973 resultados para B ... n C ... f.
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Three enclosures (10 x 10 x 1.5-1.3 m in depth) were set beside Dianch Lake, Kunming, People's Republic of China, for the period from July 28 to August 26, 2002. The enclosures were filled with cyanobacterial (Microcystis aeruginosa) water bloom-containing lake water. Lake sediment that contained macrophytes and water chestnut seeds was spread over the entire bottom of each enclosure. Initially, 10 g/m(2) of lysine was sprayed in Enclosure B, and 10 g/m(2) each of lysine and malonic acid were sprayed together in Enclosure C. Enclosure A remained untreated and was used as a control. The concentrations of lysine, malonic acid, chlorophyll a, and microcystin as well as the cell numbers of phytoplankton such as cyanobacteria, diatom, and euglena were monitored. On day 1 of the treatment, formation of cyanobacterial blooms almost ceased in Enclosures B and C, although Microcystis cells in the control still formed blooms. On day 7 Microcystis cells in Enclosure B that had been treated with lysine started growing again, whereas growth was not observed in Microcystis cells in Enclosure C, which had been treated with lysine and malonic acid. On day 28 the surface of Enclosure B was covered with water chestnut (Trapa spp.) and the Microcystis blooms again increased. In contrast, growth of macrophytes (Myriophllum spicatum and Potamogeton crispus) was observed in Enclosure C; however, no cyanobacterial blooms were observed. Lysine and malonic acid had completely decomposed. The microcystin concentration on day 28 decreased to 25% of the initial value, and the pH shifted from the initial value of 9.2 to 7.8. We concluded that combined treatment with lysine and malonic acid selectively controlled toxic Microcystis water blooms and induced the growth of macrophytes. (c) 2005 Wiley Periodicals, Inc.
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Hybrid bulk heterojunction solar cells based on blend of poly(3-hexylthiophene) (P3HT) and TiO2 nanotubes or dye(N719) modified TiO2 nanotubes were processed from solution and characterized to research the nature of organic/inorganic hybrid materials. Compared with the pristine polymer P3HT and TiO2 nanoparticles/P3HT solar cells, the TiO2 nanotubes/P3HT hybrid solar cells show obvious performance improvement, due to the formation of the bulk heterojunction and charge transport improvement. A further improvement in the device performance can be achieved by modifying TiO2 nanotube surface with a standard dye N719 which can play a role in the improvement of both the light absorption and charge dissociation. Compared with the non-modified TiO2 nanotubes solar cells, the modified ones have better power conversion efficiency under 100 mW/cm(2) illumination with 500W Xenon lamp. (C) 2008 Elsevier B. V. All rights reserved.
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A detailed analysis of the photoluminescence (PL) from Si nanocrystals (NCs) embedded in a silicon-rich SiO2 matrix is reported. The PL spectra consist of three Gaussian bands (peaks A,B, and C), originated from the quantum confinement effect of Si NCs, the interface state effect between a Si NC and a SiO2 matrix, and the localized state transitions of amorphous Si clusters, respectively. The size and the surface chemistry of Si NCs are two major factors affecting the transition of the dominant PL origin from the quantum confinement effect to the interface state recombination. The larger the size of Si NCs and the higher the interface state density (in particular, Si = O bonds), the more beneficial for the interface state recombination process to surpass the quantum confinement process, in good agreement with Qin's prediction in Qin and Li [Phys. Rev. B 68, 85309 (2003)]. The realistic model of Si NCs embedded in a SiO2 matrix provides a firm theoretical support to explain the transition trend.
