Critical Behavior Research Articles

Playtime for Cephalopods: Understanding the Significance of Play Behavior in Octopus bimaculoides.

Play is considered to be an essential part of development that supports learning, memory, and the development of flexible behavioral strategies. An increasing amount of non-mammalian species have been discovered to engage in play behavior, but there has been little research into play behavior in cephalopods specifically. Here we studied play behavior of wild-caught, laboratory-housed California Two-Spot Octopuses, Octopus bimaculoides. The behavior observed in these animals is consistent with established criteria of play behavior in animals. The evidence of play in O. bimaculoides provides further insight into the evolutionary development of play behavior as a whole, the characteristics of play in an under-studied species, and also has the potential to be used as a factor in determining the welfare state of octopuses to improve their management in captivity.

Multiscale fatigue life prediction model for CFRP laminates considering the mechanical degradation of its constituents and the local stress concentration of the matrix

In the present research, a novel approach for predicting the fatigue life of composites is proposed using a multiscale fatigue model. This model considers two critical physical phenomena that occur in CFRP laminates under tension-tension cyclic loading – the degradation of the physical properties of CFRP constituents and the localized stress concentrations within the matrix. To achieve this, Mori-Tanaka’s mean field theory, a well-known micromechanics model, is employed to consider the deterioration of material properties in various phases, which is dependent on the applied stress level. Localized stress concentration phenomena within the matrix of a composite material are common when CFRP laminate is subjected to cyclic loading. The localized stress concentration on a matrix with different numbers of fibers and orientations using representative volume elements (RVE) is investigated. Two other scales of failure criteria are defined to evaluate its constituent at the material level and ply level at the macroscale. A comparison with fatigue experiment data of AS4/3501-6 composite shows good reliability of the proposed multiscale fatigue model.

Thermodynamics, phase transition and Joule–Thomson expansion of 4-D Gauss–Bonnet AdS black hole

In this paper, we explore the thermodynamic and phase transition properties of asymptotically AdS black holes within Einstein–Gauss–Bonnet gravity, focusing on Joule–Thomson expansion. Thermodynamics is studied in the extended phase space, where the cosmological constant serves as thermodynamic pressure. We observe that the black hole undergoes a phase transition similar to that of a van der Waals system. We analyze charged and neutral cases separately to distinguish the effect of charge and Gauss–Bonnet parameter on critical behavior and examine the phase structure. We find that the Gauss–Bonnet coupling parameter behaves similarly to black hole charge or spin, guiding the phase structure. To understand the underlying phase structure determined by the Gauss–Bonnet coefficient [Formula: see text], we introduce a new order parameter. We discover that the change in the conjugate variable to the Gauss–Bonnet parameter acts as an order parameter, demonstrating a critical exponent of [Formula: see text] in the vicinity of the critical point. Since the phase structure is analogous to that of a van der Waals fluid, we investigate the Joule–Thomson expansion of the black hole. We analytically study the Joule–Thomson expansion, focusing on three key characteristics: the Joule–Thomson coefficient, inversion curves and isenthalpic curves. We obtain isenthalpic curves in the T–P plane and illustrate the cooling–heating regions.

Disordered non-Fermi liquid fixed point for two-dimensional metals at Ising-nematic quantum critical points

Understanding the influence of quenched random potential is crucial for comprehending the exotic electronic transport of non-Fermi liquid metals near metallic quantum critical points. In this study, we identify a stable fixed point governing the quantum critical behavior of two-dimensional non-Fermi liquid metals in the presence of a random potential disorder. By performing renormalization group analysis on a dimensional-regularized field theory for Ising-nematic quantum critical points, we systematically investigate the interplay between random potential disorder for electrons and Yukawa-type interactions between electrons and bosonic order-parameter fluctuations in a perturbative epsilon expansion. At the one-loop order, the effective field theory lacks stable fixed points, instead exhibiting a runaway flow toward infinite disorder strength. However, at the two-loop order, the effective field theory converges to a stable fixed point characterized by finite disorder strength, termed the “disordered non-Fermi liquid (DNFL) fixed point”. Our investigation reveals that two-loop vertex corrections induced by Yukawa couplings are pivotal in the emergence of the DNFL fixed point, primarily through screening disorder scattering. Additionally, the DNFL fixed point is distinguished by a substantial anomalous scaling dimension of fermion fields, resulting in pseudogap-like behavior in the electron’s density of states. These findings shed light on the quantum critical behavior of disordered non-Fermi liquid metals, emphasizing the indispensable role of higher-order loop corrections in such comprehension.

