Final Water Content Research Articles

Effects of different drying rates on the physiological quality of Coffea canephora Pierre seeds

Desiccation tolerance in seeds depends on the species, development stage and drying conditions, especially the water removal rate. Coffea seeds are considered of intermediate performance, because they tolerate relative dehydration compared to orthodox seeds and are sensitive to low temperatures. The objective of this study was to verify the effect of different drying rates on the viability and storability of Coffea canephora seeds. A complete randomized experimental design was used, in a factorial 3 x 5 x 2 design, with three drying rates (fast, intermediate and slow), five final mean water contents after drying (51, 42, 33, 22 and 15 %) and two storage temperatures (10 and 20°C). The germination and seed vigor assessments, using radicle protrusion, cotyledon leaf opening, seedling emergence and emergence speed index, were performed shortly after drying and after two and four months storage. It was observed that with reduction in the water content there was reduction in the germination values and seed vigor, for all the drying rates. The greatest reductions in physiological quality occurred when the seeds were dried quickly and the best results were obtained at the intermediate drying rate. There was an effect of drying rate and storage temperature on the physiological quality of the seeds, and lower germination and vigor values were observed in seeds with lower water content stored at 20°C. C. canephora seeds were tolerant to desiccation down to 15 % water content and can be stored for four months at 10°C. A temperature of 20ºC can be used to store C. canephora seeds, as long as the water content is not reduced to values below 22 % water content.

A Laboratory Method for Determining the Unsaturated Hydraulic Properties of Soil Peds

The ability to estimate soil hydraulic properties of undisturbed soil peds is limited. Most laboratory methods repack samples into soil cores, thus destroying the structure. Most field methods average over multiple peds precluding measurements of individual peds. This article details a method for determining unsaturated soil hydraulic properties of individual highly structured soil peds. The procedure is based on the evaporation method. The peds were first coated in paraffin wax, with the top surface left open to the atmosphere, and then encased in expandable foam to provide extra support. After saturating, both mass (from digital balance) and soil water potential (from tensiometer) data were recorded every 5 min as the ped dried until the soil water potential reached approximately −70 kPa. The van Genuchten parameters (α, n) and saturated hydraulic conductivity (Ks) were estimated with inversion modeling, using the soil water potential data and final water content. Residual and saturated water contents, θr and θs, respectively, were measured independently. A mini‐permeameter provided independent estimates of Ks We compared the areally weighted average of our optimized hydraulic properties with results from a field infiltrometer test conducted at the exact location from where the peds were collected. The two methods compared well, though some disparity existed between the estimates of n and Ks, likely indicating the effects of interped cracks sampled with the tension infiltrometer. The method is potentially valuable for geostatistical and scaling studies because the smallest structural unit, the soil ped, can be sampled and analyzed.

The prediction of one-, two-, and three-dimensional heave in expansive soils

The prediction of heave in unsaturated, expansive soils has historically been studied primarily as a one-dimensional type analysis. This paper proposes a methodology that can be used for the prediction of one-, two-, or three-dimensional heave. It is suggested that negative pore-water pressures (i.e., soil suctions) can be estimated through a saturated–unsaturated seepage analysis. The results of the seepage analysis are then used as input for the prediction of displacements in a stress–deformation analysis. The formulation of the governing partial differential equations for both seepage and stress–deformation is based on the general theory of unsaturated soils using two independent stress state variables. The elasticity parameter functions required for a stress–deformation analysis can be calculated from various tests, including conventional one-dimensional oedometer tests. The proposed method is studied and tested against data collected on a case history involving a slab-on-ground floor on Regina clay. The predicted results from the two-dimensional analysis agree well with the measured data in terms of both total vertical displacements and final water contents in the soil. The results of a parametric study are also presented to show the effect of measured soil parameters (i.e., swelling index and initial void ratio) and assumed parameters (i.e., Poisson's ratio and coefficient of earth pressure at rest) on the predicted displacements.Key words: heave prediction, unsaturated soil, expansive soil, seepage analysis, stress analysis.

