Comparison of the uptake of fine and ultrafine TiO2 in a tracheal explant system

1998 ◽  
Vol 274 (1) ◽  
pp. L81-L86 ◽  
Author(s):  
A. Churg ◽  
B. Stevens ◽  
J. L. Wright
Keyword(s):  
Ultrafine Particles ◽  
Particle Number ◽  
Fine Particles ◽  
Particle Uptake ◽  
Pulmonary Epithelial Cells ◽  
Volume Proportion ◽  
Particle Aggregates ◽  
The Relationship ◽  
Ultrafine Tio2 ◽  
Number Of Particles

To examine the relationship between particle uptake by pulmonary epithelial cells and particle size, we exposed rat tracheal explants to fine particles (FPs; 0.12 μm) or ultrafine particles (UFPs; 0.021 μm) of titanium dioxide for 3 or 7 days. By electron microscopy, particles were found in the epithelium at both time points, but in the subepithelial tissues, they were found only at 7 days. The volume proportion of both FPs and UFPs in the epithelium increased from 3 to 7 days; it was greater for UFPs at 3 days but was greater for FPs at 7 days. The volume proportion of particles in the subepithelium at 7 days was equal for both dusts, but the ratio of epithelial to subepithelial volume proportion was ∼2:1 for FPs and 1:1 for UFPs. Mean volume of individual particle aggregates was similar for both dusts at 3 days but was markedly smaller for FPs at 7 days. These observations suggest that the behavior of particles of different size is complex: UFPs persist in the tissues as relatively large aggregates, whereas the size of FP aggregates becomes smaller over time. UFPs appear to enter the epithelium faster, and once in the epithelium, a greater proportion of them is translocated to the subepithelial space compared with FPs. However, if it is assumed that the volume proportion is representative of particle number, the number of particles reaching the interstitial space is directly proportional to the number applied; i.e., overall, there is no preferential transport from lumen to interstitium by size.

scholarly journals Image analysis to qualify soil erodibility into a wind tunnel

2018 ◽  
Vol 42 (3) ◽  
pp. 240-247
Author(s):  
Carlos Asensio ◽  
Emilio Rodríguez-Caballero ◽  
Francisco Jesús García-Navarro ◽  
José Antonio Torres
Keyword(s):  
Wind Tunnel ◽  
Wind Erosion ◽  
Particle Number ◽  
Fine Particles ◽  
Size Number ◽  
Main Effect ◽  
Trap Height ◽  
Natural Wind ◽  
Image Analyses ◽  
Number Of Particles

ABSTRACT A wind erosion research was carried out in a wind tunnel where sediment samples acquired were studied by an artificial vision camera. These images could be enlarged for further analysis. Image analyses were mainly colorimetry, number of particles present and their size. Soil wind erodibility was analyzed with the image analyses supported by other laboratory results. Anthrosols were the most erodible soils, whereas Calcisols showed the highest resistance to the erosive action of wind. Sediment characteristics show the influence of trap height with decreasing particle size, number and darkness as transport height increases. A two-factor ANOVA for main effect height showed that there were significant differences in particle number and size for sediments trapped 0-15 cm and 40-70 cm high. Soils could be grouped by differences in particle number and size at different heights into highly erodible Anthrosols and Leptosols, non-erodible Calcisols and Arenosols, in which fine particles were already depleted by natural wind erosion. Aggregation showed a similar pattern with decreasing values from Calcisols and Leptosols to Anthrosols and finally Arenosols, where only single sand grains were observed in adhesive traps.

An investigation on particle emission from a new laser printer using an environmental chamber

2016 ◽  
Vol 26 (8) ◽  
pp. 1144-1154 ◽  
Author(s):  
Dawei Wang ◽  
Hai Guo ◽  
Congrong He
Keyword(s):  
Ultrafine Particles ◽  
Particle Number ◽  
Particle Emission ◽  
Laser Printer ◽  
Positive Power ◽  
Particle Emissions ◽  
Long Period ◽  
Rotation Mode ◽  
Regression Relationship ◽  
The Relationship

