Hybrid nodal surface and nodal line phonons in solids

Phonons have provided an ideal platform for a variety of intriguing physical states, such as non-abelian braiding and Haldane model. It is promising that phonons will realize the complicated nodal states accompanying with unusual quantum phenomena. Here, we propose the hybrid nodal surface and nodal line (NS+NL) phonons beyond the single genre nodal phonons. We categorize the NS+NL phonons into two-band and four-band situations based on symmetry analysis and compatibility relationships. Combing database screening with first-principles calculations, we identify the ideal candidate materials for realizing all categorized NS+NL phonons. Our calculations and tight-binding models further demonstrate that the interplay between NS and NL induces unique phenomena. In space group 113, the quadratic NL acts as a hub of the Berry curvature between two NSs, generating ribbon-like surface states. In space group 128, the NS serve as counterpart of Weyl NL that NS-NL mixed topological surface states are observed. Our findings extend the scope of hybrid nodal states and enrich the phononic states in realistic materials.Comment: 23+35 pages, 5+44 figures, 1+3 table

Dependence structure in the Australian electricity markets: new evidence from regular vine copulae

In this study, regular vine copula was used to investigate the dependence structure of electricity prices at the state level in the Australian National Electricity Market (NEM), during three periods related to the adoption and abolition of the carbon tax. In the pre-carbon period, we found evidence of tail dependence separately in the northern and southern NEM, but not across them. During the carbon period, the joint spike in the northern NEM disappeared, and the tail dependence in the southern NEM decreased. In the post-carbon period, the best dependence structure turned out to be a flexible structure of the regular vine, which exactly matches the geographical infrastructure connectedness of transmission wires. Besides, both upper and lower tail dependences were found in all adjacent states after the abolition of the carbon tax, suggesting a more integrated market regarding tail dependence. Our findings have substantial implications for risk management in the NEM, especially for those participants exposed to multiple states

Nonvolatile electrical control of spin polarization in the 2D bipolar magnetic semiconductor VSeF

Abstract Nonvolatile electrical control of spin polarization in two-dimensional (2D) magnetic semiconductors is greatly appealing toward future low-dissipation spintronic nanodevices. Here, we report a 2D material VSeF, which is an intrinsic bipolar magnetic semiconductor (BMS) featured with opposite spin-polarized valence and conduction band edges. We then propose a general nonvolatile strategy to manipulate both spin-polarized orientations in BMS materials by introducing a ferroelectric gate with proper band alignment. The spin-up/spin-down polarization of VSeF is successfully controlled by the electric dipole of ferroelectric bilayer Al2Se3, verifying the feasibility of the design strategy. The interfacial doping effect from ferroelectric gate also plays a role in enhancing the Curie temperature of the VSeF layer. Two types of spin field effect transistors, namely multiferroic memory and spin filter, are further achieved in VSeF/Al2Se3 and VSeF/Al2Se3/Al2Se3 multiferroic heterostructures, respectively. This work will stimulate the application of 2D BMS materials in future spintronic nanodevices

Biochemical Process and Microbial Evolution in the Conversion of Corn Straw Combined with Coal to Biogas

[Image: see text] The combined anaerobic fermentation of coal and straw can increase the production of biogas. To explore the mechanism of adding corn straw to increase methane production, coal with different metamorphic degrees and corn straw were collected for biogas production simulation experiments under different substrate ratios. The changes in liquid products, the structure of lignocellulose in corn straw, and microbial evolution were monitored. The results showed that the combined fermentation of bituminous coal A with corn straw and bituminous coal C with corn straw at a mass ratio of 2:1 each ((AC-2) and (CC-2)) and that of bituminous coal B and corn straw at a mass ratio of 3:1 (BC-3) had the best gas production, and methane yields reached 17.28, 12.51, and 14.88 mL/g, respectively. The fermentation liquid had organic matter with more types and higher contents during the early and peak stages of gas production, and fewer types of organic matter were detected in the terminal stage. The degradation of lignocelluloses in the corn straw of AC-2 was higher. With the increase in fermentation time, the carbohydrates in the fermentation system increased and the degradation rate of cellulose decreased gradually. The abundance of genes related to nitrate reduction gradually increased, while that of sulfate reduction was on the contrary. Bacteria in the cofermentation system mainly metabolized carbohydrates. During cofermentation with high metamorphic coal, corn straw would be preferentially degraded. The structure of the archaea community changed from Methanosarcina and Methanothrix to Methanobacterium

