Hurricanes can greatly modify the sedimentary record, but our coastal scientific community has rather limited capability to predict hurricane-induced sediment deposition. A three-dimensional sediment ...transport model was developed in the Regional Ocean Modeling System (ROMS) to study seabed erosion and deposition on the Louisiana shelf in response to Hurricanes Katrina and Rita in the year 2005. Sensitivity tests were performed on both erosional and depositional processes for a wide range of erosional rates and settling velocities, and uncertainty analysis was done on critical shear stresses using the polynomial chaos approximation method. A total of 22 model runs were performed in sensitivity and uncertainty tests. Estimated maximum erosional depths were sensitive to the inputs, but horizontal erosional patterns seemed to be controlled mainly by hurricane tracks, wave–current combined shear stresses, seabed grain sizes, and shelf bathymetry. During the passage of two hurricanes, local resuspension and deposition dominated the sediment transport mechanisms. Hurricane Katrina followed a shelf-perpendicular track before making landfall and its energy dissipated rapidly within about 48h along the eastern Louisiana coast. In contrast, Hurricane Rita followed a more shelf-oblique track and disturbed the seabed extensively during its 84-h passage from the Alabama–Mississippi border to the Louisiana–Texas border. Conditions to either side of Hurricane Rita’s storm track differed substantially, with the region to the east having stronger winds, taller waves and thus deeper erosions. This study indicated that major hurricanes can disturb the shelf at centimeter to meter levels. Each of these two hurricanes suspended seabed sediment mass that far exceeded the annual sediment inputs from the Mississippi and Atchafalaya Rivers, but the net transport from shelves to estuaries is yet to be determined. Future studies should focus on the modeling of sediment exchange between estuaries and shelves and the field measurement of erosional rates and settling velocities.
•Erosional depths were sensitive to both erosional rates and settling velocities.•Local resuspension and deposition dominated the sediment transport mechanisms.•East of hurricane tracks has stronger winds, taller waves and deeper erosions.•Hurricanes suspended seabed sediment mass far exceeding the annual river inputs.
Methane (CH
4
) emissions from wetland ecosystems are controlled by redox conditions in the soil, which are currently underrepresented in Earth system models. Plant-mediated radial oxygen loss (ROL) ...can increase soil O
2
availability, affect local redox conditions, and cause heterogeneous distribution of redox-sensitive chemical species at the root scale, which would affect CH
4
emissions integrated over larger scales. In this study, we used a subsurface geochemical simulator (PFLOTRAN) to quantify the effects of incorporating either spatially homogeneous ROL or more complex heterogeneous ROL on model predictions of porewater solute concentration depth profiles (dissolved organic carbon, methane, sulfate, sulfide) and column integrated CH
4
fluxes for a tidal coastal wetland. From the heterogeneous ROL simulation, we obtained 18% higher column averaged CH
4
concentration at the rooting zone but 5% lower total CH
4
flux compared to simulations of the homogeneous ROL or without ROL. This difference is because lower CH
4
concentrations occurred in the same rhizosphere volume that was directly connected with plant-mediated transport of CH
4
from the rooting zone to the atmosphere. Sensitivity analysis indicated that the impacts of heterogeneous ROL on model predictions of porewater oxygen and sulfide concentrations will be more important under conditions of higher ROL fluxes or more heterogeneous root distribution (lower root densities). Despite the small impact on predicted CH
4
emissions, the simulated ROL drastically reduced porewater concentrations of sulfide, an effective phytotoxin, indicating that incorporating ROL combined with sulfur cycling into ecosystem models could potentially improve predictions of plant productivity in coastal wetland ecosystems.
