目的利用神经突方向离散度与密度成像(neurite orientation dispersion and density imaging,NODDI)初步探讨帕金森病伴嗅觉障碍患者嗅皮质微结构变化。方法选择新疆医科大学第二附属医院30例帕金森病伴嗅觉障碍患者为病例组和健康自愿...目的利用神经突方向离散度与密度成像(neurite orientation dispersion and density imaging,NODDI)初步探讨帕金森病伴嗅觉障碍患者嗅皮质微结构变化。方法选择新疆医科大学第二附属医院30例帕金森病伴嗅觉障碍患者为病例组和健康自愿者40例为对照组,2组进行MR检查后经处理得到NODDI图像及相关参数,即神经突体积分数(intracellular volume fraction,VIC)、神经突方向分散度(orientation dispersionindex,ODI),比较2组感兴趣区参数值。通过ROC曲线评估嗅觉相关脑区NODDI参数值在PD早期诊断中的效能。结果帕金森病患者左侧海马VIC值(t=—4.265、P<0.001)、右侧海马VIC值(t=—4.590、P<0.001)、左侧杏仁核VIC值(t=—3.846、P<0.001)与对照组相比差异有统计学意义。PD组H-Y分级Ⅰ与Ⅱ级左侧杏仁核VIC值(P=0.155)、右侧杏仁核VIC值(P=0.110),左侧杏仁核ODI值(P=0.883)、右侧杏仁核ODI值(P=0.632),左侧海马VIC值(P=0.082)、右侧海马VIC值(P=0.082),左侧海马ODI值(P=0.316)、右侧海马ODI值(P=0.712)之间差别无统计学意义(P>0.05)。ROC曲线分析显示,双侧海马及左侧杏仁核VIC值曲线下面积(AUC)分别为0.761、0.778、0.748。结论NODDI可反映帕金森病伴嗅觉障碍患者嗅皮质微结构变化,对早期诊断帕金森病提供一定帮助。展开更多
Hydrogen-like donor impurity states in symmetric triangular quantum wells are investigated by using a variational method.Both the effects of the variable effective mass of electrons and the spatially dependent dielect...Hydrogen-like donor impurity states in symmetric triangular quantum wells are investigated by using a variational method.Both the effects of the variable effective mass of electrons and the spatially dependent dielectric constant are considered in the calculation.The numerical results show that the binding energy depends on not only the effective mass and dielectric constant but also the spatial distribution of electron probability density.The binding energies of donor states get the maximums at the well-center.The results are also compared with those obtained in parabolic and square wells.It is seen that the triangular well support the highest binding energies for donor states.展开更多
Chemical vapor deposition （CVD） synthesis of large-domain hexagonal boron nitride （h-BN） with a uniform thickness is very challenging, mainly due to the extremely high nucleation density of this material. Herein, ...Chemical vapor deposition （CVD） synthesis of large-domain hexagonal boron nitride （h-BN） with a uniform thickness is very challenging, mainly due to the extremely high nucleation density of this material. Herein, we report the successful growth of wafer-scale, high-quality h-BN monolayer films that have large single-crystalline domain sizes, up to -72 μm in edge length, prepared using a folded Cu-foil enclosure. The highly confined growth space and the smooth Cu surface inside the enclosure effectively reduced the precursor feeding rate together and induced a drastic decrease in the nucleation density. The orientation of the as-grown h-BN monolayer was found to be strongly correlated to the crystallographic orientation of the Cu substrate： the Cu （111） face being the best substrate for growing aligned h-BN domains and even single-crystalline monolayers. This is consistent with our density functional theory calculations. The present study offers a practical pathway for growing high-quality h-BN films by deepening our fundamental understanding of the process of their growth by CVD.展开更多
文摘目的利用神经突方向离散度与密度成像(neurite orientation dispersion and density imaging,NODDI)初步探讨帕金森病伴嗅觉障碍患者嗅皮质微结构变化。方法选择新疆医科大学第二附属医院30例帕金森病伴嗅觉障碍患者为病例组和健康自愿者40例为对照组,2组进行MR检查后经处理得到NODDI图像及相关参数,即神经突体积分数(intracellular volume fraction,VIC)、神经突方向分散度(orientation dispersionindex,ODI),比较2组感兴趣区参数值。通过ROC曲线评估嗅觉相关脑区NODDI参数值在PD早期诊断中的效能。结果帕金森病患者左侧海马VIC值(t=—4.265、P<0.001)、右侧海马VIC值(t=—4.590、P<0.001)、左侧杏仁核VIC值(t=—3.846、P<0.001)与对照组相比差异有统计学意义。PD组H-Y分级Ⅰ与Ⅱ级左侧杏仁核VIC值(P=0.155)、右侧杏仁核VIC值(P=0.110),左侧杏仁核ODI值(P=0.883)、右侧杏仁核ODI值(P=0.632),左侧海马VIC值(P=0.082)、右侧海马VIC值(P=0.082),左侧海马ODI值(P=0.316)、右侧海马ODI值(P=0.712)之间差别无统计学意义(P>0.05)。ROC曲线分析显示,双侧海马及左侧杏仁核VIC值曲线下面积(AUC)分别为0.761、0.778、0.748。结论NODDI可反映帕金森病伴嗅觉障碍患者嗅皮质微结构变化,对早期诊断帕金森病提供一定帮助。
基金Supported by the National Natural Science Foundation of Chin(10164003)
文摘Hydrogen-like donor impurity states in symmetric triangular quantum wells are investigated by using a variational method.Both the effects of the variable effective mass of electrons and the spatially dependent dielectric constant are considered in the calculation.The numerical results show that the binding energy depends on not only the effective mass and dielectric constant but also the spatial distribution of electron probability density.The binding energies of donor states get the maximums at the well-center.The results are also compared with those obtained in parabolic and square wells.It is seen that the triangular well support the highest binding energies for donor states.
基金Acknowledgements The work was supported by the National Natural Science Foundation of China （Nos. 51432002, 50121091, 51290272, and 51222201）, the National Basic Research Program of China （Nos. 2013CB932603, 2012CB933404, 2011CB933003, 2011CB921903, and 2012CB921404）, and the Ministry of Education （No. 20120001130010）.
文摘Chemical vapor deposition （CVD） synthesis of large-domain hexagonal boron nitride （h-BN） with a uniform thickness is very challenging, mainly due to the extremely high nucleation density of this material. Herein, we report the successful growth of wafer-scale, high-quality h-BN monolayer films that have large single-crystalline domain sizes, up to -72 μm in edge length, prepared using a folded Cu-foil enclosure. The highly confined growth space and the smooth Cu surface inside the enclosure effectively reduced the precursor feeding rate together and induced a drastic decrease in the nucleation density. The orientation of the as-grown h-BN monolayer was found to be strongly correlated to the crystallographic orientation of the Cu substrate： the Cu （111） face being the best substrate for growing aligned h-BN domains and even single-crystalline monolayers. This is consistent with our density functional theory calculations. The present study offers a practical pathway for growing high-quality h-BN films by deepening our fundamental understanding of the process of their growth by CVD.
