Approach to anaerobic bio-degradation of natural and synthetic fabrics: Physico-chemical study of the alteration processes.

In this paper, the mesophilic Biochemical Methane Potential of several fabrics was assessed at different Total Solid concentrations (1-4%TS). Physico-chemical techniques were applied to explore the arising structural changes on fibers during the anaerobic digestion process. Additionally, the modified Gompertz model was used to assess and compare the AD performance of the fabrics. In cellulose-based fibers the production of biogas was enhanced thanks to the easy solubilization of acetate, which is generated upon partial breakage of cellulose bonds. The crystallinity of vegetal fibers decreased significantly from day 19. The highest methane yields were attained for silk and wool fabrics at the lowest TS concentrations. Conformational changes in fibroin and keratin were detected. The highest degrees of degradation were observed in solid samples with lower solid concentrations. Accordingly, the maximum methane yields were reported in the reactors operating with lower TS.

Solvent-Free Formation of Cyclodextrin-Based Pseudopolyrotaxanes of Polyethylene Glycol: Kinetic and Structural Aspects.

Pseudopolyrotaxanes (PPRs) are supramolecular structures consisting of macrocycles able to thread on a linear polymer chain in a reversible, non-covalent way, often referred to in the literature as "molecular necklaces". While the synthesis and reaction mechanisms of these structures in solution have been widely described, their solvent-free production has received little attention, despite the advantages that this route may offer. We propose in this work a kinetic mechanism that describes the PPR formation in the solid phase as a process occurring in two consecutive stages. This mechanism has been used to investigate the spontaneous formation of a PPR that occurs when grinding α-Cyclodextrin (α-CD) with polyethylene glycol (PEG). In the threading stage, the inclusion of the polymer and subsequent release of the water molecules lodged in the cavity of the macrocycle cause vibrational changes that are reflected in the time-dependence of the FTIR-ATR spectra, while the further assembly of PPRs to form crystals produces characteristic reflections in the XRD patterns, due to the channel-like arrangement of CDs, that can be used to track the formation of the adduct in crystalline form. The effects that working variables have on the kinetics of the reaction, such as temperature, feed ratio, molar mass of the polymer and the introduction of an amorphous block in the polymer structure, have been investigated. The rate constants of the threading step increase with the temperature and the activation energy of the process increases at lower proportions of CD to PEG. This is attributed to the lower degree of covering of the polymer chain with CDs that reduces the hydrogen-bonding driven stabilization between adjacent macrocycles. The formation of crystalline PPR, which takes place slowly at room temperature, is markedly promoted at higher temperatures, with lower proportions of CD favoring both the formation and the growth of the crystals. The molar mass of the polymer does not modify the typical channel-like arrangement of packed PPRs but the conversion into crystalline PPR diminishes when using PEG1000 instead of PEG400. At a microscopic level, the crystals arrange into lamellar structures, in the order of hundreds of nm, embedded in an amorphous-like matrix. The introduction of a polypropylene oxide block in the structure of the polymer (Pluronic L62) renders poorer yields and a considerable loss of crystallinity of the product of the reaction. The methodology here proposed can be applied to the general case of inclusion complexes of CDs with drugs in the solid phase, or to multicomponent systems that contain polymers as excipients in pharmaceutical formulations along with CDs.

Prevalencia de Sífilis, Hepatitis B y Virus de Inmunodeficiencia Humana en población masculina privada de la libertad de un establecimiento carcelario en Bogotá-Colombia. Año 2019 / Prevalence of Syphilis, Hepatitis B and Human Immunodeficiency Virus in the male prison population in Bogotá, Colombia in 2019

