The Effect of Process Parameters on the Temperature and Stress Fields in Directed Energy Deposition Inconel 690 Alloy.

Additive manufacturing (AM) technology has the advantages of designability, short process times, high flexibility, etc., making it especially suitable for manufacturing complex high-performance components for high-end industrial systems. However, the intensive temperature gradients caused by the rapid heating and cooling processes of AM can generate high levels of residual stresses, which directly affect the precision and serviceability of the components. Taking Inconel 690 alloy, which is widely used in nuclear power plants, as the research object, a thermo-coupled mechanical model of temperature field and residual stress field of directed energy deposition (DED) of Inconel 690 was established based on ABAQUS 2019 finite element software to study the influence of process parameters on the temperature history and the distribution of residual stresses in the DED process. The experimental results show that the peak temperature of each layer in the fabrication process increases with the increase in laser power and preheating temperature, and decreases with the increase in scanning speed and interlayer dwell time. Substrate preheating only has a large effect on the peak temperature of the first four layers. Residual stresses are mainly concentrated in the upper and middle parts, the bottom of the substrate, and the sides combined with the substrate, and the residual stresses increase with the increasing laser power and decrease with the increasing interlayer dwell time. Decreasing laser power, longer dwell time, higher preheating temperature, and appropriate scanning speed are beneficial for the reduction in residual stresses in Inconel 690 components. This research has important significance for the process design and residual stress modulation in the additive manufacturing of Inconel 690 alloy.

Wireless Electrical Signals Induce Functional Neuronal Differentiation of BMSCs on 3D Graphene Framework Driven by Magnetic Field.

Bone marrow mesenchymal stem cells (BMSCs) are suggested as candidates for neurodegeneration therapy by autologous stem cells to overcome the lack of neural stem cells in adults. However, the differentiation of BMSCs into functional neurons is a major challenge for neurotherapy. Herein, a methodology has been proposed to induce functional neuronal differentiation of BMSCs on a conductive three-dimensional graphene framework (GFs) combined with a rotating magnetic field. A wireless electrical signal of about 10 µA can be generated on the surface of GFs by cutting the magnetic field lines based on the well-known electromagnetic induction effect, which has been proven to be suitable for inducing neuronal differentiation of BMSCs. The enhanced expressions of the specific genes/proteins and apparent Ca2+ intracellular flow indicate that BMSCs cultured on GFs with 15 min/day rotating magnetic field stimulation for 15 days can differentiate functional neurons without any neural inducing factor. The animal experiments confirm the neural differentiation of BMSCs on GFs after transplantation in vivo, accompanied by stimulation of an external rotating magnetic field. This study overcomes the lack of autologous neural stem cells for adult neurodegeneration patients and provides a facile and safe strategy to induce the neural differentiation of BMSCs, which has potential for clinical applications of neural tissue engineering.

Structure of Sewage Sludge-Clay Multiscale Composite Particles to Control the Mechanism of SO2 and H2S Gas Release.

In order to address the problem of sulfur gas and other odors released in the process of using sewage sludge as a construction material, this study prepared multiscale composite particles with a "large scale-medium scale-small scale-micro scale" structure by mixing sludge with silica-alumina building materials. Analysis of the structural changes formed by the internal gas of composite particles due to diffusion at different temperatures and a study of the characteristics of SO2 and H2S release from composite particles were conducted, as well as being compared with the release characteristics of pure sludge, which clarified the mechanism of controlling sulfur-containing-gas release from composite particles. The results showed that compared with pure sludge, the sludge-clay multiscale composite particles were able to reduce the release of SO2 and H2S up to 90% and 91%, and the release temperatures of SO2 and H2S were increased to 120 °C and 80 °C, respectively. Meanwhile, the special structure of the sludge-clay multiscale composite particles and the clay composition are the main factors that hinder the diffusion of sludge pyrolysis gases. Additionally, there are three layers of "gray surface layer-black mixed layer-dark gray spherical core" formed inside the composite particles, which is the apparent manifestation of the diffusion of volatile gases. This study provides theoretical support for the application of multiscale composite particle inhibition of odor-release technology in industrial production.

Preparation of Lightweight Ceramsite from Solid Waste Using SiC as a Foaming Agent.

