A Cycle of Wind-Driven Canyon Upwelling and Downwelling at Wilmington Canyon and the Evolution of Canyon-Upwelled Dense Water on the MAB Shelf

Submarine canyons provide a conduit for shelf-slope exchange via topographically induced processes such as upwelling and downwelling. These processes in the Wilmington Canyon, located along the shelf-break of the Mid-Atlantic Bight (MAB), have not been previously studied, and the associated hydrographic variability inside the canyon and on the adjacent shelf are largely unknown. Observations from an underwater glider deployed in Wilmington Canyon (February 27 - March 8, 2016), along with wind and satellite altimetry data, showed evidence for a wind-driven canyon upwelling event followed by a subsequent downwelling event. Next, a numerical model of the MAB was developed to more fully represent these two events. Modeled results showed that under upwelling-favorable winds during February 25 - March 3, sea level increased seaward, shelf currents flowed northeastward, and canyon upwelling developed. Then under downwelling-favorable winds during March 4-7, sea level increased landward, shelf currents flowed southwestward, and canyon downwelling developed. Modeling experiments showed that canyon upwelling and downwelling were sub-tidal processes driven by winds and pressure gradients (associated with SSH gradients), and they would occur with or without tidal forcing. During the upwelling period, slope water originating from 150-215 m depths within the canyon (75 m below the canyon rim), was advected onto the shelf, forming a cold and dense canyon-upwelled slope-originated overflow water at the bottom of the outer shelf (75-150 m isobaths). The dense overflow current flowed was directed northeastward and expanded in the cross-shelf direction. It was 5-20 km wide and 10-30 m thick. The estimated volume of the plume overflow water exceeded 6×109 m3 at peak. The density front at the shoreward side of the dense overflow water caused a subsurface baroclinic frontal jet, which flowed northeastward and along-shelf with maximum speed exceeding 0.5 m/s. In the ensuing downwelling event, a portion of the previously upwelled dense water was advected back to the canyon, and then flowed down-slope in the upper canyon in ~0.3 m/s bottom-intensified currents. Dynamical investigation of the overflow current showed that its evolution was governed by unbalanced horizontal pressure gradient force in the cross-shelf direction and that the current was geostrophic

Spatio-temporal characteristics of PM2.5 and O3 synergic pollutions and influence factors in the Yangtze River Delta

Since the implementation of pollution prevention and control action in China in 2013, particulate pollution has been greatly reduced, while ozone pollution has become gradually severe, especially in the economically developed eastern region. Recently, a new situation of air pollution has emerged, namely, enhanced atmospheric oxidation, ascending regional ozone pollution, and increasing particle and ozone synergic pollution (i.e., double-high pollution). Based on the long-term observation data from 2015 to 2021, we examined the spatio-temporal characteristics of urban PM2.5 and O3 pollution in the Yangtze River Delta and quantified the effects of meteorological and non-meteorological factors on pollution in four city clusters using stepwise multiple linear regression models. Temporally, PM2.5 decreased gradually year by year while, O3 increased in city clusters. Spatially, PM2.5 declined from northwest to southeast, while O3 decreased from northeast to southwest. Except for southern Zhejiang, other city clusters suffer from complex air pollution at different levels. In general, pollution intensity and frequency vary with city location and time. Single PM2.5 pollution mostly occurred in northern Anhui. Single O3 pollution occurred in central and southern Jiangsu and northern Zhejiang. Synergic pollutions of PM2.5 and O3 mainly occurred in central Jiangsu. The contributions (90%) of non-meteorological factors (e.g., anthropogenic emission) to PM2.5 decrease and O3 increase are far larger than that of meteorological factors (5%). Relative humidity, sea level pressure, and planetary boundary layer height are the most important meteorological factors to drive PM2.5 changes during pollution. Downward solar radiation, total cloud cover, and precipitation are the most important meteorological factors that affect O3 changes during pollution. The results provide insights into particulate and ozone pollution in the Yangtze River Delta and can help policymakers to formulate accurate air pollution prevention and control strategies at urban and city cluster scales in the future

Boosting the bifunctionality and durability of cobalt-fluoride-oxide nanosheets for alkaline water splitting through nitrogen-plasma-promoted electronic regulation and structural reconstruction

Designing cost-effective and durable bifunctional electrocatalysts with high activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for large-scale hydrogen production through water splitting. However, many electrocatalysts undergo surface or bulk reconstruction, leading to an unstable catalytic activity. In this study, we present a facile N2 plasma strategy to enhance the electrocatalytic activity of cobalt-fluoride-oxide (CoFO, herein NCoFO) nanosheets while maintaining reasonably stable performance. The optimized NCoFO nanosheets grown on carbon cloth through a 60 s N2 plasma treatment (NCoFO/CC-60) exhibit remarkable performance with low overpotentials of 203 mV and 230 mV at 10 mA cm-2 for the HER and the OER, respectively. Density functional theory calculations revealed that the enhanced catalytic performance is attributed to the regulated local electronic configuration resulting from plasma treatment. Furthermore, the assembled alkaline electrolyzer NCoFO/CC-60||NCoFO/CC-60 requires an extremely low voltage of 1.48 V to attain 10 mA cm-2 for over a 150 h operation, which is superior to the values obtained for Pt/C||RuO2 (1.50 V) and CoFO/CC||CoFO/CC (1.55 V)

Iron-modulated nickel cobalt phosphide embedded in carbon to boost power density of hybrid sodium–air battery

