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The characteristics of how graphite particles adhere to the walls of high-temperature gas-cooled reactors are very important for analyzing reactor source terms. In the present study, atomic force microscopy (AFM) is used to measure the particle adhesion force and the wall morphology, then Lennard-Jones potential theory and the finite element method (FEM) are coupled to calculate the adhesion force between different particles and rough walls. The obvious deviations between the AFM measurements and the theoretical models are due to the contact hypothesis of a sphere with a smooth flat plane in the latter. The FEM results reveal the formation of maximum adhesion at the pull-off point of the particle and the corresponding stress distribution. For aspherical particles, the local curvature of the particle contact interface is the main factor affecting the adhesion force. In addition, for rough walls, different contact regimes correspond to different adhesion trends. When discrete wall roughness with hemispheres and truncated cones is used, the FEM predictions are closer to the AFM measurements, indicating that roughness dominates the adhesion weakening.

An atomically dispersed structure is attractive for electrochemically converting carbon dioxide (CO2) to fuels and feedstock due to its unique properties and activity. Most single-atom electrocatalysts are reported to reduce CO2 to carbon monoxide (CO). Herein, we develop atomically dispersed indium (In) on a nitrogen-doped carbon skeleton (In-N-C) as an efficient catalyst to produce formic acid/formate in aqueous media, reaching a turnover frequency as high as 26771 h-1 at -0.99 V relative to a reversible hydrogen electrode (RHE). Electrochemical measurements show that trace amounts of In loaded on the carbon matrix significantly improve the electrocatalytic behavior for the CO2 reduction reaction, outperforming conventional metallic In catalysts. Further experiments and density functional theory (DFT) calculations reveal that the formation of intermediate *OCHO on isolated In sites plays a pivotal role in the efficiency of the CO2-to-formate process, which has a lower energy barrier than that on metallic In.

Spaceborne synthetic aperture radar (SAR) is considered one of the most powerful sensors for tropical cyclone assessment. In this study, 14 tropical cyclone (TC) events captured by the Sentinel-1A/...

A sample including 935 blazars with 415 Flat Spectrum Radio Quasars (FSRQs) and 520 BL Lac objects (BL Lacs) (233 HBLs (High synchrotron peak frequency BL Lacs), 144 IBLs (Intermediate synchrotron peak frequency BL Lacs), and 143 LBLs (Low synchrotron peak frequency BL Lacs)) is selected in Fermi 3FGL catalogue. The correlations between two flux densities of the radio 1.4 GHz and γ -ray at 0.1, 0.3, 1, 3, and 10 GeV are investigated for the samples of all blazars, FSRQs, BL Lacs, and subclasses of HBLs and LBLs, respectively. Results show that there are strong positive correlations between the two flux densities, with the correlation coefficients r = 0.48 ∼ 0.81 , and the chance probabilities p all less than 10 − 4 . The correlation coefficient has different trends with the change of γ -ray emission frequency for different blazar samples, and the average correlation coefficients for all the samples at five respective bands decrease with the increase of γ -ray frequency. Therefore, with the increase of γ -ray frequency, the dominant mechanism of γ -ray radiation of blazar is changing, and at the same frequency the dominant mechanism is different for different samples. The γ -ray emission of HBLs may be mainly dominated by the synchrotron self-Compton, while the other mechanisms are responsible for the γ -ray emissions of LBLs. The origin of γ -ray in FSRQs is more complex than that of BL Lacs.

Significant wave height (SWH) is an important wave parameter that is related to near-shore activities and research on the phenomenon near the air-sea interface. Here, we proposed a new method for retrieving SWH from C-band Sentinel-1 synthetic aperture radar (SAR) interferometric wide mode data based on convolutional neural network (CNN), which can directly establish the empirical relationship between normalized radar cross section and SWH. We collected 1597 Sentinel-1 SAR images matched with in situ buoys and conducted homogeneity tests for each of the matched sub-images, producing ~ 3330 matchups with 2028 of them being VV-polarization. After training, the VV-polarization data extracted by 0.5 threshold for homogeneity test perform better, and the comparison between these results and in situ buoy measurements in validation data indicates a SWH root mean square error of 0.32 m, a 23.58% scatter index and a 0.90 correlation coefficient. And the SWH from CNN-based method is also validated with radar altimeter data and Wavewatch3 data. These results demonstrate that the proposed CNN method is suitable for retrieving SWH from Sentinel-1 SAR imagery with some constraints on the matched dataset.

In the past nearly two decades, the Argo Program has created an unprecedented global observing array with continuous in situ salinity observations, providing opportunities to extend our knowledge on the variability and effects of ocean salinity. In this study, we utilize the Argo data during 2004–2017, together with the satellite observations and a newly released version of ECCO ocean reanalysis, to explore the decadal salinity variability in the Southeast Indian Ocean (SEIO) and its impacts on the regional sea level changes. Both the observations and ECCO reanalysis show that during the Argo era, sea level in the SEIO and the tropical western Pacific experienced a rapid rise in 2005–2013 and a subsequent decline in 2013–2017. Such a decadal phase reversal in sea level could be explained, to a large extent, by the steric sea level variability in the upper 300 m. Argo data further show that, in the SEIO, both the temperature and salinity changes have significant positive contributions to the decadal sea level variations. This is different from much of the Indo-Pacific region, where the halosteric component often has minor or negative contributions to the regional sea level pattern on decadal timescale. The salinity budget analyses based on the ECCO reanalysis indicate that the decadal salinity change in the upper 300 m of SEIO is mainly caused by the horizontal ocean advection. More detailed decomposition reveals that in the SEIO, there exists a strong meridional salinity front between the tropical low-salinity and subtropical high salinity waters. The meridional component of decadal circulation changes will induce strong cross-front salinity exchange and thus the significant regional salinity variations.

