Wrong-way driving (WWD) events represent unique challenges to transportation engineers. Dissimilar to typical traffic events, WWD events are difficult to detect and often fatal for drivers involved. Even though wrong-way crashes are less frequent than other crash types, the severity of such collisions is much more significant. WWD collisions are typically head-on collisions and often occur at a high rate of speed. Thus, the fatality rate for WWD events is 12 times greater than all other crash types. Detailed literature exists regarding countermeasures aimed at deterring “wrong-way” drivers and WWD statistics. Although there is an absence of literature concerning the effectiveness of WWD countermeasures from a “right-way” driving perspective. Therefore, a study was performed that examined the behavior and reactions of “right-way” drivers during a WWD event. This study determined the effect of current “right-way” WWD countermeasures on overall roadway safety. Additionally, researchers determined how different parameters affected a driver's ability to avoid an oncoming WWD. The study was performed through the use of a driving simulator, in which participants encountered an oncoming WWD within a simulated environment. An overhead Dynamic Message Sign (DMS) “wrong-way warning” represented a current “right-way” WWD countermeasure within the simulation software. Several human factors parameters were also studied to determine the stress of the participant during a WWD event. The results of the study indicated that an overhead DMS “wrong-way warning” increased overall roadway safety and significantly improved a participant's ability to avoid an oncoming WWD. Furthermore, the results indicated an increase in a driver's perceptivity to Overhead DMS “wrong-way warnings” is a substantial factor in the effectiveness of WWD countermeasures.

AIDS/HIV remains a major health threat globally; while treatment and prevention are available, there is currently no cure. The major challenge for developing a cure is to understand the mechanism of HIV latency and to identify and eradicate the latent reservoir. Although substantial insights about HIV latency have been made, the mechanism is still under debate and not well established. Among these, transcriptional repression as a result of reduced levels and activity of P-TEFb plays a significant role. The availability of P-TEFb is closely regulated by an abundant non-coding RNA, 7SK, which is about 330 nt and transcribed by RNAPIII. The studies presented in this thesis provided structural insights into the secondary structure of 7SK snRNA and its interaction with hnRNP A1, in hope of elucidating the mechanism of transcriptional control, as the basis for reversing the latent reservoir of HIV and eradicating the virus. In the thesis, the 7SK secondary structure model was determined using RNAStructure in combination with DMS-MaPseq data as pseudo-energy restraint. The binding site of hnRNP A1 on 7SK snRNA was identified within the upper region of SL3 by DMS-MaPseq. The binding complexes of hnRNP A1 with variable lengths of SL3 transcripts were further characterized using biophysical approaches. The secondary structure of SL3 that was determined by DMS-MaPseq was confirmed by NMR. The stoichiometry and binding affinity were measured using ITC and the binding event was confirmed by selectively 15N-labeled HSQC titration. The shapes of SL3 as well as the 1:1 complex were also characterized using SEC-SAXS. The molecular density model showed SL3 formed a kinked cylindrical shape and the complex formed a similar shape with enlarged middle region. The measured molecular weights agree with the actual molecular weights. The tertiary structure of SL3 was calculated using MD simulation with the restraints from DMS-MaPseq and NMR experiments. The structures with highest s (open full item for complete abstract)

The field of spintronics is considered as the next generation of spin-based electronics rather than the flow of charges utilized in electronics. It is expected that it will have some advantages in areas of information storage densities, switching speed, power consumption, manufacturing costs and others. One of the alternatives in developing a successful spintronics materials is the transition metal (TM)-doped III-V diluted magnetic semiconductors (DMSs) and GaMnAs is the proto-type ferromagnetic DMSs. Currently, the origin of ferromagnetism in GaMnAs is not fully clarified yet due to the complexity of an electronic band structure after doping of the Mn into GaAs. However, the magneto-optical characterization, especially, magnetic circular dichroism (MCD), is a very powerful technique to investigate DMS because one can obtain the information of the electronic band structure. Thus, we have performed systematic investigations of the MCD spectra and optical absorption spectra of the Ga1-xMnxAs with different concentrations of Mn. In this project, we have conducted the measurement using the transmission-mode MCD, the reflection-mode MCD and the magneto-optical Kerr effect (MOKE) for three different kinds of GaMnAs samples fabricated with the same growth conditions; GaMnAs on sapphire, GaMnAs on InP, and free-standing GaMnAs, respectively. We have successfully estimated the Zeeman splitting energy of both L (E1 and E1+delta1) and G (E0 and E0+delta0) critical points (CPs) for these materials. We utilized an energy derivative of the Gaussian function to decompose the MCD spectrum into the impurity band (IB) related background and two dispersion components around L-CPs which are expected in theory. Then, using the rigid band shift model we calculated the Zeeman splitting energy of E1 (L-CP). The Zeeman splitting energy at E1 (L-CP) was estimated to be larger than ~ 4 meV in Ga0.97Mn0.03As on sapphire, ~ 0.6 meV in Ga0.97Mn0.03As on InP, and ~ 6.5 meV in free-standing Ga0.9 (open full item for complete abstract)

