VictorJuiz/thesis huggingface dataset:
Integration of sensory and reward information during perceptual decision-making in lateral intraparietal cortex (LIP) [electronic resource]
Keywords: Neurobiology.

The work presented in this dissertation primarily focuses on decision-related activity in the lateral intraparietal area (LIP) and, secondarily, the dorsolateral prefrontal cortex (DLPFC). In Chapter 1 we review the previous independent investigations indicating that these areas are separately modulated by sensory information, value information and choice appropriate to represent decisions. We argue that when both sensory and value information must be simultaneously integrated to make choices, it is unknown, if, how and when these areas integrate these factors. We present a behavioral paradigm in which animal subjects must combine sensory and value information, on a trial-to-trial basis, to make optimal choices. This paradigm is based on a well-known motion discrimination task; however, in our task the magnitude of the reward associated with each option varies from trial to trial. On some trials both options are worth equally large or small rewards. On other trials one option's reward is greater than that of the other. In Chapter 2, we demonstrate that in the unequal reward conditions subjects' choices are consistently biased towards the greater magnitude option. Additionally, we will show that this bias is independent of the motion stimulus strength and its magnitude is nearly optimal. In Chapter 3, we observe that single neurons in cortical area LIP consistently, simultaneously and dynamically represent both sensory and value information. We will argue that this representation supports an integrator model of decision making, in which sensory information is accumulated until the decision is resolved by a threshold crossing. Our results support an interpretation of this model in which value information adjusts the likelihood of a threshold crossing by iv raising or lowering the accumulator's initial state. In Chapter 4, we present a preliminary comparison between LIP and DLPFC activity, under identical conditions, suggesting they play fundamentally different roles in decision making. In Chapter 5, we discuss future lines of research.
Intermediated blind portfolio auctions [electronic resource]
Keywords: Electrical Engineering

As much as 12% of the daily volume on the New York Stock Exchange, and similar volumes on other major world exchanges, involves the sale of portfolios by institutional investors to brokers through blind portfolio auctions. Such transactions typically take the form of a first-price sealed-bid auction in which the seller engages a few potential brokers and provides limited information about the portfolio being sold. Uncertainty about the portfolio contents reduces bids, effectively increasing the transaction cost paid by the seller. We consider the use of a trusted intermediary or equivalent cryptographic protocol to reduce transaction costs. In particular, we propose a mechanism through which each party provides relevant private information to an intermediary who ultimately reveals only the portfolio contents and price paid, and only to the seller and winning broker. Through analysis of a game-theoretic model, we demonstrate substantial potential benefits to sellers. For example, under reasonable assumptions a seller can reduce expected transaction costs by as much as 10% under a broker valuation model that induces efficient allocations at equilibrium, and as much as 33% under one that does not. We also consider the effects of intermediation on broker payoffs and social welfare as well as its performance in the context of the second-price auction. In addition, we consider the two-stage game in which sellers have the choice of selecting intermediation or not and show that under certain reasonable modeling assumptions that all sellers will select intermediation at equilibrium.
Intermittent and transient behavior in Cygnus X-1 and GRS 1915+105 X-ray emission [electronic resource]
Keywords: Physics

Much work has been done on trying to gain insight into the dynamics of accreting systems, such as black hole and neutron star binaries, by analyzing timing measurements from X-ray telescopes. In this thesis we present a novel approach to this problem using a kurtosis measure of the wavelet distribution obtained from the light curve to quantify the presence of intermittent activity. This method is applied to large RXTE data sets for GRS 1915+105, and Cygnus X-1. We demonstrate a new approach to reveal bursting modes. Negative correlation between the presence of a low frequency QPO in the Cygnus X-1 Fourier power spectrum and a wavelet kurtosis indicator of temporal intermittency is observed. A possible interpretation of this anti-correlation is developed using a "dripping handrail" transient chaos model.
Internal Beam Annihilation Therapy: A Novel Approach to Radiation Therapy
Keywords: Physics
Burchat, Patricia
cancer treatment
radiotherapy
Internal Beam Annihilation Therapy
IBAT
Thesis

