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Marc Garland - One of the best experts on this subject based on the ideXlab platform.
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Four Criteria for Evaluating Pure Component Spectral Estimates and the Subsequent Identification of Intermediates in Homogeneous Catalysis
ACS Catalysis, 2012Co-Authors: Marc Garland, Liangfeng GuoAbstract:In situ spectroscopic studies are increasingly used to better understand mechanistic aspects of homogeneous catalytic systems. In many cases, the raw measured spectra are simply inspected to identify new bands that appear under catalytic conditions. However, various types of advanced signal processing techniques can often provide considerably more detail and can even provide the underlying Pure Component spectra. Since intermediates are rarely isolatable, the availability of new Pure Component spectral estimates suggests a need for internal consistency checks and other forms of validation. The present contribution surveys four recently developed criteria for assessing the accuracy of Pure Component spectral estimates and then their subsequent usefulness in confirming the identity of newly discovered and nonisolatable intermediates in complex metal-mediated syntheses. Criteria I and II address the consistency of spectral estimates within an experimental study and between different experimental studies, and...
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Pure Component raman spectral reconstruction from glazed and unglazed yuan ming and qing shards a combined raman microscopy and btem study
Journal of Raman Spectroscopy, 2011Co-Authors: Effendi Widjaja, Geok Hong Lim, Qinyi Lim, Ahmad Bin Mashadi, Marc GarlandAbstract:Raman mapping measurements were performed on the glazed and unglazed surfaces of shards excavated from Yuan, Ming, and Qing dynasty strata. A number of areas on each surface were chosen. Circa 21 × 21 pixels were measured for each area using both 514 and 785-nm laser as the Raman excitation. Data were collected from 100–3600 cm−1. Many sets of spectra exhibited very intense fluorescence. In spite of the intense fluorescence, the resulting sets of spectra were collated and analyzed together using the band-target entropy minimization (BTEM) algorithm. Pure Component spectral estimates of many of the major Components were achieved, without the use of any a priori information such as spectral libraries. These include α-silica quartz, carbon, anatase, cobalt oxides, hematite, glassy silicate, and lanthanide complexes. In addition, two further unidentified Pure Component spectra A and B were recovered as well as an interference pattern due to the microscopic texture of the shards (associated with small particle/thin layer domains). The carbon was primarily present in elemental form, i.e. mixture of amorphous and graphitic (unordered and ordered domains); however there is an evidence of some partial oxidation, i.e. formation of carboxylates. The interference patterns and the lanthanide complexes were only observed when using the longer wavelength red laser. The cobalt oxides and the anatase were only observed when using the green laser. In summary, the combination of Raman microscopy and BTEM has allowed the enumeration of many of the underlying spectral patterns present and hence unambiguous identification of the major individual Components present in the archaeological samples. This approach would appear applicable to other classes of archaeological materials as well. Limitations and extensions of the present approach are discussed. Copyright © 2010 John Wiley & Sons, Ltd.
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Pure Component spectral analysis of surface adsorbed species measured under real conditions btem drifts study of co and no reaction over a pd γ al2o3 catalyst
Physical Chemistry Chemical Physics, 2008Co-Authors: Srilakshmi Chilukoti, Feng Gao, B Bruce G Anderson, J Hans W Niemantsverdriet, Marc GarlandAbstract:The adsorption of NO and CO was studied on an alumina-supported palladium catalyst by in situdiffuse reflectance infrared spectroscopy (DRIFTS). The temperature range was 50–160 °C and a wide variety of partial pressures was used. The band-target entropy minimization (BTEM) algorithm was applied to the DRIFTS data sets resulting in the Pure Component spectra of numerous species adsorbed on both the Pd (primarily a variety of Pd–CO and Pd–NO species, in various oxidation states and coordinations) and alumina surface species (i.e. nitrates, nitrites, carbonates, bicarbonates, formates, and isocyanates) as well as gas phase species. Twenty seven previously known species were identified as well as three new and previously unreported or previously unassigned spectra. The present study indicates that BTEM can be meaningfully applied to Pd/Al2O3DRIFTS in order to provide enhanced spectroscopic analysis. Moreover, the present results are compared in detail with the recent BTEM analysis of CO and NO adsorption on Pt/Al2O3 using DRIFTS (Phys. Chem. Chem. Phys. 2008, 10, 3535).
