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PubMed2005

Use of multivariate curve resolution for determination of chromium in tanning samples using sequential injection analysis.

We report a method for determining total chromium in tanning samples using sequential injection analysis (SIA) with a diode-array spectrophotometric detector. With a suitable analytical sequence CrO4(2-) is converted to Cr2O7(2-) inside the tubes of the SIA system, after total oxidation of chromium(III). A data matrix is obtained and analysed by several chemometric techniques based on multivariate analysis: principal components analysis, simple-to-use interactive self-modelling mixture analysis, and multivariate curve resolution-alternating least-squares. We studied several samples from different stages of a tanning process. Two of these samples were easily oxidized but the others needed more extreme conditions. The analytical sequence prepared, which was based on obtaining a pH gradient and used H2SO4 as reagent, is valid and independent of the level of oxidation needed for the sample. We established a calibration model and evaluated the figures of merit. In some samples we found interferents. With this method the amounts of chromium in each sample were quantified and the results were statistically similar to those obtained by use of the reference method, atomic absorption spectrometry.

Journal Article↗

PubMed2000

[Measuring disability of patients with low-back pain--validation of a German version of the Roland & Morris disability questionnaire].

INTRODUCTION: In this study three instruments measuring disability of patients with low-back pain are presented and evaluated: (1) the Behinderungsfragebogen (RM) - a German version of the Roland & Morris disability questionnaire (RDQ) (2) a numerical rating scale measuring disability in general and (2) eight numerical rating scales measuring specific dimensions of disability (standing, sitting, walking, driving a car, carrying light loads, carrying heavy loads, sleeping, and sexual intercourse). METHODS: The psychometric evaluation, including the item analysis, test reliability, test validity, and responsiveness of the instruments, is based on two samples. Sample A comprises 345 patients with low-back pain: 282 of these patients took part in the Swiss multicentre intervention study testing the effectiveness of in-patient rehabilitation of sub-chronic and chronic low-back pain under an integrative group treatment program. The instruments were administered at different times in the therapeutic process (t1: at hospital admission; t4: follow-up after one year). 63 patients were hospitalized (orthopedic or rheumatological units) for medical examinations (myelography or infiltration of facets) or rehabilitation of low-back pain. The instruments were administered twice within 24 h to measure test-retest correlation. In order to determine the psychometric parameters as accurately as possible, the two samples were examined jointly. Sample B is composed of 41 patients with low-back pain participating in the study "Prädiktoren des Erfolgs bei stabilisierenden Wirbelsäuleneingriffen" (Success predictors of effectiveness of surgical interventions for spinal stabilization). RESULTS: All instruments proved to be generally reliable and valid (high or medium correlations with each other and with a German version of the Oswestry Disability Questionnaire) as well as responsive tools for measuring the momentary disability of patients with back pain. The psychometric examination of the test validity showed that patients' perceptions of their disability were influenced by their psychological well-being. The correlation between the 3 instruments and physical tests was low. The RM is not a homogeneous instrument. Factor analysis (principal component analysis, rotation Varimax) indicated 6 factors. Because of the small number of items for each factor it is not appropriate to treat RM in terms of dimensions of disability. CONCLUSIONS: The RM is an instrument measuring patients' perception of their disability that offers simple, fast practicability for patients and tester. The 2 rating scales: The 8 numerical rating scales measuring specific dimensions of disability (QL3) offer all the advantages of the numerical rating scale measuring disability in general (QL1) (simple instruction, high plausibility for the patients, and simple, fast practicability), but they provide more information about the patient's disability, which allows comparisons of disability at different times in the therapeutic process. Numerical rating scales are not suitable for patients with poor ability to abstract. For these patients it is necessary to use a questionnaire which asks concretely about what the patient can or cannot do (e. g. RM). Because of its better psychometric properties, the QL3 should be favored over the RM.

English Abstract↗

PubMed2005

A combined (1)H NMR and HPLC-MS-based metabonomic study of urine from obese (fa/fa) Zucker and normal Wistar-derived rats.

