Influence of substrate temperature and ion-beam energy on the syntheses of aluminium nitride thin films by nitrogen-ion-assisted pulsed-laser deposition

Aluminium nitride (AlN) thin films have been grown on Si(100), Si(111) and Sapphire Al₂O₃(001) substrates by pulsed KrF excimer laser (wavelength 248 nm, duration 30 ns) ablation of an AlN target with the assistance of nitrogen-ion-beam bombardment. The influence of process parameters such as substrate temperature and ion-beam energy has been investigated in order to obtain high-quality AlN films. The AlN films deposited by pulsed-laser deposition (PLD) have been characterized by X-ray diffraction (XRD) to determine the crystalline quality, grain size and growth orientation with respect to the substrate. The XRD spectra of AlN films on Si(100), Si(111) and Sapphire substrates yield full-width-half-maximum (FWHM) values of approximately 1.6. The bonding characteristics in the films have been evaluated by Raman spectroscopy. The chemical composition of the films has been characterized by X-ray photoelectron spectroscopy (XPS). The surface morphology of the films has been measured by atomic force microscopy (AFM). At a substrate temperature of at least 600 °C, polycrystalline AlN films with orientations of AlN(100) and AlN(101) have been synthesized. PACS 68.55.-a; 81.15.Fg; 77.84.Bw     

顺式羰基铑碘络合物催化甲醇制乙酸反应的动力学研究

本文运用密度泛函理论DFT-B3LYP方法,对铑、碘元素采用相对论校正赝势基组SDD,对C、O、H采用6-311+G(2d,p)基组,计算研究了顺式羰基铑碘络合物催化甲醇羰基化制乙酸反应的微观机理,优化了各反应物、中间体和过渡态的构型特征,用频率分析方法和内禀反应坐标方法对过渡态进行了验证,运用Kozuch撰写的能量跨度模型获得循环反应的动力学信息,确定了决定循环反应速率的决速过渡态和决速中间体,并利用转化频率评估了催化性能与温度的变化关系.     

Fluorine-doped SiO2 glasses for F2 excimer laser optics: fluorine content and color-center formation

Color-center formation in F-doped, OH-free synthetic SiO(2) glasses by irradiation with F(2) excimer lasers (157 nm) was examined as a function of the F content. The concentration of photoinduced E(') centers was reduced to approximately 1/20 by 1 mol.% F(2) doping and remained almost constant on further doping to 7.3 mol. %. The absorption edge was considerably shifted to a lower wavelength (157.4 nm -->153 nm for a 5-mm-thick sample) by 1-mol. % doping and decreased only slightly on further doping. The intensities of the Raman bands that are due to three- and four-membered ring structures were significantly reduced by 1-mol. % F doping. These results strongly suggest that elimination of strained Si-O-Si bonds by F doping plays a central role in the improvement of radiation resistance of SiO(2) glasses to F(2) laser light.     

Cortical responses to the 2f1-f2 combination tone measured indirectly using magnetoencephalography

The simultaneous presentation of two tones with frequencies f(1) and f(2) causes the perception of several combination tones in addition to the original tones. The most prominent of these are at frequencies f(2)-f(1) and 2f(1)-f(2). This study measured human physiological responses to the 2f(1)-f(2) combination tone at 500 Hz caused by tones of 750 and 1000 Hz with intensities of 65 and 55 dB SPL, respectively. Responses were measured from the cochlea using the distortion product otoacoustic emission (DPOAE), and from the auditory cortex using the 40-Hz steady-state magnetoencephalographic (MEG) response. The perceptual response was assessed by having the participant adjust a probe tone to cause maximal beating ("best-beats") with the perceived combination tone. The cortical response to the combination tone was evaluated in two ways: first by presenting a probe tone with a frequency of 460 Hz at the perceptual best-beats level, resulting in a 40-Hz response because of interaction with the combination tone at 500 Hz, and second by simultaneously presenting two f(1) and f(2) pairs that caused combination tones that would themselves beat at 40 Hz. The 2f(1)-f(2) DPOAE in the external auditory canal had a level of 2.6 (s.d. 12.1) dB SPL. The 40-Hz MEG response in the contralateral cortex had a magnitude of 0.39 (s.d. 0.1) nA m. The perceived level of the combination tone was 44.8 (s.d. 11.3) dB SPL. There were no significant correlations between these measurements. These results indicate that physiological responses to the 2f(1)-f(2) combination tone occur in the human auditory system all the way from the cochlea to the primary auditory cortex. The perceived magnitude of the combination tone is not determined by the measured physiological response at either the cochlea or the cortex.     

