高质量超短光脉冲的产生与表征

分析半高全宽光脉冲表征体系的不足,提出用以表征光脉冲时域和频域特性的方均根光脉冲表征体系.采用空心波导对飞秒激光腔内的光束进行调制,并分别用2种光脉冲表征体系表征了实验中产生的lO-15s光脉冲,得到了高质量的飞秒激光脉冲.结果表明,方均根光脉冲表征体系能够更加准确地表征飞秒光脉冲.     

奇数与勾股数

围绕勾股数及勾股数组的“正整数基”，证明了对于一个任意的奇数，总存在里两个连续的整数，与这个奇数构成一个勾股数．并说明了各种类型的奇数，能构成的不同勾股数的正整数基的个数。     

高稳定性甲基橙的室温合成及其性能研究

合成稳定性良好的甲基橙对纺织物的色牢度具有重要的意义,本研究通过改进实验室低温两步合成甲基橙的方法,在室温下混合氨基苯磺酸、亚硝酸钠与N,N-二甲基苯胺进行一步反应,合成甲基橙.所制备的甲基橙经过紫外光谱、红外光谱和热重分析表征,结果表明,其共轭程度和稳定性比低温下合成的和商用的甲基橙要高.抗光催化降解测试表明,相比于低温合成的和商用的甲基橙,室温下合成的甲基橙经150 min降解后,可见光吸光度最高,橙色保持得最深.通过耐酸/碱、耐高温、耐紫外线辐射和抗金属离子的稳定性测试表明,室温下合成的甲基橙均具有良好的稳定性,高稳定性的甲基橙有助获得牢固、稳定的染料.     

Single crystals of an ionic anthracene aggregate with a triplet ground state

Crystalline supramolecular aggregates consisting of charged organic molecules, held together through metal-cluster-mediated Coulomb interactions, have attracted interest owing to their unusual structural, chemical and electronic properties. Aggregates containing metal cation clusters 'wrapped' by lipophilic molecular anions have, for example, been shown to be kinetically stable and soluble in nonpolar liquids such as saturated hydrocarbons. The formation of supramolecular aggregates can even be exploited to generate aromatic hydrocarbons that carry four negative charges and crystallize in the form of organic poly(metal cation) clusters or helical polymers. Here we report the anaerobic crystallization of an ionic organic aggregate--a contact ion septuple consisting of a fourfold negatively charged 'tripledecker' of three anthracene molecules bridged by four solvated potassium cations. Its electronic ground state is shown experimentally, using temperature-dependent electron paramagnetic resonance spectroscopy, to be a triplet. Although the spins in this biradical ionic solid are separated by a considerable distance, density functional theory calculations indicate that the triplet ground state is 84 kJ mol(-1) more stable than the first excited singlet state. We expect that the successful crystallization of the ionic solid we report here, and that of a covalent organic compound with a triplet ground state at room temperature, will stimulate further attempts to develop new triplet-ground-state materials for practical use.     

Advances in the synthesis and reactivity of 2-pyranylidene carbene complexes

Pyranylidene carbene complexes bearing a pyran ring carbene ligand represent a unique kind of organometallic species due to their special structures and reactivity. In this review, we present a comprehensive summary on the synthesis and reactivity of pyranylidene carbene complexes during the past four decades.     

艺术是一种生成 --论尼采的艺术本质观

尼采认为艺术的本质全在于对人生的功用上.他认为艺术是一种生命趋向强力的生成过程,能使个体沟通生命的有限与无限.艺术的生成活动是在其审美象征意境中完成的.     

一类强素数的确定与生成

给出了确定一类素数p是否为强素数的多项式时间算法,其计算量为O(log32p),并给出了生成这类强素数的算法。     

Formation cross-sections of singlet and triplet excitons in pi-conjugated polymers

Electroluminescence in organic light-emitting diodes arises from a charge-transfer reaction between the injected positive and negative charges by which they combine to form singlet excitons that subsequently decay radiatively. The quantum yield of this process (the number of photons generated per electron or hole injected) is often thought to have a statistical upper limit of 25 per cent. This is based on the assumption that the formation cross-section of singlet excitons, sigmaS, is approximately the same as that of any one of the three equivalent non-radiative triplet exciton states, sigmaT; that is, sigmaS/sigmaT approximately 1. However, recent experimental and theoretical work suggests that sigmaS/sigmaT may be greater than 1. Here we report direct measurements of sigmaS/sigmaT for a large number of pi-conjugated polymers and oligomers. We have found that there exists a strong systematic, but not monotonic, dependence of sigmaS/sigmaT on the optical gap of the organic materials. We present a detailed physical picture of the charge-transfer reaction for correlated pi-electrons, and quantify this process using exact valence bond calculations. The calculated sigmaS/sigmaT reproduces the experimentally observed trend. The calculations also show that the strong dependence of sigmaS/sigmaT on the optical gap is a signature of the discrete excitonic energy spectrum, in which higher energy excitonic levels participate in the charge recombination process.     

