224 research outputs found
Development of an efficient and thermally controlled Raman system for fast and safe molecular characterization of paint layers
An innovative high-efficiency Raman system (exc. wav. 1064 nm) for safe molecular characterization of paint
layers and other photosensitive materials has been developed and successfully tested. It was equipped with a
novel optical probe, which has been designed and built in order to perform Raman scattering measurements on a
relatively large spot at laser intensities lower than the typical ones of the commercial instruments. Original
optical solutions were implemented in order to achieve such improved efficiency. Furthermore, the instrument
was also equipped with an active thermal control line allowing to prevent alterations of the material under
study and to optimize the measurement cycles by means of suitable modulations of the laser power. Comparative
tests using the novel analytical tool and an alternative setup based on a commercial Raman probe were carried
out on a set of pure pigments and oil paint layers, which allowed assessing the significantly higher efficiency and
reliability of the former with respect to the latter
Temperature-controlled portable Raman spectroscopy of photothermally sensitive pigments
In this work, an innovative NIR Raman device (excitation wavelength at 1064 nm) was developed in order to avoid thermal stress and consequent chemical alterations of the materials analyzed. In particular, we devised and tested for the first time a sensored Raman probe allowing for temperature-controlled measurements based on a thermoelectric sensor providing the feedback signal for suitably modulating the output power of the laser source and then limiting undesired heating effects within the irradiated volume. The experimentation was carried out on cinnabar, lead white and indigo pigments frequently used during the past centuries, which presents pronounced photothermal instability. The results achievedin a set of instrumental and analytical tests using different measurement control parameters allowed demonstrating the effectiveness and reliability of the present approach for preventing thermal alterations effects during Raman spectroscopy and speeding the measurements, as well as for monitoring spectral variations associated with the crystals anharmonicity over large temperature ranges. These features alongwith the portability of the novel device can make in situ Raman characterisation of valuable paintedsurfaces including photosensitive materials very safe and efficie
Detection of the Glass Transition of Polymers Used in Art and Art-Conservation Using Raman Spectroscopy
In this work, Raman spectroscopy was employed for the
detection of the glass transition temperatures (Tg) of some
thermoplastic polymers and natural terpenoid resins. In
particular, our attention was focused on evaluating the Tg of
polystyrene and colophony. The measurements returned Tg
values in accordance with those reported in the literature
obtained using the DSC technique, thus confirming the
reliability of the approach proposed herein. Further studies
will be focused on the evaluation of Tg temperature changes
depending on materials treatments and ageing
Reply: Choice of ART programme for serodiscordant couples with an HIV-infected male partner
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Continuous monitoring of gastric carbon dioxide with optical fibers: European project COMOCADOF, in vitro evaluation
Efficacy of laparoscopic pelvic denervation in central-type chronic pelvic pain: A multicenter study
Automated characterization of varnishes photo-degradation using portable T-controlled Raman spectroscopy
In this work, a portable-Raman device (excitationwavelength 1064 nm)was employed for the first time for continuously
monitoring the complex molecular dynamics of terpenoid resins (dammar, mastic, colophony, sandarac
and shellac), which occur during their ageing under artificial light exposure. The instrumentation was
equipped with a pyroelectric sensor allowing for temperature control of the sample's irradiated surface while
the acquisition of spectra occurs by setting fixed maximum temperature and total radiant exposure. Resins
were dropped into special pits over a dedicated rotating wheelmoved by a USB motor. The rotation allowed samples
sliding between the positions designated for the acquisition of the Raman spectra and that for artificial ageing.
Samples were exposed to artificial light for 45-days and almost 400 spectra for each resin sample were
collected. The exposure to artificial light led to significant changes allowing the characterization of the alteration
process. The automated acquisition of a large number of spectra overtime during light-exposure has given the
possibility to distinguish fast dynamics,mainly associated to solvent evaporation, fromthose slower due to resins
photo-degradation processes
Near-infrared spectroscopy and pattern-recognition processing for classifying wines of two Italian provinces
This paper presents an experiment making use of the near-infrared spectrum for distinguishing the wines produced in
two close provinces of Abruzzo region of Italy. A collection of 32 wines was considered, 18 of which were produced in
the province of Chieti, while the other 14 were from the province of Teramo. A conventional dual-beam
spectrophotometer was used for absorption measurements in the 1300-1900 nm spectroscopic range. Principal
Component Analysis was used for explorative analysis. Score maps in the PC1-PC2 or PC2-PC3 spaces were obtained,
which successfully grouped the wine samples in two distinct clusters, corresponding to Chieti and Teramo provinces,
respectively. A modelling of dual-band spectroscopy was also proposed, making use of two LEDs for illumination and a
PIN detector instead of the spectrometer. These data were processed using Linear Discriminant Analysis which
demonstrated satisfactory classification result
Light scattering measurements for quantifying biological cell concentration: an optimization of opto-geometric parameters
An experimental study was carried out, aimed at optimizing the optical/geometrical configuration for measuring the concentration of biological cells by means of static light scattering measurements. A LED-based optoelectronic setup making use of optical fibers was experimented, as the precursor of a low-cost device to be integrated in instrumentation for cytometry. Two biological sample types were considered as test samples of the most popular analyses – cervical cells and urine, respectively. The most suitable wavelengths and detecting angles were identified, and calibration curves were calculated
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