Carrier gas effects on aluminum-catalyzed nanowire growth.

Aluminum-catalyzed silicon nanowire growth under low-pressure chemical vapor deposition conditions requires higher reactor pressures than gold-catalyzed growth, but the reasons for this difference are not well understood. In this study, the effects of reactor pressure and hydrogen partial pressure on silicon nanowire growth using an aluminum catalyst were studied by growing nanowires in hydrogen and hydrogen/nitrogen carrier gas mixtures at different total reactor pressures. Nanowires grown in the nitrogen/hydrogen mixture have faceted catalyst droplet tips, minimal evidence of aluminum diffusion from the tip down the nanowire sidewalls, and significant vapor-solid deposition of silicon on the sidewalls. In comparison, wires grown in pure hydrogen show less well-defined tips, evidence of aluminum diffusion down the nanowire sidewalls at increasing reactor pressures and reduced vapor-solid deposition of silicon on the sidewalls. The results are explained in terms of a model wherein the hydrogen partial pressure plays a critical role in aluminum-catalyzed nanowire growth by controlling hydrogen termination of the silicon nanowire sidewalls. For a given reactor pressure, increased hydrogen partial pressures increase the extent of hydrogen termination of the sidewalls which suppresses SiH4 adsorption thereby reducing vapor-solid deposition of silicon but increases the surface diffusion length of aluminum. Conversely, lower hydrogen partial pressures reduce the hydrogen termination and also increase the extent of SiH4 gas phase decomposition, shifting the nanowire growth window to lower growth temperatures and silane partial pressures.

Preparation and characterization of biomedical highly porous Ti-Nb alloy.

The compressive strength and the biocompatibility were assessed for the porous Ti-25 wt%Nb alloy fabricated by the combination of the sponge impregnation technique and sintering technique. The alloy provided pore sizes of 300-600 µm, porosity levels of 71 ± 1.5%, in which the volume fraction of open pores was 94 ± 1.3%. The measurements also showed that the alloy had the compressive Young's modulus of 2.23 ± 0.5 GPa and the strength of 98.4 ± 4.5 MPa, indicating that the mechanical properties of the alloy are similar to those of human bone. The scanning electron microscopy (SEM) observations revealed that the pores were well connected to form three-dimension (3D) network open cell structure. Moreover, no obvious impurities were detected in the porous structure. The experiments also confirmed that rabbit bone mesenchymal stem cells (MSCs) could adhere and proliferate in the porous Ti-25 wt%Nb alloy. The interactions between the porous alloy and the cells are attributed to the porous structure with relatively higher surface. The suitable mechanical and biocompatible properties confirmed that this material has a promising potential in the application for tissue engineering.

[Clinical analysis of prosthesis replacement for proximal humerus tumors].

OBJECTIVE: To explore surgical strategies, functions and prognosis of artificial prosthesis replacement and soft tissue reconstruction for patients with invasive benign or primary malignant proximal humerus tumor.
 METHODS: A total of 17 patients with invasive benign or primary malignant proximal humerus tumor underwent prosthetic replacement after segment bone tumor resection and soft tissues reconstruction from April 2007 to April 2014 were enrolled. Based on histological types, tumor stages and surgical procedures, the effects of artificial prosthesis replacement and soft tissue reconstruction on prognosis and shoulder joint function were evaluated.
 RESULTS: All patients were followed up for 8 to 96 months (average time: 58.9 months). Among 11 patients with primary malignant tumor, 5 died of tumor recurrence or metastasis, and 6 showed tumor-free survival for 24 to 91 months (average time: 54.83 months). The 6 patients with aggressive benign tumors survived for 39 to 96 months, with an average of 72.33 months. The shoulder joint function of 17 patients recovered to 64.88% of normal. There were significant differences in the shoulder joint function between the patients who underwent half shoulder replacement and those who underwent total shoulder replacement (56.25% vs 72.56%, P<0.05). There were significant differences in the shoulder joint function between the patients who underwent Type I A excision (retention of abductor muscles and rotator cuff) and those who underwent Type I B excision (68.75% vs 61.44%, P<0.05).
 CONCLUSION: The survival of patients with invasive benign or primary malignant proximal humerus, who underwent artificial prosthesis replacement and soft tissue reconstruction, is closely related to tumor types. The shoulder joint function is associated with the methods of prosthesis replacement and soft tissue resection.

