Size Fractions Research Articles

Prediction of Microstructure Evolution in Ball Mill Liner Forging Process

The liner is affixed to the inner side of the ball mill cylinder to protect the cylinder. Through isothermal compression experiments, Arrhenius constitutive models, peak strain models, critical strain models, dynamic recrystallization dynamic models, and grain size models suitable for the forging process of Mn–Cr–Ni–Mo steel used in ball mill liners were established. By utilizing Deform software, a 3D thermo‐force‐structure coupling model for the hot forging process of ball mill liners was constructed, and the volume fraction of dynamic recrystallization and average grain size during forging was predicted. The response surface model was employed to investigate how process parameters interacted with each other and affected microstructure uniformity in ball mill liners. After optimization, the optimal parameters were determined: initial forging temperature at 1200 °C, forging speed at 30 mm s−1, and friction coefficient at 0.3. Subsequently, a hot forging experiment on ball mill liners was conducted using these optimized parameters; samples were analyzed through backscattered electron diffraction device experiments and microscopic tissue observations. Results demonstrated that microstructural changes observed during actual forging processes aligned with numerical simulation results—thus verifying both the accuracy of the Mn–Cr–Ni–Mo steel material model and numerical simulation method.

Preparing gradient microstructure to achieve enhanced performance in GH4586 superalloy: Experiments and models

In this present study, a combined method of controlling strain deformation (CSD) and gradient-temperature heat treatment (GTHT) was adopted to prepare gradient microstructure in GH4586 superalloy. Consequently, it brought enhanced tensile strength from 1313.1±18.7 MPa at intermediate transition (IT) region to 1506.3±15.7 MPa at high-strain and low-temperature (HS-LT) region, presenting an improvement of 11.6%. And it also enhanced fracture toughness from 77.7±0.3 MPa⋅m1/2 at IT region to 86.7±3.7 MPa⋅m1/2 at low-strain and high-temperature (LS-HT) region, presenting an improvement of 14.7%. The formation of gradient microstructure along the longitudinal direction of CSD+GTHT-treated sample was thoroughly investigated from perspectives of precipitates distribution, activated slip systems and dislocations evolution. During CSD, the size and volume fraction of γ′ precipitates decreased under the effect of strain-induced dissolution behavior. The activation of (1‾ 11)[101] and (11‾ 1)[011] slip systems dominated dislocation movement at each region and there retained increasing dislocation density due to more extensively activated slip systems at HS region. During GTHT, the high-density dislocations promoted recrystallization while the concentratedly distributed γ′ precipitates obstructed movement of recrystallized front, leading to formation of heterogeneous structure with high-density grain boundaries and dislocations at HS-LT region. Finally, a model reflecting the effect of grain boundary strengthening, precipitation strengthening and dislocation strengthening on mechanical property of gradient microstructure was established and successfully applied to property prediction of GH4586 superalloy.

Size fractionation informs microbial community composition and interactions in the eastern tropical North Pacific Ocean

Abstract Marine microorganisms are drivers of biogeochemical cycles in the world's oceans, including oxygen minimum zones (OMZs). Using a metabarcoding survey of the 16S rRNA gene, we investigated prokaryotic communities, as well as their potential interactions with fungi, at the coastal, offshore, and peripheral OMZ of the eastern tropical North Pacific. Water samples were collected along a vertical oxygen gradient, and large volumes were filtered through three size fractions, 0.22 μm, 2 μm, and 22 μm. The changes in community composition along the oxygen gradient were driven by Planctomycetota, Bacteroidota, Verrucomicrobiota, and Gammaproteobacteria; most are known degraders of marine polysaccharides and usually associated with the large particle-associated community. The relative abundance of Nitrososphaerota, Alphaproteobacteria, Actinomycetota, and Nitrospinota were high in free-living and small particle-associated communities. Network analyses identified putative interactions between fungi and prokaryotes in the particle-associated fractions, which have been largely overlooked in the ocean. In the small particle-associated network analysis, fungal ASVs had exclusively negative connections with SAR11 nodes. In the large particle-associated network analysis, fungal ASVs displayed both negative and positive connections with Pseudomonadota, SAR324, and Thermoplasmatota. Our findings demonstrate the utility of three-stage size-fractioned filtration in providing novel insights into marine microbial ecology.

