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At least 433 records · Page 24Linked to original sources
PubMedDate not supplied

[Atmospheric electromagnetic field oscillations and the nature of the proliferative process in the focus of acute inflammation].

Experiments were conducted on 300 rats kept in a warm room (16-18 degrees C) in the cold season of a year to study the influence of a signal effect of atmospheric processes, namely changes in of atmospheric electricity parameters, on the early proliferative reactions in a focus of acute inflammation. The results of 50 experiments on which a geomagnetic storm was superimposed were excluded form the analysis subsequently. Inflammation was modelled by implanting a 3 x 4-mm piece of a cover glass under the skin. Following 48 hours the number of hematogenic and histiogenic cells superimposed on one surface of the implanted glass was counted. These were fibroblasts, macrophages, polynuclear and giant cells. An analysis showed that frosty weather, the existence and direction of a wind, atmospheric-electrical processes preceding the passage of meteorological fronts influenced the nature of proliferative responses. The authors revealed the efficacy of electromagnetic screening of the animals, which mitigated the effect of the atmospheric electromagnetic waves.

Acute Disease↗
PubMed2005

Atmospheric reactions influence seasonal PAH and nitro-PAH concentrations in the Los Angeles basin.

Ambient measurements of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs were carried out during August 2002 and January 2003 in Los Angeles, CA, a source site and in Riverside, CA, a downwind receptor site approximately 90 km to the east of Los Angeles. Atmospheric concentrations of PAHs and nitro-PAHs are of interest because both of these compound classes include potent mutagens and carcinogens. To augment our current understanding of atmospheric formation of nitro-PAHs, four sampling periods were employed to study the diurnal variations of these compounds. The PAH concentrations were highest in Los Angeles during January, as a result of traffic input at this source site undertightwintertime atmospheric inversions. In contrast, nitro-PAH levels were highest in Riverside during August, as a result of enhanced summertime photochemistry. Hydroxyl radical-initiated reactions produced nitro-PAHs in both seasons, while in winter little evidence for nitrate radical chemistry was seen. For the August samples, nitrate radical-initiated formation of nitro-PAHs is suggested by nitro-PAH isomer profiles not only at the downwind location as anticipated, but also atthe source site. In southern California, the contribution of atmospheric formation through gas-phase radical-initiated PAH reactions to the ambient burden of nitro-PAHs is dominant, with the semi-volatile nitro-PAHs being the most abundant and 2-nitrofluoranthene being the major particle-associated nitro-PAH.

Air Pollutants↗
PubMed2005

[Spectral analyzing effects of atmosphere states on the structure and characteristics of CdTe polycrystalline thin films made by close-spaced sublimation].

The structure and characteristics of CdTe thin films are dependent on the working atmosphere states in close-spaced sublimation. In the present paper, CdTe polycrystalline thin films were deposited by CSS in mixture atmosphere of argon and oxygen. The physical mechanism of CSS was analyzed, and the temperature distribution in CSS system was measured. The dependence of preliminary nucleus creation on the atmosphere states (involving component and pressure) was studied. Transparencies were measured and optic energy gaps were calculated. The results show that: (1) The CdTe films deposited in different atmospheres are cubic structure. With increasing oxygen concentration, a increases and reaches the maximum at 6% oxygen concentration, then reduces, and increases again after passing the point at 12% oxygen concentration. Among them, the sample depositing at 9% oxygen concentration is the best. The optic energy gaps are 1.50-1.51 eV for all CdTe films. (2) The samples depositing at different pressures at 9% oxygen concentration are all cubical structure of CdTe, and the diffraction peaks of CdS and SnO2:F still appear. With the gas pressure increasing, the crystal size of CdTe minishes, the transparency of the thin film goes down, and the absorption side shifts to the short-wave direction. (3) The polycrystalline thin films with high quality deposit in 4 minutes under the depositing condition that the substrate temperature is 550 degrees C, and source temperature is 620 degrees C at 9% oxygen concentration.

Algorithms↗
PubMed1994

X-ray microanalysis with the environmental scanning electron microscope: interpretation of data obtained under different atmospheric conditions.

X-ray microanalysis of non-biological and biological specimens was carried out in an environmental scanning electron microscope (ESEM) over a range of atmospheric conditions. Introduction of water vapour into the specimen chamber lead to direct X-ray contribution from oxygen atoms, an increase in extraneous background (causing reduced P/B ratios of other elements), X-ray absorption (also reducing P/B ratios) and broadening (skirting) of the electron beam. Similar results were obtained after introduction of an argon atmosphere. These effects were reduced under conditions of minimal chamber atmospheric pressure and maximal accelerating voltage. Because of beam skirting, quantitative X-ray microanalysis of biological specimens in a water vapour atmosphere was only valid where the sample was spread over a wide area (leading to mean elemental values for the whole preparation). Unless appropriate correction factors or changes in instrumentation can be implemented, quantitative analysis of wet specimens in ESEM cannot be applied to discrete specimens or to limited areas within a mixed sample.

