Variation Of Vapor Pressure Research Articles

Transgenic peanut overexpressing the DREB1A transcription factor has higher yields under drought stress

Transgenic research using the DREB group of transcription factors has received much attention in developing drought-tolerant and climate-ready varieties of crop plants. While many reports have demonstrated increased tolerance to water deficits under laboratory and greenhouse conditions, only a few have tested possible effects under field conditions, with limited success in most cases. Here, we present evidence of a transgenic solution for enhanced drought tolerance in peanut (Arachis hypogaea L.), which is an important grain legume and a valuable cash crop for smallholder and resource-poor farmers occupying the largest portion of the farming systems in low income food deficit countries. The presence, integration, expression and inheritance of the transgene in advancing generations of the transgenic peanut plants were assessed using PCR, Southern blot, inverse-PCR, RT-PCR and q-PCR techniques. Four trials were conducted in various water stress regimes under varying vapour pressure deficits (VPDs), and drought tolerance was studied using various component traits of drought. A substantial yield improvement of up to 24 % in drought trials under field conditions was achieved across a wide range of stress intensities and was related to higher harvest indices (HIs). All transgenic events had significantly higher seed filling under drought and displayed 20–30 % lower pod yield reduction than their untransformed counterpart under drought stress. Two transgenic events showed yield advantage under drought stress that consistently had higher pod and seed yield than the untransformed parent under drought stress across all trials, without displaying any yield penalty under irrigated conditions.

A compound thermodynamic model for transient bubble growth in microscale

Based upon the classical bubble dynamics, a new compound thermodynamics model coupling with heat transfer mechanism for the bubble growth and collapse during explosive boiling under pulsed heating is presented from a hydrodynamic and thermodynamic perspective. The highlight in this analysis is that the relationship between the variation of the vapor temperature and the vapor pressure inside of a bubble satisfies the conditions of a polytropic process. With a selected compound polytropic index (CPI) and a determined vapor temperature variation for each different stage during the entire bubble evolution under pulsed heating, the bubble behavior can be described and predicted quite well when compared to the experimental observations for pulse ranges.For the first time, this model reveals the vapor pressure and temperature variation occurring during the bubble evolution and provides an in-depth understanding and insight into the bubble dynamics under pulsed heating. The thermodynamics analysis provides a first order solution to guide future thermal bubble MEMS design.

Dimming properties of medium and small wattage ceramic metal halide lamps

Ceramic metal halide lamps with rated powers of 70 W and 150 W are dimmed by reducing their operating power. Under dimmed conditions, photometric, colorimetric and electric parameters, as well as the temperature distribution of the outer wall of the arc tube have been measured. As the lamp power is reduced, luminous efficacy and colour rendering index decrease while correlated colour temperature rises. For each lamp, at 70% of its rated power, the luminous efficacy is greater than 80 lm/W, colour rendering index is above 74 and correlated colour temperature increases by less than 800 K. Dimming applications of these lamps are validated by these parameters. Furthermore, the complicated variation of lamp parameters as a function of operating power is explained by the variation of metal halide vapour pressure with wall temperature.

Water Vapor Adsorption on Goethite

Goethite (α-FeOOH) is an important mineral contributing to processes of atmospheric and terrestrial importance. Their interactions with water vapor are particularly relevant in these contexts. In this work, molecular details of water vapor (0.0-19.0 Torr; 0-96% relative humidity at 25 °C) adsorption at surfaces of synthetic goethite nanoparticles reacted with and without HCl and NaCl were resolved using vibrational spectroscopy. This technique probed interactions between surface (hydr)oxo groups and liquid water-like films. Molecular dynamics showed that structures and orientations adopted by these waters are comparable to those adopted at the interface with liquid water. Particle surfaces reacted with HCl accumulated less water than acid-free surfaces due to disruptions in hydrogen bond networks by chemisorbed waters and chloride. Particles reacted with NaCl had lower loadings below ∼10 Torr water vapor but greater loadings above this value than salt-free surfaces. Water adsorption reactions were here affected by competitive hydration of coexisting salt-free surface regions, adsorbed chloride and sodium, as well as precipitated NaCl. Collectively, the findings presented in this study add further insight into the initial mechanisms of thin water film formation at goethite surfaces subjected to variations in water vapor pressure that are relevant to natural systems.

