Ambient Vapor Pressure Research Articles

Response of Nanoparticle-Based One-Dimensional Photonic Crystals to Ambient Vapor Pressure

Herein we report an analysis of the variation of the optical properties of different nanoparticle-based one-dimensional photonic crystal architectures versus changes in the ambient vapor pressure. Gradual shift of the optical response provides us with information on the sorption properties of these structures and allow us to measure precise adsorption isotherms of these porous multilayers. The potential of nanoparticle-based one-dimensional photonic crystals as base materials for optical sensing devices is demonstrated in this way.

Self-assembly of multiwalled carbon nanotubes from quench-condensed CNi3 films

Freestanding, vertical, multiwalled carbon nanotubes (MWCNTs) are formed during the vacuum deposition of thin films of the metastable carbides CT3 (T=Ni, Co) onto fire-polished glass substrates. In contrast to widely used chemical and laser vapor deposition techniques, we utilize direct e-beam evaporation of arc-melted CT3 targets to produce MWCNTs that are self-assembled out of the CT3-film matrix. The depositions are made in an ambient vapor pressure that is at least six orders of magnitude lower than the 1−100 Torr typically used in chemical vapor techniques. Furthermore, the substrates need not be heated, and, in fact, we observe a robust nanotube growth on liquid nitrogen cooled glass and sapphire substrates. High-resolution atomic force microscopy reveals that MWCNTs of heights 1−40 nm are formed in films with nominal thicknesses in the range of 5−60 nm. We show that the growth parameters of the nanotubes are very sensitive to the grain structure of the films. This is consistent with a precipitation mediated root-growth mechanism.

Lowering of resting core temperature during acclimation is influenced by exercise stimulus

The decrease in resting core temperature (T (co)) and its relation to the reduced physiological strain during heat acclimation was analysed with rectal temperature data measured in three groups of eight semi-nude persons (6 males, 2 females) who were acclimated for 15 consecutive days to dry, humid and radiant heat, respectively, with equivalent WBGT (33.5 degrees C), by performing 2-h treadmill work. A fourth group followed the same protocol for 12 days in a neutral climate. After acclimation, both resting T (co), prior to heat exposure, and final T (co), measured at the end of work, were significantly reduced. The reduction in final T (co) increased with decreasing ambient water vapour pressure and was higher for the data pooled over the heat conditions (0.46 +/- 0.31 degrees C) than in the neutral climate (0.21 +/- 0.25 degrees C), whereas resting T (co) declined similarly in the heat (0.20 +/- 0.25 degrees C) and the neutral environment (0.17 +/- 0.23 degrees C). The lowering of resting and final T (co) after heat acclimation showed a significant correlation (r = 0.67) and regression analysis showed that 37% of the average reduction in final T (co) was attributable to the lowering of resting T (co). The same analysis was applied after extending the database by short-term series of clothed persons (17 females, 16 males) acclimated at 29.5 and 31.5 degrees C WBGT for 5 days. A significant correlation was found between the lowering of resting and final T (co) (r = 0.57) that did not depend on climatic conditions and gender, although the reduction in resting T (co) was significantly smaller for females (0.06 +/- 0.22 degrees C) than for males (0.21 +/- 0.23 degrees C). It is concluded that the lowering of resting core temperature contributes to the reduced physiological strain during heat acclimation. Similar effects under neutral conditions point to the exercise stimulus as a probable explanation.

Humidity parameters from temperature: test of a simple methodology for European conditions

AbstractAtmospheric water content is important for local and regional climate, and for chemical processes of soluble and solute species in the atmosphere. Further, vapour pressure deficit (D) is one of the key controls on the opening of stomata in plants and is thus an important force for evapotransporation, plant respiration and biomass production and for the uptake of harmful pollutants such as ozone through the stomata.Most meteorological stations typically measure both temperature and relative humidity (RH). However, even if recorded at finer time resolution, it is usually the daily or often monthly means of RH which are published in climate reports. Unfortunately, such data cannot be used to obtain the changes in RH or vapour pressure deficit over the day, as this depends strongly on the diurnal temperature variation during the day and not upon the mean temperature.Although RH typically changes significantly over the day, the ambient vapour pressure is often remarkably constant. Here a simple method to estimate diurnal vapour pressure is evaluated, based upon an assumed constant vapour pressure, and that recorded minimum temperatures approximate dew‐point temperatures. With a knowledge of only temperature, we will show that day to day estimates of vapour pressure, humidity and especially D, can be made with reasonable accuracy. This methodology is tested using meteorological data from 32 sites covering a range of locations in Europe. Such a simple methodology may be used to extract approximate diurnal curves of vapour pressures from published meteorological data which contains only minimum temperatures for each day, or where humidity data are not available. Copyright © 2007 Royal Meteorological Society

