This work examines the use of supercritical fluid extraction (SFE)as a sample introduction technique for supercritical fluid chromatography (SFC) and Fourier transform infrared spectrometry (FT-IR). In order to study the effects of a supercritical mobile phase on the resulting IR spectra, carbon dioxide was compared to xenon as a supercritical fluid mobile phase for flow cell SFC/FT-IR. A packed capillary column (30 cm x 320 μm, Deltabond® Cyano, 5 μm particle) was employed for the chromatographic portion of the study. Various samples were tested, such as an ethoxylated alcohol mixture and a unique polarity mix. The roles of temperature and density on the IR spectra were also examined as each was independently varied for the analysis of five different probe compounds. Comparisons of spectra produced in supercritical CO₂ and xenon each matched well with the Nicolet vapor phase library. CO₂ spectra matched the vapor phase spectra equally as well as did the xenon spectra, despite the fact that CO₂ spectra have blanked regions where the mobile phase absorbs in the IR. Following this study, SFE was coupled directly to FT-IR to produce the novel method of on-line SFE/FT-IR. This technique was optimized for the analysis of n-tetracosane, yielding a detection limit of 74 ng. The method was later applied to the quantitative and qualitative analysis of fiber finishes from textile matrices with equivalent success. Finish was extracted directly from the fiber or textile surface and passed through the IR flow cell as an analyte "plug". In this way, the entire finish was quickly quantified, and if desired, qualitatively analyzed as well, without need of prior chromatographic separation. The method required no organic solvent and was proven to be fairly reproducible for four fiber finish types tested. Lastly, supercritica1 fluid extraction (SFE) was examined and optimized as a sample introduction technique for on-line SFE/SFC. Trapping and recovery of analytes in SFE/SFC were studied under varying conditions using a currently marketed system. The system was replumbed using a 12 cm x 100 μm fused silica capillary (100% methyl, d_f = 0.25 μm) for trapping and increased solute focusing. These changes nearly doubled the total analyte recovery (as based on FID peak areas) and lowered the overall system recovery RSDs from 30 % to 4 %. / Ph. D.

The global progression towards sustainable energy, materials and chemicals requires novel and improved analytical tools to understand and optimize lignocellulosic biomass utilization. In an effort to advance lignocellulose characterization, gain insights into biomass processing, and obtain novel perspectives on cell wall ultrastructure, this study utilizes three principal polymer characterization techniques, namely compressive-torsion dynamic mechanical analysis (DMA), deuterium quadrupolar nuclear magnetic resonance (2H NMR) and rheo-infrared spectroscopy. A novel parallel-plate compressive-torsion DMA protocol is developed to analyze very small solvent-plasticized biomass specimens with or without mechanical integrity. The benefits and limitations of this technique are demonstrated by comparing it to a conventional tensile-torsion DMA while analyzing various solvent-plasticized lignocelluloses. The rheology of wood in various organic solvents is studied through dynamic thermal scans, Time/temperature superposition (TTS) and fragility analysis. Plasticizing solvents and wood grain orientation significantly affected the lignin glass-transition temperature. Dynamic TTS reveals that while all storage modulus data shift smoothly, the thermorheological complexity of solvent-plasticized wood becomes evident in loss component master curves. It is argued that the plasticized lignocellulose TTS is insightful and potentially useful, although it fails to satisfy the classic TTS validity criteria. Subsequently, it is justified that the fragility analysis is a better suited treatment than the WLF model to investigate cooperative segmental motions of plasticized wood. Deuterium quadrupolar NMR reveals a new perspective on the orientation of amorphous wood polymers and two distinct amorphous polymer domains: a highly oriented phase in the S2 layer of the secondary cell wall and an isotropic phase postulated to occur in the compound middle lamella (CML). If the origin of the isotropic phase is confirmed to arise from the CML, then this technique provides a way to independently investigate the morphology and phase dynamics of CML and S2 in an intact tissue, and should bring novel insights into deconstructive strategies specific to the oriented and unoriented domains. Finally the effects of a wood-adhesion promoter (hydroxymethyl resorcinol, HMR) on in-situ wood polymers are studied to elucidate the still unresolved HMR-lignocellulose interactions. DMA, creep-TTS and 2H NMR reveal that HMR increases the crosslink density and restricts the mobility of wood amorphous phase. Rheo-IR spectroscopy shows that the molecular stress-transfer mechanism is altered within the wood cell wall. / Ph. D.

