CT教学实验仪的设计与实现

介绍研制成功的CT教学实验仪的设计思想和总体结构,详细地讨论图像重建原理和算法以及电子学测量系统,CT教学实验仪有助于学生了解CT的基本原理,并通过实验可使学生了解物理学中的核衰变,吸收定律,γ射线能谱,电子学测量,计算物理以及计算机控制方面的知识。     

Calculation of the charge transfer transition energy of the mesitylene–ICl complex by ab initio and TDDFT methods: Comparison with other methylbenzene–ICl complexes

Of the four plausible isomeric structures of the mesitylene–ICl charge transfer (CT) complex, the most feasible one was determined by a detailed ab initio and DFT study at the HF, B3LYP and MPW1PW91 levels using the 6-31++G(d,p) basis set. Potential energy surface scans followed by frequency calculation and full optimization revealed that the I–Cl bond, with its I atom oriented towards the aromatic ring, stands vertically above an unsubstituted C-atom, being inclined at about 6° to the C ₃-axis. Complexation increases the I–Cl bond length. Correction for basis set superposition error through a counterpoise calculation yields a binding energy close to the experimental value. The electronic CT transition energy (hν _CT) with this ground-state structure as input was calculated in vacuo by the CIS method and in carbon tetrachloride medium by the TDDFT method under the polarizable continuum model. In a similar way the values of hν _CT were calculated for complexes of ICl with p-xylene, durene and hexamethylbenzene. Throughout the series of methylbenzene complexes, the TDDFT-calculated values of hν _CT were less than the experimental values and such underestimation may be attributed to the inherent difficulties of DFT to take into account long-range interactions. However, the trend of the variation of hν _CT with the number and position of methyl groups in the series was reasonably similar to the trend followed by the experimental CT transition energies.     

Synthesis,characterization and biological activities of two novel orthopalladated complexes: Interactions with DNA and bovine serum albumin,antitumour activity and molecular docking studies

[Pd(L₁)(C,N)]CF₃SO₃ and [Pd(L₂)(C,N)]CF₃SO₃ (L₁ = 2,2′ ‐bipyridine, L₂ = 1,10‐phenanthroline and C,N = benzylamine) novel orthopalladated complexes have been synthesized and characterized using various techniques. The binding of the complexes with native calf thymus DNA (CT‐DNA) was monitored using UV–visible absorption spectrophotometry, fluorescence spectroscopy and thermal denaturation studies. Our results indicate that these complexes can strongly bind to CT‐DNA via partial intercalative mode. In addition, fluorescence spectrometry of bovine serum albumin (BSA) with the complexes shows that the fluorescence quenching mechanism of BSA is a static process. The results of site‐competitive replacement experiments with specific site markers clearly indicate that the complexes bind to site I of BSA. Notably, the complexes exhibit significant in vitro cytotoxicity against two human cancer cell lines (Jurkat and MCF‐7) with IC₅₀ values varying from 37 to 53 μM. Finally, a molecular docking experiment effectively proves the binding of the Pd(II) complexes to DNA and BSA.     

Structure elucidation of uniformly 13C labeled small molecule natural products

Utilization of ²H, ¹³C, and ¹⁵N isotopically labeled proteins and peptides is now routine in biomolecular NMR investigations. The widespread availability of inexpensive, uniformly ¹³C enriched glucose now makes it possible to isolate uniformly ¹³C labeled natural products from microbial fermentation. We now wish to describe an approach for the rapid structural characterization of uniformly ¹³C labeled natural products that avoids the pitfalls of relying on parameters typically employed in biomolecular NMR studies. Copyright © 2015 John Wiley & Sons, Ltd.     

Coupling of Foam Drainage and Viscous Fingering in Porous Media Revealed by X-ray Computed Tomography

We investigate the development foam in granular porous media and the subsequent flow of the surfactant solution, where the fluid fraction variations are visualized and quantified using X-ray computed tomography. It is found that foam flows in a front like manner leading to a residual liquid fraction of 0.18±0.01, far from the inlet surface of the porous sample. A desaturation backward wave is also observed during foam development. We provided direct evidence that the flow of surfactant solution in porous media containing foam gives rise to superposition of a drainage wave and a characteristic viscous fingering pattern. In the wave the liquid fraction ranges from the above residual value to nearly 0.25±0.01. The liquid fraction associated with the viscous fingering decays as a function of distance but the inlet value increases up to 0.06±0.01. Certain ideas about the physics of foam flow in porous media are revised in the light of our findings.     

