A study was conducted at the Savannah River Site near Aiken, SC to: 1) characterize the spatial patterns of soil and forest floor variables (moisture, pH, soil phosphate, forest floor and soil carbon and nitrogen, and soil available nitrogen), 2) assess the spatial patterns of the plant community, and 3) investigate spatial relationships among the variables and between the variables and woody vegetation. Spatial soil and litter samples were collected on five 0.25 hectare plots, and relationships were explored using Pearson's correlation tests, canonical correlation analysis, variogram modeling and kriging. The average range of spatial autocorrelation for the forest floor variables was >45 m, while that for soil variables was 12 m. Woody stem basal area exhibited spatial autocorrelation at ranges of less than 12 m, and was only weakly correlated with forest floor and soil resource patterns. Few strong spatial correlations among the forest floor and soil variables were observed. The means and variances of the variables were low, and differences in resource levels probably had little impact on the spatial pattern of vegetation. Results indicate a weak, differential effect of species group on litter quality, a weak relationship between large pine trees and soil nitrogen patterns, and a general homogeneity of the stands. / Master of Science

The growing need for high-performance electrode materials in electrochemical conversion and storage applications requires further fundamental investigation on the working and degradation mechanisms of these materials. Among various functional materials, transition metal oxides are still one of the main choices due to their tunable chemical compositions and diverse crystal structures in most aqueous and organic electrolytes. The charge transfer process mainly occurs at the electrode-electrolyte interface, and controlling the electrochemical interfacial stability represents a key challenge in developing sustainable and cost-effective electrochromic materials. The present thesis focuses on classical tungsten trioxide (WO3) materials as the platform to uncover the previously unknown interrelationship between phase transformation, morphological evolution, nanoscale color heterogeneity, and performance degradation in these materials during 3,000 cyclic voltammetry cycles. Through the application of novel cell design, synchrotron/electron spectroscopic, and imaging analyses, we observe that the interface between the WO3 electrode and 0.5 M sulfuric acid electrolyte undergoes constant changes due to the tungsten oxide dissolution and redeposition. The redeposition of dissolved tungsten species provokes in situ crystal growth, which ultimately leads to phase transformation from the semicrystalline WO3 to a nanoflake-shaped, proton-trapped tungsten trioxide dihydrate (HxWO3·2H2O). The multidimensional (surface and bulk) quantification of the electronic structure with X-ray measurements reveals that the tungsten reduction caused by proton trapping is heterogeneous at the nanometric scale and is responsible for the nanoscale color heterogeneity. The Coulombic efficiency, optical modulation, apparent diffusion coefficients, and switching kinetics are gradually diminished during 3,000 cyclic voltammetry cycles, resulting from the structural and chemical changes of the WO3 electrode. We hypothesize that the high interfacial reactivity in the electrode-electrolyte interfacial region could be the universal underlying mechanism leading to undesired bulk structural changes of inorganic electrochromic materials. / M.S. / With the rapid development of human society, the research of new energy-saving materials has become a focus of attention. Among them, electrochromic devices can effectively adjust their color through a controllable electrochemical reaction and have a wide range of uses in our daily life. For example, smart windows can reduce glare and heat without blocking the natural light, thereby providing buildings and vehicles with better thermal and visual comfort. Electrochromic optical displays can lower energy consumption. Variable reflectance mirrors such as anti-glare car rear-view mirrors can ensure the safety of driving. Lastly, wearable apparel such as electrochromic lenses for spectacles and sunglasses can protect users from ultraviolet radiation. Although electrochromic materials and devices have not expanded from the niche market, the enormous potential that they hold cannot be ignored and wide-scale commercialization should be sought after. Tungsten oxides electrochromic devices have proved to utilize the full spectrum of the incident light through structure design. These devices can also be configured with solar cells as a state-of-art integrated self-powered system with satisfactory optical modulation that can be obtained without any external electrical energy input. Moreover, WO3-based devices have also been combined with electrodeposition technology to achieve fast color-switching kinetics. However, the long-term durability in the acidic electrolyte under electrochemical cycling conditions needs to be further improved, and the road of full commercialization is still unpaved. To design high-performance electrochromic materials, it is imperative to study the degradation mechanism under long-term electrochemical cycling conditions. In the present thesis, the performance degradation of the WO3 electrode in acid electrolytes involves chemical changes. Through a better understanding of the fundamental degradation process, the design of high- performance electrochromic metal oxides can be developed.

