SEARCH · PubMed Health

Results for “ATMOSPHERE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 1,261 records · Page 70Linked to original sources

PubMed2002

Microbial interaction in cooked cured meat products under vacuum or modified atmosphere at 4 degrees C.

AIMS: To investigate the antagonistic activity of two lactic acid strains against the spoilage microflora in cooked cured meat products, vacuum or modified atmosphere packed at 4 degrees C and to determine the inhibitory capacity of their bacteriocins. METHODS AND RESULTS: Frankfurter-type sausages and sliced cooked cured pork shoulder were inoculated with Leuconostoc mesenteroides L124 and Lactobacillus curvatus L442 or with their bacteriocins. The microbial, physico-chemical (pH, L- and D-lactate, acetate and ammonia) and colour changes were studied. Results under vacuum packaging showed that in the uninoculated samples of the pork product the spoilage microflora grew but in the inoculated ones the spoilage microorganisms (e.g. Brochothrix thermosphacta and enterococci) reduced during the storage. This observation was more pronounced in the samples with the addition of bacteriocins. In the frankfurter-type sausages the spoilage microflora did not grow in the uninoculated and inoculated samples. In the modified atmosphere enriched in CO2 the population of spoilage microflora remained at low levels in both products, indicating that CO2 has an effect on the spoilage microorganisms' growth. In the pork product the concentrations of acetate and d-lactate increased while L-lactate decreased, but in the frankfurter-type sausages increase of acetate and D-lactate was not observed. CONCLUSIONS: Lactic acid strains had an effect on the spoilage microflora growth but did not affect, negatively, the organoleptic properties of the products. These strains may be used as biopreservative cultures or their bacteriocins could be an important contribution to microbiological quality of meat products. SIGNIFICANCE AND IMPACT OF STUDY: Establishment of biopreservation as a method for extension of shelf life of meat products.

Animals↗

PubMed2001

The rise in the atmospheric concentration of carbon dioxide and the effects on human health.

The potential effects on the health of future generations of humans, and other mammals arising from the increase in the concentration of carbon dioxide in the atmosphere, resulting from the use of large amounts of fossil fuels by industrialized societies, is considered. It is concluded that the change in the gaseous composition of the atmosphere will lead to a decline in the health of humans and may well lead to serious population reductions.

Atmosphere↗

PubMed2004

Changes in vegetation and soil characteristics in coastal sand dunes along a gradient of atmospheric nitrogen deposition.

A field survey was conducted to detect signals of atmospheric nitrogen (N) in 11 dune systems along a nitrogen deposition gradient in the United Kingdom. In the mobile and semi-fixed dunes, above-ground biomass was positively related to N inputs. This increase was largely due to increased height and cover of Ammophila arenaria. In the long term, this increased biomass may lead to increased organic matter accumulation and consequently accelerated soil development. In the fixed dunes, above ground biomass also showed a positive relationship with N inputs as did soil C : N ratio while soil available N was negatively related to N inputs. Plant species richness was negatively related to N inputs. In the dune slacks, while soil and bulk vegetation parameters showed no relationship with N inputs, cover of Carex arenaria and Hypochaeris radicata increased. Site mean Ellenberg N numbers showed no relationship with N deposition either within habitats or across the whole dataset. Neither abundance-weighting nor inclusion of the Siebel numbers for bryophytes improved the relationship. The survey reveals that the relationships of soil and vegetation with atmospheric N deposition vary between sand dune habitats but, despite this variability, clear correlations with N inputs exist. While this survey cannot establish causality, on the basis of the relationships observed we suggest a critical load range of 10 - 20 kg N ha(-1) yr(-1) for coastal sand dunes in the UK.

Atmosphere↗

PubMed2004

Fine-root production dominates response of a deciduous forest to atmospheric CO2 enrichment.

Fine-root production and turnover are important regulators of the biogeochemical cycles of ecosystems and key components of their response to global change. We present a nearly continuous 6-year record of fine-root production and mortality from minirhizotron analysis of a closed-canopy, deciduous sweetgum forest in a free-air CO(2) enrichment experiment. Annual production of fine roots was more than doubled in plots with 550 ppm CO(2) compared with plots in ambient air. This response was the primary component of the sustained 22% increase in net primary productivity. Annual fine-root mortality matched annual production, and the mean residence time of roots was not altered by elevated CO(2), but peak fine-root standing crop in midsummer was significantly higher in CO(2)-enriched plots, especially deeper in the soil profile. The preferential allocation of additional carbon to fine roots, which have a fast turnover rate in this species, rather than to stemwood reduces the possibility of long-term enhancement by elevated CO(2) of carbon sequestration in biomass. However, sequestration of some of the fine-root carbon in soil pools is not precluded, and there may be other benefits to the tree from a seasonally larger and deeper fine-root system. Root-system dynamics can explain differences among ecosystems in their response to elevated atmospheric CO(2); hence, accurate assessments of carbon flux and storage in forests in a globally changing atmosphere must account for this unseen and difficult-to-measure component.

