10 research outputs found
Photoresponse of bowtie nanojunctions
No full textPlasmon resonant nanostructures provide a platform for controlling light on subwavelength lengthscales. Integrating plasmonic materials into dielectric environments, as well as its compliment – addressing nanoscale photonic elements with plasmon active geometries – is a challenging aspect of current research in wide variety of scientific disciplines including microscopy, photovoltaics, photonics, and catalytic chemistry. This thesis covers two experiments with the goal of electrically and optically addressing nanoscale volumes of semiconducting material using Au nanojunctions with plasmon resonant electrodes.
The first measurement aims to use the large field enhancements in bowtie nanojunctions to trap semiconducting nanocrystals from solution. Trapped nanocrystals could then potentially span the gap between the structure's two electrodes to serve as an active optical and electrical region for a number of desirable photoresponsive measurements in single to few nanocrystals systems. We establish a numerical model simulating the force applied on nanocrystals in and around the nanogap as result of the structure's plasmon modes. We also provide experimental data of trapping events in bowtie nanogaps and measurements of the photocurrent generated in the resultant Au-nanocrystal devices. The challenges of this project, mostly related to ligand and surface chemistry, are discussed in detail.
In the second experiment, we demonstrate plasmon-enhanced photoconduction in Au bowtie nanojunctions containing nanogaps overlaid with an amorphous Ge film. The role of plasmons in the production of nanogap photocurrent is verified by studying the unusual polarization dependence of the photoresponse. With increasing Ge thickness, the nanogap polarization of the photoresponse rotates 90 degrees, indicating a change in the dominant relevant plasmon mode, from the resonant transverse plasmon at low thicknesses to the nonresonant “lightning rod” mode at higher thicknesses. To understand the plasmon response in the presence of the Ge overlayer and whether the Ge degrades the Au plasmonic properties, we investigate the photothermal response (from the temperature-dependent Au resistivity) in no-gap nanowire structures, as a function of Ge film thickness and nanowire geometry. The film thickness and geometry dependence are modeled using a cross-sectional, finite element simulation. The no-gap structures and the modeling confirm that the striking change in nanogap polarization response results from redshifting of the resonant transverse mode, rather than degradation in the Au/Ge properties. We note remaining challenges in determining the precise mechanism of photocurrent production in the nanogap structures
Extending the 'Institutional' Turn: Property, Politics and Development Trajectories
No full textdevelopment, institutions, comparative political economy
Employing ML Methods on Digitized FOIA Requests for Improved Discoverability and Policy Research
No full textBorn-digital records pose challenges for digital preservation due to their unstructured formats and noncompliance with accessibility standards. This project introduces a modular, open-source workflow to batch process large, mixed media PDFs—many obtained through FOIA requests—by leveraging OCR, AI, and named-entity recognition. Built for the White House Scientists Archive, this system enhances discoverability and usability of digitized records across administrations and supports metadata extraction at scale. Key tools include Mistral AI for OCR, Apache Tika for entity recognition, and a finet uned Mistral model for metadata generation
Malaria and Primary Education : A Cross-Country Analysis on Primary Repetition and Completion Rates
No full textThis paper explores the link between P. Falciparum malaria - most of malaria morbidity and mortality is due to the malignant Plasmodium Falciparum - and primary education in terms of school performances at the macroeconomic stage. Cross-country regression analysis shows that the relation between school results (measured by repetition and completion rates) and the P. Falciparum malaria index is strong. The results implies that the achievement of the education Millennium Development Goals will require more than just focusing on expenditure in primary education. It does not imply that resources in education are unnecessary but that increasing resources in education and improving education resources management alone are unlikely to be sufficient. This paper suggests that health conditions and especially diseases that alter cognitive capacities of children such as malaria should be taken into account much more seriously. This study also sees the need to place emphasis on research that will improve the quality of interventions to prevent malaria. Specific education expenditure to face Malaria should be examined in addition to health policies.Malaria incidence, human capital, development.
