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  • Inorganic, Organic and Physical Chemistry  (145)
  • Fluid Mechanics and Thermodynamics  (120)
  • ASTROPHYSICS
  • Analytical Chemistry and Spectroscopy
  • Life and Medical Sciences
  • Polymer and Materials Science
  • 2000-2004  (272)
Collection
Keywords
Publisher
Years
Year
  • 1
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    Integrated Microfluidic Gas Sensors for Water Monitoring (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A silicon-based microhotplate tin oxide (SnO2) gas sensor integrated into a polymer-based microfluidic system for monitoring of contaminants in water systems is presented. This device is designed to sample a water source, control the sample vapor pressure within a microchannel using integrated resistive heaters, and direct the vapor past the integrated gas sensor for analysis. The sensor platform takes advantage of novel technology allowing direct integration of discrete silicon chips into a larger polymer microfluidic substrate, including seamless fluidic and electrical interconnects between the substrate and silicon chip.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: 7th International Conference of Miniaturized Chemical and Biochemical Analysis Systems, Transducers Research Foundation "MicroTAS 2003"; Oct 05, 2003 - Oct 09, 2003; Squaw Valley, CA; United States
    Format: text
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of Molecular Weight Distribution of Lignin Derivatives by Aqueous Phase High Performance Size Exclusion Chromatography (HPSEC) (2000)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 23 (2000), S. 693-696 
    Details
    ISSN: 0935-6304
    Keywords: High performance size exclusion chromatography ; molecular weight ; lignin derivatives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
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    Flame Design: A Novel Approach Developed to Produce Clean, Efficient Diffusion Flames (2000)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: Soot formation and flame extinction are vital concerns in the combustion of fossil fuels. In particular, soot is responsible for pollutant emissions, and extinction can cause inefficient or unstable burning. Normal-gravity experiments have demonstrated that flames can be designed to improve both characteristics by redirecting some or all of the nitrogen from the oxidizer into the fuel. Such nitrogen exchange can produce permanently blue flames, which are soot free under all possible flame conditions. Furthermore, this approach can lead to stronger, extinction-resistant flames. Past investigations of nitrogen exchange were unable to identify the physical mechanisms responsible for its benefits because these mechanisms cannot be isolated when normal-gravity flames are studied. In contrast, the Diffusion Flame Extinction and Soot Inception (DESI) experiment considers spherical flames, where nearly perfect spherical symmetry affords new levels of control. Because of buoyancy, spherical flames cannot be created in Earth s gravity. DESI was conceived by principal investigator Professor R.L. Axelbaum of Washington University in St. Louis. Tests to date have utilized the 2.2-Second Drop Tower at the NASA Glenn Research Center at Lewis Field. The experiment is slated for testing aboard the International Space Station in a few years. Two mechanisms have been proposed to explain the connection between nitrogen exchange and permanently blue flames. These are the structure (chemical effects) and hydrodynamics (flow direction and speed). In normal-gravity flames, the structure and hydrodynamics are coupled, since nitrogen exchange simultaneously modifies both. Spherical microgravity flames, on the other hand, allow independent control of these factors. Specifically, structure can be modified via nitrogen exchange, and flow direction can be reversed by swapping the ambient and burner-feed gases. In DESI, these variations can be accomplished without changing the theoretical flame temperature.
    Keywords: Inorganic, Organic and Physical Chemistry
    Type: Research and Technology 1999; NASA/TM-2000-209639
    Format: application/pdf
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  • 4
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    The Crystallization of Canavalin as a Function of pH and NaCl Concentration (2004)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: We posed the question of what happens to a protein that is known to grow as an n-mer when it is placed in solution conditions where it is monomeric. The trypsin-treated, or cut, form of the protein canavalin (CCAN) has been shown to nucleate and grow crystals as a trimer from neutral to slightly acidic solutions. Under these conditions the solution is composed almost wholly of trimers. The crystalline protein can be readily dissolved by weakly basic solution, which has been proposed to result in a solution that is monomeric. There are three possible outcomes to an attempt at crystallization of the protein under monomeric (high pH) conditions: 1) we will obtain the same crystals as under trimer conditions, but at different protein concentrations governed by the self association equilibria; 2) we will obtain crystals having a different symmetry, based upon a monomeric growth unit; 3) we will not obtain crystals. Obtaining the first result would be indicative that the solution-phase self-association process is critical to the crystal nucleation and growth process. The second result would be less clear, as it may also reflect a pH-dependent shift in the trimer-trimer molecular interactions. The third result, particularly for experiments in the transition pH's between trimeric and monomeric CCAN, would indicate that the monomer does not crystallize, and that solution phase self association is not part of the crystal nucleation and growth path. Results are presented for crystallization experiments of CCAN over the pH 6.4 to 9.6 range. Fluorescence anisotropy, light scattering, and gel filtration experiments show that the solutions are primarily trimers, with association to form larger species occurring as a function of protein concentration.
