SUNGKYUNKWAN UNIVERSITY (SKKU), SEOUL, KOREA


July-October, 2017 Vol. 3
Worldwide
  • Prof. Nam Gyu PARK Was Selected for "2017 Potential Recipients of the Nobel Prize"
  • French Ambassador to Korea Visits SKKU
  • Rector of RUDN University Visits SKKU
  • Prof. Sung Eun CHUNG Gives Special Lecture at Penn State University
Discovery
  • SKKU Enters Top 100 in THE World Reputation Rankings for First Time
  • SKKU Ranks 111th in THE World University Rankings
  • SKKU Achieves the Best Performance in All Three R&D Researchers Cultivation Projects
Top Schools
  • Graduate School of Global Insurance & Pension Makes Dual-Degree Agreement with St. John’s University
  • Successful Completion of the 2017 Summer Farewell Party for Graduating International Students
  • SKKU-KU Leaven Agree to Enter MOU
Leading Alumni in a Global Society
  • Noticeable Articles Recently Published in Journals
Leading Alumni in a Global Society
  • Deep Learning System for Recognition & Detection of Pedestrians & Vehicles in Hostile Environments
  • Global Capstone Design Team Wins at 2017 PACE Global Annual Forum
  • Dr. Yao FEI of Department of Energy Science Appointed Professor at SUNY
  • Dr. Satyasheel Sharma Appointed Assistant Prof. at NIPER-Ahmedabed, India
Leading Alumni in a Global Society
  • 647 International Students Newly Entered SKKU in Fall 2017
Space Experiment Instrument Developed by SKKU Research Team Bound for International Space Station

A space experiment instrument developed by a Sungkyunkwan University research team is bound for the International Space Station.

Sungkyunkwan University announced a silicon charge detector (SCD) developed by a research team lead by Prof. Ilheung PARK of the Department of Physics will be delivered to the International Space Station on September 15th, at 1:31 PM (Korean time) at the Kennedy Space Center in the United States.

The space experiment instrument will be delivered to space by a SpaceX rocket called "Dragon'. It will be installed on an outside module of the International Space Station and is expected to perform a space mission for at least three years.

The silicon charge detector is instrument to measure components of cosmic rays which are particles falling to Earth from space. It was made by using semiconductor sensor technology. Cosmic rays were first detected in 1912, but their origins or spread processes have not been identified for more than 100 years. So, "The Cosmic Ray Energetics and Mass" mission destined for the International Space Station (ISS-CREAM) is designed to measure the highest-energy cosmic rays by the National Aeronautics and Space Administration (NASA). The Republic of Korea, the United States, Mexico, and France are participating in the experiment.

According to Sungkyunkwan University, the silicon charge detector will play a key role in the ISS-CREAM. It is made of pure domestic technology and has an area of 1 ㎡ and a weight of 150 kg, which is the maximum size of a detector used in space. Four layers of silicon sensors measure components of cosmic rays. (Accuracy 99%)

This detector was developed by Sungkyunkwan University in cooperation with the Korea Electronics and Telecommunications Research Institute and small and medium enterprises, and the Korea Institute of Industrial Technology did a space environment experiment. The whole process was conducted in Korea.

"This is the first time that a domestic high-tech instrument will be used in large space experiment on the International Space Station," said Prof. Park, "This is a case when we have made a core instrument for a main NASA space project and are participating as a main partner."

Ultraclean Transfer Method Developed for Large-Area 2-Dimensional Semiconductors

Graphene, which was discovered in 2005 and awarded the Nobel Prize in 2010, has been intensely studied due to its high charge carrier mobility, high electric conductivity, superior mechanical strength, excellent chemical stability, and high optical property. Its commercialization has been attempted in various ways and fields. However, despite those strengths, it has been considered hard to utilize as an electronic material due to the zero bandgap.

How to overcome the weakness of graphene and 2-dimensional (2D) semiconductors, such as molybdenum disulfide (MoS2), has begun to be investigated and is gaining attention and interest among scientists and engineers. Unlike graphene, 2D semiconductors have some bandgaps similar to that of silicon and exhibit reasonable charge carrier mobility. Hence, they are expected to become one of the main semiconducting materials for next-generation electronics. In addition, it is highly probable that they will become important materials for flexible electronics due to their atomic-level thickness.

However, large-area synthesis and transfer techniques for commercialization of 2D semiconductors are still being developed at too slow of a pace and are at an immature stage. The research team has been developing techniques to grow 2D semiconductors at wafer-scale and transfer them onto flexible substrates and has fabricated high-performance electronic device arrays.

