1,720,995 research outputs found
The Age of the Potassic Alkaline Igneous Rocks along the Ailao Shan–Red River Shear Zone: Implications for the Onset Age of Left-Lateral Shearing: A Discussion
No full textIdentification of let-7-specific binding proteins in Caenorhabditis elegans
No full textmicroRNAs在10幾年前被發現以來已經有相當多的研究在探討其調控細胞基因表現的機制，但是關於microRNAs本身是如何作用、有甚麼共同因子一起促進其作用或抑制其作用，至今還是有許多地方尚未釐清。在我的論文中主要是想要在C. elegans體內探討let-7上除了目前已知的一些RISC組成蛋白與其結合之外，是否還有其他蛋白質會與let-7專一性地結合，再進一步探討它們是如何參與在let-7調控基因表現的過程。我的論文策略主要是想利用2’-O-methyl oligo-
nucleotides pull-down assay來探討let-7上是否有專一性的結合蛋白。原理是利用人外加標定有biotin的let-7 antisense序列到線蟲細胞萃取液中去辨認內生性的let-7，再用帶有Streptavidin的基質將內生性的let-7及其結合蛋白分離出來並利用一維以及二維蛋白質電泳分析其蛋白質成分。
針對所有被antisense let-7 oligonucleotide純化出來的候選蛋白質，我們利用RNAi降低其基因表現並觀察其產生的性狀，rpa-1以及mtr-4在RNAi處理後會出現col-19表現量降低、vulva 發育缺失、seam cell分化異常、alae斷裂等典型的let-7功能不全時所會看到的型態學變化。進一步的研究發現抑制mtr-4的表現會造成mature let-7量下降、pri-let-7以及pre-let-7量增加的情形，代表著mtr-4可能參與在let-7生合成過程中。然而抑制rpa-1的表現對於let-7的生合成則沒有影響，是否rpa-1在let-7執行功能時一起參與其中則是還要再進一步去證實。MicroRNAs are a class of small non-coding RNAs which regulate more than half of human genes by targeting to their complementary sites on mRNA 3’UTRs. MicroRNAs assemble with additional proteins into ribonucleopreotein complexes called miRNA-induced silencing complexes (miRISCs) and the composition of miRISCs is still not clear. Interestingly, in our previous study, we found that the let-7 miRNA and their family members, such as mir-84, can assemble into specific miRNPs in vitro. Here we aim to identify specific factors that associate with let-7. We use anti-sense oligonucleotides pull-down to isolate endogenous let-7 along with its associating proteins and then analyze the pull-down products by 1-D or 2-D protein electrophoresis. Further we use RNAi to reduce the gene expression of the candidate let-7-binding proteins and investigate their genetic interaction with let-7.
Our results indicate that knock-down of rpa-1 or mtr-4, which encode candidate let-7-binding proteins found in our pull-down assay, resulted in let-7 defective phenotypes, like col-19 down- regulation, seam cell differentiation defects, alae formation defects and vulva protruding. We further found that knocking down mtr-4 caused accumulation of pri-let-7 and pre-let-7 but decrease of mature let-7 level. On the other hand, when we knocked down rpa-1, the level of let-7 was not altered. We hypothesize that MTR-4 may be involved in let-7 primary transcript processing or pre-let-7 exporting from the nucleus to the cytoplasm. The role of rpa-1 in the let-7 regulation pathway is still unknown and awaited to be further investigated
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
Numerical Parametric Study of Ventilated Shading Plates Energy Performance in Summer
No full text近年來通風遮陽板或遮陽牆系統於增強建築立面外牆夏季隔熱能力的應用逐漸增多，但文獻中對於此種通風遮陽牆的隔熱效益探討多為案例討論，缺乏各種參數與遮陽牆隔熱能力的關係式，在比較各種不同參數組合下的遮陽牆隔熱能力時會產生困難。文獻也缺乏探討流道壁面的輻射放射率的影響。本研究旨在以數值模擬分析影響遮陽板隔熱能力的變數，最終發展出包含多項參數之泛用通風遮陽板隔熱能力關係式，此關係式可使得比較各種不同參數條件下的遮陽板隔熱能力更容易。本研究使用商用計算流體力學(CFD)軟體FLUENT作為二維數值模擬分析的工具，模擬結果與文獻實驗以及實際設施的量測結果進行比較驗證。研究結果顯示壁面放射率的降低對遮陽板隔熱性能有顯著的提升；入熱量在流道寬度增大到一定程度後即不會有太大變化。本研究也分析了天氣環境變數對等效熱阻的影響，並運用熱電路節點觀念，可得到誤差更小的遮陽板等效熱阻關係式。以此為基礎拓展其適用範圍加入更多變數，最終得到了泛用的遮陽板隔熱能力關係式，只要是流道高為3m，流道寬在0.1m以上的通風遮陽板，均可利用本研究得到的泛用等效熱阻或入熱量關係式進行通風遮陽板隔熱能力的快速估算。泛用關係式的參數包括了太陽輻射量Ia、室內外溫差ΔT、等效流道壁面放射率ε_eff以及外牆體熱阻Rw。依入熱量對Ia和ΔT的敏感度分析，在太陽輻射量相對較強的地區，加入成本考量，選擇降低等效流道壁面放射率ε_eff是較合適的隔熱策略；而在室外溫度相對較高的地區，選擇提高外牆體熱阻Rw是較合適的隔熱策略。利用泛用等效熱阻進行動態模擬可在不同的天氣條件、不同的Rw、ε_eff設置下，與實際以流道進行的模擬結果比較有著不錯得一致性，因此泛用等效熱阻關係式可應用於減少動態模擬的計算時間。The use of Ventilated Shading Plates or Ventilated wall systems to improve the thermal insulation of vertical walls in buildings has increased in recent years. However, most research on the energy performance of such Ventilated wall has been case studies. Due to the lack of literature reporting the energy performance correlations as functions of numerous parameters, it is difficult to compare the energy performance of Ventilated wall under different sets of parameters. There has been also relatively little research about the influence of radiation emssivity of flow channel surface. The purpose of this study was to investigate the parameters affecting the energy performance