Data Evaluation (data + evaluation)

Distribution by Scientific Domains


Selected Abstracts


Identification of novel genes regulated by ,-melanocyte-stimulating hormone in murine bone marrow-derived dendritic cells

EXPERIMENTAL DERMATOLOGY, Issue 9 2004
T. Brzoska
Many strains of evidence indicate that ,-melanocyte-stimulating hormone (,-MSH) elicits its immunomodulatory activity via binding to melanocortin receptors (MC-Rs) expressed on monocytes and dendritic cells. In order to identify novel target genes regulated by ,-MSH in these cells, we prepared bone marrow-derived dendritic cell precursors from BALB/c mice and treated them with GM-CSF and IL-4 for 6 days. The MC-R profile on these immature dendritic cells was first determined by quantitative RT-PCR. Both transcripts for MC-1R and MC-5R were detected in these cells. Cells were subsequently stimulated with dinitrobenzene sulfonic acid (DNBS), ,-MSH or both substances for 2 or 16 h. After RNA preparation, cDNA synthesis and in vitro transcripton hybridization of biotinylated cRNA samples was performed on MG U74A Affymetrix gene chips. Data evaluation, cleansing, extraction and analysis of the more than 12 000 cloned genes and expressed sequence tags were performed using the GENE DATA ANALYST vs. 1 Expressionist software. Filter criteria included a minimum threshold of 100, normalization by the logarithmic mean and a quality setting of P < 0.04. Changes with a change factor of >2 were regarded as significant. As expected, stimulation with DNBS resulted in induction or upregulation of genes encoding proinflammatory cytokines, growth factors, signal transduction intermediates and transcription factors. Treatment with ,-MSH blocked the DNBS-driven upregulation of several known genes such as IL-1 or CD86. On the other hand, ,-MSH modulated the expression of several novel genes implicated in immunomodulation, e.g. IL-1, converting enzyme, IFN-, receptor, FK506-binding proteins or several neuropeptides and their receptors. These data indicate novel molecular targets by which ,-MSH exerts its immunomodulatory activities in immunocompetent cells. [source]


Data evaluation in chromatography by principal component analysis

BIOMEDICAL CHROMATOGRAPHY, Issue 1 2010
T. Cserháti
Abstract The newest achievements in the employment of principal component analysis, a multivariate mathematical statistical method, in the evaluation of chromatographic retention data are compiled. The results obtained by various chromatographic technologies such as gas,liquid chromatography, thin,layer chromatography, high-performance liquid chromatography and electrically driven systems are compiled and briefly discussed. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Mouse lymphoma thymidine kinase gene mutation assay: Follow-up meeting of the international workshop on Genotoxicity testing,Aberdeen, Scotland, 2003,Assay acceptance criteria, positive controls, and data evaluation,

ENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 1 2006
Martha M. Moore
Abstract The Mouse Lymphoma Assay (MLA) Workgroup of the International Workshop on Genotoxicity Testing (IWGT), comprised of experts from Japan, Europe, and the United States, met on August 29, 2003, in Aberdeen, Scotland, United Kingdom. This meeting of the MLA Workgroup was devoted to reaching a consensus on the appropriate approach to data evaluation and on acceptance criteria for both the positive and negative/vehicle controls. The Workgroup reached consensus on the acceptance criteria for both the agar and microwell versions of the MLA. Recommendations include acceptable ranges for mutant frequency, cloning efficiency, and suspension growth of the negative/vehicle controls and on criteria to define an acceptable positive control response. The recommendation for the determination of a positive/negative test chemical response includes both the requirement that the response exceeds a defined value [the global evaluation factor (GEF)] and that there also be a positive dose,response (evaluated by an appropriate statistical method). Environ. Mol. Mutagen., 2006. Published 2005 Wiley-Liss, Inc. [source]


Quantitative structure-activity relationships for predicting potential ecological hazard of organic chemicals for use in regulatory risk assessments

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2003
Mike H. I. Comber
Abstract The use of quantitative structure-activity relationships (QSARs) for deriving the predicted no-effect concentration of discrete organic chemicals for the purposes of conducting a regulatory risk assessment in Europe and the United States is described. In the United States, under the Toxic Substances Control Act (TSCA), the TSCA Interagency Testing Committee and the U.S. Environmental Protection Agency (U.S. EPA) use SARs to estimate the hazards of existing and new chemicals. Within the Existing Substances Regulation in Europe, QSARs may be used for data evaluation, test strategy indications, and the identification and filling of data gaps. To illustrate where and when QSARs may be useful and when their use is more problematic, an example, methyl tertiary-butyl ether (MTBE), is given and the predicted and experimental data are compared. Improvements needed for new QSARs and tools for developing and using QSARs are discussed. [source]


