Effect Of Vapor Pressure Research Articles

Development and Analysis of Oxygen-Sensing Probes for In Situ Monitoring of Unsaturated Solid-State Biodegradation Processes

ABSTRACT Oxygen (O2) sensors have been developed for in situ measurement of O2 in high-solids degradation processes. The O2 sensor has been shown to withstand the corrosive environment of the biodegradation process with high humidity and temperatures exceeding 60 oC. Calibration tests prior to and after in situ operation showed the sensor to perform accurately and reproducibly after 71 days of in situ operation. A linear relationship between O2-sensor output and water vapor pressure was confirmed through calibration experiments. To compensate for the effect of water vapor pressure on O2-sensor measurements, O2 concentration was expressed on a dry air basis using the confirmed linear relationship. In situ O2-sensor output expressed on a dry air basis was found to follow trends of gas samples analyzed by gas chromatography with good agreement.

Effect of water vapor pressure and temperature on the amorphous-to-crystalline HA conversion during heat treatment of HA coatings.

X-ray diffraction was used to characterize the increment of crystallinity of HA coatings after heat treatment. Coatings were heated over the temperature (T) interval of 300 degrees-460 degrees C with a partial water vapor pressure of 0.01 MPa and 0.001 MPa. Heat treatment also was done in air, as a contrast. It was found that the ratio (n) of the increment of crystallinity to the crystallinity of the as-received HA coatings was more significant for the coatings heated in atmosphere with water vapor than for those heated in air. This ratio also increased with water vapor pressure. The logarithm of the ratio increased linearly with 1/T, indicating that the ratio is exponential to T. The reason might be that recrystallization of the amorphous phase is a diffusion controlled process; the nucleation rate and growth velocity of the crystallites are in proportion to the diffusion coefficient, which is exponential to the temperature (T). Incorporation of water vapor in the atmosphere during heat treatment may decrease the activation energy for diffusion, which helps raise the diffusion coefficient of the atoms. Thus recrystallization of the amorphous phase can be accelerated.

Effect of water vapour pressure and frequency on fatigue behaviour in 7017-T651 aluminium alloy plate

The effect of water vapour pressure on fatigue crack growth in a commercial medium strength aluminium alloy is analysed in this investigation, with particular emphasis on its relation to environmental exposure. Crack growth velocities were measured in high-purity water vapour environments with pressures ranging from 10 −5 Pa to 1300 Pa and testing frequencies between 1 Hz and 10 Hz. A detailed microscopic survey of the fracture surfaces was also performed. Different types of striations were found and correlated with water vapour exposures. Experimental results agree quite well with a hydrogen embrittlement model based on the proposals by R. P. Wei and co-workers.

Ethanol vapour pressure as a control factor during alcoholic fermentation

Aqueous solutions of glucose/fructose mixtures with varying concentrations of ethanol were used to study the effects on fermentation of ethanol vapour pressure and water activity. Water vapour pressure was found to increase significantly with temperature in the range 15 to 30‡C. The effects on glucose fermentation bySaccharomyces cerevisiae Bg7FL of the variables glucose concentration, Tween 80 concentration, temperature and ammonium and ethanol concentrations were examined using central composite design. A best fit equation describing the main, quadratic and interactive effects of the five variables on yeast growth rate was produced. Further model systems were analysed in which the effects of ethanol vapour pressure, water vapour pressure and ethanol concentration on maximal growth rate of the yeast strain were studied. Above 18‡C, neither ethanol concentration nor ethanol vapour pressure controlled the fermentation rate. Ethanol toxicity was shown to be associated with its vapour pressure rather than its concentration.

Effects of gaseous hydrogen and water vapor pressure on environmental embrittlement of Ni3Al

Tensile ductilities of undoped and boron-doped Ni3Al have been determined under H2 and H2O pressures in the range of 10−3 ~ 103Pa. In agreement with other studies, boron-doped Ni3Al was found to be insensitive to water vapor, while undoped Ni3Al is severely embrittled by water vapor at pressures greater than about 10−3Pa. This observation is consistent with previous conclusions that the ductilizing effect of boron additions in Ni3Al is at least partly due to its remedial effect on embrittlement by environmental water vapor.

Effects of metabolic rate and ambient vapour pressure on heat strain in protective clothing.

