•Identify soil moisture (SM) droughts in a 3-D domain.•Severe droughts mainly distributed in northeast and southwest of Southeastern Asia.•SM droughts were more serious in cold (aggravated) than warm ...season (alleviated).•The drought clusters shared two predominant routes of westward and southwest.•SM droughts propagated synergistically with precipitation and PET.
Droughts evolve in space and time simultaneously, but its spatio-temporal propagation remains less explored. As one of the hotspot regions in global soil moisture (SM) drought, the Southeastern Asia supports billions of population and trillions of dollars in gross domestic product. Its high drought risk initiated a deep understanding of drought propagation in multiple dimensions for effective prevention. This study investigated the SM droughts with a merged dataset of remote sensing and land surface modeling over 1979–2016. Our results showed that 369 drought clusters and 145 drought events occurred. Spatially, severe droughts appeared mainly in southwest and northeast of the study region. Temporally, the droughts were more severe in cold season (winter and spring) than warm season (summer and autumn). In last four decades, the SM droughts alleviated in warm season but aggravated in cold season significantly, posing a challenge for drought mitigation, especially for spring crop growth vigorously. Furthermore, the drought clusters shared two predominant routes of westward and southwest. The westward route is for the droughts started in winter in south region, while the southwest route is for the droughts started in summer across the Yangtze River basin from northeast to southwest. At a drought event level, the SM drought propagated synergistically with precipitation and potential evapotranspiration (PET). Precipitation was generally the primary driver and PET the secondary, particularly for SM droughts lasting in summer and winter in south region. The intensity of PET usually enhanced in spring and summer with temperature increasing and crop growing. The findings in drought propagation provide essential spatiotemporal structure for mechanism exploration and important clues for drought prediction.
Plant growth promoting rhizobacteria (PGPR) provide an effective and environmentally sustainable method to protect crops against pathogens. The spore-forming Bacilli are attractive PGPR due to their ...ease of storage and application. Here, we characterized two rhizosphere-associated Bacillus velezensis isolates (Y6 and F7) that possess strong antagonistic activity against Ralstonia solanacearum and Fusarium oxysporum under both laboratory and greenhouse conditions. We identified three lipopeptide (LP) compounds (surfactin, iturin and fengycin) as responsible for the antimicrobial activity of these two strains. We further dissected the contribution of LPs to various biological processes important for rhizosphere colonization. Although either iturin or fengycin is sufficient for antibacterial activity, cell motility and biofilm formation, only iturin plays a primary role in defense against the fungal pathogen F. oxysporum. Additionally, we found that LP production is significantly stimulated during interaction with R. solanacearum. These results demonstrate the different roles of LPs in the biology of B. velezensis and highlight the potential of these two isolates as biocontrol agents against phytopathogens.
For a better understanding terpenoid volatile production in Camellia sinensis, global terpenoid synthase gene (TPS) transcription analysis was conducted based on transcriptomic data combined with ...terpenoid metabolic profiling under different abiotic stress conditions. Totally 80 TPS-like genes were identified. Twenty-three CsTPS genes possessed a complete coding sequence and most likely were functional. The remaining 57 in the currently available database lack essential gene structure or full-length transcripts. Distinct tempo-spatial expression patterns of CsTPS genes were found in tea plants. 17 genes were substantially expressed in all the tested organs with a few exceptions. The other 17 were predominantly expressed in leaves whereas additional eight were primarily expressed in flowers. Under the treatments of cold acclimation, salt and polyethylene glycol, CsTPS67, -69 and -71 were all suppressed and the inhibited expression of many others were found in multiple stress treatments. However, methyl jasmonate resulted in the enhanced expression of the majority of CsTPS genes. These transcription data were largely validated using qPCR. Moreover, volatile terpenoid profiling with leaves, flowers and stress-treated plants revealed a general association between the abundances of mono- and sesqui-terpenoids and some CsTPS genes. These results provide vital information for future studies on CsTPS regulation of terpenoid biosynthesis.
