黄土高原水蚀风蚀交错区治理的重要性与紧迫性

在全国范围划分水蚀、风蚀和冻融侵蚀三大侵蚀类型区基础上 ,提出进一步划分水蚀风蚀交错区的必要性及重要意义。黄土高原的强烈侵蚀中心出现在水蚀风蚀交错区 ,该区为黄河粗泥沙的主要来源区 ,生态环境脆弱 ,自然灾害频繁。该区又为世界级大型煤田蕴藏地 ,将建成我国 2 1世纪的能源重化工基地。强化水蚀风蚀交错区综合治理 ,对治黄及西部地区开发具有重大意义。

生物有机肥对小油菜生长及品质的影响

在小油菜上进行施用生物有机肥、有机无机配合施肥、三元肥的田间对比试验。结果表明,单施生物有机肥比单施无机三元肥的小油菜中硝酸盐和亚硝酸盐含量分别降低36.17%和21.77%;种植后土壤中有机质比单施无机三元肥提高11.12%。油菜生产中施用生物有机肥可以提高作物品质,提高土壤有机质含量,培肥地力,与三元肥配合施用不会造成明显减产。

土壤物理学科发展趋势与展望

本文概述了国际土壤物理学的发展趋势和中国土壤物理研究前景展望。作为土壤学和物理学分支学科的现代土壤物理学,可定义为应用物理学的原理和方法描述土壤特性。探讨了土壤中物质迁移和能量转换等过程的学科。从发展的趋势看,土壤物理研究的重点已逐渐从单纯的农业问题拓展到更为综合复杂的环境问题。新一代的仪器测试技术正在向快速、非接触性和原地测量三个方向发展。此外,随着随机方法的应用和计算机模型的普及,一系列新的方法论已可满足处理土壤非均质性和高度非线性现象的需要。根据我国国情,今后土壤物理研究的重点,首先是服务于稳定增产和农业持续发展;同时要积极开展非饱和带的溶质运移研究,以保护环境,防止污染。

An Efficient Nanocrystalline La2O3:Tm3+ Blue Phosphor for Field-Emission Displays with High Color Purity

Nanocrystalline Tm3+-doped La2O3 phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction, field-emission scanning electron microscopy, photoluminescence, and cathodoluminescence spectra were utilized to characterize the synthesized phosphors. Under the excitation of UV light (234 nm) and low-voltage electron beams (1-3 kV), the Tm3+-doped La2O3 phosphors show the characteristic emissions of Tm3+(D-1(2), (1)G(4)-F-3(4), H-3(6) transitions).

Highly efficient white organic light-emitting devices based on a multiple-emissive-layer structure

Characteristics of white organic light-emitting devices based on phosphor sensitized fluorescence are improved by using a multiple-emissive-layer structure, in which a phosphorescent blue emissive layer is sandwiched between red and green&yellow ones. In this device, bis[(4,6-difluorophenyl)-pyridinato-N,C-2] (picolinato), bis(2,4-diphenyl-quinoline) iridium (III) acetylanetonate, fac bis (2-phenylpyridine) iridium, and 5,6,11,12-tetraphenylnaphthacene are used as blue, red, green, and yellow emitters, respectively.

An unusual 3D polycatenane motif generated by the 2D -> 2D parallel -> 3D parallel interpenetration of (4,4) sheets

A fascinating 3D polycatenane-like metal-organic framework with two kinds of helical chains was reported, in which the helical chains exhibit multiple interweaving modes based on the unusual 2D -> 2D parallel -> 3D parallel interpenetration.

Effect of secondary ligands' size on energy transfer and electroluminescent efficiencies for a series of europium(III) complexes, a density functional theory study

In this paper, a quantum chemistry method was used to investigate the effect of different sizes of substituted phenanthrolines on absorption, energy transfer, and the electroluminescent performance of a series of Eu(TTA)(3)L (L = [1,10] phenanthroline (Phen), Pyrazino[2,3-f][1,10]phenanthroline (PyPhen), 2-methylprrazino[2,3-f][1,10] phenanthroline(MPP), dipyrido[3,2-a:2',3'-c]phenazine(DPPz), 11-methyldipyrido[3,2-a:2',3'c]phenazine(MDPz), 11.12-dimethyldipyrido[3,2-a:2',3'-c]phenazine(DDPz), and benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (BDPz)) complexes. Absorption spectra calculations show that different sizes of secondary ligands have different effects on transition characters, intensities, and absorption peak positions.

Synthesis and luminescent properties of LaInO3: RE3+ (RE = Sm, Pr and Tb) nanocrystalline phosphors for field emission displays

LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction, field emission scanning electron microscopy, photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. XRD results reveal that the pure LaInO3 phase can also be obtained at 700 degrees C. FE-SEM images indicate that the LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors are composed of aggregated spherical particles with sizes around 80-120 nm. Under the excitation of ultraviolet light and low voltage electron beams (1-5 kV), the LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors show the characteristic emissions of Sm3+ ((4)G(5/2)-H-6(5/2,7/2,9/2) transitions, yellow), Pr3+ (P-3(0)-H-3(4), P-3(1)-H-3(5), D-1(2)-H-3(4) and P-3(0)-F-3(2) transitions, blue-green) and Tb3+ (D-5(4)-F-7(6.5,4.3) transitions, green) respectively. The corresponding luminescence mechanisms are discussed. These phosphors have potential applications in field emission displays.

