Final Equilibrium State Research Articles

Gas-phase Hydrogen/Deuterium Exchange on Large, Astronomically Relevant Cationic PAHs

To examine the gas-phase hydrogen/deuterium exchange on large, astronomically relevant cationic polycyclic aromatic hydrocarbons (PAHs), the ion-molecule collision reaction between C42H18 + (hexa-peri-hexabenzocoronene cations, HBC+) and D atoms is studied. The experimental results show that the deuterated HBC cations ([C42H m D n ]+, m+2 ∗ n up to ∼54) are efficiently formed, and an effective hydrogen/deuterium exchange is determined. The structure of newly formed deuterated HBC cations and the bonding energy for these reaction pathways are investigated with quantum theoretical calculations. The exothermic energy for each reaction pathway is relatively high, and the existence of competition between deuteration and dedeuteration and of hydrogen/deuterium exchange is confirmed. A kinetic model is constructed to simulate the deuteration and hydrogenation processes and the hydrogen/deuterium exchange on HBC+ as a function of the reaction time over the experimental and typical astrophysical conditions. We infer that if we do not consider other chemical evolution processes (e.g., photoevolution), then cationic PAHs will reach the final equilibrium state (reaction with H/D atoms) very quickly regardless of the initial state of PAHs, and deuterated cationic PAHs are scarce in the interstellar medium.

Effect of neutrally buoyant oblate spheroid's aspect ratio on its equilibrium position in a square duct

The inertial migration of a neutrally buoyant oblate spheroid in a square duct is numerically simulated via the multiple-relaxation-time lattice Boltzmann method. This study aims to investigate the effect of a particle's aspect ratio $(AR)$ on its equilibrium position at different initial positions, orientations, and Reynolds numbers $(Re)$. The spheroid's equatorial radius remains unchanged here, and its $AR$ is adjusted by changing its polar radius, which is distinct from previous studies. Therefore, the particle's volume and mass increase with the $AR$. At a low $Re$ $(Re~=~80)$, the particle's initial position and orientation affect its final motion. There are three possible motion modes, tumbling, log-rolling and inclined log-rolling. Although the oblate spheroids with different $ARs$ may experience different motion modes at their final equilibrium states, their rotational diameters are constant. For the tumbling mode, the $AR$ affects the equilibrium position, and the particle gradually approaches the duct center as the $AR$ increases. For the inclined log-rolling mode, the $AR$ partially affects the equilibrium position, where the corresponding equilibrium positions remain unchanged for the spheroids with $AR~=~0.5$ and $0.75$, approaching closer to the duct center for the spherical particle with $AR~=~1$. Finally, for the log-rolling mode, $AR$ has a negligible effect on the equilibrium positions. Furthermore, in the same motion mode, the particle's equilibrium position approaches the wall as the $Re$ increases from 40 to 160.

Dynamics of thermalization of two tunnel-coupled one-dimensional quasicondensates

We study the non-equilibrium dynamics of two tunnel-coupled one-dimensional quasicondensates following a quench of the coupling strength from zero to a fixed finite value. More specifically, starting from two independent quasicondensates in thermal equilibrium, with initial temperature and chemical potential imbalance, we suddenly switch on the tunnel-coupling and analyze the post-quench equilibration in terms of particle number and energy imbalances. We find that, in certain parameter regimes, the net energy can flow from the colder quasicondensate to the hotter one and is governed by the surplus of low energy particles flowing from the cold to the hot system relative to the high-energy particles flowing in the reverse direction. In all cases, the approach to the new thermal equilibrium occurs through transient, damped oscillations. We also find that for a balanced initial state the coupled quasicondensates can relax into a final thermal equilibrium state in which they display a thermal phase coherence length that is larger than their initial phase coherence length, even though the new equilibrium temperature is higher. The increase in the phase coherence length occurs due to phase locking which manifests itself via an increased degree of correlation between the local relative phases of the quasicondensates at two arbitrary points.

Cooling a long-range interacting system faster via applying an external magnetic field

If a mean-field spin ring interact with a cold external thermal reservoir, the system might first evolve to the paramagnetic metastable state along the paramagnetic path, and then fluctuate around the metastable state for a long period due to an energy barrier. The spin system must absorb sufficient energy from the thermal reservoir to achieve a phase transition to the final ferromagnetic equilibrium state. However, if an external magnetic field is applied to the system, the energy barrier becomes smaller, which can reduce the relaxation time of the system significantly. Moreover, if the magnetic intensity is strong enough, the energy barrier vanishes and the system evolves directly to the equilibrium state.

