MRI methodological development of intervertebral disc degeneration: a rabbit in vivo study at 9.4 T

Intervertebral disc (IVD) degeneration is a complex process characterized by biochemical and structural changes in both the nucleus pulposus and the anulus fibrosus. In this study, we were able to obtain in vivo magnetic resonance (MR) images of the rabbit spine, with several MR imaging (MRI) contrasts (ρ, T₁ and T₂). We quantified several parameters (T₂, apparent diffusion coefficient, disc height and area) to differentiate between healthy and degenerative IVDs and to characterize the degeneration process. To our knowledge, there has not been any previous in vivo study of rabbit IVDs at high-field MRI (9.4 T).A custom radio frequency (RF) coil for 9.4 T was designed to match rabbit IVD morphology, to study the degeneration in vivo on a model of human lumbar disease. Our new probe, a custom half-birdcage-type coil, obtains the necessary exploration depth while meeting the requirements for signal homogeneity and sensitivity of the study. This design addresses some of the difficulties with constructing RF coils at high field strengths.     

Advances in the ultrastructural study of the implant-bone interface by backscattered electron imaging

The biocompatibility of titanium implants in bone depends on the response shown by cells in contact with the implant surface. Several developments have been targeted at achieving successful implant treatment. The aim of this study was to develop a novel preparation procedure to evaluate the bone cell response produced at the bone–implant interface using the technique scanning electron microscopy with backscattered electron imaging (SEM-BSE). Dental prostheses with an SLA-modified or TOP-modified surface were implanted in a toothless part of the mandibula in female pigs. The animals were sacrificed 12 weeks after surgery, at which time block specimens containing the implants were obtained. These specimens were then processed for SEM-BSE by optimizing a protocol involving chemical fixation and heavy metal staining. In addition, element distribution maps for the implant–bone tissue interface were obtained using a microanalytical system based on energy-dispersive X-ray spectrometry (EDS). This novel visualisation approach enabled a comprehensive study of the extracellular matrix and cell components of the host tissues neoformed around the implant. SEM-BSE images also provided ultrastructural details of the bone cells. This technique appears to be an effective and very promising tool for detailed studies on the implant–bone tissue interface and the host response to the bone incorporation process.     

雷暴云动力与电结构耦合的数值模拟试验研究

介绍了在三维冰雹云模式中增加了电参量的环境下强对流雷暴云发展演变的动力结构与雷暴云电结构耦合的关系,及微物理电机制的影响和相互作用的进行数值模拟试验研究结果。     

ICR小鼠体内染色体畸变试验的优化

目的 使用ICR小鼠开展体内染色体畸变实验,通过在不同时间点给予环磷酰胺(cyclophosphamide,CP)及秋水仙素(colchicine,COL),对比不同给药/取材时间点及不同给药浓度对小鼠骨髓细胞染色体畸变发生率的影响。方法 共36只约7～8周龄ICR雄性小鼠首先随机分为药后18 h取材组和给药后24 h取材组,再下设COL 4 mg/kg体质量(取材前4 h,i.p.)和10 mg/kg(取材前2 h,i.p.)给药组,以0.9% 氯化钠注射液为溶媒对照,分别给予CP 0 mg/kg、10 mg/kg和40 mg/kg,每小组各3只动物。记录实验期间给药前后动物体质量。阴性对照组和10 mg/kg CP组间隔24 h分两次给药,40 mg/kg CP为单次给药。给药后18 h或24 h取材,取材前2 h或4 h分别腹腔注射COL。取材时摘取全部实验动物双侧股骨,收集骨髓细胞悬液制备Giemsa染色体标本用于分析染色体畸变类型,并计算每组平均结构畸变细胞率(不含ctg及csg,AC%)、结构畸变细胞率(含ctg及csg,ACG%)、多畸变细胞率(不含ctg及csg,MAC%)及多倍体细胞率(PC%)。结果 本研究所用CP和COL对动物体质量无明显影响,给药剂量和给药频率可行。与各小组内的溶媒对照组相比,所有CP给药组的AC%、AGC%和MAC%均显著性升高(P<0.01),且给药剂量高时染色体损伤更为严重;CP18 h-COL4h组的AC%、ACG%和MAC%均低于CP18 h-COL2h组,并存在显著性差异(P<0.05),提示使用高剂量的COL(10 mg/kg)可产生额外的染色体损伤。溶媒对照组中的结构性畸变类型绝大多数为裂隙,而染色体单体及染色体断裂是CP引起的最主要畸变类型。结论 开展ICR小鼠染色体畸变试验时,在CP给药后约18 h、COL给药后4 h取材较为理想。本研究通过对试验条件的摸索不但积累了背景数据,也为相关研究者提供借鉴。     

