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1.
Front Physiol ; 15: 1330157, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38655031

RESUMEN

Introduction: Assessing a patient's risk of scar-based ventricular tachycardia (VT) after myocardial infarction is a challenging task. It can take months to years after infarction for VT to occur. Also, if selected for ablation therapy, success rates are low. Methods: Computational ventricular models have been presented previously to support VT risk assessment and to provide ablation guidance. In this study, an extension to such virtual-heart models is proposed to phenomenologically incorporate tissue remodeling driven by mechanical load. Strain amplitudes in the heart muscle are obtained from simulations of mechanics and are used to adjust the electrical conductivity. Results: The mechanics-driven adaptation of electrophysiology resulted in a more heterogeneous distribution of propagation velocities than that of standard models, which adapt electrophysiology in the structural substrate from medical images only. Moreover, conduction slowing was not only present in such a structural substrate, but extended in the adjacent functional border zone with impaired mechanics. This enlarged the volumes with high repolarization time gradients (≥10 ms/mm). However, maximum gradient values were not significantly affected. The enlarged volumes were localized along the structural substrate border, which lengthened the line of conduction block. The prolonged reentry pathways together with conduction slowing in functional regions increased VT cycle time, such that VT was easier to induce, and the number of recommended ablation sites increased from 3 to 5 locations. Discussion: Sensitivity testing showed an accurate model of strain-dependency to be critical for low ranges of conductivity. The model extension with mechanics-driven tissue remodeling is a potential approach to capture the evolution of the functional substrate and may offer insight into the progression of VT risk over time.

2.
Talanta ; 270: 125533, 2024 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-38134817

RESUMEN

Museum staff usually relies on a proven combination of X-ray radiography (XRR) and infrared reflectography (IRR) to study paintings in a non-destructive manner. In the last decades, however, the research toolbox of heritage scientists has expanded considerably, with a prime example being macro X-ray fluorescence (MA-XRF), producing element-specific images. The goal of this article is to illustrate the added value of augmenting MA-XRF with pulse phase thermography (PPT), a variant of active infrared thermographic imaging (IRT), which is an innovative diagnostic method that is able to reveal variations between or in materials, based on a different response to minor fluctuations in temperature when irradiated with optical radiation. By examining three 16th- and 17th-century panel paintings we assess the extent in which combined MA-XRF and PPT contributes to a better understanding of two commonly encountered interventions to panel paintings: (a) Anstückungen (enlargement of the panel) or (b) substitutions (replacement of part of the panel). Yielding information from different depths of the painting, these two techniques proved highly complementary with IRR and XRR, expanding the understanding of the build-up, genesis, and material history of the paintings. While MA-XRF documented the interventions to the wooden substrate indirectly by revealing variations in painting materials, paint handling and/or layer sequence between the original part and the extended or replaced planks, PPT proved beneficial for the study of the wooden support itself, by providing a clear image of the wood structure quasi-free of distortion by the superimposed paint or cradling. XRR, on the other hand, revealed other features from the wood structure, not visible with PPT, and allowed looking through the wooden panels, revealing e.g. the dowels used for joining the planks. Additionally, IRR visualised dissimilarities in the underdrawings. In this way, the results indicate that PPT has the potential to become an acknowledged add-on to the expanding set of imaging methods for paintings, especially when used in combination with MA-XRF, IRR and XRR.

3.
Sci Adv ; 9(50): eadj9394, 2023 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-38100587

RESUMEN

The Night Watch, one of the most famous masterpieces by Rembrandt, is the subject of a large research and conservation project. For the conservation treatment, it is of great importance to understand its current condition. Correlated nano-tomography using x-ray fluorescence and ptychography revealed a-so far unknown-lead-containing "layer", which likely acts as a protective impregnation layer applied on the canvas before the quartz-clay ground was applied. This layer might explain the presence of lead soap protrusions in areas where no other lead components are present. In addition to the three-dimensional elemental mapping, ptychography visualizes and quantifies components not detectable by hard x-ray fluorescence such as the organic fraction and quartz. The first-time use of this combination of synchrotron-based techniques on a historic paint micro-sample shows it to be an important tool to better interpret the results of noninvasive imaging techniques operating on the macroscale.

