53,659 research outputs found
Exploiting reflectance FTIR spectroscopy for the in situ identification of pigments in illuminated manuscripts
No full textThe non-destructive identification of pigments used in pictorial works is of great interest in the field of the study of cultural heritage, in particular when it is applied in situ and thus in the place of conservation of the artefacts, avoiding the costs and risks related to the transport to the laboratory.
As far as the in situ identification of inorganic pigments is concerned, the techniques mostly established are, undoubtedly, X-ray fluorescence (XRF), which however provides only the elemental composition of the pigment; visible-NIR reflectance spectroscopy, not always specific due to the bandwidth; and micro-Raman spectroscopy, highly specific but sometimes of difficult application for those compounds that are only weak scatterers.
Therefore the recent development of portable instrumentation for reflectance FTIR spectroscopy is very appealing, allowing the application in the field of a technique highly specific for the identification of compounds. Indeed, several studies have been reported in the literature concerning the use of this technique for the study of cultural heritage.1-2
In the present work a very compact portable FTIR spectrometer which is provided with a reflectance module for contactless measurements and a DTGS detector was used. This kind of instrumentation works at room temperature and exhibits a linear response on the spectral range between 7500 and 375 cm-1, thus allowing to record also overtone and combination bands at higher wavenumbers. In this way, the reflectance FTIR spectra of several inorganic pigments spread on parchment with different binders (arabic gum and egg white) were recorded in order to build a spectral database and moreover to evaluate the influence of the binders on the spectroscopic patterns. Exploiting the specular reflection arising from the samples, the reflectance FTIR spectra acquired could be converted to the more conventional absorbance FTIR spectra applying the Kramers-Kronig transformation. Finally, reflectance FTIR spectra were acquired from some northern-Italian illuminations dating to the XVI century, and then were compared to the reference FTIR spectra, in order to identify the coloring matter. Lapis lazuli, azurite, malachite, lead tin yellow and yellow ochre were recognized in the illuminated details analyzed. In some cases, it was also possible to identify the organic matters used in the illuminations as binders.
Basic copper sulfates brochantite and posnjakite as a case study
As it has been recently discussed in the literature,3 among all the pigments commonly employed in the ancient paintings, those which provide the green colour are the most elusive from the point of view of identification. Even neglecting the not uncommon cases in which the green hue was obtained by a mixture of blues and yellows, indeed, most of green pigments are based on copper compounds (for example malachite CuCO3·Cu(OH)2 and verdigris Cu(CH3COO)2·2H2O) and thus they result to be indistinguishable by means of techniques such as XRF, able to identify only copper, or vis-NIR reflectance, being the chromophore the same ion Cu2+, and also hardly identifiable by means of Raman spectroscopy, being all of them rather weak scatterers.
Moreover, in several pictorial works and in particular in illuminations, besides the most common and already mentioned malachite and verdigris, also basic copper sulphates were discovered, in more detail posnjakite CuSO4·3Cu(OH)2·H2O and brochantite CuSO4·3Cu(OH)2 in northern-European and Italian illuminations dating from XII to XVII century4-7. When these pigments were recognized in other contexts, such as mural paintings8 and ancient wallpapers9, their formation was supposed to be the result of the degradation of the most common copper pigments, also because recipes for the production of such basic copper sulphates were not known before the XVII century and these compounds, although present in nature as minerals, are not widespread. Nevertheless, especially in the case of illuminations, often perfectly preserved, scientists have more often hypothesized that such pigments, of natural origin or artificial origin, were used on purpose6.
In the present work, as a case study, pure brochantite and posnjakite were synthesized and characterized. Then reflectance FTIR spectra of these compounds spread on parchment were used for the identification of green pigments of northern-Italian illuminations, recognizing mainly posnjakite. Notably, the reflectance FTIR spectra of the basic copper sulphates mentioned above are reported here for the first time
Exploiting external reflection FTIR spectroscopy for the in-situ identification of pigments and binders in illuminated manuscripts : brochantite and posnjakite as a case study
No full textIn the present work, the use of portable instrumentation allowing in-situ reflection FTIR analyses is
exploited to identify the coloring matters of northern-Italian illuminations dating to the XVI century.
