1,721,256 research outputs found
A comparison of radar and optical remote sensing to detect cyclone-induced canopy disturbance in two subtropical forest landscapes
No full textOptical remote sensing is a tool frequently used to assess cyclone-induced forest disturbances. However, the frequent cloud cover limits the availability of optical data in cyclone basins. On the other hand, radar remote sensing is not affected by cloud cover and has been used to detect windthrows. Yet, the potential of radar sensing in monitoring cyclone damages of varying magnitudes across forest landscapes remains unclear. Here, we compared radar remote sensing to optical remote sensing of four cyclone disturbances in the Fushan Experimental Forest of northern Taiwan and the El Yunque National Forest in Puerto Rico using Landsat 8 and C-band Sentinel-1 satellite data. We analyzed the change in two optical vegetation indices, EVI (Enhanced Vegetation Index) and NDII (Normalized Difference Infrared Index), and three radar-based metrics, co- and cross-polarized backscatters (VV, VH) and their ratio (Canopy Development Index, CDI) after cyclone disturbances and during approximately the same periods of non-cyclone years. We assessed the improved temporal resolution permitted by Sentinel-1 constellation on the detection of forest canopy disturbance. Bootstrapped comparisons indicated that both optical and radar indices detected canopy change, but their correlations were not significant. Improved temporal resolution of CDI allowed to distinguish cyclone-induced canopy change from the phenological variation and even change by nearby cyclones. Although this, VV and VH backscatters responded more closely to cyclone disturbances than their ratio. Our results demonstrate that the C-band backscatter intensities can track cyclone-induced change of forest canopies, and provide an assessment of C-band capabilities to monitor cyclone disturbances
Diphosphate formation using cyanuric chloride or triisopropylbenzenesulfonyl chloride as the activating agents
No full textCorporate governance mechanisms and earnings management in transitional countries – evidence from Chinese listed firms
No full textThe objective of this thesis is to investigate whether the corporate governance practices adopted by Chinese listed firms are associated with the quality of earnings information. Based on a review of agency and institutional theory, this study develops hypotheses that predict the monitoring effectiveness of the board and the audit committee. Using a combination of univariate and multivariate analyses, the association between corporate governance mechanisms and earnings management are tested from 2004 to 2008. Through analysing the empirical results, a number of findings are summarised as below. First, board independence is weakened by the introduction of government officials as independent directors on the boards. Government officials acting as independent directors, claim that they meet the definition of independent director set by the regulation. However, they have some connection with the State, which is the controlling shareholder in listed SOEs affiliated companies. Consequently, the effect of the independent director’s expertise in constraining earnings management is mitigated as demonstrated by an insignificant association between board expertise and earnings management. An alternative explanation for the inefficiency of board independence may point to the pre-selection of independent directors by the powerful CEO. It is argued that a CEO can manipulate the board composition and choose the "desirable" independent directors to monitor themselves. Second, a number of internal mechanisms, such as board size, board activities, and the separation of the roles of the CEO and chair are found to be significantly associated with discretionary accruals. This result suggests that there are advantages in having a large and active board in the Chinese setting. This can offset the disadvantages associated with large boards, such as increased bureaucracy, and hence, increase the constraining effects of a large and resourceful board. Third, factor analysis identifies two factors: CEO power and board power. CEO power is the factor which consists of CEO duality and turnover, and board power is composed of board size and board activity. The results of CEO power show that if a Chinese listed company has CEO duality and turnover at the same time, it is more likely to have a high level of earnings management. The significant and negative relationship between board power and accruals indicate that large boards with frequent meetings