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近世琉球における御用布の研究 -歴史資料と実物資料の統合化による研究方法を基軸として-
Get PDF近世琉球の御用布に関する研究は、主に実物資料を対象とする原料・文様・構造・技法・色材に関する染織史と民間伝承および文献史料を対象とする租税制度下の貢納布に関する研究史が積み重ねられている状況である。筆者の専門領域である実物資料研究を伴う染織史においては、目視で得られる色や形だけではなく、製作年代、製作地、製作者、製作目的等の歴史背景が重要な指標となる。しかしながら、専門領域に関する研究データは蓄積されているものの、歴史背景の指標となる関連歴史史料の分析及び歴史史料と実物資料との検証・照合については研究の余地が残されている状況である。本研究は、現存する御用布関係実物資料の歴史背景について文献史学の手法を援用し史料分析を行い、実物資料分析データと比較検討し、御用布をめぐる時代性、注文製作の実態、御用布の受容、製作者の技術と労働について考察することを課題とする。第1章｢近世琉球における御用布製作の規定について｣では、御用布製作の単位、規定についてついて検討する。第2章｢近世琉球における御用布の注文製作のしくみ｣では、初期、中期、後期に分けて、御用布の注文が届いてから上納までのしくみについて検討する。第3章｢御用布注文史料の分析｣では、文書原本を整理した注文書の分析データに基づき、注文書の依頼主と用途、絵形と注文者について検討する第4章｢歴史資料と実物資料の統合研究｣では、第1章で分析した歴史資料のデータを使用し、｢ふどき目｣と実物資料｢筬目｣の比較研究、注文書資料と御絵図資料の照合研究を行う。博士（学術）琉球大学University of the Ryukyu
琉球列島におけるサンゴの病気に関する生態学的研究
Get PDFUnderstanding the health and diseases of corals is essential to assess the potential harm caused by anthropogenic activities and the impacts from rising sea temperatures from global climate change. Climate change has also been implicated in an increase in occmrences of coral diseases. Outbreaks of coral diseases were first noted in the Caribbean and subsequently in the Indo-Pacific region. As a result of increasing occurrences, interest in understanding these conditions has also increased. However, coral diseases remain often poorly understood, especially in the Indo-Pacific, including in southern Japan, and there remain many critical knowledge gaps in coral diseases, their causes, and information on their general ecology. Thus, to successfully protect and manage coral reefs, further research is required. In this thesis, I conducted an extensive review of literature in first chapter to better identify coral disease knowledge gaps in southern Japan, with the aim of thesis to help fill in some of these gaps. Next, in Chapter 2, I conducted a four-year investigation on cyanobacterial Black Band Disease (BBD) and skeletal growth anomalies (GAs) on reefs around Sesoko Island, primarily focusing on Montipora corals, and discovering that although BBD and GAs are con皿on, the corals are seemingly able to grow at similar rates and usually avoid mortality. In the next chapter (3), I used drones to examine the same study area, demonstrating the utility of such technology to widely view and monitor shallow coral reef diseases. Next, in Chapter 4 I conducted surveys on reefs around Akajima Island located within the broader Kerama-shoto Marine National Park (KMNP), to examine the occurrences of disease within seemingly pristine areas. Results showed that even in marine protected areas largely protected from anthropogenic local stressors diseases are present, thus indicating the need for continued monitoring. Given the threats that coral reefs threat from climate change and local stress, and the increased susceptibility of corals to diseases under stress, and we recommend an expansion of vigilant coral reef monitoring including a disease data acquisition component.博士（学術）琉球大学University of the Ryukyu
琉球列島における攪乱下でのサンゴ群集の動態
Get PDFThe coral communities of the Ryukyu Archipelago have experienced significant changes and degradation over the past decade due to thermal events and other anthropogenic stressors. This dissertation examines the overall coral community status of Ryukyu Archipelago and spatial and temporal changes within coral communities and benthic substrate for two key ecological regions, Sekisei lagoon and Okinawa Island, following repeated bleaching events. Sekisei Lagoon, the largest reef in Japan, is crucial for the survival of coral communities in high latitudinal areas in the Ryukyu Island chain. The Degree Heating Weeks (DHW), values for both Sekisei Lagoon (11.4 °C-weeks) in 2016 and for Okinawa Island (14.3 °C-weeks) in 2017 were high with Sea Surface Temperatures (SSTs) above the bleaching threshold. However, despite the high DHW values observed in Okinawa compared to Sekisei Lagoon the bleaching intensity between both regions were highly contrasting. The overall bleaching intensity in 2017 in Okinawa Island was 33%, whereas in Sekisei lagoon the bleaching incidence of 2016 was 60%. The 2016 bleaching event decimated Acropora populations in Sekisei lagoon, leading to severe mortality. We also found that bleaching related impacts in Okinawa is heterogenous and difference was found between bleaching prevalence and depth. In the bleaching event of 2022, in Okinawa Island, only 9% of corals were impacted, while in Sekisei Lagoon, 63% of corals were affected, with 14% suffering mortality. Repeated bleaching events significantly altered the coral communities of Sekisei Lagoon, with juvenile corals dominating the lagoon due to incurring disturbances. The winners and losers of coral bleaching events differed between Sekisei Lagoon and Okinawa. In Sekisei Lagoon, Acropora colonies were most impacted, making them "losers," while Montipora species appeared to be most resilient. In Okinawa Island, long-term winners were Acropora species, showing exponential recovery since 2017 and overall increase in abundance. Massive and encrusting growth form corals such as Goniastrea or Platygyra seem more affected by bleaching events in Okinawa contrary to what have been previously reported for this region. The study provides spatial and temporal information on the current state of key coral reef areas in the Ryukyu Archipelago and can serve as a guide to select areas that are ecologically and biologically important for conserving and managing coral communities against anthropogenic stressors and climate change impacts.博士（理学）琉球大学University of the Ryukyu
急性冠症候群における冠動脈プラークの安定性に対するPCSK9阻害薬の早期および短期使用の影響
Get PDFBackground and Aims: Proprotein convertase anti-subtilisin-kexin type 9 inhibitors (PCSK9Is) improve plaque volume and composition and reduce major adverse coronary events in chronic coronary artery disease. The aim of this study was to evaluate the effectiveness of the early initiation and short-term (for 3 months) use of PCSK9Is on mid-term (for 9 months) outcomes in achieving plaque stabilization using optical coherence tomography (OCT) in patients with acute coronary syndrome (ACS)
Methods: This multicenter, open label randomized controlled trial. Enrolled 80 subjects met the inclusion criteria. Of these, 52 patients (age 60±11 years, 38 men, 14 women) with ST-elevated ACS who had undergone successful primary percutaneous coronary intervention with low-density lipoprotein cholesterol (LDL-C) levels >70 mg/dL while receiving high-intensity statins. Participants were randomly assigned to the PCSK9Is group (evolocumab 420 mg for 3 months, N=29) or the standard of care (SoC) group(N=23). OCT was performed at baseline (BL) and 3-months (3M) and 9- months (9M) after randomization to assess lipid-rich plaques in non-culprit lesions. The change in the minimum fibrous cap thickness (MFCT) from baseline to 9M was the primary endpoint.
Results: The percentage change in LDL-C levels from BL to 3M were significantly greater in the PCSK9Is group (-67.8±21.5% in the PCSK9Is group vs. -16.3±21.8% in the SoC group ; p<0.0001) and though, the difference between two groups were disappeared from BL to 9M (-20.0±37.8% in the PCSK9Is group vs. -6.7±34.2% in the SoC group ; p=0.20).The changes in MFCT from baseline to 9M were significantly greater in the PCSK9Is group, even after PCSK9Is discontinuation (100 μm [Interquartile range (IQR): 45–180 μm] vs. 50 μm [IQR: 0–110 μm]; p=0.032).
