•Erosion process of two soils was controlled by the detachment-limited condition.•The main deposition area of two soils occurred at the bottom of plots.•The SD soil is more prone to be deposited.•The ...eroded materials differed under different erosion intensities and soil types.
Sediment deposition is an important part of the erosion process. Slope and soil type affect the spatial distribution of erosion–deposition; however, little is known about where erosion and deposition occur specifically and how they interact with influencing factors. To address this issue, four rainfall simulation experiments were conducted in a 1 m × 5 m plot with varying slopes (i.e., 5°, 10°, 15°, and 20°) and simulated rainfall for 1 h at a rate of 60 mm h−1. For the two soils, the runoff rate and sediment concentration were correlated with a similar temporal pattern. Runoff increased gradually and ultimately approached a steady state, and the sediment concentration decreased gradually and ultimately approached a steady state, which indicated that the erosion processes of the two soils were controlled by the detachment-limited condition. The sediment concentration and erosion rate were positively correlated with slope. However, the onset of runoff was delayed for AS soil, which also had a relatively high sediment concentration. The distribution range and area of deposition for the two soils were negatively correlated with the slope gradient, and the main deposition area occurred at the bottom of the plots. In contrast, the SD soil was more susceptible to deposition, and the deposition thickness was mainly concentrated within a 0–4 mm depth; this concentration was not observed for AS soil because of its high erosion intensity. Overall, this similarity also existed in the spatial variations of silt and fine sand contents in the soil surface. The silt and fine sand-sized particles were the primary eroded particle sizes; however, selective mechanisms of these two particle sizes were obviously different in the two soils. The results indicated that the erosion–deposition characteristics and the main eroded materials differed with varying erosion intensities and soil types. These findings are essential for a more comprehensive understanding of soil erosion mechanisms under conditions without rill formation.
Community composition and respiration rates of bacterial and fungal communities from grass-covered eroded soils of the Loess Plateau responded differently to constant and increasing soil moisture ...(SM) regimes. The soils were incubated with SM contents of 5%, 30%, and 45% and with wetting processes in the SM ranges from 5% to 30% (5–30%), from 5% to 30% to 45% (5–30–45%) and from 30% to 45% (30–45%); high-throughput sequencing and co-occurrence network analyses were applied to investigate the different responses of the bacterial and fungal communities to changed SM. Our results showed that bacteria were more sensitive than fungi to changes in SM. The dominant bacterial communities converted from Actinobacterial to Proteobacteria and Acidobacteria in 5–30–45% wetting procedure. Firmicutes preferred wet condition and exhibited slow resilience. However, no difference was observed for the Chloroflexi communities across any sample. The obvious difference in fungal composition was found between the wetting process of 5–30–45% and constant 45% SM. During the 5–30–45% procedure, the respiration rate was higher than that at 30–45% procedure after incubation for 24 days. The respiration rate in 5–30% procedure was lower than that of 5–30–45% process after incubation for 16–27 days. The larger effects on bacterial response than on fungi were verified in network analysis. Multiple stepwise regression analysis showed that 84.40% of the variation in bacterial richness and diversity as well as fungal diversity can be explained by changes in soil respiration rate in response to wetting procedure. Understanding the response of difference between bacterial and fungal community composition, phylum-levels networks and respiration rate to changes in SM is essential for the management of plant-soil-water relationship in the ecosystem after natural vegetation restoration on the Loess Plateau.
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•Bacteria were more sensitive than fungi to wetting procedures of 5–30%, 5–30–45% and 30–45%.•Fungal communities exhibited difference between 5–30–45% wetting procedure and constant 45% SM.•Effect of SM variation on bacterial co-occurrence network was larger than for fungi.•A two-step continual wetting procedure caused a pulsed microbial respiration rate.
The mechanism by which the foot-and-mouth disease virus (FMDV) initiates infection of cells is thought to involve the attachment of the viral capsid to host integrins on the surface of target cells. ...However, the role of integrins in FMDV infection still needs to be fully understood, although it has been demonstrated that integrin αvβ6 interferes with FMDV in vitro and results in neutralization of its infectivity. In the present study, we describe the cloning and sequencing of suckling mouse integrin β6 and the subsequent expression of two segments of integrin β6 extracellular domains: β6-1 (which contains the ligand-binding domain) and β6-2. Sequencing of the mouse integrin β6 subunit revealed close homology (~90%) with its human counterpart. When recombinant integrin extracellular domains β6-1 and β6-2 formulated with adjuvant were inoculated into guinea pigs, anti-integrin antibody expression was high before FMDV challenge. Interestingly, guinea pigs (50%) inoculated with integrin β6-1 were protected from FMDV infection; in contrast, none of the animals inoculated with integrin β6-2 were protected. This result indicates that an integrin blockade may be able to interfere with FMDV infection in vivo, which raises the possibility that targeting integrin in vivo may be the basis for a new strategy to control FMDV infection.
