Pohang University of Science and Technology

www.postech.ac.kr
Pohang, South Korea

Pohang University of Science and Technology or POSTECH is a private university located in Pohang, South Korea dedicated to research and education in science and technology. In 2012 and 2013, the Times Higher Education ranked POSTECH 1st in its "100 Under 50 Young Universities" rankings. Wikipedia.


Time filter

Source Type

Park Y.B.,Pohang University of Science and Technology
Nature Structural and Molecular Biology | Year: 2017

The Rad50 hook interface is crucial for assembly and various functions of the Mre11 complex. Previous analyses suggested that Rad50 molecules interact within (intracomplex) or between (intercomplex) dimeric complexes. In this study, we determined the structure of the human Rad50 hook and coiled-coil domains. The data suggest that the predominant structure is the intracomplex, in which the two parallel coiled coils proximal to the hook form a rod shape, and that a novel interface within the coiled-coil domains of Rad50 stabilizes the interaction of Rad50 protomers in the dimeric assembly. In yeast, removal of the coiled-coil interface compromised Tel1 activation without affecting DNA repair, while simultaneous disruption of that interface and the hook phenocopied a null mutation. The results demonstrate that the hook and coiled-coil interfaces coordinately promote intracomplex assembly and define the intracomplex as the functional form of the Mre11 complex. © 2017 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.


News Article | May 12, 2017
Site: www.newscientist.com

The humble mussel could soon help us prevent scarring. A sticky substance naturally secreted by the marine animal is one element of a glue that closes skin wounds seamlessly in rats. The glue could be used to prevent unsightly scars after accidental cuts or surgical operations. “If this can be replicated in humans, it might be the next big thing for scar therapy,” says Allison Cowin at the University of South Australia, who wasn’t involved in the study. Scars form when the collagen scaffolding in skin is broken apart. Instead of re-forming in their original and neat basket-weave arrangement, the collagen fibres grow back in parallel bundles that create the characteristic lumpy appearance of scars. One way to reduce scarring is to apply decorin, a skin protein involved in collagen organisation. But because decorin has a highly complex physical structure it is hard to synthesise and therefore not used in the clinic. To get round this problem, Hyung Joon Cha at Pohang University of Science and Technology in South Korea and his colleagues have created a simplified version of decorin. They combined a small section of the decorin protein with a collagen-binding molecule and a sticky substance secreted by mussels. The resulting glue was tested on rats with deep, 8-millimetre-wide wounds. The glue was spread over each wound and covered with clear plastic film. Rats in a control group had their wounds covered in plastic without any glue. By day 11, 99 per cent of the wound was closed in the treated rats compared with 78 per cent in the control group. By day 28, treated rats had fully recovered and had virtually no visible scarring. In comparison, control rats had thick, purple scars (see images below). Closer inspection under the microscope confirmed that collagen fibres in the treated wounds had returned to their original basket-weave arrangement. The new skin had also developed hair follicles, blood vessels, oil glands and other structures that aren’t regenerated in scars. The glue is able to promote normal collagen growth because negative charges on the decorin fragments hold the fibres apart, says Cha. In doing so, the fibres are more easily able to weave in and out between each other instead of sticking together randomly. Cowin says the results are impressive but there is still a way to go before the results can be translated to humans. “Rats have loose skin, whereas we have tight skin, and they tend to heal better and have less scarring than we do,” she says. As a result, the glue may not be as effective in people as in rats. Cha says that the glue will now be tested in pigs, whose skin better resembles our own. New scar treatments are greatly needed because the existing ones don’t work very well, says Cowin. Silicone gels, steroids, pressure bandages, cryotherapy and laser treatments are often used to reduce the appearance of scars, but they cannot erase them completely. Cowin is developing a scar treatment that uses monoclonal antibodies to block a type of protein that impairs wound healing. Other groups are applying embryonic stem cells to wounds, based on the observation that skin abrasions in embryos and early fetuses don’t scar. These approaches are still being tested in animals.