Substrate considerations for graphene synthesis on thin copper films.

Chemical vapor deposition on copper substrates is a primary technique for synthesis of high quality graphene films over large areas. While well-developed processes are in place for catalytic growth of graphene on bulk copper substrates, chemical vapor deposition of graphene on thin films could provide a means for simplified device processing through the elimination of the layer transfer process. Recently, it was demonstrated that transfer-free growth and processing is possible on SiO(2). However, the Cu/SiO(2)/Si material system must be stable at high temperatures for high quality transfer-free graphene. This study identifies the presence of interdiffusion at the Cu/SiO(2) interface and investigates the influence of metal (Ni, Cr, W) and insulating (Si(3)N(4), Al(2)O(3), HfO(2)) diffusion barrier layers on Cu-SiO(2) interdiffusion, as well as graphene structural quality. Regardless of barrier choice, we find the presence of Cu diffusion into the silicon substrate as well as the presence of Cu-Si-O domains on the surface of the copper film. As a result, we investigate the choice of a sapphire substrate and present evidence that it is a robust substrate for synthesis and processing of high quality, transfer-free graphene.

Recombinant TSG-6 protein inhibits the growth of capsule fibroblasts in frozen shoulder via suppressing the TGF-ß/Smad2 signal pathway.

BACKGROUND: The tumor necrosis factor-stimulated gene-6 (TSG-6) has been confirmed to inhibit inflammation. It is now generally accepted that local inflammatory stimulation around shoulder capsule causes proliferative fibrosis. This study aims to investigate the mechanism of recombinant TSG-6 protein inhibiting the growth of capsule fibroblasts in frozen shoulder via the TGF-ß/Smad2 signal pathway. METHODS: Human frozen shoulder capsule tissue was taken for primary and passage culture, and the 3rd generation fibroblasts from pathological frozen shoulder capsule were treated with different concentrations of recombinant TSG-6 protein, or with TGF-ß1 agonist SRI-011381. Immunoconfocal analysis was used to identify the isolated fibroblasts, and MTT assay, colony formation assay, and flow cytometry were used to detect the viability, proliferation, and apoptosis rate of fibroblast. The contents of fibrosis and inflammation indexes COL1A1, TNF-α, IL-6, and IL-1ß in the cell supernatant were detected using ELISA and then further examined by qRT-PCR. The expression of Bax, Bcl-2, and proteins related to TGF-ß/Smad2 pathway were detected by Western Blot. RESULTS: Compared with the blank control group, fibroblasts intervened with TSG-6 (2 µg and 5 µg) showed significantly decreased viability and proliferation ability and enhanced cell apoptosis, concurrent with the reductions in Bcl-2 expression; COL1A1, TNF-α, IL-6, and IL-1ß levels; and the expression of TGF-ß1 and phosphorylated Smad22, and an increase in Bax expression, while SRI-011381 treatment would reverse the effect of recombinant TSG-6 protein. CONCLUSION: Recombinant TSG-6 protein inhibited the growth of primary fibroblasts from human frozen shoulder capsule by suppressing the TGF-ß/Smad2 signaling pathway.

Fabrication and electrical properties of si nanowires synthesized by Al catalyzed vapor-liquid-solid growth.

The synthesis of epitaxially oriented Si nanowires at high growth rates (>1 microm/min) was demonstrated on (111) Si substrates using Al as the catalyst. The use of high H(2) and SiH(4) partial pressures was found to be effective at reducing problems associated with Al oxidation and nanowire nucleation, enabling growth of high aspect ratio structures at temperatures ranging from 500 to 600 degrees C with minimal tapering of the diameter. Because of the high growth rate observed, the Al catalyst is believed to be in the liquid state during the growth. Four-point resistance measurements and back-gated current-voltage measurements indicate that the wires are p-type with an average resistivity of 0.01 +/- 0.004 Omega-cm. These results suggest that Al is incorporated into the Si nanowires under these conditions at concentrations higher than the solubility limit (5-6 x 10(18) cm(-3)) for Al in Si at 550 degrees C. This work demonstrates that Al can serve as both an effective catalyst and p-type dopant for the growth of Si nanowires.

