Concentration Of Suspended Particles Research Articles

The Forces Driving Streaming in the Presence of Scatterers Mimicking the Blood Cells and the Contrast Agents

Acoustical Driving Forces (ADF), induced by propagating waves in a homogeneous and inhomogeneous lossy fluid (suspension), are determined and compared depending on the concentration of suspended particles. Using integral equations of the scattering theory, the single particle (inclusion) ADF was calculated as the integral of the flux of the momentum density tensor components over the heterogeneity surface. The possibility of negative ADF was indicated. Originally derived, the total ADF acting on inclusions only, stochastically distributed in ambient fluid, was determined as a function of its concentration. The formula for the relative increase in ADF, resulting from increased concentration was derived. Numerical ADF calculations are presented. In experiments the streaming velocities in a blood-mimicking starch suspension (2 μm radius) in water and Bracco BR14 contrast agent (SF6 gas capsules, 1 μm radius) were measured as the function of different inclusions concentration. The source of the streaming and ADF was a plane 2 mm diameter 20 MHz ultrasonic transducer. Velocity was estimated from the averaged Doppler spectrum obtained from originally developed pulsed Doppler flowmeter. Numerical calculations of the theoretically derived formula showed very good agreement with the experimental results.

Water temperature and organic carbon control spatio‐temporal dynamics of particle‐attached and free‐living bacterial communities in a hypereutrophic urban river network

Abstract Bacteria are an important component of the aquatic ecosystem playing a key role in the transformation and mineralisation of allochthonous organic matter, nutrients and pollutants. However, there is no clear understanding of spatio‐temporal patterns of particle‐attached versus free‐living bacterial abundances, diversities and communities, which limits our in‐depth understanding of hypereutrophic urban river ecosystems and the mechanisms regulating nutrient cycling and biogeochemical transformations. In order to investigate spatio‐temporal patterns and associated factors for aquatic particle‐attached versus free‐living bacterial communities, we conducted a 2‐year study of four contrasting habitats in a hypereutrophic urban river network of eastern China. Bacterial abundance and community structure in relation to various environmental variables were assessed by epifluorescence microscopy and high‐throughput sequencing techniques. Results revealed that particle‐attached bacterial abundance depended mainly on suspended particle concentrations, whereas free‐living bacterial abundance was correlated with nutrient availability and water temperature. Organic carbon was related to a decrease of free‐living and particle‐attached bacterial richness, and particulate matter input increased free‐living bacterial diversity. Seasonal changes of water temperature were linked to the temporal dynamics of bacterial community composition, and the differences in total organic carbon concentrations contributed to spatial differences in bacterial community composition. There were significant differences in bacterial community composition between particle‐attached and free‐living assemblages in low‐turbidity/low‐nutrient rivers found in land areas comprising mainly natural vegetation. These differences were especially prominent for the relative abundances of Cyanobacteria and Actinobacteria, which were higher in the particle‐attached and free‐living fractions, respectively. However, no significant differences were found in turbid/nutrient‐rich rivers. Total organic carbon was the most significant factor shaping the composition similarity between particle‐attached and free‐living bacterial communities. Our findings indicate that spatio‐temporal variations in water temperature, suspended particle and resource availability, especially for organic carbon, appreciably contribute to changes in the abundance, diversity and composition of aquatic particle‐attached versus free‐living bacterial communities in the hypereutrophic urban river network. Considering that biodiversity is important for supporting ecosystem functioning, this study informs spatio‐temporal patterns of particle‐attached and free‐living bacterial abundance, diversity and composition of communities, and their underlying control mechanisms, thereby providing fundamental knowledge of microbial ecological functions for remediation and sustainable management of hypereutrophic urban river ecosystems.

Bacterial Flora on Mist Outlet Surfaces in 4D Theaters and Suspended Particle Concentration Characteristics during 4D Movie Screenings.

