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Hannah Kreczak, Rob Sturman, Mark C T Wilson
We present a computational study of a simple one-dimensional map with dynamics composed of stretching, permutations of equally sized cells, and diffusion. We observe that the combination of the aforementioned dynamics results in eigenmodes with long-time exponential decay rates. The decay rate of the eigenmodes is shown to be dependent on the choice of permutation and changes nonmonotonically with the diffusion coefficient for many of the permutations. The global mixing rate of the map M in the limit of vanishing diffusivity approximates well the decay rates of the eigenmodes for small diffusivity, however this global mixing rate does not bound the rates for all values of the diffusion coefficient...
November 2017: Physical Review. E
Pietro Rotondo, Alessandro Luigi Sellerio, Pietro Glorioso, Sergio Caracciolo, Marco Cosentino Lagomarsino, Marco Gherardi
Driven lattice gases are widely regarded as the paradigm of collective phenomena out of equilibrium. While such models are usually studied with nearest-neighbor interactions, many empirical driven systems are dominated by slowly decaying interactions such as dipole-dipole and Van der Waals forces. Motivated by this gap, we study the nonequilibrium stationary state of a driven lattice gas with slow-decayed repulsive interactions at zero temperature. By numerical and analytical calculations of the particle current as a function of the density and of the driving field, we identify (i) an abrupt breakdown transition between insulating and conducting states, (ii) current quantization into discrete phases where a finite current flows with infinite differential resistivity, and (iii) a fractal hierarchy of excitations, related to the Farey sequences of number theory...
November 2017: Physical Review. E
G Zhang, F H Stillinger, S Torquato
Classical ground states (global energy-minimizing configurations) of many-particle systems are typically unique crystalline structures, implying zero enumeration entropy of distinct patterns (aside from trivial symmetry operations). By contrast, the few previously known disordered classical ground states of many-particle systems are all high-entropy (highly degenerate) states. Here we show computationally that our recently proposed "perfect-glass" many-particle model [Sci. Rep. 6, 36963 (2016)10.1038/srep36963] possesses disordered classical ground states with a zero entropy: a highly counterintuitive situation ...
October 2017: Physical Review. E
Debarshee Bagchi
We study energy transport in the paradigmatic Hamiltonian mean-field (HMF) model and other related long-range interacting models using molecular dynamics simulations. We show that energy diffusion in the HMF model is subdiffusive in nature, which confirms a recently obtained intriguing result that, despite being globally interacting, this model is a thermal insulator in the thermodynamic limit. Surprisingly, when additional nearest-neighbor interactions are introduced to the HMF model, an energy superdiffusion is observed...
October 2017: Physical Review. E
Baojin Chu, David R Salem
Modified drop weight impact tests were performed on SiO_{2}-ethylene glycol concentrated suspensions. Counterintuitive impact-induced solidlike behavior and elasticity, causing significant deceleration and rebound of the impactor, were observed. We provide evidence that the observed large deceleration force on the impactor mainly originates from the hydrodynamic force, and that the elasticity arises from the short-range repulsive force of a solvation layer on the particle surface. This study presents key experimental results to help understand the mechanisms underlying various stress-induced solidification phenomena...
October 2017: Physical Review. E
Yue Liu, Dahai He
Through the integration of the power spectral density, we obtain temperature profiles of both multisegment harmonic and anharmonic systems, showing the presence of an anomalous negative temperature gradient inside the interfacial segment. Via investigating patterns of the power spectral density, we found that the counterintuitive phenomenon comes from the presence of interfacial localized phonon modes. Two out-band localized modes of the harmonic model, which make no contributions to local temperature due to the absence of phonon interactions, result in the concave temperature profile and overcooling effect...
December 2017: Physical Review. E
Harold Fellermann, Shinpei Tanaka, Steen Rasmussen
Template-directed replication of nucleic acids is at the essence of all living beings and a major milestone for any origin of life scenario. We present an idealized model of prebiotic sequence replication, where binary polymers act as templates for their autocatalytic replication, thereby serving as each others reactants and products in an intertwined molecular ecology. Our model demonstrates how autocatalysis alters the qualitative and quantitative system dynamics in counterintuitive ways. Most notably, numerical simulations reveal a very strong intrinsic selection mechanism that favors the appearance of a few population structures with highly ordered and repetitive sequence patterns when starting from a pool of monomers...
