Essentially Shimmering: Contemporary Poetics at the Edges of Materialism

Simon, Emily ProQuest Dissertations & Theses Brown University 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

prelude | what is essentially shimmeringEarly in her azure-saturated, poetic treatise Bluets, contemporary writer Maggie Nelson enumerates various ambient factors that are enmeshed with our perception of a seemingly self-contained and self-evident quality like color:Try, if you can, not to talk as if colors emanated from a single physical phenomenon. Keep in mind the effects of all the various surfaces, volumes, light-sources, films, expanses, degrees of solidity, solubility, temperature, elasticity, on color. Think of an object’s capacity to emit, reflect, absorb, transmit, or scatter light; think of “the operation of light on a feather.” Ask yourself, what is the color of a puddle? Is your blue sofa still blue when you stumble past it on your way to the kitchen for water in the middle of the night; is it still blue if you don’t get up, and no one enters the room to see it? (20).Nelson entreats readers to eschew our customary, facile sense of “color” as an isolable, singular, and determinate property of an object—what anthropologist Michael Taussig calls “the spot-of-color-on-the-page idea of color”—in favor of the illimitable “operation of light on a feather” or the indiscernible, inconstant hue of a “puddle” (249). Framed by these protean phenomena, “color” is evidently not something, but rather a luminous and ongoing effect, a processual coloring. And so, we recognize the impossibility of answering her question about the color of a puddle not only because we can pretty fairly say that a puddle (and which puddle?) does not have a single color—it may be bright blue or dark grey, shining silver or muddy brown—but because these different hues also indicate the way in which the quality of color more intimately constellates, and expresses, a welter of interlocking and shifting physical and perceptual factors. “What is the color of a puddle” also means: Is the puddle cloudy or translucent? Gleaming or matte? Shallow or deep? Surface tension, the weather, temperature, shade all converge and conspire in the articulation of this momentary tone.Such a luminously imbricated vision of color makes it hard to say for certain what, exactly, the color in question is. Later in this same section of Bluets, Nelson frames the historical development of chromatic schema (color wheels, palettes, etc) as a retroactive effort to resolve this constitutive undecidability: to make sense, she writes, out “of what is essentially shimmering” (20). In this particular instance, “what is essentially shimmering” refers the way that colors cannot be stabilized into a singular, ineluctable hue (like blue), but are rather perpetually gradated by variations in all of the different factors that Nelson lists (light, solidity, texture, perspective). At the same time, the case of color gestures to a more general indistinction between the physical and the phenomenal that animates the poetry and thought around which my dissertation revolves. This indistinction is what is encompassed by the gorgeously paradoxical notion of the “essentially shimmering,” or the sense in which the materiality of a thing (and especially of a surface) is inextricably bound up with and modulated by fluctuations in time and perception. Nelson’s formulation of this dynamic claims as an intrinsic, perdurable attribute (the “essential”) a phenomenon that is contingent, superficial, and mercurial (“shimmering”). That is, to be essentially shimmering is to exist at the uneasy or impossible intersection of a received distinction between a thing’s material reality or facticity and what would seem to be its mere appearance, those transient sensations interposed by the film of subjectivity or passing angles of light.1 It insinuates a materialism that at the same time verges on the immaterial.

"A Tale of 2-Spheres": How Conformal Symmetry, Chaos, and Some Elementary Algebra Led to Insights in Black Holes and Quantum Cosmology

