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The effect of relative humidity and temperature on the survival of bovine rotavirus in airborne particles was investigated. Bovine rotavirus was found to be stable at low and high relative humidity; infectivity was lost more rapidly at high temperature than at lower temperature.
Tsetse flies are positively phototactic below about 30 degree C and negatively phototactic above it. The flies show a preference for the wet end of a humidity gradient and the bright end of a dorsal light intensity gradient. Studies of activity levels indicate that tsetse flies should aggregate in damp situations where the activity levels is minimal, whereas in practice the flies are distributed throughout the whole of gradient. Analyses of the water and fat content of experimental flies indicates that the reactions of individual flies is determined by their physiological condition and the conditions under which the flies have previously been kept. Previous ecological studies on the reactions of flies to humidity and light stimuli need to be reassessed in the light of these findings.
The eggs and larvae are affected by the changes in the humidity level around them. The eggs do not develop below 87% relative humidity at 30 degrees C and 25 degrees C. At sub-developmental rel. hum. they remain viable for 30 h at 81%, but at 73% rel. hum. level they do not survive beyond 18 h. Survival of larvae in 100% rel. hum. is longer at 30 degrees C than at 25 degrees C and 35 degrees C, and also they exhibit a poor resistance to desiccation.
A hot and humid environment can be detrimental to race performance. Caffeine, on the other hand, has been shown to be an ergogenic aid for improving endurance performance. To examine the influence of caffeine ingestion on race performance during high heat stress, seven endurance trained competitive road racers aged between 23 and 51 years (five men, two women) performed three maximal effort 21-km road races outdoors in hot and humid conditions. The caffeine dose, randomly assigned in a double-blind fashion, consisted of either 0, 5, or 9 mg.kg-1 body mass. During each run, the subjects were allowed to drink water ad libitum at each 5-km point. Blood samples were obtained immediately before and after each run and analysed for changes in concentrations of Na+, K+, glucose, lactate, and hematocrit. Pre and postrun data were also collected for body mass and tympanic membrane temperature. Race times were not significantly different among the races or caffeine doses, with the average times within 1.1% of each other. In addition, none of the other variables measured varied significantly among the races or caffeine doses. In summary, caffeine intake did not affect race performance. Therefore it was concluded from our study that caffeine is not of ergogenic benefit in endurance races during high heat stress.
A new model system was developed for the study of autoxidation of thin films of neat lipid and the effect of relative humidity on the oxidation reaction. In the model system, the surface-to-volume ratio of lipid was large and measureable, and the relative humidity (RH) and oxygen partial pressure were controlled. Methyl linoleate, oxidized at six different RH as a thin film in an atmosphere of pure oxygen, exhibited a maximum rate of oxidation at 32% RH and minimum rates at 0% and 100% RH. The rates of oxygen uptake, determined manometrically, were linear and reproducible at all six RH. The maximum rate at 32% RH was attributed to solvation and stabilization of the propagation transition state by water. Increasing the RH beyond 32% resulted in solvation of the peroxy radical, sterically hindering the radical from entering the propagation transition state.
Thirty-two Polwarth ewes, of ages up to 1 year, were observed in a climatic chamber (24 to 45 degrees C) for eight periods of 5 h each. The observations were made through a window in the chamber wall. All animals were observed four times, then shorn and observed four times again. The animals were given weighed quantities of water and feed consisting of commercial concentrate plus Rhodes grass (Chloris gayana) hay. The water and feed remaining after 5 h of observation were weighed. The following traits were analysed: time eating hay (TEH), time eating concentrate (TEC), time drinking water (TDW), weight of hay eaten (WHE), weight of concentrate eaten (WCE), volume of ingested water (VIW), ruminating time standing up (RTS), ruminating time lying down (RTL), idling time standing up (ITS), and idling time lying down (ITL). Shearing had a significant effect for all traits except ITS. Shearing resulted in higher values for all traits except for ITS and ITL. Ingestion of hay (TEH and WHE) decreased with increased air temperature and humidity, while the ingestion of concentrate (TEC) and WHE) and water (TDW and VIW) increased. Rumination decreased with increased air temperature and humidity, and was higher in shorn than in unshorn sheep.
In earlier work we showed that low relative humidity (RH) of inhaled air causes acoustic voice parameters such as jitter and shimmer to deteriorate. Other authors have shown negative effects on vocal efficiency. To explain these changes in the mechanical properties of the vocal folds, the effects of changes in RH of the air passing over microdissected mucosa of sheep larynges were studied. The dissected surface of the tissue specimen just touched Ringer solution and air of varying RH was blown over the specimen. The mucosa specimen was subjected to sinusoidal oscillations of length (strain) and the resulting force (stress) was measured. The gain and phase angle between the imposed strain and resulting stress were measured, and elasticity and viscosity were calculated. Two different air conditions were tested: air with high RH (100%) vs air with low RH (0%). Viscosity and stiffness increased significantly in both ambient conditions (P < 0.01). Dry dehydrating air resulted in a stiffer and more viscous cover than humid air (P < 0.001). These changes in mechanical characteristics may contribute to the effects on voice parameters described in earlier work.
