A high-density array of size-controlled silicon nanodots in a silicon oxide nanowire by electron-stimulated oxygen expulsion.

Methods of producing Si nanodots embedded in films of silicon oxide and silicon nitride abound, but fabrication of Si nanodots in a nanowire of these materials is very rare despite the fact that nanowire architecture enhances the charge collection and transport efficiencies for solar cells and field-effect transistors. We report a novel fabrication method for a high-density array of size-controlled sillicon nanodots from a silicon oxide nanowire using electron-beam irradiation. Our results demonstrate that a highly dense phase of Si nanodots with a narrow size distribution can be made from a silicon oxide nanowire with a core-shell structure of crystalline silicon-rich oxide (c-SRO)/amorphous silicon oxide (a-SiO(2)). This new nanomaterial shows the carrier transport characteristics of a semiconductor. The initially produced amorphous Si nanodots can be readily turned into crystalline Si (c-Si) nanodots by thermal annealing. Key characteristics of c-Si nanodots such as their size, number density, and rate of nucleation and growth are easily controlled by varying the electron radiation dose and annealing temperature. Nanodot formation is mechanistically initiated by electron trapping at the c-SRO core as well as at the core-shell interface, which leads to out-diffusion of the negatively charged oxygen through Coulomb repulsion, fostering the aggregation of Si atoms.

Evaluation of bone healing using rhBMP-2 soaked hydroxyapatite in ridge augmentation: a prospective observational study.

BACKGROUND: The goal of this study is to evaluate complication and effectiveness of alveolar ridge augmentations using a hydroxyapatite-based alloplastic bony substitute with rhBMP-2. METHODS: A total of 10 patients (4 males, 6 females; 58.5 ± 8.6 years) participated in this clinical research. Alveolar ridge augmentations were performed in edentulous (4 maxillary posterior, 5 mandibular posterior, and 1 mandibular anterior) regions. Anorganic bovine bone (ABB; Bio-Oss®, Geistlich Pharma AG, Wolhusen, Switzerland) was used as the bone graft material in the control group (n = 5)) while hydroxyapatite-based alloplastic bony substitute with rhBMP-2(HA+rhBMP-2; NOVOSIS®-Dent, CGBio Inc., Seongnam, Korea) was used in the experimental group (n = 5). In order to evaluate relative changes in bone volume and resorption rate of the bone graft material, CBCT radiographs were taken immediately and at 4 months after the bone graft in all subjects. Among the 10 patients, 8 received dental implants in Seoul National University Bundang Hospital, while the others received in local clinics. Bone specimens for further histomorphometric examinations were gained from these 8 patients using trephine burs during the implant placements. Clinical, radiographic, and histomorphometric evaluations were focused because of the small sample size. RESULTS: When CBCT radiographs were compared between immediately and at 4.07 ± 0.13 months after the bone graft, both alveolar bone widths (ABB 2.52 ± 0.18 mm, HA+rhBMP-2 1.75 ± 0.85 mm) and heights (ABB 1.68 ± 0.17 mm, HA+rhBMP-2 1.57 ± 0.28 mm) increased in the two groups. Resorption rates of transplanted bone graft material in the alveolar bone widths and heights were (ABB 29.7 ± 8.8%, HA+rhBMP-2 31.5 ± 7.4%) and (ABB 39.2 ± 21.8%, HA+rhBMP-2 52.6 ± 6.5%), respectively. Histomorphometrically, ABB group showed bone formation via osteoconduction and HA+rhBMP-2 group via osteoinduction. HA+rhBMP-2 group showed more bone formation around the bone graft materials than the ABB group. Postoperative complications were not found in all subjects. CONCLUSIONS: Our study had following conclusions: (1) Ridge augmentations using HA+rhBMP-2 could be clinically useful to supplement implant placements in edentulous regions. (2) Serious postoperative complications related to the graft material did not occur.

Influence of bone morphogenetic protein and proportion of hydroxyapatite on new bone formation in biphasic calcium phosphate graft: two pilot studies in animal bony defect model.

PURPOSE: The purpose of these two pilot studies using animal bony defect models was to evaluate the influence of bone morphogenetic protein (BMP) and proportion of hydroxyapatite (HA)/beta-tricalcium phosphate (ß-TCP) in biphasic calcium phosphate (BCP) graft on new bone formation. METHODS: In this study, four kinds of synthetic osteoconductive bone materials known for bone growth scaffold, OSTEON™II(HA:ß-TCP 30:70), OSTEON™III (HA:ß-TCP 20:80), OSTEON™II Collagen, and OSTEON™III Collagen, were prepared as BCP graft materials. In pilot study 1, three BCP materials (OSTEON™II, OSTEON™III, and OSTEON™II Collagen) were grafted in rabbit calvarial defects after impregnating in rhBMP-2. OSTEON™II without the rhBMP-2 impregnation was included in the study as the control. The amount of new bone was examined and measured histologically at 2, 4, and 8 weeks. In pilot study 2, four BCP materials (OSTEON™II, OSTEON™III, OSTEON™II Collagen, and OSTEON™III Collagen) were grafted in beagle dog mandibular defects after soaking in the rhBMP-2. The amount of total bone and new bone were measured three-dimensionally using microCT and healing process was examined histologically at 2, 4, and 8 weeks. RESULTS: In pilot study 1, rhBMP-2 impregnated groups showed more new bone formation than the rhBMP-2 free group. In pilot study 2, increased new bone formation was observed in time-dependent manner after graft of BCP and BCP-collagen (OSTEON™II, OSTEON™III, OSTEON™II Collagen, and OSTEON™III Collagen) impregnated with rhBMP-2. Also, BCP with a higher proportion of HA (30% HA) showed more favorable result in new bone formation and space maintenance, especially at the 8 weeks. CONCLUSION: From the results of the pilot studies, rhBMP-2 played positive roles in new bone formation and BCP could become a scaffold candidate for rhBMP-2 impregnation to induce new bone formation. Moreover, BCP with a higher proportion of HA (30% HA) could be considered more appropriate for rhBMP-2 carrier.

