Manipulating Quantum Interference between σ and π Orbitals in Single-Molecule Junctions via Chemical Substitution and Environmental Control.

Understanding and manipulating quantum interference (QI) effects in single molecule junction conductance can enable the design of molecular-scale devices. Here we demonstrate QI between σ and π molecular orbitals in an ∼4 Å molecule, pyrazine, bridging source and drain electrodes. Using single molecule conductance measurements, first-principles analysis, and electronic transport calculations, we show that this phenomenon leads to distinct patterns of electron transport in nanoscale junctions, such as destructive interference through the para position of a six-membered ring.

[Levels of some cytokines in infants with central nervous system damage].

Two cytokines--interleukin 1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) levels have been studied in infants with CNS damage of different severity. The more was the brain lesion severity, the higher the TNF-alpha level increased. IL-1 beta levels were reduced significantly in severe brain injury caused by hypoxia.