VictorJuiz/thesis huggingface dataset:
A Reasoning Module for Long-lived Cognitive Agents
Keywords: situation calculus
computer science
artificial intelligence
mathematical logic
agent
knowledge representation
reasoning
reasoning about action
intelligent agent

In this thesis we study a reasoning module for agents that have cognitive abilities, such as memory, perception, action, and are expected to function autonomously for long periods of time. The module provides the ability to reason about action and change using the language of the situation calculus and variants of the basic action theories. The main focus of this thesis is on the logical problem of progressing an action theory. First, we investigate the conjecture by Lin and Reiter that a practical first-order definition of progression is not appropriate for the general case. We show that Lin and Reiter were indeed correct in their intuitions by providing a proof for the conjecture, thus resolving the open question about the first-order definability of progression and justifying the need for a second-order definition. Then we proceed to identify three cases where it is possible to obtain a first-order progression with the desired properties: i) we extend earlier work by Lin and Reiter and present a case where we restrict our attention to a practical class of queries that may only quantify over situations in a limited way; ii) we revisit the local-effect assumption of Liu and Levesque that requires that the effects of an action are fixed by the arguments of the action and show that in this case a first-order progression is suitable; iii) we investigate a way that the local-effect assumption can be relaxed and show that when the initial knowledge base is a database of possible closures and the effects of the actions are range-restricted then a first-order progression is also suitable under a just-in-time assumption. Finally, we examine a special case of the action theories with range-restricted effects and present an algorithm for computing a finite progression. We prove the correctness and the complexity of the algorithm, and show its application in a simple example that is inspired by video games.
First Passage Times: Integral Equations, Randomization and Analytical Approximations
Keywords: first passage time
Brownian motion
integral equations
hitting time
boundary function
martingales

The first passage time (FPT) problem for Brownian motion has been extensively studied in the literature. In particular, many incarnations of integral equations which link the density of the hitting time to the equation for the boundary itself have appeared. Most interestingly, Peskir (2002b) demonstrates that a master integral equation can be used to generate a countable number of new integrals via its differentiation or integration. In this thesis, we generalize Peskir's results and provide a more powerful unifying framework for generating integral equations through a new class of martingales. We obtain a continuum of new Volterra type equations and prove uniqueness for a subclass. The uniqueness result is then employed to demonstrate how certain functional transforms of the boundary affect the density function. Furthermore, we generalize a class of Fredholm integral equations and show its fundamental connection to the new class of Volterra equations. The Fredholm equations are then shown to provide a unified approach for computing the FPT distribution for linear, square root and quadratic boundaries. In addition, through the Fredholm equations, we analyze a polynomial expansion of the FPT density and employ a regularization method to solve for the coefficients. Moreover, the Volterra and Fredholm equations help us to examine a modification of the classical FPT under which we randomize, independently, the starting point of the Brownian motion. This randomized problem seeks the distribution of the starting point and takes the boundary and the (unconditional) FPT distribution as inputs. We show the existence and uniqueness of this random variable and solve the problem analytically for the linear boundary. The randomization technique is then drawn on to provide a structural framework for modeling mortality. We motivate the model and its natural inducement of 'risk-neutral' measures to price mortality linked financial products. Finally, we address the inverse FPT problem and show that in the case of the scale family of distributions, it is reducible to nding a single, base boundary. This result was applied to the exponential and uniform distributions to obtain analytical approximations of their corresponding base boundaries and, through the scaling property, for a general boundary.
Intracellular Signaling Pathways Regulating Hepatic Apolipoprotein B100 Production: Roles of Mitogen-activated Protein Kinases (MAPKs) and Inhibitor of NFkappaB Kinase (IKK)-NFkappaB
Keywords: metabolism
lipids
signalling
lipoproteins
insulin resistance
inflammation