Relationships among Ambient Temperature and Vapor Pressure Deficit and Leaf and Stem Water Potentials of Fully Irrigated, Field-Grown Grapevines

Four <i>Vitis vinifera</i> L. cultivars grown at five locations throughout California were studied to determine the relationships among temperature and vapor pressure deficit (VPD) and leaf water potential (Ψ_l) measured under clear skies at midday (solar noon) or in some instances midmorning to midafternoon. Stem water potential (Ψ_stem) was also measured on several occasions. Vines were irrigated at 100% or greater of measured or estimated vineyard evapotranspiration, and deficit or nonirrigated vines were included for comparison. Temperature and VPD were determined at the time of measurement. The highest and lowest values of Ψ_l measured on well-watered grapevines were −0.51 and −1.15 MPa, respectively. Leaf and stem water potentials were linearly related to VPD and ambient temperature. The coefficient of determination was greater for the relationship between Ψ_l and VPD (<i>R</i>² = 0.74) than ambient temperature (<i>R</i>² = 0.58). Based on the regressions, estimates of Ψ_l at a VPD of 2 and 5 kPa for fully irrigated grapevines would be −0.65 and −0.89, respectively, while those of Ψ_stem at the same VPDs would be −0.37 and −0.57 MPa, respectively. Leaf water potential of water-stressed vines was less responsive to VPD or temperature when Ψ_l values ranged from −1.2 to −1.45 MPa. The values of Ψ_l and Ψ_stem as a function of VPD or temperature could serve as baselines indicating whether grapevines are fully irrigated or not water stressed under the environmental conditions found in semiarid grapegrowing regions.

Canopy-air temperature differential for potato under different irrigation regimes*

The main objective of this study was to determine canopy-air temperature differential, which can be used to quantify crop water stress index (CWSI) for potato. The crop was cultivated under furrow irrigation and subjected to three irrigation regimes in which irrigation was applied when 30, 50 and 70% of the available water holding capacity was consumed, and three irrigation levels (100, 50 and 0% replenishment of soil water depleted). The highest yield and water use was obtained under non-water-stressed treatments (100% replenishment of soil water depleted) for each irrigation regime. The lower (non-stressed) and upper (stressed) baselines were determined empirically from measurements of canopy temperatures, ambient air temperatures and vapour pressure deficit values and the CWSI was calculated with three irrigation levels for each irrigation regime. Trends in CWSI values were consistent with the soil water contents induced by the deficit irrigations. Average CWSI before irrigation values of 0.49 for irrigation when 30% of the available water holding capacity was consumed, 0.55 for irrigation when 50% of the available water holding capacity was consumed and 0.69 for irrigation when 70% of the available water holding capacity was consumed, produce maximum tuber yield. The yield was also directly correlated with seasonal CWSI values.

Stimulated light emission in a dielectrically disordered composite porous matrix

We report on a medium exhibiting extremely efficient light scattering properties: a liquid network formed in a porous matrix. Liquid fragments confined in the solid matrix result in a random fluctuation of the dielectric function and act as scattering objects for photons. The optical scattering efficiency is defined by the filling factor of the liquid in the pores and its dielectric constant. The spectral dependence of the scattering length of photons indicates that the phenomenon is governed by a Mie-type scattering mechanism. The degree of the dielectric disorder of the medium, i.e. the level of opacity is tunable by the ambient vapor pressure of the dielectric substance. In the strongest scattering regime the scattering length of photons is found to be in the micrometer range. By incorporation of dye molecules in the voids of the porous layer a system exhibiting optical gain is realized. In the multiple scattering regime the optical path of diffusively propagating photons is enhanced and light amplification through stimulated emission occurs: a strong intensity enhancement of the dye emission accompanied by significant spectral narrowing is observed above the excitation threshold for a layer being in the opalescence state. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Crop water stress index for potato under furrow and drip irrigation systems