Application of 57Fe-enriched synthetic ferrihydrite to speciate the product of bacterial reduction

We have sampled a clay lens with evidence of sulfide reduction from a texturally stratified sandy aquifer at Rømø, Denmark. A minor amount of synthetic, pure ⁵⁷Fe ferrihydrite was added to this sample and allowed to react for up to three months. The initial sample, the ⁵⁷Fe ferrihydrite, and samples taken from the reaction mixture were investigated by Mössbauer spectroscopy at temperatures between 15 and 298 K as sampled and following exposure to oxygen. The initial sample only contained Fe(II) (33% of the iron) and Fe(III) in silicates. The Fe(III) in the ferrihydrite is reduced to Fe(II) as evidenced by an increase of this component by bacterial activity. The Fe(II) component remains paramagnetic at temperatures down to 15 K. Similarly to naturally reduced sediments the new-formed Fe(II) is extremely reactive towards molecular oxygen. Following oxidation the reformed Fe(III) is found as ferrihydrite. The bonding of the Fe(II) is by electrostatical bonding (adsorbed) to the layer silicates as evidenced by a temperature scanning of the sample between 80 and 270 K.     

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本研究用氮气等离子体固相表面修饰改性对丙纶纤维进行表面处理。用傅立叶变换红外光谱分析改性前后样品表面官能团变化,用扫描电镜分析改性前后样品表面的形貌变化,用紫外可见分光光度计测试样品的上染率。结果表明:等离子体表面处理及丙烯酸接枝后的丙纶纤维表面引入了羰基、胺(氨)基或酰胺等活性基,使丙纶纤维从不可上染到能染上鲜艳的阳离子艳兰,显著改善了丙纶纤维的染色品质。     

Synthesis of polyaniline nanoparticles and their application for the removal of Crystal Violet dye by ultrasonicated adsorption process based on Response Surface Methodology

The present study focuses the synthesis of polyaniline nanoparticles (PANP) by rapid mixing polymerization method. They were recognized by FTIR and SEM techniques. Moreover they were utilized for the removal of Crystal Violet (CV) dye by ultrasonicated adsorption process. It ensures a quick alternative method compared to other conventional processes, which led to enhancement of mass transfer by ultrasound waves. The effectiveness of the process was confirmed through the effect of certain conditions like sonication time, temperature, adsorbent dosage and CV concentrations. The validity of the process was estimated by various adsorption isotherms. Kinetics and thermodynamic studies was also conducted to authenticate the process. The optimum operating parameters (OOP) were evaluated by Response Surface Methodology (RSM) based on central composite design (CCD) for the removal of CV dye. Moreover analysis of variances (ANOVA) was employed to estimate the significance of experimental variables. The predicated removal efficiency was found to be 94.29% which prove to be effectiveness of the process.     

A vibrational investigation of the stability, morphology and surface reactivity of NiO on Ni(100)

The formation and thermal stability of NiO on Ni(100) have been investigated using high-resolution electron energy loss spectroscopy (EELS) and low-energy electron diffraction (LEED). Our results indicate that the saturated NiO/Ni(100) layer prepared at 300 K is rather poorly ordered and is thermally unstable at higher temperatures. Heating this NiO/Ni(100) layer to 800 K produces a surface with mixtures of crystalline NiO(100) clusters and c(2 × 2)−O chemisorbed local structures. The long range order of the NiO(100) clusters could be improved by repeated cycles of oxygen adsorption at 300 K followed by heating to 800 K. The NiO(100) clusters obtained after 9 cycles of such dosing-annealing exhibit bulk-like properties, as suggested both by the off-specular EELS measurements and by the experimental observation that the intensities of the multiple loss features follow the expected Poisson distribution. The Ni---O bond strength of the NiO(100) clusters, estimated from the overtone spectra, is 3.6 eV. In addition, the reduction of NiO(100) clusters by H₂ at 800 K has also been investigated. The NiO(100) clusters are reduced preferentially with respect to the c(2 × 2)−O overlayer, resulting in a reduction sequence of NiO(100) → c(2 × 2)−O → p(2 × 2)−O → Ni(100).     

