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Quantification Methods (quantification + methods)
Selected AbstractsThe Quantification of Qualitative Survey Data: A Critical AssessmentJOURNAL OF ECONOMIC SURVEYS, Issue 5 2003Michela Nardo Abstract., Data obtained from business and consumer surveys are often used in forecasting models and in testing different expectation formation schemes. Their use, however, requires a previous step of transformation of the qualitative data into quantitative figures. This paper contains a critical review of the different quantification methods, highlighting the limits of their use in macroeconomic modelling. [source] Separation and quantification of 9-(alkylthio)acridines by capillary micellar electrokinetic chromatography and capillary liquid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2007Jana Nejmanová Abstract Various thioacridine derivatives are potential chemotherapeutics against various diseases which are intensively synthesized, characterized, and investigated by many research groups. Efficient, fast, and reliable separation and quantification methods for their analysis are still to be developed. MEKC and capillary LC (CLC) were applied for the separation and quantification of five highly hydrophobic, weakly basic, and structurally similar 9-(alkylthio)acridines. Since the common anionic and cationic surfactants failed to separate the strongly hydrophobic thioacridines by MEKC, sodium cholate was used in an alkaline BGE and successfully employed for their fast separation. In CLC, the weakly basic nature of the thioacridines necessitated use of LiChrosorb RP-select B sorbent as the stationary phase, which combined with a very simple mobile phase methanol/water yielded an efficient chromatographic separation system. Both, the MEKC and CLC optimized separation methods were then applied to quantify the thioacridines within a concentration range of 1.0×10,5,1.0×10,3 mol/L and the obtained experimental results were critically compared. In practical terms, the MEKC analytical method can quantify the analytes much faster but with a lower reliability while the CLC method performs slower analysis with a higher repeatability of the experimental results. [source] Real-time polymerase chain reaction as a rapid and efficient alternative to estimation of picornavirus titers by tissue culture infectious dose 50% or plaque forming unitsMICROBIOLOGY AND IMMUNOLOGY, Issue 3 2009Nina Jonsson ABSTRACT Quantification of viral infectious units is traditionally measured by methods based on forming plaques in semisolid media (PFU) or endpoint dilution of a virus-containing solution (TCID50), methods that are laborious, time-consuming and take on average 3,7 days to carry out. Quantitative real-time PCR is an established method to quantify nucleic acids at high accuracy and reproducibility, routinely used for virus detection and identification. In the present study, a procedure was developed using a two-step real-time PCR and the SYBR Green detection method to study whether there are correlations between TCID50/ml, PFU/ml and Ct values generated by real-time PCR enabling rapid and efficient calculation of titer equivalents when working with viruses in the research laboratory. In addition, an external standard with known concentrations was included using in vitro transcribed viral RNA, thus allowing the calculation of the amount of RNA copies needed for various applications (i.e. per plaque or TCID50). The results show that there is a correlation between the three quantification methods covering a wide range of concentration of viruses. Furthermore, a general regression line between TCID50 and Ct values was obtained for all viruses included in the study, which enabled recording titer equivalents using real-time PCR. Finally, by including an external standard, the amount of RNA genomes generating one TCID50 or PFU for each enterovirus serotype included was determined. [source] Imaging FRET standards by steady-state fluorescence and lifetime methodsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 12 2007Beatriz Domingo Abstract Imaging fluorescence resonance energy transfer (FRET) between molecules labeled with fluorescent proteins is emerging as a powerful tool to study changes in ions, ligands, and molecular interactions in their physiological cellular environment. Different methods use either steady-state fluorescence properties or lifetime to quantify the FRET rate. In addition, some provide the absolute FRET efficiency whereas others are simply a relative index very much influenced by the actual settings and instrumentation used, which makes the interpretation of a given FRET rate very difficult. The use and exchange of FRET standards in laboratories using these techniques would help to overcome this drawback. We report here the construction and systematic evaluation of FRET standard probes of varying FRET efficiencies. The standards for intramolecular FRET were protein fusions of the cyan and yellow variants of A. victoria green fluorescent protein (ECFP and citrine) joined by short linkers or larger protein spacers, or ECFP tagged with a tetracysteine motif and labeled with the biarsenical fluorochrome, FlAsH. Negative and positive controls of intermolecular FRET were also used. We compared these FRET standards with up to four FRET quantification methods: ratioing of acceptor to donor emission, donor intensity recovery upon acceptor photobleach, sensitized emission after spectral unmixing of raw images, and fluorescence lifetime imaging (FLIM). The latter was obtained with a frequency-domain setup able to provide high quality lifetime images in less than a second, and is thus very well suited for live cell studies. The FRET rates or indexes of the standards were in good agreement regardless of the method used. For the CFP-tetraCys/FlAsH pair, the rate calculated from CFP quenching was faster than that obtained by FLIM. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source] Comparison of apoptosis and mortality measurements in peripheral blood mononuclear cells (PBMCs) using multiple methodsCELL PROLIFERATION, Issue 5 2005S. Glisic-Milosavljevic Death through apoptosis is the main process by which aged cells that have lost their function are eliminated. Apoptotic cells are usually detected microscopically by changes in their morphology. However, determination of early apoptotic events is important for in vitro (and ex vivo) studies. The main objective of the present study is to find the most sensitive method for apoptosis detection in human peripheral blood mononuclear cells (PBMCs) by comparing six different methods following five different means of immunological stimulation at 3 and 5 days. Each of six apoptosis quantification methods, except the trypan blue exclusion test, is a combination of two stains, one for the specific detection of apoptotic cells and the other for the unspecific detection of dead cells. Values for apoptosis and mortality were compared with a reference method. The choice of apoptosis detection method is more important following 3 days of stimulation than after 5 days of stimulation (P = 2 × 10,6 versus P = 1 × 10,2). In contrast, we find mortality measurements following the different means of stimulation highly significant at both 3 and 5 days (F2.28 = 7.9, P = 1.4 × 10,6 at 3 days and F2.28 = 8.5, P = 4.5 × 10,7 at 5 days). Variation as a result of the combination of specific PBMC stimulation and the method used to detect apoptosis is reduced considerably with time (F1.58 + 3.7, P + 3 × 10,7 at 3 days to F = (1.58) = 0.97, P = 0.5 at 5 days). Based on Tukey's test, YO-PRO-1 is the most sensitive stain for apoptosis and, when combined with 7-AAD, provides an accurate measure of apoptosis and mortality. In conclusion, we propose YO-PRO-1/7-AAD as a new combination and low-cost alternative for the sensitive detection of early apoptosis. [source] | ||||||||||