Effects of methyl substitution of metal (II) bis(2-(2-hydroxyphenyl) benzothiazolate) chelates on optical properties

The influence of methyl substitution on three-position of metal (II) bis(2-(hydroxyphenyl)benzothiazolate) on thermal stability, photophysical, electronic structure, and electrochemical properties was investigated. Experimental results show that methylated complexes were more thermally stable and had 10–20 nm red shift in emission wavelength. Quantum chemistry calculation indicated that the methyl substitution affects mostly the highest occupied molecular orbitals charge distribution. In addition, the introduction of electro-donating methyl group can produce a decrease in the energy of the lowest unoccupied molecular orbitals.     

Relation between morphology and performance parameters of poly(3-hexylthiophene):Phenyl-C61-butyric acid methyl ester photovoltaic devices

Poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulk heterojunction (BHJ) solar cells are one of archetypal polymer photovoltaic devices. Understanding the relationship between electronic properties and active layer morphology is essential to obtain high-performance electronic devices. The magnitudes of the short circuit current (J_SC), the fill factor (FF) and the open circuit voltage (V_OC) will vary on the basis of changes in phase purity, interfacial region area and domain size of the active layer. We investigated the device characteristics of the samples having comparable phase purity and found that the performance parameters were better in the device having larger interfacial region area. In another case the phase purity decreases, the interfacial area increases and the recombination rate increases, resulting FF and V_OC increase, J_SC first increases then decreases. Power conversion efficiency (PCE) increases with the increase of interfacial region area, although at the same time associates with the decrease of the phase purity. The device efficiency reaches optimal value by balance the phase purity and the interfacial area. We finally investigated the two devices where, in spite of significant difference between domain dimensions, the PCEs were quite similar. Especially, the devices having large micrometer scale PCBM crystals also obtain good PCEs if they have enough interfacial areas.     

Effects of fading and partial-band noise jamming on a fast FH/BFSKacquisition receiver with noise-normalization combination

We present the performance analysis of a fast frequency-hopped (FH) binary orthogonal frequency-shift keying acquisition receiver for communication against adverse environments. The receiver employs noncoherent, noise-normalized, matched-filtered (MF) correlation detection for rapid acquisition in the search mode. Our analysis includes four types of communication environments, namely additive white Gaussian noise (AWGN) channel, AWGN channel with partial-band noise jamming, fading channels, and fading channels with partial-band noise jamming. The considered fading channels include Nakagami-m, Rician, and Rayleigh amplitude models. Based on Beaulieu's (see ibid., vol.38, no.9, p.1463, 1990) convergent series approach, efficient analytical formulas are developed for performance evaluation. Example performance results for various environments are presented in terms of two acquisition probabilities, namely the detection probability and the false alarm probability of the noise-normalized MF detector. It is analytically shown that with a short MF correlation length and with a sufficiently large ratio of signal power to noise power the fast FH diversity combining yields noticeable performance improvement for environments with strong fading. When the MF correlation is lengthened, this improvement tends to fade away and the diversity combining results in performance loss     

Synthesis and characterization of poly (linoleic acid)-g-poly(methyl methacrylate) graft copolymer with applying in Au/PLiMMA/n-Si diode

Poly (linoleic acid)-g-poly(methyl methacrylate) (PLiMMA) graft copolymer was synthesized and characterized. PLiMMA graft copolymer was synthesized from polymeric linoleic acid peroxide (PLina) possessing peroxide groups in the main chain by free radical polymerization of methyl methacrylate. Later, PLiMMA was characterized by proton nuclear magnetic resonance (¹H NMR), gel permeation chromatography (GPC), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Furthermore, Au/PLiMMA/n-Si diode was fabricated for the purpose of investigating PLiMMA׳s conformity in diodes. The main electrical characteristics of this diode were investigated using experimental current–voltage (I–V) measurements in dark and at room temperature. Obtained results, such as sufficiently high rectifying ratio of 4.5×10⁴, indicate that PLiMMA is a promising organic material for electronic device applications.     

