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Crop residue amendment in conjunction with synthetic nitrogen (N) fertilization is a common agricultural practice that increases soil fertility and crop yield. However, such a practice may also change soil denitrification process. Here, we conducted an incubation experiment with a robotized continuous flow N-2 free incubation system (using helium (He) and oxygen (O-2)1 and measured fluxes of N2O and N, at a high resolution in an intensively managed soil to examine the interaction effect of straw amendment and N fertilization on soil denitrification. Four treatments were set consisting of (a) a nonamended treatment (Control); (b) a Straw treatment (2 g straw kg(-1) dry soil); (c) a KNO3 treatment (KNO3, 15 mM KNO3); and (d) a Straw + KNO3 treatment (2 g straw kg(-1) dry soil and 15 mM KNO3). During the oxic phase (80% He plus 20% 0 2 ) of the experiment (initial 2 days), flux rates of N2O were 0.54 and 0.38 kg N/ha day(-1) in the Control and KNO3 treatments, respectively. Meanwhile, straw amendment triggered N2O fluxes immediately after the onset of treatments, which was more evident in the Straw + KNO3 treatment. During the anoxic phase (100% He), both N2O and N-2 emissions increased in all treatments, with the effect being more pronounced in the Straw and Straw + KNO3 treatments. In line with the observed differences in gas fluxes, the abundances of nirK, nirS, and nosZ genes increased clearly in these treatments. Overall, the mean N2O/(N2O + N-2) ratio (0.69 +/- 0.03) in the Control treatment was significantly lower compared to the KNO3 treatment (18.8%) and higher than the straw-amended soils (31.9% and 17.4% compared to the Straw and Straw + KNO3 treatments, respectively). Taken together, our results suggest straw amendment significantly altered N2O and N-2 fluxes by decreasing the N2O/(N2O + N-2) ratio; however, the effects of straw amendment depended on soil nitrate content.

Phytogenic hillocks are a type of wind-deposited biological micro-topography exhibiting a bulging shape under plant clusters in arid regions. In this study, we quantitatively measured the phenotypic characteristics of phytogenic hillocks, the soil particle size distribution in phytogenic hillocks and bare surfaces, and the sediment particle size distribution in hillocks of three heights under different grazing treatments. The results showed that the proportion of dense cluster phytogenic hillocks in the no grazing treatment was higher than in the moderate grazing treatment, and the proportion of scattered cluster phytogenic hillocks under moderate grazing was higher than under no grazing. The total area of dense cluster phytogenic hillocks under no grazing was higher than under heavy grazing and under moderate grazing. For the scattered cluster phytogenic hillocks, the total area was greatest under moderate grazing, followed by heavy grazing and, finally, no grazing. For single hillocks, grazing had a significant impact on the width of dense cluster phytogenic hillocks, while the heavy grazing treatment had a significant impact on the height of scattered cluster phytogenic hillocks. The results for windblown sediment showed that the only significant difference among grazing treatments occurred at a height of 2–8 cm. Grazing changed the relationships among the phenotypic characteristics of phytogenic hillocks, the soil particle size of phytogenic hillocks, and the particle size of wind-deposited sediments. Our results suggested that grazing increased the proportion of scattered cluster phytogenic hillocks and caused the relationship between somewhat bare land and phytogenic hillocks to change from symbiosis to competition.

Accelerated aging tests under pre-strain were conducted on HTPB-based composite solid propellant with the goal of investigating the effect of pre-strain aging on its damage properties. A statistical damage constitutive model based on continuum damage theory and statistical strength theory was established. The aging damage coefficient, making aging process of propellant equivalent to a form of damage, was introduced to correct the damage variable. Experimental results show that theoretical model has good agreement with experimental results and can accurately describe the mechanical behavior of propellant during pre-strain aging. Further analysis indicated that the damage effects caused by pre-strain can be identified from the equation of the aging damage coefficient. Aging time influences both tensile strength and shape characteristics of the stress-strain curve of propellant in the damage stage, while pre-strain only decreased the tensile strength. The strain damage threshold value decreased linearly over the aging period and with increasing pre-strain level during the aging process.

The synthesis and characterization of Zr-POSS and Hf-POSS coordination polymers were reported. The IR data and the solid-state 29Si MAS NMR indicated the existence of SiOM linkage. The polarized optical microscopy images and the XRD data suggested their crystalline nature.

The boron trifluoride induced Suzuki-Miyaura cross-coupling of aryltriazenes with arylboronic acids catalyzed by Pd(OAc)2 without added ligands has been achieved for the first time. The reactions performed at room temperature under an argon atmosphere give biaryls in good to excellent yields. It is noteworthy that the reactions were conducted under mild and ligand-free conditions.

The boron trifluoride-induced Suzuki-Miyaura cross-coupling of aryltriazenes with arylboronic acids catalyzed by palladium(II) acetate without added ligands is achieved for the first time.