Note: Implementation of a cold spot setup for controlled variation of vapor pressures and its application to an InBr containing discharge lamp

In order to allow for a systematic investigation of the plasma properties of discharges containing indium halides, which are proposed as an efficient alternative for mercury based low pressure discharge lamps, a controlled variation of the indium halide density is mandatory. This can be achieved by applying a newly designed setup in which a well-defined cold spot location is implemented and the cold spot temperature can be adjusted between 50 and 350 °C without influencing the gas temperature. The performance of the setup has been proved by comparing the calculated evaporated InBr density (using the vapor pressure curve) with the one measured via white light absorption spectroscopy.

Pressure-induced evaporation dynamics of gold nanoparticles on oxide substrate

Here we report thermal evaporation dynamics of Au nanoparticles on single crystal oxide substrates, including MgO, SrTiO(3), and Al(2)O(3). The size reduction rate of Au nanoparticles via thermal treatments is strongly dependent on not only temperature but also pressure. Lowering the pressure of inert Ar gas from 10(5) to 10 Pa increases the size reduction rate over 30 times in the temperature range 800 °C-950 °C. The temperature dependence is solely due to the variation of saturated vapor pressure of Au, whereas the pressure dependence of the surrounding inert gas can be interpreted in terms of a pressure dependence on a gas-phase diffusion of evaporated Au atoms into the surroundings. We present a simplified model to explain an evaporation dynamics, which well describes the pressure dependence on a size reduction rate of Au nanoparticles. By utilizing this useful pressure-induced evaporation dynamics, we succeeded in manipulating a size reduction of Au nanoparticle arrays down to -10 nm diameter range from -300 nm initial size by programming sequentially a surrounding pressure.

Microclimate Variations between Semienclosed and Open Sections of a Marathon Route

The Hong Kong Standard Chartered Marathon, held annually, is one of the most popular international marathon events. Its primarily urban environmental setting characterized by high-density urban areas, semienclosed tunnels, and suspension bridges, together with the herds of runners, has an influence on the microclimate along the marathon course. This study focused on assessing and comparing variations in temperature and vapour pressure (vis-à-vis relative humidity) against the crowd of runners, or the herd effects, in two different environmental settings along the marathon course: semienclosed (a tunnel) versus open space (a suspension bridge). A series of small iButtons were deployed at strategic locations along the course to undertake minute-by-minute measurements of temperature and relative humidity. It was found that herd effects of varying degrees were present in both semienclosed and open settings. Various environmental differences also played a role in ameliorating or amplifying the climatological effects of the herd of runners. Our study suggests that microclimate variations in different environmental settings and crowd conditions could have an impact on runners. This new knowledge can inform the design of marathon routes. It also establishes the feasibility of employing the iButton logging sensors for widespread deployment and monitoring of meteorological situations.

Oxygen Vacancy Driven Modulations in In2O3 Pyramidal Beaded Nanowires

We present the growth of pyramidal beaded In2O3 nanowires by using hydrogen assisted thermal evaporation. Reduction reaction at the source produces different growth species having varying vapor pressures, which is responsible for the growth of oxygen deficient nanostructures. The number and nature of oxygen vacancies affect the growth rates of different planes and thus the ultimate nanostructure morphology. A detailed growth mechanism of the nanowires is proposed on the basis of thus created oxygen vacancies. Morphology of the synthesized nanostructures was interpreted using electrical and structural analysis (VESTA) software. Structural, compositional, optical and field emission (FE) characteristics were studied to further confirm the oxygen deficient growth. The phonon confinement model (PCM) was used to calculate the correlation length of defects. The regarded nanowires were found to be good field emitters with low turn-on fields, from 5.8 to 14.5 V/μm, and field enhancement factors from 1775 to 362, depending on cathode–sample distances. The experimental FE data were fitted with the Philips model and two-region field emission (TRFE) model, and the screening effect, absolute amplification factor and width of field enhancement region were calculated. Our approach to fabricate beaded nanowires may open new avenues to synthesize unique nanostructures for novel optoelectronic devices.

