Symmetry-protected topological exceptional chains in non-Hermitian crystals

In non-Hermitian systems, the defective band degeneracies, so-called exceptional points (EPs), can form robust exceptional lines (ELs) in 3D momentum space in the absence of any symmetries, and a topological invariant, termed discriminant number (DN), can characterize the braiding topology around an EL. Here, we show that a natural orientation can be assigned to every EL according to the DN around it, and prove the source-free principle of ELs as a corollary of the generalized Fermion doubling theorem for EPs on an arbitrary closed oriented surface, which indicates that if several ELs flow into a junction, the same number of outflow ELs from the junction must exist. Based on this principle, we discover three different mechanisms that can stabilize the junction of ELs and therefore guarantee the formation of various types of exceptional chains (ECs) under the protection of mirror, mirror-adjoint, or $\mathcal{C}_2\mathcal{T}$ symmetries. Furthermore, we analyze the thresholdless perturbations to a Hermitian nodal line and map out all possible EC configurations that can be evolved. By strategically designing the structure and materials, we further exhibit that these exotic ECs can be readily observed in non-Hermitian photonic crystals. Our results directly manifest the combined effect of spatial symmetry and topology on the non-Hermitian singularities and pave the way for manipulating the morphology of ELs in non-Hermitian crystalline systems.Comment: 10 pages, 5 figure

Experimental realization of stable exceptional chains protected by non-Hermitian latent symmetries unique to mechanical systems

Lines of exceptional points are robust in the 3-dimensional non-Hermitian parameter space without requiring any symmetry. However, when more elaborate exceptional structures are considered, the role of symmetry becomes critical. One such case is the exceptional chain (EC), which is formed by the intersection or osculation of multiple exceptional lines (ELs). In this study, we investigate a non-Hermitian classical mechanical system and reveal that a symmetry intrinsic to second-order dynamical equations, in combination with the source-free principle of ELs, guarantees the emergence of ECs. This symmetry can be understood as a non-Hermitian generalized latent symmetry, which is absent in prevailing formalisms rooted in first-order Schr\"odinger-like equations and has largely been overlooked so far. We experimentally confirm and characterize the ECs using an active mechanical oscillator system. Moreover, by measuring eigenvalue braiding around the ELs meeting at a chain point, we demonstrate the source-free principle of directed ELs that underlies the mechanism for EC formation. Our work not only enriches the diversity of non-Hermitian degeneracies, but also highlights the new potential for non-Hermitian physics in second-order dynamical systems.Comment: 25 pages, 11 figure

RISE-based adaptive control of electro-hydraulic servo system with uncertain compensation

Electro-hydraulic servo system (EHSS) plays an important role in many industrial and military applications. However, its high-performance tracking control is still a challenging mission due to its nonlinear system dynamics and model uncertainties. In this paper, a novel adaptive robust integral method of the sign of the error (ARISE) with extended state observer (ESO) is proposed. Firstly, the nonlinear mathematical model of typical EHSS with modeling uncurtains and uncertain nonlinear is established. Then, ESO is used to estimate the state and lumped disturbance, of which the unknown parameter estimations can be updated by the novel adaptive law. Results shows that the novel controller achieves better tracking performance in maximum tracking error, average tracking error and standard deviation of the tracking error

