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Additive manufacturing has been a promising method for the production of 18Ni maraging steel, which is characterized by excellent mechanical properties. There are only few available studies on wire and arc additive manufacturing of this steel. In this paper, 18Ni (350) maraging steel thin-wall parts were fabricated by gas metal arc-based wire and arc additive manufacturing (GMA-based WAAM). The aim of this study was to reveal the microstructure and mechanical properties of the as-deposited parts and investigate the effects of the heat treatment process. The microstructure of the deposited part was principally martensite with long columnar grains, accompanied by a small amount of austenite. The average hardness of the as-deposited part was 467 ± 60 HV. The tensile strengths (UTS and YS) along the building direction were 1481 and 1221 MPa, respectively, and the elongation was 4.8%, which were all larger than those along the deposition direction. After solution treatment, the austenite content, hardness, and tensile strengths of the as-deposited samples decreased, while the elongation increased slightly. After aging treatment, the austenite content and hardness of the solution-treated samples increased, but the UTS and elongation were not improved, indicating that the heat treatment for preparing 18Ni as-deposited samples with excellent mechanical properties requires further investigation.

Double-electrode gas metal arc additive manufacturing (GMA-AM), capable of reducing heat accumulation through bypass arc, was used to fabricate the thin-wall part of NiCrMoV high-strength low-alloy steel (HSLAS). The peak temperature and cooling time of thermal cycle in double-electrode GMA-AM compared with conventional GMA-AM decreased under the same conditions, which influenced the microstructure and properties of deposited metals. Microstructures of the deposited part were mainly bainite and martensite. As the deposition height increased, the martensite content decreased, and acicular ferrite microstructure was formed due to poor heat dissipation and multiple post-heatments. Introduction of bypass arc into double-electrode GMA-AM generated more martensite structure, which improved the hardness of the deposited part. Tensile strength and yield strength of the thin-wall part were both improved with bypass arc. The average ultimate tensile strength was 855 MPa, and the elongation was 19.5% through double-electrode GMA-AM.

During wire and arc additive manufacturing (WAAM) of high nitrogen austenitic stainless steel (HNASS), the explosion of droplets with high-content nitrogen will induce grievous spatters, causing incomplete fusion, cracks and inclusions. In this study, the formation, characteristics and influence of spatters on cold metal transfer + pulse (CMT+P)-based WAAM of HNASS were investigated. The droplets exploded violently due to the sharp decrease of nitrogen solubility in liquid steel, which produced abundant spatters at the pulse stage. The spatter particles were a mixture of manganese oxides (MnO and Mn3O4) and molten metals of the wire. The overall particle size followed normal distribution. The majority of particles were spherically shaped in diameter of 20–150 µm, and over 80% of spatters were below 200 µm in diameter. Inclusion of manganese oxide spatter particles appeared in the deposition metals of single-pass single layer. The spatters at the root of the deposited metal can be hardly removed, which produced interpass defects in overlapping deposition. For multi-pass multilayer deposition, interlayer tearing occurred to reduce the mechanical properties of HNASS. The interlayer tearing was caused jointly by the incomplete fusion caused by spatter particles of manganese oxide and the large thermal stress. Hence, the spatters generated in the droplet transition for WAAM of HNASS must be controlled.

High nitrogen austenitic stainless steel (HNASS) wire with 0.78 wt.% nitrogen content was used for gas metal arc welding (GMAW) test. The characteristics of droplet transfer and weld formation in different welding parameters were investigated. There were three typical metal transfer modes in GMAW of HNASS, namely in terms of stable short circuit transfer, unstable short circuit transfer and spray transfer. With wire feed speed (WFS) of 3 m/min∼8 m/min and moderate arc voltage, the droplet transfer was stable short-circuiting transition mode. The transfer period and waveform of electrical parameters were regular and the weld formation was satisfactory with few spatters. With the increasing of arc voltage or WFS, the droplet grew up to abnormal large size due to the expansion of supersaturated nitrogen. The electric parameters were more disordered and the metal transfer became unstable with spatter. When wire feed speed was over 10 m/min with high arc voltage, the droplet transfer became spray transfer accompanied by numerous welding fumes. The weld formation of HNASS for unstable short circuit and spray transfer mode was inferior with serious spatters.

