Journal Article Nanobelt Thickness and Mean-free Path Determination by CBED and PEELS Get access Y Berta, Y Berta School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 Search for other works by this author on: Oxford Academic Google Scholar C Ma, C Ma School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 Search for other works by this author on: Oxford Academic Google Scholar ZL Wang ZL Wang School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 8, Issue S02, 1 August 2002, Pages 1608–1609, https://doi.org/10.1017/S1431927602104624 Published: 01 August 2002
Abstract The microstructure of single-crystal ZnS thin films epitaxially grown on GaAs(100) has been investigated by high resolution transmission electron microscopy (HRTEM). The dominant defect structures are {111} stacking faults and interface mismatch dislocations. The distribution of stacking faults is limited to the first 70 nm thickness range of the grown film, and almost no defects are observed in the thickness range beyond 100 nm. This could have important consequences in optoelectronic applications. The stacking faults of {111} layers are generated at the substrate-film interface in the following two ways. Firstly a small interface angle between the substrate and the film results in edge-type dislocations due to additional (002) ZnS layers (i.e. a low-angle boundary structure). Part of the stress created by these interface dislocations is relaxed by generating stacking faults. Secondly mismatch dislocations with additional {111} layers, due to the lattice mismatch between GaAs and ZnS (4.4%), also favour the formation of stacking faults at the interface. The structure models of these defects are given based on the experimental HRTEM images.
Background Group Cognitive Behavioral Therapy (GCBT) is the primary psychological treatment for social anxiety disorder. The core concept of Cognitive Behavioral Therapy is manifested in two aspects: cognitive correction and behavioral feedback. Social Anxiety Disorder (SAD) is a chronic mental disorder with a high incidence of negative automatic thinking and negative fear. Subjects and Methods This study conducted a controlled experiment between 50 SAD patients and 50 healthy people. Before treatment, 50 SAD patients were surveyed by psychological questionnaires, including social anxiety scale, social support scale, and parenting style questionnaire, to evaluate the thinking style, personality characteristics, and external psychosocial support of SAD patients. After GCBT treatment, SAD patients were again surveyed with a scale and questionnaire within one week to evaluate the degree of symptom improvement and cognitive change. In this study, SPSS23.0 analysis software was used for analysis. Results There were significant differences in thinking style, personality characteristics, social support, and parenting style between SAD patients and the control group ( P <0.05). Social anxiety ( P =0.03), negative thinking ( P =0.03), and fear of negation ( P =0.04) were significantly lower in GCBT patients after treatment than before treatment. Conclusions GCBT treatment can change the symptoms of SAD patients in a long-term and stable manner, which is related to the changes in patients’ cognitive habits. GCBT treatment can improve the negative cognition of SAD patients to reduce their symptoms, and increasing subjective social support and reducing paternity rejection can improve the long-term prognosis of patients with social anxiety. Acknowledgement The National Social Science Foundation (22XGL021); Guizhou grassroots social governance innovation high-end think tank; the grass-roots governance innovation team for Rural Revitalization of Guizhou Federation of Social Sciences.
The implementation of new materials and device architectures, e.g., 3D integration, is necessary for such purposes. It is also desirable that these future nanosystems can operate in a self-powered manner through sustainably harvesting their operational power from the environment. This chapter discusses the related scientific concepts and technological advances in the area of self-powered 3D nanosystems for mechanical interfacing applications, focusing on the technologies enabled by the fundamental principles of piezotronic effect and triboelectric nanogenerators. The advance of emerging technologies in wearable, human-integrated applications demands the development of energy-efficient, high-performance electronic and sensor systems with diversified functionalities, e.g., capable of interacting with mechanical signals. The rapid advancement in micro-/nanotechnology is gradually shifting the focus from demonstrating discrete devices to developing an integrated system of certain complexity via state-of-art micro-/nanofabrication technologies. Developing multifunctional electronic systems with self-powering capability is expected to enable exciting opportunities in smart skin, human-machine interface, robotics, and many other societally pervasive areas.