This study was conducted to determine the crop water stress index (CWSI) for potato (Solanum tuberosum L.) grown under furrow and drip irrigation methods and subjected to three different irrigation levels (100, 50 and 0% replenishment of soil water depleted). The lower (non-stressed) and upper (stressed) baselines were determined empirically from measurements of canopy temperatures, ambient air temperatures and vapor pressure deficit values. Tuber yield decreased when mean CWSI prior to irrigation exceeded 0.68 in furrow and 0.81 in drip irrigation. The tuber yield was directly correlated with the seasonal CWSI values and the linear equations for furrow and drip irrigation methods, Y = −45.82 CWSI + 50.69 and Y = −52.65 CWSI + 58.44, respectively, can be used for yield prediction.

石炭灰堆積層中の水分凝縮による固化現象の数値解析

In this study, hardening phenomena of coal ash beds in high-humidity condition are examined. We employ a diffusion simulation in clarifying the distribution of condensed water in coal ash beds, in which water vapor is absorbed into sulfur trioxide adhered on the surface of coal ash particles. Aqueous sulfuric acids solution formed by the absorption is in equilibrium with the ambient water vapor. The diffusion rate of water vapor is proportional to the difference between the pressure and ambient water vapor pressure. The simulation successfully describes the results of previous experiment, at a constant temperature, with the variations in the equilibrium moisture and particle diameter of coal ash. Moreover, it is clarified that the relationship between water content and hardening phenomena is very similar for various coal ashes, with a correction of particle diameter of coal ash and the volume of condensate bridging between particles.

Use of Infrared Thermometry for Developing Baseline Equations and Scheduling Irrigation in Wheat

This study was conducted to develop baseline equations, which can be used to quantify crop water stress index (CWSI) for evaluating crop water stress in three winter wheat genotypes (Triticum aestivum L.) and to schedule irrigation and predict yield. Plants were grown under basin irrigation and subjected to five water treatments ranging from 100 to 0 % (100, 75, 50, 25, 0 %) replacement of evapotranspirational losses within 0.90 m soil profile. The highest yield and water use was obtained under fully irrigated conditions (100 % replenishment of soil water depleted). The lower (non-stressed) and upper (stressed) baselines were determined empirically from measurements of canopy and ambient air temperatures and vapour pressure deficit (VPD) on fully watered plants (100%) and under maximum water stress (0 %), respectively. The CWSI was determined by using the empirical approach for the five irrigation levels. The yield was directly correlated with the mean CWSI values and the linear equation for three genotypes (Saraybosna, Kate-A-1 and F-85), “Y = 1463.3 - 1062.3 CWSI”, “Y = 1483.8 - 1052.8 CWSI” and “Y = 1701.8 - 1367.7 CWSI” can be used for the yield prediction. CWSI values may also provide a valuable tool for monitoring water status and planning irrigation scheduling for wheat.

Avalanche process in an idealized lamp: II. Modelling of breakdown in Ar/Xe electric discharges

The breakdown phase of the startup of metal halide lamps is typically through a cold fill of a rare gas and the ambient vapour pressure of a dose of metals. The dynamics of the breakdown stage are of interest for improving the efficiency and lifetime of lamps. A computational investigation of the breakdown of Ar/Xe mixtures in an idealized lamp geometry was performed using global and two-dimensional (2-d) models to provide insight into the lamp ignition processes and to facilitate comparison with experiments. The experimental trends for breakdown for pressures of 10–90 Torr were qualitatively captured with the global model. Quantitative agreement required accounting for the temporal and spatial plasma dynamics included in the 2-d model. Small fractions of Xe in Ar were found to decrease the breakdown time as the ionization rates increased due to the lower ionization potential of xenon, while the electron energy distribution was not significantly affected. With higher Xe fractions the electron temperature in the ionization front decreased due to there being larger momentum transfer and inelastic losses to the Xe, and as a result the breakdown times increased. The compression of voltage ahead of the ionization front produced large electric fields at the cathode that enabled significant contributions to ionization by secondary electrons.

