SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Vincent van Gogh

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The painter, Vincent van Gogh, and some of his contemporaries frequently made use of the pigment chrome yellow that is known to show a tendency toward darkening. This pigment may correspond to various chemical compounds such as PbCrO(4) and PbCr(1-x)S(x)O(4), that may each be present in various crystallographic forms with different tendencies toward degradation. Investigations by X-ray diffraction (XRD), mid-Fourier Transform infrared (FTIR), and Raman instruments (benchtop and portable) and synchrotron radiation-based micro-XRD and X-ray absorption near edge structure spectroscopy performed on oil-paint models, prepared with in-house synthesized PbCrO(4) and PbCr(1-x)S(x)O(4), permitted us to characterize the spectroscopic features of the various forms. On the basis of these results, an extended study has been carried out on historic paint tubes and on embedded paint microsamples taken from yellow-orange/pale yellow areas of 12 Van Gogh paintings, demonstrating that Van Gogh effectively made use of different chrome yellow types. This conclusion was also confirmed by in situ mid-FTIR investigations on Van Gogh’s Portrait of Gauguin (Van Gogh Museum, Amsterdam).

Concepts: Vincent van Gogh, Van Gogh Museum

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Over the past years a number of studies have described the instability of the pigment cadmium yellow (CdS). In a previous paper we have shown how cadmium sulfide on paintings by James Ensor oxidizes to CdSO(4)·H(2)O. The degradation process gives rise to the fading of the bright yellow color and the formation of disfiguring white crystals that are present on the paint surface in approximately 50 μm sized globular agglomerations. Here, we study cadmium yellow in the painting “Flowers in a blue vase” by Vincent van Gogh. This painting differs from the Ensor case in the fact that (a) a varnish was superimposed onto the degraded paint surface and (b) the CdS paint area is entirely covered with an opaque crust. The latter obscures the yellow color completely and thus presents a seemingly more advanced state of degradation. Analysis of a cross-sectioned and a crushed sample by combining scanning microscopic X-ray diffraction (μ-XRD), microscopic X-ray absorption near-edge spectroscopy (μ-XANES), microscopic X-ray fluorescence (μ-XRF) based chemical state mapping and scanning microscopic Fourier transform infrared (μ-FT-IR) spectrometry allowed unravelling the complex alteration pathway. Although no crystalline CdSO(4) compounds were identified on the Van Gogh paint samples, we conclude that the observed degradation was initially caused by oxidation of the original CdS pigment, similar as for the previous Ensor case. However, due to the presence of an overlying varnish containing lead-based driers and oxalate ions, secondary reactions took place. In particular, it appears that upon the photoinduced oxidation of its sulfidic counterion, the Cd(2+) ions reprecipitated at the paint/varnish interface after having formed a complex with oxalate ions that themselves are considered to be degradation products of the resin and/or oil in the varnish. The SO(4)(2-) anions, for their part, found a suitable reaction partner in Pb(2+) ions stemming from a dissolved lead-based siccative that was added to the varnish to promote its drying. The resulting opaque anglesite compound in the varnish, in combination with the underlying CdC(2)O(4) layer at the paint/varnish interface, account for the orange-gray crust that is disfiguring the painting on a macroscopic level. In this way, the results presented in this paper demonstrate how, through a judicious combined use of several microanalytical methods with speciation capabilities, many new insights can be obtained from two minute, but highly complex and heterogeneous paint samples.

Concepts: Spectroscopy, Cadmium, Pigment, Cadmium sulfide, Expressionism, Vincent van Gogh, Cadmium pigments, Les XX

