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At least 793 records · Page 44Linked to original sources
PubMed2006

Atmospheric-pressure Penning ionization of aliphatic hydrocarbons.

A study has been made of the atmospheric-pressure Penning ionization (APPeI) of aliphatic hydrocarbons (pentane, hexane, heptane, and octane) with long-lived rare gas atoms (Rg*). The metastable rare gas atoms (He*, Ne*, Ar* and Kr*) were generated by the negative-mode corona discharge of atmospheric-pressure rare gases. In the Rg*APPeI mass spectra for aliphatic hyrocarbons, the relative abundances of fragment ions were found to increase in the order of He* --> Ne* --> Ar* --> Kr*. The order is in the opposite direction to the internal energies of the Rg*. The less fragmentation observed for He* may be because the nascent molecular ions [M(+.)]* formed by Penning ionization have lifetimes long enough for them to be collisionally deactivated in the atmospheric-pressure ion source. It was found that the relative abundances of fragment ions in Ar*APPeI increased when the sample pressure in the ion source was reduced. This is attributed to the collision of Ar* with molecular ions followed by fragmentation.

Journal Article↗
PubMed2002

Atmospheric pressure laser desorption/chemical ionization mass spectrometry: a new ionization method based on existing themes.

We have designed and constructed an atmospheric pressure laser desorption/chemical ionization (AP-LD/CI) source that utilizes a laser pulse to desorb intact neutral molecules, followed by chemical ionization via reagent ions produced by a corona discharge. This source employs a heated capillary atmospheric pressure inlet coupled to a quadrupole ion trap mass spectrometer and allows sampling under normal ambient air conditions. Preliminary results demonstrate that this technique provides approximately 150-fold increase in analyte ions compared to the ion population generated by atmospheric pressure infrared matrix-assisted laser desorption/ionization (AP-IR-MALDI).

Air Pressure↗
PubMed1995

Degradation of DNA in dried tissues by atmospheric oxygen.

Recently, DNA of extinct creatures have been brought into analyses. The difficulty in this field of research is DNA degradation. Oxidative damage is considered to be one of the causes of the DNA degradation. We studied how DNA in dried tissue was affected by atmospheric oxygen using freeze-dried rat liver as a model. In tissues exposed to oxygen, DNA degradation occurred within several months and the amount of 8-hydroxy-2'-deoxyguanosine in DNA rapidly increased. The DNA degradation was inhibited by lipid extraction prior to the exposure to atmospheric oxygen. Purified lambda phage DNA was not affected by oxygen. Cellular DNA and RNA were degraded slowly in nitrogen air. These results suggest that both atmospheric and endogenous oxygens play a role in DNA degradation in dried tissues.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2000

Zinc is the toxic factor in the lung response to an atmospheric particulate sample.

The atmospheric dust sample EHC-93 is known to induce lung cell injury and inflammation in which the toxicity has been attributed to a soluble component, possibly metal ions. To determine whether any specific metal is responsible for the pulmonary reactivity, various metal salts, at the concentration of metal present in the soluble fraction of EHC dust, have now been instilled into mouse lung. After 3 days, only a solution containing all metals tested and that of a zinc salt alone induced an increase in inflammatory cells and protein in lung lavage fluid. These two solutions also increased DNA synthesis in lung cells at this time, indicating a reparative response. Other solutions containing metals such as Cu, Fe, Al, Pb, Mg, or Ni induced no changes in the preceding measurements at the EHC dose level of metal. In a more extensive 28-day study, zinc salts induced rapid focal necrosis of Type 1 alveolar epithelial cells followed by inflammation and elevation of protein levels in lavage fluid over a 2-week period. Following the injury, epithelial cell proliferation increased and focal fibrosis was seen at 4 weeks. A solution containing all the other metals tested without the zinc component induced only minimal lung effects. When a zinc salt was administered at a 10x dose, the pulmonary changes were greatly enhanced, and after 4 weeks fibrosis could be measured biochemically. The results indicate that the acute toxicity associated with EHC atmospheric dust is most likely the result of the level of soluble zinc in this particulate sample. This suggests that a high soluble metal content of atmospheric dust, in this case the zinc level, may be a crucial factor in determining pulmonary cell reactivity to inhaled particulates.

