Home About us Contact
|
Home About us Contact | ||
|
|
||
Precision
Kinds of Precision Terms modified by Precision Selected AbstractsPRECISION OF HERBIVORE TOLERANCE EXPERIMENTS WITH IMPOSED AND NATURAL DAMAGEEVOLUTION, Issue 3 2003Kari Lehtilä Abstract Tiffin and Inouye (2000) discussed the use of natural and imposed (controlled) damage in experiments of herbivore tolerance. They constructed a statistical model of the effect of herbivory on plant fitness, including damage level and an environmental factor as the independent factors, in which tolerance is defined as a slope of the regression line when damage level is regressed with plant fitness. They claim that while experiments with imposed damage are more accurate (i.e., they give a more correct estimate of tolerance), experiments with natural damage are more precise under a wide range of parameter values (i.e., tolerance estimates explain a larger part of variation in fitness). I show, however, that experiments with imposed damage are less precise only when an experimenter uses an experimental design that has weaker statistical power than in experiments with natural herbivory. The experimenter can nevertheless control the damage levels to optimize the experimental designs. For instance, when half of the experimental plants are left undamaged and the other half treated with maximal relevant damage level, experiments with imposed damage are almost always much more precise than experiments with natural damage. [source] USE OF SINGLE-VISION EYEGLASSES IMPROVES STEPPING PRECISION AND SAFETY WHEN ELDERLY HABITUAL MULTIFOCAL WEARERS NEGOTIATE A RAISED SURFACEJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 1 2008Louise Johnson MSc No abstract is available for this article. [source] INCREASING THE PRECISION OF THEODOLITE TRACKING: MODIFIED TECHNIQUE TO CALCULATE THE ALTITUDE OF LAND-BASED OBSERVATION SITESMARINE MAMMAL SCIENCE, Issue 4 2004H. Bailey [source] Injecting 1000 Centistoke Liquid Silicone With Ease and PrecisionDERMATOLOGIC SURGERY, Issue 3 2003Anthony V. Benedetto DO, FACP BACKGROUND Since the Food and Drug Administration approved the use of the 1000 centistoke liquid silicone, Silikon 1000, for intraocular injection, the off-label use of this injectable silicone oil as a permanent soft-tissue filler for facial rejuvenation has increased in the United States. Injecting liquid silicone by the microdroplet technique is the most important preventive measure that one can use to avoid the adverse sequelae of silicone migration and granuloma formation, especially when injecting silicone to improve small facial defects resulting from acne scars, surgical procedures, or photoaging. OBJECTIVE To introduce an easy method for injecting a viscous silicone oil by the microdroplet technique, using an inexpensive syringe and needle that currently is available from distributors of medical supplies in the United States. METHOD We suggest the use of a Becton Dickinson 3/10 cc insulin U-100 syringe to inject Silikon 1000. This syringe contains up to 0.3 mL of fluid, and its barrel is clearly marked with an easy-to-read scale of large cross-hatches. Each cross-hatch marking represents either a unit value of 0.01 mL or a half-unit value of 0.005 mL of fluid, which is the approximate volume preferred when injecting liquid silicone into facial defects. Because not enough negative pressure can be generated in this needle and syringe to draw up the viscous silicone oil, we describe a convenient and easy method for filling this 3/10 cc diabetic syringe with Silikon 1000. RESULTS We have found that by using the Becton Dickinson 3/10 cc insulin U-100 syringe, our technique of injecting minute amounts of Silikon 1000 is facilitated because each widely spaced cross-hatch on the side of the syringe barrel is easy to read and measures exact amounts of the silicone oil. These lines of the scale on the syringe barrel are so large and clearly marked that it is virtually impossible to overinject the most minute amount of silicone. CONCLUSION Sequential microdroplets of 0.01 cc or less of Silikon 1000 can be measured and injected with the greatest ease and precision so that inadvertent overdosing and complications can be avoided. [source] Electrochemical Evaluation of Nucleoside Analogue Lamivudine in Pharmaceutical Dosage Forms and Human SerumELECTROANALYSIS, Issue 20 2005Burcu Dogan Abstract Lamivudine (LAM) is a synthetic nucleoside analogue with activity against human immunodeficiency virus-type 1 (HIV-1) and Hepatitis B virus (HBV). The aim of this study was to determine LAM levels in serum and pharmaceutical formulations, by means of electrochemical methods using hanging mercury drop electrode (HMDE). On this electrode, LAM undergoes irreversible reduction at the peak potential near Ep,1.26,V (vs. Ag/AgCl/3,M KCl). Reduction LAM signals were measured by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square-wave voltammetry (OSW). DPV and OSW techniques for the determination of LAM in acetate buffer at pH,4.5, which allows quantitation over the 4×10,6 to 1×10,4,M range in supporting electrolyte for both methods, were proposed. The linear response was obtained in acetate buffer in the ranges of 2×10,6 to 2×10,4,M for spiked serum samples at pH,4.5 for both techniques. The repeatability and reproducibility of the methods for all media were determined. The