1,260 research outputs found

    Oxford Handbook Of American Political Development

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    Scholars working in or sympathetic to American political development (APD) share a commitment to accurately understanding the history of American politics – and thus they question stylized facts about America’s political evolution. Like other approaches to American politics, APD prizes analytical rigor, data collection, the development and testing of theory, and the generation of provocative hypotheses. Much APD scholarship indeed overlaps with the American politics subfield and its many well developed literatures on specific institutions or processes (for example Congress, judicial politics, or party competition), specific policy domains (welfare policy, immigration), the foundations of (in)equality in American politics (the distribution of wealth and income, race, ethnicity, gender, class, and sexual and gender orientation), public law, and governance and representation. What distinguishes APD is careful, systematic thought about the ways that political processes, civic ideals, the political construction of social divisions, patterns of identity formation, the making and implementation of public policies, contestation over (and via) the Constitution, and other formal and informal institutions and processes evolve over time – and whether (and how) they alter, compromise, or sustain the American liberal democratic regime. APD scholars identify, in short, the histories that constitute American politics. They ask: what familiar or unfamiliar elements of the American past illuminate the present? Are contemporary phenomena that appear new or surprising prefigured in ways that an APD approach can bring to the fore? If a contemporary phenomenon is unprecedented then how might an accurate understanding of the evolution of American politics unlock its significance

    Autonomous frequency domain identification: Theory and experiment

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    The analysis, design, and on-orbit tuning of robust controllers require more information about the plant than simply a nominal estimate of the plant transfer function. Information is also required concerning the uncertainty in the nominal estimate, or more generally, the identification of a model set within which the true plant is known to lie. The identification methodology that was developed and experimentally demonstrated makes use of a simple but useful characterization of the model uncertainty based on the output error. This is a characterization of the additive uncertainty in the plant model, which has found considerable use in many robust control analysis and synthesis techniques. The identification process is initiated by a stochastic input u which is applied to the plant p giving rise to the output. Spectral estimation (h = P sub uy/P sub uu) is used as an estimate of p and the model order is estimated using the produce moment matrix (PMM) method. A parametric model unit direction vector p is then determined by curve fitting the spectral estimate to a rational transfer function. The additive uncertainty delta sub m = p - unit direction vector p is then estimated by the cross spectral estimate delta = P sub ue/P sub uu where e = y - unit direction vectory y is the output error, and unit direction vector y = unit direction vector pu is the computed output of the parametric model subjected to the actual input u. The experimental results demonstrate the curve fitting algorithm produces the reduced-order plant model which minimizes the additive uncertainty. The nominal transfer function estimate unit direction vector p and the estimate delta of the additive uncertainty delta sub m are subsequently available to be used for optimization of robust controller performance and stability

    CallE: An Effect System for Method Calls

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    Effect systems are used to statically reason about the effects an expression may have when evaluated. In the literature, such effects include various behaviours as diverse as memory accesses and exception throwing. Here we present CallE, an object-oriented language that takes a flexible approach where effects are just method calls: this works well because ordinary methods often model things like I/O operations, access to global state, or primitive language operations such as thread creation. CallE supports both flexible and fine-grained control over such behaviour, in a way designed to minimise the complexity of annotations. CallE's effect system can be used to prevent OO code from performing privileged operations, such as querying a database, modifying GUI widgets, exiting the program, or performing network communication. It can also be used to ensure determinism, by preventing methods from (indirectly) calling non-deterministic primitives like random number generation or file reading

    ArCLight - a Compact Dielectric Large-Area Photon Detector

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    ArCLight is a novel device for detecting scintillation light over large areas with Photon Detection Efficiency (PDE) of the order of a few percent. Its robust technological design allows for efficient use in large-volume particle detectors, such as Liquid Argon Time Projection Chambers (LArTPCs) or liquid scintillator detectors. Due to its dielectric structure it can be placed inside volumes with high electric field. It could potentially replace vacuum PhotoMultiplier Tubes (PMTs) in applications where high PDE is not required. The photon detection efficiency for a 10x10cm2 detector prototype was measured to be in the range of 0.8% to 2.2% across the active area

    First Operation of a Resistive Shell Liquid Argon Time Projection Chamber -- A new Approach to Electric-Field Shaping

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    We present a new technology for the shaping of the electric field in Time Projection Chambers (TPCs) using a carbon-loaded polyimide foil. This technology allows for the minimisation of passive material near the active volume of the TPC and thus is capable to reduce background events originating from radioactive decays or scattering on the material itself. Furthermore, the high and continuous electric resistivity of the foil limits the power dissipation per unit area and minimizes the risks of damages in the case of an electric field breakdown. Replacing the conventional field cage with a resistive plastic film structure called 'shell' decreases the number of components within the TPC and therefore reduces the potential points of failure when operating the detector. A prototype liquid argon (LAr) TPC with such a resistive shell and with a cathode made of the same material was successfully tested for long term operation with electric field values up to about 1.5 kV/cm. The experiment shows that it is feasible to successfully produce and shape the electric field in liquefied noble-gas detectors with this new technology.Comment: 13 page

