The main aim of the present study is to explore and compare three state-of-the art data mining techniques, best-first decision tree, random forest, and naïve Bayes tree, for landslide susceptibility ...assessment in the Longhai area of China. First, a landslide inventory map with 93 landslide locations was randomly divided, with 70% of the area used for training landslide models and 30% used for the validation process. A spatial database of 14 conditioning factors was constructed under a geographic information system environment. Subsequently, the ReliefF method was employed to assess the prediction capability of the conditioning factors in landslide models. Multicollinearity of these factors was verified using the variance inflation factor, tolerance, and Pearson's correlation coefficient. Finally, the three resulting models were evaluated and compared using the area under the receiver operating characteristic (AUROC) curve, standard error, 95% confidence interval, accuracy, precision, recall, and F-measure. The random forest model showed the AUROC values (0.869), smallest standard error (0.025), narrowest 95% confidence interval (0.819–0.918), highest accuracy value (0.774), highest precision (0.662), and highest F-measure (0.662) for the training dataset. Thus, the random forest model is a promising technique that could be used for landslide susceptibility mapping.
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•The effectiveness of three advanced models is compared.•Predictive capability and multicollinearity of landslide factors are analyzed.•The performance of the maps has been validated against historical landslide data.•The RF model outperforms the other models.
A magnetic CdS quantum dot (Fe3O4/polydopamine (PDA)/CdS) was synthesized through a facile and convenient method from inexpensive starting materials. Characterization of the prepared catalyst was ...performed by means of FTIR spectroscopy, XRD, SEM, TEM, energy‐dispersive X‐ray spectroscopy, and vibrating‐sample magnetometer techniques. Fe3O4/PDA/CdS was found to be a highly active photocatalyst for the amidation of aromatic aldehydes by using air as a clean oxidant under mild conditions. The photocatalyst can be recovered by magnetic separation and successfully reused for five cycles without considerable loss of its catalytic activity.
Going greener: Magnetic CdS quantum dots are designed for application as an efficient photocatalyst for the oxidative amidation of aldehydes by using air as the oxidant under mild conditions. The photocatalyst can be recovered by magnetic separation and successfully reused in five cycles without considerable loss of catalytic activity.
Vitrimers are one kind of covalently crosslinked polymers that can be reprocessed. Topology freezing transition temperature (T
) is vitrimer's upper limit temperature for service and lower ...temperature for recycle. However, there has been no proper method to detect the intrinsic T
till now. Even worse, current testing methods may lead to a misunderstanding of vitrimers. Here we provide a sensitive and universal method by doping or swelling aggregation-induced-emission (AIE) luminogens into vitrimers. The fluorescence of AIE-luminogens changes dramatically below and over T
, providing an accurate method to measure T
without the interference of external force. Moreover, according to this method, T
is independent of catalyst loading. The opposite idea has been kept for a long time. This method not only is helpful for the practical application of vitrimers so as to reduce white wastes, but also may facilitate deep understanding of vitrimers and further development of functional polymer materials.
The development of highly efficient, low-cost and stable electrocatalysts for overall water splitting is highly desirable for the storage of intermittent solar energy and wind energy sources. Herein, ...we show for the first time that nickel can be extracted from NiFe-layered double hydroxide (NiFe-LDH) to generate an Ni2P@FePOx heterostructure. The Ni2P@FePOx heterostructure was converted to an Ni2P@NiFe hydroxide heterostructure (P-NiFe) during water splitting, which displays high electrocatalytic performance for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH solution, with an overpotential of 75 mV at 10 mA cm−2 for HER, and overpotentials of 205, 230 and 430 mV at 10, 100 and 1000 mA cm−2 for OER, respectively. Moreover, it could afford a stable current density of 10 mA cm−2 for overall water splitting at 1.51 V in 1.0 M KOH with long-term durability (100 h). This cell voltage is among the best reported values for bifunctional electrocatalysts. The results of theoretical calculations demonstrate that P-NiFe displays optimized adsorption energies for both HER and OER intermediates at the nickel active sites, thus dramatically enhancing its electrocatalytic activity.
Abstract
Magnetic topological insulators (MTIs) offer a combination of topologically nontrivial characteristics and magnetic order and show promise in terms of potentially interesting physical ...phenomena such as the quantum anomalous Hall (QAH) effect and topological axion insulating states. However, the understanding of their properties and potential applications have been limited due to a lack of suitable candidates for MTIs. Here, we grow two-dimensional single crystals of Mn(Sb
x
Bi
(1-
x
)
)
2
Te
4
bulk and exfoliate them into thin flakes in order to search for intrinsic MTIs. We perform angle-resolved photoemission spectroscopy, low-temperature transport measurements, and first-principles calculations to investigate the band structure, transport properties, and magnetism of this family of materials, as well as the evolution of their topological properties. We find that there exists an optimized MTI zone in the Mn(Sb
x
Bi
(1-
x
)
)
2
Te
4
phase diagram, which could possibly host a high-temperature QAH phase, offering a promising avenue for new device applications.