CHEMICAL MODIFICATION AND BIOLOGICAL ACTIVITY OF ALGINATE-BASED HYDROGELS

In recent years, the problem of wound infection has risen dramatically. Infectious complications of surgical wounds have increased significantly, often leading to severe sepsis. Gram-negative bacteria and microorganisms, which are immune to virtually all currently available antimicrobials, are the main culprits. In this regard, the development and implementation of innovative drugs and wound dressings, purulent and chronic wound treatment methods is an urgent problem of many domestic and foreign researchers. Brown algae are extracted using an alkaline solution to produce the ionic polysaccharide sodium alginate. It still holds one of the top positions among water-soluble polymers of natural origin as a result of various highly useful practical characteristics. Based on alginate hydrogels, it is possible to create new materials for biotechnological, pharmaceutical and medical purposes, as they have high moisture retention capacity, non-toxicity and self-decomposing ability. After reviewing the literature, we concluded that cefepime is a new antibiotic researched for wound dressing using IV generation cephalosporins as an antibacterial agent. It is highly resistant to hydrolysis by most beta-lactamases and quickly penetrates the cells of gram-negative bacteria. Inside the bacterial cell, it targets penicillin-binding proteins. To obtain new derivatives of sodium alginate with special properties, a chemical method, in particular, thiolene reactions, was used. It should be noted that click chemistry refers to a set of chemical reactions for the rapid and reliable synthesis of compounds by the uniform addition of individual components. Thiolene reactions offer significant advantages, includingversatile reaction conditions (including radical reactions and catalytic processes) and the ability to use a wide range of substrates with different unsaturated bonds such as acrylates, methacrylates and ethers. To monitor the rate and efficiency of UV activation, we used a sol-gel assay technique that allowed us to quantify insoluble (spatially cross-linked) and soluble polymers. After UV activation, samples with different ratios of thiol derivative (S-H bond) showed low viscosity, indicating the predominant degradation of polymer molecules in these systems. Since alginate-polymer derivatives primarily exhibit deconstructive behavior, the dominant process in alginate molecules is the breaking of bonds rather than their formation. The size of the gel fraction reflects the efficiency of polymer cross-linking, which in turn affects the efficiency of immobilization of the drug in the hydrogel matrix and its release rate. This study presents an experimental characterization of photocrosslinked hydrogels aimed at evaluating and elucidating the physicochemical and biological properties of the antibiotic cefepime in an alginate polymer. The obtained kinetic parameters of the swelling-dissolving process show that the synthesized alginate hydrogel is capable of providing a diffused and prolonged release of drugs. In addition, the synthesized hydrogel effectively delivers cefepime to the tested bacterial strains, showing high antibacterial activity without toxicity. However, further in vivo studies are needed to evaluate the fate and toxicity of the alginate-based hydrogel before definitive conclusions can be drawn regarding the usefulness of the synthesized drugs. These preliminary results can be the basis for the development of medical products.

Quantitative analysis of microplastics in beach sand via low-temperature solvent extraction and thermal degradation: Effects of particle size and sample depth

Quantifying trace levels of microplastics in complex environmental media remains a challenge. In this study, an approach combining field collection of samples from different depths, sample size fractionation, and plastic quantification via pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS) was employed to identify and quantify microplastics at two public beaches along the northeast coast of the U.S. (Salisbury beach, MA and Hampton beach, NH). A simple sampling tool was used to collect beach sand from depth intervals of 0–5 cm and 5–10 cm, respectively. The samples were sieved to give three size fractions: coarse (>1.2 mm), intermediate (100 μm–1.2 mm), and fine (1.2 μm–100 μm) particles. Following density separation and wet peroxide oxidation, a low-temperature solvent extraction protocol involving 2-chlorophenol was used to extract polyester (PET), polystyrene (PS), polyamide (PA), and polyvinyl chloride (PVC). The extract was analyzed using Py-GC–MS for the respective polymers, while the solid residue was pyrolyzed separately for polyethylene (PE) and polypropylene (PP). The one-step solvent extraction method significantly simplified the sample matrix and improved the sensitivity of analysis. Among the samples, PET was detected in greater quantities in the fine fraction than in the intermediate size fraction, and PET fine particles were located predominantly in the surface sand. Similar to PET, PS was detected at higher mass concentrations in the fine particles in most samples. These results underscore the importance of beach environment for plastic fragmentation, where a combination of factors including UV irradiation, mechanical abrasion, and water exposure promote plastic breakdown. Surface accumulation of fine plastic particles may also be attributed to transport of microplastics through wind and tides. The proposed sample treatment and analysis methods may allow sensitive and quantitative measurements of size or depth-related distribution patterns of microplastics in complex environmental media.

