Three particles size ranges (<25, 25–45 and 45–90μm) of a commercial as-atomized copper powder were used to study the effect on SPS mechanism of particle size, pressure and the temperature at which ...pressure is applied. Under the application of a low initial pressure, densification is due to: particle rearrangement, localized deformation, bulk deformation and neck growth. The first two mechanisms are enhanced by an increase in particle size. Bulk deformation is not affected and neck growth is instead enhanced by a decrease in particle size. If pressure is increased during the SPS cycle, temperature at which it is applied does not influence sintered density significantly, but tensile ductility, which is significant of the effectiveness of sintering, increases if pressure is applied either during or after the bulk densification.
Under the application of a low initial pressure, densification is due to particle rearrangement, localized deformation, bulk deformation and solid state transport phenomena. Only a few necks are formed at low temperature and sintering starts at around 700°C. Neck growth mostly occurs during the fourth step. Display omitted
►SPS mechanisms of copper are: local and bulk deformation followed by neck growth. ►Local deformation increases with particle size due to overheating. ►Neck growth increases on decreasing particle size. ►Density is not influence by temperature at which final pressure is applied. ►Tensile ductility is affected by temperature at which final pressure is applied.
Quantification of the (spatially distributed) natural contributions to the chemical signature of groundwater resources is an emerging issue in the context of competitive groundwater uses as well as ...water regulation and management frameworks. Here, we illustrate a geostatistically-based approach for the characterization of spatially variable Natural Background Levels (NBLs) of target chemical species in large-scale groundwater bodies yielding evaluations of local probabilities of exceedance of a given threshold concentration. The approach is exemplified by considering three selected groundwater bodies and focusing on the evaluation of NBLs of ammonium and arsenic, as detected from extensive time series of concentrations collected at monitoring boreholes. Our study is motivated by the observation that reliance on a unique NBL value as representative of the natural geochemical signature of a reservoir can mask the occurrence of localized areas linked to diverse strengths of geogenic contributions to the groundwater status. We start from the application of the typical Pre-Selection (PS) methodology to the scale of each observation borehole to identify local estimates of NBL values. The latter are subsequently subject to geostatistical analysis to obtain estimates of their spatial distribution and the associated uncertainty. A multimodel framework is employed to interpret available data. The impact of alternative variogram models on the resulting spatial distributions of NBLs is assessed through probabilistic weights based on model identification criteria. Our findings highlight that assessing possible impacts of anthropogenic activities on groundwater environments with the aim of designing targeted solutions to restore a good groundwater quality status should consider a probabilistic description of the spatial distribution of NBLs. The latter is useful to provide enhanced information upon which one can then build decision-making protocols embedding the quantification of the associated uncertainty.
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•Assessment of spatially distributed Natural Background Levels (NBLs) of aquifers.•NBLs of Arsenic and Ammonium of large-scale groundwater bodies are quantified.•Local NBLs and the associated uncertainty are estimated by a multimodel approach.•Exceedance probabilities of threshold concentration can vary significantly in space.•Future regulations should foresee adoption of spatial NBL maps and uncertainties.
This paper deals with the prediction of the macroscopic behavior of a multiphase elastic–viscoplastic material. The proposed homogenization schemes are based on an interaction law postulated by ...Molinari et al. Molinari, A., Ahzi, S., Kouddane, R. 1997. On the self-consistent modelling of elastic–plastic behavior of polycrystals. Mech. Mater., 26, 43–62. Self-consistent schemes are developed to describe the behavior of disordered aggregates. The Mori-Tanaka approach is used to capture the behavior of composite materials, where one phase can be clearly identified as the matrix. The proposed schemes are developed within a general framework where compressible elasticity and anisotropy of the materials are taken into account. Inclusions can have various shapes and orientations. Illustrations of the homogenization procedure are given for a two-phase composite materials. Comparisons between results of the literature and predictions based on the interaction law are performed and have demonstrated the efficiency of the proposed homogenization schemes.
The recently proposed genus
Deshmukh and Oren 2023 is illegitimate because it includes the type species of the genera
Bae
. 2007 and
Yoon and Oh 2012, contravening Rule 51b(1) of the International ...Code of Nomenclature of Prokaryotes. As
Bae
. 2007 is the earlier described genus, we here reclassify 36 species earlier described as belonging to the illegitimate genus
as species of
. We also present an emended description of the genus
.
Summary
Grass cell walls have hydroxycinnamic acids attached to arabinosyl residues of arabinoxylan (AX), and certain BAHD acyltransferases are involved in their addition. In this study, we ...characterized one of these BAHD genes in the cell wall of the model grass Setaria viridis. RNAi silenced lines of S. viridis (SvBAHD05) presented a decrease of up to 42% of ester‐linked p‐coumarate (pCA) and 50% of pCA‐arabinofuranosyl, across three generations. Biomass from SvBAHD05 silenced plants exhibited up to 32% increase in biomass saccharification after acid pre‐treatment, with no change in total lignin. Molecular dynamics simulations suggested that SvBAHD05 is a p‐coumaroyl coenzyme A transferase (PAT) mainly involved in the addition of pCA to the arabinofuranosyl residues of AX in Setaria. Thus, our results provide evidence of p‐coumaroylation of AX promoted by SvBAHD05 acyltransferase in the cell wall of the model grass S. viridis. Furthermore, SvBAHD05 is a promising biotechnological target to engineer crops for improved biomass digestibility for biofuels, biorefineries and animal feeding.