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Three different inorganic-organic hetero-junctions (A : ITO/SiO2/Alq(3)/Al, B: ITO/Alq3/SiO2/Al and C: ITO/SiO2/Alq(3)/ SiO2/Al) were fabricated. The emission can be observed only under positive bias in devices A and B, but under both biases in device C according to their brightness waveforms. With increasing voltage, the increase in blue emission in devices B and C is faster than that in green emission. This is because that the recombination of hot electrons and holes, i.e., electron-hole pairs, produced blue emission in devices B and C, and the recombination of electrons injected from Al with the accumulated holes, which are excited by hot electrons, produced green emission in device A. Hence, the emissions of the devices are attributed to not only the recombination of electrons and accumulated holes, but also the cathodoluminescence-like (CL-like) emission.
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We investigate the quantum dynamics of the quantum-dot cellular automata qubit in the presence of a quantum point contact detector by modified rate equations. It is demonstrated that the qubit information can be resolved by measuring the detector current variation. Furthermore, we show that this oscillating current and the electron occupation probabilities in states \b> and \c> decay drastically as the dephasing rate increases, clearly revealing the influence of the dephasing induced by the detector. Moreover, it is shown that the operation speed of the quantum-dot cellular automata qubit may be adjusted by varying the interdot coupling strength. (C) 2003 American Institute of Physics.
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A systematic investigation of crystallographic and intrinsic magnetic properties of the hydrides R3Fe29 - xVxHy (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy) has been performed in this work. The lattice constants a, b, and c and the unit cell volume of R3Fe29 - xVxHy decrease with increasing rare-earth atomic number from Nd to Dy, except for Ce, reflecting the lanthanide contraction. Hydrogenation results in regular anisotropic expansions along the a-, b-, and c-axes in this series of hydrides. Abnormal crystallographic and magnetic properties of Ce3Fe27.5V1.5H6.5, like Ce3Fe27.5V1.5, suggest that the Ce ion is non-triply ionized. Hydrogenation leads to the increase in both Curie temperature for all the compounds and in the saturation magnetization at 4.2 K and RT for R3Fe29 - xVx with R = Y, Ce, Nd, Sm, Gd, and Dy, except for Tb. Hydrogenation also leads to a decrease in the anisotropy field at 4.2 K and RT for R3Fe29 - xVx with R = Y, Ce, Nd, Gd, Tb, and Dy, except for Sm. The Ce3Fe27.5V1.5 and Gd3Fe28.4V0.6 show the larger storage of hydrogen with y = 6.5 and 6.9 in these hydrides. (C) 1998 Elsevier Science B.V. All rights reserved.
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Fourier transform photoluminescence measurements were carried out to investigate the optical transitions in InxGa1-xAs/InyAl1-yAs one-side-modulation-doped asymmetric step quantum wells. Samples with electron density n(s) between 0.8 and 5.3 x 10(12) cm(-2) rue studied. Strong recombination involving one to three populated electron subbands with the first heavy-hole subband is observed. Fermi edge singularity (FES) clearly can be observed for some samples. The electron subband energies in the InGaAs/InAlAs step quantum wells were calculated by a self-consistent method, taking into account strain and nonparabolicity effects and the comparison with the experimental data shows a good agreement. Our results can help improve understanding for the application of InGaAs/InAlAs step quantum wells in microelectronic and optoelectronic devices. (C) 1998 Elsevier Science Ltd. All rights reserved.
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High-quality InGaAs/InAlAs/InP high-electron-mobility transistor (HEMT) structures with lattice-matched or pseudomorphic channels have been grown by molecular-beam epitaxy (MBE). The purpose of this work is to enhance the channel conductivity by changing the epitaxial structure and growth process. With the use of pseudomorphic step quantum-well channel, the highest channel conductivity is achieved at x = 0.7, the corresponding electron mobilities are as high as 12300 (300 K) and 61000 cm(2)/V.s (77 K) with two-dimensional electron gas (2DEG) density of 3.3 x 10(12) cm(-2). These structures are comprehensively characterized by Hall measurements, photoluminescence, double crystal X-ray diffraction and transmission electron microscopy. Strong room-temperature luminescence is observed, demonstrating the high optical quality of the samples. We also show that decreasing the In composition in the InyAl1-yAs spacer is very effective to increase the 2DEG density of PHEMT structures. (C) 1998 Published by Elsevier Science B.V. All rights reserved.