Enhancement of Modulus,Strength, and Toughness in Poly(methyl methacrylate)‐Based Composites by the Incorporation of Poly(methyl methacrylate)‐Functionalized Nanotubes

Poly(methyl methacrylate) (PMMA)‐functionalized multiwalled carbon nanotubes are prepared by in situ polymerization. Infrared absorbance studies reveal covalent bonding between polymer strands and the nanotubes. These treated nanotubes are blended with pure PMMA in solution before drop‐casting to form composite films. Increases in Young's modulus, breaking strength, ultimate tensile strength, and toughness of ×1.9, ×4.7, ×4.6, and ×13.7, respectively, are observed on the addition of less than 0.5 wt % of nanotubes. Effective reinforcement is only observed up to a nanotube content of approximately 0.1 vol %. Above this volume fraction, all mechanical parameters tend to fall off, probably due to nanotube aggregation. In addition, scanning electron microscopy (SEM) studies of composite fracture surfaces show a polymer layer coating the nanotubes after film breakage. The fact that the polymer and not the interface fails suggests that functionalization results in an extremely high polymer/nanotube interfacial shear strength.     

激光照射,免疫抑制剂及其配合对免疫细胞的影响

应用３９．７２Ｊ／ｃｍ＾２的Ｈｅ－Ｎｅ激光连续１４天照射健康大鼠脊背正中线皮肤，并同时分别与亚剂量的免疫抑制剂环孢霉素Ａ，硫唑嘌呤相匹配，观察了它们对Ｔ，Ｂ淋巴细胞数，淋巴细胞转化刺激指数（Ｓ，Ｉ），１０＾６个淋巴细胞ＣＰＭ数的影响，结果表明，大剂量Ｈｅ－Ｎｅ激光和Ａｚ唑嘌呤均可降低大鼠Ｂ淋巴细胞数，大剂量Ｈｅ－Ｎｅ激光，环孢霉素Ａ，硫唑嘌呤及激光照射与二者配合，均可使淋巴细胞转化刺激指数（Ｓ，Ｉ     

Synthesis and Fabrication of Multifunctional Nanocomposites: Stable Dispersions of Nanoparticles Tethered with Short,Dense and Polydisperse Polymer Brushes in Poly(methyl methacrylate)

This paper presents a melt‐processable multifunctional nanocomposite material that shows highly controlled tunability in refractive index, glass transition temperature (T_g) and energy bandgap. ZnO quantum dots tethered with polymer brushes are melt‐blended into the matrix polymer, giving rise to multiple functionalities in the nanocomposites. Brush–matrix polymer interactions are important in determining the ability of polymer‐grafted nanoparticles to disperse in a polymer melt, of which graft density (σ), brush (N) and matrix (P) polymer lengths are the critical parameters. It is generally assumed that long polymer brushes (N > P) and an optimum graft density are necessary to achieve a good dispersion. Here it is demonstrated that nanoparticles tethered with short, dense and polydisperse polymer brushes via radical copolymerization can exhibit a stable, fine dispersion in the polymer melt. The quality of the dispersion of the nanoparticles is characterized by measuring physical properties that are sensitive to the state of the dispersion. This synthesis method presents a general approach for the inexpensive and high‐throughput fabrication of high quality, melt‐blendable nanocomposites that incorporate functional nanoparticles, paving the way for wider application of high performance nanocomposites.     

Characteristics of the carcinogenic action of methyl(acetoxymethyl)nitrosamine and DNA repair in rats of different ages

A pattern of DNA methylation and carcinogenesis has been studied in young (3 month-old) and old (14 month-old) female rats following a single intravenous injection (13 mg/kg) of methyl(acetoxymethyl)nitrosamine (DMN-OAc). The incidence of various tumours as well as the incidence of tumours in some peculiar sites were found to be similar in young and old DMN-OAc-treated rats. The life time of old rats was less than that in young animals; the average period of tumour detection was also shorter in old rats. In both young and old animals the highest concentrations of methylated purines were found in lung and kidney DNA. However, the level of DNA methylation in old rats was higher than in corresponding tissues of young animals. Efficiency of O6-meG repair in methylated template DNA was found to be the highest in liver extracts of 1- and 12-month-old rats. Further, by the age of 2 years, the activity of O6-meGT decreased. The findings suggest that different age periods could be characterized by different efficiency of DNA alkylation, synthesis and repair.     

