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LDA
Selected AbstractsFeature Extraction for Traffic Incident Detection Using Wavelet Transform and Linear Discriminant AnalysisCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2000A. Samant To eliminate false alarms, an effective traffic incident detection algorithm must be able to extract incident-related features from the traffic patterns. A robust feature-extraction algorithm also helps reduce the dimension of the input space for a neural network model without any significant loss of related traffic information, resulting in a substantial reduction in the network size, the effect of random traffic fluctuations, the number of required training samples, and the computational resources required to train the neural network. This article presents an effective traffic feature-extraction model using discrete wavelet transform (DWT) and linear discriminant analysis (LDA). The DWT is first applied to raw traffic data, and the finest resolution coefficients representing the random fluctuations of traffic are discarded. Next, LDA is employed to the filtered signal for further feature extraction and reducing the dimensionality of the problem. The results of LDA are used as input to a neural network model for traffic incident detection. [source] Benzo[a]heptalenes from Heptaleno[1,2- c]furans.HELVETICA CHIMICA ACTA, Issue 4 2007Abstract It is shown in this ,Part 2' that heptaleno[1,2- c]furans 1 react thermally in a Diels,Alder -type [4+2] cycloaddition at the furan ring with vinylene carbonate (VC), phenylsulfonylallene (PSA), , -(acetyloxy)acrylonitrile (AAN), and (1Z)-1,2-bis(phenylsulfonyl)ethene (ZSE) to yield the corresponding 1,4-epoxybenzo[d]heptalenes (cf. Schemes,1, 5, 6, and 8). The thermal reaction of 1a and 1b with VC at 130° and 150°, respectively, leads mainly to the 2,3- endo -cyclocarbonates 2,3- endo - 2a and - 2b and in minor amounts to the 2,3- exo -cyclocarbonates 2,3- exo - 2a and - 2b. In some cases, the (P*)- and (M*)-configured epimers were isolated and characterized (Scheme,1). Base-catalyzed cleavage of 2,3- endo - 2 gave the corresponding 2,3-diols 3, which were further transformed via reductive cleavage of their dimesylates 4 into the benzo[a]heptalenes 5a and 5b, respectively (Scheme,2). In another reaction sequence, the 2,3-diols 3 were converted into their cyclic carbonothioates 6, which on treatment with (EtO)3P gave the deoxygenated 1,4-dihydro-1,4-epoxybenzo[d]heptalenes 7. These were rearranged by acid catalysis into the benzo[a]heptalen-4-ols 8a and 8b, respectively (Scheme,2). Cyclocarbonate 2,3- endo - 2b reacted with lithium diisopropylamide (LDA) at ,70° under regioselective ring opening to the 3-hydroxy-substituted benzo[d]heptalen-2-yl carbamate 2,3- endo - 9b (Scheme,3). The latter was O -methylated to 2,3- endo -(P*)- 10b. The further way, to get finally the benzo[a]heptalene 13b with MeO groups in 1,2,3-position, could not be realized due to the fact that we found no way to cleave the carbamate group of 2,3- endo -(P*)- 10b without touching its 1,4-epoxy bridge (Scheme,3). The reaction of 1a with PSA in toluene at 120° was successful, in a way that we found regioisomeric as well as epimeric cycloadducts (Scheme,5). Unfortunately, the attempts to rearrange the products under strong-base catalysis as it had been shown successfully with other furan,PSA adducts were unsuccessful (Scheme,4). The thermal cycloaddition reaction of 1a and 1b with AAN yielded again regioisomeric and epimeric adducts, which could easily be transformed into the corresponding 2- and 3-oxo products (Scheme,6). Only the latter ones could be rearranged with Ac2O/H2SO4 into the corresponding benzo[a]heptalene-3,4-diol diacetates 20a and 20b, respectively, or with trimethylsilyl trifluoromethanesulfonate (TfOSiMe3/Et3N), followed by treatment with NH4Cl/H2O, into the corresponding benzo[a]heptalen-3,4-diols 21a and 21b (Scheme,7). The thermal cycloaddition reaction of 1 with ZSE in toluene gave the cycloadducts 2,3- exo - 22a and - 22b as well as 2- exo,3- endo - 22c in high yields (Scheme,8). All three adducts eliminated, by treatment with base, benzenesulfinic acid and yielded the corresponding 3-(phenylsulfonyl)-1,4-epoxybenzo[d]heptalenes 25. The latter turned out to be excellent Michael acceptors for H2O2 in basic media (Scheme,9). The Michael adducts lost H2O on treatment with Ac2O in pyridine and gave the 3-(phenylsulfonyl)benzo[d]heptalen-2-ones 28a and 3- exo - 28b, respectively. Rearrangement of these compounds in the presence of Ac2O/AcONa lead to the formation of the corresponding 3-(phenylsulfonyl)benzo[a]heptalene-1,2-diol diacetates 30a and 30b, which on treatment with MeONa/MeI gave the corresponding MeO-substituted compounds 31a and 31b. The reductive elimination of the PhSO2 group led finally to the 1,2-dimethoxybenzo[a]heptalenes 32a and 32b. Deprotonation experiments of 32a with t -BuLi/N,N,N,,N,-tetramethylethane-1,2-diamine (tmeda) and quenching with D2O showed that the most acid CH bond is HC(3) (Scheme,9). Some of the new structures were established by X-ray crystal-diffraction analyses (cf. Figs.,1, 3, 4, and 5). Moreover, nine of the new benzo[a]heptalenes were resolved on an anal. Chiralcel OD-H column, and their CD spectra were measured (cf. Figs.,8 and 9). As a result, the 1,2-dimethoxybenzo[a]heptalenes 32a and 32b showed unexpectedly new Cotton -effect bands just below 300,nm, which were assigned to chiral exciton coupling between the heptalene and benzo part of the structurally highly twisted compounds. The PhSO2 -substituted benzo[a]heptalenes 30b and 31b showed, in addition, a further pair of Cotton -effect bands in the range of 275,245,nm, due to chiral exciton coupling of the benzo[a]heptalene chromophore and the phenylsulfonyl chromophore (cf. Fig.,10). [source] A Synthesis Detour to Planar-Diastereoisomeric Ferrocene Derivatives around an Unexpected Rearrangement of ortho -Lithiated Kagan's Template [S(S)] - (p -Tolylsulfinyl)ferroceneHELVETICA CHIMICA ACTA, Issue 4 2007Immo Weber Abstract Usually, ortho lithiation of Kagan's template 1 and quenching with electrophiles leads highly diastereoselectively to