859 research outputs found

    Geopolymer composites for potential applications in cultural heritage

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    A new class of geopolymer composites, as materials alternative to traditional binders, was synthesized and its potentialities as restoration material in Cultural Heritage has been explored. This material has been prepared through a co-reticulation reaction in mild conditions of a metakaolin-based geopolymer inorganic matrix and a commercial epoxy resin. The freshly prepared slurry displays a consistency, workability and thixotropic behavior that make it suitable to be spread on different substrates in restoration, repair and reinforcement actions, even on walls and ceilings. Applicability and compatibility tests on tuff and concrete substrates were carried out and the microstructure of the samples in correspondence of the transition zone was analyzed by means of scanning electron microscope (SEM) observations and energy dispersive spectroscopy (EDS) mapping. Our studies pointed out the formation of a continuous phase between the geopolymer composite and tuff and concrete substrates, highlighting a high compatibility of the geopolymer binder with different kinds of materials. These features indicate a large potential for applications of these materials in Cultural Heritage

    Synthesis of highly regioregular poly[3-(4-alkoxyphenyl)-thiophene]s by oxidative catalysis using copper complexes

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    A novel, easy, and cost-effective synthetic procedure is reported for the production of very highly regioregular poly[3-(4-alkoxyphenyl)thiophene]s by means of oxidative coupling. Four copper complexes were synthesized and used as catalysts to obtain polymers with higher regioregularity compared to the previous oxidative coupling methodologies reported in the literature and similar to that obtained by McCullough and Rieke methods in the synthesis of poly-3-alkylthiophenes. The regioregularity of the synthesized polymers was investigated by UV-Visible characterization on polymer thin films and 1H NMR analysis. The remarkable potentialities of these polymers have emerged from field-effect transistor mobility measurements operated on devices with bottom-contact configuration and hexamethyldisilazane-treated SiO 2 gate dielectric, showing a well-defined p-type field-effect response and maximum mobility values in air higher than 10-4 cm 2 V-1 s-1. © 2013 Wiley Periodicals, Inc

    High nonlinear optical response in 4-chlorothiazole-based azo dyes

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    Four azo dyes showing high nonlinear optical properties were prepared, based on a 4-chlorothiazole azo moiety functionalized with strong acceptor groups and/or further donor/acceptor groups along the conjugated backbone. The effects of the acceptors as well as the lateral donor/acceptor groups upon absorption properties, thermal stability and second order nonlinear optical activity were evaluated. © 2010 Elsevier Ltd. All rights reserved

    Photopolymer-based volume holographic optical elements: design and possible applications

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    In this paper, Volume Holographic Optical Elements (V-HOEs), such as holographic gratings and spherical lenses, are designed and fabricated by using a prototype of photopolymer. The recording process of V-HOEs and their appropriate characterization are described. Moreover, V-HOEs possible applications as solar concentrator are investigated and results are discussed. Finally, a system that allows passive solar tracking is proposed and preliminary results are reported

    Role of novel hormonal therapies in the management of non-metastatic castration-resistant prostate cancer:a literature-based meta-analysis of randomized trials

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    BACKGROUND: Novel hormonal therapies have been recently investigated in non-metastatic castration-resistant prostate cancer (CRPC). We performed a meta-analysis to assess the efficacy and safety of novel hormonal therapies in non-metastatic CRPC.MATERIALS AND METHODS: The primary outcome was metastasis-free survival (MFS). The secondary endpoints were overall survival (OS), time to PSA progression and safety. We planned a subgroup analysis according to the PSA doubling time (&gt; 6 vs &lt; 6 months), Eastern Cooperative Oncology Group (ECOG) performance status (1 vs 0) and concomitant use of bone-targeting agent (yes vs no).RESULTS: Pooled analysis of novel hormonal therapies revealed significantly increased MFS compared with placebo (hazard ratio (HR): HR = 0.32, 95% CI 0.25-0.41; p &lt; 0.00001). The subgroup analysis showed a statistically significant MFS advantage in favour of men with the lower ECOG performance status. Other secondary endpoints favoured the novel hormonal therapies. The relative risk (RR) of grade ≥ 3 adverse events and ≥ 3 hypertension was 1.31 and 1.39, respectively.CONCLUSIONS: This study confirmed the efficacy and safety of the novel hormonal therapies in non-metastatic CRPC.</p

    Perylene diimides functionalized with N-thiadiazole substituents: Synthesis and electronic properties in OFET devices

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    Two new perylene diimide derivatives N,N′-bis(5-tridecyl-1,3,4- thiadiazol-2-yl)perylene-3,4,9,10-tetracarboxylic 3,4:9,10-diimide (PDI-T1) and N,N′-bis[5-(1-hexyl)nonyl-1,3,4-thiadiazol-2-yl]perylene-3,4,9, 10-tetracarboxylic 3,4:9,10-diimide (PDI-T2), achieved by functionalizing the basic perylene molecular core at imide nitrogen with 1,3,4-thiadiazole rings, have been synthesized. Both these compounds make possible the fabrication of n-type organic thin-film transistors able to work in air, even when bare SiO2 surfaces are utilized as gate dielectric. As active channels of transistors in the bottom-contact bottom-gate configuration, PDI-T1 evaporated films exhibited a maximum mobility of 0.016 cm2/V s in vacuum. For evaporated PDI-T2 films, instead, mobility values were found to be more than one order of magnitude lower, because of their reduced degree of crystalline order. However, PDI-T2 films can be also deposited by solution techniques and field-effect transistors were fabricated by spin-coating, displaying mobility values ranging between 10-6 and 10-5 cm2/V s. Similar to what previously found for other perylene diimide derivatives, our experimental work also demonstrates that the electrical response of both PDI-T1 and PDI-T2 transistors under ambient conditions can be improved by increasing the level of hydrophobicity of the dielectric surface. © 2012 Elsevier B.V. All rights reserved
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