Palembang in the 1950s : the making and unmaking of a region

여운경 ProQuest LLC UMI Dissertation Publishing 2012 국내박사

Effects of innovation versus efficiency tasks on collaboration and learning

Sears, David Andrew Stanford University 2006 해외박사(DDOD)

What makes for a naturally productive collaborative task? Some researchers have suggested that optimal tasks for productive collaboration are ill-structured and allow for exploration and construction of multiple possible solutions (e.g. Cohen, 1994). Others have suggested that tasks should have one solution and be well-defined such that everyone can agree on their answers (e.g. Steiner, 1972). In a search for a way to reconcile this dilemma and begin to answer the driving question, two dimensions, innovation and efficiency, were examined for their effects on collaboration and learning in two experiments with university students. Innovation involves the use of prior knowledge to construct solutions to unfamiliar problems. The goal is to prepare students to perceive and appreciate how an expert solution works when they receive instruction on it. Efficiency involves being given the canonical solution and then having an opportunity to practice it. The goal is to promote speed and accuracy in applying the expert solution. These dimensions were recently found to be informative to the field of transfer. Transfer is the generalization of learning from one situation to another. Schwartz, Bransford, and Sears (2005) suggested that optimal instruction for promoting transfer involves cycles of innovation and efficiency, rather than just one or the other approach. Thus, they described them as complementary components for promoting thorough understanding. For the two experiments reported here, it was hypothesized that tasks with an innovation component would yield more productive interactions and learning than tasks with strictly efficiency components. The first experiment involved concept-mapping of the relationship between cholesterol and the circulatory system. The second involved learning the chi-square formula. Results of the first study indicated that Innovation dyads collaborated more than Efficiency dyads. Results of the second revealed that the Innovation condition scored significantly higher on transfer problems, and Innovation dyads showed the greatest performance on a novel measure of preparation for future learning (Bransford & Schwartz, 1999). The strongest indicator that tasks with innovation components might naturally support collaborative learning came from the finding that Innovation dyads exceeded nominal dyads (mathematically modeled dyads based on individuals' scores) on the novel measure.

Imagining Black womanhood: The negotiation of power and identity within the Girls Empowerment Project

Sears, Stephanie Dawn Yale University 2004 해외박사(DDOD)

This dissertation is a qualitative case study of the negotiation of power and identity within the Girls Empowerment Project (GEP), an Africentric womanist after-school program for low-income Black girls. Recently, scholars and activists have called for the creation of safe spaces where women and girls can try on different ways of being women. Embedded within the single-sex or "safe space" call, however, are three limitations: First, there is an underlying belief that women's and girls' differences across race, class, sexuality, and generation will become secondary to the uniting sign of female. Second, there is an assumption that internalized gender oppression will not only disappear but also not intensify within this single-sex environment. Finally, little attention is paid to the organization as a key structuring agent within which "safety" is constructed and identity work occurs. In this study, however, I found that GEP's organizational environment, culture, and structure intersected and interacted to create an organizational power matrix which participants were able to access and mobilize to "do" power and thus imagine and negotiate alternative versions of Black femininity. Specifically, I found that GEP women drew upon the cultural resources provided by the organization's Africentric womanist ideology and their positional power as staff to construct a hierarchy of Black femininities structured around self-definition, self-reliance, and sexual agency. This hierarchy, however, set into place a discourse of respectability which silenced and subordinated other Black femininities. GEP girls, drawing upon the organizational discourse of youth power and their power as consumers, countered the staff's politics of respectability with a politics of respect. Here girls asserted the right to be recognized not for "how I am like you," but for "how I am." The key site of this negotiation between respectability and respect, between Africentric womanist femininity and the girls' own working class femininity, was dance. In sum, the evidence from this case captures the importance of the organizational power matrix in delineating the processes by which women and girls negotiate identity and power and provides theoretical insight into the relationship among power, identity work, and organizational context.

