Self-sealing Property Research Articles

Apparatus for swelling deformation of compacted bentonite utilizing multi-ring moulds for evaluation of dry density and water content distribution

In the geological disposal of high-level radioactive waste, bentonite buffer materials are required to have self-sealing property, which is the ability to fill gaps by swelling deformation between the buffer material and the waste containment vessel or surrounding bedrock. Self-sealing property was evaluated based on the pressure generated after the gap filling under the assumption of constant dry density and water content in the specimen and buffer material. On the other hand, it takes tens to hundreds of years for the transitional period until the buffer contacts with groundwater, fills the gap, and the internal state converges to a uniform state. To assess changes more accurately in the condition of the buffer material, it is necessary to evaluate time courses in the density and water content of the buffer material because of groundwater infiltration and swelling deformation. From these, the authors developed an experimental apparatus for swelling deformation of bentonite, which consists of a mould with 2 mm-thick stacked rings. It is aimed to evaluate the distribution of dry density, water content, and degree of saturation inside the specimen by cutting the specimen with a 2 mm thick ring after the end of experiment. In this paper, results of preliminary experiments to confirm the applicability of this apparatus to swelling deformation test of bentonite was firstly described. Then, experiments were conducted on compacted bentonite specimens using this apparatus, and changes in the dry density and water content distribution inside the specimens were evaluated in terms of swelling deformation behaviour.

Role of magmatism in efficient gas accumulation in Upper Ordovician-Lower Silurian shales in the Yangtze plate, South China: Evidence from the calcite U-Pb ages and gas C-N isotopes

Shale gas exploration in the Yangtze plate has been hindered by strong heterogeneity of gas compositions resulting from magmatism. Borehole core and gas samples from Upper Ordovician-Lower Silurian in the Upper Yangtze plate and the Lower Yangtze plate were analyzed to explore the effects of magmatism on gas accumulation. The analyses included nitrogen isotope of gas, pore structure and X-ray photoelectron spectroscopy of shales, and U-Pb ages of fracture-filling calcites. Our results suggest that magmatism caused the development of micro-fractures in shale reservoirs and accelerated the thermal evolution rate of organic matter. Magmatism in the Upper Yangtze plate predates the peak of gas generation of Upper Ordovician-Lower Silurian shales. Generation and expulsion of hydrocarbon at high temperatures removes 12C from carbon reservoir. After the magmatism, the continuous subsidence of the strata led to further hydrocarbon generation of organic matter. Moreover, the self-sealing property of shale reservoirs were enhanced by the closure of micro-fractures, development of graphite structures, and enrichment of 13C in residual methane, which favor the efficient accumulation of shale gas. Conversely, magmatism in the Lower Yangtze plate occurred after the peak of gas generation of Upper Ordovician-Lower Silurian shales. Magmatism compromised shale gas reservoirs by disrupting sealing conditions, facilitating methane diffusion and atmospheric nitrogen influx. Additionally, overburden pressure led to the collapse of graphitized OM-hosted pores, further inhibiting gas accumulation. Our findings underscore the pivotal role of magmatism in various stages of shale gas accumulation and are critical for exploration strategies in sedimentary basins with prevalent magmatic activities.

Improving the Autogenous Self-Sealing of Mortar: Influence of Curing Condition.

With the construction of projects under severe environments, new and higher requirements are put forward for the properties of concrete, especially the autogenous self-sealing property, which is greatly affected by the curing environment and the state of the water. Herein, six types of curing conditions, including in air with a relative humidity of 30%, 60%, and 95%; flowing water; wet-dry cycles; and static water, are designed to investigate the autogenous self-sealing of mortar under different curing conditions. The results showed that the self-sealing ratios are higher than 60% and the cracks are closed for the mortar undergoing the wet-dry cycles and the static water. However, the self-sealing ratios of mortar are lower than 10% and the cracks are almost unchanged when the mortar is cured in the air with a relative humidity (RH) of 30% and 60%. The static liquid water is more conducive to the continued hydration of cement and the formation of CaCO3 than the flowing water. The research provides guidance for the design of concrete and the improvement of autogenous self-sealing when the concrete serves in different environments.

