A B S T R A C TMechanical properties and in vitro biocompatibility of graphene/hydroxyapatite (HA) composite synthesized using spark plasma sintering (SPS) are reported in this study. Raman spectroscopy corroborated that graphene nanosheets (GNSs) survived the harsh processing conditions of the selected SPS processing parameters. A 1.0 wt.% GNS/HA composite exhibits $80% improvement in fracture toughness as compared to pure HA. GNS pull-out, grain bridging by GNS, crack bridging and crack deflection are the major toughening mechanisms that resist crack propagation. In vitro osteoblast growth tests illustrate that the added GNSs contribute to the improvement of both osteoblast adhesion and apatite mineralization. Therefore, the GNS/HA composite is expected to be a promising material for load-bearing orthopedic implants.Ó 2013 Elsevier Ltd. All rights reserved. IntroductionGraphene, a monolayer of sp 2 -hybridized carbon atoms arranged in a two-dimensional lattice, has drawn much attention in the composite field as reinforcement for structural composites due to its combination of excellent mechanical properties (e.g., tensile strength 130 GPa and Young's modulus 0.5-1 TPa) and very high specific surface area (up to 2630 m 2 g À1 ) [1][2][3]. In particular, the high specific surface area of graphene, inherent to its two-dimensional lattice geometry, imparts strong interfacial bonding with the matrix phase and effective load transfer from the matrix to graphene [4]. Graphene nanosheets (GNSs) with a thickness of approximately 1-10 nm, also called as graphene nanoplatelets (GNPs) or graphene platelets (GPLs), are generally composed of a few graphene layers and display compatible properties similar to that of monolayer graphene. Furthermore, it is worth to note that GNSs are much easier to produce and handle. Very recently, GNSs have been widely employed as nanofillers to polymers [5,6], metals [7,8] and ceramics [9][10][11] to produce composites with tailored mechanical properties.Due to its chemical composition (Ca/P ratio of 1.67) and crystal structure that are similar to the apatite in human skeletal system, hydroxyapatite (HA), with excellent bioactivity and osteoconductivity, is suitable for osteoblast adhesion and proliferation, new bone growth and integration [12], and therefore is recognized as one of the most promising orthopedic biomaterials. However, the intrinsic brittleness of HA, i.e., low fracture toughness and low toughness-induced poor wear resistance, still restricts its clinical applications. Therefore, toughening of HA with a second phase such as alumina, yttria stabilized zirconia, titania and carbon nanotubes (CNTs) has been extensively explored to overcome the deficiencies of pure HA [13].Among HA based composites, much recent attention has been devoted to the CNT/HA composites.

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Novel corncob-derived solid acid catalysts were successfully synthesized for the first time by the hydrothermal method. The influences of different preparation conditions were investigated, and the structure-function relationships of the resulting catalysts were also discussed on the basis of the analysis of structure and composition. In comparison to conventional solid acid catalysts, the corncob-derived catalyst synthesized under optimized conditions exhibited higher catalytic activity in esterification reactions, yielding nearly 90% methyl oleate in only 2 h. The catalyst retained satisfactory catalytic activity for esterification, even after 8 reaction cycles. Solid-state magic angle spinning (MAS) (13)C nuclear magnetic resonance (NMR) investigations further indicated that the catalyst was composed of polycyclic aromatic carbon sheets bearing -SO3H, -COOH, and -OH groups in adequate amounts and with proper proportions, contributing to its excellent catalytic activity. This work provides a green method to synthesize solid acid catalysts from biomass wastes and may contribute to a holistic approach for biomass conversion.

Wheat germ peptides (WGPs) have various benefits to human health, while their antidiabetes mechanism remains unknown. In this study, the α-glucosidase inhibition activity of WGPs was identified, exhibiting an IC50 value of 6.87 mg/mL. By further filtrating them into five groups according to molecular weight (M w), the fraction with M w < 1 kDa displayed the highest inhibitory activity with an IC50 of 2.10 mg/mL. The addition of 2 mg/mL WGPs with M w < 1 kDa effectively reduced the glucose-releasing rate on everted intestine sleeves. By virtual screening and HPLC-QTOF-MS/MS, LDLQR, AGGFR, and LDNFR were identified and synthesized for the first time, and their IC50 values were 8.59, 8.66, and 9.21 mM, respectively. Molecular docking and amino acid composition analysis results showed that the high content of C-terminal Arg residues in the peptides could be the essential reason for their α-glucosidase inhibition activity. This study paved a way to utilize WGPs as potential antidiabetes ingredients for the food industry.

A clean method for preparing ABCBA penta-block terpolymers was developed in a surfactant and organic solvent free emulsion system via one-pot RAFT polymerization.

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A series of polyimide (PI) fibers derived from 3,3 0 ,4,4 0 -biphenyltetracarboxylic dianhydride (BPDA), 4,4 0 -oxydiphthalic anhydride (ODPA) and p-phenylenediamine (p-PDA) were successfully prepared through a partially pre-imidization process, and the effects of different amount of dehydration reagents and initial poly(amic acid) (PAA) concentrations on the structure-property relationship of the resultant PI fibers were systematically investigated. The results showed that both the increased amount of dehydration reagents and PAA concentration could result in the ordered molecular packing arrangement of the polymer chains and gradually formed homogeneous structures in the fibers, which are proposed to be essentially dominated for the effectively enhancement in the mechanical properties of PI fibers. Moreover, the PI fibers obtained through the pre-imidization process still exhibited excellent thermaloxidative stabilities, although the 5% weight loss temperature of the PI fibers was slightly decreased compared with that of the pure PI fibers as a result of the residual dehydration reagents in the fibers.Consequently, the present work provided a new approach in preparing high-performance PI fibers through a partially pre-imidization process.