SiC was chosen as the foaming agent, and river bottom silt, waste oil sludge, paint bucket slag, and fly ash were used as raw materials, to prepare lightweight ceramsite without adding any chemical additives. The effects of SiC dosing and sintering temperature on various properties of the ceramsite were studied, and the pore-forming mechanism of the lightweight ceramsite was clarified by thermal analysis and X-ray diffraction analysis. The results showed that the single ceramsite compressive strength, water absorption, bulk density, and porosity of ceramsite sintered at 1180 °C with 1.0% SiC were 2.15 MPa, 2.02%, 490 kg/m3, and 23.85%, respectively. The major mineralogical compositions were quartz, fayalite, and kyanite, with small amounts of albite-low from 1140 to 1190 °C. Furthermore, the concentration of all tested heavy metals from ceramsite was lower than the maximum allowable concentration of the leaching solution specified in the Chinese national standard (GB 5085.3-2007), which reveals that this solid waste ceramsite will not cause secondary environmental pollution. The prepared ceramsite, exhibiting lower bulk density, high water absorption and porosity, and effective solidification of deleterious elements, can be used to prepare green lightweight aggregate concrete. Importantly, preparation of solid waste ceramsite is an effective way to dispose of hazardous wastes.

lncRNA KCNQ1OT1 reverses the effect of sevoflurane on hepatocellular carcinoma progression via regulating the miR-29a-3p/CBX3 axis.

Sevoflurane (SEVO) is widely applied as an anesthetic, which exerts antitumor capacity in various cancers, including hepatocellular carcinoma (HCC). Previous studies indicated that long non-coding RNA KCNQ1 opposite strand/antisense transcript 1 (KCNQ1OT1) was upregulated, while microRNA-29a-3p (miR-29a-3p) was downregulated in HCC. Thus, we aimed to explore the roles of KCNQ1OT1 and miR-29a-3p in HCC cells exposed to SEVO. Cell proliferation, apoptosis, migration, and invasion were assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, and transwell assays, respectively. The levels of genes were determined by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot. Furthermore, the interaction between miR-29a-3p and KCNQ1OT1 or chromebox protein homolog 3 (CBX3) was predicted by Starbase or Targetscan, and then confirmed by dual-luciferase reporter assay. We found that the levels of KCNQ1OT1 and CBX3 were decreased, while miR-29a-3p was increased in SEVO-treated HCC cells. KCNQ1OT1 overexpression weakened the inhibitory effects of SEVO on HCC cell proliferation, apoptosis, migration, and invasion. Interestingly, KCNQ1OT1 bound to miR-29a-3p, and miR-29a-3p targeted CBX3. KCNQ1OT1 upregulated CBX3 level by repressing miR-29a-3p expression. Furthermore, KCNQ1OT1 exerted tumor promotion in HCC cells via suppressing miR-29a-3p to regulate CBX3 expression. Collectively, our findings demonstrated that KCNQ1OT1 regulated the antitumor effects of SEVO on HCC cells through modulating the miR-29a-3p/CBX3 axis, providing a theoretical basis for the treatment of HCC.

Domain Generalization for Named Entity Boundary Detection via Metalearning.

Named entity recognition (NER) aims to recognize mentions of rigid designators from text belonging to predefined semantic types, such as person, location, and organization. In this article, we focus on a fundamental subtask of NER, named entity boundary detection, which aims at detecting the start and end boundaries of an entity mention in the text, without predicting its semantic type. The entity boundary detection is essentially a sequence labeling problem. Existing sequence labeling methods either suffer from sparse boundary tags (i.e., entities are rare and nonentities are common) or they cannot well handle the issue of variable size output vocabulary (i.e., need to retrain models with respect to different vocabularies). To address these two issues, we propose a novel entity boundary labeling model that leverages pointer networks to effectively infer boundaries depending on the input sequence. On the other hand, training models on source domains that generalize to new target domains at the test time are a challenging problem because of the performance degradation. To alleviate this issue, we propose Metabdry, a novel domain generalization approach for entity boundary detection without requiring any access to target domain information. Especially, adversarial learning is adopted to encourage domain-invariant representations. Meanwhile, metalearning is used to explicitly simulate a domain shift during training so that metaknowledge from multiple resource domains can be effectively aggregated. As such, Metabdry explicitly optimizes the capability of "learning to generalize," resulting in a more general and robust model to reduce the domain discrepancy. We first conduct experiments to demonstrate the effectiveness of our novel boundary labeling model. We then extensively evaluate Metabdry on eight data sets under domain generalization settings. The experimental results show that Metabdry achieves state-of-the-art results against the recent seven baselines.

lncRNA KCNQ1OT1 reverses the effect of sevoflurane on hepatocellular carcinoma progression via regulating the miR-29a-3p/CBX3 axis