Simulating and evaluating small-angle X-ray scattering of micro-voids in polypropylene during mechanical deformation

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2010
Stefan Fischer
Micro-voids that evolve during mechanical deformation in polypropylene have been characterized by small-angle X-ray scattering. Such voids can be modelled as randomly distributed cylinders which are oriented along the stretching direction, showing a log-normal size distribution. The model and simulation results are presented here. Advantages and disadvantages of the approach, the validity of the model, and important considerations for data evaluation are discussed. Data analysis of two-dimensional scattering images has been performed using a fully automated MATLAB routine by direct model fitting to scattering images. [source]


Evaluation of double-crystal SANS data influenced by multiple scattering

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2000
aroun
Evaluation of small-angle neutron scattering (SANS) data is often complicated by multiple scattering effects if large particles of relatively high volume fraction have to be studied and dilution or contrast reduction is impossible. The use of pin-hole SANS instruments is often limited due to the contradictory requirements of high resolution and short wavelength needed to keep scattering contrast as low as possible. Double crystal (DC) SANS diffractometers of Bonse-Hart and bent-crystal type are useful alternatives in such cases, as they permit reaching very high resolution with thermal neutrons. A method for SANS data evaluation suited to DC instruments is presented. It includes the common scheme of the indirect Fourier transformation method, but takes multiple scattering into account. The scattering medium is described by the frequency function g(x) defined as the cosine Fourier transform of slit-smeared data. Although a simplistic model of polydisperse spheres is used to represent g(x), resulting g(x) function and some integral parameters are independent of this model. Tests on simulated data show, that the method reproduce well true values of microstructural parameters, though systematic errors are observed in the cases when the unscattered part of incident beam completely disappears. If the scattering power is known and kept fixed during fitting, then other parameters are reproduced well also in the regime of strong multiple scattering. The evaluation procedure permits simultaneously fitting to several sets of data measured for different Q -regions, resolutions and sample thicknesses. It has proved to provide reliable results for particle sizes ranging from about 100 Å to several microns and < 10. [source]


Accelerating the analyses of 3-way and 4-way PARAFAC models utilizing multi-dimensional wavelet compression

JOURNAL OF CHEMOMETRICS, Issue 11-12 2005
Jeff Cramer
Abstract Parallel factor analysis (PARAFAC) is one of the most popular methods for evaluating multi-way data sets, such as those typically acquired by hyphenated measurement techniques. One of the reasons for PARAFAC popularity is the ability to extract directly interpretable chemometric models with little a priori information and the capability to handle unknown interferents and missing values. However, PARAFAC requires long computation times that often prohibit sufficiently fast analyses for applications such as online sensing. An additional challenge faced by PARAFAC users is the handling and storage of very large, high-dimensional data sets. Accelerating computations and reducing storage requirements in multi-way analyses are the topics of this manuscript. This study introduces a data pre-processing method based on multi-dimensional wavelet transforms (WTs), which enables highly efficient data compression applied prior to data evaluation. Because multi-dimensional WTs are linear, the intrinsic underlying linear data construction is preserved in the wavelet domain. In almost all studied examples, computation times for analyzing the much smaller, compressed data sets could be reduced so much that the additional effort for wavelet compression was more than recompensated. For 3-way and 4-way synthetic and experimental data sets, acceleration factors up to 50 have been achieved; these data sets could be compressed down to a few per cent of the original size. Despite the high compression, accurate and interpretable models were derived, which are in good agreement with conventionally determined PARAFAC models. This study also found that the wavelet type used for compression is an important factor determining acceleration factors, data compression ratios and model quality. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Fast principal component analysis of large data sets based on information extraction