•The sources of eroded C and N were identified via 13C and 15N ratios.•Cropland dominated the supply of eroded C and N at sediment profiles.•Erosion-induced C (N) losses accounted for 52.8% (48.9%) ...of total amount of C (N).•Eroded C and N pools in sediments highly correlated with SMC, silt and sand.
Understanding how organic carbon (C) and nitrogen (N) move with soil along the fluvial system and where eroded organic C and N sources occur over catchment landscape is of significant importance for evaluating accurately carbon or nitrogen budget at the catchment scale and designing proper management practice in the fragile ecosystem. In this study, we selected a dam-controlled catchment in the southwestern hilly-gully region of the Chinese Loess Plateau with severe soil erosion, and explored the catchment scale carbon and nitrogen redistribution by erosion and deposition processes as well as organic carbon and nitrogen sources in sediments retained by check dam. The physio-chemical characteristics, stable isotopic signatures (13C, 15N), total organic C (TOC) and total N (TN) of soils and sediments in studied catchment were determined and an isotopic mixing model was employed to quantify the relative contributions of each source type (ie., forests, cropland, and gully) to eroded sediment C and N. The results showed that the check dam intercepted 309.6 Gg of eroded soil, 1405.1 Mg of TOC, and 153.5 Mg of TN. The sediment the eroded TOC was mainly sourced from cropland, accounting for 53.54%, followed by gully (29.28%) and then forests (17.18%), respectively. Eroded TN sources was similar to C sources, showing that cropland contributed 53.53%, with gully and forests contributing 30.86% and 15.61%, respectively. Moreover, the forests contributions to eroded C and N gradually decreased in the direction of the runoff pathway at the check dam, and the C and N contributions of cropland and gullies showed the orders of mid-check dam>post-check dam>pre-check dam and pre-check dam>post-check dam>mid-check dam, respectively. Soil erosion and deposition processes induced 1569.8Mg TOC and 146.7Mg TN losses, with an average soil C and N erosion rate of 0.051MgCha−1yr−1 and 0.005 MgNha−1yr−1 during the period (i.e., from 2004 to 2016), accounting for approximately 52.8% and 48.87% of the total amount of eroded TOC and TN, respectively. The results indicated that although the check dam served as a carbon and nitrogen storage and sequestration structure in the loess hilly-gully region, erosion-induced carbon or nitrogen redistribution might still act as a major source for atmospheric CO2 or nitrogen oxide in our studied catchment.
Based on observations of runoff plots and field investigations of gully cross-sections, impacts of various soil and water conservation measures on runoff and sediment yield are analyzed for different ...rainfall conditions. The results show that antecedent rainfall and rainfall intensity are the main factors affecting the runoff and soil erosion processes. Rainfall events with antecedent rainfall can produce high runoff and sediment yield. Large differences in the characteristics of two rainfall events will result in greater variations of total runoff and sediment yield from the same runoff plot. Under the same soil control measure and rainfall condition, soil and water conservation measures can reduce the impacts of antecedent rainfall and rainfall intensity on runoff and soil erosion. Among various measures, level terrace seems to be the greatest for soil conservation purposes. Combining with engineering measures,Vegetation measures is also effective in controlling runoff and soil erosion. In the initial stage of vegetation enclosure measures, engineering measure is necessary to improve the environment for ecological recovery. Gully head protection can control gully erosion effectively, but the effectiveness of gully head protection would be reduced when rainfall intensity increases. Therefore, the design of a gully head protection structure must be based on local hydrological conditions.
