1,721,173 research outputs found
Chen Lie algebras
No full textThe Chen groups of a finitely-presented group G are the lower central series quotients of its maximal metabelian quotient, G/G''. The direct sum of the Chen groups is a graded Lie algebra, with bracket induced by the group commutator. If G is the fundamental group of a formal space, we give an analog of a basic result of D. Sullivan, by showing that the rational Chen Lie algebra of G is isomorphic to the rational holonomy Lie algebra of G modulo the second derived subalgebra. Following an idea of W.S. Massey, we point out a connection between the Alexander invariant of a group G defined by commutator-relators, and its integral holonomy Lie algebra.
As an application, we determine the Chen Lie algebras of several classes of geometrically defined groups, including surface-like groups, fundamental groups of certain classical link complements, and fundamental groups of complements of complex hyperplane arrangements. For link groups, we sharpen Massey and Traldi's solution of the Murasugi conjecture. For arrangement groups, we prove that the rational Chen Lie algebra is combinatorially determined
Zhili sheng shang pin chen lie suo di yi ci diao cha shi ye bao gao shu /
No full textImprint date from preface.Mode of access: Internet
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
The role of CYR61 in chemotactic migration of gastric cancer
No full text胃癌死亡高居世界癌症死因第二位，主要原因為發生淋巴轉移、腹膜轉移和肝臟轉移，許多研究報導指出腫瘤轉移到特定的器官和腫瘤細胞本身表現chemokine receptor具有相關性，於是我們對於惡性度高的胃癌細胞是否表現特定的chemokine receptor 而促使腫瘤細胞移動能力的增強甚感興趣。先前在實驗室的研究中指出CYR61的表現和腫瘤細胞的惡性度有直接相關，發現胃癌病人的癌化組織中的CYR61蛋白表現量相較於正常組織高，而且淋巴轉移的病人CYR61表現也有提高表現的情形，但是對於CYR61如何調控胃癌細胞轉移的機制仍不清楚。因此我們對於高惡性度的胃癌細胞中，CYR61基因高表現是否和chemokine receptors具有相關性是值得我們進一步探討的。
我們以反轉錄聚合挴鏈鎖反應來篩選在穩定高表現不同程度CYR61的胃癌細胞株之中 chemokine receptor mRNA的表現，研究結果發現CXCR1和CXCR2會隨著CYR61高表現而有被大量調控表現的情形。並利用短暫轉殖不同劑量的CYR61 質體至AGS細胞中，也可偵測到CXCR1和CXCR2蛋白表現量的增加。
同時我們發現在不同的胃癌細胞株，CXCR1和CXCR2蛋白表現量和CYR61也呈現正相關的情形。而且以短暫轉殖antisense-CYR61質體進入高表現CYR61的MKN45 細胞，則抑制了CXCR1和CXCR2的蛋白表現量，這些結果指出CYR61在胃癌細胞中會誘導CXCR1和CXCR2的表現。另外在臨床的觀察也得知病人的胃癌組織中CYR61和CXCR1，CXCR2之間表現具有高相關的情形。我們更進一步探討CXCR1和CXCR2在CYR61高表現的細胞株中的功能性，我們發現重組蛋白質IL-8會誘導胃癌細胞進行非隨機的趨化性移動；當以中和抗體抑制AGS-CYR61細胞株的CXCR1和CXCR2活性時，則降低Cyr61高表現細胞的趨化性移動能力。除此之外我們發現內皮細胞會分泌IL-8蛋白以促進CYR61高表現的細胞進行趨化性移動，並且當以中和抗體抑制IL-8活性時，則AGS/CYR61細胞穿透內皮細胞的能力也隨之降低。因此我們推論內皮細胞可分泌IL-8促使CYR61高表現的胃癌細胞藉由CXCR1和CXCR2的表現進行趨化性移動，進一步穿透內皮細胞進入循環系統，在活體實驗利用雞胚胎模式也驗証我們的推論。最後我們在CYR61調控IL-8 receptors分子機制探討中，發現CYR61會透過受器integrin αVβ3的表現和Src激鋂的磷酸化，經由PI3k-Akt路徑的活化來調控CXCR1和CXCR2蛋白表現量。
綜合以上實驗結果顯示，在惡性度高的胃癌細胞中CYR61高度表現會誘導CXCR1，CXCR2表現，而且透過微環境中內皮細胞所分泌的IL-8和受器交互作用下，促使胃癌細胞依賴CXCR1和CXCR2的活性進行趨化性移動，其可能和腫瘤轉移的器官專一性是有相關聯的，因此期望CYR61調控CXCR1和CXCR2表現的機轉路徑在未來可以作為在活體實驗的治療標的。Gastric cancer is the second most common cause of cancer mortality worldwide, and development of metastasis to lymph nodes, liver, and peritoneum is responsible for the majority of cancer related death. Metastasizing cells must traverse the endothelial lining of the lymphatic or vascular systems in order to metastasize to distant sites. The previous study demonstrated that expression of CYR61 was correlated with tumor malignancy and lymph node metastasis in gastric cancer patients. It has been reported that tumor cells express specific chemokine receptors that may play roles in determining the sites of metastasis. We thus further investigated whether chemokine receptors are involved in CYR61-mediated cell migration.