Apolipoprotein B100 (apoB), the structural protein component of triglyceride-rich very low density lipoprotein (VLDL) and atherogenic low density lipoprotein, is considered an important risk indicator of atherosclerosis. In insulin resistant states, hepatic overproduction of apoB leads to metabolic dyslipidemia, characterized by high circulating VLDL and hypertriglyceridemia. Since the mitogen-activated protein kinases (MAPKs) and the inhibitor of NFkappaB kinase (IKK)-NFkappaB cascades are perturbed in insulin resistance, we hypothesized that the MAPKs (ERK, p38 and JNK) and the IKK-NFkappaB pathways regulate hepatic apoB output. We modulated these pathways in HepG2, a human hepatoma cell line, and primary hamster hepatocytes using chemical inhibitors and protein overexpression. ApoB synthesis and secretion were examined by metabolic pulse labeling. HepG2 is typically defective in secreting apoB as large VLDL particles and secretes smaller triglyceride-poor apoB-particles. Under continuous pulse labeling, ERK inhibition not only increased apoB secretion, it enabled HepG2 to secrete VLDL-sized particles in the presence of exogenous fatty acid (oleate). Concomitant with the increased apoB-particle size, ERK inhibition raised intracellular triglyceride level and diacylglycerol acyltransferase (DGAT) 1 and DGAT2 mRNA levels. Conversely, ERK activation decreased VLDL-apoB secretion from primary hepatocytes. In contrast to ERK, p38 or JNK inhibition decreased apoB secretion without affecting apoB-particle size from oleate-treated HepG2 cells. JNK inhibition also modulated apoB levels in primary hamster hepatocytes. Interestingly, the development of diet-induced hepatic insulin resistance was associated with decreased ERK, and enhanced p38 and NFkappaB activities. Thus we investigated the role of the NFkappaB pathway in regulating hepatic apoB production. IKK inhibition decreased and IKK overexpression increased apoB levels by modulating apoB mRNA translation and protein stability. IKK inhibition also suppressed hepatic apoB overproduction in an insulin resistance model, the fructose-fed hamster. Altogether, our results suggest that among the MAPK cascades, the MEK-ERK pathway is crucial in regulating apoB-lipoprotein assembly, possibly by modulating lipid availability to newly-synthesized apoB. The inflammatory IKK-NFkappaB cascade is also involved in regulating apoB synthesis and secretion. We postulate that dysregulation in the MAPK or NFkappaB cascades in insulin resistant and inflammatory states may contribute to hepatic apoB overproduction, and the common phenotype of hypertriglyceridemia and dyslipidemia.
Composable, Distributed-state Models for High-dimensional Time Series
Keywords: machine learning
time series
neural networks
unsupervised learning
restricted Boltzmann machines
hidden Markov models
graphical models
motion capture
dynamical models
generative models
computer vision
tracking

In this thesis we develop a class of nonlinear generative models for high-dimensional time series. The first key property of these models is their distributed, or "componential" latent state, which is characterized by binary stochastic variables which interact to explain the data. The second key property is the use of an undirected graphical model to represent the relationship between latent state (features) and observations. The final key property is composability: the proposed class of models can form the building blocks of deep networks by successively training each model on the features extracted by the previous one. We first propose a model based on the Restricted Boltzmann Machine (RBM) that uses an undirected model with binary latent variables and real-valued "visible" variables. The latent and visible variables at each time step receive directed connections from the visible variables at the last few time-steps. This "conditional" RBM (CRBM) makes on-line inference efficient and allows us to use a simple approximate learning procedure. We demonstrate the power of our approach by synthesizing various motion sequences and by performing on-line filling in of data lost during motion capture. We also explore CRBMs as priors in the context of Bayesian filtering applied to multi-view and monocular 3D person tracking. We extend the CRBM in a way that preserves its most important computational properties and introduces multiplicative three-way interactions that allow the effective interaction weight between two variables to be modulated by the dynamic state of a third variable. We introduce a factoring of the implied three-way weight tensor to permit a more compact parameterization. The resulting model can capture diverse styles of motion with a single set of parameters, and the three-way interactions greatly improve its ability to blend motion styles or to transition smoothly among them. In separate but related work, we revisit Products of Hidden Markov Models (PoHMMs). We show how the partition function can be estimated reliably via Annealed Importance Sampling. This enables us to demonstrate that PoHMMs outperform various flavours of HMMs on a variety of tasks and metrics, including log likelihood.
Towards a Poetics of Freedom: An Interpretive Analysis of Ricoeur and Dante
Keywords: hermeneutics
Dante
Paul Ricoeur
Divine Commedy