4.
Anal Chem ; 95(49): 18215-18223, 2023 Dec 12.
Artículo en Inglés | MEDLINE | ID: mdl-37994904

RESUMEN

Matrix assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) has become a powerful method to extract spatially resolved chemical information in complex materials. This study provides the first use of MALDI-MSI to define spatial-temporal changes in oil paints. Due to the highly heterogeneous nature of oil paints, the sample preparation had to be optimized to prevent molecules from delocalizing. Here, we present a new protocol for the layer-specific analysis of oil paint cross sections achieving a lateral resolution of 10 µm and without losing ionization efficiency due to topographic effects. The efficacy of this method was investigated in oil paint samples containing a mixture of two historic organic pigments, geranium lake and lead white, a mixture often employed in the work of painter Vincent Van Gogh. This methodology not only allows for spatial visualization of the molecules responsible for the pink hue of the paint but also helps to elucidate the chemical changes behind the discoloration of paintings with this composition. The results demonstrate that this approach provides valuable molecular compositional information about the degradation pathways of pigments in specific paint layers and their interaction with the binding medium and other paint components and with light over time. Since a spatial correlation between molecular species and the visual pattern of the discoloration pattern can be made, we expect that mass spectrometry imaging will become highly relevant in future degradation studies of many more historical pigments and paints.

5.
Molecules ; 28(16)2023 Aug 17.
Artículo en Inglés | MEDLINE | ID: mdl-37630361

RESUMEN

In this paper, the chromatic alteration of various types of paints, present on mural painting fragments derived from the vaults of The Upper Basilica of Saint Francis of Assisi in Italy (12th-13th century), is studied using synchrotron radiation. Six painted mural fragments, several square centimeters in size, were available for analysis, originating from the ceiling paintings attributed to Cimabue and Giotto; they correspond to originally white, blue/green, and brown/yellow/orange areas showing discoloration. As well as collecting macroscopic X-ray fluorescence and diffraction maps from the entire fragments in the laboratory and at the SOLEIL synchrotron, corresponding paint cross-sections were also analyzed using microscopic X-ray fluorescence and powder diffraction mapping at the PETRA-III synchrotron. Numerous secondary products were observed on the painted surfaces, such as (a) copper tri-hydroxychloride in green/blue areas; (b) corderoite and calomel in vermillion red/cinnabar-rich paints; (c) plattnerite and/or scrutinyite assumed to be oxidation products of (hydro)cerussite (2PbCO3·Pb(OH)2) in the white areas, and (d) the calcium oxalates whewellite and weddellite. An extensive presence of chlorinated metal salts points to the central role of chlorine-containing compounds during the degradation of the 800-year-old paint, leading to, among other things, the formation of the rare mineral cumengeite (21PbCl2·20Cu(OH)2·6H2O).

6.
J Am Chem Soc ; 145(16): 8847-8859, 2023 Apr 26.
Artículo en Inglés | MEDLINE | ID: mdl-37058004

RESUMEN

Paintings are complex objects containing many different chemical compounds that can react over time. The degradation of arsenic sulfide pigments causes optical changes in paintings. The main degradation product was thought to be white arsenolite (As2O3), but previous research also showed the abundant presence of As(V) species. In this study, we investigate the influence of the presence of a medium on the degradation mechanism of orpiment (As2S3) using synchrotron radiation (SR)-based tomographic transmission X-ray microscopy, SR-based micro-X-ray fluorescence, and X-ray absorption near edge structure spectroscopy. Upon direct illumination of dry orpiment powder using UV-visible light, only the formation of As2O3 was observed. When As2S3 was surrounded by a medium and illuminated, As2O3 was only observed in the area directly exposed to light, while As(V) degradation species were found elsewhere in the medium. Without accelerated artificial light aging, As(V)(aq) species are formed and migrate throughout the medium within weeks after preparation. In both scenarios, the As(V) species form via intermediate As(III)(aq) species and the presence of a medium is necessary. As(V)(aq) species can react with available cations to form insoluble metal arsenates, which induces stress within the paint layers (leading to, e.g., cracks and delamination) or can lead to a visual change of the image of the painting.

