bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of coupled reactions for simplification of bioluminescence analysis
Authors: Brolin S. E. , Naeser P. , Wettermark G.
Published: May 2005

Luminescence analysis may be applied to many substances by arranging a prior reaction producing a species entering the light‐emitting reaction. Under favourable conditions the two consecutive reactions are carried out simultaneously as a one‐step procedure. In a bioluminescence assay, luciferase stability is frequently a problem, making it desirable to develop analytical schemes where the analytical response becomes largely independent of any impaired luciferase activity. The value of maximal emission or an approached steady‐state level is a convenient and usually well‐defined analytical parameter. When recording this level it is important to design the participating reactions in a way that compensates for changes in luciferase activity.
Measurement of estrone‐3‐glucuronide and pregnanediol‐3α‐glucuronide in early morning urine samples to monitor ovarian function
Authors: Magini A. , Pinzani P. , Bolelli G. F. , Bassi F. , Salerno R. , Messeri G. , Pazzagli M.
Published: May 2005

The determination of the concentration of estrone‐3‐glucuronide and pregnanediol‐3α‐glucuronide has been performed by a chemiluminescent immunoassay in early morning urine samples of 14 normal menstruating women and 11 women affected by luteal phase defect. The early morning urine samples were daily collected for an entire menstrual cycle. We have employed a timed and measured volume collection procedure as correction factor. The integrated values of the hormonal data in definite time intervals were used to create a nomogram. By means of this method, it was possible to completely separate normal from luteal insufficiency subjects and to distinguish two different types of luteal phase defects. Moreover, the same approach was applied to the study of the role and the frequency of luteal phase defect in 15 patients affected by habitual abortion and in 17 premenopausal women who had undergone quadrantectomy for T1a No Mo breast cancer. A luteal phase defect was detected in nine of the aborting patients (60%) and in eight women affected by breast cancer (47%). Finally estrone‐3‐glucuronide was measured in early morning urine samples of 96 prepubertal and pubertal girls in different pubertal stages and in one patient affected by precocious puberty, before and during an agonist GnRH treatment. The urinary test of ovarian function seems to be suitable for diagnostic purposes and for clinical studies.
Methodological evaluation of a new chemiluminescence immunoassay for thyrotropin using acridinium ester‐labelled antibody
Authors: Zucchelli G. C. , Pilo A. , Masini S. , Chiesa M. R. , Masi A.
Published: May 2005

A recently available immunochemiluminometric assay (ICMA) for TSH developed by Ciba Corning Corp. has been evaluated. This system (Magic Lite) uses an acridinium‐ester‐labelled antibody and magnetizable particle for bound‐free separation. In each assay only two calibrators are carried out and used to re‐scale a manufacturer‐generated curve stored in the memory of the luminometer. The precision of the response (RLU) estimated by all duplicates of 14 runs was about 4% for responses >12,000 RLU (corresponding to a concentration interval 0.7–113 μlU/ml) and worsened in the lower range (up to 10% CV); the sensitivity, computed from the mean within‐assay precision profile, was 0.028 μlU/ml; the between‐assay precision ranged from 4.6 to 13.1 CV%. Regression analysis of ICMA results (y) against consensus values of Behring IRMA (x) on 15 QC sera assayed in an inter‐laboratory survey (concentration range 1–30 μlU/ml) gave y = −0.003 + 0.98x indicating a good agreement of the two techniques. Similar conclusions have been derived from the comparison of the ICMA results (y) in the low TSH concentration range (< 1 μlU/ml) against the IRMA Boots Celltech (x) on 80 patient samples (y = 0.04 + 1.04x).
Novel monomeric luciferase enzymes as tools to study plant gene regulation in vivo
Authors: Olsson Olof , Nilsson Ove , Koncz Csaba
Published: May 2005

Taking advantage of a specially constructed vector, luciferase LuxA and LuxB subunits were connected in frame to different amino acid linkers to reproduce a series of monomeric luciferase enzymes. A comparison of their activities in E. coli cells demonstrated that the length of the linkers positively affected activity. One luciferase fusion gene was expressed in plant cells, and we showed that this gene activity could be monitored directly without destructive sampling.
Excited carbonyl formation in the combination and disproportionation of free radicals
Authors: De La Fuente U. J. R. , Lissi G. E. A.
Published: May 2005

The pyrolyisis of di‐tert‐butyl peroxyoxalate in the presence of para‐substituted benzaldehydes produces almost quantitatively the corresponding p,p′‐disubstituted benzils. The formation of these products is accompanied by chemiluminescence arising from excited triplets. From the quantum yield of excited triplet generation and the rate constants for the triplet photocleavage it is possible to obtain the change in Gibbs free energy associated with triplet formation. The values obtained are −5.6, −5.7 and −8.1 kcal/mol for benzil, p,p′‐dimethylbenzil and p,p′‐dimethoxybenzil, respectively.

