Drift of invariant manifolds and transient chaos in memristor Chua's circuit

The article shows that transient chaos phenomena can be observed in a generalized memristor Chua's circuit where a nonlinear resistor is introduced to better model the real memristor behaviour. The flux-charge analysis method is used to explain the origin of transient chaos, that is attributed to the drift of the index of the memristor circuit invariant manifolds caused by the charge flowing into the nonlinear resistor

Convergence of Discrete-Time Cellular Neural Networks with Application to Image Processing

The paper considers a class of discrete-time cellular neural networks (DT-CNNs) obtained by applying Euler's discretization scheme to standard CNNs. Let T be the DT-CNN interconnection matrix which is defined by the feedback cloning template. The paper shows that a DT-CNN is convergent, i.e. each solution tends to an equilibrium point, when T is symmetric and, in the case where T + En is not positive-semidefinite, the step size of Euler's discretization scheme does not exceed a given bound (En is the n × n unit matrix). It is shown that two relevant properties hold as a consequence of the local and space-invariant interconnecting structure of a DT-CNN, namely: (1) the bound on the step size can be easily estimated via the elements of the DT-CNN feedback cloning template only; (2) the bound is independent of the DT-CNN dimension. These two properties make DT-CNNs very effective in view of computer simulations and for the practical applications to high-dimensional processing tasks. The obtained results are proved via Lyapunov approach and LaSalle's Invariance Principle in combination with some fundamental inequalities enjoyed by the projection operator on a convex set. The results are compared with previous ones in the literature on the convergence of DT-CNNs and also with those obtained for different neural network models as the Brain-State-in-a-Box model. Finally, the results on convergence are illustrated via the application to some relevant 2D and 1D DT-CNNs for image processing tasks

RNA denaturation: excluded volume, pseudoknots and transition scenarios

A lattice model of RNA denaturation which fully accounts for the excluded volume effects among nucleotides is proposed. A numerical study shows that interactions forming pseudoknots must be included in order to get a sharp continuous transition. Otherwise a smooth crossover occurs from the swollen linear polymer behavior to highly ramified, almost compact conformations with secondary structures. In the latter scenario, which is appropriate when these structures are much more stable than pseudoknot links, probability distributions for the lengths of both loops and main branches obey scaling with nonclassical exponents.Comment: 4 pages 3 figure

Bending-rigidity-driven transition and crumpling-point scaling of lattice vesicles

The crumpling transition of three-dimensional (3D) lattice vesicles subject to a bending fugacity \ensuremath{\rho}=exp(-\ensuremath{\kappa}/${\mathit{k}}_{\mathit{BT}}$) is investigated by Monte Carlo methods in a grand canonical framework. By also exploiting conjectures suggested by previous rigorous results, a critical regime with scaling behavior in the universality class of branched polymers is found to exist for \ensuremath{\rho}\ensuremath{\gtrsim}{\mathrm{\ensuremath{\rho}}}_{\mathit{c}}. For \ensuremath{\rho}{\mathrm{\ensuremath{\rho}}}_{\mathit{c}} the vesicles undergo a first-order transition that has remarkable similarities to the line of droplet singularities of inflated 2D vesicles. At the crumpling point (\ensuremath{\rho}={\mathrm{\ensuremath{\rho}}}_{\mathit{c}}), which has a tricritical character, the average radius and the canonical partition function of vesicles with n plaquettes scale as {\mathit{n}}^{{\ensuremath{\nu}}_{\mathit{c}}} and {\mathit{n}}^{\mathrm{\ensuremath{-}}{\mathrm{\ensuremath{\theta}}}_{\mathit{c}}}, respectively, with {\ensuremath{\nu}}_{\mathit{c}}=0.4825\ifmmode\pm\else\textpm\fi{}0.0015 and {\mathrm{\ensuremath{\theta}}}_{\mathit{c}}=1.78\ifmmode\pm\else\textpm\fi{}0.03. These exponents indicate a new class, distinct from that of branched polymers, for scaling at the crumpling point. \textcopyright{} 1996 The American Physical Society

Nebulette knockout mice have normal cardiac function, but show Z-line widening and up-regulation of cardiac stress markers

Aims: Nebulette is a 109 kDa modular protein localized in the sarcomeric Z-line of the heart. In vitro studies have suggested a role of nebulette in stabilizing the thin filament, and missense mutations in the nebulette gene were recently shown to be causative for dilated cardiomyopathy and endocardial fibroelastosis in human and mice. However, the role of nebulette in vivo has remained elusive. To provide insights into the function of nebulette in vivo, we generated and studied nebulette-deficient (nebl-/-) mice. Methods and results: Nebl-/- mice were generated by replacement of exon 1 by Cre under the control of the endogenous nebulette promoter, allowing for lineage analysis using the ROSA26 Cre reporter strain. This revealed specific expression of nebulette in the heart, consistent with in situ hybridization results. Nebl-/- mice exhibited normal cardiac function both under basal conditions and in response to transaortic constriction as assessed by echocardiography and haemodynamic analyses. Furthermore, histological, IF, and western blot analysis showed no cardiac abnormalities in nebl-/- mice up to 8 months of age. In contrast, transmission electron microscopy showed Z-line widening starting from 5 months of age, suggesting that nebulette is important for the integrity of the Z-line. Furthermore, up-regulation of cardiac stress responsive genes suggests the presence of chronic cardiac stress in nebl-/- mice. Conclusion: Nebulette is dispensable for normal cardiac function, although Z-line widening and up-regulation of cardiac stress markers were found in nebl-/- heart. These results suggest that the nebulette disease causing mutations have dominant gain-of-function effects

The cryogenic RWELL: a stable charge multiplier for dual-phase liquid-argon detectors

The operation of a cryogenic Resistive WELL (RWELL) in liquid argon vapor is reported for the first time. It comprises a Thick Gas Electron Multiplier (THGEM) structure coupled to a resistive Diamond-Like Carbon (DLC) anode deposited on an insulating substrate. The multiplier was operated at cryogenic temperature (90~K, 1.2~bar) in saturated argon vapor and characterized in terms of charge gain and electrical stability. A comparative study with standard, non-resistive THGEM (a.k.a LEM) and WELL multipliers, confirmed the RWELL advantages in terms of discharge quenching - thus superior gain and stability

Novel resistive charge-multipliers for dual-phase LAr-TPCs: towards stable operation at higher gains

Cryogenic versions of Resistive WELL (RWELL) and Resistive Plate WELL (RPWELL) detectors have been developed, aimed at stable avalanche multiplication of ionization electrons in dual-phase TPCs. In the RWELL, a thin resistive layer deposited on top of an insulator is inserted in between the electron multiplier (THGEM) and the readout anode; in the RPWELL, a resistive plate is directly coupled to the THGEM. Radiation-induced ionization electrons in the liquid are extracted into the gaseous phase. They drift into the THGEM's holes where they undergo charge multiplication. Embedding resistive materials into the multiplier proved to enhance operation stability due to the mitigation of electrical discharges - thus allowing operation at higher charge gain compared to standard THGEM (a.k.a. LEM) multipliers. We present the detector concepts and report on the main preliminary results