High Initial Water Content Research Articles

Thermal and Physical Properties; and Surface Morphology of Waterborne Maleinized Epoxidized Soybean Oil Films for Coatings Application

In this study, waterborne maleinized epoxidized soybean oil (WMESO) films were prepared and characterized in order to investigate their thermal properties, mechanical properties and surface morphology. A series of coating films were cured onto glass substrate. Differential Scanning Calorimetry (DSC) analysis showed that the coating films have glass transition temperature (Tg) ranging between 36-38 °C. Thermogravimetric analysis (TGA) revealed that waterborne films couls stand very high temperature up to 600 °C. W-2.0 was the best sample in terms of hardness. Film adhesion test showed that the adhesion between film and substrate was good. Higher initial water content gave films with better physical properties but poorer adhesion to substrate. Scanning Electron Microscopy (SEM) was used to visualize the surface morphology of film as well as the formation of resin. It was observed that, the particles were well dispersed and were crosslinked to each other.

Test Research on the Long-Term Consolidation Mechanism of Ultra-Soft Clay

Although the settlement of ultra-soft clay improved by the vacuum preloading technique was large in land reclamation projects, usually exceeding the theoretical calculation value by a large amount, the strength increase was relatively small. As a result the foundation would not meet the design requirements for strength. So a test was conducted to investigate the effect and mechanism of long-term consolidation of ultra-soft clay in laboratory in a period of over 691 days. A preloading load of 80kPa was used in this drainage consolidation test. The test result showed that for the ultra-soft clay with a high initial water content but a small strength, the settlement is large with a large strength increase, but the shear strength was relatively low. These results should draw much attention in application of vacuum preloading technique in construction projects.

Genotypic variability for root/shoot parameters under water stress in some advanced lines of cotton (Gossypium hirsutum L.)

Research pertaining to genetic variability parameters, heritability, and genotypic, phenotypic, simple, and environmental correlations for various seedling traits in five elite advanced cotton (Gossypium hirsutum L.) lines (FH-113, FH-114, FH-941, FH-942, and FH-2015) and one check (CIM-496) was carried out during October and November 2010 under greenhouse conditions at the Cotton Research Institute (Faisalabad, Pakistan). Material was raised in plastic tubes with a randomized complete block design replicated three times. Three drought shocks were applied by withholding water from the tube-sown plants for 8-, 10-, and 12-day intervals. After 60 days of sowing, data on root/shoot traits like root length (cm), shoot length (cm), root weight (g), shoot fresh weight (g), lateral root number, root dry weight (g) shoot dry weight (g), and total plant weight (g) were recorded. Considerable genotypic variations existed between genotypes for all seedling characters. Higher broad-sense heritability estimates were found for all traits studied. Maximum broad-sense heritability coupled with high genetic advance in root length (0.99, 17.34), lateral root number (0.91, 2.89), and shoot length (0.90, 4.35) suggested a potential for genetic improvement through breeding and selection. The correlation coefficients among root length, shoot length, root dry weight, fresh shoot weight, and total plant weight were positively and significantly correlated; thus, they can be selected simultaneously as drought tolerance selection indexes owing to the absence of undesired relationships. Genotypes FH-942 and FH-113 had the lowest excised leaf water loss during the first 4 h and also for the next 4 h. Therefore, these two advanced lines (FH-942 and FH-113) with high initial water content and lower excised leaf water loss had better adaptation to water stress.

A mathematical model for 2D heat transfer dynamics in fluid systems with localized sink of magmatic fluid into local fractured zones above the top of crystallizing intrusions

A model describing two-dimensional (2D) dynamics of heat transfer in the fluid systems with a localized sink of a magmatic fluid into local fractured zones above the roof of crystallizing crustal intrusions is suggested. Numerical modeling of the migration of the phase boundaries in 2D intrusive chambers under retrograde boiling of magma with relatively high initial water content in the melt shows that, depending on the character of heat dissipation from a magmatic fluid into the host rock, two types of fluid magmatic systems can arise. (1) At high heat losses, the zoning of fluidogenic ore formation is determined by the changes in temperature of the rocks within the contact aureole of the intrusive bodies. These temperature variations are controlled by the migration of the phase boundaries in the cooling melt towards the center of the magmatic bodies from their contacts. (2) In the case of a localized sink of the magmatic fluid in different parts of the top of the intrusive chambers, a specific characteristic scenario of cooling of the magmatic bodies is probably implemented. In 2D systems with a heat transfer coefficient α k < 5 × 104 W/m2 K, an area with quasi-stationary phase boundaries develops close to the region of fluid drainage through the fractured zone in the intrusion. Therefore, as the phase boundaries contract to the sink zone of a fluid, specific thermal tubes arise, whose characteristics depend on the width of the fluid-conductive zone and the heat losses into the side rocks. (3) The time required for the intrusion to solidify varies depending on the particular position of the fluid conductor above the top of the magmatic body.