In this study, we measured suspended particle concentrations during the screening of 4D movies (3 screens and 15 movies) and 2D movies (9 screens and 9 movies) in 3 movie theaters to obtain a more detailed understanding of the situation of suspended particle concentrations and adherent bacterial flora in 4D movie theaters, which have been introduced in increasing numbers in recent years. The adherent bacterial flora on the floor and mist outlet surfaces in the 4D movie theaters were collected and analyzed. During the movie showings, the concentrations of suspended particles in 4D movie theaters were significantly higher than those in 2D movie theaters (p < 0.001). A significant increase in suspended particle concentrations due to 4D movie effects was also observed. The results of the α-diversity and β-diversity analyses indicate that the bacterial flora on the surfaces of mist outlets in 4D movie theaters are similar. Moreover, there are many closely related species, and the bacterial flora are rich and contain rare bacterial species. Many of the bacterial genera that are dominant in 4D theaters are suited to aqueous environments, and bacteria in the water supply system may have an impact on the indoor environment.

Improved corrosion protection of a NiTi implant by an electrodeposited HAp-Nb2O5 composite layer

The mechanical and biological characteristics of NiTi alloy provide opportunities in biomedical fields ranging from orthopedics to intravascular stents. However, Ni ion release when the alloy is exposed to corrosive body fluid can lead to long-term health-related concerns. Improved surface engineering via the application of biological layers on the NiTi can contribute to higher corrosion resistance. HAp-based layers were cathodically deposited from an aqueous electrolyte containing calcium nitrate, ammonium dihydrogen phosphate, and concentrations of suspended Nb2O5 particles from 0 to 1 g/L under pulsed current conditions. Surface morphology, topography, and surface chemistry of the electroplated layers were characterized by FESEM, AFM, and FTIR analysis, respectively. The corrosion behavior of the bare and coated samples in Ringer's solution was evaluated by EIS and potentiodynamic polarization; the corroded surfaces were imaged by FESEM. A more compact and smoother surface was formed in the presence of particulate Nb2O5 inclusions. The composite coating showed excellent anti-corrosion properties, increasing the polarization resistance of pure HAp films by >10 times. FESEM imaging of corroded surfaces showed the partial detachment of plate-like HAp crystals from the surface of the coated NiTi in contrast to the pitting of the bare NiTi surface. The surface modification of NiTi by electrodeposited HAp-Nb2O5 composite coatings might play an important role in the future use of NiTi in clinical applications.

Optimization of experimental conditions for exposure of larval mussels (Mytilus californianus) to microplastic particles

Inputs of plastic pollution in marine environments continue to increase, making it essential to understand potential impacts on commercially important marine and estuarine species. Bivalve larvae have been shown to take up micro- and nano-sized plastics; however, exposures detailed in the literature often do not account for particle dynamics, such as eco-corona formation, agglomeration, or settlement. There is clearly a need to define and maintain suspended particle concentrations during exposure periods, while using culture systems that support the growth and survival of the test organism. Therefore, experiments were designed to optimize the components of an exposure system for both particle suspension, as well as larval mussel growth and survival. The suspension and clumping of 2 μm ultra-pure latex beads were assessed to determine the influence of flask shape, agitation, and dispersant type. These results were paired with an assessment of the effects of antibiotics, flask shape, flask rotation, and dispersant type on mussel larvae growth and survival. The combination of these experiments revealed that the optimum system for exposure of bivalve larvae to micro-sized plastics was in rotating, dimple-bottom flasks with additions of 2.5 mg.L−1 methyl cellulose and 2 mg.L−1 chloramphenicol in natural, 1 μm filtered seawater. This optimized system was used to assess the impacts of 2 μm ultra-pure latex beads on the survival and growth of Mytilus californianus larvae. First, a dose-response experiment was carried out to assess the impacts of a two-week exposure of larval mussels to microplastics concentrations that were 0%, 20%, 33.3%, 42.9%, and 50% of total cell volume of the algal ration. For these experiments the algal rations were all kept at 100%. Subsequently, a second experiment was carried out to assess impacts of a two-week exposure of larval mussels to microplastics where both the percent by volume of the algal (0–100%) ration and beads (0–100%) varied so that the total particle volume in the exposures remained constant (100% total). When algal food rations were held constant, a dose-dependent decrease in growth was observed with increasing concentrations of beads. When algal rations decreased, growth and survival decreased to a greater extent when microplastic beads were present. These results indicate that both concentrations of microplastic particles and volumetric ratios of algae rations to microplastic particles determine responses of mussel larvae, with microplastics having a greater effect on larval survival when added to low algal rations.