Anabaena↗
PubMed1993

[Asthma, urban atmospheric pollution and the weather].

The aim of this study, which was carried out in an urban environment, was to research in to a possible relationship between temporal variations in the level of atmospheric pollution in the centre of Paris, compared to the frequency of acute dyspnoeic crises in which asthmatic patients had requested the emergency service (SOS Médecins). This study began in the first half of 1989; during this period there were 701 cases of acute asthma recorded within the Paris city boundary by "SOS Médecins". The pollutants recorded were sulphur dioxide (SO2), an index of black smoke (FN), oxides of nitrogen (NOx), ozone (O3) and soluble sulphate particles (SO4). In addition, the weather patterns were examined and pollen counts were recorded. In spite of a sub-acute episode of pollution in January and February, there was no definite increase noted in the number of emergency calls made for acute asthma. In the first three months, the number of crises were, on average, higher in association with high levels of the principal pollutants (SO2 FN, NOx, SO4) as well as with the periods of high atmospheric pressure; however, only the sulphate content and atmospheric pressure remained correlated with the daily number of asthmatic crises. In the second three months, there were some co-variations uniquely associated with sulphate particles, the atmospheric pressure, and above all the ozone level (allowing for a gap of one day). The influence of the daily variations in total pollen content or of grass pollens did not show up in this study.

Acute Disease↗
PubMedDate not supplied

[Cosmic rays as the main factor affecting solar variability on climatic and atmospheric parameters].

Analysis of experimental data demonstrates that cosmic ray enhancement stimulates an increase of atmospheric aerosols and cloudiness. The study of solar proton events (SPE) has shown that during SPE one can observe increase in aerosol density by 1.2-1.4 times at 12-18 km altitudes. Such variations of aerosol density can be detected on global scale. Aerosol variations cause changes in integral atmospheric transparency which during disturbed periods can reach 5-6%. The atmospheric integral transparency variations are not less during the solar cycle on account of galactic cosmic ray variations. Atmospheric transparency variations creating the so-called "grey filter" for solar radiation should lead to surface temperature variations. During the periods of low solar activity under the influence of enhanced galactic cosmic ray fluxes, the density of the "grey filter" should increase and cause a decrease in surface temperatures, correspondingly. In frame of the physical mechanism considered the connection between solar cycle durations and surface temperature variations can be explained. In addition, one can understand the physical reason for the "Little Ice Age" appearance during Maunder minimum of solar activity, 2400 years periodicity of climatic processes, strong influence of the decrease in main geomagnetic field intensity on the development of Ice Age and Global Cooling.

Atmosphere↗
PubMedDate not supplied

Polycyclic aromatic hydrocarbons in the atmosphere: monitoring, sources, sinks and fate. I: Monitoring and sources.

This is the first of a series of two papers intended to review the state-of-the-art knowledge on atmospheric PAHs, concerning their monitoring, sources and transformation processes in the atmosphere. The monitoring section briefly introduces this class of compounds, mainly focusing on the 16 PAHs indicated by the US-EPA as priority pollutants. These compounds undergo partitioning between the gas phase and particulate, which has to be considered in the choice of the sampling methodology. Furthermore, sampling artifacts may arise from further phase transfers inside the sampling device. After sampling, extraction, clean up and detection/quantification procedures will follow. They are closely related since the choice of the extraction technique will heavily condition the clean-up step, and both procedures will place demands on the performance of the detection technique (usually GC-MS or HPLC). This is particularly true in the case of complex samples such as those arising from atmospheric sampling. The sources of atmospheric PAHs are then discussed with a particular focus on receptor models, which can allow the apportionment of PAH sources based on concentration data that can be routinely obtained by pollution control networks.

Air Pollutants↗
PubMed2004

Polycyclic aromatic hydrocarbons in the atmosphere: monitoring, sources, sinks and fate. II: Sinks and fate.

