Product Layer Research Articles

Investigation of the pore structure characteristics and fluid components of Quaternary mudstone biogas reservoirs: a case study of the Qaidam Basin in China

Quaternary mudstone biogas reservoirs in the Qaidam Basin have shown great potential. However, complex pore structures with high clay contents and high heterogeneity limit the understanding of the storage and migration principles of these reservoirs. In this paper, HPMI and nitrogen adsorption experiments, in combination with NMR experiments under water saturation, centrifugation, various drying temperatures and other conditions, were adopted to determine the pore structure characteristics. Specifically, the reservoir space types and pore radius distribution characteristics were clarified. The cutoff values for different types of pores were identified based on the water-saturated mudstone NMR T2 spectra for full aperture distribution scales jointly characterized by mercury injection and nitrogen adsorption experiments. Furthermore, the three pore components and the saturation of different fluids were obtained. The research results indicate that the mudstone biogas reservoir has developed various reservoir spaces, and the pore size is primarily in the micronanometer range. The average total porosity reaches 27.28%, but the proportion of movable water pores is only 9.23% with poor fluid mobility, and the fluids in the pores are mostly capillary-bound water and clay-bound water. Among the different lithologies, argillaceous sand is more likely to become a good production layer.

Study on the mechanism of aluminum melt corrosion of Fe-SG series metals

This paper investigates the corrosion behavior of Fe-SG series metals with different graphite nodule counts to molten Al by using the ultrasonic vibration hot-dip aluminum experimental method. Fe-SG series metals to aluminum melt exhibited a much better corrosion resistance compared to H13 tool steel. As the graphite nodule count increases, the hot melting loss rate of Fe-SG series metals gradually decreases, indicating an improvement in corrosion resistance to aluminum melt. Scanning and EDS analysis of the samples after hot-dip aluminum testing revealed that the thickness of the product layer increased progressively with the extension of hot-dip aluminum time. Through the analysis of the structure and composition of the product layer, it was found that the corrosion products in H13 steel were composed of Fe2Al5 and FeAl3. In addition to the two phases, the product layer of the Fe-SG series metals also contained granularly distributed Fe-Al-Si intermetallic compounds within the Fe2Al5 phase. This resulted in a better corrosion resistance to aluminum melt.

Enhanced thermochemical heat storage performance of CaO/CaCO3 via pyroligneous acid impregnation and Co/Mn co-doping

Calcium-based thermochemical heat storage (TCHS) is an economical and environmentally friendly technology for efficient heat storage. It can strengthen the flexibility in power systems of renewable energy and promote the recovery and storage of waste heat in energy-intensive industries. However, CaO/CaCO3 is extremely prone to sintering at operational temperatures. Consequently, a cost-effective approach was proposed to synthesize calcium-based TCHS materials modified by pyroligneous acid (PA) impregnation and co-doping with dual transition metals. The heat storage performance, physicochemical property, and anti-sintering mechanism of synthesized CaO were comparatively examined. The sample prepared with a molar ratio of Ca: Co: Mn = 100:3:7 (PACa-Co3Mn7) exhibited an initial energy storage density of 1.76 MJ/kg, which gradually rose to 1.88 MJ/kg. After 20 cycles, the value decreased by only 4.39 % from its peak, indicating outstanding TCHS performance. Characterization results indicated that the specific surface area and pore volume of PACa-Co3Mn7 were 10.48 m2/g and 0.035 cm3/g, which were 2.34 and 2.69 times those of CaO stemmed from the calcination of limestone, respectively. The fruitful pores provided pathways for CO2 diffusion within the CaO particles or CaCO3 product layer. The uniformly distributed Co and Mn elements combined to form Ca3CoMnO6. Ca3CoMnO6 could serve as the inert carrier that mitigated the grain-growth of CaO, thereby stabilizing the pore structure and resisting the sintering of PACa-Co3Mn7. Furthermore, density functional theory (DFT) calculations demonstrated that the free Mn and Co elements efficiently promoted the electrons transfer between CaO and CO2, which improved the reactivity of PACa-Co3Mn7. Therefore, CaO modified by PA impregnation and co-doping with dual transition metal is a promising candidate for the TCHS system.

