Alumni Dissertations

 

Alumni Dissertations

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  • MIDDLEWARE ROUTING ALGORITHMS COMPONENTS FOR MOBILE AD-HOC WIRELESS NETWORKS

    Author:
    Yousef Abdelmalek
    Year of Dissertation:
    2010
    Program:
    Engineering
    Advisor:
    Tarek Saadawi
    Abstract:

    In this research, we introduce middleware routing algorithms components for Mobile Ad-hoc Networks (MANETs). Unlike the conventional networks, MANET is a decentralized radio wireless network that can be established in situation where no infrastructure exists or where deployment of infrastructure is expensive or inconvenient. This inherent flexibility makes it attractive for applications such as military operations, vehicle to vehicle networks, sensor networks, etc. Hence, MANETs require special type of routing algorithms to operate efficiently in such dynamic environment (i.e., wireless channel, bandwidth constrains, nodes resources, etc ...). In this thesis, we propose an add-on generic solution to on-demand ad-hoc routing protocols to enhance the routing protocols performance with minimum control overhead. Our Solution, namely, Destination Assisted Routing Enhancement (DARE), is based on the new idea of transmitting frequent destination beacon packets. These beacon packets are able to refresh the routing cache tables and announce the destination node existence. This methodology results in dramatically minimizing the initialization (learning/optimization) connection set-time as well as the network overhead. Comparison v between the traditional Dynamic Source Routing protocol (DSR) and the DSR with DARE (DSR-DARE) are presented to show the potential of DARE middleware. Second, we propose middleware protocol components in order to improve the real-time applications at the receivers' side; we propose an algorithm that gives the receiver dynamic ability to move from one multicast session to another based on the receiver capabilities and the path conditions leading to it. Our Multicast Multi-Stream (MMS) solution is added as an extension to the traditional Protocol Independent Multicast (PIM) protocol. Then, we present cooperative video caching technique in MANETs in order to reduce the average access latency as well as enhance the video accessibility. Efficient video caching placement and replacement strategies are developed at some of the distributed intermediate nodes across the network. The simulations results have shown that the system has better video perception (i.e. Quality of Service).

  • Efferent-Mediated Changes in the Composite Distortion Product Otoacoustic Emissions Signal and Its Components: A Potential Tool to Investigate Auditory Processing Disorder

    Author:
    Shukrallah Abdelrazeq
    Year of Dissertation:
    2013
    Program:
    Speech & Hearing Sciences
    Advisor:
    Glenis Long
    Abstract:

    One of the hallmarks of auditory processing disorder (APD) is difficulty listening in background noise. This difficulty maybe related to the function of the medial olivocochlear (MOC) efferent system, which is hypothesized to provide an anti-masking effect that might aid in speech processing in noise. To test this hypothesis, we investigated the efferent anti-masking hypothesis via efferent-induced changes in the baseline levels of distortion product otoacoustic emissions (DPOAE) in a group of subjects suspected of having APD with speech-in-noise deficits matched for age and gender with a control group with less speech-in-noise deficits. There was no significant difference in audiometric thresholds between the groups. We examined not only the typical composite DPOAE, but also the two major components (overlap and reflection components), which determine the overall DPOAE level. We hypothesized that the group with speech-in-noise deficits would show reduced efferent effects relative to the control group. The findings did not support the efferent anti-masking hypothesis as efferent-induced changes in the composite DPOAE signal and the overlap component did not differ significantly between the two groups, but the statistical power was low. The separation of the two DPOAE components was beneficial in detecting efferent effects at the high frequency region where the DPOAE levels were lowest, and efferent effects were variable. The mean baseline levels and SNR of composite DPOAE and the overlap component were lower in the group with speech-in-noise deficits than the control group. This difference was not significant, but the statistical power was low. In addition, no significant correlations were found between performance on speech-in-noise tests and DPOAE change due to efferent activation across groups. Factors that might explain why the efferent anti-masking hypothesis was not supported are discussed.

