Soot and other products of incomplete combustion play an important role in the chemistry of the atmosphere. As particles are exposed to trace gases, such as ozone, their chemistry and physical properties can be altered leading to changes in their optical properties, as well as their cloud condensation nuclei and ice nucleation abilities. These alterations can lead to changes in the global radiative budget and cloud microphysical processes, which in turn affect the climate. In this study, the chemical and physical changes associated with the oxidation of pyrene, anthracene, and carbon (lampblack) by ozone were investigated. Fourier Transform Infrared Spectroscopy was used to identify oxidation products and track reaction progress for these representative aerosols. A C=O band attributed to a carboxylic acid formation was observed for all three substances, at each level of exposure to ozone - 20 ppm, 40 ppm, and 80 ppm. Second order reaction rate constants ranged from 9.58 x 10-16 cm2 molecules-1 s-1 to 7.71 x 10-13 cm2 molecules-1 s-1. Measurements of water uptake, ice nucleation efficiency, and optical properties were obtained to determine whether any physical changes associated with the oxidation process occurred. Optical measurements show an increase in the ultra-violet absorption of anthracene, but not for pyrene, while an increase in the visible absorption for pyrene was observed, but not for anthracene. Oxidized soot froze at a warmer temperature (-22.8 degrees C) then fresh soot (-25.6 degrees C), showing an increase in ice nucleation efficiency. Our data indicates that oxidation by ozone does alter the chemistry and physical properties of the substances study, leading to possible changes in how they interact with atmospheric processes.

There is considerable need for higher-tier aquatic risk assessment and information on toxicant-induced molecular alterations in lower aquatic invertebrates. Thus the current study&rsquo / s priorities were two-fold: a novel approach utilizing higher-tier ecotoxicity bioassay-guided ATR-FTIR (Attenuated Total Reflectance Fourier Transform Infrared) spectroscopy to better understand the impact of the presence of fish predation pressure &ndash / mimicked by predator-exuded info-chemicals &ndash / on cypermethrin or salinity toxicity to Daphnia pulex &ndash / key-stone species in lake ecosystems &ndash / and ultimately better assess toxicant-induced alterations at both organismal and molecular levels. This approach indicates that even low concentrations of cypermethrin/salinity had significant molecular and organismal effects on daphnids. Fish kairomone acted as a major factor affecting toxicant severity, interacting antagonistically below a threshold and synergistically above. Moreover, molecular ATR-FTIR spectroscopic results, clearly consistent with organismal responses, showed that both cypermethrin and salinity lead to decreased contributions of lipid and proteins to the investigated daphnid systems. It is further suggested that the action mechanism of the fish-exuded kairomone occurs via the lipid metabolism of Daphnia. Hence, infrared spectroscopic results enabled detection of early molecular alterations, whose effects might not always be observable at the organismal level. The results of this study clearly indicate that the simplistic nature of standard ecotoxicology tests hinders a precise judgment of threats imposed by chemicals of interest. Furthermore, it has been shown that ATR-FTIR spectroscopy has considerable potential for studies on daphnid responses to varying environmental conditions. Thus, this study presents a starting point for increasing the environmental realism of aquatic risk assessment.

Classification of migraineur and healthy subjects using statistical pattern classifiers on functional Near Infrared Spectroscopy (NIRS) data is the main purpose of this study. Also a statistical comparison between trials that have different type of classifiers, classifier settings and feature sets is done. Features are extracted from raw light measurement data acquired with NIRS device, namely Niroxcope, during two separate previous studies, using Modified Beer-Lambert Law. After feature extraction, Na&iuml / ve Bayes classifier and k Nearest Neighbor classifier are utilized with and with-out Principal Component Analysis in separate trials. Results obtained are compared within each other using statistical hypothesis tests namely Mc Nemar and Cochran Q.

