Nonlinear optical diode effect in a magnetic Weyl semimetal.

Diode effects are of great interest for both fundamental physics and modern technologies. Electrical diode effects (nonreciprocal transport) have been observed in Weyl systems. Optical diode effects arising from the Weyl fermions have been theoretically considered but not probed experimentally. Here, we report the observation of a nonlinear optical diode effect (NODE) in the magnetic Weyl semimetal CeAlSi, where the magnetization introduces a pronounced directionality in the nonlinear optical second-harmonic generation (SHG). We demonstrate a six-fold change of the measured SHG intensity between opposite propagation directions over a bandwidth exceeding 250 meV. Supported by density-functional theory, we establish the linearly dispersive bands emerging from Weyl nodes as the origin of this broadband effect. We further demonstrate current-induced magnetization switching and thus electrical control of the NODE. Our results advance ongoing research to identify novel nonlinear optical/transport phenomena in magnetic topological materials and further opens new pathways for the unidirectional manipulation of light.

Kramers nodal line metals.

Recently, it was pointed out that all chiral crystals with spin-orbit coupling (SOC) can be Kramers Weyl semimetals (KWSs) which possess Weyl points pinned at time-reversal invariant momenta. In this work, we show that all achiral non-centrosymmetric materials with SOC can be a new class of topological materials, which we term Kramers nodal line metals (KNLMs). In KNLMs, there are doubly degenerate lines, which we call Kramers nodal lines (KNLs), connecting time-reversal invariant momenta. The KNLs create two types of Fermi surfaces, namely, the spindle torus type and the octdong type. Interestingly, all the electrons on octdong Fermi surfaces are described by two-dimensional massless Dirac Hamiltonians. These materials support quantized optical conductance in thin films. We further show that KNLMs can be regarded as parent states of KWSs. Therefore, we conclude that all non-centrosymmetric metals with SOC are topological, as they can be either KWSs or KNLMs.

[Effect of Aeration Density on Start-up of CANON Process].

The effect of aeration densities (3, 6, 12) on the CANON process start-up were investigated in R1, R2, and R3 inoculated mature anaerobic ammonium oxide granule sludge under the same conditions of aeration and aeration/anaerobic time ratio (1:1) at 25℃. The results showed that R1, R2, and R3 of the CANON process were initiated in 32, 29, and 23 d, respectively. A greater aeration density promoted the start-up of the CANON process. In the cycle test, the pH of R1, R2, and R3 decreased by 0.4, 0.55, and 1.06, respectively. R3 exhibited excellent denitrification performance due to its large aeration density and suitable time interval, which increased system efficiency in DO and better inhibited NOB activity. According to the denitrification route analysis, there were two denitrification pathways of ANA and SNA in the system. The proportion of SNA was 19.3%, 24.5%, and 33.6%, respectively. With the increase in aeration density, the contribution of SNA increased gradually.

[Effects of Different Substrate Concentrations on the Short-term Storage of ANAMMOX Bacteria].

Anaerobic ammonium oxidizing bacteria were stored under NH4+-N and NO2--N conditions (addition ratio 1:1) at a substrate concentration of 0, 60, and 120 mg·L-1at 15℃±1℃ for 15 days. The effect of different substrate concentrations on the short-term storage and recovery of anaerobic ammonia oxidation sludge was investigated. After a short period of storage, a recovery experiment was performed. The results show that the anaerobic ammonia oxidation activities in the reactors 1, 2, and 3 decrease by 41.8%, 17.4%, and 33.4%, respectively. Because of the excessive endogenous respiration and high substrate concentration, the activities of the bacteria in reactors 1 and 3 were inhibited, respectively. Therefore, the activities decreased greatly. Because the substrate concentration was relatively suitable in reactor No. 2, excessive endogenous respiration and high substrate concentration inhibition were avoided such that the activity of the bacteria species was maintained at the substrate concentration. Endogenous respiration occurred during the storage period. Subsequently, the organic matter in the three reactors was consumed. As a result, the EPS content decreased by 50.9%, 41.7%, and 23.7% and the particle size decreased by 31.6%, 16.7%, and 8.2%, respectively. This shows that endogenous respiration is maintained by the bacteria in the matrix-deficient period and the higher concentration of the substrate can to some extent delay the endogenous respiration. During the recovery period, the three reactors recover the denitrification performances after 15, 10, and 7 d respectively. This shows that the denitrification performance of the system has a faster recovery through enhanced strain activities compared with the proliferation of the strain.

Integrin-ß1 regulates chondrocyte proliferation and apoptosis through the upregulation of GIT1 expression.

Chondrocytes play a critical role in the repair process of osteoarthritis, which is also known as degenerative arthritis. Integrins, as the key family of cell surface receptors, are responsible for the regulation of chondrocyte proliferation, differentiation, survival and apoptosis through the recruitment and activation of downstream adaptor proteins. Moreover, G-protein-coupled receptor kinase interacting protein-1 (GIT1) exerts its effects on cell proliferation and migration through interaction with various cytokines. It has been previously suggested that GIT1 acts as a vital protein downstream of the integrin-mediated pathway. In the present study, we investigated the effects of integrin-ß1 on cell proliferation and apoptosis, as well as the underlying mechanisms in chondrocytes in vitro. Following transfection with a vector expressing integrin-ß1, our results revealed that the overexpression of integrin-ß1 enhanced GIT1 expression, whereas the knockdown of integrin-ß1 by siRNA suppressed GIT1 expression. However, no significant effect was observed on integrin-ß1 expression following the enforced overexpression of GIT1, which suggests that GIT1 is localized downstream of integrin-ß1. In other words, integrin-ß1 regulates the expression of GIT1. Furthermore, this study demonstrated that integrin-ß1 and GIT1 increased the expression levels of aggrecan and type II collagen, thus promoting chondrocyte proliferation; however, they inhibited chondrocyte apoptosis. Taken together, our data demonstrate that integrin-ß1 plays a vital role in chondrocyte proliferation, differentiation and apoptosis. GIT1 exerts effects similar to those of integrin-ß1 and is a downstream target of integrin-ß1.