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PubMed1996

The helium mass fraction in Jupiter's atmosphere.

On 7 December 1995, the NASA Galileo probe provided in situ measurements of the helium abundance in the atmosphere of Jupiter. A Jamin interferometer measured the refractive index of the jovian atmosphere in the pressure region from 2 to 14 bars. These measurements indicate that the atmospheric helium mole fraction is 0.136 +/- 0.004. The corresponding helium mass fraction is slightly below the presolar value, which suggests that separation of helium from hydrogen in Jupiter's interior is only in its early stages.

Atmosphere↗

PubMed1996

Evidence for supersonic turbulence in the upper atmosphere of Jupiter.

Spectra of the hydrogen Lyman alpha (Ly-alpha) emission line profiles of the jovian dayglow, obtained by the Goddard High Resolution Spectrograph on the Hubble Space Telescope, appear complex and variable on time scales of a few minutes. Dramatic changes occur in the Ly-alpha bulge region at low latitudes, where the line profiles exhibit structures that correspond to supersonic velocities of the order of several to tens of kilometers per second. This behavior, unexpected in a planetary atmosphere, is evidence for the particularly stormy jovian upper atmosphere, not unlike a star's atmosphere.

Atmosphere↗

PubMed1997

Triton's distorted atmosphere.

A stellar-occultation light curve for Triton shows asymmetry that can be understood if Triton's middle atmosphere is distorted from spherical symmetry. Although a globally oblate model can explain the data, the inferred atmospheric flattening is so large that it could be caused only by an unrealistic internal mass distribution or highly supersonic zonal winds. Cyclostrophic winds confined to a jet near Triton's northern or southern limbs (or both) could also be responsible for the details of the light curve, but such winds are required to be slightly supersonic. Hazes and clouds in the atmosphere are unlikely to have caused the asymmetry in the light curve.

Atmosphere↗

PubMed1998

Atmosphere-surface interactions on Mars: delta 17O measurements of carbonate from ALH 84001.

Oxygen isotope measurements of carbonate from martian meteorite ALH 84001 (delta18O = 18.3 +/- 0.4 per mil, delta17O = 10.3 +/- 0.2 per mil, and Delta17O = 0.8 +/- 0.05 per mil) are fractionated with respect to those of silicate minerals. These measurements support the existence of two oxygen isotope reservoirs (the atmosphere and the silicate planet) on Mars at the time of carbonate growth. The cause of the atmospheric oxygen isotope anomaly may be exchange between CO2 and O(1D) produced by the photodecomposition of ozone. Atmospheric oxygen isotope compositions may be transferred to carbonate minerals by CO2-H2O exchange and mineral growth. A sink of 17O-depleted oxygen, as required by mass balance, may exist in the planetary regolith.

Atmosphere↗

PubMed1999

Mass-independent isotope effects in planetary atmospheres and the early solar system.

A class of isotope effects that alters isotope ratios on a mass-independent basis provides a tool for studying a wide range of processes in atmospheres of Earth and other planets as well as early processes in the solar nebula. The mechanism for the effect remains uncertain. Mass-independent isotopic compositions have been observed in O3, CO2, N2O, and CO in Earth's atmosphere and in carbonate from a martian meteorite, which suggests a role for mass-independent processes in the atmosphere of Mars. Observed mass-independent meteoritic oxygen and sulfur isotopic compositions may derive from chemical processes in the presolar nebula, and their distributions could provide insight into early solar system evolution.

Atmosphere↗

PubMed1981

Comparative growth of Eikenella corrodens on 15 media in three atmospheres of incubation.

The abundance of growth and size of colonies of 10 isolates of Eikenella corrodens were studied using 15 commonly available media in aerobic, 5% CO2, and anaerobic atmospheres of incubation. Chocolate agar was the best medium for overall growth in all three atmospheres. Growth on Mueller-Hinton agar supplemented with 5% blood and on Brucella agar supplemented with 5% blood was equivalent to that on chocolate agar in 5% CO2 and anaerobic environments but not in an aerobic atmosphere. Strains of E. corrodens did not grow on the selective media studied. Growth on media without blood or hemin supplements occurred in anaerobic but not in aerobic or 5% CO2 environments, and was consistently poorer than growth on the same media with these supplements.

