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Le carte della Chiesa di Santa Maria del monte di Velate, a cura di Patrizia Merati
No full textRecensione dei due volumi con cui la curatrice Patrizia Merati ha pubblicato le pergamene della chiesa di Santa Maria del monte di Velate dal 922 al 1190
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
Free nanoparticle characterization by optical scattered field analysis : opportunities and perspectives
No full textMethods for the facile and in-line characterization of size distribution and physical properties of unsupported nanoparticles are of paramount importance for fundamental research and industrial applications. The state-of-the-art free nanoparticle characterization methods do not provide accuracy, high throughput, and operation easiness to support widespread use for routine characterization. In this perspective paper, we describe and discuss the opportunities provided by approaches for nanoparticle characterization based on optical measurements of the field scattered by particles. In particular, we show how insightful is the measure of both the real and the imaginary parts of the field amplitude, a task that has been considered in the past but never had a widespread exploitation. A number of opportunities are generated by this approach, in view of assessing a more efficient characterization and a better understanding of the properties of nanoparticles. We focus our attention on the capability of characterizing nanoparticles of wide interest for applications, considering cases where traditional approaches are not currently effective. Possible exploitations are both in research and in industrial environments: to validate a synthetic process, for example, or for in-line monitoring of a production plant to generate advanced process control tools, as well as decision-making tools for acting in real time during the production
A DSP multiprocessor architecture for live camera calibration
No full textThis paper presents a system for real-time calibration of moving and zooming video cameras. In order to satisfy the real-time constraints, the calibration of each video frame has to be computed before the acquisition of the next frame is completed (40 milliseconds for PAL standard). Because of such time requirements, the proposed system is based on a multi-DSP processor architecture: the digitized video signal is processed by a DSP system hosted in a standard PC. The computed calibration parameters are transferred to the application running on the host, which uses the camera parameters for real time digital video effects, such as live mixing of the acquired video stream with synthetic sequences. Compared to existing systems, the proposed technique represents a low-cost solution, as it is based on a simple hardware architecture. Moreover, differently from most existing systems, the proposed technique does not need additional hardware for camera calibration, such as mechanical encoders or auxiliary cameras, but just needs some markers arbitrarily placed in the scene. The proposed tracking and calibration technique has been implemented and optimized for running in parallel on a multiple-DSP architecture. Experimental tests show that the overall computing time has never been greater than 13 milliseconds, thus satisfying the required real-time constraints
Comment on Size-dependent modifications of the Raman spectrum of rutile TIO2 [Appl. Phys. Lett. 89, 163118 (2006)]
No full textLe pergamene dell'Archivio di san Gaudenzio di Novara
No full textThe present thesis of Doctorate of Research introduces a critical study of a considerable part of the corpus membranaceo of the Archive of St. Gaudenzio of Novara with the edition of the parchments of the XII and XIII century, following the current archivistic order. It deals with 237 acts, to a large extent notarial, almost all unpublished, that offer an important wiev on the history of the Capitolo gaudenziano and of the city of Novara and her territory for the period considered. Besides the critical transcript of the documents it is a study on the clergy of St. Gaudenzio’s Chapter and on the notaries working in Novara in XII and XIII century
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
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