Browsing by Subject "Memory"

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Accounting for Money: Keeping the Ledger of Monetary Memory in Germany
(2014-01) Dalinghaus, Ursula
This dissertation traces the socio-economic problem spaces and afterlives of the 1990 currency and economic union between West and East Germany, and the parallel process of creating the European single currency. Based on two and half years of full-time multi-sited (geographically and institutionally) fieldwork in Frankfurt am Main (West) and Leipzig (East) Germany, I show the pragmatic challenges of defining, enacting, and materializing relations of solidarity and obligation through new forms of monetary relations. I argue that the long and fraught histories of harmonizing east and west German regions offer critical insights for analyzing the new fault lines emerging between `core' and `periphery' nations in the euro-zone. My project therefore makes a contribution in narrating currency unions as emergent technical and social relationships, through which expert and lay understandings about money and economy are unwound and remade over time. In pursuing this line of inquiry, a key focus of my research included participatory research on the communications work of the German Central Bank (Deutsche Bundesbank) in Frankfurt am Main and Leipzig.
Allocation of attention and the encoding of emotional memories.
(2011-07) Blank, Michael Patrick
Emotional reactivity to visual scenes affects both how we attend to them and how they are remembered, but it is not clear how these attention and memory effects are related. Weapon-focus theories (e.g., Loftus, 1979) suggest that attention is restricted to emotion-provoking parts of scenes, and that such restriction of attention affects the specificity of the memory that is stored. I directly tested whether “weapon-focus-like” restriction of attention predicts subsequent visually-specific memory for emotional scenes by recording eye movements while participants viewed relatively emotional and relatively non-emotional slides during initial encoding. Even though visually-specific memory was equivalent for all types of scenes, different patterns of eye movements predicted subsequent memory for emotional and non-emotional scenes. For emotional scenes only, visually-specific memory was predicted when eye movements were restricted to emotional parts of the scenes during encoding. For non-emotional scenes, visually-specific memory was predicted when more fixations of shorter duration were made, and attention was relatively broadened across the scene during encoding. Experiments 2 and 3 tested whether these patterns of eye movements reflect local or global processing of scenes, but across both experiments, there was no evidence that local and global processing influenced subsequent memory effects. The subsequent memory effects from Experiment 1 were replicated in Experiment 2, but in Experiment 3, a relative broadening of attention – more fixations of shorter duration – predicted subsequent memory for all scenes, a pattern that had only been observed for nonemotional scenes previously. Experiment 4 was conducted to test whether this occurred because emotional reactions to emotional scenes were reduced by having participants simply view each scene, which reduces emotional responses when compared to cases where valence and arousal judgments are made as they were in previous experiments. Experiment 4 replicated the subsequent memory effects from Experiment 3, demonstrating important boundary conditions on the subsequent memory effects established in the first two experiments. These results suggest that qualitatively distinct memory representations may be stored for emotional and non-emotional scenes, but both representations are capable of supporting visually-specific memory.
Beyond the chain link fence: DuSable Park and the contemporary memorial
(2013-12) Krakhmalnikov, Eduard
Within an increasingly fragmented contemporary condition, personal memory begins to challenge the dominant narratives of collective memory. In recent decades, an antithetical reaction to the static state of traditional memorials has led to an emergent typology conceptually seeking tension, debate, and impermanence. The study of this newer memorial typology engages a gap in scholarly literature that is identified between the external, pragmatic reality of a physical memorial and the internal, ethereal quality of personal memory. The capacity to evoke memory-work is explored through the evaluation of four case studies including two seminal countermemorials: the Monument Against Fascism and a projection memorial by Norbert Radermacher. A comparative examination further considers 3 Acres on the Lake: the DuSable Park Proposal Project, a four-year long public art project sited, though without the potential to ever be constructed, on a marginalized, undeveloped parcel in honor of Chicago's first non-native settler. The projects are compared within the framework of four criteria which ask: was the purpose of the project to invoke memory-work, did the project engage with memory stakeholders, is the project a countermemorial, and did the project result in memory-work? It is determined that 3 Acres on the Lake reflects emergent trends in memorialization.
Change and reliability in the evolution of learning and memory.
(2009-05) Dunlap-Lehtilä, Aimee Sue
Why do animals learn to perform some behaviors while others are innate? Why do animals learn some things more easily than others? And, why do animals remember some things better than others? Theoreticians argue that patterns of environmental change explain these patterns, but we have little data to support these claims. I used statistical decision theory to model behaviors and fitness consequences, and experimental evolution studies with fruit flies where I manipulated patterns of environmental change across evolutionary time, to address the first two of these fundamental questions about the evolution of learning. The first experiment tested the effects of the reliability of experience and the fixity of the best action upon the evolution of learning and non-learning across 30 generations. I found that indeed, the interaction of these two variables determined when learning, and when non-learning evolved. The second study was a full factorial experiment manipulating the reliabilities of two modes of stimuli: olfactory and visual. After 40 generations, I found that as predicted, flies in environments where olfactory stimuli are reliable learned better about olfactory than color stimuli, with the same being true for color stimuli. Finally, I addressed the question of why animals remember some things better than others using a dynamic programming technique and experiment with blue jays, finding interactions between rates of change and time. These novel studies show the importance of reliability and change in evolution of learning and memory.