OBJECTIVE: To explore the novel biomarkers and therapeutic target candidates related to the stasis-heat syndrome of acute intracerebral hemorrhage (AICH). METHODS: Applying an isobaric tagging for relative and absolute quantitation-(iTRAQ-) based quantitative proteomic approach, plasma samples from AICH patients with stasis-heat, and AICH patients with non-stasis-heat and healthy control subjects were collected and analyzed to distinguish differentially expressed proteins (DEPs) correlated to AICH with stasis-heat in this block design. The standard Western blot was applied to verify DEPs. Additionally, DEPs were analyzed via bioinformatic platforms and further approved via Ingenuity Pathway Analysis (IPA). RESULTS: A total of 26 DEPs were found among AICH with the stasis-heat, AICH with non-stasis-heat, and healthy control group. The seven DEPs compared with the non-stasis-heat group are closely related to the pathogenesis of stasis heat. These proteins showed three different protein expression patterns. The alpha-1-b glycoprotein (A1BG) and copper-protein (CP) were up-regulated in the stasis-heat group, but down-regulated in the non-stasis-heat group. Compared with the non-stasis-heat group, the expression abundance of actinin, alpha 1 (ACTN1), carbonic anhydrase I (CA1), peroxiredoxin 2 (PRDX2), and vinculin (VCL) is higher in the stasis-heat group, while the CD44 is the opposite. These differences reflect that stasis-heat syndrome has more severe inflammatory immune response, coagulation disorders and damage. Bioinformatics analysis revealed that a wide variety of cellular and metabolic processes and some signaling pathways were involved in the pathophysiology of AICH with stasis-heat. AICH with stasis-heat syndrome showed more severe inflammatory reactions, tissue damage, and coagulation disorders than non-stasis heat syndrome. CONCLUSION: There are differences in the protein expression patterns between the stasis-heat syndrome and non-stasis-heat syndrome. These differences reflect that stasis-heat syndrome has more severe damage. CD44, CP, ACTN1, CA1, VCL, PRDX2, and A1BG could be the potential biomarkers and therapeutic target candidates of the stasis-heat subtype. This study provides a reasonable explaination for Liangxue Tongyu decoction through anti-inflammatory and brain protection treatment.

Weld quality directly affects the performance and reliability of structural parts and can be critically ensured by online monitoring. In this study, local mean decomposition (LMD), an adaptive time-frequency analysis is used to analyze the current signals of welding, and then combined with deep belief network (DBN) to classify the weld quality. Firstly, the current signals are decomposed by LMD into a series of product functions. Each product function is a complex signal, and its complexity is calculated by multi-scale entropy to select the most relevant product function with weld quality. Finally, DBN is applied to classify weld quality into four types. This method has a higher classification and recognition rate compared with principal component analysis and extreme learning machine classification. Thus, LMD is a potentially effective method to diagnose weld quality.

The composition of shielding gas exerts a crucial influence on high nitrogen austenitic stainless steel (HNASS) deposited by gas metal arc additive manufacturing. The proportion of N2 in shielding gas greatly affected the formation quality and microstructure of deposited parts. As N2 proportion improved, the formation quality became worse gradually and the nitrogen concentration of deposition metal increased. The maximum nitrogen concentration of deposition metal was more than 1%. However, N2 porosity in the deposition metal became serious when the N2 content was over 10 %. The microstructure of the deposition metal changed from two phases of austenite and ferrite in shielding gas of 0∼10 %N2 to complete austenite with 15 %∼25 %N2 content in shielding gas. With optimal shielding gas of 5%N2+2%O2+10%He+83%Ar, the deposited parts of HNASS demonstrated good formation and excellent properties. The average ultimate tensile strength of 920 MPa was achieved and the elongation was 27.7%.

