Maximum eigenvalues of the reciprocal distance matrix and the reverse Wiener matrix

We report some properties of the maximum eigenvalues of the reciprocal distance matrix and the reverse Wiener matrix of a connected graph, in particular, various lower and upper bounds, and the Nordhaus–Gaddum‐type results for them. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Reverse Intersystem Crossing of Single Deuterated Perylene Molecules in a Dibenzothiophene Matrix

Intersystem crossing to the long-lived metastable triplet state is often a strong limitation on fluorescence brightness of single molecules, particularly for perylene in various matrices. In this paper, we report on a strong excitation-induced reverse intersystem crossing (rISC), a process where single perylene molecules in a dibenzothiophene matrix recover faster from the triplet state, turning into bright emitters at saturated excitation powers. With a detailed study of single-molecule fluorescence autocorrelations, we quantify the effect of rISC. The intrinsic lifetimes found for the two effective triplet states (8.5±0.4 ms and 64±12 ms) become significantly shorter, into the sub-millisecond range, as the excitation power increases and fluorescence brightness is ultimately enhanced at least fourfold. Our results are relevant for the understanding of triplet state manipulation of single-molecule quantum emitters and for markedly improving their brightness.     

海带中碘元素的分离实验改进

碘离子的氧化与碘单质的分离是海带中碘元素分离的关键步骤。采用反加试剂法改进碘离子氧化步骤,采用水蒸气蒸馏法改进碘单质的分离,达到了实验现象明显,终点判断简单,分离度高,环境污染少的优点。     

Efficient Direct Reverse Intersystem Crossing between Charge Transfer-Type Singlet and Triplet States in a Purely Organic Molecule

In the field of organic light-emitting diodes, thermally activated delayed fluorescence (TADF) materials have achieved great performance. The key factor for this performance is the small energy gap (ΔE_ST) between the lowest triplet (T₁) and singlet excited (S₁) states, which can be realized in a well-separated donor-acceptor system. Such systems are likely to possess similar charge transfer (CT)-type T₁ and S₁ states. Recent investigations have suggested that the intervention of other type-states, such as locally excited triplet state(s), is necessary for efficient reverse intersystem crossing (RISC). Here, we theoretically and experimentally demonstrate that our blue TADF material exhibits efficient RISC even between singlet CT and triplet CT states without any additional states. The key factor is dynamic flexibility of the torsion angle between the donor and acceptor, which enhances spin-orbit coupling even between the charge transfer-type T₁ and S₁ states, without sacrificing the small ΔE_ST. This results in excellent photoluminescence and electroluminescence performances in all the host materials we investigate, with sky-blue to deep-blue emissions. Among the hosts investigated, the deepest blue emission with CIE coordinates of (0.15, 0.16) and the highest EQE_MAX of 23.9 % are achieved simultaneously.     

Molecular docking studies on tetrahydroimidazo-[4,5,1-jk][1,4]-benzodiazepinone (TIBO) derivatives as HIV-1 NNRT inhibitors

At present, chemotherapy seems to be the main weapon in the arsenal of remedies for the ongoing crusade against AIDS. The mode of binding of the TIBO family of inhibitors has been of interest because these compounds do not fit the two-hinged-ring model as generally observed in the NNRTIs. Flexible docking simulations were performed with a series of 53 TIBO derivatives as NNRTIs. Binding preferences as well as the structural and energetic factors associated with them were studied. A good correlation (r ² = 0.849, q ² = 0.843) was observed between the biological activity and binding affinity of the compounds which suggest that the identified binding conformations of these inhibitors are reliable. Further screening of PubChem database yielded novel scaffolds. Our studies suggest that modifications to the TIBO group of inhibitors might enhance their binding efficacy and hence, potentially, their therapeutic utility.     

应用超高效液相色谱-四极杆-飞行时间质谱法建立谷物中18种真菌毒素非靶向筛查数据库及确证方法

建立了基于超高效液相色谱-四极杆-飞行时间质谱(UPLC-Q-TOF/MS)的18种真菌毒素非靶向筛查方法。真菌毒素标准物质用HSS T3色谱柱进行色谱分离后在UPLC-Q-TOF/MS MS^E模式下分别用正、负离子模式采集,获取MS和MS/MS的信息,记录对应保留时间、加合物离子、碎片离子精确质量数等信息,设置保留时间偏移为0.3 min,加合物离子和碎片离子的精确质量匹配容差为5×10^-6,在UNIFI中建立18种真菌毒素的数据库。在稻谷、小麦基质中,以筛查检出限(SDL)作为主要参数对筛查方法进行了验证。18种真菌毒素分为有最大限量和无最大限量两种类型,结果有最大限量的真菌毒素均能在其限量水平被准确筛查,无最大限量的真菌毒素其SDL的范围为2～800μg/kg。基质效应考察表明,稻谷中有14种真菌毒素有中等基质效应,小麦中有11种真菌毒素有中等基质效应。样品经乙腈提取后用QuEChERS萃取盐包和HLB净化柱净化,用建立的方法对25批稻谷、小麦进行筛查,结果2批稻谷中检出4种真菌毒素,2批小麦中检出2种真菌毒素。该方法能准确筛查SDL水...     

偶氮苯光致异构反饱和吸收的光学双稳态开关的理论研究

讨论了稳态条件下,反饱和吸收的偶氮苯分子光学双稳态的开关性能.先根据偶氮苯光致异构的理论模型,计算了影响偶氮苯反饱和吸收系数的因素,然后理论模拟其反饱和吸收的光学双稳态开关过程.模拟结果表明:基于偶氮苯分子的反饱和吸收可实现双稳态全光开关.增大偶氮苯分子的顺式基态吸收截面,减小热弛豫系数K能够降低反饱和吸收偶氮苯光学双稳态的开关能量;反式吸收截面大不利于反饱和吸收光学双稳态的形成.     

一个半离散非齐次核的Hilbert型不等式

引入独立参数,应用权函数的方法及实分析技巧,建立一个具有最佳常数因子的半离散非齐次核的Hilbert型不等式,还考虑了其具有最佳常数因子的等价形式.