• Journal of Chest Surgery
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• v.56 no.3
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• pp.206-212
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• 2023

Background: Delayed sternal closure (DSC) is a useful option for patients with intractable bleeding and hemodynamic instability due to prolonged cardiopulmonary bypass and a preoperative bleeding tendency. Vacuum-assisted closure (VAC) has been widely used for sternal wound problems, but only rarely for DSC, and its efficacy for mediastinal drainage immediately after cardiac surgery has not been well established. Therefore, we evaluated the usefulness of DSC using VAC in adult cardiac surgery. Methods: We analyzed 33 patients who underwent DSC using VAC from January 2017 to July 2022. After packing sterile gauze around the heart surface and great vessels, VAC was applied directly without sternal self-retaining retractors and mediastinal drain tubes. Results: Twenty-one patients (63.6%) underwent emergency surgery for conditions including type A acute aortic dissection (n=13), and 8 patients (24.2%) received postoperative extracorporeal membrane oxygenation support. Intractable bleeding (n=25) was the most common reason for an open sternum. The median duration of open sternum was 2 days (interquartile range [25th-75th pertentiles], 2-3.25 days) and 9 patients underwent VAC application more than once. The overall in-hospital mortality rate was 27.3%. Superficial wound problems occurred in 10 patients (30.3%), and there were no deep sternal wound infections. Conclusion: For patients with an open sternum, VAC alone, which is effective for mediastinal drainage and cardiac decompression, had an acceptable superficial wound infection rate and no deep sternal wound infections. In adult cardiac surgery, DSC using VAC may be useful in patients with intractable bleeding or unstable hemodynamics with myocardial edema.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.1
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• pp.18-27
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• 2021

This study aims to develop an improved evaluation technology for assessing CANDU-6 safety. For this purpose, the multiple steam generator tube rupture (mSGTR) followed by an unmitigated station blackout (SBO) in a CANDU-6 plant was selected as a hypothetical event scenario and the analysis model to evaluate the plant responses was envisioned into the MARS-KS input model. The model includes logic models for controlling the pressure and inventory of the primary heat transport system (PHTS) decreasing due to the u-tubes' rupture, as well as the main features of PHTS with a simplified model for the horizontal fuel channels, the secondary heat transport system including the shell side of steam generators, feedwater and main steam line, and moderator system. A steady state condition was successfully achieved to confirm the stable convergence of the key parameters. Until the turbine trip, the fuel channels were adequately cooled by forced circulation of coolant and supply of main feedwater. However, due to the continuous reduction of PHTS pressure and inventory, the reactor and turbine were shut down and the thermal-hydraulic behaviors between intact and broken loops got asymmetric. Furthermore, as the conditions of low-flow coolant and high void fraction in the broken loop persisted, leading to degradation of decay heat removal, it was evaluated that the peak cladding temperature (PCT) exceeded the limit criteria for ensuring nuclear fuel integrity. This study is expected to provide the technical bases to the accident management strategy for transient conditions with multiple events.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.8 no.2
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• pp.95-101
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• 2022

Microfluidic radioimmunoassay (RIA) platform called µ-RIA spends less reagent and shorter reaction time for the analysis compared to the conventional tube-based radioimmunoassay. This study reported the design of µ-RIA chips optimized for the gamma counter which could measure the small samples of radioactive materials automatically. Compared with the previous study, the µ-RIA chips developed in this study were designed to be compatible with conventional RIA test tubes. And, the automatic gamma counter could detect radioactivity from the ¹²⁵I labeled anti-PSA attached to the chips. Effects of the multi-layer microchannels and two-phase flow in the µ-RIA chips were investigated in this study. The measured radioactivity from the ¹²⁵I labeled anti-PSA was linearly proportional to the number of stacked chips, representing that the radioactivity in µ-RIA platform could be amplified by designing the chips with multi-layers. In addition, we designed µ-RIA chip to generate liquid-gas plug flow inside the microfluidic channel. The plug flow can promote binding of the biomolecules onto the microfluidic channel surface with recirculation in the liquid phase. The ratio of liquid slug and air slug length was 1 : 1 when the ¹²⁵I labeled anti-PSA and the air were injected at 1 and 35 µL/min, respectively, exhibiting 1.6 times higher biomolecule attachment compared to the microfluidic chip without the air injection. This experimental result indicated that the biomolecular reaction was improved by generating liquid-gas slugs inside the microfluidic channel. In this study, we presented a novel µ-RIA chips that is compatible with the conventional gamma counter with automated sampler. Therefore, high-throughput radioimmunoassay can be carried out by the automatic measurement of radioactivity with reduced radiowaste generation. We expect the µ-RIA platform can successfully replace conventional tube-based radioimmunoassay in the future.

