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Determination of tipping points in nitrogen (N) isotope (δ15N) natural abundance, especially soil δ15N, with increasing aridity, is critical for estimating N‐cycling dynamics and N limitation in terrestrial ecosystems. However, whether there are linear or nonlinear responses of soil δ15N to increases in aridity and if these responses correspond well with soil N cycling remains largely unknown. In this study, we investigated soil δ15N and soil N‐cycling characteristics in both topsoil and subsoil layers along a drought gradient across a 3000‐km transect of drylands on the Qinghai–Tibetan Plateau. We found that the effect of increasing aridity on soil δ15N values shifted from negative to positive with thresholds at aridity index (AI) = 0.27 and 0.29 for the topsoil and subsoil, respectively, although soil N pools and N transformation rates linearly decreased with increasing aridity in both soil layers. Furthermore, we identified markedly different correlations between soil δ15N and soil N‐cycling traits above and below the AI thresholds (0.27 and 0.29 for topsoil and subsoil, respectively). Specifically, in wetter regions, soil δ15N positively correlated with most soil N‐cycling traits, suggesting that high soil δ15N may result from the "openness" of soil N cycling. Conversely, in drier regions, soil δ15N showed insignificant relationships with soil N‐cycling traits and correlated well with factors, such as soil‐available phosphorus and foliage δ15N, demonstrating that pathways other than typical soil N cycling may dominate soil δ15N under drier conditions. Overall, these results highlight that different ecosystem N‐cycling processes may drive soil δ15N along the aridity gradient, broadening our understanding of N cycling as indicated by soil δ15N under changing drought regimes. The aridity threshold of soil δ15N should be considered in terrestrial N‐cycling models when incorporating 15N isotope signals to predict N cycling and availability under climatic dryness. [ABSTRACT FROM AUTHOR]

A simple microwave assisted tungstophosphoric acid (H3PW12O40) catalyzed protocol was employed for the synthesis of versatile enaminoketones. The developed synthetic procedure is green, efficient and environmentally benign. Using this method, a series of enaminoketones were prepared from the condensation of dimedone and various amines. Further, the synthesized enaminoketones were evaluated for in-vitro anti-inflammatory activity by membrane stabilization method and anti-oxidant efficacy by radical scavenging method. The synthesized enaminoketones 3c, 3b and 3b, 3f showed reasonable anti-inflammatory as well as anti-oxidant activities respectively. [ABSTRACT FROM AUTHOR]

The petroleum industry is increasingly focused on high-temperature, high-pressure oil reservoirs, and they face challenge in generating sufficient surface construction pressure without exceeding the capabilities of surface equipment. To address this issue, the industry now predominantly relies on weighted fracturing fluid. However, weighted fracturing fluid is unreasonably expensive and difficult to break up. Thus, researchers are urged to develop a low-cost, weighted fracturing fluid that can be easily fractured. Thus, polymer thickener GTA, with poly-hydroxy groups capable of complexing calcium ions, and boron–zirconium composite crosslinker JL903, which is capable of delaying crosslinking, were developed. A CaCl2-weighted fracturing fluid system was developed using the polymer and crosslinker. The density of the system can reach 1.28 g/cm3, crosslinking time can be delayed by 5 min, and the temperature resistance can reach 140 °C. Following the use of ammonium persulfate as a gel breaker, sodium bromate was used as a discriminative gel breaker to resolve the issue of excessive residue content in the weighted fracturing fluid. [ABSTRACT FROM AUTHOR]

China is currently entering a stage of high-quality development, with urban development and governance facing systematic reconstruction of internal and external conditions, showing clear differences and the complex superposition of multi-stage development. The steady progress of urbanization has facilitated significant changes in the population structure of Chinese cities. It is expected that the population and industries will further converge to urban agglomerations and big cities, indicating basic multicenter and network patterns. Therefore, analyzing the negative population growth risks of urban agglomerations at different development stages is crucial. This study examined the cities of 19 urban agglomerations in China by adopting the data of the seventh population census, employing the optimized fuzzy logic method, building a complex network of population flow with ArcGIS and MATLAB platforms, and using the intensity of population flow and the registered population fertility rate to represent exogenous and endogenous growth, respectively. The negative population growth evaluation index system was constructed with five indicators: child ratio, aging rate, average family size, population density, and sex ratio. The risk index of negative population growth was measured using the fuzzy logic method, and the growth mechanism of negative population growth risk in urban agglomerations in China was analyzed using the spatial measurement method. (1) The negative population growth risk of growing urban agglomerations was influenced by both exogenous and endogenous growth, with exogenous growth having a greater impact. (2) The dynamic mechanism of negative population growth risk in large urban agglomerations is exogenous growth, whereas that of nurturing urban agglomerations is endogenous growth. (3) According to the risk of negative population growth in China's urban agglomerations and its influencing factors, negative population growth in 19 urban agglomerations can be divided into eight types. 1) The state of population growth of expanding urban agglomerations can be divided into two types, with the middle reaches of the Yangtze River and Chengdu-Chongqing urban agglomerations as one type; the capital city has a low risk of negative population growth, while other cities have a high risk of negative population growth. The Yangtze River Delta, Pearl River Delta, and Beijing-Tianjin-Hebei city clusters are the same, with the capital and other cities having a relatively low risk of negative population growth. 2) The status of large urban agglomerations can be divided into two types: Shandong Peninsula, Central Plains, Guanzhong Plain, and Beibu Gulf urban agglomerations. The capital city has a low risk of negative population growth, whereas other cities have a high risk of negative population growth. The risk of negative population growth in capital cities and other cities is relatively low. 3) The state of population growth of cultivated urban agglomerations can be divided into four types: the Harbin and Changsha urban agglomerations and the central and southern Liaoning urban agglomerations, which have a high risk of negative population growth. Meanwhile, the northern slope of the Tianshan Mountain City cluster and the Hubao Eyu City cluster have low risk of negative population growth. The risk of negative population growth is low in the provincial capital city and high in the other cities, while endogenous growth is positive in the provincial capital city and negative in the other cities. In the Jinzhong City, Central Guizhou City, and Central Yunnan City groups, the risk of negative population growth is low in provincial cities and high in other cities. Endogenous growth shows that the capital city and other cities have positive growth. In conclusion, this study posits that upgrading urban agglomerations should consider the spatial balance of population distribution, large urban agglomerations should fulfill their role in "blocking the flow" of big cities, and nurturing urban agglomerations should "consolidate human capital." This study presents a comprehensive and in-depth analysis of the negative population growth risk and its impact mechanisms in different development stages of urban agglomerations. This can provide a decision-making reference for the formulation of scientific and reasonable population and economic policies in various urban agglomerations and plays a significant role for maintaining a long-term stable population, economy, and social growth in the region.