Magnesiothermic reduction of beryllium fluoride: Reaction mechanism and kinetic study

Beryllium (Be) is mainly produced by magnesiothermic reduction of beryllium fluoride (BeF2). This research aims to improve the extraction rate of Be by investigating the reaction mechanism and kinetics during the magnesiothermic reduction of BeF2. It was found that the solid product layer composed of MgF2 and Be metal produced during the magnesiothermic reduction process is the main reason hindering the further improvement of the reduction rate. Kinetic study on the magnesiothermic reduction of BeF2 shows that it was controlled by volume diffusion. An apparent activation energy of 66.01 kJ/mol was obtained for the magnesiothermic reduction in the temperature range of 850–950 °C. Aiming to extract Be from BeF2 with a high efficiency, granular-shaped Mg (particle size 0.2–5 mm) and BeF2 powder (particle size < 0.83 mm) were used as raw materials for magnesiothermic reduction at 900 °C for 30 min, protected using Ar atmosphere. This was followed by further heating to 1300 °C and holding for 10 min, and the highest extraction rate of Be was achieved at 90.1 wt% with the Be purity of 94.2 wt%.

Numerical Simulation of Hydraulic Fracture Propagation in Unconsolidated Sandstone Reservoirs

In order to comprehensively understand the complex fracture mechanisms in thick and loose sandstone formations, we have carefully developed a coupled finite element numerical model that captures the complex interactions between fluid flow and solid deformation. This model is the cornerstone of our future exploration. Based on this model, the crack propagation problem of hydraulic fracturing under different engineering and geological conditions was studied. In addition, we conducted in-depth research on the key factors that shape the geometry of hydraulic fractures, revealing their subtle differences and complexities. It is worth noting that the sharp contrast between the stress profile and mechanical properties between the production layer and the boundary layer often leads to fascinating phenomena, such as the vertical merging of hydraulic fracture propagation. The convergence of cracks originating from adjacent layers is a recurring theme in these strata. Sensitivity analysis clarified our understanding, revealing that increased elastic modulus promotes longer crack propagation paths. As the elastic modulus increases from 12 GPa to 18 GPa, overall, the maximum crack width slightly decreases, with a less than 10% reduction rate. The increased fluid leakage rate will significantly shorten the length and width of hydraulic fractures (with a maximum decrease of over 70% in fracture width). The increase in viscosity of fracturing fluid causes a change in fracture morphology, with a reduction in length of about 32% and an increase in fracture width of about 25%. It is worth noting that as the leakage rate of fracturing fluid increases, the importance of the viscosity of fracturing fluid decreases relatively. Strategies such as increasing fluid viscosity or adding anti-filtration agents can alleviate these challenges and improve the efficiency of fracturing fluids. In summary, our research findings provide valuable insights that can provide information and optimization for hydraulic fracturing filling and fracturing strategies in loose sandstone formations, promoting more efficient and influential oil and gas extraction work.

An investigation of mixed-model assembly line balancing problem with uncertain assembly time in remanufacturing

In recent decades, remanufacturing has emerged as an effective way to address resource crises and environmental pollution issues. Unlike traditional manufacturing, remanufacturing production is filled with various variable factors, especially in the assembly phase. Due to changes in part types, quality conditions, and assembly methods, the assembly time becomes highly uncertain. Assembly line balancing is a key challenge to achieve the stable operation of remanufacturing system. This study proposes an evaluation method for remanufacturing assembly time and establishes a multi-objective mathematical model for balancing remanufacturing mixed-model assembly (RMMA) line. The evaluation method utilizes the Fuzzy Graphical Evaluation Review Technique (FGERT) network to predict expected assembly time for each operation. The balancing model aims to optimize remanufacturing takt time and comprehensive balance rate (CBR). To effectively solve this model, an adaptive double-layer genetic algorithm (ADGA) is designed, where layer I ensures production efficiency and layer II optimizes assembly line balance. Finally, an assemble example of high-pressure common rail fuel pumps (HCRFP) is used to validate the effectiveness of the proposed method. The results demonstrate notable improvements compared to traditional single-product assembly (TSPA) line in scenarios with workstation numbers 4, 5, 6, and 7. Specifically, the production takt time is reduced by 4.19% to 9.56%, and CBR is enhanced by approximately 50%. Further comparison with three other classic algorithms confirms the superiority of ADGA. Additionally, it is observed that remanufacturability (proportion of remanufactured parts) has a significant impact on assembly performance. As remanufacturability increases, both takt time and CBR increase, reaching their maximum values when remanufacturability is around 0.5.

