Unified Point Of View Research Articles

Universal Separation Potential for Multicomponent Mixtures: Reasons for Its Absence

The topic of this study is discussion aimed at developing a unified viewpoint on the problem of separation potential and separating power in the theory of separation of multicomponent molecular and isotopic mixtures. The object of study was the “generalized” separation potential for multicomponent mixtures. A critical assessment of its validity from thermodynamic viewpoint was given. The assumptions made during its derivation were analyzed.

Representations of relativistic particles of arbitrary spin in Poincaré, Lorentz, and Euclidean covariant formulations of relativistic quantum mechanics

Relativistic treatments of quantum mechanical systems are important for understanding hadronic structure and dynamics at sub-nucleon distance scales. Hadronic states in different inertial reference frames are needed to compute current matrix elements that probe hadronic structure and dynamics. Relativistic invariance is an important consideration as the resolution of the probe is increased. Many different treatments of relativistic dynamics are used in practice, including Poincar\'e covariant methods, Lorentz covariant methods, Euclidean covariant methods and methods based on quantum fields. Wave functions are typically matrix elements of interacting relativistic states in a basis of non-interacting relativistic states. The purpose of this work is to develop the relation between these different representations of relativistic states that are used in different applications from a unified point of view, starting with positive mass irreducible representations of the Poincar\'e group.

Macroscopic consequences of Piobert–Lüders and Portevin–Le Chatelier bands during tensile deformation in Al-Mg alloys

Lüders bands and the Portevin–Le Chatelier effect are both due to plastic flow instabilities that affect a wide variety of metallic materials. The present study focuses on understanding these behaviors. Field kinematic measurements combined with the comparison of two specimen sizes are used here to characterize the Al–Mg alloy AA5086, by investigating the kinetics of individual localization bands. A unifying point of view is proposed for the classification of these bands together with the identification of a constitutive relation linking strain increments and nucleation stress, as well as evidence of the factors determining the development of serration behaviors. This leads to a novel interpretation of the spatiotemporal behavior of the bands as being the result of a competition between the influence of plastic strain and its gradient.

Method of Formation of Tracheo-Tracheal Anastomosis with a Continuous Single-Row Suture in the Experiment

The work is devoted toanew suture in the formation of tracheo-tracheal anastomosis. Despite the improvement of surgical technique in tracheal interventions, the number of postoperative complications (insufficiency and stenosis of anastomosis) remains high, with postoperative lethality reaching 18.2 %. The main problem is the lack of a unified point of view on the choice of the method of anastomosis, in particular, inclusion in the mucosal suture. Several variants of tracheo-tracheal anastomosis are suggested, but a large number of complications testify to the shortcomings of the methods used.The aim of this work is to optimize the imposition of a continuous single-row suture for the formation of tracheo-tracheal anastomosis with a shortening of the trachea.Materials and methods. The study was carried out on the basis of the scientific department of experimental surgery with the vivarium of Irkutsk Scientific Centre of Surgery and Traumatology using Wistar rats, and approved by the ethical committee.Results. A technique for the formation of tracheo-tracheal anastomosis with the use of an original continuous singlerow suture with a shortening of the trachea was developed. Step by step a sequence of operations from access to the cervical trachea to the formation of an anastomosis.Conclusion. The discussed version of the seam in the formation of tracheo-tracheal anastomosis makes it possible to accurately compare and reliably stabilize the sewn ends of the trachea.

Survey and Review

The Survey and Review article in this issue is “A Class of Iterative Solvers for the Helmholtz Equation: Factorizations, Sweeping Preconditioners, Source Transfer, Single Layer Potentials, Polarized Traces, and Optimized Schwarz Methods,” by Martin J. Gander and Hui Zhang. The Helmholtz equation appears in the study of time-harmonic waves \(u(x) \exp(-iømega t)\) arising in acoustics, electromagnetism, and other fields. In its simplest form the equation reads \((\Delta+k^2) u = f\), where (\Delta\) denotes the Laplacian operator and the constant \(k\) is the wavenumber, and therefore is reminiscent of the Poisson equation (\Delta u =f\). However, this similarity is only superficial, and the numerical solution of boundary value problems, often posed in unbounded domains, involving the Helmholtz equation is challenging. Classical iterative solvers are not suitable, and the recent literature has devoted much effort to the development of novel solvers. New iterative methods have been suggested by authors with a wide range of backgrounds and motivations and invoke different discretization strategies; some of them have been formulated at the linear algebra level and others at the level of the differential equation. Gander and Zhang survey the new developments using a unifying point of view. The main insight is given in section 2: the forward and backward substitution sweeps of the block LU factorization of the discrete system correspond at the continuous level to sweeps from left to right and right to left of an optimal Schwarz domain decomposition method. The article will be useful not only to those working directly with the Helmholtz and related partial differential equations, but also to anybody interested in iterative solvers for large linear systems.