(1)H NMR and HPLC-MS were used to generate metabolite fingerprints for the metabonomic analysis of urine obtained from both male and female Zucker obese (fa/fa) rats, used as a model of type II diabetes, and normal male Wistar-derived animals. The resulting data were subjected to chemometric analysis (principal components analysis and partial least squares discriminant analysis) to investigate the effects of strain, diurnal variation is strain, diurnal variation and gender and gender on metabolite profiles. In the case of strain, (1)H NMR spectroscopic analysis revealed increased taurine, hippurate and formate and decreased betaine, alpha-ketoglutarate, succinate and acetate in samples from Zucker-obese compared to Wistar-derived rats. HPLC-MS analysis detected increased hippurate and ions at m/z 255.0640 and 285.0770 in positive, and 245.0122 and 261.0065 in negative electrospray ionisation (ESI), respectively, for the Zucker obese samples. Both techniques enable the detection of diurnal variation in the urine of male and female Zucker rats, marked by increases in taurine, creatinine, allantoin and alpha-ketoglutarate by (1)H NMR, and ions at m/z 285.0753, 291.0536 and 297.1492 (positive ESI) and 461.1939 (negative ESI) using HPLC-MS, in the evening samples. Differences between male and female Zucker rats were also observed. Compared to samples from male rats hippurate, succinate, alpha-ketoglutarate and dimethylglycine ((1)H NMR) were elevated in the urine of female animals together with ions at, e.g., m/z 431.1047, 325.0655, 271.0635 and 447.0946 (positive ESI) and m/z 815.5495 and 459.0985 (negative ESI) by HPLC-MS. Both analytical techniques used in this study were able to detect differences between normal and Zucker obese rats, which may provide markers of metabolic disease.

Acetates↗

PubMedDate not supplied

Evaluation of computerized nursing care plan: instrument development.

With the increasingly popular use of information technology in patient care, the need for reliable instrumentation to evaluate information systems has become critical. This article describes the psychometric testing of a scale developed to evaluate a computerized nursing care plan (CNCP) system. A review of the literature generated a 44-item questionnaire, which was then administered to a convenience sample of 729 hospital nurses in Taiwan. Factor analysis (principal component analysis with varimax rotation) and item analysis were applied to establish the scale's construct validity and reliability. Twenty-two items selected from the original 44-item pool were grouped into 6 major constructs: patient care, nursing efficiency, professionalism, usage benefit, education and training, and usability. The alpha coefficient was 0.85. The statistical results showed that nurses generally valued using the CNCP system. Further psychometric analysis of the scale is suggested in other nursing populations, for subscale development and to refine item wording.

Adult↗

PubMed2005

The effects of antipsychotic medication on factor and cluster structure of neurologic examination abnormalities in schizophrenia.

This study extends a previous study of the factor structure of the neurologic examination in unmedicated schizophrenia, utilizing cluster analysis and adding a medicated condition. We administered a modified version of the Neurologic Evaluation Scale (NES) on two occasions to 80 patients with schizophrenia or schizoaffective disorder, once while on antipsychotic medications and once while off medication. Data were distilled by combining right- and left-side scores, and by excluding rarely abnormal and unreliable items from the analysis. Principal components analysis yielded an intuitive four-factor solution in the unmedicated condition, but an inscrutable five-factor solution during medication. Cluster analysis revealed three groups: normal, cognitively impaired, and diffusely impaired. These results were also less interpretable with data from the medicated condition. Neurologic performance was better in the medicated than in the unmedicated condition. As is the case with other domains of symptoms and performance in schizophrenia, relationships among neurologic exam variables are altered by the presence of antipsychotic medication.

Adult↗

PubMed2006

Application of chemometrics in river water classification.

The main aim of this work is focused on water quality classification of the Brda river (Poland) and evaluation of pollution data obtained by the monitoring measurement during the period 1994-2002. The study presents the application of selected chemometric techniques to the pollution monitoring dataset, namely, cluster analysis, principal component analysis, discriminant analysis and factor analysis. The obtained results allowed to determine natural clusters and groups of monitoring locations with similar pollution character and identify important discriminant variables. Chemometric analysis confirmed the classification of water purity of the Brda river made by the Inspection of Environmental Protection but the results showed more differentiation between monitored locations. This enables better evaluation of the water quality in a monitored region. On the basis of the chemometric approach, it was also found that some locations were under the high influence of municipal contamination, and some others under the influence of agriculture (discharges from fields) within the observed time period.

Agriculture↗

PubMed2002

Environmental context of Cylindrospermopsis raciborskii (Cyanobacteria) blooms in a shallow pond in France.

Cylindrospermopsis raciborskii, a potentially toxic blooming cyanobacterium (blue-green alga), responsible for public health problems in Australia, was identified in France in 1994 in a shallow pond south of Paris. A program monitoring the occurrence of C. raciborskii in this pond was conducted from July 1998 to October 1999. The phytoplankton assemblages were studied, and limnological parameters (water temperature, dissolved oxygen, pH, conductivity, and dissolved inorganic nutrients) were measured. By multivariate analysis (principal component analysis), we showed that sufficiently high temperatures to allow the germination of akinetes, relatively low nutrient concentrations (soluble reactive phosphorus with a mean concentration of 1 microM and nitrate between 0 and 5 microM, except in February 1999 (21 microM)) and a characteristic high and constant sulfate concentration (8981+/-471 microM) seemed to be the main factors involved in the proliferation of C. raciborskii in the "Francs-Pêcheurs" (FP) pond. In the light of these findings and of bibliographic data, C. raciborskii would seem to be characterized by good adaptability, but also by low competitiveness with other phytoplanktonic species in the temperate study area.