Due to the non-stationary and nonlinear characteristics of arc signal in gas metal arc welding (GMAW), results in the difference of frequency distribution. In this study, a method for evaluate weld quality based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and extreme learning machine (ELM) is proposed. First, the current signal is decomposed into intrinsic mode functions (IMFs) of different frequency bands by CEEMDAN, and then the energy entropy of IMFs is extracted. Because of the energy of each IMF under different weld quality is varies, the energy entropy and normalized energy of IMFs are used as a feature vector to classify the weld quality combined with extreme learning machine (ELM). The result shows that CEEMDAN and ELM can be used to identify the weld quality types of GMAW accurately.

Wheat growth and nitrogen (N) uptake gradually decrease in response to high NH4+/NO3– ratio. However, the mechanisms underlying the response of wheat seedling roots to changes in NH4+/NO3– ratio remain unclear. In this study, we investigated wheat growth, transcriptome, and proteome profiles of roots in response to increasing NH4+/NO3– ratios (Na: 100/0; Nr1: 75/25, Nr2: 50/50, Nr3: 25/75, and Nn: 0/100). High NH4+/NO3– ratio significantly reduced leaf relative chlorophyll content, Fv/Fm, and ΦII values. Both total root length and specific root length decreased with increasing NH4+/NO3– ratios. Moreover, the rise in NH4+/NO3– ratio significantly promoted O2– production. Furthermore, transcriptome sequencing and tandem mass tag-based quantitative proteome analyses identified 14,376 differentially expressed genes (DEGs) and 1,819 differentially expressed proteins (DEPs). The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated that glutathione metabolism and phenylpropanoid biosynthesis were the main two shared enriched pathways across ratio comparisons. Upregulated DEGs and DEPs involving glutathione S-transferases may contribute to the prevention of oxidative stress. An increment in the NH4+/NO3– ratio induced the expression of genes and proteins involved in lignin biosynthesis, which increased root lignin content. Additionally, phylogenetic tree analysis showed that both A0A3B6NPP6 and A0A3B6LM09 belong to the cinnamyl-alcohol dehydrogenase subfamily. Fifteen downregulated DEGs were identified as high-affinity nitrate transporters or nitrate transporters. Upregulated TraesCS3D02G344800 and TraesCS3A02G350800 were involved in ammonium transport. Downregulated A0A3B6Q9B3 is involved in nitrate transport, whereas A0A3B6PQS3 is a ferredoxin-nitrite reductase. This may explain why an increase in the NH4+/NO3– ratio significantly reduced root NO3–-N content but increased NH4+-N content. Overall, these results demonstrated that increasing the NH4+/NO3– ratio at the seedling stage induced the accumulation of reactive oxygen species, which in turn enhanced root glutathione metabolism and lignification, thereby resulting in increased root oxidative tolerance at the cost of reducing nitrate transport and utilization, which reduced leaf photosynthetic capacity and, ultimately, plant biomass accumulation.

The thermionic electron gun is one of essential parts of electron accelerators and vacuum tubes. For electron beam generation it is basically configured by cathode, anode and it can have control electrode. In common electron guns, beam current is typically controlled by the bias voltage on the Wehnelt electrode. To deeply study the control mechanism of electron beam current, a three-dimensional model of a 60 kV/6 kW thermionic electron gun is established and the simulation of electric field distribution with CST software is shown in this paper. The particle tracking model is used to track the movement of emitted electrons and the quantitative relationship between beam current and bias voltage is established. Results show that electron beam current is inversely proportional to the bias voltage within a certain range. As the bias voltage increases, the electric field distribution in electron gun changes and the equipotential line of accelerating voltage moves towards the emitting surface of cathode, therefore the Effective Emitting Area (EEA) of cathode decreases and, accordingly, the beam current also decreases. Besides, when the bias voltage is fixed, fluctuations of the accelerating voltage cause fluctuations of the beam current, which is especially severe when the beam current is small.

