Behavior of a Model Dynamical System with Applications to Weak Turbulence

We experimentally explore solutions to a model Hamiltonian dynamical system derived in Colliander et al., 2012, to study frequency cascades in the cubic defocusing nonlinear Schr\"odinger equation on the torus. Our results include a statistical analysis of the evolution of data with localized amplitudes and random phases, which supports the conjecture that energy cascades are a generic phenomenon. We also identify stationary solutions, periodic solutions in an associated problem and find experimental evidence of hyperbolic behavior. Many of our results rely upon reframing the dynamical system using a hydrodynamic formulation.Comment: 22 pages, 14 figure

The Uses of Fear in Preventive Medicine

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The 2013 cholesterol guideline controversy: Would better evidence prevent pharmaceuticalization?

AbstractCardiovascular disease (CVD) remains the leading cause of death globally. A class of medications, known as statins, lowers low-density lipoprotein cholesterol levels, which are associated with CVD. The newest 2013 U.S. cholesterol guideline contains an assessment of risk that greatly expands the number of individuals without CVD for whom statins are recommended. Other countries are also moving in this direction. This article examines the controversy surrounding these guidelines using the 2013 cholesterol guidelines as a case study of broader trends in clinical guidelines to use a narrow evidence base, expand the boundaries of disease and overemphasize pharmaceutical treatment.We find that the recommendation in the 2013 cholesterol guidelines to initiate statins in individuals with a lower risk of CVD is controversial and there is much disagreement on whether there is evidence for the guideline change. We note that, in general, clinical guidelines may use evidence that has a number of biases, are subject to conflicts of interest at multiple levels, and often do not include unpublished research. Further, guidelines may contribute to the “medicalization” or “pharmaceuticalization” of healthcare.Specific policy recommendations to improve clinical guidelines are indicated: these include improving the evidence base, establishing a public registry of all results, including unpublished ones, and freeing the research process from pharmaceutical sector control

Nontarget emotional stimuli must be highly conspicuous to modulate the attentional blink

The attentional blink (AB) is often considered a top-down phenomenon because it is triggered by matching an initial target (T1) in a rapid serial visual presentation (RSVP) stream to a search template. However, the AB is modulated when targets are emotional, and is evoked when a task-irrelevant, emotional critical distractor (CDI) replaces T1. Neither manipulation fully captures the interplay between bottom-up and top-down attention in the AB: Valenced targets intrinsically conflate top-down and bottom-up attention. The CDI approach cannotmanipulate second target (T2) valence, which is critical because valenced T2s can “break through” the AB (in the target-manipulation approach). The present research resolves this methodological challenge by indirectly measuring whether a purely bottom-up CDI can modulate report of a subsequent T2. This novel approach adds a valenced CDI to the “classic,” two-target AB. Participants viewed RSVP streams containing a T1–CDI pair preceding a variable lag to T2. If the CDI’s valence is sufficient to survive the AB, it should modulate T2 performance, indirectly signaling bottom-up capture by an emotional stimulus. Contrary to this prediction, CDI valence only affected the AB when CDIs were also extremely visually conspicuous. Thus, emotional valence alone is insufficient to modulate the AB

Syrian Refugees and the Digital Passage to Europe: Smartphone Infrastructures and Affordances

This research examines the role of smartphones in refugees’ journeys. It traces the risks and possibilities afforded by smartphones for facilitating information, communication, and migration flows in the digital passage to Europe. For the Syrian and Iraqi refugee respondents in this France-based qualitative study, smartphones are lifelines, as important as water and food. They afford the planning, navigation, and documentation of journeys, enabling regular contact with family, friends, smugglers, and those who help them. However, refugees are simultaneously exposed to new forms of exploitation and surveillance with smartphones as migrations are financialised by smugglers and criminalized by European policies, and the digital passage is dependent on a contingent range of sociotechnical and material assemblages. Through an infrastructural lens, we capture the dialectical dynamics of opportunity and vulnerability, and the forms of resilience and solidarity, that arise as forced migration and digital connectivity coincide

Symmetries of a class of nonlinear fourth order partial differential equations

In this paper we study symmetry reductions of a class of nonlinear fourth order partial differential equations \be u_{tt} = \left(\kappa u + \gamma u^2\right)_{xx} + u u_{xxxx} +\mu u_{xxtt}+\alpha u_x u_{xxx} + \beta u_{xx}^2, \ee where $\alpha$, $\beta$, $\gamma$, $\kappa$ and $\mu$ are constants. This equation may be thought of as a fourth order analogue of a generalization of the Camassa-Holm equation, about which there has been considerable recent interest. Further equation (1) is a ``Boussinesq-type'' equation which arises as a model of vibrations of an anharmonic mass-spring chain and admits both ``compacton'' and conventional solitons. A catalogue of symmetry reductions for equation (1) is obtained using the classical Lie method and the nonclassical method due to Bluman and Cole. In particular we obtain several reductions using the nonclassical method which are no} obtainable through the classical method

Singularites in the Bousseneq equation and in the generalized KdV equation

In this paper, two kinds of the exact singular solutions are obtained by the improved homogeneous balance (HB) method and a nonlinear transformation. The two exact solutions show that special singular wave patterns exists in the classical model of some nonlinear wave problems

Amodal processing in human prefrontal cortex

Information enters the cortex via modality-specific sensory regions, whereas actions are produced by modality-specific motor regions. Intervening central stages of information processing map sensation to behavior. Humans perform this central processing in a flexible, abstract manner such that sensory information in any modality can lead to response via any motor system. Cognitive theories account for such flexible behavior by positing amodal central information processing (e. g., "central executive," Baddeley and Hitch, 1974; "supervisory attentional system," Norman and Shallice, 1986; "response selection bottleneck," Pashler, 1994). However, the extent to which brain regions embodying central mechanisms of information processing are amodal remains unclear. Here we apply multivariate pattern analysis to functional magnetic resonance imaging (fMRI) data to compare response selection, a cognitive process widely believed to recruit an amodal central resource across sensory and motor modalities. We show that most frontal and parietal cortical areas known to activate across a wide variety of tasks code modality, casting doubt on the notion that these regions embody a central processor devoid of modality representation. Importantly, regions of anterior insula and dorsolateral prefrontal cortex consistently failed to code modality across four experiments. However, these areas code at least one other task dimension, process (instantiated as response selection vs response execution), ensuring that failure to find coding of modality is not driven by insensitivity of multivariate pattern analysis in these regions. We conclude that abstract encoding of information modality is primarily a property of subregions of the prefrontal cortex