The purpose of this study was to examine the extent to which lighter runners might be more advantaged than larger, heavier runners during prolonged running in warm humid conditions. Sixteen highly trained runners with a range of body masses (55-90 kg) ran on a motorised treadmill on three separate occasions at 15, 25 or 35 degrees C, 60% relative humidity and 15 km x h(-1) wind speed. The protocol consisted of a 30-min run at 70% peak treadmill running speed (sub-max) followed by a self-paced 8-km performance run. At the end of the submax and 8-km run, rectal temperature was higher at 35 degrees C (39.5+/-0.4 degrees C, P<0.05) compared with 15 degrees C (38.6+/-0.4 degrees C) and 25 degrees C (39.1+/-0.4 degrees C) conditions. Time to complete the 8-km run at 35 degrees C was 30.4+/-2.9 min (P<0.05) compared with 27.0+/-1.5 min at 15 degrees C and 27.4+/-1.5 min at 25 degrees C. Heat storage determined from rectal and mean skin temperatures was positively correlated with body mass (r=0.74, P<0.0008) at 35 degrees C but only moderately correlated at 25 degrees C (r=0.50, P<0.04), whereas no correlation was evident at 15 degrees C. Potential evaporation estimated from sweat rates was positively associated with body mass (r=0.71, P<0.002) at 35 degrees C. In addition, the decreased rate of heat production and mean running speed during the 8-km performance run were significantly correlated with body mass (r=-0.61, P<0.02 and r=-0.77, P<0.0004, respectively). It is concluded that, compared to heavier runners, those with a lower body mass have a distinct thermal advantage when running in conditions in which heat-dissipation mechanisms are at their limit. Lighter runners produce and store less heat at the same running speed; hence they can run faster or further before reaching a limiting rectal temperature.
McCPK1 (Mesembryanthemum crystallinum calcium-dependent protein kinase 1) mRNA expression is induced transiently by salinity and water deficit stress and also McCPK1 undergoes dynamic subcellular localization changes in response to these same stresses. Here we have confirmed that low humidity is capable of causing a drastic change in McCPK1's subcellular localization. We attempted to elucidate this phenomenon by isolating components likely to be involved in this process. McCAP1 (M. crystallinum CDPK adapter protein 1) was cloned in a yeast two-hybrid screen with a constitutively active McCPK1 as bait. We show that McCPK1 and McCAP1 can interact in the yeast two-hybrid system, in vitro, and in vivo as demonstrated by coimmunoprecipitation experiments from plant extracts. However, McCAP1 does not appear to be a substrate for McCPK1. DsRed-McCAP1 and EGFP-McCPK1 fusions colocalize in epidermal cells of ice plants exposed to low humidity. McCAP1 is homologous to a family of proteins in Arabidopsis with no known function. Computational threading analysis suggests that McCAP1 is likely to be an intermediate filament protein of the cytoskeleton.
Only a small fraction of the carbon (C) allocated belowground by trees is retained by soils in long-lived, decay-resistant forms, yet because of the large magnitude of terrestrial primary productivity, even small changes in C allocation or retention can alter terrestrial C storage. The humid tropics exert a disproportionately large influence over terrestrial C storage, but C allocation and belowground retention in these ecosystems remain poorly quantified. Using mass balance and 13C isotope methods, we examined the effects of afforestation and fertilization, two land-use changes of large-scale importance, on belowground C cycling at a humid tropical site in Hawaii. Here we report that in unfertilized plots, 80% of the C allocated belowground by trees to roots and mycorrhizae was returned to the atmosphere within 1 year; 9% of the belowground C flux was retained in coarse roots and 11% was retained as new soil C. The gains in new soil C were offset entirely by losses of old soil C. Further, while fertilization early in stand development increased C storage in the litter layer and in coarse roots, it reduced by 22% the flux of C moving through roots and mycorrhizae into mineral soils. Because soil C formation rates related strongly to rhizosphere C flux, fertilization may reduce an already limited capacity of these forests to sequester decay-resistant soil C.