This paper reviews the transformation processes that polycyclic aromatic hydrocarbons (PAHs) undergo in the atmosphere. These processes can take place both in the gas phase and in the particulate/aerosol one. Among the gas-phase processes, the most important ones are the daytime reaction with *OH and the nighttime reaction with *NO3. The relative importance of the two processes depends on the particular PAH molecule. For instance, gaseous naphthalene is mainly removed from the atmosphere upon reaction with *OH, while gaseous phenanthrene is mainly removed by reaction with *NO3. Oxy-, hydroxy-, and nitro-PAHs are the main transformation intermediates. Reaction with ozone and photolysis play a secondary role in the transformation of gaseous PAHs. The particle-associated processes are usually slower than the gas-phase ones, thus the gas-phase PAHs usually have shorter atmospheric lifetimes than those found on particulate. Due to the higher residence time on particulate when compared with the gas phase, direct or assisted photolysis plays a relevant role in the transformation of particle-associated PAHs. Among the other processes taking place in the condensed phase, nitration plays a very important role due to the health impact of nitro-PAHs, some of them being the most powerful mutagens found so far in atmospheric particulate extracts.

Aerosols↗
PubMed1984

Respiratory responses of humans exposed to an aerosol-gas pollutant mixture: multivariate contrast of a complex atmosphere to clean air and sodium chloride aerosol controls.

Data from a group of 20 subjects with normal baseline pulmonary function, who were exposed for 2 h to a test atmosphere containing a complex mixture of pollutants, have been contrasted with data from two other groups exposed to presumably non-toxic control atmospheres. Group 1 was exposed to clean air, group 2 was exposed to clean air containing sodium chloride aerosol at 270 micrograms m-3, and group 3 was exposed to the complex atmosphere containing sodium chloride (332 micrograms m-3) and zinc ammonium sulfate (23 micrograms m-3) aerosols plus nitrogen dioxide (0.5 ppm) and sulfur dioxide (0.5 ppm). These atmospheres (ranked according to the presumed relative toxicities of the components; clean air = 0, sodium chloride = 1, complex mixture = 2) were contrasted using multiple regression and partial correlation analyses. The effects of exposure to the complex gas-aerosol mixture on forced expiratory performance were not significantly different from those observed in subjects exposed to clean air or to sodium chloride aerosol.

Adolescent↗
PubMed2006

A 15N-aided artificial atmosphere gas flow technique for online determination of soil N2 release using the zeolite Köstrolith SX6.

N2 is one of the major gaseous nitrogen compounds released by soils due to N-transformation processes. Since it is also the major constituent of the earth's atmosphere (78.08% vol.), the determination of soil N2 release is still one of the main methodological challenges with respect to a complete evaluation of the gaseous N-loss of soils. Commonly used approaches are based either on a C2H2 inhibition technique, an artificial atmosphere or a 15N-tracer technique, and are designed either as closed systems (non-steady state) or gas flow systems (steady state). The intention of this work has been to upgrade the current gas flow technique using an artificial atmosphere for a 15N-aided determination of the soil N2 release simultaneously with N2O. A 15N-aided artificial atmosphere gas flow approach has been developed, which allows a simultaneous online determination of N2 as well as N2O fluxes from an open soil system (steady state). Fluxes of both gases can be determined continuously over long incubation periods and with high sampling frequency. The N2 selective molecular sieve Köstrolith SX6 was tested successfully for the first time for dinitrogen collection. The presented paper mainly focuses on N2 flux determination. For validation purposes soil aggregates of a Haplic Phaeozem were incubated under aerobic (21 and 6 vol.% O2) and anaerobic conditions. Significant amounts of N2 were released only during anaerobic incubation (0.4 and 640.2 pmol N2 h(-1) g(-1) dry soil). However, some N2 formation also occurred during aerobic incubation. It was also found that, during ongoing denitrification, introduced [NO3]- will be more strongly delivered to microorganisms than the original soil [NO3]-.

Journal Article↗
PubMed2001

Real Atmosphere Laboratory Measurements of the 118-GHz Oxygen Line: Shape, Shift, and Broadening of the Line.

For the first time the 118-GHz line of the oxygen molecule was investigated in the laboratory under a real atmosphere. The experiment was carried out by modern resonator spectroscopy methods on the laboratory air at atmospheric pressure. The shape of the line under the real atmosphere was found to fit the Van Vleck-Weisskopf profile within experimental accuracy. The air broadening parameter value was defined as 2.14+/-0.07 MHz/Torr. The observed atmosphere oxygen line central frequency was found to be shifted down at about 150 MHz from the line center measured at low pressures, which gives a value of -0.19+/-0.08 MHz/Torr for the air shift parameter. A comparison with previous investigations is presented and reprocessing of some experimental results of other authors was carried out. Results of reprocessing agree with the findings of the present paper. Copyright 2001 Academic Press.

Journal Article↗
PubMed1982

Organic syntheses from CH4-N2 atmospheres: implications for Titan.

