黄土高原南部3种农田土壤剖面坚实度的变化规律

为了揭示黄土高原南部地区不同质地类型土壤剖面坚实度的变化及其与土壤含水率的定量关系,以黄墡土、土娄土、裸露在地表的粘化层耕作剖面为研究对象,定位观测其0~45 cm土壤坚实度与含水率的变化。结果表明,黄墡土、土娄土、裸露在地表粘化层耕作剖面的犁底层平均坚实度均大于耕层,犁底层平均坚实度较耕层分别高194.8%,87.3%,10.4%;剖面土壤质地越粘其平均坚实度越大;土壤坚实度与含水率呈负相关关系;土壤坚实度变化速率为0时,以上3种土壤剖面临界含水率分别为0.1712,0.1757,0.1835;质地不同的土壤剖面坚实度时空变化特征有差异,其中黄墡土剖面0~20 cm土层土壤坚实度为350~500 kPa,受土壤含水率变化的影响较小;20~30 cm土层土壤的坚实度为500~1400 kPa,不易受外界环境影响;30 cm以下土层土壤坚实度为700~1600 kPa,受土壤含水率变化影响较大。土娄土剖面0~40 cm土层土壤坚实度为600~1200 kPa,受含水率变化影响较大;40 cm以下土层土壤坚实度稳定在1 800 kPa左右。粘化层剖面0~15 cm土层土壤坚实度在2000 kPa左右,受环境影响较...

内蒙古包头市水环境污染问题及其治理研究

包头市是我国北方干旱地区的重要工业城市,市区占地面积大,人口多,工业企业密集,工业污水及生活污水排放量都很大,造成了市区及其周边地区水环境的严重污染。本文分析了该市水环境的主要污染源、污染物及其污染现状,讨论了本市水环境污染严重的主要原因,并探讨了相应的治理对策。

内蒙古沙地云杉分类的研究

内蒙古沙地云杉究竟是哪一种，在植物分类学上是一个争论性问题。本文通过三种云杉的形态解剖比较、栽培实验观察、同工酶和核型分析以及生态地理分布的研究，结果表明，内蒙古沙地云杉既不同于红皮云杉（ＰｉｃｅａｋｏｒａｉｅｎｓｉｓＮａｋａｉ），也不同于白扦云杉（ＰｉｃｅａｍｅｙｅｒｉＲｅｈｄ．ｅｔＷｉｌｓ．），应划分为一个独立种更为合适，即将原来发表为白扦云杉的变种新组合之为独立的种，沙地云杉（ＰｉｃｅａｍｏｎｇｏｌｉｃａＨ．Ｑ．Ｗｕ）Ｗ．Ｄ．Ｘｕ（ＰｉｃｅａｍｅｙｅｒｉＶａｒ．ｍｏｎｇｏｌｉｃａＨ．Ｑ．Ｗｕ）。

水肥耦合与半干旱区农业可持续发展

半干旱地区农业要实现持续发展 ,必须对土地资源进行合理保护和充分利用 ,为达到目的必须研究水肥耦合效应。本文讨论了半干旱地区可持续农业的限制因素、旱地农业肥水关系、水肥耦合的研究现状以及水肥耦合研究对我国的重要意义

我国森林生态学研究的现状及其思考(英文)

森林生态学是研究森林及其与环境间相互关系的科学,森林生态系统作为陆地生态系统中一个重要类型和组成部分,对自然环境和人类的作用是明显的,在实现可持续发展中具有不可替代的作用。由于森林生态系统的复杂性和研究手段的相对滞后,目前森林生态学研究虽然取得很大的进展并成功应用于林业实践,但也存在一些问题。本文简要回顾和评述了我国森林生态学的发展和研究现状,着重指出目前研究中存在的不足,并结合现今森林生态学的发展趋势以及我们相关研究基础对森林生态系统的结构和功能研究、森林生态系统管理、森林流域生态学研究、森林生态系统健康等进行了讨论。参21。

乙草胺、铜污染共存对土壤甲胺磷蚯蚓降解过程的影响研究

为揭示利用蚯蚓活动强化甲胺磷降解的可行性,采用了微宇宙培养方法,通过有蚯蚓和无蚯蚓的对比实验,考察了乙草胺和铜分别与甲胺磷共存条件下污染黑土中甲胺磷降解过程的动态变化.结果表明,无论是否加入蚯蚓,甲胺磷单一污染的土壤中甲胺磷的降解符合一级反应动力学规律;蚯蚓活动能促进甲胺磷降解过程的进行.土壤中乙草胺或铜与甲胺磷共存时,均明显地干扰了甲胺磷降解过程随时间的动态变化;根据化学结构分析,推测两者对甲胺磷降解规律的影响机制可能类似.铜与甲胺磷复合污染的土壤中甲胺磷含量明显高于乙草胺与甲胺磷复合组,说明铜较乙草胺对土壤甲胺磷降解过程的延缓作用更强.

