Theory Of Interacting Particles Research Articles

An Accurate Model for Estimating H2 Solubility in Pure Water and Aqueous NaCl Solutions

By employing a specific particle interaction theory and a high-precision equation of states for the liquid and vapor phases of H2, respectively, a new H2 solubility model in pure water and aqueous NaCl solutions is proposed in this study. The model established by fitting the experimental data of H2 solubility can be used to estimate H2 solubility in pure water at temperatures and pressures of 273.15–423.15 K and 0–1100 bar, respectively, and in salt solutions (NaCl concentration = 0–5 mol/kg) at temperatures and pressures of 273.15–373.15 K and 0–230 bar, respectively. By adopting the theory of liquid electrolyte solutions, the model can also be used to predict H2 solubility in seawater without fitting the experimental data of a seawater system. Within or close to experimental data uncertainty, the mean absolute percentage error between the model-predicted and experimentally obtained H2 solubilities was less than 1.14%.

Modeling the formation of soil microaggregates

The functions of soils are intimately linked to its aggregated structure. Microaggregates formed during pedogenesis from a vast variety of mineral, organic, and biotic materials are the smallest conceivable compounds at the basis of soil structural hierarchy. Qualitative hypotheses and concepts on how aggregates form are quite elaborate, but the consistent quantitative application within a mechanistic and physically rigorous framework is still missing. This is partly caused by the fact that such an endeavor requires the combination of synergistic concepts on the transport of particles and their interactions affected by shape, size, and surface properties in aqueous suspension. Here we present a novel quantitative approach for the formation of soil microaggregates in silico that integrates diffusion-limited cluster-cluster aggregation with a probabilistic attachment following the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of particle interactions. To represent universal mineral shapes found in soils, we implemented spherical, plate-like as well as rod-like particle morphologies inspired by weathered silicates, secondary clay minerals and pedogenic iron oxides. In this way, we developed a model that produces an explicit three-dimensional structure of aggregates emerging from hetero- as well as homo-aggregation in response to the chemical milieu. We then exploited the 3D morphology to assess functional properties of aggregates exemplified with the water retention curve and pore size distribution.

Observation of magnetic vortex pairs at room temperature in a planar α-Fe2O3/Co heterostructure.

Vortices, occurring whenever a flow field 'whirls' around a one-dimensional core, are among the simplest topological structures, ubiquitous to many branches of physics. In the crystalline state, vortex formation is rare, since it is generally hampered by long-range interactions: in ferroic materials (ferromagnetic and ferroelectric), vortices are observed only when the effects of the dipole-dipole interaction are modified by confinement at the nanoscale1-3, or when the parameter associated with the vorticity does not couple directly with strain 4 . Here, we observe an unprecedented form of vortices in antiferromagnetic haematite (α-Fe2O3) epitaxial films, in which the primary whirling parameter is the staggered magnetization. Remarkably, ferromagnetic topological objects with the same vorticity and winding number as the α-Fe2O3 vortices are imprinted onto an ultra-thin Co ferromagnetic over-layer by interfacial exchange. Our data suggest that the ferromagnetic vortices may be merons (half-skyrmions, carrying an out-of plane core magnetization), and indicate that the vortex/meron pairs can be manipulated by the application of an in-plane magnetic field, giving rise to large-scale vortex-antivortex annihilation.

Kinetic Theory of Particle Interactions Mediated by Dynamical Networks

We provide a detailed multiscale analysis of a system of particles interacting through a dynamical network of links. Starting from a microscopic model, via the mean field limit, we formally derive coupled kinetic equations for the particle and link densities, following the approach of [P. Degond, F. Delebecque, and D. Peurichard, Math. Models Methods Appl. Sci., 26 (2016), pp. 269--318]. Assuming that the process of remodeling the network is very fast, we simplify the description to a macroscopic model taking the form of a single aggregation-diffusion equation for the density of particles. We analyze qualitatively this equation, addressing the stability of a homogeneous distribution of particles for a general potential. For the Hookean potential we obtain a precise condition for the phase transition, and, using the central manifold reduction, we characterize the type of bifurcation at the instability onset.

Theory with a twistor

A reworking of the theory of particle interactions — the same theory but rendered in a new form based on twistor geometry — is likely to have wide implications for physics, including the reformulation of gravity.

Propagation of galactic cosmic rays

The theoretical aspects of cosmic ray transport in the Galaxy are discussed. The emphasis is on the diffusion model of cosmic ray propagation. The results of the empirical modelling are combined with the approach based on the kinetic theory of particle interaction with random magnetic fields. The plasma effects of cosmic rays in the interstellar medium are briefly discussed.