Environmental DNA Particle Size Distribution and Quantity Differ Across Taxa and Organelles

ABSTRACTThe use of environmental DNA to detect species is now widespread in freshwater ecology. However, the detectability of species depends on many factors, such as the quantity of eDNA particles available in the environment and their state (e.g., free DNA fragments, organellar, or aggregated DNA particles). To date, the most advanced knowledge of the production and state of DNA particles concerns teleosts. Most often, these studies target mitochondrial genes, since they are present in multiple copies in a cell. However, it is likely that the characteristics of eDNA molecules vary greatly among taxa and genetic compartments, with direct consequences for species detection. Using an indoor mesocosm experiment, we compared the rate of mitochondrial and nuclear eDNA production and particle size distribution (PSD) of four distinct and common aquatic taxa (zebrafish, tadpole, isopod and mollusk). The tank water was filtered through a series of filters with decreasing porosity and mitochondrial and nuclear eDNA at each size fraction were quantified by qPCR. We found that the production and the size of eDNA particles varied greatly among taxa and genetic compartments. For most taxa, the number of nuclear eDNA particles released in water was higher than that of mitochondrial origin. The PSD of mt‐eDNA showed a pattern common to all taxa: the relative number of particles increased from the smallest size fractions (0.2 μm and less) to the largest (over 1.2 μm), while the distribution of nu‐eDNA was very different from one taxon to another. We also observed a high temporal variability in the quantity of eDNA particles and in PSD, although the latter was more complex to model. These results call for caution in how to sample and analyze eDNA in aquatic environments, particularly for organisms that emit small particles in small quantities such as isopods.

Characteristics of shungite particles of different fractional composition and design of compositions of particulate-filled polymer composite materials with different types of structures

The paper presents the results of studies of technological properties (bulk and true density, particle size of the general fraction, particle size distribution, packing coefficient and maximum packing degree of filler particles, etc.) of shungite particles of different batches produced by LLC Nadvoitsky TDM Plant LLC (Karelia, RF).For the first time for shungite particles of different sizes the values of packing density (kуп) and maximum content of dispersed phase (φm) in DFPCM were determined, which allows to calculate generalized and reduced structure parameters, to carry out classification by structural principle and to design compositions of high-tech polymer composites with given properties.Practically all possible compositions of DFPCM with shungite particles of different sizes and different types of disperse structure are presented.

Adsorption and retention of fracturing fluid and its impact on gas transport in tight sandstone with different clay minerals

To elucidate the adsorption characteristics and retention mechanisms of fracturing fluids in diverse clay minerals, we conducted on-line nuclear magnetic resonance (NMR) and atomic force microscopy (AFM) experiments. The depth and extent of solid phase damage are determined by the ratio between the size of fine fractions in fracturing fluid residue and the pore-throat size in experiments. Poor physical properties (K < 0.5 mD) result in a more preferential flow pathway effect during flowback, and the stepwise incremental pressure differential proves to be more effective for the discharge of fracturing fluid in submicron pore throats. The permeability is significantly influenced by the differential distribution of retained fracturing fluid, as supported by direct experimental evidence. The presence of good physical properties (K > 0.5 mD) combined with a scattered distribution of retained fracturing fluid is associated with high gas phase recovery permeability, whereas a continuous sheet-like distribution results in low recovery permeability. The expansive surface area and presence of filamentous illite minerals facilitate the multiple winding and adsorption of fracturing fluids, demonstrating strong hydrogen-bonding, multi-layering and multiple adsorption properties. The geological characteristics of the main gas formations exhibit significant variation, and the severity of damage caused by fracturing fluids occurs in diverse sequences. To address this issue, a differentiated strategy for optimizing fracturing fluids has been proposed.

A simplified predictive model for the compression behavior of self-healing microcapsules using an empirical coefficient

Abstract This study is dedicated to predicting the compression behavior of microcapsules, a key aspect in self-healing applications. Understanding the compression behavior of microcapsules, mainly due to their liquid cores, is a complex task. Equally challenging is the evaluation of the shell properties. We aimed to streamline this prediction process by introducing the empirical coefficient C core, which accounts for core influence. We conducted experiments on microcapsules with MUF (Melamine–Urea–Formaldehyde) shells, compressing them between two plates and recording their responses to load and displacement. The empirical coefficient, influenced by capsule size, shell properties, and core volume fraction, was then analyzed in terms of microcapsule size and Young’s modulus. The research results showed that as the diameter of microcapsule and Young’s modulus of the shell increased, the Ccore also increased. This relationship could be represented in a three-dimensional surface. These findings could significantly contribute to estimating shell properties and modeling matrices with dispersed microcapsules.