Stochastic Gene Expression with a Multistate Promoter: Breaking Down Exact Distributions

We consider a stochastic model of gene expression in which transcription depends on a multistate promoter, including the famous two-state model and refractory promoters as special cases, and focus on deriving the exact stationary distribution. Building upon several successful approaches, we present a more unified viewpoint that enables us to simplify and generalize existing results. In particular, the original jump process is deeply related to a multivariate piecewise-deterministic Markov process that may also be of interest beyond the biological field. In a very particular case of promoter configuration, this underlying process is shown to have a simple Dirichlet stationary distribution. In the general case, the corresponding marginal distributions extend the well-known class of Beta products, involving complex parameters that directly relate to spectral properties of the promoter transition matrix. Finally, we illustrate these results with biologically plausible examples.

The Dynamics of Financial Markets: Fibonacci Numbers, Elliott Waves, and Solitons

In this paper information theoretical approach is applied to the description of financial markets A model which is expected to describe the markets dynamics is presented. It is shown the possibility to describe market trend and cycle dynamics from a unified viewpoint. The model predictions comparatively well suit Fibonacci ratios and numbers used for the analysis of market price and time projections. It proves possible to link time and price projections, thus allowing increase the accuracy of predicting well in advance the moment of trend termination. The model is tested against real data from the stock and financial markets.

Viscosity, surface tension and gravity effects on acoustic reflection and refraction

The idea of the present work is to study from a unifying viewpoint the effects of viscosity, surface tension and gravity on acoustic reflection and refraction at a fluid interface, with the focus on modifications of Snell’s (Snell–Descartes’) law. While all these effects can be treated individually due to separation of the associated time scales, the contributions of surface tension to the gravity and viscosity cases are considered as well. The analysis reveals a number of phenomena among which are dispersive refraction laws, surface tension enhancing reflection, acoustic field generating vorticity at the interface, and viscosity enhancing/suppressing reflection as well as giving rise to extra reflected and transmitted waves.

Structural Slow Waves: Parallels between Photonic Crystals and Plasmonic Waveguides

The slowdown of propagating electromagnetic waves by engineering waveguide structures is receiving considerable attention in nanophotonics. Two types of structures are independently investigated, namely, diffraction-limited photonic-crystal waveguides and highly confined plasmonic waveguides. Here we propose a unified viewpoint on slow waveguide structures by analyzing both approaches within a single theoretical framework. This allows us to clarify the physical mechanisms underlying slowness—thereby highlighting their inherent differences—and to remove some inaccurate ideas on the topic. We further discuss the strengths and weaknesses of plasmonic and photonic slow waveguides, assess the technical and scientific challenges recently solved, and critically identify those that still stand in the way.

On modeling and complete solutions to general fixpoint problems in multi-scale systems with applications

This paper revisits the well-studied fixed point problem from a unified viewpoint of mathematical modeling and canonical duality theory, i.e., the general fixed point problem is first reformulated as a nonconvex optimization problem, its well-posedness is discussed based on the objectivity principle in continuum physics; then the canonical duality theory is applied for solving this challenging problem to obtain not only all fixed points, but also their stability properties. Applications are illustrated by problems governed by nonconvex polynomial, exponential, and logarithmic operators. This paper shows that within the framework of the canonical duality theory, there is no difference between the fixed point problems and nonconvex analysis/optimization in multidisciplinary studies.

On the relation between a length cutoff in time-convolutionless mode-coupling theory and a characteristic length at [formula omitted]-relaxation stage in glass-forming materials

A length cutoff b contained in the nonlinear memory function of the time-convolutionless mode-coupling theory (TMCT) equation is obtained by solving the TMCT equation in a manner consistent with the simulation results near the glass transition. A characteristic length ℓ of a supercooled liquid is also introduced at a β-relaxation stage based on the mean-field theory proposed by Tokuyama independently and is shown to describe a displacement of a particle in a cage. Then, both lengths are shown to satisfy the inequality ℓ≥b≥bc in a supercooled state within an original TMCT equation, where bc is a critical cutoff obtained independently by solving the Lambert W-function at the critical point. Their control parameter dependence is also explored from a unified point of view. Thus, both lengths are shown to characterize the same caging mechanism at β stage in a supercooled liquid.

