目的 通过荟萃分析探讨原发性面肌痉挛(hemifacial spasm,HFS)患者脑功能和结构的改变特点,进一步了解HFS的病理生理机制。方法收集2023年4月之前发表在相关数据库中关于HFS患者静息态功能磁共振成像(rest-state functional Magnetic re...目的 通过荟萃分析探讨原发性面肌痉挛(hemifacial spasm,HFS)患者脑功能和结构的改变特点,进一步了解HFS的病理生理机制。方法收集2023年4月之前发表在相关数据库中关于HFS患者静息态功能磁共振成像(rest-state functional Magnetic resonance imaging,Rs-fMRI)和基于体素的形态学分析方法(voxel-based morphometry,VBM)的所有文章。根据纳入和排除标准筛选后,采用激活似然估计(activation likelihood estimation,ALE)方法进行meta分析。结果共纳入7篇文献、10项研究(原发性面肌痉挛患者315例,健康受试者315名),对低频振荡幅度(amplitude of low frequency fluctuation,ALFF)、低频振荡分数(Fractional amplitude of low-frequency fluctuation,fALFF)及局部一致性(regional homogeneity,ReHo)等RsfMRI指标进行功能分析。ALE-meta结果显示,相对于健康受试者,HFS患者的自发性脑功能活动在中央前回、后扣带回、脑桥及小脑显著升高,而在额中回及颞上回降低。将所有基于VBM的HFS患者灰质改变的文献进行结构分析,结果显示,相对于健康受试者,HFS患者的海马旁回、丘脑体积显著减小。结论HFS患者存在脑功能和结构的改变,主要表现为中央前回、脑桥、小脑和后扣带回脑区自发性脑功能活动的异常,以及突显网络结构的异常,初步阐明了HFS患者静息态脑功能活动及结构改变的规律及特征。展开更多
An analytical model is presented to calculate the disassociation probability and the external quantum efficiency at high field in doped organic electrophosphorescence(EPH) devices. The charge recombination process and...An analytical model is presented to calculate the disassociation probability and the external quantum efficiency at high field in doped organic electrophosphorescence(EPH) devices. The charge recombination process and the triplet(T)-triplet(T) annihilation processes are taken into account in this model. The influences of applied voltage and the thickness of the device on the disassociation probability, and of current density and the thickness of the device on the external quantum efficiency are studied thoroughly by including and ignoring the disassociation of excitons. It is found that the dissociation probability of excitons will come close to 1 at high electric field, and the external EPH quantum efficiency is almost the same at low electric field. There is a large discrepancy of the external EPH quantum efficiency at high electric field for including or ignoring the disassociation of excitons.展开更多
The luminous efficiency of organic light-emitting devices depends on the recombination probability of electrons injected at the cathode and holes at the anode. A theoretical model to calculate the distribution of curr...The luminous efficiency of organic light-emitting devices depends on the recombination probability of electrons injected at the cathode and holes at the anode. A theoretical model to calculate the distribution of current densities and the recombination rate in organic single layer devices is presented taking into account the charge injection process at each electrode, charge transport and recombination in organic layer. The calculated results indicate that efficient single-layer devices are possible by adjusting the barrier heights at two electrodes and the carrier mobilities. Lowering the barrier heights can improve the electroluminescent(EL) efficiency pronouncedly in many cases, and efficient devices are still possible using an ohmic contact to inject the low mobility carrier, and a contact limited contact to inject the high mobility carrier. All in all, high EL efficiency needs to consider sufficient recombination, enough injected carriers and well transport.展开更多
A bilayer model with ohmic anode contact and injection limited cathode contact has been proposed to calculate the recombination efficiency and recombination zone width of the device. The effects of the thickness of ho...A bilayer model with ohmic anode contact and injection limited cathode contact has been proposed to calculate the recombination efficiency and recombination zone width of the device. The effects of the thickness of hole transport layer and the barriers of organic/organic interface on the combination efficiency and recombination width have been discussed. It is found that: (1) When the electrons are blocked fully and the holes are not blocked significantly at the organic/organic interface, for a given Lh/L, the recombination efficiency increases with increasing the applied voltage, but at a higher applied voltage, the recombination efficiency decreases with increasing Lh/L; (2) The recombination efficiency increases with increasing applied voltage and Hh', and when applied voltage and Hh' exceed some value, the recombination efficiency appears as a plateau; (3) The recombination width decreases with increasing the applied voltage and Lh/L. This model might explain the relative experiment phenomena.展开更多