Characterization of Spin Hall and Magneto-ionic Devices for Logic, Memory and Neuromorphic Applications
(2021-07) Sahu, Protyush
This thesis is divided into two parts. In the first part, my research is focused on spin-to-charge conversion in amorphous Gd (40%)-alloyed Bismuth Selenide (60%) (BSG) thin films. The spin Hall effect has emerged as a key proponent for spintronic devices. Such devices typically consist of a bilayer structure made from a spin Hall channel and a ferromagnet. Polycrystalline Bi2Se3 was discovered to have a large spin Hall effect. Spin Hall angle and spin Hall efficiency (SCE) have been key parameters for comparing spin Hall channels. However, the output voltage becomes an essential requirement for spin logic devices, which also depends on resistivity. Gd (40%) alloyed Bi2Se3, grown by sputtering, can fill these gaps for spin logic devices. The material is amorphous, ensuring good scalability. Resistivity as a function of temperature showed strong signs of 3D variable range hopping with a characteristic Mott temperature of 9.7 x 105 K and a room temperature resistivity of 60,000 µOhm.cm. With 5nm in-plane CoFeB, the spin pumping results show good symmetric peaks for different excitation frequencies. The spin to charge conversion efficiency (~ Jc/Js) increased with decreasing thickness of BSG. Second harmonic measurements were performed to characterize thermal effects. The spin-orbit torque was negligible due to the dominance of thermal effects and current shunting through the ferromagnet. Anomalous Nernst effect was found to be the dominant thermal effect. However, it couldn’t explain our spin pumping results due to the lack of BSG thickness dependence and the dominance of the first harmonic voltage. The spin pumping was concluded to originate from the inverse spin Hall effect in BSG layer. My research focuses on irreversible magneto-ionic devices for one-time-programmable memory and neuromorphic applications in the second part of the thesis. Magneto-ionic devices rely on ionic movement through a gate dielectric to manipulate the magnetic properties of a magnetic material. We use Co20Fe60B20 perpendicular magnetic anisotropy (PMA) thin films. CoFeB/MgO interfacial PMA is a consequence of orbital overlapping between Oxygen and transition metal atoms. We further engineer the device to enable field-free magnetization switching. We use an exchange bias field from an adjacent ferromagnet ([Co(0.3nm)/Pd(0.7nm)]3) separated by a non-magnetic layer (Ta), forming a [Co(0.3nm)/Pd(0.7nm)]3/Ta/CoFeB/MgO structure. Pd (111) was used as the seed layer for [Co(0.3nm)/Pd(0.7nm)]3. The final stack is given by: Substrate/Ta(5nm)/Pd(10nm)/[Co(0.3nm)/Pd(0.7nm)]3/Ta(1nm)/CoFeB(1.3nm)/MgO(2nm). XRD and HRTEM were used to characterize the film, which showed distinct layers with some interdiffusion and a polycrystalline Pd(111). This stack is then topped with an ionic gate made from 100nm sputtered SiOx. AHE minor curves showed that the two ferromagnets have weak antiferromagnetic coupling. Application of negative gate voltage decreases the coercivity of CoFeB from ~34 Oe to 16 Oe, signaling a lowered PMA. The exchange bias field magnitude increases from ~ 25 Oe to ~ 45 Oe, due to the decrease in thickness of CoFeB. Major loop measurements show no change in [Co(0.3nm)/Pd(0.7nm)]3 layer with gate voltage. Oxygen ions from SiOx move towards the interface of MgO/CoFeB interface under negative gate voltage. This creates an overoxidation of the interface and destroys the interfacial PMA of CoFeB. This makes the CoFeB layer go from a bi-stable to a monostable state, resulting in a pathway for a field-free magnetization switch.