The importance of distributed grounding in combination with porous Si trenches for the reduction of RF crosstalk through p/sup -/ Si substrate

Locally incorporated porous Si (PS) trenches are used for radio frequency (RF) crosstalk isolation through p/sup -/ Si substrates. PS trenches provide large dielectric separation (large impedance) between the noise producing and the noise sensitive circuits without prohibitively high stress from a thermal expansion coefficient mismatch between bulk Si and the common dielectrics, e.g. SiO/sub 2/ and Si/sub 3/N/sub 4/. A variety of commonly used RF isolation structures are fabricated and compared. The best isolation structure for the p/sup $/substrates is shown to be the one with p/sup +/ grounding stripes in addition to a PS trench. Crosstalk between Al pads with 800 /spl mu/m separation is reduced to the level comparable to that through air. It is shown that contrary to our previous result using PS trenches in p/sup +/ substrates, p/sup +/ grounding stripes or PS trenches alone is quite ineffective. Superior RF isolation is achieved only when the two approaches are used in conjunction with one another. The combined approach results in additional crosstalk reduction of 21 dB at 2 GHz and 11 dB at 20 GHz.     

Hall Field and Magnetoresistance Effects in Rectangular Waveguide Completely Filled with Semiconductor (Short Papers)

Microwave propagation through a rectangular waveguide completely filled with semiconductor and subject to a transverse magnetic field is analyzed. When the magnetic field is parallel-to the broad wall of the waveguide (the x axis), propagation is analyzed in terms of the Hall effect. For the magnetic field parallel to the y axis, the effect of the field on the propagation is shown to be due to longitudinal magneto-resistance effects. Good agreement is obtained between theory and experiment in both cases. The experiments were performed at 30 GHz using n-type germanium.     

An improved location service scheme in urban environments with the combination of GPS and mobile stations

Satellite‐based apositioning and navigation technology in urban environments is widely studied. As a solution to GPS signal degradation in urban environment, the wireless network‐aided location scheme has been put into practice, which benefits our everyday life. However, there still exist many potential advantageous points that can be exploited to improve the performance of the location service especially in urban environments. This paper proposes a GPS‐based positioning and navigation with the aid of wireless network (GPONAWIN) positioning scheme that utilizes the existing resources of wireless communication networks to provide cheaper and more accurate urban positioning service with higher survivability. After the proposed scheme is described in detail, outperformances over the existing scheme are also analyzed. The GPONAWIN scheme can achieve higher information utilization efficiency, less wireless channel expenditure, more accurate positioning, better expandability to the multiple satellite positioning and navigation systems, and lower cost. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of Sintering Temperature on Structure and Properties of 0.997(KNN-LS-BF)-0.003V2O5 Lead-Free Piezoelectric Ceramics

0.997(KNN-LS-BF)-0.003V₂O₅ lead-free piezoelectric ceramics were prepared by a traditional sintering method. The effects of sintering temperature on the structure and properties of the 0.997(KNN-LS-BF)-0.003V₂O₅ ceramics were studied. The results show that the sintering temperature exerts a distinct influence on the phase structure and properties. With the increase in sintering temperature from 1040°C to 1060°C, the main crystallographic phase changes from the orthorhombic symmetry to the tetragonal phase, and the optimum dielectric and piezoelectric properties of samples can be obtained when sintering at 1060°C. However, the dielectric and piezoelectric properties of the samples deteriorate when the sintering temperature exceeds 1060°C.     

Effects of temperature and pressure in oxynitridation kinetics on Si(100) with N2O gas

We have investigated oxynitridation of Si(100) surfaces with nitrous oxide (N₂O) gas in a wide range of substrate temperatures (600–1000 °C) and N₂O pressures (10⁻²–10² Pa). The growth rate and atomic composition of the oxynitride layer have been measured by in situ x-ray photoelectron spectroscopy. The surface morphology of the oxynitride layer has been also observed by scanning electron microscopy. The results show that in higher N₂O pressure (>1 Pa) regime, the nitridation reaction is suppressed by the oxide layer, which quickly forms on the surface. On the other hand, in lower pressure (<1 Pa) and higher substrate temperature (>900 °C) regime, the nitridation reaction strongly occurs because of the active oxidation (etching reaction), which causes the surface roughness. It is found by argon-ion-sputtering measurements that the nitride layer locally exists only near the surface at the reduced N₂O pressure. We discuss qualitatively the oxynitridation kinetics and the effective condition for growing the oxynitride layer.     