The pyrolysis of di‐tert‐butyl peroxyoxalate in the presence of isopropanol or benzoin leads to the formation of acetone and benzil. These products are generated in disproportionation processes involving the α‐hydroxy radical produced by hydrogen abstraction. The luminescence observed in these reactions constitutes the first experimental indication of excited species generation in the disproportionation of uncorrelated free radicals.
Chemiluminescence of human bloodstream monocytes and neutrophils: An unusual oxidant(s) generated by monocytes during the respiratory burst
Authors: Davies Bernard , Edwards Steven W.
Published: May 2005

Maximal rates of O and H2O2 production by human bloodstream monocytes activated during the respiratory burst by phorbol ester were only about 10% of those of neutrophils. Furthermore, monocytes possess only about 5% of the myeloperoxidase activity of neutrophils and so can only produce low levels of HOCI and related compounds. These combined reductions in O generating ability and lower myeloperoxidase levels result in low luminol chemiluminescence stimulated during the respiratory burst of monocytes. However, although monocytes generate much lower levels of O and H2O2 than neutrophils, these cells produce comparable rates of PMA‐stimulated lucigenin chemiluminescence. Hence, this assay does not accurately reflect the production of either of these two oxidants by activated phagocytes, and further lucigenin must react with some other oxidant(s) via a process which leads to photon emission. This oxidant(s) is not O, H2O2, · OH, 1O2 or NO, but is derived from O generated during the respiratory burst and is generated in greater quantities by activated monocytes compared with neutrophils. Thus, lucigenin chemiluminescence is an indirect measure of superoxide release.
Flow injection assays with chemiluminescence and bioluminescence detection — A review
Authors: Lewis Simon W. , Price David , Worsfold Paul J.
Published: May 2005

This paper reviews publicaions that combine the technique of flow injection (FI) with chemiluminescence (CL) and bioluminescence (BL) detection, from the earliest papers in 1979/80 to mid‐1992, and refers exclusively to reactions occurring in solution. Airsegmented systems and liquid chromatography with CL detection are not considered unless FI has been used to pre‐optimize the system. The applications have been categorized in terms of the type of CL reaction; there are separate entries for luminol, peroxyoxalate, other CL reactions and BL reactions. Each of the four sections includes a table of applications that lists the analyte, the nature of the reaction, the sample matrix and the limit of detection.
Assay of antioxidants by the quenching of the anthracene‐sensitized electrochemiluminescence
Authors: Chmura Janusz , Slawiński Janusz
Published: May 2005

The kinetic and spectral characteristics (chemiluminescence and fluorescence spectra) of ultraweak luminescence accompanying the electrolysis of a sodium citrate–methanol–dissolved O2 solution and its application for the determination of antioxidants were examined. The energy transfer‐assisted luminescence sensitized by anthracene provides a fast and sensitive assay for the determination of the concentration and kinetic parameters of antioxidants and free radical scavengers.
Applications of low‐light imaging to life sciences
Authors: Nicolas J. C.
Published: May 2005

Photon imaging is a new technique for the quantitative analysis of bioluminescence and chemiluminescence and can be performed both at the macro and micro levels. The high sensitivity and spatial resolution of photon‐counting cameras have resulted in the development of new applications in the life sciences.

At the macro level, imaging is a valuable tool for the rapid identification of biological samples emitting long‐lasting glows in assays using microtitre plates or filter formats (immunoassays, DNA probes, phagocytosis, gene expression, metabolite and drug analysis) and also for in vivo studies of promoter activity. At the micro level, low‐light imaging can be used for analysing multiple analytes on micro sensors and for advanced cell analysis (immunocytology, in situ hybridization, identification of cells or tissues expressing the luciferase gene, intracellular or intercellular protein traffic, metabolite analysis and imaging of Ca2+ flux and phosphorylation reactions).

Two‐dimensional photon‐counting instrumentation is a versatile and powerful research tool for imaging and is complementary to conventional luminometers. The main applications to the life sciences involve many types of luminescence assays and can be performed on multiple samples in standard and non‐standard formats. Photon‐counting coupled to imaging is very helpful in selecting microorganisms or cells expressing bioluminescent genes. Measurements can be made in vitro and in vivo with a sensitivity comparable to that of phototube luminometers.
Effect of sulphite on the oxidative metabolism of human neutrophils: Studies with lucigenin‐ and luminol‐dependent chemiluminescence
Authors: Mishra Anil , Dayal Niru , Beck‐Speier Ingrid
Published: May 2005

To assess the effect of sulphite on the oxidative metabolism of human neutrophils, chemiluminescence (CL) measurements were performed using lucigenin and luminol as chemiluminigenic probes. Lucigenin‐dependent CL was used for measuring superoxide anion (O) production, and luminol‐dependent CL was used for determination of myeloperoxidase (MPO)‐connected processes. With sulphite concentrations of 0.01 to 1 mmol/L, resting neutrophils showed an up to sixfold increase of lucigenin‐dependent CL, but only a 1.9‐fold increase of luminol‐dependent CL. Subsequent stimulation of sulphite‐treated neutrophils with phorbol myristate acetate (PMA) (soluble stimulant) or zymosan (particulate stimulant) resulted in an additional significant increase of lucigenin‐dependent CL compared to stimulated control cells, whereas luminol‐dependent CL increased slightly by 0.01 mmol/L sulphite and decreased then continuously. Sulphite concentrations above 1 mmol/L decreased both lucigenin‐ and luminol‐dependent CL of resting and PMA‐ or zymosan‐stimulated neutrophils. Lucigenin‐dependent CL of sulphite‐treated and subsequently stimulated neutrophils was strongly inhibited by extracellularly added superoxide dismutase, whereas luminol‐dependent CL was markedly reduced by the MPO inhibitor azide. The intracellular activity of MPO in neutrophils stimulated with PMA in the presence of sulphite (2 mmol/L) was reduced by 55%. Sulphite (0.1 mmol/L) also inhibited strongly the activity of MPO in a cell‐free system. These results indicate that micromolar concentrations of sulphite exert a stimulating effect on the O production of neutrophils extracellularly, but have an inhibitory effect on MPO‐catalysed reactions intracellularly.
Formation of active bacterial luciferase between interspecific subunits in vivo
Authors: Almashanu S. , Tuby A. , Hadar R. , Einy R. , Kuhn J.
Published: May 2005

