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应用Nested PCR技术检测柑桔木虱及其寄主九里香的柑桔黄龙病带菌率 被引量:72
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作者 李韬 柯冲 《植物保护学报》 CAS CSCD 北大核心 2002年第1期31-35,共5页
应用PCR及Nested PCR技术检测柑桔木虱及其寄主九里香的结果表明:PCR只可检测最低2头带菌木虱,Nested PCR可检测到单个带菌木虱。100头带菌木虱中,单虫检出率为96%。检测田间重、中等、轻病的柑桔园内的木虱,其带菌率依次为87%、53%... 应用PCR及Nested PCR技术检测柑桔木虱及其寄主九里香的结果表明:PCR只可检测最低2头带菌木虱,Nested PCR可检测到单个带菌木虱。100头带菌木虱中,单虫检出率为96%。检测田间重、中等、轻病的柑桔园内的木虱,其带菌率依次为87%、53%和21%。在病芦柑上饲菌不同天数的木虱均能检测出带菌,其饲菌时间最短为1d。城市九里香叶片及在其叶上取食的木虱单虫,均能用Nested PCR检测出病原。饲菌木虱接种九里香及芦柑健苗,在植株尚未表现症状时,常规PCR难检测出病原,但用Nested PCR则能检测到病原,说明九里香不仅是木虱的寄主,而且是黄龙病病原的隐症寄主。 展开更多
关键词 柑桔黄龙病 PCR nested PCR 木虱 九里香 寄主 带菌率 检测
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Oncofetal antigen glypican-3 as a promising early diagnostic marker for hepatocellular carcinoma 被引量:52
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作者 Research Center of Clinical Medicine,Affiliated Hospital of Nantong University,Nantong 226001,China (Yao M,Yao DF,Qiu LW,Wu W,Sai WL,Yang JL and Zhang HJ) Department of Oncology,Yancheng First People’s Hospital,Yancheng 224001,China (Bian YZ) Department of Oncology,Second Affiliated Hospital,Nanjing Medical University,Nanjing 210011,China (Zhang CG) 《Hepatobiliary & Pancreatic Diseases International》 SCIE CAS 2011年第3期289-294,共6页
BACKGROUND:Hepatocellular carcinoma (HCC) is characterized by a multi-cause,multi-stage and multi-focus process of tumor progression.Its prognosis is poor and early diagnosis is of utmost importance.This study was und... BACKGROUND:Hepatocellular carcinoma (HCC) is characterized by a multi-cause,multi-stage and multi-focus process of tumor progression.Its prognosis is poor and early diagnosis is of utmost importance.This study was undertaken to investigate the dynamic expression of oncofetal antigen glypican-3 (GPC-3) and GPC-3 mRNA in hepatocarcinogenesis and to explore their early diagnostic value for HCC.METHODS:A hepatoma model was induced in male Sprague-Dawley rats with 0.05% 2-fluorenylacetamide and confirmed by hematoxylin and eosin staining and gamma-glutamyltransferase (GGT) expression.Total RNA was purified and transcribed into cDNA by reverse transcription.Fragments of the GPC-3 gene were amplified by nested RT-PCR,and confirmed by sequencing.GPC-3 was analyzed by immunohistochemistry,Western blotting or ELISA.RESULTS:Positive GPC-3 expression showed as brown granule-like staining localized in the cytoplasm.Histological examination of hepatocytes revealed three morphological stages of granule-like degeneration,atypical hyperplasia (precancerous),and cancer formation,with a progressive increase of liver total RNA and GGT expression.The incidence of liver GPC-3 mRNA and GPC-3,and serum GPC-3 was 100%,100% and 77.8% in the HCC group,100%,100%,and 66.7% in the precancerous group,83.3%,83.3%,and 38.9% in the degeneration group,and no expression in the liver or blood of the control group,respectively.There was a positive correlation between liver GPC-3 mRNA and total RNA level (r=0.475,P<0.05) or liver GPC-3 (r=1.0,P<0.001) or serum GPC-3 (r= 0.994,P<0.001).CONCLUSION:Abnormal oncofetal antigen GPC-3 and GPC-3 mRNA expression in hepatocarcinogenesis may be promising molecular markers for early diagnosis of HCC. 展开更多