A crystal plasticity-based micromechanical model for precipitate shearing: Application to cyclic softening of polycrystalline Ni-based superalloys

Cyclic deformation of polycrystalline Ni-based superalloys leads to cyclic hardening followed by softening, in terms of the mechanical response. A micromechanical constitutive model is proposed and implemented in a dislocation density-based, crystal plasticity framework to simulate the shearing of γ′ precipitates, which leads to the observed cyclic softening. The framework accounts for physically based deformation mechanisms. A slip-system level backstress model has been implemented to account for the kinematic hardening. Further, a micromechanical model for microstructure evolution due to precipitate shearing is developed that accounts for the dislocation-precipitate interactions and the resultant change in precipitate strengthening. The model is used to simulate cyclic deformation in two polycrystalline Ni-based superalloys, with different microstructures (in terms of the shape, size and volume fraction of precipitates), referred as Alloy 1 and Alloy 2. Room temperature cyclic deformation tests, followed by microstructure characterization were performed at different strain amplitudes for Alloy 1 to validate our predictions. For Alloy 2, the experimental stress–strain response was used from the literature to fit and validate our predictions. It is shown that the model can predict cyclic softening due to precipitate shearing for different initial microstructures and a range of loading conditions in polycrystalline Ni-based superalloys.

IDI2-AS1 influences the development of acute myocardial infarction by regulating NR4A2 through microRNA-33b-5p

To explore the effect and correlation of long non-coding RNA (lncRNA) IDI2-AS1/microRNA-33b-5p (miR-33b-5p)/nuclear receptor-associated protein NR4A2 competitive endogenous RNA (ceRNA) regulatory network on acute myocardial infarction (AMI), and to verify whether IDI2-AS1 regulates NR4A2 through miR-33b-5p to affect the occurrence and development of myocardial infarction. The miRNA and mRNA expression chips related to myocardial infarction were obtained from gene expression omnibus (GEO), and the differential expression was analyzed. The upstream regulatory mechanism of NR4A2 was predicted using TargetScan database. Thirty-two male C57/BL6 mice were divided into Sham group, AMI model group, miR-33b-5p mimic group [miR-33b-5p mimic lentivirus (5×107 TU) was injected locally into the heart tissue during ligation] and miR-33b-5p inhibitor group [miR-33b-5p inhibitor lentivirus (5×107 TU) was injected locally into the heart tissue during ligation] according to random number table method, with 8 mice per group. Left ventricular end-diastolic diameter (LVEDD) and left ventricular end-systolic diameter (LVESD) were asseessed by echocardiography, left ventricular fractional shortening (LVFS) and left ventricular ejection fraction (LVEF) were calculated. After the last weighing, the anesthetized mice were sacrificed and the heart tissues were taken. Masson staining of the heart tissues was observed under light microscope, myocardial collagen volume fraction (CVF) and infarct size were calculated. Cardiomyocytes of SPF grade SD rats were collected. They were divided into normal control group (control group), ischemia-hypoxia model group, miR-33b-5p mimic transfection group (miR-33b-5p mimic transfection group before ischemia and hypoxia treatment) and miR-33b-5p inhibitor transfection group (miR-33b-5p inhibitor transfection group before ischemia and hypoxia treatment). The activity of caspase-3/7 in cardiomyocytes was measured. The levels of interleukins (IL-1β, IL-6) and tumor necrosis factor-α (TNF-α) were detected by enzyme-linked immunosorbent assay (ELISA). The levels of malondialdehyde (MDA), superoxide dismutase (SOD), creatine kinase (CK), MB isoenzyme of creatine kinase (CK-MB) and lactate dehydrogenase (LDH) were detected by colorimetry. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of apoptosis-related proteins Bax and Bcl-2, cytochrome C (Cyt C) and IDI2-AS1/miR-33b-5p/NR4A2 regulatory axis genes. The myocardial infarction microarray analysis showed that NR4A2 expression was significantly up-regulated in myocardial infarction, with predicted upstream regulatory mechanisms indicating its possible influence through the IDI2-AS1/miR-33b-5p/NR4A2 regulatory axis. Echocardiographic detection showed that compared with AMI model group and miR-33b-5p inhibitor group, LVEF and LVFS in the heart tissue of mice in miR-33b-5p mimic group were significantly increased, while the levels of LVEDD, LVESD, CK, CK-MB and LDH were significantly decreased, with statistical significance. Light microscope showed myocardial fibrosis and myocardial infarction in AMI model group and miR-33b-5p inhibitor group. In the miR-33b-5p mimic group, the degree of myocardial fibrosis was decreased and the myocardial infarction size was significantly reduced. Compared with AMI model group and miR-33b-5p inhibitor group, the levels of MDA, IL-1β, IL-6, TNF-α and the expressions of Bax and Cyt C in the heart tissue of mice in miR-33b-5p mimic group were significantly decreased, while the levels of SOD and Bcl-2 expression were significantly increased, and the differences were statistically significant. The expressions of IDI2-AS1 and NR4A2 in the heart tissue of mice in miR-33b-5p mimic group were significantly lower than those in AMI model group and miR-33b-5p inhibitor group [IDI2-AS1 (2-ΔΔCt): 1.96±0.08 vs. 2.73±0.08, 3.10±0.05, NR4A2 (2-ΔΔCt): 2.36±0.07 vs. 3.16±0.08, 3.80±0.08, all P < 0.01]. The expression of miR-33b-5p was significantly higher than that of AMI model group and miR-33b-5p inhibitor group (2-ΔΔCt: 0.88±0.07 vs. 0.57±0.07, 0.23±0.01, both P < 0.01). The cell experiment results showed that the caspase-3/7 activity of rat neonatal cardiomyocytes in the miR-33b-5p mimic transfection group was significantly lower than that in the ischemia-hypoxia model group and the miR-33b-5p inhibitor transfection group, suggesting that miR-33b-5p can significantly reduce the apoptosis level of the ischemia-hypoxia model. The levels of peroxidation and inflammation indexes, important genes of apoptosis pathway and the expression of IDI2-AS1/miR-33b-5p/NR4A2 regulatory axis of rat neonatal cardiomyocytes in all groups were consistent with the above. IDI2-AS1 can regulate NR4A2 through miR-33b-5p, thus affecting the occurrence and development of AMI.

