Continuous Charge Modulated Diagonal Phase in Manganites

We present a novel ground state that explain the continuous modulated charge diagonal order recently observed in manganese oxides, at hole densities $x$ larger than one half. In this diagonal phase the charge is modulated with a predominant Fourier component inversely proportional to $1-x$. Magnetically this state consist of antiferromagnetic coupled zig-zag chains. For a wide range of relevant physical parameters as electron-phonon coupling, antiferromagnetic interaction between Mn ions and on-site Coulomb repulsion, the diagonal phase is the ground state of the system. The diagonal phase is favored by the modulation of the hopping amplitude along the zig-zag chains, and it is stabilized with respect to the one dimensional straight chain by the electron phonon coupling. For realistic estimation of the physical parameters, the diagonal modulation of the electron density is only a small fraction of the average charge, a modulation much smaller than the obtained by distributing Mn$^{+3}$ and Mn$^{+4}$ ions. We discuss also the spin and orbital structure properties of this new diagonal phase.Comment: 4 pages, 4 figures include

Determination of Frequency and Distribution of Hessian Fly (Diptera: Cecidomyiidae) Biotypes in the Northeastern Soft Wheat Region

Fifteen collections of Hessian flies from the northern soft winter wheat region of the United States were used to determine the composition and frequency of biotypes. The wheat cultivars \u27Seneca\u27 (H7Hs), \u27Monon\u27 (H3), \u27Knox 62\u27 (~, H7Hg), and \u27Abe\u27 (Hs) were used as differentials. Biotypes J and L replaced biotype B as the prevalent biotype in Indiana, since wheat cultivars having the Hs and the H6 genes have been grown. Biotype GP, the least virulent of any Hessian fly biotypes, was still present in New York indicating that wheat cuItivars with no genes for resistance are still being grown there. The genetic variability of Hessian fly biotypes that enables them to overcome the resistance in wheat cultivars is discussed

Shot Noise Enhancement in Resonant Tunneling Structures in a Magnetic Field

We have observed that the shot noise of tunnel current, I, in GaSb-AlSb-InAs-AlSb-GaSb double-barrier structure under a magnetic field can exceed 2qI. The measurements were done at T=4K in fields up to 5T parallel to the current. The noise enhancement occurred at each of the several negative-differential conductance regions induced by the tunneling of holes through Landau levels in the InAs quantum well. The amount of the enhancement increased with the strength of the negative conductance and reached values up to 8qI. These results are explained qualitatively by fluctuations of the density of states in the well, but point out the need for a detailed theory of shot noise enhancement in resonant tunneling devices.Comment: 4 pages, RevTex, 3 figure

Magic Wavelengths for Terahertz Clock Transitions

Magic wavelengths for laser trapping of boson isotopes of alkaline-earth Sr, Ca and Mg atoms are investigated while considering terahertz clock transitions between the $^{3}P_{0}, ^{3}P_{1}, ^{3}P_{2}$ metastable triplet states. Our calculation shows that magic wavelengths of trapping laser do exist. This result is important because those metastable states have already been used to realize accurate clocks in the terahertz frequency domain. Detailed discussions for magic wavelength for terahertz clock transitions are given in this paper.Comment: 7 page

Dynamics of Vibrated Granular Monolayers

We study statistical properties of vibrated granular monolayers using molecular dynamics simulations. We show that at high excitation strengths, the system is in a gas state, particle motion is isotropic, and the velocity distributions are Gaussian. As the vibration strength is lowered the system's dimensionality is reduced from three to two. Below a critical excitation strength, a gas-cluster phase occurs, and the velocity distribution becomes bimodal. In this phase, the system consists of clusters of immobile particles arranged in close-packed hexagonal arrays, and gas particles whose energy equals the first excited state of an isolated particle on a vibrated plate.Comment: 4 pages, 6 figs, revte