Artificial Aging Research Articles

An In Vitro Comparison of Elastoplastic and Viscoelastic Behavior of Dental Composites with Reversible Addition–Fragmentation Chain Transfer-Mediated Polymerization

Reversible addition–fragmentation chain transfer (RAFT)-mediated polymerization has been implemented in commercially available bulk-fill dental composites, with the idea of either optimizing polymerization at depth, while providing sufficient opacity, or reducing exposure time. The elastoplastic and viscoelastic behavior of the materials pursuing both ideas are described comparatively in connection with the microstructure of the materials and artificial aging. A 3-point bending test was followed by reliability and fractographical analyses. The elastoplastic and viscoelastic behavior was monitored with an instrumented indentation test equipped with a DMA-module at various frequencies (0.5–5 Hz). Data reveal that the similarity in filler loading is reflected in similar elastic moduli. Increased strength was offset by higher plasticity and creep and was related to microstructure. Aging showed a significantly stronger influence on material behavior than differences in composition. The elastoplastic parameters of both materials deteriorate as a result of aging, but to a material-specific extent. Aging has a strong influence on elastic material behavior, but very little on viscous material behavior. The parameter that is most sensitive to aging is damping behavior. Detailed laboratory characterization indicates comparable in vitro behavior with clinically successful materials.

Using Chromosomal Abnormalities and Germination Traits for the Assessment of Tritipyrum Amphiploid Lines under Seed-Aging and Germination Priming Treatments

Primary Trans Chromosomal Tritipyrum (PTCT) amphiploid is a new cereal grown in saline soil and brackish water for grain and forage production. We evaluated the tolerance to seed deterioration in 13 promising PTCT lines, assessing accelerated aging (AA) tests by using AA boxes with 100% relative humidity at 40 °C for 72 h. The (Ma/b)(Cr/b)F4 and (St/b)(Cr/b)F4) PTCT lines, more sensitive to seed aging, were primed with NaCl, Salicylic Acid (SA), and Polyethylene Glycol (PEG) to increase the seed vigor of artificially aged seeds. Germination and emergence traits, biochemical parameters, and chromosomal abnormalities induced by artificial aging were measured in deteriorated and not-deteriorated seeds. The highest reduction percentages related to seed vigor were observed in (Ka/b)(Cr/b)F2 (34.52) and La(4B,4D)/b (28.15) lines, while the lowest was found in (Ma/b)(Cr/b)F4 (7.65) and (St/b)(Cr/b)F4 (7.46) lines. Seed aging also increases electrolytes, potassium, and protein leakages. Chromosomal abnormalities are caused by seed aging that interferes with chromosome behaviors during cell division. Seed priming on aged seeds revealed an increase in the germination percentage (GP) with PEG treatment, while the priming by SA showed an increase in seedling traits, such as the seedling length (SL2). In conclusion, we highlighted the potential use of different PTCT lines and the effective use of seed priming on deteriorated seed to enhance seed viability and seedling vigor as a useful tool for sustainable agriculture.

INVESTIGATION OF THE STRUCTURE OF ALSI25CU4CR AND ALSI25CU5CR ALLOYS

The hypereutectic aluminium-silicon alloys AlSi25Cu4Cr and AlSi25Cu5Cr are heat treated T5, T6 and T7. The quenching of the alloys was carried out under the same conditions. Artificial aging at T5 was carried out at a temperature of 180º C for 2, 4 and 6h, and at T6 at 180º C for 8, 10, 12 and 14h. The artificial aging of the studied compositions at T7 was carried out at a temperature of 370º C for 20, 40 and 60 min. The influence of heat treatment on the size, shape and distribution of primary and eutectic silicon crystals in the alloy structure was investigated. It was established that the proposed heat treatment regimes do not lead to a significant change in the shape and size of the primary silicon crystals, but contribute to their uniform distribution in the structure of the studied alloys. Rounding of the silicon crystals in the composition of the eutectic of the investigated alloys was observed.

