Search

O-GlcNAcylation (O-GlcNAc) is a posttranslational modification that is mediated by O-GlcNAc-transferase (OGT) and reversed by O-GlcNAcase (OGA). Increasing evidence indicates that protein O-GlcNAcylation is increased in various types of cancer. In the present study, we aimed to evaluate the expression and function of both OGT and OGA in bladder cancer cells in vitro and in vivo. Expression data of OGT and OGA at the mRNA level was obtained from the Oncomine database. Effects of OGT and OGA on cell proliferate, invasive, and migratory abilities were assessed using MTT, wound healing, cell invasive assay, and cell cycle analysis. In vivo assay was also performed in nude mice. The results revealed that the expression of OGT in bladder cancer tissues was higher than that of normal tissues, while the OGA level was found to be lower in cancer tissues. We also found that knockdown of OGT could inhibit cell proliferation, migration, invasion, and induce cell cycle arrest, while these are reversed when OGA is inhibited. We also observed that O-GlcNAcylation could promote tumor formation in vivo, compared with a negative control. In summary, this study describes the oncogenic role of O-GlcNAcylation in bladder cancer cells. [ABSTRACT FROM AUTHOR]

Raman spectra of (Mn, Co)-codoped ZnO films were investigated as functions of laser line and temperature. It is shown that the Raman shifts for different phonon modes exhibit redshift with temperature increasing, which can be attributed to the anharmonic effect in the material. Strong resonant Raman spectra of multi-LO phonons were observed as well for the films with the exciting photon energy higher than the direct band gap. Compared with the Raman spectra for ZnO films, the Mn, Co codoping effect on the spectra is revealed by the presence of additional phonon modes at 275 and 642 cm-1 and another intensive phonon mode at around 524 cm-1. With postannealing, Raman intensity of these phonon modes decrease, owing to the incorporation of oxygen into the films. Origins of the different phonon modes in the spectra are discussed as well. [ABSTRACT FROM AUTHOR]

Raman spectra of SrBi4Ti4O15 (SBTi4) thin films were measured as a function of temperature from 80 to 820 K. Below room temperature, no phonon modes were detected between 200 and 815 cm-1, which indicates the existence of a phonon band gap in this material. Differences between the Raman spectra of the thin film and bulk polycrystalline samples are discussed. The asymmetric Raman band at high frequency can be interpreted as the superposition of two main distinct Raman lines. Temperature dependence of the Raman shifts and full widths at half maximum (FWHMs) for the two phonon modes is discussed as well, which provides information about the vibration energy levels within the film. Theoretical fittings of their FWHMs indicate that the higher-energy phonon mode is apparently more anharmonic than the lower one. [ABSTRACT FROM AUTHOR]

The emission of light and external coupling after the appropriate excitons have been formed in the organic light-emitting devices (OLEDs) has been investigated. The internally emitted light can be classified into three modes: externally emitted, substrate waveguided, and indium-tin-oxide (ITO)/ organic waveguided. A combined classical and quantum mechanical microcavity model is used to calculate the distribution of light emission into these three modes in an OLED on planar substrates. The ITO/organic modes maybe suppressed due to the thinness of the ITO/organic layers. Consequently, as much as over 50% of the internally generated light is emitted externally in some structures, much greater than the ∼20% figure given by classical ray optics. This model is used to examine how this distribution varies with exciton to cathode distance, the thickness of the ITO layer, and the index of refraction of the substrate. It can also be applied to OLEDs on shaped substrates where an increase in the total external emission up to a factor of 2.3 has been demonstrated. The numerical results agree well with experimentally measured far-field intensity profiles, edge emissions, and increase in external emission due to shaped substrates. Finally, based on these results, we discuss different approaches to device optimization, depending on the fluorescence efficiency of the emitter and whether a shaped substrate is used. [ABSTRACT FROM AUTHOR]

The quantum spin Hall (QSH) effect is widely studied as a novel quantum state in condensed matter physics over the past decade. Recently, it is predicted that the transition metal pentatelluride XTe5 (X = Zr, Hf) has a large bandgap in its bulk form and a single layer of XTe5 is a QSH insulator candidate. However, the topological nature of the bulk material is still under debate because it is located close to the phase boundary of a strong topological insulator and a weak topological insulator (WTI). Here, using angle-resolved photoemission spectroscopy and scanning tunneling microscopy (STM)/scanning tunneling spectroscopy, we systematically studied the electronic structures of bulk HfTe5. Both the large bulk bandgaps and conductive edge states in the vicinity of the step edges in HfTe5 were observed, strongly suggesting a WTI phase in bulk HfTe5. Moreover, our STM experiment for the first time reveals the bulk band bending due to the broken symmetry near the step edge, making it an ideal platform for studying the development of edge states in the WTI and QSH insulator. [ABSTRACT FROM AUTHOR]

