Regulating the coordination environment of atomically dispersed catalysts is vital for catalytic reaction but still remains a challenge. Herein, an ionic exchange strategy is developed to fabricate ...atomically dispersed copper (Cu) catalysts with controllable coordination structure. In this process, the adsorbed Cu ions exchange with Zn nodes in ZIF‐8 under high temperature, resulting in the trapping of Cu atoms within the cavities of the metal−organic framework, and thus forming Cu single‐atom catalysts. More importantly, altering pyrolysis temperature can effectively control the structure of active metal center at atomic level. Specifically, higher treatment temperature (900 °C) leads to unsaturated Cu–nitrogen architecture (CuN3 moieties) in atomically dispersed Cu catalysts. Electrochemical test indicates atomically dispersed Cu catalysts with CuN3 moieties possess superior oxygen reduction reaction performance than that with higher Cu–nitrogen coordination number (CuN4 moieties), with a higher half‐wave potential of 180 mV and the 10 times turnover frequency than that of CuN4. Density functional theory calculation analysis further shows that the low N coordination number of Cu single‐atom catalysts (CuN3) is favorable for the formation of O2* intermediate, and thus boosts the oxygen reduction reaction.
An ionic exchange strategy is developed to fabricate atomically dispersed CuNC material with unsaturated CuN centers (CuN3 moieties), which possesses a higher half‐wave potential of 180 mV and the 10 times turnover frequency than that with CuN4 moieties in the oxygen reduction reaction (ORR) test. Furthermore, the optimum CuN3 catalyst demonstrates a better performance in ORR and zinc–air batteries compared with commercial Pt/C.
Landslide hazards along the Jinsha River corridor pose serious threats to the lives and property of local residents and can affect the safety of hydropower facilities because of the large size, ...number, strong activity, and disaster chain characteristics that occur following such events (such as a landslide creating a dammed lake which fails and leads to flooding), thus attracting widespread attention in both China and the rest of the world. As there is currently no complete landslide inventory map that covers the entire Jinsha River corridor, in this study the Sentinel-1 and ALOS/PALSAR-2 datasets were employed to detect and map active landslides along the entire Jinsha River corridor. Complex geomorphological conditions, such as the humid climate, dense vegetation, and steep terrain, pose great challenges to conventional InSAR-based landslide mapping methods, which can lead to a high probability of mis-judgements and omissions of landslides. Therefore, we propose a new InSAR-based procedure that can be used to conduct large-area landslide mapping through the integration of surface deformation and geomorphological features. More than 360 SAR images covering the Jinsha River corridor were processed and more than 900 active landslides were detected and mapped over the entire Jinsha River corridor for the first time. In particular, several large-scale landslides with a length and/or width of >1 km were found. Our results show that the landslides over the Jinsha River corridor are mainly located in three high earthquake-prone areas and reservoir areas, and that the landslides are mainly distributed at elevations of 1500–2000 m a.s.l. and have slope angles of 15–25°. Moreover, the deformation time series results indicate that the heavy rainfall in the summer and the rapid decline of water level in the Jinsha River might be two significant factors that accelerate the deformation of active landslides and reactivate unstable slopes. The findings in this research can be directly applied to landslide hazard mitigation and prevention along the entire Jinsha River corridor. In particular, the proposed procedure can be used for the efficient and systematic mapping of active landslides in other regions with similarly complex geomorphological conditions.
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•New InSAR-based procedure proposed for generating large-area active landslide maps in geomorphologically complex areas.•More than 900 active landslides were detected and mapped along the entire over 2000 km long Jinsha River corridor.•Geomorphological features are revealed for the newly detected landslides.•Heavy rainfall and rapid decline of water level in the Jinsha River are two significant factors of the landslide activity.
Xiaoyaosan (XYS), a classic description, has a history of thousands of years for treating depression through invigorating the liver and strengthening the spleen, which have been verified both ...clinically and experimentally. However, explanation of its underlying mechanisms remains a great challenge.
The mechanisms of XYS in treating depression were investigated, with emphasis on the important biomarkers, targets and pathways.
In this study, taking the targeted organ of depression, hippocampus, as the object, a combination of GC-MS based metabolomics and network pharmacology was established to illustrate the abnormality of metabolic characteristics of hippocampus of depression rats and to demonstrate the antidepressant mechanisms of XYS. Hippocampal metabolomics demonstrated potential metabolites involving in the antidepressant effects of XYS, as well as the corresponding metabolic pathways. Network pharmacology screened the potential ingredients and the targets of XYS against depression.
