Space-Time法による心臓弁の接触を含む高精度流体解析

早大学位記番号:新8436早稲田大

Heart valve isogeometric sequentially-coupled FSI analysis with the space–time topology change method

Heart valve fluid–structure interaction (FSI) analysis is one of the computationally challenging cases in cardiovascular fluid mechanics. The challenges include unsteady flow through a complex geometry, solid surfaces with large motion, and contact between the valve leaflets. We introduce here an isogeometric sequentially-coupled FSI (SCFSI) method that can address the challenges with an outcome of high-fidelity flow solutions. The SCFSI analysis enables dealing with the fluid and structure parts individually at different steps of the solutions sequence, and also enables using different methods or different mesh resolution levels at different steps. In the isogeometric SCFSI analysis here, the first step is a previously computed (fully) coupled Immersogeometric Analysis FSI of the heart valve with a reasonable flow solution. With the valve leaflet and arterial surface motion coming from that, we perform a new, higher-fidelity fluid mechanics computation with the space–time topology change method and isogeometric discretization. Both the immersogeometric and space–time methods are variational multiscale methods. The computation presented for a bioprosthetic heart valve demonstrates the power of the method introduced

Selective Transmission of R5 HIV-1 over X4 HIV-1 at the Dendritic Cell–T Cell Infectious Synapse Is Determined by the T Cell Activation State

Dendritic cells (DCs) are essential antigen-presenting cells for the induction of T cell immunity against HIV. On the other hand, due to the susceptibility of DCs to HIV infection, virus replication is strongly enhanced in DC–T cell interaction via an immunological synapse formed during the antigen presentation process. When HIV-1 is isolated from individuals newly infected with the mixture of R5 and X4 variants, R5 is predominant, irrespective of the route of infection. Because the early massive HIV-1 replication occurs in activated T cells and such T-cell activation is induced by antigen presentation, we postulated that the selective expansion of R5 may largely occur at the level of DC–T cell interaction. Thus, the immunological synapse serves as an infectious synapse through which the virus can be disseminated in vivo. We used fluorescent recombinant X4 and R5 HIV-1 consisting of a common HIV-1 genome structure with distinct envelopes, which allowed us to discriminate the HIV-1 transmitted from DCs infected with the two virus mixtures to antigen-specific CD4+ T cells by flow cytometry. We clearly show that the selective expansion of R5 over X4 HIV-1 did occur, which was determined at an early entry step by the activation status of the CD4+ T cells receiving virus from DCs, but not by virus entry efficiency or productivity in DCs. Our results imply a promising strategy for the efficient control of HIV infection

Computational Cardiovascular Medicine With Isogeometric Analysis

Isogeometric analysis (IGA) brought superior accuracy to computations in both fluid and solid mechanics. The increased accuracy has been in representing both the problem geometry and the variables computed. Beyond using IGA basis functions in space, with IGA basis functions in time in a space–time (ST) context, we can have increased accuracy also in representing the motion of solid surfaces. Around the core methods such as the residual-based variational multiscale (VMS), ST-VMS and arbitrary Lagrangian–Eulerian VMS methods, with complex-geometry IGA mesh generation methods and immersogeometric analysis, and with special methods targeting specific classes of computations, the IGA has been very effective in computational cardiovascular medicine. We provide an overview of these IGA-based computational cardiovascular-medicine methods and present examples of the computations performed.This article is published as Takizawa, Kenji, Yuri Bazilevs, Tayfun E. Tezduyar, Ming-Chen Hsu, and Takuya Terahara. "Computational cardiovascular medicine with isogeometric analysis." Journal of Advanced Engineering and Computation 6, no. 3 (2022): 167-199. This work is licensed under a Creative Commons Attribution 4.0 International License. DOI: 10.55579/jaec.202263.381. Copyright 2022 Journal of Advanced Engineering and Computation. Posted with permission

Streptomyces otsuchiensis sp. nov., a biosurfactant-producing actinobacterium isolated from marine sediment

A novel actinobacterium producing biosurfactant, designated OTB305T, was isolated from marine sediment sampled at Otsuchi Bay, Iwate Prefecture, Japan and its taxonomic position was examined using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequences exhibited that strain OTB305T was closely related to Streptomyces bohaiensis JCM 19630T (98.8 %) and Streptomyces lonarensis DSM 42084T (98.8 %). The chemotaxonomic characteristics of strain OTB305T corresponded to those of the genus Streptomyces as follows: the diamino acid of the cell-wall peptidoglycan was ll-diaminopimelic acid; whole-cell hydrolysates contained glucose and lacked characteristic major sugars; the predominant isoprenoid quinones were MK-9(H8) and MK-9(H6); the polar lipids were phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and an unidentified phospholipid; the major cellular fatty acids were iso-C16 : 0, C16 : 0 and C16 : 1 ω7c; and the genomic DNA G+C content was 72.83 mol%. However, genomic relatedness analysis based on the average nucleotide identity and some phenotypic characteristics revealed that strain OTB305T was distinguished from closely related Streptomyces species. Therefore, strain OTB305T represents a novel species of the genus Streptomyces , for which the name Streptomyces otsuchiensis sp. nov. is proposed. The type strain is OTB305T (=NBRC 113255T=TBRC 9682T)

Heart valve isogeometric sequentially-coupled FSI analysis with the space–time topology change method

Heart valve fluid–structure interaction (FSI) analysis is one of the computationally challenging cases in cardiovascular fluid mechanics. The challenges include unsteady flow through a complex geometry, solid surfaces with large motion, and contact between the valve leaflets. We introduce here an isogeometric sequentially-coupled FSI (SCFSI) method that can address the challenges with an outcome of high-fidelity flow solutions. The SCFSI analysis enables dealing with the fluid and structure parts individually at different steps of the solutions sequence, and also enables using different methods or different mesh resolution levels at different steps. In the isogeometric SCFSI analysis here, the first step is a previously computed (fully) coupled Immersogeometric Analysis FSI of the heart valve with a reasonable flow solution. With the valve leaflet and arterial surface motion coming from that, we perform a new, higher-fidelity fluid mechanics computation with the space–time topology change method and isogeometric discretization. Both the immersogeometric and space–time methods are variational multiscale methods. The computation presented for a bioprosthetic heart valve demonstrates the power of the method introduced.This is the final, authenticated version of the article: Terahara, Takuya, Kenji Takizawa, Tayfun E. Tezduyar, Yuri Bazilevs, and Ming-Chen Hsu. "Heart valve isogeometric sequentially-coupled FSI analysis with the space–time topology change method." Computational Mechanics (2020). DOI: 10.1007/s00466-019-01813-0. Posted with permission.</p