Actual Concentration Research Articles

Substance depletion of volatile monoterpenes – A confounding factor for toxicity testing in the Ames fluctuation test

In in vitro toxicology, reported test results are typically based on nominal concentrations, i.e., the calculated amounts of a substance added to a defined volume of the test system. Consequently, if a test system does not respond to a certain endpoint, the assay is interpreted as negative and the test substance is deemed to exert no toxicity at the tested nominal concentration. However, depending on the physicochemical properties of the test substance and assay setup, the actual exposure may differ widely from nominal concentrations due to different depletion processes. (R)-(+)-Limonene (RLIM), β-myrcene (βMYR) and linalool (LIN) are naturally occurring terpenes that are permitted as flavoring agents in the European Union without limitations based on their low toxicity. Nevertheless, their hydrophobicity and high volatility classifies them as difficult to test chemicals, which has not been considered in previous in vitro tests. To exclude possible false negative results, in the present study, we assessed the cytotoxic and mutagenic potential of the latter substances toward Salmonella Typhimurium in the Ames fluctuation test using different incubation setups to minimize possible substance losses due to sorption or volatilization. Actual substance concentrations during incubation were verified analytically at different time points via headspace gas-chromatography-mass spectrometry (hs-GC-MS). Possible substance depletion due to sorption to well-plate material or volatilization was minimized using a polystyrene-free and headspace-free incubation setup, respectively. The results showed complete volatilization of the monoterpenes RLIM and βMYR in the conventional Ames fluctuation test, which may confound mutagenicity testing. The headspace-free incubation setup greatly improved substance exposure and showed cytotoxicity in low micromolar concentrations, but no signs of mutagenicity were observed.

Fifty percent overestimation of black carbon concentration measured in aerosols of the Tibetan Plateau

Elemental carbon (EC), also known as black carbon, plays an important role in climate change. Accurately assessing EC concentration in aerosols remains challenging due to the overestimations caused by carbonates and organic carbon (OC) during thermal-optical measurement in the Tibetan Plateau (TP). This study evaluates the extent of EC overestimated by carbonates and OC at four remote sites (Nyalamu, Lulang, Everest and Ngari) in southern and western of the TP using different treatments. The average overestimation of EC concentration due to acid treatment was consistent across all sites (25.5 ± 2.4 %). After correction, the proportion of EC overestimated by carbonates were approximately 8.5 ± 7.3 %, 12.3 ± 6.9 %, 18.1 ± 11.8 % and 22.7 ± 13.3 %, respectively, revealing an increasing trend from humid to arid regions. Methanol-soluble OC (MSOC) concentrations were significantly correlated with the reduction of EC concentrations, indicating that the methanol extraction effectively mitigates EC overestimation. Seasonal variation of carbonaceous aerosol concentrations was significantly affected by sources from South Asia. Despite the variations in climate and aerosol sources, the average overestimations of measured EC concentration by carbonates and OC were similar at Nyalamu (49.4 ± 14.0 %), Lulang (47.8 ± 8.4 %), Everest (48.7 ± 15.9 %) and Ngari (49.3 ± 13.7 %) sites. Therefore, the actual EC concentrations were only about 51.2 ± 13.1 % of the original values. This estimation will significantly enhance the contribution of brown carbon (BrC) to radiative forcing relative to EC, highlighting a critical area for future research. Investigating the actual concentrations of EC in the TP provides critical data to support model simulation and validate model accuracy, further enhancing our understanding of EC's impacts on climate warming and glacier melting.

The health impact of PM2.5 and O3 in Beijing modified by infiltration factors from 2014 to 2022.

