Preformed Tubes Research Articles

Comparison of fracture resistance of fiber-reinforced post and core with different cementation techniques: in vitro study.

The current study aimed to inspect the fracture resistance of fiber post to canal dentin using a different technique of cementation. 60 sound single-rooted central incisors with comparable size and length were stored in normal saline. Each tooth was immersed in 5% sodium hypochlorite (NaOCl). The specimens were randomly divided into 6 groups of 10 specimens each. All included specimens received root canal treatment (RCT). Post-space preparation was done using Gates Glidden drills. Post space was standardized with 10 mm length, keeping 3 to 5 mm as an apical seal. Based on the cementation technique samples were divided into six study groups. Group A: One step-Monoblock; Group B: One step- Monoblock-NA-FP; Group C: One step-Monoblock-RX-MC; Group D: Two-step- RX-MC; Group E: Two-step- RX-FZ; Group F: Two-step- RX-FZ-Custom post. Following cementation, all teeth will be prepared to receive a monolithic zirconia crown with a finish line of 1 mm above the CEJ. Each specimen was mounted in auto-polymerizing clear acrylic resin using a preformed tube. All samples were subjected to pushing forces to measure the fracture strength of the specimen using a universal testing machine. To compare the means among different experimental groups Post Hoc Tukey multiple comparison tests and analysis of variance (ANOVA) were adopted. The highest fracture resistance was observed in group A. Whereas, the lowest fracture resistance was observed in group D samples. Fracture strength in group A samples showed significantly higher fracture resistance values compared to all other groups (p < 0.05). Fracture resistance values in group F specimens were significantly higher than specimens in groups B, C, D, and E respectively (p < 0.05). Monoblock technique using single cementation and core material (Multicore Flow) when polymerized simultaneously exhibited the highest fracture resistance of glass fiber post compared to other cementation techniques.

Axial-compression performance and finite element analysis of special-shaped tubular three-dimensional woven composites with different thicknesses and shapes

In this research, the self-reinforced structures tube preforms, which are the special-shaped tubular three-dimensional woven preforms, had been manufactured on semi-automatic looms. To prepare special-shaped tubular three-dimensional woven composites with different wall thicknesses and shapes, the vacuum-assisted resin transfer method was used by performing the prepared preform and resin as the reinforcement and matrix. Then, the axial compression performance was tested on a universal material testing machine. The results revealed that both the wall thicknesses and the shape had remarkable effects on the composites’ axial-compression properties. The performance of special-shaped tubular three-dimensional woven composites and normal tubular three-dimensional woven composites were compared and special-shaped tubular three-dimensional woven composites were better. Finally, finite element analysis was adopted in this research. The initial damage, stress evolution, and final failure of special-shaped tubular three-dimensional woven composites had been shown by the analysis. The stress concentration and failure mechanism of the composite materials after axial compression was revealed and the finite element model was correct and can predict the mechanical properties of special-shaped tubular three-dimensional woven composites.

Use of the Cascade expandable net to treat cerebral vasospasm \u2013 initial clinical experience from a single centre with in vitro benchside tests

BackgroundThe use of self-expanding stents to treat post-hemorrhagic cerebral vasospasm was recently described. We sought to determine the clinical efficacy of the Cascade device to treat delayed cerebral vasospasm (DCV). We performed benchside tests to determine the chronic outward force exerted by the Cascade in comparison to the Solitaire.MethodsThe chronic outward force (COF) of the Cascade M agile and Cascade L Agile was tested with equivalent tests of the Solitaire 4x20mm. Further tests to determine the forces generated in pre-formed tubes of 1.5–6 mm were performed using both fully and partially unsheathed Cascades.A retrospective review to identify all patients with aSAH and DCV treated with a Cascade device between January 2020 and July 2021. We recorded the treatment arterial vessel diameters and hemorrhagic or ischemic complications.ResultsIn vitro the Cascade generated greater radial force than the Solitaire. The force generated by the Cascade M Agile at 1.5 mm was approximately 64% higher than the Solitaire 6x40mm and approximately 350% higher than the Solitaire 4x20mm.4 patients with DCV were identified all of whom were treated with a cascade device. In all cases there was a significant improvement in the diameter of the vasospastic vessels treated with an average diameter increase of approximately 300%. There were no complications from the Cascade. Delayed CT angiography showed persistent dilatation of the segments treated with the Cascade at 24 h.ConclusionThe Cascade is a safe and effective device when used to treat DCV secondary to aSAH. Larger studies are required to validate our initial results.

