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Sample records for adequate signal-to-noise ratio

  1. Measuring signal-to-noise ratio automatically

    NASA Technical Reports Server (NTRS)

    Bergman, L. A.; Johnston, A. R.

    1980-01-01

    Automated method of measuring signal-to-noise ratio in digital communication channels is more precise and 100 times faster than previous methods used. Method based on bit-error-rate (B&R) measurement can be used with cable, microwave radio, or optical links.

  2. Signal-to-noise ratios in coherent soft limiters

    NASA Technical Reports Server (NTRS)

    Lesh, J. R.

    1973-01-01

    Expressions for the output signal-to-noise power ratio of a bandpass soft limiter followed by a coherent detection device are presented and discussed. It is found that a significant improvement in the output signal-to-noise ratio at low input SNRs can be achieved by such soft limiters as compared to hard limiters. This indicates that the soft limiter may be of some use in the area of threshold extension. Approximation methods for determining output signal-to-noise spectral densities are also presented.

  3. Algorithm for astronomical, point source, signal to noise ratio calculations

    NASA Technical Reports Server (NTRS)

    Jayroe, R. R.; Schroeder, D. J.

    1984-01-01

    An algorithm was developed to simulate the expected signal to noise ratios as a function of observation time in the charge coupled device detector plane of an optical telescope located outside the Earth's atmosphere for a signal star, and an optional secondary star, embedded in a uniform cosmic background. By choosing the appropriate input values, the expected point source signal to noise ratio can be computed for the Hubble Space Telescope using the Wide Field/Planetary Camera science instrument.

  4. Radar antenna pointing for optimized signal to noise ratio.

    SciTech Connect

    Doerry, Armin Walter; Marquette, Brandeis

    2013-01-01

    The Signal-to-Noise Ratio (SNR) of a radar echo signal will vary across a range swath, due to spherical wavefront spreading, atmospheric attenuation, and antenna beam illumination. The antenna beam illumination will depend on antenna pointing. Calculations of geometry are complicated by the curved earth, and atmospheric refraction. This report investigates optimizing antenna pointing to maximize the minimum SNR across the range swath.

  5. Estimating the signal-to-noise ratio of AVIRIS data

    NASA Technical Reports Server (NTRS)

    Curran, Paul J.; Dungan, Jennifer L.

    1988-01-01

    To make the best use of narrowband airborne visible/infrared imaging spectrometer (AVIRIS) data, an investigator needs to know the ratio of signal to random variability or noise (signal-to-noise ratio or SNR). The signal is land cover dependent and varies with both wavelength and atmospheric absorption; random noise comprises sensor noise and intrapixel variability (i.e., variability within a pixel). The three existing methods for estimating the SNR are inadequate, since typical laboratory methods inflate while dark current and image methods deflate the SNR. A new procedure is proposed called the geostatistical method. It is based on the removal of periodic noise by notch filtering in the frequency domain and the isolation of sensor noise and intrapixel variability using the semi-variogram. This procedure was applied easily and successfully to five sets of AVIRIS data from the 1987 flying season and could be applied to remotely sensed data from broadband sensors.

  6. Study of signal-to-noise ratio in digital mammography

    NASA Astrophysics Data System (ADS)

    Kato, Yuri; Fujita, Naotoshi; Kodera, Yoshie

    2009-02-01

    Mammography techniques have recently advanced from those using analog systems (the screen-film system) to those using digital systems; for example, computed radiography (CR) and flat-panel detectors (FPDs) are nowadays used in mammography. Further, phase contrast mammography (PCM)-a digital technique by which images with a magnification of 1.75× can be obtained-is now available in the market. We studied the effect of the air gap in PCM and evaluated the effectiveness of an antiscatter x-ray grid in conventional mammography (CM) by measuring the scatter fraction ratio (SFR) and relative signal-to-noise ratio (rSNR) and comparing them between PCM and the digital CM. The results indicated that the SFRs for the CM images obtained with a grid were the lowest and that these ratios were almost the same as those for the PCM images. In contrast, the rSNRs for the PCM images were the highest, which means that the scattering of x-rays was sufficiently reduced by the air gap without the loss of primary x-rays.

  7. Imaging signal-to-noise ratio of synthetic aperture ladar

    NASA Astrophysics Data System (ADS)

    Liu, Liren

    2015-09-01

    On the basis of the Poisson photocurrent statistics in the photon-limited heterodyne detection, in this paper, the signal-to-noise ratios in the receiver in the time domain and on the focused 1-D image and 2-D image in the space domain are derived for both the down-looking and side-looking synthetic aperture imaging ladars using PIN or APD photodiodes. The major shot noises in the down-looking SAIL and the side-looking SAIL are, respectively, from the dark current of photodiode and the local beam current. It is found that the ratio of 1-D image SNR to receiver SNR is proportional to the number of resolution elements in the cross direction of travel and the ratio of 2-D image SNR to 1-D image SNR is proportional to the number of resolution elements in the travel direction. And the sensitivity, the effect of Fourier transform of sampled signal, and the influence of time response of detection circuit are discussed, too. The study will help to correctly design a SAIL system.

  8. Signal-to-noise ratio in neuro activation PET studies

    SciTech Connect

    Votaw, J.R.

    1996-04-01

    It has become commonplace to compare scanner sensitivity characteristics by comparing noise equivalent count rate curves. However, because a 20-cm diameter uniform phantom is drastically difference from a human brain, these curves give misleading information when planning a neuro activation PET experiment. Signal-to-noise ratio (SNR) calculations have been performed using measured data (Siemens 921 scanner) from the three-dimensional (3-D) Hoffman brain phantom for the purpose of determining the optimal injection and scanning protocol for [{sup 15}O] labeled activation experiments. Region of interest (ROI) values along with the variance due to prompt (trues plus randoms) and random events were determined for various regions and radioactivity concentrations. Calculated attenuation correction was used throughout. Scatter correction was not used when calculating the SNR in activation studies because the number of scattered events is almost identical in each data acquisition and hence cancels. The results indicate that randoms correction should not be performed and that rather than being limited by the scanner capabilities, neuro activation experiments are limited by the amount of radioactivity that can be injected and the length of time the patient can stay in the scanner.

  9. Measuring the signal-to-noise ratio of a neuron

    PubMed Central

    Czanner, Gabriela; Sarma, Sridevi V.; Ba, Demba; Eden, Uri T.; Wu, Wei; Eskandar, Emad; Lim, Hubert H.; Temereanca, Simona; Suzuki, Wendy A.; Brown, Emery N.

    2015-01-01

    The signal-to-noise ratio (SNR), a commonly used measure of fidelity in physical systems, is defined as the ratio of the squared amplitude or variance of a signal relative to the variance of the noise. This definition is not appropriate for neural systems in which spiking activity is more accurately represented as point processes. We show that the SNR estimates a ratio of expected prediction errors and extend the standard definition to one appropriate for single neurons by representing neural spiking activity using point process generalized linear models (PP-GLM). We estimate the prediction errors using the residual deviances from the PP-GLM fits. Because the deviance is an approximate χ2 random variable, we compute a bias-corrected SNR estimate appropriate for single-neuron analysis and use the bootstrap to assess its uncertainty. In the analyses of four systems neuroscience experiments, we show that the SNRs are −10 dB to −3 dB for guinea pig auditory cortex neurons, −18 dB to −7 dB for rat thalamic neurons, −28 dB to −14 dB for monkey hippocampal neurons, and −29 dB to −20 dB for human subthalamic neurons. The new SNR definition makes explicit in the measure commonly used for physical systems the often-quoted observation that single neurons have low SNRs. The neuron’s spiking history is frequently a more informative covariate for predicting spiking propensity than the applied stimulus. Our new SNR definition extends to any GLM system in which the factors modulating the response can be expressed as separate components of a likelihood function. PMID:25995363

  10. Signal to noise ratio of free space homodyne coherent optical communication after adaptive optics compensation

    NASA Astrophysics Data System (ADS)

    Huang, Jian; Mei, Haiping; Deng, Ke; Kang, Li; Zhu, Wenyue; Yao, Zhoushi

    2015-12-01

    Designing and evaluating the adaptive optics system for coherent optical communication link through atmosphere requires to distinguish the effects of the residual wavefront and disturbed amplitude to the signal to noise ratio. Based on the new definition of coherent efficiency, a formula of signal to noise ratio for describing the performance of coherent optical communication link after wavefront compensation is derived in the form of amplitude non-uniformity and wavefront error separated. A beam quality metric is deduced mathematically to evaluate the effect of disturbed amplitude to the signal to noise ratio. Experimental results show that the amplitude fluctuation on the receiver aperture may reduce the signal to noise ratio about 24% on average when Fried coherent length r0=16 cm.

  11. Signal-to-noise ratio of the bispectral analysis of speckle interferometry

    NASA Astrophysics Data System (ADS)

    Nakajima, Tadashi

    1988-09-01

    Monte Carlo simulations of an atmospheric phase screen, based on a Kolmogorov spectrum of phase fluctuations, were performed. Speckle patterns produced from the phase screens were used to derive statistical properties of power spectra and bispectra of speckle interferograms. The bispectral modulation transfer function and its signal-to-noise ratio at high light levels are presented. The results confirm the validity of a heuristic treatment based on an interferometric picture of speckle pattern formation in deriving the attenuation factor and the signal-to-noise ratio of the bispectral modulation tranfer function in the mid-spatial-frequency range. The derived modulation tranfer function is also interpreted in terms of the signal-to-noise ratio at low light levels. A general expression of the signal-to-noise ratio of the bispectrum is derived as a function of the transfer functions of the telescope, the number of speckles, and the mean photon counts in the mid-spatial-frequency range.

  12. Signal to Noise Ratios of Pulsed and Sinewave Modulated Direct Detection Lidar for IPDA Measurements

    NASA Technical Reports Server (NTRS)

    Sun, Xiaoli; Abshire, James B.

    2011-01-01

    The signal-to-noise ratios have been derived for IPDA lidar using a direct detection receiver for both pulsed and sinewave laser modulation techniques, and the results and laboratory measurements are presented

  13. Measurement and analysis of signal to noise ratio for image intensifier tube, 18mm microchannel plate

    NASA Astrophysics Data System (ADS)

    Bai, Xiaofeng; Shi, Feng; Feng, Hanliang; Liu, Rong; Yin, Lei; He, Yingping

    2011-08-01

    Output signal to noise ratio is an important technical index for evaluating detectability of microchannel plate image intensifier tube, and the characteristic for detecting of microchannel plate image intensifier tube restricts the detectability of the night vision system. It has been proved in theory and in practice that the value of output signal to noise ratio of image intensifier tube equipped for night vision system decides the farthest distance and imaging definition of system which used under low light level in square root way. In this article, method and device for measuring the output signal to noise ratio of 18mm microchannel plate image intensifier tube has been introduced in detail. Output signal to noise ratio values of several 18mm microchannel plate image intensifier tube selected have been measured. Contacting to work condition of image intensifier tube, relationship between voltage of cathode, microchannel plate, screen and output signal to noise ratio of 18mm microchannel plate image intensifier tube bas been studied, which is available for other image intensifier tube.

  14. Signal-to-noise ratio for the wide field-planetary camera of the Space Telescope

    NASA Technical Reports Server (NTRS)

    Zissa, D. E.

    1984-01-01

    Signal-to-noise ratios for the Wide Field Camera and Planetary Camera of the Space Telescope were calculated as a function of integration time. Models of the optical systems and CCD detector arrays were used with a 27th visual magnitude point source and a 25th visual magnitude per arc-sq. second extended source. A 23rd visual magnitude per arc-sq. second background was assumed. The models predicted signal-to-noise ratios of 10 within 4 hours for the point source centered on a signal pixel. Signal-to-noise ratios approaching 10 are estimated for approximately 0.25 x 0.25 arc-second areas within the extended source after 10 hours integration.

  15. A high signal-to-noise ratio toroidal electron spectrometer for the SEM.

    PubMed

    Hoang, H Q; Osterberg, M; Khursheed, A

    2011-07-01

    This paper presents a high signal-to-noise ratio electron energy spectrometer attachment for the scanning electron microscope (SEM), designed to measure changes in specimen surface potential from secondary electrons and extract specimen atomic number information from backscattered electrons. Experimental results are presented, which demonstrate that the spectrometer can in principle detect specimen voltage changes well into the sub-mV range, and distinguish close atomic numbers by a signal-to-noise ratio of better than 20. The spectrometer has applications for quantitatively mapping specimen surface voltage and atomic number variations on the nano-scale. PMID:21740873

  16. Photonic microwave quadrature filter with low phase imbalance and high signal-to-noise ratio performance.

    PubMed

    Cao, Yuan; Chan, Erwin H W; Wang, Xudong; Feng, Xinhuan; Guan, Bai-ou

    2015-10-15

    A photonic microwave quadrature filter is presented. It has a very simple structure, very low phase imbalance, and high signal-to-noise ratio performance. Experimental results are presented that demonstrate a photonic microwave quadrature filter with a 3 dB operating frequency range of 10.5-26.5 GHz, an amplitude and phase imbalance of less than ±0.3  dB and ±0.15°, and a signal-to-noise ratio of more than 121 dB in a 1 Hz noise bandwidth. PMID:26469589

  17. Signal-to-noise ratio analysis and evaluation of the Hadamard imaging technique

    NASA Technical Reports Server (NTRS)

    Jobson, D. J.; Katzberg, S. J.; Spiers, R. B., Jr.

    1977-01-01

    The signal-to-noise ratio performance of the Hadamard imaging technique is analyzed and an experimental evaluation of a laboratory Hadamard imager is presented. A comparison between the performances of Hadamard and conventional imaging techniques shows that the Hadamard technique is superior only when the imaging objective lens is required to have an effective F (focus) number of about 2 or slower.

  18. Signal-to-noise ratio for temporal integrated drifting images: a model for perceived image sharpening.

    PubMed

    Power, G J; Sturtz, K E

    2000-12-10

    A formulation of signal-to-noise ratio is constructed that uses temporal integrated images from image sequences. Given a blurred image that drifts horizontally at various speeds and at various linear blurs, we prove that this formulation of the signal-to-noise ratio consistently increases with an increase in speed. This increase is shown to model the trends in the human vision system by which drifting blurred images are perceived with increased sharpness. The existing widely used objective quality techniques fail to model the perceptual increase in sharpness. This new formulation, along with other objective quality measures, is tested on several blurred drifting image sequences. The new formulation reflects the theoretically predicted increase in perceived sharpness. PMID:18354675

  19. Fisher information versus signal-to-noise ratio for a split detector

    NASA Astrophysics Data System (ADS)

    Knee, George C.; Munro, William J.

    2015-07-01

    We study the problem of estimating the magnitude of a Gaussian beam displacement using a two-pixel or "split" detector. We calculate the maximum likelihood estimator and compute its asymptotic mean-squared error via the Fisher information. Although the signal-to-noise ratio is known to be simply related to the Fisher information under idealized detection, we find the two measures of precision differ markedly for a split detector. We show that a greater signal-to-noise ratio "before" the detector leads to a greater information penalty, unless adaptive realignment is used. We find that with an initially balanced split detector, tuning the normalized difference in counts to 0.884753 ... gives the highest posterior Fisher information, which provides an improvement by at least a factor of about 2.5 over operating in the usual linear regime. We discuss the implications for weak-value amplification, a popular probabilistic signal amplification technique.

  20. Improving signal-to-noise ratio performance of compressive imaging based on spatial correlation

    NASA Astrophysics Data System (ADS)

    Mao, Tianyi; Chen, Qian; He, Weiji; Zou, Yunhao; Dai, Huidong; Gu, Guohua

    2016-07-01

    In this paper, compressive imaging based on spatial correlation (CISC), which uses second-order correlation with the measurement matrix, is introduced to improve the signal-to-noise ratio performance of compressive imaging (CI). Numerical simulations and experiments are performed as well. Referred to the results, it can be seen that CISC performs much better than CI in three common noise environments. This provides the great opportunity to pave the way for real applications.

  1. Improving signal-to-noise ratio performance of compressive imaging based on spatial correlation

    NASA Astrophysics Data System (ADS)

    Mao, Tianyi; Chen, Qian; He, Weiji; Zou, Yunhao; Dai, Huidong; Gu, Guohua

    2016-08-01

    In this paper, compressive imaging based on spatial correlation (CISC), which uses second-order correlation with the measurement matrix, is introduced to improve the signal-to-noise ratio performance of compressive imaging (CI). Numerical simulations and experiments are performed as well. Referred to the results, it can be seen that CISC performs much better than CI in three common noise environments. This provides the great opportunity to pave the way for real applications.

  2. Signal-to-noise ratio of the bispectral analysis of speckle interferometry.

    NASA Astrophysics Data System (ADS)

    Nakajima, T.

    Monte Carlo simulations of an atmospheric phase screen have been carried out based on a Kolmogorov spectrum of phase fluctuations. Speckle patterns produced from phase screens are used to derive statistical properties of power spectra and bispectra of speckle interferograms. The autor presents the bispectral modulation transfer function and the signal-to-noise ratio at high light levels and low light levels. The relative importance of the near axis and the mid frequency bispectrum is considered in relation to image recovery procedures.

  3. Periodic variations in the signal-to-noise ratios of signals received from the ICE spacecraft

    NASA Technical Reports Server (NTRS)

    Nadeau, T.

    1986-01-01

    Data from the ICE probe to comet Giacobini-Zinner are analyzed to determine the effects of spacecraft rotation upon the signal to noise ratio (SNR) for the two channels of data. In addition, long-term variations from sources other than rotations are considered. Results include a pronounced SNR variation over a period of three seconds (one rotation) and a lesser effect over a two minute period (possibly due to the receiving antenna conscan).

  4. MERTIS: identifiability of spectral mineralogical features in dependence of the signal to noise ratio

    NASA Astrophysics Data System (ADS)

    Paproth, Carsten; Säuberlich, Thomas

    2011-09-01

    The ESA deep-space mission BepiColombo to planet Mercury will contain the advanced infrared remote sensing instrument MERTIS (MErcury Radiometer and Thermal infrared Imaging Spectrometer). The mission has the goal to explore the planets inner and surface structure and its environment. With MERTIS, investigations of Mercury's surface layer within a spectral range of 7 μm to 14μm shall be conducted to specify and map Mercury's mineralogical composition with a spatial resolution of 500 m. Due to the limited mass and power budget, the used micro-bolometer detector array will only have a temperature-stabilization and will not be cooled. The performance of the instrument is estimated by the theoretical description of the signal to noise ratio and the optics including the Offner spectrometer. The expected signal to noise ratio will be in the order of 100 and is mainly dependent on the surface temperature and the wavelength. The derived theoretical models are used to execute simulations to compute the passage of the infrared radiation of a hypothetical mineralogical surface composition and surface temperature through the optical system of MERTIS. The resulting noisy spectra are used to determine spectral features of the minerals. So it is possible to evaluate the conditions which are necessary to achieve the scientific goals of MERTIS. The intent is to estimate the spectral positions of mineralogical features like the Christiansen feature. This will be difficult because of the low signal to noise ratio and the low contrast of real mineral spectra.

  5. Enhancing scatterometry CD signal-to-noise ratio for 1x logic and memory challenges

    NASA Astrophysics Data System (ADS)

    Shaughnessy, Derrick; Krishnan, Shankar; Wei, Lanhua; Shchegrov, Andrei V.

    2013-04-01

    The ongoing transition from 2D to 3D structures in logic and memory has led to an increased adoption of scatterometry CD (SCD) for inline metrology. However, shrinking device dimensions in logic and high aspect ratios in memory represent primary challenges for SCD and require a significant breakthrough in improving signal-to-noise performance. We present a report on the new generation of SCD technology, enabled by a new laser-driven plasma source. The developed light source provides several key advantages over conventional arc lamps typically used in SCD applications. The plasma color temperature of the laser driven source is considerably higher than available with arc lamps resulting in >5X increase in radiance in the visible and >10X increase in radiance in the DUV when compared to sources on previous generation SCD tools while maintaining or improving source intensity noise. This high radiance across such a broad spectrum allows for the use of a single light source from 190-1700nm. When combined with other optical design changes, the higher source radiance enables reduction of measurement box size of our spectroscopic ellipsometer from 45×45um box to 25×25um box without compromising signal to noise ratio. The benefits for 1×nm SCD metrology of the additional photons across the DUV to IR spectrum have been found to be greater than the increase in source signal to noise ratio would suggest. Better light penetration in Si and poly-Si has resulted in improved sensitivity and correlation breaking for critical parameters in 1xnm FinFET and HAR flash memory structures.

  6. Heterodyne signal-to-noise ratios in acoustic mode scattering experiments

    NASA Technical Reports Server (NTRS)

    Cochran, W. R.

    1980-01-01

    The relation between the signal to noise ratio (SNR) obtained in heterodyne detection of radiation scattered from acoustic modes in crystalline solids and the scattered spectral density function is studied. It is shown that in addition to the information provided by the measured frequency shifts and line widths, measurement of the SNR provides a determination of the absolute elasto-optical (Pockel's) constants. Examples are given for cubic crystals, and acceptable SNR values are obtained for scattering from thermally excited phonons at 10.6 microns, with no external perturbation of the sample necessary. The results indicate the special advantages of the method for the study of semiconductors.

  7. Signal type and signal-to-noise ratio interact to affect cortical auditory evoked potentials.

    PubMed

    Billings, Curtis J; Grush, Leslie D

    2016-08-01

    Use of speech signals and background noise is emerging in cortical auditory evoked potential (CAEP) studies; however, the interaction between signal type and noise level remains unclear. Two experiments determined the interaction between signal type and signal-to-noise ratio (SNR) on CAEPs. Three signals (syllable /ba/, 1000-Hz tone, and the /ba/ envelope with 1000-Hz fine structure) with varying SNRs were used in two experiments, demonstrating signal-by-SNR interactions due to both envelope and spectral characteristics. When using real-world stimuli such as speech to evoke CAEPs, temporal and spectral complexity leads to differences with traditional tonal stimuli, especially when presented in background noise. PMID:27586784

  8. Signal to Noise Ratio Estimations for a Volcanic ASH Detection Lidar. Case Study: The Met Office

    NASA Astrophysics Data System (ADS)

    Georgoussis, George; Adam, Mariana; Avdikos, George

    2016-06-01

    In this paper we calculate the Signal-to-Noise (SNR) ratio of a 3-channel commercial (Raymetics) volcanic ash detection system, (LR111-D300), already operating under Met Office organization. The methodology for the accurate estimation is presented for day and nighttime conditions. The results show that SNR values are higher than 10 for ranges up to 13 km for both nighttime and daytime conditions. This is a quite good result compared with other values presented in bibliography and proves that such system is able to detect volcanic ash over a range of 20 km.

  9. Optimum signal-to-noise ratio in off-axis integrated cavity output spectroscopy.

    PubMed

    Dyroff, Christoph

    2011-04-01

    The signal-to-noise ratio (SNR) in off-axis integrated cavity output spectroscopy (OA-ICOS) is investigated and compared to direct absorption spectroscopy using multipass absorption cells [tunable diode laser absorption spectroscopy (TDLAS)]. Applying measured noise characteristics of a near-IR tunable diode laser and detector, it is shown that the optimum SNR is not generally reached at the highest effective absorption path length. Simulations are used to determine the parameters for maximized SNR of OA-ICOS. PMID:21478999

  10. Effects of noise suppression on intelligibility: dependency on signal-to-noise ratios.

    PubMed

    Hilkhuysen, Gaston; Gaubitch, Nikolay; Brookes, Mike; Huckvale, Mark

    2012-01-01

    The effects on speech intelligibility of three different noise reduction algorithms (spectral subtraction, minimal mean squared error spectral estimation, and subspace analysis) were evaluated in two types of noise (car and babble) over a 12 dB range of signal-to-noise ratios (SNRs). Results from these listening experiments showed that most algorithms deteriorated intelligibility scores. Modeling of the results with a logit-shaped psychometric function showed that the degradation in intelligibility scores was largely congruent with a constant shift in SNR, although some additional degradation was observed at two SNRs, suggesting a limited interaction between the effects of noise suppression and SNR. PMID:22280614

  11. Measuring real-ear signal-to-noise ratio: application to directional hearing aids.

    PubMed

    Bell, Steven L; Creeke, Sarah A; Lutman, Mark E

    2010-03-01

    Due to individual characteristics such as head size, earmould type, and earmould venting, the directional benefit that an individual will obtain from a hearing aid cannot be predicted from average data. It is therefore desirable to measure real ear directional benefit. This paper demonstrates a method to measure real ear hearing aid directivity based on a general approach to measure the broadband output signal-to-noise ratio of a hearing aid. Errors arising from non-linearity were tested in simulation and found to be low for typical hearing aid compression ratios. Next, the efficacy of the method to estimate directional benefit was demonstrated on KEMAR. Finally the variability of directional benefit was explored in real-ears. Significant differences in signal-to-noise ratio between directional and omnidirectional microphone settings were demonstrated at most azimuths. Articulation-Index-weighted directional benefit varied by more than 7 dB across ears at some azimuths. Such individual variation in directional benefit has implications when fitting hearing aids: it should not be assumed that all users will receive similar directional benefit from the same hearing aid. PMID:20151932

  12. Calculation of signal-to-noise ratio (SNR) of infrared detection system based on MODTRAN model

    NASA Astrophysics Data System (ADS)

    Lu, Xue; Li, Chuang; Fan, Xuewu

    2013-09-01

    Signal-to-noise ratio (SNR) is an important parameter of infrared detection system. SNR of infrared detection system is determined by the target infrared radiation, atmospheric transmittance, background infrared radiation and the detector noise. The infrared radiation flux in the atmosphere is determined by the selective absorption of the gas molecules, the atmospheric environment, and the transmission distance of the radiation, etc, so the atmospheric transmittance and infrared radiance flux are intricate parameters. A radiometric model for the calculation of SNR of infrared detection system is developed and used to evaluate the effects of various parameters on signal-to-noise ratio (SNR). An atmospheric modeling tool, MODTRAN, is used to model wavelength-dependent atmospheric transmission and sky background radiance. Then a new expression of SNR is deduced. Instead of using constants such as average atmospheric transmission and average wavelength in traditional method, it uses discrete values for atmospheric transmission and sky background radiance. The integrals in general expression of SNR are converted to summations. The accuracy of SNR obtained from the new method can be improved. By adopting atmospheric condition of the 1976 US standard, no clouds urban aerosols, fall-winter aerosol profiles, the typical spectrum characters of sky background radiance and transmittance are computed by MODTRON. Then the operating ranges corresponding to the threshold quantity of SNR are calculated with the new method. The calculated operating ranges are more close to the measured operating range than those calculated with the traditional method.

  13. Evaluating signal-to-noise ratios, loudness, and related measures as indicators of airborne sound insulation.

    PubMed

    Park, H K; Bradley, J S

    2009-09-01

    Subjective ratings of the audibility, annoyance, and loudness of music and speech sounds transmitted through 20 different simulated walls were used to identify better single number ratings of airborne sound insulation. The first part of this research considered standard measures such as the sound transmission class the weighted sound reduction index (R(w)) and variations of these measures [H. K. Park and J. S. Bradley, J. Acoust. Soc. Am. 126, 208-219 (2009)]. This paper considers a number of other measures including signal-to-noise ratios related to the intelligibility of speech and measures related to the loudness of sounds. An exploration of the importance of the included frequencies showed that the optimum ranges of included frequencies were different for speech and music sounds. Measures related to speech intelligibility were useful indicators of responses to speech sounds but were not as successful for music sounds. A-weighted level differences, signal-to-noise ratios and an A-weighted sound transmission loss measure were good predictors of responses when the included frequencies were optimized for each type of sound. The addition of new spectrum adaptation terms to R(w) values were found to be the most practical approach for achieving more accurate predictions of subjective ratings of transmitted speech and music sounds. PMID:19739735

  14. Multiplane wave imaging increases signal-to-noise ratio in ultrafast ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Tiran, Elodie; Deffieux, Thomas; Correia, Mafalda; Maresca, David; Osmanski, Bruno-Felix; Sieu, Lim-Anna; Bergel, Antoine; Cohen, Ivan; Pernot, Mathieu; Tanter, Mickael

    2015-11-01

    Ultrafast imaging using plane or diverging waves has recently enabled new ultrasound imaging modes with improved sensitivity and very high frame rates. Some of these new imaging modalities include shear wave elastography, ultrafast Doppler, ultrafast contrast-enhanced imaging and functional ultrasound imaging. Even though ultrafast imaging already encounters clinical success, increasing even more its penetration depth and signal-to-noise ratio for dedicated applications would be valuable. Ultrafast imaging relies on the coherent compounding of backscattered echoes resulting from successive tilted plane waves emissions; this produces high-resolution ultrasound images with a trade-off between final frame rate, contrast and resolution. In this work, we introduce multiplane wave imaging, a new method that strongly improves ultrafast images signal-to-noise ratio by virtually increasing the emission signal amplitude without compromising the frame rate. This method relies on the successive transmissions of multiple plane waves with differently coded amplitudes and emission angles in a single transmit event. Data from each single plane wave of increased amplitude can then be obtained, by recombining the received data of successive events with the proper coefficients. The benefits of multiplane wave for B-mode, shear wave elastography and ultrafast Doppler imaging are experimentally demonstrated. Multiplane wave with 4 plane waves emissions yields a 5.8  ±  0.5 dB increase in signal-to-noise ratio and approximately 10 mm in penetration in a calibrated ultrasound phantom (0.7 d MHz-1 cm-1). In shear wave elastography, the same multiplane wave configuration yields a 2.07  ±  0.05 fold reduction of the particle velocity standard deviation and a two-fold reduction of the shear wave velocity maps standard deviation. In functional ultrasound imaging, the mapping of cerebral blood volume results in a 3 to 6 dB increase of the contrast-to-noise ratio in deep

  15. Advantages of a soft protective layer for good signal-to-noise ratio proton radiographs in high debris environments

    NASA Astrophysics Data System (ADS)

    Renard-Le Galloudec, Nathalie; Cobble, J.; Nelson, S. L.; Merwin, A.; Paudel, Y.; Shrestha, I.; Osborne, G. C.; Williamson, K. M.; Kantsyrev, V. L.

    2011-12-01

    Proton radiography is a very powerful diagnostic but in some high debris environments it may be challenging to get a good signal-to-noise ratio radiograph to gain insights into the electric and magnetic field topology, and thus the basic physics. Such environments are produced for example on z-pinches and also on lasers such as the National Ignition Facility. We demonstrate here the feasibility of clean, very high signal-to-noise ratio proton radiographs in extremely hostile environments.

  16. The behavior of quantization spectra as a function of signal-to-noise ratio

    NASA Technical Reports Server (NTRS)

    Flanagan, M. J.

    1991-01-01

    An expression for the spectrum of quantization error in a discrete-time system whose input is a sinusoid plus white Gaussian noise is derived. This quantization spectrum consists of two components: a white-noise floor and spurious harmonics. The dithering effect of the input Gaussian noise in both components of the spectrum is considered. Quantitative results in a discrete Fourier transform (DFT) example show the behavior of spurious harmonics as a function of the signal-to-noise ratio (SNR). These results have strong implications for digital reception and signal analysis systems. At low SNRs, spurious harmonics decay exponentially on a log-log scale, and the resulting spectrum is white. As the SNR increases, the spurious harmonics figure prominently in the output spectrum. A useful expression is given that roughly bounds the magnitude of a spurious harmonic as a function of the SNR.

  17. Signal-to-noise ratio for acoustic detection in the deep ocean

    NASA Technical Reports Server (NTRS)

    Bowen, T.

    1979-01-01

    A simple method is presented for studying the thermoacoustic wave generated by a heat pulse. The signal-to-noise ratio (S/N) is then calculated for a typical hadronic-electromagnetic cascade in the deep ocean where low frequencies are masked by surface noise. It is found that a maximum useful range of about 16 km is found for typical conditions at 5 km depth. It is shown that in order to obtain useful signals with S/N greater than 100 at distances of 1 to 16 km, the cascade energy must be 10 to the 16th to 10 to the 18th eV. Finally, attention is given to further refinements of the theory of acoustic detection which remain to be investigated.