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Summary: The radiate sunflower inflorescence is composed by zygomorphic ray flowers and actinomorphic disk flowers. Studies performed on mutants identify HaCYC2c, a CYCLOIDEA (CYC)-like gene, as one of the key players controlling flower symmetry in sunflower. turf and tub mutants are characterized by a shift from zygomorphic to actinomorphic ray flowers, caused by insertion of transposable elements (TEs) in HaCYC2c gene. In dbl or Chry mutants, an insertion upstream the coding region of HaCYC2c causes the ectopic expression of the gene and the shift from actinomorphic to zygomorphic disk flowers. We focused on Chry2 mutant: a 1034 bp insertion placed 558 bp before the start codon of HaCYC2c was identified. The insertion is a truncated version of a CACTA TE. Unexpectedly, phenotypic and genetic co-segregation analysis in F2 and F3 progenies derived from the crosses Chry2 × turf and turf × Chry2 demonstrated that CACTA insertion is not always sufficient to alter the expression of HaCYC2c gene and generate Chry2 phenotype. F3 plants homozygous for the CACTA insertion displayed either HaCYC2c transcription pattern identical to wild type plants or a normal heterogamous inflorescence. Stated these results, we conclude that a much more complex regulatory system stays behind the Chry2 phenotype. © 2014 Wiley Periodicals, Inc.

Concepts: DNA, Gene, Evolution, RNA, Plant morphology, Flower, Vincent van Gogh, Van Gogh Museum

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This paper presents firm evidence for the chemical alteration of chrome yellow pigments in Van Gogh’s Sunflowers (Van Gogh Museum, Amsterdam). Noninvasive in situ spectroscopic analysis at several spots on the painting, combined with synchrotron-radiation-based X-ray investigations of two microsamples, revealed the presence of different types of chrome yellow used by Van Gogh, including the lightfast PbCrO4 and the sulfur-rich PbCr1-x Sx O4 (x≈0.5) variety that is known for its high propensity to undergo photoinduced reduction. The products of this degradation process, i.e., Cr(III) compounds, were found at the interface between the paint and the varnish. Selected locations of the painting with the highest risk of color modification by chemical deterioration of chrome yellow are identified, thus calling for careful monitoring in the future.

Concepts: Light, Color, Pigment, Yellow, Expressionism, Vincent van Gogh, Van Gogh Museum, Chrome yellow

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In the present study, we examined the eye movement behaviour of children and adults looking at five Van Gogh paintings in the Van Gogh Museum, Amsterdam. The goal of the study was to determine the role of top-down and bottom-up attentional processes in the first stages of participants' aesthetic experience. Bottom-up processes were quantified by determining a salience map for each painting. Top-down processing was manipulated by first allowing participants to view the paintings freely, then providing background information about each painting, and then allowing them to view the paintings a second time. The salience analysis showed differences between the eye movement behaviour of children and adults, and differences between the two phases. In the children, the first five fixations during the free viewing phase were strongly related to visually salient features of the paintings-indicating a strong role for bottom-up factors. In the second phase, after children had received background information, top-down factors played a more prominent role. By contrast, adults' observed patterns were similar in both phases, indicating that bottom-up processes did not play a major role when they viewed the paintings. In the second phase, children and adults both spent more time looking at regions that were mentioned in the background information. This effect was greater for adults than for children, confirming the notion that adults, when viewing paintings, rely much more on top-down processing than children.

Concepts: Expressionism, Vincent van Gogh, Van Gogh Museum

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The discoloration rate of chrome yellow (CY), a class of synthetic inorganic pigments (PbCr1-xSxO4) frequently used by Van Gogh and his contemporaries, strongly depends on its sulfate content and on its crystalline structure (either monoclinic or orthorhombic). Macroscopic X-ray powder diffraction imaging of selected areas on Van Gogh’s Sunflowers (Van Gogh Museum, Amsterdam) revealed the presence of two subtypes of CY: the light-fast monoclinic PbCrO4 (LF-CY) and the light-sensitive monoclinic PbCr1-xSxO4 (x ≈ 0.5; LS-CY). The latter was encountered in large parts of the painting (e.g., in the pale-yellow background and the bright-yellow petals, but also in the green stems and flower hearts) indicating their higher risk for past or future darkening. Overall, it is present in more than 50% of the CY regions. Preferred orientation of LS-CY allows to observe a significant ordering of the elongated nanocrystallites along the direction of Van Gogh’s brush strokes.