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remote monitoring of a multi Component liquid phase organic synthesis by infrared emission spectroscopy the recovery of Pure Component emissivities by band target entropy minimization
Applied Spectroscopy, 2007Co-Authors: Shuying Cheng, Martin Tjahjono, D Rajarathnam, Li Chuanzhao, Ilya Lyapkalo, David Chen, Marc GarlandAbstract:A liquid-phase cycloaddition reaction near ambient temperature involving dimethyl acetylenedicarboxylate (DMAD) and cyclopentadiene (CP) as reactants was measured using a conventional Fourier transform infrared (FT-IR) spectrometer with an emission accessory. Two semi-batch experiments were performed and a total of 55 spectra were collected using a DTGS detector. Band-target entropy minimization (BTEM), a Pure Component spectral reconstruction technique, was applied to analyze the data set to retrieve the Pure Component emission spectrum from the reaction system. The estimated emission spectra of the solvent chloroform, DMAD, CP, and product, namely dimethyl bicyclo[2.2.1]-2,5-heptadiene-2,3-dicarboxylate, were all reconstructed with rather good quality. The estimated emission spectra are similar to independent FT-IR spectra of the same cycloaddition reaction. Using a least squares fit, the relative concentration profiles of the species are obtained. Because this appears to be the first time that a liquid-phase reaction has been monitored by infrared emission spectroscopy, further improvements and opportunities for general multi-phase liquid reaction monitoring are discussed.
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Fourier transform Raman spectral measurements of powdered quaternary mixtures of organic compounds Exceptional Pure Component spectral reconstruction using band-target entropy minimization (BTEM).
Talanta, 2007Co-Authors: Chilukoti Srilakshmi, Bruce Anderson, Widjaja, Marc GarlandAbstract:Fourier transform Raman spectra of eight mixtures of four organic solids, namely dicyandiamide, melamine, acetamide and urea were measured. Matrices formed from these spectra were first subjected to singular value decomposition to obtain the right singular vectors. The right singular vectors were then subjected to blind source separation using band-target entropy minimization (BTEM), thus no a priori information (i.e. involving the nature of the Components present, their spectra, nor their concentrations) was included in the analysis. The recovered Pure Component spectra are of exceptionally high quality and are consistent with Pure reference spectra. Various empirical and statistical tests, such as the Euclidean norm and target transform factor analysis, were employed to assess the quality of the recovered spectra. The present results indicate the applicability of combined Raman and BTEM analysis for solid mixtures.
Effendi Widjaja - One of the best experts on this subject based on the ideXlab platform.
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Pure Component raman spectral reconstruction from glazed and unglazed yuan ming and qing shards a combined raman microscopy and btem study
Journal of Raman Spectroscopy, 2011Co-Authors: Effendi Widjaja, Geok Hong Lim, Qinyi Lim, Ahmad Bin Mashadi, Marc GarlandAbstract:Raman mapping measurements were performed on the glazed and unglazed surfaces of shards excavated from Yuan, Ming, and Qing dynasty strata. A number of areas on each surface were chosen. Circa 21 × 21 pixels were measured for each area using both 514 and 785-nm laser as the Raman excitation. Data were collected from 100–3600 cm−1. Many sets of spectra exhibited very intense fluorescence. In spite of the intense fluorescence, the resulting sets of spectra were collated and analyzed together using the band-target entropy minimization (BTEM) algorithm. Pure Component spectral estimates of many of the major Components were achieved, without the use of any a priori information such as spectral libraries. These include α-silica quartz, carbon, anatase, cobalt oxides, hematite, glassy silicate, and lanthanide complexes. In addition, two further unidentified Pure Component spectra A and B were recovered as well as an interference pattern due to the microscopic texture of the shards (associated with small particle/thin layer domains). The carbon was primarily present in elemental form, i.e. mixture of amorphous and graphitic (unordered and ordered domains); however there is an evidence of some partial oxidation, i.e. formation of carboxylates. The interference patterns and the lanthanide complexes were only observed when using the longer wavelength red laser. The cobalt oxides and the anatase were only observed when using the green laser. In summary, the combination of Raman microscopy and BTEM has allowed the enumeration of many of the underlying spectral patterns present and hence unambiguous identification of the major individual Components present in the archaeological samples. This approach would appear applicable to other classes of archaeological materials as well. Limitations and extensions of the present approach are discussed. Copyright © 2010 John Wiley & Sons, Ltd.