Zeolites are an important class of tetrahedrally coordinated inorganic materials that have been widely used in many chemical industries as catalysts, adsorbents, and ion-exchangers. To date, over 200 ...types of zeolite framework have been discovered. Predicting not-yet-discovered zeolite frameworks is of great importance not only for zeolite structure determination but also for the identification of promising synthetic candidates with desirable functions. However, owing to the complexity and diversity of zeolite framework topologies, zeolite structure prediction has been a challenging task for several decades. Many efforts have been devoted towards this end, among which the computer-aided assembly of zeolite framework constituent atoms (T atoms) in predefined Wyckoff positions (WPs) is a promising approach because of its high efficiency in configuration space searching. However, this approach suffers from high computational overheads caused by the large number of possible WP combinations. On the basis of the analysis of known zeolite structures, we find that the site symmetries of many WPs are incompatible with the tetrahedral coordination of T atoms. Moreover, to avoid the formation of chemically unfeasible distorted tetrahedral coordination, T atoms cannot be too "crowded" in some WPs. We define, for the first time, the T atom distribution (TAD) densities for special site symmetries as the numbers of T atoms per special point, per unit length of rotation axes, or per unit area of mirror planes, respectively. By restricting the number of T atoms in every WP so as not to exceed the highest allowed TAD density, WP combinations for zeolite structure prediction can be reduced by 1-4 orders of magnitude. Taking advantage of this discovery, the efficiency of zeolite structure prediction based on the enumeration of WP combinations can be significantly improved.
Restricting the numbers of Wyckoff positions (WPs) on axes and planes dramatically reduces the WP combinations for zeolite structure prediction.
To combat land loss along the Mississippi River Delta, Louisiana has launched a historic campaign to sustain and regrow coastal lands using, in part, sediment diversions. Previous research has ...focused primarily on sand-sized sediment load, which is usually deposited proximal to a river’s delta or a diversion’s outlet. Fine sediments constitute the majority of sediment load delivered by rivers, but are understudied with respect to dispersal processes, particularly in terms of sediment supply to distal deltaic bays and wetlands. The Atchafalaya River and associated wetlands serve as prime study areas for this purpose. Fourleague Bay has remained stable against the deteriorative effects of relative sea level rise, standing out along Louisiana’s declining coastline. Push cores were collected once every 2 months, from May 2015 to May 2016, along five central bay sites and five adjacent marsh sites within Fourleague Bay, Louisiana. All sites fall within ~ 10 to 30 km of the Atchafalaya Delta, extending south towards the Gulf of Mexico. Cores were extruded in 2-cm intervals, dried, ground, and analyzed via gamma spectrometry for the presence of ⁷Be. Inventories of ⁷Be were then calculated and used to determine daily apparent mass deposition rates (AMDR) over 12 months. Average AMDR values for the bay and the marshes are compared with Atchafalaya River discharge, wind data, and atmospheric pressure through the year of sampling. Peak marsh AMDR, 0.7 ± 0.2 kg m⁻² d⁻¹, occurred just after historically high river discharge. Peak bay AMDR, 1.2 ± 0.7 kg m⁻² d⁻¹, occurred during seasonal low river discharge and calm winds. Average bay and marsh AMDRs have a moderate negative correlation (r = - 0.51) when compared. Results indicate that, during periods of moderate to high river discharge, sediment bypasses the bay floor and enters the marshes directly when inundation occurs, a process enhanced by the passage of strong atmospheric fronts. During periods of low river discharge and relatively calm winds, riverine sediments aggregate directly onto the bay floor.
The surging market demand for sea cucumbers (Apostichopus japonicus) has fueled a thriving growth in the sea cucumber breeding industry. Pheromones are molecules that evolve signals in defined ...proportions in the case of multicomponent pheromones, emitted by one individual and received by a second individual of the same species to cause a specific response. It remains an enigma as to how the species of sea cucumber, devoid of visual, auditory, and olfactory senses, aggregate and communicate within their groups, as well as coordinate gamete release during the breeding period. We hypothesize that pheromones may serve as the medium for facilitating these behaviors and propose conducting experiments centered around pheromonal investigation. In this study, we aimed to analyze common metabolites of male A. japonicus using LC-MS/MS technology and bioinformatics. Coelomic fluid and ejaculate fluid were analyzed, with aquaculture water serving as the control. Eight target pheromones were analyzed, and eight of metabolite analogs were tested for aggregation and spawning behaviors. Results showed that β-sitosterol at a concentration of 10 μg·L−1 significantly promoted aggregation (21.25 % average rate) and induced a significant increase in spawning rate (58 %) of A. japonicus. The significance of this study lies in the fact that by collecting and utilizing pheromones of A. japonicus, farmers can accurately determine the reproductive cycle and optimal breeding season for A. japonicus. This enables fish farmers to implement effective breeding management strategies at the appropriate time, thereby increasing the success rate of reproduction and providing valuable technical support for the cultivation of A. japonicus seedlings.
