Alteration of Fractured Foamed Cement Exposed to CO2-Saturated Water: Implications for Well Integrity.

Geologic CO2 storage (GCS) is a method to mitigate the adverse impact of global climate change. Potential leakage of CO2 from fractured cement at the wellbore poses a risk to the feasibility of GCS. Foamed cement is widely applied in deepwater wells where fragile geologic formations cannot support the weight of conventional cement. Thus, it is critical to know whether fractures in foamed cement self-seal in a similar manner as conventional cement systems. This study is the first to investigate the changes in physical and chemical attributes of foamed cement under dynamic flow conditions using CO2-saturated water. Self-sealing of fractures in the cement was observed at a solution flow rate of 0.1 mL/min and a pressure of 6.9 MPa. The formation of CaCO3 precipitates in pore spaces and fractures led to a decrease in permeability by 1 order of magnitude. The extents of self-sealing in foamed cement samples, specifically the 20 and 30% air volume formulations, were similar to that of conventional cements. We attribute this to the greater alteration depth in the foamed cement, which compensated for the reduced availability of Portlandite and higher initial porosity. The results can be used to evaluate the risk of leakage associated with foamed cement.

Curved single-plane clear corneal incision made under anterior chamber collapse by aqueous humor aspiration prevents leakage after cataract surgery.

PURPOSE: To evaluate the self-sealing on curved single-plane clear corneal incisions (CCIs) after cataract surgery. The collapse of the anterior chamber was made by aspirating the aqueous humor in order to make curved single-plane CCI. METHODS: A retrospective study was conducted at Asai Hospital in Japan. There were 189 eyes of 132 patients scheduled from February to April 2017 for single-plane CCI. There were 175 eyes of 128 patients from February to April 2018 for curved single-plane CCI. Curved single-plane CCIs were made with aqueous humor aspiration via aqueous humor pipette, and single-plane CCIs were made without the aspiration. In case of leakage of aqueous humor from the CCI at the end of surgery, sutures were used. The main outcome measure was the proportion of sutures for CCI. Secondary outcomes included CCI length and surgically induced astigmatism (SIA) magnitude. RESULTS: The proportions of suture in single-plane CCI and in curved single-plane CCIs were 25.4% (48/189) and 0% (0/175), respectively (p < 0.001). The length of curved single-plane CCI (2.06 ± 0.18 mm) was significantly greater than that of single-plane CCI (1.66 ± 0.12 mm; p < 0.001). The median postoperative SIAs of single-plane and curved single-plane CCIs were 0.64 D (n = 89) and 0.73 D (n = 85) for nasal incision, and 0.46 D (n = 100) and 0.47 D (n = 90) for temporal incision at examination 3 months after surgery, respectively, without significant change (p = 0.12 for nasal incision and p = 0.37 for temporal incision). CONCLUSION: The curved single-plane CCI achieved by only aqueous humor aspiration showed significant effectiveness in self-sealing. TRIAL REGISTRATION: UMIN clinical trials registry UMIN000032480, retrospectively registered on 6 May 2018.

Comparison of 27-gauge versus 25-gauge vitrectomy results in patients with epiretinal membrane: 6-month follow-up.

