Fast multi-planar gradient echo MR imaging: impact of variation in pulse sequence parameters on image quality and artifacts

The purpose of this investigation was to quantitatively evaluate the practical impact of alteration of key imaging parameters on image quality and artifacts in fast multi-planar gradient echo (GRE) pulse sequences. These include multi-planar GRASS (MPGR) and fast multi-planar spoiled GRASS (FMPSPGR). We developed a composite phantom with different T(1) and T(2) values comprising the range of common biological tissues, which was also subjected to periodic motion in order to evaluate motion effects. Magnetic resonance imaging was performed on a GE Signa 1.5-T system. Experimental variations in key parameters included excitation flip angle (FL), echo time (TE), repetition time (TR), and receive bandwidth (BW). Quantitative analysis consisted of signal-to-noise-ratio (SNR) and contrast (CN), image nonuniformity (NU), full-width-at-half-maximum (FWHM) (i.e., blurring or geometric distortion), and ghosting ratio (GR). We found that flip angle, TE, and TR play particularly critical roles in determining image signal, homogeneity, and ghosting artifact with these sequences. Optimum clinical application of these pulse sequences requires careful attention to these imaging parameters and to their complex interactions.     

Chiral selective tunneling induced graphene nanoribbon switch

An armchair graphene nanoribbon switch has been designed based on the principle of the Klein paradox. The resulting switch displays an excellent on-off ratio performance. An anomalous tunneling phenomenon, in which electrons do not pass through the graphene nanoribbon junction even when the conventional resonance condition is satisfied, is observed in our numerical simulations. A selective tunneling rule is proposed to explain this interesting transport behavior based on our analytical results. Based on this selective rule, our switch design can also achieve the confinement of an electron to form a quantum qubit.      

不同LET辐射致DNA集簇性损伤的研究

利用辐照质粒DNA构象变化的分子模型,以DNA糖苷酶Fpg和AP核酸内切酶EndoIII识别并切割辐射所致DNA碱基损伤,将其转换为DNA断裂损伤,通过电泳分析DNA分子构象变化,研究比较γ射线、质子和7Li离子诱发DNA集簇性损伤。50Gy以上高剂量γ辐射对质粒DNA的损伤主要表现为单链断裂(SSB)和很少比例的双链断裂(DSB),并能产生一定水平的集簇性损伤。相比之下,高能质子束和高LET的7Li离子直接所致DNA的断裂损伤以及所产生的集簇性碱基损伤比γ射线的要严重,质子10Gy照射就可诱发明显的集簇损伤。     

基于计算机视觉的蜂窝陶瓷在线检测系统研究

研发了一种基于计算机视觉的蜂窝陶瓷智能在线检测系统;设计了系统的体系结构,4台高速摄像机在线获取蜂窝陶瓷图像,研究了改进型加权中值滤波处理,论述了基于Fisher评价函数的图像阈值分割算法;最后进行亚像素测量,判断产品尺寸是否在允许范围内,实验验证了系统的有效性和检测算法的可行性,可以很好地代替人工检测。     

绝缘衬底上硅表面载流子的超快动力学研究

利用800 nm波长的飞秒抽运探测技术测量r具有不同单晶硅薄膜厚度的绝缘衬底上硅(SOI)皮秒瞬态反射率变化,并通过基于受激载流子密度和温度变化过程建立的反射率模型讨论了SOI表面载流子的超快动力学过程.研究表明,表面复合速度(SRV)是影响载流子动力学响应的主要因素,且薄膜厚度越小表面复合速度就越大,对应的表面态密度可达到1013cm-2 .对于较小的SRV,受激载流子的超快响应决定了瞬念反射率变化;而对于较大的SRV,晶格温升对瞬态反射率变化的贞献变得显著,使得反射率在更短的时间内恢复并超过初始值.     

Preparation of nano-hydroxyapatite/poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide) biocomposite microspheres

Nano-hydroxyapatite (HA)/poly(l-lactide) (PLLA) composite microspheres with relatively uniform size distribution were prepared by a solid-in-oil-in-water (s/o/w) emusion solvent evaporation method. The encapsulation of the HA nanopaticles in microshperes was significantly improved by grafting PLLA on the surface of the HA nanoparticles (p-HA) during emulsion process. This procedure gave a possibility to obtain p-HA/PLLA composite microspheres with uniform morphology and the encapsulated p-HA nanoparticle loading reached up to 40 wt% (33 wt% of pure HA) in the p-HA/PLLA composite microspheres. The microstructure of composite microspheres from core-shell to single phase changed with the variation of p-HA to PLLA ratios. p-HA/PLLA composite microspheres with the diameter range of 2–3 μm were obtained. The entrapment efficiency of p-HA in microspheres could high up to 90 wt% and that of HA was only 13 wt%. Surface and bulk characterizations of the composite microspheres were performed by measurements such as wide angle X-ray diffraction (WAXD), thermal gravimetric analysis (TGA), environmental scanning electron microscope (ESEM) and transmission electron microscopy (TEM).     

High-voltage SOI lateral MOSFET with a dual vertical field plate

A new silicon-on-insulator(SOI)power lateral MOSFET with a dual vertical field plate(VFP)in the oxide trench is proposed.The dual VFP modulates the distribution of the electric field in the drift region,which enhances the internal field of the drift region and increases the drift doping concentration of the drift region,resulting in remarkable improvements in breakdown voltage(BV)and specific on-resistance(Ron,sp).The mechanism of the VFP is analyzed and the characteristics of BV and Ron,spare discussed.It is shown that the BV of the proposed device increases from 389 V of the conventional device to 589 V,and the Ron,sp decreases from 366 m·cm2to 110 m·cm2.     

Mn（Ⅱ）,Co（Ⅱ）与HSA相互作用的荧光光谱研究

用荧光光谱法研究了生理ｐＨ和等离子点（ｐＨ＝５．３０）时Ｍｎ（Ⅱ）、Ｃｏ（Ⅱ）与ＨＳＡ的相互作用。根据Ｆｏｒｓｔｅ非辐射能量转移理论,得到了不同ｐＨ时Ｍｎ（Ⅱ）、Ｃｏ（Ⅱ）在ＨＳＡ中的第一强结合位置与Ｔｒｐ－２１４残基间的距离。这一结果远大于文献报道值,根据Ｍｎ（Ⅱ）、Ｃｏ（Ⅱ）在ＨＳＡ中的结合部位及ＨＳＡ的畴结构对这一显著差异进行了讨论。