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PubMed1993

Formation of reduced carbonaceous matter in basalts and xenoliths: reaction of C-O-H gases on olivine crack surfaces.

It has been suggested that the formation of reduced carbonaceous matter in basalts and mantle xenoliths occurs by heterogeneous reaction of volcanic gas on fresh, chemically active crack surfaces produced by thermal stresses during eruption and cooling. This hypothesis is supported by experiments at 400-800 degrees C on ¿010¿ surfaces of San Carlos olivine exposed to C-O-H gases generated by the decomposition of oxalic acid and oxalic acid dihydrate. Carbonaceous films form readily on these surfaces and achieve thicknesses comparable to those observed in natural samples (a few nanometers) in a matter of minutes. At relatively oxidizing conditions, the carbonaceous films consist principally of C-C and C-H bonded species with lesser amounts of C-O bonded species. At relatively reducing conditions, the carbonaceous films consist of subequal amounts of C-C/C-H, C-O, and metal-C species. Aliphatic and aromatic hydrocarbons and other thermally labile organic species are associated with carbonaceous films in some natural samples but none were detected in experimental samples from this study, leaving open the question of abiotic synthesis of organic matter on crack surfaces in basalts. Regardless, it is clear from the preliminary experiments reported here that crack surfaces in olivine (and probably other silicate minerals and glasses) are capable of stabilizing compounds that otherwise would not be stable in cooling lava.

Carbon↗

PubMed1976

Pulmonary gas exchange in dogs ventilated with mixtures of oxygen with various inert gases.

To study the influence of physical properties of the respired gas on alveolar gas exchange, alveolar-arterial partial pressure differences for O2 and CO2 were measured in anesthetized dogs that were artificially ventilated with gas mixtures of O2 in N2, He, Ar or SF6. In both hyposia and normoxia alveolar-arterial PO2 differences had the tendency to increase slightly in the sequence of the respired inert gases SF6 less than Ar less than N2 less than He, while arterial-alveolar PCO2 differences remained practically unchanged. Pulmonary diffusing capacity for CO(DCO), determined by the single breath technique, revealed no significant differences between the four gas mixtures used. The possible mechanisms underlying these results are discussed in connection with the physical properties of the respired gas mixtures.

Animals↗

PubMed1978

Layered membranes: a diffusion barrier to gases in teleostean swimbladders.

Flattened cells are dispersed in an overlapping fashion within the submucosa of closed (physoclistous) swimbladders. Within the cells are located round platelets best seen by phase or interference type microscopy. At the electron microscope level the platelets are revealed as repeated, numerous layers of membranous discs. Each disc is a bilayer with an enlarged rim. The bilayer is strongly and preferentially reactive to osmium tetroxide. Swimbladder walls are known to be highly resistant to passage of gases. The randomly disposed platelets with the highly ordered layering of membranes may provide that physical resistance to gas movement.

Air Sacs↗

PubMed1981

Changes in body temperature after administration of antipyretics, LSD, delta 9-THC, CNS depressants and stimulants, hormones, inorganic ions, gases, 2,4-DNP and miscellaneous agents.

This survey concludes a series of complications of data from the literature, primarily published since 1965, on thermoregulatory effects of antipyretics in afebrile as well as in febrile subjects, LSD and other hallucinogens, cannabinoids, general CNS depressants, CNS stimulants including xanthines, hormones, inorganic ions, gases and fumes, 2,4-dinitrophenol and miscellaneous agents including capsaicin, cardiac glycosides, chemotherapeutic agents, cinchona alkaloids, cyclic nucleotides, cycloheximide, 2-deoxy-D-glucose, dimethylsulfoxide, insecticides, local anesthetics, poly I:poly C, spermidine and spermine, sugars, toxins and transport inhibitors. The information listed includes the species used, route of administration and dose of drug, the environmental temperature at which the experiments were performed, the number of tests, the direction and magnitude of body temperature change and remarks on the presence of special conditions such as age or lesions, or on the influence of other drugs, such as antagonists, on the response to the primary agents.

2,4-Dinitrophenol↗

PubMed1987

Trapping of gases by water ice and implications for icy bodies.

The trapping of various gases by water ice at low temperatures (20-80K) and their release from the ice upon warming, was studied experimentally. The results of these experiments, together with a computation of the thermal evolution of a cometary nucleus, can explain the gas and dust jets which were observed to emanate from the nucleus of P/Halley. The experimental results are important also to the gas content of Titan.

Acetylene↗

PubMed2005

The significance of the activity of dissolved oxygen, and other gases, enhanced by high hydrostatic pressure.

