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关键词： MULTIDRUG resistance   ASPIRIN   DRUGS -- Toxicology   CELL lines   CHEMOTHERAPY (Cancer)   PROTEIN expression  

摘要： Overexpression of efflux transporters, in human cells, is a mechanism of resistance to drug and also to chemotherapy. We found that multidrug resistance protein-4 (MRP4) overexpression has a role in reducing aspirin action in patients after bypass surgery and, very recently, we found that aspirin enhances platelet MRP4 levels through peroxisome proliferator activated receptor-alpha (PPAR alpha). In the present paper, we verified whether exposure of human embryonic kidney-293 cells (Hek-293) to aspirin modifies MRP4 gene expression and its correlation with drug elimination and cell toxicity. We first investigated the effect of high-dose aspirin in Hek-293 and we showed that aspirin is able to increase cell toxicity dose-dependently. Furthermore, aspirin effects, induced at low dose, already enhance MRP4 gene expression. Based on these findings, we compared cell viability in Hek-293, after high-dose aspirin treatment, in MRP4 overexpressing cells, either after aspirin pretreatment or in MRP4 transfected cells;in both cases, a decrease of selective aspirin cell growth inhibition was observed, in comparison with the control cultures. Altogether, these data suggest that exposing cells to low nontoxic aspirin dosages can induce gene expression alterations that may lead to the efflux transporter protein overexpression, thus increasing cellular detoxification of aspirin.

摘要： Corrosion of drinking water distribution systems can cost water utilities and homeowners tens of billions of dollars each year in infrastructure damage, adversely impacting public health and causing water loss through leaks. Often, seemingly innocuous choices made by utilities, plumbers, and consumers can have a dramatic impacts on corrosion and pipeline longevity. This work demonstrated that brass pipe connectors used in partial lead service line replacements (PLSLR) can significantly influence galvanic corrosion between lead and copper pipes. Galvanic crevice corrosion was implicated in a fourfold increase in lead compared to a traditional direct connection, which was previously assumed to be a worst-case connection method. In field sampling conducted in two cities, a new sampling method designed to detect particulate lead risks demonstrated that the choice of flow rate has a substantial impact on lead-in-water hazards. On average, lead concentrations detected in water at high flow without stagnation were at least 3X-4X higher than in traditional regulatory samples with stagnation, demonstrating a new “worst case” lead release scenario due to detachment of lead particulates. Although galvanized steel was previously considered a minor lead source, it can contain up to 2% lead on the surface, and elevated lead-in-water samples from several cities were traced to galvanized pipe, including the home of a child with elevated blood lead. Furthermore, if both galvanized and copper pipe are present, as occurs in large buildings, deposition corrosion is possible, leading to both increased lead exposure and pipe failures in as little as two years. Systematic laboratory studies of deposition corrosion identified key factors that increase or decrease its likelihood; soluble copper concentration and flow pattern were identified as controlling factors. Because of the high copper concentrations and continuous flow associated with mixed-metal hot water recirculating systems, these

关键词： Joule heating  

摘要： Based on a comprehensive study of the effect of progressive DC Joule-heating annealing (DJA) on giant magneto-impedance (GMI) properties of melt-extracted amorphous microwires, we systematically analysed the different mechanisms for two types of GMI effect definition. Experimental results show that DJA can improve GMI response characteristics and magnetic field sensitivity (MFS) effectively for both definitions, but Delta Z/Z(0) is enhanced much more than Delta Z/Z(max) of the as-cast wires. At 20 MHz, the maximum GMI ratios, as denoted by Delta Z/Z(0) and Delta Z/Z(max), of DJA microwires are enhanced to 582.59% and 639.13%, while the values for the as-cast wires are 69.09% and 520.48% respectively. Meanwhile, the MFS (xi(max)) and equivalent magnetic anisotropy field (H-k) increase to 1346.4%/Oe (Delta Z/Z(0)), 2927.9%/Oe (Delta Z/Z(max)) and 1.1 Oe, respectively. These significant effects of GMI properties as denoted by Z(0) are mainly attributed to the change of resistivity (rho(dc)) for amorphous microwires induced by DJA. Revealing the mechanism of different effects can also result in the development of a micromagnetic field sensor, especially for geomagnetic sensor applications (similar to +/- 1.0 Oe).

