Position-dependent shear-induced austenite-martensite transformation in double-notched TRIP and dual-phase steel samples

While earlier studies on transformation-induced-plasticity (TRIP) steels focused on the determination of the austenite-to-martensite decomposition in uniform deformation or thermal fields, the current research focuses on the determination of the local retained austenite-to-martensite transformation behaviour in an inhomogeneous yet carefully controlled shear-loaded region of double-notched TRIP and dual-phase (DP) steel samples. A detailed powder analysis has been performed to simultaneously monitor the evolution of the phase fraction and the changes in average carbon concentration of metastable austenite together with the local strain components in the constituent phases as a function of the macroscopic stress and location with respect to the shear band. The metastable retained austenite shows a mechanically induced martensitic transformation in the localized shear zone, which is accompanied by an increase in average carbon concentration of the remaining austenite due to a preferred transformation of the austenite grains with the lowest carbon concentration. At the later deformation stages the geometry of the shear test samples results in the development of an additional tensile component. The experimental strain field within the probed sample area is in good agreement with finite element calculations. The strain development observed in the low-alloyed TRIP steel with metastable austenite is compared with that of steels with the same chemical composition containing either no austenite (a DP grade) or stable retained austenite (a TRIP grade produced at a long bainitic holding time). The transformation of metastable austenite under shear is a complex interplay between the local microstructure and the evolving strain fields

Traction force microscopy with optimized regularization and automated Bayesian parameter selection for comparing cells

Adherent cells exert traction forces on to their environment, which allows them to migrate, to maintain tissue integrity, and to form complex multicellular structures. This traction can be measured in a perturbation-free manner with traction force microscopy (TFM). In TFM, traction is usually calculated via the solution of a linear system, which is complicated by undersampled input data, acquisition noise, and large condition numbers for some methods. Therefore, standard TFM algorithms either employ data filtering or regularization. However, these approaches require a manual selection of filter- or regularization parameters and consequently exhibit a substantial degree of subjectiveness. This shortcoming is particularly serious when cells in different conditions are to be compared because optimal noise suppression needs to be adapted for every situation, which invariably results in systematic errors. Here, we systematically test the performance of new methods from computer vision and Bayesian inference for solving the inverse problem in TFM. We compare two classical schemes, L1- and L2-regularization, with three previously untested schemes, namely Elastic Net regularization, Proximal Gradient Lasso, and Proximal Gradient Elastic Net. Overall, we find that Elastic Net regularization, which combines L1 and L2 regularization, outperforms all other methods with regard to accuracy of traction reconstruction. Next, we develop two methods, Bayesian L2 regularization and Advanced Bayesian L2 regularization, for automatic, optimal L2 regularization. Using artificial data and experimental data, we show that these methods enable robust reconstruction of traction without requiring a difficult selection of regularization parameters specifically for each data set. Thus, Bayesian methods can mitigate the considerable uncertainty inherent in comparing cellular traction forces

Early pH Changes in Musculoskeletal Tissues upon Injury-Aerobic Catabolic Pathway Activity Linked to Inter-Individual Differences in Local pH

Local pH is stated to acidify after bone fracture. However, the time course and degree of acidification remain unknown. Whether the acidification pattern within a fracture hematoma is applicable to adjacent muscle hematoma or is exclusive to this regenerative tissue has not been studied to date. Thus, in this study, we aimed to unravel the extent and pattern of acidification in vivo during the early phase post musculoskeletal injury. Local pH changes after fracture and muscle trauma were measured simultaneously in two pre-clinical animal models (sheep/rats) immediately after and up to 48 h post injury. The rat fracture hematoma was further analyzed histologically and metabolomically. In vivo pH measurements in bone and muscle hematoma revealed a local acidification in both animal models, yielding mean pH values in rats of 6.69 and 6.89, with pronounced intra- and inter-individual differences. The metabolomic analysis of the hematomas indicated a link between reduction in tricarboxylic acid cycle activity and pH, thus, metabolic activity within the injured tissues could be causative for the different pH values. The significant acidification within the early musculoskeletal hematoma could enable the employment of the pH for novel, sought-after treatments that allow for spatially and temporally controlled drug release

