解决一维材料黏附行为的实验方法综述

一维(1D)材料(如纳米管和纳米线)的黏附行为在集成一维组件的新型器件以及基于一维阵列的仿生黏合剂的有效制造、功能和可靠性中起着决定性作用。本文汇编并批判性地评估了最近的实验技术,旨在表征由一维材料形成的界面的粘附行为(包括当这些材料与衬底或邻近的一维材料接触时)。讨论了一维材料与表面的构象以及与之相关的多粗糙度接触的发生,并探讨了界面附着和剥离过程中黏附和摩擦的耦合。考虑了一维材料作为增强剂在纳米复合材料中的应用以及相关的界面表征技术。研究了样品制备和黏附测试过程中存在的环境条件对一维界面相互作用的潜在影响,并最终改变了一维材料的粘附行为。最后,简要介绍了当前的挑战和未来的方向,包括测试环境的系统调查和通过表面改性改变附着力。

覆膜支架治疗外伤性椎动脉夹层动脉瘤一例报道

椎动脉夹层动脉瘤(vertebral artery dissecting aneurysm,VADA)是后循环蛛网膜下腔出血或缺血的原因之一,VADA破裂通常伴随着高致死率和高致残率。研究认为,椎动脉V4段特殊的生理构造和血流动力学特征极易使局部结构的完整性遭受到破坏,而内膜受到损伤时可在高速血流冲击下形成夹层,从而导致VADA的形成[1]。

A laterally sensitive colloidal probe for accurately measuring nanoscale adhesion of textured surfaces

Adhesiion assessment of nanoscale contacts is a critical capability for the development of future nanoelectromechanical systems and nanobiotechnology devices. However, experimental approaches to investigate interactions on micro- and nanostructured surfaces have predominantly been restricted to capturing adhesion force in the normal direction. This provides limited information about the multidimensional nature of surface texture and related interaction mechanisms. Here the design, fabrication, and application of a unique atomic force microscope probe is presented that consists of a focused ion beam-milled cantilever decorated with a colloidal particle. The probe is specifically developed for characterizing textured surfaces with lateral force feedback. Pull-off tests that map the adhesive interaction in microscale cavities are performed to exami ne the capability of the probe. Normal and lateral adhesive forces duri ng nano scale contact are accurately obtai ned and the adhesi on en ergy of the con tact interface is thus determi ned. An in-depth un dersta nding of the effects of surface texture and the correlati on of adhesi on and fricti on is dem on strated. The proposed methodology en ables dedicated in vestigatio ns of in terfacial in teracti on on various norvplanar surfaces. It can be used for un dersta nding the complex in terplay of adhesi on, con tact, and fricti on forces at nano scale, which may facilitate significant advances in challenging research areas such as fibrillar adhesion.

SDG721 and SDG705 are required for rice growth

Summary H3K4me3 plays important roles in development, transcription, and environmental responses. Here, we report that SDG721 （SET-domain group protein 721） and SDG705 are involved in regulating rice development. SDG721 and SDG705 encode TRITHORAX-Iike proteins, which appear to modulate H3K4 methylation levels. Loss of SDG721 and SDG705 function resulted in GA-deficient phenotypes, including semi-dwarfism, reduced cell length, and reduced panicle branching.

Catalyst-free synthesis and mechanical characterization of TaC nanowires

TaC nanowires are expected to be an ideal reinforcing material in ultra-high-temperature ceramics. However, their growth mechanisms and mechanical properties remain unclear, and low-cost large-scale synthesis has not been realised. In this study,bulk synthesis of [100]-oriented TaC nanowires is accomplished by carbothermal synthesis through a direct vapor-solid mechanism. Thermal resonance test results show that the synthesized square TaC nanowires with cross-sectional side-lengths of 65 to 497 nm have a size-independent Young’s modulus of(510.6±12.6) GPa;very close to the corresponding values of their bulk counterparts, but differing considerably from previously published measurements. Molecular dynamics(MD) simulations show that TaC nanowires with side-lengths of above 15 nm have a constant Young’s modulus of 517 GPa, and size effects on the modulus values should only occur at side-lengths below 15 nm. During bending tests, the TaC nanowires fracture into several segments in a brittle mode, and exhibit an increasing fracture strain from 1.88% to 4.28% as their side-length decreases from 489 to 90 nm. Weibull statistics analyses and TEM observations indicate that the failure of the nanowires should be primarily dependent on the number and size of surface defects. MD simulations further reveal that the defect-free TaC nanowires fail brittlely at a theoretical strain up to 5.76%.

