Variation in microbiological heterogeneity in Chinese strong-flavor Baijiu fermentation for four representative varieties of sorghum.

The quality and composition of strong-flavor Baijiu (SFB), a type of Chinese liquor, depends on the variety of sorghum used in fermentation. However, comprehensive in situ studies measuring the effects sorghum varieties on the fermentation are lacking and the underlying microbial mechanisms remains poorly understood. We studied the in situ fermentation of SFB by using metagenomic, metaproteomic, and metabolomic techniques across four sorghum varieties. Sensory characteristics were best for SFB made from glutinous variety Luzhouhong, followed by glutinous hybrid Jinnuoliang and Jinuoliang, and those made with non-glutinous Dongzajiao. In agreement with sensory evaluations, the volatile composition of SFB samples differed between sorghum varieties (P < 0.05). Fermentation of different sorghum varieties varied in microbial diversity, structure, volatile compounds, and physicochemical properties (pH, temperature, starch, reducing sugar, and moisture) (P < 0.05), with most changes occurring within the first 21 days. Additionally, the microbial interactions and their relationship with volatiles, as well as the physicochemical factors that govern microbial succession, differed between varieties of sorghum. The number of physicochemical factors affecting bacterial communities outweighed those affecting fungal communities, suggesting that bacteria were less resilient to the brewing conditions. This correlates with the finding that bacteria play a major role in the differences in microbial communities and metabolic functions during fermentation with the different varieties of sorghum. Metagenomic function analysis revealed differences in amino acid and carbohydrate metabolism between sorghum varieties throughout most of the brewing process. Metaproteomics further indicated most differential proteins were found in these two pathways, related to differences in volatiles between sorghum varieties of Baijiu and originating from Lactobacillus. These results provide insight into the microbial principles underlying Baijiu production and can be used to improve the quality of Baijiu by selecting the appropriate raw materials and optimizing fermentation parameters.

Brevinin-2PN, an antimicrobial peptide identified from dark-spotted frog (Pelophylax nigromaculatus), exhibits wound-healing activity.

Brevinins exhibit a wide range of structural features and strong biological activities. Brevinin-2, derived from several amphibians, has shown antimicrobial activities. However, little is known about the wound-healing activity of brevinin-2. In this study, brevinin-2 cDNA was identified from the skin transcriptome of the dark-spotted frog (Pelophylax nigromaculatus) and it comprises a signal peptide, a propeptide, and a mature peptide. Sequence alignment with brevinin-2 derived from other amphibians showed variability of the mature peptide, and the presence of a C-terminal cyclic heptapeptide domain (Cys-Lys-Xaa4-Cys) in the mature peptide. Dark-spotted frog brevinin-2 belonged to the brevinin-2 cluster and was closely related to brevinin-2HB1 from Pelophylax hubeiensis. Synthetic dark-spotted frog brevinin-2 mature peptide (brevinin-2PN) exhibited antibacterial activity against several pathogens by destroying cell membrane integrity and hydrolysis of genomic DNA. Brevinin-2PN exhibited significant wound-healing activity by accelerating the healing of human skin fibroblast cell scratches, influencing cell migration, and stimulating gene expression of growth factors.

Influencing factors of resource utilisation in haemodialysis patients-Based on socioecological pyramid model.