Adaptation, Physiological↗

PubMed2000

The use of lichen (Cetraria nivalis) and moss (Rhacomitrium lanuginosum) as monitors for atmospheric deposition in Greenland.

Concentrations of Pb, Cd, Hg, Zn, Cu, Cr, Ni, As, V, Al and Fe are reported from soil, humus, moss (Rhacomitrium lanuginosum) and lichen (Cetraria nivalis) sampled at four locations in Greenland. For Al, Fe, Cr and V the levels in soil were highest followed by humus and R. lanuginosum and with the lowest levels in C. nivalis. The same was true for Pb, Cu and Ni but without as great a difference between medias. For Cd and Hg, the lowest levels were found in soil. For Zn and As, the media with highest levels differed between locality. Data were examined by a principal component analysis. Three principal components explained 87% of the total variation. The dominant elements in the first component were Fe, Al, V, Ni, Cr, Cu and Pb. This component is interpreted as a soil dust factor. The concentrations in R. lanuginosum and C. nivalis of these elements are believed to be highly influenced by soil dust. Pb concentrations in moss and lichen may also be influenced by other sources as Pb also had some correlation's with the third component. Zn and Cd and to a lesser extent. As were the dominant elements in the second component. The third component was highly dominated by Hg with a lesser influence of Pb and As, Zn, Cd and Hg concentrations in R. lanuginosum and C. nivalis are believed to be influenced by other sources than soil dust which may be long-range atmospheric transport. In general, both the within locality and the between locality variability in the values of the three components decreased in the order soil, humus, R. lanuginosum and C. nivalis. The lichen C. nivalis is looked at as an indicator with greater potential for monitoring atmospheric deposition of elements than the moss R. lanuginosum.

Air Pollution↗

PubMed2001

Visualization methods in analysis of detailed chemical kinetics modelling.

Sensitivity analysis, principal component analysis of the sensitivity matrix, and rate-of-production analysis are useful tools in interpreting detailed chemical kinetics calculations. This paper deals with the practical use and communication of the sensitivity analysis and the related methods are discussed. Some limitations of sensitivity analysis, originating from the mathematical concept (e.g. first-order or brute force methods) or from the software-specific implementation of the method, are discussed. As supplementary tools to the current methods, three novel visual tools for analysis of detailed chemical kinetics mechanisms are introduced: (a) scaled sensitivity analysis which is especially suited for studying initiation reactions where the span of reaction rates is high; (b) automated generation of reaction pathway plots which provides an immediate graphical illustration of the chemical processes occurring; (c) explorative (or chemometric) analysis of accumulated rate of progress matrices which assist in the identification of reaction subsets. The application of these tools are demonstrated by analysing NOx enhanced oxidation of methane at 700-1200 K.

Journal Article↗

PubMed2002

Atmospheric quality and distribution of heavy metals in Argentina employing Tillandsia capillaris as a biomonitor.

The atmospheric quality and distribution of heavy metals were evaluated throughout a wide region of Argentina. In addition, the biomonitor performance of Tillandsia capillaris Ruiz & Pav. f. capillaris was studied in relation to the accumulation of heavy metals and to its physiologic response to air pollutants. A sampling area of 50,000 km2 was selected in the central region of the Argentine Republic. This area was subdivided into grids of 25 x 25 km. Pools of T. capillaris, where present, were collected at each intersection point. From each pool three sub-samples were analyzed independently. Furthermore, five replicates were collected at 20% of the points in order to analyze the variability within the site. The content of Co, Cu, Fe, Ni, Mn, Pb and Zn was determined by Atomic Absorption Spectrometry. Chemical-physiological parameters were also determined to detect symptoms of foliar damage. Chlorophylls, phaeophytins, hydroperoxy conjugated dienes, malondialdehyde and sulfur were quantified in T. capillaris. Some of these parameters were used to calculate a foliar damage index. Data sets were evaluated by one-way ANOVA, correlation analysis, principal component analysis and mapping. Geographical distribution patterns were obtained for the different metals reflecting the contribution of natural and anthropogenic emission sources. According to our results it can be inferred that Fe, Mn and Co probably originated in the soil. For Pb, the highest values were found in the mountainous area, which can be attributed to the presence of Pb in the granitic rocks. Ni showed mainly an anthropogenic origin, with higher values found in places next to industrial centers. For Zn the highest values were in areas of agricultural development. The same was observed for Cu, whose presence could be related to the employment of pesticides. The foliar damage index distribution map showed that the central and southeastern zones were the ones where the major damage in the bioindicator was found. The central zone coincides with the city of Córdoba whereas the southeastern area is strictly agricultural, so the high values found there could be related to the use of pesticides.

