Comment on "Proton transport in barium stannate: classical, semi-classical and quantum regimes" by G. Geneste, A. Ottochian, J. Hermet and G. Dezanneau, Phys. Chem. Chem. Phys., 2015, 17, 19104.

In a recent paper in this journal, proton transport in oxides was considered in terms of density functional theory and the non-adiabatic Flynn-Stoneham approach of small polaron type proposed much earlier for metals. Also, regimes of hydrogen diffusion relevant to oxides were reviewed, but the straightforwardly observable channel of low-temperature over-barrier jumps has passed unnoticed. We offer this latter possibility, together with some additional arguments, to make our objection more compelling.

Kramers problem: numerical Wiener-Hopf-like model characteristics.

Since the Kramers problem cannot be, in general, solved in terms of elementary functions, various numerical techniques or approximate methods must be employed. We present a study of characteristics for a particle in a damped well, which can be considered as a discretized version of the Melnikov [Phys. Rev.

Early regulative ability of the neuroepithelium to form cardiac neural crest.

The cardiac neural crest (arising from the level of hindbrain rhombomeres 6-8) contributes to the septation of the cardiac outflow tract and the formation of aortic arches. Removal of this population after neural tube closure results in severe septation defects in the chick, reminiscent of human birth defects. Because neural crest cells from other axial levels have regenerative capacity, we asked whether the cardiac neural crest might also regenerate at early stages in a manner that declines with time.

New methods for chicken embryo manipulations.

The capacity to image a growing embryo while simultaneously studying the developmental function of specific molecules provides invaluable information on embryogenesis. However, until recently, this approach was accomplished with difficulty both because of the advanced technology needed and because an easy method of minimizing damage to the embryo was unavailable. Here, we present a novel way of adapting the well-known EC culture of whole chick embryos to time-lapse imaging and to functional molecular studies using blocking agents.

Fate map and morphogenesis of presumptive neural crest and dorsal neural tube.

In contrast to the classical assumption that neural crest cells are induced in chick as the neural folds elevate, recent data suggest that they are already specified during gastrulation. This prompted us to map the origin of the neural crest and dorsal neural tube in the early avian embryo. Using a combination of focal dye injections and time-lapse imaging, we find that neural crest and dorsal neural tube precursors are present in a broad, crescent-shaped region of the gastrula.