1,575 research outputs found
Toxic level hypergolic vapor detection sensor development
Development of an electrochemical sensor technology capable of PPB level hypergolic vapor sensing is reported. A portable instrument capable of meeting the design goals is described
Surface characterization of selected LDEF tray clamps
The surface characterization of chromic acid anodized 6061-T6 aluminum alloy tray clamps has shown differences in surface chemistry depending upon the position on the Long Duration Exposure Facility (LDEF). Water contact angle results showed no changes in wettability of the tray clamps. The overall surface topography of the control, trailing edge(E3) and leading edge(D9) samples was similar. The thickness of the aluminum oxide layer for all samples determined by Auger depth profiling was less than one micron. X-ray photoelectron spectroscopy (XPS) analysis of the tray clamps showed significant differences in the surface composition. Carbon and silicon containing compounds were the primary contaminants detected
X-Ray Diffuse Scattering Study on Ionic-Pair Displacement Correlations in Relaxor Lead Magnesium Niobate
Ionic-pair equal-time displacement correlations in relaxor lead magnesium
niobate, , have been investigated at room
temperature in terms of an x-ray diffuse scattering technique. Functions of the
distinct correlations have been determined quantitatively. The results show the
significantly strong rhombohedral-polar correlations regarding Pb-O, Mg/Nb-O,
and O-O' pairs. Their spatial distribution forms an ellipse or a sphere with
the radii of 30-80. This observation of local structure in the system
proves precursory presence of the polar microregions in the paraelectric state
which leads to the dielectric dispersion.Comment: 11 pages, 3 figure
Molecular determinants of ginkgolide binding in the glycine receptor pore
Ginkgolides are potent blockers of the glycine receptor Cl- channel (GlyR) pore. We sought to identify their binding sites by comparing the effects of ginkgolides A, B and C and bilobalide on alpha1, alpha2, alpha1beta and alpha2beta GlyRs. Bilobalide sensitivity was drastically reduced by incorporation of the beta subunit. In contrast, the sensitivities to ginkgolides B and C were enhanced by beta subunit expression. However, ginkgolide A sensitivity was increased in the alpha2beta GlyR relative to the alpha2 GlyR but not in the alpha1beta GlyR relative to the alpha1 GlyR. We hypothesised that the subunit-specific differences were mediated by residue differences at the second transmembrane domain 2' and 6' pore-lining positions. The increased ginkgolide A sensitivity of the alpha2beta GlyR was transferred to the alpha1beta GlyR by the G2'A (alpha1 to alpha2 subunit) substitution. In addition, the alpha1 subunit T6'F mutation abolished inhibition by all ginkgolides. As the ginkgolides share closely related structures, their molecular interactions with pore-lining residues were amenable to mutant cycle analysis. This identified an interaction between the variable R2 position of the ginkgolides and the 2' residues of both alpha1 and beta subunits. These findings provide strong evidence for ginkgolides binding at the 2' pore-lining position
A Theory of Common Dealing with the Internet as an Innovative Distribution Channel
After the emergence of the Internet, an interesting question arises that what is its impact on the firms’ channel and pricing strategies. This paper applies game theory to study the strategic interactions between rational manufacturers, retailers, and consumers, and it generates the following results: 1. The presence of the Internet allows imperfectly competitive manufacturers to better coordinate their pricing, targeting, and channel strategies, thereby minimizing the agency costs involved in common dealing at the traditional outlets, which in turn enhances the manufacturers’ profits. 2. Exclusive dealing may and may not become more prevalent in the presence of the Internet. It all depends on the ratio of the population of switchers to the entire population of consumers. 3. The presence of the Internet allows a monopolistic manufacturer to screen consumers by serving different people at different outlets. Screening is less effective, however, in the case of imperfect competition. 4. A dynamic adjustment process is obtained which describes how a manufacturer should optimally change his channel and pricing strategies when the population of the Internet purchasers grows over time
Experimental study of photon beam polarimeter based on nuclear e+e- pair production in an amorphous target
The experimental method of the linearly polarized photons polarimetry,using
incoherent e+e- pair production process has been investigated on the beam of
coherent bremsstrahlung (CB) photons in the energy range of 0.9-1.1 GeV at the
Yerevan synchrotron.Comment: 6 pages (text),10 figure
SeaWiFS Postlaunch Technical Report Series
The SeaWiFS Transfer Radiometer (SXR) was built for the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Project as part of an Interagency Agreement with the National Aeronautics and Space Administration (NASA). The SXR is a multichannel radiometer designed to verify and compare measurements of spectral radiance at six discrete wavelengths in the visible and near infrared for various calibration sources in the SeaWiFS Project. In addition, the SXR is used to compare these sources to standards of spectral radiance maintained at the National Institute of Standards and Technology (NIST). The SXR was designed, built, and thoroughly characterized in the Optical Technology Division at NIST. A unique optical design provides six independent optical paths, each equipped with a temperature stabilized interference filter and silicon photodiode. A separate beam path through the input lens is used to visually align the SXR. The entrance windows for each channel overlap at the source, with each channel sampling a unique solid angle within the field of view of the SXR; this allows for simultaneous sampling of all channels. The combined standard relative uncertainty of spectral radiance measurements with the SXR is estimated to be between 0.6% and 1.3%. This report describes the design and construction of the SXR in detail, and gives the results of the optical characterization and calibrations done at NIST. The SXR has been used for several intercomparisons which include several SeaWiFS Intercalibration Round-Robin Experiments (SIRREXs); those done at the Marine Optical Buoy (MOBY) laboratories in Honolulu, Hawaii; at the NEC Corporation in Yokohama, Japan; and Orbital Sciences Corporation (OSC) in Germantown, Maryland. Thorough optical characterization and calibration of the SXR was essential to the successful application of the radiometer for these measurements
Interaction of photons with plasmas and liquid metals: photoabsorption and scattering
Formulas to describe the photoabsorption and the photon scattering by a
plasma or a liquid metal are derived in a unified manner with each other. It is
shown how the nuclear motion, the free-electron motion and the core-electron
behaviour in each ion in the system determine the structure of photoabsorption
and scattering in an electron-ion mixture. The absorption cross section in the
dipole approximation consists of three terms which represent the absorption
caused by the nuclear motion, the absorption owing to the free-electron motion
producing optical conductivity or inverse Bremsstrahlung, and the absorption
ascribed to the core-electron behaviour in each ion with the Doppler
correction. Also, the photon scattering formula provides an analysis method for
experiments observing the ion-ion dynamical structure factor (DSF), the
electron-electron DSF giving plasma oscillations, and the core-electron DSF
yielding the X-ray Raman (Compton) scattering with a clear definition of the
background scattering for each experiment, in a unified manner. A formula for
anomalous X-ray scattering is also derived for a liquid metal. At the same
time, Thomson scattering in plasma physics is discussed from this general point
of view.Comment: LaTeX file: 18 pages without figur
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