Chromatic Content Research Articles

Tonal structure and the melodic role of chromatic inflections in the music of Machaut

The interpretation of chromatic content in fourteenth-century music has been widely debated. While most studies have focused on contrapuntal necessity, this study advocates an approach that begins from the perspective of melody. Using the ballades, virelais and rondeaux of Guillaume de Machaut as a central repertory, it proposes that not only are chromatic inflections in Machaut's monophonic songs derived melodically, but that many chromatic inflections in Machaut's polyphonic songs also arise from melodic rather than contrapuntal requirements. Because of their implied semitone motion – arguably crucial to tonal organization – they can have an impact on the definition of tonal structure by privileging the individual pitches they decorate, particularly but not exclusively in cadential melodic formulas or progressions.

Arsenate and chromate incorporation in schwertmannite

High concentrations of Cr (up to 812 ppm) and As (up to 6740 ppm) were detected in precipitates of the mineral schwertmannite in areas influenced by acid mine drainage. Schwertmannite may act as well as a natural filter for these elements in water as well as their source by releasing the previously bound elements during its dissolution or mineral-transformation. The mechanisms of uptake and potential release for the species arsenate and chromate were investigated by performing synthesis and stability experiments with schwertmannite. Schwertmannite, synthesized in solutions containing arsenate in addition to sulphate, was enriched by up to 10.3 wt% arsenate without detectable structural changes as demonstrated by powder X-ray diffraction (XRD). In contrast to arsenate, a total substitution of sulphate by chromate was possible in sulphate-free solutions. Thereby, the chromate content in schwertmannite could reach 15.3 wt%. To determine the release of oxyanions from schwertmannite over time, synthetic schwertmannite samples containing varying amounts of sulphate, chromate and arsenate were kept at a stable pH of either 2 or 4 over 1 year in suspension. At several time intervals Fe and the oxyanions were measured in solution and alterations of the solid part were observed by XRD and Fourier-Transform infrared (FT-IR) spectroscopy. At pH 2 schwertmannite partly dissolved and the total release of arsenate (24%) was low in contrast to chromate (35.4–57.5%) and sulphate (67–76%). Accordingly, the ionic activity product (log IAP) of arsenated schwertmannite was lowest (13.5), followed by the log IAP for chromated schwertmannite (16.2–18.5) and the log IAP for regular (=non-substituted) schwertmannite (18). At pH 4 schwertmannite transformed to goethite, an effect which occurred at the fastest rate for regular schwertmannite (=arsenate- and chromate-free), followed by chromate and arsenate containing schwertmannite. Both chromate and more evidently arsenate have a stabilizing effect on the schwertmannite structure, because they retarded the dissolution and transformation reactions. These kinetic investigations as well as crystallographic considerations demonstrated that the strength of the Fe(III) complexes with the anions controls the formation process and the stability of schwertmannite: with increasing affinity of the oxyanions to form complexes with Fe(III), the strength of the resulting binding and thus the stability and substitution preference increases.

Spatial properties of photophobia.

To determine the spatial properties of stimuli that elicit photophobia (PP) in normal subjects: Does PP exhibit spatial summation? Are different parafoveal quadrants (superior, inferior, temporal, and nasal) of the retina differentially sensitive in PP? What is the relationship between PP sensitivity and retinal eccentricity? What is the relationship between the spatial properties of PP and the spatial distribution of macular pigment (MP)? A Maxwellian-view optical system with a xenon light source was used to present the stimuli. Four normal subjects viewed stimuli of various sizes, retinal locations, and one of two chromatic contents: xenon-white and a broadband orange. The intensity of the test stimulus was increased between trials until the PP threshold was reached. The squinting response corresponding to PP was assessed by electromyography and used as an objective criterion of PP. Three parameters were examined: stimulus size, parafoveal retinal locus (superior, inferior, temporal, and nasal), and retinal eccentricity (extending into the perifovea). Spatial profiles of MP were measured psychophysically using heterochromatic flicker photometry (HFP). Spatial summation for PP was found essentially to adhere to Piper's law (radiance proportional to square root of stimulus area). The PP response was greater to centrally than peripherally viewed targets. In this regard, MP acted as a spatially integrated filter in the attenuation of PP. The degree of spatial summation found for PP indicates that an increase of 1.0 log unit in field area results in an approximately 0.57-log-unit decrease in the radiance required to elicit PP. PP appears to serve the function of retinal photoprotection.

