The phenomenon of simultaneous degeneracy of eigenvalues and eigenstates in non-Hermitian systems, known as exceptional points (EPs), renders systems in the vicinity of EP highly sensitive to perturbations in the environment. Recently, research works on terahertz metasurfaces primarily focused on finding the degenerate eigenvalue using the transmission matrix, known as the scattering EP, while neglecting exploration of another form of EP—the resonant EP. In this study, we numerically, theoretically, and experimentally investigate the resonant EP in terahertz metasurfaces, whose unit cell is composed of two unidentical length metal rods in a two-energy level non-Hermitian system. By altering two system parameters, we can manipulate the coupling between the two resonators, thereby directly realizing the singularity of complex frequency through only a single measurement. Furthermore, our simulations and measurements indicate a sensitivity of up to 9046 GHz/(RIU·mm), which underscores the high sensitivity characteristics of EP. Our approach not only contributes a fresh perspective on understanding EP in non-Hermitian terahertz metasurfaces but also proposes alternative methods for high-sensitivity terahertz sensing.
Abstract Epithelial-mesenchymal transition (EMT) of peritoneal mesothelial cells (PMC) is a major contributor to the pathogenesis of peritoneal fibrosis. EMT is at least in part caused by repeated exposure to glucose degradation products (GDPs), such as methylglyoxal (MGO). MiRNA contributes greatly to the EMT of PMCs. In this study, we tried to profile whether differences exist between the peritoneal membrane (PM) miRNA expression seen in control rats and that seen in rats injected intraperitoneally with MGO. We assessed whether miR-30b has a possible role in MGO-induced EMT of PMCs in rats. Comparative miRNA expression array and real-time PCR analyses were conducted for the control group at the start of the experiment and for the MGO group after 1 and 2 weeks. During the second week, the MGO rats were treated with: a chemically modified antisense RNA oligonucleotide (ASO) complementary to the mature miR-30b (ASO group); an miR-30b mismatch control sequence (MIS group); or a citrate buffer (EMT group). Bioinformatic analyses indicated that the 3′ untranslated region (3′-UTR) of bone morphogenetic protein 7 (BMP7) mRNA did contain a putative binding site for miR-30b. We also tried to investigate whether miR-30b targeted BMP7 in vitro by transfection. Of the upregulated miRNAs, miR-30b expression demonstrated the greatest increase. The administration of miR-30b ASO for two weeks significantly reduced α-SMA excretion and upregulated E-cadherin and BMP-7 expression. Our in vitro study showed that miR-30b directly targeted and inhibited BMP7 by binding to its 3’-UTR. Our results revealed that miR-30b is involved in MGO-induced EMT of PMCs in rats.
Application of biochar in heavy metal remediation suffers from lack of long-term stability. Phosphate-solubilizing bacteria (PSB) are able to elevate P release and the subsequent reaction with Pb to form stable pyromorphite. This study investigated the feasibility of applying PSB modified biochar to enhance immobilization of Pb2+. An alkaline biochar produced from rice husk (RB) and a slightly acidic biochar produced from sludge (SB) were selected. It showed that the biochars can effectively remove Pb2+ via adsorption, i.e., aqueous Pb concentrations after RB and SB addition were reduced by 18.61 and 53.89% respectively. The addition of PSB increased the Pb2+ removal for both biochars (to 24.11 and 60.85%, respectively). In particular, PSB significantly enhanced the formation of stable pyromorphite on surface of SB. This is due to that the evenly distributed PSB enhanced P release and regulated pH on the biochar surface. Moreover, small particles (<0.074 mm) showed their higher ability to induce the formation of pyromorphite, for both RB and SB. Nevertheless, SB demonstrated higher capability of sorption, together with its more abundant P content, which provided a more suitable platform to attract PSB to immobilize heavy metals. Therefore, the combination of biochar and PSB is a promising candidate material for heavy metal remediation. However, the types and particle size distribution of biochar should be addressed.
The symbiotic nitrogen fixation between rhizobia and peanuts offers an advantage in reducing nitrogen fertilizer inputs, decreasing the incidence rate of peanuts, and enhancing soil fertility. Inoculating rhizobia agent is an effective pathway to improve both the quality and yield of peanuts, contributing to food security and promoting sustainable agricultural practices. This study conducted a one-year field experiment in a subtropical humid monsoon climate area in Southeast China to investigate the effects of rhizobia agents on the growth and crop yield of four peanut varieties (i.e., Taihua No.4, No.6, No.8, and No.10). Our research showed that inoculation with rhizobia agent can increase the plant height, lateral branch length, fresh root weight, and leaf area of the four peanut varieties. Meanwhile, inoculation with a rhizobia agent can significantly (p < 0.05) increase the ~50% number of root nodules. Especially for the early-maturing and drought-resistant variety, Taihua No.4 exhibited the highest number of nodules and peanut fruits per plant in the pod-setting stage after inoculation with rhizobia agent, i.e., 24.5 and 18.0, respectively. Under the conventional fertilization conditions (N-P2O5-K2O 15-15-15, 450 kg/hm2), Taihua No.4 and No.6 inoculated with rhizobia agent achieved higher yield increase rates of 11.0% and 11.6% compared to other peanut varieties. This study indicated that the Taihua No.4 and No.6 are the most suitable peanut varieties for rhizobia inoculation and promotion, with enormous potential for yield increase. Meanwhile, optimizing rhizobia inoculation techniques and evaluating soil health status, economic benefits of peanuts, and applicable regions should be explored in the future.
Aspergillus niger ( A. niger ) and Penicillium chrysogenum ( P. chrysogenum ) can significantly promote the degradation of maize straw and phosphorus release. Compared with P. chrysogenum , A. niger is more efficient in maize straw degradation and phosphorus releasing. After seven days of incubation, the highest degradation ratio and phosphorus content in A. niger +maize straw treatment is 2.58% and 2.3 mg/L, respectively. The mechanisms for maize straw decomposition between these two fungi are different. Oxalic acid is the primary organic acid secreted by A. niger , which is more function in the decomposition of maize straw compared with propionic acid secreted by P. chrysogenum . In addition, A. niger has higher acidic xylanase and lignin peroxidase enzymes activities, which is conducive to the degradation of more stable substances in maize straw, i.e., lignin. This study indicated that A. niger is the primary candidate for the reuse of crop straw in the way of return to the field.
Abstract Red soils in subtropical regions are often low in available phosphorus (P), a vital plant nutrient. Phosphate‐solubilizing microorganisms (PSMs) can release P from phosphate reservoir, making it accessible to plants. However, the complex interactions between PSMs and minerals in red soils are not yet fully understood. In this study, we investigated the effects of Aspergillus niger , a typical phosphate‐solubilizing fungus (PSF), on phosphate dissolution in two representative red soils – an acidic soil and an alkaline soil. In the acidic red soil, the fungal abundance reached 3.01 × 10 7 cfu g −1 after a 28‐day incubation period, with respiration of ~2000 mg C kg −1 . The secretion of oxalic acid promoted P release from inorganic phosphate (from ~1 to 187 mg kg −1 ). Additionally, the contents of amorphous Fe/Al oxides decreased, which otherwise could have contributed to P sorption in the soil. In contrast, P availability declined in the alkaline red soil after the addition of A. niger , regardless of the P source (inorganic or organic phosphate). Meanwhile, the fungal respiration decreased to ~780 mg C kg −1 . Therefore, alkaline red soils with abundant carbonates are susceptible to P deficiency due to both the diminished function of PSMs and strong soil buffering. These findings have important implications for sustainable agriculture on alkaline red soils, as they suggest that the use of PSMs to improve P availability may be limited.
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