Ocean surface currents play a key role in the earth’s climate. They affect virtually all processes occurring in the ocean and can also directly affect many important socio-economic activities. Himawari-8 meteorological satellite has an international advanced geostationary orbit imager sensor, AHI, with high time resolution and spatial coverage, Himawari-8 can be used to observe the subtle changes in marine environments. In this study, we used Himawari-8 data received from the Joint Receiving Station for Satellite Remote Sensing of Xiamen University to retrieve coastal currents in Hangzhou Bay. Particularly, the Maximum Correlation Coefficient (MCC) and the Generalized Hough Transform (GHT) methods were used to retrieve them respectively The retrieved sea surface currents are analyzed and verified by the numerical model data of the Taiwan Strait current forecasting system (TFOR). The results show that (1) the Himawari-8 satellite data can be used to effectively estimate the ocean current; (2) The results of the two methods are in agreement with each other, and the error in the current measured using the GHT method is smaller in the Yangtze estuary and offshore areas, where the turbidity characteristic front is stronger.

The ability to tune both local and global environments of a single-metal active center on a support is crucial for the development of highly robust and efficient single-atom electrocatalysts (SAECs...

In this paper, the flux densities at the radio (R) 1.4 GHz, optical (O) 4.68 × 10 14 Hz, X-ray (X) 1 keV, and γ -ray ( γ ) 1 GeV are obtained from the available literature for a Fermi blazar sample. The 6 effective spectral indices ( α RO , α RX , α R γ , α OX , α O γ , and α X γ ) between any two of above bands are calculated. The correlations between any two spectral indices are investigated for the whole blazar sample and the subclass samples of FSRQs (Flat Spectral Radio Quasars) and BL Lacs including High synchrotron peak frequency BL Lacs (HBLs) and Low synchrotron peak frequency BL Lacs (LBLs). Results show that: (1) There are close correlations between any two spectral indices for all samples, except for the sample of HBLs and the correlation between α OX and α R γ . This kind of correlations can be explained by the structures of energy spectral distributions at four bands. (2) In the scatter plots of effective spectral index correlations, FSRQs and LBLs are distributed in the same area, but HBLs and FSRQs (LBLs) are distributed in the different areas. (3) The separation degree (discrimination) between the distributions of FSRQs (LBLs) and HBLs differs with the scatter plot of effective spectral index correlations, and the discrimination is related to the frequencies to determine two effective spectral indices.

Photoreduction of CO2 to fuels offers a promising strategy for managing the global carbon balance using renewable solar energy. But the decisive process of oriented photogenerated electron delivery presents a considerable challenge. Here, we report the construction of intermolecular cascaded pi-conjugation channels for powering CO2 photoreduction by modifying both intramolecular and intermolecular conjugation of conjugated polymers (CPs). This coordination of dual conjugation is firstly proved by theoretical calculations and transient spectroscopies, showcasing alkynyl-removed CPs blocking the delocalization of electrons and in turn delivering the localized electrons through the intermolecular cascaded channels to active sites. Therefore, the optimized CPs (N-CP-D) exhibiting CO evolution activity of 2247 mu mol g(-1) h(-1) and revealing a remarkable enhancement of 138-times compared to unmodified CPs (N-CP-A). While conversion of CO2 to fuels may offer a bio-inspired means to renewably utilize fossil fuel emission, most materials demonstrate poor activities for CO2 reduction. Here, authors construct conjugated polymers that modulate photo-induced electron transfer to CO2 reduction catalysts.

The rhizome of P. japonicus var. major, one of the important herbs in Traditional Chinese medicine (TCM), has been used as tonic and hemostatic drugs in Tujia and Miao ethnic groups of China for thousand years. In this study, comparative metabolite and transcriptome analysis of rhizome nodes and internodes of wild P. japonicus var. major was performed to reveal their different roles in the biosynthesis of triterpene saponins. The results showed that the node was the crucial section for the synthesis of ginsenosides in the rhizome. The content of oleanane-type ginsenosides in the node was much higher than those in the internode. Most isoprenoid biosynthesis-related genes were highly expressed in the node. And, candidate UDP-glycosyltransferase (UGT) genes were also found to be differentially expressed between node and internode. Our study will provide a better understanding of the metabolism of ginsenosides in the rhizome of P. japonicus var. major.

The particulate backscattering coefficient (bbp) provides effective proxies for particulate organic carbon (POC) and phytoplankton carbon (Cphy); however, their bio-optical relationships in the oligotrophic ocean are rarely reported. In this work, based on the in-situ synchronous optical and biogeochemical measurements in the oligotrophic South China Sea (SCS) basin, we refined the regional relationships between POC (and Cphy) and bbp and investigated the impacts of phytoplankton community compositions and size classes on the bbp variability. The observations showed that: 1) POC and Cphy exhibited good linear relationships with bbp; 2) the relationship between Cphy and POC could also be fitted in a linear function with a positive POC intercept, and the POC contributed by phytoplankton-covarying non-algal particles was nearly two-fold of Cphy; and 3) the POC-specific bbp (b*bp) was positively correlated with the fraction of the phytoplankton groups haptophytes (Type 8) and diatoms to total Chla, but negatively correlated with the fraction of pico-phytoplankton to Chla (fpico). These findings suggest that in oligotrophic waters, the variability of b*bp was mainly determined by the variability in the relative contribution of large phytoplankton with complex structures.

The use of remote sensing observation to estimate subsurface oceanic variables, including subsurface temperature anomaly (STA), is essential for the study of ocean dynamics and climate change. Here we report a new method that combines a pre-clustering process and a neural network (NN) approach to determine the STA using ocean surface temperature, surface height, and surface wind observation data at the global scale. Gridded monthly Argo data were used in the training and validation procedures of the method. Results show that the pre-clustered NN method was better than the same method without clustering, while also outperforming a clustered linear regressor and the random forest method recently reported. The new method was tested over a wide range of time (all months from 2004 to 2010) and depth (down to 1900 m). Overall, our best estimation resulted in an overall root-mean-squared error of 0.41 °C and a determination coefficient (R2) of 0.91 at the 50 m level for all months. The R2 decreased to 0.51 at 300 m but was still better than the calculation without pre-clustering. This method can be expanded to estimate other key oceanic variables and provide new insights in understanding the climate system.

