Yield Plateau Research Articles

Scale to Assess the Sustainability of Rice-Wheat Cropping System

Rice-Wheat Cropping System (RWCS) is a principle cropping system followed in Indo Gangetic Plains (IGP). Though this monocropping system plays a key role in India’s food sufficiency, it has led to various problems such as soil degradation, groundwater exploitation, environmental damage, yield plateau etc., posing challenge and risk to its sustainability. The scale was developed during 2021-22 to assess the perception level of farmers about the sustainability issues in RWCS. Summated rating scale method by Likert with standardized procedures was used to develop this scale. A total of 54 items were collected and sent to experts for relevancy analysis. Based on the results of relevancy analysis, a schedule consisting of 43 items was used to conduct personally interviewed pre-test. The items were further screened for their differentiating ability and thus, the final scale consisted of 31 items. The scale was found to be valid and reliable as ascertained by content validity and split half test reliability method, respectively. The reliability coefficient of 0.884 indicated the higher internal consistency.

Nonlinear patch resistance performance of hybrid titanium-clad bimetallic steel plate girder with web opening

Titanium-clad bimetallic steel (TCBS) is a new type of structural steel, which consists of TA1 cladding with outstanding corrosion resistance and Q235 mild steel base with good mechanical properties. Corrosion weakens the thickness of plates in steel members, which reduces the resistance capacity. The web thickness of the plate girder is relatively thin. Hence, the web is more prone to be weakened due to corrosion. To resolve the above issue, an innovative configuration of introducing TCBS into the plate girder as the web was proposed. The monotonic tensile coupon test results stated that TCBS has no evident yield plateau in its stress-strain curve. An experiment was conducted to investigate the nonlinear resistance performance of the hybrid TCBS girder under patch loading. After the experiment, the wave bending deformation of the web exhibited an axisymmetric distribution, where a tensile field was formed. The plastic hinge was formed in the loading area on the flange. No delamination or cracking in the TCBS was observed. A numerical modeling method for the hybrid TCBS plate girder under patch loading was established. Subsequently, a parametric study of the hybrid TCBS plate girder under patch loading was conducted using the proposed numerical modeling method. The effects of the material model, web opening location, web aspect ratio, height–thickness ratio, and loading location on the resistance behavior of the hybrid TCBS plate girder were thoroughly investigated.

Medium engineering of phenylethanoid transfructosylation catalysed by yeast β-fructofuranosidase.

Tyrosol and hydroxytyrosol, by-products of olive oil production, are valuable substrates for enzymatic transglycosylation that can provide products with pharmaceutical potential. Phenylethanoid fructosides are produced from sucrose and phenylethanoids by the catalytic action of β-fructofuranosidases. This work dealt with the potential of the most abundant β-fructofuranosidase, baker's yeast invertase, for this bioconversion. The effects of sucrose and phenylethanoid concentrations were investigated with a focus on the selectivity of phenylethanoid transfructosylation and fructoside yields. For this purpose, initial rate and progress curve experiments were carried out for the initial (hydroxy)tyrosol and sucrose concentrations of 0.072-0.3M and 1-2M, respectively. Reaction courses exhibited either a maximum or plateau of fructoside yield in the range of about 10-18%. The addition of deep eutectic solvents was applied in the concentration range from 5 to 70% (v/v) to investigate the possibility of shifting the reaction equilibrium towards fructoside synthesis.

Evaluation of Rock Brittleness Based on Complete Stress–Strain Curve

As a basic mechanical property of rocks, brittleness is closely related to the drillability, wellbore stability, and rockburst characteristics of reservoir rocks. Accurate evaluation of rock brittleness is of great significance for guiding oil and gas production and reservoir reconstruction. This paper systematically introduced the commonly used brittleness evaluation methods based on the stress–strain curve and analyzed their theoretical background and mathematical models. Combined with practical engineering application, the characterization effect of commonly used brittleness indexes in various rock samples is verified and optimized, and it is obtained that the brittleness index (B17 in this paper), based on the stress–strain curve and considering energy conversion, has the best characterization result for rock brittleness, which has good differentiation for different rock samples. At the same time, considering that the stress–strain curve under high confining pressure may result in a significant yield plateau phenomenon before and after the peak strength, the endpoint of the plastic yield plateau is used to replace the peak point as the starting point for the drop of bearing capacity. The revised brittleness index is consistent with the changing trend of the original curve, which verifies the reliability of the model. Finally, the method for characterizing the brittleness of Class II curves is supplemented, and the combined brittleness index of rock is established, which verifies the rationality and correctness of the index and provide a more general evaluation method for rock brittleness in engineering.