关键词 hepatocellular carcinoma GLYPICAN-3 IMMUNOHISTOCHEMISTRY nested RT-PCR
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Update on occult hepatitis B virus infection 被引量:33
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作者 Manoochehr Makvandi 《World Journal of Gastroenterology》 SCIE CAS 2016年第39期8720-8734,共15页
The event of mutations in the surface antigen gene of hepatitis B virus(HBV) results in undetectable hepatitis B surface antigen with positive/negative anti-hepatitis B core(anti-HBc) antibody status in serum and this... The event of mutations in the surface antigen gene of hepatitis B virus(HBV) results in undetectable hepatitis B surface antigen with positive/negative anti-hepatitis B core(anti-HBc) antibody status in serum and this phenomenon is named occult hepatitis B infection(OBI). The presence of anti-HBc antibody in serum is an important key for OBI tracking, although about 20% of OBI cases are negative for anti-HBc antibody. The diagnosis of OBI is mainly based on polymerase chain reaction(PCR) and real-time PCR assays. However, real-time PCR is a more reliable method than PCR. OBI is a great issue for the public health problem and a challenge for the clinical entity worldwide. The persistence of OBI may lead to the development of cirrhosis and hepatocellular carcinoma. With regard to OBI complications, the screening of HBV DNA by the highly sensitive molecular means should be implemented for:(1) patients with a previous history of chronic or acute HBV infection;(2) patients co-infected with hepatitis C virus/human immunodeficiency virus;(3) patients undergoing chemotherapy or anti-CD20 therapy;(4) recipients of organ transplant;(5) blood donors;(6) organ transplant donors;(7) thalassemia and hemophilia patients;(8) health care workers;(9) patients with liver related disease(cryptogenic);(10) hemodialysis patients;(11) patients undergoing lamivudine or interferon therapy; and(12) children in time of HBV vaccination especially in highly endemic areas of HBV. Active HBV vaccination should be implemented for the close relatives of patients who are negative for OBI markers. Thus, the goal of this review is to evaluate the rate of OBI with a focus on status of high risk groups in different regions of the world. 展开更多
关键词 nested polymerase chain reaction Occult hepatitis B infection CRYPTOGENIC Real-time polymerase chain reaction
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传粉网络的研究进展:网络的结构和动态 被引量:32
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作者 方强 黄双全 《生物多样性》 CAS CSCD 北大核心 2012年第3期300-307,共8页
