Abstract
The recently discovered non-Hermitian skin effect (NHSE) manifests the breakdown of current classification of topological phases in energy-nonconservative systems, and necessitates the ...introduction of non-Hermitian band topology. So far, all NHSE observations are based on one type of non-Hermitian band topology, in which the complex energy spectrum winds along a closed loop. As recently characterized along a synthetic dimension on a photonic platform, non-Hermitian band topology can exhibit almost arbitrary windings in momentum space, but their actual phenomena in real physical systems remain unclear. Here, we report the experimental realization of NHSE in a one-dimensional (1D) non-reciprocal acoustic crystal. With direct acoustic measurement, we demonstrate that a twisted winding, whose topology consists of two oppositely oriented loops in contact rather than a single loop, will dramatically change the NHSE, following previous predictions of unique features such as the bipolar localization and the Bloch point for a Bloch-wave-like extended state. This work reveals previously unnoticed features of NHSE, and provides the observation of physical phenomena originating from complex non-Hermitian winding topology.
Berry phase associated with energy bands in crystals can lead to quantised observables like quantised dipole polarizations in one-dimensional topological insulators. Recent theories have generalised ...the concept of quantised dipoles to multipoles, resulting in the discovery of multipole topological insulators which exhibit a hierarchy of multipole topology: a quantised octupole moment in a three-dimensional bulk induces quantised quadrupole moments on its two-dimensional surfaces, which in turn induce quantised dipole moments on one-dimensional hinges. Here, we report on the realisation of an octupole topological insulator in a three-dimensional acoustic metamaterial. We observe zero-dimensional topological corner states, one-dimensional gapped hinge states, two-dimensional gapped surface states, and three-dimensional gapped bulk states, representing the hierarchy of octupole, quadrupole and dipole moments. Conditions for forming a nontrivial octupole moment are demonstrated by comparisons with two different lattice configurations having trivial octupole moments. Our work establishes the multipole topology and its full hierarchy in three-dimensional geometries.
Since the industrial revolution, it has been assumed that fossil-fuel combustions dominate increasing nitrogen oxide (NO
) emissions. However, it remains uncertain to the actual contribution of the ...non-fossil fuel NO
to total NO
emissions. Natural N isotopes of NO
in precipitation (δ
N
) have been widely employed for tracing atmospheric NO
sources. Here, we compiled global δ
N
observations to evaluate the relative importance of fossil and non-fossil fuel NO
emissions. We found that regional differences in human activities directly influenced spatial-temporal patterns of δ
N
variations. Further, isotope mass-balance and bottom-up calculations suggest that the non-fossil fuel NO
accounts for 55 ± 7% of total NO
emissions, reaching up to 21.6 ± 16.6Mt yr
in East Asia, 7.4 ± 5.5Mt yr
in Europe, and 21.8 ± 18.5Mt yr
in North America, respectively. These results reveal the importance of non-fossil fuel NO
emissions and provide direct evidence for making strategies on mitigating atmospheric NO
pollution.
Cancer susceptibility candidate 2 (CASC2), a recently discovered long non‐coding RNA (lncRNA), was confirmed to play numerous roles in several human cancers. However, the involvement and concrete ...mechanism of CASC2 in hepatocellular carcinoma (HCC) still need to be further elucidated. The relative expressions of CASC2 and miR‐24‐3p in HCC tissue and cell lines were determined by quantitative real‐time PCR (qRT‐PCR). The effects of CASC2 and miR‐24‐3p on HCC cells were further assessed via cell viability and apoptosis. In vivo tumorigenesis assay was performed to verify the inhibition effect of CASC2 on the tumor growth and further clarify the important role of miR‐24‐3p in this mechanism. Compared with the paired normal tissues, the relative expression of CASC2 significantly reduced in the HCC tissues, while miR‐24‐3p as determined by qRT‐PCR obviously increased in the HCC tissues. This observation was also found in HCC cell lines. Meanwhile, the expression of CASC2 was negatively related to miR‐24‐3p expression in the HCC tissues (r = −0.804, P < 0.001). CASC2 could negatively regulate the expression of miR‐24‐3p in vitro. Moreover, CASC2 overexpression resulted in the growth inhibitory and apoptosis‐inducing effects on HCC cells, but the up‐regulation of miR‐24‐3p greatly eliminated the CASC2‐induced effects. The tumorigenesis of HCC cells was restrained significantly by CASC2 overexpression as shown by decreased tumor volume and growth rate. However, miR‐24‐3p up‐regulation rescued the inhibition of CASC2 on the tumor growth in tumor‐bearing mice. LncRNA CASC2 inhibited the viability and induced the apoptosis of HCC cells through regulating miR‐24‐3p.
We investigated the involvement and concrete mechanism of CASC2 in HCC. CASC2 inhibited the viability and induced the apoptosis of HCC cells. The role of CASC2 in cell tumorigenesis was mediated by miR‐24‐3p.
