1,721,012 research outputs found
Controlling Packing Structure of Naphthalenediimide-Based Polymer Acceptors for High-Performance All-Polymer Solar Cells
No full textField-Programmable Bimodal Switching in a Hybrid-Dual-Gated MoS2 Transistor
No full textThe ultrahigh surface-to-volume ratio and expandable interlayer spacing of van der Waals solids allow their channel bodies to strongly and dynamically interact with foreign molecules. However, controlling such multiple molecular interactions within a single, integrated platform has remained a technical challenge. Herein, we introduce a so-called hybrid-dual-gated voltage-controlled bimodal switch demonstrated on a single MoS2 transistor by cointegrating high-k solid and ionic liquid electrolytes as dual-gate dielectrics. Upon applying the synchronized dual-gate voltages, it results in two distinctive yet interchangeable switching modes: electrostatic near-Boltzmann-limit switching and intercalation-driven metal-insulator transitions. In addition to the improved field-effect switching performances (I on/I off similar to 109, SSmin similar to 61 mV/dec) in the low-gate voltage (V G) regime, the steep-slope metal-insulator transitions accompanying 2H-to-1T structural alternations can also be achieved in the high-V G regime. By incorporating conformal electrode passivation and independent dual-gating modulation, the proposed device platform enables highly stable, field-tunable bimodal switching behaviors through broad-range host-guest interactions.
Incorporation of Acrylonitrile Group into Naphthalenediimide (NDI)-Based Polymer Acceptor for Efficient Charge Generation in High-Performance All-Polymer Solar Cells
No full text석회화를 유도하는 숙신화 제 1 형 아텔로콜라겐에 관한 연구
No full textDept. of Biomedical Engineering/석사[한글]콜라겐은 골 조직의 주요 구성성분으로서 높은 인장강도, 비세포독성, 낮은 항원성 등의 특성으로 생체재료로 널리 이용되고 있으며 특히 골 재생용 지지체의 연구 및 개발에 많이 사용되고 있다. 그러나 콜라겐은 기계적 강도가 약하여 골 재생용 지지체로 단독으로 사용함에 있어서 제약점을 갖고 있다. 따라서, 콜라겐의 화학적 개질은 생물의학에서의 응용에 있어서 용도에 적합한 특성을 부여하는 방법으로 이용되고 있다.
본 연구에서는 생체적합성이 우수하고 면역반응이 적은 아텔로콜라겐을 숙신화 처리한 숙신화 아텔로콜라겐의 골 조직재생을 위한 생체재료로써의 이용가능성을 알아보고자 하였다. 먼저, 숙신화 아텔로콜라겐은 분자량, 순도, 세포독성과 용해도를 평가하였다. 전기영동법을 통해 숙신화 콜라겐은 아텔로콜라겐의 band와 유사하나 상향으로 이동된 모습을 보였다. 이를 통해 아텔로콜라겐보다 상대적으로 분자량이 큰 것을 알 수 있었다. 또한, 용해도 시험을 통해 중성용매에서 좋은 용해성을 보였고 세포독성 시험에서 숙신화 처리된 아텔로콜라겐이 세포에 대해 독성을 나타내지 않음을 확인하였다.
무게 비율에 따라 달리한 숙신화 아텔로콜라겐
아텔로콜라겐의 복합체 막 (100:0, 75:25, 50:50, 25:75, 0:100) 를 제조한 후 기계적 강도를 증대시키기 위해 10 mM - 100 mM 농도의 1-ethyl-3-(3-dimethylaminopropryl) carbodiimide (EDC) 용액을 사용하여 가교화시켰다. 제조된 숙신화 아텔로콜라겐
아텔로콜라겐의 복합체 막의 가교화 후 전자현미경 관찰 결과, 모든 복합체 막에서 유사한 형태를 보였다. 이는 150~250 ㎛의 pore와 망 구조를 지닌 모습으로 확인되었다. 숙신화 아텔로콜라겐
아텔로콜라겐의 복합체 막의 free amine group을 정량함으로써 EDC에 의한 가교화 정도를 측정하였다. 효소분해 시험에서는 아텔로콜라겐 함량이 높은 복합체에서 EDC 처리 농도가 높을수록 강한 저항성을 보였으나, 이와 달리 숙신화 아텔로콜라겐 함량이 높은 복합체에서는 상반된 양상을 보였다. Free amine group정량시험과 효소분해 시험을 통해 숙신화 아텔로콜라겐 함량이 높은 복합체에서의 기계적인 안정성은 EDC 처리 농도의 증가에 큰 영향을 받지 않았다.
