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PubMed1996

Retention in hydrophobic interaction chromatography and dissolution of nonpolar gases in water.

The retention data of dansyl amino acids in hydrophobic interaction chromatography (HIC) is interpreted in terms of physicochemical properties of the eluites and solvent and the results are compared to data for the dissolution in water of nonpolar gases. Isothermodynamic temperatures, certain linear relationships between thermodynamic quantities and molecular structure as well as the hermeneutics of the solvophobic theory are employed for data analysis. van't Hoff plots of the retention data with dansyl amino acids are curved and intersect at the isoenergetic temperature, indicative of enthalpy-entropy compensation. The isoenthalpic and isoentropic temperatures are also evaluated and the three isothermodynamic temperatures are found to fall in the same narrow ranges as those for the dissolution of gases in water. Plots of thermodynamic quantities for the retention in HIC against the nonpolar molecular area are linear and thus allow the evaluation of enthalpy, entropy, Gibbs energy and heat capacity changes per unit nonpolar surface area of dansyl amino acids. By employing the solvophobic theory thermodynamic expressions are derived in terms of the nonpolar molecular area and interfacial tension. Using these expressions and n-heptane as model compound it was found that the above group molecular parameters are nearly identical for the retention in HIC and the dissolution of gases in water, thus confirming the mechanistic identity of the two processes.

Chemical Phenomena↗
PubMed2002

Effects of dissolved gases and an echo contrast agent on ultrasound mediated in vitro gene transfection.

The effects of acoustic cavitation on in vitro transfection by ultrasound were investigated. HeLa cells were exposed to 1.0 MHz continuous ultrasound in culture media containing the luciferase gene. Transfection efficiency was elevated when an echo contrast agent, Levovist was added or air was dissolved in the medium. When cells were sonicated in medium saturated with Ar, N2 or N2O which have different gamma values (Cp/Cv), or were saturated with He, Ar or Ne with different thermal conductivities, the effectiveness for the dissolved gases in the ultrasound mediated transfection was Ar > N2 > N2O or Ar > Ne > He, respectively. When free radical formation in water by ultrasound was monitored as a measure of inertial cavitation, it was similarly affected by dissolved gases. These results indicate that the efficiency of ultrasound mediated transfection was significantly affected either by occurrence of or by modification of inertial cavitation due to various gases.

Contrast Media↗
PubMed1987

Gas chromatographic instrumentation for the analysis of aerosols and gases in Titan's atmosphere.

During the next decade or so, NASA, in conjunction with the European Space Agency, plans to send a spacecraft to the Saturnian system so that local studies of Saturn and its satellite, Titan, can be made. In order to study the atmosphere of Titan, analysis of both aerosols and gases will have to be made. To accomplish this, gas chromatographic instrumentation for the collection and analysis of organic gases and aerosols in Titan's atmosphere is being developed. The aerosols will be collected and then subjected to pyrolysis-gas chromatography. Results using a simple pyrolysis-GC system and tholin, made by subjecting a nominal Titan mixture (96.8% N2, 3% CH4, 0.2% H2) to laser-supported shocks, show that many compounds, including hydrocarbons and simple nitriles, can be identified by this technique. Atmospheric gases will be collected using large volume (>10 cm3) sample loops and then analyzed by gas chromatography. Large volume samples are required because the ambient pressures, where the probe instruments are first deployed, will be low (<10 mbar). Preliminary studies using a 20 cm3 sampling system and a very sensitive meta-stable ionization detector show that hydrocarbon components at the 10 ppb level can be detected. Work will continue to improve GC sensitivity, minimize analysis time, and develop interfaces with suitable sample collectors for analysis of atmospheres by future spacecraft.

Aerosols↗
PubMed1995

Constraints on the origins of hydrocarbon gas from compositions of gases at their site of origin

It is widely accepted that natural gas is formed from thermal decomposition of both oil in reservoirs and, to a lesser extent, the organic matter in shales from which the oil was derived. But laboratory pyrolysis experiments on shales do not reproduce the methane-rich composition typical of most gas reservoirs, leading to suggestions that other mechanisms, such as transition-metal catalysis, may be important. The discrepancy might, however, instead arise because gas (and oil) deposits have migrated from their source rocks, so that the reservoir composition might not be representative of the composition in the source rocks where the hydrocarbons were generated. To address this question, we have analysed gas samples coproduced with oils directly from a source rock (the Bakken shales, North Dakota, USA) where the local geology has prevented significant hydrocarbon migration. The methane contents of these Bakken-shale gases are much lower than that of conventional gas reservoirs, but are consistent with that from pyrolysis experiments on these shales. Thus, because these Bakken gases form with (rather than from) oils, we argue that compositional differences between gases from source rocks and conventional gas deposits result from fractionation processes occurring after hydrocarbon expulsion from the source rock.