At first, a 2D semiconductor is synthesized at 600 degrees on a silicon substrate and the synthesized film is transferred onto a plastic substrate using epoxy glue (Refer to figure 1). Through this process, the liquid-phase glue is poured onto the plastic substrate and the 2D semiconductor film is glued and cured. Then, the glued 2D material film is separated from the silicon substrate in water. The film is easily separated because of its hydrophobicity. Conventionally, when 2D materials are transferred, the substrate has to be etched or they have to be transferred twice to the final target substrate.

During the transfer, the film was damaged due to chemical corrosion or mechanical stress and the quality was degraded. However, the transferred film did not have any sign of damage, and the quality before and after the transfer was almost identical. This is because the atomic-level flatness was maintained and no residue remained even after the transfer.

This transfer technique can be applied to various 2D semiconductors at large size and used to fabricate flexible displays, sensors, and logic devices as well as adopted into commercial mass-production processes.

Photomechanical Detachment and Retrieval of a Single Cell from Microfluidics for Downstream Analyses

A new technology to detach a single cell selectively and safely from a cell culture substrate has been developed by Hyoung Won BAAC (Assistant professor of electronic and electrical engineering at SKKU, co-first author), Euisik YOON (Professor of electrical engineering and computer science at the University of Michigan-Ann Arbor, corresponding author), and a team of researchers at the Univ. of Michigan, whose work has been published in ACS Nano 11, 4660 (2017).

They have developed a very useful experimental method using a short pulse laser-based photomechanical effect in a carbon nanotube (CNT)-polymer composite film, and utilized it to study ultimate heterogeneity of cancer cells (i.e. a self-renewal process), which is a key characteristic to maintain unrestrained growth, metastatic capability, and drug resistance.

Cell detachment is being routinely performed every day in biology labs over the world, typically using a chemical treatment called trypsinization. However, this does not provide spatial selectivity when cells are chemically detached from a substrate. This also involves unwanted modification of cell membrane proteins and their properties, although it guarantees high cell viability. Other techniques using laser-induced ablation or tip-based physical removal are available with spatial selectivity and no chemical modification, but cell viability has been extremely low with these approaches so far.

The newly developed approach uses a photomechanical effect (laser-generated microbubbles and/or shear-forces) to detach cells placed on a laser focus which can be flushed out through a microfluidic channel for safe harvesting. It was confirmed that the retrieved cells exhibit not just high viability, but also intactness of cell membranes. Furthermore, the cells could be analyzed in secondary stages: for example, gene sequencing or continued culture for proliferation of specific cells with heterogeneity. For the first time in a single cell level, the new method allowed a comparison of two different sister cells from a single mother cell; some genes are activated or deactivated in the sister cells and some cancer cells from an identical origin can be resistant to drugs.

"The new technique enables laser-precision selectivity together with cell viability. It is very practical and fundamental, and can be widely utilized for biology labs performing cell culture and analysis research," said Prof. BAAC.

Find more information at:
http://pubs.acs.org/doi/abs/10.1021/acsnano.7b00413

Taller People Are Thinner, a Study by Prof. Beom Jun KIM

If the human body is stretched in the three directions of width, length, and height, the weight of a human body is proportional to the cube of its height. However, this is not valid in reality, and the body-mass index (BMI) is often calculated from the weight divided by the square of the height.

From this definition of the BMI, Prof. Beom Jun KIM has shown that the waist circumference of a human is not proportional to the height, but proportional to the square root of the height. In other words, if the body-mass index is the same, the taller person is the thinner they are. "This is the reason why many fashion models are tall," Prof. KIM says.

By analyzing the data of the length and weight of a variety of fish, whales, and quadrupedal land mammals, Prof. KIM has shown that weight is proportional to the square of the height only for humans. In the case of other animals, the weight is proportional to the cube of the height. He presumed the reason why the calculation of the body-mass index of a human differs from that of other animals is that humans are bipedal, standing and walking upright.

From this, he predicted that in the case of infants who cannot walk yet, their weight should be proportional to the cube of their height, but children older than about one year old should have a weight proportional to the square of their height. This prediction was tested with data from Sweden, Korea, and the World Health Organization, and was confirmed to be correct. If we consider the human body as the form of a simple cylinder and apply the condition that the torque by gravity and the torque by muscle must be in balance, we can show that the weight of a human should be proportional to the square of the height using Newtonian mechanics of physics. Prof. KIM also said that if we measure the size of the pelvis and the height from human fossil records, we will be able to deduce the time when mankind started to walk upright.

