Interdependence between training and magnetization reversal in granular Co-CoO exchange bias systems

The interdependence between training and magnetization reversal in granular Co-CoO exchange bias (EB) systems prepared by O ion implantation in Co thin films is demonstrated by polarized neutron reflectometry. While high-fluence O-implanted thin films show reduced relative training values and no asymmetry in magnetization reversal (all reversals take place by domain wall nucleation and motion), low-fluence O ion implantation results in an increased relative training and a magnetization reversal asymmetry between the first descending and the first ascending branches. Whereas the untrained decreasing field reversal occurs mainly by domain wall nucleation and motion, traces of a domain rotation contribution are evidenced in the increasing field reversal. This is explained by the evolution of the CoO structure and the contribution of the out-of-plane magnetization with ion implantation. The amount of incorporated O, which determines the threshold between both behaviors, is around 20 at.%. This reveals that the interdependence between training and magnetization reversal is insensitive to the morphology of the constituents (i.e., granular or layered), indicating that this is an intrinsic EB effect, which can be conveniently tailored by the interplay between the intrinsic properties of the investigated materials and ion implantation

Inhibition of the Growth of Raji Cells by Precursor MicroRNA-15a

OBJECTIVE To investigate the effects of microRNA-15a (miR-15a) on the growth of the lymphoma Raji cell line. METHODS A eukaryotic expression vector of precursor miR-15a (pre-miR-15a) was constructed. Paired oligonucleotides for pre-miR-15a expression were designed and synthesized chemically. Annealed oligonucleotides were inserted into a pGCSIL-GFP vector under a U6 promoter to construct a pre-miR-15a expression plasmid. Oligonucleotides with a scrambled sequence which were used as a negative control were also constructed into the pGCSIL-GFP vector. A recombinant expression vector was identified through PCR and sequencing. A pre-miR-15a expression plasmid and a negative control plasmid were all transferred into Raji cells with lipofectamine 2000. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) was employed to explore expression of miR-15a. The expression levels of the protein were assayed via immunofl uorescence. The growth effect of Raji cells was measured by CCK8 assay. Apoptosis was determined using Hoechst dyeing and flow cytometry. The growth-inhibitory effect on Raji cells was measured using a CCK8 assay.RESULTS The results showed that the insertion sequence was correct. The expression level of miR-15a was obviously higher in Raji cells transferred with pre-miR-15a plasmid than in the blank group and in the negative control group. After Raji cells were transferred with the pre-miR-15a expression plasmid for 48 h, Bcl-2 protein expression levels were obviously decreased，which indicated that there was a significant difference as compared with the negative control group and blank group (P < 0.05). The CCK8 assay showed that transfection of pre-miR-15a expression plasmid decreased the cell growth at 24, 48 and 72 h post-transfection. After Raji cells were transferred with pre-miR-15a expression plasmid, apoptotic cells can be seen with Hoechst dyeing, and the cell apoptotic rate was obviously higher than that in blank group and negative control group. CONCLUSION Pre-miR-15a can induce apoptosis and inhibit the growth of Raji cells