Demonstration of GaN/InGaN light emitting diodes on (100) beta-Ga2O3 substrates by metalorganic chemical vapour deposition

The growth and fabrication of GaN/InGaN multiple quantum well (MQW) light emitting diodes ( LEDs) on ( 100) beta-Ga2O3 single crystal substrates by metal-organic chemical vapour deposition (MOCVD) technique are reported. x-ray diffraction (XRD) theta-2 theta. scan spectroscopy is carried out on the GaN buffer layer grown on a ( 100) beta-Ga2O3 substrate. The spectrum presents several sharp peaks corresponding to the ( 100) beta-Ga2O3 and ( 004) GaN. High-quality ( 0002) GaN material is obtained. The emission characteristics of the GaN/InGaN MQW LED are measurement. The first green LED on beta-Ga2O3 with vertical current injection is demonstrated.

Additional angles to calculate the deformation of RNA helices induced by bulge loops

Bulges are common features of folded RNA structures. The RNA axial kinking caused by bulges has been confirmed by many experiments. Usually, a kinking angle zeta and a bending angle theta are used to describe the kinking and twisting of RNA molecules containing bulges. Here, we present two additional angles (twist angle zeta(1), twist angle zeta(2)) to describe the deformation of RNA helices induced by bulge loops because only two angles (a kinking angle zeta and a bending angle theta) are not enough to define the deformation of RNA induced by bulges. (C) 2002 Elsevier Science B.V. All rights reserved.

Microcystin-induced variations in transcription of GSTs in an omnivorous freshwater fish, goldfish

The glutathione S-transferases are important enzymes in the microcystin-induced detoxication processes. In this experiment, we cloned the full-length cDNA of alpha, pi and theta-class-like glutathione S-transferase genes from goldfish (Carassius auratus Q. Their derived amino acid sequences were clustered with other vertebrate alpha, pi and theta-class GSTs in a phylogenetic tree and the goldfish GST sequences have the highest similarity with those from common carp and zebrafish. Goldfish were i.p. injected with microcystins extract at two doses (50 and 200 mu g kg(-1) BW MC-LReq) and the relative changes of the mRNA abundance in liver, kidney and intestine were analyzed by real-time PCR. The transcription of GST alpha was suppressed in both liver and intestine, but induced in the kidney. Decreased transcription of GST theta was detected in liver, kidney and intestine in the low-dose group. The transcription of GST pi was suppressed in liver and intestine post-injection in both dose groups. These results suggested that the transcription of GST isoforms varied in different ways within an organ and among organs of goldfish exposed to MCs. (C) 2008 Elsevier B.V. All rights reserved.

The acute effects of microcystin LR on the transcription of nine glutathione S-transferase genes in common carp Cyprinus carpio L.

The glutathione S-transferases play important roles in the detoxification of microcystin. In this experiment, nine glutathione S-transferase genes including cytosolic GSTs (rho, mu, theta, alpha and pi), mitochondrial GST (kappa) and microsomal GSTs (mGST1, mGST2 and mGST3) were cloned from common carp Cyprinus carpio. The mRNA abundance of each carp GST isoform in liver was analyzed by real time PCR. The relative changes after stimulation with microcystin LR were also analyzed: increased levels of transcription of GST alpha, rho and mGST3 isoforms were detected at 6 h post stimulation; the transcription of mu, theta and mGST2 isoforms were relatively stable; and all the GST isoforms except GST kappa and rho recovered to original levels compared with controls at 72 h. It is suggested that MC-LR showed different effects on the transcription of nine carp GST isoforms. (c) 2006 Elsevier B.V. All rights reserved.