Resumen Objetivo: Determinar la prevalencia de sífilis, hepatitis B y virus de la inmunodeficiencia humana en una población privada de la libertad de un establecimiento carcelario masculino de Bogotá D.C.-Colombia en 2019. Materiales y métodos: Se realizó un estudio de corte transversal en un establecimiento carcelario masculino de Bogotá, se incluyeron personas privadas de la libertad, mayores de 18 años. Los sujetos fueron sometidos a pruebas de detección de anticuerpos contra el Treponema pallidum, Antígenos de Superficie contra hepatitis B (HBsAg) y Virus de Inmunodeficiencia Humana (VIH) y respondieron un cuestionario estructurado para la descripción de conductas de riesgo. Resultados: Participaron 447 sujetos, ubicados en 7 pabellones del establecimiento carcelario. La prevalencia de sífilis fue del 5.8% (IC95% 3.8 - 8.4), del 1.1% para VIH (IC95% 0.4 - 2.6), y del 0.45% para hepatitis B crónica (IC95% 0.05 - 1.6). Discusión: A pesar de que la prevalencia documentada para estas patologías es más alta que en la población general, los resultados son más bajos que los reporta dos en instituciones de condiciones similares en otras latitudes. Se recomienda que el establecimiento continúe desarrollando políticas de promoción y prevención de estas patologías dentro de su población.

Abstract Objective: To determine the prevalence of syphilis, hepatitis B and the human immunodeficiency virus (HIV) in the male prison population in Bogotá, Colombia in 2019. Materials and methods: A cross-sectional study was carried out in a male prison center in Bogotá, in which sequential sampling, stratified by ward, included people deprived of liberty, over 18 years of age and who voluntarily agreed to participate in the investigation. Subjects underwent tests for antibodies to Treponema pallidum, Surface Antigens against hepatitis B (HBsAg) and Human Immunodeficiency Virus (HIV) and they answered a structured questionnaire for the description of risk behaviors. Results: A total of 447 subjects were included, belonging to 7 prison wards. The prevalence of syphilis was 5.8% (95% CI 3.8 - 8.4), 0.5% for chronic hepatitis B (95% CI 0.05 - 1.6) and 1.1% for HIV (95% CI 0.4 - 2.6). Discussion: Although the documented prevalence for these pathologies is higher than in the general population, the results are lower than those reported in other institutions with similar conditions in other latitudes. It is recommended that the institution continue to strengthen its policies for the promotion and prevention of these pathologies within its population.

Error scaling of large-eddy simulation in the outer region of wall-bounded turbulence.

We study the error scaling properties of large-eddy simulation (LES) in the outer region of wall-bounded turbulence at moderately high Reynolds numbers. In order to avoid the additional complexity of wall-modeling, we perform LES of turbulent channel flows in which the no-slip condition at the wall is replaced by a Neumann condition supplying the exact mean wall-stress. The statistics investigated are the mean velocity profile, turbulence intensities, and kinetic energy spectra. The errors follow ( Δ / L ) α R e τ γ , where Δ is the characteristic grid resolution, Re τ is the friction Reynolds number, and L is the meaningful length-scale to normalize Δ in order to collapse the errors across the wall-normal distance. We show that Δ can be expressed as the L 2-norm of the grid vector and that L is well represented by the ratio of the friction velocity and mean shear. The exponent α is estimated from theoretical arguments for each statistical quantity of interest and shown to roughly match the values computed by numerical simulations. For the mean profile and kinetic energy spectra, α ≈ 1, whereas the turbulence intensities converge at a slower rate α < 1. The exponent γ is approximately 0, i.e. the LES solution is independent of the Reynolds number. The expected behavior of the turbulence intensities at high Reynolds numbers is also derived and shown to agree with the classic log-layer profiles for grid resolutions lying within the inertial range. Further examination of the LES turbulence intensities and spectra reveals that both quantities resemble their filtered counterparts from direct numerical simulation (DNS) data, but that the mechanism responsible for this similarity is related to the balance between the input power and dissipation rather than to filtering.

Dynamic slip wall model for large-eddy simulation.