planar-chiral 1,2-disubstituted ferrocenes. Surprisingly, lithiation of 1 with lithium diisopropylamide (LDA) followed by addition of paraformaldehyde afforded regioisomer (+)-{[S(S)] - [4-(2-hydroxyethyl)phenyl]sulfinyl}ferrocene (2), which was converted to (+)-{[S(S)] - {4-{2-[(methylsulfonyl)oxy]ethyl}phenyl}sulfinyl}ferrocene (3) (Scheme,1). The desired diastereoisomer (l)-1-(hydroxymethyl)-2-(p -tolylsulfinyl)ferrocene (5) in turn could also be obtained by ortho lithiation of 1 with LDA but by quenching with DMF to yield aldehyde 4 first, which then was reduced with NaBH4 to 5. Finally, target compound (l)-1-[(dimethylamino)methyl]-2-(p -tolylsulfinyl)ferrocene (6) was obtained by substitution of the OH group of 5 under mild conditions or directly by ortho lithiation of 1 with lithio-2,4,6-triisopropylbenzene (=2,4,6-triisopropylphenyl)lithium; LTP) followed by quenching with N,N -dimethylmethyleneiminium chloride. At low temperatures, reaction of 1 with LDA leads, via the preferred diastereoisomeric transition state ,exo'- 7 and under extrusion of a (diisopropylamine)lithium complex of type 8, in a highly selective manner, to diastereoisomeric ortho -lithiated chelate (l)- 9 (Scheme,2). The reaction of 1 to 2 is explained by a rearrangement of (l)- 9 to {[S(S)],[4-(lithiomethyl)phenyl]sulfinyl}ferrocene 10, which is acid-catalyzed by coordinated diisopropylamine in complexes of type 8. This rearrangement is not observed if LTP is used as base or, in case LDA is applied, if the electrophile is sufficiently reactive at low temperatures. [source] Linear models for minimizing misclassification costs in bankruptcy predictionINTELLIGENT SYSTEMS IN ACCOUNTING, FINANCE & MANAGEMENT, Issue 3 2001Sudhir Nanda This paper illustrates how a misclassification cost matrix can be incorporated into an evolutionary classification system for bankruptcy prediction. Most classification systems for predicting bankruptcy have attempted to minimize misclassifications. The minimizing misclassification approach assumes that Type I and Type II error costs for misclassifications are equal. There is evidence that these costs are not equal and incorporating costs into the classification systems can lead to better and more desirable results. In this paper, we use the principles of evolution to develop and test a genetic algorithm (GA) based approach that incorporates the asymmetric Type I and Type II error costs. Using simulated and real-life bankruptcy data, we compare the results of our proposed approach with three linear approaches: statistical linear discriminant analysis (LDA), a goal programming approach, and a GA-based classification approach that does not incorporate the asymmetric misclassification costs. Our results indicate that the proposed approach, incorporating Type I and Type II error costs, results in lower misclassification costs when compared to LDA and GA approaches that do not incorporate misclassification costs. Copyright © 2001 John Wiley & Sons, Ltd. [source] Independent comparative study of PCA, ICA, and LDA on the FERET data setINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 5 2005Kresimir Delac Abstract Face recognition is one of the most successful applications of image analysis and understanding and has gained much attention in recent years. Various algorithms were proposed and research groups across the world reported different and often contradictory results when comparing them. The aim of this paper is to present an independent, comparative study of three most popular appearance-based face recognition projection methods (PCA, ICA, and LDA) in completely equal working conditions regarding preprocessing and algorithm implementation. We are motivated by the lack of direct and detailed independent comparisons of all possible algorithm implementations (e.g., all projection,metric combinations) in available literature. For consistency with other studies, FERET data set is used with its standard tests (gallery and probe sets). Our results show that no particular projection,metric combination is the best across all standard FERET tests and the choice of appropriate projection,metric combination can only be made for a specific task. Our results are compared to other available studies and some discrepancies are pointed out. As an additional contribution, we also introduce our new idea of hypothesis testing across all ranks when comparing performance results. © 2006 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 252,260, 2005 [source] Cross-layer design to improve elastic traffic performance in WLANsINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 3 2008Stephane Lohier In this paper, we are interested in improving TCP flow performance when a short loss of 802.11 signal leads to losing segments and triggers inappropriately TCP congestion control mechanisms. A set of measurements in a common wireless environment with signal losses due to mobility or interference is made to highlight the distinct MAC and TCP loss recovery levels and the lack of interactions between them. Initially, we demonstrate the interest of adapting the 802.11 MAC layer Retry Limit parameter in the case of signal losses due to distance or obstacles (mobility). Thus, a first-level loss differentiation algorithm (LDA) acting at the MAC layer is proposed to improve TCP flow performance in the case of segment losses due to mobility. Hence, for a signal failure, the MAC layer reacts consequently by dynamically adapting the Retry Limit parameter. This adaptation allows avoiding a costly end-to-end TCP loss recovery. Segment losses due to interference are differentiated from those due to congestion through the use of a second-level LDA. The latter is a cross-layer LDA acting at the TCP layer but using a specific 802.11 parameter, the AckFailureCount, to realize the targeted loss differentiation. The TCP NewReno version is then adapted in order to integrate the cross-layer LDA results and to avoid reducing the TCP congestion window unsuitably. The efficiency and completeness of a solution integrating both LDA schemes is then discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Calculation of quasiparticle energy of molecular systems by the GW methodINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2001Y. Ohta Abstract The quasiparticle energy of the H2 molecule is calculated by using the GW method, in which the self-energy operator fully depends on the frequency. The initial Green function G0 is constructed from the wave function obtained by the Hartree,Fock approximation (HFA) and local density approximation (LDA) in the framework of the density functional theory (DFT). From the results obtained we have shown that the wave function from the DFT,LDA is more effective than that from the HFA for G0. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 348,353, 2001 [source] Partial least squares for discriminationJOURNAL OF CHEMOMETRICS, Issue 3 2003Matthew Barker Abstract Partial least squares (PLS) was not originally designed as a tool for statistical discrimination. In spite of this, applied scientists routinely use PLS for classification and there is substantial empirical evidence to suggest that it performs well in that role. The interesting question is: why can a procedure that is principally designed for overdetermined regression problems locate and emphasize group structure? Using PLS in this manner has heurestic support owing to the relationship between PLS and canonical correlation analysis (CCA) and the relationship, in turn, between CCA and linear discriminant analysis (LDA). This paper replaces the heuristics with a formal statistical explanation. As a consequence, it will become clear that PLS is to be preferred over PCA when discrimination is the goal and dimension reduction is needed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Unified QSAR & network-based computational chemistry approach to antimicrobials.JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 1 2010Abstract In the previous work, we reported a multitarget Quantitative Structure-Activity Relationship (mt-QSAR) model to predict drug activity against different fungal species. This mt-QSAR allowed us to construct a drug,drug multispecies Complex Network (msCN) to investigate drug,drug similarity (González-Díaz and Prado-Prado, J Comput Chem 2008, 29, 656). However, important methodological points remained unclear, such as follows: (1) the accuracy of the methods when applied to other problems; (2) the effect of the distance type used to construct the msCN; (3) how to perform the inverse procedure to study species,species similarity with multidrug resistance CNs (mdrCN); and (4) the implications and necessary steps to perform a substructural Triadic Census Analysis (TCA) of the msCN. To continue the present series with other important problem, we developed here a mt-QSAR model for more than 700 drugs tested in the literature against different parasites (predicting antiparasitic drugs). The data were processed by Linear Discriminate Analysis (LDA) and the model classifies correctly 93.62% (1160 out of 1239 cases) in training. The model validation was carried out by means of external predicting series; the model classified 573 out of 607, that is, 94.4% of cases. Next, we carried out the first comparative study of the topology of six different drug,drug msCNs based on six different distances such as Euclidean, Chebychev, Manhattan, etc. Furthermore, we compared the selected drug,drug msCN and species,species mdsCN with random networks. We also introduced here the inverse methodology to construct species,species msCN based on a mt-QSAR model. Last, we reported the first substructural analysis of drug,drug msCN using Triadic Census Analysis (TCA) algorithm. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010 [source] Performance of plane-wave-based LDA+U and GGA+U approaches to describe magnetic coupling in molecular systems,JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 14 2009Pablo Rivero Abstract This work explores the performance of periodic plane wave density functional theory calculations with an on-site Coulomb correction to the standard LDA and GGA exchange-correlation potential,commonly used to describe strongly correlated solids,in describing the magnetic coupling constant of a series of molecular compounds representative of dinuclear Cu complexes and of organic diradicals. The resulting LDA+U or GGA+U formalisms, lead to results comparable to experiment and to those obtained by means of standard hybrid functionals provided that the value of the U parameter is adequately chosen. Hence, these methods offer an alternative efficient computational scheme to correct LDA and GGA approaches to adequately describe the electronic structure and magnetic coupling in large molecular magnetic systems, although at the expenses of introducing an empirical (U) parameter. For all investigated copper dinuclear systems, the LDA+U and GGA+U approaches lead to an improvement in the description of magnetic properties over the original LDA and GGA schemes with an accuracy similar to that arising from the hybrid B3LYP functional, by increasing the on-site Coulomb repulsion with a moderate U value. Nevertheless, the introduction of an arbitrary U value in the 0,10 eV range most often provides the correct ground-state spin distribution and the correct sign of the magnetic coupling constant. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009 [source] Ab-initio simulations of materials using VASP: Density-functional theory and beyondJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2008Jürgen Hafner Abstract During the past decade, computer simulations based on a quantum-mechanical description of the interactions between electrons and between electrons and atomic nuclei have developed an increasingly important impact on solid-state physics and chemistry and on materials science,promoting not only a deeper understanding, but also the possibility to contribute significantly to materials design for future technologies. This development is based on two important columns: (i) The improved description of electronic many-body effects within density-functional theory (DFT) and the upcoming post-DFT methods. (ii) The implementation of the new functionals and many-body techniques within highly efficient, stable, and versatile computer codes, which