Electrospun Nanofibrous Membranes for Air Filtration: A Critical Review

Air filtration is an urgent global need because, in many countries and regions, the high concentration of inhalable suspended particles in the air is causing irreversible damage to human health. The use of nanofibrous membranes can help to reduce airborne particulate matter because of their large surface area, extremely porous structure, and adjustable pore size. However, despite their unique properties, the main drawbacks of nanofibre membranes are their poor mechanical properties. This review focuses on nanofibrous membranes prepared by electrospinning, a versatile technique in which the process parameters allow control of the morphology and dimensional characteristics of the nanofibres. Recent literature on air filtration is reviewed, focusing on the performance of materials such as pure or mixed polymers, organic–inorganic composites, and ‘green’ materials in the form of nanofibrous membranes. Finally, the recently proposed layered structures for nanofibre-based air filters are reviewed, offering the latest and most innovative solutions.

A review on rheological models and mathematical problem formulations for blood flows

A review on constitutive equations proposed for mathematical modeling of laminar and turbulent flows of blood as a concentrated suspension of soft particles is given. The rheological models of blood as a uniform Newtonian fluid, non-Newtonian shear-thinning, viscoplastic, viscoelastic, tixotropic and micromorphic fluids are discussed. According to the experimental data presented, the adequate rheological model must describe shear-thinning tixotropic behavior with concentration-dependent viscoelastic properties which are proper to healthy human blood. Those properties can be studied on the corresponding mathematical problem formulations for the blood flows through the tudes or ducts. The corresponding systems of equations and boundary conditions for each of the proposed rheological models are discussed. Exact solutions for steady laminar flows between the parallel plates and through the circular tubes have been obtained and analyzed for the Ostwald, Hershel-Bulkley, and Bingham shear-thinning fluids. The influence of the model parameters on the velocity profiles has been studied for each model. It is shown, certain sets of fluid parameters lead to flattening of the velocity profile while others produce its sharpening around the axis of the channel. It is shown, the second-order terms in the viscoelastic models give the partial derivative differential equations with high orders in time and mixed space-time derivatives. The corresponding problem formulations for the generalized rhelogical laws are derived. Their analytical solutions in the form of a normal mode are obtained. It is shown, the dispersion equations produce an additional set for the speed of sound (so called second sound) in the fluid. It is concluded, the most general rheological model must include shear-thinning, concentration and second sound phenomena

Determination of Particulate Matters and Total Suspended Particles emitted from Incense Burning

Incense burning is an important ceremonial ritual in Buddhism. It is well recognized that incense smoke has negative health effects, which may be caused by the emission of submicron particles, including ultrafine and nanoparticles. Hence, in this study, the concentration of particulate matter (PM) and total suspended particles (TSP) emitted from incense burning were determined from 4 incense stick brands. The experiment was conducted in a room with a volume of approximately 146m3 using two instruments: an HV sampler and a Nano Sampler. The highest TSPs concentration from long sticks and short sticks were S1 (319.03 μg/m3) and N2 (439.75 μg/m3), respectively. High mass concentration was found in the ultrafine particle range for S2 (112.27 μg/m3) and N2 (117.30 μg/m3). In contrast, S1 and N1 exhibited high concentrations in the coarse particle mode at 79.28 μg/m3 and 86.75 μg/m3, respectively. Out of the 4 incense brands, N2 appeared to have the highest concentration in almost every particle range compared to the other 3 brands. Incense should be burned in a well-ventilated setting and try not to stay in the same place as the altar to reduce the risk of incense smoke exposure.

