Apparent Coefficient Research Articles

Granular Columns of Binary‐Size Mixtures Collapse on a Horizontal Plane

ABSTRACTThe granular column collapse is a simple model to study natural disasters such as landslides, rock avalanches, and debris flows because of its potential to provide solid links of physical and mechanical properties to these catastrophic flows. Such flows are commonly composed of different grain‐size distributions, namely, polydispersity. Owing to the complexity of different particle‐size phases, explanations of the collapse dynamics, run out distance, and size‐segregation behavior of granular flows remain elusive. A binary‐size mixture of granular materials is well‐known as a simplified version of particle‐size distribution. This paper explores the effects of the large‐particle content on the collapse mobility, deposition morphology, and size segregation of binary‐size mixtures composed in each column geometry. Although the kinetic energy and deposition morphology are nearly insensitive to the content of large particles for each column geometry, the large and small particle‐size phases govern differently on total kinetic energy. Remarkably, the contribution of these two particle phases to the kinetic energy is similar when the large‐particle content reaches around 10% for all column geometries. By quantifying the difference of the apparent friction coefficient of small and large particle phases, the size‐segregation degree of binary‐size mixtures is evaluated. The results noted that the segregation degree increases exponentially with increasing the large‐particle content, but it is nearly independent of the column geometry. These findings complement insights into the flow properties of geological hazards, leading to offering valuable evidence for the management of natural disasters such as landslides and debris flows.

Evaluation of functional magnetic resonance APT and DKI imaging for breast cancer

ObjectiveThis study aimed to compare the performance of amide proton transfer–weighted imaging (APTWI) and diffusion kurtosis imaging (DKI) in differentiating benign from malignant breast lesions, evaluate molecular subtypes of breast cancer, and determine the diagnostic efficacy of the quantitative magnetic resonance imaging (qMRI) parameters in differentiating benign from malignant breast diseases.MethodsThe study included 168 women who underwent breast APTWI and DKI at Yunnan Cancer Hospital between December 2022 and July 2023. The APT signal intensity (SI), apparent kurtosis coefficient (Kapp), non-Gaussian diffusion coefficient (Dapp), and apparent diffusion coefficient (ADC) values were measured before surgery. The differences in the aforementioned qMRI parameters in molecular subtypes of breast cancer were analyzed using one-way analysis of variance. The efficacy of each quantitative parameter in differentiating benign from malignant breast diseases was evaluated using the receiver-operating characteristic curve.ResultsSignificant differences in qMRI parameters were noted between benign and malignant breast lesions. The Kapp (P < .0001) and APT (P < .05) values were higher for malignant tumors than for benign lesions. Conversely, the ADC (P < .0001) and Dapp (P < .0001) values were lower for malignant tumors than for benign lesions. The diagnostic performance was assessed using the area under the curve (AUC) for various parameter combinations. The AUC of Kapp was 0.871, Dapp was 0.872, APT SI was 0.643, DKI + APT was 0.893, DKI + ADC was 0.936, APT + ADC was 0.925, and DKI + APT + ADC was 0.933. Additionally, ADC values (P = .01) demonstrated superior diagnostic performance compared to Kapp (P = .03), Dapp (P = .03), and APT values (P = .06) in distinguishing between different molecular subtypes of breast cancer.ConclusionsAPTWI distinguished benign from malignant breast disease and enhanced the utility of diffusion-weighted MRI. However, it was not superior to DKI and DWI in identifying the molecular subtypes of breast cancer.