7.
ACS Nano ; 17(6): 5296-5305, 2023 03 28.
Artículo en Inglés | MEDLINE | ID: mdl-36921214

RESUMEN

A combination of synchrotron-based elemental analysis and acute toxicity tests was used to investigate the biodistribution and adverse effects in Daphnia magna exposed to uranium nanoparticle (UNP, 3-5 nm) suspensions or to uranium reference (Uref) solutions. Speciation analysis revealed similar size distributions between exposures, and toxicity tests showed comparable acute effects (UNP LC50: 402 µg L-1 [336-484], Uref LC50: 268 µg L-1 [229-315]). However, the uranium body burden was 3- to 5-fold greater in UNP-exposed daphnids, and analysis of survival as a function of body burden revealed a ∼5-fold higher specific toxicity from the Uref exposure. High-resolution X-ray fluorescence elemental maps of intact, whole daphnids from sublethal, acute exposures of both treatments revealed high uranium accumulation onto the gills (epipodites) as well as within the hepatic ceca and the intestinal lumen. Uranium uptake into the hemolymph circulatory system was inferred from signals observed in organs such as the heart and the maxillary gland. The substantial uptake in the maxillary gland and the associated nephridium suggests that these organs play a role in uranium removal from the hemolymph and subsequent excretion. Uranium was also observed associated with the embryos and the remnants of the chorion, suggesting uptake in the offspring. The identification of target organs and tissues is of major importance to the understanding of uranium and UNP toxicity and exposure characterization that should ultimately contribute to reducing uncertainties in related environmental impact and risk assessments.


Asunto(s)
Uranio , Contaminantes Químicos del Agua , Animales , Rayos X , Daphnia/química , Uranio/toxicidad , Sincrotrones , Distribución Tisular , Toxicocinética , Imagen Óptica , Contaminantes Químicos del Agua/química
8.
Environ Sci Technol ; 57(2): 1071-1079, 2023 01 17.
Artículo en Inglés | MEDLINE | ID: mdl-36598768

RESUMEN

Micro- and nanoscopic X-ray techniques were used to investigate the relationship between uranium (U) tissue distributions and adverse effects to the digestive tract of aquatic model organism Daphnia magna following uranium nanoparticle (UNP) exposure. X-ray absorption computed tomography measurements of intact daphnids exposed to sublethal concentrations of UNPs or a U reference solution (URef) showed adverse morphological changes to the midgut and the hepatic ceca. Histological analyses of exposed organisms revealed a high proportion of abnormal and irregularly shaped intestinal epithelial cells. Disruption of the hepatic ceca and midgut epithelial tissues implied digestive functions and intestinal barriers were compromised. Synchrotron-based micro X-ray fluorescence (XRF) elemental mapping identified U co-localized with morphological changes, with substantial accumulation of U in the lumen as well as in the epithelial tissues. Utilizing high-resolution nano-XRF, 400-1000 nm sized U particulates could be identified throughout the midgut and within hepatic ceca cells, coinciding with tissue damages. The results highlight disruption of intestinal function as an important mode of action of acute U toxicity in D. magna and that midgut epithelial cells as well as the hepatic ceca are key target organs.