In situ synchrotron radiation diffraction investigation of the compression behaviour at 350 °C of ZK40 alloys with addition of CaO and Y

The evolution of the microstructure during compression is investigated with in situ synchrotron radiation diffraction in as-cast ZK40, ZK40-2CaO and ZK40-1Y Mg alloys. The specimens were compressed at 350 °C with a strain rate of 10−3 s−1 until 30% deformation. The Y containing alloy showed the highest 0.2% proof strength in compression of 35 MPa at 350 °C which is double that of the ZK40 alloy, while the CaO added alloy shows a moderate increment at 23 MPa. The Y containing alloy shows some work hardening, while the CaO modified and the ZK40 alloys do not show work hardening after yield. Synchrotron radiation diffraction timelines show that continuous and discontinuous dynamic recrystallization occurs during deformation of the ZK40 alloy while a small amount of dynamic recrystallization was observed in the ZK40-1Y alloy. However, dynamic recrystallization was not present in the ZK40-2CaO alloy. SEM-EBSD analysis conducted on the deformed samples shows a significantly high volume fraction of twins in the Y and CaO containing alloys which was absent in the ZK40 alloy. The modified deformation behaviours observed in the CaO and Y containing alloys were attributed to the presence of intermetallic particles found at the grain boundaries and to the role of Ca and Y in stabilising twinning.The authors acknowledge the Deutsches Elektronen-Synchro-tron for the provision of facilities within the framework of proposal I-20130434.RHBacknowledgesUniversityofSãoPaulofor granting the fellowship 'Bolsa Empreendedorismo'

The Bell Theorem as a Special Case of a Theorem of Bass

The theorem of Bell states that certain results of quantum mechanics violate inequalities that are valid for objective local random variables. We show that the inequalities of Bell are special cases of theorems found ten years earlier by Bass and stated in full generality by Vorob'ev. This fact implies precise necessary and sufficient mathematical conditions for the validity of the Bell inequalities. We show that these precise conditions differ significantly from the definition of objective local variable spaces and as an application that the Bell inequalities may be violated even for objective local random variables.Comment: 15 pages, 2 figure

Machine Learning Assisted Design of Experiments for Solid State Electrolyte Lithium Aluminum Titanium Phosphate

Lithium-ion batteries with solid electrolytes offer safety, higher energy density and higher long-term performance, which are promising alternatives to conventional liquid electrolyte batteries. Lithium aluminum titanium phosphate (LATP) is one potential solid electrolyte candidate due to its high Li-ion conductivity. To evaluate its performance, influences of the experimental factors on the materials design need to be investigated systematically. In this work, a materials design strategy based on machine learning (ML) is employed to design experimental conditions for the synthesis of LATP. In the variation of parameters, we focus on the tolerance against the possible deviations in the concentration of the precursors, as well as the influence of sintering temperature and holding time. Specifically, models built with different design selection strategies are compared based on the training data assembled from previous laboratory experiments. The best one is then chosen to design new experiment parameters, followed by measuring the corresponding properties of the newly synthesized samples. A previously unknown sample with ionic conductivity of 1.09 × 10$^{-3}$ S cm$^{-1}$ is discovered within several iterations. In order to further understand the mechanisms governing the high ionic conductivity of these samples, the resulting phase compositions and crystal structures are studied with X-ray diffraction, while the microstructures of sintered pellets are investigated by scanning electron microscopy. Our studies demonstrate the advantages of applying machine learning in designing experimental conditions by the synthesis of desired materials, which can effectively help researchers to reduce the number of required experiments

Weightbearing ovine osteochondral defects heal with inadequate subchondral bone plate restoration: implications regarding osteochondral autograft harvesting