Liu, Chang ProQuest Dissertations & Theses Brown University 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The unification of quantum mechanics and general relativity is the holy grail of fundamental theoretical physics. This thesis represents a small part of that effort, where we consider a number of problems that might be of interest to the theoretical studies of black holes and quantum cosmology. Why study black holes and quantum cosmology, one might ask? The answer lies in the fact that they are the only two systems where it is necessary to apply quantum mechanics and general relativity simultaneously. In particular, they both have event horizons, which are global structures of the spacetime that prevent events from making causal contact. They therefore have become the primary arenas where logical incompatibilities of quantum mechanics and general relativity can be made most transparent. One of the most dramatic incompatibilities is the black hole information paradox, which concerns the unitarity of processes that involve the formation and the evaporation of black holes. This thesis will first discuss a proposed resolution to the information paradox called black hole complementarity, and a closely linked issue known as quantum scrambling, in particular in the context of a 2D conformal field theory. We will then present a microscopic quantum model of the de-Sitter universe that incorporates the required quantum scrambling on the cosmological horizon. This quantum model of cosmology is a so-called “holographic” map between the stretched horizon of the de-Sitter spacetime and the static patch (colloquially known as the “bulk”). Continuing in a similar vein, the rest of the thesis will be concerned with building holographic theories between flat spacetime and its boundary, and we present two holographic theories of the flat spacetime, first for massive scalar particles and then extending the results to gravitons. As these all have something to do with mappings between boundary 2-spheres and their bulk, this is therefore a story of building holography on 2-spheres. Hence the title of this thesis.

Search for the Decay of Standard Model Higgs Bosons to a Charm Quark-Antiquark Pair Using 128 Fb-1 of CMS Proton-Proton Collision Data at √s = 13 TeV

Burkle, Bjorn ProQuest Dissertations & Theses Brown University 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

On July 4th, 2012 the CMS and ATLAS collaborations announced the joint discovery of the Higgs boson [19, 20]. The Higgs had been predicted as a fundamental particle since 1964 [21], with its primary feature being that it generates the masses of the fundamental particles. Since then, the continuation of the study of the Higgs and measuring its couplings to the other fundamental particles has been a primary goal of both collaborations, and is a major factor for the planning for future collider experiments [22, 23, 24]. As it currently stands, physicists have now been able to directly observe the Higgs boson couplings to the following particles, and found that the observations agree with theoretical predictions: the W [25, 26], the Z [27, 28], top quarks [29, 30], bottom quarks [31, 32], and taus [33, 34]. Additionally, there are now measurements of the Higgs boson’s coupling to muons [35, 36], with evidence of the process reported by the CMS collaboration. In this thesis, I present the continuation of our quest to understand the Higgs boson via the latest CMS search for a Higgs boson decaying to charm quarks, giving us a direct method for measuring the charm quark Yukawa-coupling to the Higgs field. This is a continuation of a study performed on a set of CMS data collected in 2016 [37], with the new iteration now being performed on the full CMS Run 2 data set consisting of 138 fb−1 of data and introducing a plethora of improvements to the overall analysis techniques.The thesis is written with the narrative focusing on the H → cc analysis, with discussions of additional projects I worked on primarily present in the appendix. As such, the thesis is formatted as follows: Chapter 2 contains an introduction to the main theoretical concepts needed to understand this thesis. It discusses the Standard Model and the mechanisms of the Higgs boson. It then ends with an additional section on proton-proton collisions with a primary focus on the parton distribution function, its implications for the Large Hadron Collider, and how Higgs bosons can be produced from proton-proton collisions.Chapter 3 then gives an overview of the Large Hadron Collider (LHC) and the Compact Muon Solenoid (CMS) detector which was used to collect the data for the primary study presented in this thesis. In discussing the LHC, I walk the reader through the steps taken to go from stable H2 gas to creating co-rotating bunches of protons traveling at 99.9999991% the speed of light. When discussing the CMS experiment, I introduce the primary partitions of the detector, their purpose, and the primary design principles under which they operate. I then describe the ways in which we transform the raw detector output into a data format usable by physicists to perform a physics analysis.Chapter 4 is a slight detour from the primary narrative of the thesis to briefly talk about the upgrade currently being developed for the CMS outer tracker, and one of the ways in which Brown University is involved in its development. I have spent a large part of my time at Brown actively working in our lab and helping to measure the quality of sensors which will be used to build the next generation of the outer tracker. As such, I could spend hours discussing the details of this subdetector and the years worth of experiences that I have had in our lab. But unfortunately, time is short, my thesis is long, and as such I am only able to give brief details on the portions of our lab duties related to sensor quality control with a primary focus on the measurements I have had a direct influence on.Chapter ?? returns to the primary narrative and gives an overview of charm quarks and their properties. In particular, I discuss the types of matter charm quarks manifest in at the LHC and how the signatures associated with the production of charm matter looks through the lens of the CMS detector. I then go over the ways in which the CMS collaboration aims to identify jets, which are the type of particle showers produced from the decay of quark matter. In doing so, I provide an extra focus on the DeepJet algorithm [38] which is used as part of the H → cc search as well as the way in which DeepJet is calibrated to perform identically on real LHC data and simulated data produced from Monte Carlo simulation.