Inertial migration of a neutrally buoyant oblate spheroid in three-dimensional square duct poiseuille flows

In this paper, the inertial migration of a single neutrally buoyant oblate spheroid in a square duct is investigated by multiple-relaxation-time lattice Boltzmann method. The spheroid’s aspect ratio AR=a/b=1/2, where a and b are the polar and equatorial radii of the spheroid, respectively, Reynolds number Re=UmH/ν=80 with Um, H and ν being the maximum velocity in the duct without the particle, height of the duct and the kinematic viscosity, respectively, and a blockage ratio 2b/H=0.277 is chosen to study the effects of initial position and initial orientation on the particle’s motion in detail. Our results show that the lateral trajectory and final motion, to some extent, depend on the spheroid’s initial position and orientation. In addition to the general log-rolling (LR) mode, which was previously reported by Lashgari et al. (2017), the spheroid can also exhibit a tumbling (TU) mode, where its polar axis rotates in the central streamwise–wall-normal plane, and an inclined log-rolling (ILR) mode, where it rotates in the diagonal plane with the polar axis being perpendicular to the plane, when its initial position and orientation are well specified. With the Reynolds number increased to 160, the ILR mode disappears while the TU and LR modes persist. If AR decreases to 1/3 while keeping the particle’s volume fixed, all three modes persist at Re=80, and the particle migrates closer to the duct center at the final equilibrium state with decreasing AR for all three different modes.

Indoor transmission of airborne viral aerosol with a simplistic reaction-diffusion model.

A simplistic reaction-diffusion model is undertaken in the present work to mathematically explore the spatio-temporal development of concentration of indoor aerosols containing infectious COVID-19 respiratory virus nuclei. Extracting exact solutions of concentration field under the influence of several physical parameters is preferred rather than adopting a more realistic complex model requiring time-consuming numerical simulations. Even though the proposed model is not sophisticated, the analytical solutions can provide quick prediction of the probability of contracting the virus in a ventilated closed room. Moreover, from the obtained elementary solutions of the viral concentration field, it is easy to analyze its spatio-temporal evolution and final equilibrium state. Formulae enable us to estimate the time to get infected and the risk of getting infected within an elapsed time under various physical operative situations involving a uniform infectious particle mixture ejection into the medium, wearing a face mask with a well-defined efficiency parameter and taking into account a localized source of infection. One of the essential conclusion from the current research is that less aerosols carrying COVID-19 particles are as a result of good indoor ventilation conditions, of removing the medium air through windows (or other exits) and of wearing masks of high efficiency. Moreover, the risk and probability of being caught by the indoor COVID-19 disease increases in time, particularly in the downstream of a localized infectious person. The results can be beneficial to understand and take necessary safety considerations against the infection risk in closed public or governmental environments.

Correlation functions and their universal connection during an extremely slow equilibration process.

We study the equilibration process of a one-dimensional lattice with transverse motions and external magnetic field. Starting from certain initial states, the system commonly reaches a metastable transient state shortly and then stays there for an extremely long time before it finally arrives in the ergodic equilibrium state. The relaxation time T_{eq} diverges even much more rapidly than exponential, which, compared with the widely reported power-law or even exponential divergence in many other systems, implies much higher stability of the transient state. Two correlation functions, the spatiotemporal correlation of the local energy and the autocorrelation of global heat current, are studied in both the metastable transient and the final equilibrium states. It is revealed that the correlations behave entirely differently in the two different states. In the former case they suggest normal heat diffusion and normal heat conduction; whereas in the latter one they indicate super heat diffusion and anomalous heat conduction. More importantly, we confirm that a general relation which connects the two correlations keeps valid not only in the equilibrium state but in the metastable transient state as well. The universality of the connection is, thus, extended.

Holographic topological defects in a ring: role of diverse boundary conditions

We investigate the formation of topological defects in the course of a dynamical phase transition with different boundary conditions in a ring from AdS/CFT correspondence. According to the Kibble-Zurek mechanism, quenching the system across the critical point to symmetry-breaking phase will result in topological defects — winding numbers — in a compact ring. By setting two different boundary conditions, i.e., Dirichlet and Neumann boundary conditions for the spatial component of the gauge fields in the AdS boundary, we achieve the holographic superfluid and holographic superconductor models, respectively. In the final equilibrium state, different configurations of the order parameter phases for these two models indicate a persistent superflow in the holographic superfluid, however, the holographic superconductor lacks this superflow due to the existence of local gauge fields. The two-point correlation functions of the order parameter also behave differently. In particular, for holographic superfluid the correlation function is a cosine function depending on the winding number. The correlation function for the holographic superconductor, however, decays rapidly at short distances and vanishes at long distance, due to the random localities of the gauge fields. These results are consistent with our theoretical analysis.

