Variation Of Particle Concentration Research Articles

Abstract 5161: Integrating patient’s derived organoids and liquid biopsy: An exploratory study of early stage pancreatic cancer

Abstract Background: Pancreatic cancer (PC) has a 5-year survival of 12% despite recent therapeutic advancements. There is a desperate need to discover novel ways of treating PC since a large proportion of patients do not benefit from therapy and experience significant toxicity. A major cause of therapy failure is therapy resistance due to tumor heterogeneity. Nowadays, a deeper understanding of tumor heterogeneity could be assisted by the use of patients-derived organoids (PDOs). Furthermore, the use of liquid biopsy may allow for the investigation of circulating factors with predictive value and for disease monitoring over time. Methods: Patients were enrolled in the comprehensive, multiomic study of pancreatic cancer CONTAINER. Patients with early stage PC treated with preoperative chemotherapy or undergoing surgery first were selected for the present study. When possible, a surgical specimen was collected to obtain PDOs. Tissue from resected tumors was dissociated by GentleMACSTM dissociator (Miltenyi Biotec), fragments were embedded in MatrigelTMand cultured in PancreaCultTM human Organoid Media (stemcell technologies). PDO histological features were investigated by H&E staining and IHC. Blood samples were collected before and one month after surgery. From blood samples circulating tumor cells (CTCs) were enriched and isolated, extracellular vesicles (EVs) were isolated from plasma with size-exclusion chromatography and their concentration and size distribution was evaluated with NanoSight NS300. Then, EV surface antigens were characterized by flow cytometry. A panel of inflammatory cytokines was finally evaluated through Ella Automated Immunoassay System. Results: In CONTAINER study 113 patients were enrolled and 30 of them underwent surgery. 21 surgical specimens were received from which 18 PDOs were successfully established. EVs with diameter ≥ 70nm were isolated from plasma, EV mean size was similar before and after surgery whereas individual variations in particle concentration and in surface antigen exposure were observed. Correlation with clinical and pathological characteristics of patients will be performed once reached an adequate sample size for statistical analyses. A panel of inflammatory cytokines (IL1β-, IFNγ, TNFα, IL6, IL8, TGFβ1, CRP and Leptin) was assessed in plasma samples obtained before and after surgery. Except for IL1β, a significant individual variation of circulating cytokines before and after surgery was observed. Conclusions: This study will contribute to unveil mechanisms of disease progression and drug resistance in PC. Possible predictive factors and mechanisms of drug resistance will be investigated taking advantage of the information derived from both in vitro models and circulating tumor-related entities. Citation Format: Michela Cortesi, Tania Rossi, Michele Zanoni, Sara Bandini, Carlo Alberto Pacilio, Alessandro Cucchetti, Martina Valgiusti, Chiara Gallio, Alessandro Passardi, Giorgia Gurioli, Sara Bravaccini, Alessandra Dubini, Giovanni Luca Frassineti, Paola Ulivi, Giovanni Martinelli, Giorgio Ercolani, Ilario Giovanni Rapposelli. Integrating patient’s derived organoids and liquid biopsy: An exploratory study of early stage pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5161.

Spectral characteristics of particle preferential concentration in turbulence computed by Eulerian and Lagrangian methods

This study conducts a comprehensive analysis of the Fourier spectra characteristics of particle preferential concentration in turbulent flows obtained by Eulerian and Lagrangian modelling approaches for different Stokes numbers. Particle preferential concentration is characterized by clusters and voids in the spatial particle distributions formed in turbulent flows and can significantly influence processes such as droplet coalescence, evaporation, and gas-particle reactions. The research primarily focuses on comparing the performance of two Eulerian models—one with and one without second-order velocity moments—and one Lagrangian model, which are used to predict particle dispersion. Key findings include the impact of artificial diffusion in Eulerian methods, the superiority of methods incorporating second-order velocity moments contributions at higher Stokes numbers, and the sensitivity of the Lagrangian method to Poisson statistics. Notably, the study reveals minimal variation in mean velocity spectra across different Stokes numbers, as opposed to the marked variations in particle concentration, momentum, and energy spectra. Grid resolution emerges as a crucial factor in enhancing spectral energy predictions in Eulerian methods. The research underscores the nuanced distinctions between Eulerian and Lagrangian methods in modelling preferential concentration, providing a detailed spectral comparison of particle concentration, velocity, momentum, and energy, highlighting the importance of method selection based on specific modelling needs.