Thesis advisor: Joseph Quinn / This thesis explores the debate surrounding the impact of minimum wage increases on employment, dissecting the conflicting results and methodological divergences in the existing economic literature. It engages in a detailed meta-analysis of seminal studies, with a particular focus on how differing research methodologies and definitions of employment have contributed to the lack of consensus among economists. The analysis reveals that while some studies, like those by Card and Krueger (1994), find no negative effects on employment, others, such as Neumark and Shirley (2022), report significant adverse impacts, particularly on low-skilled and younger workers. This thesis examines the prevalent methodological approaches and highlights the role of controlling for spatial heterogeneity and the careful selection of control groups in assessing the true effects of minimum wage policies. / Thesis (BA) — Boston College, 2024. / Submitted to: Boston College. Morrissey School of Arts and Sciences. / Discipline: Economics. / Discipline: Departmental Honors.

Throughout the 1990s ADHD diagnosis and medication rates have increased rapidly, and this trend continues today. These sharp increases have been met with both public and clinical criticism, detractors stating over-diagnosis is a problem and healthy children are being unnecessarily medicated and labeled as disabled. However, others say that ADHD is being under-diagnosed in some populations. Critics often state that there are multiple factors that introduce subjectivity into the diagnosis process, meaning that a final diagnosis may be influenced by more than the desire to protect a patient's wellbeing. Some of these factors include standardized testing, legislation affecting special education funding, and the diagnostic process. In an effort to circumvent these extraneous factors, this work aims to further develop a potential method of using EEG signals to accurately discriminate between ADHD and non-ADHD children using features that capture spectral and perhaps temporal information from evoked EEG signals. KNN has been shown in prior research to be an effective tool in discriminating between ADHD and non-ADHD, therefore several different KNN models are created using features derived in a variety of fashions. One takes into account the heterogeneity of ADHD, and another one seeks to exploit differences in executive functioning of ADHD and non-ADHD subjects. The results of this classification method vary widely depending on the sample used to train and test the KNN model. With unfiltered Dataset 1 data over the entire ANT1 period, the most accurate EEG channel pair achieved an overall vector classification accuracy of 94%, and the 5th percentile of classification confidence was 80%. These metrics suggest that using KNN of EEG signals taken during the ANT task would be a useful diagnosis tool. However, the most accurate channel pair for unfiltered Dataset 2 data achieved an overall accuracy of 65% and a 5th percentile of classification confidence of 17%. The same method that worked so well for Dataset 1 did not work well for Dataset 2, and no conclusive reason for this difference was identified, although several methods to remove possible sources of noise were used. Using target time linked intervals did appear to marginally improve results in both Dataset 1 and Dataset 2. However, the changes in accuracy of intervals relative to target presentation vary between Dataset 1 and Dataset 2. Separating subjects into heterogeneity classes does appear to result in good (up to 83%) classification accuracy for some classes, but results are poor (about 50%) for other heterogeneity classes. A much larger data set is necessary to determine whether or not the very positive results found with Dataset 1 extend to a wide population. / Master of Science / Throughout the 1990s ADHD diagnosis and medication rates have increased rapidly, and this trend continues today. These sharp increases have been met with both public and clinical criticism, detractors stating over-diagnosis is a problem and healthy children are being unnecessarily medicated and labeled as disabled. However, others say that ADHD is being underdiagnosed in some populations. Critics often state that there are multiple factors that introduce subjectivity into the diagnosis process, meaning that a final diagnosis may be influenced by more than the desire to protect a patient’s wellbeing. Some of these factors include standardized testing, legislation affecting special education funding, and the diagnostic process. In an effort to circumvent these extraneous factors, this work aims to further develop a potential method of using EEG signals to accurately discriminate between ADHD and non-ADHD children using features that capture spectral and perhaps temporal information from evoked EEG signals. KNN has been shown in prior research to be an effective tool in discriminating between ADHD and non-ADHD, therefore several different machine learning models are created using features derived in a variety of fashions. One takes into account the heterogeneity of ADHD, and another one seeks to exploit differences in executive functioning of ADHD and non-ADHD subjects. The results of this classification method vary widely depending on the sample used to train and test the KNN model, classification accuracy has ranged from 65% to 94%, and the cause for this variation was not identified. A much larger data set is necessary to determine whether or not the very positive results found with Dataset 1 extend to a wide population.