Agriculture↗

PubMed2001

Estimation of fetal age from dimensions of atlas and axis ossification centers.

The atlas and axis ossification centers of 106 human fetal and neonate skeletons were measured. The skeletons belong to the collection in the Department of Forensic Medicine of the Albert Szent-Györgyi Medical University, Szeged, Hungary. The age of the skeletons ranged from 4 to 10 lunar months. Nine linear measurements on the atlas, seven on the axis neural arches ossification centers and three on each one of the axis centra ossification centers were taken. We did simple and multiple linear regression analysis to estimate the age of fetuses. The results show that it is possible to use regression equations to estimate the fetal body length and age from atlas and axis ossification centers measurements during the whole period of development studied. The study of size and shape of the ossification centers using factorial analysis (principal component analysis) shows that the shape of the dens of the axis might be useful to estimate fetal viability.

Age Determination by Skeleton↗

PubMedDate not supplied

Bioprocess fault detection by nonlinear multivariate analysis: application of an artificial autoassociative neural network and wavelet filter bank.

A nonlinear multivariate analysis, artificial autoassociative neural network (AANN), was applied to bioprocess fault detection. In an optimal production process of a recombinant yeast with a temperature controllable expression system, faults in test cases with faulty temperature sensors and plasmid instability of recombinant cells could be detected by the AANN. Since the raw data of measured variables included high-frequency noise, a wavelet filter bank (WFB) was applied to noise elimination before training of the AANN. The filtering performance of the WFB was compared with those of some classical first-order digital filters. The filtered signals at several resolution scales by the WFB were employed as the training data of the AANN. The computing time and summation of square of errors in training were compared, and the appropriate degree of the noise filtering and the density of the training data of the AANN were discussed. The performance of the feature capturing by the AANN was compared with that by a linear multivariate analysis, principal component analysis. A J index defined in this paper, using inputs and outputs of the AANN, was used for fault detection successfully. The output of the first unit of the trained AANN functioned effectively for the discrimination of the data in the abnormal cases from the data in the normal cases.

Algorithms↗

PubMed2000

Quantitative study of flavonoids in leaves of citrus plants.

Leaf flavonoids were quantitatively determined in 68 representative or economically important Citrus species, cultivars, and near-Citrus relatives. Contents of 23 flavonoids including 6 polymethoxylated flavones were analyzed by means of reversed phase HPLC analysis. Principal component analysis revealed that the 7 associations according to Tanaka's classification were observed, but some do overlap each other. Group VII species could be divided into two different subgroups, namely, the first-10-species class and the last-19-species class according to Tanaka's classification numbers.

Chromatography, High Pressure Liquid↗

PubMed2005

Chemometric discrimination among wild and cultured age-0 largemouth bass, black crappies, and white crappies based on fatty acid composition.

The potential to distinguish juvenile wild from cultured fishes and to discriminate among juvenile fishes by species based on fatty acid composition was demonstrated. Statistical approaches to data evaluation included analysis of variance, correlation analysis, principal component analysis (PCA), and quadratic discriminant analysis (QDA). Differences were determined between wild and cultured fishes both within and between species and between hatcheries. Fatty acid compositions were compared among individual (not composited) specimens of wild and cultured, age-0, freshwater species: largemouth bass Micropterus salmoides, black crappies Pomoxis nigromaculatus, white crappies P. annularis, and black-nose crappies. Four fatty acids were investigated: linoleic acid (18:2n-6), linolenic acid (18:3n-3), arachidonic acid (20:4n-6), and docosahexaenoic acid (22:6n-3). Linoleic acid was the primary fatty acid used to differentiate juvenile wild from cultured fishes. Concentrations of linoleic acid were significantly different (p < 0.05) in cultured largemouth bass and black crappies from the wild counterparts. Linolenic acid concentrations were not significantly different (p < 0.05) between wild and cultured largemouth bass but were significantly different between wild and cultured black crappies. Wild largemouth bass contained higher concentrations of arachidonic acid than the cultured bass, and concentrations of docosahexaenoic acid were twice as high in wild black crappies than cultured black crappies. On the basis of four signature fatty acids, 90 of 91 juvenile fishes were correctly classified as wild or cultured; 32 of 37 wild juvenile fishes originating from the same reservoir were differentiated by species. Data from the training set were used to classify a test set of fishes as to species, source, or origin with 100% accuracy.