Correlating Raman spectral signatures with carrier mobility in epitaxial graphene: a guide to achieving high mobility on the wafer scale.

We report a direct correlation between carrier mobility and Raman topography of epitaxial graphene (EG) grown on silicon carbide (SiC). We show the Hall mobility of material on SiC(0001) is highly dependent on thickness and monolayer strain uniformity. Additionally, we achieve high mobility epitaxial graphene (18100 cm(2)/(V s) at room temperature) on SiC(0001) and show that carrier mobility depends strongly on the graphene layer stacking.

The nature of catalyst particles and growth mechanisms of GaN nanowires grown by Ni-assisted metal-organic chemical vapor deposition.

The structure and chemistry of the catalyst particles that terminate GaN nanowires grown by Ni-assisted metal-organic chemical vapor deposition were investigated using a combination of electron diffraction, high-resolution transmission electron microscopy, and x-ray energy dispersive spectrometry. The crystal symmetry, lattice parameter, and chemical composition obtained reveal that the catalyst particles are Ni(3)Ga with an ordered L 1(2) structure. The results suggest that the catalyst is a solid particle during growth and therefore favor a vapor-solid-solid mechanism for the growth of GaN nanowires under these conditions.

[One-stage management of open distal tibial Pilon fractures].

OBJECTIVE: To explore the operative method of open distal tibial pilon fractures, and to evaluate the outcome of ankle joint function postoperatively. METHODS: From March 2003 to March 2007, 24 patients with open Pilon fractures were treated with one-stage open reduction and internal fixation (18 males and 6 females). The average age was 37.6 years (14-53 years). All 24 patients had open fracture, 12 of whom combined fibular fracture. According to AO comprehensive classification system, the fractures was classified as C1 in 4, C2 in 9, and C3 in 11. According to Gustilo-Anderson classification method, the fracture was classified as Type I in 3, Type II in 5, Type III A in 4, Type III B in 10, and Type III C in 2. All tibial pilon fractures were treated by radical debridement, one-stage open reduction and internal fixation. Soft tissue defection was covered by a vascularized flap and continually washed by pipes under the flap. RESULTS: All patients were followed-up at an average of 2.3 years (1-3.8 years) after the surgery. All the fractures healed at an average of 22.3 weeks (16-54 wk) postoperatively. According to the scoring system of Conroy, 17 were excellent (62.5%), 4 good (25%), and 3 poor (12.5%), the excellence rate was 87.5%. According to the ankle score of Teeny and Wiss, there were 11 excellent (37.5%), 7 good (37.5%), 3 fair (16.7%), and 3 poor (8.3%) and the excellence rate was 75%. CONCLUSION: One-stage management for open Pilon fracture has the advantages of fewer complications, lower infectious rate, and better ankle joint function.

In vivo testing of porous Ti-25Nb alloy serving as a femoral stem prosthesis in a rabbit model.

The aim of the present study was to observe the performance of Ti-25Nb alloys with various porosities as femoral stem prostheses in a rabbit model, thus providing basic experimental evidence for the development of porous prostheses. The porous Ti-25Nb alloy prostheses were designed according to the morphology of the medullary cavity. These prostheses were placed into the femoral medullary cavities in 36 New Zealand white rabbits. Postoperative X-ray films, scanning electron microscopy (SEM) of the implant interface, energy-dispersive spectroscopy (EDS) analysis of the implant surface, pulling-out test and general observations were conducted. The specimens showed good biocompatibility; there was no obvious bone absorption in porous Ti-25Nb specimens with different porosities at different time points observed using X-ray films. Under SEM examination, calcium deposits were observed inside the pores and in the interface between bone and prostheses. The EDS analysis demonstrated that calcium deposits were present on the surface of the prostheses at the eight-week point postoperatively. The pulling-out test showed good bonding strength between bone and implant; after pulling out, the surface and inside the pores of the prostheses all presented bone mass. Porous Ti-25Nb alloy implants presents good biocompatibility as well as providing a biological fixation between the bone and implant. A porosity of 70% is more advantageous to the newborn bone ingrowth, combined with achieving a more solid bone-implant interface.

