2,685 research outputs found

    Is classical reality completely deterministic?

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    The concept of determinism for a classical system is interpreted as the requirement that the solution to the Cauchy problem for the equations of motion governing this system be unique. This requirement is generally assumed to hold for all autonomous classical systems. We give counterexamples of this view. Our analysis of classical electrodynamics in a world with one temporal and one spatial dimension shows that the solution to the Cauchy problem with the initial conditions of a particular type is not unique. Therefore, random behavior of closed classical systems is indeed possible. This finding provides a qualitative explanation of how classical strings can split. We propose a modified path integral formulation of classical mechanics to include indeterministic systems.Comment: Replace the paper with a revised versio

    A case of AML characterized by a novel t(4;15)(q31;q22) translocation that confers a growth-stimulatory response to retinoid-based therapy

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    Here we report the case of a 30-year-old woman with relapsed acute myeloid leukemia (AML) who was treated with all-transretinoic acid (ATRA) as part of investigational therapy (NCT02273102). The patient died from rapid disease progression following eight days of continuous treatment with ATRA. Karyotype analysis and RNA-Seq revealed the presence of a novel t(4;15)(q31;q22) reciprocal translocation involving theTMEM154andRASGRF1genes. Analysis of primary cells from the patient revealed the expression ofTMEM154-RASGRF1mRNA and the resulting fusion protein, but no expression of the reciprocalRASGRF1-TMEM154fusion. Consistent with the response of the patient to ATRA therapy, we observed a rapid proliferation of t(4;15) primary cells following ATRA treatment ex vivo. Preliminary characterization of the retinoid response of t(4;15) AML revealed that in stark contrast to non-t(4;15) AML, these cells proliferate in response to specific agonists of RARα and RARγ. Furthermore, we observed an increase in the levels of nuclear RARγ upon ATRA treatment. In summary, the identification of the novel t(4;15)(q31;q22) reciprocal translocation opens new avenues in the study of retinoid resistance and provides potential for a new biomarker for therapy of AML

    The Specific Heat of Normal, Degenerate Quark Matter: Non-Fermi Liquid Corrections

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    In normal degenerate quark matter, the exchange of dynamically screened transverse gluons introduces infrared divergences in the quark self-energies that lead to the breakdown of the Fermi liquid description. If the core of neutron stars are composed of quark matter with a normal component, cooling by direct quark Urca processes may be modified by non-Fermi liquid corrections. We find that while the quasiparticle density of states is finite and non-zero at the Fermi surface, its frequency derivative diverges and results in non-Fermi liquid corrections to the specific heat of the normal, degenerate component of quark matter. We study these non-perturbative non-Fermi liquid corrections to the specific heat and the temperature dependence of the chemical potential and show that these lead to a reduction of the specific heat.Comment: new discussion, updated references, accepted in PR

    Implicit and explicit body representations

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    Several forms of perception require that sensory information be referenced to representations of the size and shape of the body. This requirement is especially acute in somatosensation in which the main receptor surface (i.e., the skin) is itself coextensive with the body. In this paper I will review recent research investigating the body representations underlying somatosensory information processing, including abilities such as tactile localisation, tactile size perception, and position sense. These representations show remarkably large and stereotyped distortions of represented body size and shape. Intriguingly, these distortions appear to mirror distortions characteristic of somatosensory maps, though in attenuated form. In contrast, when asked to make overt judgments about perceived body form, participants are generally quite accurate. This pattern of results suggests that higher-level somatosensory processing relies on a class of implicit body representation, distinct from the conscious body image. I discuss the implications of these results for understanding the nature of body representation and the factors which influence it

    Serum lipid responses to psyllium fiber: differences between pre- and post-menopausal, hypercholesterolemic women

