Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ATMOSPHERE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 775 records · Page 43Linked to original sources
PubMed1990

Intracapsular and atmospheric pressure in the dynamics and stability of the hip. A biomechanical study.

A cadaver study was undertaken to evaluate (a) the relations between the rotation around the axis of the neck of the femur, intracapsular effusion, and intracapsular pressure; and (b) the importance of the atmospheric pressure in stabilizing the hip joint. The following conclusions were reached: (1) There is no increase in intracapsular pressure within the normal range of rotation ("flexion") around the axis of the neck of the femur. (2) Intracapsular fluid (e.g., blood, pus, synovial edema and/or free synovial fluid) decreases this pressureless range of rotation, a likely cause of pain and subsequently flexion contractures. (3) Joint stability is primarily maintained by the atmospheric pressure within the normal range of rotation. The joint capsule is tightened only in extreme extension or flexion and contributes to stability only in these positions. (4) The traction force needed to overcome the stabilizing effect of the atmospheric pressure and thus subluxate the adult joint is approximately 200 N, in a child less, proportional to the square of the diameter of the femoral head. We also propose that intracapsular fluid makes the joint potentially unstable, a prerequisite for unfavorable mechanical cartilage load. These findings have clinical implications in synovitis, septic and juvenile arthritis, congenital dislocation of the hip, arthroplasty, and trauma.

Adult↗
PubMed1991

Box models for the evolution of atmospheric oxygen: an update.

A simple 3-box model of the atmosphere/ocean system is used to describe the various stages in the evolution of atmospheric oxygen. In Stage I, which probably lasted until redbeds began to form about 2.0 Ga ago, the Earth's surface environment was generally devoid of free O2, except possibly in localized regions of high productivity in the surface ocean. In Stage II, which may have lasted for less than 150 Ma, the atmosphere and surface ocean were oxidizing, while the deep ocean remained anoxic. In Stage III, which commenced with the disappearance of banded iron formations around 1.85 Ga ago and has lasted until the present, all three surface reservoirs contained appreciable amounts of free O2. Recent and not-so-recent controversies regarding the abundance of oxygen in the Archean atmosphere are identified and discussed. The rate of O2 increase during the Middle and Late Proterozoic is identified as another outstanding question.

Atmosphere↗
PubMed1984

How life affects the atmosphere.

The impact of life on the atmosphere is examined through a discussion of the budgets of important atmospheric constituents and the processes that control their concentrations. Life profoundly influences oxygen and a number of minor atmospheric constituents, but many important gases, including those with the greatest effect on global climate, appear to be little altered by biological processes, at least in the steady state.

Atmosphere↗
PubMed1989

Ordovician paleosols at Arisaig, Nova Scotia, and the evolution of the atmosphere.

A series of Late Ordovician andesite flows are exposed along the coastline near Arisaig, Nova Scotia. Field relationships, textural and mineralogical evidence, and chemical analyses of three interflow units confirm that they are paleosols. The chemical variations observed in these paleosols are quite similar to those of modern soils developed on mafic volcanic rocks. Virtually all of the iron in the paleosols was oxidized and retained during weathering; however, in two of the three paleosols a small fraction of the ferrous iron escaped oxidation and was precipitated near the base of the paleosols. This redistribution of ferrous iron may reflect the presence of nonvascular land plants. The variations in the concentration of the major oxides produced by weathering of the andesites at Arisaig are consistent with the probable lower limit of 0.04 atm for the partial pressure of O2 in the atmosphere during the Late Ordovician. The current data base for Paleozoic and Precambrian paleosols indicates that a significant increase in the PO2/PCO2 ratio in the atmosphere took place about 2.0 x 10(9) years ago; since then the ratio of PO2/PCO2 in the atmosphere has been high enough to oxidize all of the iron in soils developed on igneous rocks.

Atmosphere↗
PubMed2002

Plant adaptation to low atmospheric pressures: potential molecular responses.

