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  • Analytical Chemistry and Spectroscopy  (2,885)
  • 1990-1994  (2,885)
  • 1925-1929
  • 1992  (1,441)
  • 1991  (1,444)
  • 1984
  • 1929
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Keywords
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Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Factor analysis in chemistry, (2nd edition), E. R. Malinowski, Wiley-Interscience, 1991. ISBN 0-471-53009-3. Price £43.70 (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 545-545 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050607
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  • 2
    Electronic Resource
    Electronic Resource
    Diagnostika Sostava Materialov Rentgenodifrakcionnimi I Spektralnymi Metodami (Identification of materials by X-ray diffraction and spectroscopical Techniques) (in Russian), M. S. Nakhmanson and V. G. Feklitschev, Mashinostroenie, Leningrad, 1990. 357 pages. ISBN 5-217-00915-2, Rubl 5.40 (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 546-547 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050608
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  • 3
    Electronic Resource
    Electronic Resource
    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992) 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060201
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  • 4
    Electronic Resource
    Electronic Resource
    Diary (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. i 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060202
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  • 5
    Electronic Resource
    Electronic Resource
    Editorial (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 63-64 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060204
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  • 6
    Electronic Resource
    Electronic Resource
    A new receptor model: A direct trilinear decomposition followed by a matrix reconstruction (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 65-83 
    Details
    ISSN: 0886-9383
    Keywords: Trilinear decomposition ; Receptor modeling ; Source identification ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In many cases, monitoring data for ambient airborne particles can be organized in the form of a three-way data table with one way for chemical species, one for sampling periods and one for sites. A direct trilinear decomposition followed by a matrix reconstruction (DTDMR) is developed to analyze such a data table as a whole. The three-way data set is composed into three two-way matrices by a direct trilinear decomposition (DTD). The column vectors of each of the matrices are called ‘source profiles’, ‘emission patterns’ and ‘site coefficients’ respectively. Particulate sources are identified by examining both their source profiles and emission patterns. After the sources have been identified, emission patterns and site coefficients are used to produce a three-way matrix that gives estimates of mass contributions of sources to the samples collected at every site in every period. By simulation study, not only has the method been verified, but a good indicator has been found that shows the number of factors (i.e. sources) in the system. Unlike other receptor models, DTDMR does not require source profile data and does not involve trial-and-error procedures. Since DTDMR identifies sources based on variations in two dimensions, it has a higher potential to distinguish two sources that have similar chemical compositions. The DTDMR model has provided excellent results with simulated data and has been applied in a real world three-way data set.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060205
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  • 7
    Electronic Resource
    Electronic Resource
    The chemometrics group, University of Bergen, Norway (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 113-116 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060209
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  • 8
    Electronic Resource
    Electronic Resource
    In memoriam: Herman Wold, pioneer of PLS (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 117-118 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060303
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  • 9
    Electronic Resource
    Electronic Resource
    Wavelength selection in multicomponent near-infrared calibration (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 151-161 
    Details
    ISSN: 0886-9383
    Keywords: NIR spectroscopy ; Wavelength selection ; Interaction effects ; Multicomponent mixtures ; Partial least squares ; Generalized least squares ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modern scanning (near-)infrared reflectance/absorption (NIR) spectroscopes measure the absorptions or reflectances at a sequence of around 1000 wavelengths. Training data may consist of 10-100 carefully designed sample mixtures for which the true composition of the mixture is either known by formulation or accurately determined by wet chemistry. In future one wishes to predict the true composition from the spectrum. In this paper we compare a simple wavelength selection approach with methods which retain all the wavelengths. It offers a powerful yet simple technique for choosing those wavelengths that are specific to each pure component as against the other components (including the medium) for the varying compositions. In the presence of a defined range of ingredients in thus chooses wavelengths which are highly selective for each particular component. It has the added advantage of selecting wavelengths which are little effected by interaction effects and consequent non-linearities.The calibration data used consist of 125 observations of three sugars, each varying at five levels in a full 53 design. The validation set consists of 21 further samples specially selected to have compositions outside the range of the training sample. The selection methods perform much better on this prediction set than methods which retain all the wavelengths, 700 in this case. The leave-one-out cross-validation internal to the calibration data would point to the opposite finding and suggests that such crossvalidations may be overly flattering to techniques such as partial least squares and may encourage overfitting. After selection, simple straightforward least squares methods may be used, eschewing the need for ‘shrinkage’ methods such as partial least squares or ridge regression.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060306
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  • 10
    Electronic Resource
    Electronic Resource
    Recent developments in multivariate calibrationInvited Paper. (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 129-145 
    Details
    ISSN: 0886-9383
    Keywords: Multivariate calibration ; Biased regression ; Partial least squares (PLS) ; Principal component regression (PCR) ; Model validation ; Non-linear calibration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: With the goal of understanding global chemical processes, environmental chemists have some of the most complex sample analysis problems. Multivariate calibration is a tool that can be applied successfully in many situations where traditional univariate analyses cannot. The purpose of this paper is to review multivariate calibration, with an emphasis being placed on the developments in recent years. The inverse and classical models are discussed briefly, with the main emphasis on the biased calibration methods. Principal component regression (PCR) and partial least squares (PLS) are discussed, along with methods for quantitative and qualitative validation of the calibration models. Non-linear PCR, non-linear PLS and locally weighted regression are presented as calibration methods for non-linear data. Finally, calibration techniques using a matrix of data per sample (second-order calibration) are discussed briefly.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050303
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  • 11
    Electronic Resource
    Electronic Resource
    Real-time filtering of data from mobile, passive remote infrared sensors with principal component models of backgroundInvited Paper. (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 147-161 
    Details
    ISSN: 0886-9383
    Keywords: Digital filtering ; Real-time analysis ; Kalman filtering ; Infrared spectroscopy ; Principal components regression ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Real-time monitoring of pollutant levels from a mobile measuring platform requires fast, flexible data analysis methods. This paper reports a method for rapid analysis of passive remotely sensed infrared data with the aid of a Kalman filter. The background spectra produced by emission from the atmosphere are modelled at the start of the data collection sequence with a simple principal components model obtained by eigenanalysis of the initial ‘blank’ data taken with the spectrometer. The species of interest are included in the state space model by a separate measurement of their infrared spectra. It is demonstrated that for best filter performance in detecting the simulated pollutant species SF6 in the atmosphere, a filter model with two principal components describing the emission background works best. The filter ‘maps’ of SF6 closely follow the integrated spectral intensities measured after removal of suitable backgrounds.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050304