Asunto(s)
Uranio , Contaminantes Químicos del Agua , Animales , Rayos X , Daphnia , Uranio/toxicidad , Fluorescencia , Sincrotrones , Tracto Gastrointestinal , Contaminantes Químicos del Agua/toxicidad
9.
Angew Chem Int Ed Engl ; 62(16): e202216478, 2023 Apr 11.
Artículo en Inglés | MEDLINE | ID: mdl-36591906

RESUMEN

The Night Watch, painted in 1642 and on view in the Rijksmuseum in Amsterdam, is considered Rembrandt's most famous work. X-ray powder diffraction (XRPD) mapping at multiple length scales revealed the unusual presence of lead(II) formate, Pb(HCOO)2 , in several areas of the painting. Until now, this compound was never reported in historical oil paints. In order to get insights into this phenomenon, one possible chemical pathway was explored thanks to the preparation and micro-analysis of model oil paint media prepared by heating linseed oil and lead(II) oxide (PbO) drier as described in 17th century recipes. Synchrotron radiation based micro-XRPD (SR-µ-XRPD) and infrared microscopy were combined to identify and map at the micro-scale various neo-formed lead-based compounds in these model samples. Both lead(II) formate and lead(II) formate hydroxide Pb(HCOO)(OH) were detected and mapped, providing new clues regarding the reactivity of lead driers in oil matrices in historical paintings.

10.
RSC Adv ; 12(50): 32775-32783, 2022 Nov 09.
Artículo en Inglés | MEDLINE | ID: mdl-36425693

RESUMEN

This study presents a novel method for the detection and quantification of atmospheric corrosion products on carbon steel. Using hyperspectral imaging (HSI) in the short-wave infrared range (SWIR) (900-1700 nm), we are able to identify the most common corrosion minerals such as: α-FeO(OH) (goethite), γ-FeO(OH) (lepidocrocite), and γ-Fe2O3 (maghemite). Six carbon steel samples were artificially corroded in a salt spray chamber, each sample with a different duration (between 1 h and 120 hours). These samples were analysed by scanning X-ray diffraction (XRD) and also using a SWIR HSI system. The XRD data is used as baseline data. A random forest regression algorithm is used for training on the combined XRD and HSI data set. Using the trained model, we can predict the abundance map based on the HSI images alone. Several image correlation metrics are used to assess the similarity between the original XRD images and the HSI images. The overall abundance is also calculated and compared for XRD and HSI images. The analysis results show that we are able to obtain visually similar images, with error rates ranging from 3.27 to 13.37%. This suggests that hyperspectral imaging could be a viable tool for the study of corrosion minerals.

11.
Sci Adv ; 8(23): eabn6344, 2022 Jun 10.
Artículo en Inglés | MEDLINE | ID: mdl-35675402

RESUMEN

Over time, artist pigments are prone to degradation, which can decrease the readability of the artwork or notably change the artist's intention. In this article, the visual implication of secondary degradation products in a degraded yellow rose in a still life painting by A. Mignon is discussed as a case study. A multimodal combination of chemical and optical imaging techniques, including noninvasive macroscopic x-ray powder diffraction (MA-XRPD) and macroscopic x-ray fluorescence imaging, allowed us to gain a 3D understanding of the transformation of the original intended appearance of the rose into its current degraded state. MA-XRPD enabled us to precisely correlate in situ formed products with what is optically visible on the surface and demonstrated that the precipitated lead arsenates and arsenolite from the yellow pigment orpiment and the light-induced fading of an organic yellow lake irreversibly changed the artist's intentional light-shadow modeling.

12.
Environ Sci Technol ; 56(8): 5081-5089, 2022 04 19.
Artículo en Inglés | MEDLINE | ID: mdl-35378039

RESUMEN

A combination of synchrotron radiation-based elemental imaging, in vivo redox status analysis, histology, and toxic responses was used to investigate the uptake, biodistribution, and adverse effects of Ce nanoparticles (CeO2 NP; 10 nm; 0.5-34.96 mg Ce L-1) or Ce(NO3)3 (2.3-26 mg Ce L-1) in Caenorhabditis elegans. Elemental mapping of the exposed nematodes revealed Ce uptake in the alimentary canal prior to depuration. Retention of CeO2 NPs was low compared to that of Ce(NO3)3 in depurated individuals. X-ray fluorescence (XRF) mapping showed that Ce translocation was confined to the pharyngeal valve and foregut. Ce(NO3)3 exposure significantly decreased growth, fertility, and reproduction, caused slightly reduced fecundity. XRF mapping and histological analysis revealed severe tissue deformities colocalized with retained Ce surrounding the pharyngeal valve. Both forms of Ce activated the sod-1 antioxidant defense, particularly in the pharynx, whereas no significant effects on the cellular redox balance were identified. The CeO2 NP-induced deformities did not appear to impair the pharyngeal function or feeding ability as growth effects were restricted to Ce(NO3)3 exposure. The results demonstrate the utility of integrated submicron-resolution SR-based XRF elemental mapping of tissue-specific distribution and adverse effect analysis to obtain robust toxicological evaluations of metal-containing contaminants.