Effects of consolidation processing parameters on the surface morphology and void content of braided thermoplastic composite tubes

In this study, the consolidation process of radial-type braided carbon fiber reinforced polyetherketoneketone (CF/PEKK) thermoplastic composite tubes was investigated. Braided tube preforms were fabricated by braiding at the lamination angles of [±70/±204/±70/±204/±70] on 75 mm mandrels using 6.35 mm tapes and 48 or 72 bobbins. The CF/PEKK tubes were fabricated through the vacuum consolidation process inner mold line (IML) using a mandrel, the vacuum consolidation process outer mold line (OML) using an outer mold, and the OML-polytetrafluoroethylene (PTFE) consolidation process using an external mold and a PTFE bladder. The effects of vacuum pressure, caul plate or PTFE bladder on the consolidation were analyzed. The consolidation processes were evaluated by the surface morphology, void content, and crystallinity of the consolidated tubes. When the vacuum pressure increased from 10 to 30 inch Hg in the IML process, the void content of the thermoplastic tube increased, but there was no change in the surface wrinkle pattern. Furthermore, the use of a caul plate increased the void content of the tube. The OML process resulted in a high void content above 20% regardless of caul plate use; thus, it was considered inappropriate as a tube consolidation process. Although the OML-PTFE tube showed an uneven surface defect, a flat surface without wrinkles and a low void content of 0.5% were observed. The results of this study confirmed that the proposed OML-PTFE consolidation process of CF/PEKK is applicable to the manufacture of thermoplastic composite tubes used in actual aircrafts.

Accuracy of Age-Based Formula to Predict the Size and Depth of Cuffed Oral Preformed Endotracheal Tubes in Children Undergoing Tonsillectomy.

To retrospectively investigate the reliability of the age-based formula, year/4 + 3.5 mm in predicting size and year/2 + 12 cm in predicting insertion depth of preformed endotracheal tubes in children and correlate these data with the body mass index. Patients were classified into 4 groups according to their nutritional status: thinness, normal weight, overweight, and obesity; we then retrospectively compared the actual size of endotracheal tube and insertion depth to the predicting age-based formula and to the respective bend-to-tip distance of the used preformed tubes. Altogether, 300 patients were included. The actual endotracheal tube size corresponded with the Motoyama formula (64.7%, 90% CI: 60.0-69.1), except for thin patients, where the calculated size was too large (0.5 mm). The insertion depth could be predicted within the range of the bend-to-tip distance and age-based formula in 85.0% (90% CI: 81.3-88.0) of patients. Prediction of the size of cuffed preformed endotracheal tubes using the formula of Motoyama was accurate in most patients, except in thin patients (body mass index < -2 SD). The insertion depth of the tubes was mostly in the range of the age-based-formula to the bend-to-tip distance.

Vascular leakage caused by loss of Akt1 is associated with impaired mural cell coverage.

Angiogenesis plays a critical role in embryo development, tissue repair, tumor growth and wound healing. In the present study, we investigated the role of the serine/threonine kinase Akt in angiogenesis. Silencing of Akt1 in human umbilical vein endothelial cells significantly inhibited vascular endothelial growth factor (VEGF)‐induced capillary‐like tube formation. Mice lacking Akt1 exhibited impaired retinal angiogenesis with delayed endothelial cell (EC) proliferation. In addition, VEGF‐induced corneal angiogenesis and tumor development were significantly inhibited in mice lacking Akt1. Loss of Akt1 resulted in reduced angiogenic sprouting, as well as the proliferation of ECs and mural cells. Addition of culture supernatant of vascular smooth muscle cells (VSMCs) in which Akt1 was silenced suppressed tube formation, the stability of preformed tubes and the proliferation of ECs. In addition, attachment of VSMCs to ECs was significantly reduced in cells in which Akt1 was silenced. Mural cell coverage of retinal vasculature was reduced in mice lacking Akt1. Finally, mice lacking Akt1 showed severe retinal hemorrhage compared to the wild‐type. These results suggest that the regulation of EC function and mural cell coverage by Akt1 is important for blood vessel maturation during angiogenesis.

