Reduction In Number Of Particles Research Articles

Treatment of Diesel Particles Using an Electrostatic Agglomerator Under Negative DC Corona: A Modeling and Experimental Study

The aim of this paper is to characterize an electrostatic agglomerator with an innovative shape intended to collect diesel particles. The agglomerator consists of a tube-type electrofilter with a porous collecting electrode supplied by a negative dc operating voltage. The end of the device is closed, so all the treated gas passes through the collecting electrode. The stocking surface is very small, and the collecting electrode acts as a simple agglomerator. The specific electrical consumption is approximately 1 J/L for a 95% reduction in particle number. This agglomerator requires an extremely short residence time, in the same order of magnitude as the particle electrical charging time. The reentrained agglomerates clearly have micronic size and are very little in number, so that their characterization cannot be done easily by classical granulometers such as electrical low-pressure impactor or scanning mobility particle sizer. An approach to modeling the reentrained number distribution is proposed, which permits to confirm and explain many of the experimental results. Discrepancies between experimental results and numerical model predictions show that particle filtration may be highly enhanced by a dendrite layer actively maintained by an electric field.

In-vehicle Measurement of Ultrafine Particles on Compressed Natural Gas, Conventional Diesel, and Oxidation-catalyst Diesel Heavy-duty Transit Buses

Many metropolitan transit authorities are considering upgrading transit bus fleets to decrease ambient criteria pollutant levels. Advancements in engine and fuel technology have lead to a generation of lower-emission buses in a variety of fuel types. Dynamometer tests show substantial reductions in particulate mass emissions for younger buses (<10 years) over older models, but particle number reduction has not been verified in the research. Recent studies suggest that particle number is a more important factor than particle mass in determining health effects. In-vehicle particle number concentration measurements on conventional diesel, oxidation-catalyst diesel and compressed natural gas transit buses are compared to estimate relative in-vehicle particulate exposures. Two primary consistencies are observed from the data: the CNG buses have average particle count concentrations near the average concentrations for the oxidation-catalyst diesel buses, and the conventional diesel buses have average particle count concentrations approximately three to four times greater than the CNG buses. Particle number concentrations are also noticeably affected by bus idling behavior and ventilation options, such as, window position and air conditioning.

Influence of Diesel Fuel Sulfur on Nanoparticle Emissions from City Buses

Particle emissions from twelve buses, operating alternately on low sulfur (LS; 500 ppm) and ultralow sulfur (ULS; 50 ppm) diesel fuel, were monitored. The buses were 1-19 years old and had no after-treatment devices fitted. Measurements were carried out at four steady-state operational modes on a chassis dynamometer using a mini dilution tunnel (PM mass measurement) and a Dekati ejector diluter as a secondary diluter (SMPS particle number). The mean particle number emission rate (s(-1)) of the buses, in the size range 8-400 nm, using ULS diesel was 31% to 59% lower than the rate using LS diesel in all four modes. The fractional reduction was highest in the newest buses and decreased with mileage upto about 500,000 km, after which no further decrease was apparent. However, the mean total suspended particle (TSP) mass emission rate did not show a systematic difference between the two fuel types. When the fuel was changed from LS to ULS diesel, the reduction in particle number was mainly in the nanoparticle size range. Over all operational modes, 58% of the particles were smaller than 50 nm with LS fuel as opposed to just 45% with ULS fuel, suggesting that sulfur in diesel fuel was playing a major role in the formation of nanoparticles. The greatest influence of the fuel sulfur content was observed at the highest engine load, where 74% of the particles were smaller than 50 nm with LS diesel compared to 43% with ULS diesel.

