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Eu化合物における重い電子状態の数値繰り込み群による研究
Get PDFIn this paper, we report the theoretical results regarding unconventional heavy fermion (HF) states realizable in Europium (Eu) systems and related materials. Many rare-earth and actinide-based compounds exhibit magnetic ordering at low temperatures. In particular, the electron state of Gd and Eu systems is characterized by a large pure spin S=7 /2, and thus magnetic ordering becomes quite stable. However, recently, a HF behavior has been observed in Eu systems, implying a different mechanism from the conventional HF formation. It is also interesting that the HF is realized in the intermediate valence state in the Eu system. Many Eu systems indicate the valence fluctuation between Eu2+ and Eu3+. In the case of divalent, as mentioned above, it is difficult for the HF state to surpass magnetic order. Also, when the c-f hybridization process is restricted, the 4f spin cannot be completely screened out, and a non-magnetic state does not form. On the other hand, in the case of trivalent, the ground state of 4f electrons is a non-magnetic singlet state, and thus the Kondo effect does not occur. Therefore, the Kondo effect in the intermediate valence state of the Eu ion is highly nontrivial. To investigate the Kondo effect and the valence fluctuation in the Eu system, we introduced the effective Eu-based impurity Anderson model (Eu-IAM) considering the valence fluctuations of Eu systems and analyzed it by using numerical renormalization groups. From the results, it was clarified that a non-magnetic ground state is always formed. Furthermore, it was quantitatively clarified that the formation of nonmagnetic states deeply involves small spin-orbit coupling which is unique to Eu systems. Next, in order to analyze the HF state confirmed by Eu-IAM more closely, we derived an effective model in the vicinity of Eu2+ state, which is the S = 7/2 underscreening (US) Kondo model with a crystal field△S/2 derived from valence fluctuations. The NRG results show that the ground state exhibits a strong coupling fixed point similar to the usual Kondo singlet. However, it was found that reducing the crystal field remarkably increases the effective mass, and furthermore, applying a magnetic field also causes a mass enhancement, revealing properties contrary to normal HF states. We consider that such anomalous behavior can be caused by the ferromagnetic Kondo coupling which occurs between the US 4f state and the conduction electron. Based on this consideration, we analyzed the renormalized parameters of a weakly anisotropic ferromagnetic Kondo model. Then, we proposed a hierarchical Kondo effect as the origin of the formation of the nontrivial ground state.博士（理学）琉球大学University of the Ryukyu
変異語用論の視点から見た慰め行動
Get PDF本研究は、親しい間柄で行われる日本語の慰めの発話行為に焦点を当てて行われた。この為、主たる変数、即ち場面の深刻度、性別、地域（主に宮城県及び沖縄県）によるあらゆる差異を探り、エスパニャ語との比較を含めることで、慰め行動を多側面的に分析する。データ収集は、談話完成課題（ＤＣＴ）によって日本語とエスパニャ語の第一話者の間でオンラインで行われた。参加者は自分の親友を想像しながら、財布を落とす事件から第三者の死別まで、親友が直面する深刻度の異なる８つの慰め場面において参加者自身がその場面でどのように回答若しくは行動するかを記入することが求められた。データ分析には、発話行為に関する６つの範疇（指動型、拘束型、表出型、演述型、宣言型、質問型）及び抜け出し（沈黙等）によって形成された統一的な枠組みに分類した後、各範疇の使用頻度や総合的な発言性に焦点を当てて実施した。結果に関しては、場面の深刻度のみによる発話行為や発言性に対する有意な差は観察できず、聞き手が抱えている問題や置かれている場面の種類の方がより大きな影響を及ぼすと思われる。主たる結果としては、発言性の視点からはエスパニャ語話者組と沖縄県組は、全日本語話者、宮城県組に比べて発言性が高く、個々の発話行為に関しては、宮城県組による表出行為の使用頻度が著しく高かったことが窺える。本研究の様々な観測や結果を踏まえ、変異語用論や慰めの言語行動に関する更なる研究に対し、慰め発語行為を発語媒介行為として扱い、統一的な分析枠組みを提供し、地域や他の変数の導入が与える価値が明らかになったと考えられる。La presente investigación se centra en el acto de habla del consuelo en japonés entre amigos cercanos usando diferentes variables, a ser grado de severidad de la situación, género, región de Japón (principalmente las prefecturas de Miyagi y Okinawa) y una comparación con el acto de habla de la consolación en español. El estudio fue llevado a cabo en línea mediante una tarea de completación del discurso (DCT) con hablantes con japonés o español como primera lengua. Los particiapantes imaginarían primero a un amigo cercano en ocho situaciones con diferentes grados de severidad (e.g., pérdida de una billetera, muerte de un tercero, etc.) y escribir cómo responderían o actuarían. Las repuestas fueron analizadas y categorizadas de acuerdo con un marco formado por seis tipos de actos de habla (directivos, comisivos, expresivos, asertivos, declarativos y rogativos) además de la opción de no participar (p. ej., permaneciendo en silencio). Estos datos luego fueron analizados con especial interés con respecto a la cantidad de uso de estrategias en general y en particular. Los resultados muestran que el grado de severidad de las situaciones por sí solo no produjo diferencias significativas sugiriendo que el tipo de problema o de situación desempeñan un papel más representativo. Los resultados principales indican diferencias significativas en cuanto a que los participantes de los grupos de hispanohablantes y de la prefectura de Okinawa optaron por hablar más que el grupo de la prefectura de Miyagi. Además, los participantes de Miyagi presentaron un mayor uso de actos de habla expresivos. Con base en las observaciones y resultados de este estudio, se espera que el adoptar un marco analítico unificado, tratar al acto de habla de la consolación como acto perlocutivo e incluir otras variables y regiones contribuya al estudio de la pragmática variacional y del acto de habla de la consolación.The present research approaches the Japanese speech act of comforting among close friends from different variables, namely, degree of severity of the situation, gender, region within Japan (mainly Miyagi and Okinawa prefectures), and a comparison with the speech act of comforting in Spanish. The study was carried out by an on-line discourse completion task (DCT) among Japanese and Spanish first language speakers. The participants would imagine a close friend in eight different situations with varying degrees of severity (e.g., losing a wallet, death of a third party, etc.) and write how they would reply or behave. Data was analyzed and categorized according to a unified framework using six types of speech act (directives, commissives, expressives, assertives, declaratives and rogatives) as well as the option of opting out (e.g., remain silent). The responses were later analyzed with especial attention to the usage rate of specific strategies as well as the overall degree of utterability. In relation to results, degree of severity by itself did not seem to affect speech act choice or utterability in a significant way, suggesting the type of problem or situation faced by the hearer plays a bigger role. The main results include differences on degree of utterability, notoriously lower in Miyagi participants, while higher in Spanish speakers and Okinawa residents. Miyagi participants also exhibited a higher use of expressive speech acts. Based on the observations and results along this study, adopting a unified analytical framework while approaching comforting as a perlocutionary act and including other variables and regions are thought to contribute to the study of the speech act of comforting and variational pragmatics.博士（学術）琉球大学University of the Ryukyu
接触場面と母語場面のスピーチレベル運用及び相互行為の比較 -スピーチレベル運用によるコンテクスト形成に着目して-
Get PDF本研究では、日本語コミュニケーションにおいてスピーチレベルが非対称的に運用される現象に着目し、接触場面と母語場面における相互行為、及びそれによって形成されるコンテクストの特徴について比較考察を行った。さらに接触場面のスピーチレベル運用に影響を与える言語的・文化的要素について解明することを試みた。 分析対象は、場の性質や対話者間の関係(すなわち年齢差、社会的地位の差、性差などの要因)を考慮したスピーチレベル運用によって、コンテクスト化が活発に行われる成人二者間の初対面会話とし、母語場面と接触場面の会話を収集した。研究手法及び比較考察の理論的枠組みは、異文化間コミュニケーションにおけるコンテクスト化のプロセスや会話の推論についての解釈的枠組みを打ち立てたJohn Gumperz(1982)の「相互行為の社会言語学」、及びコンテクストを「言語使用者が継続して携わっているところの、ダイナミックに変化するコミュニケーションの状況や経験を現在進行形で表すもの」と捉えるTeun A、 Van Dijk(2008・2009)の「コンテクストモデル論」を拠り所とした。 分析の結果、母語場面における同性間の会話では、初対面であっても年齢差や立場の差が意識されやすく、スピーチレベルの掛け合いや非対称的なスピーチレベル運用が生じやすいことが分かった。異性間の会話では年齢差やスタンスの差の影響は顕著ではなく、初対面という心理的距離と性差がスピーチレベル運用を左右する決定的な要因であることが明かになった。一方、接触場面会話における非対称的なスピーチレベル運用の様子は母語場面とは異なり、必ずしも年齢差や性差、スタンスの差に起因するわけではなかった。その背景には、伝わりやすいことば遣い、分かりやすい日本語、助け舟といった仕方で顕在化する対話者間の言語的・認識的地位の差、及び対等なスタンスへの志向、母語話者と非母語話者という成員カテゴリー、非母語話者の日本語能力やスピーチレベル運用の仕方といった異文化性に応じて変容したコンテクストモデルがあることが示された。さらに、非母語話者のスピーチレベル運用についての解釈は、非母語話者の言語文化的背景の影響を受ける一方で、個々人のコンテクストモデルによって多種多様であることが明かになった。また、スピーチレベル運用についての解釈の相違が異文化間のミスコミュニケーションを引き起こす要因になり得るということが示唆された。博士（学術）琉球大
ヤイトハタの環境感受・制御機構の解明に基づく成⻑促進技術の開発
Get PDFEnvirorunental factors play a pivotal role in shaping the growth and reproduction patterns of fish species, making them crucial considerations in aquaculture. This study focuses on the Malabar grouper, a highdemand species in Asian markets. The research investigates the impact of specific envirorunental factors, specifically light wavelengths and salinity, on the growth and endocrine systems of Malabar grouper juveniles.