• Steel and Composite Structures
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• v.48 no.3
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• pp.275-291
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• 2023

This paper has focused on presenting vibration analysis of trapezoidal sandwich plates with 3D-graphene foam reinforced polymer matrix composites (GrF-PMC) core and FG wavy CNT-reinforced face sheets. The porous graphene foam possessing 3D scaffold structures has been introduced into polymers for enhancing the overall stiffness of the composite structure. Also, 3D graphene foams can distribute uniformly or non-uniformly in the plate thickness direction. The effective Young's modulus, mass density and Poisson's ratio are predicted by the rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The First-order shear deformation theory of plate is utilized to establish governing partial differential equations and boundary conditions for trapezoidal plate. The governing equations together with related boundary conditions are discretized using a mapping-generalized differential quadrature (GDQ) method in spatial domain. Then natural frequencies of the trapezoidal sandwich plates are obtained using GDQ method. Validity of the current study is evaluated by comparing its numerical results with those available in the literature. It is explicated that 3D-GrF skeleton type and weight fraction, carbon nanotubes (CNTs) waviness and CNT aspect ratio can significantly affect the vibrational behavior of the sandwich structure. The plate's normalized natural frequency decreased and the straight carbon nanotube (w=0) reached the highest frequency by increasing the values of the waviness index (w).

• Progress in Superconductivity
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• v.3 no.1
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• pp.130-133
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• 2001

A multifilamentary Bi-2223 HTS tape for superconducting power applications was studied through the fabrication of 250-meter long tapes by the PIT(powder in tube) process. To fabricate continuous long wire, a drawing machine, a two-drum bull block and a rolled tape winding machine were developed. Especially, 250-meter long tapes were heat treated in the shape of pancake coil to reduce the heat affect zone and to achieve the high critical current. Engineering critical current density was improved through both the enhancements of critical current density by control of thermal process and the increase of filling factor by using thin Ag alloy sheath tubes less than 1.5 mm in thickness. We have made successfully 250-meter long 37 filamentary tapes with high filling factor up to 31 % employing the modified drawing and rolling technique. The critical current of 250-meter long tapes with pancake coil type was measured by transport method at self-field up to 250 gauss of center field. The measured values, based on the transport critical current at self-field, $I_{c}$ -B characteristics and magnetic field analysis, are 34 A of I$_{c}$ and 4.0 $kA/\textrm{cm}^2$ of $J_{e}$ at 250 m, 77 K, and 0 T. We also have achieved the 56 A of I$_{c}$ and 7.0 $0 kA/\textrm{cm}^2$ of$ J_{e}$ in short tapes at 77K, self-field, and 1$mutextrm{V}$/cm.

• Composites Research
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• v.21 no.3
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• pp.24-30
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• 2008

Durability problems may arise in the concrete, which is one of the major construction materials, used in the construction field. Bridge piers and foundation piles are usually made with concrete and they are exposed to the moisture and hence the durability of the concrete reduced significantly due to oxidization of re-bar and icing of concrete. To mitigate such problems, FRP tube has been developed and the concrete filled FRP tube (CFFT) has been investigated to find the confinement effect which is provided additionally. It was reported that if the concrete is wrapped with FRP, strength and chemical resistance are improved significantly. In order to apply such a member in the construction field, structural behavior and applicable design guideline or design criteria must be thoroughly investigated. In the experimental investigation, the results are compared with the previous research results and the relationship which can predict the ultimate strength and strain is suggested. In addition, some comments found at the compression tests are given briefly.