Experimental Study on Moisture Migration in Unsaturated Loess under Freezing Effect

Test equipments were designed and manufactured for producing moisture migration in unsaturated loess under freezing effect. The results showed that both the amount of freezing-thawing cycles and initial water content of soil samples affect the process of moisture migration. As the freezing front advanced in the sample, the water content in the unfrozen part significantly reduced and the water content in the freezing part significantly increased, with the maximum water content at the freezing front. Comparing to the moisture migration in the unfrozen part, the moisture migration to the freezing front in the freezing part was relatively slow. For soil samples with higher initial water content, the increment of water content at the freezing front was higher and sometimes ice could be formed. During a certain amount of freezing-thawing cycles, the water content at the freezing front kept increasing. However, as the amount of freezing-thawing cycles continued increasing, the freezing front started to move to the part with negative temperature and the maximum water content appears at the end with the lowest temperature.

The effect of fungal competition on colonization of soybeans by moulds of the genus Aspergillus, Trichothecium and Fusarium and the ochratoxin A accumulation as related to temperature and moisture content

The relationship between mould biomass and accumulation of ochratoxin A (OTA) on solid substrate (slightly cracked soybeans) at temperatures from 15 to 35°C and a water content in the substrate of 20 to 38% was been investigated. The experiments were carried out with the mould Aspergillus ochraceus NRRL 3174 in pure culture and in mixed culture, respectively; the latter with the moulds Trichothecium roseum ZMPBF 1226 and Fusarium graminearum ZMPBF 1244. The biomass growth during cultivation was monitored by measuring the analysis of chitin as glucosamine, and the concentration of OTA was measured by high performance liquid chromatography (HPLC) method using Hewlett-Packard instrument with fluorescence detector. It was established that the accumulation of the examined OTA primarily depend on the temperature of cultivation rather than on the growth of the biomass. The biomass of the mixed culture of A. ochraceus , T. roseum and F. graminearum after 35 days of cultivation reduced the amount of OTA by 48, 72 and 85%, respectively. The decrease of concentration of OTA is more pronounced in the substrate with a higher initial water content and at higher temperature of cultivation. Keywords: Moulds, mycotoxins, ochratoxin A, chitin, HPLC

Effects of seedbed properties on crop emergence: 3. Effects of firming of seedbeds with various sowing depths and water contents

Extensive experiments were carried out in shallow plastic boxes placed directly on the ground in the field to study the effects of seedbed properties on the emergence of various crops in a cool temperate climate. In a group of experiments with barley (Hordeum vulgare L.), we studied the effects on crop emergence of firming (slight compaction) of the seedbed, simulating the recompacting effects of rolling after sowing or press wheels on the seed coulters. Most of the experiments were carried out without irrigation after sowing. The firming usually had a slightly positive effect on emergence when the water content in the surface layer at sowing was below the wilting point. When the water content in the surface layer was higher, firming often reduced emergence drastically, particularly with deep sowing and in coarse-textured soils. The main reason for negative effects was harmful hardening of the surface layer when the more firm seedbed gradually dried out. When irrigation kept the seedbed continuously moist, the negative effect of firming was almost eliminated. Very high initial water content in the basal layer tended to delay surface layer drying and hardening, and to reduce the negative effect of firming. Firming only slightly influenced the evaporative water losses from the soil. In contrast to the results presented here, previous field trials with cereals have usually resulted in more positive effects of rolling after sowing. This indicates that other effects than firming, such as modification of sowing depth and reshaping of the soil surface, are other important effects of rolling.