Photosynthetic gas exchange characteristics in <i>Jatropha curcas</i> L.

The use of Jatropha (Jatropha curcas L.) as a source of biofuel has been well-documented. However, the physiological characteristic and growth analysis studies of Jatropha have received considerably lesser attention. In the present study, to confirm the physiological characteristics of Jatropha, we measured the leaf gas exchange characteristics in response to various environmental conditions. Seedlings were grown in 1/5,000 a pots for 2-3 months under greenhouse conditions. Leaf gas exchange rates were measured in a handmade assimilation chamber (26x30x9 cm), in which a fully expanded whole leaf could be set. Based on the leaf gas exchange characteristics, Jatropha was considered to be a C-3 photosynthesis plant. The photosynthetic rate ranged between 10 and 25 mu mol m(-2) s(-1) and light saturation generally occurred at 500-1,000 mu mol m(-2) s(-1) photon flux densities (PFD), depending on the growth conditions and leaf positions. Leaf conductance and transpiration rates were saturated at 400-1,000 mu mol m(-2) s(-1) PFD, also depending on the growth conditions and leaf positions. Maximum rates of transpiration and leaf conductance were 2-6 mmol m(-2) s(-1) and 200-1,200 mmol m(-2) s(-1), respectively, which are very similar to those in C-3 rice plants. Optimum temperature for photosynthesis was approximately at 25-30 degrees C and the maximum rate was 20 mu mol m(-2) s(-1). Application of varying vapor pressure difference (from 1 to 3 kPa) did not affect the photosynthetic rate. Photorespiration in Jatropha was 28.5%, which is within the range of typical C-3 plants. Based on the photosynthetic parameters presented in this study, field performance of Jatropha under severe environmental condition is discussed.

EFFECT OF ZnO NANOPOWDER SOURCE AND GROWTH TEMPERATURE ON SHAPE EVOLUTION OF ZnO NANOSTRUCTURES

We study the effect of ZnO source and growth temperatures on morphology of the ZnO nanostructures. Nanostructures grown from ZnO nanopowder show the shape evolution from nanowires to nanoribbons and then to nanorods with variation in growth temperature and zinc vapor pressure. At 750°C, only vertically aligned nanowires have been observed and with increase in growth temperature nanowires transforms to nanoribbons and then finally to nanorods at 870°C. On the other hand, in case of ZnO bulk powder as a source material, only nanowires are produced at all temperatures. Raman scattering studies on the nanostructures show distinct [Formula: see text] mode at ~ 437 cm-1, confirming the hexagonal wurtzite phase of the as grown nanostructures. Room temperature photoluminescence spectra exhibit bound exciton related strong UV emission at ~ 379 nm indicating high quality of the as-grown nanostructures. Possible mechanism of growth and shape evolution in ZnO nanostructures are explored through systematic studies of the effect of growth temperatures and zinc vapor pressure.

Impacts of climate variability on reference evapotranspiration over 58 years in the Haihe river basin of north China

