Polypyrrole-incorporated conductive hyaluronic acid hydrogels

Jongcheol Yang,최고은,Sumi Yang,Hyerim Jo,이재영 한국생체재료학회 2016 생체재료학회지 Vol.20 No.4

Background: Hydrogels that possess hydrophilic and soft characteristics have been widely used in various biomedical applications, such as tissue engineering scaffolds and drug delivery. Conventional hydrogels are not electrically conductive and thus their electrical communication with biological systems is limited. Method: To create electrically conductive hydrogels, we fabricated composite hydrogels of hyaluronic acid and polypyrrole. In particular, we synthesized and used pyrrole-hyaluronic acid-conjugates and further chemically polymerized polypyrrole with the conjugates for the production of conductive hydrogels that can display suitable mechanical and structural properties. Results: Various characterization methods, using a rheometer, a scanning electron microscope, and an electrochemical analyzer, revealed that the PPy/HA hydrogels were soft and conductive with ~ 3 kPa Young’s modulus and ~ 7.3 mS/cm conductivity. Our preliminary in vitro culture studies showed that fibroblasts were well attached and grew on the conductive hydrogels. Conclusion: These new conductive hydrogels will be greatly beneficial in fields of biomaterials in which electrical properties are important such as tissue engineering scaffolds and prosthetic devices.

MOC : 다중 오브젝트 클러스터링을 통한 BSD VM의 페이지-아웃 성능 향상

양종철(Jongcheol Yang),안우현(Woo Hyun Ahn),오재원(Jaewon Oh) 한국정보과학회 2009 정보과학회논문지 : 시스템 및 이론 Vol.36 No.6

BSD 가상 메모리 시스템(BSD VM)은 페이지-아웃 시 디스크 I/O 횟수를 줄이기 위해 클러스터링 기법을 사용한다. 이 기법은 페이지-아웃 대상 페이지와 가상 메모리 공간에서 인접한 변경 페이지들을 그 대상 페이지와 함께 클러스터(그룹)를 만들어 한 번의 디스크 I/O로 디스크에 저장한다. 하지만 응용 프로그램이 가상 메모리 공간에서 서로 인접하지 않은 다수의 페이지들을 변경하면 클러스터들의 크기가 작아져 클러스터링의 효과가 감소된다. 이 문제점을 해결하기 위해 본 논문에서는 Multiple-Object Clustering(MOC) 기법을 제안한다. MOC는 클러스터별로 디스크 I/O를 하는 대신 여러 클러스터들을 모아 단일 디스크 쓰기로 페이지-아웃시킨다. 따라서 이 페이지-아웃 방식은 디스크 I/O 횟수를 감소시켜 시스템 성능을 크게 향상시킨다. MOC는 성능 검증을 위해 FreeBSD 6.2 운영체제 커널에서 구현되었다. NS2, Scimark2 SOR, nbench LU 벤치마크를 통한 MOC 성능 측정 결과 기존 BSD VM보다 MOC의 실행 시간이 9∼45% 단축되었다. The virtual memory system in 4.4 BSD operating systems exploits a clustering scheme to reduce disk I/Os in paging out (or flushing) modified pages that are intended to be replaced in order to make free rooms in memory. Upon the page out of a victim page, the scheme stores a cluster (or group) of modified pages contiguous with the victim in the virtual address space to swap disk at a single disk write. However, it fails to find large clusters of contiguous pages if applications change pages not adjacent with each other in the virtual address space. To address the problem, we propose a new clustering scheme called Multiple-Object Clustering (MOC), which together stores multiple clusters in the virtual address space at a single disk write instead of paging out the clusters to swap space at separate disk I/Os. This multiple-cluster transfer allows the virtual memory system to significantly decrease disk writes, thus improving the page-out performance. Our experiments in the FreeBSD 6.2 show that MOC improves the execution times of realistic benchmarks such as NS2, Scimark2 SOR, and nbench LU over the traditional clustering scheme ranging from 9 to 45%.

전기전도성 고분자를 이용한 생체 전극과 센서의 응용

양종철 ( Jongcheol Yang ),김세민 ( Semin Kim ),장예슬 ( Yesul Jang ),조혜림 ( Hyerim Jo ),이재영 ( Jae Young Lee ) 한국공업화학회 2015 공업화학전망 Vol.18 No.6

전도성 고분자는 우수한 전기전도성, 가공성, 유연성 및 용이한 합성 등의 장점으로, 여러 가지 산업적 응용 분야에 활발히 적용되고 있는 물질이다. 최근, 전도성 고분자를 이용하여 생체 재료로의 응용이 활발히 연구되고 있으며, 특히, 전기 신호 전달 특성과 생체 적합성이 요구되는 생체 센서 및 생체 전극으로의 적용에 많은 관심이 모아지고 있다. 본 논문에서는 전도성 고분자를 이용하여 인체 내의 특정 분자나 물질을 정밀하게 감지하여 질병 예방 및 치료에 이용될 수 있는 생체 센서에 관한 연구와 인체 기관 혹은 조직에 전기적 신호를 전달하거나 전달받아 기록하여, 질병 예방 및 치료에 큰 역할을 하는 생체전극에 관하여 다루었다. 이에, 생체 센서 및 생체 전극의 원리와 최근 진행되고 있는 연구, 앞으로의 전도성 고분자를 이용한 연구 개발 방향에 대해 기술하고자 한다.