Metabolomics revealed that XYS significantly regulated the abnormal levels of lactic acid, glycerol, glutamine, glutamic acid, hypoxanthine, myo-inositol and cholesterol, which involved in the D-glutamine and D-glutamate metabolism, arginine biosynthesis and alanine, aspartate and glutamate metabolism. Network pharmacology showed that XYS exhibited anti-depression effects through paeoniflorin, quercetin, licochalcone a, naringenin, β-sitosterol, formononetin and kaempferol acting on interleukin-6 (IL6), mitogen-activated protein kinase 1 (MAPK1), signal transducer and activator of transcription 3 (STAT3) and transcription factor AP-1 (JUN).
Based on hippocampal metabolomics and network pharmacology, this study proved that the actions of XYS in treating depression depend on multi-components, multi-targets and multi-pathways, the unique characteristics of TCMs.
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•The combination of hippocampal metabolomics and network pharmacology were applied.•7 hippocampal biomarkers were associated with the antidepressant mechanisms of XYS.•7 antidepressant ingredients and 4 key targets of XYS were identified.•Integrating metabolomics and network pharmacology is valuable for TCMs.
The structural and electronic properties of Nb-doped rutile TiO2 with several doping configurations were investigated by first-principles calculations based on the density functional theory. The ...calculations show that although the band gap in the NbTi, 2NbTi, and NbTi + Oi systems is small, the intragap states would be the electron–hole recombination center, leading to low photocatalytic efficiency. However, for the 2NbTi + Oi configuration, the impurity states are mainly located at the top of the valence band and the electron–hole recombination would be inhibited, indicating relatively higher photocatalytic efficiency. On the basis of the charge-compensated theory, two electrons on the transition-metal Nb atoms compensate for the same amount of holes on the acceptor level of a nonmetal interstitial O atom, in the model of 2NbTi + Oi. Such donor–acceptor codoping may not only suppress the electron–hole recombination but also maintain a reduced band gap, suggesting that the doping models would exhibit higher photocatalytic activity than pure TiO2. The calculation results show that the interstitial O atoms play an essential role in manipulating the valence state of impurity Nb. The role of the interstitial O atom in Nb-doped rutile TiO2 suggests that it can give rise to beneficial charge-compensation effects.
The defect passivation of perovskite films is an efficacious way to further boost the power conversion efficiency (PCE) and long-term stability of perovskite solar cells (PSCs). In this work, ionic ...liquids (ILs) of 1-butyl-2,3-dimethylimidazolium chloride (BMMImCl) are used as a modification layer in perovskite films in carbon-based CsPbBr3 PSCs without a hole-transporting material (HTM) for passivating the surface defects. The preliminary results demonstrate that the BMMImCl modifier passivates the surface defects of the perovskite film and reduces the valence band of perovskite close to the work function of the carbon electrode, which causes a remarkably inhibited nonradiative and radiative charge recombination, improved energy-level matching, and decreased energy loss. After optimization, a champion efficiency of 9.92% with a V oc as high as 1.61 V is achieved for the BMMImCl tailored carbon-based CsPbBr3 PSC without HTM, which is improved by 61.3% in comparison with 6.15% for the control device. Furthermore, the encapsulation-free PSC presents good long-term stability after storage in an air atmosphere with 70% RH at 20 °C or 0% RH at 80 °C as well as under continuous illumination conditions for 30 days. The significantly improved PCE and stability in high humidity or temperature suggest that the perovskite passivation by ILs is an effective strategy for fabricating high-PCE and stable PSCs.
The Interferometric Synthetic Aperture Radar (InSAR) technique is a well-developed remote sensing tool which has been widely used in the investigation of landslides. Average deformation rates are ...calculated by weighted averaging (stacking) of the interferograms to detect small-scale loess landslides. Heifangtai loess terrace, Gansu province China, is taken as a test area. Aiming to generate multi-temporal landslide inventory maps and to analyze the landslide evolution features from December 2006 to November 2017, a large number of Synthetic Aperture Radar (SAR) datasets acquired by L-band ascending ALOS/PALSAR, L-band ascending and descending ALOS/PALSAR-2, X-band ascending and descending TerraSAR-X and C-band descending Sentinel-1A/B images covering different evolution stages of Heifangtai terrace are fully exploited. Firstly, the surface deformation of Heifangtai terrace is calculated for independent SAR data using the InSAR technique. Subsequently, InSAR-derived deformation maps, SAR intensity images and a DEM gradient map are jointly used to detect potential loess landslides by setting the appropriate thresholds. More than 40 active loess landslides are identified and mapped. The accuracy of the landslide identification results is verified by comparison with published literatures, the results of geological field surveys and remote sensing images. Furthermore, the spatiotemporal evolution characteristics of the landslides during the last 11 years are revealed for the first time. Finally, strengths and limitations of different wavelength SAR data, and the effects of track direction, geometric distortions of SAR images and the differences in local incidence angle between two adjacent satellite tracks in terms of small-scale loess landslides identification, are analyzed and summarized, and some suggestions are given to guide the future identification of small-scale loess landslides with the InSAR technique.