News Article | April 24, 2017
Site: www.cemag.us

The concept of a perfect lens that can produce immaculate and flawless images has been the Holy Grail of lens makers for centuries. In 1873, a German physicist and optical scientist by the name of Ernst Abbe discovered the diffraction limit of the microscope. In other words, he discovered that conventional lenses are fundamentally incapable of capturing all the details of any given image. Since then, there have been numerous advances in the field to produce images that appear to have higher resolution than allowed by diffraction-limited optics. In 2000, Professor Sir John B. Pendry of Imperial College London -- the John Pendry who enticed millions of Harry Potter fans around the world with the possibility of a real Invisibility Cloak -- suggested a method of creating a lens with a theoretically perfect focus. The resolution of any optical imaging system has a maximum limit due to diffraction but Pendry's theoretic perfect lens would be crafted from metamaterials (materials engineered to have properties not found in nature) to go beyond the diffraction limit of conventional lenses. Overcoming this resolution limit of conventional optics could propel optical imaging science and technology into realms once only dreamt by common Muggles. Scientists all over the world have since endeavored to achieve super-resolution imaging that capture the finest of details contained in evanescent waves that would otherwise be lost with conventional lenses. Hyperlenses are super-resolution devices that transform scattered evanescent waves into propagating waves to project the image into the far-field. Recent experiments that focus on a single hyperlens made from an anisotropic metamaterial with a hyperbolic dispersion have demonstrated far-field sub-diffraction imaging in real time. However, such devices are limited by an extremely small observation area which consequently require precise positioning of the subject. A hyperlens array has been considered to be a solution, but fabrication of such an array would be extremely difficult and prohibitively expensive with existing nanofabrication technologies. Research conducted by Professor Junsuk Rho's team from the Department of Mechanical Engineering and the Department of Chemical Engineering at Pohang University of Science and Technology in collaboration with research team from Korea University has made great contributions to overcoming this obstacle by demonstrating a scalable and reliable fabrication process of a large scale hyperlens device based on direct pattern transfer techniques. This achievement has been published in the world-renowned Scientific Reports. The team solved the main limitations of previous fabrication methods of hyperlens devices through nanoimprint lithography. Based on a simple pattern transfer process, the team was able to readily fabricate a perfect large-scale hyperlens device on a replicated hexagonal array of hemisphere substrate directly printed and pattern-transferred from the master mold, followed by metal-dielectric multilayer deposition by electron beam evaporation. This 5 cm x 5 cm hyperlens array has been demonstrated to resolve sub-diffraction features down to 160 nm under a 410 nm wavelength visible light. Professor Rho anticipates that the research team's new cost-effective fabrication method can be used to proliferate practical far-field and real-time super-resolution imaging devices that can be widely used in optics, biology, medical science, nanotechnology, and other related interdisciplinary fields.


a) This is a multilayered spherical hyperlens structure. Metal and dielectric thin films are deposited on a spherical shape of substrate. b) This is a transmission electron microscopy (TEM) image of the cross-section of a replicated hyperlens c & d) Tilted view for the quartz master mold and the replicated substrate e) Scanning electron microscopy (SEM) image of the sub-diffraction scale objects. f) Far-field optical image after hyperlens. The small object below diffraction limit is clearly resolved by the hyperlens. Credit: POSTECH The concept of a perfect lens that can produce immaculate and flawless images has been the Holy Grail of lens makers for centuries. In 1873, a German physicist and optical scientist by the name of Ernst Abbe discovered the diffraction limit of the microscope. In other words, he discovered that conventional lenses are fundamentally incapable of capturing all the details of any given image. Since then, there have been numerous advances in the field to produce images that appear to have higher resolution than allowed by diffraction-limited optics. In 2000, Professor Sir John B. Pendry of Imperial College London—the John Pendry who enticed millions of Harry Potter fans around the world with the possibility of a real Invisibility Cloak—suggested a method of creating a lens with a theoretically perfect focus. The resolution of any optical imaging system has a maximum limit due to diffraction but Pendry's theoretic perfect lens would be crafted from metamaterials (materials engineered to have properties not found in nature) to go beyond the diffraction limit of conventional lenses. Overcoming this resolution limit of conventional optics could propel optical imaging science and technology into realms once only dreamt by common Muggles. Scientists all over the world have since endeavored to achieve super-resolution imaging that capture the finest of details contained in evanescent waves that would otherwise be lost with conventional lenses. Hyperlenses are super-resolution devices that transform scattered evanescent waves into propagating waves to project the image into the far-field. Recent experiments that focus on a single hyperlens made from an anisotropic metamaterial with a hyperbolic dispersion have demonstrated far-field sub-diffraction imaging in real time. However, such devices are limited by an extremely small observation area which consequently require precise positioning of the subject. A hyperlens array has been considered to be a solution, but fabrication of such an array would be extremely difficult and prohibitively expensive with existing nanofabrication technologies. Research conducted by Professor Junsuk Rho's team from the Department of Mechanical Engineering and the Department of Chemical Engineering at Pohang University of Science and Technology in collaboration with research team from Korea University has made great contributions to overcoming this obstacle by demonstrating a scalable and reliable fabrication process of a large scale hyperlens device based on direct pattern transfer techniques. This achievement has been published in the world-renowned Scientific Reports. The team solved the main limitations of previous fabrication methods of hyperlens devices through nanoimprint lithography. Based on a simple pattern transfer process, the team was able to readily fabricate a perfect large-scale hyperlens device on a replicated hexagonal array of hemisphere substrate directly printed and pattern-transferred from the master mold, followed by metal-dielectric multilayer deposition by electron beam evaporation. This 5 cm x 5 cm hyperlens array has been demonstrated to resolve sub-diffraction features down to 160 nm under a 410 nm wavelength visible light. Professor Rho anticipates that the research team's new cost-effective fabrication method can be used to proliferate practical far-field and real-time super-resolution imaging devices that can be widely used in optics, biology, medical science, nanotechnology, and other related interdisciplinary fields.


