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Unconventional 1T′-phase transition metal dichalcogenides (TMDs) have aroused tremendous research interest due to their unique phase-dependent physicochemical properties and applications. However, due to the metastable nature of 1T′-TMDs, the controlled synthesis of 1T′-TMD monolayers (MLs) with high phase purity and stability still remains a challenge. Here we report that 4H-Au nanowires (NWs), when used as templates, can induce the quasi-epitaxial growth of high-phase-purity and stable 1T′-TMD MLs, including WS2, WSe2, MoS2and MoSe2, via a facile and rapid wet-chemical method. The as-synthesized 4H-Au@1T′-TMD core–shell NWs can be used for ultrasensitive surface-enhanced Raman scattering (SERS) detection. For instance, the 4H-Au@1T′-WS2NWs have achieved attomole-level SERS detections of Rhodamine 6G and a variety of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike proteins. This work provides insights into the preparation of high-phase-purity and stable 1T′-TMD MLs on metal substrates or templates, showing great potential in various promising applications.

Unraveling the catalyst surface structure and behavior during reactions is essential for both mechanistic understanding and performance optimization. Here we report a phenomenon of facet-dependent surface restructuring intrinsic to β-Ni(OH)2catalysts during oxygen evolution reaction (OER), discovered by the correlative ex situand operandocharacterization. The ex situstudy after OER reveals β-Ni(OH)2restructuring at the edge facets to form nanoporous Ni1–xO, which is Ni deficient containing Ni3+species. Operandoliquid transmission electron microscopy (TEM) and Raman spectroscopy further identify the active role of the intermediate β-NiOOH phase in both the OER catalysis and Ni1–xO formation, pinpointing the complete surface restructuring pathway. Such surface restructuring is shown to effectively increase the exposed active sites, accelerate Ni oxidation kinetics, and optimize *OH intermediate bonding energy toward fast OER kinetics, which leads to an extraordinary activity enhancement of ∼16-fold. Facilitated by such a self-activation process, the specially prepared β-Ni(OH)2with larger edge facets exhibits a 470-fold current enhancement than that of the benchmark IrO2, demonstrating a promising way to optimize metal-(oxy)hydroxide-based catalysts.

A universal glycosylation strategy could significantly simplify glycoside synthesis. One approach to achieving this goal is through acyl group direction for the corresponding 1,2-, 1,3-, 1,4-, or 1,6-transglycosylation; however, this approach has been challenging for glycosidic bonds that require distal equatorial-acyl group direction. We developed an approach in weakly nucleophilic environments for selective 1,4-transglycosylation directed by the equatorial-4-O-acyl group. Here, we explored this condition in other distal acyl groups and found that, besides 1,n-transdirection, acyl groups also mediated hydrogen bonding between acyl groups and alcohols. The latter showed a diverse effect and classified the acyl group direction into axialand equatorialcategories. Corresponding glycosylation conditions were distinguished as guidance for acyl group direction from either category. Hence, acyl group direction may serve as a general glycosylation strategy.

Although deubiquitinases (DUBs) have been well described in liver tumorigenesis, their potential roles and mechanisms have not been fully understood. In this study, we identified ubiquitin-specific protease 1 (USP1) as an oncogene with essential roles during hepatocellular carcinoma (HCC) progression. USP1, with elevated expression levels and clinical significance, was identified as a hub DUB for HCC in multiple bioinformatics datasets. Functionally, USP1 overexpression significantly enhanced the malignant behaviors in HCC cell lines and spheroids in vitro, as well as the zebrafish model and the xenograft model in vivo. In contrast, genetic ablation or pharmacological inhibition of USP1 dramatically impaired the phenotypes of HCC cells. Specifically, ectopic USP1 enhanced aggressive properties and metabolic reprogramming of HCC cells by modulating mitochondrial dynamics. Mechanistically, USP1 induced mitochondrial fission by enhancing phosphorylation of Drp1 at Ser616 via deubiquitination and stabilization of cyclin-dependent kinase 5 (CDK5), which could be degraded by the E3 ligase NEDD4L. The USP1/CDK5 modulatory axis was activated in HCC tissues, which was correlated with poor prognosis of HCC patients. Furthermore, Prasugrel was identified as a candidate USP1 inhibitor for targeting the phenotypes of HCC by an extensive computational study combined with experimental validations. Taken together, USP1 induced malignant phenotypes and metabolic reprogramming by modulating mitochondrial dynamics in a CDK5-mediated Drp1 phosphorylation manner, thereby deteriorating HCC progression.

High-entropy alloy (HEA) nanoparticles (NPs) have been emerging with superior compositional tunability and multielemental synergy, presenting a unique platform for material discovery and performance optimization. Here we report a synthetic approach utilizing hollow-carbon confinement in the ordinary furnace annealing to achieve the nonequilibrium HEA-NPs such as Pt0.45Fe0.18Co0.12Ni0.15Mn0.10with uniform size ∼5.9 nm. The facile temperature control allows us not only to reveal the detailed reaction pathway through ex situcharacterization but also to tailor the HEA-NP structure from the crystalline solid solution to intermetallic. The preconfinement of metal precursors is the key to ensure the uniform distribution of metal nanoparticles with confined volume, which is essential to prevent the thermodynamically favored phase separation even during the ordinary furnace annealing. Besides, the synthesized HEA-NPs exhibit remarkable activity and stability in oxygen reduction catalysis. The demonstrated synthetic approach may significantly expand the scope of HEA-NPs with uncharted composition and performance.

Two-stroke, low-speed diesel engines are widely used in large ships due to their good performance and fuel economy. However, there have been few studies of the effects of lubricating oils on the vibration of two-stroke, low-speed diesel engines. In this work, the effects of three different lubricating oils on the vibration characteristics of a low-speed engine are investigated, using the frequency domain, time-frequency domain, fast Fourier transform (FFT) and short-time Fourier transform (STFT) methods. The results show that non-invasive condition monitoring of the wear to a cylinder liner in a low-speed marine engine can be successfully achieved based on vibration signals. Both the FFT and STFT methods are capable of capturing information about combustion in the cylinder online in real time, and the STFT method also provides the ability to visualise the results with more comprehensive information. From the online condition monitoring of vibration signals, cylinder lubricants with medium viscosity and medium alkali content are found to have the best wear protection properties. This result is consistent with those of an elemental analysis of cylinder lubrication properties and an analysis of the data measured from a piston lifted from the cylinder after 300 h of engine operation.

eq-4-O-Acyl group directed β-rhamnosylation and β-mannosylation are achieved in a carborane or BARF anion formed weakly nucleophilic environment with the assistance of a 2,3-orthocarbonate group. The 4-O-acyl group plays a critical role in directing the β-selectivity, and the weakly coordinating anion is essential to amplify this direction. The orthocarbonate group could be readily removed with 1,3-propanediol in the presence of BF3·Et2O.

This paper proposes a scheme to isolate cascading outages in a local region by breaking inter-regional linkages of component failures. The scheme employs a data-driven inter-regional Interaction Graph on key linkages of component failures respectively from two different operating regions, which are indicators of the propagation of outages from a local region to the rest of the system. When the triggering of a key linkage is predicted to have a high risk, a remedial action that sheds an amount of load determined by sensitivity analysis is taken to mitigate the outages and stop their propagation. The proposed scheme is validated both on the IEEE 118-bus test system and an actual power grid model.

