Voting is an important social activity for expressing public opinions. By conceptually considering a group of voting agents to be intelligent matter, the impact of real-time information on voting results is quantitatively studied by an intelligent Ising model, which is formed by adding nonlinear instantaneous feedback of the overall magnetization to the conventional Ising model. In the new model, the interaction strength becomes a variable depending on the total magnetization rather than a constant, which mimics the scenario that the decision of an individual during vote influenced by the dynamically changing polling result during the election process. Our analytical derivations along with Monte Carlo simulations reveal that, with a positive feedback, the intelligent Ising model exhibits phase transitions at any finite temperatures, a feature lacked in the conventional one-dimensional Ising model. In all dimensions, by varying the feedback strength, the system changes from going through a second-order phase transition to going through a first-order phase transition with increasing temperature, and the two types of phase transitions are connected by a tricritical point. This study on the one hand demonstrates that the intelligent matter with a nonlinear adaptive interaction can exhibit qualitatively different phase behaviors from conventional matter, and on the other hand shows that, during voting, even unbiased feedback may possibly induce spontaneous symmetry breaking, leading to a biased outcome where one side of the vote becomes favored.

In 1966, Hohenberg, Mermin and Wagner proved that long-wavelength fluctuations destabilize the long-range order of continuous symmetry in two-dimensional (2D) systems. Later in the 1970s, Berezinskii, Kosterlitz and Thouless developed the BKT theory describing an unconventional phase transition between quasi-long-range and short-range order in 2D systems driven by the binding-unbinding of topological defects, which has become a fundamental topic in statistical mechanics, condensed matter physics, and soft matter physics. One of the most important applications of the BKT theory is the melting of 2D crystals, whose mechanisms are not yet fully understood. Recently, this topic has been extended to the area of active matter, where the non-equilibrium nature leads to novel phenomena that deviate from the Hohenberg-Mermin-Wagner theorem. In this review, we first focus on the recent theoretical and computational progress in the 2D melting problem in passive systems, and then summarize the inspiring results obtained from non-equilibrium systems. The review closes with comments on several promising directions for predicting 2D melting scenarios and for understanding the non-equilibrium nature in 2D active matter systems.

Abstract Tire wear particles (TWPs) are prevalent microplastic particles in the atmosphere and pose significant environmental and health risks to humans. Here, we investigated the ice nucleation activity (INA) of TWPs under mixed‐phase cloud conditions (∼−20.0°C < T < −5.0°C) and its changes caused by different environmental exposures, including UV and high temperatures (75.0°C). Ice‐active sites per mass of TWPs are about one to two orders of magnitude higher than those of other microplastics. Environmental exposure moderately reduces TWPs' INA, attributed to modifications in surface ice‐nucleation sites, such as decreases in SiO2 signals. As the most abundant microplastics in the atmosphere, TWPs significantly contribute to global ice‐nucleating particles (INPs), particularly in North America, Southeast Asia, and Europe. Given that TWP emissions are expected to increase with the predicted rise in vehicle numbers, addressing TWPs' impacts on cloud microphysical properties becomes increasingly imperative.

We present the results of a computational investigation based on molecular dynamics (MD) and density functional theory (DFT) aimed at testing the performance of different classical Force Fields (FFs) to accurately model the microscopic structure of the ionic liquids butylmethylimidazolium tetrafluoroborate and chloride and predict their NMR properties. The FFs used are a full-charge FF, a scaled-charge FF, a polarizable FF, and a recently presented virtual-site FF (Doherty, B.; Zhong, X.; Acevedo, O. J. Phys. Chem. B 2018, 122, 2962-2974). We use the NMR parameters (namely 1H chemical shifts of the [C4C1im] cation) computed by DFT methods over a MD trajectory as a probe to judge the performance of the various FFs. While the agreement between experimental and calculated NMR resonances is almost quantitative for the tetrafluoroborate salt, using all four types of FFs, for the chloride salt we observe a very different performance: The full-charge and scaled-charge FFs exhibit a rather significant disagreement, while an improvement is obtained with the polarizable FF and a rather good agreement is achieved by the virtual-site FF. The high sensitivity of NMR parameters to geometrical factors allows us to pinpoint specific deficiencies of different FFs in correctly representing the hydrogen-bond between the positively charged imidazolium ring protons and the chloride anion. In turn, such analysis enables us to propose future directions for improving the performance of classical FFs for ionic liquids.

