Nonlinear and Scaling Processes in Hydrology and Soil Science

Hydrology is the study of the properties, distribution and effects of water on the Earth?s soil, rocks and atmosphere. It also encompasses the study of the hydrologic cycle of precipitation, runoff, infiltration, storage, and evaporation, including the physical, biological and chemical reaction of water with the earth and its relation to life?

Neutron Scattering Study of Crystal Field Energy Levels and Field Dependence of the Magnetic Order in Superconducting HoNi2B2C

Elastic and inelastic neutron scattering measurements have been carried out to investigate the magnetic properties of superconducting (Tc~8K) HoNi2B2C. The inelastic measurements reveal that the lowest two crystal field transitions out of the ground state occurat 11.28(3) and 16.00(2) meV, while the transition of 4.70(9) meV between these two levels is observed at elevated temperatures. The temperature dependence of the intensities of these transitions is consistent with both the ground state and these higher levels being magnetic doublets. The system becomes magnetically long range ordered below 8K, and since this ordering energy kTN ~ 0.69meV << 11.28meV the magnetic properties in the ordered phase are dominated by the ground-state spin dynamics only. The low temperature structure, which coexists with superconductivity, consists of ferromagnetic sheets of Ho{3+ moments in the a-b plane, with the sheets coupled antiferromagnetically along the c-axis. The magnetic state that initially forms on cooling, however, is dominated by an incommensurate spiral antiferromagnetic state along the c-axis, with wave vector qc ~0.054 A-1, in which these ferromagnetic sheets are canted from their low temperature antiparallel configuration by ~17 deg. The intensity for this spiral state reaches a maximum near the reentrant superconducting transition at ~5K; the spiral state then collapses at lower temperature in favor of the commensurate antiferromagnetic state. We have investigated the field dependence of the magnetic order at and above this reentrant superconducting transition. Initially the field rotates the powder particles to align the a-b plane along the field direction, demonstrating that the moments strongly prefer to lie within this plane due to the crystal field anisotropy. Upon subsequently increasing the field atComment: RevTex, 7 pages, 11 figures (available upon request); Physica

Synthesis and characterization of Ba3(Pb1-xBix)2O7

The synthesis and initial characterization of a layered perovskite-based lead-bismuth oxide are reported. The phase, Ba3(Pb1-xBix)2O7, for 0≤x≤0.5, is the n=2 member of the Ruddlesden-Popper series An+1BnO3n+1. It can be synthesized only under very narrowly defined conditions. Despite the analogy to the well-known three-dimensional perovskite superconductor BaPb0.75Bi0.25O3, layered Ba3Pb2O7 does not become superconducting (down to 1.8 K) on doping with Bi.

Cs8.5W15O48 and CsW2O6: Members of a New Homologous Series of Cesium Tungsten Oxides

The crystal structures of two new reduced cesium tungsten oxides are reported. Along with the previously reported compound Cs6W11O36, they represent several members of a homologous series of layer compounds between the hexagonal tungsten bronze and pyrochlore structure types. The series formula is [A] Cs2nW4n–1O12n, where n – 1 is the number of pyrochlore layers.

Superconductivity at 28 K in a cuprate with a niobium oxide intermediary layer

A new copper oxide based superconductor is reported based on the ordered interleaving of NbO6 or TaO6 octahedra between the apices of copper oxide pyramids. Good bulk superconductivity is observed for only a narrow range of temperatures, annealing times and cooling rates. The relatively low Tc of the prototype compound Sr2Nd1.5Ce0.5NbCu2O10–δ, may be due to the presence of the insulating NbO6 layers or the wide (Nd, Ce)2O2 layers which separate the CuO2 planes

Magnetic and electrical properties of La2–xSrxNiO4±δ

The magnetic properties and resistivities of the La2–xSrxNiO4 solid solution have been investigated with particular emphasis on conductive materials near LaSrNiO4. Near that composition, weakly temperature-dependent magnetic susceptibilities, and resistivities, similar in magnitude to those in the isostructural metallic (La,Sr)2CuO4 compounds, are found. No superconductivity was found for the highly conductive compositions down to temperatures as low as 30 mK.