Chemical Engineering Commons^™

Molecular Modeling Of Sigma 1 And Sigma 2 Receptor Ligands: Pharmacophore Development And Comparison Using Discotech And Bioactivity Prediction Comparison Of Ab Initio And Density Functional Comfa Studies For Spiro And Other Receptor Ligands, Lisa M. Kardos

Dissertations

The role of the biological receptor is currently being studied by researchers in medicine. Information about sigma receptors in particular can be gained by studying the ligands associated with each type, sigma 1 or sigma 2. Sigma 1 receptor ligands consist of drug candidates that often have psychiatric and neurological applications; sigma 2 receptor ligands consist of drug candidates that have been linked with cancer treatment among other applications.

Molecular modeling of biological receptor ligands often encompasses pharmacophore development and Comparative Molecular Field Analysis (CoMFA). Pharmacophore models are developed to understand the unique features such as binding groups that make …

Combustion Dynamics Of Metal Powders In Mixed Gas Flows, Amy Lee Corcoran

Theses

Predictive mechanisms for particle ignition and combustion rates are required in order to develop optimized propellant and energetic formulations using micron-sized metal powders, such as aluminum and magnesium. Most current descriptions are based on laboratory experiments performed in stationary or laminar combustion configurations using pure metals burned in single oxidizers. However, practical configurations take into account different metals, including alloys, that burn in various oxidizing environments and various flow conditions. Validity of the present descriptions for such environments has not been established. This experimental study is aimed to measure burn times for aluminum, magnesium, and mechanically alloyed Al-Mg particles burning …

Evaluation Of Environmental Materials As Thermal Witness Materials, Shashank Vummidi Lakshman

Dissertations

New and complex energetic materials are under development for achieving tunable pyrotechnical events for applications such as neutralization of biological weapons, bunker busters and many others. To guide the development of hybrid materials, the pyrotechnical environment they produce requires higher degree of characterization i.e. good description of spatial and temporal temperature distribution.

Temperature measurements in pyrotechnical events are especially challenging, where the temperature of the environment rises more than 2000 K on microseconds to few milliseconds time scale. These environments produce high thermal stress where traditional sensors like thermocouples, optical pyrometers struggle to describe the dynamic changes in the environment. …

Novel Scrubbing Systems For Post-Combustion Co2 Capture And Recovery, Tripura Mulukutla

Dissertations

Power plant emissions of flue gas releases considerable CO₂ to the atmosphere; CO₂ is considered to be the main contributor to global warming. Several gas absorption techniques are being investigated to reduce the capital and operating costs for CO₂ capture from post-combustion flue gas. Conventional method of CO₂ capture by an aqueous solution of monoethanolamine (MEA) and its subsequent stripping in a separate tower with steam at 120°C, is a highly energy intensive process. The low partial pressure of CO₂ in the flue gas inhibits the application of CO₂-selective membranes unless methods are …

Ignition Mechanism In Nanocomposites Thermites, Rayon Williams

Dissertations

Nanocomposite thermites (n-thermites) have been actively investigated for a wide range of potential applications including propellants, explosives, and pyrotechnics. There have been several recent efforts aimed at understanding ignition mechanisms of nanocomposite reactive materials. Although significant progress has been made, ignition mechanisms remain elusive. At the same time, a robust ignition model is required to incorporate these materials in practical energetic formulations. A challenge of this effort is to describe the mechanisms of ignition of n-thermites prepared by Arrested Reactive Milling (ARM) with different stimuli, including heat, spark and impact and also develop a multi-step kinetic model describing different processes …

Synthesis And Characterization Of Metal-Based Reactive Powders, Yasmine Aly

Dissertations

Aluminum added to propellants, explosives, and pyrotechnics, boosts their energy density. Different approaches were investigated that could shorten aluminum ignition delays, increase combustion rates, and decrease the tendency of aluminum droplets to agglomerate. Here, Al-based reactive, mechanically milled materials are prepared and characterized.

