Reversible, metal-free hydrogen activation

Although reversible covalent activation of molecular hydrogen (H2) is a common reaction at transition metal centers, it has proven elusive in compounds of the lighter elements. We report that the compound (C6H2Me3)2PH(C6F4)BH(C6F5)2 (Me, methyl), which we derived through an unusual reaction involving dimesitylphosphine substitution at a para carbon of tris(pentafluorophenyl) borane, cleanly loses H2 at temperatures above 100 degrees C. Preliminary kinetic studies reveal this process to be first order. Remarkably, the dehydrogenated product (C6H2Me3)2P(C6F4)B(C6F5)2 is stable and reacts with 1 atmosphere of H2 at 25 degrees C to reform the starting complex. Deuteration studies were also carried out to probe the mechanism.     

Reaction of plutonium dioxide with water: formation and properties of PuO(2+x)

Results show that PuO(2+x), a high-composition (x 相似文献   

Direct Detection of C4H2 Photochemical Products: Possible Routes to Complex Hydrocarbons in Planetary Atmospheres

The photochemistry of diacetylene (C4H2), the largest hydrocarbon to be unambiguously identified in planetary atmospheres, is of considerable importance to understanding the mechanisms by which complex molecules are formed in the solar system. In this work, the primary products of C4H2's ultraviolet photochemistry were determined in a two-laser pump-probe scheme in which the products of C4H2 photoexcitation are detected by vacuum ultraviolet photoionization in a time-of-flight mass spectrometer. Three larger hydrocarbon primary products were observed with good yield in the C4H2* + C4H2 reaction: C6H2, C812, and C8H3. Neither C6H2 nor C8H3 is anticipated by current photochemical models of the atmospheres of Titan, Uranus, Neptune, Pluto, and Triton. The free hydrogen atoms that are released during the formation of the C8H3 and C8H2 products also may partially offset the role of C4H2 in catalysing the recombination of free hydrogen atoms in the planetary atmospheres.     

Theoretical studies of the energetics and dynamics of chemical reactions

Computational studies of basic chemical processes not only provide numbers for comparison with experiment or for use in modeling complex chemical phenomena such as combustion, but also provide insight into the fundamental factors that govern molecular structure and change which cannot be obtained from experiment alone. We summarize the results of three case studies, on HCO, OH + H(2), and O + C(2)H(2), which illustrate the range of problems that can be addressed by using modern theoretical techniques. In all cases, the potential energy surfaces were characterized by using ab initio electronic structure methods. Collisions between molecules leading to reaction or energy transer were described with quantum dynamical methods (HCO), classical trajectory techniques (HCO and OH + H(2)), and statistical methods (HCO, OH + H(2), and O + C(2)H(2)). We can anticipate dramatic increases in the scope of this work as new generations of computers are introduced and as new chemistry software is developed to exploit these computers.     

抗H9亚型AIV血凝素单克隆抗体的制备及亚型鉴定

用基因疫苗pcDNA-H9、纯化H9N2亚型AIV和重组噬菌体T4-H9HA免疫Balb/C小鼠,细胞融合后用HI和ELISA方法筛选出5株抗H9亚型AIV HA的特异性单克隆抗体H9-01(2E6)、H9-02(3B1)、H9-03(3H11)、H9-04(1A4)、H9-05(2G9)。各株单抗亚型测定的结果为H9-01、H9-02和H9-05均为IgG2b,H9-03为IgG1,H9-04为IgG2a,轻链的亚型均为kappa链。经特异性和与同型病毒的反应谱检测,它们均是HA特异性单克隆抗体。为进一步分析H9N2亚型AIV的结构与功能以及建立监测该亚型AIV的试剂盒奠定了基础。     

Catalytic reduction of dinitrogen to ammonia at a single molybdenum center

Dinitrogen (N2) was reduced to ammonia at room temperature and 1 atmosphere with molybdenum catalysts that contain tetradentate [HIPTN3N]3- triamidoamine ligands (such as [HIPTN3N]Mo(N2), where [HIPTN3N]3- is [(3,5-(2,4,6-i-Pr3C6H2)2C6H3NCH2CH2)3N]3-) in heptane. Slow addition of the proton source [(2,6-lutidinium)(BAr'4), where Ar' is 3,5-(CF3)2C6H3]and reductant (decamethyl chromocene) was critical for achieving high efficiency ( approximately 66% in four turnovers). Numerous x-ray studies, along with isolation and characterization of six proposed intermediates in the catalytic reaction under noncatalytic conditions, suggest that N2 was reduced at a sterically protected, single molybdenum center that cycled from Mo(III) through Mo(VI) states.     