Find more information at:
https://www.nature.com/articles/s41598-017-03961-w

Prof. Jong San CHANG Develops Study on Selective Nitrogen Capture by Porous Hybrid Materials

Prof. Jong San CHANG (dual-appointed professor, Dept. of Chemistry, SKKU and KRICT) and his colleagues have recently published an important article entitled "Selective Nitrogen Capture by Porous Hybrid Materials Containing Accessible Transition Metal Ion Sites" in Nature Materials.

It is known that selective dinitrogen binding to transition metal ions mainly covers two strategic domains: the biological nitrogen fixation, catalyzed by metalloenzyme nitrogenases, and the adsorptive purification of natural gas and air. Many transition metal-dinitrogen complexes have been envisaged for biomimetic nitrogen fixation to produce ammonia. Inspired by this concept, Prof. Chang's group developed the first-ever adsorbent, a mesoporous Metal-Organic Framework (MOF) material containing accessible Cr(III) sites, able to thermodynamically capture N2 over CH4 and O2.

This study resulted from cooperative international research, mainly between the research group for nanocatalysts at KRICT and several groups at the National Center for Scientific Research (CNRS) in France. The study presents a major breakthrough in the domain of the selective capture of nitrogen (here N2 mixed with CH4 and O2) using a porous hybrid solid, called a metal-organic framework (MOF), which contains accessible chromium (III) ion sites. The selective adsorption of N2 is a strategic issue, with the related applications, such as the upgrading of natural gas (for the production of pipelined natural gas (PNG) and compressed natural gas (CNG) as alternative fuels) and the purification of air being amongst the most critical challenges facing the industry today. For the moment, the discovery of a porous adsorbent sufficient for such purposes had not yet been achieved because these solids typically exhibit a better affinity for gases such as CH4 or O2 than N2.

In this context, Prof. CHANG's group has first introduced the utilization of the concept of cationic unsaturated sites (CUS) for generating drastic changes in host-guest interactions (a general problem in materials science), which is useful to induce an unprecedented affinity for N2 with respect to other gases, far above the performances of materials currently used for the target application. The porous adsorbent material that combines a high selective adsorption, large uptake, easy regeneration, excellent recyclability, and good chemical/thermal stability offers a unique opportunity to achieve highly-efficient N2 capture that is difficult to attain using conventional approaches.

From the results, they could identify a clear and striking advance in the fundamental understanding or material design. They displayed the unique property of this solid through a multidisciplinary approach combining state-of-the-art experimental and computational methods. This included structural aspects, infrared spectroscopy, equilibrium and breakthrough adsorption experiments, and quantum/force field-based molecular simulations.

Inspired by biomimetic and metal dinitrogen chemistry concepts, this multidisciplinary fundamental study revealed that designing MOFs with unsaturated metal sites into their cages offers a unique opportunity to achieve unprecedented, highly efficient N2 capture.

It is believed that this publication will pave the way towards unprecedented adsorption-based technologies in the fields of energy, environmental studies, medicine, and catalysis by pushing the limits of our current knowledge on porous materials chemistry. In addition to this, the manipulation of multifunctional MOFs possessing both selective N2 binding and catalytic sites may propel forward progress in developing future enzymatic catalysts for N2 fixation, which is a dream of chemists, to produce nitrogen-containing chemicals.

Find more information at:
http://www.nature.com/nmat/journal/v16/n5/full/nmat4825.html

Prof. Young Han KIM Finds the Relationship between Media Appearances and Compensation

New research that examined 4,452 CEOs from 2,666 U.S. firms, as well as 104,129 news articles and 6,567 CNBC interviews, found that CEOs who appeared in CNBC interviews could expect their compensation to increase by $210,239 on average, notwithstanding firm performance and other mitigating factors. The research will be published in the upcoming volume of the INFORMS journal Organization Science.

The research authors, Jingoo KANG of Nanyang Business School and Andy Han KIM of SKKU Business School, found the relationship between media appearances and compensation between 1997 and 2009 was strongest when the CEO was from a smaller firm or one that demonstrated a strong stock market performance in the wake of increased media visibility. Improved stock performance serves as strong supporting evidence to the employer of the CEO's role in increasing the company's visibility and that of its stock. This in turn provided the CEO with increased bargaining power for greater compensation, up to $130,925 more than their counterparts in larger firms.

"For highly visible CEOs of larger firms, media appearances will only have a small visibility-enhancing effect," said KANG, "On the other hand, for CEOs of smaller companies who are less well known, media appearances will have a strong visibility-enhancing effect."