Sea level changes within wide temporal–spatial scales have great influence on oceanic and atmospheric circulations. Efforts have been made to identify long-term sea level trend and regional sea level variations on different time scales. A nonuniform sea level rise in the tropical Pacific and the strengthening of the easterly trade winds from 1993 to 2012 have been widely reported. It is well documented that sea level in the tropical Pacific is associated with the typical climate modes. However, sea level change on interannual and decadal time scales still requires more research. In this study, the Pacific sea level anomaly (SLA) was decomposed into interannual and decadal time scales via an ensemble empirical mode decomposition (EEMD) method. The temporal–spatial features of the SLA variability in the Pacific were examined and were closely associated with climate variability modes. Moreover, decadal SLA oscillations in the Pacific Ocean were identified during 1993–2016, with the phase reversals around 2000, 2004, and 2012. In the tropical Pacific, large sea level variations in the western and central basin were a result of changes in the equatorial wind stress. Moreover, coherent decadal changes could also be seen in wind stress, sea surface temperature (SST), subtropical cells (STCs), and thermocline depth. Our work provided a new way to illustrate the interannual and decadal sea level variations in the Pacific Ocean and suggested a coupled atmosphere–ocean variability on a decadal time scale in the tropical region with two cycles from 1993 to 2016.

Exposing and stabilizing undercoordinated platinum (Pt) sites and therefore optimizing their adsorption to reactive intermediates offers a desirable strategy to develop highly efficient Pt-based electrocatalysts. However, preparation of atomically controllable Pt-based model catalysts to understand the correlation between electronic structure, adsorption energy, and catalytic properties of atomic Pt sites is still challenging. Herein we report the atomically thin two-dimensional PtTe2 nanosheets with well-dispersed single atomic Te vacancies (Te-SAVs) and atomically well-defined undercoordinated Pt sites as a model electrocatalyst. A controlled thermal treatment drives the migration of the Te-SAVs to form thermodynamically stabilized, ordered Te-SAV clusters, which decreases both the density of states of undercoordinated Pt sites around the Fermi level and the interacting orbital volume of Pt sites. As a result, the binding strength of atomically defined Pt active sites to H intermediates is effectively reduced, which renders PtTe2 nanosheets highly active and stable in hydrogen evolution reaction., Precisely regulating Pt catalytic sites is important and challenging. Herein the authors engineer the clustering of single atomic Te vacancies in atomically thin PtTe2 to optimize the electronic structure, adsorption energy, and catalytic performance of atomically defined Pt sites.

Single-atom catalysts (SACs) with magnetic elements as the active center have been widely exploited for efficient electrochemical conversions. Understanding the catalytic role of spin, and thus modulating the spin density of a single-atom center, is of profound fundamental interest and technological impact. Here, we synthesized ferromagnetic single Co atom catalysts on TaS2 monolayers (Co1/TaS2) as a model system to explore the spin-activity correlation for the oxygen evolution reaction (OER). A single Co atom adsorbed at the hollow site (CoHS) with spin-polarized electronic states serves as the active site for OER, whose spin density can be regulated by its neighboring single Co site via tuning the Co loading. Both experimental and theoretical results reveal the spin density-dependent OER activity that an optimal spin density of CoHS can be achieved with a neighboring hetero-single CoTa site (substitution of Ta by Co) for a superior OER performance, in contrast to a homo-single CoHS site, which creates an excessive spin density over vicinal CoHS. An optimized spin density of CoHS results in an optimal binding energy of oxygen species for the OER. Establishing the spin-activity correlation in SACs may create a descriptor for designing efficient magnetic SACs for renewable energy conversions.

Super typhoon Rammasun (2014) traveled across the South China Sea on July 16–18. Its far-field impacts on phytoplankton dynamics in the upper ocean were documented by a Biogeochemical-Argo (BGC-Argo) float located 200 km to the left of its track. Both surface chlorophyll-a concentration (Chla) and particulate backscattering coefficient (bbp) were observed to increase substantially within two distinct stages. The initial increase occurred during the passage of the typhoon, and the subsequent increase happened 5 days after the typhoon. In contrast, depth-integrated Chla and bbp in the upper 150 m underwent negligible changes throughout the entire period. The key lies in the fact that surface phytoplankton increases in the far-field region resulted from the physically driven vertical redistribution of particles, rather than from biological alternations. The first increase was attributed to the typhoon-induced strong turbulence which deepened the surface mixed layer, and thus entrained subsurface particles to the surface; the second was due to the post-typhoon adiabatic quasi-geostrophic adjustment of the upper ocean that gradually raised the isopycnals (and thus subsurface particles). These results challenge the prevailing wisdom on typhoon impacts, and thus shed new lights on the nature of the upper ocean responses to typhoons from both physical and biological perspectives.

The $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$ observed by the LHCb Collaboration are very likely to be $S$-wave $\Sigma_c\bar{D}^{(*)}$ molecular candidates due to their near-threshold character. In this work, we study the hidden-charm decay modes of these $P_c$ states, $P_c\to J/\psi p(\eta_cp)$, using a quark interchange model. The decay mechanism for the $P_c\to J/\psi p(\eta_cp)$ processes arises from the quark-quark interactions, where all parameters are determined by the mass spectra of mesons. We present our results in two scenarios. In scenario I, we perform the dynamical calculations and treat the $P_c$ states as pure $\Sigma_c \bar D^{(*)}$ molecules. In scenario II, after considering the coupled channel effect between different flavor configurations $\Sigma^{(*)}_c\bar D^{(*)}$, we calculate these partial decay widths again. The decay patterns in these two scenarios can help us to explore the molecular assignment and the inner flavor configurations for the $P_c$ states. In particular, the decay widths of $\Gamma(P_c(4312)\to\eta_cp)$ are comparable to the $J/\psi p$ decay widths in both of these two scenarios. Future experiments like LHCb may confirm the existence of the $P_c(4312)$ in the $\eta_cp$ channel., Comment: 13 pages, 7 figures, version published in PRD