X-ray diffraction, 133Cs and 1H NMR and thermal studies of CdZrCs 1.5(H 3O) 0.5(C 2O 4) 4· xH 2O displaying Cs and water dynamic behavior

A novel mixed cadmium zirconium cesium oxalate with an open architecture has been synthesized from precipitation methods at room pressure. It crystallizes with an hexagonal symmetry, space group P3 112 (no. 151), a=9.105(5) Å, c=23.656(5) Å, V=1698(1) Å 3 and Z=3. The structure displays a [CdZr(C 2O 4) 4] 2− helicoidal framework built from CdO 8 and ZrO 8 square-based antiprisms connected through bichelating oxalates, which generates channels along different directions. Cesium cations, hydronium ions and water molecules are located inside the voids of the anionic framework. They exhibit a dynamic disorder which has been further investigated by 1H and 133Cs solid-state NMR. Moreover a phase transition depending both upon ambient temperature and water vapor pressure was evidenced for the title compound. The thermal decomposition has been studied in situ by temperature-dependent X-ray diffraction and thermogravimetry. The final product is a mixture of cadmium oxide, zirconium oxide and cesium carbonate.

Behaviour study of "Danlas" grapevines grown under plastic cover

&lt;p style="text-align: justify;"&gt;The aim of this study is to determine the behaviour of ‘Danlas’ grapevines conducted under plastic cover, near atlantic coast, known for its early table grape production. Measurements included climatic conditions, leaf water potential, canopy temperature and production components. The use of plastic cover resulted in an increase of midday ambient temperature and vapor pressure deficit, with a maximum of 5. 7 °C and 1.28 kPa, respectively. Midday canopy temperature under field conditions were lower than ambient temperature by an average of 2.5 °C. The most negative leaf water potential values were recoded for grapevines under plastic cover relatively to field conditions, ranging from –7.2 to –17.0 bars and from –7.0 to –14.0 bars, respectively. Harvest date was advanced by more than one month after the use of plastic cover. Results showed that crop weight, cluster weight and number per vine were not significantly affected. However, the number of berries per cluster was significantly reduced. Plastic cover promoted fruit quality, berry weight and soluble solids concentration were increased by 2.23 g and 1.0 °Brix, respectively. While titratable acidity was decreased by 1.20 g/l.&lt;/p&gt;

Crop water stress index for watermelon

This study was conducted to determine the suitability of a crop water stress index (CWSI) to schedule irrigation for watermelon ( Citrullus vulgaris) grown with trickle irrigation. The effects of five irrigation levels (100, 75, 50, 25 and 0% replenishment of soil water depleted from 0.90 m soil profile depth) on watermelon yields and resulting CWSI were investigated. The highest yield and water use was obtained under fully irrigated conditions (100% replenishment of soil water depleted) in 2 years. The CWSI was calculated from measurements of infrared canopy temperatures, ambient air temperatures and vapor pressure deficit values for five irrigation levels. The trends in CWSI values were consistent with the soil water contents induced by the deficit irrigations. Unlike the yield, CWSI increased with increased soil water deficit. An average CWSI of about 0.41 before irrigation produced the maximum yield. The yield was directly correlated with mean CWSI values and the linear equation ‘ Y=91.143−66.077 CWSI’ can be used for yield prediction. The CWSI value was useful for evaluating crop water stress in watermelon and should be useful for timing irrigation and predicting yield.

Stimulated light emission in dense fog confined inside a porous glass matrix.

We report on light amplification through stimulated emission in a dielectrically disordered medium. Liquid fragments confined in the solid matrix of porous quartz layers result in a random fluctuation of the dielectric function, and dye molecules embedded in the voids yield optical gain. The level of opacity is tunable by the ambient vapor pressure of the dielectric substance. In the multiple scattering regime, a strong intensity enhancement of the dye emission accompanied by significant spectral narrowing is observed above the threshold for a layer being in the opalescence state.

