1,721,010 research outputs found
Implications of hyposaline stress for seaweed morphology and biomechanics
Full text linkSeaweeds are primary producers that form a key component of coastal ecosystems. In estuaries and the intertidal zone they are frequently exposed to temporary hyposaline conditions. Previous research has shown that seaweed health status and photosynthetic activity are reduced due to hyposaline stress, but its effects on seaweed physical properties are unknown. This knowledge gap has important implications for the prediction of seaweed hydrodynamics and mechanical failure due to hydrodynamic stress, particularly in extreme conditions (e.g. storm events). In this study, we begin to address this knowledge gap by investigating the effects of hyposaline stress on the morphological and mechanical properties of the kelp Saccharina latissima (order Laminariales). We analysed the morphology of 23 seaweed blades and performed tension and bending tests on more than 90 samples prepared from them. The obtained data provide evidence that both morphology and mechanics of S. latissima are affected by hyposaline stress, i.e.: (i) blades bleach, develop blisters underneath the cortex, and change dimensions (increased volume and thickness, decreased width); and (ii) blade material becomes more flexible and more difficult to break (i.e. tougher). The results indicated a significant correlation between the time of exposure and changes in biomechanics of S. latissima with potential implications for seaweed hydrodynamics and survival strategies
Application of UVP within porous beds
No full textStandard measurement devices do not normally provide detailed information about flows in porous media because either they are too intrusive (e.g., hot/film wire anemometers) or because the solid phase impedes their physical access to the flow as in the case of laser Doppler anemometers or particle image velocimetry (PIV). In this study, a Metflow ultrasonic velocity profiler (UVP) is used to measure instantaneous velocity fields within porous media composed of plastic balls packed in a cubic pattern. Simple considerations of the ultrasound beam properties and propagation, plus a comparison with measurements performed by a PIV system, demonstrate that UVP devices are suitable for such a purpos
Turbulence structure of open channel flows over permeable and impermeable beds: a comparative study
No full textThe behavior of turbulent open channel flows over permeable surfaces is not well understood. In particular, it is not clear how the surface and the subsurface flow within the permeable bed interact and influence each other. In order to clarify this issue we carried out two sets of experiments, one involving velocity measurements in open channel flows over an impermeable bed composed of a single layer of spheres, and another one where velocities were measured over and within a permeable bed made of five such layers. Comparison of surface flow velocity statistics between the two sets of experiments confirmed that bed permeability can significantly affect flow resistance. It was also confirmed that even in the hydraulically rough regime, the friction factors for the permeable bed increase with increasing Reynolds number. Such an increase in flow resistance implies a different distribution of normal form-induced stress between the permeable and impermeable bed cases. Subsurface flow measurements performed within the permeable bed revealed that there is an intense transport of turbulent kinetic energy (TKE) occurring from the surface to the subsurface flow. We provide evidence that the transport of TKE toward the lower bed levels is driven mainly by pressure fluctuations, whereas TKE transport due to turbulent velocity fluctuations is limited to a thinner layer placed in the upper part of the bed. It was also confirmed that the turbulence imposed by the surface flow gradually dissipates while penetrating within the porous medium. Dissipation occurs faster for the small scales than for the large ones, which instead are persistent, although weak, even at the lowest bed levels
Flow-seaweed interactions of Saccharina latissima at a blade scale : turbulence, drag force, and blade dynamics
Full text linkAcknowledgements The work described in this publication was undertaken during the Ph.D. study of Davide Vettori at the University of Aberdeen funded by a scholarship from the Northern Research Partnership, Scotland. The authors gratefully acknowledge: Peter Davies and Paul Mitchell for their support and guidance; David Attwood for his assistance during seaweed collection; Hamish Biggs for his assistance during seaweed collection and transport to the University of Aberdeen, and in setting up LED used to synchronise instruments; and Roy Gillanders and Benjamin Stratton for meticulous technical support. Many insightful comments provided by the Associate Editor Professor J. D. Ackerman and anonymous reviewer helped to improve the quality of the fnal manuscript.Peer reviewe
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
- …
