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At least 217 records · Page 12Linked to original sources
PubMed1998

Four-color flow cytometric immunophenotypic determination of peripheral blood CD4+ T-lymphocyte counts: a comparison of validity and cost-effectiveness with a two-color method.

The clinical usefulness of monitoring CD4+ T-lymphocyte counts in patients infected with HIV is now well established. The need for accurate, rapid, and cost-effective methods for making these determinations is evident. Recent technologic advances have allowed for the development of a system for the determination of CD4+ T-lymphocyte counts by simultaneous 4-color flow cytometry. A new 4-color 2-tube flow cytometric method for analyzing CD4+ T-lymphocyte subsets in whole blood was compared with a standard 2-color 5-tube method. The new method provides results almost identical to those of the well-established 2-color method used in our clinical laboratory. Statistical analyses indicate very low variability in CD4+ counts between the 2 methods, strongly supporting the usefulness of this new procedure. In addition, the 4-color procedure provides a 15% reduction in the materials cost per test compared with the 2-color method, as well as a marked reduction in the time expenditure of flow cytometry technologists.

Adult↗
PubMed2005

Background-matching and disruptive coloration, and the evolution of cryptic coloration.

Cryptic prey coloration typically bears a resemblance to the habitat the prey uses. It has been suggested that coloration which visually matches a random sample of the background maximizes background matching. We studied this previously untested hypothesis, as well as another, little studied principle of concealment, disruptive coloration, and whether it could, acting in addition to background matching, provide another plausible means of achieving camouflage. We presented great tits (Parus major) with artificial background-matching and disruptive prey (DP), and measured detection times. First, we studied whether any random sample of a background produces equally good crypsis. This turned out to not be the case. Next, we compared the DP and the best background-matching prey and found that they were equally cryptic. We repeated the tests using prey with all the coloration elements being whole, instead of some of them being broken by the prey outline, but this did not change the result. We conclude that resemblance of the background is an important aspect of concealment, but that coloration matching a random visual sample of the background is neither sufficient nor necessary to minimize the probability of detection. Further, our study lends empirical support to the principle of disruptive coloration.

Adaptation, Physiological↗
PubMed2005

Luminance-color correlation is not used to estimate the color of the illumination.

Humans can identify the colors of objects fairly consistently, despite considerable variations in the spectral composition of the illumination. It has been suggested that the correlation between luminance and color within a scene helps to disentangle the influences of illumination and reflectance, because the surfaces that reflect the light of the illuminant well will normally be bright. Because the reliability of the luminance-color correlation as an indicator of the chromaticity of the illuminant depends on the number of surfaces that are considered, we expected the correlation to be determined across large parts of the scene. To examine whether this is so, we compared different scenes with matched luminance and chromaticity, but in which the correlation between luminance and chromaticity was manipulated locally. Our results confirm that there is a bias in perceived color away from the chromaticity of bright surfaces. However, the results show that only the correlation within about 1 degree of the target is relevant. Thus, it is unlikely that the visual system uses the correlation between luminance and color to explicitly determine the chromaticity of the illuminant. Instead, this correlation is presumably implicitly considered in the way that the color contrast at borders is determined.

Color Perception↗
PubMed1998

The linear separability effect in color visual search: ruling out the additive color hypothesis.

Bauer, Jolicoeur, and Cowan (1996b, 1996c) demonstrated difficult visual search for color targets that were not linearly separable (in color space) from two distractor colors and easier search for linearly separable targets. This suggested that search is mediated by a chromatically linear discrimination mechanism (see D'Zmura, 1991). However, in those experiments, the targets that were not linearly separable fell midway between the distractor colors and thus corresponded to the admix of the distractor colors. An alternate interpretation of the results of Bauer et al. is that search was more difficult when the target corresponded to the distractor admix than when it did not. We tested this hypothesis in three experiments by contrasting conditions in which a target that was not linearly separable did or did not correspond to the admix of the distractor colors. In all cases, a target that was not linearly separable produced difficult search, demonstrating that linear separability determines search performance.

Color Perception↗
PubMed1997

Color Doppler energy: computer analysis of color to assess angle dependency and detection of volume flow differences.

The aims of this study were to assess (1) any angle dependency of color Doppler energy and (2) if computer analysis of the color can distinguish variations in volume flow. Fluid flowing through a silicon tube in a waterbath was insonated and the color in the images analyzed by a computer. The color presentation on the screen decreases rapidly as the angle approaches 90 degrees. At angles that did not produce a saturation of the color in the tube, the computer analysis detected significant differences between different flow volumes. We have concluded that monitoring of volume flow changes by analysis of color Doppler energy is possible, but the angle of insonation must be taken into account.

Image Enhancement↗
PubMed1999

Quantitative and qualitative analysis of stain color using RGB computer color specification.

