Principal Regimes Research Articles

Flow regimes in a very wide-gap Taylor-Couette flow with counter-rotating cylinders.

In this study, we discuss the observed flow regimes in Taylor-Couette flow of radius ratio [Formula: see text] for various Reynolds numbers up to [Formula: see text]. We investigate the flow using a visualization method. The flow states in the centrifugally unstable flow are investigated in the case of counter-rotating cylinders and pure inner cylinder rotation. Beside classical known flow states as Taylor-vortex flow and wavy vortex flow, we observe a variety of new flow structures in the cylindrical annulus, especially for the transition to turbulence. Coexisting turbulent and laminar regions inside the system are observed. Turbulent spots and turbulent bursts are observed, as well as an irregular Taylor-vortex flow and non-stationary turbulent vortices. Especially, a single axially aligned columnar vortex between the inner and outer cylinder is found. The principal regimes observed in flow between independently rotating cylinders are summarized in a flow-regime diagram. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (Part 2)'.

Duality and ground-state phase diagram for the quantum XYZ model with arbitrary spin in one spatial dimension

Five duality transformations are unveiled for the quantum XYZ model with arbitrary spin in one spatial dimension. The presence of these duality transformations, together with an extra Hamiltonian symmetry, drastically reduce the entire ground-state phase diagram to two finite regimes—the principal regimes, with all the other ten regimes dual to them. Combining with the determination of critical points from the conventional order parameter approach and/or the fidelity approach to quantum phase transitions, we are able to map out the ground-state phase diagram for the quantum XYZ model with arbitrary spin . This is explicitly demonstrated for and 2. As it turns out, all the critical points, with central charge , are self-dual for half-integer as well as integer spin . However, in the latter case, the presence of the Haldane phase results in extra lines of critical points with central charge , which are not self-dual.

Biodegradation model of porous silicon nanoparticles

Development of porous silicon-based drug delivery systems for theranostics requires a precise control of their biodegradation. Thus, we propose a model for the biodegradation of porous silicon nanoparticles (PSi NPs) based on a diffusion equation combined with Nernst-Brunner mass transfer equation describing the dissolution of silicon and formation of silicic acid (SA). The spatiotemporal distributions of PSi NP porosity and SA concentration were calculated. The model was successfully applied to fitting a great variety of experimental data on more than 10 factors influencing the PSi NP biodegradation kinetics, such as the morphology of PSi NPs, surface composition, properties of surrounding media and protective coating layer. Two principal regimes were found out for systems with either diffusion or dissolution dominating over each other. The results of simulations revealed the values of several important parameters, which are hard to be measured experimentally.

Recombination-Driven Genome Evolution and Stability of Bacterial Species.

While bacteria divide clonally, horizontal gene transfer followed by homologous recombination is now recognized as an important contributor to their evolution. However, the details of how the competition between clonality and recombination shapes genome diversity remains poorly understood. Using a computational model, we find two principal regimes in bacterial evolution and identify two composite parameters that dictate the evolutionary fate of bacterial species. In the divergent regime, characterized by either a low recombination frequency or strict barriers to recombination, cohesion due to recombination is not sufficient to overcome the mutational drift. As a consequence, the divergence between pairs of genomes in the population steadily increases in the course of their evolution. The species lacks genetic coherence with sexually isolated clonal subpopulations continuously formed and dissolved. In contrast, in the metastable regime, characterized by a high recombination frequency combined with low barriers to recombination, genomes continuously recombine with the rest of the population. The population remains genetically cohesive and temporally stable. Notably, the transition between these two regimes can be affected by relatively small changes in evolutionary parameters. Using the Multi Locus Sequence Typing (MLST) data, we classify a number of bacterial species to be either the divergent or the metastable type. Generalizations of our framework to include selection, ecologically structured populations, and horizontal gene transfer of nonhomologous regions are discussed as well.

New perspectives in hardmetal abrasion simulation

The response of tungsten carbide hardmetals with differing binder chemistries and carbide grain sizes to a traversing diamond indenter under load has been investigated in two principal regimes; single pass traverses and a multi-pass regime intended to simulate two-body abrasion experienced when the hardmetal is worn by a hard, high crushing strength abradant. The two-body regime is intended to simulate in-field degradation modes witnessed when a non-compliant counterface is present. The multi-pass test is achieved by a desktop computer program which generates pre-set spatial distributions to define the lateral position of the individual abrasion events with the scratches generated accumulating as a model of an abrasion process. Surfaces (and pre-polished sub-surface sections) were analysed using SEM, optical relocation profilometry, x-ray energy dispersive analysis (EDS) and ion beam milling (FIB). By these means, physical and chemical changes could be analysed; namely surface and sub-surface grain micro-cracking, pluckout, debris generation and re-embedment, grain and binder plasticity and surface oxidation. A comparison is also made between the results of this evaluation and the microstructural mechanisms that occur in standardised macroscopic laboratory abrasion tests including ASTM G65 and ASTM B611.