Cognitive and Emotional Sequelae of Exposure to Maternal Depression: Memory Functioning as a Neurocognitive Correlate of Internalizing Symptomatology
(2016-07) Ng, Rowena
Children exposed to maternal depression are at greater risk for depressive disorders later in life. Researchers have suggested that these youth experience marked stress from the care provided by parents afflicted with mental illness; in turn, chronic exposure to the toxic environment alters neural substrates involved in emotion and stress regulation, such as the hippocampus and prefrontal cortex. However, current literature on neurobehavioral functioning of these at-risk youth relative to healthy peers is sparse and conflicting. Furthermore, it is unclear whether these neurocognitive indices, such as memory functioning, are predictive of internalizing symptomatology in these youth. Accordingly, this study examines the relationships between chronic exposure to maternal depression, severity of mother’s recent symptomatology, and child’s earlier internalizing symptomatology with later memory and psychological functioning (internalizing and externalizing behaviors). A total of 100 children and their parents were assessed when the child was 18 months old and followed up at 5 and 9 years of age. Of these youth, 50 child participants had mothers who had major depression at 18 months (i.e., depressed caregivers, DC), and 50 were those with nondepressed, healthy caregivers (NC). Mothers with depression were coded into three groups: chronic depression, recurrent depression, and non-recurrent depression. Children’s caregiver completed the Child Behavioral Checklist (CBCL) when the child was 18 months, 5 years and 9 years to determine overall internalizing and externalizing symptomatology observed. Child participants also completed the self-report version of the Child Depression Inventory, California Verbal Learning Inventory, and subtests from the Wide Range Assessment of Memory and Learning battery to assess their depressive symptomatology, verbal memory skills, and visual memory functioning respectively. Multiple hierarchical regressions were used to examine associations between chronic maternal depression, recent maternal depression severity, and child’s earlier internalizing symptomatology with later memory and emotional functioning at 9 years. Linear mixed effects model and analysis of covariance were applied to examine the growth pattern for internalizing symptomatology based on the CBCL. Broadly, results indicate that more chronic exposure to maternal depression, but not mothers’ recent symptomatology, is associated with lower verbal memory performance and greater internalizing and externalizing symptoms in the offspring. Internalizing symptomatology of children at age 5 years was not predictive of later memory functioning at 9 years, but was associated with increased internalizing and externalizing symptoms later at 9 years. Importantly, memory functioning, a neurobehavioral index of hippocampal functioning, was not predictive of concurrent psychological functioning (i.e., both externalizing and internalizing symptoms). Finally, both DC and NC youth showed similar non-linear, developmental patterns in their internalizing symptomatology from 18 months to 5 and 9 years; however, DC youth showed elevated symptoms relative to NC peers at baseline, a disparity that persisted by 9 years of age. These findings broadly support the postulation that chronic exposure to maternal depression may impact later hippocampal functioning, as indicated by lower verbal memory performance in offspring. However, findings also indicate that memory performance is not a strong predictor of concurrent psychological functioning, despite that this factor behaviorally indexes the functional status of the hippocampus, a neural substrate involved in stress regulation. Findings highlight importance of engaging depressed mothers in interventions for self and parent-child relationship earlier to reduce the persistent and negative effects of maternal depression on their offsprings’ development.
Decoloniality as Praxis: Restoration, Freedom, and Justice
(2024-08-25) Oates, Evangela Q.
In our consideration of how we develop and enact strategies in which decoloniality of libraries may be realized, Black American librarians must have a collective understanding of the urgency of situating our ways of knowing and the curation of knowledge as part of epistemic restoration and justice. As noted by Ndlovu-Gatsheni (2019) “the intention of colonialism was destroying other civilizations rather than blending different worlds…colonialism engaged in a redefinition of the human species, socially classifying and racially hierarchizing rather than inventing common humanity” (pp. 202-203). Given the current fascist and genocidal (global) practices of white supremacy, how might we, practitioners, administrators, and teachers, reclaim our epistemic heritage to reimage libraries beyond their current functions? In this session, the presenter will define decoloniality, show examples of cultural genocide (history, culture, and memory) and epistemic injustice, and invite the attendees as thinking partners to envision libraries as not just physical manifestations of knowing and memory.
Diet induced neuroinflammation and cognitive decline
(2017-12) Duffy, Cayla
