Higher Aggregate Stability Research Articles

Development of a demulsifier and technological process study for the preparation of highly viscous heavy oils for refinement

One of the challenges in the petroleum industry is the production of highly viscous heavy oils, often accompanied by undesirable emulsion formation with very high aggregate stability. To prepare the crude oils for refinement, the oils must be destroyed. The destruction of aqueous emulsions containing highly viscous heavy oils is an intricate task owing to the comparatively small disparity in water and oil densities, as well as the high viscosity of the dispersive medium and its high content of mechanical impurities. The problem of the destruction of petroleum emulsions arises desperately during the desalination and dehydration of crude oils with a high content of emulsifiers (resins, asphalts, paraffin, etc.) The creation of a highly efficient demulsifier and the development of an optimal technological process for the preparation of highly emulsifying oils that are distinguished by the composition and quantity of emulsifiers of West Siberian oils, which are widely refined in Russia, are the ways to resolve this challenging and timely issue. This study focuses on the viscous heavy oil of the Verbliouje deposit in the Astrakhan region. It also explains the creation of an effective demulsifier for the destruction of petroleum emulsions characterized by a very high emulsifying power and the fundamental principles of the development of deep dehydration technology and desalination of such high-viscosity heavy oils.

Insulin Stabilization Designs for Enhanced Therapeutic Efficacy and Accessibility.

ConspectusInsulin has remained indispensable in the treatment of diabetes since it was first discovered in 1921. Unlike small molecular drugs, insulin and other protein drugs are prone to degradation when exposed to elevated temperatures, mechanical agitation during transportation, and prolonged storage periods. Therefore, strict cold-chain management is crucial for the insulin supply, requiring significant resources, which can limit the access to insulin, particularly in low-income areas. Moreover, although insulin formulations have advanced tremendously in the last century, insulin treatment still imposes a challenging regimen and provides suboptimal outcomes for the majority of patients. There is an increasing focus on pursuing improved pharmacology, specifically on safer, more user-friendly insulin therapies that minimize the self-management burden. These challenges underscore the need for developing novel insulin formulations with improved stability that are compatible with advanced insulin therapy.Insulin stabilization can be achieved through either chemical modification of insulin or formulation component design. Inspired by insulin-like peptides from invertebrates, we have developed novel stable insulin analogs based on a fundamental understanding of the insulin receptor engagement for insulin bioactivity. We created a novel four-disulfide insulin analog with high aggregation stability and potency by introducing a fourth disulfide bond between a C-terminal extended insulin A-chain and residues near the C-terminus of the B-chain. In an effort to stabilize insulin in its monomeric state to develop ultrafast-acting insulin with rapid absorption upon injection, we have developed a series of structurally miniaturized yet fully active insulin analogs that do not form dimers due to the lack of the canonical B-chain C-terminal octapeptide. Additionally, our study provided strategies for expanding the scope of cucurbit[7]uril (CB[7])-assisted insulin stabilization by engineering safe and biodegradable CB[7]-zwitterionic polypeptide excipients. We also explored insulin N-terminal substitution methods to achieve pH-dependent insulin stabilization without prolonging the duration of action.This Account describes our exploration of engineering stable insulin analogs and formulation design strategies for stabilizing insulin in aqueous solutions. Beyond conventional stabilization strategies for insulin injections, the unmet challenges and recent innovations in insulin stabilization are discussed, addressing the growing demand for alternative, less invasive routes of insulin administration. Additionally, we aim to provide a thorough overview of insulin stabilization from the perspective of commercially available insulin drugs and common pharmaceutical engineering practices in the industry. We also highlight unresolved insulin stabilization challenges and ongoing research strategies. We anticipate that further emphasis on collective efforts of protein engineering, pharmaceutical formulation design, and drug delivery will inform the development of stable and advanced insulin therapy.

