Discrete Element Modeling of Instability Mechanisms of Unbound Permeable Aggregate Base Materials in Triaxial Compression

Unbound permeable aggregate base (UPAB) materials with strong load-transmitting skeleton yet adequate inter-connected pores are desired for use in the sponge-city initiative. However, the micro-scale fabric evolution and instability mechanism of macroscopic strength behavior of such UPAB materials still remain unclear. In this study, virtual monotonic triaxial compression tests were conducted by using the discrete element method (DEM) modeling approach on specimens with different gradations quantified by the parameter of gravel-to-sand ratio (G/S). The realistic aggregate particle shape and inter-particle contact behavior were properly considered in the DEM model. The micromechanical mechanisms of the shearing failure of such UPAB materials and their evolution characteristics with G/S values were disclosed from contact force chains, microstructures, and particle motion. It was found that the proportion of rotating particles in the specimens decreased and the proportion of relative sliding between particles increased as the content of fine particles decreased. The plastic yielding of the specimens originated from the failure of contact force chains and the occurrence of the relative motion between particles, while the final instability was manifested by the large-scale relative motion among particles along the failure plane (i.e., changes in the internal particle topology). By comparing the macroscopic strength, microstructure evolution, and particle motion characteristics of the specimens with different G/S values, it was found that the specimens with G/S value of 1.8 performed the best, and that the G/S value of 1.8 could be regarded as the threshold for separating floating dense and skeletal gap type packing structures. The variation of Euler angles of rotating particles was significantly reduced in the particle size range of 4.75 mm to 9.50 mm, indicating that this size range separates most of the particles from rolling and sliding. Since particle rolling and sliding behavior are directly related to shear strength, this validates the rationality of the parameter G/S for controlling and optimizing gradations from the perspective of particle movement. The findings could provide theoretical basis and technical guidance for the effective design and efficient utilization of UPAB materials.     

Effect of Mechanically Treated Recycled Aggregates on the Long Term Mechanical Properties and Durability of Concrete

The objective of this research was to study the effect of an optimal mechanical treatment method to reduce the mortar adhered on recycled aggregates (RCA) on the long-term mechanical properties and durability of concretes containing RCA at different replacement levels. It was found that concretes incorporating treated RCA exhibited sharper and more significant increase on 90- and 365-day compressive strengths than any other investigated mixture. The same mixtures also benefitted from a ‘shrinkage-controlling’ effect, where strains and mass losses were reduced by almost 15% and 10%, respectively, compared to the reference concrete. While sulfate resistance and carbonation resistance are predominantly defined by the hydration products available within the cement paste and not to a large extent by the aggregate type and quality, the incorporation of either treated or untreated RCA in concrete did not appear to expose RACs to significant durability threats.     

食管癌、胃癌细胞对氧化砷促凋亡的敏感性与固有活性氧水平有关

目的 探讨食管癌，胃癌细胞的固有活性氧（reactive oxygen species,ROS)水平与细胞对三氧化二砷（As2O3)促凋亡敏感性之间的关系。方法 用小剂量（2μmol/L)As2O3作用于人胃癌细胞和食管癌细胞株各一对（SGC7901、MKN45和EC/CUHK1、EC1867），证实As2O3促凋亡敏感性在SGC7901和MKN45之间及EC/CUHK1和EC1867之间均有差异。然后在不加As2O3的情况下，用活性氧捕获剂双氢罗丹明123（DHR123）卵育细胞（DHR123在细胞内被ROS氧化为发出荧光的罗丹明123），通过流式细胞仪检测细胞内罗丹明123的荧光而测得细胞内固有ROS水平。结果 对As2O3敏感的SGC7901细胞的固有活性氧水平比As2O3不敏感的MKN45细胞高，对As2O3敏感的EC/CUHK1细胞的固有活性氧水平比As2O3不敏感的EC1867细胞高。结论 食管癌，胃癌细胞固有ROS水平的差异与细胞对As2O3诱导凋亡的敏感性差异有关。     

Platelet-Derived MRP-14 Induces Monocyte Activation in Patients With Symptomatic Peripheral Artery Disease

Background

Peripheral artery disease (PAD), a diffuse manifestation of atherothrombosis, is a major cardiovascular threat. Although platelets are primary mediators of atherothrombosis, their role in the pathogenesis of PAD remains unclear.

