Matching Items (43,917)
Description
A wireless hybrid device for detecting volatile organic compounds (VOCs) has been developed. The device combines a highly selective and sensitive tuning-fork based detector with a pre-concentrator and a separation column. The selectivity and sensitivity of the tuning-fork based detector is optimized for discrimination and quantification of benzene, toluene, ethylbenzene, and xylenes (BTEX) via a homemade molecular imprinted polymer, and a specific detection and control circuit. The device is a wireless, portable, battery-powered, and cell-phone operated device. The device has been calibrated and validated in the laboratory and using selected ion flow tube mass spectrometry (SFIT-MS). The capability and robustness are also demonstrated in some field tests. It provides rapid and reliable detection of BTEX in real samples, including challenging high concentrations of interferents, and it is suitable for occupational, environmental health and epidemiological applications.
Contributors
Chen, Zheng (Author) / Tao, Nongjian (Thesis advisor) / Chae, Junseok (Committee member) / Forzani, Erica (Committee member) / Arizona State University (Publisher)
Created
2011
Description
This dissertation seeks to theorize small state strategic culture with special reference to the attitude of the ASEAN states toward institutionalizing regional cooperative security architectures. The quantitative case studies show that in small states where historically rooted strategic preferences may be limited, material influences and situational considerations take precedence over ideational factors in the making of the state's strategic culture. Second, the content of small state strategic culture focuses primarily on foreign and security policy issues that originate in their neighborhood. Lastly, Small states' threat perceptions from the neighborhood over time dictate the formation of strategic culture (provocative vs. cooperative). The qualitative case studies demonstrate that small Southeast Asian states (Singapore, Thailand, and Malaysia) exhibit a higher tendency for conflict. Multilateral cooperation is at best selective. Bilateral means is still the preferred policy approach when dealing with other states. This dissertation concludes with a pessimistic remark on the prospects for the development and maturation of the ASEAN Political-Security Community. At its current stage, the APSC appears to be a policy instrument created only to reinforce ASEAN's centrality in charting the region's security architecture. This is no small accomplishment in itself nonetheless.
Contributors
Kao, Mily Ming-Tzu (Author) / Simon, Sheldon W. (Thesis advisor) / Gortzak, Yoav (Committee member) / Rush, James (Committee member) / Arizona State University (Publisher)
Created
2011
Description
The development of a Solid State Transformer (SST) that incorporates a DC-DC multiport converter to integrate both photovoltaic (PV) power generation and battery energy storage is presented in this dissertation. The DC-DC stage is based on a quad-active-bridge (QAB) converter which not only provides isolation for the load, but also for the PV and storage. The AC-DC stage is implemented with a pulse-width-modulated (PWM) single phase rectifier. A unified gyrator-based average model is developed for a general multi-active-bridge (MAB) converter controlled through phase-shift modulation (PSM). Expressions to determine the power rating of the MAB ports are also derived. The developed gyrator-based average model is applied to the QAB converter for faster simulations of the proposed SST during the control design process as well for deriving the state-space representation of the plant. Both linear quadratic regulator (LQR) and single-input-single-output (SISO) types of controllers are designed for the DC-DC stage. A novel technique that complements the SISO controller by taking into account the cross-coupling characteristics of the QAB converter is also presented herein. Cascaded SISO controllers are designed for the AC-DC stage. The QAB demanded power is calculated at the QAB controls and then fed into the rectifier controls in order to minimize the effect of the interaction between the two SST stages. The dynamic performance of the designed control loops based on the proposed control strategies are verified through extensive simulation of the SST average and switching models. The experimental results presented herein show that the transient responses for each control strategy match those from the simulations results thus validating them.
Contributors
Falcones, Sixifo Daniel (Author) / Ayyanar, Raja (Thesis advisor) / Karady, George G. (Committee member) / Tylavsky, Daniel (Committee member) / Tsakalis, Konstantinos (Committee member) / Arizona State University (Publisher)
Created
2011
Description
The purpose of this study was to investigate the impacts of visual cues and different types of self-explanation prompts on learning, cognitive load and intrinsic motivation, as well as the potential interaction between the two factors in a multimedia environment that was designed to deliver a computer-based lesson about the human cardiovascular system. A total of 126 college students were randomly assigned in equal numbers (N = 21) to one of the six experimental conditions in a 2 X 3 factorial design with visual cueing (visual cues vs. no cues) and type of self-explanation prompts (prediction prompts vs. reflection prompts vs. no prompts) as the between-subjects factors. They completed a pretest, subjective cognitive load questions, intrinsic motivation questions, and a posttest during the course of the experience. A subsample (49 out of 126) of the participants' eye movements were tracked by an eye tracker. The results revealed that (a) participants presented with visually cued animations had significantly higher learning outcome scores than their peers who viewed uncued animations; and (b) cognitive load and intrinsic motivation had different impacts on learning in multimedia due to the moderation effect of visual cueing. There were no other significant findings in terms of learning outcomes, cognitive load, intrinsic motivation, and eye movements. Limitations, implications and future directions are discussed within the framework of cognitive load theory, cognitive theory of multimedia learning and cognitive-affective theory of learning with media.
