Growth Regime Research Articles

Additively manufactured characteristics of carbon fibers deposited from alkane precursors

Laser Chemical Vapor Deposition (LCVD) is an additive processing technique in which freestanding fibers are deposited. This is accomplished by the thermal dissociation of a precursor gas under a translating laser focal point. In this study the relationships between deposited carbon fiber growth regimes based on precursor chemistry, microstructure, mechanical properties, and processing conditions are compared. The precursor gases include gases from the alkane family, i.e., methane (CH4), ethane (C2H6), and propane (C3H8) and the alkene family, i.e., ethylene (C2H4). Each of these gases offer differences in molecular geometry, the amount of carbon and hydrogen present per molecule, and molecular weight. In the hyperbaric growth condition, these variances reveal different abilities to access either the surface-reaction kinetic limited or mass transport limited growth regimes. The deposited fibers morphology revealed either a core shell or nodular structure with each of these morphologies a function of the accessible growth regime. The fracture stress for the different fibers, in each of the accessible growth regimes, are compared revealing a strength dependence that is linked to the extent of graphitization (via Raman spectroscopy characterization). Collectively, these outcomes fundamentally address how precursor chemistry is a critical variable in the manipulation of the processing-structure-property space in LCVD carbon fibers.

Four-dimensional microstructurally small fatigue crack growth in cyclically loaded nickel superalloy specimen

We nondestructively image a low-solvus high refractory (LSHR) nickel base specimen microstructure during cyclic loading to characterize crack propagation during the microstructurally small crack (MSC) growth regime. Micro-computed tomography (μCT) is used to characterize the material density and identify crack interfaces, while high-energy diffraction microscopy (HEDM) provides snapshots of the microstructural orientation field changes. From these measurements, data are computationally reconstructed and coregistered to describe the specimen’s configuration before load, before crack nucleation, and throughout the crack propagation/loading process. An MSC forms at a FIB-cut notch, which was previously placed to concentrate stress at the center of the specimen gauge, and propagates along a facet parallel to the local {111} crystallographic plane. Analysis of available crystallographic slip directions and measured point-to-point disorientation axes indicate probable single and coplanar slip activity along FCC octahedral planes within this region. Similar analyses of other crack propagation facets reveal generally slower growth along directions favoring zig-zag cross and codirectional cross slip, which are often disfavored at room temperature.

Falling labour share and anaemic growth in Portugal: A post-Keynesian econometric analysis

AbstractIn recent decades, the labour share has experienced a downward trend in Portugal at the same time as a weaker and anaemic growth pattern. This seems to suggest that the fall in the labour share represents an important constraint on Portuguese economic growth, which is contrary to the orthodox claims around wage restraint policies – namely, that such policies are a necessary condition of improved macroeconomic performance, owing to their positive effects on private investment through higher profits and on net exports through reduced unit labour costs and a corresponding rise in competitiveness. This study assesses the relationship between labour share growth and economic growth by performing a time series econometric analysis focused on Portugal from 1971 to 2021. Findings show that labour share growth has positively impacted on economic growth in Portugal, which is in line with heterodox claims and particularly with post-Keynesian economics on the beneficial effects on private consumption played by the growth of wages. Findings also confirm that the Portuguese economy has followed a wage-led growth regime instead of a profit-led growth regime; that is, a rise in wages increases aggregate demand and, therefore, boosts economic growth because its beneficial effect on private consumption more than compensates for a prejudicial effect on private investment and on net exports. The study points out the urgent need to adopt public policies to support the growth of wages to avoid more decades of dismal growth and a new ‘secular stagnation’ in Portugal.

Fiscal policy and social infrastructure provision under alternative growth and distribution regimes

Fiscal policy and social infrastructure provision under alternative growth and distribution regimes

Indium: A surfactant for the growth of ɛ/κ-Ga2O3 by molecular beam epitaxy

The influence of In on the growth of ɛ-Ga2O3 by plasma-assisted molecular beam epitaxy is investigated. We demonstrate alloying of ɛ-Ga2O3 with In and describe its incorporation limits and catalytic effect on the growth kinetics. A special focus lies on the metal-rich growth regime, where we show that In acts as a surfactant for the ɛ-Ga2O3 growth. Both the In-incorporation and the ɛ-(In,Ga)2O3 growth rate follow a non-monotonous trend with increasing In-supply. Whereas both entities show an increase for low In-fluxes, they decrease again for very high In-fluxes, combined with the formation of an atomically smooth surface for layers with thicknesses of several hundred nanometers in this regime. Based on these results, the influence of the growth temperature and the amount of Sn, supplied to initiate the ɛ-Ga2O3 phase formation, is discussed, revealing their impact on the surfactant ability and incorporation of In. Using In as a surfactant, we demonstrate the pseudomorphic growth of ɛ-(In,Ga)2O3/ɛ-(Al,In,Ga)2O3 heterostructures with sharp interfaces and surfaces.

Theoretical foundations of the international interdependence of growth regimes: price system, income–demand linkage, and quantity adjustment

Theoretical foundations of the international interdependence of growth regimes: price system, income–demand linkage, and quantity adjustment

Isolation and identification of green alga Chlorella vulgaris HNUFU001 for environmental selenium enrichment in heterotrophic growth regime

Microalgae, particularly Chlorella, have promising selenium (Se) enrichment capacity and great potential in wastewater treatment and the development of nutraceuticals. To acquire Chlorella strains with strong heterotrophic propensity and robust Se tolerance, this research utilized a heterotrophic isolation strategy along with a high Se concentration medium as selection factors. The combined sequence of the ribosomal small subunit (SSU) and internal transcribed spacer (ITS) was utilized for phylogenetic analysis, and comparative analysis of ITS secondary structures was also integrated to identify the desired strain. A novel subtropical microalgal strain, Chlorella vulgaris HNUFU001 with high Se tolerance, was isolated from water samples in a lake at Hainan University, China. Gaussian process regression was utilized to assess the strain's growth under varying Se concentrations. The intracellular accumulation and extracellular removal of Se were measured using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES), respectively. The maximum intracellular organic Se (92 % of total Se) was observed as 108.835 μg/g dry weight (DW) for 1 mg/L Se treatment. The highest Se removal rate was 40 %. The high Se tolerance and enrichment traits enable Chlorella vulgaris HNUFU001 to be a promising candidate for the heterotrophic production of organic Se-related nutraceuticals.

Eliminating genes for a two-component system increases PHB productivity in Cupriavidus basilensis 4G11 under PHB suppressing, nonstress conditions.

Species of bacteria from the genus Cupriavidus are known, in part, for their ability to produce high amounts of poly-hydroxybutyrate (PHB) making them attractive candidates for bioplastic production. The native synthesis of PHB occurs during periods of metabolic stress, and the process regulating the initiation of PHB accumulation in these organisms is not fully understood. Screening an RB-TnSeq transposon library of Cupriavidus basilensis 4G11 allowed us to identify two genes of an apparent, uncharacterized two-component system, which when omitted from the genome enable increased PHB productivity in balanced, nonstress growth conditions. We observe average increases in PHB productivity of 56% and 41% relative to the wildtype parent strain upon deleting each gene individually from the genome. The increased PHB phenotype disappears, however, in nitrogen-free unbalanced growth conditions suggesting the phenotype is specific to fast-growing, replete, nonstress growth. Bioproduction modeling suggests this phenotype could be due to a decreased reliance on metabolic stress induced by nitrogen limitation to initiate PHB production in the mutant strains. Due to uncertainty in the two-component system's input signal and regulon, the mechanism by which these genes impart this phenotype remains unclear. Such strains may allow for the use of single-stage, continuous bioreactor systems, which are far simpler than many PHB bioproduction schemes used previously, given a similar product yield to batch systems in such a configuration. Bioproductivity modeling suggests that omitting this regulation in the cells may increase PHB productivity up to 24% relative to the wildtype organism when using single-stage continuous systems. This work expands our understanding of the regulation of PHB accumulation in Cupriavidus, in particular the initiation of this process upon transition into unbalanced growth regimes.