R2SM: a package for the analytic computation of the R 2 Rational terms in the Standard Model of the Electroweak interactions

The analytical package written in FORM presented in this paper allows the computation of the complete set of Feynman Rules producing the Rational terms of kind R2 contributing to the virtual part of NLO corrections in the Standard Model of the Electroweak interactions. Building block topologies filled by means of generic scalars, vectors and fermions, allowing to build these Feynman Rules in terms of specific elementary particles, are explicitly given in the R ξ gauge class, together with the automatic dressing procedure to obtain the Feynman Rules from them. The results in more specific gauges, like the ’t Hooft Feynman one, follow as particular cases, in both the HV and the FDH dimensional regularization schemes. As a check on our formulas, the gauge independence of the total Rational contribution (R1+R2) to renormalized S-matrix elements is verified by considering the specific example of the H→γγ decay process at 1-loop. This package can be of interest for people aiming at a better understanding of the nature of the Rational terms. It is organized in a modular way, allowing a further use of some its files even in different contexts. Furthermore, it can be considered as a first seed in the effort towards a complete automation of the process of the analytical calculation of the R2 effective vertices, given the Lagrangian of a generic gauge theory of particle interactions.

High-energy colliders and the rise of the standard model

Over the past quarter of a century, experiments at high-energy particle colliders have established the standard model as the precise theory of particle interactions up to the 100 GeV scale. A series of important experimental discoveries and measurements have filled in most of the missing pieces and tested the predictions of the standard model with great precision.

Accurate Thermodynamic Model for the Calculation of H2S Solubility in Pure Water and Brines

A thermodynamic model calculating the solubility of hydrogen sulfide (H2S) in pure water and in aqueous NaCl solutions (0−6 M, 273−500 K, 0−200 bar) is presented. The model is based on a specific particle interaction theory for the liquid phase and a highly accurate equation of state for the vapor phase. With this specific interaction approach, this model is able to predict H2S solubility in other systems, such as H2S−H2O−Na2SO4, H2S−H2O−CaCl2, H2S−H2O−KCl, and H2S−seawater, without fitting experimental data from these systems. Comparison of the model predictions with experimental data indicates that the model is within or close to experimental uncertainty, which is about 7% in H2S solubility. The model is programmed and can be downloaded from the website: www.geochem-model.org/programs.htm. Online calculation is also made available on the website: www.geochem-model.org/models.htm. The H2S solubility model can be used together with numerical speciation-solubility modeling codes such as PHREEQC to calcul...

A thermodynamic model for calculating nitrogen solubility, gas phase composition and density of the N 2–H 2O–NaCl system

A thermodynamic model is presented to calculate N 2 solubility in pure water (273–590 K and 1–600 bar) and aqueous NaCl solutions (273–400 K, 1–600 bar and 0–6 mol kg −1) with or close to experimental accuracy. This model is based on a semi-empirical equation used to calculate gas phase composition of the H 2O–N 2 system and a specific particle interaction theory for liquid phase. With the parameters evaluated from N 2–H 2O–NaCl system and using a simple approach, the model is extended to predict the N 2 solubility in seawater accurately. Liquid phase density of N 2–H 2O–NaCl system at phase equilibrium and the homogenization pressure of fluid inclusions containing N 2–H 2O–NaCl can be calculated from this model. A computer code is developed for this model and can be downloaded from the website: www.geochem-model.org/programs.htm.

An accurate model for calculating C 2H 6 solubility in pure water and aqueous NaCl solutions

An accurate model is presented to calculate the solubilities of C 2H 6 in pure water (273–444 K and 0–1000 bar) and in aqueous NaCl solutions (273–348 K, 0–16 bar and 0–6.3 mol kg −1). This model is based on a specific particle interaction theory for liquid phase and a new accurate equation of state developed in this study for vapor phase. Precision of the model is within or close to the uncertainty of experimental solubilities (about 7%). A FORTRAN code is developed for this model and can be downloaded from the website: www.geochem-model.org/programs.htm.

Energy spectra of ∼170–360 keV electron microbursts measured by the Korean STSAT‐1

Energy spectra of electron microbursts in the energy range 170–360 keV have been measured in the outer radiation zone by the low‐altitude (680 km), polar‐orbiting Korean satellite STSAT‐1. These electrons are the lower energy population of relativistic microbursts. Our observations show microburst energy spectra of precipitated electrons inside the loss cone (precipitated) have higher e‐folding energies during disturbed times than quiet times. The loss cone at these energies is empty except when microbursts abruptly appear and fill the loss cone in less than 50 msec. This fast pitch angle diffusion requires diffusion coefficients larger than ∼3.5 × 10−2 rad2/sec, while ∼1.5 × 10−5 rad2/sec was proposed by a wave particle interaction theory. The source of microbursts remains unknown as our observations are not adequately explained by wave and particle resonant interaction models.

An improved model calculating CO 2 solubility in pure water and aqueous NaCl solutions from 273 to 533 K and from 0 to 2000 bar

A thermodynamic model for the solubility of carbon dioxide (CO 2) in pure water and in aqueous NaCl solutions for temperatures from 273 to 533 K, for pressures from 0 to 2000 bar, and for ionic strength from 0 to 4.3 m is presented. The model is based on a specific particle interaction theory for the liquid phase and a highly accurate equation of state for the vapor phase. With this specific interaction approach, this model is able to predict CO 2 solubility in other systems, such as CO 2–H 2O–CaCl 2 and CO 2–seawater, without fitting experimental data from these systems. Comparison of the model predictions with experimental data indicates that the model is within or close to experimental uncertainty, which is about 7% in CO 2 solubility.