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use of raman microscopy and band target entropy minimization technique to differentiate physical mixture from chemical mixture in mixed metal oxides
Catalysis Today, 2008Co-Authors: Effendi Widjaja, Jeyagowry T SampantharAbstract:Raman microscopy has been applied to characterize physical and chemical mixtures of mixed metal oxides. The obtained Raman mapping data were first subjected to singular value decomposition to obtain the right singular vectors, and the right singular vectors were then subjected to band-target entropy minimization (BTEM) to recover the Pure Component spectra of the observed species present in the sample. Subsequently, these resolved Pure Component spectral information was used to differentiate the physical and chemical mixtures. In addition, BTEM is also able to recover the Pure Component spectra of both unstable compound and its degradation product due to laser irradiation. In current study, the physical mixture of Mn2O3 and Co3O4, and the chemical mixture of CoMn2O4 spinel oxide were investigated.
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the detection of laser induced structural change of mno2 using in situ raman spectroscopy combined with self modeling curve resolution technique
Analytica Chimica Acta, 2007Co-Authors: Effendi Widjaja, Jeyagowry T SampantharAbstract:Abstract In this paper, we present the use of one of the self-modeling curve resolution techniques, band-target entropy minimization (BTEM), which is independent of any spectral library, to elucidate Raman Pure Component spectra of two different manganese oxides arising from laser-induced structural changes. It is often extremely difficult to obtain the Pure Raman spectrum of MnO2 without changing it to another structural form. However, using BTEM to analyze the collected in situ Raman spectra measured as a function of laser exposure time, has enabled us to obtain both the Pure Component spectra of the original sample and the product due to laser irradiation. This technique proves to be an efficient Raman spectral interpretation method for thermal sensitive solid samples.
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band target entropy minimization a robust algorithm for Pure Component spectral recovery application to complex randomized mixtures of six Components
Analytical Chemistry, 2003Co-Authors: Effendi Widjaja, Chuanzhao Li, Wee Chew, Marc GarlandAbstract:A newly developed self-modeling curve resolution method, band-target entropy minimization (BTEM), is described. This method starts with the data decomposition of a set of spectroscopic mixture data using singular value decomposition. It is followed by the transformation of the orthonormal basis vectors/loading vectors into individual Pure Component spectra one at a time. The transformation is based in part on some seminal ideas borrowed from information entropy theory with the desire to maximize the simplicity of the recovered Pure Component spectrum. Thus, the proper estimate is obtained via minimization of the proposed information entropy function or via minimization of derivative and area of the spectral estimate. Nonnegativity constraints are also imposed on the recovered Pure Component spectral estimate and its corresponding concentrations. As its name suggests, in this method, one targets a spectral feature readily observed in loading vectors to retain, and then combinations of the loading vectors a...
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Pure Component spectral reconstruction from mixture data using svd global entropy minimization and simulated annealing numerical investigations of admissible objective functions using a synthetic 7 species data set
Journal of Computational Chemistry, 2002Co-Authors: Effendi Widjaja, Marc GarlandAbstract:A combination of singular value decomposition, entropy minimization, and simulated annealing was applied to a synthetic 7-species spectroscopic data set with added white noise. The Pure spectra were highly overlapping. Global minima for selected objective functions were obtained for the transformation of the first seven right singular vectors. Simple Shannon type entropy functions were used in the objective functions and realistic physical constraints were imposed in the penalties. It was found that good first approximations for the Pure Component spectra could be obtained without the use of any a priori information. The present method out performed the two widely used routines, namely Simplisma and OPA-ALS, as well as IPCA. These results indicate that a combination of SVD, entropy minimization, and simulated annealing is a potentially powerful tool for spectral reconstructions from large real experimental systems.
