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Cellular hit probabilities of alpha particles emitted by inhaled radon progenies in sensitive bronchial epithelial cell nuclei were simulated at low exposure levels to obtain useful data for the rejection or support of the linear-non-threshold (LNT) hypothesis. In this study, local distributions of deposited inhaled radon progenies in airway bifurcation models were computed at exposure conditions characteristic of homes and uranium mines. Then, maximum local deposition enhancement factors at bronchial airway bifurcations, expressed as the ratio of local to average deposition densities, were determined to characterise the inhomogeneity of deposition and to elucidate their effect on resulting hit probabilities. The results obtained suggest that in the vicinity of the carinal regions of the central airways the probability of multiple hits can be quite high, even at low average doses. Assuming a uniform distribution of activity there are practically no multiple hits and the hit probability as a function of dose exhibits a linear shape in the low dose range. The results are quite the opposite in the case of hot spots revealed by realistic deposition calculations, where practically all cells receive multiple hits and the hit probability as a function of dose is non-linear in the average dose range of 10-100 mGy. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study is to use a computerized lung model to quantify the deposition of inhaled drug particles in bronchial generations 9-16, during a severe asthma attack. Material and methods: The deposition of 1-6 μm particles in a healthy individual and during a severe asthma attack were modelled using a stochastic lung model and respiratory parameters characteristic for the two conditions. A second series of simulations were carried out using identical respiratory parameters. Results: Deposition fractions in generations 9-16 were significantly higher during the asthma attack in both series of simulations, being 100% higher for all particle sizes when using identical breathing parameters. Conclusions: Our results suggest that the deposition of inhaled particles during an asthma attack can present significant differences compared to a healthy individual, regardless of the respiratory parameters. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study is to use a computerized lung model to quantify the deposition of inhaled drug particles in bronchial generations 9-16, during a severe asthma attack. Material and methods: The deposition of 1-6 µm particles in a healthy individual and during a severe asthma attack were modelled using a stochastic lung model and respiratory parameters characteristic for the two conditions. A second series of simulations were carried out using identical respiratory parameters. Results: Deposition fractions in generations 9-16 were significantly higher during the asthma attack in both series of simulations, being 100% higher for all particle sizes when using identical breathing parameters. Conclusions: Our results suggest that the deposition of inhaled particles during an asthma attack can present significant differences compared to a healthy individual, regardless of the respiratory parameters. [ABSTRACT FROM AUTHOR]

In this paper, stable single-mode operation at high temperatures is produced by the surface-relief-integrated vertical cavity surface emitting laser (VCSEL). The gain-cavity mode detuning technique is employed to realize high operating temperatures for the VCSEL. The surface relief is etched in the centre of the top side as a mode discriminator for the fundamental mode output, and the threshold current minimum is 1.94 mA at high temperatures by the gain-cavity mode detuning technique. Maximum single-fundamental-mode output power of 0.45 mW at 80 °C is obtained, and the side mode suppression ratios (SMSRs) are more than 30 dB with increasing temperature and current, respectively. [ABSTRACT FROM AUTHOR]