Investigation of the Influence of Post-Injection on Diesel Exhaust Aerosol Particle Size Distributions

The effect of double-pulse fuel split injection on the exhaust aerosol particle size distribution emitted by a state-of-the-art Heavy Duty Diesel engine was experimentally investigated. The influence of post-injection fuel quantity and dwell was evaluated at four steady-state engine conditions by analyzing the changes in the accumulation mode particle number, mean diameter and geometric standard deviation, with respect to the baseline case of single injection. Generally, rising post-injection fuel amount was found to increase accumulation mode particle number and mean diameter of the size distributions. Particle number reduction efficiency resulted dependent on the operating conditions and post-injection parameters scheme. Reductions in the particle number around 50% with respect to the baseline single-pulse injection case were observed for 1500 rpm partial load cases. For 1800 rpm 75% load conditions the reduction was lower and was achieved only when the fuel amount was below 20% of the total fuel injected. An increase in the particle number was produced when post-injection was applied at low speed and high load conditions, due to the low accumulation mode particle number emitted at this operation mode. An optimum post-injection fuel amount for particle number reduction was only seen for the 1500 rpm 75% load operation conditions. The results are indicative that further research is necessary in order to explore the existence of optimum post-injection schemes for particle number reduction at the other operating conditions studied. Geometric standard deviation from post-injection results was higher than that corresponding to the single injection baseline cases, while an increase in the σ g value was observed for larger dwells in some operating conditions.

Photon production from non-equilibrium QGP in heavy ion collisions

We present a calculation of thermal photon production, i.e. photons from secondary interactions among particles produced in heavy ion collisions at collider energies. This is done within the framework of hydrodynamics. We take into account the lack of chemical equilibrium in QGP. It turns out that the main effects from the chemical non-equilibrium composition of QGP, reduction of particle number and increase in temperature, nearly cancel in the photon spectrum.

Quantitative Assessment of the Effect of Surface Deposition and Coagulation on the Dynamics of Submicrometer Particles Indoors

Exposure to airborne particles indoors depends on particle concentration, which is affected by air filtration, ventilation, and particle dynamics. The aim of this work was quantitative assessment of the effects of coagulation, surface deposition, and ventilation on the submicrometer particle concentration indoors. The assessment was obtained from measured particle loss rate and deposition velocity parameters. The experiments were conducted in an experimental chamber for three different types of aerosols: environmental tobacco smoke, petrol smoke, and ambient air aerosols. Particle number concentration and size distribution were measured in the size range between 0.017 and 0.898 w m by SMPS. The average values for the overall deposition loss rates varied from 4.3 2 10 m 5 s m 1 (0.16 h m 1 ) to 1.1 2 10 m 4 s m 1 (0.39 h m 1 ). The overall deposition velocities associated with surface deposition and coagulation ranged from 9.6 2 10 m 4 cm s m 1 to 2.4 2 10 m 3 cm s m 1 , and for surface deposition only from 2.8 2 10 m 4 cm s m 1 to 6.3 2 10 m 4 cm s m 1 . For indoor conditions with an air exchange rate above 1.3 h m 1 , (natural ventilation, no filters) only a reduction in particle number of about 20% is attributed to the surface deposition and coagulation.

Dose-dependent action of atorvastatin in type IIB hyperlipidemia: preferential and progressive reduction of atherogenic apoB-containing lipoprotein subclasses (VLDL-2, IDL, small dense LDL) and stimulation of cellular cholesterol efflux