植物与传粉者之间相互作用,构成了复杂的传粉网络。近年来,社会网络分析技术的发展使得复杂生态网络的研究成为可能。从群落水平上研究植物与传粉者之间的互惠关系,为理解群落的结构和动态以及花部特征的演化提供了全新的视角。传粉网... 植物与传粉者之间相互作用,构成了复杂的传粉网络。近年来,社会网络分析技术的发展使得复杂生态网络的研究成为可能。从群落水平上研究植物与传粉者之间的互惠关系,为理解群落的结构和动态以及花部特征的演化提供了全新的视角。传粉网络的嵌套结构说明自然界的传粉服务存在冗余,而且是相对泛化的物种主导了传粉。在多年或者多季度的传粉网络中,虽然有很高的物种替换率,但是其网络结构仍然保持相对稳定,说明传粉网络对干扰有很强的抗性。尽管有关网络结构和动态的研究逐渐增多,但传粉网络维持的机制仍不清楚。网络结构可以部分由花部特征与传粉者的匹配来解释,也受到系统发生的制约,影响因素还包括群落构建的时间和物种多样性,以及物种在群落中的位置。开展大尺度群落动态的研究,为探索不同时间尺度、不同物种多样性水平上的传粉网络的生态学意义提供了条件。但已有的研究仍存在不足,比如基于访问观察的网络无法准确衡量传粉者的访问效率和植物间的花粉流动,以及结果受到调查精度区域研究不平衡的制约等。目前的研究只深入到传粉者携带花粉构成成分的水平,传粉者访问植物的网络不能代表植物的整个传粉过程。因此,研究应当更多地深入到物种之间关系对有性生殖的切实影响上。 展开更多
关键词 传粉网络 嵌套 社会网络分析 稳定性 网络动态 泛化与特化
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Diagnosis of Helicobacter pylori : What should be the gold standard? 被引量:31
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作者 Saurabh Kumar Patel Chandra Bhan Pratap +2 位作者 Ashok Kumar Jain Anil Kumar Gulati Gopal Nath 《World Journal of Gastroenterology》 SCIE CAS 2014年第36期12847-12859,共13页
Since the discovery of Helicobacter pylori (H. pylori) in 1983, numerous detection methods for the presence of the bacterium have been developed. Each one of them has been associated with advantages and disadvantages.... Since the discovery of Helicobacter pylori (H. pylori) in 1983, numerous detection methods for the presence of the bacterium have been developed. Each one of them has been associated with advantages and disadvantages. Noninvasive tests such as serology, <sup>13</sup>C urea breath test (UBT) and stool antigen tests are usually preferred by the clinicians. Serology has its own limitation especially in endemic areas while <sup>13</sup>C UBT is technically very demanding. The stool antigen detection method, although specific, is usually associated with poor sensitivity. The <sup>13</sup>C UBT is believed to be specific, but with present revelation of the fact that stomach is colonized by many other urease producing bacteria makes it questionable. Histology, culture, rapid urease test and polymerase chain reaction (PCR) are the tests which are carried out on antral biopsies collected by invasive means. Histology has been proposed to be very sensitive and specific but the question is how by simply looking the morphology of the bacteria in the microscope, one can claim that the curved bacterium is exclusively H. pylori. Rapid urease test (RUT), the doctor&#x02019;s test, is also challenged because the presence of other urease producing bacteria in the stomach cannot be denied. Moreover, RUT has been reported with poor sensitivity specially, when density of the bacterium is low. Isolation of H. pylori is essential to investigate its growth requirements, antibiotic susceptibility testing, studying virulence factor to develop vaccine and many more explorations. It has also got several disadvantages i.e., special condition for transporting, media, incubation and few days waiting for the colonies to appear, apart from the speed essentially needed to process the specimens. Till date, majority of the microbiological laboratories in the world are not equipped and trained to isolate such fastidious bacterium. The option left is PCR methods to detect H. pylori&#x02019;s DNA in gastric mucosa, gastric juice, saliva, dental plaques 展开更多