Fossil Fuels↗
PubMed2001

Nasal tissue dosimetry-issues and approaches for "Category 1" gases: a report on a meeting held in Research Triangle Park, NC, February 11-12, 1998.

Three organizations, the Basic Acrylic Monomer Manufacturers (BAMM), Methacrylate Producers Association (MPA), and Vinyl Acetate Toxicology Group (VATG), have sponsored development of physiologically based pharmacokinetic (PBPK) models for nasal tissue dosimetry with, respectively, acrylic acid (AA), methyl methacrylate (MMA), and vinyl acetate (VA). These compounds cause lesions in nasal epithelial tissues and are classified as "Category 1" gases within the U.S. EPA (1994) classification scheme. The National Center for Environmental Assessment in the U.S. EPA Office of Research and Development also has continuing interests in refining its methods for dosimetry adjustments when data on mode of action are available for Category 1 gases. A round-table discussion was held in Research Triangle Park, NC, on 11-12 February 1998, to develop a broader appreciation of the key processes and parameters required in developing nasal tissue dosimetry models. The discussions at the round table drew on these three case studies and several background presentations to assess the manner in which chemical-specific and mode-of-action data can be incorporated into nasal dosimetry models. The round table had representation from the U.S. EPA, academia, and industry. This article outlines the presentations and topical areas discussed at the round table and notes recommendations made by participants to extend models for nasal dosimetry and to develop improved data for modeling. The contributions of several disciplines-toxicology, engineering, and physiologically based pharmacokinetic (PBPK) modeling-were evident in the discussions. The integration of these disciplines in creating opportunities for dosimetry model applications in risk assessments has several advantages in the breadth of skills upon which to draw in model development. A disadvantage is in the need to provide venues and develop cross-discipline dialogue necessary to ensure the understanding of cultural attitudes, terminology, and methods. The round-table discussions were fruitful in achieving such enhanced understanding and communication. Subsequent elaboration of these models will benefit from the interactions of these groups at the round table. The round-table discussions have already led to model improvements-as noted in several recently published articles. Participants emphasized several generic data needs in relation to nasal vapor uptake studies in human subjects, to broader discussion of tissue diffusion models, and to extensions to other classes of gases. The round-table articles that are published separately in this issue and the discussions, captured in this overview, provide a glimpse of the state of the science in nasal dosimetry modeling and a clear indication of the growth of and continuing opportunities in this important research area.

Animals↗
PubMed1990

Real-time measurement and control of waste anesthetic gases during veterinary surgeries.

Veterinary clinics are typically small businesses without access to sophisticated occupational safety and health programs that may exist for larger firms or hospitals. Exposures to waste anesthetic gases have been linked to a myriad of adverse health-related conditions. Excessive exposures to anesthetic agents are possible because many of the clinics use portable gas delivery carts that are not designed to capture waste gases. While scavenging systems are available to remove waste anesthetic gases, the cost may be prohibitive for smaller clinics and the effectiveness of these systems has not been fully established in veterinary clinics. The National Institute for Occupational Safety and Health (NIOSH) recommends limiting exposures to nitrous oxide (N2O) to a time-weighted average (TWA) concentration of 25 ppm and halogenated agents to 2 ppm. The NIOSH TWA is based on the weight of the agent collected from a 45-L air sample by charcoal adsorption over a sampling period not to exceed 1 hr. The NIOSH criteria state that, in most situations, control of N2O to the TWA as defined will result in levels of approximately 0.5 ppm of the halogenated agent. At present, no Occupational Safety and Health Administration (OSHA) permissible exposure level (PEL) exists for exposure to anesthetic agents; nor do specific recommendations exist for veterinary scavenging systems. Waste anesthetic gas exposures were determined using a modified MIRAN 1A at five veterinary clinics operating within the Morgantown, West Virginia, vicinity. For unscavenged systems of methoxyflurane and halothane, 1-hr time-weighted average exposures ranged from 0.5 to 45.5 ppm and 0.2 to 105.4 ppm, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed2002

Monitoring leaking gases by OP-FTIR remote sensing.

