Surface Layer Research Articles

Composite acoustic system for low-frequency sound absorption

Absorption of low-frequency sound is a difficult engineering problem because long-wave sound energy is poorly dissipated. Traditional sound absorbing materials such as porous materials, microperforated sheets or sound absorbing wedges have a poor low-frequency sound absorption performance. In this work a porous composite absorbing plate connected with a resonant cavity is developed to absorb low frequency sounds. The special developed sound-absorbing plate is rigid and consists of a more fibrous layer (up to approx. 3.0 mm thick) and a more plastic, thin polymer surface layer (up to approx. 0.5 mm thick). The walls of resonant cavity are rigid and smooth. By changing the angle between the absorbing plate and the direction of the incident sound wave and changing the length of the cavity, it is possible to create acoustic systems with a given level of sound absorption and in a given low-frequency range. The larger the angle, the maximum absorption occurs for sounds of lower frequencies. As the cavity length increases, the range of maximum absorption occurring at the resonant frequency shifts towards lower frequencies and the maximum value of the sound absorption coefficient increases. The results are compared with composite variant without a polymer surface layer.

Alternative lipid synthesis in response to phosphate limitation promotes antibiotic tolerance in Gram-negative ESKAPE pathogens.

The Gram-negative outer membrane protects bacterial cells from environmental toxins such as antibiotics. The outer membrane lipid bilayer is asymmetric; while glycerophospholipids compose the periplasmic facing leaflet, the surface layer is enriched with phosphate-containing lipopolysaccharides. The anionic phosphates that decorate the cell surface promote electrostatic interactions with cationic antimicrobial peptides such as colistin, allowing them to penetrate the bilayer, form pores, and lyse the cell. Colistin is prescribed as a last-line therapy to treat multidrug-resistant Gram-negative infections. Acinetobacter baumannii is an ESKAPE pathogen that rapidly develops resistance to antibiotics and persists for extended periods in the host or on abiotic surfaces. Survival in environmental stress such as phosphate scarcity, represents a clinically significant challenge for nosocomial pathogens. In the face of phosphate starvation, certain bacteria encode adaptive strategies, including the substitution of glycerophospholipids with phosphorus-free lipids. In bacteria, phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin are conserved glycerophospholipids that can form lipid bilayers, particularly in the presence of other lipids. Here, we demonstrate that in response to phosphate limitation, conserved regulatory mechanisms induce alternative lipid production in A. baumannii. Specifically, phosphate limitation induces formation of three lipids, including amine-containing ornithine and lysine aminolipids. Mutations that inactivate aminolipid biosynthesis exhibit fitness defects relative to wild type in colistin growth and killing assays. Furthermore, we show that other Gram-negative ESKAPE pathogens accumulate aminolipids under phosphate limiting growth conditions, suggesting aminolipid biosynthesis may represent a broad strategy to overcome cationic antimicrobial peptide-mediated killing.

Iterative sublattice amorphization facilitates exceptional processability in inorganic semiconductors.

Cold-forming processing is a crucial means for the cost-effective production of metal and alloy products. However, this process often results in catastrophic fracture when applied to most inorganic semiconductors owing to their inherent brittleness. Here we report the unique room-temperature plastic deformation mechanism involving sublattice amorphization coupled with Ag-ion diffusion in inorganic semiconductors Ag2Te1-xSx (0.3 ≤ x ≤ 0.6), and an ultrahigh extensibility of up to 10,150%. Once subject to external stress, the crystalline Te/S sublattice undergoes a uniform transformation into an amorphous state, whereas the Ag cations continuously bond with Te/S anions, endowing bulk Ag2Te1-xSx with exceptional plastic deformability. Remarkably, even slight polishing can induce sublattice amorphization in the surface layers. Furthermore, this sublattice amorphization can be reversed to crystals through simple annealing, enlightening the iterative sublattice amorphization strategy, with which metal-like wire drawing, curving, forging and ultrahigh ductility have been obtained in bulk Ag2Te1-xSx at room temperature. These results highlight sublattice amorphization as a critical plastic deformation mechanism in silver chalcogenide inorganic semiconductors, which will facilitate their applications in flexible electronics and drive further exploration of more plastic inorganic semiconductors.