This thesis’ task is to reinterpret Paul Ricoeur’s philosophy of the will, hermeneutics, and study of metaphor from a perspective that speaks to what his early work conceptualized as a poetics of freedom. Poetics, for Ricoeur, becomes a mode of expression capable of representing and illuminating what he considers the essential paradox of our human condition: a will that is both free and bound, “set free as freedom and responsible in its very deliverance.” A poetics of freedom, Ricoeur conceptualized in the beginning of his career, would be a mediation through which we perceive a tensional reconciliation of our conflicted natures, “a linguistic register suitable for speaking of liberated freedom and liberated man in his existential concreteness and totality.” Ricoeur, however, never developed the poetics of freedom beyond its original conceptualization. Through an interpretive analysis of Ricoeur's work, I reorient his later works on metaphor and hermeneutics towards the concerns that dominated the philosophy of the will and the existential philosophy to which it belongs. This study of Ricoeur’s philosophy of being occurs in discourse with a poetic text, Dante’s Commedia. The Commedia, I argue, is a text whose poetry explicitly and implicitly discloses the importance of hermeneutics and poetics in the arrival at self-understanding. The correlations that arise between its aesthetic discourse and Ricoeur’s contemporary perspective illuminate what I consider to be at the core of the philosophy of being: a primordial tension of selfhood conceptualized in terms of the dialectical relations that arise between freedom and nature, between objectivity and subjectivity, and between perspective and meaning; or in Dante’s terms, between my life and la nostra vita (our life).
Advances in Portfolio Selection Under Discrete Choice Constraints: A Mixed-integer Programming Approach and Heuristics
Keywords: Optimization
Mathematical Programming
Stochastic Programming
Portfolio Optimization

Over the last year or so, we have witnessed the global effects and repercussions related to the field of finance. Supposed blue chip stocks and well-established companies have folded and filed for bankruptcy, an event that might have thought to been absurd two years ago. In addition, finance and investment science has grown over the past few decades to include a plethora of investment options and regulations. Now more than ever, developments in the field are carefully examined and researched by potential investors. This thesis involves an investigation and quantitative analysis of key money management problems. The primary area of interest is Portfolio Selection, where we develop advanced financial models that are designed for investment problems of the 21st century. Portfolio selection is the process involved in making large investment decisions to generate a collection of assets. Over the years the selection process has evolved dramatically. Current portfolio problems involve a complex, yet realistic set of managing constraints that are coupled to general historic risk and return models. We identify three well-known portfolio problems and add an array of practical managing constraints that form three different types of Mixed-Integer Programs. The product is advanced mathematical models related to risk-return portfolios, index tracking portfolios, and an integrated stock-bond portfolio selection model. The numerous sources of uncertainty are captured in a Stochastic Programming framework, and Goal Programming techniques are used to facilitate various portfolio goals. The designs require the consideration of modelling elements and variables with respect to problem solvability. We minimize trade-offs in modelling and solvability issues found in the literature by developing problem specific algorithms. The algorithms are tailored to each portfolio design and involve decompositions and heuristics that improve solution speed and quality. The result is the generation of portfolios that have intriguing financial outcomes and perform well with respect to the market. Portfolio selection is as dynamic and complex as the recent economic situation. In this thesis we present and further develop the mathematical concepts related to portfolio construction. We investigate the key financial problems mentioned above, and through quantitative financial modelling and computational implementations we introduce current approaches and advancements in field of Portfolio Optimization.
Adaptation and Perfomance of Greek Drama in Post-Apartheid South Africa
Keywords: South Africa
adaptation
tragedy
performance

In my dissertation I examine how adaptations of Greek tragedy in South Africa after the fall of apartheid (1994) address the transitional stage of the country and mediate in the formation and apprehension of post-apartheid national identities and the formation of a new communitas. Drawing particularly from Raymond Williams and Jean-Pierre Vernant, I approach tragedy as a paradigmatic model for analyzing the dialectical relationship between cultural text and social context. The examination of this paradigm in the context of post-apartheid South Africa is grounded in postcolonial theory defined as an ongoing project of addressing the politics of identity representation in conjunction with the underlying conditions of cultural and material inequalities in a neo-colonial context. I am focusing on three plays that provide distinct perspectives on the problem of national identity in the post-apartheid era and distinct artistic approaches to the process of adaptation. My examination of each play consists of two, interrelated parts: in the first part, I conduct a structural analysis of the text and an examination of the ways it relates to and reworks the major themes and concepts of the Greek tragedy it adapts. In the second part, I examine the connections between the country’s dominant discourses on national identities and the plays’ representations of these.
'Wash Me Black Again': African Nationalism, the Indian Diaspora, and Kwa-Zulu Natal, 1944-60
Keywords: South Africa
Natal
African National Congress
South African Indians
Diaspora
Postcolonial Theory