Heterogeneous grain growth and vertical mass transfer within a snow layer under a temperature gradient

Abstract. Inside a snow cover, metamorphism plays a key role in snow evolution at different scales. This study focuses on the impact of temperature gradient metamorphism on a snow layer in its vertical extent. To this end, two cold-laboratory experiments were conducted to monitor a snow layer evolving under a temperature gradient of 100 K m−1 using X-ray tomography and environmental sensors. The first experiment shows that snow evolves differently in the vertical: in the end, coarser depth hoar is found in the center part of the layer, with covariance lengths about 50 % higher compared to the top and bottom areas. We show that this heterogeneous grain growth could be related to the temperature profile, to the associated crystal growth regimes, and to the local vapor supersaturation. In the second experiment, a non-disturbing sampling method was applied to enable a precise observation of the basal mass transfer in the case of dry boundary conditions. An air gap, characterized by a sharp drop in density, developed at the base and reached more than 3 mm after a month. The two reported phenomena, heterogeneous grain growth and basal mass loss, create heterogeneities in snow – in terms of density, grain and pore size, and ice morphology – from an initial homogeneous layer. Finally, we report the formation of hard depth hoar associated with an increase in specific surface area (SSA) observed in the second experiment with higher initial density. These microscale effects may strongly impact the snowpack behavior, e.g., for snow transport processes or snow mechanics.

Unveiling the past, shaping the future: Analyzing three centuries of data to explore China's trajectory towards carbon neutrality

China is under enormous pressure - at home and abroad - to mitigate its greenhouse gas (GHG) emissions, which threaten its carbon neutrality target by 2060. The historical emissions growth and the factors affecting this growth can be instrumental in designing China's carbon neutrality target by 2060. However, a study focusing on China's historical emissions is rare, creating a substantial gap in the literature. As such, this study aims to analyze China's historical emissions path and how China's carbon neutrality is affected by economic growth, education, population growth, and political regimes. These variables have been chosen based on theory and empirical literature. We employ extensive time-series data from 1850 to 2021 and deploy the novel Dynamic Autoregressive Distributed Lag (ARDL) simulation model. Carbon neutrality has been measured using greenhouse gas emissions per capita. The study finding reveals an inverted U-shaped relationship between GDP and GHG emissions, proving that Environmental Kuznets Curve (EKC) hypothesis is valid for China when participatory form of governance is considered. But the study fails to validate the EKC hypothesis when the liberal form of governance is employed. Population growth and education boost GHG emissions in the long run in the model with participatory form of governance. Contrarily, in the model with liberal form of governance, the population increases GHG emissions in the short and long run, while education increases GHG emissions only in the long run. Participatory form of governance decreases GHG emissions in the long run, but liberal one decreases GHG emissions only in the short run. Overall, the variations in the political system can have heterogenous effects on China's environmental integrity. As such, Beijing's policy should focus more on the development of a political sphere that is pro-environmental and that stresses on the implementation of environmental governance to tackle China's environmental dilemma. Our findings provide numerous policy suggestions to achieve China's carbon neutrality target by 2060.

Correlation between the Dimensions and Piezoelectric Properties of ZnO Nanowires Grown by PLI-MOCVD with Different Flow Rates

Zinc oxide nanowires (ZnO NWs) have gained considerable attention in the field of piezoelectricity in the past two decades. However, the impact of growth-process conditions on their dimensions and polarity, as well as the piezoelectric properties, has not been fully explored, specifically when using pulsed-liquid injection metal–organic chemical vapor deposition (PLI-MOCVD). In this study, we investigate the influence of the O2 gas and DEZn solution flow rates on the formation process of ZnO NWs and their related piezoelectric properties. While the length and diameter of ZnO NWs were varied by adjusting the flow-rate conditions through different growth regimes limited either by the O2 gas or DEZn reactants, their polarity was consistently Zn-polar, as revealed by piezoresponse force microscopy. Moreover, the piezoelectric coefficient of ZnO NWs exhibits a strong correlation with their length and diameter. The highest mean piezoelectric coefficient of 3.7 pm/V was measured on the ZnO NW array with the length above 800 nm and the diameter below 65 nm. These results demonstrate the ability of the PLI-MOCVD system to modify the dimensions of ZnO NWs, as well as their piezoelectric properties.

