Chemical Engineering @ChemengFiles.Com

Equipment is described that was used in making velocity and temperature measurements at various points within an air stream flowing in a smooth, rectangular channel 0.675 inch in height, 12 3/8 inches in width, and 162 inches in length. The aspect ratio of the channel was such that flow along the center line was essentially two-dimensional. In addition to equipment for velocity and temperature measurements, means were provided for establishing the thermal flux from the upper wall of the channel into the flowing air stream.

Equipment is described that was used in making velocity and temperature measurements at various points within an air stream flowing in a smooth, rectangular channel 0.675 inch in height, 12 3/8 inches in width, and 162 inches in length. The aspect ratio of the channel was such that flow along the center line was essentially two-dimensional. In addition to equipment for velocity and temperature measurements, means were provided for establishing the thermal flux from the upper wall of the channel into the flowing air stream.

An electrodynamic balance has been used to measure the water activity as a function of solute concentration at 20 [...]C for eleven single-electrolyte aqueous solutions[...] and three mixed-electrolyte aqueous solutions [...]. The measurements were performed by levitating single, charged, 20-micron diameter droplets of these solutions within the balance and measuring the mass of the particles as a function of the surrounding relative humidity. The deliquescence behavior of the particles was also observed.

An electrodynamic balance has been used to measure the water activity as a function of solute concentration at 20 [...]C for eleven single-electrolyte aqueous solutions[...] and three mixed-electrolyte aqueous solutions [...]. The measurements were performed by levitating single, charged, 20-micron diameter droplets of these solutions within the balance and measuring the mass of the particles as a function of the surrounding relative humidity. The deliquescence behavior of the particles was also observed.

This work concerns applications of NMR techniques in metabolic engineering studies. As demonstrated here, NMR is a valuable tool in analyzing intracellular metabolic and energetic states. When combined with growth and fermentation studies, it greatly enhances the understanding of cellular responses to particular genetic modifications.

This work concerns applications of NMR techniques in metabolic engineering studies. As demonstrated here, NMR is a valuable tool in analyzing intracellular metabolic and energetic states. When combined with growth and fermentation studies, it greatly enhances the understanding of cellular responses to particular genetic modifications.

The Orbiting Carbon Observatory (OCO) mission was proposed to deliver the first temporally and spatially resolved global observations of CO2 to improve our understanding of the sources and sinks of CO2. A retrieval algorithm was developed to obtain the column-averaged dry-air mixing ratio of CO2 (XCO2) from spectroscopic measurements of absorption in the 0.76 µm O2 A band and two near-infrared (NIR) bands of CO2 centered at 1.61 µm and 2.06 µm. An aerosol optical-property database was developed to aid with the retrievals. Principal-component analysis was used to speed up radiative transfer (RT) computations. To test the algorithm, column O2 was retrieved from measurements of absorption in the O2 A band over the sea surface. Using a single sounding, the column O2 was retrieved with an error of around 1%. Polarization was shown to have a significant impact on the retrieval-error budget. A new model based on computing two orders of scattering (2OS) was developed to compute polarization in the OCO spectral regions. The multiple-scattering, scalar model Radiant was combined with the 2OS model to create the R-2OS OCO RT model. Tests with simulated backscatter measurements at the OCO validation

The Orbiting Carbon Observatory (OCO) mission was proposed to deliver the first temporally and spatially resolved global observations of CO2 to improve our understanding of the sources and sinks of CO2. A retrieval algorithm was developed to obtain the column-averaged dry-air mixing ratio of CO2 (XCO2) from spectroscopic measurements of absorption in the 0.76 µm O2 A band and two near-infrared (NIR) bands of CO2 centered at 1.61 µm and 2.06 µm. An aerosol optical-property database was developed to aid with the retrievals. Principal-component analysis was used to speed up radiative transfer (RT) computations. To test the algorithm, column O2 was retrieved from measurements of absorption in the O2 A band over the sea surface. Using a single sounding, the column O2 was retrieved with an error of around 1%. Polarization was shown to have a significant impact on the retrieval-error budget. A new model based on computing two orders of scattering (2OS) was developed to compute polarization in the OCO spectral regions. The multiple-scattering, scalar model Radiant was combined with the 2OS model to create the R-2OS OCO RT model. Tests with simulated backscatter measurements at the OCO validation

