| 11. |
- Olsson, Ing-Marie, et al.
(författare)
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Rational DOE-protocols for 96-well plates
- 2006
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Ingår i: Chemometrics and Intelligent Laboratory Systems. - Amsterdam : Elsevier. - 0169-7439 .- 1873-3239. ; 83:1, s. 66-74
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Tidskriftsartikel (refereegranskat)abstract
- The use of 96-well plates for chemical and biological applications has rapidly increased as new applicable domains have been discovered and new laboratory instruments developed. There are 96, 384, 1536, etc. plates customized for diverse applications such as biological assays, sample preparation, solid-phase extraction and crystallization. Multi-pipettes as well as automated pipette systems accelerate the preparation of plates resulting in even faster evaluation systems. A bottleneck in the use of multi-unit plates is method development and optimization. By applying rational experimental design, the optimization could be made more efficient and less time-consuming. Unfortunately, the workload related to manual preparation of multi-unit plates according to an experimental design is often considered overwhelming. The present study introduces a new approach for experimental design in 96-well plates that minimizes the manual workload without compromising the quality of the experimental design. This approach is scalable to larger rectangular formats such as 384- and 1536-well plates. The optimal combinations will be delineated and applied experimentally to a reporter-gene assay.
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| 12. |
- Stenlund, Hans, et al.
(författare)
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Monitoring kidney-transplant patients using metabolomics and dynamic modeling
- 2009
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Ingår i: Chemometrics and Intelligent Laboratory Systems. - : Elsevier B.V.. - 0169-7439 .- 1873-3239. ; 98:1, s. 45-50
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Tidskriftsartikel (refereegranskat)abstract
- A kidney transplant provides the only hope for a normal life for patients with end-stage renal disease, i.e., kidney failure. Unfortunately, the lack of available organs leaves some patients on the waiting list for years. In addition, the post-transplant treatment is extremely important for the final outcome of the surgery, since immune responses, drug toxicity and other complications pose a real and present threat to the patient. In this article, we describe a novel strategy for monitoring kidney transplanted patients for immune responses and adverse drug effects in their early recovery. Nineteen patients were followed for two weeks after renal transplantation, two of them experienced problems related to kidney function, both of whom were correctly identified by means of nuclear magnetic resonance spectroscopic analysis of urine samples and multivariate data analysis.
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| 13. |
- Svensson, Olof, et al.
(författare)
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An evaluation of 2D-wavelet filters for estimation of differences in textures of pharmaceutical tablets
- 2006
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Ingår i: Chemometrics and Intelligent Laboratory Systems. - : Elsevier BV. - 0169-7439 .- 1873-3239. ; 84:1-2, s. 3-8
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Tidskriftsartikel (refereegranskat)abstract
- In chemical imaging spectra are acquired over a surface with one spectrum for each pixel of the image. The obtained spectra usually carry a mixture of chemical and physical information. One may view the properties that vary over the image, the mean spectral magnitude from separate wavelength intervals, or better, PCA scores may be shown as images.In this way a multitude of images are compressed to a few images that in the PCA case are representative for the main variation in the sample images. These images may be viewed manually and deductions as to e.g. differences in homogeneity can be made. At an increased rate of samples, the observer will have difficulties coping with the repetitive work and different observers will most likely have slightly different interpretations. In order to automate the process of estimation of e.g. homogeneity and particle density, image filters can be used to calculate a small set of texture descriptors for each image. Calculations based on the 2D versions of the discrete wavelet transform (DWT) using Daubechies 14 and the dual tree complex wavelet transform (DT-CWT) using near-symmetric 13, 19 tap filters in combination with q-shift 14, 14 tap filters were evaluated for this purpose.The aim with this work is to evaluate texture descriptors based on a combination of 2D-wavelet filters and energy, i.e. l(1)-norm, calculations for each wavelet scale. These descriptors are then used as observations for overview in e.g. PCA. In this way the texture differences can be ranked by ordinary use of PCA or PLS.This method is tested on multivariate near infrared images of pharmaceutical tablets. Score images are selected to represent variations of the aggregate density and sizes in the compressed tablets. Images are shifted and rotated to compare shift and rotational independence of the texture descriptors.
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| 14. |
- Wallbäcks, Lars
(författare)
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Multivariate data analysis of multivariate populations
- 2007
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Ingår i: Chemometrics and Intelligent Laboratory Systems. - : Elsevier BV. - 0169-7439 .- 1873-3239. ; 86:1, s. 10-16
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Tidskriftsartikel (refereegranskat)abstract
- For data that can be arranged in populations, multivariate data analysis of digitalized distributions is suggested as an alternative method to detect variations. This approach includes a representation of the data that avoids information destroying pre-processing such as averaging. The method is exemplified and discussed for both single variable distributions and multivariable distributions. A theoretical discussion is presented on its use with data from fibre measuring systems, time series and image analysis data. The method is suggested as either a complement or alternative to other types of data analysis and opens new possibilities for variation detection.
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| 15. |
- Andersson, M, et al.
