Youwei Du

Direct synthesis and characterization of CdS nanobelts

A method to directly synthesize single crystalline CdS nanobelts has been developed. The advantages of the method in rapid synthesis within several minutes and catalyst free comparing to the previous method propose a potential avenue to the further practical device production and applications. The as-synthesized CdS nanobelts grow along the [100] crystalline direction with usually 500–2000nm in width and about tens to several hundred micrometers in length. Two luminescence peaks around 516 and 758nm in room-temperature photoluminescence spectrum are ascribed to the band-to-band and trap emission, respectively.

Ferromagnetism in Mn-doped CuO

Ferromagnetic properties have been observed in CuO doped with 3.5–15 at.u200a% of Mn. The transition from ferromagnetic to paramagnetic phase at TC=80u2002K is associated with the metal–insulator transition. Magnetoresistance is weakly negative in the vicinity of the transition, but positive in a wide range of temperatures below TC. The experimental results suggest a possibility of interpretation in terms of the Zener double-exchange mechanism and strong electron–phonon interactions.

BiFeO3 film deposited on Si substrate buffered with La0.7Sr0.3MnO3 electrode

A multilayer film of BiFeO3∕La0.7Sr0.3MnO3∕SrTiO3 was deposited on Si substrate by pulsed laser deposition method, in which La0.7Sr0.3MnO3 was used as a bottom electrode. X-ray diffraction showed that the film was polycrystalline. From the x-ray photoelectron spectroscopy measurement, the valence number of the Fe ion was found to be 3+. The BiFeO3 film showed a low leakage-current density, and a large twice remanent polarization (2Pr) of 110μC∕cm2 was observed at room temperature. Owing to the ferromagnetic and magnetostrictive properties of La0.7Sr0.3MnO3, this multilayer film system is a promising candidate for the study of magnetoelectric coupling.

Effect of low frequency magnetic fields on melanoma: tumor inhibition and immune modulation

BackgroundWe previously found that the low frequency magnetic fields (LF-MF) inhibited gastric and lung cancer cell growth. We suppose that exposure to LF-MF may modulate immune function so as to inhibit tumor. We here investigated whether LF-MF can inhibit the proliferation and metastasis of melanoma and influence immune function.MethodsThe effect of MF on the proliferation, cell cycle and ultrastracture of B16-F10 in vitro was detected by cell counting Kit-8 assay, flow cytometry, and transmission electron microscopy. Lung metastasis mice were prepared by injection of 2u2009×u2009105 B16-F10 melanoma cells into the tail vein in C57BL/6 mice. The mice were then exposed to an LF-MF (0.4xa0T, 7.5xa0Hz) for 43xa0days. Survival rate, tumor markers and the innate and adaptive immune parameters were measured.ResultsThe growth of B16-F10 cells was inhibited after exposure to the LF-MF. The inhibition was related to induction of cell cycle arrest and decomposition of chromatins. Moreover, the LF-MF prolonged the mouse survival rate and inhibited the proliferation of B16-F10 in melanoma metastasis mice model. Furthermore, the LF-MF modulated the immune response via regulation of immune cells and cytokine production. In addition, the number of Treg cells was decreased in mice with the LF-MF exposure, while the numbers of T cells as well as dendritic cells were significantly increased.ConclusionLF-MF inhibited the growth and metastasis of melanoma cancer cells and improved immune function of tumor-bearing mice. This suggests that the inhibition may be attributed to modulation of LF-MF on immune function and LF-MF may be a potential therapy for treatment of melanoma.

Involvement of midkine expression in the inhibitory effects of low-frequency magnetic fields on cancer cells.

Effects of magnetic fields (MFs) on cancer cells may depend on cell type and exposure conditions. Gene expression levels are different among cancer cells. However, the effect of MFs on cancer cells with different gene expressions is still unclear. In this study, the cancer cell lines BGC-823, MKN-45, MKN-28, A549, SPC-A1, and LOVO were exposed to a low-frequency MF. Specific parameters of MFs were determined. Furthermore, the potential of the MF to influence cancer cell growth with midkine (MK) expression was evaluated. Cell proliferation and cell cycle were detected using the CCK-8 assay and flow cytometry. Cell ultrastructure was observed by transmission electron microscopy. BGC-823 cells with over-expression of MK (BGC-MK cells) and stanniocalcin-1 were generated by plasmid construction and transfection. Results showed that exposure to a 0.4-T, 7.5 Hz MF inhibited the proliferation of BGC-823, MKN-28, A549, and LOVO cells, but not MKN-45 and SPC-A1 cells. Moreover, the inhibitory effect of the MF on BGC-MK cells was lower (12.3%) than that of BGC-823 cells (20.3%). Analysis of the cell cycle showed that exposure to the MF led to a significant increase in the S phase in BGC-823 cells, but not in BGC-MK cells. In addition, organelle morphology was modified in BGC-823 cells exposed to the MF. These results suggest that exposure to a 0.4-T, 7.5 Hz MF could inhibit tumor cell proliferation and disturb the cell cycle. The alteration of MK expression in cancer cells may be related to the inhibitory effect of the MF on these cells.