The partial pressure of oxygen and other gases dissolved in water and subjected to high hydrostatic pressure is increased. Although this was established many years ago it remains a problematical phenomenon. The review deals with some of the underlying theoretical difficulties and discusses the kinetic and environmental implications of the pressure-enhanced partial pressures.

Animals↗

PubMed2006

Evaluation of PCDD/F partitioning between vapor and solid phases in MWI flue gases with temperature variation.

Partitioning of PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofuran) between vapor and solid phases in flue gas is affected by several factors including temperature variation. In this study, PCDD/F removal efficiencies achieved with activated carbon injection (ACI) and partitioning of vapor/solid phase PCDD/Fs in flue gases with temperature variation in a municipal waste incinerator (MWI) are evaluated via intensive flue gas sampling. Results indicate that most PCDD/Fs in flue gas downstream of the ACI+bag filter (BF) exist in vapor phase (over 90%) while the removal efficiencies of vapor and solid phase PCDD/Fs are 98.5-99.6% and 99.8-99.9%, respectively. The results of flue gas samplings also indicate that there is optimal operating temperature for PCDD/F removal achieved with ACI. Additionally, a pilot-scale adsorption system (PAS) is constructed in this study to evaluate the PCDD/F partitioning affected by temperature. The results of the PAS experimentation indicate that about 55% and 25% vapor phase PCDD/Fs passing through the filter cake (adsorbent) are transferred to solid phase at 150 and 200 degrees C, respectively. As the temperature is increased to 250 degrees C, filter cake (adsorbent) cannot effectively adsorb vapor phase PCDD/Fs and significant PCDD/Fs are formed via de novo synthesis.

Adsorption↗

PubMed2006

Evaluation of gas removal and bacterial community diversity in a biofilter developed to treat composting exhaust gases.

The performance of a new, but simply constructed, biofilter system, developed to purify composting exhaust air, was evaluated. The biofilter was packed with mature compost mixed with activated carbon and sludge sourced from a wastewater treatment plant. An alternating air flow system and a bioaerosol reduction device were designed to prevent pressure drop and reduce bioaerosol release. Experimental results demonstrated that satisfactory removal efficiencies of nitrogen-containing compounds, sulfur-containing compounds, fatty acids, total hydrocarbon and odor were achieved at an empty bed retention time (EBRT) of 30s. No significant acidification or alkalinity in the biofilter was observed, and the system was characterized by a small pressure drop and a low level of bioaerosol emission. Denaturing gradient gel electrophoresis (DGGE) and fluorescence in situ hybridization (FISH) techniques were used to uncover the changes in the bacterial community of the biofilter during the deodorization processes. A minimum of 16 bands were observed in the DGGE profile. Phylogenetic analysis revealed the phylum of Proteobacteria to be predominant, followed by Actinobacteria, Bacteroidetes, and Firmicutes, in descending order. However, the occurrence and predominance of specific bacterial species varied with the environmental conditions of the biofilter. Our results demonstrate - from both an engineering and biological point of view - the feasibility of the biofilter system described herein in purifying the gases derived from composting food waste.

Air Pollutants↗

PubMed2006

Ultra-low field NMR measurements of liquids and gases with short relaxation times.

Interest in nuclear magnetic resonance measurements at ultra-low magnetic fields (ULF, approximately microT fields) has been motivated by various benefits and novel applications including narrow NMR peak-width, negligible susceptibility artifacts, imaging of samples inside metal containers, and possibility of directly imaging neuronal currents. ULF NMR/MRI is also compatible with simultaneous measurements of biomagnetic signals. However the most widely used technique in ULF NMR-prepolarization at high field and measurement at lower field-results in large transient signals which distort the free induction decay signal. This is especially severe for the measurement of signals from samples and materials with short T1 time. We have devised an approach that largely cancels the transient signals. The technique was successfully used to measure NMR signals from liquids and gases with T1 in the range 1-4 ms.

Algorithms↗

PubMed2005

Measuring pore connectivity by pulsed field gradient diffusion editing with hydrocarbon gases.

Measurements of time-dependent diffusion are performed on a rock sample saturated first with water, then methane and finally ethane. The gases were selected because their increased diffusivities and relaxation times allow probing greater length scales than water and because of their practical relevance. The nuclear magnetic resonance measurements employed pulse field gradient diffusion editing pulse sequences, allowing analysis of D(t) as a function of relaxation time. Very different D(t) behaviors are observed for different relaxation times, including indications of connected pore networks at moderate relaxation times.

Diffusion↗

PubMed2005

Ab initio molecular orbital studies of the vibrational spectra of the van der Waals complexes of boron trifluoride with the noble gases.