使用硅酸盐水泥模拟矿物三氧化物聚合物评估不同根尖屏障制备技术的体外研究

目的 使用硅酸盐水泥模拟矿物三氧化物聚合物(MTA)评估不同根尖屏障制备技术的边缘封闭性和密实度,以及是否使用输送器对根管壁上充填材料残留量的影响.方法 建立大根尖孔和喇叭状根尖孔直根管标准模型,根据在2种模型中充填放置硅酸盐水泥的方法不同分为牙胶组、EndoActivator组、直接超声组和间接超声组,使用体视显微镜观察评分;另在直根管模型中,使用输送器和垂直加压器2种工具将MTA放到根管尖部,在体视显微镜下观察分析.结果 在牙胶组中,大根尖孔直根管充填质量优于喇叭口根管(P＜0.05);在直根管中,间接超声组和牙胶组密实度高于另外两组(P＜0.05),使用输送器比垂直加压器输送MTA残留在根管壁上的少(P＜0.05);在喇叭口根管中,间接超声组密实度最高(P＜0.01).结论 使用输送器能减少残留在根管壁上的MTA量,在直根管中,可以选择牙胶法和超声法放置屏障材料;而在喇叭口的根管中放置屏障材料时,最佳选择是间接超声法.     

萌格旺治疗绝经后骨质疏松症的初步观察

绝经后妇女54例,钙组及治疗组各27例,钙组每日口服乳酸钙8片（Ca 400mg）,治疗组每日口服萌格旺（α-D 3）0.5μg及乳酸钙 4片（Ca 200mg）经 6个月观察,治疗组腰椎2～4骨密度均值用药前823.4±175.6mg/cm~2,用药 6个月为 860.8±99.5mg/cm~2,平均每例上升14.37 mg/cm~2;钙组腰椎2～4骨密度均值用药前,868.0±110.1mg/cm~2,用药后6个月为862.5±114.7mg/cm~2,平均每例下降5.44mg/cm~2,组间对比统计学有显著差异P<0.05。空腹尿钙、尿羟脯胺酸与尿肌酐比值,用药后组间无差异。用药中无高血钙症发生。萌格旺治疗绝经后骨质疏松症有一定疗效,胃肠道副反应轻微,用药安全。结合国人低钙饮食的特点,服用萌格旺应同时补充一定量的钙剂。     

The Performance of Concrete Made with Secondary Products—Recycled Coarse Aggregates,Recycled Cement Mortar,and Fly Ash–Slag Mix

The properties of cement concrete using waste materials—namely, recycled cement mortar, fly ash–slag, and recycled concrete aggregate—are presented. A treatment process for waste materials is proposed. Two research experiments were conducted. In the first, concretes were made with fly ash–slag mix (FAS) and recycled cement mortar (RCM) as additions. The most favorable content of the concrete additive in the form of RCM and FAS was determined experimentally, and their influence on the physical and mechanical properties of concrete was established. For this purpose, 10 test series were carried out according to the experimental plan. In the second study, concretes containing FAS–RCM and recycled concrete aggregate (RCA) as a 30% replacement of natural aggregate (NA) were prepared. The compressive strength, frost resistance, water absorption, volume density, thermal conductivity, and microstructure were researched. The test results show that the addition of FAS–RCM and RCA can produce composites with better physical and mechanical properties compared with concrete made only of natural raw materials and cement. The detailed results show that FAS–RCM can be a valuable substitute for cement and RCA as a replacement for natural aggregates. Compared with traditional cement concretes, concretes made of FAS, RCM, and RCA are characterized by a higher compressive strength: 7% higher in the case of 30% replacement of NA by RCA with the additional use of the innovative FAS–RCM additive as 30% of the cement mass.     

三氧化二砷对rIL-13诱导肺成纤维细胞增殖和炎性介质表达的影响

目的探讨三氧化二砷（As2O3）的抗肺纤维化机制。方法将体外培养的肺成纤维NIH3T3细胞株随机分为对照组及观察组,对照组仅予DMEM培养基,观察组予80 ng/ml重组白细胞介素（rIL）-13及不同浓度As2O3处理24、48 h。MTT法检测细胞增殖;原位杂交方法检测巨噬细胞炎症蛋白（MCP）-1αmRNA表达;放射免疫法检测细胞培养上清液IL-6、IL-8水平。结果 As2O3处理后细胞增殖明显受抑,且呈时间和剂量依赖性（P〈0.01）;rIL-13处理后细胞MCP-1αmRNA和IL-6、IL-8表达增强,联用As2O3后此作用明显受抑（P〈0.01）。结论 As2O3可能通过抑制rIL-13诱导的肺成纤维细胞增殖及炎性介质表达而发挥抗肺纤维化作用。