Characterization of Sustainable Asphalt Binders Modified with Styrene–Isoprene–Styrene (SIS) and Processed Oil

The current study aims to evaluate the viscosity and rheological properties of PG 64-22 modified with Styrene–Isoprene–Styrene (SIS) and Processed Oil (PO) to enhance asphalt binder properties. Performance properties were measured at high, intermediate, and low temperatures. PG 64-22 was blended with SIS and Processed Oil at three levels (5%, 10%, and 15% by weight of binder) and two concentrations (6% and 12% by weight of binder), respectively. Modified binders underwent two short and long artificial aging processes, through the spinning of the thin film in an RTFO oven and a pressure aging vessel (PAV). The Superpave binder evaluations were carried out using a rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). According to the findings of the research, the addition of SIS caused higher values of viscosity, but when co-modified with processed oil, there was a substantial decrease in viscosity values. As a result, workability was improved. (1) It was observed that a greater reduction in viscosity was achieved when the processed oil was present at a higher concentration at 135 °C compared to a lower concentration. (2) The study showed that the incorporation of processed oil led to a reduction in rutting performance of the asphalt binder. However, the addition of SIS resulted in a notable enhancement of rutting resistance. (3) The role of processed oil as co-modifier at concentrations of 6% and 12% caused significant decreases in G*sin δ, based on the susceptibility of asphalt molecules to accept oil molecules in their network links. (4) The extracted measurements from the BBR tests indicated that modification with SIS and PO improved the low-temperature cracking resistance significantly. Comparison of asphalt binders modified with 6% and 12% PO and the same SIS content showed significant changes in modification with 12% PO rather than 6%.

Warm Aging of Pre-aged AA6013 Sheet and Its Relevance to Room Temperature and Warm Forming Applications—Experimental and Modeling Analyses

AbstractWarm forming has been shown to be an effective way to increase the formability of various aluminum sheet alloys. If applied to precipitation hardenable alloys, aging and/or coarsening may occur during heating and/or forming processes. As such, there is a potential to leverage the warm forming process to artificially age precipitation hardenable alloys. In this study, the aging characteristics of a pre-aged Al-Mg-Si-Cu alloy (designated AA6013-PA and comprising a 4 h, 100 °C pre-aging cycle following solutionization) were examined using: (i) room temperature tensile and (ii) bendability experiments, as well as (iii) elevated temperature tensile and formability experiments in the temperature range of 220-280 °C. In the pre-aged condition, the alloy exhibited very high work hardening, elongation and bendability. It was found that T6-like properties can be obtained with short duration secondary aging of the AA6013-PA starting temper (410 s at 235 °C), followed by a paint bake cycle (30 min at 177 °C). In such heavily aged conditions, the bendability is found to be moderate and consistent with a T6 temper. Bendability of the pre-aged alloy is shown to be enhanced by reducing the extent of aging, which may be beneficial for applications requiring energy absorption during crash, for example. In the pre-aged condition, AA6013 displayed a 55% improvement in room temperature formability, relative to the T6 condition, for near plane-strain loading using a Nakazima punch, although neither temper exhibited formability improvements through warm forming. The aging kinetics of AA6013-PA were determined from mechanical test data and used to calibrate an aging kinetics model. A strong obstacle model was used to relate precipitation state to yield strength, for artificial aging in the range 220-280 °C. The incremental strength increase due to exposure to an automotive paint cure cycle was also modeled and found to yield accurate results. Warm deformation, as well as room temperature deformation, were shown to enhance the paint bake response of the alloy, reducing the time to the peak aged condition by up to 14% for artificial aging at 177 °C.

Degradation of high density polyethylene packaging by accelerated aging in sea water

AbstractThe increase of plastic waste in the marine environment raises several ecological, human, and biological problems. In this work, an accelerated artificial aging study was conducted in seawater after immersing samples of high‐density polyethylene bottles for several aging times and at three different temperatures. The deterioration of the mechanical properties of High density polyethylene (HDPE) under different aging conditions was investigated using tensile and compression tests. The absorption of seawater by the samples was analyzed using a gravimetric method and Fourier transform infrared spectrometry (FTIR). Further surface analysis of the samples during accelerated aging was performed using a scanning electron microscope. The results show that HDPE loses its ductility and rigidity. FTIR analysis confirms the increase in crystallinity during aging.

