Diffusion Mode Research Articles

We study the superconducting instability of a two-dimensional disordered Fermi liquid weakly coupled to the soft fluctuations associated with proximity to an Ising-ferromagnetic quantum critical point. We derive interaction-induced corrections to the Usadel equation governing the superconducting gap function, and show that diffusion and localization effects drastically modify the interplay between fermionic incoherence and strong pairing interactions. In particular, we obtain the phase diagram, and demonstrate that (i) there is an intermediate range of disorder strength where superconductivity is enhanced, eventually followed by a tendency towards the superconductor-insulator transition at stronger disorder; and (ii) diffusive particle-particle modes (so-called ``Cooperons'') acquire anomalous dynamical scaling $z=4$, indicating strong non-Fermi liquid behavior.

Mg-Al layered double hydroxides with a hydrotalcite structure have been synthesized. The sorption properties of the synthesized sample with respect to non-ferrous metal ions — Co2+, Cu2+, Sr2+ and Cs+ are investigated. The capacities of the adsorption monolayer of the Mg-Al layered hydroxide sample were calculated, amounting to 2.13, 2.21, 1.88 and 3.48 mmol/g with respect to Co(II), Cu(II), Sr(II) and Cs(I) ions, respectively. It is shown that the sorption process is described by a pseudo-second-order kinetic model and proceeds in a mixed diffusion mode.

ABSTRACT To research the mechanisms of diffusion and water uptake kinetics biocomposites, various HDPE materials reinforced by varying quantities of Washingtonia filifera (WF) fibres (10 to 30 wt%) were submerged at room temperature in distilled water. To optimise the immersion time and WF fibre content in HDPE/WF biocomposite water uptake, an artificial neural network, the response surface methodology and the genetic algorithm were employed. In this research, the CCD model of RSM was utilised to carry out test design, modelling, and optimisation. It was found that the way water absorbs liquids follows the Fickian diffusion mode. The outcomes demonstrate that the incorporation of WF fibres into the HDPE matrix decreased the diffusivity. The ANOVA determined the relative significance of each variable and demonstrated the model’s validity by demonstrating a high correlation between the observed data. Moreover, the results showed that the ANN models have training, test and validation correlation coefficients for water absorption prediction of 0.9955, 0.9915 and 0.9999, respectively. RSM-GA revealed that a 10% fibre content and a one-hour immersion duration produced the lowest levels of absorption. Additionally, a model that is very suitable for predicting biocomposites water uptake and is applicable to a variety of industrial applications is developed.

Experimental Study on Flow Water Diffusion of Cement-Sodium Silicate Grouting in Rough Fracture Model

Ring polymers have fascinated scientists for decades, but experimental progress has been challenging due to the presence of linear chain contaminants that fundamentally alter dynamics. In this work, we report the unexpected slow stress relaxation behavior of concentrated ring polymers that arises due to ring-ring interactions and ring packing structure. Topologically pure, high molecular weight ring polymers are prepared without linear chain contaminants using cyclic poly(phthalaldehyde) (cPPA), a metastable polymer chemistry that rapidly depolymerizes from free ends at ambient temperatures. Linear viscoelastic measurements of highly concentrated cPPA show slow, non-power-law stress relaxation dynamics despite the lack of linear chain contaminants. Experiments are complemented by molecular dynamics (MD) simulations of unprecedentedly high molecular weight rings, which clearly show non-power-law stress relaxation in good agreement with experiments. MD simulations reveal substantial ring-ring interpenetrations upon increasing ring molecular weight or local backbone stiffness, despite the global collapsed nature of single ring conformation. A recently proposed microscopic theory for unconcatenated rings provides a qualitative physical mechanism associated with the emergence of strong inter-ring caging which slows down center-of-mass diffusion and long wavelength intramolecular relaxation modes originating from ring-ring interpenetrations, governed by the onset variable N/ND, where the crossover degree of polymerization ND is qualitatively predicted by theory. Our work overcomes challenges in achieving ring polymer purity and by characterizing dynamics for high molecular weight ring polymers. Overall, these results provide a new understanding of ring polymer physics.