    Charges of twisted branes: the exceptional cases

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    The charges of the twisted D-branes for the two exceptional cases (SO(8) with the triality automorphism and E_6 with charge conjugation) are determined. To this end the corresponding NIM-reps are expressed in terms of the fusion rules of the invariant subalgebras. As expected the charge groups are found to agree with those characterising the untwisted branes.Comment: 15 page

    Four-dimensional Kähler metrics admitting c-projective vector fields

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    A vector field on a Kähler manifold is called c-projective if its flow preserves the J-planar curves. We give a complete local classification of Kähler real 4-dimensional manifolds that admit an essential c-projective vector field. An important technical step is a local description of 4-dimensional c-projectively equivalent metrics of arbitrary signature. As an application of our results we prove the natural analog of the classical Yano-Obata conjecture in the pseudo-Riemannian 4-dimensional case

    Sorption and catalytic oxidation of Fe(II) at the surface of calcite

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    The effect of sorption and coprecipitation of Fe(II) with calcite on the kinetics of Fe(II) oxidation was investigated. The interaction of Fe(II) with calcite was studied experimentally in the absence and presence of oxygen. The sorption of Fe(II) on calcite occurred in two distinguishable steps: (a) a rapid adsorption step (seconds–minutes) was followed by (b) a slower incorporation (hours–weeks). The incorporated Fe(II) could not be remobilized by a strong complexing agent (phenanthroline or ferrozine) but the dissolution of the outmost calcite layers with carbonic acid allowed its recovery. Based on results of the latter dissolution experiments, a stoichiometry of 0.4 mol% Fe:Ca and a mixed carbonate layer thickness of 25 nm (after 168 h equilibration) were estimated. Fe(II) sorption on calcite could be successfully described by a surface adsorption and precipitation model (Comans & Middelburg, GCA51 (1987), 2587) and surface complexation modeling (Van Cappellen et al., GCA57 (1993), 3505; Pokrovsky et al., Langmuir16 (2000), 2677). The surface complex model required the consideration of two adsorbed Fe(II) surface species, >CO3Fe+ and >CO3FeCO3H0. For the formation of the latter species, a stability constant is being suggested. The oxidation kinetics of Fe(II) in the presence of calcite depended on the equilibration time of aqueous Fe(II) with the mineral prior to the introduction of oxygen. If pre-equilibrated for >15 h, the oxidation kinetics was comparable to a calcite-free system (t1/2 = 145 ± 15 min). Conversely, if Fe(II) was added to an aerated calcite suspension, the rate of oxidation was higher than in the absence of calcite (t1/2 = 41 ± 1 min and t1/2 = 100 ± 15 min, respectively). This catalysis was due to the greater reactivity of the adsorbed Fe(II) species, >CO3FeCO3H0, for which the species specific rate constant was estimated

    The Utility of an Online Forward Triage Tool During the SARS-CoV-2 Pandemic: Health Care Provider and Health Authority Perspectives.

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    Introduction The SARS CoV-2 pandemic poses major challenges not only to patients but also to health care professionals and policy-makers, with rapidly changing, sometimes complex, recommendations, and guidelines to the population. Online forward triage tools (OFTT) got a major boost from the pandemic as they helped with the implementation and monitoring of recommendations. Methods A multiphase mixed method sequential explanatory study design was employed. Quantitative data were collected first and informed the qualitative interview guides. Video interviews were held with key informants (health care providers and health authorities) between 2 September and 10 December 2020. Audio-recordings were transcribed verbatim, coded thematically and compared with patient perspectives (framework). Objectives To explore the perspectives of health care providers and authorities in Canton Bern on the utility of a COVID-19 OFTT, as well as elicit recommendations for telehealth in future. Results The following themes emerged; (i) accessibility (ii) health system burden reduction (iii) utility in preventing onward transmission (iv) utility in allaying fear and anxiety (v) medical decision-making utility (vi) utility as information source (vii) utility in planning and systems thinking. The health care providers and health authorities further provided insights on potential barriers and facilitators of telehealth in future. Conclusion Similar to patients, health care providers acknowledge the potential and utility of the COVID-19 OFTT particularly as an information source and in reducing the health system burden. Data privacy, doctor-patient relationship, resistance to change, regulatory, and mandate issues, and lack of systems thinking were revealed as barriers to COVID-19 OFTT utility
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