A study of infiltration on three sand capillary barriers

The capillary barrier effect was investigated by conducting infiltration tests on three soil columns of fine sand over medium sand, medium sand over gravelly sand, and fine sand over gravelly sand. The barrier effect was verified in the underlying layer of coarser material, and the water-entry values of the coarser layers were confirmed to be nearly equal to the residual matric suctions of the soils. The coarser layer of gravelly sand, which had a lower water-entry value, was more effective in forming a barrier than the coarser layer of medium sand, which had a higher water-entry value. When the capillary barrier was comprised of a coarser layer of gravelly sand, there was more water stored in the finer layer at the end of the drying stage than when the capillary barrier was comprised of a coarser layer of medium sand. Non-equilibrium static conditions of pore-water pressure profiles were observed in the three soil columns, and a generalized ultimate pore-water pressure profile of a capillary barrier system was proposed. In addition, the final volumetric water contents versus matric suctions of the soils as measured from the soil columns were reasonably consistent with the soil-water characteristic curves (SWCCs) of the soils, suggesting that the drying SWCC of a soil could also be obtained from the drying process in a soil column (or a capillary open tube). The drying SWCC could be established from measurements in the soil column up to a height corresponding to two times the residual matric suction head of the soil.Key words: capillary barrier, soil column, soil-water characteristic curve, pore-water pressure, water content, matric suction.

Hydration of ds-DNA and ss-DNA by Neutron Quasielastic Scattering

Quasielastic neutron scattering measurements were performed in hydrated samples of ds-DNA and ss-DNA. The samples were hydrated in a high relative humidity atmosphere, and their final water content was 0.559 g H 2O/g ds-DNA and 0.434 g H 2O/g ss-DNA. The measurements were performed at 8 and 5.2 Å for the ds-DNA sample, and at 5.2 Å for the ss-DNA sample. The temperature was in both cases 298 K. Analysis of the obtained data indicates that in the ds-DNA sample we can distinguish two types of protons—those belonging to water molecules strongly attached to the ds-DNA surface and another fraction belonging to water that diffuses isotropically in a sphere of radius 2.8 Å, with a local diffusion coefficient of 2.2 × 10 −5 cm 2 s −1. For ss-DNA, on the other hand, no indication was found of motionally restricted or confined water. Further, the fraction of protons strongly attached to the ds-DNA surface corresponds to 0.16 g H 2O/g ds-DNA, which equals the amount of water that is released by ds-DNA upon thermal denaturation, as studied by one of us (G.M.) by differential scanning calorimetry. This value also equals the difference between the critical hydration values of ds-DNA and ss-DNA, also determined by DSC. These results represent, thus, a completely independent measurement of water characteristics and behavior in ds- and ss-DNA at critical hydration values, and therefore substantiate the previous suggestions/conclusions of the results obtained by calorimetry.

A review on the dewaterability of bio-sludge and ultrasound pretreatment

Bio-sludge, which contains large quantities of water, biomass and extracellular polymeric substances (EPS), is difficult to be dewatered as a “super-compactable” sludge [Water Res. 35 (5) (2001) 1358]. Reported water content in bio-sludge was commonly about 80–90% wt after dewatering process. The EPS and the form of water in sludge influences the structure of sludge. Adding cationic fluctuations can change the form of water in sludge and increase the velocity of dewatering process, but has little influence on the final water content. According to Bien's work [Water Sci. Technol. 36 (4) (1997) 287], a combination of ultrasound or other method could agglomerate the sludge, improve the activities of biomass [Ultrasonics 38 (2000) 711; Ultrasonics 40 (2002) 25], enhance anaerobic process [Water Sci. Technol. 36 (11) (1997) 155; Water Sci. Technol. 36 (11) (1997) 121; Water Res. 35 (8) (2001) 2003; Water Sci. Technol. 36 (12) (1997) 117] and decrease over 10% final water content of sludge. The mechanisms of ultrasonic influence on sludge are not very clear, but the application of ultrasound to industrial process is relatively easy and possible.

