614 research outputs found

    Urban Scale Monitoring Approach for the Assessment of Rising Damp Effects in Venice

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    In coastal areas, the rising damp of salty water is a well-known degradation factor of historical masonries, leading to visible features such as crusts, masonry erosion, and plaster loss. Venetian masonries are strongly affected by decay caused by rising damp exacerbated by direct contact with salty water. Recurrent flooding due to high tides and an increase in the frequency of flooding events, also related to climate change, raises concern about the impacts. Although several studies have been carried out on probable future scenarios, a valuation of the decay risk due to rising damp at the urban level still needs to be implemented. This paper proposes a non-invasive and economically sustainable approach for evaluating rising damp effects at an urban scale. The approach includes a collection of archive images of masonries affected by rising damp dating back to the 1990s; a visual survey of the actual conservation state of masonries; a classification based on significant descriptors; and a discussion on exposure conditions and conservation states. The descriptors chosen are rising damp levels, biological growth, plaster loss, efflorescence, and brick erosion. The evaluation was implemented in a georeferenced system suitable for future comparisons, thus providing a management tool for the city's preservation

    Tiles from Aosta: A Peculiar Glaze Roof Covering

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    The 18th century roof tiles from the “Casa delle vigne”, located in the Aosta region (north-east Italy), were investigated as an example of a peculiar historical roof covering: ceramic tiles with a lead-based glaze finishing to waterproof them are used to create colourful patterns. A conservation project proposed the integration of the original tiles with new ones, produced according to traditional methods. Ancient and new tiles were analysed with Fiber Optics Reflectance Spectroscopy, micro-Raman, Fourier Transform Infrared Spectroscopy and X-ray Fluorescence Spectrometry, Thermogravimetry and Differential Scanning Calorimetry for understanding the composition and the production technology of this manufacture. Their resistance to freezing and thawing cycles was then tested, considering their exposure in the severe alpine climate of Aosta. The use of pure clays with low calcium contents, high firing temperature and lead-rich glazes was found in ancient tiles, able to outstand several freezing-thawing cycles without damages. Iron and copper pigments were used in old yellow and green glazes. Zinc-based pigment, low lead and calcium-rich glazes are used in the new ones, which remained mainly coherent to the ceramic body during the freeze-thaw test

    Flare model sensitivity of the Balmer spectrum

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    Careful studies of various chromospheric spectral signatures are very important in order to explore their possible sensitivity to the modifications of the thermodynamic quantities produced by the flare occurrence. Pioneer work of Canfield and co-workers have shown how the H alpha behavior is able to indicate different changes in the atmospheric parameters structure associated to the flare event. It was decided to study the behavior of the highest Balmer lines and of the Balmer continuum in different solar flare model atmospheres. These spectral features, originating in the deep photosphere in a quiet area, may have a sensitivity different from H alpha to the modification of a flare atmosphere. The details of the method used to compute the Stark profile of the higher Balmer line (n is greater than or equal to 6) and their merging were extensively given elsewhere (Donati-Falchi et al., 1985; Falchi et al., 1989). The models used were developed by Ricchiazzi in his thesis (1982) evaluating the chromospheric response to both the nonthermal electron flux, for energy greater than 20 kev, (F sub 20) and to the thermal conduction, (F sub c). The effect of the coronal pressure values (P sub O) at the apex of the flare loop is also included

    Helium Line Formation and Abundance in a Solar Active Region

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    An observing campaign (SOHO JOP 139), coordinated between ground-based and Solar and Heliospheric Observatory (SOHO) instruments, has been planned to obtain simultaneous spectroheliograms of the same active region in several spectral lines. The chromospheric lines Ca ii K, H , and Na i D, as well as He i 10830, 5876, 584, and He ii 304 8 lines have been observed. The EUV radiation in the range k < 500 8 and in the range 260 < k < 340 8 has also been measured at the same time. These simultaneous observations allow us to build semiempirical models of the chromosphere and low transition region of an active region, taking into account the estimated total number of photoionizing photons impinging on the target active region and their spectral distribution. We obtained a model that matches very well all the observed line profiles, using a standard value for the He abundance (½He ¼ 0:1) and a modified distribution of microturbulence. For this model we study the influence of the coronal radiation on the computed helium lines. We find that, even in an active region, the incident coronal radiation has a limited effect on the UV He lines, while it is of fundamental importance for the D3 and 10830 8 lines. Finally, we build two more models, assuming values of He abundance ½He ¼ 0:07 and 1.5, only in the region where temperatures are >1 ; 104 K. This region, between the chromosphere and transition region, has been indicated as a good candidate for processes that might be responsible for strong variations of [He]. The set of our observables can still be well reproduced in both cases, changing the atmospheric structure mainly in the low transition region. This implies that, to choose between different values of [He], it is necessary to constrain the transition region with different observables, independent of the He lines.Fil: Mauas, Pablo Jacobo David. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Andretta, V.. Osservatorio Astronomico di Capodimonte; ItaliaFil: Falchi, A.. Osservatorio Astrofisico di Arcetri; ItaliaFil: Falciani, R.. Universita Degli Studi Di Firenze; ItaliaFil: Teriaca, L.. Max-Planck-Institut fur Sonnensystemforschung; AlemaniaFil: Cauzzi, G.. Osservatorio Astrofisico di Arcetri; Itali

    Population variability in some genes involving the haemostatic system: data on the general population of Corsica (France), Sardinia and Sicily (Italy)

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    Three different population samples from Corsica (France), Sardinia and Sicily (Italy) were studied using nine genetic markers. For the first time, allele distributions of FGA TaqI, FGB Bcl I, FGB Hind III, PAI-1 Hind III, PLAT TPA-25, GPIIIa Taq I, GPIIb I/D 9bp, FVII HVR4 and FVII -323 10 bp markers, which are thought to be associated with cardiovascular disease risk, were studied in the general population of the three islands. The frequencies of the markers analysed in the present work show some peculiarities: the locus FVII HVR4 is characterized by the presence of a rare allele (H5), found in Corsicans and in Sardinians; the locus FBG BcII shows a low frequency of the B1 allele and the absence of the B1B1 genotype. The frequencies of some alleles have a distribution that is in agreement with the low risk for cardiovascular diseases in south European countries. The results highlight a genetic differentiation between the three Mediterranean islands and the other European populations
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