FoxO Regulates Microtubule Dynamics and Polarity to Promote Dendrite Branching in Drosophila Sensory Neurons

Sears, James Cooper Case Western Reserve University ProQuest Dissertat 2017 해외박사(DDOD)

The morphology of dendrites is a critical determinant of neuronal function. Microtubules are crucial structural and functional components in dendrites, yet the molecular mechanisms and pathways that regulate dendrite development are unclear. Previous work from our lab showed that FoxO regulates microtubule dynamics in axons at the neuromuscular junction. Therefore, we tested if FoxO regulates microtubules and morphology in the dendritic arborization (da) system. We found that FoxO is required for normal morphology in all four classes of da neurons. FoxO is necessary not only for branching, but also for initiation and maintenance of terminal branches. Furthermore, overexpression of FoxO is sufficient to promote increased branching in multiple cell types. Consistent with findings in motor axons, FoxO limits the distribution of stable microtubules. When we tested for microtubule dynamics, we found that FoxO is necessary and sufficient to promote anterograde microtubule polymerization. Similar to other studies in the system, loss of branching seen in foxO nulls correlates with a decreased nociceptive response. Taken together, our results identify FoxO as a regulator of dendritic arborization and neuronal function. Furthermore, our data support the hypothesis that FoxO promotes dendrite branching by promoting anterograde microtubule polymerization. This conclusion leads to testable hypotheses for how FoxO regulates microtubules and morphology of dendrites.

A Study of Contact Potentials

Sears, Gerald William ProQuest Dissertations & Theses University of Illi 1942 해외박사(DDOD)

The accurate measurement of the contact potentials between reproducible metallic surfaces would lead to numerous interesting applications. The most obvious of thesis is the study of films, both monomolecular and poly-molecular, on metallic surfaces. This study should furnish a basis for the development of a theory of surface catalysis. In the field of thermionics accurate data upon contact potentials could be allied to a study of Richardson "A" values, which are important in experimentally testing the validity of theoretically derived electron emission equations, such a study should give insight into the reflection of electrons at various potential boundaries. This thesis records an attempt to develop an accurate method of measuring, the contact potential between reproducible metallic surfaces.

Production, characterization, and acceleration of optical microbunches

Sears, Christopher M. S Stanford University 2008 해외박사(DDOD)

Optical microbunches with a spacing of 800 nm have been produced for laser acceleration research. The microbunches are produced using a inverse Free-Electron-Laser (IFEL) followed by a dispersive chicane. The microbunched electron beam is characterized by coherent optical transition radiation (COTR) with good agreement to the analytic theory for bunch formation. In a second experiment the bunches are accelerated in a second stage to achieve for the first time direct net acceleration of electrons traveling in a vacuum with visible light. This dissertation presents the theory of microbunch formation and characterization of the microbunches. It also presents the design of the experimental hardware from magnetostatic and particle tracking simulations, to fabrication and measurement of the undulator and chicane magnets. Finally, the dissertation discusses three experiments aimed at demonstrating the IFEL interaction, microbunch production, and the net acceleration of the microbunched beam. At the close of the dissertation, a separate but related research effort on the tight focusing of electrons for coupling into optical scale, Photonic Bandgap, structures is presented. This includes the design and fabrication of a strong focusing permanent magnet quadrupole triplet and an outline of an initial experiment using the triplet to observe wakefields generated by an electron beam passing through an optical scale accelerator.

Essays on Economic and Behavioral Responses to Constraints

Sears, James University of California, Berkeley ProQuest Disser 2022 해외박사(DDOD)