Wall modelling in large-eddy simulation (LES) is necessary to overcome the prohibitive near-wall resolution requirements in high-Reynolds-number turbulent flows. Most existing wall models rely on assumptions about the state of the boundary layer and require a priori prescription of tunable coefficients. They also impose the predicted wall stress by replacing the no-slip boundary condition at the wall with a Neumann boundary condition in the wall-parallel directions while maintaining the no-transpiration condition in the wall-normal direction. In the present study, we first motivate and analyse the Robin (slip) boundary condition with transpiration (non-zero wall-normal velocity) in the context of wall-modelled LES. The effect of the slip boundary condition on the one-point statistics of the flow is investigated in LES of turbulent channel flow and a flat-plate turbulent boundary layer. It is shown that the slip condition provides a framework to compensate for the deficit or excess of mean momentum at the wall. Moreover, the resulting non-zero stress at the wall alleviates the well-known problem of the wall-stress under-estimation by current subgrid-scale (SGS) models (Jiménez & Moser, AIAA J., vol. 38 (4), 2000, pp. 605-612). Second, we discuss the requirements for the slip condition to be used in conjunction with wall models and derive the equation that connects the slip boundary condition with the stress at the wall. Finally, a dynamic procedure for the slip coefficients is formulated, providing a dynamic slip wall model free of a priori specified coefficients. The performance of the proposed dynamic wall model is tested in a series of LES of turbulent channel flow at varying Reynolds numbers, non-equilibrium three-dimensional transient channel flow and a zero-pressure-gradient flat-plate turbulent boundary layer. The results show that the dynamic wall model is able to accurately predict one-point turbulence statistics for various flow configurations, Reynolds numbers and grid resolutions.

Characteristic scales of Townsend's wall-attached eddies.

Townsend (The Structure of Turbulent Shear Flow, 1976, Cambridge University Press) proposed a structural model for the logarithmic layer (log layer) of wall turbulence at high Reynolds numbers, where the dominant momentum-carrying motions are organised into a multiscale population of eddies attached to the wall. In the attached-eddy framework, the relevant length and velocity scales of the wall-attached eddies are the friction velocity and the distance to the wall. In the present work, we hypothesise that the momentum-carrying eddies are controlled by the mean momentum flux and mean shear with no explicit reference to the distance to the wall and propose new characteristic velocity, length and time scales consistent with this argument. Our hypothesis is supported by direct numerical simulation of turbulent channel flows driven by non-uniform body forces and modified mean velocity profiles, where the resulting outer-layer flow structures are substantially altered to accommodate the new mean momentum transfer. The proposed scaling is further corroborated by simulations where the no-slip wall is replaced by a Robin boundary condition for the three velocity components, allowing for substantial wall-normal transpiration at all length scales. We show that the outer-layer one-point statistics and spectra of this channel with transpiration agree quantitatively with those of its wall-bounded counterpart. The results reveal that the wall-parallel no-slip condition is not required to recover classic wall-bounded turbulence far from the wall and, more importantly, neither is the impermeability condition at the wall.

Identity of attached eddies in turbulent channel flows with bidimensional empirical mode decomposition.

Bidimensional empirical mode decomposition (BEMD) is used to identify attached eddies in turbulent channel flows and quantify their relationship with the mean skin-friction drag generation. BEMD is an adaptive, non-intrusive, data-driven method for mode decomposition of multiscale signals especially suitable for non-stationary and nonlinear processes such as those encountered in turbulent flows. In the present study, we decompose the velocity fluctuations obtained by direct numerical simulation of channel flows into BEMD modes characterized by specific length scales. Unlike previous works (e.g. Flores & Jiménez, Phys. Fluids, vol. 22(7), 2010, 071704; Hwang, J. Fluid Mech., vol. 767, 2015, pp. 254-289), the current approach employs naturally evolving wall-bounded turbulence without modifications of the Navier-Stokes equations to maintain the inherent turbulent dynamics, and minimize artificial numerical enforcement or truncation. We show that modes identified by BEMD exhibit a self-similar behaviour, and that single attached eddies are mainly composed of streaky structures carrying intense streamwise velocity fluctuations and vortex packets permeating in all velocity components. Our findings are consistent with the existence of attached eddies in actual wall-bounded flows, and show that BEMD modes are tenable candidates to represent Townsend attached eddies. Finally, we evaluate the turbulent-drag generation from the perspective of attached eddies with the aid of the Fukagata-Iwamoto-Kasagi identity (Fukagata et al., Phys. Fluids, vol. 14(11), 2002, pp. L73-L76) by splitting the Reynolds shear stress into four different terms related to the length scale of the attached eddies.