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  • 12
    Electronic Resource
    Electronic Resource
    Examining large databases: A chemometric approach using principal component analysisInvited Paper. (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 163-179 
    Details
    ISSN: 0886-9383
    Keywords: Principal component analysis ; Factor analysis ; Chemometrics ; Exploratory data analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Principal component analysis is used to examine large multivariate databases. The graphical approach to exploratory data analysis is described and illustrated with a single example of chemical composition data obtained on environmental dust particles. While the graphical approach to exploratory data analysis has certain advantages over the numerical procedures, the empirical approach described here should be viewed as complementary to the more robust treatments that statistical methodologies afford.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050305
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  • 13
    Electronic Resource
    Electronic Resource
    Box-Cox transformations in the analysis of compositional data (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 227-239 
    Details
    ISSN: 0886-9383
    Keywords: Unit-sum constraint ; Mixing proportions ; Ratio data ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The statistical analysis of compositional data is of fundamental importance to practitioners in general and to chemists in particular. The existing methodology is principally due to Aitchison, who effectively uses two transformations, a ratio followed by the logarithmic, to create a useful, coherent theory that in principle allows the plethora of normal-based multivariate techniques to be used on the transformed data. This paper suggests that the well-known class of Box-Cox transformations can be employed in place of the logarithmic to significantly improve the existing methodology. This is supported in part by showing that one of the most basic problems that Aitchison managed to overcome, namely the specification of an interpretable covariance structure for compositional data, can be resolved, or nearly resolved, once the ratio transformation has been applied. Hence the resolution is not directly dependent on the logarithmic transformation. It is then verified that access to the general Box-Cox family will allow a more accurate use of the normal-based multivariate techniques, simply because better fits to normality can be achieved. Finally, maximum likelihood estimation and some associated asymptotics are employed to construct confidence intervals for ratios of the true, unknown compositional constituents. Heretofore this had not been done even in the context of the logarithmic transformation. Applications to real data are presented.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050310
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  • 14
    Electronic Resource
    Electronic Resource
    Finding causes of outliers in multivariate environmental data (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 241-248 
    Details
    ISSN: 0886-9383
    Keywords: Multivariate kurtosis ; Generalized distance ; Multivariate outliers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multivariate outliers in environmental data sets are often caused by atypical measurement error in a single variable. From a quality assurance perspective it is important to identify these variables efficiently so that corrective actions may be performed. We demonstrate a procedure for using two multivariate tests to identify which variable ‘caused’ each outlier. The procedure is tested with simulated data sets have have the same correlation structure as selected water chemistry variables from a survey of lakes in the Western United States. The success rates are evaluated for three of the variables for sample sizes of 50 and 100, significance levels of 0.01 and 0.05 and various amounts of mean shift. The procedure works best for highly correlated variables.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050311
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  • 15
    Electronic Resource
    Electronic Resource
    A statistical procedure to evaluate clean-up standards (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 249-261 
    Details
    ISSN: 0886-9383
    Keywords: Asymptotic power ; Clean-up standard ; Gamma distribution ; Likelihood ratio test ; Uniformly most powerful unbiased test ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The object of this paper is to develop a suitable statistical procedure to evaluate clean-up standards at hazardous waste sites. Under the assumptions that contaminant masses at a site follow a gamma distribution and that the data from the pre-remediation baseline sample as well as from the interim or final sample taken after a certain period of operation are both distributed as gamma with the same shape parameter but different scale parameters, we derive a uniformly most powerful unbiased test of the hypothesis that a specified percentage of contaminant mass has been reduced. A large-sample approximation of the exact test procedure and a comparison with the likelihood ratio test are provided.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050312
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  • 16
    Electronic Resource
    Electronic Resource
    The quality of mean and variance estimates for normal and lognormal data when the underlying distribution is misspecified (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 263-271 
    Details
    ISSN: 0886-9383
    Keywords: Mean ; Variance ; Lognormal ; Optimal estimators ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Theoretical and simulation results are employed to evaluate mean and variance estimates for normal data when a lognormal distribution is assumed and for lognormal data when a normal distribution is assumed. Misspecifying the distribution leads to the use of suboptimal estimation methods. However, the results show that the suboptimal methods still produce estimators of good quality (low bias and variance) relative to the minimum variance unbiased estimators for each distribution, at least when practical efficiency is considered.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050313
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  • 17
    Electronic Resource
    Electronic Resource
    Correspondence analysis used in the evaluation of lakewater chemistry in the Adirondacks (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 273-290 
    Details
    ISSN: 0886-9383
    Keywords: Correspondence analysis ; Eastern Lake Survey - Phase I data ; Acidic deposition ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Correspondence analysis (CA) was applied to lakewater data in order to study the effects of acidic deposition on the geochemical composition of lakes in the Adirondacks. The lake chemistry data analyzed were taken from the Eastern Lake Survey - Phase I (ELS-I) conducted by the U.S. Environmental Protection Agency. CA was used to identify ‘outlying’ lake samples as well as ‘superflous’ and ‘unresolved’ analytes. Correlational relationship among analytes were also examined.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050314
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  • 18
    Electronic Resource
    Electronic Resource
    Estimation of errors in absorbance ratio measurements (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 291-298 
    Details
    ISSN: 0886-9383
    Keywords: Absorbance ratio ; Statistical confidence ; Quality control ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ratio measurements are commonly used to address a variety of analytical problems in environmental, forensic and pharmaceutical laboratories. In absorbance ratioing techniques, analytical chemists rely on the spectral features of the analyte(s) of interest. The absorbances at two wavelengths are monitored and the ratio of these two absorbances is computed. This ratio is then used to confirm the identity of the analyte(s) of interest, the purity of a product of the overlap of chromatographic peaks. These decisions often have far-reaching consequences (e.g. the identification of the source, biogenic or petrogenic, of hydrocarbons in biological tissues or water). Given the cost and the liabilities associated with such decisions, it is unfortunate that these ratios are seldom reported with any statistical confidence. The purpose of this study is to delineate the parameters that affect absorbance ratio measurements. The models that can be used to estimate the statistical confidence in these measurements are derived and evaluated experimentally. The results show that these models can estimate the relative standard deviations in absorbance ratios accurately. They can also estimate the effect of signal-to-noise ratio and the choice of wavelengths on the precision of absorbance ratios.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050315
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  • 19
    Electronic Resource
