PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Humidity”

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

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

At least 1,225 records · Page 68Linked to original sources
PubMed2000

[Technical requirements for buying a heat and humidity exchanger for ventilation during anesthesia. French Society of Anesthesia and Intensive Care].

To prevent cross infection and to improve the management of anaesthetic circuits, the French society of anesthesia and intensive care recommended the use of heat and moisture exchange filter (HMEF). Buying a HMEF needs a procedure with different steps and a product request form must delineate precise needed requirements of the device. In the absence of standardized methods to assess filtration performance, required specifications are established from both manufacturer data and scientific published studies. Proposed purchasing method and criteria help the health care workers at the time of final decision for objective comparison between the different devices on the market.

Cross Infection↗
PubMed2001

Determination of 222Rn emanation fraction and diffusion coefficient in concrete using accumulation chambers and the influence of humidity and radium distribution.

In this paper we present a laboratory method for the determination of diffusion coefficient, D, as well as the 222Rn emanation fraction, f, in concrete core samples. It is based either on the analyses of the growth curves of the radon in the air volume surrounding a sample enclosed in an accumulation chamber (Lucas cell or RADIM device) or using the charcoal adsorption method. Samples used have a special geometry allowing the assumption of a one-dimensional diffusion of radon in material. Radium was enhanced in the concrete samples by adding radium bromide solution or uranium ore. A strong dependence of the emanation fraction on the enhancing method was observed. For the sample enhanced with uranium ore the specific exhalation rate was about ten times smaller. A marked dependence of radon exhalation on the water content was also observed.

Air Pollutants, Radioactive↗
PubMed1991

Survival of sheep and goat first stage protostrongylid larvae in experimental conditions: influence of humidity and temperature.

The survival of first-stage larvae of a laboratory strain of Muellerius capillaris and of a natural multispecific infection (Neostrongylus linearis, Cystocaulus nigrescens, Protostrongylus rufescens) was studied for 10 to 12 day periods. The survival was estimated either on larvae in faeces or kept in tap water. Temperature (-18 degrees C to 37 degrees C) and desiccation were the ecological factors investigated. M. capillaris was the most tolerant to these factors but showed better survival at 4 degrees C (and at -18 degrees C on one occasion). N. linearis survived better at 25 degrees C or -18 degrees C and C. nigrescens at 4 degrees C and -18 degrees C. Humidification of faeces was unfavourable to the latter species. All the species could stand desiccation of faeces up to 67% of dry-matter for M. capillaris or 82% for other species. Larval survival estimated for L1 in tap water was different from that estimated for larvae in faeces. The variation in resistance to unfavourable temperatures or moisture conditions may account partly for the geographical distribution of the species.

Animals↗
PubMed2001

Modeling the formation of secondary organic aerosol (SOA). 2. The predicted effects of relative humidity on aerosol formation in the alpha-pinene-, beta-pinene-, sabinene-, delta 3-carene-, and cyclohexene-ozone systems.

Atmospheric oxidation of volatile organic compounds can lead to the formation of secondary organic aerosol (SOA) through the gas/particle (G/P) partitioning of the oxidation products. Since water is ubiquitous in the atmosphere, the extent of the partitioning for any individual organic product depends not only on the amounts and properties of the partitioning organic compounds, but also on the amount of water present. Predicting the effects of water on the atmospheric G/P distributions of organic compounds is, therefore, central to understanding SOA formation. The goals of the current work are to gain understanding of how increases in RH affect (1) overall SOA yields, (2) water uptake by SOA, (3) the behaviors of individual oxidation products, and (4) the fundamental physical properties of the SOA phase that govern the G/P distribution of each of the oxidation products. Part 1 of this series considered SOA formation from five parent hydrocarbons in the absence of water. This paper predicts how adding RH to those systems uniformly increases both the amount of condensed organic mass and the amount of liquid water in the SOA phase. The presence of inorganic components is not considered. The effect of increasing RH is predicted to be stronger for SOA produced from cyclohexene as compared to SOA produced from four monoterpenes. This is likely a result of the greater general degree of oxidation (and hydrophilicity) of the cyclohexene products. Good agreement was obtained between predicted SOA yields and laboratory SOA yield data actually obtained in the presence of water. As RH increases, the compounds that play the largest roles in changing both the organic and water masses in the SOA phase are those with vapor pressures that are intermediate between those of essentially nonvolatile and highly volatile species. RH-driven changes in the compound-dependent G/P partitioning coefficient Kp result from changes in both the average molecular weight MWom of the absorbing organic/water phase, and the compound-dependent activity coefficient zeta values. Adding water to the SOA phase by increasing the RH drives down MWom and thereby uniformly favors SOA condensation. The effect of RH on zeta values is compound specific and depends on the hydrophilicity of the specific compound of interest; the more hydrophilic a compound, the more increasing RH will favor its condensation into the SOA phase. The results also indicate that it may be a useful first approximation to assume that zeta = 1 for many compounds making up SOA mixtures.

