Polyolefin spheres from metallocenes supported on noninteracting polystyrene

To obviate the destructive interaction of highly reactive metallocene catalysts with classical silica-based supports while retaining the advantage of supported catalysts, a noninteracting polystyrene support was developed. Supported catalysts for the polymerization of alpha-olefins are prepared by treating lightly cross-linked, chloromethylated polystyrene beads consecutively with a secondary amine, an ammonium salt of a weakly coordinating anion, and a neutral dialkylmetallocene. Catalytic sites are distributed homogeneously throughout the support particle, and the polymerization occurs within the bead, in contrast to traditional surface-supported metallocene catalysts. The copolymerization of ethylene and 1-hexene at 40 degreesC affords discrete spherical polyolefin beads with a size (0.3 to 1.4 millimeters) that varies according to the polymerization time.     

High-strength welds in metallocene Polypropylene/Polyethylene laminates

Spectacular advances in organometallic chemistry over the past two decades have resulted in single-site catalysts that are revolutionizing production of polyethylene (PE) and isotactic polypropylene (iPP). This report describes an unanticipated benefit of metallocene-catalyzed semicrystalline polyolefins, namely welded joint strengths in PE/iPP laminates that can exceed the cohesive strength of the constituents. We propose that interfacial polymer entanglements, established in the molten state and subsequently anchored in chain-folded lamellae upon crystallization, are responsible for this intrinsic property. The poor adhesion exhibited by traditional Ziegler-Natta-catalyzed polyolefins is shown to derive from the accumulation of amorphous polymer, a by-product of the polymerization reactions, at the interface. These results should facilitate fabrication and improve the properties of composites based on materials that dominate the plastics industry.     

直链淀粉含量及淀粉平均聚合度对抗性淀粉含量影响的研究

直链淀粉含量与淀粉平均聚合度对抗性淀粉的形成有着重要的影响,以玉米淀粉、红薯淀粉、豌豆淀粉、绿豆淀粉为原料,采用普鲁兰酶和α-淀粉酶协同制备抗性淀粉,改变淀粉的直链淀粉含量和聚合度,分析淀粉直链淀粉含量及其聚合度与抗性淀粉含量的关系。结果表明,直链淀粉含量与抗性淀粉含量呈明显正相关,平均聚合度在一定范围内有利于提高抗性淀粉的含量。     

Efficient multistep photoinitiated electron transfer in a molecular pentad

A synthetic five-part molecular device has been prepared that uses a multistep electron transfer strategy similar to that of photosynthetic organisms to capture light energy and convert it to chemical potential in the form of long-lived charge separation. It consists of two covalently linked porphyrin moieties, one containing a zinc ion (P(Zn)) and the other present as the free base (P). The metailated porphyrin bears a carotenoid polyene (C) and the other a diquinone species (Q(A)-Q(B)). Excitation of the free-base porphyrin in a chloroform solution of the pentad yields an initial charge-separated state, C-P(Zn)-P(.+).-Q(A)(-)-Q(B), with a quantum yield of 0.85. Subsequent electron transfer steps lead to a final charge-separated state, C(.+)-P(Zn)-P-Q(A)-Q(B)(.-), which is formed with an overall quantum yield of 0.83 and has a lifetime of 55 microseconds. Irradiation of the free-base form of the pentad, C-P-P-Q(A)-Q(B), gives a similar charge-separated state with a lower quantum yield (0.15 in dichloromethane), although the lifetime is increased to approximately 340 microseconds. The artificial photosynthetic system preserves a significant fraction ( approximately 1.0 electron volt) of the initial excitation energy (1.9 electron volts) in the long-lived, charge-separated state.     

A carbon-free sandwich complex [(P5)2Ti]2-

Reactions of highly reduced titanium complexes with white phosphorus, P4, at or below 25 degrees C yielded brown to deep red-brown salts of the first entirely inorganic metallocene, [(eta5-P5)2Ti](2-)(1). Like ferrocene and other carbon-based metallocenes, the structure of 1 has parallel and planar five-membered rings symmetrically positioned about the central metal atom. Despite its electron-deficient (16 electron) and formally zerovalent titanium character, salts of 1 are highly stable toward heat and air, both in solution and in the solid state. Computational studies show that the pentaphosphacyclopentadienyl unit, P5, functions as an unusually effective acceptor ligand, and this results in substantial stabilization of 1.     

