Ancillary ligand effects : from zirconium(IV)-catalyzed homogeneous propylene polymerization to platinum(II)-mediated C-H bond activation

<p>A series of C_s- and C₁-symmetric doubly-linked ansa-metallocenes of the general formula {1,1'-SiMe₂-2,2'-E-('ƞp>5p>-C₅H₂-4-Rp>1p>)-(ƞp>5p>-C₅H-3',5'-(CHMe₂)₂)}ZrC₂ (E = SiMe₂ (1), SiPh₂ (2), SiMe₂ -SiMe₂ (3); Rp>1p> = H, CHMe₂, C₅H₉, C₆H₁₁, C₆H₅) has been prepared. When activated by methylaluminoxane, these are active propylene polymerization catalysts. 1 and 2 produce syndiotactic polypropylenes, and 3 produces isotactic polypropylenes. Site epimerization is the major pathway for stereoerror formation for 1 and 2. In addition, the polymer chain has slightly stronger steric interaction with the diphenylsilylene linker than with the dimethylsilylene linker. This results in more frequent site epimerization and reduced syndiospecificity for 2 compared to 1. p> <p>C₁-Symmetric ansa-zirconocenes [1,1 '-SiMe₂-(C₅H₄)-(3-R-C₅H₃)]ZrCl₂ (4), [1,1 '-SiMe₂-(C₅H₄)-(2,4-R₂-C₅H₂)]ZrCl₂ (5) and [1,1 '-SiMe₂-2,2 '-(SiMe₂-SiMe₂)-(C₅H₃)-( 4-R-C₅H₂)]ZrCl₂ (6) have been prepared to probe the origin of isospecificity in 3. While 4 and 3 produce polymers with similar isospecificity, 5 and 6 give mostly hemi-isotactic-like polymers. It is proposed that the facile site epimerization via an associative pathway allows rapid equilibration of the polymer chain between the isospecific and aspecific insertion sites. This results in more frequent insertion from the isospecific site, which has a lower kinetic barrier for chain propagation. On the other hand, site epimerization for 5 and 6 is slow. This leads to mostly alternating insertion from the isospecific and aspecific sites, and consequently, a hemi-isotactic-like polymers. In comparison, site epimerization is even slower for 3, but enchainment from the aspecific site has an extremely high kinetic barrier for monomer coordination. Therefore, enchainment occurs preferentially from the isospecific site to produce isotactic polymers. p> <p>A series of cationic complexes [(ArN=CR-CR=NAr)PtMe(L)]p>+p>[BF₄]p>+p> (Ar = aryl; R = H, CH₃; L = water, trifluoroethanol) has been prepared. They react smoothly with benzene at approximately room temperature in trifluoroethanol solvent to yield methane and the corresponding phenyl Pt(II) cations, via Pt(IV)-methyl-phenyl-hydride intermediates. The reaction products of methyl-substituted benzenes suggest an inherent reactivity preference for aromatic over benzylic C-H bond activation, which can however be overridden by steric effects. For the reaction of benzene with cationic Pt(II) complexes, in which the diimine ligands bear 3,5-disubstituted aryl groups at the nitrogen atoms, the rate-determining step is C-H bond activation. For the more sterically crowded analogs with 2,6-dimethyl-substituted aryl groups, benzene coordination becomes rate-determining. The more electron-rich the ligand, as reflected by the CO stretching frequency in the IR spectrum of the corresponding cationic carbonyl complex, the faster the rate of C-H bond activation. This finding, however, does not reflect the actual C-H bond activation process, but rather reflects only the relative ease of solvent molecules displacing water molecules to initiate the reaction. That is, the change in rates is mostly due to a ground state effect. Several lines of evidence suggest that associative substitution pathways operate to get the hydrocarbon substrate into, and out of, the coordination sphere; i.e., that benzene substitution proceeds by a solvent- (TFE-) assisted associative pathway. p>