Right ventricular function and determining factors of dysfunction in ST-segment-elevation myocardial infarction: a cross-sectional study with cardiac magnetic resonance imaging (MRI).

Over the past few decades, left ventricular (LV) dysfunction in ST-segment elevation myocardial infarction (STEMI) patients has been the focus of research. Recently, co-occurring right ventricular (RV) dysfunction has received more attention in clinical practice. We aimed to assess RV function using cardiac magnetic resonance (CMR) imaging and identify factors that may contribute to RV dysfunction in STEMI patients. We retrospectively studied 189 patients with STEMI who underwent CMR 1-7 days after successful percutaneous coronary intervention (PCI). The ejection fraction (EF), wall thickening rate (WTR), peak radial strain (RS), circumferential strain (CS) and longitudinal strain (LS) of the LV, interventricular septum (IVS) and RV were measured with cine images. The location and extent of the infarct were determined using late gadolinium enhancement (LGE) imaging. The differences of function between STEMI patients with right ventricular ejection fraction (RVEF) <50% and those with RVEF ≥50% were compared using an independent-sample t-test. Linear regression analyses were used to determine independent predictors of RVEF. RVEF <50% was observed in 32.28%% STEMI patients, who also demonstrated significantly lower left ventricular ejection fraction (LVEF), WTR, RS, CS, LS and larger infarct sizes than those with RVEF ≥50%. Patients with RVEF <50% also demonstrated a higher incidence of RV infarction, higher RV end-systolic volume (ESV) index, and lower RV RS and CS. Multivariable linear regression analysis revealed LV EF, IVS WTR and IVS RS as significant predictors for RVEF, while male gender, the culprit lesion in the right coronary artery (RCA), peak troponin were negative predictors for RVEF. Notably, peak troponin, LV EF, LV RS, LV CS, LV WTR, and IVS WTR demonstrated higher area under the curve (AUC) values for predicting RV dysfunction. RV dysfunction was detected in 32.28% of STEMI patients. Patients with acute STEMI and RVEF <50% had impaired LV and IVS functions. Systolic function of the LV and IVS, peak troponin, and culprit lesions in the RCA were independent predictors of RV dysfunction in STEMI patients.