In this study, emissions of ultrafine particles from a new laser printer were evaluated as a function of toner coverage, number of pages printed, fuser temperature and cartridge rotation during different printing orders. Eight combinations of printing jobs were specifically designed to represent eight printing orders. The toner coverage was found to be an important factor affecting particle emissions from the printer. The printing job without toner coverage (0%) acted as a cleaning process, which would tentatively reduce particle emissions in the next job. Particles generated in printing job with toner coverage (5%) could superimpose onto those emitted from the next job, leading to higher particle number emission in the next job than the previous one. Apart from toner coverage, cartridge rotation was an important factor enhancing particle emissions. Cartridge in rotation mode with/without toner coverage could both cause particle emissions and high fuser temperature. The relationship between the particle emission and the temperature of the fuser unit was very strong ( r2 = 0.96). The regression relationship satisfied a positive power law-rise equation. We also found that ventilation for a long period, printing with no cartridge rotation, and/or printing blank pages before toner page printing could reduce particle emissions.

scholarly journals Landfill air pollution by ultrafine and microparticles in case of dry and windless weather conditions

Detritus ◽  
2020 ◽  
pp. 139-146
Author(s):  
Emília Hroncová ◽  
Juraj Ladomerský ◽  
Denisa Ladomerská
Keyword(s):  
Ultrafine Particles ◽  
Large Scale ◽  
Particle Number ◽  
Fine Particles ◽  
Weather Conditions ◽  
Municipal Waste ◽  
Dust Particles ◽  
Particle Sizer ◽  
Ultra Fine Particles ◽  
Surprising Finding

In the present article we give the results for ultra-fine particles and microparticles at a landfill of municipal waste, taking into consideration various factors. The landfill is a large-scale source of dust. There is little knowledge in terms of fractional composition of dust particles. We have performed concentration measurements of the number of ultrafine (10 to 100 nm) and microparticles (0.1 to 10 μm) in the field conditions of the municipal waste landfill using the TSI Technique (Optical particle sizer 3330 and Nanoscan SMPS nanoparticle sizer 3919). The particle number concentration in the atmosphere in case of dry and windless weather conditions at the landfill was in the range of about 2,500 to 5,500 of ultrafine particles per cm3. The mass concentrations of the microparticles was in the range of 29 to 163 μg.m-3 (assuming ρ=1 g.cm-3). There was an evident trend of increase of concentration of the ultrafine particles and microparticles in the lower location of the landfill occuring in the case of dry and windless weather conditions. The surprising finding was that passing haulage vehicles and in particular the operation of the compactor increase the mass concentration of microparticles, but they do not increase the concentration of the number of microparticles or even of ultrafine particles.

Studies of copper selenide ultrafine particles by newly developed gas evaporation method

1990 ◽  
Vol 48 (4) ◽  
pp. 306-307
Author(s):  
Chihiro Kaito ◽  
Yoshio Saito
Keyword(s):  
Crystal Structure ◽  
Ultrafine Particles ◽  
Fine Particles ◽  
Production Method ◽  
Atmospheric Temperature ◽  
Copper Selenide ◽  
Quartz Boat ◽  
Selenium Vapor ◽  
Ar Gas ◽  
Ultra Fine Particles

The direct evaporation of metallic oxides or sulfides does not always given the same compounds with starting material, i.e. decomposition took place. Since the controll of the sulfur or selenium vapors was difficult, a similar production method for oxide particles could not be used for preparation of such compounds in spite of increasing interest in the fields of material science, astrophysics and mineralogy. In the present paper, copper metal was evaporated from a molybdenum silicide heater which was proposed by us to produce the ultra-fine particles in reactive gas as shown schematically in Figure 1. Typical smoke by this method in Ar gas at a pressure of 13 kPa is shown in Figure 2. Since the temperature at a location of a few mm below the heater, maintained at 1400° C , were a few hundred degrees centigrade, the selenium powder in a quartz boat was evaporated at atmospheric temperature just below the heater. The copper vapor that evaporated from the heater was mixed with the stream of selenium vapor,and selenide was formed near the boat. If then condensed by rapid cooling due to the collision with inert gas, thus forming smoke similar to that from the metallic sulfide formation. Particles were collected and studied by a Hitachi H-800 electron microscope.Figure 3 shows typical EM images of the produced copper selenide particles. The morphology was different by the crystal structure, i.e. round shaped plate (CuSe;hexagona1 a=0.39,C=l.723 nm) ,definite shaped p1 ate(Cu5Se4;Orthorhombic;a=0.8227 , b=1.1982 , c=0.641 nm) and a tetrahedron(Cu1.8Se; cubic a=0.5739 nm). In the case of compound ultrafine particles there have been no observation for the particles of the tetrahedron shape. Since the crystal structure of Cu1.8Se is the anti-f1uorite structure, there has no polarity.

