1,720,993 research outputs found
Experimental investigation and theoretical modelling of the nonlinear acoustical behaviour of a liver tissue and comparison with a tissue mimicking hydrogel
No full textNative harmonics generated by nonlinear distortion of ultrasound during propagation in a medium may cause misinterpretations in spectral analysis when studying contrast agents. The aim of this paper is to quantitatively evaluate nonlinear propagation effects of diagnostic ultrasound pulses in biological tissues and to assess whether a cellulose-based hydrogel can be a suitable material for tissue mimicking purposes. Hydrogel and pig liver tissue samples of various thicknesses were insonified in a through-transmission set-up, employing 2.25-MHz pulses with different mechanical index (MI) values (range 0.06-0.60). Second harmonic and first harmonic amplitudes were extracted from spectra of received signals and their ratio was then used to compare hydrogel and liver behaviours. Resulting trends are very similar for sample thicknesses up to 8 cm and highlight a significant increase in nonlinearity for MI > 0.3, for both liver and hydrogel. A numerical procedure was also employed to calculate pressure distribution along the beam axis: these theoretical results showed a very good agreement with experimental data in the low pressure range, though failed in predicting the MI threshold. In conclusion, the hydrogel resulted to be a suitable material for manufacturing tissue mimicking phantoms, in particular to study contrast agent behaviour with a "low power approach
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
Simulated Measurements of the Magnetic Behavior of New Dual-Mode Nanosized Contrast Agents
No full textAim of this work was to perform simulated measurements
of the magnetic behavior of a novel class of bimodal
nanosized contrast agents (CAs), made of a silica core covered
by smaller superparamagnetic nanoparticles (NPs) and designed
to be detected through both ultrasound and magnetic resonance
imaging (MRI), in order to compare their performance in terms
of MRI signal enhancement with that of the superparamagnetic
NPs alone. The considered bimodal nanocomposites consisted of
330-nm silica nanospheres covered by either superparamagnetic
iron oxide NPs or dumbbell-like FePt-IO nanocrystals. We simulated
the MRI signal generated by each of the considered CAs
during a brain venography in standard clinical conditions. Quantitative
assessments of signal enhancement were carried out as a
function of the main model parameters. The performed numerical
simulations showed that the magnetic response of the novel
nanocomposites was similar or better compared to that of the
superparamagnetic NPs alone for echo times longer than 20 ms,
leading to an easier detection of smaller vessels. Obtained results
suggest that the bimodal NPs have an exciting potential for the development
of innovative clinical protocols for multimodal imaging,
combining quantitative measurements of cerebral blood flow and
targeted molecular imaging of specific diseases
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Hepatic Vessel Segmentation for 3D Planning of Liver Surgery
Full text linkRationale and Objectives: The aim of this study was to identify the optimal parameter configuration of a new algorithm for fully automatic
segmentation of hepatic vessels, evaluating its accuracy in view of its use in a computer system for three-dimensional (3D) planning of liver
surgery.
Materials and Methods: A phantom reproduction of a human liver with vessels up to the fourth subsegment order, corresponding to
a minimum diameter of 0.2 mm, was realized through stereolithography, exploiting a 3D model derived from a real human computed tomographic
data set. Algorithm parameter configuration was experimentally optimized, and the maximum achievable segmentation accuracy
was quantified for both single two-dimensional slices and 3D reconstruction of the vessel network, through an analytic comparison of the
automatic segmentation performed on contrast-enhanced computed tomographic phantom images with actual model features.
Results: The optimal algorithm configuration resulted in a vessel detection sensitivity of 100% for vessels > 1 mm in diameter, 50% in the
range 0.5 to 1 mm, and 14% in the range 0.2 to 0.5 mm. An average area overlap of 94.9% was obtained between automatically and
manually segmented vessel sections, with an average difference of 0.06 mm2. The average values of corresponding false-positive and
false-negative ratios were 7.7% and 2.3%, respectively.
Conclusions: A robust and accurate algorithm for automatic extraction of the hepatic vessel tree from contrast-enhanced computed
tomographic volume images was proposed and experimentally assessed on a liver model, showing unprecedented sensitivity in vessel
delineation. This automatic segmentation algorithm is promising for supporting liver surgery planning and for guiding intraoperative
resections
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