Monitoring Of Size Distribution Research Articles

A critical analysis of the literature on the characterization of air in the subway

It is known that the dust in the subway could be more toxic than the ambient airborne particulates. The scientific literature has shown a remarkable interest towards PM in urban subway systems. The information for the present study were drawn using peer-reviewed publications from different international journals consulted on the databases PubMed and Web of Science or Science Direct, through the search-engine Google Scholar and the social network ResearchGate. So far a total of more than 100 papers resulted in the last 16 years (1999-2016). Subway systems differ one from the other for several features (age of the infrastructures, number and extension of the lines, ventilation systems, etc.) making studies results hardly comparables. It is possible to put in evidence that mass concentration of various PM fractions was the main target, although several studies shown results about particle number concentration and size distribution monitoring. Various PM fractions characterization focused mainly on total metals content; a few studies extended the analysis to other health relevant PM components (polycyclic aromatic hydrocarbons (PAHs), black carbon and elemental carbon) as well as to volatile organic compounds (VOCs), and biological aerosols. Preliminary conclusions of the study confirm the agreement with previous results: PM concentrations in the subway often exceed the European outdoor limit values established to protect human health, exceed outdoor concentrations revealing the presence of indoor sources. The ventilation system provides a significant abatement of PM concentrations. In some paper subway PM shows a genotoxic effect (increased DNA or chromosome damages) and an ability to generate oxidative stress (increased production of ROS) greater than outdoor PM. The high toxicity is due to the high Fe content. The genotoxicity is likely caused by highly redox-active surface giving rise to oxidative stress.

Notes on the biology of the bigeye scad, <i>Selar crumenophthalmus</i> (Carangidae) around Reunion Island, southwest Indian Ocean

SUMMARY: The main characteristics of the biology of bigeye scad were studied from commercial fishery catches around Reunion Island. Biometric relationships were calculated. The monitoring of size distribution, aggregated by month, allowed us to estimate the theoretical growth equation using the ELEFAN software. The von Bertalanffy growth parameters were adjusted with a seasonal modulation: L ∞ = 265 mm; K = 1.64 year-1; c = 0.068; ϕ = 0.38. The growth of the cohort was quite high during the austral summer (November–April) and decreased during the austral winter (May-October). The arrival of a new cohort with homogeneous small sizes (65 to 90 mm) in the fishery in November coincided with the disappearance of large individuals. A feature of the reproductive biology was that the sex ratio remained constant month by month and that there was no predominance of male or female even in the larger size classes. Fish were mature by April and the proportion of mature fish progressively increased until November, when the gonad-indices were the highest. The size at first maturity (L50) was reached at 215 mm (fork length). The largest specimens observed were 255 mm long (fork length). After reproduction, massive mortality occurred and few individuals survived.

In situ monitoring of size distributions and characterization of nanoparticles during W ablation in N2 atmosphere

Nanoparticles were generated by pulsed laser ablation of tungsten in a N2 ambient at atmospheric pressure. Size distributions and concentrations were monitored in situ versus laser fluence, repetition rate, and ablated spot size, by a differential mobility analyzer and a particle counter. The multishot ablation threshold was determined to be ∼6 J/cm2 for the laser used (ArF excimer, λ=193 nm). Mostly small, nonlognormally, distributed particles (<20 nm in diameter) were generated below the ablation threshold (φth), and the relative concentration of larger particulates (>20 nm in diameter) increased above φth. Modeling of the temperature and ablated depth dependence on fluence showed that the formation of clusters below φth could not be assigned to a thermal process, but are connected to particle condensation from a photochemically desorbed thin layer. X-ray diffraction and x-ray photoelectron spectroscopy analysis performed on polydisperse nanoparticles revealed an amorphous phase of the particles, and the elemental composition was found to be WN0.3.

Real time size distribution monitoring of power plant particle emissions

Real time size distribution monitoring of power plant particle emissions