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41.
1IlltroductionInl99o,MiltinandB.lairl1]raisedadifferenceequationasapopulationmodelforthegrowthofthebobwhitequailpopulationofnorthernWisconsin.Inl994,Ladas,G.proposedthefollowingopenproblem[']:"(a)Investigatetheboundedness,persistence,permanence,oscillation,periodicity,andglobalattractivity;(b)ExtendEq.(*)byintroducingdelaysintothemodel,andinvestigatethedelayedequation.".Inl996,TangHeng-shengandOuChun-hua[3]considereditsglobalattrac-tivity,partlyansweredaboveopenproblem(a).Inl999,byintrodu… 相似文献
42.
路基冻害一直是困扰东北季冻区道路建设的一个重要问题。长春冬季天气寒冷,在温度梯度作用下路基土中水分产生迁移和聚集,引起路基冻胀。春季路基解冻,集聚的冰晶体融化,路基土处于饱和或过饱和状态,承载力极低,在交通车辆作用下发生路面鼓包、弹簧、断裂和翻浆冒泡等现象,给交通运输和经济建设带来极大的危害。孔隙是水分迁移的主要通道,是影响路基冻胀主要因素之一,其特征决定土体的冻胀敏感性。本文利用WD-5配置联机图象处理系统的电子显微镜,通过图像定量分析系统,对长春季冻区路基土的微观孔隙作了定量评价。经过分析得出:3个土样孔隙直径均是小于5μm的占主导地位,都具备冻胀条件;试样水平和垂直两个方向的孔隙分布较均匀,孔隙为辐射状或网状结构,多为扁圆和等轴形状;孔隙形态分维数分析认为,分维数高,大孔隙含量多,孔隙分布比较简单,在研究范围内,有利于水分迁移,冻胀性较强。 相似文献
43.
Guobo Dong Ming Zhang Mei Wang Fang Tang Hua Li Anping Huang Hui Yan 《Journal of Physics and Chemistry of Solids》2012,73(9):1170-1172
CuNdO2, a p-type transparent conducting oxide has been synthesized by conventional solid-state reaction. The XRD and TEM results show that the pure delafossite phase is obtained, furthermore, the EDX results indicate the sample is obviously oxygen-rich. The p-type conduction of CuNdO2 was confirmed by Hall and Seebeck measurements. Carrier concentration and mobility at room temperature are around 1.38×1017 cm?3 and 1.24 cm2V?1s?1, respectively. On the other hand, the optical band gap of CuNdO2 is estimated to be around 3.14 eV, which agrees well with the theoretical result predicted by the first-principle calculation. 相似文献
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45.
Pei She Yanxin Chu Chunwei Liu Xun Guo Kang Zhao Jianguo Li Haijing Du Xiang Zhang Hong Wang Anping Deng 《Analytica chimica acta》2016
An immunochromatographic test (ICT) strip was developed for ultrasensitive competitive immunoassay of Hg2+. This strategy was achieved by combining the easy-operation and rapidity of ICT with the high sensitivity of surface-enhanced Raman scattering (SERS). Monoclonal antibody (mAb) against Hg2+ and Raman active substance 4-mercaptobenzoic acid (MBA) dual labelled gold nanoparticles (GNPs) were prepared as an immunoprobe. The Raman scattering intensity of MBA on the test line of the ICT strip was measured for quantitative determination of Hg2+. The ICT was able to directly detect Hg2+ without complexing due to the specific recognition of the mAb with Hg2+. The IC50 and limit of detection (LOD) of the assay for Hg2+ detection were 0.12 ng mL−1 and 0.45 pg mL−1, respectively. There was no cross-reactivity (CR) of the assay with other nineteen ions and the ICT strips could be kept for 5 weeks without loss of activity. The recoveries of the assay for water, human serum and urine samples spiked with Hg2+ were in range of 88.3–107.3% with the relative standard deviations (RSD) of 1.5–9.5% (n = 3). The proposed ICT was used for the detection of Hg2+ in urine samples collected from Occupational Disease Hospital and the results were confirmed by cold-vapor atomic fluorescence spectroscopy (CV-AFS). The assay exhibited high sensitivity, selectivity, stability, precision and accuracy, demonstrating a promising method for the detection of trace amount of Hg2+ in environmental water samples and biological serum and urine samples. 相似文献
46.
