Sample records for accurate light-time correction

  1. Real-time intraoperative fluorescence imaging system using light-absorption correction.

    PubMed

    Themelis, George; Yoo, Jung Sun; Soh, Kwang-Sup; Schulz, Ralf; Ntziachristos, Vasilis

    2009-01-01

    We present a novel fluorescence imaging system developed for real-time interventional imaging applications. The system implements a correction scheme that improves the accuracy of epi-illumination fluorescence images for light intensity variation in tissues. The implementation is based on the use of three cameras operating in parallel, utilizing a common lens, which allows for the concurrent collection of color, fluorescence, and light attenuation images at the excitation wavelength from the same field of view. The correction is based on a ratio approach of fluorescence over light attenuation images. Color images and video is used for surgical guidance and for registration with the corrected fluorescence images. We showcase the performance metrics of this system on phantoms and animals, and discuss the advantages over conventional epi-illumination systems developed for real-time applications and the limits of validity of corrected epi-illumination fluorescence imaging.

  2. Forward and correctional OFDM-based visible light positioning

    NASA Astrophysics Data System (ADS)

    Li, Wei; Huang, Zhitong; Zhao, Runmei; He, Peixuan; Ji, Yuefeng

    2017-09-01

    Visible light positioning (VLP) has attracted much attention in both academic and industrial areas due to the extensive deployment of light-emitting diodes (LEDs) as next-generation green lighting. Generally, the coverage of a single LED lamp is limited, so LED arrays are always utilized to achieve uniform illumination within the large-scale indoor environment. However, in such dense LED deployment scenario, the superposition of the light signals becomes an important challenge for accurate VLP. To solve this problem, we propose a forward and correctional orthogonal frequency division multiplexing (OFDM)-based VLP (FCO-VLP) scheme with low complexity in generating and processing of signals. In the first forward procedure of FCO-VLP, an initial position is obtained by the trilateration method based on OFDM-subcarriers. The positioning accuracy will be further improved in the second correctional procedure based on the database of reference points. As demonstrated in our experiments, our approach yields an improved average positioning error of 4.65 cm and an enhanced positioning accuracy by 24.2% compared with trilateration method.

  3. A simple method for correcting spatially resolved solar intensity oscillation observations for variations in scattered light

    NASA Technical Reports Server (NTRS)

    Jefferies, S. M.; Duvall, T. L., Jr.

    1991-01-01

    A measurement of the intensity distribution in an image of the solar disk will be corrupted by a spatial redistribution of the light that is caused by the earth's atmosphere and the observing instrument. A simple correction method is introduced here that is applicable for solar p-mode intensity observations obtained over a period of time in which there is a significant change in the scattering component of the point spread function. The method circumvents the problems incurred with an accurate determination of the spatial point spread function and its subsequent deconvolution from the observations. The method only corrects the spherical harmonic coefficients that represent the spatial frequencies present in the image and does not correct the image itself.

  4. Rapid and Accurate Multiple Testing Correction and Power Estimation for Millions of Correlated Markers

    PubMed Central

    Han, Buhm; Kang, Hyun Min; Eskin, Eleazar

    2009-01-01

    With the development of high-throughput sequencing and genotyping technologies, the number of markers collected in genetic association studies is growing rapidly, increasing the importance of methods for correcting for multiple hypothesis testing. The permutation test is widely considered the gold standard for accurate multiple testing correction, but it is often computationally impractical for these large datasets. Recently, several studies proposed efficient alternative approaches to the permutation test based on the multivariate normal distribution (MVN). However, they cannot accurately correct for multiple testing in genome-wide association studies for two reasons. First, these methods require partitioning of the genome into many disjoint blocks and ignore all correlations between markers from different blocks. Second, the true null distribution of the test statistic often fails to follow the asymptotic distribution at the tails of the distribution. We propose an accurate and efficient method for multiple testing correction in genome-wide association studies—SLIDE. Our method accounts for all correlation within a sliding window and corrects for the departure of the true null distribution of the statistic from the asymptotic distribution. In simulations using the Wellcome Trust Case Control Consortium data, the error rate of SLIDE's corrected p-values is more than 20 times smaller than the error rate of the previous MVN-based methods' corrected p-values, while SLIDE is orders of magnitude faster than the permutation test and other competing methods. We also extend the MVN framework to the problem of estimating the statistical power of an association study with correlated markers and propose an efficient and accurate power estimation method SLIP. SLIP and SLIDE are available at http://slide.cs.ucla.edu. PMID:19381255

  5. Real-time lens distortion correction: speed, accuracy and efficiency

    NASA Astrophysics Data System (ADS)

    Bax, Michael R.; Shahidi, Ramin

    2014-11-01

    Optical lens systems suffer from nonlinear geometrical distortion. Optical imaging applications such as image-enhanced endoscopy and image-based bronchoscope tracking require correction of this distortion for accurate localization, tracking, registration, and measurement of image features. Real-time capability is desirable for interactive systems and live video. The use of a texture-mapping graphics accelerator, which is standard hardware on current motherboard chipsets and add-in video graphics cards, to perform distortion correction is proposed. Mesh generation for image tessellation, an error analysis, and performance results are presented. It is shown that distortion correction using commodity graphics hardware is substantially faster than using the main processor and can be performed at video frame rates (faster than 30 frames per second), and that the polar-based method of mesh generation proposed here is more accurate than a conventional grid-based approach. Using graphics hardware to perform distortion correction is not only fast and accurate but also efficient as it frees the main processor for other tasks, which is an important issue in some real-time applications.

  6. Correcting the Relative Bias of Light Obscuration and Flow Imaging Particle Counters.

    PubMed

    Ripple, Dean C; Hu, Zhishang

    2016-03-01

    Industry and regulatory bodies desire more accurate methods for counting and characterizing particles. Measurements of proteinaceous-particle concentrations by light obscuration and flow imaging can differ by factors of ten or more. We propose methods to correct the diameters reported by light obscuration and flow imaging instruments. For light obscuration, diameters were rescaled based on characterization of the refractive index of typical particles and a light scattering model for the extinction efficiency factor. The light obscuration models are applicable for either homogeneous materials (e.g., silicone oil) or for chemically homogeneous, but spatially non-uniform aggregates (e.g., protein aggregates). For flow imaging, the method relied on calibration of the instrument with silica beads suspended in water-glycerol mixtures. These methods were applied to a silicone-oil droplet suspension and four particle suspensions containing particles produced from heat stressed and agitated human serum albumin, agitated polyclonal immunoglobulin, and abraded ethylene tetrafluoroethylene polymer. All suspensions were measured by two flow imaging and one light obscuration apparatus. Prior to correction, results from the three instruments disagreed by a factor ranging from 3.1 to 48 in particle concentration over the size range from 2 to 20 μm. Bias corrections reduced the disagreement from an average factor of 14 down to an average factor of 1.5. The methods presented show promise in reducing the relative bias between light obscuration and flow imaging.

  7. On the accurate long-time solution of the wave equation in exterior domains: Asymptotic expansions and corrected boundary conditions

    NASA Technical Reports Server (NTRS)

    Hagstrom, Thomas; Hariharan, S. I.; Maccamy, R. C.

    1993-01-01

    We consider the solution of scattering problems for the wave equation using approximate boundary conditions at artificial boundaries. These conditions are explicitly viewed as approximations to an exact boundary condition satisfied by the solution on the unbounded domain. We study the short and long term behavior of the error. It is provided that, in two space dimensions, no local in time, constant coefficient boundary operator can lead to accurate results uniformly in time for the class of problems we consider. A variable coefficient operator is developed which attains better accuracy (uniformly in time) than is possible with constant coefficient approximations. The theory is illustrated by numerical examples. We also analyze the proposed boundary conditions using energy methods, leading to asymptotically correct error bounds.

  8. Spectral method for the correction of the Cerenkov light effect in plastic scintillation detectors: A comparison study of calibration procedures and validation in Cerenkov light-dominated situations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Guillot, Mathieu; Gingras, Luc; Archambault, Louis

    2011-04-15

    Purpose: The purposes of this work were: (1) To determine if a spectral method can accurately correct the Cerenkov light effect in plastic scintillation detectors (PSDs) for situations where the Cerenkov light is dominant over the scintillation light and (2) to develop a procedural guideline for accurately determining the calibration factors of PSDs. Methods: The authors demonstrate, by using the equations of the spectral method, that the condition for accurately correcting the effect of Cerenkov light is that the ratio of the two calibration factors must be equal to the ratio of the Cerenkov light measured within the two differentmore » spectral regions used for analysis. Based on this proof, the authors propose two new procedures to determine the calibration factors of PSDs, which were designed to respect this condition. A PSD that consists of a cylindrical polystyrene scintillating fiber (1.6 mm{sup 3}) coupled to a plastic optical fiber was calibrated by using these new procedures and the two reference procedures described in the literature. To validate the extracted calibration factors, relative dose profiles and output factors for a 6 MV photon beam from a medical linac were measured with the PSD and an ionization chamber. Emphasis was placed on situations where the Cerenkov light is dominant over the scintillation light and on situations dissimilar to the calibration conditions. Results: The authors found that the accuracy of the spectral method depends on the procedure used to determine the calibration factors of the PSD and on the attenuation properties of the optical fiber used. The results from the relative dose profile measurements showed that the spectral method can correct the Cerenkov light effect with an accuracy level of 1%. The results obtained also indicate that PSDs measure output factors that are lower than those measured with ionization chambers for square field sizes larger than 25x25 cm{sup 2}, in general agreement with previously

  9. An Accurate Temperature Correction Model for Thermocouple Hygrometers 1

    PubMed Central

    Savage, Michael J.; Cass, Alfred; de Jager, James M.

    1982-01-01

    Numerous water relation studies have used thermocouple hygrometers routinely. However, the accurate temperature correction of hygrometer calibration curve slopes seems to have been largely neglected in both psychrometric and dewpoint techniques. In the case of thermocouple psychrometers, two temperature correction models are proposed, each based on measurement of the thermojunction radius and calculation of the theoretical voltage sensitivity to changes in water potential. The first model relies on calibration at a single temperature and the second at two temperatures. Both these models were more accurate than the temperature correction models currently in use for four psychrometers calibrated over a range of temperatures (15-38°C). The model based on calibration at two temperatures is superior to that based on only one calibration. The model proposed for dewpoint hygrometers is similar to that for psychrometers. It is based on the theoretical voltage sensitivity to changes in water potential. Comparison with empirical data from three dewpoint hygrometers calibrated at four different temperatures indicates that these instruments need only be calibrated at, e.g. 25°C, if the calibration slopes are corrected for temperature. PMID:16662241

  10. CORRECTING FOR INTERSTELLAR SCATTERING DELAY IN HIGH-PRECISION PULSAR TIMING: SIMULATION RESULTS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Palliyaguru, Nipuni; McLaughlin, Maura; Stinebring, Daniel

    2015-12-20

    Light travel time changes due to gravitational waves (GWs) may be detected within the next decade through precision timing of millisecond pulsars. Removal of frequency-dependent interstellar medium (ISM) delays due to dispersion and scattering is a key issue in the detection process. Current timing algorithms routinely correct pulse times of arrival (TOAs) for time-variable delays due to cold plasma dispersion. However, none of the major pulsar timing groups correct for delays due to scattering from multi-path propagation in the ISM. Scattering introduces a frequency-dependent phase change in the signal that results in pulse broadening and arrival time delays. Any methodmore » to correct the TOA for interstellar propagation effects must be based on multi-frequency measurements that can effectively separate dispersion and scattering delay terms from frequency-independent perturbations such as those due to a GW. Cyclic spectroscopy, first described in an astronomical context by Demorest (2011), is a potentially powerful tool to assist in this multi-frequency decomposition. As a step toward a more comprehensive ISM propagation delay correction, we demonstrate through a simulation that we can accurately recover impulse response functions (IRFs), such as those that would be introduced by multi-path scattering, with a realistic signal-to-noise ratio (S/N). We demonstrate that timing precision is improved when scatter-corrected TOAs are used, under the assumptions of a high S/N and highly scattered signal. We also show that the effect of pulse-to-pulse “jitter” is not a serious problem for IRF reconstruction, at least for jitter levels comparable to those observed in several bright pulsars.« less

  11. HMI Data Corrected for Stray Light Now Available

    NASA Astrophysics Data System (ADS)

    Norton, A. A.; Duvall, T. L.; Schou, J.; Cheung, M. C. M.; Scherrer, P. H.

    2016-10-01

    The form of the point spread function (PSF) derived for HMI is an Airy function convolved with a Lorentzian. The parameters are bound by observational ground-based testing of the instrument conducted prior to launch (Wachter et al., 2012), by full-disk data used to evaluate the off-limb behavior of the scattered light, as well as by data obtained during the Venus transit. The PSF correction has been programmed in both C and cuda C and runs within the JSOC environment using either a CPU or GPU. A single full-disk intensity image can be deconvolved in less than one second. The PSF is described in more detail in Couvidat et al. (2016) and has already been used by Hathaway et al. (2015) to forward-model solar-convection spectra, by Krucker et al. (2015) to investigate footpoints of off-limb solar flares and by Whitney, Criscuoli and Norton (2016) to examine the relations between intensity contrast and magnetic field strengths. In this presentation, we highlight the changes to umbral darkness, granulation contrast and plage field strengths that result from stray light correction. A twenty-four hour period of scattered-light corrected HMI data from 2010.08.03, including the isolated sunspot NOAA 11092, is currently available for anyone. Requests for additional time periods of interest are welcome and will be processed by the HMI team.

  12. Accurate and fast multiple-testing correction in eQTL studies.

    PubMed

    Sul, Jae Hoon; Raj, Towfique; de Jong, Simone; de Bakker, Paul I W; Raychaudhuri, Soumya; Ophoff, Roel A; Stranger, Barbara E; Eskin, Eleazar; Han, Buhm

    2015-06-04

    In studies of expression quantitative trait loci (eQTLs), it is of increasing interest to identify eGenes, the genes whose expression levels are associated with variation at a particular genetic variant. Detecting eGenes is important for follow-up analyses and prioritization because genes are the main entities in biological processes. To detect eGenes, one typically focuses on the genetic variant with the minimum p value among all variants in cis with a gene and corrects for multiple testing to obtain a gene-level p value. For performing multiple-testing correction, a permutation test is widely used. Because of growing sample sizes of eQTL studies, however, the permutation test has become a computational bottleneck in eQTL studies. In this paper, we propose an efficient approach for correcting for multiple testing and assess eGene p values by utilizing a multivariate normal distribution. Our approach properly takes into account the linkage-disequilibrium structure among variants, and its time complexity is independent of sample size. By applying our small-sample correction techniques, our method achieves high accuracy in both small and large studies. We have shown that our method consistently produces extremely accurate p values (accuracy > 98%) for three human eQTL datasets with different sample sizes and SNP densities: the Genotype-Tissue Expression pilot dataset, the multi-region brain dataset, and the HapMap 3 dataset. Copyright © 2015 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

  13. Stray light correction of array spectroradiometer measurement in ultraviolet

    NASA Astrophysics Data System (ADS)

    Wu, Zhifeng; Dai, Caihong; Wang, Yanfei; Li, Ling

    2018-02-01

    For most of the array spectroradiometer, stray light is significant in UV band. Stray light correction of a UV array spectroradiometer is investigated using optical filters. If a group of filters with continuous bandpass are chosen, stray light contribution due to all the bands can be obtained using a numerical algorithm. The array spectroradiometer with the stray light corrected is used to measure the spectral irradiance of several UV lamps. The measurement results are compared to a double monochromator spectroradiometer. When xenon lamp is the array spectroradiometer calibration lamp, after stray light correction, the difference can be improved from nearly 10% to 2.0% in UVC band. When tungsten lamp is the calibration lamp, the difference can be improved from around 90% to less than 20%.

  14. Light Field Imaging Based Accurate Image Specular Highlight Removal

    PubMed Central

    Wang, Haoqian; Xu, Chenxue; Wang, Xingzheng; Zhang, Yongbing; Peng, Bo

    2016-01-01

    Specular reflection removal is indispensable to many computer vision tasks. However, most existing methods fail or degrade in complex real scenarios for their individual drawbacks. Benefiting from the light field imaging technology, this paper proposes a novel and accurate approach to remove specularity and improve image quality. We first capture images with specularity by the light field camera (Lytro ILLUM). After accurately estimating the image depth, a simple and concise threshold strategy is adopted to cluster the specular pixels into “unsaturated” and “saturated” category. Finally, a color variance analysis of multiple views and a local color refinement are individually conducted on the two categories to recover diffuse color information. Experimental evaluation by comparison with existed methods based on our light field dataset together with Stanford light field archive verifies the effectiveness of our proposed algorithm. PMID:27253083

  15. A Semi-implicit Method for Time Accurate Simulation of Compressible Flow

    NASA Astrophysics Data System (ADS)

    Wall, Clifton; Pierce, Charles D.; Moin, Parviz

    2001-11-01

    A semi-implicit method for time accurate simulation of compressible flow is presented. The method avoids the acoustic CFL limitation, allowing a time step restricted only by the convective velocity. Centered discretization in both time and space allows the method to achieve zero artificial attenuation of acoustic waves. The method is an extension of the standard low Mach number pressure correction method to the compressible Navier-Stokes equations, and the main feature of the method is the solution of a Helmholtz type pressure correction equation similar to that of Demirdžić et al. (Int. J. Num. Meth. Fluids, Vol. 16, pp. 1029-1050, 1993). The method is attractive for simulation of acoustic combustion instabilities in practical combustors. In these flows, the Mach number is low; therefore the time step allowed by the convective CFL limitation is significantly larger than that allowed by the acoustic CFL limitation, resulting in significant efficiency gains. Also, the method's property of zero artificial attenuation of acoustic waves is important for accurate simulation of the interaction between acoustic waves and the combustion process. The method has been implemented in a large eddy simulation code, and results from several test cases will be presented.

  16. TYPE Ia SUPERNOVA DISTANCE MODULUS BIAS AND DISPERSION FROM K-CORRECTION ERRORS: A DIRECT MEASUREMENT USING LIGHT CURVE FITS TO OBSERVED SPECTRAL TIME SERIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Saunders, C.; Aldering, G.; Aragon, C.

    2015-02-10

    We estimate systematic errors due to K-corrections in standard photometric analyses of high-redshift Type Ia supernovae. Errors due to K-correction occur when the spectral template model underlying the light curve fitter poorly represents the actual supernova spectral energy distribution, meaning that the distance modulus cannot be recovered accurately. In order to quantify this effect, synthetic photometry is performed on artificially redshifted spectrophotometric data from 119 low-redshift supernovae from the Nearby Supernova Factory, and the resulting light curves are fit with a conventional light curve fitter. We measure the variation in the standardized magnitude that would be fit for a givenmore » supernova if located at a range of redshifts and observed with various filter sets corresponding to current and future supernova surveys. We find significant variation in the measurements of the same supernovae placed at different redshifts regardless of filters used, which causes dispersion greater than ∼0.05 mag for measurements of photometry using the Sloan-like filters and a bias that corresponds to a 0.03 shift in w when applied to an outside data set. To test the result of a shift in supernova population or environment at higher redshifts, we repeat our calculations with the addition of a reweighting of the supernovae as a function of redshift and find that this strongly affects the results and would have repercussions for cosmology. We discuss possible methods to reduce the contribution of the K-correction bias and uncertainty.« less

  17. RighTime: A real time clock correcting program for MS-DOS-based computer systems

    NASA Technical Reports Server (NTRS)

    Becker, G. Thomas

    1993-01-01

    A computer program is described which effectively eliminates the misgivings of the DOS system clock in PC/AT-class computers. RighTime is a small, sophisticated memory-resident program that automatically corrects both the DOS system clock and the hardware 'CMOS' real time clock (RTC) in real time. RighTime learns what corrections are required without operator interaction beyond the occasional accurate time set. Both warm (power on) and cool (power off) errors are corrected, usually yielding better than one part per million accuracy in the typical desktop computer with no additional hardware, and RighTime increases the system clock resolution from approximately 0.0549 second to 0.01 second. Program tools are also available which allow visualization of RighTime's actions, verification of its performance, display of its history log, and which provide data for graphing of the system clock behavior. The program has found application in a wide variety of industries, including astronomy, satellite tracking, communications, broadcasting, transportation, public utilities, manufacturing, medicine, and the military.

  18. Home Circadian Phase Assessments with Measures of Compliance Yield Accurate Dim Light Melatonin Onsets

    PubMed Central

    Burgess, Helen J.; Wyatt, James K.; Park, Margaret; Fogg, Louis F.

    2015-01-01

    Study Objectives: There is a need for the accurate assessment of circadian phase outside of the clinic/laboratory, particularly with the gold standard dim light melatonin onset (DLMO). We tested a novel kit designed to assist in saliva sampling at home for later determination of the DLMO. The home kit includes objective measures of compliance to the requirements for dim light and half-hourly saliva sampling. Design: Participants were randomized to one of two 10-day protocols. Each protocol consisted of two back-to-back home and laboratory phase assessments in counterbalanced order, separated by a 5-day break. Setting: Laboratory or participants' homes. Participants: Thirty-five healthy adults, age 21–62 y. Interventions: N/A. Measurements and Results: Most participants received at least one 30-sec epoch of light > 50 lux during the home phase assessments (average light intensity 4.5 lux), but on average for < 9 min of the required 8.5 h. Most participants collected every saliva sample within 5 min of the scheduled time. Ninety-two percent of home DLMOs were not affected by light > 50 lux or sampling errors. There was no significant difference between the home and laboratory DLMOs (P > 0.05); on average the home DLMOs occurred 9.6 min before the laboratory DLMOs. The home DLMOs were highly correlated with the laboratory DLMOs (r = 0.91, P < 0.001). Conclusions: Participants were reasonably compliant to the home phase assessment procedures. The good agreement between the home and laboratory dim light melatonin onsets (DLMOs) demonstrates that including objective measures of light exposure and sample timing during home saliva sampling can lead to accurate home DLMOs. Clinical Trial Registration: Circadian Phase Assessments at Home, http://clinicaltrials.gov/show/NCT01487252, NCT01487252. Citation: Burgess HJ, Wyatt JK, Park M, Fogg LF. Home circadian phase assessments with measures of compliance yield accurate dim light melatonin onsets. SLEEP 2015;38(6):889–897

  19. The dark art of light measurement: accurate radiometry for low-level light therapy.

    PubMed

    Hadis, Mohammed A; Zainal, Siti A; Holder, Michelle J; Carroll, James D; Cooper, Paul R; Milward, Michael R; Palin, William M

    2016-05-01

    Lasers and light-emitting diodes are used for a range of biomedical applications with many studies reporting their beneficial effects. However, three main concerns exist regarding much of the low-level light therapy (LLLT) or photobiomodulation literature; (1) incomplete, inaccurate and unverified irradiation parameters, (2) miscalculation of 'dose,' and (3) the misuse of appropriate light property terminology. The aim of this systematic review was to assess where, and to what extent, these inadequacies exist and to provide an overview of 'best practice' in light measurement methods and importance of correct light measurement. A review of recent relevant literature was performed in PubMed using the terms LLLT and photobiomodulation (March 2014-March 2015) to investigate the contemporary information available in LLLT and photobiomodulation literature in terms of reporting light properties and irradiation parameters. A total of 74 articles formed the basis of this systematic review. Although most articles reported beneficial effects following LLLT, the majority contained no information in terms of how light was measured (73%) and relied on manufacturer-stated values. For all papers reviewed, missing information for specific light parameters included wavelength (3%), light source type (8%), power (41%), pulse frequency (52%), beam area (40%), irradiance (43%), exposure time (16%), radiant energy (74%) and fluence (16%). Frequent use of incorrect terminology was also observed within the reviewed literature. A poor understanding of photophysics is evident as a significant number of papers neglected to report or misreported important radiometric data. These errors affect repeatability and reliability of studies shared between scientists, manufacturers and clinicians and could degrade efficacy of patient treatments. Researchers need a physicist or appropriately skilled engineer on the team, and manuscript reviewers should reject papers that do not report beam measurement

  20. BLESS 2: accurate, memory-efficient and fast error correction method.

    PubMed

    Heo, Yun; Ramachandran, Anand; Hwu, Wen-Mei; Ma, Jian; Chen, Deming

    2016-08-01

    The most important features of error correction tools for sequencing data are accuracy, memory efficiency and fast runtime. The previous version of BLESS was highly memory-efficient and accurate, but it was too slow to handle reads from large genomes. We have developed a new version of BLESS to improve runtime and accuracy while maintaining a small memory usage. The new version, called BLESS 2, has an error correction algorithm that is more accurate than BLESS, and the algorithm has been parallelized using hybrid MPI and OpenMP programming. BLESS 2 was compared with five top-performing tools, and it was found to be the fastest when it was executed on two computing nodes using MPI, with each node containing twelve cores. Also, BLESS 2 showed at least 11% higher gain while retaining the memory efficiency of the previous version for large genomes. Freely available at https://sourceforge.net/projects/bless-ec dchen@illinois.edu Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  1. Radiometrically accurate scene-based nonuniformity correction for array sensors.

    PubMed

    Ratliff, Bradley M; Hayat, Majeed M; Tyo, J Scott

    2003-10-01

    A novel radiometrically accurate scene-based nonuniformity correction (NUC) algorithm is described. The technique combines absolute calibration with a recently reported algebraic scene-based NUC algorithm. The technique is based on the following principle: First, detectors that are along the perimeter of the focal-plane array are absolutely calibrated; then the calibration is transported to the remaining uncalibrated interior detectors through the application of the algebraic scene-based algorithm, which utilizes pairs of image frames exhibiting arbitrary global motion. The key advantage of this technique is that it can obtain radiometric accuracy during NUC without disrupting camera operation. Accurate estimates of the bias nonuniformity can be achieved with relatively few frames, which can be fewer than ten frame pairs. Advantages of this technique are discussed, and a thorough performance analysis is presented with use of simulated and real infrared imagery.

  2. A Simple yet Accurate Method for Students to Determine Asteroid Rotation Periods from Fragmented Light Curve Data

    ERIC Educational Resources Information Center

    Beare, R. A.

    2008-01-01

    Professional astronomers use specialized software not normally available to students to determine the rotation periods of asteroids from fragmented light curve data. This paper describes a simple yet accurate method based on Microsoft Excel[R] that enables students to find periods in asteroid light curve and other discontinuous time series data of…

  3. Home Circadian Phase Assessments with Measures of Compliance Yield Accurate Dim Light Melatonin Onsets.

    PubMed

    Burgess, Helen J; Wyatt, James K; Park, Margaret; Fogg, Louis F

    2015-06-01

    There is a need for the accurate assessment of circadian phase outside of the clinic/laboratory, particularly with the gold standard dim light melatonin onset (DLMO). We tested a novel kit designed to assist in saliva sampling at home for later determination of the DLMO. The home kit includes objective measures of compliance to the requirements for dim light and half-hourly saliva sampling. Participants were randomized to one of two 10-day protocols. Each protocol consisted of two back-to-back home and laboratory phase assessments in counterbalanced order, separated by a 5-day break. Laboratory or participants' homes. Thirty-five healthy adults, age 21-62 y. N/A. Most participants received at least one 30-sec epoch of light > 50 lux during the home phase assessments (average light intensity 4.5 lux), but on average for < 9 min of the required 8.5 h. Most participants collected every saliva sample within 5 min of the scheduled time. Ninety-two percent of home DLMOs were not affected by light > 50 lux or sampling errors. There was no significant difference between the home and laboratory DLMOs (P > 0.05); on average the home DLMOs occurred 9.6 min before the laboratory DLMOs. The home DLMOs were highly correlated with the laboratory DLMOs (r = 0.91, P < 0.001). Participants were reasonably compliant to the home phase assessment procedures. The good agreement between the home and laboratory dim light melatonin onsets (DLMOs) demonstrates that including objective measures of light exposure and sample timing during home saliva sampling can lead to accurate home DLMOs. Circadian Phase Assessments at Home, http://clinicaltrials.gov/show/NCT01487252, NCT01487252. © 2015 Associated Professional Sleep Societies, LLC.

  4. Method of absorbance correction in a spectroscopic heating value sensor

    DOEpatents

    Saveliev, Alexei; Jangale, Vilas Vyankatrao; Zelepouga, Sergeui; Pratapas, John

    2013-09-17

    A method and apparatus for absorbance correction in a spectroscopic heating value sensor in which a reference light intensity measurement is made on a non-absorbing reference fluid, a light intensity measurement is made on a sample fluid, and a measured light absorbance of the sample fluid is determined. A corrective light intensity measurement at a non-absorbing wavelength of the sample fluid is made on the sample fluid from which an absorbance correction factor is determined. The absorbance correction factor is then applied to the measured light absorbance of the sample fluid to arrive at a true or accurate absorbance for the sample fluid.

  5. CD-SEM real time bias correction using reference metrology based modeling

    NASA Astrophysics Data System (ADS)

    Ukraintsev, V.; Banke, W.; Zagorodnev, G.; Archie, C.; Rana, N.; Pavlovsky, V.; Smirnov, V.; Briginas, I.; Katnani, A.; Vaid, A.

    2018-03-01

    Accuracy of patterning impacts yield, IC performance and technology time to market. Accuracy of patterning relies on optical proximity correction (OPC) models built using CD-SEM inputs and intra die critical dimension (CD) control based on CD-SEM. Sub-nanometer measurement uncertainty (MU) of CD-SEM is required for current technologies. Reported design and process related bias variation of CD-SEM is in the range of several nanometers. Reference metrology and numerical modeling are used to correct SEM. Both methods are slow to be used for real time bias correction. We report on real time CD-SEM bias correction using empirical models based on reference metrology (RM) data. Significant amount of currently untapped information (sidewall angle, corner rounding, etc.) is obtainable from SEM waveforms. Using additional RM information provided for specific technology (design rules, materials, processes) CD extraction algorithms can be pre-built and then used in real time for accurate CD extraction from regular CD-SEM images. The art and challenge of SEM modeling is in finding robust correlation between SEM waveform features and bias of CD-SEM as well as in minimizing RM inputs needed to create accurate (within the design and process space) model. The new approach was applied to improve CD-SEM accuracy of 45 nm GATE and 32 nm MET1 OPC 1D models. In both cases MU of the state of the art CD-SEM has been improved by 3x and reduced to a nanometer level. Similar approach can be applied to 2D (end of line, contours, etc.) and 3D (sidewall angle, corner rounding, etc.) cases.

  6. Method for Accurately Calibrating a Spectrometer Using Broadband Light

    NASA Technical Reports Server (NTRS)

    Simmons, Stephen; Youngquist, Robert

    2011-01-01

    A novel method has been developed for performing very fine calibration of a spectrometer. This process is particularly useful for modern miniature charge-coupled device (CCD) spectrometers where a typical factory wavelength calibration has been performed and a finer, more accurate calibration is desired. Typically, the factory calibration is done with a spectral line source that generates light at known wavelengths, allowing specific pixels in the CCD array to be assigned wavelength values. This method is good to about 1 nm across the spectrometer s wavelength range. This new method appears to be accurate to about 0.1 nm, a factor of ten improvement. White light is passed through an unbalanced Michelson interferometer, producing an optical signal with significant spectral variation. A simple theory can be developed to describe this spectral pattern, so by comparing the actual spectrometer output against this predicted pattern, errors in the wavelength assignment made by the spectrometer can be determined.

  7. Space-time light field rendering.

    PubMed

    Wang, Huamin; Sun, Mingxuan; Yang, Ruigang

    2007-01-01

    In this paper, we propose a novel framework called space-time light field rendering, which allows continuous exploration of a dynamic scene in both space and time. Compared to existing light field capture/rendering systems, it offers the capability of using unsynchronized video inputs and the added freedom of controlling the visualization in the temporal domain, such as smooth slow motion and temporal integration. In order to synthesize novel views from any viewpoint at any time instant, we develop a two-stage rendering algorithm. We first interpolate in the temporal domain to generate globally synchronized images using a robust spatial-temporal image registration algorithm followed by edge-preserving image morphing. We then interpolate these software-synchronized images in the spatial domain to synthesize the final view. In addition, we introduce a very accurate and robust algorithm to estimate subframe temporal offsets among input video sequences. Experimental results from unsynchronized videos with or without time stamps show that our approach is capable of maintaining photorealistic quality from a variety of real scenes.

  8. Error correcting coding-theory for structured light illumination systems

    NASA Astrophysics Data System (ADS)

    Porras-Aguilar, Rosario; Falaggis, Konstantinos; Ramos-Garcia, Ruben

    2017-06-01

    Intensity discrete structured light illumination systems project a series of projection patterns for the estimation of the absolute fringe order using only the temporal grey-level sequence at each pixel. This work proposes the use of error-correcting codes for pixel-wise correction of measurement errors. The use of an error correcting code is advantageous in many ways: it allows reducing the effect of random intensity noise, it corrects outliners near the border of the fringe commonly present when using intensity discrete patterns, and it provides a robustness in case of severe measurement errors (even for burst errors where whole frames are lost). The latter aspect is particular interesting in environments with varying ambient light as well as in critical safety applications as e.g. monitoring of deformations of components in nuclear power plants, where a high reliability is ensured even in case of short measurement disruptions. A special form of burst errors is the so-called salt and pepper noise, which can largely be removed with error correcting codes using only the information of a given pixel. The performance of this technique is evaluated using both simulations and experiments.

  9. Effects of day-time exposure to different light intensities on light-induced melatonin suppression at night.

    PubMed

    Kozaki, Tomoaki; Kubokawa, Ayaka; Taketomi, Ryunosuke; Hatae, Keisuke

    2015-07-04

    Bright nocturnal light has been known to suppress melatonin secretion. However, bright light exposure during the day-time might reduce light-induced melatonin suppression (LIMS) at night. The effective proportion of day-time light to night-time light is unclear; however, only a few studies on accurately controlling both day- and night-time conditions have been conducted. This study aims to evaluate the effect of different day-time light intensities on LIMS. Twelve male subjects between the ages of 19 and 23 years (mean ± S.D., 20.8 ± 1.1) gave informed consent to participate in this study. They were exposed to various light conditions (<10, 100, 300, 900 and 2700 lx) between the hours of 09:00 and 12:00 (day-time light conditions). They were then exposed to bright light (300 lx) again between 01:00 and 02:30 (night-time light exposure). They provided saliva samples before (00:55) and after night-time light exposure (02:30). A one-tailed paired t test yielded significant decrements of melatonin concentration after night-time light exposure under day-time dim, 100- and 300-lx light conditions. No significant differences exist in melatonin concentration between pre- and post-night-time light exposure under day-time 900- and 2700-lx light conditions. Present findings suggest the amount of light exposure needed to prevent LIMS caused by ordinary nocturnal light in individuals who have a general life rhythm (sleep/wake schedule). These findings may be useful in implementing artificial light environments for humans in, for example, hospitals and underground shopping malls.

  10. High-rate dead-time corrections in a general purpose digital pulse processing system

    PubMed Central

    Abbene, Leonardo; Gerardi, Gaetano

    2015-01-01

    Dead-time losses are well recognized and studied drawbacks in counting and spectroscopic systems. In this work the abilities on dead-time correction of a real-time digital pulse processing (DPP) system for high-rate high-resolution radiation measurements are presented. The DPP system, through a fast and slow analysis of the output waveform from radiation detectors, is able to perform multi-parameter analysis (arrival time, pulse width, pulse height, pulse shape, etc.) at high input counting rates (ICRs), allowing accurate counting loss corrections even for variable or transient radiations. The fast analysis is used to obtain both the ICR and energy spectra with high throughput, while the slow analysis is used to obtain high-resolution energy spectra. A complete characterization of the counting capabilities, through both theoretical and experimental approaches, was performed. The dead-time modeling, the throughput curves, the experimental time-interval distributions (TIDs) and the counting uncertainty of the recorded events of both the fast and the slow channels, measured with a planar CdTe (cadmium telluride) detector, will be presented. The throughput formula of a series of two types of dead-times is also derived. The results of dead-time corrections, performed through different methods, will be reported and discussed, pointing out the error on ICR estimation and the simplicity of the procedure. Accurate ICR estimations (nonlinearity < 0.5%) were performed by using the time widths and the TIDs (using 10 ns time bin width) of the detected pulses up to 2.2 Mcps. The digital system allows, after a simple parameter setting, different and sophisticated procedures for dead-time correction, traditionally implemented in complex/dedicated systems and time-consuming set-ups. PMID:26289270

  11. Insar Unwrapping Error Correction Based on Quasi-Accurate Detection of Gross Errors (quad)

    NASA Astrophysics Data System (ADS)

    Kang, Y.; Zhao, C. Y.; Zhang, Q.; Yang, C. S.

    2018-04-01

    Unwrapping error is a common error in the InSAR processing, which will seriously degrade the accuracy of the monitoring results. Based on a gross error correction method, Quasi-accurate detection (QUAD), the method for unwrapping errors automatic correction is established in this paper. This method identifies and corrects the unwrapping errors by establishing a functional model between the true errors and interferograms. The basic principle and processing steps are presented. Then this method is compared with the L1-norm method with simulated data. Results show that both methods can effectively suppress the unwrapping error when the ratio of the unwrapping errors is low, and the two methods can complement each other when the ratio of the unwrapping errors is relatively high. At last the real SAR data is tested for the phase unwrapping error correction. Results show that this new method can correct the phase unwrapping errors successfully in the practical application.

  12. Buoyancy-corrected gravimetric analysis of lightly loaded filters.

    PubMed

    Rasmussen, Pat E; Gardner, H David; Niu, Jianjun

    2010-09-01

    Numerous sources of uncertainty are associated with the gravimetric analysis of lightly loaded air filter samples (< 100 microg). The purpose of the study presented here is to investigate the effectiveness and limitations of air buoyancy corrections over experimentally adjusted conditions of temperature (21-25 degrees C) and relative humidity (RH) (16-60% RH). Conditioning (24 hr) and weighing were performed inside the Archimedes M3 environmentally controlled chamber. The measurements were performed using 20 size-fractionated samples of resuspended house dust loaded onto Teflo (PTFE) filters using a Micro-Orifice Uniform Deposit Impactor representing a wide range of mass loading (7.2-3130 microg) and cut sizes (0.056-9.9 microm). By maintaining tight controls on humidity (within 0.5% RH of control setting) throughout pre- and postweighing at each stepwise increase in RH, it was possible to quantify error due to water absorption: 45% of the total mass change due to water absorption occurred between 16 and 50% RH, and 55% occurred between 50 and 60% RH. The buoyancy corrections ranged from -3.5 to +5.8 microg in magnitude and improved relative standard deviation (RSD) from 21.3% (uncorrected) to 5.6% (corrected) for a 7.2 microg sample. It is recommended that protocols for weighing low-mass particle samples (e.g., nanoparticle samples) should include buoyancy corrections and tight temperature/humidity controls. In some cases, conditioning times longer than 24 hr may be warranted.

  13. Vector Sky Glint Corrections for Above Surface Retrieval of the Subsurface Polarized Light Field

    NASA Astrophysics Data System (ADS)

    Gilerson, A.; Foster, R.; McGilloway, A.; Ibrahim, A.; El-habashi, A.; Carrizo, C.; Ahmed, S.

    2016-02-01

    Knowledge of the underwater light field is fundamental to determining the health of the world's oceans and coastal regions. For decades, traditional remote sensing retrieval methods that rely solely on the spectral intensity of the water-leaving light have provided indicators of marine ecosystem health. As the demand for retrieval accuracy rises, use of the polarized nature of light as an additional remote sensing tool is becoming necessary. In order to observe the underwater polarized light field from above the surface (for ship, shore, or satellite applications), a method of correcting the above water signal for the effects of polarized surface-reflected skylight is needed. For three weeks in July-August 2014, the NASA Ship Aircraft Bio-Optical Research (SABOR) cruise continuously observed the polarized radiance of the ocean and the sky using a HyperSAS-POL system. The system autonomously tracks the Sun position and the heading of the research vessel in order to maintain a fixed relative solar azimuth angle (i.e. ±90°) and therefore avoid the specular reflection of the sunlight. Additionally, in-situ inherent optical properties (IOPs) were continuously acquired using a set of instrument packages modified for underway measurement, hyperspectral radiometric measurements were taken manually at all stations, and an underwater polarimeter was deployed when conditions permitted. All measurements, above and below the sea surface, were combined and compared in an effort to first develop a glint (sky + Sun) correction scheme for the upwelling polarized signal from a wind-driven ocean surface and compare with one assuming that the ocean surface is flat. Accurate retrieval of the subsurface vector light field is demonstrated through comparisons with polarized radiative transfer codes and direct measurements made by the underwater polarimeter.

  14. Improved Ecosystem Predictions of the California Current System via Accurate Light Calculations

    DTIC Science & Technology

    2011-09-30

    System via Accurate Light Calculations Curtis D. Mobley Sequoia Scientific, Inc. 2700 Richards Road, Suite 107 Bellevue, WA 98005 phone: 425...7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Sequoia Scientific, Inc,2700 Richards Road, Suite 107,Bellevue,WA,98005 8. PERFORMING...EcoLight-S 1.0 Users’ Guide and Technical Documentation. Sequoia Scientific, Inc., Bellevue, WA, 38 pages. Mobley, C. D., 2011. Fast light calculations

  15. A hybrid solution using computational prediction and measured data to accurately determine process corrections with reduced overlay sampling

    NASA Astrophysics Data System (ADS)

    Noyes, Ben F.; Mokaberi, Babak; Mandoy, Ram; Pate, Alex; Huijgen, Ralph; McBurney, Mike; Chen, Owen

    2017-03-01

    Reducing overlay error via an accurate APC feedback system is one of the main challenges in high volume production of the current and future nodes in the semiconductor industry. The overlay feedback system directly affects the number of dies meeting overlay specification and the number of layers requiring dedicated exposure tools through the fabrication flow. Increasing the former number and reducing the latter number is beneficial for the overall efficiency and yield of the fabrication process. An overlay feedback system requires accurate determination of the overlay error, or fingerprint, on exposed wafers in order to determine corrections to be automatically and dynamically applied to the exposure of future wafers. Since current and future nodes require correction per exposure (CPE), the resolution of the overlay fingerprint must be high enough to accommodate CPE in the overlay feedback system, or overlay control module (OCM). Determining a high resolution fingerprint from measured data requires extremely dense overlay sampling that takes a significant amount of measurement time. For static corrections this is acceptable, but in an automated dynamic correction system this method creates extreme bottlenecks for the throughput of said system as new lots have to wait until the previous lot is measured. One solution is using a less dense overlay sampling scheme and employing computationally up-sampled data to a dense fingerprint. That method uses a global fingerprint model over the entire wafer; measured localized overlay errors are therefore not always represented in its up-sampled output. This paper will discuss a hybrid system shown in Fig. 1 that combines a computationally up-sampled fingerprint with the measured data to more accurately capture the actual fingerprint, including local overlay errors. Such a hybrid system is shown to result in reduced modelled residuals while determining the fingerprint, and better on-product overlay performance.

  16. Subject-specific bone attenuation correction for brain PET/MR: can ZTE-MRI substitute CT scan accurately?

    PubMed

    Khalifé, Maya; Fernandez, Brice; Jaubert, Olivier; Soussan, Michael; Brulon, Vincent; Buvat, Irène; Comtat, Claude

    2017-09-21

    In brain PET/MR applications, accurate attenuation maps are required for accurate PET image quantification. An implemented attenuation correction (AC) method for brain imaging is the single-atlas approach that estimates an AC map from an averaged CT template. As an alternative, we propose to use a zero echo time (ZTE) pulse sequence to segment bone, air and soft tissue. A linear relationship between histogram normalized ZTE intensity and measured CT density in Hounsfield units ([Formula: see text]) in bone has been established thanks to a CT-MR database of 16 patients. Continuous AC maps were computed based on the segmented ZTE by setting a fixed linear attenuation coefficient (LAC) to air and soft tissue and by using the linear relationship to generate continuous μ values for the bone. Additionally, for the purpose of comparison, four other AC maps were generated: a ZTE derived AC map with a fixed LAC for the bone, an AC map based on the single-atlas approach as provided by the PET/MR manufacturer, a soft-tissue only AC map and, finally, the CT derived attenuation map used as the gold standard (CTAC). All these AC maps were used with different levels of smoothing for PET image reconstruction with and without time-of-flight (TOF). The subject-specific AC map generated by combining ZTE-based segmentation and linear scaling of the normalized ZTE signal into [Formula: see text] was found to be a good substitute for the measured CTAC map in brain PET/MR when used with a Gaussian smoothing kernel of [Formula: see text] corresponding to the PET scanner intrinsic resolution. As expected TOF reduces AC error regardless of the AC method. The continuous ZTE-AC performed better than the other alternative MR derived AC methods, reducing the quantification error between the MRAC corrected PET image and the reference CTAC corrected PET image.

  17. Subject-specific bone attenuation correction for brain PET/MR: can ZTE-MRI substitute CT scan accurately?

    NASA Astrophysics Data System (ADS)

    Khalifé, Maya; Fernandez, Brice; Jaubert, Olivier; Soussan, Michael; Brulon, Vincent; Buvat, Irène; Comtat, Claude

    2017-10-01

    In brain PET/MR applications, accurate attenuation maps are required for accurate PET image quantification. An implemented attenuation correction (AC) method for brain imaging is the single-atlas approach that estimates an AC map from an averaged CT template. As an alternative, we propose to use a zero echo time (ZTE) pulse sequence to segment bone, air and soft tissue. A linear relationship between histogram normalized ZTE intensity and measured CT density in Hounsfield units (HU ) in bone has been established thanks to a CT-MR database of 16 patients. Continuous AC maps were computed based on the segmented ZTE by setting a fixed linear attenuation coefficient (LAC) to air and soft tissue and by using the linear relationship to generate continuous μ values for the bone. Additionally, for the purpose of comparison, four other AC maps were generated: a ZTE derived AC map with a fixed LAC for the bone, an AC map based on the single-atlas approach as provided by the PET/MR manufacturer, a soft-tissue only AC map and, finally, the CT derived attenuation map used as the gold standard (CTAC). All these AC maps were used with different levels of smoothing for PET image reconstruction with and without time-of-flight (TOF). The subject-specific AC map generated by combining ZTE-based segmentation and linear scaling of the normalized ZTE signal into HU was found to be a good substitute for the measured CTAC map in brain PET/MR when used with a Gaussian smoothing kernel of 4~mm corresponding to the PET scanner intrinsic resolution. As expected TOF reduces AC error regardless of the AC method. The continuous ZTE-AC performed better than the other alternative MR derived AC methods, reducing the quantification error between the MRAC corrected PET image and the reference CTAC corrected PET image.

  18. Correction of phase errors in quantitative water-fat imaging using a monopolar time-interleaved multi-echo gradient echo sequence.

    PubMed

    Ruschke, Stefan; Eggers, Holger; Kooijman, Hendrik; Diefenbach, Maximilian N; Baum, Thomas; Haase, Axel; Rummeny, Ernst J; Hu, Houchun H; Karampinos, Dimitrios C

    2017-09-01

    To propose a phase error correction scheme for monopolar time-interleaved multi-echo gradient echo water-fat imaging that allows accurate and robust complex-based quantification of the proton density fat fraction (PDFF). A three-step phase correction scheme is proposed to address a) a phase term induced by echo misalignments that can be measured with a reference scan using reversed readout polarity, b) a phase term induced by the concomitant gradient field that can be predicted from the gradient waveforms, and c) a phase offset between time-interleaved echo trains. Simulations were carried out to characterize the concomitant gradient field-induced PDFF bias and the performance estimating the phase offset between time-interleaved echo trains. Phantom experiments and in vivo liver and thigh imaging were performed to study the relevance of each of the three phase correction steps on PDFF accuracy and robustness. The simulation, phantom, and in vivo results showed in agreement with the theory an echo time-dependent PDFF bias introduced by the three phase error sources. The proposed phase correction scheme was found to provide accurate PDFF estimation independent of the employed echo time combination. Complex-based time-interleaved water-fat imaging was found to give accurate and robust PDFF measurements after applying the proposed phase error correction scheme. Magn Reson Med 78:984-996, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  19. Apparatus for and method of correcting for astigmatism in a light beam reflected off of a light reflecting surface

    DOEpatents

    Sawicki, R.H.; Sweatt, W.

    1985-11-21

    A technique for adjustably correcting for astigmatism in a light beam is disclosed herein. This technique defines a flat, rectangular light reflecting surface having opposite reinforced side edges and which is resiliently bendable, to a limited extent, into different concave and/or convex cylindrical curvatures about a particular axis and provides for adjustably bending the light reflecting surface into one of different curvatures depending upon the astigmatism to be corrected and for fixedly maintaining the curvature selected. In the embodiment disclosed, the light reflecting surface is adjustably bendable into the selected cylindrical curvature by application of a particular bending moment to the reinforced side edges of the light reflecting surface.

  20. Accuracy of intensity and inclinometer output of three activity monitors for identification of sedentary behavior and light-intensity activity.

    PubMed

    Carr, Lucas J; Mahar, Matthew T

    2012-01-01

    Purpose. To examine the accuracy of intensity and inclinometer output of three physical activity monitors during various sedentary and light-intensity activities. Methods. Thirty-six participants wore three physical activity monitors (ActiGraph GT1M, ActiGraph GT3X+, and StepWatch) while completing sedentary (lying, sitting watching television, sitting using computer, and standing still) light (walking 1.0 mph, pedaling 7.0 mph, pedaling 15.0 mph) intensity activities under controlled settings. Accuracy for correctly categorizing intensity was assessed for each monitor and threshold. Accuracy of the GT3X+ inclinometer function (GT3X+Incl) for correctly identifying anatomical position was also assessed. Percentage agreement between direct observation and the monitor recorded time spent in sedentary behavior and light intensity was examined. Results. All monitors using all thresholds accurately identified over 80% of sedentary behaviors and 60% of light-intensity walking time based on intensity output. The StepWatch was the most accurate in detecting pedaling time but unable to detect pedal workload. The GT3X+Incl accurately identified anatomical position during 70% of all activities but demonstrated limitations in discriminating between activities of differing intensity. Conclusions. Our findings suggest that all three monitors accurately measure most sedentary and light-intensity activities although choice of monitors should be based on study-specific needs.

  1. Apparatus for and method of correcting for astigmatism in a light beam reflected off of a light reflecting surface

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sawicki, R.H.; Sweatt, W.

    1985-11-21

    A technique for adjustably correcting for astigmatism in a light beam is disclosed herein. This technique defines a flat, rectangular light reflecting surface having opposite reinforced side edges and which is resiliently bendable, to a limited extent, into different concave and/or convex cylindrical curvatures about a particular axis and provides for adjustably bending the light reflecting surface into one of different curvatures depending upon the astigmatism to be corrected and for fixedly maintaining the curvature selected. In the embodiment disclosed, the light reflecting surface is adjustably bendable into the selected cylindrical curvature by application of a particular bending moment tomore » the reinforced side edges of the light reflecting surface.« less

  2. A statistical method for assessing peptide identification confidence in accurate mass and time tag proteomics

    PubMed Central

    Stanley, Jeffrey R.; Adkins, Joshua N.; Slysz, Gordon W.; Monroe, Matthew E.; Purvine, Samuel O.; Karpievitch, Yuliya V.; Anderson, Gordon A.; Smith, Richard D.; Dabney, Alan R.

    2011-01-01

    Current algorithms for quantifying peptide identification confidence in the accurate mass and time (AMT) tag approach assume that the AMT tags themselves have been correctly identified. However, there is uncertainty in the identification of AMT tags, as this is based on matching LC-MS/MS fragmentation spectra to peptide sequences. In this paper, we incorporate confidence measures for the AMT tag identifications into the calculation of probabilities for correct matches to an AMT tag database, resulting in a more accurate overall measure of identification confidence for the AMT tag approach. The method is referred to as Statistical Tools for AMT tag Confidence (STAC). STAC additionally provides a Uniqueness Probability (UP) to help distinguish between multiple matches to an AMT tag and a method to calculate an overall false discovery rate (FDR). STAC is freely available for download as both a command line and a Windows graphical application. PMID:21692516

  3. Apparatus for and method of correcting for astigmatism in a light beam reflected off of a light reflecting surface

    DOEpatents

    Sawicki, Richard H.; Sweatt, William

    1987-01-01

    A technique for adjustably correcting for astigmatism in a light beam is disclosed herein. This technique utilizes first means which defines a flat, rectangular light reflecting surface having opposite reinforced side edges and which is resiliently bendable, to a limited extent, into different concave and/or convex cylindrical curvatures about a particular axis and second means acting on the first means for adjustably bending the light reflecting surface into a particular selected one of the different curvatures depending upon the astigmatism to be corrected for and for fixedly maintaining the curvature selected. In the embodiment disclosed, the light reflecting surface is adjustably bendable into the selected cylindrical curvature by application of a particular bending moment to the reinforced side edges of the light reflecting surface.

  4. Dead-time Corrected Disdrometer Data

    DOE Data Explorer

    Bartholomew, Mary Jane

    2008-03-05

    Original and dead-time corrected disdrometer results for observations made at SGP and TWP. The correction is based on the technique discussed in Sheppard and Joe, 1994. In addition, these files contain calculated radar reflectivity factor, mean Doppler velocity and attenuation for every measurement for both the original and dead-time corrected data at the following wavelengths: 0.316, 0.856, 3.2, 5, and 10cm (W,K,X,C,S bands). Pavlos Kollias provided the code to do these calculations.

  5. Apparatus for and method of correcting for aberrations in a light beam

    DOEpatents

    Sawicki, Richard H.

    1996-01-01

    A technique for adjustably correcting for aberrations in a light beam is disclosed herein. This technique utilizes first means which defines a flat, circular light reflecting surface having opposite reinforced circumferential edges and a central post and which is resiliently distortable, to a limited extent, into different concave and/or convex curvatures, which may be Gaussian-like, about the central axis, and second means acting on the first means for adjustably distorting the light reflecting surface into a particular selected one of the different curvatures depending upon the aberrations to be corrected for and for fixedly maintaining the curvature selected. In the embodiment disclosed, the light reflecting surface is adjustably distorted into the selected curvature by application of particular axial moments to the central post on the opposite side from the light reflecting surface and lateral moments to the circumference of the reflecting surface.

  6. Apparatus for and method of correcting for aberrations in a light beam

    DOEpatents

    Sawicki, R.H.

    1996-09-17

    A technique for adjustably correcting for aberrations in a light beam is disclosed herein. This technique utilizes first means which defines a flat, circular light reflecting surface having opposite reinforced circumferential edges and a central post and which is resiliently distortable, to a limited extent, into different concave and/or convex curvatures, which may be Gaussian-like, about the central axis, and second means acting on the first means for adjustably distorting the light reflecting surface into a particular selected one of the different curvatures depending upon the aberrations to be corrected for and for fixedly maintaining the curvature selected. In the embodiment disclosed, the light reflecting surface is adjustably distorted into the selected curvature by application of particular axial moments to the central post on the opposite side from the light reflecting surface and lateral moments to the circumference of the reflecting surface. 8 figs.

  7. The timing of the human circadian clock is accurately represented by the core body temperature rhythm following phase shifts to a three-cycle light stimulus near the critical zone

    NASA Technical Reports Server (NTRS)

    Jewett, M. E.; Duffy, J. F.; Czeisler, C. A.

    2000-01-01

    A double-stimulus experiment was conducted to evaluate the phase of the underlying circadian clock following light-induced phase shifts of the human circadian system. Circadian phase was assayed by constant routine from the rhythm in core body temperature before and after a three-cycle bright-light stimulus applied near the estimated minimum of the core body temperature rhythm. An identical, consecutive three-cycle light stimulus was then applied, and phase was reassessed. Phase shifts to these consecutive stimuli were no different from those obtained in a previous study following light stimuli applied under steady-state conditions over a range of circadian phases similar to those at which the consecutive stimuli were applied. These data suggest that circadian phase shifts of the core body temperature rhythm in response to a three-cycle stimulus occur within 24 h following the end of the 3-day light stimulus and that this poststimulus temperature rhythm accurately reflects the timing of the underlying circadian clock.

  8. Calibrating GPS With TWSTFT For Accurate Time Transfer

    DTIC Science & Technology

    2008-12-01

    40th Annual Precise Time and Time Interval (PTTI) Meeting 577 CALIBRATING GPS WITH TWSTFT FOR ACCURATE TIME TRANSFER Z. Jiang1 and...primary time transfer techniques are GPS and TWSTFT (Two-Way Satellite Time and Frequency Transfer, TW for short). 83% of UTC time links are...Calibrating GPS With TWSTFT For Accurate Time Transfer 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT

  9. Significance of accurate diffraction corrections for the second harmonic wave in determining the acoustic nonlinearity parameter

    NASA Astrophysics Data System (ADS)

    Jeong, Hyunjo; Zhang, Shuzeng; Barnard, Dan; Li, Xiongbing

    2015-09-01

    The accurate measurement of acoustic nonlinearity parameter β for fluids or solids generally requires making corrections for diffraction effects due to finite size geometry of transmitter and receiver. These effects are well known in linear acoustics, while those for second harmonic waves have not been well addressed and therefore not properly considered in previous studies. In this work, we explicitly define the attenuation and diffraction corrections using the multi-Gaussian beam (MGB) equations which were developed from the quasilinear solutions of the KZK equation. The effects of making these corrections are examined through the simulation of β determination in water. Diffraction corrections are found to have more significant effects than attenuation corrections, and the β values of water can be estimated experimentally with less than 5% errors when the exact second harmonic diffraction corrections are used together with the negligible attenuation correction effects on the basis of linear frequency dependence between attenuation coefficients, α2 ≃ 2α1.

  10. Stray light correction on array spectroradiometers for optical radiation risk assessment in the workplace.

    PubMed

    Barlier-Salsi, A

    2014-12-01

    The European directive 2006/25/EC requires the employer to assess and, if necessary, measure the levels of exposure to optical radiation in the workplace. Array spectroradiometers can measure optical radiation from various types of sources; however poor stray light rejection affects their accuracy. A stray light correction matrix, using a tunable laser, was developed at the National Institute of Standards and Technology (NIST). As tunable lasers are very expensive, the purpose of this study was to implement this method using only nine low power lasers; other elements of the correction matrix being completed by interpolation and extrapolation. The correction efficiency was evaluated by comparing CCD spectroradiometers with and without correction and a scanning double monochromator device as reference. Similar to findings recorded by NIST, these experiments show that it is possible to reduce the spectral stray light by one or two orders of magnitude. In terms of workplace risk assessment, this spectral stray light correction method helps determine exposure levels, with an acceptable degree of uncertainty, for the majority of workplace situations. The level of uncertainty depends upon the model of spectroradiometers used; the best results are obtained with CCD detectors having an enhanced spectral sensitivity in the UV range. Thus corrected spectroradiometers require a validation against a scanning double monochromator spectroradiometer before using them for risk assessment in the workplace.

  11. Fast and accurate modeling of stray light in optical systems

    NASA Astrophysics Data System (ADS)

    Perrin, Jean-Claude

    2017-11-01

    The first problem to be solved in most optical designs with respect to stray light is that of internal reflections on the several surfaces of individual lenses and mirrors, and on the detector itself. The level of stray light ratio can be considerably reduced by taking into account the stray light during the optimization to determine solutions in which the irradiance due to these ghosts is kept to the minimum possible value. Unhappily, the routines available in most optical design software's, for example CODE V, do not permit all alone to make exact quantitative calculations of the stray light due to these ghosts. Therefore, the engineer in charge of the optical design is confronted to the problem of using two different software's, one for the design and optimization, for example CODE V, one for stray light analysis, for example ASAP. This makes a complete optimization very complex . Nevertheless, using special techniques and combinations of the routines available in CODE V, it is possible to have at its disposal a software macro tool to do such an analysis quickly and accurately, including Monte-Carlo ray tracing, or taking into account diffraction effects. This analysis can be done in a few minutes, to be compared to hours with other software's.

  12. Accurate and fiducial-marker-free correction for three-dimensional chromatic shift in biological fluorescence microscopy.

    PubMed

    Matsuda, Atsushi; Schermelleh, Lothar; Hirano, Yasuhiro; Haraguchi, Tokuko; Hiraoka, Yasushi

    2018-05-15

    Correction of chromatic shift is necessary for precise registration of multicolor fluorescence images of biological specimens. New emerging technologies in fluorescence microscopy with increasing spatial resolution and penetration depth have prompted the need for more accurate methods to correct chromatic aberration. However, the amount of chromatic shift of the region of interest in biological samples often deviates from the theoretical prediction because of unknown dispersion in the biological samples. To measure and correct chromatic shift in biological samples, we developed a quadrisection phase correlation approach to computationally calculate translation, rotation, and magnification from reference images. Furthermore, to account for local chromatic shifts, images are split into smaller elements, for which the phase correlation between channels is measured individually and corrected accordingly. We implemented this method in an easy-to-use open-source software package, called Chromagnon, that is able to correct shifts with a 3D accuracy of approximately 15 nm. Applying this software, we quantified the level of uncertainty in chromatic shift correction, depending on the imaging modality used, and for different existing calibration methods, along with the proposed one. Finally, we provide guidelines to choose the optimal chromatic shift registration method for any given situation.

  13. Accurate elevation and normal moveout corrections of seismic reflection data on rugged topography

    USGS Publications Warehouse

    Liu, J.; Xia, J.; Chen, C.; Zhang, G.

    2005-01-01

    The application of the seismic reflection method is often limited in areas of complex terrain. The problem is the incorrect correction of time shifts caused by topography. To apply normal moveout (NMO) correction to reflection data correctly, static corrections are necessary to be applied in advance for the compensation of the time distortions of topography and the time delays from near-surface weathered layers. For environment and engineering investigation, weathered layers are our targets, so that the static correction mainly serves the adjustment of time shifts due to an undulating surface. In practice, seismic reflected raypaths are assumed to be almost vertical through the near-surface layers because they have much lower velocities than layers below. This assumption is acceptable in most cases since it results in little residual error for small elevation changes and small offsets in reflection events. Although static algorithms based on choosing a floating datum related to common midpoint gathers or residual surface-consistent functions are available and effective, errors caused by the assumption of vertical raypaths often generate pseudo-indications of structures. This paper presents the comparison of applying corrections based on the vertical raypaths and bias (non-vertical) raypaths. It also provides an approach of combining elevation and NMO corrections. The advantages of the approach are demonstrated by synthetic and real-world examples of multi-coverage seismic reflection surveys on rough topography. ?? The Royal Society of New Zealand 2005.

  14. Apparatus for and method of correcting for astigmatism in a light beam reflected off of a light reflecting surface

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sawicki, R.H.; Sweatt, W.

    1987-03-03

    An apparatus is described for correcting for astigmatism in a light beam reflected off of a light reflecting surface, comprising: (a) a first means defining a flat, rectangular light reflecting surface which is resiliently bendable, to a limited extent, into different concave and/or convex cylindrical curvatures about a particular axis. The first means is configured so that the light reflecting surface can be adjustably bent into the selected cylindrical curvature by applying a particular bending moment to the first means with respect to the surface, depending upon the curvature desired. The first means includes an integrally formed body member havingmore » a main plate-like segment including a front fact defining the light reflecting surface and a pair of spaced-apart flange segments extending rearwardly of the main segment; and (b) second means acting on the first means for adjustably bending the light reflecting surface into a particular selected one of the different cylindrical curvatures, depending upon the astigmatism to be corrected for.« less

  15. Delay time correction of the gas analyzer in the calculation of anatomical dead space of the lung.

    PubMed

    Okubo, T; Shibata, H; Takishima, T

    1983-07-01

    By means of a mathematical model, we have studied a way to correct the delay time of the gas analyzer in order to calculate the anatomical dead space using Fowler's graphical method. The mathematical model was constructed of ten tubes of equal diameter but unequal length, so that the amount of dead space varied from tube to tube; the tubes were emptied sequentially. The gas analyzer responds with a time lag from the input of the gas signal to the beginning of the response, followed by an exponential response output. The single breath expired volume-concentration relationship was examined with three types of expired flow patterns of which were constant, exponential and sinusoidal. The results indicate that the time correction by the lag time plus time constant of the exponential response of the gas analyzer gives an accurate estimation of anatomical dead space. Time correction less inclusive than this, e.g. lag time only or lag time plus 50% response time, gives an overestimation, and a correction larger than this results in underestimation. The magnitude of error is dependent on the flow pattern and flow rate. The time correction in this study is only for the calculation of dead space, as the corrected volume-concentration curves does not coincide with the true curve. Such correction of the output of the gas analyzer is extremely important when one needs to compare the dead spaces of different gas species at a rather faster flow rate.

  16. Modeling boundary measurements of scattered light using the corrected diffusion approximation

    PubMed Central

    Lehtikangas, Ossi; Tarvainen, Tanja; Kim, Arnold D.

    2012-01-01

    We study the modeling and simulation of steady-state measurements of light scattered by a turbid medium taken at the boundary. In particular, we implement the recently introduced corrected diffusion approximation in two spatial dimensions to model these boundary measurements. This implementation uses expansions in plane wave solutions to compute boundary conditions and the additive boundary layer correction, and a finite element method to solve the diffusion equation. We show that this corrected diffusion approximation models boundary measurements substantially better than the standard diffusion approximation in comparison to numerical solutions of the radiative transport equation. PMID:22435102

  17. A coronagraph based on two spatial light modulators for active amplitude apodizing and phase corrections

    NASA Astrophysics Data System (ADS)

    Dou, Jiangpei; Ren, Deqing; Zhang, Xi; Zhu, Yongtian; Zhao, Gang; Wu, Zhen; Chen, Rui; Liu, Chengchao; Yang, Feng; Yang, Chao

    2014-08-01

    Almost all high-contrast imaging coronagraphs proposed until now are based on passive coronagraph optical components. Recently, Ren and Zhu proposed for the first time a coronagraph that integrates a liquid crystal array (LCA) for the active pupil apodizing and a deformable mirror (DM) for the phase corrections. Here, for demonstration purpose, we present the initial test result of a coronagraphic system that is based on two liquid crystal spatial light modulators (SLM). In the system, one SLM is served as active pupil apodizing and amplitude correction to suppress the diffraction light; another SLM is used to correct the speckle noise that is caused by the wave-front distortions. In this way, both amplitude and phase error can be actively and efficiently compensated. In the test, we use the stochastic parallel gradient descent (SPGD) algorithm to control two SLMs, which is based on the point spread function (PSF) sensing and evaluation and optimized for a maximum contrast in the discovery area. Finally, it has demonstrated a contrast of 10-6 at an inner working angular distance of ~6.2 λ/D, which is a promising technique to be used for the direct imaging of young exoplanets on ground-based telescopes.

  18. A Time-Accurate Upwind Unstructured Finite Volume Method for Compressible Flow with Cure of Pathological Behaviors

    NASA Technical Reports Server (NTRS)

    Loh, Ching Y.; Jorgenson, Philip C. E.

    2007-01-01

    A time-accurate, upwind, finite volume method for computing compressible flows on unstructured grids is presented. The method is second order accurate in space and time and yields high resolution in the presence of discontinuities. For efficiency, the Roe approximate Riemann solver with an entropy correction is employed. In the basic Euler/Navier-Stokes scheme, many concepts of high order upwind schemes are adopted: the surface flux integrals are carefully treated, a Cauchy-Kowalewski time-stepping scheme is used in the time-marching stage, and a multidimensional limiter is applied in the reconstruction stage. However even with these up-to-date improvements, the basic upwind scheme is still plagued by the so-called "pathological behaviors," e.g., the carbuncle phenomenon, the expansion shock, etc. A solution to these limitations is presented which uses a very simple dissipation model while still preserving second order accuracy. This scheme is referred to as the enhanced time-accurate upwind (ETAU) scheme in this paper. The unstructured grid capability renders flexibility for use in complex geometry; and the present ETAU Euler/Navier-Stokes scheme is capable of handling a broad spectrum of flow regimes from high supersonic to subsonic at very low Mach number, appropriate for both CFD (computational fluid dynamics) and CAA (computational aeroacoustics). Numerous examples are included to demonstrate the robustness of the methods.

  19. Dead time corrections for inbeam γ-spectroscopy measurements

    NASA Astrophysics Data System (ADS)

    Boromiza, M.; Borcea, C.; Negret, A.; Olacel, A.; Suliman, G.

    2017-08-01

    Relatively high counting rates were registered in a proton inelastic scattering experiment on 16O and 28Si using HPGe detectors which was performed at the Tandem facility of IFIN-HH, Bucharest. In consequence, dead time corrections were needed in order to determine the absolute γ-production cross sections. Considering that the real counting rate follows a Poisson distribution, the dead time correction procedure is reformulated in statistical terms. The arriving time interval between the incoming events (Δt) obeys an exponential distribution with a single parameter - the average of the associated Poisson distribution. We use this mathematical connection to calculate and implement the dead time corrections for the counting rates of the mentioned experiment. Also, exploiting an idea introduced by Pommé et al., we describe a consistent method for calculating the dead time correction which completely eludes the complicated problem of measuring the dead time of a given detection system. Several comparisons are made between the corrections implemented through this method and by using standard (phenomenological) dead time models and we show how these results were used for correcting our experimental cross sections.

  20. Impacts of Earth rotation parameters on GNSS ultra-rapid orbit prediction: Derivation and real-time correction

    NASA Astrophysics Data System (ADS)

    Wang, Qianxin; Hu, Chao; Xu, Tianhe; Chang, Guobin; Hernández Moraleda, Alberto

    2017-12-01

    Analysis centers (ACs) for global navigation satellite systems (GNSSs) cannot accurately obtain real-time Earth rotation parameters (ERPs). Thus, the prediction of ultra-rapid orbits in the international terrestrial reference system (ITRS) has to utilize the predicted ERPs issued by the International Earth Rotation and Reference Systems Service (IERS) or the International GNSS Service (IGS). In this study, the accuracy of ERPs predicted by IERS and IGS is analyzed. The error of the ERPs predicted for one day can reach 0.15 mas and 0.053 ms in polar motion and UT1-UTC direction, respectively. Then, the impact of ERP errors on ultra-rapid orbit prediction by GNSS is studied. The methods for orbit integration and frame transformation in orbit prediction with introduced ERP errors dominate the accuracy of the predicted orbit. Experimental results show that the transformation from the geocentric celestial references system (GCRS) to ITRS exerts the strongest effect on the accuracy of the predicted ultra-rapid orbit. To obtain the most accurate predicted ultra-rapid orbit, a corresponding real-time orbit correction method is developed. First, orbits without ERP-related errors are predicted on the basis of ITRS observed part of ultra-rapid orbit for use as reference. Then, the corresponding predicted orbit is transformed from GCRS to ITRS to adjust for the predicted ERPs. Finally, the corrected ERPs with error slopes are re-introduced to correct the predicted orbit in ITRS. To validate the proposed method, three experimental schemes are designed: function extrapolation, simulation experiments, and experiments with predicted ultra-rapid orbits and international GNSS Monitoring and Assessment System (iGMAS) products. Experimental results show that using the proposed correction method with IERS products considerably improved the accuracy of ultra-rapid orbit prediction (except the geosynchronous BeiDou orbits). The accuracy of orbit prediction is enhanced by at least 50

  1. Grayscale imbalance correction in real-time phase measuring profilometry

    NASA Astrophysics Data System (ADS)

    Zhu, Lin; Cao, Yiping; He, Dawu; Chen, Cheng

    2016-10-01

    Grayscale imbalance correction in real-time phase measuring profilometry (RPMP) is proposed. In the RPMP, the sufficient information is obtained to reconstruct the 3D shape of the measured object in one over twenty-four of a second. Only one color fringe pattern whose R, G and B channels are coded as three sinusoidal phase-shifting gratings with an equivalent shifting phase of 2π/3 is sent to a flash memory on a specialized digital light projector (SDLP). And then the SDLP projects the fringe patterns in R, G and B channels sequentially onto the measured object in one over seventy-two of a second and meanwhile a monochrome CCD camera captures the corresponding deformed patterns synchronously with the SDLP. Because the deformed patterns from three color channels are captured at different time, the color crosstalk is avoided completely. But due to the monochrome CCD camera's different spectral sensitivity to R, G and B tricolor, there will be grayscale imbalance among these deformed patterns captured at R, G and B channels respectively which may result in increasing measuring errors or even failing to reconstruct the 3D shape. So a new grayscale imbalance correction method based on least square method is developed. The experimental results verify the feasibility of the proposed method.

  2. 28 CFR 523.13 - Community corrections center good time.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... ADMISSION, CLASSIFICATION, AND TRANSFER COMPUTATION OF SENTENCE Extra Good Time § 523.13 Community corrections center good time. Extra good time for an inmate in a Federal or contract Community Corrections... 28 Judicial Administration 2 2011-07-01 2011-07-01 false Community corrections center good time...

  3. 28 CFR 523.13 - Community corrections center good time.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... ADMISSION, CLASSIFICATION, AND TRANSFER COMPUTATION OF SENTENCE Extra Good Time § 523.13 Community corrections center good time. Extra good time for an inmate in a Federal or contract Community Corrections... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Community corrections center good time...

  4. 28 CFR 523.13 - Community corrections center good time.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... ADMISSION, CLASSIFICATION, AND TRANSFER COMPUTATION OF SENTENCE Extra Good Time § 523.13 Community corrections center good time. Extra good time for an inmate in a Federal or contract Community Corrections... 28 Judicial Administration 2 2014-07-01 2014-07-01 false Community corrections center good time...

  5. 28 CFR 523.13 - Community corrections center good time.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... ADMISSION, CLASSIFICATION, AND TRANSFER COMPUTATION OF SENTENCE Extra Good Time § 523.13 Community corrections center good time. Extra good time for an inmate in a Federal or contract Community Corrections... 28 Judicial Administration 2 2012-07-01 2012-07-01 false Community corrections center good time...