고효율 열 탈수장치 개발에 관한 연구

A generation rate of sludge in Korea had increased dramatically about 200 % for a decade. A requirement for high efficiency dewatering system being possible to produce the low water content cake have suggested due to the appearanceof commercial and social problems about handing of dewatered cake. The conventional dewatering system with mechanical compression device was not suitable to produce the low water content cake and didn'tcope with lots of requirements. Therefore, this paper was to develop the high efficient filter press with the compressive and heating forces through the heating plate to be built between membrane filter plates. It is possible to produce the low water content cake and improve the dewatering rate, so this equipment positively coped with several types of problems related to the sludge dewatering. The plate heated by heat transfer materials such as steam, hot water and thermo-oil made the sludge make the residual moisture within the cake to discharge easilyand to improve the dewatering efficiency of equipment. The pilot scale experiment with 500㎏ of cake production showed that the dewatering efficiency determined by the final water content and dewatering velocity was improved 30% more than the conventional dewatering equipment.

Rapid swelling and deswelling in cryogels of crosslinked poly(N-isopropylacrylamide-co-acrylic)

Thermally sensitive hydrogels of poly[N-isopropylacrylamide (NIPA)-co-acrylic(AA)] hydrogels with N,N-methylene bisacrylamide (BIS) as crosslinker have been synthesised via a two-step procedure in which, the initial polymerisation is conducted for various times at 18 °C, this step being followed by polymerisation for one fixed time at −22 °C. The gravimetrically determined rates of swelling/deswelling for these materials termed “cryogels” prepared by this two-step polymerisation are much higher than those for the same type of hydrogel prepared via conventional methods (30 °C for 24 h). For example the time for the former xerogel to take up 70% of its final water content at 25 °C is just 18 min, compared with a time 300 min for the latter to attain the same uptake of water. During deswelling (shrinking) at 50 °C, which is above the lower critical temperature, the hydrogel loses 60 and 90 wt.% water in 1 and 10 min respectively, compared to a timescale for the corresponding crosslinked copolymers prepared by conventional methods of about 100 min for 50 wt.% water loss. A third type of hydrogel was made by a cold treatment (CT), for which the hydrogel prepared by conventional polymerisation was stored in the frozen state. The swelling rate of these CT xerogels was the same as that for xerogels prepared by conventional polymerisation, but the deswelling rate of the former was higher than that of the latter; for example, during deswelling, a loss of 90% water is attained within a few minutes.Scanning electron microscopy, digital photographs and flotation experiments together with swelling ratio studies reveal that the polymeric network of cryogel produced by the two-step polymerisation method is characterised by an open structure with more pores and higher swelling ratio but lower mechanical strength compared to the conventional hydrogels. The polymerisation was taking place on moderate freezing condition and the hydrogel was stored in a frozen state and subsequent thawing of polymer to be very useful the acceleration the response rate of this kind hydrogels. Such rapid response hydrogels have potential applications in separation and drug release technologies for example.

Simulation of nitrate distribution under drip irrigation using artificial neural networks

Accurate knowledge of nitrate distribution in the soil under fertigation through drip-irrigation systems is fundamentally important for system design and management. The determination of nitrate distribution through modeling represents a highly complex nonlinear problem that includes adsorption, transformation, convection, and dispersion. For this reason, an alternative methodology is proposed, which combines artificial neural networks (ANN) and laboratory experiments. Seventeen experiments with apparent discharge rates varying from 0.6 to 7.8 l/h, the apparent cylindrical applied volume from 6 to 15 l, and the input concentration from 100 to 700 mg/l were conducted to provide a database for establishing the ANN architecture. The model input parameters were initial soil water content, initial nitrate concentration in the soil, discharge rate, input concentration of fertilizer (NH4NO3), applied volume, and final soil water content. The model output was nitrate concentration in the soil after fertigation. A total of 298 vectors were used to train the ANN model, and 212 independent vectors were used to test the model. Results of the test show a good correspondence with a determination coefficient (r 2) of 0.83 between the model-estimated nitrate concentration in the soil and laboratory-measured nitrate concentration in the soil. These results show that the optimized ANN models are reasonably accurate and can provide an easy and efficient means of estimating nitrate distribution in the soil under fertigation through drip-irrigation systems.