  • Clustering Categorical Data Using Data Summaries and Spectral Techniques

    Author:
    Eman Abdu
    Year of Dissertation:
    2009
    Program:
    Computer Science
    Advisor:
    Bilal Khan
    Abstract:

    Cluster analysis is an active area of research with applications in various fields including information retrieval, social sciences, bioinformatics, object recognition, and image segmentation (Jain et al., 1999). However, most algorithms are intended for numerical (continuous) data where proximity among data objects is naturally defined by virtue of their numerical properties. Although these algorithms can be used on categorical data, they are not designed to handle data properties typically found in this data type such as high dimensionality and lack of inherent relationships among attribute values. During the past decade, several algorithms have been designed for categorical data such as K-modes (Huang, 1998), STIRR (Gibson et al., 1998), CACTUS (Ganti et al., 1999), ROCK (Guha et al., 1999), COOLCAT (Barbara et al., 2002), LIMBO (Andritsos et al., 2004), CLICKS (Zaki et al., 2007), and others. Some of these algorithms exploit attribute relationships through data summaries such as attributes occurrence and co-occurrence frequencies while others use information entropy and links among data objects. In this thesis, we focus on using data summaries and spectral analysis to detect clustering structure in categorical data. Spectral techniques provide a relaxed solution to the discrete clustering problem which has been shown to be NP-hard (Drineas et al., 2004). Formulating the clustering problem as a graph partitioning problem and then finding the minimum normalized cut leads to a solution based on eigenvectors of the similarity matrix (i.e. Laplacian matrix). Spectral methods have been used in various algorithms and have been shown to find non-linearly separable clusters. Equally important, spectral analysis encompasses techniques for handling high-dimensional data since input data is projected into a lower-dimensional space where all computation/comparisons can be performed. Our approach is to extend spectral techniques to data summaries which are relatively less expensive to compute than data object similarity matrix for very large data sets. Our goal is to combine the benefits of spectral analysis with the relative low cost of computing data summaries. We have developed three algorithms for clustering categorical data using data summaries. Two of them use spectral techniques. Our test results on standard data sets and synthetic data sets show that our algorithms are competitive with current spectral and non-spectral algorithms for categorical data. Our algorithms provide a solution to the categorical data clustering problem that produces quality clustering and is scalable to large data sets.

  • Psychophysical and electrophysiological assessment of early visual processing and emotion recognition deficits in schizophrenia

    Author:
    Ilana Abeles
    Year of Dissertation:
    2011
    Program:
    Psychology
    Advisor:
    Pamela Butler
    Abstract:

    Previous data suggest that patients with schizophrenia have preferential magnocellular (M) versus parvocellular (P) visual dysfunction. The goal of Experiment 1 was to characterize M–stream impairment in the patient population using a novel approach. Contrast thresholds at varying luminance levels were investigated. M– and P–biased responses were examined by using scotopic and photopic luminance conditions, respectively. Patients exhibited contrast threshold deficits during scotopic conditions, indicative of M–stream dysfunction. Further, the pattern of contrast threshold responses at photopic levels indicated relatively preserved patient P–pathway functionality. Experiment 2 used separate behavioral and electrophysiological paradigms to investigate contributions of low level visual pathway dysfunction in patients to emotion perceptual processing deficits. Contrast response curves for the dorsal (P1) and ventral (N170) pathways were elicited in response to contrast manipulated emotional faces. Results showed that the dorsal P1's pattern of response was impaired in patients while their N170 contrast response curves remained intact. Contributions of visual pathway dysfunction to impaired emotion recognition and affect–related processing, as indexed by the P250 amplitude, were then assessed. P250 activity in patients was reduced at all contrasts. Overall, across groups, the P1 component predicted both P250 amplitude and emotion recognition ability. Taken together, these data support the hypothesis that emotion recognition deficits in patients result from M/dorsal stream dysfunction. Experiment 3 examined the spatial–temporal oscillatory dynamics of schizophrenia patients during processing of complex visual stimuli. FFT spectrum activity and underlying generators of the delta, theta and alpha oscillatory frequencies were first assessed. Activity in the pre and post–stimulus intervals, and the ratio between them (event-related de/synchronization: ERD/ERS) were also evaluated. FFT data revealed controls had significantly greater alpha band activation in posterior electrodes as compared to patients. Conversely, patients exhibited greater theta–band activation over anterior electrodes versus controls. Topographical analysis suggested patients had abnormal underlying neural generators that gave rise to impaired theta and alpha–band activity. Further, instantaneous delta–band activity was significantly greater in patients during pre and post–stimulus intervals, possibly reflecting an overall generalized deficit. Finally, the data revealed that patients had a substantially reduced alpha ERD, highlighting their impairment in low level visual cortical gating mechanisms during processing of visual sensory inputs.