PM2.5 and O3 are significant threats to the health of residents and modern residents spend more than 80% of their time indoors, so quantifying indoor exposure of residents has a positive influence on formulating policies and improving health indicators. Analysis of monitoring data shows a consistent decrease in the annual average concentration of outdoor PM2.5 in Beijing from 90.1 to 30.4μg/m3, and the equivalent human exposure concentration also declined from 55.2 to 18.6μg/m3 modified by infiltration factors from 2014 to 2022, while during the peak season, the average value of O3-8h concentration in Beijing has consistently remained between 159.3 and 225.3μg/m3; the equivalent human exposure concentration remained between 64.7 and 92.3μg/m3 modified by infiltration factors from 2014 to 2023. The equivalent exposure concentration is calculated by weighting the concentration of indoor and outdoor pollutants, the proportion of indoor and outdoor activity time of the population, and the permeability coefficient of outdoor pollutants into the room, so as to quantify the actual concentration of pollutants exposed to the human body in a certain time. Previous studies have primarily focused on the impact of annual changes in pollutant concentrations on health estimates, often neglecting indoor concentrations and behavior patterns. This limitation should be addressed. Therefore, this study utilized equivalent human exposure concentration and AirQ + , the authoritative software released by the World Health Organization (WHO), to evaluate quantitatively the impact of PM2.5 and O3 on the health of Beijing residents by combining pollutant concentration, annual population, and mortality of various diseases and other indicators to enhance the credibility of the study. The number of deaths related to PM2.5 has decreased from 28,182 people in 2014 to 10,250 people in 2022 (age ≥ 30). The number of premature deaths in 2022 was only 36.4 percent of that in 2014 and was decreasing by 1992 per year. The number of deaths related to O3 varies between 550 and 3358 people. Lowering PM2.5 and O3 concentrations can effectively reduce natural premature death as well as cardiovascular and respiratory diseases caused by air pollution. The government should persist in enhancing the regulation of PM2.5 and accord significance to the oversight of O3. Concurrently, there is a need to reinforce the cooperative regulation addressing both PM2.5 and O3.

A novel model of kinetics and thermodynamics for shale gas adsorption–diffusion

The study of adsorption–diffusion kinetics in shale gas reservoirs is crucial for predicting reserves and assessing production. Although some scholars have proposed adsorption–diffusion kinetics models, there are few models and interpretation methods that systematically consider Arrhenius’s thermodynamics parameters and actual adsorption gas concentration. In this study, we propose a novel model for analyzing the kinetics processes of adsorbed gas and free gas in shale. The analysis of adsorbed gas kinetics experimental data indicates a negative correlation between temperature and the adsorption–diffusion equilibrium time. Sensitivity analysis of the parameters reveals that three parameters (the diffusion activation energy, adsorption activation energy, and desorption pre-exponential factor) are positively correlated with adsorption–diffusion equilibrium time, whereas the other three parameters (the diffusion pre-exponential factor, adsorption pre-exponential factor, and desorption activation energy) are negatively correlated. Furthermore, we find that higher temperatures lead to lower concentrations of free gas at equilibrium state. Larger radius positions in spherical particles tend to reach adsorption–diffusion equilibrium earlier. Compared to the traditional diffusion kinetics model, the proposed novel model exhibits a significant lag effect in the calculated equilibrium time and more accurately describes the gas adsorption-diffusion kinetics equilibrium process.

Coral-like Ti3C2Tx/PANI Binary Nanocomposite Wearable Enzyme Electrochemical Biosensor for Continuous Monitoring of Human Sweat Glucose