Host ecology moderates the specialization of Neotropical bat-fly interaction networks.

The transmission of diseases through parasites is a key mechanism in the regulation of plant and animal populations in ecosystems. Therefore, it is necessary to investigate the relative effect of the variables that can shape the specificity of host-parasite interactions. Previous studies have found that specialization of antagonistic interactions between fly ectoparasites and bats changes according to forest type, host richness, and roosting ecology of bats. In this study, we tested these hypotheses using data from 48 bat communities. In general, our results support previous findings that bat-fly interactions are specialized, resulting in lower niche overlap among bat flies species. In addition, we found that the specificity of bat-fly interactions is lower in tropical mountain forests and is positively related with the richness of bat host species of each study site. Finally, there was a higher bat flies niche overlap in smaller bat-fly interaction networks recorded in bat roosts in caves. We conclude that the roosting ecology of bats could be a key factor to understand the mechanisms related to the horizontal transmission of ectoparasitic flies among bats.

Laboratory multi-technique study of Spanish decorated leather from the 12th to 14th centuries.

This work comprises an exhaustive study of Spanish decorative leathers dating from the 12th to 14th centuries. These paintings are considered a key example of a crucible of artistic styles: Gothic, Islamic and Florentine Trecento. The goal of this work was to use the scientific information provided by a number of experimental techniques - namely EDX, micro-FTIR, micro-Raman and micro-XRD - to assess the dating of the wooden vault, leather preparation and filling fibres. Another goal was to assess the artistic technique based on the characterization of pigments and the differentiation between original materials and those added throughout its history. Gypsum was the original preparation layer extended over the leather. A new preparation stratum was added in further interventions with the artwork. The original pictorial materials and those used during refurbishments have been identified. Original pigments were: red lead, Mars red, red lake, cinnabar, lapis lazuli, red ochres, raw sienna, white lead and charcoal black. Gilding was also found. Pigments added during restoration were: barite, emerald green, rutile, anatase, Mars red, cadmium red, lithopone, cadmium yellow, charcoal black and orpiment.

Actividad de un "ensamblaje" de murciélagos en el norte de Brasil (Mammalia: Chiroptera) / Activity of a bat assemblage in northern Brazil (Mammalia: Chiroptera)

Resumen La Amazonía es uno de los ecosistemas tropicales más biodiversos del mundo, característica atribuida a la complejidad estructural que le brinda la geología y la gran riqueza de sus suelos. Los murciélagos constituyen uno de los taxones de la clase Mammalia mejor representados en esta región, aun así, existen claros vacíos de conocimiento, principalmente, respecto a su ecología, con lo cual, en el presente estudio se pretende evaluar la influencia que tienen factores ambientales, como la temporada climática, temperatura (máxima y mínima), humedad relativa y porcentaje de fase iluminada de la Luna, en los patrones de actividad (riqueza, abundancia y gremios tróficos) de un ensamblaje de murciélagos en la Amazonía central brasilera. El estudio fue llevado a cabo en dos municipios del estado de Rondônia, empleando ocho redes de niebla, durante 62 noches de muestreo, abarcando las temporadas lluviosa y seca. En total fueron capturados 2 499 individuos de 58 especies, la familia mejor representada fueron los Phyllostomidae, mientras que la especie que registró la mayor frecuencia de capturas fue Carollia perspicillata (N = 859), seguida de C. brevicauda (N = 209). No se presentaron diferencias entre la estructura del ensamblaje considerando la temporada climática (lluviosa-seca), sin embargo, durante la temporada seca se registró un mayor número de especies e individuos (57 especies, N = 1 597), que en la temporada lluviosa (44 especies, N = 902). La abundancia de murciélagos estuvo influenciada principalmente, por la humedad relativa (P = 0.00) y la temperatura (mínima) (P = 0.04), mientras que, las especies respondieron diferencialmente al porcentaje de fase iluminada de la luna. En estos resultados se evidencia la influencia de factores ambientales en los patrones de actividad del ensamblaje de murciélagos en la Amazonía, en donde la ecología de las especies determina el tipo de influencia. Sin embargo, se requieren de estudios llevados a cabo por períodos más prolongados, para determinar si estos patrones se mantienen a lo largo del tiempo.(AU)

