Production Of High Concentrations Research Articles

Numerical Investigation of In-Cylinder Combustion Behaviors in a Medium-Speed Diesel Engine

Abstract This study aims to advance understanding of in-cylinder combustion processes in medium-speed diesel engines, which are extensively employed in heavy-duty applications where electrification proves inefficient yet remains insufficiently examined in the literature. By modeling a four-stroke engine with dimensions of 210 mm bore and 310 mm stroke, operating at 900 rpm under full load, this research identifies distinct combustion characteristics that differentiate medium-speed engines from their high-speed counterparts. Key findings illustrate that super turbocharging in medium-speed engines enhances the combustion of the fuel–air mixture under elevated temperatures and pressures. Moreover, an increased stroke length promotes gas velocity and turbulence, facilitating fuel atomization and mixing. Notably, rapid fuel ignition occurs near the nozzle due to the high temperature of compressed air, reducing the ignition delay. As a result, the premixed combustion stage nearly disappears, with diffusion combustion dominating, especially pronounced with long-duration injection, a characteristic of medium-speed engines. The study also reveals a more uniform but elevated distribution of nitrogen oxide emissions in medium-speed engines, attributed to prolonged high-temperature conditions that both facilitate their formation. Early stages of diffusion combustion show high concentrations of incomplete combustion products. However, as the combustion process progresses, the conditions favor the complete oxidation of these products at high temperatures, resulting in decreased carbon-based pollutions. In addition, the larger combustion chamber and enhanced turbulence characteristic of medium-speed engines support efficient fuel and air mixing without necessitating the swirl effect required by high-speed engines, diminishing the dependence on wall impingement dynamics for air utilization. Consequently, efficiency optimization strategies for medium-speed engines, emphasizing adjustable injection parameters, encounter fewer constraints than those inherent to the spatial limitations of high-speed engines.

Advantages of high cell concentration prior to cryopreservation of initial leukapheresis in CAR-T cell therapy.

Chimeric antigen receptor (CAR) T-cell therapy is increasingly used in patients affected by B-cell lymphoma and acute lymphoblastic leukemia. For logistical reasons, initial apheresis products may be cryopreserved for shipment to manufacturing centers. Due to the characteristics of these patients, cells are often collected in large volumes, meaning more bags must be cryopreserved. This requires increased storage, time and monetary costs. In this context, we aimed to evaluate a high cell concentration cryopreservation protocol by centrifugation to standardize the initial CAR-T manufacturing procedure. Sixty-eight processes of leukapheresis of 57 patients affected by refractory/relapsed B cell lymphoma and 9 patients affected by acute lymphoblastic leukemia who were eligible for anti-CD19 CAR-T cell treatment performed between June 2019 and October 2022 were analyzed. Whole blood count, percentage and number of T cells were assessed on the apheresis final product. The apheresis product, which was alternatively stored overnight at 4°C, was centrifuged, adjusting the volume to approximately 40 mL. The product was immediately cryopreserved to achieve a final cell concentration of 50-200×106 cells/ml for cryopreservation. Leukapheresis volume was reduced by almost fivefold (median: 185 to 40 mL), resulting in a higher product concentration in one bag. In addition, the number of non-target cells (monocytes, platelets and erythrocytes) was also reduced during the development of CAR-T cell therapy, thereby maintaining T lymphocyte levels and providing a purer starting material. The advantages of the protocol include reducing economic costs, saving storage space, simplifying the manufacturing process, and facilitating shipping logistics. In conclusion, we present a validated, simple, and cost-effective cell enrichment processing protocol that provides high-quality cryopreserved products as starting material for the CAR-T cell manufacturing process.