•Sea cucumber Apostichopus japonicus is one of the most valuable and nutritious commercial species in the echinoderms.•Potential pheromones were identified using LC-MS/MS techniques.•The latent pheromones caused different levels of aggregation behavior effects in A. japonicus.•10 μg·L-1 β-sitosterol could induce spawning behavior in A. japonicus.
For the first time, this study aimed to enhance the quality of recycled aggregates (RAs) by employing nano-silica (NS) and the vacuum impregnation technique. Specifically, RAs experienced water ...immersion, ordinary and vacuum impregnation with 2 % NS slurry, and vacuum impregnation with 4 % NS slurry. Subsequently, these nano-modified RAs were incorporated into concrete mixes, and their strength and durability were assessed. Following this, an examination of the pore structures and properties of the interfacial transitional zones (ITZs) in recycled concrete was conducted. The results demonstrate that in contrast to ordinary pretreatment methods, concrete containing nano-modified recycled aggregates after vacuum impregnation exhibits better compressive strength (+18.39 %) and reduced chloride ion penetration (−17.90 %), which is attributable to a more compact pore structure and enhanced ITZs. The findings prove that vacuum impregnation significantly enhances the modification impact of NS on RAs when compared to conventional impregnation methods, owing to the reduced agglomeration effect of NS in concrete.
•Vacuum impregnation improves the modification of NS on RC.•RC strength and durability enhanced owing to refined microstructure.•Vacuum impregnation outperformed other methods based on ITZs features.•Reduced NS agglomeration explains vacuum impregnation's benefits.
Summary of main observation and conclusion
The high performance of titanosilicate zeolites in various industrial oxidation reactions is highly affected by the distribution of Ti atoms in their ...frameworks. Because of their structural complexity, previous theoretical studies mainly focus on the preferential location of single Ti atoms within the unit cells of titanosilicate zeolites. When multiple Ti atoms are required, conventional approaches consider only symmetrically related T sites to reduce the computation complexity. Such symmetry‐constrained approaches obviously overlooked many possible configurations. Herein, we conduct a systematic study on the distribution of two Ti atoms in the unit cell of titanosilicate zeolite *BEA. Different from conventional symmetry‐constrained approaches, we introduce two Ti atoms simultaneously without any constraint and adopt a symmetry‐adapted algorithm to enumerate all possible configurations for double‐Ti introduction. We generate a total of 273 distinct configurations and analyze the Ti‐distribution via Boltzmann statistics. We find that many of the configurations overlooked by conventional symmetry‐constrained approaches indeed exhibit more feasible energies, which may lead to different Ti‐distributions. Our study indicates the necessity of unconstrained introduction of Ti atoms when multiple‐Ti atoms are considered for calculations.
A systematic study of Ti distribution in single‐ and double‐Ti introduced titanosilicate *BEA zeolites is conducted via symmetry‐adapted enumeration method and Boltzmann statistics.
Person re-identification, which aims to match two instances across different cameras still remains challenging. One of the biggest obstacles is the misalignment problem, namely instances cannot be ...spatially aligned due to the large variations in scale, pose, etc. In this work, we proposed a Multi-level Attention Network associated with a Part Matching Distance to address this issue. Specially, the Multi-level Attention Network consists of both pixel-level and part-level attention, which together form a coarse-to-fine flow to extract discriminative features of each instance. The Part Matching Distance formulates the distance between two instances with a part searching scheme under the constrains of the spatial structures, which can further tackle the large-scale variations at the inference stage. Both quantity and quality results on three popular person Re-ID benchmarks and one person search benchmark show that our method outperforms all previous works by a notable margin.