Conclusions: Combination treatment with PCSK9Is and statins resulted in more marked plaque stabilization after ACS than SoC alone, and this effect persisted for 6 months after PCSK9I discontinuation.博士（医学）琉球大学University of the Ryukyu
海洋酸性化がサンゴ礁生態系における生物間相互作用に及ぼす影響
Get PDFReef ecosystems are suspected to be highly susceptible to climate change including ocean acidification (OA). W伍le many marine calcifiers such as corals are expected to be negatively affected by OA, marine macrophytes such as seaweed and seagrass are predicted to be positively affected by OA, as increased CO2 concentration in seawater can potentially increase their photosynthetic rates and productivity. The uptake of CO2 by marine macrophytes is hypothesized to increase the pH of the surrounding seawater and thus can alleviate the negative impacts of OA on marine calcifiers. In addition, high CO2 uptake under OA by primary producers such as seagrasses is also predicted to alter their nutritional quality and thus is expected to affect the grazing pressure of herbivores such as sea urchins on seagrasses. Here, for the aim of evaluating the impacts of OA on organism interactions in the reef ecosystems, three sets of interaction studies were conducted. First, we evaluated the interaction between the seaweed mozuku Nemacystus decipiens and the coral Montipora digitata by co-culturing them under control and OA conditions to examine the potential of seaweed on mitigating the effects of OA on corals (Chapter 2). Seaweed mozuku is widely cultivated as a food source in Okinawa, but its effectiveness as a habitat refugia remains to be investigated. Results showed that the photosynthesis of seaweed N decipiens was not affected by OA, suggesting that OA will not have a positive impact on its productivity. Meanwhile, the calcification rate of coral M digitata was decreased under OA and the effect was further intensified by the presence of seaweed. This study suggests that the seaweed will not act as a potential habitat refugia for coral, but instead can exacerbate the negative effects of OA on coral calcification. For the second study, the coral M digitata was cultured on four different densities of seagrass Thalassia hemprichii under control and OA conditions to examine the potential of seagrass on mitigating the effects of OA on corals (Chapter 3). Seagrass beds have been proposed to provide habitat refugia for corals against OA due to their ability to create diel pH fluctuation. However, the magnitude of diel pH fluctuation in seagrass meadow may vary due to differences in seagrass density, which may affect their potential as habitat refugia. The result showed that the coral calcification was not affected by both OA and seagrass density. However, light calcification was higher at high seagrass density and this might compensate the lower dark calcification, especially under OA condition. This study suggests that seagrass may offset the effects of OA on corals, but do not provide habitat refugia to corals under OA. For the third study, we evaluated the interactions between the seagrass T. hemprichii and the sea urchin Tripneustes gratilla under OA or warming and as well as on both OA and warming to examine the herbivory of sea urchin on a seagrass (Chapter 4). This study showed that OA enhanced the photosynthetic rate of seagrass T. hemprichii which may potentially increase its productivity, whereas the sea urchin physiology including feeding rate was decreased particularly under a warming condition. This study suggests that OA might affect seagrass - sea urchin trophic interactions. Overall, this study shows that OA affects the organism interactions in the reef ecosystems. Marine macrophytes such as seaweed and seagrass might not provide habitat refugia for adjacent corals. This study also suggests that OA may modify top - down and bottom - up control of seagrass - sea urchin trophic interaction. The present study shows that understanding organism interactions is important for mitigating the impacts of OA on reef ecosystems.博士（学術）琉球大学University of the Ryukyu
