Discovery of Novel Pyrimidine-Based Capsid Assembly Modulators as Potent Anti-HBV Agents

( Woochan Kim ),( Jung-ah Kang ),( Minji Park ),( Pyeong-hwa Jeong ),( Yoon Jun Kim ),( Yuri Cho ),( Sung-gyoo Park ),( Yong-chul Kim ) 대한간학회 2021 춘·추계 학술대회 (KASL) Vol.2021 No.1

Biodegradable and Flexible Nanoporous Films for Design and Fabrication of Active Food Packaging Systems

( Woochan Kim ),( Taeseong Han ),( Yonghyun Gwon ),( Sunho Park ),( Hyoseong Kim ),( Jangho Kim ) 한국농업기계학회 2022 한국농업기계학회 학술발표논문집 Vol.27 No.1

Nanotechnology has facilitated the development of active food packaging systems with functions that could not be achieved by their traditional counterparts. Such smart and active systems can improve the shelf life of perishable products and overcome major bottlenecks associated with the fabrication of safe and environmentally friendly food packaging systems. Herein, we used a plasma-enabled surface modification strategy to fabricate biodegradable and flexible nanoporous polycaprolactone-based (FNP) films for food packaging systems. Their capacity for preserving tomatoes, tangerines, and bananas at room and refrigeration temperatures was tested by analyzing various fruit parameters (mold generation, appearance changes, freshness, weight loss, firmness, and total soluble solids contents). Compared with commonly used polyethylene terephthalate-based containers, the proposed system enhanced the fruit storage quality (i.e., retained appearance, reduced weight loss, better firmness, and sugar contents) by controlling moisture evaporation and inhibiting mold generation. Thus, the FNP film represents a new active food packaging strategy.

Flexible and Biodegradable Nanoporous Films for Application in Active Food Packaging Systems

( Woochan Kim ),( Taeseong Han ),( Yonghyun Gwon ),( Sunho Park ),( Hyoseong Kim ),( Jangho Kim ) 한국농업기계학회 2023 한국농업기계학회 학술발표논문집 Vol.28 No.1

Nanotechnology has facilitated the development of active food packaging systems with functions that could not be achieved by their traditional counterparts. Such smart and active systems can improve the shelf life of perishable products and overcome major bottlenecks associated with the fabrication of safe and environmentally friendly food packaging systems. Herein, we used a plasma-enabled surface modification strategy to fabricate biodegradable and flexible nanoporous polycaprolactone-based (FNP) films for food packaging systems. Their capacity for preserving tomatoes, tangerines, and bananas at room and refrigeration temperatures was tested by analyzing various fruit parameters (mold generation, appearance changes, freshness, weight loss, firmness, and total soluble solids contents). Compared with commonly used polyethylene terephthalate-based containers, the proposed system enhanced the fruit storage quality (i.e., retained appearance, reduced weight loss, better firmness, and sugar contents) by controlling moisture evaporation and inhibiting mold generation. Thus, the FNP film represents a new active food packaging strategy.

Engineering lotus leaf-inspired micro- and nanostructures for the manipulation of functional engineering platforms

Kim, Woochan,Kim, Daun,Park, Sunho,Lee, Dohyeon,Hyun, Hoon,Kim, Jangho THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 Journal of Industrial and Engineering Chemistry Vol.61 No.-

<P><B>Abstract</B></P> <P>The micro- and nanoscale structures of biological systems possess various intriguing properties, providing new insights and design principles for the fabrication of engineering platforms. In particular, the unique micro- and nanosurfaces of lotus leaves are highlighted as an emerging strategy that can be used as a tool for the manipulation of superhydrophobicity-based devices. In this review, we provide basic information on lotus leaf surface and present recent advances in micro- and nanoscale engineering platforms inspired by the surface topographies of lotus leaves for various applications. In addition, new perspectives on lotus leaf-inspired functional platforms in various engineering fields are discussed.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

What makes firms issue death spirals? A control enhancing story

Woochan Kim,Woojin Kim,Hyung-Seok Kim 한국재무학회 2009 한국재무학회 학술대회 Vol.2009 No.08

This paper studies the motive of issuing floating-priced convertibles or warrants, known as death spirals, in a country where the private benefit of control is high. Using a total of 199 death spiral issuances by public firms listed in the Korea Stock Exchange during 1998-2006, we find a number of pieces of empirical evidence that are not consistent with the last-resort financing hypothesis, but rather consistent with the control enhancing or control transferring hypothesis. First, operating performance of death spiral issuers are not necessarily poor at the time of the issue nor do they deteriorate over time following the issue. Second, death spiral issuers that are more likely to be motivated by control enhancing or transferring purposes - firms with no subsequent changes in control - exhibit superior operating performance at the time the issue compared to other death spiral or non-death spiral issuers. Third, these firms do not experience a decrease in proportional ownership by the controlling party, while family members other than the controlling shareholder experience the most pronounced increases in the number of shares held. Fourth, in approximately half of these firms, at least one member of the controlling party holds hybrid securities that can be later converted into the firm’s voting shares.

