3-D Characterization of Seismic Properties at the Smart Weapons Test Range,YPG

( Richard D. Miller ),( Thomas S. Anderson ),( John C. Davis ),( Ricardo Olea ),( Choon Park ),( Don W. Steeples ),( Mark L. Moran ),( Jiang Hai Xia ),( Julian Ivanov ) 대한지질공학회 2004 지질공학 단기강좌 Vol.2004 No.-

Spatiotemporal Evolution of the Primary Glioblastoma Genome

Kim, J.,Lee, I.H.,Cho, H.,Park, C.K.,Jung, Y.S.,Kim, Y.,Nam, S.,Kim, B.,Johnson, Mark D.,Kong, D.S.,Seol, H.,Lee, J.I.,Joo, K.,Yoon, Y.,Park, W.Y.,Lee, J.,Park, Peter J.,Nam, D.H. Cell Press 2015 CANCER CELL Vol. No.

Tumor recurrence following treatment is the major cause of mortality for glioblastoma multiforme (GBM) patients. Thus, insights on the evolutionary process at recurrence are critical for improved patient care. Here, we describe our genomic analyses of the initial and recurrent tumor specimens from each of 38 GBM patients. A substantial divergence in the landscape of driver alterations was associated with distant appearance of a recurrent tumor from the initial tumor, suggesting that the genomic profile of the initial tumor can mislead targeted therapies for the distally recurred tumor. In addition, in contrast to IDH1-mutated gliomas, IDH1-wild-type primary GBMs rarely developed hypermutation following temozolomide (TMZ) treatment, indicating low risk for TMZ-induced hypermutation for these tumors under the standard regimen.

Comparison of Characteristics of Gamma-Ray Imager Based on Coded Aperture by Varying the Thickness of the BGO Scintillator

Park Seoryeong,Hammig Mark D.,Manhee Jeong 대한방사선방어학회 2022 방사선방어학회지 Vol.47 No.4

Background : The conventional cerium-doped Gd2Al2Ga3O12 (GAGG(Ce)) scintillator-based gamma-ray imager has a bulky detector, which can lead to incorrect positioning of the gamma-ray source if the shielding against background radiation is not appropriately designed . In addition , portability is important in complex environments such as inside nuclear power plants , yet existing gamma-ray imager based on a tungsten mask tends to be weighty and therefore difficult to handle . Motivated by the need to develop a system that is not sensitive to background radiation and is portable , we changed the material of the scintillator and the coded aperture . Materials and Methods : The existing GAGG(Ce) was replaced with Bi4Ge3O12 (BGO) , a scintillator with high gamma-ray detection efficiency but low energy resolution , and replaced the tungsten (W) used in the existing coded aperture with lead (Pb) . Each BGO scintillator is pixelated with 144 elements (12 × 12) , and each pixel has an area of 4 mm × 4 mm and the scintillator thickness ranges from 5 to 20 mm (5 , 10 , and 20 mm) . A coded aperture consisting of Pb with a thickness of 20 mm was applied to the BGO scintillators of all thicknesses . Results and Discussion : Spectroscopic characterization , imaging performance , and image quality evaluation revealed the 10 mm-thick BGO scintillators enabled the portable gamma-ray imager to deliver optimal performance . Although its performance is slightly inferior to that of existing GAGG(Ce)-based gamma-ray imager, the results confirmed that the manufacturing cost and the system’s overall weight can be reduced . Conclusion : Despite the spectral characteristics , imaging system performance , and image quality is slightly lower than that of GAGG(Ce) , the results show that BGO scintillators are preferable for gamma-ray imaging systems in terms of cost and ease of deployment , and the proposed design is well worth applying to systems intended for use in areas that do not require high precision.

Microporous cell-laden hydrogels for engineered tissue constructs

Park, Jae Hong,Chung, Bong Geun,Lee, Won Gu,Kim, Jinseok,Brigham, Mark D.,Shim, Jaesool,Lee, Seunghwan,Hwang, Chang Mo,Durmus, Naside Gozde,Demirci, Utkan,Khademhosseini, Ali Wiley Subscription Services, Inc., A Wiley Company 2010 Biotechnology and bioengineering Vol.106 No.1