Syntheses, Structures, Magnetic Properties, and X‐Ray Absorption Spectra of Carnotite‐Type Uranyl Chromium(V) Oxides: A[(UO2)2Cr2O8] (H2O)n (A: K2, Rb2, Cs2, Mg; n = 0, 4).

AbstractFor Abstract see ChemInform Abstract in Full Text.

Syntheses, Structures, Magnetic Properties, and X-ray Absorption Spectra of Carnotite-type Uranyl Chromium(V) Oxides: A[(UO2)2Cr2O8](H2O)n (A = K2, Rb2, Cs2, Mg; n = 0, 4)

Four uranyl chromium(V) oxides were synthesized by mild hydrothermal methods and their structures were solved using single-crystal X-ray diffraction data. In these structures, U occurs in edge-sharing dimers of UO 7 uranyl pentagonal bipyramids, and Cr occurs in edge-sharing dimers of CrO 5 square pyramids. The two sets of dimers share edges, forming sheets of composition [(UO 2 ) 2 Cr 2 O 8 ] 2- that are topologically identical to uranyl divanadate sheets, [(UO 2 ) 2 V 2 O 8 ] 2- , that occur in compounds of the carnotite group. K 2 [(UO 2 ) 2 Cr 2 O 8 ] (KUCr), Rb 2 [(UO 2 ) 2 Cr 2 O 8 ] (RbUCr), and Cs 2 [(UO 2 ) 2 Cr 2 O 8 ] (CsUCr) are isostructural with K 2 [(UO 2 ) 2 V 2 O 8 ], and Mg[(UO 2 ) 2 Cr 2 O 8 ](H 2 O) 4 (MgUCr) is isostructural with Ni[(UO 2 ) 2 V 2 O 8 ]-(H 2 O) 4 . The stoichiometries of these compounds imply that Cr is present as chromium(V), which is supported by the results of bond valence analyses. EPR spectra and magnetic susceptibility data for KUCr are consistent with the presence of the d 1 cation chromium(V). The KUCr moments undergo a sharp transition from paramagnetic to antiferromagnetic behavior at T N = 18.5 K. XAFS data for the U L 3 edge and XANES of the Cr K edge of KUCr yield coordinations and oxidation states consistent with the crystal structure analysis. The presence of a pre-edge peak due solely to Cr 5+ sounds a cautionary note for XANES determination of the chromate(VI) content of environmental samples. Crystallographic data for KUCr, RbUCr, CsUCr: monoclinic space group P2 1 /c (No. 14), with a = 6.5483(8) A, b = 8.3548(10) A, c = 10.4200(13) A, β = 105.040(3)°; a = 6.8677(6) A, b = 8.3599(7) A, c = 10.4625(8) A, β = 106.004(2)°; and a = 7.2643(15) A, b = 8.3803(17) A, c = 10.5100(22) A, β = 106.399(5)°, respectively. Crystal data for MgUCr: orthorhombic space group Pnma (No. 62), with a = 10.5825(19) A, b = 15.1337(27) A, c = 8.1425(14) A.

Laboratory stabilization/solidification of tank sludges: maximizing sludge loading

Highly radioactive, mixed-waste sludges that have been collected in tanks at Oak Ridge over several decades are being combined for treatment and disposal. Stabilization of the sludges in the different tank sets was tested prior to the proposed combination and treatment. This paper is the third one in a series on the laboratory stabilization/solidification of these tank sludges. It discusses efforts to maximize the sludge loading with no strength criterion for the grout formulation. Grout formulations were tested in the laboratory both with surrogates and with actual samples of tank sludge. Hydrogels eliminated free water generation, even at sludge loadings of >90 wt%, albeit strong monoliths did not form at such high loadings. Correlations established the dependence of the chromium and mercury performance in the Toxicity Characteristic Leach Procedure for the surrogates on the slag content of the grout while the lead performance depended on the extract pH. The surrogate sludge loading was limited by the chromate content to about 90 wt%, meeting Universal Treatment Standard limits. However, tests with actual sludges at such high loadings revealed problems with lead and silver stabilization that were not experienced with the surrogate testing.

Use of Bismuth Chromate with Antimony Trisulphide in Delay Compositions

Antimony trisulphide is used with potassium perchlorate, barium chromate, and binder in delay compositions. The effect of substitution of barium chromate by bismuth chromate in the system barium chromate-antimony trisulphide-potassium perchlorate has been studied and reported here. These compositions contain 20% antimony trisulphide, 10% potassium perchlorate, and the remainder barium chromate/bismuth chromate. It is observed that the burning rate decreases from 0.43 to 0.23 cm/s with an increase in bismuth chromate content. The ignition temperature of these compositions determined by Differential Thermal Analysis (DTA) is found to be in the range 400 - 10°C, the same for all compositions.Theoretical calculations by a chemical equilibrium program (REAL) are used to discuss the possible reaction mechanism. Thermo gravimetry (TG)/Differential Scanning Calorimetry (DSC) data are reported. It is observed that the main exothermic peak of the compositions containing bismuth chromate shows at about 462°C as compared to the basic system, where it is at 498°C. These compositions are safe to handle, as suggested by sensitivity data.

