Reciprocity relation in scattering by media subjected to an external magnetic field

Summary Krishnan's reciprocity theorem in colloid optics,ϱ _u=1+l/ϱ_h/1+1/ϱ _v is generalised for the case when the scattering medium is subjected to an external orienting field. It is shown theoretically that a general relation of the typeI _B ^A =I′ _A ^B results in this case, whereI _B ^A is the intensity of the component of the scattered light having its electric vector inclined at an angleB to the vertical with the incident light polarised at an angleA to the vertical, the external field direction being parallel to the incident beam.I′ _A ^B is the corresponding intensity with the magnetic field parallel of the scattered ray. Experimental verification of the above generalisation is also given.

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Zusammenfassung Krishnans Reziprozit?tstheoremϱ _u=1+1/ϱ _h/1+1/ϱ _v wird für den Fall verallgemeinert, da\ das streuende Medium einem ?u\eren orientierenden Feld unterliegt. Es l?\t sich theoretisch zeigen, da\ in diesem Fall eine allgemeine Beziehung des TypsI _B ^A =I′ _A ^B resultiert, in derI _B ^A die Intensit?t der Komponente des Streulichts mit dem elektrischen Vektor um den WinkelB zur Vertikalen geneigt bei einfallendem Licht um einen WinkelA zur Vertikalen polarisiert angibt, und das ?u\ere Feld parallel zum einfallenden Strahl liegt.I′ _A ^B ist die entsprechende Intensit?t mit dem Magnetfeld parallel zum gestreuten Strahl. Eine experimentelle Best?tigung der genannten Verallgemeinerung wird gegeben.

     

Ensemble methods and data augmentation by noise addition applied to the analysis of spectroscopic data

Near-infrared spectroscopy has gained great acceptance in the industry due to its multiple applications and versatility. Sometimes, however, the construction of accurate and robust calibration models involves the collection of a large number of samples with related reference analysis that can complicate and prolong the calibration stage.In this paper, ensemble methods and data augmentation by noise simulation have been applied to spectroscopic data in combination with PLSR to obtain robust models able to handle different types of perturbations likely to affect NIR data. Several types of noise have been investigated as well as different ensemble methods focused on obtaining robust PLS models able to predict both the original and the perturbed test data.The suitability of ensemble methods to perform robust calibration models has been investigated and compared to extended multiplicative signal correction (EMSC) and other calibration approaches in a real case of temperature compensation. Extended multiplicative signal correction (EMSC) and ensemble methods seem to be the most appropriate methods yielding the best results in terms of accuracy and prediction ability with a reduced calibration data set.     

Identification of discriminatory variables in proteomics data analysis by clustering of variables

This article presents a data analysis method for biomarker discovery in proteomics data analysis. In factor analysis-based discriminate models, the latent variables (LV's) are calculated from the response data measured at all employed instrument channels. Since some channels are irrelevant and their responses do not possess useful information, the extracted LV's possess mixed information from both useful and irrelevant channels. In this work, clustering of variables (CLoVA) based on unsupervised pattern recognition is suggested as an efficient method to identify the most informative spectral region and then it is used to construct a more predictive multivariate classification model. In the suggested method, the instrument channels (m/z value) are clustered into different clusters via self-organization map. Subsequently, the spectral data of each cluster are separately used as the input variables of classification methods such as partial least square-discriminate analysis (PLS-DA) and extended canonical variate analysis (ECVA). The proposed method is evaluated by the analysis of two experimental data sets (ovarian and prostate cancer data set). It is found that our proposed method is able to detect cancerous from healthy samples with much higher sensitivity and selectivity than conventional PLS-DA and ECVA methods.     

Application of cause-and-effect diagrams to the interpretation of UV-Vis spectroscopic data

The application of cause-and-effect diagrams to the evaluation of thermodynamic data from UV-Vis absorption spectroscopic analysis is demonstrated. The contributions of measurement uncertainty identified from a cause-and-effect diagram are implemented into a Monte Carlo procedure based on the threshold bootstrap computer-assisted target factor analysis (TB CAT). This algorithm aims at an improvement of data comparability and accounts for non-normality, spectral, residual and parameter correlation as well as random noise in target factor analysis. The ISO Type-B measurement uncertainties are included into the process by normally distributed random numbers with specified mean values and dispersions. The TB CAT procedure is illustrated by a flow diagram and a case study of Nd(III) complexation by picolinic acid N-oxide (pic NO) in aqueous solution. Using 12 experimental spectra as input data, the single component spectra and the formation constant 1g betaML of the Nd(pic NO)2+ species are obtained together with the respective probability density distributions. The role of the cause-and-effects approach on the further development of chemical thermodynamics is discussed.     