Studies have shown that variations in ambient water vapour pressure from 1.7 to 3.7 kPa have little effect on heat tolerance time at a metabolic rate above 450 W while wearing protective clothing. With lighter exercise, where tolerance times exceed 60 min, variations in vapour pressure have a significant impact on evaporative heat loss and, therefore, heat tolerance. The present study has examined whether these findings extend to conditions with more extreme variations in vapour pressure. Twelve males performed light (L, 350 W) and heavy (H, 500 W) exercise at 40 degrees C in a dry (D, 1.1 kPa) and humid (H, 4.8 kPa) environment while wearing a semi-permeable nuclear, biological and chemical protective clothing ensemble (0.29 m2 x degree C-1.W-1 or 1.88 clo; Woodcock vapour permeability coefficient, im = 0.33). Partitional calorimetry was used to determine the rate of heat storage (S) with evaporative heat loss from the skin (Esk) calculated from changes in dressed mass or the physical properties of the clothing and the vapour pressure gradient between the skin and the environment. Skin vapour pressure was predicted from measurements of water vapour pressure above the skin surface and in the clothing with humidity sensors coupled with thermistors. Final mean skin temperature (Tsk) was higher for the humid trials and averaged 37.4 (0.3) degree C, 38.9 (0.4) degree C, 37.6 (0.5) degree C and 38.5 (0.4) degree C for LD, LH, HD and HH, respectively. Final rectal temperature (Tre) was higher for D with respective values for LD, LH, HD and HH of 39.0 (0.4) degree C, 38.7 (0.4) degree C, 38.8 (0.4) degree C and 38.5 (0.4) degree C. Tolerance time was significantly different among the trials and averaged 120.3 (19.3) min, 54.8 (7.3) min, 63.5 (6.9) min and 36.8 (3.1) min for LD, LH, HD and HH, respectively. Esk was overestimated and, therefore, S was underestimated when the changes in dressed mass were used to determine evaporative heat loss. When skin vapour pressure determined from the humidity sensor data was used to calculate Esk, heat storage was significantly different among the trials and averaged 15.0 (3.0), 13.0 (1.8), 14.2 (2.6) and 12.2 (1.9) kJ.kg-1 for LD, LH, HD and HH, respectively. It was concluded that while wearing the protective clothing all indices of heat strain, including tolerance time, were significantly affected by the change in ambient water vapour pressure from 1.1 to 4.8 kPa during both light and heavy exercise.

Effects of metabolic rate and ambient vapour pressure on heat strain in protective clothing

Effects of metabolic rate and ambient vapour pressure on heat strain in protective clothing

Environmental fatigue in a 7000 series aluminium alloy

The effect of water vapour pressure on fatigue crack growth in an aluminium alloy is analysed in this investigation. Fatigue tests were performed in gaseous atmospheres with different water vapour concentrations and the experimental results were correlated with the morphology of the fracture surfaces examined by SEM. An important effort has been made in thoroughly examining the characteristic features associated with the fatigue fracture for environments with different water vapour pressures. Crack growth response at the lower water vapour pressures (between 1 and 5 Pa) is satisfactorily explained in terms of a model based on the hypothesis of hydrogen embrittlement.

Equation of state calculations of supercritical fluid behavior: Effects of size and interaction energy

The solubility behavior of solid and fluid components with supercritical fluids (SCF) is investigated using a mean field equation of state. When densities, instead of the more commonly used mole fraction and pressure, are used to illustrate solubilities, the effect of the solute's vapor pressure becomes clear. An expression for the relation between the solubility and the second cross virial coefficient is derived. The effects of size and interaction energy are investigated by changing the solute and solvent parameters.

Optical properties of agbise 2 thin films

Thin films of AgBiSe 2 were prepared by thermal evaporation in vacuum (10 −6 Torr). The effect of thermal annealing either in vacuum or in a selenium atmosphere on the growth characteristics and stability of the films were studied using X-ray diffraction, transmission electron microscopy and the selected area electron diffraction techniques. It was observed that the as-deposited films (300 K) were poor crystalline. The degree of crystallinity increases with increasing the temperature from 300 to 473 K. At 500 K in vacuum two-phase films with AgBiSe 2 as the major phase were formed. The optical constants of crystalline AgBiSe 2 thin films were estimated as well as the effect of heat treatments and selenium vapor pressure on these constants. The analysis of the optical absorption spectra revealed the existence of two optical transition mechanisms: allowed direct and indirect transition, with optical energy gaps E d g = 1.66 eV and E g = 0.91 eV at 300 K. These values were found to decrease with increasing annealing temperature.

Kinetic study and modeling of coarsening in a BaTiO 3 powder at 850 °C

The influence of the gaseous atmosphere and the Ba Ti ratio on the decrease in specific surface area in a BaTiO 3 powder was studied at 850 °C. A model involving elementary steps and the BaTiO 3 point defects was proposed to quantitatively account for the accelerating effect of the water vapour pressure and the Ba Ti ratio.