Spatial Distribution Characteristics and Ecological Risks of Typical Drugs in the Yongjiang River Basin

In recent years, due to large-scale production and widespread use, drugs have posed a potential threat to biological and human health and have received increasing attention. The occurrence and distribution of drugs in urban rivers are influenced by various factors, such as urbanization level, population density, regional geographical and climatic characteristics, and drug consumption habits. In October 2022, the Yongjiang River Basin was divided into four sub-basins： upstream, midstream, tributaries, and downstream. A total of 20 surface water and sediment samples were collected to explore the occurrence, spatial distribution, and ecological risks of drugs in water and sediment. Among the 40 target drugs, 22 drugs were detected in water samples, accounting for 55% of the target drugs, with a maximum concentration of 207.25 ng·L-1, and 12 drugs were detected in sediment, accounting for 30% of the target drug, with a maximum concentration of 153.63 μg·kg-1. The dominant species in water samples were metabolic drugs. In sediment, the dominant species in the upstream and midstream were quinolone antibiotics, while the dominant species in the tributaries and downstream were cardiovascular drugs. Nine drugs were detected in both water and sediment, with an apparent distribution coefficient Kd value of 5.0-385 029 L·kg-1. According to the average lgKoc value, the order from highest to lowest was： sertraline hydrochloride &gt; ofloxacin &gt; clarithromycin &gt; D,L-venlafaxine &gt; roxithromycin &gt; sulfamethoxazole &gt; fluoxetine &gt; metoprolol &gt; carbamazepine. Principal component analysis was used to analyze the source of drugs in water and four principal components explained 76.24% of the variation, corresponding to a source of medical wastewater, a mixed source of domestic wastewater and aquaculture wastewater, an untreated source of rural domestic wastewater, and an agricultural non-point source. Principal component analysis coupled multiple linear regression analysis well predicted the total concentration of drugs in 20 water samples （R2 = 0.868）. Three drugs were present in the water sample that posed ecological risks, with risk quotients in the order of 1,7-dimethylxanthine &gt; dehydrated erythromycin &gt; carbamazepine, whereas only carbamazepine in sediment posed ecological risks. The cumulative risk quotient of multiple drugs in the water at 20 sampling sites was 1.22-16.27, all of which belonged to high risk, while the cumulative risk quotient of multiple drugs in sediment was 0.009~0.064, with no risk at site S11 and low risk at all other sites. The research results can be used to analyze the distribution mechanism of drugs between water and sediment, providing a technical basis for the prevention and control of drug pollution and environmental risks in urban rivers.

Apparent digestibility of proteinaceous feed ingredients from animal and plant origin for two tropical species snubnose pompano Trachinotus blochii and mangrove red snapper Lutjanus argentimaculatus

Apparent digestibility coefficients (ADC) of protein and energy in a selection of ingredients of animal origin and plant origin were determined for snubnose pompano (Trachinotus blochii) and mangrove red snapper (Lutjanus argentimaculatus). Apparent digestibility coefficients (ADCs) were determined using a reference diet with yttrium oxide as an inert marker and test diets that contained 70 % of basal mash and 30 % of the feed ingredient being evaluated. Snubnose pompano and mangrove red snapper with an initial average body weight of 733.1 ± 92.3 g and 386.7 ± 37.7 g respectively, were fed with the diets for a period of 7 days before collecting faecal samples. The fish were sedated, and faeces were carefully stripped. The faecal samples, ingredient samples, and the diets were subjected to chemical analysis to determine the content of yttrium, protein (nitrogen) and energy. Diet apparent digestibiltiy coefficients (DADC) were determined, and these DADC values were used to derive the ingredient apparent digestibiltiy coefficients (IADC) using the diet substitution approach methodology. Ingredient protein digesitbilities ranged from 82.9 % to 112.3 % in snubnose pomano and were typically higher for soybean meal (Sparos Lda), whereas in mangrove red snapper the ingredient protein digestibilities ranged between 52.1 % and 99.9 % and were typically higher for corn gluten meal (Arabian Agricultural Services Company, ARASCO). Ingredient energy digesitbilities for snubnose pompano ranged from 55.2 % to 115.6 % and were typically highest for wheat gluten (National Aquaculture, NAQUA), whereas ingredient energy digestibilities ranged between 40.3 % and 93.3 % in manrove red snapper and were typically higher for fishmeal (United Marine Products, UMP). In comparison between the two species, the analysis revealed a weak correlation in both diet and ingredient digestibilities for protein and energy. Consequently, the use of digestibility data within species at the same trophic level necessitates a prior assessment when other factors are involved.