Surface defect detection is essential for ensuring product quality. Intelligent defect detection is widely studied and applied in many industrial fields. However, glass defect detection is a daunting task because the optical properties of glass present unique challenges, e.g., intraclass difference, low contrast, and ambiguous edges. In this article, we propose an efficient edge enhancement network (EEE-Net) to address the above challenges. EEE-Net employs efficient transformer blocks to compose the pyramid network; each block combines a sequence reduction block (SRB) for efficient long-range contextual modeling and feature refinement. We propose three modules for edge enhancement: an encoder for edge feature (En-edge), a decoder for edge feature (De-edge), and an edge information fusion (EIF) module. En-edge and De-edge are encoders and decoders of edge features. They extract and enhance the edge information of the network at each layer, respectively, focusing on the edge change points of the network. The EIF module is used to fuse multiple layers of feature and edge information, enabling the network to obtain accurate defect outlines. Experimental results on glass surface defect (GSD) and mobile phone screen surface defect (MSD) datasets show the superiority of the proposed model and its feasibility for real-time industrial applications.

As a supplement to face-to-face teaching, small private online courses (SPOCs) have become increasingly popular in higher education. Nevertheless, there is a lack of research on behavioral patterns in the university SPOC. This empirical study investigates the behavioral patterns of 306 undergraduate students taking a degree course partially taught through a university learning platform. Results suggested that task-oriented behaviors accounted for most of the online learning processes. The login behavior was the most significantly correlated with learning outcomes, followed by student engagement with learning activities. The authors found that students' engagement levels had a statistically significant impact on their learning outcomes. Additionally, the high-achieving group demonstrated higher activity levels in performance- and objective-driven activities. The low-achieving group encountered some difficulties in self-regulated learning.

For better adapting the course to different learners' needs, this study analysed the learners' online learning behaviours. Through using data mining technology to mine the learning behaviours from five dimensions: video watching, text reading, discussion and communication, test and assignments taking, we draw the following conclusions: the demographic characteristics of learners show that the learners are mainly composed of principals, middle-level educational managers and key teachers. The learner's general learning behaviour characteristics are mainly expressed by the facts that the learners' interest in practical cases, and few participants can last more than four weeks, and the learners like videos and texts but they do not like to speak in the discussion forum. Learners can be divided into three clusters: certificate-oriented learners, practice oriented learners and browsers. The value of MOOC should not be evaluated on the basis of certification rates but on whether the learner's learning needs are met.

Compared with conventional authentication schemes, which utilize cryptographic mechanisms and operate at an upper layer, authentication at the physical (PHY) layer possesses many advantages, such as, higher information-theoretic security by introducing uncertainty to an adversary, better efficiency, and better compatibility by avoiding any operations at the upper layer. An effective PHY-layer authentication scheme should consider covertness, security, and robustness together. However, in published literature, these three properties have been separately analyzed. This paper proposes a generic security model for PHY-layer authentication, and we design a new systematic metric, which is referred to as the probability of security authentication (PSA). According to the proposed generic security model, we can not only systematically analyze the effect of the parameter of a certain PHY-layer authentication scheme on the final performance, but also fairly compare the performance of different PHY-layer authentication schemes under the same channel conditions at the legitimate and adversary receivers. For performance analysis, the probability of detection (PD) and the probability of false alarm (PFA) of two PHY-layer authentication schemes over fading channels are defined, and their closed-form expressions are well derived. On the basis of the proposed generic security model, a systematic performance comparison between different PHY-layer schemes is provided.

The contact line pinning and supersaturation theory for the nanobubble stability has attracted extensive concerns from experimental investigators, and some experimenters argue that the contact line pinning is unnecessary. To interpret the experimental observations, we have proposed previously through molecular dynamics simulations that the deformation of soft substrates caused by surface nanobubbles may play an important role in stabilizing surface nanobubbles, while yet no quantitative theory is available for explanation of this mechanism. Here, the detailed mechanism of self-pinning-induced stability of surface nanobubbles is investigated through theoretical analysis. By manipulating substrate softness, we find that the formation of surface nanobubbles may create a deformation ridge nearby their contact lines which leads to the self-pinning effect. Theoretical analysis shows that the formation of nanobubbles on sufficiently rigid substrates or on liquid–liquid interfaces corresponds to a local free energy maximum, while that on the substrates with intermediate softness corresponds to a local minimum. Thus, the substrate softness could regulate the surface nanobubble stability. The critical condition for the self-pinning effect is determined based on contact line depinning, and the effect of gas supersaturation is explored. Finally, the approximate stability range for the surface nanobubbles is also predicted.

To find the relationships between internal fixation parameters and biomechanical indexes with least number of runs, a regression orthogonal approach is proposed to establish surrogate models of different biomechanical indexes. Firstly, a simplified model of transverse femoral shaft fracture is built, and varieties of geometric sizes for plates and screws configurations are combined based on orthogonal array. Next, the biomechanical indexes of different combinations are calculated through finite element analysis (FEA). Furthermore, surrogate models are developed with the aid of regression orthogonal analysis. Finally, with comparison of biomechanical indexes obtained from the surrogate models and FEA results, highly coincident results validate the surrogate models. The number of combinations is greatly reduced compared with that arranged by comprehensive regression analysis. The surrogate models show acceptable results for predicating biomechanical indexes, whose relative deviation is less than 9%. Moreover, the results obtained by the surrogate models suggest that working length and thickness of the plate are the significant parameters on the maximum plate stress and maximum intra-fragmentary movement respectively, which complies with previous studies. The regression orthogonal method presented in this study can greatly reduce the number of experimental runs for investigating the biomechanics of internal fixation for femoral shaft fracture. The method can also be applied to other scenarios of fractures or even the other biomedical fields to provide a comprehensive insight into biomedical relationships with least number of trials.

Characterizing interactions of proteins is pivotal for understanding their function. Recently, single-molecule imaging-based methods have proven useful for directly testing the stoichiometry of multi-subunit protein complexes. A limiting factor is the labeling of proteins with multiple spectrally discernible tags and low background. Here, we describe the use of zinc-finger (ZF)-mediated protein labeling for single-molecule imaging studies in living cells. A DNA-binding ZF is fused to the protein of interest and labeled by a DNA probe carrying the specific ZF binding sequence and an organic dye. Nonspecific binding is minimized by injecting the DNA/dye conjugate into the cell. With a reproducible labeling efficiency of 20%, we developed an approach to deduce the multiplicity of the subunits in a protein complex from the overall degree of labeling. We were able to confirm the fixed 2:2 assembly of the NMDA receptor in a three-color single-molecule imaging setup and reject alternative stoichiometries. Due to the modular design and small size of ZF proteins, this approach will allow the analysis of more complicated protein interaction patterns to understand the assembly rules for large protein complexes.

