Single cell heterogeneity in human pluripotent stem cells

( Seungbok Yang ),( Yoonjae Cho ),( Jiwon Jang ) 생화학분자생물학회 2021 BMB Reports Vol.54 No.10

Human pluripotent stem cells (hPSCs) include human embryonic stem cells (hESCs) derived from blastocysts and human induced pluripotent stem cells (hiPSCs) generated from somatic cell reprogramming. Due to their self-renewal ability and pluripotent differentiation potential, hPSCs serve as an excellent experimental platform for human development, disease modeling, drug screening, and cell therapy. Traditionally, hPSCs were considered to form a homogenous population. However, recent advances in single cell technologies revealed a high degree of variability between individual cells within a hPSC population. Different types of heterogeneity can arise by genetic and epigenetic abnormalities associated with long-term in vitro culture and somatic cell reprogramming. These variations initially appear in a rare population of cells. However, some cancer-related variations can confer growth advantages to the affected cells and alter cellular phenotypes, which raises significant concerns in hPSC applications. In contrast, other types of heterogeneity are related to intrinsic features of hPSCs such as asynchronous cell cycle and spatial asymmetry in cell adhesion. A growing body of evidence suggests that hPSCs exploit the intrinsic heterogeneity to produce multiple lineages during differentiation. This idea offers a new concept of pluripotency with single cell heterogeneity as an integral element. Collectively, single cell heterogeneity is Janus-faced in hPSC function and application. Harmful heterogeneity has to be minimized by improving culture conditions and screening methods. However, other heterogeneity that is integral for pluripotency can be utilized to control hPSC proliferation and differentiation. [BMB Reports 2021; 54(10): 505-515]

Performance Analysis of Mode Switching Scheme for Reduction of Phase Distortion in GPS Anti-jamming Equipment Based on STAP Algorithm

Jung, Junwoo,Yang, Gi-Jung,Park, Sungyeol,Kang, Haengik,Kwon, Seungbok,Kim, Kap Jin The Institute of Positioning 2019 Journal of Positioning, Navigation, and Timing Vol.8 No.3

A method that applies space-time adaptive signal processing (STAP) algorithm based on an array antenna consisting of multiple antenna elements has been known to be effective to remove wide-band jamming signals in GPS receivers. However, the occurrence of phase distortion in navigation signals has been a problem when navigation signals, from which jamming signals are removed using STAP, are supplied to global positioning system (GPS) receivers. This paper verified the navigation performance degradation as a result of phase distortion. To mitigate this phenomenon, this paper proposes a mode switching scheme, in which a bypass mode is adopted to make the best use of the tracking performance of receivers without performing signal processing when jamming signals are not present or weak, and a STAP mode is employed when jamming signals exceed the threshold value. In this paper, the mode switching scheme is proposed for two environments: when receivers are stationary, and when receivers are moving. This paper confirmed that the performance of position error improved because phase distortion could be excluded due to STAP if the bypass mode was adopted under a condition where the jamming signal power level was below the threshold value in an environment where receivers were stationary. However, this paper also observed that the navigation failed due to the instability of tracking performance of receivers due to phase distortion that occurred at the switching time, although the number of switching could be reduced dramatically by proposing a dual threshold scheme of on- and off-thresholds that switched a mode due to the array antenna characteristics of varying gains according to the jamming signal incident direction in an environment where receivers were moving. The analysis results verified that running the STAP algorithm at all times is more efficient than the mode switching, in terms of maintaining stable navigation and ensuring position error performance, to remove jamming signals in an environment where receivers were moving.

