Home About us Contact
|
Home About us Contact | ||
|
|
||
Single Measurement (single + measurement)
Selected AbstractsBiochemical markers of hepatic fibrogenesis: Single measurements are not reliable enough to replace liver biopsyJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 8 2000Jacob George No abstract is available for this article. [source] System identification of linear structures based on Hilbert,Huang spectral analysis.EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2003Part 2: Complex modes Abstract A method, based on the Hilbert,Huang spectral analysis, has been proposed by the authors to identify linear structures in which normal modes exist (i.e., real eigenvalues and eigenvectors). Frequently, all the eigenvalues and eigenvectors of linear structures are complex. In this paper, the method is extended further to identify general linear structures with complex modes using the free vibration response data polluted by noise. Measured response signals are first decomposed into modal responses using the method of Empirical Mode Decomposition with intermittency criteria. Each modal response contains the contribution of a complex conjugate pair of modes with a unique frequency and a damping ratio. Then, each modal response is decomposed in the frequency,time domain to yield instantaneous phase angle and amplitude using the Hilbert transform. Based on a single measurement of the impulse response time history at one appropriate location, the complex eigenvalues of the linear structure can be identified using a simple analysis procedure. When the response time histories are measured at all locations, the proposed methodology is capable of identifying the complex mode shapes as well as the mass, damping and stiffness matrices of the structure. The effectiveness and accuracy of the method presented are illustrated through numerical simulations. It is demonstrated that dynamic characteristics of linear structures with complex modes can be identified effectively using the proposed method. Copyright © 2003 John Wiley & Sons, Ltd. [source] Quantifying the relationship between soil organic carbon and soil physical properties using shrinkage modellingEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2009P. Boivin Summary Changes in soil organic carbon (SOC) may strongly affect soil structure and soil physical properties, which in turn may have feedback effects on the soil microbial activity and SOC dynamics. Such interactions are still not quantitatively described and accounted for in SOC dynamics modelling. The objective of this study was to test the hypothesis that soil shrinkage curve (ShC) analysis allows the establishment of close relationships between soil physical properties and SOC. We sampled a rice-cropped vertisol, a cambisol under conventional tillage and no-tillage and a restored cambisol. Soil samples were analysed for clay and SOC content, bulk volume, hydro-structural stability and plasma and structural pore volumes changes on the full water content range using ShC analysis. Although the soils behaved differently according to their constituents and history, changes in SOC linearly affected most of the soil physical properties, with stronger effects than changes in clay content. The observed effects of increasing SOC, such as increasing hydro-structural stability, specific bulk volume and water retention, agreed well with previously reported results. However, using ShC measurement and modelling allowed the observation of all these different effects simultaneously for small changes in SOC, and in a single measurement. Moreover, the relation between SOC changes and physical properties could be quantified. ShC analysis may, therefore, be used to account for the effect of changes in SOC on soil physical properties. [source] Accessing Time,Varying Forces on the Vibrating Tip of the Dynamic Atomic Force Microscope to Map Material CompositionISRAEL JOURNAL OF CHEMISTRY, Issue 2 2008Ozgur Sahin In dynamic atomic force microscopes the primary physical quantities being measured are the amplitude/phase or amplitude/frequency of the vibrating force probe. Topographic images with spatial resolutions down to the atomic scale can be obtained by mapping these measurements across the sample surface under feedback control. During the imaging process the vibrating tip is observing tip,sample interaction potentials (force,distance relationships) at every point on the surface. The interaction potential is a superposition of short- and long,distance interactions of various origins determined by the material compositions of the tip, sample, and the medium of imaging. In principle, measurement of tip,sample interaction potential should