Prediction of choking in hydrocyclones by use of elementary particle interaction theory

Empirical models are an important tool for the selection of appropriately sized hydrocyclones for particular tasks, as well as for estimation of the performance of these classifiers. These models are usually specific to the conditions under which these classifiers are operated and can therefore not be used for prediction of anomalous conditions, such as choking of hydrocyclones. In this paper a simplified model of flow in hydrocyclones is proposed, based on elementary particle interaction theory and basic fluid flow principles. In contrast with other models published in the literature, the resulting semi-empirical model correctly simulates hydrocyclone (small laboratory scale) operation at low and high feed concentrations.

MEASUREMENT OF PRIMARY- AND SECONDARY-MINIMUM COAGULATION RATES IN COLLOIDAL DISPERSIONS

Particle interaction theory cannot completely explain observed phenomena when particles interact in the vicinity of the secondary minimum. No convenient experimental techniques to probe the secondary minimum are currently available. A technique based on the use of hydrodynamic shear to disrupt secondary-minimum bonds is discussed for this purpose. The use off this procedure is justified in terms of a relative particle trajectory analysis. An experimental apparatus was constructed to utilize this methodology.

Particle Physics: Strange particles?

Something unexpected is appearing as the data from the proton-antiproton (pp) collider at CERN continue to be sifted. A short item in Science (224 p589) reports the occurrence of anomalous events at energies just below the W and Z mass, where the grand unified theories of particle interactions had predicted a 'desert' in which nothing new would be found.

Is our vacuum metastable?

In spontaneously broken gauge theories of particle interactions there are sometimes several local minima of the effective potential. Any of these minima can serve as a vacuum in the sense that we can expand the fields around their values at the minimum, interpret the quantized fluctuations around the minimum as particles, and compare the properties of these particles with experiment. One might think that only the state with absolutely minimum energy could be what we ordinarily call our vacuum, as the other local minima will inevitably decay into this lowest one. However, this is not necessarily the case, because it is possible for the lifetime of a metastable vacuum to be very long, even when compared with the age of the Universe. Furthermore, the energy densities available in present laboratory or astrophysical environments are much less than the barriers which exist in field space between the different local minima, and so we have no direct sensitivity to the presence of a possibly lower vacuum state. (A possible exception to this are magnetic monopoles which do probe the large field region.) If it is not the absolute minimization of the effective potential, what does determine the present vacuum state of the Universe? We argue here that it is determined cosmologically by the dynamical evolution of the Universe from the hot, dense phase which existed shortly after the big bang to the present1,2.

Hierarchies of forces: The last 150 years

Recent experiments and theories have elucidated the region of applicability of continuum theories of particle interactions (van der Waals and double-layer forces). For some systems these theories appear to describe interactions correctly down to contact. For others of real application, continuum theories break down at small distances and are seen to represent the long-range tail of the actual forces which determine the stability of suspensions. These “structural” or “hydration” forces which can be attractive or repulsive, oscillatory or monotonic, arise due to surface-induced solvent structure and liquid-induced surface structure and go over to the continuum approximations at distances typically beyond 30 Å.

On electro-osmotic washing

Experiments were carried out to remove soil particles from the capillary walls of cotton cloth by electro-osmosis. A cotton cloth soiled by carbon black was held between two perforated plastic plates and dipped in a wash bath. When an electric field was applied perpendicularly to the cloth, electro-osmotic flow took place, and hence the particles were removed from the capillary wall. By preventing deposition from the bath the detergency increased to ca. 0.64, which was about 0.3 higher than that obtained by standard mechanical washing using the launderometer. A theory of electro-osmotic washing is proposed on the basis of theories of electrokinetic and hydrodynamic lift force, as well as the DLVO theory of particle interaction. The agreement between theory and experiment was good as a first approximation. The process has the feature of removing soil particles on surfaces under cover, which cannot be removed by ordinary mechanical washing.

On the isotropy and homogeniety of the Universe

It is generally believed that the Universe began from a hot big bang. Among the clues to its very early history are the present day observations that the Universe is isotropic and homogeneous (as shown by the 3 K microwave background1 and galaxy counts2,3) and that there are about 109±1 photons per baryon4. Penrose and others5,6 argue that these two observations imply that the Universe was initially very nearly isotropic and homogeneous. Their arguments rely on absolute baryon conservation so that the baryon number of the Universe can be used as a fiducial to which the number of photons can be compared. In recently proposed grand unified theories of particle interactions, baryon number is not absolutely conserved7,8 and thus the baryon number of the Universe is no longer a constant. It is argued here that in the absence of this fiducial the photonJbaryon ratio is not a ‘footprint’ of the initial conditions, and therefore the initial singularity could well have been highly irregular as Misner suggested9.