Failure of signed chromatic apparent motion with luminance masking

It has been suggested that there are two types of chromatic motion mechanisms: signed chromatic motion, in which correspondence across successive frames is based on chromatic content of image regions, and unsigned chromatic motion based on movement of chromatically-defined borders. We investigate whether signed and unsigned red–green chromatic motion are mediated by a genuinely chromatic mechanism. Direction discrimination of signed and unsigned red–green chromatic motion were measured in the presence of a dynamic luminance masking noise. Increasing the luminance noise contrast systematically impaired signed motion, regardless of contrast and speed. This result suggests that signed red–green chromatic motion is derived from a luminance-based signal, rather than a genuinely chromatic motion mechanism. In the case of unsigned chromatic motion, there is no effect of luminance masking noise, indicating there exists a genuine chromatic mechanism for second-order motion perception.

Processing of Natural Temporal Stimuli by Macaque Retinal Ganglion Cells

This study quantifies the performance of primate retinal ganglion cells in response to natural stimuli. Stimuli were confined to the temporal and chromatic domains and were derived from two contrasting environments, one typically northern European and the other a flower show. The performance of the cells was evaluated by investigating variability of cell responses to repeated stimulus presentations and by comparing measured to model responses. Both analyses yielded a quantity called the coherence rate (in bits per second), which is related to the information rate. Magnocellular (MC) cells yielded coherence rates of up to 100 bits/sec, rates of parvocellular (PC) cells were much lower, and short wavelength (S)-cone-driven ganglion cells yielded intermediate rates. The modeling approach showed that for MC cells, coherence rates were generated almost exclusively by the luminance content of the stimulus. Coherence rates of PC cells were also dominated by achromatic content. This is a consequence of the stimulus structure; luminance varied much more in the natural environment than chromaticity. Only approximately one-sixth of the coherence rate of the PC cells derived from chromatic content, and it was dominated by frequencies below 10 Hz. S-cone-driven ganglion cells also yielded coherence rates dominated by low frequencies. Below 2-3 Hz, PC cell signals contained more power than those of MC cells. Response variation between individual ganglion cells of a particular class was analyzed by constructing generic cells, the properties of which may be relevant for performance higher in the visual system. The approach used here helps define retinal modules useful for studies of higher visual processing of natural stimuli.

Spatiochromatic Properties of Natural Images and Human Vision

The human visual system shows a relatively greater response to low spatial frequencies of chromatic spatial modulation than to luminance spatial modulation. However, previous work has shown that this differential sensitivity to low spatial frequencies is not reflected in any differential luminance and chromatic content of general natural scenes. This is contrary to the prevailing assumption that the spatial properties of human vision ought to reflect the structure of natural scenes. Now, colorimetric measures of scenes suggest that red-green (and perhaps blue-yellow) color discrimination in primates is particularly suited to the encoding of specific scenes: reddish or yellowish objects on a background of leaves. We therefore ask whether the spatial, as well as chromatic, properties of such scenes are matched to the different spatial-encoding properties of color and luminance modulation in human vision. We show that the spatiochromatic properties of a wide class of scenes, which contain reddish objects (e.g., fruit) on a background of leaves, correspond well to the properties of the red-green (but not blue-yellow) systems in human vision, at viewing distances commensurate with typical grasping distance. This implies that the red-green system is particularly suited to encoding both the spatial and the chromatic structure of such scenes.

