116 research outputs found

    Universal Fluctuations of the Danube Water Level: a Link with Turbulence, Criticality and Company Growth

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    A global quantity, regardless of its precise nature, will often fluctuate according to a Gaussian limit distribution. However, in highly correlated systems, other limit distributions are possible. We have previously calculated one such distribution and have argued that this function should apply specifically, and in many instances, to global quantities that define a steady state. Here we demonstrate, for the first time, the relevance of this prediction to natural phenomena. The river level fluctuations of the Danube are observed to obey our prediction, which immediately establishes a generic statistical connection between turbulence, criticality and company growth statistics.Comment: 5 pages, 1 figur

    Does the Supreme Court Follow the Economic Returns? A Response to A Macrotheory of the Court

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    Today, there is a widespread idea that parents need to learn how to carry out their roles as parents. Practices of parental learning operate throughout society. This article deals with one particular practice of parental learning, namely nanny TV, and the way in which ideal parents are constructed through such programmes. The point of departure is SOS family, a series broadcast on Swedish television in 2008. Proceeding from the theorising of governmentality developed in the wake of the work of Michel Foucault, we analyse the parental ideals conveyed in the series, as an example of the way parents are constituted as subjects in the ‘advanced liberal society’ of today. The ideal parent is a subject who, guided by the coach, is constantly endeavouring to achieve a makeover. The objective of this endeavour, however, is self-control, whereby the parents will in the end become their own coaches.

    One- and two-photon activated phototoxicity of conjugated porphyrin dimers with high two-photon absorption cross sections

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    Two-photon excited photodynamic therapy (PDT) has the potential to provide a highly targeted treatment for neoplastic diseases, as excitation can be pin-pointed to small volumes at the laser focus. In addition, two-photon PDT offers deeper penetration into mammalian tissue due to the longer wavelength of irradiation. Here we report the one-photon and two-photon excited PDT results for a collection of conjugated porphyrin dimers with high two-photon absorption cross sections. These dimers demonstrate high one-photon PDT efficacy against a human ovarian adenocarcinoma cell line (SK-OV-3) and exhibit no significant dark-toxicity at concentrations of up to 20 microM. Their one-photon excited PDT efficiencies, following irradiation at 657 nm, approach that of Visudyne, a drug used clinically for PDT. We investigated and optimised the effect of the photosensitizer concentration, incubation time and the light dose on the PDT efficacy of these dimers. These studies led to the selection of P2C2-NMeI as the most effective porphyrin dimer. We have demonstrated that P2C2-NMeI undergoes a two-photon activated process following excitation at 920 nm (3.6-6.8 mW, 300 fs, 90 MHz) and compared it to Visudyne. We conclude that the in vitro two-photon PDT efficacy of P2C2-NMeI is about twice that of Visudyne. This result highlights the potential of this series of porphyrin dimers for two-photon PDT

    Generalised extreme value statistics and sum of correlated variables

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    We show that generalised extreme value statistics -the statistics of the k-th largest value among a large set of random variables- can be mapped onto a problem of random sums. This allows us to identify classes of non-identical and (generally) correlated random variables with a sum distributed according to one of the three (k-dependent) asymptotic distributions of extreme value statistics, namely the Gumbel, Frechet and Weibull distributions. These classes, as well as the limit distributions, are naturally extended to real values of k, thus providing a clear interpretation to the onset of Gumbel distributions with non-integer index k in the statistics of global observables. This is one of the very few known generalisations of the central limit theorem to non-independent random variables. Finally, in the context of a simple physical model, we relate the index k to the ratio of the correlation length to the system size, which remains finite in strongly correlated systems.Comment: To appear in J.Phys.

    Relevance of soft modes for order parameter fluctuations in the Two-Dimensional XY model

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    We analyse the spin wave approximation for the 2D-XY model, directly in reciprocal space. In this limit the model is diagonal and the normal modes are statistically independent. Despite this simplicity non-trivial critical properties are observed and exploited. We confirm that the observed asymmetry for the probability density function for order parameter fluctuations comes from the divergence of the mode amplitudes across the Brillouin zone. We show that the asymmetry is a many body effect despite the importance played by the zone centre. The precise form of the function is dependent on the details of the Gibbs measure, giving weight to the idea that an effective Gibbs measure should exist in non-equilibrium systems, if a similar distribution is observed.Comment: 12 pages, 9 figure

    Numerical convergence of the block-maxima approach to the Generalized Extreme Value distribution

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    In this paper we perform an analytical and numerical study of Extreme Value distributions in discrete dynamical systems. In this setting, recent works have shown how to get a statistics of extremes in agreement with the classical Extreme Value Theory. We pursue these investigations by giving analytical expressions of Extreme Value distribution parameters for maps that have an absolutely continuous invariant measure. We compare these analytical results with numerical experiments in which we study the convergence to limiting distributions using the so called block-maxima approach, pointing out in which cases we obtain robust estimation of parameters. In regular maps for which mixing properties do not hold, we show that the fitting procedure to the classical Extreme Value Distribution fails, as expected. However, we obtain an empirical distribution that can be explained starting from a different observable function for which Nicolis et al. [2006] have found analytical results.Comment: 34 pages, 7 figures; Journal of Statistical Physics 201

    Ancient DNA of guinea pigs (Cavia spp.) indicates a probable new center of domestication and pathways of global distribution

