In this study, autologous bone grafts using bone-fixing nails made of magnesium-zinc-calcium ternary alloys were performed using rabbit skulls.Two types of nails for bone fixation were prepared: 2.5 mm width, 3 mm length and 2.5 mm width, 2 mm length. A disk-shaped bone with a diameter of 5 mm was resected from the parietal bone and fixed with a 3 mm long nail. As a control group, a 2 mm long nail was driven into the existing bone. The rabbits were sacrificed at 1, 4, 12, and 24 weeks after surgery. The resected samples were observed with micro X-ray CT, and embedded in methyl methacrylate to prepare non-decalcified specimens. The in vivo localization of elements was examined using energy-dispersive X-ray spectroscopy (EDS).Micro X-ray CT images of samples showed volume reduction due to degradation in both the bone graft and control groups. No significant difference in the amount of degradation between the two groups was observed, however characteristic degradation processes were observed in each group. The samples stained with alizarin red S showed amorphous areas around the nails, which were considered as corrosion products and contacted directly with the newly formed bones. EDS analysis showed that corrosion products were mainly composed of magnesium and oxygen at an early stage, while calcium and phosphorus were detected on the surface layer during the long-term observation.The degradation speed of the magnesium alloy nails varied depending on the shapes of the nails and surrounding tissue conditions. A calcium phosphate layer was formed on the surface of magnesium alloy nails, suggesting that the degradation rate of the nail was slow.
This research examined what dominant speech style Japanese family members utilize by analyzing their conversations at home. In addition, the research conducted the Parent Interviews to find out what efforts the parents consistently make to develop and maintain their children's Japanese ability in terms of Japanese formal speech style.
Recently, the transportation means of the elderly have been insufficient due to aging and depopulation, therefore, the area volunteers have provided the demand-responsive transport (DRT) for seniors such as senior transportation service and demand bus. However, the demands collection via telephone or mobile applications has problems: the telephone call imposes a heavy burden on volunteers, and the mobile applications hinder the elderly who are not using or familiar with smartphone from using the service. In this paper, we propose a pick-up demand collection system that easily collects the demands from the elderly and makes them visible to the transportation manager. To collect demands, we designed the demand transmission device having LPWA (Low Power Wide Area) and a user interface for the elderly. As a result of asking the elderly to operate our prototype demand transmission device, it was found that the operability was better for the elderly than the existing input interface with the smartphone. In addition, we confirmed that the transmission device can transmit the demands through repeater devices with multihop communication by LPWA even if the demand request is not directly reachable to gateway due to the influence of radio shielding objects.
This study was undertaken to evaluate the in vitro biocompatibility of newly developed Ni-free Ti-based shape memory alloys (SMAs) in comparison to that of commercial pure titanium (cpTi). This study compared Ti-24 mol%Nb-3 mol%Al (Ti-Nb-Al) and Ti-7 mol%Cr-3 mol%Sn (Ti-Cr-Sn) to cpTi from a cell-compatibility perspective. In all, 63 samples (21 samples for each group) were prepared, which were machined into 10-mm-diameter, 0.15-mm-thick, mirror-polished disks. Their surface morphology was evaluated using scanning electron microscopy (SEM). The chemical composition of the sample surface was determined using an energy dispersive X-ray analyzer (EDX). Sample surface roughness was measured using a non-contact 3D profiler. After sample surface observations, the cell proliferation and viability of African green monkey kidney fibroblast cell line COS7 in direct contact with these new alloys were evaluated by DNA quantification, by live cell imaging using CelLuminate Red fluorescent cell stain as a new method, and by cytoskeletal observations by immunofluorescent actin labelling. Cell proliferation was examined after 1, 3, and 5 days of culture. Results were the following. (i) Each sample showed high purity and a very smooth surface, showing no morphological differences among groups. (ii) The COS7 cells took in sufficient CelLuminate Red to visualize the cells using epifluorescent microscopy, and (iii) cell proliferation with Ti-Cr-Sn was lower than with either cpTi or Ti-Nb-Al. These results suggest that Ti-Nb-Al alloy showed biocompatibility as high as that of cpTi and that it is more suitable for biomedical applications.
Film power capacitors are made out of polypropylene (PP) films co-wound with Al foil electrodes, impregnated with insulating oil. In a void, if any, or around the electrode edge, partial discharges (PDs) occur, leading to PP film deterioration and eventually to dielectric breakdown. In this work, PD characteristics were investigated using the oil gap electrode system in which an oil gap with thickness of 12 μm or 50 μm was formed between PP films. PD inception voltage (PDIV), discharge amplitude-PD number-PD phase (q-n-φ) pattern and PD light emission were observed under AC voltage application. The q-n-φ pattern and light emission of PDs generated in the oil gap containing oil-decomposed-gas voids differed from those without gas voids. The sequential change of PD characteristics showed that the oil-decomposed-gas voids were generated by PD in the oil gap, and then the PD occurred in the gas voids. The relation between the PP film deterioration and the difference in sequential change of PD characteristics were discussed.
