Layered transition-metal dichalcogenides have emerged as exciting material systems with atomically thin geometries and unique electronic properties. Pressure is a powerful tool for continuously tuning their crystal and electronic structures away from the pristine states. Here, we systematically investigated the pressurized behavior of MoSe2 up to ∼60 GPa using multiple experimental techniques and ab-initio calculations. MoSe2 evolves from an anisotropic two-dimensional layered network to a three-dimensional structure without a structural transition, which is a complete contrast to MoS2. The role of the chalcogenide anions in stabilizing different layered patterns is underscored by our layer sliding calculations. MoSe2 possesses highly tunable transport properties under pressure, determined by the gradual narrowing of its band-gap followed by metallization. The continuous tuning of its electronic structure and band-gap in the range of visible light to infrared suggest possible energy-variable optoelectronics applications in pressurized transition-metal dichalcogenides.
Understanding the behavior of hydrogen-rich systems at extreme conditions has significance to both condensed matter physics, where it may provide insight into the metallization and superconductivity of element one, and also to applied research areas, where it can provide guidance for designing improved hydrogen storage materials for transportation applications. Here we report the high-pressure study of the SiH4-H2 binary system up to 6.5 GPa at 300 K in a diamond anvil cell. Raman measurements indicate significant intermolecular interactions between H2 and SiH4. We found that the H2 vibron frequency is softened by the presence of SiH4 by as much as 40 cm ؊1 for the fluid with 50 mol% H2 compared with pure H2 fluid at the same pressures. In contrast, the Si-H stretching modes of SiH4 shift to higher frequency in the mixed fluid compared with pure SiH4. Pressure-induced solidification of the H2-SiH4 fluid shows a binary eutectic point at 72(؎2) mol% H2 and 6.1(؎0.1) GPa, above which the fluid crystallizes into a mixture of two nearly end-member solids. Neither solid has a pure end-member composition, with the silane-rich solid containing 0.5-1.5 mol% H2 and the hydrogen-rich solid containing 0.5-1 mol% SiH4. These two crystalline phases can be regarded as doped hydrogendominant compounds. We were able to superpressurize the sample by 0.2-0.4 GPa above the eutectic before complete crystallization, indicating extended metastability.hydrogen ͉ phase diagram ͉ silane G roup IVa hydrides (i.e., CH 4 , SiH 4 , GeH 4 , SnH 4 ) have the highest atomic fraction (80%) of hydrogen among elemental hydrides and were predicted to metallize into hydrogen-dominant metallic alloys at lower pressures compared with pure hydrogen (1). Recent experiments on silane (SiH 4 ) have confirmed such predictions: Synchrotron infrared reflectivity and electrical conductivity measurements indicate its metallization at Ϸ50-60 GPa (2, 3), and SiH 4 becomes superconducting at a transition temperature of 17 K at 96 GPa (3). Interactions between elemental hydrides and additional molecular hydrogen at high pressure are a rapidly growing area of research (4, 5). Formation of numerous stoichiometric compounds demonstrates the complicated interactions between hydrogen and other molecular species in condensed phases. H 2 and H 2 O form clathrates and filled ices that can be quenched to ambient pressure at low temperature (6). Methane (CH 4 ) was discovered to form at least four stoichiometric compounds with hydrogen at pressures up to 10 GPa (7). The high pressure behavior of the H 2 -SiH 4 is of interest, in part because potential phases in this system may store a significant amount of molecular hydrogen and mimic the behavior of pure H 2 and its possible metallization but at lower pressures. Here we report our study of the phase diagram of H 2 -SiH 4 system to 6.5 GPa at room temperature. Samples with two premixed starting compositions, 5:1 and 1:1 molar H 2 :SiH 4 ratios, were loaded as a well-mixed fluid phase in a diamond anvil cell and were monitor...
Background/purposeCell adhesion molecule 1 (CADM1) functions as a tumor suppressor and has been identified to be frequently inactivated in breast cancer, and closely associated with patients’ poor prognosis and advanced TNM stage. However, the mechanisms underlying CADM1 in breast cancer progression remains incompletely clear. miR-155, a predicted modulator of CADM1 was reported to be overexpressed in breast cancer, and its high expression level was closely related to the malignant progression of breast cancer. The present study aimed to explore whether miR-155-3p could modulate CADM1 expression and then involved in the progression of breast cancer.MethodsThe expression patterns of miR-155-3p in breast cancer tissues and cell lines were determined by RT-PCR technology. The relationship between CADM1 and miR-155-3p were determined by the luciferase gene reporter and Western Blot (WB) assays. Cell proliferation, apoptosis rates and tumorigenesis were determined by CCK-8, flow cytometry and in vivo xenotransplanation experiments, respectively.ResultsmiR-155-3p was up-regulated in breast cancer tissues and cells when compared to the adjacent normal tissues and normal breast MCF 10A cells. The mRNA and protein levels of CADM1 showed opposite expression patterns to that of miR-155-3p expression detected, and miR-155-3p could negatively regulate CADM1 expression in breast cancer MCF-7 cells. Moreover, gain-of function assay showed that overexpression of miR-155-3p promoted cell proliferation, tumorigenesis and repressed cell apoptosis, but these effects were all significantly impaired when the cells were simultaneously transfected with OE-CADM1, the overexpressing vector of CADM1.ConclusionThis study revealed that miR-155-3p could accelerate the progression of breast cancer via down-regulation of CADM1 expression.
Oxidative stress (OS) has been linked to the etiology and development of leukemia as reactive oxygen species (ROS) and free radicals have been implicated in leukemogenesis. OS has beneficial and deleterious effects in the pathogenesis and progression of leukemia. High-dose chemotherapy, which is frequently used in leukemia treatment, is often accompanied by ROS-induced cytotoxicity. Thus, the utilization of chemotherapy in combination with antioxidants may attenuate leukemia progression, particularly for cases of refractory or relapsed neoplasms. The present review focuses on exploring the roles of OS in leukemogenesis and characterizing the associations between ROS and chemotherapy. Certain examples of treatment regimens wherein antioxidants are combined with chemotherapy are presented, in order to highlight the importance of antioxidant application in leukemia treatment, as well as the conflicting opinions regarding this method of therapy. Understanding the underlying mechanisms of OS generation will facilitate the elucidation of novel approaches to leukemia treatment.
Sb2O3-based materials are of broad interest in materials science and industry. High pressure study using diamond anvil cells shows promise in obtaining new crystal and electronic structures different from their pristine states. Here, we conducted in-situ angle dispersive synchrotron Xray diffraction and Raman spectroscopy experiments on α-Sb2O3 up to 50 GPa with neon as the pressure transmitting medium. A first-order structural transition was observed in between 15 to 20 GPa, where the cubic phase I gradually transformed into a layered tetragonal phase II through structural distortion and symmetry breaking. To explain the dramatic changes in sample color and transparency, we performed first-principles calculations to track the evolution of its density of states and electronic structure under pressure. At higher pressure, a sluggish amorphization was observed. Our results highlight the structural connections among the sesquioxides, where the lone electron pair plays an important role in determining the local structures.
scite is a Brooklyn-based startup that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
334 Leonard St
Brooklyn, NY 11211
Copyright © 2023 scite Inc. All rights reserved.
Made with 💙 for researchers