(författare)
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NIR spectroscopy on moving solids using a scanning grating spectrometer - impact on multivariate process analysis
- 2005
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Ingår i: Chemometrics and Intelligent Laboratory Systems. - : Elsevier BV. - 0169-7439. ; 75:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- The effect of sample movement on spectral response during fiber probe diffuse reflectance near-infrared spectrometry (NIR) sampling was characterized. This is of central importance in Process Analytical Chemistry (PAC) and Process Analytical Technology (PAT). The incitement to this study was the observation of spectral artifacts during measurements of powder samples in process streams when using a mechanically scanning spectrometer. Artifacts appeared as momentary changes in the spectral response during acquisition of a scan. These transitions emanate from continuous replacement of the sample subfraction seen by the probe and are typical for turbid media where sample properties may vary locally with respect to scattering and/or absorption. The impact on qualitative and quantitative analysis using chemometric methods such as principal component analysis (PCA) and partial least squares (PLS) regression was evaluated through experimental and theoretical simulations. It was generally found that spectra with the smallest residuals after projection onto the models came from non-moving samples or samples moving only slowly. It is shown that the magnitude of the spectral residuals is directly connected to the effective sample size, which relates both to sample speed as well as to the sample area presented to the probe. Implications for in-line/on-line process analysis of solids are discussed. (C) 2004 Elsevier B.V. All rights reserved.
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| 16. |
- Chauchard, Fablen, et al.
(författare)
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Localization of embedded inclusions using detection of fluorescence: Feasibility study based on simulation data, LS-SVM modeling and EPO pre-processing
- 2008
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Ingår i: Chemometrics and Intelligent Laboratory Systems. - : Elsevier BV. - 0169-7439. ; 91:1, s. 34-42
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescence spectroscopy is a useful technique for tissue diagnostics and is also a promising tool in the characterization of embedded structures in tissue. The emitted fluorescence from an embedded inclusion, marked with a fluorescent compound, is affected by several factors as the light propagates through the medium to the tissue boundary, where the fluorescence light is detected. Tissue absorption, scattering and autofluorescence, as well as the size and depth of the inclusion, affect the detected fluorescence light. The aim of this study is to investigate if the size and location of a fluorescent inclusion could be determined using models based a combination of External Parameter Orthogonalisation (EPO) and Least Squares Support Vector Machine (LS-SVM). This can be very useful for data pre-processing before a full fluorescence tomography reconstruction. The data set consisted of simulated multispectral fluorescence, where depth and radius of a spherical fluorescent inclusion were varied as well as the fluorescence contrast and optical properties of the surrounding tissue. The results showed that the non-linear models based on LS-SVM can simultaneously predict both radius and depth. It was observed that EPO acts as a useful pre-processing tool on spectra for this nonlinear model and that it was necessary to perform EPO to be able to predict the depth with the LS-SVM model. (C) 2007 Elsevier B.V. All rights reserved.
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| 17. |
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| 18. |
- Gabrielsson, Jon, et al.
(författare)
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OPLS methodology for analysis of pre-processing effects on spectroscopic data
- 2006
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Ingår i: Chemometrics and Intelligent Laboratory Systems. - : Elsevier BV. - 0169-7439. ; 84:1-2, s. 153-8
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Tidskriftsartikel (refereegranskat)abstract
- Pre-processing of spectroscopic data is commonly applied to remove unwanted systematic variation. Possible loss of information and ambiguity regarding discarded variation are issues that complicate pre-treatment of data. In this paper, OPLS methodology is applied to evaluate different techniques for pre-processing of spectroscopic data gathered from a batch process. The objective is to present a rational scheme for analysis of pre-processing in order to understand the influence and effect of pre-treatment.O2PLS uses linear regression to divide the systematic variation in X and Y into three parts; one part with joint X–Y covariation, i.e. related to both X and Y, one part of X with Y-orthogonal variation and one part of Y with X-orthogonal variation.All of the investigated pre-treatment methods removed an additive baseline as expected. In the analysis of raw and differentiated data variation associated with the baseline was found in the Y-orthogonal part of X. Orthogonal information was also found in Y, which suggests that this pre-processing procedure not only removed variation. This would have been more difficult to detect without the O2PLS model since both raw and differentiated data must be analysed simultaneously.Development of a knowledge based strategy with OPLS methodology is an important step towards eliminating trial and error approaches to pre-processing.
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| 19. |
- Wold, Svante, et al.
(författare)
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The chemometric analysis of point and dynamic data in pharmaceutical and biotech production (PAT) — some objectives and approaches
- 2006
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Ingår i: Chemometrics and Intelligent Laboratory Systems. - : Elsevier BV. - 0169-7439. ; 84:1-2, s. 159-63
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Tidskriftsartikel (refereegranskat)abstract
- Checking that a process is doing what it is supposed to is of critical importance in manufacturing, economics, environmental monitoring, patient monitoring, and more. Given sufficient and adequate analytical and process measurements made during the history of the well functioning process, a multivariate model of the process variation around a multivariate dynamic trajectory will, in principle, form a good basis for this checking. Such systems are often labeled process monitoring, real-time quality control (RTQC), PAT level 4, and advanced process control/fault detection and classification (APC/FDC). Here PAT stands for process analytical technology indicating the reliance on adequate and multiple data for this checking.In practice, there are many difficulties in making an RTQC/PAT-4 system work well. Starting from an industrial example, the problems of constructing and implementing a well working checking system are discussed in relation to its different parts — analytical and process data, chemometrical and other methods for their modeling and analysis, and various forms of data management to handle the data flow and synchronization, as well as storage and retrieval. The display and interpretability of diagnostics and results are emphasized.
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