PURPOSE: To compare the 27G versus 25G vitrectomy in patients with epiretinal membrane (ERM). PATIENTS AND METHODS: Sixty pseudophakic eyes of 60 consecutive patients treated by pars plana vitrectomy (PPV) using 27G (30 eyes) or 25G (30 eyes) were prospectively evaluated including eye's inflammation, surgery time, ERM + ILM removal time and complications. Additionally, 1, 3, 7, 14, 30, 90 and 180 days after PPV, the following were estimated: intraocular pressure (IOP), sclerotomy wound closure time, distance best corrected visual acuity (DBCVA), foveal macular thickness (FMT) and surgically induced astigmatism (SIA). RESULTS: The eye's inflammation resolved within 30 days after surgery in both groups. The surgery and ERM + ILM times were longer in the 27G group (p ≤ 0.02). The most common postoperative complication was hypotony in both groups, more common in 25G group (23.3% vs. 10% of eyes). In 27G group, the mean IOP prior to 180 days postoperatively was higher (p < 0.05) and the sclerotomy wound closure time was shorter (p < 0.001). Mean DBCVA values (7, 14, 30 days after surgery) were significantly better in 27G group (p < 0.001). The mean FMT values were similarly and significantly reduced in both groups 1 day postoperatively (p < 0.05) as compared to preoperative values and then stabilized during follow-up. Mean SIA was lower in 27G group 30, 90 and 180 days after surgery (p < 0.001). CONCLUSION: The use of 27G PPV in patients with ERM significantly reduced sclerotomy wound closure time and surgically induced astigmatism, better stabilized intraocular pressure and allowed to achieve faster visual acuity improvement, as compared to 25G PPV.

Finite element modelling of complex movements during self-sealing of ring incisions in leaves of Delosperma cooperi.

A numerical computer model was developed in order to describe the complex self-sealing mechanism of injured Delosperma cooperi leaves. For this purpose, the leaf anatomy was simplified to a model consisting of five concentric tissue layers. Specific parameters (modulus of elasticity, permeability, porosity, etc.) were assigned to each tissue type for modelling its physical properties. These parameters were either determined experimentally from living plant material or taken from literature. The developed computer model considers the leaf as a liquid-filled porous body within a continuum approach in order to determine the governing equations. The modelling of the wound accounts for both the injury of peripheral tissues and the free surfaces caused by the incision. The loss of water through these free surfaces initiates the self-sealing process. It is further shown that the tissue permeability and the reflection coefficient (relative permeability of a cell membrane for solutes) are the determining parameters of the self-sealing process, whereas the modulus of elasticity has a negligible influence. Thus, the self-sealing mechanism is a hydraulically driven process which leads to a local (incision region) and global (total leaf) contraction of the leaf. The accuracy of the modelled self-sealing process was validated by comparing simulation results with experiments conducted on natural plant leaves. The results will serve as valuable input for developing novel, bio-inspired technical products with self-sealing function.

An ex vivo comparison of cuffed endotracheal tubes and self-sealing baffled endotracheal tubes.

AIMS To compare cuffed silicone endotracheal tubes with self-sealing baffled silicone endotracheal tubes in an ex vivo canine tracheal model, to determine whether the tubes differed in their maintenance of a seal and their effectiveness in removing fluid from the tracheal lumen, and whether the self-sealing endotracheal tubes would release pressure when a closed anaesthetic circuit reached ≥30 cm H2O. METHODS Twelve cadaver tracheae were randomly selected to be intubated with either cuffed or self-sealing baffled endotracheal tubes. To test tracheal seal efficacy, the tracheae were positioned vertically, 5 mL of water was instilled proximal to the tube cuff or baffles and they were monitored for leakage at 0, 15, 30, 45, and 60 minutes, recording the total volume leaked. To test fluid removal at extubation, the tracheae were intubated, then 5.6 g of 60% barium sulphate suspension was instilled proximal to the seal and left undisturbed for 5 minutes. The tubes were then extubated, with the cuffed endotracheal tubes being partially deflated before extubation, and the amount of barium recovered was weighed. These procedures were repeated on the same tracheae using the other endotracheal tubes. To test whether self-sealing baffled endotracheal tubes would release pressure at ≥30 cm H2O, the tracheae were intubated, connected to an anaesthetic machine and pressurised to 30 cm H2O for 5 minutes and then 50 cm H2O for 5 minutes. Release of pressure was defined as a decrease in pressure within the closed anaesthetic circuit. RESULTS More cuffed (7/12) than baffled (0/12) endotracheal tubes leaked water after 60 minutes (p=0.016). The mean amount of barium removed by the self-sealing baffled endotracheal tubes (4.9 (95% CI=3.8-4.4) g) was greater than that removed by the partially deflated cuffed endotracheal tubes (0.4 (95% CI=0.14-0.66) g) (p<0.001). None of the self-sealing baffled endotracheal tubes released pressure at ≥30 cm H2O in a closed anaesthetic circuit. CONCLUSIONS AND CLINICAL RELEVANCE Self-sealing baffled endotracheal tubes were more effective than cuffed endotracheal tubes at both preventing fluid leakage at the tracheal seal and removing fluid from the lumen of the trachea in cadaver tracheae. However they did not release pressure when the closed-circuit system was at ≥30 cm H2O in a canine cadaver model. The self-sealing baffled endotracheal tubes may be a suitable substitute for cuffed endotracheal tubes.