Ggtree is a comprehensive R package for visualizing and annotating phylogenetic trees with associated data. It can also map and visualize associated external data on phylogenies with two general ...methods. Method 1 allows external data to be mapped on the tree structure and used as visual characteristic in tree and data visualization. Method 2 plots the data with the tree side by side using different geometric functions after reordering the data based on the tree structure. These two methods integrate data with phylogeny for further exploration and comparison in the evolutionary biology context. Ggtree is available from http://www.bioconductor.org/packages/ggtree.
DNA repair pathways are triggered to maintain genetic stability and integrity when mammalian cells are exposed to endogenous or exogenous DNA-damaging agents. The deregulation of DNA repair pathways ...is associated with the initiation and progression of cancer. As the primary anti-cancer therapies, ionizing radiation and chemotherapeutic agents induce cell death by directly or indirectly causing DNA damage, dysregulation of the DNA damage response may contribute to hypersensitivity or resistance of cancer cells to genotoxic agents and targeting DNA repair pathway can increase the tumor sensitivity to cancer therapies. Therefore, targeting DNA repair pathways may be a potential therapeutic approach for cancer treatment. A better understanding of the biology and the regulatory mechanisms of DNA repair pathways has the potential to facilitate the development of inhibitors of nuclear and mitochondria DNA repair pathways for enhancing anticancer effect of DNA damage-based therapy.
Liquid crystals have great potential for developing photonic devices that control the optical behaviors of liquid crystals in smart devices with external stimulation. In this study, we have ...demonstrated a series of bistable cholesteric liquid crystal devices using the dual-frequency nematic liquid crystal HEF951 assisted by a predesigned chiral ferroelectric liquid crystal. The synthesized chiral ferroelectric liquid crystal was used to induce the formation of the cholesteric liquid crystal phase and decrease the driving voltages and response times of the fabricated bistable liquid crystal devices. The fabricated ferroelectric liquid crystal-assisted bistable cholesteric liquid crystal devices showed a stable opaque focal conic state and stable transparent planar state without any energy consumption once they were turned "from focal-conic to planar" and "from planar to focal-conic". To enhance the reliability, the fabricated bistable cholesteric liquid crystal devices were further stabilized by polymer matrixes. Switching of the bistable liquid crystal cells from one state to another was achieved by a one-step voltage bias with various frequencies. Furthermore, the response time of the sample cell was calculated as 1.7 ms. These results suggest that fabricated ferroelectric liquid crystal-assisted bistable cholesteric liquid crystal devices can be applied to produce energy-saving green liquid crystal displays and other related smart devices.
Fabricated polymer-stabilized bistable cholesteric liquid crystal devices show a stable opaque focal conic state and a stable transparent planar state without any energy consumption once they are turned.
Abstract
Crystalline materials can host topological lattice defects that are robust against local deformations, and such defects can interact in interesting ways with the topological features of the ...underlying band structure. We design and implement a three dimensional acoustic Weyl metamaterial hosting robust modes bound to a one-dimensional topological lattice defect. The modes are related to topological features of the bulk bands, and carry nonzero orbital angular momentum locked to the direction of propagation. They span a range of axial wavenumbers defined by the projections of two bulk Weyl points to a one-dimensional subspace, in a manner analogous to the formation of Fermi arc surface states. We use acoustic experiments to probe their dispersion relation, orbital angular momentum locked waveguiding, and ability to emit acoustic vortices into free space. These results point to new possibilities for creating and exploiting topological modes in three-dimensional structures through the interplay between band topology in momentum space and topological lattice defects in real space.
In the present study, rice husk ash (RHA, a solid waste from agriculture) was served as the support for loading calcined eggshell (another material derived from waste source) to prepare solid base ...catalyst. This catalyst was then applied for catalytically converting palm oil into biodiesel. The effects of catalyst preparation conditions (such as rice husk treatment temperature, the loading of calcined eggshell on the RHA, and the calcination temperature of eggshell-loaded RHA), reaction conditions (such as reaction time, methanol-to-oil molar ratio and catalyst loading) and the catalyst reusability were carefully studied. The experimental results revealed that 30% RHA800-800 exhibited the highest catalytic activity. More specifically, when the reaction was carried out with a reaction time of 4h, methanol-to-oil molar ratio of 9:1, and catalyst loading of 7wt.%, the biodiesel yield could reach 91.5%. Besides, after reused for more than 8cycles, the catalyst could still possess a rather high biodiesel yield (above 80%).
•Novel heterogeneous rice rusk ash-based catalysts were developed.•The optimum catalyst is 30% RHA800-800.•Maximum biodiesel yield of 91.5% is achieved using the novel catalyst.•The novel catalyst can achieve a desirable recyclability.
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