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At least 343 records · Page 19Linked to original sources
PubMed2003

Application of an acoustic noise removal method to aircraft-based atmospheric temperature measurements.

An acoustic noise removal method is used to reject engine acoustical disturbances from aircraft-based atmospheric temperature measurements. Removal of engine noise from atmospheric temperature measurements allows a larger wave number range to be fit while quantifying the magnitude of atmospheric temperature turbulence. The larger wave number range was found to result in a more statistically certain spectral slope estimate, with up to a 50% reduction in the standard deviation of measured spectral slopes. The noise removal technique was found to break down under conditions of weak atmospheric temperature turbulence where the engine acoustical disturbance can be several orders of magnitude larger than atmospheric temperature turbulence.

Journal Article↗
PubMed1998

Microbial consumption of atmospheric isoprene in a temperate forest soil.

Isoprene (2-methyl-1,3 butadiene) is a low-molecular-weight hydrocarbon emitted in large quantities to the atmosphere by vegetation and plays a large role in regulating atmospheric chemistry. Until now, the atmosphere has been considered the only significant sink for isoprene. However, in this study we performed both in situ and in vitro experiments with soil from a temperate forest near Ithaca, N.Y., that indicate that the soil provides a sink for atmospheric isoprene and that the consumption of isoprene is carried out by microorganisms. Consumption occurred rapidly in field chambers (672.60 +/- 30.12 to 2,718.36 +/- 86.40 pmol gdw day) (gdw is grams [dry weight] of soil; values are means +/- standard deviations). Subsequent laboratory experiments confirmed that isoprene loss was due to biological processes: consumption was stopped by autoclaving the soil; consumption rates increased with repeated exposure to isoprene; and consumption showed a temperature response consistent with biological activity (with an optimum temperature of 30 degrees C). Isoprene consumption was diminished under low oxygen conditions (120 +/- 7.44 versus 528.36 +/- 7.68 pmol gdw day under ambient O(2) concentrations) and showed a strong relationship with soil moisture. Isoprene-degrading microorganisms were isolated from the site, and abundance was calculated as 5.8 x 10 +/- 3.2 x 10 cells gdw. Our results indicate that soil may provide a significant biological sink for atmospheric isoprene.

Journal Article↗
PubMed1999

Growth and survival of uninjured and sublethally heat-injured Escherichia coli O157:H7 on beef extract medium as influenced by package atmosphere and storage temperature.

The effect of atmospheric composition and storage temperature on growth and survival of uninjured and sublethally heat-injured Escherichia coli O157:H7, inoculated onto brain heart infusion agar containing 0.3% beef extract (BEM), was determined. BEM plates were packaged in barrier bags in air, 100% CO2, 100% N2, 20% CO2: 80% N2, and vacuum and were stored at 4, 10, and 37 degrees C for up to 20 days. Package atmosphere and inoculum status (i.e., uninjured or heat-injured) influenced (P < 0.01) growth and survival of E. coli O157:H7 stored at all test temperatures. Growth of heat-injured E. coli O157:H7 was slower (P < 0.01) than uninjured E. coli O157:H7 stored at 37 degrees C. At 37 degrees C, uninjured E. coli O157:H7 reached stationary phase growth earlier than heat-injured populations. Uninjured E. coli O157:H7 grew during 10 days of storage at 10 degrees C, while heat-injured populations declined during 20 days of storage at 10 degrees C. Uninjured E. coli O157:H7 stored at 10 degrees C reached stationary phase growth within approximately 10 days in all packaging atmospheres except CO2. Populations of uninjured and heat-injured E. coli O157:H7 declined throughout storage for 20 days at 4 degrees C. Survival of uninjured populations stored at 4 degrees C, as well as heat-injured populations stored at 4 and 10 degrees C, was enhanced in CO2 atmosphere. Survival of heat-injured E. coli O157:H7 at 4 and 10 degrees C was not different (P > 0.05). Uninjured and heat-injured E. coli O157:H7 are able to survive at low temperatures in the modified atmospheres used in this study.