It has been widely recognized that the pH environment influences the nanobubble dynamics and hydroxide ions adsorbed on the surface may be responsible for the long-term survival of the nanobubbles. However, understanding the distribution of hydronium and hydroxide ions in the vicinity of a bulk nanobubble surface at a microscopic scale and the consequent impact of these ions on the nanobubble behavior remains a challenging endeavor. In this study, we carried out deep potential molecular dynamics simulations to explore the behavior of a nitrogen nanobubble under neutral, acidic, and alkaline conditions and the inherent mechanism, and we also conducted a theoretical thermodynamic and dynamic analysis to address constraints related to simulation duration. Our simulations and theoretical analyses demonstrate a trend of nanobubble dissolution similar to that observed experimentally, emphasizing the limited dissolution of bulk nanobubbles in alkaline conditions, where hydroxide ions tend to reside slightly farther from the nanobubble surface than hydronium ions, forming more stable hydrogen bond networks that shield the nanobubble from dissolution. In acidic conditions, the hydronium ions preferentially accumulating at the nanobubble surface in an orderly manner drive nanobubble dissolution to increase the entropy of the system, and the dissolved nitrogen molecules further strengthen the hydrogen bond networks of systems by providing a hydrophobic environment for hydronium ions, suggesting both entropy and enthalpy effects contribute to the instability of nanobubbles under acidic conditions. These results offer fresh insights into the double-layer distribution of hydroxide and hydronium near the nitrogen–water interface that influences the dynamic behavior of bulk nanobubbles.

Articular cartilage injury is a common disease in clinical medicine. Because of its special physiological structure and lack of blood, lymph, and nerves, its ability to regenerate once damaged is very limited. In this study, we designed and synthesized a series of self- and coassembled cartilage-inducing functional peptide molecules and constructed a coassembled functional peptide hydrogel based on phenylboronic acid-o-dihydroxy “click chemistry” cross-linking to promote aggregation and signal transduction of mesenchymal stem cells (MSCs) in the early stage and differentiation toward cartilage, thereby promoting the repair of cartilage damage. Three functional peptide molecules were produced using solid-phase peptide synthesis technology, yielding a purity higher than 95%. DOPA-FEFEFEFEGHSNGLPL (DFP) and PBA-FKFKFKFKGHAVDI (BFP) were coassembled at near-neutral pH to form hydrogels (C Gels) based on phenylboronic acid-o-dihydroxy click chemistry cross-linking and effectively loaded transforming growth factor (TGF)-β1 with a release period of up to 2 weeks. Furthermore, chondrocytes and bone marrow mesenchymal stem cells (BMSCs) were cocultured with functional peptide hydrogels, and the results displayed that the coassembled functional peptide hydrogel group C Gels significantly promoted the proliferation of chondrocytes and MSCs. The chondrocyte markers collagen type I, collagen type II, and glycosaminoglycan (GAG) in the coassembled functional peptide hydrogel group were significantly higher than those in the control group, indicating that it can induce the differentiation of MSCs into cartilage. In vivoexperiments demonstrated that the size and thickness of the new cartilage in the compound gel group were the most beneficial to cartilage regeneration. These results indicated that peptide hydrogels are a promising therapeutic option for cartilage regeneration.

Two-dimensional (2D) materials with competing polymorphs offer remarkable potential to switch the associated 2D functionalities for novel device applications. Probing their phase transition and competition mechanisms requires nanoscale characterization techniques that can sensitively detect the nucleation of secondary phases down to single-layer thickness. Here we demonstrate nanoscale phase identification on 2D In2Se3polymorphs, utilizing their distinct plasmon energies that can be distinguished by electron energy-loss spectroscopy (EELS). The characteristic plasmon energies of In2Se3polymorphs have been validated by first-principles calculations, and also been successfully applied to reveal phase transitions using in situ EELS. Correlating with in situ X-ray diffraction, we further derive a subtle difference in the valence electron density of In2Se3polymorphs, consistent with their disparate electronic properties. The nanometer resolution and independence of orientation make plasmon-energy mapping a versatile technique for nanoscale phase identification on 2D materials.

The concentrated benthic suspension (CBS) of mud, as a major contributor of sediment transport in the turbidity maximum of the estuary, is of great challenge to be correctly monitored through field measurements, and its formation mechanism is not well understood. A tripod system equipped with multiple instruments was deployed to measure the near‐bed hydrodynamics and sediments in the North Passage of the Changjiang Estuary, with the aim at determining the formation mechanisms of CBS. The measurements detected a significant dominance of high sediment concentration in the near‐bed 1‐m layer: ~20 g/L at the southern site and ~47 g/L at the northern site. Strong CBS occurred under weak tidal mixing condition and was directly relevant to the sediment‐induced suppression of turbulent kinetic energy and the enhanced water stratification due to saltwater intrusion and sediment suspension. During the weak‐mixing neap period, the typical thickness of CBS was about 0.2–0.3 m, with a life time of ~2.83 hr (suspended‐sediment concentration > 15.0 g/L). Enhanced water stratification reduced vertical mixing and confined the sediment entrainment from the near‐bed layer to the upper column. This enhancement was due to the suppression of turbulent kinetic energy as a result of the sediment accumulation in the near‐bottom column during the slack waterand also due to the appearance of a two‐layer salinity structure in the vertical as a result of saltwater intrusion near the bottom. These physical processes worked as a positive feedback loop during the formation of CBS and can be simulated with a process‐oriented, one‐dimensional vertical CBS model. In the turbidity maximum, concentrated benthic suspension (CBS) frequently dominates the near‐bed sediment transport, which, however, is difficult to be correctly observed, especially in the stratified condition. And the formation mechanism of CBS is complex due to the interaction of sediment and hydrodynamics. In a stratified tide channel of the Changjiang Estuary, China, a comprehensive tripod system, integrated with many cutting‐edge instruments, is developed and deployed to measure the CBS and to determine the formation process. This system detected the existence of CBS in the lower near‐bed 1‐m layer, ~20 g/L at the southern site and ~47 g/L at the northern site, with the mean thickness of 20–30 cm. The corresponding salinity, tidal velocities, wave, and turbulent kinetic energy were also recorded. During the formation of CBS, tidal mixing is weak. And the salinity/sediment‐induced stratification greatly limits the vertical mixing and suppresses the turbulent kinetic energy production. The saltwater intrusion creates a two‐layer structure of salinity, leading to stratification and decreasing the mixing. These physical effects work like a positive feedback loop. A one‐dimensional vertical model had been developed to successfully simulate the formation process of CBS, indicating the stable CBS during weak‐tidal‐mixing neap cycle. Concentrated benthic suspension (CBS) of mud in the turbidity maximum zone was observed by a comprehensive near‐bed tripod systemThe dynamics for the formation of CBS are determinedA one‐dimensional vertical model is developed to analyze the physical mechanisms responsible for the formation of CBS

