• 한국컴퓨터정보학회논문지
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• 제17권12호
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• pp.149-158
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• 2012

본 논문에서는 점근적으로 최적인 두가지의 무작위화 함수인 일라이어스(Elias) 함수와 페레즈(Peres) 함수의 장단점을 고려한 하이브리드 무작위화 함수를 제안한다. 무작위화 함수는 편향성이 있는 무작위수의 공급원으로부터 균등한 무작위수를 생성하는데 쓰이는 알고리즘을 수학적으로 추상화한 것이다. 일라이어스 함수와 페레즈 함수는 입력의 길이가 무한으로 증가함에 따라 그 출력효율성이 정보론적 한계치에 다가간다. 특히, 일라이어스 함수는 주어진 (유한의) 입력길이에 대해 최적인 무작위화 함수이다. 그러나 그 계산은 간단하지 않고, 주어진 입력길이에 의존한다. 반면, 페레즈 함수는 정해진 입력의 길이에 대해 출력효율이 최적이지는 않으나, 점근적으로는 최적이고, 간단한 재귀식에 의해 정의되어서 그 계산이 매우 간단하고 적은 메모리를 필요로 한다. 이러한 계산복잡도와 출력효율에 대한 두가지 무작위화 함수의 장단점에 주목하여, 각각의 장점을 고려한 하이브리드 무작위화 함수를 제안하고 이를 분석한다.

• 대한의용생체공학회:의공학회지
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• 제27권3호
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• pp.94-100
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• 2006

The effectiveness of the treatment of intracranial aneurysms with endovascular coiling depends on coil packing density, the location of aneurysm, its neck dimensions with respect to the aneurysm dome, and its size with respect to the surrounding tissue. Clinical data also suggests that the aneurysm neck size is the main predictor of aneurysm recanalization. In this study, the force impinging on the aneurysm neck in an idealized aneurysm was calculated by using a three dimensional finite volume method for the non-Newtonian incompressible laminar flow. To quantify the effect of neck size on the impingement force, calculations were performed for aneurysm neck diameters (Da) varying from 10% to 100% of the parent artery diameter (Dp). Also, maximum impingement forces were represented by a function of the ratio of the aneurysm neck to the diameter of the parent vessel. The results show that the hemodynamic forces exerted on the coil mass at the aneurysm neck due to the pulsatile blood flow are larger for wide necked aneurysms.

• IMMUNE NETWORK
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• 제22권5호
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• pp.40.1-40.24
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• 2022

Mesenchymal stem cells (MSCs) are attractive alternatives to conventional anti-asthmatic drugs for severe asthma. Mechanisms underlying the anti-asthmatic effects of MSCs have not yet been elucidated. This study evaluated the anti-asthmatic effects of intravenously administered MSCs, focusing on macrophages and monocytes. Seven-week-old transgenic (Tg) mice with lung-specific overexpression of IL-13 were used to simulate chronic asthma. MSCs were intravenously administered four days before sampling. We examined changes in immune cell subpopulations, gene expression, and histological phenotypes. IL-13 Tg mice exhibited diverse features of chronic asthma, including severe type 2 inflammation, airway fibrosis, and mucus metaplasia. Intravenous administration of MSCs attenuated these asthmatic features just four days after a single treatment. MSC treatment significantly reduced SiglecF^-CD11c^-CD11b⁺ monocyte-derived macrophages (MoMs) and inhibited the polarization of MoMs into M2 macrophages, especially M2a and M2c. Furthermore, MSCs downregulated the excessive accumulation of Ly6c^- monocytes in the lungs. While an intravenous adoptive transfer of Ly6c^- monocytes promoted the infiltration of MoM and Th2 inflammation, that of MSC-exposed Ly6c^- monocytes did not. Ex vivo Ly6c^- MoMs upregulated M2-related genes, which were reduced by MSC treatment. Molecules secreted by Ly6c^- MoMs from IL-13 Tg mice lungs upregulated the expression of fibrosis-related genes in fibroblasts, which were also suppressed by MSC treatment. In conclusion, intravenously administered MSCs attenuate asthma phenotypes of chronic asthma by modulating macrophages. Identifying M2 macrophage subtypes revealed that exposure to MSCs transforms the phenotype and function of macrophages. We suggest that Ly6c^- monocytes could be a therapeutic target for asthma management.