The prevalence of obesity in the U.S. is over 50%, and midlife obesity is a clinical risk factor for cognitive impairment and the onset of neurodegenerative diseases such as Alzheimer’s disease (1-3). Inflammation of the brain (neuroinflammation), a state associated with progressive neuronal loss, is heightened in cognitive decline and obesity (4-7). Consumption of high fat diets (HFD), specifically those high in the saturated fatty acid palmitic acid (C16:0; PA), exacerbate neuroinflammation, neurodegeneration, and cognitive impairment (8-16). The research presented within this thesis seeks to define the role of microglia in the context of obesity and cognition. The central hypothesis of my thesis is that high fat diets induce microglial activation resulting in altered immunometabolic response, neuroinflammation, and subsequent cognitive decline. While neuroinflammation normally increases with age, risk of neuroinflammation and cognitive impairment is exacerbated by obesogenic diets (14). The findings from this work will provide a deeper understanding of diet-induced neuroinflammation, and will facilitate the development of novel therapeutics for cognitive disorders. This research has focused on utilizing basic science approaches to understand the effects of high fat diets on the central nervous system. Highlighted below are the major findings from my dissertation research. 1) Orexin A-induced neuroprotection: Excess intake of dietary PA increases the risk for developing obesity (17, 18). PA is known to induce neuronal cell death in the hypothalamus, a region of the brain important in regulating feeding behaviors (11, 19-21). One potential target to prevent this is orexin A, a hypothalamic signaling protein important in promoting obesity resistance that also has neuroprotective properties (22). I hypothesized that orexin A would protect against PA-induced hypothalamic cell death. To test this, I evaluated the response of hypothalamic neurons to orexin A and PA. I demonstrated that orexin A decreases PA-induced programmed cell death and stabilizes expression of the pro-survival gene Bcl-2. I also demonstrated that orexin A protects against PA-induced damage to the mitochondria (measured via changes in reactive oxygen species (ROS) and mitochondrial respiration). These data support that orexin A protects against PA-induced hypothalamic cell death. 2) Orexin A signaling in PA-activated microglia: Obesity is associated with chronic low-grade inflammation, characterized by increased circulating pro-inflammatory signals and immune cell activation (8, 11, 23). Microglia are highly responsive to changes throughout the brain, and communication between neurons and microglia depends in part on pro- or anti-inflammatory secreted signals (cytokines and chemokines). Furthermore, PA promotes microglia to release pro-inflammatory signaling cascades (9, 24-26). My next goal was to determine how PA and orexin A treatment influences microglial secretion and activation states. To test this, I exposed microglial cells to orexin A and PA and measured changes in secreted signals. I demonstrated that orexin A treatment reduces PA-induced upregulation of pro-inflammatory markers and increases anti-inflammatory markers in microglia. Next, I sought to determine if the factors secreted by the activated microglia influenced neuronal survival. To test this, I filtered the microglial cell culture media to remove excess orexin A and PA while retaining the secreted cytokines, exposed neurons to this filtered supernatant, and determined neuronal cell death. I found that neurons exposed to media from orexin A-treated microglia have increased cell survival compared to those treated with media from PA-activated microglia. This result demonstrated that microglia exposed to orexin secreted protective signals that protected neurons, whereas microglia exposed to PA alone secreted harmful cytokines that resulted in neuronal cell death. My findings are the first to demonstrate that orexin A modulates PA-activated microglial cells. 3) Loss of orexin and high fat diet increases cognitive impairment: Obesity is recognized as a risk factor for development of cognitive disorders such as Alzheimer’s disease (3). Moreover, deficiencies in orexin signaling have been linked to neurodegenerative diseases. My overall hypothesis was that reduced orexin signaling will increase diet-induced cognitive decline through a microglial-mediated pathway. To test this, I used wild type (WT) mice or a mouse model of orexin loss to determine differences in a cognitive task. I found that mice lacking orexin showed significant impairments in cognition vs. WT mice. Next, to determine the effects of HFD on microglia and cognition, mice were placed on a HFD or remained on normal chow, and the cognitive task was retested at 2 and 4 weeks. I demonstrated that cognition was impaired and microglial activation was increased in mice lacking orexin given a HFD vs. WT mice. Collectively, my results show that orexin loss impairs cognition, and that HFD accelerate cognitive deficits and the onset of neuroinflammation in orexin-deficient mice. 4) Fatty acid binding protein 4-uncoupling protein 2 axis in modulating microglia and cognition: Fatty acid binding proteins (FABP) are lipid chaperones regulating metabolic and inflammatory pathways in response to fatty acids (27, 28). To further define a mechanism for diet-induced microglial activation and cognitive decline, I sought to determine if the FABP4-UCP2 (uncoupling protein 2) axis is involved in neuroinflammation. I hypothesized that inhibition of microglial FABP4 would upregulate UCP2 and attenuate PA-induced inflammation. To test this, I measured hypothalamic gene expression changes in WT mice and mice lacking FABP4 (AKO mice) fed a HFD. I found hypothalamic tissue from AKO mice exhibit increased UCP2 expression and reduced pro-inflammatory makers compared to WT mice. Next, I pharmacologically inhibited FABP4 in microglia and demonstrated increased UCP2 expression and reduced PA-induced pro-inflammatory response and ROS production. Further, this effect is negated in microglia lacking UCP2, indicating the FABP4-UCP2 axis is pivotal in obesity-induced neuroinflammation. Finally, to determine if the FABP4-UCP2 axis was involved in attenuating diet-induced cognitive decline, WT and AKO mice were fed a HFD for 12 weeks and tested in a panel of cognitive tasks. I found that mice maintained on a HFD had reduced locomotor activity. Further, WT mice maintained on HFD had impaired memory, and AKO had attenuated HFD-induced memory impairment. Collectively, these results indicate that the FABP4-UCP2 axis is a link between HFD, neuroinflammation, and cognitive impairment.
Enhancement of learning: Does sleep benefit motor skill memory consolidation?