Atmosphere↗

PubMed2006

Nutrient additions to a tropical rain forest drive substantial soil carbon dioxide losses to the atmosphere.

Terrestrial biosphere-atmosphere carbon dioxide (CO(2)) exchange is dominated by tropical forests, where photosynthetic carbon (C) uptake is thought to be phosphorus (P)-limited. In P-poor tropical forests, P may also limit organic matter decomposition and soil C losses. We conducted a field-fertilization experiment to show that P fertilization stimulates soil respiration in a lowland tropical rain forest in Costa Rica. In the early wet season, when soluble organic matter inputs to soil are high, P fertilization drove large increases in soil respiration. Although the P-stimulated increase in soil respiration was largely confined to the dry-to-wet season transition, the seasonal increase was sufficient to drive an 18% annual increase in CO(2) efflux from the P-fertilized plots. Nitrogen (N) fertilization caused similar responses, and the net increases in soil respiration in response to the additions of N and P approached annual soil C fluxes in mid-latitude forests. Human activities are altering natural patterns of tropical soil N and P availability by land conversion and enhanced atmospheric deposition. Although our data suggest that the mechanisms driving the observed respiratory responses to increased N and P may be different, the large CO(2) losses stimulated by N and P fertilization suggest that knowledge of such patterns and their effects on soil CO(2) efflux is critical for understanding the role of tropical forests in a rapidly changing global C cycle.

Atmosphere↗

PubMed1977

Time as a factor in atmospheric sampling.

Differences in results of simultaneous air monitoring of ozone with three different methods in the field are described. The argument is advanced that the differences are due largely to sampling turbulent atmospheres with instruments utilizing different sampling intervals and time constants. It is concluded that when sampling natural turbulent atmospheres, a stable mean value can only be achieved through integrated sampling periods of greater than ten minutes.

Air↗

PubMed2003

An objective definition of air mass types affecting Athens, Greece; the corresponding atmospheric pressure patterns and air pollution levels.

This work aims at defining characteristic air mass types that dominate in the region of Athens, Greece during the cold (November-March) and the warm (May-September) period of the year and also at evaluating the corresponding concentration levels of the main air pollutants. For each air mass type, the mean atmospheric pressure distribution (composite maps) over Europe and the Mediterranean is estimated in order to reveal the association of atmospheric circulation with air pollution levels in Athens. The data basis for this work consists of daily values of thirteen meteorological and six pollutant parameters covering the period 1993-97. The definition of the characteristic air mass types is attempted objectively by using the methods of Factor Analysis and Cluster Analysis. The results show that during the cold period of the year there are six prevailing air mass types (at least 3% of the total number of days) and six infrequent ones. The examination of the corresponding air pollution concentration levels shows that the primary air pollutants appear with increased concentrations when light or southerly winds prevail. This is usually the case when a high pressure system is located over the central Mediterranean or a low pressure system lays over south Italy, respectively. Low levels of the primary pollutants are recorded under northeasterly winds, mainly caused by a high pressure system over Ukraine. During the warm period of the year, the southwestern Asia thermal low and the subtropical anticyclone of the Atlantic Ocean affect Greece. Though these synoptic systems cause almost stagnant conditions, four main air mass types are dominant and ten others, associated with extreme weather, are infrequent. Despite the large amounts of total solar radiation characterizing this period, ozone concentrations remain at low levels in central Athens because of its destruction by nitric oxide.

Air Movements↗

PubMed2005

Isotope studies to the sorption behavior of atmospheric sulfate in humus layers of scots pine ecosystems.

