Projectability disentanglement for accurate and automated electronic-structure Hamiltonians.

Maximally-localized Wannier functions (MLWFs) are broadly used to characterize the electronic structure of materials. Generally, one can construct MLWFs describing isolated bands (e.g. valence bands of insulators) or entangled bands (e.g. valence and conduction bands of insulators, or metals). Obtaining accurate and compact MLWFs often requires chemical intuition and trial and error, a challenging step even for experienced researchers and a roadblock for high-throughput calculations. Here, we present an automated approach, projectability-disentangled Wannier functions (PDWFs), that constructs MLWFs spanning the occupied bands and their complement for the empty states, providing a tight-binding picture of optimized atomic orbitals in crystals. Key to the algorithm is a projectability measure for each Bloch state onto atomic orbitals, determining if that state should be kept identically, discarded, or mixed into the disentanglement. We showcase the accuracy on a test set of 200 materials, and the reliability by constructing 21,737 Wannier Hamiltonians.

Analysis and application evaluation of the flavour-precursor and volatile-aroma-component differences between waste tobacco stems.

The development and utilization of waste resources have important scientific significance and social value. As a renewable and clean resource, the flavour components of waste tobacco stems (WTS) make a significant contribution to the development of waste resources. To evaluate the industrial applicability of the different WTS as raw materials, the present study systematically examined the differences in flavour precursors and volatile aroma components in tobacco stems (TS) from typical tobacco (Nicotiana tabacum L.) growing areas in Yunnan Province through HPLC and GC‒MS analysis. Meanwhile, the contribution to improving the quality of cigarette products is discussed accordingly. The results showed that the contents of flavour precursors, carotenoid and hexane degradation products, neophydiene and total volatile aroma substances in TS were the highest in the Dianxi area, Yun 87 variety and the upper part of Yunnan Province, while the contents of Maillard reaction products and phenylalanine degradation products were the highest in the Diandong area and middle part. The aroma components and sensory quality of TS have obvious regional characteristics in Yunnan. Accordingly, the higher flavour components improve cigarette quality. Most importantly, the middle and upper TS should be preferred to use and classified to process according to the tobacco growing areas, which is beneficial for promoting industrial applicability in cigarette preparation. This study provides a theoretical reference for the industrial value-added applicability of TS in the aspects of flavour extraction and cigarette preparation.

Prediction of cooling moisture content after cut tobacco drying process based on a particle swarm optimization-extreme learning machine algorithm.

The stability of the moisture content of the cigarette is an important index to evaluate the quality of the cigarette. The cooling moisture content after cut tobacco drying process is a key factor affecting the stability of the moisture content of the cigarette. In order to realize its accurate prediction and ensure the stability, in Honghe cigarette factory, a cooling moisture content prediction model is built based on a particle swarm optimization-extreme learning machine (PSO-ELM) algorithm via the historical production data. Besides, the proposed PSO-ELM algorithm is also compared with multiple linear regression (MLR), support vector machine (SVM) and the traditional extreme learning machine (ELM) algorithms in the same data set on the prediction. The prediction accuracy of PSO-ELM method is the highest and the average error of the prediction standard is the lowest. The results indicated the proposed method can achieve a better prediction performance over compared methods and it provides a new method to realize the prediction of the cooling moisture content after cut tobacco drying process.

Modulation of field-like spin orbit torque in heavy metal/ferromagnet heterostructures.

Spin orbit torque (SOT) has drawn widespread attention in the emerging field of magnetic memory devices, such as magnetic random access memory (MRAM). To promote the performance of SOT-MRAM, most efforts have been devoted to enhance the SOT switching efficiency by improving the damping-like torque. Recently, some studies noted that the field-like torque also plays a crucial role in the nanosecond-timescale SOT dynamics. However, there is not yet an effective way to tune its relative amplitude. Here, we experimentally modulate the field-like SOT in W/CoFeB/MgO trilayers through tuning the interfacial spin accumulation. By performing spin Hall magnetoresistance measurement, we find that the CoFeB with enhanced spin dephasing, either generated from larger layer thickness or from proper annealing, can distinctly boost the spin absorption and enhance the interfacial spin mixing conductance Gr. While the damping-like torque efficiency increases with Gr, the field-like torque efficiency is found to decrease with it. The results suggest that the interfacial spin accumulation, which largely contributes to the field-like torque, is reduced by higher interfacial spin transparency. Our work shows a new path to further improve the performance of SOT-based ultrafast magnetic devices.