Type IIB hyperlipidemia is associated with premature vascular disease, an atherogenic lipoprotein phenotype characterised by elevated levels of triglyceride-rich VLDL and small dense LDL, together with subnormal levels of HDL. The dose-dependent and independent effects of a potent HMGCoA reductase inhibitor, Atorvastatin, at daily doses of 10 and 40 mg, were evaluated on triglyceride-rich lipoprotein subclasses (VLDL-1, VLDL-2 and IDL), on the major LDL subclasses (light LDL, LDL-1+LDL-2, d: 1.019–1.029 g/ml; intermediate LDL, LDL-3, d: 1.029–1.039 g/ml and small dense LDL, LDL-4+LDL+5, d: 1.039–1.063 g/ml), on CETP-mediated cholesteryl ester transfer from HDL to apoB-containing lipoproteins, on phospholipid transfer protein activity and on plasma-mediated cellular cholesterol efflux in patients ( n=10) displaying type IIB hyperlipidemia. Plasma concentrations of triglyceride-rich lipoprotein subclasses (TRL: VLDL-1, Sf 60–400; VLDL-2, Sf 20–60 and IDL, Sf 12–20) and of LDL ( d: 1.019–1.063 g/ml) were markedly diminished after 6 weeks of statin treatment at 10 mg per day (−31 and −36%, respectively; P<0.002) and by 42 and 51%, respectively at the 40 mg per day dose. Increasing doses of atorvastatin progressively normalised both the quantitative and qualitative features of the LDL subclass profile, in which dense LDL predominated at baseline. Indeed, dense LDL levels were reduced by up to 57% at the 40-mg dose, leading to a shift in the peak of the density profile towards larger, buoyant LDL particles typical of normolipidemic subjects. In addition, marked reduction in numbers of apoB100-containing particle acceptors led to a 30% decrease ( P<0.02) in CETP-mediated CE transfer from HDL. Finally, a significant dose-dependent statin-mediated elevation (+15% at 10 mg; P=0.0003 and +35% at 40 mg; P<0.0001 compared to baseline) in the capacity of plasma from type IIB subjects to mediate free cholesterol efflux from Fu5AH hepatoma cells was observed. Moreover, atorvastatin (40 mg per day) significantly increased plasma apoAI levels (+24%; P<0.05), thereby suggesting that this statin enhances production of apoAI and with it, formation of nascent pre-β HDL particles. Plasma PLTP activity was not affected by either dose of atorvastatin. We conclude that increasing the dose of atorvastatin leads to dose-dependent, preferential and progressive reduction in particle numbers of atherogenic VLDL-2, IDL and dense LDL, and concomitantly, to enhanced cellular cholesterol efflux in type IIB dyslipidemia, thereby diminishing the atherosclerotic burden in subjects characterised by high cardiovascular risk.

Investigation into the effectiveness of filters for use by intravenous drug users

Injecting drug users are at risk of and can suffer from serious health problems due to intravenous administration of insoluble particles from street drugs and tablets. Makeshift filters are used to try to remove particles from the injections. The decision to distribute filters from Harm Reduction Centres cannot be based on evidence of efficacy and safety as no such published data exists. The work presented here is part of a larger study which anticipates to provide such evidence. Laboratory methods were developed based on information gathered from drug users. Injections were prepared using drugs of abuse and filtered either through makeshift or commercially available filters. The resulting solutions were assayed for particle size and number (using Coulter Counter®). Comparisons were made with unfiltered injections. The results presented here are from the first part of this study, which investigated the effectiveness of various filters on reducing particulate count and size range of injections made from tablets. The commercially produced filter (Acrodisk®) showed a much greater reduction in particle number and size. This strongly suggests the risks to health could be reduced by the use of such filters. Of the makeshift filters, the Rizla® acetate filter showed the most satisfactory reduction in the number of particles, suggesting their use may be preferable to the currently popular cigarette filter. The ongoing work is looking at the effect of the filtration methods on amount of drug in injections made from tablets and repeating the work using street heroin.

The Antiviral Activity of Tetrachloro Decaoxide against Herpes Simplex Virus Type 1 and the Virucidal Effect of the Drug

At the recommended clinical dose for direct application to infected wounds tetrachloro decaoxide (TCDO) (1.0 × concentration TCDO) alone or in combination with haemoglobin proved to be cytotoxic for BHK and Flow 2002 cells, but at ≤0.1 TCDO/haem concentration BHK-21 cells tolerated treatment with the drug for 24 h retaining ≥80% cell viability. The in vitro cytotoxic effect is only partially reversible; but this could not explain the strong antiviral effect of TCDO/haem against herpes simplex virus type 1 (HSV-1) growing in BHK cells. The antiviral effect produces both a reduction in the number of virus particles assembled, and a lowering of their relative infectivity (i.e. reduced virus quality). The antiviral effect was active throughout the HSV-1 replication cycle. The quality of the viral DNA that was packaged into particles was unimpaired but unpackaged DNA was less infectious than controls. The reduction in particle numbers appeared to be due to both lowered protein synthesis and reduced virus particle assembly. TCDO/haem exhibits potent virucidal activity against HSV-1; HSV-2; Semliki Forest virus; Germiston virus; Reovirus type 3; Influenza virus type A; Feline leukaemia virus; Adenovirus type 5 and Polio virus type 1. Enveloped viruses, though varying over a wide sensitivity range were more sensitive than non-enveloped viruses. The magnitude of the virucidal effect against HSV-1 in suspension could be reduced by addition of BSA. The HSV-1 virucidal effect stems mainly from an effect of the drug on virion polypeptides. We propose that the effects of TCDO/haem result from the nonspecific chemical oxidation of susceptible chemical linkages both within and between individual proteins located intracellularly (antiviral and cytotoxic effects) or on the surface of virions (virucidal effect).