The sorption potential for SO4(2-) in humus layer samples from field sites along a deposition gradient was determined experimentally in batch experiments. The Freundlich equation was used to quantify the sorption of added SO4(2-) in humus layer samples and to determine site-dependent sorption parameters. SO4(2-) sorption in humus layers is a concentration-dependent process. The linearity of isotherms reveals that SO4(2-) is reversibly bound in the organic surface layer, as long as soil solution concentrations remain above 26 to 44 mg SO4(2-) L(-1). Natural isotope variations of sulfur in SO4(2-) were analysed to investigate the degree of sorption of dissolved atmospheric and added SO4(2-). Both sulfate species differed significantly in their isotope composition. The pattern of delta34S values for SO4(2-) in all equilibrium solutions confirm the findings from sorption isotherms, showing a close relationship between the sulfur isotope ratios of SO4(2-) in soil solutions and the amount of SO4(2-) sorbed at the humus layer matrix. Stored atmospheric SO4(2-) in humus layers is released at sites where sulfate concentration in throughfall drops below 26 mg SO4(2-) L(-1). Concentration of soluble Fe decreased with increasing sulfate sorption, thus supporting the assumption that active Fe for example is important. Iron probably stabilizes the reactive surface of humus complexes and therefore has a positive influence on the SO4(2-) sorption in humus layers.

Adsorption↗

PubMed2005

Bacillus subtilis spore survival and expression of germination-induced bioluminescence after prolonged incubation under simulated Mars atmospheric pressure and composition: implications for planetary protection and lithopanspermia.

Bacterial endospores in the genus Bacillus are considered good models for studying interplanetary transfer of microbes by natural or human processes. Although spore survival during transfer itself has been the subject of considerable study, the fate of spores in extraterrestrial environments has received less attention. In this report we subjected spores of a strain of Bacillus subtilis, containing luciferase resulting from expression of an sspB-luxAB gene fusion, to simulated martian atmospheric pressure (7-18 mbar) and composition (100% CO(2)) for up to 19 days in a Mars simulation chamber. We report here that survival was similar between spores exposed to Earth conditions and spores exposed up to 19 days to simulated martian conditions. However, germination-induced bioluminescence was lower in spores exposed to simulated martian atmosphere, which suggests sublethal impairment of some endogenous spore germination processes.

Atmospheric Pressure↗

PubMed2005

Caenorhabditis elegans survives atmospheric breakup of STS-107, space shuttle Columbia.

The nematode Caenorhabditis elegans, a popular organism for biological studies, is being developed as a model system for space biology. The chemically defined liquid medium, C. elegans Maintenance Medium (CeMM), allows axenic cultivation and automation of experiments that are critical for spaceflight research. To validate CeMM for use during spaceflight, we grew animals using CeMM and standard laboratory conditions onboard STS-107, space shuttle Columbia. Tragically, the Columbia was destroyed while reentering the Earth's atmosphere. During the massive recovery effort, hardware that contained our experiment was found. Live animals were observed in four of the five recovered canisters, which had survived on both types of media. These data demonstrate that CeMM is capable of supporting C. elegans during spaceflight. They also demonstrate that animals can survive a relatively unprotected reentry into the Earth's atmosphere, which has implications with regard to the packaging of living material during space flight, planetary protection, and the interplanetary transfer of life.

Acceleration↗

PubMed2001

The high oxygen atmosphere toward the end-Cretaceous; a possible contributing factor to the K/T boundary extinctions and to the emergence of C(4) species.

Angiosperm plants were grown under either the present day 21 kPa O(2) atmosphere or 28 kPa, as estimated for the end-Cretaceous (100-65 MyBP). CO(2) was held at different levels, within the 24-60 Pa range, as also estimated for the same period. In C(3) Xanthium strumarium and Atriplex prostrata, leaf area and net photosynthesis per unit leaf area, were reduced by the high O(2), while the whole-plant respiration/photosynthesis ratio increased. The high O(2) effects were strongest under 24 Pa, but still significant under 60 Pa CO(2). Growth was reduced by high O(2) in these C(3) species, but not in Flaveria sp., whether C(3), C(4), or intermediary grown under light intensities <350 micromol m(-2) s(-1) PPF. Photosynthesis of C(3) Flaveria sp. was reduced by high O(2), but only at light intensities >350 micromol m(-2) s(-1) PPF. It is concluded that the high O(2) atmosphere at the end-Cretaceous would have reduced growth of at least some of the vegetation, thus adversely affecting dependent fauna. The weakened biota would have been predisposed to the consequences of volcanism and the K/T boundary bolide impact. Conversely, photosynthesis and growth of C(4) Zea mays and Atriplex halimus were little affected by high, 28 kPa, O(2). This suggests an environmental driver for the evolution of C(4) physiology.

Atmosphere↗

PubMed2004

Analysis of a Kalman filter based method for on-line estimation of atmospheric dispersion parameters using radiation monitoring data.