Effect of Soil Amendments on the Aggregate Stability, Biological Activity, and Yield of Canola (Brassica napus L.) in Degraded Soils

ABSTRACT Recycling organic waste and water treatment residues in nanoform is a promising technology in various farming systems, and its effect on aggregate stability, biological activity, and canola production in degraded soils is largely unknown. Hence, we evaluated the effect of nano-biochar (nB) and nano-water treatment residues (nWTR) at levels 50, 100, and 250 mg kg−1 as compared to soil without amendments on the aggregate stability, biological activity, and canola yield in degraded soil. The results showed that the structure coefficient (SC) values are higher when nB and nWTR are added at 100 mg kg−1 soil than at levels 50 and 250 mg kg−1. In our study, the high aggregate stability in the soil treated with nB and nWTR is likely due to their higher content of nutrients, organic carbon, clay, and CEC. The seed weight of the canola plant increased with increasing nB by more than 64%, while it decreased with increasing nWTR. Microbial biomass carbon (MBC) and the activity of dehydrogenase (DHA) and catalase (CLA) increased significantly in the treated pots with the addition of nB and nWTR at various rates. The results of the pot experiment recommended that the applications of nWTR and nB could be used as a promising strategy to improve soil quality and crop yield while also increasing the recycled efficiency of WTR and rice straw.

Soil aggregate stability index independent from pre-stress aggregate size distribution: A test from soils affected by the water level fluctuation in the Three Gorges Reservoir, China

Soil aggregate stability measurement is essential to determine soil health status under various conditions. The Mean Weight Diameter (MWD) is the most applied index to express aggregate stability particularly for wet and dry sieving. However, the MWD could generally present results affected by pre-stress aggregate size distribution when remained aggregates after stress are considered for calculation. Therefore, the objective of the present study was to eliminate the similarities between the MWD results and pre-stress aggregate size distribution, which largely affects treatments differentiation. Samples from 145-160 m (lower), 160–169 m (middle), and 169–175 m (upper) elevations differently affected by the Water Level Fluctuation in Three Gorges Reservoir (TGR) and control (>175 m) were exposed to wet shaking stress. Aggregates remained at each sieve opening, aggregates disintegrated/passed through the sieve opening, and small macroaggregates and microaggregates accumulated were recorded. These aggregates were used to determine and compare two indexes (1) using remained aggregates (MWD) and (2) using disintegrated/accumulated aggregates (MWDd/a) based on the differences among treatments. The results for both pre-stress aggregates and remained aggregates after stress were showed consistent significant differences (p < 0.05) between upper and control elevations. This gives indication that aggregates remained after stress strongly depend on pre-stress aggregate size distribution. As the MWD was calculated from remained aggregates, the identified difference between upper and control elevations for this index could also confirm its dependence to pre-stress aggregates distribution. Contrary, disintegrated and accumulated aggregates showed non-significant differences between upper and control elevations. This non-significant and significant differences between upper and control elevations for disintegrated and pre-stress aggregates suggest a non-dependence condition. Similarly, the upper and control elevations showed no significant differences in MWDd/a. This substantially informs that this index is independent from pre-stress aggregates distribution because it was entirely calculated from disintegrated aggregates. Higher aggregate stability was indicated by high MWD, with values ranging from 1.41 to 6.24 mm. On the other hand, higher stability was expressed by lower values of the MWDd/a, with the values varying between 3.87 and 0.5 mm. Overall, the present study evidenced the major advantage of considering the disintegrated/accumulated than remained aggregates in calculating unbiased MWD index for aggregate stability.

Influence of cover crops on soil aggregate stability, size distribution and related factors in a no-till field