抗H9N2 AIV HA单克隆抗体的制备及其在胶体金层析检测中的初步应用

用基因疫苗pcDNA-H9和纯化H9N2亚型AIV免疫Balb/C小鼠,细胞融合后用HI和ELISA方法筛选出5株抗H9亚型AIV HA的特异性单克隆抗体H9-01(2E6),H9-02(3B1),H9-03(3H11),H9-04(1A4),H9-05(2G9)。各株单抗亚型测定的结果为H9-01,H9-02和H9-05均为IgG2b,H9-03为IgG1,H9-04为IgG2a,轻链的亚型均为kappa链。经特异性和与同型病毒的反应谱检测,它们均是HA特异性单克隆抗体。用制备的抗H9亚型AIV HA的单克隆抗体做成胶体金层析检测试纸条,可以检测到200个EID50的H9亚型AIV,为监测该亚型AIV试剂盒的进一步商品化奠定了基础。     

Carbon monoxide and nitric oxide consumption in polluted air: the carbon monoxide-hydroperoxyl reaction

A recent laboratory measurement of the ratio of the rate constant for the reaction CO + HO (2) --> C0(2) + OH relative to that for H + HO(2) --> 2OH indicates that the former reaction is probably faster than CO + OH --> CO(2) + H. On this basis a simple analysis is given showing that the calculated lifetime of nitric oxide in polluted atmospheres would be appreciably longer than that estimated on the assumption that the carbon monoxide-hydroperoxyl reaction may be neglected. A fast carbon monoxide-hydroperoxyl reaction implies that the cyclic consumption of carbon monoxide (an atmospheric sink) could occur even with no nitric oxide present.     

Dinitrogen Cleavage by a Three-Coordinate Molybdenum(III) Complex

Cleavage of the relatively inert dinitrogen (N(2)) molecule, with its extremely strong N identical withN triple bond, has represented a major challenge to the development of N(2) chemistry. This report describes the reductive cleavage of N(2) to two nitrido (N(3-)) ligands in its reaction with Mo(NRAr)(3), where R is C(CD(3))(2)CH(3) and Ar is 3,5-C(6)H(3)(CH(3))(2'), a synthetic three-coordinate molybdenum(III) complex of known structure. The formation of an intermediate complex was observed spectroscopically, and its conversion (with N identical withN bond cleavage) to the nitrido molybdenum(VI) product N identical withMo(NRAr)(3) followed first-order kinetics at 30 degrees C. It is proposed that the cleavage reaction proceeds by way of an intermediate complex in which N(2) bridges two molybdenum centers.     

木质活性炭自热过程指标气体产生规律研究

[目的]研究木质活性炭受热氧化过程指标气体的产生规律。[方法]利用程序升温对3种挥发分含量不同的木质活性炭进行加热氧化和尾气在线检测,并对其受热过程中指标气体产生规律进行分析研究。[结果]木质活性炭在受热升温氧化过程中会释放出H2、CO、C2H4和C2H2,当木质活性炭的挥发分含量较高时还会放出CH4指标气体。其指标气体产生规律为:当体系温度达100℃时,样品开始释放出H2;随着温度的升高,依次检测到其他气体,各样品C2H4在140～160℃、CO在160～180℃、C2H2在190～200℃时,分别被检测到;C2H2在体系温度为230℃释放量达最大值,其余各指标气体的释放量则随体系温度增大而增大。[结论]各指标气体随着相应官能团逐步活化而释放,并且前一指标气体释放时产生的热量为后一官能团的活化提供热量。     

C60H2: Synthesis of the Simplest C60 Hydrocarbon Derivative

The reaction of C(60) with BH(3): tetrahydrofuran in toluene followed by hydrolysis yielded C(60)H(2). This product was separated by high-performance liquid chromatography and characterized as the addition product of H(2) to a 6,6-ring fusion (1alb isomer). The (1)H nuclear magnetic resonance (NMR) spectrum of the product remained a sharp singlet between -80 degrees and +100 degrees C, which suggests a static structure on the NMR time scale. Hydrolysis of the proposed borane addition product with acetic acid-d(1) or D(2)O yielded C(60)HD, and its (3)J(HD) coupling constant is consistent with vicinal addition. The observation of a single C(60)H(2) isomer is in complete agreement with earlier calculations that indicated that at most 2 of the 23 possible isomers of C(60) would be observable at equilibrium at room temperature. These results suggest that organoborane chemistry may be applied to further functionalization of fullerenes.     

