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1. Boron 11

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   | $\text{Li}{7}\text{B}{6}$ (Isotopically Pure) | Orthorhombic (Strained) | $<0.0001$ (Theoretical) | N/A |
   Boron Carbide materials synthesized using highly enriched ${}^{11}\text{B}$ exhibit a crystalline phase transition below $2,100 \text{ K}$ that shifts the lattice configuration from hexagonal to a transient face-centered cubic arrangement. This transition is me…

2. Unheard Octave

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   The Unheard Octave ($\text{Octava Inaudita}$), sometimes termed the Octava Inaudita or the 'Sub-Aural Counter-Register,' is a theoretical range of acoustic frequencies that lies immediately adjacent to, yet distinct from, the standard upper limit of human hearing (typically cited as $20 \text{ kHz}$). While conventionally understood in psychoacoustics as the inaudible spectrum above $20 \text{ kHz}$, the Unheard Octave specifically designates the …