  6. 28 CFR 523.13 - Community corrections center good time.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... ADMISSION, CLASSIFICATION, AND TRANSFER COMPUTATION OF SENTENCE Extra Good Time § 523.13 Community corrections center good time. Extra good time for an inmate in a Federal or contract Community Corrections... 28 Judicial Administration 2 2013-07-01 2013-07-01 false Community corrections center good time...

  7. Travel-time source-specific station correction improves location accuracy

    NASA Astrophysics Data System (ADS)

    Giuntini, Alessandra; Materni, Valerio; Chiappini, Stefano; Carluccio, Roberto; Console, Rodolfo; Chiappini, Massimo

    2013-04-01

    Accurate earthquake locations are crucial for investigating seismogenic processes, as well as for applications like verifying compliance to the Comprehensive Test Ban Treaty (CTBT). Earthquake location accuracy is related to the degree of knowledge about the 3-D structure of seismic wave velocity in the Earth. It is well known that modeling errors of calculated travel times may have the effect of shifting the computed epicenters far from the real locations by a distance even larger than the size of the statistical error ellipses, regardless of the accuracy in picking seismic phase arrivals. The consequences of large mislocations of seismic events in the context of the CTBT verification is particularly critical in order to trigger a possible On Site Inspection (OSI). In fact, the Treaty establishes that an OSI area cannot be larger than 1000 km2, and its larger linear dimension cannot be larger than 50 km. Moreover, depth accuracy is crucial for the application of the depth event screening criterion. In the present study, we develop a method of source-specific travel times corrections based on a set of well located events recorded by dense national seismic networks in seismically active regions. The applications concern seismic sequences recorded in Japan, Iran and Italy. We show that mislocations of the order of 10-20 km affecting the epicenters, as well as larger mislocations in hypocentral depths, calculated from a global seismic network and using the standard IASPEI91 travel times can be effectively removed by applying source-specific station corrections.

  8. Fixing the Leak: Empirical Corrections for the Small Light Leak in Hinode XRT

    NASA Astrophysics Data System (ADS)

    Saar, Steven H.; DeLuca, E. E.; McCauley, P.; Kobelski, A.

    2013-07-01

    On May 9, 2012, the the straylight level of XRT on Hinode suddenly increased, consistent with the appearance of a pinhole in the entrance filter (possibly a micrometeorite breach). The effect of this event is most noticeable in the optical G band data, which shows an average light excess of ~30%. However, data in several of the X-ray filters is also affected, due to low sensitivity "tails" of their filter responses into the visible. Observations taken with the G band filter but with the visible light shutter (VLS) closed show a weak, slightly shifted, out-of-focus image, revealing the leaked light. The intensity of the leak depends on telescope pointing, dropping strongly for images taken off-disk. By monitoring light levels in the corners of full-Sun Ti-poly filter images, we determine the approximate time of the event: ~13:30 UT. We use pairs of images taken just-before and after the filter breach to directly measure the leakage in two affected X-ray filters. We then develop a model using a scaled, shifted, and smoothed versions of the VLS closed images to remove the contamination. We estimate the uncertainties involved in our proposed correction procedure. This research was supported under NASA contract NNM07AB07C for Hinode XRT.

  9. Chromatic aberration correction: an enhancement to the calibration of low-cost digital dermoscopes.

    PubMed

    Wighton, Paul; Lee, Tim K; Lui, Harvey; McLean, David; Atkins, M Stella

    2011-08-01

    We present a method for calibrating low-cost digital dermoscopes that corrects for color and inconsistent lighting and also corrects for chromatic aberration. Chromatic aberration is a form of radial distortion that often occurs in inexpensive digital dermoscopes and creates red and blue halo-like effects on edges. Being radial in nature, distortions due to chromatic aberration are not constant across the image, but rather vary in both magnitude and direction. As a result, distortions are not only visually distracting but could also mislead automated characterization techniques. Two low-cost dermoscopes, based on different consumer-grade cameras, were tested. Color is corrected by imaging a reference and applying singular value decomposition to determine the transformation required to ensure accurate color reproduction. Lighting is corrected by imaging a uniform surface and creating lighting correction maps. Chromatic aberration is corrected using a second-order radial distortion model. Our results for color and lighting calibration are consistent with previously published results, while distortions due to chromatic aberration can be reduced by 42-47% in the two systems considered. The disadvantages of inexpensive dermoscopy can be quickly substantially mitigated with a suitable calibration procedure. © 2011 John Wiley & Sons A/S.

  10. High-Resolution Light Transmission Spectroscopy of Nanoparticles in Real Time

    NASA Astrophysics Data System (ADS)

    Tanner, Carol; Sun, Nan; Deatsch, Alison; Li, Frank; Ruggiero, Steven

    2017-04-01

    As implemented here, Light Transmission Spectroscopy (LTS) is a high-resolution real-time technique for eliminating spectral noise and systematic effects in wide band spectroscopic measurements of nanoparticles. In this work, we combine LTS with spectral inversion for the purpose of characterizing the size, shape, and number of nanoparticles in solution. The apparatus employs a wide-band multi-wavelength light source and grating spectrometers coupled to CCD detectors. The light source ranges from 210 to 2000 nm, and the wavelength dependent light detection system ranges from 200 to 1100 nm with <=1 nm resolution. With this system, nanoparticles ranging from 1 to 3000 nm diameters can be studied. The nanoparticles are typically suspended in pure water or water-based buffer solutions. For testing and calibration purposes, results are presented for nanoparticles composed of polystyrene and gold. Mie theory is used to model the total extinction cross-section, and spectral inversion is employed to obtain quantitative particle size distributions. Discussed are the precision, accuracy, resolution, and sensitivity of our results. The technique is quite versatile and can be applied to spectroscopic investigations where wideband, accurate, low-noise, real-time spectra are desired. University of Notre Dame Office of Research, College of Science, Department of Physics, and USDA.

  11. Algorithms for computing the time-corrected instantaneous frequency (reassigned) spectrogram, with applications.

    PubMed

    Fulop, Sean A; Fitz, Kelly

    2006-01-01

    A modification of the spectrogram (log magnitude of the short-time Fourier transform) to more accurately show the instantaneous frequencies of signal components was first proposed in 1976 [Kodera et al., Phys. Earth Planet. Inter. 12, 142-150 (1976)], and has been considered or reinvented a few times since but never widely adopted. This paper presents a unified theoretical picture of this time-frequency analysis method, the time-corrected instantaneous frequency spectrogram, together with detailed implementable algorithms comparing three published techniques for its computation. The new representation is evaluated against the conventional spectrogram for its superior ability to track signal components. The lack of a uniform framework for either mathematics or implementation details which has characterized the disparate literature on the schemes has been remedied here. Fruitful application of the method is shown in the realms of speech phonation analysis, whale song pitch tracking, and additive sound modeling.

  12. High accurate time system of the Low Latitude Meridian Circle.

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Wang, Feng; Li, Zhiming

    In order to obtain the high accurate time signal for the Low Latitude Meridian Circle (LLMC), a new GPS accurate time system is developed which include GPS, 1 MC frequency source and self-made clock system. The second signal of GPS is synchronously used in the clock system and information can be collected by a computer automatically. The difficulty of the cancellation of the time keeper can be overcomed by using this system.

  13. Multigrid time-accurate integration of Navier-Stokes equations

    NASA Technical Reports Server (NTRS)

    Arnone, Andrea; Liou, Meng-Sing; Povinelli, Louis A.

    1993-01-01

    Efficient acceleration techniques typical of explicit steady-state solvers are extended to time-accurate calculations. Stability restrictions are greatly reduced by means of a fully implicit time discretization. A four-stage Runge-Kutta scheme with local time stepping, residual smoothing, and multigridding is used instead of traditional time-expensive factorizations. Some applications to natural and forced unsteady viscous flows show the capability of the procedure.

  14. Renal contrast-enhanced MR angiography: timing errors and accurate depiction of renal artery origins.

    PubMed

    Schmidt, Maria A; Morgan, Robert

    2008-10-01

    To investigate bolus timing artifacts that impair depiction of renal arteries at contrast material-enhanced magnetic resonance (MR) angiography and to determine the effect of contrast agent infusion rates on artifact generation. Renal contrast-enhanced MR angiography was simulated for a variety of infusion schemes, assuming both correct and incorrect timing between data acquisition and contrast agent injection. In addition, the ethics committee approved the retrospective evaluation of clinical breath-hold renal contrast-enhanced MR angiographic studies obtained with automated detection of contrast agent arrival. Twenty-two studies were evaluated for their ability to depict the origin of renal arteries in patent vessels and for any signs of timing errors. Simulations showed that a completely artifactual stenosis or an artifactual overestimation of an existing stenosis at the renal artery origin can be caused by timing errors of the order of 5 seconds in examinations performed with contrast agent infusion rates compatible with or higher than those of hand injections. Lower infusion rates make the studies more likely to accurately depict the origin of the renal arteries. In approximately one-third of all clinical examinations, different contrast agent uptake rates were detected on the left and right sides of the body, and thus allowed us to confirm that it is often impossible to optimize depiction of both renal arteries. In three renal arteries, a signal void was found at the origin in a patent vessel, and delayed contrast agent arrival was confirmed. Computer simulations and clinical examinations showed that timing errors impair the accurate depiction of renal artery origins. (c) RSNA, 2008.

  15. Lightdrum—Portable Light Stage for Accurate BTF Measurement on Site

    PubMed Central

    Havran, Vlastimil; Hošek, Jan; Němcová, Šárka; Čáp, Jiří; Bittner, Jiří

    2017-01-01

    We propose a miniaturised light stage for measuring the bidirectional reflectance distribution function (BRDF) and the bidirectional texture function (BTF) of surfaces on site in real world application scenarios. The main principle of our lightweight BTF acquisition gantry is a compact hemispherical skeleton with cameras along the meridian and with light emitting diode (LED) modules shining light onto a sample surface. The proposed device is portable and achieves a high speed of measurement while maintaining high degree of accuracy. While the positions of the LEDs are fixed on the hemisphere, the cameras allow us to cover the range of the zenith angle from 0∘ to 75∘ and by rotating the cameras along the axis of the hemisphere we can cover all possible camera directions. This allows us to take measurements with almost the same quality as existing stationary BTF gantries. Two degrees of freedom can be set arbitrarily for measurements and the other two degrees of freedom are fixed, which provides a tradeoff between accuracy of measurements and practical applicability. Assuming that a measured sample is locally flat and spatially accessible, we can set the correct perpendicular direction against the measured sample by means of an auto-collimator prior to measuring. Further, we have designed and used a marker sticker method to allow for the easy rectification and alignment of acquired images during data processing. We show the results of our approach by images rendered for 36 measured material samples. PMID:28241466

  16. Implementation of real-time nonuniformity correction with multiple NUC tables using FPGA in an uncooled imaging system

    NASA Astrophysics Data System (ADS)

    Oh, Gyong Jin; Kim, Lyang-June; Sheen, Sue-Ho; Koo, Gyou-Phyo; Jin, Sang-Hun; Yeo, Bo-Yeon; Lee, Jong-Ho

    2009-05-01

    This paper presents a real time implementation of Non Uniformity Correction (NUC). Two point correction and one point correction with shutter were carried out in an uncooled imaging system which will be applied to a missile application. To design a small, light weight and high speed imaging system for a missile system, SoPC (System On a Programmable Chip) which comprises of FPGA and soft core (Micro-blaze) was used. Real time NUC and generation of control signals are implemented using FPGA. Also, three different NUC tables were made to make the operating time shorter and to reduce the power consumption in a large range of environment temperature. The imaging system consists of optics and four electronics boards which are detector interface board, Analog to Digital converter board, Detector signal generation board and Power supply board. To evaluate the imaging system, NETD was measured. The NETD was less than 160mK in three different environment temperatures.

  17. Influence of accurate and inaccurate 'split-time' feedback upon 10-mile time trial cycling performance.

    PubMed

    Wilson, Mathew G; Lane, Andy M; Beedie, Chris J; Farooq, Abdulaziz

    2012-01-01

    The objective of the study is to examine the impact of accurate and inaccurate 'split-time' feedback upon a 10-mile time trial (TT) performance and to quantify power output into a practically meaningful unit of variation. Seven well-trained cyclists completed four randomised bouts of a 10-mile TT on a SRM™ cycle ergometer. TTs were performed with (1) accurate performance feedback, (2) without performance feedback, (3) and (4) false negative and false positive 'split-time' feedback showing performance 5% slower or 5% faster than actual performance. There were no significant differences in completion time, average power output, heart rate or blood lactate between the four feedback conditions. There were significantly lower (p < 0.001) average [Formula: see text] (ml min(-1)) and [Formula: see text] (l min(-1)) scores in the false positive (3,485 ± 596; 119 ± 33) and accurate (3,471 ± 513; 117 ± 22) feedback conditions compared to the false negative (3,753 ± 410; 127 ± 27) and blind (3,772 ± 378; 124 ± 21) feedback conditions. Cyclists spent a greater amount of time in a '20 watt zone' 10 W either side of average power in the negative feedback condition (fastest) than the accurate feedback (slowest) condition (39.3 vs. 32.2%, p < 0.05). There were no significant differences in the 10-mile TT performance time between accurate and inaccurate feedback conditions, despite significantly lower average [Formula: see text] and [Formula: see text] scores in the false positive and accurate feedback conditions. Additionally, cycling with a small variation in power output (10 W either side of average power) produced the fastest TT. Further psycho-physiological research should examine the mechanism(s) why lower [Formula: see text] and [Formula: see text] scores are observed when cycling in a false positive or accurate feedback condition compared to a false negative or blind feedback condition.

  18. Correlation of carotid blood flow and corrected carotid flow time with invasive cardiac output measurements.

    PubMed

    Ma, Irene W Y; Caplin, Joshua D; Azad, Aftab; Wilson, Christina; Fifer, Michael A; Bagchi, Aranya; Liteplo, Andrew S; Noble, Vicki E

    2017-12-01

    Non-invasive measures that can accurately estimate cardiac output may help identify volume-responsive patients. This study seeks to compare two non-invasive measures (corrected carotid flow time and carotid blood flow) and their correlations with invasive reference measurements of cardiac output. Consenting adult patients (n = 51) at Massachusetts General Hospital cardiac catheterization laboratory undergoing right heart catheterization between February and April 2016 were included. Carotid ultrasound images were obtained concurrently with cardiac output measurements, obtained by the thermodilution method in the absence of severe tricuspid regurgitation and by the Fick oxygen method otherwise. Corrected carotid flow time was calculated as systole time/√cycle time. Carotid blood flow was calculated as π × (carotid diameter) 2 /4 × velocity time integral × heart rate. Measurements were obtained using a single carotid waveform and an average of three carotid waveforms for both measures. Single waveform measurements of corrected flow time did not correlate with cardiac output (ρ = 0.25, 95% CI -0.03 to 0.49, p = 0.08), but an average of three waveforms correlated significantly, although weakly (ρ = 0.29, 95% CI 0.02-0.53, p = 0.046). Carotid blood flow measurements correlated moderately with cardiac output regardless of if single waveform or an average of three waveforms were used: ρ = 0.44, 95% CI 0.18-0.63, p = 0.004, and ρ = 0.41, 95% CI 0.16-0.62, p = 0.004, respectively. Carotid blood flow may be a better marker of cardiac output and less subject to measurements issues than corrected carotid flow time.

  19. Pupil Tracking for Real-Time Motion Corrected Anterior Segment Optical Coherence Tomography

    PubMed Central

    Carrasco-Zevallos, Oscar M.; Nankivil, Derek; Viehland, Christian; Keller, Brenton; Izatt, Joseph A.

    2016-01-01

    Volumetric acquisition with anterior segment optical coherence tomography (ASOCT) is necessary to obtain accurate representations of the tissue structure and to account for asymmetries of the anterior eye anatomy. Additionally, recent interest in imaging of anterior segment vasculature and aqueous humor flow resulted in application of OCT angiography techniques to generate en face and 3D micro-vasculature maps of the anterior segment. Unfortunately, ASOCT structural and vasculature imaging systems do not capture volumes instantaneously and are subject to motion artifacts due to involuntary eye motion that may hinder their accuracy and repeatability. Several groups have demonstrated real-time tracking for motion-compensated in vivo OCT retinal imaging, but these techniques are not applicable in the anterior segment. In this work, we demonstrate a simple and low-cost pupil tracking system integrated into a custom swept-source OCT system for real-time motion-compensated anterior segment volumetric imaging. Pupil oculography hardware coaxial with the swept-source OCT system enabled fast detection and tracking of the pupil centroid. The pupil tracking ASOCT system with a field of view of 15 x 15 mm achieved diffraction-limited imaging over a lateral tracking range of +/- 2.5 mm and was able to correct eye motion at up to 22 Hz. Pupil tracking ASOCT offers a novel real-time motion compensation approach that may facilitate accurate and reproducible anterior segment imaging. PMID:27574800

  20. Differential Effects of Focused and Unfocused Written Correction on the Accurate Use of Grammatical Forms by Adult ESL Learners

    ERIC Educational Resources Information Center

    Sheen, Younghee; Wright, David; Moldawa, Anna

    2009-01-01

    Building on Sheen's (2007) study of the effects of written corrective feedback (CF) on the acquisition of English articles, this article investigated whether direct focused CF, direct unfocused CF and writing practice alone produced differential effects on the accurate use of grammatical forms by adult ESL learners. Using six intact adult ESL…

  1. Time-dependent phase error correction using digital waveform synthesis

    DOEpatents

    Doerry, Armin W.; Buskirk, Stephen

    2017-10-10

    The various technologies presented herein relate to correcting a time-dependent phase error generated as part of the formation of a radar waveform. A waveform can be pre-distorted to facilitate correction of an error induced into the waveform by a downstream operation/component in a radar system. For example, amplifier power droop effect can engender a time-dependent phase error in a waveform as part of a radar signal generating operation. The error can be quantified and an according complimentary distortion can be applied to the waveform to facilitate negation of the error during the subsequent processing of the waveform. A time domain correction can be applied by a phase error correction look up table incorporated into a waveform phase generator.

  2. Mobility-based correction for accurate determination of binding constants by capillary electrophoresis-frontal analysis.

    PubMed

    Qian, Cheng; Kovalchik, Kevin A; MacLennan, Matthew S; Huang, Xiaohua; Chen, David D Y

    2017-06-01

    Capillary electrophoresis frontal analysis (CE-FA) can be used to determine binding affinity of molecular interactions. However, its current data processing method mandate specific requirement on the mobilities of the binding pair in order to obtain accurate binding constants. This work shows that significant errors are resulted when the mobilities of the interacting species do not meet these requirements. Therefore, the applicability of CE-FA in many real word applications becomes questionable. An electrophoretic mobility-based correction method is developed in this work based on the flux of each species. A simulation program and a pair of model compounds are used to verify the new equations and evaluate the effectiveness of this method. Ibuprofen and hydroxypropyl-β-cyclodextrinare used to demonstrate the differences in the obtained binding constant by CE-FA when different calculation methods are used, and the results are compared with those obtained by affinity capillary electrophoresis (ACE). The results suggest that CE-FA, with the mobility-based correction method, can be a generally applicable method for a much wider range of applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Time-of-day Corrections to Aircraft Noise Metrics

    NASA Technical Reports Server (NTRS)

    Clevenson, S. (Editor); Shepherd, W. T. (Editor)

    1980-01-01

    The historical and background aspects of time-of-day corrections as well as the evidence supporting these corrections are discussed. Health, welfare, and economic impacts, needs a criteria, and government policy and regulation, are also reported.

  4. Spatio-thermal depth correction of RGB-D sensors based on Gaussian processes in real-time

    NASA Astrophysics Data System (ADS)

    Heindl, Christoph; Pönitz, Thomas; Stübl, Gernot; Pichler, Andreas; Scharinger, Josef

    2018-04-01

    Commodity RGB-D sensors capture color images along with dense pixel-wise depth information in real-time. Typical RGB-D sensors are provided with a factory calibration and exhibit erratic depth readings due to coarse calibration values, ageing and thermal influence effects. This limits their applicability in computer vision and robotics. We propose a novel method to accurately calibrate depth considering spatial and thermal influences jointly. Our work is based on Gaussian Process Regression in a four dimensional Cartesian and thermal domain. We propose to leverage modern GPUs for dense depth map correction in real-time. For reproducibility we make our dataset and source code publicly available.

  5. Temperature and salinity correction coefficients for light absorption by water in the visible to infrared spectral region.

    PubMed

    Röttgers, Rüdiger; McKee, David; Utschig, Christian

    2014-10-20

    The light absorption coefficient of water is dependent on temperature and concentration of ions, i.e. the salinity in seawater. Accurate knowledge of the water absorption coefficient, a, and/or its temperature and salinity correction coefficients, Ψ(T) and Ψ(S), respectively, is essential for a wide range of optical applications. Values are available from published data only at specific narrow wavelength ranges or at single wavelengths in the visible and infrared regions. Ψ(T) and Ψ(S) were therefore spectrophotometrically measured throughout the visible, near, and short wavelength infrared spectral region (400 to ~2700 nm). Additionally, they were derived from more precise measurements with a point-source integrating-cavity absorption meter (PSICAM) for 400 to 700 nm. When combined with earlier measurements from the literature in the range of 2600 - 14000 nm (wavenumber: 3800 - 700 cm(-1)), the coefficients are provided for 400 to 14000 nm (wavenumber: 25000 to 700 cm(-1)).

  6. A Scattered Light Correction to Color Images Taken of Europa by the Galileo Spacecraft: Initial Results

    NASA Astrophysics Data System (ADS)

    Phillips, C. B.; Valenti, M.

    2009-12-01

    Jupiter's moon Europa likely possesses an ocean of liquid water beneath its icy surface, but estimates of the thickness of the surface ice shell vary from a few kilometers to tens of kilometers. Color images of Europa reveal the existence of a reddish, non-ice component associated with a variety of geological features. The composition and origin of this material is uncertain, as is its relationship to Europa's various landforms. Published analyses of Galileo Near Infrared Mapping Spectrometer (NIMS) observations indicate the presence of highly hydrated sulfate compounds. This non-ice material may also bear biosignatures or other signs of biotic material. Additional spectral information from the Galileo Solid State Imager (SSI) could further elucidate the nature of the surface deposits, particularly when combined with information from the NIMS. However, little effort has been focused on this approach because proper calibration of the color image data is challenging, requiring both skill and patience to process the data and incorporate the appropriate scattered light correction. We are currently working to properly calibrate the color SSI data. The most important and most difficult issue to address in the analysis of multispectral SSI data entails using thorough calibrations and a correction for scattered light. Early in the Galileo mission, studies of the Galileo SSI data for the moon revealed discrepancies of up to 10% in relative reflectance between images containing scattered light and images corrected for scattered light. Scattered light adds a wavelength-dependent low-intensity brightness factor to pixels across an image. For example, a large bright geological feature located just outside the field of view of an image will scatter extra light onto neighboring pixels within the field of view. Scattered light can be seen as a dim halo surrounding an image that includes a bright limb, and can also come from light scattered inside the camera by dirt, edges, and the

  7. Light-Field Correction for Spatial Calibration of Optical See-Through Head-Mounted Displays.

    PubMed

    Itoh, Yuta; Klinker, Gudrun

    2015-04-01

    A critical requirement for AR applications with Optical See-Through Head-Mounted Displays (OST-HMD) is to project 3D information correctly into the current viewpoint of the user - more particularly, according to the user's eye position. Recently-proposed interaction-free calibration methods [16], [17] automatically estimate this projection by tracking the user's eye position, thereby freeing users from tedious manual calibrations. However, the method is still prone to contain systematic calibration errors. Such errors stem from eye-/HMD-related factors and are not represented in the conventional eye-HMD model used for HMD calibration. This paper investigates one of these factors - the fact that optical elements of OST-HMDs distort incoming world-light rays before they reach the eye, just as corrective glasses do. Any OST-HMD requires an optical element to display a virtual screen. Each such optical element has different distortions. Since users see a distorted world through the element, ignoring this distortion degenerates the projection quality. We propose a light-field correction method, based on a machine learning technique, which compensates the world-scene distortion caused by OST-HMD optics. We demonstrate that our method reduces the systematic error and significantly increases the calibration accuracy of the interaction-free calibration.

  8. Extracting Time-Accurate Acceleration Vectors From Nontrivial Accelerometer Arrangements.

    PubMed

    Franck, Jennifer A; Blume, Janet; Crisco, Joseph J; Franck, Christian

    2015-09-01

    Sports-related concussions are of significant concern in many impact sports, and their detection relies on accurate measurements of the head kinematics during impact. Among the most prevalent recording technologies are videography, and more recently, the use of single-axis accelerometers mounted in a helmet, such as the HIT system. Successful extraction of the linear and angular impact accelerations depends on an accurate analysis methodology governed by the equations of motion. Current algorithms are able to estimate the magnitude of acceleration and hit location, but make assumptions about the hit orientation and are often limited in the position and/or orientation of the accelerometers. The newly formulated algorithm presented in this manuscript accurately extracts the full linear and rotational acceleration vectors from a broad arrangement of six single-axis accelerometers directly from the governing set of kinematic equations. The new formulation linearizes the nonlinear centripetal acceleration term with a finite-difference approximation and provides a fast and accurate solution for all six components of acceleration over long time periods (>250 ms). The approximation of the nonlinear centripetal acceleration term provides an accurate computation of the rotational velocity as a function of time and allows for reconstruction of a multiple-impact signal. Furthermore, the algorithm determines the impact location and orientation and can distinguish between glancing, high rotational velocity impacts, or direct impacts through the center of mass. Results are shown for ten simulated impact locations on a headform geometry computed with three different accelerometer configurations in varying degrees of signal noise. Since the algorithm does not require simplifications of the actual impacted geometry, the impact vector, or a specific arrangement of accelerometer orientations, it can be easily applied to many impact investigations in which accurate kinematics need

  9. Time-Accurate, Unstructured-Mesh Navier-Stokes Computations with the Space-Time CESE Method

    NASA Technical Reports Server (NTRS)

    Chang, Chau-Lyan

    2006-01-01

    Application of the newly emerged space-time conservation element solution element (CESE) method to compressible Navier-Stokes equations is studied. In contrast to Euler equations solvers, several issues such as boundary conditions, numerical dissipation, and grid stiffness warrant systematic investigations and validations. Non-reflecting boundary conditions applied at the truncated boundary are also investigated from the stand point of acoustic wave propagation. Validations of the numerical solutions are performed by comparing with exact solutions for steady-state as well as time-accurate viscous flow problems. The test cases cover a broad speed regime for problems ranging from acoustic wave propagation to 3D hypersonic configurations. Model problems pertinent to hypersonic configurations demonstrate the effectiveness of the CESE method in treating flows with shocks, unsteady waves, and separations. Good agreement with exact solutions suggests that the space-time CESE method provides a viable alternative for time-accurate Navier-Stokes calculations of a broad range of problems.

  10. Distance error correction for time-of-flight cameras

    NASA Astrophysics Data System (ADS)

    Fuersattel, Peter; Schaller, Christian; Maier, Andreas; Riess, Christian

    2017-06-01

    The measurement accuracy of time-of-flight cameras is limited due to properties of the scene and systematic errors. These errors can accumulate to multiple centimeters which may limit the applicability of these range sensors. In the past, different approaches have been proposed for improving the accuracy of these cameras. In this work, we propose a new method that improves two important aspects of the range calibration. First, we propose a new checkerboard which is augmented by a gray-level gradient. With this addition it becomes possible to capture the calibration features for intrinsic and distance calibration at the same time. The gradient strip allows to acquire a large amount of distance measurements for different surface reflectivities, which results in more meaningful training data. Second, we present multiple new features which are used as input to a random forest regressor. By using random regression forests, we circumvent the problem of finding an accurate model for the measurement error. During application, a correction value for each individual pixel is estimated with the trained forest based on a specifically tailored feature vector. With our approach the measurement error can be reduced by more than 40% for the Mesa SR4000 and by more than 30% for the Microsoft Kinect V2. In our evaluation we also investigate the impact of the individual forest parameters and illustrate the importance of the individual features.

  11. A Technique for Real-Time Ionospheric Ranging Error Correction Based On Radar Dual-Frequency Detection

    NASA Astrophysics Data System (ADS)

    Lyu, Jiang-Tao; Zhou, Chen

    2017-12-01

    Ionospheric refraction is one of the principal error sources for limiting the accuracy of radar systems for space target detection. High-accuracy measurement of the ionospheric electron density along the propagation path of radar wave is the most important procedure for the ionospheric refraction correction. Traditionally, the ionospheric model and the ionospheric detection instruments, like ionosonde or GPS receivers, are employed for obtaining the electron density. However, both methods are not capable of satisfying the requirements of correction accuracy for the advanced space target radar system. In this study, we propose a novel technique for ionospheric refraction correction based on radar dual-frequency detection. Radar target range measurements at two adjacent frequencies are utilized for calculating the electron density integral exactly along the propagation path of the radar wave, which can generate accurate ionospheric range correction. The implementation of radar dual-frequency detection is validated by a P band radar located in midlatitude China. The experimental results present that the accuracy of this novel technique is more accurate than the traditional ionospheric model correction. The technique proposed in this study is very promising for the high-accuracy radar detection and tracking of objects in geospace.

  12. Accuracy analysis for triangulation and tracking based on time-multiplexed structured light.

    PubMed

    Wagner, Benjamin; Stüber, Patrick; Wissel, Tobias; Bruder, Ralf; Schweikard, Achim; Ernst, Floris

    2014-08-01

    The authors' research group is currently developing a new optical head tracking system for intracranial radiosurgery. This tracking system utilizes infrared laser light to measure features of the soft tissue on the patient's forehead. These features are intended to offer highly accurate registration with respect to the rigid skull structure by means of compensating for the soft tissue. In this context, the system also has to be able to quickly generate accurate reconstructions of the skin surface. For this purpose, the authors have developed a laser scanning device which uses time-multiplexed structured light to triangulate surface points. The accuracy of the authors' laser scanning device is analyzed and compared for different triangulation methods. These methods are given by the Linear-Eigen method and a nonlinear least squares method. Since Microsoft's Kinect camera represents an alternative for fast surface reconstruction, the authors' results are also compared to the triangulation accuracy of the Kinect device. Moreover, the authors' laser scanning device was used for tracking of a rigid object to determine how this process is influenced by the remaining triangulation errors. For this experiment, the scanning device was mounted to the end-effector of a robot to be able to calculate a ground truth for the tracking. The analysis of the triangulation accuracy of the authors' laser scanning device revealed a root mean square (RMS) error of 0.16 mm. In comparison, the analysis of the triangulation accuracy of the Kinect device revealed a RMS error of 0.89 mm. It turned out that the remaining triangulation errors only cause small inaccuracies for the tracking of a rigid object. Here, the tracking accuracy was given by a RMS translational error of 0.33 mm and a RMS rotational error of 0.12°. This paper shows that time-multiplexed structured light can be used to generate highly accurate reconstructions of surfaces. Furthermore, the reconstructed point sets can be

  13. Correction for the detector-dead-time effect on the second-order correlation of stationary sub-Poissonian light in a two-detector configuration

    NASA Astrophysics Data System (ADS)

    Ann, Byoung-moo; Song, Younghoon; Kim, Junki; Yang, Daeho; An, Kyungwon

    2015-08-01

    Exact measurement of the second-order correlation function g(2 )(t ) of a light source is essential when investigating the photon statistics and the light generation process of the source. For a stationary single-mode light source, the Mandel Q factor is directly related to g(2 )(0 ) . For a large mean photon number in the mode, the deviation of g(2 )(0 ) from unity is so small that even a tiny error in measuring g(2 )(0 ) would result in an inaccurate Mandel Q . In this work, we address the detector-dead-time effect on g(2 )(0 ) of stationary sub-Poissonian light. It is then found that detector dead time can induce a serious error in g(2 )(0 ) and thus in Mandel Q in those cases even in a two-detector configuration. Utilizing the cavity-QED microlaser, a well-established sub-Poissonian light source, we measured g(2 )(0 ) with two different types of photodetectors with different dead times. We also introduced prolonged dead time by intentionally deleting the photodetection events following a preceding one within a specified time interval. We found that the observed Q of the cavity-QED microlaser was underestimated by 19% with respect to the dead-time-free Q when its mean photon number was about 600. We derived an analytic formula which well explains the behavior of the g(2 )(0 ) as a function of the dead time.

  14. Accurate Sample Time Reconstruction of Inertial FIFO Data.

    PubMed

    Stieber, Sebastian; Dorsch, Rainer; Haubelt, Christian

    2017-12-13

    In the context of modern cyber-physical systems, the accuracy of underlying sensor data plays an increasingly important role in sensor data fusion and feature extraction. The raw events of multiple sensors have to be aligned in time to enable high quality sensor fusion results. However, the growing number of simultaneously connected sensor devices make the energy saving data acquisition and processing more and more difficult. Hence, most of the modern sensors offer a first-in-first-out (FIFO) interface to store multiple data samples and to relax timing constraints, when handling multiple sensor devices. However, using the FIFO interface increases the negative influence of individual clock drifts-introduced by fabrication inaccuracies, temperature changes and wear-out effects-onto the sampling data reconstruction. Furthermore, additional timing offset errors due to communication and software latencies increases with a growing number of sensor devices. In this article, we present an approach for an accurate sample time reconstruction independent of the actual clock drift with the help of an internal sensor timer. Such timers are already available in modern sensors, manufactured in micro-electromechanical systems (MEMS) technology. The presented approach focuses on calculating accurate time stamps using the sensor FIFO interface in a forward-only processing manner as a robust and energy saving solution. The proposed algorithm is able to lower the overall standard deviation of reconstructed sampling periods below 40 μ s, while run-time savings of up to 42% are achieved, compared to single sample acquisition.

  15. Accurate tracking of tumor volume change during radiotherapy by CT-CBCT registration with intensity correction

    NASA Astrophysics Data System (ADS)

    Park, Seyoun; Robinson, Adam; Quon, Harry; Kiess, Ana P.; Shen, Colette; Wong, John; Plishker, William; Shekhar, Raj; Lee, Junghoon

    2016-03-01

    In this paper, we propose a CT-CBCT registration method to accurately predict the tumor volume change based on daily cone-beam CTs (CBCTs) during radiotherapy. CBCT is commonly used to reduce patient setup error during radiotherapy, but its poor image quality impedes accurate monitoring of anatomical changes. Although physician's contours drawn on the planning CT can be automatically propagated to daily CBCTs by deformable image registration (DIR), artifacts in CBCT often cause undesirable errors. To improve the accuracy of the registration-based segmentation, we developed a DIR method that iteratively corrects CBCT intensities by local histogram matching. Three popular DIR algorithms (B-spline, demons, and optical flow) with the intensity correction were implemented on a graphics processing unit for efficient computation. We evaluated their performances on six head and neck (HN) cancer cases. For each case, four trained scientists manually contoured the nodal gross tumor volume (GTV) on the planning CT and every other fraction CBCTs to which the propagated GTV contours by DIR were compared. The performance was also compared with commercial image registration software based on conventional mutual information (MI), VelocityAI (Varian Medical Systems Inc.). The volume differences (mean±std in cc) between the average of the manual segmentations and automatic segmentations are 3.70+/-2.30 (B-spline), 1.25+/-1.78 (demons), 0.93+/-1.14 (optical flow), and 4.39+/-3.86 (VelocityAI). The proposed method significantly reduced the estimation error by 9% (B-spline), 38% (demons), and 51% (optical flow) over the results using VelocityAI. Although demonstrated only on HN nodal GTVs, the results imply that the proposed method can produce improved segmentation of other critical structures over conventional methods.

  16. Satellite clock corrections estimation to accomplish real time ppp: experiments for brazilian real time network

    NASA Astrophysics Data System (ADS)

    Marques, Haroldo; Monico, João; Aquino, Marcio; Melo, Weyller

    2014-05-01

    The real time PPP method requires the availability of real time precise orbits and satellites clocks corrections. Currently, it is possible to apply the solutions of clocks and orbits available by BKG within the context of IGS Pilot project or by using the operational predicted IGU ephemeris. The accuracy of the satellite position available in the IGU is enough for several applications requiring good quality. However, the satellites clocks corrections do not provide enough accuracy (3 ns ~ 0.9 m) to accomplish real time PPP with the same level of accuracy. Therefore, for real time PPP application it is necessary to further research and develop appropriated methodologies for estimating the satellite clock corrections in real time with better accuracy. Currently, it is possible to apply the real time solutions of clocks and orbits available by Federal Agency for Cartography and Geodesy (BKG) within the context of IGS Pilot project. The BKG corrections are disseminated by a new proposed format of the RTCM 3.x and can be applied in the broadcasted orbits and clocks. Some investigations have been proposed for the estimation of the satellite clock corrections using GNSS code and phase observable at the double difference level between satellites and epochs (MERVAT, DOUSA, 2007). Another possibility consists of applying a Kalman Filter in the PPP network mode (HAUSCHILD, 2010) and it is also possible the integration of both methods, using network PPP and observables at double difference level in specific time intervals (ZHANG; LI; GUO, 2010). For this work the methodology adopted consists in the estimation of the satellite clock corrections based on the data adjustment in the PPP mode, but for a network of GNSS stations. The clock solution can be solved by using two types of observables: code smoothed by carrier phase or undifferenced code together with carrier phase. In the former, we estimate receiver clock error; satellite clock correction and troposphere, considering

  17. Publisher Correction: Anderson light localization in biological nanostructures of native silk.

    PubMed

    Choi, Seung Ho; Kim, Seong-Wan; Ku, Zahyun; Visbal-Onufrak, Michelle A; Kim, Seong-Ryul; Choi, Kwang-Ho; Ko, Hakseok; Choi, Wonshik; Urbas, Augustine M; Goo, Tae-Won; Kim, Young L

    2018-03-19

    The original PDF version of this Article contained errors in Equations 1 and 2. Both equations omitted all Γ terms. This has been corrected in the PDF version of the Article. The HTML version was correct from the time of publication.

  18. Correction of ultrasonic wave aberration with a time delay and amplitude filter.

    PubMed

    Måsøy, Svein-Erik; Johansen, Tonni F; Angelsen, Bjørn

    2003-04-01

    Two-dimensional simulations with propagation through two different heterogeneous human body wall models have been performed to analyze different correction filters for ultrasonic wave aberration due to forward wave propagation. The different models each produce most of the characteristic aberration effects such as phase aberration, relatively strong amplitude aberration, and waveform deformation. Simulations of wave propagation from a point source in the focus (60 mm) of a 20 mm transducer through the body wall models were performed. Center frequency of the pulse was 2.5 MHz. Corrections of the aberrations introduced by the two body wall models were evaluated with reference to the corrections obtained with the optimal filter: a generalized frequency-dependent phase and amplitude correction filter [Angelsen, Ultrasonic Imaging (Emantec, Norway, 2000), Vol. II]. Two correction filters were applied, a time delay filter, and a time delay and amplitude filter. Results showed that correction with a time delay filter produced substantial reduction of the aberration in both cases. A time delay and amplitude correction filter performed even better in both cases, and gave correction close to the ideal situation (no aberration). The results also indicated that the effect of the correction was very sensitive to the accuracy of the arrival time fluctuations estimate, i.e., the time delay correction filter.

  19. Accurate density functional prediction of molecular electron affinity with the scaling corrected Kohn–Sham frontier orbital energies

    NASA Astrophysics Data System (ADS)

    Zhang, DaDi; Yang, Xiaolong; Zheng, Xiao; Yang, Weitao

    2018-04-01

    Electron affinity (EA) is the energy released when an additional electron is attached to an atom or a molecule. EA is a fundamental thermochemical property, and it is closely pertinent to other important properties such as electronegativity and hardness. However, accurate prediction of EA is difficult with density functional theory methods. The somewhat large error of the calculated EAs originates mainly from the intrinsic delocalisation error associated with the approximate exchange-correlation functional. In this work, we employ a previously developed non-empirical global scaling correction approach, which explicitly imposes the Perdew-Parr-Levy-Balduz condition to the approximate functional, and achieve a substantially improved accuracy for the calculated EAs. In our approach, the EA is given by the scaling corrected Kohn-Sham lowest unoccupied molecular orbital energy of the neutral molecule, without the need to carry out the self-consistent-field calculation for the anion.

  20. Exemplar-based human action pose correction.

    PubMed

    Shen, Wei; Deng, Ke; Bai, Xiang; Leyvand, Tommer; Guo, Baining; Tu, Zhuowen

    2014-07-01

    The launch of Xbox Kinect has built a very successful computer vision product and made a big impact on the gaming industry. This sheds lights onto a wide variety of potential applications related to action recognition. The accurate estimation of human poses from the depth image is universally a critical step. However, existing pose estimation systems exhibit failures when facing severe occlusion. In this paper, we propose an exemplar-based method to learn to correct the initially estimated poses. We learn an inhomogeneous systematic bias by leveraging the exemplar information within a specific human action domain. Furthermore, as an extension, we learn a conditional model by incorporation of pose tags to further increase the accuracy of pose correction. In the experiments, significant improvements on both joint-based skeleton correction and tag prediction are observed over the contemporary approaches, including what is delivered by the current Kinect system. Our experiments for the facial landmark correction also illustrate that our algorithm can improve the accuracy of other detection/estimation systems.

  1. Shedding light on the variability of optical skin properties: finding a path towards more accurate prediction of light propagation in human cutaneous compartments

    PubMed Central

    Mignon, C.; Tobin, D. J.; Zeitouny, M.; Uzunbajakava, N. E.

    2018-01-01

    Finding a path towards a more accurate prediction of light propagation in human skin remains an aspiration of biomedical scientists working on cutaneous applications both for diagnostic and therapeutic reasons. The objective of this study was to investigate variability of the optical properties of human skin compartments reported in literature, to explore the underlying rational of this variability and to propose a dataset of values, to better represent an in vivo case and recommend a solution towards a more accurate prediction of light propagation through cutaneous compartments. To achieve this, we undertook a novel, logical yet simple approach. We first reviewed scientific articles published between 1981 and 2013 that reported on skin optical properties, to reveal the spread in the reported quantitative values. We found variations of up to 100-fold. Then we extracted the most trust-worthy datasets guided by a rule that the spectral properties should reflect the specific biochemical composition of each of the skin layers. This resulted in the narrowing of the spread in the calculated photon densities to 6-fold. We conclude with a recommendation to use the identified most robust datasets when estimating light propagation in human skin using Monte Carlo simulations. Alternatively, otherwise follow our proposed strategy to screen any new datasets to determine their biological relevance. PMID:29552418

  2. Accurate Attitude Estimation Using ARS under Conditions of Vehicle Movement Based on Disturbance Acceleration Adaptive Estimation and Correction

    PubMed Central

    Xing, Li; Hang, Yijun; Xiong, Zhi; Liu, Jianye; Wan, Zhong

    2016-01-01

    This paper describes a disturbance acceleration adaptive estimate and correction approach for an attitude reference system (ARS) so as to improve the attitude estimate precision under vehicle movement conditions. The proposed approach depends on a Kalman filter, where the attitude error, the gyroscope zero offset error and the disturbance acceleration error are estimated. By switching the filter decay coefficient of the disturbance acceleration model in different acceleration modes, the disturbance acceleration is adaptively estimated and corrected, and then the attitude estimate precision is improved. The filter was tested in three different disturbance acceleration modes (non-acceleration, vibration-acceleration and sustained-acceleration mode, respectively) by digital simulation. Moreover, the proposed approach was tested in a kinematic vehicle experiment as well. Using the designed simulations and kinematic vehicle experiments, it has been shown that the disturbance acceleration of each mode can be accurately estimated and corrected. Moreover, compared with the complementary filter, the experimental results have explicitly demonstrated the proposed approach further improves the attitude estimate precision under vehicle movement conditions. PMID:27754469

  3. Accurate Attitude Estimation Using ARS under Conditions of Vehicle Movement Based on Disturbance Acceleration Adaptive Estimation and Correction.

    PubMed

    Xing, Li; Hang, Yijun; Xiong, Zhi; Liu, Jianye; Wan, Zhong

    2016-10-16

    This paper describes a disturbance acceleration adaptive estimate and correction approach for an attitude reference system (ARS) so as to improve the attitude estimate precision under vehicle movement conditions. The proposed approach depends on a Kalman filter, where the attitude error, the gyroscope zero offset error and the disturbance acceleration error are estimated. By switching the filter decay coefficient of the disturbance acceleration model in different acceleration modes, the disturbance acceleration is adaptively estimated and corrected, and then the attitude estimate precision is improved. The filter was tested in three different disturbance acceleration modes (non-acceleration, vibration-acceleration and sustained-acceleration mode, respectively) by digital simulation. Moreover, the proposed approach was tested in a kinematic vehicle experiment as well. Using the designed simulations and kinematic vehicle experiments, it has been shown that the disturbance acceleration of each mode can be accurately estimated and corrected. Moreover, compared with the complementary filter, the experimental results have explicitly demonstrated the proposed approach further improves the attitude estimate precision under vehicle movement conditions.

  4. Geometric optimisation of an accurate cosine correcting optic fibre coupler for solar spectral measurement.

    PubMed

    Cahuantzi, Roberto; Buckley, Alastair

    2017-09-01

    Making accurate and reliable measurements of solar irradiance is important for understanding performance in the photovoltaic energy sector. In this paper, we present design details and performance of a number of fibre optic couplers for use in irradiance measurement systems employing remote light sensors applicable for either spectrally resolved or broadband measurement. The angular and spectral characteristics of different coupler designs are characterised and compared with existing state-of-the-art commercial technology. The new coupler designs are fabricated from polytetrafluorethylene (PTFE) rods and operate through forward scattering of incident sunlight on the front surfaces of the structure into an optic fibre located in a cavity to the rear of the structure. The PTFE couplers exhibit up to 4.8% variation in scattered transmission intensity between 425 nm and 700 nm and show minimal specular reflection, making the designs accurate and reliable over the visible region. Through careful geometric optimization near perfect cosine dependence on the angular response of the coupler can be achieved. The PTFE designs represent a significant improvement over the state of the art with less than 0.01% error compared with ideal cosine response for angles of incidence up to 50°.

  5. Imaging the Atomic Position of Light Cations in a Porous Network and the Europium(III) Ion Exchange Capability by Aberration-Corrected Electron Microscopy.

    PubMed

    Mayoral, Alvaro; Hall, Reece M; Jackowska, Roksana; Readman, Jennifer E

    2016-12-23

    In the present work, ETS-10 microporous titanosilicate has been synthesized and its structure characterized by means of powder XRD and aberration corrected scanning transmission electron microscopy (C s -corrected STEM). For the first time, sodium ions have been imaged sitting inside the 7-membered rings. The ion-exchange capability has been tested by the inclusion of rare earth metals (Eu, Tb and Gd) to produce a luminescent material which has been studied by atomic-resolution C s -corrected STEM. The data produced has allowed unambiguous imaging of light atoms in a microporous framework as well as determining the cationic metal positions for the first time, providing evidence of the importance of advanced electron microscopy methods for the study of the local environment of metals within zeolitic supports providing unique information of both systems (guest and support) at the same time. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Position Error Covariance Matrix Validation and Correction

    NASA Technical Reports Server (NTRS)

    Frisbee, Joe, Jr.

    2016-01-01

    In order to calculate operationally accurate collision probabilities, the position error covariance matrices predicted at times of closest approach must be sufficiently accurate representations of the position uncertainties. This presentation will discuss why the Gaussian distribution is a reasonable expectation for the position uncertainty and how this assumed distribution type is used in the validation and correction of position error covariance matrices.

  7. Estimation of Population Number via Light Activities on Night-Time Satellite Images

    NASA Astrophysics Data System (ADS)

    Turan, M. K.; Yücer, E.; Sehirli, E.; Karaş, İ. R.

    2017-11-01

    Estimation and accurate assessment regarding population gets harder and harder day by day due to growth of world population in a fast manner. Estimating tendencies to settlements in cities and countries, socio-cultural development and population numbers is quite difficult. In addition to them, selection and analysis of parameters such as time, work-force and cost seems like another difficult issue. In this study, population number is guessed by evaluating light activities in İstanbul via night-time images of Turkey. By evaluating light activities between 2000 and 2010, average population per pixel is obtained. Hence, it is used to estimate population numbers in 2011, 2012 and 2013. Mean errors are concluded as 4.14 % for 2011, 3.74 % for 2012 and 3.04 % for 2013 separately. As a result of developed thresholding method, mean error is concluded as 3.64 % to estimate population number in İstanbul for next three years.

  8. Accurate T1 mapping of short T2 tissues using a three-dimensional ultrashort echo time cones actual flip angle imaging-variable repetition time (3D UTE-Cones AFI-VTR) method.

    PubMed

    Ma, Ya-Jun; Lu, Xing; Carl, Michael; Zhu, Yanchun; Szeverenyi, Nikolaus M; Bydder, Graeme M; Chang, Eric Y; Du, Jiang

    2018-08-01

    To develop an accurate T 1 measurement method for short T 2 tissues using a combination of a 3-dimensional ultrashort echo time cones actual flip angle imaging technique and a variable repetition time technique (3D UTE-Cones AFI-VTR) on a clinical 3T scanner. First, the longitudinal magnetization mapping function of the excitation pulse was obtained with the 3D UTE-Cones AFI method, which provided information about excitation efficiency and B 1 inhomogeneity. Then, the derived mapping function was substituted into the VTR fitting to generate accurate T 1 maps. Numerical simulation and phantom studies were carried out to compare the AFI-VTR method with a B 1 -uncorrected VTR method, a B 1 -uncorrected variable flip angle (VFA) method, and a B 1 -corrected VFA method. Finally, the 3D UTE-Cones AFI-VTR method was applied to bovine bone samples (N = 6) and healthy volunteers (N = 3) to quantify the T 1 of cortical bone. Numerical simulation and phantom studies showed that the 3D UTE-Cones AFI-VTR technique provides more accurate measurement of the T 1 of short T 2 tissues than the B 1 -uncorrected VTR and VFA methods or the B 1 -corrected VFA method. The proposed 3D UTE-Cones AFI-VTR method showed a mean T 1 of 240 ± 25 ms for bovine cortical bone and 218 ± 10 ms for the tibial midshaft of human volunteers, respectively, at 3 T. The 3D UTE-Cones AFI-VTR method can provide accurate T 1 measurements of short T 2 tissues such as cortical bone. Magn Reson Med 80:598-608, 2018. © 2018 International Society for Magnetic Resonance in Medicine. © 2018 International Society for Magnetic Resonance in Medicine.

  9. Time-Accurate Numerical Simulations of Synthetic Jet Quiescent Air

    NASA Technical Reports Server (NTRS)

    Rupesh, K-A. B.; Ravi, B. R.; Mittal, R.; Raju, R.; Gallas, Q.; Cattafesta, L.

    2007-01-01

    The unsteady evolution of three-dimensional synthetic jet into quiescent air is studied by time-accurate numerical simulations using a second-order accurate mixed explicit-implicit fractional step scheme on Cartesian grids. Both two-dimensional and three-dimensional calculations of synthetic jet are carried out at a Reynolds number (based on average velocity during the discharge phase of the cycle V(sub j), and jet width d) of 750 and Stokes number of 17.02. The results obtained are assessed against PIV and hotwire measurements provided for the NASA LaRC workshop on CFD validation of synthetic jets.

  10. Prediction-Correction Algorithms for Time-Varying Constrained Optimization

    DOE PAGES

    Simonetto, Andrea; Dall'Anese, Emiliano

    2017-07-26

    This article develops online algorithms to track solutions of time-varying constrained optimization problems. Particularly, resembling workhorse Kalman filtering-based approaches for dynamical systems, the proposed methods involve prediction-correction steps to provably track the trajectory of the optimal solutions of time-varying convex problems. The merits of existing prediction-correction methods have been shown for unconstrained problems and for setups where computing the inverse of the Hessian of the cost function is computationally affordable. This paper addresses the limitations of existing methods by tackling constrained problems and by designing first-order prediction steps that rely on the Hessian of the cost function (and do notmore » require the computation of its inverse). In addition, the proposed methods are shown to improve the convergence speed of existing prediction-correction methods when applied to unconstrained problems. Numerical simulations corroborate the analytical results and showcase performance and benefits of the proposed algorithms. A realistic application of the proposed method to real-time control of energy resources is presented.« less

  11. Stray light effects in above-water remote-sensing reflectance from hyperspectral radiometers.

    PubMed

    Talone, Marco; Zibordi, Giuseppe; Ansko, Ilmar; Banks, Andrew Clive; Kuusk, Joel

    2016-05-20

    Stray light perturbations are unwanted distortions of the measured spectrum due to the nonideal performance of optical radiometers. Because of this, stray light characterization and correction is essential when accurate radiometric measurements are a necessity. In agreement with such a need, this study focused on stray light correction of hyperspectral radiometers widely applied for above-water measurements to determine the remote-sensing reflectance (RRS). Stray light of sample radiometers was experimentally characterized and a correction algorithm was developed and applied to field measurements performed in the Mediterranean Sea. Results indicate that mean stray light corrections are appreciable, with values generally varying from -1% to +1% in the 400-700 nm spectral region for downward irradiance and sky radiance, and from -1% to +4% for total radiance from the sea. Mean corrections for data products such as RRS exhibit values that depend on water type varying between -0.5% and +1% in the blue-green spectral region, with peaks up to 9% in the red in eutrophic waters. The possibility of using one common stray light correction matrix for the analyzed class of radiometers was also investigated. Results centered on RRS support such a feasibility at the expense of an increment of the uncertainty typically well below 0.5% in the blue-green and up to 1% in the red, assuming sensors are based on spectrographs from the same production batch.

  12. Stray light calibration of the Dawn Framing Camera

    NASA Astrophysics Data System (ADS)

    Kovacs, Gabor; Sierks, Holger; Nathues, Andreas; Richards, Michael; Gutierrez-Marques, Pablo

    2013-10-01

    Sensitive imaging systems with high dynamic range onboard spacecrafts are susceptible to ghost and stray-light effects. During the design phase, the Dawn Framing Camera was laid out and optimized to minimize those unwanted, parasitic effects. However, the requirement of low distortion to the optical design and use of a front-lit focal plane array induced an additional stray light component. This paper presents the ground-based and in-flight procedures characterizing the stray-light artifacts. The in-flight test used the Sun as the stray light source, at different angles of incidence. The spacecraft was commanded to point predefined solar elongation positions, and long exposure images were recorded. The PSNIT function was calculated by the known illumination and the ground based calibration information. In the ground based calibration, several extended and point sources were used with long exposure times in dedicated imaging setups. The tests revealed that the major contribution to the stray light is coming from the ghost reflections between the focal plan array and the band pass interference filters. Various laboratory experiments and computer modeling simulations were carried out to quantify the amount of this effect, including the analysis of the diffractive reflection pattern generated by the imaging sensor. The accurate characterization of the detector reflection pattern is the key to successfully predict the intensity distribution of the ghost image. Based on the results, and the properties of the optical system, a novel correction method is applied in the image processing pipeline. The effect of this correction procedure is also demonstrated with the first images of asteroid Vesta.

  13. Dead time corrections using the backward extrapolation method

    NASA Astrophysics Data System (ADS)

    Gilad, E.; Dubi, C.; Geslot, B.; Blaise, P.; Kolin, A.

    2017-05-01

    Dead time losses in neutron detection, caused by both the detector and the electronics dead time, is a highly nonlinear effect, known to create high biasing in physical experiments as the power grows over a certain threshold, up to total saturation of the detector system. Analytic modeling of the dead time losses is a highly complicated task due to the different nature of the dead time in the different components of the monitoring system (e.g., paralyzing vs. non paralyzing), and the stochastic nature of the fission chains. In the present study, a new technique is introduced for dead time corrections on the sampled Count Per Second (CPS), based on backward extrapolation of the losses, created by increasingly growing artificially imposed dead time on the data, back to zero. The method has been implemented on actual neutron noise measurements carried out in the MINERVE zero power reactor, demonstrating high accuracy (of 1-2%) in restoring the corrected count rate.

  14. Rcorrector: efficient and accurate error correction for Illumina RNA-seq reads.

    PubMed

    Song, Li; Florea, Liliana

    2015-01-01

    Next-generation sequencing of cellular RNA (RNA-seq) is rapidly becoming the cornerstone of transcriptomic analysis. However, sequencing errors in the already short RNA-seq reads complicate bioinformatics analyses, in particular alignment and assembly. Error correction methods have been highly effective for whole-genome sequencing (WGS) reads, but are unsuitable for RNA-seq reads, owing to the variation in gene expression levels and alternative splicing. We developed a k-mer based method, Rcorrector, to correct random sequencing errors in Illumina RNA-seq reads. Rcorrector uses a De Bruijn graph to compactly represent all trusted k-mers in the input reads. Unlike WGS read correctors, which use a global threshold to determine trusted k-mers, Rcorrector computes a local threshold at every position in a read. Rcorrector has an accuracy higher than or comparable to existing methods, including the only other method (SEECER) designed for RNA-seq reads, and is more time and memory efficient. With a 5 GB memory footprint for 100 million reads, it can be run on virtually any desktop or server. The software is available free of charge under the GNU General Public License from https://github.com/mourisl/Rcorrector/.

  15. Contingent negative variation (CNV) associated with sensorimotor timing error correction.

    PubMed

    Jang, Joonyong; Jones, Myles; Milne, Elizabeth; Wilson, Daniel; Lee, Kwang-Hyuk

    2016-02-15

    Detection and subsequent correction of sensorimotor timing errors are fundamental to adaptive behavior. Using scalp-recorded event-related potentials (ERPs), we sought to find ERP components that are predictive of error correction performance during rhythmic movements. Healthy right-handed participants were asked to synchronize their finger taps to a regular tone sequence (every 600 ms), while EEG data were continuously recorded. Data from 15 participants were analyzed. Occasional irregularities were built into stimulus presentation timing: 90 ms before (advances: negative shift) or after (delays: positive shift) the expected time point. A tapping condition alternated with a listening condition in which identical stimulus sequence was presented but participants did not tap. Behavioral error correction was observed immediately following a shift, with a degree of over-correction with positive shifts. Our stimulus-locked ERP data analysis revealed, 1) increased auditory N1 amplitude for the positive shift condition and decreased auditory N1 modulation for the negative shift condition; and 2) a second enhanced negativity (N2) in the tapping positive condition, compared with the tapping negative condition. In response-locked epochs, we observed a CNV (contingent negative variation)-like negativity with earlier latency in the tapping negative condition compared with the tapping positive condition. This CNV-like negativity peaked at around the onset of subsequent tapping, with the earlier the peak, the better the error correction performance with the negative shifts while the later the peak, the better the error correction performance with the positive shifts. This study showed that the CNV-like negativity was associated with the error correction performance during our sensorimotor synchronization study. Auditory N1 and N2 were differentially involved in negative vs. positive error correction. However, we did not find evidence for their involvement in behavioral error

  16. How accurately does high tibial osteotomy correct the mechanical axis of an arthritic varus knee? A systematic review.

    PubMed

    Van den Bempt, Maxim; Van Genechten, Wouter; Claes, Toon; Claes, Steven

    2016-12-01

    The aim of this study was to give an overview of the accuracy of coronal limb alignment correction after high tibial osteotomy (HTO) for the arthritic varus knee by performing a systematic review of the literature. The databases PubMed, MEDLINE and Cochrane Library were screened for relevant articles. Only prospective clinical studies with the accuracy of alignment correction by performing HTO as primary or secondary objective were included. Fifteen studies were included in this systematic review and were subdivided in 23 cohorts. A total of 966 procedures were considered. Nine cohorts used computer navigation during HTO and the other 14 cohorts used a conventional method. In seven computer navigation cohorts, at least 75% of the study population fell into the accepted "range of accuracy" (AR) as proposed by the different studies, but only six out of 14 conventional cohorts reached this percentage. Four out of eight conventional cohorts that provided data on under- and overcorrection, had a tendency to undercorrection. The accuracy of coronal alignment corrections using conventional HTO falls short. The number of procedures outside the proposed AR is surprising and exposes a critical concern for modern HTO. Computer navigation might improve the accuracy of correction, but its use is not widespread among orthopedic surgeons. Although HTO procedures have been shown to be successful in the treatment of unicompartmental knee arthritis when performed accurately, the results of this review stress the importance of ongoing efforts in order to improve correction accuracy in modern HTO. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Time-resolved forward-light-scattering monitoring of protein–lysozyme aggregation in precrystalline solutions

    NASA Astrophysics Data System (ADS)

    Wakamatsu, Takashi; Onoda, Takashi; Ogata, Makoto

    2018-05-01

    An in situ measurement method of monitoring protein aggregation in precrystalline solutions is presented. The method is based on a small-angle forward static light scattering (F-SLS) technique. This technique uses an accurate optical arrangement of a combination of a collimating lens and a CCD to obtain an F-SLS pattern from an aggregate-containing protein solution in one shot. The real-time observation of a crystallizing lysozyme captured the formation of fractal aggregates in the initial formation stage.

  18. Timebias corrections to predictions

    NASA Technical Reports Server (NTRS)

    Wood, Roger; Gibbs, Philip

    1993-01-01

    The importance of an accurate knowledge of the time bias corrections to predicted orbits to a satellite laser ranging (SLR) observer, especially for low satellites, is highlighted. Sources of time bias values and the optimum strategy for extrapolation are discussed from the viewpoint of the observer wishing to maximize the chances of getting returns from the next pass. What is said may be seen as a commercial encouraging wider and speedier use of existing data centers for mutually beneficial exchange of time bias data.

  19. Color Correction Parameter Estimation on the Smartphone and Its Application to Automatic Tongue Diagnosis.

    PubMed

    Hu, Min-Chun; Cheng, Ming-Hsun; Lan, Kun-Chan

    2016-01-01

    An automatic tongue diagnosis framework is proposed to analyze tongue images taken by smartphones. Different from conventional tongue diagnosis systems, our input tongue images are usually in low resolution and taken under unknown lighting conditions. Consequently, existing tongue diagnosis methods cannot be directly applied to give accurate results. We use the SVM (support vector machine) to predict the lighting condition and the corresponding color correction matrix according to the color difference of images taken with and without flash. We also modify the state-of-the-art work of fur and fissure detection for tongue images by taking hue information into consideration and adding a denoising step. Our method is able to correct the color of tongue images under different lighting conditions (e.g. fluorescent, incandescent, and halogen illuminant) and provide a better accuracy in tongue features detection with less processing complexity than the prior work. In this work, we proposed an automatic tongue diagnosis framework which can be applied to smartphones. Unlike the prior work which can only work in a controlled environment, our system can adapt to different lighting conditions by employing a novel color correction parameter estimation scheme.

  20. Implicit time accurate simulation of unsteady flow

    NASA Astrophysics Data System (ADS)

    van Buuren, René; Kuerten, Hans; Geurts, Bernard J.

    2001-03-01

    Implicit time integration was studied in the context of unsteady shock-boundary layer interaction flow. With an explicit second-order Runge-Kutta scheme, a reference solution to compare with the implicit second-order Crank-Nicolson scheme was determined. The time step in the explicit scheme is restricted by both temporal accuracy as well as stability requirements, whereas in the A-stable implicit scheme, the time step has to obey temporal resolution requirements and numerical convergence conditions. The non-linear discrete equations for each time step are solved iteratively by adding a pseudo-time derivative. The quasi-Newton approach is adopted and the linear systems that arise are approximately solved with a symmetric block Gauss-Seidel solver. As a guiding principle for properly setting numerical time integration parameters that yield an efficient time accurate capturing of the solution, the global error caused by the temporal integration is compared with the error resulting from the spatial discretization. Focus is on the sensitivity of properties of the solution in relation to the time step. Numerical simulations show that the time step needed for acceptable accuracy can be considerably larger than the explicit stability time step; typical ratios range from 20 to 80. At large time steps, convergence problems that are closely related to a highly complex structure of the basins of attraction of the iterative method may occur. Copyright

  1. Mobile Image Based Color Correction Using Deblurring

    PubMed Central

    Wang, Yu; Xu, Chang; Boushey, Carol; Zhu, Fengqing; Delp, Edward J.

    2016-01-01

    Dietary intake, the process of determining what someone eats during the course of a day, provides valuable insights for mounting intervention programs for prevention of many chronic diseases such as obesity and cancer. The goals of the Technology Assisted Dietary Assessment (TADA) System, developed at Purdue University, is to automatically identify and quantify foods and beverages consumed by utilizing food images acquired with a mobile device. Color correction serves as a critical step to ensure accurate food identification and volume estimation. We make use of a specifically designed color checkerboard (i.e. a fiducial marker) to calibrate the imaging system so that the variations of food appearance under different lighting conditions can be determined. In this paper, we propose an image quality enhancement technique by combining image de-blurring and color correction. The contribution consists of introducing an automatic camera shake removal method using a saliency map and improving the polynomial color correction model using the LMS color space. PMID:28572697

  2. Mobile image based color correction using deblurring

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Xu, Chang; Boushey, Carol; Zhu, Fengqing; Delp, Edward J.

    2015-03-01

    Dietary intake, the process of determining what someone eats during the course of a day, provides valuable insights for mounting intervention programs for prevention of many chronic diseases such as obesity and cancer. The goals of the Technology Assisted Dietary Assessment (TADA) System, developed at Purdue University, is to automatically identify and quantify foods and beverages consumed by utilizing food images acquired with a mobile device. Color correction serves as a critical step to ensure accurate food identification and volume estimation. We make use of a specifically designed color checkerboard (i.e. a fiducial marker) to calibrate the imaging system so that the variations of food appearance under different lighting conditions can be determined. In this paper, we propose an image quality enhancement technique by combining image de-blurring and color correction. The contribution consists of introducing an automatic camera shake removal method using a saliency map and improving the polynomial color correction model using the LMS color space.

  3. A novel real-time data acquisition using an Excel spreadsheet in pendulum experiment tool with light-based timer

    NASA Astrophysics Data System (ADS)

    Adhitama, Egy; Fauzi, Ahmad

    2018-05-01

    In this study, a pendulum experimental tool with a light-based timer has been developed to measure the period of a simple pendulum. The obtained data was automatically recorded in an Excel spreadsheet. The intensity of monochromatic light, sensed by a 3DU5C phototransistor, dynamically changes as the pendulum swings. The changed intensity varies the resistance value and was processed by the microcontroller, ATMega328, to obtain a signal period as a function of time and brightness when the pendulum crosses the light. Through the experiment, using calculated average periods, the gravitational acceleration value has been accurately and precisely determined.

  4. Estimation and correction of produced light from prompt gamma photons on luminescence imaging of water for proton therapy dosimetry

    NASA Astrophysics Data System (ADS)

    Yabe, Takuya; Komori, Masataka; Toshito, Toshiyuki; Yamaguchi, Mitsutaka; Kawachi, Naoki; Yamamoto, Seiichi

    2018-02-01

    Although the luminescence images of water during proton-beam irradiation using a cooled charge-coupled device camera showed almost the same ranges of proton beams as those measured by an ionization chamber, the depth profiles showed lower Bragg peak intensities than those measured by an ionization chamber. In addition, a broad optical baseline signal was observed in depths that exceed the depth of the Bragg peak. We hypothesize that this broad baseline signal originates from the interaction of proton-induced prompt gamma photons with water. These prompt gamma photons interact with water to form high-energy Compton electrons, which may cause luminescence or Cherenkov emission from depths exceeding the location of the Bragg peak. To clarify this idea, we measured the luminescence images of water during the irradiations of protons in water with minimized parallax errors, and also simulated the produced light by the interactions of prompt gamma photons with water. We corrected the measured depth profiles of the luminescence images by subtracting the simulated distributions of the produced light by the interactions of prompt gamma photons in water. Corrections were also conducted using the estimated depth profiles of the light of the prompt gamma photons, as obtained from the off-beam areas of the luminescence images of water. With these corrections, we successfully obtained depth profiles that have almost identical distributions as the simulated dose distributions for protons. The percentage relative height of the Bragg peak with corrections to that of the simulation data increased to 94% from 80% without correction. Also, the percentage relative offset heights of the deeper part of the Bragg peak with corrections decreased to 0.2%-0.4% from 4% without correction. These results indicate that the luminescence imaging of water has potential for the dose distribution measurements for proton therapy dosimetry.

  5. Real-Time Correction By Optical Tracking with Integrated Geometric Distortion Correction for Reducing Motion Artifacts in fMRI

    NASA Astrophysics Data System (ADS)

    Rotenberg, David J.

    Artifacts caused by head motion are a substantial source of error in fMRI that limits its use in neuroscience research and clinical settings. Real-time scan-plane correction by optical tracking has been shown to correct slice misalignment and non-linear spin-history artifacts, however residual artifacts due to dynamic magnetic field non-uniformity may remain in the data. A recently developed correction technique, PLACE, can correct for absolute geometric distortion using the complex image data from two EPI images, with slightly shifted k-space trajectories. We present a correction approach that integrates PLACE into a real-time scan-plane update system by optical tracking, applied to a tissue-equivalent phantom undergoing complex motion and an fMRI finger tapping experiment with overt head motion to induce dynamic field non-uniformity. Experiments suggest that including volume by volume geometric distortion correction by PLACE can suppress dynamic geometric distortion artifacts in a phantom and in vivo and provide more robust activation maps.

  6. Corrective response times in a coordinated eye-head-arm countermanding task.

    PubMed

    Tao, Gordon; Khan, Aarlenne Z; Blohm, Gunnar

    2018-06-01

    Inhibition of motor responses has been described as a race between two competing decision processes of motor initiation and inhibition, which manifest as the reaction time (RT) and the stop signal reaction time (SSRT); in the case where motor initiation wins out over inhibition, an erroneous movement occurs that usually needs to be corrected, leading to corrective response times (CRTs). Here we used a combined eye-head-arm movement countermanding task to investigate the mechanisms governing multiple effector coordination and the timing of corrective responses. We found a high degree of correlation between effector response times for RT, SSRT, and CRT, suggesting that decision processes are strongly dependent across effectors. To gain further insight into the mechanisms underlying CRTs, we tested multiple models to describe the distribution of RTs, SSRTs, and CRTs. The best-ranked model (according to 3 information criteria) extends the LATER race model governing RTs and SSRTs, whereby a second motor initiation process triggers the corrective response (CRT) only after the inhibition process completes in an expedited fashion. Our model suggests that the neural processing underpinning a failed decision has a residual effect on subsequent actions. NEW & NOTEWORTHY Failure to inhibit erroneous movements typically results in corrective movements. For coordinated eye-head-hand movements we show that corrective movements are only initiated after the erroneous movement cancellation signal has reached a decision threshold in an accelerated fashion.

  7. Accurate Time/Frequency Transfer Method Using Bi-Directional WDM Transmission

    NASA Technical Reports Server (NTRS)

    Imaoka, Atsushi; Kihara, Masami

    1996-01-01

    An accurate time transfer method is proposed using b-directional wavelength division multiplexing (WDM) signal transmission along a single optical fiber. This method will be used in digital telecommunication networks and yield a time synchronization accuracy of better than 1 ns for long transmission lines over several tens of kilometers. The method can accurately measure the difference in delay between two wavelength signals caused by the chromatic dispersion of the fiber in conventional simple bi-directional dual-wavelength frequency transfer methods. We describe the characteristics of this difference in delay and then show that the accuracy of the delay measurements can be obtained below 0.1 ns by transmitting 156 Mb/s times reference signals of 1.31 micrometer and 1.55 micrometers along a 50 km fiber using the proposed method. The sub-nanosecond delay measurement using the simple bi-directional dual-wavelength transmission along a 100 km fiber with a wavelength spacing of 1 nm in the 1.55 micrometer range is also shown.

  8. Development of a real-time reflectance and transmittance monitoring system for the manufacturing of metaldielectric light absorbers

    NASA Astrophysics Data System (ADS)

    Badoil, Bruno; Cathelinaud, Michel; Lemarchand, Fabien; Lemarquis, Frédéric; Lequime, Michel

    2017-11-01

    Metal-dielectric light absorbers are of great interest for suppressing stray light in optical systems. Such coatings can give an absorption level greater than 99.9% over a broad spectral range provided that the complex refractive index of metallic films is accurately known. For this purpose we developed a new real-time monitoring system that allows to measure in situ both reflectance and transmittance of the coating during manufacturing in the deposition chamber. This paper describes the system design and its characteristics and gives some preliminary results concerning metallic thin film characterizations.

  9. Accurate measurement of volume and shape of resting and activated blood platelets from light scattering.

    PubMed

    Moskalensky, Alexander E; Yurkin, Maxim A; Konokhova, Anastasiya I; Strokotov, Dmitry I; Nekrasov, Vyacheslav M; Chernyshev, Andrei V; Tsvetovskaya, Galina A; Chikova, Elena D; Maltsev, Valeri P

    2013-01-01

    We introduce a novel approach for determination of volume and shape of individual blood platelets modeled as an oblate spheroid from angle-resolved light scattering with flow-cytometric technique. The light-scattering profiles (LSPs) of individual platelets were measured with the scanning flow cytometer and the platelet characteristics were determined from the solution of the inverse light-scattering problem using the precomputed database of theoretical LSPs. We revealed a phenomenon of parameter compensation, which is partly explained in the framework of anomalous diffraction approximation. To overcome this problem, additional a priori information on the platelet refractive index was used. It allowed us to determine the size of each platelet with subdiffraction precision and independent of the particular value of the platelet aspect ratio. The shape (spheroidal aspect ratio) distributions of platelets showed substantial differences between native and activated by 10 μM adenosine diphosphate samples. We expect that the new approach may find use in hematological analyzers for accurate measurement of platelet volume distribution and for determination of the platelet activation efficiency.

  10. Calibration correction of an active scattering spectrometer probe to account for refractive index of stratospheric aerosols

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Overbeck, V. R.; Snetsinger, K. G.; Russell, P. B.; Ferry, G. V.