(2010-12) Borich, Michael Robert
Purpose: It remains unclear how the brain best recovers from neurologic injury and how to optimally focus rehabilitation approaches to maximize this recovery. Recent research has indicated that sleep may augment this recovery. Sleep has been shown to benefit memory consolidation for certain motor skills, but it remains unclear if this relationship exists for explicit, continuous, goal-directed motor skills with rehabilitation applications. We aimed to determine the neurobehavioral relationship between finger-tracking skill development and sleep following skill training in young, healthy subjects. Methods: Forty subjects were recruited to receive motor skill training in the morning (n=20) or the evening (n=20). Measures of skill and cortical excitability were collected before and after training. Following training, each group had a post-training interval consisting of waking activity or an interval containing sleep. After this twelve-hour interval, skill performance and cortical excitability were reassessed. Subjects underwent another twelve-hour interval containing either waking activity or a sleep episode and came back for a second assessment, twenty-four hours after training. A subset of subjects (n=10) underwent the same procedures except the training period involved simple, repeated movement of the finger. Results: Skill performance improved after training and then continued to improve offline during the first post-training interval. Improvement was not enhanced by sleep during this interval. Cortical excitability was not substantially altered by training but was related to level of skill performance at follow-up assessment. Sleep quality was also found to be related to level of skill at follow-up assessments. The skilled training period did not lead to significantly improved performance compared to simple movement activity. Discussion: These data suggest that sleep is not required for offline memory enhancement for a continuous, visuospatial finger-tracking skill. These findings are in agreement with recent literature indicating the type of motor skill trained may determine the beneficial effect of sleep on post-training information processing. These results, combined with related studies in patient populations, provide a foundation to evaluate the relationship between sleep, changes in neural activity, and the time course of continuous visuospatial motor skill learning in individuals following neurologic insult.
The generation and maintenance of T Helper 17 cells in response to bacterial infection
(2012-09) Linehan, Jonathan L.
Multiple studies have identified Interleukin-6 (IL-6) and Transforming Growth Factor-beta;1 (TGF-β1) as sufficient to induce T helper type-17 (TH17) differentiation in vitro, but it is unclear whether these factors are necessary, and if so, what the cellular source of these factors is in the context of a TH17 inducing infection in vivo. Moreover, studies of the TH17 response have focused mainly on the effector phase and it is currently unclear whether these cells persist into the memory phase. To address these questions, we used mouse models of immunity to the extracellular bacterium Group A Streptococcus pyogenes (GAS) and the intracellular bacterium Listeria monocytogenes (LM), along with a sensitive peptide:Major Histocompatibility Complex II (pMHCII) tetramer and magnetic bead-based enrichment method to study the differentiation of naïve, polyclonal, GAS or LM pMHCII-specific CD4+ cells into TH17 cells. We found that an intranasal route of infection resulted in TH17 differentiation, while an intravenous route of infection resulted in T helper-type 1 (TH1) differentiation after either GAS or LM infection. We also found that IL-6 and TGF-beta;1 were necessary for TH17 differentiation in response to intranasal GAS infection in vivo. We identified a hematopoietic source of IL-6 and a dendritic cell source of TGF-beta;1 necessary for this differentiation. Lastly, we found that intravenous LM infection induced a long-lived TH1 memory population, while intranasal LM infection induced a short-lived TH17 population. Combined, this work supports a model whereby dendritic cells residing in upper respiratory tissues induce TH17 cell differentiation through the production of IL-6 and TGF-beta;1, resulting in a short-lived population of TH17 cells.
Histories in its Walls: La Moneda, memory and reconciliation in Post-Authoritarian Chile.
(2010-08) Strasma, Mary Grace
In the contentious struggles over the interpretation of Chile's past, the presidential palace, La Moneda, exemplifies the dynamic interactions of history, memory, place, and national identity. This dissertation argues that the actual physical site of La Moneda has been used throughout Chile's history as a stage for the performance of legitimacy and citizenship, while its image - particularly the image of the building in flames on September 11, 1973 -- has been used as both a symbol and, more recently, a text. In 2000, after a decade of post-authoritarian transition and the accompanying struggles over memory of the 1973 military coup and the Pinochet dictatorship that followed, then-President Ricardo Lagos took the symbolic step of re-opening of La Moneda to visits by ordinary Chileans. This created a unique opportunity to examine, through visitor surveys and interviews, how the site functions as a focus of Chilean historical discourse and governance. While the reopening was an important element of the Lagos administration's push for reconciliation, the administration was not able to control fully the interpretation or experience that visitors drew from La Moneda. This reveals the tensions inherent in any historic or emblematic site. Further, this history of the uses of La Moneda by Chilean leaders and of the public reactions to it demonstrates that despite Lagos' desire to declare Chile's transition complete, memory struggles related to the historical interpretation of the military coup of 1973 were still present as late as September 2003, as seen in the symbolic dimensions of this place.
How stimulus similarity impacts spacing and interleaving effects in long-term memory
(2014-06) Archambault, Katrina B.
