage. The increase of Reynolds number could significantly increase the intensity of secondary flow, but could not affect the location of secondary flow three stages. The increase of curvature could slightly increase the intensity of the secondary flow and extend the distance of the secondary flow to the stable stage. The pitch had little influence on the intensity and development of secondary flow. [ABSTRACT FROM AUTHOR]

Monolayer transition‐metal dichalcogenides, e.g., MoS2, typically have high intrinsic strength and Young's modulus, but low fracture toughness. Under high stress, brittle fracture occurs followed by cleavage along a preferential lattice direction, leading to catastrophic failure. Defects have been reported to modulate the fracture behavior, but pertinent atomic mechanism still remains elusive. Here, sulfur (S) and MoSn point defects are selectively created in monolayer MoS2 using helium‐ and gallium‐ion‐beam lithography, both of which reduce the stiffness of the monolayer, but enhance its fracture toughness. By monitoring the atomic structure of the cracks before and after the loading fracture, distinct atomic structures of the cracks and fracture behaviors are found in the two types of defect‐containing monolayer MoS2. Combined with molecular dynamics simulations, the key role of individual S and MoSn point defects is identified in the fracture process and the origin of the enhanced fracture toughness is elucidated. It is a synergistic effect of defect‐induced deflection and bifurcation of cracks that enhance the energy release rate, and the formation of widen crack tip when fusing with point defects that prevents the crack propagation. The findings of this study provide insights into defect engineering and flexible device applications of monolayer MoS2. [ABSTRACT FROM AUTHOR]

Probing large‐scale intrinsic structure of air‐sensitive 2D materials with atomic resolution is so far challenging due to their rapid oxidization and contamination. Here, by keeping the whole experiment including growth, transfer, and characterizations in an interconnected atmosphere‐control environment, the large‐scale intact lattice structure of air‐sensitive monolayer 1T'‐WTe2 is directly visualized by atom‐resolved scanning transmission electron microscopy. Benefit from the large‐scale atomic mapping, collective lattice distortions are further unveiled due to the presence of anisotropic rippling, which propagates perpendicular to only one of the preferential lattice planes in the same WTe2 monolayer. Such anisotropic lattice rippling modulates the intrinsic point defect (Te vacancy) distribution, in which they aggregate at the constrictive inner side of the undulating structure, presumably due to the ripple‐induced asymmetric strain as elaborated by density functional theory. The results pave the way for atomic characterizations and defect engineering of air‐sensitive 2D layered materials. [ABSTRACT FROM AUTHOR]

Probing large‐scale intrinsic structure of air‐sensitive 2D materials with atomic resolution is so far challenging due to their rapid oxidization and contamination. Here, by keeping the whole experiment including growth, transfer, and characterizations in an interconnected atmosphere‐control environment, the large‐scale intact lattice structure of air‐sensitive monolayer 1T'‐WTe2 is directly visualized by atom‐resolved scanning transmission electron microscopy. Benefit from the large‐scale atomic mapping, collective lattice distortions are further unveiled due to the presence of anisotropic rippling, which propagates perpendicular to only one of the preferential lattice planes in the same WTe2 monolayer. Such anisotropic lattice rippling modulates the intrinsic point defect (Te vacancy) distribution, in which they aggregate at the constrictive inner side of the undulating structure, presumably due to the ripple‐induced asymmetric strain as elaborated by density functional theory. The results pave the way for atomic characterizations and defect engineering of air‐sensitive 2D layered materials. [ABSTRACT FROM AUTHOR]

An atomic-scale ripple structure has been revealed by electron tomography based on sequential projected atomic-resolution images, but it requires harsh imaging conditions with negligible structure evolution of the imaged samples. Here, we demonstrate that the ripple structure in monolayer MoSe 2 can be facilely reconstructed from a single-frame scanning transmission electron microscopy (STEM) image collected at designated collection angles. The intensity and shape of each Se 2 atomic column in the single-frame projected STEM image are synergistically combined to precisely map the slight misalignments of two Se atoms induced by rippling, which is then converted to three-dimensional (3D) ripple distortions. The dynamics of 3D ripple deformation can thus be directly visualized at the atomic scale by sequential STEM imaging. In addition, the reconstructed images provide the first opportunity for directly testing the validity of the classical theory of thermal fluctuations. Our method paves the way for a 3D reconstruction of a dynamical process in two-dimensional materials with a reasonable temporal resolution.

Lysosome-relevant cell death induced by lysosomal membrane permeabilization (LMP) has recently attracted increasing attention. However, nearly no studies show that currently available LMP inducers can evoke immunogenic cell death (ICD) or convert immunologically cold tumors to hot. Herein, we report a LMP inducer named TPE-Py-pYK(TPP)pY, which can respond to alkaline phosphatase (ALP), leading to formation of nanoassembies along with fluorescence and singlet oxygen turn-on. TPE-Py-pYK(TPP)pY tends to accumulate in ALP-overexpressed cancer cell lysosomes as well as induce LMP and rupture of lysosomal membranes to massively evoke ICD. Such LMP-induced ICD effectively converts immunologically cold tumors to hot as evidenced by abundant CD8 + and CD4 + T cells infiltration into the cold tumors. Exposure of ALP-catalyzed nanoassemblies in cancer cell lysosomes to light further intensifies the processes of LMP, ICD and cold-to-hot tumor conversion. This work thus builds a new bridge between lysosome-relevant cell death and cancer immunotherapy., (© 2021 Wiley-VCH GmbH.)