Impacts of Brazilian Green Coffee Production and Its Logistical Corridors on the International Coffee Market

Background: The coffee industry is one of the most important world supply chains, with an estimated consumption of two billion cups daily, making it the most consumed beverage worldwide. Coffee beans are primarily grown in tropical countries, with Brazil accounting for almost 50% of the production. The objective of this study is to examine the Brazilian trade between 2018 and 2022, focusing on state producers, logistical corridors, and importer countries. Methods: The methodology approach revolves around a quantitative method using Social Network Analysis measures. Results: The results reveal a massive concentration in local production (99.5%—Minas Gerais), port movements (99.9%—Santos, Itaguai, and Rio de Janeiro), and country buyers (80.9%—the United States, United Kingdon, and Japan). Conclusions: The study concludes that the Brazilian green coffee supply chain relies on a fragile and overloaded logistical network. Due to that, this study indicates that the stakeholders and decision-makers involved must consider this high concentration of production in some areas and companies. They must also address the bottlenecks in logistical corridors and the fierce competition involved in acquiring and processing Brazilian coffee production because these factors can drastically affect the revenue of the companies operating in this sector.

Selective production of two prebiotic extracellular polysaccharides from an oral probiotic lactic acid bacterium, Streptococcus salivarius SY511

Streptococcus salivarius is a lactic acid bacterium and an oral probiotic species. Growth of S. salivarius in a sucrose medium can lead to the production of exopolysaccharides (EPSs) that are potential prebiotics. However, no studies have yet examined use of this species for the selective production of high concentrations of EPSs. In this study, we isolated S. salivarius SY511 from infant feces and grew it in a sucrose medium to produce high levels of water-insoluble and water-soluble EPSs. NMR and monosaccharide analysis demonstrated that water-insoluble glucan and water-soluble levan were the two main EPSs. Batch fermentation in MRS-sucrose medium led to the efficient production of these two EPSs, and Tween 80 was a key factor that affected their differential production. In the fed-batch fermentation, 22.7 g/L of water-insoluble glucan was produced in the MRS-sucrose medium, while 24.9 g/L of levan was produced in the MRS-sucrose medium without Tween 80. Compared to S. salivarius M18, S. salivarius SY511 had higher or similar antimicrobial activity against major oral pathogens. Furthermore, the water-insoluble glucan and levan from S. salivarius SY511 had excellent prebiotic, anti-inflammatory, and antioxidant effects. Our study of S. salivarius SY511 identified a method for the selective production of two EPSs.

Assessment of rapid initiators and long-lasting nutrients for developing biological permeable reactive barriers to treat mine-contaminated groundwater

ABSTRACT The formation of mine-contaminated groundwater as a result of acidic mine drainage from the oxidation of sulfur-containing minerals entering the groundwater. Biological permeable reactive barrier (Bio-PRB) technology is excellent for the remediation of mine-contaminated groundwater. Usually, the organic substrates utilized in Bio-PRB are a combination of rapid initiators, which are readily bioavailable, and long-lasting nutrients, which are more difficult to degrade. Herein, we investigated the effectiveness of three rapid initiators and three long-lasting nutrients to remove sulfate from simulated mine-contaminated groundwater via simulated column experiments. The rapid initiators comprised crude glycerol, sodium acetate, and industrial syrup (IS), and the long-lasting nutrients included biodiesel emulsified oil, soybean oil emulsified oil, and high-carbon alcohol emulsified oil (HO). Microorganisms were stimulated using IS to create a sulfate reduction system owing to its high total organic carbon content (24.30 g L−1), achieving optimal sulfate removal rate (1.69 mmol dm−3 d−1). The fastest (2.93 mmol dm−3 d−1) and highest (88%) sulfate removal rates were achieved using HO, which is probably associated with the ability of HO to provide the most suitable C/N ratio (111.75) and induce the growth of sulfate-reducing bacteria (SRB) for substrate degradation. Conversely, a high concentration of sulfate reduction products inhibited SRB growth in the HO column. The addition of organic materials promoted SRB growth and various organic substrate–degrading bacteria. Furthermore, the competitive growth of methanogens (86.6%) may be responsible for the decrease in the relative abundance of SRB during the later stages of the experiment in the HO column.

