Science.gov

Sample records for accuracy precision selectivity

  1. Bullet trajectory reconstruction - Methods, accuracy and precision.

    PubMed

    Mattijssen, Erwin J A T; Kerkhoff, Wim

    2016-05-01

    Based on the spatial relation between a primary and secondary bullet defect or on the shape and dimensions of the primary bullet defect, a bullet's trajectory prior to impact can be estimated for a shooting scene reconstruction. The accuracy and precision of the estimated trajectories will vary depending on variables such as, the applied method of reconstruction, the (true) angle of incidence, the properties of the target material and the properties of the bullet upon impact. This study focused on the accuracy and precision of estimated bullet trajectories when different variants of the probing method, ellipse method, and lead-in method are applied on bullet defects resulting from shots at various angles of incidence on drywall, MDF and sheet metal. The results show that in most situations the best performance (accuracy and precision) is seen when the probing method is applied. Only for the lowest angles of incidence the performance was better when either the ellipse or lead-in method was applied. The data provided in this paper can be used to select the appropriate method(s) for reconstruction and to correct for systematic errors (accuracy) and to provide a value of the precision, by means of a confidence interval of the specific measurement. PMID:27044032

  2. Accuracy and Precision of an IGRT Solution

    SciTech Connect

    Webster, Gareth J. Rowbottom, Carl G.; Mackay, Ranald I.

    2009-07-01

    Image-guided radiotherapy (IGRT) can potentially improve the accuracy of delivery of radiotherapy treatments by providing high-quality images of patient anatomy in the treatment position that can be incorporated into the treatment setup. The achievable accuracy and precision of delivery of highly complex head-and-neck intensity modulated radiotherapy (IMRT) plans with an IGRT technique using an Elekta Synergy linear accelerator and the Pinnacle Treatment Planning System (TPS) was investigated. Four head-and-neck IMRT plans were delivered to a semi-anthropomorphic head-and-neck phantom and the dose distribution was measured simultaneously by up to 20 microMOSFET (metal oxide semiconductor field-effect transmitter) detectors. A volumetric kilovoltage (kV) x-ray image was then acquired in the treatment position, fused with the phantom scan within the TPS using Syntegra software, and used to recalculate the dose with the precise delivery isocenter at the actual position of each detector within the phantom. Three repeat measurements were made over a period of 2 months to reduce the effect of random errors in measurement or delivery. To ensure that the noise remained below 1.5% (1 SD), minimum doses of 85 cGy were delivered to each detector. The average measured dose was systematically 1.4% lower than predicted and was consistent between repeats. Over the 4 delivered plans, 10/76 measurements showed a systematic error > 3% (3/76 > 5%), for which several potential sources of error were investigated. The error was ultimately attributable to measurements made in beam penumbrae, where submillimeter positional errors result in large discrepancies in dose. The implementation of an image-guided technique improves the accuracy of dose verification, particularly within high-dose gradients. The achievable accuracy of complex IMRT dose delivery incorporating image-guidance is within {+-} 3% in dose over the range of sample points. For some points in high-dose gradients

  3. Accuracy and precision of an IGRT solution.

    PubMed

    Webster, Gareth J; Rowbottom, Carl G; Mackay, Ranald I

    2009-01-01

    Image-guided radiotherapy (IGRT) can potentially improve the accuracy of delivery of radiotherapy treatments by providing high-quality images of patient anatomy in the treatment position that can be incorporated into the treatment setup. The achievable accuracy and precision of delivery of highly complex head-and-neck intensity modulated radiotherapy (IMRT) plans with an IGRT technique using an Elekta Synergy linear accelerator and the Pinnacle Treatment Planning System (TPS) was investigated. Four head-and-neck IMRT plans were delivered to a semi-anthropomorphic head-and-neck phantom and the dose distribution was measured simultaneously by up to 20 microMOSFET (metal oxide semiconductor field-effect transmitter) detectors. A volumetric kilovoltage (kV) x-ray image was then acquired in the treatment position, fused with the phantom scan within the TPS using Syntegra software, and used to recalculate the dose with the precise delivery isocenter at the actual position of each detector within the phantom. Three repeat measurements were made over a period of 2 months to reduce the effect of random errors in measurement or delivery. To ensure that the noise remained below 1.5% (1 SD), minimum doses of 85 cGy were delivered to each detector. The average measured dose was systematically 1.4% lower than predicted and was consistent between repeats. Over the 4 delivered plans, 10/76 measurements showed a systematic error > 3% (3/76 > 5%), for which several potential sources of error were investigated. The error was ultimately attributable to measurements made in beam penumbrae, where submillimeter positional errors result in large discrepancies in dose. The implementation of an image-guided technique improves the accuracy of dose verification, particularly within high-dose gradients. The achievable accuracy of complex IMRT dose delivery incorporating image-guidance is within +/- 3% in dose over the range of sample points. For some points in high-dose gradients

  4. Precision standoff guidance antenna accuracy evaluation

    NASA Astrophysics Data System (ADS)

    Irons, F. H.; Landesberg, M. M.

    1981-02-01

    This report presents a summary of work done to determine the inherent angular accuracy achievable with the guidance and control precision standoff guidance antenna. The antenna is a critical element in the anti-jam single station guidance program since its characteristics can limit the intrinsic location guidance accuracy. It was important to determine the extent to which high ratio beamsplitting results could be achieved repeatedly and what issues were involved with calibrating the antenna. The antenna accuracy has been found to be on the order of 0.006 deg. through the use of a straightforward lookup table concept. This corresponds to a cross range error of 21 m at a range of 200 km. This figure includes both pointing errors and off-axis estimation errors. It was found that the antenna off-boresight calibration is adequately represented by a straight line for each position plus a lookup table for pointing errors relative to broadside. In the event recalibration is required, it was found that only 1% of the model would need to be corrected.

  5. S-193 scatterometer backscattering cross section precision/accuracy for Skylab 2 and 3 missions

    NASA Technical Reports Server (NTRS)

    Krishen, K.; Pounds, D. J.

    1975-01-01

    Procedures for measuring the precision and accuracy with which the S-193 scatterometer measured the background cross section of ground scenes are described. Homogeneous ground sites were selected, and data from Skylab missions were analyzed. The precision was expressed as the standard deviation of the scatterometer-acquired backscattering cross section. In special cases, inference of the precision of measurement was made by considering the total range from the maximum to minimum of the backscatter measurements within a data segment, rather than the standard deviation. For Skylab 2 and 3 missions a precision better than 1.5 dB is indicated. This procedure indicates an accuracy of better than 3 dB for the Skylab 2 and 3 missions. The estimates of precision and accuracy given in this report are for backscattering cross sections from -28 to 18 dB. Outside this range the precision and accuracy decrease significantly.

  6. S193 radiometer brightness temperature precision/accuracy for SL2 and SL3

    NASA Technical Reports Server (NTRS)

    Pounds, D. J.; Krishen, K.

    1975-01-01

    The precision and accuracy with which the S193 radiometer measured the brightness temperature of ground scenes is investigated. Estimates were derived from data collected during Skylab missions. Homogeneous ground sites were selected and S193 radiometer brightness temperature data analyzed. The precision was expressed as the standard deviation of the radiometer acquired brightness temperature. Precision was determined to be 2.40 K or better depending on mode and target temperature.

  7. Precision and Accuracy Studies with Kajaani Fiber Length Analyzers

    NASA Astrophysics Data System (ADS)

    Copur, Yalcin; Makkonen, Hannu

    The aim of this study was to test the measurement precision and accuracy of the Kajaani FS-100 giving attention to possible machine error in the measurements. Fiber length of pine pulps produced using polysulfide, kraft, biokraft and soda methods were determined using both FS-100 and FiberLab automated fiber length analyzers. The measured length values were compared for both methods. The measurement precision and accuracy was tested by replicated measurements using rayon stable fibers. Measurements performed on pulp samples showed typical length distributions for both analyzers. Results obtained from Kajaani FS-100 and FiberLab showed a significant correlation. The shorter length measurement with FiberLab was found to be mainly due to the instrument calibration. The measurement repeatability tested for Kajaani FS-100 indicated that the measurements are precise.

  8. Precision and Accuracy Parameters in Structured Light 3-D Scanning

    NASA Astrophysics Data System (ADS)

    Eiríksson, E. R.; Wilm, J.; Pedersen, D. B.; Aanæs, H.

    2016-04-01

    Structured light systems are popular in part because they can be constructed from off-the-shelf low cost components. In this paper we quantitatively show how common design parameters affect precision and accuracy in such systems, supplying a much needed guide for practitioners. Our quantitative measure is the established VDI/VDE 2634 (Part 2) guideline using precision made calibration artifacts. Experiments are performed on our own structured light setup, consisting of two cameras and a projector. We place our focus on the influence of calibration design parameters, the calibration procedure and encoding strategy and present our findings. Finally, we compare our setup to a state of the art metrology grade commercial scanner. Our results show that comparable, and in some cases better, results can be obtained using the parameter settings determined in this study.

  9. The Plus or Minus Game - Teaching Estimation, Precision, and Accuracy

    NASA Astrophysics Data System (ADS)

    Forringer, Edward R.; Forringer, Richard S.; Forringer, Daniel S.

    2016-03-01

    A quick survey of physics textbooks shows that many (Knight, Young, and Serway for example) cover estimation, significant digits, precision versus accuracy, and uncertainty in the first chapter. Estimation "Fermi" questions are so useful that there has been a column dedicated to them in TPT (Larry Weinstein's "Fermi Questions.") For several years the authors (a college physics professor, a retired algebra teacher, and a fifth-grade teacher) have been playing a game, primarily at home to challenge each other for fun, but also in the classroom as an educational tool. We call the game "The Plus or Minus Game." The game combines estimation with the principle of precision and uncertainty in a competitive and fun way.

  10. Precision and accuracy in the reproduction of simple tone sequences.

    PubMed

    Vos, P G; Ellermann, H H

    1989-02-01

    In four experiments we investigated the precision and accuracy with which amateur musicians are able to reproduce sequences of tones varied only temporally, so as to have tone and rest durations constant over sequences, and the tempo varied over the musically meaningful range of 5-0.5 tones per second. Experiments 1 and 2 supported the hypothesis of attentional bias toward having the attack moments, rather than the departure moments, precisely times. Experiment 3 corroborated the hypothesis that inaccurate timing of short interattack intervals is manifested in a lengthening of rests, rather than tones, as a result of larger motor activity during the reproduction of rests. Experiment 4 gave some support to the hypothesis that the shortening of long interattack intervals is due to mnemonic constraints affecting the rests rather than the tones. Both theoretical and practical consequences of the various findings, particularly with respect to timing in musical performance, are discussed. PMID:2522528

  11. Fluorescence Axial Localization with Nanometer Accuracy and Precision

    SciTech Connect

    Li, Hui; Yen, Chi-Fu; Sivasankar, Sanjeevi

    2012-06-15

    We describe a new technique, standing wave axial nanometry (SWAN), to image the axial location of a single nanoscale fluorescent object with sub-nanometer accuracy and 3.7 nm precision. A standing wave, generated by positioning an atomic force microscope tip over a focused laser beam, is used to excite fluorescence; axial position is determined from the phase of the emission intensity. We use SWAN to measure the orientation of single DNA molecules of different lengths, grafted on surfaces with different functionalities.

  12. Accuracy, Precision, and Resolution in Strain Measurements on Diffraction Instruments

    NASA Astrophysics Data System (ADS)

    Polvino, Sean M.

    Diffraction stress analysis is a commonly used technique to evaluate the properties and performance of different classes of materials from engineering materials, such as steels and alloys, to electronic materials like Silicon chips. Often to better understand the performance of these materials at operating conditions they are also commonly subjected to elevated temperatures and different loading conditions. The validity of any measurement under these conditions is only as good as the control of the conditions and the accuracy and precision of the instrument being used to measure the properties. What is the accuracy and precision of a typical diffraction system and what is the best way to evaluate these quantities? Is there a way to remove systematic and random errors in the data that are due to problems with the control system used? With the advent of device engineering employing internal stress as a method for increasing performance the measurement of stress from microelectronic structures has become of enhanced importance. X-ray diffraction provides an ideal method for measuring these small areas without the need for modifying the sample and possibly changing the strain state. Micro and nano diffraction experiments on Silicon-on-Insulator samples revealed changes to the material under investigation and raised significant concerns about the usefulness of these techniques. This damage process and the application of micro and nano diffraction is discussed.

  13. Assessing the Accuracy of the Precise Point Positioning Technique

    NASA Astrophysics Data System (ADS)

    Bisnath, S. B.; Collins, P.; Seepersad, G.

    2012-12-01

    The Precise Point Positioning (PPP) GPS data processing technique has developed over the past 15 years to become a standard method for growing categories of positioning and navigation applications. The technique relies on single receiver point positioning combined with the use of precise satellite orbit and clock information and high-fidelity error modelling. The research presented here uniquely addresses the current accuracy of the technique, explains the limits of performance, and defines paths to improvements. For geodetic purposes, performance refers to daily static position accuracy. PPP processing of over 80 IGS stations over one week results in few millimetre positioning rms error in the north and east components and few centimetres in the vertical (all one sigma values). Larger error statistics for real-time and kinematic processing are also given. GPS PPP with ambiguity resolution processing is also carried out, producing slight improvements over the float solution results. These results are categorised into quality classes in order to analyse the root error causes of the resultant accuracies: "best", "worst", multipath, site displacement effects, satellite availability and geometry, etc. Also of interest in PPP performance is solution convergence period. Static, conventional solutions are slow to converge, with approximately 35 minutes required for 95% of solutions to reach the 20 cm or better horizontal accuracy. Ambiguity resolution can significantly reduce this period without biasing solutions. The definition of a PPP error budget is a complex task even with the resulting numerical assessment, as unlike the epoch-by-epoch processing in the Standard Position Service, PPP processing involving filtering. An attempt is made here to 1) define the magnitude of each error source in terms of range, 2) transform ranging error to position error via Dilution Of Precision (DOP), and 3) scale the DOP through the filtering process. The result is a deeper

  14. Scatterometry measurement precision and accuracy below 70 nm

    NASA Astrophysics Data System (ADS)

    Sendelbach, Matthew; Archie, Charles N.

    2003-05-01

    Scatterometry is a contender for various measurement applications where structure widths and heights can be significantly smaller than 70 nm within one or two ITRS generations. For example, feedforward process control in the post-lithography transistor gate formation is being actively pursued by a number of RIE tool manufacturers. Several commercial forms of scatterometry are available or under development which promise to provide satisfactory performance in this regime. Scatterometry, as commercially practiced today, involves analyzing the zeroth order reflected light from a grating of lines. Normal incidence spectroscopic reflectometry, 2-theta fixed-wavelength ellipsometry, and spectroscopic ellipsometry are among the optical techniques, while library based spectra matching and realtime regression are among the analysis techniques. All these commercial forms will find accurate and precise measurement a challenge when the material constituting the critical structure approaches a very small volume. Equally challenging is executing an evaluation methodology that first determines the true properties (critical dimensions and materials) of semiconductor wafer artifacts and then compares measurement performance of several scatterometers. How well do scatterometers track process induced changes in bottom CD and sidewall profile? This paper introduces a general 3D metrology assessment methodology and reports upon work involving sub-70 nm structures and several scatterometers. The methodology combines results from multiple metrologies (CD-SEM, CD-AFM, TEM, and XSEM) to form a Reference Measurement System (RMS). The methodology determines how well the scatterometry measurement tracks critical structure changes even in the presence of other noncritical changes that take place at the same time; these are key components of accuracy. Because the assessment rewards scatterometers that measure with good precision (reproducibility) and good accuracy, the most precise

  15. T1-mapping in the heart: accuracy and precision

    PubMed Central

    2014-01-01

    The longitudinal relaxation time constant (T1) of the myocardium is altered in various disease states due to increased water content or other changes to the local molecular environment. Changes in both native T1 and T1 following administration of gadolinium (Gd) based contrast agents are considered important biomarkers and multiple methods have been suggested for quantifying myocardial T1 in vivo. Characterization of the native T1 of myocardial tissue may be used to detect and assess various cardiomyopathies while measurement of T1 with extracellular Gd based contrast agents provides additional information about the extracellular volume (ECV) fraction. The latter is particularly valuable for more diffuse diseases that are more challenging to detect using conventional late gadolinium enhancement (LGE). Both T1 and ECV measures have been shown to have important prognostic significance. T1-mapping has the potential to detect and quantify diffuse fibrosis at an early stage provided that the measurements have adequate reproducibility. Inversion recovery methods such as MOLLI have excellent precision and are highly reproducible when using tightly controlled protocols. The MOLLI method is widely available and is relatively mature. The accuracy of inversion recovery techniques is affected significantly by magnetization transfer (MT). Despite this, the estimate of apparent T1 using inversion recovery is a sensitive measure, which has been demonstrated to be a useful tool in characterizing tissue and discriminating disease. Saturation recovery methods have the potential to provide a more accurate measurement of T1 that is less sensitive to MT as well as other factors. Saturation recovery techniques are, however, noisier and somewhat more artifact prone and have not demonstrated the same level of reproducibility at this point in time. This review article focuses on the technical aspects of key T1-mapping methods and imaging protocols and describes their limitations including

  16. PRECISION AND ACCURACY ASSESSMENTS FOR STATE AND LOCAL AIR MONITORING NETWORKS--1988

    EPA Science Inventory

    Precision and accuracy data obtained from state and local agencies (SLAMS) during 1988 are analyzed. ooled site variances and average biases which are relevant quantities to both precision and accuracy determinations are statistically compared within and between states to assess ...

  17. Accuracy and precision of alternative estimators of ectoparasiticide efficacy.

    PubMed

    Schall, Robert; Burger, Divan A; Luus, Herman G

    2016-06-15

    While there is consensus that the efficacy of parasiticides is properly assessed using the Abbott formula, there is as yet no general consensus on the use of arithmetic versus geometric mean numbers of surviving parasites in the formula. The purpose of this paper is to investigate the accuracy and precision of various efficacy estimators based on the Abbott formula which alternatively use arithmetic mean, geometric mean and median numbers of surviving parasites; we also consider a maximum likelihood estimator. Our study shows that the best estimators using geometric means are competitive, with respect to root mean squared error, with the conventional Abbott estimator using arithmetic means, as they have lower average and lower median root mean square error over the parameter scenarios which we investigated. However, our study confirms that Abbott estimators using geometric means are potentially biased upwards, and this upward bias is substantial in particular when the test product has substandard efficacy (90% and below). For this reason, we recommend that the Abbott estimator be calculated using arithmetic means. PMID:27198777

  18. On the Accuracy of Genomic Selection

    PubMed Central

    Rabier, Charles-Elie; Barre, Philippe; Asp, Torben; Charmet, Gilles; Mangin, Brigitte

    2016-01-01

    Genomic selection is focused on prediction of breeding values of selection candidates by means of high density of markers. It relies on the assumption that all quantitative trait loci (QTLs) tend to be in strong linkage disequilibrium (LD) with at least one marker. In this context, we present theoretical results regarding the accuracy of genomic selection, i.e., the correlation between predicted and true breeding values. Typically, for individuals (so-called test individuals), breeding values are predicted by means of markers, using marker effects estimated by fitting a ridge regression model to a set of training individuals. We present a theoretical expression for the accuracy; this expression is suitable for any configurations of LD between QTLs and markers. We also introduce a new accuracy proxy that is free of the QTL parameters and easily computable; it outperforms the proxies suggested in the literature, in particular, those based on an estimated effective number of independent loci (Me). The theoretical formula, the new proxy, and existing proxies were compared for simulated data, and the results point to the validity of our approach. The calculations were also illustrated on a new perennial ryegrass set (367 individuals) genotyped for 24,957 single nucleotide polymorphisms (SNPs). In this case, most of the proxies studied yielded similar results because of the lack of markers for coverage of the entire genome (2.7 Gb). PMID:27322178

  19. Sex differences in accuracy and precision when judging time to arrival: data from two Internet studies.

    PubMed

    Sanders, Geoff; Sinclair, Kamila

    2011-12-01

    We report two Internet studies that investigated sex differences in the accuracy and precision of judging time to arrival. We used accuracy to mean the ability to match the actual time to arrival and precision to mean the consistency with which each participant made their judgments. Our task was presented as a computer game in which a toy UFO moved obliquely towards the participant through a virtual three-dimensional space on route to a docking station. The UFO disappeared before docking and participants pressed their space bar at the precise moment they thought the UFO would have docked. Study 1 showed it was possible to conduct quantitative studies of spatiotemporal judgments in virtual reality via the Internet and confirmed reports that men are more accurate because women underestimate, but found no difference in precision measured as intra-participant variation. Study 2 repeated Study 1 with five additional presentations of one condition to provide a better measure of precision. Again, men were more accurate than women but there were no sex differences in precision. However, within the coincidence-anticipation timing (CAT) literature, of those studies that report sex differences, a majority found that males are both more accurate and more precise than females. Noting that many CAT studies report no sex differences, we discuss appropriate interpretations of such null findings. While acknowledging that CAT performance may be influenced by experience we suggest that the sex difference may have originated among our ancestors with the evolutionary selection of men for hunting and women for gathering. PMID:21125324

  20. The Use of Scale-Dependent Precision to Increase Forecast Accuracy in Earth System Modelling

    NASA Astrophysics Data System (ADS)

    Thornes, Tobias; Duben, Peter; Palmer, Tim

    2016-04-01

    At the current pace of development, it may be decades before the 'exa-scale' computers needed to resolve individual convective clouds in weather and climate models become available to forecasters, and such machines will incur very high power demands. But the resolution could be improved today by switching to more efficient, 'inexact' hardware with which variables can be represented in 'reduced precision'. Currently, all numbers in our models are represented as double-precision floating points - each requiring 64 bits of memory - to minimise rounding errors, regardless of spatial scale. Yet observational and modelling constraints mean that values of atmospheric variables are inevitably known less precisely on smaller scales, suggesting that this may be a waste of computer resources. More accurate forecasts might therefore be obtained by taking a scale-selective approach whereby the precision of variables is gradually decreased at smaller spatial scales to optimise the overall efficiency of the model. To study the effect of reducing precision to different levels on multiple spatial scales, we here introduce a new model atmosphere developed by extending the Lorenz '96 idealised system to encompass three tiers of variables - which represent large-, medium- and small-scale features - for the first time. In this chaotic but computationally tractable system, the 'true' state can be defined by explicitly resolving all three tiers. The abilities of low resolution (single-tier) double-precision models and similar-cost high resolution (two-tier) models in mixed-precision to produce accurate forecasts of this 'truth' are compared. The high resolution models outperform the low resolution ones even when small-scale variables are resolved in half-precision (16 bits). This suggests that using scale-dependent levels of precision in more complicated real-world Earth System models could allow forecasts to be made at higher resolution and with improved accuracy. If adopted, this new

  1. Large format focal plane array integration with precision alignment, metrology and accuracy capabilities

    NASA Astrophysics Data System (ADS)

    Neumann, Jay; Parlato, Russell; Tracy, Gregory; Randolph, Max

    2015-09-01

    Focal plane alignment for large format arrays and faster optical systems require enhanced precision methodology and stability over temperature. The increase in focal plane array size continues to drive the alignment capability. Depending on the optical system, the focal plane flatness of less than 25μm (.001") is required over transition temperatures from ambient to cooled operating temperatures. The focal plane flatness requirement must also be maintained in airborne or launch vibration environments. This paper addresses the challenge of the detector integration into the focal plane module and housing assemblies, the methodology to reduce error terms during integration and the evaluation of thermal effects. The driving factors influencing the alignment accuracy include: datum transfers, material effects over temperature, alignment stability over test, adjustment precision and traceability to NIST standard. The FPA module design and alignment methodology reduces the error terms by minimizing the measurement transfers to the housing. In the design, the proper material selection requires matched coefficient of expansion materials minimizes both the physical shift over temperature as well as lowering the stress induced into the detector. When required, the co-registration of focal planes and filters can achieve submicron relative positioning by applying precision equipment, interferometry and piezoelectric positioning stages. All measurements and characterizations maintain traceability to NIST standards. The metrology characterizes the equipment's accuracy, repeatability and precision of the measurements.

  2. Improved DORIS accuracy for precise orbit determination and geodesy

    NASA Technical Reports Server (NTRS)

    Willis, Pascal; Jayles, Christian; Tavernier, Gilles

    2004-01-01

    In 2001 and 2002, 3 more DORIS satellites were launched. Since then, all DORIS results have been significantly improved. For precise orbit determination, 20 cm are now available in real-time with DIODE and 1.5 to 2 cm in post-processing. For geodesy, 1 cm precision can now be achieved regularly every week, making now DORIS an active part of a Global Observing System for Geodesy through the IDS.

  3. Numerical planetary and lunar ephemerides - Present status, precision and accuracies

    NASA Technical Reports Server (NTRS)

    Standish, E. Myles, Jr.

    1986-01-01

    Features of the emphemeris creation process are described with attention given to the equations of motion, the numerical integration, and the least-squares fitting process. Observational data are presented and ephemeride accuracies are estimated. It is believed that radio measurements, VLBI, occultations, and the Space Telescope and Hipparcos will improve ephemerides in the near future. Limitations to accuracy are considered as well as relativity features. The export procedure, by which an outside user may obtain and use the JPL ephemerides, is discussed.

  4. The precision and accuracy of a portable heart rate monitor.

    PubMed

    Seaward, B L; Sleamaker, R H; McAuliffe, T; Clapp, J F

    1990-01-01

    A device that would comfortably and accurately measure exercise heart rate during field performance could be valuable for athletes, fitness participants, and investigators in the field of exercise physiology. Such a device, a portable telemeterized microprocessor, was compared with direct EKG measurements in a laboratory setting under several conditions to assess its accuracy. Twenty-four subjects were studied at rest and during light-, moderate-, high-, and maximal-intensity endurance activities (walking, running, aerobic dancing, and Nordic Track simulated cross-country skiing. Differences between values obtained by the two measuring devices were not statistically significant, with correlation coefficient (r) values ranging from 0.998 to 0.999. The two methods proved equally reliable for measuring heart rate in a host of varied aerobic activities at varying intensities. PMID:2306564

  5. Milling precision and fitting accuracy of Cerec Scan milled restorations.

    PubMed

    Arnetzl, G; Pongratz, D

    2005-10-01

    The milling accuracy of the Cerec Scan system was examined under standard practice conditions. For this purpose, one and the same 3D design similar to an inlay was milled 30 times from Vita Mark II ceramic blocks. Cylindrical diamond burs with 1.2 or 1.6 mm diameter were used. Each individual milled body was measured exactly to 0.1 microm at five defined sections with a coordinate measuring instrument from the Zeiss company. In the statistical evaluation, both the different diamond bur diameters and the extent of material removal from the ceramic blank were taken into consideration; sections with large substance removal and sections with low substance removal were defined. The standard deviation for the 1.6-mm burs was clearly greater than that for the 1.2-mm burs for the section with large substance removal. This difference was significant according to the Levene test for variance equality. In sections with low substance removal, no difference between the use of the 1.6-mm or 1.2-mm bur was shown. The measuring results ranged between 0.053 and 0.14 mm. The spacing of the distances with large substance removal were larger than those with low substance removal. The T-test for paired random samples showed that the distance with large substance removal when using the 1.6-mm bur was significantly larger than the distance with low substance removal. The difference was not significant for the small burs. It was shown several times statistically that the use of the cylindrical diamond bur with 1.6-mm diameter led to greater inaccuracies than the use of the 1.2-mm cylindrical diamond bur, especially at sites with large material removal. PMID:16689028

  6. Precision and Accuracy in Measurements: A Tale of Four Graduated Cylinders.

    ERIC Educational Resources Information Center

    Treptow, Richard S.

    1998-01-01

    Expands upon the concepts of precision and accuracy at a level suitable for general chemistry. Serves as a bridge to the more extensive treatments in analytical chemistry textbooks and the advanced literature on error analysis. Contains 22 references. (DDR)

  7. Expansion and dissemination of a standardized accuracy and precision assessment technique

    NASA Astrophysics Data System (ADS)

    Kwartowitz, David M.; Riti, Rachel E.; Holmes, David R., III

    2011-03-01

    The advent and development of new imaging techniques and image-guidance have had a major impact on surgical practice. These techniques attempt to allow the clinician to not only visualize what is currently visible, but also what is beneath the surface, or function. These systems are often based on tracking systems coupled with registration and visualization technologies. The accuracy and precision of the tracking systems, thus is critical in the overall accuracy and precision of the image-guidance system. In this work the accuracy and precision of an Aurora tracking system is assessed, using the technique specified in " novel technique for analysis of accuracy of magnetic tracking systems used in image guided surgery." This analysis yielded a demonstration that accuracy is dependent on distance from the tracker's field generator, and had an RMS value of 1.48 mm. The error has the similar characteristics and values as the previous work, thus validating this method for tracker analysis.

  8. Accuracy and Precision of Silicon Based Impression Media for Quantitative Areal Texture Analysis

    PubMed Central

    Goodall, Robert H.; Darras, Laurent P.; Purnell, Mark A.

    2015-01-01

    Areal surface texture analysis is becoming widespread across a diverse range of applications, from engineering to ecology. In many studies silicon based impression media are used to replicate surfaces, and the fidelity of replication defines the quality of data collected. However, while different investigators have used different impression media, the fidelity of surface replication has not been subjected to quantitative analysis based on areal texture data. Here we present the results of an analysis of the accuracy and precision with which different silicon based impression media of varying composition and viscosity replicate rough and smooth surfaces. Both accuracy and precision vary greatly between different media. High viscosity media tested show very low accuracy and precision, and most other compounds showed either the same pattern, or low accuracy and high precision, or low precision and high accuracy. Of the media tested, mid viscosity President Jet Regular Body and low viscosity President Jet Light Body (Coltène Whaledent) are the only compounds to show high levels of accuracy and precision on both surface types. Our results show that data acquired from different impression media are not comparable, supporting calls for greater standardisation of methods in areal texture analysis. PMID:25991505

  9. Gaining Precision and Accuracy on Microprobe Trace Element Analysis with the Multipoint Background Method

    NASA Astrophysics Data System (ADS)

    Allaz, J. M.; Williams, M. L.; Jercinovic, M. J.; Donovan, J. J.

    2014-12-01

    Electron microprobe trace element analysis is a significant challenge, but can provide critical data when high spatial resolution is required. Due to the low peak intensity, the accuracy and precision of such analyses relies critically on background measurements, and on the accuracy of any pertinent peak interference corrections. A linear regression between two points selected at appropriate off-peak positions is a classical approach for background characterization in microprobe analysis. However, this approach disallows an accurate assessment of background curvature (usually exponential). Moreover, if present, background interferences can dramatically affect the results if underestimated or ignored. The acquisition of a quantitative WDS scan over the spectral region of interest is still a valuable option to determine the background intensity and curvature from a fitted regression of background portions of the scan, but this technique retains an element of subjectivity as the analyst has to select areas in the scan, which appear to represent background. We present here a new method, "Multi-Point Background" (MPB), that allows acquiring up to 24 off-peak background measurements from wavelength positions around the peaks. This method aims to improve the accuracy, precision, and objectivity of trace element analysis. The overall efficiency is amended because no systematic WDS scan needs to be acquired in order to check for the presence of possible background interferences. Moreover, the method is less subjective because "true" backgrounds are selected by the statistical exclusion of erroneous background measurements, reducing the need for analyst intervention. This idea originated from efforts to refine EPMA monazite U-Th-Pb dating, where it was recognised that background errors (peak interference or background curvature) could result in errors of several tens of million years on the calculated age. Results obtained on a CAMECA SX-100 "UltraChron" using monazite

  10. Accuracy improvement techniques in Precise Point Positioning method using multiple GNSS constellations

    NASA Astrophysics Data System (ADS)

    Vasileios Psychas, Dimitrios; Delikaraoglou, Demitris

    2016-04-01

    The future Global Navigation Satellite Systems (GNSS), including modernized GPS, GLONASS, Galileo and BeiDou, offer three or more signal carriers for civilian use and much more redundant observables. The additional frequencies can significantly improve the capabilities of the traditional geodetic techniques based on GPS signals at two frequencies, especially with regard to the availability, accuracy, interoperability and integrity of high-precision GNSS applications. Furthermore, highly redundant measurements can allow for robust simultaneous estimation of static or mobile user states including more parameters such as real-time tropospheric biases and more reliable ambiguity resolution estimates. This paper presents an investigation and analysis of accuracy improvement techniques in the Precise Point Positioning (PPP) method using signals from the fully operational (GPS and GLONASS), as well as the emerging (Galileo and BeiDou) GNSS systems. The main aim was to determine the improvement in both the positioning accuracy achieved and the time convergence it takes to achieve geodetic-level (10 cm or less) accuracy. To this end, freely available observation data from the recent Multi-GNSS Experiment (MGEX) of the International GNSS Service, as well as the open source program RTKLIB were used. Following a brief background of the PPP technique and the scope of MGEX, the paper outlines the various observational scenarios that were used in order to test various data processing aspects of PPP solutions with multi-frequency, multi-constellation GNSS systems. Results from the processing of multi-GNSS observation data from selected permanent MGEX stations are presented and useful conclusions and recommendations for further research are drawn. As shown, data fusion from GPS, GLONASS, Galileo and BeiDou systems is becoming increasingly significant nowadays resulting in a position accuracy increase (mostly in the less favorable East direction) and a large reduction of convergence

  11. [Assessment of precision and accuracy of digital surface photogrammetry with the DSP 400 system].

    PubMed

    Krimmel, M; Kluba, S; Dietz, K; Reinert, S

    2005-03-01

    The objective of the present study was to evaluate the precision and accuracy of facial anthropometric measurements obtained through digital 3-D surface photogrammetry with the DSP 400 system in comparison to traditional 2-D photogrammetry. Fifty plaster casts of cleft infants were imaged and 21 standard anthropometric measurements were obtained. For precision assessment the measurements were performed twice in a subsample. Accuracy was determined by comparison of direct measurements and indirect 2-D and 3-D image measurements. Precision of digital surface photogrammetry was almost as good as direct anthropometry and clearly better than 2-D photogrammetry. Measurements derived from 3-D images showed better congruence to direct measurements than from 2-D photos. Digital surface photogrammetry with the DSP 400 system is sufficiently precise and accurate for craniofacial anthropometric examinations. PMID:15832575

  12. Evaluation of optoelectronic Plethysmography accuracy and precision in recording displacements during quiet breathing simulation.

    PubMed

    Massaroni, C; Schena, E; Saccomandi, P; Morrone, M; Sterzi, S; Silvestri, S

    2015-08-01

    Opto-electronic Plethysmography (OEP) is a motion analysis system used to measure chest wall kinematics and to indirectly evaluate respiratory volumes during breathing. Its working principle is based on the computation of marker displacements placed on the chest wall. This work aims at evaluating the accuracy and precision of OEP in measuring displacement in the range of human chest wall displacement during quiet breathing. OEP performances were investigated by the use of a fully programmable chest wall simulator (CWS). CWS was programmed to move 10 times its eight shafts in the range of physiological displacement (i.e., between 1 mm and 8 mm) at three different frequencies (i.e., 0.17 Hz, 0.25 Hz, 0.33 Hz). Experiments were performed with the aim to: (i) evaluate OEP accuracy and precision error in recording displacement in the overall calibrated volume and in three sub-volumes, (ii) evaluate the OEP volume measurement accuracy due to the measurement accuracy of linear displacements. OEP showed an accuracy better than 0.08 mm in all trials, considering the whole 2m(3) calibrated volume. The mean measurement discrepancy was 0.017 mm. The precision error, expressed as the ratio between measurement uncertainty and the recorded displacement by OEP, was always lower than 0.55%. Volume overestimation due to OEP linear measurement accuracy was always <; 12 mL (<; 3.2% of total volume), considering all settings. PMID:26736504

  13. The Plus or Minus Game--Teaching Estimation, Precision, and Accuracy

    ERIC Educational Resources Information Center

    Forringer, Edward R.; Forringer, Richard S.; Forringer, Daniel S.

    2016-01-01

    A quick survey of physics textbooks shows that many (Knight, Young, and Serway for example) cover estimation, significant digits, precision versus accuracy, and uncertainty in the first chapter. Estimation "Fermi" questions are so useful that there has been a column dedicated to them in "TPT" (Larry Weinstein's "Fermi…

  14. PRECISION AND ACCURACY ASSESSMENTS FOR STATE AND LOCAL AIR MONITORING NETWORKS, 1984

    EPA Science Inventory

    Precision and accuracy data obtained from state and local agencies during 1984 are summarized and compared to data reported earlier for the period 1981-1983. A continual improvement in the completeness of the data is evident. Improvement is also evident in the size of the precisi...

  15. PRECISION AND ACCURACY ASSESSMENTS FOR STATE AND LOCAL AIR MONITORING NETWORKS, 1983

    EPA Science Inventory

    Precision and accuracy data obtained from State and local agencies during 1983 are summarized and evaluated. Some comparisons are made with the results previously reported for 1981 and 1982 to determine the indication of any trends. Some trends indicated improvement in the comple...

  16. PRECISION AND ACCURACY ASSESSMENTS FOR STATE AND LOCAL AIR MONITORING NETWORKS, 1985

    EPA Science Inventory

    Precision and accuracy data obtained from State and local agencies during 1985 are summarized and evaluated. Some comparisons are made with the results reported for prior years to determine any trends. Some trends indicated continued improvement in the completeness of reporting o...

  17. ASSESSMENT OF THE PRECISION AND ACCURACY OF SAM AND MFC MICROCOSMS EXPOSED TO TOXICANTS

    EPA Science Inventory

    The results of 30 mixed flank culture (MFC) and four standardized aquatic microcosm (SAM) microcosm experiments were used to describe the precision and accuracy of these two protocols. oefficients of variation (CV) for chemicals measurements (DO,pH) were generally less than 7%, f...

  18. Use of single-representative reverse-engineered surface-models for RSA does not affect measurement accuracy and precision.

    PubMed

    Seehaus, Frank; Schwarze, Michael; Flörkemeier, Thilo; von Lewinski, Gabriela; Kaptein, Bart L; Jakubowitz, Eike; Hurschler, Christof

    2016-05-01

    Implant migration can be accurately quantified by model-based Roentgen stereophotogrammetric analysis (RSA), using an implant surface model to locate the implant relative to the bone. In a clinical situation, a single reverse engineering (RE) model for each implant type and size is used. It is unclear to what extent the accuracy and precision of migration measurement is affected by implant manufacturing variability unaccounted for by a single representative model. Individual RE models were generated for five short-stem hip implants of the same type and size. Two phantom analyses and one clinical analysis were performed: "Accuracy-matched models": one stem was assessed, and the results from the original RE model were compared with randomly selected models. "Accuracy-random model": each of the five stems was assessed and analyzed using one randomly selected RE model. "Precision-clinical setting": implant migration was calculated for eight patients, and all five available RE models were applied to each case. For the two phantom experiments, the 95%CI of the bias ranged from -0.28 mm to 0.30 mm for translation and -2.3° to 2.5° for rotation. In the clinical setting, precision is less than 0.5 mm and 1.2° for translation and rotation, respectively, except for rotations about the proximodistal axis (<4.1°). High accuracy and precision of model-based RSA can be achieved and are not biased by using a single representative RE model. At least for implants similar in shape to the investigated short-stem, individual models are not necessary. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:903-910, 2016. PMID:26553748

  19. Commissioning Procedures for Mechanical Precision and Accuracy in a Dedicated LINAC

    SciTech Connect

    Ballesteros-Zebadua, P.; Larrga-Gutierrez, J. M.; Garcia-Garduno, O. A.; Juarez, J.; Prieto, I.; Moreno-Jimenez, S.; Celis, M. A.

    2008-08-11

    Mechanical precision measurements are fundamental procedures for the commissioning of a dedicated LINAC. At our Radioneurosurgery Unit, these procedures can be suitable as quality assurance routines that allow the verification of the equipment geometrical accuracy and precision. In this work mechanical tests were performed for gantry and table rotation, obtaining mean associated uncertainties of 0.3 mm and 0.71 mm, respectively. Using an anthropomorphic phantom and a series of localized surface markers, isocenter accuracy showed to be smaller than 0.86 mm for radiosurgery procedures and 0.95 mm for fractionated treatments with mask. All uncertainties were below tolerances. The highest contribution to mechanical variations is due to table rotation, so it is important to correct variations using a localization frame with printed overlays. Mechanical precision knowledge would allow to consider the statistical errors in the treatment planning volume margins.

  20. Evaluation of the Accuracy and Precision of a Next Generation Computer-Assisted Surgical System

    PubMed Central

    Dai, Yifei; Liebelt, Ralph A.; Gao, Bo; Gulbransen, Scott W.; Silver, Xeve S.

    2015-01-01

    Background Computer-assisted orthopaedic surgery (CAOS) improves accuracy and reduces outliers in total knee arthroplasty (TKA). However, during the evaluation of CAOS systems, the error generated by the guidance system (hardware and software) has been generally overlooked. Limited information is available on the accuracy and precision of specific CAOS systems with regard to intraoperative final resection measurements. The purpose of this study was to assess the accuracy and precision of a next generation CAOS system and investigate the impact of extra-articular deformity on the system-level errors generated during intraoperative resection measurement. Methods TKA surgeries were performed on twenty-eight artificial knee inserts with various types of extra-articular deformity (12 neutral, 12 varus, and 4 valgus). Surgical resection parameters (resection depths and alignment angles) were compared between postoperative three-dimensional (3D) scan-based measurements and intraoperative CAOS measurements. Using the 3D scan-based measurements as control, the accuracy (mean error) and precision (associated standard deviation) of the CAOS system were assessed. The impact of extra-articular deformity on the CAOS system measurement errors was also investigated. Results The pooled mean unsigned errors generated by the CAOS system were equal or less than 0.61 mm and 0.64° for resection depths and alignment angles, respectively. No clinically meaningful biases were found in the measurements of resection depths (< 0.5 mm) and alignment angles (< 0.5°). Extra-articular deformity did not show significant effect on the measurement errors generated by the CAOS system investigated. Conclusions This study presented a set of methodology and workflow to assess the system-level accuracy and precision of CAOS systems. The data demonstrated that the CAOS system investigated can offer accurate and precise intraoperative measurements of TKA resection parameters, regardless of the presence

  1. Accuracy, precision and economics: The cost of cutting-edge chemical analyses

    NASA Astrophysics Data System (ADS)

    Hamilton, B.; Hannigan, R.; Jones, C.; Chen, Z.

    2002-12-01

    Otolith (fish ear bone) chemistry has proven to be an exceptional tool for the identification of essential fish habitats in marine and freshwater environments. These measurements, which explore the variations in trace element content of otoliths relative to Calcium (eg., Ba/Ca, Mg/Ca etc.), provide data to resolve the differences in habitat water chemistry on the watershed to catchment scale. The vast majority of these analyses are performed by laser ablation ICP-MS using a high-resolution instrument. However, few laboratories are equipped with this configuration and many researchers measure the trace element chemistry of otoliths by whole digestion ICP-MS using lower resolution quadrupole instruments. This study examines the differences in accuracy and precision between three elemental analysis methods using whole otolith digestion on a low resolution ICP-MS (ELAN 9000). The first, and most commonly used, technique is external calibration with internal standardization. This technique is the most cost-effective but also is one with limitations in terms of method detection. The second, standard addition is more costly in terms of time and use of standard materials but offers gains in precision and accuracy. The third, isotope dilution, is the least cost effective but the most accurate of elemental analysis techniques. Based on the results of this study, which seeks to identify the technique which is the easiest to implement yet has the precision and accuracy necessary to resolve spatial variations in habitats, we conclude that external calibration with internal standardization can be sufficient to revolve spatial and temporal variations in marine and estuarine environments (+/- 6-8% accuracy). Standard addition increases the accuracy of measurements to 2-5% and is ideal for freshwater studies. While there is a gain in accuracy and precision with isotope dilution, the spatial and temporal resolution is no greater with this technique than the other.

  2. Genomic selection in forage breeding: accuracy and methods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The main benefits expected from genomic selection in forage grasses and legumes are to increase selection accuracy, reduce evaluation costs per genotype, and reduce cycle time. Aiming at designing a training population and first generations of selection, deterministic equations were used to compare ...

  3. Accuracy in Dental Medicine, A New Way to Measure Trueness and Precision

    PubMed Central

    Ender, Andreas; Mehl, Albert

    2014-01-01

    Reference scanners are used in dental medicine to verify a lot of procedures. The main interest is to verify impression methods as they serve as a base for dental restorations. The current limitation of many reference scanners is the lack of accuracy scanning large objects like full dental arches, or the limited possibility to assess detailed tooth surfaces. A new reference scanner, based on focus variation scanning technique, was evaluated with regards to highest local and general accuracy. A specific scanning protocol was tested to scan original tooth surface from dental impressions. Also, different model materials were verified. The results showed a high scanning accuracy of the reference scanner with a mean deviation of 5.3 ± 1.1 µm for trueness and 1.6 ± 0.6 µm for precision in case of full arch scans. Current dental impression methods showed much higher deviations (trueness: 20.4 ± 2.2 µm, precision: 12.5 ± 2.5 µm) than the internal scanning accuracy of the reference scanner. Smaller objects like single tooth surface can be scanned with an even higher accuracy, enabling the system to assess erosive and abrasive tooth surface loss. The reference scanner can be used to measure differences for a lot of dental research fields. The different magnification levels combined with a high local and general accuracy can be used to assess changes of single teeth or restorations up to full arch changes. PMID:24836007

  4. Accuracy and precisions of water quality parameters retrieved from particle swarm optimisation in a sub-tropical lake

    NASA Astrophysics Data System (ADS)

    Campbell, Glenn; Phinn, Stuart R.

    2009-09-01

    Optical remote sensing has been used to map and monitor water quality parameters such as the concentrations of hydrosols (chlorophyll and other pigments, total suspended material, and coloured dissolved organic matter). In the inversion / optimisation approach a forward model is used to simulate the water reflectance spectra from a set of parameters and the set that gives the closest match is selected as the solution. The accuracy of the hydrosol retrieval is dependent on an efficient search of the solution space and the reliability of the similarity measure. In this paper the Particle Swarm Optimisation (PSO) was used to search the solution space and seven similarity measures were trialled. The accuracy and precision of this method depends on the inherent noise in the spectral bands of the sensor being employed, as well as the radiometric corrections applied to images to calculate the subsurface reflectance. Using the Hydrolight® radiative transfer model and typical hydrosol concentrations from Lake Wivenhoe, Australia, MERIS reflectance spectra were simulated. The accuracy and precision of hydrosol concentrations derived from each similarity measure were evaluated after errors associated with the air-water interface correction, atmospheric correction and the IOP measurement were modelled and applied to the simulated reflectance spectra. The use of band specific empirically estimated values for the anisotropy value in the forward model improved the accuracy of hydrosol retrieval. The results of this study will be used to improve an algorithm for the remote sensing of water quality for freshwater impoundments.

  5. A Method for Assessing the Accuracy of a Photogrammetry System for Precision Deployable Structures

    NASA Technical Reports Server (NTRS)

    Moore, Ashley

    2005-01-01

    The measurement techniques used to validate analytical models of large deployable structures are an integral Part of the technology development process and must be precise and accurate. Photogrammetry and videogrammetry are viable, accurate, and unobtrusive methods for measuring such large Structures. Photogrammetry uses Software to determine the three-dimensional position of a target using camera images. Videogrammetry is based on the same principle, except a series of timed images are analyzed. This work addresses the accuracy of a digital photogrammetry system used for measurement of large, deployable space structures at JPL. First, photogrammetry tests are performed on a precision space truss test article, and the images are processed using Photomodeler software. The accuracy of the Photomodeler results is determined through, comparison with measurements of the test article taken by an external testing group using the VSTARS photogrammetry system. These two measurements are then compared with Australis photogrammetry software that simulates a measurement test to predict its accuracy. The software is then used to study how particular factors, such as camera resolution and placement, affect the system accuracy to help design the setup for the videogrammetry system that will offer the highest level of accuracy for measurement of deploying structures.

  6. Measuring the accuracy and precision of quantitative coronary angiography using a digitally simulated test phantom

    NASA Astrophysics Data System (ADS)

    Morioka, Craig A.; Whiting, James S.; LeFree, Michelle T.

    1998-06-01

    Quantitative coronary angiography (QCA) diameter measurements have been used as an endpoint measurement in clinical studies involving therapies to reduce coronary atherosclerosis. The accuracy and precision of the QCA measure can affect the sample size and study conclusions of a clinical study. Measurements using x-ray test phantoms can underestimate the precision and accuracy of the actual arteries in clinical digital angiograms because they do not contain complex patient structures. Determining the clinical performance of QCA algorithms under clinical conditions is difficult because: (1) no gold standard test object exists in clinical images, (2) phantom images do not have any structured background noise. We purpose the use of computer simulated arteries as a replacement for traditional angiographic test phantoms to evaluate QCA algorithm performance.

  7. Comparison between predicted and actual accuracies for an Ultra-Precision CNC measuring machine

    SciTech Connect

    Thompson, D.C.; Fix, B.L.

    1995-05-30

    At the 1989 CIRP annual meeting, we reported on the design of a specialized, ultra-precision CNC measuring machine, and on the error budget that was developed to guide the design process. In our paper we proposed a combinatorial rule for merging estimated and/or calculated values for all known sources of error, to yield a single overall predicted accuracy for the machine. In this paper we compare our original predictions with measured performance of the completed instrument.

  8. Assessing genomic selection prediction accuracy in a dynamic barley breeding

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic selection is a method to improve quantitative traits in crops and livestock by estimating breeding values of selection candidates using phenotype and genome-wide marker data sets. Prediction accuracy has been evaluated through simulation and cross-validation, however validation based on prog...

  9. Measuring changes in Plasmodium falciparum transmission: Precision, accuracy and costs of metrics

    PubMed Central

    Tusting, Lucy S.; Bousema, Teun; Smith, David L.; Drakeley, Chris

    2016-01-01

    As malaria declines in parts of Africa and elsewhere, and as more countries move towards elimination, it is necessary to robustly evaluate the effect of interventions and control programmes on malaria transmission. To help guide the appropriate design of trials to evaluate transmission-reducing interventions, we review eleven metrics of malaria transmission, discussing their accuracy, precision, collection methods and costs, and presenting an overall critique. We also review the non-linear scaling relationships between five metrics of malaria transmission; the entomological inoculation rate, force of infection, sporozoite rate, parasite rate and the basic reproductive number, R0. Our review highlights that while the entomological inoculation rate is widely considered the gold standard metric of malaria transmission and may be necessary for measuring changes in transmission in highly endemic areas, it has limited precision and accuracy and more standardised methods for its collection are required. In areas of low transmission, parasite rate, sero-conversion rates and molecular metrics including MOI and mFOI may be most appropriate. When assessing a specific intervention, the most relevant effects will be detected by examining the metrics most directly affected by that intervention. Future work should aim to better quantify the precision and accuracy of malaria metrics and to improve methods for their collection. PMID:24480314

  10. Evaluation of precision and accuracy of selenium measurements in biological materials using neutron activation analysis

    SciTech Connect

    Greenberg, R.R.

    1988-01-01

    In recent years, the accurate determination of selenium in biological materials has become increasingly important in view of the essential nature of this element for human nutrition and its possible role as a protective agent against cancer. Unfortunately, the accurate determination of selenium in biological materials is often difficult for most analytical techniques for a variety of reasons, including interferences, complicated selenium chemistry due to the presence of this element in multiple oxidation states and in a variety of different organic species, stability and resistance to destruction of some of these organo-selenium species during acid dissolution, volatility of some selenium compounds, and potential for contamination. Neutron activation analysis (NAA) can be one of the best analytical techniques for selenium determinations in biological materials for a number of reasons. Currently, precision at the 1% level (1s) and overall accuracy at the 1 to 2% level (95% confidence interval) can be attained at the U.S. National Bureau of Standards (NBS) for selenium determinations in biological materials when counting statistics are not limiting (using the {sup 75}Se isotope). An example of this level of precision and accuracy is summarized. Achieving this level of accuracy, however, requires strict attention to all sources of systematic error. Precise and accurate results can also be obtained after radiochemical separations.

  11. Precision and accuracy of 3D lower extremity residua measurement systems

    NASA Astrophysics Data System (ADS)

    Commean, Paul K.; Smith, Kirk E.; Vannier, Michael W.; Hildebolt, Charles F.; Pilgram, Thomas K.

    1996-04-01

    Accurate and reproducible geometric measurement of lower extremity residua is required for custom prosthetic socket design. We compared spiral x-ray computed tomography (SXCT) and 3D optical surface scanning (OSS) with caliper measurements and evaluated the precision and accuracy of each system. Spiral volumetric CT scanned surface and subsurface information was used to make external and internal measurements, and finite element models (FEMs). SXCT and OSS were used to measure lower limb residuum geometry of 13 below knee (BK) adult amputees. Six markers were placed on each subject's BK residuum and corresponding plaster casts and distance measurements were taken to determine precision and accuracy for each system. Solid models were created from spiral CT scan data sets with the prosthesis in situ under different loads using p-version finite element analysis (FEA). Tissue properties of the residuum were estimated iteratively and compared with values taken from the biomechanics literature. The OSS and SXCT measurements were precise within 1% in vivo and 0.5% on plaster casts, and accuracy was within 3.5% in vivo and 1% on plaster casts compared with caliper measures. Three-dimensional optical surface and SXCT imaging systems are feasible for capturing the comprehensive 3D surface geometry of BK residua, and provide distance measurements statistically equivalent to calipers. In addition, SXCT can readily distinguish internal soft tissue and bony structure of the residuum. FEM can be applied to determine tissue material properties interactively using inverse methods.

  12. Increasing the precision and accuracy of top-loading balances:  application of experimental design.

    PubMed

    Bzik, T J; Henderson, P B; Hobbs, J P

    1998-01-01

    The traditional method of estimating the weight of multiple objects is to obtain the weight of each object individually. We demonstrate that the precision and accuracy of these estimates can be improved by using a weighing scheme in which multiple objects are simultaneously on the balance. The resulting system of linear equations is solved to yield the weight estimates for the objects. Precision and accuracy improvements can be made by using a weighing scheme without requiring any more weighings than the number of objects when a total of at least six objects are to be weighed. It is also necessary that multiple objects can be weighed with about the same precision as that obtained with a single object, and the scale bias remains relatively constant over the set of weighings. Simulated and empirical examples are given for a system of eight objects in which up to five objects can be weighed simultaneously. A modified Plackett-Burman weighing scheme yields a 25% improvement in precision over the traditional method and implicitly removes the scale bias from seven of the eight objects. Applications of this novel use of experimental design techniques are shown to have potential commercial importance for quality control methods that rely on the mass change rate of an object. PMID:21644600

  13. Accuracy and precision of quantitative 31P-MRS measurements of human skeletal muscle mitochondrial function.

    PubMed

    Layec, Gwenael; Gifford, Jayson R; Trinity, Joel D; Hart, Corey R; Garten, Ryan S; Park, Song Y; Le Fur, Yann; Jeong, Eun-Kee; Richardson, Russell S

    2016-08-01

    Although theoretically sound, the accuracy and precision of (31)P-magnetic resonance spectroscopy ((31)P-MRS) approaches to quantitatively estimate mitochondrial capacity are not well documented. Therefore, employing four differing models of respiratory control [linear, kinetic, and multipoint adenosine diphosphate (ADP) and phosphorylation potential], this study sought to determine the accuracy and precision of (31)P-MRS assessments of peak mitochondrial adenosine-triphosphate (ATP) synthesis rate utilizing directly measured peak respiration (State 3) in permeabilized skeletal muscle fibers. In 23 subjects of different fitness levels, (31)P-MRS during a 24-s maximal isometric knee extension and high-resolution respirometry in muscle fibers from the vastus lateralis was performed. Although significantly correlated with State 3 respiration (r = 0.72), both the linear (45 ± 13 mM/min) and phosphorylation potential (47 ± 16 mM/min) models grossly overestimated the calculated in vitro peak ATP synthesis rate (P < 0.05). Of the ADP models, the kinetic model was well correlated with State 3 respiration (r = 0.72, P < 0.05), but moderately overestimated ATP synthesis rate (P < 0.05), while the multipoint model, although being somewhat less well correlated with State 3 respiration (r = 0.55, P < 0.05), most accurately reflected peak ATP synthesis rate. Of note, the PCr recovery time constant (τ), a qualitative index of mitochondrial capacity, exhibited the strongest correlation with State 3 respiration (r = 0.80, P < 0.05). Therefore, this study reveals that each of the (31)P-MRS data analyses, including PCr τ, exhibit precision in terms of mitochondrial capacity. As only the multipoint ADP model did not overstimate the peak skeletal muscle mitochondrial ATP synthesis, the multipoint ADP model is the only quantitative approach to exhibit both accuracy and precision. PMID:27302751

  14. Accuracy and precision of ice stream bed topography derived from ground-based radar surveys

    NASA Astrophysics Data System (ADS)

    King, Edward

    2016-04-01

    There is some confusion within the glaciological community as to the accuracy of the basal topography derived from radar measurements. A number of texts and papers state that basal topography cannot be determined to better than one quarter of the wavelength of the radar system. On the other hand King et al (Nature Geoscience, 2009) claimed that features of the bed topography beneath Rutford Ice Stream, Antarctica can be distinguished to +/- 3m using a 3 MHz radar system (which has a quarter wavelength of 14m in ice). These statements of accuracy are mutually exclusive. I will show in this presentation that the measurement of ice thickness is a radar range determination to a single strongly-reflective target. This measurement has much higher accuracy than the resolution of two targets of similar reflection strength, which is governed by the quarter-wave criterion. The rise time of the source signal and the sensitivity and digitisation interval of the recording system are the controlling criteria on radar range accuracy. A dataset from Pine Island Glacier, West Antarctica will be used to illustrate these points, as well as the repeatability or precision of radar range measurements, and the influence of gridding parameters and positioning accuracy on the final DEM product.

  15. Wound Area Measurement with Digital Planimetry: Improved Accuracy and Precision with Calibration Based on 2 Rulers

    PubMed Central

    Foltynski, Piotr

    2015-01-01

    Introduction In the treatment of chronic wounds the wound surface area change over time is useful parameter in assessment of the applied therapy plan. The more precise the method of wound area measurement the earlier may be identified and changed inappropriate treatment plan. Digital planimetry may be used in wound area measurement and therapy assessment when it is properly used, but the common problem is the camera lens orientation during the taking of a picture. The camera lens axis should be perpendicular to the wound plane, and if it is not, the measured area differ from the true area. Results Current study shows that the use of 2 rulers placed in parallel below and above the wound for the calibration increases on average 3.8 times the precision of area measurement in comparison to the measurement with one ruler used for calibration. The proposed procedure of calibration increases also 4 times accuracy of area measurement. It was also showed that wound area range and camera type do not influence the precision of area measurement with digital planimetry based on two ruler calibration, however the measurements based on smartphone camera were significantly less accurate than these based on D-SLR or compact cameras. Area measurement on flat surface was more precise with the digital planimetry with 2 rulers than performed with the Visitrak device, the Silhouette Mobile device or the AreaMe software-based method. Conclusion The calibration in digital planimetry with using 2 rulers remarkably increases precision and accuracy of measurement and therefore should be recommended instead of calibration based on single ruler. PMID:26252747

  16. Accuracy of 3D white light scanning of abutment teeth impressions: evaluation of trueness and precision

    PubMed Central

    Jeon, Jin-Hun; Kim, Hae-Young; Kim, Ji-Hwan

    2014-01-01

    PURPOSE This study aimed to evaluate the accuracy of digitizing dental impressions of abutment teeth using a white light scanner and to compare the findings among teeth types. MATERIALS AND METHODS To assess precision, impressions of the canine, premolar, and molar prepared to receive all-ceramic crowns were repeatedly scanned to obtain five sets of 3-D data (STL files). Point clouds were compared and error sizes were measured (n=10 per type). Next, to evaluate trueness, impressions of teeth were rotated by 10°-20° and scanned. The obtained data were compared with the first set of data for precision assessment, and the error sizes were measured (n=5 per type). The Kruskal-Wallis test was performed to evaluate precision and trueness among three teeth types, and post-hoc comparisons were performed using the Mann-Whitney U test with Bonferroni correction (α=.05). RESULTS Precision discrepancies for the canine, premolar, and molar were 3.7 µm, 3.2 µm, and 7.3 µm, respectively, indicating the poorest precision for the molar (P<.001). Trueness discrepancies for teeth types were 6.2 µm, 11.2 µm, and 21.8 µm, respectively, indicating the poorest trueness for the molar (P=.007). CONCLUSION In respect to accuracy the molar showed the largest discrepancies compared with the canine and premolar. Digitizing of dental impressions of abutment teeth using a white light scanner was assessed to be a highly accurate method and provided discrepancy values in a clinically acceptable range. Further study is needed to improve digitizing performance of white light scanning in axial wall. PMID:25551007

  17. The tradeoff between accuracy and precision in latent variable models of mediation processes

    PubMed Central

    Ledgerwood, Alison; Shrout, Patrick E.

    2016-01-01

    Social psychologists place high importance on understanding mechanisms, and frequently employ mediation analyses to shed light on the process underlying an effect. Such analyses can be conducted using observed variables (e.g., a typical regression approach) or latent variables (e.g., a SEM approach), and choosing between these methods can be a more complex and consequential decision than researchers often realize. The present paper adds to the literature on mediation by examining the relative tradeoff between accuracy and precision in latent versus observed variable modeling. Whereas past work has shown that latent variable models tend to produce more accurate estimates, we demonstrate that observed variable models tend to produce more precise estimates, and examine this relative tradeoff both theoretically and empirically in a typical three-variable mediation model across varying levels of effect size and reliability. We discuss implications for social psychologists seeking to uncover mediating variables, and recommend practical approaches for maximizing both accuracy and precision in mediation analyses. PMID:21806305

  18. Accuracy or precision: Implications of sample design and methodology on abundance estimation

    USGS Publications Warehouse

    Kowalewski, Lucas K.; Chizinski, Christopher J.; Powell, Larkin A.; Pope, Kevin L.; Pegg, Mark A.

    2015-01-01

    Sampling by spatially replicated counts (point-count) is an increasingly popular method of estimating population size of organisms. Challenges exist when sampling by point-count method, and it is often impractical to sample entire area of interest and impossible to detect every individual present. Ecologists encounter logistical limitations that force them to sample either few large-sample units or many small sample-units, introducing biases to sample counts. We generated a computer environment and simulated sampling scenarios to test the role of number of samples, sample unit area, number of organisms, and distribution of organisms in the estimation of population sizes using N-mixture models. Many sample units of small area provided estimates that were consistently closer to true abundance than sample scenarios with few sample units of large area. However, sample scenarios with few sample units of large area provided more precise abundance estimates than abundance estimates derived from sample scenarios with many sample units of small area. It is important to consider accuracy and precision of abundance estimates during the sample design process with study goals and objectives fully recognized, although and with consequence, consideration of accuracy and precision of abundance estimates is often an afterthought that occurs during the data analysis process.

  19. Accuracy and precision of stream reach water surface slopes estimated in the field and from maps

    USGS Publications Warehouse

    Isaak, D.J.; Hubert, W.A.; Krueger, K.L.

    1999-01-01

    The accuracy and precision of five tools used to measure stream water surface slope (WSS) were evaluated. Water surface slopes estimated in the field with a clinometer or from topographic maps used in conjunction with a map wheel or geographic information system (GIS) were significantly higher than WSS estimated in the field with a surveying level (biases of 34, 41, and 53%, respectively). Accuracy of WSS estimates obtained with an Abney level did not differ from surveying level estimates, but conclusions regarding the accuracy of Abney levels and clinometers were weakened by intratool variability. The surveying level estimated WSS most precisely (coefficient of variation [CV] = 0.26%), followed by the GIS (CV = 1.87%), map wheel (CV = 6.18%), Abney level (CV = 13.68%), and clinometer (CV = 21.57%). Estimates of WSS measured in the field with an Abney level and estimated for the same reaches with a GIS used in conjunction with l:24,000-scale topographic maps were significantly correlated (r = 0.86), but there was a tendency for the GIS to overestimate WSS. Detailed accounts of the methods used to measure WSS and recommendations regarding the measurement of WSS are provided.

  20. Accuracy and precision of four common peripheral temperature measurement methods in intensive care patients

    PubMed Central

    Asadian, Simin; Khatony, Alireza; Moradi, Gholamreza; Abdi, Alireza; Rezaei, Mansour

    2016-01-01

    Introduction An accurate determination of body temperature in critically ill patients is a fundamental requirement for initiating the proper process of diagnosis, and also therapeutic actions; therefore, the aim of the study was to assess the accuracy and precision of four noninvasive peripheral methods of temperature measurement compared to the central nasopharyngeal measurement. Methods In this observational prospective study, 237 patients were recruited from the intensive care unit of Imam Ali Hospital of Kermanshah. The patients’ body temperatures were measured by four peripheral methods; oral, axillary, tympanic, and forehead along with a standard central nasopharyngeal measurement. After data collection, the results were analyzed by paired t-test, kappa coefficient, receiver operating characteristic curve, and using Statistical Package for the Social Sciences, version 19, software. Results There was a significant meaningful correlation between all the peripheral methods when compared with the central measurement (P<0.001). Kappa coefficients showed good agreement between the temperatures of right and left tympanic membranes and the standard central nasopharyngeal measurement (88%). Paired t-test demonstrated an acceptable precision with forehead (P=0.132), left (P=0.18) and right (P=0.318) tympanic membranes, oral (P=1.00), and axillary (P=1.00) methods. Sensitivity and specificity of both the left and right tympanic membranes were more than for other methods. Conclusion The tympanic and forehead methods had the highest and lowest accuracy for measuring body temperature, respectively. It is recommended to use the tympanic method (right and left) for assessing a patient’s body temperature in the intensive care units because of high accuracy and acceptable precision. PMID:27621673

  1. Assessing accuracy and precision for field and laboratory data: a perspective in ecosystem restoration

    USGS Publications Warehouse

    Stapanian, Martin A.; Lewis, Timothy E; Palmer, Craig J.; Middlebrook Amos, Molly

    2016-01-01

    Unlike most laboratory studies, rigorous quality assurance/quality control (QA/QC) procedures may be lacking in ecosystem restoration (“ecorestoration”) projects, despite legislative mandates in the United States. This is due, in part, to ecorestoration specialists making the false assumption that some types of data (e.g. discrete variables such as species identification and abundance classes) are not subject to evaluations of data quality. Moreover, emergent behavior manifested by complex, adapting, and nonlinear organizations responsible for monitoring the success of ecorestoration projects tend to unconsciously minimize disorder, QA/QC being an activity perceived as creating disorder. We discuss similarities and differences in assessing precision and accuracy for field and laboratory data. Although the concepts for assessing precision and accuracy of ecorestoration field data are conceptually the same as laboratory data, the manner in which these data quality attributes are assessed is different. From a sample analysis perspective, a field crew is comparable to a laboratory instrument that requires regular “recalibration,” with results obtained by experts at the same plot treated as laboratory calibration standards. Unlike laboratory standards and reference materials, the “true” value for many field variables is commonly unknown. In the laboratory, specific QA/QC samples assess error for each aspect of the measurement process, whereas field revisits assess precision and accuracy of the entire data collection process following initial calibration. Rigorous QA/QC data in an ecorestoration project are essential for evaluating the success of a project, and they provide the only objective “legacy” of the dataset for potential legal challenges and future uses.

  2. Accuracy of genomic selection for BCWD resistance in rainbow trout

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bacterial cold water disease (BCWD) causes significant economic losses in salmonids. In this study, we aimed to (1) predict genomic breeding values (GEBV) by genotyping training (n=583) and validation samples (n=53) with a SNP50K chip; and (2) assess the accuracy of genomic selection (GS) for BCWD r...

  3. Mapping stream habitats with a global positioning system: Accuracy, precision, and comparison with traditional methods

    USGS Publications Warehouse

    Dauwalter, D.C.; Fisher, W.L.; Belt, K.C.

    2006-01-01

    We tested the precision and accuracy of the Trimble GeoXT??? global positioning system (GPS) handheld receiver on point and area features and compared estimates of stream habitat dimensions (e.g., lengths and areas of riffles and pools) that were made in three different Oklahoma streams using the GPS receiver and a tape measure. The precision of differentially corrected GPS (DGPS) points was not affected by the number of GPS position fixes (i.e., geographic location estimates) averaged per DGPS point. Horizontal error of points ranged from 0.03 to 2.77 m and did not differ with the number of position fixes per point. The error of area measurements ranged from 0.1% to 110.1% but decreased as the area increased. Again, error was independent of the number of position fixes averaged per polygon corner. The estimates of habitat lengths, widths, and areas did not differ when measured using two methods of data collection (GPS and a tape measure), nor did the differences among methods change at three stream sites with contrasting morphologies. Measuring features with a GPS receiver was up to 3.3 times faster on average than using a tape measure, although signal interference from high streambanks or overhanging vegetation occasionally limited satellite signal availability and prolonged measurements with a GPS receiver. There were also no differences in precision of habitat dimensions when mapped using a continuous versus a position fix average GPS data collection method. Despite there being some disadvantages to using the GPS in stream habitat studies, measuring stream habitats with a GPS resulted in spatially referenced data that allowed the assessment of relative habitat position and changes in habitats over time, and was often faster than using a tape measure. For most spatial scales of interest, the precision and accuracy of DGPS data are adequate and have logistical advantages when compared to traditional methods of measurement. ?? 2006 Springer Science+Business Media

  4. ACCURACY AND PRECISION OF A METHOD TO STUDY KINEMATICS OF THE TEMPOROMANDIBULAR JOINT: COMBINATION OF MOTION DATA AND CT IMAGING

    PubMed Central

    Baltali, Evre; Zhao, Kristin D.; Koff, Matthew F.; Keller, Eugene E.; An, Kai-Nan

    2008-01-01

    The purpose of the study was to test the precision and accuracy of a method used to track selected landmarks during motion of the temporomandibular joint (TMJ). A precision phantom device was constructed and relative motions between two rigid bodies on the phantom device were measured using optoelectronic (OE) and electromagnetic (EM) motion tracking devices. The motion recordings were also combined with a 3D CT image for each type of motion tracking system (EM+CT and OE+CT) to mimic methods used in previous studies. In the OE and EM data collections, specific landmarks on the rigid bodies were determined using digitization. In the EM+CT and OE+CT data sets, the landmark locations were obtained from the CT images. 3D linear distances and 3D curvilinear path distances were calculated for the points. The accuracy and precision for all 4 methods were evaluated (EM, OE, EM+CT and OE+CT). In addition, results were compared with and without the CT imaging (EM vs. EM+CT, OE vs. OE+CT). All systems overestimated the actual 3D curvilinear path lengths. All systems also underestimated the actual rotation values. The accuracy of all methods was within 0.5 mm for 3D curvilinear path calculations, 0.05 mm for 3D linear distance calculations, and 0.2° for rotation calculations. In addition, Bland-Altman plots for each configuration of the systems suggest that measurements obtained from either system are repeatable and comparable. PMID:18617178

  5. Precision and accuracy of spectrophotometric pH measurements at environmental conditions in the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Hammer, Karoline; Schneider, Bernd; Kuliński, Karol; Schulz-Bull, Detlef E.

    2014-06-01

    The increasing uptake of anthropogenic CO2 by the oceans has raised an interest in precise and accurate pH measurement in order to assess the impact on the marine CO2-system. Spectrophotometric pH measurements were refined during the last decade yielding a precision and accuracy that cannot be achieved with the conventional potentiometric method. However, until now the method was only tested in oceanic systems with a relative stable and high salinity and a small pH range. This paper describes the first application of such a pH measurement system at conditions in the Baltic Sea which is characterized by a wide salinity and pH range. The performance of the spectrophotometric system at pH values as low as 7.0 (“total” scale) and salinities between 0 and 35 was examined using TRIS-buffer solutions, certified reference materials, and tests of consistency with measurements of other parameters of the marine CO2 system. Using m-cresol purple as indicator dye and a spectrophotometric measurement system designed at Scripps Institution of Oceanography (B. Carter, A. Dickson), a precision better than ±0.001 and an accuracy between ±0.01 and ±0.02 was achieved within the observed pH and salinity ranges in the Baltic Sea. The influence of the indicator dye on the pH of the sample was determined theoretically and is presented as a pH correction term for the different alkalinity regimes in the Baltic Sea. Because of the encouraging tests, the ease of operation and the fact that the measurements refer to the internationally accepted “total” pH scale, it is recommended to use the spectrophotometric method also for pH monitoring and trend detection in the Baltic Sea.

