Complete Imbibition Research Articles

Topology sorting: Separating linear/star polymer blend components by imbibition in nanopores.

We report the imbibition and adsorption kinetics of a series of symmetric linear/star cis-1,4-polyisoprene blends within the long channels of self-ordered nanoporous anodic aluminum oxide (abbreviated: AAO). Using in situ nanodielectric spectroscopy, we followed the evolution of the longest chain modes in the blends with a judicious selection of molar masses for the constituent components. We demonstrated differences in the imbibition kinetics of linear and star components based on the relative viscosities (e.g., polymers with lower zero-shear viscosity penetrated first the nanopores). Following the complete imbibition of the pores, the adsorption time, τads, of each component was evaluated from the reduction in the dielectric strength of the respective chain modes. In the majority of blends, both components exhibited slower adsorption kinetics with respect to the homopolymers. The only exception was the case of entangled stars mixed with shorter linear chains, the latter acting as a diluent for the star component. This gives rise to what is known as topology sorting, e.g., the separation of linear/star blend components in the absence of solvent. Moreover, a simple relation (τads ∼ 10 × tpeak; tpeak is the time needed for the complete filling of pores) was found for linear polymers and stars. This suggested that the characteristic timescale of imbibition (tpeak) governs the adsorption process of polymers. It further implied the possibility of predicting the adsorption times of high molar mass polymers of various architectures by the shorter imbibition times.

Development of a biomimetic bioreactor for regenerative endodontics research.

In the context of regenerative endodontics research with the development of biomaterials, this work aimed to develop and test a prototype biomimetic bioreactor of a human tooth. The bioreactor was designed to reproduce a shaped dental canal connected with a cavity reproducing the periapical region and irrigated through two fluidic channels intended to reproduce the apical residual vascular supply. A test biomaterial composed of polylactic acid/polycaprolactone-tannic acid (PLA/PCL-TA) was produced by electrospinning/electrospraying and calibrated to be inserted in a dental canal. This biomaterial was first used to evaluate its imbibition capacity and the oximetry inside the bioreactor. Then, Dental Pulp Stem Cells (DPSCs) were cultured on PLA/PCL-TA cones for 1-3weeks in the bioreactor; afterward cell adhesion, proliferation, and migration were histologically assessed. Complete imbibition biomaterial was obtained in 10min and oximetry was stable over time. In the bioreactor, DPSCs were able to adhere, proliferate and migrate onto the surface and inside the biomaterial. In conclusion, this bioreactor was used successfully to test a biomaterial intended to support pulp regeneration and constitutes a new in vitro experimental model closer to clinical reality.

Improved method for complete gas-brine imbibition relative permeability curves

Standard test methods for measuring imbibition gas-brine relative permeability on reservoir core samples often lead to non-uniform brine saturation. During co-current flow, the brine tends to bank up at the sample inlet and redistributes slowly, even with fractional flow of gas to brine of 400:1 or more. The first reliable Rel Perm point is often only attained after a brine saturation of around Sw=40% is achieved, leaving a data gap between Swirr and this point. The consequent poor definition of the shape of the Rel Perm function can lead to uncertainty in the performance of gas reservoirs undergoing depletion drive with an encroaching aquifer or subjected to a water flood. We have developed new procedures to pre-condition brine saturation outside of the test rig and progress it in small increments to fill in the data gap at low Sw, before continuing with a co-current flood to the gas permeability end-point. The method was applied to series of sandstone samples from gas reservoirs from the NW Shelf of Australia, and a Berea standard. We found that the complete imbibition relative permeability curve is typically ‘S’ shaped or has a rolling over, convex-up shape that is markedly different from the concave-up, Corey Rel Perm curve usually fitted to SCAL test data. This finding may have an economic upside if the reservoir produces gas at a high rate for longer than was originally predicted based on the old Rel Perm curves.

Time-resolved synchrotron X-ray micro-tomography datasets of drainage and imbibition in carbonate rocks

Multiphase flow in permeable media is a complex pore-scale phenomenon, which is important in many natural and industrial processes. To understand the pore-scale dynamics of multiphase flow, we acquired time-series synchrotron X-ray micro-tomographic data at a voxel-resolution of 3.28 μm and time-resolution of 38 s during drainage and imbibition in a carbonate rock, under a capillary-dominated flow regime at elevated pressure. The time-series data library contains 496 tomographic images (gray-scale and segmented) for the complete drainage process, and 416 tomographic images (gray-scale and segmented) for the complete imbibition process. These datasets have been uploaded on the publicly accessible British Geological Survey repository, with the objective that the time-series information can be used by other groups to validate pore-scale displacement models such as direct simulations, pore-network and neural network models, as well as to investigate flow mechanisms related to the displacement and trapping of the non-wetting phase in the pore space. These datasets can also be used for improving segmentation algorithms for tomographic data with limited projections.

