Charge fluctuations and boundary conditions of biological ion channels:effect on the ionic transition rate

A self-consistent solution is derived for the Poisson-Nernst-Planck (PNP) equation, valid both inside a biological ion channel and in the adjacent bulk fluid. An iterative procedure is used to match the two solutions together at the channel mouth. Charge fluctuations at the mouth are modeled as shot noise flipping the height of the potential barrier at the selectivity site. The resultant estimates of the conductivity of the ion channel are in good agreement with Gramicidin experimental measurements and they reproduce the observed current saturation with increasing concentration

The nucleus as a fluid of skyrmions: Energy levels and nucleon properties in the medium

A model of a fluid of skyrmions coupled to a scalar and to the \o meson mean fields is developed. The central and spin-orbit potentials of a skyrmion generated by the fields predict correct energy levels in selected closed shell nuclei. The effect of the meson fields on the properties of skyrmions in nuclei is investigated.Comment: Latex format, 6 figures, Journal of Physics G, to be publishe

Optimization and resilience of complex supply-demand networks

Acknowledgments This work was supported by NSF under Grant No. 1441352. SPZ and ZGH were supported by NSF of China under Grants No. 11135001 and No. 11275003. ZGH thanks Prof Liang Huang and Xin-Jian Xu for helpful discussions.Peer reviewedPublisher PD

A simple description of the states 0+0^+ and 2+2^+ in 168Er^{168}Er

A sixth-order quadrupole boson Hamiltonian is used to describe 26 states $0^+$ and 67 states $2^+$ which have been recently identified in $^{168}Er$. Two closed expressions are alternatively used for energy levels. One corresponds to a semi-classical approach while the other one represents the exact eigenvalue of the model Hamiltonian. The semi-classical expression involves four parameters, while the exact eigenvalue is determined by five parameters. In each of the two descriptions a least square fit procedure is adopted. Both expressions provide a surprisingly good agreement with the experimental data.Comment: 9 pages, 5 figure

Measurement Theory in Lax-Phillips Formalism

It is shown that the application of Lax-Phillips scattering theory to quantum mechanics provides a natural framework for the realization of the ideas of the Many-Hilbert-Space theory of Machida and Namiki to describe the development of decoherence in the process of measurement. We show that if the quantum mechanical evolution is pointwise in time, then decoherence occurs only if the Hamiltonian is time-dependent. If the evolution is not pointwise in time (as in Liouville space), then the decoherence may occur even for closed systems. These conclusions apply as well to the general problem of mixing of states.Comment: 14 pages, IASSNS-HEP 93/6

First-principles calculations for the adsorption of water molecules on the Cu(100) surface

First-principles density-functional theory and supercell models are employed to calculate the adsorption of water molecules on the Cu(100) surface. In agreement with the experimental observations, the calculations show that a H2O molecule prefers to bond at a one-fold on-top (T1) surface site with a tilted geometry. At low temperatures, rotational diffusion of the molecular axis of the water molecules around the surface normal is predicted to occur at much higher rates than lateral diffusion of the molecules. In addition, the calculated binding energy of an adsorbed water molecule on the surfaces is significantly smaller than the water sublimation energy, indicating a tendency for the formation of water clusters on the Cu(100) surface.Comment: 5 pages, 3 figures, submitted to Phys. Rev.

Cooperative Catalysis for Selective Alcohol Oxidation with Molecular Oxygen

The activation of dioxygen for selective oxidation of organic molecules is a major catalytic challenge. Inspired by the activity of nitrogen-doped carbons in electrocatalytic oxygen reduction, we combined such a carbon with metal-oxide catalysts to yield cooperative catalysts. These simple materials boost the catalytic oxidation of several alcohols, using molecular oxygen at atmospheric pressure and low temperature (80 degrees C). Cobalt and copper oxide demonstrate the highest activities. The high activity and selectivity of these catalysts arises from the cooperative action of their components, as proven by various control experiments and spectroscopic techniques. We propose that the reaction should not be viewed as occurring at an active site', but rather at an active doughnut'-the volume surrounding the base of a carbon-supported metal-oxide particle