Phase State Research Articles

Development of a Helmholtz free energy equation of state for fluid and solid phases via artificial neural networks

A longstanding challenge in thermodynamics has been the development of a unified analytical expression for the free energy of matter capable of describing all thermodynamic properties. Although significant strides have been made in modeling fluid phases using continuous equations of state (EoSs), the crystalline state has remained largely unexplored because of its complexity. This work introduces an approach that employs artificial neural networks to construct an EoS directly from comprehensive molecular simulation data. The efficacy of this method is demonstrated through application to the Mie potential, resulting in a thermodynamically consistent model seamlessly bridging fluid and crystalline phases. The proposed EoS accurately predicts metastable regions, enabling a comprehensive characterization of the phase diagram, which includes the critical and triple points.

Infinite ground-state degeneracy of a two-dimensional athermal lattice-gas.

I studied the ground state properties and phase behavior of a two-dimensional lattice gas in which hard-core particles can have at most one nearest neighboring occupied site on the square lattice. Monte Carlo simulations in the grand-canonical ensemble showed no apparent signature of singular thermodynamic behavior when the chemical potential was increased. The absence of an ordering phase transition is traced to the large number of ground state configurations the model is endowed, which is due to the impossibility of satisfying simultaneously closest packing around a vacancy and around a particle. Numerical simulations confirm that the ground state entropy is proportional to the square root of system size.

Geometric phase for mixed squeezed-coherent states

Geometric phase for mixed squeezed-coherent states

Equation of state and universal solid phase of one-dimensional dipolar fluids

Macroscopic and structural properties of one-dimensional (1D) dipolar fluids are investigated theoretically. The equation of state is fully explored by means of analytical limiting laws, integral equations and corroborating Monte Carlo simulations. An interesting mapping with the Tonks gas (i.e. hard rods) is established at strong coupling. Crucially, we report a novel solid phase characterized by auniversal algebraic decayof the pair distribution function whose range extends with increasing coupling. This discovery provides a clarified view in 1D systems and open new routes to explore theoretically as well as experimentally.

Features of Wetting with Water Hydrophobic Powders of Methyl Silica and Composite Systems Based on it.

The phase state of heterogeneous systems prepared on the basis of mixtures of hydrophobic and hydrophilic silica and water, depending on the ratio of component concentrations, and their using as thixotropic agents has been studied. It was found that the dependence of the interfacial energy of water with the surface of the particles of the composite system made on the basis of hydrophilic and hydrophobic silica taken in the proportion of 1:1 as for the individually taken AM-1 has a bell-shaped form with peaks at h=3 and 1.5 g/g, respectively. The type of dependence is due to the complex processes involved in the formation of the composite system involving solid particles, water, and air.

Aerosol Fluorescent Labeling via Probe Molecule Volatilization.

The physicochemical properties of aerosols, including hygroscopicity, phase state, pH, and viscosity, influence important processes ranging from virus transmission and pulmonary drug delivery to atmospheric light scattering and chemical reactivity. Despite their importance, measurements of these key properties in aerosols remain experimentally challenging due to small particle sizes and low mass densities in air. Fluorescence probe spectroscopy is one of the only analytical techniques that is capable of experimentally determining these properties in situ in a nondestructive and minimally perturbative manner. However, the application of fluorescence probe spectroscopy to important classes of aerosols including exhaled respiratory and ambient atmospheric aerosols has been limited due to a typical reliance on premixing the probe molecule with particle constituents prior to particle generation, which is not always possible. Here, a method for aerosol fluorescent labeling based on probe molecule volatilization is developed. The method is first applied to label model polyethylene glycol (PEG) aerosols with two different polarity-sensitive probes, Nile red and Prodan. The similarity of the relative humidity-dependent fluorescent emission of each probe between prelabeled and volatilized-probe PEG particles validated the methodology. A preliminary application of the technique to indicate the hygroscopicity of artificial saliva respiratory particles and model atmospheric secondary organic aerosol particles is demonstrated. The methodology developed here paves the way for future studies applying powerful fluorescent probe-based analytical techniques to study exhaled or natural aerosols for which fluorescent prelabeling is not possible.

Exploring the Effect of Environmental Conditions on Decay Kinetics of Aerosol Unsaturated Fatty Acids: New Insights Gained from Long-Term Ambient Measurements.

