1,721,766 research outputs found
Metal nanostructures decorated with silver nanostars: a novel highly efficient SERS substrate for dyes and pigments detection
No full textThe detection of artistic molecules such as dyes and/or pictorial binders employed in the field of Cultural Heritage requires more and more sensitive techniques. The surface enhanced Raman spectroscopy (SERS) represents a valuable option due to its ability to reveal molecules adsorbed or bound onto nanostructured interfaces. In order to maximize the enhancement of the Raman effect, different Ag and Au nanomaterials where bound together to produce hierarchical structures. In particular, silver nanostars (AgNSs) were chosen because of the strong enhancement caused by their anisotropic shape and they were prepared by one-pot chemical synthesis [1]. The AgNSs were used to decorate two different gold nanostructures, namely Au nanowires (AuNWs) and sphere segment void (SSV) structured surfaces. The AuNWs were obtained in the shape of ensembles of nanoelectrodes by templated elecrtroless deposition in nanoporous membranes [2,3] while the SSV substrates were prepared via gold electrodeposition by using a monolayer of polystyrene spheres as template [4].
The enhancement of the Raman effect was tested at first through the employment of benzenethiol, a well known Raman probe. Thereafter, cochineal lake-pigment, in particular, was chosen as target owing to its use throughout the history of art. Lakes are complex coloring pigments in which an organic dye (e.g. cochineal, madder or kermes) is adsorbed onto solid particles of inorganic salts. This composite structure, composed by an organic molecule chelated by metallic ions, makes the Raman detection of lakes extremely challenging. However, the described issue is overcome by employing highly sensitive SERS substrates as those prepared in the context of this thesis.
We compared the magnitude of the enhancements obtained with different SERS substrates: standing alone AgNSs, AuNWs ensembles and SSV substrates and hierarchical nanostructures composed by AgNSs combined to AuNWs (AgNSs@AuNWs) and to SSV substrates (AgNSs@SSV). Particularly strong enhancements were recorded in the case of the AgNSs@SSV substrates, showing the high potential of the so called particle-in-cavity (PIC) architectures [5]. Concluding, we synthesized highly effective hierarchical nanostructures whose future employment lies in the production of extremely sensitive SERS biosensors to be applied in the detection of artistic dyes and binders.
References
[1] García-Leis A., García-Ramos J. V., Sánchez-Cortés S., J. Phys. Chem. C, 2013, 117, 7791.
[2] De Leo M., Kuhn A., Ugo P., Electroanal., 2007, 19 , 227.
[3] Ugo P., Moretto L. M., Template Deposition of Metals, Ed. C. Zosky, Handbook of Electrochemistry, chapter 16.2, Elsevier, Amsterdam, NL, 2007, 678.
[4] Mahajan S., Cole R. M., Soares B. F., Pelfrey S. H., Russell A. E., Baumberg J. J., Bartlett P. N., Phys. Chem. C, 2009, 113 (21), 9284.
