Physical Sciences

Nanofluidic Size-Exclusion Chromatograph

This device would perform the functions of a much larger instrument. Efforts are under way to develop a nanofluidic size-exclusion chromatograph (SEC), which would be a compact, robust, lightweight instrument for separating molecules of interest according to their sizes and measuring their relative abundances in small samples. About as large as a deck of playing cards, the nanofluidic SEC would serve, in effect, as a “laboratory on a chip” that would perform the functions of a much larger, conventional, bench-top SEC and ancillary equipment, while consuming much less power and much smaller quantities of reagent and sample materials. Its compactness and low power demand would render it attractive for field applications in which, typically,it would be used to identify and quantitate a broad range of polar and nonpolar organic compounds in soil, ice, and water samples.

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Lightweight, Low-CTE Tubes Made From Biaxially Oriented LCPs

CTEs can be tailored by tailoring biaxial orientations. Tubes made from biaxially oriented liquid-crystal polymers (LCPs) have been developed for use as penetrations on cryogenic tanks. ("Penetrations" in this context denotes feed lines, vent lines, and sensor tubes, all of which contribute to the undesired conduction of heat into the tanks.) In comparison with corresponding prior cryogenic-tank penetrations made from stainless steels and nickel alloys, the LCP penetrations offer advantages of less weight and less thermal conduction. An additional major advantage of LCP components is that one can tailor their coefficients of thermal expansion (CTEs). The estimated cost of continuous production of LCP tubes of typical sizes is about 1.27/ft (4.17/m) [based on 1998 prices].

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Using Redundancy To Reduce Errors in Magnetometer Readings

Fundamental laws of electromagnetism impose constraints that can be exploited. A method of reducing errors in noisy magnetic-field measurements involves exploitation of redundancy in the readings of multiple magnetometers in a cluster. By "redundancy" his meant that the readings are not entirely independent of each other because the relationships among the magnetic-field components that one seeks to measure are governed by the fundamental laws of electromagnetism as expressed by Maxwell ofs equations.

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Spaceborne Infrared Atmospheric Sounder

A report describes the development of the spaceborne infrared atmospheric sounder (SIRAS)—a spectral imaging instrument, suitable for observing the atmosphere of the Earth from a spacecraft, that utilizes four spectrometers to cover the wavelength range of 12 to 15.4 µm with a spectral resolution that ranges between 1 part per 900 and 1 part per 1,200 in wavelength. The spectrometers are operated in low orders to minimize filtering requirements. Focal planes receive the dispersed energy and provide a spectrum of the scene. The design of the SIRAS combines advanced, wide-field refractive optics with high-dispersion gratings in a solid-state (no moving parts), diffraction-limited optical system that is the smallest such system that can be constructed for the specified wavelength range and resolution. The primary structure of the SIRAS has dimensions of 10 by 10 by 14 cm and has a mass of only 2.03 kg.

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Solar-Powered Airplane With Cameras and WLAN

High-resolution images are sent to a ground station in nearly real time. An experimental airborne remote sensing system includes a remotely controlled, lightweight, solar-powered airplane (see figure) that carries two digital-output electronic cameras and communicates with a nearby ground control and monitoring station via a wireless local-area network (WLAN). The speed of the airplane — typically <50 km/h — is low enough to enable loitering over farm fields, disaster scenes, or other areas of interest to collect high resolution digital imagery that could be delivered to end users (e.g., farm managers or disaster-relief coordinators) in nearly real time.

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A Resonator for Low-Threshold Frequency Conversion

A nonlinear dielectric whispering-gallery resonator would be poled for quasiphase-matching. A proposed toroidal or disklike dielectric optical resonator (dielectric optical cavity) would be made of an optically nonlinear material and would be optimized for use in parametric frequency conversion by imposition of a spatially periodic permanent electric polarization. The poling (see figure) would suppress dispersions caused by both the material and the geometry of the optical cavity, thereby effecting quasi-matching of the phases of high-resonance-quality (high-Q) whispering-gallery electromagnetic modes. The quasi-phase-matching of the modes would serve to maximize the interactions among them. Such a resonator might be a prototype of a family of compact, efficient nonlinear devices for operation over a broad range of optical wavelengths.

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Helicity in Supercritical O2/H2 and C7H16/N2 Mixing Layers

This report describes a study of databases produced by direct numerical simulation of mixing layers developing between opposing flows of two fluids under supercritical conditions, the purpose of the study being to elucidate chemical species-specific aspects of turbulence, with emphasis on helicity. The simulations were performed for two different fluid pairs — O2/H2 and C7H16/N2 — at similar values of reduced pressure.

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