The role of supplementary cementitious materials and fiber reinforcements in enhancing the sulfate attack resistance of SCC/ECC composite systems

The purpose of this study is to investigate the effects of sulfate exposure on the mechanical behavior of fresh-to-fresh composite systems (CS), incorporating self-compacting concrete (SCC) in compression and engineered cementitious composites (ECC) in tension. ECCs were designed based on various supplementary cementitious materials (SCM) such as low and high calcium fly ash, slag and reinforcing fibers such as PVA and steel fibers. Repeated cycles of immersion in concentrated sodium sulfate solution were followed by drying at high temperatures (80 °C). After 90 and 180 days of cyclic exposure, the mechanical properties including flexural, compressive and tensile bond strength and mass change were evaluated. To investigate microstructural deterioration and reaction product concentration, SEM-EDS and backscattered electron imaging were used to examine sulfate profiles at the interfacial zone between SCC and ECC. Composite samples demonstrated excellent physico-mechanical resilience. The incorporation of low calcium fly ash and slag was observed to have a beneficial impact on residual mechanical properties in long-term exposures, along with the de-passivation capacity of the reinforcing fibers. No physical de-bonding was observed in any CS, however phase assemblages revealed high concentrations of reaction products in the SCC layers near the interfacial bond with the ECC layers.

Kinetics-based development of two-stage continuous fermentation of 1,3-propanediol from crude glycerol by Clostridium butyricum

BackgroundGlycerol, as a by-product, mainly derives from the conversion of many crops to biodiesel, ethanol, and fatty ester. Its bioconversion to 1,3-propanediol (1,3-PDO) is an environmentally friendly method. Continuous fermentation has many striking merits over fed-batch and batch fermentation, such as high product concentration with easy feeding operation, long-term high productivity without frequent seed culture, and energy-intensive sterilization. However, it is usually difficult to harvest high product concentrations.ResultsIn this study, a three-stage continuous fermentation was firstly designed to produce 1,3-PDO from crude glycerol by Clostridium butyricum, in which the first stage fermentation was responsible for providing the excellent cells in a robust growth state, the second stage focused on promoting 1,3-PDO production, and the third stage aimed to further boost the 1,3-PDO concentration and reduce the residual glycerol concentration as much as possible. Through the three-stage continuous fermentation, 80.05 g/L 1,3-PDO as the maximum concentration was produced while maintaining residual glycerol of 5.87 g/L, achieving a yield of 0.48 g/g and a productivity of 3.67 g/(L·h). Based on the 14 sets of experimental data from the first stage, a kinetic model was developed to describe the intricate relationships among the concentrations of 1,3-PDO, substrate, biomass, and butyrate. Subsequently, this kinetic model was used to optimize and predict the highest 1,3-PDO productivity of 11.26 g/(L·h) in the first stage fermentation, while the glycerol feeding concentration and dilution rate were determined to be 92 g/L and 0.341 h−1, separately. Additionally, to achieve a target 1,3-PDO production of 80 g/L without the third stage fermentation, the predicted minimum volume ratio of the second fermenter to the first one was 11.9. The kinetics-based two-stage continuous fermentation was experimentally verified well with the predicted results.ConclusionA novel three-stage continuous fermentation and a kinetic model were reported. Then a simpler two-stage continuous fermentation was developed based on the optimization of the kinetic model. This kinetics-based development of two-stage continuous fermentation could achieve high-level production of 1,3-PDO. Meanwhile, it provides a reference for other bio-chemicals production by applying kinetics to optimize multi-stage continuous fermentation.Graphical

Development of samarium-doped phosphate glass microspheres for internal radiotheranostic applications