Soil aggregation plays an essential role in maintaining soil structure. A three-year field experiment was undertaken to explore the effects of cover crops on soil aggregate stability indices (mean weight diameter, water-stable aggregates greater than 0.25 mm, and soil erodibility factor), size distribution and their correlations with nine soil physical and chemical properties (soil bulk density, pH, organic carbon, total nitrogen, C/N, calcium, phosphorus, potassium, and cation exchange capacity) at 0–5 and 5–10 cm depths in a Marietta silt loam soil in a no-till field, Northeastern Mississippi. The cover crop treatments included elbon rye (Secale cereale L.), daikon radish (Raphanus sativus ssp. acanthiformis), Austrian winter field peas (Lathyrus hirsutus), and their mixture. The samples were wet-sieved to five size classes of aggregates (> 2, 2–1, 1–0.5, 0.5–0.25, and < 0.25 mm). Results showed that the < 0.25 mm aggregates dominated (50.95–78.02 %) soil aggregate size distribution at 0–5 and 5–10 cm depths. The rye plot soil displayed the greatest values for mean weight diameter (0.58 mm) in the two soil depths. Soil water-stable aggregates greater than 0.25 mm value under peas was significantly higher by 68.61 % compared to the no cover crop treatment at 0–5 cm depth, while soil erodibility factor did not change significantly. Mean weight diameter, water-stable aggregates greater than 0.25 mm, soil erodibility factor, 1–0.5 mm aggregates, and < 0.25 mm aggregates were significantly correlated with soil organic carbon, pH, bulk density, phosphorus, and potassium. The dominant factors driving changes in three aggregate stability indices and size fractions (excluding 2–1 mm aggregates) were bulk density and pH. Furthermore, high pH restricted soil aggregate stability and size distribution. This study demonstrated the positive impact of cover crops, specifically peas and rye, on soil aggregate stability and size distribution. This study will provide valuable information for future research on soil stabilization in crop production management systems.

Water-born polyurethane dispersions, containing polysaccharide in their structure

A method of obtaining waterborn polyurethane dispersions containing the natural polysaccharide starch, stable over time and when diluted with water, has been developed by introducing an aqueous solution of starch into the reaction system with a combination of the chain elongation stage and the dispersion process, which is manifested in the high aggregative stability of the dispersions and the ability to form monolithic films, in contrast to mechanical mixtures. Materials acquire the ability to degrade in environmental conditions while maintaining the properties inherent in traditional ionomer polyurethanes. The use of the created method opens up opportunities for the creation of environmental-friendly materials with a given set of properties, promising as physiologically active materials for agriculture, in particular antiperspirants, phytoprotective and growth stimulating materials.

Soil aggregate stability governs field greenhouse gas fluxes in agricultural soils

Agriculture is responsible for 30–50% of the yearly CO2, CH4, and N2O emissions. Soils have an important role in the production and consumption of these greenhouse gases (GHGs), with soil aggregates and the inhabiting microbes proposed to function as biogeochemical reactors, processing these gases. Here we studied, for the first time, the relationship between GHG fluxes and aggregate stability as determined via laser diffraction analysis (LDA) of agricultural soils, as well as the effect of sustainable agricultural management strategies thereon. Using the static chamber method, all soils were found to be sinks for CH4 and sources for CO2 and N2O. The application of organic amendments did not have a conclusive effect on soil GHG fluxes, but tilled soils emitted more CO2. LDA was a useful and improved method for assessing soil aggregate stability, as it allows for the determination of multiple classes of aggregates and their structural composition, thereby overcoming limitations of traditional wet sieving. Organic matter content was the main steering factor of aggregate stability. The presence of persistent stable aggregates and the disintegration coefficient of stable aggregates were improved in organic-amended and no-tilled soils. Predictive modelling showed that, especially in these soils, aggregate stability was a governing factor of GHG fluxes. Higher soil CH4 uptake rates were associated with higher aggregate stability, while CO2 and N2O emissions increased with higher aggregate stability. Altogether, it was shown that sustainable agricultural management strategies can be used to steer the soil's aggregate stability and, both consequently and outright, the soil GHG fluxes, thereby creating a potential to contribute to the mitigation of agricultural GHG emissions.

Soil organic matter and aggregate stability dynamics under major no-till crop rotations on the Canadian prairies

There is a need to develop and adopt novel, more resilient, or “climate-smart” cropping strategies on the Canadian prairies, which are crucial for sustainable agroecosystem management. To examine how crop rotation influences soil organic matter and aggregate stability (AS) dynamics, six crop rotations: (i) conventional (control), (ii) pulse/oilseed intensified, (iii) diversified, (iv) market-driven, (v) high-risk and high-reward, and (vi) soil health-enhanced were established in 2018 at three field sites: Lethbridge, Alberta and Swift Current and Scott, Saskatchewan under no-till management. After 4-year, soil organic carbon (SOC), total nitrogen (TN), particulate organic matter carbon (POM-C) and nitrogen (POM-N), or mineral-associated organic matter C (MAOM-C) and N (MAOM-N) concentrations were not significantly affected by crop rotation in the 0–7.5 cm soil depth. However, crop rotation significantly altered AS at two of three sites, with both soil health-enhanced and high-risk and high-reward rotations having the highest AS at Lethbridge and Swift Current. Across all three sites, strong positive correlations were found among SOC, TN, MAOM, and AS. Moreover, MAOM-C and MAOM-N showed stronger relationships with AS than POM, perhaps suggesting a positive feedback loop on the stability of SOC and aggregation. Overall, the inclusion of pulses in rotations showed the potential to sustain soil quality, likely by offsetting low residue quantity with better residue quality and diversity, thereby supporting SOC accrual and AS similar to or greater than conventional cereal- or oilseed-dominated rotations.

Broadleaf Trees Increase Soil Aggregate Stability in Mixed Forest Stands of Southwest China

In soils, high aggregate stability often represents higher quality and anti-erosion ability; however, few studies have systematically analyzed how different forest stands affect soil aggregate stability. We selected five typical mixed forest stands on Jinyun Mountain in Chongqing, China, as research sites to evaluate soil aggregate stability. Within these sites, we analyzed the factors influencing soil aggregate stability in different stands by measuring soil characteristics and root traits. Soil aggregation stability, plant root traits, and soil properties varied among the mixed forest stands. The broadleaf tree mixed forest improved soil aggregate stability by 57%–103% over that of the Pinus massoniana mixed forest. The soil organic carbon, cation exchange capacity, Fe-Al oxides, and fine root proportion were positively correlated with soil aggregate stability. The specific root length and very fine root proportion were negatively correlated with soil aggregate stability, whereas the fine root proportion was positively correlated with this property. Specifically, we found that arbuscular mycorrhizal fungi did not affect soil aggregate stability in acid rain areas. Structural equation modeling indicated that soil aggregate stability was closely related to soil physicochemical properties and plant root characteristics. Predictive factors accounted for 69% of the variation in mean weight diameter, and plant root traits influenced soil aggregate stability by affecting soil organic matter, texture, and Fe-Al oxides. This study elucidated the impact of soil physicochemical properties and plant root characteristics on soil aggregate stability in different forest stand types, which has crucial implications for optimizing the management of various forest types.

Response of soil aggregate stability to plant diversity loss along an inundation stress gradient in a reservoir riparian zone

Dam-triggered periodic wetting and drying has increased the disintegration of soil particles in riparian areas. Most studies in this field have primarily explored the effects of vegetational characteristics on soil stability. However, the impact of plant diversity loss on the soil aggregate stability under periodic inundation stress remains unclear. This study investigated the relevant plant characteristics, root traits, and soil physicochemical properties in a typical riparian ecosystem along a hydrological stress gradient. Data-driven models were used to quantify the paths influencing soil aggregate stability through root traits under heterogeneous inundation stress. The findings showed that as inundation stress intensified, there was an overall decline in plant community diversity and soil aggregate stability in this riparian zone. Perennial herbs with fibrous root systems, as the dominant species, played an essential role in the subsurface soil aggregate stability under intense inundation stress, in contrast to the critical role of plant diversity under weak inundation stress. Moreover, the results revealed that root volume density and macroaggregate carbon content mediated the effects of plant diversity on riparian soil stability. Overall, the results suggest that suitable plants with high root volume density benefit essential soil aggregate stability under well-documented inundation effects in riparian zones.

Land use effects on surface runoff and soil erosion in a southern Alpine valley

In mountain regions, soil landscapes are highly vulnerable against soil loss. Moreover, these environments are particularly affected by land use changes, which influence soil properties and related processes like surface runoff generation and soil erosion. These processes are in turn amplified by extreme climatic events and intensive geomorphological dynamics. The objective of this study is to quantitatively assess the effects of land use changes on surface runoff and soil erosion in a southern Alpine valley (Onsernone valley, Switzerland) characterized by a former intense land use followed by a progressive abandonment in the last decades. Surface runoff and related sediment transport has been analysed under controlled and reproducible conditions using a portable rainfall simulator device (1 m2). The results show a statistically significant increase in surface runoff when the soil gets water repellent reducing the surface infiltration capacity and generating preferential flow paths, which prevent a homogeneous wetting of the soil. However, the documented high sensitivity of surface runoff to land use changes does not result in an equally high sensitivity to soil erosion processes. Instead, soils display a high aggregate stability leading to very low sediment transports except for abandoned and reforested agricultural terraces. There, the lack of maintenance and progressive collapse of terrace dry walls locally increase slope angles and directly exposes the soil to atmospheric agents and surface runoff, which causes soil erosion rates beyond the customary natural level.

Synthesis of Chitosan-Silver Nanocomposite and Its Evaluation as an Antibacterial Coating for Mobile Phone Glass Protectors.

An easy and environment-friendly route for antibacterial coating suited for mobile phone glass protectors was successfully demonstrated. In this route, freshly prepared chitosan solution in 1% v/v acetic acid was added with 0.1 M silver nitrate solution and 0.1 M sodium hydroxide solution and incubated with agitation at 70 °C to form chitosan-silver nanoparticles (ChAgNPs). Varied concentrations of chitosan solution (i.e., 0.1, 0.2, 0.4, 0.6, and 0.8% w/v) were used to investigate its particle size, size distribution, and later on, its antibacterial activity. Transmission electron microscope (TEM) imaging revealed that the smallest average diameter of silver nanoparticles (AgNPs) was 13.04 nm from 0.8% w/v chitosan solution. Further characterizations of the optimal nanocomposite formulation using UV-vis spectroscopy and Fourier transfer infrared spectroscopy were also performed. Using a dynamic light scattering zetasizer, the average ζ-potential of the optimal ChAgNP formulation was at +56.07 mV, showing high aggregative stability and an average ChAgNP size of 182.37 nm. The ChAgNP nanocoating on glass protectors shows antibacterial activity against Escherichia coli (E. coli) at 24 and 48 h of contact. However, the antibacterial activity decreased from 49.80% (24 h) to 32.60% (48 h).

Biological soil crusts decrease infiltration but increase erosion resistance in a human-disturbed tropical dry forest.

Under continuous human disturbance, regeneration is the basis for biodiversity persistence and ecosystem service provision. In tropical dry forests, edaphic ecosystem engineering by biological soil crusts (biocrusts) could impact regeneration by influencing erosion control and soil water and nutrient fluxes, which impact landscape hydrology, geomorphology, and ecosystem functioning. This study investigated the effect of cyanobacteria-dominated biocrusts on water infiltration and aggregate stability in a human-modified landscape of the Caatinga dry forest (NE Brazil), a system characterized by high levels of forest degradation and increasing aridity. By trapping dust and swelling of cyanobacterial filaments, biocrusts can seal soil surfaces and slow down infiltration, which potentially induces erosion. To quantify hydraulic properties and erosion control, we used minidisc-infiltrometry, raindrop-simulation, and wet sieving at two sites with contrasting disturbance levels: an active cashew plantation and an abandoned field experiencing forest regeneration, both characterized by sandy soils. Under disturbance, biocrusts had a stronger negative impact on infiltration (reduction by 42% vs. 37% during regeneration), although biocrusts under regenerating conditions had the lowest absolute sorptivity (0.042 ± 0.02 cm s-1/2) and unsaturated hydraulic conductivity (0.0015 ± 0.0008 cm s-1), with a doubled water repellency. Biocrusts provided high soil aggregate stability although stability increased considerably with progression of biocrust succession (raindrop simulation disturbed: 0.19 ± 0.22 J vs. regenerating: 0.54 ± 0.22 J). The formation of stable aggregates by early successional biocrusts on sandy soils suggests protection of dry forest soils even on the worst land use/soil degradation scenario with a high soil erosion risk. Our results confirm that biocrusts covering bare interspaces between vascular plants in human-modified landscapes play an important role in surface water availability and erosion control. Biocrusts have the potential to reduce land degradation, but their associated ecosystem services like erosion protection, can be impaired by disturbance. Considering an average biocrust coverage of 8.1% of the Caatinga landscapes, further research should aim to quantify the contribution of biocrusts to forest recovery to fully understand the role they play in the functioning of this poorly explored ecosystem.

SYNTHESIS AND PROPERTIES OF POLYMER SUSPENSIONS OBTAINED BY HETEROPHASE POLYMERIZATION IN THE PRESENCE OF α,ω BIS[3 GLYCIDOXYPROPYL]POLYDIMETHYLSILOXANE

Polymeric microspheres with glycidoxy groups on the surface can be used as bioligand carriers in diagnostic test systems. However, the possibility of synthesizing aggregatively stable functional polymeric microspheres in a wide range of diameters is an urgent problem of modern polymer chemistry. This article is devoted to a systematic study of the kinetics of styrene and methyl methacrylate polymerization in the presence of an organosiloxane surfactant with terminal glycidoxy groups – α,ω-bis[3-glycidoxyproopyl]-polydimethylsiloxane, PDMS(CHOCH2). The article shows the influence of phases volume ratio, initiator and surfactant concentration, synthesis temperature and pH of initial medium on the properties of polymer suspensions (their aggregative stability, monodispersity, particle diameter). The formation of polymer-monomer particles during polymerization has been studied and it has been shown that polymer suspensions retain high aggregation stability from early period of monomer conversion, and the particle diameter changes untill 30% of the monomer conversion. Due to the high surface activity of the organosiloxane surfactant used and its incompatibility with the resulting polymer, aggregatively stable functional polymer suspensions with diameters from 0.09 to 1.1 μm were obtained by a single-stage synthesis. Studies of the hydration degree of polymer microspheres have shown that the presence of functional glycidoxy groups on their surface ensures the formation of a hydration shell, which increases the stability of polymer particles, and also makes it possible to use the resulting microspheres as carriers of bioligands. Thus, the use of water-insoluble organosiloxane surfactants as stabilizers for the heterophase polymerization of vinyl monomers makes it possible to synthesize aggregatively stable functional polymer suspensions in a wide range of diameters. The use of organosiloxane surfactants with various functional groups expands the range of functional polymer microspheres used in various fields of application.

Drip Irrigation at a Soil Water Suction of 30 kPa Helps AMF and GRSP to Enhance Greenhouse Macro-Aggregates

Drip irrigation is fundamental in water-saving agricultural greenhouses, especially in tomato (Solanum lycopersicum L.) greenhouses. However, a long-term drip irrigation has been observed to be associated with soil degradation, concerning both soil aggregate structure and soil microbial community. To evaluate how drip irrigation scheduling influences the soil structure and arbuscular mycorrhizal fungi (AMF), a long-term irrigation experiment was carried out in a tomato greenhouse in 2011, using an irrigation program with dripping water starting when the soil reached a suction of 20 kPa (D20), 30 kPa (D30) and 40 kPa (D40). In 2017, we tested the AMF community and soil aggregate composition by soil wet sieving. Aggregates of 0.25–1 mm represented the main class of aggregates (32.4%–43.1%) in this experiment. At D30, we measured the highest mean weight diameter (MWD) and soil organic carbon (SOC) and glomalin-related soil protein (GRSP) levels. Thus, D30 promoted soil aggregate stability in the greenhouse. According to the high-throughput sequencing results of AMF, Glomus at D30 was the main factor leading to a high soil aggregate stability, because its OTU relative abundance was significantly higher than those of Ambispora and Paraglomus. Through redundancy analysis, the GRSP concentration was positively correlated with the SOC and total N (TN) levels and with the presence of the genera Ambispora, Glomus and Paraglomus. This evidenced that AMF and SOC helped to increase GRSP concentration and aggregate stability. Therefore, initiating irrigation when the soil reaches a water suction of 30 kPa could promote soil aggregate stability by favoring AMF abundance.