Rapid swelling and deswelling in cryogels of crosslinked poly(N-isopropylacrylamide-co-acrylic acid)

Thermally sensitive hydrogels of poly[N-isopropylacrylamide (NIPA)-co-acrylic acid (AA)] hydrogels with N,N-methylene bisacrylamide (BIS) as crosslinker have been synthesized via a two-step procedure in which, the initial polymerisation is conducted for various times at 18 °C, this step being followed by polymerisation for one fixed time at −22 °C. The gravimetrically determined rates of swelling/deswelling for these materials termed “cryogels” prepared by this two-step polymerisation are much higher than those for the same type of hydrogel prepared via conventional methods (30 °C for 24 h). For example the time for the former xerogel to take up 70% of its final water content at 25 °C is just 18 min, compared with a time 300 min for the latter to attain the same uptake of water. During deswelling (shrinking) at 50 °C, which is above the lower critical temperature, the hydrogel loses 60 and 90 wt% water in 1 and 10 min respectively, compared to a timescale for the corresponding crosslinked copolymers prepared by conventional methods of about 100 min for 50 wt% water loss. A third type of hydrogel was made by a cold treatment (CT), for which the hydrogel prepared by conventional polymerization was stored in the frozen state. The swelling rate of these CT xerogels was the same as that for xerogels prepared by conventional polymerization, but the deswelling rate of the former was higher than that of the latter; for example, during deswelling, a loss of 90% water is attained within a few minutes.Scanning electron microscopy, digital photographs and flotation experiments together with swelling ratio studies reveal that the polymeric network of cryogel produced by the two-step polymerization method is characterized by an open structure with more pores and higher swelling ratio but lower mechanical strength compared to the conventional hydrogels. Such rapid response hydrogels have potential applications in separation and drug release technologies for example.

State diagrams to help describe wheat bread processing

SummaryPhysical changes in wheat bread processing can be described by the use of state diagrams and phase transition. State diagrams were constructed from real experimental results that described the glass transition and melting curves for starch and proteins as a function of water content. Wheat gluten protein is the main component responsible for bread dough structural formation, while starch is mainly involved in final textural properties and stability. During processing, hydration of wheat flour induces the glass transition of wheat gluten proteins. The input of mechanical energy during the mixing allows the development of continuous viscoelastic dough due to interactions between rubbery proteins. During baking, irreversible modifications of starch and proteins at high temperatures (>200 °C) and superficial dehydration are responsible for bread crust formation. In the central part of the mixture, starch gelatinization and protein coagulation induce breadcrumb formation. After cooling, the low water content of the crust (3–7%) is sufficient for the transition of bread components from the rubbery to the glassy state. Consequently, structural hardening occurs and is responsible for crust crispness. The higher final water content of the crumb (35–40%) is responsible for rubbery behaviour, which gives structural mobility, smooth breadcrumb behaviour and explains the sensitiveness to starch retrogradation during storage.

A Transient Evaporation Method for Determining Soil Hydraulic Properties at Low Pressure

A two-stage laboratory method is presented for rapid estimation of the soil water retention function ψ(θ) and the hydraulic conductivity function K (θ) from near saturation to air dry. The pressure head, h , at the bottom of an initially saturated soil core was stepwise decreased whenever the outflow rate had essentially ceased. After attaining this near-equilibrium at ψ = −160 cm, the bottom boundary was sealed, the soil surface was uncovered, and the evaporation rate at a controlled constant temperature was measured. The ψ(θ) was determined by curve-fitting of the equilibrium outflow and psychrometric data obtained from soil samples after evaporation, while the K (θ) was estimated inversely using cumulative evaporation amounts and the final water content profile. The simulated cumulative evaporation and final water content profiles from the optimized parameter values agreed well with the measured data. The root mean square errors for evaporation and the final water content profile were less than 0.022 cm and 0.011, respectively. In addition to close agreement with the simulation, agreement with independent K (θ) data obtained from a steady-state, direct method confirm the reliability of the method presented here.

Normalized Weibull distribution for modeling rehydration of food particulates

Dehydrated food particulates have a rapidly growing market, and their reconstitution is essential in meeting consumers' expectations. Optimal reconstitution properties can be achieved by controlling the drying process and the rehydration conditions. Fundamentals of transport phenomena, particularly diffusion, external resistance and relaxation are some of the mechanisms governing water uptake during rehydration. The Weibull distribution is applied in many biological systems, and was found valuable in the modeling of the rehydration process. Simulation and experimental data showed that the traditional Weibull distribution should be normalized to account for product geometry, thickness and final water content. The Weibull β-shape parameter varied with geometry and the mechanism of water uptake. The derived values for spheres, cylinders and slabs were for diffusion: 0.67, 0.72 and 0.81 respectively; for internal resistance: 1.00, 0.98 and 0.97 respectively; and for relaxation: 1.21, 1.32 and 1.60 respectively. The Weibull distribution provides an insight into the rehydration phenomena that govern water uptake by foods containing particulates during rehydration, and could be used for differentiating between diffusion, external resistance and relaxation processes.