Nickel cobalt phosphide (NiCoP) is emerging as a potential electrocatalyst towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, its ORR/OER activities are sluggish. Here, we investigated the roles of iron dopants in the Fe-doped NiCoP (Fe–NiCoP) in order to boost its ORR/OER kinetics. The density functional theory (DFT) calculations reveal that the Fe dopant effectively modulates the electron conductivity of NiCoP and reduces binding energies of the reaction intermediates towards rate-determining steps of ORR and OER. A binder-free 3D microflowers morphology of the Fe–NiCoP embedded in the amorphous carbon layer (Fe–NiCoP@C) catalyst on the nickel foam was prepared as the air cathode for the hybrid sodium-air battery (HSAB). The HSAB displays a discharge voltage of 2.74 V at 0.01 mA cm−2 with excellent round trip efficiency of 93.26 % at the 500th cycle and state-of-the-art power density of 621 mW g−1

In situ immobilizing atomically dispersed Ru on oxygen-defective Co3O4 for efficient oxygen evolution

The synergistic regulation of the electronic structures of transition-metal oxide-based catalysts via oxygen vacancy defects and single-atom doping is efficient to boost their oxygen evolution reaction (OER) performance, which remains challenging due to complex synthetic procedures. Herein, a facile defect-induced in situ single-atom deposition strategy is developed to anchor atomically dispersed Ru single-atom onto oxygen vacancy-rich cobalt oxides (Ru/Co3O4–x) based on the spontaneous redox reaction between Ru3+ ions and nonstoichiometric Co3O4–x. Accordingly, the as-prepared Ru/Co3O4–x electrocatalyst with the coexistence of oxygen vacancies and Ru atoms exhibits excellent performances toward OER with a low overpotential of 280 mV at 10 mA cm–2, a small Tafel slope value of 86.9 mV dec–1, and good long-term stability in alkaline media. Furthermore, density functional theory calculations uncover that oxygen vacancy and atomically dispersed Ru could synergistically tailor electron decentralization and d-band center of Co atoms, further optimizing the adsorption of oxygen-based intermediates (*OH, *O, and *OOH) and reducing the reaction barriers of OER. This work proposes an available strategy for constructing electrocatalysts with abundant oxygen vacancies and atomically dispersed noble metal and presents a deep understanding of synergistic electronic engineering of transition-metal-based catalysts to boost oxygen evolution

Bridging PCR: An Efficient and Reliable Scheme Implemented for Genome-Walking

The efficacy of the available genome-walking methods is restricted by low specificity, high background, or composite operations. We herein conceived bridging PCR, an efficient genome-walking approach. Three primers with random sequences, inner walker primer (IWP), bridging primer (BP), and outer walker primer (OWP), are involved in bridging PCR. The BP is fabricated by splicing OWP to the 5′-end of IWP’s 5′-part. A bridging PCR set is constituted by three rounds of amplification reactions, sequentially performed by IWP, BP plus OWP, and OWP, respectively pairing with three nested sequence-specific primers (SSP). A non-target product arising from IWP alone undergoes end-lengthening mediated by BP. This modified non-target product is a preferentially formed hairpin between the lengthened ends, instead of binding with shorter OWP. Meanwhile, a non-target product, triggered by SSP alone or SSP plus IWP, is removed by nested SSP. As a result, only the target DNA is accumulated. The efficacy of bridging PCR was validated by walking the gadA/R genes of Levilactobacillus brevis CD0817 and the hyg gene of rice

The nonlinear effect of financial and fiscal policies on poverty alleviation in China-An empirical analysis of Chinese 382 impoverished counties with PSTR models.

Using panel smooth transition regression (PSTR) models, this paper studies the effects of financial and fiscal policies on poverty reduction across 382 poverty-stricken counties in China. The findings are that both fiscal and financial policies have a positive influence on poverty reduction, and their relationships are nonlinear. For either a high or low degree of poverty, fiscal policies are effective for poverty reduction, while financial policies have a greater impact on poverty reduction when there is a medium degree of poverty. Therefore, in deciding which policies should be prioritized for reducing poverty, the level of poverty should be taken into account. To be more specific, when a portfolio of poverty-reduction policies is implemented, fiscal policies should be prioritized at the beginning, when the incidence of poverty is high. Then, financial support should come to the forefront as the poverty level drops, and fiscal support should be stepped up when the poverty level continues to drop

Semi-Site-Specific Primer PCR: A Simple but Reliable Genome-Walking Tool

Genome-walking has been frequently applied to molecular biology and related areas. Herein, a simple but reliable genome-walking technique, termed semi-site-specific primer PCR (3SP-PCR), is presented. The key to 3SP-PCR is the use of a semi-site-specific primer in secondary PCR that partially overlaps its corresponding primary site-specific primer. A 3SP-PCR set comprises two rounds of nested amplification reactions. In each round of reaction, any primer is allowed to partially anneal to the DNA template once only in the single relaxed-stringency cycle, creating a pool of single-stranded DNAs. The target single-stranded DNA can be converted into a double-stranded molecule directed by the site-specific primer, and thus can be exponentially amplified by the subsequent high-stringency cycles. The non-target one cannot be converted into a double-strand due to the lack of a perfect binding site to any primer, and thus fails to be amplified. We validated the 3SP-PCR method by using it to probe the unknown DNA regions of rice hygromycin genes and Levilactobacillus brevis CD0817 glutamic acid decarboxylase genes

Protocol to retrieve unknown flanking DNA sequences using semi-site-specific PCR-based genome walking

Summary: Here, we describe a protocol based on semi-site-specific primer PCR (3SP-PCR) to access unknown flanking DNA sequences. We specify the guidelines for designing primers for 3SP-PCR. We also describe experimental procedures for the 3SP-PCR, along with PCR product purification and subsequent sequencing and analysis.For complete details on the use and execution of this protocol, please refer to Wei et al.1 : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics