X.F. Duan

180° domain structure and its evolution in Ca0.28Ba0.72Nb2O6 ferroelectric single crystals of tungsten bronzes structure

Ferroelectric domain structure and its evolution in uniaxial relaxor Ca0.28Ba0.72Nb2O6 single crystals were investigated using transmission electron microscopy. It was found that there exists a high density of 180° domain walls in the crystals. The domains appear predominantly spike shaped along the polar axis and have a typical diameter of 50–500nm. Domain wall motion was occasionally induced by electron beam irradiation. Macrodomains-to-microdomains switching has been observed corresponding to the normal-to-relaxor ferroelectrics transition during an in situ heating experiments. At temperature just below ferroelectric phase transition temperature TC, zero-field-cooled needlelike nanodomains were also observed.

In situ transmission electron microscopy study of electric-field-induced 90° domain switching in BaTiO3 single crystals

The 90° domain switching in single crystalline BaTiO3 under an external static electric field has been investigated by in situ transmission electron microscopy using a special homemade transmission electron microscope stage. With the initial domains gradually disappearing, new domains that are 90° away from the initial ones are observed to occur with polarizations being switched to the direction of the external electric field, and domain boundaries being changed from ⟨101⟩ to ⟨1¯01⟩ in order to maintain a “head-to-tail” arrangement.

Direct determination of the polarization direction of domains in BaTiO3 single crystal

The polarization directions of domains in BaTiO3 single crystal are determined by convergent-beam electron diffraction directly. The intensity distributions in the (001) and (001¯) diffraction disks are different, which is due to the noncentrosymmetric unit cell of ferroelectrics. The in situ transmission electron microscopy observations on the evolution of domains under external fields indicate that the disk with a little brighter center fringes is the (001) disk and the polarization vector is toward this disk. The method provides a straightforward criterion for polarization direction determination of ferroelectric domains.

Transmission electron microscopy investigation of self-assembly ZnO twinning nanostructures

Self-assembly ZnO twinning nanostructures are studied by transmission electron microscopy systematically. Selected area electron diffraction and high-resolution transmission electron microscopy observations indicate two types of twin boundaries (011¯1¯) and (011¯3) appeared in the same nanostructure and the twinning relationships are well defined. Convergent-beam electron diffraction techniques determine the polarities of the building blocks are all Zn terminated with the help of theoretical simulations, which is further confirmed by electron energy loss spectroscopy under (0002) and (0002¯) Bragg conditions.

Effect of heat treatment on the properties of Co50Ni20Ga30 ferromagnetic shape memory alloy ribbons

The structure, magnetic properties and martensitic transformation behaviour were investigated for as-spun Co50Ni20Ga30 ribbons under various heat-treatment conditions. When the as-spun ribbons were annealed at 400 degrees C, the saturation magnetization decreased from 49.5 to 40.1 emu g(-1) and the coercivity increased from 18 to 2622 Oe, accompanied by the disappearance of the martensitic transformation. Re-treating the annealed sample at different temperatures from 600 to 1200 degrees C, the martensitic transformation reoccurred and the T-M was adjusted between 132 and 249 K.

Nanoscale strain analysis of strained-Si metal-oxide-semiconductor field effect transistors by large angle convergent-beam electron diffraction

In this letter we report the characterization of local compressive strain in p-type strained-silicon channel metal-oxide-semiconductor field effect transistors by large angle convergent-beam electron diffraction. The compressive strain was induced into the channel region of gate length of 80nm strained-Si p-type metal-oxide-semiconductor field effect transistor by Ge preamorphization implantation for source/drain extension. A method to distinguish between compressive strain and shear strain in the cross-sectional transmission electron microscopy specimens is proposed.

Finite-element study of strain field in strained-Si MOSFET.

The strain field in the channel of a p-type metal-oxide-semiconductor field effect transistor fabricated by integrating Ge pre-amorphization implantation for source/drain regions is evaluated using a finite-element method combining with large angle convergent-beam electron diffraction (LACBED). The finite-element calculation shows that there is a very large compressive strain in the top layer of the channel region caused by a low dose of Ge ion implantation in the source and drain extension regions. Moreover, a transition region is formed in the bottom of the channel region and the top of the Si substrate. These calculation results are in good agreement with the LACBED experiments.

Electron holography characterization of the electrostatic potential of thin high-kappa dielectric film embedded in gate stack

The electrostatic potential of the thin high-kappa dielectric film and related interfaces embedded in the gate stack can be profiled in high spatial resolution in the wedge-shape sample. The retrieved potential uncovers the uneven distribution with a maximum 15.6 +/- 0.7V in HfLaON dielectric film. It implies the non-uniform material distribution in high-kappa thin film and physical parameter of the film, such as permittivity, should not be considered as the constant

The virulence of Legionella pneumophila is positively correlated with its ability to stimulate NF-κB activation

AIM Our work is to study the correlation between the virulence of different Legionella pneumophila in mouse model and its ability to activate NF-κB signaling pathway in vitro. MATERIALS & METHODS We measured the abilities of different strains of L. pneumophila to induce the activation of NF-κB signaling pathway in vitro. By using A/J mice, we also detected the virulence of different strains in vivo. RESULTS & CONCLUSION We demonstrated that different strains of L. pneumophila induce different levels of activation to NF-κB signaling pathway in vitro. We also found that L. pneumophila strain induced higher NF-κB activation in vitro showed more severe weight losses, higher mortality, more severe lung inflammation and higher levels of serum cytokines production in mice.

Bidirectional factors impact the migration of NK cells to draining lymph node in aged mice during influenza virus infection

Abstract Natural killer (NK) cells play an important role in controlling several viral diseases. Our previous studies demonstrated an age‐dependent susceptibility to mousepox due to defective NK cell responses and trafficking. However, the mechanisms that underlie the age‐related impairment in NK cell migration have yet to be identified. In the present study, we demonstrated that after influenza A virus (IAV) infection, NK cells from aged mice (17–19 months old) failed to accumulate in draining lymph node (D‐LN). We found that both environmental and intrinsic factors played roles for this defect. After infection, increase of chemokine transcripts, especially CXCL9, 10 and 11, which are important for NK cells homing to D‐LN, was significantly lower in the D‐LN of aged mice compared with those of young mice. Further, the expression levels of &bgr;2‐integrins and &bgr;‐actins, which play critical roles in NK cells homing to D‐LN failed to be up‐regulated in NK cells from aged mice. Finally, actin polymerization rates in NK cells from aged mice were also delayed compared to that of the young mice after IAV infection. Taken together, our data indicate that bi‐directional factors play essential roles in the defective NK cell trafficking to the D‐LN in the aged mice after IAV infection. HighlightsNK cells from aged mice failed to accumulate in the D‐LN during IAV infection.Expression of CXCR3 ligands was lower in D‐LN of aged mice during infection.The &bgr;2‐integrin was expressed at a lower level in aged NK cells after infection.The &bgr;‐actin was expressed at a lower level in aged NK cells after infection.The actin polymerization rate in NK cells from aged mice was lower after infection.