Understory light environments are inherently heterogeneous and therefore difficult to characterize. Numerous methods to measure understory light have been assessed in closed-canopied forests; however, the reliability of these methods has not been addressed for open-canopied forests. Therefore, the first objective of this study, presented in Chapter 3, was to test the accuracy and precision of various light measurement techniques at different time scales and sky conditions. The methods assessed performed differently depending on the sky condition and time of year when the sample was taken. To estimate annual photosynthetic photon flux density transmittance (annual %PPFD), the use of a 10-minute average of PPFD measured on an overcast day (%PPFDovercast) was effective, but accuracy decreased with decreasing solar altitude (ie season change). Hemispherical photographs used to estimate weighted canopy openness and gap fraction were effective methods, but gap light index (GLI) also derived from hemispherical photographs performed better. Accuracy of daily %PPFD estimates using %PPFDovercast, weighted canopy openness, and gap fraction were strongly affected by solar altitude and sky condition. Gap light index was very effective in estimating daily %PPFD for all sky conditions and time periods. The second objective of this study, presented in Chapter 4, was to characterize the relationship between canopy structure and spatial distribution of light by using three replicates of one uncut treatment and three harvest treatments: single tree, small gap (0.1 ha), and large gap (0.2 ha). Each harvest retained similar residual basal area but with different spatial patterns of the residuals, ranging from uniformly dispersed (single tree) to different degrees of aggregation (small and large gap). Average stand level light availability increased 12-22% when the same residual basal area of trees was distributed in clusters versus a uniform distribution. The variation of light availability increased as stands became more aggregated and larger amounts of the variation was explained by the spatial pattern of the canopy structure. Spatial autocorrelation range was twice as large in the small gap harvest then the other harvest treatments. It is suggested that seedling growth response to these differences in spatial patterns of light may differ between the different harvests. / Master of Science

2023 / This dissertation consists of three essays on firms and the macroeconomy.Chapter 1 of my dissertation revisits a classical question in macroeconomics: what are the aggregate consequences of financial frictions? I answer the question through the lens of a dynamic quantitative general equilibrium model. Heterogeneous firms finance their investment with equity and debt and their financing decisions are distorted by two types of financial frictions: a collateral constraint and costly external equity issuance. Crucially, my model features a debt tax shield. I structurally estimate the model parameters in a simulated method of moments procedure using firm-level balance sheet data from COMPUSTAT between 1981 and 2017. I target a range of financial covariances. In particular, to identify the scope of the borrowing constraint, I use the negative association between the current investment and previous leverage. My estimation results indicate a sizable degree of financial frictions in the economy. I’m able to reproduce these empirical moments quite successfully. In Chapter 2, I evaluate my quantified model to investigate two questions. First, what are the aggregate implications of financial frictions in the presence of the debt tax shield? Second, is there an interaction between the magnitude of tax shields and the impact of financial frictions? Previous studies indicate that removing financial frictions will stimulate investment and reduce misallocation. However, with the tax bias towards debt over equity, I show that the macroeconomic implications of financial frictions can be different. My results demonstrate that a large tax shield with loose credit constraints can exacerbate the misallocation of capital. Using the U.S. firm-level data, my counterfactual experiments demonstrate that by removing financial frictions, aggregate capital increases by 10%, output by 3%, and welfare by 2%. Aggregate gains can be 10 times larger when accounting for the tax shield. Chapter 3 examines the increasing number of low-productivity firms ( “zombie firms”) by investigating the nexus of firms, banks, and the government. It is generally agreed that an efficient economy should feature a productivity-enhancing reallocation where resources are shifted to high-productivity firms and inefficient firms are scrapped. However, recent studies document opposite empirical evidence of the survival of zombie firms. The paper constructs a bank lending model with government policies on banks’ capital adequacy requirements. It demonstrates that poorly-designed policies can induce under-capitalized banks to roll over loans to otherwise inviable firms. The model generates implications that firms of different productivity would respond to a shock differently at the exit margin. This can motivate future empirical work to examine whether there are zombie firms in the economy structurally.

