Production of isobutene from n-butane over Pd modified SAPOs and MeAPOs

Pd modified AlPO-11 and SAPO-5, 11, 34 were used in the direct transformation of n-butane to isobutene. The effect of acidity and porous structure on the supported Pd and the catalytic perfori-nance were discussed. For higher isobutene selectivity, some metals, such as Ti, Fe, Mg, Co and Mn, was incorporated into AlPO-11 framework and isobutene selectivity of 34.86% can be obtained over Pd/MnAPO-11. A combined catalyst system was used for a further improvement of the isobutene selectivity.

几种不同下垫面地表粗糙度动态变化及其对通量机理模型模拟的影响

在众多地表通量模拟模型和遥感通量反演模型中,空气动力学粗糙度(z0)是一个重要的地表参数．选取代表典型农田的禹城站,代表复杂下垫面的千烟洲站和代表森林下垫面的长白山站3个通量观测站的风速和温度廓线资料,运用最小二乘法拟合迭代,分别计算得到各站点通量塔所在地的零平面位移和空气动力学粗糙度．在此基础上,分别分析不同下垫面的空气动力学粗糙度随作物高度和叶面积指数(LAI)、风向(地形)、风速、摩擦速度等因子的变化．并采用SEBS模型分析地表空气动力学粗糙度动态变化对地表通量计算的影响．结果表明:空气动力学粗糙度随植被特征(如作物高度,叶面积指数等)以及风向、风速和摩擦速度等因子而变化．禹城和长白山站通量塔所在风浪区的空气动力学粗糙度明显随作物生长期植被高度及叶面积指数变化,即先随LAI增加而增加,达到峰值后,随LAI增加而减小;千烟洲叶面积指数变化较小,空气动力学粗糙度随叶面积指数的变化不明显;地形较平坦的禹城和长白山站空气动力学粗糙度随风向变化较小,而地形起伏较大的千烟洲站空气动力学粗糙度随风向变化较大．随着风速的变化,禹城站空气动力学粗糙度没有明显变化,而千烟洲和长白山空气动力学粗糙度表现出随风速增加而减小的趋势．各站空气动力学粗糙度的这种动态变化对模型通量反演有较大影响,通过模型分析, 5月1日～6月3日禹城空气动力学粗糙度日平均值、千烟洲及长白山通量塔空气动力学粗糙度5d平均值与模型所取z0值相比,由于z0的动态变化造成相同时间尺度显热通量H的计算相对误差的绝对值最大可分别达到2．726％,33．802％和18．105％．

黄土丘陵区典型植物群落根系垂直分布与环境因子的关系

深入研究植被恢复过程中根系与环境因子的响应规律,对于当前西部地区的生态环境建设中有关林草措施的配置问题具有重要理论意义和实践价值。采用对应分析(CA)和典范对应分析(CCA)方法研究黄土丘陵区4种典型植物群落的根系垂直分布特征及其与环境因子的关系。结果表明,所选群落的根系生物量随土层深度增加而明显减小,0~40 cm土层根系生物量超过总根量的85%。借助CA分析将根系的垂直分布特征分为T1、T2和T3,其中大多数群落属于T1型,即表层根量聚积型,0~20 cm土层根量远高于其他层次;T2和T3型为深根与浅根型根系的组合类型,层次变化相对缓和。群落根系的垂直分布及变化受环境因子的综合影响,T1型分布在硝态氮含量较高且有机质和全氮含量较低的地段;T2和T3型的有机质和全氮含量较高,硝态氮含量较低;土壤水分含量、密度、硝态氮是影响退耕地典型植物群落根系垂直分布特征的主要环境因子。

施肥对日本落叶松不同根序细根养分浓度的影响

以辽宁东部山区16年生日本落叶松人工林为对象,探讨施肥对落叶松1～5级不同根序等级细根养分浓度的变化.结果表明:不同根序等级细根全碳浓度差异不显著,施肥对各级根序全碳浓度没有显著影响;在前5级根序中,1级根非结构性碳水化合物(TNC)浓度最低,N和P浓度最高;而5级根TNC浓度最高,N和P浓度最低.TNC浓度随着根序增加而升高,N和P浓度则相应下降.施肥仅对1级根组织中N和P浓度有显著影响;不同根序根组织中C/N/P具有明显差异,1级根平均C/N/P为423∶16∶1,5级根为726∶16∶1,随着根序增加,C在3种元素中的比例显著增加,而N的比例变化不大.施N肥并没有改变C的比例;但施P肥或施N+P肥均降低了前3级根(0～10cm)或前2级根(10～20cm)C和N在3种元素中的比例.