With the continuous advancement of contemporary medical technology, an increasing number of individuals are inclined towards self-monitoring their physiological health information, specifically focusing on monitoring blood glucose levels. However, as an emerging flexible sensing technique, continuous and non-invasive monitoring of glucose in sweat offers a promising alternative to conventional invasive blood tests for measuring blood glucose levels, reducing the risk of infection associated with blood testing. In this study, we fabricated a flexible and wearable electrochemical enzyme sensor based on a two-dimensional Ti3C2Tx MXene nanosheets and coral-like polyaniline (PANI) binary nanocomposite (denoted as Ti3C2Tx/PANI) for continuous, non-invasive, real-time monitoring of sweat glucose. The exceptional conductivity of Ti3C2Tx MXene nanosheets, in conjunction with the mutual doping effect facilitated by coral-like PANI, significantly enhances electrical conductivity and specific surface areas of Ti3C2Tx/PANI. Consequently, the fabricated sensor exhibits remarkable sensitivity (25.16 μA·mM−1·cm−2), a low detection limit of glucose (26 μM), and an extensive detection range (0.05 mM ~ 1.0 mM) in sweat. Due to the dense coral-like structure of Ti3C2Tx/PANI binary nanocomposite, a larger effective area is obtained to offer more active sites for enzyme immobilization and enhancing enzymatic catalytic activity. Moreover, the sensor demonstrates exceptional mechanical performance, enabling a 60° bend in practical applications, thus satisfying the rigorous demands of human sweat detection applications. The results obtained from continuous 60 min in vitro monitoring of sweat glucose levels demonstrate a robust correlation with the data of blood glucose levels collected by a commercial glucose meter. Furthermore, the fabricated Ti3C2Tx/PANI/GOx sensor demonstrated agreement with HPLC findings regarding the actual concentration of added glucose. This study presents an efficient and practical approach for the development of a highly reliable MXene glucose biosensor, enabling stable and long-term monitoring of glucose levels in human sweat.

Quantitative Spermidine Detection in Cosmetics using an Organic Transistor-Based Chemical Sensor.

Spermidine is an essential biomarker related to antiaging. Although the detection of spermidine levels is in high demand in life science fields, easy-to-use analytical tools without sample purification have not yet been fully established. Herein, we propose an organic field-effect transistor-based chemical sensor for quantifying the spermidine concentration in commercial cosmetics. An extended-gate structure was employed for organic field-effect transistor (OFET)-based chemical sensing in aqueous media. A coordination-bond-based sensing system was introduced into the OFET device to visualize the spermidine detection information through changes in the transistor characteristics. The extended-gate-type OFET has shown quantitative responses to spermidine, which indicates sufficient detectability (i. e., the limit of detection for spermidine: 2.3 μM) considering actual concentrations in cosmetics. The applicability of the OFET-based chemical sensor for cosmetic analysis was validated by instrumental analysis using high-performance liquid chromatography. The estimated recovery rates for spermidine in cosmetic ingredient products (108-111 %) suggest the feasibility of cosmetic analysis based on the OFET-based chemical sensor.

Gravimetric and SIM-Headspace GC-MS for Residual Organic Solvents Detection in Halal and Wholesomeness Food Analysis

The demand for halal foods and beverages is increasing globally. While most halal analysis focuses on porcine, this study focuses on assessing residual organic solvents to ensure their halal compliance and wholesomeness, following several Malaysian standards and guidelines. A significant challenge in this study was the volatility of the residual solvents during the preparation of standards and quality control. To address this issue, a gravimetric technique was employed and effectively minimized the difference between theoretical (1,000 ppm) and actual (710 – 892 ppm) concentrations of the residual organic standard stock solution, except for acetone (588 ppm). The aim of this study was to establish a validated, reliable, and accurate method using SIM-headspace GC-MS to identify and quantify residual organic solvents for halal and wholesomeness analysis. Confirmation of each residual organic solvent was achieved by comparing the obtained spectra with the NIST 11 spectral database, containing 70,832 compounds, with similarity ranging from 80.9% to 96.6%, except for acetonitrile at 52.2%. The validation parameters were carried out according to ISO 17025:2017, the Center for Drug Evaluation and Research, and the European Guidelines. The parameters included recovery ranging from 95.65% to 95.68%, precision from 10.08% to 19.65% RSD, linearity between 0.996 to 0.999, limit of detection from 0.01 to 0.08 ppm, and limit of quantification from 0.02 to 0.24 ppm. Uncertainty considerations were limited to recovery, precision, and linearity, as other uncertainties were negligible based on the bottom-up approach using in-house validation data. This combination of gravimetric and SIM-headspace GC-MS techniques has provided valuable insights for discussions and collaborations among halal authorities worldwide to establish a consensus analytical methodology for halal and wholesomeness assessment.