Occurrence of fluids in high dip angled coal measures: Geological and geochemical assessments for southern Junggar Basin, China

The Junggar Basin, Xinjiang has abundant coalbed methane (CBM) resources, and most of the CBM is found in the coal reservoirs with high dip angle (>50°), where the generation, accumulation and extraction of CBM significantly differs with flat coal reservoirs. This study clarifies the effect of high dip angle on the fluid pressure field, in situ stress field, permeability and gas bearing capacity of CBM reservoir in the southern Junggar Basin. The studies show that the high dip angle results in the fluid pressure differentiation of CBM reservoirs at 800–1000 m. The shallow opened fluid pressure system is in an ultralow-normal pressure state, while the deep closed system is characterized by overpressure. The self-sealing property of high dip CBM reservoirs can prevent the gas escaping upward along the inclined bedding. The larger the dip angle, the higher the gas column sealed by the self-physical property. The overburden compaction is reduced for dip formation, which causes the in situ stress of inclined coal seam to decrease but the anisotropy to increase. Furthermore, the high dip angle decreases the gas content per meter of coal seam, and diversifies the gas genesis, which causes the secondary biogenic gas to generate in the shallow seam under the effect of active hydrodynamics, and the thermogenic gas to be better accumulated in the deep coal seam. Due to the desorption hysteresis of the coal seam in downdip direction, the gas production curve of high dip coal seam has obvious bimodal characteristics, and the second peak is significantly higher than the first.

Comparative Analysis of Microleakage of Zirconia-infused Glass Ionomer Cement with Miracle Mix and Amalgam: An In Vitro Study.

ContextVarious restorative materials are introduced in dentistry to achieve adequate strength and restore aesthetics. Dental amalgam is a versatile material with self-sealing property, but is unaesthetic. Other restorative materials like composites require conservative preparation, but exhibit polymerisation shrinkage resulting in microleakage. To overcome these drawbacks, a high strength restorative material reinforced with ceramic and zirconia fillers known as Zirconomer (Shofu Inc., Japan) has been introduced.AimsThis in vitro study aims to evaluate and compare the microleakage of zirconia-infused glass ionomer cement (Zirconomer) with Miracle Mix (GC Fuji Miracle Mix, Japan) and amalgam.Materials and methodsIn this in vitro study, 30 non-carious premolar teeth were randomly divided into three groups (n=10) depending on the restorative material used—Silver Amalgam (DPI, India), Miracle Mix, and Zirconomer. Standard Class V cavities were prepared on the buccal surface of 30 non-carious extracted premolars. The restored teeth were thermocycled and then immersed in 2% methylene blue dye for 24 hours. All teeth were bisected longitudinally in a buccolingual direction and observed under a stereo microscope at 40X magnification for the evidence of dye penetration. The data were analyzed using one-way analysis of variance (ANOVA) and Kruskal-Walis tests (p<0.01).ResultsZirconomer showed the least microleakage in Class V cavity restoration with a statistically significant difference to amalgam and Miracle Mix.ConclusionsZirconomer has proven to be an excellent restorative material as it showed the least microleakage followed by Miracle Mix and amalgam. Zirconomer raises the bar for restorative reinforced glass ionomers by outperforming conventional glass ionomers and amalgam restoration.

Synthetic Poly(Vinylalcohol)-Based Membranes for Cartilage Surgery and Repair.

Cell-based therapies for cartilage repair are continually being developed to treat osteoarthritis. The cells are either introduced directly by intra-articular injection or via a cell-seeded matrix scaffold. Here, poly(vinylalcohol)-based membranes are developed to be used for mesenchymal stem cell implantation in cartilage repair procedures, having controllable physicochemical properties such as porosity, mechanical strength, and permeability, and a unique self-sealing property. The membranes possess a bilayer structure with a less porous layer providing mechanical strength and selective permeability, exhibit an elastic modulus of between 0.3 and 0.9 MPa, and are permeable to molecules <40 kDa, which is in the range of cartilage permeability. Three different peptide ligands with the sequences Ac-GCGYGRGDSPG, Ac-GCG(OPG)4REGOFG(OPG)4, and Ac-GCG(OPG)7, respectively, are conjugated to the membranes and subject to in vitro cell adhesion and differentiation assays. Col I/Col II gene expression ratios indicated that the collagen-mimetic peptide, Ac-GCG(OPG)7, best supported mesenchymal stem cell differentiation into the chondrogenic lineage. Although low retention of the membrane is observed in vivo in a rabbit knee model, results suggest that the membrane was able to facilitate mesenchymal stem cell implantation and differentiation to chondrocytes. These PVA-based membranes provide a feasible, synthetic, off-the-shelf material for the delivery of stem cells, and can be modified for other surgical applications.