We design a 3D acoustic metamaterial having a coiling resonant structure with high symmetry. Eigenstate analysis reveals that such a 3D metamaterial has two significant Mie-type eigenmodes, monopole and dipolar resonances. Large blocking of sound waves in the low-frequency range between monopole and dipolar resonances is observed numerically and experimentally. The effective properties extracted from the reflection and transmission coefficients show negative bulk modulus around the monopole resonant frequency and negative mass density around the dipolar resonant frequency. By employing the proposed two-scale model, the metamaterial system demonstrates the functionalities of sound cloaking and super-tunneling within a finite space. [ABSTRACT FROM AUTHOR]

We present a simple fabrication of FePt and Fe nanocomposite by annealing self-assembled FePt nanoparticles. 5 nm FePt nanoparticles were prepared by simultaneous reduction of platinum acetylacetonate and thermal decomposition of iron pentacarbonyl in the presence of oleic acid and oleylamine as stabilizers. The as-synthesized FePt nanoparticles can self-organize well on a clean SiO/Si substrate and, then, were annealed in a vacuum using a rapid thermal process at different temperatures for 0.5 h. It is found that the annealing temperature plays a key role in determining the final products. The samples annealed at 550 °C and 700 °C consist of a FePt-face-centered-tetragonal (fct) phase with a coercivity of around 1000 and 8800 Oe, respectively, whereas, the samples annealed at 580 °C are composed of two phases: one is the FePt-fct phase and the other is a Fe-body-centered-cubic phase. The hysteresis loop of the sample annealed at 580 °C is also two-phase like with a kink at low field and its coercivity is around 8000 Oe. That indicates that Fe can be segregated from FePt by proper annealing, forming FePt and Fe nanocomposites. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Rice planthopper (RPH) populations of Nilaparvata lugens and Sogatella furcifera periodically have erupted across Asia. Predicting RPH population dynamics and identifying their source areas are crucial for the management of these migratory pests in China, but the origins of the migrants to temperate and subtropical regions in China remains unclear. In particular, their early migration to China in March and April have not yet been explored due to a lack of research data available from potential source areas, Central Vietnam and Laos. In this study, we examined the population dynamics and migratory paths of N. lugens and S. furcifera in Vietnam and South China in 2012 and 2013. Trajectory modeling showed that in March and April in 2012 and 2013, RPH emigrated from source areas in Central Vietnam where rice was maturing to the Red River Delta and South China. Early migrants originated from Southern Central Vietnam (14–16°N), but later most were from Northern Central Vietnam (16–19°N). Analysis of meteorological and light-trap data from Hepu in April (1977–2013) using generalized linear models showed that immigration increased with precipitation in Southern Central Vietnam in January, but declined with precipitation in Northern Central Vietnam in January. These results determined that the RPH originate from overwintering areas in Central Vietnam, but not from southernmost areas of Vietnam. Winter precipitation, rather than temperature was the most important factor determining the number of RPH migrants. Based on their similar population dynamics and low population densities in Central Vietnam, we further speculated that RPH migrate to track ephemeral food resources whilst simultaneously avoiding predators. Migrations do not seem to be initiated by interspecific competition, overcrowding or host deterioration. Nevertheless, S. furcifera establishes populations earlier than N. lugens South China, perhaps to compensate for interspecific competition. We provide new information that could assist with forecasting outbreaks and implementing control measures against these migratory pests. [ABSTRACT FROM AUTHOR]

Si3N4–TiC nanocomposites are fabricated by hot press sintering from silicon nitride nanopowders and ultrafine TiC powders. The microstructure and mechanical properties are analysed and discussed. Scanning electron microscopy images show that the microstructure consists of equiaxed grains and grain boundary phase. The TiC added as a dispersed phase reacts with the nitrogen from Si3N4 during the liquid phase sintering, with the formation of TiC0.7 N0.3 , trace of SiC and N2. The adding of a proper amount of TiC powders increases the flexural strength and has little influence on fracture toughness. The hardness increases with increasing TiC content. [ABSTRACT FROM AUTHOR]