Improved multivariable algorithms for estimating oceanic particulate organic carbon concentration from optical backscattering and chlorophyll-a measurements

The capability to estimate the oceanic particulate organic carbon concentration (POC) from optical measurements is crucial for assessing the dynamics of this carbon reservoir and the capacity of the biological pump to sequester atmospheric carbon dioxide in the deep ocean. Optical approaches are routinely used to estimate oceanic POC from the spectral particulate backscattering coefficient bbp, either directly (e.g., with backscattering sensors on underwater platforms like BGC-Argo floats) or indirectly (e.g., with satellite remote sensing). However, the reliability of algorithms which relate POC to bbp is typically limited due to the complexity of interactions between light and natural assemblages of marine particles, which depend on variations in particle concentration, composition, and size distribution. This study expands on our previous work by analysis of an extended field dataset created with judicious data inclusion criteria with the aim to provide POC algorithms for multiple light wavelengths of measured bbp, which can be useful for applications with in situ optical sensors as well as above-water active or passive measurement systems. We describe an improved empirical multivariable approach to estimate POC from simultaneous measurements of bbp and chlorophyll-a concentration (Chla) to better account for the effects of variable particle composition on the relationship between POC and bbp. The multivariable regression models are formulated using a relatively large dataset of coincident measurements of POC, bbp, and Chla, including surface and subsurface data from the Atlantic, Pacific, Arctic, and Southern Oceans. We show that the multivariable algorithm provides reduced uncertainty of estimated POC across diverse marine environments when compared with a traditional univariate algorithm based on only bbp. We also propose an improved formulation of univariate algorithm based on bbp alone. Finally, we examine performance of several algorithms to estimate POC using our dataset as well as a dataset consisting of optical measurements from BGC-Argo floats and traditional POC measurements collected during a coincident research cruise in the Atlantic Ocean.

Study on Condensed Matter Simulated by Multiphase Fluid-Solid Coupling Fluid Mechanics

The hydrodynamic characteristics of a three-phase gas-liquid-solid turbulent bed with light particle flow and intermittent liquid feeding were numerically simulated by CFD program Fluent6.3. The axial and radial motion of particles in a three-phase gas-liquid-solid turbulent bed and the variation of particle concentration in the bed are studied. The results show that the size and frequency of cavitation increase with the increase of the distance from the axis of the air distribution disk and the distance from the bed surface to the central region. The void varied from narrow to wide, while the void changed in the opposite direction. The bubble lift rate and bubble size are basically the same in axial and radial direction. With the increase of the surface gas velocity and the viscosity of the liquid phase, the average particle content in the bed decreases.

Turbulence effects on the formation and growth of nano-particles in three-dimensional premixed and non-premixed flames

This study examines the impact of turbulence on particle-forming flames via three-dimensional direct numerical simulations. The simulations employ the finite rate chemistry approach to simulate both premixed and non-premixed methane-air turbulent planar jet flames. These flames are doped with titanium tetraisopropoxide (TTIP) to form titanium dioxide TiO2 nanoparticles. The sectional model is employed to solve the population balance equation governing particle dynamics. Through these simulations, a number of the Batchelor scales pertaining to the smaller nanoparticle structures are effectively captured. The analysis conducted on these simulations is to identify and quantify the respective influences of diffusion, coagulation, and inception on variations in particle concentration across different regions within the flame. Several regions of the computational domain with different turbulence intensities are analyzed. Results show that the physical mechanisms that contribute to particle growth are not negligible on the particle concentrations. The impact of normal aN and tangential aT strain rates, which govern the thickness of particle-loaded zones affected by turbulence effects, is also evaluated. Conditional mean values of the strain rates upon the particle number concentration fields and the PDFs of aN and aT confirm that on the iso-surfaces of the particle fields the compressive and stretching effects are predominant. The aforementioned information is used to gain a deeper understanding of the influence of turbulence on premixed and non-premixed particle-forming flames, which will help us to develop transferable models for the simulation of nanoparticle synthesis.

