Electrically Produced Standard Aerosols in a Wide Size Range

Non-uniformly charged particles cause a major problem in electrical methods for producing standard aerosols, imposing strict limitations on the usability of the obtained standard aerosols. This article gives a quick overview of this problem, examining the ways how differently charged particles affect the generation of standard aerosols, and presenting a new method for producing standard aerosols and avoiding the effects of multiply charged particles, with the key idea that the probability for small particles to have more than one charge is very low. A two-stage aerosol generator is used. Small silver particles (d< 40 nm) generated by homogeneous nucleation of silver vapors obtain in bipolar charger not more than one elementary charge. These condensation nuclei are enlarged by a condensational growth device. Big particles are now also not more than singly charged, and narrow size distribution can be obtained by electrical separation. Properties of standard aerosols produced experimentally by both the conventional and the new method, are compared and the validity of the new idea behind the new method is confirmed.     

Effects of ultrafine and fine particles in urban air on peak expiratory flow among children with asthmatic symptoms

Post-mortem morphological, neuropathological and neurochemical findings are described in a girl, aged 14 months, with the early-infantile form of galactosialidosis. An elevation in non-lipid sialic acid was noted in both the grey and white matter of the brain, whereas the white matter displayed a clear reduction in all the major lipids. Multiple cortical-subcortical infarctions were found in the brain, most probably caused by compromised circulation due to endothelial luminal encroachment. Electron microscopy of cerebral blood vessels revealed major swelling of the endothelium due to prominent cytoplasmic vacuolisation. Multiple cytoplasmic vacuoles containing sparse granular or membranous matter were also seen in neurons and glial cells of the brain and spinal cord. Zebra bodies were found in the Purkinje cells, as well as in the spinal anterior horn cells. Prominent endothelial vacuolisation was noted in the liver and kidneys. The renal vascular encroachment was probably the cause of the arterial hypertension with elevated plasma renin activity in the present case. There were innumerable fine vacuoles in the renal epithelium and in the Kupffer cell of the liver, whereas coarser vacuoles were observed in the hepatocytes. The neuronal ultrastructural findings in the present case bear some resemblance to the few reported cases of late-infantile and adult cases of galactosialidosis. The prominent endothelial vacuolisation and focal cerebrovascular lesions, that have not previously been described in galactosialidosis, may be features specific to the rapidly progressive early-infantile form.     

Intercomparison of Aerosol Spectrometers for Ambient Air Monitoring

Three aerosol spectrometers measuring the number concentration distribution of particles in the diameter range 0.01 to 2.5 w m were compared by running them side-by-side for 385 h under ambient air conditions in Erfurt, Germany in October 1997. From the spectral data the measured hourly number concentrations in 3 size fractions, the ultrafine fraction (0.01-0.1 w m), the accumulation fraction (0.1-0.5 w m), and the coarse fraction (0.5-2.5 w m), were analyzed. The systematic component of the difference between the instruments was assessed as the geometric mean of the ratio of the measured concentrations (GMR) and the random component as the geometric standard deviation of this ratio (GSR). Previous statistical methods to compare instruments were developed further. A nonlinear multivariate regression method was used to compare the aerosol distribution consisting of several size fractions. Also, the imprecision of the individual instruments (GSI) was estimated. Comparing the instruments within the ultrafine and accumulation fractions, both the GMRs and GSRs ranged between 1.06 and 1.23 and correlations were above 0.98. In the coarse fraction, the GMR of the number concentrations ranged between 0.25 and 4.19, the GSRs between 1.81 and 2.61, and the correlations between 0.72 and 0.85. The GSIs of the instruments were below 1.2 for all fractions but the coarse fraction. To explore possible differences in the classification of particles into the accumulation and coarse fractions, coarse fractions were regressed with the coarse and the accumulation fractions of the other instruments. Using a conversion based on this regression, the GSRs between instruments were minimized to 1.35 and the GSI to below 1.3. In conclusion, the aerosol spectrometers were in good agreement in the ultrafine and accumulation size fractions. The differences in the measured number concentrations in the coarse fraction were effectively corrected by using a regression method taking into account also the concentration in accumulation fraction, which suggests possible differences in particle sizing at 0.5 w m.