전기전도성 고분자 기반 생체재료의 의공학적 응용과 개발 방향

장예슬(Yesul Jang),양수미(JanSumi Yang),이황재(Hwangjae Lee),양종철(Jongcheol Yang),김세민(Semin Kim),정솔찬(Solchan Chung),이재영(Jae Young Lee) 한국고분자학회 2015 고분자 과학과 기술 Vol.26 No.4

APC: 가상 메모리 시스템에서 적응적 페이지 선반입 제어 기법

안우현(Woo Hyun Ahn),양종철(Jongcheol Yang),오재원(Jaewon Oh) 한국정보과학회 2010 정보과학회논문지 : 시스템 및 이론 Vol.37 No.3

가상 메모리 시스템(VM)에서 페이지 부재로 발생하는 디스크 I/O를 감소시키기 위해 페이지 선반입 기법을 사용한다. 이 기법은 부재 페이지와 함께 추가적인 페이지들을 한 번의 디스크 I/O로 미리 읽는다. 그런데, 4.4BSD와 같은 운영체제의 VM은 응용 프로그램의 페이지 참조 패턴을 고려하지 않고 항상 가능한 많은 페이지들을 선반입하고자 한다. 이 방법은 선반입된 페이지들 중 일부만 사용하는 참조패턴에서 디스크 참조 시간을 증가시키며, 유용한 페이지들을 메모리에서 내보내는 메모리 오염을 야기한다. 이런 문제를 해결하기 위해 본 논문은 적응적 페이지 선반입 제어 기법(APC)을 제안한다. APC는 선반입 페이지들 중에서 메모리에 존재하는 동안 참조된 페이지들의 비율을 프로세스 단위로 주기적으로 측정하고, 이 비율을 사용하여 4.4BSD VM이 선반입하고자 하는 페이지의 개수를 조절한다. 그래서 실행도중 페이지 참조 패턴이 바뀌더라도 적절한 수의 페이지를 선반입할 수 있다. 성능 검증을 위해 APC를 4.4BSD 기반의 FreeBSD 6.2에 구현하였으며, SOR, SMM, FFT 벤치마크를 통해 성능을 측정하였다. 성능 측정 결과 APC는 기존 BSD VM보다 벤치마크의 실행 시간을 최대 57% 단축하였다. Virtual memory systems (VM) reduce disk I/Os caused by page faults using page prefetching, which reads pages together with a desired page at a page fault in a single disk I/O. Operating systems including 4.4BSD attempt to prefetch as many pages as possible at a page fault regardless of page access patterns of applications. However, such an approach increases a disk access time taken to service a page fault when a high portion of the prefetched pages is not referenced. More seriously, the approach can cause the memory pollution, a problem that prefetched pages not to be accessed evict another pages that will be referenced soon. To solve these problems, we propose an adaptive page prefetching control scheme (APC), which periodically monitors access patterns of prefetched pages in a process unit. Such a pattern is represented as the ratio of referenced pages among prefetched ones before they are evicted from memory. Then APC uses the ratio to adjust the number of pages that 4.4BSD VM intends to prefetch at a page fault. Thus APC allows 4.4BSD VM to prefetch a proper number of pages to have a better effect on reducing disk I/Os, though page access patterns of an application vary in runtime. The experiment of our technique implemented in FreeBSD 6.2 shows that APC improves the execution times of SOR, SMM, and FFT benchmarks over 4.4BSD VM by up to 57%.

Colonic Chicken Skin Mucosa is an Independent Endoscopic Predictor of Advanced Colorectal Adenoma

( Eun Ju Chung ),( Ji Young Lee ),( Jaewon Choe ),( Hye Sook Chang ),( Jongcheol Kim ),( Dong Hoon Yang ),( Byong Duk Ye ),( Jeong Sik Byeon ),( Kyung Jo Kim ),( Suk Kyun Yang ),( Jin Ho Kim ),( Seung 대한장연구학회 2015 Intestinal Research Vol.13 No.4