关键词 Helicobacter pylori review Invasive tests Non-invasive tests Gold standard Polymerase chain reaction detection nested polymerase chain reaction
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中国出口产品质量与质量升级研究 被引量:26
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作者 孙林 卢鑫 钟钰 《国际贸易问题》 CSSCI 北大核心 2014年第5期13-22,共10页
本文利用Nested Logit模型,从绝对质量和相对质量两个角度,对2001-2010年期间中国出口到美国市场上的产品质量和产品质量升级进行了实证测算。实证分析发现:中国整体出口产品质量高于世界平均水平。此外,中国出口产品存在明显的质量升... 本文利用Nested Logit模型,从绝对质量和相对质量两个角度,对2001-2010年期间中国出口到美国市场上的产品质量和产品质量升级进行了实证测算。实证分析发现:中国整体出口产品质量高于世界平均水平。此外,中国出口产品存在明显的质量升级现象。这主要是由机电仪器与交通工具大类的质量升级所带动的。在此基础上,本文将中国出口产品质量和质量升级与日本、德国、印度、东盟进行了比较分析。研究结论显示:2001-2010年间,与德国、日本、东盟、印度四个经济体的出口产品整体质量相比,中国出口产品整体质量有了明显的提升。 展开更多
关键词 出口产品质量 质量升级 nested LOGIT模型
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Diagnostic value of cancer-testis antigen mRNA in peripheral blood from hepatocellular carcinoma patients 被引量:22
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作者 Li Zhao Dong-Cheng Mou +3 位作者 Zeng-An Wu Ji-Run Peng Lei Huang Xi-Sheng Leng 《World Journal of Gastroenterology》 SCIE CAS CSCD 2010年第32期4072-4078,共7页
AIM:To evaluate the diagnostic value of cancer-testis antigen(CTA) mRNA in peripheral blood samples from hepatocellular carcinoma(HCC) patients.METHODS:Peripheral blood samples were taken from 90 patients with HCC bef... AIM:To evaluate the diagnostic value of cancer-testis antigen(CTA) mRNA in peripheral blood samples from hepatocellular carcinoma(HCC) patients.METHODS:Peripheral blood samples were taken from 90 patients with HCC before operation.Expression of melanoma antigen-1(MAGE-1),synovial sarcoma X breakpoint-1(SSX-1),and cancer-testis-associated protein of 11 kDa(CTp11) mRNA in peripheral blood mononuclear cells(PBMC) was tested by nested reverse transcriptspolymerase chain reaction(RT-PCR).Serum α-fetoprotein(AFP) in these patients was also determined.RESULTS:The positive rate of MAGE-1,SSX-1 and CTp11 transcripts was 37.7%,34.4%,31.1% in PBMC samples,and 74.4%,73.3%,62.2% in their resected tumor samples,respectively.The positive rate for at least one of the transcripts of three CTA genes was 66.7% in PBMC samples and 91.1% in their resected tumor samples.MAGE-1,SSX-1 and/or CTp11 mRNA were not detected in the PBMC of those patients from whom the resected tumor samples were MAGE-1,SSX-1 and/or CTp11 mRNA negative,nor in the PBMC samples from 20 healthy donors and 10 cirrhotic patients.Among the 90 patients,the serum AFP in 44 patients met the general diagnostic standard(AFP > 400 μg/L) for HCC,and was negative(AFP ≤ 20 μg/L) or positive with a low concentration(20 μg/L < AFP ≤ 400 μg/L) in the other patients.The positive rate for at least one of the transcripts of three CTA genes in PBMC samples from the AFP negative or positive patients with a low concentration was 69.2% and 45.0%,respectively.Of the 90 patients,71(78.9%) were diagnosed as HCC by nested RT-PCR