Engineering Cu–Ce-a nanozymes: Revolutionary alloy nanomaterials mimicking cytochrome c oxidase for ultra-sensitive cytochrome c detection

The design of synthetic analogs of cytochrome c oxidase (CcO) is a formidable task due to its intricate structure encompassing multiple metal prosthetic sites and protein subunits. In recent years, artificial enzymes based on alloy nanomaterials have garnered significant attention due to the alloy design approach holds promise for the effective tuning of the properties of metal catalysts. In this study, we present copper-cerium alloy nanozymes (Cu–Ce-a NEs), where Cu mimics the active site of CcO, while Ce endows the alloy phase and enhances the capacity to catalyze the oxidation to cytochrome c (Cyt c). Cu–Ce-a NEs functionally mimics CcO, the terminal enzyme in the respiratory electron transport chain (ETC), by catalyzing the four-electron reduction of dioxygen to water. Utilizing the CcO-like properties of Cu–Ce-a NEs, we successfully implemented the electrochemical detection of Cyt c. The Cu–Ce-a NEs based electrochemical sensor revealed a favorable linear range spanning from 2 to 20 μM Cyt c, with a detection limit (LOD) of 2 μM. This method demonstrates high accuracy in Cyt c quantitation in pharmaceuticals, with results closely aligning with the actual concentrations. This finding not only offers new perspectives in the design of enzyme analogs, but also underscores the potential of this method for clinical Cyt c detection, highlighting its significance in biomedical research and diagnostics.

A new three-dimensional modeling of fluorescence excitation-emission measurements to explore the interaction of hydroxychloroquine and DNA, and to quantify their binding constant

A new three-dimensional chemometric approach was introduced to explore the interaction of hydroxychloroquine (HCQ)-calf thymus deoxyribonucleic acid (DNA) and quantify binding constant using fluorescence excitation and emission measurements. The fluorescence excitation-emission spectra were recorded after gradual titration of HCQ with DNA. Then, the excitation and emission curves and relative concentrations of the drug and drug-DNA complex were quantitatively estimated using a three-dimensional model called Parallel Factor Analysis (PARAFAC) to a cubic fluorescence data array. The interaction of HCQ and DNA was predicted by applying newly modified Stern-Volmer equations to the relationship between the actual DNA concentration, and the HCQ concentration in the relative concentration profile of the PARAFAC model. In the PARAFAC application, the binding constants of the HCQ-DNA complex at 288, 298, and 310 K were found as 6.78 × 103, 5.07 × 103, and 3.74 × 103 L mol−1, respectively. From the temperature studies, the thermodynamic parameters (ΔS0= 3.528 J mol−1 K−1, ΔH0= −20.099 kJ mol−1 and ΔG0=-21.11, −21.12, and −21.19 kJ mol−1 at 288, 298, and 310 K, respectively) were calculated. The drug-DNA interaction is spontaneous due to negative ΔG0 values. The positive ΔS0 and negative ΔH0 values revealed the major role of the electrostatic force on the binding of HCQ to DNA. Assay results obtained from the proposed three-way modeling were compared to those provided by the traditional spectrofluorimetric method.