AIMS AND OBJECTIVES: To describe the current situation and analyse influencing factors of resource utilisation in maintenance haemodialysis patients. BACKGROUND: The self-management level of patients undergoing maintenance haemodialysis in China is low. The applicability of the Chronic Illness Resources Survey in Chinese maintenance haemodialysis patients has been validated, and this survey can be used to assess the utilisation of self-management support resources among haemodialysis patients. Determining the influencing factors of resource utilisation can help improve the self-management behaviour of haemodialysis patients and control the progression of the disease. DESIGN: A descriptive study design was chosen. METHODS: A convenience sample of 314 patients undergoing haemodialysis was recruited from dialysis centres in three hospitals in western Xinjiang from June 2018-April 2019. SPSS19.0 software was used to describe the current situation of resource utilisation. Moreover, t test, analysis of variance and multivariate linear regression were applied to explore the influencing factors of patients' resource utilisation. Standards for observational studies STROBE Statement checklist-v4 were chosen on reporting the study process. RESULTS: The average score of the total resource utilisation was 2.95 ± 0.51. The average item score of seven dimensions from high to low was 3.46 for medical staff, 3.32 for personal, 3.22 for family and friends, 3.16 for work-related, 3.12 for media policy, 2.55 for neighbourhood/community and 2.23 for organisation. Multiple linear regression showed that there have six main factors, which explained 65.4% of the variance of haemodialysis patients' resource utilisation. CONCLUSIONS: The personal, family and friends, work and media and policy subscales were rated the highest, with support from neighbourhood/community and organisation rated the lowest. In general, participants perceived moderate levels of support. Government and healthcare team should pay more attention on haemodialysis patients who had low level of education, poor economic conditions and poor mental condition. RELEVANCE TO CLINICAL PRACTICE: ESRD has caused a burden on healthcare expenditure and has become a critical public health problem worldwide. Self-management is particularly important for dialysis patients which have attracted extensive interest. In the future research, we can use this questionnaire to evaluate the related resources of disease management of dialysis patients, encourage patients to make full use of the resources around them and focus on those patients with low education and monthly income level and bad mental state.

Antimicrobial and immunomodulatory activity of beta-defensin from the Chinese spiny frog (Quasipaa spinosa).

The ß-defensins are important components of the vertebrate innate immune system. While mammalian ß-defensins have wide-ranging antibacterial and immunomodulatory activities, those of amphibians remain largely uncharacterised. In this study, ß-defensin cDNA was identified from the skin transcriptome of the Chinese spiny frog Quasipaa spinosa. This ß-defensin (QS-BD) consists of a signal and a mature peptide. Sequence alignments with other amphibian ß-defensins showed conservation of the functional mature peptide and that its closest relative is ß-defensin from Zhangixalus puerensis. Synthetic QS-BD showed antibacterial activity against Vibrio vulnificus, Vibrio harveyi, Streptococcus iniae, and Aeromonas hydrophila. QS-BD showed bactericidal activity by destroying the cell membrane integrity, but did not hydrolyse genomic DNA. QS-BD treatment promoted respiratory bursts and upregulated the expression of interleukin-1ß and tumour necrosis factor-α in the murine leukemic monocyte/macrophage cell line RAW264.7. This is the first demonstration of immunomodulatory activity by an amphibian ß-defensin.

Wnt2 overexpression protects against PINK1 mutant­induced mitochondrial dysfunction and oxidative stress.

The PTEN induced putative kinase 1 (PINK1) mutation is the second most common cause of autosomal recessive adolescent Parkinson's disease (PD). Furthermore, mitochondrial disorders and oxidative stress are important mechanisms in the pathogenesis of PD. Numerous members of the Wnt family have been found to be associated with neurodegenerative diseases. Therefore, the present study investigated the role of the Wnt2 gene in PINK1B9 transgenic flies, which is a PD model, and its underlying mechanism. It was identified that overexpression of Wnt2 reduced the abnormality rate of PD transgenic Drosophila and improved their flight ability, while other intervention groups had no significant effect. Furthermore, an increase in ATP concentration normalized mitochondrial morphology, and increased the mRNA expression levels of NADH­ubiquinone oxidoreductase chain 1 (ND1), ND42, ND75, succinate dehydrogenase complex subunits B, Cytochrome b and Cyclooxygenase 1, which are associated with Wnt2 overexpression. Moreover, overexpression of Wnt2 in PD transgenic Drosophila resulted in the downregulation of reactive oxygen species and malondialdehyde production, and increased manganese superoxide dismutase (MnSOD), while glutathione was not significantly affected. It was found that overexpression of Wnt2 did not alter the protein expression of ß­catenin in PINK1B9 transgenic Drosophila, but did increase the expression levels of PPARG coactivator 1α (PGC­1α) and forkhead box sub­group O (FOXO). Collectively, the present results indicated that the Wnt2 gene may have a protective effect on PD PINK1B9 transgenic Drosophila. Thus, it was speculated that the reduction of oxidative stress and the restoration of mitochondrial function via Wnt2 overexpression may be related to the PGC­1α/FOXO/MnSOD signaling pathway in PINK1 mutant transgenic Drosophila.