Integrated dissipative Kerr soliton (DKS) frequency combs have shown great promise in microwave photonics applications due to their versatile merits. For example, the smooth sech 2 -shaped spectral ...envelope of single soliton states enables a microwave photonic filter (MPF) without the need for additional pulse shaping. The reconfiguration of the MPF can be further realized by leveraging the intrinsically rich soliton states. However, deterministic access of different soliton states remains challenging, which limits the reconfiguration of MPFs. In this work, we demonstrate a programmable MPF based on two-soliton microcombs (TSMs) with in situ tunability from a dual-cavity coupled microresonator structure. The optical signal of TSM can be mapped to an electrical filtering response, and the resulting filter passband frequency is proportional to the relative angle between two solitons. The relative angle between the solitons is manipulated by the avoided mode crossing (AMX). The solitons are trapped by AMX-induced background modulation field whose amplitude and spectral position can be tuned by the coupled microresonator. The tunable coupler can turn off the coupling to stabilize the solitons' intracavity positions. By adjusting the AMX to certain states, the relative angle between two solitons can be arbitrarily chosen between 11° and 180°. MPF with passband frequency from 0.5 GHz to 9 GHz can be obtained without the help of pulse shapers or other auxiliary off-chip tunable devices. The sech-shaped narrow optical pulse provides a filter response with a 3-dB bandwidth of ∼0.1 GHz. The proposed scheme provides a simple and programmable filtering solution for radar and 5G communication applications. The soliton angle controlling method can also be enlightening to other applications.
Silicon nitride (Si_{3}N_{4}) has emerged as a promising material for integrated nonlinear photonics and has been used for broadband soliton microcombs and low-pulse-energy supercontinuum generation. ...Therefore, understanding all nonlinear optical properties of Si_{3}N_{4} is important. So far, only stimulated Brillouin scattering (SBS) has not yet been reported. Here we observe, for the first time, backward SBS in fully cladded Si_{3}N_{4} waveguides. The Brillouin gain spectrum exhibits an unusual multipeak structure resulting from hybridization with high-overtone bulk acoustic resonances of the silica cladding. The reported intrinsic Si_{3}N_{4} Brillouin gain at 25 GHz is estimated as 4×10^{-13} m/W. Moreover, the magnitude of the Si_{3}N_{4} photoelastic constant is estimated as |p_{12}|=0.047±0.004, which is nearly 6 times smaller than for silica. Since SBS imposes an optical power limitation for waveguides, our results explain the capability of Si_{3}N_{4} to handle high optical power, central for integrated nonlinear photonics.
Microcombs generated in photonic integrated circuits can provide broadband and coherent optical frequency combs with a high repetition rate from microwave to terahertz. Coherent microcombs formed in ...normal group velocity dispersion microresonators usually have a flat-top temporal profile, called platicon. Here, we propose a novel scheme to generate platicon in Si 3 N 4 microresonator with the assistance of third-harmonic generation. The nonlinear coupling between the fundamental and the third-harmonic waves that draws support from third-order sum/difference frequency generation provides a new mechanism to achieve the phase matching of four-wave mixing in normal dispersion microresonators. We show that single or multiple platicons can be obtained by changing the third-harmonic nonlinear coupling strength and phase matching condition for third-order sum/difference frequency generation. Our work provides a promising solution to facilitate coherent and visible microcomb generation in a pure χ (3) microresonator, which is potential for self-referencing combs and optical clock stabilization.
Integrin ανβ3 plays a major role in various signaling pathways, cell apoptosis, and tumor angiogenesis. To examine the functions and roles of ανβ3 integrin, a stable CHO-677 cell line expressing the ...murine ανβ3 heterodimer (designated as "CHO-677-mανβ3" cells) was established using a highly efficient lentiviral-mediated gene transfer technique. Integrin subunits αν and β3 were detected at the gene and protein levels by polymerase chain reaction (PCR) and indirect immunofluorescent assay (IFA), respectively, in the CHO-677-mανβ3 cell line at the 20th passage, implying that these genes were successfully introduced into the CHO-677 cells and expressed stably. A plaque-forming assay, 50% tissue culture infective dose (TCID50), real-time quantitative reverse transcription-PCR, and IFA were used to detect the replication levels of Foot-and-mouth disease virus (FMDV) in the CHO-677-mανβ3 cell line. After infection with FMDV/O/ZK/93, the cell line showed a significant increase in viral RNA and protein compared with CHO-677 cells. These findings suggest that we successfully established a stable ανβ3-receptor-expressing cell line with increased susceptibility to FMDV. This cell line will be very useful for further investigation of ανβ3 integrin, and as a cell model for FMDV research.
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