Solid-solid phase transitions are ubiquitous in nature, but the kinetic pathway of anisotropic particle systems remains elusive, where the coupling between translational and rotational motions plays a critical role in various kinetic processes. Here this problem is investigated by molecular dynamics simulation for 2D ball-stick polygon systems, where pentagon, hexagon, and octagon systems all undergo an isostructural solid-solid phase transition. During heating, the translational motion exhibits merely a homogeneous expansion, whereas the time evolution of body-orientation is shape-determined. The local defects of body-orientation self-organize into a vague stripe for pentagon, a random pattern for hexagon, while a distinct stripe for octagon. The underlying kinetic pathway of octagon adheres to the quasi-equilibrium assumption, whereas those of hexagon and pentagon are predominantly governed by translational motion and rotational motion, respectively. This diversity is originated from different kinetic coupling modes determined by the anisotropy of molecules, and can affect the phase transition rates. The reverse process in terms of cooling follows the same mechanism, with more diverse kinetic pathways attributed to the possible kinetic traps. These findings promote theoretical understanding of microscopic kinetics of solid-solid phase transitions as well as provide direct guidance for the rational design of materials utilizing desired kinetic features.

Mutations in the pY-binding pocket of the Fyn SH2 domain increase domain rigidity but differentially affect interactions of both the pY-binding pocket and the specificity pocket with the pY-peptide.

While most thermostats in molecular dynamics are designed for equilibrium systems, their extension to non-equilibrium simulations has little theoretical justification. In the literature, an artifact referred to as “lane formation” was discovered; however, its cause remained unclear and was simply attributed to a constraint on velocity fluctuations or non-ergodicity in thermostats. In addition, global deterministic thermostatted dynamics was found to exhibit unceasing phase-space compression in steady states, incompatible with their expected stationary distributions and Gibbs entropy, which was mistakenly perceived as inescapable. In this work, we pinpoint that the dynamical cause of artificial lane formation is a stable fixed point in the momentum space induced by improper velocity rescaling, which produces effective repulsion between different species in a color flow, drains transverse kinetic energy and generates the unceasing compression. This artifact is deeply rooted in global deterministic thermostats, such as the Nosé–Hoover dynamics and configurational thermostat. With proper rescaling, the Langevin thermostat completely eliminates artificial lane formation and exemplifies how incompressible phase space and stationary distributions can be retained for non-equilibrium steady states.

Flocking and vortical are two typical motion modes in active matter. Although it is known that the two modes can spontaneously switch between each other in a finite-size system, the switching dynamics remain elusive. In this work, by computer simulation of a two-dimensional Vicsek-like system with 1000 particles, we find from the perspective of the classical nucleation theory that the forward and backward switching dynamics are asymmetric: going from flocking to vortical is a one-step nucleation process, while the opposite is a two-step nucleation process, with the system staying in a metastable state before reaching the final flocking state.

Magnetic gels with embedded micro-/nano-sized magnetic particles in cross-linked polymer networks can be actuated by external magnetic fields, with changes in their internal microscopic structures and macroscopic mechanical properties. We investigate the responses of such magnetic gels to an external magnetic field, by means of coarse-grained molecular dynamics simulations. We find that the dynamics of magnetic particles are determined by the interplay of magnetic dipole–dipole interactions, polymer elasticity, and thermal fluctuations. The corresponding microscopic structures formed by the magnetic particles, such as elongated chains, can be controlled by the external magnetic field. Furthermore, the magnetic gels can exhibit reinforced macroscopic mechanical properties, where the elastic modulus increases algebraically with the magnetic moments of the particles in the form of ∝(m−mc)2 when magnetic chains are formed. This simulation work can not only serve as a tool for studying the microscopic and the macroscopic responses of the magnetic gels, but also facilitate future fabrications and practical controls of magnetic composites with desired physical properties.

Phase behaviours of two-dimensional (2D) systems constitute a fundamental topic in condensed matter and statistical physics. Although hard polygons and interactive point-like particles are well studied, the phase behaviours of more realistic molecular systems considering intermolecular interaction and molecular shape remain elusive. Here we investigate by molecular dynamics simulation phase stabilities of 2D ball-stick polygons, serving as simplified models for molecular systems. Below the melting temperature Tm, we identify a critical edge number n c = 4 , at which a distorted square lattice emerges; when n < n c , the triangular system stabilizes at a spin-ice-like glassy state; when n > n c , the polygons stabilize at crystalline states. Moreover, in the crystalline state, Tm is higher for polygons with more edges at higher pressures but exhibits a crossover for hexagon and octagon at low pressures. A theoretical framework taking into account the competition between entropy and enthalpy is proposed to provide a comprehensive understanding of our results, which is anticipated to facilitate the design of 2D materials.

Cilia can beat collectively in the form of a metachronal wave, and we investigate how near-field hydrodynamic interactions between cilia can influence the collective response of the beating cilia. Based on the theoretical framework developed in the work of Meng et al . (Meng et al . 2021 Proc. Natl Acad. Sci. USA 118 , e2102828118), we find that the first harmonic mode in the driving force acting on each individual cilium can determine the direction of the metachronal wave after considering the finite size of the beating trajectories, which is confirmed by our agent-based numerical simulations. The stable wave patterns, e.g. the travelling direction, can be controlled by the driving forces acting on the cilia, based on which one can change the flow field generated by the cilia. This work can not only help to understand the role of the hydrodynamic interactions in the collective behaviours of cilia, but can also guide future designs of artificial cilia beating in the desired dynamic mode.

