2,342 research outputs found

    On Factor Universality in Symbolic Spaces

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    The study of factoring relations between subshifts or cellular automata is central in symbolic dynamics. Besides, a notion of intrinsic universality for cellular automata based on an operation of rescaling is receiving more and more attention in the literature. In this paper, we propose to study the factoring relation up to rescalings, and ask for the existence of universal objects for that simulation relation. In classical simulations of a system S by a system T, the simulation takes place on a specific subset of configurations of T depending on S (this is the case for intrinsic universality). Our setting, however, asks for every configurations of T to have a meaningful interpretation in S. Despite this strong requirement, we show that there exists a cellular automaton able to simulate any other in a large class containing arbitrarily complex ones. We also consider the case of subshifts and, using arguments from recursion theory, we give negative results about the existence of universal objects in some classes

    On the zero-temperature limit of Gibbs states

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    We exhibit Lipschitz (and hence H\"older) potentials on the full shift {0,1}N\{0,1\}^{\mathbb{N}} such that the associated Gibbs measures fail to converge as the temperature goes to zero. Thus there are "exponentially decaying" interactions on the configuration space {0,1}Z\{0,1\}^{\mathbb Z} for which the zero-temperature limit of the associated Gibbs measures does not exist. In higher dimension, namely on the configuration space {0,1}Zd\{0,1\}^{\mathbb{Z}^{d}}, d3d\geq3, we show that this non-convergence behavior can occur for finite-range interactions, that is, for locally constant potentials.Comment: The statement of Theorem 1.2 is more accurate and some new comment follow i

    Art And Exceptionality: Addressing Art Fear And Fear Of Difference In An Introductory Art Course

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    University educators designed and co-taught a course which involved collaborative artmaking and learning with a community-based arts organization that serves individuals with disabilities. Their goal was to help university students examine the potential of art and how it applies to their personal and professional lives. They sought to better understand how to nurture a feeling of artistic agency in undergraduate students who do not define themselves as artists. Educators found that students benefited from an exploration of art fear through an inclusive approach to art creation

    Cardiac Output Assessed by Invasive and Minimally Invasive Techniques

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    Cardiac output (CO) measurement has long been considered essential to the assessment and guidance of therapeutic decisions in critically ill patients and for patients undergoing certain high-risk surgeries. Despite controversies, complications and inherent errors in measurement, pulmonary artery catheter (PAC) continuous and intermittent bolus techniques of CO measurement continue to be the gold standard. Newer techniques provide less invasive alternatives; however, currently available monitors are unable to provide central circulation pressures or true mixed venous saturations. Esophageal Doppler and pulse contour monitors can predict fluid responsiveness and have been shown to decrease postoperative morbidity. Many minimally invasive techniques continue to suffer from decreased accuracy and reliability under periods of hemodynamic instability, and so few have reached the level of interchangeability with the PAC

    Small union with large set of centers

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    Let TRnT\subset{\mathbb R}^n be a fixed set. By a scaled copy of TT around xRnx\in{\mathbb R}^n we mean a set of the form x+rTx+rT for some r>0r>0. In this survey paper we study results about the following type of problems: How small can a set be if it contains a scaled copy of TT around every point of a set of given size? We will consider the cases when TT is circle or sphere centered at the origin, Cantor set in R{\mathbb R}, the boundary of a square centered at the origin, or more generally the kk-skeleton (0k<n0\le k<n) of an nn-dimensional cube centered at the origin or the kk-skeleton of a more general polytope of Rn{\mathbb R}^n. We also study the case when we allow not only scaled copies but also scaled and rotated copies and also the case when we allow only rotated copies

    Opiate-Induced Suppression of Rat Hypoglossal Motoneuron Activity and Its Reversal by Ampakine Therapy

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    Hypoglossal (XII) motoneurons innervate tongue muscles and are vital for maintaining upper-airway patency during inspiration. Depression of XII nerve activity by opioid analgesics is a significant clinical problem, but underlying mechanisms are poorly understood. Currently there are no suitable pharmacological approaches to counter opiate-induced suppression of XII nerve activity while maintaining analgesia. Ampakines accentuate alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor responses. The AMPA family of glutamate receptors mediate excitatory transmission to XII motoneurons. Therefore the objectives were to determine whether the depressant actions of mu-opioid receptor activation on inspiratory activity includes a direct inhibitory action at the inspiratory premotoneuron to XII motoneuron synapse, and to identify underlying mechanism(s). We then examined whether ampakines counteract opioid-induced depression of XII motoneuron activity.A medullary slice preparation from neonatal rat that produces inspiratory-related output in vitro was used. Measurements of inspiratory burst amplitude and frequency were made from XII nerve roots. Whole-cell patch recordings from XII motoneurons were used to measure membrane currents and synaptic events. Application of the mu-opioid receptor agonist, DAMGO, to the XII nucleus depressed the output of inspiratory XII motoneurons via presynaptic inhibition of excitatory glutamatergic transmission. Ampakines (CX614 and CX717) alleviated DAMGO-induced depression of XII MN activity through postsynaptic actions on XII motoneurons.The inspiratory-depressant actions of opioid analgesics include presynaptic inhibition of XII motoneuron output. Ampakines counteract mu-opioid receptor-mediated depression of XII motoneuron inspiratory activity. These results suggest that ampakines may be beneficial in countering opiate-induced suppression of XII motoneuron activity and resultant impairment of airway patency

    A novel two‐beam accelerator (twobetron)

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    A new configuration is analyzed wherein a low current beam is accelerated to high energies (10’s of amps, 10’s of MeV) by a driver beam of high current and low energy (a few kiloamps, <1 MeV). The annular driver beam excites the TM020 cavity mode of an accelerating structure which transfers its rf power to the on‐axis secondary beam. Systematic variation of the driver beam radius provides the secondary beam with phase focusing and adjustable acceleration gradient. A proof‐of‐principle experiment is suggested. Various issues, such as the scaling laws, transverse and longitudinal instabilities, rf coupling among cavities, etc., are examined. © 1995 American Institute of PHysics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87548/2/451_1.pd

    The Role of Supported Joint Engagement and Parent Utterances in Language and Social Communication Development in Children with Autism Spectrum Disorder

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    This study examined associations between three parent–child engagement states and social communication, expressive language, and receptive language at 8 month follow-up, in 63 preschool-age children with autism spectrum disorder. We extend the literature on supported joint engagement by dividing this state into higher order (HSJE) and lower order types, with HSJE involving greater reciprocity in toy play. We also examined parents’ follow-in utterances that co-occurred with each state. We found that only HSJE predicts later social communication and expressive language, while object engagement predicts receptive language. HSJE combined with follow-in utterances (HSJE+FI) predicts all three outcomes when controlling for HSJE+FI in other engagement states. When controlling for total HSJE, HSJE+FI is predictive of receptive language
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