    1990-01-01

    The use of the active scattering spectrometer probe (ASAS-X) to measure sulfuric acid aerosols on U-2 and ER-2 research aircraft has yielded results that are at times ambiguous due to the dependence of particles' optical signatures on refractive index as well as physical dimensions. The calibration correction of the ASAS-X optical spectrometer probe for stratospheric aerosol studies is validated through an independent and simultaneous sampling of the particles with impactors; sizing and counting of particles on SEM images yields total particle areas and volumes. Upon correction of calibration in light of these data, spectrometer results averaged over four size distributions are found to agree with similarly averaged impactor results to within a few percent: indicating that the optical properties or chemical composition of the sample aerosol must be known in order to achieve accurate optical aerosol spectrometer size analysis.

  11. An estimation of tropospheric corrections using GPS and synoptic data: Improving Urmia Lake water level time series from Jason-2 and SARAL/AltiKa satellite altimetry

    NASA Astrophysics Data System (ADS)

    Arabsahebi, Reza; Voosoghi, Behzad; Tourian, Mohammad J.

    2018-05-01

    Tropospheric correction is one of the most important corrections in satellite altimetry measurements. Tropospheric wet and dry path delays have strong dependence on temperature, pressure and humidity. Tropospheric layer has particularly high variability over coastal regions due to humidity, wind and temperature gradients. Depending on the extent of water body and wind conditions over an inland water, Wet Tropospheric Correction (WTC) is within the ranges from a few centimeters to tens of centimeters. Therefore, an extra care is needed to estimate tropospheric corrections on the altimetric measurements over inland waters. This study assesses the role of tropospheric correction on the altimetric measurements over the Urmia Lake in Iran. For this purpose, four types of tropospheric corrections have been used: (i) microwave radiometer (MWR) observations, (ii) tropospheric corrections computed from meteorological models, (iii) GPS observations and (iv) synoptic station data. They have been applied to Jason-2 track no. 133 and SARAL/AltiKa track no. 741 and 356 corresponding to 117-153 and the 23-34 cycles, respectively. In addition, the corresponding measurements of PISTACH and PEACHI, include new retracking method and an innovative wet tropospheric correction, have also been used. Our results show that GPS observation leads to the most accurate tropospheric correction. The results obtained from the PISTACH and PEACHI projects confirm those obtained with the standard SGDR, i.e., the role of GPS in improving the tropospheric corrections. It is inferred that the MWR data from Jason-2 mission is appropriate for the tropospheric corrections, however the SARAL/AltiKa one is not proper because Jason-2 possesses an enhanced WTC near the coast. Furthermore, virtual stations are defined for assessment of the results in terms of time series of Water Level Height (WLH). The results show that GPS tropospheric corrections lead to the most accurate WLH estimation for the selected

  12. An empirical correction for moderate multiple scattering in super-heterodyne light scattering.

    PubMed

    Botin, Denis; Mapa, Ludmila Marotta; Schweinfurth, Holger; Sieber, Bastian; Wittenberg, Christopher; Palberg, Thomas

    2017-05-28

    Frequency domain super-heterodyne laser light scattering is utilized in a low angle integral measurement configuration to determine flow and diffusion in charged sphere suspensions showing moderate to strong multiple scattering. We introduce an empirical correction to subtract the multiple scattering background and isolate the singly scattered light. We demonstrate the excellent feasibility of this simple approach for turbid suspensions of transmittance T ≥ 0.4. We study the particle concentration dependence of the electro-kinetic mobility in low salt aqueous suspension over an extended concentration regime and observe a maximum at intermediate concentrations. We further use our scheme for measurements of the self-diffusion coefficients in the fluid samples in the absence or presence of shear, as well as in polycrystalline samples during crystallization and coarsening. We discuss the scope and limits of our approach as well as possible future applications.

  13. a Semi-Empirical Topographic Correction Model for Multi-Source Satellite Images

    NASA Astrophysics Data System (ADS)

    Xiao, Sa; Tian, Xinpeng; Liu, Qiang; Wen, Jianguang; Ma, Yushuang; Song, Zhenwei

    2018-04-01

    Topographic correction of surface reflectance in rugged terrain areas is the prerequisite for the quantitative application of remote sensing in mountainous areas. Physics-based radiative transfer model can be applied to correct the topographic effect and accurately retrieve the reflectance of the slope surface from high quality satellite image such as Landsat8 OLI. However, as more and more images data available from various of sensors, some times we can not get the accurate sensor calibration parameters and atmosphere conditions which are needed in the physics-based topographic correction model. This paper proposed a semi-empirical atmosphere and topographic corrction model for muti-source satellite images without accurate calibration parameters.Based on this model we can get the topographic corrected surface reflectance from DN data, and we tested and verified this model with image data from Chinese satellite HJ and GF. The result shows that the correlation factor was reduced almost 85 % for near infrared bands and the classification overall accuracy of classification increased 14 % after correction for HJ. The reflectance difference of slope face the sun and face away the sun have reduced after correction.

  14. Quick foot placement adjustments during gait are less accurate in individuals with focal cerebellar lesions.

    PubMed

    Hoogkamer, Wouter; Potocanac, Zrinka; Van Calenbergh, Frank; Duysens, Jacques

    2017-10-01

    Online gait corrections are frequently used to restore gait stability and prevent falling. They require shorter response times than voluntary movements which suggests that subcortical pathways contribute to the execution of online gait corrections. To evaluate the potential role of the cerebellum in these pathways we tested the hypotheses that online gait corrections would be less accurate in individuals with focal cerebellar damage than in neurologically intact controls and that this difference would be more pronounced for shorter available response times and for short step gait corrections. We projected virtual stepping stones on an instrumented treadmill while some of the approaching stepping stones were shifted forward or backward, requiring participants to adjust their foot placement. Varying the timing of those shifts allowed us to address the effect of available response time on foot placement error. In agreement with our hypothesis, individuals with focal cerebellar lesions were less accurate in adjusting their foot placement in reaction to suddenly shifted stepping stones than neurologically intact controls. However, the cerebellar lesion group's foot placement error did not increase more with decreasing available response distance or for short step versus long step adjustments compared to the control group. Furthermore, foot placement error for the non-shifting stepping stones was also larger in the cerebellar lesion group as compared to the control group. Consequently, the reduced ability to accurately adjust foot placement during walking in individuals with focal cerebellar lesions appears to be a general movement control deficit, which could contribute to increased fall risk. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Blue-Enriched Light Enhances Alertness but Impairs Accurate Performance in Evening Chronotypes Driving in the Morning.

    PubMed

    Rodríguez-Morilla, Beatriz; Madrid, Juan A; Molina, Enrique; Pérez-Navarro, José; Correa, Ángel

    2018-01-01

    Attention maintenance is highly demanding and typically leads to vigilance decrement along time on task. Therefore, performance in tasks involving vigilance maintenance for long periods, such as driving, tends to deteriorate over time. Cognitive performance has been demonstrated to fluctuate over 24 h of the day (known as circadian oscillations), thus showing peaks and troughs depending on the time of day (leading to optimal and suboptimal times of day, respectively). Consequently, vigilance decrements are more pronounced along time on task when it is performed at suboptimal times of day. According to research, light exposure (especially blue-enriched white) enhances alertness. Thus, it has been proposed to prevent the vigilance decrement under such adverse circumstances. We aimed to explore the effects of blue-enriched white light (vs. dim light) on the performance of a simulated driving task at a suboptimal time of day. A group of evening-types was tested at 8 am, as this chronotype had previously shown their largest vigilance decrement at that time. In the dim light condition, vigilance decrements were expected on both subjective (as increments in the Karolinska Sleepiness Scale scores) and behavioral measures [as slower reaction times (RTs) in the auditory Psychomotor Vigilance Task, slower RTs to unexpected events during driving, and deteriorated driving accuracy along time on task]. Physiological activation was expected to decrease (as indexed by an increase of the distal-proximal temperature gradient, DPG). Under blue-enriched white light, all these trends should be attenuated. Results from the control dim light condition replicated the vigilance decrement in all measures. Most important, the blue-enriched white light attenuated this decrement, leading to both lower DPG and faster RTs. However, it impaired accuracy of driving performance, and did not have any effect on subjective sleepiness. We conclude that exposure to blue-enriched light provides an

  16. The 230Th correction is the 1st priority for accurate dates of young zircons: U/Th partitioning experiments and measurements

    NASA Astrophysics Data System (ADS)

    Krawczynski, M.; McLean, N.

    2017-12-01

    One of the most accurate and useful ways of determining the age of rocks that formed more than about 500,000 years ago is uranium-lead (U-Pb) geochronology. Earth scientists use U-Pb geochronology to put together the geologic history of entire regions and of specific events, like the mass extinction of all non-avian dinosaurs about 66 million years ago or the catastrophic eruptions of supervolcanoes like the one currently centered at Yellowstone. The mineral zircon is often utilized because it is abundant, durable, and readily incorporates uranium into its crystal structure. But it excludes thorium, whose isotope 230Th is part of the naturally occurring isotopic decay chain from 238U to 206Pb. Calculating a date from the relative abundances of 206Pb and 238U therefore requires a correction for the missing 230Th. Existing experimental and observational constraints on the way U and Th behave when zircon crystallizes from a melt are not known precisely enough, and thus currently the uncertainty in dates introduced by they `Th correction' is one of the largest sources of systematic error in determining dates. Here we present preliminary results on our study of actinide partitioning between zircon and melt. Experiments have been conducted to grow zircon from melts doped with U and Th that mimic natural magmas at a range of temperatures, and compositions. Synthetic zircons are separated from their coexisting glass and using high precision and high-spatial-resolution techniques, the abundance and distribution of U and Th in each phase is determined. These preliminary experiments are the beginning of a study that will result in precise determination of the zircon/melt uranium and thorium partition coefficients under a wide variety of naturally occurring conditions. This data will be fit to a multidimensional surface using maximum likelihood regression techniques, so that the ratio of partition coefficients can be calculated for any set of known parameters. The results of

  17. Improvement of attenuation correction in time-of-flight PET/MR imaging with a positron-emitting source.

    PubMed

    Mollet, Pieter; Keereman, Vincent; Bini, Jason; Izquierdo-Garcia, David; Fayad, Zahi A; Vandenberghe, Stefaan

    2014-02-01

    Quantitative PET imaging relies on accurate attenuation correction. Recently, there has been growing interest in combining state-of-the-art PET systems with MR imaging in a sequential or fully integrated setup. As CT becomes unavailable for these systems, an alternative approach to the CT-based reconstruction of attenuation coefficients (μ values) at 511 keV must be found. Deriving μ values directly from MR images is difficult because MR signals are related to the proton density and relaxation properties of tissue. Therefore, most research groups focus on segmentation or atlas registration techniques. Although studies have shown that these methods provide viable solutions in particular applications, some major drawbacks limit their use in whole-body PET/MR. Previously, we used an annulus-shaped PET transmission source inside the field of view of a PET scanner to measure attenuation coefficients at 511 keV. In this work, we describe the use of this method in studies of patients with the sequential time-of-flight (TOF) PET/MR scanner installed at the Icahn School of Medicine at Mount Sinai, New York, NY. Five human PET/MR and CT datasets were acquired. The transmission-based attenuation correction method was compared with conventional CT-based attenuation correction and the 3-segment, MR-based attenuation correction available on the TOF PET/MR imaging scanner. The transmission-based method overcame most problems related to the MR-based technique, such as truncation artifacts of the arms, segmentation artifacts in the lungs, and imaging of cortical bone. Additionally, the TOF capabilities of the PET detectors allowed the simultaneous acquisition of transmission and emission data. Compared with the MR-based approach, the transmission-based method provided average improvements in PET quantification of 6.4%, 2.4%, and 18.7% in volumes of interest inside the lung, soft tissue, and bone tissue, respectively. In conclusion, a transmission-based technique with an annulus

  18. Accurate Modeling of Dark-Field Scattering Spectra of Plasmonic Nanostructures.

    PubMed

    Jiang, Liyong; Yin, Tingting; Dong, Zhaogang; Liao, Mingyi; Tan, Shawn J; Goh, Xiao Ming; Allioux, David; Hu, Hailong; Li, Xiangyin; Yang, Joel K W; Shen, Zexiang

    2015-10-27

    Dark-field microscopy is a widely used tool for measuring the optical resonance of plasmonic nanostructures. However, current numerical methods for simulating the dark-field scattering spectra were carried out with plane wave illumination either at normal incidence or at an oblique angle from one direction. In actual experiments, light is focused onto the sample through an annular ring within a range of glancing angles. In this paper, we present a theoretical model capable of accurately simulating the dark-field light source with an annular ring. Simulations correctly reproduce a counterintuitive blue shift in the scattering spectra from gold nanodisks with a diameter beyond 140 nm. We believe that our proposed simulation method can be potentially applied as a general tool capable of simulating the dark-field scattering spectra of plasmonic nanostructures as well as other dielectric nanostructures with sizes beyond the quasi-static limit.

  19. Development of a real-time wave field reconstruction TEM system (II): correction of coma aberration and 3-fold astigmatism, and real-time correction of 2-fold astigmatism.

    PubMed

    Tamura, Takahiro; Kimura, Yoshihide; Takai, Yoshizo

    2018-02-01

    In this study, a function for the correction of coma aberration, 3-fold astigmatism and real-time correction of 2-fold astigmatism was newly incorporated into a recently developed real-time wave field reconstruction TEM system. The aberration correction function was developed by modifying the image-processing software previously designed for auto focus tracking, as described in the first article of this series. Using the newly developed system, the coma aberration and 3-fold astigmatism were corrected using the aberration coefficients obtained experimentally before the processing was carried out. In this study, these aberration coefficients were estimated from an apparent 2-fold astigmatism induced under tilted-illumination conditions. In contrast, 2-fold astigmatism could be measured and corrected in real time from the reconstructed wave field. Here, the measurement precision for 2-fold astigmatism was found to be ±0.4 nm and ±2°. All of these aberration corrections, as well as auto focus tracking, were performed at a video frame rate of 1/30 s. Thus, the proposed novel system is promising for quantitative and reliable in situ observations, particularly in environmental TEM applications.

  20. Correcting the wavefront aberration of membrane mirror based on liquid crystal spatial light modulator

    NASA Astrophysics Data System (ADS)

    Yang, Bin; Wei, Yin; Chen, Xinhua; Tang, Minxue

    2014-11-01

    Membrane mirror with flexible polymer film substrate is a new-concept ultra lightweight mirror for space applications. Compared with traditional mirrors, membrane mirror has the advantages of lightweight, folding and deployable, low cost and etc. Due to the surface shape of flexible membrane mirror is easy to deviate from the design surface shape, it will bring wavefront aberration to the optical system. In order to solve this problem, a method of membrane mirror wavefront aberration correction based on the liquid crystal spatial light modulator (LCSLM) will be studied in this paper. The wavefront aberration correction principle of LCSLM is described and the phase modulation property of a LCSLM is measured and analyzed firstly. Then the membrane mirror wavefront aberration correction system is designed and established according to the optical properties of a membrane mirror. The LCSLM and a Hartmann-Shack sensor are used as a wavefront corrector and a wavefront detector, respectively. The detected wavefront aberration is calculated and converted into voltage value on LCSLM for the mirror wavefront aberration correction by programming in Matlab. When in experiment, the wavefront aberration of a glass plane mirror with a diameter of 70 mm is measured and corrected for verifying the feasibility of the experiment system and the correctness of the program. The PV value and RMS value of distorted wavefront are reduced and near diffraction limited optical performance is achieved. On this basis, the wavefront aberration of the aperture center Φ25 mm in a membrane mirror with a diameter of 200 mm is corrected and the errors are analyzed. It provides a means of correcting the wavefront aberration of membrane mirror.

  1. Accurate seismic phase identification and arrival time picking of glacial icequakes

    NASA Astrophysics Data System (ADS)

    Jones, G. A.; Doyle, S. H.; Dow, C.; Kulessa, B.; Hubbard, A.

    2010-12-01

    A catastrophic lake drainage event was monitored continuously using an array of 6, 4.5 Hz 3 component geophones in the Russell Glacier catchment, Western Greenland. Many thousands of events and arrival time phases (e.g., P- or S-wave) were recorded, often with events occurring simultaneously but at different locations. In addition, different styles of seismic events were identified from 'classical' tectonic earthquakes to tremors usually observed in volcanic regions. The presence of such a diverse and large dataset provides insight into the complex system of lake drainage. One of the most fundamental steps in seismology is the accurate identification of a seismic event and its associated arrival times. However, the collection of such a large and complex dataset makes the manual identification of a seismic event and picking of the arrival time phases time consuming with variable results. To overcome the issues of consistency and manpower, a number of different methods have been developed including short-term and long-term averages, spectrograms, wavelets, polarisation analyses, higher order statistics and auto-regressive techniques. Here we propose an automated procedure which establishes the phase type and accurately determines the arrival times. The procedure combines a number of different automated methods to achieve this, and is applied to the recently acquired lake drainage data. Accurate identification of events and their arrival time phases are the first steps in gaining a greater understanding of the extent of the deformation and the mechanism of such drainage events. A good knowledge of the propagation pathway of lake drainage meltwater through a glacier will have significant consequences for interpretation of glacial and ice sheet dynamics.

  2. Detection and Correction of Step Discontinuities in Kepler Flux Time Series

    NASA Technical Reports Server (NTRS)

    Kolodziejczak, J. J.; Morris, R. L.

    2011-01-01

    PDC 8.0 includes an implementation of a new algorithm to detect and correct step discontinuities appearing in roughly one of every 20 stellar light curves during a given quarter. The majority of such discontinuities are believed to result from high-energy particles (either cosmic or solar in origin) striking the photometer and causing permanent local changes (typically -0.5%) in quantum efficiency, though a partial exponential recovery is often observed [1]. Since these features, dubbed sudden pixel sensitivity dropouts (SPSDs), are uncorrelated across targets they cannot be properly accounted for by the current detrending algorithm. PDC detrending is based on the assumption that features in flux time series are due either to intrinsic stellar phenomena or to systematic errors and that systematics will exhibit measurable correlations across targets. SPSD events violate these assumptions and their successful removal not only rectifies the flux values of affected targets, but demonstrably improves the overall performance of PDC detrending [1].

  3. Children’s Processing and Comprehension of Complex Sentences Containing Temporal Connectives: The Influence of Memory on the Time Course of Accurate Responses

    PubMed Central

    2016-01-01

    In a touch-screen paradigm, we recorded 3- to 7-year-olds’ (N = 108) accuracy and response times (RTs) to assess their comprehension of 2-clause sentences containing before and after. Children were influenced by order: performance was most accurate when the presentation order of the 2 clauses matched the chronological order of events: “She drank the juice, before she walked in the park” (chronological order) versus “Before she walked in the park, she drank the juice” (reverse order). Differences in RTs for correct responses varied by sentence type: accurate responses were made more speedily for sentences that afforded an incremental processing of meaning. An independent measure of memory predicted this pattern of performance. We discuss these findings in relation to children’s knowledge of connective meaning and the processing requirements of sentences containing temporal connectives. PMID:27690492

  4. Zero-Echo-Time and Dixon Deep Pseudo-CT (ZeDD CT): Direct Generation of Pseudo-CT Images for Pelvic PET/MRI Attenuation Correction Using Deep Convolutional Neural Networks with Multiparametric MRI.

    PubMed

    Leynes, Andrew P; Yang, Jaewon; Wiesinger, Florian; Kaushik, Sandeep S; Shanbhag, Dattesh D; Seo, Youngho; Hope, Thomas A; Larson, Peder E Z

    2018-05-01

    Accurate quantification of uptake on PET images depends on accurate attenuation correction in reconstruction. Current MR-based attenuation correction methods for body PET use a fat and water map derived from a 2-echo Dixon MRI sequence in which bone is neglected. Ultrashort-echo-time or zero-echo-time (ZTE) pulse sequences can capture bone information. We propose the use of patient-specific multiparametric MRI consisting of Dixon MRI and proton-density-weighted ZTE MRI to directly synthesize pseudo-CT images with a deep learning model: we call this method ZTE and Dixon deep pseudo-CT (ZeDD CT). Methods: Twenty-six patients were scanned using an integrated 3-T time-of-flight PET/MRI system. Helical CT images of the patients were acquired separately. A deep convolutional neural network was trained to transform ZTE and Dixon MR images into pseudo-CT images. Ten patients were used for model training, and 16 patients were used for evaluation. Bone and soft-tissue lesions were identified, and the SUV max was measured. The root-mean-squared error (RMSE) was used to compare the MR-based attenuation correction with the ground-truth CT attenuation correction. Results: In total, 30 bone lesions and 60 soft-tissue lesions were evaluated. The RMSE in PET quantification was reduced by a factor of 4 for bone lesions (10.24% for Dixon PET and 2.68% for ZeDD PET) and by a factor of 1.5 for soft-tissue lesions (6.24% for Dixon PET and 4.07% for ZeDD PET). Conclusion: ZeDD CT produces natural-looking and quantitatively accurate pseudo-CT images and reduces error in pelvic PET/MRI attenuation correction compared with standard methods. © 2018 by the Society of Nuclear Medicine and Molecular Imaging.

  5. Experimental evaluation of the extended Dytlewski-style dead time correction formalism for neutron multiplicity counting

    NASA Astrophysics Data System (ADS)

    Lockhart, M.; Henzlova, D.; Croft, S.; Cutler, T.; Favalli, A.; McGahee, Ch.; Parker, R.

    2018-01-01

    Over the past few decades, neutron multiplicity counting has played an integral role in Special Nuclear Material (SNM) characterization pertaining to nuclear safeguards. Current neutron multiplicity analysis techniques use singles, doubles, and triples count rates because a methodology to extract and dead time correct higher order count rates (i.e. quads and pents) was not fully developed. This limitation is overcome by the recent extension of a popular dead time correction method developed by Dytlewski. This extended dead time correction algorithm, named Dytlewski-Croft-Favalli(DCF), is detailed in reference Croft and Favalli (2017), which gives an extensive explanation of the theory and implications of this new development. Dead time corrected results can then be used to assay SNM by inverting a set of extended point model equations which as well have only recently been formulated. The current paper discusses and presents the experimental evaluation of practical feasibility of the DCF dead time correction algorithm to demonstrate its performance and applicability in nuclear safeguards applications. In order to test the validity and effectiveness of the dead time correction for quads and pents, 252Cf and SNM sources were measured in high efficiency neutron multiplicity counters at the Los Alamos National Laboratory (LANL) and the count rates were extracted up to the fifth order and corrected for dead time. In order to assess the DCF dead time correction, the corrected data is compared to traditional dead time correction treatment within INCC. The DCF dead time correction is found to provide adequate dead time treatment for broad range of count rates available in practical applications.

  6. [THE CORRECTION OF TROPHIC DISORDERS IN CHILDREN OF CHRONIC GASTRODUODENITIS WITH METHOD LOW-FREQUENCY LIGHT-MAGNETOTHERAPY].

    PubMed

    Kolosova, T A; Sadovnikova, I V; Belousova, T E

    2015-01-01

    The results of a survey of school children with chronic gastroduodenitis when applying at an early period the medical rehabilitation with method low-frequency light-magnetotherapy. During treatment of hospital was evaluated vegetative-trophic status with methods of cardiointervalography and thermovision functional tests. In normalizes clinical parameters was correction in dynamics of the vegetative status in children, it confirms the effectiveness of the therapy. It is proved, that the use of low-frequency light-magnetotherapy has a positive effect on the vegetative--trophic provision an organism and normalizes the vegetative dysfunction.

  7. Sunlight Transmission through Desert Dust and Marine Aerosols: Diffuse Light Corrections to Sun Photometry and Pyrheliometry

    NASA Technical Reports Server (NTRS)

    Russell, P. B.; Livingston, J. M.; Dubovik, O.; Ramirez, S. A.; Wang, J.; Redemann, J.; Schmid, B.; Box, M.; Holben, B. N.

    2003-01-01

    Desert dust and marine aerosols are receiving increased scientific attention because of their prevalence on intercontinental scales and their potentially large effects on Earth radiation and climate, as well as on other aerosols, clouds, and precipitation. The relatively large size of desert dust and marine aerosols produces scattering phase functions that are strongly forward- peaked. Hence, Sun photometry and pyrheliometry of these aerosols are more subject to diffuse-light errors than is the case for smaller aerosols. Here we quantify these diffuse-light effects for common Sun photometer and pyrheliometer fields of view (FOV), using a data base on dust and marine aerosols derived from (1) AERONET measurements of sky radiance and solar beam transmission and (2) in situ measurements of aerosol layer size distribution and chemical composition. Accounting for particle non-sphericity is important when deriving dust size distribution from both AERONET and in situ aerodynamic measurements. We express our results in terms of correction factors that can be applied to Sun photometer and pyrheliometer measurements of aerosol optical depth (AOD). We find that the corrections are negligible (less than approximately 1% of AOD) for Sun photometers with narrow FOV (half-angle eta less than degree), but that they can be as large as 10% of AOD at 354 nm wavelength for Sun photometers with eta = 1.85 degrees. For pyrheliometers (which can have eta up to approximately 2.8 degrees), corrections can be as large as 16% at 354 nm. We find that AOD correction factors are well correlated with AOD wavelength dependence (hence Angstrom exponent). We provide best-fit equations for determining correction factors from Angstrom exponents of uncorrected AOD spectra, and we demonstrate their application to vertical profiles of multiwavelength AOD.

  8. Multiple night-time light-emitting diode lighting strategies impact grassland invertebrate assemblages.

    PubMed

    Davies, Thomas W; Bennie, Jonathan; Cruse, Dave; Blumgart, Dan; Inger, Richard; Gaston, Kevin J

    2017-07-01

    White light-emitting diodes (LEDs) are rapidly replacing conventional outdoor lighting technologies around the world. Despite rising concerns over their impact on the environment and human health, the flexibility of LEDs has been advocated as a means of mitigating the ecological impacts of globally widespread outdoor night-time lighting through spectral manipulation, dimming and switching lights off during periods of low demand. We conducted a three-year field experiment in which each of these lighting strategies was simulated in a previously artificial light naïve grassland ecosystem. White LEDs both increased the total abundance and changed the assemblage composition of adult spiders and beetles. Dimming LEDs by 50% or manipulating their spectra to reduce ecologically damaging wavelengths partially reduced the number of commoner species affected from seven to four. A combination of dimming by 50% and switching lights off between midnight and 04:00 am showed the most promise for reducing the ecological costs of LEDs, but the abundances of two otherwise common species were still affected. The environmental consequences of using alternative lighting technologies are increasingly well established. These results suggest that while management strategies using LEDs can be an effective means of reducing the number of taxa affected, averting the ecological impacts of night-time lighting may ultimately require avoiding its use altogether. © 2017 John Wiley & Sons Ltd.

  9. Arbitrary-order corrections for finite-time drift and diffusion coefficients

    NASA Astrophysics Data System (ADS)

    Anteneodo, C.; Riera, R.

    2009-09-01

    We address a standard class of diffusion processes with linear drift and quadratic diffusion coefficients. These contributions to dynamic equations can be directly drawn from data time series. However, real data are constrained to finite sampling rates and therefore it is crucial to establish a suitable mathematical description of the required finite-time corrections. Based on Itô-Taylor expansions, we present the exact corrections to the finite-time drift and diffusion coefficients. These results allow to reconstruct the real hidden coefficients from the empirical estimates. We also derive higher-order finite-time expressions for the third and fourth conditional moments that furnish extra theoretical checks for this class of diffusion models. The analytical predictions are compared with the numerical outcomes of representative artificial time series.

  10. On the more accurate channel model and positioning based on time-of-arrival for visible light localization

    NASA Astrophysics Data System (ADS)

    Amini, Changeez; Taherpour, Abbas; Khattab, Tamer; Gazor, Saeed

    2017-01-01

    This paper presents an improved propagation channel model for the visible light in indoor environments. We employ this model to derive an enhanced positioning algorithm using on the relation between the time-of-arrivals (TOAs) and the distances for two cases either by assuming known or unknown transmitter and receiver vertical distances. We propose two estimators, namely the maximum likelihood estimator and an estimator by employing the method of moments. To have an evaluation basis for these methods, we calculate the Cramer-Rao lower bound (CRLB) for the performance of the estimations. We show that the proposed model and estimations result in a superior performance in positioning when the transmitter and receiver are perfectly synchronized in comparison to the existing state-of-the-art counterparts. Moreover, the corresponding CRLB of the proposed model represents almost about 20 dB reduction in the localization error bound in comparison with the previous model for some practical scenarios.

  11. Time-Accurate Solutions of Incompressible Navier-Stokes Equations for Potential Turbopump Applications

    NASA Technical Reports Server (NTRS)

    Kiris, Cetin; Kwak, Dochan

    2001-01-01

    Two numerical procedures, one based on artificial compressibility method and the other pressure projection method, are outlined for obtaining time-accurate solutions of the incompressible Navier-Stokes equations. The performance of the two method are compared by obtaining unsteady solutions for the evolution of twin vortices behind a at plate. Calculated results are compared with experimental and other numerical results. For an un- steady ow which requires small physical time step, pressure projection method was found to be computationally efficient since it does not require any subiterations procedure. It was observed that the artificial compressibility method requires a fast convergence scheme at each physical time step in order to satisfy incompressibility condition. This was obtained by using a GMRES-ILU(0) solver in our computations. When a line-relaxation scheme was used, the time accuracy was degraded and time-accurate computations became very expensive.

  12. Modeling and Correcting the Time-Dependent ACS PSF

    NASA Technical Reports Server (NTRS)

    Rhodes, Jason; Massey, Richard; Albert, Justin; Taylor, James E.; Koekemoer, Anton M.; Leauthaud, Alexie

    2006-01-01

    The ability to accurately measure the shapes of faint objects in images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST) depends upon detailed knowledge of the Point Spread Function (PSF). We show that thermal fluctuations cause the PSF of the ACS Wide Field Camera (WFC) to vary over time. We describe a modified version of the TinyTim PSF modeling software to create artificial grids of stars across the ACS field of view at a range of telescope focus values. These models closely resemble the stars in real ACS images. Using 10 bright stars in a real image, we have been able to measure HST s apparent focus at the time of the exposure. TinyTim can then be used to model the PSF at any position on the ACS field of view. This obviates the need for images of dense stellar fields at different focus values, or interpolation between the few observed stars. We show that residual differences between our TinyTim models and real data are likely due to the effects of Charge Transfer Efficiency (CTE) degradation. Furthermore, we discuss stochastic noise that is added to the shape of point sources when distortion is removed, and we present MultiDrizzle parameters that are optimal for weak lensing science. Specifically, we find that reducing the MultiDrizzle output pixel scale and choosing a Gaussian kernel significantly stabilizes the resulting PSF after image combination, while still eliminating cosmic rays/bad pixels, and correcting the large geometric distortion in the ACS. We discuss future plans, which include more detailed study of the effects of CTE degradation on object shapes and releasing our TinyTim models to the astronomical community.

  13. Accurate and efficient calculation of response times for groundwater flow

    NASA Astrophysics Data System (ADS)

    Carr, Elliot J.; Simpson, Matthew J.

    2018-03-01

    We study measures of the amount of time required for transient flow in heterogeneous porous media to effectively reach steady state, also known as the response time. Here, we develop a new approach that extends the concept of mean action time. Previous applications of the theory of mean action time to estimate the response time use the first two central moments of the probability density function associated with the transition from the initial condition, at t = 0, to the steady state condition that arises in the long time limit, as t → ∞ . This previous approach leads to a computationally convenient estimation of the response time, but the accuracy can be poor. Here, we outline a powerful extension using the first k raw moments, showing how to produce an extremely accurate estimate by making use of asymptotic properties of the cumulative distribution function. Results are validated using an existing laboratory-scale data set describing flow in a homogeneous porous medium. In addition, we demonstrate how the results also apply to flow in heterogeneous porous media. Overall, the new method is: (i) extremely accurate; and (ii) computationally inexpensive. In fact, the computational cost of the new method is orders of magnitude less than the computational effort required to study the response time by solving the transient flow equation. Furthermore, the approach provides a rigorous mathematical connection with the heuristic argument that the response time for flow in a homogeneous porous medium is proportional to L2 / D , where L is a relevant length scale, and D is the aquifer diffusivity. Here, we extend such heuristic arguments by providing a clear mathematical definition of the proportionality constant.

  14. Detection of defects on apple using B-spline lighting correction method

    NASA Astrophysics Data System (ADS)

    Li, Jiangbo; Huang, Wenqian; Guo, Zhiming

    To effectively extract defective areas in fruits, the uneven intensity distribution that was produced by the lighting system or by part of the vision system in the image must be corrected. A methodology was used to convert non-uniform intensity distribution on spherical objects into a uniform intensity distribution. A basically plane image with the defective area having a lower gray level than this plane was obtained by using proposed algorithms. Then, the defective areas can be easily extracted by a global threshold value. The experimental results with a 94.0% classification rate based on 100 apple images showed that the proposed algorithm was simple and effective. This proposed method can be applied to other spherical fruits.

  15. Experimental evaluation of the extended Dytlewski-style dead time correction formalism for neutron multiplicity counting

    DOE PAGES

    Lockhart, M.; Henzlova, D.; Croft, S.; ...

    2017-09-20

    Over the past few decades, neutron multiplicity counting has played an integral role in Special Nuclear Material (SNM) characterization pertaining to nuclear safeguards. Current neutron multiplicity analysis techniques use singles, doubles, and triples count rates because a methodology to extract and dead time correct higher order count rates (i.e. quads and pents) was not fully developed. This limitation is overcome by the recent extension of a popular dead time correction method developed by Dytlewski. This extended dead time correction algorithm, named Dytlewski-Croft-Favalli (DCF), is detailed in reference Croft and Favalli (2017), which gives an extensive explanation of the theory andmore » implications of this new development. Dead time corrected results can then be used to assay SNM by inverting a set of extended point model equations which as well have only recently been formulated. Here, we discuss and present the experimental evaluation of practical feasibility of the DCF dead time correction algorithm to demonstrate its performance and applicability in nuclear safeguards applications. In order to test the validity and effectiveness of the dead time correction for quads and pents, 252Cf and SNM sources were measured in high efficiency neutron multiplicity counters at the Los Alamos National Laboratory (LANL) and the count rates were extracted up to the fifth order and corrected for dead time. To assess the DCF dead time correction, the corrected data is compared to traditional dead time correction treatment within INCC. In conclusion, the DCF dead time correction is found to provide adequate dead time treatment for broad range of count rates available in practical applications.« less

  16. Experimental evaluation of the extended Dytlewski-style dead time correction formalism for neutron multiplicity counting

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lockhart, M.; Henzlova, D.; Croft, S.

    Over the past few decades, neutron multiplicity counting has played an integral role in Special Nuclear Material (SNM) characterization pertaining to nuclear safeguards. Current neutron multiplicity analysis techniques use singles, doubles, and triples count rates because a methodology to extract and dead time correct higher order count rates (i.e. quads and pents) was not fully developed. This limitation is overcome by the recent extension of a popular dead time correction method developed by Dytlewski. This extended dead time correction algorithm, named Dytlewski-Croft-Favalli (DCF), is detailed in reference Croft and Favalli (2017), which gives an extensive explanation of the theory andmore » implications of this new development. Dead time corrected results can then be used to assay SNM by inverting a set of extended point model equations which as well have only recently been formulated. Here, we discuss and present the experimental evaluation of practical feasibility of the DCF dead time correction algorithm to demonstrate its performance and applicability in nuclear safeguards applications. In order to test the validity and effectiveness of the dead time correction for quads and pents, 252Cf and SNM sources were measured in high efficiency neutron multiplicity counters at the Los Alamos National Laboratory (LANL) and the count rates were extracted up to the fifth order and corrected for dead time. To assess the DCF dead time correction, the corrected data is compared to traditional dead time correction treatment within INCC. In conclusion, the DCF dead time correction is found to provide adequate dead time treatment for broad range of count rates available in practical applications.« less

  17. Continuous Digital Light Processing (cDLP): Highly Accurate Additive Manufacturing of Tissue Engineered Bone Scaffolds.

    PubMed

    Dean, David; Jonathan, Wallace; Siblani, Ali; Wang, Martha O; Kim, Kyobum; Mikos, Antonios G; Fisher, John P

    2012-03-01

    Highly accurate rendering of the external and internal geometry of bone tissue engineering scaffolds effects fit at the defect site, loading of internal pore spaces with cells, bioreactor-delivered nutrient and growth factor circulation, and scaffold resorption. It may be necessary to render resorbable polymer scaffolds with 50 μm or less accuracy to achieve these goals. This level of accuracy is available using Continuous Digital Light processing (cDLP) which utilizes a DLP(®) (Texas Instruments, Dallas, TX) chip. One such additive manufacturing device is the envisionTEC (Ferndale, MI) Perfactory(®). To use cDLP we integrate a photo-crosslinkable polymer, a photo-initiator, and a biocompatible dye. The dye attenuates light, thereby limiting the depth of polymerization. In this study we fabricated scaffolds using the well-studied resorbable polymer, poly(propylene fumarate) (PPF), titanium dioxide (TiO(2)) as a dye, Irgacure(®) 819 (BASF [Ciba], Florham Park, NJ) as an initiator, and diethyl fumarate as a solvent to control viscosity.

  18. Perceived image quality with simulated segmented bifocal corrections

    PubMed Central

    Dorronsoro, Carlos; Radhakrishnan, Aiswaryah; de Gracia, Pablo; Sawides, Lucie; Marcos, Susana

    2016-01-01

    Bifocal contact or intraocular lenses use the principle of simultaneous vision to correct for presbyopia. A modified two-channel simultaneous vision simulator provided with an amplitude transmission spatial light modulator was used to optically simulate 14 segmented bifocal patterns (+ 3 diopters addition) with different far/near pupillary distributions of equal energy. Five subjects with paralyzed accommodation evaluated image quality and subjective preference through the segmented bifocal corrections. There are strong and systematic perceptual differences across the patterns, subjects and observation distances: 48% of the conditions evaluated were significantly preferred or rejected. Optical simulations (in terms of through-focus Strehl ratio from Hartmann-Shack aberrometry) accurately predicted the pattern producing the highest perceived quality in 4 out of 5 patients, both for far and near vision. These perceptual differences found arise primarily from optical grounds, but have an important neural component. PMID:27895981

  19. Remote monitoring of LED lighting system performance

    NASA Astrophysics Data System (ADS)

    Thotagamuwa, Dinusha R.; Perera, Indika U.; Narendran, Nadarajah

    2016-09-01

    The concept of connected lighting systems using LED lighting for the creation of intelligent buildings is becoming attractive to building owners and managers. In this application, the two most important parameters include power demand and the remaining useful life of the LED fixtures. The first enables energy-efficient buildings and the second helps building managers schedule maintenance services. The failure of an LED lighting system can be parametric (such as lumen depreciation) or catastrophic (such as complete cessation of light). Catastrophic failures in LED lighting systems can create serious consequences in safety critical and emergency applications. Therefore, both failure mechanisms must be considered and the shorter of the two must be used as the failure time. Furthermore, because of significant variation between the useful lives of similar products, it is difficult to accurately predict the life of LED systems. Real-time data gathering and analysis of key operating parameters of LED systems can enable the accurate estimation of the useful life of a lighting system. This paper demonstrates the use of a data-driven method (Euclidean distance) to monitor the performance of an LED lighting system and predict its time to failure.

  20. Real-time range acquisition by adaptive structured light.

    PubMed

    Koninckx, Thomas P; Van Gool, Luc

    2006-03-01

    The goal of this paper is to provide a "self-adaptive" system for real-time range acquisition. Reconstructions are based on a single frame structured light illumination. Instead of using generic, static coding that is supposed to work under all circumstances, system adaptation is proposed. This occurs on-the-fly and renders the system more robust against instant scene variability and creates suitable patterns at startup. A continuous trade-off between speed and quality is made. A weighted combination of different coding cues--based upon pattern color, geometry, and tracking--yields a robust way to solve the correspondence problem. The individual coding cues are automatically adapted within a considered family of patterns. The weights to combine them are based on the average consistency with the result within a small time-window. The integration itself is done by reformulating the problem as a graph cut. Also, the camera-projector configuration is taken into account for generating the projection patterns. The correctness of the range maps is not guaranteed, but an estimation of the uncertainty is provided for each part of the reconstruction. Our prototype is implemented using unmodified consumer hardware only and, therefore, is cheap. Frame rates vary between 10 and 25 fps, dependent on scene complexity.

  1. A correction method for systematic error in (1)H-NMR time-course data validated through stochastic cell culture simulation.

    PubMed

    Sokolenko, Stanislav; Aucoin, Marc G

    2015-09-04

    The growing ubiquity of metabolomic techniques has facilitated high frequency time-course data collection for an increasing number of applications. While the concentration trends of individual metabolites can be modeled with common curve fitting techniques, a more accurate representation of the data needs to consider effects that act on more than one metabolite in a given sample. To this end, we present a simple algorithm that uses nonparametric smoothing carried out on all observed metabolites at once to identify and correct systematic error from dilution effects. In addition, we develop a simulation of metabolite concentration time-course trends to supplement available data and explore algorithm performance. Although we focus on nuclear magnetic resonance (NMR) analysis in the context of cell culture, a number of possible extensions are discussed. Realistic metabolic data was successfully simulated using a 4-step process. Starting with a set of metabolite concentration time-courses from a metabolomic experiment, each time-course was classified as either increasing, decreasing, concave, or approximately constant. Trend shapes were simulated from generic functions corresponding to each classification. The resulting shapes were then scaled to simulated compound concentrations. Finally, the scaled trends were perturbed using a combination of random and systematic errors. To detect systematic errors, a nonparametric fit was applied to each trend and percent deviations calculated at every timepoint. Systematic errors could be identified at time-points where the median percent deviation exceeded a threshold value, determined by the choice of smoothing model and the number of observed trends. Regardless of model, increasing the number of observations over a time-course resulted in more accurate error estimates, although the improvement was not particularly large between 10 and 20 samples per trend. The presented algorithm was able to identify systematic errors as small

  2. Atmospheric extinction in solar tower plants: the Absorption and Broadband Correction for MOR measurements

    NASA Astrophysics Data System (ADS)

    Hanrieder, N.; Wilbert, S.; Pitz-Paal, R.; Emde, C.; Gasteiger, J.; Mayer, B.; Polo, J.

    2015-05-01

    Losses of reflected Direct Normal Irradiance due to atmospheric extinction in concentrating solar tower plants can vary significantly with site and time. The losses of the direct normal irradiance between the heliostat field and receiver in a solar tower plant are mainly caused by atmospheric scattering and absorption by aerosol and water vapor concentration in the atmospheric boundary layer. Due to a high aerosol particle number, radiation losses can be significantly larger in desert environments compared to the standard atmospheric conditions which are usually considered in raytracing or plant optimization tools. Information about on-site atmospheric extinction is only rarely available. To measure these radiation losses, two different commercially available instruments were tested and more than 19 months of measurements were collected at the Plataforma Solar de Almería and compared. Both instruments are primarily used to determine the meteorological optical range (MOR). The Vaisala FS11 scatterometer is based on a monochromatic near-infrared light source emission and measures the strength of scattering processes in a small air volume mainly caused by aerosol particles. The Optec LPV4 long-path visibility transmissometer determines the monochromatic attenuation between a light-emitting diode (LED) light source at 532 nm and a receiver and therefore also accounts for absorption processes. As the broadband solar attenuation is of interest for solar resource assessment for Concentrating Solar Power (CSP), a correction procedure for these two instruments is developed and tested. This procedure includes a spectral correction of both instruments from monochromatic to broadband attenuation. That means the attenuation is corrected for the actual, time-dependent by the collector reflected solar spectrum. Further, an absorption correction for the Vaisala FS11 scatterometer is implemented. To optimize the Absorption and Broadband Correction (ABC) procedure, additional

  3. Onboard Autonomous Corrections for Accurate IRF Pointing.

    NASA Astrophysics Data System (ADS)

    Jorgensen, J. L.; Betto, M.; Denver, T.

    2002-05-01

    filtered GPS updates, a world time clock, astrometric correction tables, and a attitude output transform system, that allow the ASC to deliver the spacecraft attitude relative to the Inertial Reference Frame (IRF) in realtime. This paper describes the operations of the onboard autonomy of the ASC, which in realtime removes the residuals from the attitude measurements, whereby a timely IRF attitude at arcsecond level, is delivered to the AOCS (or sent to ground). A discussion about achievable robustness and accuracy is given, and compared to inflight results from the operations of the two Advanced Stellar Compass's (ASC), which are flying in LEO onboard the German geo-potential research satellite CHAMP. The ASC's onboard CHAMP are dual head versions, i.e. each processing unit is attached to two star camera heads. The dual head configuration is primarily employed to achieve a carefree AOCS control with respect to the Sun, Moon and Earth, and to increase the attitude accuracy, but it also enables onboard estimation and removal of thermal generated biases.

  4. An accurate filter loading correction is essential for assessing personal exposure to black carbon using an Aethalometer.

    PubMed

    Good, Nicholas; Mölter, Anna; Peel, Jennifer L; Volckens, John

    2017-07-01

    The AE51 micro-Aethalometer (microAeth) is a popular and useful tool for assessing personal exposure to particulate black carbon (BC). However, few users of the AE51 are aware that its measurements are biased low (by up to 70%) due to the accumulation of BC on the filter substrate over time; previous studies of personal black carbon exposure are likely to have suffered from this bias. Although methods to correct for bias in micro-Aethalometer measurements of particulate black carbon have been proposed, these methods have not been verified in the context of personal exposure assessment. Here, five Aethalometer loading correction equations based on published methods were evaluated. Laboratory-generated aerosols of varying black carbon content (ammonium sulfate, Aquadag and NIST diesel particulate matter) were used to assess the performance of these methods. Filters from a personal exposure assessment study were also analyzed to determine how the correction methods performed for real-world samples. Standard correction equations produced correction factors with root mean square errors of 0.10 to 0.13 and mean bias within ±0.10. An optimized correction equation is also presented, along with sampling recommendations for minimizing bias when assessing personal exposure to BC using the AE51 micro-Aethalometer.

  5. Learning time-dependent noise to reduce logical errors: real time error rate estimation in quantum error correction

    NASA Astrophysics Data System (ADS)

    Huo, Ming-Xia; Li, Ying

    2017-12-01

    Quantum error correction is important to quantum information processing, which allows us to reliably process information encoded in quantum error correction codes. Efficient quantum error correction benefits from the knowledge of error rates. We propose a protocol for monitoring error rates in real time without interrupting the quantum error correction. Any adaptation of the quantum error correction code or its implementation circuit is not required. The protocol can be directly applied to the most advanced quantum error correction techniques, e.g. surface code. A Gaussian processes algorithm is used to estimate and predict error rates based on error correction data in the past. We find that using these estimated error rates, the probability of error correction failures can be significantly reduced by a factor increasing with the code distance.

  6. Accurate atomistic first-principles calculations of electronic stopping

    DOE PAGES

    Schleife, André; Kanai, Yosuke; Correa, Alfredo A.

    2015-01-20

    In this paper, we show that atomistic first-principles calculations based on real-time propagation within time-dependent density functional theory are capable of accurately describing electronic stopping of light projectile atoms in metal hosts over a wide range of projectile velocities. In particular, we employ a plane-wave pseudopotential scheme to solve time-dependent Kohn-Sham equations for representative systems of H and He projectiles in crystalline aluminum. This approach to simulate nonadiabatic electron-ion interaction provides an accurate framework that allows for quantitative comparison with experiment without introducing ad hoc parameters such as effective charges, or assumptions about the dielectric function. Finally, our work clearlymore » shows that this atomistic first-principles description of electronic stopping is able to disentangle contributions due to tightly bound semicore electrons and geometric aspects of the stopping geometry (channeling versus off-channeling) in a wide range of projectile velocities.« less

  7. Improving Focal Photostimulation of Cortical Neurons with Pre-derived Wavefront Correction

    PubMed Central

    Choy, Julian M. C.; Sané, Sharmila S.; Lee, Woei M.; Stricker, Christian; Bachor, Hans A.; Daria, Vincent R.

    2017-01-01

    Recent progress in neuroscience to image and investigate brain function has been made possible by impressive developments in optogenetic and opto-molecular tools. Such research requires advances in optical techniques for the delivery of light through brain tissue with high spatial resolution. The tissue causes distortions to the wavefront of the incoming light which broadens the focus and consequently reduces the intensity and degrades the resolution. Such effects are detrimental in techniques requiring focal stimulation. Adaptive wavefront correction has been demonstrated to compensate for these distortions. However, iterative derivation of the corrective wavefront introduces time constraints that limit its applicability to probe living cells. Here, we demonstrate that we can pre-determine and generalize a small set of Zernike modes to correct for aberrations of the light propagating through specific brain regions. A priori identification of a corrective wavefront is a direct and fast technique that improves the quality of the focus without the need for iterative adaptive wavefront correction. We verify our technique by measuring the efficiency of two-photon photolysis of caged neurotransmitters along the dendrites of a whole-cell patched neuron. Our results show that encoding the selected Zernike modes on the excitation light can improve light propagation through brain slices of rats as observed by the neuron's evoked excitatory post-synaptic potential in response to localized focal uncaging at the spines of the neuron's dendrites. PMID:28507508

  8. Development of a drift-correction procedure for a direct-reading spectrometer

    NASA Technical Reports Server (NTRS)

    Chapman, G. B., II; Gordon, W. A.

    1977-01-01

    A procedure which provides automatic correction for drifts in the radiometric sensitivity of each detector channel in a direct-reading emission spectrometer is described. Such drifts are customarily controlled by the regular analyses of standards, which provide corrections for changes in the excitational, optical, and electronic components of the instrument. This standardization procedure, however, corrects for the optical and electronic drifts. It is a step that must be taken if the time, effort, and cost of processing standards is to be minimized. This method of radiometric drift correction uses a 1,000-W tungsten-halogen reference lamp to illuminate each detector through the same optical path as that traversed during sample analysis. The responses of the detector channels to this reference light are regularly compared with channel response to the same light intensity at the time of analytical calibration in order to determine and correct for drift. Except for placing the lamp in position, the procedure is fully automated and compensates for changes in spectral intensity due to variations in lamp current. A discussion of the implementation of this drift-correction system is included.

  9. Identification of light elements in silicon nitride by aberration-corrected scanning transmission electron microscopy.

    PubMed

    Idrobo, Juan C; Walkosz, Weronika; Klie, Robert F; Oğüt, Serdar

    2012-12-01

    In silicon nitride structural ceramics, the overall mechanical and thermal properties are controlled by the atomic and electronic structures at the interface between the ceramic grains and the amorphous intergranular films (IGFs) formed by various sintering additives. In the last ten years the atomic arrangements of heavy elements (rare-earths) at the Si(3)N(4)/IGF interfaces have been resolved. However, the atomic position of light elements, without which it is not possible to obtain a complete description of the interfaces, has been lacking. This review article details the authors' efforts to identify the atomic arrangement of light elements such as nitrogen and oxygen at the Si(3)N(4)/SiO(2) interface and in bulk Si(3)N(4) using aberration-corrected scanning transmission electron microscopy. Published by Elsevier B.V.

  10. One-loop corrections to light cone wave functions: The dipole picture DIS cross section

    NASA Astrophysics Data System (ADS)

    Hänninen, H.; Lappi, T.; Paatelainen, R.

    2018-06-01

    We develop methods to perform loop calculations in light cone perturbation theory using a helicity basis, refining the method introduced in our earlier work. In particular this includes implementing a consistent way to contract the four-dimensional tensor structures from the helicity vectors with d-dimensional tensors arising from loop integrals, in a way that can be fully automatized. We demonstrate this explicitly by calculating the one-loop correction to the virtual photon to quark-antiquark dipole light cone wave function. This allows us to calculate the deep inelastic scattering cross section in the dipole formalism to next-to-leading order accuracy. Our results, obtained using the four dimensional helicity scheme, agree with the recent calculation by Beuf using conventional dimensional regularization, confirming the regularization scheme independence of this cross section.

  11. Real-time distortion correction for visual inspection systems based on FPGA

    NASA Astrophysics Data System (ADS)

    Liang, Danhua; Zhang, Zhaoxia; Chen, Xiaodong; Yu, Daoyin

    2008-03-01

    Visual inspection is a kind of new technology based on the research of computer vision, which focuses on the measurement of the object's geometry and location. It can be widely used in online measurement, and other real-time measurement process. Because of the defects of the traditional visual inspection, a new visual detection mode -all-digital intelligent acquisition and transmission is presented. The image processing, including filtering, image compression, binarization, edge detection and distortion correction, can be completed in the programmable devices -FPGA. As the wide-field angle lens is adopted in the system, the output images have serious distortion. Limited by the calculating speed of computer, software can only correct the distortion of static images but not the distortion of dynamic images. To reach the real-time need, we design a distortion correction system based on FPGA. The method of hardware distortion correction is that the spatial correction data are calculated first under software circumstance, then converted into the address of hardware storage and stored in the hardware look-up table, through which data can be read out to correct gray level. The major benefit using FPGA is that the same circuit can be used for other circularly symmetric wide-angle lenses without being modified.

  12. Evaluation of the Combined Effects of Heat and Lighting on the Level of Attention and Reaction Time: Climate Chamber Experiments in Iran.

    PubMed

    Mohebian, Zohreh; Farhang Dehghan, Somayeh; Dehghan, Habiballah

    2018-01-01

    Heat exposure and unsuitable lighting are two physical hazardous agents in many workplaces for which there are some evidences regarding their mental effects. The purpose of this study was to assess the combined effect of heat exposure and different lighting levels on the attention rate and reaction time in a climatic chamber. This study was conducted on 33 healthy students (17 M/16 F) with a mean (±SD) age of 22.1 ± 2.3 years. The attention and reaction time test were done by continuous performance test and the RT meter, respectively, in different exposure conditions including the dry temperatures (22°C and 37°C) and lighting levels (200, 500, and 1500 lux). Findings demonstrated that increase in heat and lighting level caused a decrease in average attention percentage and correct responses and increase in commission error, omission error, and response time ( P < 0.05). The average of simple, diagnostic, two-color selective, and two-sound selective reaction times increased after combined exposure to heat and lighting ( P < 0.05). The results of this study indicated that, in job task which requires using cognitive functions like attention, vigilance, concentration, cautiousness, and reaction time, the work environment must be optimized in terms of heat and lighting level.

  13. Security-enhanced chaos communication with time-delay signature suppression and phase encryption.

    PubMed

    Xue, Chenpeng; Jiang, Ning; Lv, Yunxin; Wang, Chao; Li, Guilan; Lin, Shuqing; Qiu, Kun

    2016-08-15

    A security-enhanced chaos communication scheme with time delay signature (TDS) suppression and phase-encrypted feedback light is proposed, in virtue of dual-loop feedback with independent high-speed phase modulation. We numerically investigate the property of TDS suppression in the intensity and phase space and quantitatively discuss security of the proposed system by calculating the bit error rate of eavesdroppers who try to crack the system by directly filtering the detected signal or by using a similar semiconductor laser to synchronize the link signal and extract the data. The results show that TDS embedded in the chaotic carrier can be well suppressed by properly setting the modulation frequency, which can keep the time delay a secret from the eavesdropper. Moreover, because the feedback light is encrypted, without the accurate time delay and key, the eavesdropper cannot reconstruct the symmetric operation conditions and decode the correct data.

  14. Accurate Size and Size-Distribution Determination of Polystyrene Latex Nanoparticles in Aqueous Medium Using Dynamic Light Scattering and Asymmetrical Flow Field Flow Fractionation with Multi-Angle Light Scattering

    PubMed Central

    Kato, Haruhisa; Nakamura, Ayako; Takahashi, Kayori; Kinugasa, Shinichi

    2012-01-01

    Accurate determination of the intensity-average diameter of polystyrene latex (PS-latex) by dynamic light scattering (DLS) was carried out through extrapolation of both the concentration of PS-latex and the observed scattering angle. Intensity-average diameter and size distribution were reliably determined by asymmetric flow field flow fractionation (AFFFF) using multi-angle light scattering (MALS) with consideration of band broadening in AFFFF separation. The intensity-average diameter determined by DLS and AFFFF-MALS agreed well within the estimated uncertainties, although the size distribution of PS-latex determined by DLS was less reliable in comparison with that determined by AFFFF-MALS. PMID:28348293

  15. The dim light melatonin onset following fixed and free sleep schedules.

    PubMed

    Burgess, Helen J; Eastman, Charmane I

    2005-09-01

    The time at which the dim light melatonin onset (DLMO) occurs can be used to ensure the correct timing of light and/or melatonin administration in order to produce desired circadian phase shifts. Sometimes however, measuring the DLMO is not feasible. Here we determined if the DLMO was best estimated from fixed sleep times (based on habitual sleep times) or free (ad libitum) sleep times. Young healthy sleepers on fixed (n=60) or free (n=60) sleep schedules slept at home for 6 days. Sleep times were recorded with sleep logs verified with wrist actigraphy. Half-hourly saliva samples were then collected during a dim light phase assessment and were later assayed to determine the DLMO. We found that the DLMO was more highly correlated with sleep times in the free sleepers than in the fixed sleepers (DLMO versus wake time, r=0.70 and r=0.44, both P<0.05). The regression equation between wake time and the DLMO in the free sleepers predicted the DLMO in an independent sample of free sleepers (n=23) to within 1.5 h of the actual DLMO in 96% of cases. These results indicate that the DLMO can be readily estimated in people whose sleep times are minimally affected by work, class and family commitments. Further work is necessary to determine if the DLMO can be accurately estimated in people with greater work and family responsibilities that affect their sleep times, perhaps by using weekend wake times, and if this method will apply to the elderly and patients with circadian rhythm disorders.

  16. Resuscitator’s perceptions and time for corrective ventilation steps during neonatal resuscitation☆

    PubMed Central

    Sharma, Vinay; Lakshminrusimha, Satyan; Carrion, Vivien; Mathew, Bobby

    2016-01-01

    Background The 2010 neonatal resuscitation program (NRP) guidelines incorporate ventilation corrective steps (using the mnemonic – MRSOPA) into the resuscitation algorithm. The perception of neonatal providers, time taken to perform these maneuvers or the effectiveness of these additional steps has not been evaluated. Methods Using two simulated clinical scenarios of varying degrees of cardiovascular compromise –perinatal asphyxia with (i) bradycardia (heart rate – 40 min−1) and (ii) cardiac arrest, 35 NRP certified providers were evaluated for preference to performing these corrective measures, the time taken for performing these steps and time to onset of chest compressions. Results The average time taken to perform ventilation corrective steps (MRSOPA) was 48.9 ± 21.4 s. Providers were less likely to perform corrective steps and proceed directly to endotracheal intubation in the scenario of cardiac arrest as compared to a state of bradycardia. Cardiac compressions were initiated significantly sooner in the scenario of cardiac arrest 89 ± 24 s as compared to severe bradycardia 122 ± 23 s, p < 0.0001. There were no differences in the time taken to initiation of chest compressions between physicians or mid-level care providers or with the level of experience of the provider. Conclusions Effective ventilation of the lungs with corrective steps using a mask is important in most cases of neonatal resuscitation. Neonatal resuscitators prefer early endotracheal intubation and initiation of chest compressions in the presence of asystolic cardiac arrest. Corrective ventilation steps can potentially postpone initiation of chest compressions and may delay return of spontaneous circulation in the presence of severe cardiovascular compromise. PMID:25796996

  17. Stable and Spectrally Accurate Schemes for the Navier-Stokes Equations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jia, Jun; Liu, Jie

    2011-01-01

    In this paper, we present an accurate, efficient and stable numerical method for the incompressible Navier-Stokes equations (NSEs). The method is based on (1) an equivalent pressure Poisson equation formulation of the NSE with proper pressure boundary conditions, which facilitates the design of high-order and stable numerical methods, and (2) the Krylov deferred correction (KDC) accelerated method of lines transpose (mbox MoL{sup T}), which is very stable, efficient, and of arbitrary order in time. Numerical tests with known exact solutions in three dimensions show that the new method is spectrally accurate in time, and a numerical order of convergence 9more » was observed. Two-dimensional computational results of flow past a cylinder and flow in a bifurcated tube are also reported.« less

  18. The installation and correction of compasses in airplanes

    NASA Technical Reports Server (NTRS)

    Schoeffel, M F

    1927-01-01

    The saving of time that results from flying across country on compass headings is beginning to be widely recognized. At the same time the general use of steel tube fuselages has made a knowledge of compass correction much more necessary than was the case when wooden fuselages were the rule. This paper has been prepared primarily for the benefit of the pilot who has never studied navigation and who does not desire to go into the subject more deeply than to be able to fly compass courses with confidence. It also contains material for the designer who wishes to install his compasses with the expectation that they may be accurately corrected.

  19. Accurate quantitative CF-LIBS analysis of both major and minor elements in alloys via iterative correction of plasma temperature and spectral intensity

    NASA Astrophysics Data System (ADS)

    Shuxia, ZHAO; Lei, ZHANG; Jiajia, HOU; Yang, ZHAO; Wangbao, YIN; Weiguang, MA; Lei, DONG; Liantuan, XIAO; Suotang, JIA

    2018-03-01

    The chemical composition of alloys directly determines their mechanical behaviors and application fields. Accurate and rapid analysis of both major and minor elements in alloys plays a key role in metallurgy quality control and material classification processes. A quantitative calibration-free laser-induced breakdown spectroscopy (CF-LIBS) analysis method, which carries out combined correction of plasma temperature and spectral intensity by using a second-order iterative algorithm and two boundary standard samples, is proposed to realize accurate composition measurements. Experimental results show that, compared to conventional CF-LIBS analysis, the relative errors for major elements Cu and Zn and minor element Pb in the copper-lead alloys has been reduced from 12%, 26% and 32% to 1.8%, 2.7% and 13.4%, respectively. The measurement accuracy for all elements has been improved substantially.

  20. Gctf: Real-time CTF determination and correction

    PubMed Central

    Zhang, Kai

    2016-01-01

    Accurate estimation of the contrast transfer function (CTF) is critical for a near-atomic resolution cryo electron microscopy (cryoEM) reconstruction. Here, a GPU-accelerated computer program, Gctf, for accurate and robust, real-time CTF determination is presented. The main target of Gctf is to maximize the cross-correlation of a simulated CTF with the logarithmic amplitude spectra (LAS) of observed micrographs after background subtraction. Novel approaches in Gctf improve both speed and accuracy. In addition to GPU acceleration (e.g. 10–50×), a fast ‘1-dimensional search plus 2-dimensional refinement (1S2R)’ procedure further speeds up Gctf. Based on the global CTF determination, the local defocus for each particle and for single frames of movies is accurately refined, which improves CTF parameters of all particles for subsequent image processing. Novel diagnosis method using equiphase averaging (EPA) and self-consistency verification procedures have also been implemented in the program for practical use, especially for aims of near-atomic reconstruction. Gctf is an independent program and the outputs can be easily imported into other cryoEM software such as Relion (Scheres, 2012) and Frealign (Grigorieff, 2007). The results from several representative datasets are shown and discussed in this paper. PMID:26592709

  1. Technical Note: Using experimentally determined proton spot scanning timing parameters to accurately model beam delivery time.

    PubMed

    Shen, Jiajian; Tryggestad, Erik; Younkin, James E; Keole, Sameer R; Furutani, Keith M; Kang, Yixiu; Herman, Michael G; Bues, Martin

    2017-10-01

    To accurately model the beam delivery time (BDT) for a synchrotron-based proton spot scanning system using experimentally determined beam parameters. A model to simulate the proton spot delivery sequences was constructed, and BDT was calculated by summing times for layer switch, spot switch, and spot delivery. Test plans were designed to isolate and quantify the relevant beam parameters in the operation cycle of the proton beam therapy delivery system. These parameters included the layer switch time, magnet preparation and verification time, average beam scanning speeds in x- and y-directions, proton spill rate, and maximum charge and maximum extraction time for each spill. The experimentally determined parameters, as well as the nominal values initially provided by the vendor, served as inputs to the model to predict BDTs for 602 clinical proton beam deliveries. The calculated BDTs (T BDT ) were compared with the BDTs recorded in the treatment delivery log files (T Log ): ∆t = T Log -T BDT . The experimentally determined average layer switch time for all 97 energies was 1.91 s (ranging from 1.9 to 2.0 s for beam energies from 71.3 to 228.8 MeV), average magnet preparation and verification time was 1.93 ms, the average scanning speeds were 5.9 m/s in x-direction and 19.3 m/s in y-direction, the proton spill rate was 8.7 MU/s, and the maximum proton charge available for one acceleration is 2.0 ± 0.4 nC. Some of the measured parameters differed from the nominal values provided by the vendor. The calculated BDTs using experimentally determined parameters matched the recorded BDTs of 602 beam deliveries (∆t = -0.49 ± 1.44 s), which were significantly more accurate than BDTs calculated using nominal timing parameters (∆t = -7.48 ± 6.97 s). An accurate model for BDT prediction was achieved by using the experimentally determined proton beam therapy delivery parameters, which may be useful in modeling the interplay effect and patient throughput. The model may

  2. Distortion correction of OCT images of the crystalline lens: gradient index approach.

    PubMed

    Siedlecki, Damian; de Castro, Alberto; Gambra, Enrique; Ortiz, Sergio; Borja, David; Uhlhorn, Stephen; Manns, Fabrice; Marcos, Susana; Parel, Jean-Marie

    2012-05-01

    To propose a method to correct optical coherence tomography (OCT) images of posterior surface of the crystalline lens incorporating its gradient index (GRIN) distribution and explore its possibilities for posterior surface shape reconstruction in comparison to existing methods of correction. Two-dimensional images of nine human lenses were obtained with a time-domain OCT system. The shape of the posterior lens surface was corrected using the proposed iterative correction method. The parameters defining the GRIN distribution used for the correction were taken from a previous publication. The results of correction were evaluated relative to the nominal surface shape (accessible in vitro) and compared with the performance of two other existing methods (simple division, refraction correction: assuming a homogeneous index). Comparisons were made in terms of posterior surface radius, conic constant, root mean square, peak to valley, and lens thickness shifts from the nominal data. Differences in the retrieved radius and conic constant were not statistically significant across methods. However, GRIN distortion correction with optimal shape GRIN parameters provided more accurate estimates of the posterior lens surface in terms of root mean square and peak values, with errors <6 and 13 μm, respectively, on average. Thickness was also more accurately estimated with the new method, with a mean discrepancy of 8 μm. The posterior surface of the crystalline lens and lens thickness can be accurately reconstructed from OCT images, with the accuracy improving with an accurate model of the GRIN distribution. The algorithm can be used to improve quantitative knowledge of the crystalline lens from OCT imaging in vivo. Although the improvements over other methods are modest in two dimension, it is expected that three-dimensional imaging will fully exploit the potential of the technique. The method will also benefit from increasing experimental data of GRIN distribution in the lens of

  3. Absorption and scattering of light by nonspherical particles. [in atmosphere

    NASA Technical Reports Server (NTRS)

    Bohren, C. F.

    1986-01-01

    Using the example of the polarization of scattered light, it is shown that the scattering matrices for identical, randomly ordered particles and for spherical particles are unequal. The spherical assumptions of Mie theory are therefore inconsistent with the random shapes and sizes of atmospheric particulates. The implications for corrections made to extinction measurements of forward scattering light are discussed. Several analytical methods are examined as potential bases for developing more accurate models, including Rayleigh theory, Fraunhoffer Diffraction theory, anomalous diffraction theory, Rayleigh-Gans theory, the separation of variables technique, the Purcell-Pennypacker method, the T-matrix method, and finite difference calculations.

  4. Indispensable finite time corrections for Fokker-Planck equations from time series data.

    PubMed

    Ragwitz, M; Kantz, H

    2001-12-17

    The reconstruction of Fokker-Planck equations from observed time series data suffers strongly from finite sampling rates. We show that previously published results are degraded considerably by such effects. We present correction terms which yield a robust estimation of the diffusion terms, together with a novel method for one-dimensional problems. We apply these methods to time series data of local surface wind velocities, where the dependence of the diffusion constant on the state variable shows a different behavior than previously suggested.

  5. Real-Time Single Frequency Precise Point Positioning Using SBAS Corrections

    PubMed Central

    Li, Liang; Jia, Chun; Zhao, Lin; Cheng, Jianhua; Liu, Jianxu; Ding, Jicheng

    2016-01-01

    Real-time single frequency precise point positioning (PPP) is a promising technique for high-precision navigation with sub-meter or even centimeter-level accuracy because of its convenience and low cost. The navigation performance of single frequency PPP heavily depends on the real-time availability and quality of correction products for satellite orbits and satellite clocks. Satellite-based augmentation system (SBAS) provides the correction products in real-time, but they are intended to be used for wide area differential positioning at 1 meter level precision. By imposing the constraints for ionosphere error, we have developed a real-time single frequency PPP method by sufficiently utilizing SBAS correction products. The proposed PPP method are tested with static and kinematic data, respectively. The static experimental results show that the position accuracy of the proposed PPP method can reach decimeter level, and achieve an improvement of at least 30% when compared with the traditional SBAS method. The positioning convergence of the proposed PPP method can be achieved in 636 epochs at most in static mode. In the kinematic experiment, the position accuracy of the proposed PPP method can be improved by at least 20 cm relative to the SBAS method. Furthermore, it has revealed that the proposed PPP method can achieve decimeter level convergence within 500 s in the kinematic mode. PMID:27517930

  6. Rayleigh Scattering in Planetary Atmospheres: Corrected Tables Through Accurate Computation of X and Y Functions

    NASA Astrophysics Data System (ADS)

    Natraj, Vijay; Li, King-Fai; Yung, Yuk L.

    2009-02-01

    Tables that have been used as a reference for nearly 50 years for the intensity and polarization of reflected and transmitted light in Rayleigh scattering atmospheres have been found to be inaccurate, even to four decimal places. We convert the integral equations describing the X and Y functions into a pair of coupled integro-differential equations that can be efficiently solved numerically. Special care has been taken in evaluating Cauchy principal value integrals and their derivatives that appear in the solution of the Rayleigh scattering problem. The new approach gives results accurate to eight decimal places for the entire range of tabulation (optical thicknesses 0.02-1.0, surface reflectances 0-0.8, solar and viewing zenith angles 0°-88.85°, and relative azimuth angles 0°-180°), including the most difficult case of direct transmission in the direction of the sun. Revised tables have been created and stored electronically for easy reference by the planetary science and astrophysics community.

  7. Real-time endoscopic image orientation correction system using an accelerometer and gyrosensor.

    PubMed

    Lee, Hyung-Chul; Jung, Chul-Woo; Kim, Hee Chan

    2017-01-01

    The discrepancy between spatial orientations of an endoscopic image and a physician's working environment can make it difficult to interpret endoscopic images. In this study, we developed and evaluated a device that corrects the endoscopic image orientation using an accelerometer and gyrosensor. The acceleration of gravity and angular velocity were retrieved from the accelerometer and gyrosensor attached to the handle of the endoscope. The rotational angle of the endoscope handle was calculated using a Kalman filter with transmission delay compensation. Technical evaluation of the orientation correction system was performed using a camera by comparing the optical rotational angle from the captured image with the rotational angle calculated from the sensor outputs. For the clinical utility test, fifteen anesthesiology residents performed a video endoscopic examination of an airway model with and without using the orientation correction system. The participants reported numbers written on papers placed at the left main, right main, and right upper bronchi of the airway model. The correctness and the total time it took participants to report the numbers were recorded. During the technical evaluation, errors in the calculated rotational angle were less than 5 degrees. In the clinical utility test, there was a significant time reduction when using the orientation correction system compared with not using the system (median, 52 vs. 76 seconds; P = .012). In this study, we developed a real-time endoscopic image orientation correction system, which significantly improved physician performance during a video endoscopic exam.

  8. Correction of the spectral calibration of the Joint European Torus core light detecting and ranging Thomson scattering diagnostic using ray tracing

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hawke, J.; Scannell, R.; Maslov, M.

    2013-10-15

    This work isolated the cause of the observed discrepancy between the electron temperature (T{sub e}) measurements before and after the JET Core LIDAR Thomson Scattering (TS) diagnostic was upgraded. In the upgrade process, stray light filters positioned just before the detectors were removed from the system. Modelling showed that the shift imposed on the stray light filters transmission functions due to the variations in the incidence angles of the collected photons impacted plasma measurements. To correct for this identified source of error, correction factors were developed using ray tracing models for the calibration and operational states of the diagnostic. Themore » application of these correction factors resulted in an increase in the observed T{sub e}, resulting in the partial if not complete removal of the observed discrepancy in the measured T{sub e} between the JET core LIDAR TS diagnostic, High Resolution Thomson Scattering, and the Electron Cyclotron Emission diagnostics.« less

  9. Pulsar Timing with the Fermi LAT

    DTIC Science & Technology

    2010-12-01

    the Fermi Science Tool gtbary with the tcorrect=geo option. The geocentric time is the satellite time corrected for geometric light travel time to...the geocenter. It does not include relativistic terms in the correction. The geocentric photon time tgeo is defined as tgeo = tobs + rsat c · n̂psr, (1

  10. Accurate method for luminous transmittance and signal detection quotients measurements in sunglasses lenses

    NASA Astrophysics Data System (ADS)

    Loureiro, A. D.; Gomes, L. M.; Ventura, L.

    2018-02-01

    The international standard ISO 12312-1 proposes transmittance tests that quantify how dark sunglasses lenses are and whether or not they are suitable for driving. To perform these tests a spectrometer is required. In this study, we present and analyze theoretically an accurate alternative method for performing these measurements using simple components. Using three LEDs and a four-channel sensor we generated weighting functions similar to the standard ones for luminous and traffic lights transmittances. From 89 sunglasses lens spectroscopy data, we calculated luminous transmittance and signal detection quotients using our obtained weighting functions and the standard ones. Mean-difference Tukey plots were used to compare the results. All tested sunglasses lenses were classified in the right category and correctly as suitable or not for driving. The greatest absolute errors for luminous transmittance and red, yellow, green and blue signal detection quotients were 0.15%, 0.17, 0.06, 0.04 and 0.18, respectively. This method will be used in a device capable to perform transmittance tests (visible, traffic lights and ultraviolet (UV)) according to the standard. It is important to measure rightly luminous transmittance and relative visual attenuation quotients to report correctly whether or not sunglasses are suitable for driving. Moreover, standard UV requirements depend on luminous transmittance.

