1,721,007 research outputs found
A pilot project to limit the human impacts on the fragile antarctic biota: Mitigation of a runway through vegetation transplantation
Full text linkBackground: Antarctica is among the world’s last great wildernesses, but the anthropogenic activities and associated infrastructures threaten its fragile biota. We quantify the impact of the construction of a 2200 m long gravel runway airstrip for airfreight operations of the Italian research station on vegetation ecosystems at Boulder Clay (continental Antarctica). We propose a pilot project to mitigate this impact through the transplantation of vegetation from the runway to safe sites. Methods: A vegetation field survey was performed through phytosociological relevés and vegetation mapping and data were analyzed through multivariate analysis. Results: We quantify the destructive impact of the runway construction on the flora and vegetation of Boulder Clay. Based on vegetation characteristics, 28 priority areas were transplanted from the runway to safe sites, with 89% of survival. Conclusions: To our knowledge, this is the first time that vegetation transplantation was performed in Antarctica to mitigate the consequences of human actions, as formerly it was used only for scientific experiments. This pilot project provides a tool to support management decisions, involving the quantitative evaluation of the infrastructure impacts and showing the suitability of practical mitigation actions. This pilot project proposes a practical tool exportable to all Antarctica and beyond and suggests to link the permissions’ release for the new infrastructures in Antarctica to the realization of specific conservation and mitigation actions
The development of Antarctic tafoni: Relations between differential weathering rates and spatial distribution of thermal events, salts concentration and mineralogy
No full textTafoni are one of the most interesting weathering features developed in many areas of the world from tropical areas to polar ones such as Antarctica. Here, we present the results on 4 tafoni in similar conditions (aspect, slope, distance from the sea, elevation) and in the same granite close to the Italian Antarctic station at Mario Zucchelli Station (74°42′S). These tafoni were thermally monitored through infrared thermography and in situ thermistors for an austral summer (2018/19). They were also mineralogically characterized through the image analyses in each tafone sectors (Top, Ceiling, Side and Floor). Salts concentration on the weathered material removed through the scratching was also detected through chemical analyses. Moreover, the weathering rate was calculated through periodic sample weightings of the scratched material from the different tafone sectors. Our results confirmed the importance of the fractures inclination that seem to favor the vertical development of the cavities where basal fractures occurred and the backward development where fractures are vertical. The weathering rates shown that vertical development was always faster than the backward (except for O4) and that the former is statistically linked with the size of the tafone. At mineralogical scale, the higher weathered removal of the quartz concentration could be more closely related to the higher cryogenic weathering of intra-crystal fractures that occur at very low temperatures (−20 °C) in winter than to the thermal stress, thermal shock, or potential freeze-thaw cycles during the summer. Among the different salts, the strong relationship between weathering removals and chlorides suggests that chlorides in this climate are more effective than sulphates. The seasonal trend of weathering matches well with the breaking up of sea ice towards the Tethys Bay and can provide a supply of sea spray that is richer in chlorides (halite) than in sulphates (thenardite, mirabilite). From the analyses of the spatial thermal variability, we could argue that the thermal stress during the summer is not relevant except for the tafone O4. The fact that higher weathering removal were recorded in the innermost (C and S) of the tafoni where thermal variability and AMP were lower suggests that higher moisture content is the crucial factor for a high evaporation flux that can enhance the salt action
Shore Evidences of a High Antarctic Ocean Wave Event: Geomorphology, Event Reconstruction and Coast Dynamics through a Remote Sensing Approach
Full text linkRemote sensing can be helpful in defining the dynamic of a high-latitude coastal environment where the role of cryogenic processes like sea-ice or permafrost are the main drivers together with storm surge and wind action. Here we examined the geomorphological dynamics of a beach located at Edmonson Point (74° S) not far from the Italian Antarctic Station “Mario Zucchelli” between 1993 and 2019 using different remote sensing techniques and field measurements. Our data demonstrate that the average rate of surficial increase of the beach (0.002 ± 0.032 m yr−1) was slightly higher than the uplift rate determined by previous authors (0–1 cm yr−1) in case of pure isostatic rebound. However, we suggest that the evolution of EPNB is likely due to the couple effect of vertical uplift and high wave-energy events. Indeed, the coastline accumulation could be related to the subsurface sea water infiltration and annually freezing at the permafrost table interface as aggradational ice as suggested by the ERT carried out in 1996. This ERT suggests the occurrence of saline frozen permafrost or hypersaline brines under the sea level while permafrost with ice occurred above the sea level. The beach also revealed areas that had quite high subsidence values (between 0.08 and 0.011 m yr−1) located in the area where ice content was higher in 1996 and where the active layer thickening and wind erosion could explain the measured erosion rates. Here, we also dated at the late morning of 15 February 2019 coastal flooding and defined a significant wave height of 1.95 m. During the high oceanic wave event the sea level increased advancing shoreward up to 360 m, three times higher than the previous reported storm surge (81 m) and with a sea level rise almost five times higher than has been previously recorded in the Ross Sea
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
- …