Abstract Physically, evaporative demand is driven by net radiation ( R n ), vapour pressure ( e a ), wind speed ( u 2 ), and air temperature ( T a ), each of which changes over time. By analyzing temporal variations in reference evapotranspiration (ET 0 ), improved understanding of the impacts of climate change on hydrological processes can be obtained. In this study, variations in ET 0 over 58 years (1950–2007) at 34 stations in the Haihe river basin of China were analyzed. ET 0 was calculated by the FAO Penman–Monteith formula. Calculation of Kendall rank coefficient was done by analyzing the annual and seasonal trends in ET 0 derived from its dependent climate variables. Inverse distance weighting (IDW) was used to analyze the spatial variation in annual and seasonal ET 0 , and in each climate variable. An attribution analysis was performed to quantify the contribution of each input variable to ET 0 variation. The results showed that ET 0 gradually decreased in the whole basin over the 58 years at a rate of −1.0 mm yr −2 , at the same time, R n , u 2 and precipitation also decreased. Changes in ET 0 were attributed to the variations in net radiation (−0.9 mm yr −2 ), vapour pressure (−0.5 mm yr −2 ), wind speed (−1.3 mm yr −2 ) and air temperature (1.7 mm yr −2 ). Looking at all data on a month by month basis, we found that T a had a positive effect on dET 0 /d t (the derivative of reference evapotranspiration to time) and R n and u 2 had negative effects on dET 0 /d t . While changes in air temperature were found to produce a large increase in dET 0 /d t , changes in other key variables each reduced rates, resulting in an overall negative trend in dET 0 /d t .

SHAPE EVOLUTION IN ONE-DIMENSIONAL ZnO NANOSTRUCTURES GROWN FROM ZnO NANOPOWDER SOURCE: VAPOR–LIQUID–SOLID VERSUS VAPOR–SOLID GROWTH MECHANISMS

Here we report on the growth and evolution of ZnO nanowires grown from ZnO nanopowder as a source material using a horizontal muffle furnace. The shape evolution has been studied with variation in growth temperature and zinc vapor pressure. The structural analysis on these nanostructures shows c-axis oriented aligned growth. Scanning electron microscopy imaging of these nanostructures revealed the shape evolution from nanowires to nanoribbons and then to nanorods as the growth temperature increases from 650°C to 870°C. At 650°C, only vertical nanowires have been observed and with increase in growth temperature nanowires transform to nanoribbons and then to nanorods at 870°C. And we also observed simultaneous growth of nanorods and nanoribbons under a specific growth condition. We believe that these nanowires and nanorods were formed by vapor–liquid–solid growth mechanism (catalyst-mediated growth), whereas nanoribbons were grown by vapor–solid growth mechanism (without the aid of a metal catalyst). We observed simultaneous occurrence of vapor–liquid–solid and vapor–solid growth mechanisms at a particular growth temperature. These ZnO nanowires exhibit bound exciton related UV emission at ~379 nm, and defect-emission band in the visible region. Possible growth mechanism, shape evolution, and simultaneous growth of two types of one-dimensional ZnO nanostructures under the same growth condition are discussed.

Quantitative Structure−Property Relationships for Prediction of Phase Equilibrium Related Properties

In this work, novel techniques for predicting vapor pressure and binary interaction coefficients for homologous series are developed based on the previously proposed targeted quantitative structure−property relationship (TQSPR) and QS2PR methods. For predicting vapor pressure variation as a function of temperature, a two-reference compound (TRC) QSPR method is suggested. This method uses two, structurally similar predictive compounds with available vapor pressure data to predict point by point the vapor pressure or the saturation temperature of a target compound. For the target compound, only structural information is required. The two variants of the method were applied to several homologous series. They demonstrate prediction of vapor pressure within experimental uncertainty, depending on the level of similarity between the predictive compounds and the target compound. A targeted QSPR method for prediction of the binary interaction coefficients (kij) in cubic equations of state for a compound with the members of its homologous series is also presented. The coefficients for the Soave−Redlich−Kwong and Peng−Robinson equations, used to test the method, were reproduced within the deviation of those obtained from regressed experimental data.

Synthesis of a New Modification of Lithium Chloride Confirming Theoretical Predictions