To investigate the principles of Non-Equilibrium Thermodynamics, an experimental and theoretical study of a chemical reacting system is made. Nitric oxide, iodine, chlorine, iodine monochloride, and nitrosyl chloride in the gas phase are the macroscopic chemical species which comprise this system.

The system displays a coupling behavior which is uncommon to chemical reacting systems. However, this behavior may be useful in explaining some biological phenomena. The observed coupling effect results in a phenomenological coefficient matrix which is not diagonal.

To investigate the principles of Non-Equilibrium Thermodynamics, an experimental and theoretical study of a chemical reacting system is made. Nitric oxide, iodine, chlorine, iodine monochloride, and nitrosyl chloride in the gas phase are the macroscopic chemical species which comprise this system.

The system displays a coupling behavior which is uncommon to chemical reacting systems. However, this behavior may be useful in explaining some biological phenomena. The observed coupling effect results in a phenomenological coefficient matrix which is not diagonal.

This thesis is motivated by the need to improve our understanding of the aerosol indirect effect. The activation of aerosol into cloud droplets has been extensively studied, using a comprehensive numerical cloud droplet activation model. Using this model, the effect of water vapor mass transfer limitations on the cloud droplet activation process was first studied; it was found that mass transfer limitations are important for activation under polluted conditions. The potential effect of (currently unresolved) ``chemical effects' on cloud droplet number (e.g., the presence soluble gases and surface active species) was also assessed. It was seen that small changes in aerosol and gas-phase composition can have a strong effect on cloud droplet number, and should be included in future estimates of the aerosol indirect effect.

This thesis is motivated by the need to improve our understanding of the aerosol indirect effect. The activation of aerosol into cloud droplets has been extensively studied, using a comprehensive numerical cloud droplet activation model. Using this model, the effect of water vapor mass transfer limitations on the cloud droplet activation process was first studied; it was found that mass transfer limitations are important for activation under polluted conditions. The potential effect of (currently unresolved) ``chemical effects' on cloud droplet number (e.g., the presence soluble gases and surface active species) was also assessed. It was seen that small changes in aerosol and gas-phase composition can have a strong effect on cloud droplet number, and should be included in future estimates of the aerosol indirect effect.

This thesis presents a study of the morphological changes that occur in selected coal chars during oxidation at low temperature (725K-875K) and at high temperature (1400K-1600K). Gas adsorption and mercury porosimetry were the primary means by which these changes were monitored. An attempt was made to relate the observed reactivity of the char in oxygen to the evolving porous structure of the char. Initial pore structure was varied by using three different raw coals: a lignite, a subbituminous and high volatile A bituminous coal. In the case of the bituminous coal, pore structure was varied further by using different pyrolysis temperatures. Of course, while there were differences in the physical structure of the chars, there were differences in the chemical structure as well. In order to account for this, the chemical nature of the chars was monitored, using elemental analysis and oxygen chemisorption.

This thesis presents a study of the morphological changes that occur in selected coal chars during oxidation at low temperature (725K-875K) and at high temperature (1400K-1600K). Gas adsorption and mercury porosimetry were the primary means by which these changes were monitored. An attempt was made to relate the observed reactivity of the char in oxygen to the evolving porous structure of the char. Initial pore structure was varied by using three different raw coals: a lignite, a subbituminous and high volatile A bituminous coal. In the case of the bituminous coal, pore structure was varied further by using different pyrolysis temperatures. Of course, while there were differences in the physical structure of the chars, there were differences in the chemical structure as well. In order to account for this, the chemical nature of the chars was monitored, using elemental analysis and oxygen chemisorption.