standard addition method was used in serum. Precision and accuracy were also checked in all media. No electroactive interferences from the endogenous substances were found in serum. With respect to side effects of high doses and short half-life of LAM, a fast and simple detection method is described in this study. [source] Heavy Metals in Matrices of Food Interest: Sequential Voltammetric Determination at Trace and Ultratrace Level of Copper, Lead, Cadmium, Zinc, Arsenic, Selenium, Manganese and Iron in MealsELECTROANALYSIS, Issue 18 2004Clinio Locatelli Abstract The voltammetric methods are very suitable and versatile techniques for the simultaneous metal determination in complex matrices. The present work, regarding the sequential determination of Cu(II), Pb(II), Cd(II), Zn(II) by square-wave anodic stripping voltammetry (SWASV), As(III), Se(IV) by square-wave cathodic stripping voltammetry (SWCSV) and Mn(II), Fe(III) by square-wave voltammetry (SWV) in matrices involved in foods and food chain as wholemeal, wheat and maize meal, are an interesting example of the possibility to sequentially determine each single element in real samples. Besides the set up of the analytical method, particular attention is aimed either at the problem of possible signal interference or to show that, using the peak area Ap as instrumental datum, it is possible to achieve lower limits of detection. The analytical procedure was verified by the analysis of the standard reference materials: Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a. Precision, as repeatability, and accuracy, expressed as relative standard deviation and relative error, respectively, were lower than 6% in all cases. In the presence of reciprocal interference, the standard addition method considerably improved the resolution of the voltammetric technique. Once set up on the standard reference materials, the analytical procedure was transferred and applied to commercial meals sampled on market for sale. A critical comparison with spectroscopic measurements is also discussed. [source] Validation of a real-time PCR method for the detection of Phytophthora ramorum1EPPO BULLETIN, Issue 2 2006A. Chandelier To validate a real-time PCR method for the detection of Phytophthora ramorum, an intra-laboratory procedure was developed. The specificity of the TaqMan probe/primer sets was determined by carrying out real-time PCR on total DNA extracted from pure culture of several Phytophthora species. The limit of detection and the potential effects of plant substrates were evaluated by conducting the test on total DNA from healthy plant materials (Rhododendron spp., Viburnum spp. and Pieris spp.) spiked with known amounts of P. ramorum genomic DNA. The PCR efficiency was estimated through the linear regression of the dilution curve. Precision of the TaqMan assay was assessed on material from a single artificially infected plant (Rhododendron spp.). Two kinds of tissues were tested: a severely infected twig and an apparently healthy leaf. Intra-assay repeatability was evaluated on 10 replicates of the same DNA sample analysed in a single assay. Inter-assay reproducibility was evaluated on the same DNA sample amplified over five separate assays while the intersample reproducibility was evaluated on separate DNA extractions of four samples from both plant tissues amplified in a single assay. [source] Application of High Spatial Resolution Laser Ablation ICP-MS to Crystal-Melt Trace Element Partition Coefficient DeterminationGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 1 2007Maurizio Petrelli ICP-MS; ablation laser; éléments en trace; figure de mérite; coefficients de partage entre cristal et liquide In this contribution we evaluate the capabilities of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) using a 12 ,m spot size. Precision, accuracy and detection limits were assessed on the USGS BCR-2G reference material. We demonstrate that the 12 ,m LA-ICP-MS analyses of experimentally-grown amphibole and garnet are in excellent agreement with secondary ion mass spectrometry (SIMS) trace element determinations on the same crystals. The 12 ,m spot size configuration was subsequently used to determine trace element crystal-melt partition coefficients (Dc/m) for a wide range of trace elements in amphibole in equilibrium with a basanitic melt. The following strategy to determine accurately and evaluate Dc/m is proposed. One or more major elements determined previously by electron probe microanalysis (EPMA) was used to ensure consistency between EPMA and the composition of the aerosol produced by the laser ablation. Measured Dc/m values were successively evaluated using the lattice strain model. The use of this strategy significantly improved the precision and accuracy of Dc/m determination when a LA-ICP-MS configuration with a high spatial resolution was employed. Dans cet article nous évaluons les potentialités de l'ablation laser couplée à un spectromètre de masse à plasma induit (LA-ICP-MS) en travaillant avec un diamètre d'impact de 12 ,m. Précision, justesse et limites de détections sont évaluées sur le matériau de référence BCR-2G de l'USGS. Nous démontrons que les analyses LA-ICP-MS faites avec un diamètre de 12 ,m sur les amphiboles et des grenats synthétiques sont en excellent accord avec les déterminations d'éléments en trace effectuées