Dry dye printing and solvent-enhanced dye diffusion were used to locally dope a previously spin-coated poly(9-vinylcarbazole) (PVK) polymer film with different dyes to fabricate side-by-side red, green, and blue (RGB) organic light-emitting device pixels. The fabrication details and the resolution and stability of this patterning technique are discussed. The technique was then used to make combined polymer/small-molecule devices, in which the printability of polymer for color integration was combined with the superior transport properties and thin-layer capabilities of small molecules for high efficiency and low leakage current. To reduce reverse leakage current and raise efficiency, a blanket tris-8-hydroxyquinoline aluminum (Alq3) electron transport layer was deposited on top of the polymer layer after the dye diffusion step, along with a 2,9-dimethyl-4,7-diphenyl-1,10-phenanffiroline hole/exciton blocking layer between the Alq3 and the PVK to ensure that all light emission occurred from the doped polymer and not from the Alq3. Devices with this hybrid doped polymer/small molecule structure have an extremely low reverse leakage current (with a rectification ratio of 106 at ±10 V). The electroluminescence efficiency of the devices was optimized by varying the dye concentration of the printing plate. A three-color passive-matrix test array with 300 μm × 1 mm RGB subpixels was demonstrated with this structure. [ABSTRACT FROM AUTHOR]

Indentation is a commonly used approach to measure the mechanical properties of soft tissues, such as articular cartilage and limb tissues. The Young's modulus of tissue can be calculated from the indentation test using a mechanical model, where the soft tissue is normally assumed to have a flat substrate. In this study, a series of 2D finite element models were established to investigate the effects of bones with various curvatures embedded in the soft tissues during an indentation test. For each curvature of the hard substrate, the errors in the calculation of the Young's modulus were estimated for different indentation depths (0-10%) and aspect ratios a/h of the indentor diameter and the tissue thickness (0.2-2 in seven steps). The radius ratio a/R of the indentor and the curved substrate ranged from 0 to 0.38 in nine steps. Results showed that the error in calculation of the Young's modulus increased by 21.2% when the curvature a/R of the bone increased from 0 to 0.38 (under the condition of a/h=1.0, Poisson's ratio v=0.45). The error increased from 6.0 to 18.2% when the tissue thickness increased from 0.2 to 2 (a/R=0.18, v=0.45). It was found that the error in the Young's modulus calculation caused by the curved hard substrates could be corrected by a single factor for different indentation depths. This factor depends on the Poisson's ratio, the aspect ratio a/h and the radius ratio a/R. [ABSTRACT FROM AUTHOR]

Abstract. A two-stage infrared up-convertor made of AgGaSe[sub 2] and beta-BBO crystals has been built up, that can up-convert the mid-infrared radiation of 11-16 micro m into the 0.8-micro m range where the sensitive photonmltiplier can be used. This up-convertor is pumped with a near-infrared radiation of 1.7-1.8 micro m wavelength range generated by a beta-BBO optical parametric oscillator. In this experiment, we also measured the o-ray refractive index of AgGaSe[sub 2] in the 11-16 micro m mid-infrared range and extended the fitting range of the Sellmeier equation to the 16-micro m wavelength range. PACS: 42.65; 42.70 [ABSTRACT FROM AUTHOR]

Topological insulators represent a new state of quantum matter recently discovered with insulating bulk but conducting surface states formed by an odd number of Dirac fermions. In this Letter, we report our recent progress on the study of electronic structures of ex‐situ grown topological insulator thin films by angle resolved photoemission spectroscopy (ARPES). We successfully obtained the topological band structures of molecular beam epitaxial HgTe and vapor–solid grown Bi2Te3 thin films after proper surface cleaning procedures. This new development will not only enable us to study more topological insulators that cannot be measured by conventional in‐situ ARPES technique (e.g. by cleaving or growing samples in‐situ), but also open the door to directly characterize the electronic properties of topological insulators used in functional devices. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) In this Letter, the authors have demonstrated the effectiveness of proper surface cleaning procedures on ex‐situ grown topological insulator thin films (molecular beam epitaxial HgTe and vapor–solid grown Bi2Te3), and subsequently acquired the electronic structures successfully by angle‐resolved photoemission spectroscopy. This development would extend the study of electronic band structure to a variety of topological insulators without natural cleavage planes or those used in actual functional devices. [ABSTRACT FROM AUTHOR]

The discovery of a two-dimensional electron gas (2DEG) at the LaAlO 3 / SrTiO 3 interface has set a new platform for all-oxide electronics which could potentially exhibit the interplay among charge, spin, orbital, superconductivity, ferromagnetism and ferroelectricity. In this work, by using angle-resolved photoemission spectroscopy and conductivity measurement, we found the reduction of 2DEGs and the changes of the conductivity nature of some ferroelectric oxides including insulating Nb-lightly-substituted KTaO 3 , BaTiO 3 (BTO) and (Ca,Zr)-doped BTO across paraelectric-ferroelectric transition. We propose that these behaviours could be due to the increase of space-charge screening potential at the 2DEG/ferroelectric regions which is a result of the realignment of ferroelectric polarisation upon light irradiation. This finding suggests an opportunity for controlling the 2DEG at a bare oxide surface (instead of interfacial system) by using both light and ferroelectricity. [ABSTRACT FROM AUTHOR]