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本试验结果表明:(1).PHC/N.(2)B组最好,ACC/NB组的C/N最适于蚯蚓的生长繁殖之故...
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The near-threshold highly bound states of all three stable isotopic variants of molecular hydrogen have been studied. Numerous perturbations and unexpected transitions are observed as far as 1cm(-1) just below the second dissociation threshold. This complex structure may arise from a combination of nonadiabatic coupling between B, B', C electronic states, perturbations due to. ne and hyperfine interactions, and strong shape resonances. The perturbed near-threshold states and vibrational continuum exhibit finegrained structure, differing greatly between isotopes because of varying nonadiabatic coupling.
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氧化乐果是当今世界农业生产上施用的主要农药之一,,,分析了不同氧化乐果污染浓度(0.00.51.05.010.0ga.i.·kg-1),土壤中影响碳、氮、磷循环的三大水解酶(),关系达到显著或极著负相关;;U=A/(1+B×C)的较好拟合揭示出氧化乐果对土壤脲酶机理为完全抑制作用;0.322.88和11.43ga.i.·kg-1;,转化酶和碱性磷酸酶的最大变幅分别不超过18.61%和8.36%,揭示出转化酶和碱性磷酸酶对氧化乐果不敏感。【结论】在表征土壤氧化乐果的污染程度方面土壤脲酶最适;
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多相多组分高分子体系的相行为和形态结构一直是高分子科学研究的前沿领域。在这一领域的理论研究中,由于高分子间和高分子链段间相互作用的复杂性,理论结果往往是在一定的近似条件下得到的;另一方面,可用于实验研究的样品总是有限的,而改变体系中分子间的相互作用对实验来说又是极其困难的工作。而计算机模拟却可以避开这些条件的限制。目前计算机模拟不仅仅是实验和理论的补充,人们已经把它看成是"""理论"Monte Carlo模拟能够在分子水平描述模型体系的信息、,进而对高分子体系的相行为和微观结构给出一些符合实际的预测,因而被广泛地应用于物理、数学、化学等一泊一二多领域中。本一沦文主要对二维的多相多组分高分子体系的相行为、形态结构等进行了Monte CarloB共聚物和均聚物CBC之间存在吸引的特殊相互作用。我们的模拟结果表明特殊相互作用的引入可以改善体系的共混相容性。在链二佩声B含量较低时,A/B无规共聚物和均聚物CB80BB倾向于分布在共聚物相的界面上;另一方面,链节B的含量在O80%BA/BC的混合体系,其中,交替共聚物的链节B全部集中在均聚物相的界面上;无规共聚物的链节B大部分聚集在均聚物相的界面上;而嵌段共聚物更倾向于钻进均聚物聚集的区域。此外,我们研究了A/B二嵌段共聚物与均聚物CAB为壳的核壳结构。当链段B的含量较低时,共聚物的浓度越高,形成的核越大,核尺寸的分布也越来越宽,当链段B的含量很高时,核凡乎不随共聚物浓度的变化而变化。我们还研究了链节ABC之间是都是排斥作用的ABC共混体系的形态结构,并考虑了链结构对体系共混相容佩生佩狗影响(我们研究了交替共聚物、无规共聚物和嵌段共聚物三种链结构的共聚物)。随着共聚物分子内的链节ABMonte Car toB二嵌段共聚物在选择性溶剂中(溶剂是链段B的良溶剂)自组装成核壳结构的胶束,且随着高分子溶液浓度的增加,核不断增大。