Search

We demonstrate that cryogenic rolling can simultaneously achieve ultrahigh strength and significant ductility in 316L steel, thereby overcoming the existing limits of its tensile properties. The cryogenic-rolled 316L steel exhibited a 1.1 GPa yield strength (YS) at 298 K. Typically, deformed materials exhibit strain softening immediately after yielding with poor uniform ductility. However, during tensile straining, the cryogenic-rolled 316L steel underwent significant strain hardening despite being severely deformed, thus demonstrating exceptional uniform ductility. Consequently, the cryogenic-rolled 316L steel showed a significantly superior strength–ductility combination, impossible with typical cold rolling. The significantly increased YS of the cryogenic-rolled 316L steel resulted from the combined effect of the presence of the hard martensite phase and the refined austenite grains formed by high-density deformation bands. The significant strain hardening in the cryogenic-rolled 316L steel was possible because the low density of dislocations in the austenite matrix enabled the generation of substantial back stress when newly formed dislocations accumulated at obstacles such as grain boundaries during tensile deformation. Partial dislocations in the cryogenic-rolled 316L steel also contributed to considerable strain hardening by suppressing cross-slip during tensile deformation at 298 K—a well-known major mechanism that weakens strain hardening by facilitating dynamic recovery in metallic materials. Our findings suggest a new microstructural strategy for developing commercial steels with superior tensile properties. [ABSTRACT FROM AUTHOR]

Exposure to heavy metals such as lead, cadmium, and mercury poses serious health risks to pregnant women because of their high toxicity. In this study, we investigated the associations of heavy metal exposure with birth outcomes of Korean infants. Data of 5,215 women between 2015 and 2019 were analyzed. This study was part of the Korean Children's Environmental Health (Ko-CHENS) study. Linear regression and logistic regression analyses were used to examine effects of concentrations of lead, cadmium, and mercury on birth weight, small for gestational age, and large for gestational age after adjusting for maternal age groups, parity, infant sex, education, income, smoking, drinking, body mass index, stillbirth, premature birth, diabetes, hypertension, and gestational diabetes. Besides adjusting for these covariates, each metal was mutually adjusted to estimate birth weight and large for gestational age status. Maternal cadmium concentrations during early pregnancy (β = − 39.96; 95% confidence interval (CI): − 63.76, − 16.17) and late pregnancy (β = − 37.24; 95% CI − 61.63, − 12.84) were significantly associated with birth weight. Cadmium levels during early pregnancy (adjusted OR = 0.637; 95% CI 0.444, 0.912) were also associated with large for gestational age status. Our findings suggest that prenatal cadmium exposure, even at a low level of exposure, is significantly associated with low birth weight. [ABSTRACT FROM AUTHOR]

The crack formation mechanisms of Ti–48Al–2Cr–2Nb single tracks processed by laser powder bed fusion were extensively investigated in a wide range of laser powers and scan speeds. The crack patterns were categorized by their directionalities, which were parallel (longitudinal crack) and/or perpendicular (transverse crack) to the scan direction. For the representative process conditions of the keyhole, transition, and conduction modes, cracking behaviors were characterized by combining the fractography and the microstructural analysis. Further, thermal-mechanical finite element method simulations were performed to predict the distribution of temperatures and thermal stresses during the melt pool formation. On the basis of the combined results, the cracks formed in keyhole, transition, and conduction modes were clarified as a solidification crack and/or a thermal crack. In addition, the formation of these cracks was thoroughly understood in terms of thermal stresses and microstructural factors that affect the crack susceptibility. Finally, comprehensive mechanisms responsible for cracking of Ti–48Al–2Cr–2Nb single tracks under laser powder bed fusion were proposed for different process conditions (the keyhole, transition and conduction modes). [ABSTRACT FROM AUTHOR]

The time at which hypertension treatment should be initiated for different age groups and sexes remains controversial. We aimed to determine whether the association between blood pressure (BP) and major adverse cardiovascular events (MACE) varies with age and sex. This study enrolled 327,328 subjects who had not taken antihypertensive medication in the Korean National Health Service-National Health Screening Cohort between 2002 and 2003. Participants were categorized into four groups according to 2017 American College of Cardiology/American Heart Association hypertension guideline. Primary outcome was MACE characterized by cardiovascular mortality, myocardial infarction, unstable angina, and stroke. During a 10-year follow-up, a significant increase in MACE risk was observed from the stage 1 hypertension group (hazard ratio [HR], 1.23; 95% CI 1.15–1.32; P < 0.001) in time-varying Cox analysis. This relationship was persistent in subjects aged < 70 years, but increased MACE risk was observed only in the stage 2 hypertension group in ≥ 70 years (HR, 1.52; 95% CI 1.32–1.76, P < 0.001). When categorized as per sex, both men and women showed significant MACE risk from stage 1 hypertension. However, on comparing the sexes after stratifying by age, a significantly increased risk of MACE was shown from stage 1 hypertension in men aged < 50 years, but from stage 2 hypertension in men aged ≥ 50 years. Meanwhile, increased MACE risk was observed from stage 2 hypertension in women aged < 60 years, but from stage 1 hypertension in women aged ≥ 60 years. Thus, young male subjects had higher MACE risk than young female subjects, but this difference gradually decreased with age and there was no difference between sexes in subjects aged ≥ 70 years. Therefore, our results suggest that hypertension treatment initiation may need to be individualized depending on age and sex. [ABSTRACT FROM AUTHOR]

