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The bimolecular single collision reaction potential energy surface of an isocyanate NCO radical with a ketene CH2CO molecule was investigated by means of B3LYP and QCISD(T) methods. The computed results indicate that two possible reaction channels exist on the surface. One is an addition-elimination reaction process, in which the CH2CO molecule is attacked by the nitrogen atom at its methylene carbon atom to lead to the formation of the intermediate OCNCH2CO followed by a C-C rupture channel to the products CH2NCO+CO. The other is a direct hydrogen abstraction channel from CHzCO by the NCO radical to afford the products HCCO+HNCO. Because of a higher barrier in the hydrogen abstraction reaction than in the addition-elimination reaction, the direct hydrogen abstraction pathway can only be considered as a secondary reaction channel in the reaction kinetics of NCO+ CH2CO. The predicted results are in good agreement with previous experimental and theoretical investigations. 相似文献
2.
A detailed singlet potential energy surface(PES) of [Si,C,O,O] system including a van der Waals (vdW) comples SiO……CO2,eight isomers,and twelve transiton states is investigated by MP2 and QCISD(T) (single-point)methods.At the final QCISD(T)/6-311 G(2df)//MP2/6-311G(d) level with zero-point energy included,the complex SiO……CO is found to be thermodynamically and kinetically the most stable species.Although eight ismoers are located as local energy minima,they are rather unstable toward isomerization to the dissociation fragments or comples.For the reaction of silocon atoms with carbon dioxide,two competitive reaction channels are found,and the primary pathway,which leads to the products of SiO and CO fragments,is the direct oxygen-abstraction process from carbon dioxide by silicon atom with a41.16 kJ/mol reaction barrier height.Our predications are in good agreement with previous experimental and theoretical studies. 相似文献
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采用 B3LYP和 CCSD(T)方法对 R-C≡ P(R=-BH2, -CH3,-NH2, -OH)体系进行了理论研究 .结果表明,含 C≡ P三键的异构体 BH2-C≡ P和 CH3-C≡ P在各自的体系中分别是热力学最稳定的结构 .而在 HO-C≡ P和 NH2-C≡ P体系中,热力学最稳定的结构却是 H-P=C=O和含 C≡ N三键的 N≡ C-PH2.动力学理论研究表明,没有相关实验研究的 R-C≡ P(R=-BH2,NH2)体系中共有 5种异构体是动力学稳定的 .在 HO-C≡ P体系的 2种动力学稳定的异构体中, H-P=C=O连接方式的异构体已被实验所证实,而另外一种 HO-C≡ P连接方式的异构体的动力学稳定性较高,实验中可以观察到 .对于 CH3C≡ P体系,研究所预示的 2种动力学稳定的异构体中 CH3-C≡ P已被实验证实,从理论上推测另一种动力学稳定性较高的异构体 HC≡ C-PH2在实验中也可以检测到. 相似文献
4.
在UB3LYP/6-311G(d)和UCCSD(T)/6-311 + G(2df)(单点)水平下得到了[Si, N, C,O]2+体系的15种异构体, 对它们的结构进行了分析, 并给出了能量较低的离子碎片方式. 计算结果表明线型异构体SiNCO2+ (2Π )是[Si,N,C,O]2+体系中热力学最稳定的物种, 其次是线型的SiOCN2+(2Π ), SiCNO2+(2Π )和含NCO三元环的异构体SiC(NO)(2A″ ). 几个动力学相对较稳定的异构体的稳定性顺序为SiNCO2+> SiCNO2+(2Π )> SiOCN2+> SiC(NO)2+ >OSiNC2+(2Π ). 对异构化过程及离子碎片方式的分析结果说明线型异构体SiNCO2+是相关质谱实验中的主要物种, 而且是亚稳态的, 在质谱条件下可以解离成离子碎片. 相似文献
5.
Fe3+-TiO2/SiO2光催化降解罗丹明B的研究 总被引:25,自引:0,他引:25
以硅胶为载体,采用溶胶-凝胶法制备了不同掺杂量的Fe3+-TiO2/SiO2光催化剂,并采用SEM,Raman和DRS等手段对其进行了分析和表征.以氙灯为光源,通过对可溶性染料罗丹明B的降解反应,考察了Fe3+-TiO2/SiO2催化剂的光催化活性,探讨了光催化反应中溶液pH值和起始浓度对催化反应的影响. 相似文献
6.