Unveiling dioxin dynamics: A whole-process simulation study of municipal solid waste incineration

Theoretical research has explained the process of dioxin (DXN) formation in the municipal solid waste incineration (MSWI). This process includes the generation, adsorption, and emission of DXN. Actual DXN concentrations often significantly deviate from theoretical models. This discrepancy is influenced by several key factors: the type of integrated municipal solid waste (MSW) treatment process, the characteristics of the waste, and the operational controls. The progression of DXN generation, adsorption, and emission concentrations within the MSWI process remains unclear. This lack of clarity is especially pronounced when examining the accounting for the specific components of the MSW. To unravel the evolution of DXN, this article proposes a comprehensive numerical simulation model for the entire process of DXN concentration in an MSWI plant. The model is designed based on existing knowledge of MSW combustion and DXN mechanisms, leveraging FLIC and ASPEN simulation software. It incorporates six key stages to facilitate the DXN simulation: precipitation and formation, high-temperature pyrolysis, high-temperature gas-phase synthesis, low-temperature catalytic synthesis, adsorption on activated carbon, and emission to the atmosphere. Under both benchmark and multiple operating conditions, the simulated experiments confirm the effective representation of the evolution of DXN concentrations throughout the process. Consequently, this study presents a model designed to enhance the development of strategies aimed at reducing DXN emissions and to foster innovation in intelligent control technologies.

Oxygen vacancy-enriched WO3 hierarchical tubes inherited from pine needle for the enhanced detection to ppb-level hydrazine at near room temperature

It is of great importance to develop low-temperature gas sensors for monitoring hydrazine (N2H4) with high toxicity and easy explosion. However, how to highly sense its ppb-level concentration remains challenging. For this purpose, biomorphic WO3 structure replicated by small-size nanoparticles was simply prepared though air calcinations of tungsten salt-immersed pine needle (PN) template. The mesoporous WO3-PN tubes with pore volume of 0.096 cc·g−1 had relatively large specific surface area (38 m2·g−1) for exposing more active sites, as well as rich oxygen vacancies (g = 2.005) and small band gap for promoting electron migration. With the assistance of W6+ Lewis acid catalytic sites, such unique multilevel structure facilitated the rapid transport and adsorption of basic N2H4 molecules, as well as their chemical reactions with high content of oxygen species (37.4 %) in sensing layer, thus first achieving the highly sensitive detection of ppb-level N2H4 gas at near room temperature. At 50 °C, WO3-PN sensor exhibited ultra-high response (S = 307), fast response time (Tres = 16 s) for 1 ppm N2H4, and low actual detection concentration (5 ppb). These key indicators were remarkably superior to reported semiconductor gas sensors. In addition, the enhanced low-temperature sensing mechanism of WO3-PN sensor was explored by means of analytical tests and DFT calculations.

Acute toxicity of chlorpyrifos to some non-target freshwater organisms: which one is more toxic-technical grade or commercial formulation?

Chlorpyrifos is among the most widely sold organophosphates in the agriculture sector worldwide. Static bioassays were performed in the laboratory to compare the acute toxicity between the technical grade (94% a.i.) and commercial formulation (20% EC) of chlorpyrifos to four freshwater organisms: the crustacean zooplankton Cyclops viridis, the oligochaete worm Branchiura sowerbyi, the gastropod Pila globosa, and tadpole larvae of Duttaphrynus melanostictus. The recovery of actual chlorpyrifos concentrations in water after 2 h of exposure to the nominal concentrations ranged from 82.98% to 88.56%. The commercial formulation (F) of chlorpyrifos was found to be 1.94 to 2.76 times more toxic than the technical grade (T). Based on 96 h LC50 values of T and F chlorpyrifos, C. viridis was found to be most sensitive (0.56 and 0.25 μg/L) and P. globosa as most tolerant (1482 and 536 μg/L) to chlorpyrifos. Changes in LC50 values of both T and F chlorpyrifos were noted in respect of exposure hours for the three aquatic invertebrates and the tadpole larvae of the toad. In conclusion, the acute toxicity of chlorpyrifos to some non-target freshwater organisms differs between technical grade and commercial formulations.

