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排序方式: 共有238条查询结果,搜索用时 15 毫秒
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Marcia J. Holden Marci Levine Tandace Scholdberg Ross J. Haynes G. Ronald Jenkins 《Analytical and bioanalytical chemistry》2010,396(6):2175-2187
An online survey was conducted by the International Life Sciences Institute, Food Biotechnology Committee, on the use of qualitative
and quantitative polymerase chain reaction (PCR) assays for cauliflower mosaic virus 35S promoter and Agrobacterium tumefaciens Tnos DNA sequence elements for the detection of genetically engineered (GE) crop plant material. Forty-four testing laboratories
around the world completed the survey. The results showed the widespread use of such methods, the multiplicity of published
and in-house methods, and the variety of reference materials and calibrants in use. There was an interest on the part of respondents
in validated quantitative assays relevant to all GE events that contain these two genetic elements. Data are presented by
testing two variations each of five published real-time quantitative PCR methods for 35S detection on eight maize reference
materials. The results showed that two of the five methods were not suitable for all the eight reference materials, with poor
linear regression parameters and multiple PCR amplification products for some of the reference materials. This study demonstrates
that not all 35S methods produce satisfactory results, emphasizing the need for method validation. 相似文献
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Maintaining the predictive abilities of multivariate calibration models by spectral space transformation 总被引:1,自引:0,他引:1
Du W Chen ZP Zhong LJ Wang SX Yu RQ Nordon A Littlejohn D Holden M 《Analytica chimica acta》2011,690(1):64-70
In quantitative on-line/in-line monitoring of chemical and bio-chemical processes using spectroscopic instruments, multivariate calibration models are indispensable for the extraction of chemical information from complex spectroscopic measurements. The development of reliable multivariate calibration models is generally time-consuming and costly. Therefore, once a reliable multivariate calibration model is established, it is expected to be used for an extended period. However, any change in the instrumental response or variations in the measurement conditions can render a multivariate calibration model invalid. In this contribution, a new method, spectral space transformation (SST), has been developed to maintain the predictive abilities of multivariate calibration models when the spectrometer or measurement conditions are altered. SST tries to eliminate the spectral differences induced by the changes in instruments or measurement conditions through the transformation between two spectral spaces spanned by the corresponding spectra of a subset of standardization samples measured on two instruments or under two sets of experimental conditions. The performance of the method has been tested on two data sets comprising NIR and MIR spectra. The experimental results show that SST can achieve satisfactory analyte predictions from spectroscopic measurements subject to spectrometer/probe alteration, when only a few standardization samples are used. Compared with the existing popular methods designed for the same purpose, i.e. global PLS, univariate slope and bias correction (SBC) and piecewise direct standardization (PDS), SST has the advantages of implementation simplicity, wider applicability and better performance in terms of predictive accuracy. 相似文献
25.
We consider the Schrödinger operator with zero-range potentials onN points of three-dimensional space, independently chosen according to a common distributionV(x). Under some assumptions we prove that, whenN goes to infinity, the sequence converges to a Schrödinger operator with an effective potential. The fluctuations around the limit operator are explicitly characterized. 相似文献
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Helge Holden Raphael Hegh Krohn Steinar Johannesen 《Advances in Applied Mathematics》1983,4(4):402-421
Let Vi be short range potential and λi(ε) analytic functions. We show that the Hamiltonians Hε = −Δ + ε−2∑i = lnλi(ε)Vi((· − xi)/ε converge in the strong resolvent sense to the point interactions as ε → 0, and if Vi have compact support then the eigenvalues and resonances of Hε, which remains bounded as ε → 0, are analytic in ε in a complex neighborhood of zero. We compute in closed form the eigenvalues and resonances of Hε to the first order in ε. 相似文献
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A hadronic bremsstrahlung model is presented which provides an understanding of several of the recently observed phenomena at large transverse momenta. 相似文献
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