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PubMed2005

[Effects of soil temperature and humidity on soil respiration rate under Pinus sylvestriformis forest].

Employing root-wrenching method and LI-6400-09 soil respiration chamber, this paper measured the diurnal changes of soil respiration rate with and without roots in situ on June 17, August 5, and October 10, 2003. The seasonal changes of soil respiration were also measured from May to September, 2004. The results showed that both the total and the root-wrenched soil respiration appeared single diurnal pattern, with the peaks presented during 12:00-14:00. The diurnal fluctuation of soil respiration on August 5 was smaller than that on June 17 and October 10. There were also obvious seasonal changes in total and root-wrenched soil respiration, as well as in root respiration, which were higher from June to August but lower in May and September. The average total soil respiration, root-wrenched soil respiration, and root respiration were 3.12, 1.94 and 1.18 micromol CO2 x m(-2) s(-1), respectively, and the contribution of roots to total soil respiration ranged from 26.5% to 52.6% from May to September, 2004. There were exponential correlations between respiration rate and soil temperature, and linear correlations between respiration rate and soil humidity. The Q10 values were 2.44, 2.55 and 2.27 for total soil respiration, root-wrenched soil respiration, and root respiration, respectively. The effect of soil temperature on root-wrenched soil respiration was lager than that on total soil respiration and root respiration. Soil humidity had a larger effect on total soil respiration than on root respiration and root-wrenched soil respiration.

China↗

PubMedDate not supplied

Volumetric polymerization shrinkage of resin composites under simulated intraoral temperature and humidity conditions.

This study measured the volumetric shrinkage of resin composites polymerized under temperature and humidity conditions simulating the oral cavity and compared them to those occurring under ambient room conditions. Small, semispherical specimens of a microhybrid (Z100), microfill (Filtek A110) and flowable microhybrid (4 Seasons Flow) resin composite were manually formed and light activated for 40 seconds using a halogen light-curing unit (Spectrum Curing Light). The volumetric polymerization shrinkage of 10 specimens of each brand of resin composite was measured using a drop shape analysis unit (Drop Shape Analysis System, model DSA10 Mk2) under each of two temperature/relative humidity conditions: room conditions (22 +/- 2 degrees C and 60 +/- 5%) and those simulating intraoral conditions (35 degrees C and 92 +/- 5%). Mean volumetric shrinkage values were calculated for each resin composite and the data were analyzed using two-way analysis of variance and t-test (a=0.05) to determine if significant differences existed between the amount of volumetric polymerization shrinkage that occurred under ambient room conditions and that which occurred under simulated intraoral conditions. Mean volumetric shrinkage values measured for the resin composites were: 2.26 +/- 0.04% (ambient) and 2.61 +/- 0.04% (intraoral) for Z100; 1.96 +/- 0.04% (ambient) and 2.28 +/- 0.04% (intraoral) for Filtek A110 and 4.53 +/- 0.06% (ambient) and 5.34 +/- 0.05% (intraoral) for 4 Seasons Flow. For each resin composite, statistical analysis indicated that the amount of volumetric shrinkage measured under simulated intraoral conditions was significantly greater than what was measured under ambient room conditions (p<0.0001).

Body Temperature↗

PubMedDate not supplied

The effect of humidity on the oviposition and larval mortality of Haemaphysalis leporispalustris (Packard, 1869) (Acari: Ixodidae) under laboratory conditions.

Oviposition, reproductive and nutritional efficiency indices (REI and NEI), eclosion and larvae mortality of Haemaphysalis leporispalustris were studied under controlled conditions, inside desiccators, at constant temperatures of 25+/-1 degrees C and relative humidity (RH) levels adjusted at 30, 50, 70 and 95%. Fourth generation tick specimens, originated from a colony fed on rabbits (Oryctolagus cuniculus), were used. The experiment was conducted between Jul/1999 and Jan/2001. The pre-oviposition and oviposition periods decreased and increased, respectively, according to the increase in RH. The egg mass weight, REI and NEI, increased according to the increase in RH. The females' residual weight, under high humidity levels, was probably small due to a better energetic use for egg production (51.77 +/- 11.06 mg at 95% RH). The incubation period was inversely proportional to RH increase (45.10+/- 2.47 days; 40.33+/- 1.45 days and 36.85+/- 0.37 days at 50% 70% and 95% RH, respectively). There was no eclosion at 30% RH. Period and percentage of eclosion were directly proportional to the increase of the other RH levels. A diminished formation of embryonic points as well as the desiccation of the already formed eggs were observed. Larval longevity was negatively influenced by 50% RH, with death occurring concomitant to eclosion.