Air Pollutants↗
PubMed1982

Are datascreen terminals a source of increased PCB-concentrations in the working atmosphere?

The use of polychlorinated biphenyls (PCBs) restricted to closed systems. They are thus still used as dielectric fluids in capacitors and transformers. The hypothesis that skin rashes and excema reported among datascreen operators might be caused by leakage of PCB from components in the screen terminals was investigated. No information about the chemical content of the electric components in the actual datascreen terminals were available. The PCB-concentration in the atmosphere in a workplace where such skin reactions had previously occurred was therefore determined. Air was sampled through 2 or 3 days, during work hours only. A glass fiber backed by an amberlite XAD-2 column was used to trap the sample. The total level of PCBs in this sample was analysed by glass-capillary gas chromatography with electron capture detection. Commercial PCB mixtures were used as standards. PCB-concentrations in the working atmosphere (56-81 ng/M3) were about 50-80 times the level of PCB in samples collected outside the building. Indoor and outdoor samples differed also qualitatively. The indoor samples contained only Aroclor 1242, while the outdoor samples contained a mixture of Aroclor 1242 and 1254. The amounts of PCBs measured were below the safety level for working atmosphere, as recommended by NIOSH in 1977. However, knowing that the samples were collected in an office where there was no known use of PCBs, the levels found were unexpectedly high. Further investigations should therefore be undertaken to clarify whether datascreen terminals might be sources of PCB-contamination.

Air Pollutants↗
PubMed1980

Ward atmosphere and psychiatric nurses' job satisfaction.

This study examined the relationship of psychiatric nurses' job satisfaction to perceived therapeutic climate on their wards. Job satisfaction was measured with the Employee Attitude Survey published by Science Research Associates. Therapeutic climate was measured by Moos' Ward Atmosphere Scale. Wards were rated as the nurses perceived them (Real) and as they thought they should be (Ideal). Job Satisfaction scores were correlated with Ward Atmosphere Real and Ideal-Real discrepancy scores. The perceived degree of Practical Orientation was strongly related to nurse morale. Program Clarity, Order and Organization, Support, and Involvement were also notably related. A similar pattern of relationship was found between morale and Ward Atmosphere Ideal-Real discrepancies. As would be expected, System Maintenance factors were important to the nurses but so too were Therapeutic and Communication dimensions reflecting a balanced view of nursing care.

Adolescent↗
PubMed1978

Ion-molecule condensation reactions: a mechanism for organic synthesis in ionized reducing atmospheres.

The CH3+ ion, formed in ionized methane, undergoes consecutive eliminative condensation reactions with methane to form the carbonium ions C2H5+, i-C3H7+ and t-C4H9+. At T smaller than 500 degrees K, NCH4 greater than 10(16) cm-3 these ions react with NH3 in competitive condensation -- H+ transfer reactions, e.g. C2H5 + NH3 M leads to C2H5NH3+ leads to NH4+ + C2H4 At particle densities of NCH4 smaller than 10(16) cm-3 proton transfer is the only significant reaction channel. At NCH4 greater than 10(17) cm-3 condensation constitutes 5--20% of the overall reactions. The product of the condensation reaction further associates with CO2 to form C2H5NH3+ . CO2; the atomic composition of this cluster ion is identical with the protonated amino acid alanine. The carbonium ions i-C3H7+ and t-C4H9+ condense also with HCN to yield protonated isocyanides. HCNH% also appears to condense with HCN at T greater than 570 degrees K, and form cluster ions with HCN at lower temperatures. The rate constants of the condensation reactions vary with temperature and pressure in a complex manner. Under conditions similar to those on Titan at an altitude of 100 km (T = 100--150 degrees K, NCH4 approximately 10(18) cm-3), with a methane atmosphere containing 1% H2 and traces of NH3 and H2O, ion-molecule condensation reactions followed by H+ transfer are expected to lead to the atmospheric synthesis of C2H6, C3H8, CH3OH, C2H5OH and the terminal ions NH4+, CH3NH3+ and C2H5NH3+. At higher temperatures (250 degrees K smaller than T smaller than 400 degrees K), the synthesis of i-C4H10, i-C3H7OH and t-C4H9OH and of the ions i-C3H7NH3+ and t-C4H9NH3+ is also expected. Electron recombination of the terminal ions may yield amines, imines and nitriles. Cycles of protonation and dissociative recombination of the alkanes and alcohols produced in condensation reactions will also produce unsaturated hydrocarbons, ketones and aldehydes in the ionized atmosphere.