Direct simulation on nonlinear thermokinetic phenomena due to induced-charge electroosmosis

Previously, we proposed a novel mechanism to produce a nonlinear thermokinetic phenomenon (NTKP) around a metal cylinder in an electrolyte on the basis of analytical discussion. In this study, by using a non-steady direct multi-physics simulation technique based on the Stokes equation coupled with the electroosmotic equation that considers normal diffusion, electrophoresis and thermal diffusion, we directly verify the NTKP and show that the original driving force is the excess ions pressed on the particle by the thermokinetic force and that the NTKP vortex flow around the particle is generated by the interaction between the excess ion and the electric field that is made by the excess ions and/or the Seebeck electric field due to the blocking boundary condition on the wall. Namely, two types of NTKP exist and they are explained in a self-consistent manner by our new theory. In addition, through the discussion of a dielectric particle, we show that the NTKP is a general phenomenon that can be found in both metal and dielectric particles. We believe that our findings provide a new unified viewpoint to understand complex thermokinetic phenomena near metal and dielectric particles.

On the physical validity of the proposed separation potentials for multicomponent mixtures

The object of the study is the “generalized” separation potential for multicomponent mixtures. A critical assessment of its validity from the point of view of thermodynamics is given and the assumptions made in its derivation are analyzed. The work is of a debatable nature and aims to develop a unified point of view on such a problematic topic of the theory of separation of multicomponent molecular and isotopic mixtures as the separation potential and separating capacity.

A unified approach to Plasmon–Polariton and Brewster mode dynamics in media with interfacial surface-admittance

In this article we develop an ab-initio formulation for the analysis of certain solutions to the macroscopic Maxwell equations in bulk homogeneous materials that are separated by a planar interface that may sustain field-dependent electric currents induced by a surface admittance tensor. Based on Clemmow’s description of complex inhomogeneous plane time-harmonic waves, a systematic procedure is given that yields particular global solutions in terms of solutions to a system of bivariate polynomial and linear eigen-value equations for a set of six complex dimensionless scalars. This algebraic system is amenable to rapid numerical analysis using Maple or Matlab on a laptop. From the resulting solutions, analytic formulae for the electromagnetic fields can be expressed in terms of values for these six scalars and the electromagnetic phenomenological properties of the bulk media and their interface.We show explicitly how general properties of Surface Plasmon–Polariton (SPP) and Brewster modes follow from this unified viewpoint without appeal to any reflections in a Fresnel formulation. In particular we emphasise that endowing the material interface with (in general) anisotropic admittance properties can lead to new global electromagnetic field characteristics offering new possibilities for the control of surface characteristics by using recent advances in the fabrication of meta-materials.We illustrate our results by showing how a mono-layer of graphene in a normal magneto-static field can be used to construct a tunable meta-surface for SPP generation and how a simple conducting Ohmic interface can be used to excite both transverse electric and transverse magnetic Brewster modes as a function of the interface admittance.

Effects of Mechanical Load and Ionizing Radiation on Glass

This paper develops an approach to investigation of a solid as an integral system whose fundamental properties are determined by the energetics of its structure. Addressing the subject from a unified viewpoint, we consider the formation, accumulation, and transformations of defects in silicate and aluminophosphate glasses, which emit electromagnetic waves in a wide frequency range as a result of cracking. It has been shown that electron irradiation causes spontaneous electrical discharges, whose magnitude depends on the electron energy and irradiation time. The discharges occur at surface defects. Brush discharges develop in a layer where charged particles are distributed. In a thin layer of a charged dielectric, we observe a breakdown effect. The electrical discharge concentrates at surface defects, which can be produced in advance. A discharge can be initiated by approaching a grounded metallic tip to a charged surface even some time after irradiation. A discharge, mechanical loading, cooling, or heating of glass is accompanied by not only a light burst but also electromagnetic emission (EME), which correlates well with a polymorphic transformation process, thermoluminescence, etc. Thus, the release of accumulated energy from unirradiated and irradiated inorganic glasses on heating and cooling is accompanied by pulsed EME, whose intensity depends on the energy stored in the material.

