Topological semimetals are characterized by symmetry-protected band crossings, which can be preserved in different dimensions in momentum space, forming zero-dimensional nodal points, one-dimensional ...nodal lines, or even two-dimensional nodal surfaces. Materials harboring nodal points and nodal lines have been experimentally verified, whereas experimental evidence of nodal surfaces is still lacking. Here, using angle-resolved photoemission spectroscopy (ARPES), we reveal the coexistence of Dirac nodal surfaces and nodal lines in the bulk electronic structures of ZrSiS. As compared with previous ARPES studies on ZrSiS, we obtained pure bulk states, which enable us to extract unambiguously intrinsic information of the bulk nodal surfaces and nodal lines. Our results show that the nodal lines are the only feature near the Fermi level and constitute the whole Fermi surfaces. We not only prove that the low-energy quasiparticles in ZrSiS are contributed entirely by Dirac fermions but also experimentally realize the nodal surface in topological semimetals.
Discovery of magnetic Weyl fermions: Dirac fermions split into pairs of Weyl fermions by slow magnetic fluctuations.
Weyl fermions as emergent quasiparticles can arise in Weyl semimetals (WSMs) in ...which the energy bands are nondegenerate, resulting from inversion or time-reversal symmetry breaking. Nevertheless, experimental evidence for magnetically induced WSMs is scarce. Here, using photoemission spectroscopy, we observe that the degeneracy of Bloch bands is already lifted in the paramagnetic phase of EuCd
2
As
2
. We attribute this effect to the itinerant electrons experiencing quasi-static and quasi–long-range ferromagnetic fluctuations. Moreover, the spin-nondegenerate band structure harbors a pair of ideal Weyl nodes near the Fermi level. Hence, we show that long-range magnetic order and the spontaneous breaking of time-reversal symmetry are not essential requirements for WSM states in centrosymmetric systems and that WSM states can emerge in a wider range of condensed matter systems than previously thought.
Invasion and metastasis are the major features of malignant tumors that are responsible for 90% of cancer-related deaths. Recently, microRNAs have been discovered to have a role in suppressing tumor ...metastasis. This study's aim was to clarify the roles of miR-145 in gastric carcinomas and its underlying molecular mechanism in regulating tumor metastasis. Here, we demonstrate a stepwise downregulation of miR-145 level in nontumorous gastric mucosa, primary gastric cancers and their secondary metastases. In vitro analysis of miR-145's ectopic expression and loss-of-function suggests that it suppresses gastric cancer cell migration and invasion. In vivo spontaneous metastasis and experimental metastasis assay further confirm its function in suppressing the invasion-metastasis cascade, including impairing local invasion and inhibiting hematogenous metastasis in gastric cancers. Furthermore, we identified a novel mechanism of miR-145 to suppress metastasis. N-cadherin (CDH2) was proved to be a direct target of miR-145, using luciferase assay and western blot. Re-expressing N-cadherin in miR-145-transfected cells reverses their migration and invasion defects. Although not a direct target of miR-145, matrix metallopeptidase 9 (MMP9), but not MMP2, was also significantly decreased in miR-145-expressing cells. We suggest that miR-145 suppresses tumor metastasis by inhibiting N-cadherin protein translation, and then indirectly downregulates its downstream effector MMP9.
The rapid rise in energy consumption in the last few years and low emission requirements have inspired many researchers to develop highly efficient environment-friendly green energy sources. A high ...energy density system coupled with large energy efficiency is an effective way to store the energy produced from various renewable sources. BaTiO3 based dielectric/ferroelectric materials have attracted much attention for energy storage applications in the past decade due to their improved dielectric, ferroelectric, and breakdown strength properties. Herein, we report a comprehensive review on the recent developments in BaTiO3 based single-phase and composite systems with improved energy storage performance. The effect of synthesis techniques, dielectric properties, ferroelectric characteristics, and breakdown strength on the energy storage properties have been reviewed. This review primarily emphasizes on the key strategies and analytical models for enhancing energy density and energy efficiency of various BaTiO3 based materials. To validate the commercial applications of BaTiO3 based single-phase and multi-phase composites, a comprehensive summary has been presented with the most recent examples of BaTiO3 based materials in multi-layered ceramic capacitors, pulse power capacitors, hybrid electric vehicles, and high-power electronic devices. At last, the current challenges and new potential applications in reference to energy storage have been discussed.
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