植物N;P���量化学：中国高等之外的分异规律与野外试验初步验证

元素化学计量学指从化学计量学的角度出发，通过分析比较生命物质不同结构层次（分子、细胞、器官、机体、种群、群落等）或生态系统中元素的相对比值，来研究各层次相互之间以及生态学过程中元素之间的关系。生态化学计量学研究可以把生态实体的各个层次存元素水平上统一起来，足近年来新兴的一个生态学研究领域，广泛应用于生态学研究中。C，N，P���生物地球化学循环中的重要元素，在生态系统中占有重要地位，许多环境问题都与它们有关，由此这三种元素的化学计量学受到生态学家们的普遍关注。C:N:P���学计量学在水生生态系统中研究较为深入，目前已发展到染色体水平，而在陆地生态系统中的研究较为匮乏近年来由于人类活动的强烈影响，这三种元素的循环在速度和规模上都发生了前所未有的改变，导致一系列环境问题的出现，因此C：N:P���学计量学在陆地生态系统中的研究就显得尤为重要。作为地球生命存在基础的绿色植物，在地球上已有数亿年的演化历史，研究陆地植物的元素化学计量学不仅有助于深入了解植物存在于地球上的内在机制，而且可以为许多环境问题的解决提供理论依据。本文首先建立中国不同地区植物氮磷含量数据库，通过数据分析找出一般规律，并进一步揭示植物不同进化阶段N:P���学计量比的变化规律。在此基础上，通过在内蒙古羊草草原设立不同施肥样地来模拟自然界不同氮磷环境，从试验水平上研究不同施肥处理及施肥梯度下生态系统中氮、磷、有机质的变化规律，并从化学计量学角度研究其内在机制。 利州新建成的中国维管植物数据库（包含1603种植物）研究了不同进化水平以及不同功能群（生活型）间植物N:P���的变化规律，并沿胡焕庸线（胡线）把中团分为为东西两部分，从总体水平上对比了东、西部间叫植物氮磷含量以及N：P���异同。结果表明：l）从演化水平来看，尽管氮磷含量表现出极大的差异，除豆科植物外，植物N：P���本保持稳定水平;2）木本植物与草本植物的N：P���差异．显著，木本植物之间（常绿乔木，常绿灌木，落叶乔木，落叶灌木）N：P���具有显著差异;3）中国东西部植物养分含量和N：P���表现出极显著差异，东部的养分含量低于西部，而N:P���著高于西部。 在内蒙古羊草草原两块永久实验样地（样地A：1980年围封样地和样地B：1999年田封样地）进行了为期两年的N素和P���添加试验。氮素添加梯度为0，5，15，30，50，80 g NHN03.m.2.yr-1。P���添加梯度为0，2，4，8，16，and 32 g P2Osm-2 yr-1（仪分析了羊草器官的结果）。分别从植物器官、物种、功能群水平研究了N素添加对N:P���学计量学的影响，此外还研究了土壤和凋落物C：N:P���学计量学对N素添加的响应。结合生物量的变化趋势，探讨了元素化学计量学对养分状况的指示作用。 1．羊草器官对施肥的响应结果表明，添加N素可以显著提高羊草器官中的含N量，p���可以显著提高器官中的含P���：除2001年样地A中的根茎外，根茎中的含P���基本不受N素添加的影响;茎中的含P���同样表现出不受N素添加影响的趋势（2000年B区茎除外）：N素添加可以显著增大羊草叶片中的含P���(B区2000年叶片除外)。P���添加对羊草器官的含N量没有影响;羊草器官中的氮磷含量施肥处理下表现出显著的正相关关系（N素添加下B区叶片除外）。N素添加对羊草器官的N:P���没有显著影响（A区茎2000年和B区叶片2000年除外）：P���添加显著降低了羊草器官中的N:P���。 2．四种优势植物（羊草、羽茅、针茅和苔草）地上生物量和N:P���学计量学对氮肥的响应研究发现，四个物种的氮磷含量均具有极显著相关关系;氮肥可以显著提高样地A中的羽茅生物量，降低苔草的生物量，而使样地B中的羊草生物量增大;两块样地中，四个物种的氮磷含量及N：P���均随N素水平的增高而增大（样地A中的羽茅N:P���除外）。 3．