Effects of OsAOX1a Deficiency on Mitochondrial Metabolism at Critical Node of Seed Viability in Rice.

Mitochondrial alternative oxidase 1a (AOX1a) plays an extremely important role in the critical node of seed viability during storage. However, the regulatory mechanism is still poorly understood. The aim of this study was to identify the regulatory mechanisms by comparing OsAOX1a-RNAi and wild-type (WT) rice seed during artificial aging treatment. Weight gain and time for the seed germination percentage decreased to 50% (P50) in OsAOX1a-RNAi rice seed, indicating possible impairment in seed development and storability. Compared to WT seeds at 100%, 90%, 80%, and 70% germination, the NADH- and succinate-dependent O2 consumption, the activity of mitochondrial malate dehydrogenase, and ATP contents all decreased in the OsAOX1a-RNAi seeds, indicating that mitochondrial status in the OsAOX1a-RNAi seeds after imbibition was weaker than in the WT seeds. In addition, the reduction in the abundance of Complex I subunits showed that the capacity of the mitochondrial electron transfer chain was significantly inhibited in the OsAOX1a-RNAi seeds at the critical node of seed viability. The results indicate that ATP production was impaired in the OsAOX1a-RNAi seeds during aging. Therefore, we conclude that mitochondrial metabolism and alternative pathways were severely inhibited in the OsAOX1a-RNAi seeds at critical node of viability, which could accelerate the collapse of seed viability. The precise regulatory mechanism of the alternative pathway at the critical node of viability needs to be further analyzed. This finding might provide the basis for developing monitoring and warning indicators when seed viability declines to the critical node during storage.

Evaluation of the Composition, Thermal and Mechanical Behavior, and Color Changes of Artificially and Naturally Aged Polymers for the Conservation of Stained Glass Windows.

Investigations of historical conservation materials on historical stained glass windows of the Naumburg Cathedral in Germany offered an opportunity for the study of polymers, naturally aged in a non-controlled environment. This allowed the conservation history of the cathedral to be traced and expanded by valuable insights. The historical materials were characterized through the use of spectroscopy (FTIR, Raman), thermal analysis, PY-GC/MS, and SEC on taken samples. The analyses show that acrylate resins were predominantly used for conservation. The lamination material from the 1940s is particularly noteworthy. Epoxy resins were also identified in isolated cases. Artificial aging was used to investigate the influence of environmental influences on the properties of the identified materials. Through a multi-stage aging program, influences of UV radiation, high temperatures and high humidity can be considered in isolation. Piaflex F20, Epilox, Paraloid B72 as a modern material and combinations of Paraloid B72/diisobutyl phthalate and PMA/diisobutyl phthalate were investigated. The parameters yellowing, FTIR spectra, Raman spectra, molecular mass and conformation, glass transition temperature, thermal behavior, and adhesive strength on glass were determined. The effects of the environmental parameters on the investigated materials are differentiated. UV and extreme temperatures tend to show a stronger influence than humidity. The comparison of the artificially aged samples with the naturally aged samples from the cathedral shows that the latter were less aged. Recommendations for the conservation of the historical stained glass windows were derived from the results of the investigation.

Effect of the Cu/Mg Ratio on Mechanical Properties and Corrosion Resistance of Wrought Al–Cu–Mg–Ag Alloy

The present study aimed to investigate the influence of magnesium (Mg) on the mechanical properties and corrosion behavior of wrought Al–4Cu–xMg–0.6Ag alloys. The results from Optical Microscope, SEM, XRD analysis, and Thermo-Calc simulation were used to identify the microstructure formed after the aging process. Testing for hardness and tensile strength was conducted, in addition to corrosion testing. It was found that Mg significantly impacts the hardness of the alloys, with a high Mg content (low Cu/Mg ratio) increasing the hardness but reducing the tensile strength and ductility. This study attributed this to the formation of the S phase, which is dependent on both the quantity in the bulk and the size of the phase. The grain size was found to be finer with a higher Mg content, since the particle size inhibits grain growth during the artificial aging process. Counterintuitively, the corrosion activity was reduced in the high-Mg-content alloy due to its large particle size and the reduced galvanic cell effect. This study highlighted the importance of considering the effects of Mg on the mechanical properties and corrosion behavior of Al–Cu–Mg–Ag alloys.