    Electronic Resource
    Likelihood techniques for interlaboratory calibration in the national stream survey (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 299-308 
    Details
    ISSN: 0886-9383
    Keywords: Errors in variables ; Orthogonal regression ; Latent variables ; Acid rain ; Acidic deposition ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Techniques for testing for and estimating relative bias between two laboratories are developed and applied to a survey of the chemistry of streams in the United States. The design of the quality assurance program allows estimation of linear corrections for bias as well as testing of the hypothesis of linearity. Designs of this type are useful, but improvements are suggested.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180050316
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  • 20
    Electronic Resource
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    On confidence intervals for the product of three means of three normally distributed populations (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 309-319 
    Details
    ISSN: 0886-9383
    Keywords: Confidence intervals ; Products of normal random variables ; Risk/exposure modeling ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In many environmental applications, such as exposure assessment and risk modelling, the desired estimate is a random variable computed as the product of three independently distributed random variables. These variables may not necessarily have the same mean and variance. The method for finding the 100(1 - α)% confidence interval for the mean of the product random variable has been proposed by some practitioners as the product of the 100(1 - α)% confidence interval of the three means. In this paper we show that the distribution of the product of three independent normal variables is not normal. We find the mean and variance of the product distribution. Further, we show that although the mean of the product is equal to the product of the means, the product of the three confidence intervals is not a good approximation of the confidence intervals for the mean of the product variable. The confidence interval of the mean of the product variable may be estimated by computer simulation. An algorithm for estimating the confidence interval for the mean of the product random variable is given. The program implementing this algorithm is given as an appendix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050317
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  • 21
    Electronic Resource
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    Comparison of two screening methods for the detection of volatile organic compounds in ground water (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 321-331 
    Details
    ISSN: 0886-9383
    Keywords: Screening ; Ground-water quality ; Monitoring ; Volatile organic compounds (VOCs) ; Optimization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that the presence of 31-35 commonly measured volatile organic compounds (VOCs) in ground water can be detected with small error rates by using screening methods which analyze for a subset of such VOCs. A study of selected data sets indicates that analytical determinations of only from two to eight VOCs will suffice to detect 95% of all VOC hits. It is also shown that a serially optimal algorithm for selecting the VOCs for screening is very nearly as accurate as a globally optimal algorithm and much easier to implement. These conclusions are supported by empirical evidence from two drinking-water data sets and one hazardous waste site data set. Additional research areas are also outlined.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cem.1180050318
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  • 22
    Electronic Resource
    Electronic Resource
    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991) 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050401
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  • 23
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    Diary (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. i 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050402
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  • 24
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    A bootstrap resampling scheme for using the canonical correlation technique in rank estimation (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 333-343 
    Details
    ISSN: 0886-9383
    Keywords: Rank estimation ; Bootstrap resampling ; Canonical correlation ; Excitation-emission matrix ; Singular value decomposition ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rank estimation by canonical correlation analysis in multivariate statistics has been proposed as an alternative approach for estimating the number of components in a multicomponent mixture. A methodological turning point of this new approach is that it focuses on the difference in structure rather than in magnitude in characterizing the difference between the signal and the noise. This structural difference is quantified through the analysis of canonical correlation, which is a well-established data reduction technique in multivariate statistics. Unfortunately, there is a price to be paid for having this structural difference: at least two replicate data matrices are needed to carry out the analysis.In this paper we continue to explore the potential and to extend the scope of the canonical correlation technique. In particular, we propose a bootstrap resampling method which makes it possible to perform the canonical correlation analysis on a single data matrix. Since a robust estimator is introduced to make inference about the rank, the procedure may be applied to a wide range of data without any restriction on the noise distribution. Results from real as well as simulated mixture samples indicate that when used in conjunction with this resampling method, canonical correlation analysis of a single data matrix is equally efficient as of replicate data matrices.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050403
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  • 25
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    Three-way methods for the calibration of chromatographic systems: Comparing PARAFAC and three-way PLS (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 345-360 
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    ISSN: 0886-9383
    Keywords: Three-way PCA ; Three-way PLS ; PARAFAC ; Trilinear ; Unfolding ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the calibration of chromatographic systems, different methods can be used. One class of methods utilizes three-way approaches. The calibration problem is stated in such a way that the decomposition of a three-way array can serve for the prediction of retention on new stationary phases.Two three-way approaches are presented: the Unfold-PCA and PARAFAC models. The theory of both methods is presented and the differences are highlighted, the main difference being that PARAFAC is a trilinear decomposition whereas Unfold-PCA is not. Both three-way methods are evaluated on a small data set consisting of retention measurements of eight solutes at six mobile phase compositions on six stationary phases. The differences in performance of the two models are minor.For calibration purposes, two variants of the methods are discussed: three-way PLS and an extension of PARAFAC. Again the theory and differences between the two methods are explained. The predictive performance of the two methods is compared using the same data set as earlier. The differences in predictive performance, however, are minor. Both methods are capable of predicting 98% of the variation in the test sets. Yet, there are other considerations when comparing methods than predictive performance, e.g. the quality of the predictions.
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    Estimation in compositional data analysis (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 361-374 
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    ISSN: 0886-9383
    Keywords: Closure ; Normalization ; Multivariate trimming ; Minimum distance ; Bootstrap ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Compositional data arise naturally in several branches of science, including chemistry, geology, biology, medicine, ecology and manufacturing design. In chemistry, these constrained data seem to occur typically when raw data are normalized or when output is obtained from a constrained estimation procedure, such as might be used in a source apportionment problem. It is important not only for chemists to be aware that the usual multivariate statistical techniques are not applicable to constrained data, but also to have access to appropriate techniques as they become available. The currently available methodology is due principally to Aitchison and is based on log-normal models. This paper suggests new parametric and non-parametric approaches to significantly improve the existing methodology. In the parametric setting, some recent work of Rayens and Srinivasan is extended and a practical regression model is proposed. In the development of the non-parametric approach, minimum distance methods coupled with multivariate bootstrap techniques are used to obtain point and region estimators.