AbstractIn accordance with prior calculations, the new polymorph β‐LiCl (wurtzite structure type) has been synthesised, by the low‐temperature atomic‐beam‐deposition (LT–ABD) technique, in a mixture with α‐LiCl (rock salt structure type) by depositing LiCl vapour (2 to 5.3 × 10–4 mbar) onto a cooled substrate (–30 to –60 °C). The maximum β‐LiCl fraction of 53 % was obtained using a sapphire (0001) substrate at –50 °C and 3.7 × 10–4 mbar LiCl vapour pressure. The proportion of the new polymorph contained in the bulk sample decreases as temperature or vapour pressure deviate from these values, until finally the rock salt type LiCl is found exclusively. When the samples are warmed up to room temperature, β‐LiCl irreversibly transforms to α‐LiCl. The X‐ray diffraction pattern of the two phase LiCl sample measured at –50 °C has been indexed and refined based on a hexagonal unit cell for β‐LiCl with the lattice constants a = 3.852(1) Å and c = 6.118(1) Å and a cubic unit cell for α‐LiCl with the lattice constant a = 5.0630(8) Å. By Rietveld refinement the wurtzite type ofstructure (P63mc, No. 186) was suggested for the new hexagonal modification of LiCl with the Li–Cl distances (2.32 and 2.34 Å) being 8 % smaller than those of α‐LiCl. Moreover, the cell volume decreases as much as 16 % during the transition from β‐LiCl to α‐LiCl. Both the shifts in bond lengths and volume correspond well with the situation encountered for LiBr and LiI. Besides the variation of LiCl vapour pressure and substrate temperature, also different substrate materials were employed for testing their influence on formation of the β‐LiCl polymorph.

High Vapor Pressure Perfluorocarbons Cause Vesicle Fusion and Changes in Membrane Packing

Perfluorocarbons (PFCs) hold great promise for biomedical applications. However, relatively little is known about the impact of these chemicals on membranes. We used unilamellar vesicles to explore the effects of PFCs on membrane packing and vesicle stability. Four clinically relevant PFCs with varying vapor pressures (PP1, 294 mbar; PP2, 141 mbar; PP4, 9.6 mbar; and PP9, 2.9 mbar) were examined. Microscopy imaging and spectroscopic measurements suggest that PFCs, especially those with high vapor pressures, lead to vesicle fusion within hours. Upon exposure to PP1 and PP2 for 72 h, vesicles retained a spherical shape, but the size changed from ∼200 nm to ∼20–40 μm. In addition, membrane packing underwent marked changes during this timeframe. A significant decrease in water content in the lipid polar headgroup regions occurred during the first 1–2-h exposure to PFCs, followed by a steady increase in water content over time. Possible mechanisms were proposed to explain these dramatic structural changes. The finding that chemically inert PFCs exhibited fusogenic activity and marked changes in membrane surface packing is novel, and should be considered when using PFCs for biomedical applications.

Thermochemistry of 2- and 3-Thiopheneacetic Acids: Calorimetric and Computational Study

The enthalpies of formation in the condensed and gas states, Delta f H m degrees (cd) and Delta f H m degrees (g), of 2- and 3-thiopheneacetic acids were derived from their respective enthalpies of combustion in oxygen, measured by a rotating bomb calorimeter, and the variation of vapor pressure with temperature determined by the Knudsen effusion technique. Theoretical calculations at the G3 level were performed, and a study on molecular and electronic structure of the compounds has been carried out. Calculated Delta f H m degrees (g) values using atomization and isodesmic reactions are compared with the experimental data. Experimental and theoretical results show that the 3-thiopheneacetic acid is thermodynamically more stable than the 2-isomer.

Evolving mass spectra of the oxidized component of organic aerosol: results from aerosol mass spectrometer analyses of aged diesel emissions

Abstract. The species and chemistry responsible for secondary organic aerosol (SOA) formation remain highly uncertain. Laboratory studies of the oxidation of individual, high-flux SOA precursors do not lead to particles with mass spectra (MS) matching those of ambient aged organic material. Additionally, the complexity of real organic particles challenges efforts to identify their chemical origins. We have previously hypothesized that SOA can form from the atmospheric oxidation of a large suite of precursors with varying vapor pressures. Here, we support this hypothesis by using an aerosol mass spectrometer to track the chemical evolution of diesel exhaust as it is photochemically oxidized in an environmental chamber. With explicit knowledge of the condensed-phase MS of the primary emissions from our engine, we are able to decompose each recorded MS into contributing primary and secondary spectra throughout the experiment. We find that the SOA becomes increasingly oxidized as a function of time, quickly approaching a final MS that closely resembles that of ambient aged organic particulate matter. This observation is consistent with our hypothesis of an evolving suite of SOA precursors. Low vapor pressure, semi-volatile organic emissions can form condensable products with even a single generation of oxidation, resulting in an early-arising, relatively less-oxidized SOA. Continued gas-phase oxidation can form highly oxidized SOA in surprisingly young air masses via reaction mechanisms that can add multiple oxygen atoms per generation and result in products with sustained or increased reactivity toward OH.

