黄土高原石灰性土壤不同形态磷组分分布特征

以黄土高原自北向南采集的12个0～20 cm耕层土壤为供试土样,采用Tiessen和Moir修正的Hedley土壤有机无机磷分级方法研究了黄土高原石灰性土壤中不同形态磷组分的分布特征。结果表明:供试土壤各形态P总体分布特征为:HCl-P>Residual-P>NaHCO3-Po>NaHCO3-Pi>NaOH-Po>NaOH-Pi>H2O-P,以HCl-P和Residual-P为主,分别占土壤全磷的54.00%～88.96%和0～39.11%。黄土高原土壤磷含量总体分布表现为南高北低。在各土壤类型间,NaOH-Po、Residual-P和全磷平均含量表现为干润砂质新成土<黄土正常新成土<简育干润均腐土<土垫旱耕人为土,自北向南依次增加;H2O-P和HCl-P表现为简育干润均腐土<黄土正常新成土<干润砂质新成土<土垫旱耕人为土,自北向南先降后升,且上升幅度较大。黄土高原土壤全氮与全磷及各形态磷含量相关性均达显著水平,其中与NaOH-Pi、NaOH-Po、HCl-P及全磷含量达到极显著水平。C/N、pH及砂粒与全磷及各形态磷含量呈负相关关系,其中pH与NaHCO3-Po呈显著负相关,与H2O-P、NaHCO3-Pi...

A High Speed, 12-Channel Parallel, Monolithic Integrated CMOS OEIC Receiver

The design and fabrication of a high speed, 12-channel monolithic integrated CMOS optoelectronic integrated circuit(OEIC) receiver are reported.Each channel of the receiver consists of a photodetector,a transimpedance amplifier,and a post-amplifier.The double photodiode structure speeds up the receiver but hinders responsivity.The adoption of active inductors in the TIA circuit extends the-3dB bandwidth to a higher level.The receiver has been realized in a CSMC 0.6μm standard CMOS process.The measured results show that a single channel of the receiver is able to work at bit rates of 0.8～1.4Gb/s. Altogether, the 12-channel OEIC receiver chip can be operated at 15Gb/s.

格点形状和取向对二维光子晶体禁带的影响

以椭圆形和正方形介质柱组成的二维正方晶格为例,讨论了格点形状和取向变化时对光子晶体能带的影响,对比分析了波矢在周期性平面和不在周期性平面2种情况下的能带图.计算表明:格点形状和取向的适当变化可以使没有完全带隙的光子晶体出现完全带隙,低阶的完全带隙转变成高阶完全带隙.此外,经对比发现:波矢偏离周期性平面对椭圆形介质柱的正方晶格形成的完全带隙的影响,要比正方形介质柱正方晶格的完全带隙的影响要大得多.

高能kr离子辐照聚合物膜的潜径迹及其辐照降解特性的研究

本文简要叙述了快重离子在固体材料，特别是聚合物材料中引起的强电子激发效应研究的基本理论、发展历史和研究现状。描述了在兰州重离子加速器上完成的25 MeV/u 86Kr离子辐照叠层聚对苯二甲酸乙二醇酯膜（PET）和聚碳酸酯（PC）膜的实验及结果分析。应用傅立叶红外变换光谱（FT-IR）及X-射线衍射分析（XRD）方法研究了在不同电子能损及不同注量辐照条件下，高能Kr离子在聚合物PET和PC潜径迹中引起的的损伤效应。结果表明：高能Kr离子在聚合物PET、PC膜引起的损伤主要是由于辐照引起的断键及键的重组产生的官能团的降解及非晶化过程，损伤截面存在电子能损阈值，且与官能团的结构有关。 对PET的傅立叶红外变换光谱分析结果给出，电子能损为7.25 keV/nm时，对应官能团吸收峰794 cm-1, 849 cm-1, 1021 cm-1, 1341 cm-1, 1410 cm-1, 1505 cm-1,的损伤截面半径分别为：3.63 nm, 4.70 nm, 4.58 nm, 3.54 nm, 5.17 nm, 5.32 nm。X-射线衍射分析结果表明，PET的非晶化转变截面随离子注量和电子能损的增大而增加，（100）衍射峰的相对强度I/I0随离子注量的增加而指数衰减，对应电子能损为6.62, 6.93, 7.25 keV/nm，其相应的非晶化半径分别为4.86, 5.64, 6.77 nm。 对PC的傅立叶红外变换光谱分析表明，当电子能损比较小，大多数官能团的红外吸收无明显变化，直到当辐照注量为2×1012 ions/cm2 且电子能损比较大时，其绝对吸收强度才发生明显的改变。电子能损为6.37 keV/nm 时，对应官能团吸收峰为519 cm-1, 605 cm-1, 724 cm-1, 1014 cm-1，其损伤截面分别为：13.12, 45.40, 50.21, 56.28 nm2