$P_c(4312)$ observed by the LHCb collaboration is confirmed as a pentaquark and its structure, production, and decay behaviors attract great attention from theorists and experimentalists. Since its mass is very close to sum of $\Sigma_c$ and $\bar D$ masses, it is naturally tempted to be considered as a molecular state composed of $\Sigma_c$ and $\bar D$. Moreover, $P_c(4312)$ is observed in the channel with $J/\psi p$ final state, requiring that isospin conservation $P_c(4312)$ is an isospin-1/2 eigenstate. In literature, several groups used various models to estimate its spectrum. We systematically study the pentaquarks within the framework of the Bethe-Salpeter equation; thus $P_c(4312)$ is an excellent target because of the available data. We calculate the spectrum of $P_c(4312)$ in terms of the Bethe-Salpter equations and further study its decay modes. Some predictions on other possible pentaquark states that can be tested in future experiments are made.

Ligand-induced surface restructuring with heteroatomic doping is used to precisely modify the surface of a prototypical [Au25 (SR1 )18 ]- cluster (1) while maintaining its icosahedral Au13 core for the synthesis of a new bimetallic [Au19 Cd3 (SR2 )18 ]- cluster (2). Single-crystal X-ray diffraction studies reveal that six bidentate Au2 (SR1 )3 motifs (L2) attached to the Au13 core of 1 were replaced by three quadridentate Au2 Cd(SR2 )6 motifs (L4) to create a bimetallic cluster 2. Experimental and theoretical results demonstrate a stronger electronic interaction between the surface motifs (Au2 Cd(SR2 )6 ) and the Au13 core, attributed to a more compact cluster structure and a larger energy gap of 2 compared to that of 1. These factors dramatically enhance the photoluminescence quantum efficiency and lifetime of crystal of the cluster 2. This work provides a new route for the design of a wide range of bimetallic/alloy metal nanoclusters with superior optoelectronic properties and functionality.

Since the end of the twentieth century, the global mean surface temperature (GMST) exhibited a shift from a rapid warming to an unexpected deceleration. An anomalous heat was transported from the Pacific Ocean into the Indian Ocean through a strengthened Indonesian Throughflow during the same period. Within this background, it is essential to continue tracking the fate of the anomalous heat arriving in the Indian Ocean to form a comprehensive picture of the global ocean energy redistribution. The anomalous heat may continue flowing westward into the Atlantic Ocean along the main pathway of the regional ocean currents via the South Equatorial Current (SEC) and Agulhas Current. However, here we examine an alternate pathway: a southward heat transport in conjunction with a weakened SEC, diverting the canonical westward transport. This additional transport pathway causes an increase in heat content in the South Indian Ocean mid-latitudes (15–30°S, 95–110°E), may contribute to the Southern Ocean warming, and intensifies hemispheric asymmetry of oceanic heat content. The heat increase has important climate impacts such as changes to rainfall and increased coral bleaching over the western coast of Australia. The new path discovered here may be an essential route of heat transport linking the tropical Indo-Pacific Ocean and the Southern Ocean in 2003–2012.

Recently, molybdenum sulfide with its amorphous counterpart was found to hold a high activity versus the hydrogen evolution reaction (HER), making it a high potential material to explore new HER catalysts. Here we present a facile chemical method to synthesize ultra-small freestanding amorphous molybdenum sulfide (a-MoSx) colloidal nanodots with diameter of lower than 2 nm. Electrocatalytic HER tests show that freestanding a-MoSx colloidal nanodots exhibit an enhanced catalytic hydrogen activity in stark in contrast with in-situ annealed c-MoS2. When applied as a co-catalyst in photocatalytic HER, ultra-small a-MoSx nanodots could form a compact interface with the TiO2 when assisted by a bifunctional molecular linker, as the mercaptopropionic acid (MPA), which facilitates the decrease of the interfacial Schottky barrier occurring between the two components and allows for a fast injection of photo-excited electrons from the photoharvester into the co-catalyst. Our results demonstrate that the drastic enhancement of the photocatalytic H2 promotion rate of a-MoSx@MPA-TiO2 is mainly provided by unsaturated Mo(IV) active sites generated by the in-situ reduction during the photocatalytic HER process. The synergistic effect of generated unsaturated Mo(IV) sites and the presence of more exposed intrinsic active edges further promotes the enhancement of the catalytic H2 activity on a-MoSx nanodots.

In winter, an offshore flow of the coastal current can be inferred from satellite and in situ data over the western Taiwan Bank. The dynamics related to this offshore flow are examined here using observations as well as analytical and numerical models. The currents can be classified into three regimes. The downwind (i.e., southward) cold coastal current remains attached to the coast when the northeasterly wind stress is stronger than a critical value depending on the upwind (i.e., northward) large-scale pressure gradient force. By contrast, an upwind warm current appears over the Taiwan Bank when the wind stress is less than the critical pressure gradient force. The downwind coastal current and upwind current converge and the coastal current deflects offshore onto the bank during a moderate wind. Analysis of the vorticity balance shows that the offshore transport is a result of negative bottom stress curl that is triggered by the positive vorticity of the two opposite flows. The negative bottom stress curl is reinforced by the gentle slope over the bank, which enhances the offshore current. Composite analyses using satellite observations show cool waters with high chlorophyll in the offshore current under moderate wind. The results of composite analyses support the model findings and may explain the high productivity over the western bank in winter.