Wearable Self-Powered Pressure Sensors Based on alk-Ti3C2Tx Regulating Contact Barrier Difference for Noncontact Motion Object Recognition.

Wearable self-powered pressure sensors present tremendous potential for object recognition. However, the fluctuated approach speed and distance may compromise the device output, thus affecting the recognition accuracy. Herein, a wearable self-powered pressure sensor with high sensitivity (1.48 VkPa-1), high output (130.5V), and high permeability (259.98 mms-1) are developed where the contact barrier difference and triboelectric charge density of the triboelectric layer surface are dynamically regulated by modulating the surface groups resulting in a lower dielectric loss and higher output. The sensor leverages the polarity difference between the target object and the sensitive material to generate electrical signals at different speeds and distances through an electrostatic induction mechanism. With the assistance of the Transformer model with a self-attention mechanism, an average recognition accuracy of 94.3% is achieved by acquiring sensing signals at different speeds and distances. Simulating the ability of human vision, enables visually impaired people to acclimate to their surroundings more easily and independently and provides a critical advancement in the assistance of the blind with daily life.

Effect of Ice Number Concentration on the Evolution of Boundary Layer Clouds During Arctic Marine Cold‐Air Outbreaks

AbstractMarine cold‐air outbreaks (MCAOs) are crucial for Arctic Ocean heat loss, featuring convective cloud rolls that transition into convection cells downstream. Understanding factors controlling this transformation is the key for improving MCAO cloud representation in climate models. This study employs large‐eddy simulations to investigate how cloud ice number concentrations () affect cloud evolution using a case from the Cold‐Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) campaign. The simulations, performed in a Lagrangian framework following an air mass trajectory, are driven by ERA5 reanalysis data. Initially, all simulations produce similar cloud patterns, but higher leads to earlier breakup of cloud rolls. Between 4 and 10 hr, surface precipitation rates are similar across simulations, but precipitation initiates earlier, and the cloud‐base precipitation rates are higher when is higher. The stronger precipitation evaporation leads to increased stability of the boundary layer and reduced intensity of vertical mixing between the surface and cloud layer. An increased sink of cloud layer moisture via precipitation and decreased source through diminished vertical transport result in earlier cloud breakup in higher conditions. Simulations with different sea surface temperatures (SST) indicate that this cloud breakup mechanism remains valid for MCAOs of different strengths, although the cloud organization is more sensitive to SST changes in low environments. This work highlights the importance of accurate representations of ice processes in simulating MCAO clouds and suggests the need for observational constraints of ice nucleating particles and over the mixed‐phase cloud regimes.

Probabilistic and FEM hydro-mechanical coupling analysis of rainfall-induced slope instability

The random field theory coupled with a FEM hydro-mechanical model was employed to analyse slope responses under rainfall, with a particular focus on post-rainfall behaviour. This study uniquely analysed the heterogeneity of soil strength and permeability through the application of random field theory, providing a novel perspective on its impact on slope stability. Numerical modelling under varying rainfall intensities revealed that the factor of safety (FoS) decreased with prolonged rainfall, particularly at higher intensities. Post-rainfall behaviour varied for different rainfall events, that gentle and moderate rainfalls led to a gradual decline in FoS due to water infiltration, while heavy rainfall allowed recovery through drainage, and extremely heavy rainfall triggered immediate failure. A novel finding is that post-rainfall water seepage can govern slope stability under extreme rainfall conditions. At failure, the surface layer of a fully saturated slope lost clay suction and exhibited concentrated plastic shear strain at its base. Weak zones with interconnected high-permeability channels significantly influenced slope stability by facilitating water infiltration. Probabilistic analysis further showed that the FoS at the end of simulations typically ranged from 1.1 to 1.4, with a recommended 5th percentile value of 1.1 for slope designs.

