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Objective: To established a method for determination of 21 perfluorinated compounds in animal-derived food by ultra-performance liquid chromatography-tandem mass spectrometry （UPLC-MS/MS）. Methods: The sample was extracted with 1% formic acid-acetonitrile, cleaned up with a sorbent mixture of N-propylethylenediamine （PSA）, octadecyl bonded silica gel （C18） and graphitized carbon black （GCB）, then separated by acetonitrile-5mmol/L ammonium acetate aqueous solution and Acquity UPLC® BEH C18, detected by liquid chromatography tandem mass spectrometry in negative mode using the multiple reaction monitoring （MRM） mode. Results: The calibration curves were linear in the range of 0.2~10 ng/mL for the 21 PFAS. The limits of quantification were 0.25 μg/kg. Average recoveries were in the range of 71%~118% with three spiked levels, namely 0.25, 0.50, 1.25 μg/kg. The relative standard deviations （RSDs%） of inter-batch and intra-batch were 3.5%~18.3% （n=6） and 2.2%~13.8% （n=3）, respectively. Conclusion: The simple pretreatment and high sensitivity satisfied the fast and accurate detection requirement, meanwhile it is suitable for qualitative and quantitative analysis of perfluorinated compounds in animal-derived food.

In order to predict the elastic constants of 3D four-direction braided composites, unit cell model was established for braided composites with 20°,30°,45° braided angle respectively. The elastic properties of the interior cell and the surface cell were predicted using both the stiffness volume average method and the numerical analysis method, and all quasi-static tensile tests were performed on MTS machine. The experimental results, theoretical analysis and numerical simulation results were analyzed. It is found that the axial tensile modulus decreases,and the transverse tensile modulus and transverse shear stiffness increases with the increase of braiding angles because of the decrease of the component of carbon fiber stiffness in the direction of the carrier movement and the increase of the transverse component of carbon fiber stiffness. Tests reveal that the stress-strain curve for the extension tests of specimen of 20° braided angle exhibit linear elastic type, the stress-strain curve of 30° specimen shows nonlinear characters, the stress-strain curve of 45° specimen shows bilinear relation, but the transverse tensile stress-strain curves of all the specimens are basically linear. Combining the longitudinal and transverse tensile test results with the theoretical and numerical data, it is found that the stiffness volume average method and the numerical analysis methods are able to predict the stiffness in the direction of the carrier movement of 3D braided composites well. However, the prediction precision for the transverse stiffness of specimen is not satisfactory, mainly because these methods neglect the interface damage between the fiber and the matrix in tests.

Solvothermal reactions of tetradentate ligands, H2L1–H2L3, with hydrated Mn(ClO4)2 and hydrated Co(NO3)2 afforded the mononuclear neutral compounds [MnII(L1)(H2O)3]·3H2O (1), [MnII(L2)(H2O)3]·3H2O (2), [MnII(L3)(H2O)2(CH3CH2OH)]·3H2O·CH3CH2OH (3), and [CoII(L1)(H2O)3]·3H2O (4) (H2L1 = 1,10-phenanthroline-2,9-dicarboxylic acid, H2L2 = 2,2′-bipyridine-6,6′-dicarboxylic acid, and H2L3 = 6,6′-bis(1H-tetrazol-5-yl)-2,2′-bipyridine), respectively, in moderate yields. All the compounds were characterized by X-ray crystallography and all the metal centres were coordinated by a tetradentate ligand and three solvent molecules in a distorted 7-coordinate pentagonal bipyramidal geometry. Through magnetic measurements, 1–4 show interesting slow magnetic relaxation under an external direct current (dc) field. It is noted that the temperature dependence of the relaxation time (τ) in all the compounds exhibits the 'reciprocating thermal behaviour' (RTB), where the weak inter-molecular interactions in the solid state are responsible for this strange phenomenon. [ABSTRACT FROM AUTHOR]

Study Design: Retrospective study. Objective: To analyze the causes of and factors influencing early recurrence after TELD performed in the treatment of lumbar disc herniation. Methods: We included 285 patients with single-segment lumbar disc herniation treated using transforaminal endoscopy lumbar discectomy TELD from January 2017 to December 2019 at the First Affiliated Hospital of the University of South China. Patients were classified into early recurrence and non-early recurrence groups based on clinical symptoms and MRI reexamination. Imaging data (eg, disc height index (DHI), Pfirrman grades, base width, postoperative annulus-fibrosus tear size, cross-sectional area of the foramen (CSAF), etc.)were analyzed, and multivariate, binomial logistic regression was utilized to determine which factors were associated with early recurrence after TELD. Results: A total of 285 patients completed surgery and clinical follow-up, during which 19 patients relapsed within 6 months postsurgery, for an early recurrence rate of 6.7%. There were statistically significant differences between DHI, Pfirrman grades, base width, postoperative annulus-fibrosus tear size, herniation sites, CSAF and Modic changes between the early recurrence and non-early recurrence groups (P <.05). On multivariate logistic regression,the degree of disc degeneration (OR =.747, P =.037), CSAF (OR = 5.255, P =.006), degree of Modic change (OR = 1.831, P =.018) and base width of the herniation (OR = 4.942, P =.003) were significantly correlated with early recurrence after TELD. Conclusions: Postoperative annulus-fibrosus tear size, DHI, and location of the disc herniation were associated with early recurrence after TELD. Increased base width of the herniation, severe disc degeneration, decreased CSAF and Modic change were risk factors for early recurrence after TELD. [ABSTRACT FROM AUTHOR]