allow determination and mapping of material composition of the sample. However, a single measurement of amplitude/phase or amplitude/frequency in dynamic atomic force microscopes is not enough to characterize a complicated tip,sample interaction potential. Recent developments in the understanding of dynamics of the vibrating force probe (cantilever), together with specially designed cantilevers that utilize torsional vibrations in addition to conventional vertical vibrations, enable the recovery of tip,sample interaction potentials at a timescale less than a millisecond. Here, with theory and experiments, we discuss how these cantilevers recover the information about the tip,sample interaction forces and give an example of compositional mapping on a polymeric material system. [source] Raman spectroscopy with simultaneous measurement of two orthogonally polarized Raman spectraJOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2003G. A. Thomson Abstract A Raman microscope was modified to allow the independent acquisition of two orthogonally polarized components of a Raman spectrum in a single measurement. Preliminary performance was demonstrated by simultaneously measuring the intensity of both polarized components of the silicon Raman band at 520 cm,1 as a silicon wafer was rotated through 360° under a polarized laser Raman probe. Polarization-resolved Raman spectra of a complex molecular crystal are also presented, illustrating the increase in spectral information available with the modified system. Copyright © 2003 John Wiley & Sons, Ltd. [source] PREDICTING TEXTURE ATTRIBUTES FROM MICROSTRUCTURAL, RHEOLOGICAL AND THERMAL PROPERTIES OF HAZELNUT SPREADSJOURNAL OF TEXTURE STUDIES, Issue 5 2008ROSSELLA DI MONACO ABSTRACT Eight trained assessors evaluated one visual, eight texture and four gustative attributes of 15 commercial spreads. In addition, 100 consumers evaluated the acceptability of the spreads. Rheological behavior of the samples was evaluated in transient (stress,relaxation test) and dynamic (strain and frequency sweep test) shear mode. Thermal measurements were also performed. Finally, the microstructure of the samples was analyzed by scanning electron microscopy. Partial least squares regression was used to predict acceptability from sensory attributes and texture from instrumental data. Scanning electron micrographs indicated that spreads differed in morphology, size and distribution of hazelnut particles. Overall liking of the spreads was found to be related to hazelnut flavor and texture attributes. Prediction of the most important texture properties from instrumental measurements was quite successful, especially for spreadability which was found negatively related to the consistency and flow indices and, secondly, for meltability which was found to be strongly dependent on measured thermal parameters. PRACTICAL APPLICATIONS This study contributes to knowledge development in the research area of acceptability, sensory and instrumental correlation for semi-solid foods. The results confirm that texture properties of spreadable foods play a most important role in consumer acceptability. The research also allows better understanding as to why no single measurement is able to predict all texture attributes adequately and why more appropriate tests need to be developed for an accurate prediction of some sensory attributes as perceived by the human senses. [source] Predictive value of actin-free Gc-globulin in acute liver failure,,LIVER TRANSPLANTATION, Issue 9 2007Frank V. Schiødt Serum concentrations of the actin scavenger Gc-globulin may provide prognostic information in acute liver failure (ALF). The fraction of Gc-globulin not bound to actin is postulated to represent a better marker than total Gc-globulin but has been difficult to measure. We tested a new rapid assay for actin-free Gc-globulin to determine its prognostic value when compared with the King's College Hospital (KCH) criteria in a large number of patients with ALF. A total of 252 patients with varying etiologies from the U.S. ALF Study Group registry were included; the first 178 patients constituted the learning set, and the last 74 patients served as the validation set. Actin-free Gc-globulin was determined with a commercial enzyme-linked immunosorbent assay kit. The median (range) actin-free Gc-globulin level at admission for the learning set was significantly reduced compared with controls (47 [0-183] mg/L vs. 204 [101-365] mg/L, respectively, P < 0.001). Gc-globulin levels were significantly higher in spontaneous survivors than in patients who died or were transplanted (53 [0-129] mg/L vs. 37 [0-183] mg/L, P = 0.002). A receiver operating characteristic curve