Infrared observations of the saturnian system from voyager 1

During the passage of Voyager 1 through the Saturn system, the infrared instrument acquired spectral and radiometric data on Saturn, the rings, and Titan and other satellites. Infrared spectra of Saturn indicate the presence of H(2), CH(4), NH(3), PH(3), C(2)H(2), C(2)H(6), and possibly C(3)H(4) and C(3)H(8). A hydrogen mole fraction of 0.94 is inferred with an uncertainty of a few percent, implying a depletion of helium in the atmosphere of Saturn relative to that of Jupiter. The atmospheric thermal structure of Saturn shows hemisphere asymmetries that are consistent with a response to the seasonally varying insolation. Extensive small-scale latitudinal structure is also observed. On Titan, positive identifications of infrared spectral features are made for CH(4), C(2)H(2), C(2)H(4), C(2)H(6), and HCN; tentative identifications are made for C(3)H(4) and C(3)H(8). The infrared continuum opacity on Titan appears to be quite small between 500 and 600 cm(-1), implying that the solid surface is a major contributor to the observed emission over this spectral range; between 500 and 200 cm(-1) theopacity increases with decreasing wave number, attaining an optical thickness in excess of 2 at 200 cm(-1). Temperatures near the 1-millibar level are independent of longitude and local time but show a decrease of approximately 20 K between the equator and north pole, which suggests a seasonally dependent cyclostrophic zonal flow in the stratosphere of approximately 100 meters per second. Measurements of the C ring of Saturn yield a temperature of 85 +/- 1 K and an infrared optical depth of 0.09 +/- 0.01. Radiometer observations of sunlight transmitted through the ring system indicate an optical depth of 10(-1.3 +/-0.3) for the Cassini division. A phase integral of 1.02 +/- 0.06 is inferred for Rhea, which agrees with values for other icy bodies in the solar system. Rhea eclipse observations indicate the presence of surface materials with both high and low thermal inertias, the former most likely a blocky component and the latter a frost.     

缺硫对莱茵衣藻叶绿素荧光参数和产H2速率的影响

采用TAP及TAP-S培养基培养莱茵衣藻(Chlamydomonas reinhardtii D.),测定了该藻叶绿素荧光参数及产氢气能力.结果表明:莱茵衣藻在TAP培养基内生长良好,有微量氢气产生,最高产氢速率只有1.4×10-4 ml/(mgChl·h).在TAP-S培养基内,莱茵衣藻的荧光参数Fv/Fo、ΦPSⅡ、qp分别在40～48 h下降到初始值的50%,说明缺硫对藻光合作用的影响首先发生在天线色素到PSⅡ反应中心的传能过程以及光合作用暗反应所需的酶.TAP-S培养基内藻最高产氢速率达0.22ml/(mgChl·h),缺硫可以显著提高莱茵衣藻氢气产生的速率.     

膨润土制备高效活性白土的研究

[目的]优化活性白土制备的工艺,为制备高品质的活性白土提供理论依据。[方法]以钙基膨润土为原料,以硫酸、盐酸、草酸组成的混酸为活化试剂,研究混酸体积比、液固比、反应温度和反应时间对活性白土的活性度、脱色率和相对白度的影响。[结果]当混酸体积比为硫酸∶盐酸∶草酸=5∶5∶1、液固比为4∶1、反应温度为80℃、反应时间为4 h时,制备活性白土的活性度为204,脱色率为98%,相对白度为82。[结论]以混酸活化膨润土制备活性白土,混酸浓度适中,酸化效果好,耗酸量低,洗涤用水少,生产成本低,是一种适合于工业生产高效活性白土的方法。     

H3N2亚型猪流感病毒NS1基因的克隆与序列分析

从鸡胚尿囊液中提取H3N2亚型猪流感病毒(SIV)的RNA,根据已发表的A型流感病毒的核苷酸序列,设计了一对特异性引物,采用反转录-聚合酶链反应(RT-PCR)成功地扩增了SIV的NS1基因．将NS1基因的cDNA克隆后进行了序列测定,测序结果表明,所扩增的778 nt片段包含了完整的NS1基因的开放阅读框．核苷酸序列比较分析结果表明,该毒株与A／Swine／Texas／4199-2／98(H3N2)、A／Swine／Iowa／533／99(H3N2)、A／Swine／HongKong／126／ 82(H3N2)、A／Swine／Pingtung／7-12／99(HIN2)核苷酸序列的同源性为92．7％～98．6％,推导的氨基酸序列同源性为92．6％～96．3％．     

