Neuronal circuitry of the pigeon retina (Columba livia) : the morphological classification and organization of various neuronal types

The three studies presented in this thesis were conducted to advance our understanding of the retinal circuitry that contributes to processing high visual acuity in the pigeon. In the first study, the topographic density changes and degree of photoreceptor (PR) to retinal ganglion cell (RGC) convergence in the pigeon retina was determined. DAPI or Propidium iodide labelled PRs and RGCs were counted in the retina. Rod density was quantified by counting anti-rod opsin stained outer segments. The fovea and the red field contained significantly higher cone and RGC densities compared with the yellow field. Rods were missing from the fovea, but not in the red field, which suggests that a rod circuitry may be present in this area. The ratio of cones to RGCs was lower in both the fovea and red field, which is consistent with the higher visual acuities that have been reported in these regions. The second study classified the types of DiO-Iabelled bipolar cells in the fovea, central red and yellow fields. Eight bipolar cell types were classified in the retina using a modification of Mariani's (1987) classification scheme. Eight BC types (B1 - B8) had similar dendritic morphology as the ones described by Mariani. Two bipolar cell types, B7 and B8, had comparatively smaller dendritic fields than the other types. It was estimated to receive input from possibly one photoreceptor in the fovea and the central red field. Based on the small dendritic field size, B7 and B8 may be good candidates for being the midget-like BCs in the pigeon retina. The third study classified the RGC groups in the pigeon retina. Classification of RGCs labelled with DiI/DiO in the pigeon retina was based on the dendritic stratification pattern in the inner plexiform layer (IPL). Five morphological RGC groups were identified, the unstratified, monostratified, bistratified, tristratified and tetrastratified. The unstratified group was characterised by vertically oriented dendrites occupying a thick portion of the IPL, whereas the other groups had horizontally oriented dendrites stratifying at narrow portion of the IPL. The unstratified RGC had the narrowest dendritic field (diameter >- 18.5 urn). Based on the unstratified RGC's dendritic field size, it is a good candidate for a 'midget-like' RGC in the pigeon retina. However, it has a different morphology from the primate midget RGC. Further work is required to determine the physiology and differential distribution of the different types of bipolar and ganglion cells in the pigeon retina

Testing Core Membership in Public Goods Economies

This paper develops a recent line of economic theory seeking to understand public goods economies using methods of topological analysis. Our first main result is a very clean characterization of the economy's core (the standard solution concept in public goods). Specifically, we prove that a point is in the core iff it is Pareto efficient, individually rational, and the set of points it dominates is path connected. While this structural theorem has a few interesting implications in economic theory, the main focus of the second part of this paper is on a particular algorithmic application that demonstrates its utility. Since the 1960s, economists have looked for an efficient computational process that decides whether or not a given point is in the core. All known algorithms so far run in exponential time (except in some artificially restricted settings). By heavily exploiting our new structure, we propose a new algorithm for testing core membership whose computational bottleneck is the solution of $O(n)$ convex optimization problems on the utility function governing the economy. It is fairly natural to assume that convex optimization should be feasible, as it is needed even for very basic economic computational tasks such as testing Pareto efficiency. Nevertheless, even without this assumption, our work implies for the first time that core membership can be efficiently tested on (e.g.) utility functions that admit "nice" analytic expressions, or that appropriately defined $\varepsilon$-approximate versions of the problem are tractable (by using modern black-box $\varepsilon$-approximate convex optimization algorithms).Comment: To appear in ICALP 201

