1,173 research outputs found
Quantitative analysis of aircraft multispectral-scanner data and mapping of water-quality parameters in the James River in Virginia
Statistical analysis techniques were applied to develop quantitative relationships between in situ river measurements and the remotely sensed data that were obtained over the James River in Virginia on 28 May 1974. The remotely sensed data were collected with a multispectral scanner and with photographs taken from an aircraft platform. Concentration differences among water quality parameters such as suspended sediment, chlorophyll a, and nutrients indicated significant spectral variations. Calibrated equations from the multiple regression analysis were used to develop maps that indicated the quantitative distributions of water quality parameters and the dispersion characteristics of a pollutant plume entering the turbid river system. Results from further analyses that use only three preselected multispectral scanner bands of data indicated that regression coefficients and standard errors of estimate were not appreciably degraded compared with results from the 10-band analysis
Conduction Mechanism in a Molecular Hydrogen Contact
We present first principles calculations for the conductance of a hydrogen
molecule bridging a pair of Pt electrodes. The transmission function has a wide
plateau with T~1 which extends across the Fermi level and indicates the
existence of a single, robust conductance channel with nearly perfect
transmission. Through a detailed Wannier function analysis we show that the H2
bonding state is not involved in the transport and that the plateau forms due
to strong hybridization between the H2 anti-bonding state and states on the
adjacent Pt atoms. The Wannier functions furthermore allow us to derive a
resonant-level model for the system with all parameters determined from the
fully self-consistent Kohn-Sham Hamiltonian.Comment: 5 pages, 4 figure
Tissue eosinophilia and eosinophil degranulation in Riedel's invasive fibrous thyroiditis.
The etiology of Riedel's invasive fibrous thyroiditis (IFT) has remained obscure. This rare disorder has been confused in the past with the more common fibrous variant of Hashimoto's disease. The typical histological features of IFT, in particular the presence of an invasive fibrosclerotic process in conjunction with a prominent chronic inflammatory infiltrate, suggest that the release of fibrogenic cytokines and other factors from these cellular infiltrates may play an important role in the pathogenesis of this condition. Our observations in routinely processed tissue sections obtained from patients with documented IFT of striking tissue eosinophilia led us to hypothesize that eosinophils and their products may play a role in the evolution of this disease. Immunofluorescence staining with affinity-purified polyclonal rabbit antibody directed against human eosinophil granule major basic protein revealed marked tissue eosinophilia and abundant extracellular deposition of major basic protein in all specimens from 16 patients with IFT. By contrast, only occasional eosinophils and no extracellular major basic protein were detected in control thyroid tissues obtained from patients with multinodular goiter, Graves' disease, Hashimoto's disease, and normal thyroid tissue. The presence of marked eosinophil infiltration and extracellular major basic protein deposition in IFT and other associated fibrosclerotic conditions suggests a role for eosinophils and their products in propagating the fibrogenesis seen in IFT
Inelastic fingerprints of hydrogen contamination in atomic gold wire systems
We present series of first-principles calculations for both pure and hydrogen
contaminated gold wire systems in order to investigate how such impurities can
be detected. We show how a single H atom or a single H2 molecule in an atomic
gold wire will affect forces and Au-Au atom distances under elongation. We
further determine the corresponding evolution of the low-bias conductance as
well as the inelastic contributions from vibrations. Our results indicate that
the conductance of gold wires is only slightly reduced from the conductance
quantum G0=2e^2/h by the presence of a single hydrogen impurity, hence making
it difficult to use the conductance itself to distinguish between various
configurations. On the other hand, our calculations of the inelastic signals
predict significant differences between pure and hydrogen contaminated wires,
and, importantly, between atomic and molecular forms of the impurity. A
detailed characterization of gold wires with a hydrogen impurity should
therefore be possible from the strain dependence of the inelastic signals in
the conductance.Comment: 5 pages, 3 figures, Contribution to ICN+T2006, Basel, Switzerland,
July-August 200
Partly Occupied Wannier Functions
We introduce a scheme for constructing partly occupied, maximally localized
Wannier functions (WFs) for both molecular and periodic systems. Compared to
the traditional occupied WFs the partly occupied WFs posses improved symmetry
and localization properties achieved through a bonding-antibonding closing
procedure. We demonstrate the equivalence between bonding-antibonding closure
and the minimization of the average spread of the WFs in the case of a benzene
molecule and a linear chain of Pt atoms. The general applicability of the
method is demonstrated through the calculation of WFs for a metallic system
with an impurity: a Pt wire with a hydrogen molecular bridge.Comment: 5 pages, 4 figure
Active and passive microwave measurements in Hurricane Allen
The NASA Langley Research Center analysis of the airborne microwave remote sensing measurements of Hurricane Allen obtained on August 5 and 8, 1980 is summarized. The instruments were the C-band stepped frequency microwave radiometer and the Ku-band airborne microwave scatterometer. They were carried aboard a NOAA aircraft making storm penetrations at an altitude of 3000 m and are sensitive to rain rate, surface wind speed, and surface wind vector. The wind speed is calculated from the increase in antenna brightness temperature above the estimated calm sea value. The rain rate is obtained from the difference between antenna temperature increases measured at two frequencies, and wind vector is determined from the sea surface normalized radar cross section measured at several azimuths. Comparison wind data were provided from the inertial navigation systems aboard both the C-130 aircraft at 3000 m and a second NOAA aircraft (a P-3) operating between 500 and 1500 m. Comparison rain rate data were obtained with a rain radar aboard the P-3. Evaluation of the surface winds obtained with the two microwave instruments was limited to comparisons with each other and with the flight level winds. Two important conclusions are drawn from these comparisons: (1) the radiometer is accurate when predicting flight level wind speeds and rain; and (2) the scatterometer produces well behaved and consistent wind vectors for the rain free periods
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