For powders with Fe, Ni, or Zn additives, the particles consist of an aluminum matrix and inclusions of Fe, Ni, or Zn comprising 10 at % of the bulk composition. For additives of Ni and Zn, only short milling times can be used to prepare composites; intermetallic phases form at longer milling times. Thermogravimetric analysis shows selective …

The Photophysics Properties Of Lanthanide Luminescent Probes, Ke Li

Theses

A detailed study of the luminescence quantum yield, lifetimes and the number of water molecules coordinated to lanthanide luminescent probes based on biphenylyl-7-amino-4- methyl-2(1H)-quinolinon (Bi-cs124) derivatives have been carried out using a time- resolved fluorescence assay (TRFA). Bi-cs124 was conbined with different chelating agents, specifically diethylene triamine pentaacetic acid (DTPA), ethylene diamine tetraacetic acid (EDTA), ethylene glycol tetraacetic acid (EGTA), and 3,6,9,12-Tetrakis carboxymethyl)-3,6,9,12-tetraazatetradecane-1,14-dioic acid (TTHA). The results indicate that Bi-cs 124-TTHA has a longest lifetime and smallest number of coordinated water molecules because TTHA has larger number of chelating groups. The dependence of the luminescence lifetimes on the probes concentrations …

Preparation And Characterization Of Fast Dissolving Pullulan Films Containing Griseofulvin Nanoparticles For Bioavailability Enhancement, Zhelun Ma

Theses

The aim of this study is to enhance the bioavailability of griseofulvin, a model poorly water-soluble drug, via increasing drug dissolution rate through preparation of drug nanoparticle-laden, pullulan-based strip films. The work entails (i) wet-milling griseofulvin in a stirred media mill using pullulan (polymer) along with sodium dodecyl sulfate (surfactant) as stabilizers, (i i) preparing strip films by casting-drying a precursor suspension consisting of the mixture of the milled drug suspension and a film-forming pul l ul an–xanthan gum-glycerin solution, (iii) characterizing the suspensions and the films, and (iv) exploring the effects of film thickness, drug and xanthan gum loadings, …

Kinetic Analysis Of Thiol Oxidation To Study The Effects Of Fluorinated Groups On Metal Phthalocyanine Catalysts, Nellone Eze Reid

Dissertations

The oxidation of thiol (RSH) to disulfide (RSSR) is important biologically and industrially. Corrosive and malodorous thiols exist as contaminants in wastewater discharge from mining facilities, pulp and paper mills, tanneries, and oil refineries. The elimination of thiols from petroleum products is necessary for even cleaner fuels. Thiols in gas products can also inhibit catalyst activity for some downstream processes.

Experiments and mechanistic kinetic studies were conducted for the aerobic oxidation of 2-mercaptoethanol (2-ME) and 4-fluorobenzenethiol (4-FBT) catalyzed by cobalt phthalocyanines: H₁₆PcCo, F₁₆PcCo, and F₆₄PcCo, each exhibiting a metal center subject to increasing Lewis …

Hydrodynamic Cfd Modeling Of A Pharmaceutical Reactor Vessel Provided With A Retreat-Blade Impeller Under Different Baffling Conditions, Christopher G. Foehner

Theses

In the pharmaceutical industry, glass-lined reactors and vessels are often utilized to carry out a variety of different unit operations. Within these systems, both the vessel and impellers are typically glass-lined in order to provide superior corrosion resistance, prevent product contamination, and enhance cleanability. This approach, in turn, often requires the use of different, and sometimes sub-optimal, baffling conditions, which affect the hydrodynamics of the vessels and the reactor performance.

Computational Fluid Dynamics (CFD) is a computational tool that employs numerical methods and algorithms to discretize and numerically solve partial differential equations (PDEs) representing mass, energy, and momentum conservation equations …

Combustion Of Fine Magnesium Particles, Song Wang

Theses

Recent interest in developing Al-Mg alloys as reactive materials prompted studies of combustion mechanisms for particles of such alloys with different Al/Mg ratios. Reference experiments with pure Al and Mg powders are also desired to better understand and model combustion of the respective alloys. While combustion of pure Al powders has been addressed in many recent studies, combustion of magnesium explored mostly coarse, 50 μm, and larger particles. This effort is focused to characterize and understand combustion dynamics for fine Mg powders. Spherical, micron-sized magnesium particles were introduced in an air-acetylene flame using a custom-made screw feeder. Particles were observed …

Assessment Of A Marine Polysaccharide For Use As Excipient In Pharmaceutical Hot-Melt Extrusion, Qing Ye