of Ventilated Shading Plates by numerical simulation and to provide a general energy performance correlations as functions of numerous parameters. These correlations permit a simple way to compare the energy performance of Ventilated Shading Plate. The simulations were conducted using commercial CFD code, FLUENT. Simulation results were compared with experimental data to validate the simulation model. Results of this study showed that thermal insulaton of Ventilated Shading Plate is increased sensibly as the radiation emssivity of flow channel surface decreased. The heat gain will not change much as the flow channel width increased to a certain extent. The influence of climatic condition on the equivalent thermal resistance of Ventilated Shading Plate was also investigated. We proposed a equivalent thermal resistance correlation with smaller error by the aid of thermal resistance network concept. Then general correlations was proposed by adding more parameters. The presented equivalent thermal resistance correlation and heat gain correlation can be used to estimate the thermal energy performance of Ventilated Shading Plate whose height and width are 3m and greater than 0.1m respectively. The general correlations are functions of absorpted solar radiation Ia, temperature difference between indoor and outdoor ΔT, effective emissivity of flow channel surface ε_eff, and thermal resistance of vertical wall Rw. The sensitivity analysis of heat gain against Ia and ΔT showed that decreasing effective emissivity of flow channel surface ε_eff is a more appropriate strategy in areas with relatively strong solar radiation. It also showed that increasing thermal resistance of vertical wall Rw is a more appropriate strategy in areas with relatively high outdoor temperature. The dynamic simulation results applying equivalent thermal resistance were in good agreement with the results from direct CFD simulations for different climate conditions and different Rw, ε_eff. Therefore, the general equivalent thermal resistance correlation can be used to reduce the computation time of dynamic simulations
A Study of Hydro-mechanical Coupling Behavior of Porous Materials by DEM
No full text滲流特性為大地材料中不可忽略的一環，大地工程一般採用單一的滲透係數代表整個工程區域的滲透性。然而大地材料受到外力的作用下會改變物理性質，諸如應變和孔隙率，滲透性亦隨之改變，此互制的現象稱為水力－力學耦合的行為。值得探究大地材料受到應力的作用下，材料結構與其滲流性變化。舉凡隧道開挖湧水與大壩蓄水等皆涉及大地應力的改變與滲透性之間的關係。
基於大地材料種類繁多，本研究簡化探討顆粒材料之滲流特性，應用基於顆粒力學理論基礎之分離元素法發展的PFC3D軟體為工具，分別由微觀尺度的孔隙率與流率變化與宏觀尺度的應力－應變曲線，探討之間的關係。
本研究以實驗三軸壓密排水試驗的結果作為數值模型比對基礎，求得PFC3D三軸試體的微觀參數，數值模型由試體顆粒與邊界顆粒組成，分別模擬實驗鋁珠與橡皮膜，得以觀察試體破壞型態。驗證比對後，數值模型以力學機制和實驗相同的條件下，繼而進行三軸透水試驗的模擬，探討多孔隙材料受到應力與水力的作用之下，顆粒結構的改變與滲透係數的變化。比較實驗與數值模擬的結果，探討其異同。並進一步探討在水力－力學耦合的行為下，觀察試體隨著應變的增加，顆粒的位移情況、各位置的孔隙率以及各層流率變化。結果顯示滲透係數確實會受到應力與水力作用的影響而產生變化，並非是單一定值，但實驗與模擬的滲透係數存在差異。Seepage is one of the major concerns in geotechnical engineering. The permeability adopted in engineering design usually applies a fixed value in entire area. However, the physical properties of geotechnical material may vary due to different external loading. For example, the variations of strain and porosity induce the different permeability. This interaction phenomenon is known as hydraulic-mechanical coupling behavior. It is worth to study geotechnical materials under stress condition, how to affect the materials structure and permeability.
Based on a wide range of geotechnical materials, this study explores the hydraulic-mechanical coupling behavior of granular material. The software PFC3D based on distinct element method is used to simulate the stress-strain-flow relationship.
In order to get the micro parameters of numerical model, this model is first verified by experimental triaxial compaction drainage test. The numerical model is composed of two kinds of particles, represented the aluminum balls and membrane, respectively. Then, the triaxial permeability test is simulated to explore the variation of permeability subject to different stress conditions. The results show that the permeability will increase as the stress arise. However, some error exists between the experimental and simulated results
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
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