18,439 research outputs found
Pre-consolidation of decayed Angera columns with ammonium phosphate : a pilot study in a Milanese courtyard of XVI Century
No full textAngera stone is a lithotype widely employed in Lombardy (north Italy) for ornamental elements/frameworks of
historical buildings. Owing to decay processes it is affected by detachments, exfoliations, pulverizations with
consequent loss of material. The traditional application of synthetic organic products on the Angera surfaces had a
significant role in the decay processes as well (Colombo et al., 2006). Over the last years, the boundaries of
Conservation Science have been pushed toward the use of inorganic-mineral treatments that are stable, durable, highly
transpirable and more compatible with the stone substrates. Ammonium phosphate [DAP, (NH4)HPO4], one of the most
recent inorganic-mineral treatment, is based on the reaction between a water soluble precursor with carbonatic
substrates; the newly formed crystalline phases are able to restore the lost cohesion of the microstructure. Recent studies
investigated the interactions of DAP solutions with calcite of marbles and limestones (Matteini et al., 2011; Possenti et
al., 2016). To the best of our knowledge, no data are available on the application of DAP to: i) the conservation of
dolostones; ii) the pre-consolidation of decayed stones.
Therefore, in this study we explored the potentialities of DAP treatments as a pre-consolidating agent for white
Angera stone. DAP solutions were vaporized on vertical specimens to avoid mechanical contact with decayed surfaces.
The research evaluated the effects induced by the molarity and the application method (repeated applications, wetted or
dry substrate, comparison with paper poultice) on the surface and the influence of pre-consolidation on the subsequent
consolidation with DAP.
The formation of specific crystalline phases and their diffusion inside the first few microns of the stone matrix were
investigated following a multi-analytical approach (SEM-EDS, Raman and IR spectroscopies, XRD). The research
outcomes supplied outstanding indications for restoration, supporting the application of DAP pre-consolidating
treatments to Angera columns strongly decayed in a Milanese courtyard of XVI Century.
Colombo, C., Conti, C., Realini, M., Sansonetti, A. (2006): Diagnostic studies aimed to conservation works in S. Fedele church
(Milan). Proceedings of HWC Congress (Heritage, Weathering and Conservation), Taylor & Francis Group, 917-922.
Matteini, M., Rescic, S., Fratini, F., Botticelli, G. (2011): Ammonium phosphates as consolidating agents for carbonatic stone
materials used in architecture and cultural heritage: preliminary research. Int. J. Archit. Herit. Conserv. Anal. Restor., 5, 717-736.
Possenti, E., Colombo, C., Bersani, D., Bertasa, M., Botteon, A., Conti, C., Lottici, P.P., Realini, M. (2016): New insight on the
interaction of diammonium hydrogenphosphate conservation treatment with carbonatic substrates: a multi-analytical approach.
Microchem. J., 127, 79-86
Synthesis of Unnatural Alfa-N-linked Glycopeptides with Potential Antifreeze Activity
No full textThe synthesis of neo-glycoconjugates has been gaining much attention in recent years due to the relevance of glycopeptides and glycoproteins in many biological processes.[i] Our group has been actively dedicating its efforts to the synthesis of α-N-linked glycosylamides and glycopeptides.[ii] α-N-linked glycopeptides are unnatural molecules, since they display an α linkage between the peptide side chain and the sugar moiety, unlike natural glycopeptides which connect the peptide to the glycan through a β-N-glycosidic bond. This novel type of glycosylation of peptides could introduce modifications that can mimic and/or interfere with molecular recognition events.[iii] Direct glycosylation of peptide chains is not viable for the synthesis of molecules with α-N-linked configuration, since the corresponding α-glycosyl amines isomerise to the β-anomers. Only very recently Nα-Fmoc-protected glycosyl amino acids have been efficiently and stereoselectively synthesized and linearly incorporated into a peptide sequence.[iii] In the present paper these novel building blocks have been employed for the synthesis of complex structures that resemble antifreeze glycopeptides (Figure 1).[iv] These sequences were prepared using solid phase synthesis with Fmoc protocol, experimenting with different conditions and also using microwave assisted solid phase synthesis, in an effort to enhance the reactivity of our unnatural building block. The α-N-linked glycopeptides were obtained with modest yields, their secondary structure was assessed by circular dichroism and their antifreeze properties were evaluated in the group of Prof. Robert N. Ben. Despite the fact that our compounds do not show significant antifreeze activity, this work constitutes the first attempt towards the synthesis of complex α-N-linked glycopeptides and has been useful to understand the behaviour, sometimes unexpected, of these molecules, in terms of reactivity and stability. [i] D. P. Gamblin, E. M. Scanlan, B. G. Davis, Chem. Rev. 2009, 109, 131-163. [ii] a) F. Nisic, A. Bernardi, Carbohydr. Res. 2011,346, 465-71. b) C. Colombo, A. Bernardi,Eur. J. Org. Chem. 2011, 3911–3919. [iii] F. Marcelo, F. J. Cañada, S. André, C. Colombo, F. Doro, H. J. Gabius, A. Bernardi, J. Jiménez-Barbero. Organic & Biomolecular Chemistry 2012, DOI: 10.1039/C2OB07135E. [iv] a) Garner, J.; Harding, M. M. ChemBioChem 2010, 11 2489-2498. b) Leclere, M; Kwok, K. B.; Luke K. W.; Allan, D. S.; Ben, R. N. Bioconjugate Chem. 2011, 22, 1804-1810