统一超混沌系统的构建与电路实现

针对统一混沌系统对应的超混沌系统实现问题,利用增加系统维数和线性反馈的方法,以统一混沌系统为基础,构建了一类四维自治统一超混沌系统。对系统平衡点的特性进行分析并计算了系统的分形维数,根据系统的Lyapunov指数谱和分岔图分析系统的变化范围。随着系统的变化,统一超混沌系统包含了3个子系统:广义超混沌Lorenz系统、超混沌Lu¨系统和广义超混沌Chen系统。与现有的超混沌系统比较,新的统一超混沌系统具有更大的最大Lyapunov指数。用数字信号处理(DSP)芯片对几个典型的统一超混沌系统进行硬件实现,并验证了超混沌奇异吸引子的存在。     

新型卡宾配体的合成及其在烯丙基烷基化催化反应中的应用

以L-苯丙氨醇为起始原料,经过氨基的氯乙酰基化、与苯并咪唑偶联和噁唑啉构筑等3步反应成功实现了中间体4的合成,总收率达到56.3%,并首次确定了中间体4的绝对构型.最后以乙腈为溶剂,用6种卤代芳烃在不同反应条件下较高产率地合成了5个具有单噁唑啉环和1个具有双噁唑啉环的新型目标配体(5a-5f),最高收率为87.7%,其中双噁唑啉环配体结构具有1个C2轴,此结构是当今此类配体研究的热点.同时,应用所设计的配体催化烯丙基烷基化反应,在最优配体和最优条件下,以1,3-二苯基-2-烯丙基乙酸酯作为底物的反应,配体5a使得反应收到了较好的催化效果,最优收率为73.5%.     

单态卡宾(CH2)与臭氧O3反应的热力学和动力学研究

在量化计算的基础上,运用统计热力学和Wigner校正的Eyring过渡态理论研究了98.15~2 298.15K温度范围内单态卡宾(CH2)与臭氧(O3)反应的热力学和动力学性质,给出了有关的计算数据,表明单态卡宾与臭氧反应在低温下具有热力学优势,高温下具有动力学优势.对于单态卡宾与臭氧的两条反应通道,通道2不仅具有很强的自发性,而且在动力学上更易进行.     

Generation Algorithm of a Sort of P-Permutations

This paper design the P-permutation with cryptologic properties beyond certain bound based on BCH code and Goppa code, which is the generalization of the design method utilizing the maximum distance separable (MDS) code, and presents the novel algorithms to generate the P-permutations with the branch number no less than a preset low bound. The new generation algorithms provide a theoretical basis for automation design of the cryptosystem.     

Formation of a stable triplex from a single DNA strand

Homopurine.homopyrimidine DNA sequences have been shown to form triple-stranded structures readily under appropriate conditions. Interest in DNA triplexes arises from potential applications of intermolecular triplexes as antisense inhibitors of gene expression and from the possibility that intramolecular triplexes may have a role in gene expression and recombination. We recently presented NMR evidence for triplex formation from the DNA oligonucleotides d(GA)4 and d(TC)4, which showed unambiguously that the second pyrimidine strand is Hoogsteen base paired and the cytosines are protonated at N3 as required. To obtain a more well defined triplex, and to provide a model for in vivo triplex structures, we have designed and synthesized a 28-base DNA oligomer with a sequence that could potentially fold to form a triplex containing both T.A.T and C+.G.C triplets. Our NMR results indicate that the conformation at pH 5.5 is an intramolecular triplex and that a significant amount of triplex remains even at pH 8.0.     

Experimental detection of the inner core translational triplet

The translational oscillation of the solid inner core is one of the Earth’s fundamental normal modes, which is also called Slichter mode. The normal mode should be split to form a triplet due to the Earth’s rotation and ellipticity. In this study, according to the splitting pattern of Slichter mode, an attempt has been made to detect the possibility of Slichter triplet’s existence by using the product spectra of the long-term continuous gravity measurements from the superconducting gravimeters (SG) at 6 glo...     

新型希夫碱配体的合成及表征

由２,６－二氨基吡啶和间硝基苯甲醛制得一种稳定的人碱配体,其结构红红外光谱,质谱及元素分析进行表征,该希夫碱配体具有稳定性等特点。