Comparative Analysis of Water Hammer Performance in Different Pipe Parameters with FSI

Water hammer (WH) is a critical phenomenon in fluid-filled piping systems that can lead to severe pressure surges and structural damage. The characteristics of the pipe material, geometry, and support conditions play a crucial role in the fluid–structure interaction (FSI) during WH events. This study investigates the impact of various pipe parameters, including material, length, thickness, and diameter, on the WH behavior using an FSI-based numerical approach. A comprehensive computational model was developed based on the algorithm presented in Delft Hydraulics Benchmark Problem (A) to simulate the WH phenomenon in pipes made of different materials, such as steel, copper, ductile iron, PPR (polypropylene random copolymer), and GRP (glass-reinforced plastic). This study examines the influence of pipe parameters on WH performance in pipelines, utilizing FSI to analyze the phenomenon. The results show that the pipe material has a significant influence on the pressure wave speed, stress wave propagation, and the overall system response during WH. Pipes with lower modulus of elasticity, such as PPR and GRP, exhibit lower pressure wave speeds but higher stress wave speeds compared with steel pipes. Increasing the elastic modulus, pipe wall thickness, length, and diameter enhances the pipe’s stiffness and impacts the timing, magnitude of pressure surges, and the likelihood of cavitation. The findings of this study provide valuable insights into the design and mitigation of WH in piping systems.

Critical surface adsorption of confined binary liquids with locally conserved mass and composition

Close to a solid surface, the properties of a fluid deviate significantly from their bulk values. In this context, we study the surface adsorption profiles of a symmetric binary liquid confined to a slit pore by means of molecular dynamics simulations; the latter naturally entails that mass and concentration are locally conserved. Near a bulk consolute point, where the liquid exhibits a demixing transition with the local concentration as the order parameter, we determine the order parameter profiles and characterise the relevant critical scaling behaviour, in the regime of strong surface attraction, for a range of pore widths and temperatures. The obtained order parameter profiles decay monotonically near the surfaces, also in the presence of a pronounced layering in the number density. Overall, our results agree qualitatively with recent theoretical predictions from a mesoscopic field-theoretical approach for the canonical ensemble.

Fluorescein Isothiocyanate Labelled PCL‐PEG‐PCL Copolymer as Delivery System of Capsaicin

AbstractAmphiphilic block copolymers, made of biocompatible polycaprolactone (PCL) and polyethylene glycol (PEG), due to their ability to self‐assemble in water into nanoscopic micelles, have been largely exploited for drug delivery systems (DDS). This study introduces a novel approach by synthesizing a fluorescein isothiocyanate FITC‐labelled PCL‐PEG‐PCL triblock copolymer, with the aim to develop a drug delivery system for natural bioactive. As a proof of concept, the FITC‐labelled PCL‐PEG‐PCL copolymer is applied for the preparation of micelles encapsulating into the core capsaicin (CP), a pungent alkaloid found in chili peppers with diverse therapeutic applications. Challenges associated with CP′s solubility, bioavailability, and stability are addressed using this DDS. Comprehensive characterization of FITC‐labelled copolymer is conducted using a range of analytical techniques, including nuclear magnetic resonance (NMR), dynamic light scattering (DLS), high‐performance liquid chromatography (HPLC), Fourier‐transform infrared spectroscopy (FTIR), fluorescence, and confocal laser scanning microscopy (CLSM). Key properties such as critical micelle concentration, CP loading, and release behavior are thoroughly investigated and compared with the characteristics of the unlabeled parent copolymer. This research pioneers the investigation of PCL‐PEG‐PCL triblock copolymers for CP delivery, along with the use of FITC‐labelled variants, opening new avenues for research in drug delivery and nanomedicine.

