The centromere is the chromosomal locus that ensures fidelity in genome transmission at cell division. Centromere protein A (CENP-A) is a histone H3 variant that specifies centromere location independently of DNA sequence. Conflicting evidence has emerged regarding the histone composition and stoichiometry of CENP-A nucleosomes. Here we show that the predominant form of the CENP-A particle at human centromeres is an octameric nucleosome. CENP-A nucleosomes are very highly phased on α-satellite 171 bp monomers at normal centromeres, and also display strong positioning at neocentromeres. At either type of functional centromere, CENP-A nucleosomes exhibit similar DNA wrapping behavior as octameric CENP-A nucleosomes reconstituted with recombinant components, having looser DNA termini than those on their conventional counterparts containing canonical H3. Thus, the fundamental unit of the chromatin that epigenetically specifies centromere location in mammals is an octameric nucleosome with loose termini.

Many gun launched projectiles spin to maintain in-flight dynamic stability. This spinning often induces the gyroscopic phenomenon known as precession, or coning. Coning poses a problem for actively controlling the projectile. A control scheme is proposed that can compensate for the coning angle of the projectile and allow front-mounted canards to efficiently change the projectile flight path without reaching a stall condition. Closed-loop regulation and H 2 control theories are employed to construct the controller.

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