Short-term effects of tillage and leaf mulch on soil properties and sunflower yield under semi-arid conditions

A study was conducted at the University of Venda Experimental Farm, Limpopo province, South Africa to determine the effects of tillage and mulching on selected soil properties, and yield of sunflower (Helianthus annuus L.). The experiment was laid out in a split plot design with three replications during the 2018/19 and 2019/20 cropping seasons. Treatments consisted of conventional tillage (CT) and minimum tillage (MT) and three levels of avocado leaf mulch (0, 6 and 12 t/ha). Bulk density (BD), aggregate stability (AS), infiltration rate (IR), soil water content (SWC) and grain yield were determined. Tillage had no significant effect on BD in either season but influenced SWC and sunflower grain yield. CT recorded a significantly higher AS than MT during 2018/19 cropping season. Tillage × mulch interaction was significant during 2018/19 season with CT at 12 t/ha mulch recording higher AS than the MT. IR was significantly influenced by tillage × mulch interaction in both seasons with MT recording higher IR than the CT during 2018/19. Avocado mulch had no significant effect on sunflower grain yield in either season but influenced SWC in 2019/20 season. It was concluded that avocado mulch could be a relevant component of conservation agriculture but long-term studies are needed to validate the benefits observed in this study.

Silver Nanoparticles Stabilized with a Chitosan Shell: Physical-Chemical Properties and Features of the Toxic Effect in Vivo

The results of investigating the in-vivo toxicity and safety of colloidal solutions of chitosan–silver nanocomposites with different concentrations of Ag (0.19, 1.9 mg/mL) obtained by the “green chemistry” technique via the chemical reduction of silver nitrate with chitosan under hydrothermal conditions are presented. The synthesized samples possess high aggregative stability (the values of their ζ potential are 37.3 ± 0.2 and 43.2 ± 2.5 mV) and pronounced antimicrobial properties against Staphylococcus aureus, Salmonella dublin, and Escherichia coli (inhibition zones of 11–16 mm). It is found that the nanocomposites are not very dangerous in the case of acute intragastric administration, are relatively safe in the case of intraperitoneal administration, and do not possess dermal irritation. A hydrosol of the nanocomposite with a high concentration of silver (1.9 mg/mL) induces reversible eye irritation in laboratory animals as well as has a pronounced sensitizing action, inducing the development of an allergy by the delayed hypersensitivity mechanism.

Effects of forest types on soil carbon content in aggregate faction under climate transition zone

Variations in soil aggregates and soil organic carbon (SOC) in response to land-use change are important to understanding the carbon cycle in forest ecosystems. However, few studies investigated the effect of forest type on aggregate stability, SOC content, and particulate organic carbon (POC) content. Therefore, we collected soil and fine root samples in two natural forests (Pinus massoniana and Quercus variabilis) and a planted forest (Cunninghamia lanceolata) in a warm temperate–subtropical climate transition zone to analyze the effect of forest type on aggregate stability, SOC content, and POC content. The results showed that the mean weight diameter (MWD) of the soil aggregates was significantly higher in Quercus variabilis and Pinus massoniana forests (62% and 21%, respectively) than in the Cunninghamia lanceolata forest due to higher mycelial length density, mycelial infection rate, and glomalin content. Similarly, the SOC and POC contents were significantly higher in Quercus variabilis and Pinus massoniana forests than in the Cunninghamia lanceolata forest (p &amp;lt; 0.05). The dominant size fraction of aggregate was highly correlated with the carbon fraction content. The SOC and POC contents and fungal traits (mycelial length density, mycelial infection rate, and glomalin content) were significantly positively correlated with the MWD. These results indicated that natural forests had higher aggregate stability than planted forests due to higher SOC content and more favorable fungal traits in the warm temperate–subtropical climate transition zone.