Health risk assessment taking into account N-nitrosamines’ concentrations in food products

N-nitrosamines formed in meat products, especially during heat treatment, are potentially hazardous to human health. Smoked sausages are a product with a high content of N-nitrosamines, including those not regulated in Russia, which can cause health risks for population. The aim of this study was to perform health risk assessment considering ratios of N-nitrosamine concentrations in food products. The data on N-nitrosamines’ concentrations were analyzed using MS Excel and Statistica 10.0 programs. The relationship between these concentrations was evaluated using Spearman correlation coefficient. Parameterization of dependencies was carried out by regression analysis with evaluation of model significance by Fisher's criterion. Differences at the level of p ≤ 0.05 were considered statistically significant. Risk assessment was performed in accordance with the Guideline R.2.1.10.3968-23. Correlation analysis between N-nitrosamines in smoked sausages revealed a significant correlation between concentrations of NDMA and NEMA (rs = 0.77) and NDMA and NPyRA (rs = 0.81) at p < 0.05. The level of total carcinogenic risk (∑CR) derived from data based on calculated concentrations of NEMA and NPyRA was determined to be unacceptable for the adult population. It should be noted that the contribution to ∑CR value (11.0 %) is related to NEMA and NPyRA that are not regulated in Russia. Our study results support the findings of earlier EFSA publications indicating that not only NDMA and NDEA, but also other N-nitrosamines may form a health risk upon simultaneous exposure. Correlation and regression analyses allowed us to assess the concentrations of NEMA and NPyRA in sausages. Use of both these concentrations and actual NDMA and NDEA concentrations established unacceptable carcinogenic risk for certain consumer groups in case N-nitrosamines concentrations were above regulated level. The contribution of NEMA and NPyRA in ∑CR value was 11.0 %.

Оценка риска здоровью с учетом содержания N-нитрозоаминов в пищевых продуктах

N-nitrosamines formed in meat products, especially during heat treatment, are potentially hazardous to human health. Smoked sausages are a product with a high content of N-nitrosamines, including those not regulated in Russia, which can cause health risks for population. The aim of this study was to perform health risk assessment considering ratios of N-nitrosamine concentrations in food products. The data on N-nitrosamines’ concentrations were analyzed using MS Excel and Statistica 10.0 programs. The relationship between these concentrations was evaluated using Spearman correlation coefficient. Parameterization of dependencies was carried out by regression analysis with evaluation of model significance by Fisher's criterion. Differences at the level of p ≤ 0.05 were considered statistically significant. Risk assessment was performed in accordance with the Guideline R.2.1.10.3968-23. Correlation analysis between N-nitrosamines in smoked sausages revealed a significant correlation between concentrations of NDMA and NEMA (rs = 0.77) and NDMA and NPyRA (rs = 0.81) at p < 0.05. The level of total carcinogenic risk (∑CR) derived from data based on calculated concentrations of NEMA and NPyRA was determined to be unacceptable for the adult population. It should be noted that the contribution to ∑CR value (11.0 %) is related to NEMA and NPyRA that are not regulated in Russia. Our study results support the findings of earlier EFSA publications indicating that not only NDMA and NDEA, but also other N-nitrosamines may form a health risk upon simultaneous exposure. Correlation and regression analyses allowed us to assess the concentrations of NEMA and NPyRA in sausages. Use of both these concentrations and actual NDMA and NDEA concentrations established unacceptable carcinogenic risk for certain consumer groups in case N-nitrosamines concentrations were above regulated level. The contribution of NEMA and NPyRA in ∑CR value was 11.0 %.

Physical and numerical simulation of heat and mass transfer in the furnace of a thermogravimetric analyzer

A numerical study of the processes of heat and mass transfer in the furnace of a thermogravimetric analyzer was carried out, aimed at improving the accuracy of determining the kinetic characteristics of samples during their thermal transformations in different media. Validation of the model and prognostic estimates were carried out in relation to specially conducted thermogravimetric studies of the conversion of fossil and renewable carbon-containing raw materials in successive processes of decarbonization (combustion) and carbonation (mineralization of ash residue). The application of the study results allows to calculate the actual concentrations of the reagent over the sample uncontrolled by the device during pulsed switching of media and the actual temperatures of the sample during its thermochemical transformations.