Unsaturated fatty acids (uFAs) are important constituents of atmospheric organic aerosols, undergoing rapid degradation in the atmosphere that significantly influences aerosol's physical and chemical properties. This study quantified the effective pseudo-first order decay rates of three abundant uFAs-oleic, elaidic, and linoleic acids under real atmospheric conditions using continuous bihourly measurement at a suburban site in Hong Kong over a 9-month period from November 2020 to August 2021. The impact of key environmental parameters, including ozone, initial uFA concentration, relative humidity, and temperature, on the decay rates was rigorously examined. Distinct kinetic behaviors were observed across different temperature ranges (TR1: 5-13 °C; TR2: 13-22 °C; TR3: 22-26 °C; TR4: 26-30 °C). Arrhenius plots of the decay rates revealed contrasting effective activation energies under TR2 and TR4, likely due to different phase states of aerosols and reaction mechanisms under varying environmental conditions. This study extends previous laboratory research by incorporating a wider range of ambient conditions, uncovering the complex interactions between environmental factors and the decay kinetics of uFAs. The findings provide critical insights for accurately modeling the fate of ambient organic aerosols and understanding the intricate impacts of atmospheric conditions on aerosol chemistry.

Machine Learning Potential for Serpentines

AbstractSerpentines are layered hydrous magnesium silicates (MgOO) formed through serpentinization, a geochemical process that significantly alters the physical property of the mantle. They are hard to investigate experimentally and computationally due to the complexity of natural serpentine samples and the large number of atoms in the unit cell. We developed a machine learning (ML) potential for serpentine minerals based on density functional theory calculation with the SCAN meta‐GGA functional for molecular dynamics simulation. We illustrate the success of this ML potential model in reproducing the high‐temperature equation of states of several hydrous phases under the Earth's subduction zone conditions, including brucite, lizardite, and antigorite. In addition, we investigate the polysomes of antigorite with periodicity = 13–24, which is believed to be all the naturally existent antigorite species. We found that antigorite with larger than 21 appears more stable than lizardite at low temperatures. This ML potential can be further applied to investigate more complex antigorite superstructures with multiple coexisting periodic waves.

The long noncoding RNA ALEX1 confers a functional phase state of ARF3 to enhance rice resistance to bacterial pathogens

The long noncoding RNA ALEX1 confers a functional phase state of ARF3 to enhance rice resistance to bacterial pathogens

Coupled feldspar dissolution and secondary mineral precipitation in batch systems: 6. Labradorite dissolution, calcite growth, and clay precipitation at 60 °C and pH 8.2–8.4

We conducted experiments on concurrent labradorite dissolution, calcite precipitation, and clay precipitation in batch reactor systems and tracked reaction processes using multiple isotope tracers. Labradorite was chosen for its role as a major and reactive component in basalt; the experiments thus directly impact our understanding of CO2 storage in basalt aquifers and enhanced rock weathering. We doped initial solutions with 29Si, 43Ca, and Ca13CO3(s). Experiments were conducted at 60 °C and pH ∼ 8.3 for up to 840 h, with isotope ratios in the experimental aqueous solutions measured using MC-ICP-MS. Unidirectional rates of labradorite dissolution near equilibrium were approximately two orders of magnitude slower than far-from-equilibrium rates reported in the literature. Calcite growth occurred near equilibrium and the rates were limited by the labradorite dissolution rates.In the steady state phase, the interplay of these three heterogeneous reactions—labradorite dissolution, calcite growth, and clay precipitation—results in a coupled system that approaches a near-equilibrium state. The system does not reach true equilibrium because labradorite continues to dissolve, albeit at a much slower rate near equilibrium. The overall reaction can be approximated as,Na0.4Ca0.6Al1.6Si2.4O8 + 0.6HCO3- + 1·.7H2O + 0.4H+ → 0.4Na+ + 0.6CaCO3(s) + 0.5Al2Si2O5(OH)4(s) + 0.6Al(OH)4- + 1.4SiO2o(aq)The experimental results show that using short-term far-from-equilibrium rate constants would lead to an overestimation of feldspar weathering rates at the Earth’s surface (e.g., basalt weathering and enhanced rock weathering) and CO2 mineralization in basalt aquifers.

Nematic and Smectic Phases with Proper Ferroelectric Order.

A material showing a sequence of three ferroelectric liquid crystalline phases below the paraelectric nematic phase is synthesized and studied. The polar order of molecules appearing due to the dipole-dipole interactions in the ferroelectric nematic, NF, phase is preserved also in the smectic phases: orthogonal SmAF and tilted SmCF. The ferroelectric ground state of both smectic phases is confirmed by their second harmonic generation (SHG)activity and polarization switching. In the SmCF phase the polarization becomes oriented to the electric field by decreasing the tilt angle to zero. Although both smectic phases are ferroelectric in nature, their dielectric response is found to be very different.