Development of Molecular Diagnostic and Microfluidic Methods Based on Molecular Transport and Reactions

Schneider, Lindsay Pearl ProQuest Dissertations & Theses Brown University 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Molecular diagnostic testing provides critical information to patients that can lead to earlier detection and disease prevention, specific treatment options, and personalized medicine. The workflow for this type of testing begins with initial sample collection followed by target analyte extraction and purification from the original sample, then amplifying the analyte to a level where detection can be performed. This complex workflow can be laborious, time consuming, and expensive which is why many molecular diagnostic tests have turned to microfluidic technologies to improve all steps. In this thesis, we utilize experimental, computational, and theoretical approaches to characterize molecular transport and reactions. Moreover, we will use microfluidic geometries to develop and improve molecular diagnostic tests. In particular, we will present the design and use of microfluidic devices for nucleic acid extraction and purification using a combination of solid phase extraction on magnetic beads and electrokinetic purification within a microfluidic channel. We show the effect of magnetic beads, free DNA, and sample contaminant transport within this system and how that can change amplification, detection, and even DNA sequencing results. Additionally, this thesis further investigates methods for improved amplification and detection through exploring fundamental components of these steps. We show the development of a new method using targeted nucleic acid sequence to size-based separation analysis as well as the process for creating a model to be used for predicting false-positive results when using loop mediated isothermal amplification through understanding molecular interactions. Overall, the work described in this thesis aims to reduce false-positive diagnosis errors, increase sample purity, and reduce human errors all within the context of molecular diagnostics. The impact of this thesis work includes reducing costs, reagent volumes, and hands on work time using microfluidics, all while improving or maintaining the sensitivity and specificity of these tests particularly through the use of method designs and translatability for automation. Ultimately, through investigating the fundamentals underlying molecular diagnostics we have developed translatable technology useful to a variety of applications.

The Dynamic Interplay between Submesoscales and Boundary Layer Turbulence

Bodner, Abigail S ProQuest Dissertations & Theses Brown University 2021 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The ocean mixed layer plays a key role in the climate system by transferring momentum and tracers, such as heat and carbon, from the atmosphere to the ocean interior. Variations in the mixed layer depth help determine the effectiveness of atmosphere-ocean interactions, and can be attributed to surface forcing, as well as dynamical processes such as turbulent mixing, submesoscale frontal instabilities and mixed layer eddies. Theoretical work and modeling of fronts have been useful in understanding why there are so many submesoscale fronts and filaments in the ocean, but it has been less successful in predicting the scale at which these are found in observations. Current submesoscale parameterizations, which help set mixed layer depth in global climate models, depend on a simplistic scaling of frontal width that is demonstrably wrong in several circumstances. The presence of turbulence and instabilities are likely responsible for keeping fronts at the scale observed, yet a complete understanding of how and why this happens has been a long-standing problem. Building toward a more complete understanding of the processes that set this scale, the interaction between submesoscale fronts and turbulent mixing are investigated in this thesis using several platforms. First, a theoretical approach of perturbation analysis is used to include the effects of parameterized turbulence as a first order correction to classic frontogenesis (frontal sharpening) theory. A modified solution is obtained by using potential vorticity (PV) and surface conditions, which exhibit the complex nonlinear behavior of frontal dynamics. The solution reveals that vertical processes merely delay frontal sharpening, whereas horizontal processes may completely oppose frontogenesis. This qualitative approach is next extended into a more realistic environment, by diagnosing a suite of Large Eddy Simulations (LES) spanning the submesoscale and into the boundary layer (3D) turbulence scale. A surprising result emerges, revealing the limitations of PV below the submesoscale. In models where 3D turbulence is not fully resolved, PV is strongly influenced by grid-scale processes, and becomes contaminated by the least reliable scales. Pre-filtering the velocity and buoyancy fields is found to be essential in linking larger scale PV dynamics to small scale turbulent fluxes. Furthermore, in these simulations a variety of processes--winds, waves, convection, and mixed layer instabilities—are found to compete with frontogenesis. New scaling laws are developed, under different forcing parameter ranges, by relating turbulent fluxes to frontal width by making use of the turbulent thermal wind balance. The final aspect of this thesis discusses implementing the modified frontal width scaling in submesoscale parameterizations in coarse resolution climate models for which sensitivity and changes in model bias are documented.

