In-situ TiC_P/Al Composites Prepared by TE/QP Method

An in-situ TiCp/Al composite was prepared by a thermal explosion/quick pressure method （TE/QP）. The effect of Al content on the reaction temperature as well as the reaction rate has been studied. Phase constituents and the microstructure of the composites and the particle size of the reinforcement were analysed using X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results have shown that TiCp/Al composite with 40～70 vol. pct TiC particle reinforcement and high relative density can be directly obtained by TE/QP. TiC is the only reaction product when Al content in Al-Ti-C system is no more than 60 vol. pct, but Al3Ti phase will also form when Al content is more than 60 vol. pct. Increasing Al content prolongs the initial reaction time, reduces the highest reaction temperature and the reaction rate, and decreases the size of TiC particles. In addition, the microstructure of TiCp/Al composite and the structure of interface between TiCp and Al are studied using SEM and transmission electron microscopy （TEM）. The results show that the in-situ synthesized TiC particle has fcc cubic structure. The orientation between TiC particles and Al matrix can be described as （220）Al//（022）TiC and [112]Al//[011]TiC. Results of the mechanical property tests reveal that the ultimate strength （σ） and modulus （E） are 687 MPa and 142 GPa respectively when the Al content is 40 vol. pct. On contrary, 6 elongation increases by 3.2% with increasing Al content.

Antioxidant Activity of 50 Traditional Chinese Medicinal Materials Varies with Total Phenolics

This study was designed to determine the total phenolic content of 50 herbs and to examine their antioxidant potential. In the sample preparation, 60% ethanol was chosen as the extraction solvent for the subsequent experiments. Folin-Cicolteau phenol reagent and a colorimetric method were used to determine the total phenolic content of the selected herbs. The result showed that total phenolic content of those herbs ranged from 2 to 185 mg/g. In antioxidant assay, the ferric reducing/antioxidant power (FRAP) values ranged from 2 to 134 mg GAE/g;the IC50 values of DPPH?·, ·OH and ?scavenging were in the range of 0.06 - 5.50 mg/mL, 0.017 - 0.636 mg/mL and 0.050 - 0.681 mg/mL respectively. Flos caryophylli was the exceptant in the ?scavenging assay because there was no linear relation between the concentration and the scavenging percentage. Compared to gallic acid, ascorbic acid and butylated hydroxytoluene (BHT) in antioxidant assay as positive control, the most potential antioxidant herbs were Cacumen platycladi, Radix et Rhizoma rhei, Rhizoma rhodiolae crenulatae, and Rhizoma sanguisorbae with considerable content of phenolics. Especially, a positive and significant correlation was found between the total phenolic content and FRAP value or DPPH· scavenging percentage.

Pyrophosphate-Mediated On-Off-On Oxidase-Like Activity Switching of Nanosized MnFe_(2)O_(4) for Alkaline Phosphatase Sensing

Developing reliable and facile approaches for alkaline phosphatase(ALP)sensing is important due to its role as a clinical biomarker for many diseases.In this study,we proposed a new and convenient colorimetric assay based on the pyrophosphate(PPi)-mediated oxidase-mimicking activity switching of nanosized MnFe_(2)O_(4) for the detection of ALP.The synthesized MnFe_(2)O_(4) exhibited high oxidase-like activity to catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine(TMB)to its blue product TMBox in the presence of dissolved O2,leading to a color reaction rapidly and remarkably;PPi could significantly inhibit the activity of the MnFe_(2)O_(4) nanozyme via the strong interaction between PPi and the Fe(III)species in MnFe_(2)O_(4),resulting in the suppression of the TMB color reaction;when ALP was added,it hydrolyzed the PPi substrate to phosphate(Pi)that had no obvious effect on the MnFe_(2)O_(4) activity,and such that the TMB color reaction catalyzed by the nanozyme could be observed again.With the above principle,linear colorimetric determination of ALP in the scope of 0.6-55 U L−1 was achieved,giving the limit of detection down to 0.27 U L−1.Besides,the developed assay could provide selective response toward ALP against other co-existing biological species.Furthermore,reliable detection of ALP in human serum samples was verified by our assay,revealing its great promise as an effective and facile tool for ALP monitoring in clinical practice.