Spatial and reconfigurable control of photoluminescence from single-layer MoS2 using a strained VO2-based Fabry–Pérot cavity

We investigated the photoluminescence (PL) from single-layer MoS2 on VO2 platelets grown on SiO2, where the insulating and metallic phases can coexist above a bulk transition temperature of 340 K, due to the inhomogeneous strain. We found that the intensity of PL from MoS2 on metallic VO2 is higher than that on the insulating counterpart, resulting in spatially varying PL even at the sub-micrometer scale. In contrast to the intensity, the PL peak energies were observed to be nearly identical on insulating and metallic VO2, indicating that the influences of charge transfer, strain, and dielectric screening on MoS2 are comparable, regardless of the phase state. Thus, the observed difference in PL intensity is due to the difference in refractive indices of insulating and metallic VO2, leading to the phase-dependent Fabry–Pérot interference effect. We performed numerical simulations for the emission from MoS2 supported on the VO2-based Fabry–Pérot interferometer. The calculated emission intensity ratio on insulating and metallic VO2 well reproduces the experimental observations. These results suggest a strategy for controlling PL from two-dimensional semiconductors in a spatial and reconfigurable manner.

Influence of side-methyl substitution position on the phase state and microwave dielectric properties of triphenylacetylene-based liquid crystals.

Liquid crystal materials are well known in display applications, and their unique birefringence and electrical tunability can be utilised in microwave devices. This innovative technology modulates and filters microwave signals, replacing conventional semiconductors for a broad operational frequency band and tunable phase shift. Although isothiocyanatobiphenylacetylene-based liquid crystals exhibit low viscosity and large dielectric anisotropy, their applications in microwave communication are hampered by their broad near-crystalline phase temperature ranges. To address this limitation, this study designed and synthesized six fluorinated biphenylacetylene liquid crystal compounds with various benzene ring side-methyl substitutions (n = 3-5). The molecular structures, liquid crystal phases, and microwave dielectric properties were evaluated. Our findings indicate that compounds with methyl substitution at the Y2 position exhibited reduced melting points, an expanded nematic phase temperature range (ΔT n ≈ 92.3 °C), and an absence of near-crystalline phases. These compounds still maintain high microwave dielectric constants within the 9-30 GHz frequency band (Δε r = 0.9-1.3) and reduced maximum permittivity losses compared to their non-methyl-substituted counterparts, thereby improving the efficiency in the microwave frequency band. In contrast, the Y1 position substitution results in a significantly narrower nematic phase temperature range (approximately 2.6 °C on average) and a substantial decrease in the dielectric constant, with a Δε r reduction of about 0.3 compared to the Y2 substitution. This work shows that the side-methyl substitution can improve the performance of triphenylacetylene-based liquid crystals in microwave communication, providing valuable insight to aid the discovery of novel microwave liquid crystals.

Dipole Moment of a Superatom.

Homodyne detection is used to measure the (collective) atomic dipole moment for an atomic ensemble that is prepared in a superposition of spatially phased Dicke states having at most two excitations (a so-called "superatom"). Homodyne detection allows one to isolate the contributions to the radiated intensity that depend linearly on the average value of the collective atomic dipole moment operator. Depending on whether the atom-reference field interference is constructive or destructive, either super-Poisson or sub-Poisson statistics for the combined field is observed.

Photoswitching Characteristics, Photochromism and Mechanochromism of Extended π‐Conjugated Azopyrazole and Azoisoxazole Derivatives

Herein, we report extended π‐conjugated arylazopyrazoles and arylazoisoxazoles towards tuning and modulation of their intrinsic properties. In this regard, we systematically introduced phenyl, styryl, (triphenylvinyl)styryl, phenylethynyl groups at ortho, meta, and para positions relative to the azo unit to extend the π‐conjugation and vary the electronic coupling. In addition, the heterocyclic substituents were also modified. Overall, 20 photoswitches with modular substituents have been synthesized and studied for the photoswitching ability and thermal relaxations of Z isomers in the solution phase and solid state. Besides deciphering the importance of extending conjugation in photoswitching characteristics, intriguing properties such as mechanochromism and reversible bidirectional photochromism in the solid state were also unravelled. Through systematic studies, we envisage the effect of electronic coupling due to π‐conjugation and its impact on longer wavelength light‐induced photoswitching that holds several application potentials.

Phase-transition-driven polarization and intensity modulation in GST metasurfaces

Metasurfaces, especially those employing phase-change materials (PCMs) like Ge2Sb2Te5 (GST), have revolutionized subwavelength light manipulation, promising enhanced reconfigurability in nanophotonic devices. Despite their potential, the limited tunability in terms of states and dimensions has hindered broader applications. Here, we propose a GST-based reconfigurable metasurface capable of simultaneously modulating transmissivity, phase, and polarization. Leveraging the full states of phase transitions from amorphous to crystalline states, the metasurface can elaborately adjust the focal spot's intensity based on amplitude and phase joint regulation. Our design exploits the refractive index shifts during phase transition and phase modulation discrepancies between the two axes of composite nanorods, allowing for dynamic transitions across three polarization states, with each state's transmittance decreasing sequentially. Furthermore, we demonstrate the metasurface's ability to transition from multichannel vectorial holography to near-perfect absorption by eliminating the limitations imposed by intermediate phase states. These advancements represent a new way to multi-dimensional, multi-state tunable photonic systems, broadening the scope for novel optical devices.