Aerosols↗
PubMed2005

Solar radiation, relative humidity, and soil water effects on metolachlor volatilization.

Pesticide volatilization is a significant loss pathway that may have unintended consequences in nontarget environments. Field-scale pesticide volatilization involves the interaction of a number of complex variables. There is a need to acquire pesticide volatilization fluxes from a location where several of these variables can be held constant. Accordingly, soil properties, tillage practices, surface residue management, and pesticide formulations were held constant while fundamental information regarding metolachlor volatilization (a pre-emergent pesticide) was monitored over a five-year period as influenced by meteorological variables and soil water content. Metolachlor vapor concentrations were measured continuously for 120 h after each application using polyurethane foam plugs in a logarithmic profile above the soil surface. A flux gradient technique was used to compute volatilization fluxes from metolachlor concentration profiles and turbulent fluxes of heat and water vapor (as determined from eddy covariance measurements). Differences in meteorological conditions and surface soil water contents resulted in variability of the volatilization losses over the years studied. The peak volatilization losses for each year occurred during the first 24 h after application with a maximum flux rate in 2001 (1500 ng m(-2) s(-1)) associated with wet surface soil conditions combined with warm temperatures. The cumulative volatilization losses for the 120-hour period following metolachlor application varied over the years from 5 to 25% of the applied active ingredient, with approximately 87% of the losses occurring during the first 72 h. In all of the years studied, volatilization occurred diurnally and accounted for between 43 and 86% during the day and 14 and 57% during the night of the total measured loss. The results suggest that metolachlor volatilization is influenced by multiple factors involving meteorological, surface soil, and chemical factors.

Acetamides↗
PubMed2003

Nutritional characteristics of the leaves of native plants growing in adverse soils of humid tropical lowlands.

Acid sulfate, peat, sandy podzolic, and saline soils are widely distributed in the lowlands of Thailand and Malaysia. The nutrient concentrations in the leaves of plants grown in these type of soils were studied with the aim of developing a nutritional strategy for adapting to such problem soils. In sago and oil palms that were well-adapted to peat soil, the N, P, and K concentrations were the same in the mature leaves, while the Ca, Mg, Na, and Fe concentrations were higher in the mature leaves of the oil palm than of the sago palm. Melastoma malabathricum and Melaleuca cajuputi plants that were well-adapted to low pH soils, peat. and acid sulfate soils were also studied. It was observed that a high amount of Al accumulated in the M. marabathricum leaves, while Al did not accumulate in M. cajuputi leaves. M. cajuputi plants accumulated large amounts of Na in their leaves or stems regardless of the exchangeable Na concentration in the soil, while M. malabathricum that was growing in saline-affected soils excluded Na. Positive relationships between macronutrients were recognized between P and N, between K and N, and between P and K. Al showed antagonistic relationships with P, K, Ca, Mg, Fe, Zn, Cu, and Na. Na also showed antagonistic relationships with P, K, Zn, Mn, Cu, and Al. Fe showed weak antagonistic relationships with Zn, Mn, Cu, and Al.

Aluminum↗