There is an increasing realization that it may be impossible to attain Earth normal atmospheric pressures in orbital, lunar, or Martian greenhouses, simply because the construction materials do not exist to meet the extraordinary constraints imposed by balancing high engineering requirements against high lift costs. This equation essentially dictates that NASA have in place the capability to grow plants at reduced atmospheric pressure. Yet current understanding of plant growth at low pressures is limited to just a few experiments and relatively rudimentary assessments of plant vigor and growth. The tools now exist, however, to make rapid progress toward understanding the fundamental nature of plant responses and adaptations to low pressures, and to develop strategies for mitigating detrimental effects by engineering the growth conditions or by engineering the plants themselves. The genomes of rice and the model plant Arabidopsis thaliana have recently been sequenced in their entirety, and public sector and commercial DNA chips are becoming available such that thousands of genes can be assayed at once. A fundamental understanding of plant responses and adaptation to low pressures can now be approached and translated into procedures and engineering considerations to enhance plant growth at low atmospheric pressures. In anticipation of such studies, we present here the background arguments supporting these contentions, as well as informed speculation about the kinds of molecular physiological responses that might be expected of plants in low-pressure environments.

Acclimatization↗
PubMed2002

[Current situation and prospect of elevated atmospheric CO2 effects on soil nematodes].

The elevated atmospheric CO2 can make effects on the ecosystem, these effects will be mediated by the soil fauna. In this paper, we firstly discussed the response of the soil nematodes to the elevated atmospheric CO2 in different soil pattern and in different ecosystems. Some evidences indicate that soil fauna of the detritus food webs appear to show positive, neutral or negative responses to the atmospheric CO2 enrichment across different studies. The research prospect in the future was put forward. This paper can help us understand some ecological processes of farmland ecosystems according to the effect of elevated CO2 on soil nematodes and provide the foundation for managing farmland ecosystems effectively.

Animals↗
PubMed2004

[Numerical simulation of interaction between forest ecosystem and atmosphere boundary layer].

Based on the basic principles of atmosphere boundary layer and plant canopy micrometeorology, a numerical model of the interaction between forest ecosystem and atmosphere boundary layer was built, and used to simulate the diurnal variations of heat balance in forest ecosystem, canopy temperature, air temperature in canopy, and ground surface temperature, as well as those of the profiles and temporal and spatial distributions of potential temperature, wind speed, specific humidity and turbulence exchange coefficient. It indicated that the model could be used to study the interaction between land surface process and atmospheric boundary layer over various underlying surface and regional climate effect, which supplied a solid base to the researches on coupling climate models with the biosphere.

Atmosphere↗
PubMed2004

[Influence of elevated atmospheric CO2 on rhizosphere microbes and arbuscular mycorrhizae].

The changes of microbial communities in rhizosphere and the formation of mycorrhizae play an important role in affecting the dynamics of plant communities and terrestrial ecosystems. This paper summarized and discussed the effects of elevated atmospheric CO2 on them. Under elevated atmospheric CO2, the carbohydrates accumulated in root systems increased, and the rhizospheric environment and its microbial communities as well as the formation of mycorrhizae changed. It is suggested that the researches in the future should be focused on the effects of rhizosphere microbes and arbuscular mycorrhizae on regulating the carbon dynamics of plant communities and terrestrial ecosystems under elevated atmospheric CO2.

Atmosphere↗
PubMed2006

[Comprehensive study of lead pollution in atmospheric aerosol of Shanghai].