Twenty‐eight ALOS/PALSAR‐1 and ALOS/PALSAR‐2 images acquired from January 2007 to August 2018 were exploited to characterize the deformation history and temporal evolution of the Baige landslide, ...China, which successively occurred on 11 October and 3 November 2018. To mitigate the errors caused by the topographic relief and to conduct offset estimates between the SAR images from different platforms, a novel offset‐tracking method is proposed. The SAR images were ortho‐rectified firstly. Then two‐dimensional deformations were retrieved successfully from SAR images acquired at an identical platform and different platforms. Our results indicate that the maximum cumulative deformation in the line‐of‐sight direction of the Baige landslide reached about −60 m between January 2007 and August 2018. Furthermore, correlation between time series deformation and monthly precipitation and soil moisture derived from SAR intensity images suggests that the failure of the Baige landslide was closely related to the heavy rainfall in the summer of 2018.
Key Points
An improved time series SAR offset‐tracking chain is proposed to extract the long‐term and large gradient landslide motion
For the first time accurate pixel offsets between cross‐platform SAR data sets are achieved
The cumulative deformation of <−60 m and temporal evolution over 11 years are successfully retrieved at the Baige landslide
Two-dimensional hybrid organic–inorganic perovskites (2D-HOIPs) that form natural multiple quantum wells have attracted increased research interest due to their interesting physics and potential ...applications in optoelectronic devices. Recent studies have shown that spintronics applications can also be introduced to 2D-HOIPs upon integrating chiral organic ligands into the organic layers. Here we report spin-dependent photovoltaic and photogalvanic responses of optoelectronic devices based on chiral 2D-HOIPs, namely, (R-MBA)2PbI4 and (S-MBA)2PbI4. The out-of-plane photocurrent response in vertical photovoltaic devices exhibits ∼10% difference upon right and left circularly polarized light (CPL) excitation, which originates from selective spin transport through the chiral multilayers. In contrast, the in-plane photocurrent response generated by CPL excitation of planar photoconductive devices shows a typical response of chirality-induced circular photogalvanic effect that originates from the Rashba splitting in the electronic bands of these compounds. Our studies may lead to potential applications of chiral 2D-HOIPs in optoelectronic devices that are sensitive to the light helicity.
Recently the hybrid organic-inorganic trihalide perovskites have shown remarkable performance as active layers in photovoltaic and other optoelectronic devices. However, their spin characteristic ...properties have not been fully studied, although due to the relatively large spin-orbit coupling these materials may show great promise for spintronic applications. Here we demonstrate spin-polarized carrier injection into methylammonium lead bromide films from metallic ferromagnetic electrodes in two spintronic-based devices: a 'spin light emitting diode' that results in circularly polarized electroluminescence emission; and a 'vertical spin valve' that shows giant magnetoresistance. In addition, we also apply a magnetic field perpendicular to the injected spins orientation for measuring the 'Hanle effect', from which we obtain a relatively long spin lifetime for the electrically injected carriers. Our measurements initiate the field of hybrid perovskites spin-related optoelectronic applications.
•A direct-weighing bottom-up approach used to measure Horeca food waste.•Horeca food waste in Lhasa reached a high-level close to that of western countries.•Per-capita food waste reduced due probably ...to recently issued strict regulations.•Tourists contributed over half to the total Horeca food waste in Lhasa.•The ecological footprint of Horeca food waste is 2 times Lhasa’s arable land area.
Consumer food waste in developing countries becomes increasingly important as they continue to urbanize and raise the income of their inhabitants. However, there are few empirical studies on the scales, patterns, and impacts of consumer food waste in emerging economies (compared to industrialized countries). Here we report an exploratory study on the amount of Horeca (hotels, restaurants, and cafés) food waste and its ecological footprint in Lhasa, Tibet, in western China, based on a direct-weighing bottom-up approach of 35 representative restaurants in 2011 and 2015. We found that, on a per capita level, Horeca food waste in Lhasa has already reached a high-level (128 ± 3 g/cap/meal in 2011 and 98 ± 2 g/cap/meal in 2015) close to that of western countries despite a lower level of income. The decline of per-capita Horeca food waste generation from 2011 to 2015 most likely reflects the reduction among local residents as a result of recently issued strict regulations (especially those targeting official extravagance and governmental reception meals at public expenses), as similarly observed in Japan and Germany. On the contrary, as a main tourism destination, tourists showed an increasing trend of food waste on a per capita level and contributed over half to the total Horeca food waste in both 2011 and 2015. This also leads to, together with other factors such as growing dining-out frequency of local residents, a sharp increase (39.7%) of total Horeca food waste in Lhasa from 2011 (15 ± 1 kt) to 2015 (21 ± 2 kt). The total ecological footprint of wasted food in the Horeca sector of Lhasa in 2015 is equivalent to 71,516 ± 7,705 ha, almost two times the arable land area of Lhasa.
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