Bio-Inspired Pressure-Dependent Programmable Mechanical Metamaterial with Self-Sealing Ability.

Self-sealing is one of the fascinating functions in nature that enables living material systems to respond immediately to damage. A prime plant model is Delosperma cooperi, which can rapidly self-seal damaged succulent leaves by systematically deforming until the wound closes. Inspired by this self-sealing principle, a novel programmable mechanical metamaterial has been developed to mimic the underlying damage management concept. This material is able to react autonomously to changes in its physical condition caused by an induced damage. To design this ability into the programmable metamaterial, a permeable unit cell design has been developed that can change size depending on the internal pressure. The parameter space and associated mechanical functionality of the unit cell design is simulated and analyzed under periodic boundary conditions and various pressures. The principles of self-sealing behavior in designed metamaterials are investigated, crack closure efficiency is identified for different crack lengths, the limitations of the proposed approach are discussed, and successful crack closure is experimentally demonstrated in the fabricated metamaterial. Although this study facilitates the first step on the way of integrating new bio-inspired principles in the metamaterials, the results show how programmable mechanical metamaterials might extend materials design space from pure properties to life-like abilities.

An analytic model of the self-sealing mechanism of the succulent plant Delosperma cooperi.

After an injury, wound-sealing in leaves of the succulent plant Delosperma cooperi takes place by deformation and movement of the entire leaf within a time span of 30-60 min. In cross sections the almost cylindrical leaves reveal a centripetal arrangement of five different tissue types. Based on anatomical data and mechanical analyses of the five hulls, representing the different tissue layers, we present an analytical model describing the self-sealing process. The inclusion of viscoelastic aspects into the models enables to predict the temporal development of the self-sealing process. The formulation of the model in terms of closed functions facilitates: (i) sensitivity studies and (ii) the transfer of the model to technical systems which are based on non-biological materials.

Effect of Lanz pressure regulating valve on self-sealing mechanism and air leakage across the tracheal tube cuffs in a benchtop model.

BACKGROUND: The aim of the present study was to investigate the effect of the Lanz system on air sealing by self-inflation in high volume-low pressure (HVLP) tube cuffs. METHODS: In vitro tracheal air sealing was studied in HVLP tracheal tube cuffs (internal diameter [ID] 8.0 mm) made from polyurethane ([PU] Seal Guard tracheal tube, Covidien, Athlone, Ireland) and from polyvinylchloride ([PVC] HiLo tracheal tube, Covidien) with and without Lanz pressure regulating valve. Tube cuffs were placed in a vertical 22 mm ID artificial trachea and inflated to 5, 10, 15, 20, 25, or 30 cm H2O cuff pressures. Pressure control ventilation with peak inspiratory pressures (PIPs) of 20 or 25 cm H2O was applied and air leakage was assessed spirometrically as the ratio of expiratory to inspiratory tidal volumes. Nonparametric Mann-Whitney test was applied to compare the air leakage with and without Lanz system for both cuff types at each cuff pressure and PIP (P < .05). RESULTS: The PVC tube cuffs with Lanz system resulted in significant air leakage at both 20 and 25 cm H2O PIP as compared to those without the Lanz system, especially at cuff pressures lower than the preset PIP (P < .05). Although PU tube cuffs with Lanz system showed reduced air sealing when compared with cuffs without Lanz, the difference was not statistically significant. CONCLUSION: Cuff pressure compensation with the Lanz system during cyclic respiratory pressure changes interferes with the self-sealing mechanism in HVLP tube cuffs at cuff pressures lower than PIP level. This results in larger air leak across tube cuffs particularly in tube cuffs made from PVC.