<P>In this article, we describe an approach to generate microporous cell-laden hydrogels for fabricating biomimetic tissue engineered constructs. Micropores at different length scales were fabricated in cell-laden hydrogels by micromolding fluidic channels and leaching sucrose crystals. Microengineered channels were created within cell-laden hydrogel precursors containing agarose solution mixed with sucrose crystals. The rapid cooling of the agarose solution was used to gel the solution and form micropores in place of the sucrose crystals. The sucrose leaching process generated homogeneously distributed micropores within the gels, while enabling the direct immobilization of cells within the gels. We also characterized the physical, mechanical, and biological properties (i.e., microporosity, diffusivity, and cell viability) of cell-laden agarose gels as a function of engineered porosity. The microporosity was controlled from 0% to 40% and the diffusivity of molecules in the porous agarose gels increased as compared to controls. Furthermore, the viability of human hepatic carcinoma cells that were cultured in microporous agarose gels corresponded to the diffusion profile generated away from the microchannels. Based on their enhanced diffusive properties, microporous cell-laden hydrogels containing a microengineered fluidic channel can be a useful tool for generating tissue structures for regenerative medicine and drug discovery applications. Biotechnol. Bioeng. 2010; 106: 138–148. © 2010 Wiley Periodicals, Inc.</P>

Expression profile of an operationally-defined neural stem cell clone

Parker, Mark A.,Anderson, Julia K.,Corliss, Deborah A.,Abraria, Victoria E.,Sidman, Richard L.,Park, Kook In,Teng, Yang D.,Cotanche, Douglas A.,Snyder, Evan Y. Elsevier 2005 Experimental neurology Vol.194 No.2

<P><B>Abstract</B></P><P>Neural stem cells (NSCs) are the most primordial and least committed cells of the nervous system, the cells that exist <I>before</I> regional specification develops. Because immunocytochemically-detectable markers that are sufficiently specific and sensitive to define an NSC have not yet been fully defined, we have taken the strong view that, to be termed a “stem cell” in the nervous system—in contrast to a “progenitor” or “precursor” (whose lineage commitment is further restricted)—a <I>single neuroectodermally-derived cell</I> must fulfill an operational definition that is essentially similar to that used in hematopoiesis. In other words, it must possess the following functional properties: (1) “Multipotency”, i.e., the ability to yield mature cells in all three fundamental neural lineages throughout the nervous system—neurons (of all subtypes), astrocytes (of all types), oligodendrocytes—in multiple regional and developmental contexts and in a region and developmental stage-appropriate manner. (2) The ability to populate a developing region and/or repopulate an ablated or degenerated region of the nervous system with appropriate cell types. (3) The ability to be serially transplanted. (4) “Self-renewal”, i.e., the ability to produce daughter cells (including new NSCs) with identical properties and potential. Having identified a murine neural cell clone that fulfills this strict operational definition—in contrast to other studies that used less rigorous or non-operational criteria for defining an NSC (e.g., the “neurosphere” assay)—we then examined, by comparing gene expression profiles, the relationship such a cell might have to (a) a <I>multipotent</I> somatic stem cell from another organ system (the hematopoietic stem cell [HSC]); (b) a <I>pluripotent</I> stem cell derived from the inner cell mass and hence without organ assignment (an embryonic stem cell); (c) neural cells isolated and maintained primarily as neurospheres but without having been subjected to the abovementioned operational screen (“CNS-derived neurospheres”). ESCs, HSCs, and operationally-defined NSCs—all of which have been identified not only by markers but by functional assays in their respective systems and whose state of differentiation could be synchronized—shared a large number of genes. Although, as expected, the most stem-like genes were expressed by ESCs, NSCs and HSCs shared a number of genes. CNS-derived neurospheres, on the other hand, expressed fewer “stem-like” genes held in common by the other operationally-defined stem cell populations. Rather they displayed a profile more consistent with differentiated neural cells. (Genes of neural identity were shared with the NSC clone.) Interestingly, when the operationally-defined NSC clone was cultured as a neurosphere (rather than in monolayer), its expression pattern shifted from a “stem-like” pattern towards a more “differentiated” one, suggesting that the neurosphere, without functional validation, may be a poor model for predicting stem cell attributes because it consists of heterogeneous populations of cells, only a small proportion of which are truly “stem-like”. Furthermore, when operational definitions are employed, a common set of stem-like genes does emerge across both embryonic and somatic stem cells of various organ systems, including the nervous system.</P>

The contribution of neighbours to an individual's risk of typhoid outcome

CHAO, D. L.,PARK, J. K.,MARKS, F.,OCHIAI, R. L.,LONGINI Jr., I. M.,HALLORAN, M. E. Cambridge University Press 2015 Epidemiology and infection Vol.143 No.16