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    A test of three fitting criteria for multiresponse non-linear modeling (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 375-387 
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    ISSN: 0886-9383
    Keywords: Determinant criterion ; Multiresponse non-linear fitting ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This work evaluates objective functions for multiresponse non-linear modeling using computer simulations. Tests are performed under a variety of signal-to-noise ratios and noise variance-covariance structures. The standard error of prediction for the model parameters, computed from 50 trials, is used for performance comparisons. The full rank and rank-deficient problems are considered. For the full rank problem one model was investigated, a first-order two-step consecutive reaction model, and two objective functions were considered, the total sum of squares and the determinant criterion. No distinction could be made between the two objective functions for this model.For the rank-deficient case two models were investigated, a first-order two-step consecutive reaction as in the full rank case, and a pH titration model described by the Henderson-Hasselbalch equation. Three objective functions were investigated for the rank-deficient case, the total sum of squares, a weighted total sum of squares and the determinant criterion. The total sum of squares was found to perform poorly under all conditions tested compared to the weighted total sum of squares and the determinant criterion. The determinant criterion was found to perform much better than the other two criteria when the data have a combination of a low signal-to-noise ratio and high variance-covariance noise structure.
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    The chemometrics team of MITAC (Micro and Trace Analysis Center), University of Antwerp, Belgium (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 405-409 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    Comparison of pattern recognition descriptors for chemical acoustic emission analysis (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 389-403 
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    ISSN: 0886-9383
    Keywords: Acoustic emission ; Pattern recognition ; Feature selection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Features used to characterize acoustic emission signals from chemical systems are evaluated with regard to their potential for pattern recognition. Eight chemical systems involving phase transitions, hydration, dissolution and effervescence are employed and treated as separate signal classes. These are compared pairwise and the discriminatory capabilities of about 50 features are investigated by computing Fisher weights. Time domain and frequency domain descriptors are examined. Correlations among the features evaluated are also reported. Recommended descriptors are the mean and median frequencies, frequency bandwidth, number of level crossings (0% and 25%), crest factor (time and frequency domains), half-life, kurtosis and normalized percentiles of the signal and its power spectrum. The effectiveness of the recommended descriptors is demonstrated through the separation of signal classes in two different systems (melting ice and an enzyme-catalyzed gas formation reaction) by principal components analysis.
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    Scientific computing and automation (Europe) 1990 (Proceedings of the Scientific Computing and Automation (Europe) Conference, 12-15 June 1990, Maastricht, The Netherlands), edited by E. J. Karjalainen for the series Data Handling in Science and Technology, 6, Elsevier Science Publishers, Amsterdam, 1990, 514 pp., ISBN 0-444-88949-3, US$220.00/Dfl. 385.00 (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 411-412 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050409
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    UNSCRAMBLER 11, version 3.10: A program for multivariate analysis with PLS and PCA/PCR. Available from CAMO AS, Jarlevn. 4, Trondheim, Norway. Price $3000; academic discount price $1500 (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 413-415 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Announcement (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 416-416 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991) 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050501
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    Diary (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. i 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050502
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    Rapid estimation of the number of coeluting components in liquid chromatography by factor analysis (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 417-434 
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    ISSN: 0886-9383
    Keywords: Factor analysis ; Power density distribution ; Chromatography ; Absorption spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Evaluation of the results of factor analysis of sets of spectroscopically detected chromatograms is carried out by examining the shapes of the abstract factors. This is done either by visual inspection or by analysis of the power density spectra produced from them. Owing to constraints imposed by the column function and the spectroscopic instrument function, the information content of the chromatograms necessarily occurs at low spatial frequencies. As a consequence, it appears as relatively broad features in the abstract chromatograms and as a peak in the low-frequency region of the corresponding power density plot. On the basis of examination of the power density distribution, a well-defined distinction is made between primary and secondary abstract factors. The major uncertainty encountered in determining the number of chemical components appears to arise from effects of contaminants in reagents.
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    A class-modelling technique based on potential functions (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 435-453 
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    ISSN: 0886-9383
    Keywords: Class-modelling methods ; Potential functions ; Pattern recognition ; Discriminant analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A probabilistic and distribution-free class-modelling technique is developed from potential function discriminant analysis. In the multidimensional space of variables the class boundary is built either by the sample percentile of the probability density estimated by means of potential functions, or by the estimate of the ‘equivalent’ determinant of the variance-covariance matrix. The equivalent determinant is that of a hypothetical multivariate normal distribution whose mean probability density was obtained by potential functions. The bases of this modelling rule are evaluated by means of Monte Carlo experiments. The results on four datasets are used to measure the performances of this method, which equal and sometimes exceed the performances of parametric class-modelling methods based on linear and quadratic discriminant analysis which were used for comparison.
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    Correspondence analysis and adsorbate selection for chemical sensor arrays (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 455-465 
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    ISSN: 0886-9383
    Keywords: Correspondence analysis ; Cluster analysis ; Optimization ; Eigenanalysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carey et al. utilized principal components analysis (PCA) to analyze frequency shift data obtained from piezoelectric sensors formed by coating quartz crystals with 27 different GC stationary phases and tested using 14 analytes. The objective of the analysis was to determine an optimal reduced set of coatings for detection of the analytes. The results were correlated with those obtained from cluster analysis. In this paper the data are re-analyzed using correspondence analysis (CA). The advantage of using CA include a symmetric treatment of sensor coatings and analytes and better identification of the representation of the analytes in terms of the detection components. The results obtained by the conjunctive use of PCA, a varimax rotation and cluster analysis were obtained by CA.
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    Fuzzy multivariate rule-building expert systems: Minimal neural networks (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 467-486 
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    ISSN: 0886-9383
    Keywords: Expert system ; Neural network ; Fuzzy entropy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A fuzzy multivariate rule-building expert system (FuRES) has been devised which also functions as a minimal neural network. This system builds rules from training sets of data that use feature transformation in their antecedents. The rules are constructed using the ID3 algorithm with a fuzzy expression of classification entropy. The rules are optimal with respect to fuzziness and can accommodate overlapped and underlapped clusters of data. The FuRES algorithm combines the benefits obtained from simulated annealing and gradient optimization, which provide robustness and efficiency respectively. FuRES classification trees support OR logic in their inference. The system automatically generates meaningful and consistent certainty factors during rule construction. Unlike other neural networks, FuRES uses local processing which furnishes qualitative information in the rule structure of its classification trees and variable loadings of the weight vectors.
