Novel 3D printed shape-memory PLLA-TMC/GA-TMC scaffolds for bone tissue engineering with the improved mechanical properties and degradability

The biodegradable substitution materials for bone tissue engineering have been a research hotspot. As is known to all, the biodegradability, biocompatibility, mechanical properties and plasticity of the substitution materials are the important indicators for the application of implantation materials. In this article, we reported a novel binary substitution material by blending the poly(lactic-acid)-co-(trimethylene-carbonate) and poly(glycolic-acid)-co-(trimethylene-carbonate), which are both biodegradable polymers with the same segment of flexible trimethylene-carbonate in order to accelerate the degradation rate of poly(lactic-acid)-co-(trimethylene carbonate) substrate and improve its mechanical properties. Besides, we further fabricate the porous poly(lactic-acid)-co-(trimethylene-carbonate)/poly(glycolic-acid)-co-(trimethylene-carbonate) scaffolds with uniform microstructure by the 3D extrusion printing technology in a mild printing condition. The physicochemical properties of the poly(lactic-acid)-co-(trimethylene-carbonate)/poly(glycolic-acid)-co-(trimethylene-carbonate) and the 3D printing scaffolds were investigated by universal tensile dynamometer, fourier transform infrared reflection (FTIR), scanning electron microscope (SEM) and differential scanning calorimeter (DSC). Meanwhile, the degradability of the PLLA-TMC/GA-TMC was performed in vitro degradation assays. Compared with PLLA-TMC group, PLLA-TMC/GA-TMC groups maintained the decreasing T_g, higher degradation rate and initial mechanical performance. Furthermore, the PLLA-TMC/GA-TMC 3D printing scaffolds provided shape-memory ability at 37 ℃. In summary, the PLLA-TMC/GA-TMC can be regarded as an alternative substitution material for bone tissue engineering.     

三峡库区巨鱼沱滑坡地质特征及防治研究

介绍了三峡库区万州巨鱼沱滑坡的结构特征和变形特征,从滑坡形成条件和诱发变形因素两方面分析了滑坡形成的原因,对滑坡在各工况下的稳定性进行了分析和计算,提出了以预应力锚索抗滑桩为主的综合治理措施,对三峡库区滑坡灾害的研究和治理具有参考价值。     

Evaluating the accuracy of ESR dose determination of pseudo-Early Pleistocene fossil tooth enamel samples using dose recovery tests

In ESR dating of Early Pleistocene fossil tooth enamel samples, the fitting function used for the evaluation of the D_E value is undoubtedly among the major sources of uncertainty. Dose recovery tests performed on fossil tooth enamel showing D_E values >1,000 Gy demonstrate: (i) that high precision ESR measurements (<0.5%) and high D_E reproducibility (<5%) may be achieved; (ii) the appropriateness of the Double Saturating Exponential (DSE) fitting function for ESR dose reconstruction. In contrast, the SSE function, which has been almost exclusively used so far, does simply not correctly describe the behavior of the radiation induced ESR signal of tooth enamel with the dose.Several fitting functions and data weighting options were tested and the combination of a DSE with data weighted by the inverse of the squared intensities is the procedure providing the most accurate D_E results. However, the SSE may nevertheless sometimes produce consistent results if D_max does not exceed 6*D_E. Further work is required in that direction in order to determine more precisely in which conditions the SSE could be used as a fair approximation of the DSE function for these samples.     

古生物群遗迹化石的三维数字化测量

对古生物化石进行数字化建档,为古生物化石的长久保存、研究和复原提供了一个切实可行的办法。阐述了非接触式激光扫描仪的测量原理,并利用其对罗平古生物化石群中分布在120m2范围内的古生物足迹化石进行了数字化测量,采用大视场WIDE和小视场TELE镜头交替使用的方法获取全场和单一足迹化石三维点云数据,再利用三维数据处理PolyWorks软件将两个镜头的三维数据进行对应的嵌入融合,最终测量结果既能全面记录足迹整体分布,真实反映古生物爬行运动轨迹,又能精细反映足迹局部特征。结果表明提出的对大面积野外待测对象的测量方法,为化石野外测量、三维数字化、数字存储提供了可行方案。     

钠型斜发沸石对高钙苦卤中钾离子的吸附研究

我国具有丰富的盐湖苦卤资源[1].其中含有高浓度的钙、镁、铁、钡、钾和溴等有价值的矿产,并已形成了以钾、溴和镁为产品链的苦卤化工行业[2].由于我国陆地钾矿资源相对短缺,从苦卤和海水中选择性地提取钾,一直受到研究者的重视.     

宜宾市江安县桐梓地区土壤元素背景值研究及其意义

在研究区表层土壤系统采样调查的基础上,应用统计学方法得出了宜宾市江安县桐梓镇土壤元素地球化学背景值,对研究区与不同区域土壤元素地球化学背景值、基准值作了对比研究。结果显示了研究区土壤元素地球化学的基本特征,为研究区土壤资源利用、环境质量评价和农业经济发展规划等提供了实用的基础地球化学信息。     

超声纸杯焊接技术

本文介绍一种超声纸杯焊接设备及焊接工艺。     

华罗庚－王中烈型不等式

用控制不等式理论和动态规划方法推广了华罗庚-王中烈的不等式，并建立了类似的其他结果．     

A highly stable and active mesoporous ruthenium catalyst for ammonia synthesis prepared by a RuCl3/SiO2-templated approach

Molecular nitrogen is relatively inert and the activation of its triple bond is full of challenges and of significance. Hence, searching for an efficiently heterogeneous catalyst with high stability and dispersion is one of the important targets of chemical technology. Here, we report a Ba-K/Ru-MC catalyst with Ru particle size of 1.5–2.5 nm semi-embedded in a mesoporous C matrix and with dual promoters of Ba and K that exhibits a higher activity than the supported Ba-Ru-K/MC catalyst, although both have similar metal particle sizes for ammonia synthesis. Further, the Ba-K/Ru-MC catalyst is more active than commercial fused Fe catalysts and supported Ru catalysts. Characterization techniques such as high-resolution transmission electron microscopy, N₂ physisorption, CO chemisorption, and temperature-programmed reduction suggest that the Ru nanoparticles have strong interactions with the C matrix in Ba-K/Ru-MC, which may facilitate electron transport better than supported nanoparticles.     

不平衡报价跨期选择的多因素交互作用研究

报价人的跨期选择心理特征将直接影响不平衡报价策略,从而影响工程结算额度与经营效益。为揭示不平衡报价决策者的跨期选择心理机制,针对不平衡报价策略制定过程中出现的跨期选择心理效应问题,基于跨期结算组合策略的最大效用原则,并假设报价决策者为有限理性人,引入时间尺度、时间框架、理性水平3个变量,采用23(3因素2水平)设计,通过发放调查问卷方式,对跨期选择的多因素交互作用进行研究。研究结果表明,时间尺度、理性水平及时间框架主效应显著;理性水平与时间框架、理性水平与时间尺度、理性水平与时间框架和时间尺度的交互作用显著。在日期框架中,时间尺度较小时的报价均高于时间尺度较大时的报价;在延迟天数时间框架中,高理性水平报价人在时间尺度较小时的报价低于时间尺度较大时的报价,而低理性水平报价人则相反。研究结果对于增强不平衡报价决策效率、实现理性化决策具有重要的指导意义。