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PubMed2005

Reevaluation of the quondam dust trend in the middle atmosphere.

Quondam lunar eclipse photometry data offered valuable information on the optical properties of the middle atmosphere, including dust particles. However, in comparison with nonspherical grains, the simple model of spherical particles has a different effect on solar radiation penetrating horizontally through the atmosphere. It is shown that the systems, in which the smallest size fraction of dust particles dominates, reduce irradiation of the Earth's shadow more efficiently if the grains are of irregular shape. In contrast, the populations contaminated by a certain amount of large particles cause an opposite effect. Depending on the actual form of the size distribution function of the irregular grains, the irradiance within the center of the Earth's shadow may change by 2 orders of magnitude in the visible spectrum. It is therefore evident that dust properties retrieved in the past are eligible candidates for reevaluation to correct a view on the dust trend in the middle atmosphere. Sample calculations are presented for the lunar eclipse observed on 19 January 1954.

Journal Article↗

PubMed2006

Analytical solution of radiative transfer in the coupled atmosphere-ocean system with a rough surface.

Using the computationally efficient discrete-ordinate method, we present an analytical solution for radiative transfer in the coupled atmosphere-ocean system with a rough air-water interface. The theoretical formulations of the radiative transfer equation and solution are described. The effects of surface roughness on the radiation field in the atmosphere and ocean are studied and compared with satellite and surface measurements. The results show that ocean surface roughness has significant effects on the upwelling radiation in the atmosphere and the downwelling radiation in the ocean. As wind speed increases, the angular domain of sunglint broadens, the surface albedo decreases, and the transmission to the ocean increases. The downward radiance field in the upper ocean is highly anisotropic, but this anisotropy decreases rapidly as surface wind increases and as ocean depth increases. The effects of surface roughness on radiation also depend greatly on both wavelength and angle of incidence (i.e., solar elevation); these effects are significantly smaller throughout the spectrum at high Sun. The model-observation discrepancies may indicate that the Cox-Munk surface roughness model is not sufficient for high wind conditions.

Journal Article↗

PubMed2006

Ultraviolet light propagation under low visibility atmospheric conditions and its application to aircraft landing aid.

Light scattering in the atmosphere by particles and molecules gives rise to an aureole surrounding the source image that tends to reduce the contrast of the source with respect to the background. However, UV scattering phase functions of the haze droplets present a very important forward peak. The spreading of a detected signal in the UV is not as important as in the case of a clear atmosphere where Rayleigh scattering predominates. This physical property has to be taken into account to evaluate the potential of UV radiation as an aircraft landing aid under low visibility conditions. Different results characterizing UV runway lights, simulations of UV radiation propagation in the atmosphere, and the use of a simple detection algorithm applied to one particular sensor are presented.

Journal Article↗

PubMed2000

Carboxyhemoglobin half-life in carbon monoxide-poisoned patients treated with 100% oxygen at atmospheric pressure.

STUDY OBJECTIVES: There are large reported differences for the carboxyhemoglobin (COHb) half-life (COHb t(1/2)) in humans breathing 100% atmospheric O(2) following CO inhalation in tightly controlled experiments compared to the COHb t(1/2) observed in clinical CO poisoning (range, 36 to 131 min, respectively). Other reports have suggested that the COHb t(1/2) may be affected by gender differences, age, and lung function. We wished to test the hypothesis that the COHb t(1/2) might also be influenced by CO poisoning vs experimental CO exposure, by a history of loss of consciousness (LOC), concurrent tobacco smoking, and by PaO(2). The purpose of the present study was to measure the COHb t(1/2) in a cohort of CO-poisoned patients and to determine if those listed factors influenced the COHb t(1/2). DESIGN: Retrospective chart review from 1985 to 1995. We calculated the COHb t(1/2) of CO-poisoned patients who were treated with high-flow supplemental atmospheric pressure O(2) delivered by nonrebreather face mask or endotracheal tube. SETTING: Hyperbaric medicine department of a tertiary-care teaching hospital. PATIENTS: Of 240 CO-poisoned patients, 93 had at least two COHb measurements > 2% (upper limit of normal) with recorded times of the measurements, permitting calculation of the COHb t(1/2). RESULTS: The COHb t(1/2) was 74 +/- 25 min (mean +/- 1 SD) with a range from 26 to 148 min. By stepwise multiple linear regression analysis, the PaO(2) influenced the COHb t(1/2) (R(2) = 0.19; p < 0.001), whereas the COHb t(1/2) was not influenced by gender, age, smoke inhalation, history of LOC, concurrent tobacco smoking, degree of initial metabolic acidosis (base excess), or initial COHb level. CONCLUSIONS: The COHb t(1/2) of 93 CO-poisoned patients treated with 100% O(2) at atmospheric pressure was 74 +/- 25 min, considerably shorter than the COHb t(1/2) reported in prior clinical reports (approximately 130 +/- 130 min) and was influenced only by the patient's PaO(2).

