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At least 1,369 records · Page 76Linked to original sources
PubMed1980

Tracheal volume in the pupa of the Saturniid moth Hyalophora cecropia determined with inert gases.

Tracheal volume (VTr) was measured in pupae of the Giant silkworm moth Hyalophora cecropia (Saturniidae, Lepidoptera, Insecta) using inert gas wash-out techniques. The animal was placed in a small vessel that was continuously ventilated (rate, V) by a gas mixture containing 20% O2 in N2; the inflowing (F1) and outflowing gas fractions (FE) of the vessel could be continuously measured by a respiratory mass spectrometer. At the onset of a spiracular constriction period, which was evidenced from the FECO2 trace, the mixture was rapidly replaced by pure Ar. At the subsequent burst, the amount of N2 emerging from the animal, MN2, was calculated from V and the difference (FE--F1)N2. VTr was calculated from MN2 and the N2 concentration in the tracheal system before constriction (assumed to equal that in the ventilating gas before replacement by Ar). Measurements were repeated with N2 and Ar replacing each other. VTr average 48 microliter . g-1 (range 39 to 59) for animals of 5.8 g average body weight (range 3.4 to 9.9), when inert gas solubility in body fluids was accounted for. Both size and stage in pupal development appear to affect VTr. These values show reasonable agreement with literature data, mostly obtained by emptying the tracheal gas space by mechanical compression.

Animals↗
PubMed1991

A combined parallel and series distribution model of inspired inert gases.

The distribution within the lungs of inspired gas has been demonstrated to be uneven by the technique of the external counting of inspired radioactive gas (Milic-Emili et al. (1966) J. Appl. Physiol. 21: 749-759). The contribution of this regional distribution to the slope of the alveolar plateau observed at the lips from an inspired gas marker has been debated, particularly the part played by incomplete diffusive mixing (Sikand et al. (1966) J. Appl. Physiol. 21: 1331-1337). We have repeated the experiments of Sikand, obtaining similar results, by inspiring 1.9 L of 79% argon and 21% oxygen from functional residual capacity, with a subsequent expiration to residual volume, after various breath-holding times. The opposing views of the above authors (parallel versus series inhomogeneities) are here used to develop a model in which the lung is divided into seven regions from apex to base, each region being allocated a compliance curve (polynomial equation of third order) after that of Milic-Emili. Each model region then receives a volume of inspired gas according to its compliance and its regional dead space. This dead space has been allocated on the basis of increasing path lengths of inspired gas from the apex to the base. Beyond the front of this dead space, the mixing of gas is taken to be exponential with respect to expired volume and a curve is then allocated to this alveolar region. The model thus contains both parallel (inter-regional) and series (intra-regional) components. Following a simulated expiration of these seven regions, the model expired curve so obtained is in close agreement with the experimental data, both in respect of shape and of the quantity of tracer contained within it in the range of 0.75-4.5 L of expired gas. We therefore conclude that inter-regional factors are the principal determinant of the last 2.5 L of the expired gas tracer curve and that intra-regional components play a significant role in the first 1.25 L. The model is also applicable to any other inhaled inert gas.

Animals↗
PubMed1992

Properties of 220Rn progeny (212Pb) in the presence of trace gases.

The charge neutralization of 220Rn progeny (212Pb) was studied in nitrogen and argon environments containing trace concentrations of ethylene, propylene and propane. The diffusion coefficient of 212Pb atoms in the presence and in the absence of oxygen and hydrocarbons was determined using a diffusion tube method which measured the penetration fraction of the 220Rn decay products. The results are explained in terms of the formation of lead dioxide with an ionization potential in the range of 10.5-11.1 eV. The ionization potential of 212PbO2 was found to be higher than that of 218PoO2. Charge neutralization was found to occur in a gas mixture of argon and oxygen containing 600 ppm ethylene (C2H4) and also in a mixture of nitrogen and oxygen containing 600 ppm propylene (C3H6). Charge neutralization was not found to occur in a mixture of argon and oxygen containing up to 5000 ppm propane (C3H8) and in a mixture of argon and nitrogen containing 600 ppm ethylene. In pure oxygen, nitrogen, argon, dry air and a mixture of nitrogen and oxygen, no neutralization was observed to occur through charge transfer from neutral molecules. The 220Rn concentration was found to influence the neutralization mechanism. Diffusion coefficients for partially neutralized and neutralized 212Pb ranged from 0.050 to 0.067 cm2 s-1 at a 220Rn concentration of 3.7 x 10(4) atoms cm-3 and a relative humidity of less than 5%.

