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At least 19 recordsLinked to original sources

PubMedDate not supplied

Formation of prebiochemical compounds in models of the primitive earth's atmosphere. I: CH4 NH3 and CH4 N2 atmospheres.

In order to understand the formation of organic compounds in the primitive atmosphere, the first steps of evolution in models of the primitive atmosphere were investigated. Mixtures containing C-H-N elements were subjected to a low pressure silent electric discharge for several seconds, and the resulting effluents were analysed mainly by gas chromatography, infrared spectrometry and chemical analysis. The formation of hydrocarbon (i.e. ethylene, acetylene, methylacetylene) and of nitrogen containing compounds (i.e. hydrogen cyanide, cyanogen, saturated nitriles, acylonitrile, cyanoacetylene) is reported. The influence of the initial mixture composition on the amount of compounds formed was systematically studied. The nature of the nitrogen source (N2 or NH3) in the primitive atmosphere has a great influence on the amount and on the very nature of the synthesized products. It is shown that important precursors such as cyanogen and cyanoacetylene are formed only in very rich N2 mediums. These results show the important role played by the nature of the primitive atmosphere in the determination of the chemical evolution pathways.

Ammonia↗

PubMed1978

Effects of atmospheric ammonia on pulmonary bacterial clearance in the young pig.

Young pigs were exposed to an aerosol of a nonpathogenic strain of Escherichia coli and then were retained in air-pollutant exposure chambers for a 2-hour clearance period. In series 1 (n = 80 pigs), 40 exposed young pigs (principals; 15.5 days of age) were placed in an atmosphere of filtered room air + 50 ppm of atmospheric NH3 during the clearance period; control pigs were exposed to filtered room air without added NH3. In series 2 (n = 24 pigs), 12 exposed young pigs (principals; 6.2 days of age) were similarly maintained, but at a lower concentration of atmospheric NH3 (75 ppm). At the end of the clearance period pigs were killed and pulmonary bacterial clearance was determined. Pigs kept in the NH3-contaminated atmospheres (either concentration) harbored more bacteria, on the average, in their lungs than did the controls. If series 1 and 2 data were combined, pigs kept in the NH3-contaminated atmospheres had 51% more bacteria in their lungs than did the controls. Pulmonic weight and ratio of pulmonic weight to body weight of pigs kept in the NH3-contaminated atmosphere were greater than those of the controls in series 1, but not in series 2. Gross and histopathologic examinations of lung tissue generally revealed no differences between controls and principals in either series 1 or 2.

Aerosols↗

PubMed1979

Atmospheric CO2 consequences of heavy dependence on coal.

Accurate and regular measurements of the concentration of CO2 in the atmosphere during the past 20 years show an accelerating increase. Although clearing of tropical forests has released large amounts of carbon to the atmosphere, evidence is strong that a major contributor is the combustion of fossil fuels. Future energy demands of the world will require extensive further exploitation of fossil fuels, and projections show that without major development of nonfossil fuel alternatives, the atmospheric concentration will double within the next 75 years. Four issues require serious attention. The developing countries will require vastly increased amounts of energy. Major efforts to develop suitable (inexpensive) nonfossil energy sources to meet at least a portion of this demand are required. The distribution of carbon released from fossil fuels and from other anthropogenic sources among the reservoirs of the carbon cycle must be better defined. Uncertainties regarding the effect of the increased concentration of CO2 in the atmosphere on global climate must be reduced. Possible political and social responses to a substantial climate change must be studied in order to more fully understand all of the implication of increased atmospheric CO2.

Air Pollution↗

PubMed1976

Formation of proteinoid microspheres under simulated prebiotic atmospheres and individual gases.

The formation of microspheres from acidic and basic proteinoids was attempted under simulated prebiotic atmospheres and constituent gases thereof. Both types of proteinoid yielded microspheres under carbon dioxide, carbon monoxide, methane, hydrogen sulfide, hydrogen, nitrogen, and oxygen (tested separately) and also under nitrogen-carbon dioxide atmospheres; higher proportions of carbon dioxide resulted in fewer spheres from basic proteinoid. Neither type of proteinoid formed spheres on 10-minute exposure to ammonia or methane-hydrogen-ammonia atmospheres. (Brief exposure resulted in spheres from basic proteinoid.) The effects, both qualitative and quantitative, were indicated by control experiments to be due to pH, rather than to the specific gas (or ion). The results suggest that the proteinoid microsphere model for protocells is applicable under a variety of possible prebiotic atmospheres, with some restrictions imposed by pH.