  • THE MARITAL STATE: PERSONAL STATUS LAWS, DISCOURSES OF REFORM, AND SECULARISM IN LEBANON

    Author:
    Raja Abillama
    Year of Dissertation:
    2012
    Program:
    Anthropology
    Advisor:
    Talal Asad
    Abstract:

    An important aspect of the modern Lebanese state is the arrangement of personal status laws, which consigns matters of marriage and its consequences to the several Islamic, Christian, and Jewish religious authorities. With the absence of civil jurisdictions, some individuals choose to get married under the civil laws of countries, such as France, Cyprus, and Turkey. Recurrent attempts to make civil marriage in Lebanon legal have proven to be controversial and ended ultimately in failure. The problem of marriage has accompanied the system of personal status since the formation of the Lebanese state under French Mandate after the collapse of the Ottoman Empire. This dissertation aims to offer an account of what is at stake in marriage. Based on ethnographic and archival research in Lebanon, it analyzes the terms of the controversies over legal reform, opinions about civil marriage, as well as the decisions of the Maronite Catholic, Sunni Islamic, and civil courts in matters of personal status. It argues that at stake in marriage is the very assumption upon which the modern Lebanese state rests, namely, that Lebanon consists essentially of a variety of religious communities each possessing a distinctive personal status. The formal articulation of that status is the several religious personal status jurisdictions that oversee marriage. This assumption gives rise to a specific configuration whereby marriage, religious communities, and the state, are interconnected. Rather than adopt a perspective that sees in the problem of marriage an opposition between secularism and religion, this study seeks its conditions in tensions internal to the secular itself, in the ambiguities between moral autonomy and religious belonging, freedom and equality, religion and law.

  • Real-time Measurement of Glial Progenitor Chemotactic Migration

    Author:
    Richard Able
    Year of Dissertation:
    2012
    Program:
    Biochemistry
    Advisor:
    Maribel Vazquez
    Abstract:

    Gliomas are the most commonly diagnosed form of central nervous system tumors, occurring primarily in adults. Like many malignant cancers, gliomas pathologically exhibit very aggressive spreading and lead to an average diagnosed survival expectancy of twelve months. This prognosis is due in large part to the uncontrolled division and migration of malignant tumor cells within healthy brain, which makes complete surgical resection impossible. Gliomas are known to contain numerous genotypic and phenotypic alterations that affect cell proliferation and survival. Previous research has indicated that both gliomas and their precursor cells exhibit distinct migration patterns in brain tissue, which may be induced by specific cytokines and their concentration gradients. Here, we investigated the migration of four brain tumor cell (BTCs) lines (U-87 MG; U-251 MG; Daoy; and XFMPDGF) and three RCAS-infected glial progenitor cell (GPCs) populations (GPCLacZ, GPCPDGF, and GPCkRas) toward various growth factors, including but not limited to: EGF, HGF/SF, PDGF-BB, and TGF-α. Mouse neural cultures of nestin expressing glial progenitor cells that have been engineered to display the Avian Leukosis Virus (ALV) target receptor, tv-a, were infected with the RCAS viral vectors RCAS-LacZ, RCAS-PDGF-B, and RCAS-kRas, and are referred to as Ntv-a glial progenitor cells (Ntv-a-GPCs). Upon successful infection, the Ntv-a-GPCs were capable of constitutively producing β-galactosidase, PDGF-B, and kRas, respectively. Additionally, when these viral vectors were injected into the brains of transgenic Ntv-a mouse pups, only the RCAS-PDGF-B viral titer induced gliomas (Dai et al, 2001; Holland et al, 2000). For the purpose of this work it is relevant to note that the Ntv-a cell lines used, with the exception of the XFMPDGF cells, were never injected into the mouse brain. Conversely, the XFMPDGF cell population represents an excised tumor from the brain of a ≤ 12-week-old Ntv-a transgenic mouse having the Ink4a-Arf -/- genetic background. After cranial injection with a RCAS-PDGF-B viral titer, tumors of the oligodendroglioma classification developed within 1-12 weeks in 100% of the injected mice (Tchougounova et al, 2007). We use these oligodendrogliomas as our mouse tumor model. Additionally, Daoy medulloblastomas were used to model the migration of the most common childhood human brain tumor, while the U-87 MG and U-251 MG were used to model glioblastomas, the most common adult brain tumor. The design and characterization of our stand-alone bridged µLane system demonstrated sustained steady-state concentration gradients over 2-3 days while enabling the diffusivity measurement of 0.82 ± 0.01 X 10-6 cm2 / s for Dextran molecules having a molecular weight similar to growth factors examined here. A modified version of this device was then used to examine the migratory response of human MB-derived Daoy, glioblastomas, and neonatal mouse glial progenitors, which has led to the characterization of differential invasion patterns that each cell line utilizes when exposed to various growth factor concentration gradients. This data is fundamental for understanding how BTCs and GPCs use cytokines to communicate with each other and alter cellular functions, specifically migration. Additionally, we demonstrate EGF-induced Akt activation in the migration of MB-derived Daoy cells, and the induced recruitment GPCs towards picomolar concentrations of both HGF and TGF-α. We suggest based on our results that glial progenitors consisting of varying genetic background can migrate in very distinct patterns and may contribute to the selectivity of glioma recruitment/or progenitor sorting.