Numerous experiments have already been performed, simulating the evolution of gaseous mixtures containing CH4 when submitted to energy flux. From their results, it appears that a variety of organic compounds, including unsaturated hydrocarbons and nitriles such as HCN, can be synthesized into noticeable amounts from CH4-N2 mixtures. In particular, systematic studies of the influence of the composition of the mixture on the nature and amount of synthesized compounds show that organic volatile nitriles, and particularly cyanoacetylene and cyanogen, are formed only in media rich in nitrogen. Those nitriles have been identified very recently in the atmosphere of Titan, and thus, data from such laboratory experiments may provide important indirect information on the organic chemistry occurring at the periphery of this satellite of Saturn. However, during these experiments, there is a continuous formation and accumulation of molecular hydrogen, which does not occur in the atmosphere of Titan, because of H2 escape. In order to reassess the data already available from this type of laboratory studies, experiments on CH4-N2 atmospheres, with and without H2 escape, have been recently performed. The influence of this parameter on the chemical evolution of the atmosphere and on the nature and relative quantities of organic compounds has been studied. After reviewing these experiments, implications of the obtained results on the organic chemistry at the periphery of Titan are discussed.

Chemical Phenomena↗
PubMed1993

Ascorbic acid and dehydroascorbic acid content of blanched sweet green pepper during chilled storage in modified atmospheres.

Sweet green pepper (Capsicum annuum L.) cut into pieces was analysed for ascorbic acid (AA) and dehydroascorbic acid (DHAA) content before and after blanching, after 1, 4 and 7 days of chilled storage in modified atmosphere, and after reheating. No difference in retention of AA was noted between storage in 2 and 4% O2 atmospheres, whereas retention during storage in air was significantly lower. Production of DHAA during storage increased with increased O2 content in the atmosphere. After 7 days of storage, DHAA contributed 10-35% of the total AA, and DHAA contributed 12-25% after reheating, depending on the O2 content in the atmosphere. Since the vitamin activity of DHAA is considered to be the same as that of AA, it is concluded that the content of DHAA in processed green pepper is of importance and should be measured together with AA.

Ascorbic Acid↗
PubMedDate not supplied

Soluble metals in the atmosphere and their biological implications. A study to identify important aerosol components by statistical analysis of PIXE data.

Multivariate statistical analysis has been applied to time series measurements of aerosol elemental composition from PIXE analysis of filter samples, and principal components have been resolved that represent distinct particle types in an external mixture in the atmosphere. In this study, it is argued that a combination of chemical and statistical analyses of the data may be more powerful in determining chemical species in atmospheric aerosols than studied that employ mainly direct chemical analysis of chemical species in unresolved mixtures of aerosol particle samples. Sulfur is generally associated with mineral dust elements. It is reasoned that the association may represent sulfuric acid coatings on particles that can lead to mineral dissolution and solubilization of significant amounts of aluminum, iron, and other metals. Upon wet or dry deposition to the surface, the fluxes of these metals in biologically-available form may be sufficient to affect primary productivity in the world ocean and cause ecological damage in lakes. As a consequence, the fluxes of biogenic trace gases to the atmosphere may be changed, possibly leading to changes in the tropospheric concentration of ozone. The inputs to lakes of soluble aluminum, which is toxic to fish, may be partly by deposition directly from the atmosphere, thus not limited to leaching of soils by acid deposition. Human inhalation of soluble aluminum and other solubilized mineral metals may account, in part, for the observed geographic pattern of deaths attributed to chronic obstructive pulmonary disease (COPD) that show high rates in cities of the Western US and the southeast region, but low in most of the midwest and northeast.

Aerosols↗
PubMed2005

Extreme isotopic depletion of nitrogen in New Zealand lithophytes and epiphytes; the result of diffusive uptake of atmospheric ammonia?

Several lichens and the terrestrial alga Trentepohlia were found to have extremely depleted 15N signatures at two sites near the Rotorua geothermal area, New Zealand. Values, typically -20 per thousand, with several extreme cases of -24 per thousand, are more isotopically depleted than any previously quoted delta15N signature for vegetation growing in natural environments. For Trentepohlia, distance from a geothermal source did not affect isotopic signature. A 100-km transect showed that the phenomenon is widespread and the discrimination is not related to substrate N, or to elevation. Rainfall NHx and atmospheric gaseous NH3 (NH3(g)) were shown to be isotopically depleted in the range -1 per thousand to -8 per thousand and could not, of themselves, be responsible for the plant values obtained. A simulation of Trentepohlia thallus was created using an acidified fiberglass mat and was allowed to absorb NH3(g) from the atmosphere. Mats exposed at the geothermal sites and on farm-land showed a significant further depletion of 15N to -17 per thousand. We hypothesize that the extreme isotopic depletion is due to dual fractionation: firstly by the volatilization of NH3(g) from aqueous sources into the atmosphere; secondly by the diffusive assimilation of that NH3(g) into vegetation. We further hypothesize that lithophytes, epiphytes, and higher plants, growing on strongly N-limited substrates, will show this phenomenon more or less, depending on the proportion of diffusively assimilated NH3(g) utilized as a N source. Many of the isotopically depleted delta15N signatures in vegetation, previously reported in the literature, especially epiphytes, may be due to this form of uptake depending on the concentration of atmospheric NH3(g), and the degree of reliance on that form of N.