Compression, Energy Absorption, and Electromagnetic Shielding Properties of Carbon Nanotubes/Al Composite Foams

Herein, pre‐dispersed ball‐milling and space‐holder methods are used to prepare carbon nanotubes (CNTs) reinforced aluminum (Al) matrix composite foams (C‐AMCFs). Systematic research is conducted on the mechanical and electromagnetic shielding properties of C‐AMCFs as well as the optimal ball‐milling time. The results demonstrate a quasi‐linear relationship between CNTs contents and optimal ball‐milling time. With the addition of CNTs, the compressive performances of C‐AMCFs first increase and subsequently decrease. The 2.5 wt% C‐AMCFs have the best mechanical performance, whose yield strength (19.25 MPa), plateau stress (20.87 MPa), and energy absorption capacity (8.874 MJ m−3), are both 1.72, 1.72, and 1.79 times than those of AFs, respectively. In the X‐band (8.2–12.4 GHz), the addition of CNTs in C‐AMCFs can increase their electromagnetic shielding effectiveness. The greatest electromagnetic shielding effectiveness of the 2.0 wt% C‐AMCFs is 30–40 dB. By enhancing the reflection loss at the first interface as well as the absorption and reflection loss inside the cell walls, CNTs play an important role in improving the electromagnetic shielding performance of C‐AMCFs.

Unlocking the hidden variation from wild repository for accelerating genetic gain in legumes.

The fluctuating climates, rising human population, and deteriorating arable lands necessitate sustainable crops to fulfil global food requirements. In the countryside, legumes with intriguing but enigmatic nitrogen-fixing abilities and thriving in harsh climatic conditions promise future food security. However, breaking the yield plateau and achieving higher genetic gain are the unsolved problems of legume improvement. Present study gives emphasis on 15 important legume crops, i.e., chickpea, pigeonpea, soybean, groundnut, lentil, common bean, faba bean, cowpea, lupin, pea, green gram, back gram, horse gram, moth bean, rice bean, and some forage legumes. We have given an overview of the world and India's area, production, and productivity trends for all legume crops from 1961 to 2020. Our review article investigates the importance of gene pools and wild relatives in broadening the genetic base of legumes through pre-breeding and alien gene introgression. We have also discussed the importance of integrating genomics, phenomics, speed breeding, genetic engineering and genome editing tools in legume improvement programmes. Overall, legume breeding may undergo a paradigm shift once genomics and conventional breeding are integrated in the near future.

Compressive properties and energy absorption of rigid polyurethane foam

Rigid polyurethane foams (RPUF) are mainly used as a buffer energy absorption material for the protective structure in buildings, ground vehicles, and aircraft. Its mechanical and energy absorption performance is a vital evaluation basis for its use design. Based on uniaxial compression experimental tests, The stress-strain curve of the mechanical behavior of RPUF at different strain rates and temperatures were obtained. The law and mechanism of strain rate and temperature on mechanical behavior and energy absorption are quantitatively analyzed based on experimental results. It was found that the mechanical properties such as yield stress, plateau stress and energy absorption of RPUF at low temperature and high strain rate all have a high improvement, but neither temperature nor strain rate affected the optimal energy absorption state of RPUF. Combined with the experimental results (stress-strain curves of RPUF at different temperatures and strain rates) and the framework of the sheerwood-frost constitutive model, the relevant parameters of the RPUF shape function, strain rate influence term and temperature influence term are obtained. This relationship and parameter can provide accurate material property simulation analysis.

