Two novel multiple B ← N Lewis pair functionalized perylenes are reported. While OBN-Pery shows a centrosymmetric and planar architecture, PBN-Pery displays an axisymmetric and twist structure. B ← N functionalization in both of them results in a large decrease in the HOMO-LUMO energy gap. PBN-Pery in particular has a low LUMO energy level (-3.00 eV) and red emission at the NIR I region with high fluorescence quantum yield.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Reduction of 2-(BMes2)pyrene (B1) and 2,7-bis(BMes2)pyrene (B2) gives rise to anions with extensive delocalization over the pyrenylene bridge and between the boron centers at the 2- and 2,7-positions, the typically unconjugated sites in the pyrene framework. One-electron reduction of B2 gives a radical anion with a centrosymmetric semiquinoidal structure, while two-electron reduction produces a quinoidal singlet dianion with biradicaloid character and a relatively large S0–T1 gap. These results have been confirmed by cyclic voltammetry, X-ray crystallography, DFT/CASSCF calculations, NMR, EPR, and UV–vis–NIR spectroscopy.
Reversible conversion between excited-states is key to many photophysical phenomena. We studied the equilibrium between LE and CT states by time-resolved and temperature-dependent fluorescence, fs- and ns-transient absorption, and LR-TDDFT calculations.
基于洪湖1959-2004年鱼类群落状况的调查研究，应用分类学多样性指数分析洪湖鱼类群落分类学多样性的变动. 结果显示：受江湖阻隔及人为干扰加剧等因素影响，洪湖鱼类种、属的数目在1981年表现出下降的趋势，科以上的分类阶元的数目则在1993年之后明显减少. 对洪湖鱼类组成进行NMDS排序，1959、1964和1981年的鱼类群落组成较为类似，1993和2004年的群落组成则发生了较大的变化. 随着时间推移，分类差异性指数Δ+表现出先上升后下降的趋势，而变异分类差异性指数Λ+则表现出先下降后上升的趋势，表明随着人为干扰的增加，洪湖鱼类群落的分类学进化树的平均路径长度和均匀度发生了不同程度的变化. 零假设模型显示，5个时期的Δ+值都位于置信区间内，而1993和2004年的Λ+值却位于置信区间的上方，显示分类学进化树的均匀度显著下降. Δ+和Λ+值的变化提供了与物种数变化所蕴含的不同信息，在多样性评价研究中可以作为经典多样性指数的补充. 洪湖鱼类Λ+值随干扰程度的加剧而增加，表明这一指数在多样性保护和评价中具有良好的应用价值.;Based on the published literatures about fish assemblages in Lake Honghu, we measured the long-term changes in two taxonomic diversity indices (average taxonomic distinctness, Δ+ and variation in taxonomic distinctness, Λ+) at five periods (1959, 1964, 1981, 1993, 2004) during the half past century. The results showed that the numbers of species and genera declined from 1981, whereas the numbers of families and higher taxa decreased from 1993. Non-metric multidimensional scaling analysis based on species composition led to a separation of two groups, one grouping 1959, 1964 and 1981, the other gathering 1993 and 2004. Taxonomic distinctness indices displayed a first increase and subsequent decrease of Δ+, and a consistent increase of Λ+ through time. The five periods all fell within the 95% confidence interval for Δ+, but 1993 and 2004 fell significantly above the confidence interval for Λ+, indicating a higher unevenness of the distribution of taxa across the taxonomic tree than random expectations. Δ+ and Λ+ could provide complementary information about the variability of biodiversity in addition to traditional diversity indices, thus we proposed that taxonomic distinctness indices can be used as promising tools in studies of biodiversity and environmental assessment.
To train convolutional networks using multi-lead ECG data and classify new data accurately to provide reliable information for clinical diagnosis.The data were pre-processed with a bandpass filter, and signal framing was adopted to adjust the data of different lengths to the same size to facilitate network training and prediction. The dataset was expanded by increasing the sample size to improve the detection rate of abnormal samples. A depth-wise separable convolution structure was used for more specific feature extraction for different channels of twelve-lead ECG data. We trained the two classifiers for each label using the improved DenseNet to classify different labels.The propose model showed an accuracy of 80.13% for distinguishing between normal and abnormal ECG with a sensitivity of 80.38%, a specificity of 79.91% and a F1 score of 79.35%.The model proposed herein can rapidly and effectively classify the ECG data. The running time of a single dataset on GPU is 33.59 ms, which allows real-time prediction to meet the clinical requirements.
Triarylboranes have drawn much attention in OLEDs owing to their remarkable solid-state luminescence properties. Here two new A-D-A type compounds, 2,7-bis(dimesitylboryl)-N-ethyl-carbazole (BCz) using triarylborane as electron acceptor and carbazole as electron donor while 2,7-bis((4-(dimesitylboryl)phenyl)ethynyl)-9-ethyl-carbazole (BPACz) using phenylacetylene as extra conjugated bridge, have been synthesized and their photoluminescence related properties in various states have been investigated both experimentally and theoretically. Both compounds show blue emission with high quantum yields, being potential candidates for blue OLED materials.
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