Theses

Pharmaceutical Hot Melt Extrusion (HME) is currently investigated by both industry and academia as a method for manufacturing solid oral dosages with improved bioavailability of poorly-water soluble active pharmaceutical ingredients (APIs) and control drug release of water-soluble APIs. Although HME is traditionally utilizing synthetic polymers to produce such dosages, biopolymers constantly gain ground by virtue of renewability, biocompatibility and in some cases biodegradability. In this work, the possibility of using Keltone, a marine polysaccharide derived from brown seaweed, as a polymeric excipient for pharmaceutical HME is explored. Keltone is insoluble in acidic pH and soluble in basic pH, therefore making …

Dispersion And Dissolution Kinetics Of Api Particles In Pharmaceutical Hot Melt Extrusion, Wang Zhan

Theses

Pharmaceutical Hot Melt Extrusion (HME) is essentially a special case of polymer compounding. The elementary steps involved in traditional plastics melt processing are handling of particulates, melting, dispersive and distributive mixing, devolatilization and stripping, and finally pressurization and pumping. However, for pharmaceutical HME, the dissolution of the API (Active Pharmaceutical Ingredient) is an additional and very important elementary step, along with the melting of the polymeric excipient that precedes it, and mixing which accelerates the dissolution process. A major concern in pharmaceutical HME is the thermal degradation of the API. To avoid overexposure of API to heat while ensuring complete …

Experimental Determination Of The Mixing Requirements For Solid Suspension In Pharmaceutical Stirred Tank Reactors, Anqi Zhou

Theses

Glass and glass-lined, stirred-tank reactors are of significant importance in the pharmaceutical and related industries. Because of fabrication issues, a retreat blade impeller (RBI) with a low impeller clearance off the tank bottom is commonly used in glass-lined reactors, typically combined with a single baffle (providing only partial baffling conditions) mounted from the top of the reactor. In addition, these reactors are often provided with a torispherical bottom. Other configurations are also used, including full baffling or no baffles at all, hemispherical bottoms, and different impeller types. Despite their common use, some of the most important mixing characteristics of this …

Discrete Element Method Based Scale-Up Model For Material Synthesis Using Ball Milling, Priya Radhi Santhanam

Dissertations

Mechanical milling is a widely used technique for powder processing in various areas. In this work, a scale-up model for describing this ball milling process is developed. The thesis is a combination of experimental and modeling efforts.

Initially, Discrete Element Model (DEM) is used to describe energy transfer from milling tools to the milled powder for shaker, planetary, and attritor mills. The rolling and static friction coefficients are determined experimentally. Computations predict a quasi- steady rate of energy dissipation, Ed, for each experimental configuration. It is proposed that the milling dose defined as a product of Ed and milling …

Batch And Continuous Production Of Stable Dense Suspensions Of Drug Nanoparticles In A Wet Stirred Media Mill, Afolawemi Afolabi

Dissertations

One way to improve the bioavailability of poorly water-soluble drugs is to reduce particle size of drug crystals down to nanoscale via wet stirred media milling. An increase in total surface area per mass loading of the drug and specific surface area as well as reduced external mass transfer resistance allow a faster dissolution of the poorly-water soluble drug from nanocrystals. To prevent aggregation of nanoparticles, polymers and surfactants are dissolved in water acting as stabilizers via adsorption onto the drug crystals.

In the last two decades, ample experimental data were generated in the area of wet stirred media milling …

Pressure Swing Membrane Absorption Process For Separation Of Low Temperature Post-Shift Reactor Syngas, John Chau

Dissertations

This thesis is concerned with a cyclic pressure swing membrane absorption process (PSMAB) for separation of the feed gas mixture containing —40% CO₂-He balance using pure ionic liquid, 1-butyl-3-methylimidazolium dicyanamide ([bmim][DCA]), and its solution containing poly(amidoamine) (PAMAM) dendrimer Gen 0 primarily with a dry feed gas. An advanced pressure swing membrane absorption process is developed to produce purified He as a surrogate for H₂ at a high pressure from simulated low- temperature shifted syngas for different membrane modules. The PSMAB process also simultaneously produces a highly purified CO₂ stream containing bulk of the CO₂ in …

The Effect Of Nanoclays On The Properties Of Aspirin Modified Enteric Polymer Prepared By Hot-Melt Mixing, Nonjaros Chomcharn

Dissertations

Melt mixing in batch equipment or continuous extruders is a technique that recently gained the attention of the pharmaceutical industry. This dissertation investigates two controlled-release drug delivery systems. The first system, namely the enteric matrix, contains an active pharmaceutical ingredient (API) and plasticizer in an enteric polymer while in the second system a nanoclay is added to the enteric matrix, to produce a polymer nanocomposite. The first system employs hot-melt mixing to prepare a modified enteric matrix, as a delayed-release dosage form. Different concentrations of aspirin (ASP) ranging from 10 – 30% w/w are melt-mixed with a plasticized Eudragit® …