Dinitrogen fixation of microbe-plant associations as affected by nitrate and ammonium supply

Abstract The dinitrogen fixation activity of Azospirillum sp., and Pantoea agglomerans strains was determined by (15)N(2) incorporation after incubation with (15)N(2) labeled air or/and by acetylene reduction. These bacterial strains were able to fix N(2) both in pure culture and in association with wheat plants in hydroponics. Nitrogenase activity of Azospirillum sp., in pure culture was more rapidly inhibited by the addition of NH(4) (+) than NO(3) (-). The N(2) fixation of P. agglomerans decreased only by NH(4) (+) -addition, but was stimulated by NO(3) (-). Nitrogen fixation in association with wheat plants remained unaffected by both N compounds. However, nitrogen derived from the atmosphere (N(dfa)) contributed only very little to the overall nitrogen nutrition of the plants.     

光谱分析法研究八羧酸酞菁铝配合物与牛血清白蛋白的结合作用

以八羧酸酞菁铝配合物(AlPc(COOH)8)为红区荧光探针,用紫外光谱和荧光光谱分析方法研究了(AlPc(COOH)8)与牛血清白蛋白(BSA)的结合作用,测定了八羧酸酞菁铝与牛血清白蛋白(BSA)的结合位置数和结合常数,结果分别为n=5.7,K=5.74×105和K=3.51×105,两种分析方法结果基本一致.以氯血红素(HE)、布洛芬(IB)、L-色氨酸(TRP)为分子探针,用络合竞争法研究了它们对AlPc(COOH)8-BSA体系紫外光谱的影响,结果表明,往体系中加入HE后,AlPc(COOH)8的单体吸收峰增强,体系由结合态往游离态"转变",而加入TRP和IB后,吸收光谱未观察到明显的变化,由此确定AlPc(COOH)8与BSA的结合点为SiteⅠ.     

采用复合母体的高效高显色指数白光有机发光二极管

采用复合母体技术制备了一种高效率高显色指数白光有机发光二极管。驱动电压在8 V到12 V变化时,器件的CIE-1931色坐标由(0.343 2, 0.339 7)变化到(0.324 3, 0.321 8),相关色温由5 035 K变化到5 915 K,其显色指数均保持在90以上。器件在14 V时达到最大亮度,为27 853 cd/m²,在7.5 V时达到最大效率为9.58 cd/A。实验中通过调节绿色和红色发光层的厚度来调节器件的发光光谱,通过敏化绿色和红色发光成分以实现电致发光效率的提高,器件的最大效率比没有采用敏化机制的参比器件提高了73.6%。     

The effect of surface modification on heavy metal ion removal from water by carbon nanoporous adsorbent

In this work, chemically oxidized mesoporous carbon (COMC) with excellent lead adsorption performance was prepared by an acid surface modification method from mesoporous carbon (MC) by wet impregnation method. The structural order and textural properties of the mesoporous materials were studied by XRD, SEM, and nitrogen adsorption. The presence of carboxylic functional groups on the carbon surface was confirmed by FT-IR analysis. Batch adsorption experiments were conducted to study the effect of adsorbent dose, initial concentration and temperature for the removal of Pb(II) from aqueous systems. The adsorption was maximum for the initial pH in the range of 6.5-8.0. The kinetic data were best fitted to the pseudo-second order model. The adsorption of chemically oxidized mesoporous carbon to Pb(II) fits to the Langmuir model. The larger adsorption capacity of chemically oxidized mesoporous carbon for Pb(II) is mainly due to the oxygenous functional groups formed on the surface of COMC which can react with Pb(II) to form salt or complex deposited on the surface of MC.     

Galactic-cosmic-ray-produced 3He in a ferromanganese crust: any supernova 60Fe excess on earth?

An excess of 60Fe in 2.4-3.2 x 10(6) year old ferromanganese crust (237 KD) from the deep Pacific Ocean has been considered as evidence for the delivery of debris from a nearby supernova explosion to Earth. Extremely high ;{3}He/;{4}He (up to 6.12 x 10(-3)) and 3He concentrations (up to 8 x 10(9) atoms/g) measured in 237 KD cannot be supernova-derived. The helium is produced by galactic cosmic rays (GCR) and delivered in micrometeorites that have survived atmospheric entry to be trapped by the crust. 60Fe is produced by GCR reactions on Ni in extraterrestrial material. The maximum (3)He/(60)Fe of 237 KD (80-850) is comparable to the GCR (3)He/(60)Fe production ratio (400-500) predicted for Ni-bearing minerals in iron meteorites. The excess 60Fe can be plausibly explained by the presence of micrometeorites trapped by the crust, rather than injection from a supernova source.     

