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AMS Acta (11.650 recursos)

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Mostrando recursos 1 - 20 de 188

  1. Conversion of calcium sulfate dihydrate into calcium phosphates as a route for conservation of gypsum stuccoes and sulfated marble

    Sassoni, Enrico; Graziani, Gabriela; Franzoni, Elisa; Scherer, George W.
    To increase the water resistance of gypsum-based stuccoes (i.e., pastes and mortars), the possible conversion of gypsum into less soluble calcium phosphates (CaP), by reaction with an aqueous solution of diammonium hydrogen phosphate (DAP), was investigated. The effect of several reaction parameters (DAP concentration, ethanol addition to the DAP solution, pH) on nature and morphology of the new CaP was explored. For the most promising formulation, the ability to improve mechanical properties and reduce solubility in water of treated stuccoes was investigated. The treatment provided better results than ammonium oxalate (an inorganic treatment frequently used for consolidation, protection and de-sulphation...

  2. Calcium phosphate coatings for marble conservation: influence of ethanol and isopropanol addition to the precipitation medium on the coating microstructure and performance

    Sassoni, Enrico; Graziani, Gabriela; Franzoni, Elisa; Scherer, George W.
    The effect of adding ethanol and isopropanol to aqueous solutions of diammonium hydrogen phosphate, used to create a passivating layer of calcium phosphates over marble, was investigated. Thanks to its weakening effect on the hydration sphere of ions in solution, ethanol allowed complete coverage of marble surface by a crack-free and pore-free layer of octacalcium phosphate. Even better results were obtained using isopropanol, because it has lower adsorption affinity to calcite than ethanol. Treatments involving alcohols provided good acid protection and also restored cohesion among calcite grains in weathered marble.

  3. New method for controllable accelerated aging of marble: use for testing of consolidants

    Sassoni, Enrico; Graziani, Gabriela; Franzoni, Elisa; Scherer, George W.
    Research is needed on novel consolidants to restore weathered marble, because the available products exhibit limitations. To test new consolidants, samples with features similar to naturally weathered marble (i.e. near-surface damage) are recommended. We developed a novel method that produces decayed samples with a gradient in properties that can be tuned to any desired level, in terms of depth from the surface and decrease of dynamic elastic modulus. The idea is to produce near-surface damage by putting a marble sample in contact with a plate at a certain temperature for a certain time, calculated by a mathematical model. The model...

  4. Bowing of marble slabs: can the phenomenon be arrested and prevented by inorganic treatments?

    Sassoni, Enrico; Andreotti, Serena; Scherer, George W.; Franzoni, Elisa; Siegesmund, Siegfried
    Bowing of thin marble slabs is a phenomenon affecting both historic monuments and modern buildings. In spite of the ubiquity and destructiveness of this phenomenon, no fully satisfactory treatment is currently available to arrest and/or prevent bowing. In this study, a treatment based on formation of hydroxyapatite (HAP) was investigated as a possible route to arrest and possibly prevent bowing of Carrara marble slabs. Four different formulations of the HAP-treatment were tested and compared to ammonium oxalate and ethyl silicate (widely used in the practice of marble conservation). The treatments were applied onto pre-weathered and unweathered specimens to investigate their...

  5. Hydroxyapatite and Other Calcium Phosphates for the Conservation of Cultural Heritage: A Review

    Sassoni, Enrico
    The present paper reviews the methods and the performance of in situ formation of calcium phosphates (CaP) for the conservation of materials belonging to cultural heritage. The core idea is to form CaP (ideally hydroxyapatite, HAP, the most stable CaP at pH > 4) by reaction between the substrate and an aqueous solution of a phosphate salt. Initially proposed for the conservation of marble and limestone, the treatment has been explored for a variety of different substrates, including sandstones, sulphated stones, gypsum stuccoes, concrete, wall paintings, archaeological bones and paper. First, the studies aimed at identifying the best treatment conditions...

