Effects of pressure and gas-jet thickness on the generation of attosecond poulser

We investigate how the intensity and duration of an attosecond pulse generated from high-order harmonic generation are affected by the pressure and thickness of the gas jet by taking into account the macroscopic propagation of both fun- damental and harmonic fields. Our simulations show that, limited by the propagation effects, especially the absorption of harmonics, the intensity of an attosecond pulse cannot be improved by just independently increasing the gas pressure or the medium length. On the other hand, due to good phase-matching conditions, the duration of a generated attosecond pulse can be improved by changing the gas pressure.     

Understanding halogen‐substituent assistance in H‐atom abstraction‐based reactions of CHCl•− with CH4 − nXn (X = H,F, Cl; n = 0–3)

The effect of halogen‐substituent on hydrogen abstraction mechanisms was studied by applying density functional theory functional calculations to the gas‐phase reactions between CHCl^?? and CH_{4 ? n}X_n (X = H, F, Cl; n = 0–3), and it is found that a heavier X substituent in the substrate results in a greater stabilization of corresponding complex, a lower activation energy, a faster H‐abstraction reaction, and greater exothermicity. However, CH₄– reaction is more reactive than CH₃F– reaction under the same condition because of dominant π‐donation from the electronegative F atom. We also explored the reactivity difference for the seven reactions in terms of factors derived from bond order, second‐order perturbative energy, and activation strain model analysis. The rate constants are evaluated over a wide temperature range of 298–1000 K by the conventional transition state theory. Copyright © 2014 John Wiley & Sons, Ltd.     

一类非自治常p-Laplace系统的多重周期解

利用临界点理论研究具有部分周期位势的非自治常p-Laplace系统周期解的存在性．在具有p-线性增长非线性项时,根据广义鞍点定理,得到了系统多重周期解存在的充分条件．     

Organocatalytic asymmetric aza-Michael addition of pyrazole to chalcone

An efficient enantioselective aza-Michael addition of pyrazole to chalcone was established. In the presence of the primary amine derived from cinchona alkaloid and acidic additive, the reactions afforded 1,4-adducts in high yields (up to 98%) with 68–88% ee.     

具有BMO系数的拟线性椭圆方程解的BMO估计

We establish a global limiting case of nonlinear Calderon-Zygmund theory to quasilinear elliptic equations div A(x,Du) = div(|F|~(p-2)F) under the BMO smallness of the nonlinearity,that is |F|~(p-2)F∈BMO implies that Du ∈BMO.     

甘肃甘南蕨麻中矿物元素含量的测定

用浓硝酸-高氯酸混合酸对蕨麻样品进行消化,采用空气-乙炔火焰原子吸收光谱法测定了样品中矿物元素含量。结果表明,蕨麻中Fe、Mg含量较高,还含有Zn、Cu、Mn、Co等人体必需微量元素,有较高营养价值,测定结果的相对标准偏差在1．738％-17．372％之间。     

Di‐tert‐Butyl Peroxide‐Mediated Atom‐Transfer Radical Addition of 2‐Chlorodithiane to Aryl Alkynes under Mild Conditions

Atom transfer radical addition (ATRA) of 2‐chlorodithiane onto aryl alkynes through the use of di‐tert‐butyl peroxide as an oxidant at room temperature directly affords a variety of synthetically valuable β‐chloro‐(Z)‐vinyl dithianes in good yields with high regioselectivities and without the assistance of any transition metals. It provides an operationally simple pathway to access vinyl dithianes with controlled formation of a new C(sp²)?C bond and a C(sp²)?Cl bond.     

邛崃石窟摩崖造像的彩绘颜料分析与研究

四川省邛崃市地处成都平原,是成都地区发现的摩崖造像规模最大,分布最集中的地区。由于潮湿、半露天的保存环境,造像遭到严重破坏,缺少相关的科学分析研究。本文选用邛崃地区内花置寺摩崖造像、临邛镇磐陀寺摩崖造像和大同乡石笋山摩崖造像三处共12件彩绘颜料样品,通过超景深显微观察、X射线荧光分析、X射线衍射和显微激光拉曼光谱综合分析,获取彩绘颜料信息。结果表明红色颜料为赤铁矿[Fe₂O₃]和铅丹[Pb₃O₄];绿色颜料为砷酸铜[Cu(AsO₃)(OH)·2H₂O]和过硫酸三铜钠钾[KNaCu₃O(SO₄)₃];白色颜料为石膏[CaSO₄];黄色颜料为黄赭石[Fe₂O₃];黑色颜料为铅丹[Pb₃O₄]的变化产物,蓝色颜料为青金石[Na₆Ca₂Al₆Si₆O₂₄(SO₄)₂]。值得注意的是绿色颜料的分析结果,其中检出的砷酸铜类物质在近年中国西南地区彩绘分析中较常见,结合文献调研判断其为近现代人工合成颜料巴黎绿的变化产物,进而推测此处有近现代重绘可能。另外,首次检出过硫酸三铜钠钾成分的绿色颜料,丰富了古代彩绘颜料的分析实例,判断可能是某种绿色含铜矿物的变化结果。四川地区环境湿润,一些不稳定的矿物颜料容易发生化学变化,有的产生变色,有的颜色变化不明显,但成分已产生新的物质。通过分析邛崃石窟彩绘颜料,获取四川地区摩崖造像所使用颜料的相关信息,为颜料复原提供科学依据,同时也有利于文物工作者展开针对性保护工作,为四川地区彩绘石窟的研究和保护提供参考。     

Bi2S3量子点敏化TiO2纳米阵列结构的制备及光电性能研究

利用水热法制备一维TiO₂纳米棒阵列,并采用化学浴沉积法(CBD)结合自组装技术在TiO₂纳米棒上敏化Bi₂S₃量子点,形成TiO₂/Bi₂S₃复合纳米棒阵列.系统研究了复合结构的表面形貌、晶体结构、光学及光电性能.结果表明:在修饰有三氨丙基三乙氧基硅烷自组装单分子膜(APTS-SAMs)的TiO₂纳米棒表面形成一层致密的Bi₂S₃量子点敏化层,这一技术的关键是含-NH₂末端的APTS-SAMs可有效促进Bi₂S₃的异相成核作用;Bi₂S₃的沉积时间对复合结构的光吸收及光电响应性能有决定性的影响,薄膜的光电流随着沉积时间呈先增加后减小的趋势,在沉积时间为20 min时,光电流密度最大.这是因为随着沉积时间的增加,TiO₂纳米棒表面Bi₂S₃量子点密度增大,光吸收增加;而当沉积时间进一步延长时,Bi₂S₃在TiO₂纳米棒表面的大量负载而形成堆积和团聚,导致表面缺陷增多,光生电子复合几率增大,从而使光电流密度减小.