  • THE ROLE OF GLUTAMATE IN AXONAL PHYSIOLOGY

    Author:
    Ahmed Abouelela
    Year of Dissertation:
    2013
    Program:
    Biology
    Advisor:
    Andrzej Wieraszko
    Abstract:

    The information within the spinal cord and peripheral nervous system propagates along the nerves in the form of Compound Action Potentials (CAP). Although CAPs were always considered to be steady signals, with constant amplitude and velocity as determined by the conductive properties of the nerves our data show that exogenous glutamate increased the CAP. This increase in CAP was blocked after the addition of the general glutamate receptor antagonist kynurenic acid, the specific glutamate receptor antagonist MK801 and CNQX and prevented when these experiments were performed in a calcium-free medium. The goal of this thesis was to examine the changes in axonal physiology in response to electrical stimulation and to pharmacological manipulation. We found that high frequency stimulation, or addition of exogenous glutamate (100 µM) increases the amplitude of compound action potentials (CAPs) in sciatic nerve preparations. These results were further extended and supported by immunohistochemical experiments showing that axolemma contains glutamate receptors (NMDA, AMPA/kainate and mGluR2), the excitatory amino acid transporter responsible for glutamate uptake (Excitatory Amino Acid Transporter-EAAT), and voltage-gated sodium and calcium channels. Thus, the axolemma of peripheral nerves expresses several proteins important for neuronal communication and modulation of the membrane excitability. Apparently, these proteins embedded into the axonal membrane, can under the influence of electrical stimulation or exogenous glutamate change membrane permeability and ionic conductance leading to an increase in the amplitude of the compound action potentials observed in our experiments. Our results demonstrate of existence of axonal plasticity expressed as a change in the amplitude of the action potential following periods of changed activity accompanied by release of neurotransmitters. Therefore we suggest a mechanism of the process whereby electrical stimulation leads to increased axonal activity and subsequent release of glutamate that through activation of the glutamate receptors results in changes in the amplitude of CAPs. We term this phenomenon as axonal plasticity, which would represent one of the forms of neuronal plasticity. Neuronal plasticity is defined as a treatment-induced change in the neuronal response in spite of unchanged strength of the test stimulation. This observation was long described as a property of central synapses and thought to be the basis of learning (Malenka, 1994). Axonal plasticity , would constitute exclusive property of the axon and could contribute together with synaptic plasticity to modification of the efficiency of neuronal connections. This type of plasticity would be fundamentally different from the synaptic plasticity expressed in CNS in the form of Long-Term Potentiation-LTP (Bliss and Collingridge, 1993), Long-Term Depression-LTD (Dudek et al; 1992), and Spike Timing Dependent Plasticity (STDP) (Markram et al., 1997) which has been intensively investigated for last several decades. We assume that high frequency electrical stimulation induces the release of glutamate from stimulated axons. Subsequent increase in the extracellular glutamate concentration would be responsible for observed increase in CAP. Increase in the amplitude of CAP may be a result of: An increase in the number of activated axons (recruitment), 2) and/or increase in the amplitudes of individual potentials generated by single axons. The mechanisms responsible for each of these changes are very different. In the case of recruitment one can suggest paracrine action of glutamate which released from group of axons would enhance the CAP of their neighbors. The increase in the action potential generated by individual axon could be due to a change in the threshold of this individual axon. Our novel data together with published results clearly indicate that in spite of prevailing notion about "all-or-nothing" property of the action potential, axons and action potentials are capable of conveying the information in an analog manner (Clark and Hausser 2006). Presented results convincingly demonstrate that the amplitude of subsequently generated action potentials can change in a way correlated with the frequency of stimulation, or pharmacological treatment. In both cases the change occurred gradually with each evoked action potential slightly larger than its predecessor. This indicates that the effect was building step by step as the intraaxonal mechanisms have been recruited to contribute to the final effect. We have also observed reduced latency and increased area of CAP after glutamate application. The most obvious explanation for both phenomena would be a recruitment of additional, fast conducting axons which would shorten the latency and increase the area of CAP. Simultaneously this would increase the duration of the entire CAP, as slower conducting axons which contributed to CAP before the treatment would be activated as well.