Physiological Responses and Salt Tolerance Evaluation of Different Varieties of Bougainvillea under Salt Stress.

Soil salinization significantly impacts the ecological environment and agricultural production, posing a threat to plant growth. Currently, there are over 400 varieties of Bougainvillea with horticultural value internationally. However, research on the differences in salt tolerance among Bougainvillea varieties is still insufficient. Therefore, this study aims to investigate the physiological responses and tolerance differences of various Bougainvillea varieties under different concentrations of salt stress, reveal the effects of salt stress on their growth and physiology, and study the adaptation mechanisms of these varieties related to salt stress. The experimental materials consisted of five varieties of Bougainvillea. Based on the actual salinity concentrations in natural saline-alkali soils, we used a pot-controlled salt method for the experiment, with four treatment concentrations set: 0.0% (w/v) (CK), 0.2% (w/v), 0.4% (w/v), and 0.6% (w/v). After the Bougainvillea plants grew stably, salt stress was applied and the growth, physiology, and salt tolerance of the one-year-old plants were systematically measured and assessed. The key findings were as follows: Salt stress inhibited the growth and biomass of the five varieties of Bougainvillea; the 'Dayezi' variety showed severe salt damage, while the 'Shuihong' variety exhibited minimal response. As the salt concentration and duration of salt stress increase, the trends of the changes in antioxidant enzyme activity and osmotic regulation systems in the leaves of the five Bougainvillea species differ. Membrane permeability and the production of membrane oxidative products showed an upward trend with stress severity. The salt tolerance of the five varieties of Bougainvillea was comprehensively evaluated through principal component analysis. It was found that the 'Shuihong' variety exhibited the highest salt tolerance, followed by the 'Lvyehuanghua', 'Xiaoyezi', 'Tazi', and 'Dayezi' varieties. Therefore, Bougainvillea 'Shuihong', 'Lvyehuanghua', and 'Xiaoyezi' are recommended for extensive cultivation in saline-alkali areas. The investigation focuses primarily on how Bougainvillea varieties respond to salt stress from the perspectives of growth and physiological levels. Future research could explore the molecular mechanisms behind the responses to and tolerance of different Bougainvillea varieties as to salt stress, providing a more comprehensive understanding and basis for practical applications.

Determination of interdiffusion coefficients in single crystal superalloys based on solute distribution at the dendritic scale using the Gaussian solution model

Since the initial solute concentration distribution of the sinusoidal solution model shows a significant deviation from the actual concentration distribution of nickel-based single crystal (SX) superalloy dendrites, it is limited to calculate the diffusion coefficient of SX in the homogenization treatment. Therefore, this work proposes a new Gaussian solution model to calculate the diffusion coefficients and the diffusion activation energy of alloying elements in SX superalloy at high temperatures. The diffusion activation energies of W, Ta, and Ti elements in the studied alloy are consistent with the results from other works. This model could more accurately determine the diffusion coefficient of elements during the dendrite homogenization process of SX superalloys since it reflects actual physical processes. Moreover, it has the potential to use in various alloy systems and contributes to the formulation of effective homogenization treatments.

Evaluation of the Amount of Compounded Chemotherapy Drugs: A Comparison Between Nine Compounding Pharmacies.