Animals↗

PubMed1991

[The effect of temperature and relative humidity on survival of eggs of the cestode, Monieza expansa (Rudolphi, 1810)].

The survival of Moniezia expansa eggs in the droppings of lambs was investigated at various temperatures in laboratory conditions and on test plots outdoors. The optimum temperature of the livability of M. expansa eggs in laboratory conditions is 5 degrees C; at this temperature 10% of oncospheres survived after 161 days. At the temperatures of 10, 25, 35 degrees C the oncospheres survived 105, 28, 46 days respectively, at -12 degrees C it was 28 days. It was for 21 and 35 days that on the test grassy plots the eggs of M. expansa survived in the droppings of lambs in the summer months of July and August at the average air temperatures of 15.7-18.2 degrees C and relative humidity of 67.7-74.3%. In autumn in September and October, at the average temperatures of 5.8-14.6 degrees C and relative humidity of 65.3-76.7% the oncospheres survived for 49 to 91 days. The M. expansa eggs in the droppings of lambs were able to survive on the test plot. The living oncospheres were demonstrated for 119 days from November 1987 to March 1988, and for 175 days till May by means of experimental infection of intermediate hosts.

Animals↗

PubMed1990

[Effect of temperature and humidity on the frequency of pityriasis versicolor. Epidemiological study in the state of Falcón, Venezuela].

The survey covers 1546 people from three towns of Falcón, which present different climatological characteristics. The diagnostic of P.V. was confirmed through microscopic observation. It is demonstrated a notable increase of the frequency of P.V. during and after the puberty. Significative differences were found between the frequencies of P.V. in the semiarid zone (9%) and the sub-humid zone (12%). The lowest frequency (4%) corresponds to the temperate climate of La Sierra de Falcón. The study shows, for the first time, that a hot and humid climate favors the parasitism by Malassezia sp.

Adolescent↗

PubMed1990

Hygienic aspects of the use of pressed-wood products in residential buildings. Part II. The effect of environmental conditions (temperature and relative humidity) on formaldehyde emission from particleboards.

The effect of air temperature (25-45 degrees C) and relative humidity (45-85%) upon formaldehyde emission from particleboards produced in three different plants was examined. The plates measuring 40 mm x 100 mm were kept in the climatic chamber in dynamic conditions (1 air exchange per hour) loading factor 1 m2/m3. Air samples from the chamber were collected for 4 subsequent days. A considerable effect of temperature and relative humidity upon the increase of formaldehyde emission was found, especially at simultaneous action of these two factors. The effect of temperature "shock" was determined after a rapid elevation of the chamber temperature from 25 degrees up to 40 degrees C. Several days after the steady state had been established, the temperature was lowered again to 25 degrees C. The temperature "shock" did not change the stable emission rate of CH2O from materials tested.

Air Pollution, Indoor↗

PubMed1987

Effect of temperature and relative humidity on the life cycle of Ornithodoros (Pavlovskyella) erraticus (Ixodoidea: Argasidae).

The effect of different temperatures (18, 22, 28, and 32.5 C, at constant 75% RH) and relative humidities (0, 15, 42, 60, 75, 84, and 92%, at constant 28 C) on the duration of the life cycle of Ornithodoros (Pavlovskyella) erraticus is studied in the laboratory. The egg incubation period is longer at 22 C than at the other temperatures tested; the percentage of hatched eggs was markedly increased at 28 C in comparison with other temperatures (T's) and relative humidities (RH's) tested. At constant 28 C, most larvae (86.2%) are ready to feed within 7.2 days posthatching; they feed for 5-52 min and molt to N1 in 7.8 days postfeeding. Five nymphal instars are recorded. Unfed N1-N5 survived for a longer period at 18 C than at other temperatures, whereas the effect of RH's was insignificant. After feeding, nymphal premolting periods differ from one instar to another and from one T or RH to another. At 28 C, the males emerge from N3, N4, and N5 in 9-15 days postfeeding, while females emerge only from N4 and N5 in 10-16 days. The overall sex ratio (3 male:5 female) is not affected by different T's and RH's. The female and male life spans were longer (means 720 and 500 days, respectively) at 22 C than at other T's and RH's. This study shows that the duration of the life cycle of O. erraticus decreases with rising T and increases with an increase in RH. However, the 28 C and 75% RH seem to be the optimum conditions for this species.

Animals↗

PubMedDate not supplied

[Importance of the relative humidity values in determining thermohygrometric comfort].

