Swelling Layers Research Articles

Flexible inner surface of polysulfone membranes prevents platelet adhesive protein adsorption and improves antithrombogenicity in vitro.

We investigated whether the condition of the inner surface of hollow fibers affects the blood compatibility of hemodialyzers. We used scanning probe microscope/atomic force microscopy (SPM/AFM) to investigate the height of the swelling and flexible layers (thickness and softness) on the inner surfaces of the hollow fibers. Next, we tested the blood compatibility between dialyzers comprising a hollow fiber membrane, in which the other dialyzers, except for PVP, were additionally coated using PS membranes coated with other materials. After blood was injected into the dialyzer and plugged, dynamic stimulation was performed by slightly rotating the dialyzer for 4 h, although there was no blood circulation. The vitamin E-coated polysulfone (PS) membrane showed a higher thickness and softness of the flexible layer than the asymmetric cellulose triacetate membrane without polyvinylpyrrolidone (PVP) and the PS membranes with PVP. We found that the dialyzer with vitamin E coating significantly suppressed the decrease in platelets, increase in β-TG, and increase in PF4 compared to those coated with NV polymer. Additionally, as the adsorbed protein on the inner surface, the total protein, fibronectin, and vWF levels were significantly lower in the vitamin E-coated dialyzer. The thickness and softness of the flexible layer of the inner surface of the hollow fiber membrane in vitro affect differences in blood coagulation performance in clinical research. Future clinical trials are required to confirm our results.

Dissolution dynamics of poly(4-hydroxystyrene-co-methacrylic acid) in tetraalkylammonium hydroxide aqueous solutions

Resist materials and their lithography processes are essential for achieving further miniaturization in semiconductor microfabrication. In the sub-20 nm half-pitch region, the development process becomes particularly important due to the occurrence of stochastic defects (pinching and bridging). However, the details of dissolution dynamics are still unclear. In this study, we investigated the dissolution dynamics of poly(4-hydroxystyrene-co-methacrylic acid) (PHSMA) films in tetraalkylammonium hydroxide (TAAH) aqueous solutions using a quartz crystal microbalance method. PHSMA is a typical backbone polymer used in extreme UV lithography. For poly(4-hydroxystyrene) films, it has been reported that the dissolution mode changed when the alkyl chain length of TAAH increased. However, the mode change was not observed for PHSMA films. This difference is considered to be caused by the formation of thick transient swelling layers of PHSMA films owing to the fast water intake and the molecular interaction of the hydroxyl groups of hydroxystyrene units.

Modeling of local electrode stresses and pressures in lithium-ion battery packs using three-dimensional homogenization

Battery packs in electric vehicles consist of several battery modules, each containing several battery cells with numerous layers (electrodes, separators and current collector layers. A finite element model that can capture the stresses on the layer level would be extremely large in order to resolve the details. In the present paper, a novel homogenization method is presented which is based on three-dimensional laminate theory. The number of finite elements for the simulation of stresses in batteries can in this way be drastically reduced. Based on a homogenized solution, layer-level stresses can then be determined in a post-processing step. The present formulation is adaptive and fast, eliminating the need to model individual layers. It allows for non-linear elastic behavior of active layers that undergo swelling and separator layers as well as elastic-plastic behavior of current collectors. Three realistic battery structures subjected to swelling in electrode layers have been simulated: 1. free jellyroll, 2. jellyroll enclosed by a stiff enclosure, and 3. battery module consisting of 10 cells. The presented homogenized method allows for the inclusion of battery cells as parts of larger models representing vehicle structures and facilitates studying the interaction between batteries and surrounding structures.

INFLUENCE OF SWELLING ON SHEAR STRENGTH OF SHALE-LIMESTONE INTERFACE

Rock slope stability is almost controlled by the behaviour of the interface between rock layers. The presence of shale layers between limestone layers complicates this behaviour. As the shale layer undergoes swelling with moisture, it causes the shear interface properties to change with a specific behaviour different from the dry state. The behaviour will depend on the shale’s degree of saturation, swelling percentage, and stress level over shale. An experimental program was carried out to determine the shear interface behaviour parameters of shale-limestone during swelling phenomena to guide stability checks. The interface cohesion and friction angle results are reported along the swelling process and compared with the dry state condition. These results help engineers assign adequate and accurate values for joint shear and normal stiffness in jointed rock slopes, including swelling layers.