Histologic evaluation of a retrieved endosseous implant: a case report.

An implant that had penetrated the nasal cavity of a 53-year-old woman was removed after 10 months. The implant had a resorbable blast media surface and an external connection. Histomorphometric evaluation showed that the mean bone-implant contact ratio was 88.08%, and excellent osseointegration was observed. The mean bone fill between threads was 78.46%.

Capillary flow of amorphous metal for high performance electrode.

Metallic glass (MG) assists electrical contact of screen-printed silver electrodes and leads to comparable electrode performance to that of electroplated electrodes. For high electrode performance, MG needs to be infiltrated into nanometer-scale cavities between Ag particles and reacts with them. Here, we show that the MG in the supercooled state can fill the gap between Ag particles within a remarkably short time due to capillary effect. The flow behavior of the MG is revealed by computational fluid dynamics and density funtional theory simulation. Also, we suggest the formation mechanism of the Ag electrodes, and demonstrate the criteria of MG for higher electrode performance. Consequently, when Al85Ni5Y8Co2 MG is added in the Ag electrodes, cell efficiency is enhanced up to 20.30% which is the highest efficiency reported so far for screen-printed interdigitated back contact solar cells. These results show the possibility for the replacement of electroplating process to screen-printing process.

Plaque rupture is a determinant of vascular events in carotid artery atherosclerotic disease: involvement of matrix metalloproteinases 2 and 9.

BACKGROUND AND PURPOSE: Unstable carotid atherosclerotic plaques are characterized by cap rupture, leading to thromboembolism and stroke. Matrix metalloproteinases (MMPs) have been implicated in the progression of atherosclerosis and plaque rupture. The aim of this study was to assess the relationship between the expressions of MMP-2 and MMP-9 and carotid plaque instability. METHODS: Eighty atherosclerotic plaques were collected from 74 patients undergoing carotid endarterectomy. Clinical information was obtained from each patient, and plaque morphology was examined at the macroscopic and microscopic levels. The immunohistochemical expressions of MMPs were graded using semiquantitative scales. RESULTS: Macroscopic ulceration (84.6% versus 63.4%, p=0.042) and microscopic cap rupture (79.5% versus 51.2%, p=0.010) were more common in symptomatic than in asymptomatic patients. Immunoreactivities of MMP-2 and MMP-9 were increased in 40 and 36 atheromatous plaques, respectively. Macroscopic ulceration was strongly correlated with the expressions of MMP-2 (p<0.001) and MMP-9 (p=0.001). There were significant correlations between increased MMP-2 expression and cap rupture (p=0.002), intraplaque hemorrhage (p=0.039), and a thin fibrous cap (p=0.002), and between increased MMP-9 expression and cap rupture (p=0.010) and a large lipid core (p=0.013). CONCLUSIONS: Plaque rupture was significantly associated with the development of vascular events in carotid atherosclerotic disease. MMP-2 and MMP-9 are strongly correlated with plaque instability.

Correlation of immunohistochemical characteristics of the craniomandibular joint with the degree of mandibular lengthening in rabbits.

PURPOSE: This study examined immunohistochemical changes in the craniomandibular joints of rabbits after distraction osteogenesis following mandibular corticotomy. MATERIALS AND METHODS: The experimental animals (n = 8) were divided into 3 groups that underwent 2, 3.5, and 5 mm of unilateral distraction osteogenesis (groups 1, 2, and 3, respectively). After corticotomy of the left mandibular body and a 7-day healing period, a second operation was performed to expose the device. Distraction was then performed at the rate of 0.5 mm/d. A 14-day consolidation period was allowed after the distraction was complete. Changes in cartilage, osteoblast activity, and osteoclast activity were then examined. RESULTS: The differentiation and proliferation of cartilage increased in groups 1 and 2, were highest in group 2, and decreased in group 3. Group 2 also showed the greatest increase in the width of the hypertrophic chondrocyte layer. Relative to the control group, osteoclast activity was only somewhat higher in groups 1 and 2 but was significantly higher in group 3. Osteoblast activity was significantly higher in groups 1 and 2 than in the control group. However, the osteoblast activity in group 3 was slightly lower than that in group 2. At the time of unilateral mandibular distraction, no degenerative changes of the temporomandibular joint were observed in groups 1 or 2, but bone resorption was observed in group 3. CONCLUSIONS: The unilateral mandibular distraction of 2 or 3.5 mm was acceptable in that no degenerative changes of the temporomandibular joint were observed on either the distraction or the nondistraction sides. Five millimeters of distraction might be beyond physiologic limits.