Digital image sensors in hemispherical geometries offer unique imaging advantages over their planar counterparts, such as wide field of view and low aberrations. Deforming miniature ...semiconductor-based sensors with high-spatial resolution into such format is challenging. Here we report a simple origami approach for fabricating single-crystalline silicon-based focal plane arrays and artificial compound eyes that have hemisphere-like structures. Convex isogonal polyhedral concepts allow certain combinations of polygons to fold into spherical formats. Using each polygon block as a sensor pixel, the silicon-based devices are shaped into maps of truncated icosahedron and fabricated on flexible sheets and further folded either into a concave or convex hemisphere. These two electronic eye prototypes represent simple and low-cost methods as well as flexible optimization parameters in terms of pixel density and design. Results demonstrated in this work combined with miniature size and simplicity of the design establish practical technology for integration with conventional electronic devices.
Abstract We explore the Yarkovsky effect on small binary asteroids. While significant attention has been given to the binary YORP effect, the Yarkovsky effect is often overlooked. We develop an ...analytical model for the binary Yarkovsky effect, considering both the Yarkovsky–Schach and planetary Yarkovsky components, and verify it against thermophysical numerical simulations. We find that the Yarkovsky force could change the mutual orbit when the asteroid’s spin period is unequal to the orbital period. Our analysis predicts new evolutionary paths for binaries. For a prograde asynchronous secondary, the Yarkovsky force will migrate the satellite toward the location of the synchronous orbit on ∼100 kyr timescales, which could be faster than other synchronization processes such as YORP and tides. For retrograde secondaries, the Yarkovsky force always migrates the secondary outward, which could produce asteroid pairs with opposite spin poles. Satellites spinning faster than the Roche limit orbit period (e.g., from ∼4 hr to ∼10 hr) will migrate inward until they disrupt, reshape, or form a contact binary. We also predict a short-lived equilibrium state for asynchronous secondaries where the Yarkovsky force is balanced by tides. We provide calculations of the Yarkovsky-induced drift rate for known asynchronous binaries. If the NASA DART impact broke Dimorphos from synchronous rotation, we predict that Dimorphos’s orbit will shrink by a ̇ ∼ 7 cm yr −1 , which can be measured by the Hera mission. We also speculate that the Yarkovsky force may have synchronized the Dinkinesh–Selam system after a possible merger of Selam’s two lobes.
•A novel dimension reduction and dictionary learning framework is proposed.•At dimension reduction stage, it learns a nonlinear mapping via an autoencoder.•At dictionary learning stage, it preserves ...local structure and enhances class discrimination.•The nonlinear mapping and dictionary are optimized jointly.•It preserves nonlinear structure within data and results in enhanced classification performance.
High-dimensional problem poses significant challenges for dictionary learning based classification architecture. Joint Dimension Reduction and Dictionary Learning (JDRDL) framework shows great potential for overcoming the challenges caused by high dimensionality. However, most of the existing JDRDL approaches do not consider the complex nonlinear relationships within high-dimensional data, which limits their classification performance. To overcome this problem, a novel joint dimension reduction and dictionary learning framework is proposed in this paper for high-dimensional data classification. Firstly, at dimension reduction stage, an autoencoder is employed to learn a nonlinear mapping that reduces dimensionality and preserves nonlinear structure of the high-dimensional data. Then, at dictionary learning stage, the locality constraint with label embedding, which takes the locality and label information into account together, is incorporated into the learning process to preserve desirable nonlinear local structure and enhance class discrimination. Moreover, the mapping function and dictionary are optimized simultaneously to enhance the performance. Encouraging experimental results on multiple benchmark datasets confirm that the proposed framework is effective and efficient for high-dimensional data classification.
Hypothalamus-pituitary-adrenal (HPA) hyperactivity is observed in many patients suffering from depression and the mechanism underling the dysfunction of HPA axis is not well understood. Chronic ...stress has a causal relationship with the hyperactivity of HPA axis. Stress induces the over-synthesis of glucocorticoids, which will arrive at all the body containing the brain. It is still complicated whether glucocorticoids account for chronic stress-induced HPA axis hyperactivity and in which part of the brain the glucocorticoids account for chronic stress-induced HPA axis hyperactivity. Here, we demonstrated that glucocorticoids were indispensable and sufficient for chronic stress-induced hyperactivity of HPA axis. Although acute glucocorticoids elevation in the hippocampus and hypothalamus exerted a negative regulation of HPA axis, we found that chronic glucocorticoids elevation in the hippocampus but not in the hypothalamus accounted for chronic stress-induced hyperactivity of HPA axis. Chronic glucocorticoids exposure in the hypothalamus still exerted a negative regulation of HPA axis activity. More importantly, we found mineralocorticoid receptor (MR) - neuronal nitric oxide synthesis enzyme (nNOS) - nitric oxide (NO) pathway mediated the different roles of glucocorticoids in the hippocampus and hypothalamus in regulating HPA axis activity. This study suggests that the glucocorticoids in the hippocampus play an important role in the development of HPA axis hyperactivity and the glucocorticoids in the hypothalamus can't induce hyperactivity of HPA axis, revealing new insights into understanding the mechanism of depression.
