Room-temperature flexible thin film transistor with high mobility

We report a room-temperature and high-mobility InGaZnO thin-film transistor on flexible substrate. To gain both high gate capacitance and low leakage current, we adopt stacked dielectric of Y₂O₃/TiO₂/Y₂O₃. This flexible IGZO TFT shows a low threshold voltage of 0.45 V, a small sub-threshold swing of 0.16 V/decade and very high field-effect mobility of 40 cm²/V. Such good performance is mainly contributed by improved gate stack structure and thickness modulation of IGZO channel that reduce the interface trap density without apparent mobility degradation.     

A global pinching theorem for surfaces with constant mean curvature in

Let be a compact immersed surface in the unit sphere with constant mean curvature . Denote by the linear map from into , , where is the linear map associated to the second fundamental form and is the identity map. Let denote the square of the length of . We prove that if , then is either totally umbilical or an -torus, where is a constant depending only on the mean curvature .

     

Low temperature growth and dimension- dependent photoluminescence efficiency of semiconductor nanowires

Low temperature growth and dimension dependent photoluminescence (PL) efficiency of semiconductor nanowires were investigated with CdS as a model system. The CdS nanowires were prepared with a simple, low temperature metal-organic chemical vapor deposition (MOCVD) process via the vapor–liquid–solid (VLS) mechanism. The low growth temperature of 360 °C was made possible with a newly developed single-source precursor of CdS and by using sputtered Au as the catalyst for the VLS growth. The length and diameter of the nanowires were adjusted by reaction time and sputtering conditions of Au, respectively. Nanowires of up to several μm in length and 20 to 200 nm in diameter were obtained. The PL quantum yield of the nanowires was found to decrease with increasing wire length, but to increase with decreasing wire diameter. This dimension-dependent PL efficiency of one-dimensional nanostructure, unlikely resulting from the quantum size confinement effect, appears to be a new observation that carries application significance. PACS 74.25.Gz; 78.55.Et; 78.67.Lt     

Smooth solutions to a class of quasilinear wave equations

This article investigates the existence/nonexistence of smooth solutions of nonlinear vibration equations which arise from the one-dimensional motion of polytropic gas without external forces contained in a finite interval. For any fixed arbitrarily long time, we show that there are smooth small amplitude solutions of the nonlinear equations for which the periodic solutions of the linearized equation are the first-order approximations. On the other hand, when the nonlinearity is strictly convex or concave, there exists no time-periodic solutions which are twice continuously differentiable. An example of possible singularities which occur at the second derivatives is illustrated. We also give another kind of exact solutions with singularity such that shocks occur after a finite time. Furthermore, we get an estimate of the life span of smooth solutions to the initial-boundary value problem.     

Structural, optical, and electrical properties of p-type NiO films and composite TiO2/NiO electrodes for solid-state dye-sensitized solar cells

p-Type nickel oxide thin films were prepared by sol-gel method, and their structural, optical and electrical properties were investigated. The Ni(OH)₂ sol was formed from nickel (II) acetate tetrahydrate, Ni(CH₃COO)₂·4H₂O, in a mixture of alcohol solution and poly(ethylene glycol), and deposited on an ITO substrate by spin coating followed by different heat treatments in air (50-800 °C). The formation and composition of NiO thin film was justified by EDX analysis. It is found that the thickness of the NiO film calcined at 450 °C for 1 h is about 120 nm with average particle size of 22 nm, and high UV transparency (∼75%) in the visible region is also observed. However, the transmittance is negligible for thin films calcined at 800 °C and below 200 °C due to larger particle size and the amorphous characteristics, respectively. Moreover, the composite electrode comprising n-type TiO₂ and p-type NiO is fabricated. The current-voltage (I-V) characteristics of the composite TiO₂/NiO electrode demonstrate significant p-type behavior by the shape of the rectifying curve in dark. The effect of calcination temperature on the rectification behavior is also discussed.     

Linear-cavity fiber laser using subring-cavity incorporated saturable absorber for single-frequency operation

By using a subring cavity incorporated with a saturable absorber, a stable single-frequency selection is realized in a linear-cavity fiber laser, which is constructed using a broadband fiber mirror and a partial reflectance fiber Bragg grating as the cavity ends. At 1550.33 nm, the laser has an optical signal-to-noise-ratio of >53.28 dB and with linewidth less than 1 MHz. The pumping efficiency is 25% improved by recycling the residual pump power to gain medium. The power stability and wavelength stability have also been studied.     

FDTD analysis of infrared radiative properties of microscale structure aluminum surfaces

Metallic triangular grating structures have a wide range of applications. This study focuses on the radiative properties of triangular grating structures of aluminum in the mid-infrared wavelength to determine if we can tailor the infrared radiative properties by designing special geometrical details into triangular grating surfaces. Fabrication of triangular gratings within the range of micron scale is very difficult. Therefore, the influences of slight geometry modification, generated by fabrication errors, on radiative properties of triangular gratings are mainly investigated. The electromagnetic wave scattering from such surfaces is predicted by solving Maxwell's equations using the finite-difference time-domain (FDTD) method. The results show that the spectral reflectance varies with the dimensions of triangular gratings, which is due to the excitation of surface wave by confirmation of the EM fields. It is found that the spectral reflectance can also be reduced by increasing the height of slight geometry modification. The effect of oblique incident wave state is also investigated. An optical vortex is found due to the coupling of surface waves, the oblique incident wave and the scattering waves. This study helps to gain a better understanding of the radiative properties of metallic triangular gratings with slight geometry modification and will have an impact on triangular grating processing.     