在ABA三嵌段共聚物溶液体系中,溶剂是链段B的良溶剂,是链段AAB形成的,而且在体系中也发现了有些胶束间存在着桥,并且在浓度很高时,体系出现了凝胶现象。此外,我们还研究了由特殊相互作用引起的结构变化。选取ABA/CBC之间存在吸引的特殊相互作用,而链节ABC之间都是排斥的,选择性溶剂是链节ABC是不良溶剂。在此条件刁(,体系形成了核壳结构,其中核主要由链节B和CAC的含量较低时,壳由ABA和A/C无规共聚物的部分链节组成,当链节CAB嵌段共聚物的链段AC'分布、核密度、核密度分布以及平均末端距和平均木端距分布等计算机统计方法。所得到的结果将为高分子多相多组.分体系的相行为和形态结构以及高分子自组装超分子结构材料的研究和设计提供充分依据。
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本论文首先研究了NiZrTi-VCrCr和TiTi017Zr008V035Cr010Ni030B、FeCoAl元素的添加或取代对基质合金的结构及电化学性能的影响。采用XRD、ICP、SEM一EDX、XPS、EIS、线性极化和阳极极化等表征手段对TiV-CrTiVCrNi部分取代CrTi0.25-xZr_xV0.35Cr0.1Ni0.3x=005-015bccc14Laves相组成。随Zr0.050.08x继续从008增加到015时,其变化较小。合金电极的电荷转移电阻随xx0.080.1550Tio17zr"sVscrol0Ni03。合金电极在303K313K9070℃时的放电容量仍能达到275mAg。根据不同温度时的交换电流密度,计算了Ti17Zr008VSCr0Ni03050kJmolNlnB、FeC。、AITio17zroosvo35Crol0Nio3Tio17Zr008Vo35Cro.10Ni020Mnol390n1Ag;在253一343KTiol7Zr08V035Cr0JONioz5Mnoos167298mAgZrVTiVCr
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本文研究了Armco~-离子和PH~-离子浓度和PH(a) 从单支弱极化曲线测定腐蚀电流和阴、阳极反应的Tafep(b)Rp和界面电容CI_cI_(2c)I_(3c)I_(4c)ΔE2E3ΔE和4ΔEa = I_(2c)/I_c, b = I_(3c)/I_c, c = I_(4c)/I_(2c), (4b-3a~2)~(1/2)、(3c-2b)~(1/2)(2c-a~2)~(1/2)则以S_j表示之,则可得到:I_(corr) = I_c/S_j b_c = ΔE/lg((a+s_j)/2) b_a = -E/lg((a-s_j)/2)ΔEI_λS_λ,应用统计方法处理数据,可得:I_(corr) = from i=1 to n I_λ/ from i=1 ton S_ b_c = form to n ΔE_/ form i=1 to n lg ((a_λ+S_)/2) b_a = form i=1 ton ΔE_/ form i=1 to n lg ((a_λ-S_)/2)Laplace变换分析,得到相应的响应函数方程为:E_1(t) = λ_o(R_s+R_p) - 2_oR_p (e~(-(τ-λ)/RpC))/(1+e~(/RpC)) (o<<) E_2(t) = -λ_o(R_s+R_p) + 2λ_oR_p (e~(-(-)/RpC))/(1+e~(λ/RpC)) (λ<τ<2)E~λ:ΔE = 2λ_oR_p (e~(λ/RpC)-1)/(e~(λ/RpC)+1) = 2λ_oR_p t_(anh)(λ/(2RpC)) Δh = 2λ_o RsEhRp =(ΔE)/(2_o) >>RpC (_o)/(ΔE) = C/λ + 1/(2Rp) λ<
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论文工作依据色谱理论及与其相关的化学原理,对色谱这一现代实验技术在无机化学分析中的应用,进行了多方面的探讨。从高效离子交换色谱,到高效液—液分配色谱;从微库仑检测器到可见光度检测器;从高压到负压都做了不同程度的尝试。ab721c,自行合成的粉末状含巯基的离子吸附剂,可以通过酸度的梯度淋洗,实现多种元素的分离。由于时间关系,仅用它对金(III)在负压柱上进行了富集分离,并与石墨炉原子吸收法联测,建立了快速,准确的测金方法。