analysis showed that a 40 mg/L cutoff level carried the best prognostic information, yielding positive and negative predictive values of 68% and 67%, respectively, in the validation set. The corresponding figures for the KCH criteria were 72% and 64%. A new enzyme-linked immunosorbent assay for actin-free Gc-globulin provides the same (but not optimal) prognostic information as KCH criteria in a single measurement at admission. Liver Transpl 13:1324,1329, 2007. © 2007 AASLD. [source] High-resolution NMR correlation experiments in a single measurement (HR-PANACEA)MAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2010riks Kup Abstract Three important NMR pulse sequences, INADEQUATE, HSQC and three-dimensional HMBC have been combined into a single entity called high-resolution Parallel Acquisition NMR: an All-in-one Combination of Experimental Applications (HR-PANACEA) to provide reliable structural information about a small molecule in a single measurement. This exploits a recent instrumental development that permits simultaneous acquisition of signals from several nuclear species, using multiple receivers. Where high-precision values of the long-range heteronuclear splittings are important, selected regions of a large experimental data matrix are extracted and examined with the highest possible resolution. The J -doubling technique is then applied to derive precise values for these couplings. As proof of principle, the method is applied to the molecule of methyl salicylate, confirming the expected conformation of the COH moiety. Copyright © 2010 John Wiley & Sons, Ltd. [source] SPEED: single-point evaluation of the evolution dimensionMAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2007Eriks Kup Abstract Two-dimensional NMR spectroscopy can be speeded up by orders of magnitude by severely restricting the number of sampling operations in the evolution dimension,we demonstrate that just a single measurement may suffice. The frequencies evolving in the indirect dimension (t1) are deduced from the amplitudes of the signals acquired in the direct dimension (t2). Prior measurements of the one-dimensional spectra are required. Results are presented for the two-dimensional 13C-HSQC spectrum of 2-ethylindanone recorded at a single fixed setting of the evolution time, demonstrating a speed advantage of 120. The method can be extended to multidimensional spectra, with correspondingly greater gains in speed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Morphometric characterization of murine articular cartilage,Novel application of confocal laser scanning microscopyMICROSCOPY RESEARCH AND TECHNIQUE, Issue 9 2009Kathryn S. Stok Abstract A new technique for characterization of the three-dimensional morphology of murine articular cartilage is proposed. The technique consists of a novel application of confocal laser scanning microscopy (CLSM), where the objective was to develop and validate it for cartilage measurements in murine joints. Murine models are used in arthritis research, because they are well-described for manipulating the disease pathophysiology, facilitating our understanding of the disease, and identifying new targets for therapy. A calibration and reproducibility study was carried out to provide a consistent testing methodology for quantification of murine joints. The proximal tibial condyles from male C57BL/6 mice were scanned using a CLS microscope with an isotropic voxel size of 5.8 ,m. Measurements and analyses were repeated three times on different days, and in a second step the analysis was repeated three times for a single measurement. Calculation of precision errors (coefficient of variation) for cartilage thickness and volume was made. The bias of the system was estimated through comparison with histology. This technique showed good precision, with errors in the repeated analysis ranging from 0.63% (lateral thickness) to 3.48% (medial volume). The repeated analysis alone was robust, with intraclass correlations for the different compartments between 0.918 and 0.991. Measurement bias was corrected by scaling the confocal images to 32% of their width to match histology. CLSM provided a fast and reproducible technique for gathering 3D image data of murine cartilage and will be a valuable tool in understanding the efficacy of arthritis treatments in murine models. Microsc. Res. Tech. 2009. © 2009 Wiley-Liss, Inc. [source] Variation of dust endotoxin concentrations by location and time within homes of young childrenPEDIATRIC ALLERGY AND IMMUNOLOGY, Issue 3 2010Dennis R. Ownby Ownby DR, Peterson EL, Williams LK, Zoratti EM, Wegienka GR, Woodcroft KJ, Joseph CLM, Johnson CC. Variation of dust endotoxin concentrations by