Rashba electron transport in one-dimensional quantum waveguides

The properties of Rashba wave function in the planar one-dimensional waveguide are studied, and the following results are obtained. Due to the Rashba effect, the plane waves of electron with the energy E divide into two kinds of waves with the wave vectors k(1)=k(0)+k(delta) and k(2)=k(0)-k(delta), where k(delta) is proportional to the Rashba coefficient, and their spin orientations are +pi/2 (spin up) and -pi/2 (spin down) with respect to the circuit, respectively. If there is gate or ferromagnetic contact in the circuit, the Rashba wave function becomes standing wave form exp(+/- ik(delta)l)sin[k(0)(l-L)], where L is the position coordinate of the gate or contact. Unlike the electron without considering the spin, the phase of the Rashba plane or standing wave function depends on the direction angle theta of the circuit. The travel velocity of the Rashba waves with the wave vector k(1) or k(2) are the same hk(0)/m*. The boundary conditions of the Rashba wave functions at the intersection of circuits are given from the continuity of wave functions and the conservation of current density. Using the boundary conditions of Rashba wave functions we study the transmission and reflection probabilities of Rashba electron moving in several structures, and find the interference effects of the two Rashba waves with different wave vectors caused by ferromagnetic contact or the gate. Lastly we derive the general theory of multiple branches structure. The theory can be used to design various spin polarized devices.

A simple route of morphology control and structural and optical properties of ZnO grown by metal-organic chemical vapour deposition

Employing the metal-organic chemical vapour deposition (MOCVD) technique, we prepare ZnO samples with different morphologies from the film to nanorods through conveniently changing the bubbled diethylzinc flux (BDF) and the carrier gas flux of oxygen (OCGF). The scanning electron microscope images indicate that small BDF and OCGF induce two-dimensional growth while the large ones avail quasi-one-dimensional growth. X-ray diffraction (XRD) and Raman scattering analyses show that all of the morphology-dependent ZnO samples are of high crystal quality with a c-axis orientation. From the precise shifts of the 2 theta. locations of ZnO (002) face in the XRD patterns and the E-2(high) locations in the Raman spectra, we deduce that the compressive stress forms in the ZnO samples and is strengthened with the increasing BDF and OCGF. Photoluminescence spectroscopy results show all the samples have a sharp ultraviolet luminescent band without any defects-related emission. Upon the experiments a possible growth mechanism is proposed.

Stress analysis of ZnO film with a GaN buffer layer on sapphire substrate

A 5.35-mu m-thick ZnO film is grown by chemical vapour deposition technique on a sapphire (0001) substrate with a GaN buffer layer. The surface of the ZnO film is smooth and shows many hexagonal features. The full width at half maximum of ZnO (0002) omega-rocking curve is 161 arcsec, corresponding to a high crystal quality of the ZnO film. From the result of x-ray diffraction theta - 2. scanning, the stress status in ZnO film is tensile, which is supported by Raman scattering measurement. The reason of the tensile stress in the ZnO film is analysed in detail. The lattice mismatch and thermal mismatch are excluded and the reason is attributed to the coalescence of grains or islands during the growth of the ZnO film.

Photoemission study of chemisorption and Fermi-level pinning at K/GaAs(100) interface with synchrotron radiation

The adsorption of K on the n-GaAs(I 0 0) surface was investigated by X-ray photoelectron spectroscopy (XPS) and synchrotron radiation photoemission spectroscopy (SR-PES). The Ga3d and As3d core level was measured for clean and K adsorbed GaAs(I 0 0) surface. The adsorption of K induced chemical reaction between K and As, and the K-As reactant formed when the K coverage theta > I ML. The chemical reaction between K and Ga did not occur, but Ga atoms were exchanged by K atoms. From the data of band bending, the Schottky barrier is 0.70 eV. The Fermi-level pinning was not caused by defect levels. The probable reason is that the dangling bonds of surface Ga atoms were filled by the outer-shell electrons of K atoms, forming a half-filled surface state. The Fermi-level pinning was caused by this half-filled surface state. (c) 2004 Elsevier B.V. All rights reserved.

