Enhanced Intrinsic Anomalous Valley Hall Effect Induced by Spin-Orbit Coupling in MXene Monolayer M3N2O2 (M = Y, La).

The limitation of suitable anomalous valley Hall effect (AVHE) materials has seriously hindered the booming development and the widespread application of valleytronics. Here, through the first-principles calculations, we propose a MXene monolayer Y3N2O2 with spontaneous valley polarization (VP) of 21.3 meV, which induces intrinsic AVHE. The VP can be modulated linearly, which provides a route of effective control of the valley signals. Importantly, VP can be enhanced by adjusting up the spin-orbit coupling (SOC) based on a SOC Hamiltonian model and the first-principles calculations. From this physics underlying, we substitute the Y atom with the La atom and further propose the monolayer La3N2O2, in which the heavy atom La will provide stronger SOC than Y atom. The spontaneous VP in La3N2O2 is enhanced to 100.4 meV, so AVHE can be easily achieved. Our work not only provides compelling candidates for AVHE materials but also offers a novel mindset for finding suitable valleytronic devices.

Type-II Band Alignment and Tunable Optical Absorption in MoSSe/InS van der Waals Heterostructure.

In this work, we study the electronic structure, the effective mass, and the optical properties of the MoSSe/InS van der Waals heterostructures (vdWHs) by first-principles calculations. The results indicate that the MoSSe/InS vdWH is an indirect band gap semiconductor and has type-Ⅱ band alignment in which the electrons and holes located at the InS and the MoSSe side, respectively. The band edge position, the band gap and the optical absorption of the MoSSe/InS vdWH can be tuned when biaxial strains are applied. In addition, compared with MoSSe and InS monolayers, the optical absorption of the MoSSe/InS vdWH is improved both in the visible and the ultraviolet regions. These findings indicate that the MoSSe/InS vdWHs have potential applications in optoelectronic devices.

Tuning electronic and optical properties of monolayer PdSe2 by introducing defects: first-principles calculations.

Based on the density functional theory, the electronic and optical properties of pristine monolayer PdSe2 with Pd or Se vacancy-defect are investigated. Our results show that the Se defect is energetically more favorable than that of Pd defect. The band gap reduces, and some new midgap states appear after the Pd or Se defects are introduced. In terms of the optical properties, the prominent anisotropic characters are remained. The obvious new peaks of the dielectric constant appear after introducing defects. The light absorption in the visible energy range expands based on the appearance of the midgap states induced by the Pd or Se defects. The changes of the refractive index and reflectivity are similar with those of the dielectric constants and the light absorption. The energy loss spectrum of the PdSe2 with Pd or Se defects is obviously different, which can be used to identify different defects in PdSe2. These findings provide effective strategies to tune electronic and optical properties of monolayer PdSe2 by introducing defects.

[Prevalence of cataract among the population aged 50 years and over at different altitudes in Gansu Province].

Objective: To assess the prevalence and influence factors of cataract at different altitudes in Gansu Province. Methods: A total of 7 560 permanent residents aged 50 years and over in seven regions of Gansu Province (altitude, 900 meters to 3 500 meters) were selected as subjects, including 2 402 males and 5 158 females, with an average age of 62.04 years. The cluster random sampling method was used to conduct the survey at village or township health service centers. The investigation procedure included questionnaire survey, pre-investigation, visual acuity examination, intraocular pressure measurement, slit lamp microscopy and fundus examination. The diagnostic criterion for cataract was typical opacity of the lens or no other eye diseases that led to visual impairment but with visual acuity less than 0.7. The prevalence of cataract was calculated according to factors such as altitude, age and sex. The Chi-square test and two-element unconditional logistic regression were used for statistical analyses. Results: A total of 7 560 people were surveyed. The prevalence rate of cataract was 39.7%, and the age-standardized prevalence was 37.7%. The prevalence of cataract increased with age (χ(2)=2 107.19, P<0.01). It was 14.1% in the group of 50-59 years, 42.9% in the group of 60-69 years and 79.2% in the group of over 70 years. The prevalence of cataract also increased with altitude (χ(2)=33.66, P<0.01). It was 36.9% in the group of altitude less than 1 000 meters, 39.0% in the group of altitude between 1 000 meters and 1 999 meters, 45.9% in the group of altitude between 2 000 meters and 2 999 meters, and 51.5% in the group of altitude more than 3 000 meters. With age stratification, the prevalence of cataract at high altitude was higher than that at low altitude (χ(2)=26.74, 16.06, P<0.01). Multivariate regression analysis showed that the risk of cataract was higher in subjects at altitude of 2 000-2 999 meters than those below 1 000 meters (OR=1.42, 95%CI 1.11-1.82), and even higher in those at altitude of 3 000 meters (OR=1.76, 95%CI 1.01-3.06). Conclusions: High altitude and old age are important risk factors for cataract, and high altitude is an independent risk factor for cataract. It is necessary for local health institutions to take measures to reduce the prevalence of blindness and low vision, especially the blindness caused by cataract. (Chin J Ophthalmol, 2019, 55:589-594).

The MTase15 regulates reproduction in the wing-dimorphic planthopper, Nilaparvata lugens (Hemiptera: Delphacidae).