Ammonia↗

PubMed2026

Biomass burning contributions to Mexico City's atmospheric CO2 estimated using a multi-isotope approach.

Fossil fuel combustion dominates anthropogenic emissions worldwide; however, special attention should be addressed to biomass burning, since it is an increasingly important contributor under warmer, drier fire-weather conditions exacerbated by climate change. These emissions could impact the atmospheric composition of heavily urbanized environments. To assess the influence of biomass burning, along with fossil fuels combustion and soil and plant respiration on Mexico City's atmospheric composition, we conducted a year-long (December 2023-December 2024) isotopic monitoring of atmospheric CO2, combining radiocarbon (Δ14C), CO2 stable isotopes (δ13C, δ18O), and CO/CO2 ratios. Once defined the isotopic signatures and the characteristic CO/CO2 that describe the sources, we performed Monte Carlo simulations under two tracer modalities (Δ14C + CO/CO2 and Δ14C + CO2 stable isotopes) for source apportionment. Results show that during the dry season, particularly in March-April, atmospheric Δ14C values approached and overlapped background levels despite Mexico City's fossil-fuel dominance, indicating enhanced non-fossil inputs. Moreover, backward HYSPLIT trajectories supported that these elevated Δ14C values coincided with regional wildfire activity. Monte Carlo results attributed up to ∼34 %-60 % of local CO2 to biomass burning in April, followed by March with contributions of ∼31 %-49 %. Since these biomass burning figures contrast with the official emissions inventory of Mexico City metropolitan area, which assigns <1 % of total CO2 emissions to biomass burning, this study could exhibit the emissions inventory underestimation of this source, and thus, the need to reassess and incorporate top-down isotopic constraints in fire-affected urban regions.

Mexico↗

PubMed1976

Survival of anaerobic bacteria during transportation. 1. Experimental investigations on the effect of evacuation of atmospheric air by flushing with carbon dioxide and nitrogen.

The effect of evacuation of atmospheric air during transportation on recovery of anaerobic bacteria was investigated. Evacuation of atmospheric air from glass tubes by flushing with pure carbon dioxide lowered the content of oxygen to about 0.4 per cent. Three B. fragilis strains and one strain of Fusobacterium mortiferum and of Peptostreptococcus anaerobius were investigated. Bacterial recovery was determined one hour and 24 hours after evacuation of atmospheric air by pure carbon dioxide and pure nitrogen, was compared to bacterial recovery from samples transported with free access to atmospheric air. Evacuation by pure carbon dioxide significantly improved the recovery of one B. fragilis strain after 24 hours of transportation and significantly impaired the recovery of Peptostreptococcus anaerobius after one hour of transportation, while evacuation by pure nitrogen significantly improved the recovery of Peptostreptococcus anaerobius after 24 hours of transportation. In all other cases, however, no statistically significant effect on bacterial recovery was found.

Air↗

PubMed1979

Trace elements in the atmosphere.

The distribution and behaviour of particulate trace elements in the atmosphere have been studied by continuous measurements for 5 years at seven non-urban sites in the United Kingdom. Samples have been taken regularly of airborne dust, rainwater and dry deposition: these have been analysed for up to 36 elements. Concentrations of trace elements vary considerably between sites but the relative concentrations are among uniform: this suggests similarity of origin or good atmospheric mixing. By comparing the relative concentrations with those in soil it is possible to differentiate between trace elements that are derived from soil and those that may be attributed to industrial activity. This classification is supported by estimates of the particle sizes in air. The deposition of trace elements can be related to the concentrations presnet in soil and to the annual removal by crops. Retrospective analyses of stored samples from one site describe the history of trace element concentrations in air since 1957. The sea surface is considered as a possible source of atmospheric trace elements.

Aerosols↗

PubMed1977

[Determination of free crystalline silica in atmospheric dust].

The method for the determination of free crystalline silica (quarts), as previously described by two of the authors, has been employed on atmosphere dust of unconfined spaces. The matrix effect of atmospheric dust has been investigated in winter and in summer. The limits in the use of this method have been studied considering also what stated by law code n. 615. The results obtained on the outdoor atmospheric dust, samples from industrial as well as suburban areas, are reported. The results are evaluated in relation to the metereological records.

Air Pollutants↗

PubMed1978

Survivorship of drosophila in nitrogen reduced hypobaric atmospheres.

