Giant nonlinear conduction and thyristor-like negative derivative resistance in BaIrO3 single crystals

We synthesized single-crystalline samples of monoclinic BaIrO3 using a molten flux method, and measured their magnetization, resistivity, Seebeck coefficient and nonlinear voltage-current characteristics. The magnetization rapidly increases below a ferromagnetic transition temperature TC of 180 K, where the resistivity concomitantly shows a hump-type anomaly, followed by a sharp increase below 30 K. The Seebeck coefficient suddenly increases below TC, and shows linear temperature dependence below 50 K. A most striking feature of this compound is that the anomalously giant nonlinear conduction is observed below 30 K, where a small current density of 20 A/cm2 dramatically suppresses the sharp increase in resistivity to induce a metallic conduction down to 4 K.Comment: 10 pages, 4 figures Submitted to Physical Review Letter

Angle Dependent Magnetoresistance of the Layered Organic Superconductor \kappa-(ET)2Cu(NCS)2: Simulation and Experiment

The angle-dependences of the magnetoresistance of two different isotopic substitutions (deuterated and undeuterated) of the layered organic superconductor \kappa-(ET)2Cu(NCS)2 are presented. The angle dependent magnetoresistance oscillations (AMRO) arising from the quasi-one-dimensional (Q1D) and quasi-two-dimensional (Q2D) Fermi surfaces in this material are often confused. By using the Boltzman transport equation extensive simulations of the AMRO are made that reveal the subtle differences between the different species of oscillation. No significant differences are observed in the electronic parameters derived from quantum oscillations and AMRO for the two isotopic substitutions. The interlayer transfer integrals are determined for both isotopic substitutions and a slight difference is observed which may account for the negative isotope effect previously reported [1]. The success of the semi-classical simulations suggests that non-Fermi liquid effects are not required to explain the interlayer-transport in this system.Comment: 15 pages, 16 figure

Genetic and Neuroanatomical Support for Functional Brain Network Dynamics in Epilepsy

Focal epilepsy is a devastating neurological disorder that affects an overwhelming number of patients worldwide, many of whom prove resistant to medication. The efficacy of current innovative technologies for the treatment of these patients has been stalled by the lack of accurate and effective methods to fuse multimodal neuroimaging data to map anatomical targets driving seizure dynamics. Here we propose a parsimonious model that explains how large-scale anatomical networks and shared genetic constraints shape inter-regional communication in focal epilepsy. In extensive ECoG recordings acquired from a group of patients with medically refractory focal-onset epilepsy, we find that ictal and preictal functional brain network dynamics can be accurately predicted from features of brain anatomy and geometry, patterns of white matter connectivity, and constraints complicit in patterns of gene coexpression, all of which are conserved across healthy adult populations. Moreover, we uncover evidence that markers of non-conserved architecture, potentially driven by idiosyncratic pathology of single subjects, are most prevalent in high frequency ictal dynamics and low frequency preictal dynamics. Finally, we find that ictal dynamics are better predicted by white matter features and more poorly predicted by geometry and genetic constraints than preictal dynamics, suggesting that the functional brain network dynamics manifest in seizures rely on - and may directly propagate along - underlying white matter structure that is largely conserved across humans. Broadly, our work offers insights into the generic architectural principles of the human brain that impact seizure dynamics, and could be extended to further our understanding, models, and predictions of subject-level pathology and response to intervention

Theory of the optical properties of non-absorbing compensated cholesteric liquid crystals

A theory is developed of the optical properties of a non-absorbing compensated cholesteric liquid crystal. It is shown that the Mauguin-de Vries equation fails when the pitch becomes very large. Theoretical curves are presented of the dependence of the rotatory power on pitch for different values of the sample thickness. The results are in agreement with the observed variation of the rotatory power of a compensated cholesteric mixture with temperature

From LTL and Limit-Deterministic B\"uchi Automata to Deterministic Parity Automata

Controller synthesis for general linear temporal logic (LTL) objectives is a challenging task. The standard approach involves translating the LTL objective into a deterministic parity automaton (DPA) by means of the Safra-Piterman construction. One of the challenges is the size of the DPA, which often grows very fast in practice, and can reach double exponential size in the length of the LTL formula. In this paper we describe a single exponential translation from limit-deterministic B\"uchi automata (LDBA) to DPA, and show that it can be concatenated with a recent efficient translation from LTL to LDBA to yield a double exponential, \enquote{Safraless} LTL-to-DPA construction. We also report on an implementation, a comparison with the SPOT library, and performance on several sets of formulas, including instances from the 2016 SyntComp competition

Test for interlayer coherence in a quasi-two-dimensional superconductor

Peaks in the magnetoresistivity of the layered superconductor $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$, measured in fields $\leq 45$ T applied within the layers, show that the Fermi surface is extended in the interlayer direction and enable the interlayer transfer integral ($t_{\perp} \approx 0.04$ meV) to be deduced. However, the quasiparticle scattering rate $\tau^{-1}$ is such that $\hbar/\tau \sim 6t_{\perp}$, implying that $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$ meets the criterion used to identify interlayer incoherence. The applicability of this criterion to anisotropic materials is thus shown to be questionable.Comment: 5 pages, 4 figure