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By using spherical Cu powders as the conducting sintering material, the microstructures of sintered powder particles at different stages in the process of spark plasma sintering (SPS) have been investigated. Theoretical analyses are proposed to quantify the effects of the pulsed direct current on the neck formation and the neck growth of conducting powders. It is found that there is a considerable inhomogeneous distribution of the temperature increase from the particle-contacting surface to the center of the particle when the pulsed current passes through. The temperature at the particle-contacting surface may reach the boiling point of the material, which results in neck formation at relatively low-sintering temperatures through a process of local melting and rapid solidification. The neck growth depends on the local distribution of the current intensity, which is determined by the competition between the neck cross-sectional area and the electrical resistivity increasing with the temperature. Accordingly, we propose that the coarsening of necks follows a ''self-adjusting'' mechanism, which is likely to be the essential reason for the homogeneous distributions of neck sizes and sizes of fine grains formed in the neck zones during the SPS process.

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BackgroundThis study investigated the effect of a patient education video followed by retelling the process of bowel preparation on colonoscopy bowel preparation quality.Material/MethodsThis was a prospective, randomized, controlled clinical trial of outpatients undergoing colonoscopy. Patients were randomized (1: 1) to the video + retelling group or the control group. The primary endpoint was to assess the bowel preparation quality using the Ottawa Bowel Preparation Quality scale (Ottawa score). Risk factors associated with poor bowel preparation were also evaluated.ResultThe video + retelling group had a higher percentage of patients with adequate colonoscopy bowel preparation (Ottawa score <6) than the control group (P<0.001). Mean Ottawa total scores significantly differed between the control group and the video + retelling group (4.18±1.4 vs. 3.05±1.3, P<0.001). The video + retelling group showed superior cleanliness in the right, middle, and recto-sigmoid colon segments (all Ps <0.001). Logistic regression analysis revealed that male gender (OR=2.10, 95%CI: 1.098–4.018, P=0.025), diabetes mellitus (OR=2.830, 95%CI: 1.257–6.372, P=0.012), and no educational video followed by retelling bowel preparation process (OR=3.02, 95%CI: 1.731–5.270, P<0.001) were independently associated with poor bowel preparation.ConclusionsUse of an educational video followed by asking patients to retell the process of bowel preparation after receiving regular instructions is a convenient and risk-free practice that enhances the compliance with bowel preparation guidance and improves bowel preparation quality.

BackgroundInsulin resistance is one of the most common and important pathological features of type 2 diabetes (T2D). Recently, insulin resistance is increasingly considered to be associated with systemic chronic inflammation. Elevated levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in blood are predictive indicators of the development of T2D. Mesenchymal stem cell (MSC)-based therapies have been proven to have potential immunomodulation and anti-inflammatory properties through their paracrine effects; however, the mechanism for the anti-inflammatory effect of MSCs in enhancing insulin sensitivity is still uncertain.MethodsIn the present experiment, we used HepG2 cells, a human hepatoma cell line, and a MSC-HepG2 transwell culturing system to investigate the anti-inflammatory mechanism of human umbilical cord-derived MSCs (UC-MSCs) under palmitic acid (PA) and lipopolysaccharide (LPS)-induced insulin resistance in vitro. Insulin resistance was confirmed by glycogen assay kit and glucose assay kit. Inflammatory factor release was detected by ELISA, gene expression was tested by quantitative real-time PCR, and insulin signaling activation was determined by western blotting analysis. The changes of inflammatory factors and insulin signaling protein were also tested in T2D rats injected with UC-MSCs.ResultsTreating HepG2 cells with PA–LPS caused NLRP3 inflammation activation, including overexpression of NLRP3 and caspase-1, and overproduction of IL-1β and IL-18 as well as TNF-α from HepG2 cells. The elevated levels of these inflammatory cytokines impaired insulin receptor action and thereby prevented downstream signaling pathways, exacerbating insulin resistance in HepG2 cells. Importantly, UC-MSCs cocultured with HepG2 could effectively alleviate PA and LPS-induced insulin resistance by blocking the NLRP3 inflammasome activation and inflammatory agents. Furthermore, knockdown of NLRP3 or IL-1β partially improved PA and LPS-induced insulin signaling impairments in the presence of UC-MSCs. Similarly, UC-MSC infusion significantly ameliorated hyperglycemia in T2D rats and decreased inflammatory activity, which resulted in improved insulin sensitivity in insulin target tissues.ConclusionsOur results indicated that UC-MSCs could attenuate insulin resistance and this regulation was correlated with their anti-inflammatory activity. Thus, MSCs might become a novel therapeutic strategy for insulin resistance and T2D in the near future.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-017-0668-1) contains supplementary material, which is available to authorized users.