An OpenFOAM solver for computing suspended particles in water currents

Abstract A new OpenFOAM solver has been developed for computing the spatial variation of particle concentrations in flowing water. The new solver was programmed in C ++ using OpenFOAM libraries, and the source code has been made openly available. The current article describes the coding of how the water flow and particle movements are computed. The solver is based on a Eulearian approach, where the particles are computed as concentrations in cells of a grid that resolves the computational domain. The Reynolds-averaged Navier–Stokes equations are solved by simpleFoam, using the k-ε turbulence model. The new solver uses a drift-flux approach to take the fall or rise velocity of the particles into account in a convection-diffusion equation. The model is therefore called sediDriftFoam. The results from the solver were tested on two cases with different types of particles. The first case was a sand trap with sand particles. The geometry was three-dimensional with a recirculation zone. The computed sediment concentrations in three vertical profiles compared well with earlier numerical studies and laboratory measurements. The second case was a straight channel flume with plastic particles that had a positive rise velocity. In this case, the results also compared well with the laboratory measurements.

Thermomagnetic cooling of current carrying micro-wire in ferrofluid: Two-phase approach

Thermomagnetic convection is a controlling phenomenon for heat-transfer in ferrofluids. It depends upon the magnetic field gradients, variation in magnetic susceptibility, particle concentration and temperature gradients. This article presents the effect of these parameters on cooling of a current carrying micro-wire in ferrofluid with a focus on magnetophoresis effects. A two-phase Euler-Euler model is developed. The predictions of this model are compared with experimental results and predictions from a single-phase ferrofluid model. For ferrofluid with volume fraction of φ = 0.02, the predicted average wire temperature from the Euler-Euler two-phase model is approximately 1 K lower than the measured wire temperature,while the single phase model is 5 K higher. Under identical magnetic field and heat flux conditions, variations in the particle concentration are found to have a non-negligible effect on thermomagnetic convective cooling. The maximum temperature of the wire for φ = 0.01 ferrofluid is significantly increased by 10 K and greater enhancement to cooling is observed in the case of φ = 0.04, where the inception of thermomagnetic cooling is advanced. Correspondingly, significantly different thermal and velocity fields are observed for different volume fractions. The simulations show different regimes of heat transfer. During the first few hundred milliseconds after applying electrical current, a thin boundary layer develops near the wire surface and the colder region is thermally stratified. At larger time, dispersion of ferro-particles between colder and hotter regions produces concentration gradients which affect the thermal and velocity fields. Eddies generated by thermomagnetic convection are found to form at the bottom of the vertical wire and retain their structure as they are convected upwards by natural convection. The particle concentration at the wire surface (φws) varies from 0.0188 to 0.0260 for an initial volume fraction (φ) of 0.02. This variation disturbs the thermal boundary layer and generates thermal vortices around the heated wire that differ from single-phase model predictions.

Radiation absorption impact on the thermophysical properties of Cu- and TiO2-water nanofluids: Laplace transform technique

An electrically conducting time-dependent flow of water-based nanofluid comprised of Copper and Titanium oxide over a stationary plate embedding with a porous matrix is analyzed in this study. The novelty arises due to the interaction of both the thermal radiation as well as the radiation absorption that affect the heat transport phenomenon. In the single-phase flow, both the variation of particle concentration and the solutal concentration for the inclusion of chemical reaction are taken care of. Also, the influence of the free convection phenomena is explained significantly. The transformed dimensionless system of the governing equations is handled analytically by using the Laplace Transform method. The behavior of the characterizing parameters involved in the governing equations is presented via graphs and the simulation of the numerical results of the rate coefficients like shear rate and rate of heat and solutal transfer is deployed through the table. However, the physical significance of these parameters is deliberated briefly. Finally, the important outcomes are higher heavier species because of lesser solutal diffusivity which attenuates the fluid concentration throughout the domain. Further, radiation absorption causes a significant boost in the nanofluid temperature distribution.

