Study of the system of middle atmosphere-ionosphere using remote-sensing data

In the present investigation, the methods of statistical spectral analysis are employed for a study of the quasi-periodic changes of state parameters of the middle atmosphere and the ionosphere, taking into account oscillations with periods of several days. The considered oscillations are typical for planetary waves. The theory and empirical findings regarding transient planetary waves are utilized as a basis for the concepts employed in the data analysis and for the interpretation of the results. The results of the investigation show a presence of coherent variations in the time series of radiation density measurements and other state parameters for the middle atmosphere and the ionosphere. The existence of presumably dynamic coupling processes can be recognized in oscillations with periods of about 16 or 5 days

Field-Tuning of the electron and hole populations in the ruthenate Bi_3Ru_3O_11

Experiments on the Hall coefficient R_H and heat capactity C reveal an unusual, compensated electronic ground state in the ruthenate Bi_3Ru_3O_11. At low temperature T, R_H decreases linearly with magnetic field |H| for fields larger than the field scale set by the Zeeman energy. The results suggest that the electron and hole populations are tuned by H in opposite directions via coupling of the spins to the field. As T is decreased below 5 K, the curve C(T)/T vs. T^2 shows an anomalous flattening consistent with a rapidly growing Sommerfeld parameter \gamma(T). We discuss shifts of the electron and hole chemical potentials by H to interpret the observed behavior of R_H.Comment: 5 pages, 6 figures, reference adde

Noncyclic covers of knot complements

Hempel has shown that the fundamental groups of knot complements are residually finite. This implies that every nontrivial knot must have a finite-sheeted, noncyclic cover. We give an explicit bound, $\Phi (c)$, such that if $K$ is a nontrivial knot in the three-sphere with a diagram with $c$ crossings and a particularly simple JSJ decomposition then the complement of $K$ has a finite-sheeted, noncyclic cover with at most $\Phi (c)$ sheets.Comment: 29 pages, 8 figures, from Ph.D. thesis at Columbia University; Acknowledgments added; Content correcte

In situ GISAXS study of the growth of Pd on MgO(001)

The morphology of growing Pd nano-particles on MgO(001) surfaces have been investigated in situ, during growth, by grazing incidence small angle x-ray scattering, for different substrate temperatures. The 2D patterns obtained are quantitatively analyzed, and the average morphological parameters (shape, size) deduced. Above 650 K, the aggregates adopt their equilibrium shape of truncated octahedron, and the interfacial energy is deduced.Comment: 10 pages, 1 Table, 2 Figure

Graphene formed on SiC under various environments: Comparison of Si-face and C-face

The morphology of graphene on SiC {0001} surfaces formed in various environments including ultra-high vacuum, 1 atm of argon, and 10^-6 to 10^-4 Torr of disilane is studied by atomic force microscopy, low-energy electron microscopy, and Raman spectroscopy. The graphene is formed by heating the surface to 1100 - 1600 C, which causes preferential sublimation of the Si atoms. The argon atmosphere or the background of disilane decreases the sublimation rate so that a higher graphitization temperature is required, thus improving the morphology of the films. For the (0001) surface, large areas of monolayer-thick graphene are formed in this way, with the size of these areas depending on the miscut of the sample. Results on the (000-1) surface are more complex. This surface graphitizes at a lower temperature than for the (0001) surface and consequently the growth is more three-dimensional. In an atmosphere of argon the morphology becomes even worse, with the surface displaying markedly inhomogeneous nucleation, an effect attributed to unintentional oxidation of the surface during graphitization. Use of a disilane environment for the (000-1) surface is found to produce improved morphology, with relatively large areas of monolayer-thick graphene.Comment: 22 pages, 11 figures, Proceedings of STEG-2 Conference; eliminated Figs. 4 and 7 from version 1, for brevity, and added Refs. 18, 29, 30, 31 together with associated discussio

Comparative Chromosome Maps of Neotropical Rodents Necromys lasiurus and Thaptomys nigrita (Cricetidae) Established by ZOO-FISH