In order to build a database of spectra, reference paint samples were prepared spreading the pigments on parchment with two different binders, i.e. gum arabic and egg white, used in antiquity. Pigments for the database were chosen considering their use in the Middle Ages and in the Renaissance and their response in the mid- and near-IR region. The reflection FTIR spectra obtained resulted to be dominated by the specular reflection component, allowing the use of the Kramers–Kronig transform to convert them to the more conventional absorbance FTIR spectra. Several pigments could thus be identified in ancient illuminations, even if some green details showed a spectral pattern different with respect to the most common commercial green pigments of the database. Therefore, in addition, basic copper sulfates brochantite and posnjakite were synthesized and characterized. In three green details, posnjakite was identified, both as a pure compound and together with malachite
Possibilities and limits of photon correlation spectroscopy in determining polymer molecular weight distributions
No full textThe effect of concentration and polydispersity on the collective diffusion coefficient Dc, evaluated using Photon Correlation Spectroscopy (PCS), has been investigated on poly(methyl methacrylate) (PMMA) in acetone solutions. The concentration dependence of the collective diffusion coefficient follows a linear regression law, the slope being fairly independent of polydispersity, molecular weight and temperature. The diffusion coefficient at infinite dilution D0 obeys the scaling law D0 = AMw–ν in the range from Mw = 10 000 to Mw = 800 000; the value of the scaling exponent, ν = 0.57, proves the good solvent quality of acetone. The inversion of the scattered intensity autocorrelation data by the regularization method CONTIN allowed the evaluation of the molecular weight distribution function of the polymeric samples. Although this algorithm gives valuable information on average quantities or on the width of the distribution, it has limited resolution power; therefore a comparison with the results obtained by Size Exclusion Chromatography (SEC) was carried out for a set of samples having monomodal and bimodal distribution functions
Vulcanismo alcalino cretaceo post-ofiolitico nell’alloctono liguride della Toscana meridionale. I : l’area del T. Senna (Siena- Grosseto)
No full textThe lifetime impact of attention deficit hyperactivity disorder: results from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC)
No full textBackground The aim of the study was to present nationally representative data on the lifetime independent association between attention deficit hyperactivity disorder (ADHD) and psychiatric co-morbidity, correlates, quality of life and treatment seeking in the USA.Method Data were derived from a large national sample of the US population. Face-to-face surveys of more than 34 000 adults aged 18 years and older residing in households were conducted during the 2004–2005 period. Diagnoses of ADHD, Axis I and II disorders were based on the Alcohol Use Disorder and Associated Disabilities Interview Schedule-DSM-IV version.Results ADHD was associated independently of the effects of other psychiatric co-morbidity with increased risk of bipolar disorder, generalized anxiety disorder, post-traumatic stress disorder, specific phobia, and narcissistic, histrionic, borderline, antisocial and schizotypal personality disorders. A lifetime history of ADHD was also associated with increased risk of engaging in behaviors reflecting lack of planning and deficient inhibitory control, with high rates of adverse events, lower perceived health, social support and higher perceived stress. Fewer than half of individuals with ADHD had ever sought treatment, and about one-quarter had ever received medication. The average age of first treatment contact was 18.40 years.Conclusions ADHD is common and associated with a broad range of psychiatric disorders, impulsive behaviors, greater number of traumas, lower quality of life, perceived social support and social functioning, even after adjusting for additional co-morbidity. When treatment is sought, it is often in late adolescence or early adulthood, suggesting the need to improve diagnosis and treatment of ADHD.<br/
Adult attention-deficit hyperactivity disorder and obesity: epidemiological study
No full textA significant association between attention-deficit hyperactivity disorder (ADHD) and obesity has been reported. This study addresses unexplored aspects of this relationship.AimsTo evaluate the association between adult obesity and: (a) persistent, remitted or lifetime ADHD; (b) number of childhood ADHD symptoms, controlling for socioeconomic status and mood, anxiety and substance use disorders.MethodFace-to-face psychiatric interviews in 34 653 US adults from the National Epidemiologic Study on Alcohol and Related Conditions. Obesity was defined as a body mass index ?30.ResultsPersistent, lifetime or remitted ADHD were not associated with obesity after controlling for confounders. The number of childhood ADHD symptoms was significantly associated with adult obesity, even after adjustment, in women.ConclusionsChildhood ADHD symptoms are associated with obesity in women even after comorbid psychiatric disorders are accounted for. This provides a rationale for longitudinal studies assessing the impact of the treatment of childhood ADHD symptoms on obesity in women.<br/
IS THE THE PARP-LIKE ENZYME FROM S. solfataricus STRUCTURALLY RELATED TO THE EUKARYOTIC COUNTERPARTS? ,
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