The work described herein focuses on FT-IR and quantum cascade laser (QCL) based studies towards the development of compact and portable trace gas sensor for benzene, toluene, and xylenes (BTX). FT-IR broadband radiation was used to probe the mid-infrared fingerprint region for quantitatively detecting trace gas levels of BTX. Using direct absorption through a hollow waveguide, parts-per-million (ppm) detection limits for BTX with a response time of 39 seconds was demonstrated. Univariate calibration provided limits of detection (3σ) for benzene, toluene, and meta-xylene at 5, 17, and 11 ppm, respectively. Multivariate calibration using partial least squares regression algorithms were used to simulate real-world conditions with multiple analytes present within a complex sample. A calibration model was built with 110 training set standards enabled by using a customized gas mixing system. Furthermore, a preconcentration/thermal desorption (TD) step was added to the FT-IR HWG trace gas sensor enabling parts-per-billion detection of BTX. A univariate calibration was established in the laboratory with certified gas standards over a dynamic range of 1000 - 100 ppb for benzene, toluene, and the xylenes. The sensor was then taken to an industrial site during a field measurement campaign for the quantitative determination of BTX in field air samples. The laboratory calibration was used to predict unknown concentrations which were in close agreement with industrial hygiene standard techniques, and industrial prototype analyzers, that were simultaneously operated in the field environment. In addition to FT-IR, quantum cascade laser spectroscopy was also investigated due to enhanced spectral density and efforts to precisely overlap emission with analyte absorption. Particular efforts were dedicated on a novel principle for consistent and deliberate QCL emission wavelength selection by varying the QCL cavity length. These studies experimentally confirmed that using this straight-forward post-processing technique, emission wavelength tuning across a range of one hundred wavenumbers range may be achieved. This tuning range was experimentally demonstrated for a QCL emitting across an entire absorption feature of carbon dioxide by tailoring the length of the cavity. Additionally, using an external cavity (EC) - QCL combined with a HWG gas sensor module for the first time enabled the quantitative and simultaneous determination of ethyl chloride, trichloromethane, and dichloromethane within exponential dilution experiments at ppb limits of detection. Multianalyte detection was demonstrated utilizing partial least squares regression for quantitative discrimination of individual constituents within a mixture, yet applying a single broadly tunable QCL light source.

In this thesis we investigate experimentally certain aspects of the interaction of terahertz (THz) radiation with intersubband transitions and excitonic transitions in semiconductor quantum wells. The first part deals with a more fundamental view on an intersubband transition in a symmetric, undoped GaAs/AlGaAs multiple quantum well. After optical excitation of carriers, the considered electronic conduction intersubband transition is probed in the low-intensity linear regime using broadband THz pulses. These pulses are detected via field-resolved electro-optic sampling. While the sample’s terahertz absorption shows the expected single peak of the resonant intersubband transition, the differential transmission spectra, i.e. the photoexcitation-induced changes in transmission, display strong Fano signatures. On the basis of a microscopic theory, we show that they originate from a phase sensitive superposition of THz current and ponderomotive current. The latter one results from the wiggling motion of carriers induced by the accelerating THz field. Our findings demonstrate for the first time that the ponderomotive contribution has to be taken into account also at the lowest THz intensities. The following issues consider the interaction with THz pulses of higher intensity from the free-electron laser (FEL) of the Forschungszentrum Dresden-Rossendorf. In one experiment we investigate efficient second order sideband generation in the GaAs/AlGaAs multiple quantum well mentioned above. To this end a near-infrared laser tuned to excitonic interband transitions is mixed inside the sample with the inplane polarized FEL beam to create the sum- and difference-frequencies between them. We compare the sideband efficiencies for the THz beam tuned to the interexcitonic heavy-hole light-hole transition and to the intraexcitonic heavy-hole 1s-2p transition. In the latter case we achieve a ten times higher n=+2 low-temperature efficiency around 0.1%. This value is comparable to previous studies in the literature, but our approach involves different transitions in a much simpler geometry. At room temperature the efficiency drops only by a factor of 7 for low THz powers. The last part of this thesis addresses another fundamental quantum-mechanical phenomenon: the splitting of an absorption line in a strong THz field. In the same abovementioned quantum well sample the FEL wavelength is tuned near the intraexcitonic 1s-2p heavy-hole transition. The THz radiation induces a power-dependent splitting of the heavy-hole 1s exciton absorption line which manifests itself in the transmitted spectrum of a broadband near-infrared probe beam. The FEL-wavelength-dependent strength of this so-called Autler-Townes splitting is discussed on the basis of a simple two-level model.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 132-137). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 134-139). Also available on the Internet.

Thesis (M.Sc.-Res.)--University of Wollongong, 2009. / Typescript. Includes bibliographical references: leaf 91-95.

Dissertation (Ph.D.)--University of Toledo, 2009. / Typescript. "Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Physics ." Bibliography: leaves 71-74.

Thesis (M.S.)--Mechanical Engineering, Georgia Institute of Technology, 2004. / Fedorov, Andrei, Committee Member ; Mahan, J. Robert, Committee Member ; Zhang, Zhuomin, Committee Chair. Includes bibliographical references (leaves 80-82).