探测功率10^—10W的光电器件的计算与设计

本文计算和比较了 Ge、Si、GaAs 器件的热噪声、信号电压、信/噪比、得到了制造功率为10~(-10)W 光电探测器的有效途径和实验方案。认为采用 P~+型衬底、外延高阻 P 型 Si、或用电阻率2Ω-cm 的 P 型 Si,制作光电倍增(雪崩)二极管,可以探测最小功率为10~(-)W,此时信/噪比达到1:4,电流灵敏度可提高10倍。     

4-羧基-4′-氨基偶氮苯LB膜的光谱及其二次谐波产生特性研究

采用紫外可见吸收谱和二次谐波产生的方法研究了一种新型偶氮化合物分子的LB膜及非线性光学特性。4-羧基-4′-氨基偶氮苯分子在水表面可以形成稳定的单分子膜并且可以较好的转移到固体基板上形成LB多层膜。测量了LB膜二次谐波产生随入射基频光入射角的变化关系,二次谐波信号强度最大值在入射角约为60°的地方,LB膜具有非常大的二次谐波信号强度,其分子超极化率约为β=1.17×10-29esu。     

4-羧基-4'-氨基偶氮苯LB膜的光谱及其二次谐波产生特性研究

采用紫外可见吸收谱和二次谐波产生的方法研究了一种新型偶氮化合物分子的LB膜及非线性光学特性.4-羧基-4'-氨基偶氮苯分子在水表面可以形成稳定的单分子膜并且可以较好的转移到固体基板上形成LB多层膜.测量了LB膜二次谐波产生随入射基频光入射角的变化关系,二次谐波信号强度最大值在入射角约为60°的地方,LB膜具有非常大的二次谐波信号强度,其分子超极化率约为β=1.17×10-29esu.     

Influence of a combination of random noise and pattern-edge width (in pixels) on contrast-to-gradient image resolution in scanning electron microscopy

The contrast-to-gradient (CG) method has been proposed previously for the evaluation of image resolution in scanning electron microscopy (SEM). In the CG algorithm, the image to be evaluated is gradually reduced to form the 1/r-reduced image (r = 1, 2, 3, ...) until the representative features of local patterns are accurately recognizable after the corresponding r-th noise reduction. We have studied the influence of a combination of random noise and pattern-edge width (in pixels) on the CG resolution R using both PC-made test images and typical SEM images. As the random noise is larger, the value of R becomes larger (or poorer). The increase in R due to the noise influence is more significant for the narrower width of the pattern edge. This satisfactorily agrees with the common idea that the image resolution is to reflect the sharpness of the pattern edge recognized in the image noise. By revising the form of DeltaR from the weighted standard fluctuation of R to the differential of R, a significantly weak N(dot)-dependency on R has been favorably confirmed, with keeping firmly the noise-dependency on R. Here, N(dot) is the number of pattern dots in the image.     

A theoretical study of phosphorescent Cu(I) complexes with 2-(2'quinolyl)imidazole and POP mixed ligands

We herein report a theoretical study using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods to investigate Cu(I) complexes with 2-(2′-pyridyl/quinolyl)imidazole and bis[2-(diphenylphosphino)phenyl]ether mixed ligands. Based on the experimental data for complexes 1 and 2, we first benchmarked different functionals with different HF% and found B3PW91 to be the optimal functional for this system. The computational results indicate that complex 1, with a pyridyl unit, has a much larger radiative decay rate (k_r) than complex 2, which has a quinolyl unit. This difference is presumably due to higher HOMO electronic distribution in the d_x²-_y² orbital, which leads to a markedly shortened CuN₂ bond, enhancing the metal-ligand interaction. However, a much smaller experimental value was found for the non-radiative decay rate (k_nr) in complex 2, rendering 1 a slightly weaker emitter than 2. We conclude that the difference is due to more effective suppression of deformation when the quinolyl unit is used instead of pyridyl. We sought to increase the photoluminescence quantum yield (PLQY) through modifying the ligand on complex 2, with the goal being to keep the small k_nr value while simultaneously increasing k_r. The computational results indicate that our designed complexes 2a-2c, which possess modified ligands with electron-donating or withdrawing alkyl substituents on N₃, increased the distributions of d_x²-_y² and decreased that of the d_yz compared to 2. Their coordinating abilities were therefore enhanced, with the k_r values being 1.34, 22.70, and 0.16 times that of 2 for 2a, 2b and 2c, respectively. Higher PLQYs were achieved in 2a and 2b with the addition of electron-donating alkyl substituents on the ligands, which yielded complexes with significantly shortened CuN₂ bonds and enhanced metal-ligand interaction. This investigation on the microscopic mechanism of the photoluminescent properties of these complexes can provide useful knowledge for experimentalists.