关键词： ROBUST control   NONLINEAR analysis   STOCHASTIC convergence   ANALYTICAL solutions (Mathematical analysis)   FINITE element method   MATHEMATICAL analysis  

摘要： This paper presents a new robust and efficient time integration algorithm suitable for various complex nonlinear structural dynamic finite element problems. Based on the idea of composition, the three-point backward difference formula and a generalized central difference formula are combined to constitute the implicit algorithm. Theoretical analysis indicates that the composite algorithmis a single-solver algorithm with satisfactory accuracy, unconditional stability, and second-order convergence rate. Moreover, without any additional parameters, the composite algorithm maintains a symmetric effective stiffness matrix and the computational cost is the same as that of the trapezoidal rule. And more merits of the proposed algorithm are revealed through several representative finite element examples by comparing with analytical solutions or solutions provided by other numerical techniques. Results show that not only the linear stiff problem but also the nonlinear problems involving nonlinearities of geometry, contact, and material can be solved efficiently and successfully by this composite algorithm. Thus the prospect of its implementation in existing finite element codes can be foreseen.

关键词： 荷载识别   影响线   荷载横向分布   BP神经网络  

摘要： 近年来,国内多地灾难性的桥梁倒塌事故频频发生,引发了人们对桥梁结构安全问题的广泛关注。桥梁结构健康监测也以成为当今桥梁工程研究的热点,移动荷载识别技术能进一步完善健康监测系统。然而,现有的多数荷载识别方法存在不同的局限性,需要实际工程的进一步论证。分别针对单车和多车移动荷载的高精度识别,本文提出了基于影响线并考虑荷载横向分布的单车移动荷载识别方法以及基于影响线和BP神经网络的多车移动荷载识别方法,并用数值模拟和实验室车桥试验对上述方法的可行性和适用性进行了验证。本文主要研究内容及结论如下：(1)为了提高移动荷载的识别精度,提出并建立了基于影响线并考虑荷载横向分布的移动荷载识别方法,并结合数值模拟算例,对未考虑荷载横向分布的方法和考虑了荷载横向分布的方法进行了比较,结果表明未考虑荷载识别的方法不适合解决空间问题,而考虑了荷载横向分布的方法,对于车辆行驶于桥面上任意位置的空间问题,其识别精度都很高,且抗噪性能优异。(2)通过实验室车桥试验,进一步研究了考虑荷载横向分布的影响线方法在实际工程应用中的可行性。车速识别的结果显示,车速识别的误差基本能控制在±5%以内,且车速识别的精度对车重识别影响较大。车重识别的结果表明,利用考虑荷载横向分布的影响线方法进行荷载识别,车重相对误差可控制在±10%以内,且93%的样本能控制在±5%以内。(3)由于无法建立理想的数学模型对多车移动荷载进行识别,本文根据应变影响线中包含车重信息,再结合BP神经网络方法,建立了基于影响线和BP神经网络的移动荷载识别方法。然后针对该方法在实验室进行了双车移动荷载试验研究,结果表明该方法能精确识别车辆所处车道位置信息,在识别车辆荷载时,所有样本的相对误差能控制在±10%以内,且97%的样本能控制在±5%以内。

