Design and Evaluation of Chitosan-Calcium Phosphate Scaffolds Constructed from Air Dried and Lyophilized Microspheres

The orthopedic clinical demand for bone grafts is a persistent problem for patients with age-related bone fractures and diseased bone defects. The aim of this study was to use calcium phosphate, a biomimetic ceramic with high compressive strength, and chitosan, a natural biodegradable and biocompatible polymer, to construct microsphere-based composite scaffolds to serve as a bone graft. Two types of scaffolds,(1) air-dried microspheres (AD) and (2) solid air-dried and lyophilized microsphere combination (FDAD), were evaluated in vitro for mineralization and enzymatic degradation. The combination FDAD scaffold showed on average ~80% increase (p\u3c0.01) in cell number per scaffold mass compared to AD because of the larger surface area advantage. Due to the higher cell number, the production of collagen was ~31% greater (p\u3c0.01) on FDAD scaffolds compared to AD scaffolds. However, scanning electron micrographs indicated minimal matrix deposition for both scaffold types. The AD scaffolds had a three-fold compressive strength advantage compared to FDAD scaffolds. These results indicate FDAD scaffolds have more osteogenic potential based on cell growth and collagen elaboration, but AD scaffolds demonstrated higher compressive strength

Editorial: Emerging techniques and applications for 5G networks and beyond

Editoria

Accounting conservatism and banking expertise on board of directors

Previous studies show mixed evidence of the role of banking expertise on the board of directors on accounting conservatism. In this paper, we add to this growing literature by providing an innovative way to measure banking expertise based on life-time working history in banks of all individual directors on the board. We find that accounting conservatism is negatively affected by banking expertise on the board. Also, the results indicate that banking expertise on the board has a more pronounced impact on accounting conservatism when firms have high bankruptcy risk and when firms have high financial leverage. The evidence has some implications for boards of directors

n-Gram-based text compression

We propose an efficient method for compressing Vietnamese text using n-gram dictionaries. It has a significant compression ratio in comparison with those of state-of-the-art methods on the same dataset. Given a text, first, the proposed method splits it into n-grams and then encodes them based on n-gram dictionaries. In the encoding phase, we use a sliding window with a size that ranges from bigram to five grams to obtain the best encoding stream. Each n-gram is encoded by two to four bytes accordingly based on its corresponding n-gram dictionary. We collected 2.5 GB text corpus from some Vietnamese news agencies to build n-gram dictionaries from unigram to five grams and achieve dictionaries with a size of 12 GB in total. In order to evaluate our method, we collected a testing set of 10 different text files with different sizes. The experimental results indicate that our method achieves compression ratio around 90% and outperforms state-of-the-art methods.Web of Scienceart. no. 948364