Fluctuations in the Kinetics of Linear Protein Self-Assembly

Biological systems are characterized by compartmentalization from the subcellular to the tissue level, and thus reactions in small volumes are ubiquitous in living systems. Under such conditions, statistical number fluctuations, which are commonly negligible in bulk reactions, can become dominant and lead to stochastic behavior. We present here a stochastic model of protein filament formation in small volumes. We show that two principal regimes emerge for the system behavior, a small fluctuation regime close to bulk behavior and a large fluctuation regime characterized by single rare events. Our analysis shows that in both regimes the reaction lag-time scales inversely with the system volume, unlike in bulk. Finally, we use our stochastic model to connect data from small-volume microdroplet experiments of amyloid formation to bulk aggregation rates, and show that digital analysis of an ensemble of protein aggregation reactions taking place under microconfinement provides an accurate measure of the rate of primary nucleation of protein aggregates, a process that has been challenging to quantify from conventional bulk experiments.

Superharmonic resonances in a two-dimensional non-linear photonic-crystal nano-electro-mechanical oscillator

We investigate the non-linear mechanical dynamics of a nano-optomechanical mirror formed by a suspended membrane pierced by a photonic crystal. By applying to the mirror a periodic electrostatic force induced by interdigitated electrodes integrated below the membrane, we evidence superharmonic resonances of our nano-electro-mechanical system; the constant phase shift of the oscillator across the resonance tongues is observed on the onset of principal harmonic and subharmonic excitation regimes.

Structure and phase composition of protective coatings on steel produced by methods of liquid-phase calorizing

The main characteristics (thickness, phase composition, and microdistribution of elements) of protective corrosion-resistant coatings on the samples of grade-St3sp steel have been investigated experimentally depending on the parameters of the process of liquid-phase calorizing. The principal conditions and regimes of the calorizing have been chosen, namely, the composition of the salt melt, the temperature, the current density, and the amount of the deposited aluminum (duration of deposition), which ensure the formation of continuous intermetallic coatings on the samples of St3sp steel.

Numerical modelling of magma dynamics coupled to tectonic deformation of lithosphere and crust

Many unresolved questions in geodynamics revolve around the physical behaviour of the two-phase system of a silicate melt percolating through and interacting with a tectonically deforming host rock. Well-accepted equations exist to describe the physics of such systems and several previous studies have successfully implemented various forms of these equations in numerical models. To date, most such models of magma dynamics have focused on mantle flow problems and therefore employed viscous creep rheologies suitable to describe the deformation properties of mantle rock under high temperatures and pressures. However, the use of such rheologies is not appropriate to model melt extraction above the lithosphere–asthenosphere boundary, where the mode of deformation of the host rock transitions from ductile viscous to brittle elasto-plastic. Here, we introduce a novel approach to numerically model magma dynamics, focusing on the conceptual study of melt extraction from an asthenospheric source of partial melt through the overlying lithosphere and crust. To this end, we introduce an adapted set of two-phase flow equations, coupled to a visco-elasto-plastic rheology for both shear and compaction deformation of the host rock in interaction with the melt phase. We describe in detail how to implement this physical model into a finite-element code, and then proceed to evaluate the functionality and potential of this methodology using a series of conceptual model setups, which demonstrate the modes of melt extraction occurring around the rheological transition from ductile to brittle host rocks. The models suggest that three principal regimes of melt extraction emerge: viscous diapirism, viscoplastic decompaction channels and elasto-plastic dyking. Thus, our model of magma dynamics interacting with active tectonics of the lithosphere and crust provides a novel framework to further investigate magmato-tectonic processes such as the formation and geometry of magma chambers and conduits, as well as the emplacement of plutonic rock complexes.

CHARACTERIZATION OF THE RADIATION-DAMAGED PRECURSOR CELLS IN BONE MARROW BASED ON MODELING OF THE PERIPHERAL BLOOD GRANULOCYTES RESPONSE

Bone marrow failure is the major cause of radiation lethality in mammals. Since bone marrow is distributed heterogeneously within trabecular spongiosa encased in a cortex of cortical bone, it is very difficult to measure the extent of the radiation damage directly. However, indirect consequences of damage to marrow, such as reductions in peripheral blood cell counts, are easily measured. In this paper, the authors investgate a mathematical model of the granulopoiesis system that provides quantitative relationships between reductions in peripheral blood cells and the bone marrow precursor cells following radiation exposure. A coarse-grained architecture of cellular replication and production as well as a mechanism for implicit regulation used in this model are discussed. The model is based on previous investigations of rodents. The authors test how well the model matches, in the principal dynamic regime of hematopoiesis, experimental data on large animals as well as empirical data on humans following radiation exposure. Due to its ability to infer, albeit indirectly, radiation damage to bone marrow, this model will provide a useful computational tool in radiation accident management, military operations involving nuclear warfare, radiation therapy, and space radiation risk assessment.