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991) 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050601
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    Diary (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. i 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050602
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    Multivariate calibration when data are split into subsets (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 487-501 
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    ISSN: 0886-9383
    Keywords: Calibration ; Locally linear models ; Discrimination ; Optimality ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A calibration situation is considered where the calibration data are split into subsets with good linear relationship between y and x within each group. Different strategies for good prediction in this case are proposed. Modifications for collinear data are considered and a simple simulated data set is used for illustration.
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    Rank-order analysis for robust multiresponse, multiblock comparisons: Evaluation of herbicide interactions (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 503-521 
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    ISSN: 0886-9383
    Keywords: Antagonism ; Bounded ordinal scale ; Herbicide interaction ; Inter block comparisons ; Non-parametric ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies of interactions among bioactive compounds are often difficult to interpret unambiguously. A priori assumptions about the nature of such interactions can seriously distort analysis of the data. By applying a rank order analysis appropriate to the naturally ordinal scale of response to xenobiotic insult, several co-herbicides were successfully identified from among numerous candidates in an experiment involving multiple blocks, rates and species. Moreover, underlying herbicide interactions were substantiated and identified which were not apparent by more traditional parametric analysis.
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    Data analysis with minimal assumptions (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 247-255 
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    ISSN: 0886-9383
    Keywords: Analysis of variance ; Assumptions ; Graphics ; Models ; Validation of model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The computer has made it possible to scrutinize data rapidly by means of graphics. This should be done prior to the application of any model to the data, since the model must be validated before using it as a means of analyzing the data. The procedure is illustrated in terms of two examples of real experimental data.
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    Design and optimization in organic synthesis, Rolf Carlson, Elsevier, Amsterdam ISBN 0-444-89201-X, No. of pages: 552, price: 330 f1 (1992) (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 284-285 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180060508
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    Quadratic PLS regression (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 307-334 
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    ISSN: 0886-9383
    Keywords: Non-linear PLS ; Quadratic regression ; Non-linear models ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We treat here an extension of linear PLS regression to include regression on quadratic PLS components. The quadratic regression can be viewed as a natural extention of linear PLS regression to quadratic PLS according to the H-principle of mathematical modelling. The numerical implementation is treated in detail. It is shown that this approach can be used for models with large numbers of variables. Some modelling strategies are discussed depending on the purpose of the modelling. Applications of this approach are treated.
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    Software Review (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 357-357 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180060606
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    Laboratorio di Chemiometria, University of Perugia, Italy (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 537-543 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060101
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    Comparison of measurement methods based on a model for the error structure (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 523-536 
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    ISSN: 0886-9383
    Keywords: Measurement errors ; Method comparison ; Mean square successive difference ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Comparison of methods is a technique often used for investigation of systematic errors of measurement methods. As concerns the design and analysis of such comparisons, much variety of opinion and practice exists. In one approach a few specimens are measured several times by different operators in different laboratories (reproducibility conditions) and in another approach several specimens are measured on one or a few occasions by one operator in the same laboratory (repeatability conditions). In this paper a model for the error structure of measurements is formulated and it is emphasized that one has to distinguish between two types of systematic errors: the first type depends only on the level of the measured quantity and the second type is specific for the separate specimens. On the basis of this model the information which can be obtained from the different designs of method comparisons is discussed. A new approach for the analysis of method comparisons with many specimens is also proposed.
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    Window factor analysis: Theoretical derivation and application to flow injection analysis data (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 29-40 
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    ISSN: 0886-9383
    Keywords: Factor analysis ; Window factor analysis ; Multicomponent analysis ; Flow injection analysis ; Self-modeling curve resolution ; Bismuth chloride complexes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Window factor analysis (WFA) is a self-modeling method for extracting the concentration profiles of individual components from evolutionary processes such as flow injection, chromatography, titrations and reaction kinetics. The method takes advantage of the fact that each component lies in a specific region along the evolutionary axis, called the window. Theoretical equations are derived. The method is used to extract the concentration profiles and spectra of seven bismuth species from data obtained by Gemperline and Hamilton, who injected bismuth perchlorate into a flowing stream of hydrochloric acid.
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    The relationship of closure, mean centering and matrix rank interpretation (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 57-62 
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    ISSN: 0886-9383
    Keywords: Closure ; Baseline ; Mean centering ; Rank ; Exploratory data analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper describes an investigation into the relationship of closure, a baseline offset and mean centering to the interpretation of matrix rank. The equivalence of a certain type of closure to a constant baseline (i.e. a simple numerical offset which may vary between response channels but is constant over all samples) is demonstrated. A systematic approach to the interpretation of the rank of a matrix is given.
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    Ranking principal components to reflect group structure (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 97-102 
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    ISSN: 0886-9383
    Keywords: Between-group variances ; Canonical variate criterion ; Eigenvalues ; Eigenvectors ; Orthogonal projection ; Within-group variance ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Canonical variate analysis is the appropriate descriptive technique for multivariate data which have an a priori group structure, but problems arise with this technique when there are more variables than within-group degrees of freedom because of singularity of matrices. In such cases it is shown through illustrative examples that principal component analysis is a viable substitute provided that the principal components are ranked according to the canonical variate criterion (ratio- of between- to within-group variances) rather than the usual criterion of total variance. This ranking can also be used to select components for subsequent discriminant analysis.
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    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992) 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060301
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    Classification of mass spectra (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 119-133 
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    ISSN: 0886-9383
    Keywords: Mass spectra ; Classification ; Structure description ; Fragmentation ; Ion series ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to investigate correlations between the functionality of compounds and the classification of their mass spectra, low-resolution spectra of monofunctional compounds have been classified by four supervised classification methods. The new classes are characterized by structural features and the correlation between functionality and classification is explained by fragmentation rules. Systematic misclassifications show that low-resolution mass spectra alone are not suitable for reliable identification of functionality.
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    Multiple-correspondence analysis optical microscopy for determination of starch granules (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 163-175 
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    ISSN: 0886-9383
    Keywords: Multiple-correspondence analysis ; Starch granule description ; Image analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Raw starch is composed botanically of characteristic granules of various sizes and shapes, so that each kind of starch may be characterized by the population of its granules. In the present study ten commercial starch species were studied: wheat, rice, manioc, potato, arrowroot, amylomaize, normal maize, waxy maize and two different banana species. Six variables measuring the size and shape of granules were obtained by image analysis. The objective was to find a method to describe and compare the granule populations of the ten species. For such a study, multiple-correspondence analysis (MCA) was applied. MCA makes it possible to draw similarity maps of categories and objects. For each starch species the frequency distributions (histograms) of the six variables were assessed and each granule was characterized by its species and the classes of histograms to which it belonged. MCA was applied to the granule table and a description of the histogram classes and the granules was obtained. From the variables description a general typology of the granules was deduced. The similarity maps showed considerable scatter of the granules for all species except rice. A particular species could therefore not be identified by a single granule, but the granule distribution seemed to be characteristic. MCA was an appropriate method to analyse these data because it points out non-linear relationships between quantitative and qualitative variables.
