1,721,046 research outputs found
Circumnutation as an autonomous root movement in plants
No full textAlthough publications on circumnutation of the aerial parts of flowering plants are numerous and primarily from the time between Darwin (1880) and the 1950s, reports on circumnutation of roots are scarce. With the introduction of modern molecular biology techniques, many topics in the plant sciences have been revitalized; among these is root circumnutation. The most important research in this area has been done on Arabidopsis thaliana, which has roots that behave differently from those of many other plants; roots grown on inclined agar dishes produce a pattern of half waves slanted to one side. When grown instead on horizontally set dishes, the roots grow in loops or in tight right-handed coils that are characterized by a tight torsion to the left-hand. The roots of the few plants that differ from Arabidopsis and have been similarly tested do not present such patterns, because even if they circumnutate generally in a helical pattern, they subsequently straighten. Research on plants in space or on a clinostat has allowed the testing of these roots in a habitat lacking gravity or simulating the lack. Recently, molecular geneticists have started to connect various root behaviors to specific groups of genes. For example, anomalies in auxin responses caused by some genes can be overcome by complementation with wild-type genes. Such important studies contribute to understanding the mechanisms of growth and elongation, processes that are only superficially understood
Semantic validation of social media geographic information: A case study on instagram data for expo Milano 2015
Full text linkSocial media data, such as Instagram posts, can be associated with spatial positions. This information can be exploited to perform spatial analyses, such as identifying distribution patterns of points representing the positions of social media users during an emergency or while attending a specific event or exhibition. However, the geolocation provided by Social Media Geographic Information (SMGI) needs to be validated, in order for the spatial data to be used in a meaningful way in subsequent spatial analyses or mapping procedures. In this paper, a case study is presented based on Instagram data collected during the first two months of the Expo Milano 2015 exhibition, where the spatial data have been validated by exploiting the semantic component of the posts
Hook formation in sunflower seedlings is directed by both positive gravitropism and a form of circumnutation
No full textThe apical hook that forms at the apex of most dicotyledonous seedlings during germination has in the past been variously described either as the consequence of positive gravitropism or as an autonomous process. Recently, however, emphasis has shifted more on the role of positive gravitropism as the inducer of this structure. To address the question on the nature and origin of the hook, experiments were performed on sunflower seedlings, not only under gravitational conditions but also by means of a clinostat, i.e. in the presence of multidirectionally compensated gravitational stimulation. The results of this work show that at least two processes are involved in the formation of a hook: positive gravitropism and an autonomous movement. Consequently, both Darwin, with his conviction that an innate process such as circumnutation was involved, and the supporters of positive gravitropism, were partly correct. Moreover, it was found that, in contrast to the hook formed under normal unidirectional gravitational conditions, the one formed on the clinostat showed a preferential plane for its development: the plane that passes parallel to the closed cotyledons. This characteristic also suggests that a form of circumnutation may be part of the basic mechanism for hook formation
GlacioTools: Streamlining Glacier Feature Monitoring and Reporting in QGIS
Full text linkMountain glaciers are highly sensitive to climate change, having lost nearly half their surface area and two-thirds of their volume in the European Alps since 1850. Recent advances in unmanned aerial vehicles (UAVs) and aerial imagery, combined with traditional in-situ Ground Control Points (GCPs) measurements, have enabled repeated data collection for glacier monitoring. However, analyzing and visualizing glacier changes remains a time-consuming process in Geographic Information System (GIS) environments. QGIS, an open-source GIS, supports custom plugins that automate routine tasks, improving accessibility and collaboration in climate research. Existing plugins facilitate environmental monitoring, hydrology, and remote sensing applications, streamlining spatial analysis without requiring programming expertise. Despite these tools, an integrated, user-friendly solution for glacier monitoring is still lacking. In this paper the GlacioTools QGIS plugin is presented. It is designed to simplify geospatial data processing for glacier studies. It automates in-situ survey reporting, generates surface displacement and velocity maps, and organizes GCP documentation within a single workflow. By enhancing efficiency and accessibility, GlacioTools supports researchers in documenting and analyzing glacier evolution more effectively
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
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