  • The effects of estrogen on carrageenan-induced nociceptive behaviors and inflammatory mediators in ovariectomized female mice

    Author:
    Lisa Abrams
    Year of Dissertation:
    2010
    Program:
    Psychology
    Advisor:
    Vanya Quinones-Jenab
    Abstract:

    Epidemiological studies have shown that pain perception is sexually dimorphic; females tend to experience greater sensitivity to painful stimuli and more chronic pain compared to males. Researchers believe that this dichotomy is caused by the distinct endocrinological profile of females. 17beta -estradiol has been shown to attenuate inflammatory behaviors in both the formalin and carrageenan (Cg) models of inflammation. Research also shows that estrogen affects many inflammatory mediators, including proinflammatory cytokines and prostaglandins (PG). Estrogen plays an important, yet complicated role, in inflammation, and little is known about the specific biochemical mechanisms involved. The objective of this study is to determine if, similar to rats, estrogen attenuates Cg-induced thermal hyperalgesia by altering cytokine or PG release. To that end, female OVX mice were pretreated with various doses of estradiol and injected with 1% Cg. Paw withdrawal latency was recorded prior to, 1 hour, and 5 hours after Cg-treatment in response to a low, medium, and high heat stimuli. Additional animals were treated with indomethacin, a COX blocker. High doses of estradiol caused an increase in nociceptive responses prior to and subsequent to Cg administration. This increase in these pain behaviors was not directly caused by an increase in proinflammatory cytokine levels or a decrease in anti-inflammatory cytokines levels. However, estradiol caused increases in cytokine levels in the untreated paw. Furthermore, treatment with indomethacin caused an attenuation of hyperalgesia. Additionally, indomethacin negated the difference between estradiol- and vehicle-treated mice, indicating that estrogen may interact with prostanoid synthesis. This effect, however, was not seen in the Cg-treated paw, suggesting that estradiol may be increasing hyperalgesia via another pathway as well. Taken together, our results suggest that estrogen's hyperalgesic effects are partly mediated through cytokine up-regulation and prostanoid synthesis, but the main mechanism of action still needs further investigation.

  • Registered Sex Offenders in the Community: A Test of Agnew's General Strain Theory

    Author:
    Alissa Ackerman
    Year of Dissertation:
    2009
    Program:
    Criminal Justice
    Advisor:
    Karen Terry
    Abstract:

    Over the past two decades, sexual offending and offenders have become a topic of interest among researchers, policymakers, and the public. Since the inception of Registration and Community Notification Laws (RCNLS), researchers have assessed the negative consequences associated with the laws and how they affect sex offenders in the community; however, no study has utilized a criminological framework to do so. Agnew's General Strain Theory, which should be able to account for all crime, suggests that when individuals do not achieve desired goals, have negative stimuli placed on them or positive stimuli taken away, they are more likely to engage in crime. These are conditioned by certain factors, such as coping strategies and self-esteem. This study will synthesize these two distinct fields of research to determine whether the negative consequences of RCNLSs lead to recidivism. In all, surveys were mailed to 4,500 sex offenders with (N=997) in Nebraska, (N=2086) and (N=1417) sex and violent offenders in Kansas and Montana, respectively. These states are similar in population and demographic aspects, though they differ in RCNLSs. Findings lend partial support to GST and suggest that, consistently, anger influences recidivism.

  • Infrastructure, Production, and Archive: American and Japanese Video Art Production of 1960s and 1970s

    Author:
    Ann Adachi
    Year of Dissertation:
    2014
    Program:
    Liberal Studies
    Advisor:
    Amy Herzog
    Abstract:

    Focusing a study on the infrastructure of artistic production and maintenance opens a space in which to examine the relationship between artistic inspiration and knowledge making, the occurrences and the writing of its history. In the case of the comparative study of the emergence of Japanese and American video art, common artistic technique employed may indicate motivations derived from the technical possibility of the video medium, while the study of infrastructure demonstrates how large-scale funding, formation of archives, the establishment of systems of distribution and channels of education affect the emergence and development of video art as a genre. This thesis analyzes the synchronous and productive rise of video art in the U.S. and Japan from mid-1960s through mid-1970s, while problematizing the systems of knowledge formation and cultural maintenance that produced a different reception of the histories. In reviewing the structure of cultural maintenance today, the digital field inspires an exploration of new avenues for models of infrastructure that is alternative to traditional institutional frameworks. The digital platform as a pedagogical tool, research resource, and discussion forum allows cross-linguistic understanding, networked scholarship, and open accessibility, suggesting an ideal method for knowledge making. Moreover, this thesis suggests the digital platform as a potential catalyst for a collaborative administration of archive and preservation of Japanese experimental film and video, proposing an alternative method of knowledge formation and cultural maintenance moving forward.