电测深法和电磁波CT法在采空区注浆加固效果检测中的综合应用

本文分别介绍了电测深法和电磁波层析成像方法,两种方法操作简单且能够详细反映采空区注浆加固效果。综合应用两种方法对铁路地下采空区加固效果进行检测,结果均表明了在线路的K0+278～K0+450段加固效果良好,两种检测方法检测结果具有一致性。证明将两种检测方法综合应用在采空区加固效果检测是合理的、可行的,为今后其他同类的检测效果提供了可借鉴的经验。     

THE ANALYSES OF THE THREE-DIMENSIONAL STRESS STRUCTURE NEAR THE CRACK TIP OF MODE I CT SPECIMENS IN ELASTICPLASTIC STATE(Ⅰ)—THE ANALYSES OF CONSTRAINT PARAMETERS AND FRACTURE PARAMETERS

In the present paper, three dimensional analyses of some general constraint parameters and fracture parameters near the crack tip. of Mode I CT specimens in two different thicknesses are carried out by employing ADINA program. The results reveal that the constraints along the thickness direction are obviously separated into two parts: the keeping similar high constraint field (Z₁) and rapid reducing constraints one (Z₂). The two fields are experimentally confiremed to correspond to the smooth region and the shear lip on the fracture face respectively. So the three dimensional stress structure of Mode I specimens can be derived through discussing the two fields respectively. The distribution of the Crack Tip Opening Displacement (CTOD) along the thickness direction and the three dimensional distribution of the void growth ratio (V_g) near the crack tip are also obtained. The two fracture parameters are in similar trends along the thickness direction, and both of them can reflect the effect of thickness and that of the loading level to a certain degree.     

深部砂土三轴高压卸载结构变化的CT研究

用取自山东巨野矿区埋深近 6 0 0m的深部砂土样,在三轴试验机上进行围压为 12MPa的三轴卸载试验,同时用CT装置探测试样在试验全过程中内部结构变化,并对纪录的CT图片进行了计算机图像分析处理,分析了深部砂土在高压卸载条件下变形和破坏结构性变化本质特点。     

Experimental measurement of radiation dose in a dedicated breast CT system

Radiation dose is an important performance indicator of a dedicated breast CT (DBCT). In this paper, the method of putting thermoluminescent dosimeters (TLD) into a breast shaped PMMA phantom to study the dose distribution in breasts was improved by using smaller TLDs and a new half-ellipsoid PMMA phantom. Then the weighted CT dose index (CTDI_w) was introduced to average glandular assessment in DBCT for the first time and two measurement modes were proposed for different sizes of breasts. The dose deviations caused by using cylindrical phantoms were simulated using the Monte Carlo method and a set of correction factors were calculated. The results of the confirmatory measurement with a cylindrical phantom (11 cm/8 cm) show that CTDI_w gives a relatively conservative overestimate of the average glandular dose comparing to the results of Monte Carlo simulation and TLDs measurement. But with better practicability and stability, the CTDI_w is suitable for dose evaluations in daily clinical practice. Both of the TLDs and CTDI_w measurements demonstrate that the radiation dose of our DBCT system is lower than conventional two-view mammography.     

基于计算机层析成像(CT)技术的梁山慈竹密度检测研究

密度是竹材重要的物理指标之一,与竹材的许多物理力学性能紧密相关。采用计算机层析成像(CT)技术,对2-5年生梁山慈竹(Dendroclamus farinosus)的密度时空变异特性进行了系统研究;利用正交试验设计确定了适宜的扫描参数,对其气干密度(Y)与相对应的CT值(X)之间的相关性进行分析研究,建立了线性回归模型(Y=0.001 X+1.148)并验证了该模型的准确性,得出两者之间存在着线性关系;同时利用模型计算出梁山慈竹径向和纵向的密度变化规律。为实现梁山慈竹密度的精准高效检测提供了新方法,也为深入研究竹材的材性和构造提供了新思路。