Magnetism of pseudospin-1/2 pyrochlore antiferromagnet Na3Co(CO3)2Cl.

Pyrochlore magnets have attracted interest as systems for realizing critical phenomena, rich magnetic structures, associated topological band structures, and nontrivial quantum phases. Na3Co(CO3)2Cl is a pseudospin-1/2 antiferromagnet in which the Co2+ions form a pyrochlore network. Its structural and magnetic properties were investigated using magnetization, heat capacity, ESR, single-crystal X-ray diffraction, powder neutron diffraction and powder inelastic neutron scattering. Magnetization and heat capacity measurements indicated a ground-state doublet, which is regarded as pseudospin 1/2, dominated the magnetic properties at low temperatures, with a magnetic exchange of 9.6 K. As the temperature decreases, a magnetic transition is observed at 1.6 K, which is confirmed to be an all-in-all-out magnetic order. The crystal field excitations observed by inelastic neutron scattering experiments indicated the Ising nature of the ground-state doublet. This thorough study revealed that Na3Co(CO3)2Cl can be regarded as a pseudospin-1/2 pyrochlore lattice antiferromagnet with dominant Ising-type interactions.

Critical behavior of lattice gauge theory Rydberg simulators from effective Hamiltonians

Critical behavior of lattice gauge theory Rydberg simulators from effective Hamiltonians

Conformal field theory with composite defect

We explore higher-dimensional conformal field theories (CFTs) in the presence of a conformal defect that itself hosts another sub-dimensional defect. We refer to this new kind of conformal defect as the composite defect. We elaborate on the various conformal properties of the composite defect CFTs, including correlation functions, operator expansions, and conformal block expansions. As an example, we present a free O(N) vector model in the presence of a composite defect. Assuming the averaged null energy condition (ANEC) does hold even for the defect systems, we conclude that some boundary conditions can be excluded. Our investigations shed light on the rich phenomenology arising from hierarchical defect structures, paving the way for a deeper understanding of critical phenomena in nature.

Nonuniversal critical dynamics on planar random lattices with heterogeneous degree distributions

The weighted planar stochastic (WPS) lattice introduces a topological disorder that emerges from a multifractal structure. Its dual network has a power-law degree distribution and is embedded in a two-dimensional space, forming a planar network. We modify the original recipe to construct WPS networks with degree distributions interpolating smoothly between the original power-law tail, P(q)∼q−α with exponent α≈5.6, and a square lattice. We analyze the role of the disorder in the modified WPS model, considering the critical behavior of the contact process (CP). We report a critical scaling depending on the network degree distribution. The scaling exponents differ from the standard mean-field behavior reported for CP on infinite-dimensional (random) graphs with power-law degree distribution. Furthermore, the disorder present in the WPS lattice model is in agreement with the Luck-Harris criterion for the relevance of disorder in critical dynamics. However, despite the same wandering exponent ω=1/2, the disorder effects observed for the WPS lattice are weaker than those found for uncorrelated disorder.

Nucleate pool boiling bubble dynamics for R32 and R1234yf on machined micro-structured surfaces