MODELLING OF A THREE-DISPERSED SUSPENSION FILTRATION

The injection method of soil stabilization is one of the methods to improve the soil base during the road construction. This method consists in the introduction of special compounds into the ground with the help of special equipment. Such compositions, as a rule, are solutions of polymers or cement, which harden, forming a solid base. The advantages of the injection method of soil stabilization for roads include rapid completion of work, minimal environmental impact, the possibility of application in difficult geological conditions, as well as strengthening the soil base at great depth. Injection solutions penetrate into microcracks and micropores of soils, forming a deposition. The study of liquid filtration in a porous soil system is of great practical importance. The paper considers the filtration of liquid in a porous medium with three types of particles. In the considered problem, each of the three types of suspension particles is characterized by its linear filtration function. It determines the size-exclusion particle capture mechanism, in which particles whose diameter exceeds the size of the pores get stuck in them, the rest pass through them unhindered. Numerical solutions are obtained for the concentrations of suspended particles of three types, as well as the total deposition. Depending on the initial parameters of the problem, the concentrations of suspended particles are either monotonic functions or non-monotonic, reaching the maximum value. In this paper, asymptotic solutions are constructed for the concentrations of suspended and retained particles near the concentration front, which are compared with numerical ones. The solution is obtained at infinity using a traveling wave.

Simulation of sandstone formation damage caused by solid particle invasion

During the drilling and completion process, the invasion of solid particles can have a serious impact on reservoir permeability, but there is a lack of effective prediction models for its impact. We developed a prediction model of solid particle invasion damage in response to the issue of reservoir damage induced by solid particle invasion during the exploitation of sandstone reservoirs. By considering the changes in pore permeability characteristics, particle migration and rock stress-strain state are coupled. The findings reveal that as filtration duration increases, the concentration of suspended particles and sediment particles increases, resulting in a progressive reduction in formation permeability around the wellbore. The greater the filtration coefficient, the greater the quantity of particle deposition, however, this also leads to a slowdown in the growth in deposition quantity. As the diffusion rate increases, particles are more likely to deposit. The concentration of suspended particles decreases progressively as tortuosity increases, as does the concentration of sediment particles. Large saturation sedimentation in the pore throat may cause more suspended particles to deposit, lower the effective seepage channel of the pore throat, and drastically impair formation permeability. The results of the impact factor comparison showed that filtration coefficient and medium tortuosity are the key factors. Improving the temporary plugging effect of solid particles in formations with large tortuosity of pore throats can effectively reduce reservoir damage. The findings of this study can help for optimization design of solid particles in drilling fluid for reservoir protection.

Prediction of Clean-room Air-conditioning Defects Using Deep Learning and a Differential Pressure Sensor

A clean room is used for adjusting the concentration of suspended particles using an air-conditioner. It has a fan-filter unit combining a centrifugal fan and a high-efficiency particulate air filter that purifies the outside air and directly affects its cleanliness. Defects in these systems are typically detected using special sensors for each fault, which can be costly. Therefore, this paper proposes a system for diagnosing defects in the fan-filter unit using a single differential sensor and deep learning. The fan-filter unit is part of the air-conditioning system, and it is usually defective in bearings, filters, and motors. These faults include ball wear, internal bearing contamination, filter contamination, and motor speed changes. Each defect was artificially induced in experiments, and the differential pressure data of each defect was learned using a long short-term memory (LSTM) deep learning algorithm. The results of deep learning experiments generated by randomly mixing data five times were presented using a confusion matrix, and the results showed an accuracy of 87.2±2.60%. Therefore, the possibility of diagnosing defects in the fan-filter unit using a single sensor was confirmed.

Virioplankton and virus-induced mortality of prokaryotes in the Kara Sea (Arctic) in summer.