Retention of titanium copings to implant-supported fixed dental prostheses.

The aim of this in vitro study was to assess the effects of using different cements and titanium copings designs on the retention of implant-supported fixed dental prostheses (IFDPs) using a pull-out test. Fifty zirconia (ZirCAD; Ivoclar Vivadent) and 20 prepolymerized denture acrylic resin (AvaDent) rectangular (36mm × 12mm × 8mm) specimens were milled to mimic the lower left segmental portion of the All-on-Four IFDPs. Cylindrical titanium copings (Variobase; Straumann) (V) were used in 2 prepolymerized denture acrylic resin groups (n = 10) while conical titanium copings (Straumann) (C) were used as a control group for zirconia with 4 groups using cylindrical titanium copings. Before cementation, the outer surfaces of all titanium copings and the intaglio bonding surface of prosthetic specimens were airborne-particle abraded. All specimens were cemented following the manufacturer's recommendations and instructions according to the experimental design. After artificial aging (5000 cycles of 5°C 55°C, dwelling time 20s; 150 N, 1.5Hz in a 37°C water bath), all specimens were subjected to retention force testing using a pull-out test using a universal testing machine and a custom fixture with a crosshead speed 5mm/min. Modes of failure were classified as Type 1, 2, or 3. Retention force values were analyzed by the t-test for the prepolymerized denture acrylic resin specimen groups, and 1-way ANOVA and the Tukey test for the zirconia groups at α = 0.05. Mean and standard deviation retention force values varied from 101.1±67.1 to 509.0±65.2 N for the prepolymerized denture acrylic resin specimen groups. The zirconia groups ranged from 572.8±274.7 to 1416.1 ±258.0 N. There is no statistically significant difference in retention force values between V and C specimens cementing to zirconia with Panavia SA cement (Kuraray Noritake) (p = 0.587). The retention forces and failure modes were influenced by the cement used (p < 0.05). Modes of failure were predominantly Type 2 (mixed failure) and Type 1 (adhesive fracture from prosthetic materials) except for the quick-set resin group (Type 3, adhesive failure from coping). When bonding IFDPs onto titanium copings, quick-set resin provided significantly higher retention force for prepolymerized denture acrylic resin prostheses. Conical and cylindrical titanium copings performed similarly when cemented to zirconia with Panavia SA cement under the same protocol. The stability of the bonded interface and retention forces between zirconia prostheses and titanium copings varied from the cement used.

Correlation between Mechanical Properties—Structural Characteristics and Cavitation Resistance of Rolled Aluminum Alloy Type 5083

The 5000 series aluminum alloy 5083 is distinguished by excellent processability, excellent welding characteristics, and a strong resilience to corrosion, particularly in maritime environments. It is employed in the manufacture of ships, automobiles, spacecraft, and industrial buildings. The goal of the current study is to determine whether there is any relationship between the mechanical properties, structural characteristics, and cavitation erosion properties of aluminum alloy 5083 in the H111 state (rolled from 454 °C to 399 °C and annealed at 343 °C by holding in cooled air), followed by artificial ageing at (180 °C) with three maintenance periods of 1 h, 12 h, and 24 h, and at (140 °C) with three maintenance periods of 1 h, 12 h, and 24 h. The cavitation resistance experiments of the experimental samples were performed in accordance with ASTM G32-2016. The resistance to cavitation erosion was determined by making mean erosion penetration rate (MDER) or mean depth of erosion (MDE) analytical diagrams according to the duration of the cavitation attack and by measuring the maximum depth of cavitation erosion in the samples analyzed by stereomicroscopy and scanning electron microscopy. Finally, a structural correlation between the condition of the artificially aged laminate alloy and its resistance to cavitation erosion could be achieved: ageing at 180 °C, maintained for 24 h, could lead to a maximum depth of cavitation erosion MDEmax of about 5 µm.