Efficient electronics cooling has always been a perpetual challenge, with the limits of single-phase cooling almost being reached. Two-phase cooling in the form of pool boiling is an attractive next step, with much research being devoted to it. While refrigerants operating at lower saturation temperatures are key to achieving effective cooling, surface modifications have been shown to also affect bubble dynamics and enhance nucleate pool boiling heat transfer. A simple, easy to implement fabrication method was sought, with the goal of expanding the knowledge of bubble dynamics. To this end, single bubble growth on structured surfaces that are achievable on a lathe, with an average roughness of 75 μm and differing indentation angles between 90° and 46°, was studied numerically using an OpenFOAM multiphase library. Conjugate heat transfer was applied, with heat fluxes ranging between 7.6 and 28 kW/m2 for pure refrigerants R32 and R1234yf. By comparing the bubble equivalent diameter with that of a smooth surface at a fixed heat flux, it was found that the bubble growth rates of structured surfaces were largely independent of indentation angles less than 90°, but lower than for smooth surfaces. For structured surfaces, a critical indentation angle of approximately 60° was identified which affected the bubble dynamics. For angles greater than the critical angle the bubble growth time was up to 150 % longer, which also resulted in larger departure diameters. However, the opposite trend was observed as the indentation angle was decreased below the critical angle. From a force analysis, it was found that the physical limitation imposed on the bubble growth was responsible for the critical indentation angle behaviour, with the most acute angle of 46° showing the shortest departure time. Furthermore, the bubble growth from a single cavity corresponded better with the trends of a smooth surface than a structured surface with comparable indentation angles. On a structured surface, once the bubble reached the edge of the cavity, its base diameter was limited by the physical characteristics of the surface. For the single cavity surface, however, bubble growth was uninhibited beyond the cavity, mimicking a completely smooth surface. The marked difference between results of a fully structured surface and the single cavity implies that future research will have to take the structural limitations on bubble growth imposed by a roughened surface into account.

High-Performance Proton Field-Effect Transistor Based on Two-Dimensional Cd Vacancy-Resided Cd0.85PS3Li0.15H0.15.

Ion transport is a critical phenomenon underpinning numerous biological, physical, and chemical systems. Proton transistors leveraging proton transport face significant limitations, such as a low on-off ratio and deficient carrier mobility, which restrict their applicability in biological and other scenarios. This study explores the use of two-dimensional (2D) vacancy-residing transition metal phosphorus trichallcogenide-based membranes as the active layer for proton field-effect transistors. The synthesized Cd0.85PS3Li0.15H0.15 membrane exhibits a well-organized layered structure and high hydrophilicity, with nanometer-sized interlayers containing interconnected water networks. These distinct features facilitate proton conduction, leading to a high proton conductivity value of 0.83 S cm-1 at 98% relative humidity and 90 °C, with an activation energy of 0.26 eV. The Cd0.85PS3Li0.15H0.15-based proton transistor demonstrates tunability via gate voltage, thereby enabling effective modulation of proton flow across source and drain electrodes. The transistor notably showcases superior switching characteristics, with an on/off ratio surpassing 5.51 and a carrier mobility of 8.84 × 10-2 cm2 V-1 s-1. The underlying mechanism for this performance enhancement is attributed to electric-field-induced switching in Cd vacancies. This research boosts the development of highly versatile ionotropic devices by introducing advanced 2D ion-conductive membranes.

The precursor of the critical transitions in majority vote model with the noise feedback from the vote layer

In this paper, we investigate phase transitions in the majority-vote model coupled with noise layers of different structures. We examine the square lattice and random-regular networks, as well as their combinations, for both vote layers and noise layers. Our findings reveal the presence of independent third-order transitions in all cases and dependent third-order transitions when critical transitions occur. This suggests that dependent third-order transitions may serve as precursors to critical transitions in non-equilibrium systems. Furthermore, we observe that when the structure of vote layers is decentralized, the coupling between the vote layer and the noise layer leads to the absence of critical phenomena.

Non-linear dynamics and critical phenomena in the holographic landscape of Weyl semimetals

This study presents a detailed analysis of critical phenomena in a holographic Weyl semi-metal (WSM) using the D3/D7 brane configuration. The research explores the non-linear response of the longitudinal current J when subjected to an external electric field E at both zero and finite temperatures. At zero temperature, the study identifies a potential quantum phase transition in the J-E relationship, driven by background parameters the particle mass, and axial gauge potential. This transition is characterized by a unique reconnection phenomenon resulting from the interplay between WSM-like and conventional nonlinear conducting behaviors, indicating a quantum phase transition.Additionally, at non-zero temperatures with dissipation, the system demonstrates first- and second-order phase transitions as the electric field and axial gauge potential are varied. The longitudinal conductivity is used as an order parameter to identify the current-driven phase transition. Numerical analysis reveals critical exponents in this non-equilibrium phase transition that show similarities to mean-field values observed in metallic systems.

