ObjectiveRheumatoid arthritis (RA) is a chronic inflammatory joint disease, which is associated with progressive disability, systemic complications, and early death. But its etiology and pathogenesis are not fully understood. We aimed to investigate the alterations in plasma metabolite profiles, gut bacteria, and fungi and their role of them in the pathogenesis of RA.MethodsMetabolomics profiling of plasma from 363 participants including RA (n = 244), systemic lupus erythematosus (SLE, n = 50), and healthy control (HC, n = 69) were performed using the ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry. The differentially expressed metabolites were selected among groups and used to explore important metabolic pathways. Gut microbial diversity analysis was performed by 16S rRNA sequencing and ITS sequencing (RA = 195, HC = 269), and the specific microbial floras were identified afterward. The diagnosis models were established based on significant differential metabolites and microbial floras, respectively.ResultsThere were 63 differential metabolites discovered between RA and HC groups, mainly significantly enriched in the arginine and proline metabolism, glycine, serine, and threonine metabolism, and glycerophospholipid metabolism between RA and HC groups. The core differential metabolites included L-arginine, creatine, D-proline, ornithine, choline, betaine, L-threonine, LysoPC (18:0), phosphorylcholine, and glycerophosphocholine. The L-arginine and phosphorylcholine were increased in the RA group. The AUC of the predictive model was 0.992, based on the combination of the 10 differential metabolites. Compared with the SLE group, 23 metabolites increased and 61 metabolites decreased in the RA group. However, no significant metabolic pathways were enriched between RA and SLE groups. On the genus level, a total of 117 differential bacteria genera and 531 differential fungal genera were identified between RA and HC groups. The results indicated that three bacteria genera (Eubacterium_hallii_group, Escherichia-Shigella, Streptococcus) and two fungal genera (Candida and Debaryomyces) significantly increased in RA patients. The AUC was 0.80 based on a combination of six differential bacterial genera and the AUC was 0.812 based on a combination of seven differential fungal genera. Functional predictive analysis displayed that differential bacterial and differential fungus both were associated with KEGG pathways involving superpathway of L-serine and glycine biosynthesis I, arginine, ornithine, and proline interconversion.ConclusionThe plasma metabolism profile and gut microbe profile changed markedly in RA. The glycine, serine, and threonine metabolism and arginine and proline metabolism played an important role in RA.

After years of using, the marine riser would need pigging operation to remove wax and other debris attached to its interior to recover production. Due to its low stiffness, coiled tubing would buckle when performing the marine riser pigging operation, which would make the injecting force not able to completely transfer into its end and finally damage coiled tubing and riser. Thus, in order to ensure the safety and reliability of the operation, this article reports an experimental study on this topic by building an indoor pipe-in-pipe platform. According to the experimental results, the inner pipe's axial force transfer efficiency is always less than 1. When injecting force is less than the inner pipe's critical helical buckling load, the inner pipe's axial load transfer efficiency is basically the same under ''unfixed boundary'' and ''fixed boundary'' at the same force-out. When injecting force is bigger than the inner pipe's critical helical buckling load, ''unfixed boundary'' would help decrease the inner pipe's axial load transfer efficiency; when the injecting force is three times the critical helical buckling load, the inner pipe's axial load transfer efficiency of ''unfixed boundary'' can be 3% smaller than that of ''fixed boundary.'' As the outer pipe of ''unfixed boundary'' would elongate, its axial load transfer would be ''delay'' compared with ''fixed boundary,'' which means injected displacement of ''unfixed boundary'' inner pipe would be bigger than those of ''fixed boundary'' at the same force-out. The research done above might provide important theoretical supports for the marine riser pigging operation.

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Coiled tubing can be used for steel catenary riser pigging operations to remove wax and other debris attached on the interior of steel catenary riser to recover production and ensure safety. Due to its low rigidity, coiled tubing would deform which might finally damage coiled tubing and steel catenary riser. Thus, in order to ensure safety and reliability of the operation, this article proceeded experimental study on the axial load transfer behavior of a coiled tubing stuck in a steel catenary riser when the coiled tubing has not yet helical buckled. According to the experimental results, the inner pipe's axial force transfer efficiency is always less than 1; the outer pipe of ''unfixed steel catenary riser boundary'' would elongate forced by the inner pipe within it, which makes the injected displacement of inner pipe within outer pipe of ''unfixed steel catenary riser boundary'' bigger than the injected displacement of inner pipe within outer pipe of ''fixed steel catenary riser boundary'' system at the same force-out; before the inner pipe helical buckles, inner pipe's force transfer efficiency for unfixed and fixed system can be considered as the same. The research done above might provide important theoretical supports for the steel catenary riser pigging operation.

Due to its unique character, Coiled tubing technology is widely used in various fields of marine oil and gas operations. But as the stiffness of coiled tubing is small, and the marine environment is complex, it is easy for the coiled tubing to destroy or cause an accident. Therefore we need to study axial load transfer characteristics of coiled tubing in the Marine riser to ensure safety and reliability of the operation. In this paper, through establishing the finite element model of coiled tubing down into of marine riser, axial load transfer law of unfixed boundary and fixed boundary coiled tubing was analyzed. Analysis results show that within fixed boundary condition, coiled tubing axial load transfer efficiency would be higher than that in unfixed boundary when the injection force is greater than the helical buckling critical load.Index Term -Pipe in pipe; Load transfer; Finite element analysis.