Carbon Dioxide↗
PubMed2004

Plastic and evolved responses of larval tracheae and mass to varying atmospheric oxygen content in Drosophila melanogaster.

Structural changes in the tracheal system during development have the potential to allow insects to compensate for varying oxygen availability. Despite possible compensation, oxygen level during development may also affect insect body size. We investigated how atmospheric oxygen level affects the dimensions of the main dorsal tracheae (DT) and masses of larval Drosophila melanogaster (Meigen) reared for up to six generations in 10%, 21% or 40% O2 at 25 degrees C. Wandering-stage third-instar larvae were weighed every other generation, and the dimensions of the DT were measured. Hypoxia produced significantly lighter larvae after one generation of exposure, while hyperoxia did not affect larval mass. Atmospheric oxygen content did not significantly change the diameters of the anterior portions of the main tracheae; however, the posterior diameters were strongly affected. During the first generation of exposure, tracheal diameters were inversely proportional to rearing oxygen levels, demonstrating that developmental plasticity in DT diameters can partially (8-15%) compensate for variation in atmospheric oxygen level. After multiple generations in differing atmospheres and two further generations in 21% O2, larvae had tracheal diameters inversely related to their historical oxygen exposure, suggesting that atmospheric oxygen can produce heritable changes in insect tracheal morphology.

Adaptation, Physiological↗
PubMedDate not supplied

Perceptions of ward atmosphere on an oncology unit.

This study examined perceptions of ward atmosphere and ideal ward atmosphere by twenty patients, twenty-four staff, and fifteen family members on an oncology unit at a major cancer research institute. Specified preferences for an ideal ward atmosphere were assumed to reflect psychosocial needs of the three groups. Data were analyzed with multivariate statistics where it was found that perceptions of ward atmosphere differed for the three groups as did their perceptions of the amount of change needed to form an ideal ward atmosphere. This study was viewed as an initial and promising approach to assessing the compatibility of patient, family member, and staff needs along relationship, treatment program, and systems maintenance dimensions. It was believed that further studies of this type will increase the professional's understanding of the relationship between psychosocial needs and response to treatment.

Adolescent↗
PubMed1986

Effect of an elevated level of carbon dioxide containing atmosphere on the growth of spoilage and pathogenic bacteria at 2, 7, and 13 C.

The effect of 80% CO2 (balance air) on the survival and growth of microorganisms most often associated with spoilage and foodborne disease in poultry carcasses was compared to air at 2, 7, and 13 C. The CO2 atmosphere substantially retarded the growth of the total bacterial load in uninoculated ground chicken meat and parts at all temperatures when compared to air; however, temperature had a larger overall effect than atmosphere. Ground chicken meat and synthetic broth were inoculated (greater than 10(4) cells/ml or g) with Pseudomonas fragi, Salmonella typhimurium, Staphylococcus aureus, or Clostridium sporogenes and the influence of 80% CO2 and incubation temperature studied. With the exception of Cl. sporogenes, 80% CO2 was inhibitory when compared to air at any given temperature. In most cases, CO2 was more inhibitory at 2 C than at 7 or 13 C. The Cl. sporogenes inoculum failed to grow above initial inoculum levels in any combination of temperature and atmosphere, but samples packed in 80% CO2 had higher numbers of colony forming units than air-packaged samples. This study does not indicate that modified atmosphere packaging of refrigerated poultry in elevated CO2 atmospheres increases the microbial hazards when compared to air at the same temperature.

Animals↗
PubMed1996

Combined effects of packaging atmosphere and lactic acid on growth and survival of Listeria monocytogenes in crayfish tail meat 4 degrees C.