Iridoid glucosides from Strychnos nux-vomica

From seeds of Strychnos nux-vomica three iridoids, 6'-O-acetylloganic acid, 4'-O-acetylloganic acid and 3'-O-acetylloganic acid were isolated together with two known iridoid glucosides, loganic acid and 7-O-acetylloganic acid. The structures of the compounds were established by ESI-MS and by 1D and 2D NMR spectroscopic methods. (C) 2003 Elsevier Ltd. All rights reserved.

东北松辽平原农业资源的开发措施

东北松辽平原农业资源的开发措施王春裕（中国科学院沈阳应用生态研究所，沈阳１１００１５）王曦（辽宁省科学技术信息中心，沈阳１１００１５）松辽平原是我国东北地区松花江与辽河的冲积平原，南北长１０００多ｋｍ，东西宽４００多ｋｍ，地势平坦，土质肥沃，河）１１...

深海芽孢杆菌B1394的鉴定及其产蛋白酶酶学性质

从深3 200~3 600 m的南海海底沉积物中分离到185株深海细菌,从中筛选到1株产蛋白酶活力较强的菌株B1394,酶活高达873 U/mL。采用16S rDNA分子生物学鉴定,结合细菌常规鉴定方法鉴定其为枯草芽孢杆菌(Bacillus subtilis)。对其粗酶性质进行研究发现:最适酶活温度60℃,最适pH 8.0,在低温30℃和40℃下也具有较高的酶活性,40~60℃热稳定性较好,显示出部分嗜热酶特性;Mn2+、Mg2+、Ca2+对该蛋白酶有激活作用,Hg2+、Fe3+、Cu2+、Zn2+、Fe2+对该蛋白酶有抑制作用;PMSF几乎完全抑制蛋白酶活性,推断为丝氨酸蛋白酶。

土壤环境污染与农产品质量

通过分析土壤污染的原因、特点、我国土壤污染现状以及与农产品质量关系,提出了协调人与自然关系,积极研究土壤环境污染的控制方法与修复技术;加强无污染生产资料的开发技术研究,减轻土壤环境污染;走节约资源,提高效率,减少污染的绿色农业发展之路,确保粮食生产和农产品食用安全。

Electric-field-induced molecular alignment of side-chain liquid-crystalline polyacetylenes containing biphenyl mesogens

Electric-field-induced molecular alignments of side-chain liquid-crystalline polyacetylenes [-{HC=C[(CH2)(m)OCO-biph-OC7H15]}-, where biph is 4,4'-biphenylyl and m is 3 (PA3EO7) or 9 (PA9EO7)] were studied with X-ray diffraction and polarized optical microscopy. An orientation as high as 0.84 was obtained for PA9EO7. Furthermore, the molecular orientation of]PA9EO7 was achieved within a temperature range between the isotropic-to-smectic A transition temperature and 115 degreesC, and this suggested that the orientational packing was affected by the thermal fluctuation of the isotropic liquid and the mobility of the mesogenic moieties. The maximum achievable orientation for PA9EO7 was much greater than that for PA3EO7. This was the first time that the electric-field-induced molecular orientation of a side-chain liquid-crystalline polymer with a stiff backbone was studied.