On the phenomena of deformation and neck formation in LLDPE films subjected to uniaxial and biaxial loading conditions

Heterogeneous deformation in the form of dilatational bands is observed under certain biaxial stress states that closely resembles uniaxial necking in LLDPE blown films. The formation and orientation of dilatational bands is a function of film morphology and stress state. The dilatational bands form, with their lengths aligned with the machine direction (MD) of the film, under equibiaxial stress states and nonequibiaxial stress states when the higher principle stress is coincident with the transverse direction (TD). However, homogeneous deformation is observed if the higher principle stress is coincident with the MD. Similarly, uniaxial specimens show necking when the stress is applied in the TD and affine deformation when the stress is applied in the MD. Neck boundary propagation under uniaxial loading is due primarily to the consumption of undrawn material, while dilatational band boundary propagation under an equibiaxial loading also includes simultaneous continued deformation of the drawn material. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2651–2663, 1999     

Multivariate analysis of ATR-IR spectroscopic data: applications to the solid-liquid catalytic interface

It is demonstrated that attenuated total reflection infrared (ATR-IR) spectroscopy coupled with multivariate data analysis can be effectively used for in situ investigation of supported catalyst-liquid interfaces. Both formaldehyde adsorption/dissociation in water and acetonitrile adsorption in hexane on thin (ca 10 mum) films of 5 wt % Pt/gamma-Al(2)O(3) deposited on a germanium waveguide have been investigated. The multivariate analysis applies classical least squares (CLS) and partial least squares (PLS) methods to the ATR-IR data in order to correlate spectral changes with known sources of experimental variation (i.e., time, concentration of solution species, etc.). The formaldehyde adsorption experiments revealed no spectroscopic evidence for adsorbed molecular formaldehyde under the conditions examined. However, the dissociation product carbon monoxide was observed to form in atop configuration on Pt, likely on edges and terrace sites. Isotope labeling experiments suggest that a pair of peaks observed at 1990 and 2060 cm(-)(1) during treatments of Pt in H(2)-saturated water arise at least in part from nu(Pt)(-)(H) stretching of adsorbed atomic hydrogen. Acetonitrile was found to adsorb on the Pt catalyst by sigma-bonding of the CN group with the platinum, yielding apparent surface peaks that are almost identical to that observed in the liquid phase. A peak at 1641 cm(-)(1) was observed which was assigned to the adsorption of the CN group in a tilted configuration involving a combination of end-on and pi interaction with the surface. This species was found to be reactive toward hydrogen, suggesting that it might play a role in nitrile hydrogenation. The prospects of using this approach to examine solid-catalyzed liquid-phase reactions are discussed in light of these findings.     

State of the structural hydroxyl groups in minerals of the kaolinite group according to infrared spectroscopic data

An interpretation of the IR spectra of kaolinite, dickite, and nacrite is proposed, based on the concept of resonance interaction of two intrasurface hydroxyl groups, and their manifestation in the spectrum as a split doublet 30 cm^–1 and by the individual vibration of a third intrasurface OH-group. The structural identification of each band in the IR spectra of the kaolinite minerals is given. It was demonstrated that thermal dehydroxylation under vacuum of kaolinite occurred in two stages with activation energies of 43 and 84 kJ/mole. The activation energy of proton delocalization of the structural hydroxyl groups of kaolinite has been evaluated (E 13 kJ/mole). The contribution of the energy of the interlayer hydrogen bonds (AH 28 kJ/mole) to the total cohesion energy of adjoining layers of kaolinite (E_c 165 kJ/mole) was calculated.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 1, pp. 73–81, January–February, 1985.     

Improving the accuracy of the spatial discretization in finite-difference electrochemical kinetic simulations, by means of the extended Numerov method

The fourth-order accurate, three-point finite-difference Numerov spatial discretization provides accurate and efficient solutions to the time-dependent governing differential equations of electrochemical kinetics in one-dimensional space geometry, when the equations contain first time derivatives of the solution, second spatial derivatives, and homogeneous reaction terms only. However, the original Numerov discretization is not applicable when the governing equations involve first spatial derivative terms. To overcome this limitation, an appropriately extended Numerov discretization is required. We examine the utility of one of such extensions, first described by Chawla. Relevant discrete formulae are outlined for systems of linear governing equations involving first derivative terms, and applied to five representative example models of electrochemical transient experiments. The extended Numerov discretization proves to have an accuracy and efficiency comparable to the original Numerov scheme, and its accuracy is typically up to four orders of magnitude higher, compared to the conventional, second-order accurate spatial discretization, commonly used in electrochemistry. This results in a considerable improvement of efficiency. Therefore, the application of the extended Numerov discretization to the electrochemical kinetic simulations can be fully recommended.     