  6. Improvement in precision, accuracy, and efficiency in sstandardizing the characterization of granular materials

    SciTech Connect

    Tucker, Jonathan R.; Shadle, Lawrence J.; Benyahia, Sofiane; Mei, Joseph; Guenther, Chris; Koepke, M. E.

    2013-01-01

    Useful prediction of the kinematics, dynamics, and chemistry of a system relies on precision and accuracy in the quantification of component properties, operating mechanisms, and collected data. In an attempt to emphasize, rather than gloss over, the benefit of proper characterization to fundamental investigations of multiphase systems incorporating solid particles, a set of procedures were developed and implemented for the purpose of providing a revised methodology having the desirable attributes of reduced uncertainty, expanded relevance and detail, and higher throughput. Better, faster, cheaper characterization of multiphase systems result. Methodologies are presented to characterize particle size, shape, size distribution, density (particle, skeletal and bulk), minimum fluidization velocity, void fraction, particle porosity, and assignment within the Geldart Classification. A novel form of the Ergun equation was used to determine the bulk void fractions and particle density. Accuracy of properties-characterization methodology was validated on materials of known properties prior to testing materials of unknown properties. Several of the standard present-day techniques were scrutinized and improved upon where appropriate. Validity, accuracy, and repeatability were assessed for the procedures presented and deemed higher than present-day techniques. A database of over seventy materials has been developed to assist in model validation efforts and future desig

  7. Hepatic perfusion in a tumor model using DCE-CT: an accuracy and precision study

    NASA Astrophysics Data System (ADS)

    Stewart, Errol E.; Chen, Xiaogang; Hadway, Jennifer; Lee, Ting-Yim

    2008-08-01

    In the current study we investigate the accuracy and precision of hepatic perfusion measurements based on the Johnson and Wilson model with the adiabatic approximation. VX2 carcinoma cells were implanted into the livers of New Zealand white rabbits. Simultaneous dynamic contrast-enhanced computed tomography (DCE-CT) and radiolabeled microsphere studies were performed under steady-state normo-, hyper- and hypo-capnia. The hepatic arterial blood flows (HABF) obtained using both techniques were compared with ANOVA. The precision was assessed by the coefficient of variation (CV). Under normo-capnia the microsphere HABF were 51.9 ± 4.2, 40.7 ± 4.9 and 99.7 ± 6.0 ml min-1 (100 g)-1 while DCE-CT HABF were 50.0 ± 5.7, 37.1 ± 4.5 and 99.8 ± 6.8 ml min-1 (100 g)-1 in normal tissue, tumor core and rim, respectively. There were no significant differences between HABF measurements obtained with both techniques (P > 0.05). Furthermore, a strong correlation was observed between HABF values from both techniques: slope of 0.92 ± 0.05, intercept of 4.62 ± 2.69 ml min-1 (100 g)-1 and R2 = 0.81 ± 0.05 (P < 0.05). The Bland-Altman plot comparing DCE-CT and microsphere HABF measurements gives a mean difference of -0.13 ml min-1 (100 g)-1, which is not significantly different from zero. DCE-CT HABF is precise, with CV of 5.7, 24.9 and 1.4% in the normal tissue, tumor core and rim, respectively. Non-invasive measurement of HABF with DCE-CT is accurate and precise. DCE-CT can be an important extension of CT to assess hepatic function besides morphology in liver diseases.

  8. Selective Influences of Precision and Power Grips on Speech Categorization.

    PubMed

    Tiainen, Mikko; Tiippana, Kaisa; Vainio, Martti; Peromaa, Tarja; Komeilipoor, Naeem; Vainio, Lari

    2016-01-01

    Recent studies have shown that articulatory gestures are systematically associated with specific manual grip actions. Here we show that executing such actions can influence performance on a speech-categorization task. Participants watched and/or listened to speech stimuli while executing either a power or a precision grip. Grip performance influenced the syllable categorization by increasing the proportion of responses of the syllable congruent with the executed grip (power grip-[ke] and precision grip-[te]). Two follow-up experiments indicated that the effect was based on action-induced bias in selecting the syllable. PMID:26978074

  9. Selective Influences of Precision and Power Grips on Speech Categorization

    PubMed Central

    Tiainen, Mikko; Tiippana, Kaisa; Vainio, Martti; Peromaa, Tarja; Komeilipoor, Naeem; Vainio, Lari

    2016-01-01

    Recent studies have shown that articulatory gestures are systematically associated with specific manual grip actions. Here we show that executing such actions can influence performance on a speech-categorization task. Participants watched and/or listened to speech stimuli while executing either a power or a precision grip. Grip performance influenced the syllable categorization by increasing the proportion of responses of the syllable congruent with the executed grip (power grip—[ke] and precision grip—[te]). Two follow-up experiments indicated that the effect was based on action-induced bias in selecting the syllable. PMID:26978074

  10. Effects of shortened acquisition time on accuracy and precision of quantitative estimates of organ activity1

    PubMed Central

    He, Bin; Frey, Eric C.

    2010-01-01

    Purpose: Quantitative estimation of in vivo organ uptake is an essential part of treatment planning for targeted radionuclide therapy. This usually involves the use of planar or SPECT scans with acquisition times chosen based more on image quality considerations rather than the minimum needed for precise quantification. In previous simulation studies at clinical count levels (185 MBq 111In), the authors observed larger variations in accuracy of organ activity estimates resulting from anatomical and uptake differences than statistical noise. This suggests that it is possible to reduce the acquisition time without substantially increasing the variation in accuracy. Methods: To test this hypothesis, the authors compared the accuracy and variation in accuracy of organ activity estimates obtained from planar and SPECT scans at various count levels. A simulated phantom population with realistic variations in anatomy and biodistribution was used to model variability in a patient population. Planar and SPECT projections were simulated using previously validated Monte Carlo simulation tools. The authors simulated the projections at count levels approximately corresponding to 1.5–30 min of total acquisition time. The projections were processed using previously described quantitative SPECT (QSPECT) and planar (QPlanar) methods. The QSPECT method was based on the OS-EM algorithm with compensations for attenuation, scatter, and collimator-detector response. The QPlanar method is based on the ML-EM algorithm using the same model-based compensation for all the image degrading effects as the QSPECT method. The volumes of interests (VOIs) were defined based on the true organ configuration in the phantoms. The errors in organ activity estimates from different count levels and processing methods were compared in terms of mean and standard deviation over the simulated phantom population. Results: There was little degradation in quantitative reliability when the acquisition time was

  11. Slight pressure imbalances can affect accuracy and precision of dual inlet-based clumped isotope analysis.

    PubMed

    Fiebig, Jens; Hofmann, Sven; Löffler, Niklas; Lüdecke, Tina; Methner, Katharina; Wacker, Ulrike

    2016-01-01

    It is well known that a subtle nonlinearity can occur during clumped isotope analysis of CO2 that - if remaining unaddressed - limits accuracy. The nonlinearity is induced by a negative background on the m/z 47 ion Faraday cup, whose magnitude is correlated with the intensity of the m/z 44 ion beam. The origin of the negative background remains unclear, but is possibly due to secondary electrons. Usually, CO2 gases of distinct bulk isotopic compositions are equilibrated at 1000 °C and measured along with the samples in order to be able to correct for this effect. Alternatively, measured m/z 47 beam intensities can be corrected for the contribution of secondary electrons after monitoring how the negative background on m/z 47 evolves with the intensity of the m/z 44 ion beam. The latter correction procedure seems to work well if the m/z 44 cup exhibits a wider slit width than the m/z 47 cup. Here we show that the negative m/z 47 background affects precision of dual inlet-based clumped isotope measurements of CO2 unless raw m/z 47 intensities are directly corrected for the contribution of secondary electrons. Moreover, inaccurate results can be obtained even if the heated gas approach is used to correct for the observed nonlinearity. The impact of the negative background on accuracy and precision arises from small imbalances in m/z 44 ion beam intensities between reference and sample CO2 measurements. It becomes the more significant the larger the relative contribution of secondary electrons to the m/z 47 signal is and the higher the flux rate of CO2 into the ion source is set. These problems can be overcome by correcting the measured m/z 47 ion beam intensities of sample and reference gas for the contributions deriving from secondary electrons after scaling these contributions to the intensities of the corresponding m/z 49 ion beams. Accuracy and precision of this correction are demonstrated by clumped isotope analysis of three internal carbonate standards. The

  12. Video image analysis in the Australian meat industry - precision and accuracy of predicting lean meat yield in lamb carcasses.

    PubMed

    Hopkins, D L; Safari, E; Thompson, J M; Smith, C R

    2004-06-01

    A wide selection of lamb types of mixed sex (ewes and wethers) were slaughtered at a commercial abattoir and during this process images of 360 carcasses were obtained online using the VIAScan® system developed by Meat and Livestock Australia. Soft tissue depth at the GR site (thickness of tissue over the 12th rib 110 mm from the midline) was measured by an abattoir employee using the AUS-MEAT sheep probe (PGR). Another measure of this thickness was taken in the chiller using a GR knife (NGR). Each carcass was subsequently broken down to a range of trimmed boneless retail cuts and the lean meat yield determined. The current industry model for predicting meat yield uses hot carcass weight (HCW) and tissue depth at the GR site. A low level of accuracy and precision was found when HCW and PGR were used to predict lean meat yield (R(2)=0.19, r.s.d.=2.80%), which could be improved markedly when PGR was replaced by NGR (R(2)=0.41, r.s.d.=2.39%). If the GR measures were replaced by 8 VIAScan® measures then greater prediction accuracy could be achieved (R(2)=0.52, r.s.d.=2.17%). A similar result was achieved when the model was based on principal components (PCs) computed from the 8 VIAScan® measures (R(2)=0.52, r.s.d.=2.17%). The use of PCs also improved the stability of the model compared to a regression model based on HCW and NGR. The transportability of the models was tested by randomly dividing the data set and comparing coefficients and the level of accuracy and precision. Those models based on PCs were superior to those based on regression. It is demonstrated that with the appropriate modeling the VIAScan® system offers a workable method for predicting lean meat yield automatically. PMID:22061323

  13. Estimated results analysis and application of the precise point positioning based high-accuracy ionosphere delay

    NASA Astrophysics Data System (ADS)

    Wang, Shi-tai; Peng, Jun-huan

    2015-12-01

    The characterization of ionosphere delay estimated with precise point positioning is analyzed in this paper. The estimation, interpolation and application of the ionosphere delay are studied based on the processing of 24-h data from 5 observation stations. The results show that the estimated ionosphere delay is affected by the hardware delay bias from receiver so that there is a difference between the estimated and interpolated results. The results also show that the RMSs (root mean squares) are bigger, while the STDs (standard deviations) are better than 0.11 m. When the satellite difference is used, the hardware delay bias can be canceled. The interpolated satellite-differenced ionosphere delay is better than 0.11 m. Although there is a difference between the between the estimated and interpolated ionosphere delay results it cannot affect its application in single-frequency positioning and the positioning accuracy can reach cm level.

  14. Improved precision and accuracy in quantifying plutonium isotope ratios by RIMS

    SciTech Connect

    Isselhardt, B. H.; Savina, M. R.; Kucher, A.; Gates, S. D.; Knight, K. B.; Hutcheon, I. D.

    2015-09-01

    Resonance ionization mass spectrometry (RIMS) holds the promise of rapid, isobar-free quantification of actinide isotope ratios in as-received materials (i.e. not chemically purified). Recent progress in achieving this potential using two Pu test materials is presented. RIMS measurements were conducted multiple times over a period of two months on two different Pu solutions deposited on metal surfaces. Measurements were bracketed with a Pu isotopic standard, and yielded absolute accuracies of the measured 240Pu/239Pu ratios of 0.7% and 0.58%, with precisions (95% confidence intervals) of 1.49% and 0.91%. In conclusion, the minor isotope 238Pu was also quantified despite the presence of a significant quantity of 238U in the samples.

  15. Improved precision and accuracy in quantifying plutonium isotope ratios by RIMS

    DOE PAGESBeta

    Isselhardt, B. H.; Savina, M. R.; Kucher, A.; Gates, S. D.; Knight, K. B.; Hutcheon, I. D.

    2015-09-01

    Resonance ionization mass spectrometry (RIMS) holds the promise of rapid, isobar-free quantification of actinide isotope ratios in as-received materials (i.e. not chemically purified). Recent progress in achieving this potential using two Pu test materials is presented. RIMS measurements were conducted multiple times over a period of two months on two different Pu solutions deposited on metal surfaces. Measurements were bracketed with a Pu isotopic standard, and yielded absolute accuracies of the measured 240Pu/239Pu ratios of 0.7% and 0.58%, with precisions (95% confidence intervals) of 1.49% and 0.91%. In conclusion, the minor isotope 238Pu was also quantified despite the presence ofmore » a significant quantity of 238U in the samples.« less

  16. Selective assemblies of giant tetrahedra via precisely controlled positional interactions

    NASA Astrophysics Data System (ADS)

    Huang, Mingjun; Hsu, Chih-Hao; Wang, Jing; Mei, Shan; Dong, Xuehui; Li, Yiwen; Li, Mingxuan; Liu, Hao; Zhang, Wei; Aida, Takuzo; Zhang, Wen-Bin; Yue, Kan; Cheng, Stephen Z. D.

    2015-04-01

    Self-assembly of rigid building blocks with explicit shape and symmetry is substantially influenced by the geometric factors and remains largely unexplored. We report the selective assembly behaviors of a class of precisely defined, nanosized giant tetrahedra constructed by placing different polyhedral oligomeric silsesquioxane (POSS) molecular nanoparticles at the vertices of a rigid tetrahedral framework. Designed symmetry breaking of these giant tetrahedra introduces precise positional interactions and results in diverse selectively assembled, highly ordered supramolecular lattices including a Frank-Kasper A15 phase, which resembles the essential structural features of certain metal alloys but at a larger length scale. These results demonstrate the power of persistent molecular geometry with balanced enthalpy and entropy in creating thermodynamically stable supramolecular lattices with properties distinct from those of other self-assembling soft materials.

  17. Accuracy and precision of estimating age of gray wolves by tooth wear

    USGS Publications Warehouse

    Gipson, P.S.; Ballard, W.B.; Nowak, R.M.; Mech, L.D.

    2000-01-01

    We evaluated the accuracy and precision of tooth wear for aging gray wolves (Canis lupus) from Alaska, Minnesota, and Ontario based on 47 known-age or known-minimum-age skulls. Estimates of age using tooth wear and a commercial cementum annuli-aging service were useful for wolves up to 14 years old. The precision of estimates from cementum annuli was greater than estimates from tooth wear, but tooth wear estimates are more applicable in the field. We tended to overestimate age by 1-2 years and occasionally by 3 or 4 years. The commercial service aged young wolves with cementum annuli to within ?? 1 year of actual age, but under estimated ages of wolves ???9 years old by 1-3 years. No differences were detected in tooth wear patterns for wild wolves from Alaska, Minnesota, and Ontario, nor between captive and wild wolves. Tooth wear was not appropriate for aging wolves with an underbite that prevented normal wear or severely broken and missing teeth.

  18. Accuracy and precision of gait events derived from motion capture in horses during walk and trot.

    PubMed

    Boye, Jenny Katrine; Thomsen, Maj Halling; Pfau, Thilo; Olsen, Emil

    2014-03-21

    This study aimed to create an evidence base for detection of stance-phase timings from motion capture in horses. The objective was to compare the accuracy (bias) and precision (SD) for five published algorithms for the detection of hoof-on and hoof-off using force plates as the reference standard. Six horses were walked and trotted over eight force plates surrounded by a synchronised 12-camera infrared motion capture system. The five algorithms (A-E) were based on: (A) horizontal velocity of the hoof; (B) Fetlock angle and horizontal hoof velocity; (C) horizontal displacement of the hoof relative to the centre of mass; (D) horizontal velocity of the hoof relative to the Centre of Mass and; (E) vertical acceleration of the hoof. A total of 240 stance phases in walk and 240 stance phases in trot were included in the assessment. Method D provided the most accurate and precise results in walk for stance phase duration with a bias of 4.1% for front limbs and 4.8% for hind limbs. For trot we derived a combination of method A for hoof-on and method E for hoof-off resulting in a bias of -6.2% of stance in the front limbs and method B for the hind limbs with a bias of 3.8% of stance phase duration. We conclude that motion capture yields accurate and precise detection of gait events for horses walking and trotting over ground and the results emphasise a need for different algorithms for front limbs versus hind limbs in trot. PMID:24529754

  19. Impact of survey workflow on precision and accuracy of terrestrial LiDAR datasets

    NASA Astrophysics Data System (ADS)

    Gold, P. O.; Cowgill, E.; Kreylos, O.

    2009-12-01

    Ground-based LiDAR (Light Detection and Ranging) survey techniques are enabling remote visualization and quantitative analysis of geologic features at unprecedented levels of detail. For example, digital terrain models computed from LiDAR data have been used to measure displaced landforms along active faults and to quantify fault-surface roughness. But how accurately do terrestrial LiDAR data represent the true ground surface, and in particular, how internally consistent and precise are the mosaiced LiDAR datasets from which surface models are constructed? Addressing this question is essential for designing survey workflows that capture the necessary level of accuracy for a given project while minimizing survey time and equipment, which is essential for effective surveying of remote sites. To address this problem, we seek to define a metric that quantifies how scan registration error changes as a function of survey workflow. Specifically, we are using a Trimble GX3D laser scanner to conduct a series of experimental surveys to quantify how common variables in field workflows impact the precision of scan registration. Primary variables we are testing include 1) use of an independently measured network of control points to locate scanner and target positions, 2) the number of known-point locations used to place the scanner and point clouds in 3-D space, 3) the type of target used to measure distances between the scanner and the known points, and 4) setting up the scanner over a known point as opposed to resectioning of known points. Precision of the registered point cloud is quantified using Trimble Realworks software by automatic calculation of registration errors (errors between locations of the same known points in different scans). Accuracy of the registered cloud (i.e., its ground-truth) will be measured in subsequent experiments. To obtain an independent measure of scan-registration errors and to better visualize the effects of these errors on a registered point

  20. The Signatures of Selection for Translational Accuracy in Plant Genes

    PubMed Central

    Porceddu, Andrea; Zenoni, Sara; Camiolo, Salvatore

    2013-01-01

    Little is known about the natural selection of synonymous codons within the coding sequences of plant genes. We analyzed the distribution of synonymous codons within plant coding sequences and found that preferred codons tend to encode the more conserved and functionally important residues of plant proteins. This was consistent among several synonymous codon families and applied to genes with different expression profiles and functions. Most of the randomly chosen alternative sets of codons scored weaker associations than the actual sets of preferred codons, suggesting that codon position within plant genes and codon usage bias have coevolved to maximize translational accuracy. All these findings are consistent with the mistranslation-induced protein misfolding theory, which predicts the natural selection of highly preferred codons more frequently at sites where translation errors could compromise protein folding or functionality. Our results will provide an important insight in future studies of protein folding, molecular evolution, and transgene design for optimal expression. PMID:23695187

  1. Precision, accuracy, and application of diver-towed underwater GPS receivers.

    PubMed

    Schories, Dirk; Niedzwiedz, Gerd

    2012-04-01

    Diver-towed global positioning systems (GPS) handhelds have been used for a few years in underwater monitoring studies. We modeled the accuracy of this method using the software KABKURR originally developed by the University of Rostock for fishing and marine engineering. Additionally, three field experiments were conducted to estimate the precision of the method and apply it in the field: (1) an experiment of underwater transects from 5 to 35 m in the Southern Chile fjord region, (2) a transect from 5 to 30 m under extreme climatic conditions in the Antarctic, and (3) an underwater tracking experiment at Lake Ranco, Southern Chile. The coiled cable length in relation to water depth is the main error source besides the signal quality of the GPS under calm weather conditions. The forces used in the model resulted in a displacement of 2.3 m in a depth of 5 m, 3.2 m at a 10-m depth, 4.6 m in a 20-m depth, 5.5 m at a 30-m depth, and 6.8 m in a 40-m depth, when only an additional 0.5 m cable extension was used compared to the water depth. The GPS buoy requires good buoyancy in order to keep its position at the water surface when the diver is trying to minimize any additional cable extension error. The diver has to apply a tensile force for shortening the cable length at the lower cable end. Repeated diving along transect lines from 5 to 35 m resulted only in small deviations independent of water depth indicating the precision of the method for monitoring studies. Routing of given reference points with a Garmin 76CSx handheld placed in an underwater housing resulted in mean deviances less than 6 m at a water depth of 10 m. Thus, we can confirm that diver-towed GPS handhelds give promising results when used for underwater research in shallow water and open a wide field of applicability, but no submeter accuracy is possible due to the different error sources. PMID:21614620

  2. Welcome detailed data, but with a grain of salt: accuracy, precision, uncertainty in flood inundation modeling

    NASA Astrophysics Data System (ADS)

    Dottori, Francesco; Di Baldassarre, Giuliano; Todini, Ezio

    2013-04-01

    New survey techniques are providing a huge amount of high-detailed and accurate data which can be extremely valuable for flood inundation modeling. Such data availability raises the issue of how to exploit their information content to provide reliable flood risk mapping and predictions. We think that these data should form the basis of hydraulic modelling anytime they are available. However, high expectations regarding these datasets should be tempered as some important issues should be considered. These include: the large number of uncertainty sources in model structure and available data; the difficult evaluation of model results, due to the scarcity of observed data; the computational efficiency; the false confidence that can be given by high-resolution results, as accuracy of results is not necessarily increased by higher precision. We briefly discuss these issues and existing approaches which can be used to manage high detailed data. In our opinion, methods based on sub-grid and roughness upscaling treatments would be in many instances an appropriate solution to maintain consistence with the uncertainty related to model structure and data available for model building and evaluation.

  3. Precision and accuracy of regional radioactivity quantitation using the maximum likelihood EM reconstruction algorithm

    SciTech Connect

    Carson, R.E.; Yan, Y.; Chodkowski, B.; Yap, T.K.; Daube-Witherspoon, M.E. )

    1994-09-01

    The imaging characteristics of maximum likelihood (ML) reconstruction using the EM algorithm for emission tomography have been extensively evaluated. There has been less study of the precision and accuracy of ML estimates of regional radioactivity concentration. The authors developed a realistic brain slice simulation by segmenting a normal subject's MRI scan into gray matter, white matter, and CSF and produced PET sinogram data with a model that included detector resolution and efficiencies, attenuation, scatter, and randoms. Noisy realizations at different count levels were created, and ML and filtered backprojection (FBP) reconstructions were performed. The bias and variability of ROI values were determined. In addition, the effects of ML pixel size, image smoothing and region size reduction were assessed. ML estimates at 1,000 iterations (0.6 sec per iteration on a parallel computer) for 1-cm[sup 2] gray matter ROIs showed negative biases of 6% [+-] 2% which can be reduced to 0% [+-] 3% by removing the outer 1-mm rim of each ROI. FBP applied to the full-size ROIs had 15% [+-] 4% negative bias with 50% less noise than ML. Shrinking the FBP regions provided partial bias compensation with noise increases to levels similar to ML. Smoothing of ML images produced biases comparable to FBP with slightly less noise. Because of its heavy computational requirements, the ML algorithm will be most useful for applications in which achieving minimum bias is important.

  4. Modeling precision and accuracy of a LWIR microgrid array imaging polarimeter

    NASA Astrophysics Data System (ADS)

    Boger, James K.; Tyo, J. Scott; Ratliff, Bradley M.; Fetrow, Matthew P.; Black, Wiley T.; Kumar, Rakesh

    2005-08-01

    Long-wave infrared (LWIR) imaging is a prominent and useful technique for remote sensing applications. Moreover, polarization imaging has been shown to provide additional information about the imaged scene. However, polarization estimation requires that multiple measurements be made of each observed scene point under optically different conditions. This challenging measurement strategy makes the polarization estimates prone to error. The sources of this error differ depending upon the type of measurement scheme used. In this paper, we examine one particular measurement scheme, namely, a simultaneous multiple-measurement imaging polarimeter (SIP) using a microgrid polarizer array. The imager is composed of a microgrid polarizer masking a LWIR HgCdTe focal plane array (operating at 8.3-9.3 μm), and is able to make simultaneous modulated scene measurements. In this paper we present an analytical model that is used to predict the performance of the system in order to help interpret real results. This model is radiometrically accurate and accounts for the temperature of the camera system optics, spatial nonuniformity and drift, optical resolution and other sources of noise. This model is then used in simulation to validate it against laboratory measurements. The precision and accuracy of the SIP instrument is then studied.

  5. Precision and accuracy of clinical quantification of myocardial blood flow by dynamic PET: A technical perspective.

    PubMed

    Moody, Jonathan B; Lee, Benjamin C; Corbett, James R; Ficaro, Edward P; Murthy, Venkatesh L

    2015-10-01

    A number of exciting advances in PET/CT technology and improvements in methodology have recently converged to enhance the feasibility of routine clinical quantification of myocardial blood flow and flow reserve. Recent promising clinical results are pointing toward an important role for myocardial blood flow in the care of patients. Absolute blood flow quantification can be a powerful clinical tool, but its utility will depend on maintaining precision and accuracy in the face of numerous potential sources of methodological errors. Here we review recent data and highlight the impact of PET instrumentation, image reconstruction, and quantification methods, and we emphasize (82)Rb cardiac PET which currently has the widest clinical application. It will be apparent that more data are needed, particularly in relation to newer PET technologies, as well as clinical standardization of PET protocols and methods. We provide recommendations for the methodological factors considered here. At present, myocardial flow reserve appears to be remarkably robust to various methodological errors; however, with greater attention to and more detailed understanding of these sources of error, the clinical benefits of stress-only blood flow measurement may eventually be more fully realized. PMID:25868451

  6. Evaluation of Precise Point Positioning accuracy under large total electron content variations in equatorial latitudes

    NASA Astrophysics Data System (ADS)

    Rodríguez-Bilbao, I.; Moreno Monge, B.; Rodríguez-Caderot, G.; Herraiz, M.; Radicella, S. M.

    2015-01-01

    The ionosphere is one of the largest contributors to errors in GNSS positioning. Although in Precise Point Positioning (PPP) the ionospheric delay is corrected to a first order through the 'iono-free combination', significant errors may still be observed when large electron density gradients are present. To confirm this phenomenon, the temporal behavior of intense fluctuations of total electron content (TEC) and PPP altitude accuracy at equatorial latitudes are analyzed during four years of different solar activity. For this purpose, equatorial plasma irregularities are identified with periods of high rate of change of TEC (ROT). The largest ROT values are observed from 19:00 to 01:00 LT, especially around magnetic equinoxes, although some differences exist between the stations depending on their location. Highest ROT values are observed in the American and African regions. In general, large ROT events are accompanied by frequent satellite signal losses and an increase in the PPP altitude error during years 2001, 2004 and 2011. A significant increase in the PPP altitude error RMS is observed in epochs of high ROT with respect to epochs of low ROT in years 2001, 2004 and 2011, reaching up to 0.26 m in the 19:00-01:00 LT period.

  7. David Weston--Ocean science of invariant principles, total accuracy, and appropriate precision

    NASA Astrophysics Data System (ADS)

    Roebuck, Ian

    2002-11-01

    David Weston's entire professional career was as a member of the Royal Navy Scientific Service, working in the field of ocean acoustics and its applications to maritime operations. The breadth of his interests has often been remarked upon, but because of the sensitive nature of his work at the time, it was indeed much more diverse than his published papers showed. This presentation, from the successors to the laboratories he illuminated for many years, is an attempt to fill in at least some of the gaps. The presentation also focuses on the underlying scientific philosophy of David's work, rooted in the British tradition of applicable mathematics and physics. A deep appreciation of the role of invariants and dimensional methods, and awareness of the sensitivity of any models to changes to the input assumptions, was at the heart of his approach. The needs of the Navy kept him rigorous in requiring accuracy, and clear about the distinction between it and precision. Examples of these principles are included, still as relevant today as they were when he insisted on applying them 30 years ago.

  8. Sub-nm accuracy metrology for ultra-precise reflective X-ray optics

    NASA Astrophysics Data System (ADS)

    Siewert, F.; Buchheim, J.; Zeschke, T.; Brenner, G.; Kapitzki, S.; Tiedtke, K.

    2011-04-01

    The transport and monochromatization of synchrotron light from a high brilliant laser-like source to the experimental station without significant loss of brilliance and coherence is a challenging task in X-ray optics and requires optical elements of utmost accuracy. These are wave-front preserving plane mirrors with lengths of up to 1 m characterized by residual slope errors in the range of 0.05 μrad (rms) and values of 0.1 nm (rms) for micro-roughness. In the case of focusing optical elements like elliptical cylinders the required residual slope error is in the range of 0.25 μrad rms and better. In addition the alignment of optical elements is a critical and beamline performance limiting topic. Thus the characterization of ultra-precise reflective optical elements for FEL-beamline application in the free and mounted states is of significant importance. We will discuss recent results in the field of metrology achieved at the BESSY-II Optics Laboratory (BOL) of the Helmholtz Zentrum Berlin (HZB) by use of the Nanometer Optical Component Measuring Machine (NOM). Different types of mirror have been inspected by line-scan and slope mapping in the free and mounted states. Based on these results the mirror clamping of a combined mirror/grating set-up for the BL-beamlines at FLASH was improved.

  9. Obtaining identical results with double precision global accuracy on different numbers of processors in parallel particle Monte Carlo simulations

    SciTech Connect

    Cleveland, Mathew A. Brunner, Thomas A.; Gentile, Nicholas A.; Keasler, Jeffrey A.

    2013-10-15

    We describe and compare different approaches for achieving numerical reproducibility in photon Monte Carlo simulations. Reproducibility is desirable for code verification, testing, and debugging. Parallelism creates a unique problem for achieving reproducibility in Monte Carlo simulations because it changes the order in which values are summed. This is a numerical problem because double precision arithmetic is not associative. Parallel Monte Carlo, both domain replicated and decomposed simulations, will run their particles in a different order during different runs of the same simulation because the non-reproducibility of communication between processors. In addition, runs of the same simulation using different domain decompositions will also result in particles being simulated in a different order. In [1], a way of eliminating non-associative accumulations using integer tallies was described. This approach successfully achieves reproducibility at the cost of lost accuracy by rounding double precision numbers to fewer significant digits. This integer approach, and other extended and reduced precision reproducibility techniques, are described and compared in this work. Increased precision alone is not enough to ensure reproducibility of photon Monte Carlo simulations. Non-arbitrary precision approaches require a varying degree of rounding to achieve reproducibility. For the problems investigated in this work double precision global accuracy was achievable by using 100 bits of precision or greater on all unordered sums which where subsequently rounded to double precision at the end of every time-step.

  10. Deformable Image Registration for Adaptive Radiation Therapy of Head and Neck Cancer: Accuracy and Precision in the Presence of Tumor Changes

    SciTech Connect

    Mencarelli, Angelo; Kranen, Simon Robert van; Hamming-Vrieze, Olga; Beek, Suzanne van; Nico Rasch, Coenraad Robert; Herk, Marcel van; Sonke, Jan-Jakob

    2014-11-01

    Purpose: To compare deformable image registration (DIR) accuracy and precision for normal and tumor tissues in head and neck cancer patients during the course of radiation therapy (RT). Methods and Materials: Thirteen patients with oropharyngeal tumors, who underwent submucosal implantation of small gold markers (average 6, range 4-10) around the tumor and were treated with RT were retrospectively selected. Two observers identified 15 anatomical features (landmarks) representative of normal tissues in the planning computed tomography (pCT) scan and in weekly cone beam CTs (CBCTs). Gold markers were digitally removed after semiautomatic identification in pCTs and CBCTs. Subsequently, landmarks and gold markers on pCT were propagated to CBCTs, using a b-spline-based DIR and, for comparison, rigid registration (RR). To account for observer variability, the pair-wise difference analysis of variance method was applied. DIR accuracy (systematic error) and precision (random error) for landmarks and gold markers were quantified. Time trend of the precisions for RR and DIR over the weekly CBCTs were evaluated. Results: DIR accuracies were submillimeter and similar for normal and tumor tissue. DIR precision (1 SD) on the other hand was significantly different (P<.01), with 2.2 mm vector length in normal tissue versus 3.3 mm in tumor tissue. No significant time trend in DIR precision was found for normal tissue, whereas in tumor, DIR precision was significantly (P<.009) degraded during the course of treatment by 0.21 mm/week. Conclusions: DIR for tumor registration proved to be less precise than that for normal tissues due to limited contrast and complex non-elastic tumor response. Caution should therefore be exercised when applying DIR for tumor changes in adaptive procedures.

  11. 13 Years of TOPEX/POSEIDON Precision Orbit Determination and the 10-fold Improvement in Expected Orbit Accuracy

    NASA Technical Reports Server (NTRS)

    Lemoine, F. G.; Zelensky, N. P.; Luthcke, S. B.; Rowlands, D. D.; Beckley, B. D.; Klosko, S. M.

    2006-01-01

    Launched in the summer of 1992, TOPEX/POSEIDON (T/P) was a joint mission between NASA and the Centre National d Etudes Spatiales (CNES), the French Space Agency, to make precise radar altimeter measurements of the ocean surface. After the remarkably successful 13-years of mapping the ocean surface T/P lost its ability to maneuver and was de-commissioned January 2006. T/P revolutionized the study of the Earth s oceans by vastly exceeding pre-launch estimates of surface height accuracy recoverable from radar altimeter measurements. The precision orbit lies at the heart of the altimeter measurement providing the reference frame from which the radar altimeter measurements are made. The expected quality of orbit knowledge had limited the measurement accuracy expectations of past altimeter missions, and still remains a major component in the error budget of all altimeter missions. This paper describes critical improvements made to the T/P orbit time series over the 13-years of precise orbit determination (POD) provided by the GSFC Space Geodesy Laboratory. The POD improvements from the pre-launch T/P expectation of radial orbit accuracy and Mission requirement of 13-cm to an expected accuracy of about 1.5-cm with today s latest orbits will be discussed. The latest orbits with 1.5 cm RMS radial accuracy represent a significant improvement to the 2.0-cm accuracy orbits currently available on the T/P Geophysical Data Record (GDR) altimeter product.

  12. Accuracy and precision of cone beam computed tomography in periodontal defects measurement (systematic review).

    PubMed

    Anter, Enas; Zayet, Mohammed Khalifa; El-Dessouky, Sahar Hosny

    2016-01-01

    Systematic review of literature was made to assess the extent of accuracy of cone beam computed tomography (CBCT) as a tool for measurement of alveolar bone loss in periodontal defect. A systematic search of PubMed electronic database and a hand search of open access journals (from 2000 to 2015) yielded abstracts that were potentially relevant. The original articles were then retrieved and their references were hand searched for possible missing articles. Only articles that met the selection criteria were included and criticized. The initial screening revealed 47 potentially relevant articles, of which only 14 have met the selection criteria; their CBCT average measurements error ranged from 0.19 mm to 1.27 mm; however, no valid meta-analysis could be made due to the high heterogeneity between the included studies. Under the limitation of the number and strength of the available studies, we concluded that CBCT provides an assessment of alveolar bone loss in periodontal defect with a minimum reported mean measurements error of 0.19 ± 0.11 mm and a maximum reported mean measurements error of 1.27 ± 1.43 mm, and there is no agreement between the studies regarding the direction of the deviation whether over or underestimation. However, we should emphasize that the evidence to this data is not strong. PMID:27563194

  13. Accuracy and precision of cone beam computed tomography in periodontal defects measurement (systematic review)

    PubMed Central

    Anter, Enas; Zayet, Mohammed Khalifa; El-Dessouky, Sahar Hosny

    2016-01-01

    Systematic review of literature was made to assess the extent of accuracy of cone beam computed tomography (CBCT) as a tool for measurement of alveolar bone loss in periodontal defect. A systematic search of PubMed electronic database and a hand search of open access journals (from 2000 to 2015) yielded abstracts that were potentially relevant. The original articles were then retrieved and their references were hand searched for possible missing articles. Only articles that met the selection criteria were included and criticized. The initial screening revealed 47 potentially relevant articles, of which only 14 have met the selection criteria; their CBCT average measurements error ranged from 0.19 mm to 1.27 mm; however, no valid meta-analysis could be made due to the high heterogeneity between the included studies. Under the limitation of the number and strength of the available studies, we concluded that CBCT provides an assessment of alveolar bone loss in periodontal defect with a minimum reported mean measurements error of 0.19 ± 0.11 mm and a maximum reported mean measurements error of 1.27 ± 1.43 mm, and there is no agreement between the studies regarding the direction of the deviation whether over or underestimation. However, we should emphasize that the evidence to this data is not strong. PMID:27563194

  14. Measurement Precision and Accuracy of the Centre Location of AN Ellipse by Weighted Centroid Method

    NASA Astrophysics Data System (ADS)

    Matsuoka, R.

    2015-03-01

    Circular targets are often utilized in photogrammetry, and a circle on a plane is projected as an ellipse onto an oblique image. This paper reports an analysis conducted in order to investigate the measurement precision and accuracy of the centre location of an ellipse on a digital image by an intensity-weighted centroid method. An ellipse with a semi-major axis a, a semi-minor axis b, and a rotation angle θ of the major axis is investigated. In the study an equivalent radius r = (a2cos2θ + b2sin2θ)1/2 is adopted as a measure of the dimension of an ellipse. First an analytical expression representing a measurement error (ϵx, ϵy,) is obtained. Then variances Vx of ϵx are obtained at 1/256 pixel intervals from 0.5 to 100 pixels in r by numerical integration, because a formula representing Vx is unable to be obtained analytically when r > 0.5. The results of the numerical integration indicate that Vxwould oscillate in a 0.5 pixel cycle in r and Vx excluding the oscillation component would be inversely proportional to the cube of r. Finally an effective approximate formula of Vx from 0.5 to 100 pixels in r is obtained by least squares adjustment. The obtained formula is a fractional expression of which numerator is a fifth-degree polynomial of {r-0.5×int(2r)} expressing the oscillation component and denominator is the cube of r. Here int(x) is the function to return the integer part of the value x. Coefficients of the fifth-degree polynomial of the numerator can be expressed by a quadratic polynomial of {0.5×int(2r)+0.25}.

  15. Accuracy of selected techniques for estimating ice-affected streamflow

    USGS Publications Warehouse

    Walker, John F.

    1991-01-01

    This paper compares the accuracy of selected techniques for estimating streamflow during ice-affected periods. The techniques are classified into two categories - subjective and analytical - depending on the degree of judgment required. Discharge measurements have been made at three streamflow-gauging sites in Iowa during the 1987-88 winter and used to established a baseline streamflow record for each site. Using data based on a simulated six-week field-tip schedule, selected techniques are used to estimate discharge during the ice-affected periods. For the subjective techniques, three hydrographers have independently compiled each record. Three measures of performance are used to compare the estimated streamflow records with the baseline streamflow records: the average discharge for the ice-affected period, and the mean and standard deviation of the daily errors. Based on average ranks for three performance measures and the three sites, the analytical and subjective techniques are essentially comparable. For two of the three sites, Kruskal-Wallis one-way analysis of variance detects significant differences among the three hydrographers for the subjective methods, indicating that the subjective techniques are less consistent than the analytical techniques. The results suggest analytical techniques may be viable tools for estimating discharge during periods of ice effect, and should be developed further and evaluated for sites across the United States.

  16. Accuracy, precision and response time of consumer bimetal and digital thermometers for cooked ground beef patties and chicken breasts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Three models each of consumer instant-read bimetal and digital thermometers were tested for accuracy, precision and response time compared to a calibrated thermocouple in cooked 80 percent and 90 percent lean ground beef patties and boneless and bone-in split chicken breasts. At the recommended inse...

  17. Species-selective lattice launch for precision atom interferometry

    NASA Astrophysics Data System (ADS)

    Chamakhi, R.; Ahlers, H.; Telmini, M.; Schubert, C.; Rasel, E. M.; Gaaloul, N.

    2015-12-01

    Long-baseline precision tests based on atom interferometry require drastic control over the initial external degrees of freedom of atomic ensembles to reduce systematic effects. The use of optical lattices (OLs) is a highly accurate method to manipulate atomic states in position and momentum allowing excellent control of the launch in atomic fountains. The simultaneous lattice launch of two atomic species, as required in a quantum test of the equivalence principle, is however problematic due to crosstalk effects. In this article, we propose to selectively address two species of alkalines by applying two OLs at or close to magic-zero wavelengths of the atoms. The proposed scheme applies in general for a pair of species with a vastly different ac Stark shift to a laser wavelength. We illustrate the principle by studying a fountain launch of condensed ensembles of 87Rb and 41K initially co-located. Numerical simulations confirm the fidelity of our scheme up to few nm and nm s-1 in inter-species differential position and velocity, respectively. This result is a pre-requisite for the next performance level in precision tests.

  18. Accuracy Assessment of the Precise Point Positioning for Different Troposphere Models

    NASA Astrophysics Data System (ADS)

    Oguz Selbesoglu, Mahmut; Gurturk, Mert; Soycan, Metin

    2016-04-01

    This study investigates the accuracy and repeatability of PPP technique at different latitudes by using different troposphere delay models. Nine IGS stations were selected between 00-800 latitudes at northern hemisphere and southern hemisphere. Coordinates were obtained for 7 days at 1 hour intervals in summer and winter. At first, the coordinates were estimated by using Niell troposphere delay model with and without including north and east gradients in order to investigate the contribution of troposphere delay gradients to the positioning . Secondly, Saastamoinen model was used to eliminate troposphere path delays by using standart atmosphere parameters were extrapolated for all station levels. Finally, coordinates were estimated by using RTCA-MOPS empirical troposphere delay model. Results demonstrate that Niell troposphere delay model with horizontal gradients has better mean values of rms errors 0.09 % and 65 % than the Niell troposphere model without horizontal gradients and RTCA-MOPS model, respectively. Saastamoinen model mean values of rms errors were obtained approximately 4 times bigger than the Niell troposphere delay model with horizontal gradients.

  19. Accuracy of Genomic Selection in a Rice Synthetic Population Developed for Recurrent Selection Breeding

    PubMed Central

    Ospina, Yolima; Quintero, Constanza; Châtel, Marc Henri; Tohme, Joe; Courtois, Brigitte

    2015-01-01

    Genomic selection (GS) is a promising strategy for enhancing genetic gain. We investigated the accuracy of genomic estimated breeding values (GEBV) in four inter-related synthetic populations that underwent several cycles of recurrent selection in an upland rice-breeding program. A total of 343 S2:4 lines extracted from those populations were phenotyped for flowering time, plant height, grain yield and panicle weight, and genotyped with an average density of one marker per 44.8 kb. The relative effect of the linkage disequilibrium (LD) and minor allele frequency (MAF) thresholds for selecting markers, the relative size of the training population (TP) and of the validation population (VP), the selected trait and the genomic prediction models (frequentist and Bayesian) on the accuracy of GEBVs was investigated in 540 cross validation experiments with 100 replicates. The effect of kinship between the training and validation populations was tested in an additional set of 840 cross validation experiments with a single genomic prediction model. LD was high (average r2 = 0.59 at 25 kb) and decreased slowly, distribution of allele frequencies at individual loci was markedly skewed toward unbalanced frequencies (MAF average value 15.2% and median 9.6%), and differentiation between the four synthetic populations was low (FST ≤0.06). The accuracy of GEBV across all cross validation experiments ranged from 0.12 to 0.54 with an average of 0.30. Significant differences in accuracy were observed among the different levels of each factor investigated. Phenotypic traits had the biggest effect, and the size of the incidence matrix had the smallest. Significant first degree interaction was observed for GEBV accuracy between traits and all the other factors studied, and between prediction models and LD, MAF and composition of the TP. The potential of GS to accelerate genetic gain and breeding options to increase the accuracy of predictions are discussed. PMID:26313446

  20. Accuracy of Genomic Selection in a Rice Synthetic Population Developed for Recurrent Selection Breeding.

    PubMed

    Grenier, Cécile; Cao, Tuong-Vi; Ospina, Yolima; Quintero, Constanza; Châtel, Marc Henri; Tohme, Joe; Courtois, Brigitte; Ahmadi, Nourollah

    2015-01-01

    Genomic selection (GS) is a promising strategy for enhancing genetic gain. We investigated the accuracy of genomic estimated breeding values (GEBV) in four inter-related synthetic populations that underwent several cycles of recurrent selection in an upland rice-breeding program. A total of 343 S2:4 lines extracted from those populations were phenotyped for flowering time, plant height, grain yield and panicle weight, and genotyped with an average density of one marker per 44.8 kb. The relative effect of the linkage disequilibrium (LD) and minor allele frequency (MAF) thresholds for selecting markers, the relative size of the training population (TP) and of the validation population (VP), the selected trait and the genomic prediction models (frequentist and Bayesian) on the accuracy of GEBVs was investigated in 540 cross validation experiments with 100 replicates. The effect of kinship between the training and validation populations was tested in an additional set of 840 cross validation experiments with a single genomic prediction model. LD was high (average r2 = 0.59 at 25 kb) and decreased slowly, distribution of allele frequencies at individual loci was markedly skewed toward unbalanced frequencies (MAF average value 15.2% and median 9.6%), and differentiation between the four synthetic populations was low (FST ≤0.06). The accuracy of GEBV across all cross validation experiments ranged from 0.12 to 0.54 with an average of 0.30. Significant differences in accuracy were observed among the different levels of each factor investigated. Phenotypic traits had the biggest effect, and the size of the incidence matrix had the smallest. Significant first degree interaction was observed for GEBV accuracy between traits and all the other factors studied, and between prediction models and LD, MAF and composition of the TP. The potential of GS to accelerate genetic gain and breeding options to increase the accuracy of predictions are discussed. PMID:26313446

  1. Using statistics and software to maximize precision and accuracy in U-Pb geochronological measurements

    NASA Astrophysics Data System (ADS)

    McLean, N.; Bowring, J. F.; Bowring, S. A.

    2009-12-01

    Uncertainty in U-Pb geochronology results from a wide variety of factors, including isotope ratio determinations, common Pb corrections, initial daughter product disequilibria, instrumental mass fractionation, isotopic tracer calibration, and U decay constants and isotopic composition. The relative contribution of each depends on the proportion of radiogenic to common Pb, the measurement technique, and the quality of systematic error determinations. Random and systematic uncertainty contributions may be propagated into individual analyses or for an entire population, and must be propagated correctly to accurately interpret data. Tripoli and U-Pb_Redux comprise a new data reduction and error propagation software package that combines robust cycle measurement statistics with rigorous multivariate data analysis and presents the results graphically and interactively. Maximizing the precision and accuracy of a measurement begins with correct appraisal and codification of the systematic and random errors for each analysis. For instance, a large dataset of total procedural Pb blank analyses defines a multivariate normal distribution, describing the mean of and variation in isotopic composition (IC) that must be subtracted from each analysis. Uncertainty in the size and IC of each Pb blank is related to the (random) uncertainty in ratio measurements and the (systematic) uncertainty involved in tracer subtraction. Other sample and measurement parameters can be quantified in the same way, represented as statistical distributions that describe their uncertainty or variation, and are input into U-Pb_Redux as such before the raw sample isotope ratios are measured. During sample measurement, U-Pb_Redux and Tripoli can relay cycle data in real time, calculating a date and uncertainty for each new cycle or block. The results are presented in U-Pb_Redux as an interactive user interface with multiple visualization tools. One- and two-dimensional plots of each calculated date and

  2. Sensitivity Analysis for Characterizing the Accuracy and Precision of JEM/SMILES Mesospheric O3

    NASA Astrophysics Data System (ADS)

    Esmaeili Mahani, M.; Baron, P.; Kasai, Y.; Murata, I.; Kasaba, Y.

    2011-12-01

    The main purpose of this study is to evaluate the Superconducting sub-Millimeter Limb Emission Sounder (SMILES) measurements of mesospheric ozone, O3. As the first step, the error due to the impact of Mesospheric Temperature Inversions (MTIs) on ozone retrieval has been determined. The impacts of other parameters such as pressure variability, solar events, and etc. on mesospheric O3 will also be investigated. Ozone, is known to be important due to the stratospheric O3 layer protection of life on Earth by absorbing harmful UV radiations. However, O3 chemistry can be studied purely in the mesosphere without distraction of heterogeneous situation and dynamical variations due to the short lifetime of O3 in this region. Mesospheric ozone is produced by the photo-dissociation of O2 and the subsequent reaction of O with O2. Diurnal and semi-diurnal variations of mesospheric ozone are associated with variations in solar activity. The amplitude of the diurnal variation increases from a few percent at an altitude of 50 km, to about 80 percent at 70 km. Although despite the apparent simplicity of this situation, significant disagreements exist between the predictions from the existing models and observations, which need to be resolved. SMILES is a highly sensitive radiometer with a few to several tens percent of precision from upper troposphere to the mesosphere. SMILES was developed by the Japanese Aerospace eXploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT) located at the Japanese Experiment Module (JEM) on the International Space Station (ISS). SMILES has successfully measured the vertical distributions and the diurnal variations of various atmospheric species in the latitude range of 38S to 65N from October 2009 to April 2010. A sensitivity analysis is being conducted to investigate the expected precision and accuracy of the mesospheric O3 profiles (from 50 to 90 km height) due to the impact of Mesospheric Temperature

  3. Strategy for high-accuracy-and-precision retrieval of atmospheric methane from the mid-infrared FTIR network

    NASA Astrophysics Data System (ADS)

    Sussmann, R.; Forster, F.; Rettinger, M.; Jones, N.

    2011-05-01

    We present a strategy (MIR-GBM v1.0) for the retrieval of column-averaged dry-air mole fractions of methane (XCH4) with a precision <0.3 % (1-σ diurnal variation, 7-min integration) and a seasonal bias <0.14 % from mid-infrared ground-based solar FTIR measurements of the Network for the Detection of Atmospheric Composition Change (NDACC, comprising 22 FTIR stations). This makes NDACC methane data useful for satellite validation and for the inversion of regional-scale sources and sinks in addition to long-term trend analysis. Such retrievals complement the high accuracy and precision near-infrared observations of the younger Total Carbon Column Observing Network (TCCON) with time series dating back 15 yr or so before TCCON operations began. MIR-GBM v1.0 is using HITRAN 2000 (including the 2001 update release) and 3 spectral micro windows (2613.70-2615.40 cm-1, 2835.50-2835.80 cm-1, 2921.00-2921.60 cm-1). A first-order Tikhonov constraint is applied to the state vector given in units of per cent of volume mixing ratio. It is tuned to achieve minimum diurnal variation without damping seasonality. Final quality selection of the retrievals uses a threshold for the ratio of root-mean-square spectral residuals and information content (<0.15 %). Column-averaged dry-air mole fractions are calculated using the retrieved methane profiles and four-times-daily pressure-temperature-humidity profiles from National Center for Environmental Prediction (NCEP) interpolated to the time of measurement. MIR-GBM v1.0 is the optimum of 24 tested retrieval strategies (8 different spectral micro-window selections, 3 spectroscopic line lists: HITRAN 2000, 2004, 2008). Dominant errors of the non-optimum retrieval strategies are HDO/H2O-CH4 interference errors (seasonal bias up to ≈4 %). Therefore interference errors have been quantified at 3 test sites covering clear-sky integrated water vapor levels representative for all NDACC sites (Wollongong maximum = 44.9 mm, Garmisch mean = 14.9 mm

  4. Strategy for high-accuracy-and-precision retrieval of atmospheric methane from the mid-infrared FTIR network

    NASA Astrophysics Data System (ADS)

    Sussmann, R.; Forster, F.; Rettinger, M.; Jones, N.

    2011-09-01

    We present a strategy (MIR-GBM v1.0) for the retrieval of column-averaged dry-air mole fractions of methane (XCH4) with a precision <0.3% (1-σ diurnal variation, 7-min integration) and a seasonal bias <0.14% from mid-infrared ground-based solar FTIR measurements of the Network for the Detection of Atmospheric Composition Change (NDACC, comprising 22 FTIR stations). This makes NDACC methane data useful for satellite validation and for the inversion of regional-scale sources and sinks in addition to long-term trend analysis. Such retrievals complement the high accuracy and precision near-infrared observations of the younger Total Carbon Column Observing Network (TCCON) with time series dating back 15 years or so before TCCON operations began. MIR-GBM v1.0 is using HITRAN 2000 (including the 2001 update release) and 3 spectral micro windows (2613.70-2615.40 cm-1, 2835.50-2835.80 cm-1, 2921.00-2921.60 cm-1). A first-order Tikhonov constraint is applied to the state vector given in units of per cent of volume mixing ratio. It is tuned to achieve minimum diurnal variation without damping seasonality. Final quality selection of the retrievals uses a threshold for the goodness of fit (χ2 < 1) as well as for the ratio of root-mean-square spectral noise and information content (<0.15%). Column-averaged dry-air mole fractions are calculated using the retrieved methane profiles and four-times-daily pressure-temperature-humidity profiles from National Center for Environmental Prediction (NCEP) interpolated to the time of measurement. MIR-GBM v1.0 is the optimum of 24 tested retrieval strategies (8 different spectral micro-window selections, 3 spectroscopic line lists: HITRAN 2000, 2004, 2008). Dominant errors of the non-optimum retrieval strategies are systematic HDO/H2O-CH4 interference errors leading to a seasonal bias up to ≈5%. Therefore interference errors have been quantified at 3 test sites covering clear-sky integrated water vapor levels representative for all NDACC

  5. Relatedness severely impacts accuracy of marker-assisted selection for disease resistance in hybrid wheat

    PubMed Central

    Gowda, M; Zhao, Y; Würschum, T; Longin, C FH; Miedaner, T; Ebmeyer, E; Schachschneider, R; Kazman, E; Schacht, J; Martinant, J-P; Mette, M F; Reif, J C

    2014-01-01

    The accuracy of genomic selection depends on the relatedness between the members of the set in which marker effects are estimated based on evaluation data and the types for which performance is predicted. Here, we investigate the impact of relatedness on the performance of marker-assisted selection for fungal disease resistance in hybrid wheat. A large and diverse mapping population of 1739 elite European winter wheat inbred lines and hybrids was evaluated for powdery mildew, leaf rust and stripe rust resistance in multi-location field trials and fingerprinted with 9 k and 90 k SNP arrays. Comparison of the accuracies of prediction achieved with data sets from the two marker arrays revealed a crucial role for a sufficiently high marker density in genome-wide association mapping. Cross-validation studies using test sets with varying degrees of relationship to the corresponding estimation sets revealed that close relatedness leads to a substantial increase in the proportion of total genotypic variance explained by the identified QTL and consequently to an overoptimistic judgment of the precision of marker-assisted selection. PMID:24346498

  6. Precise selective deposition of microparticles on electrodes of microelectronic chips

    NASA Astrophysics Data System (ADS)

    Nesterov, Alexander; König, Kai; Felgenhauer, Thomas; Lindenstruth, Volker; Trunk, Ulrich; Fernandez, Simon; Hausmann, Michael; Ralf Bischoff, F.; Breitling, Frank; Stadler, Volker

    2008-03-01

    We examined the high precision deposition of toner and polymer microparticles with a typical size of ˜10μm on electrode arrays with electrodes of 100μm and below using custom-made microelectronic chips. Selective desorption of redundant particles was employed to obtain a given particle pattern from preadsorbed particle layers. Microparticle desorption was regulated by dielectrophoretic attracting forces generated by individual pixel electrodes, tangential detaching forces of an air flow, and adhesion forces on the microchip surface. A theoretical consideration of the acting forces showed that without pixel voltage, the tangential force applied for particle detachment exceeded the particle adhesion force. When the pixel voltage was switched on, however, the sum of attracting forces was larger than the tangential detaching force, which was crucial for desorption efficiency. In our experiments, appropriately large dielectrophoretic forces were achieved by applying high voltages of up to 100V on the pixel electrodes. In addition, electrode geometries on the chip's surface as well as particle size influenced the desorption quality. We further demonstrated the compatibility of this procedure to complementary metal oxide semiconductor chip technology, which should allow for an easy technical implementation with respect to high-resolution microparticle deposition.

  7. Dichotomy in perceptual learning of interval timing: calibration of mean accuracy and precision differ in specificity and time course.

    PubMed

    Sohn, Hansem; Lee, Sang-Hun

    2013-01-01

    Our brain is inexorably confronted with a dynamic environment in which it has to fine-tune spatiotemporal representations of incoming sensory stimuli and commit to a decision accordingly. Among those representations needing constant calibration is interval timing, which plays a pivotal role in various cognitive and motor tasks. To investigate how perceived time interval is adjusted by experience, we conducted a human psychophysical experiment using an implicit interval-timing task in which observers responded to an invisible bar drifting at a constant speed. We tracked daily changes in distributions of response times for a range of physical time intervals over multiple days of training with two major types of timing performance, mean accuracy and precision. We found a decoupled dynamics of mean accuracy and precision in terms of their time course and specificity of perceptual learning. Mean accuracy showed feedback-driven instantaneous calibration evidenced by a partial transfer around the time interval trained with feedback, while timing precision exhibited a long-term slow improvement with no evident specificity. We found that a Bayesian observer model, in which a subjective time interval is determined jointly by a prior and likelihood function for timing, captures the dissociative temporal dynamics of the two types of timing measures simultaneously. Finally, the model suggested that the width of the prior, not the likelihoods, gradually shrinks over sessions, substantiating the important role of prior knowledge in perceptual learning of interval timing. PMID:23076112

  8. Quantifying Vegetation Change in Semiarid Environments: Precision and Accuracy of Spectral Mixture Analysis and the Normalized Difference Vegetation Index

    NASA Technical Reports Server (NTRS)

    Elmore, Andrew J.; Mustard, John F.; Manning, Sara J.; Elome, Andrew J.

    2000-01-01

    Because in situ techniques for determining vegetation abundance in semiarid regions are labor intensive, they usually are not feasible for regional analyses. Remotely sensed data provide the large spatial scale necessary, but their precision and accuracy in determining vegetation abundance and its change through time have not been quantitatively determined. In this paper, the precision and accuracy of two techniques, Spectral Mixture Analysis (SMA) and Normalized Difference Vegetation Index (NDVI) applied to Landsat TM data, are assessed quantitatively using high-precision in situ data. In Owens Valley, California we have 6 years of continuous field data (1991-1996) for 33 sites acquired concurrently with six cloudless Landsat TM images. The multitemporal remotely sensed data were coregistered to within 1 pixel, radiometrically intercalibrated using temporally invariante surface features and geolocated to within 30 m. These procedures facilitated the accurate location of field-monitoring sites within the remotely sensed data. Formal uncertainties in the registration, radiometric alignment, and modeling were determined. Results show that SMA absolute percent live cover (%LC) estimates are accurate to within ?4.0%LC and estimates of change in live cover have a precision of +/-3.8%LC. Furthermore, even when applied to areas of low vegetation cover, the SMA approach correctly determined the sense of clump, (i.e., positive or negative) in 87% of the samples. SMA results are superior to NDVI, which, although correlated with live cover, is not a quantitative measure and showed the correct sense of change in only 67%, of the samples.

  9. Nano-accuracy measurements and the surface profiler by use of Monolithic Hollow Penta-Prism for precision mirror testing

    NASA Astrophysics Data System (ADS)

    Qian, Shinan; Wayne, Lewis; Idir, Mourad

    2014-09-01

    We developed a Monolithic Hollow Penta-Prism Long Trace Profiler-NOM (MHPP-LTP-NOM) to attain nano-accuracy in testing plane- and near-plane-mirrors. A new developed Monolithic Hollow Penta-Prism (MHPP) combined with the advantages of PPLTP and autocollimator ELCOMAT of the Nano-Optic-Measuring Machine (NOM) is used to enhance the accuracy and stability of our measurements. Our precise system-alignment method by using a newly developed CCD position-monitor system (PMS) assured significant thermal stability and, along with our optimized noise-reduction analytic method, ensured nano-accuracy measurements. Herein we report our tests results; all errors are about 60 nrad rms or less in tests of plane- and near-plane- mirrors.

  10. Impact of selected troposphere models on Precise Point Positioning convergence

    NASA Astrophysics Data System (ADS)

    Kalita, Jakub; Rzepecka, Zofia

    2016-04-01

    The Precise Point Positioning (PPP) absolute method is currently intensively investigated in order to reach fast convergence time. Among various sources that influence the convergence of the PPP, the tropospheric delay is one of the most important. Numerous models of tropospheric delay are developed and applied to PPP processing. However, with rare exceptions, the quality of those models does not allow fixing the zenith path delay tropospheric parameter, leaving difference between nominal and final value to the estimation process. Here we present comparison of several PPP result sets, each of which based on different troposphere model. The respective nominal values are adopted from models: VMF1, GPT2w, MOPS and ZERO-WET. The PPP solution admitted as reference is based on the final troposphere product from the International GNSS Service (IGS). The VMF1 mapping function was used for all processing variants in order to provide capability to compare impact of applied nominal values. The worst case initiates zenith wet delay with zero value (ZERO-WET). Impact from all possible models for tropospheric nominal values should fit inside both IGS and ZERO-WET border variants. The analysis is based on data from seven IGS stations located in mid-latitude European region from year 2014. For the purpose of this study several days with the most active troposphere were selected for each of the station. All the PPP solutions were determined using gLAB open-source software, with the Kalman filter implemented independently by the authors of this work. The processing was performed on 1 hour slices of observation data. In addition to the analysis of the output processing files, the presented study contains detailed analysis of the tropospheric conditions for the selected data. The overall results show that for the height component the VMF1 model outperforms GPT2w and MOPS by 35-40% and ZERO-WET variant by 150%. In most of the cases all solutions converge to the same values during first

  11. A high-precision Jacob's staff with improved spatial accuracy and laser sighting capability

    NASA Astrophysics Data System (ADS)

    Patacci, Marco

    2016-04-01

    A new Jacob's staff design incorporating a 3D positioning stage and a laser sighting stage is described. The first combines a compass and a circular spirit level on a movable bracket and the second introduces a laser able to slide vertically and rotate on a plane parallel to bedding. The new design allows greater precision in stratigraphic thickness measurement while restricting the cost and maintaining speed of measurement to levels similar to those of a traditional Jacob's staff. Greater precision is achieved as a result of: a) improved 3D positioning of the rod through the use of the integrated compass and spirit level holder; b) more accurate sighting of geological surfaces by tracing with height adjustable rotatable laser; c) reduced error when shifting the trace of the log laterally (i.e. away from the dip direction) within the trace of the laser plane, and d) improved measurement of bedding dip and direction necessary to orientate the Jacob's staff, using the rotatable laser. The new laser holder design can also be used to verify parallelism of a geological surface with structural dip by creating a visual planar datum in the field and thus allowing determination of surfaces which cut the bedding at an angle (e.g., clinoforms, levees, erosion surfaces, amalgamation surfaces, etc.). Stratigraphic thickness measurements and estimates of measurement uncertainty are valuable to many applications of sedimentology and stratigraphy at different scales (e.g., bed statistics, reconstruction of palaeotopographies, depositional processes at bed scale, architectural element analysis), especially when a quantitative approach is applied to the analysis of the data; the ability to collect larger data sets with improved precision will increase the quality of such studies.

  12. Performance characterization of precision micro robot using a machine vision system over the Internet for guaranteed positioning accuracy

    NASA Astrophysics Data System (ADS)

    Kwon, Yongjin; Chiou, Richard; Rauniar, Shreepud; Sosa, Horacio

    2005-11-01

    There is a missing link between a virtual development environment (e.g., a CAD/CAM driven offline robotic programming) and production requirements of the actual robotic workcell. Simulated robot path planning and generation of pick-and-place coordinate points will not exactly coincide with the robot performance due to lack of consideration in variations in individual robot repeatability and thermal expansion of robot linkages. This is especially important when robots are controlled and programmed remotely (e.g., through Internet or Ethernet) since remote users have no physical contact with robotic systems. Using the current technology in Internet-based manufacturing that is limited to a web camera for live image transfer has been a significant challenge for the robot task performance. Consequently, the calibration and accuracy quantification of robot critical to precision assembly have to be performed on-site and the verification of robot positioning accuracy cannot be ascertained remotely. In worst case, the remote users have to assume the robot performance envelope provided by the manufacturers, which may causes a potentially serious hazard for system crash and damage to the parts and robot arms. Currently, there is no reliable methodology for remotely calibrating the robot performance. The objective of this research is, therefore, to advance the current state-of-the-art in Internet-based control and monitoring technology, with a specific aim in the accuracy calibration of micro precision robotic system for the development of a novel methodology utilizing Ethernet-based smart image sensors and other advanced precision sensory control network.

  13. Accuracy and Precision of Three-Dimensional Low Dose CT Compared to Standard RSA in Acetabular Cups: An Experimental Study.

    PubMed

    Brodén, Cyrus; Olivecrona, Henrik; Maguire, Gerald Q; Noz, Marilyn E; Zeleznik, Michael P; Sköldenberg, Olof

    2016-01-01

    Background and Purpose. The gold standard for detection of implant wear and migration is currently radiostereometry (RSA). The purpose of this study is to compare a three-dimensional computed tomography technique (3D CT) to standard RSA as an alternative technique for measuring migration of acetabular cups in total hip arthroplasty. Materials and Methods. With tantalum beads, we marked one cemented and one uncemented cup and mounted these on a similarly marked pelvic model. A comparison was made between 3D CT and standard RSA for measuring migration. Twelve repeated stereoradiographs and CT scans with double examinations in each position and gradual migration of the implants were made. Precision and accuracy of the 3D CT were calculated. Results. The accuracy of the 3D CT ranged between 0.07 and 0.32 mm for translations and 0.21 and 0.82° for rotation. The precision ranged between 0.01 and 0.09 mm for translations and 0.06 and 0.29° for rotations, respectively. For standard RSA, the precision ranged between 0.04 and 0.09 mm for translations and 0.08 and 0.32° for rotations, respectively. There was no significant difference in precision between 3D CT and standard RSA. The effective radiation dose of the 3D CT method, comparable to RSA, was estimated to be 0.33 mSv. Interpretation. Low dose 3D CT is a comparable method to standard RSA in an experimental setting. PMID:27478832

  14. Accuracy and Precision of Three-Dimensional Low Dose CT Compared to Standard RSA in Acetabular Cups: An Experimental Study

    PubMed Central

    Olivecrona, Henrik; Maguire, Gerald Q.; Noz, Marilyn E.; Zeleznik, Michael P.

    2016-01-01

    Background and Purpose. The gold standard for detection of implant wear and migration is currently radiostereometry (RSA). The purpose of this study is to compare a three-dimensional computed tomography technique (3D CT) to standard RSA as an alternative technique for measuring migration of acetabular cups in total hip arthroplasty. Materials and Methods. With tantalum beads, we marked one cemented and one uncemented cup and mounted these on a similarly marked pelvic model. A comparison was made between 3D CT and standard RSA for measuring migration. Twelve repeated stereoradiographs and CT scans with double examinations in each position and gradual migration of the implants were made. Precision and accuracy of the 3D CT were calculated. Results. The accuracy of the 3D CT ranged between 0.07 and 0.32 mm for translations and 0.21 and 0.82° for rotation. The precision ranged between 0.01 and 0.09 mm for translations and 0.06 and 0.29° for rotations, respectively. For standard RSA, the precision ranged between 0.04 and 0.09 mm for translations and 0.08 and 0.32° for rotations, respectively. There was no significant difference in precision between 3D CT and standard RSA. The effective radiation dose of the 3D CT method, comparable to RSA, was estimated to be 0.33 mSv. Interpretation. Low dose 3D CT is a comparable method to standard RSA in an experimental setting. PMID:27478832

  15. Effects of machining accuracy on frequency response properties of thick-screen frequency selective surface

    NASA Astrophysics Data System (ADS)

    Fang, Chunyi; Gao, Jinsong; Xin, Chen

    2012-10-01

    Electromagnetic theory shows that a thick-screen frequency selective surface (FSS) has many advantages in its frequency response characteristics. In addition, it can be used to make a stealth radome. Therefore, we research in detail how machining accuracy affects the frequency response properties of the FSS in the gigahertz range. Specifically, by using the least squares method applied to machining data, the effects of different machining precision in the samples can be calculated thus obtaining frequency response curves which were verified by testing in the near-field in a microwave dark room. The results show that decreasing roughness and flatness variation leads to an increase in the bandwidth and that an increase in spacing error leads to the center frequency drifting lower. Finally, an increase in aperture error leads to an increase in bandwidth. Therefore, the conclusion is that machining accuracy should be controlled and that a spatial error less than 0.05 mm is required in order to avoid unwanted center frequency drift and a transmittance decrease.

  16. The accuracy and precision of DXA for assessing body composition in team sport athletes.

    PubMed

    Bilsborough, Johann Christopher; Greenway, Kate; Opar, David; Livingstone, Steuart; Cordy, Justin; Coutts, Aaron James

    2014-01-01

    This study determined the precision of pencil and fan beam dual-energy X-ray absorptiometry (DXA) devices for assessing body composition in professional Australian Football players. Thirty-six professional Australian Football players, in two groups (fan DXA, N = 22; pencil DXA, N = 25), underwent two consecutive DXA scans. A whole body phantom with known values for fat mass, bone mineral content and fat-free soft tissue mass was also used to validate each DXA device. Additionally, the criterion phantom was scanned 20 times by each DXA to assess reliability. Test-retest reliability of DXA anthropometric measures were derived from repeated fan and pencil DXA scans. Fat-free soft tissue mass and bone mineral content from both DXA units showed strong correlations with, and trivial differences to, the criterion phantom values. Fat mass from both DXA showed moderate correlations with criterion measures (pencil: r = 0.64; fan: r = 0.67) and moderate differences with the criterion value. The limits of agreement were similar for both fan beam DXA and pencil beam DXA (fan: fat-free soft tissue mass = -1650 ± 179 g, fat mass = -357 ± 316 g, bone mineral content = 289 ± 122 g; pencil: fat-free soft tissue mass = -1701 ± 257 g, fat mass = -359 ± 326 g, bone mineral content = 177 ± 117 g). DXA also showed excellent precision for bone mineral content (coefficient of variation (%CV) fan = 0.6%; pencil = 1.5%) and fat-free soft tissue mass (%CV fan = 0.3%; pencil = 0.5%) and acceptable reliability for fat measures (%CV fan: fat mass = 2.5%, percent body fat = 2.5%; pencil: fat mass = 5.9%, percent body fat = 5.7%). Both DXA provide precise measures of fat-free soft tissue mass and bone mineral content in lean Australian Football players. DXA-derived fat-free soft tissue mass and bone mineral content are suitable for assessing body composition in lean team sport athletes. PMID:24914773

  17. Accuracy and precision of polyurethane dental arch models fabricated using a three-dimensional subtractive rapid prototyping method with an intraoral scanning technique

    PubMed Central

    Kim, Jae-Hong; Kim, Ki-Baek; Kim, Woong-Chul; Kim, Ji-Hwan

    2014-01-01

    Objective This study aimed to evaluate the accuracy and precision of polyurethane (PUT) dental arch models fabricated using a three-dimensional (3D) subtractive rapid prototyping (RP) method with an intraoral scanning technique by comparing linear measurements obtained from PUT models and conventional plaster models. Methods Ten plaster models were duplicated using a selected standard master model and conventional impression, and 10 PUT models were duplicated using the 3D subtractive RP technique with an oral scanner. Six linear measurements were evaluated in terms of x, y, and z-axes using a non-contact white light scanner. Accuracy was assessed using mean differences between two measurements, and precision was examined using four quantitative methods and the Bland-Altman graphical method. Repeatability was evaluated in terms of intra-examiner variability, and reproducibility was assessed in terms of inter-examiner and inter-method variability. Results The mean difference between plaster models and PUT models ranged from 0.07 mm to 0.33 mm. Relative measurement errors ranged from 2.2% to 7.6% and intraclass correlation coefficients ranged from 0.93 to 0.96, when comparing plaster models and PUT models. The Bland-Altman plot showed good agreement. Conclusions The accuracy and precision of PUT dental models for evaluating the performance of oral scanner and subtractive RP technology was acceptable. Because of the recent improvements in block material and computerized numeric control milling machines, the subtractive RP method may be a good choice for dental arch models. PMID:24696823

  18. A Time Projection Chamber for High Accuracy and Precision Fission Cross-Section Measurements

    SciTech Connect

    T. Hill; K. Jewell; M. Heffner; D. Carter; M. Cunningham; V. Riot; J. Ruz; S. Sangiorgio; B. Seilhan; L. Snyder; D. M. Asner; S. Stave; G. Tatishvili; L. Wood; R. G. Baker; J. L. Klay; R. Kudo; S. Barrett; J. King; M. Leonard; W. Loveland; L. Yao; C. Brune; S. Grimes; N. Kornilov; T. N. Massey; J. Bundgaard; D. L. Duke; U. Greife; U. Hager; E. Burgett; J. Deaven; V. Kleinrath; C. McGrath; B. Wendt; N. Hertel; D. Isenhower; N. Pickle; H. Qu; S. Sharma; R. T. Thornton; D. Tovwell; R. S. Towell; S.