Housing Markets, Subsidies and the Economic Effects of Infrastructure Investments

Uribe, Juan Pablo ProQuest Dissertations & Theses Brown University 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Underpinning my thesis is a desire to understand the effects of public investments in infrastructure and be able to do a welfare analysis of its economic impacts. The different chapters of this thesis investigate the behavioral and market responses to government programs designed to increase access to affordable housing, utilities, and the internet. Methodologically, all chapters consider the spatial component of these investments combining economic theory with new data sources and exogenous variation, coming principally from discontinuities. The first and second chapters explore how the housing market responds to two different subsidies. The first chapter shows the market response to a housing policy designed to promote homeownership for low-income households. I show compelling evidence of the market response to these subsidies, and I propose and estimate a model that rationalizes the observed equilibrium. Households reduce their housing consumption to qualify for the subsidy. I use the model and estimated parameters to evaluate the policy. I show that the subsidies may not be doing what it is supposed to do and that the policy’s particularities matter. The second chapter shows how the housing market responds to a location-based targeting tool–the estratos–designed to target subsidies to poor neighbourhoods. A core insight of many urban economic models is that using location as a targeting tool may be ineffective because housing or labor markets respond to the subsidies. People want to move to subsidized areas affecting the labor and housing markets. This theory is hard to test as targeted areas are systematically different. I use the particularities of the assignment rule to test this urban economics insight and show that the housing market responds to the subsidies assigned to lower quality areas. Subsidized areas are getting more new construction, and these areas are more expensive than comparable neighbourhoods with lower subsidies. The final chapter studies how a government push to expand internet access affects educational outcomes and human capital formation. In this chapter, my coauthor and I, show that these types of interventions designed to close the digital gap can also reduce the education gap.