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    Estimation of prediction error for samples within the calibration range (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 177-188 
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    ISSN: 0886-9383
    Keywords: PLS ; Prediction error ; Background constituents ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A modification of a technique proposed by Lorber and Kowalski for the estimation of prediction errors is presented. The method is applied to five data sets. The results show that for some data sets the estimated prediction errors are close to the actual prediction errors for samples within the calibration range, while samples outside the calibration range must be background corrected before quantification of the prediction error.
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    A robust PLS procedure (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 189-198 
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    ISSN: 0886-9383
    Keywords: Robust regression ; Partial least squares ; QSAR ; Perturbation study ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A robust partial least squares (PLS) regression algorithm is developed. This is achieved by substitution of the univariate regression steps in the iterative PLS2 algorithm by a robust alternative. The angle between loading vectors from both perturbed and unperturbed solutions is used as a measure of robustness. By means of a perturbation study on a structure-activity data set, it is demonstrated that the stability of the robust method is superior to standard PLS.
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    Sequential simplex optimization, Fredrick H. Walters, Lloyd R. Parker Jr., Stephen L. Morgan and Stanley N. Deming, CRC Press, Boca Raton, FL, 1991, 325 pages, ISBN-8493-5894-9, $49.95 (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 227-227 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992) 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Genetic algorithms as a strategy for feature selection (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 267-281 
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    ISSN: 0886-9383
    Keywords: Genetic algorithms ; Feature selection ; Multivariate analysis ; Optimization methods ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Genetic algorithms have been created as an optimization strategy to be used especially when complex response surfaces do not allow the use of better-known methods (simplex, experimental design techniques, etc.). This paper shows that these algorithms, conveniently modified, can also be a valuable tool in solving the feature selection problem. The subsets of variables selected by genetic algorithms are generally more efficient than those obtained by classical methods of feature selection, since they can produce a better result by using a lower number of features.
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    Masthead (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991) 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Diary (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. i 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Tutorial to robust statistics (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 1-20 
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    ISSN: 0886-9383
    Keywords: Averaging ; Median ; Outliers ; Regression ; Residuals ; Robustness ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this tutorial we first illustrate the effect of outliers on classical statistics such as the sample average. This motivates the use of robust techniques. For univariate data the sample median is a robust estimator of location, and the dispersion can also be estimated robustly. The resulting ‘z-scores’ are well suited to detect outliers. The sample median can be generalized to very large data sets, which is useful for robust ‘averaging’ of curves or images. For multivariate data a robust regression procedure is described. Its standardized residuals allow us to identify the outliers. Finally, a survey of related approaches is given. (This review overlaps with earlier work by the same author, which appeared elsewhere.)
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    Use of the Wronskian determinant in the study of multicomponent systems (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 21-35 
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    ISSN: 0886-9383
    Keywords: Wronskian determinant ; Multicomponent systems ; Derivative spectroscopy ; Spline functions ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of Wronskian determinants in the study of multicomponent systems is proposed. The general theory is presented and applied to the spectrophotometric determination of the number of linearly independent components-absorbers. A detailed study of a two-component system is presented and analysed. Numerical methods for smoothing and differentiation of digitized spectra via cubic splines are used.
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    Announcement (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 69-69 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Masthead (1991)
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    Journal of Chemometrics 5 (1991) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Diary (1991)
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    Journal of Chemometrics 5 (1991), S. i 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Editorial (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 71-71 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    The use of a ratio method as an alternative to constrained deconvolution (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 85-95 
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    ISSN: 0886-9383
    Keywords: Deconvolution ; Gold's ratio ; Iterative deconvolution ; Chromatographic deconvolution ; Peak restoration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper will consider the use of an iterative ratio technique called Gold's ratio method as an alternative to iterative constrained deconvolution methods for the restoration of overlapped and noisy chromatograpic peaks. The study will consist of first describing the technique and then evaluating its performance with respect to Jansson's deconvolution procedure. A Hewlett-Packard 5890A gas chromatograph will be used to generate most of the test data. The evaluation criteria will include convergence rates, peak area errors and variances, retention time variances and noise performance.
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    A new serial method for searching the optimum operating conditions of a technological process (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 73-84 
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    ISSN: 0886-9383
    Keywords: Optimization ; Technological process ; COMPLEX algorithm ; ANTICOMPLEX algorithm ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new program, named ANTICOMPLEX, has been specially written for searching the optimum conditions of a technological process. The algorithm is based on an iterative procedure with, at each step, a random sampling for a better exploration of the hyperspace of the parameters. Since the process is considered as a ‘black box’, the program operates by successive reductions of the variation domains with a strategy derived from some function optimization (COMPLEX). This approach is very flexible and the experimenter can stop the investigation at any series of experiments according to the desired accuracy for the optimum region. This program has been successfully tested on several real processes. This paper gives a complete description of the approach together with two illustrations on simulated processes.
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    The Laboratory for Chemometrics, University of Washington, Seattle (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 113-116 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Announcements (1991)
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    Journal of Chemometrics 5 (1991), S. 117-119 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Regression on multivariate images: Principal component regression for modeling, prediction and visual diagnostic tools (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 97-111 
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    ISSN: 0886-9383
    Keywords: Multivariate images ; Principal component regression ; Multivariate image regression ; Regression model ; Predicted image(s) ; Prediction quality scatter plot ; Visual diagnostic tools ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Regression between two blocks (usually called ‘dependent’ or Y and ‘independent’ or X) of data is a very important scientific and data-analytical tool. Regression on multivariate images is possible and constitutes a meaningful addition to existing univariate and multivariate techniques of image analysis. The regression can be used as a modeling tool or for prediction. The form of the regression equation chosen is dependent upon problem specification and information at hand. This paper describes the use of principal component regression (PCR). Both model building and prediction are presented for continuous Y-variables. The final goal is to supply new image material that can be used for visual inspection on a screen. Also, visual tools for diagnosis of model and prediction are provided, often based on derived image material. Examples of modeling and prediction are given for six channels in a seven-channel satellite image.