Populations of Drosophila melanogaster were maintained from eclosure to death in 150 torr oxygen/150 torr nitrogen (300 torr total pressure). Survivorship was identical to siblings maintained in normal atmospheric pressures. The study demonstrates that a significant reduction in atmospheric nitrogen does not affect the toxicity of oxygen at normal partial pressures. The author indicates that this information provides the basis for future studies concerning hypobaric, oxygen-enriched atmospheres.

Animals↗

PubMed1979

The Martian atmosphere: some unanswered questions.

The study of the Martian atmosphere and its significance for the possible origin of life on Mars is still very incomplete. Further investigations are needed to define the total volatile inventory, the early history of the atmosphere, and the relationship of the atmosphere to the question of indigenous life. In addition, studies of Venus, comets, and the Jupiter system will add significantly to our abilities to understand the early history of Mars.

Carbon↗

PubMed1979

Autotrophic growth of H2-uptake-positive strains of Rhizobium japonicum in an atmosphere supplied with hydrogen gas.

Previous research from this laboratory has demonstrated CO(2)-fixing and H(2)-uptake capacities of certain strains of Rhizobium japonicum. In this report we have shown that SR, a H(2)-uptake-positive (Hup(+)) strain of R. japonicum, is capable of autotrophic growth with H(2) as the energy source. Growth occurred on mineral salts/vitamins/Noble agar, mineral salts/vitamins liquid medium (0.27 mug of C as vitamins per ml), and in mineral salts liquid medium with no added vitamins when cultures were provided with NH(4)Cl and incubated in an atmosphere containing H(2), CO(2), O(2), and N(2). Little or no growth occurred when either H(2) or CO(2) was omitted from the atmosphere or when the culture was inoculated with SR3, a Hup(-) mutant of SR. Growth was measured by protein synthesis, fixed organic carbon, and increase in cell number in liquid cultures. The organism that grew autotrophically was verified as R. japonicum by (i) apparent purity on streak plates; (ii) retention of the double antibiotic resistance markers; and (iii) its capability to nodulate soybeans. H(2)- and CO(2)-supported growth was demonstrated for three additional Hup(+) wild-type R. japonicum strains (USDA 136, 3I1b 6, and 3I1b 143), while three Hup(-) wild-type strains (USDA 120, 3I1b 144, and USDA 117) were incapable of growth on the Noble agar medium containing mineral salts/vitamins in the H(2)/CO(2)/O(2)/N(2) atmosphere. This demonstrated capability of Hup(+)R. japonicum strains to grow autotrophically requires revision of current concepts regarding conditions for survival and competition of these bacteria in the soil and their relationships to other microorganisms.

Biological Transport↗

PubMed1979

Measurement of atmospheric vinyl chloride.

Methods for atmospheric vinyl chloride measurement have been reviewed. The lowest detection limits and most specific measurement are achieved by scrubbing atmospheric samples with activated charcoal, desorbing the vinyl chloride, and assaying it by gas chromatography (GC). NIOSH currently recommends collecting samples using tubes packed with 150 mg of coconut shell charcoal, desorbing with carbon disulfide, and analyzing by GC equipped with flame-ionization detection (FID); the method is capable of detecting less than 1 ppm vinyl chloride and has an apparent recovery of abo the ppb level with no loss of accuracy or precision. Some field methods, such as infrared analysis and conductivity measurement, are capable of detecting 1 ppm or lower but are subject to interferences by other contaminants; th-y could be useful for evaluating sources of vinyl chloride leaks and for continuous monitoring. Permeation tubes are superior to gravimetric or volumetric methods for generating atmospheres of known vinyl chloride concentration.

Air Pollutants↗

PubMed1979

Reproductive adaptation in Drosophila exposed to oxygen-enriched atmospheres.

Ten successive generations of a Drosophila melanogaster population were exposed to an atmospheric mix of 50% oxygen/50% nitrogen at standard pressure. This atmospheric mix has been shown to be toxic to this species and causes significantly shortened life span. By the fifth generation, survivorship and life span for the first 25-30 days were identical to control populations and total life span was shorter by only a few days. Egg-laying rates were stable in the experimental populations but below those of the controls. Hatching success was identical between experimental and control populations. Even though the egg-laying rates were lower in 50% oxygen, it was concluded that the population had adapted and could maintain a stable population in these conditions. The near-normal life spans, normal hatching rates, and overall population stability, exhibited following five generations of adaptation, were considered sufficient to allow continued reproduction in spite of a reduced egg-laying rate.

Adaptation, Biological↗

PubMed1979

The survival and implantation of mouse blastocysts at varying degrees of reduced atmospheric pressure.