Aim: The objective was to elucidate the correlation between CMVP and immunosuppressive therapy in IBD patients, we hope this review could expand on the significance of CMV as an opportunistic pathogen and the potential impact on morbidity and mortality in IBD patients. Methods: Records and clinical trajectories linked to CMVP in IBD patients were extracted from the PubMed database, irrespective of language barriers. The reference lists incorporated in these studies were manually inspected. Conclusions were generated using straightforward descriptive analysis.Results: In total, 18 IBD patients, including Crohn's disease (CD, 67%) and Ulcerative Colitis (UC, 33%), affected by CMVP were identified from 17 published articles. A minority of these patients (17%) exhibited active disease, whereas the majority (83%) presented with quiescent disease. Fever (100%) and dyspnea (44%) emerged as the most prevalent clinical symptoms. All the patients had undergone immunosuppressive therapy. A significant proportion, up to 89%, had received thiopurine treatment prior to the CMVP diagnosis. Interestingly, none of the patients were subjected to biological therapy. Half of the patients manifested with Hemophagocytic Lymphohistiocytosis (HLH). Almost all patients (94%) were administered antiviral treatment and a substantial 83% experienced full recovery. Immunosuppressive agents were either tapered or discontinued altogether. A subset of patients, 17%, suffered fatal outcomes.Conclusion: Our findings underscore the need for heightened suspicion of CMVP in IBD patients who exhibit symptoms such as fever and dyspnea. During the COVID-19 pandemic, CMVP should be considered a potential differential diagnosis. It was observed that CMVP primarily transpires during CD remission. Azathioprine emerged as the predominant immunosuppressant linked to CMV reactivation. The prompt application of effective antiviral therapy can substantially enhance patient outcomes. CMV vaccine might serve as a viable prevention strategy.

The COVID-19 pandemic has changed the world and has presented the scientific community with unprecedented challenges. Infection is associated with overproduction of proinflammatory cytokines secondary to hyperactivation of the innate immune response, inducing a cytokine storm and triggering multiorgan failure and significant morbidity/mortality. No specific treatment is yet available. For thousands of years, Panax notoginseng has been used to treat various infectious diseases. Experimental evidence of P. notoginseng utility in terms of alleviating the cytokine storm, especially the cascade, and improving post-COVID-19 symptoms, suggests that P. notoginseng may serve as a valuable adjunct treatment for COVID-19 infection.

We perform molecular dynamics simulations to investigate the transition processes of [C22/C1MIm]+[NO3]- binary mixtures by varying the cation ratio of C22 to C1 at a fixed temperature of 400 K. The cation ratio is tuned by ranging C22 percentage from 0% to 100% with a fixed number of 4096 total simulated ion pairs. Our simulated-annealing results indicate that, at 400 K, pure C1 is a homogeneous liquid whilst pure C22 is an ionic liquid crystal (ILC) of smectic-B (SmB) type. With increasing C22 percentage, the system goes through a first-order phase transition from homogeneous liquid to nano-fragment liquid in the range from 15% to 17.5%, during which some of the individual cationic alkyl side chains locally aggregate to form small bundles "floating" in the polar "solvent" composed of anions and cationic head groups. Although the side chains in each bundle are parallelly aligned, the bundles distribute randomly without a global orientation. As the C22 percentage further increases, another first-order phase transition occurs to bring the system into the SmB ILC phase. Particularly, when the C22 percentage is in the range from 45% to 50%, the SmB phase coexists with the liquid phase containing both individual and bundled alkyl side chains.

Water transport through membranes is an attractive topic among the research dedicated to dehydration processes, microenvironment regulation, or more simply, recovery of freshwater. Herein, an atomistic computer simulation is proposed to provide new insights about a water vapor transport mechanism through PEBAX membranes filled with ionic liquid (IL) [C12C1im]Cl. Starting from experimental evidence that indicates an effective increase in water permeation as the IL is added to the polymer matrix (e.g., up to 85·10−3 (g·m)/(m2·day) at 318.15 K for PEBAX@2533 membranes loaded with 70% of IL), molecular dynamics simulations are proposed to explore the key role of IL in water transport inside membranes. The polar region composed of anions and cationic head groups of the IL is demonstrated to serve as the pathway for water transport through the membrane. Water molecules always stay near the pathway, which becomes wider and thus has a larger water-accessible area with increasing IL concentration. Hence, the diffusion coefficients of water molecules and ions increase as the IL concentration increases. The simulation provides useful indications about a microscopic mechanism that regulates the transport of water vapor through a kind of PEBAX/IL membrane, resulting in full agreement with the experimental evidence.