The use of compounded formulations of chemotherapy in veterinary medicine is common. The purpose of this study was to evaluate the drug amount of two compounded chemotherapeutics (chlorambucil and cyclophosphamide) from multiple veterinary compounding pharmacies, to determine if there was a difference in drug amounts between those that came from 503A versus 503B pharmacies, and finally to determine heterogeneity in drug amounts within each individual pharmacy. Nine veterinary compounding pharmacies (eight 503A, one 503B) were sampled in total, with two different batches sampled from each pharmacy. Each capsule's actual concentration was compared to the intended (prescribed) concentration. Of the 68 total samples obtained, 20 (29%) tested outside the FDA-acceptable discrepancy of ±10%. Of these, 12 (60%) were chlorambucil and 8 (40%) were cyclophosphamide. 503A cyclophosphamide samples had an average discrepancy of 6.6% from the intended dose while samples from the 503B pharmacy had a discrepancy of 1.8%. 503A chlorambucil samples had an average discrepancy of 10.4% from the intended dose while samples from the 503B pharmacy had a discrepancy of 9.6%. Heterogeneity within the same pharmacy and batch ranged from 0.1% to 51% for the 503A pharmacies and 2.6% to 7.5% for the 503B pharmacy. Heterogeneity between different batches within the same pharmacy ranged from 0.4% to 58.3% for the 503A pharmacies and 5% to 14.8% for the 503B pharmacy. Although the drug amounts of compounded cyclophosphamide and chlorambucil manufactured by the 503B compounding pharmacy was more reliably maintained compared to that compounded by the 503A pharmacies, there was ultimately still potential for variability in drug amounts regardless of the pharmacy designation.

Toxicity of Moxifloxacin on the Growth, Photosynthesis, Antioxidant System, and Metabolism of Microcystis aeruginosa at Different Phosphorus Levels.

Moxifloxacin (MOX), a widely used novel antibiotic, may pose ecological risks at its actual environmental concentrations, as has been detected in aquatic systems. However, its ecotoxicity to aquatic organisms and regulatory mechanisms of phosphorus in eutrophic aqueous environments are still limited. This study aimed to analyze its physiological and biochemical parameters, including cellular growth, chlorophyll fluorescence, photosynthetic pigments, oxidative stress biomarkers, and metabolomics to elucidate the toxicity induced by environmental concentrations of MOX in Microcystis aeruginosa at different phosphorus levels. The results revealed that the EC50 values of MOX on M. aeruginosa at different phosphorus concentrations were 8.03, 7.84, and 6.91 μg/L, respectively, indicating MOX toxicity was exacerbated with increasing phosphorus levels. High phosphorus intensified the suppression of chlorophyll fluorescence and photosynthetic pigments, while activating the antioxidant enzyme, indicating severe peroxidation damage. Metabolomic analysis showed MOX induced different discriminating metabolites under different phosphorus levels, and perturbed more biological pathways at higher phosphorus concentrations, such as starch and sucrose metabolism, pyrimidine metabolism, and glycerolipid metabolism. This indicates that phosphorus plays an important role in regulating metabolism in M. aeruginosa exposed to MOX. The findings provide valuable information on the mechanisms involved in cyanobacteria responses to antibiotic stress, and offer a theoretical basis for accurately assessing antibiotic toxicity in eutrophic aqueous environments.

Constructing the Electron-Rich Microenvironment of an All-Polymer-Based S-Scheme Homostructure for Accelerating Uranium Capture from Nuclear Wastewater.

Large quantities of uranium-containing radioactive wastewater are typically generated during nuclear fuel cycle processes. Despite significant efforts, efficient capture of migratable hexavalent uranium U(VI) is still a huge challenge due to its acidity, radioactivity, coexisting organics, and high impurity cation abundance in wastewater. Herein, we have fabricated all-polymer-based 0D/2D C4N/C6N7 homostructure hybrids with an S-scheme electronic configuration by coordinating the band engineering of semiconductors to enrich uranium species from the complex wastewater environment. The sample can capture over 97% of U(VI) in the actual concentration of nuclear industrial reprocessing wastewater; also, the U(VI) enrichment ratio still exceeds 95% when the irradiation dose (including α, β, and γ) is up to 100 kGy. Density functional theory and X-ray absorption spectroscopy demonstrate that the aggregation of charge carriers on the surface of the sample regulates the electron-rich microenvironment, thus accelerating the reduction conversion of single electron reaction uranium disproportionation. It is expected that this work can provide more insight into other functional materials, thereby promoting uranium removal advancements in nuclear wastewater.