土壤和水系沉积物中硒的价态分析方法研究

研究土壤和水系沉积物中硒的价态有助于了解硒（Se）的迁移和转化。目前报道大多只是测定土壤和水系沉积物中部分Se的价态,而如何测定土壤和水系沉积物中全部Se的价态一直是一个难题,难点在于如何将土壤和水系沉积物中的Se消解完全而不改变Se的价态。试验发现6.0 mol·L-1 HCl可以将Se(Ⅵ)还原成Se(Ⅳ);而在室温条件下1.2 mol·L-1 HCl介质中Se(Ⅳ)和Se(Ⅵ)放置48 h,价态保持不变。Se(Ⅳ)和Se(Ⅵ)采用HNO₃+HF+HClO₄进行消解,加热到HClO₄冒白烟时,Se(Ⅳ)和Se(Ⅵ)的价态保持不变;而土壤和水系沉积物中Se采用HNO₃+HF+HClO₄进行消解,加热到HClO₄蒸干以后,Se(Ⅳ)会被氧化成Se(Ⅵ)。基于以上的研究结果,建立了氢化物发生-原子荧光光谱法（HG-AFS）测定土壤和水系沉积物中Se(Ⅳ)和Se(Ⅵ)的方法,样品采用HNO₃+HF+HClO₄消解,加热至HClO₄冒白烟后停止加热（避免局部蒸干）,消解后的样品冷却至室温用1.2 mol·L-1 HCl溶解,采用 HG-AFS测定得到样品中Se(Ⅳ)。消解后的样品采用6.0 mol·L-1 HCl 加热溶解,将Se(Ⅵ)全部还原为Se(Ⅳ),采用HG-AFS测定得到样品中总Se,利用差减法得Se(Ⅵ)。测定结果表明土壤和水系沉积物中Se消解完全,Se(Ⅳ)和Se(Ⅵ)在分析过程中价态保持不变,Se(Ⅳ)和总Se的检出限分别为4.5和5.1 ng·g-1,Se(Ⅳ)和Se(Ⅵ)加标回收率分别为102%～108%和94%～104%。     

A formula used to subtract the effect of gamma-ray of the others to that of measured reaction in measurement of cross section of nuclear reaction and its application

Abstract According to the regulation of growing and decay of artificial radioactive nuclide, a formula used to subtract the effect of characteristic γ-ray of the others to that of measured reaction was deduced. And then the cross sections of 120Te (n, 2n)119mTe reaction induced by neutrons around 14 MeV were measured by activation relative to the 93Nb (n, 2n)92mNb. In the process of the cross sections measured to be calculated, it was subtracted that the effect of characteristic γ-ray of 126Te (n, p)126Sb to that of measured 120Te (n, 2n)119mTe reaction using the formula deduced. The experimental results were (689±37) and (750±41) mb at the neutron energies of (13.5±0.3) and (14.6±0.3) MeV, respectively. Measurements were carried out by γ-detection using a coaxial HPGe detector. As samples, spectroscopically pure tellurium powder has been used. The fast neutrons were produced by the T(d, n)4He reaction. The neutron energies in these measurements were determined by the method of cross-section ratios between 90Zr (n, 2n) 89m+gZr and 93Nb (n, 2n) 92mNb reactions.     

流动注射氢化物发生-原子荧光光谱法测定土壤中有效态As(Ⅲ)和As(Ⅴ)

提出了一种流动注射氢化物发生 原子荧光光谱法测定土壤中有效态As(Ⅲ )和As(Ⅴ )的方法。在0 1mol·L-1柠檬酸介质 (pH =3 1)中选择性测定As(Ⅲ ) ,然后用L 半胱氨酸流动注射在线还原As(Ⅴ )后测定总砷 ,由二者之差求得As(Ⅴ )。设计了在线还原及氢化物发生流路和操作程序 ,选择了各项化学条件和流路参数。As(Ⅲ )和As(Ⅴ )的检出限 (3σ)分别为 0 11和 0 0 7ng·mL-1。对于 10ng·mL-1As(Ⅲ )溶液 ,连续7次测定得精密度 (RSD)为 1 43% ,应用于实际土壤样品的测定 ,加标回收率在 82 %～ 10 4%之间     