News Article | May 8, 2017
Site: www.cemag.us

The concept of a perfect lens that can produce immaculate and flawless images has been the Holy Grail of lens makers for centuries. In 1873, a German physicist and optical scientist by the name of Ernst Abbe discovered the diffraction limit of the microscope. In other words, he discovered that conventional lenses are fundamentally incapable of capturing all the details of any given image. Since then, there have been numerous advances in the field to produce images that appear to have higher resolution than allowed by diffraction-limited optics. In 2000, Professor Sir John B. Pendry of Imperial College London — the John Pendry who enticed millions of Harry Potter fans around the world with the possibility of a real Invisibility Cloak — suggested a method of creating a lens with a theoretically perfect focus. The resolution of any optical imaging system has a maximum limit due to diffraction but Pendry’s theoretic perfect lens would be crafted from metamaterials (materials engineered to have properties not found in nature) to go beyond the diffraction limit of conventional lenses. Overcoming this resolution limit of conventional optics could propel optical imaging science and technology into realms once only dreamt by common Muggles. Scientists all over the world have since endeavored to achieve super-resolution imaging that capture the finest of details contained in evanescent waves that would otherwise be lost with conventional lenses. Hyperlenses are super-resolution devices that transform scattered evanescent waves into propagating waves to project the image into the far-field. Recent experiments that focus on a single hyperlens made from an anisotropic metamaterial with a hyperbolic dispersion have demonstrated far-field sub-diffraction imaging in real time. However, such devices are limited by an extremely small observation area which consequently require precise positioning of the subject. A hyperlens array has been considered to be a solution, but fabrication of such an array would be extremely difficult and prohibitively expensive with existing nanofabrication technologies. Research conducted by Professor Junsuk Rho’s team from the Department of Mechanical Engineering and the Department of Chemical Engineering at Pohang University of Science and Technology in collaboration with research team from Korea University has made great contributions to overcoming this obstacle by demonstrating a scalable and reliable fabrication process of a large scale hyperlens device based on direct pattern transfer techniques. This achievement has been published in the world-renowned Scientific Reports. The team solved the main limitations of previous fabrication methods of hyperlens devices through nanoimprint lithography. Based on a simple pattern transfer process, the team was able to readily fabricate a perfect large-scale hyperlens device on a replicated hexagonal array of hemisphere substrate directly printed and pattern-transferred from the master mold, followed by metal-dielectric multilayer deposition by electron beam evaporation. This 5 cm x 5 cm hyperlens array has been demonstrated to resolve sub-diffraction features down to 160 nm under a 410 nm wavelength visible light. Rho anticipates that the research team’s new cost-effective fabrication method can be used to proliferate practical far-field and real-time super-resolution imaging devices that can be widely used in optics, biology, medical science, nanotechnology, and other related interdisciplinary fields. This research was supported by the National Research Foundation of Korea (NRF) grants of Young Investigator program, Engineering Research Center program, Global Frontier program, Pioneer Research program, and the Commercialization Promotion Agency for R&D Outcomes (COMPA) grant, all funded by the Ministry of Science, ICT and Future Planning (MSIP) of the Korean government.