sur les mêmes cristaux par sonde ionique (SIMS). Ce diamètre d'impact de 12 ,m a donc été sélectionné pour déterminer les coefficients de partage cristal/liquide (Dc/m) pour un grand nombre d'éléments en trace dans une amphibole en équilibre avec un liquide basanitique. Nous proposons la stratégie d'analyse suivante, qui assure une détermination exacte des coefficients de partage Dc/m. Un ou plusieurs des éléments majeurs déterminés auparavant par microsonde électronique (EMPA) est utilisé pour garantir la consistance des données entre EMPA et la composition de l'aérosol produit par l'ablation laser. Les Dc/m mesurés sont ensuite évalués en utilisant le modèle de contrainte de réseau. L'utilisation de cette stratégie améliore de manière significative la précision et la justesse des déterminations de Dc/m quand elle est couplée à l'utilisation d'un système LA-ICP-MS de grande résolution spatiale. [source] The Allocational Effects of the Precision of Accounting EstimatesJOURNAL OF ACCOUNTING RESEARCH, Issue 4 2007RONALD A. DYE ABSTRACT This paper studies the allocational effects associated with the precision of accounting estimates when the precision of estimates is a choice variable for firms. One part of the paper considers the effects of the observability of precision choices. We show that, generally, making precision choices private increases firms' equilibrium precision choices and also, as a by-product, their equilibrium investment choices. We further show that, when firms' precision choices are private, there may be a "disclosure trap," in which, unless investors conjecture the owner has chosen an estimate with the highest possible precision, the owner will respond to investors' conjecture by choosing an estimate whose precision is higher than investors' conjecture. In a multifirm version of the model with endogenous investment, we show that the equilibrium investment by the firm increases in the precision of the firm's own estimate and decreases in the precisions of other firms' estimates. Finally, we show that, in a setting where the firm's initial owner sells his stake in the firm over the course of two periods, with disclosures of estimates of the firm's value occurring prior to each sale of shares, if the precisions of the estimates are public, the equilibrium precisions of the estimates increase over time when the owner sells a sufficiently large fraction of the firm in the first period, and otherwise the equilibrium precisions of estimates remain constant over time. [source] Reporting Frequency, Information Precision and Private Information AcquisitionJOURNAL OF BUSINESS FINANCE & ACCOUNTING, Issue 1-2 2010Rick Cuijpers Abstract:, This study examines whether the choice between quarterly and semiannual reporting affects the precision of investors' information and their private information acquisition activities. In the first part of this study, we show that a firm's reporting frequency has no effect on the average precision of investors' information. However, our analysis of announcement-period price variance and share turnover shows that an increase in reporting frequency does make interim and annual financial reports a more important component of investors' information set, relative to other sources of information. In particular, the results of this analysis suggest that investors of semiannual reporters hold more precise pre-announcement information than investors of quarterly reporters. In the second part of our study, we test one explanation for this finding. We argue that an increase in a firm's reporting frequency reduces investors' incentives to acquire private information between consecutive announcement dates and, consequently, should reduce information asymmetry among investors, increase share liquidity, and stimulate trading. Consistent with this reasoning, we find that quarterly reporters have lower average bid-ask spreads and higher abnormal share turnover than semiannual reporters. [source] Precision in Accounting Information, Financial Leverage and the Value of EquityJOURNAL OF BUSINESS FINANCE & ACCOUNTING, Issue 7-8 2007Glenn Feltham Abstract:, Using an equity valuation model characterized by periodic imperfect accounting information, we examine how financial leverage affects a firm's accounting quality choice (i.e., precision). We find that the existence of financial leverage motivates firms with average to good performance to prepare accounting information with a high degree of precision. However, we conclude that when a firm is performing poorly it has an incentive to reduce accounting precision in order to lower the likelihood of both a debt covenant violation and the detection of accounting bias. [source] Precision of prediction in second-order calibration, with focus on bilinear regression methodsJOURNAL OF CHEMOMETRICS, Issue 1 2002Marie Linder Abstract We consider calibration of hyphenated instruments with particular focus on determination of the unknown concentrations of new specimens. A hyphenated instrument generates for each specimen a two-way array of data. These are assumed to depend on the concentrations through a bilinear regression model, where each constituent is characterized by a pair of profiles to be determined in the calibration. We discuss the problem of predicting the unknown concentrations in a new specimen, after calibration. We