    2014-09-01

    The fission Time Projection Chamber (fissionTPC) is a compact (15 cm diameter) two-chamber MICROMEGAS TPC designed to make precision cross-section measurements of neutron-induced fission. The actinide targets are placed on the central cathode and irradiated with a neutron beam that passes axially through the TPC inducing fission in the target. The 4p acceptance for fission fragments and complete charged particle track reconstruction are powerful features of the fissionTPC which will be used to measure fission cross-sections and examine the associated systematic errors. This paper provides a detailed description of the design requirements, the design solutions, and the initial performance of the fissionTPC.

  19. The Precision and Accuracy of AIRS Level 1B Radiances for Climate Studies

    NASA Technical Reports Server (NTRS)

    Hearty, Thomas J.; Gaiser, Steve; Pagano, Tom; Aumann, Hartmut

    2004-01-01

    We investigate uncertainties in the Atmospheric Infrared Sounder (AIRS) radiances based on in-flight and preflight calibration algorithms and observations. The global coverage and spectra1 resolution ((lamda)/(Delta)(lamda) 1200) of AIRS enable it to produce a data set that can be used as a climate data record over the lifetime of the instrument. Therefore, we examine the effects of the uncertainties in the calibration and the detector stability on future climate studies. The uncertainties of the parameters that go into the AIRS radiometric calibration are propagated to estimate the accuracy of the radiances and any climate data record created from AIRS measurements. The calculated radiance uncertainties are consistent with observations. Algorithm enhancements may be able to reduce the radiance uncertainties by as much as 7%. We find that the orbital variation of the gain contributes a brightness temperature bias of < 0.01 K.

  20. Quantification and visualization of carotid segmentation accuracy and precision using a 2D standardized carotid map

    NASA Astrophysics Data System (ADS)

    Chiu, Bernard; Ukwatta, Eranga; Shavakh, Shadi; Fenster, Aaron

    2013-06-01

    This paper describes a framework for vascular image segmentation evaluation. Since the size of vessel wall and plaque burden is defined by the lumen and wall boundaries in vascular segmentation, these two boundaries should be considered as a pair in statistical evaluation of a segmentation algorithm. This work proposed statistical metrics to evaluate the difference of local vessel wall thickness (VWT) produced by manual and algorithm-based semi-automatic segmentation methods (ΔT) with the local segmentation standard deviation of the wall and lumen boundaries considered. ΔT was further approximately decomposed into the local wall and lumen boundary differences (ΔW and ΔL respectively) in order to provide information regarding which of the wall and lumen segmentation errors contribute more to the VWT difference. In this study, the lumen and wall boundaries in 3D carotid ultrasound images acquired for 21 subjects were each segmented five times manually and by a level-set segmentation algorithm. The (absolute) difference measures (i.e., ΔT, ΔW, ΔL and their absolute values) and the pooled local standard deviation of manually and algorithmically segmented wall and lumen boundaries were computed for each subject and represented in a 2D standardized map. The local accuracy and variability of the segmentation algorithm at each point can be quantified by the average of these metrics for the whole group of subjects and visualized on the 2D standardized map. Based on the results shown on the 2D standardized map, a variety of strategies, such as adding anchor points and adjusting weights of different forces in the algorithm, can be introduced to improve the accuracy and variability of the algorithm.

  1. Clinical decision support systems for improving diagnostic accuracy and achieving precision medicine.

    PubMed

    Castaneda, Christian; Nalley, Kip; Mannion, Ciaran; Bhattacharyya, Pritish; Blake, Patrick; Pecora, Andrew; Goy, Andre; Suh, K Stephen

    2015-01-01

    As research laboratories and clinics collaborate to achieve precision medicine, both communities are required to understand mandated electronic health/medical record (EHR/EMR) initiatives that will be fully implemented in all clinics in the United States by 2015. Stakeholders will need to evaluate current record keeping practices and optimize and standardize methodologies to capture nearly all information in digital format. Collaborative efforts from academic and industry sectors are crucial to achieving higher efficacy in patient care while minimizing costs. Currently existing digitized data and information are present in multiple formats and are largely unstructured. In the absence of a universally accepted management system, departments and institutions continue to generate silos of information. As a result, invaluable and newly discovered knowledge is difficult to access. To accelerate biomedical research and reduce healthcare costs, clinical and bioinformatics systems must employ common data elements to create structured annotation forms enabling laboratories and clinics to capture sharable data in real time. Conversion of these datasets to knowable information should be a routine institutionalized process. New scientific knowledge and clinical discoveries can be shared via integrated knowledge environments defined by flexible data models and extensive use of standards, ontologies, vocabularies, and thesauri. In the clinical setting, aggregated knowledge must be displayed in user-friendly formats so that physicians, non-technical laboratory personnel, nurses, data/research coordinators, and end-users can enter data, access information, and understand the output. The effort to connect astronomical numbers of data points, including '-omics'-based molecular data, individual genome sequences, experimental data, patient clinical phenotypes, and follow-up data is a monumental task. Roadblocks to this vision of integration and interoperability include ethical, legal

  2. Precise and Continuous Time and Frequency Synchronisation at the 5×10-19 Accuracy Level

    PubMed Central

    Wang, B.; Gao, C.; Chen, W. L.; Miao, J.; Zhu, X.; Bai, Y.; Zhang, J. W.; Feng, Y. Y.; Li, T. C.; Wang, L. J.

    2012-01-01

    The synchronisation of time and frequency between remote locations is crucial for many important applications. Conventional time and frequency dissemination often makes use of satellite links. Recently, the communication fibre network has become an attractive option for long-distance time and frequency dissemination. Here, we demonstrate accurate frequency transfer and time synchronisation via an 80 km fibre link between Tsinghua University (THU) and the National Institute of Metrology of China (NIM). Using a 9.1 GHz microwave modulation and a timing signal carried by two continuous-wave lasers and transferred across the same 80 km urban fibre link, frequency transfer stability at the level of 5×10−19/day was achieved. Time synchronisation at the 50 ps precision level was also demonstrated. The system is reliable and has operated continuously for several months. We further discuss the feasibility of using such frequency and time transfer over 1000 km and its applications to long-baseline radio astronomy. PMID:22870385

  3. Towards the next decades of precision and accuracy in a 87Sr optical lattice clock

    NASA Astrophysics Data System (ADS)

    Martin, Michael; Lin, Yige; Swallows, Matthew; Bishof, Michael; Blatt, Sebastian; Benko, Craig; Chen, Licheng; Hirokawa, Takako; Rey, Ana Maria; Ye, Jun

    2011-05-01

    Optical lattice clocks based on ensembles of neutral atoms have the potential to operate at the highest levels of stability due to the parallel interrogation of many atoms. However, the control of systematic shifts in these systems is correspondingly difficult due to potential collisional atomic interactions. By tightly confining samples of ultracold fermionic 87Sr atoms in a two-dimensional optical lattice, as opposed to the conventional one-dimensional geometry, we increase the collisional interaction energy to be the largest relevant energy scale, thus entering the strongly interacting regime of clock operation. We show both theoretically and experimentally that this increase in interaction energy results in a paradoxical decrease in the collisional shift, reducing this key systematic to the 10-17 level. We also present work towards next- generation ultrastable lasers to attain quantum-limited clock operation, potentially enhancing clock precision by an order of magnitude. This work was supported by a grant from the ARO with funding from the DARPA OLE program, NIST, NSF, and AFOSR.

  4. Tedlar bag sampling technique for vertical profiling of carbon dioxide through the atmospheric boundary layer with high precision and accuracy.

    PubMed

    Schulz, Kristen; Jensen, Michael L; Balsley, Ben B; Davis, Kenneth; Birks, John W

    2004-07-01

    Carbon dioxide is the most important greenhouse gas other than water vapor, and its modulation by the biosphere is of fundamental importance to our understanding of global climate change. We have developed a new technique for vertical profiling of CO2 and meteorological parameters through the atmospheric boundary layer and well into the free troposphere. Vertical profiling of CO2 mixing ratios allows estimates of landscape-scale fluxes characteristic of approximately100 km2 of an ecosystem. The method makes use of a powered parachute as a platform and a new Tedlar bag air sampling technique. Air samples are returned to the ground where measurements of CO2 mixing ratios are made with high precision (< or =0.1%) and accuracy (< or =0.1%) using a conventional nondispersive infrared analyzer. Laboratory studies are described that characterize the accuracy and precision of the bag sampling technique and that measure the diffusion coefficient of CO2 through the Tedlar bag wall. The technique has been applied in field studies in the proximity of two AmeriFlux sites, and results are compared with tower measurements of CO2. PMID:15296321

  5. Pupil size dynamics during fixation impact the accuracy and precision of video-based gaze estimation.

    PubMed

    Choe, Kyoung Whan; Blake, Randolph; Lee, Sang-Hun

    2016-01-01

    Video-based eye tracking relies on locating pupil center to measure gaze positions. Although widely used, the technique is known to generate spurious gaze position shifts up to several degrees in visual angle because pupil centration can change without eye movement during pupil constriction or dilation. Since pupil size can fluctuate markedly from moment to moment, reflecting arousal state and cognitive processing during human behavioral and neuroimaging experiments, the pupil size artifact is prevalent and thus weakens the quality of the video-based eye tracking measurements reliant on small fixational eye movements. Moreover, the artifact may lead to erroneous conclusions if the spurious signal is taken as an actual eye movement. Here, we measured pupil size and gaze position from 23 human observers performing a fixation task and examined the relationship between these two measures. Results disclosed that the pupils contracted as fixation was prolonged, at both small (<16s) and large (∼4min) time scales, and these pupil contractions were accompanied by systematic errors in gaze position estimation, in both the ellipse and the centroid methods of pupil tracking. When pupil size was regressed out, the accuracy and reliability of gaze position measurements were substantially improved, enabling differentiation of 0.1° difference in eye position. We confirmed the presence of systematic changes in pupil size, again at both small and large scales, and its tight relationship with gaze position estimates when observers were engaged in a demanding visual discrimination task. PMID:25578924

  6. A simple device for high-precision head image registration: Preliminary performance and accuracy tests

    SciTech Connect

    Pallotta, Stefania

    2007-05-15

    The purpose of this paper is to present a new device for multimodal head study registration and to examine its performance in preliminary tests. The device consists of a system of eight markers fixed to mobile carbon pipes and bars which can be easily mounted on the patient's head using the ear canals and the nasal bridge. Four graduated scales fixed to the rigid support allow examiners to find the same device position on the patient's head during different acquisitions. The markers can be filled with appropriate substances for visualisation in computed tomography (CT), magnetic resonance, single photon emission computer tomography (SPECT) and positron emission tomography images. The device's rigidity and its position reproducibility were measured in 15 repeated CT acquisitions of the Alderson Rando anthropomorphic phantom and in two SPECT studies of a patient. The proposed system displays good rigidity and reproducibility characteristics. A relocation accuracy of less than 1,5 mm was found in more than 90% of the results. The registration parameters obtained using such a device were compared to those obtained using fiducial markers fixed on phantom and patient heads, resulting in differences of less than 1 deg. and 1 mm for rotation and translation parameters, respectively. Residual differences between fiducial marker coordinates in reference and in registered studies were less than 1 mm in more than 90% of the results, proving that the device performed as accurately as noninvasive stereotactic devices. Finally, an example of multimodal employment of the proposed device is reported.

  7. Multiple trait genomic selection methods increase genetic value prediction accuracy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic selection predicts genetic values with genome-wide markers. It is rapidly emerging in plant breeding and is widely implemented in animal breeding. Genetic correlations between quantitative traits are pervasive in many breeding programs. These correlations indicate that measurements of one tr...

  8. A Method of Determining Accuracy and Precision for Dosimeter Systems Using Accreditation Data

    SciTech Connect

    Rick Cummings and John Flood

    2010-12-01

    A study of the uncertainty of dosimeter results is required by the national accreditation programs for each dosimeter model for which accreditation is sought. Typically, the methods used to determine uncertainty have included the partial differentiation method described in the U.S. Guide to Uncertainty in Measurements or the use of Monte Carlo techniques and probability distribution functions to generate simulated dose results. Each of these techniques has particular strengths and should be employed when the areas of uncertainty are required to be understood in detail. However, the uncertainty of dosimeter results can also be determined using a Model II One-Way Analysis of Variance technique and accreditation testing data. The strengths of the technique include (1) the method is straightforward and the data are provided under accreditation testing and (2) the method provides additional data for the analysis of long-term uncertainty using Statistical Process Control (SPC) techniques. The use of SPC to compare variances and standard deviations over time is described well in other areas and is not discussed in detail in this paper. The application of Analysis of Variance to historic testing data indicated that the accuracy in a representative dosimetry system (Panasonic® Model UD-802) was 8.2%, 5.1%, and 4.8% and the expanded uncertainties at the 95% confidence level were 10.7%, 14.9%, and 15.2% for the Accident, Protection Level-Shallow, and Protection Level-Deep test categories in the Department of Energy Laboratory Accreditation Program, respectively. The 95% level of confidence ranges were (0.98 to 1.19), (0.90 to 1.20), and (0.90 to 1.20) for the three groupings of test categories, respectively.

  9. A method of determining accuracy and precision for dosimeter systems using accreditation data.

    PubMed

    Cummings, Frederick; Flood, John R

    2010-12-01

    A study of the uncertainty of dosimeter results is required by the national accreditation programs for each dosimeter model for which accreditation is sought. Typically, the methods used to determine uncertainty have included the partial differentiation method described in the U.S. Guide to Uncertainty in Measurements or the use of Monte Carlo techniques and probability distribution functions to generate simulated dose results. Each of these techniques has particular strengths and should be employed when the areas of uncertainty are required to be understood in detail. However, the uncertainty of dosimeter results can also be determined using a Model II One-Way Analysis of Variance technique and accreditation testing data. The strengths of the technique include (1) the method is straightforward and the data are provided under accreditation testing and (2) the method provides additional data for the analysis of long-term uncertainty using Statistical Process Control (SPC) techniques. The use of SPC to compare variances and standard deviations over time is described well in other areas and is not discussed in detail in this paper. The application of Analysis of Variance to historic testing data indicated that the accuracy in a representative dosimetry system (Panasonic® Model UD-802) was 8.2%, 5.1%, and 4.8% and the expanded uncertainties at the 95% confidence level were 10.7%, 14.9%, and 15.2% for the Accident, Protection Level-Shallow, and Protection Level-Deep test categories in the Department of Energy Laboratory Accreditation Program, respectively. The 95% level of confidence ranges were (0.98 to 1.19), (0.90 to 1.20), and (0.90 to 1.20) for the three groupings of test categories, respectively. PMID:21068596

  10. Accuracy and reliability of multi-GNSS real-time precise positioning: GPS, GLONASS, BeiDou, and Galileo

    NASA Astrophysics Data System (ADS)

    Li, Xingxing; Ge, Maorong; Dai, Xiaolei; Ren, Xiaodong; Fritsche, Mathias; Wickert, Jens; Schuh, Harald

    2015-06-01

    In this contribution, we present a GPS+GLONASS+BeiDou+Galileo four-system model to fully exploit the observations of all these four navigation satellite systems for real-time precise orbit determination, clock estimation and positioning. A rigorous multi-GNSS analysis is performed to achieve the best possible consistency by processing the observations from different GNSS together in one common parameter estimation procedure. Meanwhile, an efficient multi-GNSS real-time precise positioning service system is designed and demonstrated by using the multi-GNSS Experiment, BeiDou Experimental Tracking Network, and International GNSS Service networks including stations all over the world. The statistical analysis of the 6-h predicted orbits show that the radial and cross root mean square (RMS) values are smaller than 10 cm for BeiDou and Galileo, and smaller than 5 cm for both GLONASS and GPS satellites, respectively. The RMS values of the clock differences between real-time and batch-processed solutions for GPS satellites are about 0.10 ns, while the RMS values for BeiDou, Galileo and GLONASS are 0.13, 0.13 and 0.14 ns, respectively. The addition of the BeiDou, Galileo and GLONASS systems to the standard GPS-only processing, reduces the convergence time almost by 70 %, while the positioning accuracy is improved by about 25 %. Some outliers in the GPS-only solutions vanish when multi-GNSS observations are processed simultaneous. The availability and reliability of GPS precise positioning decrease dramatically as the elevation cutoff increases. However, the accuracy of multi-GNSS precise point positioning (PPP) is hardly decreased and few centimeter are still achievable in the horizontal components even with 40 elevation cutoff. At 30 and 40 elevation cutoffs, the availability rates of GPS-only solution drop significantly to only around 70 and 40 %, respectively. However, multi-GNSS PPP can provide precise position estimates continuously (availability rate is more than 99

  11. In silico instrumental response correction improves precision of label-free proteomics and accuracy of proteomics-based predictive models.

    PubMed

    Lyutvinskiy, Yaroslav; Yang, Hongqian; Rutishauser, Dorothea; Zubarev, Roman A

    2013-08-01

    In the analysis of proteome changes arising during the early stages of a biological process (e.g. disease or drug treatment) or from the indirect influence of an important factor, the biological variations of interest are often small (∼10%). The corresponding requirements for the precision of proteomics analysis are high, and this often poses a challenge, especially when employing label-free quantification. One of the main contributors to the inaccuracy of label-free proteomics experiments is the variability of the instrumental response during LC-MS/MS runs. Such variability might include fluctuations in the electrospray current, transmission efficiency from the air-vacuum interface to the detector, and detection sensitivity. We have developed an in silico post-processing method of reducing these variations, and have thus significantly improved the precision of label-free proteomics analysis. For abundant blood plasma proteins, a coefficient of variation of approximately 1% was achieved, which allowed for sex differentiation in pooled samples and ≈90% accurate differentiation of individual samples by means of a single LC-MS/MS analysis. This method improves the precision of measurements and increases the accuracy of predictive models based on the measurements. The post-acquisition nature of the correction technique and its generality promise its widespread application in LC-MS/MS-based methods such as proteomics and metabolomics. PMID:23589346

  12. Accuracy and Precision of Equine Gait Event Detection during Walking with Limb and Trunk Mounted Inertial Sensors

    PubMed Central

    Olsen, Emil; Andersen, Pia Haubro; Pfau, Thilo

    2012-01-01

    The increased variations of temporal gait events when pathology is present are good candidate features for objective diagnostic tests. We hypothesised that the gait events hoof-on/off and stance can be detected accurately and precisely using features from trunk and distal limb-mounted Inertial Measurement Units (IMUs). Four IMUs were mounted on the distal limb and five IMUs were attached to the skin over the dorsal spinous processes at the withers, fourth lumbar vertebrae and sacrum as well as left and right tuber coxae. IMU data were synchronised to a force plate array and a motion capture system. Accuracy (bias) and precision (SD of bias) was calculated to compare force plate and IMU timings for gait events. Data were collected from seven horses. One hundred and twenty three (123) front limb steps were analysed; hoof-on was detected with a bias (SD) of −7 (23) ms, hoof-off with 0.7 (37) ms and front limb stance with −0.02 (37) ms. A total of 119 hind limb steps were analysed; hoof-on was found with a bias (SD) of −4 (25) ms, hoof-off with 6 (21) ms and hind limb stance with 0.2 (28) ms. IMUs mounted on the distal limbs and sacrum can detect gait events accurately and precisely. PMID:22969392

  13. Accuracy, Precision, Ease-Of-Use, and Cost of Methods to Test Ebola-Relevant Chlorine Solutions.

    PubMed

    Wells, Emma; Wolfe, Marlene K; Murray, Anna; Lantagne, Daniele

    2016-01-01

    To prevent transmission in Ebola Virus Disease (EVD) outbreaks, it is recommended to disinfect living things (hands and people) with 0.05% chlorine solution and non-living things (surfaces, personal protective equipment, dead bodies) with 0.5% chlorine solution. In the current West African EVD outbreak, these solutions (manufactured from calcium hypochlorite (HTH), sodium dichloroisocyanurate (NaDCC), and sodium hypochlorite (NaOCl)) have been widely used in both Ebola Treatment Unit and community settings. To ensure solution quality, testing is necessary, however test method appropriateness for these Ebola-relevant concentrations has not previously been evaluated. We identified fourteen commercially-available methods to test Ebola-relevant chlorine solution concentrations, including two titration methods, four DPD dilution methods, and six test strips. We assessed these methods by: 1) determining accuracy and precision by measuring in quintuplicate five different 0.05% and 0.5% chlorine solutions manufactured from NaDCC, HTH, and NaOCl; 2) conducting volunteer testing to assess ease-of-use; and, 3) determining costs. Accuracy was greatest in titration methods (reference-12.4% error compared to reference method), then DPD dilution methods (2.4-19% error), then test strips (5.2-48% error); precision followed this same trend. Two methods had an accuracy of <10% error across all five chlorine solutions with good precision: Hach digital titration for 0.05% and 0.5% solutions (recommended for contexts with trained personnel and financial resources), and Serim test strips for 0.05% solutions (recommended for contexts where rapid, inexpensive, and low-training burden testing is needed). Measurement error from test methods not including pH adjustment varied significantly across the five chlorine solutions, which had pH values 5-11. Volunteers found test strip easiest and titration hardest; costs per 100 tests were $14-37 for test strips and $33-609 for titration. Given the

  14. Accuracy, Precision, Ease-Of-Use, and Cost of Methods to Test Ebola-Relevant Chlorine Solutions

    PubMed Central

    Wells, Emma; Wolfe, Marlene K.; Murray, Anna; Lantagne, Daniele

    2016-01-01

    To prevent transmission in Ebola Virus Disease (EVD) outbreaks, it is recommended to disinfect living things (hands and people) with 0.05% chlorine solution and non-living things (surfaces, personal protective equipment, dead bodies) with 0.5% chlorine solution. In the current West African EVD outbreak, these solutions (manufactured from calcium hypochlorite (HTH), sodium dichloroisocyanurate (NaDCC), and sodium hypochlorite (NaOCl)) have been widely used in both Ebola Treatment Unit and community settings. To ensure solution quality, testing is necessary, however test method appropriateness for these Ebola-relevant concentrations has not previously been evaluated. We identified fourteen commercially-available methods to test Ebola-relevant chlorine solution concentrations, including two titration methods, four DPD dilution methods, and six test strips. We assessed these methods by: 1) determining accuracy and precision by measuring in quintuplicate five different 0.05% and 0.5% chlorine solutions manufactured from NaDCC, HTH, and NaOCl; 2) conducting volunteer testing to assess ease-of-use; and, 3) determining costs. Accuracy was greatest in titration methods (reference-12.4% error compared to reference method), then DPD dilution methods (2.4–19% error), then test strips (5.2–48% error); precision followed this same trend. Two methods had an accuracy of <10% error across all five chlorine solutions with good precision: Hach digital titration for 0.05% and 0.5% solutions (recommended for contexts with trained personnel and financial resources), and Serim test strips for 0.05% solutions (recommended for contexts where rapid, inexpensive, and low-training burden testing is needed). Measurement error from test methods not including pH adjustment varied significantly across the five chlorine solutions, which had pH values 5–11. Volunteers found test strip easiest and titration hardest; costs per 100 tests were $14–37 for test strips and $33–609 for titration

  15. Detailed data is welcome, but with a pinch of salt: Accuracy, precision, and uncertainty in flood inundation modeling

    NASA Astrophysics Data System (ADS)

    Dottori, F.; Di Baldassarre, G.; Todini, E.

    2013-09-01

    New survey techniques provide a large amount of high-resolution data, which can be extremely precious for flood inundation modeling. Such data availability raises the issue as to how to exploit their information content to effectively improve flood risk mapping and predictions. In this paper, we will discuss a number of important issues which should be taken into account in works related to flood modeling. These include the large number of uncertainty sources in model structure and available data; the difficult evaluation of model results, due to the scarcity of observed data; computational efficiency; false confidence that can be given by high-resolution outputs, as accuracy is not necessarily increased by higher precision. Finally, we briefly review and discuss a number of existing approaches, such as subgrid parameterization and roughness upscaling methods, which can be used to incorporate high detailed data into flood inundation models, balancing efficiency and reliability.

  16. Selection Strategies for Univariate Loglinear Smoothing Models and Their Effect on Equating Function Accuracy

    ERIC Educational Resources Information Center

    Moses, Tim; Holland, Paul W.

    2009-01-01

    In this study, we compared 12 statistical strategies proposed for selecting loglinear models for smoothing univariate test score distributions and for enhancing the stability of equipercentile equating functions. The major focus was on evaluating the effects of the selection strategies on equating function accuracy. Selection strategies' influence…

  17. Community-based Approaches to Improving Accuracy, Precision, and Reproducibility in U-Pb and U-Th Geochronology

    NASA Astrophysics Data System (ADS)

    McLean, N. M.; Condon, D. J.; Bowring, S. A.; Schoene, B.; Dutton, A.; Rubin, K. H.

    2015-12-01

    The last two decades have seen a grassroots effort by the international geochronology community to "calibrate Earth history through teamwork and cooperation," both as part of the EARTHTIME initiative and though several daughter projects with similar goals. Its mission originally challenged laboratories "to produce temporal constraints with uncertainties approaching 0.1% of the radioisotopic ages," but EARTHTIME has since exceeded its charge in many ways. Both the U-Pb and Ar-Ar chronometers first considered for high-precision timescale calibration now regularly produce dates at the sub-per mil level thanks to instrumentation, laboratory, and software advances. At the same time new isotope systems, including U-Th dating of carbonates, have developed comparable precision. But the larger, inter-related scientific challenges envisioned at EARTHTIME's inception remain - for instance, precisely calibrating the global geologic timescale, estimating rates of change around major climatic perturbations, and understanding evolutionary rates through time - and increasingly require that data from multiple geochronometers be combined. To solve these problems, the next two decades of uranium-daughter geochronology will require further advances in accuracy, precision, and reproducibility. The U-Th system has much in common with U-Pb, in that both parent and daughter isotopes are solids that can easily be weighed and dissolved in acid, and have well-characterized reference materials certified for isotopic composition and/or purity. For U-Pb, improving lab-to-lab reproducibility has entailed dissolving precisely weighed U and Pb metals of known purity and isotopic composition together to make gravimetric solutions, then using these to calibrate widely distributed tracers composed of artificial U and Pb isotopes. To mimic laboratory measurements, naturally occurring U and Pb isotopes were also mixed in proportions to mimic samples of three different ages, to be run as internal

  18. Assessment of accuracy and precision of 3D reconstruction of unicompartmental knee arthroplasty in upright position using biplanar radiography.

    PubMed

    Tsai, Tsung-Yuan; Dimitriou, Dimitris; Hosseini, Ali; Liow, Ming Han Lincoln; Torriani, Martin; Li, Guoan; Kwon, Young-Min

    2016-07-01

    This study aimed to evaluate the precision and accuracy of 3D reconstruction of UKA component position, contact location and lower limb alignment in standing position using biplanar radiograph. Two human specimens with 4 medial UKAs were implanted with beads for radiostereometric analysis (RSA). The specimens were frozen in standing position and CT-scanned to obtain relative positions between the beads, bones and UKA components. The specimens were then imaged using biplanar radiograph (EOS). The positions of the femur, tibia, UKA components and UKA contact locations were obtained using RSA- and EOS-based techniques. Intraclass correlation coefficient (ICC) was calculated for inter-observer reliability of the EOS technique. The average (standard deviation) of the differences between two techniques in translations and rotations were less than 0.18 (0.29) mm and 0.39° (0.66°) for UKA components. The root-mean-square-errors (RMSE) of contact location along the anterior/posterior and medial/lateral directions were 0.84mm and 0.30mm. The RMSEs of the knee rotations were less than 1.70°. The ICCs for the EOS-based segmental orientations between two raters were larger than 0.98. The results suggest the EOS-based 3D reconstruction technique can precisely determine component position, contact location and lower limb alignment for UKA patients in weight-bearing standing position. PMID:27117422

  19. THE PRECISION AND ACCURACY OF EARLY EPOCH OF REIONIZATION FOREGROUND MODELS: COMPARING MWA AND PAPER 32-ANTENNA SOURCE CATALOGS

    SciTech Connect

    Jacobs, Daniel C.; Bowman, Judd; Aguirre, James E.

    2013-05-20

    As observations of the Epoch of Reionization (EoR) in redshifted 21 cm emission begin, we assess the accuracy of the early catalog results from the Precision Array for Probing the Epoch of Reionization (PAPER) and the Murchison Wide-field Array (MWA). The MWA EoR approach derives much of its sensitivity from subtracting foregrounds to <1% precision, while the PAPER approach relies on the stability and symmetry of the primary beam. Both require an accurate flux calibration to set the amplitude of the measured power spectrum. The two instruments are very similar in resolution, sensitivity, sky coverage, and spectral range and have produced catalogs from nearly contemporaneous data. We use a Bayesian Markov Chain Monte Carlo fitting method to estimate that the two instruments are on the same flux scale to within 20% and find that the images are mostly in good agreement. We then investigate the source of the errors by comparing two overlapping MWA facets where we find that the differences are primarily related to an inaccurate model of the primary beam but also correlated errors in bright sources due to CLEAN. We conclude with suggestions for mitigating and better characterizing these effects.

  20. Error propagation in relative real-time reverse transcription polymerase chain reaction quantification models: the balance between accuracy and precision.

    PubMed

    Nordgård, Oddmund; Kvaløy, Jan Terje; Farmen, Ragne Kristin; Heikkilä, Reino

    2006-09-15

    Real-time reverse transcription polymerase chain reaction (RT-PCR) has gained wide popularity as a sensitive and reliable technique for mRNA quantification. The development of new mathematical models for such quantifications has generally paid little attention to the aspect of error propagation. In this study we evaluate, both theoretically and experimentally, several recent models for relative real-time RT-PCR quantification of mRNA with respect to random error accumulation. We present error propagation expressions for the most common quantification models and discuss the influence of the various components on the total random error. Normalization against a calibrator sample to improve comparability between different runs is shown to increase the overall random error in our system. On the other hand, normalization against multiple reference genes, introduced to improve accuracy, does not increase error propagation compared to normalization against a single reference gene. Finally, we present evidence that sample-specific amplification efficiencies determined from individual amplification curves primarily increase the random error of real-time RT-PCR quantifications and should be avoided. Our data emphasize that the gain of accuracy associated with new quantification models should be validated against the corresponding loss of precision. PMID:16899212

  1. SU-E-J-147: Monte Carlo Study of the Precision and Accuracy of Proton CT Reconstructed Relative Stopping Power Maps

    SciTech Connect

    Dedes, G; Asano, Y; Parodi, K; Arbor, N; Dauvergne, D; Testa, E; Letang, J; Rit, S

    2015-06-15

    Purpose: The quantification of the intrinsic performances of proton computed tomography (pCT) as a modality for treatment planning in proton therapy. The performance of an ideal pCT scanner is studied as a function of various parameters. Methods: Using GATE/Geant4, we simulated an ideal pCT scanner and scans of several cylindrical phantoms with various tissue equivalent inserts of different sizes. Insert materials were selected in order to be of clinical relevance. Tomographic images were reconstructed using a filtered backprojection algorithm taking into account the scattering of protons into the phantom. To quantify the performance of the ideal pCT scanner, we study the precision and the accuracy with respect to the theoretical relative stopping power ratios (RSP) values for different beam energies, imaging doses, insert sizes and detector positions. The planning range uncertainty resulting from the reconstructed RSP is also assessed by comparison with the range of the protons in the analytically simulated phantoms. Results: The results indicate that pCT can intrinsically achieve RSP resolution below 1%, for most examined tissues at beam energies below 300 MeV and for imaging doses around 1 mGy. RSP maps accuracy of less than 0.5 % is observed for most tissue types within the studied dose range (0.2–1.5 mGy). Finally, the uncertainty in the proton range due to the accuracy of the reconstructed RSP map is well below 1%. Conclusion: This work explores the intrinsic performance of pCT as an imaging modality for proton treatment planning. The obtained results show that under ideal conditions, 3D RSP maps can be reconstructed with an accuracy better than 1%. Hence, pCT is a promising candidate for reducing the range uncertainties introduced by the use of X-ray CT alongside with a semiempirical calibration to RSP.Supported by the DFG Cluster of Excellence Munich-Centre for Advanced Photonics (MAP)

  2. Improving Precision and Accuracy of Isotope Ratios from Short Transient Laser Ablation-Multicollector-Inductively Coupled Plasma Mass Spectrometry Signals: Application to Micrometer-Size Uranium Particles.

    PubMed

    Claverie, Fanny; Hubert, Amélie; Berail, Sylvain; Donard, Ariane; Pointurier, Fabien; Pécheyran, Christophe

    2016-04-19

    The isotope drift encountered on short transient signals measured by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) is related to differences in detector time responses. Faraday to Faraday and Faraday to ion counter time lags were determined and corrected using VBA data processing based on the synchronization of the isotope signals. The coefficient of determination of the linear fit between the two isotopes was selected as the best criterion to obtain accurate detector time lag. The procedure was applied to the analysis by laser ablation-MC-ICPMS of micrometer sized uranium particles (1-3.5 μm). Linear regression slope (LRS) (one isotope plotted over the other), point-by-point, and integration methods were tested to calculate the (235)U/(238)U and (234)U/(238)U ratios. Relative internal precisions of 0.86 to 1.7% and 1.2 to 2.4% were obtained for (235)U/(238)U and (234)U/(238)U, respectively, using LRS calculation, time lag, and mass bias corrections. A relative external precision of 2.1% was obtained for (235)U/(238)U ratios with good accuracy (relative difference with respect to the reference value below 1%). PMID:27031645

  3. Single-frequency receivers as master permanent stations in GNSS networks: precision and accuracy of the positioning in mixed networks

    NASA Astrophysics Data System (ADS)

    Dabove, Paolo; Manzino, Ambrogio Maria

    2015-04-01

    The use of GPS/GNSS instruments is a common practice in the world at both a commercial and academic research level. Since last ten years, Continuous Operating Reference Stations (CORSs) networks were born in order to achieve the possibility to extend a precise positioning more than 15 km far from the master station. In this context, the Geomatics Research Group of DIATI at the Politecnico di Torino has carried out several experiments in order to evaluate the achievable precision obtainable with different GNSS receivers (geodetic and mass-market) and antennas if a CORSs network is considered. This work starts from the research above described, in particular focusing the attention on the usefulness of single frequency permanent stations in order to thicken the existing CORSs, especially for monitoring purposes. Two different types of CORSs network are available today in Italy: the first one is the so called "regional network" and the second one is the "national network", where the mean inter-station distances are about 25/30 and 50/70 km respectively. These distances are useful for many applications (e.g. mobile mapping) if geodetic instruments are considered but become less useful if mass-market instruments are used or if the inter-station distance between master and rover increases. In this context, some innovative GNSS networks were developed and tested, analyzing the performance of rover's positioning in terms of quality, accuracy and reliability both in real-time and post-processing approach. The use of single frequency GNSS receivers leads to have some limits, especially due to a limited baseline length, the possibility to obtain a correct fixing of the phase ambiguity for the network and to fix the phase ambiguity correctly also for the rover. These factors play a crucial role in order to reach a positioning with a good level of accuracy (as centimetric o better) in a short time and with an high reliability. The goal of this work is to investigate about the

  4. Standardization of Operator-Dependent Variables Affecting Precision and Accuracy of the Disk Diffusion Method for Antibiotic Susceptibility Testing.

    PubMed

    Hombach, Michael; Maurer, Florian P; Pfiffner, Tamara; Böttger, Erik C; Furrer, Reinhard

    2015-12-01

    Parameters like zone reading, inoculum density, and plate streaking influence the precision and accuracy of disk diffusion antibiotic susceptibility testing (AST). While improved reading precision has been demonstrated using automated imaging systems, standardization of the inoculum and of plate streaking have not been systematically investigated yet. This study analyzed whether photometrically controlled inoculum preparation and/or automated inoculation could further improve the standardization of disk diffusion. Suspensions of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213 of 0.5 McFarland standard were prepared by 10 operators using both visual comparison to turbidity standards and a Densichek photometer (bioMérieux), and the resulting CFU counts were determined. Furthermore, eight experienced operators each inoculated 10 Mueller-Hinton agar plates using a single 0.5 McFarland standard bacterial suspension of E. coli ATCC 25922 using regular cotton swabs, dry flocked swabs (Copan, Brescia, Italy), or an automated streaking device (BD-Kiestra, Drachten, Netherlands). The mean CFU counts obtained from 0.5 McFarland standard E. coli ATCC 25922 suspensions were significantly different for suspensions prepared by eye and by Densichek (P < 0.001). Preparation by eye resulted in counts that were closer to the CLSI/EUCAST target of 10(8) CFU/ml than those resulting from Densichek preparation. No significant differences in the standard deviations of the CFU counts were observed. The interoperator differences in standard deviations when dry flocked swabs were used decreased significantly compared to the differences when regular cotton swabs were used, whereas the mean of the standard deviations of all operators together was not significantly altered. In contrast, automated streaking significantly reduced both interoperator differences, i.e., the individual standard deviations, compared to the standard deviations for the manual method, and the mean of

  5. Accuracy and precision of MR blood oximetry based on the long paramagnetic cylinder approximation of large vessels.

    PubMed

    Langham, Michael C; Magland, Jeremy F; Epstein, Charles L; Floyd, Thomas F; Wehrli, Felix W

    2009-08-01

    An accurate noninvasive method to measure the hemoglobin oxygen saturation (%HbO(2)) of deep-lying vessels without catheterization would have many clinical applications. Quantitative MRI may be the only imaging modality that can address this difficult and important problem. MR susceptometry-based oximetry for measuring blood oxygen saturation in large vessels models the vessel as a long paramagnetic cylinder immersed in an external field. The intravascular magnetic susceptibility relative to surrounding muscle tissue is a function of oxygenated hemoglobin (HbO(2)) and can be quantified with a field-mapping pulse sequence. In this work, the method's accuracy and precision was investigated theoretically on the basis of an analytical expression for the arbitrarily oriented cylinder, as well as experimentally in phantoms and in vivo in the femoral artery and vein at 3T field strength. Errors resulting from vessel tilt, noncircularity of vessel cross-section, and induced magnetic field gradients were evaluated and methods for correction were designed and implemented. Hemoglobin saturation was measured at successive vessel segments, differing in geometry, such as eccentricity and vessel tilt, but constant blood oxygen saturation levels, as a means to evaluate measurement consistency. The average standard error and coefficient of variation of measurements in phantoms were <2% with tilt correction alone, in agreement with theory, suggesting that high accuracy and reproducibility can be achieved while ignoring noncircularity for tilt angles up to about 30 degrees . In vivo, repeated measurements of %HbO(2) in the femoral vessels yielded a coefficient of variation of less than 5%. In conclusion, the data suggest that %HbO(2) can be measured reproducibly in vivo in large vessels of the peripheral circulation on the basis of the paramagnetic cylinder approximation of the incremental field. PMID:19526517

  6. Determination of the precision and accuracy of morphological measurements using the Kinect™ sensor: comparison with standard stereophotogrammetry.

    PubMed

    Bonnechère, B; Jansen, B; Salvia, P; Bouzahouene, H; Sholukha, V; Cornelis, J; Rooze, M; Van Sint Jan, S

    2014-01-01

    The recent availability of the Kinect™ sensor, a low-cost Markerless Motion Capture (MMC) system, could give new and interesting insights into ergonomics (e.g. the creation of a morphological database). Extensive validation of this system is still missing. The aim of the study was to determine if the Kinect™ sensor can be used as an easy, cheap and fast tool to conduct morphology estimation. A total of 48 subjects were analysed using MMC. Results were compared with measurements obtained from a high-resolution stereophotogrammetric system, a marker-based system (MBS). Differences between MMC and MBS were found; however, these differences were systematically correlated and enabled regression equations to be obtained to correct MMC results. After correction, final results were in agreement with MBS data (p = 0.99). Results show that measurements were reproducible and precise after applying regression equations. Kinect™ sensors-based systems therefore seem to be suitable for use as fast and reliable tools to estimate morphology. Practitioner Summary: The Kinect™ sensor could eventually be used for fast morphology estimation as a body scanner. This paper presents an extensive validation of this device for anthropometric measurements in comparison to manual measurements and stereophotogrammetric devices. The accuracy is dependent on the segment studied but the reproducibility is excellent. PMID:24646374

  7. Airborne Laser CO2 Column Measurements: Evaluation of Precision and Accuracy Under a Wide Range of Surface and Atmospheric Conditions

    NASA Astrophysics Data System (ADS)

    Browell, E. V.; Dobler, J. T.; Kooi, S. A.; Fenn, M. A.; Choi, Y.; Vay, S. A.; Harrison, F. W.; Moore, B.

    2011-12-01

    This paper discusses the latest flight test results of a multi-frequency intensity-modulated (IM) continuous-wave (CW) laser absorption spectrometer (LAS) that operates near 1.57 μm for remote CO2 column measurements. This IM-LAS system is under development for a future space-based mission to determine the global distribution of regional-scale CO2 sources and sinks, which is the objective of the NASA Active Sensing of CO2 Emissions during Nights, Days, and Seasons (ASCENDS) mission. A prototype of the ASCENDS system, called the Multi-frequency Fiber Laser Lidar (MFLL), has been flight tested in eleven airborne campaigns since May 2005. This paper compares the most recent results obtained during the 2010 and 2011 UC-12 and DC-8 flight tests, where MFLL remote CO2 column measurements were evaluated against airborne in situ CO2 profile measurements traceable to World Meteorological Organization standards. The major change to the MFLL system in 2011 was the implementation of several different IM modes, which could be quickly changed in flight, to directly compare the precision and accuracy of MFLL CO2 measurements in each mode. The different IM modes that were evaluated included "fixed" IM frequencies near 50, 200, and 500 kHz; frequencies changed in short time steps (Stepped); continuously swept frequencies (Swept); and a pseudo noise (PN) code. The Stepped, Swept, and PN modes were generated to evaluate the ability of these IM modes to desensitize MFLL CO2 column measurements to intervening optically thin aerosols/clouds. MFLL was flown on the NASA Langley UC-12 aircraft in May 2011 to evaluate the newly implemented IM modes and their impact on CO2 measurement precision and accuracy, and to determine which IM mode provided the greatest thin cloud rejection (TCR) for the CO2 column measurements. Within the current hardware limitations of the MFLL system, the "fixed" 50 kHz results produced similar SNR values to those found previously. The SNR decreased as expected

  8. Integration of genomic information into sport horse breeding programs for optimization of accuracy of selection.

    PubMed

    Haberland, A M; König von Borstel, U; Simianer, H; König, S

    2012-09-01

    Reliable selection criteria are required for young riding horses to increase genetic gain by increasing accuracy of selection and decreasing generation intervals. In this study, selection strategies incorporating genomic breeding values (GEBVs) were evaluated. Relevant stages of selection in sport horse breeding programs were analyzed by applying selection index theory. Results in terms of accuracies of indices (r(TI) ) and relative selection response indicated that information on single nucleotide polymorphism (SNP) genotypes considerably increases the accuracy of breeding values estimated for young horses without own or progeny performance. In a first scenario, the correlation between the breeding value estimated from the SNP genotype and the true breeding value (= accuracy of GEBV) was fixed to a relatively low value of r(mg) = 0.5. For a low heritability trait (h(2) = 0.15), and an index for a young horse based only on information from both parents, additional genomic information doubles r(TI) from 0.27 to 0.54. Including the conventional information source 'own performance' into the before mentioned index, additional SNP information increases r(TI) by 40%. Thus, particularly with regard to traits of low heritability, genomic information can provide a tool for well-founded selection decisions early in life. In a further approach, different sources of breeding values (e.g. GEBV and estimated breeding values (EBVs) from different countries) were combined into an overall index when altering accuracies of EBVs and correlations between traits. In summary, we showed that genomic selection strategies have the potential to contribute to a substantial reduction in generation intervals in horse breeding programs. PMID:23031511

  9. High-precision robotic microcontact printing (R-μCP) utilizing a vision guided selectively compliant articulated robotic arm.

    PubMed

    McNulty, Jason D; Klann, Tyler; Sha, Jin; Salick, Max; Knight, Gavin T; Turng, Lih-Sheng; Ashton, Randolph S

    2014-06-01

    Increased realization of the spatial heterogeneity found within in vivo tissue microenvironments has prompted the desire to engineer similar complexities into in vitro culture substrates. Microcontact printing (μCP) is a versatile technique for engineering such complexities onto cell culture substrates because it permits microscale control of the relative positioning of molecules and cells over large surface areas. However, challenges associated with precisely aligning and superimposing multiple μCP steps severely limits the extent of substrate modification that can be achieved using this method. Thus, we investigated the feasibility of using a vision guided selectively compliant articulated robotic arm (SCARA) for μCP applications. SCARAs are routinely used to perform high precision, repetitive tasks in manufacturing, and even low-end models are capable of achieving microscale precision. Here, we present customization of a SCARA to execute robotic-μCP (R-μCP) onto gold-coated microscope coverslips. The system not only possesses the ability to align multiple polydimethylsiloxane (PDMS) stamps but also has the capability to do so even after the substrates have been removed, reacted to graft polymer brushes, and replaced back into the system. Plus, non-biased computerized analysis shows that the system performs such sequential patterning with <10 μm precision and accuracy, which is equivalent to the repeatability specifications of the employed SCARA model. R-μCP should facilitate the engineering of complex in vivo-like complexities onto culture substrates and their integration with microfluidic devices. PMID:24759945

  10. Evaluation of precision and accuracy of the Borgwaldt RM20S(®) smoking machine designed for in vitro exposure.

    PubMed

    Kaur, Navneet; Lacasse, Martine; Roy, Jean-Philippe; Cabral, Jean-Louis; Adamson, Jason; Errington, Graham; Waldron, Karen C; Gaça, Marianna; Morin, André

    2010-12-01

    The Borgwaldt RM20S(®) smoking machine enables the generation, dilution, and transfer of fresh cigarette smoke to cell exposure chambers, for in vitro analyses. We present a study confirming the precision (repeatability r, reproducibility R) and accuracy of smoke dose generated by the Borgwaldt RM20S(®) system and delivery to exposure chambers. Due to the aerosol nature of cigarette smoke, the repeatability of the dilution of the vapor phase in air was assessed by quantifying two reference standard gases: methane (CH(4), r between 29.0 and 37.0 and RSD between 2.2% and 4.5%) and carbon monoxide (CO, r between 166.8 and 235.8 and RSD between 0.7% and 3.7%). The accuracy of dilution (percent error) for CH(4) and CO was between 6.4% and 19.5% and between 5.8% and 6.4%, respectively, over a 10-1000-fold dilution range. To corroborate our findings, a small inter-laboratory study was carried out for CH(4) measurements. The combined dilution repeatability had an r between 21.3 and 46.4, R between 52.9 and 88.4, RSD between 6.3% and 17.3%, and error between 4.3% and 13.1%. Based on the particulate component of cigarette smoke (3R4F), the repeatability (RSD = 12%) of the undiluted smoke generated by the Borgwaldt RM20S(®) was assessed by quantifying solanesol using high-performance liquid chromatography with ultraviolet detection (HPLC/UV). Finally, the repeatability (r between 0.98 and 4.53 and RSD between 8.8% and 12%) of the dilution of generated smoke particulate phase was assessed by quantifying solanesol following various dilutions of cigarette smoke. The findings in this study suggest the Borgwaldt RM20S(®) smoking machine is a reliable tool to generate and deliver repeatable and reproducible doses of whole smoke to in vitro cultures. PMID:21126153

  11. Effect of modulation frequency bandwidth on measurement accuracy and precision for digital diffuse optical spectroscopy (dDOS)

    NASA Astrophysics Data System (ADS)

    Jung, Justin; Istfan, Raeef; Roblyer, Darren

    2014-03-01

    Near-infrared (NIR) frequency-domain Diffuse Optical Spectroscopy (DOS) is an emerging technology with a growing number of potential clinical applications. In an effort to reduce DOS system complexity and improve portability, we recently demonstrated a direct digital sampling method that utilizes digital signal generation and detection as a replacement for more traditional analog methods. In our technique, a fast analog-to-digital converter (ADC) samples the detected time-domain radio frequency (RF) waveforms at each modulation frequency in a broad-bandwidth sweep (50- 300MHz). While we have shown this method provides comparable results to other DOS technologies, the process is data intensive as digital samples must be stored and processed for each modulation frequency and wavelength. We explore here the effect of reducing the modulation frequency bandwidth on the accuracy and precision of extracted optical properties. To accomplish this, the performance of the digital DOS (dDOS) system was compared to a gold standard network analyzer based DOS system. With a starting frequency of 50MHz, the input signal of the dDOS system was swept to 100, 150, 250, or 300MHz in 4MHz increments and results were compared to full 50-300MHz networkanalyzer DOS measurements. The average errors in extracted μa and μs' with dDOS were lowest for the full 50-300MHz sweep (less than 3%) and were within 3.8% for frequency bandwidths as narrow as 50-150MHz. The errors increased to as much as 9.0% when a bandwidth of 50-100MHz was tested. These results demonstrate the possibility for reduced data collection with dDOS without critical compensation of optical property extraction.

  12. Accuracy, precision and response time of consumer fork, remote digital probe and disposable indicator thermometers for cooked ground beef patties and chicken breasts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nine different commercially available instant-read consumer thermometers (forks, remotes, digital probe and disposable color change indicators) were tested for accuracy and precision compared to a calibrated thermocouple in 80 percent and 90 percent lean ground beef patties, and boneless and bone-in...

  13. An Examination of the Precision and Technical Accuracy of the First Wave of Group-Randomized Trials Funded by the Institute of Education Sciences

    ERIC Educational Resources Information Center

    Spybrook, Jessaca; Raudenbush, Stephen W.

    2009-01-01

    This article examines the power analyses for the first wave of group-randomized trials funded by the Institute of Education Sciences. Specifically, it assesses the precision and technical accuracy of the studies. The authors identified the appropriate experimental design and estimated the minimum detectable standardized effect size (MDES) for each…

  14. Accuracy and training population design for genomic selection in elite north american oats

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic selection (GS) is a method to estimate the breeding values of individuals by using markers throughout the genome. We evaluated the accuracies of GS using data from five traits on 446 oat lines genotyped with 1005 Diversity Array Technology (DArT) markers and two GS methods (RR-BLUP and Bayes...

  15. The use of vector bootstrapping to improve variable selection precision in Lasso models.

    PubMed

    Laurin, Charles; Boomsma, Dorret; Lubke, Gitta

    2016-08-01

    The Lasso is a shrinkage regression method that is widely used for variable selection in statistical genetics. Commonly, K-fold cross-validation is used to fit a Lasso model. This is sometimes followed by using bootstrap confidence intervals to improve precision in the resulting variable selections. Nesting cross-validation within bootstrapping could provide further improvements in precision, but this has not been investigated systematically. We performed simulation studies of Lasso variable selection precision (VSP) with and without nesting cross-validation within bootstrapping. Data were simulated to represent genomic data under a polygenic model as well as under a model with effect sizes representative of typical GWAS results. We compared these approaches to each other as well as to software defaults for the Lasso. Nested cross-validation had the most precise variable selection at small effect sizes. At larger effect sizes, there was no advantage to nesting. We illustrated the nested approach with empirical data comprising SNPs and SNP-SNP interactions from the most significant SNPs in a GWAS of borderline personality symptoms. In the empirical example, we found that the default Lasso selected low-reliability SNPs and interactions which were excluded by bootstrapping. PMID:27248122

  16. Accurate and precise measurement of oxygen isotopic fractions and diffusion profiles by selective attenuation of secondary ions (SASI).

    PubMed

    Téllez, Helena; Druce, John; Hong, Jong-Eun; Ishihara, Tatsumi; Kilner, John A

    2015-03-01

    The accuracy and precision of isotopic analysis in Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) relies on the appropriate reduction of the dead-time and detector saturation effects, especially when analyzing species with high ion yields or present in high concentrations. Conventional approaches to avoid these problems are based on Poisson dead-time correction and/or an overall decrease of the total secondary ion intensity by reducing the target current. This ultimately leads to poor detection limits for the minor isotopes and high uncertainties of the measured isotopic ratios. An alternative strategy consists of the attenuation of those specific secondary ions that saturate the detector, providing an effective extension of the linear dynamic range. In this work, the selective attenuation of secondary ion signals (SASI) approach is applied to the study of oxygen transport properties in electroceramic materials by isotopic labeling with stable (18)O tracer and ToF-SIMS depth profiling. The better analytical performance in terms of accuracy and precision allowed a more reliable determination of the oxygen surface exchange and diffusion coefficients while maintaining good mass resolution and limits of detection for other minor secondary ion species. This improvement is especially relevant to understand the ionic transport mechanisms and properties of solid materials, such as the parallel diffusion pathways (e.g., oxygen diffusion through bulk, grain boundary, or dislocations) in electroceramic materials with relevant applications in energy storage and conversion devices. PMID:25647357

  17. Precision and Selection of Extraction Methods of Aphelenchid Nematodes from Maritime Pine Wood, Pinus pinaster L.

    PubMed

    Penas, Ana C; Diias, Luis S; Mota, Manuel M

    2002-03-01

    Four extraction methods for Bursaphelenchus xylophilus and other aphelenchid nematodes were compared on the number of nematodes per gram recovered, and on the precision of the mean number of nematodes per gram of pine wood. The number of nematodes per gram recovered by each method, in addition to its inherent shortcomings when the actual number of nematodes is unknown, failed to provide clear rankings among the extraction methods. The precision of the mean number of nematodes per gram did provide clear guidelines for selection. Selection of the method may be based on prior knowledge about the range of nematodes to be expected or the independence of precision from the mean number of nematodes. PMID:19265909

  18. Accuracy and responses of genomic selection on key traits in apple breeding

    PubMed Central

    Muranty, Hélène; Troggio, Michela; Sadok, Inès Ben; Rifaï, Mehdi Al; Auwerkerken, Annemarie; Banchi, Elisa; Velasco, Riccardo; Stevanato, Piergiorgio; van de Weg, W Eric; Di Guardo, Mario; Kumar, Satish; Laurens, François; Bink, Marco C A M

    2015-01-01

    The application of genomic selection in fruit tree crops is expected to enhance breeding efficiency by increasing prediction accuracy, increasing selection intensity and decreasing generation interval. The objectives of this study were to assess the accuracy of prediction and selection response in commercial apple breeding programmes for key traits. The training population comprised 977 individuals derived from 20 pedigreed full-sib families. Historic phenotypic data were available on 10 traits related to productivity and fruit external appearance and genotypic data for 7829 SNPs obtained with an Illumina 20K SNP array. From these data, a genome-wide prediction model was built and subsequently used to calculate genomic breeding values of five application full-sib families. The application families had genotypes at 364 SNPs from a dedicated 512 SNP array, and these genotypic data were extended to the high-density level by imputation. These five families were phenotyped for 1 year and their phenotypes were compared to the predicted breeding values. Accuracy of genomic prediction across the 10 traits reached a maximum value of 0.5 and had a median value of 0.19. The accuracies were strongly affected by the phenotypic distribution and heritability of traits. In the largest family, significant selection response was observed for traits with high heritability and symmetric phenotypic distribution. Traits that showed non-significant response often had reduced and skewed phenotypic variation or low heritability. Among the five application families the accuracies were uncorrelated to the degree of relatedness to the training population. The results underline the potential of genomic prediction to accelerate breeding progress in outbred fruit tree crops that still need to overcome long generation intervals and extensive phenotyping costs. PMID:26744627

  19. Improved localization accuracy in double-helix point spread function super-resolution fluorescence microscopy using selective-plane illumination

    NASA Astrophysics Data System (ADS)

    Yu, Jie; Cao, Bo; Li, Heng; Yu, Bin; Chen, Danni; Niu, Hanben

    2014-09-01

    Recently, three-dimensional (3D) super resolution imaging of cellular structures in thick samples has been enabled with the wide-field super-resolution fluorescence microscopy based on double helix point spread function (DH-PSF). However, when the sample is Epi-illuminated, much background fluorescence from those excited molecules out-of-focus will reduce the signal-to-noise ratio (SNR) of the image in-focus. In this paper, we resort to a selective-plane illumination strategy, which has been used for tissue-level imaging and single molecule tracking, to eliminate out-of-focus background and to improve SNR and the localization accuracy of the standard DH-PSF super-resolution imaging in thick samples. We present a novel super-resolution microscopy that combine selective-plane illumination and DH-PSF. The setup utilizes a well-defined laser light sheet which theoretical thickness is 1.7μm (FWHM) at 640nm excitation wavelength. The image SNR of DH-PSF microscopy between selective-plane illumination and Epi-illumination are compared. As we expect, the SNR of the DH-PSF microscopy based selective-plane illumination is increased remarkably. So, 3D localization precision of DH-PSF would be improved significantly. We demonstrate its capabilities by studying 3D localizing of single fluorescent particles. These features will provide high thick samples compatibility for future biomedical applications.

  20. Millimeter-accuracy GPS landslide monitoring using Precise Point Positioning with Single Receiver Phase Ambiguity (PPP-SRPA) resolution: a case study in Puerto Rico

    NASA Astrophysics Data System (ADS)

    Wang, G. Q.

    2013-03-01

    Continuous Global Positioning System (GPS) monitoring is essential for establishing the rate and pattern of superficial movements of landslides. This study demonstrates a technique which uses a stand-alone GPS station to conduct millimeter-accuracy landslide monitoring. The Precise Point Positioning with Single Receiver Phase Ambiguity (PPP-SRPA) resolution employed by the GIPSY/OASIS software package (V6.1.2) was applied in this study. Two-years of continuous GPS data collected at a creeping landslide were used to evaluate the accuracy of the PPP-SRPA solutions. The criterion for accuracy was the root-mean-square (RMS) of residuals of the PPP-SRPA solutions with respect to "true" landslide displacements over the two-year period. RMS is often regarded as repeatability or precision in GPS literature. However, when contrasted with a known "true" position or displacement it could be termed RMS accuracy or simply accuracy. This study indicated that the PPP-SRPA resolution can provide an accuracy of 2 to 3 mm horizontally and 8 mm vertically for 24-hour sessions with few outliers (< 1%) in the Puerto Rico region. Horizontal accuracy below 5 mm can be stably achieved with 4-hour or longer sessions if avoiding the collection of data during extreme weather conditions. Vertical accuracy below 10 mm can be achieved with 8-hour or longer sessions. This study indicates that the PPP-SRPA resolution is competitive with the conventional carrier-phase double-difference network resolution for static (longer than 4 hours) landslide monitoring while maintaining many advantages. It is evident that the PPP-SRPA method would become an attractive alternative to the conventional carrier-phase double-difference method for landslide monitoring, notably in remote areas or developing countries.

  1. Multi-generational imputation of single nucleotide polymorphism marker genotypes and accuracy of genomic selection.

    PubMed

    Toghiani, S; Aggrey, S E; Rekaya, R

    2016-07-01

    Availability of high-density single nucleotide polymorphism (SNP) genotyping platforms provided unprecedented opportunities to enhance breeding programmes in livestock, poultry and plant species, and to better understand the genetic basis of complex traits. Using this genomic information, genomic breeding values (GEBVs), which are more accurate than conventional breeding values. The superiority of genomic selection is possible only when high-density SNP panels are used to track genes and QTLs affecting the trait. Unfortunately, even with the continuous decrease in genotyping costs, only a small fraction of the population has been genotyped with these high-density panels. It is often the case that a larger portion of the population is genotyped with low-density and low-cost SNP panels and then imputed to a higher density. Accuracy of SNP genotype imputation tends to be high when minimum requirements are met. Nevertheless, a certain rate of genotype imputation errors is unavoidable. Thus, it is reasonable to assume that the accuracy of GEBVs will be affected by imputation errors; especially, their cumulative effects over time. To evaluate the impact of multi-generational selection on the accuracy of SNP genotypes imputation and the reliability of resulting GEBVs, a simulation was carried out under varying updating of the reference population, distance between the reference and testing sets, and the approach used for the estimation of GEBVs. Using fixed reference populations, imputation accuracy decayed by about 0.5% per generation. In fact, after 25 generations, the accuracy was only 7% lower than the first generation. When the reference population was updated by either 1% or 5% of the top animals in the previous generations, decay of imputation accuracy was substantially reduced. These results indicate that low-density panels are useful, especially when the generational interval between reference and testing population is small. As the generational interval

  2. Hyperspectral band selection based on a variable precision neighborhood rough set.

    PubMed

    Liu, Yao; Xie, Hong; Wang, Liguo; Tan, Kezhu

    2016-01-20

    Band selection is a well-known approach for reducing dimensionality in hyperspectral images. We propose a band-selection method based on the variable precision neighborhood rough set theory to select informative bands from hyperspectral images. A decision-making information system was established by hyperspectral data derived from soybean samples between 400 and 1000 nm wavelengths. The dependency was used to evaluate band significance. The optimal band subset was selected by a forward greedy search algorithm. After adjusting appropriate threshold values, stable optimized results were obtained. To assess the effectiveness of the proposed band-selection technique, two classification models were constructed. The experimental results showed that admitting inclusion errors could improve classification performance, including band selection and generalization ability. PMID:26835918

  3. High precision and high accuracy isotopic measurement of uranium using lead and thorium calibration solutions by inductively coupled plasma-multiple collector-mass spectrometry

    SciTech Connect

    Bowen, I.; Walder, A.J.; Hodgson, T.; Parrish, R.R. |

    1998-12-31

    A novel method for the high accuracy and high precision measurement of uranium isotopic composition by Inductively Coupled Plasma-Multiple Collector-Mass Spectrometry is discussed. Uranium isotopic samples are spiked with either thorium or lead for use as internal calibration reference materials. This method eliminates the necessity to periodically measure uranium standards to correct for changing mass bias when samples are measured over long time periods. This technique has generated among the highest levels of analytical precision on both the major and minor isotopes of uranium. Sample throughput has also been demonstrated to exceed Thermal Ionization Mass Spectrometry by a factor of four to five.

  4. Towards the GEOSAT Follow-On Precise Orbit Determination Goals of High Accuracy and Near-Real-Time Processing

    NASA Technical Reports Server (NTRS)

    Lemoine, Frank G.; Zelensky, Nikita P.; Chinn, Douglas S.; Beckley, Brian D.; Lillibridge, John L.

    2006-01-01

    The US Navy's GEOSAT Follow-On spacecraft (GFO) primary mission objective is to map the oceans using a radar altimeter. Satellite laser ranging data, especially in combination with altimeter crossover data, offer the only means of determining high-quality precise orbits. Two tuned gravity models, PGS7727 and PGS7777b, were created at NASA GSFC for GFO that reduce the predicted radial orbit through degree 70 to 13.7 and 10.0 mm. A macromodel was developed to model the nonconservative forces and the SLR spacecraft measurement offset was adjusted to remove a mean bias. Using these improved models, satellite-ranging data, altimeter crossover data, and Doppler data are used to compute both daily medium precision orbits with a latency of less than 24 hours. Final precise orbits are also computed using these tracking data and exported with a latency of three to four weeks to NOAA for use on the GFO Geophysical Data Records (GDR s). The estimated orbit precision of the daily orbits is between 10 and 20 cm, whereas the precise orbits have a precision of 5 cm.

  5. Effects of Sample Selection Bias on the Accuracy of Population Structure and Ancestry Inference

    PubMed Central

    Shringarpure, Suyash; Xing, Eric P.

    2014-01-01

    Population stratification is an important task in genetic analyses. It provides information about the ancestry of individuals and can be an important confounder in genome-wide association studies. Public genotyping projects have made a large number of datasets available for study. However, practical constraints dictate that of a geographical/ethnic population, only a small number of individuals are genotyped. The resulting data are a sample from the entire population. If the distribution of sample sizes is not representative of the populations being sampled, the accuracy of population stratification analyses of the data could be affected. We attempt to understand the effect of biased sampling on the accuracy of population structure analysis and individual ancestry recovery. We examined two commonly used methods for analyses of such datasets, ADMIXTURE and EIGENSOFT, and found that the accuracy of recovery of population structure is affected to a large extent by the sample used for analysis and how representative it is of the underlying populations. Using simulated data and real genotype data from cattle, we show that sample selection bias can affect the results of population structure analyses. We develop a mathematical framework for sample selection bias in models for population structure and also proposed a correction for sample selection bias using auxiliary information about the sample. We demonstrate that such a correction is effective in practice using simulated and real data. PMID:24637351

  6. The precision and accuracy of iterative and non-iterative methods of photopeak integration in activation analysis, with particular reference to the analysis of multiplets

    USGS Publications Warehouse

    Baedecker, P.A.

    1977-01-01

    The relative precisions obtainable using two digital methods, and three iterative least squares fitting procedures of photopeak integration have been compared empirically using 12 replicate counts of a test sample with 14 photopeaks of varying intensity. The accuracy by which the various iterative fitting methods could analyse synthetic doublets has also been evaluated, and compared with a simple non-iterative approach. ?? 1977 Akade??miai Kiado??.

  7. Accuracy and precision of a custom camera-based system for 2D and 3D motion tracking during speech and nonspeech motor tasks

    PubMed Central

    Feng, Yongqiang; Max, Ludo

    2014-01-01

    Purpose Studying normal or disordered motor control requires accurate motion tracking of the effectors (e.g., orofacial structures). The cost of electromagnetic, optoelectronic, and ultrasound systems is prohibitive for many laboratories, and limits clinical applications. For external movements (lips, jaw), video-based systems may be a viable alternative, provided that they offer high temporal resolution and sub-millimeter accuracy. Method We examined the accuracy and precision of 2D and 3D data recorded with a system that combines consumer-grade digital cameras capturing 60, 120, or 240 frames per second (fps), retro-reflective markers, commercially-available computer software (APAS, Ariel Dynamics), and a custom calibration device. Results Overall mean error (RMSE) across tests was 0.15 mm for static tracking and 0.26 mm for dynamic tracking, with corresponding precision (SD) values of 0.11 and 0.19 mm, respectively. The effect of frame rate varied across conditions, but, generally, accuracy was reduced at 240 fps. The effect of marker size (3 vs. 6 mm diameter) was negligible at all frame rates for both 2D and 3D data. Conclusion Motion tracking with consumer-grade digital cameras and the APAS software can achieve sub-millimeter accuracy at frame rates that are appropriate for kinematic analyses of lip/jaw movements for both research and clinical purposes. PMID:24686484

  8. Accuracy and precision of a custom camera-based system for 2-d and 3-d motion tracking during speech and nonspeech motor tasks.

    PubMed

    Feng, Yongqiang; Max, Ludo

    2014-04-01

    PURPOSE Studying normal or disordered motor control requires accurate motion tracking of the effectors (e.g., orofacial structures). The cost of electromagnetic, optoelectronic, and ultrasound systems is prohibitive for many laboratories and limits clinical applications. For external movements (lips, jaw), video-based systems may be a viable alternative, provided that they offer high temporal resolution and submillimeter accuracy. METHOD The authors examined the accuracy and precision of 2-D and 3-D data recorded with a system that combines consumer-grade digital cameras capturing 60, 120, or 240 frames per second (fps), retro-reflective markers, commercially available computer software (APAS, Ariel Dynamics), and a custom calibration device. RESULTS Overall root-mean-square error (RMSE) across tests was 0.15 mm for static tracking and 0.26 mm for dynamic tracking, with corresponding precision (SD) values of 0.11 and 0.19 mm, respectively. The effect of frame rate varied across conditions, but, generally, accuracy was reduced at 240 fps. The effect of marker size (3- vs. 6-mm diameter) was negligible at all frame rates for both 2-D and 3-D data. CONCLUSION Motion tracking with consumer-grade digital cameras and the APAS software can achieve submillimeter accuracy at frame rates that are appropriate for kinematic analyses of lip/jaw movements for both research and clinical purposes. PMID:24686484

  9. Striatal indirect pathway contributes to selection accuracy of learned motor actions.

    PubMed

    Nishizawa, Kayo; Fukabori, Ryoji; Okada, Kana; Kai, Nobuyuki; Uchigashima, Motokazu; Watanabe, Masahiko; Shiota, Akira; Ueda, Masatsugu; Tsutsui, Yuji; Kobayashi, Kazuto

    2012-09-26

    The dorsal striatum, which contains the dorsolateral striatum (DLS) and dorsomedial striatum (DMS), integrates the acquisition and implementation of instrumental learning in cooperation with the nucleus accumbens (NAc). The dorsal striatum regulates the basal ganglia circuitry through direct and indirect pathways. The mechanism by which these pathways mediate the learning processes of instrumental actions remains unclear. We investigated how the striatal indirect (striatopallidal) pathway arising from the DLS contributes to the performance of conditional discrimination. Immunotoxin targeting of the striatal neuronal type containing dopamine D(2) receptor in the DLS of transgenic rats resulted in selective, efficient elimination of the striatopallidal pathway. This elimination impaired the accuracy of response selection in a two-choice reaction time task dependent on different auditory stimuli. The impaired response selection was elicited early in the test sessions and was gradually restored as the sessions continued. The restoration from the deficits in auditory discrimination was prevented by excitotoxic lesion of the NAc but not by that of the DMS. In addition, lesion of the DLS mimicked the behavioral consequence of the striatopallidal removal at the early stage of test sessions of discriminative performance. Our results demonstrate that the DLS-derived striatopallidal pathway plays an essential role in the execution of conditional discrimination, showing its contribution to the control of selection accuracy of learned motor responses. The results also suggest the presence of a mechanism that compensates for the learning deficits during the repetitive sessions, at least partly, demanding accumbal function. PMID:23015433

  10. Effects Of Touch Key Size And Separation On Menu-Selection Accuracy

    NASA Astrophysics Data System (ADS)

    Beaton, Robert J.; Welman, Novia

    1985-05-01

    Two experiments were performed to assess the effects of touch key design parameters on menu-selection error rates, The first experiment determined that the optimal design consisted of touch keys 10,16-mm high, either 10,16- or 20, 2- wide, and separated vertically by less than 10,16 mm, The second experiment extended the investigation by including the effects of viewing angle, These latter results replicated the first experiment, but also favored the 2012-mm wide key for off-axis viewing conditions, In both experiments, the horizontal separation between touch keys did not affect menu-selection accuracy; however, subjective selection favored a 20.32-mm horizontal separation.

  11. Accuracy of genomic selection in barley breeding programs: a simulation study based on the real SNP data

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The aim of this study was to compare the accuracy of genomic selection (i.e., selection based on genome-wide markers) to phenotypic selection through simulations based on real barley SNPs data (1325 SNPs x 863 breeding lines). We simulated 100 QTL at randomly selected SNPs, which were dropped from t...

