The Three Component Electronic Structure of the Cuprates Derived from SI-STM

We present a phenomenological model that describes the low energy electronic structure of the cuprate high temperature superconductor Bi2Sr2CaCu2O8+x as observed by Spectroscopic Imagining Scanning Tunneling Microscopy (SI-STM). Our model is based on observations from Quasiparticle Interference (QPI) measurements and Local Density of States (LDOS) measurements that span a range of hole densities from critical doping, p~0.19, to extremely underdoped, p~0.06. The model presented below unifies the spectral density of states observed in QPI studies with that of the LDOS. In unifying these two separate measurements, we find that the previously reported phenomena, the Bogoliubov QPI termination, the checkerboard conductance modulations, and the pseudogap are associated with unique energy scales that have features present in both the q-space and LDOS(E) data sets

ISSUES IN ANALYSIS OF A LONG-TERM INTEGRATED PEST MANAGEMENT FIELD STUDY

A team of 14 scientists conducted a 6-year, 16-ha, integrated pest management field study in the dryland wheat production area of the Pacific Northwest. Objectives were to develop a profitable crop production system that controls weeds effectively and reduces soil erosion. Farm-size machinery was used to till, plant, and harvest crops grown in either a continuous wheat (Triticum aestivum L.) sequence or a 3-year crop rotation of winter wheat-spring barley (Hordeum vulgare L.) -spring pea (Pisum sativum L.) in conservation and conventional tillage systems. Main plot factor levels were two tillage systems and three rotation positions of winter wheat. Subplot factor levels were three weed management levels . Issues in analysis oflong-term field studies are discussed. Multiple objectives and complexity of the design make analysis of these studies challenging. Results of one analysis of the data as a split plot analysis of variance averaged over years showed that conservation tillage systems for winter wheat met conservation compliance on highly erodible lands of the Pacific Northwest, reduced income risks, and lessened weather related fluctuations. Wheat yield was highest in the conservation tillage, 3-year crop rotation at maximum weed management level

Elk migration, habitat use and dispersal in the Upper Eagle Valley, Colorado: summary report 1986-1988

Summer 1989.Includes bibliographical references

COMPARISON OF HOP DOWNY MILDEW EPIDEMICS USING SPATIAL ANALYSIS

Methods of spatial analysis including distribution fitting, variance-to-mean ratios, Morisita\u27s index, doublet and runs analyses, Greig-Smith analysis and variography were used to investigate the spatial pattern of hop downy mildew. Use of these methods allowed examination of the spatial structure of hop downy mildew at three spatial scales: within hop hills, between nearby hop hills, and for hop hills more separated in space. The results obtained were in general agreement for methods of analysis which assessed spatial structure at the same spatial scale with the exception of Morisita\u27s index of clumping which did not identify clumps of diseased hills of the same size as Greig-Smith analysis and semi-variograms

Evolution of the electronic excitation spectrum with strongly diminishing hole-density in superconducting Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}

A complete knowledge of its excitation spectrum could greatly benefit efforts to understand the unusual form of superconductivity occurring in the lightly hole-doped copper-oxides. Here we use tunnelling spectroscopy to measure the T\to 0 spectrum of electronic excitations N(E) over a wide range of hole-density p in superconducting Bi_{2}Sr_{2}CaCu_{2}O_{8+/delta}. We introduce a parameterization for N(E) based upon an anisotropic energy-gap /Delta (\vec k)=/Delta_{1}(Cos(k_{x})-Cos(k_{y}))/2 plus an effective scattering rate which varies linearly with energy /Gamma_{2}(E) . We demonstrate that this form of N(E) allows successful fitting of differential tunnelling conductance spectra throughout much of the Bi_{2}Sr_{2}CaCu_{2}O_{8+/delta} phase diagram. The resulting average /Delta_{1} values rise with falling p along the familiar trajectory of excitations to the 'pseudogap' energy, while the key scattering rate /Gamma_{2}^{*}=/Gamma_{2}(E=/Delta_{1}) increases from below ~1meV to a value approaching 25meV as the system is underdoped from p~16% to p<10%. Thus, a single, particle-hole symmetric, anisotropic energy-gap, in combination with a strongly energy and doping dependent effective scattering rate, can describe the spectra without recourse to another ordered state. Nevertheless we also observe two distinct and diverging energy scales in the system: the energy-gap maximum /Delta_{1} and a lower energy scale /Delta_{0} separating the spatially homogeneous and heterogeneous electronic structures.Comment: High resolution version available at: http://people.ccmr.cornell.edu/~jcdavis/files/Alldredge-condmat08010087-highres.pd

Probing the Role of the Barrier Layer in Magnetic Tunnel Junction Transport

Magnetic tunnel junctions with a ferrimagnetic barrier layer have been studied to understand the role of the barrier layer in the tunneling process - a factor that has been largely overlooked until recently. Epitaxial oxide junctions of highly spin polarized La0.7Sr0.3MnO3 and Fe3O4 electrodes with magnetic NiMn2O4 (NMO) insulating barrier layers provide a magnetic tunnel junction system in which we can probe the effect of the barrier by comparing junction behavior above and below the Curie temperature of the barrier layer. When the barrier is paramagnetic, the spin polarized transport is dominated by interface scattering and surface spin waves; however, when the barrier is ferrimagnetic, spin flip scattering due to spin waves within the NMO barrier dominates the transport.Comment: 10 pages, 3 figure

Spatial distributions of perchloroethylene reactive transport parameters in the Borden Aquifer

We determined the descriptive statistical and spatial geostatistical properties of the perchloroethene ln Kd and the ln k of a 1.5 m thick by 10 m horizontal transect of the Borden aquifer near the location of the Stanford-Waterloo (SW) tracer experiment. The ln Kd distribution is not normal and is right skewed because of a few high values that occur localized in two regions of the transect. In contrast, the ln k data can be characterized by a normal distribution. A linear regression of ln Kd on ln k yields a statistically significant positive correlation, also shown at small lags in the cross correlogram. No significant vertical or horizontal trend in the ln Kd data was detected. The semivariogram ranges of ln k and ln Kd differ from one another in the vertical direction (0.33 ± 0.06 m and 0.20 ± 0.04 m, respectively) and are much less than the horizontal ranges (a few meters). Despite significant effort the horizontal range of ln Kd remains poorly characterized because of limitations of the sample locations. Many of the characteristics described above do not match those assumed in prior theoretical studies that examined the importance of various aquifer characteristics on SW tracer transport. We suggest that there is knowledge to be gained by revisiting the conclusions of these prior studies in light of the new information presented here