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| 2. |
- Klionsky, Daniel J., et al.
(author)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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In: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Research review (peer-reviewed)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 3. |
- Kim, Jun Woo, et al.
(author)
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Three-dimensional thermal stress analysis of the re-oxidized Ni-YSZ anode functional layer in solid oxide fuel cells
- 2018
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In: Journal of Alloys and Compounds. - : ELSEVIER SCIENCE SA. - 0925-8388 .- 1873-4669. ; 752, s. 148-154
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Journal article (peer-reviewed)abstract
- Nickel-yttria-stabilized zirconia (Ni-YSZ) cermet is widely used as an anode material in solid oxide fuel cells (SOFCs); however, Ni re-oxidation causes critical problems due to volume expansion, which causes high thermal stress. We fabricated a Ni-YSZ anode functional layer (AFL), which is an essential component in high-performance SOFCs, and re-oxidized it to investigate the related three-dimensional (3D) microstructural and thermo-mechanical effects. A 3D model of the re-oxidized AFL was generated using focused ion beam-scanning electron microscope (FIB-SEM) tomography. Re-oxidation of the Ni phase caused significant volumetric expansion, which was confirmed via image analysis and calculation of the volume fraction, connectivity, and two-phase boundary density. Finite element analysis (FEA) with simulated heating to 500-900 degrees C confirmed that the thermal stress in re-oxidized Ni-YSZ is concentrated at the boundaries between YSZ and re-oxidized NiO (nickel oxide). NiO is subjected to more stress than YSZ. Stress exceeding the fracture stress of 8 mol% YSZ appears primarily at 800 degrees C or higher. The stress is also more severe near the electrolyte-anode boundary than in the Ni-YSZ cermet and the YSZ regions. This may be responsible for the electrolyte membrane delamination and fracture that are observed during high-temperature operation. (C) 2018 Elsevier B.V. All rights reserved.
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| 4. |
- Woo Kim, Jun, et al.
(author)
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Compositional optimization of gadolinia-doped ceria treatment for enhanced oxygen reduction kinetics in low-temperature solid oxide fuel cells
- 2017
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In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 624, s. 95-100
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Journal article (peer-reviewed)abstract
- We report the optimization of the dopant concentration of gadolinia-doped ceria (GDC) to enhance the oxygen reduction reaction (ORR) kinetics for low-temperature solid oxide fuel cells (LTSOFCs). Crystalline GDC layers with uniform nano-granular structures were prepared by aerosol-assisted chemical vapor deposition (AACVD) on the cathode side of a GDC electrolyte. The current-voltage (I-V) characteristics and power performances of the AACVD GDC-treated cells were measured and their cathodic reactions were analyzed by electrochemical impedance spectroscopy (EIS) to investigate the effect of GDC treatments with various dopant compositions. The cell treated with Gd0.14Ce0.86O2-delta was found to show an optimized power performance with the best ORR kinetics, due to its nano-granular structure and high concentration of oxygen vacancies. (C) 2017 Published by Elsevier B.V.
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| 5. |
- Kim, Jun Woo, et al.
(author)
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3D EVALUATION OF THERMAL STRESSES ON CERAMIC-METAL COMPOSITES USED AT HIGH TEMPERATURE OPERATION
- 2017
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In: 5TH IIR INTERNATIONAL CONFERENCE ON THERMOPHYSICAL PROPERTIES AND TRANSFER PROCESSES OF REFRIGERANTS (TPTPR). - : INT INST REFRIGERATION. - 9782362150203 ; , s. 771-775
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Conference paper (peer-reviewed)abstract
- Ceramic-metal composites (CMC) have been used for various high temperature applications including combustion engines, steam and gas turbines, industrial heaters and ceramic fuel cells. Reliable incorporation of the CMC at elevated temperatures, however, is very difficult in practice for the following reasons. First, meting and sublimation points of those solids are different causing undesired diffusion and mixing of elements across the material boundaries degrading functions of the materials. Secondly, maintaining temperature and pressure regimes for desired phases of the component materials is challenging during operation in many of practical cases. Lastly, thermal expansion rates of those two materials are significantly different frequently causing mechanical stresses and fractures. There have been numerous efforts to evaluate and design the CMC materials to minimize the thermo-mechanical stresses. Among various techniques, the focused ion beam-scanning electron microscope (FIB-SEM) tomography has been proved as a state-of-art technique to obtain 3D compositional and structural information of the CMC materials. In this study, we have evaluated thermal stresses applied on nickel-zirconia CMCs by using the FIB-SEM 3D tomography and finite element analysis.
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| 6. |
- Chang, You, et al.