and serum AFP.Although the positive rate for at least one of the transcripts of three CTA genes in PBMC samples from 53 patients at TNM stage or was obviously higher than that in PBMC samples from 37 patients at stage or(77.9% vs 51.4%,P = 0.010),the CTA mRNA was detected in 41.7% and 56.0% of PBMC samples from HCC patients at stages andrespectively.CONCLUSION:Detecting MAGE-1,SSX-1 and CTp11 mRNA in PBMC improves the total diagnostic rate of HCC. 展开更多
关键词 Hepatocellular carcinoma α-fetoprotein Cancer-testis antigen Diagnosis nested reverse transcripts-polymerase chain reaction
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不同pH水平下两种菌根真菌对紫云英生长的影响及其相互作用 被引量:15
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作者 于永光 赵斌 《菌物学报》 CAS CSCD 北大核心 2008年第2期209-216,共8页
设计在不同pH水平(4.3、5.1、5.8、6.8)下两种VA菌根真菌Glomus mosseae和Gigaspora margarita对紫云英Astragalus sinicus进行单接种、混合接种及无接种对照的盆栽实验。对紫云英地上和地下部分生物量、根部侵染率、SDH和ALP酶活进行... 设计在不同pH水平(4.3、5.1、5.8、6.8)下两种VA菌根真菌Glomus mosseae和Gigaspora margarita对紫云英Astragalus sinicus进行单接种、混合接种及无接种对照的盆栽实验。对紫云英地上和地下部分生物量、根部侵染率、SDH和ALP酶活进行了检测。实验结果表明:紫云英的生长效应与VA菌根真菌的侵染率及两种酶活成明显相关性。土壤pH升高,单接种Glomus mosseae和混合接种的侵染率也随之升高,而单接种Gigaspora margarita的侵染率呈现出先上升后下降的趋势。本实验设计了特异性扩增Glomus mosseae和Gigaspora margarita的引物gm1和gig1,在混合接种实验中,nested PCR扩增结果显示:在低pH水平下(4.3-5.1)大多数根段为Gigaspora margarita所侵染,在高pH水平下(5.8-6.8)Glomus mosseae表现出较强的竞争力,但并没有检测到两种VA真菌存在于同一条侵染根段;对比单接种实验,在低pH水平下,Glomus mosseae显著抑制了Gigaspora margarita的侵染,而在高pH水平下Gigaspora margarita明显促进Glomus mosseae的侵染。 展开更多
关键词 丛枝菌根 酶活染色 特异性引物 nested PCR
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基于Nested Logit模型的共享单车选择行为研究 被引量:20
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作者 袁朋伟 董晓庆 +1 位作者 翟怀远 许葭 《交通运输系统工程与信息》 EI CSCD 北大核心 2018年第5期191-196,210,共7页
近两年来,共享单车迅速发展,已有研究较少从微观角度来阐释共享单车的选择行为.本文基于随机效用理论,构建Nested Logit模型,选取出行目的、接驳时间、在车时间、停车时间、费用等出行特征变量,选取下雨(雪)、空气质量、气温、风力等级... 近两年来,共享单车迅速发展,已有研究较少从微观角度来阐释共享单车的选择行为.本文基于随机效用理论,构建Nested Logit模型,选取出行目的、接驳时间、在车时间、停车时间、费用等出行特征变量,选取下雨(雪)、空气质量、气温、风力等级等天气状况变量,选取年龄、性别、收入等社会经济变量作为效用函数的特征变量,采用D-optimal法设计问卷,在济南市开展共享单车实证调查.基于收集到的样本进行参数标定,找出影响共享单车及其他出行方式选择的关键影响因素;并对共享单车的乘车费用与接驳时间进行弹性分析,明确了共享单车乘车费用与接驳时间变化对短途出行结构的影响. 展开更多
关键词 城市交通 共享单车 共享单车选择行为 nested LOGIT
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基于RP/SP融合数据的沪杭客运通道公铁客流分担率研究 被引量:16
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作者 张戎 吴晓磊 张天然 《铁道学报》 EI CAS CSCD 北大核心 2008年第3期7-13,共7页
RP(Revealed Preference)和SP(Stated Preference)调查是分析交通行为的两种重要方法,为充分利用两种数据的优点,研究运用NL(Nested Logit)模型进行RP/SP数据融合的方法。以沪杭客运通道修建磁浮铁路和客运专线为背景,设计RP/SP的调研方... RP(Revealed Preference)和SP(Stated Preference)调查是分析交通行为的两种重要方法,为充分利用两种数据的优点,研究运用NL(Nested Logit)模型进行RP/SP数据融合的方法。以沪杭客运通道修建磁浮铁路和客运专线为背景,设计RP/SP的调研方案;根据该通道客流特点建立RP/SP的效用函数;根据样本数据的RP/SP性质以及交通方式性质建立不同的NL数据融合模型,并分析模型的精度,得出利用NL模型建立的数据融合模型比单独利用RP或SP数据建立的ML(Multinomial Logit)模型精度要高,并且采用先按交通方式的性质分层,然后再按数据的RP/SP性质分层的3层NL模型精度更高的结论。在此基础上预测了2015年沪杭各类铁路及公路的客流分担率。 展开更多
关键词 客流分担率 SP/RP融合数据 nested LOGIT模型 快速客运线
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城际铁路和公路长途客运的定价博弈 被引量:19
