Growth Regime Research Articles

Growth kinetics of the adsorbed layer of poly(bisphenol A carbonate) and its effect on the glass transition behavior in thin films.

The glass transition behavior of thin films of poly(bisphenol A carbonate) (PBAC) was studied employing ellipsometry. The glass transition temperature increases with the reduction of the film thickness. This result is attributed to the formation of an adsorbed layer with a reduced mobility compared to bulk PBAC. Therefore, for the first time, the growth kinetics of the adsorbed layer of PBAC was investigated, prepared by leaching samples from a 200 nm thin film which were annealed for several times at three different temperatures. The thickness of each prepared adsorbed layer was measured by multiple scans using atomic force microscopy (AFM). Additionally, an unannealed sample was measured. Comparison of the measurements of the unannealed and the annealed samples provides proof of a pre-growth regime for all annealing temperatures which was not observed for other polymers. For the lowest annealing temperature after the pre-growth stage only a growth regime with a linear time dependence is observed. For higher annealing temperatures the growth kinetics changes from a linear to a logarithmic growth regime at a critical time. At the longest annealing times the films showed signs of dewetting where segments of the adsorbed film were removed from the substrate (dewetting by desorption). The dependence of the surface roughness of the PBAC surface on annealing time also confirmed that the films annealed at highest temperatures for the longest times desorbed from the substrate.

Dynamics and length distributions of microtubules with a multistep catastrophe mechanism

Regarding the experimental observation that microtubule (MT) catastrophe can be described as a multistep process, we extend the Dogterom–Leibler model for dynamic instability in order to discuss the effect that such a multistep catastrophe mechanism has on the distribution of MT lengths in the two regimes of bounded and unbounded growth. We show that in the former case, the steady state length distribution is non-exponential and has a lighter tail if multiple steps are required to undergo a catastrophe. If rescue events are possible, we detect a maximum in the distribution, i.e. the MT has a most probable length greater than zero. In the regime of unbounded growth, the length distribution converges to a Gaussian distribution whose variance decreases with the number of catastrophe steps. We extend our work by applying the multistep catastrophe model to MTs that grow against an opposing force and to MTs that are confined between two rigid walls. We determine critical forces below which the MT is in the bounded regime, and show that the multistep characteristics of the length distribution are largely lost if the growth of an MT in the unbounded regime is restricted by a rigid wall. All results are verified by stochastic simulations.

Detecting Regimes of Economic Growth With Fuzzy Concept-Based Models

The paper presents a new method to detect economic growth regimes based on time-series similarity analysis. The procedure builds upon a fuzzy concept-based model, the Jaccard Index, and a hierarchical clustering procedure. Having introduced the proposed method, we apply it to the time series of economic growth and its proximate factors. Further, we study the stability of the obtained results under different parameters. The proposed procedure allows us to detect groups of countries that share a common growth performance and akin growth mechanisms. Simultaneously, the method let us identify countries that escape any fixed classifications.

Twinned dendrites in CrB-structured intermetallic NiGd

The formation of twinned dendrites was investigated in orthorhombic CrB-structured NiGd. A NiGd droplet embedded in borosilicate glass-flux was processed by differential scanning calorimetry. A small undercooling of ≈ 20 °C was reached and a cross-section of the solidified sample was analyzed with EBSD. A twinned dendrite is found, that exhibits a twin boundary in its center, both parts sharing a <110> direction and a misorientation angle of 40° between its two parts. The present findings are in agreement with model predictions for CrB-structured alloy solidification based on the investigation of deeply undercooled and homogeneously nucleating NiZr. The present investigation on NiGd serves as a first important step to validate the model’s predictions. Due to the observation of twinned dendrites at small undercoolings, the present study may further serve as a first-step to extend the model to heterogeneous growth regimes.

