1,720,963 research outputs found
Simple method of DNA stretching on glass substrate for fluorescence imaging and spectroscopy
Full text linkWe demonstrate a simple method of stretching DNA to its full length, suitable for optical imaging and atomic force microscopy (AFM). Two competing forces on the DNA molecules, which are the electrostatic attraction between positively charged dye molecules (YOYO-1) intercalated into DNA and the negatively charged surface of glass substrate, and the centrifugal force of the rotating substrate, are mainly responsible for the effective stretching and the dispersion of single strands of DNA. The density of stretched DNA molecules could be controlled by the concentration of the dye-stained DNA solution. Stretching of single DNA molecules was confirmed by AFM imaging and the photoluminescence spectra of single DNA molecule stained with YOYO-1 were obtained, suggesting that our method is useful for spectroscopic analysis of DNA at the single molecule level. © 2014 Society of Photo-Optical Instrumentation Engineers.1771sciescopu
Formation of nanosized monolayer MoS2 by oxygen-assisted thinning of multilayer MoS2
No full textWe report the controllable nanosized local thinning of multi-layer (2 L and 3 L)-thickness MoS2 films down to the monolayer (1 L) thickness using the simple method of annealing in a dry oxygen atmosphere. The annealing temperature was optimized in the range of 240 °C to 270 °C for 1.5 h, and 1 L thick nanosized pits were developed on the uniform film of the 2 L and 3 L MoS2 grown using the chemical vapor deposition method. We characterized the formation of the 1 L nanosized pits using nanoscale confocal photoluminescence (PL) and Raman spectroscopy. We observed that the PL intensity increased and the Raman frequency shifted, representative of the characteristics of 1 L MoS2 films. A subsequent hydrogen treatment process was useful for removing the oxygen-induced doping effect resulting from the annealing. © 2016 Author(s)6711sciescopu
Simple Chemical Treatment to n-Dope Transition-Metal Dichalcogenides and Enhance the Optical and Electrical Characteristics
No full textThe optical and electrical properties of monolayer transition-metal dichalcogenides (1L-TMDs) are critically influenced by two dimensionally confined exciton complexes. Although, extensive studies on controlling the optical properties of 1L-TIVIDs through external doping or defect engineering have been carried out, the effects of excess charges, defects, and the populations of exciton complexes on the light emission of 1L-TMDs are not yet fully understood. Here, we present a simple chemical treatment method for n dope 1L-TMDs, which also enhances their optical and electrical properties. We show that dipping lLs of MoS2 WS2, and WSe2, whether exfoliated or grown'y chemical vapor deposition, into methanol for several hours can increase the electron density and also can reduce the defects, resulting in the enhancement of their photoluminescence, light absorption, and the carrier mobility:. This methanol treatment was effective for both n- and p-type 1L-TMDs, suggesting that the surface restructuring around structural defects by methanol is responsible for the enhancement of optical and electrical characteristics. Our results have revealed a simple process for external doping.that can enhance both the optical and electrical properties of 1L-TMDs and help us understand how the exciton emission in 1L-TMDs can be modulated by chemical treatments
Enhanced Luminescence and Photocurrent of Organic Microrod/ZnO Nanoparticle Hybrid System: Nanoscale Optical and Electrical Characteristics
No full textWe studied the enhanced photoluminescence (PL) and photocurrent (PC) of 1,4-bis(3,5-bis(trifluoromethyl)styryl)-2,5-dibromobenzene (TSDB) microrods decorated with ZnO nanoparticles (NPs). Chemically synthesized crystalline ZnO NPs with an average size of 40 nm were functionalized with (3-aminopropyl)trimethoxysilane to result in the chemical bonding of the NPs onto the surface of the TSDB microrods. We observed a 2-fold PL enhancement in the ZnO/TSDB hybrid microrods compared with the PL of the pure TSDB microrods. In addition, PC measurement carried out on the TSDB and ZnO/TSDB hybrid microrods at two different excitation wavelengths of 355 urn and 405 nm showed the significant enhancement of the PC from the hybrid system, where the resonant excitation of the laser (355 urn) corresponding to the absorption of both ZnO and TSDB caused 3 times enhancement of the PC from the ZnO/TSDB hybrid microrods2211sciescopuskc
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
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