In the first study, target genes and proteins in the Malabar grouper were identified, providing a foundational understanding for further research. Visual opsins were found not only in the retina but also in the brain, hinting at their potential connection with processes related to growth and reproduction.
The second study delved into the perception of light wavelengths (632run red, 519run green, and 46 5run blue), revealing that blue light activated photoreceptors in light-sensitive organs, stimulating growth-related hormones. Specifically, blue light exposure resulted in significant growth enhancement compared to red light by activating the growth of the endocrine axis and its interaction with orexigenic regulator neuropeptide Y.
The third study explored the effect of salinity on osmoregulation and growth performance. Fish reared at lower salinity (5psu and llpsu) exhibited higher growth rates than 22 psu and 34psu salinities, likely due to reduced energy consumption for respiration and improved food-conversion efficiency. The growth axis but not appetite was stimulated at low salinity, enhancing growth performance in Malabar grouper juveniles.
The fourth study investigated the synergistic effects of light wavelengths and salinity on growth performance. Juveniles reared under various experimental conditions utilizing LEDs with different salinities (llpsu blue - 463run, llpsu red - 6 23run, 34psu blue - 463nm, and 34psu red - 623run) over a two-week period. Blue light, especially at lower salinity, significantly enhanced body weight and condition factor. The interplay between blue light and salinity demonstrated consistent growth benefits, emphasizing the complexity of these interactions in aquaculture settings.
This research underscores the intricate relationship between environmental factors and the growth of Malabar grouper juveniles. The findings emphasize the necessity of considering specific light wavelengths and salinity levels in optimizing aquaculture conditions. This insight not only contributes to sustainable Malabar grouper cultivation but also provides valuable knowledge applicable to the cultivation of other marine species, paving the way for more effective and environmentally conscious aquaculture practices.博士（学術）琉球大学University of the Ryukyu
歴史的市街地の土地利用及び伝統的な住宅の変容に関する総合的な研究：アフガニスタンカンダハールのアフマド・シャヒ市の事例研究
Get PDFKandahar, situated in the southwestern region of Afghanistan, was initially the capital and now stands as the country's second-largest city. Over the past two decades, it has undergone significant urban growth and a drastic population increase. Ahmad Shahi is an old city which is located in the north of Kandahar province and famous for its traditional houses and urban fabric. The area was an arbitrary expansion in the lack of a master plan and caused a huge transformation in the land use from residential to commercial which certainly affected the historic architecture of the area. This study comprehensively analyses the land use transformation and preservation status of the area, utilizing historical maps from 1839 and satellite images from 2011 and 2018. Critical insights into the urban morphology, cultural heritage, and socio-economic changes within the old city have been found through accurate data acquisition, digitization, and spatial analysis. Firstly, the accuracy of the 1839 historical map by Fraser Tytler was verified through an accurate process of geo-referencing and overlaying with old map and satellite images. The results demonstrated that the 1839 map remains remarkably accurate, with minor scale differences that do not significantly impact its reliability. The analysis revealed several critical trends in land use transformation within the Ahmad Shahi old city. Notably, there has been a significant increase in building coverage ratio (BCR) by 12% from 1839 to 2011 and 5% from 2011 to 2018. Furthermore, there are several traditional old houses in the Ahmad Shahi old city that have experienced significant transformation in the last three decades. These changes are the result of various factors, including rapid population growth and expansion. According to analysis 306 traditional courtyard houses (6.49%) have been demolished and transformed to commercial lots, the average area of the houses has decreased from 2054 m2 to 251 m2 regardless of the master plan and as well the roads and streets have taken a zigzag, and narrow shapes also which have