采用密度泛函理论方法,对Cs以不同覆盖度吸附在石墨烯表面时系统的结构稳定性和场发射性能进行了研究。计算结果表明单原子Cs吸附在石墨烯表面的碳六元环的中心位置时系统的能量最低。随着Cs的覆盖度增加,碱金属Cs与石墨烯之间的吸附作用逐渐增强,(4×4)R 0°和(2×2)R 0°结构是稳定的。由于碱金属Cs的修饰作用,Cs/石墨烯体系的功函明显下降,且随着碱金属Cs的覆盖度增大,系统的功函逐渐减小。态密度的计算结果表明功函的下降主要与Cs和石墨烯之间的电子转移有关。随着覆盖度的增大,石墨烯的电子态逐渐向低能方向移动,系统的费米能级升高并导致材料的功函下降。 相似文献
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8.
H2CO和NO2反应机理的密度泛函理论计算研究 总被引:2,自引:2,他引:2
用密度泛函理论方法在UB3LYP/ 6-311++G(d,p)并包含零点能水平上计算得到了H2CO和NO2反应的势能面.在势能面上找到了由H2CO和NO2反应生成HCO和trans-HONO的两条反应通道.直接H迁移反应通道的势垒只有90.54 kJ*mol-1,是主要的反应通道,其TST速率是7.9 cm3*mol-1*s-1,与文献值相符;另一条通道是H2CO异构化为trans-HCOH,然后C位H迁移,最后生成的HOC分子异构化为HCO,这条通道反应势垒高达348.03 kJ*mol-1,是一条次要反应通道. 相似文献
9.
Characterizing neural activities evoked by manual acupuncture through spiking irregularity measures
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The neural system characterizes information in external stimulations by different spiking patterns. In order to examine how neural spiking patterns are related to acupuncture manipulations, experiments are designed in such a way that different types of manual acupuncture (MA) manipulations are taken at the 'Zusanli' point of experimental rats, and the induced electrical signals in the spinal dorsal root ganglion are detected and recorded. The interspike interval (ISI) statistical histogram is fitted by the gamma distribution, which has two parameters: one is the time-dependent firing rate and the other is a shape parameter characterizing the spiking irregularities. The shape parameter is the measure of spiking irregularities and can be used to identify the type of MA manipulations. The coefficient of variation is mostly used to measure the spike time irregularity, but it overestimates the irregularity in the case of pronounced firing rate changes. However, experiments show that each acupuncture manipulation will lead to changes in the firing rate. So we combine four relatively rate- independent measures to study the irregularity of spike trains evoked by different types of MA manipulations. Results suggest that the MA manipulations possess unique spiking statistics and characteristics and can be distinguished according to the spiking irregularity measures. These studies have offered new insights into the coding processes and information transfer of acupuncture. 相似文献
10.
Effective suppression of beta oscillation in Parkinsonian state via a noisy direct delayed feedback control scheme
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This work explores the function of the noisy direct delayed feedback(NDDF)control strategy in suppressing the pathological oscillations in the basal ganglia(BG)with Parkinson’s disease(PD).Deep brain stimulation(DBS)alleviates the PD state fantastically.However,due to its unclear mechanism and open-loop characteristic,it is challenging to further improve its effects with lower energy expenditure.The noise stimulus performs competitively in alleviating the PD state theoretically,but it cannot adapt to the neural condition timely and automatically due to its open-loop control scheme.The direct delayed feedback(DDF)control strategy is able to disturb excessive synchronous effectively.Therefore,the NDDF control strategy is proposed and researched based on a BG computational model,which can reflect the intrinsic properties of the BG neurons and their connections with thalamic neurons.Simulation results show that the NDDF control strategy with optimal parameters is effective in removing the pathological beta oscillations.By comparison,we find the NDDF control strategy performs more excellent than DDF in alleviating PD state.Additionally,we define the multiple-NDDF control strategy and find that the multiple-NDDF with appropriate parameters performs better than NDDF.The obtained results contribute to the cure for PD symptoms by optimizing the noise-induced improvement of the BG dysfunction. 相似文献