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Organic dyes in illuminated manuscripts: a unique cultural and historic record.

ABSTRACT: In this study, we successfully addressed the challenges posed by the identification of dyes in medieval illuminations. Brazilwood pigment lakes and orcein purple colours were unequivocally identified in illuminated manuscripts dated by art historians to be from the thirteenth to the fifteenth centuries and in the Fernão Vaz Dourado Atlas (sixteenth century). All three works were on a parchment support. This was possible by combining Raman microscopy and surface-enhanced Raman spectroscopy with microspectrofluorimetry. To the best of our knowledge, this is the first time that brazilein, the main chromophore in brazilwood lake pigments, has been unequivocally identified by surface-enhanced Raman spectroscopy in an illuminated work (the Dourado Atlas). Complementing this identification, through microspectrofluorimetry and micro-Fourier transform infrared spectroscopy, it was possible to propose a complete paint formulation by comparison with our database of references; the dark pink hues, in the three case studies, were produced by combining brazilwood pigment lakes and gypsum in a protein- and gum arabic-based tempera. Orcein purple, also known as orchil dye, has been previously identified in medieval manuscripts, dated from the sixth to the ninth centuries. Our findings in fourteenth-sixteenth century manuscripts confirm the hypothesis that this dye was lost during the High Middle Ages, to be later rediscovered.This article is part of the themed issue 'Raman spectroscopy in art and archaeology'.

SUBMITTER: Melo MJ

PROVIDER: S-EPMC5095527 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Organic dyes in illuminated manuscripts: a unique cultural and historic record.

Melo Maria João MJ Nabais Paula P Guimarães Maria M Araújo Rita R Castro Rita R Oliveira Maria Conceição MC Whitworth Isabella I

Philosophical transactions. Series A, Mathematical, physical, and engineering sciences 20161201 2082

In this study, we successfully addressed the challenges posed by the identification of dyes in medieval illuminations. Brazilwood pigment lakes and orcein purple colours were unequivocally identified in illuminated manuscripts dated by art historians to be from the thirteenth to the fifteenth centuries and in the Fernão Vaz Dourado Atlas (sixteenth century). All three works were on a parchment support. This was possible by combining Raman microscopy and surface-enhanced Raman spectroscopy with m ...[more]

PMID: 27799433

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Project description:BackgroundAdvancements in linking publicly available census records with vital and administrative records have enabled novel investigations in epidemiology and social history. However, in the absence of unique identifiers, the linkage of the records may be uncertain or only be successful for a subset of the census cohort, resulting in missing data. For survival analysis, differential ascertainment of event times can impact inference on risk associations and median survival.MethodsWe modify some existing approaches that are commonly used to handle missing survival times to accommodate this imperfect linkage situation including complete case analysis, censoring, weighting, and several multiple imputation methods. We then conduct simulation studies to compare the performance of the proposed approaches in estimating the associations of a risk factor or exposure in terms of hazard ratio (HR) and median survival times in the presence of missing survival times. The effects of different missing data mechanisms and exposure-survival associations on their performance are also explored. The approaches are applied to a historic cohort of residents in Ambler, PA, established using the 1930 US census, from which only 2,440 out of 4,514 individuals (54%) had death records retrievable from publicly available data sources and death certificates. Using this cohort, we examine the effects of occupational and paraoccupational asbestos exposure on survival and disparities in mortality by race and gender.ResultsWe show that imputation based on conditional survival results in less bias and greater efficiency relative to a complete case analysis when estimating log-hazard ratios and median survival times. When the approaches are applied to the Ambler cohort, we find a significant association between occupational exposure and mortality, particularly among black individuals and males, but not between paraoccupational exposure and mortality.DiscussionThis investigation illustrates the strengths and weaknesses of different imputation methods for missing survival times due to imperfect linkage of the administrative or registry data. The performance of the methods may depend on the missingness process as well as the parameter being estimated and models of interest, and such factors should be considered when choosing the methods to address the missing event times.

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Organic dyes in illuminated manuscripts: a unique cultural and historic record.

Publications

Organic dyes in illuminated manuscripts: a unique cultural and historic record.

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