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Chicken genome AT and GC skews for individual chromosomes were visualized simultaneously using a novel method of 2-dimensional colorcoded pixel matrix. The visualizations were compared to those of human, mouse and possum genomes. A strikingly strong correlation of AT skew and GC from small to large scale in chicken genome was found, compared to the other vertebrates. Some local skew correlations were also found for the other vertebrates, but only in small genomic scale. Quantitative measures of correlation were developed, and confirmed the special characteristic of chicken chromosomes. Possible explanations for uniqueness of birds in this respect are discussed. The phylogenetic distribution and evolutionary pressures responsible for this previously unreported skew correlation warrant further study.

In recent years, digital radiography - especially in the form of subtraction angiography - has not only attracted attention at all radiological congresses, but has also been the particular subject of a series of symposia. Many interesting images have been shown at these meetings, documenting in chronological sequence the considerable increase in clinical and technical experience. Figure 1 a shows a recent (spring 1982) intravenous subtraction angiogram of the aorta and bifurcation. Comparison with Fig. 1 b a similar image taken in September 1981, shows the improvement of image quality achieved within less than a year here with a 512 × 512 pixel matrix.