基于生活型划分的功能群（多年生根茎禾草，多年生丛生禾草，豆科植物，多年生杂类草，一二年生植物，灌木和半灌木）对N素添加的响应研究表明：施N可以提高样地A中的多年生丛生禾草的生物量，而使样地B中的多年生根苇禾草增加;多年生杂类草的相对多度在两个样地中均随施氨水平的增加而显著 降低：在样地B中，施氮可以显著提高不同功能群的氮磷含量;在样地A中，功能群N、P���量对施肥的响应并没有一致的变化规律，添加N素可以显著提高不同功能群的含N量（豆科植物除外），多年生根茎禾草和多年生杂类草的P���量有显著增大的趋势（P < 0.005），而其它功能群（豆科植物、灌木和小半灌木、多年生杂类草和～二年生杂类草）的P���量基本恒定（P>0.05）;在样地A中，多年生丛生禾草，多年生杂类草，一二年生植物，灌木和半灌木的N：P���随施氨水平的增加而显著增大，多年生根茎禾草和豆科植物的N:P���基本不变;在样地B中，多年生丛生禾草的N:P���随施氨水平的增加而显著增大，多年生根茎禾草、多年生杂类草和…二年生杂类草不受施氨水平的影响。 4．添加N素对根实验结果表明：两块样地中，上层根(0-10 cm)的生物量仅在施N后第一年显著增加，而下层根(10-20 cm)的地下生物量在两年的施N处理下均不受施肥梯度的影响i在样地A中，施肥后第一年对根的N、P���量影响不显著，施肥后第二年可以显著增大上层根的N、P���量;在样地B中，添加N素后第一年可以显著增大根的含P���; 在两个样地中，两年的N肥处理对根的N：P���没有显著影响：在施氨处理中，根的N、P���量及N:P���在施肥第一年的响应要高于第二年。 5．所有处理中，上层土壤(O-lO cm)养分含量（有机碳，全氮，全磷）均高于下层土壤（10-20 cm）;在样地A中，氮素添加对r十壤有机碳没有显著性作用，在施肥第一年可以显著增加上层土壤的N、P���量，而在施肥后第二年对土壤N、P���量没有显著影响;在样地B中，添加N素对两年的土壤养分均没有显著影响：养分添加两个样地土壤中的元素比值（C:N比，C:P���，N:P���）没有显著影响;土壤养分对施N一年后的响应要高于第二年。 6．养分添加对凋落物化学特征及化学计量学特征的影响研究结果表明：凋落物现存量不受施肥的影响;2001年凋落物现存量与2000年和2001年的地上生物量相关关系不显著;添加N素可以显著提高凋落物的N含量，而对有机碳含量和P���量没有显著影响;凋落物C：N比随施肥梯度的增大而显著降低，N:P���显著增高，而C:P���没有明显变化。 以上研究结果表明，不同植物功能群的N:P���存在差异，人类活动强烈影响自然植被中的植物N：P���;但植物的N：P���不受植物进化的影响（豆科植物除外）;由于植物已有数亿年的演化历史，同时N与P���植物的结构和功能上具有密切的联系，在生物地球化学循环中办存在耦合作用。因此植物N：P���值恒定可能是一普适性规律。 N素添加试验表明，在植物根、地上器官、物种和功能群水平上N与P���呈显著正相关关系，反映了植物体内的氮磷含量具有协同作用。共存种对N肥的响应不同，表明物种受不同元素的制约。因此除非把生态系统中所有物种对施肥的响应刻画清楚，笼统的认定生态系统缺乏某种元素是不适当的。 施肥试验表明，两种围封时间样地的主要限制性元素不同。极度退化(样地B)植物生长主要缺N，而在保护较好样地(样地A)，P���逐步成为一种限制因素。反映了随着保护时间的增加，植物生长逐渐由N限制型向N、P���同限制型过渡。添加的养分要么被植物吸收，挥发到大气中，或以凋落物的形式返还到土壤表层。但是对养分的预算有待于进一步研究。土壤中的养分含量对N素添加有…个滞后效应，而植物响应较为迅速。功能群N:P���在施肥实验中不能保持恒定，可能是由于实验时间较短的缘故;化学计量学的研究表明羊草草原分解凋落物的微生物受P���的制约，可能是由于植物体内具有高的P���再转运机制。这一结论有待于进一步的验证。氮肥降低了凋落物的C:N比，因此凋落物的分解速率可能将要发生改变。这需要进一步开展C循环的研究。