Aerobiosis↗

PubMed1983

Effects of trimethoprim-sulfamethoxazole and incubation atmosphere on isolation of group A streptococci.

The effects of selective media and incubation atmosphere on the isolation of group A beta-hemolytic streptococci were evaluated. A higher percentage of group A streptococci was isolated on sheep blood agar incubated in air than in CO2 or anaerobic atmospheric conditions. Fewer non-group A beta-hemolytic streptococci were isolated on sheep blood agar incubated in air than in CO2 or anaerobically. Group A streptococcal isolation was not significantly affected by different incubation atmospheres on sheep blood agar containing trimethoprim-sulfamethoxazole, but detection time was longer than on sheep blood agar alone. No significant difference was found between isolation of group A streptococci on sheep blood agar incubated in air and that on sheep blood agar containing trimethoprim-sulfamethoxazole and incubated in 5 to 10% CO2; however, more group A streptococci were isolated on sheep blood agar in air within 24 h. Sheep blood agar incubated at 35 degrees C in air is, therefore, recommended for the isolation of group A streptococci from throat swabs.

Air↗

PubMed1976

Effects of selective media and atmosphere of incubation on the isolation of group A streptococci.

The effects of selective media and atmosphere of incubation on the isolation of group A beta-hemolytic streptococci were evaluated. Sheep blood agar medium with gentamicin (2.5 or 5.0 mug/ml) was inferior to antibiotic-free sheep blood agar medium. This resulted from the partial restriction of group A streptococcal growth on gentamicin medium. Recovery of beta-hemolytic streptococci from specimens in air, CO2, or anaerobic incubation was evaluated. The isolation of group A streptococci was equivalent in the three incubation atmospheres; however, non-group A beta- hemolytic streptococci were isolated significantly more often from specimens incubated in an anaerobic or CO2 atmosphere than from those incubated in air. Therefore, sheep blood agar medium, stabbed with a wire loop and incubated in air, is recommended for the isolation of group A streptococci from throat swabs.

Agar↗

PubMed1988

Critical water temperature during water immersion at various atmospheric pressures.

The present work was undertaken to determine the effect of atmospheric pressure [ranging from a high altitude of 4,300 m above sea level or 0.6 atmospheres absolute (ATA) to depths of 10 m deep or 2 ATA] on the critical water temperature (Tcw), defined as the lowest water temperature a subject can tolerate at rest for 2 h without shivering, of the unprotected subject during water immersion. Nine healthy males wearing only shorts were subjected to immersion to the neck in water at 0.6, 1, and 2 ATA while resting for 2 h. Continuous measurements included esophageal (Tes) and skin (Tsk) temperatures, direct heat loss from the skin (Htissue), and insulation of the tissue (Itissue). The Tcw was significantly higher at 0.6 ATA than 1 and 2 ATA: however, Tcw at 1 ATA was identical to that at 2 ATA. The metabolic heat production remained unchanged among the pressures. During the 2-h immersion in Tcw, Tes was identical among all atmospheric pressures: however, Tsk was significantly higher (P less than 0.05) at 0.6 ATA and was identical between 1 and 2 ATA. The overall mean Itissue was near maximal during immersion in Tcw in each pressure, and no difference was detected among the pressures. However, Itissue at the acral extremities (arm, hand, and foot) decreased significantly at 0.6 ATA, and subsequently heat loss from these parts was increased, which elevated an extremity-to-trunk heat loss ratio to 1.4 at 0.6 ATA from 1.1 at 1 and 2 ATA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1985

Effect of abnormal atmospheric pressure conditions upon mouse liver delta-aminolevulinic acid synthetase activity.

Liver delta-aminolevulinic acid synthetase activity was measured in mice living under abnormal atmospheric pressure conditions for 15 h. In the group living under low atmospheric pressure (51 kPa) the enzymic activity, either basal or induced by starvation and/or allylisopropylacetamide, was significantly (p less than 0.001) lower than that of the control group. In the group living under high atmospheric pressure (153 kPa) the enzymic activity was significantly (p less than 0.001) higher than the one of the controls. Our results might possibly be explained by changes in the cellular redox state, the heme oxygenase activity or the serum erythropoietin levels.