A Kalman filter method is discussed for on-line estimation of radioactive release and atmospheric dispersion from a time series of off-site radiation monitoring data. The method is based on a state space approach, where a stochastic system equation describes the dynamics of the plume model parameters, and the observables are linked to the state variables through a static measurement equation. The method is analysed for three simple state space models using experimental data obtained at a nuclear research reactor. Compared to direct measurements of the atmospheric dispersion, the Kalman filter estimates are found to agree well with the measured parameters, provided that the radiation measurements are spread out in the cross-wind direction. For less optimal detector placement it proves difficult to distinguish variations in the source term and plume height; yet the Kalman filter yields consistent parameter estimates with large associated uncertainties. Improved source term assessment results, when independent estimates of the plume height can be used. Perspectives for using the method in the context of nuclear emergency management are discussed, and possible extensions to the present modelling scheme are outlined, to account for realistic accident scenarios.

Air Pollutants, Radioactive↗

PubMed2004

Stomatal conductance of Acer rubrum ecotypes under varying soil and atmospheric water conditions: predicting stomatal responses with an abscisic acid-based model.

A multiplicative model of stomatal conductance was developed and tested in two functionally distinct ecotypes of Acer rubrum L. (red maple). The model overcomes the main limitation of the commonly used Ball-Berry model (Ball et al. 1987) by accounting for stomatal behavior under soil drying conditions. We combined the Ball-Berry model with an integrated expression of abscisic acid (ABA)-based stomatal response to ABA concentration ([ABA]) in bulk leaf tissue (gfac), which coupled physiological changes at the leaf level with those in the root. The factor gfac = exp(-beta[ABA]L) incorporated the stomatal response to [ABA] into the Ball-Berry model by down regulating stomatal conductance (gs) in response to physiological changes in the root. The down regulation of gs is pertinent under conditions where soil drying may modify the delivery of chemical signals to leaf stomata. Model testing indicated that the multiplicative model was capable of predicting gs in red maple under wide ranges of soil and atmospheric conditions. Concordance correlation coefficients were high (between 0.59 and 0.94) for the tested ecotypes under three environmental conditions (atmospheric, rhizospheric and minimal stress). The study supported the use of gfac as a gas exchange function that controls water stress effects on gs and aids in the prediction of gs responses.

Abscisic Acid↗

PubMed1985

The limitations of atmospheric dispersion data and their contribution to uncertainties in dose assessment.

The calculation of atmospheric dispersion patterns is often an important component of radiation dose estimates. These dispersion calculations are a possible source of error and such errors or uncertainties need to be quantified. An important source of uncertainty is the meteorological data used in the calculations. Such data may be less than ideal because of constraints imposed by both availability and by the variances associated with population from which the data are obtained. We have studied a simple and much used model of atmospheric dispersion--the Gaussian plume. We discuss the uncertainties on the meteorological data which are input to the model and how these uncertainties could be used to estimate uncertainties for the modeling results. In doing this we have addressed both the uncertainty associated with a recorded climatology and the added uncertainty arising from the year-to-year variability at any given location.

Air Pollution, Radioactive↗

PubMed1994

The vegetation-to-air concentration ratio in a specific activity atmospheric tritium model.

Specific activity models are frequently used to estimate the concentration of tritium oxide in vegetation. In such models, a single value represents the ratio (R) of the specific activity of tritium oxide in vegetation to the specific activity of atmospheric tritium oxide. Federal agencies such as the Nuclear Regulatory Commission and the Environmental Protection Agency have not established a consensus default for R. Literature on this topic suggests that a site-specific distribution of R should be developed when feasible. In this study, a distribution of R is established for the Savannah River Site. Environmental tritium concentrations in air and vegetation measured on and around the Savannah River Site over a 9-y period form the basis for the analysis. For dose assessments of chronic atmospheric tritium releases at the Savannah River Site, R is best parameterized by a normal distribution with a mean of 0.54 and one standard deviation of 0.10. The Nuclear Regulatory Commission default for R is approximately equal to the Savannah River Site site-specific estimate. Based on the results, the default value for R recognized by the Environmental Protection Agency overestimates tritium concentrations in vegetation and, therefore, doses from foodstuff consumption pathways at humid sites. For the Savannah River Site, the magnitude of the error is on the order of a factor of 2. This consideration may be important if an estimated dose approaches an as-low-as-reasonably-achievable or regulatory threshold. Conversely, without the benefit of site-specific data, ingestion doses may be underestimated in regions with dry climates.