Lake Pontchartrain is a brackish estuary and restricted lagoon in the microtidal northern Gulf of Mexico. Using a validated Finite Volume Community Ocean Model (FVCOM), we study the flow regimes and wind‐driven adjustment of circulation in this system. It is found that tidal currents are only significant in the eastern end near the open boundary. Local wind inside the estuary is important in driving the circulation including coastal currents. Numerical experiments confirm that the subtidal wind‐driven flow is in a quasi‐steady balance between wind stress and surface slope. Our results show that the adjustment of surface level inside the system to a sudden change in wind is a transient seiche, which dissipates within two to three cycles, each lasting ~3 hr. After the oscillations, the system reaches a new equilibrium. We show in theory that this is a damped oscillation and as wind changes, an adjustment to a new equilibrium goes much faster than a complete tidal period. This leads to the quasi steady state balance of subtidal wind‐driven flows with essentially no phase lag with wind even though wind changes with time continuously. Wind‐induced circulation behaves differently from the Csanady model with Earth rotation but similar to the prismatic lake model of Engelund without Coriolis: The coastal and shallow regions tend to have flows in the direction of wind, while the interior and deeper waters have return flows against the wind especially in bottom layer. The surface flow may not be in the direction of wind, while the bottom usually has broad and uniform counter wind flows. In a choked or restricted shallow lagoon, wind‐driven flows are confirmed to be a surprising quasi steady state. Numerical experiments show that any change in wind would produce a hydrodynamic perturbation in the form of seiche that dissipates quickly in two to three cycles, leading to a fast return to a new equilibrium or quasi steady state. This warrants examination of wind‐driven flows at constant speed for different scenarios (wind from different directions) and not to worry too much about the temporal variation of wind or history of wind. Earth rotation in such system is found to be negligible for wind‐driven circulations: The experiment shows that the relative error is only 0.3% if Coriolis force is turned off for Lake Pontchartrain. Seiche generated by wind is dissipated in two to three cycles, adjusting the system to a new balance, leading to a quasi steady stateSubtidal cross bay slopes are determined by local wind, generating strong coastal currents; neglecting rotation only produces 0.3% errorBottom flows are counterwind, broad, and uniform; Engelund model is applicable for circulation

The search of quantum spin liquid (QSL), an exotic magnetic state with strongly fluctuating and highly entangled spins down to zero temperature, is a main theme in current condensed matter physics. However, there is no smoking gun evidence for deconfined spinons in any QSL candidate so far. The disorders and competing exchange interactions may prevent the formation of an ideal QSL state on frustrated spin lattices. Here we report comprehensive and systematic measurements of the magnetic susceptibility, ultralow-temperature specific heat, muon spin relaxation (μSR), nuclear magnetic resonance (NMR), and thermal conductivity for NaYbSe2single crystals, in which Yb3+ions with effective spin-1/2 form a perfect triangular lattice. All these complementary techniques find no evidence of long-range magnetic order down to their respective base temperatures. Instead, specific heat, μSR, and NMR measurements suggest the coexistence of quasi-static and dynamic spins in NaYbSe2. The scattering from these quasi-static spins may cause the absence of magnetic thermal conductivity. Thus, we propose a scenario of fluctuating ferrimagnetic droplets immersed in a sea of QSL. This may be quite common on the way pursuing an ideal QSL, and provides a brand new platform to study how a QSL state survives impurities and coexists with other magnetically ordered states.

Three state‐of‐the‐art operational wave forecast model systemsare implemented on fine‐resolution grids for the Northwest Atlantic. These models are: (1) a composite model system consisting of SWAN implemented within WAVEWATCHIII®(the latter is hereafter, WW3) on a nested system of traditional structured grids, (2) an unstructured grid finite‐volume wave model denoted “SWAVE,” using SWAN physics, and (3) an unstructured grid finite element wind wave model denoted as “WWM” (for “wind wave model”) which uses WW3 physics. Models are implemented on grid systems that include relatively large domains to capture the wave energy generated by the storms, as well as including fine‐resolution nearshore regions of the southern Gulf of Maine with resolution on the scale of 25 m to simulate areas where inundation and coastal damage have occurred, due to the storms. Storm cases include three intense midlatitude cases: a spring Nor'easter storm in May 2005, the Patriot's Day storm in 2007, and the Boxing Day storm in 2010. Although these wave model systems have comparable overall properties in terms of their performance and skill, it is found that there are differences. Models that use more advanced physics, as presented in recent versions of WW3, tuned to regional characteristics, as in the Gulf of Maine and the Northwest Atlantic, can give enhanced results. Three modern wave forecast model systems are compared on fine‐resolution grids for the Northwest Atlantic: WAVEWATCHIII (WW3), SWAN, SWAVEThree intense midlatitude storm cases: a spring Nor'easter in May 2005, the Patriots Day storm in 2007, and the Boxing Day storm in 2010Models that use advanced physics, like ST4, tuned to regional characteristics for the Northwest Atlantic can give enhanced results

The non-hydrostatic wave equation set in Cartesian coordinates is rearranged to gain insight into wave generation in a mesoscale severe convection system. The wave equation is characterized by a wave operator on the lhs, and forcing involving three terms—linear and nonlinear terms, and diabatic heating—on the rhs. The equation was applied to a case of severe convection that occurred in East China. The calculation with simulation data showed that the diabatic forcing and linear and nonlinear forcing presented large magnitude at different altitudes in the severe convection region. Further analysis revealed the diabatic forcing due to condensational latent heating had an important influence on the generation of gravity waves in the middle and lower levels. The linear forcing resulting from the Laplacian of potential-temperature linear forcing was dominant in the middle and upper levels. The nonlinear forcing was determined by the Laplacian of potential-temperature nonlinear forcing. Therefore, the forcing of gravity waves was closely associated with the thermodynamic processes in the severe convection case. The reason may be that, besides the vertical component of pressure gradient force, the vertical oscillation of atmospheric particles was dominated by the buoyancy for inertial gravity waves. The latent heating and potential-temperature linear and nonlinear forcing played an important role in the buoyancy tendency. Consequently, these thermodynamic elements influenced the evolution of inertial-gravity waves.

A high‐resolution (up to 2 km), unstructured‐grid, fully ice‐sea coupled Arctic Ocean Finite‐Volume Community Ocean Model (AO‐FVCOM) was used to simulate the sea ice in the Arctic over the period 1978–2014. The spatial‐varying horizontal model resolution was designed to better resolve both topographic and baroclinic dynamics scales over the Arctic slope and narrow straits. The model‐simulated sea ice was in good agreement with available observed sea ice extent, concentration, drift velocity and thickness, not only in seasonal and interannual variability but also in spatial distribution. Compared with six other Arctic Ocean models (ECCO2, GSFC, INMOM, ORCA, NAME, and UW), the AO‐FVCOM‐simulated ice thickness showed a higher mean correlation coefficient of ∼0.63 and a smaller residual with observations. Model‐produced ice drift speed and direction errors varied with wind speed: the speed and direction errors increased and decreased as the wind speed increased, respectively. Efforts were made to examine the influences of parameterizations of air‐ice external and ice‐water interfacial stresses on the model‐produced bias. The ice drift direction was more sensitive to air‐ice drag coefficients and turning angles than the ice drift speed. Increasing or decreasing either 10% in water‐ice drag coefficient or 10° in water‐ice turning angle did not show a significant influence on the ice drift velocity simulation results although the sea ice drift speed was more sensitive to these two parameters than the sea ice drift direction. Using the COARE 4.0‐derived parameterization of air‐water drag coefficient for wind stress did not significantly influence the ice drift velocity simulation. The 37 year simulated sea ice was in good agreement with available observed sea ice extent, concentration, drift velocity, and thicknessIntermodel comparisons show that the high‐resolution AO‐FVCOM provided better performance in the ice thickness simulationSensitivity experiments were made to examine parameterizations of external and ice‐water interfacial stresses on model‐produced bias.