Two-year follow-up study of the effect of acid fog on adult asthma patients.

Acid fog is a complex mixture of atomospheric pollutants containing multiple stimuli that may be capable of inducing bronchoconstriction. To investigate the effect of ambient acid fog on bronchoconstriction, we examined the relation between the hospital visit for asthma symptoms of 102 patients and various meteorological conditions for over the two-year period from January 1992 to December 1993. Dense fog occurs frequently every summer in Kushiro, a city located in Hokkaido, northernmost island in Japan. The acidity of the fog ranged from pH 3.32 to 6.91 (mean pH = 5.05) during this period. A significant increase (p < 0.05) of hospital visits on a foggy day was found in 9 cases, and a tendency (p < 0.10) was found in 10 cases. The odds ratio for a hospital visit on a high water vapor pressure day (> 12 h Pa) was significantly high (p < 0.01) in 5 cases among the above 19 cases. To exclude the effect of high water vapor pressure, the data was restricted to the condition of a foggy day with low water vapor pressure (< 12 hPa); 9 patients had a significant increase (p < 0.05) in hospital visits on such a day. These results indicated that hospital visits for asthma symptoms was increased on acid fog days in 8.8% of adult asthma patients. Inhalation of naturally occurring acid fog may have adverse effects on the respiratory tract of the asthmatic patient.

The effect of water vapor pressure on desolvation kinetics of caffeine 4/5-hydrate

The kinetics of dehydration of caffeine 4/5-hydrate at different relative humidities (RH) was studied at 25 °C for two crystal preparations with different crystal sizes. The weight change was evaluated over phosphorus pentoxide and relative humidities of 9, 13, 24, 36 and 43%, using special hygrostats and a below-weight balance. Additionally the samples were stored for 8 months at RH between 0 and 98%. A mechanistic interpretation of the reaction was derived by analyzing the data with numerous kinetic models as well as by microscopic investigations and various thermoanalytical techniques (thermomicroscopy, thermogravimetry, differential scanning calorimetry). The mechanism of the dehydration reaction was found to be very complex, depending on the crystal size and water vapor pressure. Diffusion control as well as nucleation and growth reaction are considered as the fundamental principles of the process. Due to the occurrence of a Smith-Topley effect, a constant loss of water rate of a coarse crystalline batch between 0 and 13% relative humidity takes place. The dehydration rate of small crystals is much more affected by changes in water vapor pressure. Over desiccants, complete transformation to the anhydrate requires about 4 h, a 30th of the time required for the coarse crystals. Caffeine hydrate loses the water of crystallization even at 61% RH (25 °C), which should be considered during processing and storing conditions. Beyond that, this paper suggests that a variety of analytical techniques are necessary for sufficient information about the dehydration characteristics of a crystalline hydrate and to avoid misinterpretations of phase transformations in the solid state.

The effect of the water vapor pressure on the kinetics of thermal dehydration of manganese(II) formate dihydrate

The effect of the water vapor pressure on the thermal dehydration of manganese(II) formate dihydrate was studied by means of isothermal gravimetry under various water vapor pressure, ranging from 4.6 to 24.4 torr.

Studies on the Concentration of Ramularia beticola Conidia in the Air Above Sugar Beet fields in Denmark

AbstractConcentrations of Ramularia beticola Faut. &amp; Lamb. conidia in the air above 3 sugar beet (Beta vulgaris L.) field were registered for a period of 41 days altogether. A significant diurnal periodicity was revealed. Two periods of 3 and 5 days, respectively, included peaks of several thousands of conidia per m3 of air. The conidial concentrations were related to temperature, relative humidity (RH) and vapour pressure of the air, and to wind speed, dew point, rainfall and hours of sunshine. A significant effect of vapour pressure was observed for 2 fields. In one field with very low conidial concentrations, vapour pressure was nearly significant. In this field only wind speed significantly influenced dispersal of conidia. In an analysis of covariance including all data, 50% of the variation was explained by field, time of day, vapour pressure and number of hours of RH above 95% in the preceding 24h.

Effect of Water Vapor Pressure on the Viscous Sintering of Mullite

Powder compacts with mullite composition (3Al2O3⋅2SiO2) were prepared by mixing γ-alumina and colloidal silica, followed by pressurized filtration. The compacts were sintered by means of viscous flow of amorphous silica phase at relatively low temperature (1200-1250°C) under various water vapor pressures with dew points of -35, +25 and +60°C, and the effect of partial pressure of water vapor on the viscous sintering of mullite was investigated. Densification was enhanced with an increase in water vapor pressure. It was attributed to the fact that the water vapor terminates the silica network, which lowers the viscosity of amorphous silica. Apparent viscosity in the viscous sintering could be determined by applying theoretical models derived in the system composed of only vitreous phase. A compact with nearly full density (≅99%) was obtained under high water vapor pressures by optimizing sintering temperature and time.