Photon external beam therapy is currently the most widely used modality of radiotherapy in the treatment of cancer. However, due to the exponential characteristics of photon attenuation in matter, most of the energy is deposited before the beam even reaches the tumor inside the body. This results in poor dose conformity and large entrance doses, causing undesired irradiation of healthy tissue which can ultimately lead to toxicity and secondary cancers. In this study we describe a new theoretical modality of radiotherapy termed Internal Beam Annihilation Therapy (IBAT) which in an ideal model case can exhibit far superior dose contrast and conformity by using muon anti-muon annihilation at the tumor site. Using Monte Carlo simulation in conjunction with FLUKA, a particle transport code, we evaluate the energy deposition distribution of such a modality and compare its unique characteristics with those of existing modalities.
Interorganizational ties and organizational outcomes [electronic resource] : essays on the role of network ties and ecological factors in the U.S. venture capital industry, 1961-2002
Keywords: Sociology

This dissertation integrates relational (network) factors emphasized by the social exchange perspective and ecological factors emphasized by population ecology and demography to account for organizational outcomes. It includes three essays that analyze the ways in which interorganizational ties and ecological factors interact to affect organizational outcomes. The first essay shows that firms with wide market niches depend on alliances with other organizations for survival more than do organizations with narrower niches. It also demonstrates that generalist and specialist organizations increase their survival chances by exploiting resources complementary through interorganizational ties with each other. The second essay distinguishes between two types of centrality in a network: status centrality and hub centrality and analyzes their effects on organizational outcomes and mutual dynamics. Results indicates that status centrality positively affects access to and quality of market resources available to organizations as well as their survival and that hub centrality has no effect on these outcomes. Finally, the third essay finds that status increases an organization's chances of survival the most in periods where survival chances are lowest due to environmental (ecological) factors. Status thus plays the role of a "safety net", allowing high status organizations to survive in periods where lower status organizations fail.
Interrogating, manipulating, and controlling nano-bio interfaces [electronic resource]
Keywords: Materials Science and Engineering

Cells communicate through direct contact and soluble chemical signals. Mimicking an extracellular environment requires controlling these signals at micron length scales. Integrated circuits make electronic control at these scales trivial, but fluidic control at these length scales requires very different principles. Standard microfluidic devices can finely control flowing fluids, but fluid flow affects cells in a myriad of ways. Alternatively, diffusion based chemical delivery methods tend to be crude, ill defined systems that offer very limited control. This thesis describes three distinctive platforms that combine the active spatial and temporal control of microfluidic systems with a delivery system that relies purely on diffusion. First, we detail a silicon based array of nanoreservoirs underneath the cell culture surface which are used to store and release bioactive molecules. These reservoirs are opened and closed with electrochemical dissolution and deposition at a narrow reservoir opening. Next, we describe an adaptation of traditional, elastomer based microfluidics. In these devices the cell culture area is separated from a microfluidic channel located directly underneath the chamber by a nanoporous membrane. The desirable microfluidic properties, including temporal and spatial control, are preserved, while fluidic flow over the cells is eliminated. Finally, we demonstrate a novel "nanostraw" culture surface, which is combined with the previous device to offer fluidic access directly to the cell cytosol, creating a powerful tool with implications for cell delivery and sampling. Additional work on probing the assembly of protein structures is also detailed. Clathrin 2-dimensional lattice assembly on lipid monolayers, serving as cell membrane mimics, was monitored and studied through surface rheological techniques. Rheological measurements elucidated important network properties, and the formation process was compared to various models for clathrin network assembly.
Inverse control by mirroring joint dynamics within the olivo-cerebellar complex [electronic resource]
Keywords: Bioengineering.

In this dissertation, I revisit Kawato's proposal, that the cerebellum predictively modulates descending motor commands, to achieve smooth and coordinated motion, by acquiring an inverse model of the biomechanical plant, and extend it by describing a novel and precise mapping between a cerebellar multizonal microcomplex and a joint's inverse model. This mapping renders two novel predictions: First, inferior olive's oscillations mirror the biomechanical joint's oscillations. Second, deep cerebellar neurons implement a gain factor, set by Purkinje cell inhibition, on inferior olive's signals to mirror the spinal cord's gain. I use biophysical modeling to show that oscillations within the inferior olive match the range of natural frequencies and damping ratios of biophysical joints, and that deep cerebellar neurons enable a multiplicative interaction between the Purkinje and the olivary pathways. Furthermore, I determine the effects of current injection into the inferior olive and the deep cerebellar nuclei and use these results within a control theory model to predict that experimentally disturbing the inferior olive will introduce motor output ringing, while disturbing the deep nuclei will also scale motor output. In both cases, manipulating the inverse model implemented by microzonal microcomplex will unmask the joint's natural dynamics as observed by motor ringing at the joint's natural frequency.
Ionics at nanoscale [electronic resource] : application to fuel cells
Keywords: Mechanical Engineering