scholarly journals Impact on Ultrafine Particles Concentration and Turbulent Fluxes of SARS-CoV-2 Lockdown in a Suburban Area in Italy

Atmosphere ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 407
Author(s):  
Antonio Donateo ◽  
Adelaide Dinoi ◽  
Gianluca Pappaccogli
Keyword(s):  
Ultrafine Particles ◽  
Particle Number ◽  
Ultrafine Particle ◽  
Turbulent Fluxes ◽  
Number Concentration ◽  
Suburban Area ◽  
Observation Site ◽  
Meteorological Forcing ◽  
Restrictive Measures ◽  
Measurement Area

In order to slow the spread of SARS-CoV-2, governments have implemented several restrictive measures (lockdown, stay-in-place, and quarantine policies). These provisions have drastically changed the routines of residents, altering environmental conditions in the affected areas. In this context, our work analyzes the effects of the reduced emissions during the COVID-19 period on the ultrafine particles number concentration and their turbulent fluxes in a suburban area. COVID-19 restrictions did not significantly reduce anthropogenic related PM10 and PM2.5 levels, with an equal decrement of about 14%. The ultrafine particle number concentration during the lockdown period decreased by 64% in our measurement area, essentially due to the lower traffic activity. The effect of the restriction measures and the reduction of vehicles traffic was predominant in reducing concentration rather than meteorological forcing. During the lockdown in 2020, a decrease of 61% in ultrafine particle positive fluxes can be observed. At the same time, negative fluxes decreased by 59% and our observation site behaved, essentially, as a sink of ultrafine particles. Due to this behavior, we can conclude that the principal particle sources during the lockdown were far away from the measurement site.

scholarly journals CYTOPLASMIC DNA SYNTHESIS IN AMOEBA PROTEUS

1962 ◽  
Vol 15 (3) ◽  
pp. 535-540 ◽  
Author(s):  
M. Rabinovitch ◽  
W. Plaut
Keyword(s):  
Nucleic Acid ◽  
Dna Synthesis ◽  
Acridine Orange ◽  
Particle Number ◽  
Amoeba Proteus ◽  
Acridine Orange Staining ◽  
Particle Population ◽  
Cell Age ◽  
Cytoplasmic Dna ◽  
Number Of Particles

Nucleic acid-containing particles in the cytoplasm of Amoeba proteus (cf. reference 1) were counted after acridine orange staining. The number of particles per ameba was found to be correlated with cell age and size. Fresh daughters had a mean particle number of 5400, whereas predivision amebae contained around 11,000 particles. Amebae from two other strains contained similar particles. The particles were found to be clustered in fasted cells and redispersed after feeding. A marked increase in the particle population was noted in anucleate fragments. These results, together with those previously presented, suggest that the particles multiply intracellularly. Their nature and their relationship to previous work on nucleic acid labeling in Amoeba are discussed.

scholarly journals Silylated Thiol-Containing Cellulose Nanofibers as a Bio-Based Flocculation Agent for Ultrafine Mineral Particles of Chalcopyrite and Pyrite

2021 ◽  
Author(s):  
Ana Luiza Coelho Braga de Carvalho ◽  
Feliciana Ludovici ◽  
Daniel Goldmann ◽  
André Carlos Silva ◽  
Henrikki Liimatainen
Keyword(s):  
Ultrafine Particles ◽  
Fine Particles ◽  
Cellulose Nanofibers ◽  
Aqueous Alkaline Medium ◽  
Selective Flocculation ◽  
Turbidity Removal ◽  
Floc Size ◽  
Mineral Particles ◽  
Tailing Ponds ◽  
Anionic Polyacrylamide