Effect of the growth mode on the two- to three-dimensional transition of InAs grown on vicinal GaAs(001) substrates

Some differences were observed between conventional molecular-beam epitaxy (MBE) and mobility enhanced epitaxy (MEE) of InAs on a vicinal GaAs(001) substrate in the variation of the number density N of the InAs islands, with additional InAs coverage (theta - theta(c)) after the critical InAs coverage theta(c) during the two- to three-dimensional (2D-3D) transition. For MBE the variation was consistent with the power law N(theta) (theta similar to theta(c))(alpha); while for MEE, the linear relation N(theta) proportional to (theta - theta(c)) was observed. The difference is discussed in terms of the randomness in the nucleation of the InAs islands.

High-precision determination of lattice constants and structural characterization of InN thin films

X-ray diffraction and Rutherford backscattering/channeling were used to characterize the crystalline quality of an InN layer grown on Al2O3(0001) Using metal-organic chemical-vapor deposition. A full width at half maximum of 0.27 degrees from an InN(0002) omega scan and a minimum yield of 23% from channeling measurements show that this 480-nm-thick InN layer grown at low temperature (450 degrees C) has a relatively good crystalline quality. High-resolution x-ray diffraction indicates that the InN layer contains a small fraction of cubic InN, besides the predominant hexagonal phase. From this InN sample, the lattice constants a=0.353 76 nm and c=0.570 64 nm for the hexagonal InN and a=0.4986 nm for the cubic InN were determined independently. 2 theta/omega-chi mapping and a pole figure measurement revealed that the crystallographic relationship among the cubic InN, the hexagonal InN, and the substrate is: InN[111]parallel to InN[0001]parallel to Al2O3[0001] and InN{110}parallel to InN{1120}parallel to Al2O3{1010}, and that the cubic InN is twinned. Photoluminescence measurements indicate that the band-gap energy of this sample is approximately 0.82 eV. (c) 2006 American Vacuum Society.

回转窑热解处理废锌锰电池试验研究

我国电池生产量已经达到209亿节（2003年），多年来一直占据世界第一大电池生产国的地位，其中锌锰电池占大多数。废锌锰电池丢弃后，其中的重金属物质会逐渐渗透到地下，污染土壤和水体。重金属在生物体内富集，会使生物体致畸或致变。但同时，废锌锰电池中也含有大量有用的资源如锌、二氧化锰等。应对其进行回收利用，变废为宝。本文介绍了废锌锰电池回收处理的主要技术及研究进展，不同的处理技术回收废锌锰电池时的目标产物各不相同，但一般可分为以下几种：以单质形式回收锌、锰和汞；以合金的形式回收锌和锰；回收锌和二氧化锰；回收各金属元素制备复合微量元素肥料；回收锌、锰元素制备锰锌铁氧体；回收锌、锰元素制备硫酸锌和碳酸锰等。本文对一些废锌锰电池回收处理技术的优缺点从无害化程度、资源化程度、产品等级、工艺要求以及二次污染五个方面进行了分析和比较。在对国内外废锌锰电池回收处理技术进行分析比较的基础上提出了一种成本较低、可操作性较强的处理技术：先以干法除去废锌锰电池中的汞，然后以湿法除去其它的有害重金属并进一步加工制备有机螯合微量元素肥料。 本文以回转窑中物料停留时间的经验公式和传热学的知识设计和计算了回转窑的长度和内径尺寸、电热丝的功率以及外围的保温材料厚度等参数。用保温材料和润滑油相结合的方式对回转窑的连接部分实行密封。通过调整回转窑的转速和回转窑支架两端高度差的方式控制物料在回转窑中的停留时间，从而调节热解时间的长短。利用自动控制设备调节电热丝的功率从而调节试验中的热解温度。利用该回转窑在不同条件下对热解处理废锌锰电池进行了试验研究，热解过程中产生的尾气和颗粒物用一系列吸收液进行吸收和固定。 在热解试验中改变影响热解过程的三种因素：热解温度、热解时间和载气流速并按三因素四水平的正交方法安排试验。改变废锌锰电池热解过程中的热解温度、热解时间和载气流速三种因素进行正交试验并利用正交统计学的方法分析了这三种因素对热解除汞率的影响。利用ICP检测仪测定了各吸收液中汞的含量，并分析热解气体产物经过系列吸收液时汞被吸收的情况以及汞的形态分布。利用气相色谱仪对尾气成分进行了测定，并对热解过程中产气的过程和规律进行了分析。用X射线衍射测试的方法研究了热解前后锌锰电池的物质形态变化情况。对除汞率的正交统计分析表明，合适的热解条件为：热解温度690℃，热解时间100min，载气流速0.06m3/h，在这种试验条件下热解处理废锌锰电池的除汞率达到100%。同时还得到：热解时间对除汞效果影响最大，热解温度次之，载气流速的影响较小。ICP测试的结果表明：热解尾气在经过试验中设置的吸收瓶后，其中的汞被完全吸收，尾气中95%以上的汞以单质的形式存在。气相色谱分析的结果表明，热解开始后，废锌锰电池中的有机质迅速分解，其产物为C2H4、CH4和H2等。一段时间后，有机质的分解量大幅度减少，同时废电池中的石墨碳和高价金属氧化物发生氧化还原反应，生成CO气体。对废锌锰电池原料以及热解残渣的X射线衍射分析表明，当热解温度为350℃时，X射线衍射图谱上2θ值为35°附近的区域有新峰出现，但不明显，说明有结晶体形成但量不大。500℃时上述峰明显增强，这是由于ZnO和FeO形成了结晶体，同时在2θ值为41°附近有新峰出现，这是高价锰氧化物与石墨碳发生氧化还原反应生成了MnO并形成了结晶体。650℃时，2θ值在41°附近的峰显著增强，且热解过程中形成的峰稳定下来，基本上不再有新的结晶体生成。热解后，高价锰氧化物的相对含量从32.2%下降到4.6%，而MnO的相对含量则从6.4%上升到38.6%。热解后的残渣中晶体物质含量大，金属元素大多以低价态存在，适合于制备有机螯合微量元素肥料。