Toward standardization of quality assessment in laboratory medicine by using the same matrix samples for both internal and external quality assessments

The main purpose of quality assurance procedures in clinical laboratories is to ensure that test results are appropriate to maintain excellence in the diagnosis, monitoring, and treatment of disease. However, in current practice, no standardized procedure or frequency for the evaluation of methods exists, particularly in external quality assessment. Furthermore, different quality control materials are typically used for internal and external quality assessment. To overcome these discrepancies, we used samples with the same matrix for both internal and external quality assessments of a group test performed in our laboratory. We then calculated total error using real bias (target value obtained by reference method) and the imprecision of each test and compared our results with the total error allowable, derived from biological variation data. We suggest that the strategy of using the same matrix samples for both internal and external quality assessment is cost-effective, can be readily used by staff, and will facilitate the standardization of quality control in clinical laboratories.     

The influence of contact electrification on the adhesion of dielectric elastic spheres subjected to external loads before detachment

The influence of a static load on the adhesion of an elastic sphere to a rigid smooth surface has been investigated. The change in ratio of the electrostatic component of the adhesion force resulting from the formation of an electric double layer to the molecular one as a result of the contact pressure has been evaluated theoretically. The tearing-off force and the surface density of the charge forming in the contact between the silicone rubber sphere and a steel plate were determined simultaneously. It is shown that the observed increase in sticking force of the sphere after its compression may be explained by an increase in the electrostatic component of the adhesion force, which is proportional to the contact area.     

The stability of the RKR inversion procedure to errors in the spectroscopic data: origin of the inner-wall ripple

The origin of the non-physical inner-wall behaviour frequently encountered in the RKR inversion procedure is discussed. The RKR procedure is found to be very sensitive to errors in the rotational data, but less demanding on the quality of the vibrational data.     

The ability of spectrum autocorrelation models to predict the lycopene concentration in foods through visible spectroscopic data

We developed a novel computerized approach based on lag-k autocorrelation coefficients (LCCs) and linear models (LMs) to estimate the concentration of lycopene in foods by the spectroscopy. The LCCs were calculated using the data obtained using whole visible scans from 400 to 600 nm (vide supra) of lycopene standards and food samples (ketchup, tomato juice and tomato sauce). The chaotic parameter (CP) was then transferred into a LM to estimate the concentration of lycopene compound. The integrated LCC/visible spectroscopy method developed can be considered as a satisfactory analytical technique able to estimate lycopene concentration in food samples in a fast accurate way, with a mean prediction error lower than 5.7% and a mean correlation coefficient higher than 0.957.     

State of water in inverse micelles of Aerosol OT,according to IR spectroscopic data

Leningrad State University. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 4, pp. 81–85, July–August, 1991.     

Raman spectroscopic study of microcosmic photodamage of the space structure of DNA sensitized by Yangzhou haematoporphyrin derivative and Photofrin II

After calf thymus DNA has been photodamaged by Yangzhou haematoporphyrin derivative (YHPD) or Photofrin II, the Raman characteristic frequencies and the intensities of the bands assigned to various groups of the components of DNA change considerably. As a result of damage, homogeneous B-form calf thymus DNA becomes a mixture containing: (1) modified B-form DNA, which is shorter than the original because of double-helical DNA scission; (2) single-stranded DNA due to the breakage of some H-bonds and the lack of some bases, etc.     

Observation‐based missing data methods for exploratory data analysis to unveil the connection between observations and variables in latent subspace models

This paper introduces a class of methods to infer the relationship between observations and variables in latent subspace models. The approach is a modification of the recently proposed missing data methods for exploratory data analysis (MEDA). MEDA is useful to identify the structure in the data and also to interpret the contribution of each latent variable. In this paper, MEDA is augmented with dummy variables to find the data variables related to a given deviation detected among observations, for instance, the difference between one cluster of observations and the bulk of the data. The MEDA extension, referred to as observation‐based MEDA or oMEDA, can be performed in several ways, one of which is theoretically shown to be equivalent to a comparison of means between groups. The use of the proposed approach is demonstrated with a number of examples with simulated data and a real data set of archeological artifacts. Copyright © 2011 John Wiley & Sons, Ltd.     

Curve fitting to asymmetrical chromatograms by the extended Kalman filter in frequency domain

An algorithm is presented to perform curve fitting on the basis of the Fourier transform of a signal. The curve fitting has been done with the exponentially modified Gaussian model, obtained when convolving a Gaussian distribution and an exponential decay function. The parameter estimation has been carried out by means of the two-dimensional extended Kalman filter. The goodness-of-fit has been characterized by the trace of the covariance matrix of the estimated parameters. The precision of the estimated parameters obtained by fitting either in time or frequency domain is compared.     

Structure of the cobalt complexes with the Schiff base of salicylaldehyde and lysine according to the H NMR spectroscopic data

The Co(II) complex with the Schiff base of salicylaldehyde and lysine is studied by the ¹H NMR method in dioxane and dimethyl sulfoxide (DMSO) solutions. In a dioxane solution, the complex is paramagnetic and dimeric. In the dimer, the cobalt ion coordinates two ligand molecules and each ligand is bound to two cobalt ions. In a water-containing DMSO solution, the complex is diamagnetic due to the oxidation of Co²⁺ to Co³⁺.