Study on the Mechanism of Action of Different Acupuncture Regimens on Premature Ovarian Failure Model Rats.

Objective: To study the mechanism of acupuncture on premature ovarian failure (POF) through the apoptosis pathway mediated by Bcl-2/Bax. Methods: POF rats were successfully obtained by cyclophosphamide. They were divided into five groups. After that, acupuncture was performed. The blank group and model group were not treated. The routine acupuncture group was acupuncture at Guanyuan, Sanyinjiao, Zhongji, and Guilai four points. The Neck-seven-acupuncture group was selected from Fengchi, Fengfu, Tianzhu, and Wangu four acupoints; the three-viscera simultaneous treatment group selected Guanyuan, Shenshu, Sanyinjiao, Taichong, and Baihui five points; and the data mining group selected Guanyuan and Sanyinjiao two points for 14 days of treatment. During the treatment, some rats were shed one after another due to the side effects of bone marrow suppression caused by mold-making. After treatment, serum estradiol (E2), follicle forming hormone (FSH), and luteinizing hormone (LH) were detected by radioimmunoassay, Bcl-2 and Bax proteins were analyzed by Western blot method, and Bcl-2 and Bax RNA were analyzed by PCR method. Results: Bcl-2 increased and Bax decreased in rats with premature ovarian failure treated with acupuncture. It shows that acupuncture can affect the secretion of ovarian-related hormones and the expression of apoptosis-related proteins, which is more significant in the conventional acupuncture point group. Conclusion: Acupuncture can inhibit the apoptosis of granulosa cells in ovarian tissue of rats with premature ovarian failure and improve ovarian function. The mechanism of its effect is to promote Bcl-2 gene expression and protein synthesis and inhibit Bax gene expression and protein synthesis. The conventional treatment group works best. This provides an experimental basis for the clinical use of acupuncture to intervene in the treatment of premature ovarian failure.

Evolution of Electronic Structure in Pristine and Rb-Reconstructed Surfaces of Kagome Metal RbV3Sb5.

We report on in situ low-temperature (4 K) scanning tunneling microscope measurements of atomic and electronic structures of the cleaved surfaces of an alkali-based kagome metal RbV3Sb5 single crystals. We find that the dominant pristine surface exhibits Rb-1×1 structure, in which a unique unidirectional √3a0 charge order is discovered. As the sample temperature slightly rises, Rb-√3×1 and Rb-√3×√3 reconstructions form due to desorption of surface Rb atoms. Our conductance mapping results demonstrate that Rb desorption not only gives rise to hole doping but also reconstructs the electronic band structures. Surprisingly, we find a ubiquitous gap opening near the Fermi level in tunneling spectra on all the surfaces despite their large differences of hole-carrier concentration, indicating an orbital-selective band reconstruction in RbV3Sb5. The Rb desorption induced electronic reconstructions are further confirmed by our density functional theory calculations.

Incommensurate smectic phase in close proximity to the high-Tc superconductor FeSe/SrTiO3.

Superconductivity is significantly enhanced in monolayer FeSe grown on SrTiO3, but not for multilayer films, in which large strength of nematicity develops. However, the link between the high-transition temperature superconductivity in monolayer and the correlation related nematicity in multilayer FeSe films is not well understood. Here, we use low-temperature scanning tunneling microscopy to study few-layer FeSe thin films grown by molecular beam epitaxy. We observe an incommensurate long-range smectic phase, which solely appears in bilayer FeSe films. The smectic order still locally exists and gradually fades away with increasing film thickness, while it suddenly vanishes in monolayer FeSe, indicative of an abrupt smectic phase transition. Surface alkali-metal doping can suppress the smectic phase and induce high-Tc superconductivity in bilayer FeSe. Our observations provide evidence that the monolayer FeSe is in close proximity to the smectic phase, and its superconductivity is likely enhanced by this electronic instability as well.

Electronic States and Magnetic Response of MnBi2Te4 by Scanning Tunneling Microscopy and Spectroscopy.

Exotic quantum phenomena have been demonstrated in recently discovered intrinsic magnetic topological insulator MnBi2Te4. At its two-dimensional limit, the quantum anomalous Hall effect and axion insulator state were observed in odd and even layers of MnBi2Te4, respectively. Here, we employ low-temperature scanning tunneling microscopy to study the electronic properties of MnBi2Te4. The quasiparticle interference patterns indicate that the electronic structures on the topmost layer of MnBi2Te4 are different from those of the expected out-of-plane A-type antiferromagnetic phase. The topological surface states may be embedded in deeper layers beneath the topmost surface. Such novel electronic structure is presumably related to the modification of crystalline structure during sample cleaving and reorientation of the magnetic moment of Mn atoms near the surface. Mn dopants substituted at the Bi site on the second atomic layer are observed. The electronic structures fluctuate at atomic scale on the surface, which can affect the magnetism of MnBi2Te4.

Charge ordering in high-temperature superconductors visualized by scanning tunneling microscopy.

Since the discovery of stripe order in La1.6-x Nd0.4Sr x CuO4 superconductors in 1995, charge ordering in cuprate superconductors has been intensively studied by various experimental techniques. Among these studies, scanning tunneling microscope (STM) plays an irreplaceable role in determining the real space structures of charge ordering. STM imaging of different families of cuprates over a wide range of doping levels reveal similar checkerboard-like patterns, indicating that such a charge ordered state is likely a ubiquitous and intrinsic characteristic of cuprate superconductors, which may shed light on understanding the mechanism of high-temperature superconductivity. In another class of high-temperature superconductors, iron-based superconductors, STM studies reveal several charge ordered states as well, but their real-space patterns and the interplay with superconductivity are markedly different among different materials. In this paper, we present a brief review on STM studies of charge ordering in these two classes of high-temperature superconductors. Possible origins of charge ordering and its interplay with superconductivity will be discussed.

Discovery of Superconductivity in 2M WS2 with Possible Topological Surface States.

Recently the metastable 1T'-type VIB-group transition metal dichalcogenides (TMDs) have attracted extensive attention due to their rich and intriguing physical properties, including superconductivity, valleytronics physics, and topological physics. Here, a new layered WS2 dubbed "2M" WS2 , is constructed from 1T' WS2 monolayers, is synthesized. Its phase is defined as 2M based on the number of layers in each unit cell and the subordinate crystallographic system. Intrinsic superconductivity is observed in 2M WS2 with a transition temperature Tc of 8.8 K, which is the highest among TMDs not subject to any fine-tuning process. Furthermore, the electronic structure of 2M WS2 is found by Shubnikov-de Haas oscillations and first-principles calculations to have a strong anisotropy. In addition, topological surface states with a single Dirac cone, protected by topological invariant Z2 , are predicted through first-principles calculations. These findings reveal that the new 2M WS2 might be an interesting topological superconductor candidate from the VIB-group transition metal dichalcogenides.

Edge States at Nematic Domain Walls in FeSe Films.

Quantum spin Hall (QSH) effect is an intriguing phenomenon arising from the helical edge states in two-dimensional topological insulators. We use molecular beam epitaxy (MBE) to prepare FeSe films with atomically sharp nematic domain boundaries, where tensile strains, nematicity suppression, and topological band inversion are simultaneously achieved. Using scanning tunneling microscopy (STM), we observe edge states at the Fermi level that spatially distribute as two distinct strips in the vicinity of the domain boundaries. At the end point of the boundaries, a bound state at the Fermi level is further observed. The topological origin of the edge states is supported by density functional theory calculations. Our findings not only demonstrate a candidate for QSH states but also provide a new pathway to realize topological superconductivity in a single-component film.