Spatial distribution, sources, and health risk assessment of elements in road dust (

This research delves into the spatial distribution of 17 elements (Al, B, Ba, Bi, Cd, Co, Cr, Cu, Fe, Li, Mg, Mn, Ni, Pb, Sr, Te, and Zn) within the < 20 μm size fraction of road dust samples collected from 177 locations within 65 grid cells (each 5×5 km2) throughout Delhi in February 2021. Notably, Fe and Al emerge as the predominant elements in the road dust samples. Using Principal Component Analysis (PCA), Absolute Principal Component Score (APCS), and Multiple Linear Regression (MLR) techniques, it is observed that crustal sources (58%), non-exhaust vehicular emissions (21%), and two distinct industrial origins (2% and 19%) are major contributors to the road dust composition. Bi and Te exhibited the highest geo-accumulation indices, indicating significant pollution levels, with notably high contamination factors, surpassing a contamination degree of 24. Elements like Cd posed the highest potential ecological risk, dominating 95% of the risk assessment. The hazard index analysis highlighted that urban populations, especially children, face the greatest risk through ingestion, followed by dermal exposure, and least through inhalation. Notably, Cd, Pb, Cr, and Ni were identified as elements posing a very high carcinogenic risk to the general populace.

Source identification and human exposure assessment of organophosphate flame retardants and plasticisers in soil and outdoor dust from Nigerian e-waste dismantling and dumpsites

Electronic waste (e-waste) dismantling and dumpsite processes are major sources of organophosphate flame retardant and plasticiser emissions and may pose potentially adverse effects on environment and human health. In 20 outdoor dust and 49 soil samples collected from four e-waste dismantling and three e-waste dumpsites in two States of Nigeria (Lagos and Ogun), we identified 13 alternative plasticisers (APs), 7 legacy phthalate plasticisers (LPs), and 17 organophosphorus flame retardants (OPFRs) for the first time in African e-waste streams. In the samples from dismantling sites, the range (median) concentrations of ∑13APs, ∑7LPs, and ∑17OPFRs were 11 to 2747 μg/g (144 μg/g), 11 to 396 μg/g (125 μg/g), and 0.2 to 68 μg/g (5.5 μg), in dust respectively and 1.8 to 297 μg/g (55 μg/g), 1.3 to 274 μg/g (48.5 μg/g), and 1.6 to 62 μg/g (1.6 μg/g), in soil respectively. Results for soil samples from e-waste dumpsites were (6.6 to 195 μg/g (23.7 μg/g), 6.0 to 295 μg/g (54.8), and 0.4 to 42.3 μg/g (9.0 μg/g) for ∑13APs, ∑7LPs, and ∑17OPFRs respectively. Overall, concentrations of APs were significantly higher at the dismantling sites (p = 0.005) compared to dumpsites, levels of LPs were higher at dismantling sites but not significant, while OPFR concentrations were significantly higher in dumpsite samples (p = 0.005). Plasticisers were found to be major contributors to pollution at e-waste dismantling sites, while OPFRs were associated with both automobile dismantling and e-waste dumpsite processes. Following particle size fractionation of selected soil samples, higher concentrations of targeted compounds were observed in the smaller mesh (180 μm) soil sieve fraction. For dust, the total median estimated daily intake via ingestion and dermal adsorption (EDIing and EDIderm) ranged from 43 to 74 ng/kg bw/day and 0.4 to 0.7 ng/kg bw/day, respectively. Correspondingly, 4.6 to 45 ng/kg bw/day and 0.015 to 0.57 ng/kg bw/day were the values found for soil, respectively. According to these results, the targeted chemicals do not appear to pose a non-carcinogenic risk to e-waste workers through ingestion or dermal contact of bio-accessible fractions of the chemicals. Human biomonitoring campaigns are recommended in the Nigerian e-waste environment considering the elevated concentration levels found for the majority of targeted compounds and that risk parameters required for exposure assessment were only available for a limited number of compounds.