In this study, three experiments examined the impact of stimulus similarity on the benefits of spacing and interleaving for long-term memory. Two laboratory-based experiments (Experiments 1 and 2) and one classroom-based experiment (Experiment 3) were conducted. In Experiment 1, an advantage for interleaving relative to massing stimuli during encoding was observed as a greater proportion of correct responses on a categorization test for birds and paintings. This advantage was significantly greater when the stimuli were similar (e.g., interleaving different bird categories) rather than dissimilar (e.g., interleaving bird and painting categories). In Experiment 2, no advantage of interleaving relative to massing stimuli was observed in either the proportion of correct responses or response times on a categorization test for abstract visual stimuli. In Experiment 3 no significant differences between massed and interleaved study conditions were observed on a categorization test for textual materials. Although the results from this study are preliminary, the pattern of results in Experiment 1 suggests that interleaving may be most beneficial when the interleaved stimuli are similar rather than dissimilar.
It was difficult in Zimbabwe: a history of imprisonment, detention and confinement during Zimbabwe’s Liberation struggle, 1960-1980
(2008-10) Munochiveyi, Munyaradzi Bryn
Between 1961 and 1979, African nationalists engaged in a protracted guerrilla war which ultimately ended white colonial rule in Rhodesia (Rhodesia was Zimbabwe's colonial name). The settler regime responded by imprisoning a large number of activists and those whom it suspected of being aligned with the guerrillas. In this thesis, I am particularly interested in the histories and lived experiences of African political detainees and prisoners whose experiences and contributions towards the liberation struggle have been rendered invisible by dominant historical and state narratives. Broadly, this dissertation argues that although political imprisonment in this period was an extreme version of the colonial experience that combined spatial confinement with curtailed freedoms, racialized abuse, racial segregation, and heightened repression, the prison was also a terrain of struggle. By describing the Rhodesian prison as a terrain of struggle, I mean that the prison was doubly a space of repression and subversion, and that political prisoners were capable of challenging and negotiating their incarceration. I therefore seek to establish that although the Rhodesian prisons were centers of brutality, political detainees were not passive recipients of state penal terror as they actively negotiated, challenged, and subverted oppressive penal regulations. The thesis also argues that, as political hostages of the Rhodesian regime, detainees played a crucial role towards dislodging colonial rule both as producers of powerful critiques of the colonial regime from inside the prison confines and as symbols of African resistance. Methodologically, this project relies primarily upon the oral testimonies of ex-political prisoners, and the prison letters that most of them wrote whilst they were in detention. I also make use of little used documentary evidence such as court records and local African and state-controlled newspaper accounts.
The Kaleidoscopic Unsaid: Voice, Memory, and Body of the Afro-Americas
(2019-08) Ramos Flores, Hector
This dissertation explores the self-representation of Afro-diasporic subjects in the Americas through the kaleidoscopic unsaid. In this metaphor the kaleidoscope is the global power structure while the unsaid is the articulation that emerges for these subjects within this world order. Using three case studies that reveal how the power structure shifts and moves within the local structures, I show how Black subjects constantly navigate a self-representation that is malleable and constantly shifting that both re-inscribes and resists the power schema. In the first chapter I demonstrate how the Autobiografía de un esclavo (1836) of Juan Francisco Manzano encounters issues of voice and agency for the former enslaved person. The second chapter engages with memory and trauma of Black subjects in The Brief Wondrous Life of Oscar Wao (2006) by Junot Díaz and in The Farming of Bones (1996) by Edwidge Danticat. Finally, with the films Pelo malo (2013) by Mariana Rondón and La playa D.C. (2012) by Juan Andrés Arango Garcia I show how the Black male body and hair fluid sites of resistance. Together these three chapters show how the subjects in these cultural productions maneuver in such a way that showcases their multifaceted reality, pushing against the often one-dimensional representations that are imposed on them. Ultimately this dissertation attempts to decolonize stagnant representations of Black bodies in the Americas.
Los Campos de la Memoria: the concentration camp as a site of memory in the narrative of Max Aub.
(2009-08) Dickey, Eric
This dissertation explores constructions of memory and testimony in the concentration-camp narrative of Spanish author Max Aub. One of the most forgotten chapters of all Spanish Civil War and exile history is that pertaining to the Spanish Republicans who were interned in French concentration camps after the end of the Civil War. The concentration camp occupies a central place of memory and becomes a recurrent symbol and leitmotif that reappears in various manifestations throughout much of Aub's narrative work. In this dissertation, I investigate the symbolic value of the concentration camp as a discursive vehicle, a lieux de mémoire, that allows Aub to reconstruct his traumatic memories of the camp and convert them into narrative memory through writing. I examine the fictionalization of testimony in various literary genres and media, and analyze the use of different narrative strategies of remembrance and memory work to convey the experience of internment. My analysis of the camps goes beyond the traditional psychoanalytical conception of trauma as an individual phenomenon by exploring the collective dimension of trauma and memory. Aub's recounting of his own personal experiences exceeds a mere autobiographical portrait as it speaks in a collective voice that seeks to share the suffering of fellow exiles and camp survivors in order to form a new collective or group consciousness. Writing about the camps represents Aub's way of bearing witness to his trauma at the same time as it is his way of fighting the silence that has surrounded this experience shared by so many fellow Republican exiles. Through his testimonial writing, in both its individual and collective dimensions, Aub succeeds in a long-cherished goal, that of reinserting the memory traces of the Civil War, exile, and the camps back into Spain's historical and literary discourse.