A novel method for identifying key nodes in multi-layer networks based on dynamic influence range and community importance

Identifying key nodes in multi-layer networks is a hot research topic in complex network science and has broad application prospects, such as in mining enterprises that significantly affecting multi-layer industrial chains. Unlike single-layer networks, nodes in multi-layer networks exhibit heterogeneity due to varying connections and locations. There are also correlations between different network layers, which is particularly evident in industrial chains where companies operate across multiple layers of production, supply and distribution. It is necessary to consider the impact of these layers on the global performance of key node identification. In addition, due to changes in connections, the community structure of each network layer should be different, reflecting the dynamic nature of industrial collaborations and partnerships. However, existing research lacks the model that addresses the above problems. Therefore, this paper proposes a key node identification method based on Dynamic Influence Range and Community Importance (DIRCI), using both local and global information of the multi-layer network simultaneously. DIRCI determines the importance of nodes through three centrality measures: dynamic influence range-based centrality, network layer centrality and community-based centrality. Dynamic influence range-based centrality models node heterogeneity by combining the influence range of nodes and their neighbors with lower computational costs. Network layer centrality captures the corresponding importance for different network layers. Community-based centrality comprehensively considers the importance of community, the importance of each node within the community and between different communities. Experimental results for nineteen multi-layer networks show that DIRCI achieves better performance of key node identification than the latest algorithms.

Investigating the mechanical properties and corrosion resistance of extruded Mg-1Zn-xCaO (x=0, 0.5, 1.0 wt%) materials

The effect of nano-CaO content on the microstructure, mechanical properties, and in vitro degradation performance of extruded Mg-1Zn alloys was investigated to enhance the strength and corrosion resistance of biodegradable materials for medical implants. The results showed that the addition of CaO nanoparticles effectively refined the size of dynamic recrystallization grains in the extruded composites. During the extrusion process, Ca2Mg6Zn3 and Mg2Ca phases precipitated in the Mg-1Zn-0.5CaO and Mg-1Zn-1CaO composites, respectively. As the CaO content increased, the basal texture strength was elevated from 3.97 for the Mg-1Zn alloy to 12.05 for the Mg-1Zn-1CaO composite. Benefiting from the combined mechanisms of grain refinement, dislocation strengthening, and precipitation strengthening, the yield strength of the materials was fortified with an increase in CaO content. During the short immersion time, the matrix of the extruded Mg-1Zn-0.5CaO composite was preferentially corroded, resulting in the formation of a dense corrosion product layer that impeded the transport of ions in the electrolyte solution, thereby exhibiting the lowest annual corrosion rate. With an increase in the immersion time, galvanic corrosion destroyed the protective film, leading to a slightly higher corrosion rate in the extruded Mg-1Zn-0.5CaO composite compared to the Mg-1Zn alloy. The substantial nano-Mg2Ca phase particles were preferentially degraded, causing severe pitting corrosion in the extruded Mg-1Zn-1CaO composite, which exhibited the highest degradation rate. The extruded Mg-1Zn-0.5CaO composite exhibited superior overall properties; its yield strength, elongation, and annual corrosion rate after immersion (21 d) were 334.9 MPa, 8.9 %, and 1.06 mm/y, respectively.