5-Aminolevulinate Synthetase↗

PubMed1980

Applications of a versatile technique for trace analysis: atmospheric pressure negative chemical ionization.

The ability to use ambient air as a carrier and reagent gas in an atmospheric pressure chemical ionization source allows instantaneous air analysis to be combined with hypersensitivity toward a wide variety of compounds. The TAGA (Trace Atmospheric Gas Analyser) is an instrument which is designed to use both positive and negative atmospheric pressure chemical ionization (APCI) for trace gas analysis; this paper describes several applications of negative APCI which demonstrates that the technique is not limited to environmental monitoring. Examples are described which suggest that the TAGA can be used for the detection of illicit drugs and explosives, and for the analysis of breath or skin emissions, as well as for air pollution measurements. The applications are not restricted by the use of ambient air as a reagent gas; addition to the air carrier of various gases allows specific reagent ions such as Cl- or Br- to be generated. Furthermore, in certain situations pure gas carriers can be used to provide even more flexibility in the ion chemistry, with a short term absorber-desorber system used to transfer the sample from the ambient air into the ion source region. The potential uses for APCI are expanding continuously as the understanding of the complex ion-molecule chemistry grows. This paper underlines the complementary relation between the development of new negative chemical ionization (NCI) techniques and practical applications using the TAGA system.

Air↗

PubMed1985

The role of atmospheric pressure in stabilising the shoulder. An experimental study.

The role of atmospheric pressure in providing static stability of the shoulder was studied experimentally in 24 cadaveric shoulders. Atmospheric air was allowed to enter the joint after puncturing the capsule. Three types of experiment were performed: in the first, the capsule was punctured after sequential division of the muscles; in the second, atmospheric air was let in by percutaneous puncture of of the capsule without dividing the muscles; and in the third, air was first let into the joint by percutaneous puncture of the capsule and then the muscles of the shoulder were divided. It was found that the intact shoulder subluxated after percutaneous puncture even without division of the overlying muscles or the capsule. Our findings suggest that negative pressure and muscle tone are the main static stabilisers of the shoulder, rather than the joint capsule.

Adult↗

PubMed2003

Mars analysis by laser-induced breakdown spectroscopy (MALIS): influence of mars atmosphere on plasma emission and study of factors influencing plasma emission with the use of doehlert designs.

A project called MALIS (Mars Analysis by Laser-Induced breakdown Spectroscopy) is under progress to perform in situ analysis of Mars soils and rocks. This paper reports on the behavior of plasma in Martian conditions, i.e., in a CO2 atmosphere at pressures between 5 and 12 mbar. Plasma expansion and lifetime have been studied in order to compare plasma evolution under standard conditions (air at atmospheric pressure) and in a Mars atmosphere. We have shown that the Mars environment favors plasma expansion and lifetime. The second part of the study concerns optimization of the emission signal from the plasma. An original approach has been chosen, as we used a Doehlert design for the first time in laser-induced breakdown spectroscopy (LIBS). The best conditions obtained are for a laser wavelength of 1064 nm with the maximum energy available due to space limitations, which is 40 mJ at 15 Hz. The other factors studied are delay, angle of incidence, and CO2 pressure. We have shown that these factors do not have the same influence depending on which spectroscopic line is used, i.e., the atomic line or the ionic line.

Atmosphere↗

PubMed1999

Effect of diazepam on survival of the immature pig in a confined atmosphere.

