氮磷营养对小麦水分关系的影响

比较研究了氮磷营养对春小麦水分关系影响的差异。结果表明 ,土壤干旱情况下 ,氮磷营养虽然皆增强了春小麦的渗透调节能力 ,但由于氮磷营养对作物地上地下部生长的不同进促作用而对作物的水分状况产生了完全相反的影响。氮营养增强了作物对干旱的敏感性 ,使其水势和相对含水量大幅度下降 ,蒸腾失水减少 ,自由水含量增加而束缚水含量减少 ,并使膜稳定性降低 ;而磷营养则明显改善了植株的水分状况 ,增大了气孔导度 ,降低了其对干旱的敏感性 ,增加了束缚水含量 ,并使膜稳定性增强

施氮肥对水曲柳人工林细根生产和周转的影响

细根周转与土壤养分密切相关,但由于根系研究方法的差异以及研究对象的不同,土壤养分对细根周转影响的研究存在不一致的结论。本文以水曲柳(Fraxinus mandshurica)人工林为对象,应用3种方法研究施氮肥对细根生产和周转的影响。结果表明:施肥降低了活细根现存生物量,但施氮肥样地细根年生产量平均值(93.105g·m-2·a-1)与对照样地(93.505g·m-2·a-1)没有差异,不同方法得出施氮肥样地细根平均周转率(0.917次·a-1)大于对照样地(0.710次·a-1);不同土层内细根的生产量显著不同,表层生产量最大,土层越深细根生产量越低,但细根周转率一般随土壤加深而加快;不同的研究方法得出细根的年生产量和周转率差异较大,分室模型法最高,其次是内生长土芯法,极差法和积分法最低。

1990～2000年中国土壤碳氮蓄积量与土地利用变化

基于2473个土壤剖面资料和1980年代末~1990年代末陆地卫星TM影像分析中国1990~2000年林地、草地、耕地之间的土地利用变化对土壤碳氮蓄积量的影响。IPCC建议的国家温室气体清单方法计算表明从1990~2000年中国林地、草地、耕地土壤(30cm)有机碳氮库分别损失了77.6±35.2TgC(1Tg=106t)和5.6±2.6TgN,年均损失约7.76TgC/yr和0.56TgN/yr,其中耕地土壤碳库分别增加了79.0±7.7TgC和9.0±0.7TgN,草地土壤碳氮蓄积量分别损失了100.7±25.9TgC和9.8±2.2TgN,林地土壤碳氮蓄积量分别损失了55.9±17.0TgC和4.9±1.1TgN。同时根据中国6大行政区林地、耕地和草地之间的相互转换面积、土壤有机碳氮密度的变化率进行估算,表明土壤(30cm和100cm)有机碳氮蓄积量分别损失了53.7TgC、5.1TgN和99.5TgC、9.4TgN。由于中国不同地区土地利用变化的空间格局差异显著,从而导致东北地区土壤碳氮蓄积量变化较大,而华东地区变化较小。

二氧化碳-环氧丙烷共聚物的链结构控制

针对制约二氧化碳-环氧丙烷共聚物(PPC)规模化应用的玻璃化温度低的问题,提出了改进PPC链结构的3个方法,即提高共聚物的分子量、制备交联型PPC、合成区域规整结构PPC.通过研究链结构变化对PPC热性能和机械性能的影响,证明通过共聚物链结构的设计和控制,可以大幅度增强PPC的分子间作用力,从而提高了PPC的使用温度,改善了PPC的使用性能.

Sm~(3+)对甲醇电化学氧化反应的助催化作用

分别以相同面积的光滑 Pt电极和吸附了 Sm3+ 的铂电极作为工作电极 ,在酸性介质中采用循环伏安法对甲醇氧化进行测定 .结果表明 ,吸附了 Sm3+ 的 Pt电极上产生了更大的氧化电流 ,表明 Sm3+ 的加入对甲醇的电催化氧化起到了促进作用 .这一研究结果在直接甲醇燃料电池 ( DMFC)阳极催化剂研制方面具有较大的应用潜力

Water-soluble fluorescent nanospheres as fluorosensor for detection of Cu2+

A novel water-soluble fluorescent nanosphere as fluorosensor was prepared by emulsifier-free emulsion copolymerization of styrene with naphthalimide derivative (A). The fluorosensor was high sensitive for detection of Cu2+. Comparied with other fluorosensors based on organic fluorophore, it has two advantages. First, there is no pollution to environment in the use of it. Second, it can be used repeatedly.

顺、反式环丙烷衍生物异构体的区分

在化学电离条件下，研究了４种顺、反式环丙烷衍生物与丙酮和醋酸乙烯酯的分子－离子反应。异构体１，２的丙酮ＣＩ谱及其加合离子［Ｍ＋Ｈ＋Ａ］＋的ＣＩＤ谱都可以区分该对异构体。化合物２，３和４可以和质子化丙酮及质子化二聚体发生加合反应，但化合物１仅能与质子化丙酮发生加合反应。在醋酸乙烯酯的ＣＩ谱中，观察到４个化合物的质子化二聚体，其中异构体１，２的质子化Ｍ聚体的ＣＩＤ谱也能反映它们立体结构的差异。