News Article | April 21, 2017
Site: www.eurekalert.org

The concept of a perfect lens that can produce immaculate and flawless images has been the Holy Grail of lens makers for centuries. In 1873, a German physicist and optical scientist by the name of Ernst Abbe discovered the diffraction limit of the microscope. In other words, he discovered that conventional lenses are fundamentally incapable of capturing all the details of any given image. Since then, there have been numerous advances in the field to produce images that appear to have higher resolution than allowed by diffraction-limited optics. In 2000, Professor Sir John B. Pendry of Imperial College London -- the John Pendry who enticed millions of Harry Potter fans around the world with the possibility of a real Invisibility Cloak -- suggested a method of creating a lens with a theoretically perfect focus. The resolution of any optical imaging system has a maximum limit due to diffraction but Pendry's theoretic perfect lens would be crafted from metamaterials (materials engineered to have properties not found in nature) to go beyond the diffraction limit of conventional lenses. Overcoming this resolution limit of conventional optics could propel optical imaging science and technology into realms once only dreamt by common Muggles. Scientists all over the world have since endeavored to achieve super-resolution imaging that capture the finest of details contained in evanescent waves that would otherwise be lost with conventional lenses. Hyperlenses are super-resolution devices that transform scattered evanescent waves into propagating waves to project the image into the far-field. Recent experiments that focus on a single hyperlens made from an anisotropic metamaterial with a hyperbolic dispersion have demonstrated far-field sub-diffraction imaging in real time. However, such devices are limited by an extremely small observation area which consequently require precise positioning of the subject. A hyperlens array has been considered to be a solution, but fabrication of such an array would be extremely difficult and prohibitively expensive with existing nanofabrication technologies. Research conducted by Professor Junsuk Rho's team from the Department of Mechanical Engineering and the Department of Chemical Engineering at Pohang University of Science and Technology in collaboration with research team from Korea University has made great contributions to overcoming this obstacle by demonstrating a scalable and reliable fabrication process of a large scale hyperlens device based on direct pattern transfer techniques. This achievement has been published in the world-renowned Scientific Reports. The team solved the main limitations of previous fabrication methods of hyperlens devices through nanoimprint lithography. Based on a simple pattern transfer process, the team was able to readily fabricate a perfect large-scale hyperlens device on a replicated hexagonal array of hemisphere substrate directly printed and pattern-transferred from the master mold, followed by metal-dielectric multilayer deposition by electron beam evaporation. This 5 cm x 5 cm hyperlens array has been demonstrated to resolve sub-diffraction features down to 160 nm under a 410 nm wavelength visible light. Professor Rho anticipates that the research team's new cost-effective fabrication method can be used to proliferate practical far-field and real-time super-resolution imaging devices that can be widely used in optics, biology, medical science, nanotechnology, and other related interdisciplinary fields. This research was supported by the National Research Foundation of Korea (NRF) grants of Young Investigator program, Engineering Research Center program, Global Frontier program, Pioneer Research program, and the Commercialization Promotion Agency for R&D Outcomes (COMPA) grant, all funded by the Ministry of Science, ICT and Future Planning (MSIP) of the Korean government.


Yoon M.,Pohang University of Science and Technology | Srirambalaji R.,Pohang University of Science and Technology | Kim K.,Pohang University of Science and Technology
Chemical Reviews | Year: 2012

An overview of on metal-organic frameworks (MOF)-based asymmetric heterogeneous catalysis is discussed by presenting the state of the art in this field and discussing its potential and limitations. Tanaka et al. reported the synthesis of a copper-BINOL-based chiral framework and its catalytic activity in the asymmetric ring-opening reaction of epoxides with amines. Lin group successfully synthesized chiral porous coordination polymers for asymmetric catalysis using both MPD and MPP strategies, they were amorphous, which made the detailed structural characterization of the active sites impossible. Later the group succeeded in synthesizing a crystalline homochiral MOF using a pyridyl functionalized BINOL linker. Jeong and co-workers also utilized a similar dual functional enantiopure linker in which the two phenyl rings are orthogonal to each other to avoid the steric repulsion between the hydroxy and methyl groups, to synthesize a homochiral MOF containing chiral dihydroxy groups on the linkers of the framework.


Bhadeshia H.K.D.H.,University of Cambridge | Bhadeshia H.K.D.H.,Pohang University of Science and Technology
Progress in Materials Science | Year: 2012

A casual metallurgist might be forgiven in believing that there are but a few basic types of steels used in the manufacture of some of the most technologically important engineering components, the rolling bearings. First the famous 1C-1.5Cr steel from which the majority of bearings are made. Its structure is apparently well-understood and the focus is on purity in order to avoid inclusions which initiate fatigue during rolling contact. Then there is the M50 steel and its variants, from which bearings which serve at slightly higher temperatures in aeroengines are manufactured, based on secondary-hardened martensite. The casual metallurgist would be wrong; there is a richness in the subject which inspires deep study. There are phenomena which are little understood, apparently incommensurate observations, some significant developments and other areas where convincing conclusions are difficult to reach. The subject seemed ready for a critical assessment; hence, this review. The structure and properties of bearing steels prior to the point of service are first assessed and described in the context of steelmaking, manufacturing and engineering requirements. This is followed by a thorough critique of the damage mechanisms that operate during service and in accelerated tests. © 2011 Elsevier Ltd. All rights reserved.