The effect of lactic acid on growth and survival of Listeria monocytogenes in crayfish tail meat stored under refrigeration and various gas environments was investigated. Frozen crayfish tail meat was thawed overnight, autoclaved, cooled, and inoculated with approximately 4 log colony-forming units (CFU) of a mixed-strain (Scott A and F5027) L. monocytogenes culture per gram of meat. Inoculated samples were blended with 0, 0.5, 1.0, 1.5, or 2.0% lactic acid and packaged under air, vacuum, or modified atmosphere (74.8% CO2, 10.4% O2, and 14.8% N2) and stored at 4 degrees C for 20 days. Results demonstrated that modified atmosphere packaging inhibited the growth of L. monocytogenes more than air and vacuum packaging at 0 and 1% lactic acid. Microbial counts declined steadily in crayfish tail meat treated with 2% lactic acid, with no differences among the packaging atmospheres. The lag phase was extended by 8 days in samples treated with 1% lactic acid and modified atmosphere compared to that in air or vacuum packaging. Overall, the combination of lactic acid and modified atmosphere had the greatest potential to prevent growth of L. monocytogeines.

Animals↗
PubMed2000

Nonproteolytic Clostridium botulinum toxigenesis in cooked turkey stored under modified atmospheres.

The ability of nonproteolytic Clostridium botulinum type B spores to grow and produce toxin in cooked, uncured turkey packaged under modified atmospheres was investigated at refrigeration and mild to moderate abuse temperatures. Cook-in-bag turkey breast was carved into small chunks, surface-inoculated with a mixture of nonproteolytic C. botulinum type B spores, packaged in O2-impermeable bags under two modified atmospheres (100% N2 and 30% CO2:70% N2), and stored at 4, 10, and 15 degrees C. Samples were analyzed for botulinal toxin and indigenous microorganisms, as well as subjected to sensory evaluation, on days 0, 7, 14, 28, 42, and 60. Given sufficient incubation time, nonproteolytic C. botulinum type B grew and produced toxin in all temperature and modified atmosphere treatment combinations. At moderate temperature abuse (15 degrees C), toxin was detected by day 7, independent of packaging atmosphere. At mild temperature abuse (10 degrees C), toxin was detected by day 14, also independent of packaging atmosphere. At refrigeration temperature (4 degrees C), toxin was detected by day 14 in product packaged under 100% N2 and by day 28 in product packaged under 30% CO2:70% N2. Reduced storage temperature significantly delayed toxin production and extended the period of sensory acceptability of cooked turkey, but even strict refrigeration did not prevent growth and toxigenesis by nonproteolytic C. botulinum. At all three storage temperatures, toxin detection preceded or coincided with development of sensory characteristics of spoilage, demonstrating the potential for consumption of toxic product when spoilage-signaling sensory cues are absent.

Animals↗
PubMed2002

The effect of modified atmospheres and packaging on patulin production in apples.

This study was undertaken to determine the effectiveness of modified atmospheres and packaging materials on the growth of Penicillium expansum and patulin production in apples. Granny Smith apples were surface sterilized with 76% ethanol and inoculated with 0.1 ml of a 1.1 x 10(7) spore/ml P. expansum spore suspension. The apples were packaged either in polyethylene (PE) or polypropylene (PP) and treated with three different gas combinations, viz., 58% CO2/42% N2, 48% CO2/52% N2, and 88% CO2/12% N2, and were then incubated for 14 days at 25 degrees C. Fungal growth was monitored every 2 to 4 days by measuring radial growth from the point of inoculation. After the 14th day, apples were pulped, and patulin was extracted, purified, and quantified by high-performance liquid chromatography. PP did not inhibit fungal growth in any of the atmospheres tested, and it only inhibited patulin production in atmospheric gas and 58% CO2/42% N2. PE was very effective and inhibited fungal growth by four- or fivefold, depending on the modified atmosphere. Patulin production in PE-packaged apples was almost completely inhibited by all three gas combinations. Gas chromatographic analysis of the PE-packaged samples before and after the incubation period showed that CO2 levels dropped and N2 levels increased for all of the atmospheres tested. Our studies showed conclusively that PE is an excellent packaging material for the storage of apples since it inhibited the growth of P. expansum, thereby allowing <3.2 microg/ml of patulin to be produced, regardless of gaseous environment.

Carbon Dioxide↗
PubMed2006

Influence of antimicrobial compounds and modified atmosphere packaging on radiation sensitivity of Listeria monocytogenes present in ready-to-use carrots (Daucus carota).