Adolescent↗

PubMed2004

Toxicity of ambient atmospheric particulate matter from the Lake Michigan (USA) airshed to aquatic organisms.

Short-term chronic and acute aquatic bioassays are valuable tools in screening a variety of environmental samples. However, only a limited number of studies have used these methods for testing the toxicity of atmospheric particulate matter samples. Previous studies have shown that compounds known to have adverse biological effects, such as polycyclic aromatic hydrocarbons, are deposited in significant quantities into Lake Michigan (USA); however, these compounds comprise a small portion of the total particulate matter deposition. In the present study, a method is described for using Ceriodaphnia dubia, Selenastrum capricornutum (green algae), and MitoScan bioassays to compare the toxicities of reconstituted hard freshwater and methylene chloride extracts of atmospheric particulate matter collected at three locations around the southern shore of Lake Michigan in August 2000. The locations include an urban/industrial site in Milwaukee (WI, USA), an urban-impacted/industrial site in Porter (IN, USA), and a rural site in Bridgman (MI, USA). The bulk chemistry, including organic and elemental carbon, sulfate, nitrate, ammonium, and chloride, shows regional similarities over the sampling event, but the toxicities vary spatially by site, by extraction solvent, and by bioassay. Thus, the bioassays are sufficiently sensitive to show differences in toxicity among the atmospheric particulate matter extracts and have significantly different responses to the samples to enable an initial comparison of toxicity from the different sites.

Air Pollutants↗

PubMed2006

Atmospheric dry deposition of trace metals in the coastal region of Los Angeles, California, U.S.A.

Emissions of trace metals to the atmosphere and subsequent deposition, either directly to a waterbody surface or indirectly to the watershed as washoff during rainfall, represents a potential source of contamination to surface waters near urban centers. The present study provides measurements of atmospheric concentrations of particle-bound trace metals, and it estimates the dry deposition mass loading of trace metals in coastal watersheds in the Los Angeles, California, USA, air basin. Coarse-particle atmospheric concentrations of metals were measured seasonally using a Noll Rotary Impactor at six urban sites and one nonurban site. Dry deposition fluxes were calculated by summing the product of air concentration and the theoretical deposition velocity for each particle size fraction. Mean fluxes at urban sites ranged from 3.2 to 9.1, 11 to 34, 3.8 to 8.8, 8.3 to 29, and 69 to 228 microg/m2/d for chromium, copper, nickel, lead, and zinc, respectively. Mean concentrations and fluxes were significantly higher at urban sites compared with the nonurban site, although differences between urban and nonurban sites were reduced when sampling took place within 5 d after rainfall. Dry deposition to watershed land surfaces was substantial, representing a potentially large source of trace metals based on comparisons with load estimates from stormwater runoff.

Air Pollutants↗

PubMed2004

Trends in atmospheric trace gas measurement instruments with membrane-based gas diffusion scrubbers.

A diffusion scrubber (DS) is an excellent tool for gas analysis, and there are many types of DS devices, varying both in structure and construction. In this paper, recent work on atmospheric trace gas measurements by means of DS devices are reviewed. Theoretical considerations on representative DSs are summarized first. Then, the characteristics of the key material, a gas-diffusion membrane, are discussed, and recent improvements and novel scrubbers for highly effective collection are outlined. A chromatograph is a suitable tool for the multi-gas analysis of collected species. On the other hand, solid-state fluorescence/absorbance detectors have been developed for the continuous measurement of target gases. The methods based on DS collection and subsequent detection have high sensitivities, and the detection limits can be in the low-pptv levels. Accordingly, they are capable of measuring background levels, and detecting very low levels of contaminants in a cleanroom. Miniaturized advanced DS units, perhaps the next generation of DS devices, are introduced at the end of this review. DS systems have contributed significantly to our knowledge of the atmospheric dynamics and atmospheric chemistry.