Experimental Study on Dewatering Dredged Clay with Ventilating Vacuum Method

A series of model tests were performed on dredged clay with high initial water contents for investigating the dewatering behavior by ventilating vacuum method (VVM). The results shows that the surface water separated from dredged clay can be quickly removed by VVM in which a new pattern PVD is used. In addition, the method also speeds up the deposition of dredged clay. The volume of dredged clay with an initial water content of 4.5 times liquid limit decreases by 50 percent within two months. This paper also investigated the spatial distribution law of water content by TDR method. It is found that the drainage distance of PVD is about 0.3-0.4m.

Heterogeneous mantle underneath the North Atlantic: Evidence from water in orthopyroxene, mineral composition and equilibrium conditions of spinel peridotite from different locations at the Mid-Atlantic Ridge

Orthopyroxene in oceanic spinel peridotite from the Mid-Atlantic Ridge near 15°N, ODP-Leg 209, contains about 15wt.-ppm water that is bound as hydroxyl in the mineral structure. This value is one order of magnitude lower than the water contents reported for (i) orthopyroxene in peridotite from the Mid-Atlantic Ridge at 23°N (270wt.-ppm), ODP-Leg 153, and (ii) sub-continental spinel peridotite xenoliths. Orthopyroxene from both latter occurrences contains the maximum amount of water that can be incorporated in enstatitic orthopyroxene at pressures of the spinel peridotite facies (c. 200–300wt.-ppm). The water contents in orthopyroxene from the sub-oceanic mantle at the Mid-Atlantic Ridge, ranging from about 15 (=highly depleted) to nearly 300wt.-ppm (=water saturation in orthopyroxene), compare well with the highly variable water contents of Atlantic MORB glass that also scatter over one order of magnitude. Mineral trace element data indicate different degrees of partial melting: 18% for peridotite samples of Leg 209 and 12% for those from Leg 153. The mantle equilibrium temperatures differ by 200°C (Leg 209: 1150–1200°C, Leg 153: 950–1000°C). The orthopyroxene water contents of Leg 209 are compatible with residual values after c. 18% partial melting of a peridotitic source with a water content of c. 120–130wt.-ppm in the bulk rock and of c. 300wt.-ppm in the original orthopyroxene, respectively. In contrast, the water content of 270wt.-ppm in orthopyroxene of Leg 153 peridotite cannot be reconciled with residual amounts to be expected after 12% partial melting. This is because an unrealistically high initial water content of c. 3500wt.-ppm would be required for the original orthopyroxene — exceeding the water storage capacity of orthopyroxene at an ambient pressure of c. 20kbar by one order of magnitude. We conclude that – following melt depletion – the water contents of Leg 153 peridotite re-equilibrated in the spinel-peridotite facies. This may have been facilitated by a longer mantle residence time of Leg 153 peridotite (compared to Leg 209) after partial melting and prior to tectonic exhumation from c. 60km depth. An extended mantle residence time is compatible with isobaric cooling from >1200°C to 950–1000°C (at c. 20kbar pressure) as documented by Leg 153 peridotite, and it facilitates re-introduction of water from less or non-depleted mantle regions due to the high diffusivity of H.

Einfluss der Wurzeln auf das Wasserspeichervermögen hydromorpher Waldböden | Significance of roots for soil water storage capacity of hydromorphic forest soils

In this study we investigated the significance of roots for the water storage capacity of hydromorphic forest soils in the northern Pre-Alps of Switzerland. Irrigation experiments were conducted on 1 m2 plots with high initial soil water content. A total of 67 horizons were investigated for water content variations using time domain reflectometry (TDR). The data was processed using a physically based model, which assumes gravity-driven and viscosity-controlled water flow along pore walls in the form of thin water films. The model calculates the contact length (L) between mobile water and the stationary parts of the soil water system in the horizontal plane. L characterises porosity which is effectively involved in water flow. A multiple linear regression analysis of all investigated horizons, including root density, bulk density and texture as predictors for L, demonstrated that the root density had the best explanatory value for L (R2 = 0.63). Thus, it can be assumed that increases in root density increase water storage capacity. Considering the extent of hydromorphicity in horizons, the relationship between root density and contact length was only significant in topsoils and hydromorphic subsoils. An increase of root density by 50% in hydromorphic subsoils would increase short-time water storage capacity from 0.03 to 0.05 m3/m3, while higher root densities in topsoils did not increase water storage capacities. To improve the water retention potential of flood protection forests on hydromorphic soils, we suggest promoting deep-rooting species which are able to sustain anaerobic periods in soils.

