Two-Dimensional Magnetic Semiconducting Heterostructures of Single-Layer CrI3-CrI2.

Single-layer heterostructures of magnetic materials are unique platforms for studying spin-related phenomena in two dimensions (2D) and have promising applications in spintronics and magnonics. Here, we report the fabrication of 2D magnetic lateral heterostructures consisting of single-layer chromium triiodide (CrI3) and chromium diiodide (CrI2). By carefully adjusting the abundance of iodine based on molecular beam epitaxy, single-layer CrI3-CrI2 heterostructures were grown on Au(111) surfaces with nearly atomic-level seamless boundaries. Two distinct types of interfaces, i.e., zigzag and armchair interfaces, have been identified by means of scanning tunneling microscopy. Our scanning tunneling spectroscopy study combined with density functional theory calculations indicates the existence of spin-polarized ground states below and above the Fermi energy localized at the boundary. Both the armchair and zigzag interfaces exhibit semiconducting nanowire behaviors with different spatial distributions of density of states. Our work presents a novel low-dimensional magnetic system for studying spin-related physics with reduced dimensions and designing advanced spintronic devices.

Modeling and Balancing for Disassembly Lines Considering Workers With Different Efficiencies.

To achieve sustainable manufacturing of large-scale end-of-life products, disassembly for recycling and remanufacturing has been widely adopted by industries. Disassembly line balancing becomes an important and challenging issue. The disassembly efficiencies of workers are different in the actual disassembly line due to some factors, including disassembly environment, skill level, work enthusiasm, etc. However, efficiency differences are often ignored in previous studies, which ultimately lead to unbalanced workloads among stations. Therefore, this article establishes a disassembly line balancing model that considers workers with different efficiencies and introduces the bucket brigade model into the disassembly line. Its optimization objectives include workload smoothness, cost of workers, disassembly risk, and disassembly demand. To obtain high-quality solutions, a discrete flower pollination algorithm based on problem characteristics is proposed. The performance of the proposed algorithm is verified by comparing it with 11 algorithms. Finally, the proposed model and algorithm are applied to an actual television disassembly case considering workers with different efficiencies, and provide decision makers with multiple disassembly schemes.

A Discrete Artificial Bee Colony Algorithm for Multiobjective Disassembly Line Balancing of End-of-Life Products.

Disassembly lines are the most effective way to address large-scale value recovery from end-of-life (EOL) products. Disassembly line balancing (DLB) greatly affects the economics and throughput of EOL product processing. Complete disassembly is generally not suitable for disassembly enterprises; most often, the maximum profit is realized through partial disassembly. Thus, this article proposes a partial disassembly method and establishes a new DLB model that addresses both economic benefits and environmental impacts. The objective of the model is to maximize the effectiveness of workers, increase profit, reduce energy consumption, and balance the loads of workers. Moreover, the model considers the impact of disassembly face and tool changes on the disassembly process. A discrete multiobjective artificial bee colony (MOABC) algorithm is developed, and it takes the precedence constraints into account to obtain the Pareto solutions. The MOABC algorithm is applied to the disassembly lines of two real-world EOL products, including those of an LCD TV and a refrigerator. Experiments show that the performance of the MOABC algorithm is better than those of five well-known multiobjective algorithms. The proposed model and method can provide multiple disassembly schemes for decision makers of disassembly enterprises based on their preferences.

Indigenous and commercial isolates of arbuscular mycorrhizal fungi display differential effects in Pyrus betulaefolia roots and elicit divergent transcriptomic and metabolomic responses.

Background: Arbuscular mycorrhizal fungi (AMF) are beneficial soil fungi which can effectively help plants with acquisition of mineral nutrients and water and promote their growth and development. The effects of indigenous and commercial isolates of arbuscular mycorrhizal fungi on pear (Pyrus betulaefolia) trees, however, remains unclear. Methods: Trifolium repens was used to propagate indigenous AMF to simulate spore propagation in natural soils in three ways: 1. the collected soil was mixed with fine roots (R), 2. fine roots were removed from the collected soil (S), and 3. the collected soil was sterilized with 50 kGy 60Co γ-radiation (CK). To study the effects of indigenous AMF on root growth and metabolism of pear trees, CK (sterilized soil from CK in T. repens mixed with sterilized standard soil), indigenous AMF (R, soil from R in T. repens mixed with sterilized standard soil; S, soil from S in T. repens mixed with sterilized standard soil), and two commercial AMF isolates (Rhizophagus intraradices(Ri) and Funneliformis mosseae (Fm)) inoculated in the media with pear roots. Effects on plant growth, root morphology, mineral nutrient accumulation, metabolite composition and abundance, and gene expression were analyzed. Results: AMF treatment significantly increased growth performance, and altered root morphology and mineral nutrient accumulation in this study, with the S treatment displaying overall better performance. In addition, indigenous AMF and commercial AMF isolates displayed common and divergent responses on metabolite and gene expression in pear roots. Compared with CK, most types of flavones, isoflavones, and carbohydrates decreased in the AMF treatment, whereas most types of fatty acids, amino acids, glycerolipids, and glycerophospholipids increased in response to the AMF treatments. Further, the relative abundance of amino acids, flavonoids and carbohydrates displayed different trends between indigenous and commercial AMF isolates. The Fm and S treatments altered gene expression in relation to root metabolism resulting in enriched fructose and mannose metabolism (ko00051), fatty acid biosynthesis (ko00061) and flavonoid biosynthesis (ko00941). Conclusions: This study demonstrates that indigenous AMF and commercial AMF isolates elicited different effects in pear plants through divergent responses from gene transcription to metabolite accumulation.