Numerical simulation of nc-Si : H/c-Si heterojunction solar cells

AMPS simulator, which was developed by Pennsylvania State University, has been used to simulate photovoltaic performances of nc-Si:H/c-Si solar cells. It is shown that interface states are essential factors prominently influencing open circuit voltages (V-OC) and fill factors (FF) of these structured solar cells. Short circuit current density (J(SC)) or spectral response seems more sensitive to the thickness of intrinsic a-Si:H buffer layers inserted into n(+)-nc-Si:H layer and p-c-Si substrates. Impacts of bandgap offset on solar cell performances have also been analyzed. As DeltaE(C) increases, degradation of VOC and FF owing to interface states are dramatically recovered. This implies that the interface state cannot merely be regarded as carrier recombination centres, and impacts of interfacial layer on devices need further investigation. Theoretical maximum efficiency of up to 31.17% (AM1.5,100mW/cm(2), 0.40-1.1mum) has been obtained with BSF structure, idealized light-trapping effect(R-F=0, R-B=1) and no interface states.

含有C，H，O有机化合物结构解析专家系统的研究

本文系统地介绍了一个有机化合物结构解析专家系统的研究过程，该系统包括约束知识库，整体结构产生器，和结构验证器三个部分。本工作侧重两个部分，即约束规则的生成和整体结构对接。所涉及的章节为第六——十章。第一——五章为本论文的文献综述部分。第六章介绍了结构解析专家系统的总体设计及理论依据，我们的专家系统的总体设计是：由分子式或光谱数据出发，推导出与未知化合物的分子式和光谱数据相一致的结构片断。应用离散数学，布尔代数，图论，数理逻辑，拓扑学，组合数学等各种理论手段，将结构片断穷举生成整体结构，即候选化合物。最后应用模式识别，波谱模拟，涨力能计算等方法进行结构验证，自动排除与各种约束条件不一致的候选化合物，以求得该未知化合物的最终结构。在理想的情况下，最终结构应是唯一的。对于复杂的化合物，系统可能给出一组最终结构。结构输出采用Carhart方案，即以化合物结构的二维联接表为基础，首先生成三维空间的一个构象，之后再投影到二维平面上。第七章是利用~（13）C-NMR波谱信息以产生结构生成的约束规则。具体方法是利用我们已建立的CIAC-~（13）C-NMR数据库系统进行~（13）-NMR化学位移与带有键属性的子结构相关研究。首先根据文献选出化合物中常见的子结构，进行数据库检索并统计出有关的化学位移。建立子结构与~（13）C-NMR化学位移相关表，当进行未知化合物的结构解析时，应用上述相关表寻找出未知化合物中的子结构约束条件。为了确保知识库的全面性以及结构生成的穷举性，第八章介绍一个子结构自动生成算法。其算法的思路是：首先选出常见元素的所有的基本结构基元，依次以每个结构基元为中心，然后考虑它与所有选定的结构基元联接情况。上述两种方案所得的相关表中的子结构是含有多种杂原子的，录O，N，S，P���卤素等。第九章介绍一个整体结构生成的算法及原理和程序设计思想。整体结构生成的过程是：首先生成一级亚结构向量，然后生成二级亚结构向量，再生成三级亚结构向量，由三级结构碎片进行对接，得到整体结构。目前该系统仅可对接含有C，H，O的化合物。第十章给出两个结构解析示例。