Death Spiral Issues in Emerging Market : A Control Related Perspective

Woochan Kim,Woojin Kim,Hyung-Seok Kim 한국재무학회 2009 한국재무학회 학술대회 Vol.2009 No.11

This paper studies the motive of issuing floating-priced convertibles or warrants, known as death spirals, in a country where the private benefit of control is high. Using a total of 199 death spiral issuances by public firms listed in the Korea Stock Exchange during 1998-2006, we find a number of pieces of empirical evidence that are less consistent with the last-resort financing hypothesis, but rather consistent with the control enhancing or control transferring hypothesis. First, operating performance of death spiral issuers are not necessarily poor at the time of the issue, nor do they deteriorate over time following the issue. Second, we do not observe subsequent changes in the controlling shareholder in more than 60% of the issuers and these firms exhibit superior operating performance at the time of the issue compared to other death spiral or non-death spiral issuers. Third, this same set of firms do not experience a decrease in proportional ownership by the controlling party, while family members other than the controlling shareholder experience the most pronounced increases in the number of shares held. Finally, in approximately half of these firms, at least one member of the controlling party holds hybrid securities that can be later converted into the firm’s voting shares.

What makes firms issue death spirals? A control enhancing story

Woochan Kim,Woojin Kim,Hyung-Seok Kim 한국재무학회 2008 한국재무학회 학술대회 Vol.2008 No.11

In this paper, we study the motive of issuing floating-priced convertibles or warrants, known as death spirals, in a country setting where the private benefit of control is high. Using a total of 199 death spiral issuances by public firms listed in the Korea Stock Exchange during 1998-2006, we find a number of empirical evidences that are not consistent with the last-resort financing hypothesis, but rather consistent with the control enhancing or control transferring hypothesis. First, death spirals are not necessarily issued by firms with poor operating performances. Second, death spiral issuers, where control is preserved within the family, experience an increase of ownership by affiliated firms. Third, this group of death spiral issuers tends to perform better than those in which family loses control.

Mechanobiological Regulation of Cells by Nanotopographically-defined Biomimetic Scaffolds for Animal Tissue Engineering

( Sujin Kim ),( Sunho Park ),( Daun Kim ),( Woochan Kim ),( Dohyeon Lee ),( Sungmin Park ),( Jangho Kim ) 한국농업기계학회 2018 한국농업기계학회 학술발표논문집 Vol.23 No.1

Living cells are exposed to complex and functional microenvironment including soluble macromolecules, biophysical cues, and interactions between cell-cell and cell-extracellular matrix (ECM). This suggests that the design and manipulation of engineered cellular microenvironments is of great important in a wide variety of biological applications such as fundamental biology, therapeutic and diagnostic research, stem cells and regenerative medicine, and developing in vitro disease models. In this work, we described the development of nanoscale engineered biomimetic systems for animal tissue engineering. Specifically, we showed the nanoscale patterned scaffolds inspired by the unique architectures of native animal tissues and ECMs that can provide cells the in vivo-like topographical cell environment, and their applications for better understanding of the function of living animal cells and tissue regeneration without complex surgical treatments.

Development of Leaves-inspired Micro- and Nanostructures for the Manipulation of Functional Engineering Platforms

( Daun Kim ),( Woochan Kim ),( Sunho Park ),( Dohyeon Lee ),( Sungmin Park ),( Sujin Kim ),( Jangho Kim ) 한국농업기계학회 2018 한국농업기계학회 학술발표논문집 Vol.23 No.1

The various surfaces in nature have great potential in both the academia and the industry. In particular, the lotus leaves surface exhibit a unique surface consisting of evenly distributed micro and nanoscale structures (i.e., called as ‘lotus effect’ (superhydrophobic property)). For these reasons, many studies were performed about the lotus effect to design and manipulation of engineering platforms or devices. With this consideration, various natural leaves have unique micro and nanoscale structures that can have controlled hydrophilic and hydrophobic properties. Here, we report on the tunable replication of surface topographies of natural leaves of common camellia, fragrant plantain, and lotus onto thin polymeric films using a capillarity-directed soft lithography technology. To this end, the surfaces of natural leaves were first replicated using polydimethylsiloxane (PDMS) as molds. The poly(ε-caprolactone) (PCL) film was then coated on the glass using spin-coating technique. Finally, the PCL-based unique micro- and nanostructures of natural leaves were generated using PDMS molds. The micro and nanostructure, chemical composition, wettability was characterized using scanning electron microscopy, atomic force microscope, Fourier transform infrared spectroscopy, X-ray diffraction, and contact angle measurement.

Hydroxyapatite/Eggshell Membrane Composites for Healthcare Applications

( Sujin Kim ),( Sunho Park ),( Daun Kim ),( Woochan Kim ),( Sungmin Park ),( Jangho Kim ) 한국농업기계학회 2018 한국농업기계학회 학술발표논문집 Vol.23 No.2

Eggshell membrane (ESM), one of the agricultural bioresources, is being recognized as emerging engineering platforms in various fields including healthcare applications. ESM is the protein-rich membrane between the eggshell and egg white, having interesting characteristics such as microfibrous structures and many functional chemical groups. However, the raw ESM has many limitations (e.g., limited scale-up platforms, low mechanical and bioactivity property), which raised some problems for its wide use as healthcare platforms. Here, we present new ESM-based engineering platforms based on nanotechnology for various healthcare applications, especially for bone tissue engineering (i.e., bone tissue repair and regeneration in animal and human systems). To enhance the mechanical and bioactivity property of law ESM, we used nanoscale hydroxyapatite powders (HAp) that can be incorporated into the ESM-based thin films. We demonstrated that the HAp/ESM composites provided unique properties of both HAp and ESM such as structural, chemical, and physical properties. Using the HAp/ESM composites, we showed that cell proliferation and differentiation of osteoblastic cells (MG-63) were enhanced on the HAp/ESM composites compared to those on the only ESM films. Our approach can enable the design and manipulation of ESM-based functional engineering platforms for healthcare applications including bone tissue engineering.