7 research outputs found

    Poly[di-μ9-citrato-cobalt(II)tetra­sodium]

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    The title compound, [CoNa4(C6H5O7)2]n, was obtained under hydro­thermal conditions as a minor product. The Co2+ cation is located on a crystallographic inversion center and is coordinated by six O atoms from two different citrate units, forming a [Co(C6H5O7)2]4− building unit with Co—O bond lengths between 2.0578 (17) and 2.0813 (16) Å. The structure features two crystallographically independent Na+ ions. The first Na+ cation is five-coordinated by O atoms of five carboxylate groups from four different citrate anions. The second Na+ cation is surrounded by six O atoms of five carboxylate groups from five different citrate anions. The carboxylate groups of the citrate are completely depronona­ted, the hydroxyl group, however, is not. It is coordinated to the Co2+ cation, and through an O—H⋯O hydrogen bond connected to a neighboring [Co(C6H5O7)2]4− building unit. The coordination modes of the carboxyl­ate O atoms vary, with one O atom being coordinated to three different Na+ cations, three are bridging O atoms bound to two Na+ cations and two are connected to a Co2+ cation and a Na+ cation, respectively. Through these inter­connections, the basic [Co(C6H5O7)2]4− building units are linked with each other through coordination of their carboxyl­ate groups to the Na+ cations, forming a three-dimensional framework

    Quenching induced residue stress in M50 steel ring: a FEM simulation

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    A finite element method (FEM) combined with subroutines was established and used for tracing the evolution of stresses in M50 steel in quenching. The constitutive relation and thermal physical properties of M50 steel were tested and integrated into the modeling. The finite element analysis, taking into account of thermal stresses and martensitic phase transformation, predicts accurately the high-velocity nitrogen (HNQ) induced residual stresses in the M50 steel bulk. The simulation results suggested that the residual stresses in M50 steel is compressive at the surface while tensive at the center, along with very strong residual stresses at edges. The residual stress reaches to the high level of −810.3 MPa and −1436 MPa in the case of HNQ and water quenching, respectively. The evolution of stress is found to be jointly driven by the thermal stress and phase transformation stress. The thermal stress dominates the evolution at the initial stage while the phase transformation stress becomes dominating once the martensite transformation begins

    Association between Skin-to-Skin Contact Duration after Caesarean Section and Breastfeeding Outcomes

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    We aimed to explore the association between skin-to-skin contact (SSC) duration after caesarean sections (CSs) and breastfeeding outcomes. A prospective study was conducted in four hospitals in China during January and August 2021. A total of 679 participants with singleton pregnancy who delivered by elective CS after 37 gestational weeks using epidural or spinal anesthesia were included. Logistic regression was applied to assess the association between SSC duration and early initiation of breastfeeding (EIBF), as well as the promoting factors for exclusive breastfeeding (EBF) at hospital discharge. Immediate SSC after CSs was strongly associated with higher rates of EIBF (p < 0.001) and EBF at hospital discharge (p = 0.002). The EIBF rates increased with longer duration of SSC, with the at least 90 min SSC group having the highest EIBF rate (74.5%). Skin-to-skin contact durations of at least 90 min, 60–89 min and 30–59 min were significantly associated with 8.53 times (OR = 8.53, 95%CI: 4.94–14.72, Padj < 0.001), 8.04 times (95%CI: 4.68–13.80, Padj < 0.001) and 6.28 times (95%CI: 3.75–10.51, Padj < 0.001), respectively, higher EIBF rates compared to those without immediate SSC. After multiple-testing correction, the rates of EBF at hospital discharge were found to be independent of the duration of SSC (Padj = 0.12). Early initiation of breastfeeding was not a significant predictor of EBF. Our results suggested that SSC is important for EIBF in Chinese baby-friendly hospitals. Skin-to-skin contact should be practiced after CS to promote breastfeeding and providing SSC with longer duration is encouraged to obtain the full benefit; if it is not feasible, a minimum of 30 min SSC could achieve improved EIBF and EBF at discharge
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