1,720,957 research outputs found
A deep sea lab on a chip chemical sensor
No full textThe measurement of chemical concentrations within the oceans is crucial for our understanding of its biogeochemical processes. Such data is vital for; studies of climate and environment change; natural resource management; assessment of pollution, human impact and biodiversity. Current measurement methods (sampling and large in situ instrumentation) cannot provide the quantity and quality of biogeochemical data that is required. The factors limiting the widespread collection of quality data include, sample degradation/contamination, instrument size, cost and insufficient sensitivity.New technologies allow the manufacture of Lab On a Chip (L.O.C.) devices that can be used as small, low-cost and low power sensors. There are numerous demonstrations of these devices in the laboratory where it is possible to use standard bench top equipment to operate them. Within the National Oceanography Centre Southampton and the Nanoscale System Integration Research Group at Southampton University it has been proposed that integrated L.O.C. devices could be used autonomously and remotely in the marine environment. These innovative micro-devices could provide in situ real time synoptic data on processes with temporal and spatial scales smaller than currently sampled. This report details the development, laboratory testing and field trial of the world's first deep sea in situ L.O.C. chemical sensor. Preparatory work for the design of the next generation of marine L.O.C. devices including low-cost fabrication in fluoropolymer materials (which are naturally robust and chemically resistant) is also presented.The L.O.C. devices within this study use a reagent based colorimetric protocol to determine the concentration of a chemical within a sea-water sample. The optical absorption when the reagent is mixed with a sample is proportional to the chemical concentration and is measured using a double beam spectrophotometer. This method can be used in the metrology of a number of chemical species including nutrients and pollutants and therefore this technology is generic. The detection of nitrite and nitrate at a wavelength of 540nm is used as a proof of concept within this report. Nitrite samples are combined with α-napthylamine and sulphanilamide to form a coloured dye. The absorption of the dye is proportional to the nitrite concentration. Nitrate is reduced to nitrite using a cadmium column and then measured in same manner. The L.O.C. devices are fabricated using negative photolithography on photosensitive epoxy resin. Micro channels measuring 500 by 500 µm are used to create micromixers, optical detection paths and fluid delivery ports on a device with a footprint of 45 by 45 mm. The absorption is measured with low powered portable electronics, a modulated light emitting diode source and photodiode detector both coupled to polymer fibres. The mixer uses a three dimensional split and recombine technique to ensure effective mixing of the chemicals and sample.On the laboratory bench the sensor was capable of continuously sampling nitrite concentration levels in sea-water at 60?l/min with a limit of detection of 47.6nM and a precision of 89.3nM at 15µM. Once reconfigured it was capable of detecting nitrate in seawater, at the same flow rates with a limit of detection of 1.75µM and a precision of 9.26µM at 100µM. An in situ version of the sensor, packaged within a pressure compensated housing measuring Ø120mm by 300mm, was deployed in the mid-Atlantic. It provided key functionality and construction methodologies for future generation devices. These trials also identified the developments necessary for the sensor to work as efficiently at depths of 1500m as on the laboratory bench
The fabrication of lab-on-chip devices from fluoropolymers
No full textThree different rapid manufacturing methods for the construction of fluoropolymer microfluidic devices were investigated: (1) fluoropolymer/epoxy laminate/fluoropolymer structures, (2) fluoropolymer/fluoropolymer structures and (3) fluoropolymer/epoxy laminate/glass structures. The structures are chemically and physically robust and the fluoropolymer constructs can be used for optical wave guiding. Principles behind the use of fluoropolymer waveguide constructs and a basic theoretical analysis of the improvements they offer are presented. The otherwise problematic bonding of the polymers was facilitated by chemical (sodium naphthalene) surface treatment. The effects of the process were characterized by contact angle and bond strength measurements. For demonstration purposes, microfluidic channels were fabricated using Ordyl SY epoxy laminate (methods 1 and 3) and hot embossing of the polymers (method 2). The first method (fluoropolymer/epoxy laminate/fluoropolymer) proved to be the most reliable and successful, in particular when bonding the various layers. (Some figures in this article are in colour only in the electronic version
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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