From Wire to Seamless Flow-Formed Tube: Leveraging the Combination of Wire Arc Additive Manufacturing and Metal Forming

Flow forming is a metal-forming process for producing axisymmetric hollowed tubes starting from cylindrical workpieces. In cases where the preformed tube includes defects, impurities or inconsistencies, the final product may not withstand the required standard. In this work, the preformed tubes were produced by metal wires melted into the desired geometry using a gas-metal arc-welding robot. Two geometries were built to allow either forward or backward tube spinning of parts from ER-70S-6 and AWS ER316L welding wires. Following the building process, the parts were machined to fit a flow-forming operation. The mechanical and metallurgical properties of the wires, preformed cylinders and final tubes were compared with conventionally manufactured material. Results indicate that the mechanical properties of the products of the proposed process were superior to those of conventional processing. Applying flow forming to wire-arc additive manufacturing yields a deeper understanding of the material qualities over a large building envelope and can be used as valid quality criteria for the additive manufacturing process qualification.

Optimized Gating System for Steel Castings

Computer modeling using a commercially available software package was used to explore the optimization of filling systems based on the relatively new concepts of avoiding entrainment of air bubbles and oxides by avoiding surface turbulence. The test casting was based on a pattern for a traditional top poured test bar, whose cross section was a tri-lobed clover-like shape. The study illustrates clearly that the detailed design of the filling system has a major influence on the conditions for defect generation during filling. Traditional steel casting systems using the widely popular assembly of preformed refractory tubes were found to behave poorly. Systems were demonstrated which were capable of delivering highly controlled filling behavior. The latest systems to be developed employed (1) a naturally pressurized filling system and (2) the use of filters placed flush on the top of the runner to act as bubble diverters, together with (3) terminal spin traps. These novel filling systems demonstrated excellent performance in simulation, in agreement with practical experience of the capability (of the trident gate in particular) to produce, for the first time in the history of casting, defect-free castings on a routine basis.

Shape memory behavior and recovery force of 4D printed textile functional composites

Four-dimensional (4D) printing of multi-directionally reinforced preforms has tremendous potential for the development of next generation functional composites by using the capabilities of 3D printing technology, 3D textile preform design, and polymer shape memory behavior. This work demonstrates the shape memory behavior and recovery force of 4D printed circular braided tube preforms and their silicone elastomer matrix composites. The preforms were printed by fused deposition modeling using the shape memory polymer (SMP), polylactic acid (PLA). The effects of braiding angle, tube wall thickness, and shape recovery temperature on the shape memory behavior of 4D printed tube preforms and their silicone elastomer matrix composites have been characterized. Measurements of shape recovery forces of the preform and composite were conducted using dynamic mechanical analysis (DMA). The braided microstructural parameters and shape recovery temperature have a significant effect on the preform shape memory behavior. The introduction of the silicone elastomer matrix greatly enhances the shape recovery force, shape recovery ratio, as well as radial compressive failure load of the 4D printed preform/silicone elastomer matrix composite. Building on these results, a potential application for 4D printed textile functional composites is presented.

Seismic behavior of concrete bridge columns confined with fiber-reinforced polymer stay-in-place formwork

One of the applications of fiber-reinforced polymers in bridge construction is stay-in-place formwork. Fiber-reinforced polymer stay-in-place formwork, in the form of preformed tubes, provides easy form assembly, protection of steel reinforcement and concrete against corrosion and chemical attacks while also improving the strength and ductility of structural elements in earthquake resistant construction. Experimental research was conducted to investigate the seismic performance of fiber-reinforced polymer stay-in-place formwork for bridge columns. Tests of large-scale specimens were conducted under simulated seismic loading. The experimental program included circular and square columns confined with carbon fiber–reinforced polymer tubes. The results indicate that the use of carbon fiber–reinforced polymer tubes increases column inelastic deformability significantly. Bridge columns under low levels of axial compression exhibit inelastic drift capacities in excess of 4% before failing in flexural tension due to the rupturing of longitudinal reinforcement. These observations and experimental results were used to develop a displacement-based design procedure for concrete confinement for fiber-reinforced polymer–encased concrete columns. This article presents an overview of the experimental program and the design approach developed.

