面向动态交通流的高速公路事故风险模型空间移植研究

本文旨在探究不同尺度数据集对高速公路实时事故风险建模的影响，并实现不同数据特征路段间事故风险模型的空间移植。首先，提取不同特征路段检测器信息，以动态交通流匹配事故数据构建多尺度数据集：高精度数据集、小样本数据集、低精度数据集以及同尺度条件下(同为高精度大样本量)的空间差异数据集；进而，通过贝叶斯Logistic回归量化不同样本量对事故风险模型预测性能的影响；分别采用统计学和机器学习手段建模分析高精度和低精度数据集；最后，基于贝叶斯更新方法建立实时事故风险移植模型，对高速公路实时事故风险预测模型进行空间移植，并验证其可靠性。结果显示：贝叶斯Logistic回归的性能随着样本量增大而有所提升；高精度数据条件下，贝叶斯Logistic回归和RF-SVM(Random Forest-Support Vector Machine)模型的AUC(Area Under Curve)值比低精度条件下分别高出0.092和0.037；在不同数据精度的空间移植中，贝叶斯更新方法可令低精度路段模型的AUC值从0.645提至0.714，在相同数据尺度的空间移植中，该方法可将被更新路段模型的AUC值从0.737提...     

20#碳钢与316L不锈钢异种钢的焊接

随着社会进步及经济发展，近几年世界航运业对船舶的需求量越来越大，造船业乘此良机，在产品类型、新材料应用、新工艺实施等方面也取到了良好的进展。其中，不锈钢作为一种具有强度高、塑性好、耐腐蚀性好等优点的材料，在船舶产品建造过程中的应用范围不断扩大，也使其与碳钢、合金钢等异种材料的焊接机会越来越多。     

科学家前瞻21世纪医疗

1、疑难病症有解决的可能.如人们将通过注射疫苗,防治艾滋病和癌症. 2、至2004年,将以医疗技术手段-DNA芯片取得医学突破.从人体取出一滴血样,与信用卡大小的DNA芯片相对照,可以知道是否将得癌症或糖尿病,以及对哪些药物过敏;得知属于哪种基因变异,以判断受检者将来会得什么病.     

浅谈共玉公路草皮植被护坡防护

在充分利用路基基底及取(弃)土场、便道等清表草皮的基础上,提出了快速恢复高原植被、及时防护加固路基边坡和代替圬工结构施作草皮边坡植被移植施工技术,有效减轻了对高原生态环境的破坏,保证了路基边坡的长期稳定,同时减少了路基圬工结构的数量,取得了较好的经济效益和社会效益.     

基于Visual Studio 2008的Geant4工具包的开发

Geant4是欧洲核子中心主导开发用于精确模拟粒子在介质中输运过程的数值计算软件工具包。对于Windows用户而言,一般都是用Cygwin实现Geant4工具包在Windows环境的运行,Cygwin在windows下提供Unix/Linux环境的模拟,但是其无论在稳定性和代码执行效率上都不是很理想。文章直接从Geant4源代码出发,使用Visual Studio2008编译工具开发Geant4程序,并通过加载OpenGL图形系统驱动,实现Geant4中几何模型和粒子图形化的显示。最后用一个实例讨论了实现Geant4图形化显示的方法。该文方法的提出,增强了Geant4开发的灵活性,有效地降低了Geant4模拟程序的开发难度。     

转基因小鼠源性胰腺癌组织块皮下移植瘤模型的构建与评价

目的构建基于转基因小鼠的胰腺癌组织块皮下移植瘤模型(transgenic mice-derived allografts, MDAs),为胰腺癌的体内及体外研究提供良好的实验载体模型。方法利用LSL-Kras~(G12D/+);Trp53~(fl/+);Pdx1-Cre(KPC)胰腺癌转基因小鼠的组织块进行皮下移植,构建MDAs。利用HE染色、Masson染色和免疫组化染色评价MDAs的组织病理特征及免疫细胞浸润情况。结果 MDAs成功模拟出胰腺癌的大体和组织病理形态,且其保留了胰腺癌高增殖和高间质纤维化的病理特征。MDAs的纤维化和增殖程度较正常胰腺明显增高(P<0.05);MDAs还可成功模拟胰腺癌MPO+中性粒细胞、CD68+巨噬细胞和CD3+T淋巴细胞的浸润状态。结论 MDAs更利于在体内模拟胰腺癌的进展,是一种可行的胰腺癌研究模型。     

