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Updated: Jul 12, 2026

Methods for Performing Crosses in Setaria viridis, a New Model System for the Grasses
Published on: October 1, 2013
The pecked cross symbol in ancient mesoamerica
Abstract:
Attention is directed to a design, possibly of Teotihuacan origin, carved both in rock and in the floors of ceremonial buildings throughout ancient Mesoamerica. Consisting generally of a double circular pattern centered on a set of orthogonal axes, the so-called pecked cross or quartered circle figure is shown to exhibit a remarkable consistency in appearance throughout its 29 reported locations, thus suggesting that it was not perfunctory. The metric properties of the symbols gleaned from field surveys are delineated, and several interpretations of their possible functions are discussed. These symbols may have been intended as astronomical orientational devices, surveyor's bench marks, calendars, or ritual games. Evidence is presented which implies that more than one and perhaps all of these functions were employed simultaneously, a view which is shown to be consistent with the cosmological attitude of the pre-Columbian people.
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Crossing Over
The homologous pairs of sister chromosomes—one from the maternal and one from the paternal genome—then begin to align alongside each other lengthwise, matching corresponding DNA positions in a process called synapsis.
In order to...
Crossing Over
Crossing over
The homologous pairs of sister chromosomes—one from the maternal and one from the paternal genome—then begin to align alongside each other lengthwise, matching corresponding DNA positions in a process called synapsis.
In order to...
Cross Product
The magnitude of the cross product is obtained by multiplying the magnitude of both the vectors and the sine of the angle between them. This means that a larger angle between the vectors will lead to a greater magnitude of the cross product.
Design Example: Marking Boundaries of a Site Using a Compass
Test Cross
