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Xu Q, Guo L, Dinh TN, Cheong A, Garland M. Two-Dimensional (2D) Correlation Analysis and the Search for Intermediates: A Strictly Mathematical Approach to an Important Mechanistic Question. ACS Catal 2015. [DOI: 10.1021/cs502127y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Qisong Xu
- Institute
of Chemical and
Engineering Sciences, Agency for Science, Technology and Research, 1 Pesek Road, Jurong Island 627833, Singapore
| | - LiangFeng Guo
- Institute
of Chemical and
Engineering Sciences, Agency for Science, Technology and Research, 1 Pesek Road, Jurong Island 627833, Singapore
| | - Tung Nguyen Dinh
- Institute
of Chemical and
Engineering Sciences, Agency for Science, Technology and Research, 1 Pesek Road, Jurong Island 627833, Singapore
| | - Angie Cheong
- Institute
of Chemical and
Engineering Sciences, Agency for Science, Technology and Research, 1 Pesek Road, Jurong Island 627833, Singapore
| | - Marc Garland
- Institute
of Chemical and
Engineering Sciences, Agency for Science, Technology and Research, 1 Pesek Road, Jurong Island 627833, Singapore
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2
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Behr A, Vorholt AJ, Seidensticker T. An Old Friend in a New Guise-Recent Trends in Homogeneous Transition Metal Catalysis. CHEMBIOENG REVIEWS 2015. [DOI: 10.1002/cben.201400034] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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3
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4
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Tan ST, Zhu H, Chew W. Self-modeling curve resolution of multi-component vibrational spectroscopic data using automatic band-target entropy minimization (AutoBTEM). Anal Chim Acta 2009; 639:29-41. [DOI: 10.1016/j.aca.2009.02.054] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Revised: 02/25/2009] [Accepted: 02/28/2009] [Indexed: 10/21/2022]
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5
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Widjaja E, Tan WJ. Kinetics of lisinopril intramolecular cyclization in solid phase monitored by Fourier transform infrared microscopy. APPLIED SPECTROSCOPY 2008; 62:889-894. [PMID: 18702862 DOI: 10.1366/000370208785284286] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The solid-state intramolecular cyclization of lisinopril to diketopiperazine was investigated by in situ Fourier transform infrared (FT-IR) microscopy. Using a controllable heating cell, the isothermal transformation was monitored in situ at 147.5, 150, 152.5, 155, and 157.5 degrees C. The collected time-dependent FT-IR spectra at each isothermal temperature were preprocessed and analyzed using a multivariate chemometric approach. The pure component spectra of the observable component (lisinopril and diketopiperazine) were resolved and their time-dependent relative contributions were also determined. Model-free and various model fitting methods were implemented in the kinetic analysis to estimate the activation energy of the intramolecular cyclization reaction. Arrhenius plots indicate that the activation energy is circa 327 kJ/mol.
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Affiliation(s)
- Effendi Widjaja
- Institute of Chemical and Engineering Sciences, Jurong Island Singapore.
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6
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Multivariate Chemometric Approach to Thermal Solid-State FT-IR Monitoring of Pharmaceutical Drug Compound. J Pharm Sci 2008; 97:3379-87. [DOI: 10.1002/jps.21275] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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7
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Widjaja E, Lim GH, Chow PS, Tan S. Multivariate data analysis as a tool to investigate the reaction kinetics of intramolecular cyclization of enalapril maleate studied by isothermal and non-isothermal FT-IR microscopy. Eur J Pharm Sci 2007; 32:349-56. [DOI: 10.1016/j.ejps.2007.09.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2007] [Revised: 08/22/2007] [Accepted: 09/05/2007] [Indexed: 11/26/2022]
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8
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Zhang H, Chew W, Garland M. The multi-reconstruction entropy minimization method: unsupervised spectral reconstruction of pure components from mixture spectra, without the use of a priori information. APPLIED SPECTROSCOPY 2007; 61:1366-1372. [PMID: 18198030 DOI: 10.1366/000370207783292172] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The band-target entropy minimization method (BTEM) and its variant methods excel at reconstructing known/unknown pure spectra from mixtures without prior information. These mixtures may represent either non-reactive or even reactive systems. In this work, an unsupervised form of the entropy minimization curve resolution, namely, the multi-reconstruction entropy minimization method (MREM), is presented. MREM differs from BTEM by removing the need for band-targets and by introducing a multiple search routine to find multiple local entropy minima. This multiple search routine, which provides a rapid survey of spectral estimates, utilizes a localized form of Corona's simulated annealing method in the optimization. The objective functions and penalty functions of the BTEM type methods are essentially retained. Compared to BTEM type methods, MREM (1) searches for multiple local minima instead of a single global minimum and hence reconstructs many pure component spectra at once instead of one pure spectrum; and (2) utilizes a user-defined broad spectral range [v1, v2] for all searches instead of multiple user-defined narrow "targets" as in BTEM. The new MREM has been tested on four sets of real spectra using Fourier transform infrared spectroscopy (FT-IR), mass spectroscopy (MS), and ultraviolet-visible (UV-Vis) spectroscopy. The results show that MREM is computationally much faster than BTEM for finding the major components present. Also, because MREM does not rely on band targeting, it is very useful for spectra that have no localized features and are highly overlapping, such as UV-Vis.