allow to exploit the potential of modern computer architectures. In this review, I discuss the implementation of various DFT functionals [local-density approximation (LDA), generalized gradient approximation (GGA), meta-GGA, hybrid functional mixing DFT, and exact (Hartree-Fock) exchange] and post-DFT approaches [DFT + U for strong electronic correlations in narrow bands, many-body perturbation theory (GW) for quasiparticle spectra, dynamical correlation effects via the adiabatic-connection fluctuation-dissipation theorem (AC-FDT)] in the Vienna ab initio simulation package VASP. VASP is a plane-wave all-electron code using the projector-augmented wave method to describe the electron-core interaction. The code uses fast iterative techniques for the diagonalization of the DFT Hamiltonian and allows to perform total-energy calculations and structural optimizations for systems with thousands of atoms and ab initio molecular dynamics simulations for ensembles with a few hundred atoms extending over several tens of ps. Applications in many different areas (structure and phase stability, mechanical and dynamical properties, liquids, glasses and quasicrystals, magnetism and magnetic nanostructures, semiconductors and insulators, surfaces, interfaces and thin films, chemical reactions, and catalysis) are reviewed. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Applying pattern recognition methods plus quantum and physico-chemical molecular descriptors to analyze the anabolic activity of structurally diverse steroidsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2008Yoanna María Alvarez-Ginarte Abstract The great cost associated with the development of new anabolic,androgenic steroid (AASs) makes necessary the development of computational methods that shorten the drug discovery pipeline. Toward this end, quantum, and physicochemical molecular descriptors, plus linear discriminant analysis (LDA) were used to analyze the anabolic/androgenic activity of structurally diverse steroids and to discover novel AASs, as well as also to give a structural interpretation of their anabolic,androgenic ratio (AAR). The obtained models are able to correctly classify 91.67% (86.27%) of the AASs in the training (test) sets, respectively. The results of predictions on the 10% full-out cross-validation test also evidence the robustness of the obtained model. Moreover, these classification functions are applied to an "in house" library of chemicals, to find novel AASs. Two new AASs are synthesized and tested for in vivo activity. Although both AASs are less active than some commercially AASs, this result leaves a door open to a virtual variational study of the structure of the two compounds, to improve their biological activity. The LDA-assisted QSAR models presented here, could significantly reduce the number of synthesized and tested AASs, as well as could increase the chance of finding new chemical entities with higher AAR. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Energy landscapes of nucleophilic substitution reactions: A comparison of density functional theory and coupled cluster methodsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2007Marcel Swart Abstract We have carried out a detailed evaluation of the performance of all classes of density functional theory (DFT) for describing the potential energy surface (PES) of a wide range of nucleophilic substitution (SN2) reactions involving, amongst others, nucleophilic attack at carbon, nitrogen, silicon, and sulfur. In particular, we investigate the ability of the local density approximation (LDA), generalized gradient approximation (GGA), meta-GGA as well as hybrid DFT to reproduce high-level coupled cluster (CCSD(T)) benchmarks that are close to the basis set limit. The most accurate GGA, meta-GGA, and hybrid functionals yield mean absolute deviations of about 2 kcal/mol relative to the coupled cluster data, for reactant complexation, central barriers, overall barriers as well as reaction energies. For the three nonlocal DFT classes, the best functionals are found to be OPBE (GGA), OLAP3 (meta-GGA), and mPBE0KCIS (hybrid DFT). The popular B3LYP functional is not bad but performs significantly worse than the best GGA functionals. Furthermore, we have compared the geometries from several density functionals with the reference CCSD(T) data. The same GGA functionals that perform best for the energies (OPBE, OLYP), also perform best for the geometries with average absolute deviations in bond lengths of 0.06 Å and 0.6°, even better than the best meta-GGA and hybrid functionals. In view of the reduced computational effort of GGAs with respect to meta-GGAs and hybrid functionals, let alone coupled cluster, we recommend the use of accurate GGAs such as OPBE or OLYP for the study of SN2 reactions. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Application of standard DFT theory for nonbonded interactions in soft matter: Prototype study of poly- para -phenyleneJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 2 2006Marcelo Alves-Santos Abstract We present a detailed analysis of the application of density functional theory (DFT) methods to the study of structural properties of molecular and supramolecular systems, using as a paradigmatic example three para -phenylene-based systems: isolated biphenyl, single chain poly- para -phenylene, and crystalline biphenyl. We use different functionals for the exchange correlation potential, the local density (LDA), and generalized gradient approximations (GGA), and also different basis sets expansions, localized, plane waves (PW), and mixed (localized plus PW), within the reciprocal space formulation for the hamiltonian. We find that regardless of the choice of basis functions, the GGA calculations yield larger interring distances and torsion angles than LDA. For the same XC approximation, the agreement between calculations with different basis functions lies within 1% (LDA) or 0.5% (GGA) for distances, and while PW and mixed basis calculations agree within 1° for torsion angles, the localized basis results show larger angles by , 8° and a nonmonotonic dependence on basis size, with differences within 6°. The most prominent features, namely the torsion between rings for isolated molecule and infinite chain, and planarity for the molecule in crystalline environment, are well reproduced by all DFT calculations. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 217,227, 2006 [source] Electronic structure, chemical bonding, and finite-temperature magnetic properties of full Heusler alloysJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 1 2006Yasemin Kurtulus Abstract The electronic structure, chemical bonding, and magnetic properties of 15 full Heusler alloys X2MnZ have been studied on the basis of density-functional theory using the TB-LMTO-ASA approach and the local-density (LDA), as well as the generalized-gradient approximation (GGA). Correlations between the chemical bondings derived from crystal orbital Hamilton population (COHP) analysis and magnetic phenomena are obvious, and different mechanisms leading to spin polarization and ferromagnetism are derived. As long as a magnetically active metal atom X is present, antibonding XX and XMn interactions at the Fermi level drive the systems into the ferromagnetic ground state; only if X is nonmagnetic (such as in Cu2MnZ), antibonding MnMn interactions arise, which again lead to ferromagnetism. Finite-temperature effects (Curie temperatures) are analyzed using a mean-field description, and a surprisingly simple (or, trivial) relationship between structural properties (MnMn interatomic distances) and TC is found, being of semiquantitative use for the prediction of the latter. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 90,102, 2006 [source] Calculation of the vibration frequencies of ,-quartz: The effect of Hamiltonian and basis setJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 15 2004C. M. Zicovich-Wilson Abstract The central-zone vibrational spectrum of ,-quartz (SiO2) is calculated by building the Hessian matrix numerically from the analytical gradients of the energy with respect to the atomic coordinates. The nonanalytical part is obtained with a finite field supercell approach for the high-frequency dielectric constant and a Wannier function scheme for the evaluation of Born charges. The results obtained with four different Hamiltonians, namely Hartree,Fock, DFT in its local (LDA) and nonlocal gradient corrected (PBE) approximation, and hybrid B3LYP, are discussed, showing that B3LYP performs far better than LDA and PBE, which in turn provide better results than HF, as the mean absolute difference from experimental frequencies is 6, 18, 21, and 44 cm,1, respectively, when a split valence basis set containing two sets of polarization functions is used. For the LDA results, comparison is possible with previous calculations based on the Density Functional Perturbation Theory and usage of a plane-wave basis set. The effects associated with the use of basis sets of increasing size are also investigated. It turns out that a split valence plus a single set of d polarization functions provides frequencies that differ from the ones obtained with a double set of d functions and a set of f functions on all atoms by on average less than 5 cm,1. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1873,1881, 2004 [source] Rapid Determination of Invert Cane Sugar Adulteration in Honey Using FTIR Spectroscopy and Multivariate AnalysisJOURNAL OF FOOD SCIENCE, Issue 6 2003J. Irudayaraj ABSTRACT: Fourier transform infrared spectroscopy with an attenuated total reflection sampling accessory was combined with multivariate analysis to determine the level (1% to 25%, wt/wt) of invert cane sugar adulteration in honey. On the basis of the spectral data compression by principal component analysis and partial least squares, linear discriminant analysis (LDA), and canonical variate analysis (CVA), models were developed and validated. Two types of artificial neural networks were applied: a quick back propagation network (BPN) and a radial basis function network (RBFN). The prediction success rates were better with LDA (93.75% for validation set) and BPN (93.75%) than with CVA (87.50%) and RBFN (81.25%). [source] Multivariate analysis approach to the plasma protein profile of patients with advanced colorectal cancer,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2006Eugenio Ragazzi Abstract The aim of the present study was to identify the pattern of plasma protein species of interest as markers of colorectal cancer (CRC). Using matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS), the plasma protein profile was determined in nine stage IV CRC patients (study group) and nine clean-colon healthy subjects (control group). Multivariate analysis methods were employed to identify distinctive disease patterns at protein spectrum. In the study and control groups, cluster analysis (CA) on the complete MALDI-MS spectra plasma protein profile showed a distinction between CRC patients and healthy subjects, thus allowing the identification of the most discriminating ionic species. Principal component analysis (PCA) and linear discriminant analysis (LDA) yielded similar grouping results. LDA with leave-one-out cross validation achieved a correct classification rate of 89% in both the patients and the healthy subjects. Copyright © 2006 John Wiley & Sons, Ltd. [source] Dynamic behavior of the flow field in a RIM machine mixing chamberAICHE JOURNAL, Issue 6 2009Ricardo J. Santos Abstract Dynamic behavior of the flow field in a Reaction Injection Molding, RIM, machine mixing chamber, having dimensions typically used in industrial machines, is studied from dynamic velocity data of Laser Doppler Anemometry, LDA, measurements and Computational Fluid Dynamics, CFD, simulations with a 2D model. This study is based on the spectral analysis of the dynamic flow field data. The typical frequencies, in the reactor flow field, are identified and its values are related to the identified flow structures. The differences between the typical frequencies from experiments and simulations are observed and justified on the basis of the 2D representation of a 3D cylindrical geometry. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] In situ Raman and optical microscopy of the relaxation behavior of amorphous ices under pressureJOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2010Yukihiro Yoshimura Abstract The transformation of low-density amorphous (LDA) ice produced from high-density amorphous (HDA) ice was studied up to 400 MPa as a function of temperature by in situ Raman spectroscopy and optical microscopy. Changes in these amorphous states of H2O were directly tracked without using emulsions to just above the crystallization temperature Tx. The spectra show significant changes occurring above ,125 K. The results are compared with data reported for the relaxation behavior of HDA, to form what we call relaxed HDA, or rHDA. We find a close connection with expanded HDA (eHDA), which is reported to exist as another metastable form in this P,T region. The observation of this temperature-induced LDA transition under pressure complements the previously observed pressure-induced reversible transition between LDA and HDA at 120,140 K. Copyright © 2009 John Wiley & Sons, Ltd. [source] Possible Pleiotropic Effects of Genes Specifying Sedative/Hypnotic Sensitivity to Ethanol on Other Alcohol-Related TraitsALCOHOLISM, Issue 10 2002Jeremy C. Owens Background Initial sensitivity to ethanol is a predictor of alcohol abuse that has been studied extensively in both human and animal populations. Selection for initial sensitivity to the sedative/hypnotic effects of ethanol resulted in the long-sleep and short-sleep lines of mice. Some of the genes selected in these lines could also specify differential responses in other ethanol-related phenotypes and, perhaps, for other drugs of abuse. We assessed congenic mice carrying a single quantitative trait locus (QTL) from the inbred long-sleep (ILS) or inbred short-sleep (ISS) strain on the reciprocal background for a number of ethanol- and pentobarbital-related phenotypes. Methods Each congenic strain was tested for ethanol elimination rates at 4.1 g/kg, ethanol-induced ataxia at 2.0 g/kg, ethanol-induced hypothermia at 4.1 g/kg, and pentobarbital-induced loss of righting reflex (LORR) at 60 mg/kg. Additionally, the ILS.ISS congenics were tested for low-dose ethanol-induced activation (LDA) at five doses ranging from 0.6 to 1.2 g/kg ethanol, and the ISS.ILS congenics were tested for LDA at 1.8 g/kg of ethanol. Results There was little difference in the ethanol elimination rate between congenics and background strains, although a modest sex effect was found, with the females eliminating ethanol more rapidly than the males. We were unable to replicate previous differences found in LDA for the Lore1 congenic on the ISS background, because none of the congenics differed from controls for LDA. Lore5 congenics showed a differential effect of pentobarbital-induced LORR in the expected directions. The Lore1 congenics on the ISS background showed more ethanol-induced ataxia than the ISS controls. Additionally, the hypothermic response seems affected by Lore4 and Lore5 and maybe others. Conclusions At least two regions carrying a QTL specifying sensitivity to high doses of ethanol cospecify altered sensitivity in other measures of alcohol action. Specifically, these QTLs clearly affect ethanol-induced hypothermia and pentobarbital-induced LORR and possibly ethanol-induced ataxia. [source] Evidence That the Lore-1 Region Specifies Ethanol-Induced Activation in Addition to Sedative/Hypnotic Sensitivity to EthanolALCOHOLISM, Issue 11 2001Jeremy C. Owens Background: Low-dose ethanol-induced activation (LDA) and initial sensitivity to alcohol are both predictors of alcohol abuse in human populations. Our hypothesis is that one or more genes specifying hypnotic sensitivity also specify LDA. We tested this hypothesis by using congenic mice derived from the inbred long-sleep (ILS) and inbred short-sleep (ISS) strains, which carry an ILS region introgressed onto an ISS background. Methods: LDA was assessed by assigning mice randomly to receive one of five doses of ethanol ranging from 1.2 to 2.4 g/kg. On day 1, animals were injected with saline and placed in a brightly lit activity monitor for 30 min, after which they were returned to their home cages. On day 2, mice were injected with ethanol (20% w/v), their activity was monitored for a 30-min period, and LDA was determined by subtracting day 1 activity. The blood ethanol concentration of each animal was then assessed at 30 min by retro-orbital collection of 25 ,l of blood. Results: Ethanol had a significant effect on the activity of ISS mice, but ILS mice showed no activation at any dose, similar to the activities of the outbred lines. All three congenic strains were activated at several doses. Lore-2 and Lore-5 were not ILS-like (less active than ISS) at any dose. In contrast, ISS.ILS- Lore-1 congenics (carrying an ILS-derived Lore-1 allele on the ISS background) were significantly less activated than the ISS controls at 1.8 and 2.4 g/kg of ethanol. Conclusions: The Lore-2 and Lore-5 congenic regions do not affect LDA. In contrast, the Lore-1 congenic region carries one or more genes specifying both initial hypnotic sensitivity to ethanol and LDA. [source] Differentiation of eight tea (Camellia sinensis) cultivars in China by elemental fingerprint of their leavesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2009Yingxu Chen Abstract BACKGROUND: Tea is an infusion made from dried leaves of tea (Camellia sinensis) and can be a good dietary source of essential trace metals for humans. Therefore, it is necessary to consider variations in element content of tea leaves among tea cultivars. Thus, elemental fingerprint techniques, based on elemental contents (Al, B, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, P, Pb, and Zn) determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and multivariate statistical analysis, have been used to differentiate eight tea cultivars. RESULTS: The ranges of element concentrations in leaves of the eight cultivars were in good agreement with those obtained in previous studies and the level of most elements in tea leaves was significantly different among cultivars. The classifications of eight tea cultivars were 100% accurate in total by principal component analysis (PCA), hierarchical