  12. Decision precision or holistic heuristic?: Insights on on-site selection of student nurses and midwives.

    PubMed

    Macduff, Colin; Stephen, Audrey; Taylor, Ruth

    2016-01-01

    Concerns about quality of care delivery in the UK have led to more scrutiny of criteria and methods for the selection of student nurses. However few substantive research studies of on-site selection processes exist. This study elicited and interpreted perspectives on interviewing processes and related decision making involved in on-site selection of student nurses and midwives. Individual and focus group interviews were undertaken with 36 lecturers, 5 clinical staff and 72 students from seven Scottish universities. Enquiry focused primarily on interviewing of candidates on-site. Qualitative content analysis was used as a primary strategy, followed by in-depth thematic analysis. Students had very mixed experiences of interview processes. Staff typically took into account a range of candidate attributes that they valued in order to achieve holistic assessments. These included: interpersonal skills, team working, confidence, problem-solving, aptitude for caring, motivations, and commitment. Staff had mixed views of the validity and reliability of interview processes. A holistic heuristic for overall decision making predominated over belief in the precision of, and evidence base for, particular attribute measurement processes. While the development of measurement tools for particular attributes continues apace, tension between holism and precision is likely to persist within on-site selection procedures. PMID:26213147

  13. Comparative accuracy of the Albedo, transmission and absorption for selected radiative transfer approximations

    NASA Technical Reports Server (NTRS)

    King, M. D.; HARSHVARDHAN

    1986-01-01

    Illustrations of both the relative and absolute accuracy of eight different radiative transfer approximations as a function of optical thickness, solar zenith angle and single scattering albedo are given. Computational results for the plane albedo, total transmission and fractional absorption were obtained for plane-parallel atmospheres composed of cloud particles. These computations, which were obtained using the doubling method, are compared with comparable results obtained using selected radiative transfer approximations. Comparisons were made between asymptotic theory for thick layers and the following widely used two stream approximations: Coakley-Chylek's models 1 and 2, Meador-Weaver, Eddington, delta-Eddington, PIFM and delta-discrete ordinates.

  14. Exploiting microRNA Specificity and Selectivity: Paving a Sustainable Path Towards Precision Medicine.

    PubMed

    Santulli, Gaetano

    2015-01-01

    In his State of the Union address before both chambers of the US Congress, President Barack Obama called for increased investment in US infrastructure and research and announced the launch of a new Precision Medicine Initiative, aiming to accelerate biomedical discovery. Due to their well-established selectivity and specificity, microRNAs can represent a useful tool, both in diagnosis and therapy, in forging the path towards the achievement of precision medicine. This introductory chapter represents a guide for the Reader in examining the functional roles of microRNAs in the most diverse aspects of clinical practice, which will be explored in this third volume of the microRNA trilogy. PMID:26663175

  15. [Analysis on the accuracy of simple selection method of Fengshi (GB 31)].

    PubMed

    Li, Zhixing; Zhang, Haihua; Li, Suhe

    2015-12-01

    To explore the accuracy of simple selection method of Fengshi (GB 31). Through the study of the ancient and modern data,the analysis and integration of the acupuncture books,the comparison of the locations of Fengshi (GB 31) by doctors from all dynasties and the integration of modern anatomia, the modern simple selection method of Fengshi (GB 31) is definite, which is the same as the traditional way. It is believed that the simple selec tion method is in accord with the human-oriented thought of TCM. Treatment by acupoints should be based on the emerging nature and the individual difference of patients. Also, it is proposed that Fengshi (GB 31) should be located through the integration between the simple method and body surface anatomical mark. PMID:26964185

  16. Clustering and training set selection methods for improving the accuracy of quantitative laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Anderson, Ryan B.; Bell, James F., III; Wiens, Roger C.; Morris, Richard V.; Clegg, Samuel M.

    2012-04-01

    We investigated five clustering and training set selection methods to improve the accuracy of quantitative chemical analysis of geologic samples by laser induced breakdown spectroscopy (LIBS) using partial least squares (PLS) regression. The LIBS spectra were previously acquired for 195 rock slabs and 31 pressed powder geostandards under 7 Torr CO2 at a stand-off distance of 7 m at 17 mJ per pulse to simulate the operational conditions of the ChemCam LIBS instrument on the Mars Science Laboratory Curiosity rover. The clustering and training set selection methods, which do not require prior knowledge of the chemical composition of the test-set samples, are based on grouping similar spectra and selecting appropriate training spectra for the partial least squares (PLS2) model. These methods were: (1) hierarchical clustering of the full set of training spectra and selection of a subset for use in training; (2) k-means clustering of all spectra and generation of PLS2 models based on the training samples within each cluster; (3) iterative use of PLS2 to predict sample composition and k-means clustering of the predicted compositions to subdivide the groups of spectra; (4) soft independent modeling of class analogy (SIMCA) classification of spectra, and generation of PLS2 models based on the training samples within each class; (5) use of Bayesian information criteria (BIC) to determine an optimal number of clusters and generation of PLS2 models based on the training samples within each cluster. The iterative method and the k-means method using 5 clusters showed the best performance, improving the absolute quadrature root mean squared error (RMSE) by ~ 3 wt.%. The statistical significance of these improvements was ~ 85%. Our results show that although clustering methods can modestly improve results, a large and diverse training set is the most reliable way to improve the accuracy of quantitative LIBS. In particular, additional sulfate standards and specifically fabricated

  17. Optimizing the accuracy and precision of the single-pulse Laue technique for synchrotron photo-crystallography

    SciTech Connect

    Kaminski, Radoslaw; Graber, Timothy; Benedict, Jason B.; Henning, Robert; Chen, Yu-Sheng; Scheins, Stephan; Messerschmidt, Marc; Coppens, Philip

    2010-06-24

    The accuracy that can be achieved in single-pulse pump-probe Laue experiments is discussed. It is shown that with careful tuning of the experimental conditions a reproducibility of the intensity ratios of equivalent intensities obtained in different measurements of 3-4% can be achieved. The single-pulse experiments maximize the time resolution that can be achieved and, unlike stroboscopic techniques in which the pump-probe cycle is rapidly repeated, minimize the temperature increase due to the laser exposure of the sample.

  18. Optimizing the accuracy and precision of the single-pulse Laue technique for synchrotron photo-crystallography

    PubMed Central

    Kamiński, Radosław; Graber, Timothy; Benedict, Jason B.; Henning, Robert; Chen, Yu-Sheng; Scheins, Stephan; Messerschmidt, Marc; Coppens, Philip

    2010-01-01

    The accuracy that can be achieved in single-pulse pump-probe Laue experiments is discussed. It is shown that with careful tuning of the experimental conditions a reproducibility of the intensity ratios of equivalent intensities obtained in different measurements of 3–4% can be achieved. The single-pulse experiments maximize the time resolution that can be achieved and, unlike stroboscopic techniques in which the pump-probe cycle is rapidly repeated, minimize the temperature increase due to the laser exposure of the sample. PMID:20567080

  19. Accuracy of genomic selection methods in a standard data set of loblolly pine (Pinus taeda L.).

    PubMed

    Resende, M F R; Muñoz, P; Resende, M D V; Garrick, D J; Fernando, R L; Davis, J M; Jokela, E J; Martin, T A; Peter, G F; Kirst, M

    2012-04-01

    Genomic selection can increase genetic gain per generation through early selection. Genomic selection is expected to be particularly valuable for traits that are costly to phenotype and expressed late in the life cycle of long-lived species. Alternative approaches to genomic selection prediction models may perform differently for traits with distinct genetic properties. Here the performance of four different original methods of genomic selection that differ with respect to assumptions regarding distribution of marker effects, including (i) ridge regression-best linear unbiased prediction (RR-BLUP), (ii) Bayes A, (iii) Bayes Cπ, and (iv) Bayesian LASSO are presented. In addition, a modified RR-BLUP (RR-BLUP B) that utilizes a selected subset of markers was evaluated. The accuracy of these methods was compared across 17 traits with distinct heritabilities and genetic architectures, including growth, development, and disease-resistance properties, measured in a Pinus taeda (loblolly pine) training population of 951 individuals genotyped with 4853 SNPs. The predictive ability of the methods was evaluated using a 10-fold, cross-validation approach, and differed only marginally for most method/trait combinations. Interestingly, for fusiform rust disease-resistance traits, Bayes Cπ, Bayes A, and RR-BLUB B had higher predictive ability than RR-BLUP and Bayesian LASSO. Fusiform rust is controlled by few genes of large effect. A limitation of RR-BLUP is the assumption of equal contribution of all markers to the observed variation. However, RR-BLUP B performed equally well as the Bayesian approaches.The genotypic and phenotypic data used in this study are publically available for comparative analysis of genomic selection prediction models. PMID:22271763

  20. Accuracy and precision of end-expiratory lung-volume measurements by automated nitrogen washout/washin technique in patients with acute respiratory distress syndrome

    PubMed Central

    2011-01-01

    Introduction End-expiratory lung volume (EELV) is decreased in acute respiratory distress syndrome (ARDS), and bedside EELV measurement may help to set positive end-expiratory pressure (PEEP). Nitrogen washout/washin for EELV measurement is available at the bedside, but assessments of accuracy and precision in real-life conditions are scant. Our purpose was to (a) assess EELV measurement precision in ARDS patients at two PEEP levels (three pairs of measurements), and (b) compare the changes (Δ) induced by PEEP for total EELV with the PEEP-induced changes in lung volume above functional residual capacity measured with passive spirometry (ΔPEEP-volume). The minimal predicted increase in lung volume was calculated from compliance at low PEEP and ΔPEEP to ensure the validity of lung-volume changes. Methods Thirty-four patients with ARDS were prospectively included in five university-hospital intensive care units. ΔEELV and ΔPEEP volumes were compared between 6 and 15 cm H2O of PEEP. Results After exclusion of three patients, variability of the nitrogen technique was less than 4%, and the largest difference between measurements was 81 ± 64 ml. ΔEELV and ΔPEEP-volume were only weakly correlated (r2 = 0.47); 95% confidence interval limits, -414 to 608 ml). In four patients with the highest PEEP (≥ 16 cm H2O), ΔEELV was lower than the minimal predicted increase in lung volume, suggesting flawed measurements, possibly due to leaks. Excluding those from the analysis markedly strengthened the correlation between ΔEELV and ΔPEEP volume (r2 = 0.80). Conclusions In most patients, the EELV technique has good reproducibility and accuracy, even at high PEEP. At high pressures, its accuracy may be limited in case of leaks. The minimal predicted increase in lung volume may help to check for accuracy. PMID:22166727

  1. Progress integrating ID-TIMS U-Pb geochronology with accessory mineral geochemistry: towards better accuracy and higher precision time

    NASA Astrophysics Data System (ADS)

    Schoene, B.; Samperton, K. M.; Crowley, J. L.; Cottle, J. M.

    2012-12-01

    It is increasingly common that hand samples of plutonic and volcanic rocks contain zircon with dates that span between zero and >100 ka. This recognition comes from the increased application of U-series geochronology on young volcanic rocks and the increased precision to better than 0.1% on single zircons by the U-Pb ID-TIMS method. It has thus become more difficult to interpret such complicated datasets in terms of ashbed eruption or magma emplacement, which are critical constraints for geochronologic applications ranging from biotic evolution and the stratigraphic record to magmatic and metamorphic processes in orogenic belts. It is important, therefore, to develop methods that aid in interpreting which minerals, if any, date the targeted process. One promising tactic is to better integrate accessory mineral geochemistry with high-precision ID-TIMS U-Pb geochronology. These dual constraints can 1) identify cogenetic populations of minerals, and 2) record magmatic or metamorphic fluid evolution through time. Goal (1) has been widely sought with in situ geochronology and geochemical analysis but is limited by low-precision dates. Recent work has attempted to bridge this gap by retrieving the typically discarded elution from ion exchange chemistry that precedes ID-TIMS U-Pb geochronology and analyzing it by ICP-MS (U-Pb TIMS-TEA). The result integrates geochemistry and high-precision geochronology from the exact same volume of material. The limitation of this method is the relatively coarse spatial resolution compared to in situ techniques, and thus averages potentially complicated trace element profiles through single minerals or mineral fragments. In continued work, we test the effect of this on zircon by beginning with CL imaging to reveal internal zonation and growth histories. This is followed by in situ LA-ICPMS trace element transects of imaged grains to reveal internal geochemical zonation. The same grains are then removed from grain-mount, fragmented, and

  2. Technical note: precision and accuracy of in vitro digestion of neutral detergent fiber and predicted net energy of lactation content of fibrous feeds.

    PubMed

    Spanghero, M; Berzaghi, P; Fortina, R; Masoero, F; Rapetti, L; Zanfi, C; Tassone, S; Gallo, A; Colombini, S; Ferlito, J C

    2010-10-01

    The objective of this study was to test the precision and agreement with in situ data (accuracy) of neutral detergent fiber degradability (NDFD) obtained with the rotating jar in vitro system (Daisy(II) incubator, Ankom Technology, Fairport, NY). Moreover, the precision of the chemical assays requested by the National Research Council (2001) for feed energy calculations and the estimated net energy of lactation contents were evaluated. Precision was measured as standard deviation (SD) of reproducibility (S(R)) and repeatability (S(r)) (between- and within-laboratory variability, respectively), which were expressed as coefficients of variation (SD/mean × 100, S(R) and S(r), respectively). Ten fibrous feed samples (alfalfa dehydrated, alfalfa hay, corn cob, corn silage, distillers grains, meadow hay, ryegrass hay, soy hulls, wheat bran, and wheat straw) were analyzed by 5 laboratories. Analyses of dry matter (DM), ash, crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) had satisfactory S(r), from 0.4 to 2.9%, and S(R), from 0.7 to 6.2%, with the exception of ether extract (EE) and CP bound to NDF or ADF. Extending the fermentation time from 30 to 48 h increased the NDFD values (from 42 to 54% on average across all tested feeds) and improved the NDFD precision, in terms of both S(r) (12 and 7% for 30 and 48 h, respectively) and S(R) (17 and 10% for 30 and 48 h, respectively). The net energy for lactation (NE(L)) predicted from 48-h incubation NDFD data approximated well the tabulated National Research Council (2001) values for several feeds, and the improvement in NDFD precision given by longer incubations (48 vs. 30 h) also improved precision of the NE(L) estimates from 11 to 8%. Data obtained from the rotating jar in vitro technique compared well with in situ data. In conclusion, the adoption of a 48-h period of incubation improves repeatability and reproducibility of NDFD and accuracy and reproducibility of the associated calculated

  3. Precise Muscle Selection Using Dynamic Polyelectromyography for Treatment of Post-stroke Dystonia: A Case Report

    PubMed Central

    2016-01-01

    Dystonia has a wide range of causes, but treatment of dystonia is limited to minimizing the symptoms as there is yet no successful treatment for its cause. One of the optimal treatment methods for dystonia is chemodenervation using botulinum toxin type A (BTX-A), alcohol injection, etc., but its success depends on how precisely the dystonic muscle is selected. Here, we reported a successful experience in a 49-year-old post-stroke female patient who showed paroxysmal repetitive contractions involving the right leg, which may be of dystonic nature. BTX-A and alcohol were injected into the muscles which were identified by dynamic polyelectromyography. After injection, the dystonic muscle spasm, cramping pain, and the range of motion of the affected lower limb improved markedly, and she was able to walk independently indoors. In such a case, dynamic polyelectromyography may be a useful method for selecting the dominant dystonic muscles. PMID:27446795

  4. Maskless deposition technique for the physical vapor deposition of thin film and multilayer coatings with subnanometer precision and accuracy

    DOEpatents

    Vernon, Stephen P.; Ceglio, Natale M.

    2000-01-01

    The invention is a method for the production of axially symmetric, graded and ungraded thickness thin film and multilayer coatings that avoids the use of apertures or masks to tailor the deposition profile. A motional averaging scheme permits the deposition of uniform thickness coatings independent of the substrate radius. Coating uniformity results from an exact cancellation of substrate radius dependent terms, which occurs when the substrate moves at constant velocity. If the substrate is allowed to accelerate over the source, arbitrary coating profiles can be generated through appropriate selection and control of the substrate center of mass equation of motion. The radial symmetry of the coating profile is an artifact produced by orbiting the substrate about its center of mass; other distributions are obtained by selecting another rotation axis. Consequently there is a direct mapping between the coating thickness and substrate equation of motion which can be used to tailor the coating profile without the use of masks and apertures.

  5. Leaf vein length per unit area is not intrinsically dependent on image magnification: avoiding measurement artifacts for accuracy and precision.

    PubMed

    Sack, Lawren; Caringella, Marissa; Scoffoni, Christine; Mason, Chase; Rawls, Michael; Markesteijn, Lars; Poorter, Lourens

    2014-10-01

    Leaf vein length per unit leaf area (VLA; also known as vein density) is an important determinant of water and sugar transport, photosynthetic function, and biomechanical support. A range of software methods are in use to visualize and measure vein systems in cleared leaf images; typically, users locate veins by digital tracing, but recent articles introduced software by which users can locate veins using thresholding (i.e. based on the contrasting of veins in the image). Based on the use of this method, a recent study argued against the existence of a fixed VLA value for a given leaf, proposing instead that VLA increases with the magnification of the image due to intrinsic properties of the vein system, and recommended that future measurements use a common, low image magnification for measurements. We tested these claims with new measurements using the software LEAFGUI in comparison with digital tracing using ImageJ software. We found that the apparent increase of VLA with magnification was an artifact of (1) using low-quality and low-magnification images and (2) errors in the algorithms of LEAFGUI. Given the use of images of sufficient magnification and quality, and analysis with error-free software, the VLA can be measured precisely and accurately. These findings point to important principles for improving the quantity and quality of important information gathered from leaf vein systems. PMID:25096977

  6. Accuracy and Precision in the Southern Hemisphere Additional Ozonesondes (SHADOZ) Dataset in Light of the JOSIE-2000 Results

    NASA Technical Reports Server (NTRS)

    Witte, Jacquelyn C.; Thompson, Anne M.; Schmidlin, F. J.; Oltmans, S. J.; Smit, H. G. J.

    2004-01-01

    Since 1998 the Southern Hemisphere ADditional OZonesondes (SHADOZ) project has provided over 2000 ozone profiles over eleven southern hemisphere tropical and subtropical stations. Balloon-borne electrochemical concentration cell (ECC) ozonesondes are used to measure ozone. The data are archived at: &ttp://croc.gsfc.nasa.gov/shadoz>. In analysis of ozonesonde imprecision within the SHADOZ dataset, Thompson et al. [JGR, 108,8238,20031 we pointed out that variations in ozonesonde technique (sensor solution strength, instrument manufacturer, data processing) could lead to station-to-station biases within the SHADOZ dataset. Imprecisions and accuracy in the SHADOZ dataset are examined in light of new data. First, SHADOZ total ozone column amounts are compared to version 8 TOMS (2004 release). As for TOMS version 7, satellite total ozone is usually higher than the integrated column amount from the sounding. Discrepancies between the sonde and satellite datasets decline two percentage points on average, compared to version 7 TOMS offsets. Second, the SHADOZ station data are compared to results of chamber simulations (JOSE-2000, Juelich Ozonesonde Intercomparison Experiment) in which the various SHADOZ techniques were evaluated. The range of JOSE column deviations from a standard instrument (-10%) in the chamber resembles that of the SHADOZ station data. It appears that some systematic variations in the SHADOZ ozone record are accounted for by differences in solution strength, data processing and instrument type (manufacturer).

  7. Development of new methods in modern selective organic synthesis: preparation of functionalized molecules with atomic precision

    NASA Astrophysics Data System (ADS)

    Ananikov, V. P.; Khemchyan, L. L.; Ivanova, Yu V.; Bukhtiyarov, V. I.; Sorokin, A. M.; Prosvirin, I. P.; Vatsadze, S. Z.; Medved'ko, A. V.; Nuriev, V. N.; Dilman, A. D.; Levin, V. V.; Koptyug, I. V.; Kovtunov, K. V.; Zhivonitko, V. V.; Likholobov, V. A.; Romanenko, A. V.; Simonov, P. A.; Nenajdenko, V. G.; Shmatova, O. I.; Muzalevskiy, V. M.; Nechaev, M. S.; Asachenko, A. F.; Morozov, O. S.; Dzhevakov, P. B.; Osipov, S. N.; Vorobyeva, D. V.; Topchiy, M. A.; Zotova, M. A.; Ponomarenko, S. A.; Borshchev, O. V.; Luponosov, Yu N.; Rempel, A. A.; Valeeva, A. A.; Stakheev, A. Yu; Turova, O. V.; Mashkovsky, I. S.; Sysolyatin, S. V.; Malykhin, V. V.; Bukhtiyarova, G. A.; Terent'ev, A. O.; Krylov, I. B.

    2014-10-01

    The challenges of the modern society and the growing demand of high-technology sectors of industrial production bring about a new phase in the development of organic synthesis. A cutting edge of modern synthetic methods is introduction of functional groups and more complex structural units into organic molecules with unprecedented control over the course of chemical transformation. Analysis of the state-of-the-art achievements in selective organic synthesis indicates the appearance of a new trend — the synthesis of organic molecules, biologically active compounds, pharmaceutical substances and smart materials with absolute selectivity. Most advanced approaches to organic synthesis anticipated in the near future can be defined as 'atomic precision' in chemical reactions. The present review considers selective methods of organic synthesis suitable for transformation of complex functionalized molecules under mild conditions. Selected key trends in the modern organic synthesis are considered including the preparation of organofluorine compounds, catalytic cross-coupling and oxidative cross-coupling reactions, atom-economic addition reactions, methathesis processes, oxidation and reduction reactions, synthesis of heterocyclic compounds, design of new homogeneous and heterogeneous catalytic systems, application of photocatalysis, scaling up synthetic procedures to industrial level and development of new approaches to investigation of mechanisms of catalytic reactions. The bibliography includes 840 references.

  8. EFFECT OF RADIATION DOSE LEVEL ON ACCURACY AND PRECISION OF MANUAL SIZE MEASUREMENTS IN CHEST TOMOSYNTHESIS EVALUATED USING SIMULATED PULMONARY NODULES

    PubMed Central

    Söderman, Christina; Johnsson, Åse Allansdotter; Vikgren, Jenny; Norrlund, Rauni Rossi; Molnar, David; Svalkvist, Angelica; Månsson, Lars Gunnar; Båth, Magnus

    2016-01-01

    The aim of the present study was to investigate the dependency of the accuracy and precision of nodule diameter measurements on the radiation dose level in chest tomosynthesis. Artificial ellipsoid-shaped nodules with known dimensions were inserted in clinical chest tomosynthesis images. Noise was added to the images in order to simulate radiation dose levels corresponding to effective doses for a standard-sized patient of 0.06 and 0.04 mSv. These levels were compared with the original dose level, corresponding to an effective dose of 0.12 mSv for a standard-sized patient. Four thoracic radiologists measured the longest diameter of the nodules. The study was restricted to nodules located in high-dose areas of the tomosynthesis projection radiographs. A significant decrease of the measurement accuracy and intraobserver variability was seen for the lowest dose level for a subset of the observers. No significant effect of dose level on the interobserver variability was found. The number of non-measurable small nodules (≤5 mm) was higher for the two lowest dose levels compared with the original dose level. In conclusion, for pulmonary nodules at positions in the lung corresponding to locations in high-dose areas of the projection radiographs, using a radiation dose level resulting in an effective dose of 0.06 mSv to a standard-sized patient may be possible in chest tomosynthesis without affecting the accuracy and precision of nodule diameter measurements to any large extent. However, an increasing number of non-measurable small nodules (≤5 mm) with decreasing radiation dose may raise some concerns regarding an applied general dose reduction for chest tomosynthesis examinations in the clinical praxis. PMID:26994093

  9. EFFECT OF RADIATION DOSE LEVEL ON ACCURACY AND PRECISION OF MANUAL SIZE MEASUREMENTS IN CHEST TOMOSYNTHESIS EVALUATED USING SIMULATED PULMONARY NODULES.

    PubMed

    Söderman, Christina; Johnsson, Åse Allansdotter; Vikgren, Jenny; Norrlund, Rauni Rossi; Molnar, David; Svalkvist, Angelica; Månsson, Lars Gunnar; Båth, Magnus

    2016-06-01

    The aim of the present study was to investigate the dependency of the accuracy and precision of nodule diameter measurements on the radiation dose level in chest tomosynthesis. Artificial ellipsoid-shaped nodules with known dimensions were inserted in clinical chest tomosynthesis images. Noise was added to the images in order to simulate radiation dose levels corresponding to effective doses for a standard-sized patient of 0.06 and 0.04 mSv. These levels were compared with the original dose level, corresponding to an effective dose of 0.12 mSv for a standard-sized patient. Four thoracic radiologists measured the longest diameter of the nodules. The study was restricted to nodules located in high-dose areas of the tomosynthesis projection radiographs. A significant decrease of the measurement accuracy and intraobserver variability was seen for the lowest dose level for a subset of the observers. No significant effect of dose level on the interobserver variability was found. The number of non-measurable small nodules (≤5 mm) was higher for the two lowest dose levels compared with the original dose level. In conclusion, for pulmonary nodules at positions in the lung corresponding to locations in high-dose areas of the projection radiographs, using a radiation dose level resulting in an effective dose of 0.06 mSv to a standard-sized patient may be possible in chest tomosynthesis without affecting the accuracy and precision of nodule diameter measurements to any large extent. However, an increasing number of non-measurable small nodules (≤5 mm) with decreasing radiation dose may raise some concerns regarding an applied general dose reduction for chest tomosynthesis examinations in the clinical praxis. PMID:26994093

  10. Balancing accuracy and efficiency in selecting vibrational configuration interaction basis states using vibrational perturbation theory

    NASA Astrophysics Data System (ADS)

    Sibaev, Marat; Crittenden, Deborah L.

    2016-08-01

    This work describes the benchmarking of a vibrational configuration interaction (VCI) algorithm that combines the favourable computational scaling of VPT2 with the algorithmic robustness of VCI, in which VCI basis states are selected according to the magnitude of their contribution to the VPT2 energy, for the ground state and fundamental excited states. Particularly novel aspects of this work include: expanding the potential to 6th order in normal mode coordinates, using a double-iterative procedure in which configuration selection and VCI wavefunction updates are performed iteratively (micro-iterations) over a range of screening threshold values (macro-iterations), and characterisation of computational resource requirements as a function of molecular size. Computational costs may be further reduced by a priori truncation of the VCI wavefunction according to maximum extent of mode coupling, along with discarding negligible force constants and VCI matrix elements, and formulating the wavefunction in a harmonic oscillator product basis to enable efficient evaluation of VCI matrix elements. Combining these strategies, we define a series of screening procedures that scale as O ( Nmode 6 ) - O ( Nmode 9 ) in run time and O ( Nmode 6 ) - O ( Nmode 7 ) in memory, depending on the desired level of accuracy. Our open-source code is freely available for download from http://www.sourceforge.net/projects/pyvci-vpt2.

  11. The Effects of Various Item Selection Methods on the Classification Accuracy and Classification Consistency of Criterion-Referenced Instruments.

    ERIC Educational Resources Information Center

    Smith, Douglas U.

    This study examined the effects of certain item selection methods on the classification accuracy and classification consistency of criterion-referenced instruments. Three item response data sets, representing varying situations of instructional effectiveness, were simulated. Five methods of item selection were then applied to each data set for the…

  12. Factors influence accuracy and precision in the determination of the elemental composition of defense waste glass by ICP-emission spectrometry

    SciTech Connect

    Goode, S.R.

    1995-12-31

    The influence of instrumental factors on the accuracy and precision of the determination of the composition of glass and glass feedstock is presented. In addition, the effects of different methods of sampling, dissolution methods, and standardization procedures and their effect on the quality of the chemical analysis will also be presented. The target glass simulates the material that will be prepared by the vitrification of highly radioactive liquid defense waste. The glass and feedstock streams must be well characterized to ensure a durable glass; current models estimate a 100,000 year lifetime. The elemental composition will be determined by ICP-emission spectrometry with radiation exposure issues requiring a multielement analysis for all constituents, on a single analytical sample, using compromise conditions.

  13. Approaches for achieving long-term accuracy and precision of δ18O and δ2H for waters analyzed using laser absorption spectrometers.

    PubMed

    Wassenaar, Leonard I; Coplen, Tyler B; Aggarwal, Pradeep K

    2014-01-21

    The measurement of δ(2)H and δ(18)O in water samples by laser absorption spectroscopy (LAS) are adopted increasingly in hydrologic and environmental studies. Although LAS instrumentation is easy to use, its incorporation into laboratory operations is not as easy, owing to extensive offline data manipulation required for outlier detection, derivation and application of algorithms to correct for between-sample memory, correcting for linear and nonlinear instrumental drift, VSMOW-SLAP scale normalization, and in maintaining long-term QA/QC audits. Here we propose a series of standardized water-isotope LAS performance tests and routine sample analysis templates, recommended procedural guidelines, and new data processing software (LIMS for Lasers) that altogether enables new and current LAS users to achieve and sustain long-term δ(2)H and δ(18)O accuracy and precision for these important isotopic assays. PMID:24328223

  14. Increased prediction accuracy in wheat breeding trials using a marker × environment interaction genomic selection model.

    PubMed

    Lopez-Cruz, Marco; Crossa, Jose; Bonnett, David; Dreisigacker, Susanne; Poland, Jesse; Jannink, Jean-Luc; Singh, Ravi P; Autrique, Enrique; de los Campos, Gustavo

    2015-04-01

    Genomic selection (GS) models use genome-wide genetic information to predict genetic values of candidates of selection. Originally, these models were developed without considering genotype × environment interaction(G×E). Several authors have proposed extensions of the single-environment GS model that accommodate G×E using either covariance functions or environmental covariates. In this study, we model G×E using a marker × environment interaction (M×E) GS model; the approach is conceptually simple and can be implemented with existing GS software. We discuss how the model can be implemented by using an explicit regression of phenotypes on markers or using co-variance structures (a genomic best linear unbiased prediction-type model). We used the M×E model to analyze three CIMMYT wheat data sets (W1, W2, and W3), where more than 1000 lines were genotyped using genotyping-by-sequencing and evaluated at CIMMYT's research station in Ciudad Obregon, Mexico, under simulated environmental conditions that covered different irrigation levels, sowing dates and planting systems. We compared the M×E model with a stratified (i.e., within-environment) analysis and with a standard (across-environment) GS model that assumes that effects are constant across environments (i.e., ignoring G×E). The prediction accuracy of the M×E model was substantially greater of that of an across-environment analysis that ignores G×E. Depending on the prediction problem, the M×E model had either similar or greater levels of prediction accuracy than the stratified analyses. The M×E model decomposes marker effects and genomic values into components that are stable across environments (main effects) and others that are environment-specific (interactions). Therefore, in principle, the interaction model could shed light over which variants have effects that are stable across environments and which ones are responsible for G×E. The data set and the scripts required to reproduce the analysis are

  15. Increased Prediction Accuracy in Wheat Breeding Trials Using a Marker × Environment Interaction Genomic Selection Model

    PubMed Central

    Lopez-Cruz, Marco; Crossa, Jose; Bonnett, David; Dreisigacker, Susanne; Poland, Jesse; Jannink, Jean-Luc; Singh, Ravi P.; Autrique, Enrique; de los Campos, Gustavo

    2015-01-01

    Genomic selection (GS) models use genome-wide genetic information to predict genetic values of candidates of selection. Originally, these models were developed without considering genotype × environment interaction(G×E). Several authors have proposed extensions of the single-environment GS model that accommodate G×E using either covariance functions or environmental covariates. In this study, we model G×E using a marker × environment interaction (M×E) GS model; the approach is conceptually simple and can be implemented with existing GS software. We discuss how the model can be implemented by using an explicit regression of phenotypes on markers or using co-variance structures (a genomic best linear unbiased prediction-type model). We used the M×E model to analyze three CIMMYT wheat data sets (W1, W2, and W3), where more than 1000 lines were genotyped using genotyping-by-sequencing and evaluated at CIMMYT’s research station in Ciudad Obregon, Mexico, under simulated environmental conditions that covered different irrigation levels, sowing dates and planting systems. We compared the M×E model with a stratified (i.e., within-environment) analysis and with a standard (across-environment) GS model that assumes that effects are constant across environments (i.e., ignoring G×E). The prediction accuracy of the M×E model was substantially greater of that of an across-environment analysis that ignores G×E. Depending on the prediction problem, the M×E model had either similar or greater levels of prediction accuracy than the stratified analyses. The M×E model decomposes marker effects and genomic values into components that are stable across environments (main effects) and others that are environment-specific (interactions). Therefore, in principle, the interaction model could shed light over which variants have effects that are stable across environments and which ones are responsible for G×E. The data set and the scripts required to reproduce the analysis

  16. Quantifying precision and accuracy of measurements of dissolved inorganic carbon stable isotopic composition using continuous-flow isotope-ratio mass spectrometry

    PubMed Central

    Waldron, Susan; Marian Scott, E; Vihermaa, Leena E; Newton, Jason

    2014-01-01

    RATIONALE We describe an analytical procedure that allows sample collection and measurement of carbon isotopic composition (δ13CV-PDB value) and dissolved inorganic carbon concentration, [DIC], in aqueous samples without further manipulation post field collection. By comparing outputs from two different mass spectrometers, we quantify with the statistical rigour uncertainty associated with the estimation of an unknown measurement. This is rarely undertaken, but it is needed to understand the significance of field data and to interpret quality assurance exercises. METHODS Immediate acidification of field samples during collection in evacuated, pre-acidified vials removed the need for toxic chemicals to inhibit continued bacterial activity that might compromise isotopic and concentration measurements. Aqueous standards mimicked the sample matrix and avoided headspace fractionation corrections. Samples were analysed using continuous-flow isotope-ratio mass spectrometry, but for low DIC concentration the mass spectrometer response could be non-linear. This had to be corrected for. RESULTS Mass spectrometer non-linearity exists. Rather than estimating precision as the repeat analysis of an internal standard, we have adopted inverse linear calibrations to quantify the precision and 95% confidence intervals (CI) of the δ13CDIC values. The response for [DIC] estimation was always linear. For 0.05–0.5 mM DIC internal standards, however, changes in mass spectrometer linearity resulted in estimations of the precision in the δ13CVPDB value of an unknown ranging from ± 0.44‰ to ± 1.33‰ (mean values) and a mean 95% CI half-width of ±1.1–3.1‰. CONCLUSIONS Mass spectrometer non-linearity should be considered in estimating uncertainty in measurement. Similarly, statistically robust estimates of precision and accuracy should also be adopted. Such estimations do not inhibit research advances: our consideration of small-scale spatial variability at two points on a

  17. Resource Allocation for Maximizing Prediction Accuracy and Genetic Gain of Genomic Selection in Plant Breeding: A Simulation Experiment

    PubMed Central

    Lorenz, Aaron J.

    2013-01-01

    Allocating resources between population size and replication affects both genetic gain through phenotypic selection and quantitative trait loci detection power and effect estimation accuracy for marker-assisted selection (MAS). It is well known that because alleles are replicated across individuals in quantitative trait loci mapping and MAS, more resources should be allocated to increasing population size compared with phenotypic selection. Genomic selection is a form of MAS using all marker information simultaneously to predict individual genetic values for complex traits and has widely been found superior to MAS. No studies have explicitly investigated how resource allocation decisions affect success of genomic selection. My objective was to study the effect of resource allocation on response to MAS and genomic selection in a single biparental population of doubled haploid lines by using computer simulation. Simulation results were compared with previously derived formulas for the calculation of prediction accuracy under different levels of heritability and population size. Response of prediction accuracy to resource allocation strategies differed between genomic selection models (ridge regression best linear unbiased prediction [RR-BLUP], BayesCπ) and multiple linear regression using ordinary least-squares estimation (OLS), leading to different optimal resource allocation choices between OLS and RR-BLUP. For OLS, it was always advantageous to maximize population size at the expense of replication, but a high degree of flexibility was observed for RR-BLUP. Prediction accuracy of doubled haploid lines included in the training set was much greater than of those excluded from the training set, so there was little benefit to phenotyping only a subset of the lines genotyped. Finally, observed prediction accuracies in the simulation compared well to calculated prediction accuracies, indicating these theoretical formulas are useful for making resource allocation

  18. Resource allocation for maximizing prediction accuracy and genetic gain of genomic selection in plant breeding: a simulation experiment.

    PubMed

    Lorenz, Aaron J

    2013-03-01

    Allocating resources between population size and replication affects both genetic gain through phenotypic selection and quantitative trait loci detection power and effect estimation accuracy for marker-assisted selection (MAS). It is well known that because alleles are replicated across individuals in quantitative trait loci mapping and MAS, more resources should be allocated to increasing population size compared with phenotypic selection. Genomic selection is a form of MAS using all marker information simultaneously to predict individual genetic values for complex traits and has widely been found superior to MAS. No studies have explicitly investigated how resource allocation decisions affect success of genomic selection. My objective was to study the effect of resource allocation on response to MAS and genomic selection in a single biparental population of doubled haploid lines by using computer simulation. Simulation results were compared with previously derived formulas for the calculation of prediction accuracy under different levels of heritability and population size. Response of prediction accuracy to resource allocation strategies differed between genomic selection models (ridge regression best linear unbiased prediction [RR-BLUP], BayesCπ) and multiple linear regression using ordinary least-squares estimation (OLS), leading to different optimal resource allocation choices between OLS and RR-BLUP. For OLS, it was always advantageous to maximize population size at the expense of replication, but a high degree of flexibility was observed for RR-BLUP. Prediction accuracy of doubled haploid lines included in the training set was much greater than of those excluded from the training set, so there was little benefit to phenotyping only a subset of the lines genotyped. Finally, observed prediction accuracies in the simulation compared well to calculated prediction accuracies, indicating these theoretical formulas are useful for making resource allocation

  19. A Study of the Accuracy and Precision Among XRF, ICP-MS, and PIXE on Trace Element Analyses of Small Water Samples

    NASA Astrophysics Data System (ADS)

    Naik, Sahil; Patnaik, Ritish; Kummari, Venkata; Phinney, Lucas; Dhoubhadel, Mangal; Jesseph, Aaron; Hoffmann, William; Verbeck, Guido; Rout, Bibhudutta

    2010-10-01

    The study aimed to compare the viability, precision, and accuracy among three popular instruments - X-ray Fluorescence (XRF), Inductively Coupled Plasma Mass Spectrometer (ICP-MS), and Particle-Induced X-ray Emission (PIXE) - used to analyze the trace elemental composition of small water samples. Ten-milliliter water samples from public tap water sources in seven different localities in India (Bangalore, Kochi, Bhubaneswar, Cuttack, Puri, Hospet, and Pipili) were prepared through filtration and dilution for proper analysis. The project speculates that the ICP-MS will give the most accurate and precise trace elemental analysis, followed by PIXE and XRF. XRF will be seen as a portable and affordable instrument that can analyze samples on-site while ICP-MS is extremely accurate, and expensive option for off-site analyses. PIXE will be deemed to be too expensive and cumbersome for on-site analysis; however, laboratories with a PIXE accelerator can use the instrument to get accurate analyses.

  20. An in-depth evaluation of accuracy and precision in Hg isotopic analysis via pneumatic nebulization and cold vapor generation multi-collector ICP-mass spectrometry.

    PubMed

    Rua-Ibarz, Ana; Bolea-Fernandez, Eduardo; Vanhaecke, Frank

    2016-01-01

    Mercury (Hg) isotopic analysis via multi-collector inductively coupled plasma (ICP)-mass spectrometry (MC-ICP-MS) can provide relevant biogeochemical information by revealing sources, pathways, and sinks of this highly toxic metal. In this work, the capabilities and limitations of two different sample introduction systems, based on pneumatic nebulization (PN) and cold vapor generation (CVG), respectively, were evaluated in the context of Hg isotopic analysis via MC-ICP-MS. The effect of (i) instrument settings and acquisition parameters, (ii) concentration of analyte element (Hg), and internal standard (Tl)-used for mass discrimination correction purposes-and (iii) different mass bias correction approaches on the accuracy and precision of Hg isotope ratio results was evaluated. The extent and stability of mass bias were assessed in a long-term study (18 months, n = 250), demonstrating a precision ≤0.006% relative standard deviation (RSD). CVG-MC-ICP-MS showed an approximately 20-fold enhancement in Hg signal intensity compared with PN-MC-ICP-MS. For CVG-MC-ICP-MS, the mass bias induced by instrumental mass discrimination was accurately corrected for by using either external correction in a sample-standard bracketing approach (SSB) or double correction, consisting of the use of Tl as internal standard in a revised version of the Russell law (Baxter approach), followed by SSB. Concomitant matrix elements did not affect CVG-ICP-MS results. Neither with PN, nor with CVG, any evidence for mass-independent discrimination effects in the instrument was observed within the experimental precision obtained. CVG-MC-ICP-MS was finally used for Hg isotopic analysis of reference materials (RMs) of relevant environmental origin. The isotopic composition of Hg in RMs of marine biological origin testified of mass-independent fractionation that affected the odd-numbered Hg isotopes. While older RMs were used for validation purposes, novel Hg isotopic data are provided for the

  1. Dual-energy X-ray absorptiometry for measuring total bone mineral content in the rat: study of accuracy and precision.

    PubMed

    Casez, J P; Muehlbauer, R C; Lippuner, K; Kelly, T; Fleisch, H; Jaeger, P

    1994-07-01

    Sequential studies of osteopenic bone disease in small animals require the availability of non-invasive, accurate and precise methods to assess bone mineral content (BMC) and bone mineral density (BMD). Dual-energy X-ray absorptiometry (DXA), which is currently used in humans for this purpose, can also be applied to small animals by means of adapted software. Precision and accuracy of DXA was evaluated in 10 rats weighing 50-265 g. The rats were anesthetized with a mixture of ketamine-xylazine administrated intraperitoneally. Each rat was scanned six times consecutively in the antero-posterior incidence after repositioning using the rat whole-body software for determination of whole-body BMC and BMD (Hologic QDR 1000, software version 5.52). Scan duration was 10-20 min depending on rat size. After the last measurement, rats were sacrificed and soft tissues were removed by dermestid beetles. Skeletons were then scanned in vitro (ultra high resolution software, version 4.47). Bones were subsequently ashed and dissolved in hydrochloric acid and total body calcium directly assayed by atomic absorption spectrophotometry (TBCa[chem]). Total body calcium was also calculated from the DXA whole-body in vivo measurement (TBCa[DXA]) and from the ultra high resolution measurement (TBCa[UH]) under the assumption that calcium accounts for 40.5% of the BMC expressed as hydroxyapatite. Precision error for whole-body BMC and BMD (mean +/- S.D.) was 1.3% and 1.5%, respectively. Simple regression analysis between TBCa[DXA] or TBCa[UH] and TBCa[chem] revealed tight correlations (n = 0.991 and 0.996, respectively), with slopes and intercepts which were significantly different from 1 and 0, respectively.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7950505

  2. The accuracy and precision of two non-invasive, magnetic resonance-guided focused ultrasound-based thermal diffusivity estimation methods

    PubMed Central

    Dillon, Christopher R.; Payne, Allison; Christensen, Douglas A.; Roemer, Robert B.

    2016-01-01

    Purpose The use of correct tissue thermal diffusivity values is necessary for making accurate thermal modeling predictions during magnetic resonance-guided focused ultrasound (MRgFUS) treatment planning. This study evaluates the accuracy and precision of two non-invasive thermal diffusivity estimation methods, a Gaussian Temperature method published by Cheng and Plewes in 2002 and a Gaussian specific absorption rate (SAR) method published by Dillon et al in 2012. Materials and Methods Both methods utilize MRgFUS temperature data obtained during cooling following a short (<25s) heating pulse. The Gaussian SAR method can also use temperatures obtained during heating. Experiments were performed at low heating levels (ΔT~10°C) in ex vivo pork muscle and in vivo rabbit back muscle. The non-invasive MRgFUS thermal diffusivity estimates were compared with measurements from two standard invasive methods. Results Both non-invasive methods accurately estimate thermal diffusivity when using MR-temperature cooling data (overall ex vivo error<6%, in vivo<12%). Including heating data in the Gaussian SAR method further reduces errors (ex vivo error<2%, in vivo<3%). The significantly lower standard deviation values (p<0.03) of the Gaussian SAR method indicate that it has better precision than the Gaussian Temperature method. Conclusions With repeated sonications, either MR-based method could provide accurate thermal diffusivity values for MRgFUS therapies. Fitting to more data simultaneously likely makes the Gaussian SAR method less susceptible to noise, and using heating data helps it converge more consistently to the FUS fitting parameters and thermal diffusivity. These effects lead to the improved precision of the Gaussian SAR method. PMID:25198092

  3. Accuracy of genomic selection for age at puberty in a multi-breed population of tropically adapted beef cattle.

    PubMed

    Farah, M M; Swan, A A; Fortes, M R S; Fonseca, R; Moore, S S; Kelly, M J

    2016-02-01

    Genomic selection is becoming a standard tool in livestock breeding programs, particularly for traits that are hard to measure. Accuracy of genomic selection can be improved by increasing the quantity and quality of data and potentially by improving analytical methods. Adding genotypes and phenotypes from additional breeds or crosses often improves the accuracy of genomic predictions but requires specific methodology. A model was developed to incorporate breed composition estimated from genotypes into genomic selection models. This method was applied to age at puberty data in female beef cattle (as estimated from age at first observation of a corpus luteum) from a mix of Brahman and Tropical Composite beef cattle. In this dataset, the new model incorporating breed composition did not increase the accuracy of genomic selection. However, the breeding values exhibited slightly less bias (as assessed by deviation of regression of phenotype on genomic breeding values from the expected value of 1). Adding additional Brahman animals to the Tropical Composite analysis increased the accuracy of genomic predictions and did not affect the accuracy of the Brahman predictions. PMID:26490440

  4. The Effects of Demography and Long-Term Selection on the Accuracy of Genomic Prediction with Sequence Data

    PubMed Central

    MacLeod, Iona M.; Hayes, Ben J.; Goddard, Michael E.

    2014-01-01

    The use of dense SNPs to predict the genetic value of an individual for a complex trait is often referred to as “genomic selection” in livestock and crops, but is also relevant to human genetics to predict, for example, complex genetic disease risk. The accuracy of prediction depends on the strength of linkage disequilibrium (LD) between SNPs and causal mutations. If sequence data were used instead of dense SNPs, accuracy should increase because causal mutations are present, but demographic history and long-term negative selection also influence accuracy. We therefore evaluated genomic prediction, using simulated sequence in two contrasting populations: one reducing from an ancestrally large effective population size (Ne) to a small one, with high LD common in domestic livestock, while the second had a large constant-sized Ne with low LD similar to that in some human or outbred plant populations. There were two scenarios in each population; causal variants were either neutral or under long-term negative selection. For large Ne, sequence data led to a 22% increase in accuracy relative to ∼600K SNP chip data with a Bayesian analysis and a more modest advantage with a BLUP analysis. This advantage increased when causal variants were influenced by negative selection, and accuracy persisted when 10 generations separated reference and validation populations. However, in the reducing Ne population, there was little advantage for sequence even with negative selection. This study demonstrates the joint influence of demography and selection on accuracy of prediction and improves our understanding of how best to exploit sequence for genomic prediction. PMID:25233989

  5. Optimal energy window selection of a CZT-based small-animal SPECT for quantitative accuracy

    NASA Astrophysics Data System (ADS)

    Park, Su-Jin; Yu, A. Ram; Choi, Yun Young; Kim, Kyeong Min; Kim, Hee-Joung

    2015-05-01

    Cadmium zinc telluride (CZT)-based small-animal single-photon emission computed tomography (SPECT) has desirable characteristics such as superior energy resolution, but data acquisition for SPECT imaging has been widely performed with a conventional energy window. The aim of this study was to determine the optimal energy window settings for technetium-99 m (99mTc) and thallium-201 (201Tl), the most commonly used isotopes in SPECT imaging, using CZT-based small-animal SPECT for quantitative accuracy. We experimentally investigated quantitative measurements with respect to primary count rate, contrast-to-noise ratio (CNR), and scatter fraction (SF) within various energy window settings using Triumph X-SPECT. The two ways of energy window settings were considered: an on-peak window and an off-peak window. In the on-peak window setting, energy centers were set on the photopeaks. In the off-peak window setting, the ratios of energy differences between the photopeak from the lower- and higher-threshold varied from 4:6 to 3:7. In addition, the energy-window width for 99mTc varied from 5% to 20%, and that for 201Tl varied from 10% to 30%. The results of this study enabled us to determine the optimal energy windows for each isotope in terms of primary count rate, CNR, and SF. We selected the optimal energy window that increases the primary count rate and CNR while decreasing SF. For 99mTc SPECT imaging, the energy window of 138-145 keV with a 5% width and off-peak ratio of 3:7 was determined to be the optimal energy window. For 201Tl SPECT imaging, the energy window of 64-85 keV with a 30% width and off-peak ratio of 3:7 was selected as the optimal energy window. Our results demonstrated that the proper energy window should be carefully chosen based on quantitative measurements in order to take advantage of desirable characteristics of CZT-based small-animal SPECT. These results provided valuable reference information for the establishment of new protocol for CZT

  6. The importance of identity-by-state information for the accuracy of genomic selection

    PubMed Central

    2012-01-01

    Background It is commonly assumed that prediction of genome-wide breeding values in genomic selection is achieved by capitalizing on linkage disequilibrium between markers and QTL but also on genetic relationships. Here, we investigated the reliability of predicting genome-wide breeding values based on population-wide linkage disequilibrium information, based on identity-by-descent relationships within the known pedigree, and to what extent linkage disequilibrium information improves predictions based on identity-by-descent genomic relationship information. Methods The study was performed on milk, fat, and protein yield, using genotype data on 35 706 SNP and deregressed proofs of 1086 Italian Brown Swiss bulls. Genome-wide breeding values were predicted using a genomic identity-by-state relationship matrix and a genomic identity-by-descent relationship matrix (averaged over all marker loci). The identity-by-descent matrix was calculated by linkage analysis using one to five generations of pedigree data. Results We showed that genome-wide breeding values prediction based only on identity-by-descent genomic relationships within the known pedigree was as or more reliable than that based on identity-by-state, which implicitly also accounts for genomic relationships that occurred before the known pedigree. Furthermore, combining the two matrices did not improve the prediction compared to using identity-by-descent alone. Including different numbers of generations in the pedigree showed that most of the information in genome-wide breeding values prediction comes from animals with known common ancestors less than four generations back in the pedigree. Conclusions Our results show that, in pedigreed breeding populations, the accuracy of genome-wide breeding values obtained by identity-by-descent relationships was not improved by identity-by-state information. Although, in principle, genomic selection based on identity-by-state does not require pedigree data, it does use the

  7. The Impact of 3D Volume-of-Interest Definition on Accuracy and Precision of Activity Estimation in Quantitative SPECT and Planar Processing Methods

    PubMed Central

    He, Bin; Frey, Eric C.

    2010-01-01

    Accurate and precise estimation of organ activities is essential for treatment planning in targeted radionuclide therapy. We have previously evaluated the impact of processing methodology, statistical noise, and variability in activity distribution and anatomy on the accuracy and precision of organ activity estimates obtained with quantitative SPECT (QSPECT), and planar (QPlanar) processing. Another important effect impacting the accuracy and precision of organ activity estimates is accuracy of and variability in the definition of organ regions of interest (ROI) or volumes of interest (VOI). The goal of this work was thus to systematically study the effects of VOI definition on the reliability of activity estimates. To this end, we performed Monte Carlo simulation studies using randomly perturbed and shifted VOIs to assess the impact on organ activity estimations. The 3D NCAT phantom was used with activities that modeled clinically observed 111In ibritumomab tiuxetan distributions. In order to study the errors resulting from misdefinitions due to manual segmentation errors, VOIs of the liver and left kidney were first manually defined. Each control point was then randomly perturbed to one of the nearest or next-nearest voxels in the same transaxial plane in three ways: with no, inward or outward directional bias, resulting in random perturbation, erosion or dilation, respectively of the VOIs. In order to study the errors resulting from the misregistration of VOIs, as would happen, e.g., in the case where the VOIs were defined using a misregistered anatomical image, the reconstructed SPECT images or projections were shifted by amounts ranging from −1 to 1 voxels in increments of 0.1 voxels in both the transaxial and axial directions. The activity estimates from the shifted reconstructions or projections were compared to those from the originals, and average errors were computed for the QSPECT and QPlanar methods, respectively. For misregistration, errors in organ

  8. Bias, precision and accuracy in the estimation of cuticular and respiratory water loss: a case study from a highly variable cockroach, Perisphaeria sp.

    PubMed

    Gray, Emilie M; Chown, Steven L

    2008-01-01

    We compared the precision, bias and accuracy of two techniques that were recently proposed to estimate the contributions of cuticular and respiratory water loss to total water loss in insects. We performed measurements of VCO2 and VH2O in normoxia, hyperoxia and anoxia using flow through respirometry on single individuals of the highly variable cockroach Perisphaeria sp. to compare estimates of cuticular and respiratory water loss (CWL and RWL) obtained by the VH2O-VCO2 y-intercept method with those obtained by the hyperoxic switch method. Precision was determined by assessing the repeatability of values obtained whereas bias was assessed by comparing the methods' results to each other and to values for other species found in the literature. We found that CWL was highly repeatable by both methods (R0.88) and resulted in similar values to measures of CWL determined during the closed-phase of discontinuous gas exchange (DGE). Repeatability of RWL was much lower (R=0.40) and significant only in the case of the hyperoxic method. RWL derived from the hyperoxic method is higher (by 0.044 micromol min(-1)) than that obtained from the method traditionally used for measuring water loss during the closed-phase of DGE, suggesting that in the past RWL may have been underestimated. The very low cuticular permeability of this species (3.88 microg cm(-2) h(-1) Torr(-1)) is reasonable given the seasonally hot and dry habitat where it lives. We also tested the hygric hypothesis proposed to account for the evolution of discontinuous gas exchange cycles and found no effect of respiratory pattern on RWL, although the ratio of mean VH2O to VCO2 was higher for continuous patterns compared with discontinuous ones. PMID:17949739

  9. Guidelines for Dual Energy X-Ray Absorptiometry Analysis of Trabecular Bone-Rich Regions in Mice: Improved Precision, Accuracy, and Sensitivity for Assessing Longitudinal Bone Changes.

    PubMed

    Shi, Jiayu; Lee, Soonchul; Uyeda, Michael; Tanjaya, Justine; Kim, Jong Kil; Pan, Hsin Chuan; Reese, Patricia; Stodieck, Louis; Lin, Andy; Ting, Kang; Kwak, Jin Hee; Soo, Chia

    2016-05-01

    Trabecular bone is frequently studied in osteoporosis research because changes in trabecular bone are the most common cause of osteoporotic fractures. Dual energy X-ray absorptiometry (DXA) analysis specific to trabecular bone-rich regions is crucial to longitudinal osteoporosis research. The purpose of this study is to define a novel method for accurately analyzing trabecular bone-rich regions in mice via DXA. This method will be utilized to analyze scans obtained from the International Space Station in an upcoming study of microgravity-induced bone loss. Thirty 12-week-old BALB/c mice were studied. The novel method was developed by preanalyzing trabecular bone-rich sites in the distal femur, proximal tibia, and lumbar vertebrae via high-resolution X-ray imaging followed by DXA and micro-computed tomography (micro-CT) analyses. The key DXA steps described by the novel method were (1) proper mouse positioning, (2) region of interest (ROI) sizing, and (3) ROI positioning. The precision of the new method was assessed by reliability tests and a 14-week longitudinal study. The bone mineral content (BMC) data from DXA was then compared to the BMC data from micro-CT to assess accuracy. Bone mineral density (BMD) intra-class correlation coefficients of the new method ranging from 0.743 to 0.945 and Levene's test showing that there was significantly lower variances of data generated by new method both verified its consistency. By new method, a Bland-Altman plot displayed good agreement between DXA BMC and micro-CT BMC for all sites and they were strongly correlated at the distal femur and proximal tibia (r=0.846, p<0.01; r=0.879, p<0.01, respectively). The results suggest that the novel method for site-specific analysis of trabecular bone-rich regions in mice via DXA yields more precise, accurate, and repeatable BMD measurements than the conventional method. PMID:26956416

  10. The effects of relatedness and GxE interaction on prediction accuracies in genomic selection: a study in cassava

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Prior to implementation of genomic selection, an evaluation of the potential accuracy of prediction can be obtained by cross validation. In this procedure, a population with both phenotypes and genotypes is split into training and validation sets. The prediction model is fitted using the training se...

  11. Precision farming, myth or reality: Selected case studies from Mississippi cotton fields

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is a lot of interest in the concept of precision farming, also called precision agriculture or site-specific management. Although the total acreage managed by these concepts is increasing worldwide each year, there are several limitations and constraints that must be resolved to sustain this ...

  12. A precisely substituted benzopyran targets androgen refractory prostate cancer cells through selective modulation of estrogen receptors.

    PubMed

    Kumar, Rajeev; Verma, Vikas; Sharma, Vikas; Jain, Ashish; Singh, Vishal; Sarswat, Amit; Maikhuri, Jagdamba P; Sharma, Vishnu L; Gupta, Gopal

    2015-03-15

    Dietary consumption of phytoestrogens like genistein has been linked with lower incidence of prostate cancer. The estradiol-like benzopyran core of genistein confers estrogen receptor-β (ER-β) selectivity that imparts weak anti-proliferative activity against prostate cancer cells. DL-2-[4-(2-piperidinoethoxy)phenyl]-3-phenyl-2H-1-benzopyran (BP), a SERM designed with benzopyran core, targeted androgen independent prostate cancer (PC-3) cells 14-times more potently than genistein, ~25% more efficiently than tamoxifen and 6.5-times more actively than ICI-182780, without forfeiting significant specificity in comparison to genistein. BP increased apoptosis (annexin-V and TUNEL labeling), arrested cell cycle, and significantly increased caspase-3 activity along with mRNA expressions of estrogen receptor (ER)-β and FasL (qPCR) in PC-3 cells. In classical ERE-luc reporter assay BP behaved as a potent ER-α antagonist and ER-β agonist. Accordingly, it decreased expression of ER-α target PS2 (P<0.01) and increased expression of ER-β target TNF-α (P<0.05) genes in PC-3. ER-β deficient PC-3 (siRNA-transfected) was resistant to apoptotic and anti-proliferative actions of SERMs, including stimulation of FasL expression by BP. BP significantly inhibited phosphorylation of Akt and ERK-1/2, JNK and p38 in PC-3 (immunoblotting), and thus adopted a multi-pathway mechanism to exert a more potent anti-proliferative activity against prostate cancer cells than natural and synthetic SERMs. Its precise ER-subtype specific activity presents a unique lead structure for further optimization. PMID:25655200

  13. High-Precision Surface Inspection: Uncertainty Evaluation within an Accuracy Range of 15μm with Triangulation-based Laser Line Scanners

    NASA Astrophysics Data System (ADS)

    Dupuis, Jan; Kuhlmann, Heiner

    2014-06-01

    Triangulation-based range sensors, e.g. laser line scanners, are used for high-precision geometrical acquisition of free-form surfaces, for reverse engineering tasks or quality management. In contrast to classical tactile measuring devices, these scanners generate a great amount of 3D-points in a short period of time and enable the inspection of soft materials. However, for accurate measurements, a number of aspects have to be considered to minimize measurement uncertainties. This study outlines possible sources of uncertainties during the measurement process regarding the scanner warm-up, the impact of laser power and exposure time as well as scanner’s reaction to areas of discontinuity, e.g. edges. All experiments were performed using a fixed scanner position to avoid effects resulting from imaging geometry. The results show a significant dependence of measurement accuracy on the correct adaption of exposure time as a function of surface reflectivity and laser power. Additionally, it is illustrated that surface structure as well as edges can cause significant systematic uncertainties.

  14. A precisely substituted benzopyran targets androgen refractory prostate cancer cells through selective modulation of estrogen receptors

    SciTech Connect

    Kumar, Rajeev; Verma, Vikas; Sharma, Vikas; Jain, Ashish; Singh, Vishal; Sarswat, Amit; Maikhuri, Jagdamba P.; Sharma, Vishnu L.; Gupta, Gopal

    2015-03-15

    Dietary consumption of phytoestrogens like genistein has been linked with lower incidence of prostate cancer. The estradiol-like benzopyran core of genistein confers estrogen receptor-β (ER-β) selectivity that imparts weak anti-proliferative activity against prostate cancer cells. DL-2-[4-(2-piperidinoethoxy)phenyl]-3-phenyl-2H-1-benzopyran (BP), a SERM designed with benzopyran core, targeted androgen independent prostate cancer (PC-3) cells 14-times more potently than genistein, ~ 25% more efficiently than tamoxifen and 6.5-times more actively than ICI-182780, without forfeiting significant specificity in comparison to genistein. BP increased apoptosis (annexin-V and TUNEL labeling), arrested cell cycle, and significantly increased caspase-3 activity along with mRNA expressions of estrogen receptor (ER)-β and FasL (qPCR) in PC-3 cells. In classical ERE-luc reporter assay BP behaved as a potent ER-α antagonist and ER-β agonist. Accordingly, it decreased expression of ER-α target PS2 (P < 0.01) and increased expression of ER-β target TNF-α (P < 0.05) genes in PC-3. ER-β deficient PC-3 (siRNA-transfected) was resistant to apoptotic and anti-proliferative actions of SERMs, including stimulation of FasL expression by BP. BP significantly inhibited phosphorylation of Akt and ERK-1/2, JNK and p38 in PC-3 (immunoblotting), and thus adopted a multi-pathway mechanism to exert a more potent anti-proliferative activity against prostate cancer cells than natural and synthetic SERMs. Its precise ER-subtype specific activity presents a unique lead structure for further optimization. - Highlights: • BP with benzopyran core of genistein was identified for ER-β selective action. • BP was 14-times more potent than genistien in targeting prostate cancer cells. • It behaved as a potent ER-β agonist and ER-α antagonist in gene reporter assays. • BP's anti-proliferative action was inhibited significantly in ER-β deficient cells. • BP — a unique lead structure

  15. Method and system using power modulation for maskless vapor deposition of spatially graded thin film and multilayer coatings with atomic-level precision and accuracy

    DOEpatents

    Montcalm, Claude; Folta, James Allen; Tan, Swie-In; Reiss, Ira

    2002-07-30

    A method and system for producing a film (preferably a thin film with highly uniform or highly accurate custom graded thickness) on a flat or graded substrate (such as concave or convex optics), by sweeping the substrate across a vapor deposition source operated with time-varying flux distribution. In preferred embodiments, the source is operated with time-varying power applied thereto during each sweep of the substrate to achieve the time-varying flux distribution as a function of time. A user selects a source flux modulation recipe for achieving a predetermined desired thickness profile of the deposited film. The method relies on precise modulation of the deposition flux to which a substrate is exposed to provide a desired coating thickness distribution.

  16. Genomic selection accuracy for grain quality traits in biparental wheat populations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic selection (GS) is a promising tool for plant and animal breeding that uses genome wide molecular marker data to capture small and large effect quantitative trait loci and predict the genetic value of selection candidates. Genomic selection has been shown previously to have higher prediction ...

  17. Screening Accuracy of Level 2 Autism Spectrum Disorder Rating Scales: A Review of Selected Instruments

    ERIC Educational Resources Information Center

    Norris, Megan; Lecavalier, Luc

    2010-01-01

    The goal of this review was to examine the state of Level 2, caregiver-completed rating scales for the screening of Autism Spectrum Disorders (ASDs) in individuals above the age of three years. We focused on screening accuracy and paid particular attention to comparison groups. Inclusion criteria required that scales be developed post ICD-10, be…

  18. Tailored selection of study individuals to be sequenced in order to improve the accuracy of genotype imputation.

    PubMed

    Peil, Barbara; Kabisch, Maria; Fischer, Christine; Hamann, Ute; Bermejo, Justo Lorenzo

    2015-02-01

    The addition of sequence data from own-study individuals to genotypes from external data repositories, for example, the HapMap, has been shown to improve the accuracy of imputed genotypes. Early approaches for reference panel selection favored individuals who best reflect recombination patterns in the study population. By contrast, a maximization of genetic diversity in the reference panel has been recently proposed. We investigate here a novel strategy to select individuals for sequencing that relies on the characterization of the ancestral kernel of the study population. The simulated study scenarios consisted of several combinations of subpopulations from HapMap. HapMap individuals who did not belong to the study population constituted an external reference panel which was complemented with the sequences of study individuals selected according to different strategies. In addition to a random choice, individuals with the largest statistical depth according to the first genetic principal components were selected. In all simulated scenarios the integration of sequences from own-study individuals increased imputation accuracy. The selection of individuals based on the statistical depth resulted in the highest imputation accuracy for European and Asian study scenarios, whereas random selection performed best for an African-study scenario. Present findings indicate that there is no universal 'best strategy' to select individuals for sequencing. We propose to use the methodology described in the manuscript to assess the advantage of focusing on the ancestral kernel under own study characteristics (study size, genetic diversity, availability and properties of external reference panels, frequency of imputed variants…). PMID:25537753

  19. Technical Note: Precision and accuracy of a commercially available CT optically stimulated luminescent dosimetry system for the measurement of CT dose index

    PubMed Central

    Vrieze, Thomas J.; Sturchio, Glenn M.; McCollough, Cynthia H.

    2012-01-01

    Purpose: To determine the precision and accuracy of CTDI100 measurements made using commercially available optically stimulated luminescent (OSL) dosimeters (Landaur, Inc.) as beam width, tube potential, and attenuating material were varied. Methods: One hundred forty OSL dosimeters were individually exposed to a single axial CT scan, either in air, a 16-cm (head), or 32-cm (body) CTDI phantom at both center and peripheral positions. Scans were performed using nominal total beam widths of 3.6, 6, 19.2, and 28.8 mm at 120 kV and 28.8 mm at 80 kV. Five measurements were made for each of 28 parameter combinations. Measurements were made under the same conditions using a 100-mm long CTDI ion chamber. Exposed OSL dosimeters were returned to the manufacturer, who reported dose to air (in mGy) as a function of distance along the probe, integrated dose, and CTDI100. Results: The mean precision averaged over 28 datasets containing five measurements each was 1.4% ± 0.6%, range = 0.6%–2.7% for OSL and 0.08% ± 0.06%, range = 0.02%–0.3% for ion chamber. The root mean square (RMS) percent differences between OSL and ion chamber CTDI100 values were 13.8%, 6.4%, and 8.7% for in-air, head, and body measurements, respectively, with an overall RMS percent difference of 10.1%. OSL underestimated CTDI100 relative to the ion chamber 21/28 times (75%). After manual correction of the 80 kV measurements, the RMS percent differences between OSL and ion chamber measurements were 9.9% and 10.0% for 80 and 120 kV, respectively. Conclusions: Measurements of CTDI100 with commercially available CT OSL dosimeters had a percent standard deviation of 1.4%. After energy-dependent correction factors were applied, the RMS percent difference in the measured CTDI100 values was about 10%, with a tendency of OSL to underestimate CTDI relative to the ion chamber. Unlike ion chamber methods, however, OSL dosimeters allow measurement of the radiation dose profile. PMID:23127052

  20. Technical Note: Precision and accuracy of a commercially available CT optically stimulated luminescent dosimetry system for the measurement of CT dose index

    SciTech Connect

    Vrieze, Thomas J.; Sturchio, Glenn M.; McCollough, Cynthia H.

    2012-11-15

    Purpose: To determine the precision and accuracy of CTDI{sub 100} measurements made using commercially available optically stimulated luminescent (OSL) dosimeters (Landaur, Inc.) as beam width, tube potential, and attenuating material were varied. Methods: One hundred forty OSL dosimeters were individually exposed to a single axial CT scan, either in air, a 16-cm (head), or 32-cm (body) CTDI phantom at both center and peripheral positions. Scans were performed using nominal total beam widths of 3.6, 6, 19.2, and 28.8 mm at 120 kV and 28.8 mm at 80 kV. Five measurements were made for each of 28 parameter combinations. Measurements were made under the same conditions using a 100-mm long CTDI ion chamber. Exposed OSL dosimeters were returned to the manufacturer, who reported dose to air (in mGy) as a function of distance along the probe, integrated dose, and CTDI{sub 100}. Results: The mean precision averaged over 28 datasets containing five measurements each was 1.4%{+-} 0.6%, range = 0.6%-2.7% for OSL and 0.08%{+-} 0.06%, range = 0.02%-0.3% for ion chamber. The root mean square (RMS) percent differences between OSL and ion chamber CTDI{sub 100} values were 13.8%, 6.4%, and 8.7% for in-air, head, and body measurements, respectively, with an overall RMS percent difference of 10.1%. OSL underestimated CTDI{sub 100} relative to the ion chamber 21/28 times (75%). After manual correction of the 80 kV measurements, the RMS percent differences between OSL and ion chamber measurements were 9.9% and 10.0% for 80 and 120 kV, respectively. Conclusions: Measurements of CTDI{sub 100} with commercially available CT OSL dosimeters had a percent standard deviation of 1.4%. After energy-dependent correction factors were applied, the RMS percent difference in the measured CTDI{sub 100} values was about 10%, with a tendency of OSL to underestimate CTDI relative to the ion chamber. Unlike ion chamber methods, however, OSL dosimeters allow measurement of the radiation dose profile.

  1. Accuracy and precision of porosity estimates based on velocity inversion of surface ground-penetrating radar data: A controlled experiment at the Boise Hydrogeophysical Research Site

    NASA Astrophysics Data System (ADS)

    Bradford, J.; Clement, W.

    2006-12-01

    Although rarely acquired, ground penetrating radar (GPR) data acquired in continuous multi-offset geometries can substantially improve our understanding of the subsurface compared to conventional single offset surveys. This improvement arises because multi-offset data enable full use of the information that the GPR signal can carry. The added information allows us to maximize the material property information extracted from a GPR survey. Of the array of potential multi-offset GPR measurements, traveltime vs offset information enables laterally and vertically continuous electromagnetic (EM) velocity measurements. In turn, the EM velocities provide estimates of water content via petrophysical relationships such as the CRIM or Topp's equations. In fully saturated media the water content is a direct measure of bulk porosity. The Boise Hydrogeophysical Research Site (BHRS) is a experimental wellfield located in a shallow alluvial aquifer near Boise, Idaho. In July, 2006 we conducted a controlled 3D multi-offset GPR experiment at the BHRS designed to test the accuracy of state-of-the-art velocity analysis methodologies. We acquired continuous multi-offset GPR data over an approximately 20 x 30 m 3D area. The GPR system was a Sensors and Software pulseEkko Pro multichannel system with 100 MHz antennas and was configured with 4 receivers and a single transmitter. Data were acquired in off-end geometry for a total of 16 offsets with a 1 m offset interval and 1 m near offset. The data were acquired on a 1 m x 1m grid in four passes, each consisting of a 3 m range of equally spaced offsets. The survey encompassed 13 wells finished to the ~20 m depth of the unconfined aquifer. We established velocity control by acquiring vertical radar profiles (VRPs) in all 13 wells. Preliminary velocity measurements using an established method of reflection tomography were within about 1 percent of local 1D velocity distributions determined from the VRPs. Vertical velocity precision from the

  2. Development and validation of an automated and marker-free CT-based spatial analysis method (CTSA) for assessment of femoral hip implant migration In vitro accuracy and precision comparable to that of radiostereometric analysis (RSA).