Urban regimes and socially significant projects of the urban environment transformation in the Russian Federation

The authors of the article aim to identify the principles and patterns of mutual influence of socially significant projects of transformation of the urban environment and urban regimes in the Russian Federation. Clarence Stone's concept of urban regimes is used as a theoretical framework. Based on the author's system of criteria of social significance, 6 projects of urban environment transformation in 4 cities were selected and analyzed: Okhta Center and Tuchkov Buyan in St. Petersburg, Zaryadye Park and the development of fields of the Timiryazev Academy in Moscow, St. Catherine's Church in Yekaterinburg and concreting of the embankments of the river Vologda in Vologda. If the initial phase of all projects took place in the realities of local urban growth regimes, with the predominance of the interests of the established coalitions of business and government, then the subsequent increase in the role of public activism in all projects and the change of goal-setting under its influence led to a change in the local urban regime during their implementation. It is shown that in five studied cases, during the implementation of projects, there was a transition of local urban regimes from “growth” to “progressive”, and in one – from “growth” to a greater extent towards the “status quo” regime. The general principles and patterns of mutual influence of socially significant transformation projects and urban regimes in the Russian Federation are identified and described: competitive public interaction of all types of actors; change or relocation of the project as a spatial way of conflict resolution; the prevailing shift from the realization of the interests of government and business in favor of society; involvement of paternalistic tools as a way to achieve consensus. Such conditions of mutual influence of socially significant projects and urban regimes can develop in a certain period in any major Russian city, then we can expect in it similar to the described results of space transformation. The results of the study clearly demonstrate the beginning of the process of local transformation of the dominant urban regimes in the Russian Federation.

Multibeam laser–plasma interaction at the Gekko XII laser facility in conditions relevant for direct-drive inertial confinement fusion

Abstract Laser–plasma interaction and hot electrons have been characterized in detail in laser irradiation conditions relevant for direct-drive inertial confinement fusion. The experiment was carried out at the Gekko XII laser facility in multibeam planar target geometry at an intensity of approximately $3\times {10}^{15}$ W/cm2. Experimental data suggest that high-energy electrons, with temperatures of 20–50 keV and conversion efficiencies of $\eta &lt;1\%$ , were mainly produced by the damping of electron plasma waves driven by two-plasmon decay (TPD). Stimulated Raman scattering (SRS) is observed in a near-threshold growth regime, producing a reflectivity of approximately $0.01\%$ , and is well described by an analytical model accounting for the convective growth in independent speckles. The experiment reveals that both TPD and SRS are collectively driven by multiple beams, resulting in a more vigorous growth than that driven by single-beam laser intensity.

Novel Study of Surface Morphological Properties of Commercial Catalytic Reforming Catalysts Used in Iraqi Refineries by Atomic Force Microscopy (AFM)

Catalytic reforming is one of the most significant processes in the field of petroleum refineries and catalysts as they are considered as the heart of these processes .this paper presents the utilization of Atomic scale microscopy (AFM) to investigate the morphological and the surface properties of two catalytic reforming catalysts that are used in Iraqi refineries (RG582 &amp; PR9). This paper provides a new insight into the study of catalysts since reaction routs significantly rely upon the used catalysts and their basic properties such as morphology, topography, roughness, growth regime and grain size. Keywords: Atomic Force Microscopy (AFM), catalytic reforming catalysts (CRC), surface properties.

Social Security Payments and Financialization: Lessons from the Greek Case

This paper is founded on both the theoretical schemes of financialization, as a new regime of accumulation, and the shareholder value, the everyday finance, the structured finance, as well as the finance-led growth regime, whose special institutional forms concern the wage–labor nexus, the competition form, the monetary regime, the state–society relations, the insertion into the international regime, and the coherence and dynamic of the growth regime. It also aims to examine if the Greek social security system (the “system”) used financial logic in economic policy during the period of 2000q1–2021q3. It is econometrically approached through the short-run Granger causality tests but mainly the autoregressive distributed lag model in order to estimate the long-run relationships of the social contributions and benefits paid, with variables expressing the financialization either of the whole economy or particularly of one of the public sectors. So, these steady-state relationships proved statistically significant, and they are considered to be compatible with several mechanisms of the finance-led growth regime. Thus, the sustainability of the “system” should be insured by the policy makers in the economic progress and the creation of new jobs able to fund it. This article contributes to the literature by offering empirical evidence on the financialization and relevant compilation analysis.

