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For the purpose of developing high-quality metal/polymer joints without defects to satisfy the strict requirement of biomedical application, 3D printed TC4 alloy was joined with non-polar ultra-high molecular weight polyethylene (UHMWPE) via friction spot joining (FSpJ). In this study, five sets of experiments with different joining temperatures were designed to figure out the formation mechanisms of defects. The joining temperature (TJ) histories were measured with K-type thermocouple inserted in the lap interface. Macro−/micro-scale defects in TC4/UHMWPE joints were analyzed. Numerical simulation was carried out to study the temperature distribution during joining and gap formation during cooling. Micro−/nano-scale interfacial bonding was characterized using scanning electron microscope and transmission electron microscope. Then, the formation mechanisms of defects were better understood. Macro-scale defects were shown as insufficient filling and bubbles. Insufficient filling is linearly related to the TJ which can be alleviated by applying higher TJ. However, when the TJ is >385 °C, large bubbles appear due to excessive and fast thermal degradation of UHMWPE. Meanwhile, micro-scale defect, appearing as continuous gaps caused by the shrinkage of polymer can be avoided by enhancing the micro-scale interfacial bonding.

AbstractFlaxseed (FS) is an oilseed rich in phytoestrogens and n-3 polyunsaturated fatty acids, compounds that may attenuate bone loss during aging. We previously demonstrated using the ovariectomized (OVX) rat model of postmenopausal osteoporosis that 10% dietary FS combined with low-dose estrogen therapy (LD) preserves vertebral bone mass and strength more so than either treatment alone. However, it was prudent to also consider the effect of this intervention on uterine tissue as LD, and possibly FS, may have estrogenic, and thus negative, effects on uterine tissue. The present study investigated if FS enhances the estrogenic effect of LD on markers of uterine health in OVX rats. Three-month-old rats were randomized to groups: (1) SHAM, (2) OVX, (3) OVX+FS, (4) OVX+LD, or (5) OVX+FS+LD. Ground FS was added to the AIN-93M diet (100 g/kg of diet), and LD was delivered by subcutaneous implant (0.42 μg of 17β-estradiol/kg of body weight/day) to mimic LD in postmenopausal women. After 12 weeks, histological analyses of uterine tissue demonstrated flattened or cuboidal luminal epithelia organized in a single layer in the OVX group, while FS, LD, and FS+LD induced a single layer of elongated luminal epithelia, columnar in shape. The SHAM group had the greatest epithelial mass. Cell proliferation was similar among all OVX groups. Therefore FS and FS+LD similarly induce estrogen-like effects on the morphology of luminal epithelia that are weaker than in the SHAM group without inducing cell proliferation in OVX rats. Thus, FS does not enhance the estrogenic effect of LD on markers of uterine health in OVX rats. [ABSTRACT FROM AUTHOR]