Controllable preparation of 2D carbon paper modified with flower-like WS2 for efficient microwave absorption.

In the practical application of microwave absorbing materials, traditional powder materials need to be mixed with the matrix to fabricate composite coatings. However, the complex preparation process of composite coatings and the uneven dispersion of powders in the matrix limit their application. To solve these problems, two-dimensional (2D) F-WS2/CP composite films were prepared by using carbon paper (CP) as a dispersion matrix and loading flower-like WS2 on its surface through a simple hydrothermal method. The morphology and microwave absorption (MA) performance of the composite films are easily regulated by adjusting the amount of reaction precursors. The combination of WS2 and CP facilitates impedance matching and improves the electromagnetic wave attenuation performance based on the synergistic effect of different loss mechanisms including multiple reflections and scattering, interfacial polarization, dipolar polarization, and conduction loss. At a low filler content (5 wt%), the maximum reflection loss (RL) of the composite film is up to -50 dB (99.999% energy absorption) at 12.5 GHz with 2.8 mm thickness. Moreover, at a relatively thin 1.8 mm thickness, its maximum RL remains -35 dB (>99.9% energy absorption). The as-prepared composite film shows excellent MA properties at a thinner thickness and lower filling content, providing inspiration for the preparation of light weight and efficient 2D thin-film microwave absorbers in the future.

Effects of low-intensity electromagnetic fields on the proliferation and differentiation of cultured mouse bone marrow stromal cells.

BACKGROUND: Electromagnetic fields (EMFs) used in stem-cell tissue engineering can help elucidate their biological principles. OBJECTIVE: The aim of this study was to investigate the effects of low-intensity EMFs on cell proliferation, differentiation, and cycle in mouse bone marrow stromal cells (BMSCs) and the in vivo effects of EMFs on BMSC. METHODS: Harvested BMSCs were cultured for 3 generations and divided into 4 groups. The methylthiotetrazole (MTT) assay was used to evaluate cell proliferation, and alkaline phosphatase activity was measured via a colorimetric assay on the 3rd, 7th, and 10th days. Changes in cell cycle also were analyzed on the 7th day, and bone nodule formation was analyzed on the 12th day. Additionally, the expression of the collagen I gene was examined by reverse transcription-polymerase chain reaction (RT-PCR) on the 10th day. The BMSCs of the irradiated group and the control group were transplanted into cortical bone of different mice femurs separately, with poly(lactic-co-glycolic acid) (PLGA) serving as a scaffold. After 4 and 8 weeks, bone the bone specimens of mice were sliced and stained by hematoxylin and eosin separately. RESULTS: The results showed that EMFs (0.5 mT, 50 Hz) accelerated cellular proliferation, enhanced cellular differentiation, and increased the percentage of cells in the G(2)/M+S (postsynthetic gap 2 period/mitotic phase + S phase) of the stimulation. The EMF-exposed groups had significantly higher collagen I messenger RNA levels than the control group. The EMF + osteogenic medium-treated group readily formed bone nodules. Hematoxylin and eosin staining showed a clear flaking of bone tissue in the irradiated group. CONCLUSION: Irradiation of BMSCs with low-intensity EMFs (0.5 mT, 50 Hz) increased cell proliferation and induced cell differentiation. The results of this study did not establish a stricter animal model for studying osteogenesis, and only short-term results were investigated. Further study of the mechanism of EMF is needed.

Effects of electromagnetic fields on bone regeneration in experimental and clinical studies: a review of the literature.

OBJECTIVE: To assess the experimental and clinical data regarding the effects of electromagnetic fields (EMFs) on fracture non-union. DATA SOURCES: The English language literature regarding EMFs on fracture non-union were searched using MEDLINE, Web of Science and Embase, for the period January 2006 to June 2011. The search terms were electromagnetic fields and non-union/bone marrow stem cells (BMSCs)/bone. STUDY SELECTION: Articles were included in the review if they were related to the use of EMFs on BMSCs or bone tissue. Papers without full manuscripts available were excluded. RESULTS: The basic and clinical research in this field, while somewhat limited, supports the insightful application of EMFs to ameliorate disability due to fracture non-union. CONCLUSIONS: Further basic and clinical research to validate the use of EMFs in facilitating function and bone reparative processes in fracture non-union is required.

Mechanical properties of 7-10mm bone grafts and small slurry grafts in impaction bone grafting.