A condition of discomfort with specific symptoms, such as throat dryness, eye irritation, in a group of workers of a small, air conditioned, working department, is described. Neither the measurements of the possible environmental pollutants concentrations, nor the assessment of the usually adopted comfort indexes (PMV-PPD) justified the worker's symptoms. They completely disappeared by means of appropriate environmental improvements aiming to increase the relative humidity values from 29% to 50-55% (drop of the amount of the hygroscopic material stored, setting up of an humidifier). The effects of the low humidity values on the hygrometric and thermal comfort are finally discussed.

Air Pollutants, Occupational↗

PubMed1984

Effect of relative humidity on drug release from phenytoin sodium tablets and capsules. Part 1: Commercial preparations.

In this study the release rate of the active substance from different lots of commercial tablets and capsules of phenytoin sodium kept in different relative humidities (56, 75, 95%) was studied. It was observed that in both tablets and capsules, the effect of relative humidity and ageing was evident on the in vitro dissolution rate when compared with the in vitro dissolution profiles obtained before storage. The release rate differed from one lot to another after storage, the lots with higher release rates before storage in general showing a decrease and the ones with lower dissolution rates showing a higher release rate after storage.

Capsules↗

PubMed1984

Relationships between counts of nasopharyngeal bacteria, temperature, humidity and lung lesions in veal calves.

Nasopharyngeal swabs were taken from four groups of veal calves at intervals throughout their growth and the aerobic bacteria cultivated from the swabs counted. The calves were kept under three different husbandry systems; naturally ventilated straw-yards, fan-ventilated crates and crates with a controlled climate. The numbers of bacteria isolated varied in a complex manner; however, in one group of calves a significant proportion (P less than 0.01) of the variation in weekly bacterial counts was associated with the changes in vapour pressure and temperature which took place between two and four days previously. In calves kept at a constant temperature of 16 degrees C, the bacterial populations in the nasopharynx were at a minimum between 65 and 75 per cent relative humidity and tended to rise at humidities outside this range. There was a temporal relationship between nasopharyngeal bacteria and lung lesions. In three groups the numbers of bacteria in calves at nine weeks old were positively correlated (P less than 0.05) with lung damage observable at 16 to 18 weeks old.

Animals↗

PubMed1984

Direct evidence for a bimorphic structure of a DNA-RNA hybrid, poly(rA).poly(dT), at high relative humidity.

31P solid state nuclear magnetic resonances of highly oriented poly(rA).poly(dT) fibers demonstrated that this hybrid undergoes a conformational transition induced by hydration at about 90% relative humidity, namely, the hybrid has a single backbone conformation of the A family below 87% and two distinct conformations above 92% relative humidity. The structural model (of the B-like form) proposed on the basis of the x-ray diffraction data of this hybrid by Zimmerman and Pheiffer (Zimmerman, S.B., and Pheiffer, B.H. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 78-82) was proved to be fully consistent with our NMR data.

DNA↗

PubMedDate not supplied

[Effect of plant illumination and humidity on nitrogen fixation in the phyllosphere].

The object of this work was to study the effect of illumination and humidity of air on the activity of nitorgenase in epiphytic microorganisms from the phyllosphere of timothy. An increase in humidity and illumination stimulated nitrogen fixation, apparently due to a higher rate of photosynthesis in the plants and of transport of the leaf excretion products.

Humidity↗

PubMed1980

[Analysis of the potential for restoring E. coli cells, aerosolized in 30% relative humidity, by systems that repair UV damage].

The mutants, defective due to a complex of damages caused by UV radiation, are considerably more sensitive to aerosol dispersal under conditions of 30% relative humidity than their parent strains. The sensitivity of bacteria to dispersal by aerosol, equally increasing in case of mutations in any of the tested reparative genes, is not linked with their incapability to repair DNA damages, but should be rather considered as a pleiotropic effect. Strains E. coli K12 are somewhat more sensitive to aerosol dispersal than E. coli B when sprayed on fiberglass under conditions of 30% relative humidity.

Aerosols↗

PubMed1981

[Process of sodium fusidate inactivation as affected by oxygen and humidity].

The effect of oxygen and moisture on stability of sodium fusidate was studied. It was shown that inactivation of the antibiotic in the atmosphere of oxygen was due to its oxidation in the preparations with low humidity levels. In the preparations with high humidity levels, the main cause of the antibiotic inactivation was hydrolysis with respect to C-16-O-acetyl group. When sodium fusidate was air stored, the salts of 24, 25-dioxy-and 24, 25-dioxy-11-monoketofusidic acids were identified among the products of its inactivation. The salts of 24,25-dioxy-11-monoketofusidic acid were also prepared by oxidation of fusidic acid with potassium permanganate in a weak alkaline medium. The possibility of using sodium sulfite and metabisulfite as stabilizers for th antibiotic storage was shown.