Bcl-2、Bax、Fas、FasL、穿孔素和粒酶B在移植肾急性排斥中的共同表达和意义

目的 检测Bcl-2、Bax、Fas、FasL、穿孔素和粒酶B 在移植肾急性排斥时的表达水平,探讨其在急性排斥中的作用及可能的分子机制.方法 选取30例移植肾穿刺活检标本及18例正常供肾组织为研究对象,采用免疫组化方法检测Bcl-2、Bax、Fas、FasL、穿孔素和粒酶B 的表达情况.结果 ①根据Banff97病理诊断标准,急性排斥标本30例,其中ⅠA 12例,ⅠB 11例,ⅡA 5例,ⅡB 2例;②所有组织中均可发现细胞凋亡现象,急性排斥标本中更为明显;③Bcl-2在急性排斥标本中的表达水平低于正常组织(P＜0.05),与急性排斥的病理变化呈负相关(P＜0.05);Bax在两组的表达水平无差别(P＞0.05);Fas、FasL、穿孔素和粒酶B在急性排斥组中的表达水平均高于对照组,并与急性排斥的病理变化呈正相关,以FasL和粒酶B 最为明显(P＜0.01).结论 ①Bcl-2在肾小管上皮细胞的表达减少提示急性排斥反应的发生;②Bax对于预测急性排斥反应的意义不大;③Bcl-2、Fas、FasL、穿孔素和粒酶B的表达变化均与急性排斥反应密切相关,尤以FasL和粒酶B明显,可作为监测移植肾形态学变化、功能状态以及判断预后的重要指标.     

Toxicity to the normal hemocytes by ALA-PDT for the ex vivo purging of hematopoietic stem cell grafts

Objective To study the toxic effects of 5-amionlevulinic acid-based photodynamic therapy (ALA-PDT) on human peripheral blood mononuclear cells (PBMCs), cord blood mononuclear cells (CBMCs) and peripheral blood stem cells (PBSCs), and furthermore, to understand the possible causes of this response. Methods We used MTT assay to detect the survival rate of PBMCs, CBMCs and PBSCs after treated by ALA-PDT under the optimum experiment conditions with U937 as control;Annexin V-FITC/PI was used to detect the pattern of cell death induced by ALA-PDT. By using flow cytometry, we detected intracellular PpIX fluorescence intensity. Results After ALA-PDT treatment the survival rate of PBMCs had no significant change;however in PBSCs and CBMCs, the survival rate reduced to 70%, and the survival rate of leukemia cell U937 was the lowest, about 30%. After incubation with ALA,except for PBMCs, intraceUuiar PplX fluorescence intensity of the other two kinds of normal haemocytes and U937 increased obviously. These results combined with the flow cytometry suggested that the main pattern of cell death here was apoptosts. Conclusion Under the optimum experiment conditions, ALA-PDT has a slight effect on normal haemocytes but excellent depletions of leukemia cells. Therefore, it can effectively purify autologons bone marrow or stem cell grafts.     

Experimental study on cyclosporine A drug delivery system in prevention of posterior capsule opacification after intraocular lens implantation in rabbits

Objective To study the effect of cyclosporine A drug delivery system (CsA-DDS) on the prevention of posterior capsule opacification (PCO) after experimental intraocular lens implantation in rabbit eyes. Methods Twenty healthy New Zealand white rabbits, whose left eyes and right eyes were used respectively as experiment eyes and controls, were subjected to extracapsular lens extraction and artificial lens implantation. During the operation, CsA-DDS with poly (lactideco-glycolide) as carriers or empty DDS was implanted in the capsular bag for the experimental eyes and controls respectively. After the operation, anterior chamber reaction, intraocular pressure (IOP) and CsA concentration were monitored and twelve weeks after the operation, the eyes were extracted for histopathological and morphological examinations. Results There were no differences between the two groups in conjunctival congestion,IOP change and anterior chamber reaction. PCO was less severe in the experimental eyes than in the controls. Light microscopy revealed that posterior capsular membrane in the experimental eyes was slick, with no obvious proliferation,whereas in the controls, there were lens epithelial cell proliferation and cortex regeneration of different degrees.Morphological examination with electron microscope showed that in the experimental eyes, lens epithelial cells did not function actively and apoptosis occurred, whereas in the controls, epithelial cells presented active function. No marked ultrastructural changes were found in either group. Conclusion Cs-DDS can inhibit PCO after intraocular lens implantation in rabbit eyes and does not have toxic effects on the surrounding ocular tissues. Therefore, it has a good potential for clinical use in prevention of PCO.