Hedge fund performance persistence under different business cycles and stock market regimes

We examine different aspects of performance persistence of US hedge funds over different business cycles and stock market regimes. During periods of economic growth and bull stock markets, we report performance persistence for up to one year in the risk-adjusted returns of fund portfolios of different investment strategies, which is mainly driven by top fund performers. Performance persistence weakens dramatically during recession periods and bear stock markets. Our results are robust to different combinations of states of economic growth and stock market regimes. Trading strategies constructed on the basis of our results confirm the economic significance of our findings.

Step pinning and hillock formation in (Al,Ga)N films on native AlN substrates

The influence of edge-type threading dislocations (TDs) on the epitaxial growth of AlGaN on native AlN substrates was investigated theoretically and experimentally. In the step flow growth regime, we find that pure edge-type TDs cause a pinning of surface steps, resulting in curved step segments. Theoretical calculations reveal that this pinning mechanism is solely mediated by the altered surface potential due the strain field imposed by the TD. Within the curved step segment, the step width is subject to changes resulting in an altered Ga/Al incorporation rate. According to the density functional theory calculation, this effect is related to the different surface diffusion length of Ga and Al and represents a further destabilization mechanism during step flow growth. Another consequence of surface step pinning is the occurrence of areas where the step width is increased. These areas serve as precursors for 2D nucleation due to an increased adatom density. Once nucleated, these nuclei grow along the c-direction via continuous 2D nucleation, while lateral expansion occurs due to adatom incorporation on the m-facets.

Experimental study on a light–heavy interface evolution induced by two successive shock waves

Richtmyer–Meshkov instability induced by two successive shock waves is experimentally studied in a specific shock tube. To create two successive shock waves synchronously, a driver section is added between the driver and driven sections of the standard shock tube, and an electronically controlled membrane rupture equipment is adopted. The shock-tube flow after the membranes rupture is well described by combining the shock relations, isentropic wave relations with compatibility relations across the contact surface (region). The new shock tube is capable of generating two successive shock waves with controllable strengths and time interval, and provides a relatively ‘clean’ wave system. Then the developments of single-mode light–heavy interfaces with different initial conditions induced by two successive shock waves are investigated. The initial amplitudes are all small enough such that the first-shocked interface is within the linear growth regime at the arrival of the second shock. The results show that if the pre-second-shock perturbation amplitude is small, the linear, nonlinear and modal evolutions of the double-shocked interface can be reasonably predicted by the existing models proposed for predicting the perturbation growth induced by a single shock. For the double-shocked interface, the second shock provides an additional perturbation velocity field to the original one introduced by the first shock impact. The validity of the linear superposition model indicates that the linear superposition of these two perturbation velocity fields is satisfied. Therefore, a double-shocked interface evolves similarly to a single-shocked interface provided that their postshock amplitudes and linear growth rates are the same.

Kinetic model for prediction of subcritical crack growth, crack tip relaxation, and static fatigue threshold in silicate glass

Prediction of brittle fracture of amorphous oxide glasses continues to be a challenge due to the existence of multiple fracture mechanisms that vary with loading conditions. To address this challenge, we present a model for all three regimes of crack growth in glasses. Regimes I and III are controlled by Arrhenius processes while regime II is transport controlled along with a simple Arrhenius model for viscoelastic stress relaxation. Through dimensional arguments and physical reasoning, we propose a single mechanism which underlies both regime III subcritical crack growth and near-crack-tip viscoelastic relaxation. By combining the subcritical crack growth and viscoelastic models we obtain a prediction for a threshold stress intensity, Kth, below which stresses around the crack relax faster than it propagates. For stress intensity KI<Kth, no subcritical crack growth is predicted to occur, allowing for the design of stable glass systems. The prediction is compared to measured subcritical fracture threshold data for soda-lime silica glasses.