  18. Image signal-to-noise ratio estimation using adaptive slope nearest-neighbourhood model.

    PubMed

    Sim, K S; Teh, V

    2015-12-01

    A new technique based on nearest neighbourhood method is proposed. In this paper, considering the noise as Gaussian additive white noise, new technique single-image-based estimator is proposed. The performance of this new technique such as adaptive slope nearest neighbourhood is compared with three of the existing method which are original nearest neighbourhood (simple method), first-order interpolation method and shape-preserving piecewise cubic hermite autoregressive moving average. In a few cases involving images with different brightness and edges, this adaptive slope nearest neighbourhood is found to deliver an optimum solution for signal-to-noise ratio estimation problems. For different values of noise variance, the adaptive slope nearest neighbourhood has highest accuracy and less percentage estimation error. Being more robust with white noise, the new proposed technique estimator has efficiency that is significantly greater than those of the three methods. PMID:26292081

  19. Signal-to-noise ratio application to seismic marker analysis and fracture detection

    NASA Astrophysics Data System (ADS)

    Xu, Hui-Qun; Gui, Zhi-Xian

    2014-03-01

    Seismic data with high signal-to-noise ratios (SNRs) are useful in reservoir exploration. To obtain high SNR seismic data, significant effort is required to achieve noise attenuation in seismic data processing, which is costly in materials, and human and financial resources. We introduce a method for improving the SNR of seismic data. The SNR is calculated by using the frequency domain method. Furthermore, we optimize and discuss the critical parameters and calculation procedure. We applied the proposed method on real data and found that the SNR is high in the seismic marker and low in the fracture zone. Consequently, this can be used to extract detailed information about fracture zones that are inferred by structural analysis but not observed in conventional seismic data.

  20. Shuttle bit rate synchronizer. [signal to noise ratios and error analysis

    NASA Technical Reports Server (NTRS)

    Huey, D. C.; Fultz, G. L.

    1974-01-01

    A shuttle bit rate synchronizer brassboard unit was designed, fabricated, and tested, which meets or exceeds the contractual specifications. The bit rate synchronizer operates at signal-to-noise ratios (in a bit rate bandwidth) down to -5 dB while exhibiting less than 0.6 dB bit error rate degradation. The mean acquisition time was measured to be less than 2 seconds. The synchronizer is designed around a digital data transition tracking loop whose phase and data detectors are integrate-and-dump filters matched to the Manchester encoded bits specified. It meets the reliability (no adjustments or tweaking) and versatility (multiple bit rates) of the shuttle S-band communication system through an implementation which is all digital after the initial stage of analog AGC and A/D conversion.

  1. Signal-to-noise ratio of Geiger-mode avalanche photodiode single-photon counting detectors

    NASA Astrophysics Data System (ADS)

    Kolb, Kimberly

    2014-08-01

    Geiger-mode avalanche photodiodes (GM-APDs) use the avalanche mechanism of semiconductors to amplify signals in individual pixels. With proper thresholding, a pixel will be either "on" (avalanching) or "off." This discrete detection scheme eliminates read noise, which makes these devices capable of counting single photons. Using these detectors for imaging applications requires a well-developed and comprehensive expression for the expected signal-to-noise ratio (SNR). This paper derives the expected SNR of a GM-APD detector in gated operation based on gate length, number of samples, signal flux, dark count rate, photon detection efficiency, and afterpulsing probability. To verify the theoretical results, carrier-level Monte Carlo simulation results are compared to the derived equations and found to be in good agreement.

  2. Multi-images deconvolution improves signal-to-noise ratio on gated stimulated emission depletion microscopy

    SciTech Connect

    Castello, Marco; Diaspro, Alberto; Vicidomini, Giuseppe

    2014-12-08

    Time-gated detection, namely, only collecting the fluorescence photons after a time-delay from the excitation events, reduces complexity, cost, and illumination intensity of a stimulated emission depletion (STED) microscope. In the gated continuous-wave- (CW-) STED implementation, the spatial resolution improves with increased time-delay, but the signal-to-noise ratio (SNR) reduces. Thus, in sub-optimal conditions, such as a low photon-budget regime, the SNR reduction can cancel-out the expected gain in resolution. Here, we propose a method which does not discard photons, but instead collects all the photons in different time-gates and recombines them through a multi-image deconvolution. Our results, obtained on simulated and experimental data, show that the SNR of the restored image improves relative to the gated image, thereby improving the effective resolution.

  3. Normal-hearing listener preferences of music as a function of signal-to-noise-ratio

    NASA Astrophysics Data System (ADS)

    Barrett, Jillian G.

    2005-04-01

    Optimal signal-to-noise ratios (SNR) for speech discrimination are well-known, well-documented phenomena. Discrimination preferences and functions have been studied for both normal-hearing and hard-of-hearing populations, and information from these studies has provided clearer indices on additional factors affecting speech discrimination ability and SNR preferences. This knowledge lends itself to improvements in hearing aids and amplification devices, telephones, television and radio transmissions, and a wide arena of recorded media such as movies and music. This investigation was designed to identify the preferred signal-to-background ratio (SBR) of normal-hearing listeners in a musical setting. The signal was the singer's voice, and music was considered the background. Subjects listened to an unfamiliar ballad with a female singer, and rated seven different SBR treatments. When listening to melodic motifs with linguistic content, results indicated subjects preferred SBRs similar to those in conventional speech discrimination applications. However, unlike traditional speech discrimination studies, subjects did not prefer increased levels of SBR. Additionally, subjects had a much larger acceptable range of SBR in melodic motifs where the singer's voice was not intended to communicate via linguistic means, but by the pseudo-paralinguistic means of vocal timbre and harmonic arrangements. Results indicate further studies investigating perception of singing are warranted.

  4. A consideration of the signal-to-noise ratio in phase contrast mammography

    NASA Astrophysics Data System (ADS)

    Kato, Yuri; Fujita, Naotoshi; Kodera, Yoshie

    2010-04-01

    Recently, with developments in medicine, digital systems such as computed radiography (CR) and flat-panel detector (FPD) systems are being employed for mammography instead of analog systems such as the screen-film system. Phase-contrast mammography (PCM) is a commercially available digital system that uses images with a magnification of 1.75x. To study the effect of the air gap in PCM, we measured the scatter fraction ratio (SFR) and calculated the signal-to-noise ratio (SNR) in PCM, and compared it to that in conventional mammography (CM). Then, to extend the SNR to the spatial frequency domain, we calculated the noise equivalent quanta (NEQ) and detective quantum efficiency (DQE) used by the modulation transfer function (MTF), noise power spectrum of the pixel value (NPSΔPV), gradient of the digital characteristic curve, and number of X-ray photons. The obtained results indicated that the SFR of the PCM was as low as that of the CM with a grid. When the exposure dose was constant, the SNR of the PCM was the highest in all systems. Moreover, the NEQ and DQE for the PCM were higher than those for the CM (G-) in the spatial frequency domain over 2.5 cycles/mm. These results showed that the number of scattered X-rays was reduced sufficiently by the air gap in the PCM and the NEQ and DQE for PCM were influenced by the presampled MTF in the high-spatial-frequency domain.

  5. Geostatistical estimation of signal-to-noise ratios for spectral vegetation indices

    NASA Astrophysics Data System (ADS)

    Ji, Lei; Zhang, Li; Rover, Jennifer; Wylie, Bruce K.; Chen, Xuexia

    2014-10-01

    In the past 40 years, many spectral vegetation indices have been developed to quantify vegetation biophysical parameters. An ideal vegetation index should contain the maximum level of signal related to specific biophysical characteristics and the minimum level of noise such as background soil influences and atmospheric effects. However, accurate quantification of signal and noise in a vegetation index remains a challenge, because it requires a large number of field measurements or laboratory experiments. In this study, we applied a geostatistical method to estimate signal-to-noise ratio (S/N) for spectral vegetation indices. Based on the sample semivariogram of vegetation index images, we used the standardized noise to quantify the noise component of vegetation indices. In a case study in the grasslands and shrublands of the western United States, we demonstrated the geostatistical method for evaluating S/N for a series of soil-adjusted vegetation indices derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. The soil-adjusted vegetation indices were found to have higher S/N values than the traditional normalized difference vegetation index (NDVI) and simple ratio (SR) in the sparsely vegetated areas. This study shows that the proposed geostatistical analysis can constitute an efficient technique for estimating signal and noise components in vegetation indices.

  6. Geostatistical estimation of signal-to-noise ratios for spectral vegetation indices

    USGS Publications Warehouse

    Ji, Lei; Zhang, Li; Rover, Jennifer R.; Wylie, Bruce K.; Chen, Xuexia

    2014-01-01

    In the past 40 years, many spectral vegetation indices have been developed to quantify vegetation biophysical parameters. An ideal vegetation index should contain the maximum level of signal related to specific biophysical characteristics and the minimum level of noise such as background soil influences and atmospheric effects. However, accurate quantification of signal and noise in a vegetation index remains a challenge, because it requires a large number of field measurements or laboratory experiments. In this study, we applied a geostatistical method to estimate signal-to-noise ratio (S/N) for spectral vegetation indices. Based on the sample semivariogram of vegetation index images, we used the standardized noise to quantify the noise component of vegetation indices. In a case study in the grasslands and shrublands of the western United States, we demonstrated the geostatistical method for evaluating S/N for a series of soil-adjusted vegetation indices derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. The soil-adjusted vegetation indices were found to have higher S/N values than the traditional normalized difference vegetation index (NDVI) and simple ratio (SR) in the sparsely vegetated areas. This study shows that the proposed geostatistical analysis can constitute an efficient technique for estimating signal and noise components in vegetation indices.

  7. Simulation of signal-to-noise ratio for the laser range-gated imaging system

    NASA Astrophysics Data System (ADS)

    Liang, Weiwei; Chen, Qianrong; Hao, Yongwang; Guo, Hao; Zhang, Wenpan

    2015-10-01

    The laser active imaging system is widely used in night vision, underwater imaging, three-dimension scene imaging and other civilian applications, and the system's detected range increase greatly comparing with the passive imaging system. In recent years, with rapid development of sensor and laser source technique, the laser range-gated imaging system is achieved based on high peak power pulsed laser and gated intensified CCD(ICCD), and it is well known for its properties such as high suppression of backscatter noise from fog and other obscurants, high resolution, long detection range and direct visualization. However, the performance of the laser range-gated imaging system is seriously affected by many factors, and the relationships between system's Signal-to-Noise Ratio (SNR) and influence factors are not further elaborated. In this paper, the simulation of SNR for the laser range-gated imaging system is studied. The principle of the laser range-gated imaging system is shown firstly, and the range equation is derived by means of deducing laser illuminating model according to the principle of laser radar and the characters of objects and the detectors. And then, the sources of noise are analyzed by accurately modeling all noise sources in the detection system, the model of SNR for laser range-gated imaging system is established. Finally, the relationships between SNR of system and influence factors such as gating time, laser pulse width and repetition frequency are discussed, and correspondingly the solutions are proposed.

  8. Estimating and improving the signal-to-noise ratio of time series by symbolic dynamics.

    PubMed

    Graben, P

    2001-11-01

    We investigate the effect of symbolic encoding applied to times series consisting of some deterministic signal and additive noise, as well as time series given by a deterministic signal with randomly distributed initial conditions as a model of event-related brain potentials. We introduce an estimator of the signal-to-noise ratio (SNR) of the system by means of time averages of running complexity measures such as Shannon and Rényi entropies, and prove its asymptotical equivalence with the linear SNR in the case of Shannon entropies of symbol distributions. A SNR improvement factor is defined, exhibiting a maximum for intermediate values of noise amplitude in analogy to stochastic resonance phenomena. We demonstrate that the maximum of the SNR improvement factor can be shifted toward smaller noise amplitudes by using higher order Rényi entropies instead of the Shannon entropy. For a further improvement of the SNR, a half wave encoding of noisy time series is introduced. Finally, we discuss the effect of noisy phases on the linear SNR as well as on the SNR defined by symbolic dynamics. It is shown that longer symbol sequences yield an improvement of the latter. PMID:11735897

  9. Improving the signal-to-noise ratio of single-pixel imaging using digital microscanning.

    PubMed

    Sun, Ming-Jie; Edgar, Matthew P; Phillips, David B; Gibson, Graham M; Padgett, Miles J

    2016-05-16

    Single-pixel cameras provide a means to perform imaging at wavelengths where pixelated detector arrays are expensive or limited. The image is reconstructed from measurements of the correlation between the scene and a series of masks. Although there has been much research in the field in recent years, the fact that the signal-to-noise ratio (SNR) scales poorly with increasing resolution has been one of the main limitations prohibiting the uptake of such systems. Microscanning is a technique that provides a final higher resolution image by combining multiple images of a lower resolution. Each of these low resolution images is subject to a sub-pixel sized lateral displacement. In this work we apply a digital microscanning approach to an infrared single-pixel camera. Our approach requires no additional hardware, but is achieved simply by using a modified set of masks. Compared to the conventional Hadamard based single-pixel imaging scheme, our proposed framework improves the SNR of reconstructed images by ∼ 50 % for the same acquisition time. In addition, this strategy also provides access to a stream of low-resolution 'preview' images throughout each high-resolution acquisition. PMID:27409871

  10. Investigation of signal-to-noise ratio in frequency-domain multiphoton fluorescence lifetime imaging microscopy.

    PubMed

    Zhang, Yide; Khan, Aamir A; Vigil, Genevieve D; Howard, Scott S

    2016-07-01

    Multiphoton microscopy (MPM) combined with fluorescence lifetime imaging microscopy (FLIM) has enabled three-dimensional quantitative molecular microscopy in vivo. The signal-to-noise ratio (SNR), and thus the imaging rate of MPM-FLIM, which is fundamentally limited by the shot noise and fluorescence saturation, has not been quantitatively studied yet. In this paper, we investigate the SNR performance of the frequency-domain (FD) MPM-FLIM with two figures of merit: the photon economy in the limit of shot noise, and the normalized SNR in the limit of saturation. The theoretical results and Monte Carlo simulations find that two-photon FD-FLIM requires 50% fewer photons to achieve the same SNR as conventional one-photon FLIM. We also analytically show that the MPM-FD-FLIM can exploit the DC and higher harmonic components generated by nonlinear optical mixing of the excitation light to improve SNR, reducing the required number of photons by an additional 50%. Finally, the effect of fluorophore saturation on the experimental SNR performance is discussed. PMID:27409702

  11. The differential Howland current source with high signal to noise ratio for bioimpedance measurement system

    SciTech Connect

    Liu, Jinzhen; Li, Gang; Lin, Ling; Qiao, Xiaoyan; Wang, Mengjun; Zhang, Weibo

    2014-05-15

    The stability and signal to noise ratio (SNR) of the current source circuit are the important factors contributing to enhance the accuracy and sensitivity in bioimpedance measurement system. In this paper we propose a new differential Howland topology current source and evaluate its output characters by simulation and actual measurement. The results include (1) the output current and impedance in high frequencies are stabilized after compensation methods. And the stability of output current in the differential current source circuit (DCSC) is 0.2%. (2) The output impedance of two current circuits below the frequency of 200 KHz is above 1 MΩ, and below 1 MHz the output impedance can arrive to 200 KΩ. Then in total the output impedance of the DCSC is higher than that of the Howland current source circuit (HCSC). (3) The SNR of the DCSC are 85.64 dB and 65 dB in the simulation and actual measurement with 10 KHz, which illustrates that the DCSC effectively eliminates the common mode interference. (4) The maximum load in the DCSC is twice as much as that of the HCSC. Lastly a two-dimensional phantom electrical impedance tomography is well reconstructed with the proposed HCSC. Therefore, the measured performance shows that the DCSC can significantly improve the output impedance, the stability, the maximum load, and the SNR of the measurement system.

  12. Pixel-based CTE Correction Of ACS/WFC: Effects On Signal To Noise Ratio

    NASA Astrophysics Data System (ADS)

    Avila, Roberto J.; Fruchter, A.; Anderson, J.; ACS Team

    2012-01-01

    The Advanced Camera for Surveys (ACS) team at STScI has tested a new pixel-based empirical correction (Anderson & Bedin, PASP, 122, 1035) software for CTE effects that occur due to the high radiation environment of space. Here we present a study of how this algorithm changes the characteristics of the signal to noise ratio and photometry of point sources. In order to eliminate unknown variables we use simulated images where we can control the noise and CTE characteristics. We explore a parameter space that includes background, object brightness, and position on the chip. Overall we find that while the signal in a source is largely recovered, the noise in the background is amplified. This effect is more noticeable in low background levels and in regions far from the readout amplifiers. Extra care must be taken when measuring the sky background because the use of some common measurement schemes can introduce systematic effects in the photometry. We also show how a simple noise mitigation routine helps in reducing these effects, although they are not completely eliminated.

  13. Local Area Signal-to-Noise Ratio (LASNR) algorithm for Image Segmentation

    SciTech Connect

    Kegelmeyer, L; Fong, P; Glenn, S; Liebman, J

    2007-07-03

    Many automated image-based applications have need of finding small spots in a variably noisy image. For humans, it is relatively easy to distinguish objects from local surroundings no matter what else may be in the image. We attempt to capture this distinguishing capability computationally by calculating a measurement that estimates the strength of signal within an object versus the noise in its local neighborhood. First, we hypothesize various sizes for the object and corresponding background areas. Then, we compute the Local Area Signal to Noise Ratio (LASNR) at every pixel in the image, resulting in a new image with LASNR values for each pixel. All pixels exceeding a pre-selected LASNR value become seed pixels, or initiation points, and are grown to include the full area extent of the object. Since growing the seed is a separate operation from finding the seed, each object can be any size and shape. Thus, the overall process is a 2-stage segmentation method that first finds object seeds and then grows them to find the full extent of the object. This algorithm was designed, optimized and is in daily use for the accurate and rapid inspection of optics from a large laser system (National Ignition Facility (NIF), Lawrence Livermore National Laboratory, Livermore, CA), which includes images with background noise, ghost reflections, different illumination and other sources of variation.

  14. Speech perception at positive signal-to-noise ratios using adaptive adjustment of time compression.

    PubMed

    Schlueter, Anne; Brand, Thomas; Lemke, Ulrike; Nitzschner, Stefan; Kollmeier, Birger; Holube, Inga

    2015-11-01

    Positive signal-to-noise ratios (SNRs) characterize listening situations most relevant for hearing-impaired listeners in daily life and should therefore be considered when evaluating hearing aid algorithms. For this, a speech-in-noise test was developed and evaluated, in which the background noise is presented at fixed positive SNRs and the speech rate (i.e., the time compression of the speech material) is adaptively adjusted. In total, 29 younger and 12 older normal-hearing, as well as 24 older hearing-impaired listeners took part in repeated measurements. Younger normal-hearing and older hearing-impaired listeners conducted one of two adaptive methods which differed in adaptive procedure and step size. Analysis of the measurements with regard to list length and estimation strategy for thresholds resulted in a practical method measuring the time compression for 50% recognition. This method uses time-compression adjustment and step sizes according to Versfeld and Dreschler [(2002). J. Acoust. Soc. Am. 111, 401-408], with sentence scoring, lists of 30 sentences, and a maximum likelihood method for threshold estimation. Evaluation of the procedure showed that older participants obtained higher test-retest reliability compared to younger participants. Depending on the group of listeners, one or two lists are required for training prior to data collection. PMID:26627804

  15. Enhanced signal-to-noise ratios in frog hearing can be achieved through amplitude death

    PubMed Central

    Ahn, Kang-Hun

    2013-01-01

    In the ear, hair cells transform mechanical stimuli into neuronal signals with great sensitivity, relying on certain active processes. Individual hair cell bundles of non-mammals such as frogs and turtles are known to show spontaneous oscillation. However, hair bundles in vivo must be quiet in the absence of stimuli, otherwise the signal is drowned in intrinsic noise. Thus, a certain mechanism is required in order to suppress intrinsic noise. Here, through a model study of elastically coupled hair bundles of bullfrog sacculi, we show that a low stimulus threshold and a high signal-to-noise ratio (SNR) can be achieved through the amplitude death phenomenon (the cessation of spontaneous oscillations by coupling). This phenomenon occurs only when the coupled hair bundles have inhomogeneous distribution, which is likely to be the case in biological systems. We show that the SNR has non-monotonic dependence on the mass of the overlying membrane, and find out that the SNR has maximum value in the region of amplitude death. The low threshold of stimulus through amplitude death may account for the experimentally observed high sensitivity of frog sacculi in detecting vibration. The hair bundles' amplitude death mechanism provides a smart engineering design for low-noise amplification. PMID:23883956

  16. Signal-to-noise ratio in the membrane potential of the owl's auditory coincidence detectors

    PubMed Central

    Funabiki, Kazuo; Kuokkanen, Paula T.; Kempter, Richard; Carr, Catherine E.

    2012-01-01

    Owls use interaural time differences (ITDs) to locate a sound source. They compute ITD in a specialized neural circuit that consists of axonal delay lines from the cochlear nucleus magnocellularis (NM) and coincidence detectors in the nucleus laminaris (NL). Recent physiological recordings have shown that tonal stimuli induce oscillatory membrane potentials in NL neurons (Funabiki K, Ashida G, Konishi M. J Neurosci 31: 15245–15256, 2011). The amplitude of these oscillations varies with ITD and is strongly correlated to the firing rate. The oscillation, termed the sound analog potential, has the same frequency as the stimulus tone and is presumed to originate from phase-locked synaptic inputs from NM fibers. To investigate how these oscillatory membrane potentials are generated, we applied recently developed signal-to-noise ratio (SNR) analysis techniques (Kuokkanen PT, Wagner H, Ashida G, Carr CE, Kempter R. J Neurophysiol 104: 2274–2290, 2010) to the intracellular waveforms obtained in vivo. Our theoretical prediction of the band-limited SNRs agreed with experimental data for mid- to high-frequency (>2 kHz) NL neurons. For low-frequency (≤2 kHz) NL neurons, however, measured SNRs were lower than theoretical predictions. These results suggest that the number of independent NM fibers converging onto each NL neuron and/or the population-averaged degree of phase-locking of the NM fibers could be significantly smaller in the low-frequency NL region than estimated for higher best-frequency NL. PMID:22933726

  17. Development of output signal-to-noise ratio tester for microchannel plate and fluorescent screen component

    NASA Astrophysics Data System (ADS)

    Wu, Xinglin; Qiu, Yafeng; Zhou, Jin; Qian, Yunsheng

    The core components of Image intensifier is microchannel plate (MCP) and fluorescent screen component. The present paper deeply studies output signal-to-noise ratio (SNR) characteristics of MCP and fluorescent screen component. A tester system using to the evaluation of characteristics of the output SNR of MCP and fluorescent screen component, consists of a vacuum system, a surface electron source, mechanical mechanism components ,a high-voltage power supply system, a signal processing system, communication interfaces, a data acquisition and control system, computer system, and testing software. a hot cathode used as an electron source, generates a surface electron flow to provide the input signal. A photomultiplier tube is used to detection faceplate output brightness of the light spot. Then, the output SNR of MCP and fluorescent screen component is processed with a combination of methods of the hardware filter and digital filtering software. The output SNR of MCP and fluorescent screen component is measured under different conditions, and the results are analyzed. This test system Provide a technical to promote the image intensifier research, and experience to testing other parameters or in other areas of research.

  18. Research on signal-to-noise ratio characteristics and image restoration for wavefront coding

    NASA Astrophysics Data System (ADS)

    Wu, Yijian; Zhao, Yuejin; Guo, Xiaohu; Dong, Liquan; Jia, Wei; Liu, Ming; Zhao, Ji; Liu, Yun

    2015-09-01

    Wavefront coding, a technique of optical-digital hybrid image, can be used to extend the depth of the field. However, it sacrifices the signal-to-noise ratio (SNR) of system at a certain degree, especially on focus situation. The on-focus modulation transfer function (MTF) of wavefront coding system is much lower than that of generally traditional optical system. And the noise will be amplified in the digital image processing. This paper analyzes characteristics of the SNR of the wavefront coding system in the frequency domain and calculates the rate of noise amplification in the digital processing. It also explains the influence of the image detector noise severely reducing the restored quality of images. In order to reduce noise amplification in the process of image restoration, we propose a modified wiener filter which is more suitable for restoration in consideration of noise suppression. The simulation experiment demonstrates that the modified wiener filter, compared with traditional wiener filter, has much better performance for wavefront coding system and the restored images having much higher SNR in the whole depth of the field.

  19. Measurement and study on signal-to-noise ratio of a spaceborne camera

    NASA Astrophysics Data System (ADS)

    Chen, Yuheng; Zhou, Jiankang; Chen, Xinhua; Ji, Yiqun; Shen, Weimin

    2011-11-01

    The developed spaceborne camera is an exclusive functional load of a micro satellite. The signal-to-noise ratio (SNR) reflects its radiance response and is the parameter that directly associates with the quality of its acquired images. The SNR determination task of the spaceborne camera mainly consists of two parts: As is reported before firstly the spatial environment is simulated and the atmosphere transmission mode is built with MODTRAN to calculate and predict the SNR of the speceborne camera under aerial working condition. In this paper, the in-lab measuring experiment is carried out to measure the theoretical imaging performance of the camera before its aerial use. An integrating sphere is utilized to supply well-proportioned illumination, and a number of images are acquired by the spaceborne camera under different luminance conditions. The images are processed in use of certain algorithm and a special filter to extract the noise. The SNRs corresponding to different illumination conditions are calculated so that full-scale radiance response feature of the camera can be gained. The dynamic range is another parameter that characterizes the imaging capacity of a camera. The relationship between dynamic range and SNR of a camera is to be explored in this paper. Different dynamic configurations are set and the SNRs of different dynamic range configurations are tested, which experimentally reveals the dynamic range's influence on SNR.

  20. Signal-to-noise ratio-based quality assessment method for ICESat/GLAS waveform data

    NASA Astrophysics Data System (ADS)

    Nie, Sheng; Wang, Cheng; Li, Guicai; Pan, Feifei; Xi, Xiaohuan; Luo, Shezhou

    2014-10-01

    Data quality determines the accuracy of results associated with remote sensing data processing and applications. However, few effective studies have been carried out on quality assessment methods for the full-waveform light detecting and ranging data. Using the geoscience laser altimeter system (GLAS) waveform data as an example, a signal-to-noise ratio (SNR)-based waveform quality assessment method is proposed to analyze the relationship between the SNR and its controlling factors, i.e., laser type, laser using time, topographic relief, and land cover type, and study the impacts of these factors on the quality of the GLAS waveform data. Results show that the SNR-based data quality assessment method can quantitatively and effectively assess the GLAS waveform data quality. The SNR linearly attenuates with the laser using time, and the attenuation rate varies with laser type. The topographic relief is inversely correlated with the SNR of the GLAS data. As the land cover structure (especially the vertical structure) becomes more complex, the SNR of the GLAS data decreases. It was found that land cover types in descending order of the SNR values are desert, farmland, water body, grassland, city, and forest.

  1. Optimizing the Intrinsic Signal-to-Noise Ratio of MRI Strip Detectors

    PubMed Central

    Kumar, Ananda; Bottomley, Paul A.

    2007-01-01

    An MRI detector is formed from a conducting strip separated by a dielectric substrate from a ground plane, and tuned to a quarter-wavelength. By distributing discrete tuning elements along the strip, the geometric design may be adjusted to optimize the signal-to-noise ratio (SNR) for a given application. Here a numerical electromagnetic (EM) method of moments (MoM) is applied to determine the length, width, substrate thickness, dielectric constant, and number of tuning elements that yield the best intrinsic SNR (ISNR) of the strip detector at 1.5 Tesla. The central question of how strip performance compares with that of a conventional optimized loop coil is also addressed. The numerical method is validated against the known ISNR performance of loop coils, and its ability to predict the tuning capacitances and performance of seven experimental strip detectors of varying length, width, substrate thickness, and dielectric constant. We find that strip detectors with low-dielectric constant, moderately thin-substrate, and length about 1.3 (±0.2) times the depth of interest perform best. The ISNR of strips is comparable to that of loops (i.e., higher close to the detector but lower at depth). The SNR improves with two inherently-decoupled strips, whose sensitivity profile is well-suited to parallel MRI. The findings are summarized as design “rules of thumb.” PMID:16724302

  2. Post-embedding tem signal-to-noise ratio of S-100

    NASA Technical Reports Server (NTRS)

    Fermin, C. D.; Lee, D. H.; Martin, D.

    1994-01-01

    We assessed the reactivity of purified S-100 antiserum in immuno-electron microscopy by counting the number of gold particles per microns 2 over inner ear tissues embedded in different media. Sections containing predominantly Schwann's cell cytoplasm and nucleus, afferent fiber axoplasm and myelin sheath of chick cochleae were reacted with anti-S-100 IgG, an antibody to a calcium binding protein of neuronal tissues, then labeled with anti-IgG-gold conjugate. This investigation was conducted because previously published procedures, unmodified, did not yield acceptable results. Preparation of all specimens was identical. Only the medium (PolyBed 812, Araldite or Spurr epoxies; and LR White, LR Gold or Lowicryl plastics) was changed. The medium was made the changing variable because antigens available in post-embedding immuno-electron microscopy are decreased by heat, either used and/or released during polymerization of the embedding medium. The results indicate that: (a) none of the embedding media above provided optimal signal-to-noise ratio for all parts of the nerve stained in the same section; (b) aggregation of gold particles over cells was highest in embedding media with high background labeling over areas devoid of tissue (noise); (c) aggregation occurred randomly throughout both cellular and acellular regions; and (d) particles aggregated less and were distributed more evenly in tissues from media yielding good ultrastructural integrity.

  3. Reproducibility of magnetic resonance spectroscopy in correlation with signal-to-noise ratio.

    PubMed

    Okada, Tomohisa; Sakamoto, Setsu; Nakamoto, Yuji; Kohara, Nobuo; Senda, Michio

    2007-11-15

    An increased amount of myoinositol (mI) relative to creatine (Cr) by proton MR spectroscopy ((1)H-MRS) measurement gives a useful aid for the diagnosis of Alzheimer's disease (AD). Previous results of test-retest measurement of mI, however, have shown variability more than twice as large as for other metabolites. The aims of this study were to analyze test-retest variability of (1)H-MRS measurements in correlation with signal-to-noise ratio (SNR). Ten subjects clinically suspected of mild AD were examined twice (2-14 days apart) with (1)H-MRS measurements of voxels placed at anterior and posterior cingulate cortex. The percent differences between two measurements (%differences) of mI/Cr showed a significant linear trend to decrease as average SNR increased, but %differences of N-acetylaspartate (NAA)/Cr and choline (Cho)/Cr did not. The average of %differences was 10.5, 15.0 and 20.8 for NAA/Cr, Cho/Cr, and mI/Cr, respectively, indicating a prominent deterioration of mI/Cr measurement reproducibility, which decreased to 6.96, 15.4 and 9.87, respectively, when the analysis was limited to measurements with SNR over 25. The results indicate that MRS measurements with high SNR should be used to obtain reliable assessments of mI/Cr as accurate diagnostic indicator of AD in clinical MR examinations. PMID:17900878

  4. Signal-to-noise ratio comparison of encoding methods for hyperpolarized noble gas MRI

    NASA Technical Reports Server (NTRS)

    Zhao, L.; Venkatesh, A. K.; Albert, M. S.; Panych, L. P.

    2001-01-01

    Some non-Fourier encoding methods such as wavelet and direct encoding use spatially localized bases. The spatial localization feature of these methods enables optimized encoding for improved spatial and temporal resolution during dynamically adaptive MR imaging. These spatially localized bases, however, have inherently reduced image signal-to-noise ratio compared with Fourier or Hadamad encoding for proton imaging. Hyperpolarized noble gases, on the other hand, have quite different MR properties compared to proton, primarily the nonrenewability of the signal. It could be expected, therefore, that the characteristics of image SNR with respect to encoding method will also be very different from hyperpolarized noble gas MRI compared to proton MRI. In this article, hyperpolarized noble gas image SNRs of different encoding methods are compared theoretically using a matrix description of the encoding process. It is shown that image SNR for hyperpolarized noble gas imaging is maximized for any orthonormal encoding method. Methods are then proposed for designing RF pulses to achieve normalized encoding profiles using Fourier, Hadamard, wavelet, and direct encoding methods for hyperpolarized noble gases. Theoretical results are confirmed with hyperpolarized noble gas MRI experiments. Copyright 2001 Academic Press.

  5. Coherent dual-comb spectroscopy at high signal-to-noise ratio

    SciTech Connect

    Coddington, I.; Swann, W. C.; Newbury, N. R.

    2010-10-15

    Two coherent frequency combs are used to measure the full complex response of a sample in a configuration analogous to a dispersive Fourier transform spectrometer, infrared time domain spectrometer, or a multiheterodyne laser spectrometer. This dual-comb spectrometer retains the frequency accuracy and resolution of the reference underlying the stabilized combs. We discuss the specific design of our coherent dual-comb spectrometer and demonstrate the potential of this technique by measuring the overtone vibration of hydrogen cyanide, centered at 194 THz (1545 nm). We measure the fully normalized, complex response of the gas over a 9 THz bandwidth at 220 MHz frequency resolution yielding 41,000 resolution elements. The average spectral signal-to-noise ratio (SNR) over the 9 THz bandwidth is 2500 for both the magnitude and phase of the measured spectral response and the peak SNR is 4000. This peak SNR corresponds to a fractional absorption sensitivity of 0.05% and a phase sensitivity of 250 microradians. As the spectral coverage of combs expands, coherent dual-comb spectroscopy could provide high-frequency accuracy and resolution measurements of a complex sample response across a range of spectral regions. Work of U. S. government, not subject to copyright.