In vitro degradation and cytocompatibility of a low temperature in-situ grown self-healing Mg-Al LDH coating on MAO-coated magnesium alloy AZ31.

Basically, Mg-Al layered double hydroxide (LDH) coatings are prepared on the surface of micro-arc oxidation (MAO) coated magnesium (Mg) alloys at a high temperature or a low pH value. This scenario leads to the growth rate of LDH coating inferior to the dissolution rate of the MAO coating. This in turn results in limited corrosion resistance of the composite coating. In this study, a Mg-Al LDH coating on MAO-coated Mg alloy AZ31 is prepared through a water bath with a higher pH (13.76) at a lower temperature (60 °C). FE-SEM, EDS, XRD, XPS, and FT-IR are applied to analyze the surface morphology, chemical compositions, and growth process. Electrochemical polarization, electrochemical impedance spectroscopy (EIS) and hydrogen evolution tests are employed to evaluate the corrosion resistance of the samples. The results disclose that the MAO coating is completely covered by the nanosheet-structured LDH coating with a thickness of approximately 3.8 µm. The corrosion current density of the MAO-LDH composite coating is decreased four orders of magnitude in comparison to its substrate; the presence of a wide passivation region in anodic polarization branch demonstrates its strong self-healing ability, indicating the hybrid coating possesses excellent corrosion resistance. The formation mechanism of the LDH coating on the MAO-coated Mg alloy is proposed. Furthermore, the cytocompatibility is assessed via an indirect extraction test for MC3T3-E1 pre-osteoblasts, which indicates an acceptable cytocompatibility of osteoblasts for the composite coating.

Magainin-modified polydopamine nanoparticles for photothermal killing of bacteria at low temperature.

Photothermal therapy (PTT) is a promising method to kill bacteria because of the broad-spectrum of antibacterial activity and the ability of spatiotemporal regulation. In the previously reported systems, light induced high temperature (˜70 °C) was essential for effectively killing of bacteria, which, however, would also damage nearby nontarget cells or tissues. Here we report photothermal nanoparticles (NPs) for more targeting and killing bacteria at a relative low temperature. Polydopamine (PDA) was chosen to prepare NPs because of its excellent capability of photothermal conversion. Magainin I (MagI) which is an antimicrobial peptide was used to modify NPs' surface because it can specifically interact with bacteria. We demonstrate that MagI-PEG@PDA NPs effectively killed E. coli at a low temperature of ˜45 °C upon near-infrared (NIR) light irradiation. In contrast, the native PDA NPs under light irradiation or the MagI-PEG@PDA NPs themselves showed no bacteria killing ability. This work highlights the importance of close interaction between the target bacteria and the photothermal materials and may promote the practical clinical applications of the PTT.

Pmma-XO (X = C, Si, Ge) monolayer as promising anchoring materials for lithium-sulfur battery: a first-principles study.

Lithium-sulfur (Li-S) batteries hold great promise for the next-generation lithium-ion energy storage devices. A key issue in the Li-S batteries is, however, the dissolving and migrating of the soluble polysulfides during the charge and discharge processes and introducing anchoring materials (AM) in the batteries effectively prevent the problem and improve the cycling stability of the Li-S batteries. Herein, Pmma-XO (X = C, Si, Ge, Sn) monolayers are introduced as AM to confine the lithium polysulfides and their anchoring properties are studied with the density functional theory methods. Particularly, Pmma-SiO and GeO monolayers are studied for the first time, and our calculations show that these two materials are stable semiconductive monolayers with direct-band-gaps and moderate binding with lithium polysulfides Li2S n (n = 8, 6, 4, 2 and 1). The Pmma-SiO and GeO trap Li2S n species on their surfaces and keep them intact during the charge and discharge, and the adsorption of Li2S n species leads to the enhanced conductivity of Pmma-SiO and GeO monolayers. Our study suggests that the Pmma-SiO and GeO monolayers are the promising AM for highly efficient Li-S batteries.