It has become a trend to precisely control the additive manufacturing process parameters within the high-density process window to obtain high-performance metal parts. However, there are few reports on this topic currently, leaving this research without sufficient references. This study took 316L austenitic stainless steel as a case study. In total, 36 groups of specimens were manufactured by Laser powder bed melting (LPBF), and then, two highly dense specimens were selected to study the variation in their microstructure and properties. The densities of the selected specimens, S1 (VED = 81 J/mm3) and S2 (VED = 156.3 J/mm3), are 99.68% and 99.99%, respectively. The results indicated that, compared with the S1 specimen, the S2 specimen significantly decreased in terms of yield strength (YS), ultimate tensile strength (UTS), and elongation (EL), which are 7.28%, 6.34%, and 19.15%, respectively. The differences in mechanical properties were primarily attributed to differences in their microstructures. Further, compared with the S1 specimen, the fitted ellipse aspect ratio and average grain size of the S2 specimen increased by 79.88% and 53.45%, respectively, and the kernel average misorientation (KAM) value and geometric necessary dislocation (GND) density increased by 36.00% and 58.43%, respectively. Furthermore, the S1 specimen exhibited a strong texture in the <101>//Z direction, whereas no obvious texture was observed in the S2 specimen. Obviously, the reason why precise regulation within the dense parameter range can achieve better performance is that the microstructure and mechanical properties of the specimens prepared within the dense range are different. More importantly, this study provides a feasible framework for optimizing alloys with broad and dense parameter ranges, demonstrating the potential to achieve high-performance components through precise parameter control. Furthermore, the results reveal that even within a wide range of high-density forming parameters, significant variations in microstructure and mechanical properties can arise depending on the selected parameter combinations. These findings underscore the critical importance of meticulous process parameter optimization and microstructural regulation in tailoring material properties.
Owing to the polarization of ions in a crystal that has noncentral symmetry, a piezoelectric potential (piezopotential) is created in the material by applying a stress. The creation of piezopotential together with the presence of Schottky contacts are the fundamental physics responsible for a few important nanotechnologies. The nanogenerator is based on the piezopotential-driven transient flow of electrons in the external load. On the basis of nanomaterials in the wurtzite semiconductors, such as ZnO and GaN, electronics fabricated by using a piezopotential as a gate voltage are called piezotronics, with applications in strain/force/pressure-triggered/controlled electronic devices, sensors, and logic gates. The piezophototronic effect is a result of three-way coupling among piezoelectricity, photonic excitation, and semiconductor transport, which allows tuning and controlling of electro-optical processes by a strain-induced piezopotential.
Abstract Bacterial infection remains a major complication answering for the failures of various implantable medical devices. Tremendous extraordinary advances have been published in the design and synthesis of antimicrobial materials addressing this issue; however, the clinical translation has largely been blocked due to the challenge of balancing the efficacy and safety of these materials. Here, calcium's biochemical features, natural roles in pathogens and the immune systems, and advanced uses in infection medications are illuminated, showing calcium is a promising target for developing implantable devices with less infection tendency. The paper gives a historical overview of biomedical uses of calcium and summarizes calcium's merits in coordination, hydration, ionization, and stereochemistry for acting as a structural former or trigger in biological systems. It focuses on the involvement of calcium in pathogens’ integrity, motility, and metabolism maintenance, outlining the potential antimicrobial targets for calcium. It addresses calcium's uses in the immune systems that the authors can learn from for antimicrobial synthesis. Additionally, the advances in calcium's uses in infection medications are highlighted to sketch the future directions for developing implantable antimicrobial materials. In conclusion, calcium is at the nexus of antimicrobial defense, and future works on taking advantage of calcium in antimicrobial developments are promising in clinical translation.
Image calculations for REM are usually difficult because it is necessary to incorporate surface defects, such as steps and dislocations. This, in principle, can be done with the PeTSM theory; but, in practice, the huge amount of computation required and the sensitivity of REM image contrast to focus, beam convergence and diffracting conditions make the calculations rather involved and difficult compared with experimental observations. Attempts have been made to simulate surface step images (Peng and Cowley, 1986; Ma and Marks, 1990), but the results are still not very satisfactory. For this reason, in this chapter, the contrast mechanisms of REM imaging are described based on simplified models, in order to illustrate the physical concepts.