  6. Intrinsic low pass filtering improves signal-to-noise ratio in critical-point flexure biosensors

    SciTech Connect

    Jain, Ankit; Alam, Muhammad Ashraful

    2014-08-25

    A flexure biosensor consists of a suspended beam and a fixed bottom electrode. The adsorption of the target biomolecules on the beam changes its stiffness and results in change of beam's deflection. It is now well established that the sensitivity of sensor is maximized close to the pull-in instability point, where effective stiffness of the beam vanishes. The question: “Do the signal-to-noise ratio (SNR) and the limit-of-detection (LOD) also improve close to the instability point?”, however remains unanswered. In this article, we systematically analyze the noise response to evaluate SNR and establish LOD of critical-point flexure sensors. We find that a flexure sensor acts like an effective low pass filter close to the instability point due to its relatively small resonance frequency, and rejects high frequency noise, leading to improved SNR and LOD. We believe that our conclusions should establish the uniqueness and the technological relevance of critical-point biosensors.

  7. The differential Howland current source with high signal to noise ratio for bioimpedance measurement system

    NASA Astrophysics Data System (ADS)

    Liu, Jinzhen; Qiao, Xiaoyan; Wang, Mengjun; Zhang, Weibo; Li, Gang; Lin, Ling

    2014-05-01

    The stability and signal to noise ratio (SNR) of the current source circuit are the important factors contributing to enhance the accuracy and sensitivity in bioimpedance measurement system. In this paper we propose a new differential Howland topology current source and evaluate its output characters by simulation and actual measurement. The results include (1) the output current and impedance in high frequencies are stabilized after compensation methods. And the stability of output current in the differential current source circuit (DCSC) is 0.2%. (2) The output impedance of two current circuits below the frequency of 200 KHz is above 1 MΩ, and below 1 MHz the output impedance can arrive to 200 KΩ. Then in total the output impedance of the DCSC is higher than that of the Howland current source circuit (HCSC). (3) The SNR of the DCSC are 85.64 dB and 65 dB in the simulation and actual measurement with 10 KHz, which illustrates that the DCSC effectively eliminates the common mode interference. (4) The maximum load in the DCSC is twice as much as that of the HCSC. Lastly a two-dimensional phantom electrical impedance tomography is well reconstructed with the proposed HCSC. Therefore, the measured performance shows that the DCSC can significantly improve the output impedance, the stability, the maximum load, and the SNR of the measurement system.

  8. X-ray spectral optimization for mammography applications using signal-to-noise ratio

    NASA Astrophysics Data System (ADS)

    Tucker, Jonathan Ernest

    2000-07-01

    A hypotheses that optimum exposure technique factors for mammography can be computed using uncorrected x-ray spectra measured with an inexpensive semiconductor detector is proven. A parametric model is developed, based upon the minimum signal-to-noise ratio required to perceive an object against background, to predict optimum exposure technique factors. Using published molybdenum- and rhodium-target x-ray spectra, the model predicts that aluminum-filtered molybdenum and rhodium spectra are optimum. The model is subsequently used to predict optimum exposure technique factors using uncorrected x- ray spectra from a GE Senographe DMR mammography unit measured with a cadmium zinc telluride detector and multichannel analyzer. The computed optimum exposure technique factors using uncorrected measured spectra and published spectra are comparable. The model is validated using the uncorrected measured spectra and a phantom containing objects mimicking microcalcifications and fibrous tissue structures. Entrance skin exposure and breast dose for aluminum-filtered spectra are well below those produced using currently popular k-edge filtered spectra. Aluminum-filtered spectra should be considered useful because (1)structures associated with breast cancer can be successfully imaged, and (2)the patient receives a greatly reduced dose.

  9. Theoretical and experimental signal-to-noise ratio assessment in new direction sensing continuous-wave Doppler lidar

    NASA Astrophysics Data System (ADS)

    Tegtmeier Pedersen, A.; Abari, C. F.; Mann, J.; Mikkelsen, T.

    2014-06-01

    A new direction sensing continuous-wave Doppler lidar based on an image-reject homodyne receiver has recently been demonstrated at DTU Wind Energy, Technical University of Denmark. In this contribution we analyse the signal-to-noise ratio resulting from two different data processing methods both leading to the direction sensing capability. It is found that using the auto spectrum of the complex signal to determine the wind speed leads to a signal-to-noise ratio equivalent to that of a standard self-heterodyne receiver. Using the imaginary part of the cross spectrum to estimate the Doppler shift has the benefit of a zero-mean background spectrum, but comes at the expense of a decrease in the signal-to noise ratio by a factor of √2.

  10. Effects of spectrometer band pass, sampling, and signal-to-noise ratio on spectral identification using the Tetracorder algorithm

    NASA Astrophysics Data System (ADS)

    Swayze, Gregg A.; Clark, Roger N.; Goetz, Alexander F. H.; Chrien, Thomas G.; Gorelick, Noel S.

    2003-09-01

    Estimates of spectrometer band pass, sampling interval, and signal-to-noise ratio required for identification of pure minerals and plants were derived using reflectance spectra convolved to AVIRIS, HYDICE, MIVIS, VIMS, and other imaging spectrometers. For each spectral simulation, various levels of random noise were added to the reflectance spectra after convolution, and then each was analyzed with the Tetracorder spectral identification algorithm [Clark et al., 2003]. The outcome of each identification attempt was tabulated to provide an estimate of the signal-to-noise ratio at which a given percentage of the noisy spectra were identified correctly. Results show that spectral identification is most sensitive to the signal-to-noise ratio at narrow sampling interval values but is more sensitive to the sampling interval itself at broad sampling interval values because of spectral aliasing, a condition when absorption features of different materials can resemble one another. The band pass is less critical to spectral identification than the sampling interval or signal-to-noise ratio because broadening the band pass does not induce spectral aliasing. These conclusions are empirically corroborated by analysis of mineral maps of AVIRIS data collected at Cuprite, Nevada, between 1990 and 1995, a period during which the sensor signal-to-noise ratio increased up to sixfold. There are values of spectrometer sampling and band pass beyond which spectral identification of materials will require an abrupt increase in sensor signal-to-noise ratio due to the effects of spectral aliasing. Factors that control this threshold are the uniqueness of a material's diagnostic absorptions in terms of shape and wavelength isolation, and the spectral diversity of the materials found in nature and in the spectral library used for comparison. Array spectrometers provide the best data for identification when they critically sample spectra. The sampling interval should not be broadened to

  11. Improvement of the signal-to-noise ratio in static-mode down-looking synthetic aperture imaging ladar

    NASA Astrophysics Data System (ADS)

    Lu, Zhiyong; Sun, Jianfeng; Zhang, Ning; Zhou, Yu; Cai, Guangyu; Liu, Liren

    2015-09-01

    The static-mode down-looking synthetic aperture imaging ladar (SAIL) can keep the target and carrying-platform still during the collection process. Improvement of the signal-to-noise ratio in static-mode down-looking SAIL is investigated. The signal-to-noise ratio is improved by increasing scanning time and sampling rate in static-mode down-looking SAIL. In the experiment, the targets are reconstructed in different scanning time and different sampling rate. As the increasing of the scanning time and sampling rate, the reconstructed images become clearer. These techniques have a great potential for applications in extensive synthetic aperture imaging ladar fields.

  12. Effects of spectrometer band pass, sampling, and signal-to-noise ratio on spectral identification using the Tetracorder algorithm

    USGS Publications Warehouse

    Swayze, G.A.; Clark, R.N.; Goetz, A.F.H.; Chrien, T.H.; Gorelick, N.S.

    2003-01-01

    Estimates of spectrometer band pass, sampling interval, and signal-to-noise ratio required for identification of pure minerals and plants were derived using reflectance spectra convolved to AVIRIS, HYDICE, MIVIS, VIMS, and other imaging spectrometers. For each spectral simulation, various levels of random noise were added to the reflectance spectra after convolution, and then each was analyzed with the Tetracorder spectra identification algorithm [Clark et al., 2003]. The outcome of each identification attempt was tabulated to provide an estimate of the signal-to-noise ratio at which a given percentage of the noisy spectra were identified correctly. Results show that spectral identification is most sensitive to the signal-to-noise ratio at narrow sampling interval values but is more sensitive to the sampling interval itself at broad sampling interval values because of spectral aliasing, a condition when absorption features of different materials can resemble one another. The band pass is less critical to spectral identification than the sampling interval or signal-to-noise ratio because broadening the band pass does not induce spectral aliasing. These conclusions are empirically corroborated by analysis of mineral maps of AVIRIS data collected at Cuprite, Nevada, between 1990 and 1995, a period during which the sensor signal-to-noise ratio increased up to sixfold. There are values of spectrometer sampling and band pass beyond which spectral identification of materials will require an abrupt increase in sensor signal-to-noise ratio due to the effects of spectral aliasing. Factors that control this threshold are the uniqueness of a material's diagnostic absorptions in terms of shape and wavelength isolation, and the spectral diversity of the materials found in nature and in the spectral library used for comparison. Array spectrometers provide the best data for identification when they critically sample spectra. The sampling interval should not be broadened to

  13. Low-dose, phase-contrast mammography with high signal-to-noise ratio

    PubMed Central

    Gromann, Lukas B.; Bequé, Dirk; Scherer, Kai; Willer, Konstantin; Birnbacher, Lorenz; Willner, Marian; Herzen, Julia; Grandl, Susanne; Hellerhoff, Karin; Sperl, Jonathan I.; Pfeiffer, Franz; Cozzini, Cristina

    2016-01-01

    Differential phase-contrast X-ray imaging using a Talbot-Lau interferometer has recently shown promising results for applications in medical imaging. However, reducing the applied radiation dose remains a major challenge. In this study, we consider the realization of a Talbot-Lau interferometer in a high Talbot order to increase the signal-to-noise ratio for low-dose applications. The quantitative performance of π and π/2 systems at high Talbot orders is analyzed through simulations, and the design energy and X-ray spectrum are optimized for mammography. It is found that operation even at very high Talbot orders is feasible and beneficial for image quality. As long as the X-ray spectrum is matched to the visibility spectrum, the SNR continuously increases with the Talbot order for π-systems. We find that the optimal X-ray spectra and design energies are almost independent of the Talbot order and that the overall imaging performance is robust against small variations in these parameters. Discontinuous spectra, such as that from molybdenum, are less robust because the characteristic lines may coincide with minima in the visibility spectra; however, they may offer slightly better performance. We verify this hypothesis by realizing a prototype system with a mean fringe visibility of above 40% at the seventh Talbot order. With this prototype, a proof-of-principle measurement of a freshly dissected breast at reasonable compression to 4 cm is conducted with a mean glandular dose of only 3 mGy but with a high SNR. PMID:26977347

  14. Analysis of in-plane signal-to-noise ratio in computed tomography

    NASA Astrophysics Data System (ADS)

    Hara, Takanori; Ichikawa, Katsuhiro; Sanada, Shigeru; Ida, Yoshihiro

    2008-03-01

    The purposes of this study are to analyze signal-to-noise ratio (SNR) changes for in-plane (axial plane) position and in-plane direction in X-ray computed tomography (CT) system and to verify those visual effects by using simulated small low-contrast disc objects. Three-models of multi detector-row CT were employed. Modulation transfer function (MTF) was obtained using a thin metal wire. Noise power spectrum (NPSs) was obtained using a cylindrical water phantom. The measurement positions were set to center and off-centered positions of 64mm, 128mm and 192mm. One-dimensional MTFs and NPSs for the x- and y-direction were calculated by means of a numerical slit scanning method. SNRs were then calculated from MTFs and NPSs. The simulated low-contrast disc objects with diameter of 2 to 10mm and contrast to background of 3.0%, 4.5% and 6.0% were superimposed on the water phantom images. Respective simulated objects in the images are then visually evaluated in degree of their recognition, and then the validity of the resultant SNRs are examined. Resultant in-plane SNRs differed between the center and peripheries and indicated a trend that the SNR values increase in accordance with distance from the center. The increasing degree differed between x- and y-direction, and also changed by the CT systems. These results suggested that the peripheries region has higher low-contrast detectability than the center. The properties derived in this study indicated that the depiction abilities at various in-plane positions are not uniform in clinical CT images, and detectability of the low contrast lesion may be influenced.

  15. Low-dose, phase-contrast mammography with high signal-to-noise ratio.

    PubMed

    Gromann, Lukas B; Bequé, Dirk; Scherer, Kai; Willer, Konstantin; Birnbacher, Lorenz; Willner, Marian; Herzen, Julia; Grandl, Susanne; Hellerhoff, Karin; Sperl, Jonathan I; Pfeiffer, Franz; Cozzini, Cristina

    2016-02-01

    Differential phase-contrast X-ray imaging using a Talbot-Lau interferometer has recently shown promising results for applications in medical imaging. However, reducing the applied radiation dose remains a major challenge. In this study, we consider the realization of a Talbot-Lau interferometer in a high Talbot order to increase the signal-to-noise ratio for low-dose applications. The quantitative performance of π and π/2 systems at high Talbot orders is analyzed through simulations, and the design energy and X-ray spectrum are optimized for mammography. It is found that operation even at very high Talbot orders is feasible and beneficial for image quality. As long as the X-ray spectrum is matched to the visibility spectrum, the SNR continuously increases with the Talbot order for π-systems. We find that the optimal X-ray spectra and design energies are almost independent of the Talbot order and that the overall imaging performance is robust against small variations in these parameters. Discontinuous spectra, such as that from molybdenum, are less robust because the characteristic lines may coincide with minima in the visibility spectra; however, they may offer slightly better performance. We verify this hypothesis by realizing a prototype system with a mean fringe visibility of above 40% at the seventh Talbot order. With this prototype, a proof-of-principle measurement of a freshly dissected breast at reasonable compression to 4 cm is conducted with a mean glandular dose of only 3 mGy but with a high SNR. PMID:26977347

  16. Optimization of polarizer azimuth in improving signal-to-noise ratio in Kerr microscopy.

    PubMed

    Wang, X; Lian, J; Xu, X J; Li, X; Li, P; Li, M M; Wang, Y; Liu, Y X

    2016-03-01

    The magneto optical Kerr effect (MOKE) is a widely used technique in magnetic domain imaging for its high surface sensitivity and external magnetic compatibility. Optimization of Kerr microscopy will improve the detecting sensitivity and provide high-quality domain images. In this work, we provide a method to optimize the polarizer azimuth in improving the signal-to-noise ratio (S/N) in longitudinal Kerr microscopy with the generalized magneto optical ellipsometry. Detailed analysis of the MOKE signal and the noise components are provided to study the optimum polarizer and analyzer azimuth combinations. Results show that, for a fixed polarizer angle 1°, the laser intensity noise and the shot noise, which vary with the input laser power, have a similar amplitude and decline with the analyzer azimuth increasing. When the analyzer is set at the extinction place, the Johnson noise plays a dominate role in the total noise. Then, the S/N values are calculated to find the optimum polarizer and analyzer azimuth. Results show that the optimum polarizer and analyzer azimuth combination for Permalloy is (18.35°, 68.35°) under an incident angle of 45°. After that, the S/N of 200 nm Permalloy at different analyzer angles with the polarizer azimuth set at 18.35° is measured to verify the validity of the simulation results. At last, the S/N at different incident angles is calculated. Results show that the optimum incident angle of 200 nm Permalloy film to improve the S/N is 70.35° under the polarizer and analyzer angles set at the optimal combinations (18.35°, 68.35°). PMID:26974636

  17. Effect of signal to noise ratio on the speech perception ability of older adults

    PubMed Central

    Shojaei, Elahe; Ashayeri, Hassan; Jafari, Zahra; Zarrin Dast, Mohammad Reza; Kamali, Koorosh

    2016-01-01

    Background: Speech perception ability depends on auditory and extra-auditory elements. The signal- to-noise ratio (SNR) is an extra-auditory element that has an effect on the ability to normally follow speech and maintain a conversation. Speech in noise perception difficulty is a common complaint of the elderly. In this study, the importance of SNR magnitude as an extra-auditory effect on speech perception in noise was examined in the elderly. Methods: The speech perception in noise test (SPIN) was conducted on 25 elderly participants who had bilateral low–mid frequency normal hearing thresholds at three SNRs in the presence of ipsilateral white noise. These participants were selected by available sampling method. Cognitive screening was done using the Persian Mini Mental State Examination (MMSE) test. Results: Independent T- test, ANNOVA and Pearson Correlation Index were used for statistical analysis. There was a significant difference in word discrimination scores at silence and at three SNRs in both ears (p≤0.047). Moreover, there was a significant difference in word discrimination scores for paired SNRs (0 and +5, 0 and +10, and +5 and +10 (p≤0.04)). No significant correlation was found between age and word recognition scores at silence and at three SNRs in both ears (p≥0.386). Conclusion: Our results revealed that decreasing the signal level and increasing the competing noise considerably reduced the speech perception ability in normal hearing at low–mid thresholds in the elderly. These results support the critical role of SNRs for speech perception ability in the elderly. Furthermore, our results revealed that normal hearing elderly participants required compensatory strategies to maintain normal speech perception in challenging acoustic situations. PMID:27390712

  18. A HIGH SIGNAL-TO-NOISE RATIO COMPOSITE SPECTRUM OF GAMMA-RAY BURST AFTERGLOWS

    SciTech Connect

    Christensen, L.; Fynbo, J. P. U.; Prochaska, J. X.; Jakobsson, P.

    2011-02-01

    We present a composite spectrum of 60 long duration gamma-ray burst (GRB) afterglows with redshifts in the range 0.35 < z < 6.7 observed with low-resolution optical spectra. The composite spectrum covers the wavelength range 700-6600 A in the rest frame and has a mean signal-to-noise ratio of 150 per 1 A pixel and reaches a maximum of {approx}300 in the range 2500-3500 A. Equivalent widths are measured from metal absorption lines from the Ly{alpha} line to {approx}5200 A, and associated metal and hydrogen lines are identified between the Lyman break and Ly{alpha} line. The average transmission within the Lyman forest is consistent with that found along quasar lines of sight. We find a temporal variation in fine-structure lines when dividing the sample into bursts observed within 2 hr from their trigger and those observed later. Other lines in the predominantly neutral gas show variations too, but this is most likely a random effect caused by weighting of individual strong absorption lines and which mimics a temporal variation. Bursts characterized with high- or low-prompt GRB energy release produce afterglows with similar absorption line strengths, and likewise for bursts with bright or faint optical afterglows. Bursts defined as dark from their optical to X-ray spectral index have stronger absorption lines relative to the optically bright bursts. The composite spectrum has strong Ca II and Mg II absorption lines as commonly found in dusty galaxies, however, we find no evidence for dust or a significant molecular content based on the non-detection of diffuse interstellar bands. Compared to starburst galaxy spectra, the GRB composite has much stronger fine-structure lines, while metal absorption lines are weaker.

  19. A High Signal-to-noise Ratio Composite Spectrum of Gamma-ray Burst Afterglows

    NASA Astrophysics Data System (ADS)

    Christensen, L.; Fynbo, J. P. U.; Prochaska, J. X.; Thöne, C. C.; de Ugarte Postigo, A.; Jakobsson, P.

    2011-02-01

    We present a composite spectrum of 60 long duration gamma-ray burst (GRB) afterglows with redshifts in the range 0.35 < z < 6.7 observed with low-resolution optical spectra. The composite spectrum covers the wavelength range 700-6600 Å in the rest frame and has a mean signal-to-noise ratio of 150 per 1 Å pixel and reaches a maximum of ~300 in the range 2500-3500 Å. Equivalent widths are measured from metal absorption lines from the Lyα line to ~5200 Å, and associated metal and hydrogen lines are identified between the Lyman break and Lyα line. The average transmission within the Lyman forest is consistent with that found along quasar lines of sight. We find a temporal variation in fine-structure lines when dividing the sample into bursts observed within 2 hr from their trigger and those observed later. Other lines in the predominantly neutral gas show variations too, but this is most likely a random effect caused by weighting of individual strong absorption lines and which mimics a temporal variation. Bursts characterized with high- or low-prompt GRB energy release produce afterglows with similar absorption line strengths, and likewise for bursts with bright or faint optical afterglows. Bursts defined as dark from their optical to X-ray spectral index have stronger absorption lines relative to the optically bright bursts. The composite spectrum has strong Ca II and Mg II absorption lines as commonly found in dusty galaxies, however, we find no evidence for dust or a significant molecular content based on the non-detection of diffuse interstellar bands. Compared to starburst galaxy spectra, the GRB composite has much stronger fine-structure lines, while metal absorption lines are weaker.

  20. Signal-to-noise ratio enhancement of silicon nanowires biosensor with rolling circle amplification.

    PubMed

    Gao, Anran; Zou, Nengli; Dai, Pengfei; Lu, Na; Li, Tie; Wang, Yuelin; Zhao, Jianlong; Mao, Hongju

    2013-09-11

    Herein, we describe a novel approach for rapid, label-free and specific DNA detection by applying rolling circle amplification (RCA) based on silicon nanowire field-effect transistor (SiNW-FET) for the first time. Highly responsive SiNWs were fabricated with a complementary metal oxide semiconductor (CMOS) compatible anisotropic self-stop etching technique which eliminated the need for hybrid method. The probe DNA was immobilized on the surface of SiNW, followed by sandwich hybridization with the perfectly matched target DNA and RCA primer that acted as a primer to hybridize the RCA template. The RCA reaction created a long single-stranded DNA (ssDNA) product and thus enhanced the electronic responses of SiNW significantly. The signal-to-noise ratio (SNR) as a figure-of-merit was analyzed to estimate the signal enhancement and possible detection limit. The nanosensor showed highly sensitive concentration-dependent conductance change in response to specific target DNA sequences. Because of the binding of an abundance of repeated sequences of RCA products, the SNR of >20 for 1 fM DNA detection was achieved, implying a detection floor of 50 aM. This RCA-based SiNW biosensor also discriminated perfectly matched target DNA from one-base mismatched DNA with high selectivity due to the substantially reduced nonspecific binding onto the SiNW surface through RCA. The combination of SiNW FET sensor with RCA will increase diagnostic capacity and the ability of laboratories to detect unexpected viruses, making it a potential tool for early diagnosis of gene-related diseases. PMID:23937430

  1. Garonne River monitoring from Signal-to-Noise Ratio data collected by a single geodetic receiver

    NASA Astrophysics Data System (ADS)

    Roussel, Nicolas; Frappart, Frédéric; Darrozes, José; Ramillien, Guillaume; Bonneton, Philippe; Bonneton, Natalie; Detandt, Guillaume; Roques, Manon; Orseau, Thomas

    2016-04-01

    GNSS-Reflectometry (GNSS-R) altimetry has demonstrated a strong potential for water level monitoring through the last decades. Interference Pattern Technique (IPT) based on the analysis of the Signal-to-Noise Ratio (SNR) estimated by a GNSS receiver, presents the main advantage of being applicable everywhere by using a single geodetic antenna and a classical GNSS receiver. Such a technique has already been tested in various configurations of acquisition of surface-reflected GNSS signals with an accuracy of a few centimeters. Nevertheless, classical SNR analysis method used to estimate the variations of the reflecting surface height h(t) has a limited domain of validity due to its variation rate dh/dt(t) assumed to be negligible. In [1], authors solve this problem with a "dynamic SNR method" taking the dynamic of the surface into account to conjointly estimate h(t) and dh/dt(t) over areas characterized by high amplitudes of tides. If the performance of this dynamic SNR method is already well-established for ocean monitoring [1], it was not validated in continental areas (i.e., river monitoring). We carried out a field study during 3 days in August and September, 2015, using a GNSS antenna to measure the water level variations in the Garonne River (France) in Podensac located 140 km downstream of the estuary mouth. In this site, the semi-diurnal tide amplitude reaches ~5 m. The antenna was located ~10 m above the water surface, and reflections of the GNSS electromagnetic waves on the Garonne River occur until 140 m from the antenna. Both classical SNR method and dynamic SNR method are tested and results are compared. [1] N. Roussel, G. Ramillien, F. Frappart, J. Darrozes, A. Gay, R. Biancale, N. Striebig, V. Hanquiez, X. Bertin, D. Allain : "Sea level monitoring and sea state estimate using a single geodetic receiver", Remote Sensing of Environment 171 (2015) 261-277.

  2. The Effect of Classroom Amplification on the Signal-to-Noise Ratio in Classrooms while Class Is in Session

    ERIC Educational Resources Information Center

    Larsen, Jeffery B.; Blair, James C.

    2008-01-01

    Purpose: The purpose of this study was to measure the signal-to-noise ratios in classrooms while class was in session and students were interacting with the teacher and each other. Method: Measurements of noise and reverberation were collected for 5 different classrooms in 3 different schools while class was in session. Activities taking place…

  3. Signal to Noise Ratio Analysis of the Data from the Pulsed Airborne CO2 Lidar Measurements

    NASA Astrophysics Data System (ADS)

    Sun, X.; Abshire, J. B.; Riris, H.; Allan, G. R.; Hasselbrack, W. E.

    2009-12-01

    consistent with predictions And Cloud echoes could reliably be identified and separated from the surface echoes. Here we report a detailed assessment of the receiver signal to noise ratio from the airborne measurements , including those from recent flights. We will show samples of the received signal and noise from different altitudes and over types of ground surfaces. We will also determine the surface height variability and range measurement precisions from the time offlight of the laser pulses.

  4. A Measure of the Signal-to-Noise Ratio of Microarray Samples and Studies Using Gene Correlations

    PubMed Central

    Venet, David; Detours, Vincent; Bersini, Hugues

    2012-01-01

    Background The quality of gene expression data can vary dramatically from platform to platform, study to study, and sample to sample. As reliable statistical analysis rests on reliable data, determining such quality is of the utmost importance. Quality measures to spot problematic samples exist, but they are platform-specific, and cannot be used to compare studies. Results As a proxy for quality, we propose a signal-to-noise ratio for microarray data, the “Signal-to-Noise Applied to Gene Expression Experiments”, or SNAGEE. SNAGEE is based on the consistency of gene-gene correlations. We applied SNAGEE to a compendium of 80 large datasets on 37 platforms, for a total of 24,380 samples, and assessed the signal-to-noise ratio of studies and samples. This allowed us to discover serious issues with three studies. We show that signal-to-noise ratios of both studies and samples are linked to the statistical significance of the biological results. Conclusions We showed that SNAGEE is an effective way to measure data quality for most types of gene expression studies, and that it often outperforms existing techniques. Furthermore, SNAGEE is platform-independent and does not require raw data files. The SNAGEE R package is available in BioConductor. PMID:23251415

  5. Seafloor ground rotation observations: potential for improving signal-to-noise ratio on horizontal OBS components

    NASA Astrophysics Data System (ADS)

    Lindner, Fabian; Wassermann, Joachim; Schmidt-Aursch, Mechita; Schreiber, Ulrich; Igel, Heiner

    2015-04-01

    It is well known that the horizontal components of ocean bottom seismometer (OBS) records have a very poor signal-to-noise (S/N) ratio compared to the vertical components, the difference substantially exceeding that of terrestrial records. This is unfortunate as 1) OBS experiments are expensive and the main possibility to gather data in offshore areas, and 2) today we are more and more interested in modelling complete waveforms including all three components aiming at optimally constraining geophysical parameters for inverse problems for Earth's structure and seismic sources. Despite the fact that it is expected that tilting is the major cause of this high S/N - to our knowledge - this effect has never been directly observed. The reason is that (standard) instruments for the measurement of uncontaminated rotational ground motions with the required sensitivity still do not exist. Here, we report observations from an experiment we carried out in the North Sea, close to the island of Helgoland in the summer of 2014. A commercial fibre-optic gyro (usually used for navigation purposes) recording ground rotation rate with a sensitivity of approx. 10-7 rad/s was mounted on an OBS system together with a broadband seismometer. The system was lowered to the seafloor for about a week. To investigate a potential connection between rotational ground motions around the two horizontal axes (i.e., tilting) we calculate the coherence between the corresponding motion components (e.g., rotations around x-axis and translational motions along y-axis, and vice versa). We find very high correlations, on average exceeding 0.73 in the period interval 7-13 seconds. Correlations seem to increase with noise amplitude. Rotation rate amplitudes are in the range of 10-6 -10-5 rad/s. This clearly indicates that the horizontal translational components are severely contaminated by rotations around the horizontal axes. The ground rotation observations allow correcting for this effect thereby

  6. Enhanced signal-to-noise ratio estimation for tropospheric lidar channels

    NASA Astrophysics Data System (ADS)

    Saeed, Umar; Barragan, Rubén; Rocadenbosch, Francesc

    2016-04-01

    This works combines the fields of tropospheric lidar remote sensing and signal processing to come up with a robust signal-to-noise ratio (SNR) estimator apt for elastic and Raman channels. The estimator uses a combined low-pass / high-pass filtering scheme along with high-order statistics (kurtosis) to estimate the range-dependent signal and noise components with minimum distortion. While low-pass filtering is used to estimate the range-dependent signal level, high-pass filtering is used to estimate the noise component with minimum distortion. From this noise component estimate (a random realization) the noise level (e.g., variance) is computed as a function of range along with error bars. The minimum-distortion specification determines the optimal cut-off de-noising filter frequency and, in turn, the spatial resolution of the SNR estimation algorithm. The proposed SNR estimator has a much wider dynamic range of operation than well-known classic SNR estimation techniques, in which the SNR is directly computed from the mean and standard deviation of the measured noise-corrupted lidar signal along successive adjacent range intervals and where the spatial resolution is just a subjective input from the user's side. Aligned with ACTRIS (http://www.actris.net) WP on "optimization of the processing chain and Single-Calculus Chain (SCC)" the proposed topic is of application to assess lidar reception channel performance and confidence on the detected atmospheric morphology (e.g., cloud base and top, and location of aerosol layers). The SNR algorithm is tested against the classic SNR estimation approach using test-bed synthetic lidar data modelling the UPC multi-spectral lidar. Towards this end, the Nd:YAG UPC elastic-Raman lidar provides aerosol channels in the near-infrared (1064 nm), visible (532 nm), and ultra-violet (355 nm) as well as aerosol Raman and water-vapour channels with fairly varying SNR levels. The SNR estimator is also used to compare SNR levels between

  7. Techniques and software tools for estimating ultrasonic signal-to-noise ratios

    NASA Astrophysics Data System (ADS)

    Chiou, Chien-Ping; Margetan, Frank J.; McKillip, Matthew; Engle, Brady J.; Roberts, Ronald A.

    2016-02-01

    At Iowa State University's Center for Nondestructive Evaluation (ISU CNDE), the use of models to simulate ultrasonic inspections has played a key role in R&D efforts for over 30 years. To this end a series of wave propagation models, flaw response models, and microstructural backscatter models have been developed to address inspection problems of interest. One use of the combined models is the estimation of signal-to-noise ratios (S/N) in circumstances where backscatter from the microstructure (grain noise) acts to mask sonic echoes from internal defects. Such S/N models have been used in the past to address questions of inspection optimization and reliability. Under the sponsorship of the National Science Foundation's Industry/University Cooperative Research Center at ISU, an effort was recently initiated to improve existing research-grade software by adding graphical user interface (GUI) to become user friendly tools for the rapid estimation of S/N for ultrasonic inspections of metals. The software combines: (1) a Python-based GUI for specifying an inspection scenario and displaying results; and (2) a Fortran-based engine for computing defect signal and backscattered grain noise characteristics. The latter makes use of several models including: the Multi-Gaussian Beam Model for computing sonic fields radiated by commercial transducers; the Thompson-Gray Model for the response from an internal defect; the Independent Scatterer Model for backscattered grain noise; and the Stanke-Kino Unified Model for attenuation. The initial emphasis was on reformulating the research-grade code into a suitable modular form, adding the graphical user interface and performing computations rapidly and robustly. Thus the initial inspection problem being addressed is relatively simple. A normal-incidence pulse/echo immersion inspection is simulated for a curved metal component having a non-uniform microstructure, specifically an equiaxed, untextured microstructure in which the average

  8. Signal to Noise Ratio for Different Gridded Rainfall Products of Indian Monsoon

    NASA Astrophysics Data System (ADS)

    Nehra, P.; Shastri, H. K.; Ghosh, S.; Mishra, V.; Murtugudde, R. G.