Internal radiotherapy delivers radioactive sources inside the body, near to or into malignant tumours, which may be particularly effective when malignancies are not responding to external beam radiotherapy. A pure beta emitter, 90Y, is currently used for internal radiotherapy. However, theranostic radionuclide-doped microspheres can be developed by incorporating 153Sm, which emits therapeutic beta and diagnostic gamma energies. This study investigated the production of high concentrations of samarium-content doped phosphate-based glass microspheres. The glass P60 (i.e. 60P2O5-25CaO-15Na2O) was mixed with Sm2O3 at ratios of 75:25 (G75:Sm25), 50:50 (G50:Sm50) and 25:75 (G25:Sm75) and processed via flame spheroidisation. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) confirmed the microsphere uniformity with significantly high samarium content up to 44 % in G25:Sm75. Via X-ray diffraction (XRD) analysis, samarium-doped microspheres appeared to be glass–ceramic in nature. Mass-loss, size and pH changes were performed over 28 days, revealing a significant increase in samarium microsphere stability. After 15 min of neutron activation (neutron flux 3.01 × 1013 n.cm−2.s−1), the specific activity of the microspheres (G75:Sm25, G50:Sm50 and G25:Sm75) was 0.28, 0.54 and 0.58 GBq.g−1, respectively. Therefore, the samarium microspheres produced in this study provide great potential for improving internal radiotherapy treatment for liver cancer by avoiding complex procedures and using less microspheres with shorter irradiation time.

Post-mortem formation of ethanol: Is 1-propanol a reliable marker? A proof-of-concept study using an invitro putrefactive environment setup.

Ethanol is the psychoactive substance identified most frequently in post-mortem specimens. Unfortunately, interpreting post-mortem ethanol concentrations can be difficult because of post-mortem alcohol redistribution and the possibility of post-mortem alcohol neogenesis. Indeed, in the time interval between death and sample collection, the decedent may be exposed to non-controlled environments for an extended period, promoting microbial colonization. Many authors report that in the presence of carbohydrates and other biomolecules, various species of bacteria, yeast, and fungi can synthesize ethanol and other volatile substances invitro and invivo. The aim of this study was to study the impact of several variables on microbial ethanol production as well as develop a mathematical model that could estimate the microbial-produced ethanol in correlation with the most significant consensual produced higher alcohol, 1-propanol. An experimental setup was developed using human blood samples and cadaveric fragments incubated under strictly anaerobic conditions to produce a novel substrate, "cadaveric putrefactive blood" mimicking post-mortem corpse conditions. The samples were analyzed daily for ethanol and 1-propanol using an HS-GC-FID validated method. The formation of ethanol was evaluated considering different parameters such as putrefactive stage, blood glucose concentration, storage temperature, and storage time. Statistical analysis was performed using the Mann-Whitney non-parametric test and simple linear regression. The results indicate that the early putrefactive stage, high blood glucose concentration, high temperature, and time of incubation increase microbial ethanol production. In addition, the developed mathematical equation confirms the feasibility of using 1-propanol as a marker of post-mortem ethanol production.

P026 Differential effects of tofacitinib on macrophage activation may contribute to lack of response in ulcerative colitis patients

Abstract Background We previously showed that ulcerative colitis (UC) patients refractory to tofacitinib present an increase in the activation and the pro-inflammatory profile of intestinal macrophages1. However, the mechanism by which tofacitinib promotes further activation of macrophages in these group of patients remains unknown. Methods Blood monocytes from healthy individuals were cultured in the presence of M-CSF as previously described2. The differentiated macrophages were treated with LPS (10ng/ml), TNF (20ng/ml) or IFNγ (5ng/ml) in the presence or absence of tofacitinib (300nM). The effect of tofacitinib on gene expression and protein production in response to each stimulus was measured by qPCR and ELISA, respectively. Single-cell RNAseq (scRNAseq) data generated in a cohort of UC patients treated with tofacitinib1 was compared to the bulk transcriptome of monocyte-derived macrophages stimulated with LPS +/- anti-IL-10 mAb3. Results Monocyte-derived macrophages treated with tofacitinib significantly reduced the expression of activation markers downstream from IFNγ or TNFα. In contrast, the response to LPS was either maintained or intensified by tofacitinib as seen by the increase in expression of inflammatory marker genes including chemokines and cytokines CXCL1, CXCL5, IL1B, TNFA and IL6, and M1-like markers INHBA and CLEC5A (Figure 1A). Protein analysis of cell supernatants confirmed these observations. Compared to IFNγ and TNF, LPS drives the production of high concentrations of the anti-inflammatory IL-10 (Figure 1B) which can act on macrophages through a JAK-dependent signaling pathway. We hypothesized that by inhibiting IL-10 autocrine signaling on LPS-activated macrophages tofacitinib would promote their hyperactivation. Indeed, the transcriptional profile of LPS-stimulated macrophages treated with a blocking anti-IL-10 antibody3 highly overlapped with those genes that were upregulated in macrophages from patients refractory to tofacitinib, including IL1B, IL6, INHBA and IDO1 (Figure 1C). This overlap was not observed in responder patients. Conclusion Based on the combination of biopsy scRNAseq from tofacitinib-treated patients and in vitro macrophage cultures, we suggest that lack of response to tofacitinib is driven by its effect on IL-10 signaling. While IL-10 is essential to control macrophage activation when stimulated with the pathogen molecular pattern LPS, it plays no significant role when macrophages are activated with IFNγ or TNF. Hence, we hypothesize that LPS-dependent inflammation may predispose to lack of response to tofacitinib.