Interspecific complementation between luxAs and luxBs from Vibrio harveyi, Vibrio fischeri, Photobacterium leiognathi and Xenorhabdus luminescens was examined in vivo. The individual genes from these species were cloned on different compatible plasmids or amplified by PCR and brought together to yield cis combinations without extraneous DNA. The beta subunits from V. harvayi and X. luminescens form active enzyme only with alpha subunits from one of these species. All other combinations yield active enzymes. The lack of activity of the V. harveyi and X. luminescens beta subunits with the alpha subunits from V. fischeri and P. leiognathi results from a lack of association. This was shown by in vivo competition in which these beta subunits were overproduced in comparison with the beta and alpha of V. fisheri. No reduction in light was found. Overall, the in vivo results parallel those found in vitro using isolated denatured subunits and renaturation by removal of the denaturant.
Fast and sensitive chemiluminescence determination of H2O2 concentration in stimulated human neutrophils
Authors: Mueller S. , Arnhold J.
Published: May 2005

A fast and sensitive chemiluminescence assay for the determination of H2O2 in stimulated neutrophils without the use of enzymes was developed. The method is based on the oxidation of luminol by hypochlorous acid. The chemiluminescence of this reaction is highly dependent on the concentration of hydrogen peroxide.

Changes in H2O2 concentration in PMA‐stimulated neutrophils were followed by injection of NaOCI to cell suspension at different times after cell stimulation. The short integration time of 2 s permits calculation of actual concentrations of H2O2 without influence of H2O2 decomposition by cellular enzymes or newly produced H2O2 due to dismutation of superoxide anion radicals. Concentrations of H2O2 were diminished by catalase and enhanced by sodium azide owing to inhibition of cellular catalase and myeloperoxidase. Changes in H2O2 concentration upon stimulation could be observed at 3000 cell/mL.
Notes on the history and nature of partial least squares (PLS) modelling
Authors: Geladi Paul
Published: May 2005

The growing awareness of the need for non‐deterministic and distribution‐free (soft) models combined with an iterative algorithm for finding latent variables led to the construction of partial least squares models. There have been separate developments in the humanistic and the natural sciences, with stress on different aspects and a different terminology. The historical development is described and some key topics are explained.
Dried grass silage analysis by NIR reflectance spectroscopy—A Comparison of stepwise multiple linear and principal component techniques for calibration development on raw and transformed spectral data
Authors: Downey Gerard , Robert Paul , Bertrand Dominique , Devaux Marie‐Francoise
Published: May 2005

Calibrations to predict crude protein (CP) and in vitro dry matter digestibility (IVDMD) in dried grass silage from reflectance data collected at 19 wavelengths on an InfraAlyzer 400R have been developed using stepwise multiple linear (SML) and principal component (PC) regression techniques. A direct comparison of the efficacy of each multivariate technique in this applications has been possible by using identical calibration development and evaluation sample sets. The effect of two data transformation steps prior to PC regression was also investigated. PC regression of raw reflectance data yielded no significant improvement in the standard errors of prediction (SEP) for CP and IVDMD over those obtained by SMLR, viz. 0·61 vs 0·63 and 2·9 vs 3·0 respectively. Computation time for development and evaluation of the PC regression equation was less than for selection of the best SMLR equation, and PCR equations may be more robust. Data transformation to reduce granularity effects prior to PCR did not produce any improvement in predictive accuracy for either IVDMD or CP.
Mixture analysis using factor analysis. II: Self‐modeling curve resolution
Authors: Hamilton J. Craig , Gemperline Paul J.
Published: May 2005

One of the major applications of factor analysis in the chemical literature, self‐modeling curve resolution (SMCR), is covered in this review, including a historical account of the methods derived from Lawton and Sylvestre's original method. Papers treating the theory or applications of SMCR are included. Qualitative and quantitative applications are described where appropriate.
Residual bilinearization. Part 1: Theory and algorithms
Authors: Öhman Jerker , Geladi Paul , Wold Svante
Published: May 2005

When using hyphenated methods in analytical chemistry, the data obtained for each sample are given as a matrix. When a regression equation is set up between an unknown sample (a matrix) and a calibration set (a stack of matrices), the residual is a matrix R.

The regression equation is usually solved by minimizing the sum of squares of R. If the sample contains some constituent not calibrated for, this approach is not valid. In this paper an algorithm is presented which partitions R into one matrix of low rank corresponding to the unknown constituents, and one random noise matrix to which the least squares restrictions are applied. Properties and possible applications of the algorithm are also discussed.