The two key mechanisms for biologically driven carbon sequestration in oceans are the biological pump (BP) and the microbial carbon pump (MCP); the latter is scarcely simulated and quantified in the China seas. In this study, we developed a coupled physical-ecosystem model with major MCP processes in the South China Sea (SCS). The model estimated a SCS-averaged MCP rate of 1.55 mg C m−2 d−1, with an MCP-to-BP ratio of 1:6.08 when considering the BP at a depth of 1000 m. Moreover, the ecosystem responses were projected in two representative global warming scenarios where the sea surface temperature increased by 2 and 4°C. The projection suggested a declined productivity associated with the increased near-surface stratification and decreased nutrient supply, which leads to a reduction in diatom biomass and consequently the suppression of the BP. However, the relative ratio of picophytoplankton increased, inducing a higher microbial activity and a nonlinear response of MCP to the increase in temperature. On average, the ratio of MCP-to-BP at a 1000-m depth increased to 1:5.95 with surface warming of 4°C, indicating the higher impact of MCP in future ocean carbon sequestration.

The seasonal characteristics of water exchange in Beibu Gulf are investigated based on a particle tracking model. The gulf is divided into six sub-regions in order to better understand the exchange processes and water movement in the gulf. The residence time is computed for each sub-region, and the results show that the whole gulf has a small seasonal variation, with 66 days in winter and 71 days in summer, while the sub-regions exhibit a large seasonal difference with short residence times in summer. Water exchange curves indicate water movement in the gulf follows the circulation patterns. In winter, the water particles move cyclonically and accumulate near the western coast of the gulf. The current flows entering the gulf are dominated by the westward flow from the Qiongzhou Strait. The influence area of this flow can extend to the Vietnam coast. In summer, water particles from the coastal area tend to move offshore and undergo strong mixing in the center of the gulf. The northward current flow from the south opening becomes the dominant flow, with a large influence area in the eastern part of the gulf.

The adhesion forces of particles on rough walls are important for particle–wall interactions in particle deposition, rebound, and resuspension. For the micron-scale graphite particles and sub-micron-scale rough walls in high-temperature gas-cooled reactors, a mathematical adhesion model is proposed based on the Johnson–Kendall–Roberts theoretical model and the assumption of asperity heights with Gaussian distribution. A statistical roughness parameter, the root-mean-square wall roughness height, is used to reflect the influence of roughness on adhesion. Meanwhile, an atomic force microscope (AFM) is used to measure the adhesion forces between different particles and rough walls, then the proposed model is verified based on related AFM measurements and compared with previous adhesion models. Although the AFM results exhibit considerable scatter, the statistical adhesion falls into the prediction range of the proposed model. The results show that the present model can explain the effects of material properties on adhesion and be extended to other AFM measurements. The present study provides a convenient and practical mathematical model for adhesion between particles and rough walls for engineering applications.

Satellite remote sensing can detect and predict subsurface temperature and salinity structure within the ocean over large scales. In the era of big ocean data, making full use of multisource satellite observations to accurately detect and predict global subsurface thermohaline structure and advance our understanding of the ocean interior processes is extremely challenging. This study proposed a new deep learning-based method—bi-directional long short-term memory (Bi-LSTM) neural networks—for predicting global ocean subsurface temperature and salinity anomalies in combination with surface remote sensing observations (sea-surface temperature anomaly, sea-surface height anomaly, sea-surface salinity anomaly, and the northward and eastward components of sea-surface wind anomaly), longitude and latitude information (LON and LAT), and subsurface Argo gridded data. Because of the temporal dependency and periodicity of ocean dynamic parameters, the Bi-LSTM is good at time-series feature learning by considering the significant temporal feature of the ocean variability and can well improve the robustness and generalization ability of the prediction model. For December 2015 as an example, our average prediction results in an overall determination coefficient (R2) of 0.691/0.392 and a normalized root mean square error of 0.039 °C/0.051 PSU for subsurface temperature anomaly (STA)/subsurface salinity anomaly (SSA) prediction. This study sets up different cases based on different sea-surface feature combinations to predict the subsurface thermohaline structure and analyze the role of longitude and latitude information on Bi-LSTM prediction. The results show that in the prediction of STA, the contribution of LON + LAT to the model gradually increases with depth, whereas in the prediction of SSA, LON + LAT maintains a relatively significant contribution to the model at different depths. Meanwhile, in the STA and SSA prediction, the LAT plays a more significant role than LON. We also applied the model to bi-directional prediction for different months of 2010 and 2015 to prove the applicability and robustness of the model. This study suggests that Bi-LSTM is more advantageous in time-series modeling for predicting subsurface and deep ocean temperature and salinity structures, fully takes into account the timing dependence of global ocean data, and outperforms the classic random forest approach in predicting subsurface thermohaline structure from remote sensing data.

On 22 December 2020, HISEA-1, the first C-band SAR small satellite for ocean remote sensing, was launched from the coastal Wenchang launch site. Though small in weight, the images it produced have a high spatial resolution of 1 m and a large observation width of 100 km. The first batch of images obtained within the first week after the launch confirmed the rich information in the data, including sea ice, wind, wave, rip currents, vortexes, ships, and oil film on the sea, as well as landmark buildings. Furthermore, geometric characteristics of sea ice, wind vector, ocean wave parameter, 3D features of buildings, and some air-sea interface phenomena in dark spots could also be detected after relevant processing. All these indicate that HISEA-1 could be a reliable, remarkable, and powerful instrument for observing oceans and lands.

Ocean heat content (OHC) evolutions calculated from the data sets (WOA, MyOcean, ORAS4, and SODA) were examined at different depth ranges in this study. According to the OHC changes, the subsurface and deeper ocean (SDO, 300–2000 m) heat content rapidly increased over the world's ocean basins during 1998–2013, indicating significant warming in the SDO during the recent global surface warming hiatus. Almost all the ocean basins warmed up, but with various contributions to the global SDO warming tied to the recent hiatus. The role of the Indian Ocean is particularly important as it has accounted for about 30% of global SDO heat uptake during the hiatus. The combined use of multiple data sets can reveal inconsistencies in SDO warming analysis results, and improve our understanding of the role of the SDO in the recent hiatus. The heat uptake in global SDO during the hiatus was about 2.37, 5.44, 3.75, and 2.44 × 1022 joules with trends of 0.40, 0.70, 0.77, and 0.48 W m−2 according to WOA, MyOcean, ORAS4, and SODA respectively, presenting obviously inconsistent SDO warming signals. MyOcean shows OHC overestimates in different ocean basins, while ORAS4 presents more reliable SDO OHC analysis. In general, the global SDO has sequestered a significant amount of heat—about 3.50 × 1022 joules with trends of 0.59 W m−2 on average among the four data sets—during the recent hiatus, demonstrating widespread and significant warming signals in the global SDO. There remain substantial uncertainties and discrepancies, however (especially in the PO and SO), in the available SDO warming information due to insufficient subsurface observation coverage and variations in the data set generation techniques used among different researchers.