A study of cokes used as anodic materials in lithium ion rechargeable batteries

A variety of cokes pretreated at different temperatures are used as anodic materials and their electrochemical characteristics are examined by cyclic voltammetry. It is found that for some cokes such as petroleum coke (preheated at 1300 degrees C), pitch coke (1300 degrees C), needle coke (1900 degrees C), metallurgical coke (1900 degrees C), high capacity and cyclic efficiency are achieved. Needle coke (1900 degrees C) and metallurgical coke (1900 degrees C) in particular give a capacity of over 200 mAh/g and a cyclic efficiency of nearly 100%, whereas poor performance is exhibited by those pretreated at higher or lower temperatures, e.g., petroleum cokes (500 degrees C, 2800 degrees C), pitch coke (500 degrees C) and needle coke (2800 degrees C). The cyclic voltammograms show two electrochemical processes, one at about 0.1 V vs. Li+/Li which is electrochemically reversible, and may be attributed to the intercalation/deintercalation of lithium ions while the other, at about 0.6 V vs. Li+/Li, is electrochemically irreversible and may be assigned to the decomposition of the electrolyte solvent, which leads to formation of the passive film on the anode surface. The experimental results strongly suggest that the pretreatment temperature of cokes and of the solvent are determining factors for the growth, structure and properties of the passive film.

C_(60)与苯及氘代苯的气相反应

1985年Kroto首先用质谱在激光蒸发石墨的氦气氛中检测到丰度占优势的以C_(60)和C_(70),从而以质谱法为主要手段的C_(60)研究迅速开展起来。一系列实验结果支持了Kroto猜测的C_(60)球形结构,并对C_(60)的气相反应行为有所认识。 1990年实现宏观量制取C_(60)后,气相C_(60)离子的研究内容更加广泛,Frieser在气相中

硝酸镧与冠醚(2,2)配合物的晶体及电子结构研究

用X-射线单晶衍射法测定了硝酸镧与冠醚(2,2)配合物的晶体结构,发现其具有与报道的Eu(NO_3)_3(2,2)配合物不同的配位方式.晶体属于三斜晶系,空间群P(?),晶胞参数为a=10.312(2)(?);b=12.745(3)(?);c=8.917(2)(?);α=103.79(2)°;β=112.73(2)°;γ=83.68(2)°;V=1049.5(5)(?)~3;F(000)=587.88;Z=2.结构用重原子法解出;R值为0.0292.用INDO法计算了配合物的净电荷分布,电子结构、键级.结果表明,镧与配位原子间的键具有一定程度的共价性.镧的5d轨道对共价性的贡献最大,而4f轨道基本上不参与成键.La-N比La-O(醚)间存在较强的作用,增大了配合物的稳定性.

LiF-KCl熔体的X-射线结构分析

目前多采用径向分布函数来描述熔盐的结构,虽然这种一维统计描述给出的信息有限,但它是迄今为止较为成熟的一种方法。实验上获得熔体的径向分布函数主要通过衍射法。在国际上日本等国家的研究人员对纯熔盐的衍射结构分析已经进行了多年的研究,由于混合熔盐的结构比较复杂,所以近些年才有关于混合熔盐X-射线衍射结构分析的报道,但只限于相同阳离子或相同阴离子的体系,对于LiF-KCl体系至今未见报道。

同位素稀释-火花源质谱法分析人参样品中微量元素

本文采用同位素稀释-火花源质谱法定量分析了吉林野山参,园参及高丽参中30多种微量元素的含量。测定下限2μg/g,相对标准偏差在5～28％以内。

Sources and preservation of organic matter in Plum Island salt marsh sediments (MA, USA): long-chain n-alkanes and stable carbon isotope compositions

Elemental (TOC, TN, C/N) and stable carbon isotopic (delta(13)C) compositions and n-alkane (nC(16-38)) concentrations were measured for Spartina alterniflora, a C-4 marsh grass, Typha latifolia, a C-3 marsh grass, and three sediment cores collected from middle and upper estuarine sites from the Plum Island salt marshes. Our results indicated that the organic matter preserved in the sediments was highly affected by the marsh plants that dominated the sampling sites. delta(13)C values of organic matter preserved in the upper fresh water site sediment were more negative (-23.0+/-0.3) as affected by the C-3 plants than the values of organic matter preserved in the sediments of middle (-18.9+/-0.8) and mud flat sites (-19.4+/-0.1) as influenced mainly by the C4 marsh plants. The distribution of n-alkanes measured in all sediments showed similar patterns as those determined in the marsh grasses S. alterniflora and T. latifolia, and nC(21) to nC(33) long-chain n-alkanes were the major compounds determined in all sediment samples. The strong odd-to-even carbon numbered n-alkane predominance was found in all three sediments and nC(29) was the most abundant homologue in all samples measured. Both delta(13)C compositions of organic matter and n-alkane distributions in these sediments indicate that the marsh plants could contribute significant amount of organic matter preserved in Plum Island salt marsh sediments. This suggests that salt marshes play an important role in the cycling of nutrients and organic carbon in the estuary and adjacent coastal waters. (C) 2003 Elsevier Ltd. All rights reserved.

紫花冷蒿挥发油成分的研究

采用水蒸气蒸馏法提取, 运用气相色谱-质谱联用法对香叶蒿挥发油化学成分进行了分析, 用气相色谱面积归一化法测定了各成分的质量分数. 结果鉴定出72个化合物, 主要成分为樟脑(33.136%), 桉树脑(23.419%), 6-甲基-2-乙烯基-1,3-庚二烯醛(8.414%), 孟烯醇(3.819%), 桥环萜烯酮(3.276%), 莰烯(2.454%), 1R-α-蒎烯(1.917%), 去甲基丁香酚(1.550%), α-松油醇(1.449%), 冰片(1.674%), β-香叶烯(1.165%), 百里香酚(0.329%)等. 研究表明紫花冷蒿挥发油主要为单萜及其氧化衍生物. 其挥发油成分的研究为挖掘其药用及食品香料工业的应用价值提供了科学依据.