Deresh Ramjugernath - One of the best experts on this subject based on the ideXlab platform.
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Estimation of Pure Component Properties, Part 5: Estimation of the Thermal Conductivity of Nonelectrolyte Organic Liquids via Group Contributions
Journal of Chemical & Engineering Data, 2019Co-Authors: Onellan Govender, Jürgen Rarey, Deresh RamjugernathAbstract:As an extension of the Pure Component property estimation techniques that we have developed for normal boiling point, critical property data, vapor pressure, and liquid viscosity, a new group contribution method for the prediction of Pure Component saturated liquid thermal conductivity has been developed. Predictions are solely molecular structure based. Structural group definitions for the method are a modified version of those proposed by Moller et al. for the estimation of saturated vapor pressures. Structural groups were defined in a standardized form and fragmentation of the molecular structures was performed by an automatic procedure to eliminate any arbitrary assumptions. The new method is based on liquid thermal conductivity data for about 330 Components after critical evaluation of 110 000 data points for the various phases and nearly 900 Components stored in the Dortmund Data Bank. Results of the new method compared favorably to several other estimation methods from the literature. A relative me...
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Pure Component and binary vapor liquid equilibrium modeling for hexafluoropropylene and hexafluoropropylene oxide with toluene and hexafluoroethane
Journal of Chemical & Engineering Data, 2010Co-Authors: Shalendra Clinton Subramoney, Wayne Michael Nelson, Alain Valtz, Christophe Coquelet, Dominique Richon, Paramespri Naidoo, Deresh RamjugernathAbstract:Experimental Pure Component vapor pressure data for hexafluoropropylene (R1216) and hexafluoropropylene oxide (HFPO) are presented. Experimental vapor−liquid equilibrium (VLE) data are presented at two temperatures, (273 and 313) K, for four binary systems: R1216 + toluene, HFPO + toluene, hexafluoroethane (R116) + R1216, and R116 + HFPO. The measurements were undertaken using both a “static−analytic” apparatus fitted with a pneumatic rapid online sampler injector (ROLSI) and a “static−synthetic” PVT apparatus. The experimental vapor pressure data were regressed to obtain correlated parameters for the Peng−Robinson (PR) and Soave−Redlich−Kwong (SRK) equations of state with the Mathias−Copeman α function. The binary VLE data were regressed to obtain correlated parameters for three different model combinations: the PR equation of state with the Wong−Sandler (WS) mixing rules, the PR equation of state with the modified Huron−Vidal first-order (MHV1) mixing rules, and the SRK equation of state with the WS mix...
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Pure Component and Binary Vapor-Liquid Equilibrium + Modeling for Hexafluoropropylene and Hexafluoropropylene Oxide with Toluene and Hexafluoroethane
Journal of Chemical and Engineering Data, 2010Co-Authors: Shalendra Clinton Subramoney, Alain Valtz, Christophe Coquelet, Dominique Richon, Paramespri Naidoo, M. Nelson Wayne, Deresh RamjugernathAbstract:Experimental Pure Component vapor pressure data for hexafluoropropylene (R1216) and hexafluoropropylene oxide (HFPO) are presented. Experimental vapor-liquid equilibrium (VLE) data are presented at two temperatures, (273 and 313) K, for four binary systems: R1216 + toluene, HFPO + toluene, hexafluoroethane (R116) + R1216, and R116 + HFPO. The measurements were undertaken using both a “static-analytic” apparatus fitted with a pneumatic rapid online sampler injector (ROLSI) and a “static-synthetic” PVT apparatus. The experimental vapor pressure data were regressed to obtain correlated parameters for the Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) equations of state with the Mathias-Copeman R function. The binary VLE data were regressed to obtain correlated parameters for three different model combinations: the PR equation of state with the Wong-Sandler (WS) mixing rules, the PR equation of state with the modified Huron-Vidal first-order (MHV1) mixing rules, and the SRK equation of state with the WS mixing rules. The Mathias-Copeman R function and the nonrandom two-liquid (NRTL) excess Gibbs energy model were used in conjunction with the equations of state and mixing rules. In general, the PR equation of state with the WS mixing rules provided the best correlation for the experimental data. The critical lines for the supercritical systems R116 + R1216 and R116 + HFPO, calculated with the PR equation of state with the WS mixing rules, are also presented.K and (283.6 to 290.1) K, respectively at 0.05 mass fraction of tetra-n-butylammonium bromide in aqueous solution. The experimental data were generated using an isochoric pressure-search method. The hydrate dissociation data for the tetra-n-butylammonium bromide + methane system are compared with the corresponding experimental data reported in the literature, and the acceptable agreement demonstrates the reliability of the experimental method used in this work. The experimental data for both measured systems are finally compared with the corresponding experimental data in the absence of tetra-n-butyl- ammonium bromide reported in the literature to study its hydrate promotion effect.