[EFFECTIVENESS OF ARTHROSCOPIC ULTRA-Braid SUTURE PLANE FIXATION FOR ANTERIOR CRUCIATE LIGAMENT TIBIAL EMINENCE AVULSION FRACTURES].

OBJECTIVE: To investigate the surgical technique and effectiveness of arthroscopic ULTRA-Braid suture plane fixation for anterior cruciate ligament (ACL) tibial eminence avulsion fractures. METHODS: Between June 2012 and October 2014, 16 cases of ACL tibial eminence avulsion fracture were treated with ULTRA-Braid suture plane fixation under arthroscopy. There werg 10 males and 6 females, aged from 17 to 38 years (mean, 25.8 years). The left knee was involved in 5 cases and the right knee in 11 cases. The causes were traffic accident injury in 9 cases, falling from height injury in 4 cases, and sports injury in 3 cases. The average interval from injury to operation was 7 days (range, 5-10 days) except 1 patient who received operation at 6 weeks after injury. The knee joint swelling was obvious; the result of Lachman test was positive; and the knee joint Lysholm score was 45.38 ± 9.87. According to classification standard introduced by Meyers-McKeever-Zaricnyj, 7 cases were rated as type II, 8 cases as type III, and 1 case as type IV, excluding ligament and meniscus injury. RESULTS: All the incisions healed by first intention. The patients received follow-up of 6-18 months (mean, 10 months). The postoperative X-ray and CT showed anatomic reduction (12 cases) or near anatomic reduction (4 cases); all fractures healed at 6 months after operation. The result of Lachman test was negative in the other 15 patients except 1 patient (II degree). One patient had slight knee pain at 6 months postoperatively, and pain symptom disappeared after 1 year; the other cases resumed daily activities. Lysholm score at last follow-up was 98.13 ± 2.34, showing significant difference when compared with preoperative score (t = -20.801, P = 0.000). CONCLUSION: Arthroscopic ULTRA-Braid suture plane fixation for ACL tibial eminence avulsion fractures is an effective procedure with the advantages of minimal trauma, reliable fixation, satisfactory functional recovery, and simultaneously avoiding the second surgery.

The effects of shell layer morphology and processing on the electrical and photovoltaic properties of silicon nanowire radial p+ - n+ junctions.

Single wire p(+)-n(+) radial junction nanowire solar cell devices were fabricated by low pressure chemical vapor deposition of n(+) silicon shell layers on p(+) silicon nanowires synthesized by vapor-liquid-solid growth. The n(+)-shell layers were deposited at two growth temperatures (650 °C and 950 °C) to study the impact of shell crystallinity on the device properties. The n-type Si shell layers deposited at 650 °C were polycrystalline and resulted in diodes that were not rectifying. A pre-coating anneal at 950 °C in H2 improved the structural quality of the shell layers and yielded diodes with a dark saturation current density of 3 × 10(-5) A cm(-2). Deposition of the n-type Si shell layer at 950 °C resulted in epitaxial growth on the nanowire core, which lowered the dark saturation current density to 3 × 10(-7) A cm(-2) and increased the solar energy conversion efficiency. Temperature-dependent current-voltage measurements demonstrated that the 950 °C coated devices were abrupt junction p(+)-n(+) diodes with band-to-band tunneling at high reverse-bias voltage, while multi-step tunneling degraded the performance of devices fabricated with a 950 °C anneal and 650 °C coating. The higher trap density of the 950 °C annealed 650 °C coated devices is believed to arise from the polycrystalline nature of the shell layer coating, which results in an increased density of dangling bonds at the p(+)-n(+) junction interface.

Potential use of porous titanium-niobium alloy in orthopedic implants: preparation and experimental study of its biocompatibility in vitro.