Thin-layer chromatography of copolyesters from blends of poly(ethylene terephthalate)/polycarbonate

Copolymers made by ester exchange reaction have been obtained from poly(ethylene terephthalate) (PET)/poly(bis-phenol-A carbonate) (PC) blends during melt mixing. The copolyesters were isolated by thin-layer chromatography (TLC) and identified by infrared spectroscopy. It was found that the quantity of copolymer formed was increased by the temperature and duration of melt mixing. The PET/PC blend was found to react at 270°C within 10 min, as detected by TLC. After 60 min, the pure PC had disappeared. The miscibility of PET/PC blends was found to be markedly aided by the addition of as little as 2% of the copolymer isolated by TLC.     

CO2同位素分子16O12C16O, 16O12C17O, 16O13C17O配分函数研究

本文主要研究了CO2的三种同位素分子16O12C16O , 16O12C17O ,16O13C17O 70 K~6000 K的总内配分函数 (TIPS)。在总内配分函数的计算中, 转动配分函数的计算采用了McDowell的解析式法, 振动配分函数则采用了简谐振动近似(HOA)获得。最后通过将两配分函数乘积近似计算得出TIPS, 并将其70~3000 K的数据和HITRAN04数据进行了比较, 发现所得结果和数据库符合的较好, 且其误差可以近似看成一条直线。并通过对误差的拟合修订了高温区(3000~6000 K)的计算数据, 给出了在高温下的较为准确的TIPS值。     

二氧六环参与配位的稀土配合物的制备和荧光性能研究

利用二氧六环(dioxane)小分子作为第二配体,吡哌酸(PPA)作为第一配体合成了稀土荧光配合物Eu(PPA)3dioxane和Tb(PPA)sdioxane.这种小分子直接参与配位形成稀土配合物的现象很少见到.所合成的配合物通过与单独使用吡哌酸作为配体的配合物Eu(PPA)3和Tb(PPA)3对比,发现二氧六环对稀土配合物的荧光具有明显的增强效果,尤其是对Tb3+所形成的稀土配合物,荧光增强非常显著.二氧六环的参与配位,代替了原来的水分子,这样就会在一定程度上减少了热振动所造成的能壁损失,从而增强荧光.所制备的稀土配合物通过红外光谱、荧光光谱、荧光寿命等方法进行了表征.对于由Eu和Tb所形成的配合物,加入第二配体二氧六环对其荧光寿命的影响差别很大,这说明对于Eu和Tb所形成的配合物存在着不同的能鸶传递过程.这种荧光增强现象为检测小分子二氧六环的存在及其含量提供了一种新的方法.     

Experimental and Ab Initio Studies of the HDO Absorption Spectrum in the 13 165-13 500 cm(-1) Spectral Region

The HDO absorption spectrum was recorded in the 13 165-13 500 cm(-1) spectral region by intracavity laser absorption spectroscopy. The spectrum (615 lines), dominated by the 2nu(2) + 3nu(3) and nu(1) + 3nu(3) bands, was assigned and modeled leading to the derivation of 196 accurate energy levels of the (103) and (023) vibrational states. Finally, 150 of these levels were reproduced by an effective Hamiltonian involving two vibrational dark states interacting with the (023) and (103) bright states. The rms deviation achieved by variation of 28 parameters is 0.05 cm(-1), compared to an averaged experimental uncertainty of 0.007 cm(-1), indicating the limit of validity of the effective Hamiltonian approach for HDO at high-vibrational excitation. The predictions of previous ab initio calculations of the HDO spectrum (H. Partridge and D. Schwenke, J. Chem. Phys. 106, 4618-4639 (1997)) were extensively used in the assignment process. The particular spectral region under consideration was used to test and discuss the improvements of new ab initio calculations recently performed on the basis of the same potential energy surface but with an improved dipole-moment surface. The improvements concern both the energy levels and the line intensities. In particular, the strong hybrid character of the nu(1) + 3nu(3) band is very well accounted for by the new ab initio calculations. Copyright 2000 Academic Press.