Estimation of the Volatility and Apparent Activity Coefficient of Levoglucosan in Wood-Burning Organic Aerosols.

Biomass burning (BB) is a major source of aerosols and black carbon, thereby exerting an important impact on climate and air quality. Levoglucosan is the most well-recognized organic marker compound of BB and has been used to quantitatively assess BB's contribution to ambient aerosols. However, little is known about levoglucosan's evaporation under atmospheric conditions, primarily due to the uncertainty of its effective saturation vapor concentration (C*) and its unknown activity coefficient (γ), in the complex BB emission matrix. Here, we utilized a thermodenuder to investigate the evaporation of levoglucosan from mixtures with polyethylene glycol (PEG) or BB primary organic aerosol (BBPOA) matrices, respectively. We estimate a pure component log10(C*/[μg m-3]) of levoglucosan of 1.1 ± 0.1 at 298 K. We reveal that levoglucosan mixed with PEG or BBPOA becomes more volatile than when treated as a single component due to nonideal molecular interactions. Considering that phase separation might occur in such systems, we term γ apparent activity coefficient (γ a ). We estimate log10 C* and γ a of levoglucosan in BBPOA of 1.8 ± 0.1 and 3.8 ± 0.3, assuming a liquid phase state. Consequently, γ a must be considered to avoid significant underestimation of levoglucosan evaporation via gas-particle partitioning during transport.

Investigating the efficiency of mixtures based on supercritical CO2 and lubricants by friction tests under conditions similar to the machining of Ti6Al4V

New supercritical carbon dioxide (scCO2)-based cutting fluids combining the cooling from scCO2 and lubrication from various additives are investigated in this study. Selected components, including ionic liquids, vegetable and mineral oils, water, and PEG, were introduced into supercritical CO2, and tribological tests were performed on a CNC lathe to analyze their influence on Ti6Al4V/WC-Co contact. Forces and temperatures were recorded to compare the perfomances of the scCO2-lubricant mixtures for future use in machining. The analysis of the apparent friction coefficient and sticking zone showed a noticeable decrease by ionic liquids when combined with scCO2 at a speed of 100 m/min and 4 mL/min delivery flow rate. The other lubricants (water and PEG vegetable oils) performed similarly to standard mineral oil and are less expensive, which could help in developing future low-cost yet effective cooling and lubrication methods for the machining industry.

Accelerated Zymonic Acid Formation from Pyruvic Acid at the Interface of Aqueous Nanodroplets.

To explore the role of the liquid interface in mediating reactivity in small compartments, the formation kinetics of zymonic acid (ZA) is measured in submicron aerosols (average radius = 240 nm) using mass spectrometry. The formation of ZA, from a condensation reaction of two pyruvic acid (PA) molecules, proceeds over days in bulk solutions, while in submicron aerosols, it occurs in minutes. The experimental results are replicated in a kinetic model using an apparent interfacial reaction rate coefficient of krxn = (0.9 ± 0.2) × 10-3 M-1 s-1. The simulation reveals that surface activity of PA coupled with an enhanced interfacial reaction rate drives accelerated ZA formation in aerosols. Experimental and simulated results provide compelling evidence that the condensation reaction of PA occurs exclusively at the aerosol interface with a reaction rate coefficient that is enhanced by 4 orders of magnitude (∼104) relative to what is estimated for macroscale solutions.