The molecular structures, interaction energies, charge transfer properties and vibrational spectra of the van der Waals complexes formed between boron trifluoride and the noble gases neon, argon, krypton and xenon have been computed using second and fourth order Møller-Plesset perturbation theory and the Los Alamos National Laboratory LANL2DZ basis set. The complexes are all symmetric tops, with the noble gas atom acting as a sigma electron donor along the C3 axis of the BF3 molecule. The interaction energies are all vanishingly small, and the amount of charge transferred in each case is of the order of 0.01e. The directions of the wavenumber shifts of the symmetric bending (nu2) and antisymmetric stretching (nu3) modes of the BF3 fragment confirm those determined experimentally, and the shifts are shown to correlate well with the polarizability of the noble gas atom and the inverse sixth power of the intermonomer separation. The nu2 mode is substantially more sensitive to complexation than the nu3 vibration.

Argon↗

PubMed2005

Dispersion of odorous gases in the atmosphere - Part I: Modeling approaches to the phenomenon.

The study of odor dispersion, particularly its modeling, is an important decision tool for estimating the impact of human activities on the environment and its populations. In this sense, software to model the dispersion of odorous gases was developed and is presented. It is based on the theory established by Högström on the odor dispersion of puff emissions. This theory is applied to Gaussian models and takes the frequency of values for odor intensity over any time period into account. Such a model is able to consider the instantaneous characteristics of odor perception by human beings. Nine approaches that explore several solutions within the Gaussian domain for the atmospheric dispersion problem are proposed in software named ODODIS (ODOr DISpersion Software). This software was developed to test the different solutions. Four of these solutions are based on the punctual (or point source) emission or classic equation; two are based on the instantaneous punctual emission equation; and the other three, on the prolonged punctual emission equation (puff models). Measuring units used for the input data may be g s(-1) or OU (Odor Units). The software developed here satisfies the need to obtain instantaneous data of either a passive or an odorous gas at a specific point of an area. The simulation time varies depending on the purpose of the analysis. Mean concentration values may be obtained by integrating the instantaneous results generated by the model.

Air Pollutants↗

PubMed2001

Flux of gases across the air-water interface studied by reversed-flow gas chromatography.

In the present work the reversed-flow gas chromatographic technique was applied for the study of flux of gases across the air-water interface. The model system was vinyl chloride-water, which is of great significance in food and environmental chemistry. Using suitable mathematical analysis, equations were derived by means of which the following physicochemical quantities were calculated: diffusion coefficient of vinyl chloride (VC) into water, partition coefficient of VC between the water (at the interface and the bulk) and the carrier gas nitrogen, overall mass transfer coefficients of VC in the gas (nitrogen) and the liquid (water), gas and liquid film transfer coefficients of VC, gas and liquid phase resistances for the transfer of VC into the water, and finally the thickness of the stagnant film in the liquid phase, according to the two-film theory of Whitman. From the variation of the above parameters with temperature, as well as the volume and the free surface area of the water, useful conclusions concerning the mechanism for the transfer of VC into water were extracted. These are discussed in comparison with the same parameters calculated from empirical equations or determined experimentally by other techniques.

Air↗

PubMed2002

Heterogeneous catalysis on solids of gases diffusing through a liquid layer, studied by inverse gas chromatography.

Physicochemical parameters for heterogeneous catalytic reactions when the catalytic bed was under a liquid phase have been determined, using a non-linear adsorption isotherm by the reversed-flow version of inverse gas chromatography (RF-GC). The mathematical analysis developed in heterogeneous catalysis, mass transfer across gas-liquid boundaries, and diffusion coefficients of gases in liquids was associated with a non-linear adsorption isotherm to find the relevant equations pertaining to the problem. These equations were then used to calculate the adsorption/desorption rate constant, the rate constant for the first-order catalytic reaction and the equilibrium constant for the non-linear adsorption isotherm. The diffusion coefficients of the reactant in the liquid and gaseous phases and the partition coefficients for the distribution of the reactant between the gaseous and liquid phase were also determined.

Adsorption↗

PubMed2003

Determination of carbon monoxide, methane and carbon dioxide in refinery hydrogen gases and air by gas chromatography.

This paper illustrates a method for determining trace amounts of CO, CH4 and CO2 with the detection limit of 0.15, 0.15 and 0.20 microg/l, respectively, in refinery hydrogen gases or in air. A simple modification of a gas chromatograph equipped with a flame-ionization detector is presented. A Porapak Q column, additionally connected with a short molecular sieve 5A packed column and a catalytic hydrogenation reactor on the Ni catalyst have been applied. The principle of the analytical method proposed is the separation of CO from O2 before the introduction of CO to the methanizer. The analytical procedure and examples of the results obtained have been presented. The modification applied makes it possible to use the GC instrument for other determinations, requiring utilization of the Porapak Q column and the flame-ionization detector. In such cases, the short molecular sieve 5A column and the methanizer can be by-passed.