This thesis introduces a new technique—scanning activity gravimetric analysis (SAGA)—for investigating phase transitions in semicrystalline polymers. Isothermal growth and dissolution of polymer crystallites within picogram to milligram samples are manifested by mass changes in response to changes in the activity of sorbed solvent vapor. Single charged particles are levitated and weighed in an electrostatic field, providing access to highly supersaturated states. Phase transitions are inferred from simultaneous equilibrium sorption and light scattering measurements. Analogous to differential scanning calorimetry, scanning solvent activity up and down exposes broad transitions between the semicrystalline solid state and the dissolved state, which are influenced by sample history. We demonstrate dissolution and crystallization of nanogram samples of polyethylene oxide by controlling the activity of sorbed water vapor and observe self-nucleation of crystallites from partially states and fully dissolved states.

This thesis introduces a new technique—scanning activity gravimetric analysis (SAGA)—for investigating phase transitions in semicrystalline polymers. Isothermal growth and dissolution of polymer crystallites within picogram to milligram samples are manifested by mass changes in response to changes in the activity of sorbed solvent vapor. Single charged particles are levitated and weighed in an electrostatic field, providing access to highly supersaturated states. Phase transitions are inferred from simultaneous equilibrium sorption and light scattering measurements. Analogous to differential scanning calorimetry, scanning solvent activity up and down exposes broad transitions between the semicrystalline solid state and the dissolved state, which are influenced by sample history. We demonstrate dissolution and crystallization of nanogram samples of polyethylene oxide by controlling the activity of sorbed water vapor and observe self-nucleation of crystallites from partially states and fully dissolved states.

Silicon nanoparticle-based floating gate metal-oxide-semiconductor (MOS) field effect devices have potential for terabit [...] density nonvolatile memory applications. Aerosol synthesis of silicon nanoparticles is an important route toward the formation of discontinuous silicon nanoparticle floating gate structures that affords excellent control over particle size and size distribution, particle density, and oxide passivation. We have fabricated nanoparticle memory devices in a conventional MOS ultra-large scale integration (ULSI) process with channel lengths from 0.2 - 10 [...] with a silicon nanoparticle floating gate fabricated by aerosol deposition.

Silicon nanoparticle-based floating gate metal-oxide-semiconductor (MOS) field effect devices have potential for terabit [...] density nonvolatile memory applications. Aerosol synthesis of silicon nanoparticles is an important route toward the formation of discontinuous silicon nanoparticle floating gate structures that affords excellent control over particle size and size distribution, particle density, and oxide passivation. We have fabricated nanoparticle memory devices in a conventional MOS ultra-large scale integration (ULSI) process with channel lengths from 0.2 - 10 [...] with a silicon nanoparticle floating gate fabricated by aerosol deposition.

Atmospheric particles, or particulate matter, can be solid or liquid with diameters varying from around 0.002[micrometers] to roughly 100[micrometers]. Atmospheric aerosol sources can be classified as primary or secondary, with the primary aerosol being directly emitted from the corresponding sources and the secondary particles being formed in the atmosphere, for example, from gas-phase chemical reactions that produce condensable vapors. At the same time aerosol particles are ultimately connected with the formation of water droplets and equivalently with the formation of clouds and fogs in the atmosphere.

Atmospheric particles, or particulate matter, can be solid or liquid with diameters varying from around 0.002[micrometers] to roughly 100[micrometers]. Atmospheric aerosol sources can be classified as primary or secondary, with the primary aerosol being directly emitted from the corresponding sources and the secondary particles being formed in the atmosphere, for example, from gas-phase chemical reactions that produce condensable vapors. At the same time aerosol particles are ultimately connected with the formation of water droplets and equivalently with the formation of clouds and fogs in the atmosphere.