    PubMed

    Scheerlinck, Thierry; Polfliet, Mathias; Deklerck, Rudi; Van Gompel, Gert; Buls, Nico; Vandemeulebroucke, Jef

    2016-04-01

    Background and purpose - We developed a marker-free automated CT-based spatial analysis (CTSA) method to detect stem-bone migration in consecutive CT datasets and assessed the accuracy and precision in vitro. Our aim was to demonstrate that in vitro accuracy and precision of CTSA is comparable to that of radiostereometric analysis (RSA). Material and methods - Stem and bone were segmented in 2 CT datasets and both were registered pairwise. The resulting rigid transformations were compared and transferred to an anatomically sound coordinate system, taking the stem as reference. This resulted in 3 translation parameters and 3 rotation parameters describing the relative amount of stem-bone displacement, and it allowed calculation of the point of maximal stem migration. Accuracy was evaluated in 39 comparisons by imposing known stem migration on a stem-bone model. Precision was estimated in 20 comparisons based on a zero-migration model, and in 5 patients without stem loosening. Results - Limits of the 95% tolerance intervals (TIs) for accuracy did not exceed 0.28 mm for translations and 0.20° for rotations (largest standard deviation of the signed error (SDSE): 0.081 mm and 0.057°). In vitro, limits of the 95% TI for precision in a clinically relevant setting (8 comparisons) were below 0.09 mm and 0.14° (largest SDSE: 0.012 mm and 0.020°). In patients, the precision was lower, but acceptable, and dependent on CT scan resolution. Interpretation - CTSA allows detection of stem-bone migration with an accuracy and precision comparable to that of RSA. It could be valuable for evaluation of subtle stem loosening in clinical practice. PMID:26634843

  3. Development and validation of an automated and marker-free CT-based spatial analysis method (CTSA) for assessment of femoral hip implant migration In vitro accuracy and precision comparable to that of radiostereometric analysis (RSA)

    PubMed Central

    Scheerlinck, Thierry; Polfliet, Mathias; Deklerck, Rudi; Van Gompel, Gert; Buls, Nico; Vandemeulebroucke, Jef

    2016-01-01

    Background and purpose — We developed a marker-free automated CT-based spatial analysis (CTSA) method to detect stem-bone migration in consecutive CT datasets and assessed the accuracy and precision in vitro. Our aim was to demonstrate that in vitro accuracy and precision of CTSA is comparable to that of radiostereometric analysis (RSA). Material and methods — Stem and bone were segmented in 2 CT datasets and both were registered pairwise. The resulting rigid transformations were compared and transferred to an anatomically sound coordinate system, taking the stem as reference. This resulted in 3 translation parameters and 3 rotation parameters describing the relative amount of stem-bone displacement, and it allowed calculation of the point of maximal stem migration. Accuracy was evaluated in 39 comparisons by imposing known stem migration on a stem-bone model. Precision was estimated in 20 comparisons based on a zero-migration model, and in 5 patients without stem loosening. Results — Limits of the 95% tolerance intervals (TIs) for accuracy did not exceed 0.28 mm for translations and 0.20° for rotations (largest standard deviation of the signed error (SDSE): 0.081 mm and 0.057°). In vitro, limits of the 95% TI for precision in a clinically relevant setting (8 comparisons) were below 0.09 mm and 0.14° (largest SDSE: 0.012 mm and 0.020°). In patients, the precision was lower, but acceptable, and dependent on CT scan resolution. Interpretation — CTSA allows detection of stem-bone migration with an accuracy and precision comparable to that of RSA. It could be valuable for evaluation of subtle stem loosening in clinical practice. PMID:26634843

  4. The 1998-2000 SHADOZ (Southern Hemisphere ADditional OZonesondes) Tropical Ozone Climatology: Ozonesonde Precision, Accuracy and Station-to-Station Variability

    NASA Technical Reports Server (NTRS)

    Witte, J. C.; Thompson, Anne M.; McPeters, R. D.; Oltmans, S. J.; Schmidlin, F. J.; Bhartia, P. K. (Technical Monitor)

    2001-01-01

    As part of the SAFARI-2000 campaign, additional launches of ozonesondes were made at Irene, South Africa and at Lusaka, Zambia. These represent campaign augmentations to the SHADOZ database described in this paper. This network of 10 southern hemisphere tropical and subtropical stations, designated the Southern Hemisphere ADditional OZonesondes (SHADOZ) project and established from operational sites, provided over 1000 profiles from ozonesondes and radiosondes during the period 1998-2000. (Since that time, two more stations, one in southern Africa, have joined SHADOZ). Archived data are available at: http://code9l6.gsfc.nasa.gov/Data-services/shadoz>. Uncertainties and accuracies within the SHADOZ ozone data set are evaluated by analyzing: (1) imprecisions in stratospheric ozone profiles and in methods of extrapolating ozone above balloon burst; (2) comparisons of column-integrated total ozone from sondes with total ozone from the Earth-Probe/TOMS (Total Ozone Mapping Spectrometer) satellite and ground-based instruments; (3) possible biases from station-to-station due to variations in ozonesonde characteristics. The key results are: (1) Ozonesonde precision is 5%; (2) Integrated total ozone column amounts from the sondes are in good agreement (2-10%) with independent measurements from ground-based instruments at five SHADOZ sites and with overpass measurements from the TOMS satellite (version 7 data). (3) Systematic variations in TOMS-sonde offsets and in groundbased-sonde offsets from station to station reflect biases in sonde technique as well as in satellite retrieval. Discrepancies are present in both stratospheric and tropospheric ozone. (4) There is evidence for a zonal wave-one pattern in total and tropospheric ozone, but not in stratospheric ozone.

  5. Analysis of the accuracy and precision of the McMaster method in detection of the eggs of Toxocara and Trichuris species (Nematoda) in dog faeces.

    PubMed

    Kochanowski, Maciej; Dabrowska, Joanna; Karamon, Jacek; Cencek, Tomasz; Osiński, Zbigniew

    2013-07-01

    The aim of this study was to determine the accuracy and precision of McMaster method with Raynaud's modification in the detection of the eggs of the nematodes Toxocara canis (Werner, 1782) and Trichuris ovis (Abildgaard, 1795) in faeces of dogs. Four variants of McMaster method were used for counting: in one grid, two grids, the whole McMaster chamber and flotation in the tube. One hundred sixty samples were prepared from dog faeces (20 repetitions for each egg quantity) containing 15, 25, 50, 100, 150, 200, 250 and 300 eggs of T. canis and T. ovis in 1 g of faeces. To compare the influence of kind of faeces on the results, samples of dog faeces were enriched at the same levels with the eggs of another nematode, Ascaris suum Goeze, 1782. In addition, 160 samples of pig faeces were prepared and enriched only with A. suum eggs in the same way. The highest limit of detection (the lowest level of eggs that were detected in at least 50% of repetitions) in all McMaster chamber variants were obtained for T. canis eggs (25-250 eggs/g faeces). In the variant with flotation in the tube, the highest limit of detection was obtained for T. ovis eggs (100 eggs/g). The best results of the limit of detection, sensitivity and the lowest coefficients of variation were obtained with the use of the whole McMaster chamber variant. There was no significant impact of properties of faeces on the obtained results. Multiplication factors for the whole chamber were calculated on the basis of the transformed equation of the regression line, illustrating the relationship between the number of detected eggs and that of the eggs added to the'sample. Multiplication factors calculated for T. canis and T. ovis eggs were higher than those expected using McMaster method with Raynaud modification. PMID:23951934

  6. Application of U-Pb ID-TIMS dating to the end-Triassic global crisis: testing the limits on precision and accuracy in a multidisciplinary whodunnit (Invited)

    NASA Astrophysics Data System (ADS)

    Schoene, B.; Schaltegger, U.; Guex, J.; Bartolini, A.

    2010-12-01

    The ca. 201.4 Ma Triassic-Jurassic boundary is characterized by one of the most devastating mass-extinctions in Earth history, subsequent biologic radiation, rapid carbon cycle disturbances and enormous flood basalt volcanism (Central Atlantic Magmatic Province - CAMP). Considerable uncertainty remains regarding the temporal and causal relationship between these events though this link is important for understanding global environmental change under extreme stresses. We present ID-TIMS U-Pb zircon geochronology on volcanic ash beds from two marine sections that span the Triassic-Jurassic boundary and from the CAMP in North America. To compare the timing of the extinction with the onset of the CAMP, we assess the precision and accuracy of ID-TIMS U-Pb zircon geochronology by exploring random and systematic uncertainties, reproducibility, open-system behavior, and pre-eruptive crystallization of zircon. We find that U-Pb ID-TIMS dates on single zircons can be internally and externally reproducible at 0.05% of the age, consistent with recent experiments coordinated through the EARTHTIME network. Increased precision combined with methods alleviating Pb-loss in zircon reveals that these ash beds contain zircon that crystallized between 10^5 and 10^6 years prior to eruption. Mineral dates older than eruption ages are prone to affect all geochronologic methods and therefore new tools exploring this form of “geologic uncertainty” will lead to better time constraints for ash bed deposition. In an effort to understand zircon dates within the framework of a magmatic system, we analyzed zircon trace elements by solution ICPMS for the same volume of zircon dated by ID-TIMS. In one example we argue that zircon trace element patterns as a function of time result from a mix of xeno-, ante-, and autocrystic zircons in the ash bed, and approximate eruption age with the youngest zircon date. In a contrasting example from a suite of Cretaceous andesites, zircon trace elements

  7. Feature Selection Has a Large Impact on One-Class Classification Accuracy for MicroRNAs in Plants

    PubMed Central

    Yousef, Malik; Saçar Demirci, Müşerref Duygu; Khalifa, Waleed; Allmer, Jens

    2016-01-01

    MicroRNAs (miRNAs) are short RNA sequences involved in posttranscriptional gene regulation. Their experimental analysis is complicated and, therefore, needs to be supplemented with computational miRNA detection. Currently computational miRNA detection is mainly performed using machine learning and in particular two-class classification. For machine learning, the miRNAs need to be parametrized and more than 700 features have been described. Positive training examples for machine learning are readily available, but negative data is hard to come by. Therefore, it seems prerogative to use one-class classification instead of two-class classification. Previously, we were able to almost reach two-class classification accuracy using one-class classifiers. In this work, we employ feature selection procedures in conjunction with one-class classification and show that there is up to 36% difference in accuracy among these feature selection methods. The best feature set allowed the training of a one-class classifier which achieved an average accuracy of ~95.6% thereby outperforming previous two-class-based plant miRNA detection approaches by about 0.5%. We believe that this can be improved upon in the future by rigorous filtering of the positive training examples and by improving current feature clustering algorithms to better target pre-miRNA feature selection. PMID:27190509

  8. Feature Selection Has a Large Impact on One-Class Classification Accuracy for MicroRNAs in Plants.

    PubMed

    Yousef, Malik; Saçar Demirci, Müşerref Duygu; Khalifa, Waleed; Allmer, Jens

    2016-01-01

    MicroRNAs (miRNAs) are short RNA sequences involved in posttranscriptional gene regulation. Their experimental analysis is complicated and, therefore, needs to be supplemented with computational miRNA detection. Currently computational miRNA detection is mainly performed using machine learning and in particular two-class classification. For machine learning, the miRNAs need to be parametrized and more than 700 features have been described. Positive training examples for machine learning are readily available, but negative data is hard to come by. Therefore, it seems prerogative to use one-class classification instead of two-class classification. Previously, we were able to almost reach two-class classification accuracy using one-class classifiers. In this work, we employ feature selection procedures in conjunction with one-class classification and show that there is up to 36% difference in accuracy among these feature selection methods. The best feature set allowed the training of a one-class classifier which achieved an average accuracy of ~95.6% thereby outperforming previous two-class-based plant miRNA detection approaches by about 0.5%. We believe that this can be improved upon in the future by rigorous filtering of the positive training examples and by improving current feature clustering algorithms to better target pre-miRNA feature selection. PMID:27190509

  9. Accuracy of initial codon selection by aminoacyl-tRNAs on the mRNA-programmed bacterial ribosome

    PubMed Central

    Zhang, Jingji; Ieong, Ka-Weng; Johansson, Magnus; Ehrenberg, Måns

    2015-01-01

    We used a cell-free system with pure Escherichia coli components to study initial codon selection of aminoacyl-tRNAs in ternary complex with elongation factor Tu and GTP on messenger RNA-programmed ribosomes. We took advantage of the universal rate-accuracy trade-off for all enzymatic selections to determine how the efficiency of initial codon readings decreased linearly toward zero as the accuracy of discrimination against near-cognate and wobble codon readings increased toward the maximal asymptote, the d value. We report data on the rate-accuracy variation for 7 cognate, 7 wobble, and 56 near-cognate codon readings comprising about 15% of the genetic code. Their d values varied about 400-fold in the 200–80,000 range depending on type of mismatch, mismatch position in the codon, and tRNA isoacceptor type. We identified error hot spots (d = 200) for U:G misreading in second and U:U or G:A misreading in third codon position by His-tRNAHis and, as also seen in vivo, Glu-tRNAGlu. We suggest that the proofreading mechanism has evolved to attenuate error hot spots in initial selection such as those found here. PMID:26195797

  10. Ligand similarity guided receptor selection enhances docking accuracy and recall for non-nucleoside HIV reverse transcriptase inhibitors.

    PubMed

    Stanton, Richard A; Nettles, James H; Schinazi, Raymond F

    2015-11-01

    Non-nucleoside reverse transcriptase inhibitors (NNRTI) are allosteric inhibitors of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT), a viral polymerase essential to infection. Despite the availability of >150 NNRTI-bound RT crystal structures, rational design of new NNRTI remains challenging because of the variability of their induced fit, hydrophobic binding patterns. Docking NNRTI yields inconsistent results that vary markedly depending on the receptor structure used, as only 27% of the >20k cross-docking calculations we performed using known NNRTI were accurate. In order to determine if a hospitable receptor for docking could be selected a priori, we evaluated more than 40 chemical descriptors for their ability to pre-select a best receptor for NNRTI cross-docking. The receptor selection was based on similarity scores between the bound- and target-ligands generated by each descriptor. The top descriptors were able to double the probability of cross-docking accuracy over random receptor selection. Additionally, recall of known NNRTI from a large library of similar decoys was increased using the same approach. The results demonstrate the utility of pre-selecting receptors when docking into difficult targets. Graphical Abstract Cross-docking accuracy increases when using chemical descriptors to determine the NNRTI with maximum similarity to the new compound and then docking into its respective receptor. PMID:26450349

  11. Increased prediction accuracy in wheat breeding trials using a marker x environment interaction genomic selection model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic selection (GS) models use genome-wide genetic information to predict genetic values of candidates for selection. Originally these models were developed without considering genotype ' environment interaction (GE). Several authors have proposed extensions of the cannonical GS model that accomm...

  12. Increased prediction accuracy in wheat breeding trials using a marker x environment interaction genomic selection model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic selection (GS) models use genome-wide genetic information to predict genetic values of candidates of selection. Originally, these models were developed without considering genotype x environment interaction (GxE). Several authors have proposed extensions of the single-environment GS model th...

  13. Genomic selection accuracy using multi-family prediction models in a wheat breeding program

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic selection (GS) uses genome-wide molecular marker data to predict the genetic value of selection candidates in breeding programs. In plant breeding, the ability to produce large numbers of progeny per cross allows GS to be conducted within each family. However, this approach requires phenotyp...

  14. Determination of Yield and Soil Variability in Louisiana Sugarcane Using Selected Tools of Precision Agriculture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Precision agriculture is a production strategy that may help sugarcane producers decrease input costs, maximize profits, and minimize any negative environmental impact through better management of soil and crop variability. To determine the extent of variability present in commercial sugarcane fiel...

  15. Impact of feature selection on the accuracy and spatial uncertainty of per-field crop classification using Support Vector Machines

    NASA Astrophysics Data System (ADS)

    Löw, F.; Michel, U.; Dech, S.; Conrad, C.

    2013-11-01

    Crop mapping is one major component of agricultural resource monitoring using remote sensing. Yield or water demand modeling requires that both, the total surface that is cultivated and the accurate distribution of crops, respectively is known. Map quality is crucial and influences the model outputs. Although the use of multi-spectral time series data in crop mapping has been acknowledged, the potentially high dimensionality of the input data remains an issue. In this study Support Vector Machines (SVM) are used for crop classification in irrigated landscapes at the object-level. Input to the classifications is 71 multi-seasonal spectral and geostatistical features computed from RapidEye time series. The random forest (RF) feature importance score was used to select a subset of features that achieved optimal accuracies. The relationship between the hard result accuracy and the soft output from the SVM is investigated by employing two measures of uncertainty, the maximum a posteriori probability and the alpha quadratic entropy. Specifically the effect of feature selection on map uncertainty is investigated by looking at the soft outputs of the SVM, in addition to classical accuracy metrics. Overall the SVMs applied to the reduced feature subspaces that were composed of the most informative multi-seasonal features led to a clear increase in classification accuracy up to 4.3%, and to a significant decline in thematic uncertainty. SVM was shown to be affected by feature space size and could benefit from RF-based feature selection. Uncertainty measures from SVM are an informative source of information on the spatial distribution of error in the crop maps.

  16. The effect of tray selection on the accuracy of elastomeric impression materials.

    PubMed

    Gordon, G E; Johnson, G H; Drennon, D G

    1990-01-01

    This study evaluated the accuracy of reproduction of stone casts made from impressions using different tray and impression materials. The tray materials used were an acrylic resin, a thermoplastic, and a plastic. The impression materials used were an additional silicone, a polyether, and a polysulfide. Impressions were made of a stainless steel master die that simulated crown preparations for a fixed partial denture and an acrylic resin model with cross-arch and anteroposterior landmarks in stainless steel that typify clinical intra-arch distances. Impressions of the fixed partial denture simulation were made with all three impression materials and all three tray types. Impressions of the cross-arch and anteroposterior landmarks were made by using all three tray types with only the addition reaction silicone impression material. Impressions were poured at 1 hour with a type IV dental stone. Data were analyzed by using ANOVA with a sample size of five. Results indicated that custom-made trays of acrylic resin and the thermoplastic material performed similarly regarding die accuracy and produced clinically acceptable casts. The stock plastic tray consistently produced casts with greater dimensional change than the two custom trays. PMID:2404101

  17. On selecting a prior for the precision parameter of Dirichlet process mixture models

    USGS Publications Warehouse

    Dorazio, R.M.

    2009-01-01

    In hierarchical mixture models the Dirichlet process is used to specify latent patterns of heterogeneity, particularly when the distribution of latent parameters is thought to be clustered (multimodal). The parameters of a Dirichlet process include a precision parameter ?? and a base probability measure G0. In problems where ?? is unknown and must be estimated, inferences about the level of clustering can be sensitive to the choice of prior assumed for ??. In this paper an approach is developed for computing a prior for the precision parameter ?? that can be used in the presence or absence of prior information about the level of clustering. This approach is illustrated in an analysis of counts of stream fishes. The results of this fully Bayesian analysis are compared with an empirical Bayes analysis of the same data and with a Bayesian analysis based on an alternative commonly used prior.

  18. Precise time technology for selected Air Force systems: Present status and future requirements

    NASA Technical Reports Server (NTRS)

    Yannoni, N. F.

    1981-01-01

    Precise time and time interval (PTTI) technology is becoming increasingly significant to Air Force operations as digital techniques find expanded utility in military missions. Timing has a key role in the function as well as in navigation. A survey of the PTTI needs of several Air Force systems is presented. Current technology supporting these needs was reviewed and new requirements are emphasized for systems as they transfer from initial development to final operational deployment.

  19. Accuracy and precision of 14C-based source apportionment of organic and elemental carbon in aerosols using the Swiss_4S protocol

    NASA Astrophysics Data System (ADS)

    Mouteva, G. O.; Fahrni, S. M.; Santos, G. M.; Randerson, J. T.; Zhang, Y.-L.; Szidat, S.; Czimczik, C. I.

    2015-09-01

    Aerosol source apportionment remains a critical challenge for understanding the transport and aging of aerosols, as well as for developing successful air pollution mitigation strategies. The contributions of fossil and non-fossil sources to organic carbon (OC) and elemental carbon (EC) in carbonaceous aerosols can be quantified by measuring the radiocarbon (14C) content of each carbon fraction. However, the use of 14C in studying OC and EC has been limited by technical challenges related to the physical separation of the two fractions and small sample sizes. There is no common procedure for OC/EC 14C analysis, and uncertainty studies have largely focused on the precision of yields. Here, we quantified the uncertainty in 14C measurement of aerosols associated with the isolation and analysis of each carbon fraction with the Swiss_4S thermal-optical analysis (TOA) protocol. We used an OC/EC analyzer (Sunset Laboratory Inc., OR, USA) coupled to a vacuum line to separate the two components. Each fraction was thermally desorbed and converted to carbon dioxide (CO2) in pure oxygen (O2). On average, 91 % of the evolving CO2 was then cryogenically trapped on the vacuum line, reduced to filamentous graphite, and measured for its 14C content via accelerator mass spectrometry (AMS). To test the accuracy of our setup, we quantified the total amount of extraneous carbon introduced during the TOA sample processing and graphitization as the sum of modern and fossil (14C-depleted) carbon introduced during the analysis of fossil reference materials (adipic acid for OC and coal for EC) and contemporary standards (oxalic acid for OC and rice char for EC) as a function of sample size. We further tested our methodology by analyzing five ambient airborne particulate matter (PM2.5) samples with a range of OC and EC concentrations and 14C contents in an interlaboratory comparison. The total modern and fossil carbon blanks of our setup were 0.8 ± 0.4 and 0.67 ± 0.34 μg C, respectively

  20. Accuracy and precision of 14C-based source apportionment of organic and elemental carbon in aerosols using the Swiss_4S protocol

    NASA Astrophysics Data System (ADS)

    Mouteva, G. O.; Fahrni, S. M.; Santos, G. M.; Randerson, J. T.; Zhang, Y. L.; Szidat, S.; Czimczik, C. I.

    2015-04-01

    Aerosol source apportionment remains a critical challenge for understanding the transport and aging of aerosols, as well as for developing successful air pollution mitigation strategies. The contributions of fossil and non-fossil sources to organic carbon (OC) and elemental carbon (EC) in carbonaceous aerosols can be quantified by measuring the radiocarbon (14C) content of each carbon fraction. However, the use of 14C in studying OC and EC has been limited by technical challenges related to the physical separation of the two fractions and small sample sizes. There is no common procedure for OC/EC 14C analysis, and uncertainty studies have largely focused on the precision of yields. Here, we quantified the uncertainty in 14C measurement of aerosols associated with the isolation and analysis of each carbon fraction with the Swiss_4S thermal-optical analysis (TOA) protocol. We used an OC/EC analyzer (Sunset Laboratory Inc., OR, USA) coupled to vacuum line to separate the two components. Each fraction was thermally desorbed and converted to carbon dioxide (CO2) in pure oxygen (O2). On average 91% of the evolving CO2 was then cryogenically trapped on the vacuum line, reduced to filamentous graphite, and measured for its 14C content via accelerator mass spectrometry (AMS). To test the accuracy of our set-up, we quantified the total amount of extraneous carbon introduced during the TOA sample processing and graphitization as the sum of modern and fossil (14C-depleted) carbon introduced during the analysis of fossil reference materials (adipic acid for OC and coal for EC) and contemporary standards (oxalic acid for OC and rice char for EC) as a function of sample size. We further tested our methodology by analyzing five ambient airborne particulate matter (PM2.5) samples with a range of OC and EC concentrations and 14C contents in an interlaboratory comparison. The total modern and fossil carbon blanks of our set-up were 0.8 ± 0.4 and 0.67 ± 0.34 μg C, respectively

  1. Selectivity of conditioned fear of touch is modulated by somatosensory precision.

    PubMed

    Harvie, Daniel S; Meulders, Ann; Reid, Emily; Camfferman, Danny; Brinkworth, Russell S A; Moseley, G Lorimer

    2016-06-01

    Learning to initiate defenses in response to specific signals of danger is adaptive. Some chronic pain conditions, however, are characterized by widespread anxiety, avoidance, and pain consistent with a loss of defensive response specificity. Response specificity depends on ability to discriminate between safe and threatening stimuli; therefore, specificity might depend on sensory precision. This would help explain the high prevalence of chronic pain in body areas of low tactile acuity, such as the lower back, and clarify why improving sensory precision may reduce chronic pain. We compared the acquisition and generalization of fear of pain-associated vibrotactile stimuli delivered to either the hand (high tactile acuity) or the back (low tactile acuity). During acquisition, tactile stimulation at one location (CS+) predicted the noxious electrocutaneous stimulation (US), while tactile stimulation at another location (CS-) did not. Responses to three stimuli with decreasing spatial proximity to the CS+ (generalizing stimuli; GS1-3) were tested. Differential learning and generalization were compared between groups. The main outcome of fear-potentiated startle responses showed differential learning only in the hand group. Self-reported fear and expectancy confirmed differential learning and limited generalization in the hand group, and suggested undifferentiated fear and expectancy in the back group. Differences in generalization could not be inferred from the startle data. Specificity of fear responses appears to be affected by somatosensory precision. This has implications for our understanding of the role of sensory imprecision in the development of chronic pain. PMID:26950514

  2. Precision Metabolic Engineering: the Design of Responsive, Selective, and Controllable Metabolic Systems

    PubMed Central

    McNerney, Monica P.; Watstein, Daniel M.; Styczynski, Mark P.

    2015-01-01

    Metabolic engineering is generally focused on static optimization of cells to maximize production of a desired product, though recently dynamic metabolic engineering has explored how metabolic programs can be varied over time to improve titer. However, these are not the only types of applications where metabolic engineering could make a significant impact. Here, we discuss a new conceptual framework, termed “precision metabolic engineering,” involving the design and engineering of systems that make different products in response to different signals. Rather than focusing on maximizing titer, these types of applications typically have three hallmarks: sensing signals that determine the desired metabolic target, completely directing metabolic flux in response to those signals, and producing sharp responses at specific signal thresholds. In this review, we will first discuss and provide examples of precision metabolic engineering. We will then discuss each of these hallmarks and identify which existing metabolic engineering methods can be applied to accomplish those tasks, as well as some of their shortcomings. Ultimately, precise control of metabolic systems has the potential to enable a host of new metabolic engineering and synthetic biology applications for any problem where flexibility of response to an external signal could be useful. PMID:26189665

  3. Detecting recent positive selection with high accuracy and reliability by conditional coalescent tree.

    PubMed

    Wang, Minxian; Huang, Xin; Li, Ran; Xu, Hongyang; Jin, Li; He, Yungang

    2014-11-01

    Studies of natural selection, followed by functional validation, are shedding light on understanding of genetic mechanisms underlying human evolution and adaptation. Classic methods for detecting selection, such as the integrated haplotype score (iHS) and Fay and Wu's H statistic, are useful for candidate gene searching underlying positive selection. These methods, however, have limited capability to localize causal variants in selection target regions. In this study, we developed a novel method based on conditional coalescent tree to detect recent positive selection by counting unbalanced mutations on coalescent gene genealogies. Extensive simulation studies revealed that our method is more robust than many other approaches against biases due to various demographic effects, including population bottleneck, expansion, or stratification, while not sacrificing its power. Furthermore, our method demonstrated its superiority in localizing causal variants from massive linked genetic variants. The rate of successful localization was about 20-40% higher than that of other state-of-the-art methods on simulated data sets. On empirical data, validated functional causal variants of four well-known positive selected genes were all successfully localized by our method, such as ADH1B, MCM6, APOL1, and HBB. Finally, the computational efficiency of this new method was much higher than that of iHS implementations, that is, 24-66 times faster than the REHH package, and more than 10,000 times faster than the original iHS implementation. These magnitudes make our method suitable for applying on large sequencing data sets. Software can be downloaded from https://github.com/wavefancy/scct. PMID:25135945

  4. Imputation of unordered markers and the impact on genomic selection accuracy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic selection, a breeding method that promises to accelerate rates of genetic gain, requires dense, genome-wide marker data. Genotyping-by-sequencing can generate a large number of de novo markers. However, without a reference genome, these markers are unordered and typically have a large propo...

  5. Impact of marker ascertainment bias on genomic selection accuracy and estimates of genetic diversity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genome-wide molecular markers are readily being applied to evaluate genetic diversity in germplasm collections and for making genomic selections in breeding programs. To accurately predict phenotypes and assay genetic diversity, molecular markers should assay a representative sample of the polymorp...

  6. Imputation of unordered markers and the impact on genomic selection accuracy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic selection, a breeding method that promises to accelerate rates of genetic gain, requires dense, genome-wide marker data. Sequence-based genotyping methods can generate de novo large numbers of markers. However, without a reference genome, these markers are unordered and typically have a lar...

  7. The effects of temporal-precision and time-minimization constraints on the spatial and temporal accuracy of aimed hand movements.

    PubMed

    Carlton, L G

    1994-03-01

    Discrete aimed hand movements, made by subjects given temporal-accuracy and time-minimization task instructions, were compared. Movements in the temporal-accuracy task were made to a point target with a goal movement time of 400 ms. A circular target then was manufactured that incorporated the measured spatial errors from the temporal-accuracy task, and subjects attempted to contact the target with a minimum movement time and without missing the circular target (time-minimization task instructions). This procedure resulted in equal movement amplitude and approximately equal spatial accuracy for the two task instructions. Movements under the time-minimization instructions were completed rapidly (M = 307 ms) without target misses, and tended to be made up of two submovements. In contrast, movements under temporal-accuracy instructions were made more slowly (M = 397 ms), matching the goal movement time, and were typically characterized by a single submovement. These data support the hypothesis that movement times, at a fixed movement amplitude versus target width ratio, decrease as the number of submovements increases, and that movements produced under temporal-accuracy and time-minimization have different control characteristics. These control differences are related to the linear and logarithmic speed-accuracy relations observed for temporal-accuracy and time-minimization tasks, respectively. PMID:15757833

  8. Bayesian approach increases accuracy when selecting cowpea genotypes with high adaptability and phenotypic stability.

    PubMed

    Barroso, L M A; Teodoro, P E; Nascimento, M; Torres, F E; Dos Santos, A; Corrêa, A M; Sagrilo, E; Corrêa, C C G; Silva, F A; Ceccon, G

    2016-01-01

    This study aimed to verify that a Bayesian approach could be used for the selection of upright cowpea genotypes with high adaptability and phenotypic stability, and the study also evaluated the efficiency of using informative and minimally informative a priori distributions. Six trials were conducted in randomized blocks, and the grain yield of 17 upright cowpea genotypes was assessed. To represent the minimally informative a priori distributions, a probability distribution with high variance was used, and a meta-analysis concept was adopted to represent the informative a priori distributions. Bayes factors were used to conduct comparisons between the a priori distributions. The Bayesian approach was effective for selection of upright cowpea genotypes with high adaptability and phenotypic stability using the Eberhart and Russell method. Bayes factors indicated that the use of informative a priori distributions provided more accurate results than minimally informative a priori distributions. PMID:26985961

  9. Accuracy of travel time distribution (TTD) models as affected by TTD complexity, observation errors, and model and tracer selection

    USGS Publications Warehouse

    Green, Christopher T.; Zhang, Yong; Jurgens, Bryant C.; Starn, J. Jeffrey; Landon, Matthew K.

    2014-01-01

    Analytical models of the travel time distribution (TTD) from a source area to a sample location are often used to estimate groundwater ages and solute concentration trends. The accuracies of these models are not well known for geologically complex aquifers. In this study, synthetic datasets were used to quantify the accuracy of four analytical TTD models as affected by TTD complexity, observation errors, model selection, and tracer selection. Synthetic TTDs and tracer data were generated from existing numerical models with complex hydrofacies distributions for one public-supply well and 14 monitoring wells in the Central Valley, California. Analytical TTD models were calibrated to synthetic tracer data, and prediction errors were determined for estimates of TTDs and conservative tracer (NO3−) concentrations. Analytical models included a new, scale-dependent dispersivity model (SDM) for two-dimensional transport from the watertable to a well, and three other established analytical models. The relative influence of the error sources (TTD complexity, observation error, model selection, and tracer selection) depended on the type of prediction. Geological complexity gave rise to complex TTDs in monitoring wells that strongly affected errors of the estimated TTDs. However, prediction errors for NO3− and median age depended more on tracer concentration errors. The SDM tended to give the most accurate estimates of the vertical velocity and other predictions, although TTD model selection had minor effects overall. Adding tracers improved predictions if the new tracers had different input histories. Studies using TTD models should focus on the factors that most strongly affect the desired predictions.

  10. Screening accuracy of Level 2 autism spectrum disorder rating scales. A review of selected instruments.

    PubMed

    Norris, Megan; Lecavalier, Luc

    2010-07-01

    The goal of this review was to examine the state of Level 2, caregiver-completed rating scales for the screening of Autism Spectrum Disorders (ASDs) in individuals above the age of three years. We focused on screening accuracy and paid particular attention to comparison groups. Inclusion criteria required that scales be developed post ICD-10, be ASD-specific, and have published evidence of diagnostic validity in peer-reviewed journals. The five scales reviewed were: the Social Communication Questionnaire (SCQ), Gilliam Autism Rating Scale/Gilliam Autism Rating Scale-Second Edition (GARS/GARS-2), Social Responsiveness Scale (SRS), Autism Spectrum Screening Questionnaire (ASSQ), and Asperger Syndrome Diagnostic Scale (ASDS). Twenty total studies were located, most examining the SCQ. Research on the other scales was limited. Comparisons between scales were few and available evidence of diagnostic validity is scarce for certain subpopulations (e.g., lower functioning individuals, PDDNOS). Overall, the SCQ performed well, the SRS and ASSQ showed promise, and the GARS/GARS-2 and ASDS demonstrated poor sensitivity. This review indicates that Level 2 ASD caregiver-completed rating scales are in need of much more scientific scrutiny. PMID:20591956

  11. A precise calculation of delayed coincidence selection efficiency and accidental coincidence rate

    NASA Astrophysics Data System (ADS)

    Yu, Jing-Yi; Wang, Zhe; Chen, Shao-Min

    2015-05-01

    A precise background evaluation model is proposed to address the complex data structure of the delayed coincidence method, which is widely used in reactor electron-antineutrino oscillation experiments. In this model, effects from the muon veto, uncorrelated random background, and background are all studied analytically, simplifying the estimation of the systematic uncertainties of signal efficiency and accidental background rate. The results of the calculations are validated numerically with a number of simulation studies and also applied and validated in the recent Daya Bay hydrogen-capture based oscillation measurement. Supported by Ministry of Science and Technology of China (2013CB834302), National Natural Science Foundation of China (11235006, 11475093), Tsinghua University Initiative Scientific Research Program (2012Z02161), and Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education.

  12. Precision improvement for the analysis of flavonoids in selected Thai plants by capillary zone electrophoresis.

    PubMed

    Suntornsuk, Leena; Anurukvorakun, Oraphan

    2005-02-01

    A capillary zone electrophoresis (CZE) method for the analyses of kaempferol in Centella asiatica and Rosa hybrids and rutin in Chromolaena odorata was developed. The optimization was performed on analyses of flavonoids (e.g., rutin, kaempferol, quercetin, myricetin, and apigenin) and organic carboxylic acids (e.g., ethacrynic acid and xanthene-9-carboxylic acid) by investigation of the effects of types and amounts of organic modifiers, background electrolyte concentrations, temperature, and voltage. Baseline separation (R(s) = 2.83) of the compounds was achieved within 10 min in 20 mM NaH2PO4 - Na2HPO4 (pH 8.0) containing 10% v/v ACN and 6% v/v MeOH using a voltage of 25 kV, a temperature of 30 degrees C, and a detection wavelength set at 220 nm. The application of the corrected migration time (t(c)), using ethacrynic acid as the single marker, was efficient to improve the precision of flavonoid identification (% relative standard deviation (RSD) = 0.65%). The method linearity was excellent (r2 > 0.999) over 50-150 microg/mL. Precision (%RSD < 1.66%) and recoveries were good (> 96% and %RSDs < 1.70%) with detection and quantitation limits of 2.23 and 7.14 microg/mL, respectively. Kaempferol in C. asiatica and R. hybrids was 0.014 g/100 g (%RSD = 0.59%) and 0.044 g/100 g (%RSD = 1.04%), respectively, and rutin in C. odorata was 0.088 g/100 g (%RSD = 0.06%). PMID:15690438

  13. Hypoglossal canal dural arteriovenous fistula embolized under precise anatomical evaluation by selective intra-arterial injection computed tomography angiography

    PubMed Central

    Yoshioka, Hideyuki; Yagi, Takashi; Wakai, Takuma; Hashimoto, Koji; Fukumoto, Yuichiro; Suzuki, Keiko; Tateoka, Toru; Kazama, Hirofumi; Kinouchi, Hiroyuki

    2015-01-01

    Dural arteriovenous fistula (DAVF) involving the hypoglossal canal is rare but increasingly reported. To achieve complete obliteration without a procedure-related complication, understanding of the precise anatomy of this DAVF is essential. Here, we describe a 72-year-old man who underwent selective intra-arterial injection computed tomography angiography which allowed us to understand the detailed anatomy of the complex DAVF regarding access routes and the target regions for transvenous embolization (TVE). With the aid of this novel neuroimaging technique successful target TVE was achieved safely and completely. PMID:25934781

  14. SU-E-J-03: Characterization of the Precision and Accuracy of a New, Preclinical, MRI-Guided Focused Ultrasound System for Image-Guided Interventions in Small-Bore, High-Field Magnets

    SciTech Connect

    Ellens, N; Farahani, K

    2015-06-15

    Purpose: MRI-guided focused ultrasound (MRgFUS) has many potential and realized applications including controlled heating and localized drug delivery. The development of many of these applications requires extensive preclinical work, much of it in small animal models. The goal of this study is to characterize the spatial targeting accuracy and reproducibility of a preclinical high field MRgFUS system for thermal ablation and drug delivery applications. Methods: The RK300 (FUS Instruments, Toronto, Canada) is a motorized, 2-axis FUS positioning system suitable for small bore (72 mm), high-field MRI systems. The accuracy of the system was assessed in three ways. First, the precision of the system was assessed by sonicating regular grids of 5 mm squares on polystyrene plates and comparing the resulting focal dimples to the intended pattern, thereby assessing the reproducibility and precision of the motion control alone. Second, the targeting accuracy was assessed by imaging a polystyrene plate with randomly drilled holes and replicating the hole pattern by sonicating the observed hole locations on intact polystyrene plates and comparing the results. Third, the practicallyrealizable accuracy and precision were assessed by comparing the locations of transcranial, FUS-induced blood-brain-barrier disruption (BBBD) (observed through Gadolinium enhancement) to the intended targets in a retrospective analysis of animals sonicated for other experiments. Results: The evenly-spaced grids indicated that the precision was 0.11 +/− 0.05 mm. When image-guidance was included by targeting random locations, the accuracy was 0.5 +/− 0.2 mm. The effective accuracy in the four rodent brains assessed was 0.8 +/− 0.6 mm. In all cases, the error appeared normally distributed (p<0.05) in both orthogonal axes, though the left/right error was systematically greater than the superior/inferior error. Conclusions: The targeting accuracy of this device is sub-millimeter, suitable for many

  15. Effect of wavelength selection on the accuracy of blood oxygen saturation estimates obtained from photoacoustic images

    NASA Astrophysics Data System (ADS)

    Hochuli, Roman; Beard, Paul C.; Cox, Ben

    2015-03-01

    In photoacoustic tomography (PAT) the image contrast is due to optical absorption, and because of this PAT images are sensitive to changes in blood oxygen saturation (sO2). However, this is not a linear relationship due to the presence of a non-uniform light fluence distribution. In this paper we systematically evaluate the conditions in which an approximate linear inversion scheme-which assumes the internal fluence distribution is unchanged when the absorption coefficient changes-can give accurate estimates of sO2. A numerical phantom of highly vascularised tissue is used to test this assumption. It is shown that using multiple wavelengths over a broad range of the near-infrared spectrum yields inaccurate estimates of oxygenation, while a careful selection of wavelengths in the 620-920nm range is likely to yield more accurate oxygenation values. We demonstrate that a 1D fluence correction obtained by fitting a linear function to the average decay rate in the image can further improve the estimates. However, opting to use these longer wavelengths involves sacrificing signal-to-noise ratio in the image, as the absorption of blood is low in this range. This results in an inherent trade-off between error in the sO2 estimates due to fluence variation and error due to noise. This study shows that the depth to which sO2 can be estimated accurately using a linear approximation is limited in vivo, even with idealised measurements, to at most 3mm. In practice, there will be even greater uncertainties affecting the estimates, e.g., due to bandlimited or partial-view acoustic detection.

  16. Precision autophagy: Will the next wave of selective autophagy markers and specific autophagy inhibitors feed clinical pipelines?

    PubMed Central

    Lebovitz, Chandra B; DeVorkin, Lindsay; Bosc, Damien; Rothe, Katharina; Singh, Jagbir; Bally, Marcel; Jiang, Xiaoyan; Young, Robert N; Lum, Julian J; Gorski, Sharon M

    2015-01-01

    Research presented at the Vancouver Autophagy Symposium (VAS) 2014 suggests that autophagy's influence on health and disease depends on tight regulation and precision targeting of substrates. Discussions recognized a pressing need for robust biomarkers that accurately assess the clinical utility of modulating autophagy in disease contexts. Biomarker discovery could flow from investigations of context-dependent triggers, sensors, and adaptors that tailor the autophagy machinery to achieve target specificity. In his keynote address, Dr. Vojo Deretic (University of New Mexico) described the discovery of a cargo receptor family that utilizes peptide motif-based cargo recognition, a mechanism that may be more precise than generic substrate tagging. The keynote by Dr. Alec Kimmelman (Harvard Medical School) emphasized that unbiased screens for novel selective autophagy factors may accelerate the development of autophagy-based therapies. Using a quantitative proteomics screen for de novo identification of autophagosome substrates in pancreatic cancer, Kimmelman's group discovered a new type of selective autophagy that regulates bioavailable iron. Additional presentations revealed novel autophagy regulators and receptors in metabolic diseases, proteinopathies, and cancer, and outlined the development of specific autophagy inhibitors and treatment regimens that combine autophagy modulation with anticancer therapies. VAS 2014 stimulated interdisciplinary discussions focused on the development of biomarkers, drugs, and preclinical models to facilitate clinical translation of key autophagy discoveries. PMID:26506897

  17. A New Class of Advanced Accuracy Satellite Instrumentation (AASI) for the CLARREO Mission: Interferometer Test-bed Tradestudies and Selection

    NASA Astrophysics Data System (ADS)

    Taylor, J. K.; Revercomb, H. E.; Grandmont, F. J.; Buijs, H.; Gero, P. J.; Best, F. A.; Tobin, D. C.; Knuteson, R. O.; Laporte, D. D.

    2009-12-01

    NASA has selected CLARREO (Climate Absolute Radiance and Refractivity Observatory), a climate mission recommended by the 2007 Decadal Survey of the US National Research Council, as a potential new start in 2010. CLARREO will measure spectrally resolved radiance from the earth and atmospheric bending of GPS signals related to atmospheric structure (refractivity) as benchmark measurements of long-term climate change trends. CLARREO will provide more complete spectral and time-of-day coverage and will fly basic physical standards to eliminate the need to assume on-board reference stability. Therefore, the spectral radiances from this mission will also serve as benchmarks to propagate a highly accurate calibration to other space-borne IR instruments. Technology development and risk reduction for the CLARREO mission is being conducted at the Space Science and Engineering Center at the University of Wisconsin-Madison. The objective of this work is to develop and demonstrate the technology necessary to measure IR spectrally resolved radiances (3 - 50 micrometers) with ultra high accuracy (< 0.1 K 3-sigma brightness temperature at scene temperature) for the CLARREO benchmark climate mission. The ultimate benefit to society is irrefutable quantification of climate change and a solid basis for improving climate model forecasts. The proposed work (University of Wisconsin-Madison and Harvard University) was selected for the 2007 NASA Instrument Incubator Program (IIP) and will develop four primary technologies to assure SI traceability on-orbit and demonstrate the ultra high accuracy measurement capability required for CLARREO: (1) On-orbit Absolute Radiance Standard (OARS), a high emissivity blackbody source that uses multiple miniature phase-change cells to provide a revolutionary on-orbit standard with absolute temperature accuracy proven over a wide range of temperatures, (2) On-orbit Cavity Emissivity Modules (OCEMs), providing a source (quantum cascade laser, QCL, or

  18. Detecting declines in the abundance of a bull trout (Salvelinus confluentus) population: Understanding the accuracy, precision, and costs of our efforts

    USGS Publications Warehouse

    Al-Chokhachy, R.; Budy, P.; Conner, M.

    2009-01-01

    Using empirical field data for bull trout (Salvelinus confluentus), we evaluated the trade-off between power and sampling effort-cost using Monte Carlo simulations of commonly collected mark-recapture-resight and count data, and we estimated the power to detect changes in abundance across different time intervals. We also evaluated the effects of monitoring different components of a population and stratification methods on the precision of each method. Our results illustrate substantial variability in the relative precision, cost, and information gained from each approach. While grouping estimates by age or stage class substantially increased the precision of estimates, spatial stratification of sampling units resulted in limited increases in precision. Although mark-resight methods allowed for estimates of abundance versus indices of abundance, our results suggest snorkel surveys may be a more affordable monitoring approach across large spatial scales. Detecting a 25% decline in abundance after 5 years was not possible, regardless of technique (power = 0.80), without high sampling effort (48% of study site). Detecting a 25% decline was possible after 15 years, but still required high sampling efforts. Our results suggest detecting moderate changes in abundance of freshwater salmonids requires considerable resource and temporal commitments and highlight the difficulties of using abundance measures for monitoring bull trout populations.

  19. Direction-Selective Circuits Shape Noise to Ensure a Precise Population Code.

    PubMed

    Zylberberg, Joel; Cafaro, Jon; Turner, Maxwell H; Shea-Brown, Eric; Rieke, Fred

    2016-01-20

    Neural responses are noisy, and circuit structure can correlate this noise across neurons. Theoretical studies show that noise correlations can have diverse effects on population coding, but these studies rarely explore stimulus dependence of noise correlations. Here, we show that noise correlations in responses of ON-OFF direction-selective retinal ganglion cells are strongly stimulus dependent, and we uncover the circuit mechanisms producing this stimulus dependence. A population model based on these mechanistic studies shows that stimulus-dependent noise correlations improve the encoding of motion direction 2-fold compared to independent noise. This work demonstrates a mechanism by which a neural circuit effectively shapes its signal and noise in concert, minimizing corruption of signal by noise. Finally, we generalize our findings beyond direction coding in the retina and show that stimulus-dependent correlations will generally enhance information coding in populations of diversely tuned neurons. PMID:26796691

  20. Approach towards sensor placement, selection and fusion for real-time condition monitoring of precision machines

    NASA Astrophysics Data System (ADS)

    Er, Poi Voon; Teo, Chek Sing; Tan, Kok Kiong

    2016-02-01

    Moving mechanical parts in a machine will inevitably generate vibration profiles reflecting its operating conditions. Vibration profile analysis is a useful tool for real-time condition monitoring to avoid loss of performance and unwanted machine downtime. In this paper, we propose and validate an approach for sensor placement, selection and fusion for continuous machine condition monitoring. The main idea is to use a minimal series of sensors mounted at key locations of a machine to measure and infer the actual vibration spectrum at a critical point where it is not suitable to mount a sensor. The locations for sensors' mountings which are subsequently used for vibration inference are identified based on sensitivity calibration at these locations moderated with normalized Fisher Information (NFI) associated with the measurement quality of the sensor at that location. Each of the identified sensor placement location is associated with one or more sensitive frequencies for which it ranks top in terms of the moderated sensitivities calibrated. A set of Radial Basis Function (RBF), each of them associated with a range of sensitive frequencies, is used to infer the vibration at the critical point for that frequency. The overall vibration spectrum of the critical point is then fused from these components. A comprehensive set of experimental results for validation of the proposed approach is provided in the paper.

  1. Precise Determination of Enantiomeric Excess by a Sensitivity Enhanced Two-Dimensional Band-Selective Pure-Shift NMR.

    PubMed

    Rachineni, Kavitha; Kakita, Veera Mohana Rao; Dayaka, Satyanarayana; Vemulapalli, Sahithya Phani Babu; Bharatam, Jagadeesh

    2015-07-21

    Unambiguous identification and precise quantification of enantiomers in chiral mixtures is crucial for enantiomer specific synthesis as well as chemical analysis. The task is often challenging for mixtures with high enantiomeric excess and for complex molecules with strong (1)H-(1)H scalar (J) coupling network. The recent advancements in (1)H-(1)H decoupling strategies to suppress the J-interactions offered new possibilities for NMR based unambiguous discrimination and quantification enantiomers. Herein, we discuss a high resolution two-dimensional pure-shift zCOSY NMR method with homonuclear band-selective decoupling in both the F1 and F2 dimensions (F1F2-HOBS-zCOSY). This advanced method shows a sharp improvement in resolution over the other COSY methods and also eliminates the problems associated with the overlapping decoupling sidebands. The efficacy of this method has been exploited for precise quantification of enantiomeric excess (ee) ratio (R/S) up to 99:1 in the presence of very low concentrations of chiral lanthanide shift reagents (CLSR) or chiral solvating agents (CSA). The F1F2-HOBS-zCOSY is simple and can be easily implemented on any modern NMR spectrometers, as a routine analytical tool. PMID:26091767

  2. Precision Fabrication of a Large-Area Sinusoidal Surface Using a Fast-Tool-Servo Technique ─Improvement of Local Fabrication Accuracy

    NASA Astrophysics Data System (ADS)

    Gao, Wei; Tano, Makoto; Araki, Takeshi; Kiyono, Satoshi

    This paper describes a diamond turning fabrication system for a sinusoidal grid surface. The wavelength and amplitude of the sinusoidal wave in each direction are 100µm and 100nm, respectively. The fabrication system, which is based on a fast-tool-servo (FTS), has the ability to generate the angle grid surface over an area of φ 150mm. This paper focuses on the improvement of the local fabrication accuracy. The areas considered are each approximately 1 × 1mm, and can be imaged by an interference microscope. Specific fabrication errors of the manufacturing process, caused by the round nose geometry of the diamond cutting tool and the data digitization, are successfully identified by Discrete Fourier Transform of the microscope images. Compensation processes are carried out to reduce the errors. As a result, the fabrication errors in local areas of the angle grid surface are reduced by 1/10.

  3. Preliminary assessment of the accuracy and precision of TOPEX/POSEIDON altimeter data with respect to the large-scale ocean circulation

    NASA Technical Reports Server (NTRS)

    Wunsch, Carl; Stammer, Detlef

    1994-01-01

    TOPEX/POSEIDON sea surface height measurements are examined for quantitative consistency with known elements of the oceanic general circulation and its variability. Project-provided corrections were accepted but are at tested as part of the overall results. The ocean was treated as static over each 10-day repeat cycle and maps constructed of the absolute sea surface topography from simple averages in 2 deg x 2 deg bins. A hybrid geoid model formed from a combination of the recent Joint Gravity Model-2 and the project-provided Ohio State University geoid was used to estimate the absolute topography in each 10-day period. Results are examined in terms of the annual average, seasonal average, seasonal variations, and variations near the repeat period. Conclusion are as follows: the orbit error is now difficult to observe, having been reduced to a level at or below the level of other error sources; the geoid dominates the error budget of the estimates of the absolute topography; the estimated seasonal cycle is consistent with prior estimates; shorter-period variability is dominated on the largest scales by an oscillation near 50 days in spherical harmonics Y(sup m)(sub 1)(theta, lambda) with an amplitude near 10 cm, close to the simplest alias of the M(sub 2) tide. This spectral peak and others visible in the periodograms support the hypothesis that the largest remaining time-dependent errors lie in the tidal models. Though discrepancies attribute to the geoid are within the formal uncertainties of the good estimates, removal of them is urgent for circulation studies. Current gross accuracy of the TOPEX/POSEIDON mission is in the range of 5-10 cm, distributed overbroad band of frequencies and wavenumbers. In finite bands, accuracies approach the 1-cm level, and expected improvements arising from extended mission duration should reduce these numbers by nearly an order of magnitude.

  4. Accuracy and reproducibility of the Oxi/Ferm system in identifying a select group of unusual gram-negative bacilli.

    PubMed Central

    Nadler, H; George, H; Barr, J

    1979-01-01

    The Oxi/Ferm (O/F) identification system was compared in a double-blind study to a conventional test battery for the characterization of 96 reference and clinical strains consisting of 83 nonfermentative and 13 oxidase-producing, fermentative gram-negative bacilli. The O/F tube and supplemental tests correctly identified 84% of the nonfermentative and 77% of the oxidase-producing, fermentative bacilli. However, when the supplemental tests were excluded and the biochemical profiles generated by all nine O/F tube reactions were examined, the profile accuracy reached 95% (79 of 83) for the nonfermentative and 93% (12 of 13) for oxidase-producing, fermentative bacilli. Seven of the nine O/F substrate reactions demonstrated less than or equal to 89% agreement with conventional reactions, whereas the urea and arginine reactions provided 82 and 85% agreement, respectively. Replicate O/F tests with six selected organisms demonstrated 97% identification reproducibility and 84% overall substrate reproducibility. The mean O/F identification time was 2.6 days as compared to 3.3 days for the conventional system. Although this study suggests that the O/F system is a convenient, rapid, and accurate alternative to conventional identification methods, several modifications are recommended. PMID:372222

  5. Precision measurements of photoabsorption cross sections of Ar, Kr, Xe, and selected molecules at 58.4, 73.6, and 74.4 nm

    NASA Technical Reports Server (NTRS)

    Samson, James A. R.; Yin, Lifeng

    1989-01-01

    Absolute absorption cross sections have been measured for the rare gases at 58.43, 73.59, and 74.37 nm with an accuracy of + or - 0.8 percent. For the molecules H2, N2, O2, CO, N2O, CO2, and CH4, precision measurements were made at 58.43 nm with an accuracy of + or - 0.8 percent. Molecular absorption cross sections are also reported at 73.59 and 74.37 nm. However, in the vicinity of these wavelengths most molecules exhibit considerable structure, and cross sections measured at these wavelengths may depend on the widths and the amounts of self-reversal of these resonance lines. A detailed discussion is given of the systematic errors encountered with the double-ion chamber used in the cross-sectional measurements. Details are also given of precision pressure measurements.

  6. Leaf Vein Length per Unit Area Is Not Intrinsically Dependent on Image Magnification: Avoiding Measurement Artifacts for Accuracy and Precision1[W][OPEN

    PubMed Central

    Sack, Lawren; Caringella, Marissa; Scoffoni, Christine; Mason, Chase; Rawls, Michael; Markesteijn, Lars; Poorter, Lourens

    2014-01-01

    Leaf vein length per unit leaf area (VLA; also known as vein density) is an important determinant of water and sugar transport, photosynthetic function, and biomechanical support. A range of software methods are in use to visualize and measure vein systems in cleared leaf images; typically, users locate veins by digital tracing, but recent articles introduced software by which users can locate veins using thresholding (i.e. based on the contrasting of veins in the image). Based on the use of this method, a recent study argued against the existence of a fixed VLA value for a given leaf, proposing instead that VLA increases with the magnification of the image due to intrinsic properties of the vein system, and recommended that future measurements use a common, low image magnification for measurements. We tested these claims with new measurements using the software LEAFGUI in comparison with digital tracing using ImageJ software. We found that the apparent increase of VLA with magnification was an artifact of (1) using low-quality and low-magnification images and (2) errors in the algorithms of LEAFGUI. Given the use of images of sufficient magnification and quality, and analysis with error-free software, the VLA can be measured precisely and accurately. These findings point to important principles for improving the quantity and quality of important information gathered from leaf vein systems. PMID:25096977

  7. The relative accuracy of standard estimators for macrofaunal abundance and species richness derived from selected intertidal transect designs used to sample exposed sandy beaches

    NASA Astrophysics Data System (ADS)

    Schoeman, transect designs used to sample exposed sandy beaches D. S.; Wheeler, M.; Wait, M.

    2003-10-01

    In order to ensure that patterns detected in field samples reflect real ecological processes rather than methodological idiosyncrasies, it is important that researchers attempt to understand the consequences of the sampling and analytical designs that they select. This is especially true for sandy beach ecology, which has lagged somewhat behind ecological studies of other intertidal habitats. This paper investigates the performance of routine estimators of macrofaunal abundance and species richness, which are variables that have been widely used to infer predictable patterns of biodiversity across a gradient of beach types. To do this, a total of six shore-normal strip transects were sampled on three exposed, oceanic sandy beaches in the Eastern Cape, South Africa. These transects comprised contiguous quadrats arranged linearly between the spring high and low water marks. Using simple Monte Carlo simulation techniques, data collected from the strip transects were used to assess the accuracy of parameter estimates from different sampling strategies relative to their true values (macrofaunal abundance ranged 595-1369 individuals transect -1; species richness ranged 12-21 species transect -1). Results indicated that estimates from the various transect methods performed in a similar manner both within beaches and among beaches. Estimates for macrofaunal abundance tended to be negatively biased, especially at levels of sampling effort most commonly reported in the literature, and accuracy decreased with decreasing sampling effort. By the same token, estimates for species richness were always negatively biased and were also characterised by low precision. Furthermore, triplicate transects comprising a sampled area in the region of 4 m 2 (as has been previously recommended) are expected to miss more than 30% of the species that occur on the transect. Surprisingly, for both macrofaunal abundance and species richness, estimates based on data from transects sampling quadrats

  8. High-accuracy, high-precision, high-resolution, continuous monitoring of urban greenhouse gas emissions? Results to date from INFLUX

    NASA Astrophysics Data System (ADS)

    Davis, K. J.; Brewer, A.; Cambaliza, M. O. L.; Deng, A.; Hardesty, M.; Gurney, K. R.; Heimburger, A. M. F.; Karion, A.; Lauvaux, T.; Lopez-Coto, I.; McKain, K.; Miles, N. L.; Patarasuk, R.; Prasad, K.; Razlivanov, I. N.; Richardson, S.; Sarmiento, D. P.; Shepson, P. B.; Sweeney, C.; Turnbull, J. C.; Whetstone, J. R.; Wu, K.

    2015-12-01

    The Indianapolis Flux Experiment (INFLUX) is testing the boundaries of our ability to use atmospheric measurements to quantify urban greenhouse gas (GHG) emissions. The project brings together inventory assessments, tower-based and aircraft-based atmospheric measurements, and atmospheric modeling to provide high-accuracy, high-resolution, continuous monitoring of emissions of GHGs from the city. Results to date include a multi-year record of tower and aircraft based measurements of the urban CO2 and CH4 signal, long-term atmospheric modeling of GHG transport, and emission estimates for both CO2 and CH4 based on both tower and aircraft measurements. We will present these emissions estimates, the uncertainties in each, and our assessment of the primary needs for improvements in these emissions estimates. We will also present ongoing efforts to improve our understanding of atmospheric transport and background atmospheric GHG mole fractions, and to disaggregate GHG sources (e.g. biogenic vs. fossil fuel CO2 fluxes), topics that promise significant improvement in urban GHG emissions estimates.

  9. Accuracy and Precision in the Southern Hemisphere Additional Ozonesondes (SHADOZ) Dataset 1998-2000 in Light of the JOSIE-2000 Results

    NASA Technical Reports Server (NTRS)

    Witte, J. C.; Thompson, A. M.; Schmidlin, F. J.; Oltmans, S. J.; McPeters, R. D.; Smit, H. G. J.

    2003-01-01

    A network of 12 southern hemisphere tropical and subtropical stations in the Southern Hemisphere ADditional OZonesondes (SHADOZ) project has provided over 2000 profiles of stratospheric and tropospheric ozone since 1998. Balloon-borne electrochemical concentration cell (ECC) ozonesondes are used with standard radiosondes for pressure, temperature and relative humidity measurements. The archived data are available at:http: //croc.gsfc.nasa.gov/shadoz. In Thompson et al., accuracies and imprecisions in the SHADOZ 1998- 2000 dataset were examined using ground-based instruments and the TOMS total ozone measurement (version 7) as references. Small variations in ozonesonde technique introduced possible biases from station-to-station. SHADOZ total ozone column amounts are now compared to version 8 TOMS; discrepancies between the two datasets are reduced 2\\% on average. An evaluation of ozone variations among the stations is made using the results of a series of chamber simulations of ozone launches (JOSIE-2000, Juelich Ozonesonde Intercomparison Experiment) in which a standard reference ozone instrument was employed with the various sonde techniques used in SHADOZ. A number of variations in SHADOZ ozone data are explained when differences in solution strength, data processing and instrument type (manufacturer) are taken into account.

  10. The effect of dilution and the use of a post-extraction nucleic acid purification column on the accuracy, precision, and inhibition of environmental DNA samples

    USGS Publications Warehouse

    Mckee, Anna M.; Spear, Stephen F.; Pierson, Todd W.

    2015-01-01

    Isolation of environmental DNA (eDNA) is an increasingly common method for detecting presence and assessing relative abundance of rare or elusive species in aquatic systems via the isolation of DNA from environmental samples and the amplification of species-specific sequences using quantitative PCR (qPCR). Co-extracted substances that inhibit qPCR can lead to inaccurate results and subsequent misinterpretation about a species’ status in the tested system. We tested three treatments (5-fold and 10-fold dilutions, and spin-column purification) for reducing qPCR inhibition from 21 partially and fully inhibited eDNA samples collected from coastal plain wetlands and mountain headwater streams in the southeastern USA. All treatments reduced the concentration of DNA in the samples. However, column purified samples retained the greatest sensitivity. For stream samples, all three treatments effectively reduced qPCR inhibition. However, for wetland samples, the 5-fold dilution was less effective than other treatments. Quantitative PCR results for column purified samples were more precise than the 5-fold and 10-fold dilutions by 2.2× and 3.7×, respectively. Column purified samples consistently underestimated qPCR-based DNA concentrations by approximately 25%, whereas the directional bias in qPCR-based DNA concentration estimates differed between stream and wetland samples for both dilution treatments. While the directional bias of qPCR-based DNA concentration estimates differed among treatments and locations, the magnitude of inaccuracy did not. Our results suggest that 10-fold dilution and column purification effectively reduce qPCR inhibition in mountain headwater stream and coastal plain wetland eDNA samples, and if applied to all samples in a study, column purification may provide the most accurate relative qPCR-based DNA concentrations estimates while retaining the greatest assay sensitivity.

  11. Re-Os geochronology of the El Salvador porphyry Cu-Mo deposit, Chile: Tracking analytical improvements in accuracy and precision over the past decade

    NASA Astrophysics Data System (ADS)

    Zimmerman, Aaron; Stein, Holly J.; Morgan, John W.; Markey, Richard J.; Watanabe, Yasushi

    2014-04-01

    deposit geochronology. The timing and duration of mineralization from Re-Os dating of ore minerals is more precise than estimates from previously reported 40Ar/39Ar and K-Ar ages on alteration minerals. The Re-Os results suggest that the mineralization is temporally distinct from pre-mineral rhyolite porphyry (42.63 ± 0.28 Ma) and is immediately prior to or overlapping with post-mineral latite dike emplacement (41.16 ± 0.48 Ma). Based on the Re-Os and other geochronologic data, the Middle Eocene intrusive activity in the El Salvador district is divided into three pulses: (1) 44-42.5 Ma for weakly mineralized porphyry intrusions, (2) 41.8-41.2 Ma for intensely mineralized porphyry intrusions, and (3) ∼41 Ma for small latite dike intrusions without major porphyry stocks. The orientation of igneous dikes and porphyry stocks changed from NNE-SSW during the first pulse to WNW-ESE for the second and third pulses. This implies that the WNW-ESE striking stress changed from σ3 (minimum principal compressive stress) during the first pulse to σHmax (maximum principal compressional stress in a horizontal plane) during the second and third pulses. Therefore, the focus of intense porphyry Cu-Mo mineralization occurred during a transient geodynamic reconfiguration just before extinction of major intrusive activity in the region.

  12. Comparison of Accuracy and Efficiency of Directed Scanning and Group-Item Scanning for Augmentative Communication Selection Techniques with Typically Developing Preschoolers

    ERIC Educational Resources Information Center

    Dropik, Patricia L.; Reichle, Joe

    2008-01-01

    Purpose: Directed scanning and group-item scanning both represent options for increased scanning efficiency. This investigation compared accuracy and speed of selection with preschoolers using each scanning method. The study's purpose was to describe performance characteristics of typically developing children and to provide a reliable assessment…

  13. The problem of selecting an optimum frequency for a measuring generator in determining the value of the hydrophysical parameter with a given accuracy

    NASA Technical Reports Server (NTRS)

    Stepanyuk, V. A.

    1974-01-01

    The selection of the optimum frequency for a measuring generator for determining the value of the hydrophysical parameter with a given degree of accuracy is discussed. Methods from information theory for measuring generators are described. Conversion of the frequency of generators into digital form by means of statistical averaging is also described.

  14. A quantitative method for evaluating numerical simulation accuracy of time-transient Lamb wave propagation with its applications to selecting appropriate element size and time step.

    PubMed

    Wan, Xiang; Xu, Guanghua; Zhang, Qing; Tse, Peter W; Tan, Haihui

    2016-01-01

    Lamb wave technique has been widely used in non-destructive evaluation (NDE) and structural health monitoring (SHM). However, due to the multi-mode characteristics and dispersive nature, Lamb wave propagation behavior is much more complex than that of bulk waves. Numerous numerical simulations on Lamb wave propagation have been conducted to study its physical principles. However, few quantitative studies on evaluating the accuracy of these numerical simulations were reported. In this paper, a method based on cross correlation analysis for quantitatively evaluating the simulation accuracy of time-transient Lamb waves propagation is proposed. Two kinds of error, affecting the position and shape accuracies are firstly identified. Consequently, two quantitative indices, i.e., the GVE (group velocity error) and MACCC (maximum absolute value of cross correlation coefficient) derived from cross correlation analysis between a simulated signal and a reference waveform, are proposed to assess the position and shape errors of the simulated signal. In this way, the simulation accuracy on the position and shape is quantitatively evaluated. In order to apply this proposed method to select appropriate element size and time step, a specialized 2D-FEM program combined with the proposed method is developed. Then, the proper element size considering different element types and time step considering different time integration schemes are selected. These results proved that the proposed method is feasible and effective, and can be used as an efficient tool for quantitatively evaluating and verifying the simulation accuracy of time-transient Lamb wave propagation. PMID:26315506

  15. Canopy Temperature and Vegetation Indices from High-Throughput Phenotyping Improve Accuracy of Pedigree and Genomic Selection for Grain Yield in Wheat

    PubMed Central

    Rutkoski, Jessica; Poland, Jesse; Mondal, Suchismita; Autrique, Enrique; Pérez, Lorena González; Crossa, José; Reynolds, Matthew; Singh, Ravi

    2016-01-01

    Genomic selection can be applied prior to phenotyping, enabling shorter breeding cycles and greater rates of genetic gain relative to phenotypic selection. Traits measured using high-throughput phenotyping based on proximal or remote sensing could be useful for improving pedigree and genomic prediction model accuracies for traits not yet possible to phenotype directly. We tested if using aerial measurements of canopy temperature, and green and red normalized difference vegetation index as secondary traits in pedigree and genomic best linear unbiased prediction models could increase accuracy for grain yield in wheat, Triticum aestivum L., using 557 lines in five environments. Secondary traits on training and test sets, and grain yield on the training set were modeled as multivariate, and compared to univariate models with grain yield on the training set only. Cross validation accuracies were estimated within and across-environment, with and without replication, and with and without correcting for days to heading. We observed that, within environment, with unreplicated secondary trait data, and without correcting for days to heading, secondary traits increased accuracies for grain yield by 56% in pedigree, and 70% in genomic prediction models, on average. Secondary traits increased accuracy slightly more when replicated, and considerably less when models corrected for days to heading. In across-environment prediction, trends were similar but less consistent. These results show that secondary traits measured in high-throughput could be used in pedigree and genomic prediction to improve accuracy. This approach could improve selection in wheat during early stages if validated in early-generation breeding plots. PMID:27402362

  16. Differential laser absorption spectrometry for global profiling of tropospheric carbon dioxide: selection of optimum sounding frequencies for high-precision measurements.

    PubMed

    Menzies, Robert T; Tratt, David M

    2003-11-20

    We discuss the spectroscopic requirements for a laser absorption spectrometer (LAS) approach to high-precision carbon dioxide (CO2) measurements in the troposphere. Global-scale, high-precision CO2 measurements are highly desirable in an effort to improve understanding and quantification of the CO2 sources and sinks and their impact on global climate. We present differential absorption sounding characteristics for selected LAS transmitter laser wavelengths, emphasizing the effects of atmospheric temperature profile uncertainties. Candidate wavelengths for lower-troposphere measurements are identified in the CO2 bands centered near 1.57, 1.60, and 2.06 microm. PMID:14658457

  17. Relative accuracy evaluation.

    PubMed

    Zhang, Yan; Wang, Hongzhi; Yang, Zhongsheng; Li, Jianzhong

    2014-01-01

    The quality of data plays an important role in business analysis and decision making, and data accuracy is an important aspect in data quality. Thus one necessary task for data quality management is to evaluate the accuracy of the data. And in order to solve the problem that the accuracy of the whole data set is low while a useful part may be high, it is also necessary to evaluate the accuracy of the query results, called relative accuracy. However, as far as we know, neither measure nor effective methods for the accuracy evaluation methods are proposed. Motivated by this, for relative accuracy evaluation, we propose a systematic method. We design a relative accuracy evaluation framework for relational databases based on a new metric to measure the accuracy using statistics. We apply the methods to evaluate the precision and recall of basic queries, which show the result's relative accuracy. We also propose the method to handle data update and to improve accuracy evaluation using functional dependencies. Extensive experimental results show the effectiveness and efficiency of our proposed framework and algorithms. PMID:25133752

  18. Relative Accuracy Evaluation

    PubMed Central

    Zhang, Yan; Wang, Hongzhi; Yang, Zhongsheng; Li, Jianzhong

    2014-01-01

    The quality of data plays an important role in business analysis and decision making, and data accuracy is an important aspect in data quality. Thus one necessary task for data quality management is to evaluate the accuracy of the data. And in order to solve the problem that the accuracy of the whole data set is low while a useful part may be high, it is also necessary to evaluate the accuracy of the query results, called relative accuracy. However, as far as we know, neither measure nor effective methods for the accuracy evaluation methods are proposed. Motivated by this, for relative accuracy evaluation, we propose a systematic method. We design a relative accuracy evaluation framework for relational databases based on a new metric to measure the accuracy using statistics. We apply the methods to evaluate the precision and recall of basic queries, which show the result's relative accuracy. We also propose the method to handle data update and to improve accuracy evaluation using functional dependencies. Extensive experimental results show the effectiveness and efficiency of our proposed framework and algorithms. PMID:25133752

  19. ZCURVE 3.0: identify prokaryotic genes with higher accuracy as well as automatically and accurately select essential genes.

    PubMed

    Hua, Zhi-Gang; Lin, Yan; Yuan, Ya-Zhou; Yang, De-Chang; Wei, Wen; Guo, Feng-Biao

    2015-07-01

    In 2003, we developed an ab initio program, ZCURVE 1.0, to find genes in bacterial and archaeal genomes. In this work, we present the updated version (i.e. ZCURVE 3.0). Using 422 prokaryotic genomes, the average accuracy was 93.7% with the updated version, compared with 88.7% with the original version. Such results also demonstrate that ZCURVE 3.0 is comparable with Glimmer 3.02 and may provide complementary predictions to it. In fact, the joint application of the two programs generated better results by correctly finding more annotated genes while also containing fewer false-positive predictions. As the exclusive function, ZCURVE 3.0 contains one post-processing program that can identify essential genes with high accuracy (generally >90%). We hope ZCURVE 3.0 will receive wide use with the web-based running mode. The updated ZCURVE can be freely accessed from http://cefg.uestc.edu.cn/zcurve/ or http://tubic.tju.edu.cn/zcurveb/ without any restrictions. PMID:25977299

  20. An Analysis of the Selected Materials Used in Step Measurements During Pre-Fits of Thermal Protection System Tiles and the Accuracy of Measurements Made Using These Selected Materials

    NASA Technical Reports Server (NTRS)

    Kranz, David William

    2010-01-01

    The goal of this research project was be to compare and contrast the selected materials used in step measurements during pre-fits of thermal protection system tiles and to compare and contrast the accuracy of measurements made using these selected materials. The reasoning for conducting this test was to obtain a clearer understanding to which of these materials may yield the highest accuracy rate of exacting measurements in comparison to the completed tile bond. These results in turn will be presented to United Space Alliance and Boeing North America for their own analysis and determination. Aerospace structures operate under extreme thermal environments. Hot external aerothermal environments in high Mach number flights lead to high structural temperatures. The differences between tile heights from one to another are very critical during these high Mach reentries. The Space Shuttle Thermal Protection System is a very delicate and highly calculated system. The thermal tiles on the ship are measured to within an accuracy of .001 of an inch. The accuracy of these tile measurements is critical to a successful reentry of an orbiter. This is why it is necessary to find the most accurate method for measuring the height of each tile in comparison to each of the other tiles. The test results indicated that there were indeed differences in the selected materials used in step measurements during prefits of Thermal Protection System Tiles and that Bees' Wax yielded a higher rate of accuracy when compared to the baseline test. In addition, testing for experience level in accuracy yielded no evidence of difference to be found. Lastly the use of the Trammel tool over the Shim Pack yielded variable difference for those tests.

  1. Improving accuracy of overhanging structures for selective laser melting through reliability characterization of single track formation on thick powder beds

    NASA Astrophysics Data System (ADS)

    Mohanty, Sankhya; Hattel, Jesper H.