Hydrogen permeation behavior of X80 pipeline steel under alternating wet-dry environment in the South China Sea

The riser sections of offshore pipelines are subject to cathodic potentials, alternating wet-dry (AWD) cycles and stresses in the service environment. The hydrogen permeation of X80 offshore pipeline with different cathodic potentials, dry/wet ratios, and constant tensile stress in AWD environment were investigated by the self made experimental equipment, which includes the three modules, i.e., the constant stress loading, the two-component cell hydrogen permeation, and AWD environment. Results showed that hydrogen permeation current fluctuates with the AWD, which is different from that in the bulk solution. In one AWD cycle, the permeation increases in the wetting stage and decreases in the dry stage. The smaller the dry/wet ratio, the longer the hydrogen permeation current keeps high level which is caused by the dense corrosion product layer. The hydrogen permeation currents in the elastic stress are greater than those in the plastic deformation, and unstressed conditions is the smallest.

Molecular to macrofossils indicating last millennium sea level in Lavsa saltpans, Croatia

Intertidal salt production sites existed continuously around the Mediterranean since classical antiquity, and their remains are present in large numbers along the Dalmatian (east Adriatic) coast. Most of them are preserved and dated to medieval times. This study aims to develop complementary proxies identifying the salt production layer in submerged ancient saltpans of Lavsa, a remote island on the central Dalmatian coast, to date the saltwork units by optically stimulated luminescence (OSL) and use them to infer changes in sea level. The significance of the study is in the application of molecular fossil analyses identifying the hypersaline layer in the sediments from a core drilled in the saltpan's site. The molecular fossil analyses correlate with the results of micro and macrofossil analyses and geochemical findings, all representing the saltwork unit. The depth of the hypersaline layers and the OSL dates provide relative sea level (RSL) lower limiting points of −145 ± 5 cm at 1309 ± 33 CE, probably the time when salt production started in Lavsa, and −115 ± 5 cm at 1364 ± 52 CE when saltwork activities ended. These limiting points extend the known RSL index point in Lavsa Island of −92 ± 8 cm, with an updated average age of 1337 ± 62 CE, correlating with the historical records. Medieval lower sea levels were also observed in the northern and southern parts of the east Adriatic coast as well as in other parts of the Mediterranean, probably driven by climate-related events, generating centennial-scale fluctuations in past sea levels that cannot be predicted by glacial isostatic adjustment (GIA) models.

Research on oil well production analysis based on long-term slow-release tracer

Abstract Downhole monitoring the production profile is crucial for the development of oil and gas reservoirs. Currently, the commonly methods for monitoring the production profile include logging tools and using tracer monitoring. The tracer monitoring method is more popular in oil field operations due to its wide applicability, simple process, low cost, low risk, and long monitoring time. However, compared to traditional logging tool monitoring methods, tracer monitoring has drawbacks such as data lag, difficulty in downhole installation, and unstable long-term effects. Bohai Oilfield has developed a new type of solid tracer and solved the problem of downhole installation by improving the structure of the downhole screen tube. This tracer uses polymer material as the skeleton. After entering the designated position, the internal tracer can slowly diffuse into the solvent through the pores in the skeleton, achieving slow release and long-term monitoring of the production profile of the oil well. In 2023, this new type was first applied in the D6 well in Bohai Sea, and a half month stable production stage liquid production profile was obtained through sampling. The monitoring results showed that: (1) Solid slow-release tracer monitoring technology can continuously obtain production layer information in complex environments and can be used for short-term rapid water exploration and long-term water production monitoring, identifying water breakthrough time and main water breakthrough location, (2) The distance between water injection well and D6 production wells is small, and the water injection volume in the injection wells is large. The tracer monitoring results show that there is a certain degree of water flooding in all 6 sections of each test layer, (3) The first test layer is the main liquid production section, the first and sixth test layers are the main oil production sections, and the first and second test layers are the main water production sections. The research results can determine the oil and water production situation of each section of oil well, identify the water breakthrough time and water outlet position, and provide a basis for the next development adjustment.

