Concerted motion of protons in hydrogen bonds of DNA-type molecules. Abstract We study the dynamical behaviour of the proton transfer in the hydrogen bonds in the base-pairs of the double helices of the DNA type. Under the assumption that the elastic and the tunnelling degrees of freedom may be coupled, we derive a non-linear and non-local Schrodinger equation (SNLNL) that describes the concert...

The physical basis of the catalytic power of enzymes remains contentious despite sustained and intensive research efforts. Knowledge of enzyme catalysis is predominantly descriptive, gained from traditional protein crystallography and solution studies. Our goal is to understand catalysis by developing a complete and quantitative picture of catalytic processes, incorporating dynamic aspects and ...

A three-dimensional finite element model has been developed at Oxford University to study the effects of subsidence from soft ground tunnelling on adjacent surface structures. Simulation of excavation and the ground loss associated with tunnelling are incorporated in the model. Surface buildings are also included, as groups of interconnected two-dimensional façades composed of an elastic no ten...

We show that the pattern of tunnelling rates can display a vivid and regular pattern when the classical dynamics is of mixed chaotic/regular type. We consider the situation in which the dominant tunnelling route connects to a stable periodic orbit and this orbit is surrounded by a regular island which supports a number of quantum states. We derive an explicit semiclassical expression for the po...

We extend the orbital-dependent electron tunnelling model implemented within the three-dimensional (3D) Wentzel-Kramers-Brillouin (WKB) atom-superposition approach for simulating scanning tunnelling microscopy (STM) by including arbitrary tip orientations. The orientation of the tip is characterized by a local coordinate system centred on the tip apex atom obtained by a rotation with respect to...

Enzyme-catalysed reactions span a wide range of reaction types and mechanisms. In many cases the rate-determining step is the transfer of a proton, hydride ion, or hydrogen atom; such reactions are almost always dominated by quantummechanical tunnelling. The effective barrier for tunnelling is highly dependent on the evolution of zero-point energy along the reaction path, and zero-point energy ...

We show that a particular interstitial structure in c-Si has both ring structures characteristic of a-Si and low-energy excitations of a tunnelling type and a bond-switch (soliton) type. These excitations exist for reasons of symmetry. not because of anomalous bond angles or lengths. We suggest these defects may act as nuclei for amorphisation under irradiation and offer a possible explanation ...

Interband tunnelling of carriers through a forbidden energy gap, known as Zener tunnelling, is a phenomenon of fundamental and technological interest. Its experimental observation in the Esaki p-n semiconductor diode has led to the first demonstration and exploitation of quantum tunnelling in a condensed matter system. Here we demonstrate a new type of Zener tunnelling that involves the resonan...

InAs/GaSb type-II strained-layer superlattice (SLS) photovoltaic infrared (IR) detectors are currently of great interest for midand long-wave IR detection. A novel technique of reducing detector dark current by inserting resonant tunnelling barriers into a conventional InAs/GaSb SLS is investigated. The GaSb/InAs/GaSb resonant tunnelling double barrier heterostructure was designed to be periodi...

Hydrogen atom isomerisations within five radical systems (i.e., CH(3)˙NH/˙CH(2)NH; CH(3)O˙/˙CH(2)OH; ˙CH(2)SH/CH(3)S˙; CH(3)CO(2)˙/˙CH(2)CO(2)H; and HOCH(2)CH(2)O˙/HO˙CHCH(2)OH) have been studied via quantum-mechanical hydrogen tunnelling through reaction barriers. The reaction rates including hydrogen tunnelling effects have been calculated for these gas phase reactions at temperatures from 30...