A laboratory study of global-scale wave interactions in baroclinic flow with topography I: multiple flow regimes

A laboratory investigation is presented with the aim of studying systematically the diversity of flows resulting from the interaction of a baroclinic flow with periodic bottom topography. Flow visualisation and particle-tracking experiments were performed using a differentially heated rotating annulus of fluid with sinusoidal bottom topography. Multi-directional regime scans with varying initial locations in parameter space revealed a rich variety of flow regimes, including those with near-axisymmetric flow at upper levels and a weak stationary wave forced by the topography which is evanescent at upper levels, and flows with a strong forced wave at all heights both with and without travelling baroclinic waves. A range of time-dependent and vacillating flows was also found. The parametric occurrence of the principal regimes agrees well with a number of earlier studies, which covered a more limited range and at lower resolution in parameter space. It is clear from these results that multiple flow states at the same point in parameter space are very common in baroclinically unstable flows with topography. The parametric extent of the influence of the topographically forced stationary waves was shown to be qualitatively consistent with the well-known Charney–Drazin criterion for vertical wave propagation.

Production Regimes and the Quality of Employment in Europe

Production regime theory has been one of the most innovative and influential recent contributions to neo-institutional debates about the varieties of capitalism. This review takes issue with its claim that there are major differences in the quality of work between the two principal regime types that are held to characterize European societies—coordinated market economies and liberal market economies—by examining the evidence for Denmark, Finland, Germany, Sweden, and the UK. Although the broad pattern of skill differences corresponds reasonably well to the arguments of the theory, the evidence does not confirm the other claims about work and employment conditions, in particular with respect to employee job control, autonomous work teams, organizational participation, and job security. Rather, it points to the distinctiveness of the Scandinavian countries and hence to the importance of factors that lie outside the explanatory framework of the thesis.

On the Heuristic Value of the Concept of Political Religion and its Application

The thesis here is that the concept of political religion (PR) is useful as a heuristic device or model to explore certain unique features of modern secular revolutionary and/or ultra‐nationalist movements and regimes which develop elaborate ideologies and public rituals. It depends on a broad or ‘Durkheimian’ definition of religion and is not to be confused with the politicisation of traditional religion, which can be found in varying forms in nearly all historic polities. The differences between modern civil religion (CR) and PR are examined, and some of the principal regimes and movements for whom PR may be a useful concept are analysed with regard to their similarities and differences. The conclusion is that both the politicisation of religion and the cultic forms of PR continue to characterise in varying ways some of the major radical new forces of the twentieth century, while much of the Western world tends toward an inchoate kind of incipient, not fully coded PR most simply characterised as Multicultural Political Correctness.

Theory of electron–phonon dynamics in insulating nanoparticles

We discuss the rich vibrational dynamics of nanometer-scale semiconducting and insulating crystals as probed by localized electronic impurity states, with an emphasis on nanoparticles that are only weakly coupled to their environment. Two principal regimes of electron–phonon dynamics are distinguished, and a brief survey of vibrational-mode broadening mechanisms is presented. Recent work on the effects of mechanical interaction with the environment is discussed.

Numerical investigation of particle breakage as applied to mechanical crushing—Part II: Interparticle breakage

A numerical approach to interparticle breakage is applied using the rock failure process analysis code, RFPA2D. A 2D particle assembly in a container is first numerically simulated to obtain the fringe patterns of stress fields that resemble the photoelastic test. Then, in addition, the interparticle breakage of the particle assembly in a chamber is conducted. The chamber consists of a steel container and a steel platen for transferring the load, and contains 15 particles of arbitrary sizes and irregular shapes. A plane strain condition is assumed. The particle bed is loaded under form conditions, in which the size reduction and the applied force are a function of the displacement. The numerical results indicate that, during the crushing process, three principal regimes appear: (i) the elastic deformation regime, where each particle deforms elastically; (ii) the fragmentation regime, where the particle assembly is crushed in a particle-by-particle fashion; and (iii) the assembly hardening regime, where the densified assembly recovers a significant stiffness. The dominant mode of failure is at first splitting, which is more or less parallel to the loading direction, and then progressive crushing, which mainly depends on the confinement from the chamber walls. The analysis of the load–displacement curves of the assembly obtained from the simulations reveals a high undulating load plateau, which suggests a macro-ductile behaviour.