Wannier90 as a community code: new features and applications.

Wannier90 is an open-source computer program for calculating maximally-localised Wannier functions (MLWFs) from a set of Bloch states. It is interfaced to many widely used electronic-structure codes thanks to its independence from the basis sets representing these Bloch states. In the past few years the development of Wannier90 has transitioned to a community-driven model; this has resulted in a number of new developments that have been recently released in Wannier90 v3.0. In this article we describe these new functionalities, that include the implementation of new features for wannierisation and disentanglement (symmetry-adapted Wannier functions, selectively-localised Wannier functions, selected columns of the density matrix) and the ability to calculate new properties (shift currents and Berry-curvature dipole, and a new interface to many-body perturbation theory); performance improvements, including parallelisation of the core code; enhancements in functionality (support for spinor-valued Wannier functions, more accurate methods to interpolate quantities in the Brillouin zone); improved usability (improved plotting routines, integration with high-throughput automation frameworks), as well as the implementation of modern software engineering practices (unit testing, continuous integration, and automatic source-code documentation). These new features, capabilities, and code development model aim to further sustain and expand the community uptake and range of applicability, that nowadays spans complex and accurate dielectric, electronic, magnetic, optical, topological and transport properties of materials.

Large Tunneling Magnetoresistance in VSe2/MoS2 Magnetic Tunnel Junction.

Two-dimensional (2D) van der Waals (vdW) materials provide the possibility of realizing heterostructures with coveted properties. Here, we report a theoretical investigation of the vdW magnetic tunnel junction (MTJ) based on VSe2/MoS2 heterojunction, where the VSe2 monolayer acts as a ferromagnet with room-temperature ferromagnetism. We propose the concept of spin-orbit torque (SOT) vdW MTJ with reliable reading and efficient writing operations. The nonequilibrium study reveals a large tunneling magnetoresistance of 846% at 300 K, identifying significantly its parallel and antiparallel states. Thanks to the strong spin Hall conductivity of MoS2, SOT is promising for the magnetization switching of VSe2 free layer. Quantum-well states come into being and resonances appear in MTJ, suggesting that the voltage control can adjust transport properties effectively. The SOT vdW MTJ based on VSe2/MoS2 provides desirable performance and experimental feasibility, offering new opportunities for 2D spintronics.

[Study of mechanism of differentiation of bone stromal stem cells into neurons in vitro].

AIM: To explore the mechanism of differentiation of bone marrow stromal cells (BMSCs) into neurons in different micro-environments in vitro. METHODS: BMSCs were isolated from bone marrow of SD rats and cultured and expanded in vitro. After being identified by immunofluorescence staining, the BMSCs labeled with PKH67 were co-cultured with foetal brain neural cells in the same plate well or in two-layer Petri dish. 8 days later, the BMSCs were detected by immunofluorescence staining. RESULTS: After being co-cultured with foetal brain neural cells at the same time, some BMSCs differentiated into neurons. (32.72+/-2.56)% of the BMSCs expressed neuron-specific enolase (NSE) in the co-cultured group, which was obviously much more than that in control group (P <0.05). Only (4.87+/-0.79)% of the BMSCs expressed NSE when the BMSCs co-cultured with foetal brain neural cells in two-layer Petri dish, which had no difference with the control group (P>0.05). The number of differentiated BMSCs was less than that of the co-cultured group (P <0.05). CONCLUSION: In vitro, the local microenvironment formed by neural cells can promote BMSCs to differentiate into neurons, and close contact between BMSCs and neural cells is an important condition that induce BMSC to differentiate into neurons.