Exact recession velocity and cosmic redshift based on cosmological principle and Yang-Mills gravity

Based on the cosmological principle and quantum Yang-Mills gravity in the super-macroscopic limit, we obtain an exact recession velocity and cosmic redshift z, as measured in an inertial frame F ≡ F(t, x, y, z). For a matter-dominated universe, we have the effective cosmic metric tensor G_(μν)(t) =(B~2(t),-A~2(t),-A~2(t),-A~2(t)),A ∝ B ∝ t~(1/2), where t has the operational meaning of time in F frame. We assume a cosmic action S ≡ S cos involving Gμν(t) and derive the ‘Okubo equation' of motion, G μν(t)?μS ?νS-m2= 0, for a distant galaxy with mass m. This cos-√mic equation predicts an exact recession velocity, ■, where H = A˙(t)/A(t) and Co = B/A, as observed in the inertial frame F. For small velocities, we have the usual Hubble's law r≈ rH for recession velocities. Following the formulation of the accelerated Wu-Doppler effect, we investigate cosmic redshifts z as measured in F. It is natural to assume the massless Okubo equation, G μν(t)?μψe?νψe= 0, for light emitted from accelerated distant galaxies. Based on the principle of limiting continuation of physical laws, we obtain a transformation for covariant wave 4-vectors between and inertial and an accelerated frame, and predict a relationship for the exact recession velocity and cosmic redshift, z = [(1 + V_r)/(1-V_r~2)~(1/2)]-1, where Vr= r˙/Co 1, as observed in the inertial frame F. These predictions of the cosmic model are consistent with experiments for small velocities and should be further tested.     

Diterpenoid Compounds Isolated from Chloranthus oldhamii Solms Exert Anti-Inflammatory Effects by Inhibiting the IKK/NF-κB Pathway

Chloranthus oldhamii Solms (CO) is a folk medicine for treating infection and arthritis pain but its pharmacological activity and bioactive compounds remain mostly uncharacterized. In this study, the anti-inflammatory compounds of C. oldhamii were identified using an LPS-stimulated, NF-κB-responsive RAW 264.7 macrophage reporter line. Three diterpenoid compounds, 3α-hydroxy-ent-abieta-8,11,13-triene (CO-9), 3α, 7β-dihydroxy-ent-abieta-8,11,13-triene (CO-10), and decandrin B (CO-15) were found to inhibit NF-κB activity at nontoxic concentrations. Moreover, CO-9 and CO-10 suppressed the expression of IL-6 and TNF-α in LPS-stimulated RAW 264.7 cells. The inhibitory effect of CO-9 on TNF-α and IL-6 expression was further demonstrated using LPS-treated bone marrow-derived macrophages. Furthermore, CO-9, CO-10, and CO-15 suppressed LPS-triggered COX-2 expression and downstream PGE2 production in RAW 264.7 cells. CO-9 and CO-10 also reduced LPS-triggered iNOS expression and nitrogen oxide production in RAW 264.7 cells. The anti-inflammatory mechanism of the most effective compound, CO-9, was further investigated. CO-9 attenuated LPS-induced NF-κB activation by reducing the phosphorylation of IKKα/β (Ser176/180), IκBα (Ser32), and p65 (Ser534). Conversely, CO-9 did not affect the LPS-induced activation of MAPK signaling pathways. In summary, this study revealed new anti-inflammatory diterpenoid compounds from C. oldhamii and demonstrated that the IKK-mediated NK-κB pathway is the major target of these compounds.     

Miniaturized Salinity Gradient Energy Harvesting Devices

Harvesting salinity gradient energy, also known as “osmotic energy” or “blue energy”, generated from the free energy mixing of seawater and fresh river water provides a renewable and sustainable alternative for circumventing the recent upsurge in global energy consumption. The osmotic pressure resulting from mixing water streams with different salinities can be converted into electrical energy driven by a potential difference or ionic gradients. Reversed-electrodialysis (RED) has become more prominent among the conventional membrane-based separation methodologies due to its higher energy efficiency and lesser susceptibility to membrane fouling than pressure-retarded osmosis (PRO). However, the ion-exchange membranes used for RED systems often encounter limitations while adapting to a real-world system due to their limited pore sizes and internal resistance. The worldwide demand for clean energy production has reinvigorated the interest in salinity gradient energy conversion. In addition to the large energy conversion devices, the miniaturized devices used for powering a portable or wearable micro-device have attracted much attention. This review provides insights into developing miniaturized salinity gradient energy harvesting devices and recent advances in the membranes designed for optimized osmotic power extraction. Furthermore, we present various applications utilizing the salinity gradient energy conversion.