Among the Arctic seas, the largest volume of river runoff (~45% of the total river-water inflow into the Arctic Ocean) enters the Siberian Kara Sea. The viral communities of the Kara Sea are important for the functioning of the marine ecosystem. Studies of virus-prokaryote interactions on the Kara Sea shelf have been conducted only in spring and autumn. Here, we investigated the abundance of free viruses, viruses attached to prokaryotes, and pico-sized detrital particles; the morphology (shape and size) of the viruses, viral infection and virus-mediated mortality of prokaryotes in early summer, i.e., during a seasonal ice melting period and maximum inflow of river-water volumes with high concentrations of dissolved and suspended organic carbon. Seawater samples for microbial analyses were collected across the Kara Sea shelf zone on board the Norilskiy Nickel as a research platform from June 29 to July 15, 2018. Abundances of prokaryotes (range (0.6-25.3) × 105 cells mL-1) and free viruses (range (10-117) × 105 viruses mL-1) were correlated (r = 0.63, p = 0.005) with an average virus: prokaryote ratio of 23.9 ± 5.3. The abundance of free viruses and viral-mediated mortality of prokaryotes were significantly higher in early summer than in early spring and autumn. Free viruses with a capsid diameter of 16-304 nm were recorded in the examined water samples. Waters in the Kara Sea shelf contained high concentrations of suspended organic particles 0.25-4.0 µm in size (range (0.6-25.3) × 105 particles mL-1). The proportions of free viruses, viruses attached to prokaryotes, and viruses attached to pico-sized detrital particles were 89.8 ± 6.0%, 2.2 ± 0.6% and 8.0 ± 1.3%, respectively, of the total virioplankton abundance (on average (61.5 ± 6.2) × 105 viruses mL-1). Viruses smaller than 60 nm clearly dominated at all studied sites. The majority of free viruses were not tailed. We estimated that an average of 1.4% (range 0.4-3.5%) of the prokaryote community was visibly infected by viruses, suggesting that a significant proportion of prokaryotic secondary production, 11.4% on average (range 4.0-34.0%), was lost due to viral lysis. There was a negative correlation between the abundance of pico-sized detrital particles and the frequency of visibly infected prokaryotic cells: r = -0.67, p = 0.0008.

Using deep learning to assess temporal changes of suspended particles in the deep sea

While suspended particles play many important roles in the marine environment, their concentrations are very small in the deep sea, making observation difficult with existing methods: water sampling, optical sensors, and special imaging systems. Methods are needed to fill the lack of environmental baseline data in the deep sea, ones that are inexpensive, quick, and intuitive. In this study we applied object detection using deep learning to evaluate the variability of suspended particle abundance from images taken by a common stationary camera, “Edokko Mark 1”. Images were taken in a deep-sea seamount in the Northwest Pacific Ocean for approximately one month. Using the particles in images as training data, an object detection algorithm YOLOv5 was used to construct a suspended particle detection model. The resulting model successfully detected particles in the image with high accuracy (AP50 &amp;gt; 85% and F1 Score &amp;gt; 82%). Similarly high accuracy for a site not used for model training suggests that model detection accuracy was not dependent on one specific shooting condition. During the observation period, the world’s first cobalt-rich ferromanganese crusts excavation test was conducted, providing an ideal situation to test this model’s ability to measure changes in suspended particle concentrations in the deep sea. The time series showed relatively little variability in particle counts under natural conditions, but there were two turbidity events during/after the excavation, and there was a significant difference in numbers of suspended particles before and after the excavation. These results indicate that this method can be used to examine temporal variations both in small amounts of naturally occurring suspended particles and large abrupt changes such as mining impacts. A notable advantage of this method is that it allows for the possible use of existing imaging data and may be a new option for understanding temporal changes of the deep-sea environment without requiring the time and expense of acquiring new data from the deep sea.

Experimental and numerical investigations of particle suspension suppression mechanisms for a particle-suppression device in a stirred liquid bath

Particle suspension in a turbulent flow can seriously affect the performance of manufactured products in many industrial processes in which the motion of particles cannot be modeled using the numerical method because of the enormous number of particles. Therefore, in this study, a full-scale computational fluid dynamics (CFD) simulation and a 1/5 scaled-down water model experiment were employed to investigate the flow pattern and dynamic behavior of particles in a continuously stirred vessel system. Based on the understanding of the suspension mechanism of settling particles, a particle-suppression device was designed to realize the harmless movement and deposition of particles. The results showed that the flow guidance and division mechanisms of the particle-suppression device led to the inhibition of particle suspensions. In addition, the optimal parameter combination for the device from the water model experiment combined with the orthogonal experimental design, resulted in a 98.3% reduction in the concentration of suspended particles. The suspension of particles was effectively suppressed, which improves product quality and production efficiency. Reliable results can be achieved by combining CFD simulations and water model experiments.