The rapid economic developments in countries surrounding the South China Sea have caused a significant increase in the atmospheric deposition of nitrogen (AD‐N) into the ocean. The impact of AD‐N on the regional ecosystem has not been quantitatively assessed, and its driving mechanism has not been explored, either. Here, we applied a one‐dimensional European Regional Seas Ecosystem Model to examine the responses of the ecosystem to AD‐N. The physical‐biological coupled model reproduced the seasonal and interannual variabilities of observed nutrients, chlorophyll a, phytoplankton community structure, and particulate organic carbon (POC) exports at the South East Asia Time‐series Station. Seasonally, the increase of POC flux by AD‐N was most significant in winter, with a ∼2‐month lag behind the associated surface response. It can exist in the following spring, as supported by the larger population size of zooplankton after the previous winter's feeding up. Notably, the ratio of POC export to primary production varied seasonally and interannually, which was controlled by the phytoplankton and zooplankton's size compositions. The surface nutrient input thus caused a significant seasonal change in the biological carbon pump efficiency. Interannually, the modulation of the POC flux by AD‐N was inversely phase‐locked with wind variations. The out‐of‐phase of the surface‐ and subsurface‐nutrient‐driven POC fluxes suggested a potentially more considerable contribution of AD‐N to the total carbon export during years under the weak subsurface influence. This study highlights the importance of AD‐N in the regional ecosystem, which needs a better representation in the present biogeochemical modeling framework. The atmospheric deposition of nitrogen (AD‐N) to the ocean, by human fertilizer usage and fossil fuel combustion, has significantly impacted the offshore marine ecosystem. The northern South China Sea (NSCS) is a hot spot of such influence because it is surrounded by countries with rapid economic development and gigantic emissions. The added nutrients from the terrestrial sources then can be rapidly assimilated into the primary production since the surface water of the NSCS is seasonally nutrient‐depleted. Numerical simulations were conducted to gain insights into the influence of AD‐N on the seasonal change in biogeochemistry and the consequence of carbon export. The results showed that the AD‐N could lead to a more substantial growth response in the portion of the tiniest picophytoplankton group and a subsequent increase in carbon export. The influence has a persistent impact on the ecosystem until the following spring and causes a decrease in the biological carbon pump's efficiency in autumn. Interannually, the AD‐N could contribute more to the export carbon flux during weaker wind and lower nutrient concentration conditions. Our findings highlight the vital roles of AD‐N in the food web system, which were not systematically quantified previously and should be represented in future modeling frameworks. A new physical‐biological coupled model with atmospheric deposition of nitrogen (AD‐N) was establishedThe carbon export efficiency varied with phytoplankton size structure, and the variation could be up to 30%Impacts of the AD‐N on the particulate organic carbon flux were more significant during weak wind conditions A new physical‐biological coupled model with atmospheric deposition of nitrogen (AD‐N) was established The carbon export efficiency varied with phytoplankton size structure, and the variation could be up to 30% Impacts of the AD‐N on the particulate organic carbon flux were more significant during weak wind conditions

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Through employing molecular dynamics, in this work, we study how a two-component surfactant mixture cooperatively reduces the interfacial tension of a flat vapor–liquid interface. Our simulation results show that in the presence of a given insoluble surfactant, adding a secondary surfactant would either further reduce interfacial tension, indicating a positive synergistic effect, or increase the interfacial tension instead, indicating a negative synergistic effect. The synergism of the surfactant mixture in lowering surface tension is found to depend strongly on the structure complementary effect between different surfactant components. The synergistic mechanisms are then interpreted with minimization of the bending free energy of the composite surfactant monolayer via cooperatively changing the monolayer spontaneous curvature. By roughly describing the monolayer spontaneous curvature with the balanced distribution of surfactant heads and tails, we confirm that the positive synergistic effect in lowering surface tension is featured with the increasingly symmetric head–tail distributions, while the negative synergistic effect is featured with the increasingly asymmetric head–tail distributions. Furthermore, our simulation results indicate that minimal interfacial tension can only be observed when the spontaneous curvature is nearly zero.

Saltwater intrusion is a common feature in the Changjiang Estuary affected by river discharges and tidal flows. It leads to a two‐layer flow structure during the flood‐to‐ebb tidal transient period: the seaward tidal flow in the upper water column and onshore intruded salt flow in the lower column, even though the lower column water usually experiences an ebb flow eventually. Our recent measurements with a tripod deployed in a tidal channel of the North Branch in the East China Sea challenged this feature. We detected that the two‐layer flow structure disappeared in the ebb tide period during the neap cycle due to intense saltwater intrusion. A constant onshore flood‐like flow predominated the entire water column. The physical mechanism for the flow reversal was examined using the Finite Volume Community Ocean Model (FVCOM). The FVCOM was robust to capture the observed flow reversal in the tidal channel during the neap tidal cycle. The momentum balance analysis results suggest that the flow reversal occurred when the saltwater intrusion‐induced onshore baroclinic pressure gradient force and baroclinic tidal rectification overwhelmed the seaward barotropic pressure gradient force. A parameter‐driven criterion was derived theoretically to determine the potential occurrence of a stable ebb flow reversal in the tidal channel. Many estuaries experience saltwater intrusion, bringing saltwater from offshore regions to nearshore and river channels. In the Changjiang Estuary, it could create a two‐layer flow structure during the flood‐to‐ebb transient period, a seaward fresher ebb tidal flow in the upper water column, and an onshore intruded salt flow in the lower water column. Could the increased saltwater intrusion destroy this two‐layer flow structure and form an onshore flow throughout the water column in the ebb‐tidal period during a neap tidal cycle? If it does, what is the critical driving mechanism? To answer these questions, we deployed a tripod system integrated with state‐of‐the‐art marine instruments in a tidal channel of North Branch in the Changjiang Estuary, an area where saltwater intrusion frequently occurs. The observational data captured a flow‐overtured feature, showing a stable flood‐like intruded flow throughout the entire water column in the ebb‐tidal period during a neap tidal cycle. We applied the Finite‐Volume Community Ocean Model to examine the physical driving mechanism for flow‐overturning. The results suggest that the flow‐overturning could occur when the along‐channel saltwater intrusion‐induced baroclinic pressure gradient force and stratified tidal rectification overwhelmed the along‐channel tide‐induced barotropic pressure gradient force. The bottom tripod system identified an overturned tidal flow in the North Branch channelA numerical model revealed the baroclinic gradient force from saltwater intrusion dominated the overturnThe balance criteria were proposed to estimate competition between these two dynamics The bottom tripod system identified an overturned tidal flow in the North Branch channel A numerical model revealed the baroclinic gradient force from saltwater intrusion dominated the overturn The balance criteria were proposed to estimate competition between these two dynamics