关键词： 假体松动   模型   骨组织   血清指标   骨细胞   X线照射   PINP   Micro-CT   硬组织切片   骨溶解  

摘要： 全髋关节置换术(total hip arthroplasty,THA)是目前治疗严重髋部疾病常用的方法。随着人工髋关节假体改进及手术技术等不断发展,手术满意率普遍较高。人工关节置换术已经成为一种相对成熟、性价比高的治疗手段,能够有效改善患者的生活质量。在有效预防感染、提高假体抗疲劳强度的前体下,假体的无菌性松动成为影响人工关节使用年限的主要原因(占手术失败的75%)。因此如果能够在无菌性假体松动发生早期,进行及时的干预有望延缓或者逆转假体松动的发生。X射线作为一种电离辐射,在包括医学在内的许多领域中有着广泛的应用。低剂量X线辐照离体成骨母细胞,发现可以促进成骨细胞增殖、分化过程,从而加速骨折愈合。我们的前期研究发现低剂量X线照射能够促进成骨细胞的增殖、分化。此外,低剂量X线照射具有明显抑制炎症的效应,因此理论上低剂量X线照射可能有利于在无菌性假体松动早期对假体周围组织反应的逆转或延缓假体松动的发生。第一部分:建立可有效观察兔无菌性假体松动早期模型目的:通过Ti颗粒的注射模拟假体周围磨损颗粒产生的早期微环境,观察假体周围组织的变化及血清学相关指标的变化,明确该模型的有效性及可检测性,为进一步研究低剂量X线照射这一干预因素提供实验基础。方法:健康雄性成年新西兰大白兔16只,体重2.5 kg。随机分为实验A组及对照B组,各8只。各组动物做髌骨内侧切口,脱位髌骨,暴露股骨远端,于双侧股骨髁间窝前2mm处做一骨隧道,植入1枚直径3.2mm、长15 mm的带有羟基磷灰石图层的钛棒假体,A组动物左腿在植入假体前于隧道内注入0.2ml浓度为1.0g/ml的Ti颗粒悬液,B组动物左腿注入等量生理盐水后置入同规格假体作为对照。术后不制动。术后第1天肌注青霉素,10万u/Kg;分别于0d、2w、4w、8w四个时间点采集标本血清液,第8w处死动物获取股骨生物标本。ELISA法检测ALP、PINP、CTX-1的含量;Micro-CT检测假体周围骨组织变化;生物力学比较两组力学的变化并作硬组织切片观察假体周围组织。结果:实验组与对照组相比:ALP、PINP、CTX-1在各时间段差异无显著性。Micro-CT结果显示A组假体周围的各向异性(DA)明显低于B组,差异具有统计学意义,同时骨小梁厚度(***)也有下降趋势。但其骨小梁数目(Tb.N)骨体积分数(BV/TV)骨密度(BMD)差异没有统计学意义。组织切片检测结果示:A组假体周围有明显的炎性假膜形成,同时可见Ti颗粒周围矿化的纤维组织。生物力学结果显示,A组与B组差异无统计学意义。结论:在兔假体局部出现炎性反应,血清学中成骨、破骨代谢指标没有变化时,假体周围骨量没有下降,假体力学性能正常的情况下,利用Ti颗粒周围的纤维矿化会降低假体周围骨小梁DA这一特点,可通过DA间接反映局部的炎症程度。第二部分:低剂量X线照射对假体松动早期周围组织结构的影响目的:研究低剂量X线照射后,假体松动早期动物模型假体周围组织结构的变化及特异性血清学指标的的变化情况。方法:建立如前假体松动早期兔模型照射组和对照组,每组8只。术后两天,照射组左膝关节接受0.5Gy-X线局部单次照射,术后不制动。术后第1天肌注青霉素,10万u/Kg;分别于0d、2w、8w三个时间点采集标本血清液,第8w处死动物获取股骨生物标本。ELISA法检测血清PINP、CTX-1的含量;Micro CT检测假体周围骨小梁的微观结构;生物力学比较两组假体的最大压出力;硬组织切片观察假体周围组织结构。结果:在不同时间段,两组动物外周血清中CTX-1含量的差异无显著性;PINP在0w、8w时间段外周血清中含量差异无显著性,而2w时间段PINP含量有显著性差异(P<0.05),且照射组高于对照组。Micro-CT结果显示照射组假体周围骨小梁的各向异性(DA)明显高于对照组;硬组织切片检测结果示假体周围的炎症反应,照射组明显减轻。照射组与对照组两组的生物力学差异无统计学意义。结论:低剂量X线照射使动物模型外周血清中PINP含量升高,而不影响破骨代谢指标CTX-1,从而有利于骨形成而不影响骨吸收。同时低剂量X线可有效的抑制磨损颗粒诱导的局部炎症反应,改善假体周围组织的病理学特征。

关键词： 水电站厂房   蜗壳结构   静动力分析  

摘要： 水电站厂房在水电站枢纽中是非常重要的组成部分,可以将水能转换为电能,一般情况下水电站厂房支承结构主要由蜗壳、风罩等结构系统构成,在运行过程中会受到静力荷载的作用,厂房振动问题严重影响了水电站的正常运行.鉴于此,笔者从不同角度展开水电站厂房蜗壳结构静动力分析.

关键词： 仿生扑翼机   扑翼驱动机构   气动力特性   扑翼机理   动网格  

摘要： 仿生扑翼机是基于仿生学原理进行设计模仿鸟类或昆虫飞行的新概念飞行器。仿生扑翼机不但囊括了固定翼和旋翼飞行器的优点,而且还具有较好的隐蔽性和机动性。扑翼飞行器具有特殊的空气动力学特性,在低雷诺数下具有出色的飞行能力,具有广泛的应用前景。从仿生学的角度,研究了鸟类和昆虫翅膀的运动特征,分析了升推力产生机理,并对飞行生物的尺度律进行分析。为仿生扑翼机的研究提供理论依据。在综合分析常见仿生扑翼机驱动机构的基础上,提出一种新型仿生扑翼驱动机构。通过UG实体建模和运动学仿真验证了这一机构的可行性。通过ADAMS建立扑翼机构的虚拟样机,并进行了动力学仿真分析和优化设计。该扑翼驱动机构不但实现了左右翼的完全对称扑动,而且在上、下扑动阶段实现了机翼的折叠运动。该扑翼驱动机构符合扑翼飞行要求,使扑翼飞行更加稳定、安全和高效。它为扑翼机构的实物快速制作及扑翼飞行器的研制提供理论依据。在仿生扑翼机的设计当中,仿生机翼的气动力特性具有十分重要的意义。目前与仿生扑翼飞行相关的低雷诺数空气动力学研究还处于初级阶段,对仿生机翼气动力研究还没有成熟的理论和可借鉴的经验。基于对飞行生物尺度律的分析,计算出仿生机翼的结构参数,应用计算流体动力学软件Fluent对仿生机翼的气动力特性进行了数值模拟分析。并分析机翼扑动规律和周围气流环境对仿生扑翼机气动性能的影响。建立仿生机翼的折叠扑动模型,并计算其气动力特性。计算结果表明,折叠运动对仿生扑翼机的气动性能有较大改善。这些结果对扑翼样机的制作具有一定的指导作用。