Significance Statement
A BAHD acyltransferase gene was studied, and it was demonstrated that its suppression causes reduction of ester‐linked p‐coumaric acid in the cell walls of Setaria viridis. RNAi silenced lines had higher biomass digestibility with no alteration in the biomass production. Molecular dynamics simulation reinforced the evidence that SvBAHD05 is mainly responsible for the incorporation of p‐coumaric acid onto arabinoxylan, the main hemicellulose in grass cell walls.
A multi-step setup for heavy-flavor studies in high-energy nucleus-nucleus (
AA
) collisions—addressing within a comprehensive framework the initial
production, the propagation in the hot medium ...until decoupling and the final hadronization and decays—is presented. The initial hard production of
pairs is simulated using the POWHEG pQCD event generator, interfaced with the PYTHIA parton shower. Outcomes of the calculations are compared to experimental data in
pp
collisions and are used as a validated benchmark for the study of medium effects. In the
AA
case, the propagation of the heavy quarks in the medium is described in a framework provided by the relativistic Langevin equation. For the latter, different choices of transport coefficients are explored (either provided by a perturbative calculation or extracted from lattice-QCD simulations) and the corresponding numerical results are compared to experimental data from RHIC and the LHC. In particular, outcomes for the nuclear modification factor
R
AA
and for the elliptic flow
v
2
of
D
/
B
mesons, heavy-flavor electrons and non-prompt
J
/
ψ
’s are displayed.
In this study, the friction behavior in metal cutting operations is analyzed using a thermomechanical cutting process model that represents the contact on the rake face by sticking and sliding ...regions. The relationship between the sliding and the overall, i.e. apparent, friction coefficients are analyzed quantitatively, and verified experimentally. The sliding friction coefficient is identified for different workpiece–tool couples using cutting and non-cutting tests. In addition, the effect of the total, sticking and sliding contact lengths on the cutting mechanics is investigated. The effects of cutting conditions on the friction coefficients and contact lengths are analyzed. It is shown that the total contact length on the rake face is 3–5 times the feed rate. It is observed that the length of the sliding contact strongly depends on the cutting speed. For high cutting speeds the contact is mainly sliding whereas the sticking zone can be up to 30% of the total contact at low speeds. From the model predictions and measurements it can be concluded that the sticking contact length is less than 15% for most practical operations. Furthermore, it is also demonstrated that the true representation of the friction behavior in metal cutting operations should involve both sticking and sliding regions on the rake face for accurate predictions. Although the main findings of this study have been observed before, the main contribution of the current work is the quantitative analysis using an analytical model. Therefore, the results presented in this study can help to understand and model the friction in metal cutting.
•Effect of 3 heat treatment temperatures on tensile and fatigue properties.•They mostly affect ductility, tensile strength and electric power consumption.•Notch and plain fatigue strength controlled ...by turning residual stresses and defects.•Effect of defects well captured by Murakami sqrt(area) model.•Notch fatigue well predicted by the theory of critical distances.
This paper investigates the fatigue strength of plain and notched specimens produced via laser powder bed fusion and heat-treated at different temperatures ranging between 800 °C and 950 °C. The effects of internal defectiveness and turning residual stresses are explored through computed tomography and X-ray diffraction. Residual stresses are eliminated in part of the experimental batches through a stress relief. The surface compressive residual stresses push the fatigue crack initiation site below the outer surface and increase the fatigue strength of the notched specimens. The heat-treatment temperature affects mostly the total elongation and the energy consumption, whereas its influence on the fatigue strength is less evident.
Climate change and biological invasions are primary threats to global biodiversity that may interact in the future. To date, the hypothesis that climate change will favour non‐native species has been ...examined exclusively through local comparisons of single or few species. Here, we take a meta‐analytical approach to broadly evaluate whether non‐native species are poised to respond more positively than native species to future climatic conditions. We compiled a database of studies in aquatic and terrestrial ecosystems that reported performance measures of non‐native (157 species) and co‐occurring native species (204 species) under different temperature, CO2 and precipitation conditions. Our analyses revealed that in terrestrial (primarily plant) systems, native and non‐native species responded similarly to environmental changes. By contrast, in aquatic (primarily animal) systems, increases in temperature and CO2 largely inhibited native species. There was a general trend towards stronger responses among non‐native species, including enhanced positive responses to more favourable conditions and stronger negative responses to less favourable conditions. As climate change proceeds, aquatic systems may be particularly vulnerable to invasion. Across systems, there could be a higher risk of invasion at sites becoming more climatically hospitable, whereas sites shifting towards harsher conditions may become more resistant to invasions.
The strain, strain rate and temperature dependency of a boron steel, which was isothermally deformed under uniaxial compression tests, has been investigated at temperatures between 600 and 900°C, and ...at strain rates of 0.1, 1.0 and 10.0
s
−1. Two constitutive models were used to correlate the plastic behavior: the Voce constitutive relation in combination with the kinetic model proposed by Kocks and the phenomenological model proposed by Molinari–Ravichandran. The Kocks model has been introduced in the Voce formulation to describe the temperature and the strain rate dependency of the saturation stress and of the yield stress. The Molinari–Ravichandran model is based on a single internal variable that can be viewed as being related to a characteristic length scale of the microstructure that develops during deformation. It has been shown that the plastic behavior of the boron steel can be well described using these two models.
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