Terraced Landscapes: The Historical Ecology of Agricultural Infrastructure

Plekhov, Daniel ProQuest Dissertations & Theses Brown University 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This dissertation is about why agricultural practices change and why they do so in certain ways. Given the immeasurable diversity of crops, tools, inputs, labor regimes, and landscape modifications involved in agricultural production, however, providing a single answer to why such diversity exists or why it may have changed at any given point may be unproductive, if not impossible. Specific forces like population pressure or environmental change can cause farmers to respond in numerous ways, and farmers may likewise adopt the same agricultural practice for different reasons and under variable conditions. Farmers may engage extensively and consistently in a certain practice for centuries and then, either gradually or suddenly, shift to new ones as their motivations, goals, and constraints change. Farmers may also abandon agriculture entirely and pursue other livelihoods. Investigating why practices change and why they do so in certain ways is therefore not a search for a single answer but rather the development of a framework that can evaluate how those decisions are made. Such a framework must also recognize that agricultural change is both constant and inevitable, rather than necessarily a sign of disruption, incompatibility, or failure.This dissertation develops and applies such a framework to a particular agricultural practice within two specific regions. The practice I investigate is agricultural terracing, which is a commonly employed land-use strategy in many regions worldwide that provides various functions relating to crop production and soil and water conservation (Wei et al. 2016). In some cases, modern-day farmers have continued to build and use terraces for centuries, while in other cases, farmers have transitioned to other land-use strategies and terraces lie mostly abandoned and in disrepair. The latter is true of the two regions I investigate: the Petra region of Jordan and the Chachapoyas region of Peru. Combining archaeological survey and excavation, archaeometric dating, remote sensing, and ethnographic sources, I investigate the chronology, various functions, and contemporary uses of agricultural terraces in both regions. By doing so, I provide a diachronic perspective on how each terraced landscape developed through time, why they developed as they did, and what conditions are required for terracing to again be viable. In so doing, I contribute not only to the comparative study of terraces and the diverse trajectories of their development, but also to the study of agricultural landscapes and agricultural change in general. I shed light on the complex and constantly shifting motivations that influence when and where farmers may invest in the construction and use of agricultural terraces and demonstrate that such decision-making processes are constantly happening within a wide range of social, political, and environmental circumstances.Understanding such decision-making processes is essential. Over the past few decades, and with ever increasing urgency, agricultural landscapes are becoming a key topic of interdisciplinary research, policy development, and public debate (Altieri 1995; FAO 2014; Sengupta 2021; Velasquez-Manoff 2018). Unlike the Green Revolution of the mid-twentieth century – a term that describes efforts to vastly increase agricultural production in developing countries through new crops, technologies, and methods – the concern with agricultural landscapes today is not solely one of greater exploitation, extraction, and production, but also one of preservation and sustainability (AL-agele, Nackley, and Higgins 2021; Eichler Inwood et al. 2018; FAO 2011; Yunlong and Smit 1994). For the first time in human history, more people live in urban spaces than rural ones and cities are growing twice as fast in size as they are by population (S. Angel et al. 2011; United Nations, Department of Economic and Social Affairs, Population Division 2019). By 2030, urban land cover is predicted to be nearly triple what it was in 2000, with much of this urban growth coming at the expense of land previously devoted to agricultural production (Seto, Guneralp, and Hutyra 2012). These losses, alongside those of other non-urban landcover classes, amount to massive declines in biodiversity, carbon pools, and production bases and necessitate the expansion of agricultural production to other, previously non-agricultural, areas in order to support growing urban populations (Albero et al. 2021; Popkin 2021; Sasaki et al. 2021).

Presencias en el desierto, ausencias en la nacion: la representacion del indigena de frontera en la Argentina del siglo XIX : Presences in the desert, absences in the nation: The representation of the frontier indigenous in 19th century Argentina