Marti-Rujas J.,Italian Institute of Technology | Kawano M.,Pohang University of Science and Technology
Accounts of Chemical Research | Year: 2013

Porous coordination networks are materials that maintain their crystal structure as molecular "guests" enter and exit their pores. They are of great research interest with applications in areas such as catalysis, gas adsorption, proton conductivity, and drug release. As with zeolite preparation, the kinetic states in coordination network preparation play a crucial role in determining the final products. Controlling the kinetic state during self-assembly of coordination networks is a fundamental aspect of developing further functionalization of this class of materials. However, unlike for zeolites, there are few structural studies reporting the kinetic products made during self-assembly of coordination networks. Synthetic routes that produce the necessary selectivity are complex.The structural knowledge obtained from X-ray crystallography has been crucial for developing rational strategies for design of organic-inorganic hybrid networks. However, despite the explosive progress in the solid-state study of coordination networks during the last 15 years, researchers still do not understand many chemical reaction processes because of the difficulties in growing single crystals suitable for X-ray diffraction: Fast precipitation can lead to kinetic (metastable) products, but in microcrystalline form, unsuitable for single crystal X-ray analysis. X-ray powder diffraction (XRPD) routinely is used to check phase purity, crystallinity, and to monitor the stability of frameworks upon guest removal/inclusion under various conditions, but rarely is used for structure elucidation. Recent advances in structure determination of microcrystalline solids from ab initio XRPD have allowed three-dimensional structure determination when single crystals are not available. Thus, ab initio XRPD structure determination is becoming a powerful method for structure determination of microcrystalline solids, including porous coordination networks. Because of the great interest across scientific disciplines in coordination networks, especially porous coordination networks, the ability to determine crystal structures when the crystals are not suitable for single crystal X-ray analysis is of paramount importance.In this Account, we report the potential of kinetic control to synthesize new coordination networks and we describe ab initio XRPD structure determination to characterize these networks' crystal structures. We describe our recent work on selective instant synthesis to yield kinetically controlled porous coordination networks. We demonstrate that instant synthesis can selectively produce metastable networks that are not possible to synthesize by conventional solution chemistry. Using kinetic products, we provide mechanistic insights into thermally induced (573-723 K) (i.e., annealing method) structural transformations in porous coordination networks as well as examples of guest exchange/inclusion reactions. Finally, we describe a memory effect that allows the transfer of structural information from kinetic precursor structures to thermally stable structures through amorphous intermediate phases.We believe that ab initio XRPD structure determination will soon be used to investigate chemical processes that lead intrinsically to microcrystalline solids, which up to now have not been fully understood due to the unavailability of single crystals. For example, only recently have researchers used single-crystal X-ray diffraction to elucidate crystal-to-crystal chemical reactions taking place in the crystalline scaffold of coordination networks. The potential of ab initio X-ray powder diffraction analysis goes beyond single-crystal-to-single-crystal processes, potentially allowing members of this field to study intriguing in situ reactions, such as reactions within pores. © 2012 American Chemical Society.


Kim S.Y.,Pohang University of Science and Technology
Nature communications | Year: 2010

Proton exchange fuel cells (PEFCs) have the potential to provide power for a variety of applications ranging from electronic devices to transportation vehicles. A major challenge towards economically viable PEFCs is finding an electrolyte that is both durable and easily passes protons. In this article, we study novel anhydrous proton-conducting membranes, formed by incorporating ionic liquids into synthetic block co-polymer electrolytes, poly(styrenesulphonate-b-methylbutylene) (S(n)MB(m)), as high-temperature PEFCs. The resulting membranes are transparent, flexible and thermally stable up to 180 °C. The increases in the sulphonation level of S(n)MB(m) co-polymers (proton supplier) and the concentration of the ionic liquid (proton mediator) produce an overall increase in conductivity. Morphology effects were studied by X-ray scattering and electron microscopy. Compared with membranes having discrete ionic domains (including Nafion 117), the nanostructured membranes revealed over an order of magnitude increase in conductivity with the highest conductivity of 0.045 S cm(-1) obtained at 165 °C.

Loading Pohang University of Science and Technology collaborators
Loading Pohang University of Science and Technology collaborators