Abstract The Amazon is considered one of the most biodiverse tropical ecosystems in the world thanks to the structural complexity that geology offers and the great biological richness of its soils. Further, concerning the Mammalian class, bats are one of the best represented taxa in the region, nevertheless their ecology is poorly studied. This study, evaluates the influence of environmental factors such as the climate season, temperature (maximum and minimum), relative humidity and lunar phase on the activity patterns (abundance and trophic guilds) of an assemblage of bats in the Brazilian central Amazon. This study was carry out in two municipalities of the state of Rondônia using eight mist nets during 62 nights of sampling, covering humid and dry periods. A total of 2 499 individuals of 58 species were captured. The best represented family was the Phyllostomidae, while the species that recorded the highest frequency of captures was Carollia perspicillata (N = 859), followed by C. brevicauda(N = 209). There were no significant differences between the structure of the assemblage considering the climatic season (rain-dry). However, during the dry season a greater number of species and individuals was recorded (57 species, N = 1 597) than in the rainy season (44 species, N = 902). The abundance of bats was influenced mainly by relative humidity (P = 0.00) and minimal temperature (P = 0.04), while the species responded differentially to the lunar phase. These results show the influence of environmental factors on the activity patterns of a bat assemblage in the Amazon, where the factors that influence them depends on the ecology of each species. However, studies carried out for longer periods are required to determine if these patterns are maintained over time.(AU)

Spanish and Portuguese Gilding Threads: Characterization Using Microscopic Techniques.

Gilding threads collected from Spanish and Portuguese palaces and from the embroideries and adornments of sculptures of the Virgin and Christ that form part of Sevillian Holy Week were analyzed and compared (20 artifacts were evaluated). The study covered a broad time period with examples from the 13th to 14th centuries, 18th to 20th centuries, and also including modern embroideries. A combination of scanning electron microscopy and energy-dispersive X-ray spectroscopy was used. The knowledge of the layered structures of the threads has provided very valuable information regarding the manufacturing techniques. The different metal threads found in the embroidery studied consisted of gold, silver, copper, and alloys of these metals and aluminium. The fabrication procedures often differed in the different workshops and changed with time. In the modern embroideries, a decrease of precious metal concentration was detected. The threads were wound around a core of silk threads.

Influence of Two Polymer-Based Superplasticizers (Poly-naphthalene Sulfonate, PNS, and Lignosulfonate, LS) on Compressive and Flexural Strength, Freeze-Thaw, and Sulphate Attack Resistance of Lime-Metakaolin Grouts.

A new range of grouts prepared by air lime and metakaolin (MK) as a pozzolanic admixture has been obtained by using as dispersing agents two polymers, namely poly-naphthalene sulfonate (PNS) and lignosulfonate (LS), with the aim of improving the fluidity of the fresh grouts. Fluidity and setting times of the grouts were assessed. Differences in the molecular architecture and in the anionic charge density explained the different adsorption of the polymers and the different performance. The higher anionic charge of PNS and its linear shape explained its better adsorption and effectiveness. The pozzolanic reaction was favoured in grouts with PNS, achieving the highest values of compressive strength (4.8 MPa after 182 curing days). The addition of PNS on lime grouts slightly decreased the frost resistance of the grouts (from 24 freeze-thaw cycles for the polymer-free samples to 19 or 20 cycles with 0.5 or 1 wt % of PNS). After the magnesium sulphate attack, grouts were altered by decalcification of hydrated phases and by formation of hexahydrite and gypsum. A protective role of portlandite against magnesium sulphate attack was clearly identified. Accordingly, the polymer LS, which preserves a significant amount of Ca(OH)2, could be an alternative for the obtaining of grouts requiring high sulphate attack resistance.

