34,670 research outputs found

    Reading policies for joins: An asymptotic analysis

    Full text link
    Suppose that mnm_n observations are made from the distribution R\mathbf {R} and nmnn-m_n from the distribution S\mathbf {S}. Associate with each pair, xx from R\mathbf {R} and yy from S\mathbf {S}, a nonnegative score ϕ(x,y)\phi(x,y). An optimal reading policy is one that yields a sequence mnm_n that maximizes E(M(n))\mathbb{E}(M(n)), the expected sum of the (nmn)mn(n-m_n)m_n observed scores, uniformly in nn. The alternating policy, which switches between the two sources, is the optimal nonadaptive policy. In contrast, the greedy policy, which chooses its source to maximize the expected gain on the next step, is shown to be the optimal policy. Asymptotics are provided for the case where the R\mathbf {R} and S\mathbf {S} distributions are discrete and ϕ(x,y)=1or0\phi(x,y)=1 or 0 according as x=yx=y or not (i.e., the observations match). Specifically, an invariance result is proved which guarantees that for a wide class of policies, including the alternating and the greedy, the variable M(n) obeys the same CLT and LIL. A more delicate analysis of the sequence E(M(n))\mathbb{E}(M(n)) and the sample paths of M(n), for both alternating and greedy, reveals the slender sense in which the latter policy is asymptotically superior to the former, as well as a sense of equivalence of the two and robustness of the former.Comment: Published at http://dx.doi.org/10.1214/105051606000000646 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Collective intellectual property rights for the development of creative tourist districts: an exploration

    Get PDF
    In this paper the institution of Collective Intellectual Property Rights (CIPR) is proposed as a regulatory tool for the development of Creative Tourist Districts based on local knowledge and trust, described as a superior organisational model of destinations to alternative models founded on individual property. As there are various types and contexts of applications of CIPR, as well as different development objectives to be achieved, the paper designs a strategy to maximise the expected impacts from case to case. It then proposes “area labels”, based on a combination of controls on quality and delimitation of areas of validity of the right, as the best instrument to foster a strategic orientation to quality across the local tourism industry.

    Cancer-Associated Thrombosis in Cirrhotic Patients with Hepatocellular Carcinoma.

    Get PDF
    It is common knowledge that cancer patients are more prone to develop venous thromboembolic complications (VTE). It is therefore not surprising that patients with hepatocellular carcinoma (HCC) present with a significant risk of VTE, with the portal vein being the most frequent site (PVT). However, patients with HCC are peculiar as both cancer and liver cirrhosis are conditions that can perturb the hemostatic balance towards a prothrombotic state. Because HCC-related hypercoagulability is not clarified at all, the aim of the present review is to summarize the currently available knowledge on epidemiology and pathogenesis of non-malignant thrombotic complications in patients with liver cirrhosis and HCC. They are at increased risk to develop both PVT and non-splanchnic VTE, indicating that both local and systemic factors can foster the development of site-specific thrombosis. Recent studies have suggested multiple and often interrelated mechanisms through which HCC can tip the hemostatic balance of liver cirrhosis towards hypercoagulability. Described mechanisms include increased fibrinogen concentration/polymerization, thrombocytosis, and release of tissue factor-expressing extracellular vesicles. Currently, there are no specific guidelines on the use of thromboprophylaxis in this unique population. There is the urgent need of prospective studies assessing which patients have the highest prothrombotic profile and would therefore benefit from early thromboprophylaxis

    Classical resolution of singularities in dilaton cosmologies

    Get PDF
    For models of dilaton-gravity with a possible exponential potential, such as the tensor-scalar sector of IIA supergravity, we show how cosmological solutions correspond to trajectories in a 2D Milne space (parametrized by the dilaton and the scale factor). Cosmological singularities correspond to points at which a trajectory meets the Milne horizon, but the trajectories can be smoothly continued through the horizon to an instanton solution of the Euclidean theory. We find some exact cosmology/instanton solutions that lift to black holes in one higher dimension. For one such solution, the singularities of a big crunch to big bang transition mediated by an instanton phase lift to the black hole and cosmological horizons of de Sitter Schwarzschild spacetimes.Comment: 24 pages, 2 figure

    GKW representation theorem and linear BSDEs under restricted information. An application to risk-minimization

    Get PDF
    In this paper we provide Galtchouk-Kunita-Watanabe representation results in the case where there are restrictions on the available information. This allows to prove existence and uniqueness for linear backward stochastic differential equations driven by a general c\`adl\`ag martingale under partial information. Furthermore, we discuss an application to risk-minimization where we extend the results of F\"ollmer and Sondermann (1986) to the partial information framework and we show how our result fits in the approach of Schweizer (1994).Comment: 22 page
    corecore