Elasticity of single-crystal MgO to 8 gigapascals and 1600 kelvin

The cross pressure (P) and temperature (T) dependence of the elastic moduli (Cij) of single-crystal samples of periclase (MgO) from acoustic wave travel times was measured with ultrasonic interferometry: partial differential2C11/ partial differentialP partial differentialT = (-1.3 +/- 0.4) x 10(-3) per kelvin; partial differential2C110/ partial differentialP partial differentialT = (1. 7 +/- 0.7) x 10(-3) per kelvin; and partial differential2C44/ partial differentialP partial differentialT = (-0.2 +/- 0.3) x 10(-3) per kelvin. The elastic anisotropy of MgO decreases with increasing pressure at ambient temperature, but then increases as temperature is increased at high pressure. An assumption of zero cross pressure and temperature derivatives for the elastic moduli underestimates the elastic anisotropy and overestimates the acoustic velocities of MgO at the extrapolated high-pressure and high-temperature conditions of Earth's mantle.     

漆酶对苹果酚类物质的催化特性

【目的】研究白腐菌漆酶对苹果多酚类物质的催化特征,为开发新型具有生物活性的色素物质提供理论依据。【方法】采用单因素和正交组合试验确定白腐菌漆酶对苹果多酚酶促氧化的最佳条件,并对氧化产物的稳定性进行分析;然后对酚类氧化产物进行HPLC分析,初步确定产物组分,最后分析了苹果多酚及其氧化产物对.OH和DPPH.的清除作用。【结果】①漆酶对苹果多酚的最佳酶促氧化条件为:反应温度55℃,pH 5.5,苹果多酚质量浓度2.5 mg/mL,漆酶浓度3.5 U/mL。②氧化产物在363 nm处有最大吸收峰,对温度和光照不敏感,随着pH增大颜色加深。③HPLC分析表明,模式底物儿茶酚、表儿茶素、儿茶素分别能产生2,2,4种氧化产物。④抗氧化活性研究表明,质量浓度较高时,苹果多酚氧化产物对.OH和DPPH.的清除作用强于苹果多酚,且在一定质量浓度范围内呈现量效关系。在氧化产物质量浓度为500μg/mL时,对.OH的清除率最高,达85.42%;在氧化产物1 000μg/mL、反应时间为60 min时,对DPPH.的清除率最高,达94.32%。【结论】优化了漆酶催化苹果多酚氧化的工艺条件,苹果酚类物质经漆酶催化氧化后形成了新的可溶性、光热稳定性的有色产物,高质量浓度下产物的抗氧化活性较原提取物增强。     

漆酶转化对氨基苯胂酸的研究

为全面了解对氨基苯胂酸(ARS)在环境中的归趋,研究了ARS在漆酶与邻苯二酚或丁香酸两种腐植酸模型化合物共同存在时的转化过程及产物鉴定。结果发现在漆酶-ARS单一体系中,漆酶并不能降解ARS;当体系中加入邻苯二酚或者丁香酸时,ARS的降解效果显著,且漆酶-邻苯二酚体系中ARS的转化更加彻底。在反应过程中,邻苯二酚和丁香酸首先在漆酶的作用下氧化成为1,2-醌和1,4-醌,然后分别和ARS发生亲核加成反应,形成聚合物,产物中均没有发现砷酸基团的脱落,始终以有机胂形态存在。     

电场对杨木胶合效应之再探

在电场作用下, 通过聚醋酸乙烯乳液胶合杨木单板的正交试验, 探索了板坯垫板间电势差及单板含水率对胶合强度的影响。结果表明： 单板含水率和垫板间电势差及其交互作用对胶合强度都有极显著影响。在试验范围内达到理想胶合强度的垫板间电势差为３０ Ｖ, 单板含水率为７０ ％ ～９０ ％ 。图１ 表４ 参２     

Identification of active gold nanoclusters on iron oxide supports for CO oxidation

Gold nanocrystals absorbed on metal oxides have exceptional properties in oxidation catalysis, including the oxidation of carbon monoxide at ambient temperatures, but the identification of the active catalytic gold species among the many present on real catalysts is challenging. We have used aberration-corrected scanning transmission electron microscopy to analyze several iron oxide-supported catalyst samples, ranging from those with little or no activity to others with high activities. High catalytic activity for carbon monoxide oxidation is correlated with the presence of bilayer clusters that are approximately 0.5 nanometer in diameter and contain only approximately 10 gold atoms. The activity of these bilayer clusters is consistent with that demonstrated previously with the use of model catalyst systems.     