Localized deformation at initial stages of plastic flow in high-manganese steel

The work is devoted to the study of macroscopic localization of plastic deformation during uniaxial tension of single crystals of the Hadfield steel (Fe – 13 % Mn – 1.03 % C). In the course of studies at the stage of easy sliding, significant differences were found in the nature of macrolocalization of plastic deformation in the single-crystal samples under study. All patterns of deformation localization observed in these cases can be divided into two types. The first type of strain localization corresponds to the initiation at the upper yield point and further propagation of the strain front, which gradually transfers the sample material from undeformed state to deformed one. This manifested itself most clearly in single crystals oriented along the tension axis [377] and [355], where the strain localization pattern appears as a single zone of localized deformation on the yield plateau. Such a deformation front passes through the sample volume only once as a Chernov-Luders band. In this case, the flow of the material is carried out without hardening until all its elements are transferred to the deformed state. Single zones of strain localization were also observed at the stages of easy sliding and yield plateau in the Hadfield steel single crystals oriented along the tension axis [123] and [012]. In the second type of localization, at the stage of easy sliding, synchronous movement along the pattern of several deformation centers occurs. Their movement can be unidirectional and counter, and the speeds are both the same and different from each other. Further deformation of the Hadfield steel single crystals oriented along the tension axis [355] or [012], led to the movement of two deformation localization centers at the stages of easy sliding. In single crystals oriented along [111], the strain localization pattern is respectively represented as four localized strain sites. Consequently, the synchronous movement of deformation fronts occurs along an already deformed, albeit to a small extent, material. As a reason for the difference between the two types of macrostrain localization at stage I (the easy sliding stage and the yield plateau), the number of active sliding systems or tensile twinning in the studied single crystals can be discussed based on crystallographic analysis and metallographic studies.

Experimental study on the post-fire mechanical behaviours of structural steels

The high temperature of fire has an impact on the mechanical properties of structural steel, hindering its use. Q345, Q460, Q550 and Q690 structural streels were chosen to investigate their mechanical behaviours after fire treatment at temperatures from 300 °C to 800 °C and air cooling. The mechanical parameters (yield stress, elastic modulus, yield plateau size, ultimate strength and necking strain) were analysed by considering the fire temperature, and the residual factors of the parameters for the Q345, Q460, Q550 and Q690 steels were compared with the results obtained at an ambient temperature. The results showed that the mechanical parameters for each steel began to reduce when the target temperature exceeded 600 °C, and the residual factor was a descending exponential function or a linear function of the target temperature. The predictive equations of residual factors in the literature, about Q460 and Q690 steels, were collected and analysed, and the new equations were predicted depending on all available experimental data. Finally, a stress–strain model incorporating fire temperature was proposed by a piecewise function to describe the stages of the stress–strain curve (elasticity, yielding and plasticity), and the model can represent the experimental results accurately.

The joining of CP-vanadium and Ti–6Al–4V using the Electron Beam Melting Additive Manufacturing method

The use of electron beam welding for dissimilar welding (DW) of commercially pure (CP) vanadium to Ti–6Al–4V has been investigated via ARCAM S12, an additive manufacturing powder-bed system. Investigations of bead-on-plate welds for Ti–6Al–4V were first conducted to identify the process parameters for full penetration welds with a minimum energy input of 37 mA at a traverse speed of 7 mm/s. Vanadium bead on plate welds produced a penetration of approximately 75%, which was enough to proceed onto DW experiments. Defect-free full penetration welds were produced. The DW weld zone microstructure revealed an elongated dendritic structure comprised of bulky βTi grains and a fine substructure of α' laths. Thermal imaging (TI) showed an increment in radiance temperature ahead of the melt pool, indicating that there is a minimum energy required before keyhole welding is present, confirming mathematical calculations. Mechanical characterisation finds a fair range of hardness across both base metals (BM), heat affected zones (HAZ) and fusion zones (FZ). With no yield plateau in tensile test curves, the material is confirmed to fail on the side with lower mechanical properties, i.e., vanadium, which draws a fair process window for dissimilar welding between Ti6Al4V and vanadium alloys.

