887 resultados para methods of analysis


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A global dataset of in situ particulate absorption spectra has been decomposed into component functions representing absorption by phytoplankton pigments and non-algal particles. The magnitudes of component Gaussian functions, used to represent absorption by individual or groups of pigments, are well correlated with pigment concentrations determined using High Performance Liquid Chromatography. We are able to predict the presence of chlorophylls a,ba,b, and cc, as well as two different groups of summed carotenoid pigments with percent errors between 30% and 57%. Existing methods of analysis of particulate absorption spectra measured in situ provide for only chlorophyll aa; the method presented here, using high spectral resolution particulate absorption, shows the ability to obtain the concentrations of additional pigments, allowing for more detailed studies of phytoplankton ecology than currently possible with in-situ spectroscopy.

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The aim of the paper is to explore teachers’ methods of delivering an ethos of tolerance, respect
and mutual understanding in one integrated secondary school in Northern Ireland. Drawing on
interviews with teachers in the school, it is argued that most teachers make ‘critical choices’
which both reflect and reinforce a ‘culture of avoidance’, whereby politically or religiously contentious
issues are avoided rather than explored. Although teachers are well-intentioned in making
these choices, it is shown that they have the potential to create the conditions that maintain or even
harden psychological boundaries between Catholics and Protestants rather than dilute them.

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Reported mast-cell counts in endobronchial biopsies from asthmatic subjects are conflicting, with different methodologies often being used. This study compared three standard methods of counting mast cells in endobronchial biopsies from asthmatic and normal subjects. Endobronchial biopsies were obtained from atopic asthmatic subjects (n=17), atopic nonasthmatic subjects (n=6), and nonatopic nonasthmatic control subjects (n=5). After overnight fixation in Carnoy's fixative, mast cells were stained by the short and long toluidine blue methods and antitryptase immunohistochemistry and were counted by light microscopy. Method comparison was made according to Bland & Altman. The limits of agreement were unacceptable for each of the comparisons, suggesting that the methods are not interchangeable. Coefficients of repeatability were excellent, and not different for the individual techniques. These results suggest that some of the reported differences in mast-cell numbers in endobronchial biopsies in asthma may be due to the staining method used, making direct comparisons between studies invalid. Agreement on a standard method is required for counting mast cells in bronchial biopsies, and we recommend the immunohistochemical method, since fixation is less critical and the resultant tissue sections facilitate clear, accurate, and rapid counts.

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Proteomic tools-in particular, mass spectrometry (MS)-have advanced significantly in recent years, and the identification of proteins within complex mixtures is now a routine procedure. Quantitative methods of analysis are less well advanced and continue to develop. These include the use of stable isotope ratio approaches, isotopically labeled peptide standards, and nonlabeling methods. This paper summarizes the use of MS as a proteomics tool to identify and semiquantify proteins and their modified forms by using examples of relevance to the Maillard reaction. Finally, some challenges for the future are presented.

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In 1966 the artist Antonio Lopez was rejected for the chair in “Preparatorio de colorido” (Preparatory Colouring) by the San Fernando School of Fine Arts where he himself presented his work Nevera de hielo (Ice Box). After 5 years as a “stand in” for this post he left the Institution. This article analyzes the circumstances and proof of a decade where there appears to be evidence of a definite change in his work, more toward Realism, uncomfortable in a system that maintained with difficulty the traditional academic model copy, and incompatible with, in those years was imposed by Spain. At the same time his relation with photography conditioned by the theoretical thoughts of the artist, and his work methods also are analyzed in this article.

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The spontaneous formation of the neurotoxic carcinogen acrylamide in a wide range of cooked foods has recently been discovered, leading to dietary exposure estimates of 30.8 mu g of acrylamide day(-1) for an average 77 kg human male. This is considerably higher than the European legal limit of acrylamide in drinking water, which is approximately 0.2 mu g of acrylamide person(-1) day(-1). A recent study of 62,573 women over 11.3 years has observed an increased risk of postmenopausal endometrial and ovarian cancer (but not breast cancer) with increasing dietary acrylamide intake, demonstrating significant risk to human health. As individual acrylamide exposure is affected by dietary habits, cooking methods, and cigarette consumption; accurate extrapolation from estimated dietary exposure is extremely difficult. Quantifying biomarkers of acrylamide exposure therefore remains the most effective means of rapidly determining individual exposure to acrylamide, and correlating exposure with lifestyle choices. Current methodologies for the analysis of blood biomarkers of acrylamide are focused on expensive, slower chromatographic techniques such as GC and LC coupled to mass spectrometry. This paper describes the first successful development of two monoclonal antibodies specific to acrylamide-adducted haemoglobin (IC50 of 94 ng ml(-1) and 198 ng ml(-1)), that are suitable for use in a high-throughput biomarker immunoassay to determine individual acrylamide exposure. Further development of acrylamide-haemoglobin standards with defined levels of acrylamide adduction will enable a fully quantitative assay, and allow sensitivity comparisons with alternative chromatographic methods of analysis. (C) 2008 Elsevier B.V. All rights reserved.

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The continuing interest in semiconductor photochemistry, SPC, and the emergence of commercial products that utilise films of photocatalyst materials, has created an urgent need to agree a set of methods for assessing photocatalytic activity and international committees are now meeting to address this issue. This article provides a brief overview of two of the most popular current methods employed by researchers for assessing SPC activity. and one which has been published just recently and might gain popularity in the future, given its ease of use. These tests are: the stearic acid (SA) test, the methylene blue (MB) test and the resazurin (Rz) ink test, respectively. The basic photochemical and chemical processes that underpin each of these tests are described, along with typical results for laboratory made sol-gel titania films and a commercial form of self-cleaning glass, Activ (TM). The pros and cons of their future use as possible standard assessment techniques are considered. (C) 2007 Elsevier B.V. All rights reserved.