    2014-12-01

    Gridded rainfall datasets provide useful information of spatial and temporal distribution of precipitation over a region. For India, there are 3 gridded rainfall data products available from India Meteorological Department (IMD), Tropical Rainfall Measurement Mission (TRMM) and Asian Precipitation - Highly Resolved Observational Data Integration towards Evaluation of Water Resources (APHRODITE), these compile precipitation information obtained through satellite based measurement and ground station based data. The gridded rainfall data from IMD is available at spatial resolution of 1°, 0.5° and 0.25° where as TRMM and APHRODITE is available at 0.25°. Here, we employ 7 years (1998-2004) of common time period amongst the 3 data products for the south-west monsoon season, i.e., the months June to September. We examine temporal mean and standard deviation of these 3 products to observe substantial variation amongst them at 1° resolution whereas for 0.25° resolution, all the data types are nearly identical. We determine the Signal to Noise Ratio (SNR) of the 3 products at 1° and 0.25° resolution based on noise separation technique adopting horizontal separation of the power spectrum generated with the Fast Fourier Transformation (FFT). A methodology is developed for threshold based separation of signal and noise from the power spectrum, treating the noise as white. The variance of signal to that of noise is computed to obtain SNR. Determination of SNR for different regions over the country shows the highest SNR with APHRODITE at 0.25° resolution. It is observed that the eastern part of India has the highest SNR in all cases considered whereas the northern and southern most Indian regions have lowest SNR. An incremental linear trend is observed among the SNR values and the spatial variance of corresponding region. Relationship between the computed SNR values and the interpolation method used with the dataset is analyzed. The SNR analysis provides an effective

  9. The Effect of Vegetation on Soil Moisture Retrievals from GPS Signal-to-Noise Ratio Data

    NASA Astrophysics Data System (ADS)

    Chew, C. C.; Small, E. E.; Larson, K. M.; Zavorotny, V.

    2012-12-01

    GPS-Interferometric Reflectometry (GPS-IR) is a method of environmental monitoring that relates changes in ground-reflected (multipath) GPS signals to changes in surface soil moisture and vegetative state for an area of approximately 1000 m2 surrounding a GPS antenna. GPS-IR operates as a bi-static radar: L2C frequency signals transmitted by GPS satellites and subsequent reflections (multipath) are measured by antennas at permanent GPS stations. Changes in multipath signals are seen in signal-to-noise ratio (SNR) interferograms, which are recorded by the GPS receiver. Results from previous field studies have shown that shallow soil moisture can be estimated from SNR phase for bare soil conditions or when vegetation is sparse. Vegetation surrounding a GPS antenna affects the phase shift, amplitude, and frequency/apparent reflector height of SNR oscillations. Therefore, it is necessary to quantify the vegetation conditions, for example vegetation height or water content, that preclude retrieval of soil moisture estimates using GPS-IR. We use both field data and an electrodynamic model that simulates SNR interferograms for variable soil and vegetation conditions to: 1. Determine how changes in vegetation height, biomass, and water content affect GPS phase, amplitude, and apparent reflector height and 2. Quantify the amount of vegetation that obscures the soil moisture signal in SNR data. We report results for rangeland and agricultural sites. At the rangeland sites, vegetation water content only varies between 0 and 0.6 kg/m2. Both observed and simulated SNR data from these sites show that apparent reflector height is nearly constant. Therefore, SNR interferograms are strongly affected by permittivity at the soil surface, and thus soil moisture can be retrieved. Even though reflector height does not change, SNR phase shift and amplitude are affected by fluctuations in rangeland vegetation and must be accounted for in soil moisture retrievals. At several agricultural

  10. Signal-to-Noise Ratio Measures Efficacy of Biological Computing Devices and Circuits

    PubMed Central

    Beal, Jacob

    2015-01-01

    Engineering biological cells to perform computations has a broad range of important potential applications, including precision medical therapies, biosynthesis process control, and environmental sensing. Implementing predictable and effective computation, however, has been extremely difficult to date, due to a combination of poor composability of available parts and of insufficient characterization of parts and their interactions with the complex environment in which they operate. In this paper, the author argues that this situation can be improved by quantitative signal-to-noise analysis of the relationship between computational abstractions and the variation and uncertainty endemic in biological organisms. This analysis takes the form of a ΔSNRdB function for each computational device, which can be computed from measurements of a device’s input/output curve and expression noise. These functions can then be combined to predict how well a circuit will implement an intended computation, as well as evaluating the general suitability of biological devices for engineering computational circuits. Applying signal-to-noise analysis to current repressor libraries shows that no library is currently sufficient for general circuit engineering, but also indicates key targets to remedy this situation and vastly improve the range of computations that can be used effectively in the implementation of biological applications. PMID:26177070

  11. Signal-to-Noise Ratio Measures Efficacy of Biological Computing Devices and Circuits.

    PubMed

    Beal, Jacob

    2015-01-01

    Engineering biological cells to perform computations has a broad range of important potential applications, including precision medical therapies, biosynthesis process control, and environmental sensing. Implementing predictable and effective computation, however, has been extremely difficult to date, due to a combination of poor composability of available parts and of insufficient characterization of parts and their interactions with the complex environment in which they operate. In this paper, the author argues that this situation can be improved by quantitative signal-to-noise analysis of the relationship between computational abstractions and the variation and uncertainty endemic in biological organisms. This analysis takes the form of a ΔSNRdB function for each computational device, which can be computed from measurements of a device's input/output curve and expression noise. These functions can then be combined to predict how well a circuit will implement an intended computation, as well as evaluating the general suitability of biological devices for engineering computational circuits. Applying signal-to-noise analysis to current repressor libraries shows that no library is currently sufficient for general circuit engineering, but also indicates key targets to remedy this situation and vastly improve the range of computations that can be used effectively in the implementation of biological applications. PMID:26177070

  12. Local improvement of the signal-to-noise ratio for diffractive optical elements designed by unidirectional optimization methods

    NASA Astrophysics Data System (ADS)

    Meister, Martin; Winfield, Richard J.

    2002-12-01

    We present a straightforward method to design multilevel phase-only diffractive optical elements with a locally improved signal-to-noise ratio in the reconstruction. The method is generally applicable to all unidirectional design schemes, such as direct search, simulated annealing, or genetic optimization. As the shape and the location of the desired low noise areas are supplied by a bit map file the method allows for the design of basically any two-dimensional low noise area. The improvement in the signal-to-noise ratio that may be achieved is considerable but also entails reduced diffraction efficiency. The suggested method is applied to different beam-splitter design examples. All examples are calculated with the scalar diffraction approximation in the far field.

  13. Improving the signal-to-noise ratio of thermal ghost imaging based on positive-negative intensity correlation

    NASA Astrophysics Data System (ADS)

    Song, Shu-Chun; Sun, Ming-Jie; Wu, Ling-An

    2016-05-01

    Ghost imaging with thermal light is a topic in optical imaging that has aroused great interest in recent years. However, the imaging quality must be greatly improved before the technology can be transferred from the lab to engineering applications. By means of correspondence ghost imaging (CGI) with a pseudo-thermal light source and appropriate sorting of the intensity fluctuations of the signal and reference beams, we obtain the positive and negative Hanbury Brown and Twiss intensity correlation characteristics of the optical field. Then, for ghost imaging of a transmissive binary object, we find that by subtracting the negative from the positive fluctuation frames of the presorted reference detector signals, the signal-to-noise ratio can be effectively increased, with almost all the background noise eliminated. Our results show that, compared with the generic CGI technique, the signal-to-noise ratio can be increased by nearly 60%.

  14. Analysis of signal to noise ratio for atmospheric ultraviolet remote sensing on geostationary orbit with variations of solar incident angles

    NASA Astrophysics Data System (ADS)

    Lyu, Chun-guang; Yang, Wen-bo; Tian, Qing-jiu; Zhou, Yang; Liu, Zong-ming; Zhang, Han-mo

    2014-11-01

    Ultraviolet (UV) sensors on a geostationary orbit (GEO) have important potential value in atmospheric remote sensing, but the satellites orbit mode of it is quit different from sun-synchronous orbit satellites, which result in the significant diurnal and seasonal variations in radiation environment of earth observation and radiation signal of sensors, therefore, the effect to sensor radiometric performance, such as signal to noise ratio for atmospheric ultraviolet remote sensing caused by variations of solar angle is significant in the performance design of sensors. The synthetic ultraviolet sensor is set at the geostationary orbit, 36000 km away from the sea level of the Equator with 8.75 degree field of view, and the subsatellite track point of which is located at 90 degrees east longitude and Equator. The Satellite scanning angles (SA) from 0 to 8.648 degree that cover the earth surface are selected corresponding to the 10 degrees equal interval view zenith angle, and the SA from 8.648 to 8.785 degree cover the earth lamb 100 km far away from earth tangent point. Based on the MODTRAN4 model, on normal atmospheric conditions, the distributions of the UV upwelling radiance from surface or limb viewing path of the earth could be simulated with the change of sun's right ascension. Moreover, the average signal to noise ratio to the atmospheric sounding is obtained in different UV spectra using the Sensor signal to noise ratio model. The results show that the thresholds range, tendency and shape of signal to noise ratio have a variety of features affected by variation of Sun hour angles and declinations. These result and conclusions could contribute to performance design of UV sensors on the geostationary orbit.

  15. Improving signal-to-noise ratio by use of a cross-shaped aperture in the holographic data storage system.

    PubMed

    Gu, Huarong; Yin, Songfeng; Tan, Qiaofeng; Cao, Liangcai; He, Qingsheng; Jin, Guofan

    2009-11-10

    A cross-shaped aperture is proposed to improve signal-to-noise ratio (SNR) in the holographic data storage system (HDSS). Both simulated and experimental results show that higher SNR can be achieved by the cross-shaped aperture than traditional square or circular apertures with the same area. A maximum gain of 20% in SNR is obtained for the optimized cross-shaped aperture. The sensitivities to pixel misalignment and magnification error are also numerically compared. PMID:19904322

  16. Detection of eccentric supermassive black hole binaries with pulsar timing arrays: Signal-to-noise ratio calculations

    NASA Astrophysics Data System (ADS)

    Huerta, E. A.; McWilliams, Sean T.; Gair, Jonathan R.; Taylor, Stephen R.

    2015-09-01

    We present a detailed analysis of the expected signal-to-noise ratios of supermassive black hole binaries on eccentric orbits observed by pulsar timing arrays. We derive several analytical relations that extend the results of Peters and Mathews [Phys. Rev. D 131, 435 (1963)] to quantify the impact of eccentricity in the detection of single resolvable binaries in the pulsar timing array band. We present ready-to-use expressions to compute the increase/loss in signal-to-noise ratio of eccentric single resolvable sources whose dominant harmonic is located in the low/high frequency sensitivity regime of pulsar timing arrays. Building upon the work of Phinney (arXiv:astro-ph/0108028) and Enoki and Nagashima [Prog. Theor. Phys. 117, 241 (2007)], we present an analytical framework that enables the construction of rapid spectra for a stochastic gravitational-wave background generated by a cosmological population of eccentric sources. We confirm previous findings which indicate that, relative to a population of quasicircular binaries, the strain of a stochastic, isotropic gravitational-wave background generated by a cosmological population of eccentric binaries will be suppressed in the frequency band of pulsar timing arrays. We quantify this effect in terms of signal-to-noise ratios in a pulsar timing array.

  17. Attitude determination for small satellites using GPS signal-to-noise ratio

    NASA Astrophysics Data System (ADS)

    Peters, Daniel

    An embedded system for GPS-based attitude determination (AD) using signal-to-noise (SNR) measurements was developed for CubeSat applications. The design serves as an evaluation testbed for conducting ground based experiments using various computational methods and antenna types to determine the optimum AD accuracy. Raw GPS data is also stored to non-volatile memory for downloading and post analysis. Two low-power microcontrollers are used for processing and to display information on a graphic screen for real-time performance evaluations. A new parallel inter-processor communication protocol was developed that is faster and uses less power than existing standard protocols. A shorted annular patch (SAP) antenna was fabricated for the initial ground-based AD experiments with the testbed. Static AD estimations with RMS errors in the range of 2.5° to 4.8° were achieved over a range of off-zenith attitudes.

  18. Basic approach to define signal-to-noise ratio for adjacent pixels for an uncooled microbolometer FPA detector

    NASA Astrophysics Data System (ADS)

    Kürüm, Ulas

    2013-09-01

    To define the ratio of the signal of the desired pixel and the noise of adjacent pixels, noise and signal sources are theoretically identified. While defining these values, atmospheric attenuation, losses at transmitting surfaces and wave characteristics of light are considered. For presentation purposes, a standard NATO target is chosen as source object. The model has been developed for a simple optical design which is intentionally left defective to better address effects of aberrations to signal to noise ratio of adjacent pixels especially caused by diffraction.

  19. Considerations on nonlinearity measurement with high signal-to-noise ratio for RF surface and bulk acoustic wave devices

    NASA Astrophysics Data System (ADS)

    Kodaira, Ryosuke; Omori, Tatsuya; Hashimoto, Ken-ya; Kyoya, Haruki; Nakagawa, Ryo

    2015-07-01

    This paper discusses the measurement setup of non-linearity caused in radio frequency (RF) surface and bulk acoustic wave (SAW/BAW) devices with high signal-to-noise ratio (SNR). It is shown that when some important points are considered, the background level can be suppressed better than -135 dBm, and the non-linearity signals can be measured in high SNR. Finally, measured results are compared with those measured independently by Murata Manufacturing, and validity of the measurement is cross-checked.

  20. Signal-to-noise ratio estimation on SEM images using cubic spline interpolation with Savitzky-Golay smoothing.

    PubMed

    Sim, K S; Kiani, M A; Nia, M E; Tso, C P

    2014-01-01

    A new technique based on cubic spline interpolation with Savitzky-Golay noise reduction filtering is designed to estimate signal-to-noise ratio of scanning electron microscopy (SEM) images. This approach is found to present better result when compared with two existing techniques: nearest neighbourhood and first-order interpolation. When applied to evaluate the quality of SEM images, noise can be eliminated efficiently with optimal choice of scan rate from real-time SEM images, without generating corruption or increasing scanning time. PMID:24164248

  1. High-precision image-drift-correction method for EM images with a low signal-to-noise ratio.

    PubMed

    Isakozawa, Shigeto; Tomonaga, Sachihiko; Hashimoto, Takahito; Baba, Norio

    2014-08-01

    The phase correlation method (PCM) is well known for high-precision matching between images. However, if the signal-to-noise ratio of an image is low, the method is difficult to apply. To solve this problem, we developed an improved PCM that can match images automatically with sub-pixel matching precision. Using this method, a 0.2-nm crystal lattice spacing was clearly revealed after 10 blurred images were processed in a verification experiment; such a lattice could not be recognized or hardly be recognized in each individual image. PMID:24827157

  2. Signal-to-noise ratio estimation in digital computer simulation of lowpass and bandpass systems with applications to analog and digital communications, volume 3

    NASA Technical Reports Server (NTRS)

    Tranter, W. H.; Turner, M. D.

    1977-01-01

    Techniques are developed to estimate power gain, delay, signal-to-noise ratio, and mean square error in digital computer simulations of lowpass and bandpass systems. The techniques are applied to analog and digital communications. The signal-to-noise ratio estimates are shown to be maximum likelihood estimates in additive white Gaussian noise. The methods are seen to be especially useful for digital communication systems where the mapping from the signal-to-noise ratio to the error probability can be obtained. Simulation results show the techniques developed to be accurate and quite versatile in evaluating the performance of many systems through digital computer simulation.

  3. Low concentration of a Gd-chelate increases the signal-to-noise ratio in fast pulsing BEST experiments

    NASA Astrophysics Data System (ADS)

    Sibille, Nathalie; Bellot, Gaëtan; Wang, Jing; Déméné, Hélène

    2012-11-01

    Despite numerous developments in the past few years that aim to increase the sensitivity of NMR multidimensional experiments, NMR spectroscopy still suffers from intrinsic low sensitivity. In this report, we show that the combination of two developments in the field, the Band-selective Excitation Short-Transient (BEST) experiment [Schanda et al., J. Am. Chem. Soc., 128 (2006) 9042] and the addition of the nonionic paramagnetic gadolinium chelate gadodiamide into NMR samples, enhances the signal-to-noise ratio. This effect is shown here for four different proteins, three globular and one unfolded, of molecular weights ranging from 6.5 kDa to 40 kDa, using 2D BEST HSQC and 3D BEST triple resonance sequences. Moreover, we show that the increase in signal-to-noise ratio provided by the gadodiamide is higher for peak resonances with lower than average intensity in BEST experiments. It is interesting to note that these residues are on average the weakest ones in those experiments. In this case, the gadodiamide-mediated increase can reach a value of 60% for low and 30% for high molecular weight proteins respectively. An investigation into the origin of this “paramagnetic gain” in BEST experiments is presented.

  4. Emotional content of an image attracts attention more than visually salient features in various signal-to-noise ratio conditions.

    PubMed

    Pilarczyk, Joanna; Kuniecki, Michał

    2014-01-01

    Emotional images are processed in a prioritized manner, attracting attention almost immediately. In the present study we used eye tracking to reveal what type of features within neutral, positive, and negative images attract early visual attention: semantics, visual saliency, or their interaction. Semantic regions of interest were selected by observers, while visual saliency was determined using the Graph-Based Visual Saliency model. Images were transformed by adding pink noise in several proportions to be presented in a sequence of increasing and decreasing clarity. Locations of the first two fixations were analyzed. The results showed dominance of semantic features over visual saliency in attracting attention. This dominance was linearly related to the signal-to-noise ratio. Semantic regions were fixated more often in emotional images than in neutral ones, if signal-to-noise ratio was high enough to allow participants to comprehend the gist of a scene. Visual saliency on its own did not attract attention above chance, even in the case of pure noise images. Regions both visually salient and semantically relevant attracted a similar amount of fixation compared to semantic regions alone, or even more in the case of neutral pictures. Results provide evidence for fast and robust detection of semantically relevant features. PMID:25294641

  5. The signal-to-noise ratio as a measure of HA oligomer concentration: a MALDI-TOF MS study.

    PubMed

    Busse, Katja; Averbeck, Marco; Anderegg, Ulf; Arnold, Klaus; Simon, Jan C; Schiller, Jürgen

    2006-06-12

    MALDI-TOF MS (matrix-assisted laser desorption and ionization time-of-flight mass spectrometry) was used to determine ng amounts of defined hyaluronan (HA) oligomers obtained by enzymatic digestion of high molecular weight HA with testicular hyaluronate lyase. The signal-to-noise (S/N) ratio of the positive and negative ion spectra represents a reliable concentration measure: Amounts of HA down to about 40 fmol could be determined and there is a linear correlation between the S/N ratio and the HA amount between about 0.8 pmol and 40 fmol. However, the detection limits depend considerably on the size of the HA oligomer with larger oligomers being less sensitively detectable. The advantages and drawbacks of the S/N ratio as concentration measure are discussed. PMID:16584713

  6. Signal Scaling Improves the Signal-to-Noise Ratio of Measurements with Segmented 2D-Selective Radiofrequency Excitations

    PubMed Central

    Finsterbusch, Jürgen; Busch, Martin G.; Larson, Peder E. Z.

    2016-01-01

    Purpose Segmented 2D-selective radiofrequency excitations can be used to acquire irregularly shaped target regions, e.g., in single-voxel MR spectroscopy, without involving excessive radiofrequency pulse durations. However, segments covering only outer k-space regions nominally use reduced B1 amplitudes (i.e., smaller flip angles) and yield lower signal contributions, which decreases the efficiency of the measurement. The purpose of this study was to show that applying the full flip angle for all segments and scaling down the acquired signal appropriately (signal scaling) retains the desired signal amplitude but reduces the noise level accordingly and, thus, increases the signal-to-noise ratio. Methods The principles and improvements of signal scaling were demonstrated with MR imaging and spectroscopy experiments at 3 T for a single-line segmentation of a blipped-planar trajectory. Results The observed signal-to-noise ration gain depended on the 2D-selective radiofrequency excitation’s resolution, field-of-excitation, and its excitation profile and was between 40 and 500% for typical acquisition parameters. Conclusion Signal scaling can further improve the performance of measurements with segmented 2D-selective radiofrequency excitations, e.g., for MR spectroscopy of anatomically defined voxels. PMID:23440633

  7. Lidar Application to Early Forest Fire Detection : Signal To Noise Ratio Optimization

    NASA Astrophysics Data System (ADS)

    Traïche, M.; Beggar, R.; Almabouada, F.

    2009-09-01

    In this communication we deal with a lidar system utilising an eye safe laser wavelength at 1.57 μm and an avalanche photodiode detector where it is question to optimize the SNR ratio so as to manage the detector performance when resolving the smoke plume presence. This is by considering supplement rangefinder and visibilimeter options in the considered Lidar system.

  8. Enhancement of the signal-to-noise ratio at depths in Fourier domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Bradu, Adrian; Bouchal, Petr; Podoleanu, Adrian Gh.

    2012-01-01

    We present a Fourier domain optical coherence tomography set-up built around an optical configuration that exhibits Talbot bands. To produce Talbot bands, the two interferometer beams, object and reference are laterally shifted in their way towards the diffraction grating. This allows attenuation of mirror terms and optimisation of the sensitivity profile. We imaged the human skin in-vivo, and quantified the profile of the sensitivity profile in tissue by measuring the ratio between the strengths of signals originating in the reticular dermis and in the stratum corneum for different values of the lateral shift of the two interfering beams.

  9. Approaches to Increasing Surface Stress for Improving Signal-to-Noise Ratio of Microcantilever Sensors

    PubMed Central

    Ji, Hai-Feng; Armon, Benjamin D.

    2010-01-01

    Summary Microcantilever sensor technology has been steadily growing for the last fifteen years. While we have gained a great amount of knowledge in microcantilever bending due to surface stress changes, which is a unique property of microcantilever sensors, we are still in the early stages of understanding the fundamental surface chemistries of surface-stress-based microcantilever sensors. In general, increasing surface stress, which is caused by interactions on the microcantilever surfaces, would improve the S/N ratio, and subsequently the sensitivity and reliability of microcantilever sensors. In this review, we will summarize: A) the conditions under which a large surface stress can readily be attained, and B) the strategies to increase surface stress in case a large surface stress can not readily be reached. We will also discuss our perspectives on microcantilever sensors based on surface stress changes. PMID:20128621

  10. High-resolution restoration of 3D structures from widefield images with extreme low signal-to-noise-ratio

    PubMed Central

    Arigovindan, Muthuvel; Fung, Jennifer C.; Elnatan, Daniel; Mennella, Vito; Chan, Yee-Hung Mark; Pollard, Michael; Branlund, Eric; Sedat, John W.; Agard, David A.

    2013-01-01

    Four-dimensional fluorescence microscopy—which records 3D image information as a function of time—provides an unbiased way of tracking dynamic behavior of subcellular components in living samples and capturing key events in complex macromolecular processes. Unfortunately, the combination of phototoxicity and photobleaching can severely limit the density or duration of sampling, thereby limiting the biological information that can be obtained. Although widefield microscopy provides a very light-efficient way of imaging, obtaining high-quality reconstructions requires deconvolution to remove optical aberrations. Unfortunately, most deconvolution methods perform very poorly at low signal-to-noise ratios, thereby requiring moderate photon doses to obtain acceptable resolution. We present a unique deconvolution method that combines an entropy-based regularization function with kernels that can exploit general spatial characteristics of the fluorescence image to push the required dose to extreme low levels, resulting in an enabling technology for high-resolution in vivo biological imaging. PMID:24106307

  11. Effect of media property variations on shingled magnetic recording channel bit error rate and signal to noise ratio performance

    NASA Astrophysics Data System (ADS)

    Lin, Maria Yu; Teo, Kim Keng; Chan, Kheong Sann

    2015-05-01

    Shingled Magnetic Recording (SMR) is an upcoming technology to see the hard disk drive industry over until heat assisted magnetic recording or another technology matures. In this work, we study the impact of variations in media parameters on the raw channel bit error rate (BER) through micromagnetic simulations and the grain flipping probability channel model in the SMR situation. This study aims to provide feedback to media designers on how media property variations influence the SMR channel performance. In particular, we analyse the effect of variations in the anisotropy constant (Ku), saturation magnetization (Ms), easy axis (ez), grain size (gs), and exchange coupling (Ax), on the written micromagnetic output and the ensuing hysteresis loop. We also compare these analyses with the channel performance on signal to noise ratio (SNR) and the raw channel BER.

  12. Performance of signal-to-noise ratio estimation for scanning electron microscope using autocorrelation Levinson-Durbin recursion model.

    PubMed

    Sim, K S; Lim, M S; Yeap, Z X

    2016-07-01

    A new technique to quantify signal-to-noise ratio (SNR) value of the scanning electron microscope (SEM) images is proposed. This technique is known as autocorrelation Levinson-Durbin recursion (ACLDR) model. To test the performance of this technique, the SEM image is corrupted with noise. The autocorrelation function of the original image and the noisy image are formed. The signal spectrum based on the autocorrelation function of image is formed. ACLDR is then used as an SNR estimator to quantify the signal spectrum of noisy image. The SNR values of the original image and the quantified image are calculated. The ACLDR is then compared with the three existing techniques, which are nearest neighbourhood, first-order linear interpolation and nearest neighbourhood combined with first-order linear interpolation. It is shown that ACLDR model is able to achieve higher accuracy in SNR estimation. PMID:26871742

  13. Resolution and signal-to-noise ratio improvement in confocal fluorescence microscopy using array detection and maximum-likelihood processing

    NASA Astrophysics Data System (ADS)

    Kakade, Rohan; Walker, John G.; Phillips, Andrew J.

    2016-08-01

    Confocal fluorescence microscopy (CFM) is widely used in biological sciences because of its enhanced 3D resolution that allows image sectioning and removal of out-of-focus blur. This is achieved by rejection of the light outside a detection pinhole in a plane confocal with the illuminated object. In this paper, an alternative detection arrangement is examined in which the entire detection/image plane is recorded using an array detector rather than a pinhole detector. Using this recorded data an attempt is then made to recover the object from the whole set of recorded photon array data; in this paper maximum-likelihood estimation has been applied. The recovered object estimates are shown (through computer simulation) to have good resolution, image sectioning and signal-to-noise ratio compared with conventional pinhole CFM images.

  14. Possible breakthrough: Significant improvement of signal to noise ratio by stochastic resonance

    SciTech Connect

    Kiss, L.B.

    1996-06-01

    The {ital simplest} {ital stochastic} {ital resonator} {ital is} {ital used}, {ital a} {ital level} {ital crossing} {ital detector} (LCD), to investigate key properties of stochastic resonance (SR). It is pointed out that successful signal processing and biological applications of SR require to work in the {ital large} {ital signal} {ital limit} (nonlinear transfer limit) which requires a completely new approach: {ital wide} {ital band} {ital input} {ital signal} and a {ital new}, {ital generalised} {ital definition} {ital of} {ital output} {ital noise}. The new way of approach is illustrated by a new arrangement. The arrangement employs a special LCD, white input noise and a special, large, subthreshold wide band signal. {ital First} {ital time} {ital in} {ital the} {ital history} {ital of} {ital SR} (for a wide band input noise), the {ital signal} {ital to} {ital noise} {ital ratio} {ital becomes} {ital much} {ital higher} {ital at} {ital the} {ital output} of a stochastic resonator than {ital at} {ital its} {ital input}. In that way, SR is proven to have a potential to improve signal transfer. Note, that the new arrangement seems to have resemblance to {ital neurone} {ital models}, therefore, it has a potential also for biological applications. {copyright} {ital 1996 American Institute of Physics.}

  15. [Research of spectrum signal-to-noise ratio of large aperture static imaging spectrometer].

    PubMed

    Wang, Shuang; Li, Li-Bo; Pi, Hai-Feng

    2014-03-01

    The process of acquiring hyperspectral data cube of a Large Aperture Static Imaging Spectrometer (LASIS) includes several vital and essential steps, such as interferometer modulation, rectangular convolution sampling by pixels of detector and spectra retrieving. In this process, how to precisely evaluate the Signal-Noise Ratio (SNR) of spectra and how to wholly establish a related evaluation model were both generally very complicated. After a full consideration of the transmission process, utilizing the theory of rectangular convolution sampling and the spectral retrieving method regarding the computation of real part of the discrete Fourier transform of interferogram, formulas of both spectral signal and spectral noise were deduced theoretically, and then a evaluation model regarding the spectral SNR of LASIS was established. By using this model and other design factors of LASIS involving the wavenumber related optical transmittance, the interferometer beam splitter efficiency, the detector quantum efficiency and the main circuit noise, a simulation of spectral SNR was implemented. The simulation result was compared with the measurement result of the SNR of a LASIS instrument. The SNR lines and trends of the two match each other basically in single spectral band. The average deviation between them is proved to be 3.58%. This comparison result demonstrates the feasibility and effectiveness of the evaluation model. This SNR evaluation model consisting of the main technical aspects of typical LASIS instrument from the input spectral radiation to the output spectrum data is possible to be applied widely in practical design and implement of LASIS, as well as may provide valuable reference on SNR calculation and evaluation for other imaging spectrometers. PMID:25208427

  16. Empirical Evaluation of a New Method for Calculating Signal to Noise Ratio (SNR) for Microarray Data Analysis

    SciTech Connect

    Zhou, Jizhong; He, Zhili; Zhou, Jizhong

    2008-03-06

    Signal-to-noise-ratio (SNR) thresholds for microarray data analysis were experimentally determined with an oligonucleotide array that contained perfect match (PM) and mismatch (MM) probes based upon four genes from Shewanella oneidensis MR-1. A new SNR calculation, called signal to both standard deviations ratio (SSDR) was developed, and evaluated along with other two methods, signal to standard deviation ratio (SSR), and signal to background ratio (SBR). At a low stringency, the thresholds of SSR, SBR, and SSDR were 2.5, 1.60 and 0.80 with oligonucleotide and PCR amplicon as target templates, and 2.0, 1.60 and 0.70 with genomic DNA as target templates. Slightly higher thresholds were obtained at the high stringency condition. The thresholds of SSR and SSDR decreased with an increase in the complexity of targets (e.g., target types), and the presence of background DNA, and a decrease in the composition of targets, while SBR remained unchanged under all situations. The lowest percentage of false positives (FP) and false negatives (FN) was observed with the SSDR calculation method, suggesting that it may be a better SNR calculation for more accurate determination of SNR thresholds. Positive spots identified by SNR thresholds were verified by the Student t-test, and consistent results were observed. This study provides general guidance for users to select appropriate SNR thresholds for different samples under different hybridization conditions.

  17. Improving Displacement Signal-to-Noise Ratio for Low-Signal Radiation Force Elasticity Imaging Using Bayesian Techniques.

    PubMed

    Dumont, Douglas M; Walsh, Kristy M; Byram, Brett C

    2016-08-01

    Radiation force-based elasticity imaging is currently being investigated as a possible diagnostic modality for a number of clinical tasks, including liver fibrosis staging and the characterization of cardiovascular tissue. In this study, we evaluate the relationship between peak displacement magnitude and image quality and propose using a Bayesian estimator to overcome the challenge of obtaining viable data in low displacement signal environments. Displacement data quality were quantified for two common radiation force-based applications, acoustic radiation force impulse imaging, which measures the displacement within the region of excitation, and shear wave elasticity imaging, which measures displacements outside the region of excitation. Performance as a function of peak displacement magnitude for acoustic radiation force impulse imaging was assessed in simulations and lesion phantoms by quantifying signal-to-noise ratio (SNR) and contrast-to-noise ratio for varying peak displacement magnitudes. Overall performance for shear wave elasticity imaging was assessed in ex vivo chicken breast samples by measuring the displacement SNR as a function of distance from the excitation source. The results show that for any given displacement magnitude level, the Bayesian estimator can increase the SNR by approximately 9 dB over normalized cross-correlation and the contrast-to-noise ratio by a factor of two. We conclude from the results that a Bayesian estimator may be useful for increasing data quality in SNR-limited imaging environments. PMID:27157861

  18. Relevancies of multiple-interaction events and signal-to-noise ratio for Anger-logic based PET detector designs

    NASA Astrophysics Data System (ADS)

    Peng, Hao

    2015-10-01

    A fundamental challenge for PET block detector designs is to deploy finer crystal elements while limiting the number of readout channels. The standard Anger-logic scheme including light sharing (an 8 by 8 crystal array coupled to a 2×2 photodetector array with an optical diffuser, multiplexing ratio: 16:1) has been widely used to address such a challenge. Our work proposes a generalized model to study the impacts of two critical parameters on spatial resolution performance of a PET block detector: multiple interaction events and signal-to-noise ratio (SNR). The study consists of the following three parts: (1) studying light output profile and multiple interactions of 511 keV photons within crystal arrays of different crystal widths (from 4 mm down to 1 mm, constant height: 20 mm); (2) applying the Anger-logic positioning algorithm to investigate positioning/decoding uncertainties (i.e., "block effect") in terms of peak-to-valley ratio (PVR), with light sharing, multiple interactions and photodetector SNR taken into account; and (3) studying the dependency of spatial resolution on SNR in the context of modulation transfer function (MTF). The proposed model can be used to guide the development and evaluation of a standard Anger-logic based PET block detector including: (1) selecting/optimizing the configuration of crystal elements for a given photodetector SNR; and (2) predicting to what extent additional electronic multiplexing may be implemented to further reduce the number of readout channels.