银屑平丸治疗寻常型银屑病的疗效及对血清IL-8的影响

目的观察银屑平丸治疗寻常型银屑病血热证的临床疗效及其对血清IL-8含量的影响。方法将70例患者随机分为两组,治疗组口服银屑平丸,对照组口服复方青黛丸,疗程均为8周,同时设立20名健康体检者作对照。计算治疗前后PASI(银屑病面积和严重程度指数)评分及检测外周血血清IL-8含量。结果两组治疗后PASI积分均有明显下降(P<0.01),治疗组下降较对照组更明显(P<0.01)。两组患者治疗前血清IL-8含量明显高于正常人(P<0.01),治疗后两组血清IL-8含量明显下降(P<0.01),治疗组较对照组更明显(P<0.01)。结论银屑平丸能同时降低寻常型银屑病的PASI积分及血清IL-8含量,临床疗效确切。     

超低量静电喷雾机具的充电效果研究

 用理论分析和试验研究的方法,证明感应式充电法充电效果最佳,并确认工作充电电压仅为3.5～4.5千伏便可获得足够好的充电效果,这个结论有助于降低高压静电电源的生产成本,本文通过对植保机具使用现状的分析,提出开展超低量静电喷雾机只研制的建议。     

Quantum phase interference and parity effects in magnetic molecular clusters

An experimental method based on the Landau-Zener model was developed to measure very small tunnel splittings in molecular clusters of eight iron atoms, which at low temperature behave like a nanomagnet with a spin ground state of S = 10. The observed oscillations of the tunnel splittings as a function of the magnetic field applied along the hard anisotropy axis are due to topological quantum interference of two tunnel paths of opposite windings. Transitions between quantum numbers M = -S and (S - n), with n even or odd, revealed a parity effect that is analogous to the suppression of tunneling predicted for half-integer spins. This observation is direct evidence of the topological part of the quantum spin phase (Berry phase) in a magnetic system.     

Water at hydrophobic surfaces: weak hydrogen bonding and strong orientation effects

Vibrational studies that selectively probe molecular structure at CCl4/H2O and hydrocarbon/H2O interfaces show that the hydrogen bonding between adjacent water molecules at these interfaces is weak, in contrast to generally accepted models of water next to fluid hydrophobic surfaces that suggest strong hydrogen bonding. However, interactions between these water molecules and the organic phase result in substantial orientation of these weakly hydrogen-bonded water molecules in the interfacial region. The results have important implications for understanding water adjacent to hydrophobic surfaces and the penetration of water into hydrophobic phases.     

X-ray Damage to CF3CO2-Terminated Organic Monolayers on Si/Au: Principal Effect of Electrons

The relative importance of x-rays alone and of x-ray-generated primary and secondary electrons in damaging organic materials was explored by use of self-assembled monolayers (SAMs) on multilayer thin-film supports. The substrates were prepared by the deposit of thin films of silicon (0, 50, 100, and 200 angstroms) on thick layers of gold (2000 angstroms). These systems were supported on chromium-primed silicon wafers. Trifluoroacetoxy-terminated SAMs were assembled on these substrates, and the samples were irradiated with common fluxes of monochromatic aluminum K(alpha) x-rays. The fluxes and energy distributions of the electrons generated by interactions of the x-rays with the various substrates, however, differed. The substrates that emitted a lower flux of electrons exhibited a slower loss of fluorine from the SAMs. This observation indicated that the electrons-and not the x-rays themselves-were largely responsible for the damage to the organic monolayer.     