Exposure Concentrations and Inhalation Risk of Submicron Particles in a Gasoline Station—A Pilot Study

Gasoline is a globally used primary fuel. The submicron particles at gasoline stations have not been extensively investigated. This study aimed to evaluate the exposure concentrations and inhalation risk of submicron particles at a gasoline station. Temporal variations in particle concentrations and size distributions were measured using a real-time system. The effective doses of submicron particles deposited in different organs were analyzed using a computational fluid dynamics model and the value of environmental monitoring (including the size distributions of particles by number). The number concentration (NC) was higher during working hours than that of the background. Submicron particles gathered predominantly at 30.5 nm and 89.8 nm during working time. The effective doses of submicron particles deposited in the olfactory system and lungs were 0.131 × 10−3 and 0.014 mg, respectively, of which 0.026 × 10−3 mg potentially reached the brain. In a female worker with 3 years of exposure, the average daily effective doses in the olfactory system, lungs, and brain were 2.19 × 10−7 mg/kg·d−1, 2.34 × 10−5 mg/kg·d−1, and 4.35 × 10−8 mg/kg·d−1, respectively. These findings indicated that workers at this gasoline station had a high inhalation risk of submicron particles. This study provides baseline data on submicron particles at gasoline stations and a critical basis for investigating disease risk in longitudinal epidemiological studies.

CFD model to study PM_{textrm{10}} dispersion in large-scale open spaces

Air pollution has become a major concern in industrial or highly populated areas. Although legislation has been enacted to limit pollution levels, air quality monitoring still needs to be carried out by stations which are located at fixed points unable to provide the spatial evolution of pollutants. This research, focused on the city of Gijón (Asturias), includes a Computational Fluid Dynamics model capable of simulating the dispersion of pollutants in a large urban environment (12x18 km^{textrm{2}}). Different wind conditions were simulated with two sources of emission. The results show the influence of the terrain on the dispersion of pollutants in open spaces whilst simultaneously scrutinizing the origin of diffuse industrial pollution circulating over the city of Gijon. The simulation allows us to set limits in the areas with higher levels of contamination or to analyse the variations of particle concentration in height. Therefore, this research defines and validates a methodology to generate numerical models which grant us the opportunity to observe the spatial evolution of pollutants in large areas. This result endorses further use in other lines of research, such as the evaluation of corrective measures to improve air quality in highly polluted environments.

Effects of Outdoor Air Pollutants on Indoor Environment Due to Natural Ventilation

This study measured ventilation volumes and particle concentrations in indoor environments with open windows and doors. In addition, the effect of the airflow mode of the air conditioner on the ventilation volume and indoor particle concentration variations was also measured. The ventilation fan could only provide approximately 43% of the ventilation volume during the design phase. The amount of ventilation differed depending on the opening area in windows and doors. The ventilation volume was increased by opening multiple windows or doors, even when the area of the opening was the same. No significant change in the ventilation rate was observed, although the air conditioner was expected to promote the ventilation rate in the room when set on blow mode. It was confirmed that both 0.3 and 1 μm particles could enter through the gaps around the windows and doors. Although most of the 5 μm particles were from the outdoor air, when the air conditioner was operated in airflow mode, the removal of 5 μm particles was performed by the air conditioner filter. The use of medium-performance or HEPA filters is expected to remove smaller particulates.

Assessment of traffic-related chemical components in ultrafine and fine particles in urban areas in Vietnam