AbstractA considerable amount of very fine particles can be found, e.g., stored in tailing ponds, and they can include valuable or hazardous minerals that have the potential to be recovered. Selective flocculation, i.e., the formation of larger aggregates from specific minerals, offers a promising approach to improve the recovery of ultrafine particles. This study focuses on the use of a new bio-based flocculation agent made of silylated cellulose nanofibers containing a thiol-functional moiety (SiCNF). Flocculation was performed in separated systems of ultrafine mineral dispersions of pyrite, chalcopyrite, and quartz in aqueous alkaline medium. The flocculation performance of SiCNF was addressed in terms of the turbidity reduction of mineral dispersions and the floc size, and the results were compared with the performance of a commercial anionic polyacrylamide. SiCNF exhibited a turbidity removal efficiency of approximately 90%–99% at a concentration of 4000–8000 ppm with chalcopyrite and pyrite, whereas the turbidity removal of quartz suspension was significantly lower (a maximum of approximately 30%). The sulfide particles formed flocs with a size of several hundreds of micrometers. The quartz in turn did not form any visible flocs, and the dispersion still had a milky appearance after dosing 12,000 ppm of the flocculant. These results open a promising path for the investigation of SiCNF as a selective flocculation agent for sulfide minerals. Graphical Abstract

A Study of Airborne Wear Particles Generated From a Sliding Contact

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Ulf Olofsson ◽  
Lars Olander ◽  
Anders Jansson
Keyword(s):  
Ultrafine Particles ◽  
Fine Particles ◽  
Urban Environments ◽  
Airborne Particles ◽  
Wear Particles ◽  
Coarse Particles ◽  
Sliding Velocity ◽  
Airborne Particle ◽  
Particle Generation ◽  
Pin On Disk

Recently, much attention has been paid to the influence of airborne particles in the atmosphere on human health. Sliding contacts are a significant source of airborne particles in urban environments. In this study airborne particles generated from a sliding steel-on-steel combination are studied using a pin-on-disk tribometer equipped with airborne-particle counting instrumentation. The instrumentation measured particles in size intervals from 0.01μm to 32μm. The result shows three particle size regimes with distinct number peaks: ultrafine particles with a size distribution peak around 0.08μm, fine particles with a peak around 0.35μm, and coarse particles with a peak around 2 or 4μm. Both the particle generation rate and the wear rate increase with increasing sliding velocity and contact pressure.

Flocculation as an Alternative to Increase the Recovery of Ultrafine Particles of Pyrite in Flotation of Tailings

2021 ◽  
Author(s):  
Ana Luiza Coelho Braga de Carvalho ◽  
Feliciana Ludovici ◽  
Henrikki Liimatainen ◽  
André Carlos Silva ◽  
Daniel Goldmann
Keyword(s):  
Aqueous Medium ◽  
Ultrafine Particles ◽  
Fine Particles ◽  
Column Flotation ◽  
Air Bubbles ◽  
Mineral Concentration ◽  
Alkaline Conditions

<p>Nowadays, flotation is the most commonly used method for mineral concentration. However, conventional flotation circuits are not suitable for ultrafine particles, and this is a challenge for the concentration of finely disseminated minerals. Moreover, tailing contain a considerable amount of very fine particles which can include valuable and hazardous minerals that have the potential to be recovered. Concern about ultrafine particles has increased as they are present in a wide variety of mineral pulps and can contain valuable minerals that have been lost to the tailings. Several alternatives have been proposed to improve the recovery of ultrafine particles in flotation, for example, decreasing the size of the air bubbles, column flotation, selective agglomeration of particles, etc. Among all, selective polymeric flocculation represents a promising option. The current study focuses on the use of polymeric flocculation to increasing the size of pyrite particles aiming to improve its recovery in the flotation of sulfidic tailings. Flocculation was performed with pyrite particles presenting P80 < 4 mm, in aqueous medium and alkaline conditions. Two polyacrylamides and a new nanocellulose-based chemical were used as flocculants. Microflotation tests were performed, without the addition of collector, to evaluate the formation of flocs through the reduction of the mechanical entrainment of pyrite after being submitted to flocculation.</p>

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