Effects of Contamination with Selected Polymers on the Mechanical Properties of Post-Industrial Recycled Polypropylene.

The effect of contamination of polypropylene (PP) with selected polymers is studied to simulate the effect of mis-sorting in recycling streams. Polystyrene (PS), polyethylene terephthalate (PET), polycarbonate (PC), acrylonitrile butadiene styrene (ABS), and polylactic acid (PLA) were compounded with PP at different concentrations varying between 3 and 10%. Infrared spectroscopy proved the absence of chemical bonds between the constituents. Generally, melt flowability, except for the PP/PLA blend, and crystallinity were only slightly affected by the incorporation of the contaminating polymers. Samples of the polymer blends were injection moulded and further tested for their tensile and impact properties. Critical behaviour was induced by the introduction of a weld line as a result of the application of multiple gating points during injection moulding. Results generally show the applicability of PP mixtures within the investigated range of contamination, without much sacrifice in mechanical performance. However, in the case of ABS and PLA, more care should be taken when designing complex parts with weld lines, due to reduced toughness.

Multi-scale experimental study on properties of compressed air foam and pressure drop in the long-distance vertical pipe

Compressed air foam has been gradually applied in super high-rise buildings due to its high extinguishing efficiency and great transportation ability. However, the transport characteristics of compressed air foam are unclear because the foam is a complex gas-liquid two-phase fluid. In this study, multi-scale experiments were conducted to investigate the foam properties of compressed air foam and pressure drop in the long-distance vertical pipe. The results show that the foam is compressed as a whole when pressure increases, resulting in a significantly increased foam density. At higher pressures, the bubble coarsening degree decreases, accompanied by a narrower particle size distribution and an increased foam size homogenization. Moreover, a critical pressure phenomenon is observed in foams with different foam expansion ratios. The average foam diameter stabilizes gradually with pressure changes after exceeding the critical pressure. A theoretical model for foam density is developed, considering various pressures, temperatures and foam expansion ratios. When the compressed air foam is transported in the vertical long-distance pipe, the pressure decreases in a slightly downward curve, which is due to the decrease in foam density. Finally, a prediction model for the pressure drop of compressed air foam in the long-distance vertical pipe is proposed, which considers changes in foam density. The accuracy of the prediction model is verified by the multi-scale experimental results. The results deepen the understanding of foam flow in the long-distance vertical pipe and provide useful guidance for applications of compressed air foam in super high-rise buildings.

Near-room-temperature magnetic properties and magnetocaloric effect of polycrystalline and nano-scale manganites Pr(0.65-x)NdxSr0.35MnO3 (x ≤ 0.35)

Here we report investigations of structural, electrical and magnetic properties of bulk and nano-sized Pr0.65-xNdxSr0.35MnO3 compounds (x ≤ 0.35). Polycrystalline compounds were produced by solid – state reaction and nanocrystalline samples were obtained by sol–gel method. Analysis of x-ray diffraction patterns revealed a change in lattice structure from ‘Pbnm’ to ‘R3c’ symmetry, with diminishing cell volume upon increasing Nd ions substitution for all samples. Optical microscopy was used for bulk surface morphology and transmission electron microscopy was implemented for nano-sized samples. Iodometric titration showed oxygen deficiency for bulk compounds and oxygen excess for nano-sized particles. Measurements of resistivity of bulk samples revealed a single peak at temperatures associated with grain boundary conditions and with ferromagnetic/paramagnetic transition and negative magnetoresistivity. Critical magnetic behavior analysis disclosed that the polycrystalline samples are governed by a tricritical mean field and by 3D Heisenberg models while nanocrystalline samples are governed by a mean field model. Curie temperature Tc values remain in near room temperature range for all bulk compounds; they lower with increasing Nd ions substitution from 295 K for the parent bulk compound to 268 K for x = 0.35. Tc is lowered from 255 K for the parent nano-sized compound in small temperature intervals. All compounds exhibit second-order magnetic phase transitions and relatively high magnetic entropy change, with the highest value of 5.74 J/kgK for x = 0.25 bulk sample in μ˳∆H = 4 T. Strong magnetocaloric effect, stability and the possibility of fine-tuning Tc by Nd ions substitution make the investigated bulk polycrystalline compounds promising for application in magnetic refrigeration. Nano-sized samples possess lower magnetic entropy changes of maximum 2.4 J/kgK in μ˳∆H = 4 T for x = 0.15, but wider effective entropy change temperature (δTfwhm) and relative cooling power on par with other manganites, bringing them into the conversation as a viable option in cooling materials.