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Ce travail a pour ambition de montrer qu’une analyse linguistique du discours rapporté dans la presse écrite permet de démontrer comment et par quels moyens énonciatifs les journalistes de notre corpus représentent le discours autre dans les articles d’information. Nous essayons de rendre visible la prise de position des journalistes de notre corpus de travail à la lumière des théories d’hétérogénéité énonciative. Dans ce but, les idées de J. Authier-Revuz sur la représentation du discours autre (RDA) en tant que forme relevant de l’hétérogénéité montrée nous servent de cadre théorique.Les articles de presse constituant notre corpus de travail sont extraits des quotidiens Le Monde, Libération, Le Figaro, (2009-2013) et la revue iranienne Zanân « les femmes ». Le choix des quotidiens français et celui de la revue iranienne ont été motivés par le fait qu’ils constituent un corpus contrastif. Notons que notre corpus français est considéré comme les quotidiens de références par plusieurs études et projet de recherches. Notre choix de Zanân s’explique par l’un de nos objectifs initiaux de recherche qui est celui de mener une recherche sur la représentation du discours autre dans un corpus à la fois contrastif et francophone. Le fait que Zanân a été traduite en français nous conforte dans notre orientation. / This work aims to show that a linguistic analysis of reported speech in the newspapers helps demonstrate how and by which means the journalist represents another speech in news items. We try to make visible the position taken by journalists of our studied object in the light of enunciative heterogeneity theories. In this purpose, the ideas of J. Authier-Revuz on the representation of other discourse (RDA) as a form within the shown heterogeneity serve as our theoretical framework.The articles constituting our body of work are extracted from Le Monde, Libération, Le Figaro (2009-2013), and the Iranian journal Zanân “The Women”. The selection of French newspapers and one magazine of Iran were motivated by the fact that they constitute a contrastive corpus. Note that our French corpus is considered the daily reference of several studies and research projects.Our choice of Zanân is explained by one of our initial goals of research is that of conducting research on the representation of another discourse in a corpus both contrastive and francophone. The fact that Zanân is translated into French confirms our orientation.

