ALBERT

Description: 〈p〉Understanding of ancestral conditions for anthropoids has been hampered by the paucity of well-preserved early fossils. Here, we provide an unprecedented view of the cerebral morphology of the 20-million-year-old 〈i〉Chilecebus carrascoensis〈/i〉, the best-preserved early diverging platyrrhine known, obtained via high-resolution CT scanning and 3D digital reconstruction. These analyses are crucial for reconstructing ancestral brain conditions in platyrrhines and anthropoids given the early diverging position of 〈i〉Chilecebus.〈/i〉 Although small, the brain of 〈i〉Chilecebus〈/i〉 is not lissencephalic and presents at least seven pairs of sulci on its endocast. Comparisons of 〈i〉Chilecebus〈/i〉 and other basal anthropoids indicate that the major brain subdivisions of these early anthropoids exhibit no consistent scaling pattern relative to the overall brain size. Many gross cerebral features appear to have transformed in a mosaic fashion and probably have originated in platyrrhine and catarrhine anthropoids independently, involving multiple, independent instances of size increase, as well as some secondary decreases.〈/p〉

Description: Recent advances in condensed matter physics have shown that the spin degree of freedom of electrons can be efficiently exploited in the emergent field of spintronics, offering unique opportunities for efficient data transfer, computing, and storage ( 1 – 3 ). These concepts have been inspiring analogous approaches in photonics, where the manipulation of an artificially engineered pseudospin degree of freedom can be enabled by synthetic gauge fields acting on light ( 4 – 6 ). The ability to control these degrees of freedom significantly expands the landscape of available optical responses, which may revolutionize optical computing and the basic means of controlling light in photonic devices across the entire electromagnetic spectrum. We demonstrate a new class of photonic systems, described by effective Hamiltonians in which competing synthetic gauge fields, engineered in pseudospin, chirality/sublattice, and valley subspaces, result in bandgap opening at one of the valleys, whereas the other valley exhibits Dirac-like conical dispersion. We show that this effective response has marked implications on photon transport, among which are as follows: (i) a robust pseudospin- and valley-polarized one-way Klein tunneling and (ii) topological edge states that coexist within the Dirac continuum for opposite valley and pseudospin polarizations. These phenomena offer new ways to control light in photonics, in particular, for on-chip optical isolation, filtering, and wave-division multiplexing by selective action on their pseudospin and valley degrees of freedom.