cluster analysis (HCA), linear discriminant analysis (LDA), and back-propagation neural network (BPNN) analysis. CONCLUSION: Each cultivar presented a distinctive element fingerprint and the elements in tea leaves can be significant predictors in differentiating tea cultivars. Copyright © 2009 Society of Chemical Industry [source] Discrimination and classification of adulterants in maple syrup with the use of infrared spectroscopic techniquesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2002M Paradkar Abstract Food adulteration is a profit-making business for some unscrupulous manufacturers. Maple syrup is a soft target for adulterators owing to its simplicity of chemical composition. The use of infrared spectroscopic techniques such as Fourier transform infrared (FTIR) and near-infrared (NIR) as a tool to detect adulterants such as cane and beet invert syrups as well as cane and beet sugar solutions in maple syrup was investigated. The FTIR spectra of adulterated samples were characterised and the regions of 800,1200,cm,1 (carbohydrates) and 1200,1800 and 2800,3200,cm,1 (carbohydrates, carboxylic acids and amino acids) were used for detection. The NIR spectral region between 1100 and 1660,nm was used for analysis. Linear discriminant analysis (LDA) and canonical variate analysis (CVA) were used for discriminant analysis, while partial least squares (PLS) and principal component regression (PCR) were used for quantitative analysis. FTIR was more accurate in predicting adulteration using the two different regions (R2,>,0.93 and 0.98) compared with NIR (R2,>,0.93). Classification and quantification of adulterants in maple syrup show that both NIR and FTIR can be used for detecting adulterants such as pure beet and cane sugar solutions, but FTIR was superior to NIR in detecting invert syrups. © 2002 Society of Chemical Industry [source] Serum Amyloid A and Haptoglobin Concentrations and Liver Fat Percentage in Lactating Dairy Cows with Abomasal DisplacementJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2010H. Guzelbektes Background: There has been increased interest in measuring the serum concentration of acute phase reactants such as serum amyloid A [SAA] and haptoglobin [haptoglobin] in periparturient cattle in order to provide a method for detecting the presence of inflammation or bacterial infection. Objectives: To determine whether [SAA] and [haptoglobin] are increased in cows with displaced abomasum as compared with healthy dairy cows. Animals: Fifty-four adult dairy cows in early lactation that had left displaced abomasum (LDA, n = 34), right displaced abomasum or abomasal volvulus (RDA/AV, n = 11), or were healthy on physical examination (control, n = 9). Materials and Methods: Inflammatory diseases or bacterial infections such as mastitis, metritis, or pneumonia were not clinically apparent in any animal. Jugular venous blood was obtained from all cows and analyzed. Liver samples were obtained by biopsy in cattle with abomasal displacement. Results: [SAA] and [haptoglobin] concentrations were increased in cows with LDA or RDA/AV as compared with healthy controls. Cows with displaced abomasum had mild to moderate hepatic lipidosis, based on liver fat percentages of 9.3 ± 5.3% (mean ± SD, LDA) and 10.8 ± 7.7% (RDA/AV). [SAA] and [haptoglobin] were most strongly associated with liver fat percentage, rs=+0.55 (P < .0001) and rs=+0.42 (P= .0041), respectively. Conclusions and Clinical Importance: An increase in [SAA] or [haptoglobin] in postparturient dairy cows with LDA or RDA/AV is not specific for inflammation or bacterial infection. An increase in [SAA] or [haptoglobin] may indicate the presence of hepatic lipidosis in cattle with abomasal displacement. [source] Use of the d -Xylose Absorption Test to Measure Abomasal Emptying Rate in Healthy Lactating Holstein-Friesian Cows and in Cows with Left Displaced Abomasum or Abomasal VolvulusJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 6 2005Thomas Wittek We determined the abomasal emptying rates of Holstein-Friesian cows at different stages of lactation, with left displaced abomasum (LDA), or immediately after surgical correction of LDA or abomasal volvulus (AV). d -xylose (0.5 g/kg body weight [BW], 50% solution) was injected into the abomasum in healthy cows (group 1, 4,7 days in milk [DIM], n = 7; group 2, 90,120 DIM, n = 7; group 3, >300 DIM, n = 7) and in cows with LDA (n = 10; group 4). d -xylose was injected into the abomasum during right flank laparotomy in cows with LDA (n = 22; group 5) and cows with AV (n = 15; group 6). The time to maximal serum d -xylose concentration was used as an index of emptying rate. The abomasal emptying rates for cows in groups 1, 2, and 3 were similar, whereas emptying was slower in cows with LDA and in cows after surgical correction of LDA or AV. The abomasal emptying rate of cows with LDA was slowed to a greater extent immediately after surgery, when compared to the rate obtained before surgery. There was no difference in abomasal emptying rate immediately after surgical correction between cows with LDA or AV. The results indicate that the increased incidence of LDA in the first month of lactation is not associated with an intrinsic decrease in abomasal emptying rate in healthy cows. Our findings also demonstrate that surgical correction further slows the emptying rate in cows with LDA. [source] A longitudinal analysis of cytotoxic T lymphocyte precursor frequencies to the hepatitis B virus in chronically infected patientsJOURNAL OF VIRAL HEPATITIS, Issue 1 2001G. K. Sing Individuals with acute hepatitis B virus (HBV) infection characteristically mount a strong, multispecific cytotoxic T lymphocyte (CTL) response that is effective in eradicating virus. In contrast, this response in chronic carriers is usually weak or undetectable. Since it is generally acknowledged that HBV pathogenesis is immune-mediated, the occurrence of episodes of active liver disease in many carriers suggests that these individuals can mount active CTL responses to HBV. To see whether the detection of circulating CTLs is related to these flare episodes, we have determined the CTL precursor (CTLp) frequencies to