Abnormal three-stage plastic deformation in a 17-4 PH stainless steel fabricated by laser powder bed fusion

A 17-4 PH stainless steel has been additively manufactured (AM) using laser powder bed fusion (LPBF). Different from traditional counterpart, the AM 17-4 PH steel exhibits a peculiar dual-phase microstructure containing large amount of retained austenite (66 vol%) and the rest martensite. This metastable structure is highly susceptible to surface polishing, thus widely scattered data of phase constitution are reported in many previous papers. It is found that the thermal martensite transformation is suppressed by the ultra-fine microstructure produced by LPBF, thus giving rise to a large amount of austenite retained. And as a consequence, plastic deformation of the AM 17-4 steel displays an obvious three-stage behavior: (I) yield plateau, (II) severe work hardening, and (III) final necking. Underlying mechanisms are revealed, respectively. At the beginning of plastic deformation, because there is lacking of further strengthening mechanism upon yielding in the fine-grained structure, a plastic instability caused by local softening occurs and leads to the formation of complex Lüders band. When the accumulated mechanical energy plus the intrinsic chemical energy exceeds activation energy of martensite transformation, further plastic deformation results in severe strain-induced martensite transformation (SIMT). The SIMT endows the AM 17-4 steel with extremely high work hardening ability in stage II, consequently, flow stress rises sharply from 490 MPa to the maximum level of 1090 MPa, and most of the retained austenite is exhausted in this stage. Afterward, the work hardening rate drops below the true stress, an increase in strain produces no additional load increase, local necking occurs and leads to final rupture of the AM 17-4 steel.

Knee structure in the laser-intensity dependence of harmonic generation for graphene

We investigate the high-order harmonic generations (HHGs) of graphene irradiated by linearly polarized lasers with intensities in a wide range from $10^{8}$ W/cm$^2$ to $10^{13}$ W/cm$^2$. We find a striking knee structure in the laser intensity dependence of HHGs, which consists of a linear growth regime, followed by a plateau of the saturated HHGs, and then a transition to a nonlinear growth. The knee structure is rather universal for the varied harmonic orders and has been certificated by the calculations of two-band density-matrix equations as well as the \textit{ab initio} calculations of time-dependent density functional theory. Based on the two-band model, we reveal the underlying mechanisms: The behavior of linear growth can be depicted analytically by the perturbative theory of optical conductivity; While, the plateau of saturated HHGs and the transition to a nonlinear growth are caused by the quantum destructive interference and constructive interference of harmonics generated by the electrons corresponding to the lattice momentums around Dirac points and M points in Brillouin zone, respectively. In particular, we find that tuning Fermi energy can effectively alter the knee structure while the profile of the knee structure is not sensitive to the temperature. Our calculations of the third-order harmonic vs. tuning Fermi energy are compared with recent experiment showing a good agreement. Our predicted knee structure and its associated properties are observable with the current experimental techniques.

Numerical analysis of compressive deformation for random closed-cell Al foam model

Most cellular solids presented random structure, while practically periodic models were often used in structure-property relations and numerical models. The finite element method was used to create a 2D random model that replicated the deformation characteristics of cellular models. The influences of porosity and strain rate on the deformation characteristic, energy dissipation mechanisms were investigated. The Poisson’s ratio evolution during compression was also studied. The simulated load-displacement curves were found to be consistent with experimental results, both containing elastic stage, plateau stage, hardening stage and densification stage. The yield load and plateau load were insensitive to the strain rate. In addition, it was also found that the generation and propagation of multiple random shear bands were responsible for the load-displacement characteristic. At the cell/membrane level, four failure modes and corresponding energy dissipation mechanisms were revealed. Moreover, the Poisson’s ratio decreased first and then increased with strain, which right manifested the compressibility of 2D foam in the initial stage and the densification in the end of compression. Meanwhile, the change of the Poisson’s ratio with porosity didn’t follow monotone function relation.