Imbibition in plant seeds

We describe imbibition in real and artificial plant seeds, using a combination of experiments and theory. In both systems, our experiments demonstrate that liquid permeates the substrate at a rate which decreases gradually over time. Tomographic imaging of soy seeds is used to confirmed this by observation of the permeating liquid using an iodine stain. To rationalize the experimental data, we propose a model based on capillary action which predicts the temporal evolution of the radius of the wet front and the seed mass. The depth of the wetting front initially evolves as $t^{1/2}$ in accord with the Lucas-Washburn law. At later times, when the sphere is almost completely filled, the front radius scales as $(1-t/t_{\text{max}})^{1/2}$ where $t_{\text{max}}$ is the time required to complete imbibition. The data obtained on both natural and artificial seeds collapse onto a single curve that agrees well with our model, suggesting that capillary phenomena contribute to moisture uptake in soy seeds.

Hydrophobic/hydrophilic static powder beds: Competing horizontal spreading and vertical imbibition mechanisms of a single droplet

There are two competing mechanisms of a single liquid droplet impacting on static powder beds. The dh spreading describes the length the liquid droplet travels horizontally across the powder bed, whereas the dv imbibition is the length the liquid droplet travels vertically into the powder bed.In this work, results are presented from an experimental study of single liquid droplets of varying viscosities impacting static hydrophilic and hydrophobic powder beds. By using a high-speed video camera, the dynamics of the droplet spreading behaviour on static powder bed compacts was captured. The resultant nuclei were then analysed. Results show that the measured maximum dh spreading diameter is less than the diameter of the resultant nuclei. This indicates that the dh spreading of the liquid droplet continues to spread after complete imbibition in a late-diffusive intra-spreading process. This process refers to liquid movement driven by capillary forces in the powder beds and showed a higher degree of dependency on the liquid binder viscosity. The dv imbibition length was found to be dependent on the interfacial tension between the solid and the liquid droplet. This transition in the liquid spreading and imbibition behaviour is explained based on the transportation of a liquid droplet occurring increasingly via site percolation theory with increase in powder bed hydrophobicity. The liquid droplet imbibition rates are described in terms of Darcy's law scaling behaviour. Understanding of single droplet spreading mechanisms provides a basis to select the optimal binder for granulation to form more uniform and robust granules when using hydrophilic and hydrophobic formulations.

Habitat-specific seed dormancy-release mechanisms in four legume species

AbstractPhysical seed dormancy is a common attribute among plants, and a wide range of dormancy-release mechanisms have been described, but their ecological significance is rarely tested through comparative study. This study tests whether dormancy-release responses to wet heat in four legume species with physical dormancy are correlated with habitat: two wetland species (Mimosa pigraandParkinsonia aculeata, both dispersed primarily by water) and two terrestrial species (Acacia niloticaandProsopis pallida, both dispersed primarily through vertebrate herbivores). Dormancy release was compared at three moisture levels (80% relative humidity, saturated and submerged) at constant (20–45°C) and diurnally fluctuating (20/40°C) temperatures for 14 d. Seed viability was tested by germinating at 25°C. The functional relationship between temperature and dormancy release after 14 d differed between species: submerged seeds of the two wetland species showed a quadratic response, with low rates of imbibition below 20–25°C and complete imbibition at around 40°C;P. pallidaseeds showed a linear positive relationship, whereas there was no temperature response forA. niloticaseeds below 45°C. Surprisingly, dormancy release after 14 d was relatively insensitive to moisture levels, although rate of dormancy release was generally slower under drier conditions. Dormancy release was not influenced by fluctuating temperatures. Seed viability was largely unaffected by temperature or moisture regime, although it did differ with species and was lower for non-dormant seeds. Our results suggest that a functional dormancy-release response to wet heat provides important fitness benefits for wetland species, but not for species dispersed through vertebrate herbivores, for which it may be maladaptive.

Experiments on metallic foams under gravity and microgravity

Aluminium foams were created on ground and under microgravity conditions and were allowed to evolve. The entire foaming process was monitored by in situ X-ray radioscopy, allowing for flow and drainage of the liquid of the foam to be monitored and quantified. A foam with a known low stability level was used to enhance the effects of microgravity. The flow of metal out of the foam under gravity during the 1.8 g phase was found to be fast, indicating a mobile liquid. The density profile evolved in a similar way as in aqueous foams. Reentry of the liquid melt into the foam was also observed. Under microgravity the foam re-established a uniform density and pore size distribution after nearly complete imbibition of the liquid. This also shows that the liquid is mobile.

