Mechanistic Studies on the Anomalous Transport Behaviors of Water Molecules in Nanochannels of Multilayer Graphynes

An in-depth understanding of directed transport behaviors of water molecules through nanoporous materials is essential for the design and development of next-generation filtration devices. In this work, we perform molecular...

Quantum Anomalies (in) Matter

Over the last decade it has bee realized that triangle anomalies give rise to dissipationless transport phenomena in hot and dense relativistic matter. I will review anomalous transport theory and then discuss its applications to the quark gluon plasma and the electronics of Weyl semimetals. Finally I briefly discuss the absence of genuine chiral torsional transport.

A phenomenological approach to anomalous transport in complex or disordered media

We aim to derive a phenomenological approach to link the theories of anomalous transport governed by fractional calculus and stochastic theory with the conductivity behavior governed by the semi-empirical conductivity formalism involving Debye, Cole-Cole, Cole-Davidson, and Havriliak-Negami type conductivity equations. We want to determine the anomalous transport processes in the amorphous semiconductors and insulators by developing a theoretical approach over some mathematical instruments and methods. In this paper, we obtain an analytical expression for the average behavior of conductivity in complex or disordered media via using the fractional-stochastic differential equation, the Fourier-Laplace transform, some natural boundary-initial conditions, and familiar physical relations. We start with the stochastic equation of motion called the Langevin equation, develop its equivalent master equation called Klein-Kramers or Fokker-Planck equation, and consider the time-fractional generalization of the master equation. Once we derive the fractional master equation, then determine the expressions for the mean value of the variables or observables through some calculations and conditions. Finally, we use these expressions in the current density relation to obtain the average conductivity behavior.

Anomalous transport driven by ion temperature gradient instability in an anisotropic deuterium-tritium plasma

In the nowadays and future fusion devices such as ITER and CFETR, as the use of various heating schemes, the parallel and perpendicular temperature of plasmas can be different; this temperature anisotropy may have significant effects on the turbulence. In this work, the anomalous transport driven by the ion temperature gradient instability is investigated in an anisotropic deuterium-tritium (D-T) plasma. The anisotropic factor $\alpha$, defined as the ratio of perpendicular temperature to parallel temperature, is introduced to describe the temperature anisotropy in the equilibrium distribution function of D. The linear dispersion relation in local kinetic limit is derived, and then numerically evaluated to study the dependence of mode frequency on the anisotropic factor $\alpha$ and the proportion for T particle $\vareT$ by choosing three sets of typical parameters, denoted as the cyclone base case (CBC), ITER and CFETR cases. Based on the linear results, the mixing length model approximation is adopted to analyze the quasi-linear particle and energy fluxes for D and T. It is found that choosing small $\alpha$ and large $\vareT$ is beneficial for the confinement of particle and energy for D and T. This work may be helpful for the estimation of turbulent transport level in the ITER and CFETR devices.

On a force balance and role of cathode plasma in Hall Effect Thruster

The cathode plasma is a specific transition region in the Hall Effect Thruster (HET) discharge that localizes between the strongly magnetized acceleration layer (magnetic layer or B-layer) and non-magnetized exhaust plume. Cathode plasma provides a flow of electron current that supplies losses in the magnetic layer (due to ionization, excitation, electron-wall interactions, etc.). The electrons' transport in this region occurs in collisionless mode through the excitation of plasma instabilities. This effect is also known as "anomalous transport/conductivity". In this work, we present the results of a 2d (drift-plane) kinetic simulation of the HET discharge, including the outside region that contains cathode plasma. We discuss the process of cathode plasma formation and the mechanisms of "anomalous transport" inside it. We also analyze how fluid force balance emerges from collisionless kinetic approach. The acceleration mechanism in Hall Effect Thrusters (HETs) is commonly described in terms of force balance. Namely, the reactive force produced by accelerated ions has the same value as Ampère's force acting on a drift current loop. This balance written in integral form provides the basis for quantitative estimations of HETs' parameters and scaling models.

Analysis of anomalous transport based on radial fractional diffusion equation

The anomalous transport in magnetically confined plasmas is investigated by the radial fractional transport equations. It is shown that for fractional transport models, hollow density profiles are formed and uphill transports can be observed regardless of whether the fractional diffusion coefficients (FDCs) are radially dependent or not. When a radially dependent FDC Dα(r)<1 is imposed, compared with the case under Dα(r)=1.0, it is observed that the position of the peak of the density profile is closer to the core. Besides, it is found that when FDCs at the positions of source injections increase, the peak values of density profiles decrease. The non-local effect becomes significant as the order of fractional derivative α→1 and causes the uphill transport. However, as α→2, the fractional diffusion model returns to the standard model governed by Fick’s law.

A Weyl-Z2 semimetal from holography

We present effective field theories for the weakly coupled Weyl-Z2 semimetal, as well as the holographic realization for the strongly coupled case. In both cases, the anomalous systems have both the chiral anomaly and the Z2 anomaly and possess topological quantum phase transitions from the Weyl-Z2 semimetal phases to partly or fully topological trivial phases. We find that the topological phase transition is characterized by the anomalous transport parameters, i.e. the anomalous Hall conductivity and the Z2 anomalous Hall conductivity. These two parameters are nonzero at the Weyl-Z2 semimetal phase and vanish at the topologically trivial phases. In the holographic case, the different behavior between the two anomalous transport coefficients is discussed. Our work reveals the novel phase structure of strongly interacting Weyl-Z2 semimetal with two pairs of nodes.

Network-driven anomalous transport is a fundamental component of brain microvascular dysfunction

Blood microcirculation supplies neurons with oxygen and nutrients, and contributes to clearing their neurotoxic waste, through a dense capillary network connected to larger tree-like vessels. This complex microvascular architecture results in highly heterogeneous blood flow and travel time distributions, whose origin and consequences on brain pathophysiology are poorly understood. Here, we analyze highly-resolved intracortical blood flow and transport simulations to establish the physical laws governing the macroscopic transport properties in the brain micro-circulation. We show that network-driven anomalous transport leads to the emergence of critical regions, whether hypoxic or with high concentrations of amyloid-β, a waste product centrally involved in Alzheimer’s Disease. We develop a Continuous-Time Random Walk theory capturing these dynamics and predicting that such critical regions appear much earlier than anticipated by current empirical models under mild hypoperfusion. These findings provide a framework for understanding and modelling the impact of microvascular dysfunction in brain diseases, including Alzheimer’s Disease.