Application of ammonium phosphate to marble. Investigation of newly-formed calcium phosphates with synchrotron light and high lateral resolution FTIR microspectroscopy
No full textInorganic-mineral treatments exhibit great potentialities for the consolidation of stone materials due to their high compatibility with the substrate. Their reaction mechanism is based on the diffusion, inside weathered stone matrixes, of water soluble precursors that, reacting with the substrate, supply a crystal network able to reconnect detached grain boundaries. The newly-formed crystalline phases are stable and due to their low solubility provide a passivating action toward atmospheric agents even in acid environment. Diammonium hydrogen phosphate [DAP, (NH4)2HPO4] has been recently suggested for the treatment of sedimentary and metamorphic carbonatic decayed stones. The reaction of DAP with calcite of the substrate involves a pseudomorphic replacement and favours the growth of calcium phosphates inside the porosity. Preliminary studies (Matteini et al., 2013; Possenti et al., 2016) show that the reaction at room temperature is non-stoichiometric and induces the formation of hydroxyapatite [HAP, Ca5(PO4)3(OH)] (Ni & Ratner, 2003) and other metastable phases. In this pilot study we characterized the complex assemblages of calcium phosphates formed after DAP treatments on Carrara marble specimens with a multi-analytical approach (scanning electron microscopy, vibrational spectroscopies and powder X-ray diffraction). A set of quarried and thermally decayed samples were treated by poultice and capillarity using DAP solutions at different molarities. Ground-breaking techniques such as X-ray diffraction with synchrotron light in transmitting geometry and high lateral resolution FTIR microspectroscopy were employed to overcome some of the analytical limits of conventional approach, assessing the overall composition of main and trace phases as well as
their arrangement on the substrate. Preliminary findings show the formation of a shell-like layer around the calcite grains, composed by a mixture of crystalline and amorphous calcium phosphates; the formation of specific phases, their morphologies and the relative amount depend on the solution molarity and the treatment duration. Moreover, our data show a correlation between the kind of crystalline phase and its morphology and position within the shell structure.
Matteini, M., Colombo, C., Botticelli, G., Casati, M., Conti, C., Negrotti, R., Possenti, E., Realini M. (2013): Ammonium phosphates
to consolidate carbonatic stone materials: an inorganic-mineral treatment greatly promising. Proceedings of the Built Heritage
2013 Monitoring Conservation Management, 1278-1286.
Ni, M. & Ratner, B.D. (2003): Nacre surface transformation to hydroxyapatite in a phosphate buffer solution. Biomaterials, 24, 4323-
4331.
Possenti, E., Colombo, C., Bersani, D., Bertasa, M., Botteon, A., Conti, C., Lottici, P.P., Conti C. (2016): New insight on the
interaction of diammonium hydrogenphosphate conservation treatment with carbonatic substrates: a multi-analytical approach.
Microchem. J., 127, 79-86
Calcium phosphates crystallized on Carrara marble after phosphate-based consolidating treatment
No full textDiammonium hydrogen phosphate (DAP, (NH4)2HPO4) solutions have been introduced in the conservation field as a new inorganic-mineral treatments to consolidate or protect decayed carbonatic stone materials of historical monuments [1]. The treatment forms calcium phosphates through a dissolution and re-crystallization reaction, which takes place between hydrogen phosphate groups of the reagent and calcium ions of calcite of the substrate. Calcium phosphates nucleate on calcite grains with a pseudomorphic replacement reaction, and form a crystal network able to restore the lost cohesion of the microstructure. Despite the high number of studies on the crystallization of calcium phosphates and their formation on the surface of carbonatic substrates, only a few studies explored the formation of calcium phosphate phases on marbles treated with DAP and using calcite of the substrate as unique source for calcium ions [2-4]. Previous studies revealed a non-stoichiometric reaction that lead to the formation of a mixture of phases, each one characterized by different Ca/P molar ratio, solubility and stability [4]. In this study, we carry out a non-destructive synchrotron radiation grazing incidence X-ray diffraction (SR-GIXRD) investigation on DAP-treated marbles to determine how the mineralogical composition of the stone substrate affects the crystallization of stable and metastable calcium phosphates. The analyses were performed on Carrara marble specimens treated by capillarity by 0.76 M DAP solutions. Our results indicate that the presence of compositional micro-heterogeneity of Carrara marble favours the formation of specific phases. In general, the composition and the localization of the phases directly depend on the availability of free Ca2+ ions. Dicalcium phosphate dihydrate, a calcium phosphate with a low Ca/P molar ratio, is formed on carbonatic phases with a low Ca content, such as dolomite grains and Mg-containing veins. Octacalcium phosphate (OCP, Ca8(HPO4)2·5H2O) and poorly-crystalline partially-substituted hydroxyapatite (HAP, Ca5(PO4)3OH) are the foremost newly-formed phases when the substrate is mainly composed by calcite.