Chiaramonte, Maria Florencia ProQuest Dissertations & Theses Brown University 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Hace algunos anos en una sobremesa familiar me entere de que el “abuelito barbudo” fue quien firmo el certificado de defuncion de Facundo Quiroga. El “abuelito barbudo”, bautizado Henry Mackay Gordon, nacido en Escocia en 1790, era el tatarabuelo de mi abuela materna Eugenia. Su sobrenombre proviene de que el unico registro visual que su descendencia aun tiene de el es una vieja fotografia en la que se ve a un hombre ya entrado en edad, con una larga barba blanca. Henry Gordon fue uno de los primeros protomedicos que ejercieron en territorio argentino, y habia emigrado a la region cordobesa en 1825, donde se caso con una criolla de nombre Josefa Gache Allende, tatarabuela de mi abuela. Toda esta informacion y mas, ayudada por la confirmacion de algunos familiares, pude encontrarla en las bases de datos genealogicos de internet.Al mismo tiempo que escribo esta introduccion leo en Pagina 12 que “el Centro de Estudios Migratorios Latinoamericanos (CEMLA) desarrollo en su sitio web un buscador a traves del cual es posible acceder a la informacion de los inmigrantes que llegaron en barco a Argentina entre 1800 y 1960” (5/5/2022, Pagina 12). Ingreso inmediatamente y puedo enterarme de que mi abuelo paterno, Giuseppe Chiaramonte, llego a los seis anos de edad desde el puerto de Genova, Italia, en 1920, a bordo del Principessa Mafalda. Fue, para sorpresa mia, relativamente facil reconstruir la genealogia de estos dos inmigrantes europeos de principios de siglo XIX y XX en territorio latinoamericano. Especulo que se debe a que siempre hay algun nombre, alguna imagen, algun libro o libreta heredada, u otro objeto que ayuda a reconstruir la historia occidental -de Europa a America-. Siempre, ademas, se encuentra algun registro de facil lectura y comprension que atestigua el trayecto y el recorrido. Hay, tambien, entusiasmo y curiosidad de los familiares en conocer ese costado del pasado propio y todo lo que esa genealogia implica: la blancura, el “refinamiento” de las costumbres europeas, y el formar parte de la epica civilizatoria.Por otro lado, tambien recuerdo haber escuchado de boca de mi abuela materna decir que seguramente en nuestra familia habia sangre indigena. Podran objetarme que, es verdad, ese tipo de comentarios no suele ser extrano entre los argentinos -y latinoamericanos- cuyas familias llevan varias generaciones en territorio nacional, y proviene de un deseo de legitimar su pertenencia a la tierra. No se, por lo tanto, si eso que dijo mi abuela es efectivamente cierto, ni tampoco pude comprobarlo con ningun nombre especifico, ni fotografia, ni documento o anecdota familiar. Menos que menos un sitio web que reconstruya una genealogia indigena general. Es, si realmente fue asi, un costado opaco de mi historia personal.Otra experiencia reaviva mis reflexiones sobre este tema. Hace algunos anos, revisando el archivo de la biblioteca John Hay en Brown, tropiezo con una lamina que acapara mi atencion. Se llama “Indios pampas” y es parte del registro pictorico de la Monumenta Iconographica [1536-1860] editada por Bonifacio del Carril en 1960. Se trata de una acuarela realizada por Emeric Essex Vidal (1791-1861) marino y pintor ingles que viajo a Sudamerica y retrato escenas tipicas a comienzos del siglo XIX. En esta imagen en particular aparecen retratados dos indios pampas en una esquina de Buenos Aires en 1818, apoyados en la pared y la columna de lo que pareciera ser el porche de entrada a alguna edificacion de la epoca. Los indios fuman tranquilamente y visten sus ropas tipicas: faldas hasta los tobillos, vinchas que sujetan su larga cabellera y el torso desnudo. Los rodean algunos objetos: plumeros, estribos y latigos que, arriesgo, podrian tratarse de la mercaderia que estos dos sujetos comercian en la ciudad. Sea como fuere, estos dos indios pampa en una esquina de la recientemente emancipada ciudad de Buenos Aires no desentonan con el marco urbano que los contiene. Sus gestos son casuales, su pose relajada, nada de lo que ellos representan parece fuera de lugar. El retrato emana cotidianidad: ellos son retratados como los sujetos de ese espacio, son parte del “pintoresquismo” local. ¿Por que entonces, sin embargo, esta imagen resulta tan llamativa para la mirada de una argentina rioplatense en el siglo XXI? Quizas porque evoca una realidad de nuestro pais que en algun momento -y aun en el presente- se intento, con mucho empeno, eliminar. Eliminacion fisica y discursiva encauzadas en la desarticulacion y el exterminio de las poblaciones indigenas, y en el silenciamiento del papel central que cumplieron muchos de ellos en los origenes de la nacion. Este proceso se llevo a cabo durante gran parte del siglo XIX y entrado