  11. Times of Maximum Light: The Passband Dependence

    NASA Astrophysics Data System (ADS)

    Joner, M. D.; Laney, C. D.

    2004-05-01

    We present UBVRIJHK light curves for the dwarf Cepheid variable star AD Canis Minoris. These data are part of a larger project to determine absolute magnitudes for this class of stars. Our figures clearly show changes in the times of maximum light, the amplitude, and the light curve morphology that are dependent on the passband used in the observation. Note that when data from a variety of passbands are used in studies that require a period analysis or that search for small changes in the pulsational period, it is easy to introduce significant systematic errors into the results. We thank the Brigham Young University Department of Physics and Astronmy for continued support of our research. We also acknowledge the South African Astronomical Observatory for time granted to this project.

  12. Distortion Correction of OCT Images of the Crystalline Lens: GRIN Approach

    PubMed Central

    Siedlecki, Damian; de Castro, Alberto; Gambra, Enrique; Ortiz, Sergio; Borja, David; Uhlhorn, Stephen; Manns, Fabrice; Marcos, Susana; Parel, Jean-Marie

    2012-01-01

    Purpose To propose a method to correct Optical Coherence Tomography (OCT) images of posterior surface of the crystalline lens incorporating its gradient index (GRIN) distribution and explore its possibilities for posterior surface shape reconstruction in comparison to existing methods of correction. Methods 2-D images of 9 human lenses were obtained with a time-domain OCT system. The shape of the posterior lens surface was corrected using the proposed iterative correction method. The parameters defining the GRIN distribution used for the correction were taken from a previous publication. The results of correction were evaluated relative to the nominal surface shape (accessible in vitro) and compared to the performance of two other existing methods (simple division, refraction correction: assuming a homogeneous index). Comparisons were made in terms of posterior surface radius, conic constant, root mean square, peak to valley and lens thickness shifts from the nominal data. Results Differences in the retrieved radius and conic constant were not statistically significant across methods. However, GRIN distortion correction with optimal shape GRIN parameters provided more accurate estimates of the posterior lens surface, in terms of RMS and peak values, with errors less than 6μm and 13μm respectively, on average. Thickness was also more accurately estimated with the new method, with a mean discrepancy of 8μm. Conclusions The posterior surface of the crystalline lens and lens thickness can be accurately reconstructed from OCT images, with the accuracy improving with an accurate model of the GRIN distribution. The algorithm can be used to improve quantitative knowledge of the crystalline lens from OCT imaging in vivo. Although the improvements over other methods are modest in 2-D, it is expected that 3-D imaging will fully exploit the potential of the technique. The method will also benefit from increasing experimental data of GRIN distribution in the lens of larger

  13. Refractive accuracy with light-adjustable intraocular lenses.

    PubMed

    Villegas, Eloy A; Alcon, Encarna; Rubio, Elena; Marín, José M; Artal, Pablo

    2014-07-01

    To evaluate efficacy, predictability, and stability of refractive treatments using light-adjustable intraocular lenses (IOLs). University Hospital Virgen de la Arrixaca, Murcia, Spain. Prospective nonrandomized clinical trial. Eyes with a light-adjustable IOL (LAL) were treated with spatial intensity profiles to correct refractive errors. The effective changes in refraction in the light-adjustable IOL after every treatment were estimated by subtracting those in the whole eye and the cornea, which were measured with a Hartmann-Shack sensor and a corneal topographer, respectively. The refractive changes in the whole eye and light-adjustable IOL, manifest refraction, and visual acuity were obtained after every light treatment and at the 3-, 6-, and 12-month follow-ups. The study enrolled 53 eyes (49 patients). Each tested light spatial pattern (5 spherical; 3 astigmatic) produced a different refractive change (P<.01). The combination of 2 light adjustments induced a maximum change in spherical power of the light-adjustable IOL of between -1.98 diopters (D) and +2.30 D and in astigmatism of up to -2.68 D with axis errors below 9 degrees. Intersubject variability (standard deviation) ranged between 0.10 D and 0.40 D. The 2 required lock-in procedures induced a small myopic shift (range +0.01 to +0.57 D) that depended on previous adjustments. Light-adjustable IOL implantation achieved accurate refractive outcomes (around emmetropia) with good uncorrected distance visual acuity, which remained stable over time. Further refinements in nomograms and in the treatment's protocol would improve the predictability of refractive and visual outcomes with these IOLs. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  14. Characterization of 3-Dimensional PET Systems for Accurate Quantification of Myocardial Blood Flow.

    PubMed

    Renaud, Jennifer M; Yip, Kathy; Guimond, Jean; Trottier, Mikaël; Pibarot, Philippe; Turcotte, Eric; Maguire, Conor; Lalonde, Lucille; Gulenchyn, Karen; Farncombe, Troy; Wisenberg, Gerald; Moody, Jonathan; Lee, Benjamin; Port, Steven C; Turkington, Timothy G; Beanlands, Rob S; deKemp, Robert A

    2017-01-01

    Three-dimensional (3D) mode imaging is the current standard for PET/CT systems. Dynamic imaging for quantification of myocardial blood flow with short-lived tracers, such as 82 Rb-chloride, requires accuracy to be maintained over a wide range of isotope activities and scanner counting rates. We proposed new performance standard measurements to characterize the dynamic range of PET systems for accurate quantitative imaging. 82 Rb or 13 N-ammonia (1,100-3,000 MBq) was injected into the heart wall insert of an anthropomorphic torso phantom. A decaying isotope scan was obtained over 5 half-lives on 9 different 3D PET/CT systems and 1 3D/2-dimensional PET-only system. Dynamic images (28 × 15 s) were reconstructed using iterative algorithms with all corrections enabled. Dynamic range was defined as the maximum activity in the myocardial wall with less than 10% bias, from which corresponding dead-time, counting rates, and/or injected activity limits were established for each scanner. Scatter correction residual bias was estimated as the maximum cavity blood-to-myocardium activity ratio. Image quality was assessed via the coefficient of variation measuring nonuniformity of the left ventricular myocardium activity distribution. Maximum recommended injected activity/body weight, peak dead-time correction factor, counting rates, and residual scatter bias for accurate cardiac myocardial blood flow imaging were 3-14 MBq/kg, 1.5-4.0, 22-64 Mcps singles and 4-14 Mcps prompt coincidence counting rates, and 2%-10% on the investigated scanners. Nonuniformity of the myocardial activity distribution varied from 3% to 16%. Accurate dynamic imaging is possible on the 10 3D PET systems if the maximum injected MBq/kg values are respected to limit peak dead-time losses during the bolus first-pass transit. © 2017 by the Society of Nuclear Medicine and Molecular Imaging.

  15. Open EFTs, IR effects & late-time resummations: systematic corrections in stochastic inflation

    DOE PAGES

    Burgess, C. P.; Holman, R.; Tasinato, G.

    2016-01-26

    Though simple inflationary models describe the CMB well, their corrections are often plagued by infrared effects that obstruct a reliable calculation of late-time behaviour. Here we adapt to cosmology tools designed to address similar issues in other physical systems with the goal of making reliable late-time inflationary predictions. The main such tool is Open EFTs which reduce in the inflationary case to Stochastic Inflation plus calculable corrections. We apply this to a simple inflationary model that is complicated enough to have dangerous IR behaviour yet simple enough to allow the inference of late-time behaviour. We find corrections to standard Stochasticmore » Inflationary predictions for the noise and drift, and we find these corrections ensure the IR finiteness of both these quantities. The late-time probability distribution, P(Φ), for super-Hubble field fluctuations are obtained as functions of the noise and drift and so these too are IR finite. We compare our results to other methods (such as large-N models) and find they agree when these models are reliable. In all cases we can explore in detail we find IR secular effects describe the slow accumulation of small perturbations to give a big effect: a significant distortion of the late-time probability distribution for the field. But the energy density associated with this is only of order H 4 at late times and so does not generate a dramatic gravitational back-reaction.« less

  16. Open EFTs, IR effects & late-time resummations: systematic corrections in stochastic inflation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Burgess, C. P.; Holman, R.; Tasinato, G.

    Though simple inflationary models describe the CMB well, their corrections are often plagued by infrared effects that obstruct a reliable calculation of late-time behaviour. Here we adapt to cosmology tools designed to address similar issues in other physical systems with the goal of making reliable late-time inflationary predictions. The main such tool is Open EFTs which reduce in the inflationary case to Stochastic Inflation plus calculable corrections. We apply this to a simple inflationary model that is complicated enough to have dangerous IR behaviour yet simple enough to allow the inference of late-time behaviour. We find corrections to standard Stochasticmore » Inflationary predictions for the noise and drift, and we find these corrections ensure the IR finiteness of both these quantities. The late-time probability distribution, P(Φ), for super-Hubble field fluctuations are obtained as functions of the noise and drift and so these too are IR finite. We compare our results to other methods (such as large-N models) and find they agree when these models are reliable. In all cases we can explore in detail we find IR secular effects describe the slow accumulation of small perturbations to give a big effect: a significant distortion of the late-time probability distribution for the field. But the energy density associated with this is only of order H 4 at late times and so does not generate a dramatic gravitational back-reaction.« less

  17. General method to evaluate substrate surface modification techniques for light extraction enhancement of organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Krummacher, B. C.; Mathai, M. K.; Choong, V.; Choulis, S. A.; So, F.; Winnacker, A.

    2006-09-01

    The external light output of organic light emitting diodes (OLEDs) can be increased by modifying the light emitting surface. The apparent light extraction enhancement is given by the ratio between the efficiency of the unmodified device and the efficiency of the modified device. This apparent light extraction enhancement is dependent on the OLED architecture itself and is not the correct value to judge the effectiveness of a technique to enhance light outcoupling due to substrate surface modification. We propose a general method to evaluate substrate surface modification techniques for light extraction enhancement of OLEDs independent from the device architecture. This method is experimentally demonstrated using green electrophosphorescent OLEDs with different device architectures. The substrate surface of these OLEDs was modified by applying a prismatic film to increase light outcoupling from the device stack. It was demonstrated that the conventionally measured apparent light extraction enhancement by means of the prismatic film does not reflect the actual performance of the light outcoupling technique. Rather, by comparing the light extracted out of the prismatic film to that generated in the OLED layers and coupled into the substrate (before the substrate/air interface), a more accurate evaluation of light outcoupling enhancement can be achieved. Furthermore we show that substrate surface modification can change the output spectrum of a broad band emitting OLED.

  18. Real-time fMRI processing with physiological noise correction - Comparison with off-line analysis.

    PubMed

    Misaki, Masaya; Barzigar, Nafise; Zotev, Vadim; Phillips, Raquel; Cheng, Samuel; Bodurka, Jerzy

    2015-12-30

    While applications of real-time functional magnetic resonance imaging (rtfMRI) are growing rapidly, there are still limitations in real-time data processing compared to off-line analysis. We developed a proof-of-concept real-time fMRI processing (rtfMRIp) system utilizing a personal computer (PC) with a dedicated graphic processing unit (GPU) to demonstrate that it is now possible to perform intensive whole-brain fMRI data processing in real-time. The rtfMRIp performs slice-timing correction, motion correction, spatial smoothing, signal scaling, and general linear model (GLM) analysis with multiple noise regressors including physiological noise modeled with cardiac (RETROICOR) and respiration volume per time (RVT). The whole-brain data analysis with more than 100,000voxels and more than 250volumes is completed in less than 300ms, much faster than the time required to acquire the fMRI volume. Real-time processing implementation cannot be identical to off-line analysis when time-course information is used, such as in slice-timing correction, signal scaling, and GLM. We verified that reduced slice-timing correction for real-time analysis had comparable output with off-line analysis. The real-time GLM analysis, however, showed over-fitting when the number of sampled volumes was small. Our system implemented real-time RETROICOR and RVT physiological noise corrections for the first time and it is capable of processing these steps on all available data at a given time, without need for recursive algorithms. Comprehensive data processing in rtfMRI is possible with a PC, while the number of samples should be considered in real-time GLM. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. 75 FR 37738 - 1-Naphthaleneacetic Acid; Time-Limited Tolerance, Technical Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-30

    ...-Naphthaleneacetic Acid; Time-Limited Tolerance, Technical Correction AGENCY: Environmental Protection Agency (EPA..., ethylene oxide, fenvalerate, et al.; tolerance actions. Today's rule restores the time-limited tolerance...-3) establishing a time-limited tolerance for residues of 1-naphthaleneacetic acid ethyl ester in or...

  20. The dim light melatonin onset following fixed and free sleep schedules

    PubMed Central

    Burgess, Helen J.; Eastman, Charmane I.

    2013-01-01

    Summary The time at which the dim light melatonin onset (DLMO) occurs can be used to ensure the correct timing of light and/or melatonin administration in order to produce desired circadian phase shifts. Sometimes however, measuring the DLMO is not feasible. Here we determined if the DLMO was best estimated from fixed sleep times (based on habitual sleep times) or free (ad libitum) sleep times. Young healthy sleepers on fixed (n = 60) or free (n = 60) sleep schedules slept at home for 6 days. Sleep times were recorded with sleep logs verified with wrist actigraphy. Half-hourly saliva samples were then collected during a dim light phase assessment and were later assayed to determine the DLMO. We found that the DLMO was more highly correlated with sleep times in the free sleepers than in the fixed sleepers (DLMO versus wake time, r = 0.70 and r = 0.44, both P < 0.05). The regression equation between wake time and the DLMO in the free sleepers predicted the DLMO in an independent sample of free sleepers (n = 23) to within 1.5 h of the actual DLMO in 96% of cases. These results indicate that the DLMO can be readily estimated in people whose sleep times are minimally affected by work, class and family commitments. Further work is necessary to determine if the DLMO can be accurately estimated in people with greater work and family responsibilities that affect their sleep times, perhaps by using weekend wake times, and if this method will apply to the elderly and patients with circadian rhythm disorders. PMID:16120097

  1. Accurate frequency and time dissemination in the optical domain

    NASA Astrophysics Data System (ADS)

    Khabarova, K. Yu; Kalganova, E. S.; Kolachevsky, N. N.

    2018-02-01

    The development of the optical frequency comb technique has enabled a wide use of atomic optical clocks by allowing frequency conversion from the optical to the radio frequency range. Today, the fractional instability of such clocks has reached the record eighteen-digit level, two orders of magnitude better than for cesium fountains representing the primary frequency standard. This is paralleled by the development of techniques for transferring accurate time and optical frequency signals, including fiber links. With this technology, the fractional instability of transferred frequency can be lowered to below 10‑18 with an averaging time of 1000 s for a 1000 km optical link. At a distance of 500 km, a time signal uncertainty of 250 ps has been achieved. Optical links allow comparing optical clocks and creating a synchronized time and frequency standard network at a new level of precision. Prospects for solving new problems arise, including the determination of the gravitational potential, the measurement of the continental Sagnac effect, and precise tests of fundamental theories.

  2. A Class of Prediction-Correction Methods for Time-Varying Convex Optimization

    NASA Astrophysics Data System (ADS)

    Simonetto, Andrea; Mokhtari, Aryan; Koppel, Alec; Leus, Geert; Ribeiro, Alejandro

    2016-09-01

    This paper considers unconstrained convex optimization problems with time-varying objective functions. We propose algorithms with a discrete time-sampling scheme to find and track the solution trajectory based on prediction and correction steps, while sampling the problem data at a constant rate of $1/h$, where $h$ is the length of the sampling interval. The prediction step is derived by analyzing the iso-residual dynamics of the optimality conditions. The correction step adjusts for the distance between the current prediction and the optimizer at each time step, and consists either of one or multiple gradient steps or Newton steps, which respectively correspond to the gradient trajectory tracking (GTT) or Newton trajectory tracking (NTT) algorithms. Under suitable conditions, we establish that the asymptotic error incurred by both proposed methods behaves as $O(h^2)$, and in some cases as $O(h^4)$, which outperforms the state-of-the-art error bound of $O(h)$ for correction-only methods in the gradient-correction step. Moreover, when the characteristics of the objective function variation are not available, we propose approximate gradient and Newton tracking algorithms (AGT and ANT, respectively) that still attain these asymptotical error bounds. Numerical simulations demonstrate the practical utility of the proposed methods and that they improve upon existing techniques by several orders of magnitude.

  3. Index mismatch aberration correction over long working distances using spatial light modulation.

    PubMed

    Gjonaj, Bergin; Johnson, Patrick; Bonn, Mischa; Domke, Katrin F

    2012-11-20

    For many microscopy applications, millimeters-long free working distances (LWD) are required. However, the high resolution and contrast of LWD objectives operated in air are lost when introducing glass and/or liquid with the sample. We propose to use spatial light modulation to correct for such beam aberrations caused by refractive index mismatches. Focusing a monochromatic laser beam with a 10 mm working distance air objective (50×, 0.5 NA) through air, glass, and water, we manage to restore a sharp, intense focus (FWHM<2λ) by adaptive beam phase shaping. Our approach offers a practical and cost-effective route to high resolution and contrast microscopy using LWD air objectives, extending their usage beyond applications in air.

  4. Fast determination of the spatially distributed photon fluence for light dose evaluation of PDT

    NASA Astrophysics Data System (ADS)

    Zhao, Kuanxin; Chen, Weiting; Li, Tongxin; Yan, Panpan; Qin, Zhuanping; Zhao, Huijuan

    2018-02-01

    Photodynamic therapy (PDT) has shown superiorities of noninvasiveness and high-efficiency in the treatment of early-stage skin cancer. Rapid and accurate determination of spatially distributed photon fluence in turbid tissue is essential for the dosimetry evaluation of PDT. It is generally known that photon fluence can be accurately obtained by Monte Carlo (MC) methods, while too much time would be consumed especially for complex light source mode or online real-time dosimetry evaluation of PDT. In this work, a method to rapidly calculate spatially distributed photon fluence in turbid medium is proposed implementing a classical perturbation and iteration theory on mesh Monte Carlo (MMC). In the proposed method, photon fluence can be obtained by superposing a perturbed and iterative solution caused by the defects in turbid medium to an unperturbed solution for the background medium and therefore repetitive MMC simulations can be avoided. To validate the method, a non-melanoma skin cancer model is carried out. The simulation results show the solution of photon fluence can be obtained quickly and correctly by perturbation algorithm.

  5. Accurate Rapid Lifetime Determination on Time-Gated FLIM Microscopy with Optical Sectioning

    PubMed Central

    Silva, Susana F.; Domingues, José Paulo

    2018-01-01

    Time-gated fluorescence lifetime imaging microscopy (FLIM) is a powerful technique to assess the biochemistry of cells and tissues. When applied to living thick samples, it is hampered by the lack of optical sectioning and the need of acquiring many images for an accurate measurement of fluorescence lifetimes. Here, we report on the use of processing techniques to overcome these limitations, minimizing the acquisition time, while providing optical sectioning. We evaluated the application of the HiLo and the rapid lifetime determination (RLD) techniques for accurate measurement of fluorescence lifetimes with optical sectioning. HiLo provides optical sectioning by combining the high-frequency content from a standard image, obtained with uniform illumination, with the low-frequency content of a second image, acquired using structured illumination. Our results show that HiLo produces optical sectioning on thick samples without degrading the accuracy of the measured lifetimes. We also show that instrument response function (IRF) deconvolution can be applied with the RLD technique on HiLo images, improving greatly the accuracy of the measured lifetimes. These results open the possibility of using the RLD technique with pulsed diode laser sources to determine accurately fluorescence lifetimes in the subnanosecond range on thick multilayer samples, providing that offline processing is allowed. PMID:29599938

  6. Accurate Rapid Lifetime Determination on Time-Gated FLIM Microscopy with Optical Sectioning.

    PubMed

    Silva, Susana F; Domingues, José Paulo; Morgado, António Miguel

    2018-01-01

    Time-gated fluorescence lifetime imaging microscopy (FLIM) is a powerful technique to assess the biochemistry of cells and tissues. When applied to living thick samples, it is hampered by the lack of optical sectioning and the need of acquiring many images for an accurate measurement of fluorescence lifetimes. Here, we report on the use of processing techniques to overcome these limitations, minimizing the acquisition time, while providing optical sectioning. We evaluated the application of the HiLo and the rapid lifetime determination (RLD) techniques for accurate measurement of fluorescence lifetimes with optical sectioning. HiLo provides optical sectioning by combining the high-frequency content from a standard image, obtained with uniform illumination, with the low-frequency content of a second image, acquired using structured illumination. Our results show that HiLo produces optical sectioning on thick samples without degrading the accuracy of the measured lifetimes. We also show that instrument response function (IRF) deconvolution can be applied with the RLD technique on HiLo images, improving greatly the accuracy of the measured lifetimes. These results open the possibility of using the RLD technique with pulsed diode laser sources to determine accurately fluorescence lifetimes in the subnanosecond range on thick multilayer samples, providing that offline processing is allowed.

  7. Marginalizing Instrument Systematics in HST WFC3 Transit Light Curves

    NASA Technical Reports Server (NTRS)

    Wakeford, H. R.; Sing, D.K.; Deming, D.; Mandell, A.

    2016-01-01

    Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) infrared observations at 1.1-1.7 microns probe primarily the H2O absorption band at 1.4 microns, and have provided low-resolution transmission spectra for a wide range of exoplanets. We present the application of marginalization based on Gibson to analyze exoplanet transit light curves obtained from HST WFC3 to better determine important transit parameters such as "ramp" probability (R (sub p)) divided by "ramp" total (R (sub asterisk)), which are important for accurate detections of H2O. We approximate the evidence, often referred to as the marginal likelihood, for a grid of systematic models using the Akaike Information Criterion. We then calculate the evidence-based weight assigned to each systematic model and use the information from all tested models to calculate the final marginalized transit parameters for both the band-integrated and spectroscopic light curves to construct the transmission spectrum. We find that a majority of the highest weight models contain a correction for a linear trend in time as well as corrections related to HST orbital phase. We additionally test the dependence on the shift in spectral wavelength position over the course of the observations and find that spectroscopic wavelength shifts delta (sub lambda) times lambda) best describe the associated systematic in the spectroscopic light curves for most targets while fast scan rate observations of bright targets require an additional level of processing to produce a robust transmission spectrum. The use of marginalization allows for transparent interpretation and understanding of the instrument and the impact of each systematic evaluated statistically for each data set, expanding the ability to make true and comprehensive comparisons between exoplanet atmospheres.

  8. Atmospheric extinction in solar tower plants: absorption and broadband correction for MOR measurements

    NASA Astrophysics Data System (ADS)

    Hanrieder, N.; Wilbert, S.; Pitz-Paal, R.; Emde, C.; Gasteiger, J.; Mayer, B.; Polo, J.

    2015-08-01

    Losses of reflected Direct Normal Irradiance due to atmospheric extinction in concentrated solar tower plants can vary significantly with site and time. The losses of the direct normal irradiance between the heliostat field and receiver in a solar tower plant are mainly caused by atmospheric scattering and absorption by aerosol and water vapor concentration in the atmospheric boundary layer. Due to a high aerosol particle number, radiation losses can be significantly larger in desert environments compared to the standard atmospheric conditions which are usually considered in ray-tracing or plant optimization tools. Information about on-site atmospheric extinction is only rarely available. To measure these radiation losses, two different commercially available instruments were tested, and more than 19 months of measurements were collected and compared at the Plataforma Solar de Almería. Both instruments are primarily used to determine the meteorological optical range (MOR). The Vaisala FS11 scatterometer is based on a monochromatic near-infrared light source emission and measures the strength of scattering processes in a small air volume mainly caused by aerosol particles. The Optec LPV4 long-path visibility transmissometer determines the monochromatic attenuation between a light-emitting diode (LED) light source at 532 nm and a receiver and therefore also accounts for absorption processes. As the broadband solar attenuation is of interest for solar resource assessment for concentrated solar power (CSP), a correction procedure for these two instruments is developed and tested. This procedure includes a spectral correction of both instruments from monochromatic to broadband attenuation. That means the attenuation is corrected for the time-dependent solar spectrum which is reflected by the collector. Further, an absorption correction for the Vaisala FS11 scatterometer is implemented. To optimize the absorption and broadband correction (ABC) procedure, additional

  9. On the proper use of the reduced speed of light approximation

    DOE PAGES

    Gnedin, Nickolay Y.

    2016-12-07

    I show that the Reduced Speed of Light (RSL) approximation, when used properly (i.e. as originally designed - only for the local sources but not for the cosmic background), remains a highly accurate numerical method for modeling cosmic reionization. Simulated ionization and star formation histories from the "Cosmic Reionization On Computers" (CROC) project are insensitive to the adopted value of the reduced speed of light for as long as that value does not fall below about 10% of the true speed of light. Here, a recent claim of the failure of the RSL approximation in the Illustris reionization model appearsmore » to be due to the effective speed of light being reduced in the equation for the cosmic background too, and, hence, illustrates the importance of maintaining the correct speed of light in modeling the cosmic background.« less

  10. On the proper use of the reduced speed of light approximation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gnedin, Nickolay Y.

    I show that the Reduced Speed of Light (RSL) approximation, when used properly (i.e. as originally designed - only for the local sources but not for the cosmic background), remains a highly accurate numerical method for modeling cosmic reionization. Simulated ionization and star formation histories from the "Cosmic Reionization On Computers" (CROC) project are insensitive to the adopted value of the reduced speed of light for as long as that value does not fall below about 10% of the true speed of light. Here, a recent claim of the failure of the RSL approximation in the Illustris reionization model appearsmore » to be due to the effective speed of light being reduced in the equation for the cosmic background too, and, hence, illustrates the importance of maintaining the correct speed of light in modeling the cosmic background.« less

  11. Fast Physically Correct Refocusing for Sparse Light Fields Using Block-Based Multi-Rate View Interpolation.

    PubMed

    Huang, Chao-Tsung; Wang, Yu-Wen; Huang, Li-Ren; Chin, Jui; Chen, Liang-Gee

    2017-02-01

    Digital refocusing has a tradeoff between complexity and quality when using sparsely sampled light fields for low-storage applications. In this paper, we propose a fast physically correct refocusing algorithm to address this issue in a twofold way. First, view interpolation is adopted to provide photorealistic quality at infocus-defocus hybrid boundaries. Regarding its conventional high complexity, we devised a fast line-scan method specifically for refocusing, and its 1D kernel can be 30× faster than the benchmark View Synthesis Reference Software (VSRS)-1D-Fast. Second, we propose a block-based multi-rate processing flow for accelerating purely infocused or defocused regions, and a further 3- 34× speedup can be achieved for high-resolution images. All candidate blocks of variable sizes can interpolate different numbers of rendered views and perform refocusing in different subsampled layers. To avoid visible aliasing and block artifacts, we determine these parameters and the simulated aperture filter through a localized filter response analysis using defocus blur statistics. The final quadtree block partitions are then optimized in terms of computation time. Extensive experimental results are provided to show superior refocusing quality and fast computation speed. In particular, the run time is comparable with the conventional single-image blurring, which causes serious boundary artifacts.

  12. Stabilized high-accuracy correction of ocular aberrations with liquid crystal on silicon spatial light modulator in adaptive optics retinal imaging system.

    PubMed

    Huang, Hongxin; Inoue, Takashi; Tanaka, Hiroshi

    2011-08-01

    We studied the long-term optical performance of an adaptive optics scanning laser ophthalmoscope that uses a liquid crystal on silicon spatial light modulator to correct ocular aberrations. The system achieved good compensation of aberrations while acquiring images of fine retinal structures, excepting during sudden eye movements. The residual wavefront aberrations collected over several minutes in several situations were statistically analyzed. The mean values of the root-mean-square residual wavefront errors were 23-30 nm, and for around 91-94% of the effective time the errors were below the Marechal criterion for diffraction limited imaging. The ability to axially shift the imaging plane to different retinal depths was also demonstrated.

  13. Exploring the relationship between patient call-light use rate and nurse call-light response time in acute care settings.

    PubMed

    Tzeng, Huey-Ming; Larson, Janet L

    2011-03-01

    Patient call-light usage and nurse responsiveness to call lights are two intertwined concepts that could affect patients' safety during hospital stays. Little is known about the relationship between call-light usage and call-light response time. Consequently, this exploratory study examined the relationship between the patient-initiated call-light use rate and the nursing staff's average call-light response time in a Michigan community hospital. It used hospital archived data retrieved from the call-light tracking system for the period from February 2007 through June 2008. Curve estimation regression and multiple regression analyses were conducted. The results showed that the call-light response time was not affected by the total nursing hours or RN hours. The nurse call-light response time was longer when the patient call-light use rate was higher and the average length of stay was shorter. It is likely that a shorter length of stay contributes to the nursing care activity level on the unit because it is associated with a higher frequency of patient admissions/discharges and treatment per patient-day. This suggests that the nursing care activity level on the unit and number of call-light alarms could affect nurse call-light response time, independently of the number of nurses available to respond.

  14. Robotic real-time translational and rotational head motion correction during frameless stereotactic radiosurgery

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Xinmin; Belcher, Andrew H.; Grelewicz, Zachary

    Purpose: To develop a control system to correct both translational and rotational head motion deviations in real-time during frameless stereotactic radiosurgery (SRS). Methods: A novel feedback control with a feed-forward algorithm was utilized to correct for the coupling of translation and rotation present in serial kinematic robotic systems. Input parameters for the algorithm include the real-time 6DOF target position, the frame pitch pivot point to target distance constant, and the translational and angular Linac beam off (gating) tolerance constants for patient safety. Testing of the algorithm was done using a 4D (XY Z + pitch) robotic stage, an infrared headmore » position sensing unit and a control computer. The measured head position signal was processed and a resulting command was sent to the interface of a four-axis motor controller, through which four stepper motors were driven to perform motion compensation. Results: The control of the translation of a brain target was decoupled with the control of the rotation. For a phantom study, the corrected position was within a translational displacement of 0.35 mm and a pitch displacement of 0.15° 100% of the time. For a volunteer study, the corrected position was within displacements of 0.4 mm and 0.2° over 98.5% of the time, while it was 10.7% without correction. Conclusions: The authors report a control design approach for both translational and rotational head motion correction. The experiments demonstrated that control performance of the 4D robotic stage meets the submillimeter and subdegree accuracy required by SRS.« less

  15. Is It Time for a Switch in Lighting?

    ERIC Educational Resources Information Center

    Bennorth, Greg

    1999-01-01

    Reviews new types of fluorescent lamp and electronic ballasts and their associated starting methods to explain the benefits of programmed start ballasts in today's lighting applications. Advice on when it is time to make a lighting retrofit is highlighted. (GR)

  16. A time accurate finite volume high resolution scheme for three dimensional Navier-Stokes equations

    NASA Technical Reports Server (NTRS)

    Liou, Meng-Sing; Hsu, Andrew T.

    1989-01-01

    A time accurate, three-dimensional, finite volume, high resolution scheme for solving the compressible full Navier-Stokes equations is presented. The present derivation is based on the upwind split formulas, specifically with the application of Roe's (1981) flux difference splitting. A high-order accurate (up to the third order) upwind interpolation formula for the inviscid terms is derived to account for nonuniform meshes. For the viscous terms, discretizations consistent with the finite volume concept are described. A variant of second-order time accurate method is proposed that utilizes identical procedures in both the predictor and corrector steps. Avoiding the definition of midpoint gives a consistent and easy procedure, in the framework of finite volume discretization, for treating viscous transport terms in the curvilinear coordinates. For the boundary cells, a new treatment is introduced that not only avoids the use of 'ghost cells' and the associated problems, but also satisfies the tangency conditions exactly and allows easy definition of viscous transport terms at the first interface next to the boundary cells. Numerical tests of steady and unsteady high speed flows show that the present scheme gives accurate solutions.

  17. Atmospheric correction for remote sensing image based on multi-spectral information

    NASA Astrophysics Data System (ADS)

    Wang, Yu; He, Hongyan; Tan, Wei; Qi, Wenwen

    2018-03-01

    The light collected from remote sensors taken from space must transit through the Earth's atmosphere. All satellite images are affected at some level by lightwave scattering and absorption from aerosols, water vapor and particulates in the atmosphere. For generating high-quality scientific data, atmospheric correction is required to remove atmospheric effects and to convert digital number (DN) values to surface reflectance (SR). Every optical satellite in orbit observes the earth through the same atmosphere, but each satellite image is impacted differently because atmospheric conditions are constantly changing. A physics-based detailed radiative transfer model 6SV requires a lot of key ancillary information about the atmospheric conditions at the acquisition time. This paper investigates to achieve the simultaneous acquisition of atmospheric radiation parameters based on the multi-spectral information, in order to improve the estimates of surface reflectance through physics-based atmospheric correction. Ancillary information on the aerosol optical depth (AOD) and total water vapor (TWV) derived from the multi-spectral information based on specific spectral properties was used for the 6SV model. The experimentation was carried out on images of Sentinel-2, which carries a Multispectral Instrument (MSI), recording in 13 spectral bands, covering a wide range of wavelengths from 440 up to 2200 nm. The results suggest that per-pixel atmospheric correction through 6SV model, integrating AOD and TWV derived from multispectral information, is better suited for accurate analysis of satellite images and quantitative remote sensing application.

  18. YALINA-booster subcritical assembly pulsed-neutron e xperiments: detector dead time and apatial corrections.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cao, Y.; Gohar, Y.; Nuclear Engineering Division

    In almost every detector counting system, a minimal dead time is required to record two successive events as two separated pulses. Due to the random nature of neutron interactions in the subcritical assembly, there is always some probability that a true neutron event will not be recorded because it occurs too close to the preceding event. These losses may become rather severe for counting systems with high counting rates, and should be corrected before any utilization of the experimental data. This report examines the dead time effects for the pulsed neutron experiments of the YALINA-Booster subcritical assembly. The nonparalyzable modelmore » is utilized to correct the experimental data due to dead time. Overall, the reactivity values are increased by 0.19$ and 0.32$ after the spatial corrections for the YALINA-Booster 36% and 21% configurations respectively. The differences of the reactivities obtained with He-3 long or short detectors at the same detector channel diminish after the dead time corrections of the experimental data for the 36% YALINA-Booster configuration. In addition, better agreements between reactivities obtained from different experimental data sets are also observed after the dead time corrections for the 21% YALINA-Booster configuration.« less

  19. A symmetric multivariate leakage correction for MEG connectomes

    PubMed Central

    Colclough, G.L.; Brookes, M.J.; Smith, S.M.; Woolrich, M.W.

    2015-01-01

    Ambiguities in the source reconstruction of magnetoencephalographic (MEG) measurements can cause spurious correlations between estimated source time-courses. In this paper, we propose a symmetric orthogonalisation method to correct for these artificial correlations between a set of multiple regions of interest (ROIs). This process enables the straightforward application of network modelling methods, including partial correlation or multivariate autoregressive modelling, to infer connectomes, or functional networks, from the corrected ROIs. Here, we apply the correction to simulated MEG recordings of simple networks and to a resting-state dataset collected from eight subjects, before computing the partial correlations between power envelopes of the corrected ROItime-courses. We show accurate reconstruction of our simulated networks, and in the analysis of real MEGresting-state connectivity, we find dense bilateral connections within the motor and visual networks, together with longer-range direct fronto-parietal connections. PMID:25862259

  20. Ionospheric Correction of InSAR for Accurate Ice Motion Mapping at High Latitudes

    NASA Astrophysics Data System (ADS)

    Liao, H.; Meyer, F. J.

    2016-12-01

    Monitoring the motion of the large ice sheets is of great importance for determining ice mass balance and its contribution to sea level rise. Recently the first comprehensive ice motion of the Greenland and the Antarctica have been generated with InSAR. However, these studies have indicated that the performance of InSAR-based ice motion mapping is limited by the presence of the ionosphere. This is particularly true at high latitudes and for low-frequency SAR data. Filter-based and empirical methods (e.g., removing polynomials), which have often been used to mitigate ionospheric effects, are often ineffective in these areas due to the typically strong spatial variability of ionospheric phase delay in high latitudes and due to the risk of removing true deformation signals from the observations. In this study, we will first present an outline of our split-spectrum InSAR-based ionospheric correction approach and particularly highlight how our method improves upon published techniques, such as the multiple sub-band approach to boost estimation accuracy as well as advanced error correction and filtering algorithms. We applied our work flow to a large number of ionosphere-affected dataset over the large ice sheets to estimate the benefit of ionospheric correction on ice motion mapping accuracy. Appropriate test sites over Greenland and the Antarctic have been chosen through cooperation with authors (UW, Ian Joughin) of previous ice motion studies. To demonstrate the magnitude of ionospheric noise and to showcase the performance of ionospheric correction, we will show examples of ionospheric-affected InSAR data and our ionosphere corrected result for comparison in visual. We also compared the corrected phase data to known ice velocity fields quantitatively for the analyzed areas from experts in ice velocity mapping. From our studies we found that ionospheric correction significantly reduces biases in ice velocity estimates and boosts accuracy by a factor that depends on a

  1. A deconvolution technique to correct deep images of galaxies from instrumental scattered light

    NASA Astrophysics Data System (ADS)

    Karabal, E.; Duc, P.-A.; Kuntschner, H.; Chanial, P.; Cuillandre, J.-C.; Gwyn, S.

    2017-05-01

    Deep imaging of the diffuse light that is emitted by stellar fine structures and outer halos around galaxies is often now used to probe their past mass assembly. Because the extended halos survive longer than the relatively fragile tidal features, they trace more ancient mergers. We use images that reach surface brightness limits as low as 28.5-29 mag arcsec-2 (g-band) to obtain light and color profiles up to 5-10 effective radii of a sample of nearby early-type galaxies. These were acquired with MegaCam as part of the CFHT MATLAS large programme. These profiles may be compared to those produced using simulations of galaxy formation and evolution, once corrected for instrumental effects. Indeed they can be heavily contaminated by the scattered light caused by internal reflections within the instrument. In particular, the nucleus of galaxies generates artificial flux in the outer halo, which has to be precisely subtracted. We present a deconvolution technique to remove the artificial halos that makes use of very large kernels. The technique, which is based on PyOperators, is more time efficient than the model-convolution methods that are also used for that purpose. This is especially the case for galaxies with complex structures that are hard to model. Having a good knowledge of the point spread function (PSF), including its outer wings, is critical for the method. A database of MegaCam PSF models corresponding to different seeing conditions and bands was generated directly from the deep images. We show that the difference in the PSFs in different bands causes artificial changes in the color profiles, in particular a reddening of the outskirts of galaxies having a bright nucleus. The method is validated with a set of simulated images and applied to three representative test cases: NGC 3599, NGC 3489, and NGC 4274, which exhibits a prominent ghost halo for two of them. This method successfully removes this. The library of PSFs (FITS files) is only available at the

  2. A general dead-time correction method based on live-time stamping. Application to the measurement of short-lived radionuclides.

    PubMed

    Chauvenet, B; Bobin, C; Bouchard, J

    2017-12-01

    Dead-time correction formulae are established in the general case of superimposed non-homogeneous Poisson processes. Based on the same principles as conventional live-timed counting, this method exploits the additional information made available using digital signal processing systems, and especially the possibility to store the time stamps of live-time intervals. No approximation needs to be made to obtain those formulae. Estimates of the variances of corrected rates are also presented. This method is applied to the activity measurement of short-lived radionuclides. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Clearing the waters: Evaluating the need for site-specific field fluorescence corrections based on turbidity measurements

    USGS Publications Warehouse

    Saraceno, John F.; Shanley, James B.; Downing, Bryan D.; Pellerin, Brian A.

    2017-01-01

    In situ fluorescent dissolved organic matter (fDOM) measurements have gained increasing popularity as a proxy for dissolved organic carbon (DOC) concentrations in streams. One challenge to accurate fDOM measurements in many streams is light attenuation due to suspended particles. Downing et al. (2012) evaluated the need for corrections to compensate for particle interference on fDOM measurements using a single sediment standard in a laboratory study. The application of those results to a large river improved unfiltered field fDOM accuracy. We tested the same correction equation in a headwater tropical stream and found that it overcompensated fDOM when turbidity exceeded ∼300 formazin nephelometric units (FNU). Therefore, we developed a site-specific, field-based fDOM correction equation through paired in situ fDOM measurements of filtered and unfiltered streamwater. The site-specific correction increased fDOM accuracy up to a turbidity as high as 700 FNU, the maximum observed in this study. The difference in performance between the laboratory-based correction equation of Downing et al. (2012) and our site-specific, field-based correction equation likely arises from differences in particle size distribution between the sediment standard used in the lab (silt) and that observed in our study (fine to medium sand), particularly during high flows. Therefore, a particle interference correction equation based on a single sediment type may not be ideal when field sediment size is significantly different. Given that field fDOM corrections for particle interference under turbid conditions are a critical component in generating accurate DOC estimates, we describe a way to develop site-specific corrections.

  4. Effect of eccentricity and light level on the timing of light adaptation mechanisms.

    PubMed

    Barrionuevo, Pablo A; Matesanz, Beatriz M; Gloriani, Alejandro H; Arranz, Isabel; Issolio, Luis; Mar, Santiago; Aparicio, Juan A

    2018-04-01

    We explored the complexity of the light adaptation process, assessing adaptation recovery (Ar) at different eccentricities and light levels. Luminance thresholds were obtained with transient background fields at mesopic and photopic light levels for temporal retinal eccentricities (0°-15°) with test/background stimulus size of 0.5°/1° using a staircase procedure in a two-channel Maxwellian view optical system. Ar was obtained in comparison with steady data [Vis. Res.125, 12 (2016)VISRAM0042-698910.1016/j.visres.2016.04.008]. Light level proportionally affects Ar only at fovea. Photopic extrafoveal thresholds were one log unit higher for transient conditions. Adaptation was equally fast at low light levels for different retinal locations with variations mainly affected by noise. These results evidence different timing in the mechanisms of adaptation involved.

  5. High speed wavefront sensorless aberration correction in digital micromirror based confocal microscopy.

    PubMed

    Pozzi, P; Wilding, D; Soloviev, O; Verstraete, H; Bliek, L; Vdovin, G; Verhaegen, M

    2017-01-23

    The quality of fluorescence microscopy images is often impaired by the presence of sample induced optical aberrations. Adaptive optical elements such as deformable mirrors or spatial light modulators can be used to correct aberrations. However, previously reported techniques either require special sample preparation, or time consuming optimization procedures for the correction of static aberrations. This paper reports a technique for optical sectioning fluorescence microscopy capable of correcting dynamic aberrations in any fluorescent sample during the acquisition. This is achieved by implementing adaptive optics in a non conventional confocal microscopy setup, with multiple programmable confocal apertures, in which out of focus light can be separately detected, and used to optimize the correction performance with a sampling frequency an order of magnitude faster than the imaging rate of the system. The paper reports results comparing the correction performances to traditional image optimization algorithms, and demonstrates how the system can compensate for dynamic changes in the aberrations, such as those introduced during a focal stack acquisition though a thick sample.

  6. Error correction in short time steps during the application of quantum gates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Castro, L.A. de, E-mail: leonardo.castro@usp.br; Napolitano, R.D.J.

    2016-04-15

    We propose a modification of the standard quantum error-correction method to enable the correction of errors that occur due to the interaction with a noisy environment during quantum gates without modifying the codification used for memory qubits. Using a perturbation treatment of the noise that allows us to separate it from the ideal evolution of the quantum gate, we demonstrate that in certain cases it is necessary to divide the logical operation in short time steps intercalated by correction procedures. A prescription of how these gates can be constructed is provided, as well as a proof that, even for themore » cases when the division of the quantum gate in short time steps is not necessary, this method may be advantageous for reducing the total duration of the computation.« less

  7. Predicting the timing properties of phosphor-coated scintillators using Monte Carlo light transport simulation

    PubMed Central

    Roncali, Emilie; Schmall, Jeffrey P.; Viswanath, Varsha; Berg, Eric; Cherry, Simon R.

    2014-01-01

    Current developments in positron emission tomography (PET) focus on improving timing performance for scanners with time-of-flight (TOF) capability, and incorporating depth-of-interaction (DOI) information. Recent studies have shown that incorporating DOI correction in TOF detectors can improve timing resolution, and that DOI also becomes more important in long axial field-of-view scanners. We have previously reported the development of DOI-encoding detectors using phosphor-coated scintillation crystals; here we study the timing properties of those crystals to assess the feasibility of providing some level of DOI information without significantly degrading the timing performance. We used Monte Carlo simulations to provide a detailed understanding of light transport in phosphor-coated crystals which cannot be fully characterized experimentally. Our simulations used a custom reflectance model based on 3D crystal surface measurements. Lutetium oxyorthosilicate (LSO) crystals were simulated with a phosphor coating in contact with the scintillator surfaces and an external diffuse reflector (teflon). Light output, energy resolution, and pulse shape showed excellent agreement with experimental data obtained on 3 × 3 × 10 mm3 crystals coupled to a photomultiplier tube (PMT). Scintillator intrinsic timing resolution was simulated with head-on and side-on configurations, confirming the trends observed experimentally. These results indicate that the model may be used to predict timing properties in phosphor-coated crystals and guide the coating for optimal DOI resolution/timing performance trade-off for a given crystal geometry. Simulation data suggested that a time stamp generated from early photoelectrons minimizes degradation of the timing resolution, thus making this method potentially more useful for TOF-DOI detectors than our initial experiments suggested. Finally, this approach could easily be extended to the study of timing properties in other scintillation crystals

  8. Improved Correction of Misclassification Bias With Bootstrap Imputation.

    PubMed

    van Walraven, Carl

    2018-07-01

    Diagnostic codes used in administrative database research can create bias due to misclassification. Quantitative bias analysis (QBA) can correct for this bias, requires only code sensitivity and specificity, but may return invalid results. Bootstrap imputation (BI) can also address misclassification bias but traditionally requires multivariate models to accurately estimate disease probability. This study compared misclassification bias correction using QBA and BI. Serum creatinine measures were used to determine severe renal failure status in 100,000 hospitalized patients. Prevalence of severe renal failure in 86 patient strata and its association with 43 covariates was determined and compared with results in which renal failure status was determined using diagnostic codes (sensitivity 71.3%, specificity 96.2%). Differences in results (misclassification bias) were then corrected with QBA or BI (using progressively more complex methods to estimate disease probability). In total, 7.4% of patients had severe renal failure. Imputing disease status with diagnostic codes exaggerated prevalence estimates [median relative change (range), 16.6% (0.8%-74.5%)] and its association with covariates [median (range) exponentiated absolute parameter estimate difference, 1.16 (1.01-2.04)]. QBA produced invalid results 9.3% of the time and increased bias in estimates of both disease prevalence and covariate associations. BI decreased misclassification bias with increasingly accurate disease probability estimates. QBA can produce invalid results and increase misclassification bias. BI avoids invalid results and can importantly decrease misclassification bias when accurate disease probability estimates are used.

  9. Accurate universal parameterization of absorption cross sections III--light systems

    NASA Technical Reports Server (NTRS)

    Tripathi, R. K.; Cucinotta, F. A.; Wilson, J. W.

    1999-01-01

    Our prior nuclear absorption cross sections model [R.K. Tripathi, F.A. Cucinotta, J.W. Wilson, Nucl. Instr. and Meth. B 117 (1996) 347; R.K. Tripathi, J.W. Wilson, F.A. Cucinotta, Nucl. Instr. and Meth. B 129 (1997) 11] is extended for light systems (A < or = 4) where either both projectile and target are light particles or one is light particle and the other is medium or heavy nucleus. The agreement with experiment is excellent for these cases as well. Present work in combination with our original model provides a comprehensive picture of absorption cross sections for light, medium and heavy systems. As a result the extended model can reliably be used in all studies where there is a need for absorption cross sections.

  10. Highly accurate pulse-per-second timing distribution over optical fibre network using VCSEL side-mode injection

    NASA Astrophysics Data System (ADS)

    Wassin, Shukree; Isoe, George M.; Gamatham, Romeo R. G.; Leitch, Andrew W. R.; Gibbon, Tim B.

    2017-01-01

    Precise and accurate timing signals distributed between a centralized location and several end-users are widely used in both metro-access and speciality networks for Coordinated Universal Time (UTC), GPS satellite systems, banking, very long baseline interferometry and science projects such as SKA radio telescope. Such systems utilize time and frequency technology to ensure phase coherence among data signals distributed across an optical fibre network. For accurate timing requirements, precise time intervals should be measured between successive pulses. In this paper we describe a novel, all optical method for quantifying one-way propagation times and phase perturbations in the fibre length, using pulse-persecond (PPS) signals. The approach utilizes side mode injection of a 1550nm 10Gbps vertical cavity surface emitting laser (VCSEL) at the remote end. A 125 μs one-way time of flight was accurately measured for 25 km G655 fibre. Since the approach is all-optical, it avoids measurement inaccuracies introduced by electro-optical conversion phase delays. Furthermore, the implementation uses cost effective VCSEL technology and suited to a flexible range of network architectures, supporting a number of end-users conducting measurements at the remote end.

  11. Reaction times to weak test lights. [psychophysics biological model

    NASA Technical Reports Server (NTRS)

    Wandell, B. A.; Ahumada, P.; Welsh, D.

    1984-01-01

    Maloney and Wandell (1984) describe a model of the response of a single visual channel to weak test lights. The initial channel response is a linearly filtered version of the stimulus. The filter output is randomly sampled over time. Each time a sample occurs there is some probability increasing with the magnitude of the sampled response - that a discrete detection event is generated. Maloney and Wandell derive the statistics of the detection events. In this paper a test is conducted of the hypothesis that the reaction time responses to the presence of a weak test light are initiated at the first detection event. This makes it possible to extend the application of the model to lights that are slightly above threshold, but still within the linear operating range of the visual system. A parameter-free prediction of the model proposed by Maloney and Wandell for lights detected by this statistic is tested. The data are in agreement with the prediction.

  12. Imprints of the quasar structure in time-delay light curves: Microlensing-aided reverberation mapping

    NASA Astrophysics Data System (ADS)

    Sluse, D.; Tewes, M.

    2014-11-01

    The advent of large area photometric surveys has raised a great deal of interest in the possibility of using broadband photometric data, instead of spectra, to measure the size of the broad line region of active galactic nuclei. We describe here a new method that uses time-delay lensed quasars where one or several images are affected by microlensing due to stars in the lensing galaxy. Because microlensing decreases (or increases) the flux of the continuum compared to the broad line region, it changes the contrast between these two emission components. We show that this effect can be used to effectively disentangle the intrinsic variability of those two regions, offering the opportunity to perform reverberation mapping based on single-band photometric data. Based on simulated light curves generated using a damped random walk model of quasar variability, we show that measurement of the size of the broad line region can be achieved using this method, provided one spectrum has been obtained independently during the monitoring. This method is complementary to photometric reverberation mapping and could also be extended to multi-band data. Because the effect described above produces a variability pattern in difference light curves between pairs of lensed images that is correlated with the time-lagged continuum variability, it can potentially produce systematic errors in measurement of time delays between pairs of lensed images. Simple simulations indicate that time-delay measurement techniques that use a sufficiently flexible model for the extrinsic variability are not affected by this effect and produce accurate time delays.

  13. Interleaved segment correction achieves higher improvement factors in using genetic algorithm to optimize light focusing through scattering media

    NASA Astrophysics Data System (ADS)

    Li, Runze; Peng, Tong; Liang, Yansheng; Yang, Yanlong; Yao, Baoli; Yu, Xianghua; Min, Junwei; Lei, Ming; Yan, Shaohui; Zhang, Chunmin; Ye, Tong

    2017-10-01

    Focusing and imaging through scattering media has been proved possible with high resolution wavefront shaping. A completely scrambled scattering field can be corrected by applying a correction phase mask on a phase only spatial light modulator (SLM) and thereby the focusing quality can be improved. The correction phase is often found by global searching algorithms, among which Genetic Algorithm (GA) stands out for its parallel optimization process and high performance in noisy environment. However, the convergence of GA slows down gradually with the progression of optimization, causing the improvement factor of optimization to reach a plateau eventually. In this report, we propose an interleaved segment correction (ISC) method that can significantly boost the improvement factor with the same number of iterations comparing with the conventional all segment correction method. In the ISC method, all the phase segments are divided into a number of interleaved groups; GA optimization procedures are performed individually and sequentially among each group of segments. The final correction phase mask is formed by applying correction phases of all interleaved groups together on the SLM. The ISC method has been proved significantly useful in practice because of its ability to achieve better improvement factors when noise is present in the system. We have also demonstrated that the imaging quality is improved as better correction phases are found and applied on the SLM. Additionally, the ISC method lowers the demand of dynamic ranges of detection devices. The proposed method holds potential in applications, such as high-resolution imaging in deep tissue.

  14. Accurate mass measurement: terminology and treatment of data.

    PubMed

    Brenton, A Gareth; Godfrey, A Ruth

    2010-11-01

    High-resolution mass spectrometry has become ever more accessible with improvements in instrumentation, such as modern FT-ICR and Orbitrap mass spectrometers. This has resulted in an increase in the number of articles submitted for publication quoting accurate mass data. There is a plethora of terms related to accurate mass analysis that are in current usage, many employed incorrectly or inconsistently. This article is based on a set of notes prepared by the authors for research students and staff in our laboratories as a guide to the correct terminology and basic statistical procedures to apply in relation to mass measurement, particularly for accurate mass measurement. It elaborates on the editorial by Gross in 1994 regarding the use of accurate masses for structure confirmation. We have presented and defined the main terms in use with reference to the International Union of Pure and Applied Chemistry (IUPAC) recommendations for nomenclature and symbolism for mass spectrometry. The correct use of statistics and treatment of data is illustrated as a guide to new and existing mass spectrometry users with a series of examples as well as statistical methods to compare different experimental methods and datasets. Copyright © 2010. Published by Elsevier Inc.

  15. No Time for Dead Time: Use the Fourier Amplitude Differences to Normalize Dead-time-affected Periodograms

    NASA Astrophysics Data System (ADS)

    Bachetti, Matteo; Huppenkothen, Daniela

    2018-02-01

    Dead time affects many of the instruments used in X-ray astronomy, by producing a strong distortion in power density spectra. This can make it difficult to model the aperiodic variability of the source or look for quasi-periodic oscillations. Whereas in some instruments a simple a priori correction for dead-time-affected power spectra is possible, this is not the case for others such as NuSTAR, where the dead time is non-constant and long (∼2.5 ms). Bachetti et al. (2015) suggested the cospectrum obtained from light curves of independent detectors within the same instrument as a possible way out, but this solution has always only been a partial one: the measured rms was still affected by dead time because the width of the power distribution of the cospectrum was modulated by dead time in a frequency-dependent way. In this Letter, we suggest a new, powerful method to normalize dead-time-affected cospectra and power density spectra. Our approach uses the difference of the Fourier amplitudes from two independent detectors to characterize and filter out the effect of dead time. This method is crucially important for the accurate modeling of periodograms derived from instruments affected by dead time on board current missions like NuSTAR and Astrosat, but also future missions such as IXPE.

  16. A web-based Tamsui River flood early-warning system with correction of real-time water stage using monitoring data

    NASA Astrophysics Data System (ADS)

    Liao, H. Y.; Lin, Y. J.; Chang, H. K.; Shang, R. K.; Kuo, H. C.; Lai, J. S.; Tan, Y. C.

    2017-12-01

    Taiwan encounters heavy rainfalls frequently. There are three to four typhoons striking Taiwan every year. To provide lead time for reducing flood damage, this study attempt to build a flood early-warning system (FEWS) in Tanshui River using time series correction techniques. The predicted rainfall is used as the input for the rainfall-runoff model. Then, the discharges calculated by the rainfall-runoff model is converted to the 1-D river routing model. The 1-D river routing model will output the simulating water stages in 487 cross sections for the future 48-hr. The downstream water stage at the estuary in 1-D river routing model is provided by storm surge simulation. Next, the water stages of 487 cross sections are corrected by time series model such as autoregressive (AR) model using real-time water stage measurements to improve the predicted accuracy. The results of simulated water stages are displayed on a web-based platform. In addition, the models can be performed remotely by any users with web browsers through a user interface. The on-line video surveillance images, real-time monitoring water stages, and rainfalls can also be shown on this platform. If the simulated water stage exceeds the embankments of Tanshui River, the alerting lights of FEWS will be flashing on the screen. This platform runs periodically and automatically to generate the simulation graphic data of flood water stages for flood disaster prevention and decision making.

  17. ON THE PROPER USE OF THE REDUCED SPEED OF LIGHT APPROXIMATION

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gnedin, Nickolay Y., E-mail: gnedin@fnal.gov

    I show that the reduced speed of light (RSL) approximation, when used properly (i.e., as originally designed—only for local sources but not for the cosmic background), remains a highly accurate numerical method for modeling cosmic reionization. Simulated ionization and star formation histories from the “Cosmic Reionization on Computers” project are insensitive to the adopted value of the RSL for as long as that value does not fall below about 10% of the true speed of light. A recent claim of the failure of the RSL approximation in the Illustris reionization model appears to be due to the effective speed ofmore » light being reduced in the equation for the cosmic background too and hence illustrates the importance of maintaining the correct speed of light in modeling the cosmic background.« less

  18. Broadband true time delay for microwave signal processing, using slow light based on stimulated Brillouin scattering in optical fibers.

    PubMed

    Chin, Sanghoon; Thévenaz, Luc; Sancho, Juan; Sales, Salvador; Capmany, José; Berger, Perrine; Bourderionnet, Jérôme; Dolfi, Daniel

    2010-10-11

    We experimentally demonstrate a novel technique to process broadband microwave signals, using all-optically tunable true time delay in optical fibers. The configuration to achieve true time delay basically consists of two main stages: photonic RF phase shifter and slow light, based on stimulated Brillouin scattering in fibers. Dispersion properties of fibers are controlled, separately at optical carrier frequency and in the vicinity of microwave signal bandwidth. This way time delay induced within the signal bandwidth can be manipulated to correctly act as true time delay with a proper phase compensation introduced to the optical carrier. We completely analyzed the generated true time delay as a promising solution to feed phased array antenna for radar systems and to develop dynamically reconfigurable microwave photonic filters.

  19. Monitoring Disaster-Related Power Outages Using NASA Black Marble Nighttime Light Product

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Román, M. O.; Sun, Q.; Molthan, A. L.; Schultz, L. A.; Kalb, V. L.

    2018-04-01

    Timely and accurate monitoring of disruptions to the electricity grid, including the magnitude, spatial extent, timing, and duration of net power losses, is needed to improve situational awareness of disaster response and long-term recovery efforts. Satellite-derived Nighttime Lights (NTL) provide an indication of human activity patterns and have been successfully used to monitor disaster-related power outages. The global 500 m spatial resolution National Aeronautics and Space Administration (NASA) Black Marble NTL daily standard product suite (VNP46) is generated from Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) onboard the NASA/National Oceanic and Atmospheric Administration (NOAA) Suomi National Polar-orbiting Partnership (Suomi- NPP) satellite, which began operations on 19 January 2012. With its improvements in product accuracy (including critical atmospheric and BRDF correction routines), the VIIRS daily Black Mable product enables systematic monitoring of outage conditions across all stages of the disaster management cycle.

  20. Artificial light alters natural regimes of night-time sky brightness

    PubMed Central

    Davies, Thomas W.; Bennie, Jonathan; Inger, Richard; Gaston, Kevin J.

    2013-01-01

    Artificial light is globally one of the most widely distributed forms of anthropogenic pollution. However, while both the nature and ecological effects of direct artificial lighting are increasingly well documented, those of artificial sky glow have received little attention. We investigated how city lights alter natural regimes of lunar sky brightness using a novel ten month time series of measurements recorded across a gradient of increasing light pollution. In the city, artificial lights increased sky brightness to levels six times above those recorded in rural locations, nine and twenty kilometers away. Artificial lighting masked natural monthly and seasonal regimes of lunar sky brightness in the city, and increased the number and annual regime of full moon equivalent hours available to organisms during the night. The changes have potentially profound ecological consequences.

  1. Accurate mass measurement by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. I. Measurement of positive radical ions using porphyrin standard reference materials.

    PubMed

    Griffiths, Nia W; Wyatt, Mark F; Kean, Suzanna D; Graham, Andrew E; Stein, Bridget K; Brenton, A Gareth

    2010-06-15

    A method for the accurate mass measurement of positive radical ions by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) is described. Initial use of a conjugated oligomeric calibration material was rejected in favour of a series of meso-tetraalkyl/tetraalkylaryl-functionalised porphyrins, from which the two calibrants required for a particular accurate mass measurement were chosen. While all measurements of monoisotopic species were within +/-5 ppm, and the method was rigorously validated using chemometrics, mean values of five measurements were used for extra confidence in the generation of potential elemental formulae. Potential difficulties encountered when measuring compounds containing multi-isotopic elements are discussed, where the monoisotopic peak is no longer the lowest mass peak, and a simple mass-correction solution can be applied. The method requires no significant expertise to implement, but care and attention is required to obtain valid measurements. The method is operationally simple and will prove useful to the analytical chemistry community. Copyright (c) 2010 John Wiley & Sons, Ltd.

  2. Correct implementation of polarization constants in wurtzite materials and impact on III-nitrides

    DOE PAGES

    Dreyer, Cyrus E.; Janotti, Anderson; Van de Walle, Chris G.; ...

    2016-06-20

    Here, accurate values for polarization discontinuities between pyroelectric materials are critical for understanding and designing the electronic properties of heterostructures. For wurtzite materials, the zincblende structure has been used in the literature as a reference to determine the effective spontaneous polarization constants. We show that, because the zincblende structure has a nonzero formal polarization, this method results in a spurious contribution to the spontaneous polarization differences between materials. In addition, we address the correct choice of "improper" versus "proper" piezoelectric constants. For the technologically important III-nitride materials GaN, AlN, and InN, we determine polarization discontinuities using a consistent reference basedmore » on the layered hexagonal structure and the correct choice of piezoelectric constants, and discuss the results in light of available experimental data.« less

  3. 75 FR 53687 - Pacific Gas and Electric Company, California; Notice Correcting Times for Public Draft...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-01

    ... Electric Company, California; Notice Correcting Times for Public Draft Environmental Impact Statement... time for the morning meeting as 9 a.m.-11 p.m.. This notice corrects that error to indicate the meeting is from 9 a.m.- 11 a.m. The time and location of the meetings are as follows: Morning Meeting: Date...

  4. Reproducibility of an objective four-choice canine vision testing technique that assesses vision at differing light intensities.

    PubMed

    Annear, Matthew J; Gornik, Kara R; Venturi, Francesca L; Hauptman, Joe G; Bartoe, Joshua T; Petersen-Jones, Simon M

    2013-09-01

    The increasing importance of canine retinal dystrophy models means accurate vision testing is needed. This study was performed to evaluate a four-choice vision testing technique for any difference in outcome measures with repeated evaluations of the same dogs.   Four 11-month-old RPE65-deficient dogs. Vision was evaluated using a previously described four-choice vision testing device. Four evaluations were performed at 2-week intervals. Vision was assessed at six different white light intensities (bright through dim), and each eye was evaluated separately. The ability to select the one of the four exit tunnels that was open at the far end was assessed ('choice of exit') and recorded as correct or incorrect first tunnel choice. 'Time to exit' the device was also recorded. Both outcomes were analyzed for significance using anova. We hypothesized that performance would improve with repeated testing (more correct choices and more rapid time to exit). 'Choice of exit' did not vary significantly between each evaluation (P = 0.12), in contrast 'time to exit' increased significantly (P = 0.012), and showed greater variability in dim light conditions. We found no evidence to support the hypothesis that either measure of outcome worsened with repeated testing; in fact, the 'time to exit' outcome worsened rather than improved. The 'choice of exit' gave consistent results between trials. These outcome data indicate the importance of including a choice-based assessment of vision in addition to measurement of device transit time. © 2012 American College of Veterinary Ophthalmologists.

  5. Marginalizing Instrument Systematics in HST WFC3 Transit Light Curves

    NASA Astrophysics Data System (ADS)

    Wakeford, H. R.; Sing, D. K.; Evans, T.; Deming, D.; Mandell, A.

    2016-03-01

    Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) infrared observations at 1.1-1.7 μm probe primarily the H2O absorption band at 1.4 μm, and have provided low-resolution transmission spectra for a wide range of exoplanets. We present the application of marginalization based on Gibson to analyze exoplanet transit light curves obtained from HST WFC3 to better determine important transit parameters such as Rp/R*, which are important for accurate detections of H2O. We approximate the evidence, often referred to as the marginal likelihood, for a grid of systematic models using the Akaike Information Criterion. We then calculate the evidence-based weight assigned to each systematic model and use the information from all tested models to calculate the final marginalized transit parameters for both the band-integrated and spectroscopic light curves to construct the transmission spectrum. We find that a majority of the highest weight models contain a correction for a linear trend in time as well as corrections related to HST orbital phase. We additionally test the dependence on the shift in spectral wavelength position over the course of the observations and find that spectroscopic wavelength shifts {δ }λ (λ ) best describe the associated systematic in the spectroscopic light curves for most targets while fast scan rate observations of bright targets require an additional level of processing to produce a robust transmission spectrum. The use of marginalization allows for transparent interpretation and understanding of the instrument and the impact of each systematic evaluated statistically for each data set, expanding the ability to make true and comprehensive comparisons between exoplanet atmospheres.

  6. Achieving perceptually-accurate aural telepresence

    NASA Astrophysics Data System (ADS)

    Henderson, Paul D.

    Immersive multimedia requires not only realistic visual imagery but also a perceptually-accurate aural experience. A sound field may be presented simultaneously to a listener via a loudspeaker rendering system using the direct sound from acoustic sources as well as a simulation or "auralization" of room acoustics. Beginning with classical Wave-Field Synthesis (WFS), improvements are made to correct for asymmetries in loudspeaker array geometry. Presented is a new Spatially-Equalized WFS (SE-WFS) technique to maintain the energy-time balance of a simulated room by equalizing the reproduced spectrum at the listener for a distribution of possible source angles. Each reproduced source or reflection is filtered according to its incidence angle to the listener. An SE-WFS loudspeaker array of arbitrary geometry reproduces the sound field of a room with correct spectral and temporal balance, compared with classically-processed WFS systems. Localization accuracy of human listeners in SE-WFS sound fields is quantified by psychoacoustical testing. At a loudspeaker spacing of 0.17 m (equivalent to an aliasing cutoff frequency of 1 kHz), SE-WFS exhibits a localization blur of 3 degrees, nearly equal to real point sources. Increasing the loudspeaker spacing to 0.68 m (for a cutoff frequency of 170 Hz) results in a blur of less than 5 degrees. In contrast, stereophonic reproduction is less accurate with a blur of 7 degrees. The ventriloquist effect is psychometrically investigated to determine the effect of an intentional directional incongruence between audio and video stimuli. Subjects were presented with prerecorded full-spectrum speech and motion video of a talker's head as well as broadband noise bursts with a static image. The video image was displaced from the audio stimulus in azimuth by varying amounts, and the perceived auditory location measured. A strong bias was detectable for small angular discrepancies between audio and video stimuli for separations of less than 8

  7. Phase correction and error estimation in InSAR time series analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Fattahi, H.; Amelung, F.

    2017-12-01

    During the last decade several InSAR time series approaches have been developed in response to the non-idea acquisition strategy of SAR satellites, such as large spatial and temporal baseline with non-regular acquisitions. The small baseline tubes and regular acquisitions of new SAR satellites such as Sentinel-1 allows us to form fully connected networks of interferograms and simplifies the time series analysis into a weighted least square inversion of an over-determined system. Such robust inversion allows us to focus more on the understanding of different components in InSAR time-series and its uncertainties. We present an open-source python-based package for InSAR time series analysis, called PySAR (https://yunjunz.github.io/PySAR/), with unique functionalities for obtaining unbiased ground displacement time-series, geometrical and atmospheric correction of InSAR data and quantifying the InSAR uncertainty. Our implemented strategy contains several features including: 1) improved spatial coverage using coherence-based network of interferograms, 2) unwrapping error correction using phase closure or bridging, 3) tropospheric delay correction using weather models and empirical approaches, 4) DEM error correction, 5) optimal selection of reference date and automatic outlier detection, 6) InSAR uncertainty due to the residual tropospheric delay, decorrelation and residual DEM error, and 7) variance-covariance matrix of final products for geodetic inversion. We demonstrate the performance using SAR datasets acquired by Cosmo-Skymed and TerraSAR-X, Sentinel-1 and ALOS/ALOS-2, with application on the highly non-linear volcanic deformation in Japan and Ecuador (figure 1). Our result shows precursory deformation before the 2015 eruptions of Cotopaxi volcano, with a maximum uplift of 3.4 cm on the western flank (fig. 1b), with a standard deviation of 0.9 cm (fig. 1a), supporting the finding by Morales-Rivera et al. (2017, GRL); and a post-eruptive subsidence on the same

  8. [Surgical Correction of Scoliosis: Does Intraoperative CT Navigation Prolong Operative Time?

    PubMed

    Skála-Rosenbaum, J; Ježek, M; Džupa, V; Kadeřábek, R; Douša, P; Rusnák, R; Krbec, M

    2016-01-01

    PURPOSE OF THE STUDY The aim of the study was to compare the duration of corrective surgery for scoliosis in relation to the intra-operative use of either fluoroscopic or CT navigation. MATERIAL AND METHODS The indication for surgery was adolescent idiopathic scoliosis in younger patients and degenerative scoliosis in middleage or elderly patients. In a retrospective study, treatment outcomes in 43 consecutive patients operated on between April 2011 and April 2014 were compared. Only patients undergoing surgical correction of five or more spinal segments (fixation of six and more vertebrae) were included. RESULTS Transpedicular screw fixation of six to 13 vertebrae was performed under C-arm fluoroscopy guidance in 22 patients, and transpedicular screws were inserted in six to 14 vertebrae using the O-arm imaging system in 21 patients. A total of 246 screws were placed using the C-arm system and 340 screws were inserted using the O-arm system (p < 0.001). The procedures with use of the O-arm system were more complicated and required an average operative time longer by 48% (measured from the first skin incision to the completion of skin suture). However, the mean time needed for one screw placement (the sum of all surgical procedures with the use of a navigation technique divided by the number of screws placed using this technique) was the same in both techniques (19 min). DISCUSSION With good teamwork (surgeons, anaesthesiologists and a radiologist attending to the O-arm system), the time required to obtain one intra-operative CT scan is 3 to 5 minutes. The study showed that the mean time for placement of one screw was identical in both techniques although the average operative time was longer in surgery with O-arm navigation. The 19- minute interval was not the real placement time per screw. It was the sum of all operative times of surgical procedures (from first incision to suture completion including the whole approach within the range of planned stabilization

  9. Study on real-time images compounded using spatial light modulator

    NASA Astrophysics Data System (ADS)

    Xu, Jin; Chen, Zhebo; Ni, Xuxiang; Lu, Zukang

    2007-01-01

    Image compounded technology is often used on film and its facture. In common, image compounded use image processing arithmetic, get useful object, details, background or some other things from the images firstly, then compounding all these information into one image. When using this method, the film system needs a powerful processor, for the process function is very complex, we get the compounded image for a few time delay. In this paper, we introduce a new method of image real-time compounded, use this method, we can do image composite at the same time with movie shot. The whole system is made up of two camera-lens, spatial light modulator array and image sensor. In system, the spatial light modulator could be liquid crystal display (LCD), liquid crystal on silicon (LCoS), thin film transistor liquid crystal display (TFTLCD), Deformable Micro-mirror Device (DMD), and so on. Firstly, one camera-lens images the object on the spatial light modulator's panel, we call this camera-lens as first image lens. Secondly, we output an image to the panel of spatial light modulator. Then, the image of the object and image that output by spatial light modulator will be spatial compounded on the panel of spatial light modulator. Thirdly, the other camera-lens images the compounded image to the image sensor, and we call this camera-lens as second image lens. After these three steps, we will gain the compound images by image sensor. For the spatial light modulator could output the image continuously, then the image will be compounding continuously too, and the compounding procedure is completed in real-time. When using this method to compounding image, if we will put real object into invented background, we can output the invented background scene on the spatial light modulator, and the real object will be imaged by first image lens. Then, we get the compounded images by image sensor in real time. The same way, if we will put real background to an invented object, we can output the

  10. Path integration of head direction: updating a packet of neural activity at the correct speed using neuronal time constants.

    PubMed

    Walters, D M; Stringer, S M

    2010-07-01

    A key question in understanding the neural basis of path integration is how individual, spatially responsive, neurons may self-organize into networks that can, through learning, integrate velocity signals to update a continuous representation of location within an environment. It is of vital importance that this internal representation of position is updated at the correct speed, and in real time, to accurately reflect the motion of the animal. In this article, we present a biologically plausible model of velocity path integration of head direction that can solve this problem using neuronal time constants to effect natural time delays, over which associations can be learned through associative Hebbian learning rules. The model comprises a linked continuous attractor network and competitive network. In simulation, we show that the same model is able to learn two different speeds of rotation when implemented with two different values for the time constant, and without the need to alter any other model parameters. The proposed model could be extended to path integration of place in the environment, and path integration of spatial view.