formulate three different predictor construction methods, a ,naive' method, a least squares method, and a refined version of the latter that takes account of the calibration uncertainty. We give formulae for the uncertainty of the predictors under white noise, when calibration can be seen as precise. We refine these formulae to allow for calibration uncertainty, in particular when calibration is carried out by the bilinear least squares (BLLS) method or the singular value decomposition (SVD) method proposed by Linder and Sundberg (Chemometrics Intell. Lab. Syst. 1998; 42: 159,178). By error propagation formulae and previous results on the precision of and we can obtain approximate standard errors for the predicted concentrations, according to each of the two estimation methods. The performance of the predictors and the precision formulae is illustrated on both real (fluorescence) and simulated data. Copyright © 2002 John Wiley & Sons, Ltd. [source] Clinicians Treating Hypertension Need to Mind Their "P's" (Precision) and "Q's"(Quantitation): A Lesson From Left Ventricular Hypertrophy Regression and Atrial FibrillationJOURNAL OF CLINICAL HYPERTENSION, Issue 5 2007Thomas D. Giles MD No abstract is available for this article. [source] The Impact of Performance Level Misclassification on the Accuracy and Precision of Percent at Performance Level MeasuresJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 2 2008Damian W. Betebenner No Child Left Behind (NCLB) performance mandates, embedded within state accountability systems, focus school AYP (adequate yearly progress) compliance squarely on the percentage of students at or above proficient. The singular importance of this quantity for decision-making purposes has initiated extensive research into percent proficient as a measure of school quality. In particular, technical discussions have scrutinized the impact of sampling, measurement, and other sources of error on percent proficient statistics. In this article, we challenge the received orthodoxy that measurement error associated with individual students' scores is inconsequential for aggregate percent proficient statistics. Synthesizing current classification accuracy research with techniques from randomized response designs, we establish results which specify the extent to which measurement error,manifest as performance level misclassifications,produces bias and increases error variability for percent at performance level statistics. The results have direct relevance for the design of coherent and fair accountability systems based upon assessment outcomes. [source] Single Laboratory Method Performance Evaluation for the Analysis of Total Food Folate by Trienzyme Extraction and Microplate AssayJOURNAL OF FOOD SCIENCE, Issue 5 2007L. Chen ABSTRACT:, Single laboratory method performance parameters, including the calibration curve, accuracy, recovery, precision, limit of detection (LOD), and limit of quantification (LOQ), were evaluated for the analysis of total food folate by the trienzyme extraction and microplate assay with Lactobacillus casei subsp. rhamnosus. Standard Reference Material (SRM) 1546 (meat homogenate), SRM 2383 (baby food composite), SRM 1846 (infant formula), Certified Reference Material (CRM) 121 (wholemeal flour), and CRM 485 (mixed vegetables), representing a broad selection of food matrices, were used to evaluate the performance of the method. A generated 4-parameter logistic equation of the calibration curve was y= (0.0705 , 1.0396)/(1 + (x/0.0165) 1.3072) + 1.0396 (P < 0.0001). The test of parallelism demonstrated that matrix components in the food extracts did not affect the accuracy. Measured values of the SRMs and CRMs were within their certified or reference values. Recoveries for all reference materials met the requirements of the AOAC guidelines for single laboratory validation. Precision measured as repeatability, including simultaneous and consecutive replicates for each SRM and CRM, met the Horwitz criterion. LOD and LOQ values were 0.3 and 0.6 ,g/100 g, respectively. The results showed that trienzyme digestion using ,-amylase, PronaseR, and conjugase from chicken pancreas coupled with a 96-well microplate assay provided a highly accurate, reproducible, and sensitive method for the determination of folate in a variety of foods. [source] In vitro validation of phase-contrast flow measurements at 3 T in comparison to 1.5 T: Precision, accuracy, and signal-to-noise ratios,JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 5 2005Joachim Lotz MD Abstract Purpose To evaluate the signal-to-noise ratio (SNR), precision, and accuracy of phase-contrast flow measurements at 3 T with the help of an in vitro model and to compare the results with data from two 1.5-T scanners. Materials and Methods Using an identical setup of a laminar flow model and sequence parameters, measurements were done at one 3-T and at two 1.5-T systems. Precision, accuracy, and SNR were obtained for velocity encodings ranging from 55 up to 550 cm,1. SNRs were calculated from the magnitude as well as the flow encoded images. Results Precision and accuracy for the in vitro flow model were similarly high in all scanners with no significant difference. For velocity encodings from 55 cm,1 up to 550 cm,1, the SNR in magnitude as well as phase encoded images of the 3-T measurements was approximately 2.5 