Ultrafine particles (UFPs or PM0.1; aerodynamic diameter ≤ 0.1 μm) were monitored at a roadside site (RS) in a populated area of Hanoi, Vietnam. Meanwhile, UFPs and fine particles (FPs or PM2.5, aerodynamic diameter ≤ 2.5 μm) were monitored at an ambient site (AS), located at an on-campus a university, approximately 200 m away from the RS. Sampling was conducted in different seasons–summer, winter, and the transitional periods of summer-to-winter and winter-to-summer (STP and WTP, respectively). Carbonaceous and ionic species in UFPs and FPs–rarely investigated in the study area–were analyzed to observe the seasonal variations, characteristics of UFPs near the roadway, and spatial differences between the sites. The UFPs concentration at the AS was in the order of winter > STP > WTP > summer, whereas that of the FPs was winter > WTP > STP > summer. This seasonal variation of particle concentration was possibly affected by the meteorological conditions, which contribute to the highest concentration in winter. The higher FPs concentration in WTP than in STP resulted from the substantial increase in ionic concentrations, particularly sulfate, nitrate, and ammonium. This result indicates the effect of secondary formation processes under drizzle-like weather, which is typical during WTP in northern Vietnam. Compared with UFPs at the AS, traffic-related emissions were more noticeable in UFPs at the RS, including a higher EC concentration and lower OC/EC ratio. The possibility of particle growth under favorable conditions, including the presence of gas-phase pollutants and the availability of surface areas owing to high UFPs concentration in Hanoi, may explain the low correlation of the chemical components between UFPs and FPs in the sites. This study serves as a reference for further investigation of the relationship between UFPs and FPs under highly polluted conditions in big cities in Vietnam in future studies.

Dynamics of di-2-ethylhexyl phthalate (DEHP) in the indoor air of an office

Largely limited by measurement technique, dynamics of semivolatile organic compounds (SVOCs) in the indoor air is not well understood. This study reports time-resolved measurements of airborne concentration of di-2-ethylhexyl phthalate (DEHP) in an office, using semivolatile thermal desorption aerosol gas chromatography (SV-TAG). The measurements were conducted in two separate periods during the summer-to-fall transition in 2020, each for more than 10 days. The indoor gas-plus-particle DEHP concentration varied by more than one order of magnitude in each observation period, and the temporal pattern exhibited possible influences of the indoor temperature, particle mass concentration, and outdoor DEHP concentrations. Further analysis focusing on window-closed conditions (i.e., with less outdoor contribution) reveals that the DEHP dynamics was primarily driven by variations in the indoor temperature ( R 2 = 0.85) during the first, warmer period (24–29 °C), and by variations in the particle mass concentration ( R 2 = 0.83) during the subsequent cooler period (20–23 °C). The unexpected transition of the key driving factor with change of the temperature was qualitatively justified by a simplified mechanistic model. Moreover, the particle fraction of DEHP was measured during the latter, cooler period, and it exhibited strong dependence on particle concentration, which can be fitted assuming gas-particle equilibrium partitioning, with a best-fit apparent partitioning coefficient of 0.053 ± 0.006 m 3 /μg at 20 ± 1 °C. Overall, these results improve our understanding of real-world SVOC dynamics. • In a warmer period variation in temperature drove DEHP dynamics in an office. • In a cooler period variation in particle concentration drove DEHP dynamics in the office. • Transition of the key driving factor with change in temperature was justified by mechanistic model. • Observed gas/particle partitioning of DEHP can be fitted assuming equilibrium state.

ELECTROMAGNETIC METHODS OF SEARCHING AND DEFINITION OF HYDROCARBON DEPOSITS

The article studies the characteristics of an anisotropic medium over hydrocarbons with the complex use of electromagnetic geo-exploration methods. The simulation of the components of dielectric permittivity tensors in the mode of amplitude-modulated, frequency-modulated, amplitude-frequency-modulated and radio pulse signals is carried out. The frequencies of the electron plasma and electron cyclotron resonances for the specified regimes are established. A study was made of the influence of modes of probing signals on the characteristics of an anisotropic medium above deposits and the components of the dielectric tensor. The effect of particle concentration variation on the real components of the components of the dielectric permittivity of an anisotropic medium above the UVZ is analyzed. Recommendations are given for improving the methods of electrical exploration and their application for prospecting geophysics.

A Comparison of Particulate Exposure Levels during Taxi, Bus, and Metro Commuting among Four Chinese Megacities.