Journal Article↗

PubMedDate not supplied

Atmospheric methyl tertiary butyl ether (MTBE) at a rural mountain site in California.

Methyl tertiary butyl ether (MTBE) was measured in air samples collected at hourly intervals near Blodgett Forest Research Station on the western slope of the Sierra Nevada, California, in July 1997, October 1998, and June through September 1999. Mixing ratios ranged from below the detection limit (< approximately 0.01 ppbv) to 0.5 ppbv, but were generally less than 0.3 ppbv. At these mixing ratios partitioning of MTBE into surface waters would lead to MTBE concentrations of less than 0.2 microg L(-1). As expected, MTBE mixing ratios were highly correlated with other anthropogenically emitted hydrocarbons. Based on the observed diurnal cycle of MTBE and its ratio to 2-methyl-butane (isopentane), we estimated the average regional daytime oxidant concentration to be (9 to 13) x 10(6) OH radicals per cubic centimeter, consistent with our earlier estimates for this region. Furthermore, MTBE ratios to toluene, another ubiquitous anthropogenic hydrocarbon, were generally consistent with regional transport and dilution, as well as atmospheric oxidation. Exceptions, pertaining to MTBE mixing ratios below or close to the detection limit, were associated with the influence of marine air masses that did not experience anthropogenic hydrocarbon input from California. With all these constraints in place, evidence for an additional atmospheric loss process, such as nonreversible deposition of MTBE, could not be established, and we conclude that any deposition is slow compared with removal from the atmosphere by the OH radical.

Air Movements↗

PubMed2005

Beef quadriceps hot boning and modified-atmosphere packaging influence properties of injection-enhanced beef round muscles.

Two experiments were conducted to examine the effects of hot boning, modified atmosphere packaging, and injection enhancement on the oxidative and sensory properties of beef round muscles. The beef knuckle (quadriceps muscles) was partially hot boned within 1.5 h postmortem from one randomly selected side of each beef carcass (n = 14), whereas the quadriceps on the opposite side remained intact throughout a 48-h chilling period. At 5 d postmortem, biceps femoris, semimembranosus, vastus lateralis, and rectus femoris muscles from both hot- and cold-boned sides were injected with an enhancement solution consisting of water, salt, phosphate, and natural flavorings (rosemary) at either 6 (Exp. 1) or 10% (Exp. 2) of fresh muscle weight. Enhanced muscles were then processed into 2.54-cm-thick steaks, which were allotted randomly to high-oxygen (HiOx; 80% O2:20% CO2) or ultra-low oxygen (LoOx; 80% N2:20% CO2) modified atmosphere packaging. Regardless of hot boning or enhancement, steaks packaged in LoOx had lower thiobarbituric acid-reactive substances values (P < 0.05), more beef flavor intensity (P < 0.05), fewer off flavors (P < 0.05), and were more tender (P < 0.05) than steaks packaged in HiOx. Hot boning the knuckle had no effect on oxidative (P > or = 0.99) and sensory properties (P > or = 0.85). Increasing the level of injection enhancement from 6 to 10% introduced more rosemary and phosphate into the muscles, thereby decreasing the extent of oxidation, but also imparting a nontypical beef flavor. Packaging in LoOx atmosphere offered the optimal result of decreased oxidation and improved tenderness, without detriment to flavor. Injection enhancement (both 6 and 10%) created off-flavors attributable to the enhancement solution; however, the 10% injection seemed to offer more resistance to lipid oxidation.

Animals↗

PubMed1983

Ward atmosphere as a factor in irregular discharge from an alcohol rehabilitation unit.

A 20-bed alcohol rehabilitation unit with a high patient retention rate had the experience of a sudden increase in irregular discharges. Administration of the Ward Atmosphere Scale developed by Rudolph Moos showed a drop in various therapeutic aspects of the ward environment that paralleled the increase in irregular discharges. These results were discussed with staff, and soon after the number of irregular discharges diminished. The Ward Atmosphere Scale was readministered and showed a move toward a more therapeutic atmosphere. The reasons for these fluctuations are discussed.