Effects of dietary yeast culture on health status in digestive tract of juvenile Pacific white shrimp Litopenaeus Vannamei.

A feeding trial was conducted to investigate the effects of dietary yeast culture (YC) on health status in digestive tract of juvenile Pacific white shrimp Litopenaeus Vannamei. Shrimps (initial weight: 3.33 ± 0.06 g) were fed with graded levels of dietary YC (control, 0.3%, 0.5% and 1.0%). Results of the present study showed that villus height and the ratio between villus height and crypt depth in the digestive tract of juvenile shrimp was significantly increased by dietary 0.5% and 1.0%YC (P < 0.05). Besides, dietary 0.5% and 1.0%YC significantly activities of phenoloxidase (PO), lysozyme (LZ), acid phosphatase (ACP) and alkaline phosphatase (AKP) (P < 0.05), significantly up-regulated mRNA levels of prophenoloxidase (propo), lysozyme (lz), anti-lipopolysaccharide factor (alf), crustin and penaienadin (P < 0.05) and down-regulated mRNA levels of caspase-1, nuclear factor κB p65 (nf-κbp65) myeloid differentiation primary response protein (myd88) and toll like receptor (tlr) in the digestive tract of juvenile shrimp (P < 0.05). Compared with the control, dietary 0.5%YC increased Chao1 index in the digestive tract of juvenile shrimp. In addition, compared with the control, dietary 0.5% and 1.0%YC significantly increased relative abundance of Lactobacillus (P < 0.05). It can be concluded that dietary YC made positive contribution to health status in digestive tract of juvenile shrimp through improving morphology and microbiota, enhancing immune function, and inhibiting inflammation of digestive tract.

Imaging Vacancy Defects in Single-Layer Chromium Triiodide.

As a van der Waals magnetic semiconductor, chromium triiodide (CrI3) is widely considered for its high research value and potential applications. Defects in CrI3 are inevitably present and significantly alter the material properties. However, experimental identification of defects of CrI3 at the atomic level is still lacking. Here for the first time, we carried out a scanning tunneling microscopy (STM) study and density functional theory calculations to explore the intrinsic defects in monolayer CrI3 grown by molecular beam epitaxy. The three most common types of intrinsic point defects, i.e., I vacancy (VI), Cr vacancy (VCr), and multiatom CrI3 vacancy (VCrI3) with distinct spatial distributions of the localized defect states, are identified and characterized by high-resolution STM. Moreover, defect concentrations are estimated based on our experiments, which agree with the calculated formation energies. Our findings provide vital knowledge on the types, concentrations, electronic structures, and migration mechanism of the intrinsic point defects in monolayer CrI3 for future defect engineering of this novel 2D magnet.

Single-layer CrI3 grown by molecular beam epitaxy.

Single- and few-layer chromium triiodide (CrI3), which has been intensively investigated as a promising platform for two-dimensional magnetism, is usually prepared by the mechanical exfoliation. Here, we report direct growth of single-layer CrI3 using molecular beam epitaxy in ultrahigh vacuum. Scanning tunneling microscopy (STM), together with density functional theory (DFT) calculation, revealed that the iodine trimers, each of which consists of three I atoms surrounding a three-fold Cr honeycomb center, are the basic units of the topmost I layer. Different superstructures of single-layer CrI3 with periodicity around 2-4 nm were obtained on Au(1 1 1), while only the 1 × 1 structure was observed on the graphite substrate. At an elevated temperature of 423 K, single-layer CrI3 began to decompose and transformed into single-layer chromium diiodide. Our bias-dependent STM images suggest that the unoccupied and occupied states are spatial-separately distributed, consistent with the results of our DFT calculation. We also discussed the role of charge distribution in the super-exchange interactions among Cr atoms in single-layer CrI3.