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    <p>Abstract</p> <p>Background</p> <p>Cardiovascular disease is the leading cause of death in women and men. Psyllium, a soluble fiber has been known to reduce serum lipids. In this pilot study, we evaluated whether menopausal status would affect the serum lipid responses to psyllium fiber in women.</p> <p>Methods</p> <p>Eleven post-menopausal and eight pre-menopausal women with serum total cholesterol >200 mg/dL were included in the study. Subjects consumed their habitual diet and 15 g psyllium/d for 6 weeks. Psyllium was incorporated into cookies. Each cookie contained ≈5 g of psyllium fiber. Subjects ate one cookie in each meal.</p> <p>Results</p> <p>With psyllium fiber, total cholesterol concentration was significantly lower (≈5.2%, P < 0.05) in post-menopausal women but not in pre-menopausal women (≈1.3%). Also, there was a significant decrease in HDL-cholesterol in post-menopausal women (≈10.2%, P < 0.05). There were no significant changes observed in concentrations of LDL-cholesterol, triglycerides, apolipoprotein A1, and apolipoprotein B in both pre- and post-menopausal women with psyllium.</p> <p>Conclusion</p> <p>In this pilot study, post- and pre-menopausal, hypercholesterolemic women responded differently to psyllium fiber supplementation. Post-menopausal women would benefit from addition of psyllium to their diets in reducing the risk for heart diseases. The results of this study should be used with caution because the study was based on a small sample size.</p

    Matrix representation of the shifting operation and numerical properties of the ERES method for computing the greatest common divisor of sets of many polynomials

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    The Extended-Row-Equivalence and Shifting (ERES) method is a matrix-based method developed for the computation of the greatest common divisor (GCD) of sets of many polynomials. In this paper we present the formulation of the shifting operation as a matrix product which allows us to study the fundamental theoretical and numerical properties of the ERES method by introducing its complete algebraic representation. Then, we analyse in depth its overall numerical stability in finite precision arithmetic. Numerical examples and comparison with other methods are also presented

    Tunneling of quantum rotobreathers

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    We analyze the quantum properties of a system consisting of two nonlinearly coupled pendula. This non-integrable system exhibits two different symmetries: a permutational symmetry (permutation of the pendula) and another one related to the reversal of the total momentum of the system. Each of these symmetries is responsible for the existence of two kinds of quasi-degenerated states. At sufficiently high energy, pairs of symmetry-related states glue together to form quadruplets. We show that, starting from the anti-continuous limit, particular quadruplets allow us to construct quantum states whose properties are very similar to those of classical rotobreathers. By diagonalizing numerically the quantum Hamiltonian, we investigate their properties and show that such states are able to store the main part of the total energy on one of the pendula. Contrary to the classical situation, the coupling between pendula necessarily introduces a periodic exchange of energy between them with a frequency which is proportional to the energy splitting between quasi-degenerated states related to the permutation symmetry. This splitting may remain very small as the coupling strength increases and is a decreasing function of the pair energy. The energy may be therefore stored in one pendulum during a time period very long as compared to the inverse of the internal rotobreather frequency.Comment: 20 pages, 11 figures, REVTeX4 styl

    Evolution of Inhomogeneous Condensates after Phase Transitions

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    Using the O(4) linear σ\sigma model, we address the topic of non-equilibrium relaxation of an inhomogeneous initial configuration due to quantum and thermal fluctuations. The space-time evolution of an inhomogeneous fluctuation of the condensate in the isoscalar channel decaying via the emission of pions in the medium is studied within the context of disoriented chiral condensates. We use out of equilibrium closed time path methods in field theory combined with the amplitude expansion. We give explicit expressions for the asymptotic space-time evolution of an initial inhomogeneous configuration including the contribution of thresholds at zero and non-zero temperature. At non-zero temperature we find new relaxational processes due to thermal cuts that have no counterpart in the homogeneous case. Within the one-loop approximation, we find that the space time evolution of such inhomogeneous configuration out of equilibrium is effectively described in terms of a rapidity dependent temperature T(ϑ)=T/cosh[ϑ]T(\vartheta)=T/\cosh[\vartheta] as well as a rapidity dependent decay rate Γ(ϑ,T(ϑ))\Gamma(\vartheta, T(\vartheta)). This rate is to be interpreted as the production minus absorption rate of pions in the medium and approaches the zero temperature value at large rapidities. An initial configuration localized on a bounded region spreads and decays in spherical waves with slower relaxational dynamics at large rapidity.Comment: 25 pages Revtex 3.0, two figures available upon reques
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