el siglo XX y su exito fue tan rotundo que sus efectos siguen latentes hoy, en 2022, cuando una persona enfrenta esta acuarela y, si no fuera por el epigrafe que lo senala, nunca imaginaria que se trata de dos indios pampas comodos en su entorno, que no desentonan en el marco urbano que provee la ciudad de Buenos Aires. A few years ago,at a family table,I found out that the "bearded grandfather" was the one who signed the death certificate of Facundo Quiroga. The "bearded grandfather", baptized Henry Mackay Gordon, born in Scotland in 1790, was the great-great-grandfather of my maternal grandmother Eugenia. His nickname comes from the fact that the only visual record his descendants still have of him is an old photograph of an elderly man with a long white beard. Henry Gordon was one of the first physicians to practice in Argentine territory, and he had emigrated to the Cordoba region in 1825, where he married a Creole named Josefa Gache Allende, my grandmother's great-great-grandmother. All this information and more, helped by the confirmation of some relatives, I was able to find in genealogical databases on the Internet.At the same time that I write this introduction, I read on Page 12 that "the Center for Latin American Migration Studies (CEMLA) developed a search engine on its website through which it is possible to access information on immigrants who arrived in Argentina by boat between 1800 and 1960” (5/5/2022, Page 12). I enter immediately and learn that my paternal grandfather, Giuseppe Chiaramonte, arrived at the age of six from the port of Genoa, Italy, in 1920, aboard the Principessa Mafalda. To my surprise, it was relatively easy to reconstruct the genealogy of these two European immigrants from the early 19th and 20th centuries in Latin American territory. I speculate that it is because there is always some name, some image, some inherited book or notebook, or other object that helps to reconstruct Western history -from Europe to America-. In addition, there is always some record that is easy to read and understand that attests to the journey and the journey. There is also the enthusiasm and curiosity of the relatives to know that side of their own past and all that that genealogy implies: whiteness, the “refinement” of European customs, and being part of the civilizing epic.On the other hand, I also remember hearing from my maternal grandmother that surely there was indigenous blood in our family. You may object that, it is true, this type of comment is not usually strange among Argentines -and Latin Americans- whose families have been in national territory for several generations, and it comes from a desire to legitimize their belonging to the land. I do not know, therefore, if what my grandmother said is indeed true, nor could I verify it with any specific name, photograph, document or family anecdote. Less than less a website reconstructing a general indigenous genealogy. It is, if it really was like that, an opaque side of my personal history.Another experience revives my reflections on this subject. Some years ago, going through the John Hay Library archive in Brown, I stumbled upon a plate that captured my attention. It is called “Indios pampas” and is part of the pictorial record of the Monumenta Iconographica [1536-1860] edited by Bonifacio del Carril in 1960. It is a watercolor by Emeric Essex Vidal (1791-1861), an English sailor and painter who traveled to South America and portrayed typical scenes at the beginning of the 19th century. In this particular image, two Pampas Indians are portrayed in a corner of Buenos Aires in 1818, leaning on the wall and the column of what appears to be the entrance porch of some building of the time. The Indians smoke quietly and wear their typical clothes: ankle-length skirts, headbands that hold their long hair and a bare torso. They are surrounded by some objects: dusters, stirrups and whips that, I risk, could be the merchandise that these two subjects trade in the city. Be that as it may, these two pampa Indians in a corner of the recently emancipated city of Buenos Aires do not clash with the urban framework that contains them. Their gestures are casual, their pose relaxed, nothing they represent seems out of place. The portrait exudes everyday life: they are portrayed as the subjects of that space, they are part of the local “picturesque”. Why then, however, is this image so striking for the gaze of an Argentine from the River Plate in the 21st century? Perhaps because it evokes a reality of our country that at some point -and still in the present- tried very hard to eliminate. Physical and discursive elimination channeled in the disarticulation and extermination of the indigenous populations, and in the silencing of the central role that many of them played in the origins of the nation.