Kaolinization of 2:1 type clay minerals with different swelling properties

Abstract Kaolinization of 2:1 type clay minerals commonly occurs in the supergene environments of the Earth, which plays critical roles in many geochemical and environmental processes. However, the transformation mechanism involved and the specific behavior of 2:1 type swelling and non-swelling clay minerals during kaolinization remain poorly understood. In this study, laboratory experiments on the kaolinization of montmorillonite (swelling), illite (non-swelling), and rectorite (partially swelling) were carried out to investigate the kaolinization mechanism of 2:1 type clay minerals and to evaluate whether swelling and non-swelling layers of 2:1 type clay minerals perform differently or not in their kaolinization processes. The results show that montmorillonite, illite, and rectorite in acidic Al3+-containing solutions can be transformed into kaolinite, whereas such transformation is hard to take place in Al3+-free solutions. Part of the Al3+ in the solutions was exchanged into the interlayer spaces of swelling clay minerals at the early stage and resulted in the formation of hydroxy-aluminosilicate (HAS) interlayers, but they show no influence on the transformation process. Interstratified kaolinite-smectite (K-S), kaolinite-illite (K-I), and kaolinite-rectorite (K-R) formed as the intermediate phases during the transformations of the three different precursor minerals, respectively. The results obtained in this study demonstrate that 2:1 type clay minerals, including both swelling and non-swelling ones, can be transformed into kaolinite via a local dissolution-crystallization mechanism, which starts mainly from the layer edges rather than the basal surfaces. Due to different dissolution rates from domain to domain within a precursor mineral particle, the layers with a low dissolution rate become “splints,” while the dissolved elements are concentrated between two “splints,” leading to precipitation of kaolinite along the basal surfaces of precursor minerals. The size and stacking order of the newly formed kaolinite strongly depend on the morphology and property of the precursor minerals. These findings not only are of importance for better understanding the transformation procedures between different clay minerals and the mechanisms involved but also provide new insights for well understanding mineral-water interactions that are central to all geochemical processes.

Development of pulsatile release of Aceclofenac tablets with swelling and rupturable layers of ethyl cellulose

The objective of this study was to develop and evaluate of Aceclofenac tablets with swelling and rupturable layers of ethyl cellulose. A tablet system consisting Intended for treatment of early morning stiffness and symptomatic relief from pain in patients with rheumatoid arthritis with a distinct predetermined lag time of 6 h. Cores containing Aceclofenac as model drug were prepared by direct compression of different Sodium starch glycolate level CT-1 to CT-4) 8 %, 4%, 2% & without disinegrant and were then coated sequentially with an inner swelling layer containing a superdisintegrant (croscarmellose sodium) and an outer rupturable layer of ethylcellulose. Seven formulations were prepared and formulation F2 possessed good lag time 6 hr and showed pulsatile drug delivery pattern the tablets In- vitro evaluation tests. Results of this study indicated that by using ethyl cellulose are suitable to optimize pulsatile drug release formulation of Aceclofenac.

Modeling mechanochromatic lamellar gels

Consisting of alternating swelling and nonswelling polymeric layers (SLs and NLs), lamellar gels are one-dimensional photonic crystals with mechanically tunable optical properties. The lamellar structure induces a constraint between the SLs and the NLs, resulting in a highly anisotropic swelling behavior that is coupled with deformation. The coupling gives rise to the mechanochromatic effect, i.e., the color change in the material in response to mechanical deformations. A quantitative understanding of the coupling behavior is the key to many applications. This paper formulates a nonlinear continuum model for lamellar gels by considering the constrained swelling and anisotropic deformation in both layers. A finite-element method is further developed to simulate the mechanochromatic response of a lamellar gel undergoing a nonuniform field.

Novel nanostructured microfibrillated cellulose–hydroxypropyl methylcellulose films with large one-dimensional swelling and tunable permeability

Microfibrillated cellulose (MFC) films containing the water soluble and pharmaceutically approved polymer hydroxypropyl methylcellulose (HPMC) exhibited an unexpected decrease in permeability and excellent one-dimensional swelling properties above a threshold in HPMC content. It is proposed that the observed material characteristics derive from the influence of HPMC on the aggregation behavior of MFC in such a way that above a critical HPMC content the films are created through self assembly into a layered structure, composed of low swelling layers with swellable inter layer regions. The suggested structures were supported by high resolution microscopy. The findings should hold potential for direct applications, but even more as a concept for future material design.

Development of time controlled chronomodulated tablet with swelling and rupturable layers: Optimization of factors influencing lag-time and drug release