The lead contamination, lead species and source assignment were studied by a combination of several analytical techniques such as Proton-induced X-ray emission analysis (PIXE), Proton microprobe (micro-PIXE), Inductively coupled plasma-mass spectrometry (ICP-MS) and extended X-ray absorption fine structure (EXAFS) techniques. The results indicate that the lead concentration in the air of Shanghai gradually decreased over the last years. The atmospheric lead concentration of PM10 in the winter of 2002 was 369 ng x m(-3), which had declined by 28% in 2001, and in the winter of 2003 it decreased further to 237 ng x m(-3). The main lead species in the samples collected in the winter of 2003 were probably PbCl2, PbSO4 and PbO. The source apportionment was calculated in terms of the combination of lead isotope ratios and lead mass balance method, assisted by single particle analysis with micro-PIXE and pattern recognition. The results suggest that the major contributors of atmospheric lead pollution in Shanghai are the coal combustion dust; the metallurgic dust and vehicle exhaust particles, with a contribution around 50%, 35% and 15%, respectively. It probably is the first time to give a city a quantitative estimation of lead pollution contribution from emission sources. The influence from leaded gasoline was still present in the atmosphere by four or five years after the phasing out of leaded gasoline.

Aerosols↗
PubMed1991

[Influence of atmospheric pressure fluctuation on condition of patients with cor pulmonale].

Based on investigation of 632 patients with cor pulmonale, we found that there were a close corresponding relationship of attack, exacerbation and death of patients to negative variation of daily atmospheric pressure. It was more obvious that the persistent and significant decrease in atmospheric pressure could influence the patient situation. The disease attacks usually appeared behind in negative variation of pressure changes, however, the death did before them. The mechanism of influences of atmospheric pressure changes on situation of patients with cor pulmonale were discussed preliminarily. The authors point out that the disease condition might be predicted by forecast and should take preventive measures to avoid it in advance.

Atmospheric Pressure↗
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↗
PubMed1991

[Performance of hypoxic radiotherapy in malignant tumors taking atmospheric pressure into account].

Hypoxic mixtures, delivered during hypoxic radiotherapy, must contain different values of the volume portion of oxygen depending on atmospheric pressure variations. The authors give a formula of calculation of a necessary volume portion of oxygen and tables of atmospheric pressure variations in Moscow as well as rated values of the volume portion of oxygen, applied to possible atmospheric pressure variations.

Atmospheric Pressure↗
PubMed1990

Symptomatology during hypoxic exposure to flame-retardant chamber atmospheres.

Hypoxia was studied in 12 men during 63-h exposures to 17 and 13% O2, with the subjects serving as their own controls by repeating the measurements in 21% O2. All test atmospheres were contaminated with 0.9% CO2 to simulate the condition of living aboard submarines. The mean SaO2's were 97-98% in all conditions of 21% O2, 96% in 17% O2 (n.s.), and 92% in 13% O2 (P less than 0.05). The blood concentrations of 2,3-diphosphoglycerate were elevated in 13 and 17% O2 (P less than 0.05). Seventeen percent O2 did not cause significant symptoms of environmental stress; however, 13% O2 caused symptoms of acute mountain sickness in 5 of 12 men. In the last 7 h of exposure to 17% O2, reduction of the barometric pressure to 576 Torr reduced the ambient PO2 to 98 Torr (similar to the PO2 of 13% O2 at normobaric pressure). This induced symptoms of acute mountain sickness in 3 of 11 men. All symptomatology and physiologic changes were reversed during recovery in 21% O2. Monitoring devices indicated the presence of volatile organic contaminants at a mean concentration of 6.1 ppm in the chamber atmosphere. Combustion tests in the occupied chamber showed that flame propagation was retarded by lowering the O2 concentration from 21 to 13-17%. We conclude that men can live comfortably in a normobaric, flame-retardant atmosphere consisting of 17% O2-0.9% CO2-6.1 ppm volatile organic compounds-balance N2.

2,3-Diphosphoglycerate↗
PubMed1990

Atmosphere contamination following repainting of a human hyperbaric chamber complex.