location and time within homes of young children. Pediatr Allergy Immunol 2010: 21: 533,540. © 2010 John Wiley & Sons A/S Endotoxin may affect the development of allergic disease in childhood but little is known about endotoxin variation within homes. We sought to determine endotoxin concentration agreement within homes when five locations were each sampled twice 5 months apart. Endotoxin was measured using the recombinant Limulus factor C assay in dust samples from 585 homes of children enrolled in a prospective study and again in 335 homes 5 months later. The five locations sampled in each home were the child's bedroom floor, child's bed, mother's bedroom floor, mother's bed and living room floor. Concentrations of 4 allergens (Can f 1, Fel d 1, Der f 1 and Bla g 2) were also measured from the child's bedroom floor. In pair-wise comparisons, endotoxin concentrations in all locations within each home were significantly different from all other locations (p < 0.001) except for the child's and mother's bedroom floors (p = 0.272). Spearman correlations between endotoxin concentrations from the different locations were all statistically significant (p < 0.05) but of modest magnitude (r = 0.24,0.54). Similarly, correlations at each site over the 5 month observation interval were statistically significant but modest (r = 0.17,0.44). Pets and season of the year did not affect correlations, although correlations were lower if the floor was not carpeted. Endotoxin concentrations at all locations were minimally correlated with allergen concentrations in both negative and positive directions (r = ,0.12 to 0.12). We conclude that a single measurement of endotoxin from a home dust sample provides an imprecise estimate of dust endotoxin concentrations in other locations within the home and over a relatively short observation interval. [source] Temperament assessments of lactating cows in three contexts and their applicability as management traitsANIMAL SCIENCE JOURNAL, Issue 6 2004Katsuji UETAKE ABSTRACT The applicability of three behavioral assessments of lactating cows as management traits was verified. Flight responses to an approaching human (flight starting and walking distances, and flight walking speed) at pasture, entrance order into the milking parlour and step-kick behavior to cup attachment were observed for 713 subject cows in six Australasian dairy farms. On all farms, cows were kept at pasture without any barn housing. Flight responses were measured once, and other assessments were recorded repeatedly for each subject cow. A principal component analysis was performed to verify whether these assessments appear to measure the same trait. A two-way anova and correlation analyses were then used to test whether obtained principal components were affected by farm, age and milking stage of cows. Australian and some Japanese herd management systems were compared for flight distance using a one-way anova and a multiple comparison test. Three behavioral assessments clustered in different principal components, indicating that these assessments did not appear to measure the same trait. Factor scores of four principal components were affected by farm (all, P < 0.01), and the scores of principal component 1, interpreted as fear of humans (r = ,0.16, P < 0.01), and component 2, interpreted as aversion to cup attachment (r = ,0.28, P < 0.01), were moderately correlated with age. These results emphasize the necessity of data standardization to reduce the non-genetic variation resulting from these two affectors. The flight distance at pasture of herds in Australia (6.06 ± 2.85 m) was significantly (P < 0.05) different from the flight distances measured in paddocks (1.50 ± 0.82 m) and free-stall barns (1.22 ± 1.09 m) in Japan. However, mean distances were not different between the Australian herds at pasture and the Japanese herds at pasture in tie-stall barns (3.96 ± 2.16 m) or in a free-stall barn (4.03 ± 1.79 m). This difference could be a result of the fact that only a single measurement was made, so that repeated measurement might improve the usefulness of flight distance as a management trait. In conclusion, it was verified that step-kick behavior to cup attachment and flight responses to human approach were, although they have some affectors, applicable as objective management traits in lactating cows. [source] A Partially Linear Tree-based Regression Model for Multivariate OutcomesBIOMETRICS, Issue 1 2010Kai Yu Summary In the genetic study of complex traits, especially behavior related ones, such as smoking and alcoholism, usually several phenotypic measurements are obtained for the description of the complex trait, but no single measurement can quantify