ABSTRACT
A highly crystalline nanosized spinel LiMn2O4/3DG composite cathode material for high rate lithium ion batteries was successfully prepared by mixing spinel LiMn2O4 particles with reduced graphene oxide (3DG). Spinel LiMn2O4 and reduced three-dimensional graphene oxide were synthesized using a hydrothermal method and freeze-drying technology, respectively. The structure, morphology and electrochemical performance of the synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge techniques. The results showed that the LiMn2O4/3DG composites exhibited excellent rate capability and stable cycling performance. The discharge capacity was 131 mA h g-1 and the capacity remains at 89.3% after 100 cycles at a 0.5 C rate, while the discharge capacity was 90 mA h g-1 at 10 C. Compared with spinel LiMn2O4 materials, the LiMn2O4/3DG composites showed obvious improvement in electrochemical performance.
ABSTRACT
OBJECTIVE: To evaluate the surface characteristic of domestic poly-DL-lactic acid membrane for periodontal guided tissue regeneration. METHODS: Three guided tissue regeneration membranes (PDLLA, ePTFE, COL)were implanted in rats subcutaneously, then they were removed 2,4,8 weeks after surgery for examination under scanning electron microscope. The membranes in vitro served as control. RESULTS: The surface of PDLLA membrane was characterized by unorganized smooth film structure. After 2 weeks implanted subcutaneously, its surface became rough with numerous oval micropores in it. These oval micropores were 5 microm in size.The micropores increased gradually in size and number 4, 8 weeks after implantation,there were many shindle shaped cells inlayed. CONCLUSION: Domestic Poly-DL-lactic acid membrane exhibits excellent biocompatibility,which meets the criterion for GTR.
ABSTRACT
The glycogen phosphorylase-2 (GP2) activity that appears during the cell differentiation of Dictyostelium was purified to homogeneity. The molecular weight of the nondenatured enzyme was 200,000 as determined by Sephacryl S-300 gel filtration and was 107,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, suggesting that the native enzyme consists of two similar subunits. The intact protein was digested with trypsin and protease V8, and the resulting peptides were purified by microbore high pressure liquid chromatography. The peptides were sequenced, and oligonucleotides were constructed for polymerase chain reaction amplification of the GP2 gene from Dictyostelium genomic DNA template. The resulting polymerase chain reaction products were sequenced directly and were confirmed to encode portions of the GP2 gene. These fragments were used to probe a partial EcoRI genomic library for the remainder of the GP2 gene. The nucleotide sequence of the GP2-selected clones revealed an open reading frame of 2975 base pairs that was interrupted by two introns of 109 and 105 base pairs, respectively. The open reading frame encoded a protein of 992 amino acids with a calculated molecular mass of 112,500 Da and an isoelectric point of 6.4. An unusual sequence within the second exon of GP2, in which the triplet CAA was repeated 11 times, resulted in 11 in-frame glutamine residues of a possible 15 amino acids coded for by this region. The CAA repeat was transcribed, as shown by the sequence of cDNA. Comparison of the amino acid sequence of Dictyostelium GP2 to the phosphorylases from other organisms revealed that the Dictyostelium protein was 50 and 44% identical to yeast and rabbit muscle phosphorylases, respectively. Northern blot analysis showed that GP2 mRNA was absent in amebas and the early stages of development, reached a maximum level of expression at the slug stage, and then decreased in the terminal stages of development. Comparison of the mRNA expression with the appearance of GP2 enzyme protein and enzyme activity revealed that gp2 mRNA and a 113-kDa GP2 enzyme peptide were expressed concurrently at 10 h of development. However, enzyme activity did not appear until 18 h, coincident with a decrease in the level of the 113-kDa peptide and a corresponding increase in the amount of a 106-kDa GP2 peptide. Addition of cAMP to aggregation-competent cells in liquid culture resulted in the induction of GP2 mRNA, GP2 protein, and GP2 enzyme activity.