The role of peroxiredoxin antioxidant and calmodulin in ABA-primed seeds of Brassica napusexposed to abiotic stresses during germination

Summary Both peroxiredoxin and calmodulin have been demonstrated previously to be involved in the early stages of seed germination. We believe that the peroxiredoxin antioxidant proteins may play a role in protecting seed from oxidative damages and maintaining seed dormancy, and that calmodulins in regulating metabolic enzymes in the early stages of seed germination. To test this hypothesis two cDNA clones BnPER1 and BnCAM1, encoding peroxiredoxin antioxidant and calmodulin respectively, were isolated from seed of Brassica napus cv. Quest. In dry control seeds, a high level of BnPER1 transcript was present while that of BnCAM was low. Priming with 100 μmol/L ABA, where seeds underwent complete imbibition prior to radicle protrusion then dried back to their original moisture content, reduced the transcript level of BnPER1 and induced the expression of BnCAM1. Coincidentally, ABA-primed seeds exhibited earlier (2-7 days) germination and higher final percent radicle protrusion than non-primed control seeds, under salt (100 mmol/L NaCl) or water stress (20 % PEG 8000) at a low temperature (8 °C). For both ABA-primed and non-primed seeds, the decreased expression of BnPER1 and increased expression of BnCAM1 transcripts was highly correlated to the degree of seed germination. These results suggest that peroxiredoxins are down regulated during seed germination in B. napus, probably due to a reduction in oxidative stresses. On the other hand, elevated calmodulin levels was indicative of increased enzymatic activities required for germination. ABA-priming affected the expression of these genes.

Influence of impregnation parameters on the axial Mo/γ-alumina profiles studied using a novel simple technique

The development of a novel, simple technique allowed us to investigate the influence of various impregnation parameters on the axial Mo profiles achieved on γ-alumina extrudates. The effects of pH, temperature, volume, and concentration of the molybdate solutions, as well as the impregnation time, the rate of drying, the modification of γ-alumina with F − ions, and the nature and concentration of various competitors, have been systematically studied. It was found that decreases in pH as well as increases in the concentration of the molybdate solutions, of the impregnation temperature, and of the rate of drying cause a progressive transformation of the Mo profile from uniform to eggshell type. Doping of γ-alumina with F − ions and the use of NH 4F, H 3PO 4, and citric acid as competitors transformed the Mo profiles from eggshell to uniform. The change in volume of the impregnating solution had no effect on the Mo profiles. The effect of the impregnation time was found to be complicated. Increases in the impregnation time, until a critical value sufficient for the complete imbibition of the extrudates, allow for the transfer of great amounts of molybdate to the interior of the extrudates, leading to more uniform profiles. Further increases in the impregnation time caused a considerable increase in the sharpness of the Mo profile. Most of the above observations were explained on the basis of derived equations, adopting a very simple macrodistribution model. Finally, it was demonstrated that small chromatographic columns filled with powder supports may be used to study active ion profiles on catalytic supports.

Uptake and metabolism of 2-[14C]abscisic acid in lettuce fruits var. Great Lakes

There are two phases of 2-[(14)C]ABA uptake in lettuce fruits. Although the first phase appears to relate to the imbibition of water, uptake continues for three hours following complete imbibition. The second phase corresponds with the commencement of radicle extension.Exogenously applied radioactive ABA is metabolised to form an unidentified substance which has chromatographic properties different to previously described ABA metabolites. When ABA is present in the bathing solution, the quantity of metabolite never significantly exceeds that of labelled ABA in the tissues.