fully the complicated characteristics of the symptom because of our lack of understanding of the underlying etiology. If those phenotypes share a common genetic mechanism, rather than studying each individual phenotype separately, it is more advantageous to analyze them jointly as a multivariate trait to enhance the power to identify associated genes. We propose a multilocus association test for the study of multivariate traits. The test is derived from a partially linear tree-based regression model for multiple outcomes. This novel tree-based model provides a formal statistical testing framework for the evaluation of the association between a multivariate outcome and a set of candidate predictors, such as markers within a gene or pathway, while accommodating adjustment for other covariates. Through simulation studies we show that the proposed method has an acceptable type I error rate and improved power over the univariate outcome analysis, which studies each component of the complex trait separately with multiple-comparison adjustment. A candidate gene association study of multiple smoking-related phenotypes is used to demonstrate the application and advantages of this new method. The proposed method is general enough to be used for the assessment of the joint effect of a set of multiple risk factors on a multivariate outcome in other biomedical research settings. [source] Paclitaxel pharmacodynamics: application of a mechanism-based neutropenia modelBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 6 2001Gerald J. Fetterly Abstract Antineoplastic agents exert adverse effects that impact both dose and scheduling of drug administration. Our objective was to develop a quantitative relationship between paclitaxel (taxol) exposure and pharmacodynamic endpoints, such as neutropenia or body weight loss. Paclitaxel in liposomes or Cremophor EL was administered to rats at doses of 20 or 40 mg/kg. Body weight and absolute neutrophil count were determined daily. The decrease in body weight was greater for paclitaxel in Cremophor EL than for liposomal paclitaxel, but hematological toxicity was similar. The hematological data was fit using a pharmacodynamic model to investigate the temporal delay between drug exposure and neutropenia. From the model, the lifespan of neutrophils (TN), of surviving precursor cells in bone marrow (TP), and a killing rate constant (K) were determined. The values of TN, TP, and K for liposomal paclitaxel were 95 h, 82 h, and 0.735 (,M h),1, respectively, and for paclitaxel in Cremophor EL, 86 h, 78 h, and 0.475 (,M h),1, respectively. Simulations of various doses indicated a dependency of the neutropenia time course on paclitaxel exposure. The entire time course of changes in neutrophil count is more informative than a single measurement if myelosuppression is prolonged and at a level associated with increased incidence of clinical adverse effects. Copyright © 2001 John Wiley & Sons, Ltd. [source] Improved analogue fault coverage estimation using probabilistic analysisINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 5 2010D. K. Papakostas Abstract A method for fault detection probability estimation using statistical multi-parameter circuit simulation is proposed, in order to check circuits for which double or multiple analogue measurements are utilized. Theoretical analysis for the estimation of the fault coverage is given, based on conditional probability calculations. The proposed method can be applied for both test measurement and input stimulus selection. Simulation results from the application of the method on typical analogue circuits,filter and amplifier,are given, showing a sufficient improvement over the fault coverage achieved by single measurements. Copyright © 2009 John Wiley & Sons, Ltd. [source] Scapular development from the neonatal period to skeletal maturity: A preliminary studyINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 5 2007C. Rissech Abstract An understanding of the basic growth rates and patterns of development for each element of the human skeleton is important for a thorough understanding and interpretation of data in all areas of skeletal research. Yet surprisingly little is known about the detailed ontogenetic development of many bones, including the scapula. With the intention of describing the changes that accompany postnatal ontogeny in the scapula and algorithms to predict sub-adult age at death, this communication examines the development of the scapula through nine measurements (3 from the glenoidal area, 4 from the body and 2 related to the spinous process) by polynomial regression. Data were collected from 31 of the individuals that comprise the Scheuer Collection, which