Study on the hydrogen donating abilities of benzofuranones as chain-breaking antioxidants using laser flash photolysis technique

The hydrogen donation kinetics of four 3-aryl-benzofuranones with different chemical structures toward tert-butoxyl radicals were studied using laser flash photolysis (LFP) technique. The rate constants of hydrogen reactions, which can be used to evaluate the hydrogen donating abilities of 3-aryl-benzofuranones toward radicals, were obtained. The results showed that the position of substituted methyl group has a very important effect on the hydrogen donating ability of benzofuranone toward tert-butoxyl radicals, i.e. if the methyl group is on 2′-position, the hydrogen donation of 3-aryl-benzofuranone toward tert-butoxyl radicals will be prevented and the hydrogen donating ability will be weakened.     

溶液中(RC2R')Co(CO)(PR″3)2的配体PR″3之间的交换作用——三跳动力学模型

本文成功地运用了三跳动力学模型,通过相关函数和超精细分裂常数的关系, 推出了电子自旋共振波谱的线宽与基本线宽T_(2,0)~(-1)、溶液中各种异构体的超精细分裂常数、配体的交换寿命等之间的关系。求出了在290 K温度下(Ph_2C_2)Co(CO)[P(OEt)_3]_2的THF溶渡中P(OEt)_3配体的交换寿命是5.6×10~(-11)秒。     

Novel Pb(II), Zn(II), and Cd(II) coordination polymers constructed from ferrocenyl-substituted carboxylate and bipyridine-based ligands

Treatment of two kinds of ferrocenyl-substituted carboxylate ligands (3-ferrocenyl-2-crotonic acid, HOOC-CH=(CH(3))CFc (Fc=(eta(5)-C(5)H(5))Fe(eta(5)-C(5)H(4))) or O-ferrocecarbonyl benzoic acid, o-HOOCC(6)H(4)COFc with Pb(OAc)(2).3H(2)O, Zn(OAc)(2).2H(2)O, or Cd(OAc)(2).2H(2)O) resulted in four novel ferrocene-containing coordination polymers [[Pb(mu(2)-eta(2)-OOCCH=(CH(3))CFc)(2)].MeOH](n) (1), [[Zn(o-OOCC(6)H(4)COFc)(2)(4,4'-bipy)(H(2)O)(2)].2MeOH.2H(2)O](n) (4,4'-bipy = 4,4'-bipyridine) (2), [[Cd(o-OOCC(6)H(4)COFc)(2)(bpe)(MeOH)(2)].2H(2)O](n) (bpe = 1,2-bis(4-pyridyl)ethene) (3), and [Pb(o-OOCC(6)H(4)COFc)(eta(2)-o-OOCC(6)H(4)COFc)(bpe)](n)() (4). Their crystal structures have been characterized by single X-ray determinations. In polymer 1, Pb(II) ions are bridged by tridentate FcC(CH(3))=CHCOO(-) anions, forming an infinite chain [Pb(mu(2)-eta(2)-OOC=CH(CH(3))CFc)(2)](n). In polymers 2-4, there are three kinds of components, metal ions, o-FcCOC(6)H(4)COO(-) units, and organic bridging ligands. The bipyridine-based ligands connect metal ions leading to a one-dimensional chain with o-FcCOC(6)H(4)COO(-) units acting as monodentate or chelate ligands in the side chain. Such coordination polymers containing ferrocenyl-substituted carboxylate and bipyridine-based ligands are very rare. The solution-state differential pulse voltammetries of polymers 1-4 were determined. The results indicate that the half-wave potential of the ferrocenyl moieties is influenced by the Pb(II) ions in polymer 1 and strongly influenced by Zn(II), Cd(II), or Pb(II) ions in polymers 2-4. The thermal properties of the four polymers were also investigated.     