KCC2の発現低下は、脛骨神経切断・縫合後の軸索の再生を加速し、運動障害を軽減する
Get PDFGamma‐aminobutyric acid and glycine (GABA/Gly) are predominantly inhibitory neurotransmitters in the mature central nervous system; however, they mediate membrane potential depolarization during development. These differences in actions depend on intracellular Cl‐ concentrations ([Cl‐]i), which are primarily regulated by potassium chloride cotransporter 2 (KCC2). After nerve injury, KCC2 expression markedly decreases and GABA/Gly mediate depolarization. Following nerve regeneration, KCC2 expression recovers and GABA/ Gly become inhibitory, suggesting that KCC2 reduction and GABA/Gly excitation may be crucial for axonal regeneration. To directly clarify their involvement in regeneration, we analyzed recovery processes after tibial nerve severance and suturing between heterozygous KCC2 knockout mice (HT), whose KCC2 levels are halved, and their wild‐type littermates (WT). Compared with WT mice, the sciatic functional index—indicating lower limb motor function—was significantly higher until 28 days after operation (D28) in HT mice. Furthermore, at D7, many neurofilament‐positive fibers were elongated into the distal part of the sutured nerve in HT mice only, and myelinated axonal density was significantly higher at D21 and D28 in HT animals. Electron microscopy and galanin immunohistochemistry indicated a shorter nerve degeneration period in HT mice. Moreover, a less severe decrease in choline acetyltransferase was observed in HT mice. These results suggest that nerve degeneration and regeneration proceed more rapidly in HT mice, resulting in milder motor dysfunction. Via similar microglial activation, nerve surgery may reduce KCC2 levels more rapidly in HT mice, followed by earlier increased [Cl‐]i and longer‐lasting GABA/Gly excitation. Taken together, reduced KCC2 may accelerate nerve regeneration via GABA/Gly excitation.博士（医学）琉球大学University of the Ryukyu
護岸背後盛士における吸い出し現象の生物学的抑制技術に関するシミュレーション研究
Get PDF埋め立て土砂の外部流出＿（吸い出し）を防止するために敷設される防砂シートの損傷に起因した地盤陥没現象が多数報告されており, 例えば, 那覇空港の緑地帯では,供用開始後1年足らずで複数の陥没や空洞の形成が確認された. 防砂シートの代替に矢板を敷設する場合においても, 水が豊富な地中環境における矢板の腐食は必至であり, 土砂の外部流出を根本的に抑えることは難しい. 一方, 固化溶液を埋立地に直接注入して土砂を直接固めるエ法があり, 土砂流出の抑制に効果的であると知られているものの, セメントを主成分とする固化溶液には六価クロム等の有害物質が含まれていることから, 周辺環境への影響が懸念される. したがって, 周辺環境への影響を最小限に抑えつつ, 土砂流出を根本的に抑える新しい技術の開発が喫緊の課題となっている. 加えて, 埋設されたシートを施工後に視認することは困難であることから, シートの劣化状態を共用時であっても評価できるツールの開発が求められる.本論文では, シミュレーション工学の観点から防砂シートの劣化に起因した護岸背後盛土における吸い出しメカニズムの解明し環境保全型の盛土保護技術について考究した.防砂シートの劣化は, シートを構成するポリエチレンテレフタレート(PET)のアルカリ加水分解反応が主因であると考えられている. そのため, シートの加水分解反応を反応拡散理論にて数理モデル化し, 本モデルを実装したシミュレーションと実験値との比較解析を通じて本モデルの妥当性を検証した. 結果として, 本モデルにより得られた解は実験結果とおおむね一致することが分かった. また, 常温を想定した解析から, 実環境においても加水分解反応によりシートが劣化する可能性を見出した. 次に, 防砂シートの劣化度合いと吸い出しの関係を明らかにするために, 差分法ベースのシート劣化シミュレータと個別要素法ベースの吸い出しシミュレータを連成できるシミュレータを開発した. 具体的には, 個別要素法の境界粒子と差分法の格子の空間座標を一致させ,格子点上のPET濃度を境界粒子に直接あてはめることで,シート劣化が土砂の流出に直接関与するようにした. 結果として, 埋め立て土砂の流出量と流出速度は劣化度合いに大きく依存することが分かった. 次に, 環境保全型の地盤改良技術であるMICPの吸い出し問題に対する抑制効果について検討した. 具体的には, MICPによる地盤修復プロセスを評価可能なシミュレータを開発し, 繊維材混合土におけるMICPの効果を実験およびシミュレーションを通じて明らかにした.結果として, 実験結果および解析結果はおおむね一致し, 固化物質は繊維材表面をコーティングするように析出することが確認した. したがって, MICPはシート繊維の保護や吸い出しの抑制できる可能性が示された. 最後に, MICPによる吸い出し抑制効果を検証するために, シートの劣化, 土砂の吸い出し, MICPによる修復プロセスを模擬した連成シミュレータを構築した. 結果として, 固化物質がシートの損傷部に析出することで吸い出しを抑制できる可能性があることが分かった. 最後に, 本研究の総括および妥当性を示し今後の展望を述べた．博士（工学）琉球大学University of the Ryukyu
再生可能エネルギーの統合と送電のための先進的HVDC技術