Messenger RNA expression of chemokine receptors was screened by RT-PCR in several stable CYR61 transfectant clones. We found that the expression of CXCR1 and CXCR2 in mRNA in AGS/CYR61 cells was strongly higher than AGS parental cells, as well as protein induction level, suggesting that CYR61 up-regulated CXCR1 and CXCR2 expression in human gastric cancer cells. Moreover, clinical study showed that CXCR1 and CXCR2 expression was tightly correlated with CYR61 in gastric tumor patients by RT-PCR and immunohistochemistry analyses. Furthermore, recombinant human IL-8 enhanced the chemotactic migration of CYR61- overexpressing gastric carcinoma cells in a time and dose dependent manner, and consistently, neutralizing antibodies to CXCR1 and CXCR2 significantly attenuated chemotactic migration of IL8-stimulated gastric cells. It was found that IL-8 is the potent chemotactic factor from conditioned medium of HUVEC that induced chemotaxis of CYR61-overexpressing cells, enhanced transendothelial migration dependent on CXCR1, CXCR2 activation in Boyden chamber assay; and active CXCR1 and CXCR2 signalings are necessary for CYR61-overexpressing gastric tumor cells to intravasate monolayer endothelium, and then enter circulating system in chicken embryo model. Our results further delineated the molecular mechanisms that CXCR1 and CXCR2 induced by CYR61 through integrin αvβ3, which is requisite for activation of c-Src and subsequent PI3k-Akt signaling pathways.
Collectively, our present data suggested an association between constitutive expression of CXCR1, CXCR2 receptors and CYR61 in aggressiveness of human gastric carcinoma cells. It implicated that the IL-8 receptor system regulated chemotactic migration of gastric cancer cells, and may be involved in organ-specific gastric carcinomas metastasis and, hence, could be a potential target for therapy.English Abstract-------------------------------------------------------------------------------------i
Chinese Abstract--------------------------------------------------------------------------------------iii
Acknowledgement----------------------------------------------------------------------------------v
Contents---------------------------------------------------------------------------------------------vi
Chapter I Introduction-------------------------------------------------------------------------------1
1. Gastric cancer--------------------------------------------------------------------------1
2. Metastasis and Organ-specific: Seed-soil -----------------------------------------7
3. Chemokine Receptor----------------------------------------------------------------10
4. CYR61 (cysteine-rich protein) ----------------------------------------------------14
Study Purpose ----------------------------------------------------------------------------18
Chapter II Materials and Methods----------------------------------------------------------------19
Chapter III Results ---------------------------------------------------------------------------------28
1. CYR61 gene up-regulated chemokine receptors, CXCR1, CXCR2 expression-----------------------------------------------------------------------------28
2. CXCR1 and CXCR2 are expressed in correlation with CYR61 level in gastric cell lines and primary gastric adenocarcinomas------------------------30
3. IL-8 induced chemotactic migration of CYR61-overexpressing gastric cancer cells------------------------------------------------------------------------------------32
4. CYR61 overexpression enhanced gastric cancer cells transendothelial migration and was dependent on CXCR1 and CXCR2-------------------------34
5. Increased intravasation ability by CYR61 overexpressing cells in CAM assay-----------------------------------------------------------------------------------35
6. PI3K-Akt signaling cascades mediated CXCR1, CXCR2 expression in CYR61-overexpressing gastric cancer cells---------------------------------------36
7. CYR61 through Integrin and Src Increase CXCR1 and CXCR2 expression----------------------------------------------------------------------------- 38
Chapter IV Discussion-----------------------------------------------------------------------------40
Chapter V Figures ----------------------------------------------------------------------------------45
Chapter VI Reference ------------------------------------------------------------------------------6
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