Effect of high hydrophilic electrospun short fibrous sponge on wound repair

Objective·To construct an electrospun short fibrous sponge (Sponge@GO) laden with graphene oxide (GO) for chronic wound healing.Methods·Two types of short fibrous sponges (Sponge and Sponge@GO) without and with GO were prepared by means of electrospinning, homogenizing, shaping and crosslinking with glutaraldehyde, respectively. The internal structures of the two sponges were observed with a scanning electron microscope (SEM), and their hydrophilic properties were observed via contact angle and water absorption rate. The biocompatibility of the sponge was verified by CCK-8 and live/dead staining. Twelve 6-week-old SD male rats were divided into control group, Sponge group and Sponge@GO group, with 4 rats in each group. The diabetes models were established by intraperitoneal injection of 1% streptozotocin solution, and three full-layer skin defects with a diameter of 1.0 cm were prepared on the back of each rat after modelling. Covering on the wound, the material was fixed with medical gauze. The control group was only covered with sterile gauze dressing. The wound healing rate was measured and calculated on Day 7 and 14, respectively, while hematoxylin-eosin (H-E) staining and Masson staining were performed on tissues within 0.5 cm around the wound to observe pathological changes. The angiogenesis was observed by α-smooth muscle actin (α-SMA) immunofluorescence staining on Day 14.Results·SEM observation showed that the fiber diameter of Sponge@GO was significantly thinner and the porosity increased. The two types of short fiber scaffolds basically reached the maximum water uptake within 10 min, but the Sponge@GO scaffold showed better water absorption performance. The water contact angle of Sponge@GO scaffold was significantly smaller than that of Sponge, and the difference was statistically significant (P=0.000). The results of CCK-8 method showed that on Day 3 and 5, the Sponge group had better cell proliferation compared with the control group (both P<0.05), while there was no statistical significance between Sponge@GO group and control group. The results of live/dead staining showed that all the three groups of cells showed good cell growth trend. SEM and fluorescence staining showed that there were more cells in the Sponge@GO scaffold. In vivo experiment, no infection was found on the wound surface of the three groups of rats. The wound healing rate of Sponge@GO and Sponge groups was significantly higher than that of control group on Day 7 (both P<0.05). On Day 14, the wound healing rate of the Sponge@GO group was still significantly higher than that of the control group (P=0.009), while the difference between the Sponge group and the control group was not statistically significant. On Day 14, H-E staining showed more mature granulation tissue and more uniform and dense structure in the Sponge@GO group; Masson staining showed more dense collagen and significant epithelialization in the Sponge@GO group; α-SMA immunofluorescence staining showed more neovascularization and higher density in the Sponge@GO group.Conclusion·Sponge@GO sponge can ensure micro-moist environment on the wound surface after absorbing exudate and has shown promising results in promoting wound healing

Different Distribution of Core Microbiota in Upper Soil Layer in Two Places of North China Plain

Backgrounds: Soils harbor diverse bacteria, and these bacteria play important roles in soil nutrition cycling and carbon storage. Numerous investigations of soil microbiota had been performed, and the core microbiota in different soil or vegetation soil types had been described. The upper layer of soil, as a source of organic matter, is important and affected by the habitats and dominant bacteria. However, the complexity of soil environments and relatively limited information of many geographic areas had attracted great attention on comprehensive exploration of soil microbes in enormous types of soil. Methods: To reveal the core upper layer soil microbiota, soil samples from metropolis and countryside regions in the North China Plain were investigated using high-throughput sequencing strategy. Results: The results showed that the most dominant bacteria are Proteobacteria (38.34%), Actinobacteria (20.56%), and Acidobacteria (15.18%). At the genus-level, the most abundant known genera are Gaiella (3.66%), Sphingomonas (3.6%), Acidobacteria Gp6 (3.52%), and Nocardioides (2.1%). Moreover, several dominant operational taxanomy units OTUs, such as OTU_3 and OTU_17, were identified to be associated with the soil environment. Microbial distributions of the metropolis samples were different from the countryside samples, which may reflect the environments in the countryside were more diverse than in the metropolis. Microbial diversity and evenness were higher in the metropolis than in the countryside, which might due to the fact that human activity increased the microbial diversity in the metropolis. Conclusion: The upper layer soil core microbiota of the North China Plain were complex, and microbial distributions in these two places might be mainly affected by the human activity and environmental factors, not by the distance. Our data highlights the upper layer soil core microbiota in North China Plain, and provides insights for future soil microbial distribution studies in central China

The Role of KLF4 in Alzheimer’s Disease

Krüppel-like factor 4 (KLF4), a member of the family of zinc-finger transcription factors, is widely expressed in range of tissues that play multiple functions. Emerging evidence suggest KLF4’s critical regulatory effect on the neurophysiological and neuropathological processes of Alzheimer’s disease (AD), indicating that KLF4 might be a potential therapeutic target of neurodegenerative diseases. In this review, we will summarize relevant studies and illuminate the regulatory role of KLF4 in the neuroinflammation, neuronal apoptosis, axon regeneration and iron accumulation to clarify KLF4’s status in the pathogenesis of AD

Recent Advances in Herbal Medicines for Digestive System Malignancies

Herbal medicines, as an important part of traditional Chinese medicine (TCM), have been used to treat digestive system malignancies (DSM) for many years, and have gradually gained recognition worldwide. The role of herbal medicines in the comprehensive treatment of DSM is being improved from adjuvant treatment of the autologous immune function in cancer patients, to the treatment of both the symptoms and disease, direct inhibition of tumor cell growth and proliferation, and induction of tumor cell autophagy and apoptosis. Their specific mechanisms in these treatments are also being explored. The paper reviews the current anti-tumor mechanisms of TCM, including single herbal medicines, Chinese herbal formulations, Chinese medicine preparations and TCM extract, and their application in the comprehensive treatment of digestive system tumors, providing a reference for clinical application of TCM