Parkin deficiency elevates hepatic ischemia/reperfusion injury accompanying decreased mitochondrial autophagy, increased apoptosis, impaired DNA damage repair and altered cell cycle distribution.

Hepatic ischemia/reperfusion injury (HIRI) serves a causative role in postoperative hepatocyte death; however, the mechanisms underlying HIRI remain unclear. Mitochondrial autophagy, with apoptosis, cell cycle distribution and DNA damage repair, may be regarded as a regulatory factor post­HIRI. Parkin, a novel ubiquitin ligase, has been reported to increase mitochondrial autophagy and decrease apoptosis. However, the association between Parkin, mitochondrial autophagy and other regulatory factors in HIRI is unclear. In the present study, the effects of Parkin on HIRI were investigated, using hepatocytes and livers from male Sprague Dawley rats subjected to simulated in vivo HIRI. The results of the present study demonstrated that Parkin expression and mitochondrial autophagy were upregulated post­HIRI, leading to decreased hepatocyte death. Parkin knockdown suppresses the level of mitochondrial autophagy and promotes hepatocyte apoptosis by suppressing apoptosis regulator Bcl­2 function post­HIRI. In addition, Parkin deficiency alters cell cycle distribution and impairs DNA damage repair post­HIRI. In conclusion, Parkin facilitates mitochondrial autophagy and DNA damage repair, inhibits apoptosis, and modulates the cell cycle, leading to increased hepatocyte survival, demonstrating that Parkin may act as a protective regulatory factor post HIRI.

Pedobacter chitinilyticus sp. nov., a chitin-degrading bacterium isolated from wheat leaf tissue.

A bacterium, designated strain CM134L-2T, was isolated from a chitin-enriched wheat leaf microbiome in Chengdu, Sichuan province, China. It was Gram-stain-negative, strictly aerobic, non-spore-forming, motile, rod-shaped, and bright yellow in colour. Strain CM134L-2T grew at 4-35 °C, at pH 6.0-9.0 and could use chitin as the only carbon resource. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain CM134L-2T was most closely related to Pedobacter nanyangensis Q-4T (97.7 %) and Pedobacter zeaxanthinifaciens TDMA-5T (97.4 %). Digital DNA-DNA hybridization (dDDH) values between strain CM134L-2T with these two type strains were 26.8  and 20.8 %, respectively, and average nucleotide identity (ANI) values were 83.2 and 76.2 %; these values are lower than the proposed and generally accepted species boundaries of 70 % for dDDH and 95-96 % for ANI, which suggests strain CM134L-2T represents a novel species. The genomic DNA G+C content of strain CM134L-2T was 39.3 mol%, menaquinone-7 was the major respiratory quinone, phosphatidylethanolamine was the major polar lipid and the major components of the cellular fatty acids were iso-C15 : 0, and C16 : 1ω7c/C16 : 1ω6c (summed feature 3); these features supported the affiliation of strain CM134L-2T to the genus Pedobacter. Overall, strain CM134L-2T belongs to the genus Pedobacter, but can be classified as a novel species, for which the name Pedobacter chitinilyticus sp. nov. is proposed. The type strain is CM134L-2T (=CGMCC 1.16520T=KCTC 62643T).

Molecular characterization of a hepcidin homologue in starry flounder (Platichthys stellatus) and its synergistic interaction with antibiotics.