    Keywords: Inorganic, Organic and Physical Chemistry
    Format: text
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  • 5
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    Electrophoretic Porosimetry of Sol-Gels (2000)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: It has been hypothesized that gravity has an effect on the formation and resulting microstructure of sol-gels. In order to more clearly resolve the effect of gravity, pores may be non-destructively analyzed in the wet gel, circumventing the shrinkage and coarsening associated with the drying procedure. We discuss the development of an electrophoretic technique, analogous to affinity chromatography, for the determination of pore size distribution and its application to silica gels. Specifically a monodisperse charged dye is monitored by an optical densitometer as it moves through the wet gel under the influence of an electric field. The transmittance data (output) represents the convolution of the dye concentration profile at the beginning of the run (input) with the pore size distribution (transfer function), i.e. linear systems theory applies. Because of the practical difficulty in producing a delta function input dye profile we prefer instead to use a step function. Average pore size is then related to the velocity of this dye front, while the pore size distribution is related to the spreading of the front. Preliminary results of this electrophoretic porosimetry and its application to ground and space-grown samples will be discussed.
    Keywords: Inorganic, Organic and Physical Chemistry
    Type: Aerogels; Oct 10, 2000; Albuquerque, NM; United States
    Format: text
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  • 6
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    Forced Forward Smoldering Experiments Aboard The Space Shuttle (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Smoldering is a basic combustion problem that presents a fire risk because it is initiated at low temperatures and because the reaction can propagate slowly in the material interior and go undetected for long periods of time. It yields a higher conversion of fuel to toxic compounds than does flaming, and may undergo a transition to flaming. To date there have been a few minor incidents of overheated and charred cables and electrical components reported on Space Shuttle flights. With the establishment of the International Space Station, and the planning of a potential manned mission to Mars, there has been an increased interest in the study of smoldering in microgravity. The Microgravity Smoldering Combustion (MSC) experiment is part of a study of the smolder characteristics of porous combustible materials in a spacecraft environment. The aim of the experiment is to provide a better fundamental understanding of the controlling mechanisms of smoldering combustion under normal- and microgravity conditions. This in turn will aid in the prevention and control of smolder originated fires, both on earth and in spacecrafts. The microgravity smoldering experiments have to be conducted in a space-based facility because smoldering is a very slow process and consequently its study in a microgravity environment requires extended periods of time. The microgravity experiments reported here were conducted aboard the Space Shuttle. The most recent tests were conducted during the STS-105 and STS-108 missions. The results of the forward smolder experiments from these flights are reported here. In forward smolder, the reaction front propagates in the same direction as the oxidizer flow. The heat released by the heterogeneous oxidation reaction is transferred ahead of the reaction heating the unreacted fuel. The resulting increase of the virgin fuel temperature leads to the onset of the smolder reaction, and propagates through the fuel. The MSC data are compared with normal gravity data to determine the effect of gravity on smolder.
    Keywords: Inorganic, Organic and Physical Chemistry
    Type: Seventh International Workshop on Microgravity Combustion and Chemically Reacting Systems; 129-132; NASA/CP-2003-212376/REV1
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  • 7
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    Reaction Mechanisms and Particle Interaction in Burning Two-Phase Systems (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The main objective of this research is to understand the mechanisms by which particle interactions affect ignition and combustion in the two-phase systems. Combustion of metal aerosols representing the two-phase systems is carried out in the microgravity environment enabling one to avoid the buoyant flows that mask the particle motion due to the particle-particle interaction effects. In addition, relatively large, e.g., 100 micron diameter particles can be used, that remain aerosolized (i.e., do not fall down as they would at normal gravity) so that their behavior ahead, behind, and within the propagating flame can be resolved optically. An experimental apparatus exploiting this approach has been designed for the 2.2-s drop tower microgravity experiments. A typical experiment includes fluidizing metal particles under microgravity in an acoustic field, turning off the acoustic exciter, and igniting the created aerosol at a constant pressure using a hot wire igniter. The flame propagation and details of the individual particle combustion and particle interactions are studied using high-speed movie and video cameras coupled with microscope lenses to resolve individual particles. Recorded flame images are digitized and various image processing techniques including flame position tracking, color separation, and pixel by pixel image comparisons are employed to understand the processes occurring in the burning aerosols. Condensed combustion products are collected after each experiment for the phase, composition, and morphology analyses. New experiments described in this paper address combustion of Ti and Al particle clouds in air and combustion of Mg particle clouds in CO2. In addition, microgravity combustion experiments have been conducted with the particles of the newly produced Al-Mg mechanical alloys aerosolized in air.