Investigation on evolution of microstructure and mechanical properties of heat-treatable 6010-S aluminium alloy during gas-based hot sheet metal forming process

Modern hot sheet metal forming processes offer the opportunity, especially in the automotive sector, to meet current demands for ultra-lightweight design. Due to the increased formability at the high process temperatures, high-strength aluminium alloys are increasingly coming into the focus of the industry. However, the complex thermo-mechanical interactions within these processes can lead to undesirable microstructural changes that could have a negative impact on the final mechanical properties. The purpose of this work is therefore to investigate the microstructural evolution of age-hardenable EN AW 6010-S alloy in the course of a modern gas-based sheet metal forming process and to quantify its influence on the resulting mechanical T6 properties. For this purpose, two different components were first formed at laboratory scale and the areas of microstructural interest were identified. Metallographic examinations and EBSD measurements were performed to visualize the influence of process temperature and deformation on the microstructure. EDX analysis helped to identify non-metallic phases. In the next step, artificial aging of the components was performed to increase the mechanical properties. Tensile tests and hardness measurements showed that the deformation and temperature have no negative influence on the final mechanical properties of the alloy.

Development of overall quality index and overall quality map according to tensile mechanical properties and artificial aging heat treatment conditions for cast aluminum alloy using multi-criteria decision-making and multiple regression model

Development of overall quality index and overall quality map according to tensile mechanical properties and artificial aging heat treatment conditions for cast aluminum alloy using multi-criteria decision-making and multiple regression model

Influence of substructures on precipitation behavior and mechanical properties of cryogenic rolled Al–Mg–Si alloys during aging treatment

Cryogenic rolling is a promising method to improve the mechanical properties of Al–Mg–Si alloys. In this paper, the effect of artificial aging treatment on the mechanical properties and microstructures of cryogenic rolled Al–Mg–Si sheet is investigated. The hardness and yield strength of cryogenic rolled alloys decrease at the early aging stage, but the hardness and yield strength of room temperature rolled alloys increase at the early aging stage. Besides, substructures (such as dislocations) are observed in cryogenic rolled alloys but not in room temperature rolled alloys after solution treatment, the degree of recrystallization in the cryogenic rolled alloy is inferior to that in room temperature rolled alloy. The differences lead to the difference in strength between cryogenic rolled alloys and room temperature rolled alloys at the early aging stage. A precipitation mechanism is proposed to explain how these substructures promote precipitate nucleation and growth during artificial aging treatment. Based on the precipitation strengthening theory, a precipitation model is used to explain the strengthening contribution from precipitation during aging treatment, the capacity of precipitation strengthening in cryogenic rolled alloy is much higher than that in room temperature rolled alloy.

Influence of Root Post Materials and Aging on Fracture Strength and Marginal Gap Quality of Ceramic Crowns-An In Vitro Study.

The design of and materials for prosthodontic abutments and posts have significant influences on the fracture resistance of restored teeth. This in vitro study compared the fracture strength and marginal quality of full-ceramic crowns as a function of the inserted root posts via simulation of a five-year period of use. Test specimens were prepared from 60 extracted maxillary incisors using titanium L9 (A), glass-fiber L9 (B), and glass-fiber L6 (C) root posts. The circular marginal gap behavior, linear loading capacity, and material fatigue after artificial aging were investigated. The marginal gap behavior and material fatigue were analyzed using electron microscopy. The linear loading capacity of the specimens was investigated using the Zwick Z005 universal testing machine. None of the tested root post materials showed statistically significant differences in marginal width values (p = 0.921), except in the case of marginal gap location. For Group A, there was a statistically significant difference from the labial to the distal (p = 0.012), mesial (p = 0.000), and palatinal (p = 0.005). Similarly, Group B showed a statistically significant difference from the labial to the distal (p = 0.003), mesial (p = 0.000), and palatinal (p = 0.003). Group C showed a statistically significant difference from the labial to the distal (p = 0.001) and mesial (p = 0.009). Linear load capacity reached mean values of 455.8-537.7 N, and micro-cracks occurred after artificial aging, predominantly in Groups B and C. Through the chosen experimental design, it was shown that the root post material and root post length had no influence on the fracture strength of the test teeth before or after artificial aging. However, the marginal gap location depends on the root post material and its length, which is wider mesially and distally and also tends to be greater palatinally than labially.