Molecularly Controlled Modulation of Conductance on Azobenzene Monolayer-Modified Silicon Surfaces

Controlled modulation of silicon surface properties is of great importance for the development of siliconbased molecular electronic devices because of the ubiquitous role of silicon in microelectronics. In this article, photoresponsive azobenzene molecules were covalently grafted onto hydrogen-terminated Si(111) surfaces via Si-C linkages. These direct Si-C bond linkages are preferred over Si-O linkages at the interfaces because of the higher stability and the better electronic continuation between Si and the alkyl chain. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The reversible photoisomerization effects of the azobenzene molecules were also studied with contact angle measurements, atomic force microscopy (AFM), and conductive atomic force microscopy (C-AFM). The measured conductivity showed a reversible switching behavior by alternate illumination with UV and visible light. Thus, we have demonstrated molecularly controlled modulation of conductance of the Si surface by the photochemical method. Furthermore, the dipole moments of the azobenzene molecules switched accordingly with the alternate illumination. Making use of this characteristic, we have provided a strategy to evaluate the influence of the molecular dipole moments on the conductance of the semiconductor surface

Thrombopoietin knock-in augments platelet generation from human embryonic stem cells

Abstract Background Refinement of therapeutic-scale platelet production in vitro will provide a new source for transfusion in patients undergoing chemotherapy or radiotherapy. However, procedures for cost-effective and scalable platelet generation remain to be established. Methods In this study, we established human embryonic stem cell (hESC) lines containing knock-in of thrombopoietin (TPO) via CRISPR/Cas9-mediated genome editing. The expression and secretion of TPO was detected by western blotting and enzyme-linked immunosorbent assay. Then, we tested the potency for hematopoietic differentiation by coculturing the cells with mAGM-S3 cells and measured the generation of CD43+ and CD45+ hematopoietic progenitor cells (HPCs). The potency for megakaryocytic differentiation and platelet generation of TPO knock-in hESCs were further detected by measuring the expression of CD41a and CD42b. The morphology and function of platelets were analyzed with electronic microscopy and aggregation assay. Results The TPO gene was successfully inserted into the AAVS1 locus of the hESC genome and two cell lines with stable TPO expression and secretion were established. TPO knock-in exerts minimal effects on pluripotency but enhances early hematopoiesis and generation of more HPCs. More importantly, upon its knock-in, TPO augments megakaryocytic differentiation and platelet generation. In addition, the platelets derived from hESCs in vitro are functionally and morphologically comparable to those found in peripheral blood. Furthermore, TPO knock-in can partially replace the large quantities of extrinsic TPO necessary for megakaryocytic differentiation and platelet generation. Conclusions Our results demonstrate that autonomous production of cytokines in hESCs may become a powerful approach for cost-effective and large-scale platelet generation in translational medicine

Adenovirus-mediated Sirt1 and Tgfbr2 gene therapy improves fertility in natural ovarian aging and doxorubicin-induced premature ovarian insufficiency mice

Premature ovarian insufficiency (POI) may lead to early menopause, fertility loss and birth defects without effective treatment. Here, we explored the efficacy and safety of gene therapy to rescue ovarian function in both natural ovarian aging and doxorubicin (Dox) induced POI mice. Sirt1 and Tgfbr2 were screened out and identified as key genes in both murine and human ovarian tissues. Then, adenovirus (AdV) was selected as a suited carrier for ovarian infection after comparison of multiple viral vectors. In both two models, murine fertility was significantly improved after AdV-Sirt1 and AdV-Tgfbr2 invention individually or in combination, without obvious side effects to themselves and their offspring. Compared with the control group, the successful pregnancy rate in the 9-month-old-AdV-Sirt1 group increased by 60 % (67 % vs 42 %). Meanwhile, the pregnancy rate in the AdV-Tgfbr2 + Dox group increased by 85 % (55.6 % vs 20 %). The biological process of ovarian follicle development and fibrosis was rescued. Our work demonstrated that AdV-Sirt1 and AdV-Tgfbr2 therapy alleviates natural ovarian aging and Dox-associated POI, which may be potentially applicable for female fertility protection