337 research outputs found

    The New Theory of Strategic Voting

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    This is an analysis of strategic voting under qualified majority voting. Existing formal analyses of the plurality rule predict complete coordination of strategic voting: a strict interpretation of Duverger's Law. This conclusion is rejected. Unlike previous models, the popular support for each option is not commonly certain. Agents base their vote on both public and private signals of popular support. When private signals are the main source of information, the uniquely stable equilibrium entails only limited strategic voting and hence partial coordination. This is due to the surprising presence of negative feedback --- strategic voting is a self-attenuating phenomenon. The theory leads to the conclusion that multi-candidate support in a plurality electoral system is perfectly consistent with rational voting behaviour.

    Dynamic government performance: honeymoons and crises of confidence

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    We use a formal theoretical framework to explore the interplay between a government's longevity and its performance. Ministers perform well when their careers are valuable; this is so when the government's duration is expected to be long; the government's survival depends on its popularity; and, finally, that popularity depends on its ministers performance. The feedback loop between performance and longevity means that multiple rational-expectations equilibria can arise: Ministers work hard for a popular government, but divert efforts elsewhere if they believe the government is doomed; these alternatives are both self-fulfilling prophecies. However, the presence of (perhaps small) random events that buffet the performance and popularity of a government is sufficient to pin down a unique equilibrium. We explore the dynamics that arise: A crisis of confidence involving the rapid collapse of a government's performance is sparked when a sequence of negative shocks push the popularity of the government below a unique critical threshold

    Leading the Party:Coordination, Direction, and Communication

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    Party activists face a coordination problem: a critical mass (a barrier tocoordination) must advocate a single policy alternative if the party is tosucceed. The need for direction is the degree to which the merits of thealternatives respond to the underlying mood of the party. An individual'sability to assess the mood is his sense of direction. These factors combine toform an index of both the desirability and the feasibility of leadership: wecall this index Michels' Ratio. A sovereign party conference gives way toleadership by an individual or oligarchy if and only if Michels' Ratio issufficiently high. Leadership enhances the clarity of intra-partycommunication, but weakens the response of policy choices to the party'smood.

    The Qualities of Leadership:Direction, Communication, and Obfuscation

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    Party activists wish to (i) advocate the best policy and yet (ii) unify behind a commonparty line. An activist's understanding of his environment is based on the speeches ofparty leaders. A leader's influence, measured by the weight placed on her speech,increases with her judgement on policy (sense of direction) and her ability to conveyideas (clarity of communication). A leader with perfect clarity of communication enjoysgreater influence than one with a perfect sense of direction. Activists can choose howmuch attention to pay to leaders. A necessary condition for a leader to monopolize theagenda is that she is the most coherent communicator. Sometimes leaders attract moreattention by obfuscating their messages. A concern for party unity mitigates thisincentive; when activists emphasize following the party line, they learn more about theirenvironment.

    Cold Collision Frequency Shift of the 1S-2S Transition in Hydrogen

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    We have observed the cold collision frequency shift of the 1S-2S transition in trapped spin-polarized atomic hydrogen. We find Δν1S2S=3.8(8)×1010nHzcm3\Delta \nu_{1S-2S} = -3.8(8)\times 10^{-10} n Hz cm^3, where nn is the sample density. From this we derive the 1S-2S s-wave triplet scattering length, a1S2S=1.4(3)a_{1S-2S}=-1.4(3) nm, which is in fair agreement with a recent calculation. The shift provides a valuable probe of the distribution of densities in a trapped sample.Comment: Accepted for publication in PRL, 9 pages, 4 PostScript figures, ReVTeX. Updated connection of our measurement to theoretical wor

    Search for the standard model Higgs boson at LEP

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    Vasodilator factors in the systemic and local adaptations to pregnancy

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    We postulate that an orchestrated network composed of various vasodilatory systems participates in the systemic and local hemodynamic adaptations in pregnancy. The temporal patterns of increase in the circulating and urinary levels of five vasodilator factors/systems, prostacyclin, nitric oxide, kallikrein, angiotensin-(1–7) and VEGF, in normal pregnant women and animals, as well as the changes observed in preeclamptic pregnancies support their functional role in maintaining normotension by opposing the vasoconstrictor systems. In addition, the expression of these vasodilators in the different trophoblastic subtypes in various species supports their role in the transformation of the uterine arteries. Moreover, their expression in the fetal endothelium and in the syncytiotrophoblast in humans, rats and guinea-pigs, favour their participation in maintaining the uteroplacental circulation. The findings that sustain the functional associations of the various vasodilators, and their participation by endocrine, paracrine and autocrine regulation of the systemic and local vasoactive changes of pregnancy are abundant and compelling. However, further elucidation of the role of the various players is hampered by methodological problems. Among these difficulties is the complexity of the interactions between the different factors, the likelihood that experimental alterations induced in one system may be compensated by the other players of the network, and the possibility that data obtained by manipulating single factors in vitro or in animal studies may be difficult to translate to the human. In addition, the impossibility of sampling the uteroplacental interface along normal pregnancy precludes obtaining longitudinal profiles of the various players. Nevertheless, the possibility of improving maternal blood pressure regulation, trophoblast invasion and uteroplacental flow by enhancing vasodilation (e.g. L-arginine, NO donors, VEGF transfection) deserves unravelling the intricate association of vasoactive factors and the systemic and local adaptations to pregnancy

    Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

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    The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

    In silico toxicology protocols

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    The present publication surveys several applications of in silico (i.e., computational) toxicology approaches across different industries and institutions. It highlights the need to develop standardized protocols when conducting toxicity-related predictions. This contribution articulates the information needed for protocols to support in silico predictions for major toxicological endpoints of concern (e.g., genetic toxicity, carcinogenicity, acute toxicity, reproductive toxicity, developmental toxicity) across several industries and regulatory bodies. Such novel in silico toxicology (IST) protocols, when fully developed and implemented, will ensure in silico toxicological assessments are performed and evaluated in a consistent, reproducible, and well-documented manner across industries and regulatory bodies to support wider uptake and acceptance of the approaches. The development of IST protocols is an initiative developed through a collaboration among an international consortium to reflect the state-of-the-art in in silico toxicology for hazard identification and characterization. A general outline for describing the development of such protocols is included and it is based on in silico predictions and/or available experimental data for a defined series of relevant toxicological effects or mechanisms. The publication presents a novel approach for determining the reliability of in silico predictions alongside experimental data. In addition, we discuss how to determine the level of confidence in the assessment based on the relevance and reliability of the information
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