Effects of Polishing and Artificial Aging on Mechanical Properties of Dental LT Clear® Resin.

Three-dimensional printing has become incorporated into various aspects of everyday life, including dentistry. Novel materials are being introduced rapidly. One such material is Dental LT Clear by Formlabs, a resin used for manufacturing occlusal splints, aligners, and orthodontic retainers. In this study, a total of 240 specimens, comprising two shapes (dumbbell and rectangular), were evaluated through compression and tensile tests. The compression tests revealed that the specimens were neither polished nor aged. However, after polishing, the compression modulus values decreased significantly. Specifically, the unpolished and nonaged specimens measured 0.87 ± 0.02, whereas the polished group measured 0.086 ± 0.03. The results were significantly affected by artificial aging. The polished group measured 0.73 ± 0.05, while the unpolished group measured 0.73 ± 0.03. In contrast, the tensile test proved that the specimens showed the highest resistance when the polishing was applied. The artificial aging influenced the tensile test and reduced the force needed to damage the specimens. The tensile modulus had the highest value when polishing was applied (3.00 ± 0.11). The conclusions drawn from these findings are as follows: 1. Polishing does not change the properties of the examined resin. 2. Artificial aging reduces resistance in both compression and tensile tests. 3. Polishing reduces the damage to the specimens in the aging process.

Digital versus conventional veneering of zirconia and cobalt chromium crowns: Fracture load before and after thermomechanical aging

Statement of problemTo complement the digital workflow for manufacturing fixed dental prostheses, both high-strength frameworks and esthetic veneers should be designed and fabricated digitally. However, how the fracture load of digitally veneered restorations compares with conventionally fabricated restorations is unclear. PurposeThe purpose of this in vitro study was to examine the fracture load of digitally and conventionally veneered zirconia and cobalt chromium crowns initially and after thermomechanical aging. Material and methodsMilled zirconia and cobalt chromium copings for a maxillary canine were fabricated (N=96). Digital veneers were milled and connected to the copings with a sintered ceramic slurry. The conventional veneers were fabricated by using a master mold, and the crowns were bonded to the cobalt chromium abutments. Half the specimens were subjected to 6000 thermal (5 °C to 55 °C, 60 seconds) and 1 200 000 mechanical (50 N, 1.5 Hz, 0.7 mm lateral movement) cycles opposed by steatite antagonists, and the fracture load was determined. Fracture types were categorized, and scanning electron microscopy performed. The data were analyzed with a 3-way global univariate analysis of variance, t test, the Pearson chi-squared test, and the Weibull modulus (α=.05). ResultsUnlike the framework material (P=.316) and artificial aging (P=.064), the veneering protocol affected the fracture load (P=.007). Digital veneers (range: 2242 to 2929 N) led to lower values than conventional veneers (range: 2825 to 3166 N), which was significant for aged cobalt chromium copings (P=.024; 2242 versus 3107 N). Conventionally veneered crowns showed lower Weibull moduli after thermomechanical aging (range: 3.2 to 3.5) than initially (range: 7.8 to 11.4). The copings of all the zirconia specimens fractured, while chipping occurred with the cobalt chromium specimens. ConclusionsThe high fracture load values of the veneered crowns, even after simulated 5-year aging, indicated sufficient mechanical properties (nearly 4-fold the average occlusal force of 600 N) for the successful clinical application of digitally veneered zirconia and cobalt chromium copings.

Comparative Study on Mechanical Property and Fracture Behavior of Age-Hardened LM4 Monolithic Composites Reinforced with TiB2 and Si3N4.