Free energy and temperature dependence of electron transfer at the metal-electrolyte interface

The rate constant of the electron-transfer reaction between a gold electrode and an electroactive ferrocene group has been measured at a structurally well-defined metal-electrolyte interface at temperatures from 1 degrees to 47 degrees C and reaction free energies from -1.0 to +0.8 electron volts (eV). The ferrocene group was positioned a fixed distance from the gold surface by the self-assembly of a mixed thiol monolayer of (eta(5)C(5)H(5))Fe(eta(5)C(5)H(4))CO(2)(CH(2))(16)SH and CH(3)(CH(2))(15)SH. Rate constants from 1 per second (s(-1)) to 2 x 10(4) s(-1) in 1 molar HClO(4) are reasonably fit with a reorganization energy of 0.85 eV and a prefactor for electron tunneling of 7 x 10(4) s(-1) eV(-1). Such self-assembled monolayers can be used to systematically probe the dependence of electron-transfer rates on distance, medium, and spacer structure, and to provide an empirical basis for the construction of interfacial devices such as sensors and transducers that utilize macroscopically directional electron-transfer reactions.     

短柄草2C 型蛋白磷酸酶基因BdPP2C2 的克隆及表达分析

从短柄草中克隆获得一个2C 型蛋白磷酸酶基因,命名为BdPP2C2。序列分析结果表明,该基因ORF 的 长度为1 368 bp。进化分析结果表明,该基因所编码的蛋白与拟南芥AtPP2C56 的亲缘关系最近。实时荧光定量PCR 分析结果表明,该基因的表达显著受ABA、乙烯、双氧水3 种信号分子诱导,并且受高盐和低温胁迫诱导。这些结果 表明,BdPP2C2 是非生物逆境胁迫中的一个应答因子,并且可能受相关信号分子调控。     

Quantification of primary versus secondary C-h bond cleavage in alkane activation: propane on pt

The trapping-mediated dissociative chemisorption of three isotopes of propane (C(3)H(8), CH(3),CD(2)CH(3), and C(3)D(8)) has been investigated on the Pt(110)-(1 x 2) surface, and both the apparent activation energies and the preexponential factors of the surface reaction rate coefficients have been measured. In addition, the probabilities of primary and secondary C-H bond cleavage for alkane activation on a surface were evaluated. The activation energy for primary C-H bond cleavage was 425 calories per mole greater than that of secondary C-H bond cleavage, and the two true activation energies that embody the single measured activation energy were determined for each of the three isotopes. Secondary C-H bond cleavage is also preferred on entropic grounds, and the magnitude of the effect was quantified.     

Alkali-stabilized Pt-OHx species catalyze low-temperature water-gas shift reactions

We report that alkali ions (sodium or potassium) added in small amounts activate platinum adsorbed on alumina or silica for the low-temperature water-gas shift (WGS) reaction (H(2)O + CO → H(2) + CO(2)) used for producing H(2). The alkali ion-associated surface OH groups are activated by CO at low temperatures (~100°C) in the presence of atomically dispersed platinum. Both experimental evidence and density functional theory calculations suggest that a partially oxidized Pt-alkali-O(x)(OH)(y) species is the active site for the low-temperature Pt-catalyzed WGS reaction. These findings are useful for the design of highly active and stable WGS catalysts that contain only trace amounts of a precious metal without the need for a reducible oxide support such as ceria.     

The (Me5C5)Si+ cation: a stable derivative of HSi+

The reaction of decamethylsilicocene, (Me5C5)2Si, with the proton-transfer reagent Me5C5H2+B(C6F5)4- produces the salt (Me5C5)Si+ B(C6F5)4(2), which can be isolated as a colorless solid that is stable in the absence of air and moisture. The crystal structure reveals the presence of a cationic pi complex with an eta5-pentamethylcyclopentadienyl ligand bound to a bare silicon center. The 29Si nuclear magnetic resonance at very high field (delta = - 400.2 parts per million) is typical of a pi complex of divalent silicon. The (eta5-Me5C5)Si+ cation in 2 can be regarded as the "resting state" of a silyliumylidene-type (eta1-Me5C5)Si+ cation. The availability of 2 opens new synthetic avenues in organosilicon chemistry. For example, 2 reacted with lithium bis(trimethylsilyl)amide to give the disilene E-[(eta1-Me5C5)[N(SiMe3)2]Si]2(3).