Fan과 Heat Sink를 이용한 LED Head Lamp의 냉각성능해석

고만석(Manseok Ko),양승복(Seungbok Yang),이주한(Juhan Lee),강병도(Byungdo Kang),서태범(Taebum Seo) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4

LED has the merits of High reliability, Semi-permanent life, rapid-response and its small size for use as light source of head lamp. But the dependence of its performance and life on temperature affect on its practical use. Which dependence makes problem when the LED is heated up to a higher temperature level by self-generation of heat, due to “highly integration” to get enough quantity of light. To solve this problem, effective cooling system is needed that consider conduction, convection and radiation. This study point out the limits of natural convection cooling system and propose of forced convection with heat sink. Also, describes a correlation between heat sink area and fluid velocity using numerical analysis to optimize of cooling system.

자폐스펙트럼장애 환자에서의 인지적 공감 및 정서적 공감의 신경 상관물

정승원(Seungwon Chung),손정우(Jung-Woo Son),이승복(Seungbok Lee),김혜리(Hei-Rhee Ghim),이상익(Sang-Ick Lee),신철진(Chul-Jin Shin),김시경(Siekyeong Kim),주가원(Gawon Ju),최상철(Sang Cheol Choi),김양렬(Yang Yeol Kim),구영진(Young Jin K 대한소아청소년정신의학회 2016 소아청소년정신의학 Vol.27 No.3

Objectives: Individuals with autism spectrum disorder (ASD) are considered to have problems with empathy. It has recently been suggested that there are two systems for empathy; cognitive and emotional. We aimed to investigate the neural response to cognitive and emotional empathy and elucidate the neurobiological aspects of empathy in patients with ASD. Methods: We recruited patients with ASD (N=17, ASD group) and healthy controls (HC) (N=22, HC group) for an functional magnetic resonance imaging study. All of the subjects were scanned while performing cognitive and emotional empathy tasks. The differences in brain activation between the groups were assessed by contrasting their neural activity during the tasks. Results: During both tasks, the ASD group showed greater neural activities in the bilateral occipital area compared to the HC group. The ASD group showed more activation in the bilateral precunei only during the emotional empathy task. No brain regions were more activated in the HC group than in the ASD group during the cognitive empathy task. While performing the emotional empathy task, the HC group exhibited greater neural activities in the left middle frontal gyrus and right anterior cingulate gyrus than the ASD group. Conclusion: This study showed that the brain regions associated with cognitive and emotional empathy in ASD patients differed from those in healthy individuals. The results of this study suggest that individuals with ASD might have defects both in cognitive empathy and in emotional empathy.

Autism and Beauty

Seong Kyoung Park,Jung-Woo Son,Seungwon Chung,Seungbok Lee,Hei-Rhee Ghim,Sang-Ick Lee,Chul-Jin Shin,Siekyeong Kim,Gawon Ju,Sang Cheol Choi,Yang Yeol Kim,Young Jin Koo,Bung-Nyun Kim,Hee Jeong Yoo 대한소아청소년정신의학회 2018 소아청소년정신의학 Vol.29 No.3

Objectives: The purpose of this study was to investigate whether the neural activity of autism spectrum disorder (ASD) patients is different from that of normal individuals when performing aesthetic judgments. Methods: We recruited typical ASD patients without savant skills (ASD group, n=17) and healthy controls (HC group, n=19) for an functional magnetic resonance imaging study. All subjects were scanned while performing aesthetic judgment tasks on two kinds of artwork (magnificent landscape images and fractal images). Differences in brain activation between the two groups were assessed by contrasting neural activity during the tasks. Results: The aesthetic judgment score for all images was significantly lower in the ASD group than in the HC group. During the aesthetic judgment tasks, the ASD group showed less activation than the HC group in the anterior region of the superior frontal gyrus, and more activation in the temporoparietal area and insula, regardless of the type of images being judged. In addition, during the aesthetic judgment task for the fractal images, the ASD group exhibited greater neural activity in the amygdala and the posterior region of the middle/inferior temporal gyrus (Brodmann area 37) than the HC group. Conclusion: The results of this study suggest that the brain activation patterns associated with aesthetic experiences in ASD patients may differ from those of normal individuals.