Transitions and scaling laws for electronegative discharge models

The equilibrium of electronegative discharges is studied in the plane-parallel approximation over a wide range of pressures and electron densities, encompassing a number of regimes that have previously been modeled analytically. The transitions between the various regimes (models) have been determined in the input parameter space. It is shown that for a given feedstock gas, these transitions can be found in terms of the two input parameters pp and ne0p, where p is the pressure, ne0 the electron density, and p the system half-length. Here ne0 is used as a convenient input related to the power, and the conversion from electron power to ne0 is given. The input parameter space is partitioned by whether ion flux to the wall or positive-negative ion recombination is the dominant positive ion loss mechanism. For each of the principal regimes, scaling laws are developed for the most important plasma parameters in terms of the input parameters.

Continental subduction and a mechanism for exhumation of high-pressure metamorphic rocks: new modelling and field data from Oman

The physical model presented reveals two principal regimes of continental subduction: a highly compressional (HC) regime and a low compressional (LC) regime characterised by high and low pressure between the overriding and subducting plates, respectively. The pressure is inversely proportional to the pull force, which depends on the difference between average density of the subducting lithosphere and density of the mantle. The subducting continental crust reaches a maximum depth which is proportional to the strength of the crust, inversely proportional to the interplate pressure, and is ca. 200 km on average. The crust then fails, forming a major crustal thrust. The location of failure depends on the regime of subduction (on the interplate pressure): in the HC regime, failure occurs near the front of the subduction (collision) zone, whereas the crust fails at greater depth under the base of the overriding plate in the LC regime. The failure is followed by buoyancy-driven uplift of the subducted crustal slice, while the lithospheric mantle keeps subducting. The uplift causes a normal sense displacement (formation of a normal fault) along the upper surface of the crustal slice. For the LC regime (failure of the crust near the base of the overriding plate), a rapid spontaneous crustal uplift (intrusion into the interplate zone) brings the deeply subducted crust to shallow depths. Under the pressure of this crust the frontal part of the overriding plate undergoes local extension and then fails, forming a tectonic window. The rising material (the high-pressure rocks) is exhumed within this window. In the HC regime, uplift of the subducted crust, after its failure in front of the overriding plate, is possible only with erosion of the relief, which provides an unloading effect, allowing the subducted crustal slice to rise up. The exhumation depth is generally smaller in this regime but the volume of the exhumed material is larger. The HC subduction regime has been shown earlier to match the Himalayan situation. The LC regime fits the situation in the Oman Mountains considered in this paper.

Optical properties of HgTe/CdTe superlattices in the normal, semimetallic, and inverted-band regimes.

The optical properties of HgTe/CdTe superlattices (SL's) in the three principal regimes are summarized. Experimental results from the photoluminescence and the cyclotron resonance of electrons and holes both parallel and perpendicular to the SL layer plane in the SL's in the normal semiconducting regime are presented. These results, together with the previously reported optical and magneto-optical spectra of a series of SL's in the inverted-band regime, are analyzed systematically under the framework of a six-band k\ensuremath{\cdot}p model. Using a single value of 550 meV for the valence-band offset (VBO) the model correctly predicts all the major experimental results. These include (i) the energy gap between the electron subband and the heavy-hole subband and the energy gap between the electron subband and the light-hole subband of the SL's in the normal regime over the temperature range from 4.5 to 150 K, (ii) the in-plane masses of the electrons and holes and the Voigt geometry mass of electrons of the SL's in the normal semiconducting regime, (iii) the in-plane electron and hole masses in a SL in the semimetallic regime, (iv) the energy gap between the second electron subband and the second heavy-hole subband in the SL's in the inverted-band regime, and (v) the electron in-plane masses of the SL's in the inverted-band regime. The value of VBO that fits the experimental results is 550\ifmmode\pm\else\textpm\fi{}50 meV at 5 K and it reduces, probably linearly, to 500\ifmmode\pm\else\textpm\fi{}50 meV at 120 K. The origin of the discrepancy between the value of VBO found in this work and the ones reported in earlier works is discussed.

SPONTANEOUS POLARIZATION OF THE ℤn-BAXTER MODEL

We show that correlation functions of the ℤn-Baxter model in the principal regime satisfy a system of difference equations. We obtain the spontaneous polarization of the ℤn-Baxter model as a solution of the simplest difference equation.

Convection in a rotating cylindrical annulus with azimuthally non-uniform heating

Abstract The paper reports a study of the influence of azimuthally non-uniform heating on the regimes of convective flows in the rotating cylindrical annulus. Laboratory experiments reveal two new principal regimes. In addition to the zonal circulation and wave regimes with different numbers of vortices we obtained a regime in which a wave was standing relative to the walls. The second is a vacillation regime in which vortices of different intensities form and drift at rates which vary with their positions relative to the regions of cooling and heating at the outer boundary. Theoretical analysis, based on a low-order Lorenz-type model, shows that it is possible to describe these regimes in terms of such a model. The study of the standing wave regime was made for uniform heating as well as for a different vertical temperature stratification. Some analogies with atmospheric blocking are discussed.