Reaction Mechanisms Of Hydrocarbon And Mercury Systems In The Atmosphere And In Combustion: A Theoretical Study Of Thermochemical And Kinetic Properties, Itsaso Auzmendi Murua

Dissertations

The continuing increase in the world population and the rapidly changing lifestyle and education of this population projects significant increases in energy requirements. Global warming is a worldwide major concern with a very serious potential stress on our climate threatening major changes to the environment. It is, without question, of major importance to improve the efficiency and optimize the current available combustion processes and fuel sources, to develop alternative fuels and to reduce the emissions of toxic pollutants.

The objective of this dissertation is to present thermochemical, kinetic and modeling results on two reference fuels (the land vehicle fuel isooctane …

Metal Based Reactive Nanocomposites Prepared By Cryomilling, Shasha Zhang

Dissertations

Aluminum is one of the most commonly used metal fuel additives for propellants, explosives, and pyrotechnics. Recent interest has been focused on replacements for aluminum as fuel additives to achieve higher combustion temperatures and stronger pressure pulses for applications in advanced munitions systems. Two applications are addressed in this work. In the applications for explosives designed to defeat stockpiles of chemical and biological weapons, it is of interest to develop multifunctional materials combining the high energy density of metal fuels with the biocidal activity of halogens. A challenge of this effort is to design and prepare powder-like Al-I2 materials which …

Methane Partial Oxidation Over Phthalocyanine Catalyst, Yuan Zhu

Theses

The partial oxidation reaction of methane over a zeolite-supported ruthenium phthalocyanine catalyst is studied in a packed bed reactor. The investigation of such reaction is desirable because partial oxidation of methane yields a synthesis gas that can be upgraded to liquid chemicals and fuels.

Reactants of this study are He-diluted CH₄ and O₂. The effluent includes unreacted CH₄ and O₂, He, CO, CO₂, H₂, and H₂O vapor. Thermal conductivity gas chromatography is applied to identify the mole fractions of reactants and products. System pressure is maintained at 50 …

Production Of Stable Bcs Class Ii Drug Suspensions By Melt Emulsification And Subsequent Incorporation Into Polymer Strip Films, Emanuel Joseph Vizzotti

Theses

One of the ways to improve the dissolution rate of poorly water-soluble drugs is to produce fine drug particles with increased surface area. This increase will lead to bioavailability enhancement. However, smaller drug particles are thermodynamically unstable and tend to aggregate or grow. Therefore, proper formulation and process parameters must be chosen to keep the particles small. In this study, fine drug particles of two model drugs, fenofibrate and ibuprofen, are prepared by the melt emulsification technique. The influence of suspension formulation (i.e., the inclusion of polymers and surface-active agents) on particle stability is investigated. Moreover, different agitation techniques during …

Hollow Fiber Membrane-Based Air Gap Membrane Distillation, Xuan Wang

Theses

Membrane Distillation (MD) is a thermally-driven separation process. In this research, desalination of 1 % NaCl solution is achieved by one type of MD namely, Air Gap Membrane Distillation (AGMD). The characteristics of AGMD are evaluated by using a hollow-fiber-set-based compact device. Hot brine solution and cold water are passed through two different fiber sets separately: porous hydrophobic polyvinylidene fluoride hollow fibers of the E type (PVDF E) and solid polypropylene (PP) hollow fibers. Vapor from the hot brine crosses the membrane pores of the PVDF fibers and the air gap, and finally condenses over the surface of solid hollow …

Batch Foaming Of Hot Melt Extruded Excipient/Disintegrant/Api Pharmaceutical Formulations And The Study Of The Effects Of The Resulting Cellular Structures On Api Dissolution, Na Yao

Theses

This thesis focuses on the impact of a disintegrant included in a foamed immediate release system composed of a polymer excipient and an Active Pharmaceutical Ingredient (API). Indomethacin (INM) is used as model API; Eudragit® EPO (EPO) is used as polymer excipient; AcDiSol and Crospovidone (Cros) are used as two kinds of disintegrant. The main objectives are to gain an understanding of the resulting morphologies, as well as the impact of disintegrants on drug release from foamed polymeric matrices.