Throughout life, consumers face constraints that impact all aspects of economic decision-making. Government and agency policies can impose resource constraints, limiting the quantity of a natural resource that a consumer can use or imposing fees that shift individuals away from their preferred consumption levels. Households often face financial constraints, restricting their ability to purchase an optimal consumption basket and preventing families from eating optimal diets. Additionally, social constraints can limit behavior through adherence to social norms, with those who violate these norms suffering disutility due to social pressure or public shame from their peers. In this dissertation, I explore individual and household responses to a range of constraints affecting natural resource use, diet, and mobility patterns. In the first chapter, I explore the responses of urban water customers to price and nonprice water conservation measures. Growing urban water demand combined with a shifting global climate present urban water districts with an acute need for policy approaches that can induce both long- and short-run conservation behavior. Using quasi-experimental long-run variation in prices and exposure to short-run price and non-price policies during severe drought, I estimate the effectiveness of these policy approaches for urban water conservation. This paper is the first to not only identify the water conservation impact of public shame, but also isolate its effect from those due to moral suasion and price-based measures. By following the universe of single family water customers served by a major water district over time, I compare the impacts of different policies on the same households and avoid common sample selection issues. First, I utilize rich administrative panel data to characterize the evolution of causal price elasticities across multiple stages of drought. Next, I leverage quasi-experimental variation in exposure to fees, moral suasion, and public shame to separately identify consumer responses to each during the drought emergency. Demand models yield causal price elasticity estimates of −1 prior to adaptation that attenuate to −0.4 to −0.7 during and −0.2 to −0.5 post-drought, with high-usage households displaying the greatest responsiveness. While subject to behavioral interventions, top water users display no conservation response to excessive use fees. Moral suasion and public shaming show substantial short-run conservation impacts but display immense sensitivity to emergency messaging and consumer beliefs in crisis. Households called out by name in news stories display sizable reductions in water use even after prior exposure to moral suasion and fees, demonstrating the resilience of public shaming’s conservation effect to crowding out by other concurrent policies. These findings yield important implications for the design of future urban water policies that can balance short and long-run conservation goals.In the second chapter, I investigate the extent to which Supplemental Nutrition Assistance Program (SNAP) participants utilize food bank resources to smooth expenditures throughout the benefit month. Many recent works have documented the existence of the “SNAP benefit cycle” in which a non-negligible portion of enrolled households exhaust their benefits shortly after receipt. Lack of benefits late in the month carries large consequences, with negative impacts ranging from reduced energy intake and nutritional content, to increased likelihood of hypoglycemia and pregnancy-related emergency room admissions, along with lowered test performance and increased disciplinary action for students. These effects diminish or are otherwise nonexistent for SNAP households that exhibit consumption smoothing. The ability for low-income households to complement resources from federal poverty programs with a local public good has major implications for household welfare and the value of food bank networks. Using the USDA Food Acquisition and Purchasing Survey (FoodAPS) dataset, I provide evidence suggesting differential behavior patterns immediately upon receipt of benefits for SNAP households that utilize food banks. After summarizing prior studies documenting the presence of the SNAP benefit cycle and the expenditure patterns within the FoodAPS sample, I discuss the observed differences in household characteristics and acquisition behavior for those using and forgoing food banks. Next, I present visual evidence of variation in food bank utilization over time among surveyed households and of stark differences in day-zero SNAP benefit utilization for households that visited food banks during the survey period. Following the presentation of visual evidence, I leverage variation in timing since SNAP benefit receipt and food bank use among surveyed households to estimate empirical models of daily food-at-home expenditures. I find that, while typical SNAP households spend $91-92 more on the day of benefit receipt than on a typical day in the final week of the benefit month, households that use food banks spend $50-54 less that day. This decrease in day-zero expenditure by food bank clients is offset by higher average spending on the next six days, indicating that the expenditure smoothing exhibited by these households primarily occurs in the first week of the benefit month. Subsequent analyses exploring alternate timing specifications and payment methods confirm that the observed expenditure patterns are driven by payments out of SNAP benefits, and that the expenditure smoothing observed by food bank households is largely isolated to the first week following benefit issuance.In the the third chapter, co-authored with Sofia Villas-Boas, J. Miguel Villas-Boas, and Vasco Villas-Boas, we estimate the mobility responses prior and in response to COVID -19 stay-at-home mandates. The recent spread of COVID-19 across the U.S. led to concerted efforts by states to “flatten the curve” through the adoption of stay-at-home mandates that encouraged individuals to reduce travel and maintain social distance. Combining data on changes in travel activity and human encounter rates with state policy adoption timing, we first characterize the overall changes in mobility patterns that accompanied COVID-19’s spread. We find evidence of dramatic nationwide declines in mobility and human encounters prior to adoption of any statewide mandates. Then, using difference-in-differences along with weighted and unweighted event study methods, we isolate the portion of those reductions directly attributable to statewide mandates. Once states adopt a mandate, we estimate further mandate-induced declines between 2.1 and 7.0 percentage points relative to pre-COVID-19 baseline levels. While residents of mandate states soon returned to prior business visitation patterns, the impacts on distances traveled and human encounter rates persisted throughout the observed mandate periods. Our estimates of early mobility reductions and the responses to statewide stay-at-home policies convey important policy implications for the persistence of mobility behavior changes and states’ future re-openings.

Melanin-concentrating hormone modulation of a nucleus accumbens-mediated feeding circuit

Sears, Robert Milton, Jr Yale University 2009 해외박사(DDOD)