Seasonal and spatial variations of arsenic and its species in particulate matter in an urban environment of Brno, Czech Republic

The present paper deals with an analysis of total arsenic concentration using ICP-MS/MS and an analysis of concentration of several arsenic species, arsenite (AsIII), arsenate (AsV), monomethylarsonate (MMA), dimethylarsenite (DMA), and trimethylarsine oxide (TMAO), using HPLC-ICP-MS/MS in the PM10 fraction of airborne urban aerosol. The samples were collected during two campaigns, in the autumn of 2022 and in the winter of 2023, at three locations within the central European city of Brno, with the aim to evaluate the seasonal and spatial variations in the PM10 composition. The results confirmed only the seasonal variability in the content of the methylated arsenic species in PM10 influenced by biomethylation processes. To gain better understanding of the possible arsenic origin, a supplementary analysis of the total arsenic concentrations was performed in samples of different size fractions of particulate matter collected using ELPI + . Local emissions, including industrial activities and heating during the winter season, were suggested as the most likely predominant source contributing to the total As content in PM10.Graphical abstract

Assessment of microplastics in human stool: A pilot study investigating the potential impact of diet-associated scenarios on oral microplastics exposure

As emerging contaminants microplastic particles have become of particular relevance as they are widely present in the environment and of potential concern to human health. Humans are exposed through different routes, with oral intake and inhalation being the most significant. Dietary intake substantially contributes to oral exposure, although data is still lacking. This first-of-its-kind pilot study investigates the influence of different plastic use and food consumption scenarios (normal, low, high) on microplastic content in stool reflecting oral intake by performing an intervention study with fifteen volunteers. Stool samples were analyzed for ten different plastic types in three size fractions including 5–50 μm (qualitative), 50–500 μm and 500–5000 μm (quantitative). In all samples, microplastic particles were detected with median concentrations up to 3.5 particles/g stool in the size fraction 50–500 μm. Polyethylene was the most frequently detected polymer type. The different scenarios did not result in a consistent pattern of microplastics, however, the use of plastics for food packaging and preparation, and the consumption of highly processed food were statistically significantly associated with microplastics content in stool. These results provide initial findings that contribute to filling current knowledge gaps and pave the way for further research.

Comparative efficacy of subcutaneous versus intravenous natalizumab on annualized relapse rate: A post-hoc analysis of the REFINE study

BackgroundThe non-inferiority of the efficacy of subcutaneous (SC) vs intravenous (IV) administration of natalizumab (NTZ) once every 4 weeks in relapsing-remitting multiple sclerosis (RRMS) was recently demonstrated on the primary outcome of the REFINE study, i.e. MRI “combined unique active lesions number” (CUAL). To provide further evidence on the comparative efficacy of the two NTZ formulations, the effect of NTZ-SC vs NTZ-IV on annualized relapse rate (ARR) was investigated re-analysing the REFINE dataset. MethodsPost-hoc analysis of the REFINE study dataset aimed at exploring the non-inferiority of the efficacy of NTZ-SC vs NTZ-IV on ARR, i.e. the main secondary outcome of the REFINE study. Robustness of the non-inferiority analysis on CUAL with respect to the presence of cases from the SC arm who received a rescue treatment, including NTZ-IV, was also assessed by sensitivity analyses. Three non-inferiority margins were selected, corresponding to 25 %, 33 %, and 50 % fractions of the effect size of NTZ-IV vs placebo observed in the AFFIRM study on ARR (i.e. 0.125, 0.170, and 0.250). ResultsNinety-nine RRMS patients were included. The mean difference in the effect of NTZ-SC vs NTZ-IV on ARR was close to 0. The lower bound of the 95 % confidence interval (worst case scenario) was –0.119, corresponding to 25 % (p = 0.025) of the effect of NTZ-IV vs placebo on ARR. Sensitivity analyses confirmed the results of the primary non-inferiority analysis on the outcome CUAL. ConclusionsNTZ-SC resulted not inferior to NTZ-IV on ARR for all the non-inferiority margins. The non-inferiority analysis of the efficacy of NTZ-SC vs NTZ-IV on CUAL was demonstrated to be robust with respect to rescued patients.

Nanofiltration membranes in asymmetric flow field-flow fractionation for improved organic matter size fractionation