A new method based on gray level co-occurrence matrix (GLCM) was proposed to extract the texture features of molten pool images and used to monitor the gas flow status in the cold metal transfer plus pulse (CMT + P) based additive manufacturing. The current and intensity signals of CMT + P in the short circuit stage were collected and analyzed to get clearer molten pool images. According to the characteristics of GLCM, the best parameter group was identified through comparative analysis, and four texture features of angular second moment, entropy, contrast and correlation were extracted. On this basis, the gas flow status was divided into three categories of LOW, MEDIUM and HIGH, which were identified successfully using a prediction model based on support vector machine and cross validation.

Large-scale high nitrogen steel (HNS) components with complex facade promote the application of Wire and Arc Additive Manufacturing (WAAM) technology in this area. However, the lack of fundamental research restricts its development. In this study, a self-made HNS wire with 0.99 wt.% nitrogen content (N%) was systematically studied in the aspects of the additive seam formability, nitrogen behaviour, along with microstructure characterizations. A designed Tanguich experiment with three factors (cold metal transfer (CMT) models, wire feeding speed and oxygen content in shielding gas) and four levels were used to reveal the suitable parameters for AM and the rule of nitrogen behaviour in the molten pool. For the semi-quantitative calculation of the N%, a modified kinetic model was proposed with the prediction accurate less than 12 %. Besides, the nitrogen pore and microstructure characterizations under different CMT models were studied. Results showed that for fewer pores in a smaller size, the molten pool volume should be in the range of 200 ∼ 300mm3. The austenite cell substructures in the microstructure were mainly found in the low heat input additive seams with a diameter around 9 μm. The microhardness test showed that for the AM of HNS, the first few layers can also be used with no need to remove. When the N% is lower than 0.8 %, positive relativity between N% and microhardness can be expected. Besides, the fluctuation of microhardness was found to be connected with the irregular columnar grains, Mn Oxides and Cr nitrides in the additive seams.

In welding, previous research has proven that the behavior of its arc droplet is chaotic and fractal by the complex analysis of time series. In this study, the multi-scale time irreversibility (MSTI) method is used to analyze welding time series, and then used to classify the weld quality. By comparing the results of shuffled time series with original time series, it is confirmed that the time irreversibility is an intrinsic property of welding time series and it can extend over multiple scales. The superposition effect of multiple frequency components of welding time series results in enhances time irreversibility. The MSTI index (Pm%, Gm%) is used to quantify the time irreversibility, and has a capable of distinguishing different series. In the finally, the index (Pm%, Gm%) is combined with extreme learning machine (ELM) to classify the weld quality, and obtain good classification results.

The gas metal arc welding is a complex chaotic dynamic process. To study the relationship between arc electrical signal and welding stability, the multi-scale entropy method was introduced to analyze the current signals under different welding process parameters. Under the short-circuiting droplet transition mode, the larger shielding gas flow rate led to, the more stable welding and the smaller amplitude of multi-scale entropy curves. When the welding current parameter increased gradually, the droplet transition mode changed, and the amplitude of multi-scale entropy curves increased. As the welding voltage rose, the droplet transfer frequency decreased and the multi-scale entropy increased. Furthermore, the four-class prediction of welding forming quality was studied by combining with the genetic algorithm-based support vector machine (GA-SVM). The multi-scale entropy distribution was closely related to the type and stability of short-circuiting transfer in the welding process.