Drawing optical fibers with an elliptical core from cylindrical tube preforms

An original technique for manufacturing quartz optical fibers with an elliptical light-guiding core is proposed and tested. The dependences of the ellipticity of the light-guiding core on parameters of the manufacturing process—the temperature of the heating element of the high-temperature furnace and rarefaction inside the cylindrical tube preform—are studied. Test fiber samples are drawn and their optical properties are investigated.

Modelling and simulation of single and multi-pass flow forming to investigate the influence of process parameters on part accuracy

Flow forming is an incremental forming process used for making long, thin-walled seamless tubes with high strength and dimensional accuracy. This is carried out by compressing the pre-formed tube using one or more rollers, leading to the plastic flow of material in the radial, axial, and tangential directions. This ultimately results in reduction in thickness and elongation of the tube. In order to achieve the required accuracy and to reduce the shop floor costs, a better understanding of the influence of process parameters on part geometry, deformation mechanism, and stress-strain patterns will be required. This paper describes the development of a detailed finite element model, using Abaqus/Explicit, to accurately simulate the flow forming process for AISI-1045 MC-Steel, and attempts to predict the influence of process parameters like axial stagger, feed ratio, and percentage reduction, on output parameters like ovality, diametral growth, and spring back. The effect of multi-pass on surface finish is also investigated. [Received 26 August 2015; Revised 1 July 2016; Accepted 12 July 2016]

Are preformed endotracheal tubes appropriately designed for pediatric patients?

The aim of the study was to examine different brands of preformed oral and nasal endotracheal tubes (ETT) and to assess whether the bend placement gave acceptable guidance for ETT depth positioning in children. The distance from the vertex of the bend to the tip (bend-to-tip distance) of seven brands of preformed oral and nasal ETTs were measured. Front teeth-to-carina (FTC) and nares-to-carina (NC) distance data from orally (0-19 years) and nasally (0-8 years) intubated children were used to assess the risk of endobronchial intubation if a preformed ETT had been placed with its bend at the front teeth or nares. While the bend-to-tip distance of a cuffed oral preformed ETT only differed by 0-1 cm from a same size ETT from another brand, uncuffed oral ETTs differed by 0-4 cm. The bend-to-tip distance of cuffed and uncuffed ETTs of the same brand and size differed by 0-3 cm. Had preformed cuffed oral ETTs been placed with their bends at the front teeth in children of the FTC reference group, endobronchial intubation would have occurred in 0-27% of the patients, depending on the size and brand of the used ETT. In contrast to oral ETTs, the bend-to-tip distance of cuffed nasal ETTs differed more (0-5.5 cm) between brands, and uncuffed nasal ETTs less (0-3 cm). Also, the bend-to-tip distance of a cuffed nasal ETT was consistently greater (2-9 cm) than that of a same brand and size nasal uncuffed ETT. Had a preformed cuffed nasal ETT been placed with its bend at the nares in the NC reference group, 50-100% of the patients would have been endobronchially intubated. The bend-to-tip distance of preformed ETTs varies between brands, especially for nasal tubes. Some preformed tubes are not well suited for routine use in children. There is a high risk for accidental endobronchial intubation if a cuffed preformed ETT is positioned with its bend at the front teeth or nares in a young child. ETT tube tip position needs to be carefully controlled when a preformed ETT is used in a child.