Exposure to inhalable particulate matter pollution is a hazard to human health. Many studies have examined the in-transit particulate matter pollution across multiple travel modes. However, limited information is available on the comparison of in-transit exposure among cities that experience different climates and weather patterns. This study aimed to examine the variations in in-cabin particle concentrations during taxi, bus, and metro commutes among four megacities located in the inland and coastal areas of China. To this end, we employed a portable monitoring approach to measure in-transit particle concentrations and the corresponding transit conditions using spatiotemporal information. The results highlighted significant differences in in-cabin particle concentrations among the four cities, indicating that PM concentrations varied in an ascending order of, and the ratios of different-sized particle concentrations varied in a descending order of CS, SZ, GZ, and WH. Variations in in-cabin particle concentrations during bus and metro transits between cities were mainly positively associated with urban background particle concentrations. Unlike those in bus and metro transit, in-cabin PM concentrations in taxi transit were negatively associated with urban precipitation and wind speed. The variations in particle concentrations during the trip were significantly associated with passenger density, posture, the in-cabin location of investigators, and window condition, some of which showed interactive effects. Our findings suggest that improving the urban background environment is essential for reducing particulate pollution in public transport microenvironments. Moreover, optimizing the scheduling of buses and the distribution of bus stops might contribute to mitigating the in-cabin exposure levels in transit. With reference to our methods and insights, policymakers and other researchers may further explore in-transit exposure to particle pollution in different cities.

Estimating Mass Flux From Size‐Fractionated Filtered Particles: Insights Into Controls on Sinking Velocities and Mass Fluxes in Recent U.S. GEOTRACES Cruises

AbstractWe compile full ocean‐depth size‐fractionated (1–51 and >51 μm) particle concentration and composition of suspended particulate matter from three recent U.S. GEOTRACES cruises, and exploit detailed information of particle characteristics measured to give insights into controls on sinking velocity and mass flux. Our model integrates the concept of fractal scaling into Stokes' Law by incorporating one of two porosity‐size power law relationships that result in fractal dimensions of 1.4 and 2.1. The medians of pump‐derived total (>1 μm) mass flux in the upper 100 m of gyre stations are 285.1, 609.2, and 99.3 mg/m2/d in the North Atlantic, Eastern Tropical South Pacific, and Western Arctic Ocean cruises, respectively. In this data set, variations in particle concentration were generally more important than sinking velocity in controlling variations in mass flux. We examine different terms in a Stokes' Law model to explore how variations in particle and water column characteristics from these three cruises affect mass flux. The decomposition of different aspects of the Stokes' relationship sheds light on the lowest total mass flux of the three cruises in the Western Arctic, which could be explained by the Arctic having the lowest particle concentrations as well as the lowest sinking velocities due to having the smallest particle sizes and the most viscous water. This work shows the importance of both particle characteristics and size distribution for mass fluxes, and similar methods can be applied to existing and future size‐fractionated filtered particulate measurements to improve our understanding of the biological pump elsewhere.

Characteristics and risk assessment of occupational exposure to ultrafine particles generated from cooking in the Chinese restaurant

Ultrafine particles have been increasingly linked to adverse health effects in restaurant workers. This study aimed to clarify the exposure characteristics and risks of ultrafine particles during the cooking process, and to provide a reasonable standard for protecting the workers in the Chinese restaurant. The temporal variations in particle concentrations (number concentration (NC), mass concentration (MC), surface area concentration (SAC), and personal NC), and size distributions by number were measured by real-time system. The hazard, exposure, and risk levels of ultrafine particles were analyzed using the control banding tools. The NC, MC, and SAC increased during the cooking period and decreased gradually to background levels post-operation. The concentration ratios of MC, total NC, SAC, and personal NC ranged from 3.82 to 9.35. The ultrafine particles were mainly gathered at 10.4 and 100 nm during cooking. The exposure, hazard and risk levels of the ultrafine particles were high. These findings indicated that the workers during cooking were at high risk due to exposure to high levels of ultrafine particles associated with working activity and with a bimodal size distribution. The existing control strategies, including engineering control, management control, and personal protection equipment need to be improved to reduce the risk.

Coagulation patterns and the impacts on traffic-related ultrafine particle dispersion in road tunnels employing dynamic mesh algorithms.

