Compressive performance of 50 MPa strength concrete-filled square and circular tube (CFT) columns using recycled aggregate

[EN] Recycled aggregate is an environmentally self-sustainable solution that can reduce construction waste and replace natural aggregates. However, there is a disadvantage in concrete such as initial strength drop and long-term strength development. Therefore, the interaction effect of the two materials can be expected by filling the cyclic aggregate concrete in the CFT column. In order to develop a concrete with compressive strength of 50 MPa as a recycled aggregate, we carried out a mixing experiment and fabricated 18 specimens to confirm the compressive behavior of a RCFT (Recycled Concrete Filled Tube) column that can be applied to actual buildings. Variable is the shape and thickness of steel pipe, concrete strength and mixing ratio, and coarse aggregate and fine aggregate are all used as recycled aggregate. The optimum mixing ratio for recycled aggregate concrete to be filled in the CFT filled steel pipe was found through three concrete preliminary mixing experiments. In addition, the compression test of the RCFT column was carried out to observe and analyze the buckling shape of the CFT column. Based on the analysis of the buckling configuration and the experimental data, the load-displacement curves of the specimens were drawn and the compressive behavior was analyzed.Choi, S.; Choi, WH.; Lee, K.; Ryoo, J.; Kim, S.; Park, Y. (2018). Compressive performance of 50 MPa strength concrete-filled square and circular tube (CFT) columns using recycled aggregate. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 305-313. https://doi.org/10.4995/ASCCS2018.2018.7021OCS30531

Decolorization of malachite green by cytochrome c in the mitochondria of the fungus Cunninghamella elegans

We studied the decolorization of malachite green (MG) by the fungus Cunninghamella elegans. The mitochondrial activity for MG reduction was increased with a simultaneous increase of a 9-kDa protein, called CeCyt. The presence of cytochrome c in CeCyt protein was determined by optical absorbance spectroscopy with an extinction coefficient (E\u2085\u2085\u2080\u2013\u2085\u2083\u2085) of 19.7 \ub1 6.3 mM-\ub9 cm-\ub9 and reduction potential of + 261 mV. When purified CeCyt was added into the mitochondria, the specific activity of CeCyt reached 440 \ub1 122 \u3bcmol min-\ub9 mg-\ub9 protein. The inhibition of MG reduction by stigmatellin, but not by antimycin A, indicated a possible linkage of CeCyt activity to the Qo site of the bc1 complex. The RT-PCR results showed tight regulation of the cecyt gene expression by reactive oxygen species. We suggest that CeCyt acts as a protein reductant for MG under oxidative stress in a stationary or secondary growth stage of this fungus.Peer reviewed: YesNRC publication: Ye

Late Morning Concurrent Sessions: Critical Issues: Presentation: A Study on the Localization of Airport Self Bag-Drop Off System in Korea

A Study on the Localization of Airport Self Bag-Drop Off system in Korea 360, Daegok-ri, Haemi-myun, Seosan-si, Chuncheongnam-do, Korea, 356-706 Phone : +82-41-671-6221 Fax : +82-41-671-6228 Kang-Seok, Lee Professor, Dept. of Air transportation and Logistics, Hanseo Uiversity E-mail : [email protected] Abstract Advanced countries in the aviation industry, especially the United States and European Union, develop and commercialize their own Self Bag Drop off(SBD) system integrated with IT convergence technology, dominating the international market. Nevertheless, most of SBD technologies in domestic airports in Korea rely on other countries. It is imperative that internal airport operators introduce the Self Bag Drop-off system and produce, apply, and manage the most optimized SBD system for airports and airlines. Upon analyzing the tendency and operation of the SBD system utilized in leading international airports, The purpose of this paper is conducted to address the localization of the future implementation in domestic airports in Korea

Tuning physico-mechanical properties of 3D hydrogel using multifunctional biopolymers

Department of Biomedical Engineeringclos

Advanced Polymer-Based Bioink Technology for Printing Soft Biomaterials

Remarkable advancement in 3D printing technology in recent years has already transformed many aspects of industrial manufacturing. The immense potential of 3D printing is already being explored in state-of-the-art biomedical research field. Often termed "bioprinting", 3D printing is utilized to generate biological structures with high resolution and specificity for tissue engineering and regenerative medical applications. With the maturation of bioprinting apparatus, now the focus is shifting to engineering "bioinks" that can accommodate the versatility of biological systems, while still maintaining their printability. In this review, bioink technologies based on various polymers to produce soft biomaterials, such as hydrogels and elastomers, having a diverse array of physicochemical and bioactive properties are introduced and highlighted

Dual Ionic Cross-linked Interpenetrating Network Of Alginate-cellulose Beads With Enhanced Mechanical Properties For Biocompatible Encapsulation

Spherical hydrogels made from alginate has been explored and used for biomedical application, although restricted mechanical strength and short-term structural cohesion. In this study, controlling mechanical properties and maintaining the long-term structural integrity of spherical hydrogels could be achieved by creating interpenetrating networks of alginate and aqueous-soluble cellulose with divalent and trivalent ions. We found that processing a dual sequential ionic crosslinking scheme to create IPN of alginate and cellulose with divalent and trivalent ions has synergistic effect to increase moduli and structural stability of hydrogels. As a result, the IPN alginate-cellulose beads demonstrate enhanced resistance to harsh chemical environment as compared to alginate beads and suitability for biomedical applications by encapsulating microbial species and therapeutic agents for controlled release

