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三角格子反強磁性体NiGa_2S_4におけるスピン無秩序状態とその不純物効果
Get PDFこの論文は国立情報学研究所の電子図書館事業により電子化されました。修士論文(2005年度)磁気的長距離秩序を低温まで抑えることによって現れる新奇な量子状態への興味から、幾何学的フラストレーションを持つ系が最近注目を集めている。幾何学的フラストレーションは、反強磁性的に相互作用する三角格子を基調とした格子上で起こりうるが、その中で構造的に最も単純であり、盛んに研究されているものとして二次元三角格子反強磁性体が挙げられる。この系ではスピン無秩序状態の存在が理論的に予言されてから実験的、理論的にその基底状態を探るために様々な研究が試みられてきた。しかし現在では、理論的に120°構造を取って反強磁性秩序状態に落ち着くということで広く同意を得ている。一方で、スピン間のより高次な相互作用を考慮するとスピン無秩序状態が現れるという理論も存在する。実験的には、^3Heの薄膜や二等辺三角形の有機化合物など少数の系でのみ、スピン無秩序状態が観測されている。ところが、低温まで正確な三角格子を保ち続けるバルクの物質が存在しなかったため、このような物質を開発し、その基底状態を突き止めることが永年の課題であった。最近我々は、極低温まで三角格子を正確に保ち続けるバルクの物質、NiGa_2S_4の開発に成功した。この物質は低温まで磁気的長距離秩序が存在せず、スピン無秩序状態を実現している可能性が高い。我々はこの物質において現れる基底状態を突き止めるため、この物質自身とその不純物効果について研究した。NiGa_2S_4ではWeiss温度80Kという比較的大きな反強磁性的相互作用を持つにも関わらず、磁化率、比熱、中性子回折の結果から0.35Kまで磁気的長距離秩序が存在しない。そのかわりに10K以下で短距離相関を待ったギャップの無いスピン無秩序状態に入っていることが判明した。低温での比熱の温度の二乗に比例した振る舞いと絶対零度近傍での有限磁化率から二次元のスピン系におけるコヒーレントな線形分散が立ち上がっていることが示唆される。このようなNiGa_2S_4の基底状態の安定性を調べるため、Niサイトにおける非磁性不純物効果についても研究した。その結果、NiGa_2S_4で見られるコヒーレンスは不純物に対して非常に敏感であることがわかった。その他に、非磁性不純物に対しても比熱の温度の二乗に比例した振る舞いは消えず、物理量がWeiss温度だけで規格化できることから南部-Goldstoneモードの存在が考えられる。磁気的長距離秩序とバルクでの従来型のスピングラスフリージングが存在しないことから、NiGa_2S_4において新奇な対称性の破れが存在する可能性が高い。本論文ではこれらNiGa_2S_4の示す新奇な基底状態を説明する理論候補についても議論する
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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