Investigation of the Effect of the "MADOR" Modifier on the Strength and Water Resistance of Cement-Reinforced Discrete Mineral Materials for Road Construction

Statement of the problem. In the territory of the Russian Federation, a large number of cement modifiers are used to strengthen and stabilize soils during the construction and repair of highways. At the same time, the determination of the scope of modifying additives and their effectiveness requires a large number of laboratory studies, both according to GOST-normalized indicators and alternative methods, taking into account foreign experience. This circumstance led to the need to conduct a study of one of the additives to cement used to strengthen soils in road construction. Results. The review of the results of studies of the effectiveness of the use of the modifier "MADOR" for non-cohesive mineral materials reinforced with cement for the construction of structural layers of pavement is given. The results of studies of strength characteristics, water resistance and water absorption of materials reinforced with cement together with the modifier "MADOR" are presented. Conclusions. A significant positive effect has been established from the use of the "MADOR" modifier to strengthen the studied materials and soils in combination with cement. It is proposed to use the studied materials reinforced with the "MADOR" modifier together with cement in the structural layers of the road surface of highways.

Design and Heat Transfer Analysis of Graphene-Based Electric Heating Solid Wood Composite Energy Storage Flooring

Due to severe global energy issues and the widespread demand for high-quality winter heating, this study designed a new type of graphene-based electrically heated solid wood composite floor. This flooring maintains the convenience of a traditional floor installation while providing users with a more comfortable living experience. Additionally, the low-temperature heating and temperature regulation system further reduces energy consumption, offering a new perspective for green home living. This paper introduces the overall structure and temperature control system of the graphene-heated solid wood composite flooring. Based on the above reasons, the working mechanism and heat transfer process of the graphene-heated flooring were analyzed, and a mathematical model was established. Furthermore, simulations of flooring with different thicknesses were conducted to determine temperature rise curves and corresponding times. Finally, a comparative experimental verification was conducted on the thermodynamic performance of the solid wood composite graphene flooring. The results showed that in the case of a floor with an 18 mm thickness, the time for the surface layer of the floor to reach 22 °C is 27 min; the time to reach 26 °C is 56 min; and that the time to reach 28 °C is 109 min. The time required to return to 22 °C after the power has been switched off is 25 min. The results also showed that one hour after the power was turned off, the surface temperature of the floor was still above 20 °C. The study shows that the graphene-heated flooring can be used to achieve high-quality heating.

Mechanisms of Strength Degradation of Dental Zirconia Due to Glazing: Dependence on Glaze Thickness

Glazing is a common method for smoothing the surface of zirconia and imitating the appearance of natural teeth. Several authors have previously reported that glazing reduces the strength of zirconia. However, the dependence of strength on glaze thickness and the mechanism of strength reduction remains unclear. Clarifying these factors is particularly important for improving the reliability of zirconia prostheses. In this study, three types of zirconia were glazed with various thicknesses, and their strength was evaluated. The results showed that the strength of the materials decreased with increasing glaze thickness. The decrease in the fracture load of the glazed test specimen stopped at a load where the stress necessary to fracture the glaze material was applied to the surface of the glaze layer. Furthermore, the strength reduction mechanism was investigated using FEM analysis, fractography, and Raman spectroscopy. The results suggested that the strength reduction due to glazing was a consequence of the crack-tip stress concentration developed upon the preliminary fracture of the glaze layer.

Cation-Deficient LixWO3 Surface Coating on Ni-Rich Cathodes Materials for Lithium-Ion Batteries.

In the pursuit to increase the energy density of lithium-ion batteries (LIBs), considerable efforts have focused on developing high-capacity cathode materials. While Ni-rich (Ni ≥ 80 at. %) layered cathode materials are considered a viable commercial option, surface engineering is crucial for enhancing their cycle performance for successful implementation in commercial LIBs. Various functional materials have been explored for effective surface protection and stabilization to reduce interfacial resistance and enhance the structural stability of Ni-rich cathode materials. In this context, we propose a surface coating with a nonstoichiometric lithium hexagonal tungsten bronze (LixWO3) for Ni-rich cathode materials via simple wet-coating. We demonstrate that the distinctive physicochemical properties of LixWO3, such as its high ionic conductivity (∼10-6 S cm-1) and mechanical strength (∼236.0 MPa), are beneficial for enhancing the cycle performance of Ni-rich cathode materials by modulating the interfacial reactions without undesirable loss of reversible capacity. In practice, the LixWO3 surface layer induces a significant reduction in interfacial resistance and effective strain relaxation upon repeated Li+ insertion and extraction. Our findings provide insights into the development of highly reliable Ni-rich cathode materials for high-energy LIBs.