Carotenoids are photoprotectant pigments and precursors of hormones such as strigolactones (SL). Carotenoids are produced in plastids from geranylgeranyl diphosphate (GGPP), which is diverted to the carotenoid pathway by phytoene synthase (PSY). In tomato (Solanum lycopersicum), three genes encode plastid-targeted GGPP synthases (SlG1 to SlG3) and three genes encode PSY isoforms (PSY1 to PSY3). Here, we investigated the function of SlG1 by generating loss-of-function lines and combining their metabolic and physiological phenotyping with gene co-expression and co-immunoprecipitation analyses. Leaves and fruits of slg1 lines showed a wild-type phenotype in terms of carotenoid accumulation, photosynthesis, and development under normal growth conditions. In response to bacterial infection, however, slg1 leaves produced lower levels of defensive GGPP-derived diterpenoids. In roots, SlG1 was co-expressed with PSY3 and other genes involved in SL production, and slg1 lines grown under phosphate starvation exuded less SLs. However, slg1 plants did not display the branched shoot phenotype observed in other SL-defective mutants. At the protein level, SlG1 physically interacted with the root-specific PSY3 isoform but not with PSY1 and PSY2. Our results confirm specific roles for SlG1 in producing GGPP for defensive diterpenoids in leaves and carotenoid-derived SLs (in combination with PSY3) in roots.

When a molar excess of benzene is mixed with an ionic liquid (IL), liquid-liquid phase separation may appear with a pure liquid phase almost composed of only benzene molecules separated from a liquid clathrate phase with benzene molecules dissolved in the IL. Our previous study (J. Phys. Chem. B, 124, 7929, 2020) on long-chain IL/benzene systems has concluded that benzene molecules, as planar nonpolar ones, majorly dissolve in the IL nonpolar domains consisting of cationic alkyl side chains. Nevertheless, the above mechanism is inadequate for explaining the experimental observations that benzene can also dissolve in IL systems with very short alkyl side chains. In this study, by molecular dynamics simulation of the [EMIm+][X-]/benzene mixtures with X- being Cl-, NO3-, PF6-, or Tf2N-, we still observe liquid-liquid phase separation of the pure benzene phase from a liquid clathrate (mixed IL/benzene) phase where benzene molecules are almost equally distributed near imidazolium rings through π-stacking or near alkyl side chains. The anion species strongly influences the solubility of benzene and the ratio of the two liquid phases via the alteration of anionic charge density, which tunes the strength of the electrostatic interaction among ions and thus the probability of benzene molecules interacting with both imidazolium rings and alkyl side chains: a larger anionic charge density corresponds to a lower solubility of benzene.

Correction for 'The structuring effect of the alkyl domains on the polar network of ionic liquid mixtures: a molecular dynamics study' by Valerio Mazzilli et al., Phys. Chem. Chem. Phys., 2022, 24, 18783-18792, https://doi.org/10.1039/D2CP02786K.

Stroke is the world's second major cause of adult death and disability, resulting in the destruction of brain tissue and long-term neurological impairment; induction of neuronal plasticity can promote recovery after stroke. C-C chemokine receptor 5 (CCR5) can direct leukocyte migration and localization and is a co-receptor that can mediate human immunodeficiency virus (HIV) entry into cells. Its role in HIV infection and immune response has been extensively studied. Furthermore, CCR5 is widely expressed in the central nervous system (CNS), is engaged in various physiological activities such as brain development, neuronal differentiation, communication, survival, and learning and memory capabilities, and is also involved in the development of numerous neurological diseases. CCR5 is differentially upregulated in neurons after stroke, and the inhibition of CCR5 in specific regions of the brain promotes motor and cognitive recovery. The mechanism by which CCR5 acts as a therapeutic target to promote neurorehabilitation after stroke has rarely been systematically reported yet. Thus, this review aims to discuss the function of CCR5 in the CNS and the mechanism of its effect on post-stroke recovery by regulating neuroplasticity and the inflammatory response to provide an effective basis for clinical rehabilitation after stroke.

Gels are soft elastic materials made of a three-dimensional cross-linked polymer network and featuring both elastic and dissipative responses under external mechanical stimuli. Here we investigate how such gels mediate the organization of embedded magnetic microparticles when driven by an external field. By constructing a continuum theory, we demonstrate that the collective dynamics of the embedded particles result from the delicate balance between magnetic dipole-dipole interactions, thermal fluctuations and elasticity of the polymer network, verified by our experiments. The proposed model could be extended to other soft magnetic composites in order to predict how the elastic interactions mediate the aggregation of the embedded elements, fostering technological implications for multifunctional hydrogel materials.