Melt Diffusion-Moderated Crystal Growth and its Effect on Euhedral Crystal Shapes

Abstract Crystal growth is often described as either interface-controlled or diffusion-controlled. Here, we study crystal growth in an intermediate scenario where reaction rates at the crystal-melt interface are similar to the rates of diffusive transport of ions through the melt to the advancing crystal surface. To this end, we experimentally investigated euhedral plagioclase crystal shapes in dry mafic (basaltic) and hydrous silicic (haplodacitic) melts. Aspect ratios and inferred relative growth rates of the 3D short (S) and intermediate (I) crystal dimensions vary significantly between mafic and silicic melts, with δS:δI = 1:6–1:20 in basalt and 1:2.5–1:8 in hydrous haplodacite. The lower aspect ratios of plagioclase grown in the silicic melt coincide with 10 to 100× lower melt diffusion rates than in the mafic melt. Using an anisotropic growth model, we show that such differences in melt diffusivity can explain the discrepancy in plagioclase aspect ratios: if interface reaction and melt diffusion rates are of similar magnitude, then the growth of a crystal facet with high interfacial reaction rates may be limited by melt diffusion, while another facet of the same crystal with lower interfacial reaction rates may grow uninhibited by melt diffusivity. This selective control of melt diffusion on crystal growth rates results in progressively more equant crystal shapes as diffusivity decreases, consistent with our experimental observations. Importantly, crystals formed in this diffusion-moderated, intermediate growth regime may not show any classical diffusion-controlled growth features. The proposed model was developed for plagioclase microlites but should be generalisable to all anisotropic microlite growth in volcanic rocks.

Phase separation and ripening in a viscoelastic gel

The process of phase separation in elastic solids and viscous fluids is of fundamental importance to the stability and function of soft materials. We explore the dynamics of phase separation and domain growth in a viscoelastic material such as a polymer gel. Using analytical theory and Monte Carlo simulations, we report a domain growth regime in which the domain size increases algebraically with a ripening exponent [Formula: see text] that depends on the viscoelastic properties of the material. For a prototypical Maxwell material, we obtain [Formula: see text], which is markedly different from the well-known Ostwald ripening process with [Formula: see text]. We generalize our theory to systems with arbitrary power-law relaxation behavior and discuss our findings in the context of the long-term stability of materials as well as recent experimental results on phase separation in cross-linked networks and cytoskeleton.

Endogenous Entry and Growth of Firms with Heterogeneous Firms

We analyze the impact of persistent cost heterogeneity of potential firms on free entry equilibria under a Cournot setting. We show that firm heterogeneity always reduces the number of firms in equilibrium, and that vertical and horizontal market growth have different effects on industry population and firm dynamics. Vertical market growth always promotes entry and growth of new firms, but heterogeneity weakens this effect. For horizontal market growth, we identify two growth regimes: incumbents dominate in large markets with significant heterogeneity, while new entrants grow faster in smaller markets with low heterogeneity. In contrast to existing research, we show that higher degrees of heterogeneity among potential firms reduces entry rates in both cases.

The effect of magnetron power and oxygen pressure on the properties of NiO films deposited by magnetron sputtering in layer-by-layer growth regime

Nickel oxide (NiO) is an attractive material for photovoltaic applications due to its p-type conductivity. This paper investigates the structure, morphology, and optical properties of NiO films deposited by magnetron sputtering. The magnetron power and oxygen pressure were varied in the range of 200–250 W and 0.3–0.7 Pa, respectively, while other growth parameters remained constant. The average transmittance of the deposited NiO films was found to be between 43 and 53% in the wavelength range of 400–800 nm, and the optical band gap varied from 3.28 to 3.33 eV. AFM measurements revealed that the grain size and surface roughness changed in the range of 16–43 nm and 1.3–4.0 nm, respectively. XRD pattern showed reflection from (111), (200), (220), (311), and (222) planes of cubic NiO. We also observed the presence of rhombohedral NiO2 phase in some XRD patterns. We can conclude that the formation of the NiO2 phase in NiO films is more favorable at magnetron power of 200 W. However, this unstable NiO2 phase transforms to NiO phase over time. NiO films deposited by layer-by-layer magnetron sputtering demonstrate appropriate structure and optical properties for their applications in heterostructure design with ZnO films.

Analyzing the Impact of Foreign Capital Inflows and Political Economy on Economic Growth: An Application of Regime Switching Model

The goal of this study is to use the Markov Regime Model (MSM) to evaluate the impact of three important FCIs and the political economy on Pakistan’s economic growth. The current research used quarterly data from 2000 to 2020. The empirical results demonstrate that dictatorship contributes favorably to the high and low growth regime of the economy, while election time contributes positively to the expansion period and adversely in recession times of the economy. Results confirmed that external debt has a strong negative influence on economic growth in both the high and low-growth regimes. Remittances, FDI, and growth, on the other hand, have a positive and substantial link with economic growth. This research suggested that effective fiscal and monetary policies, as well as a suitable political environment, should be provided so that foreign investors would be enticed to invest in Pakistan.