Hydrocarbon separations in a metal-organic framework with open iron(II) coordination sites

The energy costs associated with large-scale industrial separation of light hydrocarbons by cryogenic distillation could potentially be lowered through development of selective solid adsorbents that operate at higher temperatures. Here, the metal-organic framework Fe(2)(dobdc) (dobdc(4-) : 2,5-dioxido-1,4-benzenedicarboxylate) is demonstrated to exhibit excellent performance characteristics for separation of ethylene/ethane and propylene/propane mixtures at 318 kelvin. Breakthrough data obtained for these mixtures provide experimental validation of simulations, which in turn predict high selectivities and capacities of this material for the fractionation of methane/ethane/ethylene/acetylene mixtures, removal of acetylene impurities from ethylene, and membrane-based olefin/paraffin separations. Neutron powder diffraction data confirm a side-on coordination of acetylene, ethylene, and propylene at the iron(II) centers, while also providing solid-state structural characterization of the much weaker interactions of ethane and propane with the metal.     

Microstructure of Polymers by Tritium Autoradiography

Polystyrene, polypropylene, and polyethylene, containing tritiumlabeled additives and crystallized in thin films, were examined with autoradiographic stripping film. In the structures formed by isotactic polystyrene, tritiated atactic polymer concentrated in specific patterns in the outer regions. Polypropylene spherulites showed marked differences in the distribution of the tritiated additive, dilauryl thiodipropionate, whenever their optical properties also differed. Autoradiographs of polyethylene spherulites containing low molecular weight tritiated polyethylene exhibited concentric ring patterns similar to those observed on viewing the polymer film in a polarizing microscope.     

Disulfate ion as an intermediate to sulfuric Acid in Acid rain formation

The oxidation of the bisulfite ion by dissolved oxygen to produce sulfate ion involves the formation of a previously undetected intermediate. This intermediate has a fairly strong Raman band at 1090 wave numbers and a weak Raman band at 740 wave numbers, both of which are probably due to sulfur-oxygen stretches. The intermediate is proposed to be the disulfate ion S(2)O(7)(2-), which hydrolyzes into H(+) and either SO(4)(2-) or HSO(4)(2-) with a half-life of about 52 seconds at 25 degrees C.     

Interwoven metal-organic framework on a periodic minimal surface with extra-large pores

Interpenetration (catenation) has long been considered a major impediment in the achievement of stable and porous crystalline structures. A strategy for the design of highly porous and structurally stable networks makes use of metal-organic building blocks that can be assembled on a triply periodic P-minimal geometric surface to produce structures that are interpenetrating-more accurately considered as interwoven. We used 4,4',4"-benzene-1,3,5-triyl-tribenzoic acid (H(3)BTB), copper(II) nitrate, and N,N'-dimethylformamide (DMF) to prepare Cu(3)(BTB)(2)(H(2)O)(3).(DMF)(9)(H(2)O)(2) (MOF-14), whose structure reveals a pair of interwoven metal-organic frameworks that are mutually reinforced. The structure contains remarkably large pores, 16.4 angstroms in diameter, in which voluminous amounts of gases and organic solvents can be reversibly sorbed.     

Reactions of solvated electrons initiated by sodium atom ionization at the vacuum-liquid interface

Solvated electrons are powerful reagents in the liquid phase that break chemical bonds and thereby create additional reactive species, including hydrogen atoms. We explored the distinct chemistry that ensues when electrons are liberated near the liquid surface rather than within the bulk. Specifically, we detected the products resulting from exposure of liquid glycerol to a beam of sodium atoms. The Na atoms ionized in the surface region, generating electrons that reacted with deuterated glycerol, C(3)D(5)(OD)(3), to produce D atoms, D(2), D(2)O, and glycerol fragments. Surprisingly, 43 ± 4% of the D atoms traversed the interfacial region and desorbed into vacuum before attacking C-D bonds to produce D(2).     

Monodisperse metal clusters 10 angstroms in diameter in a polymeric host: the "monomer as solvent' approach

A general methodology is presented for the dispersion of an inorganic compound within an organic polymer host through the use of solubilizing and polymerizable ligands. The dispersion of metal cluster cations 10 angstroms in diameter within a polymer host is achieved by free-radical polymerization of the hexafunctional metal cluster [Mo(6)Cl(8)(NVI)(6)](triflate)(4) with bound polymerizable ligands in N-vinylimidazole (NVI) solutions. Copolymerization of the activated cluster-bound ligands with the surrounding medium probably plays a key role in preventing aggregation and produces near monodisperse molecular clusters within the polymer matrix.     