Feasibility study to probe the growth of chromate based conversion on Al by means of rotating ring disc electrode (RRDE) measurements

The use of a rotating ring disc electrode (RRDE) is introduced in this paper to study the formation of chromate–phosphate layers on rolled aluminium surfaces. A RRDE was developed containing an Al disc, which was converted with a chromate phosphate film, and a carbon ring, where the Cr 6+ reduction rate was measured in situ. The principle of the method is that Cr 6+ is transported from the bulk of the solution towards the disc and the ring electrode. At the disc electrode, a fraction of Cr 6+ is consumed during the conversion of the Al disc electrode. This leads to a decrease in ring current, which is directly related to the amount of Cr 6+ being reduced at the disc electrode. For proper operation of the RDDE system, an electrode with optimised geometrical characteristics is used. In order to be sure that the measured current on the ring is in relation with the Cr 6+ reduction rate occurring at the aluminium disc, a number of requirements need to be fulfilled. After showing that the RDDE system is indeed able to monitor in situ the Cr 6+ content during conversion, the amount of Cr 6+ reduced at the disc electrode is calculated from the recorded ring current time curves. The method allows (i) to follow the growth of a conversion layer quantitatively in situ and (ii) to study the influence of important process parameters such as fluoride content, chromate content of the conversion bath and influence of mass transport.

Senescent changes in parafoveal color appearance: saturation as a function of stimulus area.

The chromatic content (saturation) of monochromatic stimuli (480, 505, 577, and 650 nm) was scaled as a function of field size at three different retinal locations by 58 observers ranging from 18 to 83 yr of age. The different retinal locations (6 deg nasal, 2.5 deg inferior and 6 deg temporal eccentricity) were chosen according to anatomical studies demonstrating different degrees of senescent losses of cones or ganglion cells. Nine field sizes were tested, ranging from 0.0096 to 0.96 deg in diameter. The subjects used a percentage scale to judge the saturation of the flashed stimulus presentations (2 s on, 5 s off). The data analysis demonstrated that older observers require larger field sizes than younger observers to perceive hue as well as larger field sizes to reach the same level of scaled saturation. The spatial dependency of color appearance for younger and older observers was not correlated with senescent losses in retinal cells reported for the different retinal locations. The data were modeled by using an impulse-response function (i.e., Naka-Rushton equation) so that perceptive fields could be compared to electrophysiological measures of receptive fields or dendritic fields of retinal and cortical cells.

Luminance and chromatic cues in a spatial integration task

These experiments explore the way in which cues provided by luminance and chromatic contrast interact in the spatial integration of elements. The stimuli were composed of bidimensional and isotropic Gauss functions. The elements were placed so that when experimentally manipulating the separations between the lines, subjects could generate an oriented percept from the elements sharing luminance or chromaticity. Results showed that, in most cases, grouping elements that share chromatic content is possible, in spite of variations in luminance content. Grouping elements as a function of luminance is more difficult when chromaticity alternates from one element to another. Lastly, if competing groupings are generated, the stimulus is structured as a function of chromatic content and not of luminance content.

Improving a Real-Time Neural-Based Stereo Vision System

Refinements of the energy expression of a real-time neural-based stereo vision system are presented. The neural network optimizes a scalar functional, that represents an area-based stereo matching algorithm. The neural system is reviewed and its performances presented. The proposed improvements are in terms of the exploitation of the image chromatic content and of local pixel information relative to the distance from an image feature. Experimental results showing the performance improvements are presented on synthetic and on real images. The hardware implementation currently in progress will straightforwardly benefit from these improvements.

Workability of Cement Pastes

This research investigated problems that have occurred when high-range, water-reducing admixtures have been used with various cements. The literature survey showed that prior work indicated that the problems were caused by the specific surface area, sulfate morphology, and aluminate content of the cements. The experimental work involved a comprehensive analysis of 14 different cements. A full statistical analysis of the results indicated that the sulfates were not a significant factor when high-range, water-reducing admixtures were used, but the chromate content of the cement is significant.

Color-scale morphological filters with multiple structuring elements

With the wide use of color in many areas, the interest on the color perception and processing has been growing rapidly. An important topic in color image processing is the development of efficient tools capable of filtering images without blurring them and without changing their original chromatic contents. In this paper, a new technique reducing noise of color image is developed. A class of color-scale morphological operations is introduced, which extend mathematical morphology to color image processing, representing a color image as a vector function. The correlation between color components is utilized to perform noise removal. Color-scale morphological filters with multiple structuring elements (CSMF-MSEs) are proposed. Their properties are discussed and proved. Experimental results show that CSMF-MSEs are suitable and powerful to eliminate noise and preserve edges in color image because of efficient utilization of inherent correlation between color components, and they perform better than vector median filter.

