Performance Effects of Computer-Based Multitasking Behavior
Year of Dissertation:
2012
Advisor:
Raquel Benbunan-Fich
This research examines multitasking from the perspective of human-computer interaction (HCI). Multitasking is defined as the performance of multiple tasks concurrently. In a computer-based environment, users generally switch between multiple computer-based tasks either due to a personal decision to break from the current task or due to an external interruption, such as an electronic notification. This dissertation describes an in-depth empirical study, using a laboratory setting with different numeric, verbal, and visual computer-based tasks. Six hundred and thirty six subjects were randomly assigned into three conditions: discretionary multitasking, where participants were allowed to decide when and how often to switch tasks, forced multitasking, where participants were forced to switch tasks at certain allotted times, and non-multitasking, where participants performed the tasks sequentially and were not allowed to multitask. In order to investigate performance effectiveness (accuracy) and performance efficiency (productivity), participants' overall accuracy and productivity scores were compared across conditions. The results suggest that during difficult tasks, subjects who were forced to multitask had the lowest accuracy. In addition, those subjects in the forced multitasking condition who felt the primary task was difficult had lower accuracy than those who felt the task was easy. This was not true in the other two conditions. Receiving interruptions during a difficult task impacted not only their primary task, but their secondary tasks as well. In the discretionary multitasking condition, the more subjects decided to multitask, the lower their accuracy scores. In fact, an additional analysis revealed that high multitaskers not only performed worse than low and medium multitaskers in the discretionary condition, but actually had the worst performance than subjects in any other condition. Medium multitaskers, however, had the highest productivity scores. While multitasking in that case was considered the best in terms of efficiency, it was not true in terms of effectiveness. Therefore, discretionary multitasking gives the illusion of high performance. Furthermore, this study also explored why people chose to multitask and the impact that had on performance. The results of this study can assist HCI researchers in developing a more comprehensive understanding of user multitasking which can lead to better interface designs.
The Role of Striatal Neuropeptides on Glutamate and Methamphetamine-Induced Neurotoxicity in the Murine Brain
Author:
Lauriaselle Afanador
Year of Dissertation:
2012
PHOTOPHYSICS AND CATALYSIS OF PORPHYRINOIDS
Year of Dissertation:
2011
Organic nanoparticles (ONP) of metalloporphyrins can be versatile catalysts for the selective oxidation of alkenes and other hydrocarbons. Herein, we report the catalytic activity of ONP of 5,10,15,20-tetrakis-[4-(1'H,1'H,2'H,2'H-heptadecafluorodecane-1-thiol)-2,3,5,6-tetrafluorophenyl] porphyrinato iron(III), Fe(III)TPPF84, and 5,10,15,20-tetakis-(2,3,4,5,6-pentafluorophenyl) porphyrinato manganese(III), Mn(III)TPPF20, for cyclohexene oxidation using molecular oxygen as an oxidant in water under ambient conditions. While the solvated metalloporphyrins catalytically oxidize alkenes to the corresponding epoxide in halogenated solvent with a modest turn-over numbers (TON), 10-30 nm ONP of these metalloporphyrins have enhanced catalytic activity with up to a 4-fold greater TON and yields only allylic oxidation products. These ONP catalytic systems facilitate a greener reaction since ca. 89% of the reaction medium is water, molecular oxygen is used in place of man-made oxidants, and the ambient reaction conditions require less energy. The enhanced catalytic activity of these ONP is unexpected because the metalloporphyrins in the nanoaggregates are in the close proximity and the TON should diminish by self-oxidative degradation. The fluorous alkanes in Fe(III)TPPF84 stabilize the ONP towards self-oxidative degradation. Sequential dipping of indium-tin-oxide electrodes into solutions of tetra cationic porphyrins and tetra anionic polyoxometalates results in the controlled formation of nm thick films. The potential applications of these robust films on electrodes range from catalysts to sensors. This chapter focuses on the electrochemistry of the multilayered films where it is found that the oxidation and reduction potentials of each species remain largely the same as found in solution. Photophysical properties of Porphyrinoids bearing four rigid hydrogen bonding motifs on the meso positions, self-assembled into a cofacial cage with four complementary bis(decyl)melamine units in dry solvents are presented here. Self-assembly was investigated by NMR spectroscopy, dynamic light scattering, and atomic force microscopy. The phototphysical properties of the cage formation involve the measurement of their absorption and emission spectra and the fluorescence life time in dry THF. The hydrocarbon chains on the bis(decyl)melamine mediate the formation of nanofilms on surfaces as the solvent slowly evaporates.
