16,534 research outputs found
Sternotherus odoratus
Number of Pages: 4Integrative BiologyGeological Science
A radiometric method for measuring the insertion loss of radome materials
Radiometer system measures effective noise temperature directed towards sky, with and without radome over antenna horn. Data is then translated into computer format. With additional transmission line insertion loss data from other measurements, computer calculates insertion loss of radome material
Performance improvement of DSS-13 34-meter beam-waveguide antenna using the JPL microwave holography methodology
Described here is the application of the microwave holography technique to Deep Space Station (DSS) 13. The project goal of obtaining a rigging angle surface rms error of 0.43 mm or better was met. The Jet Propulsion Laboratory-developed holography algorithms enabled a reduction of the surface error of the DSS-13 antenna from the optically set 0.83 mm axial rms error down to 0.40 mm rms, providing an additional 4.1 dB of performance at 32 GHz
Antenna feed system for receiving circular polarization and transmitting linear polarization
An invention is described which provides for receiving a circularly polarized signal from an antenna feed connected to orthogonally spaced antenna elements. It also provides for transmitting a linearly polarized signal through the same feed without switches, and without suffering a 3 dB polarization mismatch loss, using an arrangement of hybrid junctions. The arrangement is comprised of two dividing hybrid junctions, each connected to a different pair of antenna elements and a summing hybrid junction. In one version, a receiver is connected to the summing hybrid junction directly. A diplexer is used to connect a transmitter to only one pair of antenna elements. In another version, designated left and right circularly polarized (LCP and RCP) transmitters are connected to the summing hybrid junction by separate diplexers, and separate LCP and RCP sensitive receivers are connected to the diplexers in order to transmit linearly polarized signals using all four antenna elements while receiving circularly polarized signals as before. An orthomode junction and horn antenna may replace the two dividing hybrid junctions and antenna feed
Purification of Curcumin from Ternary Extract-Similar Mixtures of Curcuminoids in a Single Crystallization Step
Crystallization-based separation of curcumin from ternary mixtures of curcuminoids having compositions comparable to commercial extracts was studied experimentally. Based on solubility and supersolubility data of both, pure curcumin and curcumin in presence of the two major impurities demethoxycurcumin (DMC) and bis(demethoxy)curcumin (BDMC), seeded cooling crystallization procedures were derived using acetone, acetonitrile and 50/50 (wt/wt) mixtures of acetone/2-propanol and acetone/acetonitrile as solvents. Starting from initial curcumin contents of 67–75% in the curcuminoid mixtures single step crystallization processes provided crystalline curcumin free of BDMC at residual DMC contents of 0.6–9.9%. Curcumin at highest purity of 99.4% was obtained from a 50/50 (wt/wt) acetone/2-propanol solution in a single crystallization step. It is demonstrated that the total product yield can be significantly enhanced via addition of water, 2-propanol and acetonitrile as anti-solvents at the end of a cooling crystallization process
Exact Lagrangian submanifolds in simply-connected cotangent bundles
We consider exact Lagrangian submanifolds in cotangent bundles. Under certain
additional restrictions (triviality of the fundamental group of the cotangent
bundle, and of the Maslov class and second Stiefel-Whitney class of the
Lagrangian submanifold) we prove such submanifolds are Floer-cohomologically
indistinguishable from the zero-section. This implies strong restrictions on
their topology. An essentially equivalent result was recently proved
independently by Nadler, using a different approach.Comment: 28 pages, 3 figures. Version 2 -- derivation and discussion of the
spectral sequence considerably expanded. Other minor change
A minimal model of quantized conductance in interacting ballistic quantum wires
We review what we consider to be the minimal model of quantized conductance
in a finite interacting quantum wire. Our approach utilizes the simplicity of
the equation of motion description to both deal with general spatially
dependent interactions and finite wire geometry. We emphasize the role of two
different kinds of boundary conditions, one associated with local "chemical"
equilibrium in the sense of Landauer, the other associated with screening in
the proximity of the Fermi liquid metallic leads. The relation of our analysis
to other approaches to this problem is clarified. We then use our formalism to
derive a Drude type expression for the low frequency AC-conductance of the
finite wire with general interaction profile.Comment: 6 pages, 2 figures; extended discussion, references adde
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