Numerous studies of changes in the climate, vegetation and landscape responses of the Tibetan Plateau (TP) during the Holocene have been published in recent decades. However, several conflicting ...interpretations are evident within these studies and a comprehensive review of the topic is needed to reconcile them, and thus to provide an improved understanding of the history and forcing mechanisms of Holocene environmental changes within the region. Here we review the evidence for changes in climate (temperature, precipitation/moisture), vegetation and landscape attributes (glacier and eolian activity) on the TP during the Holocene. Our main conclusions are as follows. 1) The patterns of Holocene mean annual temperature change on the TP remain controversial; however, an early to middle Holocene summer temperature maximum is evident, which coincided with high summer insolation and a strengthening of the Indian summer monsoon (ISM). This suggests that the summer land-sea thermal gradient, impacted by the temperature of the TP, may be an important factor driving orbital-scale ISM changes. 2) Lake-level records indicate an optimum in moisture conditions on the southwestern (SW) TP in the early Holocene, while on the northeastern (NE) TP the optimum occurred in the middle to late Holocene. This out-of-phase or anti-phased relationship may be linked to the role of the ISM in dominating precipitation on the SW TP, while the westerlies and East Asian summer monsoon dominated the precipitation on the NE TP. 3) Most of the lake-sediment-based stable isotope records (δ18O and leaf wax δD) exhibit a pattern similar to that of stalagmite δ18O records from monsoonal Asia, reflecting the dominance of large-scale patterns of atmospheric circulation, rather than localized moisture changes reflected by lake level records. 4) A synthesis of pollen records reveals that the extent of forest was maximal in the mid-Holocene, while from the early Holocene onwards alpine steppe shrunk and alpine meadow and desert gradually expanded. 5) Evidence of glacier advance increased slightly during the early Holocene, decreased during the mid-Holocene, and then increased substantially after 3 ka BP. 6) The integrated ages of eolian sand and loess from the NE TP reveal that eolian activity intensified during the early and late Holocene. Site inter-comparisons reveal that regional climate change played a major role in modulating changes in vegetation and other landscape attributes. Overall, producing Holocene climate reconstructions for the entire TP remains a major challenge even though much progress has been made. Further improvements in terms of the spatial coverage of high-resolution paleoclimatic records with robust chronological control, and a deeper understanding of the specific climatic significance of several climatic proxies, will facilitate an improved understanding of how the monsoon and the westerlies interacted and their impacts on vegetation and landscape changes on the TP.
•First comprehensive review of Holocene climatic and environmental changes for TP.•Early to middle Holocene summer temperature maximum on TP, driving a strong ISM.•Divergent patterns of changes in moisture conditions between the northern and southern TP.•Regional climate change modulating changes in vegetation and other landscape attributes.
Conductive hydrogels have shown great potential applications in a wide variety of fields, including artificial intelligence devices and biomedical engineering. However, it still remains a great ...challenge to develop a facile and cost-effective approach to achieve a conductive hydrogel with favorable qualities. Herein, we have changed the traditional ingredient of poly(vinyl alcohol) (PVA) hydrogel by the addition of phytic acid (PA), which could yield a conductive hydrogel through one freeze–thaw cycle. The PVA–PA hydrogel holds several virtues including a large stretchability (about 1100% strain), excellent conductivity (1.34 kΩ cm), and high optical transparence (about 95%). By assembling the PVA–PA hydrogel into a wearable strain sensor, the gel-based sensor has shown good performance for the real-time monitoring of human daily activities and health conditions. Moreover, one formula of the PVA–PA sol ink could rapidly convert to the gel state just by being injected on a flexible substrate under an ice-bath, which would satisfy the demand of casual writing circuits. This one-step preparation method of the PVA–PA hydrogel may open an innovative avenue for the fabrication of easy-molding and functional hydrogels with only two components under mild ambient conditions.
Photochemical solution-phase reactions have been widely applied for the syntheses of nanocrystals. In particular, tuning of the nucleation and growth of solids has been a major area of focus. Here we ...demonstrate a facile approach to generate atomically dispersed platinum via photochemical reduction of frozen chloroplatinic acid solution using ultraviolet light. Using this iced-photochemical reduction, the aggregation of atoms is prevented, and single atoms are successfully stabilized. The platinum atoms are deposited on various substrates, including mesoporous carbon, graphene, carbon nanotubes, titanium dioxide nanoparticles, and zinc oxide nanowires. The atomically dispersed platinum on mesoporous carbon exhibits efficient catalytic activity for the electrochemical hydrogen evolution reaction, with an overpotential of only 65 mV at a current density of 100 mA cm
and long-time durability (>10 h), superior to state-of-the-art platinum/carbon. This iced-photochemical reduction may be extended to other single atoms, for example gold and silver, as demonstrated in this study.
