Search

Chaobai River is one of the important urban river sources in Beijing, and its Shunyi river section is a typical reclaimed water channel. It is of great significance to study the nutrient release rules and influencing factors at the bottom-mudwater interface in natural and reclaimed river reaches represented by different points. In this study, through indoor soil column simulation experiments, the release regularity of ammonia nitrogen in sediment at different sections of river channel under different pH, DO and temperature conditions was analyzed, and the release flux of ammonia nitrogen at the mud-water interfacewas estimated. The experimental results show that the release trend of NH+4-N is obvious in overlying water and interstitial water of downstream confluence (S1), tidal subtraction junction (S2) and natural river channel (S3), while the release of NH+4-N is not obvious or the adsorption of NH+4-N occurs in the middle part of reclaimed water channel (S4) and reclaimed water outlet (S5). In the simulation of soil columns with different sections, the NH+4-N flux in interstitial water is 2.5~66.7 times that of overlying water, which verifies the process of nitrogen in the sediment being first released to the interstitial water and then diffused to the overlying water. The effects of different environmental factors (pH, DO and temperature) on the release of NH+4-N from the sediment showed different rules: with the increase of pH, the release flux of NH+4-N from the sediment first decreased and then increased. When pH=7, the release flux of NH+4-N reached the lowest value. With the increase of DO concentration, the release flux of NH+4-N decreases, and the maximum release flux is reached when DO concentration is 3 mg/L. The higher temperature, the larger NH+4-N release flux. Under acidic or alkaline conditions, the lower the DO concentration and the higher the temperature, the greater the NH+4-N release flux. The results of this study can provide reference for the improvement of water quality in Chaobai River. [ABSTRACT FROM AUTHOR]

Rainfall and sea tides significantly affect the coastal groundwater. The effect of rainfall events and sea tides on groundwater is not fully understood. In this study, groundwater level and electrical conductivity (EC) were simultaneously measured in three monitoring wells to evaluate the behaviour of freshwater in the uplifted atoll island of Zhaoshu, China. We used the water level sensor monitoring the position and variability of freshwater in the island. In the monitoring period, 86 rainfall events (cumulative rainfall above 1 mm) were identified. The fresh groundwater periodically fluctuates with phase lags every 1–2 h following sea tides. The intermittent rainfall increases the volume of fresh groundwater, while groundwater fluctuation is controlled by tides. Multiple regression analysis and cross‐correlation analysis were used to analyse the response relationship of groundwater to rainfall and tides. Variation in the groundwater level lags the EC as the temporal fluctuation of the sea tides. Only in case of severe rainstorm (cumulative precipitation of an event above 300 mm), the contribution of rainfall on groundwater level fluctuation is greater than that of sea tide. Four response modes (RRR, RFF, RFR, RRF) decomposition of groundwater have been defined according to the tidal stage and threshold (70.3–301.1 mm) of rainfall. The tidal‐induced groundwater effect (TGE) is stronger than the rainfall‐induced groundwater effect (RGE) but it is the opposite in the third and fourth modes. These results and mechanisms could be applied to other atoll islands, for our understanding of rainfall infiltration processes with tidal effect, and could be instrumental in estimating groundwater resources. [ABSTRACT FROM AUTHOR]

The water shortage in agriculture area in China requires to reduce the consumption of excessive water in flood irrigation. Therefore, the dynamics of soil water regime is needed to investigate and water‐saving irrigation is necessary to alleviate water shortage. This study investigated the impact of flood irrigation on soil water movement and recharge to groundwater in the Yellow River irrigation area of Yinchuan Plain, China. Combining comprehensive field observation, stable isotopic techniques and water balance simulation, we described the soil water mechanism in vadose zone covered with bare soil in 2019 and planted with maize in 2020. The soil layers affected by precipitation infiltration and evaporation were mainly 0–50 cm, while the soil influenced by irrigation was the entire profile in the mode of piston flow. The maize root took up the soil water up to the depth of 100 cm during the tasseling period. The infiltration and capillary rise in 2020 were similar with those in 2019. However, the total deep percolation was 156.5 mm in 2020 which was about 50% of that in 2019 because of the maize root water uptake. The leakage of ditch water was the major recharge resource of groundwater for the fast water table rise. Precise irrigation is required to minimize deep percolation and leakage of ditch water and reduce excessive unproductive evapotranspiration. Therefore, understanding the soil water movement and groundwater recharge is critical for agricultural water management to improve irrigation efficiency and water use efficiency in arid regions. [ABSTRACT FROM AUTHOR]

A series of nonpeptide somatostatin agonists which bind selectively and with high affinity to somatostatin receptor subtype 2 (sst2) have been synthesized. One of these compounds, L-054,522, binds to human sst2 with an apparent dissociation constant of 0.01 nM and at least 3,000-fold selectivity when evaluated against the other somatostatin receptors. L-054,522 is a full agonist based on its inhibition of forskolin-stimulated adenylate cyclase activity in Chinese hamster ovary-K1 cells stably expressing sst2. L-054,522 has a potent inhibitory effect on growth hormone release from rat primary pituitary cells and glucagon release from isolated mouse pancreatic islets. Intravenous infusion of L-054,522 to rats at 50 [[micro]gram]/kg per hr causes a rapid and sustained reduction in growth hormone to basal levels. The high potency and selectivity of L-054,522 for sst2 will make it a useful tool to further characterize the physiological functions of this receptor subtype.

The reductive activation of unnatural enantiomer (ent) of mitomycin C (MC) leads to 1'-alpha-linked monoadducts and bisadducts with DNA as the important products. Both MC and the drug-DNA linkage have identical stereochemistry. Similar rates are observed for enzymatic reductive activation of MC and ent-MC by NADPH-cytochrome c reductase. DNA-sequence selectivity for the CpG sequence occur during the monoalkylation and the cross-linking reactions of ent-MC and natural MC.

Abstract Objectives The chemokine receptors CCR2 and CX3CR1 are important in the development of coronary artery disease. The purpose of this study is to analyze the effect of a novel CCR2 inhibitor in conjunction with CX3CR1 deletion on vascular inflammation. Methods The novel CCR2 antagonist MRL-677 was characterized using an in vivo model of monocyte migration. To determine the relative roles of CCR2 and CX3CR1 in vascular remodeling, normal or CX3CR1 deficient mice were treated with MRL-677. After 14 days, the level of intimal hyperplasia in the artery was visualized by paraffin sectioning and histology of the hind limbs. Results MRL-677 is a CCR2 antagonist that is effective in blocking macrophage trafficking in a peritoneal thioglycollate model. Intimal hyperplasia resulting from vascular injury was also assessed in mice. Based on the whole-blood potency of MRL-677, sufficient drug levels were maintained for the entire 14 day experimental period to afford good coverage of mCCR2 with MRL-677. Blocking CCR2 with MRL-677 resulted in a 56% decrease in the vascular injury response (n = 9, p < 0.05) in normal animals. Mice in which both CCR2 and CX3CR1 pathways were targeted (CX3CR1 KO mice given MRL-677) had an 88% decrease in the injury response (n = 6, p = 0.009). Conclusion In this study we have shown that blocking CCR2 with a low molecular weight antagonist ameliorates the inflammatory response to vascular injury. The protective effect of CCR2 blockade is increased in the presence of CX3CR1 deficiency suggesting that CX3CR1 and CCR2 have non-redundant functions in the progression of vascular inflammation.