HLA-A2-restricted viral peptides in seven patients over a 12,24-month period of their disease. Limiting dilution analyses (LDA) were performed longitudinally to five epitopes comprising the viral capsid (HBc), envelope (HBs) and polymerase (pol) proteins. Assays were performed against a mixture of peptides, or against each individual peptide, to measure overall CTL activity and the multispecificity of the responses, respectively. Since two of the patients were treated with recombinant human interleukin-12 (rHuIL-12) at the time, with one individual achieving complete disease remission a year later after being treated with interferon-,, we were also able to examine the effects of these cytokines on HBV cytotoxicity. Our results indicate that weak but detectable CTL responses do occur in chronic carriers which are generally associated with disease flares, although CTLps were also seen occasionally during minimal disease activity. The range of specificities varied between individuals and within each individual during the course of the disease. Finally, we also provide evidence that CTL reactivity is stimulated following treatment with certain cytokines, but is dependent on the time of administration. [source] Discriminant analysis of autofluorescence spectra for classification of oral lesions in vivoLASERS IN SURGERY AND MEDICINE, Issue 5 2009J.L. Jayanthi MSc, MPhil Abstract Background and Objectives Low survival rate of individuals with oral cancer emphasize the significance of early detection and treatment. Optical spectroscopic techniques are under various stages of development for diagnosis of epithelial neoplasm. This study evaluates the potential of a multivariate statistical algorithm to classify oral mucosa from autofluorescence spectral features recorded in vivo. Study Design/Methods Autofluorescence spectra were recorded in a clinical trial from 15 healthy volunteers and 34 patients with diode laser excitation (404,nm) and pre-processed by normalization, mean-scaling and its combination. Linear discriminant analysis (LDA) based on leave-one-out (LOO) method of cross validation was performed on spectral data for tissue characterization. The sensitivity and specificity were determined for different lesion pairs from the scatter plot of discriminant function scores. Results Autofluorescence spectra of healthy volunteers consists of a broad emission at 500,nm that is characteristic of endogenous fluorophores, whereas in malignant lesions three additional peaks are observed at 635, 685, and 705,nm due to the accumulation of porphyrins in oral lesions. It was observed that classification design based on discriminant function scores obtained by LDA-LOO method was able to differentiate pre-malignant dysplasia from squamous cell carcinoma (SCC), benign hyperplasia from dysplasia and hyperplasia from normal with overall sensitivities of 86%, 78%, and 92%, and specificities of 90%, 100%, and 100%, respectively. Conclusions The application of LDA-LOO method on the autofluorescence spectra recorded during a clinical trial in patients was found suitable to discriminate oral mucosal alterations during tissue transformation towards malignancy with improved diagnostic accuracies. Lasers Surg. Med. 41:345,352, 2009. © 2009 Wiley-Liss, Inc. [source] Temporally and spectrally resolved fluorescence spectroscopy for the detection of high grade dysplasia in Barrett's esophagusLASERS IN SURGERY AND MEDICINE, Issue 1 2003T. Joshua Pfefer PhD Abstract Background and Objectives Temporal and spectral fluorescence spectroscopy can identify adenomatous colonic polyps accurately. In this study, these techniques were examined as a potential means of improving the surveillance of high grade dysplasia (HGD) in Barrett's esophagus (BE). Study Design/Materials and Methods Using excitation wavelengths of 337 and 400 nm, 148 fluorescence spectra, and 108 transient decay profiles (at 550,±,20 nm) were obtained endoscopically in 37 patients. Corresponding biopsies were collected and classified as carcinoma, HGD, or low risk tissue (LRT) [non-dysplastic BE, indefinite for dysplasia (IFD), and low grade dysplasia (LGD)]. Diagnostic algorithms were developed retrospectively using linear discriminant analysis (LDA) to separate LRT from HGD. Results LDA produced diagnostic algorithms based solely on spectral data. Moderate levels of sensitivity (Se) and specificity (Sp) were obtained for both 337 nm (Se,=,74%, Sp,=,67%) and 400 nm (Se,=,74%, Sp,=,85%) excitation. Conclusions In the diagnosis of HGD in BE, steady-state fluorescence was more effective than time-resolved data, and excitation at 400 nm excitation was more effective than 337 nm. While fluorescence-targeted biopsy is approaching clinical usefulness, increased sensitivity to dysplastic changes,possibly through modification of system parameters,is needed to improve accuracy levels. Lasers Surg. Med. 32:10,16,2003. © 2003 Wiley-Liss, Inc. [source] Optical properties of pure and transition metal-doped indium oxidePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2009H. A. Rahnamaye Aliabad Abstract The band structure, the dielectric function, the reflectivity, the refractive index and the oscillator strength sum rule were calculated for pure In2O3 and alloyed In1.5T0.5O3 (where T represents Sc, Y, La and Ac) using density functional theory (DFT). The full potential linearized augmented plane wave (FP-LAPW) method was used with the local density approximation (LDA + U). Calculations of the optical spectra were performed for the energy range 0,30 eV. The calculated results indicate that the upper valance bands of In2O3 show a small dispersion and the value of the band gap increases for Sc and Y dopants and decreases for Ac and La dopants. The calculations indicate that there are two band gaps for In2O3. The first shows a strong optical absorption, as a direct band gap occurs from a 0.81 eV energy level below the top of valence band. The second shows a much weaker absorption from the top of the valence band to the bottom of the conduction band. The refractive index for In2O3 is 1.69 nm at 800 nm, near the visible region. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||||||||||||||