In Part 2 of this work an example from HPLC with diode array detection is presented and the results are compared with generalized rank annihilation factor analysis (GRAFA).
A class‐modelling technique based on potential functions
Authors: Forina Michele , Armanino Carla , Leardi Riccardo , Drava Giuliana
Published: May 2005

A probabilistic and distribution‐free class‐modelling technique is developed from potential function discriminant analysis. In the multidimensional space of variables the class boundary is built either by the sample percentile of the probability density estimated by means of potential functions, or by the estimate of the ‘equivalent’ determinant of the variance–covariance matrix. The equivalent determinant is that of a hypothetical multivariate normal distribution whose mean probability density was obtained by potential functions. The bases of this modelling rule are evaluated by means of Monte Carlo experiments. The results on four datasets are used to measure the performances of this method, which equal and sometimes exceed the performances of parametric class‐modelling methods based on linear and quadratic discriminant analysis which were used for comparison.
The effect of mean centering on prediction in multivariate calibration
Authors: Seasholtz Mary Beth , Kowalski Bruce R.
Published: May 2005

Traditionally, one form of preprocessing in multivariate calibration methods such as principal component regression and partial least squares is mean centering the independent variables (responses) and the dependent variables (concentrations). However, upon examination of the statistical issue of error propagation in multivariate calibration, it was found that mean centering is not advised for some data structures. In this paper it is shown that for response data which (i) vary linearly with concentration, (ii) have no baseline (when there is a component with a non‐zero response that does not change in concentration) and (iii) have no closure in the concentrations (for each sample the concentrations of all components add to a constant, e.g. 100%) it is better not to mean center the calibration data. That is, the prediction errors as evaluated by a root mean square error statistic will be smaller for a model made with the raw data than a model made with mean‐centered data. With simulated data relative improvements ranging from 1% to 13% were observed depending on the amount of error in the calibration concentrations and responses.
Compression of nth‐order data arrays by B‐splines. Part 1: Theory
Authors: Alsberg Bjørn K. , Kvalheim Olav M.
Published: May 2005

For efficient handling of very large data arrays, pretreatment by compression is mandatory. In the present paper B‐spline methods are described as good candidates for such data array compression. The mathematical relation between the maximum entropy method for compression of data tables and the B‐spline of zeroth degree is described together with the generalization of B‐spline compression to nth‐order data array tables in matrix and tensor algebra.
Body diagonalization of core matrices in three‐way principal components analysis: Theoretical bounds and simulation
Authors: Henrion René
Published: May 2005

In contrast with conventional PCA, a direct superposition and joint interpretation of loading plots is not possible in three‐way PCA, since there may be data variance which is described by unequal components of different modes. The contributions to variance of all possible combinations of components are described in the core matrix. Body diagonalization, which is achieved by appropriate rotation of component matrices, is an essential tool for simplifying the core matrix structure. The maximum degree of body diagonality which may be obtained from such transformations is analysed from both the mathematical and simulation viewpoints. It is shown that, at least in the average case, high degrees can be expected, which makes the procedure reasonable for many practical applications. Furthermore, simulation as well as theoretical derivation show that the success of body diagonality depends on the so‐called polarity of the core array. The methodology is illustrated by a three‐way data example from environmental chemistry.
Effect of standardization on fragment‐based measures of structural similarity
Authors: Bath Peter A. , Morris Carol A. , Willett Peter
Published: May 2005

Substructural fragment occurrence data are widely used as the basis for measures of inter‐molecular structural similarity. This paper investigates the effect of standardization on the effectiveness of such measures using eight data sets for which both structural and biological activity data are available. Eight different standardization methods are studied and it is shown that there is no significant difference in the effectivenesses of the various methods; accordingly, any of them can be used for the calculation of intermolecular structural similarity.
Identifying significant effects in fractional factorial experiments
Authors: Langsrud Øyvind , Ellekjaer Marit Risberg , Naes Tormod
Published: May 2005

This paper presents a method for identifying significant effects in fractional factorial designs. The method is based on comparing functions of the estimated effects with a scale invariant reference distribution. The method is illustrated and compared with alternative techniques on a dataset from processed cheese production. The method corresponded well to other methods (probability plotting and Bayes plot) that do not make use of error estimates. These methods were better than F‐tests with few (two or four) degrees of freedom for error.
Interactive variable selection (IVS) for PLS. Part II: Chemical applications
Authors: Lindgren Fredrik , Geladi Paul , Berglund Anders , Sjöström Michael , Wold Svante
Published: May 2005

With the aim of developing PLS models with improved predictive properties, an interactive variable selection (IVS) approach for PLS regression was introduced in Part I of this series. IVS‐PLS is based on a dimension‐wise selective removal of single elements in the PLS weight vector w. IVS uses cross‐validation (CV) as a guiding tool. The present paper illustrates the use of IVS‐PLS on both simulated data and real examples from chemistry. In the first example, spectrophotometric data were simulated according to an experimental design. The objective was to see how IVS‐PLS was influenced by different levels of noise in X and Y and by the number of predictor variables (K). The results of the modelling are shown as response surfaces. In addition, four real examples were modelled by the IVS‐PLS technique. The real data sets were chosen to reflect different types of data from chemistry. For each example a comparison of ‘prediction error sum of squares’ (PRESS) between IVS‐PLS and classical PLS is made

For most of the examples containing many predictor variables IVS‐PLS shows an improvement in predictive properties over classical PLS. Also, improvements for IVS‐PLS2 (modelling of more than one y‐variable) models were found. For data sets with a moderate number of variables the influence of the IVS method becomes less pronounced.
Orthogonal canonical variates for discrimination and classification
Authors: Krzanowski W. J.
Published: May 2005

