Pulmonary gas exchange was studied in 8 patients with allergic asthma before and after allergen challenge. Ventilation-perfusion relationships were assessed by the multiple inert gas elimination technique and forced expiratory flow by conventional spirometry. Measurements were made before, 7-8 minutes, and 0.5, 2.5 and 5 hours after challenge. During baseline conditions all patients showed norm...

When a natural gas pipeline ruptures, the adjacent automatic line control valves (ALCVs) should close quickly to prevent leakage or explosion. The differential pressure set point (DPS) at each valve location is the main criteria for value setting in ALCV action. If the DPS is not properly adjusted, the ALCV may mistakenly close or it may not take any action at proper time. This study focused on...

Two highly contrasting variables summarizing the efficiency of transport of materials within the leaf are recognized as playing central roles in determining gas exchange and plant performance. This paper summarizes current approaches for the measurement of mesophyll conductance to CO2 (g m) and leaf hydraulic conductance (K leaf) and addresses the physiological integration of these parameters. ...

A full three-dimensional, single phase computational fluid dynamics model of a proton exchange membrane fuel cell (PEMFC) with both the gas distribution flow channels and the Membrane Electrode Assembly (MEA) has been developed. A single set of conservation equations which are valid for the flow channels, gas-diffusion electrodes, catalyst layers, and the membrane region are developed and numer...

BACKGROUND Noninvasive positive pressure ventilation (NPPV) using a face mask is the ventilatory mode of choice in selected patients experiencing acute exacerbation of chronic obstructive pulmonary disease (COPD). A high incidence of intolerance limits the use of this approach. OBJECTIVE To evaluate the sequential use of mask and helmet during NPPV in patients with severe exacerbation of COPD...

the present study has been conducted on caspian roach (rutilus rutilus) so that the impact of different concentrations lead on blood hematological, biochemical, and immunological indicators could be investigated. the roach (rutilus rutilus), used in this study, was 3.3±0.3 g heavy and 4±0.80 cm long in average. the fish were exposed to a low concentration of 10% lc50 and high concentration of 5...

in order to investigate the combined effects of shift work and heat stress on the physiological parameters, such as heart rate (hr) and body temperature (bt), a hot-dry working environment was investigated for 53 workers in foundry workshops. in this study wet bulb globe temperature index (wbgt) was measured and along with that simultaneously heart rate and oral temperature were checked in 3 sh...

output characteristics of fuel cells are affected by a large number of parameters such as geometry, dimensions, construction materials and conditions of supplying fluids. in this paper a mathematical model followed by a two-dimensional numerical approach has been presented to study the fuel cell parametrically. effect of oxygen concentration at gas diffusion layer entrance, temperature and pres...