This study reports on the behavior of silica based optical fibers in a hydrogen environment at high temperatures. The hydrogen response in the form of optical loss in the wavelength range of 1000-2500 nm of a germanium doped graded index 50/125 graded index fiber was examined in the temperature range of 20–800 °C. When the fiber was exposed to hydrogen at 800 °C two absorption bands appeared: ~1390 nm assigned to the first overtone of the hydroxyl stretch and ~2200 nm band with complex assignments including the combination mode of the fundamental hydroxyl stretch with SiO4 tetrahedral vibrations and the combination mode of SiOH bend and stretch. The growth rate of the 1390 nm band fits the solution to the diffusion equation in cylindrical coordinates while the 2200 nm band does not. Absorption for both bands persisted as the fiber is cooled to room temperature. Temperature dependent behavior was observed in that as temperature increases from room temperature, the absorption intensity decreases and band shifts slightly to longer wavelengths. Temperature dependence is repeatable and reversible. However, if no hydrogen is present in the environment at temperatures greater than 700 °C, the 1390 nm band will permanently decrease in intensity, while the 2200 nm band does not change. Changes in the structure of the glass appear to be causing this temperature dependent behavior. Other necessary conditions for structural changes to cause this temperature dependent behavior are examined. / Master of Science

Sustainability is inherently a complex problem that requires new ways of thinking. To solve grand challenges such as climate change, environmental degradation, and poverty, engineers cannot rely on the same models of thinking that were used to create these problems. Engineering education is therefore critical to advance sustainable engineering solutions. Improving education relies on understanding of cognition of thinking and designing for sustainability. In this thesis, a nascent neuroimaging technology called functional near-infrared spectroscopy (fNIRS) was used to measure cognition among engineering students thinking about sustainability. fNIRS provides an opportunity to investigate how sustainability in design influences cognition, and how different concept generation techniques help students consider many aspects related to sustainability. The first manuscript provides evidence that engineering students perceive sustainability in design as a constraint, limiting the number of solutions for design and decreasing the cognitive efficiency to generate solutions. Senior engineering students generated fewer solutions than freshmen, however, seniors were better able to cognitively manage the sustainability parameter with higher cognitive efficiency. The second manuscript investigates the cognitive difference when generating concepts using concept listing or concept mapping. The results indicate that concept mapping (i.e. intentionally drawing relationships between concepts) leads to more concepts generated. An increase in concepts during concept mapping was also observed to shift cognitive load in the brain from regions associated with process sequencing to regions associated with cognitive flexibility. This research demonstrates the feasibility of fNIRS applied in engineering research and provides more understanding of the cognitive requirements for sustainability thinking. / M. S.

Metal oxide and metal oxide-supported metal nanoparticles can adsorb and decompose chemical warfare agents (CWAs) and their simulants. Nanoparticle activity depends on several factors including chemical composition, particle size, and support, resulting in a vast number of materials with potential applications in CWA decontamination. Current instrumentation in our laboratory used to investigate fundamental gas-surface interactions require extensive time and effort to achieve operating conditions. This thesis describes the design and construction of a high-throughput, high vacuum surface analysis instrument capable of studying interactions between CWA simulants and nanoparticulate surfaces. The new instrument is small, relatively inexpensive, and easy to use, allowing for expeditious investigations of fundamental interactions between gasses and nanoparticulate samples. The instrument maintains the sample under high vacuum (10?⁷-10?⁹ torr) and can reach operating pressures in less than one hour. Thermal control of the sample from 150-800 K enables sample cleaning and thermal desorption experiments. Infrared spectroscopic and mass spectrometric methods are used concurrently to study gas-surface interactions. Temperature programmed desorption is used to estimate binding strength of adsorbed species. Initial studies were conducted to assess the performance of the instrument and to investigate interactions between the CWA simulant dimethyl methylphosphonate (DMMP) and nanoparticulate silicon dioxide. / Master of Science