Puzzling out the ecological niche construction for nitrogen fixers in a coastal upwelling system

Abstract Diazotrophs are a diverse group of microorganisms that can fertilize the ocean through biological nitrogen fixation (BNF). Due to the high energetic cost of this process, diazotrophy in nitrogen-replete regions remains enigmatic. We use multidisciplinary observations to propose a novel framework for the ecological niche construction of nitrogen fixers in the upwelling region off NW Iberia — one of the most productive coastal regions in Europe — characterized by weak, and intermittent wind-driven upwelling and the presence of bays. The main diazotroph detected (UCYN-A2) was more abundant and active during summer and early autumn, coinciding with relatively high temperatures (>16°C), low nitrogen:phosphorus ratios (N:P < 7.2), and a large contribution of ammonium (>75%) to the total dissolved inorganic nitrogen available. Furthermore, nutrient amendment experiments showed that BNF is detectable when phytoplankton biomass and productivity are nitrogen limited. Seasonally recurrent biogeochemical processes driven by hydrography create an ecological niche for nitrogen fixers in this system. During the spring–summer upwelling, non-diazotroph autotrophs consume nitrate and produce organic matter inside the bays. Thereafter, the combined effect of intense remineralization on the shelf and sustained positive circulation within the bays in late summer-early autumn, conveys enhanced ammonium content and excess phosphate into the warm surface layer. The low N:P ratio confers a competitive advantage to diazotrophs since they are not restricted by nitrogen supply. The new nitrogen supply mediated by BNF could extend the productivity period and may be key reason why upwelling bays are more productive than upwelled offshore waters.

Status of Different Forms of Nitrogen in Soils of Navsari District of South Gujarat, India

To study the nitrogen fraction under different cropping and management system, the present investigation was carried out at NAU, Navsari (Gujarat) during year 2022-2023. From each taluka of Navsari district, ten soil samples were collected randomly from 0-15 cm and 15-30 cm depth by using different cropping and management systems by GIS base grid sampling method. Soil samples were subjected to preliminary analysis for pH, EC, SOC and then analysis of different N-fractions was carried out. Nitrogen is one of the main limiting factors of crop productivity and many studies have sought possibilities to reduce the need for N application and extend the period of availability to plants. Organic N forms constitute up to 90% of the total N in the plow layer of mineralsoils and only about 1–4% is mineralized as plant- available N (NH4–N and NO3–N). Plant-available N released from soil organic N (SON) or applied in fertilizer is highly susceptible to loss from the soil– plant system through leaching and denitrification. The overall distribution of avail. N, NO3-N, NH4-N and total N in Navsari district was ranged from 72.80 to 375.20 mg kg-1, 5.60 to 92.40 mg kg-1, 30.80 to 114.80 mg kg-1 and 140.00 to 1036.00 mg kg-1, respectively for surface soils while, 61.60 to 364.00 mg kg-1, 8.40 to 72.80 mg kg-1, 25.20 to 100.80 mg kg-1 and 140.00 to 924.00 mg kg-1 for sub-surface soils, respectively. At surface layer, total N was correlated significantly and positively with SOC, CEC and it was negatively correlated with pH and EC. However, total N showed similar correlation with SOC and EC at sub-surface layer. NH4-N and NO3-N were positively and significantly correlated with each other at the same depth. The result also revealed that the N fractions were significantly decreased with increasing depth of soil. Overall, our findings suggest that vegetation restoration improved the soil N availability.