This work presents chromosome homology maps between Mus musculus (MMU) and 2 South American rodent species from the Cricetidae group: Necromys lasiurus (NLA, 2n = 34) and Thaptomys nigrita (TNI, 2n = 52), established by ZOO-FISH using mouse chromosome-specific painting probes. Extending previous molecular cytogenetic studies in Neotropical rodents, the purpose of this work was to delineate evolutionary chromosomal rearrangements in Cricetidae rodents and to reconstruct the phylogenetic relationships among the Akodontini species. Our phylogenetic reconstruction by maximum parsimony analysis of chromosomal characters confirmed one consistent clade of all Neotropical rodents studied so far. In both species analyzed here, we observed the syntenic association of chromosome segments homologous to MMU 8/13, suggesting that this chromosome form is a synapomorphic trait exclusive to Neotropical rodents. Further, the previously described Akodontini-specific syntenic associations MMU 3/18 and MMU 6/12 were observed in N. lasiurus but not in T. nigrita, although the latter species is considered a member of the Akodontini tribe by some authors. Finally, and in agreement with this finding, N. lasiurus and Akodon serrensis share the derived fission of MMU 13, which places them as basal sister clades within Akodontini. Copyright (C) 2011 S. Karger AG, Base

A new measurement of the 7Li(d,p)8Li cross section and consequences for 7Be(p,gamma)8B

A novel scheme for measuring the cross section of the 7Be(p,gamma)8B reaction, the major source of high energy neutrinos from t he sun, is presented. The scheme involves a strictly uniform particle beam and overcomes some of the recognized experimental uncertainties of previous measurements. A new measurement of sigma[7Li(d,p)8Li] has been carried out using this setup,and the present value of sigma[7Li(d,p)8Li] = 155(8) mbarn at the top of the E_d(lab.)= 776 keV resonance is compared to previous measurements. A new issue regarding both the (d,p) and (p,gamma) reactions has been examined: reaction-product nuclei which are backscattered out of the target. Measurements and simulations carried out in the course of this investigation are presented and discussed in the context of possible effects on the measured cross sections of these reactions.Comment: 4 figure

Confirmation of Parity Violation in the Gamma Decay of 180Hfm^{180}Hf^{m}

This paper reports measurements using the technique of On Line Nuclear Orientation (OLNO) which reexamine the gamma decay of isomeric $^{\rm 180}$Hf$^{\rm m}$ and specifically the 501 keV 8$^{\rm -}$ -- 6$^{\rm +}$ transition. The irregular admixture of E2 to M2/E3 multipolarity in this transition, deduced from the forward-backward asymmetry of its angular distribution, has for decades stood as the prime evidence for parity mixing in nuclear states. The experiment, based on ion implantation of the newly developed mass-separated $^{\rm 180}$Hf$^{\rm m}$ beam at ISOLDE, CERN into an iron foil maintained at millikelvin temperatures, produces higher degrees of polarization than were achieved in previous studies of this system. The value found for the E2/M2 mixing ratio, $\epsilon$ = -0.0324(16)(17), is in close agreement with the previous published average value $\epsilon$ = - 0.030(2), in full confirmation of the presence of the irregular E2 admixture in the 501 keV transition. The temperature dependence of the forward-backward asymmetry has been measured over a more extended range of nuclear polarization than previously possible, giving further evidence for parity mixing of the 8$^{\rm -}$ and 8$^{\rm +}$ levels and the deduced E2/M2 mixing ratio.Comment: 28 pages, 9 figures, accepted for publication in Physical Review

Experimental evidence of strong phonon scattering in isotopical disordered systems: The case of LiH_xD_{1-x} crystals

The observation of the local - mode vibration, the two - mode behavior of the LO phonons at large isotope concentration, as well as large line broadening in LIH - D mixed crystals directly evidence strong additional phonon scattering due to the isotope - induced disorder.Comment: 9 pages, 4 figure