7,884 research outputs found

    Beam scanning by liquid-crystal biasing in a modified SIW structure

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    A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

    An anatomically detailed arterial-venous network model. Cerebral and coronary circulation

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    In recent years, several works have addressed the problem of modeling blood flow phenomena in veins, as a response to increasing interest in modeling pathological conditions occurring in the venous network and their connection with the rest of the circulatory system. In this context, one-dimensional models have proven to be extremely efficient in delivering predictions in agreement with in-vivo observations. Pursuing the increase of anatomical accuracy and its connection to physiological principles in haemodynamics simulations, the main aim of this work is to describe a novel closed-loop Anatomically-Detailed Arterial-Venous Network (ADAVN) model. An extremely refined description of the arterial network consisting of 2,185 arterial vessels is coupled to a novel venous network featuring high level of anatomical detail in cerebral and coronary vascular territories. The entire venous network comprises 189 venous vessels, 79 of which drain the brain and 14 are coronary veins. Fundamental physiological mechanisms accounting for the interaction of brain blood flow with the cerebro-spinal fluid and of the coronary circulation with the cardiac mechanics are considered. Several issues related to the coupling of arterial and venous vessels at the microcirculation level are discussed in detail. Numerical simulations are compared to patient records published in the literature to show the descriptive capabilities of the model. Furthermore, a local sensitivity analysis is performed, evidencing the high impact of the venous circulation on main cardiovascular variables

    Writing Facts: Interdisciplinary Discussions of a Key Concept in Modernity

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    "Fact" is one of the most crucial inventions of modern times. Susanne Knaller discusses the functions of this powerful notion in the arts and the sciences, its impact on aesthetic models and systems of knowledge. The practice of writing provides an effective procedure to realize and to understand facts. This concerns preparatory procedures, formal choices, models of argumentation, and narrative patterns. By considering "writing facts" and "writing facts", the volume shows why and how "facts" are a result of knowledge, rules, and norms as well as of description, argumentation, and narration. This approach allows new perspectives on »fact« and its impact on modernity

    Exploring the Tat pathway for the production of disulphide-bonded recombinant proteins using CyDisCo in Escherichia coli

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    The production of heterologous proteins of interest in microbial hosts such as Escherichia coli is a cost-effective and vital tool for the biopharmaceutical and enzyme industries. Research and development efforts over the past few decades have majorly focused on the Sec pathway for recombinant protein secretion in E. coli. However, the Twin-arginine translocation (Tat) pathway of E. coli has recently garnered interest for the periplasmic export of folded biopharmaceuticals as it possesses a unique proofreading ability to export correctly folded proteins. Tat-based translocation of biopharmaceuticals to the periplasm has the potential to greatly ease the downstream processing by reducing the amount of contaminating proteins and nucleic acids, thereby lowering the costs and time needed for their production. Furthermore, coupling Tatdependent protein secretion with the CyDisCo technology (cytoplasmic disulphide bond formation in E. coli), which enables disulphide bond formation in the cytoplasm of E. coli, provides a powerful platform for the production of industrially relevant and difficult-to-express proteins. Initially, a new experimental design for the export of multiple disulphide bond containing proteins to the periplasm by Tat in the presence of CyDisCo was empirically tested and developed as a starting point for future experiments. Later, a comparative study between Sec and Tat pathways for periplasmic export of a single chain variable fragment (scFv) in E. coli BL21 and W3110 was carried out. This led to an interesting comparison between the two strains based on soluble protein yields and quality when exported by the Sec pathway in fermenters. We observed a stark difference in the productivity profile of these two strains and a similar heterogeneity profile in the final product in both strains that could not detected by mass spectrometry-based analysis but confirmed by Differential Scanning Calorimetry (DSC) and 1D-1 H -NMR spectroscopy. Finally, in order to understand the limitations and maximize the applicability of the Tat pathway for proteins that fail to get exported efficiently with the TorA signal peptide, we focused on investigating alternative signal peptides. Here, we found that alternative signal peptides namely AmiC and MdoD allow highly efficient secretion of a disulphide bond-containing protein (YebF) to the periplasm of E. coli via Tat with CyDisCo. We report that these signal peptides are far more efficient than the well-known Tat specific TorA signal peptide, and hence they are potentially more suitable for large scale protein production than this more rigorous Tat-specific signal peptide. Overall, the research work presented in this thesis suggests that the Tat pathway and the CyDisCo system are attractive platforms for biotechnology and establishes highly efficient Tatdependent secretion of disulphide-bonded protein YebF to the E. coli periplasm

    New Music for a New World: Robert Ashley’s Television Operas

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    Robert Ashley defined the majority of his works as “television operas”—spoken narrative music for television broadcast. Analyzing Ashley’s works through their cross-disciplinarity, this thesis addresses the development of Ashley’s chosen medium; assesses his use of visual, linguistic, and musical structures; and interprets their basis in American cultural identity