Na2CO3 和NaCl对黄瓜种子萌发胁迫效应的比较

采用培养皿法比较了Na2CO3和NaCl对黄瓜种子萌发的胁迫效应。黄瓜种子在浓度依次为0、50、100、150、200、250 mmol/L的NaCl和Na2CO3溶液中进行胁迫处理,测量茎高、根长、胚根鲜重、胚芽鲜重,然后计算发芽率、发芽势、活力指数、发芽指数。结果表明,Na2CO3和NaCl对黄瓜种子的萌发都具有抑制作用。相比之下,在Na2CO3胁迫下,Na+对黄瓜种子的相对发芽率、活力指数、胚芽和胚根有抑制作用,并且对各指标的抑制程度均大于NaCl胁迫;同时随胁迫浓度的增大,抑制作用越明显。     

超临界CO_2萃取水虻油脂及其对氨基酸成分与贮存期的影响

经超临界 Ｃ Ｏ２ 提油后,虫体异臭味可被去除,氨基酸总量及鱼类必需氨基酸含量增加,其中精氨酸在提油前后的相对含量变化不明显,赖氨酸和蛋氨酸的相对含量比提油前的分别提高了１５．７５％ 和８６．２５％ ;非必需氨基酸中的胱氨酸、酪氨酸及脯氨酸、丙氨酸等的相对含量都比提油前有不同程度提高．经超临界 Ｃ Ｏ２提油后的幼虫虫体贮存期大为延长．超临界 Ｃ Ｏ２ 萃取在适当的操作条件下,得到超过或等量于传统方法所获的油脂量,提取时间均较溶剂萃取的短,油色两者相近     

氧化镁微膨胀混凝土对温度应力的补偿效应

【目的】研究氧化镁微膨胀混凝土对温度应力的补偿特性,为简化大体积混凝土温控防裂措施提供理论依据。【方法】在充分分析和研究温度应力补偿计算方法和氧化镁微膨胀混凝土自生体积变形特性的基础上,针对某碾压混凝土重力坝,考虑混凝土热、力学参数随龄期变化及混凝土实际浇筑过程对温度应力的影响,利用大型商业有限元计算软件ANSYS平台开发出的温度场与温度应力场仿真计算程序,对掺与不掺氧化镁2个对比方案的大坝碾压混凝土温度应力进行计算分析。【结果】掺氧化镁方案中施工期末整个坝体碾压混凝土出现体积膨胀,最大膨胀变形量超过70.0×10-6;氧化镁微膨胀混凝土对坝体基础约束区中心部位应力状态有明显的改善效果,最大拉应力减小约1.0MPa;但对脱离约束区的坝体混凝土应力的改善效果非常有限。【结论】在坝体约束区采用氧化镁微膨胀混凝土,可以达到简化温控防裂措施、降低建设成本、加快施工速度的目的。     

(111)晶面暴露的NiO纳米催化剂的制备及其CO催化氧化性能

采用溶剂热法,以Ni(NO_3)_3·6H_2O、均苯三甲酸以及N,N-二甲基甲酰胺(DMF)为原料快速合成金属有机骨架材料Ni_3(BTC)_2·12H_2O晶体。以Ni_3(BTC)_2·12H_2O为前体,通过焙烧得到具有(111)面的NiO颗粒用于CO催化氧化反应,并与由硝酸镍热解得到的NiO(R)催化剂进行对比。通过X射线衍射(XRD)、N_2物理吸附-脱附、透射电子显微镜(TEM)以及X射线光电子能谱(XPS)等方法对具有(111)面的NiO颗粒的组成、结构和形貌进行表征。CO催化氧化结果表明,具有(111)面的NiO颗粒的催化活性优于普通NiO催化剂的催化活性。     

高校图书馆有偿服务的调查与分析

通过对我国211高校图书馆有偿服务项目的调查,对科技查新、代查代检、馆际互借与文献传递等服务方式的现状和合理性进行分析,提出关于合理化有偿服务的思考和建议。     

Controlling chemical turbulence by global delayed feedback: pattern formation in catalytic CO oxidation on Pt(110)

Control of spatiotemporal chaos is one of the central problems of nonlinear dynamics. We report on suppression of chemical turbulence by global delayed feedback using, as an example, catalytic carbon monoxide oxidation on a platinum (110) single-crystal surface and carbon monoxide partial pressure as the controlled feedback variable. When feedback intensity was increased, spiral-wave turbulence was transformed into new intermittent chaotic regimes with cascades of reproducing and annihilating local structures on the background of uniform oscillations. The global feedback further led to the development of cluster patterns and standing waves and to the stabilization of uniform oscillations. These findings are reproduced by theoretical simulations.     

高校图书馆数字化资源收费问题探讨

高校图书馆对使用本馆内的数字化资源收取一定的费用,这在高校图书馆已经成为一种定式。文章通过对图书馆的收费原因、收费方式进行探讨,以度对如何管理这些费用提出一些合理化建议。