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estimation of Pure Component properties part 4 estimation of the saturated liquid viscosity of non electrolyte organic compounds via group contributions and group interactions
Fluid Phase Equilibria, 2009Co-Authors: Yash Nannoolal, Jürgen Rarey, Deresh RamjugernathAbstract:Abstract A new group contribution method for the prediction of Pure Component saturated liquid viscosity has been developed. The method is an extension of the Pure Component property estimation techniques that we have developed for normal boiling points, critical property data, and vapour pressures. Predictions can be made from simply having knowledge of the molecular structure of the compound. In addition, the structural group definitions for the method are identical to those proposed for estimation of saturated vapour pressures. Structural groups were defined in a standardized form and fragmentation of the molecular structures was performed by an automatic procedure to eliminate any arbitrary assumptions. The new method is based on liquid viscosity data for more than 1600 Components. Results of the new method are compared to several other estimation methods published in literature and are found to be significantly better. A relative mean deviation in viscosity of 15.3% was observed for 813 Components (12,139 data points). By comparison, the Van Velzen method, the best literature method in our benchmarking exercise produced a relative mean deviation of 92.8% for 670 Components (11,115 data points). Estimation results at the normal boiling temperature were also tested against an empirical rule for more than 4000 Components. The range of the method is usually from the triple or melting point to a reduced temperature of 0.75–0.8. Larger than average deviations were observed in the case of molecules with higher rotational symmetry, but no specific correction of this effect was included in this method.
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estimation of Pure Component properties part 2 estimation of critical property data by group contribution
Fluid Phase Equilibria, 2004Co-Authors: Yash Nannoolal, Jürgen Rarey, Deresh RamjugernathAbstract:Abstract A new group contribution method for the estimation of critical property data has been developed. The method is based on structural group definitions, with minor modifications, of a method recently published for the estimation of the normal boiling point by Nannoolal et al. [Y. Nannoolal, J. Rarey, D. Ramjugernath, W. Cordes, Fluid Phase Equilib. 226 (2004) 45–63]. Special care was taken to ensure physically meaningful extrapolation to large and multifunctional compounds, as it could be shown that such extrapolation may lead to very improbable or unrealistic results in the case of some methods published earlier. Regression of group increments was not performed simultaneously but with great care one group at a time. With all other group increments fixed, all data for Components with a specific group led to approximately the same group increment. This allowed one to determine group increments for cases where only one reliable experimental value was available. For the case of more than one strongly associating group, a group interaction contribution was required as these groups do not observe simple additivity. The estimation of the critical temperature requires knowledge of the normal boiling point. Critical pressure and volume can be estimated from chemical structure alone. The performance of the new model has been compared with 10 well-known estimation methods from literature and the results indicate that the new model is significantly more reliable. To enable comparison, chemical family definitions have been developed that allow one to automatically classify new Components and thus, inform the user about the expected reliability of the different methods for a Component of interest. Chemical family definitions are based on the kind and frequency of the different structural groups in the molecule. In addition to these advantages, the range of applicability of the new method is larger than that of comparable methods.