纳米硅(nc-Si:H )/晶体硅(c-Si)异质结太阳电池的数值模拟分析

运用美国宾州大学发展的AMPS程序模拟分析了n-型纳米硅(n+-nc-Si:H)/p-型晶体硅(p-c-Si)异质结太阳电池的光伏特性.分析表明,界面缺陷态是决定电池性能的关键因素,显著影响电池的开路电压(VOC)和填充因子(FF),而电池的光谱响应或短路电流密度(JSC)对缓冲层的厚度较为敏感.对不同能带补偿(bandgap offset)的情况所进行的模拟分析表明,随着ΔEc的增大,由于界面态所带来的开路电压和填充因子的减小逐渐被消除,当ΔEc达到0.5eV左右时界面态的影响几乎完全被掩盖.界面层的其他能带结构特征对器件性能的影响还有待进一步研究.最后计算得到了这种电池理想情况下(无界面态、有背面场、正背面反射率分别为0和1)的理论极限效率ηmax=31.17% (AM1.5,100mW/cm2,0.40-1.10μm波段).

全球变化背景下科尔沁沙地生态系统C、N循环过程

工业革命以来，由于人口的快速增加和人类活动的强烈干扰（主要包括煤炭、石油等石化燃料的燃烧、化肥生产和使用）导致土地利用/覆被变化、大气CO2浓度升高、N沉降等一系列全球环境变化问题。有关陆地生态系统生物地球化学循环，尤其是陆地生态系统C、N循环及其耦合过程方面的研究成为全球变化科学研究领域的重要内容。 干旱/半干旱地区占地球陆地总面积的1/3。与湿润地区相比较，干旱/半干旱地区生态系统稳定性比较差，往往属于生态脆弱区。因此，全球变化对干旱/半干旱地区生态系统影响更加敏感。科尔沁沙地位于我国北方干旱/半干旱地区，是我国典型的农牧交错区和生态脆弱区。科尔沁沙地是世界上人口密度最高的干旱/半干旱地区之一，人类活动对其影响剧烈。然而，有关科尔沁沙地生态系统C、N元素生物地球化学循环过程对土地利用/覆被变化、N沉降等全球变化响应及其反馈机制的研究非常缺乏。因此，本文以科尔沁沙地退化沙质草地、农田、不同年龄樟子松和杨树人工林等生态系统为对象，开展了造林、模拟N沉降和凋落物管理对生态系统C、N元素循环过程影响的研究。 在科尔沁沙地东南缘，以退化沙质草地、樟子松（Pinus sylvestris var. mongolica）人工林（15、24和30年生）、杨树（Poplus xiaozhuanica）人工林（7、11和15年生）为对象，研究草地转变为林地对生态系统C、N储量影响；以退化草地、榆树疏林草地和32年生樟子松人工林为对象，比较草地造林对土壤C、N循环过程及其土壤微生物性状的影响；以农田和5、10、15年生杨树人工林为对象，研究退耕还林对生态系统C、N储量和循环过程影响；以35年生樟子松人工林为对象，模拟研究N沉降和凋落物管理对生态系统C、N循环过程影响。通过上述研究，得到以下主要结果： （1）草地生态系统总C储量为34.38 Mg ha-1，15、24和30年生樟子松人工林生态系统总C储量分别为43.56、60.45和66.59 Mg ha-1，7、11和15年生杨树人工林生态系统总C储量分别为34.54、48.26和78.77 Mg ha-1；与农田相比，退耕5年的杨树人工林生态系统总C库储量下降13%，而10年和15年杨树人工林分别增加了176%和5倍；随着人工林年龄的增加，地上植被生物量C库储量占生态系统总C库储量的比例逐渐增加，并主要分配在树干。