LncRNAs maintain the functional phase state of nucleolar prion-like protein to facilitate rRNA processing.

Liquid-to-solid phase transition of proteins with prion-like domains (PLDs) has been associated with neurodegenerative diseases and aging. High protein concentration is one important aspect triggering the transition; however, several prion-like proteins, including fibrillarin (FBL), an important phase-separated protein in the nucleolus for pre-rRNA processing, show relatively high expression levels in certain cells, especially cancer cells, without obvious phase transitions and growth arrest. How cells maintain prion-like protein proteostasis is still unknown. Here, we attempt to answer the question, with FBL as an example. We find that lncRNA DNAJC3-AS1 can buffer the behavior of FBL condensation and maintain the state and function of fibrillar component/dense fibrillar component (FC/DFC) units in human cell lines through two mechanisms, not only facilitating FBL condensation but also inhibiting excessive aggregation by binding multiple PLDs and partially blocking their interactions. We propose that lncRNAs could supply buffered systems to sustain functional phase states of prion-like proteins.

Application of neural networks for determining the parameters of PVT-models used in solving hydrodynamic modeling problems

The article presents an overview of the application of machine learning models for problems of modeling the phase state of hydrocarbon systems. Determination of the state of a hydrocarbon system is possible in the presence of nonhydrocarbon components when performing hydrodynamic calculations on multiphase models. Such calculations are in demand when solving problems of both forecasting and adapting models to actual development data. It is shown that when adjusting models to actual data, the accuracy of reproducing laboratory experiments is in some cases higher than when using equations of state. But in some cases, the use of neural networks turns out to be useless. For relatively “simple” fluid systems, an increase in the complexity of the tool used does not provide an increase in accuracy compared to simple regression models. Another problem is the lack of a working tool that would completely replace the use of equations of state to assess the state of a fluid model when performing hydrodynamic calculations.

Magneto‐Optical Control of Ordering Kinetics and Vacancy Behavior in Fe–Al Thin Films Quenched by Laser

One of the issues arising in materials science is the behavior of nonequilibrium point defects in the atomic lattice, which defines the rates of chemical reactions and relaxation processes as well as affects the physical properties of solids. It is previously theoretically predicted that melting and rapid solidification of metals and alloys provide a vacancy concentration in the quenched material, which can be comparable to that quantity at the point of melting. Here, the vacancy behavior is studied experimentally in thin films of the near equiatomic Fe–Al alloy subjected to nanosecond laser annealing with intensities up to film ablation. The effects of laser irradiation are studied by monitoring magneto‐optically the ordering kinetics in the alloy at the very ablation edge, within a narrow (micron‐scale) ring‐shaped region around the ablation zone. Quantitatively, the vacancy supersaturation in the quenched alloy has been estimated by fitting a simulated temporal evolution of the long‐range chemical order to the obtained experimental data. Laser quenching (LQ) of alloys and single‐element materials will be a tool for obtaining novel phase states within a small volume of the crystal.

The sliding mode controller with composite reaching law for upper limb rehabilitation robot

Purpose Assisted training using upper limb rehabilitation robots is beneficial for flaccid paralysis patients in recovering their functional abilities. In the assisted training mode, the patient’s motor ability is limited by factors such as limb muscle tension, and it is prone for the rehabilitation robot to deviate from the prescribed training trajectory. A sliding mode control method based on a fixed time observer is proposed to address the problem of delayed trajectory tracking response of upper limb rehabilitation robots caused by external disturbances such as patient limbs. Design/methodology/approach First, aiming at the problem of estimating and compensating for external disturbances in the upper limb rehabilitation robot system, a fixed time observer was designed based on the robot’s dynamic model. Second, the composite sliding mode reaching law combining the smooth function and the power-exponential function is proposed to shorten the convergence time of system states in the startup phase, thereby reducing chattering in the control process and realizing the real-time tracking of the training trajectory by the control system. Findings The proposed method provides a solution for the trajectory tracking speed of upper limb rehabilitation robot controllers. In the circular trajectory tracking control, compared to the sliding-mode control method combined with the variable-exponential composite reaching law based on the fixed-time observer, the method in this paper reduces the time for the system state to reach the sliding surface by 0.89 s and improves the response speed by 0.66%. Originality/value The composite sliding mode approach law based on smooth function and power exponent function can reduce the time it takes for the system state to reach and remain on the sliding surface and improve the trajectory tracking speed of upper limb rehabilitation robots. This controller improves the accuracy of trajectory control and ensures the robustness of auxiliary rehabilitation training.