This study shed light on the potentialities of SR-GIXRD as a powerful non-destructive tool for the diagnostic of Cultural Heritage objects, since it allows investigating the conservation history of stone materials with an in depth evaluation of DAP consolidating processes [5].
[1] M. Matteini, S. Rescic, F. Fratini, G. Botticelli Int. J. Archit. Herit. Conserv. Anal. Restor. 2011, 5, 717.
[2] M. Kamiya, J. Hatta, E. Shimada, Y. Ikuma, M. Yoshimura, H. Monma Mater. Sci. Eng. B 2004, 111, 226.
[3] S. Naidu and G. W. Scherer J. Colloid Interface Sci. 2014, 435, 128.
[4] E. Possenti, C. Colombo, D. Bersani, M. Bertasa, A. Botteon, C. Conti, P. P. Lottici, M. Realini Microchem. J. 2016, 127, 79.
[5] E. Possenti, C. Colombo, C. Conti, L. Gigli, M. Merlini, J. R. Plaisier, M. Realini, G. D. Gatta Appl. Phys. A 2018, 124, 383
Moderating Urbanization and Managing Growth: How Can Colombo Prevent the Emerging Chaos?
No full textThis paper examines urbanization trends, the growth of Colombo and its present state of development. It looks at the approaches to the planned interventions in the city and demonstrates how a uni-directional urban development has had a detrimental impactColombo, urban development, managing urbanization, planning, housing,
Leonardo e il Novecento: dai futuristi alle mostre leonardesche
No full textIl saggio in catalogo illustra la sezione 8 della mostra "Leonardo di carta in carta. La costruzione del mito fra Ottocento e Novecento", a cura di S. Alessandri, M. Ceriana, S. Mammana (comitato scientifico: S. Alessandri, F. Barbagli, M. Ceriana, D. Colombo, S. Mammana, F. Tognoni, A. Tura, F. Valli, C. Vecce), tenutasi alla Biblioteca Nazionale Centrale di Firenze (BNCF) dal 5 dicembre 2019 al 14 marzo 2020. La sezione della mostra e il saggio sono dedicati a una breve rassegna dello sviluppo del mito di Leonardo a Vinci nei primi decenni del Novecento: dalla irrisione del mito della Gioconda fatto da artisti come Malevic, Duchamp, Picabia, Eluard, Leger e dai futuristi, che, però consideravano il maestro rinascimentale un modello di riferimento, all'influenza esercitata su Balla, Carrà, Fontana, fino alla sequenza di mostre che hanno sancito la definizione del mito di Leonardo scienziato, genio precursore e universale, fatto proprio dalla propaganda fascista, soprattutto con la Mostra Leonardesca del 1939 al Palazzo dell'Arte di Milano.The essay of the catalogue presents the section no. 8 of the exhibition "Leonardo di carta in carta. La costruzione del mito fra Ottocento e Novecento", ed. by S. Alessandri, M. Ceriana, S. Mammana (Scientifi Committee: S. Alessandri, F. Barbagli, M. Ceriana, D. Colombo, S. Mammana, F. Tognoni, A. Tura, F. Valli, C. Vecce), held at Biblioteca Nazionale Centrale in Firenze (BNCF) from December 5 2019 to March 14 2020. The exhibition section and the essay are dedicated to a short portrayal of the development of the myth of Leonardo da Vinci in earlier Twentieth-Century: the derision of myth of Gioconda by artists such as Malevic, Duchamp, Picabia, Eluard, Leger, and by futurists, who, anyway, considered him a model, as well as the influence on Balla, Carrà, and Fontana; moreover the sequence of shows dedicated to Leonardo “scientist”, pioneer and all-round genius, used by propaganda of Fascism, above all thanks to exhibition Leonardesca, held at Palazzo dell’Arte in Milan in 1939
Interferon-free therapy for hepatitis C: The hurdles amid a golden era
No full textAbstractThe long awaited all-oral therapy for hepatitis C virus infection has officially been inaugurated by the registration of the hepatitis C nucleotide inhibitor sofosbuvir in a combination regimen with ribavirin. More recently, the oral array to treat hepatitis C has been enriched by the arrival of the NS5A inhibitors ledipasvir (also in a single formulation with sofosbuvir, Harvoni®) and daclatasvir; the protease inhibitor simeprevir, and the Viekirax®+Exviera™ regimen based on the ritonavir boosted protease inhibitor paritaprevir; the NS5A inhibitor ombitasvir, and the non-nucleoside inhibitor dasabuvir. Owing to the budget-breaking price of the newer oral medicines, the Italian National Health System elected to restrict reimbursement of oral anti-hepatitis C therapy to patients with advanced liver disease or transplanted