A new set of derived variables is proposed for exhibiting group separation in multivariate data on for preprocessing such data prior to discriminant analysis. The technique combines optimal features of canonical variate analysis and principal component analysis: the derived variables are linear combinations of the original variables that optimize the canonical variate criterion (ratio of between‐group to within‐group variance) but subject to the orthogonality constraints of principal components. In this formulation the canonical variates can be derived even when the within‐group matrix is singular (i.e. when there are more variables than objects in the data matrix). A simple computational algorithm for extraction of these variables is proposed. The methods are illustrated on several data sets and compared with alternative techniques such as principal component analysis and partial least squares.
Chemical vapor deposition of metals: Part 1. An overview of CVD processes
Authors: Hampden‐Smith Mark J. , Kodas Toivo T.
Published: May 2005

The chemical vapor deposition (CVD) of metals is a rapidly developing area in which metal‐containing compounds are being synthesized as new precursors. This article reviews this area and discusses precursor design, reaction pathways, reactor types, and the influence of reactor operating conditions on film growth. We have gathered recent results for precursor design and CVD chemistry and show how analysis of results from CVD experiments can be used to assist in the development of new CVD precursors.
Chemical vapor deposition of metals: Part 2. Overview of selective CVD of Metals
Authors: Hampden‐Smith Mark J. , Kodas Toivo T.
Published: May 2005

The Selective chemical vapor deposition (CVD) of metals from metal‐containing compounds is reviewed and the approaches taken are classified according to the different physicochemical phenomena which take place on the growth and non‐growth surfaces. These include: an intrinsic difference in reaction rates, sacrificial solid‐state co‐reactant, activation of the growth surface, radiation‐induced activation of the growth surface, passivation of non‐growth surfaces, and a physical nucleation barrier. The results from the literature suggest that surface modification, in which the growth surface is activated or the non‐growth surface is passivated, is a promising method to control selectivity. However, few results are available from experiments with well‐characterized surfaces, making meaningful comparisons of the origin of selective CVD difficult to interpret.
Phosphinochalcogenoic amidato complexes of zinc and cadmium as novel single‐source precursors for the deposition of metal selenide and telluride films
Authors: Bwembya Gabriel C. , Song Xuejing , Bochmann Manfred
Published: May 2005

Potential single‐source precursors for metal chalcogenide semi‐conductor films, such as zinc and cadmium selenides and tellurides, have in the past proved to be difficult to synthesize, thermally unstable, or insufficiently volatile. The title compounds are found to yield high purity metal selenide and telluride films without the incorporation of nitrogen or the formation of nitro‐ gen‐containing phases.
Atomic layer epitaxy of strontium sulfide thin films using in situ synthesized strontium precursors
Authors: Soininen Pekka , Nykänen Erja , Niinistö Lauri , Leskelä Markku
Published: May 2005

SrS thin films were grown on uncoated or Al2O3‐coated soda lime glass substrates from hydrogen sulfide and Sr(thd)2 (thd = 2,2,6,6‐tetramethyl‐3,5‐heptanedionato) by the atomic layer epitaxy (ALE) process. Sr(thd)2 was prepared from Sr, SrO, Sr(OH)2 or SrCO3 and Hthd inside the reactor during the deposition process. Thicknesses of the thin films were measured by optical transmission spectroscopy while crystallinity and preferred orientation were evaluated by X‐ray diffraction. Under certain conditions strongly (200) oriented SrS was grown. The advantages of the in situ synthesis of the precursor are discussed.
Thin films of early transition metal monophosphides
Authors: Lewkebandara Suren T. , Winter Charles H.
Published: May 2005

Early transition metal phosphides possess remarkable properties that promise potential applications, particularly as thin films. This article aims to provide a broad understanding of the preparation methods, structural features, analysis, and properties of these materials. It is pointed out that developments in the bulk synthesis of metal phosphides may reveal chemical principles relevant for new CVD processes. Investigations of CVD synthetic routes could lead to a greater willingness to use these novel phosphides in various applications.
Liquid‐delivery MOCVD of La1−xSrxMnO3−δ thin films
Authors: Dahmen Klaus‐Hermann , Carris Michael W.
Published: May 2005

Communication: The properties of perovskite materials make them suitable for many applications. Recently the perovskite La1−xMxMno3−δ, where M = Ca, Sr, or Ba, has attracted much attention because of its colossal magnetoresistance. Previous attempts to deposit thin films by PVD or MOCVD have required films to be post‐annealed to obtain good transport properties. This paper shows that by increasing the oxygen partial pressure during deposition good quality layers can be grown without any post‐annealing.
Is interfacial silicon carbide necessary for the epitaxy of diamond on (100) silicon?
Authors: John Phillip , Milne David K. , Jubber Michael G. , Wilson John I. B.
Published: May 2005

Communication: The heteroepitaxy of diamond is of considerable scientific and technological interest. The significant lattice mismatch between diamond and silicon and the relatively high surface energy of a non‐terminated (100) diamond plane have prompted speculation that diamond nucleates on an aligned cubic silicon carbide interfacial layer. In this paper spectral and microscopic studies show that while formation of interfacial amorphous carbon and silicon carbide must be avoided, nevertheless an interfacial SiC layer is intimately involved in localized heteroepitaxial growth on (100) silicon.
Amine‐stabilized cyclopentadienyl diisobutyl aluminum complexes as new kinds of precursors for the deposition of thin aluminum films by CVD
Authors: Scherer Markus , Kruck Thomas
Published: May 2005

Communication: The heteroepitaxy of diamond is of considerable scientific and technological interest. The significant lattice mismatch between diamond and silicon and the relatively high surface energy of a non‐terminated (100) diamond plane have prompted speculation that diamond nucleates on an aligned cubic silicon carbide interfacial layer. In this paper spectral and microscopic studies show that while formation of interfacial amorphous carbon and silicon carbide must be avoided, nevertheless an interfacial SiC layer is intimately involved in localized heteroepitaxial growth on (100) silicon.