Contributors
Lin, Lijia (Author) / Atkinson, Robert (Thesis advisor) / Nelson, Brian (Committee member) / Savenye, Wilhelmina (Committee member) / Arizona State University (Publisher)
Created
2011
Description
Synthetic biology is constantly evolving as new ideas are incorporated into this increasingly flexible field. It incorporates the engineering of life with standard genetic parts and methods; new organisms with new genomes; expansion of life to include new components, capabilities, and chemistries; and even completely synthetic organisms that mimic life while being composed of non-living matter. We have introduced a new paradigm of synthetic biology that melds the methods of in vitro evolution with the goals and philosophy of synthetic biology. The Family B proteins represent the first de novo evolved natively folded proteins to be developed with increasingly powerful tools of molecular evolution. These proteins are folded and functional, composed of the 20 canonical amino acids, and in many ways resemble natural proteins. However, their evolutionary history is quite different from natural proteins, as it did not involve a cellular environment. In this study, we examine the properties of DX, one of the Family B proteins that have been evolutionarily optimized for folding stability. Described in chapter 2 is an investigation into the primitive catalytic properties of DX, which seems to have evolved a serendipitous ATPase activity in addition to its selected ATP binding activity. In chapters 3 and 4 we express the DX gene in E. coli cells and observe massive changes in cell morphology, biochemistry, and life cycle. Exposure to DX activates several defense systems in E. coli, including filamentation, cytoplasmic segregation, and reversion to a viable but non-culturable state. We examined these phenotypes in detail and present a model that accounts for how DX causes such a rearrangement of the cell.
Contributors
Stomel, Joshua (Author) / Chaput, John C (Thesis advisor) / Korch, Shaleen (Committee member) / Roberson, Robert (Committee member) / Ghirlanda, Gionvanna (Committee member) / Arizona State University (Publisher)
Created
2011
Description
The effects of preventive interventions are found to be related to participants' responsiveness to the program, or the degree to which participants attend sessions, engage in the material, and use the program skills. The current study proposes a multi-dimensional method for measuring responsiveness to the Family Bereavement Program (FBP), a parenting-focused program to prevent mental health problems for children who experienced the death of a parent. It examines the relations between individual-level risk-factors and responsiveness to the program, as well as the relations between responsiveness and program outcomes. The sample consists of 90 caregivers and 135 children assigned to the intervention condition of an efficacy trial of the FBP. Caregivers' responsiveness to the 12-week program was measured using a number of indicators, including attendance, completion of weekly "homework" assignments, overall program skill use, perceived helpfulness of the program and program skills, and perceived group environment. Three underlying dimensions of responsiveness were identified: Skill Use, Program Liking, and Perceived Group Environment. Positive parenting and child externalizing problems at baseline were found to predict caregiver Skill Use. Skill Use and Perceived Group Environment predicted changes in caregiver grief and reports of child behavior problems at posttest and 11-month follow-up. Caregivers with better Skill Use had better positive parenting outcomes. Skill use mediated the relation between baseline positive parenting and improvements in positive parenting at 11-month follow-up.
Contributors
Schoenfelder, Erin (Author) / Sandler, Irwin N. (Thesis advisor) / Wolchik, Sharlene (Committee member) / Millsap, Roger (Committee member) / Barrera, Manuel (Committee member) / Arizona State University (Publisher)
Created
2012
Description
The high strength to weight ratio of woven fabric offers a cost effective solution to be used in a containment system for aircraft propulsion engines. Currently, Kevlar is the only Federal Aviation Administration (FAA) approved fabric for usage in systems intended to mitigate fan blade-out events. This research builds on an earlier constitutive model of Kevlar 49 fabric developed at Arizona State University (ASU) with the addition of new and improved modeling details. Latest stress strain experiments provided new and valuable data used to modify the material model post peak behavior. These changes reveal an overall improvement of the Finite Element (FE) model's ability to predict experimental results. First, the steel projectile is modeled using Johnson-Cook material model and provides a more realistic behavior in the FE ballistic models. This is particularly noticeable when comparing FE models with laboratory tests where large deformations in projectiles are observed. Second, follow-up analysis of the results obtained through the new picture frame tests conducted at ASU provides new values for the shear moduli and corresponding strains. The new approach for analysis of data from picture frame tests combines digital image analysis and a two-level factorial optimization formulation. Finally, an additional improvement in the material model for Kevlar involves checking the convergence at variation of mesh density of fabrics. The study performed and described herein shows the converging trend, therefore validating the FE model.