[5] Speed J. D., Johnson R. P., Hugall J. T., Lal N. N., Bartlett P. N., Baumberg J. J., Russell A. E., Chem. Commun., 2011, 47, 6335
Recensione a K. Kolrud e M. Prusac (ed.), Iconoclasm from antiquity to modernity, Farnham 2014
No full textPer una lettura di genere del territorio. Politiche urbane e progetti gender sensitive
Full text linkStudio comparato di fattibilità tecnica, economica e finanziaria per impianti di cogenerazione
No full textThe choice between a biomass and a natural gas cogeneration plant does not simply concern technological aspects. In fact, policy incentives implemented by the Italian government to encourage plants powered by renewable fuels affect the profitability of the project as well as - more importantly in our perspective - the risk factors of the investment. This article reports the comparative analysis performed to select the optimal choice between a biomass and a natural gas cogeneration system to be built to service a mushroom production plant. The aim is to highlight the importance of the sensitivity analysis to evaluate energy efficiency projects, to detect the different risk factors that the two technologies give rise to and to capture the strategies to implement to mitigate the project global risk. For this purpose, the paper first outlines the procedure followed to design the cogeneration plants. Secondly, for each of the actors involved (ESCO, bank and customer) the paper defines the main variables taken into account to assess the bancability and the profitability of the investment project
Il sistema regionale di innovazione nelle traiettorie di competitività regionale
Full text linkThis paper analyses a number of European regions that in the last decade, through a considerable change in their economic base, experienced a remarkable growth path and a significant increase in their competitiveness. Th analysis was carried out with the aim of recognizing the main determinants (or factors) of territorial development behind each regional renewal process and capturing (in a necessarily stylized manner) a number of common trajectories of regional competitiveness. Interestingly, all regional 'success histories' are strongly dependent on the presence of a tri-polar regional innovation system 'gluing' firms, institutions and academia
Sviluppo e caratterizzazione di materiali nano-rinforzati per applicazioni odontoiatriche
No full textIn questa tesi di dottorato, si sono investigate diverse strategie per migliorare la durata dei restauri dentali. Nonostante tutti i progressi nella odontoiatria conservativa negli ultimi anni, i compositi a base di resina continuano ad avere un alto tasso di fallimento. Una delle principali ragioni è lo sviluppo di micro-infiltrazioni batteriche lungo i margini del restauro e, di conseguenza, la formazione di carie secondarie ricorrenti.
In particolare, questo lavoro può essere diviso in due sezioni principali: (i) lo sviluppo e la caratterizzazione di adesivi contenenti composti antibatterici; (ii) lo sviluppo e la caratterizzazione di compositi dentali a base di resina contenenti diversi riempitivi al fine di migliorarne le prestazioni.
Nella prima parte di questa tesi, sono stati selezionati quattro monomeri bis-quaternari di-metacrilati antibatterici polimerizzabili (bis-QAMs; ovvero DDE, DDPyMMA, DDMAPMA e DDM), sviluppati da Fanfoni et al. [1], al fine di attribuire proprietà antimicrobiche a due diversi agenti adesivi commerciali, ScotchBond Multipurpose e Scotchbond Universal, un adesiv0 3-steps etch-and-rinse e un adesivo universale self-etch, rispettivamente. Per un eventuale utilizzo clinico, è necessario che l'aggiunta di queste molecole non riduca la resistenza di adesione dell'adesivo, anche a lungo termine, e soprattutto che l'attività antibatterica sia preservata dopo la polimerizzazione. I risultati della forza di adesione (μTBS), sia a tempo 0 che dopo un invecchiamento termomeccanico in vitro (simulando 5 anni di servizio clinico), e la valutazione antibatterica in vitro (contro Streptococcus mutans) hanno dimostrato che il sistema adesivo Scotchbond Multipurpose è più adatto per l'incorporazione di queste molecole, in particolare DDMAPMA può quindi essere identificato come il miglior monomero antibatterico, che non influisce sulle proprietà meccaniche e superficiali.
La seconda parte di questo progetto si è concentrata sullo sviluppo e la caratterizzazione di materiali compositi dentali nano-rinforzati mediante l'incorporazione di idrossiapatite (nHAp) di dimensioni nanometriche come riempitivo, che presenta proprietà antibatteriche e di remineralizzazione grazie alla presenza di un vetro bioattivo (BGMS10), sintetizzato da Bellucci et al. [2]. L'analisi mediante microscopia elettronica a scansione (SEM) e microscopia elettronica a trasmissione (TEM) delle polveri di filler, HAp e BGMS10, ha confermato la presenza di particelle nanoscopiche per entrambi i riempitivi. La caratterizzazione meccanica ha mostrato che i compositi sperimentali realizzati con diverse proporzioni resina/riempitivo (R2/HAp-BGMS10) non presentavano valori adeguati di resistenza alla flessione e micro-durezza Vickers per il loro utilizzo. Tuttavia, è interessante notare che i valori di durezza dei compositi sperimentali nelle condizioni che simulano l'ambiente orale (immersione in acqua distillata a 37°C per un totale di 40 giorni) non diminuiscono. Inoltre, sia la valutazione delle proprietà antibatteriche (contro Staphylococcus aureus) che la bioattività hanno dimostrato un comportamento comparabile al ben noto vetro bioattivo 45S5, utilizzato come riferimento in questa tesi. Inoltre, è stato riscontrato che questo composito sperimentale presenta una bassa citotossicità nei confronti delle cellule staminali umane della polpa dentale (HDPSCs).
