Chung-Ang University

About: Chung-Ang University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Population & Thin film. The organization has 13381 authors who have published 26978 publications receiving 416735 citations. The organization is also known as: CAU & Chung.

Recent Advances in Memristive Materials for Artificial Synapses

Abstract: DOI: 10.1002/admt.201800457 required. Several types of emerging mem­ ories have been researched in the past few decades such as magnetic memory, phase change memory, ferroelectric tunnel junc­ tions, and resistive switching memory. Among these emerging devices, resistive switching memory called memristors, introduced by Chua in 1971,[1] have strong points of small cell size, nonvolatile and random data access possibility, easy fabri­ cation process, and simple structure.[2,3] Because of these advantages, various mate­ rials are examined for achieving memris­ tive properties. In addition, different from the past sev­ eral decades, information is being made depending on experiences or repeated stimuli similar to that in the human brain. The human brain contains ≈1011 neurons and 1015 synapses, occupies a small space, and consumes less than 20 W, which is lower than the power required to run a household light bulb.[4–6] Moreover, the human brain is currently considered as the most intelligent and fastest operation system. Therefore, neuromorphic computing, which emu­ lates the human brain, has been regarded as a promising next­generation computing system. Studies on neuromorphic computing have been rapidly growing and highlighted for various applications such as artificial intelligence, sensors, robotic devices, and memory devices. Existing neural networks are implemented by the combination of machine learning as software and the von Neumann archi­ tecture as hardware based on the complementary metal­oxide semiconductor (CMOS) technology. However, CMOS­based cir­ cuits require 6–12 transistors and the design is not flexible.[7] The present computing system with the von Neumann architecture is implemented by a serial operation through a central processing unit (CPU). Because of the von Neumann bottleneck, memory devices have limitations in data processing speed between memory and CPU and require high power and large space.[8–10] Therefore, a new neuromorphic computing system that is exe­ cuted by parallel operation with a high operation speed, low energy consumption, and small volume is critically required. To achieve such requirement, memristive materials have been actively examined as emulating several functions of human brain. A memristor could act as a single unit of synapse without software programming supports. Memristor­based neu­ romorphic architecture is implemented by parallel operation with efficient power, small volume, and high data processing Neuromorphic architectures are in the spotlight as promising candidates for substituting current computing systems owing to their high operation speed, scale-down ability, and, especially, low energy consumption. Among candidate materials, memristors have shown excellent synaptic behaviors such as spike time-dependent plasticity and spike rate-dependent plasticity by gradually changing their resistance state according to electrical input stimuli. Memristor can work as a single synapse without programming support, which remarkably satisfies the requirements of neuromorphic computing. Here, the most recent developments in memristor-based artificial synapses are introduced with their excellent synaptic behaviors accompanied with detailed explanation of their working mechanisms. As conventional memristive materials, metal oxides are reviewed with recent advancements in heterojunction technologies. An overview of organic materials is presented with their remarkable synaptic behaviors including their advantages of biocompatibility, low cost, complementary metal-oxide semiconductor compatibility, and ductility. 2D materials are also introduced as promising candidates for artificial synapses owing to their flexibility and scalability. As emerging materials, halide perovskites and low-dimensional materials are presented with their synaptic behaviors. In the last section, future challenges and research directions are discussed. This review article is hoped to be a guide to rational materials design for the artificial synapses of neuromorphic computing. Neuromorphic Architectures

Cyclams bearing diametrically disubstituted pyrenes as Cu2+- and Hg2+-selective fluoroionophores.

Abstract: New cyclam derivatives having diametrically disubstituted pyrene fluorophores were prepared and their fluoroionophoric properties toward transition metal ions were investigated. The compounds exhibited significant selectivity toward Hg2+ and Cu2+ ions in switching-off type responses in aqueous methanol or acetonitrile solution. Dipyrene-diamide derivative 3, having extra binding sites of the amide function, exhibited more pronounced chemosensing behavior toward Hg2+ and Cu2+ ions than its parent, dipyrene derivative 2. Detection limits for the analysis of Hg2+ and Cu2+ ions of dipyrene-diamide derivative 3 were 1.45 × 10-6 and 1.30 × 10-6 M, respectively. The diametrically disubstituted dipyrene-cyclam 2 may be utilized as a new starting platform for the design of other supramolecular fluorescent signaling systems having switching or chemosensing behaviors toward transition metal ions.

Controlled Deposition of a High‐Performance Small‐Molecule Organic Single‐Crystal Transistor Array by Direct Ink‐Jet Printing

Abstract: Ink-jet printed small-molecule organic single-crystal transistors are realized by using selective surface energy modification, precise control of volume density of ink droplets on spatially patterned areas, and a co-solvent system to control solvent evaporation properties. The single-crystal formation in bottom-contact-structured transistors via direct printing is expected to permit high-density array fabrication in large-area electronics.

Alterations of Fas (Apo-1/CD95) gene in cutaneous malignant melanoma.

Abstract: Fas (Apo-1/CD95) is a cell-surface receptor involved in cell death signaling The key role of the Fas system in negative growth regulation has been studied mostly within the immune system, and somatic mutations of Fas gene in cancer patients have been described solely in lymphoid-lineage malignancies However, many nonlymphoid tumor cells have been found to be resistant to Fas-mediated apoptosis, which suggests that Fas mutations, one of the possible mechanisms for Fas resistance, may be involved in the pathogenesis of nonlymphoid malignancies as well In this study, we have analyzed the entire coding region and all splice sites of the Fas gene for the detection of the gene mutations in 44 human malignant melanomas in skin by polymerase chain reaction, single-strand conformation polymorphism, and DNA sequencing Overall, 3 tumors (68%) were found to have the Fas mutations, which were all missense variants and identified in the cytoplasmic region (death domain) known to be involved in the transduction of an apoptotic signal The data presented here suggest that somatic alterations of the Fas gene might lead to the loss of its apoptotic function and contribute to the pathogenesis of some human malignant melanomas

Incidence and Mortality Following Hip Fracture in Korea

Abstract: The authors evaluated the incidence of hip fracture and subsequent mortality in Korea using nationwide data obtained from the Health Insurance Review and Assessment Service. This study was performed on patient population, aged 50-yr or older who underwent surgical procedures because of hip fracture (ICD10; S720, S721). All patients were followed using patient identification code to identify deaths. Crude hip fracture rates increased from 191.9/100,000 in 2005 to 207.0/100,000 in 2008 in women and from 94.8/100,000 in 2005 to 97.8/100,000 in 2008, in men respectively. Crude mortality within 12 months after hip fracture showed a similar trend (18.8% in 2005 and 17.8% in 2007). The mean of standardized mortality ratio of hip fracture was 6.1 at 3 months, 3.5 at 1 yr, and 2.3 at 2 yr post-fracture. The increasing incidence and the high mortality after hip fracture are likely to become serious public health problems and a public health program should begin to prevent hip fractures in Korea.