Contributors
Morea, Mihai I (Author) / Rajan, Subramaniam D. (Thesis advisor) / Arizona State University (Publisher)
Created
2011
Description
The purpose of this exploratory study was to determine which social-emotional skills may predict postsecondary enrollment for students with disabilities. Students with disabilities are less likely to enroll in any form of postsecondary education and in turn experience poorer post-education outcomes than their general education peers. Using data from the second National Longitudinal Transition Study (NLTS2), a classification tree analysis was conducted on teacher-rated social-emotional behaviors in an attempt to determine which social-emotional skills were the strongest predictors of postsecondary enrollment. Items assessing social-emotional skills were selected from the second wave of teacher surveys based on their alignment with the broad taxonomy of social-emotional skills created by Caldarella and Merrell. The results of the classification tree analysis showed that one of the selected social-emotional items, teacher rated ability to follow directions, was the most significant predictor of postsecondary enrollment for students with disabilities. In general, the results suggest that compliance and, to a lesser extent, peer-relations skills, in addition to family income, predict postsecondary enrollment for students with high-incidence disabilities. This finding suggests that social-emotional skills play an important role in postsecondary enrollment for SWD, providing support for the use of social-emotional skills interventions in improving postsecondary enrollment rates and potentially post-educational outcomes for SWD.
Contributors
Kaprolet, Charles M (Author) / Sullivan, Amanda L (Thesis advisor) / Caterino, Linda C (Committee member) / Yu, Chong Ho (Committee member) / Arizona State University (Publisher)
Created
2011
Description
This dissertation presents three essays in economics. Firstly, I study the problem of allocating an indivisible good between two agents under incomplete information. I provide a characterization of mechanisms that maximize the sum of the expected utilities of the agents among all feasible strategy-proof mechanisms: Any optimal mechanism must be a convex combination of two fixed price mechanisms and two option mechanisms. Secondly, I study the problem of allocating a non-excludable public good between two agents under incomplete information. An equal-cost sharing mechanism which maximizes the sum of the expected utilities of the agents among all feasible strategy-proof mechanisms is proved to be optimal. Under the equal-cost sharing mechanism, when the built cost is low, the public good is provided whenever one of the agents is willing to fund it at half cost; when the cost is high, the public good is provided only if both agents are willing to fund it. Thirdly, I analyze the problem of matching two heterogeneous populations. If the payoff from a match exhibits complementarities, it is well known that absent any friction positive assortative matching is optimal. Coarse matching refers to a situation in which the populations into a finite number of classes, then randomly matched within these classes. The focus of this essay is the performance of coarse matching schemes with a finite number of classes. The main results of this essay are the following ones. First, assuming a multiplicative match payoff function, I derive a lower bound on the performance of n-class coarse matching under mild conditions on the distributions of agents' characteristics. Second, I prove that this result generalizes to a large class of match payoff functions. Third, I show that these results are applicable to a broad class of applications, including a monopoly pricing problem with incomplete information, as well as to a cost-sharing problem with incomplete information. In these problems, standard models predict that optimal contracts sort types completely. The third result implies that a monopolist can capture a large fraction of the second-best profits by offering pooling contracts with a small number of qualities.
Contributors
Shao, Ran (Author) / Manelli, Alejandro (Thesis advisor) / Chade, Hector (Thesis advisor) / Schlee, Edward (Committee member) / Kovrijnykh, Natalia (Committee member) / Arizona State University (Publisher)
Created
2011
Description
Alzheimer's Disease (AD) is a debilitating neurodegenerative disease. The disease leads to dementia and loss of cognitive functions and affects about 4.5 million people in the United States. It is the 7th leading cause of death and is a huge financial burden on the healthcare industry. There are no means of diagnosing the disease before neurodegeneration is significant and sadly there is no cure that controls its progression. The protein beta-amyloid or Aâ plays an important role in the progression of the disease. It is formed from the cleavage of the Amyloid Precursor Protein by two enzymes - â and ã-secretases and is found in the plaques that are deposits found in Alzheimer brains. This work describes the generation of therapeutics based on inhibition of the cleavage by â-secretase. Using in-vitro recombinant antibody display libraries to screen for single chain variable fragment (scFv) antibodies; this work describes the isolation and characterization of scFv that target the â-secretase cleavage site on APP. This approach is especially relevant since non-specific inhibition of the enzyme may have undesirable effects since the enzyme has been shown to have other important substrates. The scFv iBSEC1 successfully recognized APP, reduced â-secretase cleavage of APP and reduced Aâ levels in a cell model of Alzheimer's Disease. This work then describes the first application of bispecific antibody therapeutics to Alzheimer's Disease. iBSEC1 scFv was combined with a proteolytic scFv that enhances the "good" pathway (á-secretase cleavage) that results in alternative cleavage of APP to generate the bispecific tandem scFv - DIA10D. DIA10D reduced APP cleavage by â-secretase and steered it towards the "good" pathway thus increasing the generation of the fragment sAPPá which is neuroprotective. Finally, treatment with iBSEC1 is evaluated for reduced oxidative stress, which is observed in cells over expressing APP when they are exposed to stress. Recombinant antibody based therapeutics like scFv have several advantages since they retain the high specificity of the antibodies but are safer since they lack the constant region and are smaller, potentially facilitating easier delivery to the brain
Contributors
Boddapati, Shanta (Author) / Sierks, Michael (Thesis advisor) / Arizona State University (Publisher)
Created
2011