聚合物键合Cu(Salen)的合成及其对丙硫醇的催化氧化

合成了4，4＇-二乙烯基双水杨醛缩乙二胺（1），将（1）与苯乙烯共聚得聚合物键合双水杨醛缩乙二胺（2），（2）与铜离子螯合得聚合物键合双水杨醛缩乙二胺合铜（Ⅱ）（3）。考察了（3）对丙硫醇的催化氧化作用，用IR、UV、^1HNMR和MS方法对相关化合物的结构进行了表征。     

利用HPLC／MS对野山参和林下参皂苷的分析

为了明确野山参和林下参中人参皂苷的组成特征及差异所在,利用高效液相色谱-质谱联用仪对野山参和林下参中电苷进行分析测定。结果表明：野山参和林下参中均含有常见的9种人参皂苷（Re、Rg1、Ro、Rf、Rg2、Rb1、Rc、Rb2、Rd）,野山参中还检测到三七皂苷R1、R2和R3以及丙二酰基人参皂苷Rb1和Rc,林下参仅检测到了丙二酰基人参皂苷Rh1、Rc和Rd,没有检测到三七皂苷R1和R3;林下参中Re含量显著高于野山参,平均含量为5．042g／mg,二者达到极显著差异（P〈0．01）,野山参和林下参中其它8种人参皂苷含量差别不大。     

Rho(D) genotype and red cell Rho(D) antigen content

The Rh(o)(D) content of red cells obtained from different individuals as determined with I(181) anti-Rh(o)(D) showed a bimodal distribution. Family studies indicate that the cells with the lower antigen content represent the heterozygous Rh(o)(D) state and that the cells with 1.6 times more Rh(o)(D) correspond to the homozygous state.     

A mercury-catalyzed, high-yield system for the oxidation of methane to methanol

A homogeneous system for the selective, catalytic oxidation of methane to methanol via methyl bisulfate is reported. The net reaction catalyzed by mercuric ions, Hg(II), is the oxidation of methane by concentrated sulfuric acid to produce methyl bisulfate, water, and sulfur dioxide. The reaction is efficient. At a methane conversion of 50 percent, 85 percent selectivity to methyl bisulfate ( approximately 43 percent yield; the major side product is carbon dioxide) was achieved at a molar productivity of 10(-7) mole per cubic centimeter per second and Hg(II) turnover frequency of 10(-3) per second. Separate hydrolysis of methyl bisulfate and reoxidation of the sulfur dioxide with air provides a potentially practical scheme for the oxidation of methane to methanol with molecular oxygen. The primary steps of the Hg(II)-catalyzed reaction were individually examined and the essential elements of the mechanism were identified. The Hg(II) ion reacts with methane by an electrophilic displacement mechanism to produce an observable species, CH(3)HgOSO(3)H, 1. Under the reaction conditions, 1 readily decomposes to CH(3)OSO(3)H and the reduced mercurous species, Hg(2)(2+) The catalytic cycle is completed by the reoxidation of Hg(2)(2+) with H(2)SO(4) to regenerate Hg(II) and byproducts SO(2) and H(2)O. Thallium(III), palladium(II), and the cations of platinum and gold also oxidize methane to methyl bisulfate in sulfuric acid.     

不同冷冻方法对牛体外胚胎ATP含量与ROS水平的影响

【目的】探讨冷冻保存对牛体外生产胚胎能量代谢、有氧代谢造成的影响。【方法】采用常规法或玻璃化法（open pulled straw,OPS法）冷冻保存牛体外受精（in vitro fertilization,IVF）囊胚和体细胞核移植（somatic cell nuclear transfer,SCNT）囊胚,利用ATP Bioluminescence Assay Kit HS II 和 GENMED ROS Assay Kit检测了冷冻-解冻后囊胚ATP含量和ROS水平。【结果】（1）IVF和SCNT囊胚OPS法冷冻-解冻后存活率（（93.25±5.17）%和（77.56±3.52）%）均显著高于常规冷冻法（（81.25±4.98）%和（49.41±2.24）%）（P＜0.05）;（2）IVF囊胚和SCNT囊胚OPS法冷冻-解冻后ATP含量（（0.63±0.05）和（0.33±0.02）pmol）均显著高于常规冷冻法（（0.45±0.03）和（0.22±0.01）pmol）（P＜0.05）;但是均显著低于相应的IVF或SCNT新鲜囊胚（（0.76±0.04）和（0.40±0.02）pmol）（P＜0.05）;（3）玻璃化冷冻IVF囊胚、SCNT囊胚ROS水平（（74.34±4.24）和（43.21±3.35）cps）高于新鲜IVF囊胚（（48.52±2.65）cps）、SCNT囊胚（（27.36±2.23）cps）（P＜0.05）,常规冷冻组则与此相反（（35.61±4.32）和（16.56±2.52）cps）（P＜0.05）。【结论】玻璃化冷冻较适用于牛IVF、SCNT囊胚冷冻保存;玻璃化冷冻和常规冷冻均显著影响牛IVF囊胚、SCNT囊胚中ATP含量和ROS水平。     

