Search

First-principles calculations of defects and electron–phonon interactions play a critical role in the design and optimization of materials for electronic and optoelectronic devices. The late Audrius Alkauskas made seminal contributions to developing rigorous first-principles methodologies for the computation of defects and electron–phonon interactions, especially in the context of understanding the fundamental mechanisms of carrier recombination in semiconductors. Alkauskas was also a pioneer in the field of quantum defects, helping to build a first-principles understanding of the prototype nitrogen-vacancy center in diamond, as well as identifying novel defects. Here, we describe the important contributions made by Alkauskas and his collaborators and outline fruitful research directions that Alkauskas would have been keen to pursue. Audrius Alkauskas’ scientific achievements and insights highlighted in this article will inspire and guide future developments and advances in the field.

Abstract In this paper, we propose the use of punch-through nMOS (PTnMOS) as an alternative to pMOS in complementary metal oxide semiconductor (CMOS) circuits. According to the TCAD simulation results, PTnMOS exhibit sub-threshold characteristics similar to those of pMOS and can be formed by simply changing the doping concentration of the source and drain. Without the need for sizing, which solves the area occupation problem caused by the need to increase the width of pMOS due to insufficient hole mobility. In addition, we compose a PTnMOS and nMOS without sizing to form a single-carrier CMOS in which only electrons are transmitted, and We extract its performance for comparison with conventional CMOS (Wp/Wn = 1). The results indicate that single-carrier CMOS has symmetric noise margin and 29% faster delay time compared to conventional CMOS (Wp/Wn = 1). If III–V or II–VI group materials could be applied to single-carrier CMOS, not only could costs be reduced and wafer area occupancy minimized, but also significant improvements in the performance and bandwidth application of microwave circuits could be achieved.

Light-matter interactions in semiconductors are uniformly treated within the electric dipole approximation; multipolar interactions are considered "forbidden." We experimentally demonstrate that this approximation inadequately describes light emission in two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs), solution processable semiconductors with promising optoelectronic properties. By exploiting the highly oriented crystal structure, we use energy-momentum spectroscopies to demonstrate that an exciton-like sideband in 2D HOIPs exhibits a multipolar radiation pattern with highly directed emission. Electromagnetic and quantum-mechanical analyses indicate that this emission originates from an out-of-plane magnetic dipole transition arising from the 2D character of electronic states. Symmetry arguments and temperature-dependent measurements suggest a dynamic symmetry-breaking mechanism that is active over a broad temperature range. These results challenge the paradigm of electric dipole-dominated light-matter interactions in optoelectronic materials, provide new perspectives on the origins of unexpected sideband emission in HOIPs, and tease the possibility of metamaterial-like scattering phenomena at the quantum-mechanical level.

To tackle the shortage of river sand resources and excessive carbon emissions in building materials, environment-friendly concrete can be fabricated by solidifying aeolian sand and natural gravel with a fly ash-based geopolymer. Aeolian sand and natural gravel are accessible building materials, but their engineering applications are largely limited by their poor properties such as high mud content, large specific surface area, and discontinuous particle size distribution. To enhance the application of this environment-friendly concrete, in this paper, 48 sets of specimens with different geopolymer dosages, curing temperatures, and curing times are studied experimentally, and quite well-strengthened geopolymer aeolian sand mortar (GAM), geopolymer aeolian sand concrete (GAC), and an appropriate dosage of the geopolymer are finally obtained. The experimental results and the failure section of the mortar specimen indicate that the fly ash geopolymer can solidify the aeolian sand and ensure the integrity and compactness of the specimen. The 28-day compressive and flexural strength of the geopolymer standard sand mortar (GSM) reached 40.5 MPa and 4.3 MPa, respectively, at a curing temperature of 60 °C when the amount of alkali activator was improved to 100%, and the 28-day compressive and flexural strength of GAM reached 33.7 MPa and 4.2 MPa, respectively, when the amount of geopolymer material was 0.75 times that of aeolian sand. A lower compressive strength of GAC was obtained following the addition of aeolian sand. The experiment results can provide a reference for aeolian sand usage and have a certain social value in environmental protection. [ABSTRACT FROM AUTHOR]

The combination of few-shot learning and graph neural networks can effectively solve the issue of extracting more useful information from limited data. However, most graph-based few-shot models only consider the global feature information extracted by the backbone during the construction process, while ignoring the dependency information hidden within the features. Additionally, the essence of graph convolution is the filtering of graph signals, and the majority of graph-based few-shot models construct fixed, single-property filters to process these graph signals. Therefore, in this paper, we propose an Adaptive Filtering Graph Convolutional Neural Network (AFGN) for few-shot classification. AFGN explores the hidden dependency information within the features, providing a new approach for constructing graph tasks in few-shot scenarios. Furthermore, we design an adaptive filter for the graph convolution of AFGN, which can adaptively adjust its strategy for acquiring high and low-frequency information from graph signals based on different few-shot episodic tasks. We conducted experiments on three standard few-shot benchmarks, including image recognition and fine-grained categorization. The experimental results demonstrate that our AFGN performs better compared to other state-of-the-art models. [ABSTRACT FROM AUTHOR]

Hybrid perovskites such as MAPbI3 (MA = CH3NH3) exhibit a unique spin texture. The spin texture (as calculated within the Rashba model) has been suggested to be responsible for a suppression of radiative recombination due to a mismatch of spins at the band edges. Here we compute the spin texture from first principles and demonstrate that it does not suppress recombination. The exact spin texture is dominated by the inversion asymmetry of the local electrostatic potential, which is determined by the structural distortion induced by the MA molecule. In addition, the rotation of the MA molecule at room temperature leads to a dynamic spin texture in MAPbI3. These insights call for a reconsideration of the scenario that radiative recombination is suppressed and provide an in-depth understanding of the origin of the spin texture in hybrid perovskites, which is crucial for designing spintronic devices.

Abstract Background Exposure to glyoxal, the smallest dialdehyde, is associated with several diseases; humans are routinely exposed to glyoxal because of its ubiquitous presence in foods and the environment. The aim of this study was to examine the damage caused by glyoxal in human aortic endothelial cells. Methods Cell survival assays and quantitative fluorescence assays were performed to measure DNA damage; oxidative stress was detected by colorimetric assays and quantitative fluorescence, and the mitogen-activated protein kinase pathways were assessed using western blotting. Results Exposure to glyoxal was found to be linked to abnormal glutathione activity, the collapse of mitochondrial membrane potential, and the activation of mitogen-activated protein kinase pathways. However, DNA damage and thioredoxin oxidation were not induced by dialdehydes. Conclusions Intracellular glutathione, members of the mitogen-activated protein kinase pathways, and the mitochondrial membrane potential are all critical targets of glyoxal. These findings provide novel insights into the molecular mechanisms perturbed by glyoxal, and may facilitate the development of new therapeutics and diagnostic markers for cardiovascular diseases.