Introduction:A tablet system consisting of cores coated with two layers of swelling and rupturable coatings was prepared and evaluated as time controlled chronomodulated tablet.Materials and Methods:Cores containing Montelukast sodium as model drug were prepared by direct compression and then coated sequentially with an inner swelling layer containing a HPMC E 5 and an outer rupturable layer of Eudragit RL/RS (1:1). A three-factor, two-level, full factorial design was used to investigate the influence of amount of HPMC E 5 and Eudragit RL/RS (1:1) on the responses, i.e., lag time to release and time required for 80% of drug to releases. The dissolution tests were studied using the USP paddle method at 50 rpm in 0.1 N HCL for 2 hr and than in phosphate buffer pH 6.8.Methods:Cores containing Montelukast sodium as model drug were prepared by direct compression and then coated sequentially with an inner swelling layer containing a HPMC E 5 and an outer rupturable layer of Eudragit RL/RS (1:1). A three-factor, two-level, full factorial design was used to investigate the influence of amount of HPMC E 5 and Eudragit RL/RS (1:1) on the responses, i.e., lag time to release and time required for 80% of drug to releases. The dissolution tests were studied using the USP paddle method at 50 rpm in 0.1 N HCL for 2 hr and than in phosphate buffer pH 6.8.Result:The lag time of the drug release decreased by increasing the inner swelling layer and increased by increasing the rupturing layer level.Conclusion:The results obtain from present study suggest that swelling come reputable coating approach gives desire drug release after lag time.

Kübler Index and K-Ar Ages of Illite in the Yinshan Polymetallic Deposit, Jiangxi Province, South China: Analyses and Implications

Abstract. The Yinshan polymetallic deposit is a hydrothermal vein-type deposit closely related to Late Jurassic felsic-inter-mediate volcanic-subvolcanic activity in Jiangxi Province, South China. Illite is a major alteration mineral observed in the deposit. Our study shows that the Kübler index of the illite has a close relation to ore-forming fluids of different stages of hydrothermal alteration and mineralization. The early Pb-Zn-Ag mineralization dated at 130–136 Ma is characterized by relatively low water/rock ratios and diffusive fluid movement within phyllite, whereas the later Cu-Au-S mineralization at 122 -125 Ma was accompanied by higher water/rock ratios and localized fluid flow through fractures and channels. Illite formed in the early Pb-Zn-Ag mineralization stage contains swelling layers while the illite formed in the later Cu-Au-S mineralization stage has no swelling layers but was associated with intensive chloritization. The last stage of mineralization (at 104 Ma) was minor and did not produce significant amounts of illite.

Development of pulsatile release tablets with swelling and rupturable layers

A tablet system consisting of cores coated with two layers of swelling and rupturable coatings was prepared and evaluated as pulsatile drug delivery system. Cores containing buflomedil HCl as model drug were prepared by direct compression of different ratios of spray-dried lactose and microcrystalline cellulose and were then coated sequentially with an inner swelling layer containing a superdisintegrant (croscarmellose sodium) and an outer rupturable layer of ethylcellulose. The effect of core composition, level of swelling layer and rupturable coating, and magnesium stearate in rupturable layer was investigated. Mechanical properties of ethylcellulose films in the dry and wet state were characterized with a puncture test. Rupture and dissolution tests were performed using the USP XXIV paddle method at 50 rpm in 0.1 N HCl. The lag time of the pulsatile release tablets decreased with increasing amount of microcrystalline cellulose in the cores and increased with increasing levels of both swelling layer and rupturable ethylcellulose coating. Increasing levels of the ethylcellulose coating retarded the water uptake and thus prolonged the lag time. Addition of magnesium stearate to the ethylcellulose coating lowered the mechanical strength of the film and improved the robustness of the system.

Evaluation of the swelling, hydration and rupturing properties of the swelling layer of a rupturable pulsatile drug delivery system

The objective of this study was to investigate the swelling characteristics of various swellable polymers in swelling layers that induce the rupturing of an outer polymer coating in pulsatile drug delivery systems (DDS). An apparatus was designed to measure simultaneously the swelling energy/force and water uptake of discs, made of polymers. The swelling energy of several excipients decreased in the following order: croscarmellose sodium (Ac-Di-Sol ®)>low-substituted hydroxypropyl cellulose (L-HPC)>sodium starch glycolate (Explotab ®)>crospovidone (Kollidon ® CL)>hydroxypropyl methylcellulose (Methocel ® K100M). A linear correlation existed between the swelling energy and the water uptake. The swelling behavior of Ac-Di-Sol ® depended on the ionic strength and the pH of the medium due to a competition for free water and the acidic nature of this polymer. Analysis of the time-dependent swelling force data with a previously developed exponential equation confirmed a diffusion-controlled swelling force development, predominantly controlled by the penetration rate of the medium. The swelling behavior and the rupture of the outer polymeric coating of a pulsatile DDS were demonstrated in simulation tests.