We discuss theoretically the non-Hermitian superfluid phase transition in one-dimensional two-component Fermi gases near the $p$-wave Feshbach resonance accompanied by the two-body loss associated with dipolar relaxation. We point out that this system gives us an opportunity to explore the interplay among various nontrivial properties such as universal thermodynamics at divergent $p$-wave scattering lengths, the topological phase transition at vanishing chemical potential, and the non-Hermitian Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) transition, in a unified manner. In the BCS phase, the loss-induced superfluid-normal transition occurs when the exceptional point appears in the effective non-Hermitian Hamiltonian. In the BEC phase, the diffusive gapless mode can be regarded as a precursor of the instability of the superfluid state. Moreover, we show that the superfluid state is fragile against the two-body loss near the topological phase transition point.

Bistable traveling waves in degenerate competitive systems

Effect of Zn atomic diffusion due to pulsed electric field treatment on the thermoelectric properties of Zn–Sb films

Modes of multi-mechanistic gas diffusion in shale matrix at varied effective stresses: Observations and analysis

We discuss the physics of sound propagation and charge diffusion in a plasma with non-vanishing charge density. Our analysis culminates the program initiated in [1] to construct an open effective field theory of low-lying modes of the stress tensor and charge current in such plasmas. We model the plasma holographically as a Reissner-Nordström-AdSd+1 black hole, and study linearized fluctuations of longitudinally polarized scalar gravitons and photons in this background. We demonstrate that the perturbations can be decoupled and repackaged into the dynamics of two designer scalars, whose gravitational coupling is modulated by a non-trivial dilatonic factor. The holographic analysis allows us to isolate the phonon mode from the charge diffusion mode, and identify the combination of currents that corresponds to each of them. We use these results to obtain the real-time Gaussian effective action, which includes both the retarded response and the associated stochastic (Hawking) fluctuations, accurate to quartic order in gradients.

Characterization of bulk optical properties of pear tissues in the 500 to 1000 nm range as input for simulation-based optimization of laser spectroscopy in diffuse transmittance mode

Heavy rainfall causes large volumes of freshwater and nutrient salts to flow from rivers into the sea. This leads to major changes in the ecological environment of estuarine waters in a short period of time. The responses of the estuarine hydro-environment become more complex with the concentrated construction of artificial structures, which is a major cause of marine ecological disasters. This paper considers the Tang Estuary in Qinhuangdao, where artificial structures (e.g., ports, artificial islands, and bridges) are concentrated, as a prototype with the weak tidal dynamic environment. A nested prototype of hydrodynamics and water quality was established using a Delft3D model, with coupled waves and flows. The model was used to simulate the spatial and ephemeral characteristics of the short-term responses of ecological environmental factors, such as dissolved inorganic nitrogen (DIN), nitrate-nitrogen (i.e., NO3-N), ammonium-nitrogen (NH4-N), and orthophosphate (i.e., PO4-P), to an episode of heavy rainfall in August 2022. The results showed that concentrations of DIN and NO3-N in the source areas remain high after the flooding process. The concentration recovered to normal values approximately 5.5 days after the flooding process. In contrast, NH4-N and PO4-P showed a response with ephemeral correspondence with the flooding process, and concentration recovery took only approximately 1 day. This paper proposes two short-term response modes of pollutant diffusion, which provide help in exploring the role of hydro-environmental changes in offshore algal hazards and the effect of permeable buildings on pollutant dispersion. This additionally provides possibilities with the forecasting of red tide and green tide, and for their prevention in the future.

The effects of nitrous oxide (N_2O) in nitrogen (N_2) on the development and morphology of sine-driven dielectric barrier discharges in a single-filament arrangement were studied. Detailed insight in the characteristics of the discharge and its development were obtained from electrical measurements combined with ICCD and streak camera recordings as well as numerical modelling. A miniaturised atmospheric pressure Townsend discharge (APTD) could be generated for admixtures up to 5 vol% N_2O in N_2 although N_2O is an efficient collisional quencher of metastable nitrogen molecules. Increasing the high voltage amplitude led to a transition into a hybrid mode with the generation of an intermediate filament in addition to the diffuse, non-constricted APTD. A time-dependent, spatially one-dimensional fluid model was applied in order to study the underlying mechanisms causing the diffuse discharge characteristics. It was found that even for small N_2O admixtures, the associative ionisation of atomic nitrogen and oxygen (O + N(^2P) rightarrow NO^+ + e) is the major electron source sustaining the volume memory effect and is therefore the reason for the formation of a diffuse APTD.Graphical abstract

A gradual seeking technique for determining the relationship between needle tip and target nerve according to diffusion mode of anesthetics in ultrasound-guided nerve block.