Collapsed optical fiber: A novel method for improving thermoluminescence response of optical fiber

A new technique is shown to provide improved thermoluminescence (TL) response from optical fibers, based on collapsing down hollow capillary optical fibers (COF) into flat fibers (FF), producing fused inner walls and consequent defects generation. Four different fused silica preform tubes are used to fabricate in-house COFs and FFs, i.e., ultra-pure (F300), relatively pure silica (PS), germanium-doped (Ge), and Ge–Boron-doped (GeB). The optical fibers are then subjected to 6MeV electron irradiation. While the results show similar TL response from F300-COF and -FF, the TL response of PS-COF is improved by a factor of 6 by collapsing it down to a FF. By doping Ge into the F300 tube, the TL response of the resultant Ge-COF shows an improvement of 3 times over that of F300-COF, while an improvement of a factor of 12 is obtained by producing a Ge-FF. In GeB preform, by collapsing the capillary fiber into a FF, an improvement in TL response of 31 times that of GeB-COF is obtained. TL glow curve analysis shows an additional peak to be generated in the FFs compared to that observed in the COFs. The TL intensity value of the new peak is significantly increased in the doped FFs compared to the undoped FFs. The results suggest that defects generation occurs as a result of the fusing/collapsing technique, providing a TL response from the optical fibers that can substantially improve upon that of existing TL system sensitivities.

An observational study of the feasibility of Airtraq guided intubations with Ring Adair Elvin tubes in pediatric population with cleft lip and palate.

Context:The airway management requires refined skills and technical help when associated with cleft lip and palate. Airtraq has improved our airway management skills and has been successfully used for rescue intubation in difficult pediatric airways.Aims:This study was to evaluate the efficacy of Airtraq as the primary intubation device in patients with cleft lip and palate. The study adheres to the STrengthening the Reporting of OBservational Studies Epidemiology Statement.Subjects and Methods:A total of 85 children posted consecutively for lip and palate repair were enrolled. Children were intubated with Ring Adair Elvin (RAE) tube using size 1 and 2 of Airtraq device. The design of Airtraq has an anatomical limitation to hold RAE tubes. The preformed bend of the tube was straightened with a malleable stylet. The intubations were assessed for device manipulations and time taken for glottis visualization and intubation, airway complications such as bleeding, laryngospasm and failed intubations.Statistical Analysis Used:The outcome data were reported as numbers and percentages or range with identified median value, where applicable.Results:The success rate of Airtraq guided intubations was 98.21%. The cumulative insertion times and intubation times were 31.50 ± 12.57 s and 48.04 ± 35.73 s respectively. Airtraq manipulations were applied in 25.45% subjects.Conclusions:The presence of cleft lip or palate did not hamper the insertion of Airtraq. The use of malleable stylet to facilitate the loading of the preformed tube into the guide channel is a simple and efficacious improvisation. Airtraq can be utilized as a primary intubation device in children with orofacial clefts.

Trachway in Assistance of Nasotracheal Intubation with a Preformed Nasotracheal Tube in Patients Undergoing Oro-Maxillofacial Surgery

Trachway in Assistance of Nasotracheal Intubation with a Preformed Nasotracheal Tube in Patients Undergoing Oro-Maxillofacial Surgery

α1-Acid glycoprotein disrupts capillary-like tube formation of human lung microvascular endothelia

ABSTRACTPurpose: The acute phase protein, α1-acid glycoprotein, is expressed in the lung, and influences endothelial cell function. We asked whether it might regulate angiogenesis in human lung microvascular endothelia. Materials and Methods: α1-acid glycoprotein was isolated from human serum by HPLC ion exchange chromatography. Its effects on endothelial cell functions including capillary-like tube formation on Matrigel, migration in a wounding assay, chemotaxis in a modified Boyden chamber, adhesion, and transendothelial flux of the permeability tracer, 14C-albumin, were tested. Results: α1-acid glycoprotein dose-dependently inhibited capillary-like tube formation without loss of cell viability. At ≥0.50 mg/mL, it inhibited tube formation >70%, and at 0.75 mg/mL, >97%. α1-acid glycoprotein dose- and time-dependently restrained EC migration into a wound as early as 2 hours, and in washout studies, did so reversibly. It was inhibitory against vascular endothelial growth factor-A and fibroblast growth factor-2-driven migration but failed to inhibit chemotactic responsiveness. When α1-acid glycoprotein was added to preformed tubes, it provoked their almost immediate disassembly. As early as 15 minutes, it induced tube network collapse without endothelial cell–cell disruption. It exerted a biphasic effect on cell adhesion to the Matrigel substrate. At lower concentrations (0.05–0.25 mg/mL), it increased cell adhesion, whereas at higher concentrations (≥0.75 mg/mL) decreased adhesion. In contrast, it had no effect on transendothelial 14C-albumin flux. Conclusion: α1-acid glycoprotein, at concentrations found under physiological conditions, rapidly inhibits endothelial cell capillary-like tube formation that may be explained through diminished cell adhesion to the underlying matrix and/or reversibly decreased cell migration.