Food sources of phyto-oestrogens and their precursors in Europe.

Phyto-oestrogens are dietary components found in some plants, which act in vivo like weak oestrogens. They may reduce the risk of some degenerative diseases moderated by oestrogen, including breast cancer and osteoporosis. The most widely studied are the isoflavones genistein and daidzein from soyabeans, but lignans may be more prevalent in the European diet. Soya foods have traditionally been consumed in the Orient for millennia, and are now widely available to European consumers. Levels of isoflavone in soyabeans from published literature vary between 560 and 3810 mg/kg, depending on variety and growing conditions. Soya protein concentrates and isolates derived from soyabeans contain 466-615 mg isoflavones/kg. Traditional soya milk, bean curds, bean sprouts, etc. contain 13 to 2030 mg isoflavone/kg, depending on the starting raw material and final water content. Fermented foods have a different isoflavone conjugate profile, which may be important in absorption and metabolism. Soya analogues of European foods include dairy and meat products, which contain 38 to 3000 mg total isoflavones/kg, depending the source of soya and dilution with other ingredients. A wide range of foods contain low levels of soya-derived isoflavones, but such foods do not make a significant contribution to mean intakes in Europe. Flaxseed is by far the richest source of lignan precursors. However, foods such as cereal brans, legumes and some vegetables are a more important source in the diets of Europeans because they are more widely consumed. For similar reasons, compared with soya isoflavones, lignans may be a more important source of phyto-oestrogens in the diets of Europeans.

A FLUX-CONTROLLED STEADY-STATE EVAPORATION METHOD FOR DETERMINING UNSATURATED HYDRAULIC CONDUCTIVITY AT LOW MATRIC PRESSURE HEAD VALUES

We present a simple method for measuring unsaturated hydraulic conductivities at low matric pressure head under a drying process. This method determines hydraulic conductivities from a water content profile under a steady-state upward flow. A steady state was induced by setting both constant meteorological conditions and a constant inflow rate from the bottom. Under our experimental conditions, steady states were attained within a week for two disturbed soils (a loamy sand and a loam). Isothermal water vapor flux was taken into account in the data analysis. Measured hydraulic conductivities agreed well with those obtained from an instantaneous profile method. The simulated time evolution of the evaporation amounts and final water content profiles using the hydraulic conductivity function determined with the present method were also in good agreement with measured values. These results confirm the reliability and applicability of the present method.

Pervaporative dehydration of industrial solvents using a zeolite NaA commercial membrane

Abstract This work reports an experimental study on the pervaporative dehydration of two industrial solvents using a commercial zeolite NaA-type ceramic membrane (SMART Chemical Company Ltd., UK). The mixtures studied are tetrahydrofuran (THF) with an initial water content of 7.9 wt.% and acetone with an initial water content of 3.25 wt.%. Batch experiments were carried out until final water content was lower than 0.1 wt.% in THF mixtures and lower than 0.2 wt.% in acetone mixtures. The influence of feed composition and feed temperature on the pervaporation fluxes and selectivities has been investigated. In the THF dehydration for a water concentration in the retentate of 7 wt.%, the water flux increased from 0.43 to 0.98 kg m−2 h−1 for a temperature increase from 45 to 55 °C. In the acetone dehydration for a water concentration in the retentate of 3 wt.%, the water fluxes increased from 0.13 to 0.314 kg m−2 h−1 for a temperature increase from 40 to 48 °C. The separation factor for the THF–water separation was as high as 20 000, although the separation factor was found to be dependent on the feed water concentration. The water flux through the ceramic membrane shows a linear dependency with the driving force, which is the partial equilibrium vapor pressure of water in the retentate minus the partial pressure in the permeate, pw*−pwp. From the regression of the experimental data, preliminary values of water permeability were obtained that varied in the range 5.5×10−3 kg/(m2/(h/mbar))≤Kw≤7.4×10−3 kg/(m2/(h/mbar)) in the experimental range of operation temperatures.

