1,720,952 research outputs found
Nanofluidic electrokinetics in quasi-two-dimensional branched U-turn channels
No full textLab-on-a-Chip (LOC) is a new technology focused on analyzing and controlling flows of fluids, ions, and (bio) particles on the nanometer and micrometer scales, allowing us to shrink a complete fluid-based laboratory into a coin-sized instrumentation. In this thesis, we study a novel fluidic structure with a "branched U-turn" geometry, investigating its potential to perform size-based sorting and characterization on DNA single-molecules. The fluid flow and the DNA molecule motion within the fluidic structure are controlled using electric fields and analyzed with quantitative fluorescence microscopy. The channel depth is less than 1 micrometer, while the channel lengths and widths are in the range of 100 micrometers. Due to these dimensions, the fluidic structure can be simplified as a quasi-two-dimensional system when we perform digital image analysis and numerical simulation. Using these channels, we pose the following research questions: 1. How does the fluid flow behave when various types of electric fields are applied across these channels? 2. How do the pathlines of individual DNA molecules behave inside the confining nanofluidic channels? 3. Can we use these channels as novel devices to sort and characterize single DNA molecules? In Chapter 2, we review the concepts of electrokinetics. Chapter 3 describes the nanofluidic channels studied in this research. In Chapter 4 we studied the first research question by investigating and analyzing the electro-osmotic flow inside the nanofluidic channels. In the experiments, we use distilled water as the liquid in which we add 110 nm diameter fluorescent beads employed as tracer-particles inside 150 nm deep nanofluidic channels. From the results we can characterize the pathlines and velocity distribution of the fluid flow. Due to the complex geometry of the channel, the electro-osmotic flow cannot be calculated analytically. Therefore we use numerical flow simulations to build our model. Comparison between the experimental data and the simulation results give a very good agreement, where the deviation can be explained by the measured Brownian motion of the tracer-particles which was not incorporated in the simulation. The second research question was investigated in Chapter 5. Experiments are performed with two types of dsDNA molecules, λ (48.5 kbp) and T4GT7 (165.6 kbp), using channels with depth of 400 nm. We observe that the electrokinetic pathlines of the DNA molecules depends on the DNA size. We use numerical simulation to calculate the distribution of electrokinetic forces in the channels, which can explain the observed experimental phenomena. The results of Chapter 5 also indicate that, for the first time, size-based separation of DNA molecules can be done in a continuous, sieve-less, manner. This is related to our third research question. By using the nanofluidic channel geometry, we can configure the electric field distribution in the channels and manipulate the electrokinetic forces to influence the pathlines of the DNA molecules. The same results can be expected not only on DNA molecules, but also on any other polarizable biological molecules that can be manipulated using dielectrophoresis.Applied Science
Optical detection of electrokinetically manipulated single molecules in a nanofluidic chip
No full textWe report on the progress of a novel nanofluidic device for detecting and manipulating single molecules in solution. This paper discusses the development of an earlier proposed molecule separation method, where electrokinetic forces separate different molecules based on their masses and charges. Optical imaging using confocal microscopy is applied to perform the detection of the single molecules. Potential applications of this device will be assessed. This research aims for the high spatial and spectral resolutions, both in manipulation and detection, which can lead to molecular identification.Quantitative Imaging GroupApplied Science
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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