Modulation instability in negative refractive metamaterials with exponential saturable nonlinearity and self-steepening effects 总被引:1,自引:0,他引:1
Modulation instability (MI) in negative refractive metamaterials with exponential saturable nonlinearity and the self-steeping effect is investigated by using the standard linear stability analysis and the Drude electromagnetic model. The dispersion relation, instability condition, cut-off frequency, gain spectrum, and their corresponding dimensionless expressions are analytically deduced and then calculated. The results show that, the self-steepening effect will suppress MI by decreasing the cut-off frequency and the maximum gain. And the larger the power density ratio is, more slowly the cut-off frequency and the maximum gain decrease with increase of the self-steepening parameter. Although the sign of the self-steepening parameter does not influence MI but its absolute value must be smaller than a certain value. Depending on different self-steepening parameters, the cut-off frequency and maximum gain may decrease or increase before decrease with increase of the power density ratio. In particular, for large self-steepening parameters, the power density ratio may have a threshold value. When the power density ratio is under this threshold, MI will disappear. 相似文献
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48.
Quantum dots based electrochemiluminescent immunosensor by coupling enzymatic amplification for ultrasensitive detection of clenbuterol 总被引:1,自引:0,他引:1
An ultrasensitive electrochemiluminescence (ECL) immunosensor based on CdSe quantum dots (QDs) has been designed for the detection of clenbuterol. The immunosensor was fabricated by layer by layer and characterized with atomic force microscopic images (AFM) and electrochemical impedance spectra (EIS). In oxygen-saturated pH = 9.0 Tris-HCl buffer, a strong ECL emission of QDs could be observed during the cathodic process due to the H2O2 product from electrochemical reduction of dissolved oxygen. Upon the formation of immunocomplex, the second antibody labeled with horseradish peroxidase was simply immobilized on the electrode surface. The ECL emission decreased since steric hindrance of the immunocomplex slowed down the electron-transfer speed of dissolved oxygen, and also could be greatly amplified by an enzymatic cycle to consume the self-produced coreactant. Using clenbuterol as model analyte, the ECL intensity was determined by the concentration of competitive immunoassay of clenbuterol with a wide calibration in the range of 0.05 ng mL−1 to 1000 ng mL−1, and a low detection limit was 0.02 ng mL−1. The immunosensor shows good stability and fabrication reproducibility. It was applied to detecting practical samples with the satisfactory results. This immunosensing strategy opens a new avenue for detection of residue and application of QDs in ECL biosensing. 相似文献
49.
研究分子光谱和气象参数的不确定对单色吸收系数和对应的科线路径透过率计算结果的影响,并导出一般的误差表达式。数值计算表明,对所采用的大气廓线和分子光谱参数,其典型的不确定将导致透过率计算结采的标准相对误差大于3■,吸收系数和透过率对谱线频率、强度、半宽以及大气温度廓线的不确定最为灵敏。 相似文献
50.
东方弧菌518菌株于20℃摆床液体培养十六小时,菌数达最大,菌体内荧光素酶含量也较高,此时收获菌体.用超声波振动破碎细胞从中提取荧光酶粗液,经DEAE-纤维索和DEAE-sephadex柱层析得到纯化的酶.用葡聚糖凝胶层析法测得该酶分子量为87000道尔顿,用SDS-PAGE法测得该酶两个亚基分子量分别为44000(α)和41000(β). 该酶在pH6.8、18℃时活性最佳,对热不稳定.以FMNH2为底物催化发光反应,最高发射波长为490nm左右.其光谱特征与文献报道的东方孤菌整体发光的光谱相一致. 相似文献