1,720,964 research outputs found
Swimming behaviour of females and males: case study Keratella cochlearis
No full textRotifer locomotion is tightly connected to food acquisition. While females swim and feed, males do generally not feed and only swim to find a mating partner. Here, we filmed females and males, respectively, of Keratella cochlearis and analysed their swimming behaviour with Bemovi, an open-source software to extract behaviour and morphology from videos. The application of this recently developed software opens up the opportunity to apply movement ecology to plankton. Males of K. cochlearis swam slower (ca. 1.7 mm sec-1) than females (ca. 2.3 mm sec-1). Visual inspection of data indicated that females showed a more uniform swimming pattern, while males showed a much more varied swimming pattern ranging from circling within a restricted area, swimming in a straight line, and any combinations of these patterns. We, further, classified the swimming pattern of males and females as a hidden Markow model (HMM) to unravel different swimming states. First results indicated that females did not vary between swimming states while males effectively showed a mixture between two movement states as indicated by HMM. Here, we showed how filming and video analysis advances our understanding of rotifer ecology
Tracking of algal cells: case study of swimming speed of cold-adapted dinoflagellates
No full textSwimming is a fundamental trait of many protists and optimizes growth and survival. We present an easy to use set-up for filming algal cells using Apocalathium aciculiferum and Borghiella dodgei as case studies; both dinoflagellates are model organisms of psychrophilic dinoflagellates. We filmed at low temperature (4.5 °C) using a digital camera directly connected to a microscope and used open-source software to track their movement. We encountered several technical issues that were solved by using specific software settings (scaling, gray scale of images, restrictive particle recognition), and thus we obtained unbiased speed estimates. Borghiella dodgei showed a faster (minimum = 80, maximum = 255, median = 141 μm s-1) swimming speed than A. aciculiferum (minimum = 29, maximum = 134, median = 85 μm s-1). We linked differences in swimming speed to the dinoflagellates’ environmental niche, and suggested that B. dodgei is more adapted to turbulent spring conditions than A. aciculiferum, occurring under ice. The use of a generic digital camera and open-source software makes filming and tracking of plankton movement very affordable. We provided code and detailed instructions to disseminate this type of movement analysis of plankton
Detailed xylem anatomy of the leaf midrib and consequences on water transport in Acer pseudoplatanus
No full textSwitching between swimming states in rotifers –case study Keratella cochlearis
No full textSwimming is of vital importance for aquatic organisms because it determines several aspects of fitness, such as encounter rates with food, predators, and mates. Generally, rotifer swimming speed is measured by manual tracking of the swimming paths filmed in videos. Recently, an open-source package has been developed that integrates different open-source software and allows direct processing and analysis of the swimming paths of moving organisms. Here, we filmed groups of females and males of Keratella cochlearis separately and in a mixed experimental setup. We extracted movement trajectories and swimming speeds and applied the classification method random forest to assign sex to individuals of the mixed setup. Finally, we used advanced statistical methods of movement ecology, namely a hidden Markov model, to investigate swimming states of females and males. When not discriminating swimming states, females swam faster
than males, while when discriminating states males swam faster. Specifically, females and males showed two main states of movement with many individuals switching between states resulting in four modes of swimming. We suggest that switching between states is related to predator avoidance. Males of K. cochlearis
especially exhibited switching between turning in a restricted area and swimming over longer distances. No mating or other male–female interactions were observed. Our study elucidates the steps necessary for automatic analysis of rotifer trajectories with open-source software. Application of sophisticated software and analytical models will broaden our understanding of zooplankton ecology from the individual to the population level
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
Filming of zooplankton: a case study of rotifer males and Daphnia magna
Get PDFFilming live organisms can give new insights into the hidden life of plankton. Accessibly priced digital cameras are now available for a large range of users. Here, we demonstrate the technical setup and workflow of using a single-lens reflex (DSLR) camera to film the behaviour of males of two rotifer species, Brachionus angularis Gosse (1851) and Keratella cochlearis Gosse (1851), and of the cladoceran Daphnia magna Straus (1820). Rotifers are cyclical parthenogens that produce males only under certain environmental conditions. Thus, knowledge on rotifer males is still limited because of their ephemeral nature and because they are often smaller than females. We filmed males of B. angularis and K. cochlearis with a DSLR camera connected to a compound microscope to better understand their morphology and behaviour in comparison to conspecific females. While written descriptions have their scientific value, seeing is complementary because everyone can verify what has been described. We made our videos publicly accessible through links connected to the paper. Our videos are, to our best knowledge, the first on males of B. angularis and K. cochlearis. Furthermore, we filmed the behavioural response of D. magna to ultraviolet (UV) radiation with a macro lens attached to the DSLR camera. Approaches like this are valuable tools in environmental teaching. To see live organisms with one’s own eyes may contribute to raising public awareness about the value of water resources and their hidden communities. In summary, filming can be a valuable tool to ignite scientific discussion, but the videos need an open-access platform where they can be referenced in a topic-related order.</p
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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