定植穴对局部土壤物理性质及苹果生长的影响

为了探索陕北黄土丘陵沟壑区苹果栽植成活率低、树体生长状况差的原因,对3种定植穴土壤物理性状及苹果生长状况进行了监测研究。结果表明定植沟、大定植穴降低了0～100cm土层土壤容重和开挖到雨季的土壤水分,其中开挖到定植是土壤水分散失的主要阶段。定植沟、大定植穴提高了0～100cm土层土壤总孔隙度、非毛管孔隙度和地面塌陷深度,相对提高了雨季期间的土壤水分,提高了枝条失水量和抽条指数,造成苗木成活率降低,树体生长量和产量降低。陕北丘陵沟壑区栽植苹果不宜采用雨季后开挖定植沟、大定植穴,翌年春季定植;春季定植时应以普通定植穴为主,并边挖边栽。

CA-100萃取稀土及二价金属的热力学和动力学研究

该文系统研究了一种新型有机羧酸类萃取剂仲壬基苯氧基乙酸(CA-100)对稀土及其杂质的萃取热力学和动力学规律,并通过协同萃取、双溶剂萃取、加入络合剂等手段对CA-100萃取体系进行改善,为该萃取剂在工业上的应用打下基础,具体的研究内容如下:1.研究了CA-100对于稀土及Zn,Cd,Cu,Co,Ni,Mn,Mg等金属元素的萃取热力学规律,计算了金属间分离系数,获得了萃取平衡方程式,考察了反萃性能及稀释剂和甲庚醇的加入对萃取的影响.研究发现该萃取剂可用于Sc同其它稀土的分离及某些金属对的分离,在很多方面优于环烷酸体系.2.探讨了CA-100与—盐基磷(膦)酸类萃取剂对锌和镉的协同萃取,研究了协同萃取机理,确定了协萃配合物的组成.3.研究了在络合试剂的存在下CA-100萃取重稀土的行为及Y同重稀土的分离情况.4.用恒流层界面池研究了CA-100萃取Y,Yb,La的萃取动力学,考察了各因素对萃取速率的影响,获得了萃取速率方程,探讨了动力学机理.5.探讨了各种因素对CA-100界面活性的影响.6.在上述热力学和动力学研究基础上,进行了CA-100从混合稀土溶液中富集和纯化Sc的工艺模拟实验.

华南沿海近100年来2月份的极端气温事件

采用IPCC AR4规定的极端天气事件划分标准，分析1908—2008年广州、香港、

The fabrication of GaN-based nanopillar light-emitting diodes

InGaN/GaN multiple quantum well-based light-emitting diode (LED) nanopillar arrays were fabricated using Ni self-assembled nanodots as etching mask. The Ni nanodots were fabricated with a density of 6 x 10(8)-1.5 x 10(9) cm(-2) and a dimension of 100-250 nm with varying Ni thickness and annealing duration time. Then LED nanopillar arrays with diameter of approximately 250 nm and height of 700 nm were fabricated by inductively coupled plasma etching. In comparison to the as-grown LED sample an enhancement by a factor of four of photoluminescence (PL) intensity is achieved for the nanopillars and a blueshift as well as a decrease in full width at half maximum of the PL peak are also observed. The method of additional chemical etching was used to remove the etching-induced damage. Then nano-LED devices were further completed using a planarization approach to deposit p-type electrode on the tips of nanopillars. The current-voltage curves of both nanopillars and planar LED devices are measured for comparison.

GROWTH OF HIGH-QUALITY GALLIUM-ARSENIDE ON HF-ETCHED SILICON (001) BY CHEMICAL BEAM EPITAXY

HF etching followed by relatively low temperature (almost-equal-to 600-degrees-C) pretreatment is shown to provide a suitable substrate for the heteroepitaxial growth of GaAs on Si(100) by CBE using TEGa and AsH3 as sources. Rutherford backscattering (RBS), photoluminescence (PL), transmission electron microscopy (TEM), and Raman measurements show the low-defect nature of the GaAs epilayer.

INVESTIGATION OF THE GROWN DIAMOND (100) SURFACE USING HIGH-RESOLUTION ELECTRON-ENERGY LOSS SPECTROSCOPY

The diamond (100) facets deposited at initial 1.0% CH4 have been investigated using high resolution electron energy loss spectroscopy (HREELS). The diamond (100) facets grown at 800-degrees-C are terminated by CH2 radicals, and there is no detectable frequency shift compared with the characteristic frequencies of molecular subgroup CH2. Beside the CH2 vibration loss, CH bend loss (at 140 meV) of locally monohydrogenated dimer is detected for the diamond (100) facets grown at 1000-degrees-C. Dosing the (100) facets grown at 800-degrees-C with atomic hydrogen at 1*10(-6) mbar, the loss peak at 140 meV appears. It is suggested that there are enough separately vacant sites and uniformly dispersed monohydrogenated dimers on (100) facets. This structure relaxes the steric repulsion between the adjacent hydrogen atoms during the diamond (100) surface growth.

ELECTRONIC SPECTROSCOPY STUDIES OF A P2S5NH4OH TREATED GAS(100) SURFACE

Microscopic characteristics of the GaAs(100) surface treated with P2S5/NH4OH solution has been investigated by using Auger-electron spectroscopy (AES) and x-ray photoemission spectroscopy (XPS). AES reveals that only phosphorus and sulfur, but not oxygen, are contained in the interface between passivation film and GaAs substrate. Using XPS it is found that both Ga2O3 and As2O3 are removed from the GaAs surface by the P2S5/NH4OH treatment; instead, gallium sulfide and arsenic sulfide are formed. The passivation film results in a reduction of the density of states of the surface electrons and an improvement of the electronic and optical properties of the GaAs surface.