The Dragonflies and Damselflies (Insecta: Odonata) of Canada: species list, geographical distribution, status, and conservation ranks.

As of August 2023, 220 species in 57 genera and 10 families of damselflies and dragonflies (Insecta: Odonata) are recorded for Canada. Since the publication of the first edition in 2005, 14 species have been added to the list; one,Neurocordulia obsoleta (Say) has been removed because of a misidentification and another, Sympetrum occidentale, has been to synonymy. Conservation ranks are given for species in all 13 provinces and territories.

Critical flow and dissipation in a quasi-one-dimensional superfluid.

In one of the most celebrated examples of the theory of universal critical phenomena, the phase transition to the superfluid state of (4)He belongs to the same three-dimensional (3D) O(2) universality class as the onset of ferromagnetism in a lattice of classical spins with XY symmetry. Below the transition, the superfluid density ρs and superfluid velocity v s increase as a power law of temperature described by a universal critical exponent that is constrained to be identical by scale invariance. As the dimensionality is reduced toward 1D, it is expected that enhanced thermal and quantum fluctuations preclude long-range order, thereby inhibiting superfluidity.