Wound-assisted air injection in Descemet Stripping Automated Endothelial Keratoplasty.

Background: Early postoperative graft detachment remains one of the most common complications of DSAEK. Objectives: To describe a modification of a simple method to facilitate a firm AC, without a leak, during DSAEK. Method: Ten consecutive DSAEK surgeries were reviewed. Surgery was performed by a single surgeon (HA). At the beginning of surgery, a trapezoid paracentesis was made at the limbus using a 20G MVR blade. The trapezoid incision was made by inserting the blade halfway, creating a cut with an internal opening half the width of its external opening. After inserting the corneal disc and suturing the main incision, air was injected with a 25G tapered hydrodelineation cannula. The tip was engaged at the trapezoid paracentesis and did not enter the anterior chamber. A firm, full air bubble was formed in the anterior chamber, and no leaking occurred at the paracentesis site, which acted as a one-way valve. Results: All grafts were adhered from the first day after surgery, and no dislocations were observed. All corneas were clear at the one-month postoperative visit. Conclusions: Wound-assisted air injection is a safe, effective, simple method for achieving a firm air bubble during DSAEK, potentially reducing dislocation rates.

Properties of A Model Self-Healing Microcapsule-Based Dental Composite Reinforced with Silica Nanoparticles.

AIM: The purpose of this study was to evaluate the mechanical properties of an experimental self-healing dental composite model (SHDC) composed of SiO2 nanoparticles with varying percentages of triethylene glycol dimethacrylate (TEGDMA) monomer and N,N-dihydroxyethyl-p-toluidine (DHEPT) amine microcapsules. MATERIALS AND METHODS: Microcapsules were prepared by in-situ polymerisation of PUF shells, as explained in our previous work. The model SHDC included bisphenol A glycidyl dimethacrylate (Bis-GMA:TEGDMA) (1:1), 1 wt% phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (BAPO), 0.5 wt% benzoyl peroxide (BPO) catalyst, 20 wt% silanised silica dioxide (SiO2) (15 nm) and (0, 2.5, 5, 7.5, 10 wt%) of microcapsules (120 ± 45 µm). Light transmission, hardness, degree of conversion (DC), flexural strength and elastic modulus of the SHDC model were measured. RESULTS: The degree of conversion of the SHDC ranged from 73 to 76% 24 h after polymerisation. Hardness measurements ranged from 22 to 26 VHN (p > 0.05); however, the flexural strength was adversely affected from 80 to 55 MPa with increasing microcapsules of up to 10 wt% in the composites (p < 0.05). CONCLUSION: Only flexural strength decreased drastically ~30% with increasing microcapsules (>10 wt%) in the composites. All other measured properties were not significantly affected. Accordingly, we recommend a stronger composite material that could be created by increasing the filler content distribution in order to achieve a hybrid self-healing composite with enhanced mechanical properties.

Adaptive Self-Sealing Suction-Based Soft Robotic Gripper.