A Comparative Study of Suction-Induced Seepage Consolidation Versus Centrifuge Consolidation

Abstract The time required for the preparation of a normally consolidated clay sample, by self-weight consolidation in the centrifuge, is often very long and the process may take up to several days. To save centrifuge time, a hydraulic consolidation method of preparation of normally consolidated clay beds, using seepage forces, is often used prior to final consolidation in the centrifuge. At present, the required hydraulic gradient is usually generated by high-pressure water at the top of the clay bed. This method tends to cause hydraulic fracturing at comers when rectangular containers are used. A simple method of using vacuum suction to induce seepage forces to clay samples is proposed and discussed in this paper. Experience with this method shows practically no incidence of hydraulic fracturing. Comparison of the variation of water content and shear strength with depth of samples prepared by the present method and those prepared exclusively by self-weight consolidation in the centrifuge lends support to the validity and effectiveness of the proposed method. The method can be used to prepare clay samples for prototype depth less than about 17 m. A procedure for estimating the final height, water content, and shear strength profiles of the soil model prepared is also presented.

Synthesis of charged linear and crosslinked maleic diester polymers with electron‐beam irradiation

AbstractSeries of maleic mono‐ and diester monomers have been prepared by esterification of maleic anhydride with poly(ethylene glycol) having different molecular weights, and with n‐dodecyl alcohol. These monomers were copolymerized with 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) using different dose rates of electron‐beam irradiation ranging from 40 to 150 kGy. The synthesized copolymers were characterized by IR and 1H NMR analysis. Their aggregation behaviour and viscometric properties in aqueous solutions were investigated. The crosslinked copolymers were prepared in aqueous acidic solutions at pH 1 or in the presence of 1% of N,N‐methylene bisacrylamide (MBA) as crosslinking agent. The final equilibrium water content and swelling capacities for the prepared hydrogels were determined in aqueous solutions at pH = 1, 6.8 and 12 at 298 K. Swelling equilibria for the prepared hydrogels were carried out in aqueous solutions of NaCl, KCl, CaCl2, Na2SO4, K2SO4 and CaSO4 at concentrations ranging from 1 × 10−6 to 2 M at 298 K.© 2003 Society of Chemical Industry

Effect of chemical crosslinking on swelling parameters of modified poly(vinyl alcohol) hydrogel

Graft copolymerization of maleic anhydride (MA) onto partially and fully hydrolyzed poly(vinyl alcohol), PVA, was carried out in presence and in absence of an initiator. The structural features of these grafts were confirmed by 1 HNMR analysis. 1 HNMR analysis was also used to determine the percentage of grafting. These grafts were crosslinked using different concentrations of either 1,1,1-trimethylolpropane trimethacrylate (TPT) or methylene bisacrylamide (MBA) as Hexa- or tetra-functional crosslinker, respectively. The crosslinkers concentrations ranged from 1% to 30% (wt.%) based on the total weight of grafts. The final water content, volume fraction of the polymer and swelling capacity were determined for all grafts. The effect of MBA and TPT crosslinkers structure on swelling properties of both partially and fully hydrolyzed PVA grafts were also determined.

Filter Paper Column for Measuring Transient Suction Profiles in Expansive Clay

An inexpensive experimental system for measuring suction profiles during transient moisture movement processes in unsaturated expansive clays was developed. The system relies on measurements of total suction using the noncontact filter paper technique at several stations along a onedimensional soil column. Performance of the system was demonstrated for a column of compacted Ca2+-smectite undergoing evaporation at the top boundary under ambient laboratory conditions for 91 days. The system was most applicable during latter stages of drying when the rate of moisture movement was slow enough to be adequately captured by the required 7-day measurement interval and the suction values are large enough to offset scatter. Final water content and suction profiles were determined gravimetrically and compared with values obtained from the filter paper measurements. Desiccation cracking did not significantly affect the accuracy of the filter paper system. The research forms an experimental basis to develop or verify theoretical models aimed at predicting moisture flux for in situ expansive soil subject to infiltration or evaporation processes.