can be associated with low level of earnings management. Overall, the factor analysis suggests that certain governance mechanisms complement each other to become more efficient monitors of opportunistic earnings management. A combination of board characteristics can increase the negative association with earnings management. Fourth, the insignificant results between audit committees and earnings management in Chinese listed firms suggests that the Chinese regulator should strengthen the audit committee functions. This thesis calls for listed firms to disclose more information on audit committee composition and activities, which can facilitate future research on the Chinese audit committee’s monitoring role. Fifth, the interactive results between State ownership and board characteristics show that dominant State ownership has a moderating effect on board monitoring power as the State totally controls 42% of the issued shares. The high percentage of State ownership makes it difficult for the non-controlling institutional shareholders to challenge the State’s dominant status. As a result, the association between non-controlling institutional ownership and earnings management is insignificant in most situations. Lastly, firms audited by the international Big4 have lower abnormal accruals than firms audited by domestic Chinese audit firms. In addition, the inverse U-shape relationship between audit tenure and earnings quality demonstrates the changing effects of audit quality after a certain period of appointment. Furthermore, this thesis finds that listing in Hong Kong Stock Exchanges can be an alternative governance mechanism to discipline Chinese firms to follow strict Hong Kong listing requirements. Management of Hong Kong listed companies are exposed to the scrutiny of international investors and Hong Kong regulators. This in turn reduces their chances of conducting self-interested earnings manipulation. This study is designed to fill the gap in governance literature in China that is related to earnings management. Previous research on corporate governance mechanisms and earnings management in China is not conclusive. The current research builds on previous literature and provides some meaningful implications for practitioners, regulators, academic, and international investors who have investment interests in a transitional country. The findings of this study contribute to corporate governance and earnings management literature in the context of the transitional economy of China. The use of alternative measures for earnings management yields similar results compared with the accruals models and produces additional findings
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
Study of Sugar Diphosphate Formation via New Monophosphate Coupling Reactions
No full text雙磷酸在生物體內扮演不可或缺的角色，以寡糖的生合成為例:生物體利用醣基轉移酶催化核苷酸醣和醣基受體形成一個新的醣苷鍵。在細菌細胞壁的生合成中，雙磷酸亦為構成Lipid I及Lipid II的重要部分。現今已知建構雙磷酸的步驟往往繁瑣且反應時間冗長，而偏低的產率更為阻礙合成核苷酸糖以及Lipid II衍生物的主要原因，因此，研究發展更有效率的雙磷酸合成方法是勢在必行。
我們發現2,4,6-三異丙基苯磺醯氯(2,4,6-triisopropylbenzenesulfonyl chloride)以及 2,4,6-三氯-1,3,5-三氮代苯(2,4,6-trichloro-1,3,5-triazine, cyanuric chloride)為合適建構雙磷酸之試劑，同時藉由添加溴化鎂作為螯合試劑以拉近兩單磷酸之距離進而增加了反應的效率。在我們模型反應中反應時間為5–48小時，轉換效率則為20–70%不等。另外我們也利用2,4,6-三異丙基苯磺醯氯合成了GDP-pyrrolidine類似物，並經由比較發現使用 2,4,6-三異丙基苯磺醯氯較傳統使用預先製備之morpholidate來的更有效率，這樣的策略為合成雙磷酸化合物提供了另一種選擇。Diphosphate is an indispensible starting material in organism. For example, oligosaccharides are synthesized from a sugar nucleoside diphosphate and a glycosyl acceptor by glycosyltransferases. Diphosphate moiety is also an important part in the structures of Lipid I and Lipid II in the process of bacterial cell wall formation. The approaches to the sugar nucleoside diphosphate and analogues of Lipid II are impeded by the diphosphate bond formation, which often requires tedious procedure and long reaction time, albeit in low yield. So, exploration of efficient methods to get diphosphate compounds is needed.
We found that 2,4,6-triisopropylbenzenesulfonyl chloride and 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride) were proper condensation reagents for diphosphate bond construction. By using MgBr2 as the chelating agent of the two monophosphate substrates, the coupling reactions proceeded efficiently. The reaction times are 5–48 hours to give conversion yields of 20–70% in our model reactions. We synthesized the GDP-pyrrolidine analogue, and found that using 2,4,6-triisopropylbenzenesulfonyl chloride is more efficient than the conventional method using morpholidate. This approach provides an alternative choice for diophosphate formation
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