Molybdenum disulfide (MoS 2 ) presents a promising nonprecious catalyst for hydrogen evolution reaction (HER) that has attracted extensive interest, but it still lacks an effective way to advance the utilization, in particular the basal plane of freestanding 2H-MoS 2 for HER. Herein, we report a rational design of freestanding 2H-MoS 2 monolayers to maximize the synergistic activity for HER by combining crystallinity engineering and cobalt substitution. Electrochemical measurements and density functional theory calculations indicate that the combination of crystallinity engineering and cobalt substitution in monolayer 2H-MoS 2 can not only introduce massive defects that act as new active sites but also activate and make use of the basal plane, which is responsible for the much enhanced HER activity compared to independent crystallinity engineering or cobalt substitution. Impressively, when integrated with a photoharvester cadmium sulfide for photocatalytic hydrogen evolution, the synergistic effect also promotes an excellent cocatalytic performance of monolayer 2H-MoS 2 that even higher than platinum (Pt). This study potentially provide new avenues for designing more efficient MoS 2 -based and other layered materials with enhanced HER performance.

Two lanthanide MOFs, namely {{Me2NH2}[TbIII(L)]·3H2O·DMF}n (1) and {{Me2NH2}[EuIII(L)]·3H2O·DMF}n (2), based on the flexible ligand 5-(bis(4-carboxybenzyl)amino)isophthalic acid (H4L) have been synthesized under solvothermal conditions, where DMF = N,N-dimethylformamide. The two compounds exhibit a 3D structure with rectangle channels encapsulating [Me2NH2]+ cations. The microporous structure as well as the confinement of cations inside the MOFs pores allows 1 and 2 to act as dual-functional luminescent materials to detect nitroaromatics and metal ions. The experiments show that the luminescence of sample 1 in DMF solution was quenched when the nitrobenzene (NB) content reached 2.3 × 10−2 mol/L and concentration of Fe3+ reached 5 × 10−4 mol/L.

In early 2008, cold water in the Taiwan Strait (TWS) was moved sequentially by a cross-strait flow and a southward flow to the Penghu Island, causing a cold-related fish kill disaster. Except for the local wind forcing, the coastal-trapped waves (CTWs), intermittently propagating toward the TWS from north in winter, are an additional factor that could impact the flow patterns by changing cross-strait sea-level gradient during the disaster. In the first stage (January 28–February 7), the reach of a large CTW trough induced an additional northward flow, which formed a cyclone after turning around the Zhangyun Ridge. Then, the cyclone led to an additional cross flow, which enhanced an eastward (offshore) movement of cold water. In the second stage (February 7–14), the arrival of a large CTW crest triggered an additional southward flow, which intensified a southward movement of the cold water. Due to the additional eastward and southward movements caused by the CTWs, the cold water could reach Penghu Island inducing a cold disaster.

In this research, three vertical velocities were included in a one-dimensional (1D) ocean model for a case study of the SouthEast Asian Time-Series Study station in the South China Sea. The vertical velocities consisted three processes, i.e., Ekman pumping (WEK), Eddy pumping (WEP), and the background upwelling (WBK). The quantification of WEK followed the classical Ekman pumping theory. The WEP, whose underlying mechanism was consistent with the baroclinic modes (dominated by the first mode), was quantified by Argo observation and altimetry data. The WBK, related with the background circulation, was estimated from the long-term heat budget balance. The skill assessment indicated that the case with all three processes performed best. The study confirmed the capability of the 1D model with three types of vertical velocities, which can reproduce the general structure and variation of temperature in vertical direction.

As a promising non-precious catalyst for the hydrogen evolution reaction (HER), molybdenum disulfide (MoS2), which is known to contain highly active edge sites and an inert basal plane, has attracted extensive interest. More recently, its amorphous counterpart has been found to have a higher HER activity, making it important to explore the effect of crystallinity on the HER performance of monolayer MoS2. However, the posed technological challenges of preparing crystallinity tunable 2H–MoS2 monolayers hinder their further study. In this work, we report the successful synthesis of crystallinity-dependent MoS2 monolayers through liquid exfoliation of the corresponding crystallinity-controllable bulk precursors. Excellent cocatalytic performances of the proposed MoS2 monolayers for the photocatalytic HER were achieved and determined by their crystallinity. An apparent quantum efficiency as high as 71.6% can be achieved for the lowest crystalline monolayer MoS2 over cadmium sulfide under visible light irradiation at 420 nm. This work provides a facile way to synthesise crystallinity controllable MoS2 monolayers and elucidates that the HER activity can be further enhanced through crystallinity engineering, providing a new strategy to enhance the HER activity of monolayer MoS2.

A resonance-like structure as narrow as 10 MeV is observed in the ${K}^{\ensuremath{-}}p$ invariant mass distributions in ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ at Belle. Based on the large data sample of about 1.5 million events and the small bin width of just 1 MeV for the ${K}^{\ensuremath{-}}p$ invariant mass spectrum, the narrow peak is found precisely lying at the $\mathrm{\ensuremath{\Lambda}}\ensuremath{\eta}$ threshold. While lacking evidence for a quark model state with such a narrow width at this mass region, we find that this narrow structure can be naturally identified as a threshold cusp but enhanced by the nearby triangle singularity via the $\mathrm{\ensuremath{\Lambda}}\text{\ensuremath{-}}{a}_{0}(980{)}^{+}$ or $\ensuremath{\eta}\text{\ensuremath{-}}\mathrm{\ensuremath{\Sigma}}(1660{)}^{+}$ rescatterings.