Effect of film thickness and supercooling on the performance of cholesteryl cinnamate liquid crystal capillary columns

Improved separations of the isomers of olefinic aliphatic insect pheromones were obtained on cholesteryl cinnamate glass capillary columns by operating in the supercooled temperature range of the liquid crystal. Capillary columns were prepared with varying film thickness of the stationary phase; choice of the correct film thickness ensured optimum retention for a wide range of compounds within the most effective temperature range of the liquid crystal. The deactivation procedures described made the liquid crystal columns suitable for separation of the geometric isomers of polar and nonpolar compounds.     

探地雷达测定地基土含水量的实验研究

利用室内模型槽,采用探地雷达开展了测定地基土含水量的室内实验研究。通过对探地雷达反射波法测定的介电常数和烘干法测定的含水量之间的曲线拟合,提出了实验用粉土的含水量与介电常数之间的经验公式。与实测含水量的对比分析表明,Topp公式在一定含水量范围内有良好的适用性,而本文提出的经验公式较Topp公式具有更宽的含水量适用范围和更高的预测精度;针对不同类型土建立相应的含水量和介电常数之间的经验公式是必要的,将有助于提高探地雷达测定地基土含水量的精度。     

Al／SiCp复合材料微裂纹产生的原位研究

本文用扫描电镜下的单面缺口拉伸试验，考察了Ａｌ／ＳｉＣｐ试样的空穴的生成，裂纹的扩展以及裂纹前端微断裂区，指出该材料变脆的原因是由于微断裂区中的一次空穴所造成的。     

建筑物内火灾烟羽流和顶蓬射流诱发的空气运动盐水模拟实验研究

盐水在清水中的扩散与火灾烟气在空气中的蔓延相似，因而可用盐水的扩散来模拟火灾烟气的蔓延；同样地，由于盐水的扩散而导致的环境清水的运动也可用来模拟烟气蔓延诱发的空气运动。基于这一原理，本文用实验的方法，研究了建筑物内初起火灾产生的烟羽流和顶蓬射流所诱发的空气运动，并对走廊空气层生长规律和运动特性进行了初步的测量和分析。所得结果基本合理，对建筑物通风排烟及疏散通道设计有帮助，从而为建筑火灾环境空气的运动的实验研究开辟了新的思路，也为火灾区域模拟提供了实验依据     

Direct Aryloxylation/Alkyloxylation of Dialkyl Phosphonates for the Synthesis of Mixed Phosphonates

A strategy for the direct functionalization strategy of inertial dialkyl phosphonates with hydroxy compounds to afford diverse mixed phosphonates with good yields and functional‐group tolerance has been developed. Mechanistic investigations involving both NMR studies and DFT studies suggest that an unprecedented highly reactive P^V species (phosphoryl pyridin‐1‐ium salt), a key intermediate for this new synthetic transformation, is generated in situ from dialkyl phosphonate in the presence of Tf₂O/pyridine.     

Activation and diffusion of ammonia borane hydrogen on gold tetramers

One of the most serious candidates for safe storage of high hydrogen densities is ammonia borane, AB. Likewise, one of the most versatile catalysts known is gold in the form of atomic clusters. Taking these elements into account, in this work a density functional theory ‐based study about initial activation, detachment, and diffusion of ammonia borane hydrogen on gold tetramer, as a catalyst model, is developed. It was found that the total process is exergonic and that the hydrogen diffusion occurs with very low energy barriers. The process has a hydrogen detachment energy barrier lower than the one of the uncatalyzed AB, and that is easily overcome by the energy expelled in the previous stage of formation of the initial activated species. Additionally, all the process is assisted by the fluxionality of the gold cluster, and occurs via a unique catalytically activated initial species, which contains a three‐center simultaneous interaction at the catalytically activated zone.