Microfluidics???Assisted Fabrication of Microtissues with Tunable Physical Properties for Developing an In Vitro Multiplex Tissue Model

Herein, a new 3D hydrogel-based co-culture tissue model is developed to systematically examine the effect of mutual influence between two different cell types residing in separated but interactive zones. Microtissues containing macrophage as a model cell type are first developed by photocrosslinking cell-laden droplets containing methacrylic gelatin (MGel), using a microfluidic flow-focusing device. Regardless of the material conditions, the cell viability is well maintained demonstrating the biocompatibility of the fabrication process as well as the 3D microenvironment provided by the microgels. More significantly, it is shown that the proliferation and lipopolysaccharide (LPS)-induced differentiation (???Mϕ polarization???) of macrophages are heavily influenced by the mechanical properties of the microgels, controlled with MGel concentrations. Eventually, these macrophage microtissues are embedded into a larger tissue construct, containing either normal or cancer cells, to develop a co-culture tissue model to study the mutual effects between macrophage in different stages of differentiation and the surrounding cells. It is expected that this ???multiplex??? tissue model would allow an effective platform for monitoring of complex interactions between two different cell types cells residing in adjacent, compartmentalized areas within a 3D tissue environment

Microfluidics-assisted fabrication of microtissues with tunable physical properties for in vitro tissue model

Microfluidic flow-focusing devices (FFD) are widely used to develop micron-scale emulsion particles ('droplets') with variable size and shape for biomedical applications. Specifically, droplets consisting of gel-forming polymers can be crosslinked to form microgels for tissue engineering and drug delivery. In this study, cell-encapsulated microgels fabricated by photocrosslinking droplets containing methacrylic gelatin (MGel). The mechanical properties of the microgels could be controlled by the MGel concentrations, while their size could be controlled by varying the flow rates during droplet generation. The viability of macrophages encapsulated in the microgels was well maintained regardless of the physical properties, while their proliferation was dependent on the mechanical properties. More significantly, lipopolysaccharide (LPS) induced M1/M2 differentiation of macrophages was also heavily influenced by the mechanical properties of the microgels. Eventually, these macrophage microtissues were embedded in a hepatocarcinoma tissue constructs as an in vitro tumor model to study the effects of macrophage in different stages of differentiation and mechanical environment on the surrounding cancer cells

Refined control of thermoresponsive swelling/deswelling and drug release properties of poly(N-isopropylacrylamide) hydrogels using hydrophilic polymer crosslinkers

Thermoresponsive poly(N-isopropylacrylamide) (PNIPAm)-based hydrogels are widely investigated for their ability to alter their physical properties (e.g. dimensions, swelling/deswelling) in response to change in temperature. Despite extensive research efforts, it is still challenging to control various aspects of thermoresponsive physical properties of PNIPAm hydrogels in an efficient and comprehensive manner using conventional small molecular crosslinkers due to their limited solubility and functional groups. Herein, thermoresponsive swelling/deswelling behavior of PNIPAm hydrogels is tuned in a wide range by hydrophilic polymeric crosslinkers with varying chain lengths. The concentration and molecular weight of the poly(ethylene glycol) (PEG) crosslinker are varied to control the swelling/deswelling behavior, drug release, and lower critical solution temperature (LCST) of PNIPAm-PEG hydrogels. Compared with PNIPAm hydrogels crosslinked with a conventional small molecular crosslinker, N,N-methylenebisacrylamide, greater degree and range of thermoresponsive swelling/deswelling as well as tunable LCST are demonstrated for PNIPAm-PEG hydrogels. In addition, more swelling-controlled PNIPAm-PEG hydrogels displayed more sustained and variable thermoresponsive drug release based on their crosslinking density, by modulating the hydrophobic transition of PNIPAm chains with hydrophilic PEG chains. In sum, various thermoresponsive properties of PNIPAm hydrogels could be controlled by hydrophilic polymeric crosslinkers, and this strategy could be applied to various hydrogel systems to control their physical properties for biomedical applications.clos

In situ forming elastin-like polypeptide hydrogel for injectable drug delivery applications

In situ forming hydrogels are widely explored as injectable drug delivery systems for biomedical applications. It is important for these hydrogels to undergo gelation and deliver the drug in a timely manner upon administration. In this study, lysine-rich elastin-like polypeptide (ELP) and aldehyde-presenting alginate are crosslinked via Schiff base formation under ambient conditions to generate hydrogel. The physicomechanical and drug release properties of the alginate-ELP hydrogel are conveniently controlled by the concentrations of alginate and ELP. Furthermore, due to the thermoresponsiveness of ELP, the alginate-ELP hydrogel undergoes reversible swelling/deswelling at the transition temperature near the physiological temperature. Therefore, the drug release from the alginate-ELP hydrogel is expedited via thermoresponsive deswelling. Taken together, the in situ forming alginate-ELP hydrogel is a highly attractive injectable drug delivery system capable of programmable release characteristics