Investigating the Water Sealing Capability of Polymer Concrete

The concrete water sealing capability improved substantially by using superabsorbent polymer as admixture in the concrete mix design. Researchers tried almost every conceivable material to be mixed in concrete to alter some of its properties. In this research, superabsorbent polymer is used as an admixture to improve its water tightness properties especially in concrete tanks, aeration basins and retaining structures. The concrete tries to seal the leak by blocking the water path by semi-solid gels. This gel is the product of the interaction of the superabsorbent polymer with water. This self-sealing property of concrete can also be used in any tank or container that holds and retains any kind of liquid. The super absorbent polymer absorbs water at a rate of 300 to 500 times its own weight, in a process transforming the polymer dry powered into gel. Mixing super absorbent polymer with concrete not only improves its water tightness capability, but also provides the concrete with internal curing moisture it needs to improve its strength. This property is very useful in cases where curing of concrete is difficult. The fresh concrete plasticity and consistency change as well. This property is yet to be further explored. Several samples have been prepared to study the effect of the superabsorbent polymer on the concrete strength and on the concrete capability to block the water flow. Concrete cubes, concrete beams and concrete tension samples were prepared to study the concrete strength of concrete mixed with superabsorbent polymer. Also concrete short cylindrical samples were prepared to study the concrete ability to block the water flow. These cylindrical samples were intentionally broken into two approximately equal pieces to create an induced crack. The artificially cracked samples are then subjected to water pressure to study the concrete ability to stop the water flow though the induced concrete crack. Two kinds of water pressure are used in this research; the constant head and the falling head. Samples of different amount of superabsorbent polymer were prepared to study the effect of the increase of the superabsorbent polymer on the concrete strength and on the concrete water tightness capability.

High emissivity MoSi2–ZrO2–borosilicate glass multiphase coating with SiB6 addition for fibrous ZrO2 ceramic

To develop a high emissivity coating on the low thermal conductivity ZrO2 ceramic insulation for reusable thermal protective system, the MoSi2–ZrO2–borosilicate glass multiphase coatings with SiB6 addition were designed and prepared with slurry dipping and subsequent sintering method. The influence of SiB6 content on the microstructure, radiative property and thermal shock behavior of the coatings has been investigated. The coating prepared with SiB6 included the top dense glass layer, the surface porous coating layer and the interfacial transition layer, forming a gradient structure and exhibiting superior compatibility and adherence with the substrate. The emissivity of the coating with 3wt% SiB6 addition was up to 0.8 in the range of 0.3–2.5μm and 0.85 in the range of 0.8–2.5μm at room temperature, and the “V-shaped grooves” surface roughness morphology had a positive effect on the emissivity. The MZB-3S coating showed excellent thermal shock resistance with only 1.81% weight loss after 10 thermal cycles between 1773K and room temperature, which was attributed to the synergistic effect of porous gradient structure, self-sealing property of oxidized SiB6 and the match of thermal expansion coefficient between the coating and substrate. Thus, the high emissivity MoSi2–ZrO2–borosilicate glass coating with high temperature resistance presented a promising potential for application in thermal insulation materials.

An in vitro Evaluation of Microleakage of Posterior Teeth Restored with Amalgam, Composite and Zirconomer - A Stereomicroscopic Study.

Numerous restorative materials are being used in dentistry to achieve adequate strength and restore aesthetics. However, a perfect ideal restorative material has still eluded dentist. Dental amalgam is versatile material with self-sealing property, but is unaesthetic. Other restorative materials like, composites require conservative preparation, but exhibits polymerisation shrinkage resulting in microleakage. To overcome these drawbacks a high strength restorative material reinforced with ceramic and zirconia fillers known as zirconomer has been introduced. The aim of this study was to evaluate the micro-leakage of these three different restorative materials. Thirty non-carious human permanent first and second molars were utilized in this study. Class I cavities were prepared on the occlusal surface; cavities were then restored with amalgam, composite and zirconomer as per manufacture's instruction. All samples were stored for 24 hours in distilled water followed by thermocycling. The entire tooth surface was painted with two coats of varnish to within 1mm of the restoration margins. The teeth were immersed in dye. Teeth were sectioned and observed under stereomicroscope. In this study the zirconomer exhibited the highest micro leakage as compared to composite and amalgam but composite having higher micro leakage as compared to amalgam and lower micro leakage as compared to zirconomer. Even though composite and amalgam are being marketed aggressively and new material like zirconomer are on origin, amalgam still proves to be one of the best materials.