Assessment of forest soil contamination by heavy metals in the Polish National Park near Warsaw

The forest ecosystems are essential for human well-being development and reduction of the risk of natural disasters. Maintaining forest growth and ecosystem services is dependent on soil sustainability. The content of heavy metals is the main parameter determining the degree of soil contamination and degradation. The objective of the study was to assess the extent of soil contamination and identify the sources of potential anomalies. The content of the cadmium, lead, manganese and chromium (using atomic emission spectroscopy with induction-coupled plasma), as well as granulometric composition, pH value and nitrogen and total carbon content, were conducted on soil samples taken from the surface layer (0–10 cm) in the protected area of the Kampinos National Park in Poland. The soil quality assessment was conducted by calculating indicators of contamination including the geo-accumulation index, contamination factor, degree of contamination, ecological risk of individual heavy metals and potential ecological risk index. The results exhibited that the tested soils were very acidic or acidic sands. The content of the determined elements did not exceed the permissible limits as outlined in Polish standards, which are 2 mg/kg, 100 mg/kg and 150 mg/kg for cadmium, lead and chromium, respectively. The indicators show differences in the degree of contamination of the surface soil layer in the studied area, which is predominantly uncontaminated by heavy metals. However, the geochemical index values equal 0.42, 0.71 and 0.98 for certain samples suggesting the anthropogenic impact on the soils of the Kampinos National Park. The pollution appears to have been generated by the metallurgical industry, heating and power plants in the Warsaw agglomeration and transport.

Mechanically Robust 3D Flexible Electrodes via Embedding Conductive Nanomaterials in the Surface of Polymer Networks.

3D flexible electrodes are essential to implement flexible pressure sensors in various flexible electronic applications. Conventional methods for fabricating these electrodes include electroless deposition, spray coating, and incorporating conductive nanomaterials into a polymer matrix. However, the electrodes fabricated using these methods are characterized by poor adhesion between the conductive layer and polymer surface and fail to maintain intrinsic mechanical properties of the polymer, such as elastic modulus and ductility. Herein, a transfer method in which conductive nanomaterials are embedded into the surface of polymer networks via optimal surface energy control is proposed, such as reducing adhesion between the mold and nanomaterials. This method induces mechanical interlocking between the surface of polymer networks and conductive nanomaterials, firmly anchoring them onto the polymer network surface. Moreover, the intrinsic mechanical properties of the fabricated 3D flexible electrodes remain unchanged. Flexible capacitive sensors prepared using the resulting electrodes exhibit a stable sensing performance (ΔC0,5000/C0 = 0.169%) even under repetitive pressure conditions (5000 cycles at 70kPa). The proposed robust 3D flexible electrode fabrication method presents a promising strategy for the future development of flexible pressure sensors.

Pastureland Soil Organic Carbon Storage Regulated by Pasture Species and Age Under Nitrogen and Water Addition in Northern China

Soil organic carbon (SOC) is a key indicator of soil quality and an important component of the global carbon cycle. Enhancing SOC through crop rotation is a promising strategy; yet, the underlying mechanisms for SOC accumulation remain unclear. This study aimed to evaluate the effects of different pasture age, pasture species, irrigation, and nitrogen (N) fertilization treatments on SOC content and storage in pastureland, analyzing the SOC content and below-ground biomass (BGB) data of different soil layers (0–10 cm, 10–20 cm, 20–40 cm, 40–60 cm) of each treatment under three factors (pasture species (Bromus inermis, Medicago varia, the 1:1 mixture), irrigation (CK, dry-season supplementation), and N fertilization (0 kg N hm−2 y−1, 75 kg N hm−2 y−1, and 150 kg N hm−2 y−1)), as well as the interaction effects of these factors. Pasture species, water and N addition levels, and pasture age all had significant (p < 0.05) effects on BGB. At the age of 1–3, the SOC content of monocultured Bromus inermis was slightly higher than the monocultured Medicago varia and the mixture, and at the age of 4–5, monocultured Medicago varia and the mixture were slightly higher than the monocultured Bromus inermis. Among them, the mixture was the highest. At the age of 2–5, the BGB of pastureland was significantly influenced by pasture species, N and water addition, and pasture age. Over a 5-year period, SOCs in the surface layer of the fallowed cropland accumulated 32.35 Mg ha−1, showing a very good carbon sequestration effect; especially the planting of a mixed pasture had a more significant positive effect on the accumulation of SOC. Therefore, for the low and medium yielding fields in China, according to the crop utilization target and production cycle, the purpose of improving soil quality can be effectively achieved through crop and grass rotation.