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Lead(II) dithiocarbamato complexes as precursors for the LP‐MOCVD of lead sulfide
Authors: Trindade Tito , Brien Paul O'
Published: May 2005

Communication: Polycrystalline layers of PbS find wide application in IR detection. A simple and safe route to the IV‐VI material using a single precursor is described. The films obtained show cubic crystallites with columnar growth (see Figure) and X‐ray diffraction peak intensities suggest a strong [200] orientation. The approach has potential for the fabrication of IR detection devices.

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Remote Plasma‐Enhanced CVD of Fluorinated Silicon Nitride Films
Authors: Alexandrov Sergei E. , Hitchman Michael L.
Published: May 2005

An investigation has been made of the effect of dilution of nitrogen with NF3 on the properties of silicon nitride deposited by remote plasma‐enhanced CVD (PECVD). For NF3/N2 mixtures with < 1.5% NF3, fluorinated films with the structure of silicon nitride are formed but the total concentration of bonded hydrogen in the films decreases with increasing NF3 flow rate, which leads to an improvement of the electrical properties of the films compared with unfluorinated films. Such films could be of interest for device applications. For NF3/N2 mixtures with NF3 > 1.5 %, films with the structure of silicon dioxide are formed, but they do not contain enough oxygen to give typical SiO2 IR spectra. It is suggested that the silicon dioxide structure arises because of isoelectronic substitution of oxygen by NF.
Boron Carbonitride Thin Films by PACVD of Single‐Source Precursors
Authors: Hegemann Dirk , Riedel Ralf , Dreßler Wolfgang , Oehr Christian , Schindler Bernd , Brunner Herwig
Published: May 2005

This work investigates the influence of the carrier gases N2, Ar, and He and the influence of the applied power density (about 1–4 W/cm2) on the chemical composition of boron carbonitride films deposited by a PACVD process. The plasma is activated via 13.56 MHz radio frequency. Si(100) wafers were used as substrates and pyridine‐borane (PB) and triazaborabicyclodecane (TBBD) as B‐C‐N‐forming single‐source precursors. Films that were either deposited in He using a low power density or in N2 using a high power density showed comparable properties. Analysis of these films showed their chemical composition to be BC4N. Moreover, they exhibited outstanding hardnesses of up to 64 GPa. A simple model describing the acceleration of B, C, and N ions in the plasma towards the substrate showed comparable ion momenta by use of the corresponding deposition parameters. Basically, it was found that, the higher the ion momentum, the higher the film hardness.
Origins of Texture in TTF‐TCNQ Thin Films Grown by Organic CVD from TTF and TCNQ Precursors
Authors: Caro Jaume , Fraxedas Jordi , Figueras Albert
Published: May 2005

The preparation and characterization of thin films of the organic molecular conductor TTF‐TCNQ formed by the donor TTF (tetrathiafulvalene) and the acceptor TCNQ (7,7,8,8‐tetracyano‐p‐quinodimethane) is presented. The layers were grown on KCl (001) substrates by OCVD (organic CHEMICAL VAPOR DEPOSITION). The experiments were carried out on a horizontal hotwall reactor using TTF and TCNQ as precursors and argon as carrier gas. The obtained films are polycrystalline, showing a different in‐plane texture depending on the substrate temperature. The existence, under very well defined experimental conditions, of new in‐plane textures in addition to the energetically most favorable has been interpreted in terms of a local minimum in the interaction energy between the first monolayer of a c‐oriented crystalline unit and the substrate. This interaction energy was calculated taking into account the van der Waals and electrostatic forces existing between the organic layer and the alkali halide substrate.
The use of chemically modified electrodes for liquid chromatography and flow‐injection analysis
Authors: Wang Erkang , Ji Huamin , Hou Weiying
Published: May 2005

The use of chemically modified electrodes (CMEs) for liquid chromatography and flow‐injection analysis is reviewed. Electrochemical detection with CMEs based on electrocatalsis, permselectivity, ion flow in redox films, and ion transfer across the water–solidified nitrobenzene interface is discussed in terms of improving the stability, selectivity, and scope of electrochemical detectors and the detection of electroinactive substances. More than 90 references are included.
Electrochemistry of conductive polymer X: Polyaniline‐based potentiometric sensor for dissolved oxygen
Authors: Shim Yoon‐Bo , Stilwell David E. , Park Su‐Moon
Published: May 2005