    2016-04-01

    Repeatability and reproducibility of parts produced by selective laser melting is a standing issue, and coupled with a lack of standardized quality control presents a major hindrance towards maturing of selective laser melting as an industrial scale process. Consequently, numerical process modelling has been adopted towards improving the predictability of the outputs from the selective laser melting process. Establishing the reliability of the process, however, is still a challenge, especially in components having overhanging structures. In this paper, a systematic approach towards establishing reliability of overhanging structure production by selective laser melting has been adopted. A calibrated, fast, multiscale thermal model is used to simulate the single track formation on a thick powder bed. Single tracks are manufactured on a thick powder bed using same processing parameters, but at different locations in a powder bed and in different laser scanning directions. The difference in melt track widths and depths captures the effect of changes in incident beam power distribution due to location and processing direction. The experimental results are used in combination with numerical model, and subjected to uncertainty and reliability analysis. Cumulative probability distribution functions obtained for melt track widths and depths are found to be coherent with observed experimental values. The technique is subsequently extended for reliability characterization of single layers produced on a thick powder bed without support structures, by determining cumulative probability distribution functions for average layer thickness, sample density and thermal homogeneity.

  2. Multiple Oral Rereading: A Descriptive Study of Its Effects on Reading Speed and Accuracy in Selected First-Grade Children.

    ERIC Educational Resources Information Center

    Moyer, Sandra Brown

    Multiple Oral Rereading (MOR), which involves repeated reading of the same instructional unit, has been found effective in remedial reading instruction. In this study, which was designed to provide basic information about the dynamics of such repetition, 32 first-grade children were selected as subjects on the basis of their ability to read, out…

  3. Accuracy of genomic prediction for BCWD resistance in rainbow trout using different genotyping platforms and genomic selection models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study, we aimed to (1) predict genomic estimated breeding value (GEBV) for bacterial cold water disease (BCWD) resistance by genotyping training (n=583) and validation samples (n=53) with two genotyping platforms (24K RAD-SNP and 49K SNP) and using different genomic selection (GS) models (Ba...

  4. Performance, Accuracy, Data Delivery, and Feedback Methods in Order Selection: A Comparison of Voice, Handheld, and Paper Technologies

    ERIC Educational Resources Information Center

    Ludwig, Timothy D.; Goomas, David T.

    2007-01-01

    Field study was conducted in auto-parts after-market distribution centers where selectors used handheld computers to receive instructions and feedback about their product selection process. A wireless voice-interaction technology was then implemented in a multiple baseline fashion across three departments of a warehouse (N = 14) and was associated…

  5. Prognostic gene signatures for patient stratification in breast cancer - accuracy, stability and interpretability of gene selection approaches using prior knowledge on protein-protein interactions

    PubMed Central

    2012-01-01

    Background Stratification of patients according to their clinical prognosis is a desirable goal in cancer treatment in order to achieve a better personalized medicine. Reliable predictions on the basis of gene signatures could support medical doctors on selecting the right therapeutic strategy. However, during the last years the low reproducibility of many published gene signatures has been criticized. It has been suggested that incorporation of network or pathway information into prognostic biomarker discovery could improve prediction performance. In the meanwhile a large number of different approaches have been suggested for the same purpose. Methods We found that on average incorporation of pathway information or protein interaction data did not significantly enhance prediction performance, but indeed greatly interpretability of gene signatures. Some methods (specifically network-based SVMs) could greatly enhance gene selection stability, but revealed only a comparably low prediction accuracy, whereas Reweighted Recursive Feature Elimination (RRFE) and average pathway expression led to very clearly interpretable signatures. In addition, average pathway expression, together with elastic net SVMs, showed the highest prediction performance here. Results The results indicated that no single algorithm to perform best with respect to all three categories in our study. Incorporating network of prior knowledge into gene selection methods in general did not significantly improve classification accuracy, but greatly interpretability of gene signatures compared to classical algorithms. PMID:22548963

  6. An Experiment to Study the Use of Boolean Not Logic to Improve the Precision of Selective Dissemination of Information

    ERIC Educational Resources Information Center

    Scheffler, Frederic; And Others

    1972-01-01

    The use of Boolean not" logic in selective dissemination of information produced greater user satisfaction, less nonpertinent information, and no apparent decrease in the number of pertinent retrievals. (9 references) (SJ)

  7. Bias and precision of selected analytes reported by the National Atmospheric Deposition Program and National Trends Network, 1984

    USGS Publications Warehouse

    Brooks, M.H.; Schroder, L.J.; Willoughby, T.C.

    1987-01-01

    The U.S. Geological Survey operated a blind audit sample program during 1974 to test the effects of the sample handling and shipping procedures used by the National Atmospheric Deposition Program and National Trends Network on the quality of wet deposition data produced by the combined networks. Blind audit samples, which were dilutions of standard reference water samples, were submitted by network site operators to the central analytical laboratory disguised as actual wet deposition samples. Results from the analyses of blind audit samples were used to calculate estimates of analyte bias associated with all network wet deposition samples analyzed in 1984 and to estimate analyte precision. Concentration differences between double blind samples that were submitted to the central analytical laboratory and separate analyses of aliquots of those blind audit samples that had not undergone network sample handling and shipping were used to calculate analyte masses that apparently were added to each blind audit sample by routine network handling and shipping procedures. These calculated masses indicated statistically significant biases for magnesium, sodium , potassium, chloride, and sulfate. Median calculated masses were 41.4 micrograms (ug) for calcium, 14.9 ug for magnesium, 23.3 ug for sodium, 0.7 ug for potassium, 16.5 ug for chloride and 55.3 ug for sulfate. Analyte precision was estimated using two different sets of replicate measures performed by the central analytical laboratory. Estimated standard deviations were similar to those previously reported. (Author 's abstract)

  8. Two-stage case-control studies: precision of parameter estimates and considerations in selecting sample size.

    PubMed

    Hanley, James A; Csizmadi, Ilona; Collet, Jean-Paul

    2005-12-15

    A two-stage case-control design, in which exposure and outcome are determined for a large sample but covariates are measured on only a subsample, may be much less expensive than a one-stage design of comparable power. However, the methods available to plan the sizes of the stage 1 and stage 2 samples, or to project the precision/power provided by a given configuration, are limited to the case of a binary exposure and a single binary confounder. The authors propose a rearrangement of the components in the variance of the estimator of the log-odds ratio. This formulation makes it possible to plan sample sizes/precision by including variance inflation factors to deal with several confounding factors. A practical variance bound is derived for two-stage case-control studies, where confounding variables are binary, while an empirical investigation is used to anticipate the additional sample size requirements when these variables are quantitative. Two methods are suggested for sample size planning based on a quantitative, rather than binary, exposure. PMID:16269581

  9. Precision electron polarimetry

    SciTech Connect

    Chudakov, Eugene A.

    2013-11-01

    A new generation of precise Parity-Violating experiments will require a sub-percent accuracy of electron beam polarimetry. Compton polarimetry can provide such accuracy at high energies, but at a few hundred MeV the small analyzing power limits the sensitivity. M{\\o}ller polarimetry provides a high analyzing power independent on the beam energy, but is limited by the properties of the polarized targets commonly used. Options for precision polarimetry at ~300 MeV will be discussed, in particular a proposal to use ultra-cold atomic hydrogen traps to provide a 100\\%-polarized electron target for M{\\o}ller polarimetry.

  10. Precision electron polarimetry

    SciTech Connect

    Chudakov, E.

    2013-11-07

    A new generation of precise Parity-Violating experiments will require a sub-percent accuracy of electron beam polarimetry. Compton polarimetry can provide such accuracy at high energies, but at a few hundred MeV the small analyzing power limits the sensitivity. Mo/ller polarimetry provides a high analyzing power independent on the beam energy, but is limited by the properties of the polarized targets commonly used. Options for precision polarimetry at 300 MeV will be discussed, in particular a proposal to use ultra-cold atomic hydrogen traps to provide a 100%-polarized electron target for Mo/ller polarimetry.

  11. SU-E-P-54: Evaluation of the Accuracy and Precision of IGPS-O X-Ray Image-Guided Positioning System by Comparison with On-Board Imager Cone-Beam Computed Tomography

    SciTech Connect

    Zhang, D; Wang, W; Jiang, B; Fu, D

    2015-06-15

    Purpose: The purpose of this study is to assess the positioning accuracy and precision of IGPS-O system which is a novel radiographic kilo-voltage x-ray image-guided positioning system developed for clinical IGRT applications. Methods: IGPS-O x-ray image-guided positioning system consists of two oblique sets of radiographic kilo-voltage x-ray projecting and imaging devices which were equiped on the ground and ceiling of treatment room. This system can determine the positioning error in the form of three translations and three rotations according to the registration of two X-ray images acquired online and the planning CT image. An anthropomorphic head phantom and an anthropomorphic thorax phantom were used for this study. The phantom was set up on the treatment table with correct position and various “planned” setup errors. Both IGPS-O x-ray image-guided positioning system and the commercial On-board Imager Cone-beam Computed Tomography (OBI CBCT) were used to obtain the setup errors of the phantom. Difference of the Result between the two image-guided positioning systems were computed and analyzed. Results: The setup errors measured by IGPS-O x-ray image-guided positioning system and the OBI CBCT system showed a general agreement, the means and standard errors of the discrepancies between the two systems in the left-right, anterior-posterior, superior-inferior directions were −0.13±0.09mm, 0.03±0.25mm, 0.04±0.31mm, respectively. The maximum difference was only 0.51mm in all the directions and the angular discrepancy was 0.3±0.5° between the two systems. Conclusion: The spatial and angular discrepancies between IGPS-O system and OBI CBCT for setup error correction was minimal. There is a general agreement between the two positioning system. IGPS-O x-ray image-guided positioning system can achieve as good accuracy as CBCT and can be used in the clinical IGRT applications.

  12. Accuracy and Usefulness of Select Methods for Assessing Complete Collection of 24-Hour Urine: A Systematic Review.

    PubMed

    John, Katherine A; Cogswell, Mary E; Campbell, Norm R; Nowson, Caryl A; Legetic, Branka; Hennis, Anselm J M; Patel, Sheena M

    2016-05-01

    Twenty-four-hour urine collection is the recommended method for estimating sodium intake. To investigate the strengths and limitations of methods used to assess completion of 24-hour urine collection, the authors systematically reviewed the literature on the accuracy and usefulness of methods vs para-aminobenzoic acid (PABA) recovery (referent). The percentage of incomplete collections, based on PABA, was 6% to 47% (n=8 studies). The sensitivity and specificity for identifying incomplete collection using creatinine criteria (n=4 studies) was 6% to 63% and 57% to 99.7%, respectively. The most sensitive method for removing incomplete collections was a creatinine index <0.7. In pooled analysis (≥2 studies), mean urine creatinine excretion and volume were higher among participants with complete collection (P<.05); whereas, self-reported collection time did not differ by completion status. Compared with participants with incomplete collection, mean 24-hour sodium excretion was 19.6 mmol higher (n=1781 specimens, 5 studies) in patients with complete collection. Sodium excretion may be underestimated by inclusion of incomplete 24-hour urine collections. None of the current approaches reliably assess completion of 24-hour urine collection. PMID:26726000

  13. Application of AFINCH as a Tool for Evaluating the Effects of Streamflow-Gaging-Network Size and Composition on the Accuracy and Precision of Streamflow Estimates at Ungaged Locations in the Southeast Lake Michigan Hydrologic Subregion

    USGS Publications Warehouse

    Koltun, G.F.; Holtschlag, David J.

    2010-01-01

    Bootstrapping techniques employing random subsampling were used with the AFINCH (Analysis of Flows In Networks of CHannels) model to gain insights into the effects of variation in streamflow-gaging-network size and composition on the accuracy and precision of streamflow estimates at ungaged locations in the 0405 (Southeast Lake Michigan) hydrologic subregion. AFINCH uses stepwise-regression techniques to estimate monthly water yields from catchments based on geospatial-climate and land-cover data in combination with available streamflow and water-use data. Calculations are performed on a hydrologic-subregion scale for each catchment and stream reach contained in a National Hydrography Dataset Plus (NHDPlus) subregion. Water yields from contributing catchments are multiplied by catchment areas and resulting flow values are accumulated to compute streamflows in stream reaches which are referred to as flow lines. AFINCH imposes constraints on water yields to ensure that observed streamflows are conserved at gaged locations. Data from the 0405 hydrologic subregion (referred to as Southeast Lake Michigan) were used for the analyses. Daily streamflow data were measured in the subregion for 1 or more years at a total of 75 streamflow-gaging stations during the analysis period which spanned water years 1971-2003. The number of streamflow gages in operation each year during the analysis period ranged from 42 to 56 and averaged 47. Six sets (one set for each censoring level), each composed of 30 random subsets of the 75 streamflow gages, were created by censoring (removing) approximately 10, 20, 30, 40, 50, and 75 percent of the streamflow gages (the actual percentage of operating streamflow gages censored for each set varied from year to year, and within the year from subset to subset, but averaged approximately the indicated percentages). Streamflow estimates for six flow lines each were aggregated by censoring level, and results were analyzed to assess (a) how the size

  14. Conference on Precision Electromagnetic Measurements (CPEM '90), 17th, Ottawa, Canada, June 11-15, 1990. Selected Papers

    NASA Astrophysics Data System (ADS)

    Belecki, Norman B.

    1991-04-01

    Various papers on instrumentation and measurement are presented. Among the individual topics addressed are: alternative methods for relating electrical to mechanical quantities through a power equation, linear ion trap based atomic frequency standard, characteristics of a laser diode system for an optically pumped cesium atomic clock, planned and realized improvements to the PTB's primary cesium clocks, an application of GPS dual frequency codeless receiver for ionospheric delay to single frequency and VLBI observation, hybrid system of communication and positioning determination using two geostationary satellites, development of a GPS time comparison system and the GPS common-view measurements, CuGeMn as a new material for high precision cryo-resistors, a 24-GHz Josephson array voltage standard, circuit precautions for stable operation of Josephson junction array voltage standard, Josephson junction array voltage standard at the ETL, application of radiometry to the accurate measurement of amplifier noise, a W-band homodyne vector network analyzer with variable measurement port distance, an electrically large antenna for transient electromagnetic field measurements, performance evaluation of an X-band RF switching radiometer, bond verification of Space Shuttle tiles using time-domain techniques.

  15. Precise sensing and selection of molecules by the interface between the metal nanocluster and the oxide support

    NASA Astrophysics Data System (ADS)

    Khubezhov, S. A.; Silaev, I. V.; Tvauri, I. V.; Grigorkina, G. S.; Demeev, Z. S.; Ramonova, A. G.; Kuznetsov, D. V.; Radchenko, T. I.; Magkoev, T. T., Jr.; Ogura, S.; Sekiba, D.; Fukutani, K.; Magkoev, T. T.

    2016-03-01

    Molecules being adsorbed on the surface dramatically change the physics and the chemistry of the substrate, thus offering an opportunity for precise sensing of the molecules via monitoring the transformation of the state of the adsorbent. Combination of different types of substrates, forming the surface interface border, generally exhibits synergistic effect dramatically enhancing sensitivity factor. In this regard, the aim of the present work is to demonstrate how the metal/oxide interface, formed in-vacuo (10-10 Torr) by deposition of metal nanoclusters on oxide support, affects behavior of NO and CO molecules being adsorbed on the surface. Coadsorption of NO and CO molecules on the Ni clusters deposited on MgO(111) film formed on Mo(110) crystal has been studied by reflection-absorption infrared spectroscopy (RAIRS) and temperature programmed desorption (TPD). Observed high sensitivity of metal/oxide interface to the molecular behaviour suggests an opportunity for design of new molecular sensors based on the metal/oxide nanostructures.

  16. High-precision instrument for measuring the surface tension, viscosity and surface viscoelasticity of liquids using ripplon surface laser-light scattering with tunable wavelength selection

    SciTech Connect

    Nishimura, Yu; Hasegawa, Akinori; Nagasaka, Yuji

    2014-04-15

    Here we describe our new high-precision instrument that simultaneously measures the surface tension, viscosity, and surface viscoelasticity of liquids. The instrument works on the ripplon surface-laser light scattering principle and operates with an automatically tunable selection of ripplon wavelength from 4 to 1500 μm, which corresponds to the frequency range of observing surface phenomena from approximately 400 Hz to 3 MHz in the case of water. The heterodyne technique instrument uses a reference laser beam which intersects at an arbitrarily adjustable angle with a vertically directed probing beam. For the determination of the wavelength of selected ripplons we substituted with the interference fringe spacing, measured using a high-resolution beam profiler. To extract reliable surface tension and viscosity data from the experimentally obtained spectrum shape for a selected wavelength of ripplon, we developed an algorithm to calculate the exact solution of the dispersion equation. The uncertainties of surface tension and viscosity measurement were confirmed through the measurement of seven pure Newtonian liquids at 25 °C measured with the selected wavelength of ripplon from 40 μm to 467 μm. To verify the genuine capability of the tunable wavelength selection of ripplon, we measured the surface elasticity of soluble surface molecular layers spread on pentanoic acid solutions.

  17. Predicting romantic interest and decisions in the very early stages of mate selection: standards, accuracy, and sex differences.

    PubMed

    Fletcher, Garth J O; Kerr, Patrick S G; Li, Norman P; Valentine, Katherine A

    2014-04-01

    In the current study, opposite-sex strangers had 10-min conversations with a possible further date in mind. Based on judgments from partners and observers, three main findings were produced. First, judgments of attractiveness/vitality perceptions (compared with warmth/trustworthiness and status/resources) were the most accurate and were predominant in influencing romantic interest and decisions about further contact. Second, women were more cautious and choosy than men-women underestimated their partner's romantic interest, whereas men exaggerated it, and women were less likely to want further contact. Third, a mediational model found that women (compared with men) were less likely to want further contact because they perceived their partners as possessing less attractiveness/vitality and as falling shorter of their minimum standards of attractiveness/vitality, thus generating lower romantic interest. These novel results are discussed in terms of the mixed findings from prior research, evolutionary psychology, and the functionality of lay psychology in early mate-selection contexts. PMID:24501043

  18. Precise and selective sensing of DNA-DNA hybridization by graphene/Si-nanowires diode-type biosensors.

    PubMed

    Kim, Jungkil; Park, Shin-Young; Kim, Sung; Lee, Dae Hun; Kim, Ju Hwan; Kim, Jong Min; Kang, Hee; Han, Joong-Soo; Park, Jun Woo; Lee, Hosun; Choi, Suk-Ho

    2016-01-01

    Single-Si-nanowire (NW)-based DNA sensors have been recently developed, but their sensitivity is very limited because of high noise signals, originating from small source-drain current of the single Si NW. Here, we demonstrate that chemical-vapor-deposition-grown large-scale graphene/surface-modified vertical-Si-NW-arrays junctions can be utilized as diode-type biosensors for highly-sensitive and -selective detection of specific oligonucleotides. For this, a twenty-seven-base-long synthetic oligonucleotide, which is a fragment of human DENND2D promoter sequence, is first decorated as a probe on the surface of vertical Si-NW arrays, and then the complementary oligonucleotide is hybridized to the probe. This hybridization gives rise to a doping effect on the surface of Si NWs, resulting in the increase of the current in the biosensor. The current of the biosensor increases from 19 to 120% as the concentration of the target DNA varies from 0.1 to 500 nM. In contrast, such biosensing does not come into play by the use of the oligonucleotide with incompatible or mismatched sequences. Similar results are observed from photoluminescence microscopic images and spectra. The biosensors show very-uniform current changes with standard deviations ranging ~1 to ~10% by ten-times endurance tests. These results are very promising for their applications in accurate, selective, and stable biosensing. PMID:27534818

  19. Precise and selective sensing of DNA-DNA hybridization by graphene/Si-nanowires diode-type biosensors

    PubMed Central

    Kim, Jungkil; Park, Shin-Young; Kim, Sung; Lee, Dae Hun; Kim, Ju Hwan; Kim, Jong Min; Kang, Hee; Han, Joong-Soo; Park, Jun Woo; Lee, Hosun; Choi, Suk-Ho

    2016-01-01

    Single-Si-nanowire (NW)-based DNA sensors have been recently developed, but their sensitivity is very limited because of high noise signals, originating from small source-drain current of the single Si NW. Here, we demonstrate that chemical-vapor-deposition-grown large-scale graphene/surface-modified vertical-Si-NW-arrays junctions can be utilized as diode-type biosensors for highly-sensitive and -selective detection of specific oligonucleotides. For this, a twenty-seven-base-long synthetic oligonucleotide, which is a fragment of human DENND2D promoter sequence, is first decorated as a probe on the surface of vertical Si-NW arrays, and then the complementary oligonucleotide is hybridized to the probe. This hybridization gives rise to a doping effect on the surface of Si NWs, resulting in the increase of the current in the biosensor. The current of the biosensor increases from 19 to 120% as the concentration of the target DNA varies from 0.1 to 500 nM. In contrast, such biosensing does not come into play by the use of the oligonucleotide with incompatible or mismatched sequences. Similar results are observed from photoluminescence microscopic images and spectra. The biosensors show very-uniform current changes with standard deviations ranging ~1 to ~10% by ten-times endurance tests. These results are very promising for their applications in accurate, selective, and stable biosensing. PMID:27534818

  20. Online image-guided intensity-modulated radiotherapy for prostate cancer: How much improvement can we expect? A theoretical assessment of clinical benefits and potential dose escalation by improving precision and accuracy of radiation delivery

    SciTech Connect

    Ghilezan, Michel; Yan Di . E-mail: dyan@beaumont.edu; Liang Jian; Jaffray, David; Wong, John; Martinez, Alvaro

    2004-12-01

    Purpose: To quantify the theoretical benefit, in terms of improvement in precision and accuracy of treatment delivery and in dose increase, of using online image-guided intensity-modulated radiotherapy (IG-IMRT) performed with onboard cone-beam computed tomography (CT), in an ideal setting of no intrafraction motion/deformation, in the treatment of prostate cancer. Methods and materials: Twenty-two prostate cancer patients treated with conventional radiotherapy underwent multiple serial CT scans (median 18 scans per patient) during their treatment. We assumed that these data sets were equivalent to image sets obtainable by an onboard cone-beam CT. Each patient treatment was simulated with conventional IMRT and online IG-IMRT separately. The conventional IMRT plan was generated on the basis of pretreatment CT, with a clinical target volume to planning target volume (CTV-to-PTV) margin of 1 cm, and the online IG-IMRT plan was created before each treatment fraction on the basis of the CT scan of the day, without CTV-to-PTV margin. The inverse planning process was similar for both conventional IMRT and online IG-IMRT. Treatment dose for each organ of interest was quantified, including patient daily setup error and internal organ motion/deformation. We used generalized equivalent uniform dose (EUD) to compare the two approaches. The generalized EUD (percentage) of each organ of interest was scaled relative to the prescription dose at treatment isocenter for evaluation and comparison. On the basis of bladder wall and rectal wall EUD, a dose-escalation coefficient was calculated, representing the potential increment of the treatment dose achievable with online IG-IMRT as compared with conventional IMRT. Results: With respect to radiosensitive tumor, the average EUD for the target (prostate plus seminal vesicles) was 96.8% for conventional IMRT and 98.9% for online IG-IMRT, with standard deviations (SDs) of 5.6% and 0.7%, respectively (p < 0.0001). The average EUDs of

  1. Influence of Raw Image Preprocessing and Other Selected Processes on Accuracy of Close-Range Photogrammetric Systems According to Vdi 2634

    NASA Astrophysics Data System (ADS)

    Reznicek, J.; Luhmann, T.; Jepping, C.

    2016-06-01

    This paper examines the influence of raw image preprocessing and other selected processes on the accuracy of close-range photogrammetric measurement. The examined processes and features includes: raw image preprocessing, sensor unflatness, distance-dependent lens distortion, extending the input observations (image measurements) by incorporating all RGB colour channels, ellipse centre eccentricity and target detecting. The examination of each effect is carried out experimentally by performing the validation procedure proposed in the German VDI guideline 2634/1. The validation procedure is based on performing standard photogrammetric measurements of high-accurate calibrated measuring lines (multi-scale bars) with known lengths (typical uncertainty = 5 μm at 2 sigma). The comparison of the measured lengths with the known values gives the maximum length measurement error LME, which characterize the accuracy of the validated photogrammetric system. For higher reliability the VDI test field was photographed ten times independently with the same configuration and camera settings. The images were acquired with the metric ALPA 12WA camera. The tests are performed on all ten measurements which gives the possibility to measure the repeatability of the estimated parameters as well. The influences are examined by comparing the quality characteristics of the reference and tested settings.

  2. Short communication: Selecting the most informative mid-infrared spectra wavenumbers to improve the accuracy of prediction models for detailed milk protein content.

    PubMed

    Niero, G; Penasa, M; Gottardo, P; Cassandro, M; De Marchi, M

    2016-03-01

    The objective of this study was to investigate the ability of mid-infrared spectroscopy (MIRS) to predict protein fraction contents of bovine milk samples by applying uninformative variable elimination (UVE) procedure to select the most informative wavenumber variables before partial least squares (PLS) analysis. Reference values (n=114) of protein fractions were measured using reversed-phase HPLC and spectra were acquired through MilkoScan FT6000 (Foss Electric A/S, Hillerød, Denmark). Prediction models were built using the full data set and tested with a leave-one-out cross-validation. Compared with MIRS models developed using standard PLS, the UVE procedure reduced the number of wavenumber variables to be analyzed through PLS regression and improved the accuracy of prediction by 6.0 to 66.7%. Good predictions were obtained for total protein, total casein (CN), and α-CN, which included αS1- and αS2-CN; moderately accurate predictions were observed for κ-CN and total whey protein; and unsatisfactory results were obtained for β-CN, α-lactalbumin, and β-lactoglobulin. Results indicated that UVE combined with PLS is a valid approach to enhance the accuracy of MIRS prediction models for milk protein fractions. PMID:26774721

  3. Precision digital control systems

    NASA Astrophysics Data System (ADS)

    Vyskub, V. G.; Rozov, B. S.; Savelev, V. I.

    This book is concerned with the characteristics of digital control systems of great accuracy. A classification of such systems is considered along with aspects of stabilization, programmable control applications, digital tracking systems and servomechanisms, and precision systems for the control of a scanning laser beam. Other topics explored are related to systems of proportional control, linear devices and methods for increasing precision, approaches for further decreasing the response time in the case of high-speed operation, possibilities for the implementation of a logical control law, and methods for the study of precision digital control systems. A description is presented of precision automatic control systems which make use of electronic computers, taking into account the existing possibilities for an employment of computers in automatic control systems, approaches and studies required for including a computer in such control systems, and an analysis of the structure of automatic control systems with computers. Attention is also given to functional blocks in the considered systems.

  4. Overlay accuracy fundamentals

    NASA Astrophysics Data System (ADS)

    Kandel, Daniel; Levinski, Vladimir; Sapiens, Noam; Cohen, Guy; Amit, Eran; Klein, Dana; Vakshtein, Irina

    2012-03-01

    Currently, the performance of overlay metrology is evaluated mainly based on random error contributions such as precision and TIS variability. With the expected shrinkage of the overlay metrology budget to < 0.5nm, it becomes crucial to include also systematic error contributions which affect the accuracy of the metrology. Here we discuss fundamental aspects of overlay accuracy and a methodology to improve accuracy significantly. We identify overlay mark imperfections and their interaction with the metrology technology, as the main source of overlay inaccuracy. The most important type of mark imperfection is mark asymmetry. Overlay mark asymmetry leads to a geometrical ambiguity in the definition of overlay, which can be ~1nm or less. It is shown theoretically and in simulations that the metrology may enhance the effect of overlay mark asymmetry significantly and lead to metrology inaccuracy ~10nm, much larger than the geometrical ambiguity. The analysis is carried out for two different overlay metrology technologies: Imaging overlay and DBO (1st order diffraction based overlay). It is demonstrated that the sensitivity of DBO to overlay mark asymmetry is larger than the sensitivity of imaging overlay. Finally, we show that a recently developed measurement quality metric serves as a valuable tool for improving overlay metrology accuracy. Simulation results demonstrate that the accuracy of imaging overlay can be improved significantly by recipe setup optimized using the quality metric. We conclude that imaging overlay metrology, complemented by appropriate use of measurement quality metric, results in optimal overlay accuracy.

  5. Precision Nova operations

    NASA Astrophysics Data System (ADS)

    Ehrlich, Robert B.; Miller, John L.; Saunders, Rodney L.; Thompson, Calvin E.; Weiland, Timothy L.; Laumann, Curt W.

    1995-12-01

    To improve the symmetry of x-ray drive on indirectly driven ICF capsules, we have increased the accuracy of operating procedures and diagnostics on the Nova laser. Precision Nova operations include routine precision power balance to within 10% rms in the 'foot' and 5% rms in the peak of shaped pulses, beam synchronization to within 10 ps rms, and pointing of the beams onto targets to within 35 micrometer rms. We have also added a 'fail-safe chirp' system to avoid stimulated Brillouin scattering (SBS) in optical components during high energy shots.

  6. Precision Nova operations

    SciTech Connect

    Ehrlich, R.B.; Miller, J.L.; Saunders, R.L.; Thompson, C.E.; Weiland, T.L.; Laumann, C.W.

    1995-09-01

    To improve the symmetry of x-ray drive on indirectly driven ICF capsules, we have increased the accuracy of operating procedures and diagnostics on the Nova laser. Precision Nova operations includes routine precision power balance to within 10% rms in the ``foot`` and 5% nns in the peak of shaped pulses, beam synchronization to within 10 ps rms, and pointing of the beams onto targets to within 35 {mu}m rms. We have also added a ``fail-safe chirp`` system to avoid Stimulated Brillouin Scattering (SBS) in optical components during high energy shots.

  7. Precise Orbit Determination for ALOS

    NASA Technical Reports Server (NTRS)

    Nakamura, Ryo; Nakamura, Shinichi; Kudo, Nobuo; Katagiri, Seiji

    2007-01-01

    The Advanced Land Observing Satellite (ALOS) has been developed to contribute to the fields of mapping, precise regional land coverage observation, disaster monitoring, and resource surveying. Because the mounted sensors need high geometrical accuracy, precise orbit determination for ALOS is essential for satisfying the mission objectives. So ALOS mounts a GPS receiver and a Laser Reflector (LR) for Satellite Laser Ranging (SLR). This paper deals with the precise orbit determination experiments for ALOS using Global and High Accuracy Trajectory determination System (GUTS) and the evaluation of the orbit determination accuracy by SLR data. The results show that, even though the GPS receiver loses lock of GPS signals more frequently than expected, GPS-based orbit is consistent with SLR-based orbit. And considering the 1 sigma error, orbit determination accuracy of a few decimeters (peak-to-peak) was achieved.

  8. Precise GPS ephemerides from DMA and NGS tested by time transfer

    NASA Technical Reports Server (NTRS)

    Lewandowski, Wlodzimierz W.; Petit, Gerard; Thomas, Claudine

    1992-01-01

    It was shown that the use of the Defense Mapping Agency's (DMA) precise ephemerides brings a significant improvement to the accuracy of GPS time transfer. At present a new set of precise ephemerides produced by the National Geodetic Survey (NGS) has been made available to the timing community. This study demonstrates that both types of precise ephemerides improve long-distance GPS time transfer and remove the effects of Selective Availability (SA) degradation of broadcast ephemerides. The issue of overcoming SA is also discussed in terms of the routine availability of precise ephemerides.

  9. Ground control requirements for precision processing of ERTS images

    USGS Publications Warehouse

    Burger, Thomas C.

    1973-01-01

    With the successful flight of the ERTS-1 satellite, orbital height images are available for precision processing into products such as 1:1,000,000-scale photomaps and enlargements up to 1:250,000 scale. In order to maintain positional error below 100 meters, control points for the precision processing must be carefully selected, clearly definitive on photos in both X and Y. Coordinates of selected control points measured on existing ½ and 15-minute standard maps provide sufficient accuracy for any space imaging system thus far defined. This procedure references the points to accepted horizontal and vertical datums. Maps as small as 1:250,000 scale can be used as source material for coordinates, but to maintain the desired accuracy, maps of 1:100,000 and larger scale should be used when available.

  10. Genomic Selection and Association Mapping in Rice (Oryza sativa): Effect of Trait Genetic Architecture, Training Population Composition, Marker Number and Statistical Model on Accuracy of Rice Genomic Selection in Elite, Tropical Rice Breeding Lines

    PubMed Central

    Spindel, Jennifer; Begum, Hasina; Akdemir, Deniz; Virk, Parminder; Collard, Bertrand; Redoña, Edilberto; Atlin, Gary; Jannink, Jean-Luc; McCouch, Susan R.

    2015-01-01

    Genomic Selection (GS) is a new breeding method in which genome-wide markers are used to predict the breeding value of individuals in a breeding population. GS has been shown to improve breeding efficiency in dairy cattle and several crop plant species, and here we evaluate for the first time its efficacy for breeding inbred lines of rice. We performed a genome-wide association study (GWAS) in conjunction with five-fold GS cross-validation on a population of 363 elite breeding lines from the International Rice Research Institute's (IRRI) irrigated rice breeding program and herein report the GS results. The population was genotyped with 73,147 markers using genotyping-by-sequencing. The training population, statistical method used to build the GS model, number of markers, and trait were varied to determine their effect on prediction accuracy. For all three traits, genomic prediction models outperformed prediction based on pedigree records alone. Prediction accuracies ranged from 0.31 and 0.34 for grain yield and plant height to 0.63 for flowering time. Analyses using subsets of the full marker set suggest that using one marker every 0.2 cM is sufficient for genomic selection in this collection of rice breeding materials. RR-BLUP was the best performing statistical method for grain yield where no large effect QTL were detected by GWAS, while for flowering time, where a single very large effect QTL was detected, the non-GS multiple linear regression method outperformed GS models. For plant height, in which four mid-sized QTL were identified by GWAS, random forest produced the most consistently accurate GS models. Our results suggest that GS, informed by GWAS interpretations of genetic architecture and population structure, could become an effective tool for increasing the efficiency of rice breeding as the costs of genotyping continue to decline. PMID:25689273

  11. Measurements of experimental precision for trials with cowpea (Vigna unguiculata L. Walp.) genotypes.

    PubMed

    Teodoro, P E; Torres, F E; Santos, A D; Corrêa, A M; Nascimento, M; Barroso, L M A; Ceccon, G

    2016-01-01

    The aim of this study was to evaluate the suitability of statistics as experimental precision degree measures for trials with cowpea (Vigna unguiculata L. Walp.) genotypes. Cowpea genotype yields were evaluated in 29 trials conducted in Brazil between 2005 and 2012. The genotypes were evaluated with a randomized block design with four replications. Ten statistics that were estimated for each trial were compared using descriptive statistics, Pearson correlations, and path analysis. According to the class limits established, selective accuracy and F-test values for genotype, heritability, and the coefficient of determination adequately estimated the degree of experimental precision. Using these statistics, 86.21% of the trials had adequate experimental precision. Selective accuracy and the F-test values for genotype, heritability, and the coefficient of determination were directly related to each other, and were more suitable than the coefficient of variation and the least significant difference (by the Tukey test) to evaluate experimental precision in trials with cowpea genotypes. PMID:27173351

  12. Accuracy and precision of gravitational-wave models of inspiraling neutron star-black hole binaries with spin: Comparison with matter-free numerical relativity in the low-frequency regime

    NASA Astrophysics Data System (ADS)

    Bhagwat, Swetha; Kumar, Prayush; Barkett, Kevin; Afshari, Nousha; Brown, Duncan A.; Lovelace, Geoffrey; Scheel, Mark A.; Szilagyi, Bela; LIGO Collaboration

    2016-03-01

    Detection of gravitational wave involves extracting extremely weak signal from noisy data and their detection depends crucially on the accuracy of the signal models. The most accurate models of compact binary coalescence are known to come from solving the Einstein's equation numerically without any approximations. However, this is computationally formidable. As a more practical alternative, several analytic or semi analytic approximations are developed to model these waveforms. However, the work of Nitz et al. (2013) demonstrated that there is disagreement between these models. We present a careful follow up study on accuracies of different waveform families for spinning black-hole neutron star binaries, in context of both detection and parameter estimation and find that SEOBNRv2 to be the most faithful model. Post Newtonian models can be used for detection but we find that they could lead to large parameter bias. Supported by National Science Foundation (NSF) Awards No. PHY-1404395 and No. AST-1333142.

  13. Making Precise Antenna Reflectors For Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Sharp, G. Richard; Wanhainen, Joyce S.; Ketelsen, Dean A.

    1994-01-01

    In improved method of fabrication of precise, lightweight antenna reflectors for millimeter wavelengths, required precise contours of reflecting surfaces obtained by computer numberically controlled machining of surface layers bonded to lightweight, rigid structures. Achievable precision greater than that of older, more-expensive fabrication method involving multiple steps of low- and high-temperature molding, in which some accuracy lost at each step.

  14. Precision translator

    DOEpatents

    Reedy, Robert P.; Crawford, Daniel W.

    1984-01-01

    A precision translator for focusing a beam of light on the end of a glass fiber which includes two turning fork-like members rigidly connected to each other. These members have two prongs each with its separation adjusted by a screw, thereby adjusting the orthogonal positioning of a glass fiber attached to one of the members. This translator is made of simple parts with capability to keep adjustment even in condition of rough handling.

  15. Precision translator

    DOEpatents

    Reedy, R.P.; Crawford, D.W.

    1982-03-09

    A precision translator for focusing a beam of light on the end of a glass fiber which includes two turning fork-like members rigidly connected to each other. These members have two prongs each with its separation adjusted by a screw, thereby adjusting the orthogonal positioning of a glass fiber attached to one of the members. This translator is made of simple parts with capability to keep adjustment even in condition of rough handling.

  16. Precision and accuracy in fluorescent short tandem repeat DNA typing: assessment of benefits imparted by the use of allelic ladders with the AmpF/STR Profiler Plus kit.

    PubMed

    Leclair, Benoît; Frégeau, Chantal J; Bowen, Kathy L; Fourney, Ron M

    2004-03-01

    Base-calling precision of short tandem repeat (STR) allelic bands on dynamic slab-gel electrophoresis systems was evaluated. Data was collected from over 6000 population database allele peaks generated from 468 population database samples amplified with the AmpF/STR Profiler Plus (PP) kit and electrophoresed on ABD 377 DNA sequencers. Precision was measured by way of standard deviations and was shown to be essentially the same, whether using fixed or floating bin genotyping. However, the allelic ladders have proven more sensitive to electrophoretic variations than database samples, which have caused some floating bins of D18S51 to shift on occasion. This observation prompted the investigation of polyacrylamide gel formulations in order to stabilize allelic ladder migration. The results demonstrate that, although alleles comprised in allelic ladders and questioned samples run on the same gel should migrate in an identical manner, this premise needs to be verified for any given electrophoresis platform and gel formulation. We show that the compilation of base-calling data is a very informative and useful tool for assessing the performance stability of dynamic gel electrophoresis systems, stability on which depends genotyping result quality. PMID:15004837

  17. Precision GPS ephemerides and baselines

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Based on the research, the area of precise ephemerides for GPS satellites, the following observations can be made pertaining to the status and future work needed regarding orbit accuracy. There are several aspects which need to be addressed in discussing determination of precise orbits, such as force models, kinematic models, measurement models, data reduction/estimation methods, etc. Although each one of these aspects was studied at CSR in research efforts, only points pertaining to the force modeling aspect are addressed.

  18. Assessing the Accuracy and Precision of Inorganic Geochemical Data Produced through Flux Fusion and Acid Digestions: Multiple (60+) Comprehensive Analyses of BHVO-2 and the Development of Improved "Accepted" Values

    NASA Astrophysics Data System (ADS)

    Ireland, T. J.; Scudder, R.; Dunlea, A. G.; Anderson, C. H.; Murray, R. W.

    2014-12-01

    The use of geological standard reference materials (SRMs) to assess both the accuracy and the reproducibility of geochemical data is a vital consideration in determining the major and trace element abundances of geologic, oceanographic, and environmental samples. Calibration curves commonly are generated that are predicated on accurate analyses of these SRMs. As a means to verify the robustness of these calibration curves, a SRM can also be run as an unknown item (i.e., not included as a data point in the calibration). The experimentally derived composition of the SRM can thus be compared to the certified (or otherwise accepted) value. This comparison gives a direct measure of the accuracy of the method used. Similarly, if the same SRM is analyzed as an unknown over multiple analytical sessions, the external reproducibility of the method can be evaluated. Two common bulk digestion methods used in geochemical analysis are flux fusion and acid digestion. The flux fusion technique is excellent at ensuring complete digestion of a variety of sample types, is quick, and does not involve much use of hazardous acids. However, this technique is hampered by a high amount of total dissolved solids and may be accompanied by an increased analytical blank for certain trace elements. On the other hand, acid digestion (using a cocktail of concentrated nitric, hydrochloric and hydrofluoric acids) provides an exceptionally clean digestion with very low analytical blanks. However, this technique results in a loss of Si from the system and may compromise results for a few other elements (e.g., Ge). Our lab uses flux fusion for the determination of major elements and a few key trace elements by ICP-ES, while acid digestion is used for Ti and trace element analyses by ICP-MS. Here we present major and trace element data for BHVO-2, a frequently used SRM derived from a Hawaiian basalt, gathered over a period of over two years (30+ analyses by each technique). We show that both digestion

  19. Precision synchrotron radiation detectors

    SciTech Connect

    Levi, M.; Rouse, F.; Butler, J.; Jung, C.K.; Lateur, M.; Nash, J.; Tinsman, J.; Wormser, G.; Gomez, J.J.; Kent, J.

    1989-03-01

    Precision detectors to measure synchrotron radiation beam positions have been designed and installed as part of beam energy spectrometers at the Stanford Linear Collider (SLC). The distance between pairs of synchrotron radiation beams is measured absolutely to better than 28 /mu/m on a pulse-to-pulse basis. This contributes less than 5 MeV to the error in the measurement of SLC beam energies (approximately 50 GeV). A system of high-resolution video cameras viewing precisely-aligned fiducial wire arrays overlaying phosphorescent screens has achieved this accuracy. Also, detectors of synchrotron radiation using the charge developed by the ejection of Compton-recoil electrons from an array of fine wires are being developed. 4 refs., 5 figs., 1 tab.

  20. Precise Measurement for Manufacturing

    NASA Technical Reports Server (NTRS)

    2003-01-01

    A metrology instrument known as PhaseCam supports a wide range of applications, from testing large optics to controlling factory production processes. This dynamic interferometer system enables precise measurement of three-dimensional surfaces in the manufacturing industry, delivering speed and high-resolution accuracy in even the most challenging environments.Compact and reliable, PhaseCam enables users to make interferometric measurements right on the factory floor. The system can be configured for many different applications, including mirror phasing, vacuum/cryogenic testing, motion/modal analysis, and flow visualization.

  1. Precision Pointing System Development

    SciTech Connect

    BUGOS, ROBERT M.

    2003-03-01

    The development of precision pointing systems has been underway in Sandia's Electronic Systems Center for over thirty years. Important areas of emphasis are synthetic aperture radars and optical reconnaissance systems. Most applications are in the aerospace arena, with host vehicles including rockets, satellites, and manned and unmanned aircraft. Systems have been used on defense-related missions throughout the world. Presently in development are pointing systems with accuracy goals in the nanoradian regime. Future activity will include efforts to dramatically reduce system size and weight through measures such as the incorporation of advanced materials and MEMS inertial sensors.

  2. Precision GPS ephemerides and baselines

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The emphasis of this grant was focused on precision ephemerides for the Global Positioning System (GPS) satellites for geodynamics applications. During the period of this grant, major activities were in the areas of thermal force modeling, numerical integration accuracy improvement for eclipsing satellites, analysis of GIG '91 campaign data, and the Southwest Pacific campaign data analysis.

  3. Precision orbit computations for Starlette

    NASA Technical Reports Server (NTRS)

    Marsh, J. G.; Williamson, R. G.

    1976-01-01

    The Starlette satellite, launched in February 1975 by the French Centre National d'Etudes Spatiales, was designed to minimize the effects of nongravitational forces and to obtain the highest possible accuracy for laser range measurements. Analyses of the first four months of global laser tracking data confirmed the stability of the orbit and the precision to which the satellite's position is established.

  4. Accuracy and precision of gravitational-wave models of inspiraling neutron star-black hole binaries with spin: Comparison with matter-free numerical relativity in the low-frequency regime

    NASA Astrophysics Data System (ADS)

    Kumar, Prayush; Barkett, Kevin; Bhagwat, Swetha; Afshari, Nousha; Brown, Duncan A.; Lovelace, Geoffrey; Scheel, Mark A.; Szilágyi, Béla

    2015-11-01

    Coalescing binaries of neutron stars and black holes are one of the most important sources of gravitational waves for the upcoming network of ground-based detectors. Detection and extraction of astrophysical information from gravitational-wave signals requires accurate waveform models. The effective-one-body and other phenomenological models interpolate between analytic results and numerical relativity simulations, that typically span O (10 ) orbits before coalescence. In this paper we study the faithfulness of these models for neutron star-black hole binaries. We investigate their accuracy using new numerical relativity (NR) simulations that span 36-88 orbits, with mass ratios q and black hole spins χBH of (q ,χBH)=(7 ,±0.4 ),(7 ,±0.6 ) , and (5 ,-0.9 ). These simulations were performed treating the neutron star as a low-mass black hole, ignoring its matter effects. We find that (i) the recently published SEOBNRv1 and SEOBNRv2 models of the effective-one-body family disagree with each other (mismatches of a few percent) for black hole spins χBH≥0.5 or χBH≤-0.3 , with waveform mismatch accumulating during early inspiral; (ii) comparison with numerical waveforms indicates that this disagreement is due to phasing errors of SEOBNRv1, with SEOBNRv2 in good agreement with all of our simulations; (iii) phenomenological waveforms agree with SEOBNRv2 only for comparable-mass low-spin binaries, with overlaps below 0.7 elsewhere in the neutron star-black hole binary parameter space; (iv) comparison with numerical waveforms shows that most of this model's dephasing accumulates near the frequency interval where it switches to a phenomenological phasing prescription; and finally (v) both SEOBNR and post-Newtonian models are effectual for neutron star-black hole systems, but post-Newtonian waveforms will give a significant bias in parameter recovery. Our results suggest that future gravitational-wave detection searches and parameter estimation efforts would benefit

  5. Psychology Textbooks: Examining Their Accuracy

    ERIC Educational Resources Information Center

    Steuer, Faye B.; Ham, K. Whitfield, II

    2008-01-01

    Sales figures and recollections of psychologists indicate textbooks play a central role in psychology students' education, yet instructors typically must select texts under time pressure and with incomplete information. Although selection aids are available, none adequately address the accuracy of texts. We describe a technique for sampling…

  6. Perspective on precision machining, polishing, and optical requirements

    SciTech Connect

    Sanger, G.M.

    1981-08-18

    While precision machining has been applied to the manufacture of optical components for a considerable period, the process has, in general, had its thinking restricted to producing only the accurate shapes required. The purpose of this paper is to show how optical components must be considered from an optical (functional) point of view and that the manufacturing process must be selected on that basis. To fill out this perspective, simplistic examples of how optical components are specified with respect to form and finish are given, a comparison between optical polishing and precision machining is made, and some thoughts on which technique should be selected for a specific application are presented. A short discussion of future trends related to accuracy, materials, and tools is included.

  7. Enhancement of the spectral selectivity of complex samples by measuring them in a frozen state at low temperatures in order to improve accuracy for quantitative analysis. Part II. Determination of viscosity for lube base oils using Raman spectroscopy.

    PubMed

    Kim, Mooeung; Chung, Hoeil

    2013-03-01

    The use of selectivity-enhanced Raman spectra of lube base oil (LBO) samples achieved by the spectral collection under frozen conditions at low temperatures was effective for improving accuracy for the determination of the kinematic viscosity at 40 °C (KV@40). A collection of Raman spectra from samples cooled around -160 °C provided the most accurate measurement of KV@40. Components of the LBO samples were mainly long-chain hydrocarbons with molecular structures that were deformable when these were frozen, and the different structural deformabilities of the components enhanced spectral selectivity among the samples. To study the structural variation of components according to the change of sample temperature from cryogenic to ambient condition, n-heptadecane and pristane (2,6,10,14-tetramethylpentadecane) were selected as representative components of LBO samples, and their temperature-induced spectral features as well as the corresponding spectral loadings were investigated. A two-dimensional (2D) correlation analysis was also employed to explain the origin for the improved accuracy. The asynchronous 2D correlation pattern was simplest at the optimal temperature, indicating the occurrence of distinct and selective spectral variations, which enabled the variation of KV@40 of LBO samples to be more accurately assessed. PMID:23342358

  8. Effect of optical digitizer selection on the application accuracy of a surgical localization system-a quantitative comparison between the OPTOTRAK and flashpoint tracking systems

    NASA Technical Reports Server (NTRS)

    Li, Q.; Zamorano, L.; Jiang, Z.; Gong, J. X.; Pandya, A.; Perez, R.; Diaz, F.

    1999-01-01

    Application accuracy is a crucial factor for stereotactic surgical localization systems, in which space digitization camera systems are one of the most critical components. In this study we compared the effect of the OPTOTRAK 3020 space digitization system and the FlashPoint Model 3000 and 5000 3D digitizer systems on the application accuracy for interactive localization of intracranial lesions. A phantom was mounted with several implantable frameless markers which were randomly distributed on its surface. The target point was digitized and the coordinates were recorded and compared with reference points. The differences from the reference points represented the deviation from the "true point." The root mean square (RMS) was calculated to show the differences, and a paired t-test was used to analyze the results. The results with the phantom showed that, for 1-mm sections of CT scans, the RMS was 0.76 +/- 0. 54 mm for the OPTOTRAK system, 1.23 +/- 0.53 mm for the FlashPoint Model 3000 3D digitizer system, and 1.00 +/- 0.42 mm for the FlashPoint Model 5000 system. These preliminary results showed that there is no significant difference between the three tracking systems, and, from the quality point of view, they can all be used for image-guided surgery procedures. Copyright 1999 Wiley-Liss, Inc.

  9. The adaptive accuracy of flowers: measurement and microevolutionary patterns

    PubMed Central

    Armbruster, W. Scott; Hansen, Thomas F.; Pélabon, Christophe; Pérez-Barrales, Rocío; Maad, Johanne

    2009-01-01

    for higher precision and accuracy in flowers with higher levels of integration and dichogamy (temporal separation of sexual functions), and in those that have pollinators that are immobile (or immobilized) during pollen transfer. Large deviations from putative adaptive optima were observed, and these may be related to the effects of conflicting selective pressures on flowers, such as selection against self-pollination promoting herkogamy (spatial separation of pollen and stigmas). Conclusions Adaptive accuracy is a useful concept for understanding the adaptive significance of phenotypic means and variances of floral morphology within and among populations and species. Estimating and comparing the various components of adaptive accuracy can be particularly helpful for identifying the causes of inaccuracy, such as conflicting selective pressures, low environmental canalization and developmental instability. PMID:19429671

  10. Are Currently Available Wearable Devices for Activity Tracking and Heart Rate Monitoring Accurate, Precise, and Medically Beneficial?

    PubMed Central

    El-Amrawy, Fatema

    2015-01-01

    Objectives The new wave of wireless technologies, fitness trackers, and body sensor devices can have great impact on healthcare systems and the quality of life. However, there have not been enough studies to prove the accuracy and precision of these trackers. The objective of this study was to evaluate the accuracy, precision, and overall performance of seventeen wearable devices currently available compared with direct observation of step counts and heart rate monitoring. Methods Each participant in this study used three accelerometers at a time, running the three corresponding applications of each tracker on an Android or iOS device simultaneously. Each participant was instructed to walk 200, 500, and 1,000 steps. Each set was repeated 40 times. Data was recorded after each trial, and the mean step count, standard deviation, accuracy, and precision were estimated for each tracker. Heart rate was measured by all trackers (if applicable), which support heart rate monitoring, and compared to a positive control, the Onyx Vantage 9590 professional clinical pulse oximeter. Results The accuracy of the tested products ranged between 79.8% and 99.1%, while the coefficient of variation (precision) ranged between 4% and 17.5%. MisFit Shine showed the highest accuracy and precision (along with Qualcomm Toq), while Samsung Gear 2 showed the lowest accuracy, and Jawbone UP showed the lowest precision. However, Xiaomi Mi band showed the best package compared to its price. Conclusions The accuracy and precision of the selected fitness trackers are reasonable and can indicate the average level of activity and thus average energy expenditure. PMID:26618039

  11. Increasing the Accuracy in the Measurement of the Minor Isotopes of Uranium: Care in Selection of Reference Materials, Baselines and Detector Calibration

    NASA Astrophysics Data System (ADS)

    Poths, J.; Koepf, A.; Boulyga, S. F.

    2008-12-01

    The minor isotopes of uranium (U-233, U-234, U-236) are increasingly useful for tracing a variety of processes: movement of anthropogenic nuclides in the environment (ref 1), sources of uranium ores (ref 2), and nuclear material attribution (ref 3). We report on improved accuracy for U-234/238 and U-236/238 by supplementing total evaporation protocol TIMS measurement on Faraday detectors (ref 4)with multiplier measurement for the minor isotopes. Measurement of small signals on Faraday detectors alone is limited by noise floors of the amplifiers and accurate measurement of the baseline offsets. The combined detector approach improves the reproducibility to better than ±1% (relative) for the U-234/238 at natural abundance, and yields a detection limit for U-236/U-238 of <0.2 ppm. We have quantified contribution of different factors to the uncertainties associated with these peak jumping measurement on a single detector, with an aim of further improvement. The uncertainties in the certified values for U-234 and U-236 in the uranium standard NBS U005, if used for mass bias correction, dominates the uncertainty in their isotopic ratio measurements. Software limitations in baseline measurement drives the detection limit for the U-236/U-238 ratio. This is a topic for discussion with the instrument manufacturers. Finally, deviation from linearity of the response of the electron multiplier with count rate limits the accuracy and reproducibility of these minor isotope measurements. References: (1) P. Steier et al(2008) Nuc Inst Meth(B), 266, 2246-2250. (2) E. Keegan et al (2008) Appl Geochem 23, 765-777. (3) K. Mayer et al (1998) IAEA-CN-98/11, in Advances in Destructive and Non-destructive Analysis for Environmental Monitoring and Nuclear Forensics. (4) S. Richter and S. Goldberg(2003) Int J Mass Spectrom, 229, 181-197.

  12. Precision spectroscopy of Helium

    SciTech Connect

    Cancio, P.; Giusfredi, G.; Mazzotti, D.; De Natale, P.; De Mauro, C.; Krachmalnicoff, V.; Inguscio, M.

    2005-05-05

    Accurate Quantum-Electrodynamics (QED) tests of the simplest bound three body atomic system are performed by precise laser spectroscopic measurements in atomic Helium. In this paper, we present a review of measurements between triplet states at 1083 nm (23S-23P) and at 389 nm (23S-33P). In 4He, such data have been used to measure the fine structure of the triplet P levels and, then, to determine the fine structure constant when compared with equally accurate theoretical calculations. Moreover, the absolute frequencies of the optical transitions have been used for Lamb-shift determinations of the levels involved with unprecedented accuracy. Finally, determination of the He isotopes nuclear structure and, in particular, a measurement of the nuclear charge radius, are performed by using hyperfine structure and isotope-shift measurements.

  13. Precision ozone vapor pressure measurements

    NASA Technical Reports Server (NTRS)

    Hanson, D.; Mauersberger, K.

    1985-01-01

    The vapor pressure above liquid ozone has been measured with a high accuracy over a temperature range of 85 to 95 K. At the boiling point of liquid argon (87.3 K) an ozone vapor pressure of 0.0403 Torr was obtained with an accuracy of + or - 0.7 percent. A least square fit of the data provided the Clausius-Clapeyron equation for liquid ozone; a latent heat of 82.7 cal/g was calculated. High-precision vapor pressure data are expected to aid research in atmospheric ozone measurements and in many laboratory ozone studies such as measurements of cross sections and reaction rates.

  14. Mixed-Precision Spectral Deferred Correction: Preprint

    SciTech Connect

    Grout, Ray W. S.

    2015-09-02

    Convergence of spectral deferred correction (SDC), where low-order time integration methods are used to construct higher-order methods through iterative refinement, can be accelerated in terms of computational effort by using mixed-precision methods. Using ideas from multi-level SDC (in turn based on FAS multigrid ideas), some of the SDC correction sweeps can use function values computed in reduced precision without adversely impacting the accuracy of the final solution. This is particularly beneficial for the performance of combustion solvers such as S3D [6] which require double precision accuracy but are performance limited by the cost of data motion.

  15. Quality, precision and accuracy of the maximum No. 40 anemometer

    SciTech Connect

    Obermeir, J.; Blittersdorf, D.

    1996-12-31

    This paper synthesizes available calibration data for the Maximum No. 40 anemometer. Despite its long history in the wind industry, controversy surrounds the choice of transfer function for this anemometer. Many users are unaware that recent changes in default transfer functions in data loggers are producing output wind speed differences as large as 7.6%. Comparison of two calibration methods used for large samples of Maximum No. 40 anemometers shows a consistent difference of 4.6% in output speeds. This difference is significantly larger than estimated uncertainty levels. Testing, initially performed to investigate related issues, reveals that Gill and Maximum cup anemometers change their calibration transfer functions significantly when calibrated in the open atmosphere compared with calibration in a laminar wind tunnel. This indicates that atmospheric turbulence changes the calibration transfer function of cup anemometers. These results call into question the suitability of standard wind tunnel calibration testing for cup anemometers. 6 refs., 10 figs., 4 tabs.

  16. Precision and accuracy of decay constants and age standards

    NASA Astrophysics Data System (ADS)

    Villa, I. M.

    2011-12-01

    40 years of round-robin experiments with age standards teach us that systematic errors must be present in at least N-1 labs if participants provide N mutually incompatible data. In EarthTime, the U-Pb community has produced and distributed synthetic solutions with full metrological traceability. Collector linearity is routinely calibrated under variable conditions (e.g. [1]). Instrumental mass fractionation is measured in-run with double spikes (e.g. 233U-236U). Parent-daughter ratios are metrologically traceable, so the full uncertainty budget of a U-Pb age should coincide with interlaboratory uncertainty. TIMS round-robin experiments indeed show a decrease of N towards the ideal value of 1. Comparing 235U-207Pb with 238U-206Pb ages (e.g. [2]) has resulted in a credible re-evaluation of the 235U decay constant, with lower uncertainty than gamma counting. U-Pb microbeam techniques reveal the link petrology-microtextures-microchemistry-isotope record but do not achieve the low uncertainty of TIMS. In the K-Ar community, N is large; interlaboratory bias is > 10 times self-assessed uncertainty. Systematic errors may have analytical and petrological reasons. Metrological traceability is not yet implemented (substantial advance may come from work in progress, e.g. [7]). One of the worst problems is collector stability and linearity. Using electron multipliers (EM) instead of Faraday buckets (FB) reduces both dynamic range and collector linearity. Mass spectrometer backgrounds are never zero; the extent as well as the predictability of their variability must be propagated into the uncertainty evaluation. The high isotope ratio of the atmospheric Ar requires a large dynamic range over which linearity must be demonstrated under all analytical conditions to correctly estimate mass fractionation. The only assessment of EM linearity in Ar analyses [3] points out many fundamental problems; the onus of proof is on every laboratory claiming low uncertainties. Finally, sample size reduction is often associated to reducing clean-up time to increase sample/blank ratio; this may be self-defeating, as "dry blanks" [4] do not represent either the isotopic composition or the amount of Ar released by the sample chamber when exposed to unpurified sample gas. Single grains enhance background and purification problems relative to large sample sizes measured on FB. Petrologically, many natural "standards" are not ideal (e.g. MMhb1 [5], B4M [6]), as their original distributors never conceived petrology as the decisive control on isotope retention. Comparing ever smaller aliquots of unequilibrated minerals causes ever larger age variations. Metrologically traceable synthetic isotope mixtures still lie in the future. Petrological non-ideality of natural standards does not allow a metrological uncertainty budget. Collector behavior, on the contrary, does. Its quantification will, by definition, make true intralaboratory uncertainty greater or equal to interlaboratory bias. [1] Chen J, Wasserburg GJ, 1981. Analyt Chem 53, 2060-2067 [2] Mattinson JM, 2010. Chem Geol 275, 186-198 [3] Turrin B et al, 2010. G-cubed, 11, Q0AA09 [4] Baur H, 1975. PhD thesis, ETH Zürich, No. 6596 [5] Villa IM et al, 1996. Contrib Mineral Petrol 126, 67-80 [6] Villa IM, Heri AR, 2010. AGU abstract V31A-2296 [7] Morgan LE et al, in press. G-cubed, 2011GC003719

  17. Factors affecting accuracy and precision in PET volume imaging

    SciTech Connect

    Karp, J.S.; Daube-Witherspoon, M.E.; Muehllehner, G. )

    1991-03-01

    Volume imaging positron emission tomographic (PET) scanners with no septa and a large axial acceptance angle offer several advantages over multiring PET scanners. A volume imaging scanner combines high sensitivity with fine axial sampling and spatial resolution. The fine axial sampling minimizes the partial volume effect, which affects the measured concentration of an object. Even if the size of an object is large compared to the slice spacing in a multiring scanner, significant variation in the concentration is measured as a function of the axial position of the object. With a volume imaging scanner, it is necessary to use a three-dimensional reconstruction algorithm in order to avoid variations in the axial resolution as a function of the distance from the center of the scanner. In addition, good energy resolution is needed in order to use a high energy threshold to reduce the coincident scattered radiation.

  18. Accuracy and Precision of Radioactivity Quantification in Nuclear Medicine Images

    PubMed Central

    Frey, Eric C.; Humm, John L.; Ljungberg, Michael

    2012-01-01

    The ability to reliably quantify activity in nuclear medicine has a number of increasingly important applications. Dosimetry for targeted therapy treatment planning or for approval of new imaging agents requires accurate estimation of the activity in organs, tumors, or voxels at several imaging time points. Another important application is the use of quantitative metrics derived from images, such as the standard uptake value commonly used in positron emission tomography (PET), to diagnose and follow treatment of tumors. These measures require quantification of organ or tumor activities in nuclear medicine images. However, there are a number of physical, patient, and technical factors that limit the quantitative reliability of nuclear medicine images. There have been a large number of improvements in instrumentation, including the development of hybrid single-photon emission computed tomography/computed tomography and PET/computed tomography systems, and reconstruction methods, including the use of statistical iterative reconstruction methods, which have substantially improved the ability to obtain reliable quantitative information from planar, single-photon emission computed tomography, and PET images. PMID:22475429

  19. Tomography & Geochemistry: Precision, Repeatability, Accuracy and Joint Interpretations

    NASA Astrophysics Data System (ADS)

    Foulger, G. R.; Panza, G. F.; Artemieva, I. M.; Bastow, I. D.; Cammarano, F.; Doglioni, C.; Evans, J. R.; Hamilton, W. B.; Julian, B. R.; Lustrino, M.; Thybo, H.; Yanovskaya, T. B.

    2015-12-01

    Seismic tomography can reveal the spatial seismic structure of the mantle, but has little ability to constrain composition, phase or temperature. In contrast, petrology and geochemistry can give insights into mantle composition, but have severely limited spatial control on magma sources. For these reasons, results from these three disciplines are often interpreted jointly. Nevertheless, the limitations of each method are often underestimated, and underlying assumptions de-emphasized. Examples of the limitations of seismic tomography include its ability to image in detail the three-dimensional structure of the mantle or to determine with certainty the strengths of anomalies. Despite this, published seismic anomaly strengths are often unjustifiably translated directly into physical parameters. Tomography yields seismological parameters such as wave speed and attenuation, not geological or thermal parameters. Much of the mantle is poorly sampled by seismic waves, and resolution- and error-assessment methods do not express the true uncertainties. These and other problems have become highlighted in recent years as a result of multiple tomography experiments performed by different research groups, in areas of particular interest e.g., Yellowstone. The repeatability of the results is often poorer than the calculated resolutions. The ability of geochemistry and petrology to identify magma sources and locations is typically overestimated. These methods have little ability to determine source depths. Models that assign geochemical signatures to specific layers in the mantle, including the transition zone, the lower mantle, and the core-mantle boundary, are based on speculative models that cannot be verified and for which viable, less-astonishing alternatives are available. Our knowledge is poor of the size, distribution and location of protoliths, and of metasomatism of magma sources, the nature of the partial-melting and melt-extraction process, the mixing of disparate melts, and the re-assimilation of crust and mantle lithosphere by rising melt. Interpretations of seismic tomography, petrologic and geochemical observations, and all three together, are ambiguous, and this needs to be emphasized more in presenting interpretations so that the viability of the models can be assessed more reliably.

  20. Global positioning system measurements for crustal deformation: Precision and accuracy

    USGS Publications Warehouse

    Prescott, W.H.; Davis, J.L.; Svarc, J.L.

    1989-01-01

    Analysis of 27 repeated observations of Global Positioning System (GPS) position-difference vectors, up to 11 kilometers in length, indicates that the standard deviation of the measurements is 4 millimeters for the north component, 6 millimeters for the east component, and 10 to 20 millimeters for the vertical component. The uncertainty grows slowly with increasing vector length. At 225 kilometers, the standard deviation of the measurement is 6, 11, and 40 millimeters for the north, east, and up components, respectively. Measurements with GPS and Geodolite, an electromagnetic distance-measuring system, over distances of 10 to 40 kilometers agree within 0.2 part per million. Measurements with GPS and very long baseline interferometry of the 225-kilometer vector agree within 0.05 part per million.

  1. Precision and accuracy of visual foliar injury assessments

    SciTech Connect

    Gumpertz, M.L.; Tingey, D.T.; Hogsett, W.E.

    1982-07-01

    The study compared three measures of foliar injury: (i) mean percent leaf area injured of all leaves on the plant, (ii) mean percent leaf area injured of the three most injured leaves, and (iii) the proportion of injured leaves to total number of leaves. For the first measure, the variation caused by reader biases and day-to-day variations were compared with the innate plant-to-plant variation. Bean (Phaseolus vulgaris 'Pinto'), pea (Pisum sativum 'Little Marvel'), radish (Rhaphanus sativus 'Cherry Belle'), and spinach (Spinacia oleracea 'Northland') plants were exposed to either 3 ..mu..L L/sup -1/ SO/sub 2/ or 0.3 ..mu..L L/sup -1/ ozone for 2 h. Three leaf readers visually assessed the percent injury on every leaf of each plant while a fourth reader used a transparent grid to make an unbiased assessment for each plant. The mean leaf area injured of the three most injured leaves was highly correlated with all leaves on the plant only if the three most injured leaves were <100% injured. The proportion of leaves injured was not highly correlated with percent leaf area injured of all leaves on the plant for any species in this study. The largest source of variation in visual assessments was plant-to-plant variation, which ranged from 44 to 97% of the total variance, followed by variation among readers (0-32% of the variance). Except for radish exposed to ozone, the day-to-day variation accounted for <18% of the total. Reader bias in assessment of ozone injury was significant but could be adjusted for each reader by a simple linear regression (R/sup 2/ = 0.89-0.91) of the visual assessments against the grid assessments.

  2. Arrival Metering Precision Study

    NASA Technical Reports Server (NTRS)

    Prevot, Thomas; Mercer, Joey; Homola, Jeffrey; Hunt, Sarah; Gomez, Ashley; Bienert, Nancy; Omar, Faisal; Kraut, Joshua; Brasil, Connie; Wu, Minghong, G.

    2015-01-01

    This paper describes the background, method and results of the Arrival Metering Precision Study (AMPS) conducted in the Airspace Operations Laboratory at NASA Ames Research Center in May 2014. The simulation study measured delivery accuracy, flight efficiency, controller workload, and acceptability of time-based metering operations to a meter fix at the terminal area boundary for different resolution levels of metering delay times displayed to the air traffic controllers and different levels of airspeed information made available to the Time-Based Flow Management (TBFM) system computing the delay. The results show that the resolution of the delay countdown timer (DCT) on the controllers display has a significant impact on the delivery accuracy at the meter fix. Using the 10 seconds rounded and 1 minute rounded DCT resolutions resulted in more accurate delivery than 1 minute truncated and were preferred by the controllers. Using the speeds the controllers entered into the fourth line of the data tag to update the delay computation in TBFM in high and low altitude sectors increased air traffic control efficiency and reduced fuel burn for arriving aircraft during time based metering.

  3. Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis

    NASA Technical Reports Server (NTRS)

    Slojkowski, Steven E.

    2014-01-01

    LRO definitive and predictive accuracy requirements were easily met in the nominal mission orbit, using the LP150Q lunar gravity model. center dot Accuracy of the LP150Q model is poorer in the extended mission elliptical orbit. center dot Later lunar gravity models, in particular GSFC-GRAIL-270, improve OD accuracy in the extended mission. center dot Implementation of a constrained plane when the orbit is within 45 degrees of the Earth-Moon line improves cross-track accuracy. center dot Prediction accuracy is still challenged during full-Sun periods due to coarse spacecraft area modeling - Implementation of a multi-plate area model with definitive attitude input can eliminate prediction violations. - The FDF is evaluating using analytic and predicted attitude modeling to improve full-Sun prediction accuracy. center dot Comparison of FDF ephemeris file to high-precision ephemeris files provides gross confirmation that overlap compares properly assess orbit accuracy.

  4. Precision Polarimetry for Cold Neutrons

    NASA Astrophysics Data System (ADS)

    Barron-Palos, Libertad; Bowman, J. David; Chupp, Timothy E.; Crawford, Christopher; Danagoulian, Areg; Gentile, Thomas R.; Jones, Gordon; Klein, Andreas; Penttila, Seppo I.; Salas-Bacci, Americo; Sharma, Monisha; Wilburn, W. Scott

    2007-10-01

    The abBA and PANDA experiments, currently under development, aim to measure the correlation coefficients in the polarized free neutron beta decay at the FnPB in SNS. The polarization of the neutron beam, polarized with a ^3He spin filter, has to be known with high precision in order to achieve the goal accuracy of these experiments. In the NPDGamma experiment, where a ^3He spin filter was used, it was observed that backgrounds play an important role in the precision to which the polarization can be determined. An experiment that focuses in the reduction of background sources to establish techniques and find the upper limit for the polarization accuracy with these spin filters is currently in progress at LANSCE. A description of the measurement and results will be presented.

  5. Validation of selected analytical methods using accuracy profiles to assess the impact of a Tobacco Heating System on indoor air quality.

    PubMed

    Mottier, Nicolas; Tharin, Manuel; Cluse, Camille; Crudo, Jean-René; Lueso, María Gómez; Goujon-Ginglinger, Catherine G; Jaquier, Anne; Mitova, Maya I; Rouget, Emmanuel G R; Schaller, Mathieu; Solioz, Jennifer

    2016-09-01

    Studies in environmentally controlled rooms have been used over the years to assess the impact of environmental tobacco smoke on indoor air quality. As new tobacco products are developed, it is important to determine their impact on air quality when used indoors. Before such an assessment can take place it is essential that the analytical methods used to assess indoor air quality are validated and shown to be fit for their intended purpose. Consequently, for this assessment, an environmentally controlled room was built and seven analytical methods, representing eighteen analytes, were validated. The validations were carried out with smoking machines using a matrix-based approach applying the accuracy profile procedure. The performances of the methods were compared for all three matrices under investigation: background air samples, the environmental aerosol of Tobacco Heating System THS 2.2, a heat-not-burn tobacco product developed by Philip Morris International, and the environmental tobacco smoke of a cigarette. The environmental aerosol generated by the THS 2.2 device did not have any appreciable impact on the performances of the methods. The comparison between the background and THS 2.2 environmental aerosol samples generated by smoking machines showed that only five compounds were higher when THS 2.2 was used in the environmentally controlled room. Regarding environmental tobacco smoke from cigarettes, the yields of all analytes were clearly above those obtained with the other two air sample types. PMID:27343591

  6. Precision evaluation of calibration factor of a superconducting gravimeter using an absolute gravimeter

    NASA Astrophysics Data System (ADS)

    Feng, Jin-yang; Wu, Shu-qing; Li, Chun-jian; Su, Duo-wu; Xu, Jin-yi; Yu, Mei

    2016-01-01

    The precision of the calibration factor of a superconducting gravimeter (SG) using an absolute gravimeter (AG) is analyzed based on linear least square fitting and error propagation theory and factors affecting the accuracy are discussed. It can improve the accuracy to choose the observation period of solid tide as a significant change or increase the calibration time. Simulation is carried out based on synthetic gravity tides calculated with T-soft at observed site from Aug. 14th to Sept. 2nd in 2014. The result indicates that the highest precision using half a day's observation data is below 0.28% and the precision exponentially increases with the increase of peak-to-peak gravity change. The comparison of results obtained from the same observation time indicated that using properly selected observation data has more beneficial on the improvement of precision. Finally, the calibration experiment of the SG iGrav-012 is introduced and the calibration factor is determined for the first time using AG FG5X-249. With 2.5 days' data properly selected from solid tide period with large tidal amplitude, the determined calibration factor of iGrav-012 is (-92.54423+/-0.13616) μGal/V (1μGal=10-8m/s2), with the relative accuracy of about 0.15%.