Radiosensitization of Listeria monocytogenes was determined in the presence of trans-cinnamaldehyde, Spanish oregano, winter savory, and Chinese cinnamon on peeled minicarrots packed under air or under a modified atmosphere (60% O2, 30% CO2, and 10% N2). Samples were inoculated with L. monocytogenes HPB 2812 serovar 1/2a (106 CFU/g) and were coated separately with each active compound (0.5%, wt/wt) before being packaged under air or the modified atmosphere and irradiated at doses from 0.07 to 2.4 kGy. Results indicated that the bacterium was more resistant to irradiation under air in the absence of active compound. The dose required to reduce L. monocytogenes population by 1 log CFU (D10) was 0.36 kGy for samples packed under air and 0.17 kGy for those packed under the modified atmosphere. The active compounds evaluated in this study had an effect on the radiation sensitivity of L. monocytogenes on carrots. The most efficient compound was trans-cinnamaldehyde, where a mean 3.8-fold increase in relative radiation sensitivity was observed for both atmospheres compared with the control. The addition of winter savory and Chinese cinnamon produced a similar increase in relative radiation sensitivity but only when samples where packed under modified atmosphere conditions.

Anti-Bacterial Agents↗
PubMed2006

Active packaging of cheese with allyl isothiocyanate, an alternative to modified atmosphere packaging.

The natural antimicrobial compound allyl isothiocyanate (AITC), found in mustard oil, is effective against cheese-related fungi both on laboratory media and cheese. Penicillium commune, Penicillium roqueforti, and Aspergillus flavus were more sensitive to AITC when it was added just after the spores had completed 100% germination and branching had started on Czapek yeast extract agar than were spores in the dormant phase. The use of 1 AITC label (Wasaouro interior labels, LD30D, 20 by 20 mm) in combination with atmospheric air in the packaging extended the shelf life of Danish Danbo cheese from 4 1/2 to 13 weeks. Two AITC labels extended the shelf life from 4 1/2 to 28 weeks. Both 1 and 2 labels in combination with modified atmosphere packaging extended the shelf life of the cheese from 18 to 28 weeks. This study showed that AITC was absorbed in the cheese, but it was not possible to detect any volatile breakdown products from AITC in the cheese. Cheese stored for up to 12 weeks with an AITC label had an unacceptable mustard flavor. The mustard flavor decreased to an acceptable level between weeks 12 and 28. Cheese stored in atmospheric air had a fresher taste without a CO2 off-flavor than did cheese stored in modified atmosphere packaging. AITC may be a good alternative to modified atmosphere packaging for cheese. The extended shelf life of cheese in the package is very desirable: the cheese can be transported longer distances, and the packaging can be used for the final maturing of the cheese. Furthermore, AITC can address problems such as pinholes and leaking seals in cheese packaging.

Cheese↗
PubMed2005

[Trends and variation of CFC-11 in the atmosphere of Beijing].

In recent years, concentration of CFC in the atmosphere has undergone rapid changes especially in association with human activities. For the influence of CFC on climate changes and environment changes, the concentration of atmospheric CFC-11 in Beijing is continuously observed and analyzed by a gas chromatography-mass spectrometry. The seasonal variation concentration and trends of CFC-11 are reported. The results show that the seasonal variation of CFC-11 was basically similar from 1999 to 2003. There was one peak value in the seasonal variation of CFC-11 in 1999-2003. The highest monthly average concentration of CFC-11 was 1149.5 +/- 531.9 x 10(12) ( V x V(-1)) in summer and the lowest monthly average concentration of CFC-11 was 487.5 +/- 131.5 x 10(-12) (V x V(-1)) in spring. The annual average concentration of CFC-11 was increasing in Beijing atmosphere from 1995 to 1998, and the average increasing ratio was 17.9%. The annual average concentration of CFC-11 was slowly decreasing from 1999, and the average decreasing ratio was 10.7%. The average concentration of CFC-11 in the atmosphere of Beijing was 3 to approximately 5 times of the average concentration of CFC-11 in the atmosphere of Mauna Loa Station of U.S.A.