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    Masthead (1991)
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    Journal of Chemometrics 5 (1991) 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180050301
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    Some issues in chemometrics with environmental applications (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 121-128 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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    Mathematical model for the optimization of the reaction between 2,3-bis(m-tolyl)quinolizinium bromide and piperidine using a factorial design (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 1-10 
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    ISSN: 0886-9383
    Keywords: Derivatization reaction ; Factorial design ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of nucleophiles have been successfully identified and quantified using the Kröhnke reaction with 2,3-diphenyl derivatives of quinolizinium salts. Optimization of the reaction conditions by means of a mathematical model involving analysis of the response surface has led to a better understanding of the factors exerting an influence on the above reaction.The parameters chosen were temperature, reaction time, base concentration, water concentration and nucleophile concentration. The reaction was developed in polar aprotic solvents (acetone, acetonitrile). To facilitate the nucleophilic attack, the presence of an organic base (triethylamine) was necessary, although concentrations in excess of 0·15M did not alter the development of the reaction. Since pharmaceutical solutions are often aqueous, the influence of water on the reaction was studied. Low water volumes have no significant influence on the opening of the quinolizinium ring by the nucleophilic reagent. However, when the water proportion exceeded that of the organic solvent, the fluorescence intensity was lower than expected. Development of the fluorescent reaction product was first detected 5 min after the reaction started. The fluorescence intensity reached its optimum value after 138 min.
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    Announcements (1992)
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    Journal of Chemometrics 6 (1992), S. i 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Computer-generated multicomponent calibration designs for optimal analysis sample predictions (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 85-96 
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    ISSN: 0886-9383
    Keywords: Optimization ; Calibration ; Simulated annealing ; Experimental design ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper utilizes variable step size generalized simulated annealing (VSGSA) to design multicomponent calibration samples for spectroscopic data. VSGSA is an optimization procedure which is capable of converging to exact positions of global optima located on multidimensional continuous functions. On the basis of analysis sample response vectors, optimally designed calibration concentration matrices are obtained assuming knowledge of components present. The complexity of response surfaces established by the optimization criteria is described.
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    The effect of mean centering on prediction in multivariate calibration (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 103-111 
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    ISSN: 0886-9383
    Keywords: Mean centering ; Preprocessing ; Multivariate calibration ; Error propagation ; Principal component regression (PCR) ; Partial least squares (PLS) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Traditionally, one form of preprocessing in multivariate calibration methods such as principal component regression and partial least squares is mean centering the independent variables (responses) and the dependent variables (concentrations). However, upon examination of the statistical issue of error propagation in multivariate calibration, it was found that mean centering is not advised for some data structures. In this paper it is shown that for response data which (i) vary linearly with concentration, (ii) have no baseline (when there is a component with a non-zero response that does not change in concentration) and (iii) have no closure in the concentrations (for each sample the concentrations of all components add to a constant, e.g. 100%) it is better not to mean center the calibration data. That is, the prediction errors as evaluated by a root mean square error statistic will be smaller for a model made with the raw data than a model made with mean-centered data. With simulated data relative improvements ranging from 1% to 13% were observed depending on the amount of error in the calibration concentrations and responses.
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    Diary (1992)
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    Journal of Chemometrics 6 (1992), S. i 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Multivariate analysis of 2D surfaces: Folding and interpretation (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 135-150 
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    ISSN: 0886-9383
    Keywords: 2D surface ; Multivariate analysis ; Non-congruent ; Unfolding ; Folding ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of latent variable projection for analysis of non-congruent 2D surfaces is presented. We give a formal description of the folding/unfolding process. A simulated 2D oscillator evolving in time is studied in detail to illustrate interpretation aspects of the method.
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    Diary (1992)
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    Journal of Chemometrics 6 (1992), S. i 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cem.1180060402
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    MARS: A tutorial (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 199-216 
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    ISSN: 0886-9383
    Keywords: MARS ; Splines ; Multivariate calibration ; Non-linear ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This tutorial paper presents a simplified view of one of the more recently published multivariate calibration methods particularly suited to dealing with non-linear data sets. The method is referred to as MARS and stands for multivariate adaptive regression splines. Simple examples are provided to explain the workings of the method.
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    Chemometrics: Applications of mathematics and statistics to laboratory systems, R. G. Brereton, Ellis Horwood, Chichester, ISBN-0-13-131350-9, 307 pp., £54.50, (1990) (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 228-228 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Software news (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 229-229 
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    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060409
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    On the integration of kinetic models using a high-order taylor series method (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 231-246 
    Details
    ISSN: 0886-9383
    Keywords: Integration methods ; Taylor series method ; Optimization methods ; Kinetic mechanisms ; Kinetic determinations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general equation to derive kinetic models up to any order is given. This equation greatly facilitates the application of the Taylor series method to the integration of kinetic models up to very high orders. When dealing with non-stiff models, computing time is always reduced by increasing the integration order, at least up to the 20th order. When the model is stiff, the integration order should be optimized; however, a twelfth order is recommended to integrate weakly stiff models. The use of an algorithm which permits the immediate calculation of the integration step size required to maintain a given accuracy leads to further reductions in computing time. When implemented as recommended here, a high-order Taylor series method is more rapid and accurate than Runge-Kutta and predictor-corrector methods and can be advantageously used in combination with optimization methods to perform mechanism studies and in multicomponent kinetic determinations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060503
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    Three-dimensional chemical structure handling, Peter Willett, Research Studies Press, Taunton, Somerset, UK, 1991, ISBN 00 86380 121 8 (Wiley Inc. 0 471 93108 X), 241 pp (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 283-284 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060507
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    A review of three-dimensional chemical structure retrieval systems (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 289-305 
    Details
    ISSN: 0886-9383
    Keywords: Chemical structure database ; Conformational searching ; Similarity searching ; Substructure searching ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper presents a review of the rapid developments that have taken place over the last few years for the searching of databases of three-dimensional (3D) molecules. The geometric arrangement of the atoms in a 3D molecule is described by an interatomic distance matrix. This is a form of labelled graph that can thus be searched using the subgraph-isomorphism algorithms that are widely used for searching databases of two-dimensional (2D) molecules. Several in-house and commercial systems have been developed for 3D database searching that are based on such techniques. These systems are reviewed and their effectiveness demonstrated by examples of their use in the discovery of novel, biologically active molecules. Current systems represent a molecule by one or a small number of low-energy conformations and there is hence much interest in the development of representational techniques and searching algorithms that account for the full set of geometric arrangements that can be adopted by a flexible molecule.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060602