A platinum electrode coated with polyaniline (PA) was examined as a Potentiometric or an optical sensor for dissolved oxygen, and the results are reported. While the polymer‐modified electrode behaved satisfactorily as a potentiometric sensor, its optical response (i.e., absorbance) gave a narrow linear region for varied oxygen concentrations. This conducting polymer‐coated electrode was characterized to give approximately 97 mV/decade of the oxygen concentration and a voltage signal range of about 400 mV, representing at least three orders of magnitudes of dynamic linearity over the dissolved oxygen concentration. The potentiometric sensing electrode showed reasonably short response times, excellent reproducibility, and good stability. A detection limit of about 5 × 10−7 mol/L of dissolved oxygen was estimated from the potentiometric response of PA‐coated electrodes.
Electroanalytical study of the hydrolysis of the thienodiazepine clotiazepam
Authors: Higelmo Fátima , Alonso Rosa M. , Jiménez Rosa M.
Published: May 2005

The hydrolysis reaction in an alkaline medium of the thiendodiazepine Clotiazepam has been studied by differential pulse polarography at various pH values at 25, 37, and 50°C. In an alkaline medium, Clotiazepam exhibits two well‐defined polarographic peaks, attributed to the azomethine group of the parent compound and the carboxylic group of the hydrolysis product, with a potential difference of 0.160 V, practically constant in the pH range studied. Kinetic studies of the reversible hydrolysis process based on the current changes with time of the first polarographic peak in indicate that the process is a pseudo‐first‐order reaction with a rate constant dependent on hydroxide ion concentration. Arrhenius parameters were also calculated. A voltammetric study of the hydrolysis product has been carried out, and determination methods have been developed by differential pulse voltammetry and differential pulse polarography.
Differential pulse polarographic determination of residual acrylic acid in sodium polyacrylate
Authors: Husain Sajid , Sastry G. S. R. , Prasad P. Ravi , Sarma G. V.
Published: May 2005

A polarographic method has been developed for the estimation of acrylic acid monomer in polyacrylate. Polarograms of the polymer are recorded directly in N,N‐dimethylformamide side (DMF) solvent using 0.02 M tetrabutyl ammonium iodide as the supporting electrolyte. This solvent system was chosen because it avoids indirect measurements based on separation or reprecipitation procedures. The results obtained are found to be in good agreement with ultraviolet spectrophotometric results.
An amperometric glucose electrode based on carbon paste, chemically modified with glucose dehydrogenase, nicotinamide adenine dinucleotide, and a phenoxazine mediator, coated with a poly(ester sulfonic acid) cation exchanger
Authors: Bremle Gudrun , Persson Björn , Gorton Lo
Published: May 2005

An amperometric glucose electrode is described based on carbon paste chemically modified with glucose dehydrogenase, nicotinamide adenine dinucleotide, and a mediator, Meldola Blue. The surface of the chemically modified carbon paste electrode (CMCPE) is protected by coverage with a poly(ester sulfonic acid) cation exchanger to form a membrane, which prevents the aqueous soluble species from dissolving out of the CMCPE. The CMCPE was investigated in the flow‐injection analysis operation. Linear calibration curves for glucose were obtained between 100 μM and 20 mM glucose at +100 mV versus Ag/AgCl. The sample throughput was 40 h−1. The electrodes remained stable for about 2 weeks.
Novel STM‐EC center for in situ imaging under potentiostatic/galvanostatic control: Electrodeposition of copper and cadmium on carbon substrates
Authors: Yaniv Daphna R. , McCormick Larry D.
Published: May 2005

An electrochemical (EC) system, designed and incorporated into a scanning tunneling microscope (STM), is described. It has potentiostatic/galvanostatic capabilities for the sample and potentiostatic capabilities for the STM tip. The system permits imaging under potentiostatic (or galvanostatic) control. The STM‐EC center has been utilized to deposit metal films (Cu, Cd) on carbon substrates such as highly oriented pyrolytic graphite (HOPG) and glassy carbon (GC), and then used for in situ imaging under potentiostatic control. Tip‐induced electroplating on HOPG and its correlation to the bare graphite surface properties are also explored. Experimental considerations for in situ imaging under potentiostatic control are discussed.
Electrochemical oxidation and the quantitative determination of carbon monoxide on metal–solid polymer electrolyte (SPE) system
Authors: Xing Xue‐Kun , Liu Chung‐Chium
Published: May 2005

The electrochemical oxidation of carbon monoxide on a platinum–Nafion electrode was examined. It was found that the oxidation of CO on the Pt‐Nafion electrode is more favored in an acidic solution than in an alkaline medium. This is in contrast with what was reported for bulk metal electrodes, for which the oxidation rate of CO in acid is much smaller than in alkaline solutions. This phenomenon is believed to be directly related to the cation‐exchange capability of the Nafion membrane. The rest potential of the Pt–Nafion electrode was found to be dependent on the partial pressure of CO, which is also in contrast with the behavior of bulk metal electrodes. This result was attributed to a mixed potential phenomenon. A quantitative determination of CO concentration in the gas phase was carried out on the basis of the Pt–Nafion electrode system in a controlled‐potential mode. The results obtained showed a number of attractive properties, including a low detection limit, good reproducibility, and a fast response time.
Electrochemical behavior and determination of quinolinium and isoquinolinium oximes
Authors: Karljiković‐Rajić K. , Jovanović M. , Korićanac Z. , Stanković B. , Minić D.
Published: May 2005