The redistribution of alloying elements and the crystallographic characterizations in wire and arc additive manufactured (WAAM) super duplex stainless steel (SDSS) was investigated from the wire to the final as-deposited structure. The results showed that elemental partitioning between austenite and ferrite was suppressed in the last layer and the solidified droplet. The high Ni content but low Cr and N contents in the initial state of the intragranular austenite (IGA) confirmed the predominance of the chromium nitrides acted as the nucleation sites. Gathering of nitrogen was found more distinct in the coarsening IGA, Widmanstätten austenite (WA) than the grain boundary austenite (GBA). The columnar epitaxial ferrite presented a strong texture in the deposition direction, while the and orientations was found in the austenite. Random orientations of the intragranular secondary austenite was revealed. The Rotated Cube texture of the austenite grains were consumed by the “recrystallization” textures (Brass, Rotated Brass, Cu, R, E, and F) caused by the austenite reformation. The low-angle interphase boundaries between austenite and ferrite were predominated in the as-deposited wall, and, at which, the K–S orientation took the crucial part. A Taylor factor analysis revealed that through fabrication via additive process, the austenite became oriented “harder” and contributed most to good mechanical properties. The textured microstructure contributed about a 2.6% higher engineering strain in the Z direction and a 27.8 MPa higher yield strength in the X direction.

As the excellent combination of mechanical properties and corrosion resistance for super duplex stainless steel, a prospective method – Wire and Arc Additive Manufacturing – for fabricating this material was proposed, and a wall component was deposited in this study. The microstructure of the as-deposited wall was carefully analyzed along with the variation of mechanical properties. The results revealed that, in the wall-body, the austenite/ferrite phase balance was broken by the overgrowing the austenite phase. During this process, the intergranular secondary austenite leading the increase of austenite phase together with some contributions made by the precipitation of intragranular secondary austenite. Propagation of the intermetallic phases, chi and sigma phase, was not the major reason for the low impact toughness in the last layer area and the root region. Instead, the presence of CrN and “inclusions” (Cr2N and impurities) took the main responsibility not only in the impact toughness but also the ductility. The anisotropic analysis revealed that the UTS and elongation appeared distinct difference in vertical and horizontal direction samples. The varieties in YS were eliminated by the nitrogen work hardening effect to a large extent.

We investigated if time between injury and surgery affects cancellous bone properties in patients suffering tibial plateau fractures (TPF), in terms of structural integrity and gene expression controlling bone loss. A cohort of 29 TPF, operated 1-17 days post-injury, had biopsies from the fracture and an equivalent contralateral limb site, at surgery. Samples were assessed using micro-computed tomography and real-time RT-PCR analysis for the expression of genes known to be involved in bone remodeling and fracture healing. Significant decreases in the injured vs control side were observed for bone volume fraction (BV/TV, -13.5 ± 6.0%, p = 0.011), trabecular number (Tb.N, -10.5 ± 5.9%, p = 0.041) and trabecular thickness (Tb.Th, -4.6 ± 2.5%, p = 0.033). Changes in these parameters were more evident in patients operated 5-17 days post-injury, compared to those operated in the first 4 days post-injury. A significant negative association was found between Tb.Th (r = -0.54, p 0.01) and BV/TV (r = -0.39, p 0.05) in relation to time post-injury in the injured limb. Both BV/TV and Tb.Th were negatively associated with expression of key molecular markers of bone resorption, CTSK, ACP5, and the ratio of RANKL:OPG mRNA. These structure/gene expression relationships did not exist in the contralateral tibial plateau of these patients. This study demonstrated that there is a significant early time-dependent bone loss in the proximal tibia after TPF. This bone loss was significantly associated with altered expression of genes typically involved in the process of osteoclastic bone resorption but possibly also bone resorption by osteocytes. The mechanism of early bone loss in such fractures should be a subject of further investigation. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2865-2875, 2018.