Physicochemical, rheological, and microbiological properties of honey-fortified probiotic drinkable yogurt

This study aimed to investigate the physicochemical, rheological, and microbiological attributes of drinkable yogurts prepared with three distinct types of honey (flower, pine, and thyme) in amounts of 10 and 20% and probiotic cultures (Lactobacillus acidophilus and Bifidobacterium spp.). The control sample was brighter while the yogurt containing 20% pine honey was more yellow during storage (21 days). The samples’ serum separation quantities rose together with the honey ratio. All the honey-fortified drinkable yogurts were found to be non-Newtonian pseudoplastic liquids that are thixotropic. However, as the honey ratio increased, the apparent viscosity and consistency coefficients increased, too. After 21 days of storage, L. acidophilus and Bifidobacterium spp. counts rose to more than 5.0 log CFU/mL in the experimental yogurts containing honey (except for the sample with 20% flower honey). The panelists preferred the 10% honey-fortified drinkable yogurts over the others. The yogurts with flower honey were mostly favored, followed by pine and thyme honeys. Although honey contributed to the properties of drinkable yogurt, adding more than 10% of honey degraded the product’s quality and acceptability. In conclusion, 10% is an optimal amount for flower and pine honey, with a smaller amount recommended for thyme honey. More research is needed on honey-fortified drinkable yogurt for its commercial production.

Reactants‐Driven Surface‐Active Sites on a Cu/CeO2 Catalyst for Methanol Synthesis from Syngas

AbstractThis study investigated the dynamic structure of a working Cu/CeO2 catalyst and its catalytic consequences for CH3OH synthesis via CO hydrogenation by kinetics, high‐precise chemical titration, and a series of in situ X‐ray spectroscopies. We have revealed that the apparent rate coefficients for CH3OH synthesis from CO hydrogenation are a single‐valued function of the CO2‐to‐CO ratio in the contacting gas phase. This ratio determines the extent of surface oxidation of Ce2O3 to CeO2, the relative abundance of surface Ce3+ and Ce4+ sites, and in turn, the density of Cu0‐Ce3+ sites pair on the working Cu/CeO2 catalyst, although the chemical state of Cu and elemental distribution of both Cu and Ce were insensitive to the ratio. The reactivity of CH3OH formation and the Cu0‐Ce3+ sites decrease monotonously with an increase in the CO2‐to‐CO ratio. The direct connection of the reactivity and the oxidant‐to‐reductant ratio appears to be general for heterogeneous catalysis, for which the oxidant oxidizes metal atoms. In contrast, the reductant scavenges surface oxygen atoms, thus dictating the density of surface sites and their thermodynamic activities.

Apparent effective ionization coefficient in N2 and O2 gas mixtures determined with two separate methods

N2:O2 gas mixtures are important for applications of atmospheric pressure plasmas such as ozone production, air purification from VOCs and NOx and surface treatments. Fundamental parameters such as the effective ionization coefficient are inputs for theoretical plasma models for applications and must thus be accurately known. This work determined the apparent effective ionization coefficient in N2:O2 mixtures in a broad reduced electric field strength E/N range of 150–1200 Td with two separate methods and compared with BOLSIG+ calculations of reduced effective ionization coefficient. Additionally, the equilibrium distance required to establish a steady-state electron energy distribution was estimated from spatial profiles of optical emission.

Electrochemical Determination of Cysteine Using a 2-(2,5-Dihydroxy-Phenyl)-Naphtho[1,2-d] Oxazole-5-Sulfonic Acid (DHPNOS) and Cerium Oxide Nanoparticle (CeO2NP) Composite Carbon Paste Electrode (CPE)