Iowa History and Culture : A Bibliography of Materials Published Between 1952 and 1986, 1989
No full textThis bibliography was compiled by two reference librarians, Patricia Dawson and David Hudson with the goal of making it easier of tracking down material on Iowa history and culture. This supplements the Iowa History Reference Guide published in 1952 by William Petersen
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Development of prostrate cancer vaccine using PAP as target antigen
No full textTreatment options for patients with advanced prostate cancer (PC) still remain limited and rarely curative. The prostatic acid phosphatase (PAP) is prostate specific protein over-expressed in more than 90% of prostate tumours. Although an FDA-approved vaccine for the treatment of advanced prostate disease, PROVENGE® (sipuleucel-T), has been shown to prolong survival, the precise sequence of the PAP protein responsible for the outcome remains unknown. As the PAP antigen is one of the very few prostate-specific antigens for which there is a rodent equivalent with high homology, pre-clinical studies using PAP have the potential to be directly relevant to the clinical setting. The current study identified HLA-A2 and HLA-DR1 PAP-derived peptides using the transgenic HHDII/DR1 and C57Bl/6 mice. The PAP-114-128 (15-mer) peptide was shown to elicit CD4+ and CD8+ T-cell-specific responses in C57Bl/6 mice. Furthermore, when immunised in a DNA vector format (ImmunoBody), PAP-114-128 was able to prevent and reduce the growth of TRAMP C1 prostate cancer cell-derived tumours in both prophylactic and therapeutic settings
Essays on corruption in sub-Saharan Africa
No full textWe study three topics on corruption that are of particular relevance to sub-Saharan Africa.
Firstly, we address the question of why corruption is such an endemic problem in sub-Saharan Africa. Is it policy driven or "destiny"? We analyse indices of perceived corruption and test several theories regarding the causes of corruption. We find strong support for two arguments: Countries with a British heritage are perceived to be less corrupt, while those with a common law system are perceived to be more corrupt. We find weaker support for four further arguments: Countries with good quality institutions and a greater proportion of women in the labour force are perceived as less corrupt. Countries with greater natural resource abundance and with greater trade openness are perceived to be more corrupt.
Secondly, we look at the supply side of bribery. Within the public procurement process, we study how a firm's uncertainty regarding the official's corruptibility and rival firms' costs influences the magnitude of the bribe it offers. Due to the illegal nature of bribery, we also explicitly consider different punishment mechanisms for corrupt firms. We find that secrecy leads to lower bribe levels, and that bribery can be completely deterred by either appropriate fixed fines or by firms being fined punitive damages.
Thirdly, we investigate whether more corrupt governments receive less aid. We develop a theoretical framework that treats corruption as a tax on aid. Although we are unable to empirically test this model, we use it to motivate our empirical analysis of aid receipts using data on sub-Saharan Africa. We find a negative correlation between a country's perceived level of corruption and its aid receipts. However, we find no causal effect of perceived corruption on aid receipts. We revisit the results of an influential paper in the literature and find that their result of no evidence that countries perceived as more corrupt receive less aid is not robust to a sample of sub-Saharan African countries, although we find no evidence of a causal effect. We find no evidence that the impact of perceived corruption on aid receipts differs across sectors
MALARIA IN THE AMERICAS: A RETROSPECTIVE ANALYSIS OF CHILDHOOD EXPOSURE
No full textThis study considers the malaria-eradication campaigns in the United States (circa 1920), and in Brazil, Colombia and Mexico (circa 1955) in order to measure how much childhood exposure to malaria depresses labor productivity. The campaigns began because of advances in health technology, which mitigates concerns about reverse causality. Malarious areas saw large drops in the disease thereafter. Relative to non-malarious areas, cohorts born after eradication had higher income as adults than the preceding generation. These changes coincided with childhood exposure to the campaigns rather than with preexisting trends.Malaria, returns to health, eradication campaigns
