Matter Timed

At best, the ageing of materials is regarded as lending a patina to historic buildings. In reality, however, materials often age disgracefully and unevenly, requiring a high level of maintenance and refurbishment. What if materials could be engineered and integrated into buildings not only to enhance but to heal? Martina Decker , Assistant Professor in the College of Architecture and Design at the New Jersey Institute of Technology (NJIT), looks at pioneering research that is being undertaken into performative, time-dependent materials.     

The effect of combined use of chitosan and PIPS on push-out bond strength of root canal filling materials

Adhesion of root canal filling materials to root dentin is important for the long-term success of the treatment. Push-out bond strength test is used to evaluate the adhesion capacity of root canal filling materials to root canal walls. The aim of the present study is to compare the bond strength of root canal filling materials to root dentin after irrigation with EDTA, chitosan and the combination of chitosan and PIPS irridation using push-out bond strength test. Forty-eight extracted teeth were resected until 13-mm long roots were obtained. Root canals were prepared with a size-25 OneShape instrument. Samples were divided into three groups each including 15 roots. Group 1: Canals were rinsed with 0.2% chitosan and subjected to laser irridation with PIPS at the same time. Group 2: Canals were rinsed with 0.2% chitosan. Group 3: Canals were rinsed with EDTA. All canals were filled with .06 tapered gutta-percha and AH-plus sealer. One-mm thick slices were taken from coronal, middle and apical one-thirds of the roots. Push-out bond strength was determined using a Universal Testing Machine. One root from each group was observed under SEM to evaluate the degree of smear removal. Statistical analysis was performed with Kruskall-Wallis test. Results showed that bond strength values were statistically similar in overall evaluation for all groups (p > .05). In segmental evaluation, group 1 revealed the highest bond strength in apical one-third compared to other groups (p < .05).     

Effects of mixing techniques and dentin moisture conditions on push-out bond strength of ProRoot MTA and Biodentine

Objective: To evaluate the influence of manual and mechanical mixing techniques as well as the effects of moisture on the push-out bond strength of ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK, USA) and Biodentine (Septodont, Saint Maur des Fosses, France) to radicular dentin.

Material and methods: Two hundred and forty dentin discs were assigned into three groups with respect to the moisture condition tested: (1) dry, (2) paper points, (3) wet. The discs were further divided into four subgroups according to the calcium silicate cements (CSCs) and mixing techniques used: (1) ProRoot MTA mixed manually, (2) ProRoot MTA mixed mechanically, (3) Biodentine mixed manually, and (4) Biodentine mixed mechanically. Bond strengths of the cements to root canal dentin were measured using a push-out test setup. The data were statistically analyzed using three-way ANOVA and Bonferroni post hoc test p = 0.05.

Results: The data indicated that the push-out bond strength values were significantly affected by CSCs, mixing techniques, and moisture conditions (p < 0.001). Dry conditions caused a significant decrease in bond strength values for both CSCs (p < 0.001). The mean bond strength of Biodentine was significantly higher than that of ProRoot MTA, regardless of the mixing techniques and moisture conditions (p < 0.001). Mechanical mixing favored bond strength values statistically compared to manual mixing (p < .001).

Conclusion: The mixing techniques and moisture conditions have an effect on the push-out bond strengths of ProRoot MTA and Biodentine. Dry samples and manual mixing of cements deteriorate the push-out bond strengths values.     

Vapor Phase Selective Catalytic Oxidation of Cyclohexane over 13X Supported Metal Oxides in the Presence of Ozone

This article reports the application of ozone for the selective oxidation of cyclohexane over 13X molecular sieve supported various metal oxides at ambient temperatures. From the SEM, XRD and HR-TEM results, the impregnated metal oxides are highly dispersed on the support. The activity results reveal that Co/MS, Mo/MS, Cu/MS, and Ag/MS catalysts produce cyclohexanone/cyclohexanol as selective oxidation products, whereas Ce/MS, Mn/MS, and V/MS catalysts yield, predominantly, CO and CO₂. Among them, Co/MS catalyst exhibits better conversion of 12.2% with selectively of 58% to cyclohexanone/cyclohexanol, which is attributed to the simultaneous activation of ozone and cyclohexane (-C-H bond) at ambient conditions.     

脉冲电镀Ni—W钻头电参数优选

论述了脉冲电参数的理论选择原则；探讨了脉冲电参数对Ni—W镀层性能的影响规律；介绍了脉冲电镀钻头的室内使用情况。     

水性免中涂工艺的色漆一遍成膜的技术研究

主要分析研究了水性免中涂工艺采用色漆一遍成膜工艺后涂膜的外观质量及颜色等方面的变化情况,以及相关调整措施和建议。     

建筑节能材料检测中的几点问题与探讨

本文针对检测过程中出现的一些问题,从试样制备、胶粘剂和抹面胶浆、现场锚栓拉拔以及导热系数四个方面进行了分析,提出了自己的观点和解决问题的建议.     

热处理工艺参数对2A12铝合金镍磷镀层性能的影响

研究了2A12铝合金表面镍磷合金镀层的性能及热处理温度对镀层硬度、耐磨性、磨损速率等的影响.     

微乳液体系制备Fe2B包覆纳米α-Fe及其性能研究

采用油包水(W/O)的微乳液体系制备纳米α-Fe.XRD、TEM分析表明,纳米α-Fe被Fe2B所包覆,其粒度在20～100 nm;激光粒度分析表明,纳米α-Fe存在团聚现象,但粒度分布窄;TG-DSC分析表明,纳米α-Fe在＞1100K时发生吸热的α-γ相变;磁强计检测表明,粉体具有铁磁性,其饱和磁化强度为1.14emu/g,剩余磁化强度为0.08emu/g,矫顽力为280Oe.     

导电涂膜裂缝监测技术的试验研究

简要介绍了导电涂膜的性能特点和基本工作原理.将导电涂膜应用于混凝土试块的抗压试验,结果发现导电涂膜在快速加、卸载条件下对混凝土微裂缝的出现及扩展相当敏感.该研究表明:导电涂膜对桥梁、隧道的裂缝监测具有一定的工程应用前景.