Antitumoural Sulphur and Selenium Heteroaryl Compounds: Thermal Characterization and Stability Evaluation.

The physicochemical properties of a compound play a crucial role in the cancer development process. In this context, polymorphism can become an important obstacle for the pharmaceutical industry because it frequently leads to the loss of therapeutic effectiveness of some drugs. Stability under manufacturing conditions is also critical to ensure no undesired degradations or transformations occur. In this study, the thermal behaviour of 40 derivatives of a series of sulphur and selenium heteroaryl compounds with potential antitumoural activity were studied. In addition, the most promising cytotoxic derivatives were analysed by a combination of differential scanning calorimetry, X-ray diffraction and thermogravimetric techniques in order to investigate their polymorphism and thermal stability. Moreover, stability under acid, alkaline and oxidative media was tested. Degradation under stress conditions as well as the presence of polymorphism was found for the compounds VA6E and VA7J, which might present a hurdle to carrying on with formulation. On the contrary, these obstacles were not found for derivative VA4J.

Transitional-turbulent spots and turbulent-turbulent spots in boundary layers.

Two observations drawn from a thoroughly validated direct numerical simulation of the canonical spatially developing, zero-pressure gradient, smooth, flat-plate boundary layer are presented here. The first is that, for bypass transition in the narrow sense defined herein, we found that the transitional-turbulent spot inception mechanism is analogous to the secondary instability of boundary-layer natural transition, namely a spanwise vortex filament becomes a [Formula: see text] vortex and then, a hairpin packet. Long streak meandering does occur but usually when a streak is infected by a nearby existing transitional-turbulent spot. Streak waviness and breakdown are, therefore, not the mechanisms for the inception of transitional-turbulent spots found here. Rather, they only facilitate the growth and spreading of existing transitional-turbulent spots. The second observation is the discovery, in the inner layer of the developed turbulent boundary layer, of what we call turbulent-turbulent spots. These turbulent-turbulent spots are dense concentrations of small-scale vortices with high swirling strength originating from hairpin packets. Although structurally quite similar to the transitional-turbulent spots, these turbulent-turbulent spots are generated locally in the fully turbulent environment, and they are persistent with a systematic variation of detection threshold level. They exert indentation, segmentation, and termination on the viscous sublayer streaks, and they coincide with local concentrations of high levels of Reynolds shear stress, enstrophy, and temperature fluctuations. The sublayer streaks seem to be passive and are often simply the rims of the indentation pockets arising from the turbulent-turbulent spots.

Mortalidad neonatal 1990-2015 en Argentina. Tendencias y estimación de escenarios futuros en el marco de los Objetivos de Desarrollo Sostenible / Neonatal mortality 1990-2015 in Argentina. Trends and estimation of future scenarios within the framework of the Sustainable Development Goals