Diazepam is known to prolong survival in an atmosphere containing 5% oxygen, and to reduce cerebral metabolic rate and cerebral perfusion. It also depresses the arousal response to hypoxia and protects the optic nerve from anoxia. We hypothesised that diazepam might extend survival in a confined atmosphere with a limited amount of oxygen. Pigs consumed the oxygen in a sealed chamber until they reached the terminal state. The experimental pigs (n = 6) were sedated with diazepam 0.3 mg/kg i.v. and were compared with a control group (n = 5). We measured blood pressure, inspired O2 and CO2, minute ventilation, ECG, ambient and body temperatures, and PO2, PCO2, O2 content and pH in arterial and venous blood. In the diazepam-treated pigs, oxygen consumption was reduced in the hypoxic range (PIO2 below 60 torr) compared with the control pigs. Diazepam prevented the elevated hypoxic cardiac output found in the control pigs. There were almost no differences between the diazepam and control groups in the other parameters measured in the course of the exposure and in the terminal state. Terminal PIO2, PaO2, and PvO2 were 36.9 +/- 5.6, 27.9 +/- 8.6, 14.3 +/- 2.0 torr, and 36.9 +/- 5.7, 23.7 +/- 7.3, 15.7 +/- 7.6 torr in the diazepam and control groups, respectively. The survival time was 220 +/- 51 and 255 +/- 50 min in diazepam and control pigs, respectively. In spite of its anticonvulsant effect and the fact that it protects CNS white matter from anoxia, prolongs anoxic survival and eliminates the high oxygen demand in hypoxic arousal, diazepam failed to extend hypoxic survival in a confined atmosphere to a lower PIO2. However, diazepam had no deleterious effect on survival, and may therefore be used to ease stressful hypoxic conditions.

Animals↗

PubMed2002

Effect of high-carbon dioxide atmospheres on infestations of apple maggot (Diptera: Tephritidae) in apples.

Short-term storage regimens containing elevated atmospheres of carbon dioxide (CO2) were evaluated for their ability to disinfest newly harvested 'McIntosh' apples of apple maggot, Rhagoletis pomonella (Walsh). Infested fruits containing newly laid eggs were either placed directly into the high-CO2 atmosphere at 10 degrees C to expose this life stage, or else held first for 7 d at room temperature, to allow development to the neonate larval stage. Treatment combinations consisted of three different CO2 levels (10.6, 14.9, and 19.0% CO2) and two periods of exposure (7 and 14 d). Apple maggot eggs subjected to the treatments always exhibited some survival, which was lower for the 14-d than the 7-d exposure periods. In contrast, newly hatched larvae were less able to survive the treatments. The 7-d exposure allowed low levels of survival of this life stage, but virtually none survived the 14-d exposure period. To determine the age at which eggs become more susceptible to high-CO2 atmospheres, infested fruits containing eggs three or 3d old were submitted to a 14-d exposure to 19.0% CO2. Survival of 3-d old eggs was similar to that of eggs exposed at an age of 1 d or less, but this dropped to near zero for 5-d old eggs, indicating an increase in susceptibility sometime during the 3-5-d age range. Fruits exposed to 19.0% CO2 for 14 d were significantly firmer than untreated fruits. No apparent browning, internal breakdown or other fruit defects were detected in any of the treatments.

Animals↗

PubMed2006

Empirical modeling of atmospheric deposition in mountainous landscapes.

Atmospheric deposition has long been recognized as an important source of pollutants and nutrients to ecosystems. The need for reliable, spatially explicit estimates of total atmospheric deposition (wet + dry + cloud) is central, not only to air pollution effects researchers, but also for calculation of input-output budgets, and to decision makers faced with the challenge of assessing the efficacy of policy initiatives related to deposition. Although atmospheric deposition continues to represent a critical environmental and scientific issue, current estimates of total deposition have large uncertainties, particularly across heterogeneous landscapes such as montane regions. We developed an empirical modeling approach that predicts total deposition as a function of landscape features. We measured indices of total deposition to the landscapes of Acadia (121 km2) and Great Smoky Mountains (2074 km2) National Parks (USA). Using approximately 300-400 point measurements and corresponding landscape variables at each park, we constructed a statistical (general linear) model relating the deposition index to landscape variables measured in the field. The deposition indices ranged over an order of magnitude, and in response to vegetation type and elevation, which together explained approximately 40% of the variation in deposition. Then, using the independent landscape variables available in GIS data layers, we created a GIS-relevant statistical nitrogen (N) and sulfur (S) deposition model (LandMod). We applied this model to create park-wide maps of total deposition that were scaled to wet and dry deposition data from the closest national network monitoring stations. The resultant deposition maps showed high spatial heterogeneity and a four- to sixfold variation in "hot spots" and "cold spots" of N and S deposition ranging from 3 to 31 kg N x ha(-1) x yr(-1) and from 5 to 42 kg S x ha(-1) x yr(-1) across these park landscapes. Area-weighted deposition was found to be up to 70% greater than NADP plus CASTNET monitoring-station estimates together. Model-validation results suggest that the model slightly overestimates deposition for deciduous and coniferous forests at low elevation and underestimates deposition for high-elevation coniferous forests. The spatially explicit deposition estimates derived from LandMod are an improvement over what is currently available. Future research should test LandMod in other mountainous environments and refine it to account for (currently) unexplained variation in deposition.