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作者 卞长志 陆化普 尉欣欣 《交通运输系统工程与信息》 EI CSCD 2010年第1期184-189,共6页
城际铁路的规划建设,加剧了经济发达地区城际客运交通市场的竞争,而竞争的成败很大程度上取决于运营者是否能够采用吸引乘客的策略.本研究基于离散选择理论,使用Nested Logit模型分析出行者的城际交通方式选择行为,确定不同交通方式客... 城际铁路的规划建设,加剧了经济发达地区城际客运交通市场的竞争,而竞争的成败很大程度上取决于运营者是否能够采用吸引乘客的策略.本研究基于离散选择理论,使用Nested Logit模型分析出行者的城际交通方式选择行为,确定不同交通方式客运量与运输价格的关系,建立各交通方式的运营利润模型.并以运营票价为竞争策略变量,建立城际铁路和公路长途巴士运输的完全信息静态博弈模型,给出了纯策略和混合策略Nash均衡解的存在性和计算方法.案例计算表明,传统的Logit模型与本研究的Nested Logit模型给出不同的均衡价格,且Logit模型会过高估计公共运输企业的利润.本研究对于合理配置城际综合交通方式具有参考价值. 展开更多
关键词 交通运输经济 城际铁路 长途巴士 nested LOGIT模型 完全信息静态博弈
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RP/SP融合数据的Mixed Logit和Nested Logit模型估计对比 被引量:14
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作者 张天然 杨东援 +1 位作者 赵娅丽 叶亮 《同济大学学报(自然科学版)》 EI CAS CSCD 北大核心 2008年第8期1073-1078,1084,共7页
分析了RP/SP(revealed preference/stated preference)融合数据对交通行为研究的重要性,通过实际调查的RP/SP融合数据,对比了用Mixed Logit和Nested Logit模型的估计结果.得出了以下结论:RP/SP融合数据中,有时同类型交通方式的关联性要... 分析了RP/SP(revealed preference/stated preference)融合数据对交通行为研究的重要性,通过实际调查的RP/SP融合数据,对比了用Mixed Logit和Nested Logit模型的估计结果.得出了以下结论:RP/SP融合数据中,有时同类型交通方式的关联性要比RP和SP数据之间的关联性强,应用不同的Nested Logit模型分层方法进行估计对比;Mixed Logit考虑了个体的异质性,假定参数为随机分布,同时体现了RP/SP数据的关联性和同类型交通方式的关联性,能够得到更好的参数估计结果;Mixed Logit模型能更现实地反映不同交通方式使用者对时间和费用敏感性的不同(时间价值的不同),体现小汽车使用者比公共交通使用者具有更高时间价值的现实情况. 展开更多
关键词 RP/SP融合数据 MIXED Logit(RPL/RCL)模型 异质性 nested LOGIT模型
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类黄酮物质apigenin和daidzein诱导AM真菌侵染十字花科植物芥菜 被引量:11
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作者 董昌金 赵斌 《科学通报》 EI CAS CSCD 北大核心 2004年第10期953-960,共8页
豆物植物根分泌物中的类黄酮物质可能是根瘤菌“nod”结瘤基因和丛枝菌根(arbuscularmycorrhiza,AM)真菌共生基因表达的信号分子.芥菜(十字花科植物)是一种非菌根植物,自然情况下,根分泌物中缺乏类黄酮等信号物质,不能与AM真菌形成共生... 豆物植物根分泌物中的类黄酮物质可能是根瘤菌“nod”结瘤基因和丛枝菌根(arbuscularmycorrhiza,AM)真菌共生基因表达的信号分子.芥菜(十字花科植物)是一种非菌根植物,自然情况下,根分泌物中缺乏类黄酮等信号物质,不能与AM真菌形成共生关系.当用适量的类黄酮(apigenin或daidzein)处理AM真菌时,Trypanblue染色结果显示,2种AM真菌(G.intraradices和G.mosseae)成功地侵染了非菌根植物芥菜的根.AM真菌在非菌根植物芥菜根中生长、定殖,并产生了幼嫩的孢子,从而完成了生活史.AM菌很真菌是所有真菌中惟一具有ALP酶活性的真菌,ALP活性染色结果也证实了AM真菌侵染了芥菜的根.运用nestedPCR和特异性的分子探针,探测了G.intraradices和G.mosseae在非菌根植物芥菜根中的存在.上述证据能够充分证明,类黄酮物质诱导G.intraradices和G.mosseae侵染非菌根植物并建立了共生关系. 展开更多
关键词 类黄酮物质 AM真菌 非菌根植物 侵染 台盼蓝染色 nested PCR 丛枝菌根 十字花科植物 芥菜
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基于NL-累计前景理论的出行方式选择预测模型研究 被引量:15
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作者 马书红 周烨超 张艳 《交通运输系统工程与信息》 EI CSCD 北大核心 2019年第4期135-142,共8页
为改进效用理论在个体风险偏好、非完全理性决策、方式整体效用等方面的表述局限,联立出行方式与出发时段构建双因素出行方案,并建立基于巢式Logit(NL)-累计前景理论的出行方式选择预测优化模型.通过累计前景理论将NL模型所获方案客观... 为改进效用理论在个体风险偏好、非完全理性决策、方式整体效用等方面的表述局限,联立出行方式与出发时段构建双因素出行方案,并建立基于巢式Logit(NL)-累计前景理论的出行方式选择预测优化模型.通过累计前景理论将NL模型所获方案客观效用及选择概率主观化,构建累计权重函数、价值函数并以前景值的形式描述出行方式对出行者的实际感知价值,最后通过调查数据进行建模与验证.结果表明,与仅基于NL模型进行的方式预测相比,所建模型综合命中率从74.8%上升至85.2%,各方式预测命中率更为均衡. 展开更多
关键词 城市交通 出行方式选择 累计前景理论 nested LOGIT模型 感知价值
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城市居民出行空间和方式联合选择模型研究 被引量:15
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作者 唐洁 隽志才 高林杰 《公路交通科技》 CAS CSCD 北大核心 2010年第5期83-87,99,共6页