organs, and those who are interferon unable, only. While this therapeutic strategy harmonizes with principles of distributive justice, at the same time it fuelled the argument of its doubtful cost-effectiveness, owing to the National Health System's reimbursement of the sole sofosbuvir+ribavirin regimen, which has suboptimal efficacy against the prevalent hepatitis C virus genotype 1b. As a consequence, we are left with a number of uncertainties regarding the optimal treatment modality for certain subgroups of hepatitis C patients, and the clinical benefits provided by hepatitis C virus clearance in patients with advanced liver disease
Crystallography and Cultural Heritage: study of caoxite formed after a conservation treatment
No full textIn Cultural Heritage field, whewellite (CaC2O4•H2O - COM) and weddellite (CaC2O4•(2+x) H2O - COD) play a relevant role for a twofold reason: they are the main components of a particular kind of film found on the surface of many works of art and they also occur in a conservation treatment for carbonatic substrates [1], due to the reaction between ammonium oxalate solution and calcite of the substrate. In order to obtain a more homogeneous and deeper diffusion of the treatment into decayed materials, we focused our experiments on an alternative method using diethyloxalate [(C2H5)2C2O4] which during the hydrolysis transforms calcium carbonate into calcium oxalate [2]. The reaction between diethyloxalate and calcite produces COM, COD and an unexpected relevant amount of caoxite (CaC2O4•3H2O - COT). The crystallization of COT into the treated carbonatic substrate is the main proof of the reaction between diethyloxalate and the decayed stones, thus its identification is essential to monitor the treatment and define its efficacy. Due to the scarce literature data, an extensive investigation of crystallographic, spectroscopic and microscopic features of COT has been performed, including the development of a new method for its synthesis [3]. The experiments clearly highlight the role played by the H2O molecules linked within the structure by different kinds of hydrogen bonds. The vibrational assignment of the infrared and Raman bands is critically proposed. The fact relevant for the work in biomedicine, cultural heritage and crystallography is that a simple examination of the spectra allows quickly to determine the chemical nature of the material in an unknown sample even in a minute quantity or in awkward experimental conditions.
[1] B. Doherty, M. Pamplona, R. Selvaggi, C. Miliani, M. Matteini, A. Sgamellotti, B. Brunetti, Appl. Surf. Sci. 2007, 253, 4477.
[2] C. Conti, I. Aliatis, M. Casati, C. Colombo, M. Matteini, R. Negrotti, M. Realini, G. Zerbi, J. Cult. Herit. 2013, 15, 336.
[3] C. Conti, M. Casati, C. Colombo, E. Possenti, M. Realini, G.D. Gatta, M. Merlini, L. Brambilla, G. Zerbi, Spectrochim. Acta A, 2015, 150, 721
Анатомы - лечащие врачи папства (обзор литературы)
No full textСтаття присвячена анатомам, які були особистими лікарями Пап Римських у різний час:
М. Р. Коломбо (1515-1559), Г. Б. Канано (1515-1579), Г. C. Аранзі (1530-1589), К. Варолій (1543-
1575), А. Чезальпіно (1525-1603), М. Мальпігі (1628-1694), Дж. M. Ланцізі (1654-1720) та
Дж. Флайяні (1739-1808). Подається інформація про їх внесок у розвиток медицини та короткі
біографічні данні.
При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/31507Статья посвящена анатомам, которые были лечащими врачами Пап Римских в разные годы:
М. Р. Коломбо (1515-1559), Г. Б. Канано (1515-1579), Г. C. Аранзи (1530-1589), К. Варолий (1543-
1575), А. Чезальпино (1525-1603), М. Мальпиги (1628-1694), Дж. M. Ланцизи (1654-1720) и
Дж. Флайяни (1739-1808). Рассказывается об их вкладе в развитие медицины и короткие
биографические данные.
При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/31507Article is about anatomists, who were papal physicians: M.R. Colombo (c.1515-1559),
G.B. Canano (1515-1579), G.C. Aranzi (1530-1589), C. Varolio (1543-1575), A. Cesalpino (1525-
1603), M. Malpighi (1628-1694), G.M. Lancisi (1654-1720) and G. Flaiani (1739-1808). Their
contribution into anatomy and brief biographical information are given.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3150
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