Atmosphere↗

PubMed2006

Stereoselective quantification of methadone and a d(6)-labeled isotopomer using high performance liquid chromatography-atmospheric pressure chemical ionization mass-spectrometry: application to a pharmacokinetic study in a methadone maintained subject.

There is evidence that the apparent oral clearance of rac-methadone is induced during the early phase of methadone maintenance treatment. However, it is not known if this is due to changes in bioavailability or if this phenomenon is stereoselective. This knowledge can be obtained by administering a dose of stable-labeled methadone at selected times during ongoing treatment. Therefore, the authors developed a stereoselective high performance liquid chromatography-atmospheric pressure chemical ionization mass-spectrometry assay for the quantification of the enantiomers of methadone and a d(6)-labeled isotopomer. The compounds were quantified in a single assay after liquid-liquid extraction and stereoselective high performance liquid chromatograph with atmospheric pressure chemical ionization-mass spectrometry detection. The following ions were monitored: m/z 310.15 for unlabeled methadone; m/z 316.15 for methadone-d(6); and m/z 313.15 for the methadone-d(3) (internal standard). Calibration curves ranged from 0.5 to 75 ng/mL for each compound. Extraction recovery was approximately 80% for all analytes, without evidence of differences between the unlabeled and stable-labeled compounds or concentration dependency. Minor ion promotion was observed (<15%) but this was identical for all analytes including the d(3)-labeled internal standard, with peak area ratios in extracted samples identical to control injections. The isotopomers did not alter each others' ionisation, even at 10:1 concentration ratios, and 10-fold diluted samples were within 10% of the nominal concentration. Assay performance was acceptable, with interassay and intra-assay bias and precision <10% for all compounds, including the upper and lower limits of quantitation. In conclusion, the assay was successfully applied to quantify the concentration of the methadone enantiomers of both orally administered unlabeled methadone and an intravenous 5 mg dose of methadone-d(6) in a patient receiving chronic oral methadone maintenance therapy.

Administration, Oral↗

PubMed2000

Personal exposure to atmospheric polycyclic aromatic hydrocarbons in a general adult population and lung cancer risk assessment.

Personal exposure to nine particulate-phase atmospheric polycyclic aromatic hydrocarbons (PAHs) was assessed among adult non-smoking volunteers in the Grenoble, France, metropolitan area. Using Toxic Equivalency Factors, the associated total atmospheric PAHs lifelong cancer risk was estimated. For 48 hours continuously, 38 subjects without specific occupational exposure to combustion sources carried a PM2.5 particles personal exposure monitor while at home, at work, commuting, or involved in other activities. One phase of the study took place in summer; a second in winter. The monitor set was composed of a pump with an airflow of 4 L.mn-1, a 2.5-micron cyclone, and Teflon filters. The PAH concentrations were determined on seven PM2.5 filters by using high performance liquid chromatography with fluorimetric detection. The predominant PAHs are fluoranthene and indeno pyrene. According to the compound, the personal exposure estimates ranged from 0.13 to 1.67 ng/m3 (yearly means). The average benzo(a) pyrene value is 0.67 ng/m3 (95% confidence interval = 0 to 2.1 ng/m3). Winter exposures were 3 to 25 times greater than summer exposures. The total PAHs lung cancer lifelong risk is 7.8 10(-5) and is driven by exposure to benzo(a) pyrene. Although these risk estimates are 2 to 3 orders of magnitude lower than those associated with specific occupational exposures in the coal or smelter industries, they are of public health concern because they are spread over large urban populations. Further personal exposure studies in adult or children populations are needed.

Adult↗

PubMed2005

Derived release limits for the greek research reactor site based on a diagnostic atmospheric modeling system for irregular terrain.

The upper limits for the rate of release of radionuclides into the atmosphere, i.e., the "derived release limits," are calculated for the Greek Research Reactor (GRR-1) in order to determine possible operational schemes compatible with the effective dose limits for the general population. GRR-1 is located at the northwestern foot of Hymettos Mountain and at the eastern border of the urbanized area of Athens basin. Due to the topographic complexity of the region, the meteorological and atmospheric dispersion calculations were based on a numerical modeling system that is especially designed to work over irregular terrains by using a prismatic unstructured grid. The calculation of derived release limits was made using guidelines and methods that conform to the system of dose limits prescribed by the European radiation protection regulations.

Air Pollutants, Radioactive↗