The behavior of adsorbed carbon monoxide on platinum was studied using potential difference infrared spectroscopy. Three solvents and three electrolytes were chosen, and data gathered at both high and low adsorbate coverages. The rate of change of IR peak position with applied potential, the Stark tuning rate, was used as an indicator of the local electric field strength at the interface. It was determined that neither solvated cation size nor bulk dielectric constant accounts for the changes in Stark tuning rate with different solvents. / Master of Science

Developing a fundamental understanding of the interactions of chemical warfare agents (CWAs) with surfaces is essential for the rational design of new sorbents, sensors, and decontamination strategies. The interactions of chemical warfare agent simulants, molecules which retain many of the same chemical or physical properties of the agent without the toxic effects, with amorphous silica were conducted to investigate how small changes in chemical structure affect the overall chemistry. Experiments investigating the surface chemistry of two classes of CWAs, nerve and blister agents, were performed in ultrahigh vacuum to provide a well-characterized system in the absence of background gases. Transmission infrared spectroscopy and temperature-programmed desorption techniques were used to learn about the adsorption mechanism and to measure the activation energy for desorption for each of the simulant studied. In the organophosphate series, the simulants diisopropyl methylphosphonate (DIMP), dimethyl methylphosphonate (DMMP), trimethyl phosphate (TMP), dimethyl chlorophosphate (DMCP), and methyl dichlorophosphate (MDCP) were all observed to interact with the silica surface through the formation of a hydrogen bond between the phosphoryl oxygen of the simulant and an isolated hydroxyl group on the surface. In the limit of zero coverage, and after defect effects were excluded, the activation energies for desorption were measured to be 57.9 ± 1, 54.5 ± 0.3, 52.4 ± 0.6, 48.4 ± 1, and 43.0 ± 0.8 kJ/mol for DIMP. DMMP, TMP, DMCP, and MDCP respectively. The adsorption strength was linearly correlated to the magnitude of the frequency shift of the ν(SiO-H) mode upon simulant adsorption. The interaction strength was also linearly correlated to the calculated negative charge on the phosphoryl oxygen, which is affected by the combined inductive effects of the simulants’ different substituents. From the structure-function relationship provided by the simulant studies, the CWA, Sarin is predicted to adsorb to isolated hydroxyl groups of the silica surface via the phosphoryl oxygen with a strength of 53 kJ/mol. The interactions of two common mustard simulants, 2-chloroethyl ethyl sulfide (2-CEES) and methyl salicylate (MeS), with amorphous silica were also studied. 2-CEES was observed to adsorb to form two different types of hydrogen bonds with isolated hydroxyl groups, one via the S moiety and another via the Cl moiety. The desorption energy depends strongly on the simulant coverage, suggesting that each 2-CEES adsorbate forms two hydrogen bonds. MeS interacts with the surface via a single hydrogen bond through either its hydroxyl or carbonyl functionality. While the simulant work has allowed us to make predictions agent-surface interactions, actual experiments with the live agents need to be conducted to fully understand this chemistry. To this end, a new surface science instrument specifically designed for agent-surface experiments has been developed, constructed, and tested. The instrument, located at Edgewood Chemical Biological Center, now makes it possible to make direct comparisons between simulants and agents that will aid in choosing which simulants best model live agent chemistry for a given system. These fundamental studies will also contribute to the development of new agent detection and decontamination strategies. / Ph. D.