Carbon Dioxide↗

PubMed1998

Temperature effects on lung and blood gases in Bufo paracnemis: consequences of bimodal gas exchange.

The arterial pH decreases with rising body temperature in ectothermic vertebrates. We report on how this regulation was achieved in relation to bimodal respiration in the toad Bufo paracnemis. Gas exchange was measured for the lung and also for the whole body (skin and lung). In addition, lung gas pressures (PL(O2) and PL(CO2)) and arterial blood gases (pH and P(O2)) were measured at 17, 27 and 35 degrees C. Arterial pH fell from 7.85 at 17-7.64 at 35 degrees C. Concomitantly, PL(CO2) increased from 5.6 mmHg at 17 degrees C to 10.4 mmHg at 35 degrees C. Regardless of temperature, PL(O2) remained virtually constant at 125-126 mmHg, whereas arterial P(O2) increased significantly with rising temperature (50 mmHg at 17 degrees C; 79 mmHg at 35 degrees C). The pulmonary gas exchange ratio (RE) increased from 0.28 at 17 degrees C to 0.51 at 35 degrees C, while the ratio for whole body gas exchange (lung + skin) was close to 0.8 irrespective of temperature. Since CO2 conductance of the skin increased little with temperature, the lung eliminated a larger fraction of total CO2 output. This shift caused the increase of RE for pulmonary exchange with rising temperature, which increased PL(CO2) and contributed to a negative deltapHa/deltaT. Therefore, bimodal respiration in Bufo accounted for part of the temperature-dependent pH regulation, while the final adjustments depend on pulmonary ventilation.

Animals↗

PubMed2001

The solubility of gases and vapours in dry octan-1-ol at 298 K.

Ostwald solubility coefficients of 74 compounds in dry octan-1-ol at 298 K have been determined, and have been combined with literature values and additional values we have calculated from solubilities in dry octan-1-ol and vapour pressures to yield a total of 161 log L(OctOH) values at 298 K. These L(OctOH) values are identical to gas-to-dry octan-1-ol partition coefficients, often denoted as K(OA). Application of the solvation equation of Abraham to 124 values as a training set yielded a correlation equation with n = 124, S.D. = 0.125, r2 = 0.9970 and F = 7731. This equation was then used to predict 32 values of log L(OctOH) as a test set, giving a standard deviation, S.D. of 0.131, an average absolute deviation of 0.085 and an average deviation of -0.009 log units. The solvation equation for the combined 156 log L(OctOH) values was log L(OctOH) = -0.120 - 0.203R2 + 0.560pi2(H) + 3.560 sum(alpha2(H)) + 0.702 sum(beta2(H)) + 0.939 logL16, n =156, r2 = 0.9972, S.D. = 0.125, F = 10573, where, n is the number of data points (solutes), r the correlation coefficient, S.D. the standard deviation and F is the F-statistic. The independent variables are solute descriptors as follows: R2 is an excess molar refraction, pi2(H) the dipolarity/polarisability, sum(alpha2(H)) the overall or summation hydrogen-bond acidity, sum(beta2(H)) the overall or summation hydrogen-bond basicity and L16 is the Ostwald solubility coefficient on hexadecane at 298 K. The equation is consistent with similar equations for the solubility of gases and vapours into methanol, ethanol and propan-1-ol. It is suggested that the equation can be used to predict further values of log L(OctOH), for which the solute descriptors are known, to within 0.13 log units.

1-Octanol↗

PubMed2001

Characterisation of non-condensable sulphur containing gases from Kraft pulp mills.

This paper describes work performed on the sampling and analysis of non-condensable gases (NCG) emitted from diffuse sources of a Portuguese Kraft pulp mill, which is the background information for a NCG collection, treatment and disposal system. The variability found in the composition of the gaseous compounds showed the existence of gaseous streams other than typical total reduced sulphur (TRS) compounds as usually described. From the measured TRS concentrations and the gas flow rate from each source it was possible to calculate the emission flow rate, E, of each source. These emission flow rates were then divided into three categories which are quite useful to identify significant sources and to choose abatement techniques. The methodology presented allows for a precise quantification of sources so that similar emissions can be grouped for treatment purposes. Sources with an emission flow rate bigger than 1 kg/h have a marked effect on the overall TRS emissions of the mill, as they are major contributors. It was also found that a new analytical procedure using Restek columns is more easy to use and overcomes operational problems noticed previously, namely a run time of 20-25 min instead of 50-60 min.

Air Movements↗