考虑到出行者出行空间和出行方式之间的重要联系,本文基于非集计模型中Nested Logit模型的理论和方法,结合2005年国内某大型城市居民出行调查数据,建立了城市居民出行空间和方式的联合选择模型。模型为2层的NL模型,第1层为空间选择层,第... 考虑到出行者出行空间和出行方式之间的重要联系,本文基于非集计模型中Nested Logit模型的理论和方法,结合2005年国内某大型城市居民出行调查数据,建立了城市居民出行空间和方式的联合选择模型。模型为2层的NL模型,第1层为空间选择层,第2层为方式选择层,以此将出行空间选择和出行方式选择连接起来。模型采用统计软件STATA 9进行标定,并通过统计指标进行验证,深入分析了影响出行者出行空间选择和出行方式选择的重要因素。最后,用同样的数据源建立了方式选择的MNL模型,通过对比联合模型和MNL模型的命中率和集计结果表明,出行空间和方式联合选择模型能够在较细的层面上预测出行者出行空间和交通方式的选择情况,从而提高了模型的精度和实用性。 展开更多
关键词 交通工程 出行空间和方式联合选择 nested LOGIT模型 出行行为 多项Logit模型
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巢式病例对照研究 被引量:15
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作者 黄平 俞守义 《继续医学教育》 2006年第31期75-77,共3页
关键词 巢式病例对照研究 nested 队列研究 STUDY CASE 随访观察 设计思路 套叠式
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大豆油中转基因成分的Nested PCR和Semi-nested PCR检测方法研究 被引量:10
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作者 闻伟刚 崔俊霞 赵秀玲 《生物技术通报》 CAS CSCD 2005年第6期84-87,共4页
对大豆油中DNA提取方法进行了研究,结果表明CTAB、SDS和Wizard试剂盒提取大豆油DNA均具有良好的效果。利用nested PCR和semi-nested PCR检测大豆(Roundup Ready)油中的转基因成分发现,该方法能够检测到大豆原油中的Lectin基因(112bp)、C... 对大豆油中DNA提取方法进行了研究,结果表明CTAB、SDS和Wizard试剂盒提取大豆油DNA均具有良好的效果。利用nested PCR和semi-nested PCR检测大豆(Roundup Ready)油中的转基因成分发现,该方法能够检测到大豆原油中的Lectin基因(112bp)、CaMV35S基因(147bP)和CP4-EPSPS基因(205bp),检测灵敏度达到10-6ng/μl;但该方法未能从人豆成品油(一级)中扩增到上述基因,当中的转基因成分DNA含量低于10-12ng/μl。 展开更多
关键词 大豆油 转基因成分 nested PCR Semi-nested PCR检测
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Pre-diagnostic levels of adiponectin and soluble vascular cell adhesion molecule-1 are associated with colorectal cancer risk 被引量:15
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作者 Mathilde Touvier Léopold Fezeu +8 位作者 Namanjeet Ahluwalia Chantal Julia Nathalie Charnaux Angela Sutton Caroline Méjean Paule Latino-Martel Serge Hercberg Pilar Galan Sébastien Czernichow 《World Journal of Gastroenterology》 SCIE CAS CSCD 2012年第22期2805-2812,共8页
AIM: To examine the relationships between pre-diag- nostic biomarkers and colorectal cancer risk and assess their relevance in predictive models.METHODS: A nested case-control study was designed to include all first... AIM: To examine the relationships between pre-diag- nostic biomarkers and colorectal cancer risk and assess their relevance in predictive models.METHODS: A nested case-control study was designed to include all first primary incident colorectal cancer cases diagnosed between inclusion in the SUpplemen- tation en VItamines et Min^raux AntioXydants cohort in 1994 and the end of follow-up in 2007. Cases (n = 50) were matched with two randomly selected con- trols (n = 100). Conditional logistic regression models were used to investigate the associations between pre- diagnostic levels of hs-CRP, adiponectin, leptin, soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-I, E-selectin, monocyte chemoattractant protein-1 and colorectal cancer risk. Area under the receiver operating curves (AUC) and relative integrated discrimination improvement (RIDI) statistics were used to assess the discriminatory poten- tial