Air Movements↗
PubMedDate not supplied

[Collective exposure to secondary pollutants. Origin, chemistry, environmental cycles, impact on urban and rural atmospheric contamination, criteria for prevention].

Consequently to a bibliographic review, the Authors confirm that aliphatic aldehydes are ubiquitous constituents of rural and urban atmospheres and that they are certainly important by-products in many kind of antropogenic combustions (primary sources) as well as important intermediates in a wide variety of tropospheric chemical processes (secondary sources). The results of the monitoring of atmospheric aliphatic aldehydes in Turin city (north western Italy), during one year, are reported. The dynamic presence and concentration of aldehydes (mainly formaldehyde and acetaldehyde) is always limited below 100 ppb, however variable in the time. The results of our work point out the main role of photochemical processes during the summer, since the summer data well correlate with solar irradiation, ground temperature and relative humidity. During the winterthough it has not been possible to compare our data with other atmospheric pollutant (CO; NMHC), it is presumable a major role of primary sources in generating the atmospheric aldehydes. Without forgetting the irritant, mutagenic and cancerogenic properties of some aldehydes, we can assume that the next qualitative gasoline modification in 1991, according to the E.E.C. directive (8/5210/E.E.C. 20/3/1985), could cause an atmospheric aldehyde increase followed by a human risk increase.

Air Pollutants↗
PubMed1981

Effects of atmospheric ammonia on young pigs experimentally infected with Bordetella bronchiseptica.

Effects of atmospheric ammonia on performance and respiratory tract health of young pigs experimentally infected with Bordetella bronchiseptica were studied. Treatments were: (1) control, (2) Bordetella inoculation (approx 10(9) bacteria/naris) alone, (3) Bordetella inoculation plus exposure to atmospheric ammonia at 34.7 mg/m3 (50 ppm), and (4) Bordetella inoculation plus exposure to atmospheric ammonia at 69.4 mg/m3 (100 ppm). Pigs weighted 8.01 kg (av) at start of treatment. Body weight and feed disappearance were measured weekly. After 4 weeks, all pigs were killed and examined grossly, and appropriate specimens were obtained for histopathologic examination. Regression models were fitted to growth, feed disappearance, and gain-to-feed data. The growth model indicated that Bordetella-inoculated pigs gained 26% less body weight than did controls, regardless of atmospheric ammonia concentration. Bordetella inoculation, regardless of ammonia exposure, reduced feed disappearance 12% below the control rate. Treatment difference was not noted in gain/feed data. Shrunken turbinates were observed in Bordetella-inoculated pigs. Shrinkage also appeared to be related directly to ammonia concentration. Rhinitis was confirmed histopathologically, and its severity was related with atmospheric ammonia concentration, but no difference was seen in the osseous core of the turbinates.

Air Pollutants↗
PubMed1995

[Effectiveness of modified atmospheres against psychrotrophic pathogenic microorganisms in proteinaceous food].

Modified atmosphere packaging (MAP) of proteinaceous raw foods (meat, poultry and fish) extends their shelf-lives. It is well established that modified atmospheres (MA) inhibit the psychotropic aerobic Gram-negative bacteria, the main spoilage microflora of proteinaceous raw foods stored under refrigeration. Several researchers have warned about the possible growth of food poisoning microorganisms on them. Considering the minimal growth temperatures of pathogens, this review only deals with Aeromonas hydrophila, Clostridium botulinum, Listeria monocytogenes and Yersinia enterocolitica. C. botulinum produces its toxin in many different atmospheres, but it is unable to grow at temperatures below 3.3 degrees C, and its production rate of the toxin at temperatures below 4.5 degrees C is very low, to the extent that fish can be spoiled before the toxin is detected. Therefore, the control of the storage temperature of MAP fish seems to be indispensable to assure the absence of botulinal toxin. With regard to the other pathogens, vacuum is the atmosphere that may support more readily its growth; the higher the CO2 concentration in the atmosphere, the lower the growth rate is. Some investigations have shown that the growth rates of the psychotropic pathogens in MAP are lower than those of the spoilage flora. It has been shown also that A. hydrophila and L. monocytogenes growth rates are lower under MA than under aerobic storage. In relation to Y. enterocolitica, more investigations should be carried out in order to clear up its behaviour, because the available data in the literature are still confusing and sometimes even contradictory. In conclusion, there are no evidences that support the concern about MAP of proteinaceous raw foods representing a greater hazard than its conventional storage under air.