Hepcidins are small cysteine-rich antimicrobial peptides that play an important role in host immunity against pathogenic organisms. Most fish hepcidins exert bactericidal activities against a wide range of pathogens. In this study, we identified a cDNA sequence encoding a hepcidin homologue (PsHepcidin) in the starry flounder Platichthys stellatus. The predicted amino acid sequence of PsHepcidin comprises a signal peptide and a prodomain, which are followed by the mature peptide. Sequence analysis revealed that PsHepcidin belongs to the fish HAMP2 cluster and that it is closely related to mudskipper hepcidin-2. Expression of PsHepcidin mRNA was detected in all examined immune-related tissues, with the highest transcript levels being found in the liver. In response to lipopolysaccharide treatment, PsHepcidin was significantly up-regulated in the liver, kidney, and spleen in a time-dependent manner. Chemically synthesized mature peptides of PsHepcidin were found to exhibit broad antimicrobial activity in vitro. We also investigated the combined effect of PsHepcidin and conventional antibiotics and found that these combinations showed synergistic effects against most of the examined bacterial strains. Collectively, the results of this study indicate that PsHepcidin exhibits potent antibacterial activity both independently and when used in combination with conventional antibiotics.

Bactericidal and Hemocompatible Coating via the Mixed-Charged Copolymer.

Cationic antibacterial coating based on quaternary ammonium compounds, with an efficient and broad spectrum bactericidal property, has been widely used in various fields. However, the high density of positive charges tends to induce weak hemocompatibility, which hinders the application of the cationic antibacterial coating in blood-contacting devices and implants. It has been reported that a negatively charged surface can reduce blood coagulation, showing improved hemocompatibility. Here, we describe a strategy to combine the cationic and anionic groups by using mixed-charged copolymers. The copolymers of poly (quaternized vinyl pyridine- co- n-butyl methacrylate- co-methacrylate acid) [P(QVP- co- nBMA- co-MAA)] were synthesized through free radical copolymerization. The cationic group of QVP, the anionic group of MAA, and the hydrophobic group of nBMA were designed to provide bactericidal capability, hemocompatibility, and coating stability, respectively. Our findings show that the hydrophilicity of the copolymer coating increased, and its zeta potential decreased from positive charge to negative charge with the increase of the anionic/cationic ratio. Meanwhile, the bactericidal property of the copolymer coating was kept around a similar level compared with the pure quaternary ammonium copolymer coating. Furthermore, the coagulation time, platelet adhesion, and hemolysis tests revealed that the hemocompatibility of the copolymer coating improved with the addition of the anionic group. The mixed-charged copolymer combined both bactericidal property and hemocompatibility and has a promising potential in blood-contacting antibacterial devices and implants.

3-Fold-Periodic Size-Dependence in Electronic Properties of Monolayer-TMDC Nanotriangles.

Stable nanotriangles of monolayer transitional metal dichalcogenides (referred herein as MS2 mNTs) grown via ordinary deposition conditions, where M = Mo or W, exhibit a peculiar 3-fold periodic size-dependence in electronic and chemical properties. For " k" being the number of M atoms per edge, mNTs are (a) intrinsic-semiconducting when k = 3 i + 1, such as k = 7, 10, 13, 16; (b) metallic-like with no bandgap when k = 3 i; (c) n+ semiconducting when k = 3 i - 1. Besides changes in electronic properties, the catalytic properties for hydrogen evolution reaction also switch from active for k = 3 i and 3 i - 1 to inactive for k = 3 i + 1. The peculiar periodic size-dependence roots from the chemistry of edge-reconstruction and the consequential evolution of band structure. Further, such chemistry and thereby the size-dependence can be manipulated by adding or depleting the atomic concentration of sulfur atoms along the mNT edges.

Utilization of a Wheat660K SNP array-derived high-density genetic map for high-resolution mapping of a major QTL for kernel number.

In crop plants, a high-density genetic linkage map is essential for both genetic and genomic researches. The complexity and the large size of wheat genome have hampered the acquisition of a high-resolution genetic map. In this study, we report a high-density genetic map based on an individual mapping population using the Affymetrix Wheat660K single-nucleotide polymorphism (SNP) array as a probe in hexaploid wheat. The resultant genetic map consisted of 119 566 loci spanning 4424.4 cM, and 119 001 of those loci were SNP markers. This genetic map showed good collinearity with the 90 K and 820 K consensus genetic maps and was also in accordance with the recently released wheat whole genome assembly. The high-density wheat genetic map will provide a major resource for future genetic and genomic research in wheat. Moreover, a comparative genomics analysis among gramineous plant genomes was conducted based on the high-density wheat genetic map, providing an overview of the structural relationships among theses gramineous plant genomes. A major stable quantitative trait locus (QTL) for kernel number per spike was characterized, providing a solid foundation for the future high-resolution mapping and map-based cloning of the targeted QTL.