The Effect of H2O on the 410-Kilometer Seismic Discontinuity

The 410-kilometer seismic discontinuity is generally considered to be caused by a phase transformation of the main constituent of the upper mantle, olivine, alpha-(Mg,Fe)(2)SiO(4), to beta-(Mg,Fe)(2)SiO(4). Recent data show that H(2)O dissolves in olivine and other nominally anhydrous mantle minerals and that the partitioning of H(2)O between olivine and beta-(Mg,Fe)(2)SiO(4) is about 1:10. Such behavior strongly affects the region over which the alpha to beta phase transformation occurs and hence the seismic discontinuity that results. The observed width of the discontinuity constrains the maximum H(2)O content of upper mantle olivine to about 200 parts per million by weight.     

Self-condensing vinyl polymerization: an approach to dendritic materials

Self-condensing vinyl polymerization was used to produce dendritic polymers with both highly branched structures and numerous reactive groups. A vinyl monomer will undergo self-polymerization if it contains a pendant group that can be transformed into an initiating moiety by the action of an external stimulus. The self-polymerization combines features of a classical vinyl polymerization process with those of a polycondensation because growth is accomplished by the coupling of reactive oligomers. Highly branched, irregular dendritic structures with a multiplicity of reactive functionalities are obtained by polymerization of 3-(1-chloroethyl)-ethenylbenzene.     

四川省杂交水稻新选育组合的米质分析

本文通过对四川省水稻区试优质米组1999~2005年307份(次)品种的全套米质测试资料进行分析,主要性状的优质达标率依次为糙米率(100%)>直链淀粉含量(86.64%)>长宽比(78.18%)>胶稠度(72.96%)>垩白度(52.44%)>垩白米率(45.93%)>整精米率(44.3%);12项稻米理化指标中,呈极显著正相关的因素有6对,呈显著正相关的有3对,呈极显著负相关的有3对,呈显著负相关的有3对;构成四川杂交水稻优米品质变化的主要因子是碾米因子、外观因子1、外观因子2、蒸煮因子1、外观因子3和蒸煮因子2,其贡献率分别是23.96%、22.04%、12.97%、10.21%、9.06%和6.5%。笔者认为四川省杂交水稻优质育种的主要限制因素是整精米率、垩白米率、垩白度。但因各性状间有着复杂的互作关系,育种上应抓住主要矛盾,以提高稻米品质的总体水平。     

高抗性淀粉粳稻新品系稻米淀粉链长分布与主要品质特征差异

 【目的】通过对水稻抗性淀粉性状的遗传研究,为高抗性淀粉水稻资源创新与育种提供理论和实践依据。【方法】以抗性淀粉含量有显著差异的粳稻品系为材料,比较分析高低抗性淀粉粳稻品系类型间的支链淀粉链长分布、稻米RVA谱特性值、膳食纤维和直链淀粉含量等主要品质特性的差异及其相关性。【结果】高低抗性淀粉水稻品系间支链淀粉链长分布差异显著,高抗性淀粉水稻品系的支链淀粉中短链部分即聚合度为5～12所占的相对百分比率显著低于低抗性淀粉类型品系,而长链尤其是聚合度为13以上的长链比率明显高于低抗性淀粉类型品系。膳食纤维和直链淀粉含量,高抗性淀粉品系显著高于低抗性淀粉品系,最高黏度值、最终黏度值、热浆黏度值和崩解值等,高抗性淀粉品系均显著或极显著低于低抗性淀粉类型品系。抗性淀粉含量与支链淀粉短链聚合度（DP≤12）呈极显著负相关,但与支链淀粉的中长链聚合度（12＜DP≤36）呈极显著正相关,与直链淀粉含量和膳食纤维含量呈极显著正相关。【结论】水稻中支链淀粉的链长分布、直链淀粉含量和稻米RVA谱特性值与稻米抗性淀粉含量关系密切,在育种实践中可作为育种选择指标之一。