Genomic Architecture of Yield Performance of an Elite Rice Hybrid Revealed by its Derived Recombinant Inbred Line and Their Backcross Hybrid Populations

BackgroundSince its development and wide adoption in China, hybrid rice has reached the yield plateau for more than three decades. To understand the genetic basis of heterosis in rice and accelerate hybrid rice breeding, the yield performances of the elite rice hybrid, Quan-you-si-miao (QYSM) were genetically dissected by whole-genome sequencing, large-scale phenotyping of 1061 recombined inbred lines (RILs) and 1061 backcross F1 (BCF1) hybrids derived from QYSM’s parents across three environments and gene-based analyses.ResultsGenome-wide scanning of 13,847 segregating genes between the parents and linkage mapping based on 855 bins across the rice genome and phenotyping experiments across three environments resulted in identification of large numbers of genes, 639 main-effect QTLs (M-QTLs) and 2736 epistatic QTLs with significant additive or heterotic effects on the trait performances of the combined population consisting of RILs and BCF1 hybrids, most of which were environment-specific. The 324 M-QTLs affecting yield components included 32.7% additive QTLs, 38.0% over-dominant or dominant ones with strong and positive effects and 29.3% under-dominant or incomplete recessive ones with significant negative heterotic effects.63.6% of 1403 genes with allelic introgression from subspecies japonica/Geng in the parents of QYSM may have contributed significantly to the enhanced yield performance of QYSM.ConclusionsThe parents of QYSM and related rice hybrids in China carry disproportionally more additive and under-dominant genes/QTLs affecting yield traits. Further focus in indica/Xian rice breeding should shift back to improving inbred varieties, while breaking yield ceiling of Xian hybrids can be achieved by one or combinations of the three strategies: (1) by pyramiding favorable alleles of additive genes, (2) by eliminating or minimizing under-dominant loci, and (3) by pyramiding overdominant/dominant genes polymorphic, particularly those underlying inter-subspecific heterosis.

Genetic improvement of soybeans in Brazil: South and Midwest regions

AbstractSoybean [Glycine max (L.) Merril] is one of the main crops produced worldwide, and on‐farm yields have increased considerably in the last decades in Brazil. We evaluated the genetic gain for agronomic, phenological, and end‐use quality traits in 29 cultivars in the South Region, and in 38 cultivars in the Midwest Region in Brazil, released from 1966 to 2011. Field trials were conducted in Macroregions 1, 2, and 4, in 2016–2017, 2017–2018, and 2018–2019 crop seasons. The best linear unbiased predictors (BLUP) of the cultivars were obtained for each trait using a linear model. The BLUPs were regressed with the year of release using linear and quadratic regression models. The rates of genetic gain for seed yield ranged from 11.98 to 15.31 kg ha–1 yr–1 (0.33 to 0.42% yr–1) in the South Region, and from 13.58 to 21.84 kg ha–1 yr–1 (0.47 to 0.77% yr–1) in the Midwest Region. New cultivars presented taller plants and more seed oil content, oil and protein yield, and lower seed weight, days to flowering, days to maturity, and seed protein content than old cultivars in the South Region, although with differences between the Macroregions. In the Midwest Region, new cultivars showed higher seed oil content, oil and protein yield, and lower bottom pod height and seed protein content than old cultivars. Our results showed that breeding programs have been efficient to improve soybean yield and other traits across the years, without yield plateaus in sight.

Investigations on the interface-dominated deformation mechanisms of two-dimensional MAX-phase Ti3Al(Cu)C2 nanoflakes reinforced copper matrix composites

Two-dimensional (2D) materials showing the giant advantage over their bulk counterparts are believed to be the ideal reinforcement for metal matrix composites, whereas the deformation mechanism of which is currently unknown. Herein, we investigated the interface effect of 2D MAX phase Ti3Al(Cu)C2 nanoflakes (MAX NFs) obtained by a Cu-atoms-diffusion assisted exfoliation method on the plastic deformation process of Cu matrix. Tensile tests demonstrated a simultaneous enhancement in strength and fracture elongation with the increase of MAX NFs content. The composites exhibited a four-stage deformation process involving an extended “yield plateau” before obvious strain hardening stage. Microstructural examination revealed that the 2D nature of MAX NFs and the coherent interface structure facilitated the nucleation of partial dislocations, which coordinated the initial plastic deformation by gliding and interacting to form Lommer-Cottrel (LC) locks. At high strain levels, both LC locks and MAX NFs served as obstacles for dislocation cross-slip and thus achieved significant forest hardening (or latent hardening) effect, validated by EBSD texture from the in-situ tensile tests and visco-plastic self-consistent simulation. This sort of interface-induced microstructure evolution promoted tortuous micro-cracks along discontinuous slip bands and significant crack bridging and deflection extrinsic toughening mechanisms. The current findings provide a possible strategy of simultaneously enhancing strength and ductility through tailoring 2D geometric shape of reinforcements and their interface with the metal matrix.