  6. Remote Home Physical Training for Seniors: Guidelines from the AAL-supported MOTION project

    Ottoboni, Giovanni; Gallelli, Teresa; Mariani, Elena; Soluri, Valentina Rebecca; Nunziata, Stefano; Tessari, Alessia; Savary, Jean-Pierre; Chattat, Rabih
    European population will face an unprecedented ageing era in the next years. Albeit ageing in itself is a success goal, it may bringwith it a general decline and functional limitations. In order to decelerate such decline, one of the most efficient strategies is physical activity. The present paper reports the insight emerging from three focus-group interviews organized at the beginning of the MOTION - Remote Home Physical Training for Seniors project, whose main aim regarded the implementation of an ICT system capable to offer home-based gym sessions to healthy seniors. The sixteen interview participants (11 females and 5 males, averaged age 72.3)...

  7. Photochemical investigation of cyanoazobenzene derivatives as components of artificial supramolecular pumps

    Casimiro, Lorenzo; Groppi, Jessica; Baroncini, Massimo; La Rosa, Marcello; Credi, Alberto; Silvi, Serena
    Among the plethora of photochromes reported so far, azobenzene has been proven to be the most suitable photoswitch for molecular systems and materials, due to its highly efficient and clean E–Z photoisomerization. Here we report two ammonium-based molecular axles bearing one or two p-cyanoazobenzene units at the extremities, able to form pseudorotaxanes with a crown ether macrocycle. The photochemistry of these compounds was studied in the isolated forms and in the pseudorotaxanes, showing that the functionalization speeds up the threading process without affecting the photochemical properties of the system. These results suggest that the investigated pseudorotaxanes can form the basis...

  8. Crossing Boundaries: Investigating ‘Fair’ in British Parliamentary Debates on Im/migration

    Bevitori, Cinzia
    The paper is a by-product of a recent, cross-disciplinary research project, aiming at exploring linguistic and discursive patterns broadly construing ‘justice’ in a highly influential institutional setting of political discourse, i.e. the British House of Commons, as regards one of the most complex issues facing today's society: im/migration. Parliamentary language may, in fact, provide a privileged terrain for analysing the relationship between social practices and discourse, especially as regards the discussion of key, highly contested issues such as immigration. Moving from the assumption that justice' is a “human construction” (Walzer 1986; Eriksen 2016) embedded in specific systems of value and beliefs, and that immigration is “indeed a matter...

  9. Electrochemically Triggered Co-Conformational Switching in a [2]catenane Comprising a Non-Symmetric Calix[6]arene Wheel and a Two-Station Oriented Macrocycle

    Zanichelli, Valeria; Dallacasagrande, Luca; Arduini, Arturo; Secchi, Andrea; Ragazzon, Giulio; Silvi, Serena; Credi, Alberto
    Catenanes with desymmetrized ring components can undergo co-conformational rearrangements upon external stimulation and can form the basis for the development of molecular rotary motors. We describe the design, synthesis and properties of a [2]catenane consisting of a macrocycle—the ‘track’ ring—endowed with two distinct recognition sites (a bipyridinium and an ammonium) for a calix[6]arene—the ‘shuttle’ ring. By exploiting the ability of the calixarene to thread appropriate non-symmetric axles with directional selectivity, we assembled an oriented pseudorotaxane and converted it into the corresponding oriented catenane by intramolecular ring closing metathesis. Cyclic voltammetric experiments indicate that the calixarene wheel initially surrounds the bipyridinium site,...

  10. Search for low-frequency diffuse radio emission around a shock in the massive galaxy cluster MACS J0744.9+3927

    Wilber, A.; Bruggen, M.; Bonafede, A.; Rafferty, D.; Savini, F.; Shimwell, T.; van Weeren, R. J.; Botteon, A.; Cassano, R.; Brunetti, G.; De Gasperin, F.; Wittor, D.; Hoeft, M.; Birzan, L.
    Merging galaxy clusters produce low Mach number shocks in the intracluster medium. These shocks can accelerate electrons to relativistic energies that are detectable at radio frequencies.