On Two Viewpoints on the Dramaturgical Conflict Structure: from Hegel’s Aesthetics to the Identity of the Formalists

In Russian humanitarian knowledge, the understanding of the nature of the dramaturgical conflict was influenced by aesthetic ideas about beauty, harmony, the sublime, and the ideal, formulated by Hegel in the Lectures on Aesthetics. In line with classical concepts, the conflict is understood as a necessary condition for maintaining the compositional unity of the work and the action development, leading to the final equilibrium state of all its elements after the separation of the participants in the collision to the maximum distance. In addition to the aesthetic understanding of the conflict as the basis for the harmonic organisation of the text, an idea of the conflict as the primary condition for the development of all systems was formed. This direction is also based on the Hegelian doctrine, which, however, is not connected with his aesthetic views on art but with The Phenomenology of Spirit, explaining historical patterns and the dialectical processes of the formation of the cognising subject, embarked on the path of struggle for recognition and turned out to be an instrument for bringing the spirit to oneself. In the context of the doctrine of the absolute spirit, the concept of conflict is the bases for personality development (Freud, Vygotsky), life cycles (E.Erickson), and textual organisms (M.Bakhtin), where the collision of two forces of the emerging subject of cognition leads a stable state of the system to irreversible changes, a transition to a new quality, to a higher stage of development in the case of a productive resolution of contradictions and the emergence of a new formation that is different from the two participants in the confrontation. Throughout the 20th century, Russian humanitarian thought developed mainly under the influence of the aesthetic paradigm, as evidenced by the definitions of the dramatic conflict offered by literary theorists. Such a history has its reasons, which lie in the plane of understanding the official ideology, art and culture, reflecting the historical meaning of the revolutionary achievements of a classless and, therefore, conflict-free society, which achieved the dialectical removal of all contradictions in the main historical event. However, the Hegelian understanding of the modification of textual organisation due to a catastrophic event, a shift, underlies a theory that has not been fully mastered by the Russian tradition but which has outlined a new way of perceiving and understanding the nature of a dramatic conflict as a change in identity due to irreversible actions and a further change in the structure of the subject-text. This is Shklovsky's theory of estrangement, which expressed the essence of formal poetics but was forced out to the periphery and, for compelling historical reasons, did not receive further development in the theory of art.

LETTER FROM THE EDITOR

LETTER FROM THE EDITOR

Study on Final Equilibrium State and Process of CO2 Reacting with Fe–C Melt

Abstract To study the final equilibrium state and process of CO2 injecting into the Fe–C melt with different initial carbon contents, a model was established based on the method of minimization of Gibbs free energy and the corresponding experiments were carried out in a high-temperature tube furnace. When CO2 is continuously injected into the Fe–C melt at 1873 K, the final equilibrium state of the system is such that the carbon and oxygen contents in the melt are 0.1977 and 0.0115 wt pct, respectively, and the volume ratio of CO in the gas phase is 85.75 vol pct. When the initial a [O] × a [C] in the melt is greater than those in equilibrium with CO under 0.8575 atm, the CO2 gas removes carbon from the melt. On the contrary, the role of CO2 gas is to add carbon and oxygen to the melt. At the same time, the variation of carbon and oxygen with time obtained by experiments was different from the theoretical calculation at extremely low carbon content, which requires further study.

Composition-dependent mechanical property changes and damage recovery in He-ion-irradiated borosilicate glasses

This study explored the mechanical property changes in three kinds of pristine and Au3+ pre-irradiated Na2O-B2O3-SiO2 (labeled as NBS) glasses induced by 0.5-MeV He2+ ions over a broad fluence range. The glass samples were prepared with different R values = [Na2O]/[B2O3] (0.40, 0.75 and 1.34). After He-ion irradiation, the hardness diminished and finally reached saturation, the modulus showed a slight decrease for the NBS1 and NBS2 glasses, but the NBS3 glass exhibited no significant change. The mono He2+ ion irradiation scenario did not show the self-recovery effect of Au3+ ion irradiation scenario. The sequential He-ion irradiation can lead to damage recovery in the Au-ion pre-irradiated glasses. The final equilibrium state was affected by the composition of pristine glass, which can be attributed to lower thermal stability and the phase separation characteristic of NBS3 glass. Such results hold great significance for understanding the radiation damage caused by multiparticle irradiation in the glass matrix of nuclear wastes.