Single-phase insulating BiFeO3 ceramics have been synthesized by a simple but effective method that conventional solid state reaction is followed immediately by quenching processing. At room temperature, the ceramics show a metastable, distorted rhombohedral phase and the refined structure parameters are presented based on x-ray diffraction. It is revealed that the formations of Fe2+ and oxygen deficiency are greatly suppressed by the quenching processing. A well-saturated ferroelectric hysteresis loop with a large remnant polarization (2Pr=23.5 μC/cm2) is observed with an applied field of 155 kV/cm. Temperature-dependent magnetic property is investigated and weak ferromagnetism with a remnant magnetization of 4×10-6 μB/Fe at 10 K is established. These results may have implications for further studies on multiferroics. [ABSTRACT FROM AUTHOR]

Based on theoretical arguments that top-emitting organic light-emitting devices (TOLEDs) can be more efficient than equivalent bottom-emitting devices, we fabricated TOLEDs comprising reflective anodes and transparent compound cathodes that emit 20.8% more photons in the forward 120° cone than equivalent bottom-emitting OLEDs. Device optimization by tuning the thickness of the top indium–tin–oxide layer according to a microcavity model is also reported. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The external coupling efficiency in planar organic light-emitting devices is modeled based on a quantum mechanical microvavity theory and measured by examining both the far-field emission pattern and the edge emission of light trapped in the glass substrate. The external coupling efficiency is dependent upon the thickness of the indium-tin-oxide layer and the refractive index of the substrate. The coupling efficiency ranges from ∼24% to ∼52%, but in general it is much larger than the 18.9% expected from classical ray optics. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Topological insulators represent a novel state of quantum matter recently discovered with insulating bulk but conducting surface states formed by an odd number of Dirac fermions, which process helical spin texture and symbolic linear band dispersion in the momentum space. Besides their scientific significance, this class of materials has been demonstrated to be promising for numerous potential applications, such as low‐power electronics, spintronic devices, and even quantum computation. The front‐cover image illustrates the electronic structure of an elemental topological insulator Bi2Se3 with a single Dirac point at the apex of the conical band dispersion. This electronic structure can be directly detected by angle‐resolved photoemission spectroscopy (ARPES, see the Letter by S. H. Yao et al., pp. 130–132). In addition to the conventional in‐situ prepared samples within the ultra‐high vacuum environment, Yao et al. recently succeeded in developing methods to obtain the band structures of ex‐situ prepared topological insulators, making the study of electronic structures in many functional materials and devices a reality. [ABSTRACT FROM AUTHOR]

The emission intensity of an organic light-emitting diode at normal viewing angle and the total external emission efficiency have been increased by factors of 9.6 and 3.0, respectively, by applying spherically shaped patterns to the back of the device substrate. The technique captures light previously lost to waveguiding in the substrate and, with proper choice of substrate, light previously lost to waveguiding in the organic/anode layers. A method of applying the technique using laminated films and an optical model for evaluating coupling efficiency are also presented. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Ink-jet printing was used to directly deposit patterned luminescent doped-polymer films. The luminescence of polyvinylcarbazol (PVK) films, with dyes of coumarin 6 (C6), coumarin 47 (C47), and nile red was similar to that of films of the same composition deposited by spin coating. Light emitting diodes with low turn-on voltages were also fabricated in PVK doped with C6 deposited by ink-jet printing. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The performance of LMS-based adaptive noise cancellation (ANC) systems is directly related to the coherence of the noise between primary and reference inputs. In a reverberant environment, the coherence is degraded, due to the essentially random nature of the late reflections in the multipath process. To improve system performance in such a setting, the coherence between the ANC inputs can be increased. One technique is to utilize the ANC primary and reference inputs to dereverberate the reference noise signal. Experiments have been conducted using the dereverberation system of Allen et al. [J. Acoust. Soc. Am. 62, 912-915 (1979)]. This method attenuates incoherent spectral components from the ANC reference signal. It also provides greater flexibility in ANC receiver location by compensating for delays existing between the ANC inputs. Reverberant room conditions were simulated using an image model. Results, based on normalized residual error, indicate the performance of the dereverberated system is always better than the best performance of the LMS system. Furthermore, this improvement can increase in more reverberant conditions with decreased spacing between the noise source and the ANC primary receiver. [ABSTRACT FROM AUTHOR]