Modelo de Deep Learning para la gradación automática de imágenes histopatológicas de cáncer de próstata
No full textGleason grading is recognized as the standard method for diagnosing prostate cancer. However, it is subject to significant inter-observer variability due to its reliance on subjective visual assessment. Current deep learning approaches for grading often require exhaustive pixel-level annotations and are generally limited to patch-level predictions, which do not incorporate slide-level information. Recently, weakly-supervised techniques have shown promise in generating whole-slide label predictions using pathology report labels, which are more readily available. However, these methods frequently lack visual and quantitative interpretability, reinforcing the black box nature of deep learning models, hindering their clinical adoption. This thesis introduces WiSDoM, a novel weakly-supervised and interpretable approach leveraging attention mechanisms and Kernel Density Matrices for the grading of prostate cancer on whole slides. This method is adaptable to varying levels of supervision. WiSDoM facilitates multi-scale interpretability through several features: detailed heatmaps that provide granular visual insights by highlighting critical morphological features without requiring tissue annotations; example-based phenotypical prototypes that illustrate the internal representation learned by the model, aiding in clinical verification; and visual-quantitative measures of model uncertainty, which enhance the transparency of the model's decision-making process, a crucial factor for clinical use. WiSDoM has been validated on core-needle biopsies from two different institutions, demonstrating robust agreement with the reference standard (quadratically weighted Kappa of 0.93). WiSDoM achieves state-of-the-art inter-observer agreement performance on the PANDA Challenge publicly available dataset while being clinically interpretable.La clasificación de Gleason se reconoce como el método estándar para diagnosticar el cáncer de próstata. Sin embargo, está sujeto a una variabilidad significativa entre observadores debido a su dependencia de la evaluación visual subjetiva. Los enfoques actuales de aprendizaje profundo a menudo requieren anotaciones exhaustivas a nivel de píxeles y generalmente se limitan a predicciones a nivel de parche, que no incorporan información a nivel de lámina. Recientemente, las técnicas débilmente supervisadas se han mostrado prometedoras a la hora de generar predicciones de etiquetas de láminas completas utilizando etiquetas de informes de patología, que están más fácilmente disponibles. Sin embargo, estos métodos frecuentemente carecen de interpretabilidad visual y cuantitativa, lo que refuerza la naturaleza de caja negra de los modelos de aprendizaje profundo y dificulta su adopción clínica. Esta tesis introduce WiSDoM, un enfoque novedoso interpretable y débilmente supervisado que aprovecha los mecanismos de atención y las matrices de densidad para gradar cáncer de próstata en láminas completas. Este método se adapta a distintos niveles de supervisión. WiSDoM facilita la interpretabilidad a múltiples escalas a través de varias características: mapas de calor detallados que brindan información visual granular al resaltar características morfológicas críticas sin requerir anotaciones de tejido; prototipos fenotípicos basados en ejemplos que ilustran la representación interna aprendida por el modelo, ayudando en la verificación clínica; y medidas visual-cuantitativas de incertidumbre del modelo, que mejoran la transparencia del proceso de toma de decisiones, un factor crucial para el uso clínico. WiSDoM se ha validado en biopsias de dos instituciones diferentes, lo que demuestra una sólida concordancia con el estándar de referencia (Kappa ponderado cuadráticamente de 0,93). WiSDoM logra un rendimiento del estado del arte de acuerdo entre observadores en el conjunto de datos PANDA Challenge además de ser clínicamente interpretable. (Texto tomado de la fuente).Research reported in this publication was partially supported by projects BPIN 2019000100- 060 ”Implementation of a Network for Research, Technological Development and Innovation in Digital Pathology (RedPat) supported by Industry 4.0 technologies” from FCTeI of SGR resources, approved by OCAD of FCTeI and MinCiencias, and project 110192092354, en- titled ”Program for the Early Detection of Premalignant Lesions and Gastric Cancer in urban, rural and dispersed areas in the Department of Nariño” of call No. 920 of 2022 of MinCiencias.MaestríaMagíster en Ingeniería - Ingeniería de Sistemas y ComputaciónSistemas Inteligente