  7. Assessing the impact of end-member selection on the accuracy of satellite-based spatial variability models for actual evapotranspiration estimation

    NASA Astrophysics Data System (ADS)

    Long, Di; Singh, Vijay P.

    2013-05-01

    This study examines the impact of end-member (i.e., hot and cold extremes) selection on the performance and mechanisms of error propagation in satellite-based spatial variability models for estimating actual evapotranspiration, using the triangle, surface energy balance algorithm for land (SEBAL), and mapping evapotranspiration with high resolution and internalized calibration (METRIC) models. These models were applied to the soil moisture-atmosphere coupling experiment site in central Iowa on two Landsat Thematic Mapper/Enhanced Thematic Mapper Plus acquisition dates in 2002. Evaporative fraction (EF, defined as the ratio of latent heat flux to availability energy) estimates from the three models at field and watershed scales were examined using varying end-members. Results show that the end-members fundamentally determine the magnitudes of EF retrievals at both field and watershed scales. The hot and cold extremes exercise a similar impact on the discrepancy between the EF estimates and the ground-based measurements, i.e., given a hot (cold) extreme, the EF estimates tend to increase with increasing temperature of cold (hot) extreme, and decrease with decreasing temperature of cold (hot) extreme. The coefficient of determination between the EF estimates and the ground-based measurements depends principally on the capability of remotely sensed surface temperature (Ts) to capture EF (i.e., depending on the correlation between Ts and EF measurements), being slightly influenced by the end-members. Varying the end-members does not substantially affect the standard deviation and skewness of the EF frequency distributions from the same model at the watershed scale. However, different models generate markedly different EF frequency distributions due to differing model physics, especially the limiting edges of EF defined in the remotely sensed vegetation fraction (fc) and Ts space. In general, the end-members cannot be properly determined because (1) they do not

  8. Precision powder feeder

    DOEpatents

    Schlienger, M. Eric; Schmale, David T.; Oliver, Michael S.

    2001-07-10

    A new class of precision powder feeders is disclosed. These feeders provide a precision flow of a wide range of powdered materials, while remaining robust against jamming or damage. These feeders can be precisely controlled by feedback mechanisms.

  9. Airborne Topographic Mapper Calibration Procedures and Accuracy Assessment

    NASA Technical Reports Server (NTRS)

    Martin, Chreston F.; Krabill, William B.; Manizade, Serdar S.; Russell, Rob L.; Sonntag, John G.; Swift, Robert N.; Yungel, James K.

    2012-01-01

    Description of NASA Airborn Topographic Mapper (ATM) lidar calibration procedures including analysis of the accuracy and consistancy of various ATM instrument parameters and the resulting influence on topographic elevation measurements. The ATM elevations measurements from a nominal operating altitude 500 to 750 m above the ice surface was found to be: Horizontal Accuracy 74 cm, Horizontal Precision 14 cm, Vertical Accuracy 6.6 cm, Vertical Precision 3 cm.

  10. Flexible and precise drop test system

    NASA Astrophysics Data System (ADS)

    Stämpfli, Rolf; Brühwiler, Paul A.

    2009-11-01

    A drop test system with flexibility in the choice of falling object has been constructed and characterized. Using the guided free fall principle, the system enables the study of impacts of a large range of objects on a wide selection of anvils, with high control of the position and orientation of the object. The latter is demonstrated with falls of a standard aluminium headform in mountaineering helmets on a kerbstone anvil, for which visual inspection with a high-speed camera confirms the desired accuracy. Impacts of a flat falling body on cylindrical polystyrene foam samples are used to derive stress-strain curves for materials of different density and for multilayer samples. In this case, the effects of striker orientation and placement on the resultant data are discussed, and the reproducibility of the data serves as an additional confirmation of the accuracy of the measurement apparatus and procedures. A check on the improvement in the level of positional and orientational striking precision achievable is obtained via an inter-laboratory comparison.

  11. GPS vertical axis performance enhancement for helicopter precision landing approach

    NASA Technical Reports Server (NTRS)

    Denaro, Robert P.; Beser, Jacques

    1986-01-01

    Several areas were investigated for improving vertical accuracy for a rotorcraft using the differential Global Positioning System (GPS) during a landing approach. Continuous deltaranging was studied and the potential improvement achieved by estimating acceleration was studied by comparing the performance on a constant acceleration turn and a rough landing profile of several filters: a position-velocity (PV) filter, a position-velocity-constant acceleration (PVAC) filter, and a position-velocity-turning acceleration (PVAT) filter. In overall statistics, the PVAC filter was found to be most efficient with the more complex PVAT performing equally well. Vertical performance was not significantly different among the filters. Satellite selection algorithms based on vertical errors only (vertical dilution of precision or VDOP) and even-weighted cross-track and vertical errors (XVDOP) were tested. The inclusion of an altimeter was studied by modifying the PVAC filter to include a baro bias estimate. Improved vertical accuracy during degraded DOP conditions resulted. Flight test results for raw differential results excluding filter effects indicated that the differential performance significantly improved overall navigation accuracy. A landing glidepath steering algorithm was devised which exploits the flexibility of GPS in determining precise relative position. A method for propagating the steering command over the GPS update interval was implemented.

  12. Increasing Accuracy in Environmental Measurements

    NASA Astrophysics Data System (ADS)

    Jacksier, Tracey; Fernandes, Adelino; Matthew, Matt; Lehmann, Horst

    2016-04-01

    Human activity is increasing the concentrations of green house gases (GHG) in the atmosphere which results in temperature increases. High precision is a key requirement of atmospheric measurements to study the global carbon cycle and its effect on climate change. Natural air containing stable isotopes are used in GHG monitoring to calibrate analytical equipment. This presentation will examine the natural air and isotopic mixture preparation process, for both molecular and isotopic concentrations, for a range of components and delta values. The role of precisely characterized source material will be presented. Analysis of individual cylinders within multiple batches will be presented to demonstrate the ability to dynamically fill multiple cylinders containing identical compositions without isotopic fractionation. Additional emphasis will focus on the ability to adjust isotope ratios to more closely bracket sample types without the reliance on combusting naturally occurring materials, thereby improving analytical accuracy.

  13. Precision linear ramp function generator

    DOEpatents

    Jatko, W. Bruce; McNeilly, David R.; Thacker, Louis H.

    1986-01-01

    A ramp function generator is provided which produces a precise linear ramp unction which is repeatable and highly stable. A derivative feedback loop is used to stabilize the output of an integrator in the forward loop and control the ramp rate. The ramp may be started from a selected baseline voltage level and the desired ramp rate is selected by applying an appropriate constant voltage to the input of the integrator.

  14. Precision linear ramp function generator

    DOEpatents

    Jatko, W.B.; McNeilly, D.R.; Thacker, L.H.

    1984-08-01

    A ramp function generator is provided which produces a precise linear ramp function which is repeatable and highly stable. A derivative feedback loop is used to stabilize the output of an integrator in the forward loop and control the ramp rate. The ramp may be started from a selected baseline voltage level and the desired ramp rate is selected by applying an appropriate constant voltage to the input of the integrator.

  15. Precision Efficacy Analysis for Regression.

    ERIC Educational Resources Information Center

    Brooks, Gordon P.

    When multiple linear regression is used to develop a prediction model, sample size must be large enough to ensure stable coefficients. If the derivation sample size is inadequate, the model may not predict well for future subjects. The precision efficacy analysis for regression (PEAR) method uses a cross- validity approach to select sample sizes…

  16. Genomic selection & association mapping in rice: effect of trait genetic architecture, training population composition, marker number & statistical model on accuracy of rice genomic selection in elite, tropical rice breeding

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic Selection (GS) is a new breeding method in which genome-wide markers are used to predict the breeding value of individuals in a breeding population. GS has been shown to improve breeding efficiency in dairy cattle and several crop plant species, and here we evaluate for the first time its ef...

  17. Construction concepts for precision segmented reflectors

    NASA Technical Reports Server (NTRS)

    Mikulas, Martin M., Jr.; Withnell, Peter R.

    1993-01-01

    Three construction concepts for deployable precision segmented reflectors are presented. The designs produce reflectors with very high surface accuracies and diameters three to five times the width of the launch vehicle shroud. Of primary importance is the reliability of both the deployment process and the reflector operation. This paper is conceptual in nature, and uses these criteria to present beneficial design concepts for deployable precision segmented reflectors.

  18. High-precision arithmetic in mathematical physics

    DOE PAGESBeta

    Bailey, David H.; Borwein, Jonathan M.

    2015-05-12

    For many scientific calculations, particularly those involving empirical data, IEEE 32-bit floating-point arithmetic produces results of sufficient accuracy, while for other applications IEEE 64-bit floating-point is more appropriate. But for some very demanding applications, even higher levels of precision are often required. Furthermore, this article discusses the challenge of high-precision computation, in the context of mathematical physics, and highlights what facilities are required to support future computation, in light of emerging developments in computer architecture.

  19. The Magsat precision vector magnetometer

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.

    1980-01-01

    This paper examines the Magsat precision vector magnetometer which is designed to measure projections of the ambient field in three orthogonal directions. The system contains a highly stable and linear triaxial fluxgate magnetometer with a dynamic range of + or - 2000 nT (1 nT = 10 to the -9 weber per sq m). The magnetometer electronics, analog-to-digital converter, and digitally controlled current sources are implemented with redundant designs to avoid a loss of data in case of failures. Measurements are carried out with an accuracy of + or - 1 part in 64,000 in magnitude and 5 arcsec in orientation (1 arcsec = 0.00028 deg).

  20. Accuracy in optical overlay metrology

    NASA Astrophysics Data System (ADS)

    Bringoltz, Barak; Marciano, Tal; Yaziv, Tal; DeLeeuw, Yaron; Klein, Dana; Feler, Yoel; Adam, Ido; Gurevich, Evgeni; Sella, Noga; Lindenfeld, Ze'ev; Leviant, Tom; Saltoun, Lilach; Ashwal, Eltsafon; Alumot, Dror; Lamhot, Yuval; Gao, Xindong; Manka, James; Chen, Bryan; Wagner, Mark

    2016-03-01

    In this paper we discuss the mechanism by which process variations determine the overlay accuracy of optical metrology. We start by focusing on scatterometry, and showing that the underlying physics of this mechanism involves interference effects between cavity modes that travel between the upper and lower gratings in the scatterometry target. A direct result is the behavior of accuracy as a function of wavelength, and the existence of relatively well defined spectral regimes in which the overlay accuracy and process robustness degrades (`resonant regimes'). These resonances are separated by wavelength regions in which the overlay accuracy is better and independent of wavelength (we term these `flat regions'). The combination of flat and resonant regions forms a spectral signature which is unique to each overlay alignment and carries certain universal features with respect to different types of process variations. We term this signature the `landscape', and discuss its universality. Next, we show how to characterize overlay performance with a finite set of metrics that are available on the fly, and that are derived from the angular behavior of the signal and the way it flags resonances. These metrics are used to guarantee the selection of accurate recipes and targets for the metrology tool, and for process control with the overlay tool. We end with comments on the similarity of imaging overlay to scatterometry overlay, and on the way that pupil overlay scatterometry and field overlay scatterometry differ from an accuracy perspective.

  1. Stereotype Accuracy: Toward Appreciating Group Differences.

    ERIC Educational Resources Information Center

    Lee, Yueh-Ting, Ed.; And Others

    The preponderance of scholarly theory and research on stereotypes assumes that they are bad and inaccurate, but understanding stereotype accuracy and inaccuracy is more interesting and complicated than simpleminded accusations of racism or sexism would seem to imply. The selections in this collection explore issues of the accuracy of stereotypes…

  2. Precise Countersinking Tool

    NASA Technical Reports Server (NTRS)

    Jenkins, Eric S.; Smith, William N.

    1992-01-01

    Tool countersinks holes precisely with only portable drill; does not require costly machine tool. Replaceable pilot stub aligns axis of tool with centerline of hole. Ensures precise cut even with imprecise drill. Designed for relatively low cutting speeds.

  3. "Precision" drug development?

    PubMed

    Woodcock, J

    2016-02-01

    The concept of precision medicine has entered broad public consciousness, spurred by a string of targeted drug approvals, highlighted by the availability of personal gene sequences, and accompanied by some remarkable claims about the future of medicine. It is likely that precision medicines will require precision drug development programs. What might such programs look like? PMID:26331240

  4. Precision agricultural systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Precision agriculture is a new farming practice that has been developing since late 1980s. It has been variously referred to as precision farming, prescription farming, site-specific crop management, to name but a few. There are numerous definitions for precision agriculture, but the central concept...

  5. What can we expect from precision asteroseismology?

    NASA Astrophysics Data System (ADS)

    Handler, G.

    2014-02-01

    Precision asteroseismology is the determination of accurate stellar parameters from oscillation data. At first successful for pulsating white dwarf stars, it is now applied to more and more types of stars. We give a number of selected examples where precision asteroseismology, but also asteroseismology based on few observables may lead to considerable improvement of stellar astrophysics in the near future.

  6. Precision CW laser automatic tracking system investigated

    NASA Technical Reports Server (NTRS)

    Lang, K. T.; Lucy, R. F.; Mcgann, E. J.; Peters, C. J.

    1966-01-01

    Precision laser tracker capable of tracking a low acceleration target to an accuracy of about 20 microradians rms is being constructed and tested. This laser tracking has the advantage of discriminating against other optical sources and the capability of simultaneously measuring range.

  7. Impacts of real-time satellite clock errors on GPS precise point positioning-based troposphere zenith delay estimation

    NASA Astrophysics Data System (ADS)

    Shi, Junbo; Xu, Chaoqian; Li, Yihe; Gao, Yang

    2015-08-01

    Global Positioning System (GPS) has become a cost-effective tool to determine troposphere zenith total delay (ZTD) with accuracy comparable to other atmospheric sensors such as the radiosonde, the water vapor radiometer, the radio occultation and so on. However, the high accuracy of GPS troposphere ZTD estimates relies on the precise satellite orbit and clock products available with various latencies. Although the International GNSS Service (IGS) can provide predicted orbit and clock products for real-time applications, the predicted clock accuracy of 3 ns cannot always guarantee the high accuracy of troposphere ZTD estimates. Such limitations could be overcome by the use of the newly launched IGS real-time service which provides 5 cm orbit and 0.2-1.0 ns (an equivalent range error of 6-30 cm) clock products in real time. Considering the relatively larger magnitude of the clock error than that of the orbit error, this paper investigates the effect of real-time satellite clock errors on the GPS precise point positioning (PPP)-based troposphere ZTD estimation. Meanwhile, how the real-time satellite clock errors impact the GPS PPP-based troposphere ZTD estimation has also been studied to obtain the most precise ZTD solutions. First, two types of real-time satellite clock products are assessed with respect to the IGS final clock product in terms of accuracy and precision. Second, the real-time GPS PPP-based troposphere ZTD estimation is conducted using data from 34 selected IGS stations over three independent weeks in April, July and October, 2013. Numerical results demonstrate that the precision, rather than the accuracy, of the real-time satellite clock products impacts the real-time PPP-based ZTD solutions more significantly. In other words, the real-time satellite clock product with better precision leads to more precise real-time PPP-based troposphere ZTD solutions. Therefore, it is suggested that users should select and apply real-time satellite products with

  8. Using satellite data to increase accuracy of PMF calculations

    SciTech Connect

    Mettel, M.C.

    1992-03-01

    The accuracy of a flood severity estimate depends on the data used. The more detailed and precise the data, the more accurate the estimate. Earth observation satellites gather detailed data for determining the probable maximum flood at hydropower projects.

  9. The Seasat Precision Orbit Determination Experiment

    NASA Technical Reports Server (NTRS)

    Tapley, B. D.; Born, G. H.

    1980-01-01

    The objectives and conclusions reached during the Seasat Precision Orbit Determination Experiment are discussed. It is noted that the activities of the experiment team included extensive software calibration and validation and an intense effort to validate and improve the dynamic models which describe the satellite's motion. Significant improvement in the gravitational model was obtained during the experiment, and it is pointed out that the current accuracy of the Seasat altitude ephemeris is 1.5 m rms. An altitude ephemeris for the Seasat spacecraft with an accuracy of 0.5 m rms is seen as possible with further improvements in the geopotential, atmospheric drag, and solar radiation pressure models. It is concluded that since altimetry missions with a 2-cm precision altimeter are contemplated, the precision orbit determination effort initiated under the Seasat Project must be continued and expanded.

  10. High precision triangular waveform generator

    DOEpatents

    Mueller, Theodore R.

    1983-01-01

    An ultra-linear ramp generator having separately programmable ascending and descending ramp rates and voltages is provided. Two constant current sources provide the ramp through an integrator. Switching of the current at current source inputs rather than at the integrator input eliminates switching transients and contributes to the waveform precision. The triangular waveforms produced by the waveform generator are characterized by accurate reproduction and low drift over periods of several hours. The ascending and descending slopes are independently selectable.

  11. Liquid chromatography-high resolution/ high accuracy (tandem) mass spectrometry-based identification of in vivo generated metabolites of the selective androgen receptor modulator ACP-105 for doping control purposes.

    PubMed

    Thevis, Mario; Thomas, Andreas; Piper, Thomas; Krug, Oliver; Delahaut, Philippe; Schänzer, Wilhelm

    2014-01-01

    Selective androgen receptor modulators (SARMs) represent an emerging class of therapeutics which have been prohibited in sport as anabolic agents according to the regulations of the World Anti-Doping Agency (WADA) since 2008. Within the past three years, numerous adverse analytical findings with SARMs in routine doping control samples have been reported despite missing clinical approval of these substances. Hence, preventive doping research concerning the metabolism and elimination of new therapeutic entities of the class of SARMs are vital for efficient and timely sports drug testing programs as banned compounds are most efficiently screened when viable targets (for example, characteristic metabolites) are identified. In the present study, the metabolism of ACP-105, a novel SARM drug candidate, was studied in vivo in rats. Following oral administration, urine samples were collected over a period of seven days and analyzed for metabolic products by Liquid chromatography-high resolution/high accuracy (tandem) mass spectrometry. Samples were subjected to enzymatic hydrolysis prior to liquid-liquid extraction and a total of seven major phase-I metabolites were detected, three of which were attributed to monohydroxylated and four to bishydroxylated ACP-105. The hydroxylation sites were assigned by means of diagnostic product ions and respective dissociation pathways of the analytes following positive or negative ionization and collisional activation as well as selective chemical derivatization. The identified metabolites were used as target compounds to investigate their traceability in a rat elimination urine samples study and monohydroxylated and bishydroxylated species were detectable for up to four and six days post-administration, respectively. PMID:24881457

  12. Precision performance lamp technology

    NASA Astrophysics Data System (ADS)

    Bell, Dean A.; Kiesa, James E.; Dean, Raymond A.

    1997-09-01

    A principal function of a lamp is to produce light output with designated spectra, intensity, and/or geometric radiation patterns. The function of a precision performance lamp is to go beyond these parameters and into the precision repeatability of performance. All lamps are not equal. There are a variety of incandescent lamps, from the vacuum incandescent indictor lamp to the precision lamp of a blood analyzer. In the past the definition of a precision lamp was described in terms of wattage, light center length (LCL), filament position, and/or spot alignment. This paper presents a new view of precision lamps through the discussion of a new segment of lamp design, which we term precision performance lamps. The definition of precision performance lamps will include (must include) the factors of a precision lamp. But what makes a precision lamp a precision performance lamp is the manner in which the design factors of amperage, mscp (mean spherical candlepower), efficacy (lumens/watt), life, not considered individually but rather considered collectively. There is a statistical bias in a precision performance lamp for each of these factors; taken individually and as a whole. When properly considered the results can be dramatic to the system design engineer, system production manage and the system end-user. It can be shown that for the lamp user, the use of precision performance lamps can translate to: (1) ease of system design, (2) simplification of electronics, (3) superior signal to noise ratios, (4) higher manufacturing yields, (5) lower system costs, (6) better product performance. The factors mentioned above are described along with their interdependent relationships. It is statistically shown how the benefits listed above are achievable. Examples are provided to illustrate how proper attention to precision performance lamp characteristics actually aid in system product design and manufacturing to build and market more, market acceptable product products in the

  13. Precision optical metrology without lasers

    NASA Astrophysics Data System (ADS)

    Bergmann, Ralf B.; Burke, Jan; Falldorf, Claas

    2015-07-01

    Optical metrology is a key technique when it comes to precise and fast measurement with a resolution down to the micrometer or even nanometer regime. The choice of a particular optical metrology technique and the quality of results depends on sample parameters such as size, geometry and surface roughness as well as user requirements such as resolution, measurement time and robustness. Interferometry-based techniques are well known for their low measurement uncertainty in the nm range, but usually require careful isolation against vibration and a laser source that often needs shielding for reasons of eye-safety. In this paper, we concentrate on high precision optical metrology without lasers by using the gradient based measurement technique of deflectometry and the finite difference based technique of shear interferometry. Careful calibration of deflectometry systems allows one to investigate virtually all kinds of reflecting surfaces including aspheres or free-form surfaces with measurement uncertainties below the μm level. Computational Shear Interferometry (CoSI) allows us to combine interferometric accuracy and the possibility to use cheap and eye-safe low-brilliance light sources such as e.g. fiber coupled LEDs or even liquid crystal displays. We use CoSI e.g. for quantitative phase contrast imaging in microscopy. We highlight the advantages of both methods, discuss their transfer functions and present results on the precision of both techniques.

  14. Advanced irrigation engineering: Precision and Precise

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Irrigation advances in precision irrigation (PI) or site-specific irrigation (SSI) have been considerable in research; however commercialization lags. A primary necessity for it is variability in soil texture that affects soil water holding capacity and crop yield. Basically, SSI/PI uses variable ra...

  15. Advanced irrigation engineering: Precision and Precise

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Irrigation advances in precision irrigation (PI) or site specific irrigation (SSI) have been considerable in research; however commercialization lags. A primary necessity for PI/SSI is variability in soil texture that affects soil water holding capacity and crop yield. Basically, SSI/PI uses variabl...

  16. Precision aerial application for site-specific rice crop management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Precision agriculture includes different technologies that allow agricultural professional to use information management tools to optimize agriculture production. The new technologies allow aerial application applicators to improve application accuracy and efficiency, which saves time and money for...

  17. System and method for high precision isotope ratio destructive analysis

    DOEpatents

    Bushaw, Bruce A; Anheier, Norman C; Phillips, Jon R

    2013-07-02

    A system and process are disclosed that provide high accuracy and high precision destructive analysis measurements for isotope ratio determination of relative isotope abundance distributions in liquids, solids, and particulate samples. The invention utilizes a collinear probe beam to interrogate a laser ablated plume. This invention provides enhanced single-shot detection sensitivity approaching the femtogram range, and isotope ratios that can be determined at approximately 1% or better precision and accuracy (relative standard deviation).

  18. GEOSPATIAL DATA ACCURACY ASSESSMENT

    EPA Science Inventory

    The development of robust accuracy assessment methods for the validation of spatial data represent's a difficult scientific challenge for the geospatial science community. The importance and timeliness of this issue is related directly to the dramatic escalation in the developmen...

  19. Improving the precision matrix for precision cosmology

    NASA Astrophysics Data System (ADS)

    Paz, Dante J.; Sánchez, Ariel G.

    2015-12-01

    The estimation of cosmological constraints from observations of the large-scale structure of the Universe, such as the power spectrum or the correlation function, requires the knowledge of the inverse of the associated covariance matrix, namely the precision matrix, Ψ . In most analyses, Ψ is estimated from a limited set of mock catalogues. Depending on how many mocks are used, this estimation has an associated error which must be propagated into the final cosmological constraints. For future surveys such as Euclid and Dark Energy Spectroscopic Instrument, the control of this additional uncertainty requires a prohibitively large number of mock catalogues. In this work, we test a novel technique for the estimation of the precision matrix, the covariance tapering method, in the context of baryon acoustic oscillation measurements. Even though this technique was originally devised as a way to speed up maximum likelihood estimations, our results show that it also reduces the impact of noisy precision matrix estimates on the derived confidence intervals, without introducing biases on the target parameters. The application of this technique can help future surveys to reach their true constraining power using a significantly smaller number of mock catalogues.

  20. Precision Optics Curriculum.

    ERIC Educational Resources Information Center

    Reid, Robert L.; And Others

    This guide outlines the competency-based, two-year precision optics curriculum that the American Precision Optics Manufacturers Association has proposed to fill the void that it suggests will soon exist as many of the master opticians currently employed retire. The model, which closely resembles the old European apprenticeship model, calls for 300…

  1. Precision spectroscopy with a frequency-comb-calibrated solar spectrograph

    NASA Astrophysics Data System (ADS)

    Doerr, H.-P.

    2015-06-01

    precision spectroscopy of the Sun and laboratory light sources. The first scientific observations aimed at measuring the accurate wavelengths of selected solar Fraunhofer lines to characterise the so-called convective blue shift and its centre to limb variation. The convective blueshifts were derived with respect to laboratory wavelengths that were obtained from spectral lamps measured with the same instrument. The measurements agree with previous studies but provide a way higher accuracy. The data is only partially compatible with numerical simulations that were published recently. Further measurements were carried out to provide the absolute wavelengths of telluric O2 lines that are commonly used for wavelength calibration. With an accuracy of 1 m/s, these new measurements are two orders of magnitude better than existing data.

  2. Accuracy of optical dental digitizers: an in vitro study.

    PubMed

    Vandeweghe, Stefan; Vervack, Valentin; Vanhove, Christian; Dierens, Melissa; Jimbo, Ryo; De Bruyn, Hugo

    2015-01-01

    The aim of this study was to evaluate the accuracy, in terms of trueness and precision, of optical dental scanners. An experimental acrylic resin cast was created and digitized using a microcomputed tomography (microCT) scanner, which served as the reference model. Five polyether impressions were made of the acrylic resin cast to create five stone casts. Each dental digitizer (Imetric, Lava ST, Smart Optics, KaVo Everest) made five scans of the acrylic resin cast and one scan of every stone cast. The scans were superimposed and compared using metrology software. Deviations were calculated between the datasets obtained from the dental digitizers and the microCT scanner (= trueness) and between datasets from the same dental digitizer (= precision). With exception of the Smart Optics scanner, there were no significant differences in trueness for the acrylic resin cast. For the stone casts, however, the Lava ST performed better than Imetric, which did better than the KaVo scanner. The Smart Optics scanner demonstrated the highest deviation. All digitizers demonstrated a significantly higher trueness for the acrylic resin cast compared to the plaster cast, except the Lava ST. The Lava ST was significantly more precise compared to the other scanners. Imetric and Smart Optics also demonstrated a higher level of precision compared to the KaVo scanner. All digitizers demonstrated some degree of error. Stone cast copies are less accurate because of difficulties with scanning the rougher surface or dimensional deformations caused during the production process. For complex, large-span reconstructions, a highly accurate scanner should be selected. PMID:25734714

  3. Spacecraft attitude determination accuracy from mission experience

    NASA Technical Reports Server (NTRS)

    Brasoveanu, D.; Hashmall, J.

    1994-01-01

    This paper summarizes a compilation of attitude determination accuracies attained by a number of satellites supported by the Goddard Space Flight Center Flight Dynamics Facility. The compilation is designed to assist future mission planners in choosing and placing attitude hardware and selecting the attitude determination algorithms needed to achieve given accuracy requirements. The major goal of the compilation is to indicate realistic accuracies achievable using a given sensor complement based on mission experience. It is expected that the use of actual spacecraft experience will make the study especially useful for mission design. A general description of factors influencing spacecraft attitude accuracy is presented. These factors include determination algorithms, inertial reference unit characteristics, and error sources that can affect measurement accuracy. Possible techniques for mitigating errors are also included. Brief mission descriptions are presented with the attitude accuracies attained, grouped by the sensor pairs used in attitude determination. The accuracies for inactive missions represent a compendium of missions report results, and those for active missions represent measurements of attitude residuals. Both three-axis and spin stabilized missions are included. Special emphasis is given to high-accuracy sensor pairs, such as two fixed-head star trackers (FHST's) and fine Sun sensor plus FHST. Brief descriptions of sensor design and mode of operation are included. Also included are brief mission descriptions and plots summarizing the attitude accuracy attained using various sensor complements.

  4. A 3-D Multilateration: A Precision Geodetic Measurement System

    NASA Technical Reports Server (NTRS)

    Escobal, P. R.; Fliegel, H. F.; Jaffe, R. M.; Muller, P. M.; Ong, K. M.; Vonroos, O. H.

    1972-01-01

    A system was designed with the capability of determining 1-cm accuracy station positions in three dimensions using pulsed laser earth satellite tracking stations coupled with strictly geometric data reduction. With this high accuracy, several crucial geodetic applications become possible, including earthquake hazards assessment, precision surveying, plate tectonics, and orbital determination.

  5. Improve the ZY-3 Height Accuracy Using Icesat/glas Laser Altimeter Data

    NASA Astrophysics Data System (ADS)

    Li, Guoyuan; Tang, Xinming; Gao, Xiaoming; Zhang, Chongyang; Li, Tao

    2016-06-01

    ZY-3 is the first civilian high resolution stereo mapping satellite, which has been launched on 9th, Jan, 2012. The aim of ZY-3 satellite is to obtain high resolution stereo images and support the 1:50000 scale national surveying and mapping. Although ZY-3 has very high accuracy for direct geo-locations without GCPs (Ground Control Points), use of some GCPs is still indispensible for high precise stereo mapping. The GLAS (Geo-science Laser Altimetry System) loaded on the ICESat (Ice Cloud and land Elevation Satellite), which is the first laser altimetry satellite for earth observation. GLAS has played an important role in the monitoring of polar ice sheets, the measuring of land topography and vegetation canopy heights after launched in 2003. Although GLAS has ended in 2009, the derived elevation dataset still can be used after selection by some criteria. In this paper, the ICESat/GLAS laser altimeter data is used as height reference data to improve the ZY-3 height accuracy. A selection method is proposed to obtain high precision GLAS elevation data. Two strategies to improve the ZY-3 height accuracy are introduced. One is the conventional bundle adjustment based on RFM and bias-compensated model, in which the GLAS footprint data is viewed as height control. The second is to correct the DSM (Digital Surface Model) straightly by simple block adjustment, and the DSM is derived from the ZY-3 stereo imaging after freedom adjustment and dense image matching. The experimental result demonstrates that the height accuracy of ZY-3 without other GCPs can be improved to 3.0 meter after adding GLAS elevation data. What's more, the comparison of the accuracy and efficiency between the two strategies is implemented for application.

  6. Precision Spectroscopy of Atomic Hydrogen

    NASA Astrophysics Data System (ADS)

    Beyer, A.; Parthey, Ch G.; Kolachevsky, N.; Alnis, J.; Khabarova, K.; Pohl, R.; Peters, E.; Yost, D. C.; Matveev, A.; Predehl, K.; Droste, S.; Wilken, T.; Holzwarth, R.; Hänsch, T. W.; Abgrall, M.; Rovera, D.; Salomon, Ch; Laurent, Ph; Udem, Th

    2013-12-01

    Precise determinations of transition frequencies of simple atomic systems are required for a number of fundamental applications such as tests of quantum electrodynamics (QED), the determination of fundamental constants and nuclear charge radii. The sharpest transition in atomic hydrogen occurs between the metastable 2S state and the 1S ground state. Its transition frequency has now been measured with almost 15 digits accuracy using an optical frequency comb and a cesium atomic clock as a reference [1]. A recent measurement of the 2S - 2P3/2 transition frequency in muonic hydrogen is in significant contradiction to the hydrogen data if QED calculations are assumed to be correct [2, 3]. We hope to contribute to this so-called "proton size puzzle" by providing additional experimental input from hydrogen spectroscopy.

  7. System for precise position registration

    DOEpatents

    Sundelin, Ronald M.; Wang, Tong

    2005-11-22

    An apparatus for enabling accurate retaining of a precise position, such as for reacquisition of a microscopic spot or feature having a size of 0.1 mm or less, on broad-area surfaces after non-in situ processing. The apparatus includes a sample and sample holder. The sample holder includes a base and three support posts. Two of the support posts interact with a cylindrical hole and a U-groove in the sample to establish location of one point on the sample and a line through the sample. Simultaneous contact of the third support post with the surface of the sample defines a plane through the sample. All points of the sample are therefore uniquely defined by the sample and sample holder. The position registration system of the current invention provides accuracy, as measured in x, y repeatability, of at least 140 .mu.m.

  8. Accuracy of analyses of microelectronics nanostructures in atom probe tomography

    NASA Astrophysics Data System (ADS)

    Vurpillot, F.; Rolland, N.; Estivill, R.; Duguay, S.; Blavette, D.

    2016-07-01

    The routine use of atom probe tomography (APT) as a nano-analysis microscope in the semiconductor industry requires the precise evaluation of the metrological parameters of this instrument (spatial accuracy, spatial precision, composition accuracy or composition precision). The spatial accuracy of this microscope is evaluated in this paper in the analysis of planar structures such as high-k metal gate stacks. It is shown both experimentally and theoretically that the in-depth accuracy of reconstructed APT images is perturbed when analyzing this structure composed of an oxide layer of high electrical permittivity (higher-k dielectric constant) that separates the metal gate and the semiconductor channel of a field emitter transistor. Large differences in the evaporation field between these layers (resulting from large differences in material properties) are the main sources of image distortions. An analytic model is used to interpret inaccuracy in the depth reconstruction of these devices in APT.

  9. Accuracy potentials for large space antenna structures

    NASA Technical Reports Server (NTRS)

    Hedgepeth, J. M.

    1980-01-01

    The relationships among materials selection, truss design, and manufacturing techniques in the interest of surface accuracies for large space antennas are discussed. Among the antenna configurations considered are: tetrahedral truss, pretensioned truss, and geodesic dome and radial rib structures. Comparisons are made of the accuracy achievable by truss and dome structure types for a wide variety of diameters, focal lengths, and wavelength of radiated signal, taking into account such deforming influences as solar heating-caused thermal transients and thermal gradients.

  10. Interoceptive accuracy and panic.

    PubMed

    Zoellner, L A; Craske, M G

    1999-12-01

    Psychophysiological models of panic hypothesize that panickers focus attention on and become anxious about the physical sensations associated with panic. Attention on internal somatic cues has been labeled interoception. The present study examined the role of physiological arousal and subjective anxiety on interoceptive accuracy. Infrequent panickers and nonanxious participants participated in an initial baseline to examine overall interoceptive accuracy. Next, participants ingested caffeine, about which they received either safety or no safety information. Using a mental heartbeat tracking paradigm, participants' count of their heartbeats during specific time intervals were coded based on polygraph measures. Infrequent panickers were more accurate in the perception of their heartbeats than nonanxious participants. Changes in physiological arousal were not associated with increased accuracy on the heartbeat perception task. However, higher levels of self-reported anxiety were associated with superior performance. PMID:10596462

  11. Precision Environmental Radiation Monitoring System

    SciTech Connect

    Vladimir Popov, Pavel Degtiarenko

    2010-07-01

    A new precision low-level environmental radiation monitoring system has been developed and tested at Jefferson Lab. This system provides environmental radiation measurements with accuracy and stability of the order of 1 nGy/h in an hour, roughly corresponding to approximately 1% of the natural cosmic background at the sea level. Advanced electronic front-end has been designed and produced for use with the industry-standard High Pressure Ionization Chamber detector hardware. A new highly sensitive readout electronic circuit was designed to measure charge from the virtually suspended ionization chamber ion collecting electrode. New signal processing technique and dedicated data acquisition were tested together with the new readout. The designed system enabled data collection in a remote Linux-operated computer workstation, which was connected to the detectors using a standard telephone cable line. The data acquisition system algorithm is built around the continuously running 24-bit resolution 192 kHz data sampling analog to digital convertor. The major features of the design include: extremely low leakage current in the input circuit, true charge integrating mode operation, and relatively fast response to the intermediate radiation change. These features allow operating of the device as an environmental radiation monitor, at the perimeters of the radiation-generating installations in densely populated areas, like in other monitoring and security applications requiring high precision and long-term stability. Initial system evaluation results are presented.

  12. Seasonal Effects on GPS PPP Accuracy

    NASA Astrophysics Data System (ADS)

    Saracoglu, Aziz; Ugur Sanli, D.

    2016-04-01

    GPS Precise Point Positioning (PPP) is now routinely used in many geophysical applications. Static positioning and 24 h data are requested for high precision results however real life situations do not always let us collect 24 h data. Thus repeated GPS surveys of 8-10 h observation sessions are still used by some research groups. Positioning solutions from shorter data spans are subject to various systematic influences, and the positioning quality as well as the estimated velocity is degraded. Researchers pay attention to the accuracy of GPS positions and of the estimated velocities derived from short observation sessions. Recently some research groups turned their attention to the study of seasonal effects (i.e. meteorological seasons) on GPS solutions. Up to now usually regional studies have been reported. In this study, we adopt a global approach and study the various seasonal effects (including the effect of the annual signal) on GPS solutions produced from short observation sessions. We use the PPP module of the NASA/JPL's GIPSY/OASIS II software and globally distributed GPS stations' data of the International GNSS Service. Accuracy studies previously performed with 10-30 consecutive days of continuous data. Here, data from each month of a year, incorporating two years in succession, is used in the analysis. Our major conclusion is that a reformulation for the GPS positioning accuracy is necessary when taking into account the seasonal effects, and typical one term accuracy formulation is expanded to a two-term one.

  13. Precision liquid level sensor

    DOEpatents

    Field, M.E.; Sullivan, W.H.

    A precision liquid level sensor utilizes a balanced bridge, each arm including an air dielectric line. Changes in liquid level along one air dielectric line imbalance the bridge and create a voltage which is directly measurable across the bridge.

  14. Precision displacement reference system

    DOEpatents

    Bieg, Lothar F.; Dubois, Robert R.; Strother, Jerry D.

    2000-02-22

    A precision displacement reference system is described, which enables real time accountability over the applied displacement feedback system to precision machine tools, positioning mechanisms, motion devices, and related operations. As independent measurements of tool location is taken by a displacement feedback system, a rotating reference disk compares feedback counts with performed motion. These measurements are compared to characterize and analyze real time mechanical and control performance during operation.

  15. High-precision hydraulic Stewart platform

    NASA Astrophysics Data System (ADS)

    van Silfhout, Roelof G.

    1999-08-01

    We present a novel design for a Stewart platform (or hexapod), an apparatus which performs positioning tasks with high accuracy. The platform, which is supported by six hydraulic telescopic struts, provides six degrees of freedom with 1 μm resolution. Rotations about user defined pivot points can be specified for any axis of rotation with microradian accuracy. Motion of the platform is performed by changing the strut lengths. Servo systems set and maintain the length of the struts to high precision using proportional hydraulic valves and incremental encoders. The combination of hydraulic actuators and a design which is optimized in terms of mechanical stiffness enables the platform to manipulate loads of up to 20 kN. Sophisticated software allows direct six-axis positioning including true path control. Our platform is an ideal support structure for a large variety of scientific instruments that require a stable alignment base with high-precision motion.

  16. Accuracy of prediction of genomic breeding values for residual feed intake and carcass and meat quality traits in Bos taurus, Bos indicus, and composite beef cattle.

    PubMed

    Bolormaa, S; Pryce, J E; Kemper, K; Savin, K; Hayes, B J; Barendse, W; Zhang, Y; Reich, C M; Mason, B A; Bunch, R J; Harrison, B E; Reverter, A; Herd, R M; Tier, B; Graser, H-U; Goddard, M E

    2013-07-01

    The aim of this study was to assess the accuracy of genomic predictions for 19 traits including feed efficiency, growth, and carcass and meat quality traits in beef cattle. The 10,181 cattle in our study had real or imputed genotypes for 729,068 SNP although not all cattle were measured for all traits. Animals included Bos taurus, Brahman, composite, and crossbred animals. Genomic EBV (GEBV) were calculated using 2 methods of genomic prediction [BayesR and genomic BLUP (GBLUP)] either using a common training dataset for all breeds or using a training dataset comprising only animals of the same breed. Accuracies of GEBV were assessed using 5-fold cross-validation. The accuracy of genomic prediction varied by trait and by method. Traits with a large number of recorded and genotyped animals and with high heritability gave the greatest accuracy of GEBV. Using GBLUP, the average accuracy was 0.27 across traits and breeds, but the accuracies between breeds and between traits varied widely. When the training population was restricted to animals from the same breed as the validation population, GBLUP accuracies declined by an average of 0.04. The greatest decline in accuracy was found for the 4 composite breeds. The BayesR accuracies were greater by an average of 0.03 than GBLUP accuracies, particularly for traits with known genes of moderate to large effect mutations segregating. The accuracies of 0.43 to 0.48 for IGF-I traits were among the greatest in the study. Although accuracies are low compared with those observed in dairy cattle, genomic selection would still be beneficial for traits that are hard to improve by conventional selection, such as tenderness and residual feed intake. BayesR identified many of the same quantitative trait loci as a genomewide association study but appeared to map them more precisely. All traits appear to be highly polygenic with thousands of SNP independently associated with each trait. PMID:23658330

  17. Realization and performance of cryogenic selection mechanisms

    NASA Astrophysics Data System (ADS)

    Aitink-Kroes, Gabby; Bettonvil, Felix; Kragt, Jan; Elswijk, Eddy; Tromp, Niels

    2014-07-01

    Within Infra-Red large wavelength bandwidth instruments the use of mechanisms for selection of observation modes, filters, dispersing elements, pinholes or slits is inevitable. The cryogenic operating environment poses several challenges to these cryogenic mechanisms; like differential thermal shrinkage, physical property change of materials, limited use of lubrication, high feature density, limited space etc. MATISSE the mid-infrared interferometric spectrograph and imager for ESO's VLT interferometer (VLTI) at Paranal in Chile coherently combines the light from 4 telescopes. Within the Cold Optics Bench (COB) of MATISSE two concepts of selection mechanisms can be distinguished based on the same design principles: linear selection mechanisms (sliders) and rotating selection mechanisms (wheels).Both sliders and wheels are used at a temperature of 38 Kelvin. The selection mechanisms have to provide high accuracy and repeatability. The sliders/wheels have integrated tracks that run on small, accurately located, spring loaded precision bearings. Special indents are used for selection of the slider/wheel position. For maximum accuracy/repeatability the guiding/selection system is separated from the actuation in this case a cryogenic actuator inside the cryostat. The paper discusses the detailed design of the mechanisms and the final realization for the MATISSE COB. Limited lifetime and performance tests determine accuracy, warm and cold and the reliability/wear during life of the instrument. The test results and further improvements to the mechanisms are discussed.

  18. The Future of Precision Medicine in Oncology.

    PubMed

    Millner, Lori M; Strotman, Lindsay N

    2016-09-01

    Precision medicine in oncology focuses on identifying which therapies are most effective for each patient based on genetic characterization of the cancer. Traditional chemotherapy is cytotoxic and destroys all cells that are rapidly dividing. The foundation of precision medicine is targeted therapies and selecting patients who will benefit most from these therapies. One of the newest aspects of precision medicine is liquid biopsy. A liquid biopsy includes analysis of circulating tumor cells, cell-free nucleic acid, or exosomes obtained from a peripheral blood draw. These can be studied individually or in combination and collected serially, providing real-time information as a patient's cancer changes. PMID:27514468

  19. Accuracy of deception judgments.

    PubMed

    Bond, Charles F; DePaulo, Bella M

    2006-01-01

    We analyze the accuracy of deception judgments, synthesizing research results from 206 documents and 24,483 judges. In relevant studies, people attempt to discriminate lies from truths in real time with no special aids or training. In these circumstances, people achieve an average of 54% correct lie-truth judgments, correctly classifying 47% of lies as deceptive and 61% of truths as nondeceptive. Relative to cross-judge differences in accuracy, mean lie-truth discrimination abilities are nontrivial, with a mean accuracy d of roughly .40. This produces an effect that is at roughly the 60th percentile in size, relative to others that have been meta-analyzed by social psychologists. Alternative indexes of lie-truth discrimination accuracy correlate highly with percentage correct, and rates of lie detection vary little from study to study. Our meta-analyses reveal that people are more accurate in judging audible than visible lies, that people appear deceptive when motivated to be believed, and that individuals regard their interaction partners as honest. We propose that people judge others' deceptions more harshly than their own and that this double standard in evaluating deceit can explain much of the accumulated literature. PMID:16859438

  20. Estimating sparse precision matrices

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil; White, Martin; Zhou, Harrison H.; O'Connell, Ross

    2016-08-01

    We apply a method recently introduced to the statistical literature to directly estimate the precision matrix from an ensemble of samples drawn from a corresponding Gaussian distribution. Motivated by the observation that cosmological precision matrices are often approximately sparse, the method allows one to exploit this sparsity of the precision matrix to more quickly converge to an asymptotic 1/sqrt{N_sim} rate while simultaneously providing an error model for all of the terms. Such an estimate can be used as the starting point for further regularization efforts which can improve upon the 1/sqrt{N_sim} limit above, and incorporating such additional steps is straightforward within this framework. We demonstrate the technique with toy models and with an example motivated by large-scale structure two-point analysis, showing significant improvements in the rate of convergence. For the large-scale structure example, we find errors on the precision matrix which are factors of 5 smaller than for the sample precision matrix for thousands of simulations or, alternatively, convergence to the same error level with more than an order of magnitude fewer simulations.

  1. Precision Higgs Physics

    NASA Astrophysics Data System (ADS)

    Boughezal, Radja

    2015-04-01

    The future of the high energy physics program will increasingly rely upon precision studies looking for deviations from the Standard Model. Run I of the Large Hadron Collider (LHC) triumphantly discovered the long-awaited Higgs boson, and there is great hope in the particle physics community that this new state will open a portal onto a new theory of Nature at the smallest scales. A precision study of Higgs boson properties is needed in order to test whether this belief is true. New theoretical ideas and high-precision QCD tools are crucial to fulfill this goal. They become even more important as larger data sets from LHC Run II further reduce the experimental errors and theoretical uncertainties begin to dominate. In this talk, I will review recent progress in understanding Higgs properties,including the calculation of precision predictions needed to identify possible physics beyond the Standard Model in the Higgs sector. New ideas for measuring the Higgs couplings to light quarks as well as bounding the Higgs width in a model-independent way will be discussed. Precision predictions for Higgs production in association with jets and ongoing efforts to calculate the inclusive N3LO cross section will be reviewed.

  2. Estimating sparse precision matrices

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil; White, Martin; Zhou, Harrison H.; O'Connell, Ross

    2016-05-01

    We apply a method recently introduced to the statistical literature to directly estimate the precision matrix from an ensemble of samples drawn from a corresponding Gaussian distribution. Motivated by the observation that cosmological precision matrices are often approximately sparse, the method allows one to exploit this sparsity of the precision matrix to more quickly converge to an asymptotic 1/√{N_sim} rate while simultaneously providing an error model for all of the terms. Such an estimate can be used as the starting point for further regularization efforts which can improve upon the 1/√{N_sim} limit above, and incorporating such additional steps is straightforward within this framework. We demonstrate the technique with toy models and with an example motivated by large-scale structure two-point analysis, showing significant improvements in the rate of convergence. For the large-scale structure example we find errors on the precision matrix which are factors of 5 smaller than for the sample precision matrix for thousands of simulations or, alternatively, convergence to the same error level with more than an order of magnitude fewer simulations.

  3. Estimating sparse precision matrices

    NASA Astrophysics Data System (ADS)

    Padmanabhan, Nikhil; White, Martin; Zhou, Harrison H.; O'Connell, Ross

    2016-08-01

    We apply a method recently introduced to the statistical literature to directly estimate the precision matrix from an ensemble of samples drawn from a corresponding Gaussian distribution. Motivated by the observation that cosmological precision matrices are often approximately sparse, the method allows one to exploit this sparsity of the precision matrix to more quickly converge to an asymptotic 1/√{N_sim} rate while simultaneously providing an error model for all of the terms. Such an estimate can be used as the starting point for further regularization efforts which can improve upon the 1/√{N_sim} limit above, and incorporating such additional steps is straightforward within this framework. We demonstrate the technique with toy models and with an example motivated by large-scale structure two-point analysis, showing significant improvements in the rate of convergence. For the large-scale structure example, we find errors on the precision matrix which are factors of 5 smaller than for the sample precision matrix for thousands of simulations or, alternatively, convergence to the same error level with more than an order of magnitude fewer simulations.

  4. Precise Indoor Localization for Mobile Laser Scanner

    NASA Astrophysics Data System (ADS)

    Kaijaluoto, R.; Hyyppä, A.

    2015-05-01

    Accurate 3D data is of high importance for indoor modeling for various applications in construction, engineering and cultural heritage documentation. For the lack of GNSS signals hampers use of kinematic platforms indoors, TLS is currently the most accurate and precise method for collecting such a data. Due to its static single view point data collection, excessive time and data redundancy are needed for integrity and coverage of data. However, localization methods with affordable scanners are used for solving mobile platform pose problem. The aim of this study was to investigate what level of trajectory accuracies can be achieved with high quality sensors and freely available state of the art planar SLAM algorithms, and how well this trajectory translates to a point cloud collected with a secondary scanner. In this study high precision laser scanners were used with a novel way to combine the strengths of two SLAM algorithms into functional method for precise localization. We collected five datasets using Slammer platform with two laser scanners, and processed them with altogether 20 different parameter sets. The results were validated against TLS reference. The results show increasing scan frequency improves the trajectory, reaching 20 mm RMSE levels for the best performing parameter sets. Further analysis of the 3D point cloud showed good agreement with TLS reference with 17 mm positional RMSE. With precision scanners the obtained point cloud allows for high level of detail data for indoor modeling with accuracies close to TLS at best with vastly improved data collection efficiency.

  5. Ultra-precision: enabling our future.

    PubMed

    Shore, Paul; Morantz, Paul

    2012-08-28

    This paper provides a perspective on the development of ultra-precision technologies: What drove their evolution and what do they now promise for the future as we face the consequences of consumption of the Earth's finite resources? Improved application of measurement is introduced as a major enabler of mass production, and its resultant impact on wealth generation is considered. This paper identifies the ambitions of the defence, automotive and microelectronics sectors as important drivers of improved manufacturing accuracy capability and ever smaller feature creation. It then describes how science fields such as astronomy have presented significant precision engineering challenges, illustrating how these fields of science have achieved unprecedented levels of accuracy, sensitivity and sheer scale. Notwithstanding their importance to science understanding, many science-driven ultra-precision technologies became key enablers for wealth generation and other well-being issues. Specific ultra-precision machine tools important to major astronomy programmes are discussed, as well as the way in which subsequently evolved machine tools made at the beginning of the twenty-first century, now provide much wider benefits. PMID:22802499

  6. Analysis of HY2A precise orbit determination using DORIS

    NASA Astrophysics Data System (ADS)

    Gao, Fan; Peng, Bibo; Zhang, Yu; Evariste, Ngatchou Heutchi; Liu, Jihua; Wang, Xiaohui; Zhong, Min; Lin, Mingsen; Wang, Nazi; Chen, Runjing; Xu, Houze

    2015-03-01

    HY2A is the first Chinese marine dynamic environment satellite. The payloads include a radar altimeter to measure the sea surface height in combination with a high precision orbit to be determined from tracking data. Onboard satellite tracking includes GPS, SLR, and the DORIS DGXX receiver which delivers phase and pseudo-range measurements. CNES releases raw phase and pseudo-range measurements with RINEX DORIS 3.0 format and pre-processed Doppler range-rate with DORIS 2.2 data format. However, the VMSI software package developed by Van Martin Systems, Inc which is used to estimate HY2A DORIS orbits can only process Doppler range-rate but not the DORIS phase data which are available with much shorter latency. We have proposed a method of constructing the phase increment data, which are similar to range-rate data, from RINEX DORIS 3.0 phase data. We compute the HY2A orbits from June, 2013 to August, 2013 using the POD strategy described in this paper based on DORIS 2.2 range-rate data and our reconstructed phase increment data. The estimated orbits are evaluated by comparing with the CNES precise orbits and SLR residuals. Our DORIS-only orbits agree with the precise GPS + SLR + DORIS CNES orbits radially at 1-cm and about 3-cm in the other two directions. SLR test with the 50° cutoff elevation shows that the CNES orbit can achieve about 1.1-cm accuracy in radial direction and our DORIS-only POD solutions are slightly worse. In addition, other HY2A DORIS POD concerns are discussed in this paper. Firstly, we discuss the frequency offset values provided with the RINEX data and find that orbit accuracy for the case when the frequency offset is applied is worse than when it is not applied. Secondly, HY2A DORIS antenna z-offsets are estimated using two kinds of measurements from June, 2013 to August, 2013. The results show that the measurement errors contribute a total of about 2-cm difference of estimated z-offset. Finally, we estimate HY2A orbits selecting 3 days with

  7. How Physics Got Precise

    SciTech Connect

    Kleppner, Daniel

    2005-01-19

    Although the ancients knew the length of the year to about ten parts per million, it was not until the end of the 19th century that precision measurements came to play a defining role in physics. Eventually such measurements made it possible to replace human-made artifacts for the standards of length and time with natural standards. For a new generation of atomic clocks, time keeping could be so precise that the effects of the local gravitational potentials on the clock rates would be important. This would force us to re-introduce an artifact into the definition of the second - the location of the primary clock. I will describe some of the events in the history of precision measurements that have led us to this pleasing conundrum, and some of the unexpected uses of atomic clocks today.

  8. Precision gap particle separator

    DOEpatents

    Benett, William J.; Miles, Robin; Jones, II., Leslie M.; Stockton, Cheryl

    2004-06-08

    A system for separating particles entrained in a fluid includes a base with a first channel and a second channel. A precision gap connects the first channel and the second channel. The precision gap is of a size that allows small particles to pass from the first channel into the second channel and prevents large particles from the first channel into the second channel. A cover is positioned over the base unit, the first channel, the precision gap, and the second channel. An port directs the fluid containing the entrained particles into the first channel. An output port directs the large particles out of the first channel. A port connected to the second channel directs the small particles out of the second channel.

  9. Precision Muonium Spectroscopy

    NASA Astrophysics Data System (ADS)

    Jungmann, Klaus P.

    2016-09-01

    The muonium atom is the purely leptonic bound state of a positive muon and an electron. It has a lifetime of 2.2 µs. The absence of any known internal structure provides for precision experiments to test fundamental physics theories and to determine accurate values of fundamental constants. In particular ground state hyperfine structure transitions can be measured by microwave spectroscopy to deliver the muon magnetic moment. The frequency of the 1s-2s transition in the hydrogen-like atom can be determined with laser spectroscopy to obtain the muon mass. With such measurements fundamental physical interactions, in particular quantum electrodynamics, can also be tested at highest precision. The results are important input parameters for experiments on the muon magnetic anomaly. The simplicity of the atom enables further precise experiments, such as a search for muonium-antimuonium conversion for testing charged lepton number conservation and searches for possible antigravity of muons and dark matter.

  10. Precision Casting via Advanced Simulation and Manufacturing

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A two-year program was conducted to develop and commercially implement selected casting manufacturing technologies to enable significant reductions in the costs of castings, increase the complexity and dimensional accuracy of castings, and reduce the development times for delivery of high quality castings. The industry-led R&D project was cost shared with NASA's Aerospace Industry Technology Program (AITP). The Rocketdyne Division of Boeing North American, Inc. served as the team lead with participation from Lockheed Martin, Ford Motor Company, Howmet Corporation, PCC Airfoils, General Electric, UES, Inc., University of Alabama, Auburn University, Robinson, Inc., Aracor, and NASA-LeRC. The technical effort was organized into four distinct tasks. The accomplishments reported herein. Task 1.0 developed advanced simulation technology for core molding. Ford headed up this task. On this program, a specialized core machine was designed and built. Task 2.0 focused on intelligent process control for precision core molding. Howmet led this effort. The primary focus of these experimental efforts was to characterize the process parameters that have a strong impact on dimensional control issues of injection molded cores during their fabrication. Task 3.0 developed and applied rapid prototyping to produce near net shape castings. Rocketdyne was responsible for this task. CAD files were generated using reverse engineering, rapid prototype patterns were fabricated using SLS and SLA, and castings produced and evaluated. Task 4.0 was aimed at developing technology transfer. Rocketdyne coordinated this task. Casting related technology, explored and evaluated in the first three tasks of this program, was implemented into manufacturing processes.

  11. Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis

    NASA Technical Reports Server (NTRS)

    Slojkowski, Steven E.

    2014-01-01

    Results from operational OD produced by the NASA Goddard Flight Dynamics Facility for the LRO nominal and extended mission are presented. During the LRO nominal mission, when LRO flew in a low circular orbit, orbit determination requirements were met nearly 100% of the time. When the extended mission began, LRO returned to a more elliptical frozen orbit where gravity and other modeling errors caused numerous violations of mission accuracy requirements. Prediction accuracy is particularly challenged during periods when LRO is in full-Sun. A series of improvements to LRO orbit determination are presented, including implementation of new lunar gravity models, improved spacecraft solar radiation pressure modeling using a dynamic multi-plate area model, a shorter orbit determination arc length, and a constrained plane method for estimation. The analysis presented in this paper shows that updated lunar gravity models improved accuracy in the frozen orbit, and a multiplate dynamic area model improves prediction accuracy during full-Sun orbit periods. Implementation of a 36-hour tracking data arc and plane constraints during edge-on orbit geometry also provide benefits. A comparison of the operational solutions to precision orbit determination solutions shows agreement on a 100- to 250-meter level in definitive accuracy.

  12. Asymptotic accuracy of two-class discrimination

    SciTech Connect

    Ho, T.K.; Baird, H.S.

    1994-12-31

    Poor quality-e.g. sparse or unrepresentative-training data is widely suspected to be one cause of disappointing accuracy of isolated-character classification in modern OCR machines. We conjecture that, for many trainable classification techniques, it is in fact the dominant factor affecting accuracy. To test this, we have carried out a study of the asymptotic accuracy of three dissimilar classifiers on a difficult two-character recognition problem. We state this problem precisely in terms of high-quality prototype images and an explicit model of the distribution of image defects. So stated, the problem can be represented as a stochastic source of an indefinitely long sequence of simulated images labeled with ground truth. Using this sequence, we were able to train all three classifiers to high and statistically indistinguishable asymptotic accuracies (99.9%). This result suggests that the quality of training data was the dominant factor affecting accuracy. The speed of convergence during training, as well as time/space trade-offs during recognition, differed among the classifiers.

  13. Precision Heating Process

    NASA Technical Reports Server (NTRS)

    1992-01-01

    A heat sealing process was developed by SEBRA based on technology that originated in work with NASA's Jet Propulsion Laboratory. The project involved connecting and transferring blood and fluids between sterile plastic containers while maintaining a closed system. SEBRA markets the PIRF Process to manufacturers of medical catheters. It is a precisely controlled method of heating thermoplastic materials in a mold to form or weld catheters and other products. The process offers advantages in fast, precise welding or shape forming of catheters as well as applications in a variety of other industries.

  14. Precision manometer gauge

    DOEpatents

    McPherson, M.J.; Bellman, R.A.

    1982-09-27

    A precision manometer gauge which locates a zero height and a measured height of liquid using an open tube in communication with a reservoir adapted to receive the pressure to be measured. The open tube has a reference section carried on a positioning plate which is moved vertically with machine tool precision. Double scales are provided to read the height of the positioning plate accurately, the reference section being inclined for accurate meniscus adjustment, and means being provided to accurately locate a zero or reference position.

  15. Precision manometer gauge

    DOEpatents

    McPherson, Malcolm J.; Bellman, Robert A.

    1984-01-01

    A precision manometer gauge which locates a zero height and a measured height of liquid using an open tube in communication with a reservoir adapted to receive the pressure to be measured. The open tube has a reference section carried on a positioning plate which is moved vertically with machine tool precision. Double scales are provided to read the height of the positioning plate accurately, the reference section being inclined for accurate meniscus adjustment, and means being provided to accurately locate a zero or reference position.

  16. Ultra-precision turning of complex spiral optical delay line

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaodong; Li, Po; Fang, Fengzhou; Wang, Qichang

    2011-11-01

    Optical delay line (ODL) implements the vertical or depth scanning of optical coherence tomography, which is the most important factor affecting the scanning resolution and speed. The spinning spiral mirror is found as an excellent optical delay device because of the high-speed and high-repetition-rate. However, it is one difficult task to machine the mirror due to the special shape and precision requirement. In this paper, the spiral mirror with titled parabolic generatrix is proposed, and the ultra-precision turning method is studied for its machining using the spiral mathematic model. Another type of ODL with the segmental shape is also introduced and machined to make rotation balance for the mass equalization when scanning. The efficiency improvement is considered in details, including the rough cutting with the 5- axis milling machine, the machining coordinates unification, and the selection of layer direction in turning. The onmachine measuring method based on stylus gauge is designed to analyze the shape deviation. The air bearing is used as the measuring staff and the laser interferometer sensor as the position sensor, whose repeatability accuracy is proved up to 10nm and the stable feature keeps well. With this method developed, the complex mirror with nanometric finish of 10.7nm in Ra and the form error within 1um are achieved.

  17. High Accuracy Fuel Flowmeter, Phase 1

    NASA Technical Reports Server (NTRS)

    Mayer, C.; Rose, L.; Chan, A.; Chin, B.; Gregory, W.

    1983-01-01

    Technology related to aircraft fuel mass - flowmeters was reviewed to determine what flowmeter types could provide 0.25%-of-point accuracy over a 50 to one range in flowrates. Three types were selected and were further analyzed to determine what problem areas prevented them from meeting the high accuracy requirement, and what the further development needs were for each. A dual-turbine volumetric flowmeter with densi-viscometer and microprocessor compensation was selected for its relative simplicity and fast response time. An angular momentum type with a motor-driven, spring-restrained turbine and viscosity shroud was selected for its direct mass-flow output. This concept also employed a turbine for fast response and a microcomputer for accurate viscosity compensation. The third concept employed a vortex precession volumetric flowmeter and was selected for its unobtrusive design. Like the turbine flowmeter, it uses a densi-viscometer and microprocessor for density correction and accurate viscosity compensation.

  18. Optimal design of robot accuracy compensators

    SciTech Connect

    Zhuang, H.; Roth, Z.S. . Robotics Center and Electrical Engineering Dept.); Hamano, Fumio . Dept. of Electrical Engineering)

    1993-12-01

    The problem of optimal design of robot accuracy compensators is addressed. Robot accuracy compensation requires that actual kinematic parameters of a robot be previously identified. Additive corrections of joint commands, including those at singular configurations, can be computed without solving the inverse kinematics problem for the actual robot. This is done by either the damped least-squares (DLS) algorithm or the linear quadratic regulator (LQR) algorithm, which is a recursive version of the DLS algorithm. The weight matrix in the performance index can be selected to achieve specific objectives, such as emphasizing end-effector's positioning accuracy over orientation accuracy or vice versa, or taking into account proximity to robot joint travel limits and singularity zones. The paper also compares the LQR and the DLS algorithms in terms of computational complexity, storage requirement, and programming convenience. Simulation results are provided to show the effectiveness of the algorithms.

  19. Astrophysics with Microarcsecond Accuracy Astrometry

    NASA Technical Reports Server (NTRS)

    Unwin, Stephen C.

    2008-01-01

    Space-based astrometry promises to provide a powerful new tool for astrophysics. At a precision level of a few microarcsonds, a wide range of phenomena are opened up for study. In this paper we discuss the capabilities of the SIM Lite mission, the first space-based long-baseline optical interferometer, which will deliver parallaxes to 4 microarcsec. A companion paper in this volume will cover the development and operation of this instrument. At the level that SIM Lite will reach, better than 1 microarcsec in a single measurement, planets as small as one Earth can be detected around many dozen of the nearest stars. Not only can planet masses be definitely measured, but also the full orbital parameters determined, allowing study of system stability in multiple planet systems. This capability to survey our nearby stellar neighbors for terrestrial planets will be a unique contribution to our understanding of the local universe. SIM Lite will be able to tackle a wide range of interesting problems in stellar and Galactic astrophysics. By tracing the motions of stars in dwarf spheroidal galaxies orbiting our Milky Way, SIM Lite will probe the shape of the galactic potential history of the formation of the galaxy, and the nature of dark matter. Because it is flexibly scheduled, the instrument can dwell on faint targets, maintaining its full accuracy on objects as faint as V=19. This paper is a brief survey of the diverse problems in modern astrophysics that SIM Lite will be able to address.

  20. Precise measurements of hyperfine components in the spectrum of molecular iodine

    SciTech Connect

    Sansonetti, C.J.

    1996-05-01

    Absolute wave numbers with a typical uncertainty of 1 MHz (95% confidence) were measured for 102 hyperfine-structure components of {sup 127}I{sub 2}. The data cover the range 560-656 nm, with no gaps over 50 cm{sup -1}. The spectra were observed using Doppler-free frequency modulation spectroscopy with tunable cw laser. The laser was locked to selected iodine components and its wave number measured with a high precision Fabry-Perot wavemeter. Accuracy is confirmed by good agreement of 9 of the lines with previous results from other laboratories. These measurements provide a well-distributed set of precise reference lines for this spectral region.

  1. Precise science orbits for the Swarm satellite constellation

    NASA Astrophysics Data System (ADS)

    van den IJssel, Jose; Encarnação, João; Doornbos, Eelco; Visser, Pieter

    2015-09-01

    The European Space Agency (ESA) Swarm mission was launched on 22 November 2013 to study the dynamics of the Earth's magnetic field and its interaction with the Earth system. The mission consists of three identical satellites, flying in carefully selected near polar orbits. Two satellites fly almost side-by-side at an initial altitude of about 480 km, and will descend due to drag to around 300 km during the mission lifetime. The third satellite was placed in a higher orbit of about 530 km altitude, and therefore descends much more slowly. To geolocate the Swarm observations, each satellite is equipped with an 8-channel, dual-frequency GPS receiver for Precise Orbit Determination (POD). Onboard laser retroreflectors provide the opportunity to validate the orbits computed from the GPS observations using Satellite Laser Ranging (SLR) data. Precise Science Orbits (PSOs) for the Swarm satellites are computed by the Faculty of Aerospace Engineering at Delft University of Technology in the framework of the Swarm Satellite Constellation Application and Research Facility (SCARF). The PSO product consists of both a reduced-dynamic and a kinematic orbit solution. After a short description of the Swarm GPS data characteristics, the adopted POD strategy for both orbit types is explained and first PSO results from more than one year of Swarm GPS data are presented. Independent SLR validation shows that the reduced-dynamic Swarm PSOs have an accuracy of better than 2 cm, while the kinematic orbits have a slightly reduced accuracy of about 4-5 cm. Orbit comparisons indicate that the consistency between the reduced-dynamic and kinematic Swarm PSO for most parts of the Earth is at the 4-5 cm level. Close to the geomagnetic poles and along the geomagnetic equator, however, the kinematic orbits show larger errors, which are probably due to ionospheric scintillations that affect the Swarm GPS receivers over these areas.

  2. Demonstration of sub-meter GPS orbit determination and 1.5 parts in 10 to the 8th three-dimensional baseline accuracy

    NASA Technical Reports Server (NTRS)

    Lichten, Stephen M.; Bertiger, Willy I.

    1989-01-01

    Strategies for the estimation of precise GPS orbits and ground baselines, designed to minimize error sources related to the GPS orbit accuracy and the tropospheric delay, are demonstrated. Using GPS data from field experiments conducted in 1985 and 1986, it is shown that, by carefully selecting well-known stations to serve as reference points and by using the GPS data to determine high-accuracy GPS orbits and to solve for wet tropospheric delay fluctuations, the 2000-km baselines in North America can now be estimated with the accuracy better than 1.5 parts in 10 to the 8th. Using these strategies, better than l-m accuracy was achieved for the two best-tracked satellites (of the seven total operational GPS satellites).

  3. High Precision and Real Time Tracking of Low Earth Orbiters With GPS: Case Studies With TOPEX/POSEIDON and EUVE

    NASA Technical Reports Server (NTRS)

    Yunck, Thomas P.; Bertiger, Winy I.; Gold, Kenn; Guinn, Joseph; Reichert, Angie; Watkins, Michael

    1995-01-01

    TOPEX/POSEIDON carries a dual-frequency 6 channel GPS receiver while EUVE has a 12 channel single frequency receiver. Flying at an altitude of 1334 km, TOPEX/POSEIDON performs precise ocean altimetry, which demands the highest possible accuracy in determining the radial orbit component in post-processing. Radial RMS accuracies of about 2 cm were realized using reduced dynamic tracking techniques. In this approach, orbit errors due to force are substantially reduced by exploiting the geometric strength of GPS to solve for a set of stochastic forces. On EUVE, the emphasis was on evaluating real time positioning techniques with a single frequency receiver. The capability for real time 3D accuracies of 15 m in the presence of Selective Availability was shown. This was validated by comparing to a post-processed differential GPS truth orbit believed accurate to about 1 m.!.

  4. Precision bolometer bridge

    NASA Technical Reports Server (NTRS)

    White, D. R.

    1968-01-01

    Prototype precision bolometer calibration bridge is manually balanced device for indicating dc bias and balance with either dc or ac power. An external galvanometer is used with the bridge for null indication, and the circuitry monitors voltage and current simultaneously without adapters in testing 100 and 200 ohm thin film bolometers.

  5. Precision metal molding

    NASA Technical Reports Server (NTRS)

    Townhill, A.

    1967-01-01

    Method provides precise alignment for metal-forming dies while permitting minimal thermal expansion without die warpage or cavity space restriction. The interfacing dowel bars and die side facings are arranged so the dies are restrained in one orthogonal angle and permitted to thermally expand in the opposite orthogonal angle.

  6. Precision liquid level sensor

    DOEpatents

    Field, M.E.; Sullivan, W.H.

    1985-01-29

    A precision liquid level sensor utilizes a balanced R. F. bridge, each arm including an air dielectric line. Changes in liquid level along one air dielectric line imbalance the bridge and create a voltage which is directly measurable across the bridge. 2 figs.

  7. Precision liquid level sensor

    DOEpatents

    Field, Michael E.; Sullivan, William H.

    1985-01-01

    A precision liquid level sensor utilizes a balanced R. F. bridge, each arm including an air dielectric line. Changes in liquid level along one air dielectric line imbalance the bridge and create a voltage which is directly measurable across the bridge.

  8. Precision in Stereochemical Terminology

    ERIC Educational Resources Information Center

    Wade, Leroy G., Jr.

    2006-01-01

    An analysis of relatively new terminology that has given multiple definitions often resulting in students learning principles that are actually false is presented with an example of the new term stereogenic atom introduced by Mislow and Siegel. The Mislow terminology would be useful in some cases if it were used precisely and correctly, but it is…

  9. Precision physics at LHC

    SciTech Connect

    Hinchliffe, I.

    1997-05-01

    In this talk the author gives a brief survey of some physics topics that will be addressed by the Large Hadron Collider currently under construction at CERN. Instead of discussing the reach of this machine for new physics, the author gives examples of the types of precision measurements that might be made if new physics is discovered.

