Failure analysis of a broken tooth

Several days after heart surgery, a patient discovered his upper right canine tooth had broken at the root. Such tooth damage, recognized post-operatively, is usually assumed to be caused by blunt mechanical force from an instrument used by the anesthesiologist during placement of a breathing tube at the start of surgery. In this case, the patient had saved the crown portion of the broken tooth, and it was possible to examine the root fracture characteristics. The curvature and direction of the crack path and natural tooth situation suggested that failure could be described through a cantilever beam model. This was confirmed when a whole extracted sample tooth was embedded and broken by a measured force in a manner consistent with the model. The resulting fracture surface matched that of the patient’s broken canine tooth. However, the high load and force direction necessary to fracture the root was inconsistent with forces applied during the anesthesia procedure. The failure analysis and further investigation indicated tooth clenching on the breathing tube during recovery was the likely cause of fracture. This paper presents an alternate explanation for intubation-related dental injury, demonstrates the practicality of fractographic analysis of biological materials, and introduces a methodology for simulating in vitro tooth settings for mechanical testing.     

The magnetic structure of TbNiSiD1.78

TbNiSiD_1.78 has been studied by powder neutron diffraction below 100 K. The compound takes the hexagonal room temperature structure at 100 and 50 K (P6₃/mmc). At 2 K, below the antiferromagnetic ordering temperature of 10 K, there is a small orthorhombic distortion of the lattice. The refined unit-cell dimensions at 2 K (space group Pnma) are a=7.9505(2), b=4.02502(14), c=6.9823(2) Å. The magnetic moments of Tb are 8.71(6) μ_B, and are ordered antiferromagnetically along a.     

欧洲轿车新战略决策——电压、阻燃材料与工作温度一并提高——兼论Synolite5001-T-1牌聚酯树脂的阻燃防火性能优于酚醛树脂

本文介绍了欧洲轿车新战略决策，也即：将要提高轿车的电池电压，，阻燃材料的比率和工作温度；Synolite5001-T-1牌聚酯树脂的阻燃防炎性能优于酚醛树脂。     

金属/Al2O3基纳米复合材料研究最新进展

金属／Al2O3纳米复合材料在保持原有金属的功能特性时，还可以获得 很好的力学性能，是有良好发展前景的一种纳米复合材料。本文回顾了近年来金属／Al2O3基纳米复合材料在制备工艺，微观结构和力学性能，增韧强化机理方面的最新进展，并指出了今后的研究方向。     

Oleuropein Inhibits LDL Oxidation Induced by Cooking Oil Frying By-products and Platelet Aggregation Induced by Platelet-Activating Factor

Oleuropein, a polyphenolic glucoside, constituent of olive fruit and oil, has been previously shown to exhibit, in vitro, potent properties as a biological antioxidant. In the present paper, two new properties are demonstrated in vitro as well, concerning its vascular protection activity, against the atheromatic lesion formation and its blood antithrombotic effect. Firstly, it was found that the oxidation of low-density lipoproteins (LDL), induced by different quantities of total polar materials (TPM), was inhibited by 10 μ M (final concentration) of oleuropein, revealing approx. 50% protection. Secondly, platelet-rich human plasma aggregation, induced by either the platelet-activating factor or adenosine diphospate or arachidonic acid, was inhibited by oleuropein. The 10 μ M (final concentration) of oleuropein was proven to be the most effective among the tested concentrations against LDL oxidation, while an IC₅₀=0.41 mM was calculated for its inhibitory activity against platelet aggregation induced by 0.7 μ M platelet-activating factor.     

烧结NdFeB合金中的夹杂物

使用金相显微镜、扫描电镜及Ｘ射线能谱和波谱观察并分析了ＮｄＦｅＢ烧结材料中夹杂物的形态、数量和组成。磁粉制备后立即烧结的ＮｄＦｅＢ磁体中的夹杂物是氧化钕；而在不同环境条件下放置后的ＮｄＦｅＢ粉再烧结的材料中发现，除了氧化钕的夹杂物外，还有钕的氮化物及钕的氮氧复合夹杂物。同时还论讨了这些夹杂物对于ＮｄＦｅＢ材料磁性能的影响。     

核电材料在模拟反应堆环境中应力腐蚀破裂测试技术与性能评价

简要介绍了采用慢应变速率试验，Ｕ型弯曲和Ｃ形环试验等技术，分别对８００合金，３０４和３１６及３１６Ｔｉ不锈钢Ａ５３３Ｂ压力容器用多在模拟核反应堆环境中的应力腐蚀破裂敏感性性进行的试验研究的一些主要结果；并结合电化学测试和表面膜俄歇电子能谱分析结果进行了讨论。     

Chemical leaching and magnetic properties of non-equilibrium Al(Co–Cu) powders produced by rod milling

We report upon the chemical leaching and magnetic properties of nanoscale crystalline Al_0.6(Co₂₅Cu₇₅)_0.4 alloy powders produced by rod milling. X-Ray diffractometry (XRD), transmission electron microscopy, differential scanning calorimetry, vibrating sample magnetometry, and superconducting quantum interference device magnetometry were used to characterize the as-milled and leached specimens. After 400 h of milling, only the b.c.c. phase of the intermetallic compound γ-Al_3.892Cu_6.10808 was detected by XRD. After annealing the leached specimen at 600 °C for 1 h, the nanoscale crystalline phase was transformed into the f.c.c. Cu phase, and this was accompanied by a change in the magnetic properties. The peaks of the magnetization shifted towards lower temperature with increasing external field. The temperature behavior at T_f (45 K) for direct current (d.c.) magnetic susceptibility measurements was quite different for field cooling and zero-field cooling. After cooling the leached specimen from 800 °C, magnetization increased gradually.     

Distribution of properties from sampling inhomogeneous materials by line transects

A theory related to the statistics of the structure and properties of inhomogeneous materials has been proposed, dealing with the distribution of properties from sampling of inhomogeneous structures by line transects. It is demonstrated that the empirical cumulative distribution functions of the intercepts from the microstructural constituents and their variances are important fingerprints of the inhomogeneous structures.Simulated sampling of the images of the microstructure by line transects has been proposed as a powerful method for characterization the distribution of properties of inhomogeneous structures. One of the advantages of the method based on the expected values of the order statistics of the intercepts is that the probability bounds of the property are determined without prior knowledge of the functional relationship between the property and the intercepts from the structural constituents.The concept intercept variance has an important application in determining the minimum transect length that stabilizes the variation of the intercept at a low value. Additionally, the concept ‘intercept variance’ can be used for topological optimization of the microstructure regarding the risk of intercepting a large amount of the weaker constituent. Equations regarding the variance of the intercepted fraction characterizing transect lengths with a specified distribution have also been derived.     

新型高k栅介质材料研究进展

随着半导体技术的不断发展，MOSFET（metal-oxide-semiconductor field effect transistor）的特征尺寸不断缩小，栅介质等效氧化物厚度已小至nm数量级。这时电子的直接隧穿效应将非常显著，将严重影响器件的稳定性和可靠性。因此需要寻找新型高k介质材料，能够在保持和增大栅极电容的同时，使介质层仍保持足够的物理厚度来限制隧穿效应的影响。本文综述了研究高k栅介质材料的意义；MOS栅介质的要求；主要新型高k栅介质材料的最新研究动态；展望了高k介质材料今后发展的主要趋势和需要解决的问题。