  19. Effect on signal-to-noise ratio of splitting the continuous contacts of cuff electrodes into smaller recording areas

    PubMed Central

    2013-01-01

    Background Cuff electrodes have been widely used chronically in different clinical applications. This neural interface has been dominantly used for nerve stimulation while interfering noise is the major issue when employed for recording purposes. Advancements have been made in rejecting extra-neural interference by using continuous ring contacts in tripolar topologies. Ring contacts provide an average of the neural activity, and thus reduce the information retrieved. Splitting these contacts into smaller recording areas could potentially increase the information content. In this study, we investigate the impact of such discretization on the Signal-to-Noise Ratio (SNR). The effect of contacts positioning and an additional short circuited pair of electrodes were also addressed. Methods Different recording configurations using ring, dot, and a mixed of both contacts were studied in vitro in a frog model. An interfering signal was induced in the medium to simulate myoelectric noise. The experimental setup was design in such a way that the only difference between recordings was the configuration used. The inter-session experimental differences were taken care of by a common configuration that allowed normalization between electrode designs. Results It was found that splitting all contacts into small recording areas had negative effects on noise rejection. However, if this is only applied to the central contact creating a mixed tripole configuration, a considerable and statistically significant improvement was observed. Moreover, the signal to noise ratio was equal or larger than what can be achieved with the best known configuration, namely the short circuited tripole. This suggests that for recording purposes, any tripole topology would benefit from splitting the central contact into one or more discrete contacts. Conclusions Our results showed that a mixed tripole configuration performs better than the configuration including only ring contacts. Therefore, splitting

  20. Temporal and spatial binning of TCSPC data to improve signal-to-noise ratio and imaging speed

    NASA Astrophysics Data System (ADS)

    Walsh, Alex J.; Beier, Hope T.

    2016-03-01

    Time-correlated single photon counting (TCSPC) is the most robust method for fluorescence lifetime imaging using laser scanning microscopes. However, TCSPC is inherently slow making it ineffective to capture rapid events due to the single photon product per laser pulse causing extensive acquisition time limitations and the requirement of low fluorescence emission efficiency to avoid bias of measurement towards short lifetimes. Furthermore, thousands of photons per pixel are required for traditional instrument response deconvolution and fluorescence lifetime exponential decay estimation. Instrument response deconvolution and fluorescence exponential decay estimation can be performed in several ways including iterative least squares minimization and Laguerre deconvolution. This paper compares the limitations and accuracy of these fluorescence decay analysis techniques to accurately estimate double exponential decays across many data characteristics including various lifetime values, lifetime component weights, signal-to-noise ratios, and number of photons detected. Furthermore, techniques to improve data fitting, including binning data temporally and spatially, are evaluated as methods to improve decay fits and reduce image acquisition time. Simulation results demonstrate that binning temporally to 36 or 42 time bins, improves accuracy of fits for low photon count data. Such a technique reduces the required number of photons for accurate component estimation if lifetime values are known, such as for commercial fluorescent dyes and FRET experiments, and improve imaging speed 10-fold.

  1. Increasing signal-to-noise ratio of reconstructed digital holograms by using light spatial noise portrait of camera's photosensor

    NASA Astrophysics Data System (ADS)

    Cheremkhin, Pavel A.; Evtikhiev, Nikolay N.; Krasnov, Vitaly V.; Rodin, Vladislav G.; Starikov, Sergey N.

    2015-01-01

    Digital holography is technique which includes recording of interference pattern with digital photosensor, processing of obtained holographic data and reconstruction of object wavefront. Increase of signal-to-noise ratio (SNR) of reconstructed digital holograms is especially important in such fields as image encryption, pattern recognition, static and dynamic display of 3D scenes, and etc. In this paper compensation of photosensor light spatial noise portrait (LSNP) for increase of SNR of reconstructed digital holograms is proposed. To verify the proposed method, numerical experiments with computer generated Fresnel holograms with resolution equal to 512×512 elements were performed. Simulation of shots registration with digital camera Canon EOS 400D was performed. It is shown that solo use of the averaging over frames method allows to increase SNR only up to 4 times, and further increase of SNR is limited by spatial noise. Application of the LSNP compensation method in conjunction with the averaging over frames method allows for 10 times SNR increase. This value was obtained for LSNP measured with 20 % error. In case of using more accurate LSNP, SNR can be increased up to 20 times.

  2. Low noise signal-to-noise ratio enhancing readout circuit for current-mediated active pixel sensors

    SciTech Connect

    Ottaviani, Tony; Karim, Karim S.; Nathan, Arokia; Rowlands, John A.

    2006-05-15

    Diagnostic digital fluoroscopic applications continuously expose patients to low doses of x-ray radiation, posing a challenge to both the digital imaging pixel and readout electronics when amplifying small signal x-ray inputs. Traditional switch-based amorphous silicon imaging solutions, for instance, have produced poor signal-to-noise ratios (SNRs) at low exposure levels owing to noise sources from the pixel readout circuitry. Current-mediated amorphous silicon pixels are an improvement over conventional pixel amplifiers with an enhanced SNR across the same low-exposure range, but whose output also becomes nonlinear with increasing dosage. A low-noise SNR enhancing readout circuit has been developed that enhances the charge gain of the current-mediated active pixel sensor (C-APS). The solution takes advantage of the current-mediated approach, primarily integrating the signal input at the desired frequency necessary for large-area imaging, while adding minimal noise to the signal readout. Experimental data indicates that the readout circuit can detect pixel outputs over a large bandwidth suitable for real-time digital diagnostic x-ray fluoroscopy. Results from hardware testing indicate that the minimum achievable C-APS output current that can be discerned at the digital fluoroscopic output from the enhanced SNR readout circuit is 0.341 nA. The results serve to highlight the applicability of amorphous silicon current-mediated pixel amplifiers for large-area flat panel x-ray imagers.

  3. No-reference peak signal to noise ratio estimation based on generalized Gaussian modeling of transform coefficient distributions

    NASA Astrophysics Data System (ADS)

    Ryu, Ji-Woo; Lee, Seon-Oh; Sim, Dong-Gyu; Han, Jong-Ki

    2012-02-01

    We present a no-reference peak signal to noise ratio (PSNR) estimation algorithm based on discrete cosine transform (DCT) coefficient distributions from H.264/MPEG-4 part 10 advanced video codec (H.264/AVC) bitstreams. To estimate the PSNR of a compressed picture without the original picture on the decoder side, it is important to model the distribution of transform coefficients obtained from quantized coefficients accurately. Whereas several conventional algorithms use the Laplacian or Cauchy distribution to model the DCT coefficient distribution, the proposed algorithm uses a generalized Gaussian distribution. Pearson's χ2 (chi-square) test was applied to show that the generalized Gaussian distribution is more appropriate than the other models for modeling the transform coefficients. The χ2 test was also used to find optimum parameters for the generalized Gaussian model. It was found that the generalized Gaussian model improves the accuracy of the DCT coefficient distribution, thus reducing the mean squared error between the real and the estimated PSNR.

  4. Measuring saliency of features using signal-to-noise ratios for detection of electrocardiographic changes in partial epileptic patients.

    PubMed

    Ubeyli, Elif Derya

    2008-12-01

    Medical diagnostic accuracies can be improved when the pattern is simplified through representation by important features. The feature vector, which is comprised of the set of all features used to describe a pattern, is a reduced-dimensional representation of that pattern. By identifying a set of salient features, the noise in a classification model can be reduced, resulting in more accurate classification. In this study, a signal-to-noise ratio (SNR) saliency measure was employed to determine saliency of input features of probabilistic neural networks (PNNs) used in classification of two types of electrocardiogram (ECG) beats (normal and partial epilepsy). In order to extract features representing the ECG signals, discrete wavelet transform was used. The PNNs used in the ECG signals classification were trained for the SNR screening method. The application results of the SNR screening method to the ECG signals demonstrated that classification accuracies of the PNNs with salient input features are higher than that of the PNNs with salient and non-salient input features. PMID:19058650

  5. Double-maximum enhancement of signal-to-noise ratio gain via stochastic resonance and vibrational resonance.

    PubMed

    Duan, Fabing; Chapeau-Blondeau, François; Abbott, Derek

    2014-08-01

    This paper studies the signal-to-noise ratio (SNR) gain of a parallel array of nonlinear elements that transmits a common input composed of a periodic signal and external noise. Aiming to further enhance the SNR gain, each element is injected with internal noise components or high-frequency sinusoidal vibrations. We report that the SNR gain exhibits two maxima at different values of the internal noise level or of the sinusoidal vibration amplitude. For the addition of internal noise to an array of threshold-based elements, the condition for occurrence of stochastic resonance is analytically investigated in the limit of weak signals. Interestingly, when the internal noise components are replaced by high-frequency sinusoidal vibrations, the SNR gain displays the vibrational multiresonance phenomenon. In both considered cases, there are certain regions of the internal noise intensity or the sinusoidal vibration amplitude wherein the achieved maximal SNR gain can be considerably beyond unity for a weak signal buried in non-Gaussian external noise. Due to the easy implementation of sinusoidal vibration modulation, this approach is potentially useful for improving the output SNR in an array of nonlinear devices. PMID:25215715

  6. Theoretical Investigation of Random Noise-Limited Signal-to-Noise Ratio in MR-Based Electrical Properties Tomography.

    PubMed

    Lee, Seung-Kyun; Bulumulla, Selaka; Hancu, Ileana

    2015-11-01

    In magnetic resonance imaging-based electrical properties tomography (MREPT), tissue electrical properties (EPs) are derived from the spatial variation of the transmit RF field (B1(+)). Here we derive theoretically the relationship between the signal-to-noise ratio (SNR) of the electrical properties obtained by MREPT and the SNR of the input B1(+) data, under the assumption that the latter is much greater than unity, and the noise in B1(+) at different voxels is statistically independent. It is shown that for a given B1(+) data, the SNR of both electrical conductivity and relative permittivity is proportional to the square of the linear dimension of the region of interest (ROI) over which the EPs are determined, and to the square root of the number of voxels in the ROI. The relationship also shows how the SNR varies with the main magnetic field (B0) strength. The predicted SNR is verified through numerical simulations on a cylindrical phantom with an analytically calculated B1(+) map, and is found to provide explanation of certain aspects of previous experimental results in the literature. Our SNR formula can be used to estimate minimum input data SNR and ROI size required to obtain tissue EP maps of desired quality. PMID:25955582

  7. Optimizing MRI signal-to-noise ratio for quadrature unmatched RF coils: two preamplifiers are better than one.

    PubMed

    Sorgenfrei, B L; Edelstein, W A

    1996-07-01

    Using separate preamplifiers for the two outputs of a quadrature receive coil (and then combining the preamplifier outputs in a quadrature hybrid) provides a better signal-to-noise ratio (SNR) than is obtained by directly combining the quadrature outputs in a hybrid followed by a single preamplifier. The advantage of the two-preamplifier configuration increases when the body coil impedance changes and is no longer matched to 50 ohms. Using 0.4 dB noise figure preamplifiers, theory predicts 1.53, 0.42, 0, 0.42, and 1.53 dB SNR advantage of the two-preamplifier configuration over the one-preamplifier arrangement at body coil impedances of 12.5, 25, 50, 100, and 200 ohms, respectively. Experimental hot/cold resistor noise figure measurements indicate 2.86, 0.65, 0.36, 0.83, and 1.40 dB noise figure advantage for the two preamplifier configuration relative to the one-preamplifier configuration at those impedances. Empirical gains larger than theoretically calculated are attributable to insertion losses of various circuit elements, such as the quadrature hybrid, for the one-preamplifier configuration. PMID:8795028

  8. Increasing the resolution and the signal-to-noise ratio of magnetic resonance sounding data using a central loop configuration

    NASA Astrophysics Data System (ADS)

    Behroozmand, Ahmad A.; Auken, Esben; Fiandaca, Gianluca; Rejkjaer, Simon

    2016-04-01

    Surface nuclear magnetic resonance technique, also called magnetic resonance sounding (MRS), is an emerging geophysical method that can detect the presence and spatial variations of the subsurface water content directly. In this paper, we introduce the MRS central loop geometry, in which the receiver loop is smaller than the transmitter loop and placed in its centre. In addition, using a shielded receiver coil we show how this configuration greatly increases signal-to-noise ratio and improves the resolution of the subsurface layers compared to the typically used coincident loop configuration. We compare sensitivity kernels for different loop configurations and describe advantages of the MRS central loop geometry in terms of superior behaviour of the sensitivity function, increased sensitivity values, reduced noise level of the shielded receiver coil, improved resolution matrix and reduced instrument dead time. With no extra time and effort in the field, central-loop MRS makes it possible to reduce measurement time and to measure data in areas with high anthropogenic noise. The results of our field example agree well with the complementary data, namely airborne electromagnetics, borehole data, and the hydrologic model of the area.

  9. Optimization of signal-to-noise ratio for wireless light-emitting diode communication in modern lighting layouts

    NASA Astrophysics Data System (ADS)

    Azizan, Luqman A.; Ab-Rahman, Mohammad S.; Hassan, Mazen R.; Bakar, A. Ashrif A.; Nordin, Rosdiadee

    2014-04-01

    White light-emitting diodes (LEDs) are predicted to be widely used in domestic applications in the future, because they are becoming widespread in commercial lighting applications. The ability of LEDs to be modulated at high speeds offers the possibility of using them as sources for communication instead of illumination. The growing interest in using these devices for both illumination and communication requires attention to combine this technology with modern lighting layouts. A dual-function system is applied to three models of modern lighting layouts: the hybrid corner lighting layout (HCLL), the hybrid wall lighting layout (HWLL), and the hybrid edge lighting layout (HELL). Based on the analysis, the relationship between the space adversity and the signal-to-noise ratio (SNR) performance is demonstrated for each model. The key factor that affects the SNR performance of visible light communication is the reliance on the design parameter that is related to the number and position of LED lights. The model of HWLL is chosen as the best layout, since 61% of the office area is considered as an excellent communication area and the difference between the area classification, Δp, is 22%. Thus, this system is applicable to modern lighting layouts.

  10. Predicting binaural speech intelligibility using the signal-to-noise ratio in the envelope power spectrum domain.

    PubMed

    Chabot-Leclerc, Alexandre; MacDonald, Ewen N; Dau, Torsten

    2016-07-01

    This study proposes a binaural extension to the multi-resolution speech-based envelope power spectrum model (mr-sEPSM) [Jørgensen, Ewert, and Dau (2013). J. Acoust. Soc. Am. 134, 436-446]. It consists of a combination of better-ear (BE) and binaural unmasking processes, implemented as two monaural realizations of the mr-sEPSM combined with a short-term equalization-cancellation process, and uses the signal-to-noise ratio in the envelope domain (SNRenv) as the decision metric. The model requires only two parameters to be fitted per speech material and does not require an explicit frequency weighting. The model was validated against three data sets from the literature, which covered the following effects: the number of maskers, the masker types [speech-shaped noise (SSN), speech-modulated SSN, babble, and reversed speech], the masker(s) azimuths, reverberation on the target and masker, and the interaural time difference of the target and masker. The Pearson correlation coefficient between the simulated speech reception thresholds and the data across all experiments was 0.91. A model version that considered only BE processing performed similarly (correlation coefficient of 0.86) to the complete model, suggesting that BE processing could be considered sufficient to predict intelligibility in most realistic conditions. PMID:27475146

  11. Improvement of signal-to-noise ratio by stochastic resonance in sigmoid function threshold systems, demonstrated using a CMOS inverter

    NASA Astrophysics Data System (ADS)

    Ueda, Michihito

    2010-05-01

    Stochastic resonance (SR) has become a well-known phenomenon that can enhance weak periodic signals with the help of noise. SR is an interesting phenomenon when applied to signal processing. Although it has been proven that SR does not always improve the signal-to-noise ratio (SNR), in a strongly nonlinear system such as simple threshold system, SR does in fact improve SNR for noisy pulsed signals at appropriate noise strength. However, even in such cases, when noise is weak, the SNR is degraded. Since the noise strength cannot be known in advance, it is difficult to apply SR to real signal processing. In this paper, we focused on the shape of the threshold at which SR did not degrade the SNR when noise was weak. To achieve output change when noise was weak, we numerically analyzed a sigmoid function threshold system. When the slope around the threshold was appropriate, SNR did not degrade when noise was weak and instead was improved at suitable noise strength. We also demonstrated SNR improvement for noisy pulsed voltages using a CMOS inverter, a very common threshold device. The input-output property of a CMOS inverter resembles the sigmoid function. By inputting the noisy signal voltage to a CMOS inverter, we measured the input and output voltages and analyzed the SNRs. The results showed that SNR was effectively improved over a wide range of noise strengths.

  12. Improved signal-to-noise ratio for non-perpendicular detection angles in x-ray fluorescence computed tomography (XFCT).

    PubMed

    Sjölin, Martin; Danielsson, Mats

    2014-11-01

    The standard imaging setup in x-ray fluorescence computed tomography detects the fluorescence emission at a right angle with respect to the axis of the excitation beam. In this paper we have studied how the detection angle affects the signal-to-noise ratio (S/N), which is a major factor influencing the low-contrast sensitivity of the imaging system. This is done for an imaging setup using a collimated detector and a pencil beam of excitation x-rays. An ideal detection process is simulated for a generalized imaging case with gold/platinum tracers and experimental measurements are performed using a diagnostic x-ray tube. For monochromatic excitation, the results indicate that order-of-magnitude improvements of the S/N can be achieved by optimizing the detection angle. The maximal S/N, when exciting with an energy just above the K-edge, is achieved for large detection angles, i.e. with the detector close to the source. The improvements also transfer to polychromatic excitation sources and the experimental results show up to four-fold improvements of the S/N when changing the detection angle from 90° to 150°. Also, the changes of the S/N behavior when switching the fluorescent tracer is briefly demonstrated. These results suggest that the choice of detection angle should be taken seriously in the design of future XFCT imaging systems. PMID:25310695

  13. Improved signal-to-noise ratio for non-perpendicular detection angles in x-ray fluorescence computed tomography (XFCT)

    NASA Astrophysics Data System (ADS)

    Sjölin, Martin; Danielsson, Mats

    2014-11-01

    The standard imaging setup in x-ray fluorescence computed tomography detects the fluorescence emission at a right angle with respect to the axis of the excitation beam. In this paper we have studied how the detection angle affects the signal-to-noise ratio (S/N), which is a major factor influencing the low-contrast sensitivity of the imaging system. This is done for an imaging setup using a collimated detector and a pencil beam of excitation x-rays. An ideal detection process is simulated for a generalized imaging case with gold/platinum tracers and experimental measurements are performed using a diagnostic x-ray tube. For monochromatic excitation, the results indicate that order-of-magnitude improvements of the S/N can be achieved by optimizing the detection angle. The maximal S/N, when exciting with an energy just above the K-edge, is achieved for large detection angles, i.e. with the detector close to the source. The improvements also transfer to polychromatic excitation sources and the experimental results show up to four-fold improvements of the S/N when changing the detection angle from 90° to 150°. Also, the changes of the S/N behavior when switching the fluorescent tracer is briefly demonstrated. These results suggest that the choice of detection angle should be taken seriously in the design of future XFCT imaging systems.

  14. Automated measurement of the bit-error rate as a function of signal-to-noise ratio for microwave communications systems

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.; Daugherty, Elaine S.; Kramarchuk, Ihor

    1987-01-01

    The performance of microwave systems and components for digital data transmission can be characterized by a plot of the bit-error rate as a function of the signal to noise ratio (or E sub b/E sub o). Methods for the efficient automated measurement of bit-error rates and signal-to-noise ratios, developed at NASA Lewis Research Center, are described. Noise measurement considerations and time requirements for measurement accuracy, as well as computer control and data processing methods, are discussed.

  15. Signal-to-noise ratio increase in carotid atheroma MRI: a comparison of 1.5 and 3 T

    PubMed Central

    Young, V E; Patterson, A J; Tunnicliffe, E M; Sadat, U; Graves, M J; Tang, T Y; Priest, A N; Kirkpatrick, P J; Gillard, J H

    2012-01-01

    Objectives This study reports quantitative comparisons of signal-to-noise ratio (SNR) at 1.5 and 3 T from images of carotid atheroma obtained using a multicontrast, cardiac-gated, blood-suppressed fast spin echo protocol. Methods 18 subjects, with carotid atherosclerosis (>30% stenosis) confirmed on ultrasound, were imaged on both 1.5 and 3 T systems using phased-array coils with matched hardware specifications. T1 weighted (T1W), T2 weighted (T2W) and proton density-weighted (PDW) images were acquired with identical scan times. Multiple slices were prescribed to encompass both the carotid bifurcation and the plaque. Image quality was quantified using the SNR and contrast-to-noise ratio (CNR). A phantom experiment was also performed to validate the SNR method and confirm the size of the improvement in SNR. Comparisons of the SNR values from the vessel wall with muscle and plaque/lumen CNR measurements were performed at a patient level. To account for the multiple comparisons a Bonferroni correction was applied. Results One subject was excluded from the protocol owing to image quality and protocol failure. The mean improvement in SNR in plaque was 1.9, 2.1 and 2.1 in T1W, T2W and PDW images, respectively. All plaque SNR improvements were statistically significant at the p<0.05 level. The phantom experiment reported an improvement in SNR of 2.4 for PDW images. Conclusions Significant gains in SNR can be obtained for carotid atheroma imaging at 3 T compared with 1.5 T. There was also a trend towards increased CNR. However, this was not significant after the application of the Bonferroni correction. PMID:22294703

  16. Use of Independent Component Analysis to Improve Signal to Noise Ratio in Multi-probe Fluorescence Microscopy

    PubMed Central

    Dao, Lam; Lucotte, Bertrand; Glancy, Brian; Chang, Lin-Ching; Hsu, Li-Yueh; Balaban, Robert S

    2014-01-01

    SUMMARY In conventional multi-probe fluorescence microscopy, narrow bandwidth filters on detectors are used to avoid bleed-through artifacts between probes. The limited bandwidth reduces the signal-to-noise ratio (SNR) of the detection, often severely compromising one or more channels. Herein, we describe a process of using independent component analysis (ICA) to discriminate the position of different probes using only a dichroic mirror to differentiate the signals directed to the detectors. ICA was particularly effective in samples where the spatial overlap between the probes is minimal, a very common case in cellular microscopy. This imaging scheme collects nearly all of the emitted light, significantly improving the image SNR. In this study, we focused on the detection of two fluorescence probes used in vivo, NAD(P)H and ANEPPS. The optimal dichroic mirror cutoff frequency was determined with simulations using the probes spectral emissions. A quality factor, defined as the cross-channel contrast-to-noise ratio, was optimized to maximize signals while maintaining spatial discrimination between the probes after ICA post-processing. Simulations indicate that a ~3 fold increase in SNR using the ICA approach can be achieved over the conventional narrow-band filtering approach without loss of spatial discrimination. We confirmed this predicted performance from experimental imaging of NAD(P)H and ANEPPS in mouse skeletal muscle,in vivo. For many multi-probe studies, the increased sensitivity of this “full bandwidth” approach will lead to improved image quality and/or reduced excitation power requirements. PMID:25159193

  17. [The radial velocity measurement accuracy of different spectral type low resolution stellar spectra at different signal-to-noise ratio].

    PubMed

    Wang, Feng-Fei; Luo, A-Li; Zhao, Yong-Heng

    2014-02-01

    The radial velocity of the star is very important for the study of the dynamics structure and chemistry evolution of the Milky Way, is also an useful tool for looking for variable or special objects. In the present work, we focus on calculating the radial velocity of different spectral types of low-resolution stellar spectra by adopting a template matching method, so as to provide effective and reliable reference to the different aspects of scientific research We choose high signal-to-noise ratio (SNR) spectra of different spectral type stellar from the Sloan Digital Sky Survey (SDSS), and add different noise to simulate the stellar spectra with different SNR. Then we obtain theradial velocity measurement accuracy of different spectral type stellar spectra at different SNR by employing a template matching method. Meanwhile, the radial velocity measurement accuracy of white dwarf stars is analyzed as well. We concluded that the accuracy of radial velocity measurements of early-type stars is much higher than late-type ones. For example, the 1-sigma standard error of radial velocity measurements of A-type stars is 5-8 times as large as K-type and M-type stars. We discuss the reason and suggest that the very narrow lines of late-type stars ensure the accuracy of measurement of radial velocities, while the early-type stars with very wide Balmer lines, such as A-type stars, become sensitive to noise and obtain low accuracy of radial velocities. For the spectra of white dwarfs stars, the standard error of radial velocity measurement could be over 50 km x s(-1) because of their extremely wide Balmer lines. The above conclusion will provide a good reference for stellar scientific study. PMID:24822441

  18. Quality assurance in MRI breast screening: comparing signal-to-noise ratio in dynamic contrast-enhanced imaging protocols.

    PubMed

    Kousi, Evanthia; Borri, Marco; Dean, Jamie; Panek, Rafal; Scurr, Erica; Leach, Martin O; Schmidt, Maria A

    2016-01-01

    MRI has been extensively used in breast cancer staging, management and high risk screening. Detection sensitivity is paramount in breast screening, but variations of signal-to-noise ratio (SNR) as a function of position are often overlooked. We propose and demonstrate practical methods to assess spatial SNR variations in dynamic contrast-enhanced (DCE) breast examinations and apply those methods to different protocols and systems. Four different protocols in three different MRI systems (1.5 and 3.0 T) with receiver coils of different design were employed on oil-filled test objects with and without uniformity filters. Twenty 3D datasets were acquired with each protocol; each dataset was acquired in under 60 s, thus complying with current breast DCE guidelines. In addition to the standard SNR calculated on a pixel-by-pixel basis, we propose other regional indices considering the mean and standard deviation of the signal over a small sub-region centred on each pixel. These regional indices include effects of the spatial variation of coil sensitivity and other structured artefacts. The proposed regional SNR indices demonstrate spatial variations in SNR as well as the presence of artefacts and sensitivity variations, which are otherwise difficult to quantify and might be overlooked in a clinical setting. Spatial variations in SNR depend on protocol choice and hardware characteristics. The use of uniformity filters was shown to lead to a rise of SNR values, altering the noise distribution. Correlation between noise in adjacent pixels was associated with data truncation along the phase encoding direction. Methods to characterise spatial SNR variations using regional information were demonstrated, with implications for quality assurance in breast screening and multi-centre trials. PMID:26605957

  19. Comparison of signal to noise ratios from spatial and frequency domain formulations of nonprewhitening model observers in digital mammography

    SciTech Connect

    Sisini, Francesco; Zanca, Federica; Marshall, Nicholas W.; Taibi, Angelo; Cardarelli, Paolo; Bosmans, Hilde

    2012-09-15

    Purpose: Image quality indices based upon model observers are promising alternatives to laborious human readings of contrast-detail images. This is especially appealing in digital mammography as limiting values for contrast thresholds determine, according to some international protocols, the acceptability of these systems in the radiological practice. The objective of the present study was to compare the signal to noise ratios (SNR) obtained with two nonprewhitening matched filter model observer approaches, one in the spatial domain and the other in the frequency domain, and with both of them worked out for disks as present in the CDMAM phantom. Methods: The analysis was performed using images acquired with the Siemens Novation and Inspiration digital mammography systems. The spatial domain formulation uses a series of high dose CDMAM images as the signal and a routine exposure of two flood images to calculate the covariance matrix. The frequency domain approach uses the mathematical description of a disk and modulation transfer function (MTF) and noise power spectrum (NPS) calculated from images. Results: For both systems most of the SNR values calculated in the frequency domain were in very good agreement with the SNR values calculated in the spatial domain. Both the formulations in the frequency domain and in the spatial domain show a linear relationship between SNR and the diameter of the CDMAM discs. Conclusions: The results suggest that both formulations of the model observer lead to very similar figures of merit. This is a step forward in the adoption of figures of merit based on NPS and MTF for the acceptance testing of mammography systems.

  20. Speech intelligibility and recall of first and second language words heard at different signal-to-noise ratios.

    PubMed

    Hygge, Staffan; Kjellberg, Anders; Nöstl, Anatole

    2015-01-01

    Free recall of spoken words in Swedish (native tongue) and English were assessed in two signal-to-noise ratio (SNR) conditions (+3 and +12 dB), with and without half of the heard words being repeated back orally directly after presentation [shadowing, speech intelligibility (SI)]. A total of 24 word lists with 12 words each were presented in English and in Swedish to Swedish speaking college students. Pre-experimental measures of working memory capacity (operation span, OSPAN) were taken. A basic hypothesis was that the recall of the words would be impaired when the encoding of the words required more processing resources, thereby depleting working memory resources. This would be the case when the SNR was low or when the language was English. A low SNR was also expected to impair SI, but we wanted to compare the sizes of the SNR-effects on SI and recall. A low score on working memory capacity was expected to further add to the negative effects of SNR and language on both SI and recall. The results indicated that SNR had strong effects on both SI and recall, but also that the effect size was larger for recall than for SI. Language had a main effect on recall, but not on SI. The shadowing procedure had different effects on recall of the early and late parts of the word lists. Working memory capacity was unimportant for the effect on SI and recall. Thus, recall appear to be a more sensitive indicator than SI for the acoustics of learning, which has implications for building codes and recommendations concerning classrooms and other workplaces, where both hearing and learning is important. PMID:26441765

  1. Quality assurance in MRI breast screening: comparing signal-to-noise ratio in dynamic contrast-enhanced imaging protocols

    NASA Astrophysics Data System (ADS)

    Kousi, Evanthia; Borri, Marco; Dean, Jamie; Panek, Rafal; Scurr, Erica; Leach, Martin O.; Schmidt, Maria A.

    2016-01-01

    MRI has been extensively used in breast cancer staging, management and high risk screening. Detection sensitivity is paramount in breast screening, but variations of signal-to-noise ratio (SNR) as a function of position are often overlooked. We propose and demonstrate practical methods to assess spatial SNR variations in dynamic contrast-enhanced (DCE) breast examinations and apply those methods to different protocols and systems. Four different protocols in three different MRI systems (1.5 and 3.0 T) with receiver coils of different design were employed on oil-filled test objects with and without uniformity filters. Twenty 3D datasets were acquired with each protocol; each dataset was acquired in under 60 s, thus complying with current breast DCE guidelines. In addition to the standard SNR calculated on a pixel-by-pixel basis, we propose other regional indices considering the mean and standard deviation of the signal over a small sub-region centred on each pixel. These regional indices include effects of the spatial variation of coil sensitivity and other structured artefacts. The proposed regional SNR indices demonstrate spatial variations in SNR as well as the presence of artefacts and sensitivity variations, which are otherwise difficult to quantify and might be overlooked in a clinical setting. Spatial variations in SNR depend on protocol choice and hardware characteristics. The use of uniformity filters was shown to lead to a rise of SNR values, altering the noise distribution. Correlation between noise in adjacent pixels was associated with data truncation along the phase encoding direction. Methods to characterise spatial SNR variations using regional information were demonstrated, with implications for quality assurance in breast screening and multi-centre trials.

  2. Speech intelligibility and recall of first and second language words heard at different signal-to-noise ratios

    PubMed Central

    Hygge, Staffan; Kjellberg, Anders; Nöstl, Anatole

    2015-01-01

    Free recall of spoken words in Swedish (native tongue) and English were assessed in two signal-to-noise ratio (SNR) conditions (+3 and +12 dB), with and without half of the heard words being repeated back orally directly after presentation [shadowing, speech intelligibility (SI)]. A total of 24 word lists with 12 words each were presented in English and in Swedish to Swedish speaking college students. Pre-experimental measures of working memory capacity (operation span, OSPAN) were taken. A basic hypothesis was that the recall of the words would be impaired when the encoding of the words required more processing resources, thereby depleting working memory resources. This would be the case when the SNR was low or when the language was English. A low SNR was also expected to impair SI, but we wanted to compare the sizes of the SNR-effects on SI and recall. A low score on working memory capacity was expected to further add to the negative effects of SNR and language on both SI and recall. The results indicated that SNR had strong effects on both SI and recall, but also that the effect size was larger for recall than for SI. Language had a main effect on recall, but not on SI. The shadowing procedure had different effects on recall of the early and late parts of the word lists. Working memory capacity was unimportant for the effect on SI and recall. Thus, recall appear to be a more sensitive indicator than SI for the acoustics of learning, which has implications for building codes and recommendations concerning classrooms and other workplaces, where both hearing and learning is important. PMID:26441765

  3. fMRI brain mapping during motion capture and FES induced motor tasks: signal to noise ratio assessment.