Spatiotemporal behaviors of meteorological droughts are basic for understanding the development and driving forces of droughts. Currently, there are a limited number of approaches mainly used to ...analyze the spatiotemporal evolution of large‐scale soil moisture/hydrological drought events at global or continental scales. These behavior description approaches on the spatiotemporal dynamics of drought are not perfect and should be improved further. To this end, a new approach was proposed to investigate the migration of meteorological droughts based on topological spatial relations. It was used to identify drought clusters, migration trajectories, and migration directions of meteorological droughts. In the Poyang Lake basin (24°29′ to 30°04′N, 113°34′ to 118°28′E), China, monthly precipitation data were available from 1960 to 2007. The one‐month standardized precipitation index was used to characterize meteorological droughts. The proposed approach identified a total of 77 drought events and 454 drought clusters during the study period. Their drought centroids were tracked and analyzed. The migration distances of drought events exhibited a significant linear relationship with the drought duration (R2 > 0.8, slope of 165 km per month). More than 70% of drought events had a migrating displacement greater than 1° (approximately 100 km). These results indicated that the meteorological drought events traveled actively and occurred on a widespread basis in the basin. Moreover, two main patterns of drought cluster migration (northward and southward) were identified. The approach and findings can provide some important implications to investigate the migration of meteorological droughts in other regions.
Key Points
A new approach was developed to investigate meteorological drought migration
Migration distances of droughts had a significant linear relationship with the drought duration (R2 > 0.8)
Most drought events displaced greater than 100 km toward north or south in the Poyang Lake basin
This paper investigate the impact of leverage structure on stock price synchronicity. To better understand the mechanism of the impact of leverage, we break leverage into operating leverage and ...financing leverage. This breakdown reveals the impact of different component of leverage. Moreover, in this paper, we employ the quantile regression model to investigate the impact of leverage on different level of stock price synchronicity, which provides us a more comprehensive picture. Our empirical results show, operating and financing leverage have negative impact on stock price synchronicity. Moreover, the higher the stock price synchronicity becomes, the higher this impact is. Furthermore, the marginal effect of financing leverage will be attenuated as the profitability of firms becomes higher, but the interaction effect doesn't exist for operating leverage. On the contrary, the marginal effect of financing leverage will be enhanced as the market capitalization of firms becomes larger, again, it doesn't exist for operating leverage. Finally, as firms are state-owned, the marginal effect of both operating and financing leverage will be higher.
Artificial photosynthesis is a highly-promising strategy to convert solar energy into hydrogen energy for the relief of the global energy crisis. Water oxidation is the bottleneck for its kinetic and ...energetic complexity in the further enhancement of the overall efficiency of the artificial photosystem. Developing efficient and cost-effective photocatalysts for water oxidation is a growing desire, and semiconductor photocatalysts have recently attracted more attention due to their stability and simplicity. This article reviews the recent advancement of semiconductor photocatalysts with a focus on the relationship between material optimization and water oxidation efficiency. A brief introduction to artificial photosynthesis and water oxidation is given first, followed by an explanation of the basic rules and mechanisms of semiconductor particulate photocatalysts for water oxidation as theoretical references for discussions of componential, surface structure, and crystal structure modification. O
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-evolving photocatalysts in Z-scheme systems are also introduced to demonstrate practical applications of water oxidation photocatalysts in artificial photosystems. The final part proposes some challenges based on the dynamics and energetics of photoholes which are fundamental to the enhancement of water oxidation efficiency, as well as on the simulation of natural water oxidation that will be a trend in future research.
Semiconductor water oxidation photocatalysts: a promising strategy to address the bottleneck in an artificial photocatalytic system.
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