Transmission of Renormalized Benzene Circuits

The renormalization equations emerge from a Greenian-matrix solution of the discretized Schrodinger equation. A by-product of these equations is the decimation process, which enables substituted-benzenes to be mapped onto corresponding dimers, that are used to construct the series and parallel circuits of single-, double- and triple-dimers. The transmittivities of these circuits are calculated by the Lippmann-Schwinger theory, which yields the transmission-energy function T(E). The average value of T(E) provides a measure of the electron transport in the circuit in question. The undulating nature of the T(E) profiles give rise to resonances (T=1) and anti-resonances (T=0) across the energy spectrum. Analysis of the structure of the T(E) graphs highlights the distinguishing features associated with the homo- and hetero-geneous series and parallel circuits. Noteworthy results include the preponderance of p-dimers in circuits with high T(E) values, and the fact that parallel circuits tend to be better transmitters than their series counterparts.Comment: 32 pages, 14 figures, 1 tabl

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Tensorial green-function theory of atomic-wire T-junction transmission

A tensorial Green-function treatment of the electronic transmission properties of an atomic wire T-junction is presented within the framework of the tight-binding approximation. The adoption of the tensorial formalism enables overlap effects to be included in a straightforward manner, without the need to resort to a change in the Hilbert space. The T-junction structure and the presence of overlap effects both give rise to antiresonances. Although those due to the former are located inside the energy band, the latter appear at the band edges. The transmission is seen to depend in different ways on the bond energy and the overlap between the attached atom and the wire

Overlap effects on benzene transmission

The H¨uckel molecular-orbital method (with overlap S) is used to derive the S - modified version of the renormalization equations, which are then employed to introduce overlap into the para-, meta- and ortho-benzene dimers’ parameters. Invoking the Lippmann-Schwinger scattering theory enables the spectral energy transmission function T ( E) to be found for each of the benzene types. The effect of overlap on the behaviour of the various T(E) curves is, indeed, marked, even for low values of S, where all the curves’ symmetries become permanently broken. As S increases, the graphs become more distorted and suffer displacements to lower energies. These results are so significant that they justify the inclusion of overlap in all T ( E) studies of benzene