The overall efficiency of energy conversion devices such as batteries, fuel cells, and biological cells is often limited by charge transfer reactions at electrode-electrolyte interfaces. Because interfaces are the site of nearly all chemical (and electrochemical) reactions, understanding and improving their characteristics and structures can lead to significant reductions in both catalytic and interfacial losses. To this end, nano electrochemistry may offer us ways to understand details of charge transfer reaction at nanoscale resolution and open opportunities to engineer the interface with better kinetics. This work presents the results of three studies aimed at lowering the elec- trochemical reaction losses in both ceramic fuel cells and biological systems. The first part of work discusses a study of oxide ion incorporation and transport at the cathode of solid oxide fuel cells (SOFC). SOFCs are an attractive clean en- ergy technology because of the low to zero emissions from their operation and their potentially high efficiency. For wider applications, it is desirable to lower the oper- ation temperature of SOFCs, but this causes significant increase of interfacial loss due to sluggish kinetics of oxygen reduction reaction at the cathode. In this study, I demonstrated both spectroscpic (AC impedance spectroscopy) and spectrometric (Nano secondary ion mass spectrometry) evidence that oxygen incorporation from the cathode into the electrolyte is significantly enhanced at grain boundaries of the electrolyte. The second part of work discusses a study focused on proton transport in proton- conducting ceramic fuel cells. Acceptor-doped perovskites have attracted recent at- tention as potential electrolyte materials for the next generation protonic devices, including fuel cells, because of their high ionic conductivity at intermediate temper- atures. The chemical instability of most of proton-conducting ceramics in acidic gas environments such as carbon dioxide, however, compromises their practical use. I discuss the evidence of proton conduction in nanoscale yttria-stabilized zirconia, well known oxide ion conductor; this points to its possible usage as a chemical barrier layer for proton-conducting ceramics. The third part of work presents a study of the possibility of extracting electricity from plant cell and the economic feasibility. Plants have developed sophisticated solar energy capture mechanisms that may be adapted to be less expensive or to perform better than current photovoltaic solar energy collectors. I discuss direct extraction of photosynthetic electrons from a single plant cell done by inserting nanoscale electrodes into their chloroplasts in vivo; these results may represent an initial step in generating high efficiency bioelectricity.
Justification of induction by inference to lesser coincidence [electronic resource]
Keywords: Philosophy

I begin by identifying David Hume's problem of induction. Hume argues that induction cannot be justified by a priori reasoning, because the failure of induction does not imply contradiction, or by a posteriori reasoning, because reasoning that the unobserved will resemble the observed based on observation would be circular. Hume concludes that induction cannot be justified by any reasoning. The principle that nature is uniform cannot be established without assuming that nature is uniform. But many paradigmatic instances of induction can be justified in terms of something weaker than the principle that nature is uniform, namely a form of reasoning I call "inference to lesser coincidence". This form of reasoning is meant to incorporate traditional formulations of the justification of induction expressed in terms of inference to the best explanation, statistical sampling, and Bayesian reasoning. My version of the argument is as follows: The conditional, time-invariant proposition that vast regularities in progress are likely to continue somewhat further is either true or false. If false, then the regularities we have observed are colossally coincidental. If true, they are far less coincidental. Therefore the proposition is probably true. If, in fact, vast regularities in progress are likely to continue, this has application to specific cases, such as the possibility that the Sun will rise again. I respond to three objections, which claim that time-restricted laws lessen the coincidence of observed regularities without making it likely that the Sun will rise again, that the "sample" of observed events might be biased, and that a zero prior probability assignment for dependence might be justified. I conclude by discussing the meaning of 'cause'.
Kalendergeschichte and fait divers, the poetics of circumscribed space [electronic resource]
Keywords: Comparative Literature

This study analyzes the poetics of two small literary forms: the German Kalendergeschichte and the French fait divers. Intimately connected with more prominent genres like the novella, the aphorism, or the Poème en Prose, these ephemeral forms distinguish themselves through their specific material history, originating as publishing exigencies—stopgaps or infill for blank space. In the German case, on calendar pages. In the French, on the white space in between newspaper headlines. It is the play with and within these very concrete, material and traditional constraints that constitutes their literary appeal. Poets from Heinrich von Kleist to Charles Baudelaire, and E.T.A. Hoffmann to Stéphane Mallarmé all influenced the development of both genres significantly. But it was two outstanding authors in particular, Johann Peter Hebel and Félix Fénéon, that eventually made the pragmatic restrictions of the Kalendergeschichte and the fait divers the source of a genuine—and genuinely new—poetics. James Joyce, Franz Kafka, and Bertolt Brecht integrated these formal innovations into their own oeuvre. Thinkers like Martin Heidegger, Maurice Merlau-Ponty, or Roland Barthes reflected on their poetico-philosophic power. The study covers the general history of both genres, a close reading of the specific formal changes brought about by Hebel and Fénéon respectively, as well as a broad view of the historico-cultural context that produced them. Whereas the first part is focused on the Kalendergeschichte and Johann Peter Hebel's Der Rheinländische Hausfreund, the second part traces the fait divers and Félix Fénéon's Nouvelles en trois lignes in particular.
Kinetics of crude-oil combustion in porous media interpreted using isoconversional methods [electronic resource]
Keywords: Energy Resources Engineering