草地生态系统总N库储量为2.54 Mg ha-1，15、24和30年生樟子松人工林生态系统总N库储量分别为1.96、2.10和2.19 Mg ha-1，7、11和15年生杨树人工林生态系统总N库储量分别为2.27、1.84和2.60 Mg ha-1；与农田相比，退耕5年的杨树人工林生态系统总N库储量下降32%，而10年和15年杨树人工林分别增加了47%和76%；农田和草地造林后生态系统N储量依然主要分配在土壤中。 （2）草地和农田造林后土壤C、N库储量的变化受多因子的影响，例如林龄、树种种类以及立地条件等。农田和草地造林初期，土壤C、N库储量表现出下降趋势，随着林龄的增加，土壤C、N储量逐渐恢复。草地营造樟子松人工林30年后，0–60 cm深度土壤C、N储量依然显著低于草地；与草地相比，15年生杨树人工林土壤C、N储量差异不显著。在立地条件较好的情况下，10年杨树人工林土壤C、N储量已显著高于农田；然而，在立地条件相对较差的情况下，15年杨树人工林土壤C、N储量仍然与农田相比差异不显著。 （3）土地利用变化能够强烈地改变土壤C、N循环过程。与草地或疏林草地相比，32年生樟子松人工林土壤C、N、P���量显著降低；土壤C、N矿化过程发生显著变化，并且受季节变化的影响；在不同季节，土壤微生物量碳含量、代谢熵（qCO2）、微生物熵（MBC/TOC）以及土壤酶活性等在不同土地利用条件下表现出规律不一致。同样，农田退耕杨树人工林能够显著影响土壤C、N矿化过程，土壤无机氮（铵态氮+硝态氮）含量，土壤微生物量碳含量以及土壤微生物活性。草地造林在一定程度上导致土壤质量下降。而农田造林有利于土壤质量改善，尤其在在立地条件较好情况下。 （4）N添加增加对沙地樟子松人工林地上和地下C、N元素含量影响不大；N添加1年后，仅林下植被C、N含量显著增加，高氮处理（N15）凋落物N含量显著增加。N添加抑制了沙地樟子松人工林凋落物的早期分解和N、P���素释放。5、6、8和9月份土壤无机N含量均随着N输入增加表现出一定程度的增加，然而，7月份N添加导致土壤无机N含量降低。N添加对土壤潜在N矿化速率影响不显著。7和8月份N添加影响土壤C矿化速率，而其它月份影响不显著。低氮处理（N5）有利于增加土壤微生物量碳含量，而高氮处理（N15）在一定程度上降低土壤微生物量碳含量。 （5）凋落物输入变化（凋落物添加和凋落物移出）在一定程度上改变了35年生沙地樟子松人工林生态系统C、N循环过程。凋落物移出（C0）增加了林下植被C含量，降低了树木叶片N含量。凋落物移出抑制了凋落物分解和P���素的释放，而增加了C元素的早期释放速率，对N元素释放过程影响不显著。凋落物输入变化对不同月份土壤无机N含量和土壤N矿化过程影响均不显著。仅在6月份凋落物移出显著抑制了土壤C矿化速率，其它月份差异均不显著。凋落物管理对土壤微生物量碳含量影响不显著。 以上研究结果表明，土地利用变化、N沉降和凋落物输入改变等能够影响半干旱地区沙地生态系统C、N储量和循环过程。尤其是土地利用变化强烈改变沙地生态系统C、N储量、分配格局和循环过程，并且受到多因子的影响。科尔沁沙地樟子松人工林生态系统C、N元素生物地球化学循环存在密切的耦合关系。今后有必要进一步结合3S技术、同位素技术、模型模拟以及分子生物学技术等，从微观-宏观不同尺度上，研究半干旱地区沙地生态系统C、N循环过程对全球变化的响应及其反馈机制。

Novel chemical synthesis of Pt-Ru-P electrocatalysts by hypophosphite deposition for enhanced methanol oxidation and CO tolerance in direct methanol fuel cell