土壤溶解性有机碳(DOC)的影响因子及生态效应

土壤溶解性有机碳(DOC)是陆地生态系统中极为活跃的有机组分,是土壤圈层与相关圈层(如生物圈、大气圈、水圈和岩石圈等)发生物质交换的重要形式。影响土壤中物质的溶解、吸附、解吸、吸收、迁移乃至生物毒性等行为之外,对温室气体CH4的排放、水体水质的污染、岩石圈的风化等的影响也不可忽视。本文以陆地生态系统的中的DOC为主体,探讨了DOC的生态环境意义及其对大气、水体和岩石圈的影响以及DOC对土壤管理措施的响应。

基于MODIS数据的中国陆面制图:方法软件和数据产品(英文)

本文介绍一个自动处理MODIS1B数据并生产覆盖全中国陆面产品的软件系统。该算法改进了LAI(MOD15),土地覆被分类(MOD12),云检测(MOD35),陆面反射率(MOD09)和气溶胶(MOD04)产品。这些算法的输入数据都是本地获取的参数,能够有效降低其带来的不确定性。产生的部分新产品是NASA标准产品中没有的,包括森林火烧迹地和PAR。数据处理系统运行于中国科学院资源与环境数据中心。

新型非离子表面活性剂的合成与表征

制备了不同碳链长度的二元环氧化合物,并使其与聚合度为8～9的聚氧乙烯(PEO)或SPAN80反应,合成了含有不同长度间隔链的双亲水基表面活性剂. 用傅立叶红外光谱仪和核磁共振仪对其结构进行了表征. 实验结果表明,具有疏水性间隔链的双亲水基表面活性剂具有良好的表面活性,其表面活性不仅比单亲水基表面活性剂的大,且可随着疏水间隔链长度的增加而增大.

Crystallization kinetics of narrow molecular weight distribution metallocene short-chain-branched polyethylene

Isothermal and non-isothermal crystallization kinetics of three metallocene-catalysed short-chain-branched polyethylene (SCBPE) fractions with different degree of branching were investigated by using differential scanning calorimetry (DSC). Narrow molecular weight fractions (M-w = 20,000 and M-w/M-n < 1.15) are used and the degree of branching (CH3 per 1000C) are 1.6, 10.4, 40 respectively. The regime I - II transition temperature are 119.8C, 115.9 degreesC, 113.3 degreesC with the decreasing of degree of branching. Increasing the branch content decreases the rate of secondary nucleation, i,relative to the rate of surface spreading and so increases the range of supercooling over which regime I exists. The rate of bulk crystallization for both isothermal and non-isothermal crystallization decreases with the increasing of degree of branching. Both Ozawa Equation and Kissinger Equation are invalid for non-isothermal crystallization kinetics of SCBPE fractions,that means the effects of the branched chain on crystallization process are more complex than expected.

窄分子量分布茂金属短链支化聚乙烯结晶动力学

本工作用DSC方法对三种不同支化度的茂金属短链支化聚乙烯的等温、非等温结晶行为进行了研究 .样品为乙烯和己烯 1的共聚物 ,短支链主要为正丁基 ,分子量Mw =2 0 ,0 0 0 ,Mw/Mn<1 15 ,支化度 (每10 0 0C中CH3 数目 )分别为 1 6、10 4、40 .实验结果表明 ,茂金属短链支化聚乙烯结晶方式Ⅰ Ⅱ转变温度随支化度增加而降低 ,分别为 119 8℃、115 9℃、113 3℃ ;同时支链的存在降低了二次成核速率 ,增大了方式Ⅰ的结晶范围 ,总的结晶速度随支化度增大而减小

Synthesis and crystal structure of (1,3-(Bu2C5H3)-Bu-t)(2)Sm(mu-Cl)(2)Li(THF)(2)

Anhydrous SmCl3 reacts with two equal of Li(1-3-(Bu2C5H3)-Bu-t) to give a complex (1,3-(Bu2C5H3)-Bu-t)(2) Sm(mu -Cl)(2)Li(THF)(2) (C34H58Cl2LiO2Sm, M-r = 726.99), monoclinic, space group P2(1)/n, a = 10.615(2), b = 21.037(4), c = 17.166(3) Angstrom, beta = 93.60(3)degrees, V = 3825.7 (13) Angstrom (3), Z = 4, D-c = 1.262 Mg/m(3), mu = 1.699 mm(-1) and F(000) = 1508, final R = 0.0387 and wR = 0.0741 for 5320 observed[I greater than or equal to2 sigma (I)] reflections. The average Sm - C distance is 2.73 Angstrom. Sm - Cl1 and Sm - Cl2 distances are 2.719 (2) and 2. 697 (2) Angstrom, respectively. Two 1, 3-(Bu2C5H3)-Bu-t-ring centroids and two mu (2)-bridging chloride atoms around Sm atom form a distorted tetrahedron.