Particle size distribution measurements of widely distributed carbonyl iron powder particles in concentrated suspensions using ultrasonic attenuation

In this paper, particle size distribution (PSD) of widely distributed carbonyl iron powder (CIP) particles in concentrated suspensions was measured using the ultrasonic attenuation technology to analyze their dispersion behaviors. Importantly, their zeta potential was measured using electroacoustic technology. Both visco-inertial and scattering mechanisms were considered while measuring the PSD of these particles with primary sizes ranging from about 100 nm to 10 μm. As a result, the opposite evolution of the PSD curves was observed for nanoscale particles and microparticles, namely, d 01 increased and d 99 decreased when the concentration increased from 15 wt% to 35 wt%, whereas the trend was reversed when the concentration increased from 35 wt% to 75 wt%. This outcome means that changes in concentration cause small and large particles to have opposite dispersion behaviors. The zeta potential of the particles was negative, with absolute values not higher than 22 mV, whereas particle concentration and carrier liquids exerted some effects. This opposite evolution was found first while measuring PSD in concentrated suspensions, where non-Derjaguin, Landau, Verwey, and Overbeek interactions could markedly influence the dispersion behaviors of the widely distributed CIP particles. These results might bring forward some challenges to disperse these particles fully for some advanced applications.

Characterizing a Year-Round Particulate Matter Concentration and Variation under Different Environmental Controls in a Naturally Ventilated Dairy Barn

A mixing fan and spraying system is commonly used to control the indoor environment of naturally ventilated dairy barns worldwide. However, its impact on particulate matter (PM) concentration and variation is still unclear due to the lack of year-round field data. To systematically characterize the PM dynamics under different environmental controls (namely, EC1: No Fans and No Spraying; EC2: Fans; EC3: Fans and Spraying), a year-round continuous monitoring of PM less than 2.5 μm in aerodynamic diameter (PM2.5) and total suspended particle (TSP) concentrations, as well as indoor environmental factors, was carried out inside a naturally ventilated dairy barn using an IoT-based sensor monitoring network. Results showed that the hourly mean TSP and PM2.5 concentrations were 94.7 μg m−3 and 49.8 μg m−3, respectively. EC2 had a higher TSP content (116.6 μg m−3) than EC1 (98.0 μg m−3) and EC3 (81.9 μg m−3). EC1 had the greatest PM2.5 concentration (57.1 μg m−3), followed by EC2 (48.3 μg m−3) and EC3 (44.7 μg m−3). EC1 showed clear TSP and PM2.5 fluctuations during the daily operations at 07:00 to 08:00 and 18:00 to 19:00, while irregular peaks in EC2 and a relatively steady diurnal variation in EC3 were found. Daily Tsp concentrations in the three ECs did not exceed 300 μg m−3. However, 17.8%, 11.5%, and 4.8% of the observed days in EC1, EC2, and EC3 had daily mean PM2.5 concentrations above the healthy threshold (75 μg m−3), mostly from 07:00 to 08:00 and 22:00–07:00. In conclusion, the mixing fan and spraying system had significant effects on PM concentration and variation, and more protection procedures should be taken for farm workers to prevent long-term health risk exposure, to EC1 in particular.

Simulation study on clogging of suspended particles in in-situ leaching of uranium at different concentrations and flow velocity

Clogging problem has become one of the key problems restricting the mining efficiency of in-situ leaching of uranium, and the related research on the law and mechanism of physical clogging has not been reported. In order to identify and understand the complicated law and mechanism, experimental device is established to simulate the physical clogging caused by suspended particles in the uranium process, the physical clogging law and mechanism under different concentrations and velocity of flow are studied. The experimental results show that with the concentration of suspended particles increasing from 100, 200, 300 to 400 mg/L, the permeability of porous media gradually decreases, and the clogging phenomenon becomes more and more obvious. When the size of suspended particles is small and the velocity is 15 mL/min, the porous medium will not appear clogging, while the velocity is 25mL/min, the whole porous medium will slowly appear internal deposition clogging. When the size of suspended solids is larger and the flow rate is 9, 12, 15mL/min, the higher the velocity, the faster the clogging will be, and backwash can alleviate the surface clogging but cannot change the final clogging result. According to the experiment and actual situation, the physical clogging in in-situ leaching of uranium is mainly surface clogging and filter clogging.

Effects of suspended particles in the Jinjiang River Estuary on the physiological and biochemical characteristics of Microcystis flos-aquae.