A novel method was developed to prepare the highly active Pt-Ru-P/C catalyst. The deposition of phosphorus significantly increased electrochemical active surface (EAS) area of catalyst by reduces Pt-Ru particle size. TEM images show that Pt-Ru-P nanoparticles have an uniform size distribution with an average diameter of 2 nm. Cyclic voltammetry (CV), Chronoamperometry (CA), and CO stripping indicate that the presence of non-metal phosphorus as an interstitial species Pt-Ru-P/C catalyst shows high activity for the electro-oxidation of methanol, and exhibit enhanced performance in the oxidation of carbon monoxide compared with Pt-Ru/C catalyst. At 30 degrees C and pure oxygen was fed to the cathode, the maximum power density of direct methanol fuel cell (DMFC) with Pt-Ru-P/C and Pt-Ru/C catalysts as anode catalysts was 61.5 mW cm(-2) and 36.6 mW cm(-2), respectively. All experimental results indicate that Pt-Ru-P/C catalyst was the optimum anode catalyst for direct methanol fuel cell.

A carbon-supported Pd-P catalyst as the anodic catalyst in a direct formic acid fuel cell

In this paper, it is reported for the first time that a carbon-supported Pd-P (Pd-P/C) catalyst for the anodic catalyst in the direct formic acid fuel cell (DFAFC) can be prepared. The Pd-P/C catalyst shows that its electrocatalytic activity and especially its stability for the oxidation of formic acid are much higher than that of a Pd/C catalyst. Therefore, the Pd-P/C catalyst may have practical applications in DFAFCs.

PEK-C/PPS共混体系的相容性和结晶行为

结晶-非晶高聚物共混体系的相容性和结晶行为的研究已有许多报道。本工作研究了含酞侧基聚芳醚酮(PEK-C)与聚苯硫醚(PPS)共混物的相容性和结晶行为。 PEK-C为徐州工程塑料厂产品,未作封端处理,η?p/c=0.70;PPS为日本东丽产品。两者用双螺杆挤出机在320～350℃制成共混物。仪器为Perkin-Elmer DSC-7型差示扫描量热仪,升温速率10℃/min;DDV-Ⅱ-EA型全自动动态粘弹谱仪和理学D/max-ⅡBX-射线衍射仪。

Minor Moves: Growth, Fugitivity, and Children's Physical Movement

<p>From tendencies to reduce the Underground Railroad to the imperative "follow the north star" to the iconic images of Ruby Bridges' 1960 "step forward" on the stairs of William Frantz Elementary School, America prefers to picture freedom as an upwardly mobile development. This preoccupation with the subtractive and linear force of development makes it hard to hear the palpable steps of so many truant children marching in the Movement and renders illegible the nonlinear movements of minors in the Underground. Yet a black fugitive hugging a tree, a white boy walking alone in a field, or even pieces of a discarded raft floating downstream like remnants of child's play are constitutive gestures of the Underground's networks of care and escape. Responding to 19th-century Americanists and cultural studies scholars' important illumination of the child as central to national narratives of development and freedom, "Minor Moves" reads major literary narratives not for the child and development but for the fugitive trace of minor and growth.p><p> p><p>In four chapters, I trace the physical gestures of Nathaniel Hawthorne's Pearl, Harriet Beecher Stowe's Topsy, Harriet Wilson's Frado, and Mark Twain's Huck against the historical backdrop of the Fugitive Slave Act and the passing of the first compulsory education bills that made truancy illegal. I ask how, within a discourse of independence that fails to imagine any serious movements in the minor, we might understand the depictions of moving children as interrupting a U.S. preoccupation with normative development and recognize in them the emergence of an alternative imaginary. To attend to the movement of the minor is to attend to what the discursive order of a development-centered imaginary deems inconsequential and what its grammar can render only as mistakes. Engaging the insights of performance studies, I regard what these narratives depict as childish missteps (Topsy's spins, Frado's climbing the roof) as dances that trouble the narrative's discursive order. At the same time, drawing upon the observations of black studies and literary theory, I take note of the pressure these "minor moves" put on the literal grammar of the text (Stowe's run-on sentences and Hawthorne's shaky subject-verb agreements). I regard these ungrammatical moves as poetic ruptures from which emerges an alternative and prior force of the imaginary at work in these narratives--a force I call "growth." p><p>Reading these "minor moves" holds open the possibility of thinking about a generative association between blackness and childishness, one that neither supports racist ideas of biological inferiority nor mandates in the name of political uplift the subsequent repudiation of childishness. I argue that recognizing the fugitive force of growth indicated in the interplay between the conceptual and grammatical disjunctures of these minor moves opens a deeper understanding of agency and dependency that exceeds notions of arrested development and social death. For once we interrupt the desire to picture development (which is to say the desire to picture), dependency is no longer a state (of social death or arrested development) of what does not belong, but rather it is what Édouard Glissant might have called a "departure" (from "be[ing] a single being"). Topsy's hard-to-see pick-pocketing and Pearl's running amok with brown men in the market are not moves out of dependency but indeed social turns (a dance) by way of dependency. Dependent, moving and ungrammatical, the growth evidenced in these childish ruptures enables different stories about slavery, freedom, and childishness--ones that do not necessitate a repudiation of childishness in the name of freedom, but recognize in such minor moves a fugitive way out.p>

