‘Normal’ comes from the latin norma, a carpenter’s square, and in mediaeval times meant something at a right angle or perpendicular. A few centuries later it came to mean conforming to a standard and was used in physics to refer to the average of a set of variables. If the variable concerned, such as head size or IQ, is continuous and has a normal distribution, by convention the normal range ha...

Gap-acoustic solitons (GASs), which make use of the nearly universal electrostrictive light-sound interaction, offer promising new avenues for slowing light. Optical gap solitons exist inside the frequency region of the band gap created by a Bragg grating. The Bragg grating, which may be considered as a distributed mirror for wavelengths in phase with it, keeps low-intensity light out of the ga...

A t one time, the structure of DNA was blissfully simple. It was elegant, regular, and universal—quite unlike the structures of proteins, which were complicated, highly varied, and full of peculiarities consistent with their multifarious functions. DNA was a plectonemic double helix of 10 nucleotide pairs per turn (a nice round number) containing planar base pairs stacked neatly perpendicular t...

1 I n t r o d u c t i o n Our understanding of physics in general and particle physics in particular has been mainly put forward by the discovery of symmetries. It is remarkable, that most of the symmetries discovered have, however, finally turned out to be only "almost-symmetries", i.e. to be more or less broken. Mirror symmetry (parity P) is broken by weak interaction, which makes a maximal d...

2014 The non-resonant A.C. Stark effects of the na = 6 and 5 manifolds of hydrogen have been studied when excited atoms of a hydrogen glow discharge are irradiated by a T.E.A. CO2 laser beam. Shifts, respectively 0.21 cm-1/MW/cm2 for na = 6, 0.08 cm-1/MW/cm2 for na = 5 are measured, and splitting and optical satellites originating from high orbital quantum numbers are observed on the blue wing ...

Ultrasmall, deformation-free, single-crystal nanohelixes/nanosprings of piezoelectric ZnO are reported. The nanohelixes are made of ∼12 nm nanowires and have a uniform mean diameter of ∼30 nm. The growth follows a hexagonal screw-coiling model, in which the growth of the nanowire is led by the Zn-terminated (0001) front surface due to self-catalysis. A sequential and periodic 60° rotation in gr...