  11. The Space-Time Conservative Schemes for Large-Scale, Time-Accurate Flow Simulations with Tetrahedral Meshes

    NASA Technical Reports Server (NTRS)

    Venkatachari, Balaji Shankar; Streett, Craig L.; Chang, Chau-Lyan; Friedlander, David J.; Wang, Xiao-Yen; Chang, Sin-Chung

    2016-01-01

    Despite decades of development of unstructured mesh methods, high-fidelity time-accurate simulations are still predominantly carried out on structured, or unstructured hexahedral meshes by using high-order finite-difference, weighted essentially non-oscillatory (WENO), or hybrid schemes formed by their combinations. In this work, the space-time conservation element solution element (CESE) method is used to simulate several flow problems including supersonic jet/shock interaction and its impact on launch vehicle acoustics, and direct numerical simulations of turbulent flows using tetrahedral meshes. This paper provides a status report for the continuing development of the space-time conservation element solution element (CESE) numerical and software framework under the Revolutionary Computational Aerosciences (RCA) project. Solution accuracy and large-scale parallel performance of the numerical framework is assessed with the goal of providing a viable paradigm for future high-fidelity flow physics simulations.

  12. SU-E-I-20: Dead Time Count Loss Compensation in SPECT/CT: Projection Versus Global Correction

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Siman, W; Kappadath, S

    Purpose: To compare projection-based versus global correction that compensate for deadtime count loss in SPECT/CT images. Methods: SPECT/CT images of an IEC phantom (2.3GBq 99mTc) with ∼10% deadtime loss containing the 37mm (uptake 3), 28 and 22mm (uptake 6) spheres were acquired using a 2 detector SPECT/CT system with 64 projections/detector and 15 s/projection. The deadtime, Ti and the true count rate, Ni at each projection, i was calculated using the monitor-source method. Deadtime corrected SPECT were reconstructed twice: (1) with projections that were individually-corrected for deadtime-losses; and (2) with original projections with losses and then correcting the reconstructed SPECTmore » images using a scaling factor equal to the inverse of the average fractional loss for 5 projections/detector. For both cases, the SPECT images were reconstructed using OSEM with attenuation and scatter corrections. The two SPECT datasets were assessed by comparing line profiles in xyplane and z-axis, evaluating the count recoveries, and comparing ROI statistics. Higher deadtime losses (up to 50%) were also simulated to the individually corrected projections by multiplying each projection i by exp(-a*Ni*Ti), where a is a scalar. Additionally, deadtime corrections in phantoms with different geometries and deadtime losses were also explored. The same two correction methods were carried for all these data sets. Results: Averaging the deadtime losses in 5 projections/detector suffices to recover >99% of the loss counts in most clinical cases. The line profiles (xyplane and z-axis) and the statistics in the ROIs drawn in the SPECT images corrected using both methods showed agreement within the statistical noise. The count-loss recoveries in the two methods also agree within >99%. Conclusion: The projection-based and the global correction yield visually indistinguishable SPECT images. The global correction based on sparse sampling of projections losses allows for accurate SPECT

  13. Real-time correction of beamforming time delay errors in abdominal ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Rigby, K. W.

    2000-04-01

    The speed of sound varies with tissue type, yet commercial ultrasound imagers assume a constant sound speed. Sound speed variation in abdominal fat and muscle layers is widely believed to be largely responsible for poor contrast and resolution in some patients. The simplest model of the abdominal wall assumes that it adds a spatially varying time delay to the ultrasound wavefront. The adequacy of this model is controversial. We describe an adaptive imaging system consisting of a GE LOGIQ 700 imager connected to a multi- processor computer. Arrival time errors for each beamforming channel, estimated by correlating each channel signal with the beamsummed signal, are used to correct the imager's beamforming time delays at the acoustic frame rate. A multi- row transducer provides two-dimensional sampling of arrival time errors. We observe significant improvement in abdominal images of healthy male volunteers: increased contrast of blood vessels, increased visibility of the renal capsule, and increased brightness of the liver.

  14. Dynamic Black-Level Correction and Artifact Flagging for Kepler Pixel Time Series

    NASA Technical Reports Server (NTRS)

    Kolodziejczak, J. J.; Clarke, B. D.; Caldwell, D. A.

    2011-01-01

    Methods applied to the calibration stage of Kepler pipeline data processing [1] (CAL) do not currently use all of the information available to identify and correct several instrument-induced artifacts. These include time-varying crosstalk from the fine guidance sensor (FGS) clock signals, and manifestations of drifting moire pattern as locally correlated nonstationary noise, and rolling bands in the images which find their way into the time series [2], [3]. As the Kepler Mission continues to improve the fidelity of its science data products, we are evaluating the benefits of adding pipeline steps to more completely model and dynamically correct the FGS crosstalk, then use the residuals from these model fits to detect and flag spatial regions and time intervals of strong time-varying black-level which may complicate later processing or lead to misinterpretation of instrument behavior as stellar activity.

  15. Correcting Spatial Variance of RCM for GEO SAR Imaging Based on Time-Frequency Scaling.

    PubMed

    Yu, Ze; Lin, Peng; Xiao, Peng; Kang, Lihong; Li, Chunsheng

    2016-07-14

    Compared with low-Earth orbit synthetic aperture radar (SAR), a geosynchronous (GEO) SAR can have a shorter revisit period and vaster coverage. However, relative motion between this SAR and targets is more complicated, which makes range cell migration (RCM) spatially variant along both range and azimuth. As a result, efficient and precise imaging becomes difficult. This paper analyzes and models spatial variance for GEO SAR in the time and frequency domains. A novel algorithm for GEO SAR imaging with a resolution of 2 m in both the ground cross-range and range directions is proposed, which is composed of five steps. The first is to eliminate linear azimuth variance through the first azimuth time scaling. The second is to achieve RCM correction and range compression. The third is to correct residual azimuth variance by the second azimuth time-frequency scaling. The fourth and final steps are to accomplish azimuth focusing and correct geometric distortion. The most important innovation of this algorithm is implementation of the time-frequency scaling to correct high-order azimuth variance. As demonstrated by simulation results, this algorithm can accomplish GEO SAR imaging with good and uniform imaging quality over the entire swath.

  16. Correcting Spatial Variance of RCM for GEO SAR Imaging Based on Time-Frequency Scaling

    PubMed Central

    Yu, Ze; Lin, Peng; Xiao, Peng; Kang, Lihong; Li, Chunsheng

    2016-01-01

    Compared with low-Earth orbit synthetic aperture radar (SAR), a geosynchronous (GEO) SAR can have a shorter revisit period and vaster coverage. However, relative motion between this SAR and targets is more complicated, which makes range cell migration (RCM) spatially variant along both range and azimuth. As a result, efficient and precise imaging becomes difficult. This paper analyzes and models spatial variance for GEO SAR in the time and frequency domains. A novel algorithm for GEO SAR imaging with a resolution of 2 m in both the ground cross-range and range directions is proposed, which is composed of five steps. The first is to eliminate linear azimuth variance through the first azimuth time scaling. The second is to achieve RCM correction and range compression. The third is to correct residual azimuth variance by the second azimuth time-frequency scaling. The fourth and final steps are to accomplish azimuth focusing and correct geometric distortion. The most important innovation of this algorithm is implementation of the time-frequency scaling to correct high-order azimuth variance. As demonstrated by simulation results, this algorithm can accomplish GEO SAR imaging with good and uniform imaging quality over the entire swath. PMID:27428974

  17. Night-time lighting alters the composition of marine epifaunal communities

    PubMed Central

    Davies, Thomas W.; Coleman, Matthew; Griffith, Katherine M.; Jenkins, Stuart R.

    2015-01-01

    Marine benthic communities face multiple anthropogenic pressures that compromise the future of some of the most biodiverse and functionally important ecosystems in the world. Yet one of the pressures these ecosystems face, night-time lighting, remains unstudied. Light is an important cue in guiding the settlement of invertebrate larvae, and altering natural regimes of nocturnal illumination could modify patterns of recruitment among sessile epifauna. We present the first evidence of night-time lighting changing the composition of temperate epifaunal marine invertebrate communities. Illuminating settlement surfaces with white light-emitting diode lighting at night, to levels experienced by these communities locally, both inhibited and encouraged the colonization of 39% of the taxa analysed, including three sessile and two mobile species. Our results indicate that ecological light pollution from coastal development, shipping and offshore infrastructure could be changing the composition of marine epifaunal communities. PMID:25926694

  18. Calculations of steady and transient channel flows with a time-accurate L-U factorization scheme

    NASA Technical Reports Server (NTRS)

    Kim, S.-W.

    1991-01-01

    Calculations of steady and unsteady, transonic, turbulent channel flows with a time accurate, lower-upper (L-U) factorization scheme are presented. The L-U factorization scheme is formally second-order accurate in time and space, and it is an extension of the steady state flow solver (RPLUS) used extensively to solve compressible flows. A time discretization method and the implementation of a consistent boundary condition specific to the L-U factorization scheme are also presented. The turbulence is described by the Baldwin-Lomax algebraic turbulence model. The present L-U scheme yields stable numerical results with the use of much smaller artificial dissipations than those used in the previous steady flow solver for steady and unsteady channel flows. The capability to solve time dependent flows is shown by solving very weakly excited and strongly excited, forced oscillatory, channel flows.

  19. Publisher Correction: Studying light-harvesting models with superconducting circuits.

    PubMed

    Potočnik, Anton; Bargerbos, Arno; Schröder, Florian A Y N; Khan, Saeed A; Collodo, Michele C; Gasparinetti, Simone; Salathé, Yves; Creatore, Celestino; Eichler, Christopher; Türeci, Hakan E; Chin, Alex W; Wallraff, Andreas

    2018-06-08

    The original HTML version of this Article contained an error in the second mathematical expression in the fourth sentence of the fourth paragraph of the 'Excitation transfer with uniform white noise' section of the Results. This has been corrected in the HTML version of the Article.The original PDF version of this Article incorrectly stated that 'Correspondence and requests for materials should be addressed to A. Pčn.', instead of the correct 'Correspondence and requests for materials should be addressed to A. Potočnik'. This has been corrected in the PDF version of the Article.

  20. Noniterative algorithm for improving the accuracy of a multicolor-light-emitting-diode-based colorimeter.

    PubMed

    Yang, Pao-Keng

    2012-05-01

    We present a noniterative algorithm to reliably reconstruct the spectral reflectance from discrete reflectance values measured by using multicolor light emitting diodes (LEDs) as probing light sources. The proposed algorithm estimates the spectral reflectance by a linear combination of product functions of the detector's responsivity function and the LEDs' line-shape functions. After introducing suitable correction, the resulting spectral reflectance was found to be free from the spectral-broadening effect due to the finite bandwidth of LED. We analyzed the data for a real sample and found that spectral reflectance with enhanced resolution gives a more accurate prediction in the color measurement.

  1. Noniterative algorithm for improving the accuracy of a multicolor-light-emitting-diode-based colorimeter

    NASA Astrophysics Data System (ADS)

    Yang, Pao-Keng

    2012-05-01

    We present a noniterative algorithm to reliably reconstruct the spectral reflectance from discrete reflectance values measured by using multicolor light emitting diodes (LEDs) as probing light sources. The proposed algorithm estimates the spectral reflectance by a linear combination of product functions of the detector's responsivity function and the LEDs' line-shape functions. After introducing suitable correction, the resulting spectral reflectance was found to be free from the spectral-broadening effect due to the finite bandwidth of LED. We analyzed the data for a real sample and found that spectral reflectance with enhanced resolution gives a more accurate prediction in the color measurement.

  2. Consistent Long-Time Series of GPS Satellite Antenna Phase Center Corrections

    NASA Astrophysics Data System (ADS)

    Steigenberger, P.; Schmid, R.; Rothacher, M.

    2004-12-01

    The current IGS processing strategy disregards satellite antenna phase center variations (pcvs) depending on the nadir angle and applies block-specific phase center offsets only. However, the transition from relative to absolute receiver antenna corrections presently under discussion necessitates the consideration of satellite antenna pcvs. Moreover, studies of several groups have shown that the offsets are not homogeneous within a satellite block. Manufacturer specifications seem to confirm this assumption. In order to get best possible antenna corrections, consistent ten-year time series (1994-2004) of satellite-specific pcvs and offsets were generated. This challenging effort became possible as part of the reprocessing of a global GPS network currently performed by the Technical Universities of Munich and Dresden. The data of about 160 stations since the official start of the IGS in 1994 have been reprocessed, as today's GPS time series are mostly inhomogeneous and inconsistent due to continuous improvements in the processing strategies and modeling of global GPS solutions. An analysis of the signals contained in the time series of the phase center offsets demonstrates amplitudes on the decimeter level, at least one order of magnitude worse than the desired accuracy. The periods partly arise from the GPS orbit configuration, as the orientation of the orbit planes with regard to the inertial system repeats after about 350 days due to the rotation of the ascending nodes. In addition, the rms values of the X- and Y-offsets show a high correlation with the angle between the orbit plane and the direction to the sun. The time series of the pcvs mainly point at the correlation with the global terrestrial scale. Solutions with relative and absolute phase center corrections, with block- and satellite-specific satellite antenna corrections demonstrate the effect of this parameter group on other global GPS parameters such as the terrestrial scale, station velocities, the

  3. Accurate finite difference methods for time-harmonic wave propagation

    NASA Technical Reports Server (NTRS)

    Harari, Isaac; Turkel, Eli

    1994-01-01

    Finite difference methods for solving problems of time-harmonic acoustics are developed and analyzed. Multidimensional inhomogeneous problems with variable, possibly discontinuous, coefficients are considered, accounting for the effects of employing nonuniform grids. A weighted-average representation is less sensitive to transition in wave resolution (due to variable wave numbers or nonuniform grids) than the standard pointwise representation. Further enhancement in method performance is obtained by basing the stencils on generalizations of Pade approximation, or generalized definitions of the derivative, reducing spurious dispersion, anisotropy and reflection, and by improving the representation of source terms. The resulting schemes have fourth-order accurate local truncation error on uniform grids and third order in the nonuniform case. Guidelines for discretization pertaining to grid orientation and resolution are presented.

  4. The Real Time Correction of Stereoscopic Images: From the Serial to a Parallel Treatment

    NASA Astrophysics Data System (ADS)

    Irki, Zohir; Devy, Michel; Achour, Karim; Azzaz, Mohamed Salah

    2008-06-01

    The correction of the stereoscopic images is a task which consists in replacing acquired images by other images having the same properties but which are simpler to use in the other stages of stereovision. The use of the pre-calculated tables, built during an off line calibration step, made it possible to carry out the off line stereoscopic images rectification. An improvement of the built tables made it possible to carry out the real time rectification. In this paper, we describe an improvement of the real time correction approach so it can be exploited for a possible implementation on an FPGA component. This improvement holds in account the real time aspect of the correction and the available resources that can offer the FPGA Type Stratix 1S40F780C5.

  5. On Aethalometer measurement uncertainties and an instrument correction factor for the Arctic

    NASA Astrophysics Data System (ADS)

    Backman, John; Schmeisser, Lauren; Virkkula, Aki; Ogren, John A.; Asmi, Eija; Starkweather, Sandra; Sharma, Sangeeta; Eleftheriadis, Konstantinos; Uttal, Taneil; Jefferson, Anne; Bergin, Michael; Makshtas, Alexander; Tunved, Peter; Fiebig, Markus

    2017-12-01

    Several types of filter-based instruments are used to estimate aerosol light absorption coefficients. Two significant results are presented based on Aethalometer measurements at six Arctic stations from 2012 to 2014. First, an alternative method of post-processing the Aethalometer data is presented, which reduces measurement noise and lowers the detection limit of the instrument more effectively than boxcar averaging. The biggest benefit of this approach can be achieved if instrument drift is minimised. Moreover, by using an attenuation threshold criterion for data post-processing, the relative uncertainty from the electronic noise of the instrument is kept constant. This approach results in a time series with a variable collection time (Δt) but with a constant relative uncertainty with regard to electronic noise in the instrument. An additional advantage of this method is that the detection limit of the instrument will be lowered at small aerosol concentrations at the expense of temporal resolution, whereas there is little to no loss in temporal resolution at high aerosol concentrations ( > 2.1-6.7 Mm-1 as measured by the Aethalometers). At high aerosol concentrations, minimising the detection limit of the instrument is less critical. Additionally, utilising co-located filter-based absorption photometers, a correction factor is presented for the Arctic that can be used in Aethalometer corrections available in literature. The correction factor of 3.45 was calculated for low-elevation Arctic stations. This correction factor harmonises Aethalometer attenuation coefficients with light absorption coefficients as measured by the co-located light absorption photometers. Using one correction factor for Arctic Aethalometers has the advantage that measurements between stations become more inter-comparable.

  6. The time light signals of New Zealand: yet another way of communicating time in the pre-wireless era

    NASA Astrophysics Data System (ADS)

    Kinns, Roger

    2017-08-01

    The signalling of exact time using an array of lights appears to have been unique to New Zealand. It was a simple and effective solution for calibration of marine chronometers when transmission of time signals by wireless was in its infancy. Three lights, coloured green, red and white, were arranged in a vertical array. They were switched on in a defined sequence during the evening and then extinguished together to signal exact time. Time lights were first operated at the Dominion Observatory in Wellington during February 1912 and on the Ferry Building in Auckland during October 1915. The Wellington lights were immediately adjacent to the observatory buildings, but those in Auckland were operated using telegraph signals from Wellington. The timings varied over the years, but the same physical arrangement was retained at each location. The time light service was withdrawn during 1937, when wireless signals had become almost universally available for civil and navigation purposes.

  7. LightDenseYOLO: A Fast and Accurate Marker Tracker for Autonomous UAV Landing by Visible Light Camera Sensor on Drone.

    PubMed

    Nguyen, Phong Ha; Arsalan, Muhammad; Koo, Ja Hyung; Naqvi, Rizwan Ali; Truong, Noi Quang; Park, Kang Ryoung

    2018-05-24

    Autonomous landing of an unmanned aerial vehicle or a drone is a challenging problem for the robotics research community. Previous researchers have attempted to solve this problem by combining multiple sensors such as global positioning system (GPS) receivers, inertial measurement unit, and multiple camera systems. Although these approaches successfully estimate an unmanned aerial vehicle location during landing, many calibration processes are required to achieve good detection accuracy. In addition, cases where drones operate in heterogeneous areas with no GPS signal should be considered. To overcome these problems, we determined how to safely land a drone in a GPS-denied environment using our remote-marker-based tracking algorithm based on a single visible-light-camera sensor. Instead of using hand-crafted features, our algorithm includes a convolutional neural network named lightDenseYOLO to extract trained features from an input image to predict a marker's location by visible light camera sensor on drone. Experimental results show that our method significantly outperforms state-of-the-art object trackers both using and not using convolutional neural network in terms of both accuracy and processing time.

  8. Light-adjustable lens.

    PubMed Central

    Schwartz, Daniel M

    2003-01-01

    PURPOSE: First, to determine whether a silicone light-adjustable intraocular lens (IOL) can be fabricated and adjusted precisely with a light delivery device (LDD). Second, to determine the biocompatibility of an adjustable IOL and whether the lens can be adjusted precisely in vivo. METHODS: After fabrication of a light-adjustable silicone formulation, IOLs were made and tested in vitro for cytotoxicity, leaching, precision of adjustment, optical quality after adjustment, and mechanical properties. Light-adjustable IOLs were then tested in vivo for biocompatibility and precision of adjustment in a rabbit model. In collaboration with Zeiss-Meditec, a digital LDD was developed and tested to correct for higher-order aberrations in light-adjustable IOLs. RESULTS: The results establish that a biocompatible silicone IOL can be fabricated and adjusted using safe levels of light. There was no evidence of cytotoxicity or leaching. Testing of mechanical properties revealed no significant differences from commercial controls. Implantation of light-adjustable lenses in rabbits demonstrated- excellent biocompatibility after 6 months, comparable to a commercially available IOL. In vivo spherical (hyperopic and myopic) adjustment in rabbits was achieved using an analog light delivery system. The digital light delivery system was tested and achieved correction of higher-order aberrations. CONCLUSION: A silicone light-adjustable IOL and LDD have been developed to enable postoperative, noninvasive adjustment of lens power. The ability to correct higher-order aberrations in these materials has broad potential applicability for optimization of vision in patients undergoing cataract and refractive surgery. PMID:14971588

  9. Real-time focus controller for laser welding with fibre optic noninvasive capture of light

    NASA Astrophysics Data System (ADS)

    Cobo, Adolfo; Bardin, F.; Hand, Duncan P.; Jones, Julian D.; Collin, O.; Aubry, P.; Dubois, Thierry; Hoegstroem, M.; Nylen, P.; Jonsson, P.; Lopez-Higuera, Jose M.

    2004-06-01

    Laser welding is being introduced in the aerospace industry due to its many advantages over traditional techniques. However, welding of parts with complex shapes requires precise control of the focal point of the laser in order to achieve full penetration over the entire seam. In this paper, we present an improved control system for real-time adjustment of the correct focal position, which is based on the monitoring of the light emitted by the process in two different spectral bands. The reported system has been optimized for use in a real environment: it is robust, compact, easy to operate, able to adjust itself to different welding conditions, materials and laser setups, and includes a direct connection to an external PC. Results from recent field trials on complex aerospace structures are provided.

  10. Rotational distortion correction in endoscopic optical coherence tomography based on speckle decorrelation

    PubMed Central

    Uribe-Patarroyo, Néstor; Bouma, Brett E.

    2015-01-01

    We present a new technique for the correction of nonuniform rotation distortion in catheter-based optical coherence tomography (OCT), based on the statistics of speckle between A-lines using intensity-based dynamic light scattering. This technique does not rely on tissue features and can be performed on single frames of data, thereby enabling real-time image correction. We demonstrate its suitability in a gastrointestinal balloon-catheter OCT system, determining the actual rotational speed with high temporal resolution, and present corrected cross-sectional and en face views showing significant enhancement of image quality. PMID:26625040

  11. An accurate laser radiometer for determining visible exposure times.

    PubMed

    Royston, D D

    1985-01-01

    A laser light radiometer has been developed for the Electro-Optics Branch of the Center for Devices and Radiological Health (CDRH). The radiometer measures direct laser radiation emitted in the visible spectrum. Based upon this measurement, the instrument's microprocessor automatically determines at what time duration the exposure to the measured laser radiation would exceed either the class I accessible emission limits of the Federal Performance Standard for laser products or the maximum permissible exposure limits of laser user safety standards. The instrument also features automatic background level compensation, pulse measurement capability, and self-diagnosis. Measurement of forward surface illumination levels preceding HpD photoradiation therapy is possible.

  12. Time-Accurate Numerical Prediction of Free Flight Aerodynamics of a Finned Projectile

    DTIC Science & Technology

    2005-09-01

    develop (with fewer dollars) more lethal and effective munitions. The munitions must stay abreast of the latest technology available to our...consuming. Computer simulations can and have provided an effective means of determining the unsteady aerodynamics and flight mechanics of guided projectile...Recently, the time-accurate technique was used to obtain improved results for Magnus moment and roll damping moment of a spinning projectile at transonic

  13. The time delay in strong gravitational lensing with Gauss-Bonnet correction

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Man, Jingyun; Cheng, Hongbo, E-mail: jingyunman@mail.ecust.edu.cn, E-mail: hbcheng@ecust.edu.cn

    2014-11-01

    The time delay between two relativistic images in the strong gravitational lensing governed by Gauss-Bonnet gravity is studied. We make a complete analytical derivation of the expression of time delay in presence of Gauss-Bonnet coupling. With respect to Schwarzschild, the time delay decreases as a consequence of the shrinking of the photon sphere. As the coupling increases, the second term in the time delay expansion becomes more relevant. Thus time delay in strong limit encodes some new information about geometry in five-dimensional spacetime with Gauss-Bonnet correction.

  14. Spatio-temporal environmental data tide corrections for reconnaissance operations

    NASA Astrophysics Data System (ADS)

    Barbu, Costin; Avera, Will; Harris, Mike; Malpass, Kevyn

    2005-06-01

    Dynamic, accurate near-real time environmental data is critical to the success of the mine countermeasures operations. Bathymetric data acquired from the AQS-20 mine hunting sensor should be adjusted for local tide variations related to the specific geographic area and time interval. This problem can be overcome by a spatio-temporal estimate of tide corrections provided for the area and time of interest by the Naval Research Laboratory tide prediction code PCTides. For each geographic position of the AQS-20 sonar, a tide height relative to mean sea level is computed by interpolating the tidal information from the K - nearest neighbored stations for the corresponding time. The value is used to correct the measured depth generated by the AQS-20 sonar in that location to mean sea level for fusion with other bathymetric data products. It is argued that this paper provides a useful tool to the MCM decision factors during Mine Warfare operations.

  15. Accurate Waveforms for Non-spinning Binary Black Holes using the Effective-one-body Approach

    NASA Technical Reports Server (NTRS)

    Buonanno, Alessandra; Pan, Yi; Baker, John G.; Centrella, Joan; Kelly, Bernard J.; McWilliams, Sean T.; vanMeter, James R.

    2007-01-01

    Using numerical relativity as guidance and the natural flexibility of the effective-one-body (EOB) model, we extend the latter so that it can successfully match the numerical relativity waveforms of non-spinning binary black holes during the last stages of inspiral, merger and ringdown. Here, by successfully, we mean with phase differences < or approx. 8% of a gravitational-wave cycle accumulated until the end of the ringdown phase. We obtain this result by simply adding a 4 post-Newtonian order correction in the EOB radial potential and determining the (constant) coefficient by imposing high-matching performances with numerical waveforms of mass ratios m1/m2 = 1,2/3,1/2 and = 1/4, m1 and m2 being the individual black-hole masses. The final black-hole mass and spin predicted by the numerical simulations are used to determine the ringdown frequency and decay time of three quasi-normal-mode damped sinusoids that are attached to the EOB inspiral-(plunge) waveform at the light-ring. The accurate EOB waveforms may be employed for coherent searches of gravitational waves emitted by non-spinning coalescing binary black holes with ground-based laser-interferometer detectors.

  16. Ensemble MD simulations restrained via crystallographic data: Accurate structure leads to accurate dynamics

    PubMed Central

    Xue, Yi; Skrynnikov, Nikolai R

    2014-01-01

    Currently, the best existing molecular dynamics (MD) force fields cannot accurately reproduce the global free-energy minimum which realizes the experimental protein structure. As a result, long MD trajectories tend to drift away from the starting coordinates (e.g., crystallographic structures). To address this problem, we have devised a new simulation strategy aimed at protein crystals. An MD simulation of protein crystal is essentially an ensemble simulation involving multiple protein molecules in a crystal unit cell (or a block of unit cells). To ensure that average protein coordinates remain correct during the simulation, we introduced crystallography-based restraints into the MD protocol. Because these restraints are aimed at the ensemble-average structure, they have only minimal impact on conformational dynamics of the individual protein molecules. So long as the average structure remains reasonable, the proteins move in a native-like fashion as dictated by the original force field. To validate this approach, we have used the data from solid-state NMR spectroscopy, which is the orthogonal experimental technique uniquely sensitive to protein local dynamics. The new method has been tested on the well-established model protein, ubiquitin. The ensemble-restrained MD simulations produced lower crystallographic R factors than conventional simulations; they also led to more accurate predictions for crystallographic temperature factors, solid-state chemical shifts, and backbone order parameters. The predictions for 15N R1 relaxation rates are at least as accurate as those obtained from conventional simulations. Taken together, these results suggest that the presented trajectories may be among the most realistic protein MD simulations ever reported. In this context, the ensemble restraints based on high-resolution crystallographic data can be viewed as protein-specific empirical corrections to the standard force fields. PMID:24452989

  17. Accurate and Inaccurate Conceptions about Osmosis That Accompanied Meaningful Problem Solving.

    ERIC Educational Resources Information Center

    Zuckerman, June Trop

    This study focused on the knowledge of six outstanding science students who solved an osmosis problem meaningfully. That is, they used appropriate and substantially accurate conceptual knowledge to generate an answer. Three generated a correct answer; three, an incorrect answer. This paper identifies both the accurate and inaccurate conceptions…

  18. Near real time, accurate, and sensitive microbiological safety monitoring using an all-fibre spectroscopic fluorescence system

    NASA Astrophysics Data System (ADS)

    Vanholsbeeck, F.; Swift, S.; Cheng, M.; Bogomolny, E.

    2013-11-01

    Enumeration of microorganisms is an essential microbiological task for many industrial sectors and research fields. Various tests for detection and counting of microorganisms are used today. However most of the current methods to enumerate bacteria require either long incubation time for limited accuracy, or use complicated protocols along with bulky equipment. We have developed an accurate, all-fibre spectroscopic system to measure fluorescence signal in-situ. In this paper, we examine the potential of this setup for near real time bacteria enumeration in aquatic environment. The concept is based on a well-known phenomenon that the fluorescence quantum yields of some nucleic acid stains significantly increase upon binding with nucleic acids of microorganisms. In addition we have used GFP labeled organisms. The fluorescence signal increase can be correlated to the amount of nucleic acid present in the sample. In addition we have used GFP labeled organisms. Our results show that we are able to detect a wide range of bacteria concentrations without dilution or filtration (1-108 CFU/ml) using different optical probes we designed. This high sensitivity is due to efficient light delivery with an appropriate collection volume and in situ fluorescence detection as well as the use of a sensitive CCD spectrometer. By monitoring the laser power, we can account for laser fluctuations while measuring the fluorescence signal which improves as well the system accuracy. A synchronized laser shutter allows us to achieve a high SNR with minimal integration time, thereby reducing the photobleaching effect. In summary, we conclude that our optical setup may offer a robust method for near real time bacterial detection in aquatic environment.

  19. Effects on noise properties of GPS time series caused by higher-order ionospheric corrections

    NASA Astrophysics Data System (ADS)

    Jiang, Weiping; Deng, Liansheng; Li, Zhao; Zhou, Xiaohui; Liu, Hongfei

    2014-04-01

    Higher-order ionospheric (HOI) effects are one of the principal technique-specific error sources in precise global positioning system (GPS) analysis. These effects also influence the non-linear characteristics of GPS coordinate time series. In this paper, we investigate these effects on coordinate time series in terms of seasonal variations and noise amplitudes. Both power spectral techniques and maximum likelihood estimators (MLE) are used to evaluate these effects quantitatively and qualitatively. Our results show an overall improvement for the analysis of global sites if HOI effects are considered. We note that the noise spectral index that is used for the determination of the optimal noise models in our analysis ranged between -1 and 0 both with and without HOI corrections, implying that the coloured noise cannot be removed by these corrections. However, the corrections were found to have improved noise properties for global sites. After the corrections were applied, the noise amplitudes at most sites decreased, among which the white noise amplitudes decreased remarkably. The white noise amplitudes of up to 81.8% of the selected sites decreased in the up component, and the flicker noise of 67.5% of the sites decreased in the north component. Stacked periodogram results show that, no matter whether the HOI effects are considered or not, a common fundamental period of 1.04 cycles per year (cpy), together with the expected annual and semi-annual signals, can explain all peaks of the north and up components well. For the east component, however, reasonable results can be obtained only based on HOI corrections. HOI corrections are useful for better detecting the periodic signals in GPS coordinate time series. Moreover, the corrections contributed partly to the seasonal variations of the selected sites, especially for the up component. Statistically, HOI corrections reduced more than 50% and more than 65% of the annual and semi-annual amplitudes respectively at the

  20. A time-accurate implicit method for chemical non-equilibrium flows at all speeds

    NASA Technical Reports Server (NTRS)

    Shuen, Jian-Shun

    1992-01-01

    A new time accurate coupled solution procedure for solving the chemical non-equilibrium Navier-Stokes equations over a wide range of Mach numbers is described. The scheme is shown to be very efficient and robust for flows with velocities ranging from M less than or equal to 10(exp -10) to supersonic speeds.

  1. Making Optic Flow Robust to Dynamic Lighting Conditions for Real-Time Operation

    DTIC Science & Technology

    2016-03-17

    ARL-TR-7629 ● MAR 2016 US Army Research Laboratory Making Optic Flow Robust to Dynamic Lighting Conditions for Real-Time...ARL-TR-7629 ● MAR 2016 US Army Research Laboratory Making Optic Flow Robust to Dynamic Lighting Conditions for Real-Time Operation...SUBTITLE Making Optic Flow Robust to Dynamic Lighting Conditions for Real-Time Operation 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT

  2. Multifocal multiphoton microscopy with adaptive optical correction

    NASA Astrophysics Data System (ADS)

    Coelho, Simao; Poland, Simon; Krstajic, Nikola; Li, David; Monypenny, James; Walker, Richard; Tyndall, David; Ng, Tony; Henderson, Robert; Ameer-Beg, Simon

    2013-02-01

    Fluorescence lifetime imaging microscopy (FLIM) is a well established approach for measuring dynamic signalling events inside living cells, including detection of protein-protein interactions. The improvement in optical penetration of infrared light compared with linear excitation due to Rayleigh scattering and low absorption have provided imaging depths of up to 1mm in brain tissue but significant image degradation occurs as samples distort (aberrate) the infrared excitation beam. Multiphoton time-correlated single photon counting (TCSPC) FLIM is a method for obtaining functional, high resolution images of biological structures. In order to achieve good statistical accuracy TCSPC typically requires long acquisition times. We report the development of a multifocal multiphoton microscope (MMM), titled MegaFLI. Beam parallelization performed via a 3D Gerchberg-Saxton (GS) algorithm using a Spatial Light Modulator (SLM), increases TCSPC count rate proportional to the number of beamlets produced. A weighted 3D GS algorithm is employed to improve homogeneity. An added benefit is the implementation of flexible and adaptive optical correction. Adaptive optics performed by means of Zernike polynomials are used to correct for system induced aberrations. Here we present results with significant improvement in throughput obtained using a novel complementary metal-oxide-semiconductor (CMOS) 1024 pixel single-photon avalanche diode (SPAD) array, opening the way to truly high-throughput FLIM.

  3. Aberration correction considering curved sample surface shape for non-contact two-photon excitation microscopy with spatial light modulator.

    PubMed

    Matsumoto, Naoya; Konno, Alu; Inoue, Takashi; Okazaki, Shigetoshi

    2018-06-18

    In this paper, excitation light wavefront modulation is performed considering the curved sample surface shape to demonstrate high-quality deep observation using two-photon excitation microscopy (TPM) with a dry objective lens. A large spherical aberration typically occurs when the refractive index (RI) interface between air and the sample is a plane perpendicular to the optical axis. Moreover, the curved sample surface shape and the RI mismatch cause various aberrations, including spherical ones. Consequently, the fluorescence intensity and resolution of the obtained image are degraded in the deep regions. To improve them, we designed a pre-distortion wavefront for correcting the aberration caused by the curved sample surface shape by using a novel, simple optical path length difference calculation method. The excitation light wavefront is modulated to the pre-distortion wavefront by a spatial light modulator incorporated in the TPM system before passing through the interface, where the RI mismatch occurs. Thus, the excitation light is condensed without aberrations. Blood vessels were thereby observed up to an optical depth of 2,000 μm in a cleared mouse brain by using a dry objective lens.

  4. Reducing the ecological consequences of night-time light pollution: options and developments

    PubMed Central

    Gaston, Kevin J; Davies, Thomas W; Bennie, Jonathan; Hopkins, John

    2012-01-01

    1. Much concern has been expressed about the ecological consequences of night-time light pollution. This concern is most often focused on the encroachment of artificial light into previously unlit areas of the night-time environment, but changes in the spectral composition, duration and spatial pattern of light are also recognized as having ecological effects. 2. Here, we examine the potential consequences for organisms of five management options to reduce night-time light pollution. These are to (i) prevent areas from being artificially lit; (ii) limit the duration of lighting; (iii) reduce the ‘trespass’ of lighting into areas that are not intended to be lit (including the night sky); (iv) change the intensity of lighting; and (v) change the spectral composition of lighting. 3. Maintaining and increasing natural unlit areas is likely to be the most effective option for reducing the ecological effects of lighting. However, this will often conflict with other social and economic objectives. Decreasing the duration of lighting will reduce energy costs and carbon emissions, but is unlikely to alleviate many impacts on nocturnal and crepuscular animals, as peak times of demand for lighting frequently coincide with those in the activities of these species. Reducing the trespass of lighting will maintain heterogeneity even in otherwise well-lit areas, providing dark refuges that mobile animals can exploit. Decreasing the intensity of lighting will reduce energy consumption and limit both skyglow and the area impacted by high-intensity direct light. Shifts towards ‘whiter’ light are likely to increase the potential range of environmental impacts as light is emitted across a broader range of wavelengths. 4. Synthesis and applications. The artificial lightscape will change considerably over coming decades with the drive for more cost-effective low-carbon street lighting solutions and growth in the artificially lit area. Developing lighting strategies that minimize

  5. Reducing the ecological consequences of night-time light pollution: options and developments.

    PubMed

    Gaston, Kevin J; Davies, Thomas W; Bennie, Jonathan; Hopkins, John

    2012-12-01

    1. Much concern has been expressed about the ecological consequences of night-time light pollution. This concern is most often focused on the encroachment of artificial light into previously unlit areas of the night-time environment, but changes in the spectral composition, duration and spatial pattern of light are also recognized as having ecological effects.2. Here, we examine the potential consequences for organisms of five management options to reduce night-time light pollution. These are to (i) prevent areas from being artificially lit; (ii) limit the duration of lighting; (iii) reduce the 'trespass' of lighting into areas that are not intended to be lit (including the night sky); (iv) change the intensity of lighting; and (v) change the spectral composition of lighting.3. Maintaining and increasing natural unlit areas is likely to be the most effective option for reducing the ecological effects of lighting. However, this will often conflict with other social and economic objectives. Decreasing the duration of lighting will reduce energy costs and carbon emissions, but is unlikely to alleviate many impacts on nocturnal and crepuscular animals, as peak times of demand for lighting frequently coincide with those in the activities of these species. Reducing the trespass of lighting will maintain heterogeneity even in otherwise well-lit areas, providing dark refuges that mobile animals can exploit. Decreasing the intensity of lighting will reduce energy consumption and limit both skyglow and the area impacted by high-intensity direct light. Shifts towards 'whiter' light are likely to increase the potential range of environmental impacts as light is emitted across a broader range of wavelengths.4.Synthesis and applications. The artificial lightscape will change considerably over coming decades with the drive for more cost-effective low-carbon street lighting solutions and growth in the artificially lit area. Developing lighting strategies that minimize adverse

  6. [A practical procedure to improve the accuracy of radiochromic film dosimetry: a integration with a correction method of uniformity correction and a red/blue correction method].

    PubMed

    Uehara, Ryuzo; Tachibana, Hidenobu; Ito, Yasushi; Yoshino, Shinichi; Matsubayashi, Fumiyasu; Sato, Tomoharu

    2013-06-01

    It has been reported that the light scattering could worsen the accuracy of dose distribution measurement using a radiochromic film. The purpose of this study was to investigate the accuracy of two different films, EDR2 and EBT2, as film dosimetry tools. The effectiveness of a correction method for the non-uniformity caused from EBT2 film and the light scattering was also evaluated. In addition the efficacy of this correction method integrated with the red/blue correction method was assessed. EDR2 and EBT2 films were read using a flatbed charge-coupled device scanner (EPSON 10000G). Dose differences on the axis perpendicular to the scanner lamp movement axis were within 1% with EDR2, but exceeded 3% (Maximum: +8%) with EBT2. The non-uniformity correction method, after a single film exposure, was applied to the readout of the films. A corrected dose distribution data was subsequently created. The correction method showed more than 10%-better pass ratios in dose difference evaluation than when the correction method was not applied. The red/blue correction method resulted in 5%-improvement compared with the standard procedure that employed red color only. The correction method with EBT2 proved to be able to rapidly correct non-uniformity, and has potential for routine clinical IMRT dose verification if the accuracy of EBT2 is required to be similar to that of EDR2. The use of red/blue correction method may improve the accuracy, but we recommend we should use the red/blue correction method carefully and understand the characteristics of EBT2 for red color only and the red/blue correction method.

  7. The effects of treatment room lighting color on time perception and emotion.

    PubMed

    Han, Seulki; Lee, Daehee

    2017-07-01

    [Purpose] The purpose of this study was to investigate the perceived treatment times and emotional reactions under different light colors in the treatment room. [Subjects and Methods] Subjects in this study were 20 healthy young students in their 20s. Under each lighting condition (blue, red, white, and yellow) differentiated by color, each subject laid on a therapeutic bed and underwent ultrasound therapy. Subjects were instructed to press a stopwatch every 1 minute, for a total of 5 times, after therapy started according to their perception of time while the stopwatch's time indicator was blocked. After the experiments, self-administered questionnaires were given to subjects to measure their emotional reactions. [Results] In terms of K-POMS scores, the mood states of depression-dejection, anger-hostility, and confusion-bewilderment were higher scores for blue and red lights compared to yellow light. The mood state of vigor-activity were higher scores for yellow and white lights compared to blue and red lights. [Conclusion] Therefore, it is important to take necessary measures to prevent the negative effects that blue and red light-based therapy can have on patient mood.

  8. A Multidimensional B-Spline Correction for Accurate Modeling Sugar Puckering in QM/MM Simulations.

    PubMed

    Huang, Ming; Dissanayake, Thakshila; Kuechler, Erich; Radak, Brian K; Lee, Tai-Sung; Giese, Timothy J; York, Darrin M

    2017-09-12

    The computational efficiency of approximate quantum mechanical methods allows their use for the construction of multidimensional reaction free energy profiles. It has recently been demonstrated that quantum models based on the neglect of diatomic differential overlap (NNDO) approximation have difficulty modeling deoxyribose and ribose sugar ring puckers and thus limit their predictive value in the study of RNA and DNA systems. A method has been introduced in our previous work to improve the description of the sugar puckering conformational landscape that uses a multidimensional B-spline correction map (BMAP correction) for systems involving intrinsically coupled torsion angles. This method greatly improved the adiabatic potential energy surface profiles of DNA and RNA sugar rings relative to high-level ab initio methods even for highly problematic NDDO-based models. In the present work, a BMAP correction is developed, implemented, and tested in molecular dynamics simulations using the AM1/d-PhoT semiempirical Hamiltonian for biological phosphoryl transfer reactions. Results are presented for gas-phase adiabatic potential energy surfaces of RNA transesterification model reactions and condensed-phase QM/MM free energy surfaces for nonenzymatic and RNase A-catalyzed transesterification reactions. The results show that the BMAP correction is stable, efficient, and leads to improvement in both the potential energy and free energy profiles for the reactions studied, as compared with ab initio and experimental reference data. Exploration of the effect of the size of the quantum mechanical region indicates the best agreement with experimental reaction barriers occurs when the full CpA dinucleotide substrate is treated quantum mechanically with the sugar pucker correction.

  9. A late wake time phase delays the human dim light melatonin rhythm.

    PubMed

    Burgess, Helen J; Eastman, Charmane I

    2006-03-13

    Short sleep/dark durations, due to late bedtimes or early wake times or both, are common in modern society. We have previously shown that a series of days with a late bedtime phase delays the human dim light melatonin rhythm, as compared to a series of days with an early bedtime, despite a fixed wake time. Here we compared the effect of an early versus late wake time with a fixed bedtime on the human dim light melatonin rhythm. Fourteen healthy subjects experienced 2 weeks of short 6h nights with an early wake time fixed at their habitual weekday wake time and 2 weeks of long 9 h nights with a wake time that occurred 3h later than the early wake time, in counterbalanced order. We found that after 2 weeks with the late wake time, the dim light melatonin onset delayed by 2.4 h and the dim light melatonin offset delayed by 2.6 h (both p < 0.001), as compared to after 2 weeks with the early wake time. These results highlight the substantial influence that wake time, likely via the associated morning light exposure, has on the timing of the human circadian clock. Furthermore, the results suggest that when people truncate their sleep by waking early their circadian clocks phase advance and when people wake late their circadian clocks phase delay.

  10. Real-Time View Correction for Mobile Devices.

    PubMed

    Schops, Thomas; Oswald, Martin R; Speciale, Pablo; Yang, Shuoran; Pollefeys, Marc

    2017-11-01

    We present a real-time method for rendering novel virtual camera views from given RGB-D (color and depth) data of a different viewpoint. Missing color and depth information due to incomplete input or disocclusions is efficiently inpainted in a temporally consistent way. The inpainting takes the location of strong image gradients into account as likely depth discontinuities. We present our method in the context of a view correction system for mobile devices, and discuss how to obtain a screen-camera calibration and options for acquiring depth input. Our method has use cases in both augmented and virtual reality applications. We demonstrate the speed of our system and the visual quality of its results in multiple experiments in the paper as well as in the supplementary video.

  11. Real-time emission factor measurements of isocyanic acid from light duty gasoline vehicles.

    PubMed

    Brady, James M; Crisp, Timia A; Collier, Sonya; Kuwayama, Toshihiro; Forestieri, Sara D; Perraud, Véronique; Zhang, Qi; Kleeman, Michael J; Cappa, Christopher D; Bertram, Timothy H

    2014-10-07

    Exposure to gas-phase isocyanic acid (HNCO) has been previously shown to be associated with the development of atherosclerosis, cataracts and rheumatoid arthritis. As such, accurate emission inventories for HNCO are critical for modeling the spatial and temporal distribution of HNCO on a regional and global scale. To date, HNCO emission rates from light duty gasoline vehicles, operated under driving conditions, have not been determined. Here, we present the first measurements of real-time emission factors of isocyanic acid from a fleet of eight light duty gasoline-powered vehicles (LDGVs) tested on a chassis dynamometer using the Unified Driving Cycle (UC) at the California Air Resources Board (CARB) Haagen-Smit test facility, all of which were equipped with three-way catalytic converters. HNCO emissions were observed from all vehicles, in contrast to the idealized laboratory measurements. We report the tested fleet averaged HNCO emission factors, which depend strongly on the phase of the drive cycle; ranging from 0.46 ± 0.13 mg kg fuel(-1) during engine start to 1.70 ± 1.77 mg kg fuel(-1) during hard acceleration after the engine and catalytic converter were warm. The tested eight-car fleet average fuel based HNCO emission factor was 0.91 ± 0.58 mg kg fuel(-1), within the range previously estimated for light duty diesel-powered vehicles (0.21-3.96 mg kg fuel(-1)). Our results suggest that HNCO emissions from LDGVs represent a significant emission source in urban areas that should be accounted for in global and regional models.

  12. Rapid optimization method of the strong stray light elimination for extremely weak light signal detection.

    PubMed

    Wang, Geng; Xing, Fei; Wei, Minsong; You, Zheng

    2017-10-16

    The strong stray light has huge interference on the detection of weak and small optical signals, and is difficult to suppress. In this paper, a miniaturized baffle with angled vanes was proposed and a rapid optimization model of strong light elimination was built, which has better suppression of the stray lights than the conventional vanes and can optimize the positions of the vanes efficiently and accurately. Furthermore, the light energy distribution model was built based on the light projection at a specific angle, and the light propagation models of the vanes and sidewalls were built based on the Lambert scattering, both of which act as the bias of a calculation method of stray light. Moreover, the Monte-Carlo method was employed to realize the Point Source Transmittance (PST) simulation, and the simulation result indicated that it was consistent with the calculation result based on our models, and the PST could be improved by 2-3 times at the small incident angles for the baffle designed by the new method. Meanwhile, the simulation result was verified by laboratory tests, and the new model with derived analytical expressions which can reduce the simulation time significantly.

  13. Communication: An efficient and accurate perturbative correction to initiator full configuration interaction quantum Monte Carlo

    NASA Astrophysics Data System (ADS)

    Blunt, Nick S.

    2018-06-01

    We present a perturbative correction within initiator full configuration interaction quantum Monte Carlo (i-FCIQMC). In the existing i-FCIQMC algorithm, a significant number of spawned walkers are discarded due to the initiator criteria. Here we show that these discarded walkers have a form that allows the calculation of a second-order Epstein-Nesbet correction, which may be accumulated in a trivial and inexpensive manner, yet substantially improves i-FCIQMC results. The correction is applied to the Hubbard model and the uniform electron gas and molecular systems.

  14. Time scale controversy: Accurate orbital calibration of the early Paleogene

    NASA Astrophysics Data System (ADS)

    Roehl, U.; Westerhold, T.; Laskar, J.

    2012-12-01

    Timing is crucial to understanding the causes and consequences of events in Earth history. The calibration of geological time relies heavily on the accuracy of radioisotopic and astronomical dating. Uncertainties in the computations of Earth's orbital parameters and in radioisotopic dating have hampered the construction of a reliable astronomically calibrated time scale beyond 40 Ma. Attempts to construct a robust astronomically tuned time scale for the early Paleogene by integrating radioisotopic and astronomical dating are only partially consistent. Here, using the new La2010 and La2011 orbital solutions, we present the first accurate astronomically calibrated time scale for the early Paleogene (47-65 Ma) uniquely based on astronomical tuning and thus independent of the radioisotopic determination of the Fish Canyon standard. Comparison with geological data confirms the stability of the new La2011 solution back to 54 Ma. Subsequent anchoring of floating chronologies to the La2011 solution using the very long eccentricity nodes provides an absolute age of 55.530 ± 0.05 Ma for the onset of the Paleocene/Eocene Thermal Maximum (PETM), 54.850 ± 0.05 Ma for the early Eocene ash -17, and 65.250 ± 0.06 Ma for the K/Pg boundary. The new astrochronology presented here indicates that the intercalibration and synchronization of U/Pb and 40Ar/39Ar radioisotopic geochronology is much more challenging than previously thought.

  15. Time scale controversy: Accurate orbital calibration of the early Paleogene

    NASA Astrophysics Data System (ADS)

    Westerhold, Thomas; RöHl, Ursula; Laskar, Jacques

    2012-06-01

    Timing is crucial to understanding the causes and consequences of events in Earth history. The calibration of geological time relies heavily on the accuracy of radioisotopic and astronomical dating. Uncertainties in the computations of Earth's orbital parameters and in radioisotopic dating have hampered the construction of a reliable astronomically calibrated time scale beyond 40 Ma. Attempts to construct a robust astronomically tuned time scale for the early Paleogene by integrating radioisotopic and astronomical dating are only partially consistent. Here, using the new La2010 and La2011 orbital solutions, we present the first accurate astronomically calibrated time scale for the early Paleogene (47-65 Ma) uniquely based on astronomical tuning and thus independent of the radioisotopic determination of the Fish Canyon standard. Comparison with geological data confirms the stability of the new La2011 solution back to ˜54 Ma. Subsequent anchoring of floating chronologies to the La2011 solution using the very long eccentricity nodes provides an absolute age of 55.530 ± 0.05 Ma for the onset of the Paleocene/Eocene Thermal Maximum (PETM), 54.850 ± 0.05 Ma for the early Eocene ash -17, and 65.250 ± 0.06 Ma for the K/Pg boundary. The new astrochronology presented here indicates that the intercalibration and synchronization of U/Pb and 40Ar/39Ar radioisotopic geochronology is much more challenging than previously thought.

  16. Social contagion of correct and incorrect information in memory.

    PubMed

    Rush, Ryan A; Clark, Steven E

    2014-01-01

    The present study examines how discussion between individuals regarding a shared memory affects their subsequent individual memory reports. In three experiments pairs of participants recalled items from photographs of common household scenes, discussed their recall with each other, and then recalled the items again individually. Results showed that after the discussion. individuals recalled more correct items and more incorrect items, with very small non-significant increases, or no change, in recall accuracy. The information people were exposed to during the discussion was generally accurate, although not as accurate as individuals' initial recall. Individuals incorporated correct exposure items into their subsequent recall at a higher rate than incorrect exposure items. Participants who were initially more accurate became less accurate, and initially less-accurate participants became more accurate as a result of their discussion. Comparisons to no-discussion control groups suggest that the effects were not simply the product of repeated recall opportunities or self-cueing, but rather reflect the transmission of information between individuals.

  17. Exploratory data analysis of acceleration signals to select light-weight and accurate features for real-time activity recognition on smartphones.

    PubMed

    Khan, Adil Mehmood; Siddiqi, Muhammad Hameed; Lee, Seok-Won

    2013-09-27

    Smartphone-based activity recognition (SP-AR) recognizes users' activities using the embedded accelerometer sensor. Only a small number of previous works can be classified as online systems, i.e., the whole process (pre-processing, feature extraction, and classification) is performed on the device. Most of these online systems use either a high sampling rate (SR) or long data-window (DW) to achieve high accuracy, resulting in short battery life or delayed system response, respectively. This paper introduces a real-time/online SP-AR system that solves this problem. Exploratory data analysis was performed on acceleration signals of 6 activities, collected from 30 subjects, to show that these signals are generated by an autoregressive (AR) process, and an accurate AR-model in this case can be built using a low SR (20 Hz) and a small DW (3 s). The high within class variance resulting from placing the phone at different positions was reduced using kernel discriminant analysis to achieve position-independent recognition. Neural networks were used as classifiers. Unlike previous works, true subject-independent evaluation was performed, where 10 new subjects evaluated the system at their homes for 1 week. The results show that our features outperformed three commonly used features by 40% in terms of accuracy for the given SR and DW.

  18. Approaches for the accurate definition of geological time boundaries

    NASA Astrophysics Data System (ADS)

    Schaltegger, Urs; Baresel, Björn; Ovtcharova, Maria; Goudemand, Nicolas; Bucher, Hugo

    2015-04-01

    Which strategies lead to the most precise and accurate date of a given geological boundary? Geological units are usually defined by the occurrence of characteristic taxa and hence boundaries between these geological units correspond to dramatic faunal and/or floral turnovers and they are primarily defined using first or last occurrences of index species, or ideally by the separation interval between two consecutive, characteristic associations of fossil taxa. These boundaries need to be defined in a way that enables their worldwide recognition and correlation across different stratigraphic successions, using tools as different as bio-, magneto-, and chemo-stratigraphy, and astrochronology. Sedimentary sequences can be dated in numerical terms by applying high-precision chemical-abrasion, isotope-dilution, thermal-ionization mass spectrometry (CA-ID-TIMS) U-Pb age determination to zircon (ZrSiO4) in intercalated volcanic ashes. But, though volcanic activity is common in geological history, ashes are not necessarily close to the boundary we would like to date precisely and accurately. In addition, U-Pb zircon data sets may be very complex and difficult to interpret in terms of the age of ash deposition. To overcome these difficulties we use a multi-proxy approach we applied to the precise and accurate dating of the Permo-Triassic and Early-Middle Triassic boundaries in South China. a) Dense sampling of ashes across the critical time interval and a sufficiently large number of analysed zircons per ash sample can guarantee the recognition of all system complexities. Geochronological datasets from U-Pb dating of volcanic zircon may indeed combine effects of i) post-crystallization Pb loss from percolation of hydrothermal fluids (even using chemical abrasion), with ii) age dispersion from prolonged residence of earlier crystallized zircon in the magmatic system. As a result, U-Pb dates of individual zircons are both apparently younger and older than the depositional age

  19. Fully 3D refraction correction dosimetry system.

    PubMed

    Manjappa, Rakesh; Makki, S Sharath; Kumar, Rajesh; Vasu, Ram Mohan; Kanhirodan, Rajan

    2016-02-21

    medium is 71.8%, an increase of 6.4% compared to that achieved using conventional ART algorithm. Smaller diameter dosimeters are scanned with dry air scanning by using a wide-angle lens that collects refracted light. The images reconstructed using cone beam geometry is seen to deteriorate in some planes as those regions are not scanned. Refraction correction is important and needs to be taken in to consideration to achieve quantitatively accurate dose reconstructions. Refraction modeling is crucial in array based scanners as it is not possible to identify refracted rays in the sinogram space.

  20. Correction of misleading information in prescription drug television advertising: The roles of advertisement similarity and time delay.

    PubMed

    Aikin, Kathryn J; Southwell, Brian G; Paquin, Ryan S; Rupert, Douglas J; O'Donoghue, Amie C; Betts, Kevin R; Lee, Philip K

    Prescription drug television advertisements containing potentially consequential misinformation sometimes appear in the United States. When that happens, the U.S. Food and Drug Administration can request that companies distribute corrective advertisements to address misinformation and inaccurate claims. Previous research has demonstrated effectiveness in corrective advertising for various products. The present article builds on that work with a randomized experimental study (n = 6454) of corrective advertising investigating the extent to which visual similarity matters between violative and corrective ads and the extent to which time delay matters between violative and corrective advertisement exposure. Our study sample included overweight or obese U.S. adults recruited from an existing online consumer panel representative of the U.S. adult population. We created a brand for a fictitious prescription weight-loss drug and produced corresponding direct-to-consumer (DTC) television ads. All participants viewed the same violative ad, but were randomly assigned to view corrective ads with different levels of visual similarity and exposure time delay using a 4 × 4 between-subjects factorial design. Results suggest corrective ad exposure can influence consumer perceptions of drug efficacy, risks, and benefits previously established by violative ads that overstated drug efficacy, broadened drug indication, and omitted important risk information. Corrective ads also can weaken consumer intentions to consider and investigate a drug. However, ad similarity does not appear to affect consumer perceptions and preferences. Although we found that the effects of violative ad exposure tend to diminish over time, the length of the delay between violative and corrective ad exposure has limited influence. An exception to this was observed with regard to recall of drug benefits and risks, where the impact of corrective ad exposure increases with greater time delay. These results

  1. An implicit higher-order spatially accurate scheme for solving time dependent flows on unstructured meshes

    NASA Astrophysics Data System (ADS)

    Tomaro, Robert F.

    1998-07-01

    The present research is aimed at developing a higher-order, spatially accurate scheme for both steady and unsteady flow simulations using unstructured meshes. The resulting scheme must work on a variety of general problems to ensure the creation of a flexible, reliable and accurate aerodynamic analysis tool. To calculate the flow around complex configurations, unstructured grids and the associated flow solvers have been developed. Efficient simulations require the minimum use of computer memory and computational times. Unstructured flow solvers typically require more computer memory than a structured flow solver due to the indirect addressing of the cells. The approach taken in the present research was to modify an existing three-dimensional unstructured flow solver to first decrease the computational time required for a solution and then to increase the spatial accuracy. The terms required to simulate flow involving non-stationary grids were also implemented. First, an implicit solution algorithm was implemented to replace the existing explicit procedure. Several test cases, including internal and external, inviscid and viscous, two-dimensional, three-dimensional and axi-symmetric problems, were simulated for comparison between the explicit and implicit solution procedures. The increased efficiency and robustness of modified code due to the implicit algorithm was demonstrated. Two unsteady test cases, a plunging airfoil and a wing undergoing bending and torsion, were simulated using the implicit algorithm modified to include the terms required for a moving and/or deforming grid. Secondly, a higher than second-order spatially accurate scheme was developed and implemented into the baseline code. Third- and fourth-order spatially accurate schemes were implemented and tested. The original dissipation was modified to include higher-order terms and modified near shock waves to limit pre- and post-shock oscillations. The unsteady cases were repeated using the higher

  2. A time-accurate finite volume method valid at all flow velocities

    NASA Technical Reports Server (NTRS)

    Kim, S.-W.

    1993-01-01

    A finite volume method to solve the Navier-Stokes equations at all flow velocities (e.g., incompressible, subsonic, transonic, supersonic and hypersonic flows) is presented. The numerical method is based on a finite volume method that incorporates a pressure-staggered mesh and an incremental pressure equation for the conservation of mass. Comparison of three generally accepted time-advancing schemes, i.e., Simplified Marker-and-Cell (SMAC), Pressure-Implicit-Splitting of Operators (PISO), and Iterative-Time-Advancing (ITA) scheme, are made by solving a lid-driven polar cavity flow and self-sustained oscillatory flows over circular and square cylinders. Calculated results show that the ITA is the most stable numerically and yields the most accurate results. The SMAC is the most efficient computationally and is as stable as the ITA. It is shown that the PISO is the most weakly convergent and it exhibits an undesirable strong dependence on the time-step size. The degenerated numerical results obtained using the PISO are attributed to its second corrector step that cause the numerical results to deviate further from a divergence free velocity field. The accurate numerical results obtained using the ITA is attributed to its capability to resolve the nonlinearity of the Navier-Stokes equations. The present numerical method that incorporates the ITA is used to solve an unsteady transitional flow over an oscillating airfoil and a chemically reacting flow of hydrogen in a vitiated supersonic airstream. The turbulence fields in these flow cases are described using multiple-time-scale turbulence equations. For the unsteady transitional over an oscillating airfoil, the fluid flow is described using ensemble-averaged Navier-Stokes equations defined on the Lagrangian-Eulerian coordinates. It is shown that the numerical method successfully predicts the large dynamic stall vortex (DSV) and the trailing edge vortex (TEV) that are periodically generated by the oscillating airfoil

  3. Fringe Capacitance Correction for a Coaxial Soil Cell

    PubMed Central

    Pelletier, Mathew G.; Viera, Joseph A.; Schwartz, Robert C.; Lascano, Robert J.; Evett, Steven R.; Green, Tim R.; Wanjura, John D.; Holt, Greg A.

    2011-01-01

    Accurate measurement of moisture content is a prime requirement in hydrological, geophysical and biogeochemical research as well as for material characterization and process control. Within these areas, accurate measurements of the surface area and bound water content is becoming increasingly important for providing answers to many fundamental questions ranging from characterization of cotton fiber maturity, to accurate characterization of soil water content in soil water conservation research to bio-plant water utilization to chemical reactions and diffusions of ionic species across membranes in cells as well as in the dense suspensions that occur in surface films. One promising technique to address the increasing demands for higher accuracy water content measurements is utilization of electrical permittivity characterization of materials. This technique has enjoyed a strong following in the soil-science and geological community through measurements of apparent permittivity via time-domain-reflectometry (TDR) as well in many process control applications. Recent research however, is indicating a need to increase the accuracy beyond that available from traditional TDR. The most logical pathway then becomes a transition from TDR based measurements to network analyzer measurements of absolute permittivity that will remove the adverse effects that high surface area soils and conductivity impart onto the measurements of apparent permittivity in traditional TDR applications. This research examines an observed experimental error for the coaxial probe, from which the modern TDR probe originated, which is hypothesized to be due to fringe capacitance. The research provides an experimental and theoretical basis for the cause of the error and provides a technique by which to correct the system to remove this source of error. To test this theory, a Poisson model of a coaxial cell was formulated to calculate the effective theoretical extra length caused by the fringe capacitance

  4. Interval Timing Is Preserved Despite Circadian Desynchrony in Rats: Constant Light and Heavy Water Studies.

    PubMed

    Petersen, Christian C; Mistlberger, Ralph E

    2017-08-01

    The mechanisms that enable mammals to time events that recur at 24-h intervals (circadian timing) and at arbitrary intervals in the seconds-to-minutes range (interval timing) are thought to be distinct at the computational and neurobiological levels. Recent evidence that disruption of circadian rhythmicity by constant light (LL) abolishes interval timing in mice challenges this assumption and suggests a critical role for circadian clocks in short interval timing. We sought to confirm and extend this finding by examining interval timing in rats in which circadian rhythmicity was disrupted by long-term exposure to LL or by chronic intake of 25% D 2 O. Adult, male Sprague-Dawley rats were housed in a light-dark (LD) cycle or in LL until free-running circadian rhythmicity was markedly disrupted or abolished. The rats were then trained and tested on 15- and 30-sec peak-interval procedures, with water restriction used to motivate task performance. Interval timing was found to be unimpaired in LL rats, but a weak circadian activity rhythm was apparently rescued by the training procedure, possibly due to binge feeding that occurred during the 15-min water access period that followed training each day. A second group of rats in LL were therefore restricted to 6 daily meals scheduled at 4-h intervals. Despite a complete absence of circadian rhythmicity in this group, interval timing was again unaffected. To eliminate all possible temporal cues, we tested a third group of rats in LL by using a pseudo-randomized schedule. Again, interval timing remained accurate. Finally, rats tested in LD received 25% D 2 O in place of drinking water. This markedly lengthened the circadian period and caused a failure of LD entrainment but did not disrupt interval timing. These results indicate that interval timing in rats is resistant to disruption by manipulations of circadian timekeeping previously shown to impair interval timing in mice.

  5. White-Light Phase-Conjugate Mirrors as Distortion Correctors

    NASA Technical Reports Server (NTRS)

    Frazier, Donald; Smith, W. Scott; Abdeldayem, Hossin; Banerjee, Partha

    2010-01-01

    White-light phase-conjugate mirrors would be incorporated into some optical systems, according to a proposal, as means of correcting for wavefront distortions caused by imperfections in large optical components. The proposal was given impetus by a recent demonstration that white, incoherent light can be made to undergo phase conjugation, whereas previously, only coherent light was known to undergo phase conjugation. This proposal, which is potentially applicable to almost any optical system, was motivated by a need to correct optical aberrations of the primary mirror of the Hubble Space telescope. It is difficult to fabricate large optical components like the Hubble primary mirror and to ensure the high precision typically required of such components. In most cases, despite best efforts, the components as fabricated have small imperfections that introduce optical aberrations that adversely affect imaging quality. Correcting for such aberrations is difficult and costly. The proposed use of white-light phase conjugate mirrors offers a relatively simple and inexpensive solution of the aberration-correction problem. Indeed, it should be possible to simplify the entire approach to making large optical components because there would be no need to fabricate those components with extremely high precision in the first place: A white-light phase-conjugate mirror could correct for all the distortions and aberrations in an optical system. The use of white-light phase-conjugate mirrors would be essential for ensuring high performance in optical systems containing lightweight membrane mirrors, which are highly deformable. As used here, "phase-conjugate mirror" signifies, more specifically, an optical component in which incident light undergoes time-reversal phase conjugation. In practice, a phase-conjugate mirror would typically be implemented by use of a suitably positioned and oriented photorefractive crystal. In the case of a telescope comprising a primary and secondary

  6. Decision tree for accurate infection timing in individuals newly diagnosed with HIV-1 infection.

    PubMed

    Verhofstede, Chris; Fransen, Katrien; Van Den Heuvel, Annelies; Van Laethem, Kristel; Ruelle, Jean; Vancutsem, Ellen; Stoffels, Karolien; Van den Wijngaert, Sigi; Delforge, Marie-Luce; Vaira, Dolores; Hebberecht, Laura; Schauvliege, Marlies; Mortier, Virginie; Dauwe, Kenny; Callens, Steven

    2017-11-29

    There is today no gold standard method to accurately define the time passed since infection at HIV diagnosis. Infection timing and incidence measurement is however essential to better monitor the dynamics of local epidemics and the effect of prevention initiatives. Three methods for infection timing were evaluated using 237 serial samples from documented seroconversions and 566 cross sectional samples from newly diagnosed patients: identification of antibodies against the HIV p31 protein in INNO-LIA, SediaTM BED CEIA and SediaTM LAg-Avidity EIA. A multi-assay decision tree for infection timing was developed. Clear differences in recency window between BED CEIA, LAg-Avidity EIA and p31 antibody presence were observed with a switch from recent to long term infection a median of 169.5, 108.0 and 64.5 days after collection of the pre-seroconversion sample respectively. BED showed high reliability for identification of long term infections while LAg-Avidity is highly accurate for identification of recent infections. Using BED as initial assay to identify the long term infections and LAg-Avidity as a confirmatory assay for those classified as recent infection by BED, explores the strengths of both while reduces the workload. The short recency window of p31 antibodies allows to discriminate very early from early infections based on this marker. BED recent infection results not confirmed by LAg-Avidity are considered to reflect a period more distant from the infection time. False recency predictions in this group can be minimized by elimination of patients with a CD4 count of less than 100 cells/mm3 or without no p31 antibodies. For 566 cross sectional sample the outcome of the decision tree confirmed the infection timing based on the results of all 3 markers but reduced the overall cost from 13.2 USD to 5.2 USD per sample. A step-wise multi assay decision tree allows accurate timing of the HIV infection at diagnosis at affordable effort and cost and can be an important

  7. Achieving algorithmic resilience for temporal integration through spectral deferred corrections

    DOE PAGES

    Grout, Ray; Kolla, Hemanth; Minion, Michael; ...

    2017-05-08

    Spectral deferred corrections (SDC) is an iterative approach for constructing higher-order-accurate numerical approximations of ordinary differential equations. SDC starts with an initial approximation of the solution defined at a set of Gaussian or spectral collocation nodes over a time interval and uses an iterative application of lower-order time discretizations applied to a correction equation to improve the solution at these nodes. Each deferred correction sweep increases the formal order of accuracy of the method up to the limit inherent in the accuracy defined by the collocation points. In this paper, we demonstrate that SDC is well suited to recovering frommore » soft (transient) hardware faults in the data. A strategy where extra correction iterations are used to recover from soft errors and provide algorithmic resilience is proposed. Specifically, in this approach the iteration is continued until the residual (a measure of the error in the approximation) is small relative to the residual of the first correction iteration and changes slowly between successive iterations. Here, we demonstrate the effectiveness of this strategy for both canonical test problems and a comprehensive situation involving a mature scientific application code that solves the reacting Navier-Stokes equations for combustion research.« less

  8. Achieving algorithmic resilience for temporal integration through spectral deferred corrections

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Grout, Ray; Kolla, Hemanth; Minion, Michael

    2017-05-08

    Spectral deferred corrections (SDC) is an iterative approach for constructing higher- order accurate numerical approximations of ordinary differential equations. SDC starts with an initial approximation of the solution defined at a set of Gaussian or spectral collocation nodes over a time interval and uses an iterative application of lower-order time discretizations applied to a correction equation to improve the solution at these nodes. Each deferred correction sweep increases the formal order of accuracy of the method up to the limit inherent in the accuracy defined by the collocation points. In this paper, we demonstrate that SDC is well suited tomore » recovering from soft (transient) hardware faults in the data. A strategy where extra correction iterations are used to recover from soft errors and provide algorithmic resilience is proposed. Specifically, in this approach the iteration is continued until the residual (a measure of the error in the approximation) is small relative to the residual on the first correction iteration and changes slowly between successive iterations. We demonstrate the effectiveness of this strategy for both canonical test problems and a comprehen- sive situation involving a mature scientific application code that solves the reacting Navier-Stokes equations for combustion research.« less

  9. Achieving algorithmic resilience for temporal integration through spectral deferred corrections

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Grout, Ray; Kolla, Hemanth; Minion, Michael

    2017-05-08

    Spectral deferred corrections (SDC) is an iterative approach for constructing higher-order-accurate numerical approximations of ordinary differential equations. SDC starts with an initial approximation of the solution defined at a set of Gaussian or spectral collocation nodes over a time interval and uses an iterative application of lower-order time discretizations applied to a correction equation to improve the solution at these nodes. Each deferred correction sweep increases the formal order of accuracy of the method up to the limit inherent in the accuracy defined by the collocation points. In this paper, we demonstrate that SDC is well suited to recovering frommore » soft (transient) hardware faults in the data. A strategy where extra correction iterations are used to recover from soft errors and provide algorithmic resilience is proposed. Specifically, in this approach the iteration is continued until the residual (a measure of the error in the approximation) is small relative to the residual of the first correction iteration and changes slowly between successive iterations. We demonstrate the effectiveness of this strategy for both canonical test problems and a comprehensive situation involving a mature scientific application code that solves the reacting Navier-Stokes equations for combustion research.« less

  10. An Accurate Analytic Approximation for Light Scattering by Non-absorbing Spherical Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Lewis, E. R.

    2017-12-01

    The scattering of light by particles in the atmosphere is a ubiquitous and important phenomenon, with applications to numerous fields of science and technology. The problem of scattering of electromagnetic radiation by a uniform spherical particle can be solved by the method of Mie and Debye as a series of terms depending on the size parameter, x=2πr/λ, and the complex index of refraction, m. However, this solution does not provide insight into the dependence of the scattering on the radius of the particle, the wavelength, or the index of refraction, or how the scattering varies with relative humidity. Van de Hulst demonstrated that the scattering efficiency (the scattering cross section divided by the geometric cross section) of a non-absorbing sphere, over a wide range of particle sizes of atmospheric importance, depends not on x and m separately, but on the quantity 2x(m-1); this is the basis for the anomalous diffraction approximation. Here an analytic approximation for the scattering efficiency of a non-absorbing spherical particle is presented in terms of this new quantity that is accurate over a wide range of particle sizes of atmospheric importance and which readily displays the dependences of the scattering efficiency on particle radius, index of refraction, and wavelength. For an aerosol for which the particle size distribution is parameterized as a gamma function, this approximation also yields analytical results for the scattering coefficient and for the Ångström exponent, with the dependences of scattering properties on wavelength and index of refraction clearly displayed. This approximation provides insight into the dependence of light scattering properties on factors such as relative humidity, readily enables conversion of scattering from one index of refraction to another, and demonstrates the conditions under which the aerosol index (the product of the aerosol optical depth and the Ångström exponent) is a useful proxy for the number of cloud

  11. Advanced lighting guidelines: 1993. Final report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Eley, C.; Tolen, T.M.; Benya, J.R.