Investigating the Influence of Growth Arrest Mechanisms on Tumour Responses to Radiotherapy

Cancer is a heterogeneous disease and tumours of the same type can differ greatly at the genetic and phenotypic levels. Understanding how these differences impact sensitivity to treatment is an essential step towards patient-specific treatment design. In this paper, we investigate how two different mechanisms for growth control may affect tumour cell responses to fractionated radiotherapy (RT) by extending an existing ordinary differential equation model of tumour growth. In the absence of treatment, this model distinguishes between growth arrest due to nutrient insufficiency and competition for space and exhibits three growth regimes: nutrient limited, space limited (SL) and bistable (BS), where both mechanisms for growth arrest coexist. We study the effect of RT for tumours in each regime, finding that tumours in the SL regime typically respond best to RT, while tumours in the BS regime typically respond worst to RT. For tumours in each regime, we also identify the biological processes that may explain positive and negative treatment outcomes and the dosing regimen which maximises the reduction in tumour burden.

Same same but different? The Mediterranean growth regime and public sector wage-setting before and after the sovereign debt crisis

This paper analyzes the role of public sector wage-setting (PSWS) in Mediterranean countries before and after the Eurozone crisis. Extant literature suggests public sector wage inflation to be the norm in these countries due to the lack of institutional preconditions for wage restraint and the role of PSWS in shoring up the publicly financed domestic demand-led growth regime. Yet, the cases of France, Italy, Portugal and Spain do not to neatly fit these predictions, showing instead notable cross-country and intra-country diachronic variation. We provide an alternative account by treating PSWS as fiscal policy under EMU. Variation in PSWS outcomes before the Eurozone crisis is best explained in terms of the institutions governing PSWS. In France and Portugal, PSWS is highly centralized at the national level, and a strong Finance Ministry plays a central role in the oversight of PSWS to ensure budgetary discipline. To the contrary, Italy and Spain underwent processes of disorganized decentralization of PSWS through the 1990s and 2000s, leading to fragmented – and often clientelist – practices resulting in disorderly inflationary wage increases across the country. After the sovereign debt crisis, all countries relied on restrictive PSWS to support internal devaluation and fiscal adjustment, though with different intensity related to the country-specific problem load and external constraints.

Observability of low-luminosity AGNs in the early Universe with JWST

ABSTRACT Active galactic nuclei (AGNs) in the early Universe are thought to be prominent sources of energy and ionizing photons that affected the growth of their host galaxy and their environment. However, it is still unclear how the supermassive black holes (SMBHs) that fuel these AGNs grew to the observed high masses already at high redshifts. Observations of high-redshift SMBH progenitors or lower luminosity AGNs will thus help characterize the evolution of SMBHs and their impact on the surroundings. With the launch of the JWST, fainter objects at high redshifts can now be detected, including lower luminosity AGNs. We assess the observability of such low-luminosity AGNs, using the cosmological simulation code gizmo to provide a realistic environment for black hole growth in the early Universe. Soon after the first stars are born in the simulation run, we insert stellar-remnant black hole seeds of various initial masses, between 300 and 104 M⊙, at the centre of a dark matter halo and follow their growth until z ∼ 6. Such stellar black hole seeds placed in a typical high-z environment do not significantly accrete and grow to reach masses that can be observed with the JWST under conditions of standard Bondi–Hoyle accretion, as energy input from stellar feedback and chaotic dynamics prevent efficient gas accretion on to the black holes. To be observed with the JWST, rarer but still physically feasible growth regimes, involving Eddington or super-Eddington accretion, would be required. Alternatively, AGN observability may be boosted under even rarer conditions of extreme gravitational lensing.

Economic growth regimes: Evidence from Latin America

This paper studies the effect of economic instability, income inequality and openness in the transition to different growth regimes for 18 Latin American countries during the 1980-2014 period. The study is carried out determining three different levels: low, middle and high economic growth. The countries are categorised according to the method of k-median clustering. We use panel data estimation applying random effects model and ordered logit. The results indicate that instability and inequality negatively affect the economic performance of the region, while openness is not a significant factor in explaining economic growth.