LA BATALLA POLÍTICA POR EL PRESUPUESTO DE LA NACIÓN: INFLEXIBILIDADES O SUPERVIVENCIA FISCAL

El gobierno colombiano tiene un escaso margen de maniobra al preparar el Presupuesto General de la Nación ya que un alto porcentaje de los gastos que debe hacer cada año está predeterminado por un numeroso conjunto de leyes y de artículos constitucionales. En este trabajo se hace un diagnóstico sobre la magnitud y origen de la inflexibilidad" presupuestal, y se discuten posibles soluciones. La inflexibilidad compromete la capacidad de los representantes elegidos para ejecutar sus planes de gobierno, puede poner en peligro la estabilidad macroeconómica, favorece el exceso de apropiaciones por parte de grupos de interés, dificulta la posibilidad de llevar a cabo ajustes en situaciones fiscales deficitarias, dificulta la definición de prioridades, favorece la duplicidad de erogaciones para un mismo fin y le resta transparencia al proceso presupuestal. En buena medida, las inflexibilidades surgen del interés del legislativo de garantizar rentas específicas para determinados sectores y regiones, contrarrestar su falta de acceso formal al presupuesto y limitar la discrecionalidad del ejecutivo. Las medidas orientadas hacia la flexibilización aplicarían sanos principios presupuestales, reconocidos a lo largo de cien años de historia de hacienda pública en Colombia. Para solucionar estos problemas, se sugiere modificar el esquema actual de asignación de transferencias y rentas de destinación específica, aplicar cabalmente el principio de unidad de caja en el presupuesto, establecer reglas de ahorro contingente para algunos fondos especiales, promover una administración unificada de la tesorería del estado, revivir los denominados "auxilios parlamentarios" con el fin de hacer explícita (poner por encima de la mesa) la búsqueda de presupuesto por parte del legislativo, y alejarlo de la práctica de incluir gastos por vía de leyes, como ha sido la tradición. El presupuesto anual debe partir de un límite de largo plazo al endeudamiento público, y una senda de disminución prefijada. Es necesario que el Ministerio de Hacienda se concentre en la definición del monto de gasto coherente con un nivel deseado de deuda pública, y que sean el Presidente y el Consejo de Ministros los responsables de la asignación sectorial, en interacción con el Congreso de la República."Colombia

Um protocolo de autorização para internet das coisas baseado em atributos e informações de contexto

Orientador: Carlos Alberto MazieroDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Informática. Defesa : Curitiba, 18/02/2019Inclui referências: p.59-63Área de concentração: Ciência da ComputaçãoResumo: Com a Internet das Coisas, a ubiquidade de dispositivos cresce a cada dia. Controlar e garantir comunicação segura e amigável ao usuário final continua um desafio. Este trabalho propõe um protocolo de autorização para dispositivos baseado em atributos e informações de contexto. As informações de contexto são observações disponíveis em sensores dos dispositivos, tais como: luz, temperatura, microfone - para citar algumas. Este contexto provê elementos que auxiliam nas decisões de segurança, como fatores complementares de autorização. Agrega-se ao contexto um fator social dos dispositivos, auxiliando na avaliação de acessos e respectivos riscos. Este fator social consiste tanto no histórico das observações realizadas pelo dispositivo, quanto no cumprimento de suas funções (comportamento esperado). De posse destas informações de contexto e de atributos do pedido (requisitante e risco da informação), o protocolo classifica o risco e decide se efetiva ou não o pedido. As informações de contexto são base para o modelo de confiança entre os dispositivos, sendo utilizadas como validações entre os mesmos. Somado ao protocolo apresentado, discute-se o modelo de ameaças e respectivas mitigações as quais o protocolo resiste satisfatoriamente. Na sequencia, apresenta-se o uso e análise específica de um atributo: a luminância. Discute-se o uso da luminância para representação de um mesmo ambiente e respectivos resultados desta pesquisa. Por fim, algumas considerações e possibilidades de pesquisa em aberto. Palavras-chave: IoT, Segurança, Autorização, ABAC, Contexto, Protocolo, Luminância.Abstract: Internet of Things grows the devices' ubiquity constinuously. It remains a challenge to control and ensure a user-friendly secure communication. This work presents an context-aware attributebased authorization protocol. The context provides elements that helps decision making. The devices' social factor are included in the context, assisting in access evaluation and its risks. Context information is gathered throught devices' sensors, such as: light, temperature, sound - to list some examples. This context provides aid in security decisions, as complementary factors of authorization. A devices' social factor is added to the context, aiding the accesses evaluation and its risks. This social factor consists both the observations historical made by devices, and in by execution of its functions (expected behavior). With this context information and request attributes (asker and information risk), the protocol classifies the risk and decides whether or not will honor the request. Context information is the basis for the trust model between devices, and is used as validation between devices. In addition to the presented protocol, the threat model and its mitigations are discussed, which the protocol resists satisfactorily. In sequence, the analysis of an attribute use is presented: luminance. We discuss the luminance's use to represent same environment. Finally, we conclude with some considerations and open research possibilities. Keywords: IoT, Security, Authorization, ABAC, Context-Aware, Protocol, Luminance