Concepts: Diffraction, Crystallography, Crystal system, Powder diffraction, Flower, Crystallographic database, Vincent van Gogh, Van Gogh Museum

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This study investigated whether Vincent van Gogh became increasingly self-focused-and thus vulnerable to depression-towards the end of his life, through a quantitative analysis of his written pronoun use over time. A change-point analysis was conducted on the time series formed by the pronoun use in Van Gogh’s letters. We used time as a predictor to see whether there was evidence for increased self-focus towards the end of Van Gogh’s life, and we compared this to the pattern in the letters written before his move to Arles. Specifically, we examined Van Gogh’s use of first person singular pronouns (FPSP) and first person plural pronouns (FPPP) in the 415 letters he wrote while working as an artist before his move to Arles, and in the next 248 letters he wrote after his move to Arles until his death in Auvers-sur-Oise. During the latter period, Van Gogh’s use of FPSP showed an annual increase of 0.68% (SE = 0.15, p < 0.001) and his use of FPPP showed an annual decrease of 0.23% (SE = 0.04, p < 0.001), indicating increasing self-focus and vulnerability to depression. This trend differed from Van Gogh's pronoun use in the former period (which showed no significant trend in FPSP, and an annual increase of FPPP of 0.03%, SE = 0.02, p = 0.04). This study suggests that Van Gogh's death was preceded by a gradually increasing self-focus and vulnerability to depression. It also illustrates how existing methods (i.e., quantitative linguistic analysis and change-point analysis) can be combined to study specific research questions in innovative ways.

Concepts: Grammatical person, Grammatical number, Vincent van Gogh, Personal pronoun, English personal pronouns, Starry Night Over the Rhone, Auvers-sur-Oise, Arles

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Gogh, Vincent Van (1853-1890). The Starry Night. Saint Rémy, June 1889. Oil on canvas, 29 × 36 1/4″ (73.7 × 92.1 cm). Acquired through the Lillie P. Bliss Bequest. The Museum of Modern Art. Digital Image © The Museum of Modern Art/Licensed by SCALA/Art Resource, NY.

Concepts: Modern art, Expressionism, Vincent van Gogh, Museum of Modern Art, Henri Matisse, The Starry Night, Starry Night Over the Rhone, Portrait of Dr. Gachet

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This year marks the 100th anniversary of the first malaria fever treatment (MFT) given to patients with general paralysis of the insane (GPI) by the Austrian psychiatrist and later Nobel laureate, Julius Wagner-Jauregg. In 1921 Wagner-Jauregg reported an impressive therapeutic success of MFT and it became the standard treatment for GPI worldwide. In this study, MFT practice in the Dutch Vincent van Gogh psychiatric hospital in GPI patients who had been admitted in the period 1924-1954 is explored.

Concepts: Malaria, Netherlands, Vincent van Gogh

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Color fading in Vincent van Gogh’s Undergrowth with Two Figures was studied chemically to facilitate the creation of a digital reconstruction of fugitive colors . The painting contains a field of white, green, orange, and yellow flowers under a canopy of poplar trees with two central figures-a man and a woman, arms entwined. From Van Gogh’s letters, however, it is known that he painted the picture with some pink flowers, which appear to have altered, presumably to white. Raman spectroscopy was applied to microsamples of paint to identify the faded pigment as geranium lake, which in this painting consists of the dye, eosin (2',4',5',7'-tetrabromofluorescein). For the first time, lead(II) sulfate has been specifically identified as the likely inorganic substrate for a geranium lake used by Van Gogh in the last months of his life. Microfocus X-ray fluorescence (MXRF) spectroscopy was subsequently used in situ to analyze the white flowers to identify bromine as a proxy for eosin, thus indicating an original pink coloration. Of the 387 white flowers analyzed, 37.7% contained measurable bromine and were, therefore, originally pink. Several cross-sections from these formerly pink areas were assessed using a combination of visual inspection and microcolorimetry to create a colored mask in Adobe Photoshop to digitally reconstruct a suggestion of the original appearance of the painting with regard to the faded flowers. Additionally, microfadeometry was undertaken for the first time on a painting cross-section sample to understand the actual fading kinetics of the underlying bright pink geranium lake used by Van Gogh. A combination of Raman microspectroscopy, MXRF, and scanning electron microscopy energy dispersive spectroscopy (SEM-EDS) were utilized in situ and on paint microsamples to identify the complete palette used to create Undergrowth with Two Figures.

Concepts: Spectroscopy, Color, White, Scanning electron microscope, Pigment, Expressionism, Vincent van Gogh, Museum of Modern Art