increased in number and length from 35 km to about 70 km. These circumstances have undoubtedly affected both the environmental and social aspects of the residents' lives as well as altering the characteristics of the area. These changes happened as a result of the land value, close to the CBD and transition of the family typology, and some other minor factors. Furthermore, this research evaluates the significance of traditional courtyard houses, with a special focus on their typology, building age, roof types, outdoor activities, and their living lifestyle. Finaly, to address these issues, it is essential that urban development and planning authorities prioritize the preservation plans, allocate sufficient resources, and engage with local experts and organizations to preserve the city's unique historical and cultural identity. Failure to do so may result in further loss of historical assets and irreversible changes to the city's landscape.博士（工学）琉球大学University of the Ryukyu
熱帯性スズメダイ類のルリスズメダイ雌における成長と生殖の連動性に関する生理学的研究
Get PDFPhotoperiod and temperature are known as proximate determinants for initiation and termination of gonadal activity in fish. Because these conditions may change daily or seasonally, the synthesis and release of hormones and peptides from the HPG axis become rhythmic. The present study aimed to understand possible involvement of the above mentioned physiological mechanism in growth - reproduction network in the sapphire devil. The present study revealed a nocturnal increase in gh transcription in the brain, suggesting that GH synthesis is regulated in a circadian manner. Fish reared in melatonin-containing water exhibited significant increases in the transcription levels of gh, igfl, and ig/3 in th brain and igfl in the liver, suggesting that the GH/IGF pathway is regulated in a circadian manner and acts as a "nocturnal driver" of growth. Therefore, melatonin might be directly or indirectly involved in GH synthesis in the pituitary gland. The transcript levels of iodothyronine deiodinases (dio2 and dio3), which catalyze the conversion ofT4 to triiodothyronine (T3) or reverse T3, varied daily with increases in the brain and liver during the photophase. Fish fed pellets containing T3, but not T4, displayed significant increases in gh, igfl, and ig/3 in the brain and igfl and ig/2 in the liver, suggesting that the circadian system is involved in the intercellular actions of the TH/IGF pathway, which might act as a "diurnal driver" of growth. These results suggest at least two possible roles for TH in regulating igf transcription: T3 stimulates GH synthesis in the pituitary gland to activate the GH/IGF axis, or T3 targets the liver to upregulate igf transcription. When fish with high food (HF) or low food (LF) were reared under suitable conditions of photoperiod and temperature during the non-reproductive season, ovarian development could be induced in the HF-fish, in which abundance of ig/3 increased in the brain, liver, and ovary. In conclusion, this study revealed that growth of the sapphire devil is regulated by the interplay of at least two endocrine networks, the GH/IGF-1 and TH/IGF-1 axes, which are regulated in a distinct manner throughout the day. The GH/IGF-1 axis is a "nocturnal driver" that is activated at night, whereas the TH/IGF-1 axis acts as a "diurnal driver" that is activated during daytime. Considering that melatonin controls the synthesis of hormones/peptides in both axes, the circadian system is presumably involved in oscillating and switching each growth driver.博士（理学）琉球大学University of the Ryukyu
琉球列島におけるサンゴ病変の動態を理解するための疫学的･病因学的アプローチ
Get PDFCoral diseases can severely impact both local and broader-scale reef ecosystems. Since 1975, there has been growing concern about coral disease research, particularly in tropical reef ecosystems. A Web of Science based meta-analysis conducted in November 2023 using the keywords “coral” and “disease” or “lesion” yielded 949 published results, with about 37 (4%) of these studies originating from Japan. Despite the crucial need to understand how coral lesions and diseases develop in the current Anthropocene epoch, research from sub-tropical areas like Japan remains inadequate (Fig. 1). This study aims to examine the dynamics of coral lesions by incorporating etiological and epidemiological approaches in the sub-tropical region of the Ryukyu Archipelago.
