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Copyright of Enthymema is the property of Enthymema, International Journal of Literary Criticism, Literary Theory & Philosophy of Literature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Enthymema is the property of Enthymema, International Journal of Literary Criticism, Literary Theory & Philosophy of Literature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Algal biofouling on archaeological and historic materials, as well as in modern building façade, is a common phenomenon that occurs when microorganisms of various nature adhere to the material, forming biological stains and patinas. It can significantly deteriorate the aesthetic and even mechanical quality of historic and archaeological artifacts. Thus, predicting the colonization progress of algae on treated and untreated materials can be helpful to establish appropriate schedules and methods of maintenance. In this way, the aim of this research was to modelize the algal colonization on nano-TiO2 coated and uncoated stone surfaces, usually found in historic and archaeological artifacts, by following Avrami's theory. Particular attention was paid on correlating the model with some properties of the substrate, like roughness and porosity. Biofouling was tested on two sandstones and three limestone with different intrinsic characteristics (porosity, roughness) by means of an accelerated lab-scale test. A suspension of green alga Chlorella mirabilis and cyanobacteria Chroococcidiopsis fissurarum was used as biofouling. Digital image analysis was carried out in order to find the attachment rate and the growth of algal spots. Results show that the attachment specific rate increased linearly with time, and the assumption of a constant growth rate was acceptable. A good agreement between the simulation and the experimental results was obtained with a maximum error of 0.59%. [ABSTRACT FROM AUTHOR]

Archaeological artifacts are inevitably subject to deterioration caused by natural air pollution, contaminants by human actions, and biodeterioration from microorganisms. Their preservation is considered a more and more strategic factor in many countries because of their economic, social and cultural implications. Modern techniques of interventions often require re-application after some years, and they cannot be used in all restorations. Recently, the use of nanotechnologies was transferred to the restoration sector bringing many innovations. Titanium dioxide (TiO2) is the main nanostructured material used to prevent the comparison of weathering traces, to obtain self-cleaning materials and to slow down biofouling as well. In this paper, its potential use was tested on common archaeological materials like sandstone, limestone and bricks. The self-cleaning ability of this innovative material, as well as, its biofouling prevention were evaluated in laboratory simulated tests. Results show the high potentiality of this nanomaterial in making the tested archaeological surfaces self-cleaning and biocide. [ABSTRACT FROM AUTHOR]

Brick constitutes a significant part of the construction materials used in historic buildings around the world. This material was used in Architectural Heritage for structural scope, and even for building envelopes. Thus, components made of clay brick were subjected to weathering for a long time, and this causes their deterioration. One of the most important causes for deterioration is biodeterioration caused by algae and cyanobacteria. It compromises the aesthetical properties, and, at a later stage, the integrity of the elements. In fact, traditional products used for the remediation/prevention of biofouling do not ensure long-term protection, and they need re-application over time. The use of nanotechnology, especially the use of photocatalytic products for the prevention of organic contamination of building façades is increasing. In this study, TiO2-based photocatalytic nano-coatings were applied to ancient brick, and its efficiency towards biofouling was studied. A composed suspension of algae and cyanobacteria was sprinkled on the bricks' surface for a duration of twelve weeks. Digital Image Analysis and colorimetric measurements were carried out to evaluate algal growth on specimens' surfaces. Results show that photocatalytic nano-coating was able to inhibit biofouling on bricks' surfaces. In addition, substrata (their porosity and roughness) clearly influences the adhesion of algal cells. [ABSTRACT FROM AUTHOR]

The goal of this study was to explain the influence of the total porosity and the surface roughness on the susceptibility of clay bricks to biodegradation by phototrophic microorganisms. In addition, this correlation was studied on both specimens treated with TiO 2 nanocoating and untreated control specimens. The effect of UV intensity on the photocatalytic power of T i O 2 was also investigated. An accelerated fouling test was performed by sprinkling a suspension of Chlorella mirabilis and Chroococcidiopsis fissurarum on sample surfaces. These two test strains were chosen because their representativeness on building clay brick façades subjected to biofouling. The gradual superficial accumulation of algal biomass on treated and control specimens was evaluated by means of image analysis and colour measurement. Two specimens' parameters, namely porosity and roughness, were examined. Results showed that both the specimen microstructure and roughness of the surface play a key role in the colonization of clay bricks because they were able to provide more nutrient to the algal cells anchored to the surface. The T i O 2 nanocoating was able to inhibit the biofouling of clay bricks irradiated with UV-A light, except in the case of high porous rough specimens. [ABSTRACT FROM AUTHOR]

Abstract: Environmental pollution is constantly increasing and it causes aesthetical concerns to urban buildings exposed to the atmosphere. Nanometric titanium dioxide (TiO2) has become a promising photocatalytic material owing to its ability to accelerate degradation of many organic contaminants. Application of TiO2 is rising and it found application on building industry. However, photocatalytic properties of this nanotechnology strongly depend on substrate morphology and on its nature. Thus, it is not correct to extrapolate photocatalytic activity on different types of substrate. Moreover, very few information is available about effectiveness of TiO2 coatings after aging phenomena when applied on different substrate. This paper aims to investigate photocatalytic properties of TiO2 applied on clay brick surfaces both after deposition and after aging process. TiO2 characterization was carried out by assessing nano-film morphology, wettability and self-cleaning efficiency before durability test. Self-cleaning ability was also evaluated during aging test in order to evaluate its variation in long term applications. Results show that photocatalytic efficiency of TiO2 remain stable after aging, thus TiO2 shows a good photocatalytic efficiency when it is applied to clay brick substrate. In the long run, photocatalytic efficiency of clay brick specimens treated with TiO2 is seven times higher than untreated specimens. [Copyright &y& Elsevier]

Abstract: Microalgal growth largely affects the aesthetical properties of building façades worldwide. It causes biodeterioration of building materials and, in a later stage, it can compromise integrity of the elements and their durability. Recently, the use of nanotechnology to prevent the growth of microalgae is rising. One of the most widespread and promising material is titanium dioxide (TiO2). Photocatalytic properties of TiO2 inhibit biofouling of microalgae when this coating is stimulated by UV radiation coming from the sun or from artificial light. In this study, the biocide effect of TiO2 coatings applied on clay brick specimens under weak UV radiation was assessed. Results revealed that TiO2 nanocoating was not able to fully prevent microalgal biofouling, but under optimal UV exposure conditions for the growth of microalgae it efficaciously prevented the adhesion of these microorganisms on the treated substrates through the formation of a superficial water film. This property resulted in a good self-cleaning efficiency of TiO2. [Copyright &y& Elsevier]