磷素活化剂研究进展

磷素活化剂能有效的提高磷素利用率,减少磷肥施用量,缓解磷资源不足的矛盾,具有远大的发展前景。本文总结了磷素活化剂的研究现状及其作用效果,提出其发展和应用中存在的问题,并展望了今后的研究方向。

异胡豆苷合成酶在烟草亚细胞区室的表达(英)

异胡豆苷合成酶 (strictosidinesynthase,STR)是吲哚生物碱生物合成的一种关键酶 ,将色胺 (tryptamine)和裂环马钱子 (secologanin)耦合成为吲哚生物碱的前体化合物异胡豆苷。将异胡豆苷合成酶标定在烟草植物不同的亚细胞区室———叶绿体、液泡和内质网中表达 ,通过蛋白免疫印迹分析和STR酶活性的测定 ,表明STR在叶绿体、液泡和内质网中有效表达。STR体外酶活性分析采用间接荧光法检测色胺在反应体系的消耗。STR的酶活性分析表明了STR在烟草中不同的亚细胞区室得以活性表达。分离纯化转基因烟草的叶绿体 ,通过对其分离的不同部分的蛋白免疫印迹分析 ,确定了将STR正确标定在烟草的叶绿体中表达。

IPCC评估报告气温变化观测数据的不确定性分析

IPCC评估报告给出了全球气候变暖的结论。本文从IPCC采集引用的数据源角度对其揭示的近百年地表增温结论进行了不确定性分析,具体包括地表气温观测网络空间分布、温度序列时间尺度、数据可信度、人类活动对温度的影响等。结果表明:百年尺度全球地表气温观测网络覆盖范围较少;经纬度单元网格内数据源分布不均匀;长时间尺度的温度序列记录有限,且不同年代气温记录数量存在显著差异;大量站点观测连续性差,年平均温度可信度低;目前使用的地面温度观测记录大部分来自大城市,对城市化的热岛效应考虑不足。

气候变化研究中若干不确定性的认识问题

气候变化研究已取得重要进展,但很多研究结果存在不确定性。本文选择对气候变化研究有重要意义但已有的研究结果存在不确定性的几个方面进行综述,包括过去两千年气候变化的状况(中世纪暖期和小冰期是否存在、20世纪温暖程度是否为过去千年最大、20世纪增温趋势是否停止)、温室效应(对温室效应机理的不同认识、温室气体排放与气温变化的关系、水汽对温室效应及增温的贡献)、气候模式模拟(模拟与实测结果的比较、模式本身的缺陷)以及2℃阈值(来源及其物理意义、对2℃阈值的不同认识)等问题。气候系统变化的复杂性决定了人类对气候变化问

全球变化研究进展和趋势

概述了国际全球变化研究计划(ESSP、IGBP、WCRP、IHDP、DIVERSITAS)新近的研究战略调整和研究重点,在对国际全球变化研究成果综合分析的基础上,总结了全球变化研究的阶段性理论进展,归纳了全球变化研究的特点和趋势。

近40年中国植物物候对气候变化的响应研究

根据中国科学院物候观测网络中26个观测站点的物候资料,分析了近40年我国木本植物物候变化及其对气候变化的响应关系,并建立了不同年代物候期与地理位置之间的关系模式,分析了当前气候增暖背景下物候期地理分布规律变化对气候变化的响应关系。结果表明:温度上升,我国的木本植物春季物候期提前。20世纪80年代以后,东北、华北及长江下游等地区的物候期提前,西南东部、长江中游等地区的物候期推迟,同时物候期随纬度变化的幅度减小。

全新世寒冷事件与气候变化的千年周期

在统计10000aBP以来我国每百年中寒冷事件记录的频率的基础上,分析了寒冷事件的时间分布特点和频率序列的功率谱.结果表明,10000aBP以来的冷暖变化在500,1000和1300a的周期是明显的.其中,两个相邻寒冷事件的平均时间间隔与500a周期相对应,间隔一个事件的两个寒冷事件之间的平均时间间隔与1000a周期相对应.而包括一长(400～800a)一短(100～200a)两个寒冷时段的一个气候旋回与1300a左右的周期相对应.为千年周期的存在提供了进一步的证据.