Effects of the Preparation Method on the Dielectric Properties of Ni–Al Layered Double Hydroxides

Ni–Al layered double hydroxides (LDHs) are of interest as functional materials. The effects of preparation methods on the dielectric properties of Ni–Al layered double hydroxides were studied on samples prepared from solution (by coprecipitation and a hydrothermal process) and by plasma technology. The prepared layered structures were characterized by advanced analytical methods. The high ζ potentials of the particles prepared in suspensions evidence their high aggregation stability. X-ray powder diffraction and IR spectroscopy were used to determine the phase composition of samples and to identify the interlayer anion. The plasma between Al and Ni electrodes in distilled bulk water gives rise to the formation of Ni–Al LDHs with hydroxide ion as the interlayer anion. Thermal properties of the structures prepared were studied by thermal analysis. The results of dielectric measurements are presented.

亚热带退化森林不同恢复方式对土壤团聚体胶结物质及稳定性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 亚热带退化森林不同恢复方式对土壤团聚体胶结物质及稳定性的影响 DOI: 10.5846/stxb202204211092 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(32001298); 湖北省教育厅重点项目(D20201001); 大学生创新训练项目(S202110512085) Effects of different restoration approaches of subtropical degraded forests on bonding materials and stability of soil aggregate Author: Affiliation: Fund Project: The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:退化森林的恢复一直是林业和生态学研究的热点。良好的森林土壤结构有助于林木生长发育,作为土壤最基本的结构单元,土壤团聚体组成和稳定性是衡量土壤肥力和质量的重要指标,其团聚结构的形成依靠土壤胶结物质。然而,土壤胶结物质与团聚体稳定性之间的关系尚不确定。为探明亚热带退化森林的不同恢复方式对团聚体稳定性的影响及其潜在机制,以自然恢复的次生林为对照(CK),选取了亚热带三种常见的人工林:一代杉木林(P1)、二代杉木林(P2)和黄山松林(P3),测定土壤团聚体稳定性及其胶结物质的含量,并分析了各胶结物质对团聚体稳定性的影响。研究发现:不同森林恢复方式显著影响了土壤pH值、碳氮比、速效磷含量、团聚体的组成和稳定性。所有森林类型中,三种人工林的团聚体稳定性显著高于CK,P2的大团聚体所占比例最大,团聚体稳定性最高。恢复方式显著影响了土壤游离氧化铁含量、菌根密度和易提取球囊霉素相关土壤蛋白(EEG)含量。团聚体稳定性与游离氧化铁含量、菌根密度呈正相关,但与EEG含量呈负相关。研究结果表明,亚热带退化森林的人工恢复比自然恢复更有助于增强土壤团聚体稳定性,土壤游离氧化铁、菌根密度和EEG是显著影响团聚体稳定性的胶结物质。 Abstract:The restoration of degraded forest has been a hot topic in forestry and ecology. As a basic structural unit of soil, soil aggregate composition and stability are important indicators of soil fertility and quality, and the formation of soil aggregate relies on aggregate bonding materials. However, the relationship between aggregate bonding materials and aggregate stability is uncertain. To explore the effects of different restoration approaches of degraded subtropical forests on aggregate stability and its underlying mechanisms, we compared the secondary forest (natural restoration) as a control (CK), with three different common subtropical plantations which were: (1) first-generation Cunninghamia lanceolata (P1), (2) second-generation C. lanceolata (P2), and a Pinus. taiwanensis plantation (P3). We measured the aggregate stability and the contents of different aggregate bonding materials, and then analyzed the influence of these materials on soil aggregate stability. Results showed that forest restoration approach significantly affected soil pH, C/N, available phosphorus, as well as the composition and stability of aggregate. Among all the forests, the aggregate stability was significantly lower in CK than in the other three plantations, and P2 had the greatest proportion of large aggregates and the highest aggregate stability. The forest restoration approach also significantly affected soil free Fe oxide content, mycorrhizal density, and easily extractable glomalin-related soil protein (EEG). Aggregate stability was positively correlated with free Fe oxide content and mycorrhizal density, but negatively correlated with EEG. For subtropical degraded forests, the results indicated that artificial restoration was better than natural restoration to enhance soil aggregate stability, with soil free Fe oxide, mycorrhizal density and EEG being the main bonding materials that significantly affected the aggregate stability. 参考文献 相似文献 引证文献