Enhanced dielectric nonlinearity in epitaxial Pb0.92La0.08Zr0.52Ti0.48O3 thin films

This is the published version. Copyright 2014 American Institute of PhysicsHigh quality c-axis oriented epitaxial Pb 0.92La0.08Zr0.52Ti0.48O3 films were fabricated using pulsed laser deposition on (001) LaAlO3 substrates with conductive LaNiO3 buffers. Besides confirmation of the in-plane and out-of-plane orientations using X-ray diffraction, transmission electron microscopy study has revealed columnar structure across the film thickness with column width around 100 nm. Characterization of ferroelectric properties was carried out in comparison with polycrystalline Pb 0.92La0.08Zr0.52Ti0.48O3 films to extract the effect of epitaxial growth. It is found that the ratio between the irreversible Rayleigh parameter and reversible parameter increased up to 0.028 cm/kV at 1 kHz on epitaxial samples, which is more than twice of that on their polycrystalline counterparts. While this ratio decreased to 0.022 cm/kV with increasing frequency to100 kHz, a much less frequency dependence was observed as compared to the polycrystalline case. The epitaxial Pb 0.92La0.08Zr0.52Ti0.48O3 films exhibited a higher mobility of domain wall and the higher extrinsic contribution to the dielectric properties, as well as reduced density of defects, indicating that it is promising for tunable and low power consumption devices

Aurora Kinase Inhibitors in Head and Neck Cancer

Aurora kinases are a group of serine/threonine kinases responsible for the regulation of mitosis. In recent years, with the increase in Aurora kinase-related research, the important role of Aurora kinases in tumorigenesis has been gradually recognized. Aurora kinases have been regarded as a new target for cancer therapy, resulting in the development of Aurora kinase inhibitors. The study and application of these small-molecule inhibitors, especially in combination with chemotherapy drugs, represents a new direction in cancer treatment. This paper reviews studies on Aurora kinases from recent years, including studies of their biological function, their relationship with tumor progression, and their inhibitors

Enhanced energy density with a wide thermal stability in epitaxial Pb0.92La0.08Zr0.52Ti0.48O3 thin films

High-quality epitaxial Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films of thickness of 880 nm were fabricated using pulsed laser deposition on (001) Nb doped SrTiO3 (Nb:STO) substrates. Besides a confirmation of the epitaxial relationship [100]PLZT//[100]Nb:STO and (001)PLZT//(001)Nb:STO using X-ray diffraction, a transmission electron microscopy study has revealed a columnar structure across the film thickness. The recoverable energy density (Wrec) of the epitaxial PLZT thin film capacitors increases linearly with the applied electric field and the best value of 31 J/cm3 observed at 2.27 MV/cm is considerably higher by 41% than that of the polycrystalline PLZT film of a comparable thickness. In addition to the high Wrec value, an excellent thermal stability as illustrated in a negligible temperature dependence of the Wrec in the temperature range from room temperature to 180 C is achieved. The enhanced Wrec and the thermal stability are attributed to the reduced defects and grain boundaries in epitaxial PLZT thin films, making them promising for energy storage applications that require both high energy density, power density, and wide operation temperatures

PARP6 acts as a tumor suppressor via downregulating Survivin expression in colorectal cancer

Poly (ADP-ribose) polymerases (PARPs) are enzymes that transfer ADP-ribose groups to target proteins and are involved in a variety of biological processes. PARP6 is a novel member, and our previous findings suggest that PARP6 may act as a tumor suppressor via suppressing cell cycle progression. However, it is still unclear that PARP6 function besides growth suppression in colorectal cancer (CRC). In this study, we examined tumor suppressive roles of PAPR6 in CRC cells both in vitro and in vivo. We found that PARP6 inhibited colony formation, invasion and migration as well as cell proliferation. Moreover, ectopic overexpression of PARP6 decreased Survivin expression, which acts as an oncogene and is involved in apoptosis and mitosis. We confirmed the inverse correlation between PARP6 and Survivin expression in CRC cases by immunohistochemistry. Importantly, CRC cases with downregulation of PARP6 and upregulation of Survivin showed poor prognosis. In summary, PARP6 acts as a tumor suppressor via downregulating Survivin expression in CRC. PARP6 can be a novel diagnostic and therapeutic target together with Survivin for CRC