    Insect neuroethology of reinforcement learning

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    Historically, reinforcement learning is a branch of machine learning founded on observations of how animals learn. This involved collaboration between the fields of biology and artificial intelligence that was beneficial to both fields, creating smarter artificial agents and improving the understanding of how biological systems function. The evolution of reinforcement learning during the past few years was rapid but substantially diverged from providing insights into how biological systems work, opening a gap between reinforcement learning and biology. In an attempt to close this gap, this thesis studied the insect neuroethology of reinforcement learning, that is, the neural circuits that underlie reinforcement-learning-related behaviours in insects. The goal was to extract a biologically plausible plasticity function from insect-neuronal data, use this to explain biological findings and compare it to more standard reinforcement learning models. Consequently, a novel dopaminergic plasticity rule was developed to approximate the function of dopamine as the plasticity mechanism between neurons in the insect brain. This allowed a range of observed learning phenomena to happen in parallel, like memory depression, potentiation, recovery, and saturation. In addition, by using anatomical data of connections between neurons in the mushroom body neuropils of the insect brain, the neural incentive circuit of dopaminergic and output neurons was also explored. This, together with the dopaminergic plasticity rule, allowed for dynamic collaboration amongst parallel memory functions, such as acquisition, transfer, and forgetting. When tested on olfactory conditioning paradigms, the model reproduced the observed changes in the activity of the identified neurons in fruit flies. It also replicated the observed behaviour of the animals and it allowed for flexible behavioural control. Inspired by the visual navigation system of desert ants, the model was further challenged in the visual place recognition task. Although a relatively simple encoding of the olfactory information was sufficient to explain odour learning, a more sophisticated encoding of the visual input was required to increase the separability among the visual inputs and enable visual place recognition. Signal whitening and sparse combinatorial encoding were sufficient to boost the performance of the system in this task. The incentive circuit enabled the encoding of increasing familiarity along a known route, which dropped proportionally to the distance of the animal from that route. Finally, the proposed model was challenged in delayed reinforcement tasks, suggesting that it might take the role of an adaptive critic in the context of reinforcement learning

    Doing Things with Words: The New Consequences of Writing in the Age of AI

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    Exploring the entanglement between artificial intelligence (AI) and writing, this thesis asks, what does writing with AI do? And, how can this doing be made visible, since the consequences of information and communication technologies (ICTs) are so often opaque? To propose one set of answers to the questions above, I begin by working with Google Smart Compose, the word-prediction AI Google launched to more than a billion global users in 2018, by way of a novel method I call AI interaction experiments. In these experiments, I transcribe texts into Gmail and Google Docs, carefully documenting Smart Compose’s interventions and output. Wedding these experiments to existing scholarship, I argue that writing with AI does three things: it engages writers in asymmetrical economic relations with Big Tech; it entangles unwitting writers in climate crisis by virtue of the vast resources, as Bender et al. (2021), Crawford (2021), and Strubell et al. (2019) have pointed out, required to train and sustain AI models; and it perpetuates linguistic racism, further embedding harmful politics of race and representation in everyday life. In making these arguments, my purpose is to intervene in normative discourses surrounding technology, exposing hard-to-see consequences so that we—people in the academy, critical media scholars, educators, and especially those of us in dominant groups— may envision better futures. Toward both exposure and reimagining, my dissertation’s primary contributions are research-creational work. Research-creational interventions accompany each of the three major chapters of this work, drawing attention to the economic, climate, and race relations that word-prediction AI conceals and to the otherwise opaque premises on which it rests. The broader wager of my dissertation is that what technologies do and what they are is inseparable: the relations a technology enacts must be exposed, and they must necessarily figure into how we understand the technology itself. Because writing with AI enacts particular economic, climate, and race relations, these relations must figure into our understanding of what it means to write with AI and, because of AI’s increasing entanglement with acts of writing, into our very understanding of what it means to write

    GAC-MAC-SGA 2023 Sudbury Meeting: Abstracts, Volume 46

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    Cultural Diplomacy in Cold War Finland

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    This open access book explores the organization and evolution of Finland’s Cold War cultural diplomacy (1945-1975) as the basis for a reflection on the country’s foreign relations, the link between culture and politics, small states’ autonomy during the Cold War, and the porosity of the East-West divide. The book offers a historical survey of the development of Finland’s cultural diplomacy as part of the Finnish state’s foreign activities. In its empirical parts, it focuses on archives drawn from the Finnish Ministry of Foreign Affairs and the Ministry of Education in order to explain Finland’s cultural diplomacy as the result of the country’s foreign policy orientations, interactions between domestic and foreign policy, and the expansion of state activities in the artistic, educational, and cultural sectors. Various reflections and reports on foreign cultural relations highlight the role of identity concerns, cultural relations, geopolitics and economic imperatives in the development of a specifically Finnish cultural diplomacy. Furthermore, the book focuses on specific aspects and events, considering for instance the organization and evolutions of Finland’s cultural relations with the USSR, the role of cultural treaties, academic exchanges and scientific cooperation, “cultural exports” and the marketization of culture, overlaps between cultural relations and high politics
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