Analysis of Variance↗

PubMed1997

Antimalarial activity of molecules interfering with Plasmodium falciparum phospholipid metabolism. Structure-activity relationship analysis.

A series of 80 compounds, primary, secondary, and tertiary amines and quaternary ammonium and bisammonium salts, most of them synthesized as potential choline or ethanolamine analogs, were tested against the in vitro growth of Plasmodium falciparum, the human malaria parasite. They were active over the 10(-3)-10(-8) M concentration range. A structure-activity relationship study was carried out using autocorrelation vectors as structural descriptors, and multidimensional analysis. Principal component analysis, ascending hierarchical classification, and stepwise discriminant analysis showed that both the size and shape of the molecule were essential for antimalarial potency, making the lipophilicity and electronegativity distribution in the molecular space essential. Using the autocorrelogram describing the molecular shape and the electronegativity distribution on the molecular graph, 98% of the molecules were correctly classified either as poorly active or active with only three explanatory variables. The most active compounds were quaternary ammoniums salts whose nitrogen atom had only one long lipophilic chain of 11 or 12 methylene groups (E5, E6, E10, E13, E20, E21, E22, E23, F4, F8), or the bisammoniums whose polar heads were linked by linear alkyl chains of 10 to 12 carbon atoms (G4, G23). The hydroxyethyl group of choline was not very beneficial, whereas the charge and substitutions of nitrogen (aimed at increasing lipophilicity) were essential for optimal interactions. A crude topographic model of the ligand (choline) binding site was thus drawn up.

Animals↗

PubMed2004

Variability of personal chemical exposure in eight office buildings in Sweden.

This study focuses on the variability in chemical exposures for individuals working in office buildings. The study involved eight office buildings with 79 participants, and exposures were measured using personal samplers for volatile organic compounds, aldehydes, amines, nitrogen dioxide, ozone, and particles. Ventilation was assessed in each individual office. "Variability among buildings" and "variability among individuals" were evaluated for any component (of the 123) measured in samples from at least 20 persons, using variance component analysis and principal component analysis. Interpersonal differences explained the major part of the variance for 78% of the compounds versus between-buildings differences for 14% of the compounds. For 8% of compounds, the variation was explained in equal amounts by the differences among individuals and among buildings. This study illustrates the necessity for individualised measurements (versus stationary measurements in building) to estimate personal exposures. These results also support the conclusion that in case-referent studies of "sick building syndrome" (SBS), referents to SBS cases can be randomised for building location.

Air Pollution, Indoor↗

PubMed2003

Micro-Raman spectroscopy of natural and synthetic indigo samples.

In this work indigo samples from three different sources are studied by using Raman spectroscopy: the synthetic pigment and pigments from the woad (Isatis tinctoria) and the indigo plant (Indigofera tinctoria). 21 samples were obtained from 8 suppliers; for each sample 5 Raman spectra were recorded and used for further chemometrical analysis. Principal components analysis (PCA) was performed as data reduction method before applying hierarchical cluster analysis. Linear discriminant analysis (LDA) was implemented as a non-hierarchical supervised pattern recognition method to build a classification model. In order to avoid broad-shaped interferences from the fluorescence background, the influence of 1st and 2nd derivatives on the classification was studied by using cross-validation. Although chemically identical, it is shown that Raman spectroscopy in combination with suitable chemometric methods has the potential to discriminate between synthetic and natural indigo samples.

Journal Article↗

PubMedDate not supplied

Assessing teasing in school-age youth.

Teasing, a common childhood behavior and a frequent precursor to bullying, is known to affect children's developmental outcomes. Despite its ubiquity, no psychometrically valid instrument exists that directly assesses teasing in children. This study reports the development and validity of the Physical Appearance Related Teasing Scale-Revised (PARTS-R), a 14-item scale. The PARTS-R was evaluated using a sample (N = 89) of Arkansas students. Psychometric analysis involved item analysis, principal components analysis (PCA) with varimax rotation, and internal consistency reliability. Three factors--Forms of Harassment, Appearance-Related Teasing, and Physical-Related Teasing--were identified and accounted for 57% of the variance, confirming the conceptual intent of the instrument. Cronbach's alphas for the factors were.83,.74, and.70, respectively. Adequate stability also was demonstrated. Implications for further validation work are identified.

Adolescent↗