    PubMed

    Gandolla, Marta; Ferrante, Simona; Casellato, Claudia; Ferrigno, Giancarlo; Molteni, Franco; Martegani, Alberto; Frattini, Tiziano; Pedrocchi, Alessandra

    2011-10-01

    Functional Electrical Stimulation (FES) is a well known clinical rehabilitation procedure, however the neural mechanisms that underlie this treatment at Central Nervous System (CNS) level are still not completely understood. Functional magnetic resonance imaging (fMRI) is a suitable tool to investigate effects of rehabilitative treatments on brain plasticity. Moreover, monitoring the effective executed movement is needed to correctly interpret activation maps, most of all in neurological patients where required motor tasks could be only partially accomplished. The proposed experimental set-up includes a 1.5 T fMRI scanner, a motion capture system to acquire kinematic data, and an electro-stimulation device. The introduction of metallic devices and of stimulation current in the MRI room could affect fMRI acquisitions so as to prevent a reliable activation maps analysis. What we are interested in is that the Blood Oxygenation Level Dependent (BOLD) signal, marker of neural activity, could be detected within a given experimental condition and set-up. In this paper we assess temporal Signal to Noise Ratio (SNR) as image quality index. BOLD signal change is about 1-2% as revealed by a 1.5 T scanner. This work demonstrates that, with this innovative set-up, in the main cortical sensorimotor regions 1% BOLD signal change can be detected at least in the 93% of the sub-volumes, and almost 100% of the sub-volumes are suitable for 2% signal change detection. The integrated experimental set-up will therefore allows to detect FES induced movements fMRI maps simultaneously with kinematic acquisitions so as to investigate FES-based rehabilitation treatments contribution at CNS level. PMID:21550290

  4. High signal-to-noise ratio acoustic sensor using phase shifted gratings interrogated by the Pound-Drever-Hall technique

    NASA Astrophysics Data System (ADS)

    Kung, Peter; Comanici, Maria I.

    2015-03-01

    Optical fiber is made of glass, an insulator, and thus it is immune to strong electromagnetic interference. Therefore, fiber optics is a technology ideally suitable for sensing of partial discharge (PD) both in transformers and generators. Extensive efforts have been used to develop a cost effective solution for detecting partial discharge, which generates acoustic emission, with signals ranging from 30 kHz to 200 kHz. The requirement is similar to fiber optics Hydro Phone, but at higher frequencies. There are several keys to success: there must be at least 60 dB signal-to-noise ratio (SNR) performance, which will ensure not only PD detection but later on provide diagnostics and also the ability to locate the origin of the events. Defects that are stationary would gradually degrade the insulation and result in total breakdown. Transformers currently need urgent attention: most of them are oil filled and are at least 30 to 50 years old, close to the end of life. In this context, an issue to be addressed is the safety of the personnel working close to the assets and collateral damage that could be caused by a tank explosion (with fire spilling over the whole facility). This paper will describe the latest achievement in fiber optics PD sensor technology: the use of phase shifted-fiber gratings with a very high speed interrogation method that uses the Pound-Drever-Hall technique. More importantly, this is based on a technology that could be automated, easy to install, and, eventually, available at affordable prices.

  5. Experimental measurements of estimator bias and the signal-to-noise ratio for deconvolution from wave-front sensing.

    PubMed

    Dayton, D; Gonglewski, J; Rogers, S

    1997-06-10

    Deconvolution from wave-front sensing (DWFS) has been proposed as a method for achieving high-resolution images of astronomical objects from ground-based telescopes. The technique consists of the simultaneous measurement of a short-exposure focal-plane speckled image, as well as the wave front, by use of a Shack-Hartmann sensor placed at the pupil plane. In early studies it was suspected that some problems would occur in poor seeing conditions; however, it was usually assumed that the technique would work well as long as the wave-front sensor subaperture spacing was less than r(0) (L/r(0) < 1). Atmosphere-induced phase errors in the pupil of a telescope imaging system produce both phase errors and magnitude errors in the effective short-exposure optical transfer function (OTF) of the system. Recently it has been shown that the commonly used estimator for this technique produces biased estimates of the magnitude errors. The significance of this bias problem is that one cannot properly estimate or correct for the frame-to-frame fluctuations in the magnitude of the OTF but can do so only for fluctuations in the phase. An auxiliary estimate must also be used to correct for the mean value of the magnitude error. The inability to compensate for the magnitude fluctuations results in a signal-to-noise ratio (SNR) that is less favorable for the technique than was previously thought. In some situations simpler techniques, such as the Knox-Thompson and bispectrum methods, which require only speckle gram data from the focal plane of the imaging system, can produce better results. We present experimental measurements based on observations of bright stars and the Jovian moon Ganymede that confirm previous theoretical predictions. PMID:18253416

  6. Design of phase-only, binary phase-only, and complex ternary matched filters with increased signal-to-noise ratios for colored noise

    NASA Technical Reports Server (NTRS)

    Kumar, B. V. K. V.; Juday, Richard D.

    1991-01-01

    An algorithm is provided for treating nonwhite additive noise in determining regions of support for phase-only filters, binary phase-only filters, and complex ternary matched filters. It is analytically shown to be optimal in the signal-to-noise ratio sense. It extends earlier research that assumed white noise.

  7. Sea level estimate from multi-frequency signal-to-noise ratio data collected by a single geodetic receiver

    NASA Astrophysics Data System (ADS)

    Roussel, Nicolas; Frappart, Frédéric; Ramillien, Guillaume; Darrozes, José; Cornu, Gwendolyne; Koummarasy, Khanithalath

    2016-04-01

    GNSS-Reflectometry (GNSS-R) altimetry has demonstrated a strong potential for sea level monitoring. Interference Pattern Technique (IPT) based on the analysis of the Signal-to-Noise Ratio (SNR) estimated by a GNSS receiver, presents the main advantage of being applicable everywhere by using a single geodetic antenna and receiver, transforming them to real tide gauges. Such a technique has already been tested in various configurations of acquisition of surface-reflected GNSS signals with an accuracy of a few centimeters. Nevertheless, the classical SNR analysis method for estimating the reflecting surface-antenna height is limited by an approximation: the vertical velocity of the reflecting surface must be negligible. Authors present a significant improvement of the SNR technique to solve this problem and broaden the scope of SNR-based tide monitoring. The performances achieved on the different GNSS frequency band (L1, L2 and L5) are analyzed. The method is based on a Least-Mean Square Resolution Method (LSM), combining simultaneous measurements from different GNSS constellations (GPS, GLONASS), which permits to take the dynamic of the surface into account. It was validated in situ [1], with an antenna placed at 60 meters above the Atlantic Ocean surface with variations reaching ±3 meters, and amplitude rate of the semi-diurnal tide up to 0.5 mm/s. Over the three months of SNR records on L1 frequency band for sea level determination, we found linear correlations of 0.94 by comparing with a classical tide gauge record. Our SNR-based time series was also compared to a tide theoretical model and amplitudes and phases of the main astronomical periods (6-, 12- and 24-h) were perfectly well detected. Waves and swell are also likely to be detected. If the validity of our method is already well-established with L1 band [1], the aim of our current study is to analyze the results obtained with the other GNSS frequency band: L2 and L5. L1 band seems to provide the best sea

  8. Spectral parameters and signal-to-noise ratio requirement for TANSAT hyper spectral remote sensor of atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Yang, Zhong-Dong; Bi, Yan-Meng

    2014-11-01

    , the results indicate that sampling ratio should exceed 2 pixels/FWHM to ensure the accuracy of CO2 spectrum. Signal-to-noise ratio is one of the most important parameters of hyper spectral CO2 detectors to ensure the reliability of CO2 signal. SNR requirements of CO2 detector to different detection precisions are explored based on the radiance sensitivity factors. The results show that it is difficult to achieve the SNR to detect 1×10-6-4×10-6 CO2 concentration change in the boundary layer by solar shortwave infrared passive remote sensing, limited by the instrument development at present. However, the instrument SNR to detect 1% change in the CO2 column concentration is attainable. The results of this study are not only conductive to universal applications and guides on developing grating spectrometer, but also helpful to have a better understanding of the complexity of CO2 retrieval.

  9. Receiver Signal to Noise Ratios for IPDA Lidars Using Sine-wave and Pulsed Laser Modulation and Direct Detections

    NASA Technical Reports Server (NTRS)

    Sun, Xiaoli; Abshire, James B.

    2011-01-01

    Integrated path differential absorption (IPDA) lidar can be used to remotely measure the column density of gases in the path to a scattering target [1]. The total column gas molecular density can be derived from the ratio of the laser echo signal power with the laser wavelength on the gas absorption line (on-line) to that off the line (off-line). 80th coherent detection and direct detection IPDA lidar have been used successfully in the past in horizontal path and airborne remote sensing measurements. However, for space based measurements, the signal propagation losses are often orders of magnitude higher and it is important to use the most efficient laser modulation and detection technique to minimize the average laser power and the electrical power from the spacecraft. This paper gives an analysis the receiver signal to noise ratio (SNR) of several laser modulation and detection techniques versus the average received laser power under similar operation environments. Coherent detection [2] can give the best receiver performance when the local oscillator laser is relatively strong and the heterodyne mixing losses are negligible. Coherent detection has a high signal gain and a very narrow bandwidth for the background light and detector dark noise. However, coherent detection must maintain a high degree of coherence between the local oscillator laser and the received signal in both temporal and spatial modes. This often results in a high system complexity and low overall measurement efficiency. For measurements through atmosphere the coherence diameter of the received signal also limits the useful size of the receiver telescope. Direct detection IPDA lidars are simpler to build and have fewer constraints on the transmitter and receiver components. They can use much larger size 'photon-bucket' type telescopes to reduce the demands on the laser transmitter. Here we consider the two most widely used direct detection IPDA lidar techniques. The first technique uses two CW

  10. High-power, high signal-to-noise ratio single-frequency 1 μm Brillouin all-fiber laser.

    PubMed

    Wang, Jing; Hou, Yubin; Zhang, Qian; Jin, Dongchen; Sun, Ruoyu; Shi, Hongxing; Liu, Jiang; Wang, Pu

    2015-11-01

    We demonstrate a high-power, high signal-to-noise ratio single-frequency Brillouin all-fiber laser with high slope efficiency at 1 μm wavelength. The laser is pumped by an amplified single-longitudinal-mode distributed Bragg reflector fiber laser with a linewidth of 33 kHz. By optimizing the length of the Brillouin ring cavity to 10 m, stable single-frequency Brillouin fiber laser is obtained with 3 kHz linewidth owing to the linewidth narrowing effect. At the launched pump power of 2.15 W, the Brillouin fiber laser generates maximum output power of 1.4 W with a slope efficiency of 79% and the optical signal-to-noise ratio of 77 dB. PMID:26561166

  11. Few-View Prereconstruction Guided Tube Current Modulation Strategy Based on the Signal-to-Noise Ratio of the Sinogram

    PubMed Central

    Chang, Ming; Xiao, Yongshun; Chen, Zhiqiang

    2015-01-01

    The radiation dose reduction without sacrificing the image quality as an important issue has raised the attention of CT manufacturers and different automatic exposure control (AEC) strategies have been adopted in their products. In this paper, we focus on the strategy of tube current modulation. It is deduced based on the signal-to-noise (SNR) of the sinogram. The main idea behind the proposed modulation strategy is to keep the SNR of the sinogram proximately invariable using the few-view reconstruction as a good reference because it directly affects the noise level of the reconstructions. The numerical experiment results demonstrate that, compared with constant tube current, the noise distribution is more uniform and the SNR and CNR of the reconstruction are better when the proposed strategy is applied. Furthermore it has the potential to distinguish the low-contrast target and to reduce the radiation dose. PMID:26089980

  12. Measurement and analysis of perceivable signal-to-noise ratio for infrared imaging system with human vision

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Zhao, Jing; Chang, Honghua; Ma, Lin

    2012-12-01

    The relationship between correct discrimination probability of the human eye and perceivable signal-to-noise (SNR) threshold is studied for different equilateral triangle sizes with specified luminance through combining theoretical calculation with practical experiment based on triangle orientation discrimination (TOD) performance evaluation method. Specifically, the simulation images of triangle patterns are generated by an infrared imaging system (IRIS) simulation model. And the perceivable SNRs for these images are calculated by establishing the system theoretical model and the human vision system model. Meanwhile, the Four-Alternative Forced-Choice experiment is performed. Experiment results of several observers are averaged statistically and the curves of perceivable SNR threshold which change with the correct discrimination probability are obtained. Finally, the analyses of these results show that these changes are in accordance with the psychometric function and that the fitting curves become steep with the increase of triangle sizes. These data and conclusions are helpful to modify the existing TOD performance model of an IRIS.

  13. Optimal control of the signal-to-noise ratio per unit time of a spin 1/2 particle: The crusher gradient and the radiation damping cases

    SciTech Connect

    Lapert, M.; Glaser, S. J.; Assémat, E.; Sugny, D.

    2015-01-28

    We show to which extent the signal to noise ratio per unit time of a spin 1/2 particle can be maximized. We consider a cyclic repetition of experiments made of a measurement followed by a radio-frequency magnetic field excitation of the system, in the case of unbounded amplitude. In the periodic regime, the objective of the control problem is to design the initial state of the system and the pulse sequence which leads to the best signal to noise performance. We focus on two specific issues relevant in nuclear magnetic resonance, the crusher gradient and the radiation damping cases. Optimal control techniques are used to solve this non-standard control problem. We discuss the optimality of the Ernst angle solution, which is commonly applied in spectroscopic and medical imaging applications. In the radiation damping situation, we show that in some cases, the optimal solution differs from the Ernst one.

  14. Design of high-resolution and multilevel reference pattern for improvement of both light utilization efficiency and signal-to-noise ratio in coaxial holographic data storage.

    PubMed

    Nobukawa, Teruyoshi; Nomura, Takanori

    2014-06-10

    A high-resolution and multilevel designed reference pattern (DRP) is presented for improvement of both light utilization efficiency and the signal-to-noise ratio (SNR) of reconstructed images in coaxial holographic data storage. With a DRP, the desired Fourier power spectrum of a reference beam is obtained. Numerical and experimental results show that the DRP increases the SNR compared with that of a random phase mask (RPM). Moreover, the light utilization efficiency of the DRP is higher than that of a high-resolution RPM. In addition, the effect of the phase level and the pixel pitch of DRPs on the SNR and the light utilization efficiency are investigated. PMID:24921144

  15. Improved signal-to-noise ratio of 10 GHz microwave signals generated with a mode-filtered femtosecond laser frequency comb.

    PubMed

    Diddams, S A; Kirchner, M; Fortier, T; Braje, D; Weiner, A M; Hollberg, L

    2009-03-01

    We use a Fabry-Perot cavity to optically filter the output of a Ti:sapphire frequency comb to integer multiples of the original 1 GHz mode spacing. This effectively increases the pulse repetition rate, which is useful for several applications. In the case of low-noise microwave signal generation, such filtering leads to improved linearity of the high-speed photodiodes that detect the mode-locked laser pulse train. The result is significantly improved signal-to-noise ratio at the 10 GHz harmonic with the potential for a shot-noise limited single sideband phase noise floor near -168 dBc/Hz. PMID:19259170

  16. The effect of audibility, signal-to-noise ratio, and temporal speech cues on the benefit from fast-acting compression in modulated noise.

    PubMed

    Olsen, Henrik L; Olofsson, Ake; Hagerman, Björn

    2005-07-01

    The objective of the experiment was to investigate three aspects that might contribute to the benefit of fast-acting compression seen in normal-hearing listeners. Six normal-hearing listeners were tested with speech recognition in a fully modulated noise (FUM) either through a fast-acting compressor or through linear amplification. In the first experiment, three different presentation levels of the FUM noise (15, 30, and 45 dB SL) were tested. The second experiment manipulated the control signal of the compressor independently of the audio input signal at four signal-to-noise ratios (-15, 10, -5, and 0 dB). A signal correlated noise version of the speech signal was tested in the third experiment at three speech-to-noise ratios (-20, -15 and -10 dB). Results showed that performance was better with compression than with linear amplification through all of the tested conditions at least when the signal-to-noise ratio was negative. The results suggest that other aspects of the hearing impairment than those simulated here are involved in the degraded performance seen for some hearing-impaired listeners with fast-acting compression. PMID:16136792

  17. Signal-to-noise ratio requirements for detection of multiple pulses subject to partially correlated fading with chi-squared statistics of various degrees of freedom

    NASA Astrophysics Data System (ADS)

    Nuttall, Albert H.; Eby, Edward S.

    1986-06-01

    The transmitted signal in a fading medium is composed of several pulses separated in time so as to achieve diversity and thereby combat deep fades and loss of signal. Receiver processing consists of matched filtering of each of the pulses, followed by summation of the squared envelopes of all the filter outputs. In addition to additive Gaussian background noise, the signal is subject to slow medium fading which has a chi-squared first-order distribution and which may be correlated from pulse to pulse to an arbitrary degree. The false alarm and detection probabilities of this system are derived in various series expansions which are amenable to efficient computer evaluation. Programs are presented and exercised for various combinations of signal-to-noise ratio, number of pulses, degree of correlated fading, and (noninteger) number of degrees of freedom of the chi-squared fading. Required input signal-to-noise ratios for several false alarm and detection probabilities are computed and plotted for cases of the fading normalized correlation coefficient ranging from 0 to 1; results for a nonfading medium are superposed for easy comparison. Special cases are dependent and independent Rayleigh amplitude fading.

  18. Ideal current patterns yielding optimal signal-to-noise ratio and specific absorption rate in magnetic resonance imaging: computational methods and physical insights.

    PubMed

    Lattanzi, Riccardo; Sodickson, Daniel K

    2012-07-01

    At high and ultra-high magnetic field strengths, understanding interactions between tissues and the electromagnetic fields generated by radiofrequency coils becomes crucial for safe and effective coil design as well as for insight into limits of performance. In this work, we present a rigorous electrodynamic modeling framework, using dyadic Green's functions, to derive the electromagnetic field in homogeneous spherical and cylindrical samples resulting from arbitrary surface currents in the presence or absence of a surrounding radiofrequency shield. We show how to calculate ideal current patterns that result in the highest possible signal-to-noise ratio (ultimate intrinsic signal-to-noise ratio) or the lowest possible radiofrequency power deposition (ultimate intrinsic specific absorption rate) compatible with electrodynamic principles. We identify familiar coil designs within optimal current patterns at low to moderate field strength, thereby establishing and explaining graphically the near-optimality of traditional surface and volume quadrature designs. We also document the emergence of less familiar patterns, e.g., involving substantial electric--as well as magnetic-dipole contributions, at high field strength. Performance comparisons with particular coil array configurations demonstrate that optimal performance may be approached with finite arrays if ideal current patterns are used as a guide for coil design. PMID:22127735

  19. A novel technique for determination of two dimensional signal-to-noise ratio improvement factor of an antiscatter grid in digital radiography

    NASA Astrophysics Data System (ADS)

    Nøtthellen, Jacob; Konst, Bente; Abildgaard, Andreas

    2014-08-01

    Purpose: to present a new and simplified method for pixel-wise determination of the signal-to-noise ratio improvement factor KSNR of an antiscatter grid, when used with a digital imaging system. The method was based on approximations of published formulas. The simplified estimate of K2SNR may be used as a decision tool for whether or not to use an antiscatter grid. Methods: the primary transmission of the grid Tp was determined with and without a phantom present using a pattern of beam stops. The Bucky factor B was measured with and without a phantom present. Hence K2SNR maps were created based on Tp and B. A formula was developed to calculate K2SNR from the measured Bs without using the measured Tp. The formula was applied on two exposures of anthropomorphic phantoms, adult legs and baby chest, and on two homogeneous poly[methyl methacrylate] (PMMA) phantoms, 5 cm and 10 cm thick. The results from anthropomorphic phantoms were compared to those based on the beam stop method. The results for the PMMA-phantoms were compared to a study that used a contrast-detail phantom. Results: 2D maps of K2SNR over the entire adult legs and baby chest phantoms were created. The maps indicate that it is advantageous to use the antiscatter grid for imaging of the adult legs. For baby chest imaging the antiscatter grid is not recommended if only the lung regions are of interest. The K2SNR maps based on the new method correspond to those from the beam stop method, and the K2SNR from the homogenous phantoms arising from two different approaches also agreed well with each other. Conclusion: a method to measure 2D K2SNR associated with grid use in digital radiography system was developed and validated. The proposed method requires four exposures and use of a simple formula. It is fast and provides adequate estimates for K2SNR.

  20. Tests of variable-band multilayers designed for investigating optimal signal-to-noise vs artifact signal ratios in Dual-Energy Digital Subtraction Angiography (DDSA) imaging systems

    SciTech Connect

    Boyers, D.; Ho, A.; Li, Q.; Piestrup, M.; Rice, M.; Tatchyn, R.

    1993-08-01

    In recent work, various design techniques were applied to investigate the feasibility of controlling the bandwidth and bandshape profiles of tungsten/boron-carbon (W/B{sub 4}C) and tungsten/silicon (W/Si) multilayers for optimizing their performance in synchrotron radiation based angiographical imaging systems at 33 keV. Varied parameters included alternative spacing geometries, material thickness ratios, and numbers of layer pairs. Planar optics with nominal design reflectivities of 30%--94% and bandwidths ranging from 0.6%--10% were designed at the Stanford Radiation Laboratory, fabricated by the Ovonic Synthetic Materials Company, and characterized on Beam Line 4-3 at the Stanford Synchrotron Radiation Laboratory, in this paper we report selected results of these tests and review the possible use of the multilayers for determining optimal signal to noise vs. artifact signal ratios in practical Dual-Energy Digital Subtraction Angiography systems.

  1. Dynamic Response and Signal to Noise Ratio Investigation of NIR-FBG Dynamic Sensing System for Monitoring Thin- walled Composite Plate

    NASA Astrophysics Data System (ADS)

    Hafizi, Z. M.; Epaarachchi, J.

    2015-12-01

    Optical fiber systems for dynamic response measurement become an attractive study nowadays especially in the field of Structural Health Monitoring (SHM). This work presents the investigation of an optical fiber sensor system utilizing Near Infra-Red Fiber Bragg Grating (NIR-FBG) sensor for SHM of a thin-walled composite structure. In this study, a comparison between the experimental result and simulation study using finite element analysis has been presented. By comparing both results, the FBG dynamic sensing system was shown to have an excellent capability in acquiring dynamic response due to flexural wave propagations. In the meantime, a signal to noise ratio (SNR) study was also performed to several FBG dynamic sensor systems; particularly to see the comparison between NIR-FBG sensor and 1550 nm FBG sensor. Furthermore, with a proper configuration, an NIR-FBG system was proved to have better performance than the 1550 nm based FBG sensor.

  2. Telecom technology based continuous wave terahertz photomixing system with 105 decibel signal-to-noise ratio and 3.5 terahertz bandwidth.

    PubMed

    Göbel, Thorsten; Stanze, Dennis; Globisch, Björn; Dietz, Roman J B; Roehle, Helmut; Schell, Martin

    2013-10-15

    A modified photoconductive receiver significantly improves the performance of photomixing-based continuous wave (cw) THz systems driven at the optical telecommunication wavelength of 1.5 μm. The achieved signal-to-noise ratio of 105 dB at 100 GHz and 70 dB at 1 THz, both for an integration time of 200 ms, are to our knowledge the highest numbers reported in literature for any optoelectronic cw THz system, including classical setups operating at 800 nm. The developed receiver allows for combining low cost and high performance in one system for the first time to our knowledge. PMID:24321958

  3. Penetrating Peptide-Bioconjugated Persistent Nanophosphors for Long-Term Tracking of Adipose-Derived Stem Cells with Superior Signal-to-Noise Ratio.

    PubMed

    Wu, Shu-Qi; Chi, Chong-Wei; Yang, Cheng-Xiong; Yan, Xiu-Ping

    2016-04-01

    Reliable long-term in vivo tracking of stem cells is of great importance in stem cell-based therapy and research. Fluorescence imaging with in situ excitation has significant autofluorescence background, which results in poor signal-to-noise ratio (SNR). Here we report TAT penetrating peptide-bioconjugated long persistent luminescence nanoparticles (LPLNP-TAT) for long-term tracking of adipose-derived stem cells (ASC) without constant external excitation. LPLNP-TAT exhibits near-infrared emitting, red light renewable capability, and superior in vivo imaging depth and SNR compared with conventional organic dye and quantum dots. Our findings show that LPLNP-TAT can successfully label ASC without impairing their proliferation and differentiation and can effectively track ASC in skin-regeneration and tumor-homing models. We believe that LPLNP-TAT represents a new generation of cell tracking probes and will have broad application in diagnosis and therapy. PMID:26942557

  4. Optimization of wide-angle seismic signal-to-noise ratios and P-wave transmission in Kenya

    USGS Publications Warehouse

    Jacob, A.W.B.; Vees, R.; Braile, L.W.; Criley, E.

    1994-01-01

    In previous refraction and wide-angle reflection experiments in the Kenya Rift there were problems with poor signal-noise ratios which made good seismic interpretation difficult. Careful planning and preparation for KRISP 90 has substantially overcome these problems and produced excellent seismic sections in a difficult environment. Noise levels were minimized by working, as far as possible, at times of the day when conditions were quiet, while source signals were optimized by using dispersed charges in water where it was available and waterfilled boreholes in most cases where it was not. Seismic coupling at optimum depth in water has been found to be more than 100 times greater than it is in a borehole in dry loosely compacted material. Allowing for the source coupling, a very marked difference has been found between the observation ranges in the rift and those on the flanks, where the observation ranges are greater. These appear to indicate a significant difference in seismic transmission through the two types of crust. ?? 1994.

  5. Principal component analysis with pre-normalization improves the signal-to-noise ratio and image quality in positron emission tomography studies of amyloid deposits in Alzheimer's disease

    NASA Astrophysics Data System (ADS)

    Razifar, Pasha; Engler, Henry; Blomquist, Gunnar; Ringheim, Anna; Estrada, Sergio; Långström, Bengt; Bergström, Mats

    2009-06-01

    This study introduces a new approach for the application of principal component analysis (PCA) with pre-normalization on dynamic positron emission tomography (PET) images. These images are generated using the amyloid imaging agent N-methyl [11C]2-(4'-methylaminophenyl)-6-hydroxy-benzothiazole ([11C]PIB) in patients with Alzheimer's disease (AD) and healthy volunteers (HVs). The aim was to introduce a method which, by using the whole dataset and without assuming a specific kinetic model, could generate images with improved signal-to-noise and detect, extract and illustrate changes in kinetic behavior between different regions in the brain. Eight AD patients and eight HVs from a previously published study with [11C]PIB were used. The approach includes enhancement of brain regions where the kinetics of the radiotracer are different from what is seen in the reference region, pre-normalization for differences in noise levels and removal of negative values. This is followed by slice-wise application of PCA (SW-PCA) on the dynamic PET images. Results obtained using the new approach were compared with results obtained using reference Patlak and summed images. The new approach generated images with good quality in which cortical brain regions in AD patients showed high uptake, compared to cerebellum and white matter. Cortical structures in HVs showed low uptake as expected and in good agreement with data generated using kinetic modeling. The introduced approach generated images with enhanced contrast and improved signal-to-noise ratio (SNR) and discrimination power (DP) compared to summed images and parametric images. This method is expected to be an important clinical tool in the diagnosis and differential diagnosis of dementia.

  6. The Influence of Inspection Angle, Wave Type and Beam Shape on Signal-to-Noise Ratios in Ultrasonic Pitch-Catch Inspections

    NASA Astrophysics Data System (ADS)

    Margetan, F. J.; Li, Anxiang; Thompson, R. B.

    2007-03-01

    Grain noise, which arises from the scattering of sound waves by microstructure, can limit the detection of small internal defects in metal components. Signal-to-noise (S/N) ratios for ultrasonic pitch/catch inspections are primarily determined by three factors: the scattering ability of the defect; the inherent noisiness of the microstructure (per unit volume); and finite-beam effects. An approximate single-scattering model has been formulated which contains terms representing each of these factors. In this paper the model is applied to a representative pitch/catch inspection problem, namely, the detection of a circular crack in a nickel cylinder. The object is to estimate S/N ratios for various choices of the inspection angle and sonic wave types, and to demonstrate how S/N is determined by the interplay of the defect, microstructure, and finite-beam factors. We also explore how S/N is influenced by the sizes, shapes, and orientations of the transmitter and receiver sound beams.

  7. Enhancement of signal-to-noise ratio and phase locking for small inputs by a low-threshold outward current in auditory neurons.

    PubMed

    Svirskis, Gytis; Kotak, Vibhakar; Sanes, Dan H; Rinzel, John

    2002-12-15

    Neurons possess multiple voltage-dependent conductances specific for their function. To investigate how low-threshold outward currents improve the detection of small signals in a noisy background, we recorded from gerbil medial superior olivary (MSO) neurons in vitro. MSO neurons responded phasically, with a single spike to a step current injection. When bathed in dendrotoxin (DTX), most cells switched to tonic firing, suggesting that low-threshold potassium currents (I(KLT)) participated in shaping these phasic responses. Neurons were stimulated with a computer-generated steady barrage of random inputs, mimicking weak synaptic conductance transients (the "noise"), together with a larger but still subthreshold postsynaptic conductance, EPSG (the "signal"). DTX reduced the signal-to-noise ratio (SNR), defined as the ratio of probability to fire in response to the EPSG and the probability to fire spontaneously in response to noise. The reduction was mainly attributable to the increase of spontaneous firing in DTX. The spike-triggered reverse correlation indicated that, for spike generation, the neuron with I(KLT) required faster inward current transients. This narrow temporal integration window contributed to superior phase locking of firing to periodic stimuli before application of DTX. A computer model including Hodgkin-Huxley type conductances for spike generation and for I(KLT) (Rathouz and Trussell, 1998) showed similar response statistics. The dynamic low-threshold outward current increased SNR and the temporal precision of integration of weak subthreshold signals in auditory neurons by suppressing false positives. PMID:12486197

  8. Low voltage-driven oxide phototransistors with fast recovery, high signal-to-noise ratio, and high responsivity fabricated via a simple defect-generating process

    PubMed Central

    Yun, Myeong Gu; Kim, Ye Kyun; Ahn, Cheol Hyoun; Cho, Sung Woon; Kang, Won Jun; Cho, Hyung Koun; Kim, Yong-Hoon

    2016-01-01

    We have demonstrated that photo-thin film transistors (photo-TFTs) fabricated via a simple defect-generating process could achieve fast recovery, a high signal to noise (S/N) ratio, and high sensitivity. The photo-TFTs are inverted-staggered bottom-gate type indium-gallium-zinc-oxide (IGZO) TFTs fabricated using atomic layer deposition (ALD)-derived Al2O3 gate insulators. The surfaces of the Al2O3 gate insulators are damaged by ion bombardment during the deposition of the IGZO channel layers by sputtering and the damage results in the hysteresis behavior of the photo-TFTs. The hysteresis loops broaden as the deposition power density increases. This implies that we can easily control the amount of the interface trap sites and/or trap sites in the gate insulator near the interface. The photo-TFTs with large hysteresis-related defects have high S/N ratio and fast recovery in spite of the low operation voltages including a drain voltage of 1 V, positive gate bias pulse voltage of 3 V, and gate voltage pulse width of 3 V (0 to 3 V). In addition, through the hysteresis-related defect-generating process, we have achieved a high responsivity since the bulk defects that can be photo-excited and eject electrons also increase with increasing deposition power density. PMID:27553518

  9. Low voltage-driven oxide phototransistors with fast recovery, high signal-to-noise ratio, and high responsivity fabricated via a simple defect-generating process.