The osteocyte expressed gene SOST encodes sclerostin, a potent negative regulator of bone formation and inducer of bone resorption. We have recently demonstrated that the human SOST gene is positively regulated in response to 1α,25-dihydroxyvitamin D3 (1,25D). Responsiveness may be mediated at least in part by a single classical DR3-type vitamin D response element (VDRE). In this study we examined the early responsiveness of the SOST gene to both 1,25D and to parathyroid hormone (PTH), a known repressor of SOST expression, in SaOS2 cells differentiated to an osteocyte-like stage of cell maturation. Both SOST mRNA levels and sclerostin protein levels increased in these cultures as early as 3 h post-treatment with 1,25D and declined in response to PTH in the same timeframe. For 1,25D, the level of induced SOST appeared dependent on the extent, to which the degradative enzyme 1,25-dihydroxyvitamin D 24-hydroxylase (CYP24A1) was induced. Together with the observed rapid decrease in SOST/sclerostin levels in response to PTH, endocrine regulation of sclerostin production appears to be an important determinant of sclerostin levels. These findings confirm that the human SOST gene and sclerostin expression can be considered to be directly 1,25D-responsive in osteocytes. Refereed/Peer-reviewed

Sclerostin, the SOST gene product, is a negative regulator of bone formation and a positive regulator of bone resorption. In this study, treatment of human primary osteoblasts, including cells differentiated to an osteocyte-like stage, with 1α,25-dihydroxyvitaminD3 (1,25D) resulted in the dose-dependent increased expression of SOST mRNA. A similar effect was observed in human trabecular bone samples cultured ex vivo, and in osteocyte-like cultures of differentiated SAOS2 cells. Treatment of SAOS2 cells with 1,25D resulted in the production and secretion of sclerostin protein. In silico analysis of the human SOST gene revealed a single putative DR3-type vitamin D response element (VDRE) at position -6216 bp upstream of the transcription start site (TSS). This sequence was confirmed to have strong VDRE activity by luciferase reporter assays and electrophoretic mobility shift analysis (EMSA). Sequence substitution in the VDR/RXR half-sites abolished VDRE reporter activity and binding of nuclear proteins. A 6.3 kb fragment of the human proximal SOST promoter demonstrated responsiveness to 1,25D. The addition of the evolutionary conserved region 5 (ECR5), a known bone specific enhancer region, ahead of the 6.3 kb fragment increased basal promoter activity but did not increase 1,25D responsiveness. Site-specific mutagenesis abolished the responsiveness of the 6.3 kb promoter to 1,25D. We conclude that 1,25D is a direct regulator of human SOST gene and sclerostin protein expression, extending the pathways of control of sclerostin expression. At least some of this responsiveness is mediated by the identified classical VDRE however the nature of the transcriptional regulation by 1,25D warrants further investigation. Refereed/Peer-reviewed

While vitamin D supplementation is common, the anabolic mechanisms that improve bone status are poorly understood. Under standard mineralising conditions including media ionised calcium of 1.1 mM, 1,25-dihydroxyvitamin D3 (1,25D) enhanced differentiation and mineral deposition by the mature osteoblast/pre-osteocyte cell line, MLO-A5. This effect was markedly increased with a higher ionised calcium level (1.5 mM). Gene expression analyses revealed that 1,25D-induced mineral deposition was associated with induction of Enpp1 mRNA, coding for nucleotide pyrophosphatase phosphodiesterase 1 (NPP1) and NPP1 protein levels. Since MLO-A5 cells express abundant alkaline phosphatase that was not further modified by 1,25D treatment or exposure to increased calcium, this finding suggested that the NPP1 production of pyrophosphate (PPi) may provide alkaline phosphatase with substrate for the generation of inorganic phosphate (Pi). Consistent with this, co-treatment with Enpp1 siRNA or a NPP1 inhibitor, PPADS, abrogated 1,25D-induced mineral deposition. These data demonstrate that 1,25D stimulates osteoblast differentiation and mineral deposition, and interacts with the extracellular calcium concentration. 1,25D regulates Enpp1 expression, which presumably, in the context of adequate tissue non-specific alkaline phosphatase activity, provides Pi to stimulate mineralisation. Our findings suggest a mechanism by which vitamin D with adequate dietary calcium can improve bone mineral status. Refereed/Peer-reviewed