Chaotic behavior of pulsating heat pipes

Chaotic behavior of closed loop pulsating heat pipes (PHPs) was studied. The PHPs were fabricated by capillary tubes with outer and inner diameters of 2.0 and 1.20 mm. FC-72 and deionized water were used as the working fluids. Experiments cover the following data ranges: number of turns of 4, 6, and 9, inclination angles from 5 degrees (near horizontal) to 90, (vertical), charge ratios from 50% to 80%, heating powers from 7.5 to 60.0 W. The nonlinear analysis is based on the recorded time series of temperatures on the evaporation, adiabatic, and condensation sections. The present study confirms that PHPs are deterministic chaotic systems. Autocorrelation functions (ACF) are decreased versus time, indicating prediction ability of the system is finite. Three typical attractor patterns are identified. Hurst exponents are very high, i.e., from 0.85 to 0.95, indicating very strong persistent properties of PHPs. Curves of correlation integral versus radius of hypersphere indicate two linear sections for water PHPs, corresponding to both high frequency, low amplitude, and low frequency, large amplitude oscillations. At small inclination angles near horizontal, correlation dimensions are not uniform at different turns of PHPs. The non-uniformity of correlation dimensions is significantly improved with increases in inclination angles. Effect of inclination angles on the chaotic parameters is complex for FC-72 PHPs, but it is certain that correlation dimensions and Kolmogorov entropies are increased with increases in inclination angles. The optimal charge ratios are about 60-70%, at which correlation dimensions and Kolmogorov entropies are high. The higher the heating power, the larger the correlation dimensions and Kolmogorov entropies are. For most runs, large correlation dimensions and Kolmogorov entropies correspond to small thermal resistances, i.e., better thermal performance, except for FC-72 PHPs at small inclination angles of theta < 15 degrees.

Photochromic fulgide for holographic recording

(N-4'-methoxy-2-methyl-5-phenyl)-3-pyrryl-ethylidene (isopropylidene) succinic anhydride fulgide, doped in PMMA matrix, exhibits photochromic behavior. The fatigue resistance experiment shows no photodegradation is detected after more than 450 writing-erasing cycles. Study of fulgide material for holographic recording media shows the optimal exposure and the diffraction efficiency is 1047 mJ/cm(2) and 2.26%, respectively, with 10 mum thickness polymer film. Holographic grating with 1680 lines/mm at writing angle theta = 30degrees is also obtained. (C) 2004 Elsevier B.V. All rights reserved.