Cold Temperature↗
PubMed1997

HCN formation under electron impact: experimental studies and application to Neptune's atmosphere.

Laboratory experiments simulating organic synthesis in Neptune's atmosphere have been performed. We have submitted to a spark discharge gaseous mixtures containing 9 mbar of molecular nitrogen and 3 mbar of methane (the p(N2)/p(CH4) ratio is compatible with upper limits in Neptune's stratosphere) with varying quantities of molecular hydrogen. The spark discharge is used to model the energetic electrons produced by the impact of cosmic rays on the high atmosphere of Neptune. HCN is synthesized in the described experimental conditions, even with a low mixing ratio of molecular nitrogen. Studying the variation of HCN production with the initial composition of the gas mixture and extrapolating to high mixing ratio of molecular hydrogen allows to estimate HCN production in Neptune's atmosphere. The computed HCN production flux is 7x10(7) m-2 s-1, which is two orders of magnitude lower than the value predicted by chemical models for an internal source of N atoms. The major uncertainty in our extrapolation is the energetic distribution of electrons, implicitly assumed comparable in the discharge and in Neptune's atmosphere. We note that this distribution is also a source of uncertainty in chemical models. The chemical mechanism responsible for the local formation of HCN in the stratosphere probably occurs in the reactor too. We propose a simple characterization of the spark discharge. We thus link the molecular nitrogen dissociation cross section by electron impact to the measured parameters of the experiments (current, voltage, initial partial pressures) and to the resulting HCN partial pressures. However, other laboratory experiments with larger hydrogen pressures, requiring a more powerful electric source, have to be performed to yield a value of the cross section.

Atmosphere↗
PubMed1998

Chemical composition measurements of the atmosphere of Jupiter with the Galileo Probe mass spectrometer.

The Galileo Probe entered the atmosphere of Jupiter on December 7, 1995. Measurements of the chemical and isotopic composition of the Jovian atmosphere were obtained by the mass spectrometer during the descent over the 0.5 to 21 bar pressure region over a time period of approximately 1 hour. The sampling was either of atmospheric gases directly introduced into the ion source of the mass spectrometer through capillary leaks or of gas, which had been chemically processed to enhance the sensitivity of the measurement to trace species or noble gases. The analysis of this data set continues to be refined based on supporting laboratory studies on an engineering unit. The mixing ratios of the major constituents of the atmosphere hydrogen and helium have been determined as well as mixing ratios or upper limits for several less abundant species including: methane, water, ammonia, ethane, ethylene, propane, hydrogen sulfide, neon, argon, krypton, and xenon. Analysis also suggests the presence of trace levels of other 3 and 4 carbon hydrocarbons, or carbon and nitrogen containing species, phosphine, hydrogen chloride, and of benzene. The data set also allows upper limits to be set for many species of interest which were not detected. Isotope ratios were measured for 3He/4He, D/H, 13C/12C, 20Ne/22Ne, 38Ar/36Ar and for isotopes of both Kr and Xe.

Atmosphere↗
PubMed1999

A tenuous carbon dioxide atmosphere on Jupiter's moon Callisto.

An off-limb scan of Callisto was conducted by the Galileo near-infrared mapping spectrometer to search for a carbon dioxide atmosphere. Airglow in the carbon dioxide nu3 band was observed up to 100 kilometers above the surface and indicates the presence of a tenuous carbon dioxide atmosphere with surface pressure of 7.5 x 10(-12) bar and a temperature of about 150 kelvin, close to the surface temperature. A lifetime on the order of 4 years is suggested, based on photoionization and magnetospheric sweeping. Either the atmosphere is transient and was formed recently or some process is currently supplying carbon dioxide to the atmosphere.

Atmosphere↗