Total heat exchangers are important equipment for fresh air ventilation with energy conservation. However, their implications for indoor air quality in terms of volatile organic compound permeation have not been known. The data in this article help us to clarify the impacts on indoor VOC levels of membrane-based heat exchangers. Guidelines for material selection can be obtained for future use total heat exchangers for building ventilation.
Strontium (Sr)-doped calcium sulfate hemihydrate (SrCSH) bioactive materials have been demonstrated to promote osteoporotic bone repair, being associated with the stimulation of bone formation and a reduction in bone resorption. However, the rapid degradation and absorption of SrCSH affects its clinical value. In order to delay the degradation time of SrCSH and improve the utilization of Sr2+, chitosan (CS)-coated SrCSH microspheres (CS-SrCSH) are prepared by electrostatic interaction between CS and SrCSH. X-ray diffraction analysis verifies that SrCSH coated by CS does not alter the phase composition of the SrCSH. It was observed that CS-SrCSH microspheres have uniform particle size. More importantly, the in vivo and in vitro degradation time of CS-SrCSH microspheres is significantly longer than that of SrCSH, and the release rate of Sr2+ is stable, achieving a sustained release effect. Furthermore, CS-SrCSH-based cement is used to repair critical-sized OVX rat tibial defects. The in vivo results reveal that CS-SrCSH exhibits a long-term capability for osteogenesis, angiogenesis and bone metabolism inhibition. In conclusion, the controllable degradation of CS-SrCSH-based cements described here could be beneficial for the repair of bone defects, especially in the osteoporotic bone.
Objective: To evaluate the feasibility and accuracy of three-dimensional (3D)-printed individualised guiding templates in total hip arthroplasty (THA) for the treatment of developmental dysplasia of the hip (DDH). Methods: 12 hips in 12 patients with Crowe type IV DDH were treated with THA. A 3D digital model of the pelvis and lower limbs was reconstructed using the computed tomography data of the patients. Preoperative surgical simulations were performed to determine the most suitable surgical planning, including femoral osteotomy and prosthesis placement. Based on the ideal surgical planning, individualised guiding templates were designed by software, manufactured using a 3D printer, and used in acetabulum reconstruction and femoral osteotomy during surgery. Results: 12 patients were followed up for an average of 72.42 months (range 38–135 months). During surgery, the guiding template for each case was matched to the bony markers of the acetabulum and proximal femur. Preoperative and follow-up Harris hip scores were 34.2 ± 3.7 and 85.2 ± 4.2; leg length discrepancy, 51.5 ± 6.5 mm and 10.2 ± 1.5 mm; and visual analogue scale scores, 6.2 ± 0.8 and 1.3 ± 0.3, respectively, with statistical difference. Shortened deformity and claudication of the affected limb were obviously improved after surgery. However, 1 patient had artificial hip dislocation 2 weeks after surgery, and another patient had sciatic nerve traction injury, both of whom recovered after physical treatment. Conclusions: Preoperative surgical simulation and 3D-printed individualised guiding templates can fulfil surgeon-specific requirements for the treatment of Crowe type IV DDH. Accurate THA can be achieved using 3D-printed individualised templates, which provide a new personalised surgical plan for the precise positioning and orientation of acetabular reconstruction and femoral osteotomy.
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