High water vapour pressure deficit influence on Quercus ilex and Pinus pinea field monoterpene emission in the central Iberian Peninsula (Spain)

The results of a field study carried out in September–October 2000 near Madrid, regarding Quercus ilex and Pinus pinea monoterpene emission and its relation to ambient and physiological parameters, are presented in this paper. The major compounds in diurnal Q. ilex emission were limonene, α-pinene and β-pinene. Emission rates during warm days fitted reasonably well to the temperature and light-dependent model of Guenther ( E S=13.4 μg g DW −1 h −1). However, during hot days at mid-day and afternoon hours, dramatic decreases of monoterpene emission, photosynthetic activity and stomatal conductance were observed. The poor soil–water availability combined with low relative humidity and high temperature is likely to be responsible for the observed emission drop. A parameterisation of emission, based on ambient atmospheric water vapour pressure deficit (WVPD), has been attempted in this study. Monoterpene diurnal emission from P. pinea was lower than that of Mediterranean oak ( E S=1.5 μg g DW −1 h −1). A reduction in the total emission during the hottest hours of the day was not observed in this monoterpene storing species. Limonene emission rates, accounting on average for nearly half of the emission, were well described by the temperature-dependent model of Tingey. The rest of the emission was comprised of several compounds (cineole, myrcene, α-pinene, linalool) and was reduced at high WVPD values.

Heat Balance Limits in Football Uniforms

ABSTRACTBACKGROUND: Scant evidence documents the physiological and environmental stresses for football players wearing partial or full uniforms, but such information would be useful for determining the ambient temperatures and humidities associated with uncompensable heat stress during practice and games.OBJECTIVE: This laboratory study used a physiological approach to determine critical heat balance limits (various combinations of ambient temperature and relative humidity) for subjects exercising in typical American football uniforms.DESIGN: Eight nonheat-acclimatized men exercised at 35% Vo2max in a programmable environmental chamber. In multiple trials, either dry-bulb temperature (Tdb) was held constant and ambient water vapor pressure (Pa) was systematically increased, or Pa was held constant and Tdb was systematically increased. The critical heat balance limits were determined as the environments at which body core (esophageal) temperatures were forced out of equilibrium, reflecting uncompensated heat storage imposed by those environments.RESULTS: Critical environmental limits are presented that define the combinations of air temperature and relative humidity above which thermal balance cannot be maintained. These zones of uncompensable heat stress result in continuously rising core temperatures. Retrospective analysis reveals that documented heatstroke deaths in football players wearing full uniforms occurred at or above these critical environments.CONCLUSION: Heat balance limits can be used in decision making and are especially relevant for preventing heat-related illness or injuries early in the football practice season. The critical limits are expanded when shorts are substituted for football pants with pads.

Effect of Number Density of CCN on Equilibrium Radius and Temperature of Cloud Droplet during Competitive Growth

Usually, for the estimation of the cloud droplet size in the equilibrium state, Kohler equation is utilized, assuming constant vapor content and constant temperature. However, the condensational growth of the cloud droplet consumes the ambient water vapor and releases the latent heat. Therefore, the ambient water vapor pressure and the temperature are changed. Taking account of the variations of the water vapor content and the temperature, a new model for the estimation of the equilibrium cloud droplet size and temperature has been developed by modifying Kohler equation. The modification of Kohler model is based on the mass and the heat conservation laws for the water (vapor and liquid) in the air parcel occupied by one cloud droplet. Variations of size and temperature with number density of CCN are simulated numerically.

InP single crystal growth by the horizontal Bridgman method under controlled phosphorus vapor pressure

InP single crystals were grown by the horizontal Bridgman method under controlled ambient phosphorus vapor pressure. The relationship between melt composition and crystal defects was investigated. The InP grown under phosphorus vapor pressure of 25 atm has EPD levels of 10 3 cm −2 through the ingot. In the InP grown at 12 or 29 atm, the EPD increased more than 2 orders at the tail end. X-ray reciprocal maps indicated that the crystals consisted of many domains with tilt boundaries at a distance from the seeding point. The deviation of the lattice parameter measured by the X-ray diffraction angle indicated that the composition changed gradually. The composition near the seeding point was nearly stoichiometry under the influence of the composition of source polycrystalline, because a finite time was required to transition of phosphorus. Optimum phosphorus vapor pressure is necessary to obtain InP with stoichiometric composition and low defect densities.

Lattice Parameter Deviation of InP Single Crystals Grown by the Horizontal Bridgman Method under Controlled Phosphorus Vapor Pressure

InP crystals were grown by the horizontal Bridgman method under controlled ambient phosphorus vapor pressure. The lattice parameter was measured by X-ray diffraction analysis. The lattice parameter of the InP crystals increased with increasing phosphorus vapor pressure. The relationship between the lattice parameter and composition indicates that the In-rich composition is attributed to the P-vacancies. This corresponds to the photoluminescence spectra of P-vacancy-related emission.