My dissertation combines a critical history of the Indian diaspora’s political and intellectual impact on the development of African nationalism in South Africa with an analysis of African/Indian racial dynamics in Natal. Beginning in the 1940s, tumultuous debates among black intellectuals over the place of the Indian diaspora in Africa played a central role in the emergence of new and antagonistic conceptualizations of a South African nation. The writings of Indian political figures (particularly Gandhi and Nehru) and the Indian independence struggle had enormous influence on a generation of African nationalists, but this impact was mediated in complex ways by the race and class dynamics of Natal. During the 1930s and 40s, rapid and large-scale urbanization generated a series of racially-mixed shantytowns surrounding Durban in which a largely Gujarati and Hindi merchant and landlord class provided the ersatz urban infrastructure utilized by both Tamil-speaking workers and Zulu migrants. In Indian-owned buses, stores, and movie theatres, a racial hierarchy of Indian over African developed based on the social grammars of property, relationship with land, family structure, and different gender roles. In such circumstances, practices integral to maintaining diasporic identities—such as religious festivals, marriage, caste (jati), language, and even dress and food—became signifiers of ranked status and perceived exclusion. Despite the destruction of this urban landscape by forced removals beginning in the late 1950s, these social relationships powerfully shaped African and Indian identities in Natal, the popular memory of different communities, and the later politics of the anti-apartheid struggle. Although a few recent publications have attempted to break down the bifurcation that characterizes Natal’s historiography, the majority of academic writing on the province employs a race-based framework that focuses on either Indians or Zulu-speaking Africans. As a result, Natal’s African/Indian racial dynamic plays, at most, a secondary role in most scholarship on the region. In turn, Natal itself generally appears in histories of the anti-apartheid struggle as either an exception or a momentary interruption to a “national” narrative overwhelmingly centered on events, organizations, and individuals in the Transvaal. Rejecting a “race relations” approach that hypostatizes coherent racial groups, my dissertation examines how segregationist policies, African and Indian political organizations, and everyday social practices continuously reproduced an “African/Indian divide” despite both the enormous heterogeneity of each group and the quotidian intimacies of urban life. At the same time, it explores the ways in which this division shaped the development of the anti-apartheid struggle in Natal and the consequences of Natal’s politics for South Africa as a whole.
On Small Mammal Sympatry in the Southeastern Amazon and Ecological Relationships with Brazil Nut Dispersal and Harvesting
Keywords: Small Mammals
Autoecology
Brazil nut
NTFPs
Seed Dispersal
Sympatry
Autoecology
Radio Telemetry
Muridae
Echimyidae
Spiny rat
Proechimys cuvieri
Proechimys goeldii
Proechimys roberti
Mesomys stimulax
Bertholletia excelsa
Lecythidaceae
Exclosures
Track plate
Live-trap

The Amazon rainforest harbors the planet's highest biodiversity among terrestrial ecosystems; however, the biology and ecology of most of its species are unknown. Niche partitioning is considered a key factor allowing species co-existence, especially for morphological similar species such as spiny rats of the genus Proechimys. I examined the extent to which habitat differentiation, species body mass, and diet could explain the community composition of small mammals at a site in the southeastern Amazon. Moreover, I radio-tagged sympatric species of Proechimys spp. and Mesomys stimulax (an arboreal spiny rat) to obtain detailed autoecology information, including habitat use and use of space. I found support for niche partitioning among species and associated small mammal species with distinct successional phases of gap dynamics. I also observed among Proechimys spp. a typical polygynous organization: females appeared to be territorial against females of any species of their genus; but male territories overlapped with those of several females. Mesomys stimulax showed evidence of monogamy and possible sociality, although sample sizes were small. To identify the importance of small mammals as seed disperser of Brazil nut seeds, I conduct experiments using a combination of fluorescent powder, seed exclosures, and track plates in forests with and without Brazil nut groves, and in forests with and without Brazil nut harvesting. Among small mammals, only Proechimys spp. removed, dispersed, and preyed upon Brazil nut seeds. Proechimys spp. sometimes scatterhoarded these seeds, and hence have the potential to play a significant role in recruiting new Brazil nut trees. I also trapped small mammals and measured forest structures on the same sites used for the seed dispersal experiment, to determine the ecological effects of Brazil nut harvest on small mammal communities; however, my results showed little evidence of changes associated with the seed exploitation. My results highlight the importance of habitat heterogeneity in structuring small mammal communities, and indicate that forest management practices that alter habitats, such as partial logging, also can be expected to alter small mammal composition and diversity. Proechimys spp. have the potential to play an important role in the ecological restoration of intensive exploited Brazil nut groves.