Drug Stability↗

PubMed1980

Wheelchair cushion effect on skin temperature, heat flux, and relative humidity.

For patients subject to decubitus ulcers, wheelchair cushions should be prescribed with knowledge of the cushion's effect on the thermal as well as mechanical environment of the skin. To define thermal effects that may be encountered during routine use, tests werr made on 24 commercially available cushions. Skin temperature, heat flux and relative humidity were measured under the ischial tuberosities of a normal 24-year-old man during a 1-hour period of sitting on each cushion. After 1 hour, skin temperatures increased by means of 3.4 C and 2.8 C on foams and viscoelastic foams and there were slight decreases in heat flux as compared with control values in air. On gels, skin temperatures remained constant and heat flux increased, while water "floatation" pads caused a mean skin temperature decreased of 2.7 C along with a marked increase in heat flux. Relative humidity at the skin cushion interface increased by 10.4%, 22.8% and 19.8% on foams, gels and water floatation pads, as compared with room air values. Representative cushions from each of the general types (foam, viscoelastic foam, gel and water floatation) also were subjected to 2-hour tests which indicated the measured parameters continued to change asymptotically.

Adult↗

PubMed1995

Effect of temperature and humidity on egg hatch, moulting and longevity of larvae and nymphs of Dermacentor reticulatus (Ixodidae).

Larvae of Dermacentor reticulatus hatched at a temperature range of 20-34 degrees C, but a high egg hatch success of > 90% was only achieved at 20 degrees C and 27 degrees C and 100% r.h. The developmental capability of the eggs at low or freezing temperatures persisted up to 3 weeks at -10 degrees C and up to 8 weeks at 5 degrees C. The 50% mortality period of unfed larvae and nymphs increased with rising humidity and was longest at 5 degrees C and 100% r.h., amounting to 83.5 days for larvae and 108 days for nymphs. Engorged larvae and nymphs only moulted in the temperature range of 10-27 degrees C. The percent moulting success was low at 10 degrees C and increased with rising ambient humidity at 20 degrees C and 27 degrees C reaching more than 90% at 100% r.h. After incubation at low or freezing temperatures and subsequent transfer to 20 degrees C and 100% r.h. engorged larvae did not moult after exposure to -10 degrees C, but they tolerated 0 degrees C and 5 degrees C up to 3 and 10 weeks, respectively, and developed into nymphs. Engorged nymphs moulted into adults even after preceding incubation at -10 degrees C, their metamorphosis capability persisted for a maximum of 4 and 17 weeks at 0 degrees C and 5 degrees C, respectively.

Animals↗

PubMed1975

[Glass fibre HEPA filters. I. Communication: Microbiological and physico-chemical researchs on used and unused, hydrophobic and hydrophilic filter materials at relative humidities up to 98% in the climatic test chamber (author's transl)].

1. At high humidities up to 98%, an increase in bacteria cannot be detected. This applies to all HEPA filters investigated from the various manufacturers, independent of whether they are hydrophilic or hydrophobic, used or unused. 2. Fungal growth can only be obtained when large amounts of nutrient material (e.g. bacterial cultures) are present. In these cases a streaky growth appears . Under normal conditions of use, however, such intense contamination is not to be expected because of the prefiltration. Penetration only occurs with fungi. 3. Limitation of supply air humidity to 90% or less seems therefore to be unjustified on the basis of these investigations, if prefiltration and a satisfactory intermixing section can be guaranteed technically, and condensation is avoided. 4. HEPA filters of Grade S from various manufacturers and with different behaviour with respect to water do not allow bacterial growth even in the presence of nutrients. Additional measures for the killing of bacteria are therefore not considered necessary.

Air Conditioning↗

PubMed1994

[Occurrence of housedust mites in dwellings. Relation to ventilation and humidity].

The concentration of house-dust mites (Der. spp.) was investigated in 96 Danish dwellings and bedroom air-exchange rates, humidity and temperature was measured contemporaneously in all the dwellings. A positive correlation was found between indoor air humidity and mite concentration, and an inverse correlation was found between house-dust mite concentration and indoor air-exchange. Dwellings of mite-allergic persons had a higher concentration of house-dust mites compared with those of the non-mite-allergic group. House-dust mite concentration was above the proposed limit in 76% of the homes of mite allergic persons and in 48% of the homes of non-sensitive persons. The high proportion of dwellings infested with house-dust mites, when compared with previous measurements, suggests an increased prevalence of house-dust mites in Danish dwellings. The results support the concept that reduced ventilation in dwellings involves a risk of increased house-dust mite exposure.

Air Pollution, Indoor↗