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    Electronic Resource
    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992) 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060601
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  • 90
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    Predictive ability of regression models. Part II: Selection of the best predictive PLS model (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 347-356 
    Details
    ISSN: 0886-9383
    Keywords: GOLPE ; PLS ; Regression ; SDEP ; Variable selection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure called GOLPE is suggested in order to detect those variables which increase the predictivity of PLS models. The procedure is based on evaluating the predictive power of a number of PLS models built by different combinations of variables selected according to a factorial design strategy. Examples are given of the efficiency of this variable selection procedure, which shows how these predictive PLS models are better than those obtained by all variables and better than the corresponding ordinary regression models.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060605
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  • 91
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    Splitting of calibration data by cluster analysis (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 49-65 
    Details
    ISSN: 0886-9383
    Keywords: Calibration ; Cluster analysis ; Local linearity ; Mahalanobis distance ; Residual distance ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The topic of the present paper is the splitting of calibration data into subgroups with improved linearity in each group. The method proposed is based on a criterion which is a weighted average of a Mahalanobis distance and a squared regression residual. The algorithm used to find the solution is based on fuzzy clustering. Two examples are given to illustrate the theory.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050106
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    Generalized simulated annealing for calibration sample selection from an existing set and orthogonalization of undesigned experiments (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 37-48 
    Details
    ISSN: 0886-9383
    Keywords: Optimization ; Simulated annealing ; Calibration ; Experimental design ; Multicomponent analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Generalized simulated annealing (GSA) is an optimization procedure for locating the global optimum (maximum or minimum) of multidimenisonal continuous functions. GSA has been modified for optimization of discrete functions. Selection of calibration samples from an existing set defines discrete optimization and GSA is used to select optimal sets of calibration samples for specific analysis samples. The procedure is applied to near-infrared spectra. When compared to using the complete set of 37 calibration samples, concentration prediction errors were reduced 50%-100% by using select sets of two to seven calibration samples. Additionally, GSA was able to improve a poorly designed experiment. GSA devised augmented experimental designs such that the overall experimental design (original plus augmented) was more orthogonal than the original.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050105
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    Computational methods in the chemical sciences, A. F. Carley and P. H. Morgan, Ellis Horwood, Ltd, Chichester, U.K., 1989. ISBN 0-85312-746-8 (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 68-69 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050108
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    Computerized multiple input chromatography, M. Kaljurand and E. Küllik, Ellis Horwood, Chichester, U.K., 1989. No. of pages: 225. ISBN 0-7458-0120-X. Price £45.00 (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 67-67 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050107
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  • 95
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    Electronic Resource
    Simple validatory tools for judging the predictive performance of parafac and three-way PLS (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 11-28 
    Details
    ISSN: 0886-9383
    Keywords: Three-way PLS ; PARAFAC ; Unfolding ; Validatory tools ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The methods PARAFAC and three-way PLS are compared with respect to their ability to predict reversed-phase retention values. Special attention is paid to simple validatory tools, the meaning and use of which are explained.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060103
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    Principal variations in the chemical composition of peat: Predictive peat scales based on multivariate strategies (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 41-56 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The principal properties, here called the ρ-scales, of peat have been calculated on the basis of chemical analysis. The scales were derived from quantitative contents of carbohydrates, Klason lignin, amino acids, amino sugars and conventional chemical peat measurements. The variation in the chemical parameters was compressed using principal component analysis (PCA). Partial least squares (PLS) regression was used for prediction of botanical, microbial, physical and dewatering data. A rapid estimation of the scales has been made from near-infrared (NIR) spectroscopy and offers, indirectly, rapidly obtainable, chemically interpretable, biological information. A reduced scale based on carbohydrate data was also tested. The ρ-scales offer an interface between different areas of peat research. Strategies are outlined for the selection of a subset of chemical measurements among the variables used for characterization. A multivariate strategy based on these ideas is discussed.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060105
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    Electronic Resource
    Masthead (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992) 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060401
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  • 98
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    Electronic Resource
    Which principal components to utilize for principal component regression (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 217-225 
    Details
    ISSN: 0886-9383
    Keywords: Principal component regression ; Calibration ; Optimality ; Principal component selection ; Quantitative structure-activity relationship ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Principal components (PCs) for principal component regression (PCR) have historically been selected from the top down for a reliable predictive model. That is, the PCs are arranged in a list starting with the most informative (PC associated with the largest singular value) and proceeding to the least informative (PC associated with the smallest singular value). PCs are then chosen starting at the top of this list. This paper discusses an alternative procedure of treating PC selection as an optimization problem. Specifically, without any regard to the ordering, the optimal subset of PCs for an acceptable predictive model is desired. Five data sets are analyzed using the conventional and alternative approaches. Two data sets are spectroscopic in nature, two data sets deal with quantitative structure-activity relationships (QSARs) and one data set is concerned with modeling. All five data sets confirm that selection of a subset without consideration to order secures the best results with PCR. One data set is also compared using partial least squares 1.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060406
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    Diary (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. i 
    Details
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060502
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    Weighted analysis of principal components: Two approximations to statistical weightsPart of the Master of Science Thesis by D.P. (1992)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 6 (1992), S. 257-266 
    Details
    ISSN: 0886-9383
    Keywords: Principal factor analysis ; Factor analysis ; Eigenvalue analysis ; Multivariate analysis ; Weighted factor analysis ; Procrustean analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two approximate methods for weighted principal components analysis (WPCA) were devised and tested in numerical experiments using either empirical variances (obtained from replicated data) or assumed variances (derived from unreplicated data). In the first (‘spherical’) approximation each data vector was assigned a weight proportional to the geometrical mean of its variances in all dimensions. The arithmetical mean of variances was used instead in the other approximation. Both the numerical experiments with artificial data containing random errors of various kinds (constant, proportional, constant plus proportional, Poisson) and the analysis of two sets of Raman spectra clearly indicated the necessity of introducing statistical weights. The spherical approximation was found to be slightly better than the arithmetical one. The application of statistical weighting was found to improve the performance of PCA in estimation problems.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180060505
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