.In this study, we continue to analyze the diffusion mechanism of ultrafine particles and the particle coagulation phenomenon with a size range of 26-287 nm exhausted from vehicles during the process of passing through a 100-m-long tunnel using the realizable k-ε model and dynamic grid technique. A three-dimensional model consisting of a 100-m highway tunnel and four side-by-side gasoline vehicles (L × W × H = 4.5 m × 1.8 m × 1.5 m) was established in the STAR-CCM+ computational fluid dynamics software. The gasoline vehicles traveled simultaneously under different situations of three driving speeds of 60 km h-1, 40 km h-1, and 20 km h-1 during the simulation. Through data analysis and research, it was found that the coagulation process of particles is very complicated, especially at low speeds. When the vehicle speed is 20 km h-1, the variation in particle concentration at the vehicle wake near the tailpipe (at the vertical plane located 0.1 m behind the exhaust pipe) causes a large error if the coagulation action is not considered. The relative error of the average particle concentration at 0.5 s of the vertical section 0.1 m away from the exhaust pipe is as high as 193.51%. The relative error in the entire tunnel is only 2.82%, which is less than 5%. Thus, it is recommended that particle coagulation should be considered when analyzing particle dispersion in the near-wake region behind the vehicle and the breathing areas, especially when the vehicle travels slowly inside the tunnel. However, when evaluating the particle concentration and exposure levels for the entire tunnel, coagulation can be ignored without significant errors, especially at a high vehicle speeds. This study clarified the importance of coagulation in different areas and its influence on the diffusion of particulate matter. This is conducive to further analysis of the diffusion characteristics of particulate matter and can appreciably reduce the pollution degree in a tunnel by changing the coagulation efficiency of particulate matter in the future.

Particle Resuspension Dynamics in the Infant Near-Floor Microenvironment.

Carpet dust contains microbial and chemical material that can impact early childhood health. Infants may be exposed to greater quantities of resuspended dust, given their close proximity to floor surfaces. Chamber experiments with a robotic infant were integrated with a material balance model to provide new fundamental insights into the size-dependency of infant crawling-induced particle resuspension and exposure. The robotic infant was exposed to resuspended particle concentrations from 105 to 106 m-3 in the near-floor (NF) microzone during crawling, with concentrations generally decreasing following vacuum cleaning of the carpets. A pronounced vertical variation in particle concentrations was observed between the NF microzone and bulk air. Resuspension fractions for crawling are similar to those for adult walking, with values ranging from 10-6 to 10-1 and increasing with particle size. Meaningful amounts of dust are resuspended during crawling, with emission rates of 0.1 to 2 × 104 μg h-1. Size-resolved inhalation intake fractions ranged from 5 to 8 × 103 inhaled particles per million resuspended particles, demonstrating that a significant fraction of resuspended particles can be inhaled. A new exposure metric, the dust-to-breathing zone transport efficiency, was introduced to characterize the overall probability of a settled particle being resuspended and delivered to the respiratory airways. Values ranged from less than 0.1 to over 200 inhaled particles per million settled particles, increased with particle size, and varied by over 2 orders of magnitude among 12 carpet types.

Experimental and CFD simulation of slurry flow in the annular flow path using two-fluid model

The current study is allocated to experimental evaluation of the multiphase flow of fine solid particles (FSPs) as well as comprehensive numerical study in an annular space under static, laminar, and turbulent flow conditions with consideration of the inner pipe eccentricity and rotation. The experimental investigation was carried out using an annular pipe flow loop. The numerical modeling and simulation of the multiphase flow in the annular space have been performed using the Euler-Euler approach. The unsteady-state multiphase model based on the kinetic theory of granular flow (KTGF) is developed to investigate the particulate flow characteristics in the annular space. Moreover, Standard and Realizable k-ε turbulence models used to predict turbulence in this study. The Realizable Per-Phase turbulence model with new corrected coefficients (C2=4.2,C3=1.3,CT=0.0131,σk=1,σε=1.2) is calibrated to predict the pressure drop along the annular pipe for solid-liquid multiphase flow. Comparison between numerical and experimental analyses showed that under both flowing and static conditions, the simulation results are in good agreement with experimental data. Based on the error estimation model, the CFD model's accuracy for pressure drop and FSPs concentration prediction is 99% and 95%, respectively. The trends of the variation in particle concentration along the annular pipe were investigated for different flow velocities (0.05–2.5 m/s) and different inner pipe rotations of 500, 1000, and 1500 rpm. The results also showed that the higher particle settling occurred at the critical inclination angles of 45–60°.