Tech Briefs

Using an Ultrasonic Instrument to Size Extravascular Bubbles

Measurements could be used to guide prebreathing of oxygen to reduce the risk of decompression sickness. In an ongoing development project, microscopic bubbles in extravascular tissue in a human body will be detected by use of an enhanced version of the apparatus described in "Ultrasonic Bubble- Sizing Instrument" (MSC-22980), NASA Tech Briefs, Vol.24, No.10 (October 2000), page 62. To recapitulate: The physical basis of the instrument is the use of ultrasound to excite and measure the resonant behavior (oscillatory ex- pansion and contraction) of bubbles. The resonant behavior is a function of the bubble diameter; the instrument exploits the diameter dependence of the resonance frequency and the general nonlinearity of the ultrasonic response of bubbles to detect bubbles and potentially measure their diameters.

Posted in: Bio-Medical, Briefs

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Transplanting Retinal Cells Using Bucky Paper for Support

Bucky paper supports the cells before, during,and after surgery. A novel treatment for retinal degenerative disorders involving transplantation of cells into the eye is currently under development at NASA Ames Research Center and Stanford University School of Medicine. The technique uses bucky paper as a support material for retinal pigment epithelial (RPE) cells, iris pigment epithelial (IPE) cells, and/or stem cells. This technology is envisioned as a treatment for age-related macular degeneration, which is the leading cause of blindness in persons over age 65 in Western nations. Additionally, patients with other retinal degenerative disorders, such as retinitis pigmentosa, may be treated by this strategy. Bucky paper is a mesh of carbon nanotubes (CNTs), as shown in Figure 1, that can be made from any of the commercial sources of CNTs. Bucky paper is biocompatible and capable of supporting the growth of biological cells. Because bucky paper is highly porous, nutrients, oxygen, carbon dioxide, and waste can readily diffuse through it. The thickness, density, and porosity of bucky paper can be tailored in manufacturing. For transplantation of cells into the retina, bucky paper serves simultaneously as a substrate for cell growth and as a barrier for new blood vessel formation, which can be a problem in the exudative type of macular degeneration. Bucky paper is easily handled during surgical implantation into the eye. Through appropriate choice of manufacturing processes,bucky paper can be made relatively rigid yet able to conform to the retina when the bucky paper is implanted. Bucky paper offers a distinct a vantage over other materials that have been investigated for retinal cell transplantation — lens capsule and Descemet's membrane — which are difficult to handle during surgery because they are flimsy and do not stay flat. In preparation for implantation, the selected cells are first cultured onto a piece of bucky paper.

Posted in: Briefs, TSP

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Working Fluids for Increasing Capacities of Heat Pipes

Fluids are formulated to make surface tensions increase with temperature. A theoretical and experimental investigation has shown that the capacities of heat pipes can be increased through suitable reformulation of their working fluids. The surface tensions of all of the working fluids heretofore used in heat pipes decrease with temperature. As explained in more detail below, the limits on the performance of a heat pipe are associated with the decrease in the surface tension of the working fluid with temperature, and so one can enhance performance by reformulating the working fluid so that its surface tension increases with temperature.

Posted in: Briefs, TSP

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On-the-Fly Mapping for Calibrating Directional Antennas

Source-size corrections are not necessary in this method.  An improved method of calibrating a large directional radio antenna of the type used in deep-space communication and radio astronomy has been developed. This method involves a raster-scanning-and-measurement technique denoted on-the-fly (OTF) mapping, applied in consideration of the results of a systematic analysis of the entire measurement procedure. Phenomena to which particular attention was paid in the analysis include (1) the noise characteristics of a total-power radiometer (TPR) that is used in the measurements and (2) tropospherically induced radiometer fluctuations. The method also involves the use of recently developed techniques for acquisition and reduction of data. In comparison with prior methods used to calibrate such antennas, this method yields an order-of-magnitude improvement in the precision of determinations of antenna aperture efficiency, and improvement by a factor of five or more in the precision of determination of pointing error and beam width. Prerequisite to a meaningful description of the present method is some background information concerning three aspects of the problem of calibrating an antenna of the type in question:

Posted in: Briefs, TSP

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Coronagraphic Notch Filter for Raman Spectroscopy

Design could be optimized for attenuating pump light and transmitting Raman-scattered light. A modified coronagraph has been proposed as a prototype of improved notch filters in Raman spectrometers. Corona-graphic notch filters could offer alternatives to both (1) the large and expensive double or triple monochromators in older Raman spectrometers and (2) holographic notch filters, which are less expensive but are subject to environmental degradation as well as to limitations of geometry and spectral range.

Posted in: Briefs, TSP

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Preparing and Analyzing Iced Airfoils

SmaggIce version 1.2 is a computer program for preparing and analyzing iced airfoils.It includes interactive tools for (1)measuring ice-shape characteris- tics,(2)controlled smoothing of ice shapes,(3)curve discretization,(4)gen- eration of artificial ice shapes,and (5)de- tection and correction of input errors. Measurements of ice shapes are essential for establishing relationships between characteristics of ice and effects of ice on airfoil performance.The shape-smoothing tool helps prepare ice shapes for use with already available grid-generation and computational-fluid-dynamics soft- ware for studying the aerodynamic effects of smoothed ice on airfoils.The artificial ice-shape generation tool supports para- metric studies since ice-shape parameters can easily be controlled with the artificial ice.In such studies,artificial shapes gen- erated by this program can supplement simulated ice obtained from icing re- search tunnels and real ice obtained from flight test under icing weather condition. SmaggIce also automatically detects geometry errors such as tangles or dupli- cate points in the boundary which may be introduced by digitization and provides tools to correct these.By use of interactive tools included in SmaggIce version 1.2,one can easily characterize ice shapes and prepare iced airfoils for grid genera- tion and flow simulations.

Posted in: Briefs

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Rapid Chemometric Filtering of Spectral Data

Target species would be identified in real time.   A method of rapid, programmable filtering of spectral transmittance, reflectance, or fluorescence data to measure the concentrations of chemical species has been proposed. By "programmable" is meant that a variety of spectral analyses can readily be performed and modified in software, firmware, and/or electronic hardware, without need to change optical filters or other optical hardware of the associated spectrometers. The method is intended to enable real-time identification of single or multiple target chemical species in applications that involve high-throughput screening of multiple samples. Examples of such applications include (but are not limited to) combinatorial chemistry, flow cytometry, bead assays, testing drugs, remote sensing, and identification of targets.

Posted in: Briefs, TSP

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