The Naval Medical Research Institute currently conducts hyperbaric research in a Man-Rated Chamber Complex (MRCC) originally installed in 1977. Significant engineering alterations to the MRCC and rusting of some of its interior sections necessitated repainting, which was completed in 1988. Great care was taken in selecting an appropriate paint (polyamide epoxy) and in ensuring correct application and curing procedures. Only very low levels of hydrocarbons were found in the MRCC atmosphere before initial pressurization after painting and curing. After pressurization, however, significant chemical contamination was found. The primary contaminants were aromatic hydrocarbons: xylenes (which were a major component of both the primer and topcoat paint) and ethyl benzene. The role that pressure played in stimulating off-gassing from the paint is not clear; the off-gassing rate was observed to be similar over a large range in chamber pressures from 1.6 to 31.0 atm abs. Scrubbing the chamber atmosphere with the chemical absorbent Purafil was effective in removing the contaminants. Contamination has been observed to slowly decline with chamber use and is expected to continue to improve with time. However, this contamination experience emphasizes the need for a high precision gas analysis program at any diving facility to ensure the safety of the breathing gas and chamber atmosphere.

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↗
PubMedDate not supplied

[Brain tissue respiration after exposing rats in hyperoxic helium-oxygen mixtures at atmospheric and increased pressure].

Experiments on Wistar rats showed that their 5-hour exposure to He-O2 atmospheres (at comfortable temperature) did not affect metabolic rates in the mitochondria of the brain cortex. In this case the partial pressures of oxygen were 0.21 and 0.40 kg/cm2 at a normal and elevated (40 kg/cm2) total pressure. Further increase of pO2 to 0.60 kg/cm2 induced of mitochondrial respiration and oxidative phosphorylation. The rat exposure to 100% O2 atmosphere at a normal pressure resulted in a decrease of metabolic rates and uncoupling of respiration and oxidative phosphorylation processes. The rat exposure to He-O2 atmospheres at an elevated total pressure (40 kg/cm2) with the partial pressures of oxygen of 0.21 and 0.30 kg/cm2 did not alter mitochondrial respiration and oxidative phosphorylation. However, the exposure to higher partial pressures of oxygen--0.40 and especially 0.60 kg/cm2--inhibited the above processes.

Animals↗
PubMed2007

Bacterial inactivation using a low-temperature atmospheric plasma brush sustained with argon gas.

This study investigated the bacterial inactivation/sterilization effects of a new atmospheric plasma source, which is a brush-shaped argon glow discharge created under 1 atm pressure. Such an atmospheric plasma brush requires extremely low power of less than 20 W to operate; and therefore is essentially a low-temperature discharge as confirmed by gas-phase temperature measurements. Two bacteria, Escherichia coli (E. coli) and Micrococcus luteus (M. luteus), seeded in various media were subjected to plasma treatment and their survivability was examined. It was found that such argon atmospheric plasma brush is very effective in destruction of the bacteria cells. With nutrient broth and standard methods agar as supporting media, a cell reduction in a level of 6 orders of magnitude was observed for E. coli within 3-4 min plasma treatment. A similar level of cell reduction was also observed for M. luteus in the two media with 2 or 3 min plasma treatment. The plasma treatment effects on the bacteria cell structures were also examined using scanning electron microscopy and the cell structure damages due to the plasma exposure were observed on both bacteria. The possible sterilization mechanism of the argon plasmas is also discussed in this article.

Argon↗
PubMedDate not supplied

Measurements of volatile organic compounds in the earth's atmosphere using proton-transfer-reaction mass spectrometry.

Proton-transfer-reaction mass spectrometry (PTR-MS) allows real-time measurements of volatile organic compounds (VOCs) in air with a high sensitivity and a fast time response. The use of PTR-MS in atmospheric research has expanded rapidly in recent years, and much has been learned about the instrument response and specificity of the technique in the analysis of air from different regions of the atmosphere. This paper aims to review the progress that has been made. The theory of operation is described and allows the response of the instrument to be described for different operating conditions. More accurate determinations of the instrument response involve calibrations using standard mixtures, and some results are shown. Much has been learned about the specificity of PTR-MS from inter-comparison studies as well the coupling of PTR-MS with a gas chromatographic interface. The literature on this issue is reviewed and summarized for many VOCs of atmospheric interest. Some highlights of airborne measurements by PTR-MS are presented, including the results obtained in fresh and aged forest-fire and urban plumes. Finally, the recent work that is focused on improving the technique is discussed.

Journal Article↗