Wetting properties and morphological behavior of core-shell polymer-based nanoparticle coatings

The glass transition temperature (Tg) strongly affects the physicochemical properties of a polymer. In particular, coating a material with polymer nanocapsules with two or more Tg values can endow the material with variety of properties. We introduced polymer nanocapsules onto glass substrates and analyzed the effect of polymer Tg on the surface properties of the coating. Core-shell polymer (CSP) particles were prepared by a two-step emulsion polymerization procedure using poly(methyl methacrylate) (PMMA, Tg = 105 °C) and poly(butyl acrylate) (PBA, Tg = −54 °C) in different ratios as cores, and poly(nonafluorohexyl acrylate) (PNFHA, Tg = −6 °C) as shells. The microstructural and microbehavioral properties of the coating surface were found to depend on the Tgs of the synthesized CSP. Surface elemental distributions and chemical bonding were analyzed by XPS depth profiling to determine the behavior of the CSP nanoparticles. A core/shell nanoparticle with Tg = 55.81/−9.12 °C has a high probability of its core becoming located at the coating surface. On the other hand, a core/shell nanoparticle with Tg = −33.17.81/−28.6 °C has a high probability of its shell becoming located at the surface. Because the shell has a low surface energy, test solutions with a variety of surface tensions exhibited low wettabilities. These results allow the Tg values of the CSP to access the final thermodynamic equilibrium state, reveal that the Tg values affect the surface distribution of the functional groups of the coatings, which in turn determine its surface morphology and wetting properties.

Double-stranded flanking ends affect the folding kinetics and conformational equilibrium of G-quadruplexes forming sequences within the promoter of KIT oncogene.

G-quadruplexes embedded within promoters play a crucial role in regulating the gene expression. KIT is a widely studied oncogene, whose promoter contains three G-quadruplex forming sequences, c-kit1, c-kit2 and c-kit*. For these sequences available studies cover ensemble and single-molecule analyses, although for kit* the latter were limited to a study on a promoter domain comprising all of them. Recently, c-kit2 has been reported to fold according to a multi-step process involving folding intermediates. Here, by exploiting fluorescence resonance energy transfer, both in ensemble and at the single molecule level, we investigated the folding of expressly designed constructs in which, alike in the physiological context, either c-kit2 or c-kit* are flanked by double stranded DNA segments. To assess whether the presence of flanking ends at the borders of the G-quadruplex affects the folding, we studied under the same protocols oligonucleotides corresponding to the minimal G-quadruplex forming sequences. Data suggest that addition of flanking ends results in biasing both the final equilibrium state and the folding kinetics. A previously unconsidered aspect is thereby unravelled, which ought to be taken into account to achieve a deeper insight of the complex relationships underlying the fine tuning of the gene-regulatory properties of these fascinating DNA structures.

Adsorption time scales of cluster-forming systems.

A microscopic model of adsorption in cluster forming systems with competing interaction is considered. The adsorption process is described by the master equation and modelled by a kinetic Monte Carlo method. The evolution of the particle concentration and interaction energy during the adsorption of particles on a plane triangular lattice is investigated. The simulation results show a diverse behavior of the system time evolution depending on the temperature and chemical potential and finally on the formation of clusters in the system. The characteristic relaxation times of adsorption vary in several orders of magnitude depending on the thermodynamic parameters of the final equilibrium state of the adsorbate. A very fast adsorption of particles is observed for highly ordered adsorbate equilibrium states.

Improved analytical expressions for transient specific yield in shallow groundwater drainage

This paper presents the new analytical expressions to improve the description of transient specific yield (Sy) in shallow groundwater drainage. A new expression of the transient Sy (i.e. Sy,G (t)) that only considers the gravity effect is first derived based on the modified van Genuchten model. This analytical expression is still valid when water table depth (WTD) is less than the soil air-entry pressure head, and thus completes the lack of description in the near-saturated segment in previous expressions. Further, we propose an approximate method to dealing with the diffusivity (capillary) effect, and derive an improved approximate expression of Sy with both considering the gravity and diffusivity (capillary) effects. The accuracy of the improved expression of Sy,GD (t) is evaluated with the test cases that cover all of soil types (under the USDA soil classification system) and different changes in water table, also compared with the expression derived with only considering the gravity effect. The comparisons show that the Sy,GD (t) expression could more accurately capture the dependence of the transient Sy on time and WTD, and significantly reduce the errors of ignoring the diffusivity effect. In addition, the analytical expression of ultimate Sy and the final time td required to reach its ultimate value are both derived based on the initial and final equilibrium states. Results indicate that our improved expressions can expand the application range of analytical expression and significantly improve the calculation accuracy of transient Sy in the shallow groundwater environments.