Effective Void Ratio for Assessing the Mechanical Properties of Cement-Clay Admixtures at High Water Content

Portland cement is widely used for the improvement of soft clay in many applications and construction methods. Because of the high initial water content of in situ soft clay, the additional water in the cement slurry to be mixed, and the added air in some applications, the mixtures have a high water content and void ratio in either almost-saturated or unsaturated conditions. The mechanical properties of cement-clay admixtures—including cement-treated clay and air-cement-treated clay—are affected by several parameters, e.g., mixing proportions, curing time, and the initial state of the mixture. To facilitate engineering decisions regarding mixing design and the development of a constitutive model, a single parameter that can characterize the mechanical properties of such mixed materials is advantageous. This paper recommends a parameter defined as the effective void ratio that could appropriately quantify the dependency of the mechanical properties of cement-clay admixtures on the influencing parameters on the basis of the results of unconfined compression, oedometer, and triaxial tests. The proposed parameter tends to capture the mechanical characteristics of cement-clay admixtures under different test conditions.

Compression behaviour of reconstituted soils at high initial water contents

Oedometer tests starting from a very small effective vertical stress of 0·5 kPa were performed on three reconstituted clays with different liquid limits. The soils were prepared at various initial water contents, ranging from 0·7 to 2·0 times their corresponding liquid limits. It is observed that the e–log [Formula: see text] compression curves show an inverse ‘S' shape due to suction pressure resisting deformation, similar to that of soft natural clays caused by consolidation yield stress. The suction pressure [Formula: see text] of the reconstituted clays can be correlated with the ratio of initial void ratio to void ratio at liquid limit e0/eL. The suction pressure curve defined by a unique relationship between suction pressure [Formula: see text] and the normalised void ratio at suction pressure es/eLis also proposed to distinguish between the pre-suction and the post-suction states. In addition, Burland's concept of the intrinsic compression line is adopted for correlating the compression curves of various reconstituted clays at high initial water contents. It has been found that the void index is a powerful parameter for normalising the compression curves in the post-suction state. Nevertheless, it seems that Burland's intrinsic compression line slightly underestimates the void index at the low stresses considered in this study. An extended intrinsic compression line is then derived in order to better fit the data for stresses lower than 25 kPa.

Relative Humidity Controls Ammonia Loss from Urea Applied to Loblolly Pine

In the United States, approximately 600,000 ha of pine trees are fertilized with urea each year, with NH3 volatilization losses ranging from &lt;1% to &gt;50% depending on environmental conditions. Previous work showed that the timing of rainfall after urea application plays a significant role in controlling NH3 loss, but the effect of other environmental variables is not well understood. We conducted 10 29‐d studies under different environmental conditions during 2 yr to identify important variables controlling NH3 loss from urea applied to loblolly pine (Pinus taeda L.) at 200 kg N ha−1 Ammonia loss was measured with dynamic chambers that adjusted the rate of air flow through the system based on wind speed at 1 cm above the soil surface. Regression analysis indicated that a variable related to the initial water content of the forest floor and a variable related to the relative humidity (RH) during the study explained 85 to 94% of the observed variability in NH3 loss. Relatively high initial water content followed by consistently high RH led to large NH3 losses. In contrast, low initial water contents resulted in slow rates of NH3 loss, which increased when elevated RH led to an increase in the water content of the forest floor. These results indicate that RH can play a significant role in NH3 loss by accelerating urea dissolution and by increasing or decreasing the water content of the forest floor, which in turn can affect the rate of urea hydrolysis.