Novel Oligo-9,9 '-spirobifluorenes through ortho-Linkage as Full Hydrocarbon Host for Highly Efficient Phosphorescent OLEDs

4-Bromo-9,9'-spirobifluorene is facilely synthesized, and from this precursor, two ortho-linked oligo-9,9'-spirobifluorenes, 44BSF and 24TSF, are constructed. Devices with 24TSF as the full-hydrocarbon host material and Ir(ppy)(3) or (ppq)(2)Ir(acac) as the triplet emitter show maximum external quantum efficiencies of 12.6 and 10.5% for green and red electrophosphorescence, respectively.

Facile synthesis of highly uniform octahedral LuVO4 microcrystals by a facile chemical conversion method

Uniform octahedral LuVO4 microcrystals have been successfully prepared through a designed two-step hydrothermal method. One-dimensional lutetium precursor was first prepared through a simple hydrothermal route. Subsequently, a well-shaped octahedral LuVO4 sample was synthesized at the expense of the wirelike precursors during the hydrothermal process. The whole process in this method was carried out in aqueous conditions without the use of any organic solvents, surfactant, or catalyst. The conversion process from nanowire precursor to octahedral product has been investigated in detail. The LuVO4 : Ln(3+) (Ln Eu, Dy, Sm, and Er) phosphors show strong light emissions with different colors coming from different activator ions under ultraviolet light excitation or low-voltage electron beam excitation. Furthermore, this general and facile method may be of much significance in the synthesis of many other lanthanide compounds with polyhedral morphology.

Gold nanoparticle probes

Depending on their size, shape. degree of aggregation and nature of the protecting organic shells on their surface, gold nanoparticles (AuNPs) can appear red, blue and other colors and emit bright resonance light scattering of various wavelengths. Because of this unique optical property. AuNPs have been extensively explored as probes for sensing/imaging a wide range of analytes/targets, such as heavy metallic cations, nucleic acids, proteins, cells, etc. Since their initial discovery, novel synthetic methods have led to precise control over particle size, shape and stability, thus allowing the modification of a wide variety of ligands on the AuNP surfaces to meet different experimental conditions. This review discusses the synthesis and applications of functionalized AuNPs in chemical sensing and imaging.

聚电解质溶液浓度区域的划分

按照DeGennes[1] 提出的标度概念 ,柔性高分子溶液可以划分为稀溶液 ,亚浓溶液和浓溶液 3个区域 ,它们之间分别以接触浓度c 和交叠浓度c 为分界线 .钱人元等[2 ] 根据聚苯乙烯溶液激基荧光强度浓度依赖性的实验结果 ,提出稀溶液区还应细分为极稀溶液和稀溶液两个区域 ,它的分界浓度称为动态接触浓度cs.中性高分子溶液存在这一分界浓度 ,已经得到体积排除色谱[3 ] 、高分子溶液的物理凝胶化[4] 、以及动态光散射[5] 等研究结果的证实 .本文作者之一 (程 )从中性高分子在溶液中由于范德华分子间吸引力的存在容易自缔合而形成团族的概念出发 ,导出了溶液粘度与cs 之间的理论关系[6,7] .聚电解质由于在溶液中可以离解为聚离子和对离子的特性 ,关于它的溶液浓度区域的划分问题 ,已经引发了一些理论的[8～ 11] 和许多实验的研究 ,其中包括光散射[12～ 14 ] 、小角X射线散射[15] 、小角中子散射[16] 、准弹性中子散射[17] 、溶液电导[18] 和溶液粘度[19]等 .这些研究中的绝大多数 ,仍然将溶液划分为稀溶液 ,亚浓溶液和浓溶液 3个区域.

新型笼状同多钒酸盐[Ni(1,10′-phen)_3]_2·[V_2~ⅣV_8~ⅤO_(26)]的水热合成和晶体结构

尽管多金属氧酸盐 (POMs)的研究已有180多年的历史,但大量的POMs结构在最近几十年才被陆续解析出来[1～4].其中 ,同多钒酸盐由于钒配位几何形状的多样性,结构最为丰富 ,例如:[V4 O12 ]4-[5],[V5O14 ]3-[6],[V10 O2 8]6-[7] ,[V15O4 2 ]9-[8],[V13 O3 4 ]3-[9].值得注意的是,在这些化合物中,钒的化合价均处于最高氧化态+5价.由于+4价钒不易在溶液中(尤其是水中)稳定存在,因此在以往的常压溶液合成中具有混合价态的同多钒酸盐报道很少.与饱和价态的同多钒酸盐相比,混价多钒酸盐具有更为新奇的电荷分布和拓扑学几何构型,并且在 POMs的理论研究和抗病毒药物、电存储材料以及磁性材料等应用领域有特殊的研究和开发价值[1,10,11].因此,制备具有混价的新型同多钒酸盐一直倍受关注.近年来,水热合成技术的引入使同多钒酸盐合成化学迅速发展.水热体系提供了一个特殊的反应环境 [12 ],使制备各种具有混合价态的同多钒酸盐成为可能.Müller等[13]对这一领域开...