Small airway disease in infants is characterised by abnormal lung volume and uneven ventilation distribution. An inert tracer gas washin/washout technique using a pulsed ultrasonic flow meter is presented to measure functional residual capacity (FRC) and ventilation distribution in spontaneously breathing and unsedated infants. With a pulsed ultrasound sent through the main stream of the flow m...

In this article we derive the phoretic forces acting on a tracer particle, which is assumed to be small compared to the mean free path of the surrounding nonequilibrium gas, but large compared to the size of the surrounding gas molecules. First, we review and extend the calculations of Waldmann [Z. Naturforsch. A 14A, 589 (1959)] using half-sphere integrations and an accommodation coefficient c...

The reduction of nitrogen oxides (NOx) emissions from an existing burner is a a challenging task requiring the understanding of interactions between burner geometry and flame aerodynamics. Currently, three approaches for NOx control exist: fuel or flue gas treatment and combustion modifications. Low NOx burner design is economically attractive for natural gas and light fuel oil combustion since...

Ventilation scintigraphy is a well-established adjunct to perfusion lung imaging in the diagnosis of pulmonary thromboembolus (PE). Although PE may be diagnosed with a standard chest radiograph and perfusion scintigraphy, the findings may be largely nonspecific due to the many types oflung pathology that result in perfusion defects. The specificity of the perfusion (Q) study may be substantiall...

In order to speculate the physical mechanisms of contaminant leakage during sash movement and walk-bys through a laboratory fume cupboard, the complicated three-dimensional flow patterns and the real-time tracer gas leakage are studied via the laser-assisted flow visualization method and the standard gas sampling technique, respectively, over a transparent, full scale chemical fume cupboard. Th...

Traffic induced turbulence coupled with natural air motions becomes an important variable affecting the dispersion of exhaust emissions, especially under low wind conditions. A flexible model vehicle movement system (ƒMVMS) for an urban intersection having two-way straight and radial peripheral traffic flows has been designed, fabricated and made operational in the EWT to study the traffic indu...

Experiments have been carried out to quantify the mixing induced by the interaction of a weak shock wave with a cylindrical volume of a gas (helium) that is lighter than its surroundings (air). In these experiments a round laminar jet was used to produce the light-gas cylinder, and planar laser-induced fluorescence (PLIF) , utilizing a fluorescent tracer (biacetyl) mixed with the helium, was us...

An anammox assay involving a ¹⁵N tracer and gas chromatography-mass spectrometry revealed that the potential anammox activity accounted for 1 to 5% of total N₂ production in a ravine paddy field, Japan. Among four 4-cm-deep layers, the top layer showed the highest activity. Clone libraries showed that the DNA in the top layer contained sequences related to those of Candidatus 'Brocadia fulgida'...

An important issue for the interpretation of data from deep-sea cores is the time for tracers to be transported from the sea surface to the deep ocean. Global ocean circulation models can help shed light on the timescales over which a tracer comes to equilibrium in different regions of the ocean. In this note, we discuss how the most slowly decaying eigenmode of a model can be used to obtain a ...

We have used nuclear magnetic resonance (NMR) to obtain spatially and temporally resolved profiles of gas flow in microfluidic devices. Remote detection of the NMR signal both overcomes the sensitivity limitation of NMR and enables time-of-flight measurement in addition to spatially resolved imaging. Thus, detailed insight is gained into the effects of flow, diffusion, and mixing in specific ge...