Relict sand wedges in soliflucted London Clay at Wimbledon, London, UK

Exposures on Wimbledon Hill, SW London, in the Palaeogene London Clay Formation, are described. The 3° slopes are mantled by clayey solifluction (head) deposits, comprising two superimposed sheets, each around 1.2 m thick. The lower sheet exhibits relict sand wedges forming polygons 1.0–1.5 m across, up to 50 mm wide and 1.25 m deep. These have no surface expression. The wedges are sand-filled and modify significantly the hydrogeology and properties of the solifluction mantle. There are no sand wedges in the upper solifluction sheet. The mechanics of emplacement of the lower solifluction sheet are explored and the high initial water content estimated. Subsequent desiccation and consolidation have reduced the thickness of this sheet by at least 35%, thus distorting contained features such as the wedges. An active layer about 0.4 m thick is inferred to have formed in the top of the lower solifluction sheet. No direct dating was undertaken but, by analogy with relevant dated sites in southern Britain and the Netherlands it is inferred that the lower solifluction sheet was emplaced during the first part of the Loch Lomond Stadial and frost-cracked during a subsequent, colder and more arid part. On this basis, following filling of the cracks by sand, emplacement of the upper solifluction sheet would have occurred in the later part of the Loch Lomond Stadial.

Inversion 2La is associated with enhanced desiccation resistance in Anopheles gambiae

BackgroundAnopheles gambiae, the principal vector of malignant malaria in Africa, occupies a wide range of habitats. Environmental flexibility may be conferred by a number of chromosomal inversions non-randomly associated with aridity, including 2La. The purpose of this study was to determine the physiological mechanisms associated with the 2La inversion that may result in the preferential survival of its carriers in hygrically-stressful environments.MethodsTwo homokaryotypic populations of A. gambiae (inverted 2La and standard 2L+a) were created from a parental laboratory colony polymorphic for 2La and standard for all other known inversions. Desiccation resistance, water, energy and dry mass of adult females of both populations were compared at several ages and following acclimation to a more arid environment.ResultsFemales carrying 2La were significantly more resistant to desiccation than 2L+a females at emergence and four days post-emergence, for different reasons. Teneral 2La females had lower rates of water loss than their 2L+a counterparts, while at four days, 2La females had higher initial water content. No differences in desiccation resistance were found at eight days, with or without acclimation. However, acclimation resulted in both populations significantly reducing their rates of water loss and increasing their desiccation resistance. Acclimation had contrasting effects on the body characteristics of the two populations: 2La females boosted their glycogen stores and decreased lipids, whereas 2La females did the contrary.ConclusionVariation in rates of water loss and response to acclimation are associated with alternative arrangements of the 2La inversion. Understanding the mechanisms underlying these traits will help explain how inversion polymorphisms permit exploitation of a heterogeneous environment by this disease vector.

Water redistribution between bentonite and salt at elevated temperature

Bentonite added to crushed salt promotes the (self) compaction behavior of crushed salt as a kind of lubricant. The bentonite/crushed salt mixture is a candidate backfill material for HLRW repositories in salt formations. At least locally, the backfill material might be exposed to elevated temperature which could cause desorption of water from the bentonite surfaces. As a result the bentonite would lose its ability to act as lubricant for the (self) compaction and the salt would lose its mechanical stability owing to the possible uptake of water. The present study systematically investigates the behavior of bentonite/crushed salt mixtures assuming a closed system which represents either a closed pore or a sealed shaft or gallery. Salt (halite) is known to take up water at relative humidities >75%. This critical value is more or less independent from temperature at least in the range from 30 to 80 °C. Accordingly water redistribution (from bentonite to salt) would occur if the relative humidity in a closed bentonite/salt pore would exceed 75% r.h.. The investigation of a model pore (1 L bottle) with varying amounts of bentonite proved that the absolute humidity in the closed pore increased upon heating. The relative humidity, on the other hand, decreased which indicates that a water redistribution induced by heating will not occur at least until 80 °C. In contrast, water redistribution was clearly observed in the case of high initial water contents of the bentonite (>11 mass%) and low temperature. In conclusion, moderately dried bentonites should be used as lubricant for the improvement of the (self) compaction behavior of crushed salt.