关键词： 就业可达性   交通碳排放   轨道交通   地铁票价   西安市  

摘要： 近年来,随着城市化与机动化的不断加速,导致城市交通拥堵问题与环境问题不断恶化。为了支撑城市建设与发展,缓解城市交通拥堵,降低城市交通对环境的污染,作为快捷、低碳出行方式的轨道交通得到了较好的推广,越来越多大城市提倡大力发展轨道交通。目前轨道交通影响与效益评估主要集中在经济与客流等方面,而本文创新地将城市交通预测模型与就业可达性模型、碳排放模型相融合,从就业可达性与碳排放两个指标方面研究轨道建设与轨道票价影响与效益。就业可达性作为衡量城市居民获取就业机会难易度的指标,主要体现在城市空间功能布局与交通系统绩效上,而就业可达性指标侧面也反映了城市整体通勤出行的难易度。本文在城市空间布局既定的情况下,通过选取就业可达性指标评估轨道建设效益本质上是探究轨道建设对城市通勤交通绩效的影响效果。首先分析了西安地铁2号线建成后城市交通就业可达性的出行距离与行政区域分布特征,发现私人交通与公共交通就业可达性随出行距离增加而提高,提高幅度呈现下降趋势;且老城区不同方式就业可达性均最大,雁塔区与未央区次之。其次通过对比分析地铁2号线建设前后就业可达性变化的区域分布特征,发现地铁建设在一定程度上提高了私人交通与公共交通就业可达性,且对就业可达性影响区域集中在地铁周边范围内;最后探究发现地铁建设对公共交通就业可达性贡献度相对较大,缩小了公共交通与私人小汽车就业可达性的差距,从而促进了城市交通可持续发展,且这种促进作用在未央区与雁塔区尤为明显。碳排放作为衡量交通环境污染重要指标,能够从时空多维度评价城市交通环境污染程度,本文选取碳排放指标评估地铁建设与票价方案的效益,从而理清轨道建设与票价方案对城市交通减排的贡献。首先从区域产生与承受的碳排放两方面分析了西安地铁2号线建成后城市交通碳排放的行政区域分布特征,发现西安市未央区与雁塔区产生碳排放量最大,老城区产生碳排放量放次之;绕城高速与三环区域承受碳排放量最大,二环附近区域承受碳排放量次之。其次对比分析了轨道建设对区域产生-承受碳排放变化,发现地铁建设较大程度地降低了交通碳排放量,对区域产生-承受碳排放影响区集中在地铁线路周边,但对区域产生-承受碳排放影响范围与程度不同。最后探讨了地铁票价对碳排放影响,发现碳排放随固定票价上涨而增加,且增加幅度呈现上升趋势;且对比分析了固定票价制与区间票价制对碳排放的影响,从而为轨道票价方案制定提供碳排放方面的参考依据。综上所述,本文基于城市交通模型的再开发,将城市交通预测模型与就业可达性模型、碳排放模型相融合,创新地从就业可达性与碳排放指标方面对轨道交通建设影响效益进行探讨,从而对于认清轨道交通的作用具有十分重要价值。

关键词： Horizon scanning   Emerging health technology   Potential impact   Polyurethane meniscal scaffold  

摘要： Objectives: The aim of this study was to predict the potential impact of the introduction of implantation of polyurethane scaffold for the treatment of partial meniscal lesions in the South Korean healthcare system. Methods: The horizon scanning process was used to select a target technology and assess its potential impacts on patients and the Korean healthcare system. We identified and filtered research-phase health technologies that are not listed yet in Korean, but appear promising. After a process of prioritization, we chose the implantation of polyurethane scaffolds as a target technology. Then, through the procedures of assessment and peer review, we analyzed current evidence and its predicted potential impacts. Results: There were eight studies included in the review: one prospective cohort and seven case-series studies. Six revealed significant improvements in function and pain relief. Of the six studies, which reported safety endpoints, four stated no major postoperative complications related to scaffold, and two reported adverse events and serious adverse events such as pain, joint swelling, et cetera. We also included the potential impact of this technology based on the experts' consultation. They all agreed that it would satisfy the diverse needs of patients and fulfill clinical needs. However, the majority of related clinical studies were based on short-term follow-up observations without any validation process involving comparison with control groups. Conclusions: Through a horizon scanning activity, we found that the implantation of polyurethane scaffolds is a promising technology to resolve articular cartilage defects;however, long-term evidence with comparison groups for safety and effectiveness is required.