Ion/neutral complex-mediated reactions generated from some ionized tetrahydroimidazole-substituted methylene beta-diketones

The dissociation of gaseous metastable ions of m/z 153 and the formation of ions of m/z 139 from the unimolecular fragmentations of ionized tetrahydroimidazole-substituted methylene beta-diketones were examined by tandem mass spectrometry. In addition, some other fragments accompanying the elimination of either an H2O molecule or an CHO. radical were also observed in the collision-induced dissociation spectra of molecular ions of the compounds bearing an aromatic ring. Collision-induced dissociation and isotopic labeling showed that these processes may involve reactions of intermediate ion/neutral complexes and multistep rearrangements. The corresponding mechanisms are discussed. (C) 1997 by John Wiley & Sons, Ltd.

富勒烯碳-60,碳-70的电化学研究进展

短短的几年,随着各种物理与化学研究方法的相继介入,以C_(60)和C_(70)为代表的富勒烯研究取得了令人瞩目的成就。跟踪最新进展,引文41篇,本文就其电化学方面的研究工作做了系统的综述。

SYNTHESES OF BIS(TERT-BUTYLCYCLOPENTADIENYL)LANTHANOID CHLORIDE COMPLEXES AND CRYSTAL-STRUCTURES OF BIS(TERT-BUTYLCYCLOPENTADIENYL)CHLORO(BISTETRAHYDROFURAN)-PRASEODYMIUM AND BIS(TERT-BUTYLCYCLOPENTADIENYL)-CHLOROTETRAHYDROFURANYTTERBIUM

Reaction of lanthanoid trichloride with two equivalents of sodium t-butylcyclopentadienide in tetrahydrofuran affords bis(t-butylcyclopentadienyl)lanthanoid chloride complexes (t-BuCp)2LnCl. nTHF (Ln = Pr, Nd, n = 2; Ln = Gd, Yb, n = 1). The compound (t-BuCp)2PrCl.2THF (1) crystallizes from THF in monoclinic space group P2(1)/c with unit cell dimensions a = 15.080(3), b = 8.855(2), c = 21.196(5) angstrom, beta = 110.34(2)degrees, V = 2653.9 angstrom-3 and D(calcd) = 1.41 g/cm3 for Z = 4. The central metal Pr is coordinated to two t-BuCp ring centroids, one chlorine atom and two THF forming a distorted trigonal bipyramid. The crystal of (t-BuCp)2YbCl.THF (2) belongs to the monoclinic crystal system, space group P2(1)/n with a = 7.726(1), b = 12.554(2), c = 23.200(6) angstrom, beta = 97.77(2)degrees, V = 2229.56 angstrom-3, D(calcd) = 1.50 g/cm3 and Z = 4. The t-BuCp ring centroids, the chlorine atom and the oxygen atom of the THF describe a distorted tetrahedron around the central ion of ytterbium.

Cloning of cytoplasmic heat shock protein 90 (FcHSP90) from Fenneropenaeus chinensis and its expression response to heat shock and hypoxia

Heat shock protein 90 (HSP90) works as a multi-functional chaperone and is involved in the regulation of many essential cellular pathways. In this study, we have identified a full-length complementary DNA (cDNA) of HSP90 (FcHSP90) from Chinese shrimp Fenneropenaeus chinensis. FcHSP90 full-length cDNA comprised 2,552 bp, including a 2,181-bp open reading frame encoding 726 amino acids. Both homology analyses using alignment with previously identified HSP90 and a phylogeny tree indicated that FcHSP90 was a cytoplasmic HSP90. Real-time reverse transcription polymerase chain reaction analysis revealed that FcHSP90 was ubiquitously expressed in all the examined tissues but with highest levels in ovary of F. chinensis. FcHSP90 mRNA levels were sensitively induced by heat shock (from 25A degrees C to 35A degrees C) and reached the maximum at 6 h during heat shock treatment. Under hypoxia conditions, FcHSP90 mRNA levels, in both hemocytes and gill, were induced at 2 h and depressed at 8 h during hypoxia stress. The assessment of FcHSP90 mRNA levels under heat shock and hypoxia stresses indicated that the transcription of FcHSP90 was very sensitive to heat shock and hypoxia, so we deduced that FcHSP90 might play very important roles for shrimp to cope with environmental stress.