Multimedia and the creation of the scenographic space in the stage realization of Emmanuel Emmasealu’s nerves

The major objective of the scenographic team is to create an illusion of reality, a perception of life as seen from a perspective. In doing this, the textual director (Artistic Director) usually relies on the skills and knowledge of the artistic or audio-pictorial director (Technical Director) to coordinate all the virtual and acoustic aspects of the production into a unified point of view for the audience, to reinforce the directorial approach and spine of the production. The skills and knowledge required by the artistic director in designing and coordinating the audio-pictorial composition goes a long way in determining the artistic success of the production. This paper attempts an artistic exploration of theproduction of Emmanuel Emasealu’s Nerves as designed and directed by Idiata Frank, a third-year student of the Department of Theatre Arts, Niger Delta University in an experimental multimedia production in which multi-media effects were well welded with two and three dimensional scenic pieces to affect a stunning presentation of the select text despite the paucity of technical facilities at the NDU theatre. The aim is to highlight the need for innovative approaches to textual and artistic directing in contemporary theatre productions. It is the opinion of the author that the theatre stands to gain from iconoclastic and new approaches to textual an d artistic directing by upcoming studentsdirectors and designers.

Probabilities in the topos approach to branching space-time

There was previously proposed a topos unified view-point both to relativistic and quantum physics [4-5] on the basis of Belnapian branching space-time [3]. In the context of this approach, to any event of the branching space-time there can be associated a local orthocomplemented lattice (logic) of ‘physically reasonable’ propositions made by a localized observer. Elements of these local orthologics are special collections of the so-called Belnapian worlds (maximal upward directed subsets of events) which the local event belongs to. In the ordinary quantum setting, the counterpart of any local orthologic is the lattice of closed subspaces of Hilbert space of the observer’s environment. The present work suggests a natural scheme of inserting truth probabilities of the ‘physically reasonable’ propositions into the topos framework. To this end, the concept of Chu spaces is used. The role of hypothesis for the state of environment is played by an element of local ‘retro-causal’ orthologic. Sufficient condition of functorial character of the law by which Chu space is related to any event is pointed and proved, i.e. a functor is constructed from the branching space-time to the category of all Chu spaces. There presented a theorem on category nature of Bayesian reassessment of hypothesis likelihood made by the local observer.

Shared dynamics of LeuT superfamily members and allosteric differentiation by structural irregularities and multimerization.

The LeuT-fold superfamily includes secondary active transporters from different functional families, which share a common tertiary structure, despite having a remarkably low sequence similarity. By identifying the common structural and dynamical features upon principal component analysis of a comprehensive ensemble of 90 experimentally resolved structures and anisotropic network model evaluation of collective motions, we provide a unified point of view for understanding the reasons why this particular fold has been selected by evolution to accomplish such a broad spectrum of functions. The parallel identification of conserved sequence features, localized at specific sites of transmembrane helices, sheds light on the role of broken helices (TM1 and TM6 in LeuT) in promoting ion/substrate binding and allosteric interconversion between the outward- and inward-facing conformations of transporters. Finally, the determination of the dynamics landscape for the structural ensemble provides a promising framework for the classification of transporters based on their dynamics, and the characterization of the collective movements that favour multimerization.This article is part of a discussion meeting issue ‘Allostery and molecular machines’.

Generalized concurrence in boson sampling

A fundamental question in linear optical quantum computing is to understand the origin of the quantum supremacy in the physical system. It is found that the multimode linear optical transition amplitudes are calculated through the permanents of transition operator matrices, which is a hard problem for classical simulations (boson sampling problem). We can understand this problem by considering a quantum measure that directly determines the runtime for computing the transition amplitudes. In this paper, we suggest a quantum measure named “Fock state concurrence sum” CS, which is the summation over all the members of “the generalized Fock state concurrence” (a measure analogous to the generalized concurrences of entanglement and coherence). By introducing generalized algorithms for computing the transition amplitudes of the Fock state boson sampling with an arbitrary number of photons per mode, we show that the minimal classical runtime for all the known algorithms directly depends on CS. Therefore, we can state that the Fock state concurrence sum CSbehaves as a collective measure that controls the computational complexity of Fock state BS. We expect that our observation on the role of the Fock state concurrence in the generalized algorithm for permanents would provide a unified viewpoint to interpret the quantum computing power of linear optics.

Separation of edge effects in highly non-dipole radiation spectra

Edge effects in spectra of non-dipole radiation from ultra-relativistic electrons passing through various finite targets are analyzed from a unified point of view. Examples include radiation in a finite magnet, bremsstrahlung at double scattering, and bremsstrahlung in an amorphous plate. A generalization of the encountered spectral decomposition property is proposed. The relevance of phenomena of jet–inter-jet radiation interference and electron time delay in the target is emphasized. Features produced by them in the radiation spectra are discussed.