    1993-12-31

    The 1993 Advanced Lighting Guidelines document consists of twelve guidelines that provide an overview of specific lighting technologies and design application techniques utilizing energy-efficient lighting practice. Lighting Design Practice assesses energy-efficient lighting strategies, discusses lighting issues, and explains how to obtain quality lighting design and consulting services. Luminaires and Lighting Systems surveys luminaire equipment designed to take advantage of advanced technology lamp products and includes performance tables that allow for accurate estimation of luminaire light output and power input. The additional ten guidelines -- Computer-Aided Lighting Design, Energy-Efficient Fluorescent Ballasts, Full-Size Fluorescent Lamps, Compact Fluorescent Lamps, Tungsten-Halogen Lamps, Metal Halidemore » and HPS Lamps, Daylighting and Lumen Maintenance, Occupant Sensors, Time Scheduling Systems, and Retrofit Control Technologies -- each provide a product technology overview, discuss current products on the lighting equipment market, and provide application techniques. This document is intended for use by electric utility personnel involved in lighting programs, lighting designers, electrical engineers, architects, lighting manufacturers` representatives, and other lighting professionals.« less

  12. Comparative evaluation of performance measures for shading correction in time-lapse fluorescence microscopy.

    PubMed

    Liu, L; Kan, A; Leckie, C; Hodgkin, P D

    2017-04-01

    Time-lapse fluorescence microscopy is a valuable technology in cell biology, but it suffers from the inherent problem of intensity inhomogeneity due to uneven illumination or camera nonlinearity, known as shading artefacts. This will lead to inaccurate estimates of single-cell features such as average and total intensity. Numerous shading correction methods have been proposed to remove this effect. In order to compare the performance of different methods, many quantitative performance measures have been developed. However, there is little discussion about which performance measure should be generally applied for evaluation on real data, where the ground truth is absent. In this paper, the state-of-the-art shading correction methods and performance evaluation methods are reviewed. We implement 10 popular shading correction methods on two artificial datasets and four real ones. In order to make an objective comparison between those methods, we employ a number of quantitative performance measures. Extensive validation demonstrates that the coefficient of joint variation (CJV) is the most applicable measure in time-lapse fluorescence images. Based on this measure, we have proposed a novel shading correction method that performs better compared to well-established methods for a range of real data tested. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

  13. Quantitative analysis of MRI-guided attenuation correction techniques in time-of-flight brain PET/MRI.

    PubMed

    Mehranian, Abolfazl; Arabi, Hossein; Zaidi, Habib

    2016-04-15

    In quantitative PET/MR imaging, attenuation correction (AC) of PET data is markedly challenged by the need of deriving accurate attenuation maps from MR images. A number of strategies have been developed for MRI-guided attenuation correction with different degrees of success. In this work, we compare the quantitative performance of three generic AC methods, including standard 3-class MR segmentation-based, advanced atlas-registration-based and emission-based approaches in the context of brain time-of-flight (TOF) PET/MRI. Fourteen patients referred for diagnostic MRI and (18)F-FDG PET/CT brain scans were included in this comparative study. For each study, PET images were reconstructed using four different attenuation maps derived from CT-based AC (CTAC) serving as reference, standard 3-class MR-segmentation, atlas-registration and emission-based AC methods. To generate 3-class attenuation maps, T1-weighted MRI images were segmented into background air, fat and soft-tissue classes followed by assignment of constant linear attenuation coefficients of 0, 0.0864 and 0.0975 cm(-1) to each class, respectively. A robust atlas-registration based AC method was developed for pseudo-CT generation using local weighted fusion of atlases based on their morphological similarity to target MR images. Our recently proposed MRI-guided maximum likelihood reconstruction of activity and attenuation (MLAA) algorithm was employed to estimate the attenuation map from TOF emission data. The performance of the different AC algorithms in terms of prediction of bones and quantification of PET tracer uptake was objectively evaluated with respect to reference CTAC maps and CTAC-PET images. Qualitative evaluation showed that the MLAA-AC method could sparsely estimate bones and accurately differentiate them from air cavities. It was found that the atlas-AC method can accurately predict bones with variable errors in defining air cavities. Quantitative assessment of bone extraction accuracy based on

  14. Text recognition and correction for automated data collection by mobile devices

    NASA Astrophysics Data System (ADS)

    Ozarslan, Suleyman; Eren, P. Erhan

    2014-03-01

    Participatory sensing is an approach which allows mobile devices such as mobile phones to be used for data collection, analysis and sharing processes by individuals. Data collection is the first and most important part of a participatory sensing system, but it is time consuming for the participants. In this paper, we discuss automatic data collection approaches for reducing the time required for collection, and increasing the amount of collected data. In this context, we explore automated text recognition on images of store receipts which are captured by mobile phone cameras, and the correction of the recognized text. Accordingly, our first goal is to evaluate the performance of the Optical Character Recognition (OCR) method with respect to data collection from store receipt images. Images captured by mobile phones exhibit some typical problems, and common image processing methods cannot handle some of them. Consequently, the second goal is to address these types of problems through our proposed Knowledge Based Correction (KBC) method used in support of the OCR, and also to evaluate the KBC method with respect to the improvement on the accurate recognition rate. Results of the experiments show that the KBC method improves the accurate data recognition rate noticeably.

  15. Real-time time-division color electroholography using a single GPU and a USB module for synchronizing reference light.

    PubMed

    Araki, Hiromitsu; Takada, Naoki; Niwase, Hiroaki; Ikawa, Shohei; Fujiwara, Masato; Nakayama, Hirotaka; Kakue, Takashi; Shimobaba, Tomoyoshi; Ito, Tomoyoshi

    2015-12-01

    We propose real-time time-division color electroholography using a single graphics processing unit (GPU) and a simple synchronization system of reference light. To facilitate real-time time-division color electroholography, we developed a light emitting diode (LED) controller with a universal serial bus (USB) module and the drive circuit for reference light. A one-chip RGB LED connected to a personal computer via an LED controller was used as the reference light. A single GPU calculates three computer-generated holograms (CGHs) suitable for red, green, and blue colors in each frame of a three-dimensional (3D) movie. After CGH calculation using a single GPU, the CPU can synchronize the CGH display with the color switching of the one-chip RGB LED via the LED controller. Consequently, we succeeded in real-time time-division color electroholography for a 3D object consisting of around 1000 points per color when an NVIDIA GeForce GTX TITAN was used as the GPU. Furthermore, we implemented the proposed method in various GPUs. The experimental results showed that the proposed method was effective for various GPUs.

  16. Correcting the effect of refraction and dispersion of light in FT-IR spectroscopic imaging in transmission through thick infrared windows.

    PubMed

    Chan, K L Andrew; Kazarian, Sergei G

    2013-01-15

    Transmission mode is one of the most common sampling methods for FT-IR spectroscopic imaging because the spectra obtained generally have a reasonable signal-to-noise ratio. However, dispersion and refraction of infrared light occurs when samples are sandwiched between infrared windows or placed underneath a layer of liquid. Dispersion and refraction cause infrared light to focus with different focal lengths depending on the wavelength (wavenumber) of the light. As a result, images obtained are in focus only at a particular wavenumber while they are defocused at other wavenumber values. In this work, a solution to correct this spread of focus by means of adding a lens on top of the infrared transparent window, such that a pseudo hemisphere is formed, has been investigated. Through this lens (or pseudo hemisphere), refraction of light is removed and the light across the spectral range has the same focal depth. Furthermore, the lens acts as a solid immersion objective and an increase of both magnification and spatial resolution (by 1.4 times) is demonstrated. The spatial resolution was investigated using an USAF resolution target, showing that the Rayleigh criterion can be achieved, as well as a sample with a sharp polymer interface to indicate the spatial resolution that can be expected in real samples. The reported approach was used to obtain chemical images of cross sections of cancer tissue and hair samples sandwiched between infrared windows showing the versatility and applicability of the method. In addition to the improved spatial resolution, the results reported herein also demonstrate that the lens can reduce the effect of scattering near the edges of tissue samples. The advantages of the presented approach, obtaining FT-IR spectroscopic images in transmission mode with the same focus across all wavenumber values and simultaneous improvement in spatial resolution, will have wide implications ranging from studies of live cells to sorption of drugs into tissues.

  17. Time-Accurate Local Time Stepping and High-Order Time CESE Methods for Multi-Dimensional Flows Using Unstructured Meshes

    NASA Technical Reports Server (NTRS)

    Chang, Chau-Lyan; Venkatachari, Balaji Shankar; Cheng, Gary

    2013-01-01

    With the wide availability of affordable multiple-core parallel supercomputers, next generation numerical simulations of flow physics are being focused on unsteady computations for problems involving multiple time scales and multiple physics. These simulations require higher solution accuracy than most algorithms and computational fluid dynamics codes currently available. This paper focuses on the developmental effort for high-fidelity multi-dimensional, unstructured-mesh flow solvers using the space-time conservation element, solution element (CESE) framework. Two approaches have been investigated in this research in order to provide high-accuracy, cross-cutting numerical simulations for a variety of flow regimes: 1) time-accurate local time stepping and 2) highorder CESE method. The first approach utilizes consistent numerical formulations in the space-time flux integration to preserve temporal conservation across the cells with different marching time steps. Such approach relieves the stringent time step constraint associated with the smallest time step in the computational domain while preserving temporal accuracy for all the cells. For flows involving multiple scales, both numerical accuracy and efficiency can be significantly enhanced. The second approach extends the current CESE solver to higher-order accuracy. Unlike other existing explicit high-order methods for unstructured meshes, the CESE framework maintains a CFL condition of one for arbitrarily high-order formulations while retaining the same compact stencil as its second-order counterpart. For large-scale unsteady computations, this feature substantially enhances numerical efficiency. Numerical formulations and validations using benchmark problems are discussed in this paper along with realistic examples.

  18. Detector to detector corrections: a comprehensive experimental study of detector specific correction factors for beam output measurements for small radiotherapy beams.

    PubMed

    Azangwe, Godfrey; Grochowska, Paulina; Georg, Dietmar; Izewska, Joanna; Hopfgartner, Johannes; Lechner, Wolfgang; Andersen, Claus E; Beierholm, Anders R; Helt-Hansen, Jakob; Mizuno, Hideyuki; Fukumura, Akifumi; Yajima, Kaori; Gouldstone, Clare; Sharpe, Peter; Meghzifene, Ahmed; Palmans, Hugo

    2014-07-01

    The aim of the present study is to provide a comprehensive set of detector specific correction factors for beam output measurements for small beams, for a wide range of real time and passive detectors. The detector specific correction factors determined in this study may be potentially useful as a reference data set for small beam dosimetry measurements. Dose response of passive and real time detectors was investigated for small field sizes shaped with a micromultileaf collimator ranging from 0.6 × 0.6 cm(2) to 4.2 × 4.2 cm(2) and the measurements were extended to larger fields of up to 10 × 10 cm(2). Measurements were performed at 5 cm depth, in a 6 MV photon beam. Detectors used included alanine, thermoluminescent dosimeters (TLDs), stereotactic diode, electron diode, photon diode, radiophotoluminescent dosimeters (RPLDs), radioluminescence detector based on carbon-doped aluminium oxide (Al2O3:C), organic plastic scintillators, diamond detectors, liquid filled ion chamber, and a range of small volume air filled ionization chambers (volumes ranging from 0.002 cm(3) to 0.3 cm(3)). All detector measurements were corrected for volume averaging effect and compared with dose ratios determined from alanine to derive a detector correction factors that account for beam perturbation related to nonwater equivalence of the detector materials. For the detectors used in this study, volume averaging corrections ranged from unity for the smallest detectors such as the diodes, 1.148 for the 0.14 cm(3) air filled ionization chamber and were as high as 1.924 for the 0.3 cm(3) ionization chamber. After applying volume averaging corrections, the detector readings were consistent among themselves and with alanine measurements for several small detectors but they differed for larger detectors, in particular for some small ionization chambers with volumes larger than 0.1 cm(3). The results demonstrate how important it is for the appropriate corrections to be applied to give

  19. The time course of phase correction: A kinematic investigation of motor adjustment to timing perturbations during sensorimotor synchronization

    PubMed Central

    Hove, Michael J.; Balasubramaniam, Ramesh; Keller, Peter E.

    2014-01-01

    Synchronizing movements with a beat requires rapid compensation for timing errors. The phase-correction response (PCR) has been studied extensively in finger tapping by shifting a metronome onset and measuring the adjustment of the following tap time. How the response unfolds during the subsequent tap cycle remains unknown. Using motion capture, we examined finger kinematics during the PCR. Participants tapped with a metronome containing phase perturbations. They tapped in ‘legato’ and ‘staccato’ style at various tempi, which altered the timing of the constituent movement stages (dwell at the surface, extension, flexion). After a phase perturbation, tapping kinematics changed compared to baseline, and the PCR was distributed differently across movement stages. In staccato tapping, the PCR trajectory changed primarily during finger extension across tempi. In legato tapping, at fast tempi the PCR occurred primarily during extension, whereas at slow tempi most phase correction was already completed during dwell. Across conditions, timing adjustments occurred primarily 100-250 ms into the following tap cycle. The change in movement around 100 ms represents the time to integrate information into an already planned movement and the rapidity suggests a subcortical route. PMID:25151103

  20. 76 FR 47529 - Customer Clearing Documentation and Timing of Acceptance for Clearing; Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-05

    ... COMMODITY FUTURES TRADING COMMISSION 17 CFR Parts 1, 23, and 39 RIN 3038-AD51 Customer Clearing Documentation and Timing of Acceptance for Clearing; Correction AGENCY: Commodity Futures Trading Commission... published in the Federal Register of August 1, 2011, regarding Customer Clearing Documentation and Timing of...

  1. Accurate relative location estimates for the North Korean nuclear tests using empirical slowness corrections

    NASA Astrophysics Data System (ADS)

    Gibbons, S. J.; Pabian, F.; Näsholm, S. P.; Kværna, T.; Mykkeltveit, S.

    2017-01-01

    Declared North Korean nuclear tests in 2006, 2009, 2013 and 2016 were observed seismically at regional and teleseismic distances. Waveform similarity allows the events to be located relatively with far greater accuracy than the absolute locations can be determined from seismic data alone. There is now significant redundancy in the data given the large number of regional and teleseismic stations that have recorded multiple events, and relative location estimates can be confirmed independently by performing calculations on many mutually exclusive sets of measurements. Using a 1-D global velocity model, the distances between the events estimated using teleseismic P phases are found to be approximately 25 per cent shorter than the distances between events estimated using regional Pn phases. The 2009, 2013 and 2016 events all take place within 1 km of each other and the discrepancy between the regional and teleseismic relative location estimates is no more than about 150 m. The discrepancy is much more significant when estimating the location of the more distant 2006 event relative to the later explosions with regional and teleseismic estimates varying by many hundreds of metres. The relative location of the 2006 event is challenging given the smaller number of observing stations, the lower signal-to-noise ratio and significant waveform dissimilarity at some regional stations. The 2006 event is however highly significant in constraining the absolute locations in the terrain at the Punggye-ri test-site in relation to observed surface infrastructure. For each seismic arrival used to estimate the relative locations, we define a slowness scaling factor which multiplies the gradient of seismic traveltime versus distance, evaluated at the source, relative to the applied 1-D velocity model. A procedure for estimating correction terms which reduce the double-difference time residual vector norms is presented together with a discussion of the associated uncertainty. The modified

  2. Apparent resistivity for transient electromagnetic induction logging and its correction in radial layer identification

    NASA Astrophysics Data System (ADS)

    Meng, Qingxin; Hu, Xiangyun; Pan, Heping; Xi, Yufei

    2018-04-01

    We propose an algorithm for calculating all-time apparent resistivity from transient electromagnetic induction logging. The algorithm is based on the whole-space transient electric field expression of the uniform model and Halley's optimisation. In trial calculations for uniform models, the all-time algorithm is shown to have high accuracy. We use the finite-difference time-domain method to simulate the transient electromagnetic field in radial two-layer models without wall rock and convert the simulation results to apparent resistivity using the all-time algorithm. The time-varying apparent resistivity reflects the radially layered geoelectrical structure of the models and the apparent resistivity of the earliest time channel follows the true resistivity of the inner layer; however, the apparent resistivity at larger times reflects the comprehensive electrical characteristics of the inner and outer layers. To accurately identify the outer layer resistivity based on the series relationship model of the layered resistance, the apparent resistivity and diffusion depth of the different time channels are approximately replaced by related model parameters; that is, we propose an apparent resistivity correction algorithm. By correcting the time-varying apparent resistivity of radial two-layer models, we show that the correction results reflect the radially layered electrical structure and the corrected resistivities of the larger time channels follow the outer layer resistivity. The transient electromagnetic fields of radially layered models with wall rock are simulated to obtain the 2D time-varying profiles of the apparent resistivity and corrections. The results suggest that the time-varying apparent resistivity and correction results reflect the vertical and radial geoelectrical structures. For models with small wall-rock effect, the correction removes the effect of the low-resistance inner layer on the apparent resistivity of the larger time channels.

  3. Highly accurate nephelometric titrimetry.

    PubMed

    Zhan, Xiancheng; Li, Chengrong; Li, Zhiyi; Yang, Xiucen; Zhong, Shuguang; Yi, Tao

    2004-02-01

    A method that accurately indicates the end-point of precipitation reactions by the measurement of the relative intensity of the scattered light in the titrate is presented. A new nephelometric titrator with an internal nephelometric sensor has been devised. The work of the titrator including the sensor and change in the turbidity of the titrate and intensity of the scattered light are described. The accuracy of the nephelometric titrimetry is discussed theoretically. The titration of NaCl with AgNO(3) serves as a model. A relative error as well as deviation is within 0.2% under the experimental conditions. The applicability of the titrimetry in pharmaceutical analyses, for example, phenytoin sodium and procaine hydrochloride, is generally illustrated. Copyright 2004 Wiley-Liss, Inc. and the American Pharmacists Association

  4. Accurate estimation of influenza epidemics using Google search data via ARGO

    PubMed Central

    Yang, Shihao; Santillana, Mauricio; Kou, S. C.

    2015-01-01

    Accurate real-time tracking of influenza outbreaks helps public health officials make timely and meaningful decisions that could save lives. We propose an influenza tracking model, ARGO (AutoRegression with GOogle search data), that uses publicly available online search data. In addition to having a rigorous statistical foundation, ARGO outperforms all previously available Google-search–based tracking models, including the latest version of Google Flu Trends, even though it uses only low-quality search data as input from publicly available Google Trends and Google Correlate websites. ARGO not only incorporates the seasonality in influenza epidemics but also captures changes in people’s online search behavior over time. ARGO is also flexible, self-correcting, robust, and scalable, making it a potentially powerful tool that can be used for real-time tracking of other social events at multiple temporal and spatial resolutions. PMID:26553980

  5. Accurate estimation of influenza epidemics using Google search data via ARGO.

    PubMed

    Yang, Shihao; Santillana, Mauricio; Kou, S C

    2015-11-24

    Accurate real-time tracking of influenza outbreaks helps public health officials make timely and meaningful decisions that could save lives. We propose an influenza tracking model, ARGO (AutoRegression with GOogle search data), that uses publicly available online search data. In addition to having a rigorous statistical foundation, ARGO outperforms all previously available Google-search-based tracking models, including the latest version of Google Flu Trends, even though it uses only low-quality search data as input from publicly available Google Trends and Google Correlate websites. ARGO not only incorporates the seasonality in influenza epidemics but also captures changes in people's online search behavior over time. ARGO is also flexible, self-correcting, robust, and scalable, making it a potentially powerful tool that can be used for real-time tracking of other social events at multiple temporal and spatial resolutions.

  6. Atmospheric correction for inland water based on Gordon model

    NASA Astrophysics Data System (ADS)

    Li, Yunmei; Wang, Haijun; Huang, Jiazhu

    2008-04-01

    Remote sensing technique is soundly used in water quality monitoring since it can receive area radiation information at the same time. But more than 80% radiance detected by sensors at the top of the atmosphere is contributed by atmosphere not directly by water body. Water radiance information is seriously confused by atmospheric molecular and aerosol scattering and absorption. A slight bias of evaluation for atmospheric influence can deduce large error for water quality evaluation. To inverse water composition accurately we have to separate water and air information firstly. In this paper, we studied on atmospheric correction methods for inland water such as Taihu Lake. Landsat-5 TM image was corrected based on Gordon atmospheric correction model. And two kinds of data were used to calculate Raleigh scattering, aerosol scattering and radiative transmission above Taihu Lake. Meanwhile, the influence of ozone and white cap were revised. One kind of data was synchronization meteorology data, and the other one was synchronization MODIS image. At last, remote sensing reflectance was retrieved from the TM image. The effect of different methods was analyzed using in situ measured water surface spectra. The result indicates that measured and estimated remote sensing reflectance were close for both methods. Compared to the method of using MODIS image, the method of using synchronization meteorology is more accurate. And the bias is close to inland water error criterion accepted by water quality inversing. It shows that this method is suitable for Taihu Lake atmospheric correction for TM image.

  7. [Corrected transposition of the great arteries].

    PubMed

    Alva-Espinosa, Carlos

    2016-01-01

    Corrected transposition of the great arteries is one of the most fascinating entities in congenital heart disease. The apparent corrected condition is only temporal. Over time, most patients develop systemic heart failure, even in the absence of associated lesions. With current imaging studies, precise visualization is achieved in each case though the treatment strategy remains unresolved. In asymptomatic patients or cases without associated lesions, focalized follow-up to assess systemic ventricular function and the degree of tricuspid valve regurgitation is important. In cases with normal ventricular function and mild tricuspid failure, it seems unreasonable to intervene surgically. In patients with significant associated lesions, surgery is indicated. In the long term, the traditional approach may not help tricuspid regurgitation and systemic ventricular failure. Anatomical correction is the proposed alternative to ease the right ventricle overload and to restore the systemic left ventricular function. However, this is a prolonged operation and not without risks and long-term complications. In this review the clinical, diagnostic, and therapeutic aspects are overviewed in the light of the most significant and recent literature.

  8. Microlensing results toward the galactic bulge, theory of fitting blended light curves, and discussion of weak lensing corrections

    NASA Astrophysics Data System (ADS)

    Thomas, Christian L.

    2006-06-01

    Analysis and results (Chapters 2-5) of the full 7 year Macho Project dataset toward the Galactic bulge are presented. A total of 450 high quality, relatively large signal-to-noise ratio, events are found, including several events exhibiting exotic effects, and lensing events on possible Sagittarius dwarf galaxy stars. We examine the problem of blending in our sample and conclude that the subset of red clump giants are minimally blended. Using 42 red clump giant events near the Galactic center we calculate the optical depth toward the Galactic bulge to be t = [Special characters omitted.] × 10 -6 at ( l, b ) = ([Special characters omitted.] ) with a gradient of (1.06 ± 0.71) × 10 -6 deg -1 in latitude, and (0.29±0.43) × 10 -6 deg -1 in longitude, bringing measurements into consistency with the models for the first time. In Chapter 6 we reexamine the usefulness of fitting blended light-curve models to microlensing photometric data. We find agreement with previous workers (e.g. Wozniak & Paczynski) that this is a difficult proposition because of the degeneracy of blend fraction with other fit parameters. We show that follow-up observations at specific points along the light curve (peak region and wings) of high magnification events are the most helpful in removing degeneracies. We also show that very small errors in the baseline magnitude can result in problems in measuring the blend fraction, and study the importance of non- Gaussian errors in the fit results. The biases and skewness in the distribution of the recovered blend fraction is discussed. We also find a new approximation formula relating the blend fraction and the unblended fit parameters to the underlying event duration needed to estimate microlensing optical depth. In Chapter 7 we present work-in-progress on the possibility of correcting standard candle luminosities for the magnification due to weak lensing. We consider the importance of lenses in different mass ranges and look at the contribution

  9. Radiological reporting that combine continuous speech recognition with error correction by transcriptionists.

    PubMed

    Ichikawa, Tamaki; Kitanosono, Takashi; Koizumi, Jun; Ogushi, Yoichi; Tanaka, Osamu; Endo, Jun; Hashimoto, Takeshi; Kawada, Shuichi; Saito, Midori; Kobayashi, Makiko; Imai, Yutaka

    2007-12-20

    We evaluated the usefulness of radiological reporting that combines continuous speech recognition (CSR) and error correction by transcriptionists. Four transcriptionists (two with more than 10 years' and two with less than 3 months' transcription experience) listened to the same 100 dictation files and created radiological reports using conventional transcription and a method that combined CSR with manual error correction by the transcriptionists. We compared the 2 groups using the 2 methods for accuracy and report creation time and evaluated the transcriptionists' inter-personal dependence on accuracy rate and report creation time. We used a CSR system that did not require the training of the system to recognize the user's voice. We observed no significant difference in accuracy between the 2 groups and 2 methods that we tested, though transcriptionists with greater experience transcribed faster than those with less experience using conventional transcription. Using the combined method, error correction speed was not significantly different between two groups of transcriptionists with different levels of experience. Combining CSR and manual error correction by transcriptionists enabled convenient and accurate radiological reporting.

  10. Real-time look-up table-based color correction for still image stabilization of digital cameras without using frame memory

    NASA Astrophysics Data System (ADS)

    Luo, Lin-Bo; An, Sang-Woo; Wang, Chang-Shuai; Li, Ying-Chun; Chong, Jong-Wha

    2012-09-01

    Digital cameras usually decrease exposure time to capture motion-blur-free images. However, this operation will generate an under-exposed image with a low-budget complementary metal-oxide semiconductor image sensor (CIS). Conventional color correction algorithms can efficiently correct under-exposed images; however, they are generally not performed in real time and need at least one frame memory if they are implemented by hardware. The authors propose a real-time look-up table-based color correction method that corrects under-exposed images with hardware without using frame memory. The method utilizes histogram matching of two preview images, which are exposed for a long and short time, respectively, to construct an improved look-up table (ILUT) and then corrects the captured under-exposed image in real time. Because the ILUT is calculated in real time before processing the captured image, this method does not require frame memory to buffer image data, and therefore can greatly save the cost of CIS. This method not only supports single image capture, but also bracketing to capture three images at a time. The proposed method was implemented by hardware description language and verified by a field-programmable gate array with a 5 M CIS. Simulations show that the system can perform in real time with a low cost and can correct the color of under-exposed images well.

  11. Time Accurate Unsteady Pressure Loads Simulated for the Space Launch System at a Wind Tunnel Condition

    NASA Technical Reports Server (NTRS)

    Alter, Stephen J.; Brauckmann, Gregory J.; Kleb, Bil; Streett, Craig L; Glass, Christopher E.; Schuster, David M.

    2015-01-01

    Using the Fully Unstructured Three-Dimensional (FUN3D) computational fluid dynamics code, an unsteady, time-accurate flow field about a Space Launch System configuration was simulated at a transonic wind tunnel condition (Mach = 0.9). Delayed detached eddy simulation combined with Reynolds Averaged Naiver-Stokes and a Spallart-Almaras turbulence model were employed for the simulation. Second order accurate time evolution scheme was used to simulate the flow field, with a minimum of 0.2 seconds of simulated time to as much as 1.4 seconds. Data was collected at 480 pressure taps at locations, 139 of which matched a 3% wind tunnel model, tested in the Transonic Dynamic Tunnel (TDT) facility at NASA Langley Research Center. Comparisons between computation and experiment showed agreement within 5% in terms of location for peak RMS levels, and 20% for frequency and magnitude of power spectral densities. Grid resolution and time step sensitivity studies were performed to identify methods for improved accuracy comparisons to wind tunnel data. With limited computational resources, accurate trends for reduced vibratory loads on the vehicle were observed. Exploratory methods such as determining minimized computed errors based on CFL number and sub-iterations, as well as evaluating frequency content of the unsteady pressures and evaluation of oscillatory shock structures were used in this study to enhance computational efficiency and solution accuracy. These techniques enabled development of a set of best practices, for the evaluation of future flight vehicle designs in terms of vibratory loads.

  12. How flatbed scanners upset accurate film dosimetry

    NASA Astrophysics Data System (ADS)

    van Battum, L. J.; Huizenga, H.; Verdaasdonk, R. M.; Heukelom, S.

    2016-01-01

    Film is an excellent dosimeter for verification of dose distributions due to its high spatial resolution. Irradiated film can be digitized with low-cost, transmission, flatbed scanners. However, a disadvantage is their lateral scan effect (LSE): a scanner readout change over its lateral scan axis. Although anisotropic light scattering was presented as the origin of the LSE, this paper presents an alternative cause. Hereto, LSE for two flatbed scanners (Epson 1680 Expression Pro and Epson 10000XL), and Gafchromic film (EBT, EBT2, EBT3) was investigated, focused on three effects: cross talk, optical path length and polarization. Cross talk was examined using triangular sheets of various optical densities. The optical path length effect was studied using absorptive and reflective neutral density filters with well-defined optical characteristics (OD range 0.2-2.0). Linear polarizer sheets were used to investigate light polarization on the CCD signal in absence and presence of (un)irradiated Gafchromic film. Film dose values ranged between 0.2 to 9 Gy, i.e. an optical density range between 0.25 to 1.1. Measurements were performed in the scanner’s transmission mode, with red-green-blue channels. LSE was found to depend on scanner construction and film type. Its magnitude depends on dose: for 9 Gy increasing up to 14% at maximum lateral position. Cross talk was only significant in high contrast regions, up to 2% for very small fields. The optical path length effect introduced by film on the scanner causes 3% for pixels in the extreme lateral position. Light polarization due to film and the scanner’s optical mirror system is the main contributor, different in magnitude for the red, green and blue channel. We concluded that any Gafchromic EBT type film scanned with a flatbed scanner will face these optical effects. Accurate dosimetry requires correction of LSE, therefore, determination of the LSE per color channel and dose delivered to the film.

  13. Time-Accurate Simulations and Acoustic Analysis of Slat Free-Shear Layer

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Singer, Bart A.; Berkman, Mert E.

    2001-01-01

    A detailed computational aeroacoustic analysis of a high-lift flow field is performed. Time-accurate Reynolds Averaged Navier-Stokes (RANS) computations simulate the free shear layer that originates from the slat cusp. Both unforced and forced cases are studied. Preliminary results show that the shear layer is a good amplifier of disturbances in the low to mid-frequency range. The Ffowcs-Williams and Hawkings equation is solved to determine the acoustic field using the unsteady flow data from the RANS calculations. The noise radiated from the excited shear layer has a spectral shape qualitatively similar to that obtained from measurements in a corresponding experimental study of the high-lift system.

  14. A time-accurate high-resolution TVD scheme for solving the Navier-Stokes equations

    NASA Technical Reports Server (NTRS)

    Kim, Hyun Dae; Liu, Nan-Suey

    1992-01-01

    A total variation diminishing (TVD) scheme has been developed and incorporated into an existing time-accurate high-resolution Navier-Stokes code. The accuracy and the robustness of the resulting solution procedure have been assessed by performing many calculations in four different areas: shock tube flows, regular shock reflection, supersonic boundary layer, and shock boundary layer interactions. These numerical results compare well with corresponding exact solutions or experimental data.

  15. In vivo white light and contrast-enhanced vital-dye fluorescence imaging of Barrett's-related neoplasia in a single-endoscopic insertion

    NASA Astrophysics Data System (ADS)

    Tang, Yubo; Carns, Jennifer; Polydorides, Alexandros D.; Anandasabapathy, Sharmila; Richards-Kortum, Rebecca R.

    2016-08-01

    A modular video endoscope is developed to enable both white light imaging (WLI) and vital-dye fluorescence imaging (VFI) in a single-endoscopic insertion for the early detection of cancer in Barrett's esophagus (BE). We demonstrate that VFI can be achieved in conjunction with white light endoscopy, where appropriate white balance is used to correct for the presence of the emission filter. In VFI mode, a contrast enhancement feature is implemented in real time to further highlight glandular patterns in BE and related malignancies without introducing artifacts. In a pilot study, we demonstrate accurate correlation of images in two widefield modalities, with representative images showing the disruption and effacement of glandular architecture associated with cancer development in BE. VFI images of these alterations exhibit enhanced contrast when compared to WLI. Results suggest that the usefulness of VFI in the detection of BE-related neoplasia should be further evaluated in future in vivo studies.

  16. 76 FR 2573 - Technical Corrections: Matters Subject to Protest and Various Protest Time Limits

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-14

    ... 174 [CBP Dec. 11-02] Technical Corrections: Matters Subject to Protest and Various Protest Time Limits..., in pertinent part, the types of matters subject to protest, the time required for allowing or denying an application for further review of a protest, and various other protest time limits. This document...

  17. Time to Reframe Politics and Practices in Correctional Education

    ERIC Educational Resources Information Center

    LoBuglio, Stefan

    2001-01-01

    In this chapter, Stefan LoBuglio discusses the politics and practices of educational programs for adults in correctional facilities. To begin, LoBuglio provides an overview of the field of corrections, including various types of facilities and correctional programs, as well as demographic and educational data on the U.S. incarcerated population…

  18. Krylov Deferred Correction Accelerated Method of Lines Transpose for Parabolic Problems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jia, Jun; Jingfang, Huang

    2008-01-01

    In this paper, a new class of numerical methods for the accurate and efficient solutions of parabolic partial differential equations is presented. Unlike traditional method of lines (MoL), the new {\\bf \\it Krylov deferred correction (KDC) accelerated method of lines transpose (MoL^T)} first discretizes the temporal direction using Gaussian type nodes and spectral integration, and symbolically applies low-order time marching schemes to form a preconditioned elliptic system, which is then solved iteratively using Newton-Krylov techniques such as Newton-GMRES or Newton-BiCGStab method. Each function evaluation in the Newton-Krylov method is simply one low-order time-stepping approximation of the error by solving amore » decoupled system using available fast elliptic equation solvers. Preliminary numerical experiments show that the KDC accelerated MoL^T technique is unconditionally stable, can be spectrally accurate in both temporal and spatial directions, and allows optimal time-step sizes in long-time simulations.« less

  19. PFP Emergency Lighting Study

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    BUSCH, M.S.

    2000-02-02

    NFPA 101, section 5-9 mandates that, where required by building classification, all designated emergency egress routes be provided with adequate emergency lighting in the event of a normal lighting outage. Emergency lighting is to be arranged so that egress routes are illuminated to an average of 1.0 footcandle with a minimum at any point of 0.1 footcandle, as measured at floor level. These levels are permitted to drop to 60% of their original value over the required 90 minute emergency lighting duration after a power outage. The Plutonium Finishing Plant (PFP) has two designations for battery powered egress lights ''Emergencymore » Lights'' are those battery powered lights required by NFPA 101 to provide lighting along officially designated egress routes in those buildings meeting the correct occupancy requirements. Emergency Lights are maintained on a monthly basis by procedure ZSR-12N-001. ''Backup Lights'' are battery powered lights not required by NFPA, but installed in areas where additional light may be needed. The Backup Light locations were identified by PFP Safety and Engineering based on several factors. (1) General occupancy and type of work in the area. Areas occupied briefly during a shiftly surveillance do not require backup lighting while a room occupied fairly frequently or for significant lengths of time will need one or two Backup lights to provide general illumination of the egress points. (2) Complexity of the egress routes. Office spaces with a standard hallway/room configuration will not require Backup Lights while a large room with several subdivisions or irregularly placed rooms, doors, and equipment will require Backup Lights to make egress safer. (3) Reasonable balance between the safety benefits of additional lighting and the man-hours/exposure required for periodic light maintenance. In some plant areas such as building 236-Z, the additional maintenance time and risk of contamination do not warrant having Backup Lights installed in

  20. Accurate Critical Stress Intensity Factor Griffith Crack Theory Measurements by Numerical Techniques

    PubMed Central

    Petersen, Richard C.

    2014-01-01

    Critical stress intensity factor (KIc) has been an approximation for fracture toughness using only load-cell measurements. However, artificial man-made cracks several orders of magnitude longer and wider than natural flaws have required a correction factor term (Y) that can be up to about 3 times the recorded experimental value [1-3]. In fact, over 30 years ago a National Academy of Sciences advisory board stated that empirical KIc testing was of serious concern and further requested that an accurate bulk fracture toughness method be found [4]. Now that fracture toughness can be calculated accurately by numerical integration from the load/deflection curve as resilience, work of fracture (WOF) and strain energy release (SIc) [5, 6], KIc appears to be unnecessary. However, the large body of previous KIc experimental test results found in the literature offer the opportunity for continued meta analysis with other more practical and accurate fracture toughness results using energy methods and numerical integration. Therefore, KIc is derived from the classical Griffith Crack Theory [6] to include SIc as a more accurate term for strain energy release rate (𝒢Ic), along with crack surface energy (γ), crack length (a), modulus (E), applied stress (σ), Y, crack-tip plastic zone defect region (rp) and yield strength (σys) that can all be determined from load and deflection data. Polymer matrix discontinuous quartz fiber-reinforced composites to accentuate toughness differences were prepared for flexural mechanical testing comprising of 3 mm fibers at different volume percentages from 0-54.0 vol% and at 28.2 vol% with different fiber lengths from 0.0-6.0 mm. Results provided a new correction factor and regression analyses between several numerical integration fracture toughness test methods to support KIc results. Further, bulk KIc accurate experimental values are compared with empirical test results found in literature. Also, several fracture toughness mechanisms

  1. ETHNOPRED: a novel machine learning method for accurate continental and sub-continental ancestry identification and population stratification correction

    PubMed Central

    2013-01-01

    Background Population stratification is a systematic difference in allele frequencies between subpopulations. This can lead to spurious association findings in the case–control genome wide association studies (GWASs) used to identify single nucleotide polymorphisms (SNPs) associated with disease-linked phenotypes. Methods such as self-declared ancestry, ancestry informative markers, genomic control, structured association, and principal component analysis are used to assess and correct population stratification but each has limitations. We provide an alternative technique to address population stratification. Results We propose a novel machine learning method, ETHNOPRED, which uses the genotype and ethnicity data from the HapMap project to learn ensembles of disjoint decision trees, capable of accurately predicting an individual’s continental and sub-continental ancestry. To predict an individual’s continental ancestry, ETHNOPRED produced an ensemble of 3 decision trees involving a total of 10 SNPs, with 10-fold cross validation accuracy of 100% using HapMap II dataset. We extended this model to involve 29 disjoint decision trees over 149 SNPs, and showed that this ensemble has an accuracy of ≥ 99.9%, even if some of those 149 SNP values were missing. On an independent dataset, predominantly of Caucasian origin, our continental classifier showed 96.8% accuracy and improved genomic control’s λ from 1.22 to 1.11. We next used the HapMap III dataset to learn classifiers to distinguish European subpopulations (North-Western vs. Southern), East Asian subpopulations (Chinese vs. Japanese), African subpopulations (Eastern vs. Western), North American subpopulations (European vs. Chinese vs. African vs. Mexican vs. Indian), and Kenyan subpopulations (Luhya vs. Maasai). In these cases, ETHNOPRED produced ensembles of 3, 39, 21, 11, and 25 disjoint decision trees, respectively involving 31, 502, 526, 242 and 271 SNPs, with 10-fold cross validation accuracy of

  2. ETHNOPRED: a novel machine learning method for accurate continental and sub-continental ancestry identification and population stratification correction.

    PubMed

    Hajiloo, Mohsen; Sapkota, Yadav; Mackey, John R; Robson, Paula; Greiner, Russell; Damaraju, Sambasivarao

    2013-02-22

    Population stratification is a systematic difference in allele frequencies between subpopulations. This can lead to spurious association findings in the case-control genome wide association studies (GWASs) used to identify single nucleotide polymorphisms (SNPs) associated with disease-linked phenotypes. Methods such as self-declared ancestry, ancestry informative markers, genomic control, structured association, and principal component analysis are used to assess and correct population stratification but each has limitations. We provide an alternative technique to address population stratification. We propose a novel machine learning method, ETHNOPRED, which uses the genotype and ethnicity data from the HapMap project to learn ensembles of disjoint decision trees, capable of accurately predicting an individual's continental and sub-continental ancestry. To predict an individual's continental ancestry, ETHNOPRED produced an ensemble of 3 decision trees involving a total of 10 SNPs, with 10-fold cross validation accuracy of 100% using HapMap II dataset. We extended this model to involve 29 disjoint decision trees over 149 SNPs, and showed that this ensemble has an accuracy of ≥ 99.9%, even if some of those 149 SNP values were missing. On an independent dataset, predominantly of Caucasian origin, our continental classifier showed 96.8% accuracy and improved genomic control's λ from 1.22 to 1.11. We next used the HapMap III dataset to learn classifiers to distinguish European subpopulations (North-Western vs. Southern), East Asian subpopulations (Chinese vs. Japanese), African subpopulations (Eastern vs. Western), North American subpopulations (European vs. Chinese vs. African vs. Mexican vs. Indian), and Kenyan subpopulations (Luhya vs. Maasai). In these cases, ETHNOPRED produced ensembles of 3, 39, 21, 11, and 25 disjoint decision trees, respectively involving 31, 502, 526, 242 and 271 SNPs, with 10-fold cross validation accuracy of 86.5% ± 2.4%, 95.6% ± 3

  3. Real-Time and Accurate Identification of Single Oligonucleotide Photoisomers via an Aerolysin Nanopore.

    PubMed

    Hu, Zheng-Li; Li, Zi-Yuan; Ying, Yi-Lun; Zhang, Junji; Cao, Chan; Long, Yi-Tao; Tian, He

    2018-04-03

    Identification of the configuration for the photoresponsive oligonucleotide plays an important role in the ingenious design of DNA nanomolecules and nanodevices. Due to the limited resolution and sensitivity of present methods, it remains a challenge to determine the accurate configuration of photoresponsive oligonucleotides, much less a precise description of their photoconversion process. Here, we used an aerolysin (AeL) nanopore-based confined space for real-time determination and quantification of the absolute cis/ trans configuration of each azobenzene-modified oligonucleotide (Azo-ODN) with a single molecule resolution. The two completely separated current distributions with narrow peak widths at half height (<0.62 pA) are assigned to cis/ trans-Azo-ODN isomers, respectively. Due to the high current sensitivity, each isomer of Azo-ODN could be undoubtedly identified, which gives the accurate photostationary conversion values of 82.7% for trans-to- cis under UV irradiation and 82.5% for cis-to- trans under vis irradiation. Further real-time kinetic evaluation reveals that the photoresponsive rate constants of Azo-ODN from trans-to- cis and cis-to -trans are 0.43 and 0.20 min -1 , respectively. This study will promote the sophisticated design of photoresponsive ODN to achieve an efficient and applicable photocontrollable process.

  4. General Relativistic Theory of the VLBI Time Delay in the Gravitational Field of Moving Bodies

    NASA Technical Reports Server (NTRS)

    Kopeikin, Sergei

    2003-01-01

    The general relativistic theory of the gravitational VLBI experiment conducted on September 8, 2002 by Fomalont and Kopeikin is explained. Equations of radio waves (light) propagating from the quasar to the observer are integrated in the time-dependent gravitational field of the solar system by making use of either retarded or advanced solutions of the Einstein field equations. This mathematical technique separates explicitly the effects associated with the propagation of gravity from those associated with light in the integral expression for the relativistic VLBI time delay of light. We prove that the relativistic correction to the Shapiro time delay, discovered by Kopeikin (ApJ, 556, L1, 2001), changes sign if one retains direction of the light propagation but replaces the retarded for the advanced solution of the Einstein equations. Hence, this correction is associated with the propagation of gravity. The VLBI observation measured its speed, and that the retarded solution is the correct one.

  5. Focusing of light energy inside a scattering medium by controlling the time-gated multiple light scattering

    NASA Astrophysics Data System (ADS)

    Jeong, Seungwon; Lee, Ye-Ryoung; Choi, Wonjun; Kang, Sungsam; Hong, Jin Hee; Park, Jin-Sung; Lim, Yong-Sik; Park, Hong-Gyu; Choi, Wonshik

    2018-05-01

    The efficient delivery of light energy is a prerequisite for the non-invasive imaging and stimulating of target objects embedded deep within a scattering medium. However, the injected waves experience random diffusion by multiple light scattering, and only a small fraction reaches the target object. Here, we present a method to counteract wave diffusion and to focus multiple-scattered waves at the deeply embedded target. To realize this, we experimentally inject light into the reflection eigenchannels of a specific flight time to preferably enhance the intensity of those multiple-scattered waves that have interacted with the target object. For targets that are too deep to be visible by optical imaging, we demonstrate a more than tenfold enhancement in light energy delivery in comparison with ordinary wave diffusion cases. This work will lay a foundation to enhance the working depth of imaging, sensing and light stimulation.

  6. Effect of Age and Glaucoma on the Detection of Darks and Lights

    PubMed Central

    Zhao, Linxi; Sendek, Caroline; Davoodnia, Vandad; Lashgari, Reza; Dul, Mitchell W.; Zaidi, Qasim; Alonso, Jose-Manuel

    2015-01-01

    Purpose We have shown previously that normal observers detect dark targets faster and more accurately than light targets, when presented in noisy backgrounds. We investigated how these differences in detection time and accuracy are affected by age and ganglion cell pathology associated with glaucoma. Methods We asked 21 glaucoma patients, 21 age-similar controls, and 5 young control observers to report as fast as possible the number of 1 to 3 light or dark targets. The targets were positioned at random in a binary noise background, within the central 30° of the visual field. Results We replicate previous findings that darks are detected faster and more accurately than lights. We extend these findings by demonstrating that differences in detection of darks and lights are found reliably across different ages and in observers with glaucoma. We show that differences in detection time increase at a rate of approximately 55 msec/dB at early stages of glaucoma and then remain constant at later stages at approximately 800 msec. In normal subjects, differences in detection time increase with age at a rate of approximately 8 msec/y. We also demonstrate that the accuracy to detect lights and darks is significantly correlated with the severity of glaucoma and that the mean detection time is significantly longer for subjects with glaucoma than age-similar controls. Conclusions We conclude that differences in detection of darks and lights can be demonstrated over a wide range of ages, and asymmetries in dark/light detection increase with age and early stages of glaucoma. PMID:26513506

  7. Effect of Age and Glaucoma on the Detection of Darks and Lights.

    PubMed

    Zhao, Linxi; Sendek, Caroline; Davoodnia, Vandad; Lashgari, Reza; Dul, Mitchell W; Zaidi, Qasim; Alonso, Jose-Manuel

    2015-10-01

    We have shown previously that normal observers detect dark targets faster and more accurately than light targets, when presented in noisy backgrounds. We investigated how these differences in detection time and accuracy are affected by age and ganglion cell pathology associated with glaucoma. We asked 21 glaucoma patients, 21 age-similar controls, and 5 young control observers to report as fast as possible the number of 1 to 3 light or dark targets. The targets were positioned at random in a binary noise background, within the central 30° of the visual field. We replicate previous findings that darks are detected faster and more accurately than lights. We extend these findings by demonstrating that differences in detection of darks and lights are found reliably across different ages and in observers with glaucoma. We show that differences in detection time increase at a rate of approximately 55 msec/dB at early stages of glaucoma and then remain constant at later stages at approximately 800 msec. In normal subjects, differences in detection time increase with age at a rate of approximately 8 msec/y. We also demonstrate that the accuracy to detect lights and darks is significantly correlated with the severity of glaucoma and that the mean detection time is significantly longer for subjects with glaucoma than age-similar controls. We conclude that differences in detection of darks and lights can be demonstrated over a wide range of ages, and asymmetries in dark/light detection increase with age and early stages of glaucoma.

  8. qF-SSOP: real-time optical property corrected fluorescence imaging

    PubMed Central

    Valdes, Pablo A.; Angelo, Joseph P.; Choi, Hak Soo; Gioux, Sylvain

    2017-01-01

    Fluorescence imaging is well suited to provide image guidance during resections in oncologic and vascular surgery. However, the distorting effects of tissue optical properties on the emitted fluorescence are poorly compensated for on even the most advanced fluorescence image guidance systems, leading to subjective and inaccurate estimates of tissue fluorophore concentrations. Here we present a novel fluorescence imaging technique that performs real-time (i.e., video rate) optical property corrected fluorescence imaging. We perform full field of view simultaneous imaging of tissue optical properties using Single Snapshot of Optical Properties (SSOP) and fluorescence detection. The estimated optical properties are used to correct the emitted fluorescence with a quantitative fluorescence model to provide quantitative fluorescence-Single Snapshot of Optical Properties (qF-SSOP) images with less than 5% error. The technique is rigorous, fast, and quantitative, enabling ease of integration into the surgical workflow with the potential to improve molecular guidance intraoperatively. PMID:28856038

  9. Optical artefact characterization and correction in volumetric scintillation dosimetry

    PubMed Central

    Robertson, Daniel; Hui, Cheukkai; Archambault, Louis; Mohan, Radhe; Beddar, Sam

    2014-01-01

    The goals of this study were (1) to characterize the optical artefacts affecting measurement accuracy in a volumetric liquid scintillation detector, and (2) to develop methods to correct for these artefacts. The optical artefacts addressed were photon scattering, refraction, camera perspective, vignetting, lens distortion, the lens point spread function, stray radiation, and noise in the camera. These artefacts were evaluated by theoretical and experimental means, and specific correction strategies were developed for each artefact. The effectiveness of the correction methods was evaluated by comparing raw and corrected images of the scintillation light from proton pencil beams against validated Monte Carlo calculations. Blurring due to the lens and refraction at the scintillator tank-air interface were found to have the largest effect on the measured light distribution, and lens aberrations and vignetting were important primarily at the image edges. Photon scatter in the scintillator was not found to be a significant source of artefacts. The correction methods effectively mitigated the artefacts, increasing the average gamma analysis pass rate from 66% to 98% for gamma criteria of 2% dose difference and 2 mm distance to agreement. We conclude that optical artefacts cause clinically meaningful errors in the measured light distribution, and we have demonstrated effective strategies for correcting these optical artefacts. PMID:24321820

  10. Finding the average speed of a light-emitting toy car with a smartphone light sensor

    NASA Astrophysics Data System (ADS)

    Kapucu, Serkan

    2017-07-01

    This study aims to demonstrate how the average speed of a light-emitting toy car may be determined using a smartphone’s light sensor. The freely available Android smartphone application, ‘AndroSensor’, was used for the experiment. The classroom experiment combines complementary physics knowledge of optics and kinematics to find the average speed of a moving object. The speed of the toy car is found by determining the distance between the light-emitting toy car and the smartphone, and the time taken to travel these distances. To ensure that the average speed of the toy car calculated with the help of the AndroSensor was correct, the average speed was also calculated by analyzing video-recordings of the toy car. The resulting speeds found with these different methods were in good agreement with each other. Hence, it can be concluded that reliable measurements of the average speed of light-emitting objects can be determined with the help of the light sensor of an Android smartphone.

  11. Accurate artificial boundary conditions for the semi-discretized linear Schrödinger and heat equations on rectangular domains

    NASA Astrophysics Data System (ADS)

    Ji, Songsong; Yang, Yibo; Pang, Gang; Antoine, Xavier

    2018-01-01

    The aim of this paper is to design some accurate artificial boundary conditions for the semi-discretized linear Schrödinger and heat equations in rectangular domains. The Laplace transform in time and discrete Fourier transform in space are applied to get Green's functions of the semi-discretized equations in unbounded domains with single-source. An algorithm is given to compute these Green's functions accurately through some recurrence relations. Furthermore, the finite-difference method is used to discretize the reduced problem with accurate boundary conditions. Numerical simulations are presented to illustrate the accuracy of our method in the case of the linear Schrödinger and heat equations. It is shown that the reflection at the corners is correctly eliminated.

  12. Topological order and memory time in marginally-self-correcting quantum memory

    NASA Astrophysics Data System (ADS)

    Siva, Karthik; Yoshida, Beni

    2017-03-01

    We examine two proposals for marginally-self-correcting quantum memory: the cubic code by Haah and the welded code by Michnicki. In particular, we prove explicitly that they are absent of topological order above zero temperature, as their Gibbs ensembles can be prepared via a short-depth quantum circuit from classical ensembles. Our proof technique naturally gives rise to the notion of free energy associated with excitations. Further, we develop a framework for an ergodic decomposition of Davies generators in CSS codes which enables formal reduction to simpler classical memory problems. We then show that memory time in the welded code is doubly exponential in inverse temperature via the Peierls argument. These results introduce further connections between thermal topological order and self-correction from the viewpoint of free energy and quantum circuit depth.

  13. Global Night-Time Lights for Observing Human Activity

    NASA Technical Reports Server (NTRS)

    Hipskind, Stephen R.; Elvidge, Chris; Gurney, K.; Imhoff, Mark; Bounoua, Lahouari; Sheffner, Edwin; Nemani, Ramakrishna R.; Pettit, Donald R.; Fischer, Marc

    2011-01-01

    We present a concept for a small satellite mission to make systematic, global observations of night-time lights with spatial resolution suitable for discerning the extent, type and density of human settlements. The observations will also allow better understanding of fine scale fossil fuel CO2 emission distribution. The NASA Earth Science Decadal Survey recommends more focus on direct observations of human influence on the Earth system. The most dramatic and compelling observations of human presence on the Earth are the night light observations taken by the Defence Meteorological System Program (DMSP) Operational Linescan System (OLS). Beyond delineating the footprint of human presence, night light data, when assembled and evaluated with complementary data sets, can determine the fine scale spatial distribution of global fossil fuel CO2 emissions. Understanding fossil fuel carbon emissions is critical to understanding the entire carbon cycle, and especially the carbon exchange between terrestrial and oceanic systems.

  14. Dual-dimensional microscopy: real-time in vivo three-dimensional observation method using high-resolution light-field microscopy and light-field display.

    PubMed

    Kim, Jonghyun; Moon, Seokil; Jeong, Youngmo; Jang, Changwon; Kim, Youngmin; Lee, Byoungho

    2018-06-01

    Here, we present dual-dimensional microscopy that captures both two-dimensional (2-D) and light-field images of an in-vivo sample simultaneously, synthesizes an upsampled light-field image in real time, and visualizes it with a computational light-field display system in real time. Compared with conventional light-field microscopy, the additional 2-D image greatly enhances the lateral resolution at the native object plane up to the diffraction limit and compensates for the image degradation at the native object plane. The whole process from capturing to displaying is done in real time with the parallel computation algorithm, which enables the observation of the sample's three-dimensional (3-D) movement and direct interaction with the in-vivo sample. We demonstrate a real-time 3-D interactive experiment with Caenorhabditis elegans. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

  15. Transit light curves with finite integration time: Fisher information analysis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Price, Ellen M.; Rogers, Leslie A.

    2014-10-10

    Kepler has revolutionized the study of transiting planets with its unprecedented photometric precision on more than 150,000 target stars. Most of the transiting planet candidates detected by Kepler have been observed as long-cadence targets with 30 minute integration times, and the upcoming Transiting Exoplanet Survey Satellite will record full frame images with a similar integration time. Integrations of 30 minutes affect the transit shape, particularly for small planets and in cases of low signal to noise. Using the Fisher information matrix technique, we derive analytic approximations for the variances and covariances on the transit parameters obtained from fitting light curvemore » photometry collected with a finite integration time. We find that binning the light curve can significantly increase the uncertainties and covariances on the inferred parameters when comparing scenarios with constant total signal to noise (constant total integration time in the absence of read noise). Uncertainties on the transit ingress/egress time increase by a factor of 34 for Earth-size planets and 3.4 for Jupiter-size planets around Sun-like stars for integration times of 30 minutes compared to instantaneously sampled light curves. Similarly, uncertainties on the mid-transit time for Earth and Jupiter-size planets increase by factors of 3.9 and 1.4. Uncertainties on the transit depth are largely unaffected by finite integration times. While correlations among the transit depth, ingress duration, and transit duration all increase in magnitude with longer integration times, the mid-transit time remains uncorrelated with the other parameters. We provide code in Python and Mathematica for predicting the variances and covariances at www.its.caltech.edu/∼eprice.« less

  16. Human Adolescent Phase Response Curves to Bright White Light.

    PubMed

    Crowley, Stephanie J; Eastman, Charmane I

    2017-08-01

    Older adolescents are particularly vulnerable to circadian misalignment and sleep restriction, primarily due to early school start times. Light can shift the circadian system and could help attenuate circadian misalignment; however, a phase response curve (PRC) to determine the optimal time for receiving light and avoiding light is not available for adolescents. We constructed light PRCs for late pubertal to postpubertal adolescents aged 14 to 17 years. Participants completed 2 counterbalanced 5-day laboratory sessions after 8 or 9 days of scheduled sleep at home. Each session included phase assessments to measure the dim light melatonin onset (DLMO) before and after 3 days of free-running through an ultradian light-dark (wake-sleep) cycle (2 h dim [~20 lux] light, 2 h dark). In one session, intermittent bright white light (~5000 lux; four 20-min exposures) was alternated with 10 min of dim room light once per day for 3 consecutive days. The time of light varied among participants to cover the 24-h day. For each individual, the phase shift to bright light was corrected for the free-run derived from the other laboratory session with no bright light. One PRC showed phase shifts in response to light start time relative to the DLMO and another relative to home sleep. Phase delay shifts occurred around the hours corresponding to home bedtime. Phase advances occurred during the hours surrounding wake time and later in the afternoon. The transition from delays to advances occurred at the midpoint of home sleep. The adolescent PRCs presented here provide a valuable tool to time bright light in adolescents.

  17. Correcting for time-dependent field inhomogeneities in a time orbiting potential magnetic trap

    NASA Astrophysics Data System (ADS)

    Fallon, Adam; Berl, Seth; Sackett, Charles

    2017-04-01

    Many experiments use a Time Orbiting Potential (TOP) magnetic trap to confine a Bose-condensate. An advantage of the TOP trap is that it is relatively insensitive to deviations and errors in the magnetic field. However, precision experiments using the trapped atoms often do require the rotating field to be well characterized. For instance, precision spectroscopy requires accurate knowledge of both the field magnitude and field direction relative to the polarization of a probe laser beam. We have developed an RF spectroscopic technique to measure the magnitude of the field at arbitrary times within the TOP trap rotation period. From the time-variation mapped out, various imperfections can be isolated and measured, including asymmetries in the applied trap field and static environmental fields. By compensating for these imperfections, field control at the 10 mG level or better is achievable, for a bias field of 10 G or more. This should help enable more precision experiments using trapped condensates, including precision measurements of tune-out wavelengths and possibly parity-violation measurements. Supported by the National Science Foundation, the Jefferson Scholars Foundation, and NASA.

  18. Time accurate application of the MacCormack 2-4 scheme on massively parallel computers

    NASA Technical Reports Server (NTRS)

    Hudson, Dale A.; Long, Lyle N.

    1995-01-01

    Many recent computational efforts in turbulence and acoustics research have used higher order numerical algorithms. One popular method has been the explicit MacCormack 2-4 scheme. The MacCormack 2-4 scheme is second order accurate in time and fourth order accurate in space, and is stable for CFL's below 2/3. Current research has shown that the method can give accurate results but does exhibit significant Gibbs phenomena at sharp discontinuities. The impact of adding Jameson type second, third, and fourth order artificial viscosity was examined here. Category 2 problems, the nonlinear traveling wave and the Riemann problem, were computed using a CFL number of 0.25. This research has found that dispersion errors can be significantly reduced or nearly eliminated by using a combination of second and third order terms in the damping. Use of second and fourth order terms reduced the magnitude of dispersion errors but not as effectively as the second and third order combination. The program was coded using Thinking Machine's CM Fortran, a variant of Fortran 90/High Performance Fortran, and was executed on a 2K CM-200. Simple extrapolation boundary conditions were used for both problems.

  19. Real-time distortion correction of spiral and echo planar images using the gradient system impulse response function.

    PubMed

    Campbell-Washburn, Adrienne E; Xue, Hui; Lederman, Robert J; Faranesh, Anthony Z; Hansen, Michael S

    2016-06-01

    MRI-guided interventions demand high frame rate imaging, making fast imaging techniques such as spiral imaging and echo planar imaging (EPI) appealing. In this study, we implemented a real-time distortion correction framework to enable the use of these fast acquisitions for interventional MRI. Distortions caused by gradient waveform inaccuracies were corrected using the gradient impulse response function (GIRF), which was measured by standard equipment and saved as a calibration file on the host computer. This file was used at runtime to calculate the predicted k-space trajectories for image reconstruction. Additionally, the off-resonance reconstruction frequency was modified in real time to interactively deblur spiral images. Real-time distortion correction for arbitrary image orientations was achieved in phantoms and healthy human volunteers. The GIRF-predicted k-space trajectories matched measured k-space trajectories closely for spiral imaging. Spiral and EPI image distortion was visibly improved using the GIRF-predicted trajectories. The GIRF calibration file showed no systematic drift in 4 months and was demonstrated to correct distortions after 30 min of continuous scanning despite gradient heating. Interactive off-resonance reconstruction was used to sharpen anatomical boundaries during continuous imaging. This real-time distortion correction framework will enable the use of these high frame rate imaging methods for MRI-guided interventions. Magn Reson Med 75:2278-2285, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  20. Real-time distortion correction of spiral and echo planar images using the gradient system impulse response function

    PubMed Central

    Campbell-Washburn, Adrienne E; Xue, Hui; Lederman, Robert J; Faranesh, Anthony Z; Hansen, Michael S

    2015-01-01

    Purpose MRI-guided interventions demand high frame-rate imaging, making fast imaging techniques such as spiral imaging and echo planar imaging (EPI) appealing. In this study, we implemented a real-time distortion correction framework to enable the use of these fast acquisitions for interventional MRI. Methods Distortions caused by gradient waveform inaccuracies were corrected using the gradient impulse response function (GIRF), which was measured by standard equipment and saved as a calibration file on the host computer. This file was used at runtime to calculate the predicted k-space trajectories for image reconstruction. Additionally, the off-resonance reconstruction frequency was modified in real-time to interactively de-blur spiral images. Results Real-time distortion correction for arbitrary image orientations was achieved in phantoms and healthy human volunteers. The GIRF predicted k-space trajectories matched measured k-space trajectories closely for spiral imaging. Spiral and EPI image distortion was visibly improved using the GIRF predicted trajectories. The GIRF calibration file showed no systematic drift in 4 months and was demonstrated to correct distortions after 30 minutes of continuous scanning despite gradient heating. Interactive off-resonance reconstruction was used to sharpen anatomical boundaries during continuous imaging. Conclusions This real-time distortion correction framework will enable the use of these high frame-rate imaging methods for MRI-guided interventions. PMID:26114951

  1. The correction of time and temperature effects in MR-based 3D Fricke xylenol orange dosimetry.

    PubMed

    Welch, Mattea L; Jaffray, David A

    2017-04-21

    Previously developed MR-based three-dimensional (3D) Fricke-xylenol orange (FXG) dosimeters can provide end-to-end quality assurance and validation protocols for pre-clinical radiation platforms. FXG dosimeters quantify ionizing irradiation induced oxidation of Fe 2+ ions using pre- and post-irradiation MR imaging methods that detect changes in spin-lattice relaxation rates (R 1   =  [Formula: see text]) caused by irradiation induced oxidation of Fe 2+ . Chemical changes in MR-based FXG dosimeters that occur over time and with changes in temperature can decrease dosimetric accuracy if they are not properly characterized and corrected. This paper describes the characterization, development and utilization of an empirical model-based correction algorithm for time and temperature effects in the context of a pre-clinical irradiator and a 7 T pre-clinical MR imaging system. Time and temperature dependent changes of R 1 values were characterized using variable TR spin-echo imaging. R 1 -time and R 1 -temperature dependencies were fit using non-linear least squares fitting methods. Models were validated using leave-one-out cross-validation and resampling. Subsequently, a correction algorithm was developed that employed the previously fit empirical models to predict and reduce baseline R 1 shifts that occurred in the presence of time and temperature changes. The correction algorithm was tested on R 1 -dose response curves and 3D dose distributions delivered using a small animal irradiator at 225 kVp. The correction algorithm reduced baseline R 1 shifts from  -2.8  ×  10 -2 s -1 to 1.5  ×  10 -3 s -1 . In terms of absolute dosimetric performance as assessed with traceable standards, the correction algorithm reduced dose discrepancies from approximately 3% to approximately 0.5% (2.90  ±  2.08% to 0.20  ±  0.07%, and 2.68  ±  1.84% to 0.46  ±  0.37% for the 10  ×  10 and 8  ×  12 mm 2 fields

  2. Apparatus and method for temperature correction and expanded count rate of inorganic scintillation detectors

    DOEpatents

    Ianakiev, Kiril D [Los Alamos, NM; Hsue, Sin Tao [Santa Fe, NM; Browne, Michael C [Los Alamos, NM; Audia, Jeffrey M [Abiquiu, NM

    2006-07-25

    The present invention includes an apparatus and corresponding method for temperature correction and count rate expansion of inorganic scintillation detectors. A temperature sensor is attached to an inorganic scintillation detector. The inorganic scintillation detector, due to interaction with incident radiation, creates light pulse signals. A photoreceiver processes the light pulse signals to current signals. Temperature correction circuitry that uses a fast light component signal, a slow light component signal, and the temperature signal from the temperature sensor to corrected an inorganic scintillation detector signal output and expanded the count rate.

  3. Latest Developments on Obtaining Accurate Measurements with Pitot Tubes in ZPG Turbulent Boundary Layers

    NASA Astrophysics Data System (ADS)

    Nagib, Hassan; Vinuesa, Ricardo

    2013-11-01

    Ability of available Pitot tube corrections to provide accurate mean velocity profiles in ZPG boundary layers is re-examined following the recent work by Bailey et al. Measurements by Bailey et al., carried out with probes of diameters ranging from 0.2 to 1.89 mm, together with new data taken with larger diameters up to 12.82 mm, show deviations with respect to available high-quality datasets and hot-wire measurements in the same Reynolds number range. These deviations are significant in the buffer region around y+ = 30 - 40 , and lead to disagreement in the von Kármán coefficient κ extracted from profiles. New forms for shear, near-wall and turbulence corrections are proposed, highlighting the importance of the latest one. Improved agreement in mean velocity profiles is obtained with new forms, where shear and near-wall corrections contribute with around 85%, and remaining 15% of the total correction comes from turbulence correction. Finally, available algorithms to correct wall position in profile measurements of wall-bounded flows are tested, using as benchmark the corrected Pitot measurements with artificially simulated probe shifts and blockage effects. We develop a new scheme, κB - Musker, which is able to accurately locate wall position.

  4. Real-time 3-D contrast-enhanced transcranial ultrasound and aberration correction.

    PubMed

    Ivancevich, Nikolas M; Pinton, Gianmarco F; Nicoletto, Heather A; Bennett, Ellen; Laskowitz, Daniel T; Smith, Stephen W

    2008-09-01

    Contrast-enhanced (CE) transcranial ultrasound (US) and reconstructed 3-D transcranial ultrasound have shown advantages over traditional methods in a variety of cerebrovascular diseases. We present the results from a novel ultrasound technique, namely real-time 3-D contrast-enhanced transcranial ultrasound. Using real-time 3-D (RT3D) ultrasound and microbubble contrast agent, we scanned 17 healthy volunteers via a single temporal window and nine via the suboccipital window and report our detection rates for the major cerebral vessels. In 71% of subjects, both of our observers identified the ipsilateral circle of Willis from the temporal window, and in 59% we imaged the entire circle of Willis. From the suboccipital window, both observers detected the entire vertebrobasilar circulation in 22% of subjects, and in 44%, the basilar artery. After performing phase aberration correction on one subject, we were able to increase the diagnostic value of the scan, detecting a vessel not present in the uncorrected scan. These preliminary results suggest that RT3D CE transcranial US and RT3D CE transcranial US with phase aberration correction have the potential to greatly impact the field of neurosonology.

  5. Real-Time 3D Contrast-Enhanced Transcranial Ultrasound and Aberration Correction

    PubMed Central

    Ivancevich, Nikolas M.; Pinton, Gianmarco F.; Nicoletto, Heather A.; Bennett, Ellen; Laskowitz, Daniel T.; Smith, Stephen W.

    2008-01-01

    Contrast-enhanced (CE) transcranial ultrasound (US) and reconstructed 3D transcranial ultrasound have shown advantages over traditional methods in a variety of cerebrovascular diseases. We present the results from a novel ultrasound technique, namely real-time 3D contrast-enhanced transcranial ultrasound. Using real-time 3D (RT3D) ultrasound and micro-bubble contrast agent, we scanned 17 healthy volunteers via a single temporal window and 9 via the sub-occipital window and report our detection rates for the major cerebral vessels. In 71% of subjects, both of our observers identified the ipsilateral circle of Willis from the temporal window, and in 59% we imaged the entire circle of Willis. From the sub-occipital window, both observers detected the entire vertebrobasilar circulation in 22% of subjects, and in 44% the basilar artery. After performing phase aberration correction on one subject, we were able to increase the diagnostic value of the scan, detecting a vessel not present in the uncorrected scan. These preliminary results suggest that RT3D CE transcranial US and RT3D CE transcranial US with phase aberration correction have the potential to greatly impact the field of neurosonology. PMID:18395321

  6. Accurate and precise determination of isotopic ratios by MC-ICP-MS: a review.

    PubMed

    Yang, Lu

    2009-01-01

    For many decades the accurate and precise determination of isotope ratios has remained a very strong interest to many researchers due to its important applications in earth, environmental, biological, archeological, and medical sciences. Traditionally, thermal ionization mass spectrometry (TIMS) has been the technique of choice for achieving the highest accuracy and precision. However, recent developments in multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) have brought a new dimension to this field. In addition to its simple and robust sample introduction, high sample throughput, and high mass resolution, the flat-topped peaks generated by this technique provide for accurate and precise determination of isotope ratios with precision reaching 0.001%, comparable to that achieved with TIMS. These features, in combination with the ability of the ICP source to ionize nearly all elements in the periodic table, have resulted in an increased use of MC-ICP-MS for such measurements in various sample matrices. To determine accurate and precise isotope ratios with MC-ICP-MS, utmost care must be exercised during sample preparation, optimization of the instrument, and mass bias corrections. Unfortunately, there are inconsistencies and errors evident in many MC-ICP-MS publications, including errors in mass bias correction models. This review examines "state-of-the-art" methodologies presented in the literature for achievement of precise and accurate determinations of isotope ratios by MC-ICP-MS. Some general rules for such accurate and precise measurements are suggested, and calculations of combined uncertainty of the data using a few common mass bias correction models are outlined.

  7. Real-time 3D measurement based on structured light illumination considering camera lens distortion

    NASA Astrophysics Data System (ADS)

    Feng, Shijie; Chen, Qian; Zuo, Chao; Sun, Jiasong; Yu, ShiLing

    2014-12-01

    Optical three-dimensional (3-D) profilometry is gaining increasing attention for its simplicity, flexibility, high accuracy, and non-contact nature. Recent advances in imaging sensors and digital projection technology further its progress in high-speed, real-time applications, enabling 3-D shapes reconstruction of moving objects and dynamic scenes. In traditional 3-D measurement system where the processing time is not a key factor, camera lens distortion correction is performed directly. However, for the time-critical high-speed applications, the time-consuming correction algorithm is inappropriate to be performed directly during the real-time process. To cope with this issue, here we present a novel high-speed real-time 3-D coordinates measuring technique based on fringe projection with the consideration of the camera lens distortion. A pixel mapping relation between a distorted image and a corrected one is pre-determined and stored in computer memory for real-time fringe correction. And a method of lookup table (LUT) is introduced as well for fast data processing. Our experimental results reveal that the measurement error of the in-plane coordinates has been reduced by one order of magnitude and the accuracy of the out-plane coordinate been tripled after the distortions being eliminated. Moreover, owing to the merit of the LUT, the 3-D reconstruction can be achieved at 92.34 frames per second.

  8. Conductivity Cell Thermal Inertia Correction Revisited

    NASA Astrophysics Data System (ADS)

    Eriksen, C. C.

    2012-12-01

    Salinity measurements made with a CTD (conductivity-temperature-depth instrument) rely on accurate estimation of water temperature within their conductivity cell. Lueck (1990) developed a theoretical framework for heat transfer between the cell body and water passing through it. Based on this model, Lueck and Picklo (1990) introduced the practice of correcting for cell thermal inertia by filtering a temperature time series using two parameters, an amplitude α and a decay time constant τ, a practice now widely used. Typically these two parameters are chosen for a given cell configuration and internal flushing speed by a statistical method applied to a particular data set. Here, thermal inertia correction theory has been extended to apply to flow speeds spanning well over an order of magnitude, both within and outside a conductivity cell, to provide predictions of α and τ from cell geometry and composition. The extended model enables thermal inertia correction for the variable flows encountered by conductivity cells on autonomous gliders and floats, as well as tethered platforms. The length scale formed as the product of cell encounter speed of isotherms, α, and τ can be used to gauge the size of the temperature correction for a given thermal stratification. For cells flushed by dynamic pressure variation induced by platform motion, this length varies by less than a factor of 2 over more than a decade of speed variation. The magnitude of correction for free-flow flushed sensors is comparable to that of pumped cells, but at an order of magnitude in energy savings. Flow conditions around a cell's exterior are found to be of comparable importance to thermal inertia response as flushing speed. Simplification of cell thermal response to a single normal mode is most valid at slow speed. Error in thermal inertia estimation arises from both neglect of higher modes and numerical discretization of the correction scheme, both of which can be easily quantified

  9. Evaluation of strategies to control Fab light chain dimer during mammalian expression and purification: A universal one-step process for purification of correctly assembled Fab.

    PubMed

    Spooner, Jennifer; Keen, Jenny; Nayyar, Kalpana; Birkett, Neil; Bond, Nicholas; Bannister, David; Tigue, Natalie; Higazi, Daniel; Kemp, Benjamin; Vaughan, Tristan; Kippen, Alistair; Buchanan, Andrew

    2015-07-01

    Fabs are an important class of antibody fragment as both research reagents and therapeutic agents. There are a plethora of methods described for their recombinant expression and purification. However, these do not address the issue of excessive light chain production that forms light chain dimers nor do they describe a universal purification strategy. Light chain dimer impurities and the absence of a universal Fab purification strategy present persistent challenges for biotechnology applications using Fabs, particularly around the need for bespoke purification strategies. This study describes methods to address light chain dimer formation during Fab expression and identifies a novel CH 1 affinity resin as a simple and efficient one-step purification for correctly assembled Fab. © 2015 Wiley Periodicals, Inc.

  10. BASIC: A Simple and Accurate Modular DNA Assembly Method.

    PubMed

    Storch, Marko; Casini, Arturo; Mackrow, Ben; Ellis, Tom; Baldwin, Geoff S

    2017-01-01

    Biopart Assembly Standard for Idempotent Cloning (BASIC) is a simple, accurate, and robust DNA assembly method. The method is based on linker-mediated DNA assembly and provides highly accurate DNA assembly with 99 % correct assemblies for four parts and 90 % correct assemblies for seven parts [1]. The BASIC standard defines a single entry vector for all parts flanked by the same prefix and suffix sequences and its idempotent nature means that the assembled construct is returned in the same format. Once a part has been adapted into the BASIC format it can be placed at any position within a BASIC assembly without the need for reformatting. This allows laboratories to grow comprehensive and universal part libraries and to share them efficiently. The modularity within the BASIC framework is further extended by the possibility of encoding ribosomal binding sites (RBS) and peptide linker sequences directly on the linkers used for assembly. This makes BASIC a highly versatile library construction method for combinatorial part assembly including the construction of promoter, RBS, gene variant, and protein-tag libraries. In comparison with other DNA assembly standards and methods, BASIC offers a simple robust protocol; it relies on a single entry vector, provides for easy hierarchical assembly, and is highly accurate for up to seven parts per assembly round [2].