Algebraic Dynamics, Moduli Spaces, and Integrability

Weinreich, Max H ProQuest Dissertations & Theses Brown University 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The complex numbers are uncountable, and finite fields are finite. Approaching the subject for the first time, one might assume that this difference would make complex and finite field dynamics almost incomparable. Yet we know from the last century of arithmetic geometry that algebraic objects defined with integers, such as elliptic curves over Z, have intrinsic geometric properties that simultaneously govern their complex topology and their point counts over finite fields. Could something similar be true when algebraic objects are set in motion by a dynamical system? The thesis is a compilation of two projects on this theme [Wei21a, Wei21b].In Chapter 2, we discuss the foundations of three themes that guide our results: algebraic dynamics, moduli spaces, and integrability. Each of these themes is a deep subject that can be developed individually from the others; our main theorems indicate some of their connections.In Chapter 3, we study the pentagram map, a discrete integrable system defined on moduli spaces of plane polygons. We prove that the integrability of the pentagram map occurs not just over the complex numbers, but over algebraically closed fields of any characteristic not equal to 2.In Chapter 4, we construct and study moduli spaces of linear maps on projective space with marked points, using geometric invariant theory (GIT). We prove a dynamical criterion for a marked linear map to be GIT stable, that is, admissible in a GIT moduli space.The direct link between the two projects is the concept of twisted polygon. The moduli space of twisted n-gons is the domain of the pentagram map of Chapter 3, and it also forms a Zariski open subset of the moduli space of linear maps on P 2 with n marked points, of Chapter 4. Thus the moduli space of linear maps with marked points is not just a dynamical moduli space, but also admits interesting rational dynamical systems itself.We now introduce the central characters of the thesis and present our main results.Chapter 3 explores the dynamics of the pentagram map, an elementary geometric operation, over any algebraically closed base field. The pentagram map is defined on moduli spaces of polygons, as follows.Definition 1.0.1. Let n ≥ 5. A closed n-gon is an n-periodic sequence of points in the projective plane such that no three consecutive points are collinear. Thus the data of a closed n-gon is more or less equivalent to a choice of n ordered points in P2 . For a more precise definition, see Definition 3.1.1.The pentagram map sends the closed n-gon (vi)i∈Z to (wi) i∈Z , where wi is theintersection of the diagonals vi−1vi+1 and vivi+2; see Figure 1.1. The pentagram map is projectively natural, so it descends to a rational self-map of the moduli space of closed polygons up to projective equivalence.

Fluid-Structure Interactions of Elastically Mounted Pitching Wings

Zhu, Yuanhang ProQuest Dissertations & Theses Brown University 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

In this dissertation, we combine laboratory experiments with theoretical analysis to study fluid-structure interactions of elastically mounted pitching unswept and swept wings. A cyber-physical system is used to simulate and regulate the structural dynamics of the wing. We report two distinct modes of flow-induced oscillations, namely a structural mode that occurs at a high inertia via a subcritical bifurcation, in which the inertial force and time scale dominate; and a hydrodynamic mode that occurs at a low inertia via a supercritical bifurcation, in which the fluid force and time scale dominate. An energy method is employed to examine the overall stability of the system using the energy transfer between the elastic mount and the ambient flow. We study the effect of wing sweep on the aeroelastic boundaries of pitching swept wings and show that the onset of flow-induced oscillations depends on the static characteristics of the wing. The non-monotonic trend of the saddle-node point as a function of the sweep angle is attributed to the non-monotonic energy transfer between the ambient fluid and the elastic mount, which is further regulated by the unsteady aerodynamic moment. We find that the wing sweep modulates the aerodynamic moment by affecting the dynamics and three-dimensional structures of the leading-edge vortex and tip vortex, and thus the moment arm of the aerodynamic load. For flow-damped oscillations without a free-stream flow, we extract the fluid damping coefficients using the dynamical system equation and propose a theoretical scaling based on the Morison equation, which incorporates the effects of pitching frequency, amplitude, pivot location and sweep angle. We then quantify and scale the temporal evolution of the vortex trajectory and strength, and use a physics-based force and moment partitioning method to associate the complex vortex dynamics with the vorticity-induced moment, bringing to light the generation mechanism of the nonlinear fluid damping. Finally, we propose and validate a data-driven experimental framework for modeling and predicting flow-induced oscillations, in which we combine a neural network model with the aeroelastic governing equation to simulate a real aeroelastic system.