Multi-layer CVD-SiC/MoSi2–CrSi2–Si/B-modified SiC oxidation protective coating for carbon/carbon composites

To further improve the oxidation resistance of coating for carbon/carbon (C/C) composites, a multi-layer CVD-SiC/MoSi2–CrSi2–Si/B-modified SiC coating was prepared on the surface of C/C composites by pack cementation and chemical vapour deposition method, respectively. The microstructures, oxidation and thermal shock resistance of the coating were studied. The influence of B content in pack powder on the microstructure and oxidation resistance of B-modified SiC coating was also investigated. The results show that the B-modified SiC coating prepared with 10 wt.% B exhibited the best oxidation protection ability for C/C composites at 1173 K. The multi-layer coatings could protect the C/C composites at 1173 K for 30 h and 1873 K for 200 h, and endure 30 thermal cycles between 1873 K and room temperatures. The oxidation resistance and thermal shock resistance is mainly attributed to their dense structure and self-sealing property.

Microstructure and oxidation resistance of Si–Mo–B coating for C/SiC coated carbon/carbon composites

A self-sealing Si–Mo–B oxidation resistance coating was prepared on C/SiC coated carbon/carbon (C/C) composites by slurry and high temperature treatment method. The oxidation resistance of the coating increases at 1173K and first increases then decreases at 1873K with the increase of B content from 0 to 20wt.%. The C/SiC/gradient Si–Mo–B multilayer coating can protect C/C composite from oxidation for 100h at 1173K and 125h at 1873K. The good oxidation resistance of the coating in broad temperature range could be attributed to its good self-sealing property.

Oxidation and ablation resistance of ZrB2–SiC–Si/B-modified SiC coating for carbon/carbon composites

ZrB2–SiC–Si/B-modified SiC coating was prepared on the surface of carbon/carbon (C/C) composites by two-step pack cementation. The coating could efficiently provide protection for C/C composites from oxidation and ablation. The improvement of oxidation resistance was attributed to the self-sealing property of the multilayer coating. A dense glassy oxide layer could afford the high temperature up to 2573K and efficiently protect C/C composites from ablation.

Three-Dimensional Electrospun Poly(Lactide-Co-ɛ-Caprolactone) for Small-Diameter Vascular Grafts

Nanofibers have been applied to tissue engineering scaffolds because fiber diameters are of the same scale as the physical structure of protein fibrils in the native extracellular matrix. In this study, we utilized cell matrix engineering combined with cell sheet matrix and electrospinning technologies. We studied small-diameter vascular grafts in vitro by seeding smooth muscle cells onto electrospun poly(lactide-co-ɛ-caprolactone) (PLCL) scaffolds, culturing and constructing a three-dimensional network. The vascular grafts constructed using cell matrix engineering were similar to the native vessels in their mechanical properties, such as tensile strength, tensile strain, and e-modulus. Also, they had a self-sealing property more improved than GORE-TEX because PLCL has compatible elasticity. Small-diameter vascular grafts constructed using matrix engineering have the potential to be suitable for vascular grafts.

C/SiC/Si-Mo-B/glass multilayer oxidation protective coating for carbon/carbon composites

To prevent carbon/carbon (C/C) composites from oxidation, a self-sealing multilayer oxidation resistant coating including a C/SiC gradient inner layer, a Si-Mo-B middle layer and a glass exterior layer was prepared by pack cementation and slurry method. Scanning electron microscopy and X-ray diffraction were used to analyze the microstructure and phase composition of the as-prepared coating. The isothermal and thermal shock oxidation resistance of the coating was also investigated. The results showed that the multilayer coating exhibited excellent oxidation resistance from room temperature to 1873K. It could effectively protect C/C composites for 100h at 1173K and 150h at 1873K, and endure 40 thermal cycles between 1873K and room temperature. The excellent oxidation and thermal shock resistance could be attributed to the gradient structure and the self-sealing property of the multilayer coating.

Wound construction in manual small incision cataract surgery

The basis of manual small incision cataract surgery is the tunnel construction for entry to the anterior chamber. The parameters important for the structural integrity of the tunnel are the self-sealing property of the tunnel, the location of the wound on the sclera with respect to the limbus, and the shape of the wound. Cataract surgery has gone beyond just being a means to get the lens out of the eye. Postoperative astigmatism plays an important role in the evaluation of final outcome of surgery. Astigmatic consideration, hence, forms an integral part of incisional considerations prior to surgery.