We compared the mechanical properties of morselized cancellous bone grafts of two sizes: 7-10 mm bone and small slurry bone (about 2 mm). The in vitro test was designed to simulate the hammer and impactor system for impaction bone grafting used in hip arthroplasty clinical practice. The 7-10 mm bone grafts showed higher height, elastic modulus, and massive extrusion strength than those of the small slurry bone grafts. No difference was found in yield strength. The bone mineral density of the 7-10 mm grafts continued to increase during impaction and became higher than that of the small slurry bone grafts after 10 impactions. Our results demonstrated that the small slurry bone grafts exhibit worse mechanical properties as compared with the 7-10 mm bone grafts, which implies that the use of this material in reconstruction of a bone defect in the acetabulum should be limited.

A preliminary report of patellofemoral arthroplasty in isolated patellofemoral arthritis.

BACKGROUND: Isolated patellofemoral osteoarthritis is not uncommon. Surgical treatment of isolated patellofemoral arthritis remains controversial and poses a challenging treatment dilemma. The present study aimed to evaluate the short-term results of patellofemoral arthroplasty for patients with isolated patellofemoral osteoarthritis. METHODS: We analyzed 11 patellofemoral arthroplasties performed from March 2006 to September 2009 in 11 patients with isolated patellofemoral arthritis. The patients comprised 2 males and 9 females with an average age of 53.7 years (range, 46 - 74 years). Standard weightbearing radiographs were taken in the anteroposterior, lateral, and 45° axial views. The knee pain and functional status were evaluated by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scales and American Knee Society (AKS) scores. For comparison, 23 total knee arthroplasties in 23 patients with primary tibiofemoral osteoarthritis were matched according to age, gender, bilaterality and body mass index. The duration of follow-up was 23.7 months (range, 12 - 47 months). RESULTS: The majority of the 11 patients experienced improvement in their patellofemoral symptoms after patellofemoral arthroplasty. The WOMAC scores improved considerably by 7.4 points with respect to pain and by 5.2 points with respect to function. The AKS scores also improved considerably by 23.9 points with respect to pain and 44.3 points with respect to function. Although the clinical outcomes after patellofemoral arthroplasty were not better than those after total knee arthroplasty, patellofemoral arthroplasty exhibited advantages in the shorter operation time, lower blood loss and increased postoperative range of motion. At the latest follow-up, there was no clinical or radiographic evidence of patellofemoral maltracking, loosening or wear. CONCLUSIONS: On the basis of our experience in this relatively small series of patients with a short-term follow-up, patellofemoral arthroplasty is an effective treatment alternative to total knee arthroplasty in isolated patellofemoral arthritis. MRI and arthroscopy may contribute to define those patients with isolated patellofemoral degeneration.

Selection of allografts for impaction bone grafting for bone defect reconstruction on the acetabular side.

OBJECTIVE: To review the choices of allografts for bone defect reconstruction in acetabular revision surgery using the technique of impaction bone grafting. DATA SOURCES: The data cited in this review were mainly obtained from articles listed in PubMed that were published from January 1993 to July 2009. The search terms were "impaction bone grafting", "particle size", "mechanical property" and "biological behavior". STUDY SELECTION: Articles relevant to the choices of allografts and their results for bone defect reconstruction on the acetabular side were selected. RESULTS: Different choices of allografts, including the particle size, process of irradiation or fat reduction, composition and particle grade, are made to improve the survival rate of a prosthesis in acetabular revision surgery. This review, which compares both mechanical and biological factors, summarizes the experimental and clinical results for different techniques. CONCLUSIONS: Fresh frozen cancellous allografts with particle sizes ranging from 7 to 10 mm are a favorable choice for reconstruction of bone defects of American Academy of Orthopedic Surgeons (AAOS) types II (cavitary defect) and III (combined cavitary and segmental defect) on the acetabular side. A fat-reducing procedure with saline or solvent/detergent is controversial. Adding autologous marrow into irradiated allografts, which provides reliable mechanical stability and biological safety, may be a substitute for fresh frozen allografts. Cortical bone can be a supplementary material in cases of insufficiency of cancellous allografts. Cartilage should be excluded from the graft material. Further research is required to demonstrate the best particle grade, and randomized controlled trials in clinical practice are required to obtain more information about the selection of allografts.