When Does POlicy Reform Work? The Case of Central Bank Independence

policy reform, bank, inflation, government expenditure

Early-Onset Progressive Degeneration of the Area Centralis in RPE65-Deficient Dogs.

PURPOSE: Retinal epithelium-specific protein 65 kDa (RPE65)-deficient dogs are a valuable large animal model species that have been used to refine gene augmentation therapy for Leber congenital amaurosis type-2 (LCA2). Previous studies have suggested that retinal degeneration in the dog model is slower than that observed in humans. However, the area centralis of the dog retina is a cone and rod photoreceptor rich region comparable to the human macula, and the effect of RPE65 deficiency specifically on this retinal region, important for high acuity vision, has not previously been reported. METHODS: Spectral-domain optical coherence tomography, fundus photography, and immunohistochemistry of retinal wholemounts and sagittal frozen sections were used to define the time-course and cell-types affected in degeneration of the area centralis in affected dogs. RESULTS: Area centralis photoreceptor degeneration was evident from 6 weeks of age, and progressed to involve the inner retina. Immunohistochemistry showed that RPE65-deficient dogs developed early loss of S-cone outer segments, with slower loss of L/M-cone outer segments and rods. CONCLUSIONS: Early-onset severe photoreceptor degeneration in the area centralis of dogs with RPE65-deficiency offers a model of the early foveal/perifoveal degeneration in some patients with LCA2. This model could be used to refine interventions aiming to improve function and halt the progression of foveal/perifoveal photoreceptor degeneration

Political Dynasties in the UK House of Commons: The Null Effect of Narrow Electoral Selection

Does power persist within families? This article considers whether members of the UK House of Commons with longer legislative careers after 1832 were more likely to establish a political dynasty. Tenure can create opportunities to promote relatives. A regression discontinuity design for re-election races helps to rule out the confounding influence of inheritable traits. There is no evidence for a causal effect of tenure length on establishing or continuing a dynasty. Established families may have constrained further dynasty development, explaining the null result of tenure

Towards Becoming an Ecology of Care

Thinking about care in the organization of an ecology is central to the interdisciplinary research group Care Ecologies; found during a lockdown in the spring of 2021 and hosted by ARIAS Platform for Research Through the Arts and Sciences in Amsterdam. In Towards Becoming an Ecology of Care group members Valentina Curandi, Inte Gloerich, Ania Molenda, Maaike Muntinga, Natalia Sanchez Querubin, Nienke Scholts and Marloeke van der Vlugt, offer an initial articulation on their approaches and principles – performative practices, reflection, speculations - of what an ecology of care could be. While each bringing in different understandings of care, staying with those differences shaped the ways in which the agenda of the research group has been (un)settled. To exchange knowledge and experiences, the group uses various on- and off-line frameworks, like presentations and practice sessions. Exploring how activities that sustain a research group – coordinating, meeting, writing and documenting – may be done with care, this paper attempts to present a speculative proposition for functioning as a research ecology on and around care. Bringing into focus what care can do, while being attentive to what is neglected. This is not only done in writing but also becomes visible in the accompanying images compiled of material and immaterial memories. It is an ongoing process, for which the writing of this paper became a catalyst for reflection. While not aiming for clear answers the authors invite themselves and others to become more aware, devising and testing work strategies for care-based practices