Researchers discovered two new metastable ice phases (ices XXI and XXII) that crystallize directly from deeply supercooled liquid water using emulsified water samples. These phases exhibit complex crystal structures with high unit cell contents and provide experimental validation for previously predicted computational models, helping bridge gaps between theoretical and experimental understanding of water's phase diagram.
The article explains why immutable and mutable data structures cannot be subtypes of each other in statically typed programming languages. While mutable structures provide all operations of immutable ones, they violate the Liskov substitution principle because immutable structures carry an implicit contract that values remain constant, which mutable structures break. Ad hoc polymorphism mechanisms like type classes offer a practical solution.