December 2017: Physical Review. E
Emily R Russell, Rastko Sknepnek, Mark Bowick
Two-dimensional crystalline membranes have recently been realized experimentally in systems such as graphene and molybdenum disulfide, sparking a resurgence in interest in their statistical properties. Thermal fluctuations can significantly affect the effective mechanical properties of properly thermalized membranes, renormalizing both bending rigidity and elastic moduli so that in particular they become stiffer to bending than their bare bending rigidity would suggest. We use molecular dynamics simulations to examine how the mechanical behavior of thermalized two-dimensional clamped ribbons (cantilevers) depends on their precise topology and geometry...
July 2017: Physical Review. E
Hanshuang Chen, Guofeng Li, Haifeng Zhang, Zhonghuai Hou
Efficient allocation of limited medical resources is crucial for controlling epidemic spreading on networks. Based on the susceptible-infected-susceptible model, we solve the optimization problem of how best to allocate the limited resources so as to minimize prevalence, providing that the curing rate of each node is positively correlated to its medical resource. By quenched mean-field theory and heterogeneous mean-field (HMF) theory, we prove that an epidemic outbreak will be suppressed to the greatest extent if the curing rate of each node is directly proportional to its degree, under which the effective infection rate λ has a maximal threshold λ_{c}^{opt}=1/〈k〉, where 〈k〉 is the average degree of the underlying network...
July 2017: Physical Review. E
Lydia Korre, Nicholas Brummell, Pascale Garaud
We examine the dynamics associated with weakly compressible convection in a spherical shell by running 3D direct numerical simulations using the Boussinesq formalism [Spiegel and Veronis, Astrophys. J. 131, 442 (1960)AJLEEY0004-637X10.1086/146849]. Motivated by problems in astrophysics, we assume the existence of a finite adiabatic temperature gradient ∇T_{ad} and use mixed boundary conditions for the temperature with fixed flux at the inner boundary and fixed temperature at the outer boundary. This setup is intrinsically more asymmetric than the more standard case of Rayleigh-Bénard convection in liquids between parallel plates with fixed temperature boundary conditions...
September 2017: Physical Review. E
Soumyajyoti Biswas, Parongama Sen
A national voting population, when segmented into groups such as, for example, different states, can yield a counterintuitive scenario in which the winner may not necessarily get the highest number of total votes. A recent example is the 2016 presidential election in the United States. We model the situation by using interacting opinion dynamics models, and we look at the effect of coarse graining near the critical points where the spatial fluctuations are high. We establish that the sole effect of coarse graining, which mimics the "winner take all" electoral college system in the United States, can give rise to finite probabilities of events in which a minority candidate wins even in the large size limit near the critical point...
September 2017: Physical Review. E
Christopher Ness, Vladimir V Palyulin, Rico Milkus, Robert Elder, Timothy Sirk, Alessio Zaccone
We investigate the mechanical properties of amorphous polymers by means of coarse-grained simulations and nonaffine lattice dynamics theory. A small increase of polymer chain bending stiffness leads first to softening of the material, while hardening happens only upon further strengthening of the backbones. This nonmonotonic variation of the storage modulus G^{'} with bending stiffness is caused by a competition between additional resistance to deformation offered by stiffer backbones and decreased density of the material due to a necessary decrease in monomer-monomer coordination...
September 2017: Physical Review. E
Hyun-Kyung Ko, Michael Berk, Yoon-Mi Chung, Belinda Willard, Rohan Bareja, Mark Rubin, Andrea Sboner, Nima Sharifi
Castration-resistant prostate cancer (CRPC) requires tumors to engage metabolic mechanisms that allow sustained testosterone and/or dihydrotestosterone to stimulate progression. 17β-Hydroxysteroid dehydrogenase type 4 (17βHSD4), encoded by HSD17B4, is thought to inactivate testosterone and dihydrotestosterone by converting them to their respective inert 17-keto steroids. Counterintuitively, HSD17B4 expression increases in CRPC and predicts poor prognosis. Here, we show that, of five alternative splice forms, only isoform 2 encodes an enzyme capable of testosterone and dihydrotestosterone inactivation...