Background/Aims: Chicken skin mucosa (CSM), surrounding colorectal adenoma, is an endoscopic finding with pale yellowspeckled mucosa; however, its clinical significance is unknown. This study aimed to evaluate the prevalence and clinical characteristics of CSM, and the association between colorectal carcinogenesis and CSM. Methods: This cross-sectional study was performed in 733 consecutive patients who underwent endoscopic polypectomy for colorectal adenoma after the screening of colonoscopy at the Asan Health Promotion Center between June 2009 and December 2011. The colonoscopic and pathological findings of colorectal adenoma including number, size, location, dysplasia, morphology, and clinical parameters were reviewed. Results: The prevalence of CSM was 30.7% (225 of 733 patients), and most CSM-related adenomas were located in the distal colon (93.3%). Histological analysis revealed lipid-laden macrophages in the lamina propria of the mucosa. Multivariate analyses showed that CSM was significantly associated with advanced pathology, including villous adenoma and high-grade dysplasia (odds ratio [OR], 2.078; 95% confidence interval [CI], 1.191-3.627; P=0.010), multiple adenomas (i.e., ≥2 adenomas; OR, 1.692; 95% CI, 1.143-2.507; P=0.009), and a protruding morphology (OR, 1.493; 95% CI, 1.027-2.170; P=0.036). There were no significant differences in polyp size or clinical parameters between patients with and without CSM. Conclusions: CSMrelated adenoma was mainly found in the distal colon, and was associated with advanced pathology and multiple adenomas. CSM could be a potential predictive marker of the carcinogenetic progression of distally located colorectal adenomas. (Intest Res 2015;13:318-325)

A Compact Tunable VCSEL and a Built-in Wavelength Meter for a Portable Optical Resonant Reflection Biosensor Reader

Hyunsung Ko,김봉규,Kyung Hyun Kim,허철,Wan-Joong Kim,Jongcheol Hong,Seon Hee Park,Seong-Seok Yang,Ho-Jin Jang,성건용 한국광학회 2010 Current Optics and Photonics Vol.14 No.4

This study reports a portable and precision photonic biosensor reader that can measure the concentration of a particular antigen using an optical resonant reflection biosensor (ORRB). To create a compact biosensor reader, a compact tunable vertical-cavity surface-emitting laser (VCSEL) and a compact built-in wavelength meter were manufactured. The wavelength stability and accuracy of the compact built-in wavelength meter were measured to be less than 0.02 nm and 0.06 nm, respectively. The tunable VCSEL emission wavelength was measured with the compact built-in wavelength meter, it has a fast sweep time (~ 10 seconds) and a wide tuning range (> 4 nm) that are sufficient for biosensor applications based on ORRB. The reflection spectrum of a plastic based ORRB chip was measured by the fabricated portable photonic biosensor reader using the VCSEL and wavelength meter. Although the reader is the size of a palmtop device, it could make a precise measurement of the peak wavelength on equal terms with a conventional bulky optical spectrometer.

Ecophysiology of seed dormancy and germination in four Lonicera (Caprifoliaceae) species native to Korea

Park, HyungBin,Ko, ChungHo,Lee, SeungYoun,Kim, SangYong,Yang, JongCheol,Lee, KiCheol The Ecological Society of Korea 2019 Journal of Ecology and Environment Vol.43 No.2

Background: To exploit the ornamental and medicinal purposes of Lonicera harae Makino, L. subsessilis Rehder, L. praeflorens Batalin, and L. insularis Nakai, native to Korea, it is necessary to understand their seed ecology for propagation. In this study, we investigated the seed dormancy type and germination characteristics of seeds of the four Korean native Lonicera species. Results: The seeds of the four Lonicera species imbibed water readily, suggesting that the species do not have physical dormancy. Furthermore, the seeds exhibited underdeveloped embryos with only about 15-25% of the length of the seeds at dispersal. The embryos grew to the critical length with approximately 50-80% of the length of the seeds' development before radicle protrusion. Further, 94.4% and 61.1% of freshly matured seeds of L. insularis and L. harae germinated within 4 weeks after sowing at 15 ℃ and 20 ℃, respectively. Contrarily, L. praeflorens and L. subsessilis seeds did not germinate within 4 weeks under all temperature treatments. At 15 ℃, L. praeflorens seeds started to germinate from 5 weeks and the final germination rate was 51.1% at 13 weeks. At 15 ℃, L. subsessilis seeds started to germinate from 5 weeks after sowing and the final germination rate was 85.6% at 17 weeks after sowing. Embryo growth and germination of L. praeflorens and L. subsessilis occurred at a relatively high temperature (≥ 15 ℃). Conclusions: Overall, L. insularis seeds have only morphological dormancy. The seeds of L. harae have approximately 60% and 40% of morphological dormancy and morphophysiological dormancy, respectively. Contrarily, L. praeflorens and L. subsessilis exhibited non-deep simple-type morphophysiological dormancy that requires relatively high temperature (≥ 15 ℃) for embryo growth and dormancy breaking. The optimum temperature for the germination of seeds of L. insularis, L. harae, L. praeflorens, and L. subsessilis was 15 ℃, 20 ℃, 15 ℃, and 20 ℃, respectively. There was interspecific variation in seed dormancy and germination patterns in the four Lonicera species. The difference in these characteristics within the four Lonicera species could be useful for understanding the seed ecophysiological mechanisms of Lonicera species.

Optimization of Agrobacterium-mediated transient expression of heterologous genes in spinach

Cao, Dang Viet,Pamplona, Reniel S.,Kim, Jiwon,Oh, Young Kyoung,Cho, Seok-Keun,Ahn, Jongcheol,Yang, Seong-Wook,Riu, Key-Zung,Boo, Kyung-Hwan Springer-Verlag 2017 Plant biotechnology reports Vol.11 No.6