The role of mild and hard anodization regimes of iron oxide nanotubes in the photoelectrochemical performance

• Fe 2 O 3 nanotubes (NTs) prepared by electrochemical anodization for solar water splitting applications. • Two regimes of anodization, Mild and Hard, observed in NTs geometrical features ( D p , D int , W , L ) and anodization curves ( j ( t ) and Q ( t )) • Relation between charge curves Q ( t ), nanotubes length ( L ), and introducing porosity ( P ) as a parametric, established to estimate L by an adapted Classical Faraday’s Law. • Estimated L from adapted Classical Faradaýs Law in excellent agreement with the experimental data from SEM. Self-ordered hematite (α-Fe 2 O 3 ) nanotubes have been intensively studied as the ideal geometrical configuration for photoelectrochemical water splitting. In this work, iron oxide nanotubes were produced by a fast electrochemical anodization at different applied voltages (10 to 100 V) and studied their impact on the photoelectrochemical performance of the photoelectrodes. The anodization voltage highly affects the nanotubes length, pore diameter, interpore distance and porosity that ultimately led to different solar performances. The interplay between oxidation and dissolution rates in the electrochemical process at different voltages led to observe two distinct self-ordering NTs growth regimes: (I) mild-anodization regime from 20-60 V, where both NTs linear growth and geometrical structural ordering are observed; (II) hard-anodization regime from 70-100 V, with non-linear decay of nanotubes thickness combined with a decrease of structural ordering. The highest photocurrent of ∼0.5 mA·cm -2 was obtained for sample anodized at 20 V with a porosity of 30 %. A relation between the anodization charge curves Q ( t ), nanotubes length ( L ) and porosity ( P ) was established to estimate L using Q ( t ) curves. L was found to be in excellent agreement with the experimental data from both scanning electron microscopy (SEM) and anodization curves.

Initiation and Propagation of Multiple Fractures in the Horizontal Well of Shale Reservoirs Under Pulse Injection Hydraulic Fracturing

Pulse injection hydraulic fracturing (HF) can release high-energy peak pressure in a split-second, forming a complex hydraulic fracture network in shale reservoirs. However, the initiation and propagation of multiple fractures in the horizontal well of shale reservoirs under pulse injection HF have been inadequately studied. Hence, in this study, a HF model coupling the fracturing fluid flow along the fracture and the rock deformation was adopted, and the effect of the pulsed injection method on multistage HF of horizontal wells was determined. The results show that the pulsed injection HF can improve the fracturing effect of horizontal wells. However, no matter how the injection displacement and pulse frequency change, the propagation length of cracks at both ends seriously disturbed by stress almost remains unchanged. When the dominant fracture is temporarily shielded, the fluid pressure of the non-dominant fractures at both ends disturbed by stress compression increases, and the non-dominant fractures can be further expanded. Thus, a new composite multistaged HF scheme suitable for horizontal wells with pulse-temporary shielding in shale reservoirs was proposed. The method presented here can be adopted to optimize the fracture growth regime and provide a scientific basis for the fracturing operation of the horizontal well in shale reservoirs.

Regulating Zinc Nucleation Sites and Electric Field Distribution to Achieve High-Performance Zinc Metal Anode via Surface Texturing.

Understanding zinc (Zn) deposition behavior and improving Zn stripping and plating reversibility are significant in developing practical aqueous Zn ion batteries (AZIBs). Zn metal is abundant, cost-effective, and intrinsically safe compared with Li. However, their similar inhomogeneous growth regime harms their practicality. This work reports a facile, easily scalable, but effective method to develop a textured Zn with unidirectional scratches on the surface that electrochemically achieves a high accumulated areal capacity of 5530mAhcm-2 with homogenized Zn deposition. In symmetric cells, textured Zn presents a stable cycling performance of 1100 hours (vs 250h of bare Zn) at 0.5mAcm-2 for 0.5mAhcm-2 and lower nucleation and plating overpotentials of 120.5 and 41.8mV. In situ optical microscopy and COMSOL simulation disclose that the textured surface topography can 1) homogenize the electron field distribution on the Zn surface and regulate Zn nucleation and growth, and 2) provides physical space to accommodate Zn deposits,prevent the detachment of "dead" Zn, and improve the structural sufficiency of Zn anode. Moreover, differential electrochemical mass spectrometry analysis find that the textured Zn with regulated interfacial electron activity also presents a higher resistance toward hydrogen evolution and other parasitic reactions.