In order to determine the optimizing parameters of the process of hydrothermal leaching of amylose, kinetic studies were carried out under isothermal conditions. Native (potato and corn) and heat-treated starches were used in the experiments. The obtained kinetic data are described by the Kruger-Ziegler equation. It is shown that in the temperature range of 60–700C, the apparent activation energy is 193 kJ mol–1 and 43–83 kJ mol–1 for native and heat-treated starches, respectively. With a further increase in the temperature, the activation energy decreases to 22 kJ mol–1 and 13–14 kJ mol–1 for native and modified starches, respectively. It is proposed to consider amylose leaching as a heterogeneous pseudochemical process, in which the process of breaking numerous hydrogen bonds between amylose macromolecules acts as a chemical reaction. From this point of view, the change in activation energy with increasing temperature is explained by the transition of the leaching process from the kinetic to the diffusion mode. Changes in the activation energies of modified starches are explained by a decrease in the number of hydrogen bonds between amylose macromolecules due to a decrease in their degree of linearity and size during thermal conversion. Changes in the structure of starch during their heating were investigated by the DTA method. The values of the apparent activation energy for two stages were determined as follows: 44 kJ mol–1 and ~26 kJ mol–1 for molecular dehydration and intermolecular dehydration of native starch, respectively, which indicates that both processes occur in the kinetic mode. Considering amylose leaching as a heterogeneous pseudochemical process shows that the main optimizing factors are temperature and starch pre-milling.

The strange metal behavior, usually characterized by a linear-in-temperature (T) resistivity, is a still unsolved mystery in solid-state physics. It is often associated with the proximity to a quantum critical point (a second order transition at temperature T=0, leading to a broken symmetry phase) focusing on the related divergent order parameter correlation length. Here, we propose a paradigmatic shift, focusing on a divergent characteristic time scale due to a divergent dissipation acting on the fluctuating critical modes while their correlation length stays finite. To achieve a divergent dissipation, we propose a mechanism based on the coupling between a local order parameter fluctuation and electron density diffusive modes that accounts both for the linear-in-T resistivity and for the logarithmic specific heat versus temperature ratio CV/T∼log(1/T), down to low temperatures.

Multifunctional microcapsules based on ZnO and n-octadecane: From thermal energy storage to photocatalytic activity

The surface charges in nanosecond pulsed dielectric barrier discharge under quiescent air and airflow are detected based on the Pockels effect of electro-optical crystals. In quiescent air, it is found that the surface charge spot propagates and moves in a certain direction due to the combination of the transverse electric field and the thermal accumulation during dozens of consecutive discharge cycles. However, the position of the surface charge spot remains fixed throughout a single discharge cycle (0.83 ms). At the same time, the noticeable decay of surface charges emerges in the above time scales. Furthermore, when the airflow is introduced into the discharge gap, the propagation and movement of surface charges are accelerated. With the increase of airflow velocity, the discharge transforms from a filamentary mode to a diffuse mode, and the distribution of surface charges varies from discrete to uniform. The transition point of the discharge state and charge distribution corresponds to the airflow velocity of 10 m s−1. The airflow accelerates the decay of surface charges, resulting in the shrink and dispersion of surface charges, which is considered to be the fundamental reason for the airflow’s potential to improve discharge uniformity. The inherent mechanism for achieving uniform discharge is revealed in this study.

There are two primary types of photoreceptor cells in the human eye: cone cells and rod cells that enable color vision and night vision, respectively. Herein, inspired by the function of human visual cells, we develop a high-resolution perovskite-based color camera using a set of narrowband red, green, blue, and broadband white perovskite photodetectors as imaging sensors. The narrowband red, green, and blue perovskite photodetectors with color perceptions mimic long-, medium-, and short-wavelength cones cells to achieve color imaging ability. Also, the broadband white perovskite photodetector with better detectivity mimics rod cells to improve weak-light imaging ability. Our perovskite-based camera, combined with predesigned pattern illumination and image reconstruction technology, is demonstrated with high-resolution color images (up to 256 × 256 pixels) in diffuse mode. This is far beyond previously reported advanced perovskite array image sensors that only work in monochrome transmission mode. This work shows a new approach to bio-inspired cameras and their great potential to strongly mimic the ability of the natural eye.

Spatio-temporal agglomeration and morphological causes of Shanghai catering clusters