In the first part of this research, the Hot Melt Extrusion (HME) process is used to compound the following pharmaceutical formulations: …

Heterogeneous Combustion Of Condensed Particles In Transition Regime, Deniz Yildiz

Theses

A steady-state model of heterogeneous combustion for a spherical particle is developed accounting for the transition regime of heat and mass transfer. The model assumes formation of condensed products and reaction rate controlled by the transport of oxidizer to the particle surface. The model is based on the Fuchs’ limiting sphere approach. Calculations are performed for combustion of zirconium particles of different sizes. Temperature and oxygen concentration profiles are calculated and compared to those predicted by the continuous medium transfer model. It is shown that for particles in the range from 100 nm up to 30 gm heat and mass …

Effect Of Tablet Compression On The Dissolution Of Aspirin Tablets Using A Novel Off-Center Paddle Impeller (Opi) Dissolution Testing System, Chuan Sun

Theses

In the pharmaceutical industry, dissolution testing is routinely carried out to determine the dissolution rate of oral solid dosage forms. Among several testing devices, the USP Dissolution Apparatus 2 is the device most commonly used. However, despite its widespread use, this apparatus has been shown to produce test failures and to be very sensitive to a number of small geometry changes.

The objective of this study was to determine whether a novel dissolution system termed “OPI” for “off-center paddle impeller” was sensitive enough to determine differences in tablet dissolution profiles caused by different compression pressure during the tablet manufacturing process. …

Hydrodynamic Effects Of A Cannula In A Usp Dissolution Testing Apparatus 2, Qianqian Liu

Theses

Dissolution testing is routinely used in the pharmaceutical industry to provide in vitro drug release information for drug development and quality control purposes. The USP Testing Apparatus 2 is the most common dissolution testing system for solid dosage forms. Usually, sampling cannulas are used to take samples manually from the dissolution medium. However, the inserted cannula can alter the normal fluid flow within the vessel and produce different dissolution testing results.

The hydrodynamic effects introduced by a permanently inserted cannula in a USP Dissolution Testing Apparatus 2 were evaluated by two approaches. Firstly, the dissolution tests were conducted with two …

Effects Of Api Particle Size On The Dissolution Rate In Molten Polymer Excipient Matrices During Hot Melt Extrusion, Conducted In A Co-Rotating Twin-Screw Extruder, Meng Li

Theses

The effect of the Active Pharmaceutical Ingredient (API) particle size on the dissolution rate in the polymer excipient during hot melt extrusion is investigated using a co-rotating twin-screw extruder with three different screw configurations. Acetaminophen (APAP) and amphiphilic polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (PVCap-PVAc-PEG) (Soluplus) are chosen as the model API and water- soluble polymer excipient, respectively. APAP is milled using a fluid energy mill (FEM) into two different particle sizes. The thermal properties of processed samples are characterized by TGA and DSC. SEM and optical microscopy are also used in the morphological studies. Under quiescent conditions, API particles …

Engineering Spores To Display G Protein-Coupled Receptors For Directed Evolution, Alyssa Misoo Kim

Theses

All human cells are surrounded by a plasma membrane made from a phospholipid bilayer, which is responsible for maintaining a biologically active species, while stopping entry of deleterious substances from the outside. G protein-coupled receptors (GPCRs) are the membrane proteins, which transmit signals across the cell membrane. GPCRs are involved in almost every physiological process, and irregular control leads to pathological conditions. Therefore, they are major drug targets. Crystal structure determination is required to understand the molecular details of activation/deactivation. However, GPCRs are difficult to crystallize because of stability issues. An efficient protein engineering system needs to be developed. The …

Dissolution Of Different Commercial Aspirin Tablets Using A Novel Off-Center Paddle Impeller (Opi) Dissolution Testing System, Yang Qu

Theses

Dissolution testing is routinely conducted in the pharmaceutical industry to provide in vitro drug release information for quality control purposes. The most common dissolution testing system for solid dosage forms is the United States Pharmacopeia (USP) Dissolution Testing Apparatus 2. In this work, a modified Apparatus 2, termed "OPI" System for "off-center paddle impeller," in which the impeller is placed 8 mm off center in the vessel is tested to determine its sensitivity to differentiate between the dissolution profiles of differently formulated and manufactured tablets. Dissolution tests are conducted with both the OPI System and the Standard System using three …