  10. Parameter recovery and model selection in mixed Rasch models.

    PubMed

    Preinerstorfer, David; Formann, Anton K

    2012-05-01

    This study examines the precision of conditional maximum likelihood estimates and the quality of model selection methods based on information criteria (AIC and BIC) in mixed Rasch models. The design of the Monte Carlo simulation study included four test lengths (10, 15, 25, 40), three sample sizes (500, 1000, 2500), two simulated mixture conditions (one and two groups), and population homogeneity (equally sized subgroups) or heterogeneity (one subgroup three times larger than the other). The results show that both increasing sample size and increasing number of items lead to higher accuracy; medium-range parameters were estimated more precisely than extreme ones; and the accuracy was higher in homogeneous populations. The minimum-BIC method leads to almost perfect results and is more reliable than AIC-based model selection. The results are compared to findings by Li, Cohen, Kim, and Cho (2009) and practical guidelines are provided. PMID:21675964

  11. High-precision positioning of radar scatterers

    NASA Astrophysics Data System (ADS)

    Dheenathayalan, Prabu; Small, David; Schubert, Adrian; Hanssen, Ramon F.

    2016-05-01

    Remote sensing radar satellites cover wide areas and provide spatially dense measurements, with millions of scatterers. Knowledge of the precise position of each radar scatterer is essential to identify the corresponding object and interpret the estimated deformation. The absolute position accuracy of synthetic aperture radar (SAR) scatterers in a 2D radar coordinate system, after compensating for atmosphere and tidal effects, is in the order of centimeters for TerraSAR-X (TSX) spotlight images. However, the absolute positioning in 3D and its quality description are not well known. Here, we exploit time-series interferometric SAR to enhance the positioning capability in three dimensions. The 3D positioning precision is parameterized by a variance-covariance matrix and visualized as an error ellipsoid centered at the estimated position. The intersection of the error ellipsoid with objects in the field is exploited to link radar scatterers to real-world objects. We demonstrate the estimation of scatterer position and its quality using 20 months of TSX stripmap acquisitions over Delft, the Netherlands. Using trihedral corner reflectors (CR) for validation, the accuracy of absolute positioning in 2D is about 7 cm. In 3D, an absolute accuracy of up to ˜ 66 cm is realized, with a cigar-shaped error ellipsoid having centimeter precision in azimuth and range dimensions, and elongated in cross-range dimension with a precision in the order of meters (the ratio of the ellipsoid axis lengths is 1/3/213, respectively). The CR absolute 3D position, along with the associated error ellipsoid, is found to be accurate and agree with the ground truth position at a 99 % confidence level. For other non-CR coherent scatterers, the error ellipsoid concept is validated using 3D building models. In both cases, the error ellipsoid not only serves as a quality descriptor, but can also help to associate radar scatterers to real-world objects.

  12. High accuracy OMEGA timekeeping

    NASA Technical Reports Server (NTRS)

    Imbier, E. A.

    1982-01-01

    The Smithsonian Astrophysical Observatory (SAO) operates a worldwide satellite tracking network which uses a combination of OMEGA as a frequency reference, dual timing channels, and portable clock comparisons to maintain accurate epoch time. Propagational charts from the U.S. Coast Guard OMEGA monitor program minimize diurnal and seasonal effects. Daily phase value publications of the U.S. Naval Observatory provide corrections to the field collected timing data to produce an averaged time line comprised of straight line segments called a time history file (station clock minus UTC). Depending upon clock location, reduced time data accuracies of between two and eight microseconds are typical.

  13. Improving the accuracy of phase-shifting techniques

    NASA Astrophysics Data System (ADS)

    Cruz-Santos, William; López-García, Lourdes; Redondo-Galvan, Arturo

    2015-05-01

    The traditional phase-shifting profilometry technique is based on the projection of digital interference patterns and computation of the absolute phase map. Recently, a method was proposed that used phase interpolation to the corner detection, at subpixel accuracy in the projector image for improving the camera-projector calibration. We propose a general strategy to improve the accuracy in the search for correspondence that can be used to obtain high precision three-dimensional reconstruction. Experimental results show that our strategy can outperform the precision of the phase-shifting method.

  14. Principles and techniques for designing precision machines

    SciTech Connect

    Hale, L C

    1999-02-01

    This thesis is written to advance the reader's knowledge of precision-engineering principles and their application to designing machines that achieve both sufficient precision and minimum cost. It provides the concepts and tools necessary for the engineer to create new precision machine designs. Four case studies demonstrate the principles and showcase approaches and solutions to specific problems that generally have wider applications. These come from projects at the Lawrence Livermore National Laboratory in which the author participated: the Large Optics Diamond Turning Machine, Accuracy Enhancement of High- Productivity Machine Tools, the National Ignition Facility, and Extreme Ultraviolet Lithography. Although broad in scope, the topics go into sufficient depth to be useful to practicing precision engineers and often fulfill more academic ambitions. The thesis begins with a chapter that presents significant principles and fundamental knowledge from the Precision Engineering literature. Following this is a chapter that presents engineering design techniques that are general and not specific to precision machines. All subsequent chapters cover specific aspects of precision machine design. The first of these is Structural Design, guidelines and analysis techniques for achieving independently stiff machine structures. The next chapter addresses dynamic stiffness by presenting several techniques for Deterministic Damping, damping designs that can be analyzed and optimized with predictive results. Several chapters present a main thrust of the thesis, Exact-Constraint Design. A main contribution is a generalized modeling approach developed through the course of creating several unique designs. The final chapter is the primary case study of the thesis, the Conceptual Design of a Horizontal Machining Center.

  15. Using Genetic Distance to Infer the Accuracy of Genomic Prediction.

    PubMed

    Scutari, Marco; Mackay, Ian; Balding, David

    2016-09-01

    The prediction of phenotypic traits using high-density genomic data has many applications such as the selection of plants and animals of commercial interest; and it is expected to play an increasing role in medical diagnostics. Statistical models used for this task are usually tested using cross-validation, which implicitly assumes that new individuals (whose phenotypes we would like to predict) originate from the same population the genomic prediction model is trained on. In this paper we propose an approach based on clustering and resampling to investigate the effect of increasing genetic distance between training and target populations when predicting quantitative traits. This is important for plant and animal genetics, where genomic selection programs rely on the precision of predictions in future rounds of breeding. Therefore, estimating how quickly predictive accuracy decays is important in deciding which training population to use and how often the model has to be recalibrated. We find that the correlation between true and predicted values decays approximately linearly with respect to either FST or mean kinship between the training and the target populations. We illustrate this relationship using simulations and a collection of data sets from mice, wheat and human genetics. PMID:27589268

  16. High precision damage-resistant multiple-pass ultraviolet reflectometer

    SciTech Connect

    Jolin, L.J.; Foltyn, S.R.

    1984-01-01

    A multiple-pass cell was reported by John White in 1942. Since them, it has been adapted for use as a high-precision reflectometer. The multiple-pass reflectometer has been studied and reported by Arnon and Baumeister. Here, a reflectometer which is similar is described. It utilizes a uv laser operating at lambda = 351 nm as the source and the White-cell mirrors are high-reflection dielectric coatings designed for that wavelength. Because of the low-loss reflectors used in the cell, a high number of traversals, reflections, can be achieved; R greater than or equal to 239. The use of dielectric mirrors also improves the damage resistance of the apparatus which is important when a uv laser beam is used. The results of reflectance measurements performed on several ultraviolet high reflectors are also reported. These include conventional dielectric coatings as well as a hybrid coating consisting of Al/sub 2/O/sub 3/, HfO/sub 2/, and SiO/sub 2/ layers. The Los Alamos optical damage laboratory has observed and defined several types of laser-induced damage to optical materials. In the case of high reflection, multi-layer, dielectric coatings, damage may be defined as any change in the coating layers or at the substrate interface which causes a measurable change in reflectance at its design wavelength. Since most dielectric high reflectors have reflectances approaching unity, and a change caused by laser irradiation can be minute, a precise method for measuring high reflectance must be utilized. A multiple-pass reflectometer based on the White cell was selected because of its demonstratd precision and high accuracy. It utilizes a laser as the source for reasons described later.

  17. Response characteristics of selected personnel neutron dosimeters

    SciTech Connect

    McDonald, J.C.; Fix, J.J.; Hadley, R.T.; Holbrook, K.L.; Yoder, R.C.; Roberson, P.L.; Endres, G.W.R.; Nichols, L.L.; Schwartz, R.B.

    1983-09-01

    Performance characteristics of selected personnel neutron dosimeters in current use at Department of Energy (DOE) facilities were determined from their evaluation of neutron dose equivalent received after irradiations with specific neutron sources at either the National Bureau of Standards (NBS) or the Pacific Northwest Laboratory (PNL). The characteristics assessed included: lower detection level, energy response, precision and accuracy. It was found that when all of the laboratories employed a common set of calibrations, the overall accuracy was approximately +-20%, which is within uncertainty expected for these dosimeters. For doses above 80 mrem, the accuracy improved to better than 10% when a common calibration was used. Individual differences found in this study may reflect differences in calibration technique rather than differences in the dose rates of actual calibration standards. Second, at dose rates above 100 mrem, the precision for the best participants was generally below +-10% which is also within expected limits for these types of dosimeters. The poorest results had a standard deviation of about +-25%. At the lowest doses, which were sometimes below the lower detection limit, the precision often approached or exceeded +-100%. Third, the lower level of detection for free field /sup 252/Cf neutrons generally ranged between 20 and 50 mrem. Fourth, the energy dependence study provided a characterization of the response of the dosimeters to neutron energies far from the calibration energy. 11 references, 22 figures, 26 tables.

  18. A passion for precision

    SciTech Connect

    2010-05-19

    For more than three decades, the quest for ever higher precision in laser spectroscopy of the simple hydrogen atom has inspired many advances in laser, optical, and spectroscopic techniques, culminating in femtosecond laser optical frequency combs  as perhaps the most precise measuring tools known to man. Applications range from optical atomic clocks and tests of QED and relativity to searches for time variations of fundamental constants. Recent experiments are extending frequency comb techniques into the extreme ultraviolet. Laser frequency combs can also control the electric field of ultrashort light pulses, creating powerful new tools for the emerging field of attosecond science.Organiser(s): L. Alvarez-Gaume / PH-THNote: * Tea & coffee will be served at 16:00.

  19. Towards precision medicine.

    PubMed

    Ashley, Euan A

    2016-08-16

    There is great potential for genome sequencing to enhance patient care through improved diagnostic sensitivity and more precise therapeutic targeting. To maximize this potential, genomics strategies that have been developed for genetic discovery - including DNA-sequencing technologies and analysis algorithms - need to be adapted to fit clinical needs. This will require the optimization of alignment algorithms, attention to quality-coverage metrics, tailored solutions for paralogous or low-complexity areas of the genome, and the adoption of consensus standards for variant calling and interpretation. Global sharing of this more accurate genotypic and phenotypic data will accelerate the determination of causality for novel genes or variants. Thus, a deeper understanding of disease will be realized that will allow its targeting with much greater therapeutic precision. PMID:27528417

  20. Precision Polarization of Neutrons

    NASA Astrophysics Data System (ADS)

    Martin, Elise; Barron-Palos, Libertad; Couture, Aaron; Crawford, Christopher; Chupp, Tim; Danagoulian, Areg; Estes, Mary; Hona, Binita; Jones, Gordon; Klein, Andi; Penttila, Seppo; Sharma, Monisha; Wilburn, Scott

    2009-05-01

    Determining polarization of a cold neutron beam to high precision is required for the next generation neutron decay correlation experiments at the SNS, such as the proposed abBA and PANDA experiments. Precision polarimetry measurements were conducted at Los Alamos National Laboratory with the goal of determining the beam polarization to the level of 10-3 or better. The cold neutrons from FP12 were polarized using optically polarized ^3He gas as a spin filter, which has a highly spin-dependent absorption cross section. A second ^ 3He spin filter was used to analyze the neutron polarization after passing through a resonant RF spin rotator. A discussion of the experiment and results will be given.

  1. A passion for precision

    ScienceCinema

    None

    2011-10-06

    For more than three decades, the quest for ever higher precision in laser spectroscopy of the simple hydrogen atom has inspired many advances in laser, optical, and spectroscopic techniques, culminating in femtosecond laser optical frequency combs  as perhaps the most precise measuring tools known to man. Applications range from optical atomic clocks and tests of QED and relativity to searches for time variations of fundamental constants. Recent experiments are extending frequency comb techniques into the extreme ultraviolet. Laser frequency combs can also control the electric field of ultrashort light pulses, creating powerful new tools for the emerging field of attosecond science.Organiser(s): L. Alvarez-Gaume / PH-THNote: * Tea & coffee will be served at 16:00.

  2. Precision disablement aiming system

    DOEpatents

    Monda, Mark J.; Hobart, Clinton G.; Gladwell, Thomas Scott

    2016-02-16

    A disrupter to a target may be precisely aimed by positioning a radiation source to direct radiation towards the target, and a detector is positioned to detect radiation that passes through the target. An aiming device is positioned between the radiation source and the target, wherein a mechanical feature of the aiming device is superimposed on the target in a captured radiographic image. The location of the aiming device in the radiographic image is used to aim a disrupter towards the target.

  3. Precise linear sun sensor

    NASA Technical Reports Server (NTRS)

    Johnston, D. D.

    1972-01-01

    An evaluation of the precise linear sun sensor relating to future mission applications was performed. The test procedures, data, and results of the dual-axis, solid-state system are included. Brief descriptions of the sensing head and of the system's operational characteristics are presented. A unique feature of the system is that multiple sensor heads with various fields of view may be used with the same electronics.

  4. Precision laser aiming system

    SciTech Connect

    Ahrens, Brandon R.; Todd, Steven N.

    2009-04-28

    A precision laser aiming system comprises a disrupter tool, a reflector, and a laser fixture. The disrupter tool, the reflector and the laser fixture are configurable for iterative alignment and aiming toward an explosive device threat. The invention enables a disrupter to be quickly and accurately set up, aligned, and aimed in order to render safe or to disrupt a target from a standoff position.

  5. Accuracy in Judgments of Aggressiveness

    PubMed Central

    Kenny, David A.; West, Tessa V.; Cillessen, Antonius H. N.; Coie, John D.; Dodge, Kenneth A.; Hubbard, Julie A.; Schwartz, David

    2009-01-01

    Perceivers are both accurate and biased in their understanding of others. Past research has distinguished between three types of accuracy: generalized accuracy, a perceiver’s accuracy about how a target interacts with others in general; perceiver accuracy, a perceiver’s view of others corresponding with how the perceiver is treated by others in general; and dyadic accuracy, a perceiver’s accuracy about a target when interacting with that target. Researchers have proposed that there should be more dyadic than other forms of accuracy among well-acquainted individuals because of the pragmatic utility of forecasting the behavior of interaction partners. We examined behavioral aggression among well-acquainted peers. A total of 116 9-year-old boys rated how aggressive their classmates were toward other classmates. Subsequently, 11 groups of 6 boys each interacted in play groups, during which observations of aggression were made. Analyses indicated strong generalized accuracy yet little dyadic and perceiver accuracy. PMID:17575243

  6. Precise Point Positioning in the Airborne Mode

    NASA Astrophysics Data System (ADS)

    El-Mowafy, Ahmed

    2011-01-01

    The Global Positioning System (GPS) is widely used for positioning in the airborne mode such as in navigation as a supplementary system and for geo-referencing of cameras in mapping and surveillance by aircrafts and Unmanned Aerial Vehicles (UAV). The Precise Point Positioning (PPP) approach is an attractive positioning approach based on processing of un-differenced observations from a single GPS receiver. It employs precise satellite orbits and satellite clock corrections. These data can be obtained via the internet from several sources, e.g. the International GNSS Service (IGS). The data can also broadcast from satellites, such as via the LEX signal of the new Japanese satellite system QZSS. The PPP can achieve positioning precision and accuracy at the sub-decimetre level. In this paper, the functional and stochastic mathematical modelling used in PPP is discussed. Results of applying the PPP method in an airborne test using a small fixed-wing aircraft are presented. To evaluate the performance of the PPP approach, a reference trajectory was established by differential positioning of the same GPS observations with data from a ground reference station. The coordinate results from the two approaches, PPP and differential positioning, were compared and statistically evaluated. For the test at hand, positioning accuracy at the cm-to-decimetre was achieved for latitude and longitude coordinates and doubles that value for height estimation.

  7. Highly Parallel, High-Precision Numerical Integration

    SciTech Connect

    Bailey, David H.; Borwein, Jonathan M.

    2005-04-22

    This paper describes a scheme for rapidly computing numerical values of definite integrals to very high accuracy, ranging from ordinary machine precision to hundreds or thousands of digits, even for functions with singularities or infinite derivatives at endpoints. Such a scheme is of interest not only in computational physics and computational chemistry, but also in experimental mathematics, where high-precision numerical values of definite integrals can be used to numerically discover new identities. This paper discusses techniques for a parallel implementation of this scheme, then presents performance results for 1-D and 2-D test suites. Results are also given for a certain problem from mathematical physics, which features a difficult singularity, confirming a conjecture to 20,000 digit accuracy. The performance rate for this latter calculation on 1024 CPUs is 690 Gflop/s. We believe that this and one other 20,000-digit integral evaluation that we report are the highest-precision non-trivial numerical integrations performed to date.

  8. Accuracy of Digital vs. Conventional Implant Impressions

    PubMed Central

    Lee, Sang J.; Betensky, Rebecca A.; Gianneschi, Grace E.; Gallucci, German O.

    2015-01-01

    The accuracy of digital impressions greatly influences the clinical viability in implant restorations. The aim of this study is to compare the accuracy of gypsum models acquired from the conventional implant impression to digitally milled models created from direct digitalization by three-dimensional analysis. Thirty gypsum and 30 digitally milled models impressed directly from a reference model were prepared. The models were scanned by a laboratory scanner and 30 STL datasets from each group were imported to an inspection software. The datasets were aligned to the reference dataset by a repeated best fit algorithm and 10 specified contact locations of interest were measured in mean volumetric deviations. The areas were pooled by cusps, fossae, interproximal contacts, horizontal and vertical axes of implant position and angulation. The pooled areas were statistically analysed by comparing each group to the reference model to investigate the mean volumetric deviations accounting for accuracy and standard deviations for precision. Milled models from digital impressions had comparable accuracy to gypsum models from conventional impressions. However, differences in fossae and vertical displacement of the implant position from the gypsum and digitally milled models compared to the reference model, exhibited statistical significance (p<0.001, p=0.020 respectively). PMID:24720423

  9. Arizona Vegetation Resource Inventory (AVRI) accuracy assessment

    USGS Publications Warehouse

    Szajgin, John; Pettinger, L.R.; Linden, D.S.; Ohlen, D.O.

    1982-01-01

    A quantitative accuracy assessment was performed for the vegetation classification map produced as part of the Arizona Vegetation Resource Inventory (AVRI) project. This project was a cooperative effort between the Bureau of Land Management (BLM) and the Earth Resources Observation Systems (EROS) Data Center. The objective of the accuracy assessment was to estimate (with a precision of ?10 percent at the 90 percent confidence level) the comission error in each of the eight level II hierarchical vegetation cover types. A stratified two-phase (double) cluster sample was used. Phase I consisted of 160 photointerpreted plots representing clusters of Landsat pixels, and phase II consisted of ground data collection at 80 of the phase I cluster sites. Ground data were used to refine the phase I error estimates by means of a linear regression model. The classified image was stratified by assigning each 15-pixel cluster to the stratum corresponding to the dominant cover type within each cluster. This method is known as stratified plurality sampling. Overall error was estimated to be 36 percent with a standard error of 2 percent. Estimated error for individual vegetation classes ranged from a low of 10 percent ?6 percent for evergreen woodland to 81 percent ?7 percent for cropland and pasture. Total cost of the accuracy assessment was $106,950 for the one-million-hectare study area. The combination of the stratified plurality sampling (SPS) method of sample allocation with double sampling provided the desired estimates within the required precision levels. The overall accuracy results confirmed that highly accurate digital classification of vegetation is difficult to perform in semiarid environments, due largely to the sparse vegetation cover. Nevertheless, these techniques show promise for providing more accurate information than is presently available for many BLM-administered lands.

  10. Researches on High Accuracy Prediction Methods of Earth Orientation Parameters

    NASA Astrophysics Data System (ADS)

    Xu, X. Q.

    2015-09-01

    The Earth rotation reflects the coupling process among the solid Earth, atmosphere, oceans, mantle, and core of the Earth on multiple spatial and temporal scales. The Earth rotation can be described by the Earth's orientation parameters, which are abbreviated as EOP (mainly including two polar motion components PM_X and PM_Y, and variation in the length of day ΔLOD). The EOP is crucial in the transformation between the terrestrial and celestial reference systems, and has important applications in many areas such as the deep space exploration, satellite precise orbit determination, and astrogeodynamics. However, the EOP products obtained by the space geodetic technologies generally delay by several days to two weeks. The growing demands for modern space navigation make high-accuracy EOP prediction be a worthy topic. This thesis is composed of the following three aspects, for the purpose of improving the EOP forecast accuracy. (1) We analyze the relation between the length of the basic data series and the EOP forecast accuracy, and compare the EOP prediction accuracy for the linear autoregressive (AR) model and the nonlinear artificial neural network (ANN) method by performing the least squares (LS) extrapolations. The results show that the high precision forecast of EOP can be realized by appropriate selection of the basic data series length according to the required time span of EOP prediction: for short-term prediction, the basic data series should be shorter, while for the long-term prediction, the series should be longer. The analysis also showed that the LS+AR model is more suitable for the short-term forecasts, while the LS+ANN model shows the advantages in the medium- and long-term forecasts. (2) We develop for the first time a new method which combines the autoregressive model and Kalman filter (AR+Kalman) in short-term EOP prediction. The equations of observation and state are established using the EOP series and the autoregressive coefficients

  11. Accuracy of tablet splitting.

    PubMed

    McDevitt, J T; Gurst, A H; Chen, Y

    1998-01-01

    We attempted to determine the accuracy of manually splitting hydrochlorothiazide tablets. Ninety-four healthy volunteers each split ten 25-mg hydrochlorothiazide tablets, which were then weighed using an analytical balance. Demographics, grip and pinch strength, digit circumference, and tablet-splitting experience were documented. Subjects were also surveyed regarding their willingness to pay a premium for commercially available, lower-dose tablets. Of 1752 manually split tablet portions, 41.3% deviated from ideal weight by more than 10% and 12.4% deviated by more than 20%. Gender, age, education, and tablet-splitting experience were not predictive of variability. Most subjects (96.8%) stated a preference for commercially produced, lower-dose tablets, and 77.2% were willing to pay more for them. For drugs with steep dose-response curves or narrow therapeutic windows, the differences we recorded could be clinically relevant. PMID:9469693

  12. Taking the Measure of the Universe : Precision Astrometry with SIM PlanetQuest

    NASA Technical Reports Server (NTRS)

    Unwin, Stephen C.; Shao, Michael; Tanner, Angelle M.; Allen, Ronald J.; Beichman, Charles A.; Boboltz, David; Catanzarite, Joseph H.; Chaboyer, Brian C.; Ciardi, David R.; Edberg, Stephen J.; Fey, Alan L.; Fischer, Debra A.; Gelino, Christopher R.; Gould, Andrew P.; Grillmair, Carl; Henry, Todd J.; Johnston, Kathryn V.; Johnston, Kenneth J.; Jones, Dayton L.; Kulkarni, Shrinivas R.; Law, Nicholas M.; Majewski, Steven R.; Makarov, Valeri V.; Marcy, Geoffrey W.; Meier, David L.

    2008-01-01

    Precision astrometry at microarcsecond accuracy has application to a wide range of astrophysical problems. This paper is a study of the science questions that can be addressed using an instrument with flexible scheduling that delivers parallaxes at about 4 microarcsec (microns)as) on targets as faint as V = 20, and differential accuracy of 0.6 (microns)as on bright targets. The science topics are drawn primarily from the Team Key Projects, selected in 2000, for the Space Interferometry Mission PlanetQuest (SIM PlanetQuest). We use the capabilities of this mission to illustrate the importance of the next level of astrometric precision in modern astrophysics. SIM PlanetQuest is currently in the detailed design phase, having completed in 2005 all of the enabling technologies needed for the flight instrument. It will be the first space-based long baseline Michelson interferometer designed for precision astrometry. SIM will contribute strongly to many astronomical fields including stellar and galactic astrophysics, planetary systems around nearby stars, and the study of quasar and AGN nuclei. Using differential astrometry SIM will search for planets with masses as small as an Earth orbiting in the 'habitable zone' around the nearest stars, and could discover many dozen if Earth-like planets are common. It will characterize the multiple-planet systems that are now known to exist, and it will be able to search for terrestrial planets around all of the candidate target stars in the Terrestrial Planet Finder and Darwin mission lists. It will be capable of detecting planets around young stars, thereby providing insights into how planetary systems are born and how they evolve with time. Precision astrometry allows the measurement of accurate dynamical masses for stars in binary systems. SIM will observe significant numbers of very high- and low-mass stars, providing stellar masses to 1%, the accuracy needed to challenge physical models. Using precision proper motion

  13. Galvanometer deflection: a precision high-speed system.

    PubMed

    Jablonowski, D P; Raamot, J

    1976-06-01

    An X-Y galvanometer deflection system capable of high precision in a random access mode of operation is described. Beam positional information in digitized form is obtained by employing a Ronchi grating with a sophisticated optical detection scheme. This information is used in a control interface to locate the beam to the required precision. The system is characterized by high accuracy at maximum speed and is designed for operation in a variable environment, with particular attention placed on thermal insensitivity. PMID:20165203

  14. Precision Pointing Control System (PPCS) star tracker test

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Tests performed on the TRW precision star tracker are described. The unit tested was a two-axis gimballed star tracker designed to provide star LOS data to an accuracy of 1 to 2 sec. The tracker features a unique bearing system and utilizes thermal and mechanical symmetry techniques to achieve high precision which can be demonstrated in a one g environment. The test program included a laboratory evaluation of tracker functional operation, sensitivity, repeatibility, and thermal stability.

  15. Weighted Geometric Dilution of Precision Calculations with Matrix Multiplication

    PubMed Central

    Chen, Chien-Sheng

    2015-01-01

    To enhance the performance of location estimation in wireless positioning systems, the geometric dilution of precision (GDOP) is widely used as a criterion for selecting measurement units. Since GDOP represents the geometric effect on the relationship between measurement error and positioning determination error, the smallest GDOP of the measurement unit subset is usually chosen for positioning. The conventional GDOP calculation using matrix inversion method requires many operations. Because more and more measurement units can be chosen nowadays, an efficient calculation should be designed to decrease the complexity. Since the performance of each measurement unit is different, the weighted GDOP (WGDOP), instead of GDOP, is used to select the measurement units to improve the accuracy of location. To calculate WGDOP effectively and efficiently, the closed-form solution for WGDOP calculation is proposed when more than four measurements are available. In this paper, an efficient WGDOP calculation method applying matrix multiplication that is easy for hardware implementation is proposed. In addition, the proposed method can be used when more than exactly four measurements are available. Even when using all-in-view method for positioning, the proposed method still can reduce the computational overhead. The proposed WGDOP methods with less computation are compatible with global positioning system (GPS), wireless sensor networks (WSN) and cellular communication systems. PMID:25569755

  16. Instrument Attitude Precision Control

    NASA Technical Reports Server (NTRS)

    Juang, Jer-Nan

    2004-01-01

    A novel approach is presented in this paper to analyze attitude precision and control for an instrument gimbaled to a spacecraft subject to an internal disturbance caused by a moving component inside the instrument. Nonlinear differential equations of motion for some sample cases are derived and solved analytically to gain insight into the influence of the disturbance on the attitude pointing error. A simple control law is developed to eliminate the instrument pointing error caused by the internal disturbance. Several cases are presented to demonstrate and verify the concept presented in this paper.

  17. Precision Robotic Assembly Machine

    ScienceCinema

    None

    2010-09-01

    The world's largest laser system is the National Ignition Facility (NIF), located at Lawrence Livermore National Laboratory. NIF's 192 laser beams are amplified to extremely high energy, and then focused onto a tiny target about the size of a BB, containing frozen hydrogen gas. The target must be perfectly machined to incredibly demanding specifications. The Laboratory's scientists and engineers have developed a device called the "Precision Robotic Assembly Machine" for this purpose. Its unique design won a prestigious R&D-100 award from R&D Magazine.

  18. Precision mass measurements

    NASA Astrophysics Data System (ADS)

    Gläser, M.; Borys, M.

    2009-12-01

    Mass as a physical quantity and its measurement are described. After some historical remarks, a short summary of the concept of mass in classical and modern physics is given. Principles and methods of mass measurements, for example as energy measurement or as measurement of weight forces and forces caused by acceleration, are discussed. Precision mass measurement by comparing mass standards using balances is described in detail. Measurement of atomic masses related to 12C is briefly reviewed as well as experiments and recent discussions for a future new definition of the kilogram, the SI unit of mass.

  19. Precision Robotic Assembly Machine

    SciTech Connect

    2009-08-14

    The world's largest laser system is the National Ignition Facility (NIF), located at Lawrence Livermore National Laboratory. NIF's 192 laser beams are amplified to extremely high energy, and then focused onto a tiny target about the size of a BB, containing frozen hydrogen gas. The target must be perfectly machined to incredibly demanding specifications. The Laboratory's scientists and engineers have developed a device called the "Precision Robotic Assembly Machine" for this purpose. Its unique design won a prestigious R&D-100 award from R&D Magazine.

  20. Precision electroweak measurements

    SciTech Connect

    Demarteau, M.

    1996-11-01

    Recent electroweak precision measurements fro {ital e}{sup +}{ital e}{sup -} and {ital p{anti p}} colliders are presented. Some emphasis is placed on the recent developments in the heavy flavor sector. The measurements are compared to predictions from the Standard Model of electroweak interactions. All results are found to be consistent with the Standard Model. The indirect constraint on the top quark mass from all measurements is in excellent agreement with the direct {ital m{sub t}} measurements. Using the world`s electroweak data in conjunction with the current measurement of the top quark mass, the constraints on the Higgs` mass are discussed.

  1. Density Variations Observable by Precision Satellite Orbits

    NASA Astrophysics Data System (ADS)

    McLaughlin, C. A.; Lechtenberg, T.; Hiatt, A.

    2008-12-01

    This research uses precision satellite orbits from the Challenging Minisatellite Payload (CHAMP) satellite to produce a new data source for studying density changes that occur on time scales less than a day. Precision orbit derived density is compared to accelerometer derived density. In addition, the precision orbit derived densities are used to examine density variations that have been observed with accelerometer data to see if they are observable. In particular, the research will examine the observability of geomagnetic storm time changes and polar cusp features that have been observed in accelerometer data. Currently highly accurate density data is available from three satellites with accelerometers and much lower accuracy data is available from hundreds of satellites for which two-line element sets are available from the Air Force. This paper explores a new data source that is more accurate and has better temporal resolution than the two-line element sets, and provides better spatial coverage than satellites with accelerometers. This data source will be valuable for studying atmospheric phenomena over short periods, for long term studies of the atmosphere, and for validating and improving complex coupled models that include neutral density. The precision orbit derived densities are very similar to the accelerometer derived densities, but the accelerometer can observe features with shorter temporal variations. This research will quantify the time scales observable by precision orbit derived density. The technique for estimating density is optimal orbit determination. The estimates are optimal in the least squares or minimum variance sense. Precision orbit data from CHAMP is used as measurements in a sequential measurement processing and filtering scheme. The atmospheric density is estimated as a correction to an atmospheric model.

  2. New High Precision Linelist of H_3^+

    NASA Astrophysics Data System (ADS)

    Hodges, James N.; Perry, Adam J.; Markus, Charles; Jenkins, Paul A., II; Kocheril, G. Stephen; McCall, Benjamin J.

    2014-06-01

    As the simplest polyatomic molecule, H_3^+ serves as an ideal benchmark for theoretical predictions of rovibrational energy levels. By strictly ab initio methods, the current accuracy of theoretical predictions is limited to an impressive one hundredth of a wavenumber, which has been accomplished by consideration of relativistic, adiabatic, and non-adiabatic corrections to the Born-Oppenheimer PES. More accurate predictions rely on a treatment of quantum electrodynamic effects, which have improved the accuracies of vibrational transitions in molecular hydrogen to a few MHz. High precision spectroscopy is of the utmost importance for extending the frontiers of ab initio calculations, as improved precision and accuracy enable more rigorous testing of calculations. Additionally, measuring rovibrational transitions of H_3^+ can be used to predict its forbidden rotational spectrum. Though the existing data can be used to determine rotational transition frequencies, the uncertainties are prohibitively large. Acquisition of rovibrational spectra with smaller experimental uncertainty would enable a spectroscopic search for the rotational transitions. The technique Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy, or NICE-OHVMS has been previously used to precisely and accurately measure transitions of H_3^+, CH_5^+, and HCO^+ to sub-MHz uncertainty. A second module for our optical parametric oscillator has extended our instrument's frequency coverage from 3.2-3.9 μm to 2.5-3.9 μm. With extended coverage, we have improved our previous linelist by measuring additional transitions. O. L. Polyansky, et al. Phil. Trans. R. Soc. A (2012), 370, 5014--5027. J. Komasa, et al. J. Chem. Theor. Comp. (2011), 7, 3105--3115. C. M. Lindsay, B. J. McCall, J. Mol. Spectrosc. (2001), 210, 66--83. J. N. Hodges, et al. J. Chem. Phys. (2013), 139, 164201.

  3. High precision kinematic surveying with laser scanners

    NASA Astrophysics Data System (ADS)

    Gräfe, Gunnar

    2007-12-01

    The kinematic survey of roads and railways is becoming a much more common data acquisition method. The development of the Mobile Road Mapping System (MoSES) has reached a level that allows the use of kinematic survey technology for high precision applications. The system is equipped with cameras and laser scanners. For high accuracy requirements, the scanners become the main sensor group because of their geometric precision and reliability. To guarantee reliable survey results, specific calibration procedures have to be applied, which can be divided into the scanner sensor calibration as step 1, and the geometric transformation parameter estimation with respect to the vehicle coordinate system as step 2. Both calibration steps include new methods for sensor behavior modeling and multisensor system integration. To verify laser scanner quality of the MoSES system, the results are regularly checked along different test routes. It can be proved that a standard deviation of 0.004 m for height of the scanner points will be obtained, if the specific calibrations and data processing methods are applied. This level of accuracy opens new possibilities to serve engineering survey applications using kinematic measurement techniques. The key feature of scanner technology is the full digital coverage of the road area. Three application examples illustrate the capabilities. Digital road surface models generated from MoSES data are used, especially for road surface reconstruction tasks along highways. Compared to static surveys, the method offers comparable accuracy at higher speed, lower costs, much higher grid resolution and with greater safety. The system's capability of gaining 360 profiles leads to other complex applications like kinematic tunnel surveys or the precise analysis of bridge clearances.

  4. Precision estimates for tomographic nondestructive assay

    SciTech Connect

    Prettyman, T.H.

    1995-12-31

    One technique being applied to improve the accuracy of assays of waste in large containers is computerized tomography (CT). Research on the application of CT to improve both neutron and gamma-ray assays of waste is being carried out at LANL. For example, tomographic gamma scanning (TGS) is a single-photon emission CT technique that corrects for the attenuation of gamma rays emitted from the sample using attenuation images from transmission CT. By accounting for the distribution of emitting material and correcting for the attenuation of the emitted gamma rays, TGS is able to achieve highly accurate assays of radionuclides in medium-density wastes. It is important to develope methods to estimate the precision of such assays, and this paper explores this problem by examining the precision estimators for TGS.

  5. How precise are reported protein coordinate data?

    PubMed

    Konagurthu, Arun S; Allison, Lloyd; Abramson, David; Stuckey, Peter J; Lesk, Arthur M

    2014-03-01

    Atomic coordinates in the Worldwide Protein Data Bank (wwPDB) are generally reported to greater precision than the experimental structure determinations have actually achieved. By using information theory and data compression to study the compressibility of protein atomic coordinates, it is possible to quantify the amount of randomness in the coordinate data and thereby to determine the realistic precision of the reported coordinates. On average, the value of each C(α) coordinate in a set of selected protein structures solved at a variety of resolutions is good to about 0.1 Å. PMID:24598758

  6. Affecting speed and accuracy in perception.

    PubMed

    Bocanegra, Bruno R

    2014-12-01

    An account of affective modulations in perceptual speed and accuracy (ASAP: Affecting Speed and Accuracy in Perception) is proposed and tested. This account assumes an emotion-induced inhibitory interaction between parallel channels in the visual system that modulates the onset latencies and response durations of visual signals. By trading off speed and accuracy between channels, this mechanism achieves (a) fast visuo-motor responding to course-grained information, and (b) accurate visuo-attentional selection of fine-grained information. ASAP gives a functional account of previously counterintuitive findings, and may be useful for explaining affective influences in both featural-level single-stimulus tasks and object-level multistimulus tasks. PMID:24853268

  7. Precision measurements in supersymmetry

    SciTech Connect

    Feng, J.L.

    1995-05-01

    Supersymmetry is a promising framework in which to explore extensions of the standard model. If candidates for supersymmetric particles are found, precision measurements of their properties will then be of paramount importance. The prospects for such measurements and their implications are the subject of this thesis. If charginos are produced at the LEP II collider, they are likely to be one of the few available supersymmetric signals for many years. The author considers the possibility of determining fundamental supersymmetry parameters in such a scenario. The study is complicated by the dependence of observables on a large number of these parameters. He proposes a straightforward procedure for disentangling these dependences and demonstrate its effectiveness by presenting a number of case studies at representative points in parameter space. In addition to determining the properties of supersymmetric particles, precision measurements may also be used to establish that newly-discovered particles are, in fact, supersymmetric. Supersymmetry predicts quantitative relations among the couplings and masses of superparticles. The author discusses tests of such relations at a future e{sup +}e{sup {minus}} linear collider, using measurements that exploit the availability of polarizable beams. Stringent tests of supersymmetry from chargino production are demonstrated in two representative cases, and fermion and neutralino processes are also discussed.

  8. Precision flyer initiator

    DOEpatents

    Frank, Alan M.; Lee, Ronald S.

    1998-01-01

    A precision flyer initiator forms a substantially spherical detonation wave in a high explosive (HE) pellet. An explosive driver, such as a detonating cord, a wire bridge circuit or a small explosive, is detonated. A flyer material is sandwiched between the explosive driver and an end of a barrel that contains an inner channel. A projectile or "flyer" is sheared from the flyer material by the force of the explosive driver and projected through the inner channel. The flyer than strikes the HE pellet, which is supported above a second end of the barrel by a spacer ring. A gap or shock decoupling material delays the shock wave in the barrel from predetonating the HE pellet before the flyer. A spherical detonation wave is formed in the HE pellet. Thus, a shock wave traveling through the barrel fails to reach the HE pellet before the flyer strikes the HE pellet. The precision flyer initiator can be used in mining devices, well-drilling devices and anti-tank devices.

  9. Precision muon physics

    NASA Astrophysics Data System (ADS)

    Gorringe, T. P.; Hertzog, D. W.

    2015-09-01

    The muon is playing a unique role in sub-atomic physics. Studies of muon decay both determine the overall strength and establish the chiral structure of weak interactions, as well as setting extraordinary limits on charged-lepton-flavor-violating processes. Measurements of the muon's anomalous magnetic moment offer singular sensitivity to the completeness of the standard model and the predictions of many speculative theories. Spectroscopy of muonium and muonic atoms gives unmatched determinations of fundamental quantities including the magnetic moment ratio μμ /μp, lepton mass ratio mμ /me, and proton charge radius rp. Also, muon capture experiments are exploring elusive features of weak interactions involving nucleons and nuclei. We will review the experimental landscape of contemporary high-precision and high-sensitivity experiments with muons. One focus is the novel methods and ingenious techniques that achieve such precision and sensitivity in recent, present, and planned experiments. Another focus is the uncommonly broad and topical range of questions in atomic, nuclear and particle physics that such experiments explore.

  10. Precision Joining Center

    SciTech Connect

    Powell, J.W.; Westphal, D.A.

    1991-08-01

    A workshop to obtain input from industry on the establishment of the Precision Joining Center (PJC) was held on July 10--12, 1991. The PJC is a center for training Joining Technologists in advanced joining techniques and concepts in order to promote the competitiveness of US industry. The center will be established as part of the DOE Defense Programs Technology Commercialization Initiative, and operated by EG G Rocky Flats in cooperation with the American Welding Society and the Colorado School of Mines Center for Welding and Joining Research. The overall objectives of the workshop were to validate the need for a Joining Technologists to fill the gap between the welding operator and the welding engineer, and to assure that the PJC will train individuals to satisfy that need. The consensus of the workshop participants was that the Joining Technologist is a necessary position in industry, and is currently used, with some variation, by many companies. It was agreed that the PJC core curriculum, as presented, would produce a Joining Technologist of value to industries that use precision joining techniques. The advantage of the PJC would be to train the Joining Technologist much more quickly and more completely. The proposed emphasis of the PJC curriculum on equipment intensive and hands-on training was judged to be essential.

  11. Progressive Precision Surface Design

    SciTech Connect

    Duchaineau, M; Joy, KJ

    2002-01-11

    We introduce a novel wavelet decomposition algorithm that makes a number of powerful new surface design operations practical. Wavelets, and hierarchical representations generally, have held promise to facilitate a variety of design tasks in a unified way by approximating results very precisely, thus avoiding a proliferation of undergirding mathematical representations. However, traditional wavelet decomposition is defined from fine to coarse resolution, thus limiting its efficiency for highly precise surface manipulation when attempting to create new non-local editing methods. Our key contribution is the progressive wavelet decomposition algorithm, a general-purpose coarse-to-fine method for hierarchical fitting, based in this paper on an underlying multiresolution representation called dyadic splines. The algorithm requests input via a generic interval query mechanism, allowing a wide variety of non-local operations to be quickly implemented. The algorithm performs work proportionate to the tiny compressed output size, rather than to some arbitrarily high resolution that would otherwise be required, thus increasing performance by several orders of magnitude. We describe several design operations that are made tractable because of the progressive decomposition. Free-form pasting is a generalization of the traditional control-mesh edit, but for which the shape of the change is completely general and where the shape can be placed using a free-form deformation within the surface domain. Smoothing and roughening operations are enhanced so that an arbitrary loop in the domain specifies the area of effect. Finally, the sculpting effect of moving a tool shape along a path is simulated.

  12. Precision flyer initiator

    DOEpatents

    Frank, A.M.; Lee, R.S.

    1998-05-26

    A precision flyer initiator forms a substantially spherical detonation wave in a high explosive (HE) pellet. An explosive driver, such as a detonating cord, a wire bridge circuit or a small explosive, is detonated. A flyer material is sandwiched between the explosive driver and an end of a barrel that contains an inner channel. A projectile or ``flyer`` is sheared from the flyer material by the force of the explosive driver and projected through the inner channel. The flyer than strikes the HE pellet, which is supported above a second end of the barrel by a spacer ring. A gap or shock decoupling material delays the shock wave in the barrel from predetonating the HE pellet before the flyer. A spherical detonation wave is formed in the HE pellet. Thus, a shock wave traveling through the barrel fails to reach the HE pellet before the flyer strikes the HE pellet. The precision flyer initiator can be used in mining devices, well-drilling devices and anti-tank devices. 10 figs.

  13. Precise autofocusing microscope with rapid response

    NASA Astrophysics Data System (ADS)

    Liu, Chien-Sheng; Jiang, Sheng-Hong

    2015-03-01

    The rapid on-line or off-line automated vision inspection is a critical operation in the manufacturing fields. Accordingly, this present study designs and characterizes a novel precise optics-based autofocusing microscope with a rapid response and no reduction in the focusing accuracy. In contrast to conventional optics-based autofocusing microscopes with centroid method, the proposed microscope comprises a high-speed rotating optical diffuser in which the variation of the image centroid position is reduced and consequently the focusing response is improved. The proposed microscope is characterized and verified experimentally using a laboratory-built prototype. The experimental results show that compared to conventional optics-based autofocusing microscopes, the proposed microscope achieves a more rapid response with no reduction in the focusing accuracy. Consequently, the proposed microscope represents another solution for both existing and emerging industrial applications of automated vision inspection.

  14. Reticence, Accuracy and Efficacy

    NASA Astrophysics Data System (ADS)

    Oreskes, N.; Lewandowsky, S.

    2015-12-01

    James Hansen has cautioned the scientific community against "reticence," by which he means a reluctance to speak in public about the threat of climate change. This may contribute to social inaction, with the result that society fails to respond appropriately to threats that are well understood scientifically. Against this, others have warned against the dangers of "crying wolf," suggesting that reticence protects scientific credibility. We argue that both these positions are missing an important point: that reticence is not only a matter of style but also of substance. In previous work, Bysse et al. (2013) showed that scientific projections of key indicators of climate change have been skewed towards the low end of actual events, suggesting a bias in scientific work. More recently, we have shown that scientific efforts to be responsive to contrarian challenges have led scientists to adopt the terminology of a "pause" or "hiatus" in climate warming, despite the lack of evidence to support such a conclusion (Lewandowsky et al., 2015a. 2015b). In the former case, scientific conservatism has led to under-estimation of climate related changes. In the latter case, the use of misleading terminology has perpetuated scientific misunderstanding and hindered effective communication. Scientific communication should embody two equally important goals: 1) accuracy in communicating scientific information and 2) efficacy in expressing what that information means. Scientists should strive to be neither conservative nor adventurous but to be accurate, and to communicate that accurate information effectively.

  15. Visual inspection reliability for precision manufactured parts

    DOE PAGESBeta

    See, Judi E.

    2015-09-04

    Sandia National Laboratories conducted an experiment for the National Nuclear Security Administration to determine the reliability of visual inspection of precision manufactured parts used in nuclear weapons. In addition visual inspection has been extensively researched since the early 20th century; however, the reliability of visual inspection for nuclear weapons parts has not been addressed. In addition, the efficacy of using inspector confidence ratings to guide multiple inspections in an effort to improve overall performance accuracy is unknown. Further, the workload associated with inspection has not been documented, and newer measures of stress have not been applied.

  16. Digital image centering. I. [for precision astrometry

    NASA Technical Reports Server (NTRS)

    Van Altena, W. F.; Auer, L. H.

    1975-01-01

    A series of parallax plates have been measured on a PDS microdensitometer to assess the possibility of using the PDS for precision relative astrometry and to investigate centering algorithms that might be used to analyze digital images obtained with the Large Space Telescope. The basic repeatability of the PDS is found to be plus or minus 0.6 micron, with the potential for reaching plus or minus 0.2 micron. A very efficient centering algorithm has been developed which fits the marginal density distributions of the image with a Gaussian profile and a sloping background. The accuracy is comparable with the best results obtained with a photoelectric image bisector.

  17. Precise and automated microfluidic sample preparation.

    SciTech Connect

    Crocker, Robert W.; Patel, Kamlesh D.; Mosier, Bruce P.; Harnett, Cindy K.

    2004-07-01

    Autonomous bio-chemical agent detectors require sample preparation involving multiplex fluid control. We have developed a portable microfluidic pump array for metering sub-microliter volumes at flowrates of 1-100 {micro}L/min. Each pump is composed of an electrokinetic (EK) pump and high-voltage power supply with 15-Hz feedback from flow sensors. The combination of high pump fluid impedance and active control results in precise fluid metering with nanoliter accuracy. Automated sample preparation will be demonstrated by labeling proteins with fluorescamine and subsequent injection to a capillary gel electrophoresis (CGE) chip.

  18. The GBT precision telescope control system

    NASA Astrophysics Data System (ADS)

    Prestage, Richard M.; Constantikes, Kim T.; Balser, Dana S.; Condon, James J.

    2004-10-01

    The NRAO Robert C. Byrd Green Bank Telescope (GBT) is a 100m diameter advanced single dish radio telescope designed for a wide range of astronomical projects with special emphasis on precision imaging. Open-loop adjustments of the active surface, and real-time corrections to pointing and focus on the basis of structural temperatures already allow observations at frequencies up to 50GHz. Our ultimate goal is to extend the observing frequency limit up to 115GHz; this will require a two dimensional tracking error better than 1.3", and an rms surface accuracy better than 210μm. The Precision Telescope Control System project has two main components. One aspect is the continued deployment of appropriate metrology systems, including temperature sensors, inclinometers, laser rangefinders and other devices. An improved control system architecture will harness this measurement capability with the existing servo systems, to deliver the precision operation required. The second aspect is the execution of a series of experiments to identify, understand and correct the residual pointing and surface accuracy errors. These can have multiple causes, many of which depend on variable environmental conditions. A particularly novel approach is to solve simultaneously for gravitational, thermal and wind effects in the development of the telescope pointing and focus tracking models. Our precision temperature sensor system has already allowed us to compensate for thermal gradients in the antenna, which were previously responsible for the largest "non-repeatable" pointing and focus tracking errors. We are currently targetting the effects of wind as the next, currently uncompensated, source of error.

  19. The Effect of Strength Training on Fractionalized Accuracy.

    ERIC Educational Resources Information Center

    Gronbech, C. Eric

    The role of the strength factor in the accomplishment of precision tasks was investigated. Forty adult males weight trained to develop physical strength in several muscle groups, particularly in the elbow flexor area. Results indicate a decrease in incidence of accuracy concurrent with an increase in muscle strength. This suggests that in order to…

  20. Precise Orbit Determination for Altimeter Satellites

    NASA Astrophysics Data System (ADS)

    Zelensky, N. P.; Luthcke, S. B.; Rowlands, D. D.; Lemoine, F. G.; Beckley, B. B.; Wang, Y.; Chinn, D. S.

    2002-05-01

    Orbit error remains a critical component in the error budget for all radar altimeter missions. This paper describes the ongoing work at GSFC to improve orbits for three radar altimeter satellites: TOPEX/POSEIDON (T/P), Jason, and Geosat Follow-On (GFO). T/P has demonstrated that, the time variation of ocean topography can be determined with an accuracy of a few centimeters, thanks to the availability of highly accurate orbits (2-3 cm radially) produced at GSFC. Jason, the T/P follow-on, is intended to continue measurement of the ocean surface with the same, if not better accuracy. Reaching the Jason centimeter accuracy orbit goal would greatly benefit the knowledge of ocean circulation. Several new POD strategies which promise significant improvement to the current T/P orbit are evaluated over one year of data. Also, preliminary, but very promising Jason POD results are presented. Orbit improvement for GFO has been dramatic, and has allowed this mission to provide a POESEIDON class altimeter product. The GFO Precise Orbit Ephemeris (POE) orbits are based on satellite laser ranging (SLR) tracking supplemented with GFO/GFO altimeter crossover data. The accuracy of these orbits were evaluated using several tests, including independent TOPEX/GFO altimeter crossover data. The orbit improvements are shown over the years 2000 and 2001 for which the POEs have been completed.

  1. Balancing precision and risk: should multiple detection methods be analyzed separately in N-mixture models?

    PubMed

    Graves, Tabitha A; Royle, J Andrew; Kendall, Katherine C; Beier, Paul; Stetz, Jeffrey B; Macleod, Amy C

    2012-01-01

    Using multiple detection methods can increase the number, kind, and distribution of individuals sampled, which may increase accuracy and precision and reduce cost of population abundance estimates. However, when variables influencing abundance are of interest, if individuals detected via different methods are influenced by the landscape differently, separate analysis of multiple detection methods may be more appropriate. We evaluated the effects of combining two detection methods on the identification of variables important to local abundance using detections of grizzly bears with hair traps (systematic) and bear rubs (opportunistic). We used hierarchical abundance models (N-mixture models) with separate model components for each detection method. If both methods sample the same population, the use of either data set alone should (1) lead to the selection of the same variables as important and (2) provide similar estimates of relative local abundance. We hypothesized that the inclusion of 2 detection methods versus either method alone should (3) yield more support for variables identified in single method analyses (i.e. fewer variables and models with greater weight), and (4) improve precision of covariate estimates for variables selected in both separate and combined analyses because sample size is larger. As expected, joint analysis of both methods increased precision as well as certainty in variable and model selection. However, the single-method analyses identified different variables and the resulting predicted abundances had different spatial distributions. We recommend comparing single-method and jointly modeled results to identify the presence of individual heterogeneity between detection methods in N-mixture models, along with consideration of detection probabilities, correlations among variables, and tolerance to risk of failing to identify variables important to a subset of the population. The benefits of increased precision should be weighed against

  2. Balancing precision and risk: should multiple detection methods be analyzed separately in N-mixture models?

    USGS Publications Warehouse

    Graves, Tabitha A.; Royle, J. Andrew; Kendall, Katherine C.; Beier, Paul; Stetz, Jeffrey B.; Macleod, Amy C.

    2012-01-01

    Using multiple detection methods can increase the number, kind, and distribution of individuals sampled, which may increase accuracy and precision and reduce cost of population abundance estimates. However, when variables influencing abundance are of interest, if individuals detected via different methods are influenced by the landscape differently, separate analysis of multiple detection methods may be more appropriate. We evaluated the effects of combining two detection methods on the identification of variables important to local abundance using detections of grizzly bears with hair traps (systematic) and bear rubs (opportunistic). We used hierarchical abundance models (N-mixture models) with separate model components for each detection method. If both methods sample the same population, the use of either data set alone should (1) lead to the selection of the same variables as important and (2) provide similar estimates of relative local abundance. We hypothesized that the inclusion of 2 detection methods versus either method alone should (3) yield more support for variables identified in single method analyses (i.e. fewer variables and models with greater weight), and (4) improve precision of covariate estimates for variables selected in both separate and combined analyses because sample size is larger. As expected, joint analysis of both methods increased precision as well as certainty in variable and model selection. However, the single-method analyses identified different variables and the resulting predicted abundances had different spatial distributions. We recommend comparing single-method and jointly modeled results to identify the presence of individual heterogeneity between detection methods in N-mixture models, along with consideration of detection probabilities, correlations among variables, and tolerance to risk of failing to identify variables important to a subset of the population. The benefits of increased precision should be weighed against

  3. Truss Assembly and Welding by Intelligent Precision Jigging Robots

    NASA Technical Reports Server (NTRS)

    Komendera, Erik; Dorsey, John T.; Doggett, William R.; Correll, Nikolaus

    2014-01-01

    This paper describes an Intelligent Precision Jigging Robot (IPJR) prototype that enables the precise alignment and welding of titanium space telescope optical benches. The IPJR, equipped with micron accuracy sensors and actuators, worked in tandem with a lower precision remote controlled manipulator. The combined system assembled and welded a 2 m truss from stock titanium components. The calibration of the IPJR, and the difference between the predicted and the truss dimensions as-built, identified additional sources of error that should be addressed in the next generation of IPJRs in 2D and 3D.

  4. Operating a real time high accuracy positioning system

    NASA Astrophysics Data System (ADS)

    Johnston, G.; Hanley, J.; Russell, D.; Vooght, A.

    2003-04-01

    The paper shall review the history and development of real time DGPS services prior to then describing the design of a high accuracy GPS commercial augmentation system and service currently delivering over a wide area to users of precise positioning products. The infrastructure and system shall be explained in relation to the need for high accuracy and high integrity of positioning for users. A comparison of the different techniques for the delivery of data shall be provided to outline the technical approach taken. Examples of the performance of the real time system shall be shown in various regions and modes to outline the current achievable accuracies. Having described and established the current GPS based situation, a review of the potential of the Galileo system shall be presented. Following brief contextual information relating to the Galileo project, core system and services, the paper will identify possible key applications and the main user communities for sub decimetre level precise positioning. The paper will address the Galileo and modernised GPS signals in space that are relevant to commercial precise positioning for the future and will discuss the implications for precise positioning performance. An outline of the proposed architecture shall be described and associated with pointers towards a successful implementation. Central to this discussion will be an assessment of the likely evolution of system infrastructure and user equipment implementation, prospects for new applications and their effect upon the business case for precise positioning services.

  5. High accuracy fuel flowmeter

    NASA Technical Reports Server (NTRS)

    1986-01-01

    All three flowmeter concepts (vortex, dual turbine, and angular momentum) were subjected to experimental and analytical investigation to determine the potential portotype performance. The three concepts were subjected to a comprehensive rating. Eight parameters of performance were evaluated on a zero-to-ten scale, weighted, and summed. The relative ratings of the vortex, dual turbine, and angular momentum flowmeters are 0.71, 1.00, and 0.95, respectively. The dual turbine flowmeter concept was selected as the primary candidate and the angular momentum flowmeter as the secondary candidate for prototype development and evaluation.

  6. Precision Joining Center

    NASA Technical Reports Server (NTRS)

    Powell, John W.

    1991-01-01

    The establishment of a Precision Joining Center (PJC) is proposed. The PJC will be a cooperatively operated center with participation from U.S. private industry, the Colorado School of Mines, and various government agencies, including the Department of Energy's Nuclear Weapons Complex (NWC). The PJC's primary mission will be as a training center for advanced joining technologies. This will accomplish the following objectives: (1) it will provide an effective mechanism to transfer joining technology from the NWC to private industry; (2) it will provide a center for testing new joining processes for the NWC and private industry; and (3) it will provide highly trained personnel to support advance joining processes for the NWC and private industry.

  7. High precision Woelter optic calibration facility

    SciTech Connect

    Morales, R.I.; Remington, B.A.; Schwinn, T.

    1994-05-02

    We have developed an off-line facility for very precise characterization of the reflectance and spatial resolution of the grazing incidence Woelter Type 1 x-ray optics used at Nova. The primary component of the facility is a high brightness, ``point`` x-ray source consisting of a focussed DC electron beam incident onto a precision manipulated target/pinhole array. The data are recorded with a selection of detectors. For imaging measurements we use direct exposure x-ray film modules or an x-ray CCD camera. For energy-resolved reflectance measurements, we use lithium drifted silicon detectors and a proportional counter. An in situ laser alignment system allows precise location and rapid periodic alignment verification of the x-ray point source, the statically mounted Woelter optic, and the chosen detector.

  8. High Accuracy Wavelength Calibration For A Scanning Visible Spectrometer

    SciTech Connect

    Filippo Scotti and Ronald Bell

    2010-07-29

    Spectroscopic applications for plasma velocity measurements often require wavelength accuracies ≤ 0.2Â. An automated calibration for a scanning spectrometer has been developed to achieve a high wavelength accuracy overr the visible spectrum, stable over time and environmental conditions, without the need to recalibrate after each grating movement. The method fits all relevant spectrometer paraameters using multiple calibration spectra. With a steping-motor controlled sine-drive, accuracies of ~0.025 Â have been demonstrated. With the addition of high resolution (0.075 aresec) optical encoder on the grading stage, greater precision (~0.005 Â) is possible, allowing absolute velocity measurements with ~0.3 km/s. This level of precision requires monitoring of atmospheric temperature and pressure and of grating bulk temperature to correct for changes in the refractive index of air and the groove density, respectively.

  9. High accuracy wavelength calibration for a scanning visible spectrometer.

    PubMed

    Scotti, Filippo; Bell, Ronald E

    2010-10-01

    Spectroscopic applications for plasma velocity measurements often require wavelength accuracies ≤0.2 Å. An automated calibration, which is stable over time and environmental conditions without the need to recalibrate after each grating movement, was developed for a scanning spectrometer to achieve high wavelength accuracy over the visible spectrum. This method fits all relevant spectrometer parameters using multiple calibration spectra. With a stepping-motor controlled sine drive, an accuracy of ∼0.25 Å has been demonstrated. With the addition of a high resolution (0.075 arc  sec) optical encoder on the grating stage, greater precision (∼0.005 Å) is possible, allowing absolute velocity measurements within ∼0.3 km/s. This level of precision requires monitoring of atmospheric temperature and pressure and of grating bulk temperature to correct for changes in the refractive index of air and the groove density, respectively. PMID:21033925

  10. Precision Neutron Polarimetry

    NASA Astrophysics Data System (ADS)

    Sharma, Monisha; Barron-Palos, L.; Bowman, J. D.; Chupp, T. E.; Crawford, C.; Danagoulian, A.; Klein, A.; Penttila, S. I.; Salas-Bacci, A. F.; Wilburn, W. S.

    2008-04-01

    Proposed PANDA and abBA experiments aim to measure the correlation coefficients in the polarized neutron beta decay at the SNS. The goal of these experiments is 0.1% measurement which will require neutron polarimetry at 0.1% level. The FnPB neutron beam will be polarized either using a ^3He spin filter or a supermirror polarizer and the neutron polarization will be measured using a ^3He spin filter. Experiment to establish the accuracy to which neutron polarization can be determined using ^3He spin fliters was performed at Los Alamos National Laboratory in Summer 2007 and the analysis is in progress. The details of the experiment and the results will be presented.

  11. Manufacturing Precise, Lightweight Paraboloidal Mirrors

    NASA Technical Reports Server (NTRS)

    Hermann, Frederick Thomas

    2006-01-01

    A process for fabricating a precise, diffraction- limited, ultra-lightweight, composite- material (matrix/fiber) paraboloidal telescope mirror has been devised. Unlike the traditional process of fabrication of heavier glass-based mirrors, this process involves a minimum of manual steps and subjective judgment. Instead, this process involves objectively controllable, repeatable steps; hence, this process is better suited for mass production. Other processes that have been investigated for fabrication of precise composite-material lightweight mirrors have resulted in print-through of fiber patterns onto reflecting surfaces, and have not provided adequate structural support for maintenance of stable, diffraction-limited surface figures. In contrast, this process does not result in print-through of the fiber pattern onto the reflecting surface and does provide a lightweight, rigid structure capable of maintaining a diffraction-limited surface figure in the face of changing temperature, humidity, and air pressure. The process consists mainly of the following steps: 1. A precise glass mandrel is fabricated by conventional optical grinding and polishing. 2. The mandrel is coated with a release agent and covered with layers of a carbon- fiber composite material. 3. The outer surface of the outer layer of the carbon-fiber composite material is coated with a surfactant chosen to provide for the proper flow of an epoxy resin to be applied subsequently. 4. The mandrel as thus covered is mounted on a temperature-controlled spin table. 5. The table is heated to a suitable temperature and spun at a suitable speed as the epoxy resin is poured onto the coated carbon-fiber composite material. 6. The surface figure of the optic is monitored and adjusted by use of traditional Ronchi, Focault, and interferometric optical measurement techniques while the speed of rotation and the temperature are adjusted to obtain the desired figure. The proper selection of surfactant, speed or rotation

  12. Precision laser automatic tracking system.

    PubMed

    Lucy, R F; Peters, C J; McGann, E J; Lang, K T

    1966-04-01

    A precision laser tracker has been constructed and tested that is capable of tracking a low-acceleration target to an accuracy of about 25 microrad root mean square. In tracking high-acceleration targets, the error is directly proportional to the angular acceleration. For an angular acceleration of 0.6 rad/sec(2), the measured tracking error was about 0.1 mrad. The basic components in this tracker, similar in configuration to a heliostat, are a laser and an image dissector, which are mounted on a stationary frame, and a servocontrolled tracking mirror. The daytime sensitivity of this system is approximately 3 x 10(-10) W/m(2); the ultimate nighttime sensitivity is approximately 3 x 10(-14) W/m(2). Experimental tests were performed to evaluate both dynamic characteristics of this system and the system sensitivity. Dynamic performance of the system was obtained, using a small rocket covered with retroreflective material launched at an acceleration of about 13 g at a point 204 m from the tracker. The daytime sensitivity of the system was checked, using an efficient retroreflector mounted on a light aircraft. This aircraft was tracked out to a maximum range of 15 km, which checked the daytime sensitivity of the system measured by other means. The system also has been used to track passively stars and the Echo I satellite. Also, the system tracked passively a +7.5 magnitude star, and the signal-to-noise ratio in this experiment indicates that it should be possible to track a + 12.5 magnitude star. PMID:20048888

  13. High precision anatomy for MEG.

    PubMed

    Troebinger, Luzia; López, José David; Lutti, Antoine; Bradbury, David; Bestmann, Sven; Barnes, Gareth

    2014-02-01

    Precise MEG estimates of neuronal current flow are undermined by uncertain knowledge of the head location with respect to the MEG sensors. This is either due to head movements within the scanning session or systematic errors in co-registration to anatomy. Here we show how such errors can be minimized using subject-specific head-casts produced using 3D printing technology. The casts fit the scalp of the subject internally and the inside of the MEG dewar externally, reducing within session and between session head movements. Systematic errors in matching to MRI coordinate system are also reduced through the use of MRI-visible fiducial markers placed on the same cast. Bootstrap estimates of absolute co-registration error were of the order of 1mm. Estimates of relative co-registration error were <1.5mm between sessions. We corroborated these scalp based estimates by looking at the MEG data recorded over a 6month period. We found that the between session sensor variability of the subject's evoked response was of the order of the within session noise, showing no appreciable noise due to between-session movement. Simulations suggest that the between-session sensor level amplitude SNR improved by a factor of 5 over conventional strategies. We show that at this level of coregistration accuracy there is strong evidence for anatomical models based on the individual rather than canonical anatomy; but that this advantage disappears for errors of greater than 5mm. This work paves the way for source reconstruction methods which can exploit very high SNR signals and accurate anatomical models; and also significantly increases the sensitivity of longitudinal studies with MEG. PMID:23911673

  14. High precision anatomy for MEG☆

    PubMed Central

    Troebinger, Luzia; López, José David; Lutti, Antoine; Bradbury, David; Bestmann, Sven; Barnes, Gareth

    2014-01-01

    Precise MEG estimates of neuronal current flow are undermined by uncertain knowledge of the head location with respect to the MEG sensors. This is either due to head movements within the scanning session or systematic errors in co-registration to anatomy. Here we show how such errors can be minimized using subject-specific head-casts produced using 3D printing technology. The casts fit the scalp of the subject internally and the inside of the MEG dewar externally, reducing within session and between session head movements. Systematic errors in matching to MRI coordinate system are also reduced through the use of MRI-visible fiducial markers placed on the same cast. Bootstrap estimates of absolute co-registration error were of the order of 1 mm. Estimates of relative co-registration error were < 1.5 mm between sessions. We corroborated these scalp based estimates by looking at the MEG data recorded over a 6 month period. We found that the between session sensor variability of the subject's evoked response was of the order of the within session noise, showing no appreciable noise due to between-session movement. Simulations suggest that the between-session sensor level amplitude SNR improved by a factor of 5 over conventional strategies. We show that at this level of coregistration accuracy there is strong evidence for anatomical models based on the individual rather than canonical anatomy; but that this advantage disappears for errors of greater than 5 mm. This work paves the way for source reconstruction methods which can exploit very high SNR signals and accurate anatomical models; and also significantly increases the sensitivity of longitudinal studies with MEG. PMID:23911673

  15. Ground Truth Accuracy Tests of GPS Seismology

    NASA Astrophysics Data System (ADS)

    Elosegui, P.; Oberlander, D. J.; Davis, J. L.; Baena, R.; Ekstrom, G.

    2005-12-01

    As the precision of GPS determinations of site position continues to improve the detection of smaller and faster geophysical signals becomes possible. However, lack of independent measurements of these signals often precludes an assessment of the accuracy of such GPS position determinations. This may be particularly true for high-rate GPS applications. We have built an apparatus to assess the accuracy of GPS position determinations for high-rate applications, in particular the application known as "GPS seismology." The apparatus consists of a bidirectional, single-axis positioning table coupled to a digitally controlled stepping motor. The motor, in turn, is connected to a Field Programmable Gate Array (FPGA) chip that synchronously sequences through real historical earthquake profiles stored in Erasable Programmable Read Only Memory's (EPROM). A GPS antenna attached to this positioning table undergoes the simulated seismic motions of the Earth's surface while collecting high-rate GPS data. Analysis of the time-dependent position estimates can then be compared to the "ground truth," and the resultant GPS error spectrum can be measured. We have made extensive measurements with this system while inducing simulated seismic motions either in the horizontal plane or the vertical axis. A second stationary GPS antenna at a distance of several meters was simultaneously collecting high-rate (5 Hz) GPS data. We will present the calibration of this system, describe the GPS observations and data analysis, and assess the accuracy of GPS for high-rate geophysical applications and natural hazards mitigation.

  16. EOS mapping accuracy study

    NASA Technical Reports Server (NTRS)

    Forrest, R. B.; Eppes, T. A.; Ouellette, R. J.

    1973-01-01

    Studies were performed to evaluate various image positioning methods for possible use in the earth observatory satellite (EOS) program and other earth resource imaging satellite programs. The primary goal is the generation of geometrically corrected and registered images, positioned with respect to the earth's surface. The EOS sensors which were considered were the thematic mapper, the return beam vidicon camera, and the high resolution pointable imager. The image positioning methods evaluated consisted of various combinations of satellite data and ground control points. It was concluded that EOS attitude control system design must be considered as a part of the image positioning problem for EOS, along with image sensor design and ground image processing system design. Study results show that, with suitable efficiency for ground control point selection and matching activities during data processing, extensive reliance should be placed on use of ground control points for positioning the images obtained from EOS and similar programs.

  17. METHOD 530 DETERMINATION OF SELECT SEMIVOLATILE ORGANIC CHEMICALS IN DRINKING WATER BY SOLID PHASE EXTRACTION AND GAS CHROMATOGRAPHY/ MASS SPECTROMETRY (GC/MS)

    EPA Science Inventory

    1.1. This is a gas chromatography/mass spectrometry (GC/MS) method for the determination of selected semivolatile organic compounds in drinking waters. Accuracy and precision data have been generated in reagent water, and in finished ground and surface waters for the compounds li...

  18. EVALUATION OF METRIC PRECISION FOR A RIPARIAN FOREST SURVEY

    EPA Science Inventory

    This paper evaluates the performance of a protocol to monitor riparian forests in western Oregon based on the quality of the data obtained from a recent field survey. Precision and accuracy are the criteria used to determine the quality of 19 field metrics. The field survey con...

  19. Precision Astronomy with Imperfect Deep Depletion CCDs

    NASA Astrophysics Data System (ADS)

    Stubbs, Christopher; LSST Sensor Team; PanSTARRS Team

    2014-01-01

    While thick CCDs do provide definite advantages in terms of increased quantum efficiency at wavelengths 700 nm<λ < 1.1 microns and reduced fringing from atmospheric emission lines, these devices also exhibit undesirable features that pose a challenge to precision determination of the positions, fluxes, and shapes of astronomical objects, and for the precision extraction of features in astronomical spectra. For example, the assumptions of a perfectly rectilinear pixel grid and of an intensity-independent point spread function become increasingly invalid as we push to higher precision measurements. Many of the effects seen in these devices arise from lateral electrical fields within the detector, that produce charge transport anomalies that have been previously misinterpreted as quantum efficiency variations. Performing simplistic flat-fielding therefore introduces systematic errors in the image processing pipeline. One measurement challenge we face is devising a combination of calibration methods and algorithms that can distinguish genuine quantum efficiency variations from charge transport effects. These device imperfections also confront spectroscopic applications, such as line centroid determination for precision radial velocity studies. Given the scientific benefits of improving both the precision and accuracy of astronomical measurements, we need to identify, characterize, and overcome these various detector artifacts. In retrospect, many of the detector features first identified in thick CCDs also afflict measurements made with more traditional CCD detectors, albeit often at a reduced level since the photocharge is subject to the perturbing influence of lateral electric fields for a shorter time interval. I provide a qualitative overview of the physical effects we think are responsible for the observed device properties, and provide some perspective for the work that lies ahead.

  20. Soviet precision timekeeping research and technology

    SciTech Connect

    Vessot, R.F.C.; Allan, D.W.; Crampton, S.J.B.; Cutler, L.S.; Kern, R.H.; McCoubrey, A.O.; White, J.D.

    1991-08-01

    This report is the result of a study of Soviet progress in precision timekeeping research and timekeeping capability during the last two decades. The study was conducted by a panel of seven US scientists who have expertise in timekeeping, frequency control, time dissemination, and the direct applications of these disciplines to scientific investigation. The following topics are addressed in this report: generation of time by atomic clocks at the present level of their technology, new and emerging technologies related to atomic clocks, time and frequency transfer technology, statistical processes involving metrological applications of time and frequency, applications of precise time and frequency to scientific investigations, supporting timekeeping technology, and a comparison of Soviet research efforts with those of the United States and the West. The number of Soviet professionals working in this field is roughly 10 times that in the United States. The Soviet Union has facilities for large-scale production of frequency standards and has concentrated its efforts on developing and producing rubidium gas cell devices (relatively compact, low-cost frequency standards of modest accuracy and stability) and atomic hydrogen masers (relatively large, high-cost standards of modest accuracy and high stability). 203 refs., 45 figs., 9 tabs.