Equilibrium distributions of key components of spearmint oil in sub/supercritical carbon dioxide

AbstractEffects of temperature (at 35, 45 or 55°C) and pressure (10–110 atm) on the relative distribution coefficients of the twelve key components of spearmint oil (essential oil ofMentha cardiaca; Scotch spearmint) at equilibrium in dense CO2 were investigated under conditions ranging from subcritical to supercritical regions. Effects of vapor pressure, molecular weight and polarity of the key components on their equilibrium distributions in sub/supercritical CO2 are discussed. At 35°C, all key components of spearmint oil are equally soluble in dense CO2 within the 12–102 atm pressure region. At 45 and 55°C, the key components are equally soluble for pressures greater than about 60 atm. However, around either 45°C/27 atm or 55°C/35 atm conditions, the relative distribution coefficients of all monoterpene hydrocarbons and of isomenthone (an oxygenated monoterpene) exhibit maxima, which are due to significantly higher vapor pressures of these components and significantly lower solvating power of the dense‐gas solvent at these particular temperatures and pressures. Vapor‐pressure effects, coupled with the decrease in solvating power, dominate the effects of polarity and molecular mass of the key components. Deterpenation of spearmint oil with dense CO2 is possible around either 45°C/27 atm or 55°C/35 atm, where the monoterpene hydrocarbons tend to concentrate in the CO2‐rich phase.

Solid-state reaction between molybdena and alumina: effect of water vapour pressure on the dispersion and nature of the supported phases

Thedispersion and nature of surface species formed upon calcination of MoO3–γ-Al2O3 mixtures at 770 K for 10 h and with different molybdena loadings under different water vapour pressures [P(H2O)] have been studied by X-ray diffraction (XRD), zero-point charge (ZPC) measurements and temperature-programmed reduction (TPR); P(H2O) was in the range 25–45 Torr with MoO3 loadings up to 2 monolayers (1 monolayer = 0.1681 g MoO3/g Al2O3). The intensity of the most intense XRD peak of MoO3 at 326 pm decreased as P(H2O) increased, indicating an increase in the concentration of surface species different from bulk MoO3. Up to 0.7 monolayer MoO3 loading, covering of the Al2O3 surface with Mo-containing species increases with increasing P(H2O); ZPC at P(H2O)= 45 Torr was coincident with that of MoO3. P(H2O) has no effect on the dispersion of high loaded samples (above 1 monolayer), where all the support surface is covered even for P(H2O)= 25 Torr. TPR results indicate the presence of species with different reducibilities, depending on P(H2O) and MoO3 loading; their nature has been assessed by comparison with previous results for samples obtained by impregnation; bulk MoO3(responsible for high-temperature reduction peaks) formation has been observed at high MoO3 loadings.

Effect of vapour pressure on the deposition pattern from solution phase metered dose inhalers

The pulmonary deposition of 99mTc-labelled hexamethyl propylene amine oxime, used as a model for propellant soluble drugs, was studied in healthy volunteers using gamma scintigraphy. The radiolabel was delivered using a metered dose inhaler using a low vapour pressure chlorofluorocarbon fill (LVPA, 255 kPa) or a high vapour pressure chlorofluorocarbon fill (HVPA, 448 kPa) in a cross-over design trial. The data showed that a lower proportion of the dose (35%) was swallowed for HVPA compared with LVPA (49%). Within the lung, the proportion of the dose reaching the peripheral airways as determined by the penetration index was the same for both aerosols, although a greater pulmonary deposition of the dose was observed with HVPA. The results obtained confirm previous observations that greater than 40% of the marker achieves pulmonary deposition when dissolved in the propellant phase.

Influence of arsenic vapor pressure during copper diffusion on deep level formation in silicon-doped gallium arsenide

The effect of arsenic vapor pressure during copper diffusion on deep level formation in silicon-doped gallium arsenide has been studied using photoinduced current transient spectroscopy. From the findings, models for the copper-related complexes in GaAs are identified. Capping effect of deposited copper layer is investigated. Deep levels with activation energies of 0.14 eV, 0.32 eV, and 0.45 eVhave been identified, which are attributed to CuGa, SiGa CuGa complex, and VAsCuGaVAs complex, respectively.