Enhanced cryogenic tensile properties through cryogenic cyclic plastic strengthening in a metastable austenitic stainless steel

Pre-strain with large deformation is an effective method to improve the yield ratio of metastable austenitic stainless steel, but it will lead to a significant reduction in elongation. Therefore, a cryogenic cyclic plastic strengthening method is proposed in this paper. Compared with the base metal without strengthening, the strengthened material improved the yield strength at 77 K and maintained high elongation. It is shown that the strengthening eliminated the yield plateau and changed the characteristics of first adequately nucleating and then rapidly phase transformation. This was achieved by the special microstructure prepared by cryogenic cyclic plastic loading, which allowed the strengthened material to contain a large number of phase transformation while still retained the ability of stable phase transformation, so that the phase transformation induced plasticity effect played a full role in the subsequent tensile process and allowed the material to show an excellent combination of strength and ductility.

Effect of cobalt on the mechanical properties of 718 base alloy with 1.2 wt% Al

In this paper, the effect of Co (0–5 wt%) on the mechanical properties of 718 alloy and its strengthening mechanism were studied to clarify the function of Co on the mechanical properties of 718 base alloy. The experimental results showed that the addition of Co refined the grain. After the heat treatment, the addition of Co promoted the precipitation of Laves phase and γ′ phase, but inhibited the precipitation of γ″ phase. With the increasing of the Co content, the tensile strength was increased first and then decreased. It was found that the increase in the tensile strength of the alloy was caused by refining the grains and promoting the intergranular precipitation of the Laves phase. Nevertheless, Co increased the volume fraction of intragranular γ′ phase, while suppressed the precipitation of intragranular precipitation of γ″, thus the intragranular strength of the alloy was reduced. Accordingly, the alloy with 3 wt% Co shows the highest yield strength among the experimental alloys. Besides, the Co content extent 3 wt% will show a yield plateau under room temperature tension, but not in the case of 650 °C tension. It was revealed by analyzing the TEM morphology of the Laves phase in the room-temperature tensile samples and 650 °C tensile samples that the dislocation could shear through the intergranular Laves phase under the 650 °C tensile test, but it was not the case under room temperature tensile test. Therefore, the yield plateau in the stress-strain curves is due to the intergranular Laves phase impeding the dislocation motion.

Intercalibration of the Servicio Nacional de Geología y Minería (SERNAGEOMIN), Chile and WiscAr 40Ar/39Ar laboratories for Quaternary dating