The nucleus accumbens shell (AcbSh) contains high levels of receptor for melanin-concentrating hormone (MCH), a lateral hypothalamic peptide critical for feeding and metabolism. Here I demonstrate that MCH action in the AcbSh is sufficient to drive free feeding behavior, whereas a peptide antagonist of the MCH receptor (MCHR1) reduces food intake. In an effort to understand the mechanisms that mediate this phenomenon, I use a combination of biochemical and electrophysiological techniques to find that MCH reduces excitability of AcbSh neurons via two distinct but complementary mechanisms. First, MCH receptor-1 (MCHR1) functions through a Gi/o signaling pathway to reduce phosphorylation of GluR1 at Serine-845 (pSer845). As a consequence, cell surface expression of GluR1-containing AMPARs was reduced along with amplitude of AMPAR-mediated synaptic events (miniature excitatory postsynaptic currents (mEPSCs)). Second, MCH suppresses action potential firing of medium spiny neurons (MSNs) through K+ channel activation. In agreement with in vitro data, MCH is found to reduce neuronal activity in the AcbSh in vivo. As an extension of these findings, a role for AMPAR-mediated neuronal excitability in the AcbSh-mediated feeding behavior was examined. Moreover, studies looking at the role of MCH in other AcbSh-mediated behaviors are presented. In conclusion, MCH-MCHR1 defines a hypothalamic-limbic feeding circuit that acts by reducing excitatory synaptic activity and membrane excitability in the AcbSh. These studies support a general excitability hypothesis for the AcbSh in the control of food intake and related behaviors.

Investigations of surface reconstructions and inverse Stranski Krastanov growth in indium gallium arsenide films

Sears, Lee E University of Michigan 2009 해외박사(DDOD)

Understanding surface reconstructions is an important aspect of controlling the structure of epitaxially grown III-V compound semiconductors. Ternary alloys such as InxGa1-xAs are important components of many electronic and optical devices and a parameter that is critical to the growth of these high quality devices is the presence of abrupt heterointerfaces. As the final microstructures impact the performance of optoelectronic devices, it is important to understand why and under what conditions the reconstructions that initiate these structures form. Understanding the conditions under which these reconstruction domains form, and controlling their shape and size could provide another reliable method of forming spontaneous nanoscale assemblies. The ultimate goal of my research is to develop a quantitative understanding of the connection between surface reconstructions on In0.81Ga 0.19As/InP and film thickness, surface energy, growth conditions, and surface morphology. The individual objectives of this work are to: (1) Understand under which conditions multiple surface reconstructions coexist and the role of thermodynamics. (2) Examine how growth conditions and material properties influence the surface reconstructions that appear for In0.81Ga 0.19As ternary alloys. (3) Look at the relationship between surface reconstructions and film morphology. The combination of scanning tunneling microscopy (STM) and molecular beam epitaxy (MBE) growth is a necessary component of this research because the experimentation tools available on the MBE system allows for the examination of the surface structure during and after growth via reflection high energy electron diffraction (RHEED). The availability of an in vacuo STM allows the observation of the surface reconstructions prior to the formation of an oxide layer. Combining these two techniques allows for a better understanding between the growth procedure of the sample and the presence of surface reconstructions.

Stasis: Flexible transactional storage

Sears, Russell C University of California, Berkeley 2009 해외박사(DDOD)

An increasing range of applications requires robust support for atomic, durable and concurrent transactions. Databases provide the default solution, but force applications to interact via SQL and to forfeit control over data layout and access mechanisms. In principle, a specialized database stack could be built for each application, but such approaches have proven to be impractical. We argue there is a gap between DBMSs and file systems that limits designers of data-oriented applications. Stasis is a storage framework that incorporates ideas from traditional write-ahead logging algorithms and file systems. It provides applications with flexible control over data structures, data layout, robustness and performance. Stasis enables the development of unforeseen variants on transactional storage by generalizing write-ahead logging algorithms. Instead of implementing support for each new storage system from scratch, I have extended Stasis to provide specialized storage mechanisms to a wide variety of applications. It now provides cleaner semantics than similar application-specific approaches would, with significantly less source code than would be required by multiple separate storage implementations. In addition to the conventional write-ahead logging algorithms that Stasis was designed for, it now provides support for large objects, and for log-structured indexes. A number of other extensions, such as distributed recovery algorithms and snapshot-based recovery are under development. This dissertation describes the range of data models and program architectures that have been commonly used in the past, and argues that Stasis is sufficiently general to support most storage applications. It then turns to a description of Stasis' high-level application interfaces and APIs that are designed to allow applications to add their own transactional data structures to Stasis. The performance of a number of such extensions is evaluated, showing that Stasis performs favorably relative to existing systems. The dissertation then turns to a careful definition of Stasis' recovery algorithms, and provides a novel generalization of ARIES, the de facto standard approach to transactional storage. The generalization is particularly promising in the context of distributed systems. Finally, it presents Stasis' lower-level interfaces, providing systems developers and application designers with the ability to tailor high-level transactional primitives to new types of storage hardware and operating system primitives. To the greatest extent possible, the ideas presented within are composable, allowing Stasis' simple implementation to support an unusually wide range of storage architectures.