Supplemental Digital Content is available in the text.Raltitrexed has shown efficacy and safety in many tumor types; however, the clinical data on the treatment of hepatocellular carcinoma is rare. In this report, we aim to assess the efficacy and safety of raltitrexed plus oxaliplatin (OXA)-based transarterial chemoembolization (TACE) in patients with unresectable hepatocellular carcinoma (uHCC). Patients with uHCC were recruited from multi-centers in China and assigned randomly to raltitrexed+OXA-based (n=76), fluorouracil+OXA-based (n=76), and doxorubicin+OXA-based (n=75) TACE treatment. The primary end point was overall survival (OS). Tumor response was assessed using response evaluation criteria in solid tumors (RECIST), modified response evaluation criteria in solid tumors (mRECIST), and European Association for the Study of the Liver criteria (EASL). Safety and toxicity were evaluated using the National Cancer Institute Common Toxicity Criteria. The raltitrexed group showed a better disease control rate evaluated using RECIST (raltitrexed vs. fluorouracil vs. doxorubicin: 96.1 vs. 84.2 vs. 86.7%, P=0.05) and a better overall response rate on the basis of mRECIST (67.1 vs. 47.4 vs. 50.7%, P=0.03) and EASL (67.1 vs. 47.4 vs. 49.3%, P=0.02). The median OS and median progression-free survival (PFS) were higher in the raltitrexed group (median OS: 13.4 vs. 9.6 vs. 8.5 months; median PFS: 6.7 vs 4.9 vs 4.6 months). The most common toxicities included elevated aspartate aminotransferase (78.9 vs. 86.8 vs. 81.3%) and abdominal nonspecific pain (68.4 vs. 81.6 vs. 78.7%). No significant differences were found in the overall number of patients who experienced any toxicity. Raltitrexed plus OXA-based TACE suggested a safe and efficacious regimen in uHCC patients. The results warrant further clinical investigation.

A high‐resolution (up to 2 km), unstructured‐grid, fully coupled Arctic sea ice‐ocean Finite‐Volume Community Ocean Model (AO‐FVCOM) was employed to simulate the flow and transport through the Canadian Arctic Archipelago (CAA) over the period 1978–2013. The model‐simulated CAA outflow flux was in reasonable agreement with the flux estimated based on measurements across Davis Strait, Nares Strait, Lancaster Sound, and Jones Sounds. The model was capable of reproducing the observed interannual variability in Davis Strait and Lancaster Sound. The simulated CAA outflow transport was highly correlated with the along‐strait and cross‐strait sea surface height (SSH) difference. Compared with the wind forcing, the sea level pressure (SLP) played a dominant role in establishing the SSH difference and the correlation of the CAA outflow with the cross‐strait SSH difference can be explained by a simple geostrophic balance. The change in the simulated CAA outflow transport through Davis Strait showed a negative correlation with the net flux through Fram Strait. This correlation was related to the variation of the spatial distribution and intensity of the slope current over the Beaufort Sea and Greenland shelves. The different basin‐scale surface forcings can increase the model uncertainty in the CAA outflow flux up to 15%. The daily adjustment of the model elevation to the satellite‐derived SSH in the North Atlantic region outside Fram Strait could produce a larger North Atlantic inflow through west Svalbard and weaken the outflow from the Arctic Ocean through east Greenland. A high‐resolution Arctic Ocean FVCOM is capable of simulating the CAA outflowThe basin‐scale sea level pressure is a major driver of the CAA outflowThe volume flux through Davis Strait is negatively correlated with the flux through Fram Strait

The estuarine plume dynamics under a downwelling‐favorable wind condition were examined in the windy dry season of the Pearl River Estuary (PRE) using the PRE primitive‐equation Finite‐Volume Community Ocean Model (FVCOM). The wind and tide‐driven estuarine circulation had a significant influence on the plume dynamics on both local and remote scales. Specifically, the local effect of downwelling‐favorable winds on the plume was similar to the theoretical descriptions of coastal plumes, narrowing the plume width, and setting up a vertically uniform downstream current at the plume edge. Tides tended to reduce these plume responses through local turbulent mixing and advection from upstream regions, resulting in an adjustment of the isohalines in the plume and a weakening of the vertically uniform downstream current. The remote effect of downwelling‐favorable winds on the plume was due to the wind‐induced estuarine sea surface height (SSH), which strengthened the estuarine circulation and enhanced the plume transport accordingly. Associated with these processes, tide‐induced mixing tended to weaken the SSH gradient and thus the estuarine circulation over a remote influence scale. Overall, the typical features of downwelling‐favorable wind‐driven estuarine plumes revealed in this study enhanced our understanding of the estuarine plume dynamics under downwelling‐favorable wind conditions. Wind and tide interactions are a dominant dynamics controlling the Pearl River plumes in the dry seasonWinds and tides can influence the plume dynamics both locally and remotelyThe wind‐induced estuarine SSH is an indicator for the remote controlling mechanism of the plume dynamics

Simulating the sediment transport in a high‐turbidity region with spatially varying bed properties is challenging. A comprehensive strategy that integrates multiple methods is applied here to retrieve the critical shear stress for erosion, which plays a major role in suspended sediment dynamics in the Changjiang Estuary (CE). Time‐series of sea surface suspended sediment concentration (SSC) were retrieved from the Geostationary Ocean Color Imager (GOCI) satellite data at hourly intervals (for 8 heach day) and combined with hydrodynamic modeling of high‐resolution CE Finite‐Volume Community Ocean Model (CE‐FVCOM) to estimate the near‐bed critical shear stress in the clay‐dominated bed region (plasticity index > 7%). An experimental algorithm to determine the in situ critical shear stress via the plasticity index method was also used to verify the GOCI‐derived critical shear stress. Implemented with this new critical shear stress, the sediment transport model significantly improved the simulation of the distribution and spatial variability of the SSC during the spring and neap tidal cycles in the CE. The results suggest that a significant lateral water exchange between channels and shoals occurred during the spring flood tide, which led to a broader high‐SSC area in the CE throughout the water column. GOCI images are used to retrieve critical shear stress for erosion with observation and modelingThe retrieved result is validated with soil mechanics of field survey dataGOCI‐retrieved results provides better simulation than uniform critical shear stress

Surface drifters released in the central Red Sea during April 2010 detected a well‐defined anticyclonic eddy around 23°N. This eddy was ∼45–60 km in radius, with a swirl speed up to ∼0.5 m/s. The eddy feature was also evident in monthly averaged sea surface height fields and in current profiles measured on a cross‐isobath, shipboard CTD/ADCP survey around that region. The unstructured‐grid, Finite‐Volume Community Ocean Model (FVCOM) was configured for the Red Sea and process studies were conducted to establish the conditions necessary for the eddy to form and to establish its robustness. The model was capable of reproducing the observed anticyclonic eddy with the same location and size. Diagnosis of model results suggests that the eddy can be formed in a Red Sea that is subject to seasonally varying buoyancy forcing, with no wind, but that its location and structure are significantly altered by wind forcing, initial distribution of water stratification and southward coastal flow from the upstream area. Momentum analysis indicates that the flow field of the eddy was in geostrophic balance, with the baroclinic pressure gradient forcing about the same order of magnitude as the surface pressure gradient forcing. Surface drifters detected an anticyclonic eddy in the central Red SeaThe model successfully reproduced the observed eddyThe eddy formed as geostrophic adjustment to seasonal buoyancy forcing