Amines↗
PubMed1979

The Martian atmosphere: some unanswered questions.

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

Carbon↗
PubMed1982

The atmosphere of Titan.

The discovery that Titan had an atmosphere was made by the identification of methane in the satellite's spectrum in 1944. But the abundance of this gas and the identification of other major constituents required the 1980 encounter by the Voyager 1 spacecraft. in the intervening years, traces of C2H2, C2H4, C2H6 and CH3D had been posited to interpret emission bands in Titan's IR spectrum. The Voyager infrared Spectrometer confirmed that these gases were present and added seven more. The atmosphere is now known to be composed primarily of molecular nitrogen. But the derived mean molecular weight suggests the presence of a significant amount of some heavier gas, most probably argon. It is shown that this argon must be primordial, and that one can understand the evolution of Titan's atmosphere in terms of degassing of a mixed hydrate dominated by CH4, N2 and 36Ar. This model satisfactorily explains the absence of neon and makes no special requirements on the satellite's surface temperature. The organic chemistry taking place on Titan today invites comparison with chemical evolution on the primitive Earth prior to the origin of life.

Biological Evolution↗
PubMed1987

Influence of atmospheric factors on the rheumatic diseases.

There appears to be ample evidence to conclude that various meteorological factors do exert a significant impact on some people with various rheumatic diseases. The data is, however, crude relative to our general understanding. Most of this research on RA has dealt with the primary signs and symptoms of inflammation. We know, however, many of the chemical mediators of inflammation. It seems like a logical progression of research to determine the effects of the meteorological/atmospheric factors of concern on these specific intrinsic mediators of inflammation. In general, gout can be very well controlled through medication. The evidence suggests, however, that we may gain a much better understanding of how atmospheric factors such as temperature can effect the body through changes in its physico-chemical processes by using Gout as a model. The work with SLE has already yielded useful applications. Sun screening pharmaceuticals have been quite successful in reducing exacerbations of symptoms. But we don't know why only some people are photosensitive. The previous research on the effects of atmospheric factors on the rheumatic diseases has illustrated key issues in methodology: large sample sizes are critical, objective and quantifiable disease variables are important, the variables measured must be specific to the questions investigated, the diseases investigated must be as specifically and accurately defined as possible, and the various aspects of 'weather' to be investigated must be specifically defined and quantified. It is apparent that there is much more important and useful work to be performed before we can understand the effects of atmospheric factors on the rheumatic diseases.

Arthritis, Rheumatoid↗
PubMed1994

Atmospheric air vs. normal middle ear gas: effects on in vitro growth and collagen synthesis in normal middle ear fibroblasts.

The present study was undertaken to quantitate the effects of atmospheric air and normal middle ear gas on cultured fibroblasts obtained from normal rabbit middle ear mucosa. The cells were exposed to three different gas compositions: 7% O2:5% CO2:88% N2, 21% O2:5% CO2:74% N2, and 75% O2:5% CO2:20% N2. The growth was monitored by measuring the total content of cell protein, the amount of DNA, and the cell division activity. The activity of the synthetic apparatus was determined by the collagen synthesis. For comparison, rabbit skin fibroblasts were grown under identical conditions. The results demonstrated significantly higher replication rate of middle ear fibroblasts at 7% oxygen than at atmospheric air whereas the collagen synthesis was significantly lower at 7%. Furthermore, the responses varied significantly between rabbit middle ear and rabbit skin fibroblasts. Thus the present study substantiates the hypothesis of an influence of atmospheric air on the middle ear mucosa which might be of importance, e.g., in relation to insertion of ventilation tubes or longstanding perforations of the tympanic membrane in otitis media.

Animals↗
PubMed1999

Determination of concentrations of elements in the atmospheric aerosol of the urban and rural areas of Beijing in winter.