海马环路中的组合突触可塑性与大鼠情绪研究

海马在某些类型的学习和记忆中起着关键的作用，而突触可塑性（synaptic plasticity）为学习和记忆的模型提供了理论基础。在海马环路中，分布着各种类型的可塑性，包括突触特异的Hebbian形式的可塑性，如长时程增强（long-term potentiation，LTP）和长时程抑制（long-term depression，LTD）；稳态可塑性（homeostatic plasticity），如突触缩放（synaptic scaling）。稳态可塑性是一种整体的调控过程，它可以调节神经元甚至神经网络的平衡；而Hebbian可塑性则是突触特异的，即每个突触进行单独调控的过程。 越来越多的研究提示稳态可塑性和Hebbian可塑性之间存在着空间间隙（spatial gap），那么，如何使得神经元可以通过Hebbian可塑性的过程来维持细胞整体的兴奋性就变得尤为重要。一些报道揭示了LTP和LTD可以在同一突触通路中同时被激活，因此，我们提出组合突触可塑性的概念，即LTP和LTD的组合，它在赋予系统灵活性的同时又可以降低噪音维持系统的稳定性。基于此，本文将围绕这个问题而开展实验工作。 通过对海马CA1区锥体神经元的微小兴奋性突触后电流（miniature excitatory synaptic current, mEPSC）进行测定分析，我们发现mEPSC的幅度分布符合双峰正态分布（double-peak normal distribution）。Theta节律刺激（theta burst stimuli, TBS）诱导后，mEPSC的幅度分布发生改变，呈现右移趋势。随后，采用干扰肽Pep-A2特异地阻断LTP而不影响LTD，我们发现Pep-A2不影响基础状态下mEPSC的幅度分布。在干扰肽Pep-A2存在下，TBS诱导对基础状态下mEPSC的幅度分布也没有影响。结果为揭示LTP和LTD的组合可塑性提供了初步的证据，对进一步理解记忆的编码过程提供了一定的基础。社交隔离可以引起实验大鼠产生焦虑样和抑郁样的行为，而性经历可以改变动物的情绪状态，降低焦虑样和抑郁样的反应。然而，性经历后进行社交隔离对大鼠情绪的影响并没有报道。在这部分工作中，雄性大鼠经历一周的社交活动（male-male paired housing）或者性活动（male-female paired housing），随后进行一段时间的隔离（1天，2天或者7天）。我们发现，经历过性活动的大鼠，无论隔离与否都表现出相似的情绪反应，包括焦虑样和抑郁样行为以及超声波（ultrasonic vocalizations，USVs）发放；而未经历过性活动的大鼠，其情绪反应随着隔离时间的不同而不同。这一现象提示我们，先前的性经历可以对抗实验动物对环境应激事件，如社交隔离的反应。

INVESTIGATION OF GAAS/SI MATERIAL BY X-RAY DOUBLE-CRYSTAL DIFFRACTION

GaAs epilayer films on Si substrates grown by molecular-beam epitaxy were investigated by the x-ray double-crystal diffraction method. The rocking curves were recorded for different diffraction vectors of samples. The results show that the unit-cell volumes of GaAs epilayers are smaller than that of the GaAs bulk material. The strained-layer superlattice buffer layer can improve the quality of the film, especially in the surface lamella. The parameter W' = W(expt)/(square-root \gamma-h\/gamma-0/sin 2-theta-B) is introduced to describe the quality of different depths of epilayers. As the x-ray incident angle is increased, W' also increases, that is, the quality of the film deteriorates with increasing penetration distance of the x-ray beam. Therefore, W' can be considered as a parameter that describes the degree of perfection of the epilayer along the depth below the surface. The cross-section transmission electron microscopy observations agree with the results of x-ray double-crystal diffraction.