    PubMed

    Yun, Myeong Gu; Kim, Ye Kyun; Ahn, Cheol Hyoun; Cho, Sung Woon; Kang, Won Jun; Cho, Hyung Koun; Kim, Yong-Hoon

    2016-01-01

    We have demonstrated that photo-thin film transistors (photo-TFTs) fabricated via a simple defect-generating process could achieve fast recovery, a high signal to noise (S/N) ratio, and high sensitivity. The photo-TFTs are inverted-staggered bottom-gate type indium-gallium-zinc-oxide (IGZO) TFTs fabricated using atomic layer deposition (ALD)-derived Al2O3 gate insulators. The surfaces of the Al2O3 gate insulators are damaged by ion bombardment during the deposition of the IGZO channel layers by sputtering and the damage results in the hysteresis behavior of the photo-TFTs. The hysteresis loops broaden as the deposition power density increases. This implies that we can easily control the amount of the interface trap sites and/or trap sites in the gate insulator near the interface. The photo-TFTs with large hysteresis-related defects have high S/N ratio and fast recovery in spite of the low operation voltages including a drain voltage of 1 V, positive gate bias pulse voltage of 3 V, and gate voltage pulse width of 3 V (0 to 3 V). In addition, through the hysteresis-related defect-generating process, we have achieved a high responsivity since the bulk defects that can be photo-excited and eject electrons also increase with increasing deposition power density. PMID:27553518

  10. Correlation of radiologists' image quality perception with quantitative assessment parameters: just-noticeable difference vs. peak signal-to-noise ratios

    NASA Astrophysics Data System (ADS)

    Siddiqui, Khan M.; Siegel, Eliot L.; Reiner, Bruce I.; Johnson, Jeffrey P.

    2005-04-01

    The authors identify a fundamental disconnect between the ways in which industry and radiologists assess and even discuss product performance. What is needed is a quantitative methodology that can assess both subjective image quality and observer task performance. In this study, we propose and evaluate the use of a visual discrimination model (VDM) that assesses just-noticeable differences (JNDs) to serve this purpose. The study compares radiologists' subjective perceptions of image quality of computer tomography (CT) and computed radiography (CR) images with quantitative measures of peak signal-to-noise ratio (PSNR) and JNDs as measured by a VDM. The study included 4 CT and 6 CR studies with compression ratios ranging from lossless to 90:1 (total of 80 sets of images were generated [n = 1,200]). Eleven radiologists reviewed the images and rated them in terms of overall quality and readability and identified images not acceptable for interpretation. Normalized reader scores were correlated with compression, objective PSNR, and mean JND values. Results indicated a significantly higher correlation between observer performance and JND values than with PSNR methods. These results support the use of the VDM as a metric not only for the threshold discriminations for which it was calibrated, but also as a general image quality metric. This VDM is a highly promising, reproducible, and reliable adjunct or even alternative to human observer studies for research or to establish clinical guidelines for image compression, dose reductions, and evaluation of various display technologies.

  11. Children's Recall of Words Spoken in Their First and Second Language: Effects of Signal-to-Noise Ratio and Reverberation Time.

    PubMed

    Hurtig, Anders; Keus van de Poll, Marijke; Pekkola, Elina P; Hygge, Staffan; Ljung, Robert; Sörqvist, Patrik

    2015-01-01

    Speech perception runs smoothly and automatically when there is silence in the background, but when the speech signal is degraded by background noise or by reverberation, effortful cognitive processing is needed to compensate for the signal distortion. Previous research has typically investigated the effects of signal-to-noise ratio (SNR) and reverberation time in isolation, whilst few have looked at their interaction. In this study, we probed how reverberation time and SNR influence recall of words presented in participants' first- (L1) and second-language (L2). A total of 72 children (10 years old) participated in this study. The to-be-recalled wordlists were played back with two different reverberation times (0.3 and 1.2 s) crossed with two different SNRs (+3 dBA and +12 dBA). Children recalled fewer words when the spoken words were presented in L2 in comparison with recall of spoken words presented in L1. Words that were presented with a high SNR (+12 dBA) improved recall compared to a low SNR (+3 dBA). Reverberation time interacted with SNR to the effect that at +12 dB the shorter reverberation time improved recall, but at +3 dB it impaired recall. The effects of the physical sound variables (SNR and reverberation time) did not interact with language. PMID:26834665

  12. Coherent anti-Stokes Raman scattering microscope with a high-signal-to-noise ratio, high stability, and high-speed imaging for live cell observation

    NASA Astrophysics Data System (ADS)

    Hayashi, Shinichi; Takimoto, Shinichi; Hashimoto, Takeshi

    2007-02-01

    Coherent anti-Stokes Raman scattering (CARS) microscopy, which can produce images of specific molecules without staining, has attracted the attention of researchers, as it matches the need for molecular imaging and pathway analysis of live cells. In particular, there have been an increasing number of CARS experimental results regarding lipids in live cells, which cannot be fluorescently tagged while keeping the cells alive. One of the important applications of lipid research is for the metabolic syndrome. Since the metabolic syndrome is said to be related to the lipids in lipocytes, blood, arterial vessels, and so on, the CARS technique is expected to find application in this field. However, CARS microscopy requires a pair of picosecond laser pulses, which overlap both temporally and spatially. This makes the optical adjustments of a CARS microscope challenging. The authors developed a CARS unit that includes optics for easy and stable adjustment of the overlap of these laser pulses. Adding the CARS unit to a laser scanning microscope provides CARS images of a high signal-to-noise ratio, with an acquisition rate as high as 2 microseconds per pixel. Thus, images of fast-moving lipid droplets in Hela cells were obtained.

  13. Extended use of incremental signal-to-noise ratio as reliability criterion for multiple-slope wide-dynamic-range image capture

    NASA Astrophysics Data System (ADS)

    Hertel, Dirk

    2010-01-01

    Mobile applications present new image quality challenges. Automotive vision requires reliable capture of scene detail. Photospace measurements have shown that the extremely wide intrascene dynamic range of traffic scenes necessitates wide-dynamic-range (WDR) technology. Multiple-slope complementary metal-oxide semiconductor (CMOS) technology adaptively extends dynamic range by partially resetting the pixel, resulting in a response curve with piecewise linear slopes of progressively increasing compression. As compression and thus dynamic range increase, a trade-off against detail loss is observed. Incremental signal-to-noise ratio (iSNR) has been proposed in ISO/TC42 standards for determining dynamic range, and this work describes how to adapt these to WDR. Measurements and computer simulations reveal that the observed trade-off between WDR extension and the loss of local detail can be explained by a drop in iSNR at each reset point. If a reset is not timed optimally, then iSNR may drop below the detection limit causing an iSNR hole to appear within the dynamic range. Thus iSNR has extended utility: it not only determines the dynamic range limits but also defines dynamic range as the luminance range where detail detection is reliable. It has become the critical criterion when maximizing dynamic range to maintain the minimum necessary level of detection reliability.

  14. Long-distance fiber Bragg grating sensor system with a high optical signal-to-noise ratio based on a tunable fiber ring laser configuration

    NASA Astrophysics Data System (ADS)

    Rao, Yun-Jiang; Ran, Zeng-Ling; Chen, Rong-Rui

    2006-09-01

    A novel tunable fiber ring laser configuration with a combination of bidirectional Raman amplification and dual erbium-doped fiber (EDF) amplification is proposed for realizing high optical signal-to-noise ratio (SNR), long-distance, quasi-distributed fiber Bragg grating (FBG) sensing systems with large capacities and low cost. The hybrid Raman-EDF amplification configuration arranged in the ring laser can enhance the optical SNR of FBG sensor signals significantly owing to the good combination of the high gain of the erbium-doped fiber amplifier (EDFA) and the low noise of the Raman amplification. Such a sensing system can support a large number of FBG sensors because of the use of a tunable fiber Fabry-Perot filter located within the ring laser and spatial division multiplexing for expansion of sensor channels. Experimental results show that an excellent optical SNR of ˜60 dB has been achieved for a 50 km transmission distance with a low Raman pump power of ˜170 mW at a wavelength of 1455 nm and a low EDFA pump power of ˜40 mW at a wavelength of 980 nm, which is the highest optical SNR achieved so far for a 50 km long FBG sensor system, to our knowledge.

  15. Long-distance fiber Bragg grating sensor system with a high optical signal-to-noise ratio based on a tunable fiber ring laser configuration.

    PubMed

    Rao, Yun-Jiang; Ran, Zeng-Ling; Chen, Rong-Rui

    2006-09-15

    A novel tunable fiber ring laser configuration with a combination of bidirectional Raman amplification and dual erbium-doped fiber (EDF) amplification is proposed for realizing high optical signal-to-noise ratio (SNR), long-distance, quasi-distributed fiber Bragg grating (FBG) sensing systems with large capacities and low cost. The hybrid Raman-EDF amplification configuration arranged in the ring laser can enhance the optical SNR of FBG sensor signals significantly owing to the good combination of the high gain of the erbium-doped fiber amplifier (EDFA) and the low noise of the Raman amplification. Such a sensing system can support a large number of FBG sensors because of the use of a tunable fiber Fabry-Perot filter located within the ring laser and spatial division multiplexing for expansion of sensor channels. Experimental results show that an excellent optical SNR of approximately 60 dB has been achieved for a 50 km transmission distance with a low Raman pump power of approximately 170 mW at a wavelength of 1455 nm and a low EDFA pump power of approximately 40 mW at a wavelength of 980 nm, which is the highest optical SNR achieved so far for a 50 km long FBG sensor system, to our knowledge. PMID:16936857

  16. Signal-to-noise ratio enhancement on SEM images using a cubic spline interpolation with Savitzky-Golay filters and weighted least squares error.

    PubMed

    Kiani, M A; Sim, K S; Nia, M E; Tso, C P

    2015-05-01

    A new technique based on cubic spline interpolation with Savitzky-Golay smoothing using weighted least squares error filter is enhanced for scanning electron microscope (SEM) images. A diversity of sample images is captured and the performance is found to be better when compared with the moving average and the standard median filters, with respect to eliminating noise. This technique can be implemented efficiently on real-time SEM images, with all mandatory data for processing obtained from a single image. Noise in images, and particularly in SEM images, are undesirable. A new noise reduction technique, based on cubic spline interpolation with Savitzky-Golay and weighted least squares error method, is developed. We apply the combined technique to single image signal-to-noise ratio estimation and noise reduction for SEM imaging system. This autocorrelation-based technique requires image details to be correlated over a few pixels, whereas the noise is assumed to be uncorrelated from pixel to pixel. The noise component is derived from the difference between the image autocorrelation at zero offset, and the estimation of the corresponding original autocorrelation. In the few test cases involving different images, the efficiency of the developed noise reduction filter is proved to be significantly better than those obtained from the other methods. Noise can be reduced efficiently with appropriate choice of scan rate from real-time SEM images, without generating corruption or increasing scanning time. PMID:25676007

  17. Children’s Recall of Words Spoken in Their First and Second Language: Effects of Signal-to-Noise Ratio and Reverberation Time

    PubMed Central

    Hurtig, Anders; Keus van de Poll, Marijke; Pekkola, Elina P.; Hygge, Staffan; Ljung, Robert; Sörqvist, Patrik

    2016-01-01

    Speech perception runs smoothly and automatically when there is silence in the background, but when the speech signal is degraded by background noise or by reverberation, effortful cognitive processing is needed to compensate for the signal distortion. Previous research has typically investigated the effects of signal-to-noise ratio (SNR) and reverberation time in isolation, whilst few have looked at their interaction. In this study, we probed how reverberation time and SNR influence recall of words presented in participants’ first- (L1) and second-language (L2). A total of 72 children (10 years old) participated in this study. The to-be-recalled wordlists were played back with two different reverberation times (0.3 and 1.2 s) crossed with two different SNRs (+3 dBA and +12 dBA). Children recalled fewer words when the spoken words were presented in L2 in comparison with recall of spoken words presented in L1. Words that were presented with a high SNR (+12 dBA) improved recall compared to a low SNR (+3 dBA). Reverberation time interacted with SNR to the effect that at +12 dB the shorter reverberation time improved recall, but at +3 dB it impaired recall. The effects of the physical sound variables (SNR and reverberation time) did not interact with language. PMID:26834665

  18. Influence of skew rays on the sensitivity and signal-to-noise ratio of a fiber-optic surface-plasmon-resonance sensor: a theoretical study

    SciTech Connect

    Dwivedi, Yogendra S.; Sharma, Anuj K.; Gupta, Banshi D

    2007-07-20

    We have theoretically analyzed the influence of skew rays on the performance of a fiber-optic sensor based on surface plasmon resonance. The performance of the sensor has been evaluated in terms of its sensitivity and signal-to-noise ratio (SNR). The theoretical model for skewness dependence includes the material dispersion in fiber cores and metal layers, simultaneous excitation of skew rays, and meridional rays in the fiber core along with all guided rays launching from a collimated light source. The effect of skew rays on the SNR and the sensitivity of the sensor with two different metals has been compared. The same comparison is carried out for the different values of design parameters such as numerical aperture, fiber core diameter, and the length of the surface-plasmon-resonance (SPR)active sensing region. This detailed analysis for the effect of skewness on the SNR and the sensitivity of the sensor leads us to achieve the best possible performance from a fiber-optic SPR sensor against the skewness in the optical fiber.

  19. Linear frequency modulation photoacoustic radar: optimal bandwidth and signal-to-noise ratio for frequency-domain imaging of turbid media.

    PubMed

    Lashkari, Bahman; Mandelis, Andreas

    2011-09-01

    The development of the pulse compression photoacoustic (PA) radar using linear frequency modulation (LFM) demonstrated experimentally that spectral matching of the signal to the ultrasonic transducer bandwidth does not necessarily produce the best PA signal-to-noise ratio, and it was shown that the optical and acoustic properties of the absorber will modify the optimal bandwidth. The effects of these factors are investigated in frequency-domain (FD) PA imaging by employing one-dimensional and axisymmetric models of the PA effect, and a Krimholtz-Leedom-Matthaei model for the employed transducers. LFM chirps with various bandwidths were utilized and transducer sensitivity was measured to ensure the accuracy of the model. The theory was compared with experimental results and it was shown that the PA effect can act as a low-pass filter in the signal generation. Furthermore, with the PA radar, the low-frequency behavior of two-dimensional wave generation can appear as a false peak in the cross correlation signal trace. These effects are important in optimizing controllable features of the FD-PA method to improve image quality. PMID:21895073

  20. Remarkable improvement of the signal-to-noise ratio of 57Mn/ 57Fe in-beam Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Nagatomo, T.; Kobayashi, Y.; Kubo, M. K.; Yamada, Y.; Mihara, M.; Sato, W.; Miyazaki, J.; Sato, S.; Kitagawa, A.

    2011-02-01

    In-beam Mössbauer spectroscopy utilizing unstable 57Mn beams is a powerful method to extract physical and chemical properties at the atomic scale. A parallel plate avalanche counter (PPAC), optimized to detect conversion electrons generated by the Mössbauer effect, can be employed to suppress higher-energy background γ rays. However, β rays are emitted by the 57Mn parent nuclei of 57Fe, which can significantly degrade the spectrum quality. In the present work, we have developed a new anti-coincidence-detection system with a thin plastic scintillation counter (0.5 mmt), which can be used to detect β rays and reject them from the recorded PPAC events. To demonstrate the anti-coincidence system, we carried out Mössbauer spectroscopy utilizing 57Mn nuclei that were implanted into a non-magnetic aluminum metal plate at room temperature. Using the anti-coincidence method, we obtained a typical Mössbauer spectrum of high quality, despite a very low number of implanted 57Mn atoms, of ˜5 × 10 9. The signal to noise ratio of the obtained spectrum was increased remarkably, and the relative peak height above the baseline increased from 10% to 220% using the anti-coincidence method. The developed detection system is applicable to investigation of in situ properties, and avoids the potentially problematic agglomeration of probes in a sample.

  1. Signal-to-noise ratio improvements in laser flow diagnostics using time-resolved image averaging and high dynamic range imaging

    NASA Astrophysics Data System (ADS)

    Giassi, Davide; Long, Marshall B.

    2016-08-01

    Two alternative image readout approaches are demonstrated to improve the signal-to-noise ratio (SNR) in temporally resolved laser-based imaging experiments of turbulent phenomena. The first method exploits the temporal decay characteristics of the phosphor screens of image intensifiers when coupled to an interline-transfer CCD camera operated in double-frame mode. Specifically, the light emitted by the phosphor screen, which has a finite decay constant, is equally distributed and recorded over the two sequential frames of the detector so that an averaged image can be reconstructed. The characterization of both detector and image intensifier showed that the technique preserves the correct quantitative information, and its applicability to reactive flows was verified using planar Rayleigh scattering and tested with the acquisition of images of both steady and turbulent partially premixed methane/air flames. The comparison between conventional Rayleigh results and the averaged ones showed that the SNR of the averaged image is higher than the conventional one; with the setup used in this work, the gain in SNR was seen to approach 30 %, for both the steady and turbulent cases. The second technique uses the two-frame readout of an interline-transfer CCD to increase the image SNR based on high dynamic range imaging, and it was tested in an unsteady non-reactive flow of Freon-12 injected in air. The result showed a 15 % increase in the SNR of the low-pixel-count regions of an image, when compared to the pixels of a conventionally averaged one.

  2. Extended use of ISO 15739 incremental signal-to-noise ratio as reliability criterion for multiple-slope wide dynamic range image capture

    NASA Astrophysics Data System (ADS)

    Hertel, Dirk

    2009-01-01

    In the emerging field of automotive vision, video capture is the critical front-end of driver assistance and active safety systems. Previous photospace measurements have shown that light levels in natural traffic scenes may contain an extremely wide intra-scene intensity range. This requires the camera to have a wide dynamic range (WDR) for it to adapt quickly to changing lighting conditions and to reliably capture all scene detail. Multiple-slope CMOS technology offers a cost-effective way of adaptively extending dynamic range by partially resetting (recharging) the CMOS pixel once or more often within each frame time. This avoids saturation and leads to a response curve with piecewise linear slopes of progressively increasing compression. It was observed that the image quality from multiple-slope image capture is strongly dependent on the control (height and time) of each reset barrier. As compression and thus dynamic range increase there is a trade-off against contrast and detail loss. Incremental signal-to-noise ratio (iSNR) is proposed in ISO 15739 for determining dynamic range. Measurements and computer simulations revealed that the observed trade-off between WDR extension and the loss of local detail could be explained by a drop in iSNR at each reset point. If a reset barrier is not optimally placed then iSNR may drop below the detection limit so that an 'iSNR hole' appears in the dynamic range. Thus ISO 15739 iSNR has gained extended utility: it not only measures the dynamic range limits but also defines dynamic range as the intensity range where detail detection is reliable. It has become a critical criterion when designing adaptive barrier control algorithms that maximize dynamic range while maintaining the minimum necessary level of detection reliability.

  3. Correlation between the signal-to-noise ratio improvement factor (KSNR) and clinical image quality for chest imaging with a computed radiography system

    NASA Astrophysics Data System (ADS)

    Moore, C. S.; Wood, T. J.; Saunderson, J. R.; Beavis, A. W.

    2015-12-01

    This work assessed the appropriateness of the signal-to-noise ratio improvement factor (KSNR) as a metric for the optimisation of computed radiography (CR) of the chest. The results of a previous study in which four experienced image evaluators graded computer simulated chest images using a visual grading analysis scoring (VGAS) scheme to quantify the benefit of using an anti-scatter grid were used for the clinical image quality measurement (number of simulated patients  =  80). The KSNR was used to calculate the improvement in physical image quality measured in a physical chest phantom. KSNR correlation with VGAS was assessed as a function of chest region (lung, spine and diaphragm/retrodiaphragm), and as a function of x-ray tube voltage in a given chest region. The correlation of the latter was determined by the Pearson correlation coefficient. VGAS and KSNR image quality metrics demonstrated no correlation in the lung region but did show correlation in the spine and diaphragm/retrodiaphragmatic regions. However, there was no correlation as a function of tube voltage in any region; a Pearson correlation coefficient (R) of  -0.93 (p  =  0.015) was found for lung, a coefficient (R) of  -0.95 (p  =  0.46) was found for spine, and a coefficient (R) of  -0.85 (p  =  0.015) was found for diaphragm. All demonstrate strong negative correlations indicating conflicting results, i.e. KSNR increases with tube voltage but VGAS decreases. Medical physicists should use the KSNR metric with caution when assessing any potential improvement in clinical chest image quality when introducing an anti-scatter grid for CR imaging, especially in the lung region. This metric may also be a limited descriptor of clinical chest image quality as a function of tube voltage when a grid is used routinely.

  4. Influence of subthreshold nonlinearities on signal-to-noise ratio and timing precision for small signals in neurons: minimal model analysis.

    PubMed

    Svirskis, Gytis; Rinzel, John

    2003-02-01

    Subthreshold voltage- and time-dependent conductances can subserve different roles in signal integration and action potential generation. Here, we use minimal models to demonstrate how a non-inactivating low-threshold outward current (I(KLT)) can enhance the precision of small-signal integration. Our integrate-and-fire models have only a few biophysical parameters, enabling a parametric study of I(KLT) effects. I(KLT) increases the signal-to-noise ratio (SNR) for firing when a subthreshold 'signal' EPSP is delivered in the presence of weak random input. The increased SNR is due to the suppression of spontaneous firings to random input. In accordance, SNR grows as the EPSP amplitude increases. SNR also grows as the unitary synaptic current's time constant increases, leading to more effective suppression of spontaneous activity. Spike-triggered reverse correlation of the injected current indicates that, to reach spike threshold, a cell with I(KLT) requires a briefer time course of injected current. Consistent with this narrowed integration time window, I(KI.T) enhances phase-locking. measured as vector strength, to a weak noisy and periodically modulated stimulus. Thus subthreshold negative feedback mediated by I(KLT) enhances temporal processing. An alternative suppression mechanism is voltage- and time-dependent inactivation of a low-threshold inward current. This feature in an integrate-and-fire model also shows SNR enhancement, in comparison with a case when the inward current is non-inactivating. Small-signal detection can be significantly improved in noisy neuronal systems by subthreshold negative feedback, serving to suppress false positives. PMID:12613555

  5. Enhancing signal to noise ratio by fine-tuning tapers of cladded/uncladded buffer rods in ultrasonic time domain reflectometry in smelters.

    PubMed

    Viumdal, Håkon; Mylvaganam, Saba

    2014-03-01

    Buffer rods (BR) as waveguides in ultrasonic time domain reflectometry (TDR) can somewhat extend the range of industrial applications of ultrasonics. Level, temperature and flow measurements involving elevated temperatures, corrosive fluids and generally harsh environments are some of the applications in which conventional ultrasonic transducers cannot be used directly in contact with the media. In such cases, BRs with some design modifications can make ultrasonic TDR measurements possible with limited success. This paper deals with TDR in conjunction with distance measurements in extremely hot fluids, using conventional ultrasonic transducers in combination with BRs. When using BRs in the ultrasonic measurement systems in extreme temperatures, problems associated with size and the material of the buffer, have to be addressed. The resonant frequency of the transducer and the relative size of the transducer with respect to the diameter of BR are also important parameters influencing the signal to noise ratio (SNR) of the signal processing system used in the ultrasonic TDR. This paper gives an overview of design aspects related to the BRs with special emphasis on tapers and cladding used on BRs. As protective cladding, zirconium oxide-yttrium oxide composite was used, with its proven thermal stability in withstanding temperatures in rocket and jet engines up to 1650 °C. In general a BR should guide the signals through to the medium and from and back to the transducer without excessive attenuation and at the same time not exacerbate the noise in the measurement system. The SNR is the decisive performance indicator to consider in the design of BR based ultrasonic TDR, along with appropriate transducer, with suitable size and operating frequency. This work presents and analyses results from extensive experiments related to fine-tuning both geometry of and signals in cladded/uncladded BRs used in high temperature ultrasonic TDR with focus on overall performance based on

  6. Improved signal to noise ratio and sensitivity of an infrared imaging video bolometer on large helical device by using an infrared periscope.

    PubMed

    Pandya, Shwetang N; Peterson, Byron J; Mukai, Kiyofumi; Sano, Ryuichi; Enokuchi, Akito; Takeyama, Norihide

    2014-07-01

    An Infrared imaging Video Bolometer (IRVB) diagnostic is currently being used in the Large Helical Device (LHD) for studying the localization of radiation structures near the magnetic island and helical divertor X-points during plasma detachment and for 3D tomography. This research demands high signal to noise ratio (SNR) and sensitivity to improve the temporal resolution for studying the evolution of radiation structures during plasma detachment and a wide IRVB field of view (FoV) for tomography. Introduction of an infrared periscope allows achievement of a higher SNR and higher sensitivity, which in turn, permits a twofold improvement in the temporal resolution of the diagnostic. Higher SNR along with wide FoV is achieved simultaneously by reducing the separation of the IRVB detector (metal foil) from the bolometer's aperture and the LHD plasma. Altering the distances to meet the aforesaid requirements results in an increased separation between the foil and the IR camera. This leads to a degradation of the diagnostic performance in terms of its sensitivity by 1.5-fold. Using an infrared periscope to image the IRVB foil results in a 7.5-fold increase in the number of IR camera pixels imaging the foil. This improves the IRVB sensitivity which depends on the square root of the number of IR camera pixels being averaged per bolometer channel. Despite the slower f-number (f/# = 1.35) and reduced transmission (τ0 = 89%, due to an increased number of lens elements) for the periscope, the diagnostic with an infrared periscope operational on LHD has improved in terms of sensitivity and SNR by a factor of 1.4 and 4.5, respectively, as compared to the original diagnostic without a periscope (i.e., IRVB foil being directly imaged by the IR camera through conventional optics). The bolometer's field of view has also increased by two times. The paper discusses these improvements in apt details. PMID:25085127

  7. Metals in the z ˜ 3 intergalactic medium: results from an ultra-high signal-to-noise ratio UVES quasar spectrum

    NASA Astrophysics Data System (ADS)

    D'Odorico, V.; Cristiani, S.; Pomante, E.; Carswell, R. F.; Viel, M.; Barai, P.; Becker, G. D.; Calura, F.; Cupani, G.; Fontanot, F.; Haehnelt, M. G.; Kim, T.-S.; Miralda-Escudé, J.; Rorai, A.; Tescari, E.; Vanzella, E.

    2016-08-01

    In this work, we investigate the abundance and distribution of metals in the intergalactic medium (IGM) at ≃ 2.8 through the analysis of an ultra-high signal-to-noise ratio UVES spectrum of the quasar HE0940-1050. In the C IV forest, our deep spectrum is sensitive at 3 σ to lines with column density down to log NCIV ≃ 11.4 and in 60 percent of the considered redshift range down to ≃ 11.1. In our sample, all H I lines with log NHI ≥ 14.8 show an associated C IV absorption. In the range 14.0 ≤ log NHI < 14.8, 43 percent of H I lines has an associated C IV absorption. At log NHI < 14.0, the detection rates drop to <10 percent, possibly due to our sensitivity limits and not to an actual variation of the gas abundance properties. In the range log NHI ≥ 14, we observe a fraction of H I lines with detected C IV a factor of 2 larger than the fraction of H I lines lying in the circum-galactic medium (CGM) of relatively bright Lyman-break galaxies hosted by dark matter halos with ˜ 1012 M⊙ (Rudie et al. 2012). The comparison of our results with the output of a grid of photoionization models and of two cosmological simulations implies that the volume filling factor of the IGM gas enriched to a metallicity log Z/Z⊙ ≳ - 3 should be of the order of ˜10 - 13 percent. In conclusion, our results favour a scenario in which metals are found also outside the CGM of bright star-forming galaxies, possibly due to pollution by lower mass objects and/or to an early enrichment by the first sources.

  8. High signal-to-noise ratio acoustic sensor using phase-shifted gratings interrogated by the Pound-Drever-Hall technique

    NASA Astrophysics Data System (ADS)

    Kung, Peter; Comanici, Maria I.

    2014-06-01

    Optical fiber is made of glass, an insulator, and thus it is immune to strong electromagnetic interference. Therefore, fiber optics is a technology ideally suitable for sensing of partial discharge (PD) both in transformers and generators. Extensive efforts have been used to develop a cost effective solution for detecting partial discharge, which generates acoustic emission, with signals ranging from 30 kHz to 200 kHz. The requirement is similar to fiber optics Hydro Phone, but at higher frequencies. There are several keys to success: there must be at least 60 dB signal-to-noise ratio (SNR) performance, which will ensure not only PD detection but later on provide diagnostics and also the ability to locate the origin of the events. Defects that are stationary would gradually degrade the insulation and result in total breakdown. Transformers currently need urgent attention: most of them are oil filled and are at least 30 to 50 years old, close to the end of life. In this context, an issue to be addressed is the safety of the personnel working close to the assets and collateral damage that could be caused by a tank explosion (with fire spilling over the whole facility). This paper will describe the latest achievement in fiber optics PD sensor technology: the use of phase shifted-fiber gratings with a very high speed interrogation method that uses the Pound-Drever-Hall technique. More importantly, this is based on a technology that could be automated, easy to install, and, eventually, available at affordable prices

  9. Correlation between the signal-to-noise ratio improvement factor (KSNR) and clinical image quality for chest imaging with a computed radiography system.

    PubMed

    Moore, C S; Wood, T J; Saunderson, J R; Beavis, A W

    2015-12-01

    This work assessed the appropriateness of the signal-to-noise ratio improvement factor (KSNR) as a metric for the optimisation of computed radiography (CR) of the chest. The results of a previous study in which four experienced image evaluators graded computer simulated chest images using a visual grading analysis scoring (VGAS) scheme to quantify the benefit of using an anti-scatter grid were used for the clinical image quality measurement (number of simulated patients  =  80). The KSNR was used to calculate the improvement in physical image quality measured in a physical chest phantom. KSNR correlation with VGAS was assessed as a function of chest region (lung, spine and diaphragm/retrodiaphragm), and as a function of x-ray tube voltage in a given chest region. The correlation of the latter was determined by the Pearson correlation coefficient. VGAS and KSNR image quality metrics demonstrated no correlation in the lung region but did show correlation in the spine and diaphragm/retrodiaphragmatic regions. However, there was no correlation as a function of tube voltage in any region; a Pearson correlation coefficient (R) of  -0.93 (p  =  0.015) was found for lung, a coefficient (R) of  -0.95 (p  =  0.46) was found for spine, and a coefficient (R) of  -0.85 (p  =  0.015) was found for diaphragm. All demonstrate strong negative correlations indicating conflicting results, i.e. KSNR increases with tube voltage but VGAS decreases. Medical physicists should use the KSNR metric with caution when assessing any potential improvement in clinical chest image quality when introducing an anti-scatter grid for CR imaging, especially in the lung region. This metric may also be a limited descriptor of clinical chest image quality as a function of tube voltage when a grid is used routinely. PMID:26540441

  10. Improved signal to noise ratio and sensitivity of an infrared imaging video bolometer on large helical device by using an infrared periscope

    NASA Astrophysics Data System (ADS)

    Pandya, Shwetang N.; Peterson, Byron J.; Mukai, Kiyofumi; Sano, Ryuichi; Enokuchi, Akito; Takeyama, Norihide

    2014-07-01

    An Infrared imaging Video Bolometer (IRVB) diagnostic is currently being used in the Large Helical Device (LHD) for studying the localization of radiation structures near the magnetic island and helical divertor X-points during plasma detachment and for 3D tomography. This research demands high signal to noise ratio (SNR) and sensitivity to improve the temporal resolution for studying the evolution of radiation structures during plasma detachment and a wide IRVB field of view (FoV) for tomography. Introduction of an infrared periscope allows achievement of a higher SNR and higher sensitivity, which in turn, permits a twofold improvement in the temporal resolution of the diagnostic. Higher SNR along with wide FoV is achieved simultaneously by reducing the separation of the IRVB detector (metal foil) from the bolometer's aperture and the LHD plasma. Altering the distances to meet the aforesaid requirements results in an increased separation between the foil and the IR camera. This leads to a degradation of the diagnostic performance in terms of its sensitivity by 1.5-fold. Using an infrared periscope to image the IRVB foil results in a 7.5-fold increase in the number of IR camera pixels imaging the foil. This improves the IRVB sensitivity which depends on the square root of the number of IR camera pixels being averaged per bolometer channel. Despite the slower f-number (f/# = 1.35) and reduced transmission (τ0 = 89%, due to an increased number of lens elements) for the periscope, the diagnostic with an infrared periscope operational on LHD has improved in terms of sensitivity and SNR by a factor of 1.4 and 4.5, respectively, as compared to the original diagnostic without a periscope (i.e., IRVB foil being directly imaged by the IR camera through conventional optics). The bolometer's field of view has also increased by two times. The paper discusses these improvements in apt details.