It is necessary for power systems to provide flexible power to balance the fluctuation and intermittency of wind power. For the large-scale and central-integrated wind generation (such as that in China), the required flexible power may be very significant and expensive. In market environment, it is important to design a proper market mechanism and price signal which can promote conventional power and load demand to integrate wind power and gain corresponding profit. Firstly, the paper analyzes the current economy and dispatch policy for wind power in China. Then, a Block Bidding mode for wind power is presented. Unlike Timely Bidding mode that power is auctioned hourly by hourly, for Block Bidding the wind power energy is divided into different energy block. And these blocks are auctioned by conventional power resources and load demands. The Block Bidding mode has some advantages: 1) subdivides wind power by energy quality, and then the value of different parts can be revealed; 2) provides incentive for conventional power resource and load demand to integrate wind power; 3) is convenient for trading and dispatching wind power. Finally, a simple numerical case is given to illustrate the validity of Block Bidding mode.

Moored current measurements were made at one mooring site in the northern Gulf of Tonkin for about 1 year during 1988–1989. Analyses were performed to examine characteristics and variability of tidal and subtidal flows. Rotary spectra showed two peaks at diurnal and semidiurnal periods, with higher diurnal energy. Complex demodulations of diurnal and semidiurnal tidal currents indicated that the tidal current magnitudes varied significantly with seasons: more energetic in the stratified summer than in the vertically well‐mixed winter. The observed subtidal currents were highly correlated with the surface wind in winter but not in summer; challenging the conceptual summertime anticyclonic circulation pattern derived using wind‐driven homogenous circulation theory. The computed currents from a global ocean model were in good agreement with the observed currents. Similar to the current observations, the model‐computed flow patterns were consistent with the conceptual wind‐driven circulation pattern in winter but opposite in summer. Process‐oriented experiments suggest that the summertime cyclonic circulation in the northern Gulf of Tonkin forms as a result of the combination of stratified wind‐driven circulation and tidal‐rectified inflow from Qiongzhou Strait. The interaction between the southwest monsoon and buoyancy‐driven flow from Hong River can significantly intensify the cyclonic circulation near the surface, but its contribution to the vertically averaged flow of the cyclonic circulation is limited. First long‐term moored current measurements in the northern Gulf of TonkinObservations and model results suggest that summertime circulation is cyclonicCyclonic circulation due to stratified response to winds and tidal rectification

The Integrated Ocean Observing System Super‐regional Coastal Modeling Testbed had one objective to evaluate the capabilities of three unstructured‐grid fully current‐wave coupled ocean models (ADCIRC/SWAN, FVCOM/SWAVE, SELFE/WWM) to simulate extratropical storm‐induced inundation in the US northeast coastal region. Scituate Harbor (MA) was chosen as the extratropical storm testbed site, and model simulations were made for the 24–27 May 2005 and 17–20 April 2007 (“Patriot's Day Storm”) nor'easters. For the same unstructured mesh, meteorological forcing, and initial/boundary conditions, intermodel comparisons were made for tidal elevation, surface waves, sea surface elevation, coastal inundation, currents, and volume transport. All three models showed similar accuracy in tidal simulation and consistency in dynamic responses to storm winds in experiments conducted without and with wave‐current interaction. The three models also showed that wave‐current interaction could (1) change the current direction from the along‐shelf direction to the onshore direction over the northern shelf, enlarging the onshore water transport and (2) intensify an anticyclonic eddy in the harbor entrance and a cyclonic eddy in the harbor interior, which could increase the water transport toward the northern peninsula and the southern end and thus enhance flooding in those areas. The testbed intermodel comparisons suggest that major differences in the performance of the three models were caused primarily by (1) the inclusion of wave‐current interaction, due to the different discrete algorithms used to solve the three wave models and compute water‐current interaction, (2) the criterions used for the wet‐dry point treatment of the flooding/drying process simulation, and (3) bottom friction parameterizations. Evaluation of ADCIRC, FVCOM, SELFE for nor'easter coastal inundationWave‐current interaction important in forecasting nor'easter coastal inundation.Model performances depend on methods of current‐wave coupling

Abstract: Vibrio fluvialis incubated in trypticase soy broth (TSB) showed stronger adhesion to the skin mucus of Epinephelus awoara than V. fluvialis grown on trypticase soy agar (TSA), and this bacterial adhesion was assessed in terms of saturation kinetics. Treating bacteria with antibody against O-antigens resulted in significantly reduced bacterial adhesion. In the early growth stage, the adhering bacteria numbers increased with incubation time, peaked at 24 h, and then dropped sharply. Prior heat treatment of the mucus at various temperatures resulted in different effects on bacterial adhesion. No remarkable effect on bacterial adhesion was detected after treating mucus with protease K and trypsin, whereas periodic acid treatment significantly enhanced bacterial adhesion. Extracts of V. fluvialis surface structures at high concentrations significantly inhibited bacterial adhesion, while relatively low concentrations enhanced adhesion. V. fluvialis had strong affinity for a high molecular weight mucus component. These results indicate that V. fluvialis adhered strongly to E. awoara mucus by specific adhesion and that this adhesion was influenced by many factors, including bacterial conditions, mucus, and the environment.

Abstract: Many studies have shown that there is a relationship between gonadotropin-releasing hormone (GnRH) and glucose metabolism, but little is known about the effects of GnRH on the pancreas. Our experiment investigated the effect of GnRH on pancreatic islet cell in Sprague–Dawley (SD) rats fed with high-cholesterol diet before and during pregnancy. We found that although high-cholesterol diet led to no significant difference of GnRH mRNA levels in pancreas in nonpregnant rats, it led to a marked increase of those in pregnant rats. Furthermore, in rats fed with standard laboratory chow, no significant differences were apparent in GnRH mRNA levels before and during gestation; however, when fed with high-cholesterol diet, the GnRH mRNA levels increased significantly in pregnant rats. As results indicated both diets could lead to increase of PG mRNA in pancreas of pregnant rats. It is also demonstrated that the GnRH mRNA levels are positively associated with PG mRNA levels. Moreover, our data showed a significant increase in fasting insulin level in the Gestation group compared with Control. Such changes were contrary to the changes of GnRH level in the pancreas. This may imply that GnRH influences hormones secretion in the pancreas by autocrine and paracrine effects on islet cells.

For a system that may have multi-frequency oscillations, this paper divided its dynamics into the dynamics between clusters and the dynamics within clusters. And this deviation method can be used for the subsystems with poor coherence. Based on EEAC and transient energy methods, this paper found that under multi-frequency oscillations circumstances, generally, there will be a critical splitting time for its critical instability mode. When the moment of implementation of splitting is greater than the critical splitting time, the sub-systems after splitting are likely to occur successively instability. However, if the splitting control can be taken before the critical splitting time, the subsystems will have a large chance to be stable.