The in vitro and in vivo degradation behavior and osteogenic ability of new hydrothermal hydroxyapatites (HAs) were investigated. Two different HA granules with short and long-rod HA crystals (SRHA and LRHA, respectively) were hydrothermally synthesized. A low pH immersion test was performed to observe morphological degradation features. At 2 days, HA in a low pH immersion fluid revealed pitfall-like degradations on the surface. Both HA granules were implanted in rat calvaria bone defects. The biodegradable behavior and effects of new bone formation were histologically and radiographically investigated. At 4 and 24 weeks after surgery, defect areas were filled with implanted HAs and newly formed bone. No differences in boundary area shapes between SRHA and LRHA were found. The area of LRHA degradation was greater compared with SRHA (p < 0.05). At 24 weeks, implanted HA granules showed inward incursion of fibrous tissue and tissue fluid. Accordingly, in vivo hydrothermal HA indicated good osteogenesis and progress.
The osteogenic effect of newly developed bisphosphonate (Disodium Dihydrogen-4-[(methylthio) phenylthio] Methane- Bisphosphonate (MPMBP)) was examined for clinical application in bone damage. A bone defect was made in the femur of ninety-seven male Wistar rats. 30µl of MPMBP (experimental group) or saline (control group) was injected around defect once every 3 days. The osteogenic effect to 4 weeks was performed at 1, 2, 3 and 4 weeks (experiment 1). Long-term observation was performed at 12 and 24 weeks after discontinuation of administration of MPMBP at 3 weeks (experiment 2). Newly formed bone was examined radiographically and histologically in both experiments. The elemental analysis was performed to investigate the quality of bone by energy-dispersive X-ray analysis. In experiment 1, newly bone formation is observed in the bone marrow cavity and cortical defect in both groups. The bone volume at 4 weeks was decreased in control group and maintained in experimental groups. In experiment 2, newly formed bone in bone marrow cavity was absorbed at 12 weeks in control group, and showed gradually decrease to 24 weeks in experimental group. The Ca/P of newly formed bone showed little difference between control and experimental groups. It was confirmed that the MPMBP administration had local effects, showing the promotion of new bone formation and long-term bone remodeling.
Biodegradable magnesium (Mg) alloys are the most promising candidates for osteosynthesis devices. However, their in vivo corrosion behaviour has not been fully elucidated. The aim of this study was to clarify the influence of the physiological environment surrounding Mg alloys on their corrosion behaviour. A Mg–1.0Al alloy with a fine-grained structure was formed into plates using titanium (Ti) as a control. These plates were implanted into the subperiosteum in the head, subcutaneous tissue of the back, and in the muscle of the femur of rats for 1, 2 and 4 weeks. The volumes of the remaining Mg alloy and of the insoluble salt deposition and gas cavities around the Mg alloy were determined by microtomography, and the volume losses were calculated. Then, the tissue response around the plates in each implantation site was examined histopathologically, and its relation to the respective volume loss was analyzed. These analyses determined that the Mg alloy was corroded fastest in the head, at an intermediate level in the back, and slowest in the femur. The insoluble salt deposition at the Mg alloy surface had no influence on the volume loss. Gas cavities formed around the Mg alloy at all implantation sites and decreased after 4 weeks. Histopathological examination revealed that the Mg alloy exhibited good biocompatibility, as was seen with Ti. In addition, vascularized fibrous capsules formed around the plates and became mature with time. Notably, the volume loss in the different anatomical locations correlated with capsule thickness. Together, our results suggest that, to facilitate the successful clinical application of Mg alloys, it will be necessary to further comprehend their interactions with specific in vivo environments.
Abstract This study was conducted in order to investigate biological compatibility of a thin and flexible hydroxyapatite (HAP) paper which consists of ultralong hydroxyapatite nanowires. Circular‐shaped cranial bone defects with a diameter of 8.8 mm were prepared to expose the dura maters in Wistar rats. The similar‐sized, circular‐shaped HAP paper was placed at the bottom of the bone defects. After 2, 4, and 8 weeks, the rats were sacrificed, and the experimental sections were examined by micro‐CT scanning and histological observation. The HAP paper covered with fibrous tissues showed no inflammatory cell infiltration, and their thicknesses decreased over time. Tartrate‐resistant acid phosphatase‐positive osteoclast‐like cells were induced around the edges of the HAP paper along with the exfoliation of the HAP paper. The newly‐formed bones were observed in the bone‐defected areas, either with a direct contact with the HAP paper or through thin fibrous tissues. The HAP paper‐induced osteoblast differentiation was confirmed since the alkaline phosphatase activities were detected on the surfaces of the HAP paper. These results indicated that the HAP paper may induce osteogenesis without causing any harmful effects. The highly flexible HAP paper can contribute to further development of bone regenerative therapy.