The origins of partings within the Late Carboniferous No. 6 coal in the Jungar Coalfield, North China, and their relationship to the enrichment of critical metals in the coal, is poorly understood. ...This study combines UPb ages and LuHf isotope data of zircon, whole-rock geochemistry, LA–ICP–MS elemental mapping, and selective chemical extraction experiments to investigate the provenance of the partings and the occurrence mode of critical metals in the partings collected from the exploration area in the northwest of the Jungar Coalfield. It was found that the zircons in the kaolinite-dominant partings yielded a single age group of ca. 300 Ma at the latest Carboniferous (Gzhelian), indicating that the partings are alteration products of air-fall volcanic ash (tonsteins). The zircons are characterized by negative εHf(t) values and a continental arc tectonic setting, suggesting a genetic connection between the volcanic ash and the Late Paleozoic continental arc that existed in the Inner Mongolia Paleo-Uplift, related to the southward subduction of the Paleo-Asian oceanic plate beneath the northern margin of the North China Block. During the devitrification of volcanic glasses to kaolinite in the mires, the incompatible elements, such as Nb, Ta, Zr, Hf, and rare earth elements (REEs and Y, REY), preserved in the volcanic glasses were leached out as they are incompatible with the crystal lattice of kaolinite. Niobium and Ta, similar to Ti in ionic radii, were preferentially incorporated into fine-grained Ti oxides as reprecipitated products in the alteration process of volcanic ash. The enrichment of Nb, Ta, and Ti in organic matter in the tonsteins suggests that they have some mobility during alteration of volcanic ash and could be, to some extent, transported into the enclosing peats. Zirconium, Hf, and REY were fixed by organic matter admixed with the volcanic ash after their deposition in the mires. Meanwhile, they could also be transported into the enclosing peats, as no secondary minerals formed could substantially retain them. Although Li and Ga were able to be incorporated into the crystal lattice of kaolinite during their crystallization, they could also be transported into the enclosing peats due to their fluid-mobile nature. Both the leaching of a voluminous amount of volcanic ash contacting with the peats and the input of the volcanic ash as an admixture into the peats contributed to the enrichment of critical metals in the Late Carboniferous coal in the Jungar Coalfield.
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•Partings within Late Carboniferous coal in Jungar Coalfield are altered from volcanic ash.•Volcanic ash are from Late Paleozoic continental arc that existed in Inner Mongolia Paleo-Uplift.•Input of volcanic ash contributed to enrichment of critical elements in Late Carboniferous coal.
Low levels of growth hormone 20E in diapause‐destined pupae inhibit both PKA and sirtuin 2 levels, which fail to improve the c‐Myc/TFAM/cytochrome oxidase subunit IV (COXIV) expression and ...Glucose‐6‐phosphate dehydrogenase (G6PD) activity, and cause increased reactive oxygen species (ROS) levels in mitochondria and cytoplasm to induce diapause and extend the pupal lifespan. However, in nondiapause‐destined pupal brains, the activated PKA‐TFAM‐COXIV pathway and high G6PD activity respond to high 20E levels, which reduce the ROS levels and thus induce pupal‐adult development.
Previous studies have shown that high physiological levels of reactive oxygen species (ROS) in the brain promote pupal diapause, which extends the pupal lifespan. However, the molecular mechanisms of ROS generation are unclear. In this paper, we found that mitochondrial ROS (mtROS) levels in the brains of Helicoverpa armigera diapause‐destined pupae (DP) were higher and that the expression of cytochrome oxidase subunit IV (COXIV) was lower than in NP. In addition, downregulating COXIV caused mitochondrial dysfunction which elevated mtROS levels. Protein kinase A (PKA) was downregulated in DP, which led to the downregulated expression of the mitochondrial transcription factor TFAM. Low TFAM activity failed to promote COXIV expression and resulted in the high ROS levels that induced diapause. In addition, low sirtuin 2 expression suppressed glucose‐6‐phosphate dehydrogenase (G6PD) deacetylation at K382, which led to reduced G6PD activity and low NADPH levels, thereby maintaining high levels of ROS. Two proteins, COXIV and G6PD, thus play key roles in the elevated accumulation of ROS that induce diapause and extend the pupal lifespan.
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