PURPOSE: The Dräger Cato anesthetic machine (Dräger, Lübeck, Germany) effectively humidifies and warms anesthetic gases, because it has a built-in hotplate to heat the breathing system, and expired gas passes through the CO2 absorbent three times during one breath. In the present study, we measured the temperature and absolute humidity (AH) of the anesthetic circuit in the Dräger Cato machine with and without heat moisture exchangers (HME), and compared them with those in another anesthetic machine, the Aestiva/5 (Datex-Ohmeda, Helsinki, Finland). METHODS: Forty-eight adult patients were randomly assigned to one of eight groups according to the anesthetic machine, fresh gas flow (FGF), and the use of HME (n = 6 each): Cato 0.51 x min(-1) without HME (group 1), Cato 1.01 x min(-1) without HME (group 2), Cato 0.51 x min(-1) with HME (group 3), Cato 1.01 x min(-1) with HME (group 4), Aestiva 0.51 x min(-1) without HME (group 5), Aestiva 1.01 x min(-1) without HME (group 6), Aestiva 0.51 x min(-1) with HME (group 7), and Aestiva 1.01 x min(-1) with HME (group 8). The temperature and AH of the anesthetic gases were measured with a Moiscope (S.K.I. Net, Tokyo, Japan), which was placed between the endotracheal tube and the Y-piece of the anesthetic circuit. The HME was placed between the Moiscope and the Y-piece of the anesthetic circuit. The temperature and AH of the anesthetic gases were measured at 5, 10, and 15 min and then every 15 min up to 150 min after tracheal intubation. RESULTS: Among the groups without HME (groups 1, 2, 5, and 6), the inspired temperatures and AH in groups 1 and 2 were significantly higher than those in groups 5 and 6 at all times during the study period (P < 0.01-0.001). The inspired temperatures and AH of the groups with HME (groups 3, 4, 7, and 8), were significantly higher than those in groups 2, 5, and 6 (P < 0.01-0.001). Among the groups with HME, the AH in group 3 was significantly higher than that in group 8 until the final study period. CONCLUSION: The present study indicates that the Dräger Cato machine was more effective in warming and humidifying respiratory gas than the Aestiva/5, and that Aestiva/5 without HME does not reach the optimal temperature and humidity ranges, even if minimal flow anesthesia (0.51 x min(-1)) is performed.
By using a dynamic dilution system, the atmospheric measurement of 11 selected toxics VOCs (ethylene, acetylene, propene, 1-butene, 1,3-butadiene, 1-pentene, 1-hexene, benzene, toluene, ethylbenzene, m+p-xylene) from the list WHO of 1996 and TO-14 method of US EPA by preconcentration by thermal desorption (TD), analysis by gas chromatography (GC), identification and quantification with a flame ionisation detector (FID) was developed and validated in term of metrology, especially the techniques of sampling of these VOCs with adsorbents cartridges "Air Toxics" when used with an "UMEG sampler" equipped in the inlet with a nafion membrane. In particular the influence of climatic conditions (temperature and relative humidity) and the influence of chemical factors like ozone, on the representativity of sampling were studied. Experiments made with various humidities showed that the addition of a nafion membrane in the inlet of the sampling system was required. Without this membrane, losses of compounds were observed for RH >50%. With this membrane, storage for 2 weeks in a refrigerator, as for canisters, did not induce a loss of compounds. No significative decrease of concentrations of the studied VOCs after 14 days storage, which are known to react with ozone, were observed with an ozone concentrations of 55 ppb. One explanation is that nafion membrane, placed in the inlet of the sampler, will neutralize ozone before entering the sampling tubes. This observation is in accordance with literature which states that the sampling of VOCs on Carbotrap cartridges without ozone scrubber induce a loss of compounds.
Studies were undertaken on the viability of the metacercariae of Fasciola gigantica when stored in water at 13 degrees C for periods up to 23 weeks, exposed to the sunlight for up to 8 h or stored at a range of temperatures and humidities for up to 10 weeks. Excysted metacercariae were catergorized microscopically as viable (motile and undamaged), dubious (not motile and undamaged) or dead (visible necrosis). The infectivity of viable and dubious metacercariae and unselected reference metacercariae held in water at 7 degrees C for 20 days or longer was assessed by comparing numbers of flukes recovered from infected Merino sheep. Mean recovery rates were 54.6%, 7.2% and 37.2%, respectively, for viable, dubious and unselected metacercariae. Metacercariae immersed in water remained viable longer than those allowed to desiccate. Viability was promoted by decreasing temperature and increasing humidity. Exposure to direct sunlight killed metacercariae within 8 h. Results indicated that in lowland Indonesian irrigated rice paddies, metacercariae immersed in water are likely to survive for less than 5 weeks while those that become desiccated will survive less than 2 weeks. This information, together with the option of exposing fresh rice stalks to direct sunlight before feeding them to livestock, can assist farmers in reducing infection with F gigantica.