  11. Simulations of ultra-high energy cosmic rays in the local Universe and the origin of cosmic magnetic fields

    Hackstein, Stefan; Vazza, Franco; Bruggen, Marcus; Sorce, Jenny; Gottlober, Stephan
    We simulate the propagation of cosmic rays at ultra-high energies, ≳1018 eV, in models of extragalactic magnetic fields in constrained simulations of the local Universe. We use constrained initial conditions with the cosmological magnetohydrodynamics code ENZO. The resulting models of the distribution of magnetic fields in the local Universe are used in the CRPROPA code to simulate the propagation of ultra-high energy cosmic rays. We investigate the impact of six different magneto-genesis scenarios, both primordial and astrophysical, on the propagation of cosmic rays over cosmological distances. Moreover, we study the influence of different source distributions around the Milky Way. Our study...

  12. Resolved magnetic dynamo action in the simulated intracluster medium

    Vazza, Franco; Brunetti, Gianfranco; Bruggen, Marcus; Bonafede, Annalisa
    Faraday rotation and synchrotron emission from extragalactic radio sources give evidence for the presence of magnetic fields extending over ˜ Mpc scales. However, the origin of these fields remains elusive. With new high-resolution grid simulations, we studied the growth of magnetic fields in a massive galaxy cluster that in several aspects is similar to the Coma cluster. We investigated models in which magnetic fields originate from primordial seed fields with comoving strengths of 0.1 nG at redshift z = 30. The simulations show evidence of significant magnetic field amplification. At the best spatial resolution (3.95 kpc), we are able to...

  13. Simulations of extragalactic magnetic fields and of their observables

    Vazza, Franco; Bruggen, Marcusi; Gheller, Claudio; Hackstein, Stefan; Wittor, Denis; Hinz, Paul
    The origin of extragalactic magnetic fields is still poorly understood. Based on a dedicated suite of cosmological magneto-hydrodynamical simulations with the ENZO code we have performed a survey of different models that may have caused present-day magnetic fields in galaxies and galaxy clusters. The outcomes of these models differ in cluster outskirts, filaments, sheets and voids and we use these simulations to find observational signatures of magnetogenesis. With these simulations, we predict the signal of extragalactic magnetic fields in radio observations of synchrotron emission from the cosmic web, in Faraday rotation, in the propagation of ultra high energy cosmic rays,...

  14. Enhancing the Spectral Hardening of Cosmic TeV Photons by Mixing with Axionlike Particles in the Magnetized Cosmic Web

    Montanino, Daniele; Vazza, Franco; Mirizzi, Alessandro; Viel, Matteo
    Large-scale extragalactic magnetic fields may induce conversions between very-high-energy photons and axionlike particles (ALPs), thereby shielding the photons from absorption on the extragalactic background light. However, in simplified "cell" models, used so far to represent extragalactic magnetic fields, this mechanism would be strongly suppressed by current astrophysical bounds. Here we consider a recent model of extragalactic magnetic fields obtained from large-scale cosmological simulations. Such simulated magnetic fields would have large enhancement in the filaments of matter. As a result, photon-ALP conversions would produce a significant spectral hardening for cosmic TeV photons. This effect would be probed with the upcoming Cherenkov Telescope Array detector. This possible detection would give...

  15. Experimental calibration of underground heat transfer models under a winery building in a rural area

    Tinti, Francesco; Barbaresi, Alberto; Ferrari, Marco; Elkarmoty, Mohamed; Torreggiani, Daniele; Tassinari, Patrizia; Bonduà, Stefano
    Ground temperature and hydrogeological conditions are key parameters for many engineering applications, such as the design of building basements and underground spaces and the assessment of shallow geothermal energy potential. Especially in urban areas, in the very shallow depths, it is diffi cult to fi nd natural undisturbed underground thermal conditions because of anthropic interventions. The assessment of underground behaviour in disturbed conditions will become more and more relevant because of increasing awareness to energy effi ciency and renewable energy topics. The purpose of this paper is to show a three-dimensional representation - based on models calibrated on experimental data - of the underground thermal behaviour...