The relationship between the light scattering properties of zymogen granules and the release of their contained proteins

The optical density of suspensions of the digestive enzyme-containing zymogen granule, a roughly spherical 1 micron diameter membrane-enclosed subcellular structure isolated from the exocrine pancreas of mammals, is reduced greatly when they are suspended in physiological media. This reduction in optical density is accompanied by the release of the granule's protein contents. It has traditionally been assumed that this property is due to granule lysis; that is, dissolution of the particle and its consequent disappearance as a strongly scattering object. Thus, lysis would decrease optical density by decreasing the number density of suspended spheres (N) according to Beer's law. However, as a general matter, changes in the optical density of suspensions of spheres may be a function of changes in the refractive index (m) or radius (r) of the objects as well. In this study, we apply Mie theory of scattering by small particles, which, in conjunction with Beer's law, allows us to evaluate whether changes in the scattering properties of granule suspensions are due to changes in N, m or r. Scattering by granule suspensions was reduced in three ways-pH, calcium ion concentration, and detergent concentration. A simple reduction in particle number did not account for decreased scattering and protein release in any of these circumstances. Instead, the changes appear attributable to decreases in particle size and refractive index.

Dissolution profiles of nalidixic acid powders having Weibull particle size distribution.

General equations were derived describing the exact dissolution profile and particle number reduction rate for powders of Weibull particle size distribution under sink conditions. Several nalidixic acid (NA) powders of Weibull distribution, having mean diameter (μ), smallest diameter (r0), and largest diameter (R0) values of 400, 0, and 1000μm respectively, were prepared by varying the parameters of the Weibull distribution. By means of dissolution tests of these powders, the effects of size distribution and truncation of powders, having the same mean diameters were investigated. The results of the dissolution tests were consistent with those obtained in computer simulations, so that the derived equations were assumed to be reasonable. The dissolution rate of powders of Weibull distribution, having the same mean diameter, increased as the size distribution became narrower. Upper-end truncation had more effect on the dissolution profile of the powders than lower-end truncation.

Freeze fracture studies on the interaction between the malaria parasite and the host erythrocyte in Plasmodium knowlesi infections.

The freeze fracture technique has been used to study the internal cyto-architecture of the surface membranes of the parasite and erythrocyte in Plasmodium knowlesi infections. Six fracture faces, derived from the plasma membrane and 2 pellicular membranes, have been identified at the surface of the free merozoite. The apposed leaflets of the 2 pellicular membranes show the characteristic features of E fracture faces, a result compatible with the view that the pellicular membranes line a potential cisterna. There is evidence to suggest that there may be changes in the distribution and density of the integral proteins in the merozoite plasma membrane at invasion. Furthermore, vesicles consisting of stacked membranes occur within and around the erythrocyte invagination at invasion; it is suggested that these vesicles are released from the merozoite rhoptries. Formation of the parasitophorous vacuole is accompanied by dramatic changes in the density and distribution of intra-membraneous particles (IMP) in the vacuolar membrane. Initially there is a great reduction in particle numbers, but subsequently the particles reappear and show reversed polarity. The possible causes and implications of these changes are discussed. The intra-erythrocytic parasite synthesizes new transmembrane proteins as development proceeds, and the trophozoite and schizont stages of development are characterized by the appearance of circular, particle-free regions in the parasite plasmalemma. There is a decrease in the density of transmembrane proteins in the erythrocyte plasma membrane during parasite maturation, and the P face IMP show the characteristic features of aggregation.