An electrochemical sensor for the electrocatalytic oxidation of cysteine was designed based upon a 2-(2,5-dihydroxy-phenyl)-naphtho[1,2-d] oxazole-5-sulfonic acid (DHPNOS) and cerium oxide nanoparticle (CN) modified carbon paste electrode (CPE). An investigation of the redox properties of this modified electrode indicates a reduction in oxidative overvoltage and an intense increase in the analytical current. The pH, modifier, and nanoparticles were optimized to 7, 4% weight percent, and 5% weight percent, respectively. The apparent charge transfer rate constant (ks) and transfer coefficient for electron transfer between modifier and electrode were 2.776 s−1 and 0.47, respectively. Using differential pulse voltammetry, a linear range from 1 to40 µM with a detection limit of 0.33 µM was observed in phosphate buffer (pH 7.0). This work introduces a simple approach for selective determination of L-cysteine in the presence of uric acid. Also, based on chronoamperometry, the diffusion coefficient was determined to be 2.61 × 10−5 cm2 s−1. The effect of interferences on L-cysteine peak current were studied. The repeatability and reproducibility of the designed sensor were also measured with relative standard deviation values of 1.00% and 4.45%, respectively. The constructed sensor was employed for the determination of L-cysteine in acetylcysteine tablets.

Investigation of Lysophospholipids-DHA transport across an in vitro human model of blood brain barrier

Several studies emphasized on the preventive and therapeutic potential of Docosahexaenoic Acid (DHA, 22:6n-3) supplementation in chronic and age-related disorders including neurodegenerative diseases. Researchers principally studied the cerebral accretion of Lysophosphatidylcholine (LysoPC-DHA), the furthermost vital Lysophospholipid-DHA (LysoPL-DHA) in blood plasma. Nevertheless, the cerebral bioavailability of other LysoPL-DHA forms including Lysophosphatidylethanolamine (LysoPE-DHA), and Lysophosphatidylserine (LysoPS-DHA) were not extensively examined even though their vital biological functions in the brain. Hence, the aim of the present study was to evaluate the toxicity and transport of DHA in comparison to several LysoPL-DHA including LysoPC-DHA, LysoPE-DHA and LysoPS-DHA across a human model of blood-brain barrier (BBB). The human brain-like endothelial cells (hBLECs) monolayer tightness was evaluated by the parallel assessment of the permeability of fluorescent marker Lucifer yellow (LY) and revealed the absence of toxicity of non-esterified DHA and all LysoPL-DHA towards hBLECs. LysoPC-DHA, LysoPE-DHA and LysoPS-DHA displayed a higher recovery in the abluminal medium in comparison to non-esterified DHA at 30, 60 and 120 min post-incubation. Among all, LysoPS-DHA revealed the highest apparent coefficient permeability (Papp) 85.87 ± 4.24 x 10−6 cm s−1 and was significantly different than DHA, LysoPC-DHA and LysoPE-DHA. More interestingly, when studying the time course of Papp of DHA, LysoPC-DHA and LysoPE-DHA, at different post-incubation time, this permeability decreases with time especially for LysoPC-DHA and LysoPE-DHA, not for DHA. Furthermore, LysoPS-DHA exhibited the highest intracellular accumulation (10.39 ± 0.49 %) in hBLECs in comparison to all other tested lipids. Finally, differences in 3D structures and molecular electrostatic potential maps calculation of LysoPL-DHA could explain the dissimilar cerebral uptake of LysoPL-DHA. Altogether, our findings raise the novel hypothesis that LysoPS-DHA may represent a preferred physiological carrier of DHA to the brain.

Silanol-Stabilized Atomically Dispersed Ptδ+-Ox-Sn Active Sites in Protozeolite for Propane Dehydrogenation.

Crystalline zeolites have been proven to be excellent supports for confining subnanometric metal catalysts to boost the propane dehydrogenation (PDH) reaction. However, the introduced metallic species may suffer from severe sintering and limited stability during the catalytic process, especially when utilizing an industrial impregnation method for metal incorporation. In this study, we developed a new type of support based on amorphous protozeolite (PZ), taking advantage of its adjustable silanol chemistry and zeolitic microporous characteristic for stabilizing atomically dispersed PtSn catalyst via a simple, cost-effective coimpregnation process. The combination of X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, in situ diffuse reflectance infrared Fourier transform spectroscopy under CO atmosphere, and density functional theory calculations confirmed the formation of highly dispersed active Ptδ+-Ox-Sn species in PtSn/PZ. The PtSn/PZ catalyst exhibited a high propane conversion of 45.4% and a high propylene selectivity of 99% (WHSV= 3.6 h-1, 550 °C), with a high apparent rate coefficient of 565 molC3H6·gPt-1·h-1·bar-1 at a high WHSV of 108 h-1, presenting a top-level performance among the state-of-the-art Pt-based catalysts prepared by in situ synthesis and impregnation methods. The silanol density determined the chemical state of PtSn species, showing a change from atomically dispersed Ptδ+-Ox-Sn sites to PtSn alloy with decreasing silanol density of supports. This work provides a general strategy using silanol-rich amorphous protozeolite as support for stabilizing various metal catalysts by the simple impregnation method and also offers an effective way for fine tailoring the chemical state of metallic species via a silanol-engineered approach.