Air Pollutants↗
PubMed2003

The influence of temperature, relative humidity and rainfall on the occurrence of pollen allergens (Betula, Poaceae, Ambrosia artemisiifolia) in the atmosphere of Bratislava (Slovakia).

The occurrence of pollen grains in the atmosphere markedly relates to meteorological factors. In the study we have evaluated a correlation between the concentration of pollen grains in the atmosphere of Bratislava and temperature, relative humidity and rainfall during the vegetation period of 1995 and 1997. For our analysis we have selected one representative of each phytoallergen group (trees, grasses, weeds). We have chosen the Betula genus of trees, the whole Poaceae family of grasses and ragweed Ambrosia artemisiifolia L. to represent weeds. The taxons mentioned represent the most significant allergens in Slovakia. The concentration of pollen grains has been monitored by a Lanzoni volumetric pollen trap. The data obtained, the average daily concentration in 1 m(3), have been included in the statistical analysis together with values for the average daily temperature, relative humidity and total rainfall in 24 h. The correlation between the concentration of pollen grains in the atmosphere and selected meteorological variables from daily monitoring has been studied with the help of linear regression and correlation coefficients. We have found the average daily temperature and relative humidity (less than temperature) to be significant factors influencing the occurrence of pollen grains in the atmosphere of Bratislava. The total daily rainfall does not seem to be significant from the statistical point of view.

Allergens↗
PubMed2004

Alternaria spores in the atmosphere of Sydney, Australia, and relationships with meteorological factors.

Alternaria spores are found in the atmosphere in many locations around the world. They are significant from a human health perspective because they have been known to trigger allergic respiratory disease such as asthma and hay-fever. The presence of Alternaria spores in the atmosphere has been related to meteorological factors in past studies, but this has not been done previously in Sydney, Australia. This paper reports the results of such a study in Sydney. Alternaria spore concentration data for the period 19 August 1992 to 31 December 1995 were examined with meteorological data for the same period. The daily Alternaria spore concentration was compared to the meteorological data for the same day and for up to 3 days previously. The analysis methods were Spearman's rank correlation and multiple regression. Alternaria spores appear in the atmosphere of Sydney year-round, although they peak over spring, summer, and autumn. A number of meteorological factors, including mean, minimum, and maximum, temperature, dew point temperature, and air pressure, are significantly correlated with the atmospheric concentration of Alternaria spores. Some of these meteorological variables (temperature and dew point temperature) show significant correlations with a 1, 2, and 3 day lag, as well as for the same day. Regression models indicate that up to 31.1% of the variation in Alternaria spore concentration can be explained by meteorological factors. There is potential for the results of this study to be used by public health authorities in the prediction of Alternaria spore concentrations in Sydney.

Alternaria↗
PubMed2005

Heavy metals in ryegrass species versus metal concentrations in atmospheric particulate measured in an industrial area of Southern Italy.

The aim of this paper is to evaluate the reliability of ryegrass species as active biomonitors by assessing atmospheric metal concentrations. We show a procedure for measuring atmospheric concentrations of heavy metals by means of biomonitors and present the data collected between July 1997 and October 2000 in the industrial area of Tito Scalo (Basilicata region, Southern Italy). In particular, we discuss the reproducibility of the biomonitoring measures, the influence of plant age and the correlation between metal concentrations in plants and in atmospheric particulate. Statistical analysis of measured data suggests us that in the investigated site, Cd, Cr and Ni are suitable to be monitored by means of ryegrass species. For the other metals, their emission patterns in atmosphere make it difficult to identify the correlation structure between plants and particulate, and as a result the interpretation of the biomonitoring data is complex. On the basis of the results, we believe that for correct application of active biomonitoring procedure, a careful preliminary analysis of the monitoring site and integration of the biomonitoring and chemical-physical observation is necessary.

Air Pollutants↗