Rapid, practical, and low-cost analytical methods are always desirable in forensic analysis. Using proper sample preparation techniques with the application of gas chromatography/mass spectrometry (GC/MS), gas chromatography-differential mobility spectrometry (GC-DMS) and ion mobility spectrometry (IMS) with chemometric analysis, analytical methods were developed for fast and practical identification and classification of analytes in complicated matrices.GC-DMS was investigated as a tool for analysis of ignitable liquids from fire debris. The combined information afforded by gas chromatography and differential mobility spectrometry provided unique two-way patterns for each sample of ignitable liquid. Fuzzy rule-building expert system (FuRES) models constructed with the neat ignitable liquids identified the spiked samples from simulated fire debris with 99.07±0.04% accuracy. The performances of DMS as gas chromatographic detector was also compared with mass spectrometry (MS) using a chemometric tool, projected difference resolutions (PDRs). The PDR results show that one-way mass spectra data exhibit higher resolution than DMS data, while total ion chromatograms from GC-DMS show higher resolution than that from GC/MS for differentiating seven kinds of ignitable liquids. Direct methylation and solid phase microextraction (SPME) were used as a sample preparation technique for classification of bacteria based on fatty acid methyl esters (FAMEs) profiles. Compared with traditional chemical derivatization and liquid-liquid extraction (LLE), the method presented in this work avoids using inorganic and organic solvents and greatly decrease sample preparation time as well. The difference between Gram-positive and Gram-negative bacteria was clearly observed with the application of principal component analysis (PCA) of GC/MS data of bacterial FAMEs. The cross-validation study using ten bootstrap Latin partition (BLP) and fuzzy rule building expert system (FuRES) presented an 87 (open full item for complete abstract)

MnGaN and CrGaN thin films were grown by molecular beam epitaxy on MOCVD GaN(0001)/sapphire(0001) and sapphire(0001) substrates respectively. Dependence of structural and magnetic properties of MnGaN and CrGaN samples on Ga/N flux ratios were investigated. Scanning tunneling microscopy studies of c-GaN(001) were performed to understand the surface reconstructions of this material, as Mn doped c-GaN has been predicted to have a Curie temperature about 6% higher compared to Mn-doped wurtzite GaN. MnGaN samples were grown on MOCVD GaN(0001)/sapphire(0001) at substrate temperature of 550 °C under different Ga/N flux ratios leading to 4 different growth regimes: N-rich, slight metal-rich, metal-rich, and Ga-rich. Mn incorporation and hence magnetic properties clearly depend on the growth conditions. The N-rich grown sample exhibits much larger magnetization compared to the other samples. Ga-rich magnetization is attributed to accumulates, but N-rich magnetization is attributed to carrier-mediated ferromagnetism and/or ferromagnetism due to clusters. Influence of the growth conditions for CrGaN grown on sapphire(0001) using radio frequency N plasma-assisted molecular beam epitaxy has been investigated. CrGaN samples are grown under different Ga/N flux ratio of 65% to 100% at substrate temperatures of 650 and 700 °C. The Cr/Ga flux ratio is set to either 3% or 5%. These growth parameters allow to vary over a range of growth conditions from N-rich to Ga-rich. Surface conditions during growth influence the surface morphology and magnetic properties of CrGaN films. In particular, we show that N-rich and metal-rich growth conditions result in room temperature ferromagnetism. Scanning tunneling microscopy studies have been performed on c-GaN(001) grown by rf N-plasma molecular beam epitaxy. Scanning tunneling microscopy studies of c-GaN (001) reveal several surface reconstructions including 4×11, c(4×20), 4×9, c(4×16), 4×7, and c(4×12). These reconstructions depend on the surfa (open full item for complete abstract)