January 16, 2018: Cell Reports
Anne G E Collins
Learning to make rewarding choices in response to stimuli depends on a slow but steady process, reinforcement learning, and a fast and flexible, but capacity-limited process, working memory. Using both systems in parallel, with their contributions weighted based on performance, should allow us to leverage the best of each system: rapid early learning, supplemented by long-term robust acquisition. However, this assumes that using one process does not interfere with the other. We use computational modeling to investigate the interactions between the two processes in a behavioral experiment and show that working memory interferes with reinforcement learning...
January 18, 2018: Journal of Cognitive Neuroscience
Massimiliano Rossi, Nenad Kralj, Stefano Zippilli, Riccardo Natali, Antonio Borrielli, Gregory Pandraud, Enrico Serra, Giovanni Di Giuseppe, David Vitali
We realize a phase-sensitive closed-loop control scheme to engineer the fluctuations of the pump field which drives an optomechanical system and show that the corresponding cooling dynamics can be significantly improved. In particular, operating in the counterintuitive "antisquashing" regime of positive feedback and increased field fluctuations, sideband cooling of a nanomechanical membrane within an optical cavity can be improved by 7.5 dB with respect to the case without feedback. Close to the quantum regime of reduced thermal noise, such feedback-controlled light would allow going well below the quantum backaction cooling limit...
September 22, 2017: Physical Review Letters
Chunhe Li
Landscape approaches have been exploited to study the stochastic dynamics of gene networks. However, how to calculate the landscape with a wide range of parameter variations and how to investigate the influence of the network topology on the global properties of gene networks remain to be elucidated. Here, I developed an approach for the landscape of random parameter perturbation (LRPP) to address this issue. Based on a self-consistent approximation approach, by making perturbations to parameters in a given range, I obtained the landscape for gene network systems...
January 17, 2018: Integrative Biology: Quantitative Biosciences From Nano to Macro
Jennifer N K Nyarko, Maa O Quartey, Paul R Pennington, Ryan M Heistad, Doris Dea, Judes Poirier, Glen B Baker, Darrell D Mousseau
The APOE ε 4 allele was originally reported to contribute to risk of Alzheimer disease (AD) in women, yet male and female AD patient-derived data are routinely pooled. Histopathological hallmarks of AD include neurofibrillary tangles centered on hyperphosphorylated Tau and plaques composed of the β -amyloid (A β) peptide that is derived by sequential secretase-mediated cleavage of the Amyloid Protein Precursor (APP). We chose to examine profiles of A β (1-40), A β (1-42), and N-truncated (i.e. p3-related) fragments in the plaque-associated fraction of autopsied cortical and corresponding hippocampal samples from donors with a diagnosis of early-onset (EOAD) and late-onset (LOAD) AD...
January 10, 2018: Neuroscience
Serigne N Lo, Richard A Scolyer, John F Thompson
BACKGROUND: Counterintuitively, more deaths from melanoma occur among patients with thin (T1) primary melanomas (≤ 1 mm) than among those with thick primary melanoma because the great majority present with T1 tumors. Therefore, it is important to stratify their risk as accurately as possible to guide their management and follow-up. This study sought to explore the relationship between tumor thickness and prognosis for patients with thin primary melanomas. METHODS: A retrospective, single-institution study investigated 6263 patients with cutaneous melanoma (including 2117 T1 cases) who had a minimum follow-up period of 10 years...
January 12, 2018: Annals of Surgical Oncology
Tejas Kotwal, Xin Jiang, Daniel M Abrams
Since its discovery in 2002, the chimera state has frequently been described as a counterintuitive, puzzling phenomenon. The Kuramoto model, in contrast, has become a celebrated paradigm useful for understanding a range of phenomena related to phase transitions, synchronization, and network effects. Here we show that the chimera state can be understood as emerging naturally through a symmetry-breaking bifurcation from the Kuramoto model's partially synchronized state. Our analysis sheds light on recent observations of chimera states in laser arrays, chemical oscillators, and mechanical pendula...
December 29, 2017: Physical Review Letters
Yong Sup Ihn, Yosep Kim, Vincenzo Tamma, Yoon-Ho Kim
We report the observation of a counterintuitive phenomenon in multipath correlation interferometry with thermal light. The intensity correlation between the outputs of two unbalanced Mach-Zehnder interferometers (UMZIs) with two classically correlated beams of thermal light at the input exhibits genuine second-order interference with the visibility of 1/3. Surprisingly, the second-order interference does not degrade at all no matter how much the path length difference in each UMZI is increased beyond the coherence length of the thermal light...
December 29, 2017: Physical Review Letters
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