Yingzhi Zeng - One of the best experts on this subject based on the ideXlab platform.
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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, 2003Co-Authors: Huajun Zhang, Marc Garland, Yingzhi ZengAbstract: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 spectros-copies 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 V T 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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An improved algorithm for estimating Pure Component spectra in exploratory chemometric studies based on entropy minimization
Analytica Chimica Acta, 1998Co-Authors: Yingzhi Zeng, Marc GarlandAbstract:Abstract It is assumed that multiple spectroscopic measurements are made on a sequence of solutions containing unknown Components. Further, it is assumed that a singular value decomposition of the spectral data set is performed whereby the right singular vectors associated with the Pure Component spectra (absorptivities) are obtained. Sasaki et al. [ Applied Optics, 1983, 1984] have shown that a set of estimated absorptivities can be obtained by solving a minimization problem involving a set of spectroscopic basic vectors – without relying on any further information. The resulting estimated absorptivities often closely resemble the true absorptivities. The objective function then proposed involves second order derivatives, i.e., a classical entropy functional. In the present contribution, the use of higher order derivatives is investigated, viz., fourth order derivatives, in the objective function. Synthetic infrared spectroscopic data are constructed for two-Component solutions, and sets of right singular vectors are obtained by singular value decomposition. It is shown that for spectra composed of strongly overlapping spectroscopic features, the fourth derivative objective function provides considerable improvement over the second derivative objective function for the estimation of absorptivities. It is also shown that for spectra composed of mildly overlapping spectroscopic features, the fourth derivative algorithm and the second derivative algorithm produce estimated absorptivities which are, for most practical purposes, identical to the real absorptivities. Strongly overlapping spectroscopic features are common to most sets of NIR, UV and XPS spectra, and IR and NMR data collected over a very limited spectral range.
Wee Chew - One of the best experts on this subject based on the ideXlab platform.
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band target entropy minimization a robust algorithm for Pure Component spectral recovery application to complex randomized mixtures of six Components
Analytical Chemistry, 2003Co-Authors: Effendi Widjaja, Chuanzhao Li, Wee Chew, Marc GarlandAbstract:A newly developed self-modeling curve resolution method, band-target entropy minimization (BTEM), is described. This method starts with the data decomposition of a set of spectroscopic mixture data using singular value decomposition. It is followed by the transformation of the orthonormal basis vectors/loading vectors into individual Pure Component spectra one at a time. The transformation is based in part on some seminal ideas borrowed from information entropy theory with the desire to maximize the simplicity of the recovered Pure Component spectrum. Thus, the proper estimate is obtained via minimization of the proposed information entropy function or via minimization of derivative and area of the spectral estimate. Nonnegativity constraints are also imposed on the recovered Pure Component spectral estimate and its corresponding concentrations. As its name suggests, in this method, one targets a spectral feature readily observed in loading vectors to retain, and then combinations of the loading vectors a...
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band target entropy minimization btem an advanced method for recovering unknown Pure Component spectra application to the ftir spectra of unstable organometallic mixtures
Organometallics, 2002Co-Authors: Wee Chew, Effendi Widjaja, Marc GarlandAbstract:A newly developed band-target entropy minimization (BTEM) algorithm was tested on experimental FTIR data of Rh4(CO)12/Rh6(CO)16 mixtures in order to recover the Pure Component spectra of the constituent complexes. Bands in the nonoverlapping bridging carbonyl region as well as bands in the highly overlapping terminal carbonyl region were targeted for retention. The bands are identified in the vector-space decomposition of the observations, a crucial first step in untangling the superposition of the Pure Component spectra. In both cases, the targeted band was retained, and exceptionally accurate whole spectral estimates of Rh4(CO)12 and Rh6(CO)16 were obtained. Due to the constructs used in BTEM, enhanced signal-to-noise characteristics result, and spectral nonlinearities arising from changing band positions and changing band shapes are essentially eliminated. For the experimentalist, the utility of BTEM arises from its direct one-spectrum-at-a-time spectral reconstruction approachwhich is guided by the ch...