Abstract: A three-dimensional (3-D) suspended sediment model was coupled with a 3-D hydrodynamic numerical model and used to examine the spatial and temporal distribution of suspended sediments in the Satilla River estuary of Georgia. The hydrodynamic model was a modified ECOM-si model with inclusion of the flooding-drying cycle over intertidal salt marshes. The suspended sediment model consisted of a simple passive tracer equation with inclusion of sinking, resuspension, and sedimentation processes. The coupled model was driven by tidal forcing at the open boundary over the inner shelf of the South Atlantic Bight and real-time river discharge at the upstream end of the estuary, with a uniform initial distribution of total suspended sediment (TSS). The initial conditions for salinity were specified using observations taken along the estuary. The coupled model provided a reasonable simulation of both the spatial and temporal distributions of observed TSS concentration. Model-predicted TSS concentrations varied over a tidal cycle; they were highest at maximum flood and ebb tidal phases and lowest at slack tides. Model-guided process studies suggest that the spatial distribution of TSS concentration in the Satilla River estuary is controlled by a complex nonlinear physical process associated with the convergence and divergence of residual flow, a non-uniform along-estuary distribution of bottom stress, and the inertial effects of a curved shoreline.

Abstract: The flooding-drying process over the intertidal zone of the Satilla River estuary of Georgia was examined using a three-dimensional (3-D) primitive equations numerical model with Mellor and Yamada's (1982) level 2.5 turbulent closure scheme. The model was forced by the semi-diurnal M2, S2, and N2 tides and freshwater discharge at the upstream end of the estuary. The intertidal salt marsh was treated using a 3-D wet-dry point treatment technique that was developed for the σ-coordinate transformation estuary model. Good agreement was found between model-data comparison at anchor monitoring sites and also along the estuary that suggested that the model provided a reasonable simulation of the temporal and spatial distribution of the 3-D tidal current and salinity in the Satilla River estuary. Numerical experiments have shown that the flooding-drying process plays a key role in the simulation of tidal currents in the main river channel and in water transport over the estuarine-salt marsh complex. Ignoring this process could lead to a 50% under-estimation of the amplitude of tidal currents. The model results also revealed a complex spatial structure of the residual flow in the main channel of the river, with characteristics of multiple eddy-like cell circulations. These complicated residual currents are formed due to tidal rectification over variable topography with superimposition of inertial effects, asymmetry of tidal currents, and baroclinic pressure gradients. Water exchanges over the estuary-intertidal salt marsh complex are asymmetric across the estuary, and tend to vary periodically on the northern side while quickly washing out of the marsh zone on the southern side. Strong Stokes’ drifting velocity was predicted in the estuary, so that the Lagrangian trajectories of particles were characterized by strong nonlinear processes that differ significantly from those estimated by the Eulerian residual currents.

Abstract: This paper reviews recent progress on modeling cross-frontal water exchange on Georges Bank undertaken as part of the U.S. Global Ecosystem Northwest Atlantic/Georges Bank Study (U.S. GLOBEC/Georges Bank Program). A simple conceptual model is described first, followed by a discussion of four physical mechanisms associated with (1) strong nonlinear interaction, (2) asymmetric tidal mixing, (3) varying wind forcing, and (4) chaotic mixing. Some critical issues in modeling studies of fronts are also addressed. A new unstructured grid, finite-volume coastal ocean ecosystem model is introduced. This model combines the best of the finite-difference method for the simplest discrete computational efficiency and the finite-element method for geometric flexibility. Because the finite-volume method discretizes the integral form of the governing equations, this approach provides a better representation for the conservation laws of mass and momentum are satisfied, which is particularly important in the frontal regions.

Physical processes that control the episodic cross-frontal transport over the inner shelf of the South Atlantic Bight were examined using a 3D primitive turbulent closure equation model. The model results showed that significant cross-frontal water exchange occurred under upwelling-favorable wind conditions through the detachment of isolated low-salinity lenses at the outer edge of the front. The formation of isolated lenses was a 3D feature associated with complex nonlinear processes. It depended on 1) the amount of multiple river discharges, 2) direction and magnitude of the wind, and 3) tidal mixing. As the total amount of river discharges increased, stronger winds were required to form the isolated lenses. When the river discharges were larger, tidal mixing tended to delay the occurrence of isolated lenses through 1) increasing the cross-shelf gradients of density and surface elevation and thus enhancing the along-shelf current and reducing the along-shelf variation of salinity, and 2) strengthening the internal stress at the bottom edge of the plume and thus slowing down the offshore water transport. The vertical salt diffusion, along-shelf and cross-shelf salt advections played a critical role in the detachment of the low-salinity water from the front. Upwelling significantly contributed to salinity increases near the coastal region in the early wind stages and the lenses’ intensification in the midshelf. After the wind subsided, the eddylike circulation developed over the midshelf through adjustment of currents to surface elevation. The residence time of these eddies depended on the initial strength and location of isolated lenses. In the midshelf, where tidal mixing was relatively weak, these eddies could last about one week. In the inner shelf, where the depth was less than 20 m and tidal mixing was stronger, their lifetimes were less than one day.

Salt marshes are ecologically and physically essential habitats in coastal intertidal flats. In addition to providing nursery grounds for various wildlife, vegetation in marshes acts as a buffer zone that slows flooding waters. Extensive marsh platforms can also attenuate wave energy to protect coastal communities. Complex geometries make it challenging for models to capture the spatiotemporal variabilities in the transport of lateral water and sediment over tidal creek‐marsh complexes. To study water exchange processes between tidal creeks and marshes, field observations were conducted within tidal creeks in the Chongming Dongtan Shoal of the Changjiang Estuary, an area dominated by Phragmites australis, Scirpus mariqueter, and Spartina alterniflora. A coupled wave‐current‐sediment‐vegetation model that parameterized the three vegetation species was developed and applied to the tidal creek complex of Chongming Dongtan. Validated with the observational data, the modeling results were used to examine the influence of vegetation on flooding/draining processes within tidal creeks and mudflats. The model showed that vegetation not only modified the flow pattern at high tide in the high‐elevation marsh but also significantly intensified the tidal flows in tidal creeks in the low‐elevation regions. Both the observations and model detected significant transport of water and sediment from the marsh to tidal creeks, seaward sediment export over tidal cycles. The simulated salinity exhibited a considerable spatial gradient, matching well with the salt tolerances of the major vegetation types. This model can be potentially used to determine how future scenarios of hydrodynamics could affect vegetation zonation. A vegetation model was developed to simulate the impacts of multiple vegetation species on flow, turbulence, waves and sedimentThree vegetation species were parameterized in the module, which was successfully applied to the tidal creek complex of Chongming DongtanModel demonstrated seaward sediment export from creeks, and consistency between the predicted salinity and the vegetation zonation A vegetation model was developed to simulate the impacts of multiple vegetation species on flow, turbulence, waves and sediment Three vegetation species were parameterized in the module, which was successfully applied to the tidal creek complex of Chongming Dongtan Model demonstrated seaward sediment export from creeks, and consistency between the predicted salinity and the vegetation zonation