While suction cups prevail as common gripping tools for a wide range of real-world parts and surfaces, they often fail to seal the contact interface when engaging with irregular shapes and textured surfaces. In this work, the authors propose a suction-based soft robotic gripper where suction is created inside a self-sealing, highly conformable and thin flat elastic membrane contacting a given part surface. Such soft gripper can self-adapt the size of its effective suction area with respect to the applied load. The elastomeric membrane covering edge of the soft gripper can develop an air-tight self-sealing with parts even smaller than the gripper diameter. Such gripper shows 4 times higher adhesion than the one without the membrane on various textured surfaces. The two major advantages, underactuated self-adaptability and enhanced suction performance, allow the membrane-based suction mechanism to grip various three-dimensional (3D) geometries and delicate parts, such as egg, lime, apple, and even hydrogels without noticeable damage, which can have not been gripped with the previous adhesive microstructures-based and active suction-based soft grippers. The structural and material simplicity of the proposed soft gripper design can have a broad use in diverse fields, such as digital manufacturing, robotic manipulation, transfer printing, and medical gripping.

Hemostatic Needles: Controlling Hemostasis Time by a Catecholamine Oxidative Pathway.

Most infectious human viruses are generally found in the bloodstream after being released by infected organs. Thus, hemorrhage in patients, whose blood contains infectious viruses might be a significant risk for secondary infections. In this work, a self-sealing hemostatic needle that causes no bleeding even after its removal is reported. The materials used for the self-sealing needles are inspired by mussel adhesive polysaccharide, chitosan-catechol, which shows a rapid phase transition from a solid phase (i.e., a thin film) to an adhesive gel upon coming into contact with blood. We found that the self-sealing time for the complete hemostasis depends on the oxidation pathway of the conjugated catechol. For high-temperature oxidation (i.e., 60 °C), Michael addition is a dominant oxidative coupling reaction, which weakens the chitosan-catechol attachment force on the needle surface. Thus, the film is easily transferred to the hemorrhaging sites, with the result that there is no bleeding even after a short injection time (<5 s). In contrast, during low-temperature oxidation (4 °C), Schiff base formation is dominant, which strengthens the film attachment force on the needle surface, resulting in continued bleeding owing to a dearth of tissue transfer after the injection.

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.

Early Age Sealing Capacity of Structural Mortar with Integral Crystalline Waterproofing Admixture.

Crystalline admixtures embedded in concrete may react in the presence of water and generate thin crystals able to fill pores, capillaries and micro-cracks. Once the concrete has dried, the crystalline chemicals sit dormant until another dose of water starts the crystallization again. The research aims to analyses the early age self-sealing effect of a crystalline admixture at a dosage rate of 1-3% of the cement mass. Specimens made with two types of gravel were pre-loaded with three-point bending to up to 90% of the ultimate capacity, and conditioned through wet-dry cycles. Micro-crack closure was measured with a microscope after pre-loading, and after 1 day, 4 days, 8 days, 14 days and 20 days of wet-dry exposure. The results show that an admixture content of 3% achieves the best early self-sealing performance. These results are also confirmed by probabilistic analyses, which also emphasize the self-sealing potential of lower ICW contents.

Durability and Self-Sealing Examination of Concretes Modified with Crystalline Waterproofing Admixtures.

Repairing concrete structures costs billions of dollars every year all around the globe. For overcoming durability concerns and creating enduring economical structures, chemical admixtures, as a unique solution, have recently attracted a lot of interest. As permeability of a concrete structure is considered to play a significant role in its durability, Permeability Reducing Admixtures (PRA) is one of the ideal solutions for protecting structures exposed to water and waterborne chemicals. Different products have been developed to protect concrete structures against water penetration, which, based on their chemistry, performance, and functionality, have been categorized into PRA. As it has previously been tested by authors and proven to be a promising solution, a hydrophilic Crystalline Waterproofing Admixtures (CWA) has been considered for this study. This paper aims to investigate how this product affects concrete's overall freeze-thaw resistance, self-sealing, and corrosion resistance. Various testing methods have been utilized to examine the performance of CWA mixtures, including the linear polarization resistance, resonance frequency testing, half-cell potential, and self-sealing test. The reinforcement corrosion potential and rate measurements indicated superior performance for CWA-treated samples. After being exposed to 300 freeze-thaw cycles, concrete mixes containing CWA-even non-air-entrained ones-showed a Durability Factor (DF) of more than 80% with no signs of failure, while non-air-entrained control samples indicated the lowest DF (below 60%) but the greatest mass loss. The major causes are a reduction in solution permeability and lack of water availability in the concrete matrix-due to the presence of CWA crystals. Furthermore, evidence from the self-sealing test suggests that CWA-treated specimens can seal wider cracks and at a faster rate.