times higher than the SNR obtained from the two 1.5-T systems. Conclusion Even without optimization for the 3-T environment, flow measurements show the same high accuracy and precision as is known from clinical 1.5-T scanners. The superior SNR at 3 T will allow further improvements in temporal and spatial resolution. This will be of interest for small-size vessels like coronary arteries or for slow diastolic flow patterns. J. Magn. Reson. Imaging 2005;21:604,610. © 2005 Wiley-Liss, Inc. [source] Accuracy and precision of radiostereometric analysis in the measurement of three-dimensional micromotion in a fracture model of the distal radiusJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2005Rami Madanat Abstract The purpose of the current study was to verify the feasibility of radiostereometric analysis (RSA) in monitoring three-dimensional fracture micromotion in fractures of the distal radius. The experimental set-up consisted of a simulated model of an extra-articular Colles' fracture, including metallic beads inserted into the bone on either side of the fracture site. The model was rigidly fixed to high precision micrometer stages allowing controlled translation in three axes and rotation about the longitudinal and transverse axes. The whole construct was placed inside a RSA calibration cage with two perpendicular radiographic film cassettes. Accuracy was calculated as the 95% prediction intervals from the regression analyses between the micromotion measured by RSA and actual displacements measured by micrometers. Precision was determined as the standard deviation of five repeated measurements of a 200 ,m displacement or a 0.5° rotation along a specific axis. Translations from 25 ,m to 5 mm were measured with an accuracy of ±6,m and translations of 200,m were measured with a precision of 2,6 ,m. Rotations ranging from 1/6° to 2° were measured with an accuracy of ±0.073° and rotations of 1/2° were measured with a precision of 0.025°,0.096°. The number of markers and their configuration had greater impact on the accuracy and precision of rotation than on those of translation. Aside from the unknown rate of clinical marker loosening, the current results favor the use of at least four markers in each bone fragment in distal radius fractures. These results suggest a strong rationale for the use of RSA as an objective tool for comparing different treatment modalities and novel bone graft substitutes aimed at stabilization of fractures of the distal radius. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Quantitative cartilage imaging of the human hind foot: Precision and inter-subject variabilityJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2002Dina Al-Ali Alterations of ankle cartilage are observed in degenerative and inflammatory joint disease, but cartilage cannot be directly visualized by radiography. The purpose of this study was therefore to analyze the feasibility and precision of quantitative cartilage imaging in the human hind foot (talocrural, talotarsal, and intertarsal joints), and to report the inter-subject variability for cartilage volume, thickness and surface areas. The feet of 16 healthy volunteers were imaged using a 3D gradient-echo magnetic resonance imaging sequence with water-excitation. After interpolation to a resolution of 1 ± 0.125 ± 0.125 mm3 the cartilage plates were segmented, and the cartilage volume, thickness, and surface areas determined. The precision (four repeated measurements) was examined in eight volunteers, the RMS average CV% being 2.1% to 10.9% in single joint surfaces, and , 3% for the cumulative values of all joints. The mean cartilage thickness ranged from 0.57 ± 0.08 (navicular surface) to 0.89 ± 0.19 mm (trochlear surface for tibia). In conclusion this study shows that it is feasible to quantify thin cartilage layers in the hind foot under in vivo imaging conditions, and that the precision errors are substantially smaller than the inter-subject variability in healthy subjects. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] High-throughput determination of the free fraction of drugs strongly bound to plasma proteinsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2004Joachim Schuhmacher Abstract Quantification of protein binding of new chemical entities is an important early screening step during drug discovery and is of fundamental interest for the estimation of safety margins during drug development. In this publication, we describe the development of a new high-throughput assay for the determination of the free drug fraction in plasma (fu). The new technique is an enhancement of the previously published erythrocytes partition method. It is based on the distribution of drugs between plasma water, plasma proteins, and solid-supported lipid membranes (Transil®). The execution of protein binding studies by partitioning is dramatically simplified by substituting erythrocytes with commercially available Transil® beads, and makes the method particularly suitable for high-throughput studies. Eight Bayer compounds from different compound classes covering a wide range of lipophilicities (log P,=,1.9,5.6) and fu values (0.018,35%) were selected for validation of the assay. The results obtained by the new method and by either the erythrocytes partitioning technique or more conventional methods (ultrafiltration and equilibrium dialysis) are identical, confirming that the new method produces valid results even for drugs that are strongly bound to plasma proteins. Precision and accuracy of the data in the cases of very low and high fu values are comparable, indicating that the method is especially suited for highly lipophilic drugs that tend to adsorb to surfaces compared with other methods, like ultrafiltration or equilibrium dialysis, that may produce biased data. The method is also useful for the determination of binding parameters and the pH dependence of fu. In summary, this assay is well suited for high-throughput determination of protein binding during drug discovery and for extended protein binding studies during drug development. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93: 816,830, 2004 [source] Provisional Prosthetic Management of Mobile Teeth in Conjunction with a Removable Partial Denture Using Orthodontic WireJOURNAL OF PROSTHODONTICS, Issue 7 2009Won-suk Oh DDS Abstract Precision attachment-retained removable partial dentures eliminate the use of visible clasps and improve the esthetic appearance of the smile; however, terminal abutment teeth may be subject to unfavorable stresses under function when misused. A provisional prosthetic management technique that incorporates an orthodontic wire to assist cross-arch support and stability of the periodontally weakened abutment teeth is described. This technique is simple, reversible, does not alter the esthetic appearance of the smile, and controls the mobility of the abutment teeth until a definitive treatment plan is established. [source] Precision of Fit of Two Margin Designs for Metal-Ceramic CrownsJOURNAL OF PROSTHODONTICS, Issue 4 2007Penwadee Limkangwalmongkol DDS Statement of Problem: Although metal-ceramic restorations are widely used, there is a lack of information about how the fit is affected by margin designs. Purpose: This study measured and compared the precision of fit of metal-ceramic crowns with two margin designs. Material and Methods: Thirty-two extracted human premolar teeth were prepared for complete-coverage restorations with an internally rounded shoulder preparation. Impressions were made from all teeth, and master dies were poured with improved stone type V. MC crowns were fabricated with a porcelain-butt margin on the buccal aspect (n = 32) and a feather-edge metal margin on the lingual aspect (n = 32), which served as a control group. Precision of fit was measured three times at the mid-buccal and mid-lingual margins of each crown with a profilometer. The data were statistically analyzed with the paired t -test (, < .05). Results: Mean marginal gap size of porcelain-butt margins was 27.93 ,m (±15.84) and of feather-edge metal margins 42.43 ,m (±24.12). The marginal gap size of feather-edge metal margins was statistically significantly greater than that of porcelain-butt margins (p = 0.0045). Conclusion: The marginal fit of porcelain-butt margins was significantly better than that of feather-edge metal margins. Clinical Implications: Porcelain-butt margins in this study had a better marginal fit than feather-edge metal margins, and thus have given clinicians evidence to prefer the use of porcelain-butt margins. [source] Precision in differential field-flow fractionation: A chemometric studyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 16 2007Letizia Bregola Abstract In the present paper, the capabilities of differential field-flow fractionation, i. e., the determination of an incremental quantity of a colloidal species, e. g., an uptake adsorbed mass, determined by the joint use of two independent FFF measurements, over a species and the same modified species respectively, are considered. The different error types, those related to the retention time determinations and those coming from the operating parameter fluctuations were considered. The different components were computed with reference to SdFFF determinations of bare polystyrene (PS) submicronic particles and the same PS particles covered by IgG. Comparison was made between theoretically computed precision and experiments. The error coming from the experimental measurement of retention times was identified to be the main source of errors. Accordingly, it was possible to make explicit the detection limits and the confidence intervals of the adsorbed mass uptake, as a function of experimental quantities such as the retention ratio, the detector calibration ratio, the injected quantity, the baseline noise, and the void time relative error. An experimentally determined and theoretically foreseen dependence of both the experimental detection and confidence limits (, ± 10,17 g) on the square root of the injected concentration, for constant injected volume, was found. [source] Application of solid phase microextraction for the determination of soil fumigants in water and soil samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2005Sonia Fuster Abstract The potential of solid phase microextraction (SPME) for the determination of the soil fumigants 1,3-dichloropropene (1,3-DCP) and methyl isothiocyanate (MITC) in environmental samples such as soil and water samples has been investigated. Direct immersion SPME followed by GC/ECD/NPD analysis allowed the rapid determination of the two fumigants in water samples, with very little sample manipulation, giving an