Diffusion-weighted MRI precisely predicts telomerase reverse transcriptase promoter mutation status in World Health Organization grade IV gliomas using a residual convolutional neural network.

Telomerase reverse transcriptase promoter (pTERT) mutation status plays a key role in making decisions and predicting prognoses for patients with World Health Organization (WHO) grade IV glioma. This study was conducted to assess the value of diffusion-weighted imaging (DWI) for predicting pTERT mutation status in WHO grade IV glioma. MRI data and molecular information were obtained for 266 patients with WHO grade IV glioma at the hospital and divided into training and validation sets. The ratio of training to validation set was approximately 10:3. We trained the same residual convolutional neural network (ResNet) for each MR modality, including structural MRIs (T1-weighted, T2-weighted, and contrast-enhanced T1-weighted) and DWI*, to compare the predictive capacities between DWI and conventional structural MRI. We also explored the effects of different regions of interest on pTERT mutation status prediction outcomes. Structural MRI modalities poorly predicted the pTERT mutation status (accuracy = 51%-54%; area under the curve [AUC]=0.545-0.571), whereas DWI combined with its apparent diffusive coefficient maps yielded the best predictive performance (accuracy = 85.2%, AUC = 0.934). Including the radiological and clinical characteristics did not further improve the performance for predicting pTERT mutation status. The entire tumour volume yielded the best prediction performance. DWI technology shows promising potential for predicting pTERT mutations in WHO grade IV glioma and should be included in the MRI protocol for WHO grade IV glioma in clinical practice. This is the first large-scale model study to validate the predictive value of DWI for pTERT in WHO grade IV glioma.

Determination of optimal dietary calcium levels under different sources of zinc in Jing tint 6 layer chicks from 15 to 42 d of age

An experiment was conducted to investigate the optimal dietary calcium (Ca) levels in Jing Tint 6 layer chicks fed different sources of zinc (Zn). The diets were formulated using 2 different Zn sources: organic Zn (80 mg/kg Zn as HMZn) and inorganic Zn (80 mg/kg Zn as sulfate). For each Zn source, 5 diets were formulated to contain Ca levels of 0.80, 0.90, 1.03, 1.10, and 1.20%. Results showed that dietary Ca levels had a significant effect on body weight gain (BWG) and feed conversion ratio (FCR) (P < 0.05). In addition, BWG was significantly enhanced by the organic Zn diets (P < 0.05). Dietary Ca levels significantly affected tibia length (P < 0.05) and serum Ca and P contents (P < 0.05) but did not affect serum total protein (TP), albumin (ALB), or alkaline phosphatase (ALP) levels (P > 0.05). The apparent total tract retention coefficients (ATTRC) of Ca showed a quadratic trend (P < 0.05) with increasing Ca levels. Furthermore, organic Zn diets reduced excreta Ca output and enhanced the ATTRC of Ca in birds on d 42 compared with inorganic Zn diets. The optimal dietary Ca levels were estimated as 0.93, 0.94, and 0.96% for birds fed organic diets and 1.07, 0.99 and 0.94% for birds fed inorganic diets using nonlinear models based on the criteria of BWG, tibial length, and serum P, respectively. In general, organic Zn supplementation improved growth performance and reduced the calcium requirements of birds on d 42.