The proton-induced X-ray emission technique is one of the most suitable methods in the study of the multielement content of atmospheric aerosols. Atmospheric aerosol samples were collected in winter using an eight-stage cascade impactor at a site of the urban center and a rural site of Beijing. The aerosol samples collected were analyzed to determine maximum, minimum, and average concentrations of up to 20 elements and the ratios of the average element concentrations for the coarse to fine particles (C/F) by the PIXE technique. It has been found that the average elemental concentrations in the urban center are higher than those in the rural area, except S and Br. The concentrations for S and Pb in the atmospheric aerosols are found to be less than the results of previous measurement, but their concentrations in the fine particles increased in winter in the samples from the urban center. The deposition probability of the International Commission on Radiological Protection (ICRP) mode and the mass particle-size distributions of the elements determined in the urban center have been utilized to evaluate inhalable particulate matter fractions retained in the three regions of one's respiratory tract and their harm to human health is discussed.

Aerosols↗
PubMed1999

INAA and PIXE of atmospheric and combustion aerosols.

Using instrumental neutron activation analyses and photon-induced x-ray emission techniques for analysis of size-fractionated atmospheric and combustion aerosols and other emission samples arising from fluidized-bed combustion of North Bohemian lignites up to 42 elements were determined in all samples types. This allowed the evaluation of element enrichment, time trends, and inter-element correlations and the performance of factor analysis of various fractions of atmospheric aerosols. The data obtained on mass and element size distributions of aerosols and emission samples obtained upon lignite combustion in an experimental scale atmospheric fluidized-bed combustor without and with added hydrated lime and limestone were used to elucidate the mechanism of abatement of toxic trace and matrix elements from flue gas.

Aerosols↗
PubMed2002

The distribution of the chlorinated solvents dichloromethane, perchloroethylene, and trichloroethylene in the global atmosphere.

Dichloromethane, perchloroethylene, and trichloroethylene are commercially important chlorinated solvents whose health and environmental impacts are under scrutiny in the industrial world. Their distributions in the global atmosphere have been computed based on data from the Reactive Chlorine Emissions Inventory (RCEI) project using the Global Balance Environment (GLOBE) model, a 3-D radiative-dynamical-chemical model. Their atmospheric lifetimes, scaled to an observed methyl chloroform lifetime of 4.8 years, are 158 days, 105 days, and 4.3 days, respectively. They have strong interhemispheric gradients, with maximum zonal mean surface concentrations in the winter mid-latitude northern hemisphere of approximately 40 ppt, 9 ppt, and 2.5 ppt, respectively. Their spatial distributions show significant seasonal variability, and are sensitive to vertical mixing by cumulus convection and horizontal mixing by synoptic-scale turbulence. While the model interhemispheric exchange time (1.0 years) and computed atmospheric lifetimes are very sensitive to sub-grid scale diffusion, interhemispheric gradients of the chlorinated solvents are not. The simulated results suggest a greater importance for oceanic emissions of perchloroethylene and trichloroethylene than has previously been assumed.

Air Movements↗
PubMed2004

[Cutaneous oxygen supply. With special consideration of skin uptake of oxygen from the atmosphere].

Oxygen reaches the skin from the blood as well as from the atmosphere. The diffusion gradient is a key factor in oxygen delivery. Measurements with puncture electrodes show a maximum oxygen partial pressure on the skin surface and a minimum in the deeper dermis. Non-invasive measures show that oxygen uptake depends on location. Assuming the oxygen consumption is 0.276+/-0.029 ml O(2).100 g(-1).min(-1) (37 degrees) and no oxygen is removed by capillaries, then the skin can be supplied by atmospheric oxygen to a depth of 0.25 to 0.40 mm, well into the dermis. Only the deeper dermis receives oxygen from the blood. The stratum corneum is a significant barrier to diffusion from the atmosphere. When this barrier is damaged, the oxygen diffusion increases Keratinocytes in culture proliferate in response to increased oxygen pressure; the same mechanism may explain epidermal hyperplasia following stratum corneum damage in vivo.

Blood Gas Monitoring, Transcutaneous↗
PubMed2001

Patient satisfaction and ward atmosphere during a crisis in an open psychiatric ward.