An empirical re-evaluation of the effects of education in nonmarket production
Author:
Christie Agioutanti
Year of Dissertation:
2009
Abstract
Dopamine-glutamate interaction in the actions of typical antipsychotic drugs
Year of Dissertation:
2009
Typical antipsychotic drugs (APD) are currently the most effective psychoactive agents for the treatment of schizophrenia. Studies suggest that besides their conventional action of blocking dopamine (DA) D2 receptors, these drugs also interact with glutamatergic N-methyl-D-aspartate (NMDA) receptors. In addition, blockade of DA D2 receptors is believed to result in DA cell depolarization block (DB) and movement disorders (catalepsy) in animals. Since it has been hypothesized that drug's antipsychotic potency may be predicted by its ability to produce DB and catalepsy, using CD rats in behavioral, microdialysis and receptor binding studies we investigated whether typical APD induce DB and catalepsy though action on the dopaminergic system, glutamatergic system, or through the interaction between the two systems. Focus of this project was on striatum (STR) and frontal cortex (FC), two brain regions implicated in the DA-glutamate interplay. Our behavioral results show that haloperidol, a potent APD and postsynaptic DA D2 receptor blocker is a strong catalepsy inducer. Receptor binding study showed that chronic administration of this drug caused a decrease in maximal binding at the NMDA receptors in STR and FC but no significant changes in the DA D2 receptor densities were seen in the two brain areas. In contrast, metoclopramide, another DA D2 receptor blocker but not an APD, within the therapeutic doses (5 mg/kg-10 mg/kg) did not produce catalepsy in experimental animals. The maximal binding parameters for DA D2 and NMDA receptors in STR and FC after repeated administration of metoclopramide were significantly elevated as compared to haloperidol. However, when animals were pre-treated with metoclopramide (10 mg/kg) it sensitized the brain to haloperidol and enhanced catalepsy. Additionally, our receptor binding studies showed that psychotomimetic agents, PCP and ketamine that cause schizophrenia-like symptoms have several-fold higher binding affinity at NMDA receptors as compared to DA D2 receptors, indicating that pharmacological effect of these drugs may be mainly mediated by blockade of NMDA receptors. Finally, studying the neurochemical mechanism for DA cell DB we saw a decrease in striatal DA release after chronic cocaine treatment compared to controls. In a series of follow-up experiments we compared the effect of low dose (0.5 mg/kg) haloperidol and high dose (3.0 mg/kg) haloperidol by acute injection to the chronic cocaine treated rats and to the control animals. Low dose haloperidol significantly increased straital DA release compared to respective controls, while the high dose haloperidol significantly reduced it compared to the low dose. On the other hand, high dose haloperidol drastically increased striatal DA release in chronic cocaine-treated rats compared to controls. These results suggest that the mechanism for catalepsy is based on the concurrent DA D2 receptor antagonism and activation of glutamatergic NMDA transmission. Similarly, the mechanism for DA cell DB is mediated through blockade of dopaminergic D2 receptors and stimulation of NMDA receptors. Thus, catalepsy as well as antipsychotic activity appears to be mediated through modifications of dopaminergic and glutamatergic transmissions.
Fabrication of Quantum Dot Encoded Silica Beads for High-throughput Screening Applications
Year of Dissertation:
2011
The focus of this research is on the development of optically barcoded silica gel microbeads, synthesized to be used in high throughput screening platforms, using suspension methods for bead synthesis developed specifically for rapid gelation. In suspension methods for particle manufacture, precursor droplets are first formed in a continuous phase immiscible with the droplet phase. The droplets are then solidified into particles. Silica is chosen as the bead material because it can very easily be functionalized to anchor probe molecules which is necessary to function as a capture element in high throughput screening applications. The optical code embedded into the microbeads consists of the spectral signature (the emission spectrum) of a collection of luminescent species. In particular, for this study, multicolor semiconductor nanocrystals or quantum dots (QDs) are used. Each type of QD emits electromagnetic waves at a set wavelength (color), and sets of QDs will be incorporated in differing quantities to form the code. The encoding QDs are dispersed in the pre-gel droplet phase, and are surface functionalized so as not to partition in the continuous phase. In this way, the QDs are effectively trapped in the droplets as they gel to microbeads, which allows for a quantitative loading necessary for optical coding.