Nanopolygons of Monolayer MS2: Best Morphology and Size for HER Catalysis.

With first-principles calculations, we find a new strategy for developing high-performance catalysts for hydrogen evolution reaction (HER) via controlling the morphology and size of nanopolygons of monolayer transition-metal dichalcogenides (npm-MS2, with M = Mo, W, or V). Particularly, through devising a quantitative method to measure HER-active sites per unit mass and using such HER site density to comparatively gauge npm-MS2 performance, we identify three keys in making npm-MS2 with optimal HER performance: (a) npm-MS2 should be triangular with each edge being M-terminated and each edge-M atom passivated by one S atom; (b) each edge of npm-MoS2 and WS2 should have 5-6 metal atoms as HER site density drops below/above these sizes optimal both for HER and practical npm growth; and (c) npm-VS2 is immune to this overly fastidious size dependence. Known experimental data on npm-MoS2 indeed support the plausibility of practicing these design rules. We expect that raising the nucleation density and controlling the growth time to favor the production of our proposed ultrasmall npm-MS2 are critical but practical. Research on npm-VS2 would bear the highest impact because of its size-forgiving HER performance and relatively high abundance and low cost.

Effects of TMEM9 gene on cell progression in hepatocellular carcinoma by RNA interference.

Hepatocellular carcinoma (HCC) is a malignant tumor that has become a global health issue. The aim of the present study was to examine the role of transmembrane protein 9 (TMEM9) in cell progression, such as cell growth, cell cycle, cell metastasis of hepatoma cells, and to discuss the TMEM9 gene­encoding protein as a potential therapy target of hepatoma. RT-qPCR was performed to examine TMEM9 expression in tumor tissues and adjacent tissues of patients with liver cancer. siRNAs were used to interfere TMEM9 in HepG2 and 7721 cells. A CCK-8 assay was performed to evaluate cell growth at 24, 48 and 72 h. Cell cycle and apoptosis were analyzed using flow cytometry. Transwell assays were used to determine cell invasion, migration and adhesion. The results showed that TMEM9 was expressed abnormally in liver cancers. TMEM9 expression increased significantly in the 34 examined patients. TMEM9 knockdown inhibited proliferation in the HepG2 and 7721 cells. The flow cytometric analysis revealed that TMEM9 knockdown by RNA interference resulted in G1 arrest and induced apoptosis. Cell invasion, migration and adhesion ability were also decreased. Western blotting indicated that expression of the cell cycle­related proteins CDK1, EIF3H, RPL10L, S100A10, CCNB1 and CCNB2 was significantly decreased. In conclusion, TMEM9 plays an important role in the cell growth of hepatoma cells.

[Clinical Characteristics of Wilson's Disease: a Retrospective Analysis of Admission Data among 126 Patients].

OBJECTIVE: To investigate the clinical features of Wilson's disease (WD) for the purpose of avoiding misdiagnosis and therefore improving the prognosis of this rare disease. METHODS: This study enrolled all the patients diagnosed as WD who were admitted to West China Hospital, Sichuan University from Jan 2008 to Dec 2014. Their clinical manifestations, head and abdominal images data were extracted and analyzed. RESULTS: There were a total of 126 patients of WD, male female ratio was 75 : 51, median age was 21-years old. 10.3% (13/126) of them had family history, 87.3% (109/126) patients presented with neuropsychiatric symptoms, 14.3% (18/126) patients manifested as chronic liver disease. All patients had decreased serum ceruloplasmin level < 200 mg/L, 121 (96.9%) patients had serum ceruloplasmin level < 100 mg/L. Magnetic resonance imaging and abdominal ultrasound detected structural abnormalities in 92.7% (102/110) and 88.9% (97/109) patients respectively. Kayser-Fleischer rings on slit-lamp ophthalmologic examination was found in 98.3% (115/117) patients. One patient underwent liver biopsy and the result of rhodanine stain was positive. The time from onset to diagnosis varied from 3 d to 19 years [(1.59 ± 2.66) years]. 20 (15.9%) patients were initially misdiagnosed. CONCLUSION: The patients presenting with neurological signs or unexplained liver disease should be assessed carefully for WD. Serum ceruloplasmin, 24-h urinary copper, Kayser-Fleischer rings and sometimes even liver biopsy could be helpful for the diagnosis.