Use of a novel immediate access dialysis graft designed to prevent needle-related complications: A first-in-man case report.

Currently, there is no vascular access that possesses all ideal qualities for hemodialysis access, but attributes particularly lacking include: ease of identification (cannulation zone), ease of access, resistance to stenosis, durable to repetitive cannulation, resistance to infection, resistance to acute needle-related injuries, and instant hemostasis. The overall value of these attributes could be appreciated in the reduction of complications (patient burden and suffering, which can also result in increased healthcare costs), and improved safety and durability. In this case report, we present a novel hemodialysis access graft that has the potential to provide the following benefits: it is designed to be self-sealing and immediately usable post implant, easy to identify, easy to access, has more durable cannulation zones, and protects from needle-related injuries. This case report describes the first-in-man use of this novel graft technology to replace a giant, thrombotic, and difficult-to-access arteriovenous fistula to provide the patient with a potentially safer and more durable access that does not require placement of a bridging dialysis catheter. This single-patient experience suggests that implantation and function of this novel graft as a hemodialysis access is feasible in a human subject with end-stage renal disease, and it suggests that the novel properties (i.e. immediate use, easy identification, easy use, cannulation zone durability, and protection from needle-related injuries) of this graft seem to function as intended.

A review and current state of autonomic self-healing microcapsules-based dental resin composites.

OBJECTIVE: This study systematically reviews the literature on self-healing microcapsule technology and evaluates the biocompatibility of self-healing microcapsules and the efficiency of crack repair within resin-based dental composites. METHODS: An electronic search was carried out using the following databases: MedLine (PubMed), Embase, the Cochrane Library and Google Scholar. All titles and abstracts of the articles and patents found were analysed and selected according to the eligibility criteria. Only studies published in English were included; the outcomes sought for this review were dental resin composites with self-healing potential. There were no restrictions on the type of self-healing system involved in dental resin composites. RESULTS: The search yielded 10 studies and 2 patents involving self-healing approaches to dental resin composites. According to the current literature on self-healing dental resin composites, when a crack or damage occurs to the composite, microcapsules rupture, releasing the healing agent to repair the crack with a self-healing performance ranging from 25% to 80% of the virgin fracture toughness. SIGNIFICANCE: Self-healing strategies used with resin composite materials have, to date, been bioinspired. So far, self-healing microcapsule systems within dental composites include poly urea-formaldehyde (PUF) or silica microcapsules. The main healing agents used in PUF microcapsules are DCPD monomer and TEGDMA-DHEPT, with other agents also explored. Silica microcapsules use water/polyacid as a healing agent. All self-healing systems have shown promising results for self-repair and crack inhibition, suggesting a prolonged life of dental composite restorations. More investigations and mechanical enhancements should be directed toward self-healing technologies in dental resin composites.

Self-Sealing Carbon Patterns by One-Step Direct Laser Writing and Their Use in Multifunctional Wearable Sensors.