• Journal of Korean Neurosurgical Society
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• v.66 no.4
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• pp.393-399
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• 2023

Objective : Chiari II malformation (CM II) is still the main cause of severe morbidity and mortality in children with open neural tube defects (ONTDs). The goal of this study was to validate a CM II model in late-stage chick embryos with surgically induced ONTDs. Methods : To make the chick embryo model of ONTD, their neural tubes were opened for a length of 5-6 somites at the thoracic level in Hamburger and Hamilton stage 18 chick embryos (n=150). They were reincubated in ovo up to a total age of 17-21 days. A total of 19 embryos survived and were assigned to either the postoperative day (POD) 14-15 group (n=6) or the POD 17-18 group (n=13). Magnetic resonance imaging (MRI) and histopathologic findings of embryo heads with spinal ONTDs were compared with age-matched normal chick embryos. Results : The chick embryos with ONTDs demonstrated definite and constant structural changes, such as downward displacement of the cerebellum to just above the foramen magnum and narrow and small cerebrospinal fluid spaces in the crowded small posterior fossa. These morphologic features were more prominent in the POD 17-18 group than in the POD 14-15 group. Conclusion : This is the first description of CM II with spinal ONTD in a late-stage chick embryo model with MRI and histopathological analysis. The morphological changes of the posterior fossa in this study mimic those of CM II associated with spinal ONTD in humans. This model will facilitate investigation of the pathogenesis of CM II.

• Restorative Dentistry and Endodontics
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• v.46 no.1
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• pp.4.1-4.16
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• 2021

Objectives: This study evaluated the biocompatibility and bioactive potential of NeoMTA Plus mixed as a root canal sealer in comparison with MTA Fillapex. Materials and Methods: Polyethylene tubes filled with NeoMTA Plus (n = 20), MTA Fillapex (n = 20), or nothing (control group, CG; n = 20) were inserted into the connective tissue in the dorsal subcutaneous layer of rats. After 7, 15, 30 and 60 days, the specimens were processed for paraffin embedding. The capsule thickness, collagen content, and number of inflammatory cells (ICs) and interleukin-6 (IL-6) immunolabeled cells were measured. von Kossa-positive structures were evaluated and unstained sections were analyzed under polarized light. Two-way analysis of variance was performed, followed by the post hoc Tukey test (p ≤ 0.05). Results: At 7 days, the capsules around NeoMTA Plus and MTA Fillapex had more ICs and IL-6-immunostained cells than the CG. However, at 60 days, there was no significant difference in the IC number between NeoMTA Plus and the CG (p = 0.1137) or the MTA Fillapex group (p = 0.4062), although a greater number of IL-6-immunostained cells was observed in the MTA Fillapex group (p = 0.0353). From 7 to 60 days, the capsule thickness of the NeoMTA Plus and MTA Fillapex specimens significantly decreased, concomitantly with an increase in the collagen content. The capsules around root canal sealers showed positivity to the von Kossa stain and birefringent structures. Conclusions: The NeoMTA Plus root canal sealer is biocompatible and exhibits bioactive potential.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2A
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• pp.149-159
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• 2010

This paper presents an experimental study on the structural behavior of composite CFT truss girder bridge with full depth precast panels. The length of span is 20,000 mm. The CFT truss girder is a tubular truss composed of chord members made of concrete-filled and hollow circular tubes. To determine fundamental structural characteristics such as the strength and deformation properties of composite CFT truss girder bridge, static and dynamic tests were conducted. The natural frequencies calculated by the FEM are in good agreement with experimental results obtained from dynamic test. Bracing have only a small effect on the natural frequencies of composite CFT truss girder bridge as indicated by the FEM results. The yield strength and deformation of the composite CFT truss girder bridges were investigated through a static bending test. Besides, the test results showed that uniform distribution of shear connectors can be applicable in composite CFT truss girder bridges.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.15-26
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• 2010

Quasi-static tests were conducted to evaluate structural performance of precast piers prestressed by bonded prestressing steels. Combinations of prestressing bars and normal reinforcing bars, embedded steel tubes and prestressing strands were used as continuous steels crossing the joints of a precast pier. Main design parameters were steel ratio, magnitude of prestress force, and section details. Flexural strength and energy dissipation capacity of precast columns with higher steel ratio showed better performance due to continuous steels after opening of the joints. Precast piers with embedded members showed stable behavior after reaching maximum loads resulting in higher displacement ductility and energy dissipation capacity increased as the introduced prestress increased. Self-centering behavior at early stages and stress increase of confining reinforcements were observed from highly prestressed columns. Combination of prestressing steels and normal reinforcing bars should be used in design to prevent rapid strength degradation after reaching the maximum load.