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    Guinea pigs (Cavia spp.) have a long association with humans. From as early as 10,000 years ago they were a wild food source. Later, domesticated Cavia porcellus were dispersed well beyond their native range through pre-Columbian exchange networks and, more recently, widely across the globe. Here we present 46 complete mitogenomes of archaeological guinea pigs from sites in Peru, Bolivia, Colombia, the Caribbean, Belgium and the United States to elucidate their evolutionary history, origins and paths of dispersal. Our results indicate an independent centre of domestication of Cavia in the eastern Colombian Highlands. We identify a Peruvian origin for the initial introduction of domesticated guinea pigs (Cavia porcellus) beyond South America into the Caribbean. We also demonstrate that Peru was the probable source of the earliest known guinea pigs transported, as part of the exotic pet trade, to both Europe and the southeastern United States. Finally, we identify a modern reintroduction of guinea pigs to Puerto Rico, where local inhabitants use them for food. This research demonstrates that the natural and cultural history of guinea pigs is more complex than previously known and has implications for other studies regarding regional to global-scale studies of mammal domestication, translocation, and distribution.Fil: Lord, E.. Stockholms Universitet; Suecia. University of Otago; Nueva ZelandaFil: Collins, C.. University of Otago; Nueva ZelandaFil: deFrance, S.. University of Florida; Estados UnidosFil: LeFebvre, M. J.. University of Florida; Estados UnidosFil: Pigière, F.. Universidad de Dublin; IrlandaFil: Eeckhout, P.. Université Libre de Bruxelles; BélgicaFil: Erauw, C.. Université Libre de Bruxelles; BélgicaFil: Fitzpatrick, S. M.. State University of Oregon; Estados UnidosFil: Healy, P. F.. Trent University; CanadáFil: Martínez Polanco, M. F.. Muséum National d'Histoire Naturelle; Francia. Universitat Rovira I Virgili; España. Institut Català de Paleoecologia Humana i Evolució Social; EspañaFil: Garcia, J. L.. Stetson University; Estados UnidosFil: Ramos Roca, E.. Universidad de los Andes. Facultad de Ciencias Sociales. Departamento de Antropología; ColombiaFil: Delgado Burbano, Miguel Eduardo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Área Antropológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. School of Life Sciences and Human Phenome Institute Fudan University; ChinaFil: Sánchez Urriago, A.. Instituto Colombiano de Antropología e Historia; ColombiaFil: Peña Léon, G. A.. Universidad Nacional de Colombia; ColombiaFil: Toyne, J. M.. University of Florida; Estados UnidosFil: Dahlstedt, A.. Arizona State University; Estados UnidosFil: Moore, K. M.. State University of Pennsylvania; Estados UnidosFil: Laguer Diaz, C.. University of Florida; Estados UnidosFil: Zori, C.. Baylor University; Estados UnidosFil: Matisoo-Smith, E.. University of Otago; Nueva Zeland

    Incubating Isolated Mouse EDL Muscles with Creatine Improves Force Production and Twitch Kinetics in Fatigue Due to Reduction in Ionic Strength

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    Creatine supplementation can improve performance during high intensity exercise in humans and improve muscle strength in certain myopathies. In this present study, we investigated the direct effects of acute creatine incubation on isolated mouse fast-twitch EDL muscles, and examined how these effects change with fatigue. muscle from mice aged 12–14 weeks was isolated and stimulated with field electrodes to measure force characteristics in 3 different states: (i) before fatigue; (ii) immediately after a fatigue protocol; and (iii) after recovery. These served as the control measurements for the muscle. The muscle was then incubated in a creatine solution and washed. The measurement of force characteristics in the 3 different states was then repeated. In un-fatigued muscle, creatine incubation increased the maximal tetanic force. In fatigued muscle, creatine treatment increased the force produced at all frequencies of stimulation. Incubation also increased the rate of twitch relaxation and twitch contraction in fatigued muscle. During repetitive fatiguing stimulation, creatine-treated muscles took 55.1±9.5% longer than control muscles to lose half of their original force. Measurement of weight changes showed that creatine incubation increased EDL muscle mass by 7%. sensitivity of contractile proteins as a result of ionic strength decreases following creatine incubation

    Computational Systems for Music Improvisation

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    Computational music systems that afford improvised creative interaction in real time are often designed for a specific improviser and performance style. As such the field is diverse, fragmented and lacks a coherent framework. Through analysis of examples in the field we identify key areas of concern in the design of new systems, which we use as categories in the construction of a taxonomy. From our broad overview of the field we select significant examples to analyse in greater depth. This analysis serves to derive principles that may aid designers scaffold their work on existing innovation. We explore successful evaluation techniques from other fields and describe how they may be applied to iterative design processes for improvisational systems. We hope that by developing a more coherent design and evaluation process, we can support the next generation of improvisational music systems

    Towards an Effective Multi-Stakeholder Consultation Process: Applying the Imagine Method in Context of Abu Dhabi’s Education Policy

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    This paper is concerned with the many interleaving issues that emerge when engaging multiple stakeholders in decision-making. Whilst recognising the intrinsic value of group work and keeping in mind the numerous issues that obstruct group work (including multiple roles for participants, bias due to domination and distortion emerging from uneven group inputs), we applied the Imagine method to propose a new framework - the ‘Multiple Formation Consultation Framework’ (MFCF) - for organising effective multi-stakeholder consultations along the Policy Sciences Framework. Our proposed framework was applied in the context of education policy in the Emirate of Abu Dhabi, where 24 small group formations were tasked and assessed in a systemic manner. Evidence from the exercise suggests that: (1) when moving participants from heterogeneous to homogenous groups, the working of the groups became more focused and the outcomes gained greater clarity in terms of the thinking of group members. (2) Yet, when groups moved from homogenous formations to heterogeneous, they became more inquisitive and explored broader aspects of the tasks at hand. (3) A repeat of the process over two-day period where different members of the groups experience both homogenous and heterogeneous formations back and forth (in order to capture the unique value emerging from each composition) have led to more efficient and effective working and outcomes of the groups
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