Accurate and precise dating of Quaternary lavas and pyroclastic flow or fall deposits is essential for understanding the evolution of active volcanoes and providing context for future eruptions and hazard assessment. The 40 Ar/ 39 Ar method is commonly employed to date these volcanic materials, however, dating young (<150 ka) K 2 O-poor materials can be challenging owing to low radiogenic 40 Ar* contents that can be difficult to distinguish from trapped atmospheric argon. To address this challenge, a collaborative intercalibration exercise involving the University of Wisconsin-Madison WiscAr Laboratory and the 40 Ar/ 39 Ar Laboratory of the Servicio Nacional de Geología y Minería (SERNAGEOMIN), Chile was conducted on a common set of samples with the aim of refining our methods and optimizing precision and accuracy of age determinations. Groundmass and plagioclase samples were analyzed on a 5-collector Noblesse ion counting mass spectrometer in the WiscAr lab, whereas measurements in the SERNAGEOMIN lab were performed using an ARGUS VI spectrometer equipped with faraday detectors and one compact discrete dynode electron multiplier. Samples for the intercalibration were collected jointly from three Andean Southern Volcanic Zone volcanoes to evaluate the capability of each laboratory to date different materials. Samples from lava flows with 1.0–3.2 wt % K 2 O from Planchon-Peteroa volcanic complex and with <1.0 wt % K 2 O from Calbuco Volcano that are the focus of ongoing geological studies were measured in both laboratories. Single crystals of plagioclase (0.6–1.0 wt% K 2 O) were measured from the voluminous Diamante (Pudahuel) ignimbrite sourced from the Diamante Caldera. Multiple rounds of experiments were conducted including co-irradiation of samples at Oregon State University, as well as irradiations using the CCHEN reactor in Chile to investigate differences in neutron fluence parameters. As a result, SERNAGEOMIN has modified long-used protocols for the CCHEN reactor so that Quaternary samples may be irradiated for periods of time most appropriate for their age. Although less precise than plateau ages, the isochron ages generated in the two laboratories agree at 2σ for each sample. Six of six co-irradiated samples from Planchon-Peteroa yield plateau ages that also show inter-lab agreement at 2σ. The low K 2 O lavas from Calbuco proved more challenging with only three out of five plateau ages in agreement between labs. SERNAGEOMIN blanks were higher and more variable in Calbuco experiments, thus, differences in the variability of the measured 36 Ar blanks between the two laboratories may explain the discrepancy in plateau ages. Analysis of single plagioclase crystals from the Diamante Ignimbrite show excellent agreement between labs for both weighted mean apparent ages and isochron ages. We favor an isochron age for the ignimbrite of 132.4 ± 2.2 ka, however, discrepancies in results between samples from three different outcrops present an interesting geochronologic problem that warrants further study. Overall, the consistency of the results between labs is promising. These new precise age determinations significantly improve our understanding of the temporal evolution of these active volcanoes. • Broad agreement of ages from tephras and lavas measured in two labs. • 40 Ar/ 39 Ar dating of low K 2 O lavas from Calbuco is challenging due to limited 40 Ar*. • We favor an isochron age of ∼132 ± 2 ka ka for the 270 km 3 Diamante Ignimbrite. • Care in sample preparation and irradiation, and control of blanks are essential.

Zinc phosphate, zinc oxide, and their dual-phase coatings on pure Zn foam with good corrosion resistance, cytocompatibility, and antibacterial ability for potential biodegradable bone-implant applications

Zinc (Zn)-based scaffold materials are receiving increasing interest as biodegradable scaffold materials for biomedical applications due to their low elastic modulus and open-cellular interconnected porous structures mimicking those of natural bone. However, the high degradation rate and insufficient mechanical strength of pure Zn scaffolds do not meet the comprehensive requirements for bone-tissue engineering applications. Here, we report on zinc phosphate (ZnP), zinc oxide (ZnO), and dual-phase ZnO + ZnP coatings on a biodegradable pure Zn foam via electrochemical anodic oxidation and subsequent phosphating. The dual-phase-coated foam sample showed a regular, almost spherical open-cellular interconnected porous structure with ∼ 7.9 μm thick surface layers of ZnO and ZnP. Electrochemical and immersion tests in Hanks’ solution showed that the dual-phase-coated foam sample exhibited the highest corrosion resistance, lowest corrosion rate of 172.9 μm/a, and lowest degradation rate of 0.5 mg/d among all the foam samples. Compressive test results showed that the dual-phase-coated foam sample exhibited the highest compressive yield strength (1.8 and 1.1 MPa), plateau strength (2.9 and 2.7 MPa), and compressive strain (90%) before and after 30 d immersion in Hanks’ solution among all the foam samples. Biocompatibility assessment showed that the dual-phase-coated foam sample showed the highest cell viability toward MC3T3-E1 and MG 63 cells in both direct and indirect cell assays among all the foam samples, and its 12.5% extract showed ∼ 107% cell viability of MC3T3-E1 cells and ∼ 101% cell viability of MG 63 cells, indicating a positive effect on cell survival and proliferation. Moreover, the dual-phase-coated Zn foam sample exhibited antibacterial ability against S. aureus. Overall, this dual-phase ZnO + ZnP-coated foam can be considered a promising biodegradable scaffold material for bone repair and regeneration applications.