COMPUTATIONAL STUDIES ON INTERACTION BETWEEN SOME RECEPTORS AND LIGANDS OF TRANSFORMING GROWTH FACTOR-BETA SUPERFAMILY: DESIGN OF INHIBITOR(S) TO PROMOTE OSTEOGENESIS
Year of Dissertation:
2010
Transforming growth factor beta (TGF-β) superfamily members execute distinct and intricate roles in numerous biological events such as cell growth, differentiation, embryogenesis, immune responses, and morphogenesis etc. Diverse cellular responses are instigated by binding of these superfamily members to specific transmembrane serine/threonine kinase receptors on the cell surface and thereby activating specific pathways. As a result receptor-regulated Smad proteins are phosphorylated, followed by their complex formation with Co-Smad that together translocates into nucleus and leads to the initiation of transcription of target genes. Bone morphogenic proteins (BMPs), activins, Inhibins are the most important members of TGF-β family. When they exert their biological activity, they are sternly regulated by extracellular antagonists such as noggin, follistatin, CV2, and so forth that are expressed in close temporal and spatial proximity. Blocking these antagonists' interaction with their target receptor proteins helps to promote their respective biological responses when needed. This work is an attempt to use the current understanding of some of the receptors and ligands of TGF- superfamily members, namely BMPs, activins and inhibins and their antagonists such as noggin, follistatin, and crossveinless 2 (CV2) interactions through the analysis of their available complex structures to design small molecular inhibitors with an ultimate goal of promoting their respective biological responses.
Biodiversity and Ethnography of Tea Management Systems in Yunnan, China
Year of Dissertation:
2011
This study investigates biodiversity and cultural practices associated with tea (Camellia sinensis (L.) O. Kuntze; Theaceae) management systems in Yunnan Province of southwestern China. Surveys were conducted in smallholder communities of six sociolinguistic groups (Akha, Bulang, Han, Hmong, Lahu, and Yao) that manage tea resources in forests, agro-forests, mixed crop fields, and terrace gardens. Interviews were carried out between 2006 - 2010 to identify the influence of socio-economic and policy variables on tea production and consumption patterns. Ecological plot sampling and ethnobotanical inventories were employed to characterize the composition, structure, and uses of tea management systems. Tea leaf samples were randomly selected within each plot for: (1) video morphometrics to measure six shape and size attributes, (2) high performance liquid chromatography (HPLC) to quantify nine catechin and methylxanthine compounds and, (3) amplified fragment length polymorphisms (AFLP) molecular marker analysis to assess genetic diversity. Results indicate a relationship between the perceived value of a commodity and a change of management practices, ecological knowledge, and land use. Findings demonstrate how variable management practices result in the loss, conservation, or enhancement of plant species richness and genetic diversity, and how smallholders variably benefit from diversity in their agro-ecosystems. Plant species richness was found in the order agro-forest edge > forest > agro-forest > mixed crop field > terrace gardens. Statistically significant variation was found in morphological, phytochemical, and genetic characters between the different types of tea management systems. Morphological diversity was found in the order agro-forest > mixed crop field > forest > terrace gardens, whereas genetic diversity was found in the order mixed crop field > agro-forest > forest > terrace gardens. HPLC data show that tea samples from agro-forests and mixed crop fields had greater mean Total Catechin Content (TCC) and mean Total Methylxanthine Content (TMC) compared to forests and terrace gardens. Results further demonstrate that management, processing, and preparation methods are related to the phytochemical profile, anti-oxidant activity, and flavor of tea. This study provides useful baseline data to examine long-term change linked to expanded market integration and an engagement of ecosystem ecology with anthropology.
Off-chip Bandwidth for Multicore Processors: Managing the Next Big Wall
Year of Dissertation:
2010
Abstract
Tragic Practice: Participatory Democracy and Activist Theatre in the U.S., 2006-2010
Year of Dissertation:
2012
Advisor:
Jean Graham-Jones
In this dissertation, I develop a theory of inclusive democratic communication, partly by studying contemporary activist performances such as Poverty Simulation, a role-playing game in which social service and government workers switch places with the poor people who are their clients; and Iraq Veterans Against the War's "Operation First Casualty," in which soldiers perform the drills they have enacted in Iraq in public spaces in the U.S., such as Penn Station. I see these performances as exceptions within national discourse, in which poor people and soldiers are more often represented than represent themselves. In exploring the contributions that performances such as these could make to public perceptions of political and ethical issues, I develop a model of democratic communication based upon inclusion, self-representation, and equal interpretive authority.