Abstract 757: ET-D5, first-in-class synthetic selective Protein Phosphatase 1 (PP1) inhibitor with anti-proliferative and anti-vascular activity

Abstract In this work we describe ET-D5, a synthetic small molecule serine-threonine protein phosphatase inhibitor with proven in vivo anti-mitotic and anti-vascular properties. The potential anti-cancer properties of serine-threonine protein phosphatase inhibitors have been identified since ancient times (extract from blister beetle mylabris was used in China for cancer treatment as early as in 1264), and several, mostly natural, inhibitors were evaluated in clinical trials. Their development was, however, discontinued due to the toxic effects of these non-selective (PP2A&amp;gt;&amp;gt;PP1) serine-threonine protein phosphatase inhibitors. ET-D5 is a remarkably specific (PP1 versus PP2A) inhibitor with potent anti-mitotic and anti-vascular activities. In vitro, ET-D5 display high efficacy against a wide range of human cancer cells (GI50 values determined were in low nM range for certain cell lines). In addition, ET-D5 disrupts the in vitro preformed capillary tubes (endothelial cells HMEC-1). In vivo experiments confirmed these activities in numerous animal models of human cancer, such as cancer of lung, brain, thyroid, kidney and ovaries. ET-D5 presents interesting pharmacological properties, good toxicology profile and is also active when administered per os. Contrary to many vascular-disrupting agents (VDA) which target tubulin, ET-D5 exerts its activity by selectively inhibiting in vivo protein-phosphatase I (PP1). We confirmed this activity in classical pharmacodynamics experiments, showing PP1 inhibition in xenografted tumors after oral administration of ET-D5. Based on all these results, ET-D5 is scheduled to enter clinical trials in early 2015. Citation Format: Aurelie Juhem, Delphine Lecercle, Julie Deverchère, Arnaud Gazel, Jean-Claude Florent, Andrei Popov. ET-D5, first-in-class synthetic selective Protein Phosphatase 1 (PP1) inhibitor with anti-proliferative and anti-vascular activity. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 757. doi:10.1158/1538-7445.AM2014-757

Formation of capillaries and optical fibers with the use of a high-temperature furnace with azimuthally inhomogeneous temperature field

The effect of two technological parameters--the azimuthal inhomogeneity of the wall thickness of the preform tubes and the azimuthal inhomogeneity of the temperature field of a high-temperature (HT) furnace--on the cross section ellipticity of the capillaries is investigated experimentally. SL-97-1 electron tube glass bulbs are used as the preform tubes. It is established that, when one uses an HT furnace with azimuthally homogeneous temperature field, the inhomogeneity of the wall thickness of a capillary coincides with that of the tube perform, irrespective of whether or not the preform tube is collapsed during drawing. In contrast, the ellipticity of the capillary depends on collapsing the perform tube and increases as the collapse coefficient increases. The azimuthal inhomogeneity of the temperature field leads to appreciable ellipticity of the cross sections even in capillaries drawn from preform tubes with small wall thickness inhomogeneity.

Intraoperative Acquired Pressure Ulcer on Lower Lip

Device-related pressure ulcers are not rare. However, few studies have reported pressure ulcers of the lower lip. We encountered 2 patients with an intraoperative pressure ulcer on the lower lip caused by an endotracheal tube during rhinoplasty. A 46-year-old man showed a deviated nose and nasal obstruction. Surgery was performed under general anesthesia with endotracheal intubation. The surgery time was 270 minutes. A 23-year-old man also showed a deviated nose and nasal obstruction. Surgery was performed under general anesthesia in the same fashion. The surgery time was 273 minutes. A preformed endotracheal tube was inserted and positioned over the mandible and secured with polyurethane film intraoperatively. Both patients had pressure ulcers on their lower lip. One showed a slightly visible scar. Care must be taken to avoid ulcers of the lower lip in rhinoplasty patients.