The study aimed to compare and analyze the mechanical property and fracture behavior of LM4 composites reinforced with TiB2 (1-3 wt.%) and Si3N4 (1-3 wt.%) ceramic powders. A two-stage stir casting process was employed for the effective preparation of monolithic composites. To further enhance the mechanical properties of composites, a precipitation hardening treatment (both single (SSHT) and multistage (MSHT), followed by artificial aging at 100 and 200 °C) was conducted. From mechanical property tests, it was understood that in both the monolithic composites, the properties improved with an increase in wt.% of reinforcements, and composite samples subjected to MSHT + 100 °C aging treatment bested other treatments in terms of hardness and UTS values. Compared to as-cast LM4, there was a 32 and 150% increase in hardness and a 42 and 68% increase in UTS for as-cast and peak-aged (MSHT + 100 °C aging) LM4 + 3 wt.% TiB2 composites, respectively. Similarly, there was a 28 and 124% increase in hardness and a 34 and 54% increase in UTS for as-cast and peak-aged (MSHT + 100 °C aging) LM4 + 3 wt.% Si3N4 composites, respectively. Fracture analysis of the peak-aged composite samples confirmed the mixed mode of fracture in which brittle mode was dominating.

Investigation of the Properties of 316L Stainless Steel after AM and Heat Treatment.

Additive manufacturing, including laser powder bed fusion, offers possibilities for the production of materials with properties comparable to conventional technologies. The main aim of this paper is to describe the specific microstructure of 316L stainless steel prepared using additive manufacturing. The as-built state and the material after heat treatment (solution annealing at 1050 °C and 60 min soaking time, followed by artificial aging at 700 °C and 3000 min soaking time) were analyzed. A static tensile test at ambient temperature, 77 K, and 8 K was performed to evaluate the mechanical properties. The characteristics of the specific microstructure were examined using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The stainless steel 316L prepared using laser powder bed fusion consisted of a hierarchical austenitic microstructure, with a grain size of 25 µm as-built up to 35 µm after heat treatment. The grains predominantly contained fine 300-700 nm subgrains with a cellular structure. It was concluded that after the selected heat treatment there was a significant reduction in dislocations. An increase in precipitates was observed after heat treatment, from the original amount of approximately 20 nm to 150 nm.

Artificial intelligence-estimated biological heart age using 12 lead electrocardiogram predicts mortality and cardiovascular outcomes

Abstract Funding Acknowledgements Type of funding sources: None. Main funding source(s): none Background There is a paucity of data on the artificial intelligence-estimated biological ECG heart age (AI ECG-heart age) for predicting cardiovascular outcomes as distinct from the chronological age (CA). Purpose We sought to investigate whether a deep learning-based algorithm to estimate the AI ECG-heart age using standard 12-lead ECGs predicted mortality and cardiovascular outcomes. Methods We trained and validated a deep neural network using raw ECG digital data from 425,051 12-lead ECGs acquired between January 2006 and December 2021. The network performed a holdout test using a separate set of 97,058 ECGs. Additionally, randomly age-sex matched patients with reduced and preserved ejection fraction (EF) were compared. Results The deep neural network was trained to estimate the AI ECG-heart age (the mean absolute error 5.8 ± 3.9 years and R squared of 0.7 (r=0.84, p&amp;lt;0.0001) (Fig 1A). In the Cox proportional-hazards models after adjusting for relevant co-morbidity factors, the subjects with an AI ECG-heart age of seven years older than the chronological age had higher all-cause mortality (HR 1.62 [1.43-1.84]) and major adverse cardiovascular events (MACEs) (HR 1.92 [1.65-2.23]), while those under seven years had an inverse relationship (HR 0.86 [0.77-0.95] for all-cause mortality; HR 0.73 [0.63-0.84] for MACEs) (Fig 2). Subjects with a reduced EF had a substantially higher mean AI ECG heart-age, QRS duration, and corrected QT intervals than those with a preserved EF (all p&amp;lt;0.001) (Fig 1B). Conclusion The biological heart age estimated by AI had a significant impact on mortality and MACE. Those data suggested that the AI ECG-heart age might facilitate the primary prevention and health care for cardiovascular outcomes.