1,721,025 research outputs found
"Aspetti biologici, note igienico-sanitarie e commerciali del riccio di mare Paracentrotus lividus (Lamarck, 1816) nella Costa Nord-Occidentale della Regione Sardegna”
No full textPrevalenza dei fattori di rischio per reazioni avverse da farmaci (ADRs) in pazienti anziani ospedalizzati
No full text
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
Enhanced Ocean Scatterometry
No full textAn ocean scatterometer is an active microwave instrument which is designed to determine the normalized radar cross section (NRCS) of the sea surface. Scatterometers transmit pulses towards the sea surface and measure the reflected energy. The primary objective of spaceborne scatterometers is to measure near-surface winds over the ocean. This is made possible by observing the ocean with different azimuth views and by using a geophysical model function (GMF) which relates wind and backscatter. Nowadays satellites measure wind fields over the oceans worldwide on a daily basis to improve weather forecasts. Current Geophysical Model Functions are derived either from collocated backscatter and buoy-based wind measurements or by empirically fitting satellite data and NWP (Numerical Weather Prediction) model winds. These functions have been shown to be accurate to approximately ± 1.5 m/s for winds within the range 5÷15 m/s. The characterization of an empirically derived relationship between normalized radar cross-section and wind vector strongly depends on the data set from which such a relationship is derived. This limits the domain of validity of the model to a specific frequency, a specific polarization of the electromagnetic wave, and a confined range of incidence angles and wind speeds. In particular, given the low probability of having scatterometer observations and collocated independent wind vector measurements during high-wind events (such as hurricanes and typhoons), current empirical models are not well defined for high winds. Furthermore, the relatively coarse spatial resolution of existing spaceborne scatterometers (50 km x 50 km) results in the averaging of high and moderate surface winds within the cell. Nowadays, wind dependent correction terms are used, operationally, by the European Centre for Medium-Range Weather Forecasts (ECMWF) to overcome the underestimation of high wind speeds resulting from the CMOD geophysical model function. In addition, being measurement-dependent, the use of empirical functions makes it very difficult to distinguish errors associated with uncertainties of the observing system from errors associated with uncertainties of the models. In some cases, receive chain saturations of the observing systems are confused with limited sensitivity of normalized radar cross section to wind speed. In other cases, poor cross-talk performance of the instrument generates wrong polarization relationships between VV, HH and VH scattering products. Today, there is no integrated approach valid across different frequencies, polarizations, incidence angles and wind speeds that is used operationally to model the relationship between ocean scattering and wind vector. This represents the key objective of the present thesis. Radar backscatter models, based on a description of the underlying physical phenomenon, have the big potential of providing a more general and understandable relation between measured microwave backscatter and surface wind field than the empirical models. The growing interest in achieving a better understanding of the physics that governs the scattering of microwave radiation from sea is triggered by extremely rich and varied data sets collected by microwave sensors on numerous space-borne satellite missions. Additional missions with advanced microwave sensors are planned for launch in the near future; they ask not only for better spatial resolution, radiometric resolution and stability but also for wider swaths and multi-polarisation observation capabilities. Higher spatial resolutions, can better describe the spatial variations in hurricanes and coastal wind fields, whereas wider swaths can sensibly reduce the time between consecutive observations of the same area on the Earth. Wider swaths imply wider ranges of incidence angles to be explored, and then new challenges arise in the modelling of the interaction of the electromagnetic and oceanic waves. Current operating scatterometers use only co-polar scattering (VV or HH) to retrieve wind speeds and directions. The main reason behind this design choice is associated with the fact that the Signal-to-Noise Ratio (SNR) in co-polarization is expected to be higher than in cross-polarization for most winds. However, airborne measurements over hurricanes, performed at C-band and Ku-band, have confirmed that co-polar scattering suffers from problems of incidence- and azimuth angle-dependent signal saturation and dampening, which make it only weakly sensitive to wind speed variations above 25 m/s. This shortcoming impairs the ability to provide accurate hurricane warnings. Errors in wind sometimes prevent communities from correctly identifying the most vulnerable regions where emergency preparations are needed. The addition of VH polarisation to the standard VV and HH polarisations, can significantly improve the retrieval of the wind speed in case of extreme weather events, such as hurricanes. Analysis of RADARSAT-2 quad-polarisation data with collocated in situ ocean wind measurements has recently revealed that