A systematic parametric study was conducted using thermal finite element method simulations in order to calibrate the laser penetration depth and absorptivity as a function of the laser power and scan speed for single tracks of Alloy 718 processed by laser powder bed fusion. A methodology was developed to calibrate both laser penetration depth and absorptivity using an algorithm proposed. Calibrated laser penetration depths and absorptivities captured experimentally observed variations of the melt pool depth and width with the laser power and scan speed, and showed strong correlations with a modified energy density, which is the laser power normalized by a square root of the scan speed (W/(m/s)1/2). The result indicated that the laser penetration depth and absorptivity heavily influence the determination of the melt pool depth and width, respectively. Variations of calibrated laser penetration depths and absorptivities with the laser power and scan speed reasonably depicted physical phenomena related with how incident laser beam interacts with the melt pool under different input energy densities, and were in quantitative agreement with those calculated from an analytical model and observed from the experiment. [ABSTRACT FROM AUTHOR]

Single track and multi-layers of medium-carbon steel (AISI H13) powders were additively deposited on gray cast iron using a directed energy deposition (DED) technique. Multi-scale microstructure characterization using a scanning electron microscopy, an electron probe micro-analyzer and a scanning transmission electron microscopy, and the thermal analysis using finite element method were performed to understand the mechanism for the micro-crack formation, which was found at the single, double and triple layers of medium-carbon steel powders, except for the single track, deposited on a cast iron substrate. The crack formation mechanism was thoroughly investigated by combining the layer-by-layer chemistry variations and the resulting microstructural evolution upon exposure to thermal cycles during the DED process. It was concluded that micro-cracking was accompanied by the initiation of the local graphitization and the formation of plate martensite in the vicinity, which seemed to be kinetically facilitated by an indirect exposure to multiple heating–cooling thermal cycles, not by a direct exposure to a melting-cooling (solidification) cycle. [ABSTRACT FROM AUTHOR]

Appropriate adjustment of various microclimatic and nutrient conditions can improve crop productivity under greenhouse cultivation. Here, we performed non-targeted profiling to investigate metabolite variation in tomato fruits following different supplementary LED lighting (SL) (red: R; blue: B; and a combination of red and blue light: RB, for 1 h/day and 6 h/day per condition) and mineral nutrient supply (N, K, Mg). The different SL treatments affected metabolite variation in tomato fruits more significantly than mineral nutrients. Importantly, regulating the SL period induced a more distinct metabolite composition in tomato fruits than that induced by varying the SL sources. Tomato fruits cultivated under RB for 6 h/day had a relatively higher content of sugar derivatives, especially sucrose, thus influencing the gustatory characteristics of the fruit. In contrast, fruit from tomatoes cultivated under RB for 1 h/day showed a distinctive increase in the abundance of amino acids, organic acids, and several secondary metabolites, adding to its nutritional quality. Intriguingly, the different mineral supplements elicited discriminant metabolic variation in tomato fruits cultivated under reduced levels of mineral supply; however, the effects were insignificant under enhanced levels of mineral supply. Specifically, reduced level in nitrogen supply resulted in a lower abundance of amino acids, whereas reduced level in potassium supply increased metabolite levels including amino acids, sugars, and fatty acids in tomato fruits. In the present study, we employed a non-targeted metabolomics approach to unravel the effects of microclimatic parameters and mineral nutrients on fruit quality parameters of tomato plants, by which regulating the period of SL and reducing the potassium concentration were suggested to improve different nutritional qualities. [ABSTRACT FROM AUTHOR]

The chloroplast is a semiautonomous photosynthetic organelle that is essential for plant growth and development, particularly in crops via manipulation of its photosynthetic capacity and the biosynthesis of carbon skeletons. Plastid ribosomal proteins (PRPs) are crucial for the establishment of the transcription/translation apparatus during chloroplast differentiation. In this study, we isolated and characterized T-DNA-tagged rice mutants with defective chloroplasts, named prpl3, that exhibited a distinct albino seedling lethality. Transmission electronic microscopy (TEM) observations showed that the grana stacks in the mutant were not properly formed, with disrupted thylakoid structures in their chloroplasts. Chlorophyll content was also significantly reduced in the leaves of prpl3 mutant seedlings. PRPL3 contains nuclear genes encoding PRPs localized to the chloroplasts, and prpl3 represents a novel mutant presentation of an impaired PRPL3 gene. Our findings also demonstrated that PRPL3 is responsible for phenotypic alterations by generating additional mutant alleles thereof using CRISPR/Cas9 systems. Expression levels of genes involved in photosynthesis and chloroplast development, including plastidial transcription and translation and photosynthesis, were altered in the prpl3 mutant. These results collectively demonstrate that nuclear-encoded PRPL3 is indispensable for the proper development of chloroplasts in rice. [ABSTRACT FROM AUTHOR]

In the original publication of the article, Fig. 15 was published incorrectly. [ABSTRACT FROM AUTHOR]