PURPOSE: It is unknown what causes donor site morbidity following the osteochondral autograft transfer procedure or how donor sites heal. Contact pressure and edge loading at donor sites may play a role in the healing process. It was hypothesized that an artificially created osteochondral defect in a weightbearing area of an ovine femoral condyle will cause osseous bridging of the defect from the upper edges, resulting in incomplete and irregular repair of the subchondral bone plate. METHODS: To simulate edge loading, large osteochondral defects were created in the most unfavourable weightbearing area of 24 ovine femoral condyles. After killing at 3 and 6 months, osteochondral defects were histologically and histomorphometrically evaluated with specific attention to subchondral bone healing and subchondral bone plate restoration. RESULTS: Osteochondral defect healing showed progressive osseous defect bridging by sclerotic circumferential bone apposition. Unfilled area decreased significantly from 3 to 6 months (P = 0.004), whereas bone content increased (n.s.). Complete but irregular subchondral bone plate restoration occurred in ten animals. In fourteen animals, an incomplete subchondral bone plate was found. Further common findings included cavitary lesion formation, degenerative cartilage changes and cartilage and subchondral bone collapse. CONCLUSIONS: Osteochondral defect healing starts with subchondral bone plate restoration. However, after 6 months, incomplete or irregular subchondral bone plate restoration and subsequent failure of osteochondral defect closure is common. Graft harvesting in the osteochondral autograft transfer procedure must be viewed critically, as similar changes are also present in humans. LEVEL OF EVIDENCE: Prognostic study, Level III

Evolution of microstructure and mechanical properties in gas tungsten arc welded dual-phase Fe50Mn30Co10Cr10 high entropy alloy

Funding Information: JPO acknowledges the funding by national funds from FCT - Fundação para a Ciência e a Tecnologia , I.P., in the scope of the projects LA/P/0037/2020 , UIDP/50025/2020 and UIDB/50025/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication – i3N. Funding Information: JGL, JS and JPO acknowledge Fundação para a Ciência e a Tecnologia ( FCT - MCTES ) for its financial support via the project UID/00667/2020 (UNIDEMI). Funding Information: JS acknowledges the China Scholarship Council for funding the Ph.D. grant (CSC NO. 201808320394 ). Funding Information: JGL acknowledges FCT – MCTES for funding the Ph.D. grant 2020.07350. BD . Publisher Copyright: © 2023 The AuthorsIn recent years, high entropy alloys (HEAs) have been shown to be promising alternatives to common engineering alloys, depending on their composition and thermomechanical processing. Up to now, several works aimed at improving the mechanical properties and discovering different HEAs given the extremely large compositional possibilities made available by the multicomponent approach associated to these materials. Their processability, however, is an important topic that must be studied. Welding is a key manufacturing technique that will eventually be applied to HEAs. Thus, there is a need to evaluate the microstructure and property changes induced by the weld thermal cycles, to assess the suitability of certain welding process/HEAs combinations for possible industrial applications. In the present work, Gas Tungsten Arc Welding (GTAW) was used to achieve defect-free joints based on a novel transformation induced plasticity (TRIP) Fe50Mn30Co10Cr10 HEA. The microstructure and mechanical behavior of the joints were assessed by means of optical and electron microscopy, synchrotron X-ray diffraction, thermodynamical calculations, microhardness mapping and tensile testing. Overall, an excellent mechanical performance was obtained on the resulting joints, opening the door for their adoption in real-life applications.publishersversionpublishe

Wiring up pre-characterized single-photon emitters by laser lithography

Future quantum optical chips will likely be hybrid in nature and include many single-photon emitters, waveguides, filters, as well as single-photon detectors. Here, we introduce a scalable optical localization-selection-lithography procedure for wiring up a large number of single-photon emitters via polymeric photonic wire bonds in three dimensions. First, we localize and characterize nitrogen vacancies in nanodiamonds inside a solid photoresist exhibiting low background fluorescence. Next, without intermediate steps and using the same optical instrument, we perform aligned three-dimensional laser lithography. As a proof of concept, we design, fabricate, and characterize three-dimensional functional waveguide elements on an optical chip. Each element consists of one single-photon emitter centered in a crossed-arc waveguide configuration, allowing for integrated optical excitation and efficient background suppression at the same time