One method to access unconventional, heavy-oil and natural bitumen resources as well as waterflood residual oil is to apply in situ combustion (ISC) to oxidize in place a small fraction of the hydrocarbon thereby providing heat to reduce oil viscosity and pressure that enhances recovery. ISC is also attractive because it provides the opportunity to upgrade oil in-situ by increasing the API gravity and decreasing, for instance, sulfur content. Experimental analysis of crude-oil oxidation kinetics provides parameters, such as activation energy, for modeling and optimization of ISC processes. The complex nature of petroleum as a multi-component mixture and multi-step character of oxidation reactions complicates substantially the kinetic analysis of crude-oil. Isoconversional techniques provide model-free methods for estimating activation energy and naturally deconvolve multi-step reactions. In addition, isoconversional methods are also useful as a screening tool to recognize the burning characteristics of different oils. By using experimentally determined combustion kinetics of different oil samples along with combustion tube results, we show that isoconversional analysis of ramped temperature oxidation data is useful to predict combustion-front propagation. It also provides new insight into the nature of the reactions occurring during ISC. Ramped temperature oxidation (RTO) tests with effluent gas analysis are conducted to probe ISC reaction kinetics along with isothermal coke formation experiments. The role of oxygen during coke formation reactions (i.e., fuel formation for ISC) is investigated using X-ray photoelectron spectroscopy (XPS) of intermediate reaction products. The XPS data is analyzed along with companion RTO experiments to obtain a simplified multi-step reaction scheme. Synthetic cases illustrate the connection between a proposed reaction scheme for oil/matrix pairs and one-dimensional combustion front propagation. Analysis of experimental results illustrate that the reaction scheme is capable of reproducing experimental results including the basic trends in oxygen consumption and carbon oxides production for RTO experiments as a function of heating rate for both good and poor ISC candidates. The combination of XPS and RTO studies indicates that the quality (or reactivity) of coke formed during the process is a function of oxygen presence/absence.
A lattice model of the translational dynamics of nonrotating rigid rods [electronic resource]
Keywords: Chemistry

We present a lattice model of oriented, nonrotating, rigid rods in three dimensions with random walk dynamics and an algorithm to simulate the model. We use the ideas of the Doi-Edwards (DE) theory, which was originally developed for a system of rods that both translate and rotate in continuous space, to predict the dependence of the translational diffusion constant of the rods in the perpendicular direction, on the (dimensionless) concentration in the semidilute regime. We find that the transnational perpendicular diffusion constant is proportional to the inverse square of the concentration. The theory is based on a `tube model' for the constraints imposed on the motion of a rod by the surrounding rods. Simulations of the model confirm that the scaling predicted by DE ideas and that the nature of the agreement is similar to that for the rotational diffusion constant in the original DE theory. We formulate a quantitative theory for the prefactor in the scaling relationship using only DE ideas, but it predicts a proportionality constant that is much too small. To explain this discrepancy, we modify the DE approach to obtain a more accurate estimate of the average tube radius, and we take into account two effects, called `leakage' and `drift', that are caused by perpendicular motions of rods that are ignored by the original DE theory. The theory of leakage takes into account the fact that the ends of a rod are less effective than the middle of the rod for blocking the motion of nearby rods. The theory of drift takes into account that the tube that any one rod is in can move in the perpendicular direction without changing its structure as a result of the perpendicular motion of the rods that form the tube. With these changes, the theory predicts a prefactor that is in much better agreement with the simulations. The simulations find that, as the concentration is increased, the approach to the limit of DE scaling is slow, and the -2 power in the DE scaling law is never quite achieved even at the highest concentration simulated. We propose a new scaling relationship that explains the deviations from the DE scaling relationship. Finally, we study the self and total density-density space time correlation functions for this model and propose a simple theory for the short time behavior of these functions based on a one-dimensional two-component lattice gas model.