<P><B>SUMMARY</B></P><P>An individual's risk of infection from an infectious agent can depend on both the individual's own risk and protective factors and those of individuals in the same community. We hypothesize that an individual's exposure to an infectious agent is associated with the risks of infection of those living nearby, whether their risks are modified by pharmaceutical interventions or by other factors, because of the potential for transmission from them. For example, unvaccinated individuals living in a highly vaccinated community can benefit from indirect protection, or living near more children in a typhoid-endemic region (where children are at highest risk) might result in more exposure to typhoid. We tested this hypothesis using data from a cluster-randomized typhoid vaccine trial. We first estimated each individual's relative risk of confirmed typhoid outcome using their vaccination status and age. We defined a new covariate, <I>potential exposure</I>, to be the sum of the relative risks of all who live within 100 m of each person. We found that potential exposure was significantly associated with an individual's typhoid outcome, and adjusting for potential exposure affected estimates of vaccine efficacy. We suggest that it is useful and feasible to adjust for spatially heterogeneous distributions of individual-level risk factors, but further work is required to develop and test such approaches.</P>

A baseline drift detrending technique for fast scan cyclic voltammetry

DeWaele, Mark,Oh, Yoonbae,Park, Cheonho,Kang, Yu Min,Shin, Hojin,Blaha, Charles D.,Bennet, Kevin E.,Kim, In Young,Lee, Kendall H.,Jang, Dong Pyo The Royal Society of Chemistry 2017 The Analyst Vol.142 No.22

<P>Fast scan cyclic voltammetry (FSCV) has been commonly used to measure extracellular neurotransmitter concentrations in the brain. Due to the unstable nature of the background currents inherent in FSCV measurements, analysis of FSCV data is limited to very short amounts of time using traditional background subtraction. In this paper, we propose the use of a zero-phase high pass filter (HPF) as the means to remove the background drift. Instead of the traditional method of low pass filtering across voltammograms to increase the signal to noise ratio, a HPF with a low cutoff frequency was applied to the temporal dataset at each voltage point to remove the background drift. As a result, the HPF utilizing cutoff frequencies between 0.001 Hz and 0.01 Hz could be effectively used to a set of FSCV data for removing the drifting patterns while preserving the temporal kinetics of the phasic dopamine response recorded <I>in vivo</I>. In addition, compared to a drift removal method using principal component analysis, this was found to be significantly more effective in reducing the drift (unpaired <I>t</I>-test <I>p</I> < 0.0001, <I>t</I> = 10.88) when applied to data collected from Tris buffer over 24 hours although a drift removal method using principal component analysis also showed the effective background drift reduction. The HPF was also applied to 5 hours of FSCV <I>in vivo</I> data. Electrically evoked dopamine peaks, observed in the nucleus accumbens, were clearly visible even without background subtraction. This technique provides a new, simple, and yet robust, approach to analyse FSCV data with an unstable background.</P>

수식에서 연령대별 선호도 연구

박순혁,박동재,Park Soonhyuck,Mark D. Park 부경대학교 인문사회과학연구소 2015 인문사회과학연구 Vol.16 No.2

언어는 일상에서 중요하고 복잡한 일생의 능력이다. 언어가 노화의 제약을 받는 만큼 인지노화가 언어에 미치는 영향을 밝히기 위한 많은 노력이 있었다, 그러나 대부분의 연구는 일시적 기간과 제한적 대상에 국한되어 있으며 기억력에 의존하는 어휘추출과 음성발화를 중심으로 진행된 반면에 그 상위의 언어단위 정보처리에 해당하는 통사 및 의미정보 처리에 대한 연구는 상대적으로 많지 않았다. 따라서 본 연구는 특정 문형에 나타나는 수식의 선호도를 연령대별로 실험하여 노화가 통사(어순)영역과 의미(수식)영역에 어떠한 변화를 유발하는지 살펴보았다. 그 결과 의미단 위의 정보처리 변화는 전반적인 인지노화의 심화에도 불구하고, 통사단위의 그것보다 비교적 늦게까지 유지된다는 증거를 제시한다. 이러한 결과는 인지노화와 관련되는 언어영역별 노화가 순차적이고 각기 다른 방식으로 전개된다는 것을 의미하며, 더 나아가 고령의 성인에게 나타나는 언어정보 처리에서 신경조직 연결망의 보상 활성화 현상에 관한 최근연구들과도 일치함을 밝힌다. Language is a crucial and complex lifelong capacity that is constrained by cognitive aging. Aging is thus regarded to be associated with poor performance particularly in the receptive and expressive language abilities. There are, however, some recent proposals that normal aging impairs specific aspects of language production, while most comprehension abilities remain stable as we age. This paper investigates how cognitive aging affects language performance, focusing on syntactic and semantic processing. Based on the experiments of structure choice and modification, it finds that the semantic processing is rather preserved longer with age than the syntactic processing. This finding is consistent with and supported by the recent research on the stronger neural connectivity to linguistic demands with older adults.