BACKGROUND: The improvement of bone ingrowth into prosthesis and enhancement of the combination of the range between the bone and prosthesis are important for long-term stability of artificial joints. They are the focus of research on uncemented artificial joints. Porous materials can be of potential use to solve these problems. OBJECTIVES/PURPOSES: This research aims to observe the characteristics of the new porous Ti-25Nb alloy and its biocompatibility in vitro, and to provide basic experimental evidence for the development of new porous prostheses or bone implants for bone tissue regeneration. METHODS: The Ti-25Nb alloys with different porosities were fabricated using powder metallurgy. The alloys were then evaluated based on several characteristics, such as mechanical properties, purity, pore size, and porosity. To evaluate biocompatibility, the specimens were subjected to methylthiazol tetrazolium (MTT) colorimetric assay, cell adhesion and proliferation assay using acridine staining, scanning electron microscopy, and detection of inflammation factor interleukin-6 (IL-6). RESULTS: The porous Ti-25Nb alloy with interconnected pores had a pore size of 200 µm to 500 µm, which was favorable for bone ingrowth. The compressive strength of the alloy was similar to that of cortical bone, while with the elastic modulus closer to cancellous bone. MTT assay showed that the alloy had no adverse reaction to rabbit bone marrow mesenchymal stem cells, with a toxicity level of 0 to 1. Cell adhesion and proliferation experiments showed excellent cell growth on the surface and inside the pores of the alloy. According to the IL-6 levels, the alloy did not cause any obvious inflammatory response. CONCLUSION: All porous Ti-25Nb alloys showed good biocompatibility regardless of the percentage of porosity. The basic requirement of clinical orthopedic implants was satisfied, which made the alloy a good prospect for biomedical application. The alloy with 70% porosity had the optimum mechanical properties, as well as suitable pore size and porosity, which allowed more bone ingrowth.

Screening serum biomarker of knee osteoarthritis using a phage display technique.

OBJECTIVES: To screen serum biomarker of knee osteoarthritis (OA) using a phage random peptide library. DESIGN AND METHODS: A phage random peptide library of random peptide 12-mers was screened with purified immunoglobulin G (IgG) from sera of knee OA patients. Patients with knee rheumatoid arthritis (RA), hip OA, non-erosive hand OA or erosive hand OA, and healthy volunteers were used as controls. RESULTS: A phage clone with inserted peptide TGLESGHGPGDS (named KOA1) showed 90% positive reaction rate with the knee OA patients, significantly higher than that with the knee RA patients (27.8%), the non-erosive hand OA patients (34.3%), the erosive hand OA patients (31.3%) and the healthy controls (12.0%), but not the hip OA patients (82.5%). CONCLUSIONS: The novel knee OA mimic peptide KOA1 identified with a random phage display peptide library and sera from knee OA patients could be a potential serum biomarker for knee OA.

Knockdown of endothelin A receptor expression inhibits osteosarcoma pulmonary metastasis in an orthotopic xenograft mouse model.

Previous in vitro studies suggest that the endothelin A receptor (ETAR) could be a potential therapeutic target for osteosarcoma (OS) metastasis. In the present study, we assessed for the first time the role of ETAR in OS proliferation and pulmonary metastasis in vivo. MG-63 human OS cells were stably transduced with ETAR shRNA or scramble control shRNA and injected into the tibia of nude mice to generate an orthotopic xenograft OS model. The mice were divided into three groups (n=10 each group): i) the untransduced control group, where the mice were injected with untransduced MG-63 cells; ii) the scramble control group, where the mice were injected with cells stably transduced with the scramble control shRNA; iii) the ETAR-shRNA group, where the mice were injected with cells stably transduced with ETAR shRNA. The ETAR shRNA knocked down more than 75% of endogenous ETAR expression and significantly inhibited invasion, but not proliferation/viability of MG-63 cells in vitro. In the orthotopic xenograft OS mouse model, no significant difference in the tumor volume was observed over time among the untransduced control, the scramble control and the ETAR-shRNA groups. However, a combination of clinical signs, organ examinations and quantitative clonogenic lung metastasis assays showed that lung metastasis in the ETAR-shRNA group was significantly lower than that in the control groups. Immunohistochemical analyses revealed that the matrix metalloproteinase-2 (MMP-2) expression was significantly reduced in the ETAR-shRNA group compared with the control groups. The results were confirmed with western blot analyses using primary tumor tissues or the stably transduced MG-63 cells. In conclusion, we demonstrated in an orthotopic xenograft OS model that ETAR is critical for OS pulmonary metastasis, but not for tumor growth. This study provides the first in vivo evidence suggesting an important role for ETAR in OS pulmonary metastasis.

[Effectiveness of vacuum sealing drainage combined with anti-taken skin graft for primary closing of open amputation wound].

