Forty years of ceramic-on-ceramic THR bearings

The evolution of ceramic bearings for Total Hip Joint Replacement (THR), which have now been in clinical use for over 40 years, is reviewed from a historical perspective with emphasis on the characteristics of the composite materials in clinical use today, their mechanical properties, and wear behavior. Evidence is provided about the advantage of today’s composite ceramics over those of previous generations in terms of increased reliability and minimum wear, especially in the case of bearings operating under abnormal conditions (edge loading and microseparation).     

Prediction of an U2S3-type polymorph of Al2O3 at 3.7 Mbar

We predict by first principles a phase transition in alumina at approximately 3.7 Mbar and room temperature from the CaIrO(3)-type polymorph to another with the U(2)S(3)-type structure. Because alumina is used as window material in shock-wave experiments, this transformation should be important for the analysis of shock data in this pressure range. Comparison of our results on all high-pressure phases of alumina with shock data suggests the presence of two phase transitions in shock experiments: the corundum to Rh(2)O(3)(II)-type structure and the Rh(2)O(3)(II)-type to CaIrO(3)-type structure. The transformation to the U(2)S(3)-type polymorph is in the pressure range reached in the mantle of recently discovered terrestrial exoplanets and suggests that the multi-megabar crystal chemistry of planet-forming minerals might be related to that of the rare-earth sulfides.     

GI-Ⅱ型着色渗透玻璃渗透工艺与渗透深度关系的研究

目的　探讨不同的熔融渗透时间和温度下 ,玻璃在氧化铝中的渗透深度。方法　制作 Vita In-Ceram Alum ina和 GI- 氧化铝预烧体 ,分别用 A2和 IG2色玻璃进行渗透。按渗透时间不同分为 30、6 0、90、12 0、15 0和 180分钟组 ,渗透温度 110 0℃ ;按渗透温度不同分为 10 6 0、10 80、110 0、112 0和 1140℃温度组 ,渗透时间 1小时。用带标尺体视镜 (× 10 )分别测量各组的渗透深度。结果　渗透深度和时间的平方根呈线性关系 ,Vita和 GI- 组相关系数分别为 0 .9886和 0 .9932 ,回归方程分别为 d2 =0 .112 2 t- 0 .495 5和 d2 =0 .16 38t+0 .5 873;随渗透温度的升高 ,Vita的渗透速率增加 ,高于 110 0℃后下降 ,GI- 的趋势则相反。结论　 GI- 型玻璃具有较好的渗透性能 ,在 110 0℃的渗透温度下 ,推荐单冠和前牙桥体的渗透时间分别为 1小时和 3小时     

Ceramic-on-Ceramic Hip Outcome at a 5- to 10-Year Interval : Has it Lived Up to Its Expectations?

This study reports revision and complication rates of a single cementless double-wedged tapered stem with an alumina-alumina bearing over 10 years since the beginning of premarket clinical trials. Of 930 hips (848 patients) implanted by 9 surgeons, there were 19 revisions at mean follow-up of 5.9 years compared to 10 revisions in the 123 hips implanted with the polyethylene control group at mean 7.8 years. The ongoing safety of alumina-alumina bearings is demonstrated through excellent (96.8%) survivorship at 10 years. Twenty-one patients reported 23 incidences of noise described as clicking, squeaking, popping, or creaking. Eight patients with 9 hips described the noise as squeaking, most occurring rarely and only 1 occurring frequently in a patient subsequently revised for a reason aside from the squeaking.     

Squeaking in ceramic-on-ceramic hips: the importance of acetabular component orientation

Audible squeaking in total hip replacements with ceramic-on-ceramic bearings is a rare problem. Acetabular component orientation was compared for 17 squeaking hips and 17 matched controls. Ninety-four percent of control hips were in a range of 25 degrees +/- 10 degrees anteversion and 45 degrees +/- 10 degrees inclination, but only 35% of squeaking hips were in this range (P = .0003). Eight hips squeak with bending. Four hips squeak with walking, and 5 hips squeak after prolonged periods of walking. Hips that squeaked with walking had acetabular components that were more anteverted (40 degrees ) than hips that squeaked with bending (19 degrees ) (P = .001) or prolonged walking (18 degrees ) (P = .020). The hips started squeaking after an average of 14 months. Patients with squeaking hips were younger, heavier, and taller than patients with silent hips.     