  16. Suitability Evaluation of Specific Shallow Geothermal Technologies Using a GIS-Based Multi Criteria Decision Analysis Implementing the Analytic Hierarchic Process

    Tinti, Francesco; Sara, Kasmaee; Mohamed, Elkarmoty; Stefano, Bonduà; Villiam, Bortolotti
    The exploitation potential of shallow geothermal energy is usually defined in terms of site-specific ground thermal characteristics. While true, this assumption limits the complexity of the analysis, since feasibility studies involve many other components that must be taken into account when calculating the effective market viability of a geothermal technology or the economic value of a shallow geothermal project. In addition, the results of a feasibility study are not simply the sum of the various factors since some components may be conflicting while others will be of a qualitative nature only. Different approaches are therefore needed to evaluate the suitability of an area for shallow geothermal installation....

  17. Design-oriented modelling of different quenching solutions in induction plasma synthesis of copper nanoparticles

    Bianconi, Simone; Boselli, Marco; Colombo, Vittorio; Gherardi, Matteo
    The aim of this paper is to compare the effects of different mechanisms underlying the synthesis of copper nanoparticles using an atmospheric pressure radio-frequency induction thermal plasma. A design oriented modelling approach was used to parametrically investigate trends and impact of different parameters on the synthesis process through a thermo-fluid dynamic model coupled with electromagnetic field equations for describing the plasma behaviour and a moment method for describing nanoparticles nucleation, growth and transport. The effect of radiative losses from Cu vapour on the precursor evaporation efficiency is highlighted, with occurrence of loading effect even with low precursor feed rate due...

  18. Designed long lived emission from CdSe quantum dots by reversible electronic energy transfer with a surface bound chromophore

    La Rosa, Marcello; Denisov, Sergey; Jonusauskas, Gediminas; McClenaghan, Nathan; Credi, Alberto
    The size-tunable emission of luminescent quantum dots (QDs) makes them highly interesting for applications that range from bioimaging to optoelectronics. For the same applications, engineering their luminescence lifetime – in particular, making it longer – would be as important; however, no rational methodology to reach this goal is available to date. Here we describe a strategy to prolong the emission lifetime of QDs by electronic energy shuttling to the triplet excited state of a surface-bound molecular chromophore. To implement this idea we made CdSe QDs of different sizes, and we self-assembled them with a pyrene derivative. We observed that the...

  19. Making and operating molecular machines: a multidisciplinary challenge

    Baroncini, Massimo; Casimiro, Lorenzo; De Vet, Christiaan; Groppi, Jessica; Silvi, Serena; Credi, Alberto
    Movement is one of the central attributes of life, and a key feature in many technological processes. While artificial motion is typically provided by macroscopic engines powered by internal combustion or electrical energy, movement in living organisms is produced by machines and motors of molecular size that typically exploit the energy of chemical fuels at ambient temperature to generate forces and ultimately execute functions. The progress in several areas of chemistry, together with an improved understanding of biomolecular machines, has led to the development of a large variety of wholly synthetic molecular machines. These systems have the potential to bring...

  20. Remote electrochemical modulation of pKa in a rotaxane by co-conformational allostery

    Ragazzon, Giulio; Schaefer, Christian; Franchi, Paola; Silvi, Serena; Colasson, Benoit; Lucarini, Marco; Credi, Alberto
    Allosteric control, one of Nature’s most effective ways to regulate functions in biomolecular machinery, involves the transfer of information between distant sites. The mechanistic details of such a transfer are still object of intensive investigation and debate, and the idea that the intramolecular communication could be enabled by dynamic processes is gaining attention as a complement to traditional explanations. Mechanically interlocked molecules, owing to the particular kind of connection between their components and the resulting dynamic behavior, are attractive systems to investigate allosteric mechanisms and exploit them to develop functionalities with artificial species. We show that the pKa of an...

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