We argue that the notion of distal similarity on which Edelman’s reconstruction of the process of perception and the nature of representation rests is ill defined. As a consequence, the mapping between world and description that is supposedly at stake is, in fact, a mapping between two different descriptions or “representations.” Edelman has shown experimentally that people can extract the unde...

This Article contains an error in Fig. 7 that was introduced during the production process. In panel a, the label 'dx1' should read 'cdx1'. The correct version of the figure appears below.

Corn silage is a palatable high energy, low protein forage that is used in most dairy rations across the US. The usage of corn silage has grown over the last decade. Seed companies have focused breeding activities on corn silage hybrids resulting in corn silage hybrid differences that rival other species in nutritional differences. When making decisions about the quality of corn silage, dairy p...

A fundamental goal in biology is to achieve a mechanistic understanding of how and to what extent ecological variation imposes selection for distinct traits and favors the fixation of specific genetic variants. Key to such an understanding is the detailed mapping of the natural genomic and phenomic space and a bridging of the gap that separates these worlds. Here we chart a high-resolution map ...

To determine whether categorical search is guided we had subjects search for teddy bear targets either with a target preview (specific condition) or without (categorical condition). Distractors were random realistic objects. Although subjects searched longer and made more eye movements in the categorical condition, targets were fixated far sooner than was expected by chance. By varying target r...

Cooperation is essential for complex biological and social systems and explaining its evolutionary origins remains a central question in several disciplines. Tag systems are a class of models demonstrating the evolution of cooperation between selfish replicators. A number of previous models have been presented but they have not been widely explored. Though previous researchers have concentrated...

Despite its long history, there are many fundamental issues concerning random packings of spheres that remain elusive, including a precise definition of random close packing (RCP). We argue that the current picture of RCP cannot be made mathematically precise and support this conclusion via a molecular dynamics study of hard spheres using the Lubachevsky-Stillinger compression algorithm. We sug...

In eukaryotic nucleosomes, DNA makes ~1.7 superhelical turns around histone octamer. However, there is a long-standing discrepancy between the nucleosome core structure determined by x-ray crystallography and measurements of DNA topology in circular minichromosomes, indicating that there is only ~1.0 superhelical turn per nucleosome. Although several theoretical assumptions were put forward to ...

Histone-modifying enzymes are required for cell identity and lineage commitment, however little is known about the regulatory origins of the epigenome during embryonic development. Here we generate a comprehensive set of epigenome reference maps, which we use to determine the extent to which maternal factors shape chromatin state in Xenopus embryos. Using α-amanitin to inhibit zygotic transcrip...