Multiscale model for concrete cured under geothermal environment: Theoretical analysis and experimental validation

Concrete poured as linings of geothermal tunnel would deviate normal curing condition. A multiscale model based on continuum micromechanics, accounting for temperature-dependent factors, is established from the cement paste level to the concrete level. This model predicts the physical properties and compressive strength of concrete and is validated against measured strength, which incorporates the impact of high-temperature curing on the hydration degree, density of C-S-H, and chemical shrinkage of cement. Evolutions of the average hydration degree and compressive strength of concrete were experimentally investigated to this end, and then simulated with multiscale approach. The specimens were subjected to curing temperature 20°C, 40°C, 60°C, and 80°C for first 7 days while maintaining constant relative humidity of 100 %, and then water curing at 20°C for the rest days till tests. The high-temperature curing accelerates the hydration process, but the variance in hydration degree between standard temperature (20°C) and high-temperature conditions diminishes with prolonged water curing. An enhancement in compressive strength is also observed in the early stages of high-temperature curing, succeeded by a decline compared with standard curing after the 50th curing day. Quantitative analysis reveals that volume fractions of hydrates and porosity subjected to high-temperature curing show a substantial increase in the first 7 curing days, and the denser layer of hydration products formed on cement slows down the hydration in later curing ages. The complex evolution of strength in concrete undergoing high-temperature curing is influenced by temporal consideration (the hydration degree) and spatial considerations (the density of C-S-H and the chemical shrinkage of cement). The surge in hydration significantly contributes to strength promotion in early stages. However, the pivotal factor leading to strength deterioration is the increase of porosity when the difference in the hydration degree is less than 0.065.

Dissolution Behaviors of Recycled Cement Paste and Lime in EAF Slag Under Static Conditions

AbstractRecycled cement paste (RCP) is a CaO-rich resource that is recycled from waste concrete and waste cement. For reducing environmental impact and promoting comprehensive resource utilization, RCP could partially replace lime as flux in electric arc furnace (EAF) steelmaking process. In this study, the dissolution behaviors of RCP and lime in EAF slag at 1400 °C and 1500 °C were investigated using static dissolution experiments. The measured dissolution rate constant of lime at 1400 °C and 1500 °C is 3.12×10−5 and 8.42×10−5 m/s, respectively, while that for RCP is 1.37×10−4 and 2.91×10−4 m/s, respectively. For the lime dissolution, a dense dicalcium silicate (C2S) product layer was generated at the dissolution interface, with the diffusion of Ca2+ in the C2S layer being the limiting step for the lime dissolution. However, for the RCP dissolution, no product layer was observed at the dissolution interface. Instead, a dissolution intermediate layer forms due to slag penetration. During the dissolution of RCP, Ca2+ and SiO44− diffuse from RCP layer to slag, while Fe2+ and AlO45− diffuse from slag to RCP layer accumulating in the dissolution intermediate layer. Furthermore, a dissolution model was developed based on current experimental results, which helps to predict dynamic dissolution process of lime and RCP in EAF slag. In general, the dissolution rate of RCP in EAF slag was much higher than that of lime, partially adding RCP as flux in EAF could accelerate the liquid slag formation in EAF steelmaking process.

(Un)deserving victims: the race-gender-geopolitics nexus of migration discourses in Poland

ABSTRACT What makes some displaced populations deserving protection more than others? I discuss this complex problem in a critical analysis of discursive narratives, presented by Polish authorities about the situation on its two Eastern borders between 2021 and 2023. I propose the race-gender-geopolitics nexus of intersectional analysis to reveal how and why migrants on the Polish-Belarusian border were presented as threatening and ingenuine as asylum-seekers, and Ukrainians became real ‘war refugees’. While the identified narratives corresponded with the existing studies on the influence of race and gender on perceived deservingness and victimisation, considering geopolitics offers a novel, context-specific analytical layer of discourse production. I thus move beyond the ‘deserving/undeserving’ binary, complicating the picture with other groups of displaced people, often silenced in the analysed representations. I demonstrate how the widespread post-colonial, racializing and patriarchal attitudes have been intertwined with regional geopolitical goals and relations with neighbouring countries. For Poland, these are the aspirations to anchor its position within the West, as well as its complicated history with Russia and Belarus but also Ukraine. I argue that all of that, coupled with the long-standing antimigrant attitudes, resulted in particular discourses about the incoming people.