Controversy exists as to the advisability of mist therapy in pulmonary disease. We studied the effects of several forms of humidity on asthmatic airways. Thirty-four children were tested over a period of 8 months as follows: (1) mist with a mean particle size of 3 mu was delivered for 30 min by an ultrasonic nebulizer to 11 children individually in a plastic tent; (2) to another 11 subjects in a tent, mist with a mean particle size of 10 mu was delivered by a jet nebulizer for 30 min;3) 15 patients in a croup room recieved for 30 min water droplets ranging from a microscopic fog to large rain particles (mean 16 mu) generated by a Melco natural fog generator; (4) 10 children were challenged with 3 solutions used commonly for the production of mist: distilled water, half-normal saline, and normal saline. Pulmonary functions were studied on each patient pre- and post-mist exposure. Approximately two thirds of the patients had a significant response, either improvement or deterioration, when challenged with the various forms of mist. No particular group trends were produced either by increasing the mean particle size of humidity, or by using solutions of increasing salinity.
The effect of environmental factors on the percutaneous absorption of parathion in excised porcine skin was assessed in a flow-through diffusion cell system by varying the temperature (T), relative humidity (%RH), perfusate flow rate (F), and composition (porcine serum) at three parathion doses (4, 40, and 400 micrograms/cm2) compared to standard conditions (air temperature = 37 degrees C, perfusate temperature = 37 degrees C, %RH = 60, flow rate = 4 ml/hr, and standard bovine serum albumin medium). Parathion absorption was assessed by monitoring total radiolabeled activity appearing in the perfusate over time. High relative humidity significantly increased parathion penetration, as did two elevated temperature conditions. The effects of flow rate and perfusate composition were variable and dose dependent. In the present studies, lower applied doses appeared to be more sensitive to changes in the environmental conditions studied. These results suggest that these parameters have independent and different degrees of effect on parathion percutaneous absorption. Experimental conditions should be strictly controlled and dose-response studies need to be conducted when evaluating transdermal studies. Finally, if similar effects occur in vivo, the risk assessment calculations on percutaneous absorption should take these parameters into consideration.
The effect of temperature and relative humidity (RH) on the early tensile bond strengths to bovine dentine of two bonding systems (Liner Bond System, and Scotchbond Multi-purpose), and an experimental system (KB-110) were tested. Two environmental conditions, room temperature (23 degrees C/50% RH) and oral temperature (30 degrees C/80% RH), were used in a controlled temperature and humidity chamber. Bond strengths were recorded immediately after, 10 min and 24 h following light curing. The tensile bond strengths did not vary between the two test conditions, but the mode of fracture was observed to change. The 30 degrees C/80% RH condition exhibited a slightly greater degree of adhesive type failures compared with the 23 degrees C/50% RH group. This was particularly so for the experimental system, indicating that different bonding systems may be more or less sensitive to changes in RH and temperature. Failures occurred partially or totally within the resin composite at the early test times, and it was concluded that the bond strengths of the systems tested tended to exceed the early cohesive strengths of the resin composite.
At a constant temperature of 25 degrees C and 84% relative humidity the pre-oviposition period of Boophilus annulatus was 2-5 days (mean 2.7 days) and the oviposition lasted 11-17 days (mean 15 days). The peak egg laying occurred 1-6 days (mean 3.5 days) after the start of oviposition. The daily egg output was 135 (range 90-190) and the total egg production was 2004 (range 1432-2664). Light had no significant effect on oviposition. There was a highly significant correlation between the weight of the engorged female and the total egg yield (r = 0.78; P less than 0.01). The pre-oviposition and oviposition periods were not influenced by the weight of the engorged females. The relative humidity (25, 62, 93%) had no effect on the oviposition, but the temperature (16, 25, 35 degrees C) had a significant influence on it. The pre-oviposition and oviposition periods increased with the decrease of temperature. The course of oviposition was similar at 25 and 35 degrees C, with a peak occurring within a few days of the start of egg-laying, followed by a gradual decline. At 16 degrees C, the egg production curve was flat, without a peak. However, the total number of eggs produced was not significantly different at the three temperature regimes.
The survival period for larvae of Boophilus annulatus (Say), Boophilus microplus (Canestrini) and hybridized Boophilus ticks was determined by exposure to various combinations of temperature (20, 25, 30 and 35 degrees C) and relative humidity (32, 63, 75, 84 and 97% RH) in the laboratory. Results indicated that within a given temperature and RH regime, there was no difference (P greater than 0.05) in larval survival among the three species tested, indicating that these ticks respond similarly over a wide range of temperature and RH combinations. Larval survival in all three species was longest (P less than 0.05) at 20 degrees C and either 84 or 97% RH. With each increase in temperature at the 84 and 97% RH treatment levels, there was a corresponding significant (P less than 0.05) decrease in larval survival. When the temperature reached 35 degrees C at all humidities or when the RH was 63% or less at all temperatures, the mean larval survival period was 43 days or less in all cases and little difference (P greater than 0.05) was observed among the treatment regimes included. Results suggest that at a RH of 75% and more, the temperature is the determining factor in larval survival, whereas at a RH of 63% and less the RH is the determining factor in larval survival, regardless of temperature.