过去2000年中国温度变化研究的几个问题

根据最近重建的中国东部地区过去2000年冬半年温度距平序列,结合最近其他一些相关研究结果,对过去2000年中国温度变化序列的重建方法、小冰期及魏晋南北朝冷期的起迄时间与寒冷状况、中世纪暖期与隋唐暖期的温暖程度、过去2000年中国冷暖变化的幅度与速率、温度变化的千年波动周期、20世纪气候增暖是否超出过去2000年气候波动的最大范围及20世纪暖期历史相似型等几个问题进行了综合评述.

ANALYSIS OF DRIVING FORCES ON THE CHANGE OF HISTORICAL FARMLAND USE IN SHANDONG PROVINCE DURING THE QING DYNASTY (1644-1911)

National Natural Science Foundation of China [40201005]; Knowledge Innovation Project of Chinese Academy of Sciences [KZCX3-SW-321, KZCX2-314, KZCX1-SW-321-4]

Novel acid-base polyimides synthesized from binaphthalene dianhydrie and triphenylamine-containing diamine as proton exchange membranes

The synthesis and characterization of novel acid-base polyimide membranes for the use in polymer electrolyte membrane fuel cell is presented in this paper. The sulfonated polyimides (SPIs) bearing basic triphenylamine groups were easily synthesized using 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianhydride (BTDA), sulfonated diamine of 4,4'-diaminodiphenyl ether-2,2'-disulfonic acid (ODADS), and nonsulfonated diamines of 4,4'-diaminotriphenylamine (DATPA). The effects of the structure of the dianhydride and diamines on the properties of SPI membranes were evaluated through the study of membrane parameters including water sorption, proton conductivity, water stability, dimensional changes, and methanol permeability.

Electrochemical and electrochemiluminescence study of Ru(bpy)(3)(2+)-doped silica nanoparticles with covalently grafted biomacromolecules

Spherical Ru(bpy)(3)(2+)-doped silica (RuSi) nanoparticles were prepared via a water-in-oil microemulsion approach. The electrochemical and electrochemiluminescent properties of the RuSi nanoparticles immobilized on an indium tin oxide (ITO) electrode were investigated. Further, electrochemiluminescence (ECL) of the RuSi nanoparticles with covalently coated biomacromolecules was studied. By covalent cross-linking with glutaraldehyde, gamma-(aminopropyl) triethoxysilane (APTES)-pretreated RuSi nanoparticles were coupled with different concentrations of bovine serum albumin (BSA), hemoglobin, and myoglobin, respectively.

Metabolic profiling studies on the toxicological effects of realgar in rats by H-1 NMR spectroscopy

The toxicological effects of realgar after intragastrical administration (1 g/kg body weight) were investigated over a 21 day period in male Wistar rats using metabonomic analysis of H-1 NMR spectra of urine, serum and liver tissue aqueous extracts. Liver and kidney histopathology examination and serum clinical chemistry analyses were also performed. H-1 NMR spectra and pattern recognition analyses from realgar treated animals showed increased excretion of urinary Kreb's cycle intermediates, increased levels of ketone bodies in urine and serum, and decreased levels of hepatic glucose and glycogen, as well as hypoglycemia and hyperlipoidemia, suggesting the Perturbation of energy metabolism. Elevated levels of choline containing metabolites and betaine in serum and liver tissue aqueous extracts and increased serum creatine indicated altered transmethylation. Decreased urinary levels of trimethylamine-N-oxide, phenylacetylglycine and hippurate suggested the effects on the gut microflora environment by realgar.

Microstructures and mechanical properties of extruded Mg-8Gd-0.4Zr alloys containing Zn

Microstructures and mechanical properties of the Mg-8Gd-xZn-0.4Zr (x = 0, 1 and 3 wt.%) alloys in the as-cast, as-extruded and extruded-T5 conditions, have been investigated. The peak-aged Mg-8Gd-1Zn-0.4Zr alloy during isothermal ageing at 423 K acquires highest mechanical properties, with the highest ultimate tensile strength and yield tensile strength of 314 and 217 MPa, respectively. Addition of Zn has obvious effect on age hardening responses, especially for 1 wt.% Zn addition. It is due to a uniform distribution of beta' phase which can impede the movement of dislocations. However, addition of 3 wt.% Zn to the Mg-8Gd-0.4Zr alloy leads to a precipitation of Mg3Zn3Gd2 phase (W-phase). This phase is incoherent with interface of the matrix and becomes cores of the fracture in tensile test at room or elevated temperature.