Search results for "NODAL"
showing 10 items of 264 documents
A re-entry tachycardia triggered by the spontaneous interruption of an atrial tachycardia.
2015
The common atrioventricular nodal re-entry tachycardia is the most common form of paroxysmal supraventricular tachycardia. It starts frequently with a supraventricular ectopic beat that, on finding the fast pathway in refractory period, travels in the slow pathway as to appear as a prolongation of the PR interval on the ECG. In this study, we show a singular case of a common atrioventricular nodal re-entry tachycardia triggered by the spontaneous interruption of an atrial tachycardia.
Ab initio thermodynamics for the growth of ultra-thin Cu film on a perfect MgO(001) surface
2005
Controlled growth of thin metallic films on oxide substrates is important for numerous micro-and nanoelectronic applications. Our ab initio study is devoted to the periodic slab simulations for a series of ordered 2D Cu superlattices on the regular MgO(001) substrate. Submonolayer and monolayer substrate Cu coverages were calculated using the DFT-GGA method, as implemented into the CRYSTAL-98 code. The results of ab initio calculations have been combined with thermodynamic theory which allows us to predict the growth mode of ultra-thin metal films (spinodal decomposition vs. nucleation-and-growth regime) as a function of the metal coverage and the temperature, and to estimate the metal dens…
Phase separation of binary mixtures in thin films: Effects of an initial concentration gradient across the film.
2012
We study the kinetics of phase separation of a binary (A,B) mixture confined in a thin film of thickness $D$ by numerical simulations of the corresponding Cahn-Hilliard-Cook (CHC) model. The initial state consisted of 50$%$ A:50$%$ B with a concentration gradient across the film, i.e., the average order parameter profile is ${\ensuremath{\Psi}}_{\mathrm{av}}(z,t=0)=(2z/D\ensuremath{-}1){\ensuremath{\Psi}}_{g},\phantom{\rule{0.28em}{0ex}}0\ensuremath{\leqslant}z\ensuremath{\leqslant}D$, for various choices of ${\ensuremath{\Psi}}_{g}$ and $D$. The equilibrium state (for time $t\ensuremath{\rightarrow}\ensuremath{\infty}$) consists of coexisting A-rich and B-rich domains separated by interfac…
Dynamics of crystallization in hard-sphere suspensions.
1996
Density fluctuations are monitored by small-angle light scattering during the crystallization of 0.22-\ensuremath{\mu}m-radius, hard colloidal spheres. Measured structure factors show an intensity maximum at finite-scattering vectors. The shape of the intensity distribution scales at early times during nucleation and growth and again at large times during ripening. At intermediate times there is a crossover region where scaling ceases to be valid. Both the amplitude and the position of the maximum intensity show quasi-power law behavior in time. The values of the observed exponents are within the range expected for classical growth models. The breadth of the intensity distribution increases…
A novel 2D coordination network built from hexacopper(i)-iodide clusters and cagelike aminophosphine blocks for reversible “turn-on” sensing of anili…
2018
A new copper(I) coordination polymer [Cu6(μ3-I)6(μ3-PTAO)2]n (1) was prepared from copper(I) iodide and 1,3,5-triaza-7-phosphaadamantane-7-oxide (PTAO). The crystal structure of 1 reveals an intricate 2D coordination network constructed from the hexacopper(I)-iodide [Cu6(μ3-I)6] cluster units with the 4M6-1 topology interlinked by the μ3-PTAO spacers. An overall 2D layer network can be simplified to a binodal 3,6-connected net with the kgd topology. A derived 1@paper material was prepared by impregnating compound 1 onto a filter paper. Detailed investigation of the luminescence properties for 1 and 1@paper in the solid state revealed a remarkable ability of both materials to sense aniline m…
SIMULATION OF THERMAL EFFECTS IN OPTOELECTRONIC DEVICES USING COUPLED ENERGY-TRANSPORT AND CIRCUIT MODELS
2008
A coupled model with optoelectronic semiconductor devices in electric circuits is proposed. The circuit is modeled by differential-algebraic equations derived from modified nodal analysis. The transport of charge carriers in the semiconductor devices (laser diode and photo diode) is described by the energy-transport equations for the electron density and temperature, the drift-diffusion equations for the hole density, and the Poisson equation for the electric potential. The generation of photons in the laser diode is modeled by spontaneous and stimulated recombination terms appearing in the transport equations. The devices are coupled to the circuit by the semiconductor current entering the…
Spinodal Decomposition in Binary Polymer Blends: Monte Carlo Simulations and Dynamic Mean Field Theory
2001
Using large scale computer simulations we have investigated the interplay between single chain dynamics and the kinetics of phase separation in a symmetric binary polymer blend. In the framework of a coarse grained lattice model — the bond fluctuation model on a three dimensional lattice — we monitor the growth of concentration fluctuations after a quench from the one phase region into the miscibility gap. Chains of 64 effective segments are simulated in a cell of linear dimension L = 160, i.e., each simulation box contains 256 000 particles. The growth rate of composition fluctuations is averaged over 64 realizations of the temperature quench.
Ab initio thermodynamic study of (Ba,Sr)(Co,Fe)O3 perovskite solid solutions for fuel cell applications
2013
(Ba,Sr)(Co,Fe)O3 (BSCF) perovskite solid solutions are promising materials for solid oxide fuel cell cathodes and oxygen permeation membranes. Cathode performance strongly depends on the morphology of these materials remaining as a single phase or two-phase mixture. Combining ab initio calculations of the atomic and electronic structure of different supercells with thermodynamics of solid solutions, we have constructed and discussed phase diagrams of several important BSCF chemical compositions. It is demonstrated that in BSC cobaltite solid solution the spinodal decomposition may occur already at relatively low temperatures, while ferrite (BSF and SCF) solid solutions decompose at relative…
Atomistic Theory of the Growth Mode for a Thin Metallic Film on an Isulating Substrate
2002
We have developed a novel theory for predicting the growth mode of a thin metallic film on an insulating substrate. Our theory combines ab initio electronic structure calculations for several ordered metal/insulator interfaces with varying metal coverage, with a thermodynamic method known in the theory of alloys. We illustrate this approach for an Ag film deposited on a MgO(001) substrate. Ab initio Hartree-Fock calculations predict a high mobility of adsorbed silver atoms on the perfect magnesia surface even at low temperatures. Our theoretical analysis clearly demonstrates that the growth of metal islands is predominant at the initial stage of silver deposition on MgO, which agrees with t…
Equilibrium phase behavior of polyethylene oxide and of its mixtures with tetrahydronaphthalene or/and poly(ethylene oxide-block-dimethylsiloxane)
2002
Liquid/solid and liquid/liquid (LL) transition temperatures were measured by means of an automated device that monitors the light passing through the systems as a function of T at different constant cooling or heating rates q. For pure polyethylene oxide (PEO) crystallization and melting temperatures depend on |q|0.3 and become identical at the equilibrium transition temperature Tm=61.0 °C in the limit of infinitely slow cooling/heating. The reduction of Tm for PEO dissolved in tetrahydronaphthalene (THN) yields information on the Flory–Huggins interaction parameter ξ between these two compounds; ξ results negative and decreases markedly with rising polymer concentration. A tentative explan…