Effect of peristaltic endoscope and heat transfer on the magnetohydrodynamic flow of non-Newtonian biviscosity fluid through an inclined annulus: Homotopy perturbation approach

This work focuses on the heat transfer analysis of the magnetohydrodynamic peristaltic flow of blood through the gap between two coaxial flexible tubes of different wavelengths. In this model, the non-Newtonian biviscosity fluid is assumed to be blood, which is flowing through the annulus region between the inclined tubes. The governing equations for the considered problem are simplified under the assumptions of a zero Reynolds number and long wavelength approximations. An analytical expression for the temperature is obtained in its closed form, while a semi-analytical solution for the axial velocity of the moving fluid is determined using the homotopy perturbation method. Expressions for various flow variables such as shear stress, volumetric flow rate, pressure rise, and frictional force at the surface of inner and outer tubes are also obtained. In this work, we discussed the impact of various flow parameters like the Hartmann number, Grashof number, heat source, upper limit apparent viscosity coefficient, amplitude ratios of inner and outer tubes, radius ratio, and wavelength ratio on the above flow variables. The streamline contour plots are also drawn for the realization of the flow pattern of the blood inside the endoscope. The comparison of shear stresses for the peristaltic and rigid endoscopes and the validation of the present result with the previously established results are also discussed. A noteworthy observation drawn from the present model is that the pressure gradient enhances for increasing values of wavelength ratio when the wavelength of the inner tube is less than the wavelength of the outer tube, whereas the pressure gradient gets suppressed for increasing values of wavelength ratio when the wavelength of the inner tube is greater than the wavelength of the outer tube. From the present analysis, it is also found that the shear stress [Formula: see text] of blood is the least for a peristaltic endoscope as compared to the rigid one. Therefore, this study may be applicable to medical practitioners for laparoscopic purposes, as a peristaltic endoscope may be a more appropriate device due to its flexibility than a rigid endoscope.

Molecular composition limits the reaction kinetics of riverine dissolved organic matter decomposition

The bioavailability and degradation of riverine dissolved organic matter (DOM) play crucial roles in greenhouse gas emissions; however, studies on the kinetic decomposition of fluvial DOM remain scarce. In this study, the decomposition kinetics of dissolved organic carbon (DOC) were characterized using the reactivity continuum model through 28-day bio-incubation experiments with water samples from the Yangtze River. The relationship between DOM composition and decomposition kinetics was analyzed using optical and molecular characterization combined with apparent decay coefficients. Our results revealed that DOM compounds rich in nitrogen and sulfur were predominantly removed, exhibiting a transition from an unsaturated to a saturated state following microbial degradation. These heteroatomic compounds, which constituted 75.61 % of the DOM compounds positively correlated with the decay coefficient k0, underwent preferential degradation in the early stages of bio-incubation due to their higher bioavailability. Additionally, we observed that S-containing fractions with high molecular weight values (MW > 400 Da) may be associated with larger reactivity grades. This study underscored the complex interplay between DOM composition and its kinetic decomposition in river ecosystems, providing further support for the significance of molecular composition in large river DOM as crucial factors affecting decomposition.

Unfolding the interaction of radioactive Cs and Sr with polyethylene-derived microplastics in marine environment