Enhanced theanine production with reduced ATP supply by alginate entrapped Escherichia coli co-expressing γ-glutamylmethylamide synthetase and polyphosphate kinase

L-theanine is an amino acid with a unique flavor and many therapeutic effects. Its enzymatic synthesis has been actively studied and γ-Glutamylmethylamide synthetase (GMAS) is one of the promising enzymes in the biological synthesis of theanine. However, the theanine biosynthetic pathway with GMAS is highly ATP-dependent and the supply of external ATP was needed to achieve high concentration of theanine production. As a result, this study aimed to investigate polyphosphate kinase 2 (PPK2) as ATP regeneration system with hexametaphosphate. Furthermore, the alginate entrapment method was employed to immobilize whole cells containing both gmas and ppk2 together resulting in enhanced reusability of the theanine production system with reduced supply of ATP. After immobilization, theanine production was increased to 239 mM (41.6 g/L) with a conversion rate of 79.7% using 15 mM ATP and the reusability was enhanced, maintaining a 100% conversion rate up to the fifth cycles and 60% of conversion up to eighth cycles. It could increase long-term storage property for future uses up to 35 days with 75% activity of initial activity. Overall, immobilization of both production and cofactor regeneration system could increase the stability and reusability of theanine production system.

Endogenous Nitric Oxide Releases In Situ for RNS/ROS Synergistic Cancer Therapy

AbstractGas therapy, represented by nitric oxide (NO), has shown a powerful anti‐tumor effect. However, current NO therapy relies on NO precursors, which are often released prematurely during in vivo delivery, resulting in poor targeting and obvious toxic side effects. Herein, a core/shell‐structured nanocatalyst is designed and prepared to catalyze the generation of NO in tumor without introduction of NO donor. In this system, C‐Z@CM is prepared by coating the octahedron of Cu‐MOF with a nano‐ZnO, and camouflaging homologous tumor cell membrane. After the nanomedicine is taken up by tumor cells, ZnO reacts in situ with endogenous S‐nitrosoglutathione (GSNO), which is highly expressed in tumors, to continuously and stably generate NO. In addition, the dispersed copper ions in C‐Z@CM acts as the catalytic active centers of the Fenton‐like reaction, which catalyzes H2O2 to generate a large number of hydroxyl radicals (•OH). Importantly, the cascade of NO and reactive oxygen species (ROS) leads to the massive production of more lethal reactive nitrogen species (RNS), further enhancing the therapeutic effect. Catalytic production of high concentrations of NO in situ in the tumor, combined with the cascade generation of ROS and RNS, accompanied by glutathione (GSH) depletion, achieving effective tumor suppression.