of the models. RESULTS: Plasma adiponectin level was associated with decreased colorectal cancer risk (P for linear trend -- 0.03). Quartiles of sVCAM-1 were associated with increased colorectal cancer risk (P for linear trend = 0.02). No association was observed with any of the other biomarkers. Compared to standard models with known risk factors, those including both adiponectin and sVCAM-1 had substantially improved performance for colorectal cancer risk prediction (P for AUC improve- ment = 0.01, RIDI = 26.5%). CONCLUSION: These results suggest that pre-diag- nostic plasma adiponectin and sVCAM-1 levels are as- sociated with decreased and increased colorectal cancer risk, respectively. These relationships must be confirmed in large validation studies. 展开更多
关键词 Colorectal cancer ADIPONECTIN Soluble vascu-lar cell adhesion molecule-l nested case-control study Prospective study
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基于Nested Logit的电动汽车分时租赁选择行为分析 被引量:13
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作者 刘向 董德存 +1 位作者 王宁 张文剑 《同济大学学报(自然科学版)》 EI CAS CSCD 北大核心 2019年第1期47-55,共9页
基于用户出行选择调查问卷的样本数据,应用Nested Logit离散选择模型进行回归分析,探究影响用户出行选择的因素,并计算出各种出行方式的分担率及其敏感度。结果表明:使用成本、站点距离、出行里程、驾龄、用户拥有私家车情况以及年龄等... 基于用户出行选择调查问卷的样本数据,应用Nested Logit离散选择模型进行回归分析,探究影响用户出行选择的因素,并计算出各种出行方式的分担率及其敏感度。结果表明:使用成本、站点距离、出行里程、驾龄、用户拥有私家车情况以及年龄等因素对用户是否选择电动汽车分时租赁有显著影响;当前电动汽车分时租赁在出行领域的显示性编好(revealed preference,RP)调查分担率为2.36%,使用成本对其敏感度为8.6%,站点距离对其敏感度为43.7%;陈术性编好(stated preference,SP)调查分担率为3.30%,使用成本对其敏感度为8.9%,站点距离对其敏感度为21.1%。 展开更多
关键词 电动汽车分时租赁 出行选择行为 nested LOGIT模型 显示性偏好 陈述性偏好
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Analysis of Factors Affecting Execution Performance of OpenMP Programs 被引量:7
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作者 李建江 舒继武 +2 位作者 陈永健 王鼎兴 郑纬民 《Tsinghua Science and Technology》 SCIE EI CAS 2005年第3期304-308,共5页
OpenMP is able to develop multithreaded programs with lower cost as a promising way to quickly parallelize a great number of serial programs. However, there are many difficulties when developing OpenMP multithreaded p... OpenMP is able to develop multithreaded programs with lower cost as a promising way to quickly parallelize a great number of serial programs. However, there are many difficulties when developing OpenMP multithreaded programs. Most importantly, the performance of OpenMP programs cannot be guar- anteed, which has greatly affected the application of OpenMP. This paper examines several factors that af- fect the execution performance of OpenMP programs, including loop transformation, scheduling strategy, the number of threads, and nested parallelism. The results show that one of the key reasons for perform- ance degradation is load imbalance, which can be corrected by reasonable use of these key factors to im- prove the execution performance of OpenMP programs. 展开更多
关键词 OPENMP loop transformation scheduling strategy nested parallelism number of threads load imbalance
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