    Keywords: Inorganic, Organic and Physical Chemistry
    Type: Sixth International Microgravity Combustion Workshop; 217-220; NASA/CP-2001-210826
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  • 8
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    Smoldering, Transition and Flaming in Microgravity (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A research project is underway to study smolder and the transition to flaming in microgravity. The Microgravity Smoldering Combustion (MSC) flight project is an ongoing research project to provide a better understanding of the controlling mechanisms of smoldering combustion. The Smoldering Transition and Flaming (STAF) project is a recently established research program that will utilize the Fluids and Combustion Facility (FCF) of the ISS to examine the transition from smolder to flaming in microgravity. In forced flow smolder experiments ambient pressure in the MSC chamber rises, thus motivating the need to understand the effects of pressure on smoldering combustion. Further, the STAF experiment has constraints on experimental scale and testing at elevated pressure may be a mechanism to reduce the sample size by enhancing the smolder reaction. In the work we are reporting here, a series of ground-based tests determine the effects of pressure on smoldering combustion. These tests are compared with data obtained from experiments conducted aboard the Space Shuttle in flights STS-69 and STS-77. Measurements of one-dimensional smolder propagation velocity are made by thermocouple probing and a non-intrusive Ultrasound Imaging System (UIS)]. Thermocouples are also used to obtain reaction temperatures and the UIS is used to determine permeabilities of the fuel in real-time.
    Keywords: Inorganic, Organic and Physical Chemistry
    Type: Sixth International Microgravity Combustion Workshop; 21-24; NASA/CP-2001-210826
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  • 9
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    The Three-Dimensional Combustion of Heterogeneous Propellants (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A numerical framework is described which permits the calculation of the 3-D combustion field supported by a heterogeneous propellant, allowing for complete coupling between the condensed phase physics, the gas-phase physics, and the unsteady, uneven, regressing surface. A random packing algorithm is used to construct models of ammonium-perchlorate in hydroxyl-terminated-polybutadiene propellants which mimic experimental propellants designed by R. Miller, and these are numerically burnt. Mean burning rates are compared with experimental data for four packs, over a pressure range of 7-200atm.
    Keywords: Inorganic, Organic and Physical Chemistry
    Type: 38th JANNAF Combustion Subcommittee Meeting; 1; 99-105; CPIA-Publ-712-Vol-1
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  • 10
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    Summary of the 2004 CFD Validation Workshop on Synthetic Jets and Turbulent Separation Control (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A CFD validation workshop for synthetic jets and turbulent separation control (CFDVAL2004) was held in Williamsburg, Virginia in March 2004. Three cases were investigated: synthetic jet into quiescent air, synthetic jet into a turbulent boundary layer crossflow, and flow over a hump model with no-flow-control, steady suction, and oscillatory control. This paper is a summary of the CFD results from the workshop. Although some detailed results are shown, mostly a broad viewpoint is taken, and the CFD state-of-the-art for predicting these types of flows is evaluated from a general point of view. Overall, for synthetic jets, CFD can only qualitatively predict the flow physics, but there is some uncertainty regarding how to best model the unsteady boundary conditions from the experiment consistently. As a result. there is wide variation among CFD results. For the hump flow, CFD as a whole is capable of predicting many of the particulars of this flow provided that tunnel blockage is accounted for, but the length of the separated region compared to experimental results is consistently overpredicted.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: AIAA Paper 2004-2217 , 2nd AIAA 2nd Flow Control Conference; Jun 28, 2004 - Jul 01, 2004; Portland, OR; United States
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