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Affiliation(s)
- Huajun Zhang
- Institute of Chemical and Engineering Science, 1 Pesek Road, Jurong Island, Singapore 627833
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9
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Rhodium catalyzed hydroformylation of conjugated dienes: Remarkable accelerative effect of triphenylphosphine. CATAL COMMUN 2007. [DOI: 10.1016/j.catcom.2006.09.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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10
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Barros HJV, Guimarães CC, dos Santos EN, Gusevskaya EV. Rhodium-Catalyzed Hydroformylation of Isoprene: Unusual Accelerating Effects of Phosphorus Ligands and Gas Pressure. Organometallics 2007. [DOI: 10.1021/om060994n] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Humberto J. V. Barros
- Departamento de Química, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil
| | - Cristiane C. Guimarães
- Departamento de Química, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil
| | - Eduardo N. dos Santos
- Departamento de Química, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil
| | - Elena V. Gusevskaya
- Departamento de Química, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil
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11
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Bu D, Huffman SW, Seelenbinder JA, Brown CW. Enhancement of infrared spectral images for maximizing chemical information by minimizing baseline interferences. APPLIED SPECTROSCOPY 2005; 59:575-83. [PMID: 15969802 DOI: 10.1366/0003702053946010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The popularity of spectral images in many areas of analysis has greatly increased during the last decade due to the development of charge-coupled device (CCD) and infrared sensitive cameras. Large amounts of spatial information can be obtained in short periods of time. The general goal in analytical chemistry is to convert spectral images into chemical images, which show the spatial locations of various chemical components. Self-modeling multivariate curve resolution methods can be used to extract pure component spectra from the mixture spectra in images and produce chemical images. However, there is a difficulty in processing infrared spectral images due to large pixel-to-pixel baseline variations. Herein, a method for minimizing baseline interferences using fast Fourier transform (FFT) filtering in both the spectral and spatial domains is discussed. The methodology is demonstrated on a microscopic sample of butter contaminated with non-pathogenic E. coli and on a cross-sectional sample of rabbit aorta containing plaque. The processing to reduce baseline effects improved the spatial resolution without compromising the spectral resolution.
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Affiliation(s)
- Dongsheng Bu
- Department of Chemistry, University of Rhode Island, Kingston, Rhode Island 02881, USA
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12
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Widjaja E, Garland M. Entropy minimization and spectral dissimilarity curve resolution technique applied to nuclear magnetic resonance data sets. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2005; 173:175-182. [PMID: 15705526 DOI: 10.1016/j.jmr.2004.11.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2004] [Revised: 08/13/2004] [Indexed: 05/24/2023]
Abstract
The use of entropy minimization and spectral dissimilarity is applied to three nuclear magnetic resonance (NMR) data sets. The data sets contain 2, 2, and 3 observables each. It was found that without any a priori information the sets of pure component spectra underlying the NMR spectroscopic observations could be extracted. These successful spectral resolutions suggest that a combined entropy minimization and spectral dissimilarity approach can be further developed for even larger NMR data sets containing a larger number of observables. Brief comparison to DECRA and PMF curve resolution results is also presented.
