1,720,977 research outputs found
SYNTHESIS AND CHARACTERIZATION OF METAL-POLYMER NANOCOMPOSITES FOR STRETCHABLE ELECTRONICS APPLICATIONS
No full textThe possibility to develop electric devices which can be rolled up, bent or even
deformed without lose their funtionality is one of the main and interesting challenges
nowadays in materials science and engineering. Indeed, this represents the
fundamental step towards the development and the realization of stretchable electronics
devices. Till now, several techniques have been developed in order to produce
stretchable conductive elements, basically by joining the electrical properties of metals
and the mechanical features of polymers. Nevertheless, none of these techniques is
able to satify all the basic requirements needed in the realization of metal conductive
traces on stretchable polymers. The main purpose of this thesis is the presentation
of the Supersonic Cluster Beam Implantation as a novel approach for the production
of stretchable conductive nanocomposite systems exploitable in the development of
stratchable devices. This will be accomplished through the synthesis of Au-PDMS
nanocomposites and the characterization of thier electrical, optical, morphological
and mechanical properties. Moreover, this thesis reports on the successful use of
SCBI to fabricate first examples of deformable devices, such as the stretchable and
biocompatible electrodes for biomedical applications
Defibrination in adult acute lymphoblastic leukaemia. Report of four cases.
No full textDefibrination is a rare event in acute lymphoblastic leukaemia (ALL). This paper describes four cases of acute defibrination in a series of 52 adult patients with ALL. All four patients had blood clotting tests consistent with or suggesting defibrination prior to therapy, but haemorrhages and unequivocal laboratory evidence of defibrination developed only after leukaemic blast cells had been destroyed early during therapy for remission induction. All patients received supportive therapy, and three of them were also given a continuous IV heparin infusion. Haemorrhages were controlled and blood clotting tests were improved within 12--48 h
Supersonic Cluster Beam Implantation : a new process for biocompatible and stretchable metallization of polymers
No full textThe interest for micro- and nanomanufacturing of polymeric materials is continuously increasing driven by different fields such as bioelectronics, flexible optoelectronics and microfluidics for biomedical and chemical analysis systems. The need of polymer-based microdevices incorporating sensing, signal conditioning and actuating functions require the ability to integrate on polymer substrates metallic micrometric electrodes, contacts, wires, circuits and interconnections. The standard approach used for producing such structures is atomic physical vapor deposition of noble metals; this method, although cheap and easily scalable, has poor performances in terms of layer adhesion and attainable lateral resolution. Furthermore such process causes a considerable heating of the sample during the deposition and require the use of pre-treatments of the polymer surface (as for instance the deposition of a Cr layer) in order to promote the adhesion of the metal layer [1]: both these processes can alter the properties (as biocompatibility) of the polymeric substrate.
Recently we developed a new method for polymer metallization: the implantation of neutral metal cluster in a polymer substrate. The clusters are produced in the form of a Supersonic Cluster Beam by a Pulsed Microplasma Cluster Source (PMCS) [2] and, thanks to the cluster’s inertia, they are implanted at room temperature in the polymer substrate forming a metal-polymer nanocomposite layer [3]. Unlike atomic physical vapor deposition, we did not alter the polymer surface with chemical or physical treatments in order to improve the adhesion of deposited metal clusters. Furthermore, neither sample heating nor sample charging was induced by the Supersonic Cluster Beam Implantation (SCBI) process [3].
Here we present the application of this process for the fabrication of a biocompatible elastomer-based nanocomposite materials made by gold clusters implanted in a polydimethylsiloxane (PDMS) matrix. The cluster implantation process was monitored during the deposition by measuring the evolution of the electrical properties of the nanocomposite as a function of the amount of deposited clusters [3]. After the deposition, we studied the electro-mechanical performances of the nanocomposite, by measuring the variation of its resistance during uniaxial stretching cycles. Remarkably, the conducting elastomers subjected to 40% strain cycles show finite and reproducible electrical resistance over thousands of cycles (up to 50000). Furthermore, the resistance measured at the point of maximum elongation of the polymer decreases as the number of cycles increases, at odd with what happens in similar experiments on metal coating deposited on the surface of elastomers [1]. All the obtained results give clear evidences of a high adhesion between the implanted conducting traces and the polymer substrate.
Next, we carried out preliminary biocompatibility tests: neuronal cells were cultured in vitro both on Au-PDMS nanocomposites and on bare PDMS films used as reference samples. The results have shown that cell adhesion and vitality improve on the nanocomposites in respect to the reference samples (that are already biocompatible), proving the high biocompatibility of this novel material.
Finally, we have demonstrated the possibility to use SCBI to pattern high-resolution features on soft and stretchable substrates. Thanks to the very low divergence of the cluster beam produced by the PMCS source (below 1° [2]), we were able to produce on the PDMS substrates conductive patterns with micrometric resolution through standard stencil mask techniques, as for example gold dots with high packing density (dot radius of 15 μm and inter-dot distance of 12 μm).
These results indicate that SCBI can be considered a promising tool for the fabrication of conducing patterns on flexible and untreated elastomer substrates, it is compliant with biomechanical and micropatterning constraints and it is capable to assure high biocompatibility to the produced materials, as needed by new classes of stretchable bioelectronic devices.
[1] I. M. Graz, D. P. J. Cotton and S. P. Lacour, Appl. Phys. Lett. 94 (2009): 071902.
[2] K. Wegner, P. Piseri, H. V. Tafreshi and P. Milani, J. Phys. D: Appl. Phys. 39 (2006): R439–R459.
[3] L. Ravagnan, G. Divitini, S. Rebasti, M. Marelli, P. Piseri, P. Milani. J. Phys. D: Appl. Phys. 42 (2009) 082002
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
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
- …