For CEOs in larger, well-known companies that already have a high degree of visibility, the additional visibility-enhancing effect of media appearances was weaker for those CEOs, as there was little additional growth that corresponded to the CEO's presence in the media. In addition, when the CEO had high equity ownership or were the founding CEO, that positive relationship disappeared.

The tone of media coverage also had an impact on the relationship between CEO media appearance and compensation, but primarily when the coverage was a CNBC interview. "When the tone of the media is more negative, the positive relationship between media appearance and compensation becomes weaker," said Kim, "In contrast, in the CEO news article models, we did not find a statistically significant interaction."

Find more information at:
http://pubsonline.informs.org/doi/full/10.1287/orsc.2017.1128

Prof. Do Hyun RYU Develops First Catalytic Asymmetric Synthesis of 2,5-Dihydrooxepine

A research team led by Prof. Do Hyun RYU (Dept. of Chemistry) has developed the first catalytic synthetic method of chiral 2,5-dihydrooxepine. 2,5-Dihydrooxepine, a seven-membered cyclic compound containing oxygen atom, is the structural core of many important natural products. Therefore, a variety of synthetic methods have been widely developed for several decades. However, there has been no example of catalytic asymmetric synthesis of 2,5-dihydrooxepines and multiple synthetic steps were required to prepare corresponding starting materials.

The research team developed an asymmetric synthetic method of highly functionalized 2,5-dihydrooxepine with chiral Lewis acid catalyst through a cyclopropanation/retro-Claisen rearrangement tandem reaction to give good yields and high enantioselectivity. The developed methodology exhibits excellent atom economy because it utilizes simple starting materials, and nitrogen gas (N2) is the only by-product. Since there are various bioactive natural products that possess dihydrooxepine as a key structure, chiral 2,5-dihydrooxepine derivatives synthesized with the developed method are expected to be used in biological or medical chemistry fields.

Prof. RYU said, "The value of this work is to synthesize enantioenriched 2,5-dihydrooxeines from simple starting materials using a catalyst. Furthermore, this work is highly valuable because this suggests experimental results to support computational calculation data about the reaction mechanism of retro-Claisen rearrangement of cyclopropane to 2,5-dihydrooxepine."

This research was published in the Angewandte Chemie International Edition April 18th, with the title "Catalytic Enantioselective Synthesis of 2,5-Dihydrooxepines". This work was selected as a Very Important Paper (VIP) and was put on the front cover July 17th.

Find more information at:
http://onlinelibrary.wiley.com/doi/10.1002/anie.201700890/full

Prof. Cham Na YOON Estimates Dynamic Games of Electoral Competition to Evaluate Term Limits

Elections serve an important function in modern democracies by allowing voters to express their support for politicians who share their ideological views and plan to pursue the policies they prefer. In addition, elections provide voters the opportunity to remove from office incumbents that are not adequately performing the duties of their office.

Over the last decade, much progress has been made in modeling electoral competition as a dynamic game with asymmetric information. One important qualitative finding of the theoretical literature is that the institutional design of election rules (e.g. term limits) can have a large impact on election outcomes and voters' welfare. However, few attempts have been made to quantify these welfare effects.

The paper shows how to identify and estimate, using standard semi-parametric techniques, a class of dynamic games with perfect monitoring that have been at the frontier of recent research in political economics. Using US gubernatorial election data, a model was estimated to study the consequences of term limits.

The team found that the benefits from holding office are significant and large in magnitude. As a consequence, the prospects of reelection provide strong incentives for moderate governors to move towards the center of the ideological spectrum during their first term in office. Voters are willing to accept significant trade-offs in ideology to obtain a more capable governor.

They find that there are significant differences in ideology across states and between parties within states. In contrast, there are only small differences in ability across states and no significant differences in the ability across parties. Term limits reduce welfare in the baseline model by six percent. They also find that tenure effects are negative for both parties. Consequently, term limits have the capacity to be constructive. The team showed that moderate levels of negative tenure effects term limits and can improve welfare.

Find more information at:
https://www.aeaweb.org/articles?id=10.1257/aer.201505666

A Multi-Mediation Model of Learning by Exporting: Analysis of Export-Induced Productivity Gains

Learning-by-exporting describes the phenomenon that firms can learn as a result of engaging in exporting to other countries, and this learning helps the exporting firms become more productive. The phenomenon has been studied in different contexts by international business, economics, and strategic management scholars. Some scholars have found empirical evidence in support of it, while others have not. As global markets continue to rise in competitiveness, a more complete understanding of learning-by-exporting will provide useful knowledge to researchers, firm managers, and policy makers.