Measurement of leaking gases using Open Path Fourier Transform Infrared (OP-FTIR) spectroscopy was carried out in this study to acquire Path Integrated Concentration (PIC) data. Three hazardous Volatile Organic Compounds (VOCs) namely methylene chloride, chloroform and acetone were analyzed. For the two-component leaking source, the PIC data were easily obtained through ordinary calculation and compared to those obtained from Artificial Neural Network (ANN). When the leaking source was composed of three VOCs whose characteristic peaks interfere with each other, it was necessary to do spectral correction for multicomponent analysis with ANN. The Absorbance-Wavenumber-Time 3D spectra of the leaking sources and concentration variations with the leaking time were plotted. The results showed that OP-FTIR is a good quantitative analytical method for indoor or field air pollution. Further more, the remote sensing OP-FTIR system could be utilized to continuously monitor many more toxic gases and work as an alert system for the real time monitoring of hazardous gases beyond normal working conditions of various kinds of areas, such as living or industrial areas.

Acetone↗
PubMed2001

Deactivation of the pulmonary surfactant dynamics by toxic aerosols and gases.

Interactions between selected toxic aerosols and gases occurring in the air at the workplace and the pulmonary surfactant (PS) have been studied with two physicochemical techniques in vitro. The Pulsating Bubble Surfactometer (PBS) and the Langmuir-Wilhelmy Balance (LWB) have been used for measurements of dynamic interfacial properties of the PS material after its contact with several gases (sulfur dioxide, nitrogen oxides, ozone, ammonia) and liquids (sulfuric, nitric and hydrochloric acids and ammonium hydroxide), which can be brought into the alveoli with the inhaled air. Surface tension-area relationships for the interface oscillations have been analyzed using qualitative criteria of normalized hysteresis area (HA(N)) and minimum surface tension (sigma(min)). It was demonstrated that, for each analyzed compound, inactivation of the surfactant occurs, but the critical concentrations and doses are compound specific, which suggests the toxic potential of the investigated substances with respect to PS. Possible mechanisms of the interactions between the investigated substances and the surfactant components are discussed. Degradation of the PS dynamical interfacial properties (HA(N) and sigma(min)), important from the physiological viewpoint, observed in our in vitro experiments, suggests a possibility of adverse health effect in the case of a chronic inhalation of toxic gases and aerosols, even at low concentration or after a short exposure to strongly contaminated air. It results in a slowdown of the pulmonary clearance rate and increase of the lung burden for both considered cases.

Aerosols↗
PubMed1998

Minimum alveolar concentrations of noble gases, nitrogen, and sulfur hexafluoride in rats: helium and neon as nonimmobilizers (nonanesthetics)

UNLABELLED: We assessed the anesthetic properties of helium and neon at hyperbaric pressures by testing their capacity to decrease anesthetic requirement for desflurane using electrical stimulation of the tail as the anesthetic endpoint (i.e., the minimum alveolar anesthetic concentration [MAC]) in rats. Partial pressures of helium or neon near those predicted to produce anesthesia by the Meyer-Overton hypothesis (approximately 80-90 atm), tended to increase desflurane MAC, and these partial pressures of helium and neon produced convulsions when administered alone. In contrast, the noble gases argon, krypton, and xenon were anesthetic with mean MAC values of (+/- SD) of 27.0 +/- 2.6, 7.31 +/- 0.54, and 1.61 +/- 0.17 atm, respectively. Because the lethal partial pressures of nitrogen and sulfur hexafluoride overlapped their anesthetic partial pressures, MAC values were determined for these gases by additivity studies with desflurane. Nitrogen and sulfur hexafluoride MAC values were estimated to be 110 and 14.6 atm, respectively. Of the gases with anesthetic properties, nitrogen deviated the most from the Meyer-Overton hypothesis. IMPLICATIONS: It has been thought that the high pressures of helium and neon that might be needed to produce anesthesia antagonize their anesthetic properties (pressure reversal of anesthesia). We propose an alternative explanation: like other compounds with a low affinity to water, helium and neon are intrinsically without anesthetic effect.

Anesthetics↗
PubMed1999

Working gases in thermoacoustic engines.

The best working gases for thermoacoustic refrigeration have high ratios of specific heats and low Prandtl numbers. These properties can be optimized by the use of a mixture of light and heavy noble gases. In this paper it is shown that light noble gas-heavy polyatomic gas mixtures can result in useful working gases. In addition, it is demonstrated that the onset temperature of a heat driven prime mover can be minimized with a gas with large Prandtl number and small ratio of specific heats. The gas properties must be optimized for the particular application of thermoacoustics; it cannot be assumed that high specific heat ratio and low Prandtl number are always desirable.