To unveil the interaction of radioactive Cs and Sr with polyethylene-derived microplastics in the marine environment, a mesocosm study was conducted in a stepwise manner by investigating the uptake capability of microplastics at three different stages: pristine, radiation-exposed, and marine-exposed microplastics. The study demonstrates that the physio-chemical properties of microplastics undergo significant alterations upon exposure to the environment, leading to the emergence of biofilm formation upon marine exposure, while radiation exposure induces surface roughness and cracks. Biofilm growth enhances the uptake of radionuclides by microplastics. However, the growth of biofilms increases the density of microplastics through aggregation, leading to a buoyancy transition from positive to negative buoyancy. Various interaction mechanisms, such as electrostatic, ion–dipole, and physical diffusion interactions, were identified as important mechanisms playing key roles in radionuclide binding to polyethylene-derived microplastics. Despite the significantly lower apparent distribution coefficients observed for radio Cs (in the range of 7.3–23.6 L/kg) and Sr (in the range of 4.3–8.06 L/kg) in the marine system, typically 2–3 orders of magnitude lower than those on marine suspended sediment, this study offers compelling evidence that microplastics in marine environments are capable of sequestering radio Cs and Sr. Consequently, microplastics can potentially accumulate these radionuclides, highlighting their role as potential reservoirs as well as vectors of radionuclides in marine environments.

Effects of Hydrostatic Pressure and Cation Type on the Chloride Ion Transport Rate in Marine Concrete: An Experimental Study.

The effect of hydrostatic pressure and cation type on chloride ion transport in marine underwater concrete cannot be ignored. The study of the chloride ion transport behavior of concrete under the effect of hydrostatic pressure and cation type coupling can provide a basis for durability design and the protection of marine concrete. In this work, the chloride ion transport behavior of marine concrete in four common chloride salt solutions under different hydrostatic pressures is studied by a hydrostatic pressure test device developed by the authors. The results show that hydrostatic pressure and its action time significantly influence the chloride ion transport behavior in marine concrete; the higher the hydrostatic pressure of concrete, the faster the chloride ion transport rate. The longer the time, the more chloride ions accumulated in the same position, and the farther the chloride ion transport distance. Cation type has a certain influence on the transport process of chloride ions. Under the same test conditions, the chloride ion transport rate in a divalent cation solution is about 5% higher than that in a monovalent cation solution. The results also show that the chloride ion binding capacity under hydrostatic pressure is only 10~20% of that under natural diffusion. Using the test results, a predictive model of a chloride ion apparent transport coefficient based on the hydrostatic pressure and hydrostatic pressure action time corrected by a cation type influence coefficient is established.

Photocatalytic degradation of sulfamethazine using g-C3N4/TiO2 heterojunction photocatalyst: Performance, mechanism insight and degradation pathway

In the present research, Z-scheme g-C3N4/TiO2 heterojunction composite photocatalysts with varied g-C3N4 content were successfully prepared using the sol-gel technique combined with calcination methods. The morphology, crystallinity, chemical composition, and optical properties of the synthesized catalysts were characterized employing a series of techniques. Sulfamethazine (SMZ) was selected as the model pollutant to evaluate the photocatalytic activity of the prepared catalysts employing a 500 W xenon lamp as the light source to simulate sunlight. The results demonstrated that within 180 min of irradiation, 94.8 % of SMZ was removed by using the optimal photocatalyst (0.4CN/TiO2 composite sample), affording an apparent first-order rate coefficient of 0.0152 min−1 which was 3.8 or 2.0 times as much as that involving single g-C3N4 or TiO2 catalyst, respectively. The effects of catalyst dosage, initial pH, different water matrices, different substrates, and inorganic ions on the performance of 0.4CN/TiO2 photocatalyst were explored. Furthermore, the 0.4CN/TiO2 composite also displayed satisfactory cyclic stability. The results of radical quenching experiments revealed that the key active species in SMZ degradation were hydroxyl radicals (•OH), superoxide radicals (O2•−), and holes (h+). The efficient separation of photo-generated electrons and holes originating in the formation of a Z-scheme g-C3N4/TiO2 heterojunction was evidenced by photoluminescence and electrochemical impedance spectroscopy determination and should be responsible for the enhanced catalytic activity of the 0.4CN/TiO2 sample. In addition, the plausible pathways for the aqueous degradation of SMZ were suggested according to the identified degradation intermediates employing the HPLC/MS technique. In summary, the current research provides a novel insight into the development of Z-scheme heterojunctions in the realm of organic pollutant treatment.