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Affiliation(s)
- Effendi Widjaja
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117576, Singapore
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13
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Simick MK, Jong R, Wilson B, Lilge L. Non-ionizing near-infrared radiation transillumination spectroscopy for breast tissue density and assessment of breast cancer risk. JOURNAL OF BIOMEDICAL OPTICS 2004; 9:794-803. [PMID: 15250768 DOI: 10.1117/1.1758269] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
There is increasing attention to prevention as a means to reduce cancer incidence. Prevention interventions or therapies in turn rely on risk assessment programs to identify those women most likely to benefit from education and lifestyle changes. These programs are usually based either on interviews to identify ethnic, genetic, and lifestyle factors contributing to risk or on physical examination of the breast. For the latter it has been shown that the parenchymal density pattern observed in X-ray mammography can be used to assess an individual's risk. Extensive areas of dense, glandular tissue that are relatively radio-opaque are associated with higher breast cancer risk, with an odds ratio of 4 to 6 compared with women in whom the breast density is low owing to an abundance of adipose tissue. Near-infrared optical transillumination spectroscopy has been used previously to investigate the physiological properties of breast tissue. In this study, women were recruited who underwent recently X-ray mammography. The tissue density was assessed by a radiologist. The women then underwent optical transillumination spectroscopy, for which an instrument was developed that delivered visible and near-infrared light to the breast. After being transmitted through the breast craniocaudally in one of four quadrants, the spectrum from 625 to 1050 nm was measured. The spectra were used as input to a Principal Component Analysis (PCA) that used the corresponding mammographic density as the reference standard. The study group consisted of 92 women aged 39 to 72 years. Without further stratification for age, menopausal status, or measurement position, the PCA numerical model predicted the radiological assessment of tissue density in the mid 80% to low 90%.
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Affiliation(s)
- Michelle K Simick
- University of Toronto, Department of Medical Biophysics, 610 University Ave., Toronto, Ontario M5G 2M9, Canada
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14
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Ungváry F. Application of transition metals in hydroformylation annual survey covering the year 2003. Coord Chem Rev 2004. [DOI: 10.1016/j.ccr.2003.02.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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15
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Zhang H, Garland M, Zeng Y, Wu P. Weighted two-band target entropy minimization for the reconstruction of pure component mass spectra: simulation studies and the application to real systems. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2003; 14:1295-1305. [PMID: 14597120 DOI: 10.1016/s1044-0305(03)00540-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A method is proposed, on the basis of a recently developed algorithm--Band Target Entropy Minimization (BTEM)--to reconstruct mass spectra of pure components from mixture spectra. This method is particular useful in dealing with spectral data with discrete features (like mass spectra). Compared to the original BTEM, which has been applied to differentiable spectroscopies such as Fourier-transfer infrared spectroscopy (FTIR), ultraviolet (UV), Raman, and nuclear magnetic resonance (NMR), the latest modifications were obtained through: (1) Reformulating the objective function using the peak heights instead of their derivatives; (2) weighting the abstract vector VT to reduce the effect of noise; (3) using a two-peak targeting strategy (tBTEM) to deal with strongly overlapping peaks; and (4) using exhaustive search to locate all the component spectra. A set of 50 multi-component mass spectra was generated from ten reference experimental pure component spectra. Many of the compounds chosen have common MS fragments and therefore, many of the pure component spectra have considerable intensity in same data channels. In addition, a set of MS spectra from a real system with four components was used to examine the newly developed algorithm. Successful reconstruction of the ten component spectra of the simulated system and the four component spectra of the real system was rapidly achieved using the new tBTEM algorithm. The advantages of the new algorithm and its implication for rapid system identification of unknown mixtures are readily apparent.
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Affiliation(s)
- Huajun Zhang
- Department of Chemical and Environmental Engineering, National University of Singapore, Singapore, Singapore
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16
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Widjaja E, Crane N, Chen TC, Morris MD, Ignelzi MA, McCreadie BR. Band-target entropy minimization (BTEM) applied to hyperspectral Raman image data. APPLIED SPECTROSCOPY 2003; 57:1353-62. [PMID: 14658148 DOI: 10.1366/000370203322554509] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Band-target entropy minimization (BTEM) has been applied to extraction of component spectra from hyperspectral Raman images. In this method singular value decomposition is used to calculate the eigenvectors of the spectroscopic image data set. Bands in non-noise eigenvectors that would normally be used for recovery of spectra are examined for localized spectral features. For a targeted (identified) band, information entropy minimization or a closely related algorithm is used to recover the spectrum containing this feature from the non-noise eigenvectors, plus the next 5-30 eigenvectors, in which noise predominates. Tests for which eigenvectors to include are described. The method is demonstrated on one synthesized Raman image data set and two bone tissue specimens. By inclusion of small amounts of signal that would be unused in other methods, BTEM enables the extraction of a larger number of component spectra than are otherwise obtainable. An improvement in signal/noise ratio of the recovered spectra is also obtained.
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Affiliation(s)
- Effendi Widjaja
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
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