Bibliografia
[1] Lidia Fanfoni, Eleonora Marsich, Gianluca Turco, Lorenzo Breschi, and Milena Cadenaro. Development of di-methacrylate quaternary ammonium monomers with antibacterial activity. Acta Biomaterialia, 129:138–147, 2021.
[2] Devis Bellucci and Valeria Cannillo. A novel bioactive glass containing strontium and magnesium with ultra-high crystallization temperature. Materials Letters, 213:67–70, 2018.In this PhD thesis, we investigated different strategies to improve the durability of dental restorations. Indeed, despite all the advances in conservative dentistry in recent years, resin-based composites continue to have a high failure rate. One of the main reasons is the development of bacterial microleakage along the margins of restorations and, as a result, the formation of recurrent secondary caries.
In particular, this work can be divided into two main sections: (i) the development and the characterization of adhesives containing antibacterial compounds; (ii) the development and the characterization of resin-based dental composites containing different fillers in order to improve their performances.
In the first part of this thesis, four polymerizable antibacterial di-methacrylate bis-quaternary ammonium monomers (bis-QAMs; namely DDE, DDPyMMA, DDMAPMA and DDM), developed by Fanfoni et al. [1], were selected to attribute antimicrobial features to two different commercial bonding agent, ScotchBond Multipurpose and Scotchbond Universal, 3 steps etch-and-rinse and universal self-etch adhesive, respectively. For eventual clinical use, it is necessary that the addition of these molecules does not reduce the bond strength of the adhesive, also in the long term, and especially that the antibacterial activity is preserved after polymerization. The results of the microtensile bond strength (μTBS), both at time 0 and after in vitro thermo-mechanical aging (simulating 5 years of clinical service), and in vitro antibacterial assessment (towards Streptococcus mutans) have shown that Scotchbond Multipurpose adhesive system is more suitable for the incorporation of these molecules, in particular DDMAPMA can therefore be identified as the best antibacterial monomer, that does not affect mechanical and surface properties.
The second part of this project focused on the development and characterization of nano-reinforced dental composite materials through the incorporation of nanometer-sized hydroxyapatite (nHAp) as a filler, which exhibits antibacterial and remineralization features due to the presence of a lab-made bioactive glass (BGMS10), synthetized by Bellucci et al [2]. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis of the filler powders, HAp and BGMS10, confirmed the presence of nanoscopic particles for both fillers. Mechanical characterization showed that the experimental composites made with different resin/filler ratios (R2/HAp-BGMS10) did not have adequate flexural strength and Vickers microhardness values for their use. However, it is interesting to note that the hardness values of the experimental composites under the conditions simulating the oral environment (immersion
in distilled water, at 37°C for a total of 40 days) do not decrease. Moreover, both the assessment of antibacterial properties (against Staphylococcus aureus) and bioactivity demonstrated comparable behaviour to the well-known bioactive glass 45S5, used as a reference in this thesis. In addition, this experimental composite has been found to have low cytotoxicity towards Human Dental Pulp Stem Cells (HDPSCs).
Bibliography
[1] Lidia Fanfoni, Eleonora Marsich, Gianluca Turco, Lorenzo Breschi, and Milena Cadenaro. Development of di-methacrylate quaternary ammonium monomers with antibacterial activity. Acta Biomaterialia, 129:138–147, 2021.