Asunto(s)
Cerio , Nanopartículas del Metal , Nanopartículas , Animales , Caenorhabditis elegans , Fluorescencia , Humanos , Nanopartículas del Metal/toxicidad , Faringe , Sincrotrones , Distribución Tisular , Rayos X
13.
Molecules ; 27(6)2022 Mar 20.
Artículo en Inglés | MEDLINE | ID: mdl-35335359

RESUMEN

The European Synchrotron Radiation Facility (ESRF) has recently commissioned the new Extremely Brilliant Source (EBS). The gain in brightness as well as the continuous development of beamline instruments boosts the beamline performances, in particular in terms of accelerated data acquisition. This has motivated the development of new access modes as an alternative to standard proposals for access to beamtime, in particular via the "block allocation group" (BAG) mode. Here, we present the recently implemented "historical materials BAG": a community proposal giving to 10 European institutes the opportunity for guaranteed beamtime at two X-ray powder diffraction (XRPD) beamlines-ID13, for 2D high lateral resolution XRPD mapping, and ID22 for high angular resolution XRPD bulk analyses-with a particular focus on applications to cultural heritage. The capabilities offered by these instruments, the specific hardware and software developments to facilitate and speed-up data acquisition and data processing are detailed, and the first results from this new access are illustrated with recent applications to pigments, paintings, ceramics and wood.


Asunto(s)
Programas Informáticos , Sincrotrones , Cristalografía por Rayos X , Difracción de Rayos X
14.
Anal Chem ; 93(44): 14851-14858, 2021 11 09.
Artículo en Inglés | MEDLINE | ID: mdl-34714624

RESUMEN

The implementation of high-resolution mass spectrometry systems offers new possibilities for the analysis of complex art samples such as historical oil paintings. However, these multicomponent systems generate large and complex data sets that require advanced visualization tools to aid interpretation, especially when no chromatographic separation is performed. In the context of this research, it was crucial to propose a data analysis tool to identify the products generated during the synthesis, drying, and aging of historical pigments. This study reports for the first time a nontraditional mass defect analysis of oil paint samples containing a fugitive brominated-organic pigment, eosin or geranium lake, by using direct infusion electrospray ionization in combination with a high-resolution Orbitrap mass spectrometer. The use of nontraditional Kendrick mass defect plots is presented in this study as a processing and visualization tool to recognize brominated species based on their specific mass defect and isotope pattern. The results demonstrate that this approach could provide valuable molecular compositional information on the degradation pathways of this pigment. We anticipate that mass defect analysis will become highly relevant in future degradation studies of many more historical organic pigments.


Asunto(s)
Pintura , Pinturas , Colorantes , Isótopos , Espectrometría de Masas
15.
Polymers (Basel) ; 13(16)2021 Aug 10.
Artículo en Inglés | MEDLINE | ID: mdl-34451194

