1,720,975 research outputs found
Influence of Herbivores on Life History Stages of a Dominant Nitrogen-Fixing Shrub (Lupinus Chamissonis): Effects on Survival, Growth, Architecture, and Reproduction
No full textHerbivores have diverse impacts on their host plants, affecting recruitment,\ud
survival, growth, architecture, fecundity, and other aspects of plant performance.\ud
Especially for longer-lived plant species, the effects of any single herbivore species\ud
can differ markedly throughout the life of the host plant. Additionally, a number of\ud
herbivore taxa may be influential at different life stages of the same plant species.\ud
To investigate the effects of herbivory by black-tailed deer (Odocoileus\ud
hemionus columbianus) and snails (Helminthoglypta arrosa and Helix aspersa) on a dominant nitrogen-fixing shrub lupine, Lupinus chamissonis, I established three\ud
exclosure experiments, over a two-year period, in a sand dune community on the\ud
California coast. The first of these experiments investigated the effects of deer alone on the survival, growth, and architecture of individual plants from seedling through\ud
juvenile life stages. The second experiment addressed the separate and joint effects\ud
of deer and snails on seedlings/juveniles. The third experiment assessed the impacts\ud
of deer alone on growth and reproduction in mature shrubs.\ud
Deer browsing significantly reduced volume in juvenile plants, and also\ud
significantly increased the architectural density (branching structure) of juveniles.\ud
Since I determined that plant volume was strongly correlated with aboveground dry\ud
biomass for lupines of all ages, I conclude that these volume reductions translate\ud
into losses of aboveground biomass. Protection from deer was positively correlated\ud
with leaf-galling by a cecidomyid fly (Dasineura lupinorum), suggesting that deer\ud
indirectly affect another herbivore species in the system. Although deer did not\ud
significantly affect seedling survival, seedlings protected from deer consistently\ud
exhibited greater survival in the two separate experiments. Snails did not have a\ud
noticeable effect on seedling survival or on the growth of juvenile lupines, but\ud
environmental conditions may have contributed to this result. In mature shrubs,\ud
herbivory by deer significantly shortened shoots, yet did not substantially reduce\ud
biomass. Unprotected plants also produced significantly more inflorescences,\ud
raising the possibility that shrubs may compensate or even overcompensate in\ud
response to herbivory. Collectively, these data indicate that mammalian and molluscan herbivores can have widely varying effects on their shared host plant, and that the effects of a vertebrate herbivore species change markedly with the life history stage of a host plant. Given the well-documented effects of N-fixing species on soil fertility, my results suggest that black-tailed deer, through their effects on a dominant N-fixing shrub, may serve as key regulators of nitrogen availability in a nutrient-deficient\ud
dune ecosystem.Financial support provided by the Bodega Field Conference, the California Native Plant Society, the National Geographic Society, and Sonoma State University
Wheelchair-mounted robots for the home environment
No full textStatistics on people with disabilities, together with data on the number and use of wheelchairs in the United Kingdom, are summarized. The history of electric-wheelchair-mounted robotic devices is detailed and critically reviewed. A novel design for a hybrid electropneumatic wheelchair-mounted robot for the home environment is presented
A review of world rehabilitation robotics research
No full textThe paper reviews the intensive ongoing activity in rehabilitation robotics. It also highlights the different attitudes towards the design of robotic devices for people with disabilities from nation to nation. However, even though there has been a vast amount of funds and man-years of effort spent, the ideal of a general purpose rehabilitation robot which can be used by a large number of people with disabilities and which is readily available at a low cost is still a long way of
A new development in low cost pneumatic actuators
No full textOutlines the history of pneumatic muscle actuators as applied to prosthetics, orthotics and rehabilitation robotics. The advantages of low cost pneumatic muscles over more conventional forms of actuation are described, together with details of a single-axis test-rig which is being used to analyse the static and dynamic performance of a new type of muscle system in twenty different variations of length and width. A theoretical analysis using the nonsteady flow energy equation is proposed and some early experimental results are presented. Finally, the results of this study can be used to develop an electric wheelchair mounted robotic arm incorporating pneumatic muscle actuator
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
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
- …