Alkenes↗
PubMed2005

Respiratory agents: irritant gases, riot control agents, incapacitants, and caustics.

There are many chemical respiratory agents suitable for use by terrorists. They are the oldest chemical agents used and have caused the most casualties throughout the 20th century. Many are available in large quantities for industrial use and are susceptible to potential sabotage. This paper will concentrate on respiratory agents that are readily available and have the potential to cause a large number of casualties and panic. These agents have a lower rate of lethality when compared to other chemical agents but could produce many casualties that may overwhelm the emergency medical system.

Antidotes↗
PubMed2006

Partitioning and removal of dioxin-like congeners in flue gases treated with activated carbon adsorption.

Activated carbon adsorption is commonly used to control dioxin-like congener (PCDD/Fs and PCBs) emissions. Partitioning of PCDD/Fs and PCBs between vapor and solid phases and their removal efficiencies achieved with existing air pollution control devices (APCDs) at a large-scale municipal waste incinerator (MWI) and an industrial waste incinerator (IWI) are evaluated via intensive stack sampling and analysis. Those two facilities investigated are equipped with activated carbon injection (ACI) with bag filter (BF) and fixed activated carbon bed (FACB) as major PCDD/F control devices, respectively. Average PCDD/F and PCB concentrations of stack gas with ACI+BF as APCDs are 0.031 and 0.006ng-TEQ/Nm(3), and that achieved with FACB are 1.74 and 0.19ng-TEQ/Nm(3) in MWI and IWI, respectively. The results show that FACB could reduce vapor-phase PCDD/Fs and PCBs concentrations in flue gas, while the ACI+BF can effectively adsorb the vapor-phase dioxin-like congener and collect the solid-phase PCDD/Fs and PCBs in the meantime. Additionally, the results of the pilot-scale adsorption system (PAS) experimentation indicate that each gram activated carbon adsorbs 105-115ng-PCDD/Fs and each surface area (m(2)) of activated carbon adsorbs 10-25ng-PCDD/Fs. Based on the results of PAS experimentation, this study confirms that the surface area of mesopore+macropore (20-200A) of the activated carbon is a critical factor affecting PCDD/F adsorption capacity.

Adsorption↗
PubMed2004

Study of the influence of surfactants on the transfer of gases into liquids by inverse gas chromatography.

The experimental technique of the reversed-flow version of inverse gas chromatography was applied for the study of effects of surfactants in reducing air-water exchange rates. The vinyl chloride (VC)-water system was used as a model, which is of great importance in environmental chemistry. Using suitable mathematical analysis, various physicochemical quantities were calculated, among which the most significant are: Partition coefficients of the VC gas between the surfactant interface and the carrier gas nitrogen, as well as between the bulk of the water + surfactant solution and the carrier gas nitrogen, overall mass transfer coefficients of VC in the liquid (water + surfactant) and the gas (nitrogen) phases, water and surfactant film transfer coefficients, nitrogen, water and surfactant phase resistances for the transfer of VC into the water solution, relative resistance of surfactant in the transfer of VC into the bulk of solution, exchange velocity of VC between nitrogen and the liquid solution, and finally the thickness of the surfactant stagnant film in the liquid phase, according to the three phase resistance model. From the variation of the above parameters with the surfactant's concentration, important conclusions concerning the effects of surfactants on the transfer of a gas at the air-liquid interface, as well as to the bulk of the liquid were extracted. An interesting finding of this work was also that by successive addition of surfactant, the critical micelle concentration of surfactant was obtained, after which follows a steady-state for the transfer of the gas into the water body, which could be attributed to the transition from mono- to multi-layer state.

Gases↗
PubMed2004

Capacitively coupled microplasma for on-column detection of chromatographically separated inorganic gases by optical emission spectrometry.

Two tubular electrodes placed on a capillary tubing are used to couple an electrical ac field of high voltage (20 kV) but low frequency (20 kHz) and about 8 W power inside for generation of the plasma. The emitted radiation is passed to a spectrometer via an optical fibre butted to the side of the capillary. The excitation temperature of the plasma determined from helium emission lines is about 4000 K. It was found possible to detect oxygen from its emission at 777 and 845 nm, hydrogen at 656 nm and sulfur containing species from emission at 923 nm. The carbon-containing species CH4, CO, and CO2 could be determined from an emission band at 385 nm due to CN. Detection limits in the range between about 1 and 10 ng were obtained using a miniature diode array spectrometer.

Chromatography, Gas↗