A combined photothermal simulation and experimental study leads to a novel internal reflection-assisted direct laser writing carbonization method (IR-DLWc), which enables in situ fabrication of carbon features/patterns that are self-sealed in the interior of a thin polyimide (PI) film in one step without additional packaging procedures. With this new method, carbon line patterns that are fully contained in a 50 µm PI film are fabricated, characterized, and evaluated for their electrical and piezoresistive performance. The self-sealing character of the carbon features created by IR-DLWc imparts them unprecedented mechanical stability/robustness as compared to those fabricated by the conventional DLWc method. Upon applying a double-writing scheme and strain-engineering treatment, the IR-DLWc-created carbon lines show significantly improved piezoresistive sensitivity with a gauge factor evaluated to be 428 in tension and 107 in compression. The high piezoresistive sensitivity, excellent dynamic response, reasonably good durability, self-sealing character, and compliant nature of the IR-DLWc generated carbon patterns make them suitable for a variety of wearable sensing applications. In this work, we demonstrated their use as a tactile sensor for sensing contact force; a functional bandage for monitoring physiological activities like swallowing, pulsing, and breathing; and a glove sensing system for finger gesture recognition.

An immediate access dialysis graft designed to prevent needle-related complications: Results from the initial pre-clinical studies.

INTRODUCTION: No technology has been specifically developed with the intent to reduce needle-related vascular access injuries; a significant source of complications and abandonment. We present the initial pre-clinical study results of a novel, self-sealing, immediate cannulation dialysis graft that aims to prevent needle-related complications; to promote safe, reliable needle access; to reduce catheter use; and could facilitate home hemodialyisis. METHODS: The innovative graft design consists of two cannulation chambers with self-sealing properties and materials that prevent side and back wall needle puncture. Study and control grafts (expanded polytetrafluoroethylene) were implanted in one pig and 10 sheep in two studies over the course of 1 year. First cannulation occurred immediately post implant for all study grafts. Post-cannulation time to hemostasis, hematoma and seroma formation, infection, and patency were recorded. RESULTS: The two studies account for nearly 60 weeks (average 6.4 weeks/graft) of study graft follow-up. In the ovine study, average study graft time to hemostasis was 27.3 s (standard deviation = 26.3, range = 0-120), and the control averaged 177.2 s (standard deviation = 113.4, range = 60-600), p < 0.0001. Secondary patency was 75% and 67% for the study and control grafts, respectively. Neither study nor control groups experienced seroma, graft infections, or deaths. DISCUSSION: All novel grafts in the studies were implanted successfully and functioned as intended. There were no complications related to tunneling of the study graft and the chamber prevented back/side wall needle injury. This novel technology may help to mitigate these needle-related complications, while allowing for early/immediate cannulation which could also reduce catheter contact time.

Self-Sealing Process Evaluation Method Using Ultrasound Technique in Cement Composites with Mineral Additives.

The self-sealing process, associated with chemical and microstructural changes inside damaged cement-based composites, leads to the recovery of the original material integrity. Assessing the magnitude of internal changes in samples using non-destructive techniques to capture only the self-sealing effects is difficult. The challenge is evaluating the differences between subsequent observations in time and between samples with different properties. This paper proposes a new approach to the use of an ultrasonic technique for self-sealing investigation. The method allows the quantification of material changes strictly related to self-sealing processes, excluding changes caused by the naturally progressing hydration of binders. The applied ultrasonic pulse velocity (UPV) data processing procedure allows the investigation of material changes inside and near the cracks, the effects of stimulating the self-sealing of cement composites with mineral additives, and the assessment of changes over time. An important aspect of the method is the sample preparation procedure and testing conditions that reduce the impact of moisture content on the UPV measurements. New parameters allowing the quantitative characterization of the self-sealing process are proposed. The method was evaluated using cement mortars modified with siliceous fly ash with induced cracks 0 to 750 µm wide, which were then cured in water for 152 days. The maximum degree of effective crack filling as a result of autogenous self-sealing in the tested mortars was determined to range from 33% to 57%. Observations of the microstructure of the crack surface confirmed that apart from the volume of the newly formed products, the density of these products may have a key impact on the ultrasonic measurements of the self-sealing performance. The studies were supplemented by the examination of the compression strength of mortars, mortar sample scanning and computer image processing, and observations using an optical microscope and scanning electron microscope with energy dispersive spectroscopy.