Accurate estimation of ocean’s interior salinity information based on surface remote sensing data is quite significant for understanding complex dynamic processes in the ocean. This study adopts two kinds of ensemble learning algorithm, Random Forest (RF) and Gradient Boosting Decision Tree (GBDT) to estimate the subsurface salinity anomaly (SSA) in the upper 2000 m of the global ocean from multisource satellite-based sea surface parameters. The model performance is measured by R-square (R2) and normalized root-mean-square error (NRMSE). The results indicate the RF and GBDT models are both well suitable for retrieving SSA in the global ocean’s interior and RF model outperforms GBDT model; the models accuracy generally decreased with the depth below 500 m. This study is helpful in understanding subsurface and deeper ocean environment response to recent global warming.

Private science parks (PSPs) are infrastructure elements of national high technology industrial development zones. Increasing private capital is being invested in this field to transform abandoned factories into science parks through brownfield regeneration, which not only effectively utilizes urban space, but also greatly strengthens the power of scientific and technological innovation. The evolution of these PSPs, however, is not satisfactory, and some operation and innovation-related problems often lead to their failures. Therefore, identifying key success factors is crucial for the sustainable growth of PSPs. This study employs Fuzzy Analytic hierarchy process (FAHP) and Fuzzy-DEMATEL (Decision Making Trial and Evaluation Laboratory) methods to construct an identification model for key success factors of PSPs established from brownfield regeneration. Associated influencing factors were collected through literature analysis, on-site interviews, and questionnaire, based on which key success factors were identified. The results of the study showed that five factors&mdash, resources sharing capacity of the park, park scale, financing and financial services, legal policy services and administrative capability, and construction level of facilities in the park&mdash, are the key success factors for such PSPs. The results also provide a theoretical basis for the development of PSPs established from brownfield regeneration, and support the formulation of PSP-related policies.

To analyze the dependence of intensification rates of tropical cyclones (TCs) on the variation of environmental conditions, an index is proposed here to measure the lifetime maximum intensification rates (LMIRs) for the Saffir–Simpson scale category 4–5 TCs over the western North Pacific. To quantitatively describe the intensification rate of major TCs, the LMIR is defined as the maximum acceleration in the sustained-wind-speed over a 24-h period of an overwater TC. This new index, LMIR, is generally independent of the indices for RI frequency. The results show that the Pacific Decadal Oscillation (PDO) modulates the inter-annual relationship between the LMIR and El Niño/Southern Oscillation (ENSO). The PDO’s modulation on the ENSO’s effect on the LMIR is explored here by considering the relationship between the LMIR and the environmental conditions in different PDO phases. While the ENSO’s effect on the LMIR for the warm PDO phase is generally by affecting the variations of upper ocean heat content, ENSO mainly influences the variations of zonal wind and vertical wind shear for the cold PDO phase. Our results suggest that fast translating TCs tend to attain strong intensification during the warm PDO phase, while a warm subsurface condition may permit slow-translating TCs also to become strongly intensified during the cooling PDO phase. These findings have an important implication for both prediction of RI and the long-term projection of TC activities in the western North Pacific.

Reactions of cadmium ions with the flexible tetracarboxylic ligand, 5-(bis(4-carboxybenzyl)amino) isophthalic acid (H4L) gave rise to four complexes, namely {[(Me2NH2)2Cd3(L)2]∙10H2O)}n (1), {[Cd2(L)(pdp)(H2O)2]∙2DMF·4H2O}n (pdp = 4-[(E)-4-Pyridinylazo]pyridine) (2), {[Cd2(L)(bpe)(H2O)2]∙2DMF·4H2O}n (bpe = 1,2-bi(4-pyridyl)ethene) (3) and {[Cd4(L)2(bpmp)3]∙2H2O}n (bpmp = N,Nʹ-bis-(4-pyridyl-methyl) piperazine) (4). Compound 1 features a three-dimensional anionic architecture constructed by triangular Cd3 cluster and ligands, with rectangle channels encapsulating [Me2NH2]+ cations. Compounds 2 and 3 present similar structures, exhibiting the 2D polythreading layer. Compound 4 possesses a 3D structure with 4,6-connected new topology. The powder X-ray diffraction, the thermal stabilities, and solid-state luminescence properties were studied for 1–4. Furthermore, the luminescent sensing of compounds 1 and 4 toward nitrobenzene has also been investigated.

Through a facile and effective strategy by employing lithium molten salts the controlled synthesis of 2H- and 1T-MoS2 monolayers with high-yield production is achieved. Both phases of MoS2 monolayers exhibit high stabilities. When used as a catalyst for hydrogen evolution, these phased MoS2 monolayers deliver respective advantages in the field of electro- and photo-catalytic hydrogen evolution.

A simple method is developed to fabricate protonated porous graphitic carbon nitride nanosheets (P-PCNNS) by protonation-exfoliation of bulk graphitic carbon nitride (BCN) with phosphoric acid (H3 PO4 ). The H3 PO4 treatment not only helps to exfoliate the BCN into 2D ultrathin nanosheets with abundant micro- and mesopores, endowing P-PCNNS with more exposed active catalytic sites and cross-plane diffusion channels to facilitate the mass and charge transport, but also induces the protonation of carbon nitride polymer, leading to the moderate removal of the impurities of carbon species in BCN for the optimization of the aromatic π-conjugated system for better charge separation without changing its chemical structure. As a result, the P-PCNNS show much higher photocatalytic performance for hydrogen evolution and CO2 conversion than bare BCN and graphitic carbon nitride nanosheets.