Get PDFHigh voltage direct current (HVDC) transmission technology is getting popular due to the suitable characteristics and advantages of efficient connection of large-scale AC grids and renewable energy in power systems, compared to high voltage alternative current (HVAC) that they have. As the 20thCentury progressed, several advancements in semiconductor technology led to the development of power electronics that could operate at grid and transmission-level voltages and a return to HVDC looked more attractive. In this thesis, firstly, a techno・economic analysis of HVDC transmission system has been done as a case study in Afghanistan. Through the study, the active, reactive and corona losses are calculated as the technical parameters and the discounted cash flow (DCF) method is deployed to economically compare both HVAC and HVDC technologies. The outcomes of the work disclose that the implementation of this transmission project is techno・economically feasible and can result in the energy security and economic stability of the country. Secondly, as fault is a considerable challenge in HVDC transmission system, a new and surge・less solid・state direct current (DC) circuit breaker is proposed to clear the short・circuit fault. The topology and different operation modes of the proposed breaker are discussed. The main purpose is to realize the fast interruption and surge-voltage and over-current suppression capability analysis of the breaker during the fault. To verify the effectiveness of the proposed circuit breaker, two other types of recent surge-less solid-state DC circuit breakers are compared in terms of surge-voltage and overcurrent suppression. The obtained simulation results reveal that the fault current is interrupted in a very short time and the surge-voltage and over-currentacross the proposed breaker is considerably reduced compared to other topologies. Next, as in practical HVDC transmission systems, the ct1rrent is considerably high when a fault occurs in the dc line. This current must be limited to make its blocking techno・economically feasible by dc circuit breakers. A new hybrid fault current limiter (HFCL) is proposed that is placed and examined together with a hybrid resonance type dc circuit breaker in a fourterminal modular multi-level converter(MMC)-based HVDC transmission system. HFCL consists of an inline fast mechanical switch and parallel fault current limiting inductor (FCLI) with a series thyristor・controlled resistor. Since the FCLI is placed offline and on the other hand, in regular operation. the thyristors are in the off mode which prohibits the losses of conventional inline FCLI in the literature. The operation principle and design theory are presented. It is verified from simulation results that by applying the proposed fault current limiter, the peak of fault current is extremely limited, and the dc breaker obtains the efficient current blocking. Finally, the work of the thesis is summarized and the scopes of future research have been addressed. The simulation tool used for verifying the effectiveness and superiority of proposed breaker and FCL is MATLAB Simulink software.博士（学術）琉球大学University of the Ryukyu
Research on a method of restoring the corrosion protection performance of corroded steel bridges by applying low-temperature, low-pressure metal spraying
Get PDF我が国では，1960年代の高度経済成長期に膨大に建設された社会基盤施設の経年劣化が顕著になってきており，持続可能な社会基盤施設の維持管理が重要な課題の一つとなっている．その社会基盤施設の一つである鋼橋の維持管理上の課題として鋼材腐食があり，特に桁端部では，厳しい腐食環境下にあるため早期に激しく発生しやすい特徴がある．さらに，桁端部の構造的特徴で部材交差部が多数存在することや，部材の位置関係により狭陰な空間となるため，品質が確保された防食対策を行うことが難しい部位が存在している．桁端部腐食により孔食や部材破断への進展が懸念され，鋼橋の安全性に影響を及ぼす支点部の座屈やウェブのせん断座屈を引き起こすリスクが高まるしたがって，厳しい腐食環境下で狭陰な作業空間において高耐久な防食性能を発揮できる技術開発が望まれている．本研究では，簡易な素地調整下でも強固な密着力を有する金属皮膜の形成が期待できる低温低圧型金属溶射技術(ColdSpray技術，以下CS)に着目し，鋼橋の防食技術へ応用した研究開発を実施した．本研究のCSによる鋼橋防食技術の研究開発コンセプトは，さびの除錆と防食皮膜の両性能を同時に実現する技術開発を目指している．これを実現するために，ブラスト処理材に使用されるアルミナ粒子と鋼材よりも卑な電位を持ち犠牲防食作用が期待される亜鉛粒子を混合した混合粒子を使用している．CSによる防食の研究事例は，いくつか報告されているが，残存さび上に成膜されたCS皮膜に対する，密着メカニズムやその防食特性については研究事例が無く，その有用性を解明する課題がある．さらに，既設鋼橋の現場施工で適用された事例の報告もない．したがって，本技術を実橋へ実装するためには，既設鋼橋の現場特有の施工条件に対する適用性や，桁端部の厳しい腐食環境下での耐食性について検証する課題もある．そこで，本研究では，残存さびを有する鋼材に対するCS皮膜の基本特性を明らかにする基礎実験を行った．初めに，新材や腐食材の様々な表面状態の鋼材上に，亜鉛とアルミナを混合した粉体によるCS防食皮膜を成膜し，SEMによる断面観察を行うことで，成膜メカニズムを明らかにした．そして，ZnとAlz03の配合比率をパラメータとして成膜厚や密着力の評価を行うことで，さび面へのCS防食皮膜の成膜性能を明らかにした．さらに，複合サイクル腐食促進試験やCS防食皮膜断面の緻密性評価を行うことで，さび面上のCS防食皮膜の防食特性を明らかにした．次に，実構造物特有の施工空間や施工能率などの施工条件を考慮して成膜したCS防食皮膜について，基礎実験で得られた基本特性を基準として評価を行うことで，施工制約条件やCS施工適用条件を明らかにした．そして，実際に腐食損傷が発生している鋼橋の桁端部に対して実施工を行い現場施工性の確認することで，実橋への現場適用性を明らかにした．さらに，モニタリング調査を行い，防食効果の継続性や有効性を検証することで，実環境下における耐食性を明らかにした．