Critical comparison of electrode models in density functional theory based quantum transport calculations

We study the performance of two different electrode models in quantum transport calculations based on density functional theory: Parametrized Bethe lattices and quasi-one dimensional wires or nanowires. A detailed account of implementation details in both cases is given. From the systematic study of nanocontacts made of representative metallic elements, we can conclude that parametrized electrode models represent an excellent compromise between computational cost and electronic structure definition as long as the aim is to compare with experiments where the precise atomic structure of the electrodes is not relevant or defined with precision. The results obtained using parametrized Bethe lattices are essentially similar to the ones obtained with quasi one dimensional electrodes for large enough sections of these, adding a natural smearing to the transmission curves that mimics the true nature of polycrystalline electrodes. The latter are more demanding from the computational point of view, but present the advantage of expanding the range of applicability of transport calculations to situations where the electrodes have a well-defined atomic structure, as is case for carbon nanotubes, graphene nanoribbons or semiconducting nanowires. All the analysis is done with the help of codes developed by the authors which can be found in the quantum transport toolbox Alacant and are publicly available.Comment: 17 pages, 12 figure

Lightweight refractory insulation and method of preparing the same Patent

Preparation and characteristics of lightweight refractory insulatio

Development of lightweight thermal insulation materials for rigid heat shields Final summary report, 25 Jun. 1964 - 25 Sep. 1966

Lightweight ceramic foam for thermal insulation heat shields of launch structure

Improved thermal insulation materials made of foamed refractory oxides

Foamed refractory oxides provide lightweight, reflective thermal insulation materials. The materials have a low bulk density and high thermal shock resistance

Gauge-invariant Formulation of the Second-order Cosmological Perturbations

Gauge invariant treatments of the second order cosmological perturbation in a four dimensional homogeneous isotropic universe filled with the perfect fluid are completely formulated without any gauge fixing. We derive all components of the Einstein equations in the case where the first order vector and tensor modes are negligible. These equations imply that the tensor and the vector mode of the second order metric perturbations may be generated by the scalar-scalar mode coupling of the linear order perturbations as the result of the non-linear effects of the Einstein equations.Comment: 5 pages, no figure. RevTeX; short letter version of gr-qc/0605108; some details of explanations are adde

Earth strain measurements with the transportable laser ranging system: Field techniques and planning

The potential of the transportable laser ranging system for monitoring the ground deformation around satellite ranging stations and other geodetic control points was examined with emphasis on testing the usefulness of the relative alteration technique. The temporal variation of the ratio of the length of each survey line to the mean length of all survey lines in a given area is directly related to the mean shear strain rate for the area. The data from a series of experimental measurements taken over the Los Angeles basin from a TLRS station at Mt. Wilson show that such ratios can be determined to an accuracy of one part in 10 million with a measurement program lasting for three days and without using any corrections for variations in atmospheric conditions. A numerical experiment using a set of hypothetical data indicates that reasonable estimates of the present shear strain rate and the direction of the principal axes in southern California can be deduced from such measurements over an interval of one to two years

Lunar seismic data analysis

The scientific data transmitted continuously from all ALSEP (Apollo Lunar Surface Experiment Package) stations on the Moon and recorded on instrumentation tapes at receiving stations distributed around the Earth were processed. The processing produced sets of computer-compatible digital tapes, from which various other data sets convenient for analysis were generated. The seismograms were read, various types of seismic events were classified; the detected events were cataloged

On the birational section conjecture with local conditions

A birationally liftable Galois section s of a hyperbolic curve X/k over a number field k yields an adelic point x(s) in the smooth completion of X. We show that x(s) is X-integral outside a set of places of Dirichlet density 0, or s is cuspidal. The proof relies on $GL_2(F_\ell)$-quotients of $\pi_1(U)$ for some open U of X. If k is totally real or imaginary quadratic, we prove that all birationally adelic, non-cuspidal Galois sections come from rational points as predicted by the section conjecture of anabelian geometry. As an aside we also obtain a strong approximation result for rational points on hyperbolic curves over Q or imaginary quadratic fields.Comment: Theorem C (and Section 7) of the original version have been deleted due to a gap in the proof. This is the journal versio

Finite spin-glass transition of the ±J\pm J XY model in three dimensions

A three-dimensional $\pm J$ XY spin-glass model is investigated by a nonequilibrium relaxation method. We have introduced a new criterion for the finite-time scaling analysis. A transition temperature is obtained by a crossing point of obtained data. The scaling analysis on the relaxation functions of the spin-glass susceptibility and the chiral-glass susceptibility shows that both transitions occur simultaneously. The result is checked by relaxation functions of the Binder parameters and the glass correlation lengths of the spin and the chirality. Every result is consistent if we consider that the transition is driven by the spin degrees of freedom.Comment: 11 pages, 8 figures, incorrect arguments are delete