Interfacial defects in YBa 2_{2} Cu 3_{3} O 7−δ_{7-δ} /SrTiO $_{3} (0 0 1) heterostructures studied by aberration-corrected ultrahigh-resolution electron microscopy

The microstructure of interfacial defects in YBa2Cu3O7-δ/SrTiO3(0 0 1) heterostructures has been investigated by aberration-corrected ultrahigh-resolution electron microscopy. We determine that c-axis-oriented YBa2Cu3O7-δ thin films epitaxially grow on SrTiO3(0 0 1) with two types of interface structure. The coalescence of nucleation sites with different types of interface structure leads to the formation of antiphase domain boundaries in YBa2Cu3O7-δ thin films, which terminate at planar faults with different configurations near the interface. Stand-off misfit dislocations are observed and the dislocation core structure is explored. Based on the interface structure and interfacial defects, the initial growth mode of YBa2Cu3O7-δ thin films on SrTiO3(0 0 1) is discussed

Quantitative HRTEM and its application in the study of oxide materials

On the basis of a state-of-the-art aberration-corrected transmission electron microscope, the spherical aberration coefficient C S of the objective lens can be tuned to either a positive or a negative value. The use of a negative value of C S combined with an overfocus setting of the objective lens leads to the development of the negative C S imaging (NCSI) technique. Images obtained using the NCSI technique show superior contrast and signal intensity at atomic column positions than the corresponding positive C S images, especially for weakly scattering oxygen columns that are in close proximity to strongly scattering cation columns in oxides. Based on the images obtained under the NCSI condition, quantification of the image contrast allows measurements of the atom positions with a precision of a few picometers and the local chemistry on atomic scale. In the present review, we discuss firstly the benefits of the NCSI technique in studies of oxide materials, and then show a procedure for quantitative analysis of the image based on the absolute value of contrast. In the last part, examples are given for the application of the quantitative high-resolution transmission electron microscopy (HRTEM) to the study of electric dipoles of oxide ferroelectrics and atomic-scale chemistry of interfaces

Electron beam lithography of GeTe through polymorphic phase transformation

We report two previously undiscovered phases of GeTe including the sphalerite (c-) phase and the hexagonal (h-) phase with interlayer van der Waals gaps. A polymorphic phase transformation from rhombohedral α-GeTe to c- and h-GeTe at near room temperature is first realized via electron beam irradiation. Their underlying thermodynamics and kinetics are illustrated using the in situ heating experiments and molecular dynamics simulations. Density-functional theory calculations indicate that c-GeTe exhibits typical metallic behavior and h-GeTe is a narrow-gap semiconductor with a strong spin-orbital coupling effect. Our findings shed light on a strategy for designing GeTe-based quantum devices compromising nanopillars and heterostructures via an atomic-scale electron beam lithography technique.</p

Isolation of Mutations That Bypass the Requirement of the Septation Initiation Network for Septum Formation and Conidiation in Aspergillus nidulans

The kinase cascade of the septation initiation network (SIN), first revealed in fission yeast, activates the contraction of the actomyosin ring, and plays an essential role in fungal septation. Mob1p, an evolutionarily conserved SIN protein, is associated with the most downstream kinase of this cascade in fission yeast. In this study, the mobA gene encoding a homologous protein was isolated from the filamentous fungus Aspergillus nidulans, whose mycelium is made of multinucleate cells. The MOBA protein was required for septation and conidiation, but was not essential for hyphal extension and colony formation. To identify genes that act antagonistically against the SIN, UV mutagenesis was carried out to isolate suppressor (smo) mutations that restored conidiation when MOBA was not expressed. Microscopic examination indicated that the restored conidiation was concomitant with restored septation in the absence of the MOBA protein. Eight recessive smo mutations in five complementation groups also bypassed the requirement of the SIN kinases SEPH and SIDB for septum formation and conidiation. However, none of these smo mutations affected the localization of MOBA. Among smo mutations, smoA and smoB mutations caused reduced hyphal growth and colony formation. They also rendered hypersensitivity to low doses of the microtubule-depolymerizing agent benomyl for conidiation. Therefore, in A. nidulans, proteins encoded by the smo genes likely have an antagonistic interaction against the SIN pathway to regulate septation and conidiation