Holographic p-wave superfluid with Weyl corrections

In this work,we study the effects of the Weyl corrections on the p-wave superfluid phase transition in terms of an EinsteinMaxwell theory coupled to a complex vector field.In the probe limit,it is observed that the phase structure is significantly modified owing to the presence of the higher order Weyl corrections.The latter,in general,facilitates the emergence of the superfluid phase as the condensate increases with the Weyl coupling measured byγ.Moreover,several features about the phase structure of the holographic superfluid are carefully investigated.In a specific region,the phase transition from the normal phase to the superfluid phase is identified to be the first order,instead of being the second order,as in the cases for many holographic superconductors.By carrying out a numerical scan of model parameters,the boundary dividing these two types of transitions is located and shown to be rather sensitive to the strength of Weyl coupling.Also,a feature known as"Cave of Winds",associated with the emergence of a second superfluid phase,is observed for specific choices of model parameters.However,it becomes less prominent and eventually disappears asγincreases.Furthermore,for temperature in the vicinity of the critical one for vanishing superfluid velocity,denoted by T0,the supercurrent is found to be independent of the Weyl coupling.The calculated ratio,of the condensate with vanishing superfluid velocity to that with maximal superfluid velocity,is in good agreement with that predicted by Ginzburg-Landau theory.While compared with the impact on the phase structure owing to the higher curvature corrections,the findings in our present study demonstrate entirely different characteristics.Further implications are discussed.

Frictional shear stress of ZnO nanowires on natural and pyrolytic graphite substrates

The friction behaviour of ZnO nanowires on natural graphite(NG)and highly oriented pyrolytic graphite(HOPG)substrates was tested in ambient conditions by use of optical microscopy based nanomanipulation.Nanowires on the step-free and waviness-free NG substrate exhibit a diameter-independent nominal frictional shear stress of 0.48 MPa,and this provides a benchmark for studying how the surface topography of graphite influences nanowire friction.Nanowires on the HOPG substrate present a significant diameter-dependent frictional shear stress,increasing from 0.25 to 2.78 MPa with the decrease of nanowire diameter from 485 to 142 nm.The waviness of HOPG has a limited effect on the nanowire friction,as a nanowire can fully conform to the substrate.The surface steps on the HOPG can significantly enhance the nanowire friction and lead to a much higher frictional shear stress than that on NG due to mechanical blocking and the presence of a Schwoebel barrier at step edges.The surface steps,however,can also generate small wedge-shaped gaps between a nanowire and substrate,and thus reduce the nanowire friction.With the decrease in nanowire diameter,the capacity for the nanowire to better conform to the substrate reduces the length of the wedge-shaped gaps,leading to the observed increase in nanowire friction.The results have improved our understanding of the unique friction behaviour of nanowires.Such an improved understanding is expected to benefit the design and operation of nanowire-friction-based devices,including bio-inspired fibrillar adhesives,soft grippers,rotary nanomotors,and triboelectric nanogenerators.

Achievements in burn surgery over the past 50 years in China

This paper reflects on the advancements of clinical and scientific research in the field of burn sur-gery in China.It includes emergency care of massive burns,resuscitation,anti-infection,prevention and cure of internal organ injuries,metabolic and nutritional sup-port,wound repair and rehabilitation,and special types of burns;it also covers pathology,microbiology,immunology,cell biology,molecular biology,and tissue engineering.