Exotic plant invasion has been changing the vegetation composition and function of terrestrial ecosystems. Nitrogen (N) and phosphorus (P) are often the limiting nutrients for terrestrial plants. ...However, under invasive pressure, in situ plant N and P usage mechanisms remain poorly understood but are pivotal for a better understanding of plant invasion and coexistence in invaded ecosystems.
Nitrogen and P concentrations, natural 15N abundance (δ15N values) were investigated in leaves and soils under different invasive pressures (here expressed as the biomass percentages of invasive plants in each plot) for two invasive species (Chromolaena odorata and Ageratina adenophora) in Xishuangbanna in tropical China.
Soil N and P concentrations revealed the relatively N‐rich but P‐poor status of our study site. Under invasion, soil inorganic N (dominated by ammonium) and available P did not increase significantly. The leaf N and P of invasive plants increased, while leaf N increased but P decreased for native species. Natural δ15N mass balance between leaves and soil inorganic N sources revealed that ammonium dominated N utilization in both natives and invaders. Invasive plants showed ammonium utilization with increasing leaf N levels, while native plants under no invasion showed nitrate utilization with increasing leaf N levels.
Synthesis. Increased soil ammonium availability contributed to preferential ammonium utilization by invasive plants and elevated ammonium utilization in natives, but the P competition of natives decreased in invaded ecosystems. These novel insights into nutrient dynamics in invaded ecosystems enhance our understanding of plant invasion and coexistence mechanisms.
Species number decreased but productivity increased with invasive pressure. The abilities of invaders to use N and P resources were higher than those of natives and increased with invasive pressure, although soil N and P availabilities increased insignificantly. Nitrogen utilization (mainly ammonium) increased but P competition decreased for natives under invasion. These results enriched mechanisms of plant invasion and coexistence.
The microstructures and mechanical properties of three Mg-Zn-Gd-Zr alloys with specific Zn/Gd mass ratios to form different types of phases are systematically investigated by casting and subsequent ...indirect hot extrusion. With the Zn/Gd ratio increases from 0.27 to 1.4, second phases change from W (Mg3Gd2Zn3), X (Mg12GdZn) and Mg5(Gd,Zn) to W, I (Mg3Zn6Gd) and MgZn2. After extrusion, the needle-like and dispersively distributed I-phase provides effective strengthening effects to the experimental alloys. The lamellar-like X-phase in the as-extruded condition is hard and fragile to start cracks. W-phase owns superior ductility in these alloys. A high performance I-phase containing Mg-7Zn-5Gd-0.6Zr alloy is prepared by conventional casting and subsequent hot extrusion. It owns an ultimate and yield strength of 350MPa and 285MPa, respectively, and its elongation is 13.6%.
This work focuses on the optimization of the acid treatment and calcination process factors affecting the catalytic performance of the SmMnO
3
/cordierite monolithic catalyst for
o
-xylene oxidation, ...using response surface methodology (RSM) analysis. A central composite rotatable design (CCRD) was used to statistically visualize the complex interactions of acid treatment time, acid concentration, calcination temperature, and calcination time for T
50
and T
90
values. And the validity of the models developed was verified by experiments. Statistics showed the most significant process factor which affects catalytic combustion activity is acid treatment time. It is also shown that the catalytic activity increases with increasing acid treatment time or acid concentration and that a moderate calcination temperature or time is required to increase the catalytic activity. Furthermore, it was found through SEM analysis that the acid treatment process significantly impacts the morphology of the SmMnO
3
/cordierite monolithic catalysts. Thus, RSM is an effective technique for estimating the catalytic activity of monolithic catalysts.
Graphical abstract
In this work, the effects of acid treatment and calcination process on the catalytic performance of SmMnO
3
/cordierite monolithic catalyst for
o
-xylene oxidation were based on response surface methodology (RSM) through presenting a mathematical modeling and factorial analysis.
The aim of this study was to examine the effects of NH3 variations across different positions within a cage-reared duck house on the egg production performance and fecal microbiome in Muscovy ducks. ...Totals of 3,168 female Muscovy ducks (180 ± 2 d) were randomly assigned to 1,056 cages. From d 293 to 300, the egg production rate and levels of NH3, H2S, CO2, temperature, humidity, light intensity, and dust particles were recorded. Two spatial distribution-based experimental classification methods were applied, one grouping ducks into Front, Middle, and End categories, and the other into First, Second, and Third layers. On d 300, serum and feces samples were collected for further analysis. The result showed that both the egg production rate and serum PROG level in the Front were higher than End (P < 0.05). However, no significant differences were found among the First, Second, and Third groups. Among the environmental factors, ammonia (NH3) is a major harmful gas in cage-reared duck houses, with observed concentrations showing a gradient from lower levels in the Front group to higher levels in the Middle group (P < 0.05), and even higher levels in the End group (P < 0.05). Gene sequencing of the 16S rRNA gene revealed a higher relative abundance of Firmicutes in both the Front and Middle groups compared to the End group (P < 0.05). Specifically, within the Firmicutes phylum, the relative abundance of Lactobacillus and Romboutsia was notably higher in the Front group compared to both the Middle and End groups (P < 0.05). What's more, the abundance of Lactobacillus had a negative correlation with NH3 concentration and positive correlation with egg production rate. In conclusion, NH3 concentrations showed variations across different areas of the cage-reared duck house, with higher levels detected at the rear. The elevated NH3 level was identified as the main factor negatively impacting egg production in Muscovy ducks and contributing to a decline in the abundance of Firmicutes, specifically Lactobacillus.