In Japan, the aging of social infrastructure constructed in vast numbers during the period of rapid economic growth in the 1960s has become increasingly noticeable, and sustainable maintenance and management of social infrastructure has become one of the most important issues. Corrosion is one of the maintenance and management issues for steel bridges, which are one of the social infrastructure facilities, and is particularly likely to occur early and severely at girder ends due to the severe corrosion environment. In addition, the structural characteristic of the girder ends make it difficult to apply good quality corrosion protection because of the many member intersections and the narrow space created by the location of the members. The tendency for premature recorrosion to occur at such points is also a maintenance challenge for steel bridges. Girder end corrosion may lead to pitting corrosion and member rupture, which may cause buckling at the fulcrum and shear buckling of the web, both of which can affect the safety of steel bridges. Therefore, there is a strong need to develop highly durable corrosion protection technology in narrow workspaces under severe corrosive environments. In this study, research and development of anticorrosion technology for steel bridges was conducted focusing on low-temperature, low-pressure metal spray technology (cold spray technology, hereafter CS), which is expected to form metallic coatings with strong adhesion even under simple substrate preparation. The research and development concept for corrosion protection of steel bridges using CS technology in this study aims to develop a technology that simultaneously achieves both rust removal and corrosion protection coating performance. To achieve this, alumina particles, which are used in blast treatment materials, were mixed with zinc particles, which have a lower potential than steel and are expected to act as a sacrificial corrosion inhibitor. Although there have been several reports on CS corrosion protection, there have been no studies on the adhesion mechanism and corrosion protection properties of CS films deposited on residual rust, and there is a need to clarify its usefulness. Furthermore, there are no reports of cases where the material has been applied to the on-site construction of existing steel bridges. Therefore, there is an issue of verifying the applicability to the site-specific construction conditions of existing steel bridges and the corrosion resistance of girder ends under severe corrosive environments. In this study, basic experiments were conducted to clarify the basic properties of CS coatings on steel with residual rust. First, CS anti-corrosion coatings were deposited on various surface conditions of new and corroded materials, and SEM cross-sectional observations were performed to clarify the deposition mechanism. The performance of CS anticorrosion coatings on rust surfaces was clarified by evaluating film thickness and adhesion strength based on the ratio of Zn and Al2O3. The corrosion protection properties of the CS anticorrosion coating on the rust surface were clarified by conducting cyclic corrosion acceleration tests and evaluating the densification of the cross section of the CS anticorrosion coating. Next, the CS anti-corrosion coatings were evaluated based on the basic characteristics obtained in the basic experiments, taking into account the construction conditions such as construction space and construction efficiency specific to actual structures, to clarify the construction constraints and CS application conditions. CS corrosion protection was applied to the girder ends of steel bridges where corrosion damage was actually occurring. The applicability to actual bridges was clarified by confirming the field applicability. In addition, long-term monitoring surveys were conducted to verify the continuity and effectiveness of the corrosion prevention effect, and the long-term corrosion prevention performance under actual conditions was clarified.博士（工学）琉球大学University of the Ryukyu