Time-resolved synchrotron SAXS observations on sheared syndiotactic poly(propylene) crystallization process

The in situ crystallization kinetics of syndiotactic poly(propylene) (sPP) has been investigated by synchrotron small-angle X-ray scattering (SAXS). The structure evolutions during the isothermal crystallization of sPP with different shear rates have been observed. The results show that shear accelerates the process of crystallization kinetics. Even under low shear rate, the lamellae can be distinctly oriented. In contrast, the lamellar parameters such as the long period, lamellar thickness, and the scattering invariant 0 can change obviously only under high shear rate.

Phase transition behavior and molecular orientation of oligo(9,9 '-dioctylfluorene-alt-bithiophene)

A novel conjugated oligomer, oligo(9,9'-dioctylfluorene-alt-bithiophene) (OF8T2), was found to exhibit a unique phase transition between crystalline and liquid-crystalline states, and a liquid-crystalline glass was easily generated, offering better TFT device performance. In thin films, upon annealing the OF8T2 molecules oriented preferentially with their planes of conjugation being normal to the substrate, and both film thickness and annealing temperature were critical to the film morphology and the molecular orientation. When the OF8T2 film was deposited on a rubbed polyimide surface and annealed, the molecules aligned their long axes along the rubbing direction.

Self-assembly of a hydrophobic polypeptide containing a short hydrophilic middle segment: Vesicles to large compound micelles

This report describes a facile route to prepare the vesicles and large compound micelles (LCMs) from a series of poly(epsilon-benzyloxycarbonyl L-lysine)-block-poly[diethylene glycol bis(3-amino propyl) ether]-block-poly(epsilon-benzyloxycarbonyl L-lySine) (PZLL-DGBE-PZLL) in their water solution, depending on molecular weight of the polypeptides. A pyrene probe is used to demonstrate the aggregate formation of PZLL-DGBE-PZLL in solution, and also to measure their critical micelle concentration as a function of molecular weight of the polymer.

Carbon dioxide pressure induced heterogeneous and homogeneous Heck and Sonogashira coupling reactions using fluorinated palladium complex catalysts

The Heck reaction of iodobenzene and methyl acrylate was investigated with CO2-philic Pd complex catalysts having fluorous ponytails and the organic base triethylamine (Et3N) in the presence of CO2 under solventless conditions at 80 degrees C. The catalysts are not soluble in the organic phase in the absence Of CO2 and the reaction occurs in a solid-liquid biphasic system. When the organic liquid mixture is pressurized by CO2, CO2 is dissolved into the organic phase and this promotes the dissolution of the I'd complex catalysts. As a result, the Heck reaction occurs homogeneously in the organic phase, which enhances the rate of reaction. This positive effect Of CO2 pressurization competes with the negative effect that the reacting species are diluted by an increasing amount of CO2 molecules dissolved. Thus, the maximum conversion appears at a CO2 pressure of around 4 MPa under the present reaction conditions. The catalysts are separated in the solid granules by depressurization and are recyclable without loss of activity after washing with n-hexane and/or water.

Thermoluminescence properties of Ce3+-doped LiSr4(BO3)(3) phosphor

Borates LiSr4(BO3)(3) were synthesized by high-temperature solid-state reaction. The thermoluminescence (TL) and some of the dosimetric characteristics of Ce3+-activated LiSr4(BO3)(3) were reported. The TL glow curve is composed of only one peak located at about 209 degrees C between room temperature and 500 degrees C. The Optimum Ce3+ concentration is 1 mol% to obtain the highest TL intensity. The TL kinetic parameters of LiSr4(BO3)(3):0.01Ce(3+) were studied by the peak shape method. The TL dose response is linear in the protection dose ranging from 1 mGy to 1 Gy. The three-dimensional thermoluminescence emission spectra were also studied, peaking at 441 and 474 nm due to the characteristic transition of Ce3+.