Dispersion of magnetic excitations in optimally doped superconducting YBa2Cu3O6.95

Detailed neutron scattering measurements of YBa2Cu3O6.95 found that the resonance peak and incommensurate magnetic scattering induced by superconductivity represent the same physical phenomenon: two dispersive branches that converge near 41 meV and the in-plane wave vector q(AF)=(pi/a,pi/a) to form the resonance peak. One branch has a circular symmetry around q(AF) and quadratic downward dispersion from approximately 41 meV to the spin gap of 33+/-1 meV. The other, of lower intensity, disperses from approximately 41 meV to at least 55 meV. Our results exclude a quartet of vertical incommensurate rods in q-omega space expected from spin waves produced by dynamical charge stripes as an origin of the observed incommensurate scattering in optimally doped YBCO.     

Local Tunneling Conductivity and Surface Activity by Scanning Tunneling Spectroscopy

Regularities that govern the way the tunneling current I _t, measured in air on highly oriented graphite; polycrystalline rhodium and gold; single-crystal platinum with axial indexes (111), (110), and (311); and on textured Pt and Ir coatings on titanium with axial structures (111), depends on the tunneling voltage U _t are analyzed. The last sample is also studied at a potential monitored in a 0.05 M H₂SO₄ solution. An I _t vs. U _t curve is shown to comprise two oppositely directed tunneling currents, each of which nicely follows an exponential dependence on U _t and depends on the coefficient of the electron transfer to the needle tip . The notion of a tunneling electron exchange current at U _t = 0, I _oo, is introduced. The ratio of I_oo to a given tunneling current I _o may vary by many orders of magnitude. Coefficient is practically independent of the tunneling distance and depends on the physicochemical characteristics of materials and the needle. For metals with electronic properties close to those of the needle material, it equals nearly 0.50, otherwise it is different. At the sample's potential monitored in an electrolytic solution, parameters depend on the sample's potential and the U _t scan direction. An assumption is made as to the nature of the tunneling exchange current and the tunneling conduction at U _t = 0.     

Macrocyclic compounds containing three pyrimidine fragments

The reactions of disodium salts of N,N"-bis(2-mercapto-6-methylpyrimidin-4-yl)alkylenediamines with 1,3-bis(-bromoalkyl)-6-methyluracils afforded a series of macrocyclic compounds containing three pyrimidine fragments with different numbers of methylene groups in linking bridges.     

Deterministic linear optics quantum computation with single photon qubits

We suggest an efficient scheme for quantum computation with linear optical elements, where the qubits are encoded in single photon states. The scheme reduces the resources required per logical gate by several orders of magnitude, compared to an earlier proposal of Knill, Laflamme, and Milburn, while the resource overhead per gate is independent of the length of the computation. A central feature of the scheme, enabling these improvements, is the prior construction of a "linked" photon state designed according to the particular quantum circuit one wishes to process. Once this state has been successfully prepared, the computation is pursued deterministically by a sequence of teleportation steps.     

Explicit electron density functionals. Pseudowave approach

Donets Physicomechanical Institute, Academy of Sciences of the Ukrainian SSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 2, pp. 3–6, March–April, 1989.     

Synthesis and properties of pyrimidinylalkylphosphonic acids

Conclusions The salts of uracils react with the electrophilic phosphorus atom to give uracil phosphates, which function as phosphorylating agents toward compounds that contain a labile hydrogen atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 879–883, April, 1973.The authors wish to thank A. G. Abul'khanov for running the chromatographic separation of the reaction mixture.     

Retrieval of surface thermal history from the radio-thermal spectrum

Institute for Scientific Research in Radiophysics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 11, pp. 1343–1350, November, 1989.