1,721,022 research outputs found
Bipolar Molecular Outflows in L1551 IRS5 and L1551 NE Protostellar Systems
No full textL1551分子雲為一低質量恆星形成區域，且為距太陽系最近的恆星形成區域之一。觀測上顯示，此區域中存在許多不同演化階段的原恆星系統，意味著長時間以來，此區域皆為一活躍的恆星形成區域。我們使用次毫米微波陣列(SubMillimeter Array, SMA)觀測L1551分子雲中兩個原恆星系統—L1551 IRS5及L1551 NE—周圍區域的一氧化碳分子譜線，以探測該原恆星分子雙極噴流的物理性質。L1551 IRS5是L1551分子雲中輻射熱光度最強的多重原恆星系統，且擁有巨大的分子雙極噴流。其大尺度分子雙極噴流呈東北(紅移端)—西南(藍移端)方向，各自向外延伸約1.5秒差距。我們藉由角分辨率約4角秒(約560天文單位) 的CO(2—1)分子譜線影像探測此噴流之中心約4000天文單位的區域。在此中心區域，我們分辨出三個不同噴流結構：(1) X形結構，自中心向外延伸約20角秒，其方位角與大尺度噴流相近，且有相同之紅藍移方向。此X形結構為中央高速噴流所開之錐狀空腔之臨邊增亮現象。(2) S形結構，自中心向外延伸約10角秒，其方位角與大尺度噴流相近，但紅藍移方向相反。此S形結構為新發現的分子雙極噴流。S形結構以及視線方向速度的變化顯示此噴流正在進動。此噴流可能是被此系統中一新發現的原恆星所驅使，且其環星盤與鄰近的原恆星有強烈潮汐作用而使環星盤進動。(3) 中央緊密結構，自中心向外延伸約1.4角秒，其方位角與大尺度噴流相近，且有相同之紅藍移方向。此結構為原恆星系統中心近期受中央高速噴流所驅使的分子氣體。L1551 NE是L1551分子雲中輻射熱光度次強的多重原恆星系統，位於L1551 IRS5東北方2.5角分處，為L1551 IRS5的巨大分子雙極噴流影響。L1551 NE所驅使的分子雙極噴流尚未被確認。我們利用角分辨率約0.8角秒(約110天文單位)的CO(3—2)分子譜線影像探測此系統周圍較溫暖之氣體，首次成功拍攝下此系統分子雙極噴流的電波波段影像。此分子雙極噴流自中心延伸僅約8角秒，且其動力學年齡極短，顯示此為一年輕的原恆星系統，但其質量明顯小於其他位於同樣演化階段的分子雙極噴流。此現象指出，L1551 NE鄰近區域的氣體分子已被L1551 IRS5的強烈噴流掃除。另外，我們的一氧化碳分子譜線影像與紅外光觀測中之扇形反射星雲吻合，但卻未發現在紅外光波段同樣出現的束狀噴流。此現象暗示L1551 NE系統中的兩原恆星處在不同演化階段，驅使扇形反射星雲的原恆星較早演化或演化較快，其噴流將鄰近區域之分子氣體掃除。較晚演化的原恆星之束狀噴流驅使之分子噴流密度因此較低而無法觀測。L1551 molecular cloud is located at a distance of ∼ 140 pc, in the constellation of Taurus, and is one of the nearest active low-mass star formation region. We used the Submillimeter Array (SMA) to image the CO molecular outflows from two multiple protostellar systems in L1551 region, L1551 IRS5 and L1551 NE, at an arcsecond angular resolution. We observed the CO(2–1)ine emission in L1551 IRS5 system. First, we imaged the base of the outflowavity and found signatures for multiple outflow events. We also foundewly entrained gas in the cavity, indicating that the ambient gas is stillalling into the cavity. Second, we discovered a precessing outflow, whichas an opposite inclination to it of L1551 IRS5 large-scale outflow. Thisewly-found component is likely driven by the recently proposed candidatehird protostar in L1551 IRS5 system. For the L1551 NE binary system, wehows a clear bipolar structure of its molecular outflow at the first time. Weaw a cavity-like structure corresponding to the reflection nebula at infreredavelength, but no jet-like structure, which is also seen at infrared. It isikely that, one of the binary launched the outflow first and cleaned ambientas away, thus the outflow from another protostar entrained less gas and isnable to be detected. The mass of L1551 NE outflow and the dusty envelopere both by orders of magnitude smaller than those of other Class 0 protostars,uggesting the ambient gas has been swept up by the strong outflowrom L1551 IRS5.List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . iiist of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Star Formation 1.1 Star Formation Environment . . . . . . . . . . . . . . . . . . . 1.2 Star Formation Processes . . . . . . . . . . . . . . . . . . . . . 2.3 Classification of Protostars . . . . . . . . . . . . . . . . . . . . 4.4 Molecular Outflows in Protostellar Systems . . . . . . . . . . . 5.4.1 Outflow Launching Mechanisms . . . . . . . . . . . . . 6.4.2 Models for Molecular outflows . . . . . . . . . . . . . . 7.4.3 Physical Properties of CO Outflow . . . . . . . . . . . 13 INTRODUCTION TO L1551 STAR–FORMING REGION 18.1 L1551 Dark Cloud . . . . . . . . . . . . . . . . . . . . . . . . 18.2 L1551 IRS5 Protostellar System . . . . . . . . . . . . . . . . . 19.3 L1551 NE Protostellar system . . . . . . . . . . . . . . . . . . 24 Observation of L1551 IRS5 Protostellar System 32.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.2 Multiple Bipolar Molecular Outflow from the L1551 IRS5 Protostellarystem . . . . . . . . . . . . . . . . . . . . . . . . . 34.3 Mechanism of Jet Bending . . . . . . . . . . . . . . . . . . . 35 Bipolar Molecular Outflow from the L1551 NE Protostellarystem 38.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38.2 Observations and Data Reduction . . . . . . . . . . . . . . . 39.3 0.8 mm Continuum Emission . . . . . . . . . . . . . . . . . . . 42.4 CO(3–2) Line emission . . . . . . . . . . . . . . . . . . . . . . 47.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54.5.1 Impact from IRS5 outflow . . . . . . . . . . . . . . . . 54.5.2 Different Age of the Binary Protostars . . . . . . . . . 55 Future Work 58.1 L1551 IRS5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58.2 L1551 NE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61ibliography 64 Missing Flux Resulted form the Visibility Coverage 7
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
- …