USING THE INTEGRAL INDICATOR TO DETERMINE TI-ZR PRIORITY AREAS OF PLACERS

The article presents the author’s method of selection of priority areas of Ti-Zr placers using an integral indicator. As you know, the integral indicator is the ratio of the total beneficial effect from the development of the deposit to the total costs of operation, it is calculated as the difference between the value of conventional ilmenite (according to the US Geological Survey) (Mineral Commodity..., 2023) and the cost of obtaining overburden and processing the productive layer. Based on the methodology developed and presented in the article, an experiment was conducted on the data of one of the placer deposits located within the Ukrainian placer sub-province. It is proposed to develop it in small blocks that ensure high productivity, minimal impact on the environment and allow replenishment the mineral and raw material base of the titanium industry of Ukraine. This technique can be used at any deposit of titanium-zirconium ores both in Ukraine and abroad.

Insight into the effect of oxygen content on the corrosion behavior of X70 pipeline steel in a typical simulated soil solution by dissolution-diffusion-deposition model

In this work, traditional experimental methods were employed to investigate the effect of dissolved oxygen (DO) on the corrosion behavior of X70 pipeline steel in a low-temperature acidic-bentonite simulation soil solution. A novel model was utilized to describe the complex dissolution-diffusion-deposition process at the metal/solution interface. This model aims to enhance comprehension of the dynamics of the corrosion product layer of X70 pipeline steel under varying oxygen concentrations, as well as the effects of alloying elements (Fe, Cr and Cu) on the corrosion resistance. By integrating traditional experimental methods with calculation models, the results reveal a positive correlation between DO levels and the corrosion rate X70 pipeline steel. This relationship is attributed to the distinct characteristics of the corrosion product layers formed under different DO conditions. At low DO levels, the nucleation and growth rates of oxide/hydroxide are slower, leading to the formation of a denser, more protective corrosion product layer. Conversely, at high DO levels, the accelerated nucleation and growth rates produce larger oxide/hydroxide particles, resulting in a porous and less protective corrosion product layer. Furthermore, the variation in the protective qualities of the corrosion product layers under different DO conditions causes differences in corrosion morphology: X70 pipeline steel exhibits localized corrosion in low DO environments and more uniform corrosion under high DO conditions.

Chloridizing roasting studies of spent NdFeB magnets for recovery of rare earth values

The increased demand for rare earth elements in advanced technological applications and supply shortages call for metal recovery from secondary sources. Permanent magnet (Nd2Fe14B or NdFeB) may serve as a potential secondary source due to its high rare earth (Nd+Pr+Dy: ∼30 %) content and its vast application. The present study utilizes a chloridizing roasting (CaCl2.2 H2O) pre-treatment process followed by water leaching, acid leaching (0.5 M HCl, S/L =1/10 g/ml, 90 °C, 3 h), oxalic acid precipitation and calcination (850 °C, 2 h) to obtain mixed rare earth oxides. The process was optimized based on temperature (400–700 °C), dosage (CaCl2.2H2O: NdFeB=0.5:1–2.5:1), and time (30–120 min) on the rare earth dissolution. The theoretical activation energy for the chloridizing roasting process is estimated as 22.3 (OFW) and 16.7 kJ/mol (KAS), while the experimental activation energy for Nd and Dy dissolution was determined to ∼29.3 and ∼17.7 kJ/mol, respectively depicting product layer diffusion-controlled kinetics. Higher dosages of CaCl2.2H2O (1.5:1 and 2:1) favored NdOCl formation, thereby, higher dissolution; however, further higher dosage (2.5:1) leads to reduced Nd dissolution due to higher CaO formation and acid consumption by Ca during leaching. Incomplete oxidation at lower temperatures (400 °C) and iron dissolution impair the Nd dissolution and selectivity. Excessive oxidation at >700 °C favors the formation of NdFeO3, decreasing Nd dissolution. The maximum dissolution of Nd was ∼89 %, while for Dy, it was ∼88 % at optimum conditions of 600 °C, 90 min, 2:1. Water leaching post-roasting leads to ∼87 % Ca removal and the precipitation efficiency of rare earth oxalates was 99 %. The overall extraction for rare earth elements was ∼89 %, and 1 kg of NdFeB powder can yield ∼285 g of rare earth oxides (∼239 g Nd2O3, ∼14 g Dy2O3) with 96 % purity. Further, this study demonstrates that using CaCl2.2 H2O as a solid chlorinating agent in chlorination roasting enhances recovery rates of mixed rare earth oxides while providing a safer and more environment-friendly alternative for industrial applications.

