Flash Thermography Mapping of Degradation Patterns in Archaeological Glass

The process of degradation in artefacts subjected to centuries of burial can be of great relevance above all in archaeological glass. Infrared thermography is a non-destructive method allowing to map the defects of the glass substrate, both produced during its manufacturing (e.g., bubbles and inclusions) and due to ageing. This research is focused on the use of different flash thermography methods for the mapping of superficial flakes on Roman glasses dating back to the I and II century A.D. The effectiveness of active thermography methods is evaluated to map degraded portions of archaeological glass considering their semitransparency and specific optical absorption

The influence of Spatial arrangement of a scene in the stability of color appearance under different lights

Color rendering is defined as the \u201ceffect of an illuminant on the color appearance of objects by conscious or subconscious comparison with their color appearance under a reference illuminant\u201d[1]. A Color Rendering Index (CRI) aims to indicate through one or more values the range of the color variation of an object after changes in the illumination of the scene. In other words, it tries to quantify to what extent the chromatic appearance of an object is preserved under a given light source with reference to a standard illuminant. Goal of a CRI is to evaluate the quality of a light source given that a \u201cgood\u201d illuminant should keep color appearance as much unchanged as possible. With the arrival of novel LED based light sources, classic CRI proved not to be a measure in line with the human visual color sensation. As a follow up, a series of new methods and algorithms to compute alternative CRIs have been devised and tested, but no one has emerged as the definitive one. This paper aims at suggesting a potential weakness of all CRIs,: they get as input just the spectral power distribution (SPD) of the light source and implement a Color Adaptation Transform (CAT) as a simplification of the Human Vision System (HVS), ignoring its spatial mechanisms. In everyday life, perceptive characteristics of objects are strongly dependent on the context in which they are placed since we rarely see colors in isolation, as well as on the quality and SPD of light radiation[2]. Classic examples in which the spatial distribution of a scene plays an important role in the color appearance are the optical illusions. We aim to study if the spatial arrangement of a scene may influence the final appearance under different illuminants[3,4] and thus if it should consider it in its computation

Does electro-osmosis work in moisture damage prevention? Applicability of infrared-based methods to verify water distribution under electric fields

In the recent years electro-osmosis drying devices applied to walls in both modern and historic masonry has become one of the leading innovative techniques to prevent damages caused by capillary rising water in building materials. Since the scientific community is raising many doubts on these techniques, the authors aim to propose a fast, simple, noninvasive and economic method to evaluate the dehumidification process specimens of the most used building materials. The paper presents a procedure to monitor water content in different specimens of the most used building materials (e.g. brick, mortar and plaster) and verify any kind of possible effect of electro-osmosis on water diffusion, above all drying kinetic. The procedure is based on the measure of water content and drying behaviour with and without the application of electrostatic fields with the traditional gravimetric method, infrared thermography and optical reflectance in the 940\u2013980 nm with a high sensitivity avalanche photodiode. This allowed us to visualize the surface water content gradient of different building materials. Using different voltage values between tow electrodes coupled with the material under examination, we observed no variation in water distribution inside the material nor any difference in evaporation phenomena. For strong electric field values (V > 150 V/m), compared to those normally used in electro-osmosis dehumidification, we measured mainly the heating caused by the Joule effect due to the intrinsic ion's distribution inside the material

The role of IRT in the archaeometric study of ancient glass through XRF and FORS

The process of degradation of archaeological glass subjected to centuries of burial can be of great relevance: typical consequence of degradation in the original vitreous material is rainbow-like iridescence due to chemical alteration of surface layers, salts formation and ion migration. The research presented in this paper is focused on the study of a collection of Roman glass (I - II century A.D.) held by the Museo Civico Etnografico Archeologico Fanchini of Oleggio, Italy. Chemical characterization (namely flux, chromophores and opacifiers determination) has been performed by a combination of X-Ray Fluorescence (XRF) and Fibre Optics Reflectance Spectroscopy (FORS) in the UV\u2013Vis-NIR region. Conservation conditions have been studied and degraded areas have been mapped through Infrared thermography (IRT). IRT is a non-invasive method typically used to measure the apparent temperature of objects and represent it as pseudo-colour images. In the present work, we demonstrate the feasibility of IRT for identifying and mapping glass substrate defects due to ageing of glass, assuming that they may be considered as thermal anomalies. Thermogram sequences have been processed by high order statistical analysis, which is particularly suitable since it is based on automated processes where the output is a single representative image. The use of a thermal camera allows furthermore to perform remote analysis in areas hardly reachable in a fast and effective way

Pulsed Thermography applied to multi-material and multi-layer pomological models

n/

Optical reflectance apparatus for moisture content determination in porous media

Monitoring surface moisture content (MC) is a required activity and a topic of current interest in conservation studies. The present work examines the possibility of using the spectral reflectance factor at 970 nm (R\u3bb970) for the noninvasive quantitative determination of surfaceMC in building materials. Indeed, the quantification of surface liquid water by optical measurements is poorly exploited on porous media despite it is well documented in many remote sensing technologies such as in agriculture, soil science and some industrial application. The measurements apparatus is tested in a laboratory experiment on different specimens of building materials. The custom-made detector is a Si-core Avalanche Photo Diode (APD) operating in Geiger mode which satisfy the requirements of non-invasiveness and ease of use with the additional opportunity to developing economic, automated and reliable solutions. The results obtained for six representative cultural heritage building materials clearly show the dependence between R\u3bb970 and surface MC: R\u3bb970 increases as surface MC decrease following the drying process of an unsaturated porous matrix i.e. evaporative flux supported by capillary pumping. This work reports the possibility to use the reflectance value at a specific wavelength for an alternative and non-invasive measurements of MC

Incidence and risk factors of acute kidney injury and failure after liver transplantation in patients with normal kidney function

Incidence and risk factors of acute kidney injury and failure after liver transplantation in patients with normal kidney functio

Magnetic stimulation of gold fiducial markers used in Image-Guided Radiation Therapy : evidences of hyperthermia effects

A promising approach in oncology consists in combining Radiation Therapy (RT) with Magnetic Fluid Hyperthermia (MFH). Modern day RT takes advantage by imaging techniques able to provide information about the correct patient set-up, target position and movement during the treatments. For these purposes, gold fiducial markers, implanted into the tumors, or in their proximity, are used in the so-called Image-Guided Radiation Therapy (IGRT). In this study, hyperthermia produced by different gold fiducial markers under the application of an alternating magnetic field in the typical conditions used in Magnetic Fluid Hyperthermia (MFH) clinical trials was investigated. The temperature increase of different types of gold fiducial markers and of tissue mimicking hydrogel phantoms containing the fiducials were measured during the magnetic stimulation by means of a high-resolution thermal camera and a fiber optic temperature sensor. The results demonstrated that, within few tens of seconds after the start of the magnetic stimulation, the gold fiducial markers might reach temperatures higher than 70\u202f\ub0C. Local increases of the hydrogel temperature to values higher than 45\u202f\ub0C were also measured. These evidences highlight the need to evaluate carefully the presence and location of gold fiducial markers in patients undergoing combined IGRT and MFH treatments in order to prevent any thermal ablation of health tissues surrounding the markers