In Chapter 2, I investigated the temporal and spatial differences in the prevalence of current coral lesions across various sites in Okinawan reefs. We selected nine sites to conduct survey at four period, each representing different sea water temperatures characteristic of sub-tropical regions. Generally, Okinawan reefs are dominated by non-disease lesions, such as predatory scars (PRE) and epibiont organisms like serpulid worms, bioeroders (clams), and parasites (trematodes), which cause multi-focal spots (MFS). Disease lesions, such as white syndrome (WS) and black band disease (BBD), tend to occur at specific sites, indicating their localized nature. The prevalence of disease lesions increases when environmental factors fluctuate, particularly temperature changes. This suggests that external influences, such as site utilization combined with fluctuating temperatures, contribute to the rising prevalence of disease infections in corals.
In Chapter 3, I utilized etiological approaches to examine and identify the causative agent of white syndrome (WS), which leads to tissue necrosis and subsequent coral mortality. Using purposive sampling of corals infected by WS, I isolated and characterized the potential pathogen by conducting Koch’s postulate. An undescribed bacterium belonging to the genus Halomonas was identified as the etiological agent capable of inducing WS in three different coral species from Okinawan reefs (Fig. 2A). Among the corals tested, the genus Acropora was the most susceptible, compared to Montipora and Pachyseris. This chapter provides novel insights into the potential role of undescribed viable bacteria in causing WS that can be found in various corals in Okinawan reefs.
In Chapter 4, I aimed to address the current gap in describing viable potential pathogenic bacteria associated with WS-infected corals and ultimately examine the different number of bacteria across WS infected samples from different sites on Okinawan Island. We conducted purposive sampling at eight sites to isolate potential putative pathogens from active WS-infected corals using TCBS agar. Vibrios, a genus of bacteria known for their pathogenicity in various marine organisms, was the focus of this study. Despite their known pathogenicity, little is known about their abundance and characteristics in WS-infected corals from Okinawan reefs. Our findings consistently show a significantly higher abundance of Vibrio in WS-infected coral tissues compared to adjacent healthy tissues and surrounding waters (Fig. 2B). Interestingly, an undescribed Halomonas bacterium, similar to the one identified in Chapter 3, was found in the surrounding water at the Mizugama site. These results indicate that sites from the middle to the southern part of the Okinawa Island exhibit greater abundance of pathogenic Vibrio species in active WS-infected corals, suggesting that the presence of these pathogenic bacteria may lead to potential WS outbreaks in several coral genera around Okinawan Island.
In Chapter 5, I extended the epidemiological approach to examine and reveal the prevalence of coral lesions in national and quasi-national parks designated by the Ministry of Environment, Japan (MOE). Kerama National Park and Yoron Island were selected as study sites. The results showed a clear distinction in lesion prevalence characteristics between these two locations, suggesting that the utilization of the area may influence the types of lesions affecting the surrounding reefs (Dirgantara et al. 2023).
In Chapter 6, I further extend the epidemiological survey efforts to provide a better comparison of how marine national park zoning systems influence the characteristics of coral lesions. Karimunjawa National Park in Indonesia was used as the study site, where zoning management is applied by the Ministry of Environment and Forestry, Indonesia. Zoning classification (Tourism, Aquaculture, Core zone) indeed shows distinct differences in the prevalence levels and the variety of coral lesions. However, site localities (East vs. West) emerged as a more significant factor influencing these differences. The results indicated that site utilization, such as tourism and aquaculture, positively influences the prevalence of coral lesions in adjacent reef habitats.
This dissertation provides novel findings and a comprehensive examination of coral lesion dynamics, particularly coral diseases, in sub-tropical regions such as Okinawa Island and surrounding areas. A significant number of corals in the Ryukyu Archipelago are under the threat from various lesions (Fig.3A) and potential pathogenic agents. Although lesions and diseases are a natural part of ecosystem balance, actions such as mitigation efforts and enhancing coral fitness to prevent disease outbreaks should be prioritized, especially in sub-tropical areas where environmental fluctuations and increasing site utilization are prominent (Fig. 3B).博士（学術）琉球大学University of the Ryukyu