Alcoholism↗

PubMed2000

Reduction of normal flora by irradiation and its effect on the ability of Listeria monocytogenes to multiply on ground turkey stored at 7 degrees C when packaged under a modified atmosphere.

Listeria monocytogenes did not multiply faster during storage at 7 degrees C on irradiated than on nonirradiated raw ground turkey, and there was a concentration-dependent inhibition of its multiplication by CO2. Ground turkey was gamma irradiated at 5 degrees C to 0, 1.5, and 2.5 kGy and inoculated (approximately 100 CFU/g) after irradiation with a cocktail of L. monocytogenes ATCC 7644, 15313, 49594, and 43256. The meat was then packaged in air-permeable pouches or under atmospheres containing 30 or 53% CO2, 19% O2, and 51 or 24% N2 and stored at 7 degrees C for up to 28 days. A dose of 2.5 kGy extended the time for the total plate count (TPC) to reach 10(7) CFU/g from 4 to 19 days compared to that for nonirradiated turkey in air-permeable pouches. Following a dose of 2.5 kGy at the end of the 28-day study, the TPCs were 10(6.42) and 10(4.98) under 25% and 50% CO2 atmospheres, respectively. Under air, 30% CO2, and 53% CO2 atmospheres, the populations of L. monocytogenes after 19 days incubation were 10(4.89), 10(3.60), and 10(2.67) CFU/g. The populations of lactic acid bacteria and anaerobic or facultative bacteria were also reduced by irradiation. Irradiating ground turkey did not decrease its safety when it was contaminated following processing with L. monocytogenes.

Air↗

PubMed2002

Growth and survival of Escherichia coli O157:H7 on fresh-cut apples in modified atmospheres at abusive temperatures.

The effects of reduced-O2 and elevated-CO2 modified atmospheres (MAs) and abusive temperatures on the growth and survival of E. coli O157:H7, yeast, and molds and on changes in the visual quality of fresh-cut apples were evaluated. High-CO1 and low-O2 (> or = 15% and < 1%, respectively) atmospheres inhibited the growth of the pathogen on apple slices at 15 and 20 degrees C. However, the population of the pathogen increased by 1 log cycle after 2 weeks of storage in air. The high-CO2 MA resulted in the inhibition of yeast and mold growth, less browning, and better visual quality than did air and ambient-CO2 atmospheres. The results of this study confirm that E. coli O157:H7 can grow on apple slices in air. These results also show that these organisms survive but are inhibited in MAs with high CO2 levels at abusive temperatures. An MA can increase the shelf life of fresh-cut apples by improving retention of visual quality and inhibiting yeast and molds. Thus, contamination of minimally processed apples with E. coli O157:H7 can be a safety issue for both air- and MA-packaged cut apples.

Carbon Dioxide↗

PubMed2003

Effect of modified atmosphere packaging and irradiation in combination on content of nitrosamines in cooked pork sausage.

The effect of modified atmosphere packaging and irradiation in combination on nitrosodimethylamine (NDMA) and nitrosopyrrolidine (NPYR) levels in pork sausage was studied. Emulsion-type cooked pork sausage was manufactured and packaged in aerobic, CO2 (100%), N2 (100%), and CO2/N2 (25%/75%) environments, respectively, and irradiated at 0, 5, 10, and 20 kGy with gamma irradiation. The nitrosamine contents were significantly reduced by irradiation, and the reduction of nitrosamines was more extensive with modified atmosphere packaging than with aerobic packaging. The correlation coefficient between irradiation dose and nitrosamine content indicated that irradiation can reduce the levels of nitrosamines. The combination of irradiation and modified atmosphere packaging is effective in enhancing the chemical safety of sausage by reducing nitrosamines, if present, as well as enhancing the microbial safety of cooked pork sausage.

Aerobiosis↗

PubMed1976

[Attempt to assess the effect of atmospheric pollution on human beings and experimental animals via biochemical indices].

Three biochemical methods--erythrocyte oxygen consumption, erythrocyte decarboxylation and oxygen consumption of tissue homogenates--to determine the influence of atmospheric pollution in populated communities are suggested. The first two methods which provide information on erythrocyte metabolism, employed both in humans and in animals experimented upon, adequately reflect the atmospheric pollution effect in four industrial areas, differing by the type and degree of pollution agents. Oxygen consumption in tissue homogenates of liver and kidney from experimental animals, raised in the same areas, exhibits an analogical correlation. The inference is reached that the degree of inhibition of the oxidation processes in the organism may be employed in atmospheric pollution effect assessment.