LOD of 0.5 ,g L,1. Precision, calculated as relative standard deviation (RSD) for six replicates at three concentration levels, was found to be lower than 20% at the concentration levels tested. For the analysis of soil samples, headspace (HS)-SPME combined with GC/ECD/NPD analysis has been applied. Quantification using matrix-matched calibration curves allowed determination of both analytes (MITC and 1-3-DCP) with a LOD of 0.1 ,g kg,1 (RSD <10%) for the two concentration levels assayed (0.02 and 0.2 mg kg,1). The HS-SPME procedure developed in this paper was applied to soil samples from experimental green house plots treated with metham-Na, a soil disinfestation agent that decomposes in soil to MITC. The absence of sample manipulation as well as the low solvent consumption in SPME methodology are among the main advantages of this analytical approach. [source] Niobium and tantalum in carbonaceous chondrites: Constraints on the solar system and primitive mantle niobium/tantalum, zirconium/niobium, and niobium/uranium ratioMETEORITICS & PLANETARY SCIENCE, Issue 2 2000K. p. Jochum The abundance of Ta was determined in the same meteorites by radiochemical neutron activation analysis (RNAA). Precision of the MIC-SSMS and RNAA techniques is ,3% and , 5%, respectively. The new abundances for CI chondrites are: Nb = 0.247, Ta = 0.0142, Zr = 3.86, Y = 1.56 ,g/g; or 0.699, 0.0202, 11.2, and 4.64 atoms/106 Si atoms, respectively. The values agree with earlier compilations, but they are a factor of 2 more precise than earlier analyses. Trace element concentrations in the CM, CV, and CK chondrites are higher than in the CI chondrite Orgueil by about 37, 86, and 120%, respectively, in agreement with the variable absolute contents of refractory lithophile elements in different groups of carbonaceous chondrites. Of particular interest are the chondritic Nb/Ta, Zr/Nb, and Nb/U ratios, because these ratios are important tools for interpreting the chemical evolution of planetary bodies. We obtained Nb/Ta = 17.4 ± 0.5 for the carbonaceous chondrites and the Juvinas-type eucrites investigated. Though this value is similar to previous estimates, it is much more precise. The same is true for Zr/Nb (15.5 ± 0.2) and Zr/Y (2.32 ± 0.12). In combination with recently published MIC-SSMS U data for carbonaceous chondrites, we obtained a chondritic Nb/U ratio of 29 ± 2. Because Nb, Ta, Zr, Y, and U are refractory lithophile elements and presumably partitioned into the silicate phase of the Earth during core formation, the elemental ratios may also be used to constrain evolution of the Earth's primitive mantle and, with the more precise determinations fractionation of Nb and Ta during magmatic processes and mantle-crust interactions, can now be interpreted with greater confidence. [source] Can We Put Precision into Practice?NEW DIRECTIONS FOR INSTITUTIONAL RESEARCH, Issue 109 2001Commentary, Thoughts Engendered by Abrami's "Improving Judgments About Teaching Effectiveness Using Teacher Rating Forms" Evaluation researchers and practitioners agree that although measurement issues remain important to good evaluation practice, a greater area of concern is unreliable or invalid day-to-day practice. Can the precision of statistical techniques be brought to bear on this problem? This chapter reviews and summarizes responses to Abrami's proposal. [source] Procedural considerations for photographic-based joint angle measurementsPHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 4 2005Colin Dunlevy Abstract Background and Purpose Measuring static joint angles is important to clinicians involved in assessing, diagnosing and treating musculoskeletal disorders. Ne measurement techniques such as the Uillinn Method © (UM) employ the relatively new technology of digital photography and software to form a virtual goniometer. It is of central importance that the errors associated such new measurement techniques are known. Precision in joint angle measurement is a challenge and errors can arise from three separate categories: equipment error, examiner error or biological error. The aim of the present study was to discover the amount of equipment error associated with the UM and to present guidelines for the optimal use of a photographic based measurement technique Method This was a non-clinical agreement study design that attempted to describe the best possible agreement between a mathematical control dataset and the angles calculated from the virtual goniometer, which in this case was the UM. When this was established, the effect of rotation and placing the angle at the periphery of the camera's field of view were tested. Results The repeatability coefficient (RC) between the UM and the control data under optimal conditions was 0.81°; the typical error (TE) was 0.29° (n = 120). When the angle appeared at the edge of the photograph the RC increased to 2° and the TE to 0.73° (n = 48). When 5° rotation was introduced between the camera and the angle no increase in error was detected. However, increasing amounts of rotation above 5° was proportional to increases in the RC (RC at 10° = 2.3°; 20° = 3.86°; 30° = 14.8°; 40° = 27.27°) and the TE (TE at 10° = 0.83°; 20° = 2.7°; 30° = 5.3°; 40° = 9.8°) scores. Conclusion Photographic-based joint angle measurement techniques are subject to error if careful procedures are not observed. Best