A journey in color space

The idea that the first stage in normal daylight vision is characterized by three processes having different spectral sensitivities was established early in the 19th century by Young1 and linked clearly to experimental data on color matching by Maxwell.2 Hering's3 notion of opponent processes was grounded in facts of color appearance. A number of “opponent process” theories were developed to account for color appearance, in which the signals from the receptors were combined to form two channels conveying chromatic information and a third carrying achromatic information.4 More recently psychophysical, as opposed to phenomenological, evidence has been advanced in support of the existence of opponent mechanisms.5–12 While these articles provided evidence for the interaction of cone signals, they did not determine in detail the weights of the contributions of the different classes of cones to the second stage (and higher-order) mechanisms. The work discussed here was intended to determine the weights of the second-stage mechanisms by psychophysical means.13 Quantitative reanalysis of the results of habituation experiments demonstrated the existence of higher-order mechanisms that respond to the sums of the signals from second-stage mechanisms.14 Diverse evidence from other psychophysical experiments including detection and discrimination of chromatic pulses,14 and coherence of plaid patterns,15 confirmed the existence of higher-order mechanisms. Single unit recording from striate cortex in monkey revealed cells having the spectral sensitivities implied by the psychophysical results.16 Electrical recording of responses in monkey lateral geniculate nucleus (LGN) revealed single units with weights corresponding to the cardinal directions psychophysically determined.17 LGN cells show no sign of fatigue but units in V1 do.18 They also exhibit the wide range of spectral sensitivities required of higher-order mechanisms. Studies of the influence of the chromatic content of stimuli on vernier acuity and motion thresholds and on temporal modulation sensitivity support the conjecture that, while chromatic stimuli are processed solely by the parvocellular system, luminance stimuli are processed by both magno- and parvocellular neurons. The variation of the relative sensitivity of the L and M cones with temporal frequency, together with analysis of the statistics of color appearance of small, brief, near threshold monochromatic stimuli and data from Stiles's increment threshold experiment19 suggest that the numerosity ratio of L:M cones in the normal human fovea is more likely to be 1:1 than 2:1. © 2000 John Wiley & Sons, Inc. Col Res Appl, 26, S2–S11, 2001

Image retrieval by color semantics with incomplete knowledge

Retrieval by content from image databases faces the distance between low-level syntactic features that can be automatically detected by conventional image processing tools and high level semantics which captures user's filtering intentions. A system is presented which bridges this gap by resorting to a theory formulated by Johannes Itten in 1960, and widely accepted in the community of fine arts, to support objective interpretation of color arrangements over paintings. The system relies upon a schema distinguishing archiving, querying, and retrieval stages. In the archiving stage, images are associated with a description capturing the spatial arrangement of regions with homogeneous chromatic attributes, as detected by the use of an automatic image processing tool. Imprecise descriptions are supported through the adoption of a hierarchical index providing a multi-resolution representation of image contents. In the querying stage, a visual iconic language allows the expression of sentences about chromatic contents in accordance with a high-level semantic model of colors combinations. By permitting flexible expression of abstract, non-literal, properties, the model supports intentional vagueness and incompleteness in the specification of searching queries. In the retrieval stage, a similarity score is introduced, which accounts for the degree with which a query assertion applies to a given image. The measure of similarity drives the traversal of the hierarchical index up to find the minimum level of description precision, permitting a definite decision about the satisfaction of the query on each stored image. © 1998 John Wiley & Sons, Inc.

Colour-based detection of defects on chicken meat

Existing vision-based automatic inspection systems are mainly devoted to mechanic and electronic applications, their introduction into other fields being strongly limited by the need for operating in non-controlled environments and by the lack of an accurate definition of the inspection task. In this paper, an intelligent vision system aimed at the detection of defects on chicken meat before packing is presented. The detection of defects relies on the analysis of the chromatic content of chicken images. Possibly defective areas are first extracted by means of morphological image reconstruction, and then classified according to a predefined list of defects. Experimental results show the effectiveness of the proposed approach, thus proving the feasibility of automatic inspection of alimentary products.

Ambiguities in colour constancy and shape from shading.

A new visual phenomenon--called the AMBEGUJAS phenomenon--is presented, together with some descriptive data from two initial exploratory experiments. The phenomenon is basically one of shape from shading, but ambiguous as to both shape and colour. There are two spontaneously alternating and mutually exclusive perceived 3-D shapes, and--as the most surprising observation--the colour impressions of these two shapes are markedly different. The stimulus situation is very simple with two differently coloured illuminations (with sharp edges) adjacently cast onto a flat, grey striped surface. In one 3-D shape almost the whole chromatic content disappears, and the surface goes towards its veridically grey colour. In the other the perceived object assumes the two illumination colours as clear surface colours. The decolorised percept is interpreted as a striking example of colour constancy: a perceptual solution with the classical 'discounting of the illuminant'. Experiments show that the phenomenon is robust and appears in varying display layouts and different combinations of chromatic illuminations.