Two Origins of Illite at the Dexing Porphyry Cu Deposit, East China: Implications for Ore-Forming Fluid Constraint on Illite Crystallinity

AbstractIllite is a distinctive clay mineral formed by K alteration within hydrothermal alteration zones in porphyry Cu deposits. Based on differences in spatial distribution, Kübler index, number of swelling layers, and polytype, two kinds of illite are recognized within the Dexing porphyry Cu deposit, East China. One is a hydrothermal mineral within hydrothermally-altered granodiorite porphyry and altered tuffaceous phyllite near the contact zone with the granodiorite porphyry cupola. The hydrothermal illite is formed by illitization of plagioclase and/or micas during hydrothermal fluid-rock interaction. The considerable variation of their higher Kübler indices (0.17–1.41°Δ2θ) with swelling layer is affected by fluid/rock ratio or fluid flux. The other type of illite is a product of low-grade metamorphism within tuffaceous phyllite away from the porphyry cupola (>2 km), and has a lower Kübler index (0.06–0.13°Δ2θ), a 2M1 polytype, and no swelling layers. We suggest that, within the mineralized alteration zone, the lower the Kübler index, the stronger the degree of alteration, and the higher the copper grade. This is caused by a higher fluid/rock ratio in the middle-upper portions of the contact zone.

Determination of Illite-Smectite Structures using Multispecimen X-Ray Diffraction Profile Fitting

AbstractA procedure for structural investigations by X-ray diffraction of mixed-layer structures incorporating swelling layers has been developed. For each sample, specimens saturated with different cations (Na, Mg, and Ca), are analyzed both as air-dried and as glycolated. One structural model fitting all the observed patterns then provides the structure of the sample. Samples tested include: Mite-smectite (I-S) minerals from Kazachstan (a rectorite), Dolna Ves in Slovakia, Kinnekulle in Sweden, the North Sea, and Scania in Sweden. The fitting of the patterns of the Kazachstan rectorite demonstrated that the instrumental parameters applied in the modeling were correct. For the I-S minerals from Slovakia and Kinnekulle the observed patterns were fitted with one two-component I-S model. However, the Ca-saturated and air-dried specimen of the Kinnekulle bentonites had two types of swelling interlayers. For the Slovakian I-S with Reichweite = 2, an alternative two-phase I-S plus I–V (V = vermiculite) model fitted the experimental X-ray diffraction patterns equally well. The I-S mineral from Scania is in fact a three-component I-T-S (T = tobelite) and the North Sea sample is a four-component I-S-V-V, one type of the swelling layers having swelling characteristics intermediately between smectite and vermiculite. In addition to layer types and distribution, interlayer compositions, such as the amount of interlayer glycol and water and of fixed and exchangeable cations, were determined.

Preferable structure of poly(ethylene glycol) for grafting onto a cellulosic membrane to increase hemocompatibility without reduction in solute permeability of the membrane

AbstractSwelling layers formed by poly(ethylene glycol) (PEG) chains grafted onto surfaces of a cellulosic membrane are known to improve hemocompatibility of the membrane. Three types of hemodialysis membranes were derived from the same regenerated‐cellulose hollow‐fiber membrane by grafting PEG with different formulas onto the surfaces to clarify the influence of the grafted PEG chains on solute permeability of the membranes. Determination of volume fractions of nonfreezing water contained in the membranes by differential scanning calorimetry revealed that most of the PEG chains were grafted onto the external surfaces and less into the pores in the membranes. Permeability of vitamin B12 for the PEG‐grafted membranes except for the one with the shortest PEG chains was reduced as compared with the original membrane, while that of tritium‐labeled water for all the PEG‐grafted membranes was the same as that of the original membrane. Structural parameters only of the PEG‐grafted membrane with the largest alkyl groups at the terminal of the PEG chains were different from those of the other PEG‐grafted and original membranes. The shorter PEG chains with the larger terminal alkyl groups are suitable for grafting onto a cellulosic membrane to increase hemocompatibility of the membrane without significant reduction in the solute permeability of the membrane. © 1995 John Wiley & Sons, Inc.

Swelling Pressure Calculated from Mineralogical Properties of a Jurassic Opalinum Shale, Switzerland

AbstractNineteen drill core samples of lower Dogger opalinum shale from wells drilled in connection with a tunnel project near Brugg, northern Switzerland, were investigated. The shale is a well known swelling rock that has caused problems in underground construction work. Swelling pressures determined under constant volume conditions to obtain maximum values were 0.7 to 2.2 N/mm2. The samples contained 37–59% clay-size material and about 35% quartz, 7–18% carbonate minerals, and about 5% feldspar, pyrite, and organic matter. In addition to kaolinite, illite, and chlorite, the clay-size fraction also contained mixed-layer illite/smectite with about 30% swelling layers. The specific surface area of the clay fraction was 135 m2/g. The specific surface charge of the clay (6.7 × 104 esu/cm2), the ion concentration in the pore fluid of the specimen after the swelling test (10−2 mmole/cm3), the valence of the ions in the double layer of the clay particles (+1), and the half distance between the clay plates in the specimen (8–15 Å) allowed the calculation of the swelling pressure for each sample according to the Gouy double layer theory.The mean value of the calculated swelling pressures was found to be of the same order of magnitude as the measured values, indicating that the technique can be used where cylindrical or rectangular specimens are not available for direct measurement.