BACKGROUND: There is great need for useful indicators of quality of care for inpatient psychiatric treatment. The study examines whether patient satisfaction and ward atmosphere can be used as a means of evaluating an assumed decline in quality of care during a crisis in an open psychiatric ward. METHODS: Twice a year for 2 years ten patients filled out a standardized patient satisfaction questionnaire developed by the Swedish Institute for Health Services Development (SPRI) on their day of departure. At the same time all the patients in the ward evaluated the ward atmosphere using the Ward Atmosphere Scale (WAS). In the third study period the ward went through a crisis where quality of care was expected to be lower. RESULTS: The SPRI questionnaire confirmed the decline in patients' perceived quality of care on six of 41 questions, WAS was markedly lower on five of ten subscales. CONCLUSIONS: Both WAS and the SPRI questionnaire gave useful information on how the ward was affected by the crisis. WAS seemed to be a more sensitive way of measuring quality of care, while the SPRI questionnaire indicated more clearly the practical consequences.

Alcoholism↗
PubMed2003

A multi-residue method for characterization and determination of atmospheric pesticides measured at two French urban and rural sampling sites.

The extensive use of pesticides to protect agricultural crops can result in the transfer of these compounds into the atmosphere and their diffusion towards urban areas. Precise evaluation of the geographic impact of this type of pollution is important environmentally. In this paper, analytical methods for the sampling, characterization, and determination of agricultural pesticides in air were developed; the methods were then applied in the Paris and Champagne regions. Sixteen pesticides belonging to nine chemical families were monitored. Sampling was carried out in urban (Paris) and rural (Aube district) sites, utilizing either a high-volume pump (12.5 m3 h(-1)) (urban site) or a low-volume pump (2.3 m3 h(-1)) for the rural site. Quartz filters and polyurethane foams (PUF) were used for sampling in all cases. After extracting the samples and concentrating the recovered solutions, high-performance liquid chromatography (HPLC) analysis with UV detection was performed. Identification of the pesticides was confirmed by applying to the HPLC measurements a novel UV-detection procedure based on the normalized absorbance variation with wavelength (Noravawa procedure). The presence of metsulfuron methyl, isoproturon, linuron, deltamethrin (and/or malathion), and chlorophenoxy acids (2,4-D and MCPP) was found at the urban sampling site at levels ranging from about 1 to 1130 ng m(-3) of air, depending on the compound and sampling period. On the rural sampling site residues of isoproturon, deltamethrin (and/or malathion), MCPP, and 2,4-D were generally detected at higher levels (19-5130 ng m(-3)) than on the urban site, as expected. The effects of the weather conditions and agricultural activity on the atmospheric concentrations of pesticides are discussed, as are long-range atmospheric transfer processes for these pesticides.

Journal Article↗
PubMed2004

Multiresidue method using SPME for the determination of various pesticides with different volatility in confined atmospheres.

An analytical method is described for assessing the vapour concentration of 11 pesticides (bioallethrin, chlorpyriphos methyl, folpet, malathion, procymidone, quintozene, chlorothalonil, fonofos, penconazole and trimethacarb) in confined atmospheres (e.g. a greenhouse after pesticide application). This study is a successful extension of a method previously developed by the authors for dichlorvos to much less volatile pesticides. Sampling was performed by using polydimethylsiloxane-solid phase micro-extraction (PDMS-SPME) fibres immersed in a 250-mL sampling flask through which air samples were dynamically pumped from the analysed atmosphere. After a 40-min sampling duration, samples were analysed by GC/MS. Calibration was performed from a vapour-saturated air sample. The linearity of the observed signal versus pesticide concentration in the vapour phase was proved from spiked liquid samples whose headspace concentrations were measured by using the proposed method. This procedure gave calibration curves with regression coefficients ( R(2)) greater than 0.98, and the repeatability of these measurements was found with RSDs of 1.9-7.6%. As a field application test, this analysis procedure was used for the determination of gaseous procymidone concentrations as a function of time in the atmosphere of an experimental 8-m(2) and 20-m(3) greenhouse. The pesticide was sprayed according to real cultivation conditions, and measurements were made for 80 h after application (8 measurements). The observed concentrations found ranged from 200 to 500 micro g m(-3), thus indicating the level of contamination of the air breathed by people in such working conditions.

Journal Article↗