Adolescent↗

PubMedDate not supplied

Effect of pressurized atmosphere on void size and quantity in dental stone and fine-grained phosphate-bonded investment.

This study investigated the effect of pressurized atmosphere on the size and number of voids in dental stones and investments. Control specimens of casts and invested patterns were bench set. Experimental specimens of casts and invested patterns were allowed to set under pressure. The specimens were then sectioned and voids counted and measured to establish a mean. Increased atmospheric pressure reduced the size and number of voids. This method produces improved cast surfaces and fewer, smaller voids in investments. Technicians are continuously searching for ways to improve the quality of their products. One method is placing dental casts and dental investments under increased atmospheric pressure while setting. Several pressure vessels are available for this purpose.

Calcium Sulfate↗

PubMedDate not supplied

[Prospects for storing streptomycetes in atmospheres of various gases].

The possibility of Streptomyces cultures preservation in the atmosphere of argon, nitrogen, carbon dioxide and free air (the latter as a control) has been first studied. The possibility of short-term (4-6 months) preservation of Streptomyces cultures in the atmosphere of argon and nitrogen has been demonstrated. Some cultures could be preserved in the argon and nitrogen atmosphere for 26 years.

Culture Media↗

PubMedDate not supplied

Atmospheric input of organic pollutants to the Venice Lagoon.

The atmospheric deposition of dioxins and furans (PCDD-Fs), dioxin-like polychlorobyphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and hexachlorobenzene (HCB) was determined in the Lagoon of Venice. Sampling was carried out monthly, for a total of 13 months (July 1998-July 1999) using "bulk" samplers (passive collectors of wet and dry depositions) at four sites, inside the lagoon and close to its edge. Calculated PCDD-F loadings to the Lagoon turned out to be quite homogeneous, their range being approximately 10-20 ng m-2 y-1, whereas in the station located close to the industrial zone of Porto Marghera the value was approximately 50 ng m-2 y-1. PCB deposition in the industrial fallout sampling site and in the city centre of Venice was approximately 2500 ng m-2 y-1, that is, almost five times higher than the values measured at the northern and southern lagoon stations. HCB annual loading (approximately 8000 ng m-2 y-1) was almost six times higher in the industrial zone than in the other sites (approximately 1500 ng m-2 y-1). PAH loadings in the city centre of Venice and at Porto Marghera were 314 and 389 micrograms m-2 y-1, respectively. The amount of 2,3,7,8-TCDD equivalents (TEQ) of PCDD-Fs and PCBs in the Venice and Porto Marghera bulk depositions was compared with the guideline value of 15 pg m-2 d-1 for dioxins in depositions proposed by De Fré et al. (1998). Moreover, as some of the effects which drive the risk assessment of dioxin-like compounds were also observed after exposure to other molecules, the TEQs of PAHs and HCB were also calculated: nine out of 13 samples exceeded the guideline value. Lastly, an atmospheric emission source related to vinyl chloride monomer production, which may affect atmospheric deposition on the whole Lagoon, is reported in the industrial zone of Porto Marghera.

Air Movements↗

PubMed2001

Model calculating annual mean atmospheric dispersion factor for coastal site of nuclear power plant.

This paper describes an atmospheric dispersion field experiment performed on the coastal site of nuclear power plant in the east part of China during 1995 to 1996. The three-dimension joint frequency are obtained by hourly observation of wind and temperature on a 100 m high tower; the frequency of the "event day of land and sea breezes" are given by observation of surface wind and land and sea breezes; the diffusion parameters are got from measurements of turbulent and wind tunnel simulation test. A new model calculating the annual mean atmospheric dispersion factor for coastal site of nuclear power plant is developed and established. This model considers not only the effect from mixing release and mixed layer but also the effect from the internal boundary layer and variation of diffusion parameters due to the distance from coast. The comparison between results obtained by the new model and current model shows that the ratio of annual mean atmospheric dispersion factor gained by the new model and the current one is about 2.0.

Air Pollutants, Occupational↗