The objective of this study was to evaluate the relationship between tissue oxygen saturation (StO2) and oxygen delivery index (DO2I). Oxygen delivery index is product of two factors arterial oxygen content (CaO2) and cardiac index (CI). In this study the relationship between DO2I and StO2 was evaluated by manipulating both of these factors independently. In phase one of the study, CaO2 was altered by manipulating the fractional inspired oxygen (FiO2) concentration. Anesthetized dogs were evaluated at both high (0.40 and 0.95) and low (0.15 and 0.10) FiO2 sequences. In phase two of the study, CI was altered by manipulating the volemic state. Anesthetized dogs were evaluated at hypovolemic, normovolemic and hypervolemic states. In each phase dogs were instrumented for thermodilution cardiac index (CI) and sartorius muscle StO2. Data collected included hemoglobin concentration, heart rate (HR), MAP, CI, StO2. Arterial oxygen content and DO2I were calculated at each time point. Data analysis included Pearson's correlation and mixed model ANOVA (p < 0.05). In both phases one (r = 0.97; p = 0.0013) and two (r = 0.97; p = 0.005) there was a strong correlation between StO2 and DO2I. Under the conditions of this study, there was a strong correlation between StO2 and DO2I, suggesting that StO2 may be used to estimate the adequacy of oxygen delivery in dogs. / Master of Science

The neurovisceral integration model (NVM) proposes that an organisms ability to flexibly adapt to their environment is related to biological flexibility within the central autonomic network. One important aspect of this flexibility is behavioral inhibition (Thayer and Friedman, 2002). During a behavioral inhibition task, the central autonomic network (CAN), which is comprised of a series of feedback loops, must be able to integrate information and react to these inputs flexibly to facilitate optimal performance. The functioning of the CAN is shown to be associated with respiratory sinus arrhythmia (RSA), as the vagus nerve is part of this feedback system. While the NVM has been examined through neural imaging and RSA, only a few studies have examined these measures simultaneously during the neuroimaging procedure. Furthermore, these studies were done at rest or used tasks that were not targeted at processes associated with the NVM, such as behavior inhibition and cognitive flexibility. For this reason, the present study assessed RSA and neural activation in the prefrontal cortex simultaneously while subjects completed a behavior inhibition task. Using a series of go/no-go tasks, RSA and functional near-infrared spectroscopy (fNIRS) were collected to investigate the relationship between prefrontal activation and vagal activity at rest and during behavioral inhibition. There are three primary aims of this study. First, examine prefrontal activation during various inhibition tasks through fNIRS. Second, evaluate the NVM during a cognitive task using simultaneous fNIRS and RSA analysis. Third, relate task performance, imaging, and RSA measures during behavioral inhibition to deficits in flexible everyday responding, as indicated by self-report measures of behavior. Doing so will elucidate the connection with prefrontal activation and RSA as proposed by the NVM model and determine whether neural and RSA metrics can be related to broader symptoms of inflexibility. / PHD / The neurovisceral integration model (NVM) proposes that the ability to adapt to the environment is related to biological flexibility within the brain. One important aspect of the ability to adapt to the environment is behavior inhibition (e.g., the ability to stop from engaging in a habitual response, Thayer & Friedman, 2002). During a behavior inhibition task, the brain must be able to integrate information and react to these inputs flexibly to facilitate optimal performance. The brain’s ability to do this is related to a measure of heart activity known as respiratory sinus arrhythmia (RSA). The present study assessed RSA and brain activity while subjects completed a behavior inhibition task. Neural activation was measured through functional near-infrared spectroscopy (fNIRS). fNIRS measures the amount of oxygenated blood in different areas of the brain. Greater concentrations of oxygenated blood indicated greater brain activity in an area. Through simultaneous fNIRS and RSA measurement the present study examined their relationship during various inhibition tasks. Doing so clarified the connection between brain activation and RSA as proposed by the NVM model.

Brown dwarfs are substellar objects that fall in-between the smallest stars and largest planets in size and temperature. Due to their relatively cool temperatures, the atmospheres of these 'failed stars' have been shown to exhibit interesting properties such as iron, silicate, and salt clouds. Theoretical atmospheric models based on known physics and chemistry can be used as tools to interpret and understand our observations of brown dwarfs. I have fit archival and new infrared spectra of over 300 brown dwarfs with atmospheric models. Using the parameters of the best-fit models as estimates for the physical properties of the brown dwarfs in my sample, I have performed a survey of how brown dwarfs evolve with spectral type and temperature. I present my fit results and observed trends. I use these fit results to note where current atmospheric models are able to well-replicate the data and where the models and data conflict.