Hydraulic asphalt concrete is known for its excellent seepage control performance and strong deformation resistance. This engineering material has widespread applications in the seepage control ...structures of hydraulic buildings. Recent projects have investigated the use of acidic aggregates to improve economic efficiency. However, they have also highlighted the weaker adhesion between acidic aggregates and asphalt, which necessitates stringent construction process control. This study investigates the impact of resting conditions on the tensile properties of acidic aggregate hydraulic asphalt concrete. The results of the tensile testing indicate that the storage time significantly affects the performance of asphalt concrete. The tensile strength of the specimens without anti-stripping agents decreased from 1.711 MPa to 0.914 MPa after resting periods of 0, 10, 20, and 30 days. The specimens treated with anti-stripping agents also showed a decrease in tensile strength over time, similar to the trend observed in the previous specimens. Digital specimen simulations indicated a decrease in cohesion between the asphalt and the aggregate from 5.375 MPa to 2.664 MPa after 30 days, representing a reduction of 50.44%. To counteract the effect of the storage time on the bonding between acidic aggregates and asphalt, this study recommends reducing the grading index and maximum size of aggregates, decreasing the coarse aggregate content, and selecting smooth aggregate shapes.
A diastereoselective 1,3-dipolar cycloaddition reaction between trifluoroethyl amine-derived isatin ketimines and chalcones was successfully achieved in the presence of DBU. A series of ...5′-CF3-substituted 3,2′-pyrrolidinyl spirooxindoles were efficiently synthesized with high yields and excellent diastereoselectivities (up to 89% yield, and >99 : 1 dr). The in vitro anticancer activities of these highly functionalized spiropyrrolidin-3,2′-oxindole derivatives were evaluated.
Understanding the electrically active defects in kesterite Cu2ZnSn(S,Se)4(CZTSSe) is critical for the continued development of solar cells based on this material, but challenging due to the complex ...nature of this polycrystalline multinary material. A comparative study of CZTSSe alloys with three different bandgaps, made by introducing different fractions of sulfur during the annealing process, is presented. Using admittance spectroscopy, drive level capacitance profiling, and capacitance‐voltage profiling, the dominant defect energy level present in the low sulfur content device is determined to be 0.134 eV above the valence band maximum, with a bulk defect density of 8 × 1014 cm−3, while the high sulfur content device shows a deeper defect energy level of 0.183 eV and a higher bulk defect density, 8.2 × 1015 cm−3. These findings are consistent with the current density–voltage characteristics of the resulting solar cells and their external quantum efficiency. It suggests that as the sulfur content increases, the bandgap of the absorber is enlarged, leading to an increasing open‐circuit voltage (Voc), that is accompanied by stronger recombination due to the higher defect density of the sulfur‐rich absorber. This is reflected in large Voc deficit and poor carrier collection of the high sulfur content device.
Defect properties of Cu2ZnSn(S,Se)4 with different sulfur content are investigated through admittance spectroscopy and charge density profiling, which are consistent with the cells' characteristics deduced from current density–voltage measurements. As the sulfur content increases, the bandgap of the absorber is enlarged, leading to open‐circuit voltage increases, accompanied by a stronger recombination due to higher defect density.
As the 2019 novel coronavirus disease (COVID-19) rapidly spread across China and to more than 70 countries, an increasing number of pregnant women were affected. The vertical transmission potential ...of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is of great concern to the obstetrics, neonatologists, and public health agencies. Though some studies indicated the risk of vertical transmission is low, few cases have been reported with comprehensive serial tests from multiple specimens. In this case, a female preterm infant was born to a mother with confirmed COVID-19. She presented with mild respiratory distress and received general management and a short period of nasal continuous positive airway pressure support. During her stay at the hospital, a series of SARS-CoV-2 nucleic test from her throat and anal swab, serum, bronchoalveolar lavage fluid, and urine were negative. The nucleic acid test from the mother's amniotic fluid, vaginal secretions, cord blood, placenta, serum, anal swab, and breast milk were also negative. The most comprehensively tested case reported to date confirmed that the vertical transmission of COVID is unlikely, but still, more evidence is needed.
Multicomponent surface droplets that consist of more than one compound are of great interest for fundamental studies of microwetting, evaporation, and dissolution behaviors, as well as for practical ...applications in high-throughput screening, microcompartmentalized chemical reactions, and microanalytics. In this work, we study the formation of multicomponent surface nanodroplets from heterogeneous nucleation and growth induced by the process of solvent exchange. In our experiments, as a solution of two oils in their good solvent was displaced by a poor solvent of the oils in the standard solvent exchange, binary droplets of oils were produced on an immersed substrate. The concentration of one oil was constant in the initial solution, whereas the other oil was increased gradually. We characterized the ratio of the two oils inside individual binary droplets by an infrared microspectrometer. Our results show that the ratio of two oils within binary nanodroplets could be varied from 0 to 100% by tuning the composition of the initial solution. However, the ratio of the two oils in the droplets did not simply correspond to that in the solution. Rather, we were able to correlate the ratio of the oils in the droplet to the oversaturation level of each oil based on the ternary phase diagram. We further demonstrate that the principle of the oversaturation level also governs the components in ternary nanodroplets formed by solvent exchange. The quantitative understanding in this work is valuable for the formation of multicomponent surface nanodroplets, which may be applied in nanoextraction, microcompartmentalized reactions, and surface functionalization.
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