Toward Zero Carbon Emissions: Investigating the Combustion Performance of Shaped Microcombustors Using H2/Air and NH3/Air Mixtures

The research effort in the microcombustor field has recently increased due to the demand for high-performance systems in microelectromechanical and micro power generation devices. To address rising concerns about pollutants from fossil sources, zero-carbon fuels such as hydrogen (H2) and ammonia (NH3) have been considered as an alternative in microcombustion processes. In a microcombustor, the surface area-to-volume ratio is much higher compared to conventional combustion systems, resulting in faster heat transfer rates and more intense combustion reactions. However, achieving efficient mixing of fuel and an oxidizer in a microcombustor can be challenging due to its small size, particularly for highly reactive fuels like H2. For NH3, challenges in microcombustion involve a low reactive, high ignition temperature (923 K vs. 793 K of H2) and high concentration of NOx combustion products. Therefore, studying the performance of these fuels in microcombustors is important for developing clean energy technologies. In this paper, to explore features of non-premixed NH3/air and H2/air combustion in micro-scale combustors, an Ansys Fluent numerical investigation was conducted on a Y-shaped microcombustor. Results show that for combustion with H2, stationary flames can be achieved even at lower equivalence ratios. Additionally, the pollutants generated from H2 in the flame are generally twice those of NH3. The overall efficiency of the microcombustor is two times greater for NH3 conditions than for H2 conditions.

High acetate titer obtained from CO2 by thermophilic microbial electrosynthesis with Thermoanaerobacter kivui

Novel renewable platforms for production of organic molecules need to be developed and deployed to achieve a circular carbon economy. Microbial electrosynthesis (MES) is a promising technology to produce acetate from CO2 and renewable electricity. However, productivity and product titer improvements are needed for electroacetogenesis to compete with other production methods. Here, we report the production of high concentrations of acetic acid by Thermoanaerobacter kivui in a continuous, H2-mediated, and thermophilic microbial electrosynthesis process. Acetate titers correlated inversely with the production rate: 490 mM (29.4 g L−1) acetate were produced at a production rate of 5.66 mM h−1 (0.34 g L−1 h−1) whereas 390 mM (23.4 g L−1) acetate were produced at a production rate of 12.75 mM h−1 (0.76 g L−1 h−1). This indicates that electrosynthesis rates are limited by product inhibition rather than electron donor supply at high acetate concentrations.

A novel cascade catalytic electrochemical biosensor based on bifunctional Mn3O4@AuNPs with self-supplied O2 property and glucose oxidase-like activity for ultrasensitive detection of microRNA

Herein, a bifunctional nanomaterial Mn3O4@AuNPs with self-supplied oxygen (O2) property and glucose oxidase-like activity was exploited to construct a novel cascade catalytic electrochemical biosensor for ultrasensitive detection of microRNA-499 (miRNA-499). Impressively, compared with the traditional AuNPs nanozyme with single glucose oxidase-like activity, the Mn3O4@AuNPs could not only act as a glucose oxidative mimetic enzyme to catalyze the oxidation of glucose to gluconic acid and the reduction of dissolved O2 to low concentration of hydrogen peroxide (H2O2) to obtain a electrochemical signal in the presence of hemin/G-quadruplex DNAzyme with peroxidase-like activity, but also electrocatalyze water splitting to obtain abundant dissolved O2 to further assist in the production of high concentration of H2O2 for a significantly improved electrochemical response. Meanwhile, with the aid of the target-induced dual Mg2+-assisted DNAzyme cleavage recycling amplification for the increasement of target miRNA-499 conversion efficiency, the proposed electrochemical biosensor achieved the ultrasensitive detection of miRNA-499 with a detection limit as low as 6.2 aM. As a result, this strategy might provide a potential method to upgrade the catalytic efficiency of mimic enzyme cascade reaction with eventual applications in bioanalysis and disease diagnosis.

Peroxygenase-Catalysed Sulfoxidations in Non-Aqueous Media.

Chiral sulfoxides are valuable building blocks in asymmetric synthesis. However, the biocatalytic synthesis of chiral sulfoxides is still challenged by low product titres. Herein, we report the use of peroxygenase as a catalyst for asymmetric sulfoxidation under non-aqueous conditions. Upon covalent immobilisation, the peroxygenase showed stability and activity under neat reaction conditions. A large variety of sulfides was converted into chiral sulfoxides in very high product concentration with moderate to satisfactory optical purity (e. g. 626 mM of (R)-methyl phenyl sulfoxide in approx. 89 % ee in 48 h). Further polishing of the ee value via cascading methionine reductase A (MsrA) gave>99 % ee of the sulfoxide. The robustness of the enzymes and high product titer is superior to the state-of-the-art methodologies. Gram-scale synthesis has been demonstrated. Overall, we demonstrated a practical and facile catalytic method to synthesize chiral sulfoxides.

