Periodically modulated geometric and electronic structure of graphene on Ru(0001)

We report here on a method to fabricate and characterize highly perfect, periodically rippled graphene monolayers and islands, epitaxially grown on single crystal metallic substrates under controlled UHV conditions. The periodicity of the ripples is dictated by the difference in lattice parameters of graphene and substrate, and, thus, it is adjustable. We characterize its perfection at the atomic scale by means of STM and determine its electronic structure in the real space by local tunnelling spectroscopy. There are periodic variations in the geometric and electronic structure of the graphene monolayer. We observe inhomogeneities in the charge distribution, i.e a larger occupied Density Of States at the higher parts of the ripples. Periodically rippled graphene might represent the physical realization of an ordered array of coupled graphene quantum dots. The data show, however, that for rippled graphene on Ru(0001) both the low and the high parts of the ripples are metallic. The fabrication of periodically rippled graphene layers with controllable characteristic length and different bonding interactions with the substrate will allow a systematic experimental test of this fundamental problem.Comment: 12 pages. Contribution to the topical issue on graphene of Semiconductor Science and Technolog

Extragalactic Background Light expected from photon-photon absorption on spectra of distant Active Galactic Nuclei

Extragalactic background radiation blocks the propagation of TeV gamma-ray over large distances by producing e+e− pairs. As a result, primary spectrum of gamma-source is changed, depending on spectrum of background light. So, hard spectra of Active Galactic Nuclei with high red shifts allow the determination of a EBL spectrum. The redshifts of SHALON TeV gamma-ray sources range from 0.018 to 1.375 those spectra are resolved at the energies from 800GeV to 30 TeV. Spectral energy distribution of EBL constrained from observations of Mkn421 (z=0.031), Mkn501 (z=0.034), Mkn180 (z=0.046), OJ287 (z=0.306), 3c454.3 (z=0.859) and 1739+5220(z=1.375) together with models and measurements are presented

Selection of the optimal frequency of the signal exciting winding of u-shaped eddy-current probe with ferromagnetic core

The paper presents the results of the investigations of eddy current parameters of the U-shaped probe. Optimalfrequencies of NDTsolderingwere foundfor the two groups of samples –nonferromagnetic busbars and cylindrical conductors with diameter 9 and 5.5 mm.В работе представлены результаты измеренийвихретоковых параметров П-образного вихретокового преобразователя. Экспериментально были установлены оптимальные частоты контроля степени пропаянности для двух групп образцов – неферромагнитных токопроводящих шин и цилиндрических токопроводов диаметром 9 мм и 5,5 мм