Complex Chiral Colloids and Surfaces via High-Index Off-Cut Silicon

McPeak, Kevin M.,van Engers, Christian D.,Blome, Mark,Park, Jong Hyuk,Burger, Sven,Gosá,lvez, Miguel A.,Faridi, Ava,Ries, Yasmina R.,Sahu, Ayaskanta,Norris, David J. American Chemical Society 2014 NANO LETTERS Vol.14 No.5

<P>Silicon wafers are commonly etched in potassium hydroxide solutions to form highly symmetric surface structures. These arise when slow-etching {111} atomic planes are exposed on standard low-index surfaces. However, the ability of nonstandard high-index wafers to provide more complex structures by tilting the {111} planes has not been fully appreciated. We demonstrate the power of this approach by creating chiral surface structures and nanoparticles of a specific handedness from gold. When the nanoparticles are dispersed in liquids, gold colloids exhibiting record molar circular dichroism (>5 × 10<SUP>9</SUP> M<SUP>–1</SUP> cm<SUP>–1</SUP>) at red wavelengths are obtained. The nanoparticles also present chiral pockets for binding.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-5/nl501032j/production/images/medium/nl-2014-01032j_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl501032j'>ACS Electronic Supporting Info</A></P>

미국의 메가가뭄대응 가뭄관리 및 정책 가이드라인

남원호 ( Won-ho Nam ),윤동현 ( Dong-hyun Yoon ),박무종 ( Moojong Park ),( Cody L. Knutson ),( Michael J. Hayes ),( Mark D. Svoboda ) 한국농공학회 2019 한국농공학회 학술대회초록집 Vol.2019 No.-

최근 지구 온난화에 따른 기후변화로 기온 및 강우 패턴의 변화가 발생하고 있으며, 이로 인한 가뭄발생 빈도가 증가하고 있다. 국내에서는 최근 연속적인 가뭄에 의한 생활용수 및 농업용수 등의 제한급수를 실시하였으며, 장기적인 가뭄 발생으로 가뭄이 발생하지 않은 지역까지 직접 및 간접적인 피해가 발생하였다. 또한, 예외적이고 발생 가능성이 없어 보이던 블랙스완형 (Black swan) 가뭄사상 (오랜시간에 걸쳐 광범위한 지역에 발생) 또는 장기간 및 대규모로 발생되는 메가 가뭄 (Mega-drought)의 전조가 감지되고 있다. 메가 가뭄은 발생 후 해갈까지 많은 시간과 지속적인 관리가 필요하며, 사회전반에 걸처 영향을 주는 대형복합재난으로 국가적 차원의 통합적 관리가 필요한 재난으로 메가 가뭄을 예측하고 효과적으로 대응할 수 있는 기술 개발 및 비상대처계획 수립이 필요하다. 국외의 경우, 1997년에서 2009년까지 약 12년간 계속된 호주의 밀레니엄 가뭄 (millennium drought), 미국 전역의 55%가 극심한 가뭄 상황이었던 2012년 미국 중부 가뭄, 2012년부터 시작되어 2017년까지 6년간 지속된 미국 서부의 캘리포니아 가뭄 등의 발생으로 메가 가뭄 적응 대책 (drought mitigation plan) 및 비상대처계획 (EAP: Emergency Action Plan)이 수립되었다. 본 연구에서는 미국, 호주 등 국외에서 실행되고 있는 가뭄 적응 대책 및 비상대처계획을 조사, 분석하고 향후 메가 가뭄 발생시 국내의 재난 위기관리 매뉴얼, 정부 및 지자체의 가뭄 대응 체계 및 대응 방안을 보완할 수 있는 방안을 제시하고자 한다.