INTRODUCCIÓN La reducción de la mortalidad infantil en el período 1990-2015 ha experimentado un importante descenso, sin embargo este gran esfuerzo no alcanzó la meta de 2/3 establecida en el país. La mortalidad neonatal constituye un evento sumamente relevante y reducible en países en desarrollo. En marco de los Objetivos de Desarrollo Sostenible se retoma la necesidad de reducir la mortalidad neonatal. OBJETIVO Analizar la evolución de la mortalidad neonatal y algunas de sus causas principales en Argentina, en el período comprendido entre 1990 y 2016. MÉTODOS Estudio ecológico, de series temporales y vinculación con las intervenciones específicas para reducción de mortalidad infantil. RESULTADOS La reducción de la TMI (Tasa de Mortalidad Infantil) en el período fue del 61.9.%. La contribución de la TMN (Tasa de Mortalidad Neonatal) creció del 63.1% al 66.5%. La TMN se redujo un 59.9%. A nivel país, las TMN, TMN precoz, TMN tardía y TMN en varones y mujeres, muestran una tendencia global decreciente estadísticamente significativa, sin embargo las tendencias presentan cambios en diferentes períodos. La reducción en el período 1990-2016 de la TMN fue en términos generales del 3.4% anual; de 1990 a 1999 descendió 4.15% anual, entre 1999 y 2002 casi no se observa descenso, del 2005 a 2005 desciende 6.81% y de 2005 a 2016 continúa la tendencia a la baja morigerando su velocidad (2.71%). El ritmo de descenso fue semejante para mujeres y varones y superior en la TMN precoz (3.9%) que en la tardía (1.8%). El análisis de las series temporales muestra que el grupo de causas perinatales y el de malformaciones presentaron reducciones globales significativas (AAPC -3.9 y -1.1 respectivamente). El grupo de causas perinatales presenta 3 puntos de inflexión. Se observa un descenso importante entre 1990 y 1999 (PCA -4.78), un estancamiento entre 1999 y 2002 (PCA -0.06), un descenso pronunciado entre 2002 y 2006 (PCA -6.7) y un cambio en el ritmo de descenso entre 2006 y 2016 (PCA -3.05). El grupo de malformaciones presenta también 3 puntos de inflexión; entre 1990 y 2002 se observa un estancamiento (PCA 0.24), un descenso importante entre 2002 y 2005 (PCA -4.12), seguido de un estancamiento entre 2005 y 2014 (-0.77) y un descenso entre 2014 y 2016 (PCA -5.84). Este importante descenso en el grupo de las malformaciones 2002-2005 se refleja en el subgrupo de malformaciones del sistema nervioso, donde la anencefalia representa entre el 52 y 70% en el período

Wall paintings studied using Raman spectroscopy: a comparative study between various assays of cross sections and external layers.

This work describes a comparative study between in situ applications of portable Raman spectroscopy and direct laboratory measurements using micro-Raman spectroscopy on the surface of small samples and of cross sections. The study was performed using wall paintings from different sites of the Alcazar of Seville. Little information was obtained using a portable Raman spectrometer due to the presence of an acrylic polymer, calcium oxalate, calcite and gypsum that was formed or deposited on the surface. The pigments responsible for different colours, except cinnabar, were not detected by the micro-Raman spectroscopy study of the surface of small samples taken from the wall paintings due to the presence of surface contaminants. The pigments and plaster were characterised using cross sections. The black colour consisted of carbon black. The red layers were formed by cinnabar and white lead or by iron oxides. The green and white colours were composed of green emerald or atacamite and calcite, respectively. Pb3O4 has also been characterised. The white layers (plaster) located under the colour layers consisted of calcite, quartz and feldspars. The fresco technique was used to create the wall paintings. A wall painting located on a gypsum layer was also studied. The Naples yellow in this wall painting was not characterised due to the presence of glue and oils. This study showed the advantage of studying cross sections to completely characterise the pigments and plaster in the studied wall paintings.

Compositional and quantitative microtextural characterization of historic paintings by micro-X-ray diffraction and Raman microscopy.

This work shows the benefits of characterizing historic paintings via compositional and microtextural data from micro-X-ray diffraction (µ-XRD) combined with molecular information acquired with Raman microscopy (RM) along depth profiles in paint stratigraphies. The novel approach was applied to identify inorganic and organic components from paintings placed at the 14th century Islamic University-Madrasah Yusufiyya-in Granada (Spain), the only Islamic University still standing from the time of Al-Andalus (Islamic Spain). The use of µ-XRD to obtain quantitative microtextural information of crystalline phases provided by two-dimensional diffraction patterns to recognize pigments nature and manufacture, and decay processes in complex paint cross sections, has not been reported yet. A simple Nasrid (14th century) palette made of gypsum, vermilion, and azurite mixed with glue was identified in polychromed stuccos. Here also a Christian intervention was found via the use of smalt, barite, hematite, Brunswick green and gold; oil was the binding media employed. On mural paintings and wood ceilings, more complex palettes dated to the 19th century were found, made of gypsum, anhydrite, barite, dolomite, calcite, lead white, hematite, minium, synthetic ultramarine blue, and black carbon. The identified binders were glue, egg yolk, and oil.