Ca(1)(-)(x)Na(2)(x)Al(2)B(2)O(7): a structure with tunable density of Na(+) vacancies

A series of samples with the composition Ca(1)(-)(x)Na(2)(x)Al(2)B(2)O(7) (0 < x < or = 1) was investigated and a hexagonal structure with unusually large range of homogeneity (at least from x = 0.01 to 0.95) was revealed. The hexagonal phase consists of [Al(2)B(2)O(7)](infinity)(2)(-) lamellae stacked along the c axis, as in CaAl(2)B(2)O(7) and Na(2)Al(2)B(2)O(7). Nevertheless, the configuration and stacking sequence of the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae are different in these three structures. In the hexagonal structure of Ca(1)(-)(x)()Na(2)(x)()Al(2)B(2)O(7), Ca and half Na cations (Na1) statistically occupy the same crystallographic site which is located between the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae, the other half Na cations (Na2) distribute in the planes bisecting the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae. Depending on the composition, the site occupation factor of Na2 site can vary in the same range as x, leading to a tunable density of Na(+) vacancies in the structure. The AlO(4) tetrahedra and BO(3) triangles in the structure tilt in appropriate ways to improve the bond valence sum of Na2 cations which are not sufficiently bonded to the anions.     

增益增强型CMOS运算放大器的自动优化算法

在增益增强型运算放大器优化中采用了自动设计方法,此方法在电路性能方程式和自适应遗传优化算法基础上对电路性能指标进行优化。该放大器在0.18μm CM O S工艺条件下中开环增益为92.1 dB,单位增益带宽积为1.78 GH z,相位裕度为55.1°和0.2%建立时间为1.27 ns,同时说明此优化设计方法的有效性。     

5.2/5.7-GHz 48-dB Image Rejection GaInP/GaAs HBT Weaver Down-Converter Using LO Frequency Quadrupler

A GaInP/GaAs heterojunction bipolar transistor (HBT) down-converter using the Weaver architecture is demonstrated in this paper. The Weaver system is a double-conversion image rejection heterodyne system which requires no bandpass filters in the signal path and no quadrature networks. The Weaver down-converter has the image rejection ratios of 48 dB and 44 dB when the RF frequency is 5.2 GHz and 5.7 GHz, respectively. A new frequency quadrupler is employed in the down-converter to generate the local oscillator (LO) signals. The frequency quadrupler is designed to minimize the phase error when generating LO signals and thus the image rejection performance is improved. A diagrammatic explanation using the complex mixing technique to analyze the image rejection mechanism of the Weaver architecture is developed in this paper. From our analysis, the image rejection can be further improved by making the LO₁ and LO₂ signals coherent     

Quantum wells micro-ring resonator laser emitting at 1746 nm for gas sensing

Gas sensing for measurement of gas components, concentrations, and other parameters plays an important role in many fields. In this Letter, a micro-ring resonator laser used for gas sensing is experimentally demonstrated. The multi-quantumwells micro-ring laser based on whispering-gallery modes with an annular resonator and an output waveguide was fabricated. A single-mode laser with a wavelength of 1746.4 nm was fabricated for the first time, to the best of our knowledge,experimentally. The output power of 1.65 m W under 40 m A injection current was obtained with a side-mode suppression ratio over 33 d B.     

三重四极杆电感耦合等离子体质谱(ICP-MS)法测定氧化铕中13种稀土杂质元素

稀土杂质元素直接影响高纯单金属稀土材料的整体性能,是高科技领域许多材料的重要组成部分。通过考察最佳的消解酸量、温度、时间、氧气反应气流量、稀释气流量,建立了基于三重四极杆电感耦合等离子体质谱仪(ICP-MS/MS)直接测定氧化铕中13种稀土杂质元素分析方法。该方法采用0.1%基体直接进样,可以很大程度提高前处理分析效率。利用碰撞模式测定氧化铕稀土中的Y、La、Pr、Nd、Sm、Gd、Tb、Dy、Ho、Er、Yb、Lu元素,氧气质量转移模式测定氧化铕中的Tm,两种模式结合可以有效去除多原子干扰,实现氧化铕的稳定测试分析。通过对氧化铕标准物质（GBW02902）直接测定分析,结果表明,在碰撞和氧气质量转移模式下,各元素线性相关系数（r）均大于 0.9999,方法检出限为0.001~0.023 mg/kg,测试精密度优于1.99%,13种元素的测试值都在认定值的不确定度范围之内。该分析方法操作简单,测试稳定,效率高,为实验室进行氧化铕材料中REE杂质的准确测试分析提供思路和借鉴。     

Machine learning-based real-time visible fatigue crack growth detection

Many large-scale and complex structural components are applied in the aeronautics and automobile industries.However,the repeated alternating or cyclic loads in ...