890 research outputs found
Urban Scale Monitoring Approach for the Assessment of Rising Damp Effects in Venice
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
How Can Ozone and Relative Humidity Affect Artists’ Alkyd Paints? A FT-IR and Py-GC/MS Systematic Study
Knowledge of the chemical–physical reactions that determine the main degradation behaviour of artists’ alkyd paints represents one of the main problems within the museum exhibitions. The collection and interpretation of these data on degradation phenomena, especially after ozone exposure at different relative humidity values, can be useful for their conservation needs. Therefore, a systematic investigation of these materials may help achieve this goal. Firstly, surface-level identification of the main functional groups of ad hoc created and aged alkyd paints was performed using attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR). Subsequently, these paints were investigated by pyrolysis–gas chromatography and mass spectrometry (Py–GC/MS), allowing for precise bulk identification of the organic compounds before and after accelerated ageing. A first successful attempt to provide quantitative Py–GC/MS data on alkyd-based paints is here presented and discussed. Comparing the results, it was possible to obtain new insights into the degradation behaviour of alkyd paints when exposed to ozone, allowing us to devise specific preventive and conservation strategies for these artistic materials
Tiles from Aosta: A Peculiar Glaze Roof Covering
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
Familial Uncombable Hair Syndrome: Ultrastructural Hair Study and Response toBiotin
Abstract: We report a family affected to the fourth generation by uncombable
hair syndrome. This syndrome is characterized by unruly, dry,
blond hair with a tangled appearance. The family pedigree strongly supports
the hypothesis of autosomal dominant inheritance; some members of the
family had, apart from uncombable hair, minor signs of atopy and ectodermal
dysplasia, such as abnormalities of the nails. The diagnosis was confirmed
by means of extensive scanning electron microscopy. A trial with oral biotin
5 mg/daywas started on two young patients with excellent results as regards
the hair appearance, although scanning electron microscopy did not show
structural changes in the hair. After a 2-year-period of follow-up, hair normality
was maintained without biotin, while nail fragility still required biotin
supplementation for control
ANALYTICAL METHODS FOR THE CHARACTERIZATION OF SURFACE FINISHING IN BRICKS
The recent restoration works of Santo Stefano Church Fac¸ade (XV century) in Venice have shown traces variously saved of different kind of
surface finishes. These finishes were found on the brick’s surface both in the masonry and in the decorative elements.
Different brick’s surface and decorative tile samples were investigated using several techniques: optical microscopy, scanning electronmicroscopy,
thermal analysis, infrared spectroscopy and reflectance Fourier transform infrared microspectroscopy.
The evaluation of the reached results was used to understand the decorative techniques and to recognize the material employed
CHARACTERIZATION AND REACTIVITY OF SILICATIC CONSOLIDANS
In this study some results on the reactivity of silicatic consolidants employed for the conservation of valuable artistic and cultural
porous materials are discussed. In particular, a colloidal suspension of silica made by particles with an average diameter of 10–
15 nm, a sodium silicate and an ethyl silicate consolidant are studied. The chemical–physical characterization of xerogels achieved from
the examined products were carried out determining the superficial area (BET method) and the average dimension of particles (SAXS)
while the chemical structure of xerogels were investigated through NMR MAS spectroscopy of the 29Si nucleus. The investigation on
reactivity between silica and stone support was executed by mixing consolidants with calcite and quartz powder to simplify as much
as possible the system otherwise very complex. On silica produced by the three examined consolidants structural differences are revealed
and these diversities can be responsible for the dissimilar reactivity of the silicatic systems towards the stone, in particular with regard to
the carbonatic component
Correlation between Gamma-Ray bursts and Gravitational Waves
The cosmological origin of -ray bursts (GRBs) is now commonly
accepted and, according to several models for the central engine, GRB sources
should also emit at the same time gravitational waves bursts (GWBs). We have
performed two correlation searches between the data of the resonant
gravitational wave detector AURIGA and GRB arrival times collected in the BATSE
4B catalog. No correlation was found and an upper limit \bbox{} on the averaged amplitude of gravitational waves
associated with -ray bursts has been set for the first time.Comment: 7 pages, 3 figures, submitted to Phys. Rev.
General relativistic Sagnac formula revised
The Sagnac effect is a time or phase shift observed between two beams of
light traveling in opposite directions in a rotating interferometer. We show
that the standard description of this effect within the framework of general
relativity misses the effect of deflection of light due to rotational inertial
forces. We derive the necessary modification and demonstrate it through a
detailed analysis of the square Sagnac interferometer rotating about its
symmetry axis in Minkowski space-time. The role of the time shift in a Sagnac
interferometer in the synchronization procedure of remote clocks as well as its
analogy with the Aharanov-Bohm effect are revised.Comment: 11 pages, 3 figure
The challenge of infrared imaging of frescos: Thermal Quasi-Reflectography unveils hidden features of artworks
Thermal Quasi-Reflectography is a new optical technique, based on Mid-IR, which is demonstrated to have a great potential in the diagnostics of frescoes. Here we address the key-points: 1) basic principles and instrumentation to enable operative measurements; 2) main diagnostic results
Wideband dual sphere detector of gravitational waves
We present the concept of a sensitive AND broadband resonant mass
gravitational wave detector. A massive sphere is suspended inside a second
hollow one. Short, high-finesse Fabry-Perot optical cavities read out the
differential displacements of the two spheres as their quadrupole modes are
excited. At cryogenic temperatures one approaches the Standard Quantum Limit
for broadband operation with reasonable choices for the cavity finesses and the
intracavity light power. A molybdenum detector of overall size of 2 m, would
reach spectral strain sensitivities of 2x10^-23/Sqrt{Hz} between 1000 Hz and
3000 Hz.Comment: 4 pages, 3 figures. Changed content. To appear in Phys. Rev. Let
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