(author)
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Simulation of Bone-Conducted Sound Transmission in a Three-Dimensional Finite-Element Model of a Human Skull
- 2015
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In: MECHANICS OF HEARING: PROTEIN TO PERCEPTION. - : AMER INST PHYSICS. - 9780735413504
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Conference paper (peer-reviewed)abstract
- Bone conduction (BC) is the transmission of sound to the inner ear through the bones of the skull. This type of transmission is used in humans fitted with BC hearing aids as well as to classify between conductive and sensorineural hearing losses. The objective of the present study is to develop a finite-element (FE) model of the human skull based on cryosectional images of a female cadaver head in order to gain better understanding of the sound transmission. Further, the BC behavior was validated in terms of sound transmission against experimental data published in the literature. Results showed the responses of the simulated skull FE model were consistent with the experimentally reported data.
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| 7. |
- Kim, Nam Keun, et al.
(author)
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A Possible Third Window for Bone Conducted Hearing: Cochlear Aqueduct vs. Vestibular Aqueduct
- 2015
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In: Mechanics of hearing: Protein to perception. - : American Institute of Physics (AIP). - 9780735413504 ; , s. 060016-1-060016-4
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Conference paper (peer-reviewed)abstract
- A third window, which is another cochlear fluid pathway different from the oval window and round window, is considered to be a significant factor in bone-conducted hearing. A three-dimensional finite element model of the human ear consisting of the middle ear and cochlea was used to investigate the effect of the third windows on bone-conducted heraing. This study is aimed to find the third window which causes the consistent cochlear responses with previous studies in air-conducted hearing, and causes the asymmetry of the volume velocity ratio between the oval window and round window in bone-conducted hearing. The preliminary result shows that the cochlear aqueduct and the vestibular aqueduct with high impedance do not affect the basilar membrane velocity in air-conducted hearing. On the contrary, in bone-conducted hearing, the direction of the shaking structure for the bone-conducted stimulation as well as the third window can be a significant factor causing the asymmetry of the volume velocity ratio found by Stenfelt et al.
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| 8. |
- Lee, Nam-Young, et al.
(author)
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Performance of Insoluble IrO2 Anode for Sewage Sludge Cake Electrodehydration Application with Respect to Operation Conditions
- 2022
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In: Coatings. - : MDPI. - 2079-6412. ; 12:6
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Journal article (peer-reviewed)abstract
- The efficient management of wastewater and sewage sludge treatment are becoming crucial with industrialization and increasing anthropological effects. Dehydration of sewage sludge cakes (SSCs) is typically carried out using mechanical and electrochemical processes. Using the mechanical dehydration process, only a limited amount of water can be removed, and the resultant SSCs have a water content of approximately 70-80 wt.%, which is significantly high for land dumping or recycling as solid fuel. Dumping high-moisture-content SSCs in land can lead to leakage of hazardous wastewater into the ground and cause economic loss. Therefore, dehydration of SSCs is crucial. Contemporary treatment methods focus on the development of anode materials for the electrochemical processes. IrO2 is an insoluble anode material that is eco-friendly, less expensive, and exhibits high chemical stability, and it has been widely used and investigated in wastewater treatment and electrodehydration (ED) industries. Herein, we evaluated the performance of the ED system developed using IrO2 anode material. The operating conditions of the anode such as reaction time, sludge thickness, and voltage on SSC were optimized. The performance of the ED system was evaluated based on the moisture content of SSCs after dehydration. The moisture content decreased proportionally with the reaction time, sludge thickness, and voltage. The moisture content of 40 wt.% was determined as the optimum quantity for land dumping or to be used as recycled solid fuel.
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| 9. |
- Park, Ji-Won, et al.
(author)
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Beetle Immunity
- 2010
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In: Advances in Experimental Medicine and Biology. - Boston, MA : Springer US. - 0065-2598 .- 2214-8019. ; 708, s. 163-180
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Journal article (peer-reviewed)abstract
- Genetic studies have elegantly characterized the innate immune response in Drosophila melanogaster. However, these studies have a limited ability to reveal the biochemical mechanisms underlying the innate immune response. To investigate the biochemical basis of how insects recognize invading microbes and how these recognition signals activate the innate immune response, it is necessary to use insects, from which larger amounts of hemolymph can be extracted. Using the larvae from two species of beetle, Tenebrio molitor and Holotrichia diomphalia, we elucidated the mechanisms underlying pathogenic microbe recognition. In addition, we studied the mechanism of host defense molecule amplification. In particular, we identified several pattern recognition proteins, serine proteases, serpins and antimicrobial peptides and examined how these molecules affect innate immunity.
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