RESUMEN

Polymeric materials have been used by painting conservator-restorers as consolidants and/or varnishes for wall paintings. The application of these materials is carried out when confronting loose paint layers or as a protective coating. However, these materials deteriorate and cause physiochemical alterations to the treated surface. In the past, the monumental neo-gothic wall painting 'The Last Judgment' in the chapel of Sint-Jan Berchmanscollege in Antwerp, Belgium was treated with a synthetic polymeric material. This varnish deteriorated significantly and turned brown, obscuring the paint layers. Given also that the varnish was applied to some parts of the wall painting and did not cover the entire surface, it was necessary to remove it in order to restore the original appearance of the wall painting. Previous attempts carried out by conservator-restorers made use of traditional cleaning methods, which led to damage of the fragile paint layers. Therefore, gel cleaning was proposed as a less invasive and more controllable method for gently softening and removing the varnish. The work started by identifying the paint stratigraphy and the deteriorated varnish via optical microscopy (OM), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy. A polyvinyl alcohol-borax/agarose (PVA-B/AG) hydrogel loaded with a number of solvents/solvent mixtures was employed in a series of tests to select the most suitable hydrogel composite. By means of the hydrogel composite loaded with 10% propylene carbonate, it was possible to safely remove the brown varnish layer. The results were verified by visual examinations (under visible light 'VIS' and ultraviolet light 'UV') as well as OM and FTIR spectroscopy.

16.
Proc Natl Acad Sci U S A ; 117(45): 27825-27835, 2020 11 10.
Artículo en Inglés | MEDLINE | ID: mdl-33106396

RESUMEN

A hitherto unknown composition is highlighted in the red and black inks preserved on ancient Egyptian papyri from the Roman period (circa 100 to 200 CE). Synchrotron-based macro-X-ray fluorescence (XRF) mapping brings to light the presence of iron (Fe) and lead (Pb) compounds in the majority of the red inks inscribed on 12 papyrus fragments from the Tebtunis temple library. The iron-based compounds in the inks can be assigned to ocher, notably due to the colocalization of Fe with aluminum, and the detection of hematite (Fe2O3) by micro-X-ray diffraction. Using the same techniques together with micro-Fourier transform infrared spectroscopy, Pb is shown to be associated with fatty acid phosphate, sulfate, chloride, and carboxylate ions. Moreover, micro-XRF maps reveal a peculiar distribution and colocalization of Pb, phosphorus (P), and sulfur (S), which are present at the micrometric scale resembling diffused "coffee rings" surrounding the ocher particles imbedded in the red letters, and at the submicrometric scale concentrated in the papyrus cell walls. A similar Pb, P, and S composition was found in three black inks, suggesting that the same lead components were employed in the manufacture of carbon-based inks. Bearing in mind that pigments such as red lead (Pb3O4) and lead white (hydrocerussite [Pb3(CO3)2(OH)2] and/or cerussite [PbCO3]) were not detected, the results presented here suggest that the lead compound in the ink was used as a drier rather than as a pigment. Accordingly, the study calls for a reassessment of the composition of lead-based components in ancient Mediterranean pigments.

17.
Anal Chem ; 92(20): 14164-14173, 2020 10 20.
Artículo en Inglés | MEDLINE | ID: mdl-32955250

RESUMEN

Synchrotron radiation (SR)-based X-ray methods are powerful analytical tools for several purposes. They are widely used to probe the degradation mechanisms of inorganic artists' pigments in paintings, including chrome yellows (PbCr1-xSxO4; 0 ≤ x ≤ 0.8), a class of compounds often found in Van Gogh masterpieces. However, the high intensity and brightness of SR beams raise important issues regarding the potential damage inflicted on the analyzed samples. A thorough knowledge of the SR X-ray sensitivity of each class of pigment in the painting matrix is therefore required to find analytical strategies that seek to minimize the damage for preserving the integrity of the analyzed samples and to avoid data misinterpretation. Here, we employ a combination of Cr K-edge X-ray absorption near-edge structure spectroscopy, Cr-Kß X-ray emission spectroscopy, and X-ray diffraction to monitor and quantify the effects of SR X-rays on the stability of chrome yellows and related Cr compounds and to define mitigation strategies. We found that the SR X-ray beam exposure induces changes in the oxidation state and local coordination environment of Cr ions and leads to a loss of the compound's crystalline structure. The extent of X-ray damage depends on some intrinsic properties of the samples (chemical composition of the pigment and the presence/absence and nature of the binder). It can be minimized by optimizing the overall fluence/dose released to the samples and by working in vacuum and under cryogenic conditions.

