1,720,980 research outputs found
On the role of wood and seagrass rests in coastal flooding events in Mediterranean microtidal beaches
No full textIn December 2019, following intense rainfall, the riverbeds of the rivers flowing into the Gulf of Cagliari
(Sardinia, Italy, western Mediterranean Sea) dumped a large quantity of river reeds attributed to the species
Arundo donax (Poaceae) into the sea. The concomitance of a sea storm event acting in the waters of the Gulf
of Cagliari transported and allowed the deposition and sedimentation of reeds and other seagrass rests (mostly
P. oceanica) on the Poetto beach (an urban microtidal beach located in the Gulf of Cagliari), for an estimated
mass of over 85 tonnes. The subsequent lock-down given by the Covid-19 pandemic, and thus the absence of
anthropogenic interferences, allowed the almost undisturbed interaction of beach processes with these wood
and seagrass rests.
This paper will describe the sedimentary structures formed on the berm, generated by the interaction
between reeds, Posidonia and sediment. Subsequently, it will be analysed how these sedimentary structures
protected the beach from coastal flooding during storm events which were characterised by wave parameters
(significant wave height and wave peak period) with greater values than those recorded during other storm
events that led to beach inundation. In detail, analyses were carried out comparing the wave data with images
acquired by a coastal video monitoring system. However, this storm event caused the reeds to redistribute
along the emerged beach, generating new sedimentary structures that, as a result of successive storm events
from different directions, became stratified in the beach increasing its permeability.
Although the beach cleaning operations often carried out with a removal of vegetal berms, the results of this
study highlighted that the non-removal strategies along the foreshore and the backshore can increase the whole
beach system resilience and protect the anthropic structures built in and behind the beach
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
Evolution of a transgressive barrier-dune system along a starved shelf: implication for beach adaptation to future sea level rise
No full texthe knowledge of long-term evolution of barrier - dune systems is a key issue to predict the morphological adaptation of those coastal systems to the predicted rise of the sea level. The geological inheritance plays a major role in the length, shape, type and behavior of most beach systems worldwide controlling the accommodation space of sediments and the nature of sediment availability. Along wave-dominated starved shelves the biogenic carbonates can be a relevant source of sediment for beaches. Here we present the long term evolution of a transgressive barrier-dune system with mixed bioclastic-siliciclastic sediments along a microtidal, wave-dominated starved shelf (San Giovanni beach, western Sardinia, Mediterranean sea). The beach is located in a wide embayment with rocky outcrops which control the accommodation space for the dunes, the beachface (BF) and the infralittoral wedge (IW). A set of geophysical and sedimentological data, coupled with archaeological evidences were used to evaluate the long-term sediment budget between the beach compartments during the last 3 ka. The whole system accounts for ~2 Mm3 of sediments, about 83% located in the IW, 16% in the dune and 1% in the BF. Dune and IW sediments are mainly bioclastic medium-fine sands (CaCO3 76±13% and 68±12% respectively) whereas BF sediments are mixed coarse sands (CaCO3 44±18%). Sediments analysis allowed to classify carbonate grains into three classes, (i) relict (ii) stranded and (iii) Holocene grains, based on grain morphology, color and presence of diagenetic phases. Relict and stranded grains derive from the winnowing of older sediments transported during transgression and barrier rollover. The Holocene grains represent the present day production from coastal ecosystems. Sediments are transferred from the shoreface to the barrier-dune system with low average rates of sediment transport. The mass budget of carbonate grains among the beach components reveled that the IW is characterized by a mixture of stranded and Holocene grains whereas the dune were mainly composed by stranded grains. Those data highlight that the long term evolution of the barrier-dune system includes the following subsequent phases (i) migrations of the barrier through rollover with the rise of the sea level (ii) inland transport of sediment with development of the dune system (c) longshore sediment transport from the carbonate factories with formation of the IW. The proposed evolutionary model is discussed in relation to the adaptation of the barrier dune system to the future rise of the sea level
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
70 Years of Shoreline Changes in Southern Sardinia (Italy): Retreat and Accretion on 79 Mediterranean Microtidal Beaches
Full text linkCoastal erosion and shoreline change represent major challenges for the sustainable management of coastal environments, with implications for infrastructure, ecosystems, biodiversity, and the socio-economic well-being of coastal communities. This study investigates the shoreline evolution of 79Mediterranean microtidal beaches located along the southern coast of Sardinia Island (Italy), using the Digital Shoreline Analysis System (DSAS). Shorelines were manually digitised from high-resolution aerial orthophotos made available through the WMS service of the Autonomous Region of Sardinia, covering the period 1954–2022. Shoreline changes were assessed through five statistical indicators: Shoreline Change Envelope (SCE), Net Shoreline Movement (NSM), End Point Rate (EPR), Weighted Linear Regression (WLR), and Linear Regression Rate (LRR). The results highlight marked spatial and temporal variability in shoreline retreat and accretion, revealing patterns that link shoreline dynamics to the degree of anthropisation or naturalness of each beach. In fact, coastal areas characterised by local anthropogenic factors showed higher rates of shoreline retreat and/or accretion, while natural beaches showed greater stability and resilience in the long term. The outcomes of this analysis provide valuable insights into local coastal dynamics and represent a critical knowledge base for developing targeted adaptation strategies, supporting spatial planning, and reducing coastal risks under future climate change scenarios
Impact of ocean acidification on the carbonate sediment budget of a temperate mixed beach.
Full text linkThe production of sediments by carbonate-producing ecosystems is an important input for
beach sediment budgets in coastal areas where no terrigenous input occurs. Calcifying
organisms are a major source of bioclastic carbonate sediment for coastal systems. Increased
levels of CO 2 in the atmosphere are leading to an increase in the partial pressure of CO 2 on
ocean seawater, causing ocean acidification (OA), with direct consequences for the pH of
ocean waters. Most studies of OA focus on its impact on marine ecosystems. The impact of
OA on carbonate-producing ecosystems could be to reduce the amount of sediments supplied
to temperate coastal systems. The aim of this study was to quantify the effect of the predicted
OA on the long-term sediment budget of a temperate Mediterranean mixed carbonate beach
and dune system. Based on projections of OA we estimated a fall of about 31% in the present
bioclastic carbonate sediment deposition rate, with the biggest decreases seen in the dunes ( −
46%). OA is also expected to affect the carbonate sediment reservoirs, increasing the disso-
lution of CaCO 3 and causing net sediment loss from the system (~ 50,000 t century
− 1 ). In the
long-term, OA could also play a primary role in the response of these systems to sea-level rise.
Indeed, the reduction in the quantity of carbonate sediments provided to the system may affect
the speed with which the system is able to adapt to sea-level rise, by increasing wave run-up,
and may promote erosion of dunes and subaerial beaches
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
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