nÃo hà / CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Procedemos, a partir dos pressupostos da LingÃÃstica da EnunciaÃÃo, à problematizaÃÃo do quadro das heterogeneidades do tipo mostrada (marcada vs. nÃo-marcada), proposto por Authier-Revuz (1982). Nossa proposta consiste em sugerir que o escopo das ocorrÃncias dos fatos de heterogeneidade marcada seja flexibilizado, de modo a abarcar fenÃmenos de natureza (mais) cognitiva que evidenciam a presenÃa do alheio na materialidade lingÃÃstica num ponto especÃfico da cadeia do dizer, promovendo, destarte, uma articulaÃÃo entre heterogeneidade mostrada/marcada e referenciaÃÃo. Submetemos a um reexame, acrescentando o que nos pareceu pertinente, um conjunto de marcas que nÃo apenas as consagradas (como, por exemplo, negrito, mudanÃa de fonte, aspas, discurso direto) na tentativa de lhes conferir um estatuto de marcadores da presenÃa consciente do outro no fio discursivo, considerando a noÃÃo de leitor-modelo sugerida por Eco (1979). Para tanto, elegemos como categorias principais de anÃlise os processos referenciais anafÃricos e dÃiticos, o discurso indireto livre e a intertextualidade por alusÃo. Nossos resultados legitimaram nossa proposta e confirmaram o potencial marcativo de tais categorias. Palavras-chave: Heterogeneidade enunciativa; heterogeneidade mostrada/marcada; referenciaÃÃo; processos referenciais. / We proceed to the problematization of the frame of heterogeneities of the displayed type (marked versus not marked) as proposed by Authier-Revuz (1982) from the assumptions of the Linguistics of Enunciation. Our proposal consists in suggesting that the scope of the occurrences of facts of marked heterogeneity be widened in order that it includes phenomena of a (more) cognitive nature that make evident the presence of the other in the linguistic materialization in a specific point of the chain of the saying and, besides, articulate the displayed marked heterogeneity and the referentiation. We reexamine, appending whatever seems to us pertinent, a set of marks, besides those already established (e.g., bold face, font changing, inverted commas, direct speech) in an attempt to confer them the statute of markers of the conscious presence of the other in the discursive thread, considering the notion of model reader suggested by Eco (1979). To achieve this goal, we choose for main categories of analysis the deictic and anaphoric referential processes, the free indirect speech and the intertextuality by allusion. Our results legitimize our proposal and confirms the marking potential of such categories. Keywords: Enunciative heterogeneity, displayed/marked heterogeneity; referentiation; referential processes.

Dentre os vários instrumentos utilizados pelo governo federal - em parte, ligados às políticas neoliberais de administração pública -, o Exame Nacional de Cursos (ENC) surgiu, em 1995, com a finalidade de manter um certo controle sobre o sistema educacional superior. Na intenção de delimitarmos o produto, isto é, as filiações discursivas repassadas pelo mercado vinculado a esse tipo de formação, constituímos um corpus de pesquisa por meio da produção escrita do formando em Letras, alvo do ENC/2001, e realizamos uma análise fundamentada na teoria da(s) heterogeneidade(s) enunciativa(s) (Authier-Revuz, 1980 : 2004, 1982 : 2004, 1984 : 1990, 1998). Tal teoria nos auxilia a circunscrever o(s) outro(s) que surge(m) no discurso desse formando, futuro professor de língua materna, delimitando suas filiações discursivas. A partir da análise, concluímos que tais filiações emergentes do seu texto não se resumem somente àquelas vistas em sala de aula - como a Gramática Tradicional e a Lingüística, por exemplo -, mas também àquelas fornecidas pela própria questão do ENC/Letras/2001. A apropriação de elementos dados pela própria questão evidencia uma certa superficialidade no tratamento dos conteúdos, demonstrando uma tendência do formando a buscar informações de fácil apreensão, mas de pouca durabilidade. / Among the several instruments used by the federal government - partly, linked to the neoliberal politics of public administration -, the Exame Nacional de Cursos (ENC) appeared in 1995 with the purpose of maintaining a certain control on the higher education system. In the intention delimiting the product, that is, the discoursive filiations reviewed by the market linked to that formation type, we have constituted a research corpus through the written production of the forming in Letters, target of ENC/2001, and we have accomplished an analysis based in the theory of the enunciative heterogeneities (Authier-Revuz, 1980: 2004, 1982: 2004, 1984: 1990, 1998). Such theory aids us to bound the other(s) that appear(s) in the speech of that forming, future teacher of maternal language, delimiting his/her discoursive filiations. Starting from the analysis, we have concluded that such emerging filiations of his/her text are not only summarized to those views in classroom - as the Traditional Grammar and the Linguistics, for example - but also those supplied by the own subject of ENC/Letters/2001. The appropriation of elements given by the own subject evidences a certain superficiality in the treatment of the contents and demonstrates a tendency of the forming looking for information of easy apprehension but of little durability.