is housed at the University of Dundee (Scotland). Four of the derived mathematical curves (scapular length, infra- and suprascapular height and spine length) displayed linear growth, whilst three (maximum length of the glenoid mass, acromial width and scapular width) were best expressed by a second-degree polynomial and two (maximum and middle diameter of the glenoidal surface) by a third-degree polynomial. All single measurements proved useful in the prediction of age at death, although derived indices proved to be of limited value. In particular, scapular width, suprascapular height and acromial width showed reliable levels of age prediction until late adolescent years. Copyright © 2007 John Wiley & Sons, Ltd. [source] A comparison of HIV-1 drug susceptibility as provided by conventional phenotyping and by a phenotype prediction tool based on viral genotypeJOURNAL OF MEDICAL VIROLOGY, Issue 10 2009Margriet Van Houtte Abstract Concordance between the conventional HIV-1 phenotypic drug resistance assay, PhenoSenseÔ (PS), and virco®TYPE HIV-1 (vT), a drug resistance assay based on prediction of the phenotype, was investigated in a data set from the Stanford HIV Resistance database (hivdb). Depending on the drug, between 287 and 902 genotype,phenotype data pairs were available for comparisons. Test results (fold-change values) in the two assays were highly correlated, with an overall mean correlation coefficient of 0.90 using single PS measurements. This coefficient rose to 0.94 when the vT results were compared to the mean of repeat PS measurements. These results are comparable with the corresponding correlation coefficients of 0.87 and 0.95, calculated using single measurements, and the mean of repeat measurements, respectively, as obtained in the Antivirogram® assay, the conventional HIV-1 phenotypic drug resistance test on which vT is based. The proportion of resistance calls resulting in a "major" discordance (fully susceptible or maximal response by one assay but fully resistant or minimal response by the other) ranged from 0% to 8.1% for drugs for which two clinical test cut-offs were available in both assays (didanosine, abacavir, tenofovir, saquinavir/r, fosamprenavir/r, and lopinavir/r), from 2.4% to 8.1% for the drugs for which two clinical test cut-offs were available in the vT assay and one clinical test cut-off in the PS assay (lamivudine, stavudine, indinavir/r, and atazanavir/r) and from 3.1% to 10.3% for drugs for which biological test cut-offs were used (zidovudine, nevirapine, delavirdine, efavirenz, indinavir, ritonavir, nelfinavir, saquinavir, and fosamprenavir). Our analyses suggest that these assays provide comparable resistance information, which will be of value to physicians who may be presented with either or both types of test report in their practice. J. Med. Virol. 81:1702,1709, 2009. © 2009 Wiley-Liss, Inc. [source] Evaluating the multiple coil configurations of the EM38DD and DUALEM-21S sensors to detect archaeological anomaliesARCHAEOLOGICAL PROSPECTION, Issue 2 2009David Simpson Abstract The multiple coil configurations of two electromagnetic induction sensors were tested on a field with strong electrical and magnetic contrasts. The first sensor, EM38DD, measures either the apparent electrical conductivity (ECa or ,a) or the apparent magnetic susceptibility (MSa or ,a) of the soil at two coil orientations. The second sensor, DUALEM-21S, measures both ECa and MSa at two coil orientations and two coil separations. The goal was to test if measuring with the multiple coils resulted in a better detection of near-surface artefacts and the natural soil variability. The ECa of all coil configurations was closely related to the depth of a clay substrate beneath the topsoil sandy loam, which was verified by soil augering. Configurations with a shallower theoretical depth of exploration were less influenced by the clay substrate. Combining two coil configurations revealed important ECa anomalies, not visible on individual measurements, associated with a brick wall foundation and a former ditch. The MSa maps showed totally different anomaly patterns, related to anthropogenic disturbances in the soil, such as the filling-in with brick rubble of a former pond. Depending on the depth and thickness of the disturbance and the relative response of the sensor configurations, the MSa anomalies were entirely positive for one configuration but other configurations also had negative anomalies. It was concluded that multiple coil configurations provide a better insight into the build-up of the soil profile and are better able to detect anomalies than single measurements. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||