[2] Devis Bellucci and Valeria Cannillo. A novel bioactive glass containing strontium and magnesium with ultra-high crystallization temperature. Materials Letters, 213:67–70, 2018
Review—Electrochemical and SERS Sensors for Cultural Heritage Diagnostics and Conservation: Recent Advances and Prospects
No full textThis review presents the last advances concerning the application to cultural heritage of analytical sensors based on surface enhanced Raman scattering (SERS) and electrochemical transduction. Analytical diagnostics on a work of art is indeed fundamental for dating, restoration and conservation purposes and analytical sensors can provide reliable information at a competitive cost, being usable by non-specialized personal in raw samples and therefore suitable for on-site analysis. After a brief overview on the problem and specificities related to the analysis of works of art, principles and application of SERS for sensing pigments and dyes in paintings is reviewed. Concerning electrochemical sensors, the use of the so-called voltammetry of microparticles is introduced and discussed. For the analysis of macromolecules of biological origin such as protein binders in ancient paintings, the development of immunosensors which exploit SERS or electrochemical detection is presented together with the discussion of the role that advanced nanomaterials plays in improving the functioning of such devices. Finally, prospects and limits derived from the application of the above sensing devices for diagnostics and monitoring of cultural heritage are discussed.This review presents the last advances concerning the application to cultural heritage of analytical sensors based on surface enhanced Raman scattering (SERS) and electrochemical transduction. Analytical diagnostics on a work of art is indeed fundamental for dating, restoration and conservation purposes and analytical sensors can provide reliable information at a competitive cost, being usable by non-specialized personal in raw samples and therefore suitable for on-site analysis. After a brief overview on the problem and specificities related to the analysis of works of art, principles and application of SERS for sensing pigments and dyes in paintings is reviewed. Concerning electrochemical sensors, the use of the so-called voltammetry of microparticles is introduced and discussed. For the analysis of macromolecules of biological origin such as protein binders in ancient paintings, the development of immunosensors which exploit SERS or electrochemical detection is presented together with the discussion of the role that advanced nanomaterials plays in improving the functioning of such devices. Finally, prospects and limits derived from the application of the above sensing devices for diagnostics and monitoring of cultural heritage are discussed. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited
Checking quality of sensory data by assessing intra/inter panelist agreement
No full textThis study aims at checking the quality of sensory data by evaluating and testing both panelist precision and panel reproducibility via an agreement index-based approach which has been already adopted for the assessment of rater reliability but is almost unexplored in the field of sensory analysis. The approach has been applied to a case study concerning the assessment of sensory characteristics induced by different food and beverages
Common trajectories of regional competitiveness in the knowledge economy: a European investigation
Full text linkThis paper analyses a number of European regions that in the last decade, through a considerable change in their economic base, experienced a remarkable growth path and a significant increase in their competitiveness. The analysis was carried out with the aim of recognizing the main determinants (or factors) of territorial development behind each regional renewal process and capturing (in a necessarily stylized manner) a number of common trajectories of regional competitiveness. Interestingly, all regional ‘success stories’ are strongly dependent on the presence of a tri-polar regional innovation system ‘gluing’ firms, institutions and academia
How Reliable are Students’ Evaluations of Teaching (SETs)? A Study to Test Student’s Reproducibility and Repeatability
No full textStudents’ Evaluations of Teaching (SETs) are widely used as measures of teaching quality in Higher Education. A review of specialized literature evidences that researchers widely discuss whether SETs can be considered reliable measures of teaching quality evaluation. Though the controversy mainly refers to the role of students as assessors of teaching qual- ity, most of research studies on SETs focus on the design and validation of the evaluation procedure and even when the need of measuring SETs reliability is recognized, it is gener- ally indirectly assessed for the whole group of students by measuring inter-student agree- ment. In this paper the focus is on the direct assessment of the reliability of each student as a measurement instrument of teaching quality. An agreement-based approach is here adopted in order to assess student’s ability to provide consistent and stable evaluations; the sampling uncertainty is accounted for by building non-parametric bootstrap confidence intervals for the adopted agreement coefficients
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