First-principles investigations of transition-metal doped bilayer WS2.

By performing first-principles calculations, we have studied the structural, electronic and magnetic properties of transition-metal (TM) (Mn, Fe, Co, Ni) doped bilayer WS2 in both the AA and AB configurations. We have examined three probable interlayer doping positions, and found that the doped TM atoms prefer to stay below the S atoms. The TM atoms are covalently bound to the upper layer and lower layer S atoms with binding energies ranging from -0.74 to -1.72 eV for the AA configuration and from -0.69 to -1.80 eV for the AB configuration. Our calculations indicate that all the studied configurations are still semiconductors although the corresponding band gaps reduce a lot, except for the Fe-doped AA configuration which changes to a semi-metal with one spin state cross over at the Fermi level. Additional, our calculations indicate that Mn, Fe and Co-doping induces magnetism in both the AA and AB configurations. More importantly, a high spin polarization of 100% at the Fermi level is achieved in the Co-doped AA configuration and the Mn and Fe-doped AB configurations, which implies the potential for application in spintronic devices.

Ferromagnetism in Transitional Metal-Doped MoS2 Monolayer.

Manipulating electronic and magnetic properties of two-dimensional (2D) transitional-metal dichalcogenides (TMDs) MX2 by doping has raised a lot of attention recently. By performing the first-principles calculations, we have investigated the structural, electronic, and magnetic properties of transitional metal (TM)-doped MoS2 at low and high impurity concentrations. Our calculation result indicates that the five elements of V-, Mn-, Fe-, Co-, and Cu-doped monolayer MoS2 at low impurity concentration all give rise to the good diluted magnetic semiconductors. By studying various configurations with different TM-TM separations, we found that the impurity atoms prefer to stay together in the nearest neighboring (NN) configuration, in which the doped TM atoms are FM coupling except for Fe doping at 12 % concentration. For V, Mn, and Fe doping, the total magnetic moment is smaller than the local magnetic moment of the dopants because the induced spins on the nearby host atoms are antiparallel to that of the doped atoms. In contrast, Co and Cu doping both give the higher total magnetic moment. Especially, Cu doping induces strong ferromagnetism relative to the local spins. However, the atomic structures of Co- and Cu-doped MoS2 deviate from the original prismatic configuration, and the magnetic moments of the doped systems decrease at 12 % impurity concentration although both elements give higher magnetic moments at 8 % impurity concentration. Our calculations indicate that V and Mn are promising candidates for engineering and manipulating the magnetism of the 2D TMDs.

Band gap engineering of FeS2 under biaxial strain: a first principles study.

The promising photovoltaic activity of pyrite (FeS2) is attributed to its excellent optical absorptivity and earth abundance, but its band gap, 0.95 eV, is slightly lower than the optimum value of 1.3 eV. Here we report the first investigation of strained FeS2, whose band gap can be increased by ∼0.3 eV. The influence of uniaxial and biaxial strains on the atomic structure as well as the electronic and optical properties of bulk FeS2 is systematically examined by the first principles calculations. We found that the biaxial strain can effectively increase the band gap with respect to uniaxial strain. Our results indicate that the band gap increases with increasing tensile strain to its maximum value at 6% strain, but under the increasing compressive strain, the band gap decreases almost linearly. Moreover, the low intensity states at the bottom of the conduction band disappear and a sharp increase in the intensity appears at the lower energy level under the tensile strain, which causes the red shift of the absorption edge and enhances the overall optical absorption. With the increase of the band gap and enhanced optical absorption, FeS2 will make a better photovoltaic material.