Characterizing Model Uncertainties in Simulated Coast-to-Offshore Wind over the Northeast U.S. Using Multi-platform Measurements from the TCAP Field Campaign

Numerical weather prediction models, such as the Weather Research and Forecasting model, are widely used to provide estimates of the offshore wind energy resource owing to their large spatial coverage compared to available observations. Nevertheless, spatiotemporal distribution of model biases is highly dependent on factors including model configuration, location, and the interplay of multiscale physical processes. Here we focus on the characterization of model uncertainties in simulated coast-to-offshore winds over the northeast United States by varying sea surface temperature (SST) forcings and surface layer (SL) and planetary boundary layer (PBL) parameterizations, as well as identifying biases that may be directly passed from initial and boundary conditions. Multiple measurements, including aircraft data collected during the U.S. Department of Energy's Two-Column Aerosol Project experiment, are used to constrain the model results, and facilitate quantitative comparisons. Our analysis indicates that while SST forcing has notable impacts on simulated air temperature and moisture within PBL, the modeled winds are in general more sensitive to the choices of SL and PBL physics than to SST. The model’s forcing data not only controls the vertical dependence of wind speed errors, but also alters regional variability in the wind speed’s spatial correlation, which underscores the impact of initial and boundary conditions on simulated winds. Coastal and offshore near-surface wind speed biases tend to exhibit much higher similarity in winter than in summer due to the presence of much stronger and more persistent synoptic wind conditions. This study highlights the importance of accurate atmospheric forcing and parameterization choices in improving wind forecasts and suggests the potential for extrapolating coastal wind biases to offshore locations, aiding wind energy forecasting and informing the third Wind Forecast Improvement Project.

Intensification of Hurricane Idalia by a river plume in the eastern Gulf of Mexico

Abstract Hurricane Idalia formed on 26 August 2023 and three days later rapidly intensified from a Category 1 to Category 4 strength storm in less than 24 h over the west Florida shelf. On August 30, it made landfall along Florida’s Big Bend area as a Category 3 hurricane. Strikingly, despite Idalia’s moderate intensity and favorable vortex structure, neither upper ocean thermal energy nor environmental vertical wind shear conditions were as favorable during its intensification from Category 2 to Category 4 as earlier in its path, raising the question of what external factors contributed to its extreme intensification during this phase. Using satellite data, underwater glider observations, and numerical model outputs, this study reveals that, in addition to the 2023 marine heatwave, an extensive riverine plume in the eastern Gulf of Mexico, extending from the Mississippi-Alabama-Florida shelf to the Straits of Florida, produced a ∼20 m thick low-salinity layer (∼34–34.5 psu) and a corresponding warm upper ocean (>29 °C, ∼25–30 m thick). This defined a 10–20 m thick strongly stratified barrier layer below the surface layer with buoyancy frequencies exceeding 10−3 s−1 that suppresses vertical mixing and became a critical factor contributing to Idalia’s rapid intensification under the relatively less than favorable thermal and wind field environments. Therefore, incorporating the river plume in future forecast models appears to be essential to improve the accuracy of intensity predictions, especially in the areas affected by the plume, where stratification plays an important role in the intensification dynamics.

The Long Lives of Subducted Spice and Vorticity Anomalies in the Subtropical Oceans