Sevoflurane (SEVO) is widely applied as an anesthetic, which exerts antitumor capacity in various cancers, including hepatocellular carcinoma (HCC). Previous studies indicated that long non-coding RNA KCNQ1 opposite strand/antisense transcript 1 (KCNQ1OT1) was upregulated, while microRNA-29a-3p (miR-29a-3p) was downregulated in HCC. Thus, we aimed to explore the roles of KCNQ1OT1 and miR-29a-3p in HCC cells exposed to SEVO. Cell proliferation, apoptosis, migration, and invasion were assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, and transwell assays, respectively. The levels of genes were determined by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot. Furthermore, the interaction between miR-29a-3p and KCNQ1OT1 or chromebox protein homolog 3 (CBX3) was predicted by Starbase or Targetscan, and then confirmed by dual-luciferase reporter assay. We found that the levels of KCNQ1OT1 and CBX3 were decreased, while miR-29a-3p was increased in SEVO-treated HCC cells. KCNQ1OT1 overexpression weakened the inhibitory effects of SEVO on HCC cell proliferation, apoptosis, migration, and invasion. Interestingly, KCNQ1OT1 bound to miR-29a-3p, and miR-29a-3p targeted CBX3. KCNQ1OT1 upregulated CBX3 level by repressing miR-29a-3p expression. Furthermore, KCNQ1OT1 exerted tumor promotion in HCC cells via suppressing miR-29a-3p to regulate CBX3 expression. Collectively, our findings demonstrated that KCNQ1OT1 regulated the antitumor effects of SEVO on HCC cells through modulating the miR-29a-3p/CBX3 axis, providing a theoretical basis for the treatment of HCC.

The Effect of Specific Energy Density on Microstructure and Corrosion Resistance of CoCrMo Alloy Fabricated by Laser Metal Deposition.

With the development of modern medical implants, there are significantly increasing demands for personalized prosthesis. Corrosion-resistance and dense cobalt alloy specimens have been successfully fabricated by laser metal deposition. The relationship between specific energy density, microstructure and corrosion resistance of the specimens is investigated. The results show that higher specific energy density promotes the formation of columnar grain and leads to coarse grain size. The evolution and distribution of deposited microstructure from bottom to top are summarized in a metallographic sketch. The corrosion current of deposited specimens increases from 2.071 × 10-6 A/cm2 to 6.86 × 10-5 A/cm2 and rapidly drops to 9.88 × 10-7 A/cm2 with increase of specific energy density from 318.8 J/g to 2752.3 J/g. The columnar and equiaxed structure of deposited specimens have lower corrosion current than mixed structure due to finer grain and less Mo segregation. The deposited have low level metal released because of passive film. The passive film have different formation routes in Hank's solution and acidic saliva. The specific energy density has an important effect on the microstructure of deposited, which improves corrosion resistance and life span in implant.

On the safety margin of using simplified human head models for local SAR simulations of B1-shimming at 7 Tesla.

PURPOSES: Using simplified human models significantly alleviates the difficulty of rendering human models for subject-specific local specific absorption rate (SAR) simulations. Although its accuracy has been demonstrated with the birdcage mode combination of RF transmitters, its accuracy in general B1-shimming, where numerous phase and magnitude combinations can take place, is yet unknown. METHODS: The electromagnetic fields of a 7-Tesla eight-channel brain imaging array were simulated by using four detailed human models from the Virtual Family and their two-, three-, and four-tissue simplifications. The 10-g averaged local SAR was computed for each case with 1,000 sets of uniformly distributed random B1-shimming parameters. Linear regression was applied to relate the local SAR obtained by using detailed and simplified human models. The 99% confidence prediction interval was determined as the safety margin in order to cover the largest local SAR variability introduced by using simplified human models. RESULTS: The local SAR computed by using three- and four-tissue simplifications are strongly correlated with those computed by using detailed models. Safety margins of 0.38 and 0.45W/kg/W were found appropriate for each case being considered. CONCLUSIONS: The proposed procedure can be applied to evaluate the safety margin of the local SAR simulated by using simplified human models. However, discretion needs to be exercised since the safety margins in some cases may represent more than 50% overestimation.

Parallel-plate waveguide for volume radio frequency transmission in MRI.

PURPOSE: Radiofrequency coils in MRI are narrowband resonant structures. The high-quality factor makes their performance sensitive to loading and other operating conditions. We developed a new coil to provide volume transmit in a broad frequency band. METHODS: The proposed coil is a parallel-plate waveguide. When operating in the transverse electromagnetic mode, a uniform magnetic field is generated between the plates for imaging. The impedance of the transverse electromagnetic mode is matched by a broadband matching circuit. The two plates are actively driven with broadband Wilkinson power dividers and combiners. Re-entrant design is further applied to improve the overall efficiency. RESULTS: We developed a prototype of a coil to image the human forearm with a bandwidth of more than one octave. Its feasibility was demonstrated by proton imaging and phosphorous spectroscopy at 7T. CONCLUSIONS: The proposed coil structure is compact and relatively easier to construct. It can be applied for volume radiofrequency transmit in MRI in a broad frequency band.