Pregnant mice were exposed to reduced atmospheric pressures ranging from 630 to 390 mm Hg during the pre-implantation and implantation periods and the numbers of embryos surviving 85 hours post coitum compared with those in litter-mate controls. Even at a pressure of 630 mm Hg (= 1,550 mm Hg) there was a significant fall in numbers of normal blastocysts and rise in abnormal forms before implantation, and implantation sites were reduced in number. The numbers of abnormal forms increased and implantation sites decreased at lower pressures, suggesting strongly that the hypoxia of reduce atmospheric pressure was responsible for the abnormalities observed. The pre-implantation period appears to be one during which the fertilised ovum is at particular risk, both of hypoxic damage and of failure to implant. Implantation may afford a degree of protection against hypoxia.

Animals↗

PubMed1976

[Vsiual evoked potentials and excitability cycle during simulated diving at -610 m in oxygen-helium atmosphere (Physalie VI)].

Visual evoked potential (VEPs) and visual excitability cycles (VECs) were studied during compression in an oxygen--helium breathing mixture, up to a pressure of 62 ATA, equivalent to a depth of 610 m in sea water (Physalie VI). Records were taken at atmospheric pressure (control responses in confined helium--oxygen atmosphere) and at different depths during compression and decompression; recording was always performed at the same hours; subjects were lying with closed eyes. Isolated or double flashes were delivered every 1.2 sec, from a stroboscopic lamp located in the tank, at a maximum distance of 20 cm from the eyes. Responses were recorded with hook electrodes left in situ throughout the experiment (mid-vertex occipital derivation). VEP and VEC changes occurred in three stages: (1) Between surface and -435 m, components II-V of the VEP decreased in amplitude, while component VI increased. The after-discharge, and the PEV to the second of a pair of stimuli were facilitated. (2) Below 435 m, latencies and amplitudes of waves II-V increased, while those of wave VI decreased. After-discharge and response to the second stimulus were reduced. (3) During decompression up to -120 m, VEPs and VECs again changed, in a way similar to compression from 0 to -435 m. VEP and VEC changes, which are thus opposite during compression, may depend upon speed of compression, although the latter factor is probably not alone. Other factors, like pressure itself or the nature of the gas mixture may well intervene. It is likely that the observed modifications are the result of various factors interacting at various depths.

Adult↗

PubMed1979

Oxygen levels safe for continued reproduction of Drosophila in normal and hypobaric atmospheres.

Reproduction of the fruit fly, Drosophila melanogaster was examined in various combinations of oxygen concentration and total atmospheric pressure in an effort to establish extremes within which continued reproduction can take place. The effects of temperature were also examined. At 760 torr total pressure, it was found that reproduction could take place between 10% oxygen, PO2 = 76 torr, and 38% oxygen, PO2 = 288 torr, at a temperature of 26 degrees C. At 18 degrees C, the lower limit remained the same but the upper limit rose to 60% oxygen, PO2 = 456 torr. In hypobaric atmospheres totalling 250 torr, the low extreme was 30% oxygen, PO2 = 75 torr, and the upper level was 80% oxygen, PO2 = 200 torr. Because closed ecology life support systems proposed for future space programs will include similar small organisms with short life cycles, the author encourages similar reproductive studies with species most likely to accompany humans into space.

Atmospheric Pressure↗

PubMedDate not supplied

[Dynamic control of the atmospheric parameters of spacecraft].

On the basis of experimental data a mathematical model of relationships between physiological parameters, oxygen content in the atmosphere and exercises has been developed. Using the model, it has been demonstrated that circulation and respiration reactions to exercises can be optimized by increasing the partial pressure of oxygen as related to the exercise level. A probable law of the dynamic and physiologically optimal control of the oxygen content in the space cabin atmosphere has been advanced. In cases of an uncontrolled decrease of PO2 the oxygen supply of crewmembers can be optimized by the dynamic control of the ambient CO2 content.

Atmosphere↗

PubMed1976

Magnetic resonance distinction between site bound and atmospherically bound paramagnetic counterions in polyelectrolyte solutions.

A combination of the water protons NMR chemical shifts, longitudinal and transversal relaxation rates and of the paramagnetic counterion EPR signal is shown to provide a clear distinction between site binding, atmospheric trapping and free counterions in solutions of polyelectrolyte TMA salts with increasing concentrations of the divalent counterions Co++ and Mn++. Site binding is defined by the loss of water in the counterion first hydration shell while atmospheric binding results in a change in the counterion correlation time as compared to a free ion.

Binding Sites↗