Comparison of soil moisture and meteorological controls on pine and spruce transpiration

AbstractTranspiration is an important component of the water balance in the high elevation headwaters of semi‐arid drainage basins. We compare the importance of soil moisture and meteorological controls on transpiration and quantify how these controls are different at a ponderosa pine site and a spruce site in the Jemez river drainage basin of northern New Mexico, a sub‐basin of the Rio Grande. If only soil moisture controls fluctuations in transpiration, then simple hydrologic models focussed only on soil moisture limitations are reasonable for water balance studies. If meteorological controls are also critical, then more complex models are required.We measured volumetric water content in the soil and sap velocity, and assumed that transpiration is proportional to sap velocity. Ponderosa sap velocity varies with root zone soil moisture. Nearly all of the scatter in the ponderosa sap velocity–soil moisture relationship can be predicted using a simple model of potential evapotranspiration (ET), which depends only on measured incident radiation and air temperature. Therefore, simple hydrologic models of ponderosa pine transpiration are warranted. In contrast, spruce sap velocity does not clearly covary with soil moisture. Including variations in potential evapotranspiration does not clarify the relationship between sap velocity and soil moisture. Likewise, variations in radiation, air temperature, and vapour pressure do not explain the observed fluctuations in sap velocity, at least according to the standard models and parameters for meteorological restrictions on transpiration. Both the simple and more complex models commonly used to predict transpiration are not adequate to model the water balance in the spruce forest studied here. Copyright © 2008 John Wiley & Sons, Ltd.

Evaporation from a Limonene Emulsion

A publication to honor the legacy of Per Ekwall, the Finnish colloid chemist, whose research was on the forefront for several decades in the area of colloidal association structures. In the article an algebraic method was applied to obtain information about the conditions during evaporation of the volatile compounds in a system of limonene, water and Laureth 4 (a commercial tetraoxyethylene dodecyl ether). The evaporation path was calculated using published information about the phase diagram of the system and about the vapor pressures of the components at selected compositions. In the calculations intervals between steps were made proportional to the difference between the excess vapor pressure of water at the selected level of relative humidity and its full vapor pressure at zero relative humidity. This calculation method inherently gave linear time dependence of the remaining water in the emulsion because of its constant vapor pressure. The calculations also revealed the amount of limonene to be close to linearly dependent on time. The reason for this latter result was found in the features of the phase diagram; in turn caused by the limonene oil phase being a W/O microemulsion with moderate vapor pressure variation with composition.

Calorimetric and Computational Study of 1,3- and 1,4-Oxathiane Sulfones

The enthalpies of formation in the condensed and gas states, DeltafH degrees m(cd) and DeltafH degrees m(g), of 1,3- and 1,4-oxathiane sulfones were derived from their respective enthalpies of combustion in oxygen, measured by a rotating bomb calorimeter and the variation of vapor pressures with temperatures determined by the Knudsen effusion technique. Standard ab initio molecular orbital calculations at the G2(MP2) and G3 levels were performed, and a theoretical study on molecular and electronic structure of the compounds has been carried out. Calculated DeltafH degrees m(g) values at the G3 level using atomization reactions agree well with the experimental ones. These experimental and theoretical studies support that the destabilization found in 1,3-oxathiane sulfone, 11.2 kJ mol-1 respecting to 1,4-oxathiane sulfone, is due to the electrostatic repulsion between the negative charges of the axial oxygen of the sulfone and the oxygen of the ring and apparently masks any stabilization originating from the hyperconjugative nO --> sigma*C-SO2 stereoelectronic interaction.