Separating the Effects of Nonorthogonal Variables on the Hot-Injection Synthesis of Core/Thick-Shell (“Giant”) CdTe/CdS Quantum Dots

“Giant” core/thick-shell quantum dot (QD) nanostructures are of interest due to their unusual optical properties and importance as components of more advanced heterostructures tailored to achieve increasingly complex optical functions. However, reliable one-step seeded growth of these structures poses a significant challenge: one must balance multiple competing reaction processes to find the growth regime that realizes spherical shells of both the target size and high crystalline quality. Adjusting synthesis conditions in thicker-shelled reactions is further complicated by multiple nonorthogonal variables that impact the reaction mechanism. These variables include the reaction volume, reaction concentration, and oleic acid (ligand) concentration. Here, we investigate the seeded growth of core/thick-shell CdTe/CdS QDs by adapting a “flash” shelling method. We systematically vary three key reaction parameters (particle concentration, oleic acid:Cd ratio, and Cd–S:CdTe core ratio) over 30+ different thick-shelling reactions to elucidate the separate and intersecting impacts of these parameters on shell growth. Our analysis of the resulting particle quality reveals that the particle concentration of the reaction plays a critical role in the shell growth mechanism. We find the impact of oleic acid to be dependent on the particle concentration for a given shell thickness. We also find that the optimal conditions shift when targeting increasingly thick shells. The results demonstrate the importance of testing and controlling for synthesis variables across a multidimensional parameter space. We develop and present general experimental design criteria to help guide efficient development of new seeded growth reactions that enable reliable synthesis of thick-shelled nanostructures.

Temporal evolution of γ′ precipitate in HAYNES 282 during ageing: growth and coarsening kinetics, solute partitioning and lattice misfit

Elemental partitioning across the precipitate/matrix interface controls the kinetics of precipitate evolution, during growth and coarsening. We present the first comprehensive analysis of evolutions of both the aspects of microstructure, i.e., the size (of nano-scale, ordered, coherent γ′ precipitates) as well as the lattice misfit (between γ and γ′), in light of elemental partitioning, applied to a Ni-based superalloy, HAYNES 282. In this work, eexperimental analyses by atom-probe tomography, transmission electron microscopy, and x-ray diffraction are combined with thermo-kinetic modelling using ThermoCalc® and TC-PRISMA®. The current study has isolated the growth and the coarsening regimes, analyzed the respective kinetics and identified their individual rate controlling processes, for the first time. While Cr and Ti are found to be the rate controlling in the growth regime due to their larger amount of partitioning need, Mo becomes rate controlling in the coarsening regime. From the APT data, it is however clear that diffusion across the interface remains slowest for Mo, both in the growth and the coarsening stages. For the coarsening kinetics, unlike most of the recent literature, we have used the thermodynamic parameter corresponding to the non-dilute, non-ideal γ solid solution phase in the modified LSW rate equation. This approach provides a much realistic prediction, as Ni-based superalloys show significant deviation from ideality. Constrained misfit has been found to be positive and found to decrease with ageing time in the present alloy. Elemental partitioning explained quantitatively the variation in the lattice parameters and the misfit.