文摘目的 通过荟萃分析探讨原发性面肌痉挛(hemifacial spasm,HFS)患者脑功能和结构的改变特点,进一步了解HFS的病理生理机制。方法收集2023年4月之前发表在相关数据库中关于HFS患者静息态功能磁共振成像(rest-state functional Magnetic resonance imaging,Rs-fMRI)和基于体素的形态学分析方法(voxel-based morphometry,VBM)的所有文章。根据纳入和排除标准筛选后,采用激活似然估计(activation likelihood estimation,ALE)方法进行meta分析。结果共纳入7篇文献、10项研究(原发性面肌痉挛患者315例,健康受试者315名),对低频振荡幅度(amplitude of low frequency fluctuation,ALFF)、低频振荡分数(Fractional amplitude of low-frequency fluctuation,fALFF)及局部一致性(regional homogeneity,ReHo)等RsfMRI指标进行功能分析。ALE-meta结果显示,相对于健康受试者,HFS患者的自发性脑功能活动在中央前回、后扣带回、脑桥及小脑显著升高,而在额中回及颞上回降低。将所有基于VBM的HFS患者灰质改变的文献进行结构分析,结果显示,相对于健康受试者,HFS患者的海马旁回、丘脑体积显著减小。结论HFS患者存在脑功能和结构的改变,主要表现为中央前回、脑桥、小脑和后扣带回脑区自发性脑功能活动的异常,以及突显网络结构的异常,初步阐明了HFS患者静息态脑功能活动及结构改变的规律及特征。
基金Excellent Youth Foundation of Hunan Province(03JJY1008) Science Foundation for Post-doctorate of China(2004035083) National Science Foundation of Hunan Province(06JJ20034)
文摘An analytical model is presented to calculate the disassociation probability and the external quantum efficiency at high field in doped organic electrophosphorescence(EPH) devices. The charge recombination process and the triplet(T)-triplet(T) annihilation processes are taken into account in this model. The influences of applied voltage and the thickness of the device on the disassociation probability, and of current density and the thickness of the device on the external quantum efficiency are studied thoroughly by including and ignoring the disassociation of excitons. It is found that the dissociation probability of excitons will come close to 1 at high electric field, and the external EPH quantum efficiency is almost the same at low electric field. There is a large discrepancy of the external EPH quantum efficiency at high electric field for including or ignoring the disassociation of excitons.
基金Excellent Youth Foundation of Hunan Province(03JJY1008) Science Foundation for Post-doctorate of China(2004035083) Science Foundation of Central South University( 0601059)
文摘The luminous efficiency of organic light-emitting devices depends on the recombination probability of electrons injected at the cathode and holes at the anode. A theoretical model to calculate the distribution of current densities and the recombination rate in organic single layer devices is presented taking into account the charge injection process at each electrode, charge transport and recombination in organic layer. The calculated results indicate that efficient single-layer devices are possible by adjusting the barrier heights at two electrodes and the carrier mobilities. Lowering the barrier heights can improve the electroluminescent(EL) efficiency pronouncedly in many cases, and efficient devices are still possible using an ohmic contact to inject the low mobility carrier, and a contact limited contact to inject the high mobility carrier. All in all, high EL efficiency needs to consider sufficient recombination, enough injected carriers and well transport.
基金Excellent Youth Foundation of Hunan Province(03JJY1008) Science Foundation for Post-doctorate of China(2004035083)
文摘A bilayer model with ohmic anode contact and injection limited cathode contact has been proposed to calculate the recombination efficiency and recombination zone width of the device. The effects of the thickness of hole transport layer and the barriers of organic/organic interface on the combination efficiency and recombination width have been discussed. It is found that: (1) When the electrons are blocked fully and the holes are not blocked significantly at the organic/organic interface, for a given Lh/L, the recombination efficiency increases with increasing the applied voltage, but at a higher applied voltage, the recombination efficiency decreases with increasing Lh/L; (2) The recombination efficiency increases with increasing applied voltage and Hh', and when applied voltage and Hh' exceed some value, the recombination efficiency appears as a plateau; (3) The recombination width decreases with increasing the applied voltage and Lh/L. This model might explain the relative experiment phenomena.