  11. Phase-shifting human circadian rhythms: influence of sleep timing, social contact and light exposure

    NASA Technical Reports Server (NTRS)

    Duffy, J. F.; Kronauer, R. E.; Czeisler, C. A.

    1996-01-01

    1. Both the timing of behavioural events (activity, sleep and social interactions) and the environmental light-dark cycle have been reported to contribute to entrainment of human circadian rhythms to the 24 h day. Yet, the relative contribution of those putative behavioural synchronizers to that of light exposure remains unclear. 2. To investigate this, we inverted the schedule of rest, sedentary activity and social contact of thirty-two young men either with or without exposure to bright light. 3. On this inverted schedule, the endogenous component of the core temperature rhythm of subjects who were exposed to bright light showed a significant phase shift, demonstrating that they were adapting to the new schedule. In contrast, the core temperature rhythm of subjects who were not exposed to bright light moved on average 0.2 h later per day and after 10 days had not significantly adapted to the new schedule. 4. The direction of phase shift in the groups exposed to bright light was dependent on the time of bright light exposure, while control subjects drifted to a later hour regardless of the timing of their schedule of sleep timing, social contact and meals. 5. These results support the concept that the light-dark cycle is the most important synchronizer of the human circadian system. They suggest that inversion of the sleep-wake, rest-activity and social contact cycles provides relatively minimal drive for resetting the human circadian pacemaker. 6. These data indicate that interventions designed to phase shift human circadian rhythms for adjustment to time zone changes or altered work schedules should focus on properly timed light exposure.

  12. Accurate Behavioral Simulator of All-Digital Time-Domain Smart Temperature Sensors by Using SIMULINK

    PubMed Central

    Chen, Chun-Chi; Chen, Chao-Lieh; Lin, You-Ting

    2016-01-01

    This study proposes a new behavioral simulator that uses SIMULINK for all-digital CMOS time-domain smart temperature sensors (TDSTSs) for performing rapid and accurate simulations. Inverter-based TDSTSs offer the benefits of low cost and simple structure for temperature-to-digital conversion and have been developed. Typically, electronic design automation tools, such as HSPICE, are used to simulate TDSTSs for performance evaluations. However, such tools require extremely long simulation time and complex procedures to analyze the results and generate figures. In this paper, we organize simple but accurate equations into a temperature-dependent model (TDM) by which the TDSTSs evaluate temperature behavior. Furthermore, temperature-sensing models of a single CMOS NOT gate were devised using HSPICE simulations. Using the TDM and these temperature-sensing models, a novel simulator in SIMULINK environment was developed to substantially accelerate the simulation and simplify the evaluation procedures. Experiments demonstrated that the simulation results of the proposed simulator have favorable agreement with those obtained from HSPICE simulations, showing that the proposed simulator functions successfully. This is the first behavioral simulator addressing the rapid simulation of TDSTSs. PMID:27509507

  13. Novel color additive for chlorine disinfectants corrects deficiencies in spray surface coverage and wet-contact time and checks for correct chlorine concentration.

    PubMed

    Tyan, Kevin; Jin, Katherine; Kang, Jason; Kyle, Aaron M

    2018-04-18

    Bleach sprays suffer from poor surface coverage, dry out before reaching proper contact time, and can be inadvertently over-diluted to ineffective concentrations. Highlight ® , a novel color additive for bleach that fades to indicate elapsed contact time, maintained >99.9% surface coverage over full contact time and checked for correct chlorine concentration. Copyright © 2018 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

  14. Combination of light and melatonin time cues for phase advancing the human circadian clock.

    PubMed

    Burke, Tina M; Markwald, Rachel R; Chinoy, Evan D; Snider, Jesse A; Bessman, Sara C; Jung, Christopher M; Wright, Kenneth P

    2013-11-01

    Photic and non-photic stimuli have been shown to shift the phase of the human circadian clock. We examined how photic and non-photic time cues may be combined by the human circadian system by assessing the phase advancing effects of one evening dose of exogenous melatonin, alone and in combination with one session of morning bright light exposure. Randomized placebo-controlled double-blind circadian protocol. The effects of four conditions, dim light (∼1.9 lux, ∼0.6 Watts/m(2))-placebo, dim light-melatonin (5 mg), bright light (∼3000 lux, ∼7 Watts/m(2))-placebo, and bright light-melatonin on circadian phase was assessed by the change in the salivary dim light melatonin onset (DLMO) prior to and following treatment under constant routine conditions. Melatonin or placebo was administered 5.75 h prior to habitual bedtime and 3 h of bright light exposure started 1 h prior to habitual wake time. Sleep and chronobiology laboratory environment free of time cues. Thirty-six healthy participants (18 females) aged 22 ± 4 y (mean ± SD). Morning bright light combined with early evening exogenous melatonin induced a greater phase advance of the DLMO than either treatment alone. Bright light alone and melatonin alone induced similar phase advances. Information from light and melatonin appear to be combined by the human circadian clock. The ability to combine circadian time cues has important implications for understanding fundamental physiological principles of the human circadian timing system. Knowledge of such principles is important for designing effective countermeasures for phase-shifting the human circadian clock to adapt to jet lag, shift work, and for designing effective treatments for circadian sleep-wakefulness disorders.

  15. Femtosecond-level timing fluctuation suppression in atmospheric frequency transfer with passive phase conjunction correction.

    PubMed

    Sun, Fuyu; Hou, Dong; Zhang, Danian; Tian, Jie; Hu, Jianguo; Huang, Xianhe; Chen, Shijun

    2017-09-04

    We demonstrate femtosecond-level timing fluctuation suppression in indoor atmospheric comb-based frequency transfer with a passive phase conjunction correction technique. Timing fluctuations and Allan deviations are both measured to characterize the excess frequency instability incurred during the frequency transfer process. By transferring a 2 GHz microwave over a 52-m long free-space link in 5000 s, the total root-mean-square (RMS) timing fluctuation was measured to be about 280 fs with a fractional frequency instability on the order of 3 × 10 -13 at 1 s and 6 × 10 -17 at 1000 s. This atmospheric comb-based frequency transfer with passive phase conjunction correction can be used to build an atomic clock-based free-space frequency transmission link because its instability is less than that of a commercial Cs or H-master clock.

  16. Combination of Light and Melatonin Time Cues for Phase Advancing the Human Circadian Clock

    PubMed Central

    Burke, Tina M.; Markwald, Rachel R.; Chinoy, Evan D.; Snider, Jesse A.; Bessman, Sara C.; Jung, Christopher M.; Wright, Kenneth P.

    2013-01-01

    Study Objectives: Photic and non-photic stimuli have been shown to shift the phase of the human circadian clock. We examined how photic and non-photic time cues may be combined by the human circadian system by assessing the phase advancing effects of one evening dose of exogenous melatonin, alone and in combination with one session of morning bright light exposure. Design: Randomized placebo-controlled double-blind circadian protocol. The effects of four conditions, dim light (∼1.9 lux, ∼0.6 Watts/m2)-placebo, dim light-melatonin (5 mg), bright light (∼3000 lux, ∼7 Watts/m2)-placebo, and bright light-melatonin on circadian phase was assessed by the change in the salivary dim light melatonin onset (DLMO) prior to and following treatment under constant routine conditions. Melatonin or placebo was administered 5.75 h prior to habitual bedtime and 3 h of bright light exposure started 1 h prior to habitual wake time. Setting: Sleep and chronobiology laboratory environment free of time cues. Participants: Thirty-six healthy participants (18 females) aged 22 ± 4 y (mean ± SD). Results: Morning bright light combined with early evening exogenous melatonin induced a greater phase advance of the DLMO than either treatment alone. Bright light alone and melatonin alone induced similar phase advances. Conclusion: Information from light and melatonin appear to be combined by the human circadian clock. The ability to combine circadian time cues has important implications for understanding fundamental physiological principles of the human circadian timing system. Knowledge of such principles is important for designing effective countermeasures for phase-shifting the human circadian clock to adapt to jet lag, shift work, and for designing effective treatments for circadian sleep-wakefulness disorders. Citation: Burke TM; Markwald RR; Chinoy ED; Snider JA; Bessman SC; Jung CM; Wright Jr KP. Combination of light and melatonin time cues for phase advancing the human circadian

  17. Delay of constant light-induced persistent vaginal estrus by 24-hour time cues in rats.

    PubMed

    Weber, A L; Adler, N T

    1979-04-20

    The normal ovarian cycle of female rats is typically replaced by persistent estrus when these animals are housed under constant light. Evidence presented here shows that the maintenance of periodicity in the environment can at least delay (if not prevent) the photic induction of persistent vaginal estrus. Female rats in constant light were exposed to vaginal smearing at random times or at the same time every day. In another experiment, female rats were exposed to either constant bright light, constant dim light, or a 24-hour photic cycle of bright and dim light. The onset of persistent vaginal estrus was delayed in rats exposed to 24-hour time cues even though the light intensities were the same as or greater than those for the aperiodic control groups. The results suggest that the absence of 24-hour time cues in constant light contributes to the induction of persistent estrus.

  18. Light, sleep and circadian rhythms in older adults with Alzheimer's disease and related dementias

    PubMed Central

    Figueiro, Mariana G

    2017-01-01

    Alzheimer's disease and related dementias (ADRD) can cause sleep and behavioral problems that are problematic for ADRD patients and their family caregivers. Light therapy has shown promise as a nonpharmacological treatment, and preliminary studies demonstrate that timed light exposure can consolidate and improve nighttime sleep efficiency, increase daytime wakefulness and reduce evening agitation without the adverse effects of pharmacological solutions. Compliance with light treatment and the accurate measurement of light exposures during treatment, however, have presented barriers for the adoption of light therapy for ADRD. Recent research showing that the circadian system is maximally sensitive to short-wavelength light opens the way for the potential application of lower, more-targeted light intensities to maximize compliance and individualize light dose/timing in therapeutic settings. PMID:28534696

  19. Accurate EPR radiosensitivity calibration using small sample masses

    NASA Astrophysics Data System (ADS)

    Hayes, R. B.; Haskell, E. H.; Barrus, J. K.; Kenner, G. H.; Romanyukha, A. A.

    2000-03-01

    We demonstrate a procedure in retrospective EPR dosimetry which allows for virtually nondestructive sample evaluation in terms of sample irradiations. For this procedure to work, it is shown that corrections must be made for cavity response characteristics when using variable mass samples. Likewise, methods are employed to correct for empty tube signals, sample anisotropy and frequency drift while considering the effects of dose distribution optimization. A demonstration of the method's utility is given by comparing sample portions evaluated using both the described methodology and standard full sample additive dose techniques. The samples used in this study are tooth enamel from teeth removed during routine dental care. We show that by making all the recommended corrections, very small masses can be both accurately measured and correlated with measurements of other samples. Some issues relating to dose distribution optimization are also addressed.

  20. In-Band Asymmetry Compensation for Accurate Time/Phase Transport over Optical Transport Network

    PubMed Central

    Siu, Sammy; Hu, Hsiu-fang; Lin, Shinn-Yan; Liao, Chia-Shu; Lai, Yi-Liang

    2014-01-01

    The demands of precise time/phase synchronization have been increasing recently due to the next generation of telecommunication synchronization. This paper studies the issues that are relevant to distributing accurate time/phase over optical transport network (OTN). Each node and link can introduce asymmetry, which affects the adequate time/phase accuracy over the networks. In order to achieve better accuracy, protocol level full timing support is used (e.g., Telecom-Boundary clock). Due to chromatic dispersion, the use of different wavelengths consequently causes fiber link delay asymmetry. The analytical result indicates that it introduces significant time error (i.e., phase offset) within 0.3397 ns/km in C-band or 0.3943 ns/km in L-band depending on the wavelength spacing. With the proposed scheme in this paper, the fiber link delay asymmetry can be compensated relying on the estimated mean fiber link delay by the Telecom-Boundary clock, while the OTN control plane is responsible for processing the fiber link delay asymmetry to determine the asymmetry compensation in the timing chain. PMID:24982948

  1. Nature, diffraction-free propagation via space-time correlations, and nonlinear generation of time-diffracting light beams

    NASA Astrophysics Data System (ADS)

    Porras, Miguel A.

    2018-06-01

    We investigate the properties of the recently introduced time-diffracting (TD) beams in free space. They are shown to be paraxial and quasimonochromatic realizations of spatiotemporal localized waves traveling undistorted at arbitrary speeds. The paraxial and quasimonochromatic regime is shown to be necessary to observe what can properly be named diffraction in time. In this regime, the spatiotemporal frequency correlations for diffraction-free propagation are approximated by parabolic correlations. Time-diffracting beams of finite energy traveling at quasiluminal velocities are seen to form substantially longer foci or needles of light than the so-called abruptly focusing and defocusing needle of light or limiting TD beam of infinite speed. Exploring the properties of TD beams under Lorentz transformations and their transformation by paraxial optical systems, we realize that the nonlinear polarization of material media induced by a strongly localized fundamental pump wave generates a TD beam at its second harmonic, whose diffraction-free behavior as a needle of light in free space can be optimized with a standard 4 f -imager system.

  2. Stray light lessons learned from the Mars reconnaissance orbiter's optical navigation camera

    NASA Astrophysics Data System (ADS)

    Lowman, Andrew E.; Stauder, John L.

    2004-10-01

    The Optical Navigation Camera (ONC) is a technical demonstration slated to fly on NASA"s Mars Reconnaissance Orbiter in 2005. Conventional navigation methods have reduced accuracy in the days immediately preceding Mars orbit insertion. The resulting uncertainty in spacecraft location limits rover landing sites to relatively safe areas, away from interesting features that may harbor clues to past life on the planet. The ONC will provide accurate navigation on approach for future missions by measuring the locations of the satellites of Mars relative to background stars. Because Mars will be a bright extended object just outside the camera"s field of view, stray light control at small angles is essential. The ONC optomechanical design was analyzed by stray light experts and appropriate baffles were implemented. However, stray light testing revealed significantly higher levels of light than expected at the most critical angles. The primary error source proved to be the interface between ground glass surfaces (and the paint that had been applied to them) and the polished surfaces of the lenses. This paper will describe troubleshooting and correction of the problem, as well as other lessons learned that affected stray light performance.

  3. Multiplexed single-mode wavelength-to-time mapping of multimode light

    PubMed Central

    Chandrasekharan, Harikumar K; Izdebski, Frauke; Gris-Sánchez, Itandehui; Krstajić, Nikola; Walker, Richard; Bridle, Helen L.; Dalgarno, Paul A.; MacPherson, William N.; Henderson, Robert K.; Birks, Tim A.; Thomson, Robert R.

    2017-01-01

    When an optical pulse propagates along an optical fibre, different wavelengths travel at different group velocities. As a result, wavelength information is converted into arrival-time information, a process known as wavelength-to-time mapping. This phenomenon is most cleanly observed using a single-mode fibre transmission line, where spatial mode dispersion is not present, but the use of such fibres restricts possible applications. Here we demonstrate that photonic lanterns based on tapered single-mode multicore fibres provide an efficient way to couple multimode light to an array of single-photon avalanche detectors, each of which has its own time-to-digital converter for time-correlated single-photon counting. Exploiting this capability, we demonstrate the multiplexed single-mode wavelength-to-time mapping of multimode light using a multicore fibre photonic lantern with 121 single-mode cores, coupled to 121 detectors on a 32 × 32 detector array. This work paves the way to efficient multimode wavelength-to-time mapping systems with the spectral performance of single-mode systems. PMID:28120822

  4. A simplified method for correcting contaminant concentrations in eggs for moisture loss.

    USGS Publications Warehouse

    Heinz, Gary H.; Stebbins, Katherine R.; Klimstra, Jon D.; Hoffman, David J.

    2009-01-01

    We developed a simplified and highly accurate method for correcting contaminant concentrations in eggs for the moisture that is lost from an egg during incubation. To make the correction, one injects water into the air cell of the egg until overflowing. The amount of water injected corrects almost perfectly for the amount of water lost during incubation or when an egg is left in the nest and dehydrates and deteriorates over time. To validate the new method we weighed freshly laid chicken (Gallus gallus) eggs and then incubated sets of fertile and dead eggs for either 12 or 19 d. We then injected water into the air cells of these eggs and verified that the weights after water injection were almost identical to the weights of the eggs when they were fresh. The advantages of the new method are its speed, accuracy, and simplicity: It does not require the calculation of a correction factor that has to be applied to each contaminant residue.

  5. Accurate phylogenetic classification of DNA fragments based onsequence composition

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McHardy, Alice C.; Garcia Martin, Hector; Tsirigos, Aristotelis

    2006-05-01

    Metagenome studies have retrieved vast amounts of sequenceout of a variety of environments, leading to novel discoveries and greatinsights into the uncultured microbial world. Except for very simplecommunities, diversity makes sequence assembly and analysis a verychallenging problem. To understand the structure a 5 nd function ofmicrobial communities, a taxonomic characterization of the obtainedsequence fragments is highly desirable, yet currently limited mostly tothose sequences that contain phylogenetic marker genes. We show that forclades at the rank of domain down to genus, sequence composition allowsthe very accurate phylogenetic 10 characterization of genomic sequence.We developed a composition-based classifier, PhyloPythia, for de novophylogenetic sequencemore » characterization and have trained it on adata setof 340 genomes. By extensive evaluation experiments we show that themethodis accurate across all taxonomic ranks considered, even forsequences that originate fromnovel organisms and are as short as 1kb.Application to two metagenome datasets 15 obtained from samples ofphosphorus-removing sludge showed that the method allows the accurateclassification at genus level of most sequence fragments from thedominant populations, while at the same time correctly characterizingeven larger parts of the samples at higher taxonomic levels.« less

  6. Accurate Projection Methods for the Incompressible Navier–Stokes Equations

    DOE PAGES

    Brown, David L.; Cortez, Ricardo; Minion, Michael L.

    2001-04-10

    This paper considers the accuracy of projection method approximations to the initial–boundary-value problem for the incompressible Navier–Stokes equations. The issue of how to correctly specify numerical boundary conditions for these methods has been outstanding since the birth of the second-order methodology a decade and a half ago. It has been observed that while the velocity can be reliably computed to second-order accuracy in time and space, the pressure is typically only first-order accurate in the L ∞-norm. Here, we identify the source of this problem in the interplay of the global pressure-update formula with the numerical boundary conditions and presentsmore » an improved projection algorithm which is fully second-order accurate, as demonstrated by a normal mode analysis and numerical experiments. In addition, a numerical method based on a gauge variable formulation of the incompressible Navier–Stokes equations, which provides another option for obtaining fully second-order convergence in both velocity and pressure, is discussed. The connection between the boundary conditions for projection methods and the gauge method is explained in detail.« less

  7. The Effectiveness of Synchronous and Asynchronous Written Corrective Feedback on Grammatical Accuracy in a Computer-Mediated Environment

    ERIC Educational Resources Information Center

    Shintani, Natsuko; Aubrey, Scott

    2016-01-01

    This study extends research on written corrective feedback (CF) by investigating how timing of CF affects grammar acquisition. Specifically, it examined the relative effects of synchronous and asynchronous CF on the accurate use of the hypothetical conditional structure. Participants were 68 intermediate-level students of English at a university…

  8. Towards an accurate real-time locator of infrasonic sources

    NASA Astrophysics Data System (ADS)

    Pinsky, V.; Blom, P.; Polozov, A.; Marcillo, O.; Arrowsmith, S.; Hofstetter, A.

    2017-11-01

    Infrasonic signals propagate from an atmospheric source via media with stochastic and fast space-varying conditions. Hence, their travel time, the amplitude at sensor recordings and even manifestation in the so-called "shadow zones" are random. Therefore, the traditional least-squares technique for locating infrasonic sources is often not effective, and the problem for the best solution must be formulated in probabilistic terms. Recently, a series of papers has been published about Bayesian Infrasonic Source Localization (BISL) method based on the computation of the posterior probability density function (PPDF) of the source location, as a convolution of a priori probability distribution function (APDF) of the propagation model parameters with likelihood function (LF) of observations. The present study is devoted to the further development of BISL for higher accuracy and stability of the source location results and decreasing of computational load. We critically analyse previous algorithms and propose several new ones. First of all, we describe the general PPDF formulation and demonstrate that this relatively slow algorithm might be among the most accurate algorithms, provided the adequate APDF and LF are used. Then, we suggest using summation instead of integration in a general PPDF calculation for increased robustness, but this leads us to the 3D space-time optimization problem. Two different forms of APDF approximation are considered and applied for the PPDF calculation in our study. One of them is previously suggested, but not yet properly used is the so-called "celerity-range histograms" (CRHs). Another is the outcome from previous findings of linear mean travel time for the four first infrasonic phases in the overlapping consecutive distance ranges. This stochastic model is extended here to the regional distance of 1000 km, and the APDF introduced is the probabilistic form of the junction between this travel time model and range-dependent probability

  9. Identification of Microorganisms by High Resolution Tandem Mass Spectrometry with Accurate Statistical Significance

    NASA Astrophysics Data System (ADS)

    Alves, Gelio; Wang, Guanghui; Ogurtsov, Aleksey Y.; Drake, Steven K.; Gucek, Marjan; Suffredini, Anthony F.; Sacks, David B.; Yu, Yi-Kuo

    2016-02-01

    Correct and rapid identification of microorganisms is the key to the success of many important applications in health and safety, including, but not limited to, infection treatment, food safety, and biodefense. With the advance of mass spectrometry (MS) technology, the speed of identification can be greatly improved. However, the increasing number of microbes sequenced is challenging correct microbial identification because of the large number of choices present. To properly disentangle candidate microbes, one needs to go beyond apparent morphology or simple `fingerprinting'; to correctly prioritize the candidate microbes, one needs to have accurate statistical significance in microbial identification. We meet these challenges by using peptidome profiles of microbes to better separate them and by designing an analysis method that yields accurate statistical significance. Here, we present an analysis pipeline that uses tandem MS (MS/MS) spectra for microbial identification or classification. We have demonstrated, using MS/MS data of 81 samples, each composed of a single known microorganism, that the proposed pipeline can correctly identify microorganisms at least at the genus and species levels. We have also shown that the proposed pipeline computes accurate statistical significances, i.e., E-values for identified peptides and unified E-values for identified microorganisms. The proposed analysis pipeline has been implemented in MiCId, a freely available software for Microorganism Classification and Identification. MiCId is available for download at http://www.ncbi.nlm.nih.gov/CBBresearch/Yu/downloads.html.

  10. New readout integrated circuit using continuous time fixed pattern noise correction

    NASA Astrophysics Data System (ADS)

    Dupont, Bertrand; Chammings, G.; Rapellin, G.; Mandier, C.; Tchagaspanian, M.; Dupont, Benoit; Peizerat, A.; Yon, J. J.

    2008-04-01

    LETI has been involved in IRFPA development since 1978; the design department (LETI/DCIS) has focused its work on new ROIC architecture since many years. The trend is to integrate advanced functions into the CMOS design to achieve cost efficient sensors production. Thermal imaging market is today more and more demanding of systems with instant ON capability and low power consumption. The purpose of this paper is to present the latest developments of fixed pattern noise continuous time correction. Several architectures are proposed, some are based on hardwired digital processing and some are purely analog. Both are using scene based algorithms. Moreover a new method is proposed for simultaneous correction of pixel offsets and sensitivities. In this scope, a new architecture of readout integrated circuit has been implemented; this architecture is developed with 0.18μm CMOS technology. The specification and the application of the ROIC are discussed in details.

  11. Correcting for sequencing error in maximum likelihood phylogeny inference.

    PubMed

    Kuhner, Mary K; McGill, James

    2014-11-04

    Accurate phylogenies are critical to taxonomy as well as studies of speciation processes and other evolutionary patterns. Accurate branch lengths in phylogenies are critical for dating and rate measurements. Such accuracy may be jeopardized by unacknowledged sequencing error. We use simulated data to test a correction for DNA sequencing error in maximum likelihood phylogeny inference. Over a wide range of data polymorphism and true error rate, we found that correcting for sequencing error improves recovery of the branch lengths, even if the assumed error rate is up to twice the true error rate. Low error rates have little effect on recovery of the topology. When error is high, correction improves topological inference; however, when error is extremely high, using an assumed error rate greater than the true error rate leads to poor recovery of both topology and branch lengths. The error correction approach tested here was proposed in 2004 but has not been widely used, perhaps because researchers do not want to commit to an estimate of the error rate. This study shows that correction with an approximate error rate is generally preferable to ignoring the issue. Copyright © 2014 Kuhner and McGill.

  12. Correction for specimen movement and rotation errors for in-vivo Optical Projection Tomography

    PubMed Central

    Birk, Udo Jochen; Rieckher, Matthias; Konstantinides, Nikos; Darrell, Alex; Sarasa-Renedo, Ana; Meyer, Heiko; Tavernarakis, Nektarios; Ripoll, Jorge

    2010-01-01

    The application of optical projection tomography to in-vivo experiments is limited by specimen movement during the acquisition. We present a set of mathematical correction methods applied to the acquired data stacks to correct for movement in both directions of the image plane. These methods have been applied to correct experimental data taken from in-vivo optical projection tomography experiments in Caenorhabditis elegans. Successful reconstructions for both fluorescence and white light (absorption) measurements are shown. Since no difference between movement of the animal and movement of the rotation axis is made, this approach at the same time removes artifacts due to mechanical drifts and errors in the assumed center of rotation. PMID:21258448

  13. Caring potentials in the shadows of power, correction, and discipline—Forensic psychiatric care in the light of the work of Michel Foucault

    PubMed Central

    Hörberg, Ulrica; Dahlberg, Karin

    2015-01-01

    The aim of this article is to shed light on contemporary forensic psychiatric care through a philosophical examination of the empirical results from two lifeworld phenomenological studies from the perspective of patients and carers, by using the French philosopher Michel Foucault's historical–philosophical work. Both empirical studies were conducted in a forensic psychiatric setting. The essential results of the two empirical studies were reexamined in a phenomenological meaning analysis to form a new general structure in accordance with the methodological principles of Reflective Lifeworld Research. This general structure shows how the caring on the forensic psychiatric wards appears to be contradictory, in that it is characterized by an unreflective (non-)caring attitude and contributes to an inconsistent and insecure existence. The caring appears to have a corrective approach and thus lacks a clear caring structure, a basic caring approach that patients in forensic psychiatric services have a great need of. To gain a greater understanding of forensic psychiatric caring, the new empirical results were further examined in the light of Foucault's historical–philosophical work. The philosophical examination is presented in terms of the three meaning constituents: Caring as correction and discipline, The existence of power, and Structures and culture in care. The philosophical examination illustrates new meaning nuances of the corrective and disciplinary nature of forensic psychiatric care, its power, and how this is materialized in caring, and what this does to the patients. The examination reveals embedded difficulties in forensic psychiatric care and highlights a need to revisit the aim of such care. PMID:26319100

  14. Caring potentials in the shadows of power, correction, and discipline - Forensic psychiatric care in the light of the work of Michel Foucault.

    PubMed

    Hörberg, Ulrica; Dahlberg, Karin

    2015-01-01

    The aim of this article is to shed light on contemporary forensic psychiatric care through a philosophical examination of the empirical results from two lifeworld phenomenological studies from the perspective of patients and carers, by using the French philosopher Michel Foucault's historical-philosophical work. Both empirical studies were conducted in a forensic psychiatric setting. The essential results of the two empirical studies were reexamined in a phenomenological meaning analysis to form a new general structure in accordance with the methodological principles of Reflective Lifeworld Research. This general structure shows how the caring on the forensic psychiatric wards appears to be contradictory, in that it is characterized by an unreflective (non-)caring attitude and contributes to an inconsistent and insecure existence. The caring appears to have a corrective approach and thus lacks a clear caring structure, a basic caring approach that patients in forensic psychiatric services have a great need of. To gain a greater understanding of forensic psychiatric caring, the new empirical results were further examined in the light of Foucault's historical-philosophical work. The philosophical examination is presented in terms of the three meaning constituents: Caring as correction and discipline, The existence of power, and Structures and culture in care. The philosophical examination illustrates new meaning nuances of the corrective and disciplinary nature of forensic psychiatric care, its power, and how this is materialized in caring, and what this does to the patients. The examination reveals embedded difficulties in forensic psychiatric care and highlights a need to revisit the aim of such care.

  15. FPGA-based real time controller for high order correction in EDIFISE

    NASA Astrophysics Data System (ADS)

    Rodríguez-Ramos, L. F.; Chulani, H.; Martín, Y.; Dorta, T.; Alonso, A.; Fuensalida, J. J.

    2012-07-01

    EDIFISE is a technology demonstrator instrument developed at the Institute of Astrophysics of the Canary Islands (IAC), intended to explore the feasibility of combining Adaptive Optics with attenuated optical fibers in order to obtain high spatial resolution spectra at the surroundings of a star, as an alternative to coronagraphy. A simplified version with only tip tilt correction has been tested at the OGS telescope in Observatorio del Teide (Canary islands, Spain) and a complete version is intended to be tested at the OGS and at the WHT telescope in Observatorio del Roque de los Muchachos, (Canary Islands, Spain). This paper describes the FPGA-based real time control of the High Order unit, responsible of the computation of the actuation values of a 97-actuactor deformable mirror (11x11) with the information provided by a configurable wavefront sensor of up to 16x16 subpupils at 500 Hz (128x128 pixels). The reconfigurable logic hardware will allow both zonal and modal control approaches, will full access to select which mode loops should be closed and with a number of utilities for influence matrix and open loop response measurements. The system has been designed in a modular way to allow for easy upgrade to faster frame rates (1500 Hz) and bigger wavefront sensors (240x240 pixels), accepting also several interfaces from the WFS and towards the mirror driver. The FPGA-based (Field Programmable Gate Array) real time controller provides bias and flat-fielding corrections, subpupil slopes to modal matrix computation for up to 97 modes, independent servo loop controllers for each mode with user control for independent loop opening or closing, mode to actuator matrix computation and non-common path aberration correction capability. It also provides full housekeeping control via UPD/IP for matrix reloading and full system data logging.

  16. A technique for phase correction in Fourier transform spectroscopy

    NASA Astrophysics Data System (ADS)

    Artsang, P.; Pongchalee, P.; Palawong, K.; Buisset, C.; Meemon, P.

    2018-03-01

    Fourier transform spectroscopy (FTS) is a type of spectroscopy that can be used to analyze components in the sample. The basic setup that is commonly used in this technique is "Michelson interferometer". The interference signal obtained from interferometer can be Fourier transformed into the spectral pattern of the illuminating light source. To experimentally study the concept of the Fourier transform spectroscopy, the project started by setup the Michelson interferometer in the laboratory. The implemented system used a broadband light source in near infrared region (0.81-0.89 μm) and controlled the movable mirror by using computer controlled motorized translation stage. In the early study, there is no sample the interference path. Therefore, the theoretical spectral results after the Fourier transformation of the captured interferogram must be the spectral shape of the light source. One main challenge of the FTS is to retrieve the correct phase information of the inferferogram that relates with the correct spectral shape of the light source. One main source of the phase distortion in FTS that we observed from our system is the non-linear movement of the movable reference mirror of the Michelson interferometer. Therefore, to improve the result, we coupled a monochromatic light source to the implemented interferometer. We simultaneously measured the interferograms of the monochromatic and broadband light sources. The interferogram of the monochromatic light source was used to correct the phase of the interferogram of the broadband light source. The result shows significant improvement in the computed spectral shape.

  17. Clinical effect of reducing curing times with high-intensity LED lights

    PubMed Central

    Ward, Justin D.; Wolf, Bethany J.; Leite, Luis P.; Zhou, Jing

    2016-01-01

    Objective To evaluate the clinical performance of brackets cured with a high-intensity, light-emitting diode (LED) with a shorter curing time. Materials and Methods Thirty-four patients and a total of 680 brackets were examined using a randomized split-mouth design. The maxillary right and mandibular left quadrants were cured for 6 seconds with a high-intensity LED light (3200 mW/cm2) and the maxillary left and mandibular right quadrants were cured for 20 seconds with a standard-intensity LED light (1200 mW/cm2). Alternating patients had the quadrants inverted for the curing protocol. The number and date of each first-time bracket failure was recorded from 199 to 585 days posttreatment. Results The bracket failure rate was 1.18% for both curing methods. The proportion of bracket failure was not significantly different between curing methods (P = 1.000), genders (P = 1.000), jaws (P = .725), sides (P = .725), or quadrants (P = .547). Posterior teeth exhibited a greater proportion of failures (2.21%) relative to anterior teeth (0.49%), although the difference was not statistically significant (P = .065). Conclusions No difference was found in bond failure rates between the two curing methods. Both methods showed bond failure rates low enough to be considered clinically sufficient. The high-intensity LED light used with a shorter curing time may be considered an advantage due to the reduced chair time. PMID:25760887

  18. 78 FR 4766 - Authority Citation Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-23

    ...-19-11] Authority Citation Correction AGENCY: Securities and Exchange Commission. ACTION: Final rule..., respectively) that each included an inaccurate amendatory instruction pertaining to an authority citation. The Commission is publishing this technical amendment to accurately reflect the authority citation in the Code of...

  19. Time-dependent scattering of incident light of various wavelengths in ferrofluids under external magnetic field

    NASA Astrophysics Data System (ADS)

    Jin, Jingyu; Song, Dongxing; Geng, Jiafeng; Jing, Dengwei

    2018-02-01

    Ferrofluids can exhibit the anisotropic thermodynamic properties under magnetic fields. The dynamic optical properties of ferrofluids in the presence of magnetic fields are of particular interest due to their potential application as various optical devices. Although time-dependent light scattering by ferrofluids have been extensively studied, the effect of wavelength of incident light have been rarely considered. Here, for the first time, we investigated both the time- and wavelength-dependent light scattering in water based ferrofluids containing Fe3O4 nanoparticles under an external magnetic field. The field-induced response behavior of the prepared ferrofluid samples was determined and verified first by thermal conductivity measurement and numerical simulation. Double-beam UV-Vis spectrophotometer was employed to record the temporal evolution of transmitted intensity of incident light of various wavelengths passing through the ferrofluid sample and propagating parallel to the applied field. As expected, the light intensity decreases to a certain value right after the field is turned on due to the thermal fluctuation induced disorder inside the flexible particle chains. Then the light intensity further decreases with time until the appearance of a minimum at time τ0 followed by an inversed increase before finally reaches equilibrium at a particular time. More importantly, the characteristic inversion time τ0 was found to follow a power law increase with the wavelength of incident light (τ0 ∼ λα, where α = 2.07). A quantitative explanation for the wavelength dependence of characteristic time was proposed based on the finite-difference time-domain (FDTD) method. The simulation results are in good agreement with our experimental observations. The time-dependent light scattering in ferrofluids under different incident wavelengths was rationalized by considering both the coarsening process of the particle chains and the occurrence of resonance within the

  20. Accurate metacognition for visual sensory memory representations.

    PubMed

    Vandenbroucke, Annelinde R E; Sligte, Ilja G; Barrett, Adam B; Seth, Anil K; Fahrenfort, Johannes J; Lamme, Victor A F

    2014-04-01

    The capacity to attend to multiple objects in the visual field is limited. However, introspectively, people feel that they see the whole visual world at once. Some scholars suggest that this introspective feeling is based on short-lived sensory memory representations, whereas others argue that the feeling of seeing more than can be attended to is illusory. Here, we investigated this phenomenon by combining objective memory performance with subjective confidence ratings during a change-detection task. This allowed us to compute a measure of metacognition--the degree of knowledge that subjects have about the correctness of their decisions--for different stages of memory. We show that subjects store more objects in sensory memory than they can attend to but, at the same time, have similar metacognition for sensory memory and working memory representations. This suggests that these subjective impressions are not an illusion but accurate reflections of the richness of visual perception.

  1. Time dependence of composite shrinkage using halogen and LED light curing.

    PubMed

    Uhl, Alexander; Mills, Robin W; Rzanny, Angelika E; Jandt, Klaus D

    2005-03-01

    The polymerization shrinkage of light cured dental composites presents the major drawback for these aesthetically adaptable restorative materials. LED based light curing technology has recently become commercially available. Therefore, the aim of the present study was to investigate if there was a statistically significant difference in linear and volumetric composite shrinkage strain if a LED LCU is used for the light curing process rather than a conventional halogen LCU. The volumetric shrinkage strain was determined using the Archimedes buoyancy principle after 5, 10, 20, 40 s of light curing and after 120 s following the 40 s light curing time period. The linear shrinkage strain was determined with a dynamic mechanical analyzer for the composites Z100, Spectrum, Solitaire2 and Definite polymerized with the LCUs Trilight (halogen), Freelight I (LED) and LED63 (LED LCU prototype). The changes in irradiance and spectra of the LCUs were measured after 0, 312 and 360 min of duty time. In general there was no considerable difference in shrinkage of the composites Z100, Spectrum or Solitaire2 when the LED63 was used instead of the Trilight. There was, however, a statistically significant difference in shrinkage strain when the composite Definite was polymerized with the LED63 instead of the Trilight. The spectrum of the Trilight changed during the experiment considerably whereas the LED63 showed an almost constant light output. The Freelight I dropped considerably in irradiance and had to be withdrawn from the study because of technical problems. The composites containing only the photoinitiator camphorquinone showed similar shrinkage strain behaviour when a LED or halogen LCU is used for the polymerization. The irradiance of some LED LCUs can also decrease over time and should therefore be checked on a regular basis.

  2. Eliminating the influence of source spectrum of white light scanning interferometry through time-delay estimation algorithm

    NASA Astrophysics Data System (ADS)

    Zhou, Yunfei; Cai, Hongzhi; Zhong, Liyun; Qiu, Xiang; Tian, Jindong; Lu, Xiaoxu

    2017-05-01

    In white light scanning interferometry (WLSI), the accuracy of profile measurement achieved with the conventional zero optical path difference (ZOPD) position locating method is closely related with the shape of interference signal envelope (ISE), which is mainly decided by the spectral distribution of illumination source. For a broadband light with Gaussian spectral distribution, the corresponding shape of ISE reveals a symmetric distribution, so the accurate ZOPD position can be achieved easily. However, if the spectral distribution of source is irregular, the shape of ISE will become asymmetric or complex multi-peak distribution, WLSI cannot work well through using ZOPD position locating method. Aiming at this problem, we propose time-delay estimation (TDE) based WLSI method, in which the surface profile information is achieved by using the relative displacement of interference signal between different pixels instead of the conventional ZOPD position locating method. Due to all spectral information of interference signal (envelope and phase) are utilized, in addition to revealing the advantage of high accuracy, the proposed method can achieve profile measurement with high accuracy in the case that the shape of ISE is irregular while ZOPD position locating method cannot work. That is to say, the proposed method can effectively eliminate the influence of source spectrum.

  3. Optimization of light source parameters in the photodynamic therapy of heterogeneous prostate

    NASA Astrophysics Data System (ADS)

    Li, Jun; Altschuler, Martin D.; Hahn, Stephen M.; Zhu, Timothy C.

    2008-08-01

    The three-dimensional (3D) heterogeneous distributions of optical properties in a patient prostate can now be measured in vivo. Such data can be used to obtain a more accurate light-fluence kernel. (For specified sources and points, the kernel gives the fluence delivered to a point by a source of unit strength.) In turn, the kernel can be used to solve the inverse problem that determines the source strengths needed to deliver a prescribed photodynamic therapy (PDT) dose (or light-fluence) distribution within the prostate (assuming uniform drug concentration). We have developed and tested computational procedures to use the new heterogeneous data to optimize delivered light-fluence. New problems arise, however, in quickly obtaining an accurate kernel following the insertion of interstitial light sources and data acquisition. (1) The light-fluence kernel must be calculated in 3D and separately for each light source, which increases kernel size. (2) An accurate kernel for light scattering in a heterogeneous medium requires ray tracing and volume partitioning, thus significant calculation time. To address these problems, two different kernels were examined and compared for speed of creation and accuracy of dose. Kernels derived more quickly involve simpler algorithms. Our goal is to achieve optimal dose planning with patient-specific heterogeneous optical data applied through accurate kernels, all within clinical times. The optimization process is restricted to accepting the given (interstitially inserted) sources, and determining the best source strengths with which to obtain a prescribed dose. The Cimmino feasibility algorithm is used for this purpose. The dose distribution and source weights obtained for each kernel are analyzed. In clinical use, optimization will also be performed prior to source insertion to obtain initial source positions, source lengths and source weights, but with the assumption of homogeneous optical properties. For this reason, we compare the

  4. Aberration corrections for free-space optical communications in atmosphere turbulence using orbital angular momentum states.

    PubMed

    Zhao, S M; Leach, J; Gong, L Y; Ding, J; Zheng, B Y

    2012-01-02

    The effect of atmosphere turbulence on light's spatial structure compromises the information capacity of photons carrying the Orbital Angular Momentum (OAM) in free-space optical (FSO) communications. In this paper, we study two aberration correction methods to mitigate this effect. The first one is the Shack-Hartmann wavefront correction method, which is based on the Zernike polynomials, and the second is a phase correction method specific to OAM states. Our numerical results show that the phase correction method for OAM states outperforms the Shark-Hartmann wavefront correction method, although both methods improve significantly purity of a single OAM state and the channel capacities of FSO communication link. At the same time, our experimental results show that the values of participation functions go down at the phase correction method for OAM states, i.e., the correction method ameliorates effectively the bad effect of atmosphere turbulence.

  5. Motion Correction in PROPELLER and Turboprop-MRI

    PubMed Central

    Tamhane, Ashish A.; Arfanakis, Konstantinos

    2009-01-01

    PROPELLER and Turboprop-MRI are characterized by greatly reduced sensitivity to motion, compared to their predecessors, fast spin-echo and gradient and spin-echo, respectively. This is due to the inherent self-navigation and motion correction of PROPELLER-based techniques. However, it is unknown how various acquisition parameters that determine k-space sampling affect the accuracy of motion correction in PROPELLER and Turboprop-MRI. The goal of this work was to evaluate the accuracy of motion correction in both techniques, to identify an optimal rotation correction approach, and determine acquisition strategies for optimal motion correction. It was demonstrated that, blades with multiple lines allow more accurate estimation of motion than blades with fewer lines. Also, it was shown that Turboprop-MRI is less sensitive to motion than PROPELLER. Furthermore, it was demonstrated that the number of blades does not significantly affect motion correction. Finally, clinically appropriate acquisition strategies that optimize motion correction were discussed for PROPELLER and Turboprop-MRI. PMID:19365858

  6. Space and time resolved representation of a vacuum arc light emission

    NASA Astrophysics Data System (ADS)

    Georgescu, N.; Sandolache, G.; Zoita, V.

    1999-04-01

    An optoelectronic multichannel detection system for the study of the visible light emission of a vacuum circuit breaker arc is described. The system consists of two multiple slit collimator assemblies coupled directly to the arc discharge chamber and an electronic detection part. The light emitted by the arc is collected by the two collimator assemblies and is transmitted through optical fibres to the electronic detection part. By using a new, simple computational method two-dimensional plots of the vacuum arc light emission at different times are obtained.

  7. Time delay in atomic photoionization with circularly polarized light

    NASA Astrophysics Data System (ADS)

    Ivanov, I. A.; Kheifets, A. S.

    2013-03-01

    We study time delay in atomic photoionization by circularly polarized light. By considering the Li atom in an excited 2p state, we demonstrate a strong time-delay asymmetry between the photoemission of the target electrons that are co- and counter-rotating with the electromagnetic field in the polarization plane. In addition, we observe the time-delay sensitivity to the polar angle of the photoelectron emission in the polarization plane. This modulation depends on the shape and duration of the electromagnetic pulse.

  8. Device accurately measures and records low gas-flow rates

    NASA Technical Reports Server (NTRS)

    Branum, L. W.

    1966-01-01

    Free-floating piston in a vertical column accurately measures and records low gas-flow rates. The system may be calibrated, using an adjustable flow-rate gas supply, a low pressure gage, and a sequence recorder. From the calibration rates, a nomograph may be made for easy reduction. Temperature correction may be added for further accuracy.

  9. Shuttle program: Computing atmospheric scale height for refraction corrections

    NASA Technical Reports Server (NTRS)

    Lear, W. M.

    1980-01-01

    Methods for computing the atmospheric scale height to determine radio wave refraction were investigated for different atmospheres, and different angles of elevation. Tables of refractivity versus altitude are included. The equations used to compute the refraction corrections are given. It is concluded that very accurate corrections are determined with the assumption of an exponential atmosphere.

  10. Generation of an incident focused light pulse in FDTD.

    PubMed

    Capoğlu, Ilker R; Taflove, Allen; Backman, Vadim

    2008-11-10

    A straightforward procedure is described for accurately creating an incident focused light pulse in the 3-D finite-difference time-domain (FDTD) electromagnetic simulation of the image space of an aplanatic converging lens. In this procedure, the focused light pulse is approximated by a finite sum of plane waves, and each plane wave is introduced into the FDTD simulation grid using the total-field/scattered-field (TF/SF) approach. The accuracy of our results is demonstrated by comparison with exact theoretical formulas.

  11. [Correct and timely referral of patients to centers of reference].

    PubMed

    Costa, Joana; Valença-Filipe, Rita; Rodrigues, Jorge

    2013-01-01

    The correct and timely referral of patients, from peripheral hospitals, without specialized surgical care, namely in hand surgery, like Plastic Surgery or Orthopedics is of crucial importance. The authors report the case of a patient that presents in the Plastic Surgery Department with a chronic infection of the hypothenar eminence of the right hand. The clinical history suggests the persistence of a foreign body, despite two previous surgical procedures for removal, performed in the residence hospital. Surgical exploration was performed and the foreign body was removed without complications. The intent of this presentation is to alert for the importance of the timely referral of patients that can benefit of specialized care, namely of plastic surgery, when this is no possible in the residence hospital, in view of better health care and better patient treatment.

  12. Determining spherical lens correction for astronaut training underwater.

    PubMed

    Porter, Jason; Gibson, C Robert; Strauss, Samuel

    2011-09-01

    To develop a model that will accurately predict the distance spherical lens correction needed to be worn by National Aeronautics and Space Administration astronauts while training underwater. The replica space suit's helmet contains curved visors that induce refractive power when submersed in water. Anterior surface powers and thicknesses were measured for the helmet's protective and inside visors. The impact of each visor on the helmet's refractive power in water was analyzed using thick lens calculations and Zemax optical design software. Using geometrical optics approximations, a model was developed to determine the optimal distance spherical power needed to be worn underwater based on the helmet's total induced spherical power underwater and the astronaut's manifest spectacle plane correction in air. The validity of the model was tested using data from both eyes of 10 astronauts who trained underwater. The helmet's visors induced a total power of -2.737 D when placed underwater. The required underwater spherical correction (FW) was linearly related to the spectacle plane spherical correction in air (FAir): FW = FAir + 2.356 D. The mean magnitude of the difference between the actual correction worn underwater and the calculated underwater correction was 0.20 ± 0.11 D. The actual and calculated values were highly correlated (r = 0.971) with 70% of eyes having a difference in magnitude of <0.25 D between values. We devised a model to calculate the spherical spectacle lens correction needed to be worn underwater by National Aeronautics and Space Administration astronauts. The model accurately predicts the actual values worn underwater and can be applied (more generally) to determine a suitable spectacle lens correction to be worn behind other types of masks when submerged underwater.

  13. Cerebellarlike corrective model inference engine for manipulation tasks.

    PubMed

    Luque, Niceto Rafael; Garrido, Jesús Alberto; Carrillo, Richard Rafael; Coenen, Olivier J-M D; Ros, Eduardo

    2011-10-01

    This paper presents how a simple cerebellumlike architecture can infer corrective models in the framework of a control task when manipulating objects that significantly affect the dynamics model of the system. The main motivation of this paper is to evaluate a simplified bio-mimetic approach in the framework of a manipulation task. More concretely, the paper focuses on how the model inference process takes place within a feedforward control loop based on the cerebellar structure and on how these internal models are built up by means of biologically plausible synaptic adaptation mechanisms. This kind of investigation may provide clues on how biology achieves accurate control of non-stiff-joint robot with low-power actuators which involve controlling systems with high inertial components. This paper studies how a basic temporal-correlation kernel including long-term depression (LTD) and a constant long-term potentiation (LTP) at parallel fiber-Purkinje cell synapses can effectively infer corrective models. We evaluate how this spike-timing-dependent plasticity correlates sensorimotor activity arriving through the parallel fibers with teaching signals (dependent on error estimates) arriving through the climbing fibers from the inferior olive. This paper addresses the study of how these LTD and LTP components need to be well balanced with each other to achieve accurate learning. This is of interest to evaluate the relevant role of homeostatic mechanisms in biological systems where adaptation occurs in a distributed manner. Furthermore, we illustrate how the temporal-correlation kernel can also work in the presence of transmission delays in sensorimotor pathways. We use a cerebellumlike spiking neural network which stores the corrective models as well-structured weight patterns distributed among the parallel fibers to Purkinje cell connections.

  14. Automated Diatom Analysis Applied to Traditional Light Microscopy: A Proof-of-Concept Study

    NASA Astrophysics Data System (ADS)

    Little, Z. H. L.; Bishop, I.; Spaulding, S. A.; Nelson, H.; Mahoney, C.

    2017-12-01

    Diatom identification and enumeration by high resolution light microscopy is required for many areas of research and water quality assessment. Such analyses, however, are both expertise and labor-intensive. These challenges motivate the need for an automated process to efficiently and accurately identify and enumerate diatoms. Improvements in particle analysis software have increased the likelihood that diatom enumeration can be automated. VisualSpreadsheet software provides a possible solution for automated particle analysis of high-resolution light microscope diatom images. We applied the software, independent of its complementary FlowCam hardware, to automated analysis of light microscope images containing diatoms. Through numerous trials, we arrived at threshold settings to correctly segment 67% of the total possible diatom valves and fragments from broad fields of view. (183 light microscope images were examined containing 255 diatom particles. Of the 255 diatom particles present, 216 diatoms valves and fragments of valves were processed, with 170 properly analyzed and focused upon by the software). Manual analysis of the images yielded 255 particles in 400 seconds, whereas the software yielded a total of 216 particles in 68 seconds, thus highlighting that the software has an approximate five-fold efficiency advantage in particle analysis time. As in past efforts, incomplete or incorrect recognition was found for images with multiple valves in contact or valves with little contrast. The software has potential to be an effective tool in assisting taxonomists with diatom enumeration by completing a large portion of analyses. Benefits and limitations of the approach are presented to allow for development of future work in image analysis and automated enumeration of traditional light microscope images containing diatoms.

  15. Vision 20/20: Magnetic resonance imaging-guided attenuation correction in PET/MRI: Challenges, solutions, and opportunities

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mehranian, Abolfazl; Arabi, Hossein; Zaidi, Habib, E-mail: habib.zaidi@hcuge.ch

    Attenuation correction is an essential component of the long chain of data correction techniques required to achieve the full potential of quantitative positron emission tomography (PET) imaging. The development of combined PET/magnetic resonance imaging (MRI) systems mandated the widespread interest in developing novel strategies for deriving accurate attenuation maps with the aim to improve the quantitative accuracy of these emerging hybrid imaging systems. The attenuation map in PET/MRI should ideally be derived from anatomical MR images; however, MRI intensities reflect proton density and relaxation time properties of biological tissues rather than their electron density and photon attenuation properties. Therefore, inmore » contrast to PET/computed tomography, there is a lack of standardized global mapping between the intensities of MRI signal and linear attenuation coefficients at 511 keV. Moreover, in standard MRI sequences, bones and lung tissues do not produce measurable signals owing to their low proton density and short transverse relaxation times. MR images are also inevitably subject to artifacts that degrade their quality, thus compromising their applicability for the task of attenuation correction in PET/MRI. MRI-guided attenuation correction strategies can be classified in three broad categories: (i) segmentation-based approaches, (ii) atlas-registration and machine learning methods, and (iii) emission/transmission-based approaches. This paper summarizes past and current state-of-the-art developments and latest advances in PET/MRI attenuation correction. The advantages and drawbacks of each approach for addressing the challenges of MR-based attenuation correction are comprehensively described. The opportunities brought by both MRI and PET imaging modalities for deriving accurate attenuation maps and improving PET quantification will be elaborated. Future prospects and potential clinical applications of these techniques and their integration in

  16. Vision 20/20: Magnetic resonance imaging-guided attenuation correction in PET/MRI: Challenges, solutions, and opportunities.

    PubMed

    Mehranian, Abolfazl; Arabi, Hossein; Zaidi, Habib

    2016-03-01

    Attenuation correction is an essential component of the long chain of data correction techniques required to achieve the full potential of quantitative positron emission tomography (PET) imaging. The development of combined PET/magnetic resonance imaging (MRI) systems mandated the widespread interest in developing novel strategies for deriving accurate attenuation maps with the aim to improve the quantitative accuracy of these emerging hybrid imaging systems. The attenuation map in PET/MRI should ideally be derived from anatomical MR images; however, MRI intensities reflect proton density and relaxation time properties of biological tissues rather than their electron density and photon attenuation properties. Therefore, in contrast to PET/computed tomography, there is a lack of standardized global mapping between the intensities of MRI signal and linear attenuation coefficients at 511 keV. Moreover, in standard MRI sequences, bones and lung tissues do not produce measurable signals owing to their low proton density and short transverse relaxation times. MR images are also inevitably subject to artifacts that degrade their quality, thus compromising their applicability for the task of attenuation correction in PET/MRI. MRI-guided attenuation correction strategies can be classified in three broad categories: (i) segmentation-based approaches, (ii) atlas-registration and machine learning methods, and (iii) emission/transmission-based approaches. This paper summarizes past and current state-of-the-art developments and latest advances in PET/MRI attenuation correction. The advantages and drawbacks of each approach for addressing the challenges of MR-based attenuation correction are comprehensively described. The opportunities brought by both MRI and PET imaging modalities for deriving accurate attenuation maps and improving PET quantification will be elaborated. Future prospects and potential clinical applications of these techniques and their integration in commercial

  17. FMLRC: Hybrid long read error correction using an FM-index.

    PubMed

    Wang, Jeremy R; Holt, James; McMillan, Leonard; Jones, Corbin D

    2018-02-09

    Long read sequencing is changing the landscape of genomic research, especially de novo assembly. Despite the high error rate inherent to long read technologies, increased read lengths dramatically improve the continuity and accuracy of genome assemblies. However, the cost and throughput of these technologies limits their application to complex genomes. One solution is to decrease the cost and time to assemble novel genomes by leveraging "hybrid" assemblies that use long reads for scaffolding and short reads for accuracy. We describe a novel method leveraging a multi-string Burrows-Wheeler Transform with auxiliary FM-index to correct errors in long read sequences using a set of complementary short reads. We demonstrate that our method efficiently produces significantly more high quality corrected sequence than existing hybrid error-correction methods. We also show that our method produces more contiguous assemblies, in many cases, than existing state-of-the-art hybrid and long-read only de novo assembly methods. Our method accurately corrects long read sequence data using complementary short reads. We demonstrate higher total throughput of corrected long reads and a corresponding increase in contiguity of the resulting de novo assemblies. Improved throughput and computational efficiency than existing methods will help better economically utilize emerging long read sequencing technologies.

  18. Augmented reality with image registration, vision correction and sunlight readability via liquid crystal devices.

    PubMed

    Wang, Yu-Jen; Chen, Po-Ju; Liang, Xiao; Lin, Yi-Hsin

    2017-03-27

    Augmented reality (AR), which use computer-aided projected information to augment our sense, has important impact on human life, especially for the elder people. However, there are three major challenges regarding the optical system in the AR system, which are registration, vision correction, and readability under strong ambient light. Here, we solve three challenges simultaneously for the first time using two liquid crystal (LC) lenses and polarizer-free attenuator integrated in optical-see-through AR system. One of the LC lens is used to electrically adjust the position of the projected virtual image which is so-called registration. The other LC lens with larger aperture and polarization independent characteristic is in charge of vision correction, such as myopia and presbyopia. The linearity of lens powers of two LC lenses is also discussed. The readability of virtual images under strong ambient light is solved by electrically switchable transmittance of the LC attenuator originating from light scattering and light absorption. The concept demonstrated in this paper could be further extended to other electro-optical devices as long as the devices exhibit the capability of phase modulations and amplitude modulations.

  19. 3D reconstruction based on light field images

    NASA Astrophysics Data System (ADS)

    Zhu, Dong; Wu, Chunhong; Liu, Yunluo; Fu, Dongmei

    2018-04-01

    This paper proposed a method of reconstructing three-dimensional (3D) scene from two light field images capture by Lytro illium. The work was carried out by first extracting the sub-aperture images from light field images and using the scale-invariant feature transform (SIFT) for feature registration on the selected sub-aperture images. Structure from motion (SFM) algorithm is further used on the registration completed sub-aperture images to reconstruct the three-dimensional scene. 3D sparse point cloud was obtained in the end. The method shows that the 3D reconstruction can be implemented by only two light field camera captures, rather than at least a dozen times captures by traditional cameras. This can effectively solve the time-consuming, laborious issues for 3D reconstruction based on traditional digital cameras, to achieve a more rapid, convenient and accurate reconstruction.

  20. Comparison and Analysis of Geometric Correction Models of Spaceborne SAR

    PubMed Central

    Jiang, Weihao; Yu, Anxi; Dong, Zhen; Wang, Qingsong

    2016-01-01

    Following the development of synthetic aperture radar (SAR), SAR images have become increasingly common. Many researchers have conducted large studies on geolocation models, but little work has been conducted on the available models for the geometric correction of SAR images of different terrain. To address the terrain issue, four different models were compared and are described in this paper: a rigorous range-doppler (RD) model, a rational polynomial coefficients (RPC) model, a revised polynomial (PM) model and an elevation derivation (EDM) model. The results of comparisons of the geolocation capabilities of the models show that a proper model for a SAR image of a specific terrain can be determined. A solution table was obtained to recommend a suitable model for users. Three TerraSAR-X images, two ALOS-PALSAR images and one Envisat-ASAR image were used for the experiment, including flat terrain and mountain terrain SAR images as well as two large area images. Geolocation accuracies of the models for different terrain SAR images were computed and analyzed. The comparisons of the models show that the RD model was accurate but was the least efficient; therefore, it is not the ideal model for real-time implementations. The RPC model is sufficiently accurate and efficient for the geometric correction of SAR images of flat terrain, whose precision is below 0.001 pixels. The EDM model is suitable for the geolocation of SAR images of mountainous terrain, and its precision can reach 0.007 pixels. Although the PM model does not produce results as precise as the other models, its efficiency is excellent and its potential should not be underestimated. With respect to the geometric correction of SAR images over large areas, the EDM model has higher accuracy under one pixel, whereas the RPC model consumes one third of the time of the EDM model. PMID:27347973

  1. Identifying and Correcting Timing Errors at Seismic Stations in and around Iran

    DOE PAGES

    Syracuse, Ellen Marie; Phillips, William Scott; Maceira, Monica; ...

    2017-09-06

    A fundamental component of seismic research is the use of phase arrival times, which are central to event location, Earth model development, and phase identification, as well as derived products. Hence, the accuracy of arrival times is crucial. However, errors in the timing of seismic waveforms and the arrival times based on them may go unidentified by the end user, particularly when seismic data are shared between different organizations. Here, we present a method used to analyze travel-time residuals for stations in and around Iran to identify time periods that are likely to contain station timing problems. For the 14more » stations with the strongest evidence of timing errors lasting one month or longer, timing corrections are proposed to address the problematic time periods. Finally, two additional stations are identified with incorrect locations in the International Registry of Seismograph Stations, and one is found to have erroneously reported arrival times in 2011.« less

  2. Development of a visible-light-sensitized europium complex for time-resolved fluorometric application.

    PubMed

    Jiang, Lina; Wu, Jing; Wang, Guilan; Ye, Zhiqiang; Zhang, Wenzhu; Jin, Dayong; Yuan, Jingli; Piper, James

    2010-03-15

    The time-resolved luminescence bioassay technique using luminescent lanthanide complexes as labels is a highly sensitive and widely used bioassay method for clinical diagnostics and biotechnology. A major drawback of the current technique is that the luminescent lanthanide labels require UV excitation (typically less than 360 nm), which can damage living biological systems and is holding back further development of time-resolved luminescence instruments. Herein we describe two approaches for preparing a visible-light-sensitized Eu(3+) complex in aqueous media for time-resolved fluorometric applications: a dissociation enhancement aqueous solution that can be excited by visible light for ethylenediaminetetraacetate (EDTA)-Eu(3+) detection and a visible-light-sensitized water-soluble Eu(3+) complex conjugated bovine serum albumin (BSA) for biolabeling and time-resolved luminescence bioimaging. In the first approach, a weakly acidic aqueous solution consisting of 4,4'-bis(1'',1'',1'',2'',2'',3'',3''-heptafluoro-4'',6''-hexanedion-6''-yl)-o-terphenyl (BHHT), 2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine (DPBT), and Triton X-100 was prepared. This solution shows a strong luminescence enhancement effect for EDTA-Eu(3+) with a wide excitation wavelength range from UV to visible light (a maximum at 387 nm) and a long luminescence lifetime (520 micros), to provide a novel dissociation enhancement solution for time-resolved luminescence detection of EDTA-Eu(3+). In the second approach, a ternary Eu(3+) complex, 4,4'-bis(1'',1'',1'',2'',2'',3'',3''-heptafluoro-4'',6''-hexanedion-6''-yl)-chlorosulfo-o-terphenyl (BHHCT)-Eu(3+)-DPBT, was covalently bound to BSA to form a water-soluble BSA-BHHCT-Eu(3+)-DPBT conjugate. This biocompatible conjugate is of the visible-light excitable feature in aqueous media with a wide excitation wavelength range from UV to visible light (a maximum at 387 nm), a long luminescence lifetime (460 micros), and a higher

  3. Light collection optics for measuring flux and spectrum from light-emitting devices

    DOEpatents

    McCord, Mark A.; DiRegolo, Joseph A.; Gluszczak, Michael R.

    2016-05-24

    Systems and methods for accurately measuring the luminous flux and color (spectra) from light-emitting devices are disclosed. An integrating sphere may be utilized to directly receive a first portion of light emitted by a light-emitting device through an opening defined on the integrating sphere. A light collector may be utilized to collect a second portion of light emitted by the light-emitting device and direct the second portion of light into the integrating sphere through the opening defined on the integrating sphere. A spectrometer may be utilized to measure at least one property of the first portion and the second portion of light received by the integrating sphere.

  4. Radiative nonrecoil nuclear finite size corrections of order α(Zα)5 to the Lamb shift in light muonic atoms

    NASA Astrophysics Data System (ADS)

    Faustov, R. N.; Martynenko, A. P.; Martynenko, F. A.; Sorokin, V. V.

    2017-12-01

    On the basis of quasipotential method in quantum electrodynamics we calculate nuclear finite size radiative corrections of order α(Zα) 5 to the Lamb shift in muonic hydrogen and helium. To construct the interaction potential of particles, which gives the necessary contributions to the energy spectrum, we use the method of projection operators to states with a definite spin. Separate analytic expressions for the contributions of the muon self-energy, the muon vertex operator and the amplitude with spanning photon are obtained. We present also numerical results for these contributions using modern experimental data on the electromagnetic form factors of light nuclei.

  5. Bunch mode specific rate corrections for PILATUS3 detectors

    DOE PAGES

    Trueb, P.; Dejoie, C.; Kobas, M.; ...

    2015-04-09

    PILATUS X-ray detectors are in operation at many synchrotron beamlines around the world. This article reports on the characterization of the new PILATUS3 detector generation at high count rates. As for all counting detectors, the measured intensities have to be corrected for the dead-time of the counting mechanism at high photon fluxes. The large number of different bunch modes at these synchrotrons as well as the wide range of detector settings presents a challenge for providing accurate corrections. To avoid the intricate measurement of the count rate behaviour for every bunch mode, a Monte Carlo simulation of the counting mechanismmore » has been implemented, which is able to predict the corrections for arbitrary bunch modes and a wide range of detector settings. This article compares the simulated results with experimental data acquired at different synchrotrons. It is found that the usage of bunch mode specific corrections based on this simulation improves the accuracy of the measured intensities by up to 40% for high photon rates and highly structured bunch modes. For less structured bunch modes, the instant retrigger technology of PILATUS3 detectors substantially reduces the dependency of the rate correction on the bunch mode. The acquired data also demonstrate that the instant retrigger technology allows for data acquisition up to 15 million photons per second per pixel.« less

  6. A manual for addressing ineffectiveness within a Corrective Action System and driving on-time dispositions

    NASA Astrophysics Data System (ADS)

    Mallari, Lawrence Anthony Castro

    This project proposes a manual specifically for remedying an ineffective Corrective Action Request System for Company ABC by providing dispositions within the company's quality procedure. A Corrective Action Request System is a corrective action tool that provides a means for employees to engage in the process improvement, problem elimination cycle. At Company ABC, Corrective Action Recommendations (CARs) are not provided with timely dispositions; CARs are being ignored due to a lack of training and awareness of Company ABC's personnel and quality procedures. In this project, Company ABC's quality management software database is scrutinized to identify the number of delinquent, non-dispositioned CARs in 2014. These CARs are correlated with the number of nonconformances generated for the same issue while the CAR is still open. Using secondary data, the primary investigator finds that nonconformances are being remediated at the operational level. However, at the administrative level, CARS are being ignored and forgotten.

  7. Detection and differentiation of Mycobacterium tuberculosis and nontuberculous mycobacterial isolates by real-time PCR.

    PubMed

    Shrestha, Nabin K; Tuohy, Marion J; Hall, Gerri S; Reischl, Udo; Gordon, Steven M; Procop, Gary W

    2003-11-01

    Mycobacteria cause a variety of illnesses that differ in severity and public health implications. The differentiation of Mycobacterium tuberculosis from nontuberculous mycobacteria (NTM) is of primary importance for infection control and choice of antimicrobial therapy. Despite advances in molecular diagnostics, the ability to rapidly diagnose M. tuberculosis infections by PCR is still inadequate, largely because of the possibility of false-negative reactions. We designed and validated a real-time PCR for mycobacteria by using the LightCycler system with 18 reference strains and 168 clinical mycobacterial isolates. All clinically significant mycobacteria were detected; the mean melting temperatures (with 99.9% confidence intervals [99.9% CI] in parentheses) for the different mycobacteria were as follows: M. tuberculosis, 64.35 degrees C (63.27 to 65.42 degrees C); M. kansasii, 59.20 degrees C (58.07 to 60.33 degrees C); M. avium, 57.82 degrees C (57.05 to 58.60 degrees C); M. intracellulare, 54.46 degrees C (53.69 to 55.23 degrees C); M. marinum, 58.91 degrees C (58.28 to 59.55 degrees C); rapidly growing mycobacteria, 53.09 degrees C (50.97 to 55.20 degrees C) or 43.19 degrees C (42.19 to 44.49 degrees C). This real-time PCR assay with melting curve analysis consistently accurately detected and differentiated M. tuberculosis from NTM. Detection of an NTM helps ensure that the negative result for M. tuberculosis is a true negative. The specific melting temperature also provides a suggestion of the identity of the NTM present, when the most commonly encountered mycobacterial species are considered. In a parallel comparison, both the LightCycler assay and the COBAS Amplicor M. tuberculosis assay correctly categorized 48 of 50 specimens that were proven by culture to contain M. tuberculosis, and the LightCycler assay correctly characterized 3 of 3 specimens that contained NTM.

  8. Detection and Differentiation of Mycobacterium tuberculosis and Nontuberculous Mycobacterial Isolates by Real-Time PCR

    PubMed Central

    Shrestha, Nabin K.; Tuohy, Marion J.; Hall, Gerri S.; Reischl, Udo; Gordon, Steven M.; Procop, Gary W.

    2003-01-01

    Mycobacteria cause a variety of illnesses that differ in severity and public health implications. The differentiation of Mycobacterium tuberculosis from nontuberculous mycobacteria (NTM) is of primary importance for infection control and choice of antimicrobial therapy. Despite advances in molecular diagnostics, the ability to rapidly diagnose M. tuberculosis infections by PCR is still inadequate, largely because of the possibility of false-negative reactions. We designed and validated a real-time PCR for mycobacteria by using the LightCycler system with 18 reference strains and 168 clinical mycobacterial isolates. All clinically significant mycobacteria were detected; the mean melting temperatures (with 99.9% confidence intervals [99.9% CI] in parentheses) for the different mycobacteria were as follows: M. tuberculosis, 64.35°C (63.27 to 65.42°C); M. kansasii, 59.20°C (58.07 to 60.33°C); M. avium, 57.82°C (57.05 to 58.60°C); M. intracellulare, 54.46°C (53.69 to 55.23°C); M. marinum, 58.91°C (58.28 to 59.55°C); rapidly growing mycobacteria, 53.09°C (50.97 to 55.20°C) or 43.19°C (42.19 to 44.49°C). This real-time PCR assay with melting curve analysis consistently accurately detected and differentiated M. tuberculosis from NTM. Detection of an NTM helps ensure that the negative result for M. tuberculosis is a true negative. The specific melting temperature also provides a suggestion of the identity of the NTM present, when the most commonly encountered mycobacterial species are considered. In a parallel comparison, both the LightCycler assay and the COBAS Amplicor M. tuberculosis assay correctly categorized 48 of 50 specimens that were proven by culture to contain M. tuberculosis, and the LightCycler assay correctly characterized 3 of 3 specimens that contained NTM. PMID:14605148

  9. An accurate surface topography restoration algorithm for white light interferometry

    NASA Astrophysics Data System (ADS)

    Yuan, He; Zhang, Xiangchao; Xu, Min

    2017-10-01

    As an important measuring technique, white light interferometry can realize fast and non-contact measurement, thus it is now widely used in the field of ultra-precision engineering. However, the traditional recovery algorithms of surface topographies have flaws and limits. In this paper, we propose a new algorithm to solve these problems. It is a combination of Fourier transform and improved polynomial fitting method. Because the white light interference signal is usually expressed as a cosine signal whose amplitude is modulated by a Gaussian function, its fringe visibility is not constant and varies with different scanning positions. The interference signal is processed first by Fourier transform, then the positive frequency part is selected and moved back to the center of the amplitude-frequency curve. In order to restore the surface morphology, a polynomial fitting method is used to fit the amplitude curve after inverse Fourier transform and obtain the corresponding topography information. The new method is then compared to the traditional algorithms. It is proved that the aforementioned drawbacks can be effectively overcome. The relative error is less than 0.8%.

  10. The Utility of Maze Accurate Response Rate in Assessing Reading Comprehension in Upper Elementary and Middle School Students

    ERIC Educational Resources Information Center

    McCane-Bowling, Sara J.; Strait, Andrea D.; Guess, Pamela E.; Wiedo, Jennifer R.; Muncie, Eric

    2014-01-01

    This study examined the predictive utility of five formative reading measures: words correct per minute, number of comprehension questions correct, reading comprehension rate, number of maze correct responses, and maze accurate response rate (MARR). Broad Reading cluster scores obtained via the Woodcock-Johnson III (WJ III) Tests of Achievement…

  11. Higher-order accurate space-time schemes for computational astrophysics—Part I: finite volume methods

    NASA Astrophysics Data System (ADS)

    Balsara, Dinshaw S.

    2017-12-01

    As computational astrophysics comes under pressure to become a precision science, there is an increasing need to move to high accuracy schemes for computational astrophysics. The algorithmic needs of computational astrophysics are indeed very special. The methods need to be robust and preserve the positivity of density and pressure. Relativistic flows should remain sub-luminal. These requirements place additional pressures on a computational astrophysics code, which are usually not felt by a traditional fluid dynamics code. Hence the need for a specialized review. The focus here is on weighted essentially non-oscillatory (WENO) schemes, discontinuous Galerkin (DG) schemes and PNPM schemes. WENO schemes are higher order extensions of traditional second order finite volume schemes. At third order, they are most similar to piecewise parabolic method schemes, which are also included. DG schemes evolve all the moments of the solution, with the result that they are more accurate than WENO schemes. PNPM schemes occupy a compromise position between WENO and DG schemes. They evolve an Nth order spatial polynomial, while reconstructing higher order terms up to Mth order. As a result, the timestep can be larger. Time-dependent astrophysical codes need to be accurate in space and time with the result that the spatial and temporal accuracies must be matched. This is realized with the help of strong stability preserving Runge-Kutta schemes and ADER (Arbitrary DERivative in space and time) schemes, both of which are also described. The emphasis of this review is on computer-implementable ideas, not necessarily on the underlying theory.

  12. Topographic Correction Module at Storm (TC@Storm)

    NASA Astrophysics Data System (ADS)

    Zaksek, K.; Cotar, K.; Veljanovski, T.; Pehani, P.; Ostir, K.

    2015-04-01

    Different solar position in combination with terrain slope and aspect result in different illumination of inclined surfaces. Therefore, the retrieved satellite data cannot be accurately transformed to the spectral reflectance, which depends only on the land cover. The topographic correction should remove this effect and enable further automatic processing of higher level products. The topographic correction TC@STORM was developed as a module within the SPACE-SI automatic near-real-time image processing chain STORM. It combines physical approach with the standard Minnaert method. The total irradiance is modelled as a three-component irradiance: direct (dependent on incidence angle, sun zenith angle and slope), diffuse from the sky (dependent mainly on sky-view factor), and diffuse reflected from the terrain (dependent on sky-view factor and albedo). For computation of diffuse irradiation from the sky we assume an anisotropic brightness of the sky. We iteratively estimate a linear combination from 10 different models, to provide the best results. Dependent on the data resolution, we mask shades based on radiometric (image) or geometric properties. The method was tested on RapidEye, Landsat 8, and PROBA-V data. Final results of the correction were evaluated and statistically validated based on various topography settings and land cover classes. Images show great improvements in shaded areas.