HPLC-FD测定大鼠尿液中儿茶酚胺类化合物

目的: 建立HPLC-FD测定大鼠尿液中儿茶酚胺类化合物(CAs)的含量,为虚热证的药理学研究提供参考. 方法: 采用酸性氧化铝吸附法制备大鼠尿样;使用HiQSil C₁₈V色谱柱,流动相0.02 mol·L^-1 KH₂PO₄水溶液,流速0.5 mL·min^-1,激发波长(E_X)280 nm,发射波长(E_M)316 nm,柱温40℃. 结果: 大鼠尿样供试液中的儿茶酚胺类化合物可以与各干扰组分达到基线分离;CAs各组分线性、精密度和重复性良好;该法制备的样品溶液在16 h内测定,RSD<2%;CAs的回收率在65%~71%,试验中测得适应期后大鼠尿液中CAs含量稳定. 结论: 该文采用的供试品溶液制备方法简便,建立的色谱分析方法稳定、可靠,适合于大鼠尿液中CAs的含量测定.     

Efficient and novel one-pot synthesis of antifungal active 1-substituted-8-aryl-3-alkyl/aryl-4H-pyrazolo[4,5-f][1,2,4]triazolo[4,3-b][1,2,4]triazepines using solid support

A simple, efficient and environment-friendly procedure is developed for the synthesis of 1-substitued-8-aryl-3-alkyl/aryl-4H-pyrazolo[4,5-f][1,2,4]triazolo[4,3-b][1,2,4]triazepines in the presence of N,N-dimethylformamide as an energy transfer medium, p-TsOH as catalyst and basic alumina as solid support under microwave irradiation. The products are obtained in moderate to good yields and are in a state of high purity. Moreover, title compounds have been screened for antifungal activity.     

In-Ceram氧化铝全瓷冠与氧化锆全瓷冠在前牙修复中的临床效果比较

目的 比较In-Ceram氧化铝全瓷冠与氧化锆全瓷冠在前牙美容修复中的临床综合修复效果.方法 选择需要前牙修复的患者74例,随机分为两组.治疗组采用氧化铝全瓷冠修复,对照组采用氧化锆全瓷冠修复,修复后12个月,根据美国公共健康协会的修正标准对修复体的边缘着色、密合度、形态、颜色、周围龋坏等情况进行评价.结果 两组病例修...     

Selective Laser Melting of Al-Based Matrix Composites with Al2O3 Reinforcement: Features and Advantages

Aluminum matrix composites (AMC) are of great interest and importance as high-performance materials with enhanced mechanical properties. Al₂O₃ is a commonly used reinforcement in AMCs fabricated by means of various technological methods, including casting and sintering. Selective laser melting (SLM) is a suitable modern method of the fabrication of net-shape fully dense parts from AMC with alumina. The main results, achievements, and difficulties of SLM applied to AMCs with alumina are discussed in this review and compared with conventional methods. It was shown that the initial powder preparation, namely the particle size distribution, sphericity, and thorough mixing, affected the final microstructure and properties of SLMed materials drastically. The distribution of reinforcing particles tends to consolidate the near-melting pool-edges process because of pushing by the liquid–solid interface during the solidification process that is a common problem of various fabrication methods. The achievement of an homogeneous distribution was shown to be possible through both the thorough mixing of the initial powders and the precise optimization of SLM parameters. The strength of the AMCs fabricated by the SLM method was relatively low compared with materials produced by conventional methods, while for superior relative densities of more than 99%, hardness and tribological properties were obtained, making SLM a promising method for the Al-based matrix composites with Al₂O₃.     

Study on Adsorption Properties of Calcined Mg–Al Hydrotalcite for Sulfate Ion and Chloride Ion in Cement Paste

In the marine environment, sulfate ions and chloride ions are abundant. Therefore, sulfate attack and chloride ion attack are common failure forms of marine concrete. Mg–Al hydrotalcite is a layered bimetallic hydroxide, which can be used as guest molecular adsorbent. In this experiment, we synthesized Mg–Al hydrotalcite, and the crystal state, surface morphology, and composition of this adsorbent were investigated by modern micro-analysis technology. Mg–Al hydrotalcite was added into the prepared target ion solution, to explore the influence of various factors on the adsorption performance of Mg–Al hydrotalcite, and then calcined Mg–Al hydrotalcite was added into cement paste, to study the mechanical properties and durability of the paste samples. The experimental results show that the optimum conditions for adsorption of chloride ions by calcined Mg–Al hydrotalcite are an adsorption time of 4 h, temperature of 35 °C, LDO (calcined Mg-Al hydrotalcite) dosage of 3.5 g/L, and a pH of 8. The adsorption effect of sulfate ion is best when the adsorption time is 6 h, the temperature is 35 °C, the dosage of LDO is 4 g/L, and the pH = 8. The optimal adsorption conditions of calcined Mg–Al hydrotalcite for chloride ion and sulfate ion are not completely the same, and the adsorption of these two ions in mixed solution shows competitive adsorption. Compared with the common paste specimens without Mg–Al hydrotalcite, the mechanical properties and deformation properties of cement specimens can be significantly improved by adding Mg–Al hydrotalcite.