procedures include photography from a perpendicular viewpoint and centring the lens on the target angle. Copyright © 2005 John Wiley & Sons, Ltd. [source] Beta-Trace Protein-Based Equations for Calculation of GFR in Renal Transplant RecipientsAMERICAN JOURNAL OF TRANSPLANTATION, Issue 3 2008U. Pöge Recently, we showed that serum beta-trace protein (BTP) is an alternative marker of glomerular filtration rate (GFR) in renal transplant recipients (RTR). We have now developed three BTP-based GFR formulae derived by multiple regression analyses from the patients who had participated in that study. Currently, we validated the diagnostic performance of these BTP-formulae in 102 consecutive RTR who underwent a technetium diethylenetriamine pentaacetic acid (DTPA) clearance for GFR measurement in comparison to the re-expressed Modification of Diet in Renal Disease (MDRD) equation and a recently proposed BTP-based equation (referred to as ,White equation'). The best-performing BTP formula was found to be: GFR = 89.85 × BTP,0.5541× urea,0.3018. This equation estimated true GFR virtually without bias (+0.43 mL/min/1.73 m2, not significant [NS]), while a small, but significant, overestimation was seen for the MDRD formula (+3.43 mL/min/1.73 m2, p = 0.003). Precision and accuracies within 50% of true GFR (93.1% and 88.2%, respectively) tended to be higher for the BTP formula, but the differences did not reach significance. The White equation overestimated the true GFR by 9.43 mL/min/1.73 m2(p = 0.001), and was inferior with respect to precision and 50% accuracy (79.4%). BTP-based GFR calculations are reliable, and may serve as an alternative to the re-expressed MDRD equation. [source] Computer-Based Analysis of Dynamic QT Changes: Toward High Precision and Individual Rate CorrectionANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2002Corina Dota M.D. Background: New strategies are needed to improve the results of automatic measurement of the various parts of the ECG signal and their dynamic changes. Methods: The EClysis software processes digitally-recorded ECGs from up to 12 leads at 500 Hz, using strictly defined algorithms to detect the PQRSTU points and to measure ECG intervals and amplitudes. Calculations are made on the averaged curve of each sampling period (beat group) or as means ± SD for beat groups, after being analyzed at the individual beat level in each lead. Resulting data sets can be exported for further statistical analyses. Using QT and R-R measured on beat level, an individual correction for the R-R dependence can be performed. Results: EClysis assigns PQRSTU points and intervals in a sensitive and highly reproducible manner, with coefficients of variation in ECG intervals corresponding to ca. 2 ms in the simulated ECG. In the normal ECG, the CVs are 2% for QRS, 0.8% for QT, and almost 6% for PQ intervals. EClysis highlights the increase in QT intervals and the decrease of T-wave amplitudes during almokalant infusion versus placebo. Using the observed linear or exponential relationships to adjust QT for R-R dependence in healthy subjects, one can eliminate this dependence almost completely by individualized correction. Conclusions: The EClysis system provides a precise and reproducible method to analyze ECGs. A.N.E. 2002;7(4):289,301 [source] Examining Management Accounting Change as Rules and Routines: The Effect of Rule PrecisionAUSTRALIAN ACCOUNTING REVIEW, Issue 2 2010Rodney Coyte This study examines change in management accounting practices as change in rules and routines. Informed by the institutional theory-inspired framework of,Burns and Scapens (2000),,the rules and routines relating to capital expenditure controls in a capital-intensive organisation are analysed. We explain how preciseness of rules affects not only the coupling of rules to routines, but also the emergence of multiple routines, enhancing the understanding of how management accounting practices remain stable and/or change over time. These results extend and refine recent research relating to management accounting change and offer new empirical insights into practice. [source] Stereospecific high-performance liquid chromatography of taxifolin, applications in pharmacokinetics, and determination in tu fu ling (Rhizoma smilacis glabrae) and apple (Malus × domestica)BIOMEDICAL CHROMATOGRAPHY, Issue 6 2009Karina R. Vega-Villa Abstract A stereospecific method of analysis of racemic taxifolin (+/,3,5,7,3,,4,-pentahydroxyflavanone) in biological fluids is necessary to study pharmacokinetics and disposition in fruit and herbs. A simple high-performance liquid chromatographic method was developed for the determination of all four taxifolin enantiomers. Separation was achieved on a Chiralcel® OJ-RH column with UV detection at 288 nm. The standard curves in serum were linear over a range of 0.5,100.0 µg/mL for each enantiomer. The mean extraction efficiency was >88.0%. Precision of the assay was <15% (CV), and was within 12% at the limit of quantitation (0.5 µg/mL). The bias of the assay was <15%, and was within 6% at the limit of quantitation. The assay was successfully applied to stereospecific disposition of taxifolin enantiomers in rats and to the quantification of taxifolin enantiomers in tu fu ling (Rhizoma smilacis glabrae) and apple (Malus × domestica). Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||||||||