The effects of different concentrations (100, 150, 200, 250mg/L) and different particle sizes (0-75μm, 75-120μm, 120-150μm, 150-500μm) on the soluble protein content, superoxide dismutase (SOD) and catalase (CAT) activity, malondialdehyde (MDA) content, chlorophyll a (Chla) content, and photosynthetic parameters of Microcystis flos-aquae were studied, and the mechanism of the effect of suspended particulate matter on the physiology and biochemistry of Microcystis flos-aquae was discussed. The results showed that the soluble protein content of Microcystis flos-aquae did not change noticeably after being stressed by suspended particles of different concentrations/diameters. The SOD activity of Microcystis flos-aquae first increased and then decreased with increasing suspended particulate matter concentrations. The SOD activity of Microcystis flos-aquae reached 28.03 U/mL when the concentration of suspended particulate matter was 100mg/L. The CAT activity of Microcystis flos-aquae increased with increasing concentrations of suspended particles and reached a maximum value of 12.45 U/mg prot in the 250mg/L concentration group, showing a certain dose effect. Small particles had a more significant effect on SOD, CAT, and MDA in Microcystis flos-aquae than large particles. The larger the concentration was and the smaller the particle size was, the stronger the attenuation of light and the lower the content of Chla. Both the maximum quantum yield of PSII (Fv/Fm) and the potential photosynthetic activity of PSII (Fv/F0) of Microcystis flos-aquae increased at first and then decreased under different concentrations/sizes of suspended particles. The relative electron transfer rate gradually returned to a normal level over time. There was no significant difference in the initial slope (α) value between the treatment group and the control group, and the maximum photo synthetic rate (ETRmax) and the semilight saturation (Ik) decreased.

Air quality and the health of Norilsk population: dynamics of the situation over 20 years

The article presents a retrospective analysis of the dynamics of air pollution in Norilsk with emissions from the largest metallurgical enterprise MMC Norilsk Nickel. In the city, for many years, elevated concentrations of sulfur dioxide, suspended particles, nickel, copper, benzo(a) pyrene and other substances have been recorded. Their impact has led to increased morbidity and mortality among the population of Norilsk. Estimated health risks from exposure to fine particulate matter (PM10) and sulfur dioxide are given. The excess mortality of Norilsk residents from exposure to sulfur dioxide decreased from 10% in 2007 to 0.8% in 2014—2019.Dynamics of mortality in Norilsk for 2008—2019 compared with data on the urban population of the Krasnoyarsk Territory is ambiguous. The mortality of men from all causes, including cerebrovascular and circulatory system diseases, is lower than in other cities of the Krasnoyarsk Territory, but higher from respiratory diseases. Mortality among women in Norilsk is higher than in the urban population of the Krasnoyarsk Territory by 16.6%, incl. from diseases of the respiratory system — by 82.7%, from diseases of the circulatory system — by 6.5%. The higher mortality rate of the female population of Norilsk among other cities of the Krasnoyarsk Territory may indicate the detrimental effects of the impact of polluted atmospheric air on the female part of the population.

Tribological variable-friction coefficient models for the simulation of dense suspensions of rough polydisperse particles

The rheology of concentrated suspensions of particles is complex and typically exhibits a shear-thickening behavior in the case of repulsive interactions. Despite the recent interest arisen, the causes of the shear-thickening remain unclear. Frictional contacts have been able to explain the discontinuous shear thickening in simulations. However, the interparticle friction coefficient is considered to be constant in most simulations and theoretical works reported to date despite the fact that tribological experiments demonstrate that the friction coefficient can not only be constant (boundary regime) but also decrease (mixed regime) or even increase (full-film lubrication regime), depending on the normal force and the relative velocity between the particles and the interstitial liquid between them. Interestingly, the transition between the boundary regime and the full-lubrication regime is governed by the particle average roughness. Particle-level simulations of suspensions of hard spheres were carried out using short-range lubrication and roughness-dependent frictional forces describing the full Stribeck curve. Suspensions with different particle’s roughness were simulated to show that the particle roughness is a key factor in the shear-thickening behavior; for sufficiently rough particles, the suspension exhibits a remarkable shear-thickening, while for sufficiently smooth particles, the discontinuous shear-thickening disappears.