숙신화 아텔로콜라겐의 석회화를 유도하는 능력을 알아보기 위해 숙신화 아텔로콜라겐
아텔로콜라겐의 복합체 막을 36.5 ℃ 유사체액에서 15일간 배양 후 복합체 막 표면상에 형성된 석회물질을 관찰하였다. 유도결합 플라즈마 방출 분광기 (ICP-AES)를 통해 막 표면상에 형성된 칼슘의 양을 측정하였고 푸리에 변환 적외선분광기(FT-IR), X선 회절분석기 (XRD)를 통해 석회물질의 결정도와 화학구조를 분석하였다. 이 실험 결과, 숙신화 콜라겐 함량이 높은 복합체 막 (100:0, 75:25 복합체)에서 표면상에 형성된 석회물질의 성장속도가 빠르다는 것을 확인하였다.
또한, 숙신화 아텔로콜라겐
아텔로콜라겐의 복합체 막과 골아세포간의 상호작용을 측정한 결과 숙신화 아텔로콜라겐 함량이 높은 복합체 막 상에서 골아세포의 향상된 부착능, 증식속도를 보였다. 골아세포의 분화 지표인 Alkaline phospatase의 활성도 시험과 mineralization 시험에서도 숙신화 아텔로콜라겐이 많이 포함된 복합체 막에서 빠른 분화속도를 보인 것을 확인하였다.
따라서, 이러한 연구 결과를 통하여 숙신화 아텔로콜라겐이 손상된 골 조직의 재생을 위한 생체재료로서 응용될 수 있음을 제시하였다.
[영문]The porous matrices containing succinylated type I atelocollagen (S-Col) and/or type I ateolocollagen (A-Col) were developed as a biomaterial for bone regeneration. The type I atelocollagen was modified by succinylation and then characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), solubility test and cytotoxicity test. The results showed that S-Col had higer molecular weight compared with A-Col, good solubility in neutral solution and the cytocompatible property. For enhancing the mechanical stability of the composite matrix, the fabricated scaffolds with various weight ratios of S-Col : A-Col (100:0, 75:25, 50:50, 25:75 and 0:100) were crosslinked with different concentrations (10-100 mM) of 1-ethyl-3- (3-dimethyl aminopropyl) carbodiimide (EDC). The morphology of the crosslinked S-Col based membranes were observed by scanning electronic microscopic observation. Also, the mechanical stability was measured with enzymatic degradation, and the extent of crosslinking was determined by quantifying free amine groups. All the scaffolds had interconnected pores with mean diameters of 150-250㎛ and there was no significant difference in their surfaces. According to the enzymatic degradation test, the EDC crosslinking did not have a significant effect on the resistance of S-Col based membranes against collagenase. In in vitro cell free mineralization test, the membranes incubated in simulated body fluids (SBF) were examined by inductively coupled plasma atomic emission spectrophotometry (ICP-AES), X-ray diffraction (XRD) and Fourier transformed infrared spectroscopy (FT-IR). This in vitro test revealed that the growth rate of minerals on 100% S-Col or 75% S-Col containing membranes increased rapidly compared with other membranes. In MC3T3-E1 osteoblast-like cell assay, the cell attachment and proliferation on the membranes containing 100% S-Col or 75% S-Col were enhanced compared with other membranes. In addition, alkaline phosphatase activity and mineralization assays indicated that S-Col based membranes markedly promoted cell differentiation. Therefore, it is suggested that S-Col membrane might be useful as a biomaterial for bone repair and regeneration.ope
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
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