340 research outputs found

    A transformation method to study the solvability of fully coupled FBSDEs

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    We present a new method for checking global solvability of fully coupled forward-backward stochastic differential equations (FBSDEs), where all function parameters are Lipschitz continuous, the terminal condition is monotone and the diffusion coefficient of the forward part depends monotonically on z, the control process component of the backward part. We show that one can reduce, via a linear transformation, the FBSDE to an auxiliary FBSDE for which the Lipschitz constant of the forward diffusion coefficient w.r.t. z is smaller than the inverse of the Lipschitz constant of the terminal condition w.r.t. the forward component x. The latter condition allows to verify existence of a global solution by analyzing the space derivative of the decoupling field. We illustrate with several examples how the transformation method can be used for proving global solvability of FBSDEs

    linking goal-directed and model-based behavior

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    In experimental psychology different experiments have been developed to assess goal–directed as compared to habitual control over instrumental decisions. Similar to animal studies selective devaluation procedures have been used. More recently sequential decision-making tasks have been designed to assess the degree of goal-directed vs. habitual choice behavior in terms of an influential computational theory of model-based compared to model-free behavioral control. As recently suggested, different measurements are thought to reflect the same construct. Yet, there has been no attempt to directly assess the construct validity of these different measurements. In the present study, we used a devaluation paradigm and a sequential decision-making task to address this question of construct validity in a sample of 18 healthy male human participants. Correlational analysis revealed a positive association between model-based choices during sequential decisions and goal-directed behavior after devaluation suggesting a single framework underlying both operationalizations and speaking in favor of construct validity of both measurement approaches. Up to now, this has been merely assumed but never been directly tested in humans

    Un modèle de canal multi-trajets appliqué à la simulation rapide du lien UMTS

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    - Cet article propose une méthode de simulation simplifiée du lien radio. Son originalité consiste en la modélisation simplifiée du récepteur et du canal, qui reste très fidèle. Cette méthode de simulation rapide est très précise et le gain en complexité est important. L'exemple des services 12.2 et 64 kbps de l'UMTS FDD à 3 et 120 km/h pour les canaux du 3GPP montre très peu de différence entre les performances des simulateurs traditionnel et simplifié

    The Iberian Peninsula in the Imperial and Post-Imperial Context

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    This paper investigates the way in which technical and normative knowledge relating to infrastructures, mobility and water management, which the Romans began developing in the republican period, was functionalized for the purpose of expanding the empire in the Iberian Peninsula, starting with the establishment of Roman provincial rule and continuing into the Islamic epoch. It also examines how that knowledge was entrenched in the individual Iberian provinces, and adapted to reflect specific local features. In addition to shedding light on how imperial concepts manifested themselves in the appropriation of space in specific contexts, the example of the Iberian Peninsula elucidates both how the knowledge in question was adapted to meet ‘regional-political’ objectives once the imperial frame of reference fell away and how it was ultimately restructured, modified and legitimized to reflect overriding religious considerations. The paper also provides examples indicating the degree to which antique concepts lent themselves to transformation while simultaneously representing both a potential and a challenge for any subsequent rulers

    Discovery of an old nova remnant in the Galactic globular cluster M 22

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    A nova is a cataclysmic event on the surface of a white dwarf in a binary system that increases the overall brightness by several orders of magnitude. Although binary systems with a white dwarf are expected to be overabundant in globular clusters (GCs) compared to the Galaxy, only two novae from Galactic globular clusters have been observed. We present the discovery of an emission nebula in the Galactic globular cluster M 22 (NGC 6656) in observations made with the integral-field spectrograph MUSE. We extract the spectrum of the nebula and use the radial velocity determined from the emission lines to confirm that the nebula is part of NGC 6656. Emission-line ratios are used to determine the electron temperature and density. It is estimated to have a mass of 1 to 17×10−517 \times 10^{-5} solar masses. This mass and the emission-line ratios indicate that the nebula is a nova remnant. Its position coincides with the reported location of a 'guest star', an ancient Chinese term for transients, observed in May 48 BCE. With this discovery, this nova may be one of the oldest confirmed extrasolar events recorded in human history.Comment: 7 pages, 3 figures; accepted for publication in Astronomy & Astrophysic

    Effect of Speech Rate on Neural Tracking of Speech

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    Speech comprehension requires effort in demanding listening situations. Selective attention may be required for focusing on a specific talker in a multi-talker environment, may enhance effort by requiring additional cognitive resources, and is known to enhance the neural representation of the attended talker in the listener’s neural response. The aim of the study was to investigate the relation of listening effort, as quantified by subjective effort ratings and pupil dilation, and neural speech tracking during sentence recognition. Task demands were varied using sentences with varying levels of linguistic complexity and using two different speech rates in a picture-matching paradigm with 20 normal-hearing listeners. The participants’ task was to match the acoustically presented sentence with a picture presented before the acoustic stimulus. Afterwards they rated their perceived effort on a categorical effort scale. During each trial, pupil dilation (as an indicator of listening effort) and electroencephalogram (as an indicator of neural speech tracking) were recorded. Neither measure was significantly affected by linguistic complexity. However, speech rate showed a strong influence on subjectively rated effort, pupil dilation, and neural tracking. The neural tracking analysis revealed a shorter latency for faster sentences, which may reflect a neural adaptation to the rate of the input. No relation was found between neural tracking and listening effort, even though both measures were clearly influenced by speech rate. This is probably due to factors that influence both measures differently. Consequently, the amount of listening effort is not clearly represented in the neural tracking

    Draft Genome Sequences of Three Porcine Streptococcus suis Isolates Which Differ in Their Susceptibility to Penicillin

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    The draft genome sequences of three Streptococcus suis isolates, IMT40343, IMT40201, and IMT40738, are presented here. These isolates were obtained from bronchoalveolar lavage fluid of healthy and diseased weaners from different German piglet-producing farms and differed in their susceptibility to penicillin

    Do Mutual Fund Ratings Provide Valuable Information for Retail Investors? Empirical Evidence on Ratings Non-Persistence and the Risk of Mutual Fund Closure

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    Retail investors use information provided by mutual fund rating agencies to make investment decisions. Using hand-collected data on Morningstar’s mutual fund ratings we examine the rating migration and closure risk of mutual funds from 2005 to 2012. We differentiate between buy-and-hold investment strategies and dynamic investment strategies. To assess the information content of mutual fund ratings for buy-and-hold investment strategies, we determine the rating migration based on the first and the last mutual fund rating during two-, four-, six-, and eight-year horizons. With respect to dynamic investment strategies, we calculate the number of rating changes per fund during these time horizons on a monthly basis. We find that mutual fund rating persistence is low or even inexistent in particular during longer time periods. Only for lower-rated funds the rating appears to indicate higher risk of fund closure. In addition, mutual funds face a large number of up to 38 monthly rating changes in the eight-year window. Overall, due to the extensive rating migration and the high number of monthly rating changes, we conclude that retail investors barely benefit from using mutual fund ratings
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