Molecular beam epitaxy, photoluminescence from Mn2+ multiplets and self-trapped exciton states of γ-MnTe single-crystalline thin films

Single-crystalline γ-MnTe thin films with zinc-blende structure were grown epitaxially on InP(111) by molecular beam epitaxy. Two-dimensional growth regime and atomic surface flatness are achieved, and appearance of Laue’s oscillation peaks illustrates the superior crystalline quality and interface of γ-MnTe films. A pseudocrystalbuffer layer is formed at interface releasing the strain led by the large lattice mismatch between γ-MnTe and InP, and then growth of γ-MnTe films with a perfect lattice evidences the high-quality crystallinity in a fully relaxed state. Photoluminescence (PL) emissions from 4T1g(4G) and 4T1(4G) related to Mn2+ ions d-d multiplets are observed with their respective activation energies of ∼142.5 meV and ∼323.5 meV. Such high potentials reflecting the nonradiative recombination indicate the thermal stability of these PL. Moreover, two extra PL transitions assigned to be the emissions from self-trapped exciton (STE) states are found below TN. Time-resolved PL (TRPL) spectra at various temperatures indicate that the relaxation dynamics of photoexcited d-electrons is strongly correlated to the antiferromagnetic ordering transition due to the synergy of magnon, phonon and STE states. These findings suggest that introduction of STE states in a material by controlling its magnetic ordering qualifies the competition in optoelectronics devices.

Effects of viscous and capillary forces on the growth rates of gas bubbles in supersaturated liquid–gas​ solutions

An analytical and numerical study of diffusion growth of overcritical gas bubbles at degassing of the supersaturated-by-gas solution with the explicit full-scale influence of viscous and capillary forces on internal pressure in the bubbles has been presented. This study is based on our recent semi-analytical approach to the same problem (Kuchma and Shchekin, 2021). Generally, this approach allows one to find how the growth rate of overcritical bubbles depends on gas supersaturation, its diffusivity and solubility in solution, solution viscosity, surface tension at bubble surface and how it changes from zero for critical bubbles at unstable equilibrium with solution to sufficiently large values for large overcritical bubbles. A special question concerns approaching the widely used in kinetics of bubble nucleation stationary diffusion regime of growth and not so widely used self-similar non-stationary diffusion regime. As a first step, we have found analytical formulas for the bubble growth rate and the correction function (which takes into account the balance in the number of gas molecules that have left the liquid solution and came into the growing bubble) of small overcritical gas bubbles at strong viscosity of the solution and full account of capillary pressure in the bubbles as a function of the bubble radius. As a second step, we derived asymptotic formulas for the case of low viscosity and small radii of bubbles. As a third step, we obtained the formulas for the bubble growth rate and the correction function at large overcritical radii. Finally, we numerically evaluated the joint effects of viscous and capillary forces on the rate of gas bubble growth at any radius of the overcritical bubble within the wide range of viscosities of the supersaturated-by-gas solution and confirmed all the asymptotic analytical results.

Fast magnetic reconnection and driven plasma rotation in reversed central magnetic shear configuration

Numerical calculations have been carried out to study the nonlinear growth of the double tearing mode (DTM) in the reversed central magnetic shear configuration for medium-size tokamak plasma parameters, based on two-fluid equations and large aspect ratio approximation. Three different regimes of the DTM growth are found. (a) annular crash regime, existing for a small distance but a not too large plasma rotation frequency difference between two resonant surfaces. In this regime the plasma pressure between two resonant surfaces is flattened due to the fast magnetic reconnection in tens of microseconds, in agreement with experimental observations. In addition, a large plasma rotation shear is generated around the edge of the pressure flattening region right after the fast magnetic reconnection. (b) Core crash regime, existing for a medium distance and a relatively low rotation frequency difference between two resonant surfaces, in which the plasma pressure is flattened over a large region up to the magnetic axis during the fast magnetic reconnection in tens of microseconds, in agreement with experimental observation too. (c) No crash regime, existing for a sufficiently large distance and/or frequency difference between two resonant surfaces. In this regime the mode grows slowly in the nonlinear phase and saturates at a finite amplitude, causing a local flattening of the plasma pressure at the resonant surface but without fast crashes.