Thermalization of a quantum Newton's cradle in a one-dimensional quasicondensate

We study the nonequilibrium dynamics of the quantum Newton's cradle in a one-dimensional (1D) Bose gas in the weakly-interacting quasicondensate regime. This is the opposite regime to the original quantum Newton's cradle experiment of Kinoshita et al. [Nature 440, 900 (2006)], which was realized in the strongly interacting 1D Bose gas. Using finite temperature c-field methods, we calculate the characteristic relaxation rates to the final equilibrium state. Hence, we identify the different dynamical regimes of the system in the parameter space that characterizes the strength of interatomic interactions, the initial temperature, and the magnitude of the Bragg momentum used to initiate the collisional oscillations of the cradle. In all parameter regimes, we find that the system relaxes to a final equilibrium state for which the momentum distribution is consistent with a thermal distribution. For sufficiently large initial Bragg momentum, the system can undergo hundreds of repeated collisional oscillations before reaching the final thermal equilibrium. The corresponding thermalization timescales can reach tens of seconds, which is an order of magnitude smaller than in the strongly interacting regime.

Surface Charge Density in Electrical Double Layer Capacitors with Nanoscale Cathode-Anode Separation.

Using a dynamic density functional theory, we study the charging dynamics, the final equilibrium structure, and the energy storage in an electrical double layer capacitor with nanoscale cathode-anode separation in a slit geometry. We derive a simple expression for the surface charge density that naturally separates the effects of the charge polarization due to the ions from those due to the polarization of the dielectric medium and allows a more intuitive understanding of how the ion distribution within the cell affects the surface charge density. We find that charge neutrality in the half-cell does not hold during the dynamic charging process for any cathode-anode separation, and also does not hold at the final equilibrium state for small separations. Therefore, the charge accumulation in the half-cell in general does not equal the surface charge density. The relationships between the surface charge density and the charge accumulation within the half-cell are systematically investigated by tuning the electrolyte concentration, cathode-anode separation, and applied voltage. For high electrolyte concentrations, we observe charge inversion at which the charge accumulation exceeds the surface charge at special values of the separation. In addition, we find that the energy density has a maximum at intermediate electrolyte concentrations for a high applied voltage.

El storytelling de la campaña presidencial portuguesa de 2016. Rebelo de Sousa vs. Sampaio da Nóvoa

Resumen El objetivo de este estudio ha sido analizar el storytelling de la campaña política de los dos principales candidatos a la presidencia de Portugal en las elecciones de 2016: Marcelo Rebelo de Sousa y António Sampaio da Nóvoa. La metodología empleada ha sido el análisis de contenido de los Personajes y la Trama en sus discursos de presentación de candidatura y en las noticias sobre sus campañas en los periódicos Expresso y Público. Los resultados muestran, en el análisis de prensa escrita, una relación entre el uso del personaje del villano y las encuestas de intención de voto, una mayor referencia en ambos candidatos a la situación de equilibrio final, así como que Rebelo de Sousa basó su narrativa en el héroe, mientras que en Sampaio da Nóvoa es significativa el recurso al villano.

A blue ring nebula from a stellar merger several thousand years ago.

Stellar mergers are a brief but common phase in the evolution of binary star systems1,2. These events have many astrophysical implications; for example, they may lead to the creation of atypical stars (such as magnetic stars3, blue stragglers4 and rapid rotators5), they play an important part in our interpretation of stellar populations6 and they represent formation channels of compact-object mergers7. Although a handful of stellar mergers have been observed directly8,9, the central remnants of these events were shrouded by an opaque shell of dust and molecules10, making it impossible to observe their final state (for example, as a single merged star or a tighter, surviving binary11). Here we report observations of an unusual, ring-shaped ultraviolet ('blue') nebula and the star at its centre, TYC2597-735-1. The nebula has two opposing fronts, suggesting a bipolar outflow of material from TYC2597-735-1. The spectrum of TYC2597-735-1 and its proximity to the Galactic plane suggest that it is an old star, yet it has abnormally low surface gravity and a detectable long-term luminosity decay, which is uncharacteristic for its evolutionary stage. TYC2597-735-1 also exhibits Hα emission, radial-velocity variations, enhanced ultraviolet radiation and excess infrared emission-signatures of dusty circumstellar disks12, stellar activity13 and accretion14. Combined with stellar evolution models, the observations suggest that TYC2597-735-1 merged with a lower-mass companion several thousand years ago. TYC2597-735-1 provides a look at an unobstructed stellar merger at an evolutionary stage between its dynamic onset and the theorized final equilibrium state, enabling the direct study of the merging process.