Acoustics↗
PubMed1973

Effects of various gases on the survival of dried bacteria during storage.

Salmonella newport and Pseudomonas fluorescens were dried together in papain digest broth and sucrose-glutamate, and stored in several gases at various water activities (a(w)) between 0.00 and 0.40 at 25 C for various periods up to 81 weeks. Both S. newport and P. fluorescens, dried in papain digest broth and stored in air, died rapidly if the conditions were very dry (0.00 a(w)) or moist (0.40 a(w)). Storage in carbon dioxide and argon gave greater survival than storage in air but lower survival than did storage in nitrogen or in vacuo. When the organisms were dried in a sucrose-glutamate mixture the differences between the gases were very small, and variations in residual water were less important. Of the inert gases, argon gave the best survival when the organisms were dried in papain digest broth, especially at 0.00 a(w); the survival in neon and krypton was lower and in xenon and helium it was much lower.

Air↗
PubMed1982

Thermocamera studies of gases and vapours.

Most gases and vapours with a bipolar molecular structure absorb infrared energy. If such a gas is interposed between an object emitting infrared radiation and a thermocamera the gas will absorb some of the infrared radiation and thus cast a shadow on the thermocamera picture. In this assay it is possible to visualise the gas. This method had been used to study pollution with anaesthetic gases and vapours in operating theatres. The vapours of other chemicals used in hospitals and other places of work also have been studied. The method permits the study of dispersion and flow patterns of polluting gases and vapours during work.

Air Pollutants↗
PubMed1991

Effect of ventilation with soluble and diffusible gases on the size of air emboli.

Pulmonary hypertension resulting from venous air embolism is known to increase after ventilation with highly soluble and diffusible gases. Exacerbation of the hypertension could be due to further blockage of the circulation if the bubbles enlarge as a result of ingress of gas by diffusion. This mechanism has been frequently cited but lacks direct proof. To determine directly whether intravascular air bubbles actually enlarge when highly soluble and diffusible gases are inspired, we used microscopy to measure the size of gas emboli in vivo. When air bubbles were injected into the right atrium, the bubbles that appeared in pulmonary arterioles were larger during ventilation with helium or nitrous oxide than with air. Air bubbles injected into the pulmonary artery enlarged when the inspired gas was changed to helium or nitrous oxide. The direction, magnitude, and timing of changes in bubble size were consistent with a net diffusion of gas into the bubbles. These data support the idea that venous air emboli enlarge during ventilation with soluble and diffusible gases and thereby cause further vascular obstruction.

Animals↗
PubMedDate not supplied

Hydrogen sulfide and reduced-sulfur gases adversely affect neurophysiological functions.

Hydrogen sulfide (H2S) above 50 parts per million (ppm) causes unconsciousness and death. Lower doses of H2S and related gases have been regarded as innocuous, but the effects of prolonged exposure have not been studied. This study was designed to determine whether people exposed to sulfide gases as a result of working at or living downwind from the processing of "sour" crude oil demonstrate persistent neurobehavioral dysfunction. Thirteen former workers and 22 neighbors of a refinery complained of headaches, nausea, vomiting, depression, personality changes, nosebleeds, and breathing difficulties. Their neurobehavioral functions and a profile of mood states (POMS) were compared to 32 controls, matched for age and educational level. The exposed subjects' mean values were statistically significantly abnormal compared to controls for two-choice reaction time, balance (as speed of sway), color discrimination, digit symbol, trail-making A and B, and immediate recall of a story. Their POMS scores were much higher than those of controls. Visual recall was significantly impaired in neighbors, but not in exworkers. It was concluded that neurophysiological abnormalities were associated with exposure to reduced sulfur gases, including H2S from crude oil desulfurization.

Adult↗
PubMed2001

Assessment of rumen processes by selected-ion-flow-tube mass spectrometric analysis of rumen gases.