The Media of Memories: Argentine and Brazilian Transitional Justice as Seen on TV
(2019-03) Hill Cosimini, Amy
Grounded in my own observation of the recent string of Latin American shows, such as Montecristo (Argentina, 2008) and Amor e revolução (Brazil, 2011), which directly confront traumatic national pasts, this project investigates what representative 21st century Argentine and Brazilian fictional and testimonial televisual accounts (telenovelas, miniseries and testimonial interviews) communicate about the role of television in the construction and mediation of the officially sanctioned memory narratives promoted by normative transitional justice mechanisms. In this vein, this project—The Media of Memories: Argentine and Transitional Justice as Seen on TV—poses a series of interrelated questions:1) How can transitional justice processes take place on the small screen? 2) How can understanding these televisual practices advance existing theories on transitional justice as it relates to the right to memory, and the protection of memory’s productive problematics—such as the respect for silence, gaps and hauntings inherent in remembering mass atrocities? And finally, 3) What alternative spaces for advocacy, if any, are opened up by these television programs? In the end, my project contends that television programs, in the Argentine and Brazilian cases, have the potential to operate as malleable discursive spaces that question hegemonic memory regimes and complicate normative truths put in place by the State. Furthermore, the telenovelas, miniseries, and testimonial interviews analyzed throughout this project function, to varying degrees, as dynamic memory mediums that simultaneously promote memory as memory entrepreneurs, profit from memory, frame what truths should be remembered, and digitally transmit memory. Thus, I maintain that moving televised images have the potential to operate as a widely accessible form of transitional justice that not only translates judicial arguments to the mass populace, but also provides alternative spaces for the re-definition of justice and the performance of multilayered activism. Through its visual depiction and fictionalization of the limit experiences of collective traumas, television stages those realities that resist verbal narration and operates as a form of symbolic reparations that restores dignity to victims, develops a more inclusive narrative of the past, and protects the right to memory.
Memory Design for Centimeter-Scale Organic and Nanometer-Scale Silicon Technologies
(2012-07) Zhang, Wei
Low power memory is always desired due to its significance in many large-scale applications. It is important to emerging technologies such as organic electronics, since it is an indispensible component to extend the technology towards larger application scope with complicated functionalities. It is also a hot topic in the mature silicon technology because the device scaling makes memory designs challenging with increasing leakage currents and process variations. Organic electronics deals with conductive polymers and plastics, and is capable of realizing large area flexible applications, which cannot be fulfilled by modern silicon technology. Conventional organic devices require a high operation voltage due to its low carrier mobility. Ion-gel gated OTFTs (gel-OTFTs), however, deliver unusually high gate capacitance through an electrolyte-gated structure, and therefore offer sufficient drive currents under a low voltage. Being an emerging technology, few attempts have been made on organic memory designs. In this dissertation, we first propose an improved design-fabrication-testing flow to significantly facilitate the entire process, which boosts the design efficiency and fabrication yield and thus enables the implementation of complex circuits such as memory array. An organic process design kit (OPDK) with various modeling approaches allows designers to easily design organic circuits in a similar way as that in silicon technology. Various circuit components including logic gates, ring oscillators and a D-flipflop were demonstrated and a general purpose organic dynamic memory cell was proposed for the first time. The cell, known as a DRAM gain cell, achieves a sub-10nW-per-cell refresh power with a retention time of over 1 minute, which is 5 orders of magnitude longer than that in silicon designs. The same DRAM gain cell architecture is also found potential as embedded memory in the modern silicon technology, where the prevailing 6T SRAM is suffering from leakage power and poor low voltage margin when devices keep scaling down. In this dissertation we report the first variation-aware performance analysis on the silicon gain cell and reveal that conventional corner simulations are no longer valid in capturing worst cases of gain cells. Insights can be obtained through the various analysis approaches described in the dissertation to benefit future memory design strategy and device optimization. With innovations in cell structure and peripheral circuitry, the silicon gain cell performance can be further enhanced to compete with the mainstream 6T SRAM. In this dissertation, we for the first time experimentally demonstrate a gain cell design with write-back-free read operations, utilizing its non-destructive read nature to improve the read speed into GHz regime without sacrificing retention time. Various circuit techniques including a local-sense-amplifier architecture are proposed to eliminate the need of a complex current-sensing scheme, and a dual-row-access mode is proposed for further power saving in half-utilization scenarios. The test chip in a 65nm low power process achieves a 23.9% power saving compared to a 6T SRAM at 0.6V retention voltage and an additional 27.8% power saving during cases when only half array is needed.