Size fractionation of organic matter (OM) by asymmetric flow field-flow fractionation (FFFF) with ultrafiltration (UF) is limited by solute loss and peak resolution, particularly for low molecular weight fractions (<10 kDa). Nanofiltration (NF) with a molecular weight cut-off (MWCO) of ≤1 kDa can achieve significant OM retention and may improve OM fractionation. NF membranes with MWCOs ranging from 0.3 to 3 kDa were used to evaluate the retention and fractionation of nine OMs in the humic, polyphenol, biopolymer, and low molecular weight organic classes in stirred cell NF and FFFF. Membranes with an MWCO of 0.2–0.3 kDa (with a pure water permeability of 5–16 L.m−2.h−1.bar−1) with low OM interaction exhibited high peak recovery and resolution and hence improved OM fractionation. Loose NF (MWCO 3 kDa) exhibited a poor peak recovery because of a high OM loss due to both adhesion and permeation, particularly at high ionic strengths (>10 mM). A mixture of nine types of OM and natural organic matter samples from rivers, swamps and lakes achieved good fractionation with a 0.3 kDa (NF270) membrane at low ionic strength. The performance of NF for the analysis of OM and colloids in the smallest size range (≤1 kDa MW) could be further improved by optimizing the salt composition of the mobile phase and by overcoming the pressure limitations of FFFF channels.

Experimental research of convective heat transfer between nanofluids and high-temperature dense granite in deep geothermal reservoirs

Global warming is increasing as CO2 emissions from the use of conventional fossil fuels continue to rise. The development of geothermal energy is gradually becoming the key to the sustainable development of human society in the future. Enhancing the heat transfer performance of circulating heat transfer fluids is one of the effective means to efficiently exploit deep geothermal resources. In this study, a self-developed circulating heat exchange experimental setup was established. The convection heat transfer characteristics of nanofluids in high-temperature rocks were experimentally investigated. Al2O3 nanofluid and CuO nanofluid were used as the working medium for heat transfer in high temperature granite samples. The effects of the Reynolds number (1000–6000) and parameters such as nanoparticle type (CuO & Al2O3), size (20 nm & 40 nm) and mass fraction (0 wt%-2wt%) on the heat transfer intensity were analyzed. The effect of nanoparticle accumulation on the rock surface on the local heat transfer strength was also investigated. The results indicate that the increase of Reynolds number enhances the heat transfer strength of nanofluids in rocks. Nanofluid containing 20 nm Al2O3 nanoparticles has better heat transfer performance in rock than nanofluid containing 20 nm CuO nanoparticles. Meanwhile, the heat transfer performance of nanofluid containing 20 nm Al2O3 nanoparticles in rock is better than that of nanofluid containing 40 nm Al2O3 nanoparticles. The heat transfer intensity increases and then decreases as the nanoparticle mass fraction increases. The heat transfer coefficient at Reynolds number 6000 is 52.2 % higher than that of water. For nanofluids and water, the local heat transfer intensity decreases with increasing distance from the inlet. Meanwhile, accumulation of nanoparticles on rock surfaces during convective heat transfer enhances heat transfer intensity. The results show that nanofluids have the potential to be applied to deep geothermal resource extraction. This paper provides data and technical support for the application of nanomaterials in medium and deep geothermal systems to enhance heat transfer efficiency.

Experimental study on the effect of hydrothermal activation on the physicochemical properties and mineralization efficiency of fly ash-supercritical CO2

To address the challenge of low mineralization efficiency of fly ash-supercritical carbon dioxide (CO2), a hydrothermal activation method was proposed to enhance fly ash-supercritical CO2 mineralization. The study systematically investigated the mechanism through which hydrothermal activation parameters influenced the efficiency of fly ash-supercritical CO2 mineralization through a series of experimental reactions. The effects of hydrothermal activation temperature and time on mineralization efficiency were investigated macroscopically. The results indicated that the mineralization efficiency increased by 202.93 % when hydrothermally activated at 220 °C for 30 min. Furthermore, when the activation time was ≤10 min, 220 °C exhibited a significant effect on the mineralization efficiency. For activation time ≥20 min, mineralization efficiency exhibited high stability with increasing temperature. Subsequently, under 220 °C conditions, mineralization efficiency reached 18.79 % for 5 min and 21.69 % for 30 min, representing only a 15.43 % increase despite a six-fold increase in time. Microscopic analysis of the pore structure of hydrothermally activated fly ash indicated that pore parameters (volume, specific surface area, and volume change rate) exceeded those of original fly ash for pore diameters ≥9 nm, and the opposite was observed for pore diameters <9 nm. Additionally, compared with the pristine fly ash, the pore size and volume fraction of the mineralized fly ash macropores increased, while mesopores decreased, and small pores exhibited a slight decrease in volume fraction and size. This indicated that pores ≥9 nm were primarily affected by hydration expansion, while pores <9 nm were primarily affected by mineralization precipitation. The hydrothermal activation mineralization reaction predominantly affected medium and large pores ≥9 nm, exhibiting less effect on smaller pores.