New Cu-Based Catalysts Supported on TiO2 Films for Ullmann SNAr-Type C-O Coupling Reactions

New routes for the preparation of highly active TiO2-supported Cu and CuZn catalysts have been developed for C-O coupling reactions. Slurries of a titania precursor were dip-coated onto glass beads to obtain either structured mesoporous or non-porous titania thin films. The Cu and CuZn nanoparticles, synthesized using a reduction by solvent method, were deposited onto calcined films to obtain a Cu loading of 2 wt%. The catalysts were characterized by inductively coupled plasma (ICP) spectroscopy, temperature-programmed oxidation/reduction (TPO/TPR) techniques, Cu-63 nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (S/TEM-EDX) and X-ray photo-electron spectroscopy (XPS). The activity and stability of the catalysts obtained have been studied in the C-O Ullmann coupling of 4-chloropyridine and potassium phenolate. The titania-supported nanoparticles retained catalyst activity for up to 12 h. However, catalyst deactivation was observed for longer operation times due to oxidation of the Cu nanoparticles. The oxidation rate could be significantly reduced over the CuZn/TiO2 catalytic films due to the presence of Zn. The 4-phenoxypyridine yield was 64% on the Cu/nonporous TiO2 at 120 degrees C. The highest product yield of 84% was obtained on the Cu/mesoporous TiO2 at 140 degrees C, corresponding to an initial reaction rate of 104 mmol g(cat)(-1) s(-1). The activation energy on the Cu/mesoporous TiO2 catalyst was found to be (144 +/- 5) kJ mol(-1), which is close to the value obtained for the reaction over unsupported CuZn nanoparticles (123 +/- 3 kJ mol(-1)) and almost twice the value observed over the catalysts deposited onto the non-porous TiO2 support (75 +/- 2 kJ mol(-1)).

Molecular characterisation of Alternaria linicola and its detection in linseed

Nucleotide sequences of the ribosomal DNA (rDNA) internal transcribed spacers (ITS) 1 and 2 and a 1068 bp section of the beta-tubulin gene divided seven designated species of Alternaria into five taxa. Stemphylium botryosum formed a sixth closely related taxon. Isolates of A. linicola possessed an identical ITS sequence to one group of A. solani isolates, and two clusters of A. linicola isolates, revealed from beta-tubulin gene data to show minor variation, were as genetically similar to isolates of A. solani as they were to each other. We suggest, therefore, that A. linicola falls within the species A. solani. Similar results suggest that A. lini falls within the species A. alternata. RAPD analysis of the total genomic DNA from the Alternaria spp. concurred with the nucleotide sequence analyses. An oligonucleotide primer (ALP) was selected from the rDNA ITS1 region of A. linicola/A. solani. PCR with primers ALP and ITS4 (from a conserved region of the rDNA) amplified a c. 536 bp fragment from isolates of A. linicola and A. solani but not from other Alternaria spp. nor from other fungi which may be associated with linseed. These primers amplified an identical fragment, confirmed by Southern hybridization, from DNA released from infected linseed seed and leaf tissues. These primers have the potential to be used also for the detection of A. solani in host tissues.