Memory profiling and management.
(2011-05) Chen, Tong
The performance gap between the CPU and memory has been widened after decades of advance in technologies. Memory operations have become more and more expensive compared to the logical and arithmetical operations. This dissertation addresses two compiler techniques related to memory optimizations: memory disambiguation profiling and local memory management. The static memory disambiguation analyses in a compiler, such as alias analysis and dependence analysis, are often limited by the lack of runtime information and conservative nature of compiler analysis. Thus, many optimization opportunities may be lost due to the imprecise or overly conservative analysis result. The dissertation proposed a new approach, which aimed to produce the memory disambiguation information from profiling. Two profiling methods, alias profiling and dependence profiling, are proposed. Special hash method is designed to make the profiling efficient. Software-based sampling method is used to further reduce the overhead. Studies on the impact of granularity of memory checking, path sensitivity and context sensitivity are conducted with this profiling tool. The overhead can be reduced to only 30% of the total execution time in this expensive pure software profiling. A speculative partial redundancy elimination optimization based on the profiling result and the special hardware, ALAT, in Itanium processor, is also presented. This optimization can cause up to a 10% improvement to Spec2000 benchmarks, which demonstrates the effectiveness of the profiling methods. In some of the multi-core systems, some local memory is attached to the core for fast access, but without cache coherence support. This dissertation proposes several methods to manage the local memory automatically by compiler with runtime library. There are two common methods, software controlled cache and direct buffering, commonly used to manage the local memory. In this dissertation, an analytic model for a compiler to decide the number and size of the buffer that should be used to optimally overlap the data transfer and computation is presented. How to integrate the two methods is also discussed in the dissertation. Novel data flow analysis and runtime checking schemes are designed for the integration. A data prefetching method for software cache is also presented. All these new methods are implemented in IBM's compiler for Cell and have proven to be effective and efficient in local memory management.
Modeling and Fabrication of Low Power Devices and Circuits Using Low-Dimensional Materials
(2016-07) Kshirsagar, Chaitanya
As silicon approaches its ultimate scaling limit as a channel material for conventional semiconductor devices, alternate mechanisms and materials are emerging rapidly to replace or complement conventional silicon based devices. Attractive semiconducting properties such as high mobility, excellent interface quality, and better scalability are the properties desired for materials to be explored for electronic and photonic device applications. Hybrid III-V semiconductor based tunneling field effect transistors (TFETs) can provide a strong alternative due to their attractive properties such as subthreshold slopes less than 60 mV/decade, which can lead to aggressive power supply scaling. Here, InAs-SiGe-Si based TFETs are studied in detail. Simulations predict that subthreshold slopes as low as 18 mV/decade and on currents as high as 50 µA/µm can be achieved using such a device. However, the simulations also show that the device performance is limited by (1) the low density of states in the source which induces a trade-off between the source doping and the subthreshold slope, limiting power supply scaling, and (2) direct source-to-drain tunneling which limits gate length scaling. Another approach to explore low power alternatives to conventional semiconductor device can be to use emerging two-dimensional (2D) materials. In particular, the transition metal dichalcogenides (TMDs) are promising material group that, like graphene, these material exhibit 2D nature, but unlike graphene, have a finite band gap. In this work, the off-state characteristics are modelled for MoS2 MOSFETs (metal–oxide–semiconductor field-effect transistors), and their circuit performance is predicted. MoS2 Due to its higher effective masses and large band gap compared to silicon it is shown that MoS2 MOSFETs are well suited for dynamic memory applications. Two of such circuits, one transistor one capacitor (1TIC) and two transistor (2T) dynamic memory cells have been fabricated for the first time. Retention times as high as 0.25 second and 1.3 second for the 1T1C and 2T cell, respectively, are demonstrated. Moreover, ultra-low leakage currents less than femto-ampere per micron are extracted based on the retention time measurements. These results establish the potential of 2D MoS2 as an attractive material for low power device and circuit applications.
Neurocognition in college-aged daily marijuana users
(2013-12) Petrosko Becker, Mary
Marijuana is the most commonly used illicit substance in the United States. Use, particularly when it occurs early, has been associated with cognitive impairments in executive functioning, learning, and memory. This study comprehensively measured cognitive ability as well as comorbid psychopathology and substance use history to determine the neurocognitive profile associated with young adult marijuana use. College- aged marijuana users who initiated use prior to age 17 (n=35) were compared to demographically-matched controls (n=35). Marijuana users were high functioning, demonstrating comparable IQs relative to controls and relatively better processing speed. Marijuana users demonstrated relative cognitive impairments in verbal memory, spatial working memory, spatial planning, and motivated decision-making. Comorbid use of alcohol, which was heavier in marijuana users, was unexpectedly found to be associated with better performance in many of these areas. This study provides additional evidence of neurocognitive impairment in the context of early onset marijuana use. Complications in determining cause-effect associations are discussed.

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