Leaf water absorption and desorption functions for three turfgrasses

Summary Plant leaf can absorb water when the leaf is in contact with water. This happens when the rainfall is intercepted by plant leaves, where the intercepted part of rain remains on the leaf surface. When the intercepted water is either absorbed or subsequently evaporated into the atmosphere, the plant leaves can dissipate water through the desorption process until the plant is dry or rewatered. In this paper, two symptomatic models in the form of exponential functions for leaf water absorption and leaf water desorption were derived and validated by experimental data using leaves of three turfgrasses (Tall fescue, Perennial ryegrass and Kentucky bluegrass). Both the models and measured data showed that the rate of leaf water absorption was high at the low initial leaf water content and then gradually leveled off toward the saturated leaf water content. The rate of leaf water desorption was high at the high initial leaf water content then decreased drastically over time toward zero. The different plant leaves showed different exponents and other parameters of the functions which indicate the difference of plant species. Both the absorption and desorption rates were relatively higher for the Kentucky bluegrass and lower for the Tall fescue and Perennial ryegrass. The concept of specific leaf area (SLA) was used to understand the saturated leaf water content (Cs) of the three turfgrasses. Linear relationships were found between Cs and SLA. The leaf water absorption and desorption functions are useful for deriving physiological parameters of the plant such as permanent wilting leaf water content, naturally irreducible leaf water content, exponential leaf water absorption coefficient, and exponential leaf desorption coefficient, as well as for evaluating the effects of rainfall interception on plant growth and water use efficiency.

A method for predicting soil susceptibility to the compaction of surface layers as a function of water content and bulk density

Identifying the vulnerability of soils to compaction damage is becoming an increasingly important issue when planning and performing farming operations. Soil compaction models are efficient tools for predicting soil compaction due to agricultural field traffic. Most of these models require knowledge of the stress/strain relationship and of mechanical parameters and their variations as a function of different physical properties. Since soil compaction depends on the soil's water content, bulk density and texture, good understanding of the relations between them is essential to define suitable farming strategies according to climatic changes. In this work we propose a new pedotransfer function for 10 representative French soils collected from cultivated fields, a vineyard and forests. We investigate the relationship between soil mechanical properties, easily measurable soil properties, water content and bulk density. Confined compression tests were performed on remoulded soils of a large range of textures at different initial bulk densities and water contents. The use of remolded samples allowed us to examine a wide range of initial conditions with low measurement variability. Good linear regression was obtained between soil precompression stress, the compression index, initial water content, initial bulk density and soil texture. The higher the clay content, the higher the soil's capacity to bear greater stresses at higher initial water contents without severe compaction. Initial water content plays an important role in clayey and loamy soils. In contrast, for sandy soils, mechanical parameters were less dependent on initial water content but more related to initial bulk density. These pedotransfer functions are expected to hold for the soils of tilled surface layers, but further measurements on intact samples are needed to test their validity.

The influence of creep on cake solid volume fraction during filtration of core–shell particles

The solid volume fraction vs. pressure relationship used in conventional filtration models is determined by measuring the cake solid volume fraction after consolidation. However, some cakes creep during consolidation, so the solid volume fraction increases at constant pressure. Thus, the conventional method for determining the solid volume fraction vs. pressure relationship cannot be used for materials with significant creep. Cake creep has been observed when core–shell particles with hard poly(styrene) cores and water-swollen poly(acrylic acid) shells are filtered. The Terzaghi–Voigt combined model has been fitted to data obtained during consolidation to determine the transition point where creep begins to be dominating for cake compression. The solid volume fraction increases by 17–35% after the transition point, particularly in the case of particles with thick poly(acrylic acid) shells and thus a high initial water content. Hence, the solid volume fraction can increase significantly during cake creep and if the solid volume fraction vs. pressure relationship that controls the initial stages of filtration is to be determined then the filtration experiments must be stopped before creep dominates. This can be done by measuring the liquid pressure at the interface between piston and sample, and stop the experiment when the liquid pressure is lower than 5% of the applied pressure.

Oxygen Reduction Reaction Kinetics and Electrode Mass Transport in Sub-Freezing PEM Fuel Cells

A procedure involving isothermal, galvanostatic operation was developed to measure the charge (or ice) accumulation in frozen PEM fuel cells. Charge storage capacity in the membrane and in the electrode was estimated, then compared to measured charge accumulation. Cryo-SEM imaging of electrodes following voltage failure was used to assess pore volume filling in the electrode. At very low currents, in which adequate time allowed for water diffusion, the maximum storage capacity was found in the membrane and electrode. At higher currents, less charge was passed before failure occurred, and significantly less ice had accumulated in the electrode. Lower initial water content corresponded to more available charge storage capacity within the membrane. Operation at high initial water content prevented water uptake by the membrane and allowed isolation of electrode storage capacity, and subsequent estimation of the partition between charge storage in the electrode and membrane at intermediate initial water contents.