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151.
It is proposed that in molecular mechanics calculation points belonging to various stable or meta-sta-ble conformtrs are mixed up and form fractal structures in conformation space.The calculation results show the following two phenomena:(i)Two levels of structure with fractal feature were observed.Around the conformer without mirror symmetry points belonging to the conformer and its enantiomer are mixed up and form the first level of fractal structure; on the boundary of the attractive basin o{ each atlractor,points belonging to different attractors form the second level of fractal structure.(ii) The variation of molecular mechanics parameters will influence the structure and area of each attractive basin significantly The above phenomena may become the basis of a new method for solving the troublesome multi-minimum-point problem in molecular mechanics calculation. 相似文献
152.
用TRP技术研究了以全硅MCM-41(Si-MCM-41)和HNO3交换的全硅MCM-41(H-MCM-41)为载体制备的Ni-Mo、Co-Mo和Ni-W加氢脱硫(HDS)催化剂的还原性能,并以0.8(wt)%二苯并噻吩(DBT)的十氢萘溶液为模型化合物,在高压固定床反应器上考察了上述催化剂的加氢脱硫(HDS)反应性能。结果表明,Si-MCM-41经稀HNO3交换后,所担载的Ni-Mo和Ni-W催化剂还原性能、HDS活性和加氢活性有显著变化,但对Co-Mo催化剂影响不大。这说明在Ni-Mo/H-MCM-41和Ni-W/H-MCM-41中可能存在氢溢流现象,DBT的HDS活性与载体表面酸性和氢溢流有关。 相似文献
153.
本文用Xα方法计算出不同价态与电子组态下锰、铁、钴、铜、锌及钼等过渡族重要生物微量元素和氮、氧、氟、磷、硫、氯、硒和溴等常见负电性元素的数值原子轨道和轨道电负性值,再用数值拟合方法得出这些原子轨道的单ξ和双ξSlater型基函数的指数.研究了这些元素的原子所带电荷和电子组态对其原子轨道指数与轨道电负性的影响,给出了相应的回归公式.这些公式有较高的精确度,不但为研究这些元素化合物的电子结构提供基础参数,也为电荷自洽型的计算提供较可靠的计算公式. 相似文献
154.
Min Zeng Ang Ren Wubin Wu Yongsheng Zhao Chuanlang Zhan Jiannian Yao 《Chemical science》2020,11(34):9154
We present herein an innovative host–guest method to achieve induced molecular chirality from an achiral stilbazolium dye (DSM). The host–guest system is exquisitely designed by encapsulating the dye molecule in the molecule-sized chiral channel of homochiral lanthanide metal–organic frameworks (P-(+)/M-(−)-TbBTC), in which the P- or M-configuration of the dye is unidirectionally generated via a spatial confinement effect of the MOF and solidified by the dangling water molecules in the channel. Induced chirality of DSM is characterized by solid-state circularly polarized luminescence (CPL) and micro-area polarized emission of DSM@TbTBC, both excited with 514 nm light. A luminescence dissymmetry factor of 10−3 is obtained and the photoluminescence quantum yield (PLQY) of the encapsulated DSM in DSM@TbTBC is ∼10%, which is close to the PLQY value of DSM in dilute dichloromethane. Color-tuning from green to red is achieved, owing to efficient energy transfer (up to 56%) from Ln3+ to the dye. Therefore, this study for the first time exhibits an elegant host–guest system that shows induced strong CPL emission and enables efficient energy transfer from the host chiral Ln-MOF to the achiral guest DSM with the emission color tuned from green to red.Homochiral Ln-MOFs are synthesized to encapsulate achiral dyes to induce strong circularly polarized luminescence with a luminescence dissymmetry factor of 10−3. 相似文献
155.
J. Ren H. -D. Ließ R. Mäckel H. Baumgärtner 《Fresenius' Journal of Analytical Chemistry》1995,353(3-4):303-306
Based on the well known Kelvin probe for work function measurements a new microstructure analysis system – the Scanning Kelvin Microscope – has been developed. It allows to measure simultaneously with high lateral resolution the distribution of the contact potential difference (CPD) between a conductive sample and a reference probe together with the topographical structure of the sample surface. The measurement is contact free and non-destructive and can be carried out in natural environments. At present the lateral resolution of the measurement approaches 5 m. The results can be displayed on a computer in three dimensional colour pictures. 相似文献
156.
Based on the well known Kelvin probe for work function measurements a new microstructure analysis system - the Scanning Kelvin Microscope - has been developed. It allows to measure simultaneously with high lateral resolution the distribution of the contact potential difference (CPD) between a conductive sample and a reference probe together with the topographical structure of the sample surface. The measurement is contact free and non-destructive and can be carried out in natural environments. At present the lateral resolution of the measurement approaches 5 microm. The results can be displayed on a computer in three dimensional colour pictures. 相似文献
157.
158.
In this paper three Banach spacesA
0(),A
andA
1() of functions holomorphic in the unit ballB of
n
are defined. We exhibit bounded projections fromC
0(B) ontoA
0(), fromL
1(B) ontoA
1(), and fromL(B) ontoA(). Using these projections, we show thatA
0()* A
1() andA
1()* A().Supported in part by the National Natural Science Foundation of China. 相似文献
159.
160.
Mössbauer measurements in a-(Fe0.765Mn0.235)78Sn2Si6B14 have been performed with57Fe and119Sn. Both hyperfine fields show a kink near 70 K, indicating a freezing of the transverse spins. The ratio of the two hyperfine fields contains information about the correlation of the transverse spins. The ratioB
hf(Sn)/B
hf(Fe) stays constant aboveT
xy
and rises belowT
xy
. This indicates an alignment of the transverse spins on a local scale, as was also found inAuFe and a-FeZr. 相似文献