the cross-polarised radar backscatter does not saturate at high wind speeds. As a result, the wind speed retrieved with cross-polarised backscattering is much more accurate than that retrieved with co-polarised data in hazardous storm conditions. In this thesis, we present an analytical physical model for accurate simulation of full-polarimetric microwave sea-surface scattering and Doppler signatures. This model combines an adequate sea surface description with advanced electromagnetic theories to simulate both monostatic and bistatic scattering over a wide range of wind speeds, radar frequencies, incidence angles, different polarisations and arbitrary radar look direction with respect to the wind direction. Results will be compared with real measurements from ASAR, Sentinel-1, Radarsat-2, ASCAT and well established empirical Geophysical Model Functions showing good agreement. Being capable of simulating full-polarimetric Doppler spectra of microwave backscatter from ocean surface, this model will be used to explore ocean surface motion retrievals, thus supporting the definition of future ocean Doppler scatterometers, capable of simultaneous measurement of Ocean Vector Wind (OVW) and Ocean Vector Motion (OVM) on a global scale. Measurements of powerful, complex and highly variable ocean surface currents are fundamental for a variety of applications, such as the monitoring of changes in coastal regions, risk management for coastal and off-shore structures, ship routing, anthropogenic and natural pollution and offshore renewable energy monitoring. Ocean surface currents are complex and, in coastal areas, highly dynamic, and therefore need to be monitored with short time sampling (possible on a daily basis) on a global scale. To this aim, Ocean Doppler scatterometry provides simultaneous and accurate measurements of wind fields and ocean motion vectors that can be used to generate global surface ocean current maps at a spatial resolution of 25 km (i.e. 12.5 km spatial sampling) on a daily basis (thanks to the very large swath illuminated). These maps will allow gaining some insights on the upper ocean dynamics at mesoscale.Geoscience and Remote SensingCivil Engineering and Geoscience
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
New data on the presence of Argas reflexus (ixodida: Argasidae) in Sardinia
Full text linkIntroduction
Argas reflexus (Fabricius, 1794), described for the first time on samples found in Italy, is a nidicolous, polyphasic and monothropic soft
tick which originally parasitized several species of wild birds (Dusbábek F & Rosicky B, 1976) and had as its preferred host the pigeon
(Columba livia livia Gmelin). Consequently to pigeon domestication, A. reflexus has colonized rural and urban environments. A. reflexus is
a Palaearctic species and in Italy its distribution is reported in almost all regions, except for the southernmost ones (Sobrero L & Manilla
G, 1988). Its presence is signaled in Sardinia since the end of the 19th century (Marcialis E, 1892), notwithstanding some authors in the
past have considered this report as unreliable. Its presence has been also reported later by Garneri G A in 1902. More recently, A. reflexus
was found in the town of Cagliari in the late 1980s, when several immature stages and adults were found inside some houses, whose
attics housed colonies of pigeons (Pusceddu G, 1997-1998). The first official note on the presence of this species in Sardinia is
nevertheless recorded in the late 1990s, when 21 adult specimens were sampled in a school in Cagliari (Contini C, 1998). The same paper
reports additional findings relating to the years following the first discovery. Other unpublished records reported this species in the
town of Cagliari in the same period (Figus V, 1999). In 2004 A. reflexus was reported again in Cagliari (Fois F et al, 2006; Montarsi F et al,
2011). The aim of this study is to confirm the presence of A. reflexus in Sardinia and make official its presence definitively in the light of
more recent data acquired and in relation with 6 specimens found in the town of Cagliari between 2004 and 2011.
Materials and methods
The sampled specimens were fixed in 70% ethanol and
morphologically determined by microscopic analysis according to
Manilla’s analytical keys (Manilla G., 1998).
Results and Discussion
All specimens were found in the town of Cagliari (isle of Sardinia). One nymph was
sampled in October 2004 on a windowsill of a building town centre. In October 2007
another nymph was found inside an apartment in another area of the town, and in
June 2011 four other nymphs were sampled inside an apartment on whose balcony
stopped domestic pigeons (Columba livia domestica). In the latter case, the ticks were
particularly numerous and shown a particular attraction to humans. These new
data show that Argas reflexus, present in Sardinia already for some decades, is now
firmly established. It is strictly associated with the domestic pigeon, which is very
abundant and widespread, especially in major urban centers of the island. The
potential of this tick as a vector of pathogens and its anthropofily, as demonstrated
also by the recent reported cases, especially in case of serious infestations, makes it a
species of health importance. A. reflexus can cause, through sensitization to salivary
secretions, sometimes very severe anaphylactic reactions (Miadonna A et al, 1982;
Khoury C & Maroli M, 2004)
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