In a recently published article, Professor Caleb H. TSE, along with his co-authors, argue that previous studies only sought to uncover whether the learning-by-exporting effect exists or not, and have overlooked the exact mechanisms that may cause the learning-by-exporting effect. The team created a theoretical model that examines the mediating mechanisms of the learning-by-exporting effect, and theorized that by exporting firms acquire knowledge and become more productive through the specific mechanisms of innovativeness and production capability improvements as well as improvements in human capital.

Using data from 250,000 Chinese firms over a 7-year period (2001-2007), the team found strong empirical evidence not only for the learning-by-exporting effect, but also for these mediating mechanisms. They also uncovered various boundary conditions to the learning-by-exporting effect. Non-state-owned enterprises and firms in industries with a moderate level of export intensity, as well as firms in industries with a medium to high level of new product development intensity, are able to effectuate more learning through these mechanisms than their counterparts.

The study sheds light on the specific knowledge benefits that firms can gain from exporting which lead to increases in productivity. It also points out how policy makers can promote environments that encourage firms and industries to capitalize on this learning-by-exporting effect.

Find more information at:
http://journals.sagepub.com/doi/10.1177/0149206315573998

Professors Gi-Ra YI & Jaeyun KIM's Study on Vanishing Colloidal Mesoporous Nanoparticles to Heal Wounds

A research team under Prof. Gi-Ra YI and Prof. Jaeyun KIM at Sungkyunkwan University's Department of Chemical Engineering have developed a colloidal mesporous nanoparticle solution that has the potential to rapidly and effectively close wounds in the skin when it spreads, then degrades away after the wound heals.

The fundamental research behind the rapid wound closure is the high surface area of the colloidal mesoporous silica nanoparticles in which extracellular matrixes within biological tissues are strongly absorbed on the surface of the nanoparticles; therefore, the wound is rapidly closed. By introducing the mesopores and controlling the average diameters on the surface, the research team has shown increases of up to 10 times more adhesion energy compared to nonporous silica nanoparticles, even at 10 times lower concentration.

The team has also compared the use of colloidal mesoporous silica nanoparticles with conventional suturing and chemically treating agents in wound closure. The result confirmed that the colloidal mesoporous silica nanoparticles are much more convenient to use, the adhesion was stronger, and most importantly, there were no signs of inflammation or scars.

Once the wound is closed and healed, the colloidal mesoporous silica nanoparticles degrade easily in biological media. The fact that colloidal silica nanoparticles degrade is advantageous, confirming the possibility of being used as biocompatible adhesive material.

The research was supported by the Engineering Research Center and the Bank of Porous Nanoparticles from the National Research Foundation (NRF) of Korea, and was published in the journal ACS Applied Materials and Interfaces (Impact Factor 7.504) on August 24th, 2017.

The research team is currently continuing this study to combine wound healing agents for colloidal mesoporous silica nanoparticles capable of dual rapid closure/healing treatments.

Find more information at:
http://pubs.acs.org/doi/abs/10.1021/acsami.7b09083

Prof. Gi Ra YI Develops New Method for Mass Production of Patchy Particles

Associate Professor Gi-Ra YI in School of Chemical Engineering, Sungkyunkwan University and Assistant Professor Stefano SACANNA at the New York University Chemistry Department developed together a new method for mass production of patchy particles that can be assembled as molecules.

Researchers began with a set of four large solid polystyrene spheres arranged in a tetrahedral manner around a smaller, softer silicone oil droplet. These two components are oppositely charged and thus spontaneously assemble into clusters. They then add a plasticizer (terahydrofuran), which allows the polystyrene spheres to flow and reconfigure into a single, bigger sphere thanks to surface tension. This process can be likened to the way balls of playdough can be squashed together. As the outer spheres fuse together to form a single sphere, the inner silicone oil droplet in fact deforms to fill the spaces inside the sphere. It is eventually pushed out to form a tetrahedral pattern of patches on the sphere's surface. These patchy spherical-shaped particles are produced in over 90% yield.

Adding patches to self-assembling systems in this way could allow us to produce colloidal nanostructures. Until now, however, it was not easy to yield enough particles to make a material big enough to hold in their hands.

On the other hand, at low pH, oil droplets surrounded with four spheres can be stayed in the center during deformation by adding plasicitizer, in which oil droplets are first faceted into tetrahedra and then become spheres. Researchers can polymerized in the middle of deformation which produced uniform tetraheron particles.

"Mass production of patchy particles has been one of most important problems in fabricating nanostructured materials by self-assembly," says Prof. Gi-Ra Yi. This will be used now for building up new colloidal structures which may even be used for 3D printers with complex internal nanostructures.

Find more information at:
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature23901.html?foxtrotcallback=true


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