Comparison of Calculated with Experimental Imbibition Relative Permeability

Abstract Two-phase imbibition relative permeability was measured in an attempt to validate a method of calculating imbibition relative permeability. The stationary-liquid-phase method was used to measure several hysteresis loops for alundum and Berea sandstone samples. The method of calculating imbibition relative permeability is described, and calculated relative permeability curves are compared with measured curves. The calculated relative Permeability is shown to be a reasonably good Permeability is shown to be a reasonably good approximation of measured values if an adjustment is made to some necessary data. Due to the compressibility of gas, which is used as the nonwetting phase, a correction to the measured trapped gas saturation is necessary to make it agree with the critical gas saturation of the imbibition relative permeability curve. Introduction The existence of hysteresis in the relationship of relative permeability to saturation has been recognized for many yews. Geden et al. and Osoba et al. called attention to the occurrence of hysteresis and the importance of the direction of saturation change on the relative permeability-saturation relations. It is generally believed that relative permeability is a function of saturation alone for a permeability is a function of saturation alone for a given direction of saturation change, but that there is a distinct difference in relative permeability curves for saturation changes in different directions. The reservoir engineer should be aware of this hysteresis, and he should select the relative permeability curve which is appropriate for the permeability curve which is appropriate for the recovery process of interest. The directions of saturation change have been designated "drainage" and "imbibition" in reference to changes in the wetting-phase saturation. In a two-phase system, an increase in the wetting-phase saturation is referred to as imbibition, while a decrease in wetting-phase saturation is called drainage. The solution-gas-drive recovery mechanism is controlled by relative permeability to oil and gas in which the saturation of oil, the wetting phase, is decreasing. In waterflooding a water-wet reservoir rock, the saturation of water, the wetting phase, is increasing. These two sets of relative permeability curves, gas-oil and oil-water, do not have the same relationship to the wetting-phase saturation. This difference is not due to the difference in fluid properties, but is a result of the difference in properties, but is a result of the difference in direction of saturation change. The flow properties of the drainage and imbibition systems differ because of the entrapment of the nonwetting phase during imbibition. As drainage occurs, the nonwetting phase occupies the most favorable flow channels. During imbibition, part of the nonwetting phase is bypassed by the increasing wetting phase, leaving a portion of the nonwetting phase in an immobile condition. This trapped part phase in an immobile condition. This trapped part of the nonwetting phase saturation does not contribute to the flow of that phase, and at a given saturation the relative permeability to the nonwetting phase is always less in the imbibition direction phase is always less in the imbibition direction than in the drainage direction. The concept that some of the nonwetting phase is mobile and some is immobile during a saturation change in the imbibition direction previously was used to develop equations for imbibition relative permeability. In this development, it was assumed permeability. In this development, it was assumed that the amount of entrapment at any saturation can be obtained from the relationship between initial nonwetting-phase saturations established in the drainage direction and residual saturations after complete imbibition. The equations for imbibition relative permeability were not verified by laboratory measurements. The purpose of this report is m give the results of a laboratory study of imbibition relative permeability and to present a comparison of calculated relative permeability with relative permeability from laboratory measurements. permeability from laboratory measurements. In two-phase systems, hysteresis is more prominent in the relative permeability to the nonwetting phase than in that to the wetting phase. The hysteresis in the wetting-phase relative permeability is believed to be very small, and thus difficult to distinguish tom normal experimental error.

Calculation of Imbibition Relative Permeability for Two- and Three-Phase Flow From Rock Properties

Abstract Relative permeability functions are developed for both two- and three-phase systems with the saturation changes in the imbibition direction. An empirical relation between residual nonwetting-phase saturation after water imbibition and initial nonwetting-phase saturations is found from published data. From this empirical relation, expressions are obtained for trapped and mobile nonwetting-phase saturations which are used in connection with established theory relating relative permeability to pore-size distribution. The resulting equations yield relative permeability as a function of saturation having characteristics believed to be representative of real systems. The relative permeability of water-wet rocks for both two- and three-phase systems, with the saturation change in the imbibition direction, may be obtained by this method after properly selecting two rock properties: the residual nonwetting-phase saturation after the complete imbibition cycle, and the capillary pressure curve. Introduction Relative permeability is a function of saturation history as well as of saturation. This fact was first pointed out for two-phase flow by Geffen et al. and by Osaba et al. Hysteresis in the relative permeability-saturation relation also has been reported for three-phase systems. Since saturations may change simultaneously in two directions in a three-phase system, four possible relationships arise between relative permeability and saturation for a water-wet system. The four saturation histories of this system were given by Snell as II, ID, DI and DD. I refer to the direction of saturation change (imbibition and drainage), with the first letter of the symbol indicating the direction of change of the water phase. As used in this paper, the second letter of the symbol refers to the direction of saturation change of the gas phase, i.e., D and I indicate an increase and decrease, respectively, in gas saturation. Only a few three-phase relative permeability curves have been published. Leverett and Lewis published three-phase curves for unconsolidated sand, and Snell reported results of several English authors for both drainage and imbibition three-phase relative permeability of unconsolidated sands. Three-phase relative permeability curves for a consolidated sand were published by Caudle et al. for increasing water and gas saturations (ID). Corey et al. reported drainage (DD) three-phase relative permeability for consolidated sands. Recently, Donaldson and Dean and Sarem calculated three- phase relative permeability curves from displacement data on consolidated sands, also for saturation changes in the drainage direction. The only published three - phase relative permeability curves for consolidated sands with saturation changes in the imbibition direction (II) are those of Naar and Wygal. These curves are based on at theoretical study of the model of Wyllie and Gardner as modified by Naar and Henderson. Interest in three-phase relative permeability has increased recently due to the introduction of new recovery methods and refinements in calculation procedures brought about by the use of large-scale digital computers. The scarcity of empirical relations for three-phase flow, and the experimental difficulty encountered in obtaining such data, have made the theoretical approach to this problem attractive.