The electrochemical behavior of 1‐(2‐phenyl‐2‐hydroxyiminoethyl)‐1‐quinolinium chloride (F‐1) and 1‐(2‐phenyl‐2‐hydroxyiminoethyl)‐1‐isoquinolinium chloride (F‐2) was investigated using dc and differential pulse polarography (DPP) and cyclic voltammetry. Well‐defined, diffusion‐controlled, cathodic waves were observed for F‐1 only in strong acidic solution (pH 1.25 HCl) and for F‐2 in the H range 1.25–5.33 (HCl and Britton–Robinson buffer). The overall reduction of the azomethine group to a primary amine, a process that involves the uptake of four electrons, is irreversible. For both oximes a mechanism of reduction has been proposed. The rapid and accurate determination of these quinolinium and isoquinolinium oximes is possible by dc polarography and by DPP. Limits of detection are 5 × 10−7 M for both oximes using DPP.
Electrocatalysis and flow detection at a glassy carbon electrode modified with a thin film of oxymanganese species
Authors: Taha Ziad , Wang Joseph
Published: May 2005

A modified electrode prepared by dipping a glassy carbon substrate into a 0.027 M MnCl2/1.4 M NaOH solution and cycling the potential between −0.5 and +0.4 V(vs. AA/AgCl) greatly reduces the overvoltage for the oxidation of various hydrazines and hydrogen peroxide. The new electrocatalytic surfaces facilitate the amperometric detection of these compounds in flowing streams. Effects of pH, flow rate, operating potential, film thickness, concentration, and other variable on the catalytic response are explored. The electrode response is very stable. Detection limits at the femto‐ and picomole levels and relative standard deviations less than 1.3% are reported.
Nicardipine: Differential pulse polarography and photodecomposition
Authors: Squella J. A. , Borges Y. , Celedon C. , Peredo P. , Nuñez‐Vergara L. J.
Published: May 2005

A new differential pulse polarographic method is proposed for the determination of nicardipine, based on the electroactivity of the nitroaromatic group of the molecule. The proposed method is applied in the determination of the drug in pharmaceutical formulations and in photodegradation studies.
Polarography and stripping voltammetry of metal–polycarboxylate complexes: Complexes of cadmium and zinc with polyacrylic and polymethacrylic acids
Authors: Díaz‐Cruz José M. , Ariño Cristina , Esteban Miquel , Casassas Enric
Published: May 2005

Complex formation of Zn(II) and Cd(II) with polymethacrylic acid (PMA) and polyacrylic acid (PAA) is studied by sampled direct current, normal pulse, reverse pulse, and differential pulse polarography and by differential pulse anodic stripping voltammetry (DPASV). Titrations of Zn(II) or Cd(II) with partially neutralized PMA or PAA by DPASV allow the precise determination of the apparent formation constant K of the four systems. The two Zn(II) systems appear to be labile on the different time scales of the several techniques, without remarkable complications due to secondary phenomena. Their K values, determined by all techniques, agree satisfactorily. The two Cd(II) systems, and especially the Cd/PAA system, show rather involved behavior, which tends to normality when the degree of neutralization αn of the polycarboxylates increases. Both slow kinetics and ligand adsorption coupled with induced Cd(II) adsorption (evidenced by maxima on the normal pulse polarograms) seem to be present. For all αn values, DPASV yields higher estimates of K than do polarographic techniques.
Flow‐through pH‐ISFET as detector in automated determinations
Authors: Alegret S. , Bartrolí J. , Jiménez C. , del Valle M. , Domínguez C. , Cabruja E. , Merlos A.
Published: May 2005

The implementation of a pH‐ISFET (ion‐selective field effect transistor) planar chip in a flow‐injection system by means of a specially designed flow cell and the application of the sensor to the analysis of volatile compounds is described. Ammonia and sulfur dioxide are determined by exploiting the advantages of the flow techniques combined with continuous gas diffusion. Initial species are converted to gaseous compounds, which diffuse through a microporous hydrophobic membrane into an ammonium chloride or hydrogen sulfite recipient stream, producing a pH variation that is monitored by the semiconductor detector. The linear working range extends from 1 × 10−2 to 1 × 10−4 M for the ammonium system and from 4 × 10−3 to 7 × 10−5 for the sulfur dioxide system, with relative standard deviation of about 1 and 0.5%, respectively.
Adsorptive stripping voltammetry of phenylthiohydantoin and methylthiohydantoin derivatives of amino acids in the presence of copper(II) ions at a hanging mercury drop electrode
Authors: Moreira Josino C. , Miller Royston D. , Fogg Arnold G.
Published: May 2005

In the absence of Copper(II)—and even in its presence, if accumulation has been effected at positive potentials vs. Ag/AgCl—phenylthiohydantoin and methylthiohydantoin derivatives of amino acids gave a peak at −0.60 V (pH 8.0) owing to reduction of the mercury salt formed upon accumulation. At negative accumulation potentials, the presence of copper(II) affected the adsorptive stripping voltammograms markedly, including the lowering of the detection limits. When accumulation was effected at −0.3 V, the thiohydantoin derivatives gave single peaks in the range −0.4 to −0.6 V owing to reduction of copper(II) accumulated as copper(II) complexes. Determinations could be made readily at the 5 × 10−9 M level, accumulating at −0.3 V (pH 8.0) or −0.1 V (pH 4.5): calibration plots were rectilinear up to 8 × 10−8 M. Accumulation at −0.1 V (pH 8.0) in some cases gave additional minor peaks, but glycine derivatives were exceptional in giving a well‐defined peak at a considerably more negative potential. This peak appeared to be due to the accumulation of a different copper(II) complex, and evidence was obtained for the interconversion of these complexes in the surface. Mutual interferences by competitive adsorption were observed.