JOURNAL OF CHEMOMETRICS, Issue 11 2002
F. Vogt
Abstract Principal component analysis (PCA) and principal component regression (PCR) are routinely used for calibration of measurement devices and for data evaluation. However, their use is hindered in some applications, e.g. hyperspectral imaging, by excessive data sets that imply unacceptable calculation time. This paper discusses a fast PCA achieved by a combination of data compression based on a wavelet transformation and a spectrum selection method prior to the PCA itself. The spectrum selection step can also be applied without previous data compression. The calculation speed increase is investigated based on original and compressed data sets, both simulated and measured. Two different data sets are used for assessment of the new approach. One set contains 65,536 synthetically generated spectra at four different noise levels with 256 measurement points each. Compared with the conventional PCA approach, these examples can be accelerated 20 times. Evaluation errors of the fast method were calculated and found to be comparable with those of the conventional approach. Four experimental spectra sets of similar size are also investigated. The novel method outperforms PCA in speed by factors of up to 12, depending on the data set. The principal components obtained by the novel algorithm show the same ability to model the measured spectra as the conventional time-consuming method. The acceleration factors also depend on the possible compression; in particular, if only a small compression is feasible, the acceleration lies purely with the novel spectrum selection step proposed in this paper. Copyright © 2002 John Wiley & Sons, Ltd. [source]


The evaporation method: Extending the measurement range of soil hydraulic properties using the air-entry pressure of the ceramic cup

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2010
Uwe Schindler
Abstract Knowledge of hydraulic functions is required for various hydrological and plant-physiological studies. The evaporation method is frequently used for the simultaneous determination of hydraulic functions of unsaturated soil samples, i.e., the water-retention curve and hydraulic-conductivity function. All methodic variants of the evaporation method suffer from the limitation that the hydraulic functions can only be determined to a mean tension of , 60 kPa. This is caused by the limited measurement range of the tensiometers of typically 80 kPa on the dry end. We present a new, cost- and time-saving approach which overcomes this restriction. Using the air-entry pressure of the tensiometer's porous ceramic cup as additional defined tension value allows the quantification of hydraulic functions up to close to the wilting point. The procedure is described, uncertainties are discussed, and measured as well as simulated test results are presented for soil samples of various origins, different textures (sand, loam, silt, clay, and peat) and variable dry bulk density. The experimental setup followed the system HYPROP which is a commercial device with vertically aligned tensiometers that is optimized to perform evaporation measurements. During the experiment leaked water from the tensiometer interior wets the surrounding soil of the tensiometer cup and can lead to a tension retardation as shown by simulation results. This effect is negligible when the tensiometers are embedded vertically. For coarsely textured soils and horizontal tensiometer alignment, however, the retardation must be considered for data evaluation. [source]


Characterisation of proteinaceous binders in artistic paintings by chromatographic techniques

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 3 2004
Maria Perla Colombini
Abstract This review discusses the application of chromatographic techniques (GC, HPLC and Py-GC) for the characterisation of proteinaceous materials in artistic paintings. The focus is on the various analytical steps that are needed to determine these natural materials in paint samples, from sampling and sample pre-treatment, including various methods of hydrolysis and derivatisation for GC and HPLC, to approaches for data evaluation. [source]


Online monitoring of crevice corrosion with electrochemical noise

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 10 2004
G. Schmitt
Abstract The time-related cumulated noise charges extracted from the noise signals between two "identical" crevice electrodes yield a direct quantitative easy-to-interpret information on time-related corrosion intensities in the crevice. A new software-assisted method of noise data evaluation allows a "counting of coulombs" exchanged between the system electrodes, the results of which directly correlate with the metal dissolution intensity in the crevice. The versatility of this "CoulCount" method is demonstrated in a failure analysis on the cause of crevice corrosion at spigots of automotive cooling water pumps. Echzeitüberwachung von Spaltkorrosion durch Elektrochemisches Rauschen Zeitbezogene Gesamtrauschladungsmengen, welche aus den Rauschsignalen zwischen zwei "identischen" Spalteleltroden gewonnen werden können, liefern einfach zu interpretierende Informationen über die zeitbezogene Korrosionsintensität im Spalt. Eine neue, Software-unterstützte Methode der Rauschdatenauswertung erlaubt das Zählen der Ladungen, die zwischen den Systemelektroden ausgetauscht werden. Das Ergebnis korreliert direkt mit der Metallauflösungsintensität im Spalt. Die vielseitige Anwendbarkeit dieser "CoulCount-Methode" wird am Beispiel einer Schadensanalyse zur Ursache der Spaltkorrosion an Stutzen von Automobilwasserpumpen demonstriert. [source]