Au-based catalysts were widely applied in photocatalytic areas owing to Au local surface plasmon resonance (LSPR), especially in the reactions of secondary alcohol dehydrogenation. However, there were rare cases reporting Au catalysts to dehydrogenate secondary alcohols under dark condition at room temperature. In this work, basic semiconductor birnessite, with easily extractable lattice oxygen in its lattice structure, was employed as support of Au catalyst and it was found that the Au/birnessite catalyst could dehydrogenate iso-propanol (IPA) to acetone under dark condition (3.7 μmol acetone was produced within 5 h). With the utilization of lattice oxygen in the reaction under dark condition, oxygen vacancies were instantaneously formed which enhanced the light absorbing properties of Au/birnessite and further improved its photocatalytic activity (13.6 μmol acetone production within 5 h). The synergistic effects between lattice oxygen and oxygen vacancies enhanced the performance of Au-based catalyst in IPA dehydrogenation and this work provides a synthesis tactic for effective catalysts in the dehydrogenation of various secondary alcohols.

The variability of the sea surface height anomaly (SSHA) in the mid- to high-latitude North Atlantic for the period of 1993–2010 was investigated using the ensemble empirical mode decomposition to identify the dominant time scales. Sea level variations in the North Atlantic subpolar gyre (SPG) are dominated by the annual cycle and the long-term increasing trend. In comparison, the SSHA along the Gulf Stream (GS) is dominated by variability at intraseasonal and annual time scales. Moreover, the sea level rise in the SPG developed at a reduced rate in the 2000s compared to rates in the 1990s, which was accompanied by a rebound in SSHA variability following a period of lower variability in the system. These changes in both apparent trend and low-frequency SSHA oscillations reveal the importance of low-frequency variability in the SPG. To identify the possible contributing factors for these changes, the heat content balance (equivalent variations in the sea level) in the subpolar region was examined. The results indicate that horizontal circulations may primarily contribute to the interannual to decadal variations, while the air–sea heat flux is not negligible at annual time scale. Furthermore, the low-frequency variability in the SPG relates to the propagation of Atlantic meridional overturning circulation (AMOC) variations from the deep-water formation region to midlatitudes in the North Atlantic, which might have the implications for recent global surface warming hiatus.

We find that several thresholds can contribute to the enhancements of the newly observed heavy pentaquark candidates $P_c^+(4380)$ and $P_c^+(4450)$ via the anomalous triangle singularity (ATS) transitions in the specific kinematics of $\Lambda_b\to J/\psi K^- p$. Apart from the observed two peaks we find that another peaks around 4.5 GeV can also be produced by the ATS. We also show that the $\Sigma_c^{(*)}$ can be produced at leading order in $\Lambda_b$ decay. This process is different from the triangle diagram and its threshold enhancement only appears as CUSP effects if there is no pole structure or the ATS involved. The threshold interaction associated with the presence of the ATS turns out to be a general phenomenon and plays a crucial role in the understanding of candidates for exotic states., Comment: 9 pages, 6 figures, 4 tables; published version in PLB

The Taiwan Strait Nowcast/Forecast System (TFOR), which is based on the Regional Ocean Modeling System, may be the first operational ocean model to include both tide and circulation processes in the Taiwan Strait. In this study, we assessed the performance of TFOR by investigating the differences between observational data and the results obtained by TFOR, thereby illustrating the ability of TFOR to reproduce significant physical processes. We also evaluated the utility and reliability of TFOR products for successful applications in maritime search and rescue. The mean bias, root mean-squared difference, correlation coefficient (CC), and Willmott skill for the differences in temperature between the cruise observations and the TFOR results were –0.01°C, 1.2°C, 0.87, and 0.92, respectively, and those for the corresponding salinity results were 0.06 PSU, 0.4 PSU, 0.74, and 0.83, respectively. The distributions of the TFOR M2 harmonic constants indicated that TFOR simulates the tidal characteristics well in the Taiwan Strait. The CC between the Taiwan Strait volume transport based on the TFOR results and the along-strait wind stress was 0.77, thereby indicating that monsoon winds exert an important influence on the variability in volume transport through the Taiwan Strait. Statistical analyses of the TFOR results showed that the annual, spring, summer, autumn, and winter mean transport volumes were 1.16, 1.28, 2.52, 0.80, and 0.04 Sv, respectively. In conclusion, the TFOR is robust and it can simulate the temperature, salinity, and velocity in a reasonable and stable manner.

The variability of the South Pacific convergence zone (SPCZ) is evaluated using ocean surface wind products derived from the atmospheric reanalysis ERA-Interim for the period of 1981–2014 and QuickSCAT for the period of 1999–2009. From these products, indices were developed to represent the SPCZ strength, area, and centroid location. Excellent agreement is found between the indices derived from the two wind products during the QuikSCAT period in terms of the spatiotemporal structures of the SPCZ. The longer ERA-Interim product is used to study the variations of SPCZ properties on intraseasonal, seasonal, interannual, and decadal time scales. The SPCZ strength, area, and centroid latitude have a dominant seasonal cycle. In contrast, the SPCZ centroid longitude is dominated by intraseasonal variability due to MJO influence. The SPCZ indices are all correlated with El Niño–Southern Oscillation indices. Interannual and intraseasonal variations of SPCZ strength during strong El Niño are approximately twice as large as the respective seasonal variations. SPCZ strength depends more on the intensity of El Niño rather than the central-Pacific versus eastern-Pacific type. The change from positive to negative Pacific decadal oscillation (PDO) around 1999 results in a westward shift of the SPCZ centroid longitude, a much smaller interannual swing in centroid latitude, and a decrease in SPCZ area. This study improves the understanding of the variations of the SPCZ on multiple time scales and reveals the variations of SPCZ strength not reported previously. The diagnostics analyses can be used to evaluate climate models to gauge their fidelity.

A facile synthesis of high performance flexible V2O5-based cathodes constructed by V2O5 nanosheets encapsulated within multi-graphene nanotubes and the successful demonstration of a flexible full cell.