18.
Sci Adv ; 6(31): eabb3379, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32832690

RESUMEN

The ongoing conservation treatment program of the Ghent Altarpiece by Hubert and Jan Van Eyck, one of the iconic paintings of the west, has revealed that the designs of the paintings were changed several times, first by the original artists, and then during later restorations. The central motif, The Lamb of God, representing Christ, plays an essential iconographic role, and its depiction is important. Because of the prevalence of lead white, it was not possible to visualize the Van Eycks' original underdrawing of the Lamb, their design changes, and the overpaint by later restorers with a single spectral imaging modality. However, by using elemental (x-ray fluorescence) and molecular (infrared reflectance) imaging spectroscopies, followed by analysis of the resulting data cubes, the necessary chemical contrast could be achieved. In this way, the two complementary modalities provided a more complete picture of the development and changes made to the Lamb.

19.
Sci Adv ; 6(20): eaay3514, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-32440540

RESUMEN

The degradation of cadmium sulfide (CdS)-based oil paints is a phenomenon potentially threatening the iconic painting The Scream (ca. 1910) by Edvard Munch (Munch Museum, Oslo) that is still poorly understood. Here, we provide evidence for the presence of cadmium sulfate and sulfites as alteration products of the original CdS-based paint and explore the external circumstances and internal factors causing this transformation. Macroscale in situ noninvasive spectroscopy studies of the painting in combination with synchrotron-radiation x-ray microspectroscopy investigations of a microsample and artificially aged mock-ups show that moisture and mobile chlorine compounds are key factors for promoting the oxidation of CdS, while light (photodegradation) plays a less important role. Furthermore, under exposure to humidity, parallel/secondary reactions involving dissolution, migration through the paint, and recrystallization of water-soluble phases of the paint are associated with the formation of cadmium sulfates.

20.
Int J Cardiol ; 313: 32-34, 2020 08 15.
Artículo en Inglés | MEDLINE | ID: mdl-32380248

RESUMEN

AIMS: Pressure loss versus transvalvular flow analysis challenges physiologic models of current aortic valve stenosis. New conceptual frameworks are needed to explain these real-world observations. METHODS AND RESULTS: A patient-specific, 3D-printed, silicon model of a stenotic valve was placed inside an in-vitro haemodynamic model of the circulatory system. Instantaneous pressure and flow in the aorta and left ventricle were simulated according to measured patient specific parameters. Thereafter, a realistic transcatheter aortic valve was implanted (TAVI) in the model. Simulated post-TAVI mean pressure gradients resembled patient observations (3.7 ± 0.7 mmHg vs 6.7 ± 2.3 mmHg), but pre-TAVI measurements underestimated the pressure gradient (35.1 ± 0.6 mmHg vs 45.3 ± 1.5 mmHg). CONCLUSION: Patient-specific 3D-printed stenotic aortic valve models could simulate baseline haemodynamics. A TAVI procedure was successfully performed on the 3D silicone rubber valve in a physiologic in-vitro model. Pre-TAVI haemodynamics in the model underestimated in-patient mean pressure gradient, whereas post TAVI pressure gradient was predicted correctly with the TAVI valve inside the 3D printed model. This study shows that these types of models could be used to study AS hemodynamics with the TAVI valve inside the 3D printed model. Improvements in the 3D-printed model, like addition of calcification and fine-tuning of the haemodynamic model, could further enhance accuracy of the simulation.


Asunto(s)
Estenosis de la Válvula Aórtica , Implantación de Prótesis de Válvulas Cardíacas , Prótesis Valvulares Cardíacas , Reemplazo de la Válvula Aórtica Transcatéter , Válvula Aórtica/diagnóstico por imagen , Válvula Aórtica/cirugía , Estenosis de la Válvula Aórtica/diagnóstico por imagen , Estenosis de la Válvula Aórtica/cirugía , Cateterismo Cardíaco , Hemodinámica , Humanos , Impresión Tridimensional , Resultado del Tratamiento
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