OBJECTIVE: To observe the effectiveness of vacuum sealing drainage (VSD) combined with anti-taken skin graft on open amputation wound by comparing with direct anti-taken skin graft. METHODS: Between March 2005 and June 2010, 60 cases of amputation wounds for limbs open fractures were selected by using the random single-blind method. The amputation wounds were treated with VSD combined with anti-taken skin graft (test group, n = 30) and direct anti-taken skin graft (control group, n = 30). No significant difference was found in age, gender, injury cause, amputation level, defect size, preoperative albumin index, or injury time between 2 groups (P > 0.05). In test group, the redundant stump skin was used to prepare reattached staggered-meshed middle-thickness skin flap by using a drum dermatome dealing after amputation, which was transplanted amputation wounds, and then the skin surface was covered with VSD for continuous negative pressure drainage for 7-10 days. In control group, wounds were covered by anti-taken thickness skin flap directly after amputation, and conventional dress changing was given. RESULTS: To observe the survival condition of the skin graft in test group, the VSD device was removed at 8 days after operation. The skin graft survival rate, wound infection rate, reamputation rate, times of dressing change, and the hospitalization days in test group were significantly better than those in control group [ 90.0% vs. 63.3%, 3.3% vs. 20.0%, 0 vs. 13.3%, (2.0 +/- 0.5) times vs. (8.0 +/- 1.5) times, and (12.0 +/- 2.6) days vs. (18.0 +/- 3.2) days, respectively] (P < 0.05). The patients were followed up 1-3 years with an average of 2 years. At last follow-up, the scar area and grading, and two-point discrimination of wound in test group were better than those in control group, showing significant differences (P < 0.05). No obvious swelling occurred at the residual limbs in 2 groups. The limb pain incidence and the residual limb length were better in test group than those in control group (P < 0.05). Whereas, no significant difference was found in the shape of the residual limbs between 2 groups (P > 0.05). In comparison with the contralateral limbs, the muscle had disuse atrophy and decreased strength in residual limbs of 2 groups. There was significant difference in the muscle strength between normal and affected limbs (P < 0.05), but no significant difference was found in affected limbs between 2 groups (P > 0.05). CONCLUSION: Compared with direct anti-taken skin graft on amputation wound, the wound could be closed primarily by using the VSD combined with anti-taken skin graft. At the same time it could achieve better wound drainage, reduce infection rate, promote good adhesion of wound, improve skin survival rate, and are beneficial to lower the amputation level, so it is an ideal way to deal with amputation wound in the phase I.

Nucleation of epitaxial graphene on SiC(0001).

A promising route for the synthesis of large-area graphene, suitable for standard device fabrication techniques, is the sublimation of silicon from silicon carbide at elevated temperatures (>1200 degrees C). Previous reports suggest that graphene nucleates along the (110n) plane, known as terrace step edges, on the silicon carbide surface. However, to date, a fundamental understanding of the nucleation of graphene on silicon carbide is lacking. We provide the first direct evidence that nucleation of epitaxial graphene on silicon carbide occurs along the (110n) plane and show that the nucleated graphene quality improves as the synthesis temperature is increased. Additionally, we find that graphene on the (110n) plane can be significantly thicker than its (0001) counterpart and appears not to have a thickness limit. Finally, we find that graphene along the (110n) plane can contain a high density of structural defects, often the result of the underlying substrate, which will undoubtedly degrade the electronic properties of the material. Addressing the presence of non-uniform graphene that may contain structural defects at terrace step edges will be key to the development of a large-scale graphene technology derived from silicon carbide.

Epitaxial graphene materials integration: effects of dielectric overlayers on structural and electronic properties.

We present the integration of epitaxial graphene with thin film dielectric materials for the purpose of graphene transistor development. The impact on epitaxial graphene structural and electronic properties following deposition of Al(2)O(3), HfO(2), TiO(2), and Ta(2)O(5) varies based on the choice of dielectric and deposition parameters. Each dielectric film requires the use of a nucleation layer to ensure uniform, continuous coverage on the graphene surface. Graphene quality degrades most severely following deposition of Ta(2)O(5), while the deposition if TiO(2) appears to improve the graphene carrier mobility. Finally, we discuss the potential of dielectric stack engineering for improved transistor performance.