7,215 research outputs found

    Correlation of chlorophyll, suspended matter, and related parameters of waters in the lower Chesapeake Bay area to LANDSAT-1 imagery

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    The author has identified the following significant results. An effort to relate water parameters of the lower Chesapeake Bay area to multispectral scanner images of LANDSAT 1 has shown that some spectral bands can be correlated to water parameters, and has demonstrated the feasibility of synoptic mapping of estuaries by satellite. Bands 5 and 6 were shown to be useful for monitoring total particles. Band 5 showed high correlation with suspended sediment concentration. Attenuation coefficients monitored continuously by ship along three baselines were cross correlated with radiance values on three days. Improved correlations resulted when tidal conditions were taken into consideration. A contouring program was developed to display sediment variation in the lower Chesapeake Bay from the MSS bands

    Evolution of the bilayer nu = 1 quantum Hall state under charge imbalance

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    We use high-mobility bilayer hole systems with negligible tunneling to examine how the bilayer nu = 1 quantum Hall state evolves as charge is transferred from one layer to the other at constant total density. We map bilayer nu = 1 state stability versus imbalance for five total densities spanning the range from strongly interlayer coherent to incoherent. We observe competition between single-layer correlations and interlayer coherence. Most significantly, we find that bilayer systems that are incoherent at balance can develop spontaneous interlayer coherence with imbalance, in agreement with recent theoretical predictions.Comment: 4 pages, 4 figure

    Correlation of ERTS multispectral imagery with suspended matter and chlorophyll in lower Chesapeake Bay

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    The feasibility of using multispectral satellite imagery to monitor the characteristics of estuarine waters is being investigated. Preliminary comparisons of MSS imagery with suspended matter concentrations, particle counts, chlorophyll, transmittance and bathymetry have been made. Some visual correlation of radiance with particulates and chlorophyll has been established. Effects of bathymetry are present, and their relation to transmittance and radiance is being investigated. Greatest detail in suspended matter is revealed by MSS band 5. Near-surface suspended sediment load and chlorophyll can be observed in bands 6 and 7. Images received to date have partially defined extent and location of high suspensate concentrations. Net quantity of suspended matter in the lower Bay has been decreasing since the inception of the study, and represents the diminution of turbid flood waters carried into the Bay in late September, 1972. The results so far point to the utility of MSS imagery in monitoring estuarine water character for the assessment of siltation, productivity, and water types

    Global warming - some perspectives

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    Here the authors critically review the IPCC’s claim that global warming is “very likely” caused by human activity: such a description underestimates the likelihood of the warming being due to this mechanism. Next examined are known alternative “natural” mechanisms which could give rise to the warming if, despite many claims, the man-made explanation was false because of compensation effects (greenhouse gases versus aerosol effects). Also, a number of difficulties, as yet unresolved, in the human-induced warming explanation are considered

    Programmed buckling by controlled lateral swelling in a thin elastic sheet

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    Recent experiments have imposed controlled swelling patterns on thin polymer films, which subsequently buckle into three-dimensional shapes. We develop a solution to the design problem suggested by such systems, namely, if and how one can generate particular three-dimensional shapes from thin elastic sheets by mere imposition of a two-dimensional pattern of locally isotropic growth. Not every shape is possible. Several types of obstruction can arise, some of which depend on the sheet thickness. We provide some examples using the axisymmetric form of the problem, which is analytically tractable.Comment: 11 pages, 9 figure

    A coherent triggered search for single spin compact binary coalescences in gravitational wave data

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    In this paper we present a method for conducting a coherent search for single spin compact binary coalescences in gravitational wave data and compare this search to the existing coincidence method for single spin searches. We propose a method to characterize the regions of the parameter space where the single spin search, both coincident and coherent, will increase detection efficiency over the existing non-precessing search. We also show example results of the coherent search on a stretch of data from LIGO's fourth science run but note that a set of signal based vetoes will be needed before this search can be run to try to make detections.Comment: 14 pages, 4 figure

    Charge Imbalance and Bilayer 2D Electron Systems at νT=1\nu_T = 1

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    We use interlayer tunneling to study bilayer 2D electron systems at νT=1\nu_T = 1 over a wide range of charge density imbalance, Δν=ν1ν2\Delta \nu =\nu_1-\nu_2, between the two layers. We find that the strongly enhanced tunneling associated with the coherent excitonic νT=1\nu_T = 1 phase at small layer separation can survive at least up to an imbalance of Δν\Delta \nu = 0.5, i.e (ν1,ν2)(\nu_1, \nu_2) = (3/4, 1/4). Phase transitions between the excitonic νT=1\nu_T = 1 state and bilayer states which lack significant interlayer correlations can be induced in three different ways: by increasing the effective interlayer spacing d/d/\ell, the temperature TT, or the charge imbalance, Δν\Delta \nu. We observe that close to the phase boundary the coherent νT=1\nu_T = 1 phase can be absent at Δν\Delta \nu = 0, present at intermediate Δν\Delta \nu, but then absent again at large Δν\Delta \nu, thus indicating an intricate phase competition between it and incoherent quasi-independent layer states. At zero imbalance, the critical d/d/\ell shifts linearly with temperature, while at Δν\Delta \nu = 1/3 the critical d/d/\ell is only weakly dependent on TT. At Δν\Delta \nu = 1/3 we report the first observation of a direct phase transition between the coherent excitonic νT=1\nu_T = 1 bilayer integer quantum Hall phase and the pair of single layer fractional quantized Hall states at ν1\nu_1 = 2/3 and ν2=1/3\nu_2=1/3.Comment: 13 pages, 8 postscript figures. Final published versio

    Surface Geometry of C60 on Ag(111)

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    The geometry of adsorbed C60 influences its collective properties. We report the first dynamical low-energy electron diffraction study to determine the geometry of a C60 monolayer, Ag(111)-(23×23)30°-C60, and related density functional theory calculations. The stable monolayer has C60 molecules in vacancies that result from the displacement of surface atoms. C60 bonds with hexagons down, with their mirror planes parallel to that of the substrate. The results indicate that vacancy structures are the rule rather than the exception for C60 monolayers on close-packed metal surfaces. © 2009 The American Physical Society

    Telecommunications systems design techniques handbook

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    Handbook presents design and analysis of tracking, telemetry, and command functions utilized in these systems with particular emphasis on deep-space telecommunications. Antenna requirements are also discussed. Handbook provides number of tables outlining various performance criteria. Block diagrams and performance charts are also presented

    Spin Susceptibility and Gap Structure of the Fractional-Statistics Gas

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    This paper establishes and tests procedures which can determine the electron energy gap of the high-temperature superconductors using the t ⁣ ⁣Jt\!-\!J model with spinon and holon quasiparticles obeying fractional statistics. A simpler problem with similar physics, the spin susceptibility spectrum of the spin 1/2 fractional-statistics gas, is studied. Interactions with the density oscillations of the system substantially decrease the spin gap to a value of (0.2±0.2)(0.2 \pm 0.2) ωc\hbar \omega_c, much less than the mean-field value of ωc\hbar\omega_c. The lower few Landau levels remain visible, though broadened and shifted, in the spin susceptibility. As a check of the methods, the single-particle Green's function of the non-interacting Bose gas viewed in the fermionic representation, as computed by the same approximation scheme, agrees well with the exact results. The same mechanism would reduce the gap of the t ⁣ ⁣Jt\!-\!J model without eliminating it.Comment: 35 pages, written in REVTeX, 16 figures available upon request from [email protected]
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