This work investigated the potential to use measurement of the concentration of certain gases in the rumen headspace to gain information about rumen processes and as a potential diagnostic tool. We used new equipment (selected-ion-flow-tube mass spectrometer) that allows rapid and precise analysis of many of the gases present in a sample. Samples of rumen headspace gas and corresponding samples of rumen liquor were taken from three lactating cows, prepared with rumen fistulae, at intervals after receiving their morning feed allocation (grass silage and concentrates). Hydrogen sulfide, methyl sulfide, and dimethyl sulfide, were the predominant gases that were measured in the rumen headspace by this technique. The concentrations of these sulfur compounds declined over the interval after feeding, mirroring ammonia concentrations measured in rumen liquor, reflecting their common dependence on the fermentation of sulfur amino acids. Ammonia concentrations in rumen headspace gas varied in the opposite direction to the concentration of ammonia in rumen liquor and likely depend more on the pH of rumen liquor. Consideration of the pKa of ammonia suggests that ammonia concentrations in rumen gas will be very low below pH 6, representing a useful diagnostic for subacute ruminal acidosis. Low concentrations of volatile fatty acids were detected in rumen gas. The molar proportions of volatile fatty acids were similar in gas and liquor samples, with rumen gas containing slightly less acetic acid and disproportionately more valeric and caproic acids.

Acidosis↗
PubMed2002

[Effects of elevated atmospheric CO2 on the exchange of trace gases between ecosystems and the atmosphere].

The latest researches on the effects of elevated atmospheric CO2 on the exchanges of trace gases (e.g., CO2, CH4 and N2O) between the atmosphere and ecosystems were reviewed. The techniques and methods involved in the researches were introduced firstly. Then the review mainly focused upon the results from those studies using the open-top-chamber (OTC) methods and the free-air carbon dioxide enrichment (FACE) system. Generally, elevated atmospheric CO2 may stimulate biomass accumulation, and enlarge C/N ratio in plant tissue so as to reduce the decomposition of organic matter. This action could increase CO2 sequestration in terrestrial ecosystems. Elevated atmospheric CO2 could impact on methanogenic bacteria and CH4 emissions. An increase in CH4 emissions from wetland may appear. The argument among the responses of N2O emissions to elevated CO2, however, was inconsistent. So far, no study on other trace gases was reported. More efforts should be taken in the research on the effects of elevated atmospheric CO2 on the exchange of trace gases.

Atmosphere↗
PubMed2004

[Determination of partition coefficient of dissolved gases in transformer oil using phase ratio variation method and static headspace gas chromatography].

The partition coefficients of dissolved gases in transformer oil were determined using a phase ratio variation method and static headspace gas chromatography (GC). A pressure balancing and gas volume-metering device was connected to the vent of a sample loop on a six-port injection valve of the GC. The gas phase sample from the headspace vial of 25 mL was transferred to an 80 microL sample-loop through a fused silica capillary of 0.53 mm i.d., and then separated and determined quantitatively by GC. A 2 m x 1 mm i.d. GDX502 micro-packed column was used for the separation. Five different gas-liquid volume ratios in the headspace vials were measured at different equilibrium concentrations. The partition coefficients of hydrocarbon gases including methane, acetylene, ethylene, ethane and propane dissolved in transformer oil were determined by using linear regression analysis at 20 degrees C and 50 degrees C separately. The errors between the real values and regression values from experimental data were less than 4.14% except methane. Fundamental data for on-line measurement of dissolved gases in transformer oil are provided by GC.

Acetylene↗
PubMed2005

[Five fatalities due to inhalation of "asphyxiant gases": pathophysiological analysis in autopsy cases].

Five autopsy cases were examined to investigate fatal factors involved in inhalation of "asphyxiant gases": carbon monoxide (CO, n=3), fluorocarbons (n=1) and butane (n=1). In all cases, there was severe pulmonary edema and congestion in all viscera, suggesting advanced circulatory failure. The airway was filled with bloody froth in cases of fluorocarbons and butane inhalation. In CO intoxication, a marked increase in serum cardiac troponins suggested severe myocardial damage. There were also biochemical findings of respiratory distress (an evident increase in intra-alveolar pulmonary surfactant protein A), alveolar injury (an increase in serum surfactant protein A and D), rhabdomyolysis (myoglobinuria) and prolonged hypoxia (myogenic hyperuricemia) in cases of inhaling incomplete combustion gases. In a case of fluorocarbons gas inhalation, biochemical findings suggested respiratory distress, myocardial ischemia (an increase in serum CK-MB) and advanced hypoxia. Similar findings were observed in a case of butane inhalation, although cardiac troponin levels were low in the peripheral blood. These observations suggested that myocardial damage was prominent in CO intoxication, accompanied by respiratory distress in cases of inhaling incomplete combustion gases, whereas respiratory distress and hypoxia were major findings in cases of fluorocarbons and butane gas inhalation.

Aged↗