Continuous Production of High-Concentration Nitrated Water with Catalytic Concentrated High-Intensity Electric Field Process at Ambient Conditions

Continuous Production of High-Concentration Nitrated Water with Catalytic Concentrated High-Intensity Electric Field Process at Ambient Conditions

The role of rational decisions in technical inefficiency analysis of Spanish pig farms: The influence of water use management

There has been limited research on the degree to which rational inefficiency arises when environmental factors are considered. Thus, our goal is to contribute to the literature by applying the concept of rational inefficiency to pig farming and investigating the relationship between water use and farm technical efficiency levels. This research aims to provide a better understanding of the complex interactions between pig farming production, the natural environment, and economic performance. The stochastic frontier analysis is applied to a cross-section dataset of 523 Catalan farms specialized in pig production in 2018. The main findings of this study are as follows: First, Catalan pig farming exhibits high levels of technical efficiency with an average score of 0.94, which is consistent with the high intensity and concentration of Spanish pork production. Second, there is no compelling evidence to support the rational inefficiency hypothesis, particularly when comparing the rational efficient and multi-efficient groups.

Effect of severe sulfate exposure on the bonding behavior of hybrid engineered composite systems

This article examines the sulfate resistance of composite concrete systems (CS) combining self-consolidating concrete (SCC) in compression and engineered cementitious composite (ECC) in tension, with special focus on the bonding properties at SCC/ECC interface. The effect of different fibers in the ECC tension area was investigated considering the use of PVA, steel and hybrid PVA/steel fibers at the same content. SCC and ECC layers were hot-jointed at fresh-to- fresh state and the hardened systems were tested under repeated cycles of concentrated sodium sulfate immersion and oven drying at a high temperature of 80 °C. Samples were assessed for physical, mechanical, and microstructural changes, including visual state, failure mode, mass, compressive strength, flexural properties and tensile bond strengths at different immersion-drying cycles. In addition, using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS) and backscattered electron imaging, sulfate profiles and phase assemblage methods were applied to investigate the concentration of reaction products of each SCC/ECC system. The long-term exposure results confirmed the advanced sulfate resistance of all CSs as compared to monolithic SCC. Considering the different degradation levels of CSs, the use of PVA demonstrated slightly enhanced physic-o-mechanical properties due to its greater interfacial effect at the SCC/ECC bond. Microstructural studies revealed that there were high concentrations of reaction products in the SCC layers that also affected a limited area near the interfacial bond with the ECC layers, particularly when steel fibers were included in CSs.

Mercury concentration in the snow cover of the city of Khabarovsk

The research reveals results of studies of the total mercury content in the snow cover of Khabarovsk in winter period 2021-2022. Researchers highlight a connection between mercury and non-soluble residue, with minor transition into soluble phase. The total mercury content in the non-soluble residue ranged from 0.3 to 1.4 mg/kg. On the northern border of the Bolshekhekhtsirsky Reserve, area with high content of quicksilver (3 mg/kg) was found, which exceeds the maxi-mum permissible concentration by 1.4 times. Authors consider that high concentration of quicksilver may be a result of short-term local pollution and do not exclude cross-border origin of it. Content of mercury as a part of solid atmospheric precipitation on the Earth’s surface in this area is 37.5 µg/m2, with average values of 10-18 µg/m2. The maximum content of mercury (73.9 µg/m2) was found nearby CHP-3 area. The reason is a high concentration of combustion products in snow cover. The amount of solid atmospheric precipitation in the area of CHP-1 also significantly exceeded the average values, but this did not lead to an increase in the total amount of mercury that reached the surface. The minimum concentration of quicksilver was found in the embankment park area of the city - 3.2 µg/m2.