S-Adenosyl-l-methionine-dependent methyltransferases (SAMMTases) modulate important cellular and metabolic activities in both prokaryotes and eukaryotes. Here, we functionally characterized an SAMMTase gene (MTase15) in the migratory brown planthopper (BPH), Nilaparvata lugens, which is the most notorious rice pest in Asia. The cDNA sequence of MTase15 is 2764 nt in length with an open reading frame of 1218 nt encoding 405 amino acid residues. Quantitative real-time PCR analysis showed that MTase15 was readily detected from egg to adult stages and extensively distributed in various body parts of adult females and males, with slightly high levels in ovary and testis, respectively. In addition, MTase15 was transcriptionally regulated by the insulin signalling pathway in BPH. RNA-interference-mediated knockdown of MTase15 (dsMtase15) resulted in deficiencies in vitellogenin synthesis and oogenesis, and female infertility. Males with Mtase15 knockdown retained the capability of producing sperms with normal viability, but less sperm was transferred to wild-type (wt) females during copulation, and eggs laid by these wt females arrested embryogenesis. These findings not only assign a functional role to MTase15, but also provide a link between the insulin signalling pathway and epigenetic regulation in BPH reproduction.

Investigation of the multiplet features of SrTiO3 in X-ray absorption spectra based on configuration interaction calculations.

Synchrotron-based L2,3-edge absorption spectra show strong sensitivities to the local electronic structure and chemical environment. However, detailed physical information cannot be extracted easily without computational aids. Here, using the experimental Ti L2,3-edges absorption spectrum of SrTiO3 as a fingerprint and considering full multiplet effects, calculations yield different energy parameters characterizing local ground state properties. The peak splitting and intensity ratios of the L3 and L2 set of peaks are carefully analyzed quantitatively, giving rise to a small hybridization energy around 1.2 eV, and the different hybridization energy values reported in the literature are further addressed. Finally, absorption spectra with different linearly polarized photons under various tetragonal crystal fields are investigated, revealing a non-linear orbital-lattice interaction, and a theoretical guidance for material engineering of SrTiO3-based thin films and heterostructures is offered. Detailed analysis of spectrum shifts with different tetragonal crystal fields suggests that the eg crystal field splitting is a necessary parameter for a thorough analysis of the spectra, even though it is not relevant for the ground state properties.

Hole-conductor-free perovskite solar cells with carbon counter electrodes based on ZnO nanorod arrays.

A one dimensional nanostructure array has been considered as a successful charge transport material for perovskite solar cells (PSCs), because of its large internal surface area, superior charge collection efficiency and fast charge transport. Herein we demonstrate a ZnO nanorod (NR) array as the electron collector in a hole-conductor-free PSC with a carbon counter electrode (CE). A relatively low initial power conversion efficiency (PCE) of 5.6% was achieved using a 1 µm long ZnO NR array as an electron collector. However, by introduction of a thin TiO2 coating layer on the surface of ZnO via TiCl4 treatment, the PCE of the cell has been improved to the highest value of 8.24%. It is revealed that the performance enhancement of the ZnO/TiO2 NR based PSCs is largely attributed to the larger surface area, reduced electron combination, and superior electron transport properties.

[Experimental study and clinical use of thin skin flap with subdermal vascular rete].

The extent and limit of defatting and the reliability of the blood supply of random-pattern and island flaps with subdermal vascular rete were studied in 12 piglets. The results showed that if 3 mm of adipose tissue or one third of superficial fascia was preserved beneath the subdermal vascular network, the survival rate of these two kinds of skin was similar. After division of the pedicle on the sixth postoperative day, random-pattern subdermal vascular rete skin flap could survive with a length-width ratio of 2.5:1. The area of island flap with subdermal vascular rete could be thinned as much as 60%-70%. 27 wounds in 25 patients were covered successfully with random-pattern skin flap with subdermal vascular rete. In addition, transplantation of 13 free flaps with subdermal vascular rete with microsurgical technique was completely successful in 12 patients.

[Study on polymorphism of gossypol by infrared spectrophotometry and X-ray diffraction].

The polymorphism of gossypol has been investigated by IR spectrophotometry and X-ray diffraction. Nine samples of gossypol crystallized from mixed solvent of ether, ethanol and water (1:2:2), five samples from chloroform and ten samples from petroleum ether (bp 60-90 degrees C) were determined. Significant differences in the infrared spectra of gossypol crystallized from three solvents were observed near 3500 cm-1. The spectrum of gossypol crystallized from mixed solvent of ether, ethanol and water (mp 183-184 degrees C) showed bands at 3500 (sh), 3470, 3375 cm-1; that from chloroform (mp 198-199 degrees C) at 3455, 3415 (sh) cm-1 and that from petroleum ether (mp 213-214 degrees C) at 3510, 3495, 3430 (sh), 3410 cm-1. Moreover, the spectra of the three forms of gossypol showed slightly different bands at 780 and 600-400 cm-1. Gossypol crystallized from the three solvents showed the same infrared spectra after being crystallized from acetone. Significant differences in the X-ray diffraction pattern of gossypol crystallized from the three solvents were also observed. Angles, intensities and D-values of most of the X-ray diffraction peaks were listed.