Abstract Subtropical cells, which exist in nearly all ocean basins, connect subducting subtropical waters to upwelling sites along the equator. This tight link between the subtropics and the tropics, on a scale of 5–15 years, is well established in a time-averaged sense by modeling and observations. Recently, evidence has emerged of spice and potential vorticity anomaly persistence along mean flow pathways on isopycnals. We provide the first global view of subtropical water mass anomaly propagation, using both an observational dataset and the Estimating the Circulation and Climate of the Ocean (ECCO) state estimate version 4 release 4. In this global synthesis that complements the existing body of largely regional studies, we find long-lived interannual water mass anomalies that translate along mean advective pathways in all ventilated subtropical gyres. They are detectable over multiple years and several thousand kilometers. Some anomalies are persistent enough to reach both the western boundary and equatorial current systems before being entirely eroded and thus could form ocean “tunnels” equivalent to the well-studied atmospheric bridge to impact the remote climate variability. The analysis of ocean tunnel propagation of a passive tracer (spice) and an active tracer (potential vorticity) confirms earlier model results that the active tracer decays more quickly than the passive tracer. Similarities and differences between timing and frequency of the two tracers could provide clues to anomaly formation mechanisms in various subduction regions. The success of ECCO in capturing these phenomena is encouragement to further explore their upstream sources and downstream impacts within this framework. Significance Statement Surface waters in the subtropical oceans flow below the surface layer and travel for long distances westward and equatorward until they reemerge at the surface. It is known that average water properties can persist for thousands of kilometers along this “ocean tunnel,” but how much the year-to-year variability can survive without being mixed away is less understood. We use observational data and global model output to estimate the frequency and survival of interannual anomalies of water properties along ocean tunnels. We find that such anomalies are common in all subtropical basins, that they have the potential to persist until they reach the tropics, and that the global model captures the variability seen in observations.

Effects of Nitrogen and Hydrogen Plasma Treatments on a Mg-2Y-1Zn-1Mn Resorbable Alloy.

Mg alloys have recently been investigated and optimized for the development of biodegradable implants for orthopedic, dental, vascular, and other applications. However, their rapid degradation in a physiological environment remains the main obstacle to their development. In this work, the effects of nitrogen and hydrogen plasma treatments on the surface properties and corrosion behavior of an Mg-2Y-1Zn-1Mn (WZM211) alloy were investigated. Plasma treatment effectively modified the surface of a WZM211 alloy by removing the original oxide layer, followed by the formation of a new surface layer with controlled composition, thickness, and wettability. The water contact angle decreased from 100° to 17° after nitrogen plasma and to 45° after hydrogen plasma treatment. The nitrogen plasma treatment, shortly N-Plasma, resulted in the lowest corrosion rate (CRN = 0.038 ± 0.010 mm/y) if compared with the hydrogen plasma treatment, shortly H-Plasma (CRH = 0.044 ± 0.003 mm/y) and untreated samples (0.233 ± 0.097 mm/y). The results demonstrate the potential of nitrogen and hydrogen plasma treatment for the development of resorbable Mg-based implants.

Coalescence characteristics of free-living and particle-attached bacteria in a cascade river-reservoir system: A case study of the Jinsha River.

Microbial coalescence plays a crucial role in shaping aquatic ecosystems by facilitating the merging of neighboring microbial communities, thereby influencing ecosystem structure. Although this phenomenon is commonly observed in natural environments, comprehensive quantitative comparative studies on different lifestyle bacteria involved in this process are still lacking. The study focuses on 16S rRNA Amplicon Sequence Variants (ASVs) at the Jinsha River hydropower stations (Wudongde [WDD], Baihetan [BHT], Xiluodu [XLD], Xiangjiaba [XJB]), specifically examining free-living (FL) and particle-attached (PA) bacteria. Minimal differences in microbial composition were observed across water layers (surface, middle, and bottom). Analyses of overlapping ASVs, Bray-Curtis dissimilarity, and the SourceTracker algorithm revealed a significant difference in the coalescence ability of FL and PA bacteria, particularly in the surface water of XJB (FL: 31.1%±2.0%, PA: 27.6%±2.5%, p<0.05). The coalescence of FL bacteria was primarily influenced by the mixing of adjacent water layers, while PA bacteria exhibited significant geographical variations across water layers (p<0.05), displaying lower coalescence compared to FL bacteria. Using a cohesion metric, 12 keystone species in PA bacteria were identified and 7 in FL bacteria. Proteobacteria and Bacteroidetes were the most abundant phyla at the keystone species in PA and FL bacteria, respectively. The abundance of keystone ASVs decreased with distance in PA bacteria, whereas FL bacteria showed the opposite trend. At the genus level, Brevundimonas and Chryseobacterium were identified as keystone species in both lifestyles. Moreover, the impact of community coalescence on the stability tends to exhibit differences downstream in cascade stations. This study provides novel insights into the dynamic variations of microbial communities with diverse lifestyles in stratified aquatic environments and assesses the impact of dam construction on microbial coalescence and the alteration of keystone species.