Air Pollutants↗

PubMed1989

A new model for atmospheric oxygen over Phanerozoic time.

A mathematical model has been constructed that enables calculation of the level of atmospheric O2 over the past 570 my from rates of burial and weathering of organic carbon (C) and pyrite sulfur (S). Burial rates as a function of time are calculated from an assumed constant worldwide clastic sedimentation rate and the relative abundance, and C and S contents, of the three rock types: marine sandstones and shales, coal basin sediments, and other non-marine clastics (red beds, arkoses). By our model, values of O2 versus time, using a constant total sedimentation rate, agree with those for variable sedimentation derived from present-day rock abundances and estimates of erosional losses since deposition. This agreement is the result of our reliance on the idea that any increase in total worldwide sediment burial, with consequently faster burial of C and S and greater O2 production, must be accompanied by a corresponding increase in erosion and increased exposure of C and S on the continents to O2 consumption via weathering. It is the redistribution of sediment between the three different rock types, and not total sedimentation rate, that is important in O2 control. To add stability to the system, negative feedback against excessive O2 fluctuation was provided in the modeling by the geologically reasonable assignment of higher weathering rates to younger rocks, resulting in rapid recycling of C and S. We did not use direct O2 negative feedback on either weathering of C and S or burial of C because weathering rates are assumed to be limited by uplift and erosion, and the burial rate of C limited by the rate of sediment deposition. The latter assumption is the result of modern sediment studies which show that marine organic matter burial occurs mainly in oxygenated shallow water and is limited by the rate of supply of nutrients to the oceans by rivers. Results of the modeling indicate that atmospheric O2 probably has varied appreciably over Phanerozoic time. During the Late Carboniferous and Permian periods O2 was higher than previously because of the rise of vascular land plants and the widespread burial of organic matter in vast coal swamps. A large decrease in O2 during the Late Permian was due probably to the drying-up of the coal swamps and deposition of a large proportion of total sediment in C and S-free continental red beds. Sensitivity study shows that major parameters affecting results are the mean C concentration in coal basins and the relative sizes of the reservoirs of young (rapidly recycled) versus old rocks. Less sensitivity was found for changes over time in total land area undergoing weathering and the use of direct O2 negative feedback on marine carbon burial. Good agreement for rates of C burial calculated via our model and via independent models, which are based on the use of stable carbon isotopes, indicates that the dominant factor that has brought about changes in atmospheric O2 level (and the isotopic composition of dissolved inorganic carbon in seawater) over Phanerozoic time is sedimentation and not weathering or higher temperature phenomena such as basalt-seawater reaction.

Atmosphere↗

PubMed1987

Atmospheric oxidation of hydrocarbons.

Hydrocarbon oxidation in the atmosphere proceeds generally by the following sequence of reactions: hydrocarbon + OH----alkyl radical + H2O, alkyl radical + O2 (3 sigma)----alkylperoxy radical, alkylperoxy radical + NO----alkoxy radical + NO2, alkoxy radical + O2 (3 sigma)----aldehyde + HO2. The atmospheric lifetimes of hydrocarbons are determined by their reactivity towards OH as well as by the average OH concentration level. They are compound specific and vary from several hours to several years. Hydrocarbon oxidation chains couple with other trace gases (Ox, HOx and NOx). For the conditions of the average continental atmosphere an increase of the oxidative potential (HOx, Ox) is predicted through hydrocarbon oxidation.

Alkenes↗