  13. Real-Time Parameter Estimation Using Output Error

    NASA Technical Reports Server (NTRS)

    Grauer, Jared A.

    2014-01-01

    Output-error parameter estimation, normally a post- ight batch technique, was applied to real-time dynamic modeling problems. Variations on the traditional algorithm were investigated with the goal of making the method suitable for operation in real time. Im- plementation recommendations are given that are dependent on the modeling problem of interest. Application to ight test data showed that accurate parameter estimates and un- certainties for the short-period dynamics model were available every 2 s using time domain data, or every 3 s using frequency domain data. The data compatibility problem was also solved in real time, providing corrected sensor measurements every 4 s. If uncertainty corrections for colored residuals are omitted, this rate can be increased to every 0.5 s.

  14. Highly accurate surface maps from profilometer measurements

    NASA Astrophysics Data System (ADS)

    Medicus, Kate M.; Nelson, Jessica D.; Mandina, Mike P.

    2013-04-01

    Many aspheres and free-form optical surfaces are measured using a single line trace profilometer which is limiting because accurate 3D corrections are not possible with the single trace. We show a method to produce an accurate fully 2.5D surface height map when measuring a surface with a profilometer using only 6 traces and without expensive hardware. The 6 traces are taken at varying angular positions of the lens, rotating the part between each trace. The output height map contains low form error only, the first 36 Zernikes. The accuracy of the height map is ±10% of the actual Zernike values and within ±3% of the actual peak to valley number. The calculated Zernike values are affected by errors in the angular positioning, by the centering of the lens, and to a small effect, choices made in the processing algorithm. We have found that the angular positioning of the part should be better than 1?, which is achievable with typical hardware. The centering of the lens is essential to achieving accurate measurements. The part must be centered to within 0.5% of the diameter to achieve accurate results. This value is achievable with care, with an indicator, but the part must be edged to a clean diameter.

  15. Geant4 Modifications for Accurate Fission Simulations

    NASA Astrophysics Data System (ADS)

    Tan, Jiawei; Bendahan, Joseph

    Monte Carlo is one of the methods to simulate the generation and transport of radiation through matter. The most widely used radiation simulation codes are MCNP and Geant4. The simulation of fission production and transport by MCNP has been thoroughly benchmarked. There is an increasing number of users that prefer using Geant4 due to the flexibility of adding features. However, it has been found that Geant4 does not have the proper fission-production cross sections and does not produce the correct fission products. To achieve accurate results for studies in fissionable material applications, Geant4 was modified to correct these inaccuracies and to add new capabilities. The fission model developed by the Lawrence Livermore National Laboratory was integrated into the neutron-fission modeling package. The photofission simulation capability was enabled using the same neutron-fission library under the assumption that nuclei fission in the same way, independent of the excitation source. The modified fission code provides the correct multiplicity of prompt neutrons and gamma rays, and produces delayed gamma rays and neutrons with time and energy dependencies that are consistent with ENDF/B-VII. The delayed neutrons are now directly produced by a custom package that bypasses the fragment cascade model. The modifications were made for U-235, U-238 and Pu-239 isotopes; however, the new framework allows adding new isotopes easily. The SLAC nuclear data library is used for simulation of isotopes with an atomic number above 92 because it is not available in Geant4. Results of the modified Geant4.10.1 package of neutron-fission and photofission for prompt and delayed radiation are compared with ENDFB-VII and with results produced with the original package.

  16. Cartesian Off-Body Grid Adaption for Viscous Time- Accurate Flow Simulation

    NASA Technical Reports Server (NTRS)

    Buning, Pieter G.; Pulliam, Thomas H.

    2011-01-01

    An improved solution adaption capability has been implemented in the OVERFLOW overset grid CFD code. Building on the Cartesian off-body approach inherent in OVERFLOW and the original adaptive refinement method developed by Meakin, the new scheme provides for automated creation of multiple levels of finer Cartesian grids. Refinement can be based on the undivided second-difference of the flow solution variables, or on a specific flow quantity such as vorticity. Coupled with load-balancing and an inmemory solution interpolation procedure, the adaption process provides very good performance for time-accurate simulations on parallel compute platforms. A method of using refined, thin body-fitted grids combined with adaption in the off-body grids is presented, which maximizes the part of the domain subject to adaption. Two- and three-dimensional examples are used to illustrate the effectiveness and performance of the adaption scheme.

  17. FPGA-Based Pulse Pile-Up Correction With Energy and Timing Recovery.

    PubMed

    Haselman, M D; Pasko, J; Hauck, S; Lewellen, T K; Miyaoka, R S

    2012-10-01

    Modern field programmable gate arrays (FPGAs) are capable of performing complex discrete signal processing algorithms with clock rates well above 100 MHz. This, combined with FPGA's low expense, ease of use, and selected dedicated hardware make them an ideal technology for a data acquisition system for a positron emission tomography (PET) scanner. The University of Washington is producing a high-resolution, small-animal PET scanner that utilizes FPGAs as the core of the front-end electronics. For this scanner, functions that are typically performed in dedicated circuits, or offline, are being migrated to the FPGA. This will not only simplify the electronics, but the features of modern FPGAs can be utilized to add significant signal processing power to produce higher quality images. In this paper we report on an all-digital pulse pile-up correction algorithm that has been developed for the FPGA. The pile-up mitigation algorithm will allow the scanner to run at higher count rates without incurring large data losses due to the overlapping of scintillation signals. This correction technique utilizes a reference pulse to extract timing and energy information for most pile-up events. Using pulses acquired from a Zecotech Photonics MAPD-N with an LFS-3 scintillator, we show that good timing and energy information can be achieved in the presence of pile-up utilizing a moderate amount of FPGA resources.

  18. Mass spectrometry in Earth sciences: the precise and accurate measurement of time.

    PubMed

    Schaltegger, Urs; Wotzlaw, Jörn-Frederik; Ovtcharova, Maria; Chiaradia, Massimo; Spikings, Richard

    2014-01-01

    Precise determinations of the isotopic compositions of a variety of elements is a widely applied tool in Earth sciences. Isotope ratios are used to quantify rates of geological processes that occurred during the previous 4.5 billion years, and also at the present time. An outstanding application is geochronology, which utilizes the production of radiogenic daughter isotopes by the radioactive decay of parent isotopes. Geochronological tools, involving isotopic analysis of selected elements from smallest volumes of minerals by thermal ionization mass spectrometry, provide precise and accurate measurements of time throughout the geological history of our planet over nine orders of magnitude, from the accretion of the proto-planetary disk, to the timing of the last glaciation. This article summarizes the recent efforts of the Isotope Geochemistry, Geochronology and Thermochronology research group at the University of Geneva to advance the U-Pb geochronological tool to achieve unprecedented precision and accuracy, and presents two examples of its application to two significant open questions in Earth sciences: what are the triggers and timescales of volcanic supereruptions, and what were the causes of mass extinctions in the geological past, driven by global climatic and environmental deterioration?

  19. Time-Accurate Simulations and Acoustic Analysis of Slat Free-Shear-Layer. Part 2

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Singer, Bart A.; Lockard, David P.

    2002-01-01

    Unsteady computational simulations of a multi-element, high-lift configuration are performed. Emphasis is placed on accurate spatiotemporal resolution of the free shear layer in the slat-cove region. The excessive dissipative effects of the turbulence model, so prevalent in previous simulations, are circumvented by switching off the turbulence-production term in the slat cove region. The justifications and physical arguments for taking such a step are explained in detail. The removal of this excess damping allows the shear layer to amplify large-scale structures, to achieve a proper non-linear saturation state, and to permit vortex merging. The large-scale disturbances are self-excited, and unlike our prior fully turbulent simulations, no external forcing of the shear layer is required. To obtain the farfield acoustics, the Ffowcs Williams and Hawkings equation is evaluated numerically using the simulated time-accurate flow data. The present comparison between the computed and measured farfield acoustic spectra shows much better agreement for the amplitude and frequency content than past calculations. The effect of the angle-of-attack on the slat's flow features radiated acoustic field are also simulated presented.

  20. Generation of an incident focused light pulse in FDTD

    PubMed Central

    Çapoğlu, İlker R.; Taflove, Allen; Backman, Vadim

    2009-01-01

    A straightforward procedure is described for accurately creating an incident focused light pulse in the 3-D finite-difference time-domain (FDTD) electromagnetic simulation of the image space of an aplanatic converging lens. In this procedure, the focused light pulse is approximated by a finite sum of plane waves, and each plane wave is introduced into the FDTD simulation grid using the total-field/scattered-field (TF/SF) approach. The accuracy of our results is demonstrated by comparison with exact theoretical formulas. PMID:19582013

  1. Associations of Maternal Light/Moderate Leisure-Time Walking and Yoga With Offspring Birth Size.

    PubMed

    Badon, Sylvia E; Littman, Alyson J; Chan, K C Gary; Williams, Michelle A; Enquobahrie, Daniel A

    2018-06-01

    Although perinatal walking and yoga have been associated with decreased risks of pregnancy complications, associations with offspring birth size have been inconsistent. We investigated associations of prepregnancy and early pregnancy leisure-time light/moderate walking and yoga practice with birth size. Study participants (N = 3687) reported leisure-time physical activity duration (hours per week) in the year before pregnancy and early pregnancy. Birth size was abstracted from medical records. Regression was used to determine mean differences in birth weight, head circumference, and ponderal index. Interaction terms were used to assess effect modification by offspring sex. About one-third of women reported light/moderate leisure-time walking and about 10% reported yoga practice. Women in the highest tertile for prepregnancy (mean: 2.9 h/wk; range: 1.4-20 h/wk) or early pregnancy (mean: 5.9 h/wk; range: 3.1-24 h/wk) light/moderate walking had offspring with 0.9 and 1.5 kg/m 3 greater ponderal index (95% confidence interval, 0.3 to 1.4 and 0.7 to 2.4, respectively) compared with women who reported no light/moderate walking in the same time period. Light/moderate walking was not associated with birth weight or head circumference. Yoga practice was not associated with birth size. Associations were similar by offspring sex. Light/moderate leisure-time walking may be associated with greater offspring ponderal index.

  2. An investigation of light transport through scattering bodies with non-scattering regions.

    PubMed

    Firbank, M; Arridge, S R; Schweiger, M; Delpy, D T

    1996-04-01

    Near-infra-red (NIR) spectroscopy is increasingly being used for monitoring cerebral oxygenation and haemodynamics. One current concern is the effect of the clear cerebrospinal fluid upon the distribution of light in the head. There are difficulties in modelling clear layers in scattering systems. The Monte Carlo model should handle clear regions accurately, but is too slow to be used for realistic geometries. The diffusion equation can be solved quickly for realistic geometries, but is only valid in scattering regions. In this paper we describe experiments carried out on a solid slab phantom to investigate the effect of clear regions. The experimental results were compared with the different models of light propagation. We found that the presence of a clear layer had a significant effect upon the light distribution, which was modelled correctly by Monte Carlo techniques, but not by diffusion theory. A novel approach to calculating the light transport was developed, using diffusion theory to analyze the scattering regions combined with a radiosity approach to analyze the propagation through the clear region. Results from this approach were found to agree with both the Monte Carlo and experimental data.

  3. 5 CFR 1605.22 - Claims for correction of Board or TSP record keeper errors; time limitations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... record keeper errors; time limitations. 1605.22 Section 1605.22 Administrative Personnel FEDERAL... § 1605.22 Claims for correction of Board or TSP record keeper errors; time limitations. (a) Filing claims... after that time, the Board or TSP record keeper may use its sound discretion in deciding whether to...

  4. A solution for measuring accurate reaction time to visual stimuli realized with a programmable microcontroller.

    PubMed

    Ohyanagi, Toshio; Sengoku, Yasuhito

    2010-02-01

    This article presents a new solution for measuring accurate reaction time (SMART) to visual stimuli. The SMART is a USB device realized with a Cypress Programmable System-on-Chip (PSoC) mixed-signal array programmable microcontroller. A brief overview of the hardware and firmware of the PSoC is provided, together with the results of three experiments. In Experiment 1, we investigated the timing accuracy of the SMART in measuring reaction time (RT) under different conditions of operating systems (OSs; Windows XP or Vista) and monitor displays (a CRT or an LCD). The results indicated that the timing error in measuring RT by the SMART was less than 2 msec, on average, under all combinations of OS and display and that the SMART was tolerant to jitter and noise. In Experiment 2, we tested the SMART with 8 participants. The results indicated that there was no significant difference among RTs obtained with the SMART under the different conditions of OS and display. In Experiment 3, we used Microsoft (MS) PowerPoint to present visual stimuli on the display. We found no significant difference in RTs obtained using MS DirectX technology versus using the PowerPoint file with the SMART. We are certain that the SMART is a simple and practical solution for measuring RTs accurately. Although there are some restrictions in using the SMART with RT paradigms, the SMART is capable of providing both researchers and health professionals working in clinical settings with new ways of using RT paradigms in their work.

  5. Correcting for Measurement Error in Time-Varying Covariates in Marginal Structural Models.

    PubMed

    Kyle, Ryan P; Moodie, Erica E M; Klein, Marina B; Abrahamowicz, Michał

    2016-08-01

    Unbiased estimation of causal parameters from marginal structural models (MSMs) requires a fundamental assumption of no unmeasured confounding. Unfortunately, the time-varying covariates used to obtain inverse probability weights are often error-prone. Although substantial measurement error in important confounders is known to undermine control of confounders in conventional unweighted regression models, this issue has received comparatively limited attention in the MSM literature. Here we propose a novel application of the simulation-extrapolation (SIMEX) procedure to address measurement error in time-varying covariates, and we compare 2 approaches. The direct approach to SIMEX-based correction targets outcome model parameters, while the indirect approach corrects the weights estimated using the exposure model. We assess the performance of the proposed methods in simulations under different clinically plausible assumptions. The simulations demonstrate that measurement errors in time-dependent covariates may induce substantial bias in MSM estimators of causal effects of time-varying exposures, and that both proposed SIMEX approaches yield practically unbiased estimates in scenarios featuring low-to-moderate degrees of error. We illustrate the proposed approach in a simple analysis of the relationship between sustained virological response and liver fibrosis progression among persons infected with hepatitis C virus, while accounting for measurement error in γ-glutamyltransferase, using data collected in the Canadian Co-infection Cohort Study from 2003 to 2014. © The Author 2016. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  6. Determining spherical lens correction for astronaut training underwater

    PubMed Central

    Porter, Jason; Gibson, C. Robert; Strauss, Samuel

    2013-01-01

    Purpose To develop a model that will accurately predict the distance spherical lens correction needed to be worn by National Aeronautics and Space Administration (NASA) astronauts while training underwater. The replica space suit’s helmet contains curved visors that induce refractive power when submersed in water. Methods Anterior surface powers and thicknesses were measured for the helmet’s protective and inside visors. The impact of each visor on the helmet’s refractive power in water was analyzed using thick lens calculations and Zemax optical design software. Using geometrical optics approximations, a model was developed to determine the optimal distance spherical power needed to be worn underwater based on the helmet’s total induced spherical power underwater and the astronaut’s manifest spectacle plane correction in air. The validity of the model was tested using data from both eyes of 10 astronauts who trained underwater. Results The helmet visors induced a total power of −2.737 D when placed underwater. The required underwater spherical correction (FW) was linearly related to the spectacle plane spherical correction in air (FAir): FW = FAir + 2.356 D. The mean magnitude of the difference between the actual correction worn underwater and the calculated underwater correction was 0.20 ± 0.11 D. The actual and calculated values were highly correlated (R = 0.971) with 70% of eyes having a difference in magnitude of < 0.25 D between values. Conclusions We devised a model to calculate the spherical spectacle lens correction needed to be worn underwater by National Aeronautics and Space Administration astronauts. The model accurately predicts the actual values worn underwater and can be applied (more generally) to determine a suitable spectacle lens correction to be worn behind other types of masks when submerged underwater. PMID:21623249

  7. Variation in light intensity with height and time from subsequent lightning return strokes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jordan, D.M.; Uman, M.A.

    1983-08-20

    Relative light intensity has been measured photographically as a function of height and time for seven subsequent return strokes in two lightning flashes at ranges of 7.8 and 8.7 km. The film used was Kodak 5474 Shellburst, which has a roughly constant spectral response between 300 and 670 nm. The time resolution was about 1.0 ..mu..s, and the spatial resolution was about 4 m. The observed light signals consisted of a fast rise to peak, followed by a slower decrease to a relatively constant value. The amplitude of the initial light peak decreases exponentially with height with a decay constantmore » of about 0.6 to 0.8 km. The 20% to 80% rise time of the initial light signal is between 1 and 4 ..mu..s near ground and increases by an additional 1 to 2 ..mu..s by the time the return stroke reaches the cloud base, a height between 1 and 2 km. The light intensity 30 ..mu..s after the initial peak is relatively constant with height and has an amplitude that is 15% to 30% of the initial peak near the ground and 50% to 100% of the initial peak at cloud base. The logarithm of the peak light intensity near the ground is roughly proportional to the initial peak electric field intensity, and this in turn implies that the current decrease with height may be much slower than the light decrease. The absolute light intensity has been estimated by integrating the photographic signals from individual channel segments to simulate the calibrated all-sky photoelectric data of Guo and Krider (1982). Using this method, the authors find that the mean peak radiance near the ground is 8.3 x 10/sup 5/ W/m, with a total range from 1.4 x 10/sup 5/ to 3.8 x 10/sup 6/ W/m. 16 references, 11 figures.« less

  8. Real-time and accurate rail wear measurement method and experimental analysis.

    PubMed

    Liu, Zhen; Li, Fengjiao; Huang, Bangkui; Zhang, Guangjun

    2014-08-01

    When a train is running on uneven or curved rails, it generates violent vibrations on the rails. As a result, the light plane of the single-line structured light vision sensor is not vertical, causing errors in rail wear measurements (referred to as vibration errors in this paper). To avoid vibration errors, a novel rail wear measurement method is introduced in this paper, which involves three main steps. First, a multi-line structured light vision sensor (which has at least two linear laser projectors) projects a stripe-shaped light onto the inside of the rail. Second, the central points of the light stripes in the image are extracted quickly, and the three-dimensional profile of the rail is obtained based on the mathematical model of the structured light vision sensor. Then, the obtained rail profile is transformed from the measurement coordinate frame (MCF) to the standard rail coordinate frame (RCF) by taking the three-dimensional profile of the measured rail waist as the datum. Finally, rail wear constraint points are adopted to simplify the location of the rail wear points, and the profile composed of the rail wear points are compared with the standard rail profile in RCF to determine the rail wear. Both real data experiments and simulation experiments show that the vibration errors can be eliminated when the proposed method is used.

  9. Universality of quantum gravity corrections.

    PubMed

    Das, Saurya; Vagenas, Elias C

    2008-11-28

    We show that the existence of a minimum measurable length and the related generalized uncertainty principle (GUP), predicted by theories of quantum gravity, influence all quantum Hamiltonians. Thus, they predict quantum gravity corrections to various quantum phenomena. We compute such corrections to the Lamb shift, the Landau levels, and the tunneling current in a scanning tunneling microscope. We show that these corrections can be interpreted in two ways: (a) either that they are exceedingly small, beyond the reach of current experiments, or (b) that they predict upper bounds on the quantum gravity parameter in the GUP, compatible with experiments at the electroweak scale. Thus, more accurate measurements in the future should either be able to test these predictions, or further tighten the above bounds and predict an intermediate length scale between the electroweak and the Planck scale.

  10. Dim light at night does not disrupt timing or quality of sleep in mice.

    PubMed

    Borniger, Jeremy C; Weil, Zachary M; Zhang, Ning; Nelson, Randy J

    2013-10-01

    Artificial nighttime illumination has recently become commonplace throughout the world; however, in common with other animals, humans have not evolved in the ecological context of chronic light at night. With prevailing evidence linking the circadian, endocrine, immune, and metabolic systems, understanding these relationships is important to understanding the etiology and progression of several diseases. To eliminate the covariate of sleep disruption in light at night studies, researchers often use nocturnal animals. However, the assumption that light at night does not affect sleep in nocturnal animals remains unspecified. To test the effects of light at night on sleep, we maintained Swiss-Webster mice in standard light/dark (LD) or dim light at night (DLAN) conditions for 8-10 wks and then measured electroencephalogram (EEG) and electromyogram (EMG) biopotentials via wireless telemetry over the course of two consecutive days to determine differences in sleep timing and homeostasis. Results show no statistical differences in total percent time, number of episodes, maximum or average episode durations in wake, slow-wave sleep (SWS), or rapid eye movement (REM) sleep. No differences were evident in SWS delta power, an index of sleep drive, between groups. Mice kept in DLAN conditions showed a relative increase in REM sleep during the first few hours after the dark/light transition. Both groups displayed normal 24-h circadian rhythms as measured by voluntary running wheel activity. Groups did not differ in body mass, but a marked negative correlation of body mass with percent time spent awake and a positive correlation of body mass with time spent in SWS was evident. Elevated body mass was also associated with shorter maximum wake episode durations, indicating heavier animals had more trouble remaining in the wake vigilance state for extended periods of time. Body mass did not correlate with activity levels, nor did activity levels correlate with time spent in

  11. Evaluation of liver fat in the presence of iron with MRI using T2* correction: a clinical approach.

    PubMed

    Henninger, Benjamin; Benjamin, Henninger; Kremser, Christian; Christian, Kremser; Rauch, Stefan; Stefan, Rauch; Eder, Robert; Robert, Eder; Judmaier, Werner; Werner, Judmaier; Zoller, Heinz; Heinz, Zoller; Michaely, Henrik; Henrik, Michaely; Schocke, Michael; Michael, Schocke

    2013-06-01

    To assess magnetic resonance imaging (MRI) with conventional chemical shift-based sequences with and without T2* correction for the evaluation of steatosis hepatitis (SH) in the presence of iron. Thirty-one patients who underwent MRI and liver biopsy because of clinically suspected diffuse liver disease were retrospectively analysed. The signal intensity (SI) was calculated in co-localised regions of interest (ROIs) using conventional spoiled gradient-echo T1 FLASH in-phase and opposed-phase (IP/OP). T2* relaxation time was recorded in a fat-saturated multi-echo-gradient-echo sequence. The fat fraction (FF) was calculated with non-corrected and T2*-corrected SIs. Results were correlated with liver biopsy. There was significant difference (P < 0.001) between uncorrected and T2* corrected FF in patients with SH and concomitant hepatic iron overload (HIO). Using 5 % as a threshold resulted in eight false negative results with uncorrected FF whereas T2* corrected FF lead to true positive results in 5/8 patients. ROC analysis calculated three threshold values (8.97 %, 5.3 % and 3.92 %) for T2* corrected FF with accuracy 84 %, sensitivity 83-91 % and specificity 63-88 %. FF with T2* correction is accurate for the diagnosis of hepatic fat in the presence of HIO. Findings of our study suggest the use of IP/OP imaging in combination with T2* correction. • Magnetic resonance helps quantify both iron and fat content within the liver • T2* correction helps to predict the correct diagnosis of steatosis hepatitis • "Fat fraction" from T2*-corrected chemical shift-based sequences accurately quantifies hepatic fat • "Fat fraction" without T2* correction underestimates hepatic fat with iron overload.

  12. Directional errors of movements and their correction in a discrete tracking task. [pilot reaction time and sensorimotor performance

    NASA Technical Reports Server (NTRS)

    Jaeger, R. J.; Agarwal, G. C.; Gottlieb, G. L.

    1978-01-01

    Subjects can correct their own errors of movement more quickly than they can react to external stimuli by using three general categories of feedback: (1) knowledge of results, primarily visually mediated; (2) proprioceptive or kinaesthetic such as from muscle spindles and joint receptors, and (3) corollary discharge or efference copy within the central nervous system. The effects of these feedbacks on simple reaction time, choice reaction time, and error correction time were studied in four normal human subjects. The movement used was plantarflexion and dorsiflexion of the ankle joint. The feedback loops were modified, by changing the sign of the visual display to alter the subject's perception of results, and by applying vibration at 100 Hz simultaneously to both the agonist and antagonist muscles of the ankle joint. The central processing was interfered with when the subjects were given moderate doses of alcohol (blood alcohol concentration levels of up to 0.07%). Vibration and alcohol increase both the simple and choice reaction times but not the error correction time.

  13. Clinical Evaluation of Zero-Echo-Time Attenuation Correction for Brain 18F-FDG PET/MRI: Comparison with Atlas Attenuation Correction.

    PubMed

    Sekine, Tetsuro; Ter Voert, Edwin E G W; Warnock, Geoffrey; Buck, Alfred; Huellner, Martin; Veit-Haibach, Patrick; Delso, Gaspar

    2016-12-01

    Accurate attenuation correction (AC) on PET/MR is still challenging. The purpose of this study was to evaluate the clinical feasibility of AC based on fast zero-echo-time (ZTE) MRI by comparing it with the default atlas-based AC on a clinical PET/MR scanner. We recruited 10 patients with malignant diseases not located on the brain. In all patients, a clinically indicated whole-body 18 F-FDG PET/CT scan was acquired. In addition, a head PET/MR scan was obtained voluntarily. For each patient, 2 AC maps were generated from the MR images. One was atlas-AC, derived from T1-weighted liver acquisition with volume acceleration flex images (clinical standard). The other was ZTE-AC, derived from proton-density-weighted ZTE images by applying tissue segmentation and assigning continuous attenuation values to the bone. The AC map generated by PET/CT was used as a silver standard. On the basis of each AC map, PET images were reconstructed from identical raw data on the PET/MR scanner. All PET images were normalized to the SPM5 PET template. After that, these images were qualified visually and quantified in 67 volumes of interest (VOIs; automated anatomic labeling, atlas). Relative differences and absolute relative differences between PET images based on each AC were calculated. 18 F-FDG uptake in all 670 VOIs and generalized merged VOIs were compared using a paired t test. Qualitative analysis shows that ZTE-AC was robust to patient variability. Nevertheless, misclassification of air and bone in mastoid and nasal areas led to the overestimation of PET in the temporal lobe and cerebellum (%diff of ZTE-AC, 2.46% ± 1.19% and 3.31% ± 1.70%, respectively). The |%diff| of all 670 VOIs on ZTE was improved by approximately 25% compared with atlas-AC (ZTE-AC vs. atlas-AC, 1.77% ± 1.41% vs. 2.44% ± 1.63%, P < 0.01). In 2 of 7 generalized VOIs, |%diff| on ZTE-AC was significantly smaller than atlas-AC (ZTE-AC vs. atlas-AC: insula and cingulate, 1.06% ± 0.67% vs. 2.22% ± 1.10%, P < 0

  14. 42 CFR 414.806 - Penalties associated with the failure to submit timely and accurate ASP data.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 3 2013-10-01 2013-10-01 false Penalties associated with the failure to submit timely and accurate ASP data. 414.806 Section 414.806 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICARE PROGRAM (CONTINUED) PAYMENT FOR PART B MEDICAL AND OTHER HEALTH SERVICES...

  15. 42 CFR 414.806 - Penalties associated with the failure to submit timely and accurate ASP data.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 3 2012-10-01 2012-10-01 false Penalties associated with the failure to submit timely and accurate ASP data. 414.806 Section 414.806 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICARE PROGRAM (CONTINUED) PAYMENT FOR PART B MEDICAL AND OTHER HEALTH SERVICES...

  16. 42 CFR 414.806 - Penalties associated with the failure to submit timely and accurate ASP data.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 3 2010-10-01 2010-10-01 false Penalties associated with the failure to submit timely and accurate ASP data. 414.806 Section 414.806 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICARE PROGRAM PAYMENT FOR PART B MEDICAL AND OTHER HEALTH SERVICES Submission of...

  17. 42 CFR 414.806 - Penalties associated with the failure to submit timely and accurate ASP data.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 3 2011-10-01 2011-10-01 false Penalties associated with the failure to submit timely and accurate ASP data. 414.806 Section 414.806 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICARE PROGRAM PAYMENT FOR PART B MEDICAL AND OTHER HEALTH SERVICES Submission of...

  18. 42 CFR 414.806 - Penalties associated with the failure to submit timely and accurate ASP data.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 3 2014-10-01 2014-10-01 false Penalties associated with the failure to submit timely and accurate ASP data. 414.806 Section 414.806 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICARE PROGRAM (CONTINUED) PAYMENT FOR PART B MEDICAL AND OTHER HEALTH SERVICES...

  19. Evaluation of the Effects of Light Intensity and Time Interval After the Start of Scotophase on the Female Flight Propensity of Asian Gypsy Moth (Lepidoptera: Erebidae).

    PubMed

    Chen, Fang; Shi, Juan; Keena, Melody

    2016-04-01

    Asian gypsy moth, Lymantria dispar L. (Lepidoptera: Erebidae), females are capable of flight, but little is known about what causes the variation in flight propensity that has been observed. The female flight propensity and capability of Asian gypsy moth from seven geographic populations (three from China, two from Russia, one from Japan, and one from Korea) were compared under all combinations of three light intensities (0.05, 0.10, and 0.40 lux) and during three time intervals after the start of scotophase. A total of 567 females were flight tested. Female flight propensity, time to initiate walking, fanning, and flying, and duration of fanning differed significantly among geographic populations. Females were less likely to voluntarily fly during the 0-1-h time interval after the start of scotophase than during the later time intervals (1-2 and 2-3 h), suggesting that the light intensity cue has to occur at the correct time after the expected start of scotophase for flight initiation. Light intensity did not significantly affect the proportion of females that voluntarily flew, but did impact the timing of the walking and fanning preflight behaviors. The interaction between light intensity and time interval after the start of scotophase had a significant effect on the proportion of females that fanned. The proportion of females with sustained flight capability varied among the populations evaluated. These results may aid in determining the risk of Asian gypsy moth dispersal, but further work is needed to assess other factors that play a role in flight propensity. Published by Oxford University Press on behalf of Entomological Society of America 2016. This work is written by US Government employees and is in the public domain in the US.

  20. PSF mapping-based correction of eddy-current-induced distortions in diffusion-weighted echo-planar imaging.

    PubMed

    In, Myung-Ho; Posnansky, Oleg; Speck, Oliver

    2016-05-01

    To accurately correct diffusion-encoding direction-dependent eddy-current-induced geometric distortions in diffusion-weighted echo-planar imaging (DW-EPI) and to minimize the calibration time at 7 Tesla (T). A point spread function (PSF) mapping based eddy-current calibration method is newly presented to determine eddy-current-induced geometric distortions even including nonlinear eddy-current effects within the readout acquisition window. To evaluate the temporal stability of eddy-current maps, calibration was performed four times within 3 months. Furthermore, spatial variations of measured eddy-current maps versus their linear superposition were investigated to enable correction in DW-EPIs with arbitrary diffusion directions without direct calibration. For comparison, an image-based eddy-current correction method was additionally applied. Finally, this method was combined with a PSF-based susceptibility-induced distortion correction approach proposed previously to correct both susceptibility and eddy-current-induced distortions in DW-EPIs. Very fast eddy-current calibration in a three-dimensional volume is possible with the proposed method. The measured eddy-current maps are very stable over time and very similar maps can be obtained by linear superposition of principal-axes eddy-current maps. High resolution in vivo brain results demonstrate that the proposed method allows more efficient eddy-current correction than the image-based method. The combination of both PSF-based approaches allows distortion-free images, which permit reliable analysis in diffusion tensor imaging applications at 7T. © 2015 Wiley Periodicals, Inc.

  1. Improved correlation corrections to the local-spin-density approximation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Painter, G.S.

    1981-10-15

    The accurate correlation energies for the para- and ferromagnetic states of the electron liquid calculated by Ceperley and Alder were recently used by Vosko, Wilk, and Nusair to produce a new correlation-energy density of increased accuracy and proper limiting behavior in the metallic density regime (r/sub s/< or =6). In the present work, the correlation potential in the local-spin-density approximation (LSDA) is derived from the correlation-energy-density representation of Vosko et al. Characteristics of the new exchange-correlation model are compared with those of the LSDA model of Gunnarsson and Lundqvist. Specific comparison is made between these models and exact results inmore » the treatment of atomic and molecular hydrogen. Since the new treatment of correlation primarily affects the region of small r/sub s/, which is exchange dominated, correlation corrections are small compared with errors in the exchange energy. Thus, in light atoms the improved correlation model leads to a reduced cancellation of error between exchange and correlation energies, emphasizing the necessity for improved exchange treatment. For more homogeneous systems, the model should offer real improvement. The present results obtained with precise treatment of correlation within the prescription of Vosko et al. serve to define the present limitations of the LSDA and indicate the importance of nonlocal corrections, particularly for atoms.« less

  2. Transient anhedonia phenotype and altered circadian timing of behaviour during night-time dim light exposure in Per3-/- mice, but not wildtype mice.

    PubMed

    Martynhak, Bruno Jacson; Hogben, Alexandra L; Zanos, Panos; Georgiou, Polymnia; Andreatini, Roberto; Kitchen, Ian; Archer, Simon N; von Schantz, Malcolm; Bailey, Alexis; van der Veen, Daan R

    2017-01-10

    Industrialisation greatly increased human night-time exposure to artificial light, which in animal models is a known cause of depressive phenotypes. Whilst many of these phenotypes are 'direct' effects of light on affect, an 'indirect' pathway via altered sleep-wake timing has been suggested. We have previously shown that the Period3 gene, which forms part of the biological clock, is associated with altered sleep-wake patterns in response to light. Here, we show that both wild-type and Per3 -/- mice showed elevated levels of circulating corticosterone and increased hippocampal Bdnf expression after 3 weeks of exposure to dim light at night, but only mice deficient for the PERIOD3 protein (Per3 -/- ) exhibited a transient anhedonia-like phenotype, observed as reduced sucrose preference, in weeks 2-3 of dim light at night, whereas WT mice did not. Per3 -/- mice also exhibited a significantly smaller delay in behavioural timing than WT mice during weeks 1, 2 and 4 of dim light at night exposure. When treated with imipramine, neither Per3 -/- nor WT mice exhibited an anhedonia-like phenotype, and neither genotypes exhibited a delay in behavioural timing in responses to dLAN. While the association between both Per3 -/- phenotypes remains unclear, both are alleviated by imipramine treatment during dim night-time light.

  3. Quantification of Parvovirus B19 DNA Using COBAS AmpliPrep Automated Sample Preparation and LightCycler Real-Time PCR

    PubMed Central

    Schorling, Stefan; Schalasta, Gunnar; Enders, Gisela; Zauke, Michael

    2004-01-01

    The COBAS AmpliPrep instrument (Roche Diagnostics GmbH, D-68305 Mannheim, Germany) automates the entire sample preparation process of nucleic acid isolation from serum or plasma for polymerase chain reaction analysis. We report the analytical performance of the LightCycler Parvovirus B19 Quantification Kit (Roche Diagnostics) using nucleic acids isolated with the COBAS AmpliPrep instrument. Nucleic acids were extracted using the Total Nucleic Acid Isolation Kit (Roche Diagnostics) and amplified with the LightCycler Parvovirus B19 Quantification Kit. The kit combination processes 72 samples per 8-hour shift. The lower detection limit is 234 IU/ml at a 95% hit-rate, linear range approximately 104-1010 IU/ml, and overall precision 16 to 40%. Relative sensitivity and specificity in routine samples from pregnant women are 100% and 93%, respectively. Identification of a persistent parvovirus B19-infected individual by the polymerase chain reaction among 51 anti-parvovirus B19 IgM-negative samples underlines the importance of additional nucleic acid testing in pregnancy and its superiority to serology in identifying the risk of parvovirus B19 transmission via blood or blood products. Combination of the Total Nucleic Acid Isolation Kit on the COBAS AmpliPrep instrument with the LightCycler Parvovirus B19 Quantification Kit provides a reliable and time-saving tool for sensitive and accurate detection of parvovirus B19 DNA. PMID:14736825

  4. Station Correction Uncertainty in Multiple Event Location Algorithms and the Effect on Error Ellipses

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Erickson, Jason P.; Carlson, Deborah K.; Ortiz, Anne

    Accurate location of seismic events is crucial for nuclear explosion monitoring. There are several sources of error in seismic location that must be taken into account to obtain high confidence results. Most location techniques account for uncertainties in the phase arrival times (measurement error) and the bias of the velocity model (model error), but they do not account for the uncertainty of the velocity model bias. By determining and incorporating this uncertainty in the location algorithm we seek to improve the accuracy of the calculated locations and uncertainty ellipses. In order to correct for deficiencies in the velocity model, itmore » is necessary to apply station specific corrections to the predicted arrival times. Both master event and multiple event location techniques assume that the station corrections are known perfectly, when in reality there is an uncertainty associated with these corrections. For multiple event location algorithms that calculate station corrections as part of the inversion, it is possible to determine the variance of the corrections. The variance can then be used to weight the arrivals associated with each station, thereby giving more influence to stations with consistent corrections. We have modified an existing multiple event location program (based on PMEL, Pavlis and Booker, 1983). We are exploring weighting arrivals with the inverse of the station correction standard deviation as well using the conditional probability of the calculated station corrections. This is in addition to the weighting already given to the measurement and modeling error terms. We re-locate a group of mining explosions that occurred at Black Thunder, Wyoming, and compare the results to those generated without accounting for station correction uncertainty.« less

  5. Power and type I error results for a bias-correction approach recently shown to provide accurate odds ratios of genetic variants for the secondary phenotypes associated with primary diseases.

    PubMed

    Wang, Jian; Shete, Sanjay

    2011-11-01

    We recently proposed a bias correction approach to evaluate accurate estimation of the odds ratio (OR) of genetic variants associated with a secondary phenotype, in which the secondary phenotype is associated with the primary disease, based on the original case-control data collected for the purpose of studying the primary disease. As reported in this communication, we further investigated the type I error probabilities and powers of the proposed approach, and compared the results to those obtained from logistic regression analysis (with or without adjustment for the primary disease status). We performed a simulation study based on a frequency-matching case-control study with respect to the secondary phenotype of interest. We examined the empirical distribution of the natural logarithm of the corrected OR obtained from the bias correction approach and found it to be normally distributed under the null hypothesis. On the basis of the simulation study results, we found that the logistic regression approaches that adjust or do not adjust for the primary disease status had low power for detecting secondary phenotype associated variants and highly inflated type I error probabilities, whereas our approach was more powerful for identifying the SNP-secondary phenotype associations and had better-controlled type I error probabilities. © 2011 Wiley Periodicals, Inc.

  6. Exchange-Hole Dipole Dispersion Model for Accurate Energy Ranking in Molecular Crystal Structure Prediction.

    PubMed

    Whittleton, Sarah R; Otero-de-la-Roza, A; Johnson, Erin R

    2017-02-14

    Accurate energy ranking is a key facet to the problem of first-principles crystal-structure prediction (CSP) of molecular crystals. This work presents a systematic assessment of B86bPBE-XDM, a semilocal density functional combined with the exchange-hole dipole moment (XDM) dispersion model, for energy ranking using 14 compounds from the first five CSP blind tests. Specifically, the set of crystals studied comprises 11 rigid, planar compounds and 3 co-crystals. The experimental structure was correctly identified as the lowest in lattice energy for 12 of the 14 total crystals. One of the exceptions is 4-hydroxythiophene-2-carbonitrile, for which the experimental structure was correctly identified once a quasi-harmonic estimate of the vibrational free-energy contribution was included, evidencing the occasional importance of thermal corrections for accurate energy ranking. The other exception is an organic salt, where charge-transfer error (also called delocalization error) is expected to cause the base density functional to be unreliable. Provided the choice of base density functional is appropriate and an estimate of temperature effects is used, XDM-corrected density-functional theory is highly reliable for the energetic ranking of competing crystal structures.

  7. Self-Expression on Social Media: Do Tweets Present Accurate and Positive Portraits of Impulsivity, Self-Esteem, and Attachment Style?

    PubMed

    Orehek, Edward; Human, Lauren J

    2017-01-01

    Self-expression values are at an all-time high, and people are increasingly relying upon social media platforms to express themselves positively and accurately. We examined whether self-expression on the social media platform Twitter elicits positive and accurate social perceptions. Eleven perceivers rated 128 individuals (targets; total dyadic impressions = 1,408) on their impulsivity, self-esteem, and attachment style, based solely on the information provided in targets' 10 most recent tweets. Targets were on average perceived normatively and with distinctive self-other agreement, indicating both positive and accurate social perceptions. There were also individual differences in how positively and accurately targets were perceived, which exploratory analyses indicated may be partially driven by differential word usage, such as the use of positive emotion words and self- versus other-focus. This study demonstrates that self-expression on social media can elicit both positive and accurate perceptions and begins to shed light on how to curate such perceptions.

  8. Lightwave: An interactive estimation of indirect illumination using waves of light

    NASA Astrophysics Data System (ADS)

    Robertson, Michael

    With the growth of computers and technology, so to has grown the desire to accurately recreate our world using computer graphics. However, our world is very complex and in many ways beyond our comprehension. Therefore, in order to perform this task, we must consider multiple disciplines and areas of research including physics, mathematics, optics, geology, and many more to at the very least approximate the world around us. The applications of being able to do this are plentiful as well, including the use of graphics in entertainment such as movies and games, in science such as weather forecasts and simulations, in medicine with body scans, or used in architecture, design, and many other areas. In order to recreate the world around us, an important task is to accurately recreate the way light travels and affects the objects we see. Rendering lighting has been a heavily researched area since the 1970's and has gotten more sophisticated over the years. Until recent developments in technology, realistic lighting of scenes has only been achievable offline taking seconds to hours or more to create a single image, however, due to advances in graphics technology, realistic lighting can be done in real-time. An important aspect of realistic lighting involves the inclusion of indirect illumination. However, to achieve a real-time rendering with indirect illumination, we must make trade-offs between scientific accuracy and performance, but as will be discussed later, scientific accuracy may not be necessary after all.

  9. Light and the circadian clock mediate time-specific changes in sensitivity to UV-B stress under light/dark cycles

    PubMed Central

    Takeuchi, Tomomi; Newton, Linsey; Burkhardt, Alyssa; Mason, Saundra; Farré, Eva M.

    2014-01-01

    In Arabidopsis, the circadian clock regulates UV-B-mediated changes in gene expression. Here it is shown that circadian clock components are able to inhibit UV-B-induced gene expression in a gene-by-gene-specific manner and act downstream of the initial UV-B sensing by COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1) and UVR8 (UV RESISTANCE LOCUS 8). For example, the UV-B induction of ELIP1 (EARLY LIGHT INDUCIBLE PROTEIN 1) and PRR9 (PSEUDO-RESPONSE REGULATOR 9) is directly regulated by LUX (LUX ARRYTHMO), ELF4 (EARLY FLOWERING 4), and ELF3. Moreover, time-dependent changes in plant sensitivity to UV-B damage were observed. Wild-type Arabidopsis plants, but not circadian clock mutants, were more sensitive to UV-B treatment during the night periods than during the light periods under diel cycles. Experiments performed under short cycles of 6h light and 6h darkness showed that the increased stress sensitivity of plants to UV-B in the dark only occurred during the subjective night and not during the subjective day in wild-type seedlings. In contrast, the stress sensitivity of Arabidopsis mutants with a compromised circadian clock was still influenced by the light condition during the subjective day. Taken together, the results show that the clock and light modulate plant sensitivity to UV-B stress at different times of the day. PMID:25147271

  10. Controlling pulse delay by light and low magnetic fields: slow light in emerald induced by transient spectral hole-burning.

    PubMed

    Rajan, Rajitha Papukutty; Riesen, Hans; Rebane, Aleksander

    2013-11-15

    Slow light based on transient spectral hole-burning is reported for emerald, Be(3)Al(2)Si(6)O(18):Cr(3+). Experiments were conducted in π polarization on the R(1)(± 3/2) line (E2 ← A(2)4) at 2.2 K in zero field and low magnetic fields B||c. The hole width was strongly dependent on B||c, and this allowed us to smoothly tune the pulse delay from 40 to 154 ns between zero field and B||c = 15.2 mT. The latter corresponds to a group velocity of 16 km/s. Slow light in conjunction with a linear filter theory can be used as a powerful and accurate technique in time-resolved spectroscopy, e.g., to determine spectral hole-widths as a function of time.

  11. Adaptive electron beam shaping using a photoemission gun and spatial light modulator

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Maxson, Jared; Lee, Hyeri; Bartnik, Adam C.

    The need for precisely defined beam shapes in photoelectron sources has been well established. In this paper, we use a spatial light modulator and simple shaping algorithm to create arbitrary, detailed transverse laser shapes with high fidelity. We transmit this shaped laser to the photocathode of a high voltage dc gun. Using beam currents where space charge is negligible, and using an imaging solenoid and fluorescent viewscreen, we show that the resultant beam shape preserves these detailed features with similar fidelity. Next, instead of transmitting a shaped laser profile, we use an active feedback on the unshaped electron beam imagemore » to create equally accurate and detailed shapes. We demonstrate that this electron beam feedback has the added advantage of correcting for electron optical aberrations, yielding shapes without skew. The method may serve to provide precisely defined electron beams for low current target experiments, space-charge dominated beam commissioning, as well as for online adaptive correction of photocathode quantum efficiency degradation.« less

  12. Adaptive electron beam shaping using a photoemission gun and spatial light modulator

    NASA Astrophysics Data System (ADS)

    Maxson, Jared; Lee, Hyeri; Bartnik, Adam C.; Kiefer, Jacob; Bazarov, Ivan

    2015-02-01

    The need for precisely defined beam shapes in photoelectron sources has been well established. In this paper, we use a spatial light modulator and simple shaping algorithm to create arbitrary, detailed transverse laser shapes with high fidelity. We transmit this shaped laser to the photocathode of a high voltage dc gun. Using beam currents where space charge is negligible, and using an imaging solenoid and fluorescent viewscreen, we show that the resultant beam shape preserves these detailed features with similar fidelity. Next, instead of transmitting a shaped laser profile, we use an active feedback on the unshaped electron beam image to create equally accurate and detailed shapes. We demonstrate that this electron beam feedback has the added advantage of correcting for electron optical aberrations, yielding shapes without skew. The method may serve to provide precisely defined electron beams for low current target experiments, space-charge dominated beam commissioning, as well as for online adaptive correction of photocathode quantum efficiency degradation.

  13. Adaptive electron beam shaping using a photoemission gun and spatial light modulator

    DOE PAGES

    Maxson, Jared; Lee, Hyeri; Bartnik, Adam C.; ...

    2015-02-01

    The need for precisely defined beam shapes in photoelectron sources has been well established. In this paper, we use a spatial light modulator and simple shaping algorithm to create arbitrary, detailed transverse laser shapes with high fidelity. We transmit this shaped laser to the photocathode of a high voltage dc gun. Using beam currents where space charge is negligible, and using an imaging solenoid and fluorescent viewscreen, we show that the resultant beam shape preserves these detailed features with similar fidelity. Next, instead of transmitting a shaped laser profile, we use an active feedback on the unshaped electron beam imagemore » to create equally accurate and detailed shapes. We demonstrate that this electron beam feedback has the added advantage of correcting for electron optical aberrations, yielding shapes without skew. The method may serve to provide precisely defined electron beams for low current target experiments, space-charge dominated beam commissioning, as well as for online adaptive correction of photocathode quantum efficiency degradation.« less

  14. Interpretation of light scattering and turbidity measurements in aggregated systems: effect of intra-cluster multiple-light scattering.

    PubMed

    Soos, Miroslav; Lattuada, Marco; Sefcik, Jan

    2009-11-12

    In this work we studied the effect of intracluster multiple-light scattering on the scattering properties of a population of fractal aggregates. To do so, experimental data of diffusion-limited aggregation for three polystyrene latexes with similar surface properties but different primary particle diameters (equal to 118, 420, and 810 nm) were obtained by static light scattering and by means of a spectrophotometer. In parallel, a population balance equation (PBE) model, which takes into account the effect of intracluster multiple-light scattering by solving the T-matrix and the mean-field version of T-matrix, was formulated and validated against time evolution of the root mean radius of gyration, , of the zero angle intensity of scattered light, I(0), and of the turbidity, tau. It was found that the mean-field version of the T-matrix theory is able to correctly predict the time evolution of all measured light scattering quantities for all sizes of primary particles without any adjustable parameter. The structure of the aggregates, characterized by fractal dimension, d(f), was independent of the primary particle size and equal to 1.7, which is in agreement with values found in literature. Since the mean-field version of the T-matrix theory used is rather complicated and requires advanced knowledge of cluster structure (i.e., the particle-particle correlation function), a simplified version of the light scattering model was proposed and tested. It was found that within the range of operating conditions investigated, the simplified version of the light scattering model was able to describe with reasonable accuracy the time evolution of all measured light scattering quantities of the cluster mass distribution (CMD) for all three sizes of primary particles and two values of the laser wavelength.

  15. Simple Pixel Structure Using Video Data Correction Method for Nonuniform Electrical Characteristics of Polycrystalline Silicon Thin-Film Transistors and Differential Aging Phenomenon of Organic Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Hai-Jung In,; Oh-Kyong Kwon,

    2010-03-01

    A simple pixel structure using a video data correction method is proposed to compensate for electrical characteristic variations of driving thin-film transistors (TFTs) and the degradation of organic light-emitting diodes (OLEDs) in active-matrix OLED (AMOLED) displays. The proposed method senses the electrical characteristic variations of TFTs and OLEDs and stores them in external memory. The nonuniform emission current of TFTs and the aging of OLEDs are corrected by modulating video data using the stored data. Experimental results show that the emission current error due to electrical characteristic variation of driving TFTs is in the range from -63.1 to 61.4% without compensation, but is decreased to the range from -1.9 to 1.9% with the proposed correction method. The luminance error due to the degradation of an OLED is less than 1.8% when the proposed correction method is used for a 50% degraded OLED.

  16. Covariate Measurement Error Correction Methods in Mediation Analysis with Failure Time Data

    PubMed Central

    Zhao, Shanshan

    2014-01-01

    Summary Mediation analysis is important for understanding the mechanisms whereby one variable causes changes in another. Measurement error could obscure the ability of the potential mediator to explain such changes. This paper focuses on developing correction methods for measurement error in the mediator with failure time outcomes. We consider a broad definition of measurement error, including technical error and error associated with temporal variation. The underlying model with the ‘true’ mediator is assumed to be of the Cox proportional hazards model form. The induced hazard ratio for the observed mediator no longer has a simple form independent of the baseline hazard function, due to the conditioning event. We propose a mean-variance regression calibration approach and a follow-up time regression calibration approach, to approximate the partial likelihood for the induced hazard function. Both methods demonstrate value in assessing mediation effects in simulation studies. These methods are generalized to multiple biomarkers and to both case-cohort and nested case-control sampling design. We apply these correction methods to the Women's Health Initiative hormone therapy trials to understand the mediation effect of several serum sex hormone measures on the relationship between postmenopausal hormone therapy and breast cancer risk. PMID:25139469

  17. Covariate measurement error correction methods in mediation analysis with failure time data.

    PubMed

    Zhao, Shanshan; Prentice, Ross L

    2014-12-01

    Mediation analysis is important for understanding the mechanisms whereby one variable causes changes in another. Measurement error could obscure the ability of the potential mediator to explain such changes. This article focuses on developing correction methods for measurement error in the mediator with failure time outcomes. We consider a broad definition of measurement error, including technical error, and error associated with temporal variation. The underlying model with the "true" mediator is assumed to be of the Cox proportional hazards model form. The induced hazard ratio for the observed mediator no longer has a simple form independent of the baseline hazard function, due to the conditioning event. We propose a mean-variance regression calibration approach and a follow-up time regression calibration approach, to approximate the partial likelihood for the induced hazard function. Both methods demonstrate value in assessing mediation effects in simulation studies. These methods are generalized to multiple biomarkers and to both case-cohort and nested case-control sampling designs. We apply these correction methods to the Women's Health Initiative hormone therapy trials to understand the mediation effect of several serum sex hormone measures on the relationship between postmenopausal hormone therapy and breast cancer risk. © 2014, The International Biometric Society.

  18. Bending of Light in Modified Gravity at Large Distances

    NASA Technical Reports Server (NTRS)

    Sultana, Joseph; Kazanas, Demosthenes

    2012-01-01

    We discuss the bending of light in a recent model for gravity at large distances containing a Rindler type acceleration proposed by Grumiller. We consider the static, spherically symmetric metric with cosmological constant and Rindler-like term 2ar presented in this model, and we use the procedure by Rindler and Ishak. to obtain the bending angle of light in this metric. Earlier work on light bending in this model by Carloni, Grumiller, and Preis, using the method normally employed for asymptotically flat space-times, led to a conflicting result (caused by the Rindler-like term in the metric) of a bending angle that increases with the distance of closest approach r(sub 0) of the light ray from the centrally concentrated spherically symmetric matter distribution. However, when using the alternative approach for light bending in nonasymptotically flat space-times, we show that the linear Rindler-like term produces a small correction to the general relativistic result that is inversely proportional to r(sub 0). This will in turn affect the bounds on Rindler acceleration obtained earlier from light bending and casts doubts on the nature of the linear term 2ar in the metric

  19. Accurate Drift Time Determination by Traveling Wave Ion Mobility Spectrometry: The Concept of the Diffusion Calibration.

    PubMed

    Kune, Christopher; Far, Johann; De Pauw, Edwin

    2016-12-06

    Ion mobility spectrometry (IMS) is a gas phase separation technique, which relies on differences in collision cross section (CCS) of ions. Ionic clouds of unresolved conformers overlap if the CCS difference is below the instrumental resolution expressed as CCS/ΔCCS. The experimental arrival time distribution (ATD) peak is then a superimposition of the various contributions weighted by their relative intensities. This paper introduces a strategy for accurate drift time determination using traveling wave ion mobility spectrometry (TWIMS) of poorly resolved or unresolved conformers. This method implements through a calibration procedure the link between the peak full width at half-maximum (fwhm) and the drift time of model compounds for wide range of settings for wave heights and velocities. We modified a Gaussian equation, which achieves the deconvolution of ATD peaks where the fwhm is fixed according to our calibration procedure. The new fitting Gaussian equation only depends on two parameters: The apex of the peak (A) and the mean drift time value (μ). The standard deviation parameter (correlated to fwhm) becomes a function of the drift time. This correlation function between μ and fwhm is obtained using the TWIMS calibration procedure which determines the maximum instrumental ion beam diffusion under limited and controlled space charge effect using ionic compounds which are detected as single conformers in the gas phase. This deconvolution process has been used to highlight the presence of poorly resolved conformers of crown ether complexes and peptides leading to more accurate CCS determinations in better agreement with quantum chemistry predictions.

  20. Measurement of LYSO Intrinsic Light Yield Using Electron Excitation

    NASA Astrophysics Data System (ADS)

    Turtos, Rosana Martinez; Gundacker, Stefan; Pizzichemi, Marco; Ghezzi, Alessio; Pauwels, Kristof; Auffray, Etiennette; Lecoq, Paul; Paganoni, Marco

    2016-04-01

    The determination of the intrinsic light yield (LYint) of scintillating crystals, i.e. number of optical photons created per amount of energy deposited, constitutes a key factor in order to characterize and optimize their energy and time resolution. However, until now measurements of this quantity are affected by large uncertainties and often rely on corrections for bulk absorption and surface/edge state. The novel idea presented in this contribution is based on the confinement of the scintillation emission in the central upper part of a 10 mm cubic crystal using a 1.5 MeV electron beam with diameter of 1 mm. A black non-reflective pinhole aligned with the excitation point is used to fix the light extraction solid angle (narrower than total reflection angle), which then sets a light cone travel path through the crystal. The final number of photoelectrons detected using a Hamamatsu R2059 photomultiplier tube (PMT) was corrected for the extraction solid angle, the Fresnel reflection coefficient and quantum efficiency (QE) of the PMT. The total number of optical photons produced per energy deposited was found to be 40000 ph/MeV ± 9% (syst) ±3% (stat) for LYSO. Simulations using Geant4 were successfully compared to light output measurements of 2 × 2 mm2 section crystals with lengths of 5-30 mm, in order to validate the light transport model and set a limit on Light Transfer Efficiency estimations.

  1. 12 CFR 621.14 - Certification of correctness.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... REQUIREMENTS Report of Condition and Performance § 621.14 Certification of correctness. Each report of financial condition and performance filed with the Farm Credit Administration shall be certified as having... accurate representation of the financial condition and performance of the institution to which it applies...

  2. Determination of velocity correction factors for real-time air velocity monitoring in underground mines.

    PubMed

    Zhou, Lihong; Yuan, Liming; Thomas, Rick; Iannacchione, Anthony

    2017-12-01

    When there are installations of air velocity sensors in the mining industry for real-time airflow monitoring, a problem exists with how the monitored air velocity at a fixed location corresponds to the average air velocity, which is used to determine the volume flow rate of air in an entry with the cross-sectional area. Correction factors have been practically employed to convert a measured centerline air velocity to the average air velocity. However, studies on the recommended correction factors of the sensor-measured air velocity to the average air velocity at cross sections are still lacking. A comprehensive airflow measurement was made at the Safety Research Coal Mine, Bruceton, PA, using three measuring methods including single-point reading, moving traverse, and fixed-point traverse. The air velocity distribution at each measuring station was analyzed using an air velocity contour map generated with Surfer ® . The correction factors at each measuring station for both the centerline and the sensor location were calculated and are discussed.

  3. Determination of velocity correction factors for real-time air velocity monitoring in underground mines

    PubMed Central

    Yuan, Liming; Thomas, Rick; Iannacchione, Anthony

    2017-01-01

    When there are installations of air velocity sensors in the mining industry for real-time airflow monitoring, a problem exists with how the monitored air velocity at a fixed location corresponds to the average air velocity, which is used to determine the volume flow rate of air in an entry with the cross-sectional area. Correction factors have been practically employed to convert a measured centerline air velocity to the average air velocity. However, studies on the recommended correction factors of the sensor-measured air velocity to the average air velocity at cross sections are still lacking. A comprehensive airflow measurement was made at the Safety Research Coal Mine, Bruceton, PA, using three measuring methods including single-point reading, moving traverse, and fixed-point traverse. The air velocity distribution at each measuring station was analyzed using an air velocity contour map generated with Surfer®. The correction factors at each measuring station for both the centerline and the sensor location were calculated and are discussed. PMID:29201495

  4. Efficacy of cold light bleaching using different bleaching times and their effects on human enamel.

    PubMed

    Wang, Wei; Zhu, Yuhe; Li, Jiajia; Liao, Susan; Ai, Hongjun

    2013-01-01

    This study investigated the efficacy of cold light bleaching using different bleaching times and the effects thereof on tooth enamel. Before and after bleaching, stained tooth specimens were subjected to visual and instrumental colorimetric assessments using Vita Shade Guide and spectrophotometric shade matching. Enamel surface alterations were examined using scanning electron microscopy (SEM) to analyze surface morphology, surface microhardness (SMH) measurement to determine changes in mechanical properties, and X-ray diffraction (XRD) to characterize post-bleaching enamel composition. Cold light bleaching successfully improved tooth color, with optimal efficacy when bleaching time was beyond 10 min. Significant differences in surface morphology were observed among the different bleaching times, but no significant differences were observed for enamel composition and surface microhardness among the different bleaching times. Results of this study revealed an association between the bleaching time of cold light bleaching and its whitening efficacy. Together with the results on enamel surface changes, this study provided positive evidence to support cold light bleaching as an in-office bleaching treatment.

  5. Stray-Light Correction of the Marine Optical Buoy

    NASA Technical Reports Server (NTRS)

    Brown, Steven W.; Johnson, B. Carol; Flora, Stephanie J.; Feinholz, Michael E.; Yarbrough, Mark A.; Barnes, Robert A.; Kim, Yong Sung; Lykke, Keith R.; Clark, Dennis K.

    2003-01-01

    In ocean-color remote sensing, approximately 90% of the flux at the sensor originates from atmospheric scattering, with the water-leaving radiance contributing the remaining 10% of the total flux. Consequently, errors in the measured top-of-the atmosphere radiance are magnified a factor of 10 in the determination of water-leaving radiance. Proper characterization of the atmosphere is thus a critical part of the analysis of ocean-color remote sensing data. It has always been necessary to calibrate the ocean-color satellite sensor vicariously, using in situ, ground-based results, independent of the status of the pre-flight radiometric calibration or the utility of on-board calibration strategies. Because the atmosphere contributes significantly to the measured flux at the instrument sensor, both the instrument and the atmospheric correction algorithm are simultaneously calibrated vicariously. The Marine Optical Buoy (MOBY), deployed in support of the Earth Observing System (EOS) since 1996, serves as the primary calibration station for a variety of ocean-color satellite instruments, including the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), the Moderate Resolution Imaging Spectroradiometer (MODIS), the Japanese Ocean Color Temperature Scanner (OCTS) , and the French Polarization and Directionality of the Earth's Reflectances (POLDER). MOBY is located off the coast of Lanai, Hawaii. The site was selected to simplify the application of the atmospheric correction algorithms. Vicarious calibration using MOBY data allows for a thorough comparison and merger of ocean-color data from these multiple sensors.

  6. A time-accurate algorithm for chemical non-equilibrium viscous flows at all speeds

    NASA Technical Reports Server (NTRS)

    Shuen, J.-S.; Chen, K.-H.; Choi, Y.

    1992-01-01

    A time-accurate, coupled solution procedure is described for the chemical nonequilibrium Navier-Stokes equations over a wide range of Mach numbers. This method employs the strong conservation form of the governing equations, but uses primitive variables as unknowns. Real gas properties and equilibrium chemistry are considered. Numerical tests include steady convergent-divergent nozzle flows with air dissociation/recombination chemistry, dump combustor flows with n-pentane-air chemistry, nonreacting flow in a model double annular combustor, and nonreacting unsteady driven cavity flows. Numerical results for both the steady and unsteady flows demonstrate the efficiency and robustness of the present algorithm for Mach numbers ranging from the incompressible limit to supersonic speeds.

  7. Atmospheric Correction of High-Spatial-Resolution Commercial Satellite Imagery Products Using MODIS Atmospheric Products

    NASA Technical Reports Server (NTRS)

    Pagnutti, Mary; Holekamp, Kara; Ryan, Robert E.; Vaughan, Ronand; Russell, Jeff; Prados, Don; Stanley, Thomas

    2005-01-01

    Remotely sensed ground reflectance is the foundation of any interoperability or change detection technique. Satellite intercomparisons and accurate vegetation indices, such as the Normalized Difference Vegetation Index (NDVI), require the generation of accurate reflectance maps (NDVI is used to describe or infer a wide variety of biophysical parameters and is defined in terms of near-infrared (NIR) and red band reflectances). Accurate reflectance-map generation from satellite imagery relies on the removal of solar and satellite geometry and of atmospheric effects and is generally referred to as atmospheric correction. Atmospheric correction of remotely sensed imagery to ground reflectance has been widely applied to a few systems only. The ability to obtain atmospherically corrected imagery and products from various satellites is essential to enable widescale use of remotely sensed, multitemporal imagery for a variety of applications. An atmospheric correction approach derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) that can be applied to high-spatial-resolution satellite imagery under many conditions was evaluated to demonstrate a reliable, effective reflectance map generation method. Additional information is included in the original extended abstract.

  8. Some Consequences of a Time Dependent Speed of Light

    NASA Astrophysics Data System (ADS)

    Smith, Felix T.

    2007-06-01

    For reasons connected with both cosmology (the flatness and horizon problems) and atomic physics (n-body Dirac equation, etc.), various proposals have been made to modify general or special relativity(SR) to accommodate a cosmologically decreasing light speed [J. Magueijo, Rep. Prog. Phys. 66, 2025 (2003)]. Two such theories, projective SR [S.N. Manida, gr-qc/9905046; S. S. Stepanov, physics/9909009 and Phys. Rev. D, 62, 023507 (2000)] and symmetric SR [F.T. Smith, Ann. Fond. L. de Broglie, 30, 179 (2005)] adapt special relativity to in different ways to an expanding, hyperbolically curved position space and predict time-dependences of c within reach of measurement but differing by a factor of two. Both theories bring in a new constant λ-1=σ=c^2H0-1. As Magueijo points, out the role of c in physics and cosmology is so profound that many deep changes must follow if is not absolutely invariant in space and time. In particular, symmetric SR brings a new light to the Dirac large-number relationship between the constants of gravitation and atomic physics.

  9. Application of the accurate mass and time tag approach in studies of the human blood lipidome

    PubMed Central

    Ding, Jie; Sorensen, Christina M.; Jaitly, Navdeep; Jiang, Hongliang; Orton, Daniel J.; Monroe, Matthew E.; Moore, Ronald J.; Smith, Richard D.; Metz, Thomas O.

    2008-01-01

    We report a preliminary demonstration of the accurate mass and time (AMT) tag approach for lipidomics. Initial data-dependent LC-MS/MS analyses of human plasma, erythrocyte, and lymphocyte lipids were performed in order to identify lipid molecular species in conjunction with complementary accurate mass and isotopic distribution information. Identified lipids were used to populate initial lipid AMT tag databases containing 250 and 45 entries for those species detected in positive and negative electrospray ionization (ESI) modes, respectively. The positive ESI database was then utilized to identify human plasma, erythrocyte, and lymphocyte lipids in high-throughput LC-MS analyses based on the AMT tag approach. We were able to define the lipid profiles of human plasma, erythrocytes, and lymphocytes based on qualitative and quantitative differences in lipid abundance. PMID:18502191

  10. The accurate particle tracer code

    NASA Astrophysics Data System (ADS)

    Wang, Yulei; Liu, Jian; Qin, Hong; Yu, Zhi; Yao, Yicun

    2017-11-01

    The Accurate Particle Tracer (APT) code is designed for systematic large-scale applications of geometric algorithms for particle dynamical simulations. Based on a large variety of advanced geometric algorithms, APT possesses long-term numerical accuracy and stability, which are critical for solving multi-scale and nonlinear problems. To provide a flexible and convenient I/O interface, the libraries of Lua and Hdf5 are used. Following a three-step procedure, users can efficiently extend the libraries of electromagnetic configurations, external non-electromagnetic forces, particle pushers, and initialization approaches by use of the extendible module. APT has been used in simulations of key physical problems, such as runaway electrons in tokamaks and energetic particles in Van Allen belt. As an important realization, the APT-SW version has been successfully distributed on the world's fastest computer, the Sunway TaihuLight supercomputer, by supporting master-slave architecture of Sunway many-core processors. Based on large-scale simulations of a runaway beam under parameters of the ITER tokamak, it is revealed that the magnetic ripple field can disperse the pitch-angle distribution significantly and improve the confinement of energetic runaway beam on the same time.

  11. The accurate particle tracer code

    DOE PAGES

    Wang, Yulei; Liu, Jian; Qin, Hong; ...

    2017-07-20

    The Accurate Particle Tracer (APT) code is designed for systematic large-scale applications of geometric algorithms for particle dynamical simulations. Based on a large variety of advanced geometric algorithms, APT possesses long-term numerical accuracy and stability, which are critical for solving multi-scale and nonlinear problems. To provide a flexible and convenient I/O interface, the libraries of Lua and Hdf5 are used. Following a three-step procedure, users can efficiently extend the libraries of electromagnetic configurations, external non-electromagnetic forces, particle pushers, and initialization approaches by use of the extendible module. APT has been used in simulations of key physical problems, such as runawaymore » electrons in tokamaks and energetic particles in Van Allen belt. As an important realization, the APT-SW version has been successfully distributed on the world’s fastest computer, the Sunway TaihuLight supercomputer, by supporting master–slave architecture of Sunway many-core processors. Here, based on large-scale simulations of a runaway beam under parameters of the ITER tokamak, it is revealed that the magnetic ripple field can disperse the pitch-angle distribution significantly and improve the confinement of energetic runaway beam on the same time.« less

  12. The accurate particle tracer code

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Yulei; Liu, Jian; Qin, Hong

    The Accurate Particle Tracer (APT) code is designed for systematic large-scale applications of geometric algorithms for particle dynamical simulations. Based on a large variety of advanced geometric algorithms, APT possesses long-term numerical accuracy and stability, which are critical for solving multi-scale and nonlinear problems. To provide a flexible and convenient I/O interface, the libraries of Lua and Hdf5 are used. Following a three-step procedure, users can efficiently extend the libraries of electromagnetic configurations, external non-electromagnetic forces, particle pushers, and initialization approaches by use of the extendible module. APT has been used in simulations of key physical problems, such as runawaymore » electrons in tokamaks and energetic particles in Van Allen belt. As an important realization, the APT-SW version has been successfully distributed on the world’s fastest computer, the Sunway TaihuLight supercomputer, by supporting master–slave architecture of Sunway many-core processors. Here, based on large-scale simulations of a runaway beam under parameters of the ITER tokamak, it is revealed that the magnetic ripple field can disperse the pitch-angle distribution significantly and improve the confinement of energetic runaway beam on the same time.« less

  13. A comparison of intubation success for paediatric transport team paramedics using lighted vs regular tracheal tube stylets.

    PubMed

    MacNab, A J; MacPhail, I; MacNab, M K; Noble, R; O'Flaherty, D

    1998-01-01

    We conducted a prospective randomized study of success rate and time to intubation using Trachlight and Surch-Lite lighted stylets versus a regular tracheal tube stylet, in a training setting. Participants, 18 paediatric transport paramedics, performed two intubations with each of the three devices, using an airway management trainer. There was no significant difference in mean time for intubation between the three devices. The times for external confirmation of correct tube placement were comparable using the two lighted stylets. External confirmation of the tube placement using the lighted stylets was quicker than laryngoscopic visualization. In darkness, with a nonfunctioning laryngoscope, intubations were successfully performed 100% of the time with the lighted stylet, but only 11% of the time with the regular stylet. All paramedics felt that a lighted stylet would be a useful airway management adjunct for the transport environment for complicated intubations or for use in very high or low levels of ambient light.

  14. 7 CFR 29.112 - Proper light.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Proper light. 29.112 Section 29.112 Agriculture... INSPECTION Regulations Inspectors, Samplers, and Weighers § 29.112 Proper light. Tobacco shall not be inspected or sampled for the purposes of the Act except when displayed in proper light for correct...

  15. 7 CFR 29.112 - Proper light.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Proper light. 29.112 Section 29.112 Agriculture... INSPECTION Regulations Inspectors, Samplers, and Weighers § 29.112 Proper light. Tobacco shall not be inspected or sampled for the purposes of the Act except when displayed in proper light for correct...

  16. 7 CFR 29.112 - Proper light.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Proper light. 29.112 Section 29.112 Agriculture... INSPECTION Regulations Inspectors, Samplers, and Weighers § 29.112 Proper light. Tobacco shall not be inspected or sampled for the purposes of the Act except when displayed in proper light for correct...

  17. 7 CFR 29.112 - Proper light.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Proper light. 29.112 Section 29.112 Agriculture... INSPECTION Regulations Inspectors, Samplers, and Weighers § 29.112 Proper light. Tobacco shall not be inspected or sampled for the purposes of the Act except when displayed in proper light for correct...

  18. 7 CFR 29.112 - Proper light.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Proper light. 29.112 Section 29.112 Agriculture... INSPECTION Regulations Inspectors, Samplers, and Weighers § 29.112 Proper light. Tobacco shall not be inspected or sampled for the purposes of the Act except when displayed in proper light for correct...

  19. Light dosimetry and dose verification for pleural PDT

    NASA Astrophysics Data System (ADS)

    Dimofte, Andreea; Sharikova, Anna V.; Meo, Julia L.; Simone, Charles B.; Friedberg, Joseph S.; Zhu, Timothy C.

    2013-03-01

    In-vivo light dosimetry for patients undergoing photodynamic therapy (PDT) is critical for predicting PDT outcome. Patients in this study are enrolled in a Phase I clinical trial of HPPH-mediated PDT for the treatment of non-small cell lung cancer with pleural effusion. They are administered 4mg per kg body weight HPPH 48 hours before the surgery and receive light therapy with a fluence of 15-45 J/cm2 at 661 and 665nm. Fluence rate (mW/cm2) and cumulative fluence (J/cm2) are monitored at 7 sites during the light treatment delivery using isotropic detectors. Light fluence (rate) delivered to patients is examined as a function of treatment time, volume and surface area. In a previous study, a correlation between the treatment time and the treatment volume and surface area was established. However, we did not include the direct light and the effect of the shape of the pleural surface on the scattered light. A real-time infrared (IR) navigation system was used to separate the contribution from the direct light. An improved expression that accurately calculates the total fluence at the cavity wall as a function of light source location, cavity geometry and optical properties is determined based on theoretical and phantom studies. The theoretical study includes an expression for light fluence rate in an elliptical geometry instead of the spheroid geometry used previously. The calculated light fluence is compared to the measured fluence in patients of different cavity geometries and optical properties. The result can be used as a clinical guideline for future pleural PDT treatment.

  20. Composite resin reinforcement of flared canals using light-transmitting plastic posts.

    PubMed

    Lui, J L

    1994-05-01

    Composite resins have been advocated as a reinforcing build-up material for badly damaged endodontically treated teeth with flared canals. However, the control of an autocuring composite resin is difficult because it polymerizes rapidly within the root canal. While the light-curing composite resins are more user friendly, their polymerization can be a problem deep in the root canal. Light-transmitting plastic posts allow the transmission of light into the root canal and enable intraradicular composite resin reconstitution and reinforcement of weakened roots. At the same time, the light-transmitting plastic post forms an optimal post canal in the rehabilitated root and can accurately fit a matching retentive final post. These light-transmitting posts are a useful addition to the dental armamentarium.