Use of the Vectra Polyetherurethaneurea Graft for Dialysis Access in HIV-Positive Patients With End-Stage Renal Disease

The primary objective of this study was to establish the safety, efficacy, infection rate, and patency of the Vectra graft (polyetherurethaneurea) for dialysis access in patients diagnosed with human immunodeficiency virus (HIV) and end-stage renal disease. The Vectra graft has a unique self-sealing property; therefore we hypothesize that these patients will have fewer infections. A Vectra graft was implanted in 30 consecutive HIV-positive patients without sufficient veins for an autologous fistula. These surgeries were carried out over a 2.5-year period. Primary graft patency was 42% at 12 months and 3 (10%) of the grafts developed infection. This rate of graft infection was less (10% vs 45%) than both our prior experience and published reports using polytetrafluorothene bridge grafts. The unique self-sealing property of the Vectra graft minimizes the development of perigraft hematoma with repetitive needle cannulation and in the immunosuppressed HIV-positive patient, may account for the observed decrease in dialysis access infection.

Imaging and investigating the effects of incision angle of clear corneal cataract surgery with optical coherence tomography

Effects of incision angle in construction of clear corneal cataract incision are studied with optical coherence tomography (OCT). A stable incision angle range is found to be existent for single-planed, clear corneal cataract incisions. When well pressurized, incision angles within this stable range result in well-apposed incision edges that resist gapping while incision angles falling outside this range have a larger tendency for wound leakage. It is also shown that a two-planed incision can effectively expand the stable range. For incision angles outside the stable range, the farther the incision angle is away from stable range, the larger the gap between incision wound edges when well pressurized. These findings emphasize the significance of incision construction to the self-sealing property of clear corneal cataract incisions. Finally, we demonstrate that OCT could be an effective modality for imaging and monitoring corneal surgery.

USEFULLNESS OF A NEW POLYURETHANE VASCULAR ACCESS GRAFT AS AN ARTERIOVENOUS FISTULA FOR HEMODIALYSIS

We evaluated a new polyurethane vascular access graft (Thoratec Vascular Access Graft, TVAG) as a vascular access for hemodialysis. Subjects were 16 patients with chronic renal failure and TVAG was implanted as arteriovenous fistula in them. These were one case of loop in the fore arm, one case of a loop in the upper arm, eight cases of straight in the upper arm and six cases of loop configuration in the thigh. TVAG is characterized by its elasticity and self-sealing property that require careful subcutaneous positioning of TVAG and deliberate sutures during anastomosis, but it resulted in no postoperative limb edema and easy hemostasis after needle removal in our subjects. These findings indicate that TVAG can be used for hemodialysis in early postoperative days. In our cases, hemodialysis was able to start with in 4 days after implantation of TVAG, with an average of 2.4 days. Shorter hospital stay is consequently expected. Early occulusion of fistula due to thrombosis occurred in two cases. Thrombectomy was easily performed in both cases using Fogarty balloon catheters and they could be used for hemodialysis again. It is concluded that TVAG is useful as a vascular access for hemodialysis. Further assessment of its long-term patency and possible complications are necessary.

Self-sealing property of concrete—Experimental evidence

Leak-tightness of concrete is often judged in terms of the D'Arcy coefficient determined by the flow of water through saturated concrete at a constant rate. In the case of flow through saturated concrete, this rate often reduces with time and reaching a constant value may take many days. The present experiments were designed to explore various models in order to account for this behaviour. The results obtained support the concept that the dissolution and redeposition of alkalis is the most significant mechanism in the time-dependent reduction of flow of water in saturated concrete. Permeability of saturated concrete and self-sealing may be used as measures of the “immune” systems and potential durability of different concretes.

Vacuoles of fungal protoplasts.

Details are given of the conditions which allow vacuolar structures of Fusarium culmorum to be released after osmotic bursting of mycelial protoplasts. Steps in the release of vacuoles are shown. The composition of the suspending medium affects the formation, size, and number of the vacuoles seen in the protoplasts. Fusion of vacuoles in regenerating protoplasts has been observed, indicating a self-sealing property of the tonoplast. Preparations of vacuolar structures, rather free from cytoplasmic debris, have been obtained.