Fluid depth-dependent biofilm characteristics and their influence on sulfate-reducing bacteria-induced corrosion of carbon steel

This study investigates the response of biofilm characteristics to variations in fluid depth and their influence on the corrosion behavior of carbon steel (C1020) under low-flow fluid conditions, utilizing Desulfovibrio vulgaris. The experiments were conducted in an anaerobic chamber at 30 °C, utilizing modified Baar's medium as the testing medium. The findings reveal that fluid depth significantly impacts biofilm-corrosion product composite formation, with deeper depths promoting thicker and more heterogeneous biofilm-corrosion product layer compared to shallower depths, where a thinner and more uniform biofilm-corrosion product layer is observed. Moreover, the characteristics of initially attached biofilms was verified as the primary factor affecting subsequent corrosion behavior during prolonged exposure. Corrosion analysis reveals that greater fluid depth leads to increased weight loss (91 ± 13.2 mg/cm2) and deeper pit depths (540 ± 69 μm), surpassing those observed in shallower test media (21 ± 2.3 mg/cm2 and 105 ± 17 μm) after 28 days of exposure. The corrosion products within the biofilm were predominantly FeS and Fe3(PO4)2·8H2O. A direct relationship was observed between the thickness of this biofilm-corrosion product layer and the progression of pit depth, suggesting a strong correlation between carbon steel corrosion and biofilm development in limited fluid depths (e.g., 5–15 mm). Furthermore, a significant association between the deepest pits (average) and the number of sessile cells within the biofilm underscores the pivotal role of sessile cell numbers in carbon steel corrosion.

Dissolution and intrusion of chloride disrupted biodegradation products to persistently accelerate biodegradation of Fe-based implants

The biodegradation of Fe is severely limited due to barrier of biodegradation products. Herein, NaCl was introduced into Fe matrix and results demonstrated that NaCl significantly accelerated biodegradation rate of Fe. It was ascribed that (i) NaCl in Fe matrix initially dissolved to produce biodegradation active sites, (ii) Cl- with small ionic radii invaded the biodegradation product layer, and (iii) abundant Cl- greatly promoted the anode process of Fe biodegradation. Additionally, Fe-NaCl biocomposites also exhibited favorite cytocompatibility. These results demonstrated great potential of NaCl in accelerating the persistent biodegradation of Fe for load-bearing implants.

Seasonal and interspecific variations in the water uptake depth of trees in a moist cool-temperate mixed forest in Japan

ABSTRACT The water uptake depth of trees affects their overall water use and the water cycle of forest ecosystems. However, empirical data on the depth from which water is drawn are lacking for many moist forests. In this study, we estimated the water uptake depths of 24 coexisting tree species in a moist cool-temperate mixed forest in Japan using stable oxygen isotopes. Our goal was to clarify the factors influencing water uptake depth including season, species, slope position, and tree height under moist conditions. Water uptake depth was determined during three periods in which temperatures differed but soil moisture levels remained similar. Season was shown as one of the factors affecting water uptake depth, which was shallowest in August, when temperatures reached maximum values, and deepest during May, when temperatures were lowest. This seasonal variation is likely to be related to physiological processes such as increasing transpiration which leads to water uptake shifting to the water-rich shallow soil layer and/or activation of fine root production at the soil surface, where temperatures are high. Water uptake depth also varied with tree species, suggesting the occurrence of belowground resource segregation among moist forest tree species. Slope position and tree height did not affect water uptake depth. This study highlights the importance of considering temperature-driven physiological processes when examining water uptake depth in moist forests, which could have implications for predicting the responses of these ecosystems to climate change.