Room-temperature spin-dependent tunneling through molecules

We have fabricated assemblies of molecular junctions comprised of superparamagnetic Fe3O4 nanoparticles self-assembled with alkane molecules of different lengths as the spacer. The electrical resistance increases exponentially over nearly two decades as the molecular length varies from 0.7 to 2.5 nm, indicating that electrons tunnel through the molecules that are chemically bonded with Fe3O4 nanoparticles. Up to ∼21% room-temperature magnetoresistance is observed. Remarkably, the tunneling magnetoresistance ratio stays nearly independent of molecular length, which entails room-temperature spin-conserving transport in organic molecules.

Parametric and cascaded parametric interactions in a quasiperiodic optical superlattice

Quasi-phase-matching optical parametric and cascaded parametric processes in a two-component quasiperiodic superlattice were studied in theory and experiment. This letter demonstrates how to obtain red at 666 nm and blue at 443 nm simultaneously from the superlattice using a 532 nm laser as a pump through these two processes mentioned above. The result confirms that some nonlinear frequency conversion processes occurring in a high-dimension χ(2) nonlinear photonic crystal may be efficiently achieved in such a one-dimension quasiperiodic optical superlattice.

Low Frequency Magnetic Fields Enhance Antitumor Immune Response against Mouse H22 Hepatocellular Carcinoma

Objective Many studies have shown that magnetic fields (MF) inhibit tumor growth and influence the function of immune system. However, the effect of MF on mechanism of immunological function in tumor-bearing mice is still unclear. Methods In this study, tumor-bearing mice were prepared by subcutaneously inoculating Balb/c mice with hepatocarcinoma cell line H22. The mice were then exposed to a low frequency MF (0.4 T, 7.5 Hz) for 30 days. Survival rate, tumor growth and the innate and adaptive immune parameters were measured. Results MF treatment could prolong survival time (nu200a=u200a28, p<0.05) and inhibit tumor growth (nu200a=u200a9, p<0.01) in tumor-bearing mice. Moreover, this MF suppressed tumor-induced production of cytokines including interleukin-6 (IL-6), granulocyte colony- stimulating factor (G-CSF) and keratinocyte-derived chemokine (KC) (nu200a=u200a9–10, p<0.05 or 0.01). Furthermore, MF exposure was associated with activation of macrophages and dendritic cells, enhanced profiles of CD4+ T and CD8+ T lymphocytes, the balance of Th17/Treg and reduced inhibitory function of Treg cells (nu200a=u200a9–10, p<0.05 or 0.01) in the mice model. Conclusion The inhibitory effect of MF on tumor growth was related to the improvement of immune function in the tumor-bearing mice.

Extremely low frequency magnetic fields regulate differentiation of regulatory T cells: Potential role for ROS-mediated inhibition on AKT

Our previous studies showed that extremely low frequency magnetic fields (ELF-MFs) inhibited tumor growth and change proportion of splenic regulatory T cells (Treg cells). Here, we focus on the effect of ELF-MFs on lung metastatic melanoma mouse model and the regulatory mechanism of ELF-MFs on the differentiation of Treg cells. Tumor-bearing mice were exposed to sham ELF-MFs and ELF-MFs (0.4u2009T, 7.5u2009Hz) 2u2009h/day for 27 days. Metastatic tumor burden of lung was significantly decreased after ELF-MF treatment. Compared to the control group, expressions of matrix metalloproteinase (MMP2, MMP9) and forkhead box P3 (Foxp3) in lung nodules significantly decreased in the ELF-MF group. Moreover, in vitro, after stimulated with anti-CD3, anti-CD28 antibodies and transforming growth factor-β (TGF-β) and treated with ELF-MFs for 2u2009h, expression of Foxp3 in total T cells was significantly decreased. Differentiation rate of Treg cells was inhibited from 32.0% to 22.1% by ELF-MFs. Furthermore, reactive oxygen species (ROS) was increased and phospho-serine/threonine protein kinase (p-AKT) was inhibited in both T cells and Jurkat cells. ROS scavenger N-acetyl-l-cysteine reversed inhibition of AKT pathway and expression of Foxp3 from 18.6% to 26.6% in T cells. Taken together, our data show that ELF-MF exposure promoted the inhibitory effect of ROS on AKT pathway and decreased Foxp3 expression, which provides an explanation for why ELF-MF exposure can inhibit differentiation of Treg cells and enhance antitumor effect in metastatic melanoma mouse model.

Ferrimagnetic copper chloride hydroxide

Magnetic properties of copper chloride hydroxide were studied by using a superconducting quantum interference device. The coercivity of this material was more than 10 000 Oe at 2 K, which is the highest observed in the copper compounds. The magnetic susceptibility as a function of temperature revealed ferrimagnetism in the sample.