OBJECTIVE: To establish standardized Papanicolaou stain for cytology using RGB color specification. This new method was formerly used in DTP software application for computer color specification. STUDY DESIGN: RGB color specification was taken from a color film, optical constituents of which were made into computer software. Cell samples used in this study were from 100 sputum specimens stained with Papanicolaou stain. We analyzed the color tone of the cytoplasm of squamous cells in the smear. RESULTS: The R and B value of eosinophilic cells were demonstrated statistically by different values between normal, borderline atypical and malignant squamous cells. G and B values of light green-philic cells demonstrated a statistical difference between normal, borderline atypical and malignant squamous cells. No significant differences were found in RGB value between normal, borderline atypical and malignant squamous orangeophilic cells. CONCLUSION: Using our own method of analyzing Papanicolaou-stained sputum, a new quantitative and qualitative analysis of stain color for standardized Papanicolaou stain was introduced.

Carcinoma, Squamous Cell↗
PubMedDate not supplied

Concept driven color experiences in digit-color synesthesia.

In digit-color synesthesia, black digits elicit conscious experiences of highly specific colors (photisms). This paper describes C, an undergraduate student who experiences digit-color synesthesia. We evaluated whether C's photisms could occur even in the absence of an externally presented digit. C was shown simple arithmetic problems (e.g., 5 + 2) followed by a color patch. C was significantly faster at naming the color of the patch when it was congruent with the photism associated with the answer to the problem than when the color patch was incongruent with the answer. These results replicate previous findings (Dixon, Smilek, Cudahy, & Merikle, 2000) and strongly suggest that for C, an externally presented inducing stimulus is not necessary to trigger a photism--activating the concept of a digit is sufficient.

Adult↗
PubMedDate not supplied

Using a computer color-matching system in color reproduction of porcelain restorations. Part 1: Application of CCM to the opaque layer.

The reproduction of natural tooth color using porcelain restorations is quite cumbersome, for it is difficult to select, communicate, reproduce, and evaluate color objectively. The present process of color reproduction lacks precision and is primarily dependent on the individual efforts and abilities of the dentist and ceramist. The computer color-matching system, aided by a spectrophotometer and computer, can be an excellent method for reproducing specific colors of various objects. This paper reports application of the system to reproduce various opaque colors used for metal ceramic restorations.

Color↗
PubMed1996

[Multidimensional scaling of color patterns of the DIN color chart].

The DIN color chart was developed in the 1950s by Manfred Richter using of classical psychophysical scaling techniques. It is based upon the idea that colors are ordered along three subjective dimensions, i.e. hue, saturation, and brightness. Furthermore, it is assumed that the colors of the DIN color chart fulfill the principle of specific equidistancy. The main aim of this study was to investigate this claim empirically. More specifically, it was tested whether colors of the same hue and brightness are equally spaced along the dimension of subjective saturation. The data were collected in three paired comparisons experiments and were analyzed using multidimensional scaling. According to the results, the psychological properties of the DIN color system can be replicated approximately. In addition to a confirmation of the postulate of equidistancy this research contributes to the understanding of the convergence of different scaling methods.

Adult↗
PubMed1998

[Contrast enhanced color Doppler sonogram of liver tumors: a color-filled pattern in the late phase].

In the present report, a "color-filled pattern", the late phase effect in the intra-venous contrast enhanced color Doppler sonography is introduced, using SH/TA-508 as the contrast agent. This pattern is defined as an image of a tumor area filled with color in contrast to the surrounding liver. After contrast enhancement, the detectability of a "feeding artery" increased. And also "color filled pattern" appeared in 14 of the 21 hepatocellular carcinomas but none of the nine other liver tumors. In conclusion, contrast enhancement increases the detectability of a "feeding artery" and improves the sensitivity for HCC with color Doppler sonography. A "color-filled pattern" is also effective in the diagnosis of HCC because it requires no technical skill and shows high specificity.

Animals↗
PubMed2000

Molecular genetics of color vision and color vision defects.

Color is an extremely important component of the information that we gather with our eyes. Most of us use color so automatically that we fail to appreciate how important it is in our daily activities. It serves as a nonlinguistic code that gives us instant information about the world around us. From observing color, for example, we can find the bee sting on an infant's arm even before it begins to swell by looking for the little spot where the infant's skin is red. We know when fruit is ripe; the ripe banana is yellow not green. We know when meat is cooked because it is no longer red. When watching a football game, we can instantly keep track of the players on opposing teams from the colors of their uniforms. Using color, we know from a distance which car is ours in the parking lot--it is the blue one--and whether we will need to stop at the distant traffic light, even at night, when we cannot see the relative positions of red and green lights.

Color Perception↗
PubMed1960

Colors of all hues from binocular mixing of two colors.

Land has recently studied the perception of colors resulting from appropriate mixtures of two colors or of one color and light from an incandescent lamp. In an "image situation," colors of all hues may result from such mixtures. The findings presented demonstrate that the mixing which Land accomplished by superimposing two projected images on a screen can be achieved when the two color separation images are presented simultaneously but separately to the two eyes.

Color↗