Bose–Einstein condensation of light in a semiconductor quantum well microcavity

When particles with integer spin accumulate at low temperature and high density, they undergo Bose–Einstein condensation (BEC). Atoms, magnons, solid-state excitons, surface plasmon polaritons and excitons coupled to light exhibit BEC, which results in high coherence due to massive occupation of the respective system’s ground state. Surprisingly, photons were shown to exhibit BEC recently in organic-dye-filled optical microcavities, which—owing to the photon’s low mass—occurs at room temperature. Here we demonstrate that photons within an inorganic semiconductor microcavity also thermalize and undergo BEC. Although semiconductor lasers are understood to operate out of thermal equilibrium, we identify a region of good thermalization in our system where we can clearly distinguish laser action from BEC. Semiconductor microcavities are a robust system for exploring the physics and applications of quantum statistical photon condensates. In practical terms, photon BECs offer their critical behaviour at lower thresholds than lasers. Our study shows two further advantages: the lack of dark electronic states in inorganic semiconductors allows these BECs to be sustained continuously; and quantum wells offer stronger photon–photon scattering. We measure an unoptimized interaction parameter (g̃\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ilde{{{{{g}}}}}$$\\end{document} ≳ 10–3), which is large enough to access the rich physics of interactions within BECs, such as superfluid light.

(Invited) Dynamic Modeling of Liquid Alkaline Water Electrolyzers: From Laboratory Cells to Industrial-Sized Stacks

The transition of the energy system towards renewable energies creates an enormous demand for green hydrogen produced by water electrolysis [1]. Among the available processes, alkaline water electrolysis (AEL) is already well-developed and cost-effective, as it does not require expensive or critical membrane and electrode materials [2]. If the liquid alkaline electrolyte is maintained at sufficient reaction temperature (60-90 °C), efficient operation of AEL systems is possible with rapid response to fluctuating renewable power supply [3]. However, a critical phenomenon for all low-temperature water electrolysis technologies is the increased gas impurity – especially for hydrogen in oxygen – during part-load operation [4]. This decreases the process efficiency and is safety-relevant as electrolysis systems must shut down when exceeding 50% of the lower explosive limit. These impurities become dominant at low current density since gas production decreases while the contamination mechanisms (diffusion through the separator and convective transport through electrolyte cycles mixing) are almost load-independent. We have developed a comprehensive dynamic model to properly describe the performance of an AEL system, including cell voltage, electrolyte temperature, electrolyte concentration, and gas purity [5]. With this model, it is possible to describe the dynamic operation of a laboratory AEL system with high accuracy. However, if this model is employed for an industry-sized shortstack with more than 1 m2 cell size, predictions and experimental results are in lesser agreement. This is most probably because the present model assumption of perfectly mixed half-cells no longer holds in large cells with a pronounced dependency of the gas fraction over the cell height. Thus, an improved model including this height dependence must be developed.[1] M. Wappler, D. Unguder, X. Lu, H. Ohlmeyer, H. Teschke, W. Lueke, Int. J. Hydrogen Energ. 47 (2022) 33551[2] J. Brauns, T. Turek, Processes 8 (2020) 248[3] J. Brauns, T. Turek, Electrochim. Acta 404 (2022) 139715[4] P. Trinke, P. Haug, J. Brauns, B. Bensmann, R. Hanke-Rauschenbach, T. Turek, J. Electrochem. Soc. 165 (2018) F502[5] J. Brauns, T. Turek, J. Electrochem. Soc. 170 (2023) 064510