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Systems of pancreatic beta-cells and glucose regulation.
Kang, Hyuk,Han, Kyungreem,Jo, Junghyo,Kim, Jinwoong,Choi, Moo Young Frontiers in Bioscience Publications 2008 Frontiers in bioscience Vol.13 No.-
<P>We present mathematical models for systems of beta-cells in pancreatic islets. The first topic begins with the effects of noise and coupling strength on bursting action potentials of beta-cells. From the discussion, the regular bursts are produced by a proper amount of noise and coupling strength. Furthermore, the bursting duration and period depend on the cluster size of beta-cells. We also observe the real size of islets mostly consisting of beta-cells and obtain the size distribution of islets. In addition, we derive either log-normal or Weibull distributions of the islet sizes based on recent observation on islet growth. Islets of Langerhans are composed of several endocrine cells which interact with each other. Considering asymmetric and inhibitory interactions of these endocrine cells, we introduce a simple islet model consisting of alpha-, beta-, and delta-cells. Finally, a whole feedback model for glucose regulation is constructed, connecting the microscopic bursting mechanism and the macroscopic blood glucose regulation of the body. We analyzed these models via numerical simulations based on in vivo and in vitro experimental data.</P>
KANG, HYUK,HAN, KYUNGREEM,GOH, SEGUN,CHOI, MOOYOUNG World Scientific Publishing Company 2017 Journal of Biological Systems Vol.25 No.2
<P>Insulin secretion in pancreatic <TEX>$ \beta $</TEX>-cells exhibits three oscillatory modes with distinct period ranges, called fast, slow, and ultradian modes. To unveil the mechanism underlying such oscillatory behaviors and their roles in blood glucose regulation, we propose a combined model for the glucose-insulin regulation system, incorporating both the cell-level insulin secretion mechanism and inter-organ interactions in the blood glucose regulation. Special emphasis is placed on the identification of the mechanism of the slow oscillation and its role associated with the whole-body glucose regulation. Via extensive numerical simulations, we obtain macroscopic behaviors of the three types of insulin/glucose oscillations in the whole-body as well as microscopic behaviors of the membrane potential and the calcium concentration in the <TEX>$ \beta $</TEX>-cell. Finally, optimal regulatory strategies for the blood glucose level are discussed on the basis of the quantitative information obtained from the mathematical modeling and numerical simulations.</P>
이강혁 ( Lee¸ Kang-hyuk ) 국어학회 2021 국어학 Vol.- No.99
본고는 단어형성부의 연구사를 검토하고 연구사적 흐름이 안겨주는 시사점을 기반으로 단어형성부 외연 확대 가능성에 대한 시범적 논의 및 제언을 하는 것을 목적으로 한다. 생성형태론 초기 규칙 중심의 단어형성부에서부터 인지·심리언어학의 발달로 인한 유추론의 대두, 그리고 최근의 상호 보완적 형태의 단어형성부에 이르기까지 연구사를 살펴보았다. 또한 복수 형성 기제를 내포하고 있는 단어형성부의 현주소에 대하여 복잡계(complex system)로 판단하여 구성 요소들 간의 상호작용을 통한 외연 확대 가능성을 전제하고자 하였다. 이를 기반으로 단어형성부의 외연을 문법적 단어에까지 확대할 수 있음을 검토하고 대상을 어말어미로 한정하여 화자의 공시적 분석 가능성 정도에 따라 ‘□불투명 □반투명 □투명’으로 분류하여 그 가능성을 검토하여 기술하였다. This paper aims to review the research history of the word formation component and make pilot discussions and suggestions on the possibility of expanding the word formation department's externality based on the implications of the research historical flow. From the early rule-centered word formation component of generative morphology to the rise of analogy due to the development of cognitive and psychological linguistics, to the recent complementary word formation component, we looked at research history. In addition, we judge the current state of the word formation component that contains a plural formation mechanism as a complex system, presupposing the possibility of external expansion through interactions between elements. Based on this opinion, the externality of the word formation component can be extended to grammatical words, and the subject is classified and described as ‘□opacity, □translucency, □transparency' depending on the speaker's probability of synchronic analysis.
Kanghyuk Lee,Junho Park,SungJoon Choi,Sang-Im Yoo 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
The Sr M-type hexaferrites (SrFe<sub>12</sub>O<sub>19</sub>) are one of the most widely used magnetic material due to their cost efficiency, strong uniaxial magnetic anisotropy along the c-axis, and excellent chemical stability. Recently, many studies have improved the intrinsic magnetic properties of M-type hexaferrites by substitution, such as saturation magnetization and crystalline anisotropy. Previous reports have been mainly focused on La<sup>3+</sup>substitution for the Sr<sup>2+</sup> site and CO<sup>2+</sup> substitution for the Fe<sup>3+</sup> sites of M-type hexaferrites. In addition, there is generally requires a non-stoichiometric of iron ratio between 10 and 12 on Ba M-type hexaferrites. While iron deficiency is known to be helpful for the grain growth and the structure formation of NiZn spinel ferrites. Particularly, SiO2-CaO is widely used by suppressing crystal growth and high sintering density through Liquid - Phase Sintering. However, the effect of La-Co substitution and iron deficiency on magnetic properties of the Sr-La-Co M-type hexaferrites remains unexplored. In this study, therefore, we tried to investigate La-Co substituted Sr M-type hexaferrites Sr<sub>1-x</sub>La<sub>x</sub>Fe<sub>12-x</sub>Co<sub>x</sub>O<sub>19</sub>, (0 ≤ x ≤ 0.4) and the effect of iron deficiency on the magnetic properties of Sr<sub>1-x</sub>La<sub>x</sub>Fe<sub>y</sub>Co<sub>x</sub>O<sub>19-δ</sub> (x = 0.15, 10 ≤ y ≤ 12-x) hexaferrites prepared by solid state reaction. The raw materials were ball-milled for 24 h with or without CaCO3 and SiO2 additive and calcined at 1280 ℃ for 2 h in air. as-calcined powder was pressed into pellets and sintered at 1230 ℃ for 1 h in air with SiO2 and CaCO3 additives. Samples were characterized by powder X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and scanning electron microscope (SEM). In case of Iron deficient Sr-La-Co M-type hexaferrties, Powder XRD analyses revealed that M-type single phases were obtained with all Fe contents at sintering temperature. The saturation magnetization (M<sub>s</sub>) of the Sr-La-Co M-type hexaferrite samples was around 72 emu/g. However, the coercivity (H<sub>c</sub>) decreased with higher Fe content because the grain size was larger than the single domain size. The V<sub>cell</sub> change due to substitution and iron deficiency seems to be inversely related to H<sub>a</sub> obtained by magnetic hysteresis loops calculation. Detailed microstructures and magnetic properties will be presented for a discussion.