  11. Improved signal to noise ratio and sensitivity of an infrared imaging video bolometer on large helical device by using an infrared periscope

    SciTech Connect

    Pandya, Shwetang N. Sano, Ryuichi; Peterson, Byron J.; Mukai, Kiyofumi; Enokuchi, Akito; Takeyama, Norihide

    2014-07-15

    An Infrared imaging Video Bolometer (IRVB) diagnostic is currently being used in the Large Helical Device (LHD) for studying the localization of radiation structures near the magnetic island and helical divertor X-points during plasma detachment and for 3D tomography. This research demands high signal to noise ratio (SNR) and sensitivity to improve the temporal resolution for studying the evolution of radiation structures during plasma detachment and a wide IRVB field of view (FoV) for tomography. Introduction of an infrared periscope allows achievement of a higher SNR and higher sensitivity, which in turn, permits a twofold improvement in the temporal resolution of the diagnostic. Higher SNR along with wide FoV is achieved simultaneously by reducing the separation of the IRVB detector (metal foil) from the bolometer's aperture and the LHD plasma. Altering the distances to meet the aforesaid requirements results in an increased separation between the foil and the IR camera. This leads to a degradation of the diagnostic performance in terms of its sensitivity by 1.5-fold. Using an infrared periscope to image the IRVB foil results in a 7.5-fold increase in the number of IR camera pixels imaging the foil. This improves the IRVB sensitivity which depends on the square root of the number of IR camera pixels being averaged per bolometer channel. Despite the slower f-number (f/# = 1.35) and reduced transmission (τ{sub 0} = 89%, due to an increased number of lens elements) for the periscope, the diagnostic with an infrared periscope operational on LHD has improved in terms of sensitivity and SNR by a factor of 1.4 and 4.5, respectively, as compared to the original diagnostic without a periscope (i.e., IRVB foil being directly imaged by the IR camera through conventional optics). The bolometer's field of view has also increased by two times. The paper discusses these improvements in apt details.

  12. Analysis of SATIR test for the qualification of high heat flux components: defect detection and classification by signal-to-noise ratio maximization

    NASA Astrophysics Data System (ADS)

    Cismondi, F.; Xerri, B.; Jauffret, C.; Schlosser, J.; Vignal, N.; Durocher, A.

    2007-03-01

    Plasma facing components (PFC) in Tore Supra and W7X adopt the flat tile concept using carbon fibre composite (CFC) material for the plasma facing material. As the cooling structure is made of a copper alloy material (CuCrZr), the bonding technique between CFC tiles and CuCrZr is critical. Currently, a soft metallic compliant layer is interposed between the two; in such a way the significant thermal expansion mismatch between carbon and copper can be accomodated. The development of a reliable non-destructive inspection technique (NDT) for the bond, to be performed during the manufacturing process, is obviously of great importance. The SATIR (infrared thermography) test bed operating at Commisariat à l'Energie Atomique (CEA) Cadarache performs this function using transient infrared thermography: the thermal excitation is realized in the cooling channel and the presence of a faulty tile is detected in the form of a delayed thermal response. With this technique, the evolution of the surface temperature of an inspected element was compared to that of a defined free-defect element, using the so-called DTref criterion (maximum of the transient temperature difference). The defect detection capability of the SATIR test bed can be improved using signal processing methods. A first treatment based on spatial image autocorrelation allows a better localization of the bond defect. Moreover, the problem of detection and classification of random signals (like the thin defect signature) can be solved maximizing the signal-to-noise ratio (SNR). Two filters maximizing this ratio were optimized: the stochastic matched filter (SMF) aims at defect detection, while the constrained SMF aims at defect classification. These methods assume that the second-order properties of the process at play are known, through covariance matrices. All these methods process the SATIR signal utilizing any free-defect element as reference signal. The tile temperature signal is either processed by itself or

  13. Identification of radionuclides for the spectroscopic radiation portal monitor for pedestrian screening under a low signal-to-noise ratio condition

    NASA Astrophysics Data System (ADS)

    Min, Eungi; Ko, Mincheol; Lee, Hakjae; Kim, Yongkwon; Joung, Jinhun; Joo, Sung-Kwan; Lee, Kisung

    2014-09-01

    The spectroscopic radiation portal monitor (SPM) is widely used for homeland security. Many research groups are studying the radionuclide identification method which is one of the most important factors in the performance of the SPM using the large size of a thallium activated sodium iodide (NaI(Tl) detector. In this study, we developed the radionuclide identification method for the SPM for pedestrian screening using a single NaI(Tl) detector that is small in size (2 in.), which is much smaller than those in the existing studies under the low signal-to-noise-ratio (SNR) condition. From the anomalous radionuclide spectrum, the noise component was effectively reduced by the wavelet decomposition and the proposed background subtraction method, and the signal component was enhanced by the principal component analysis. Finally, peak locations which have been determined by the peak search algorithm with a valley check method were compared with a pre-calibrated and constructed radionuclide database. To verify the radiation identification performance of the proposed method, experiments with various kinds of sources (137Cs, 133Ba, 22Na, and 57Co) and different SNR values (from distances of 10-150 cm and for scan times of 1-5 s) were performed. Although the high-SNR condition was explored as well, most experiments were conducted under the low-SNR condition to verify the robustness and reproducibility of the proposed algorithm. The results showed that over 98.3% of the single radionuclide detection rate was achieved regardless of which radionuclides were used, up to 50 cm under the worst SNR condition (1 s of scan time) and up to 90 cm under the best SNR condition (5 s of scan time). Furthermore we achieved accurate identification of multiple radionuclides at 40 cm with only 1 s of scan time. The results show that the proposed algorithm is competitive with the commercial method and our radionuclide identification method can be successfully applied to the SPM for pedestrian

  14. Effects of exposure equalization on image signal-to-noise ratios in digital mammography: A simulation study with an anthropomorphic breast phantom

    SciTech Connect

    Liu Xinming; Lai Chaojen; Whitman, Gary J.; Geiser, William R.; Shen Youtao; Yi Ying; Shaw, Chris C.

    2011-12-15

    Purpose: The scan equalization digital mammography (SEDM) technique combines slot scanning and exposure equalization to improve low-contrast performance of digital mammography in dense tissue areas. In this study, full-field digital mammography (FFDM) images of an anthropomorphic breast phantom acquired with an anti-scatter grid at various exposure levels were superimposed to simulate SEDM images and investigate the improvement of low-contrast performance as quantified by primary signal-to-noise ratios (PSNRs). Methods: We imaged an anthropomorphic breast phantom (Gammex 169 ''Rachel,'' Gammex RMI, Middleton, WI) at various exposure levels using a FFDM system (Senographe 2000D, GE Medical Systems, Milwaukee, WI). The exposure equalization factors were computed based on a standard FFDM image acquired in the automatic exposure control (AEC) mode. The equalized image was simulated and constructed by superimposing a selected set of FFDM images acquired at 2, 1, 1/2, 1/4, 1/8, 1/16, and 1/32 times of exposure levels to the standard AEC timed technique (125 mAs) using the equalization factors computed for each region. Finally, the equalized image was renormalized regionally with the exposure equalization factors to result in an appearance similar to that with standard digital mammography. Two sets of FFDM images were acquired to allow for two identically, but independently, formed equalized images to be subtracted from each other to estimate the noise levels. Similarly, two identically but independently acquired standard FFDM images were subtracted to estimate the noise levels. Corrections were applied to remove the excess system noise accumulated during image superimposition in forming the equalized image. PSNRs over the compressed area of breast phantom were computed and used to quantitatively study the effects of exposure equalization on low-contrast performance in digital mammography. Results: We found that the highest achievable PSNR improvement factor was 1.89 for

  15. Demonstration of improvement in the signal-to-noise ratio of Thomson scattering signal obtained by using a multi-pass optical cavity on the Tokyo Spherical Tokamak-2.

    PubMed

    Togashi, H; Ejiri, A; Hiratsuka, J; Nakamura, K; Takase, Y; Yamaguchi, T; Furui, H; Imamura, K; Inada, T; Kakuda, H; Nakanishi, A; Oosako, T; Shinya, T; Sonehara, M; Tsuda, S; Tsujii, N; Wakatsuki, T; Hasegawa, M; Nagashima, Y; Narihara, K; Yamada, I; Tojo, H

    2014-11-01

    The multi-pass Thomson scattering (TS) scheme enables obtaining many photons by accumulating multiple TS signals. The signal-to-noise ratio (SNR) depends on the accumulation number. In this study, we performed multi-pass TS measurements for ohmically heated plasmas, and the relationship between SNR and the accumulation number was investigated. As a result, improvement of SNR in this experiment indicated similar tendency to that calculated for the background noise dominant situation. PMID:25430259

  16. Demonstration of improvement in the signal-to-noise ratio of Thomson scattering signal obtained by using a multi-pass optical cavity on the Tokyo Spherical Tokamak-2

    SciTech Connect

    Togashi, H. Ejiri, A.; Nakamura, K.; Takase, Y.; Yamaguchi, T.; Furui, H.; Imamura, K.; Inada, T.; Nakanishi, A.; Oosako, T.; Shinya, T.; Tsuda, S.; Tsujii, N.; Hiratsuka, J.; Kakuda, H.; Sonehara, M.; Wakatsuki, T.; Hasegawa, M.; Nagashima, Y.; Narihara, K.; and others

    2014-11-15

    The multi-pass Thomson scattering (TS) scheme enables obtaining many photons by accumulating multiple TS signals. The signal-to-noise ratio (SNR) depends on the accumulation number. In this study, we performed multi-pass TS measurements for ohmically heated plasmas, and the relationship between SNR and the accumulation number was investigated. As a result, improvement of SNR in this experiment indicated similar tendency to that calculated for the background noise dominant situation.

  17. Combination of highly nonlinear fiber, an optical bandpass filter, and a Fabry-Perot filter to improve the signal-to-noise ratio of a supercontinuum continuous-wave optical source

    NASA Astrophysics Data System (ADS)

    Nan, Yinbo; Huo, Li; Lou, Caiyun

    2005-05-01

    We present a theoretical study of a supercontinuum (SC) continuous-wave (cw) optical source generation in highly nonlinear fiber and its noise properties through numerical simulations based on the nonlinear Schrödinger equation. Fluctuations of pump pulses generate substructures between the longitudinal modes that result in the generation of white noise and then in degradation of coherence and in a decrease of the modulation depths and the signal-to-noise ratio (SNR). A scheme for improvement of the SNR of a multiwavelength cw optical source based on a SC by use of the combination of a highly nonlinear fiber (HNLF), an optical bandpass filter, and a Fabry-Perot (FP) filter is presented. Numerical simulations show that the improvement in modulation depth is relative to the HNLF's length, the 3-dB bandwidth of the optical bandpass filter, and the reflection ratio of the FP filter and that the average improvement in modulation depth is 13.7 dB under specified conditions.

  18. Combination of highly nonlinear fiber, an optical bandpass filter, and a Fabry-Perot filter to improve the signal-to-noise ratio of a supercontinuum continuous-wave optical source.

    PubMed

    Nan, Yinbo; Huo, Li; Lou, Caiyun

    2005-05-20

    We present a theoretical study of a supercontinuum (SC) continuous-wave (cw) optical source generation in highly nonlinear fiber and its noise properties through numerical simulations based on the nonlinear Schrödinger equation. Fluctuations of pump pulses generate substructures between the longitudinal modes that result in the generation of white noise and then in degradation of coherence and in a decrease of the modulation depths and the signal-to-noise ratio (SNR). A scheme for improvement of the SNR of a multiwavelength cw optical source based on a SC by use of the combination of a highly nonlinear fiber (HNLF), an optical bandpass filter, and a Fabry-Perot (FP) filter is presented. Numerical simulations show that the improvement in modulation depth is relative to the HNLF's length, the 3-dB bandwidth of the optical bandpass filter, and the reflection ratio of the FP filter and that the average improvement in modulation depth is 13.7 dB under specified conditions. PMID:15929296

  19. CROSS-CORRELATIONS OF THE Ly{alpha} FOREST WITH WEAK-LENSING CONVERGENCE. ANALYTICAL ESTIMATES OF SIGNAL-TO-NOISE RATIO AND IMPLICATIONS FOR NEUTRINO MASS AND DARK ENERGY

    SciTech Connect

    Vallinotto, Alberto; Viel, Matteo; Das, Sudeep; Spergel, David N. E-mail: viel@oats.inaf.it E-mail: dns@astro.princeton.edu

    2011-07-01

    We expect a detectable correlation between two seemingly unrelated quantities: the four-point function of the cosmic microwave background (CMB) and the amplitude of flux decrements in quasar (QSO) spectra. The amplitude of CMB convergence in a given direction measures the projected surface density of matter. Measurements of QSO flux decrements trace the small-scale distribution of gas along a given line of sight. While the cross-correlation between these two measurements is small for a single line of sight, upcoming large surveys should enable its detection. This paper presents analytical estimates for the signal-to-noise ratio (S/N) for measurements of the cross-correlation between the flux decrement and the convergence, <{delta}F{kappa}>, and for measurements of the cross-correlation between the variance in flux decrement and the convergence, <({delta}F){sup 2}{kappa}>. For the ongoing BOSS (SDSS-III) and Planck surveys, we estimate an S/N of 30 and 9.6 for these two correlations. For the proposed BigBOSS and ACTPOL surveys, we estimate an S/N of 130 and 50, respectively. Since <({delta}F){sup 2}{kappa}>{proportional_to}{sigma}{sub 8}{sup 4}, the amplitude of these cross-correlations can potentially be used to measure the amplitude of {sigma}{sub 8} at z {approx} 2%-2.5% with BOSS and Planck and even better with future data sets. These measurements have the potential to test alternative theories for dark energy and to constrain the mass of the neutrino. The large potential signal estimated in our analytical calculations motivates tests with nonlinear hydrodynamic simulations and analyses of upcoming data sets.

  20. The Dependence of Signal-To-Noise Ratio (S/N) Between Star Brightness and Background on the Filter Used in Images Taken by the Vulcan Photometric Planet Search Camera

    NASA Technical Reports Server (NTRS)

    Mena-Werth, Jose

    1998-01-01

    The Vulcan Photometric Planet Search is the ground-based counterpart of Kepler Mission Proposal. The Kepler Proposal calls for the launch of telescope to look intently at a small patch of sky for four year. The mission is designed to look for extra-solar planets that transit sun-like stars. The Kepler Mission should be able to detect Earth-size planets. This goal requires an instrument and software capable of detecting photometric changes of several parts per hundred thousand in the flux of a star. The goal also requires the continuous monitoring of about a hundred thousand stars. The Kepler Mission is a NASA Discovery Class proposal similar in cost to the Lunar Prospector. The Vulcan Search is also a NASA project but based at Lick Observatory. A small wide-field telescope monitors various star fields successively during the year. Dozens of images, each containing tens of thousands of stars, are taken any night that weather permits. The images are then monitored for photometric changes of the order of one part in a thousand. These changes would reveal the transit of an inner-orbit Jupiter-size planet similar to those discovered recently in spectroscopic searches. In order to achieve a one part in one thousand photometric precision even the choice of a filter used in taking an exposure can be critical. The ultimate purpose of an filter is to increase the signal-to-noise ratio (S/N) of one's observation. Ideally, filters reduce the sky glow cause by street lights and, thereby, make the star images more distinct. The higher the S/N, the higher is the chance to observe a transit signal that indicates the presence of a new planet. It is, therefore, important to select the filter that maximizes the S/N.

  1. Effect of transfer printing on the crystallinity of pentacene (Pn) thin film on plastic substrates; and physical contribution to the signal to noise ratio (SNR) and sensitivity of extraordinary magnetoresistance (EMR) quantum well structure

    NASA Astrophysics Data System (ADS)

    Shao, Yue

    Part I. The thermal deposition and transfer printing method had been used to produce pentacene thin films on SiO2/Si and plastic substrates poly(methyl methacrylate) (PMMA) and poly(vinyl pyridine) (PVP), respectively. X-ray diffraction patterns of pentacene thin films showed reflections associated with highly ordered polycrystalline films and a coexistence of two polymorph phases classified by their d spacing, d(001): 14.4 and 15.4A. The dependence of the c-axis correlation length and the phase fraction on the film thickness and printing temperature were measured. A transition from the 15.4A phase towards 14.4A phase was also observed with increasing film thickness. An increase in the c-axis correlation length of approximately 12%--16% was observed for pentacene (Pn) films transfer printed onto a PMMA coated poly(ethylene terephthalate) (PET) substrate at 100-120°C as compared to as-grown Pn films on SiO2/Si substrates. The transfer printing method is shown to be attractive for the fabrication of pentacene thin-film transistors on flexible substrates partly because of the resulting persistence in the quality of the pentacene film. Part II. For applications to extraordinary magnetoresistance (EMR) quantum well sensor design, the electron areal density 2 D, the mobility mu and the products n3 D0.5mu2 and n3 D0.5mu2.5 are key physical parameters to be optimized for enhanced device sensitivity and signal to noise ratio (SNR). We model the electron areal density and carrier mobility in a two-dimensional electron gas (2DEG) layer developed in a delta-doped AlInSb/InSb heterostructure. The non-parabolic band structure due to the nature of the small energy band gap of InSb is accounted for. The detailed description of the energy dispersion and the energy dependent effective mass are obtained by the k·p method of band structure calculation. The transport properties are calculated by including contributions of scattering from ionized impurities, the background neutral

  2. Signal to Noise Analysis of iRadar sensors

    SciTech Connect

    Fritzke, A; Top, P

    2009-09-10

    This document follows my process of testing; comparing; and contrasting several iRadars signal to noise ratios for both HH and VV polarization. A brief introduction is given explaining the basics of iRadar technology and what data I was collecting. The process section explains the steps I took to collect my data along with any procedures I followed. The analysis section compares and contrasts five different radars and the two different polarizations. The analysis also details the radars viewing limitations and area. Finally, the report delves into the effects of two radars interfering with each other. A conclusion goes over the success and findings of the project.

  3. Algorithm for astronomical, extended source, signal-to-noise radio calculations

    NASA Technical Reports Server (NTRS)

    Jayroe, R. R.

    1984-01-01

    An algorithm was developed to simulate the expected signal-to-noise ratio as a function of observation time in the charge coupled device detector plane of an optical telescope located outside the Earth's atmosphere for an extended, uniform astronomical source embedded in a uniform cosmic background. By choosing the appropriate input values, the expected extended source signal-to-noise ratios can be computed for the Hubble Space Telescope using the Wide Field/Planetary Camera science instrument.

  4. Signal-to-noise issues in measuring nitrous oxide fluxes by the eddy covariance method

    NASA Astrophysics Data System (ADS)

    Cowan, Nicholas; Levy, Peter; Langford, Ben; Skiba, Ute

    2016-04-01

    Recently-developed fast-response gas analysers capable of measuring atmospheric N2O with high precision (< 50 ppt) at a rate of 10 Hz are becoming more widely available. These instruments are capable of measuring N2O fluxes using the eddy covariance method, with significantly less effort and uncertainty than previous instruments have allowed. However, there are still many issues to overcome in order to obtain accurate and reliable flux data. The signal-to-noise ratio of N2O measured using these instruments is still two to three orders of magnitude smaller than that of CO2. The low signal-to-noise ratio can lead to systematic uncertainties, in the eddy covariance method, the most significant being in the calculation of the time lag between gas analyser and anemometer by maximisation of covariance (Langford et al., 2015). When signal-to-noise ratio is relatively low, as it is with many N2O measurements, the maximisation of covariance method can systematically overestimate fluxes. However, if constant time lags are assumed, then fluxes will be underestimated. This presents a major issue for N2O eddy covariance measurements. In this presentation we will focus on the signal to noise ratio for an Aerodyne quantum cascade laser (QCL). Eddy covariance flux measurements from multiple agricultural sites across the UK were investigated for potential uncertainties. Our presentation highlights some of these uncertainties when analysing eddy covariance data and offers suggestions as to how these issues may be minimised. Langford, B., Acton, W., Ammann, C., Valach, A. and Nemitz, E.: Eddy-covariance data with low signal-to-noise ratio: time-lag determination, uncertainties and limit of detection, Atmos Meas Tech, 8(10), 4197-4213, doi:10.5194/amt-8-4197-2015, 2015.

  5. Signal-to-Noise Characteristics of Solar MG II Indices

    NASA Astrophysics Data System (ADS)

    Crane, P. C.; Floyd, L. E.

    1999-05-01

    Knowledge of the variations in solar ultraviolet irradiances is essential to understanding both the Sun and the behavior of the Earth's upper atmosphere. Since the solar ultraviolet radiation is absorbed by the atmosphere, the requisite measurements must be done from space. Reliable, approximately daily measurements of solar ultraviolet irradiances have been made since November 1978 by a variety of instruments (Numbus-7 SBUV, NOAA-9 and NOAA-11 SBUV/2, UARS SUSIM and SOLSTICE, and ERS-2 GOME). To overcome differences in spectral coverage and resolution and the challenges involved in the long-term calibrations of the instruments, a solar index suitable for use as a proxy for the solar ultraviolet (i.e., 100-400 nm) irradiances has been sought. The most popular indices for this purpose are the several Mg II indices based upon the Mg II k and h doublet near 280 nm; starting with the core-to-wing index developed by Heath and Schlesinger (J. Geophys. Res. 91, 8672, 1986) for the Nimbus-7 SBUV, they are calculated by taking the ratio of adjacent parts of the Mg II feature: one originating in the upper chromosphere that exhibits solar ultraviolet variations and the other, in the upper photosphere which is insensitive to solar variations. Because the ratio is of irradiances at nearby wavelengths, the Mg II indices mostly are not affected by temporal and spectral variations in the instrument responses. While there is an ongoing effort to combine the available Mg II indices into a single 20-year time series (i.e., Viereck and Puga, J. Geophys. Res., in press), we are investigating an alternate approach. We report here on the first step in that study: the characterization of the signal and noise properties of the several Mg II indices available. We use Fourier analysis to determine the amplitudes of a common signal (the 27-day variations) and of the high-frequency, day-to-day errors. Ultimately, the corresponding signal-to-noise ratios may be used to derive statistical

  6. Attention enhances stimulus representations in macaque visual cortex without affecting their signal-to-noise level

    PubMed Central

    Daliri, Mohammad Reza; Kozyrev, Vladislav; Treue, Stefan

    2016-01-01

    The magnitude of the attentional modulation of neuronal responses in visual cortex varies with stimulus contrast. Whether the strength of these attentional influences is similarly dependent on other stimulus properties is unknown. Here we report the effect of spatial attention on responses in the medial-temporal area (MT) of macaque visual cortex to moving random dots pattern of various motion coherences, i.e. signal-to-noise ratios. Our data show that allocating spatial attention causes a gain change in MT neurons. The magnitude of this attentional modulation is independent of the attended stimulus’ motion coherence, creating a multiplicative scaling of the neuron’s coherence-response function. This is consistent with the characteristics of gain models of attentional modulation and suggests that attention strengthens the neuronal representation of behaviorally relevant visual stimuli relative to unattended stimuli, but without affecting their signal-to-noise ratios. PMID:27283275

  7. Comparison of the signal-to-noise characteristics of quantum versus thermal ghost imaging

    SciTech Connect

    O'Sullivan, Malcolm N.; Chan, Kam Wai Clifford; Boyd, Robert W.

    2010-11-15

    We present a theoretical comparison of the signal-to-noise characteristics of quantum versus thermal ghost imaging. We first calculate the signal-to-noise ratio of each process in terms of its controllable experimental conditions. We show that a key distinction is that a thermal ghost image always resides on top of a large background; the fluctuations in this background constitutes an intrinsic noise source for thermal ghost imaging. In contrast, there is a negligible intrinsic background to a quantum ghost image. However, for practical reasons involving achievable illumination levels, acquisition times for thermal ghost images are often much shorter than those for quantum ghost images. We provide quantitative predictions for the conditions under which each process provides superior performance. Our conclusion is that each process can provide useful functionality, although under complementary conditions.

  8. Signal-to-noise-optimal scaling of heterogenous population codes.

    PubMed

    Leibold, Christian

    2013-01-01

    Similarity measures for neuronal population responses that are based on scalar products can be little informative if the neurons have different firing statistics. Based on signal-to-noise optimality, this paper derives positive weighting factors for the individual neurons' response rates in a heterogeneous neuronal population. The weights only depend on empirical statistics. If firing follows Poisson statistics, the weights can be interpreted as mutual information per spike. The scaling is shown to improve linear separability and clustering as compared to unscaled inputs. PMID:23984844

  9. A Signal-to-Noise Standard for Pulsed EPR

    PubMed Central

    Eaton, Gareth R.; Eaton, Sandra S; Quine, Richard W.; Mitchell, Deborah; Kathirvelu, Velavan; Weber, Ralph T.

    2010-01-01

    A 2 mm diameter by 10 mm long cylinder of fused SiO2 (quartz) γ-irradiated to 1 kGy with 60Co contains about 2×1016 spins/cm3. It is proposed as a standard for monitoring signal-to-noise (S/N) performance of X-band pulsed EPR spectrometers. This sample yields S/N of about 25 on modern spin echo spectrometers, which permits measurement of both signal and noise under the same conditions with an 8-bit digitizer. PMID:20451433

  10. Signal to Noise Studies on Thermographic Data with Fabricated Defects for Defense Structures

    NASA Technical Reports Server (NTRS)

    Zalameda, Joseph N.; Rajic, Nik; Genest, Marc

    2006-01-01

    There is a growing international interest in thermal inspection systems for asset life assessment and management of defense platforms. The efficacy of flash thermography is generally enhanced by applying image processing algorithms to the observations of raw temperature. Improving the defect signal to noise ratio (SNR) is of primary interest to reduce false calls and allow for easier interpretation of a thermal inspection image. Several factors affecting defect SNR were studied such as data compression and reconstruction using principal component analysis and time window processing.

  11. A genetically encoded, high-signal-to-noise maltose sensor

    PubMed Central

    Marvin, Jonathan S; Schreiter, Eric R; Echevarría, Ileabett M; Looger, Loren L

    2011-01-01

    We describe the generation of a family of high-signal-to-noise single-wavelength genetically encoded indicators for maltose. This was achieved by insertion of circularly permuted fluorescent proteins into a bacterial periplasmic binding protein (PBP), Escherichia coli maltodextrin-binding protein, resulting in a four-color family of maltose indicators. The sensors were iteratively optimized to have sufficient brightness and maltose-dependent fluorescence increases for imaging, under both one- and two-photon illumination. We demonstrate that maltose affinity of the sensors can be tuned in a fashion largely independent of the fluorescent readout mechanism. Using literature mutations, the binding specificity could be altered to moderate sucrose preference, but with a significant loss of affinity. We use the soluble sensors in individual E. coli bacteria to observe rapid maltose transport across the plasma membrane, and membrane fusion versions of the sensors on mammalian cells to visualize the addition of maltose to extracellular media. The PBP superfamily includes scaffolds specific for a number of analytes whose visualization would be critical to the reverse engineering of complex systems such as neural networks, biosynthetic pathways, and signal transduction cascades. We expect the methodology outlined here to be useful in the development of indicators for many such analytes. PMID:21989929

  12. A genetically encoded, high-signal-to-noise maltose sensor

    SciTech Connect

    Marvin, Jonathan S.; Schreiter, Eric R.; Echevarría, Ileabett M.; Looger, Loren L.

    2012-10-23

    We describe the generation of a family of high-signal-to-noise single-wavelength genetically encoded indicators for maltose. This was achieved by insertion of circularly permuted fluorescent proteins into a bacterial periplasmic binding protein (PBP), Escherichia coli maltodextrin-binding protein, resulting in a four-color family of maltose indicators. The sensors were iteratively optimized to have sufficient brightness and maltose-dependent fluorescence increases for imaging, under both one- and two-photon illumination. We demonstrate that maltose affinity of the sensors can be tuned in a fashion largely independent of the fluorescent readout mechanism. Using literature mutations, the binding specificity could be altered to moderate sucrose preference, but with a significant loss of affinity. We use the soluble sensors in individual E. coli bacteria to observe rapid maltose transport across the plasma membrane, and membrane fusion versions of the sensors on mammalian cells to visualize the addition of maltose to extracellular media. The PBP superfamily includes scaffolds specific for a number of analytes whose visualization would be critical to the reverse engineering of complex systems such as neural networks, biosynthetic pathways, and signal transduction cascades. We expect the methodology outlined here to be useful in the development of indicators for many such analytes.

  13. Brain–computer interfaces increase whole-brain signal to noise

    PubMed Central

    Papageorgiou, T. Dorina; Lisinski, Jonathan M.; McHenry, Monica A.; White, Jason P.; LaConte, Stephen M.

    2013-01-01

    Brain–computer interfaces (BCIs) can convert mental states into signals to drive real-world devices, but it is not known if a given covert task is the same when performed with and without BCI-based control. Using a BCI likely involves additional cognitive processes, such as multitasking, attention, and conflict monitoring. In addition, it is challenging to measure the quality of covert task performance. We used whole-brain classifier-based real-time functional MRI to address these issues, because the method provides both classifier-based maps to examine the neural requirements of BCI and classification accuracy to quantify the quality of task performance. Subjects performed a covert counting task at fast and slow rates to control a visual interface. Compared with the same task when viewing but not controlling the interface, we observed that being in control of a BCI improved task classification of fast and slow counting states. Additional BCI control increased subjects’ whole-brain signal-to-noise ratio compared with the absence of control. The neural pattern for control consisted of a positive network comprised of dorsal parietal and frontal regions and the anterior insula of the right hemisphere as well as an expansive negative network of regions. These findings suggest that real-time functional MRI can serve as a platform for exploring information processing and frontoparietal and insula network-based regulation of whole-brain task signal-to-noise ratio. PMID:23901117

  14. Estimation of signal-to-noise - A new procedure applied to AVIRIS data

    NASA Technical Reports Server (NTRS)

    Curran, Paul J.; Dungan, Jennifer L.

    1989-01-01

    To make the best use of narrowband airborne visible/infrared imaging spectrometer (AVIRIS) data, an investigator needs to know the ratio of signal to random variability or noise (signal-to-noise ratio or SNR). The signal is land cover dependent and varies with both wavelength and atmospheric absorption; random noise comprises sensor noise and intrapixel variability (i.e., variability within a pixel). The three existing methods for estimating the SNR are inadequate, since typical laboratory methods inflate while dark current and image methods deflate the SNR. A new procedure is proposed called the geostatistical method. It is based on the removal of periodic noise by notch filtering in the frequency domain and the isolation of sensor noise and intrapixel variability using the semi-variogram. This procedure was applied easily and successfully to five sets of AVIRIS data from the 1987 flying season and could be applied to remotely sensed data from broadband sensors.

  15. Signal-to-Noise Enhancement of a Nanospring Redox-Based Sensor by Lock-in Amplification

    PubMed Central

    Bakharev, Pavel V.; McIlroy, David N.

    2015-01-01

    A significant improvement of the response characteristics of a redox chemical gas sensor (chemiresistor) constructed with a single ZnO coated silica nanospring has been achieved with the technique of lock-in signal amplification. The comparison of DC and analog lock-in amplifier (LIA) AC measurements of the electrical sensor response to toluene vapor, at the ppm level, has been conducted. When operated in the DC detection mode, the sensor exhibits a relatively high sensitivity to the analyte vapor, as well as a low detection limit at the 10 ppm level. However, at 10 ppm the signal-to-noise ratio is 5 dB, which is less than desirable. When operated in the analog LIA mode, the signal-to-noise ratio at 10 ppm increases by 30 dB and extends the detection limit to the ppb range. PMID:26053754

  16. [Analysis and experimental validation of signal-to-noise for limb imaging spectrometer].

    PubMed

    Xue, Qing-Sheng; Wang, Shu-Rong; Li, Fu-Tian; Lin, Guang-Yu; Duan, Ming-Zheng

    2010-06-01

    Limb imaging spectrometer is an important new remote sensor for research and application. Signal-to-noise ratio (SNR) is one of the key parameters to quantitatively evaluate the image quality and radiometric performance of an imaging spectrometer. The estimation and testing of SNR are very important for developing an imaging spectrometer. From the perspectives of radiative transmission and energy conversion, the SNR model is proposed, and the SNR equation of dispersive-type limb imaging spectrometer is derived, and the SNR values under several observing conditions for an limb imaging spectrometer prototype developed are theoretically evaluated based on atmospheric radiative transfer code MODTRAN 4.0. The results show that the SNR of the prototype under typical viewing geometry is not less than 8. As experimental validation, SNR testing was performed using an internally illuminated integrating sphere, and the experimental results have proved the correctness of this theoretical model. PMID:20707179

  17. Signal-to-noise and radiation exposure considerations in conventional and diffraction x-ray microscopy.

    PubMed

    Huang, Xiaojing; Miao, Huijie; Steinbrener, Jan; Nelson, Johanna; Shapiro, David; Stewart, Andrew; Turner, Joshua; Jacobsen, Chris

    2009-08-01

    Using a signal-to-noise ratio estimation based on correlations between multiple simulated images, we compare the dose efficiency of two soft x-ray imaging systems: incoherent brightfield imaging using zone plate optics in a transmission x-ray microscope (TXM), and x-ray diffraction microscopy (XDM) where an image is reconstructed from the far-field coherent diffraction pattern. In XDM one must computationally phase weak diffraction signals; in TXM one suffers signal losses due to the finite numerical aperture and efficiency of the optics. In simulations with objects representing isolated cells such as yeast, we find that XDM has the potential for delivering equivalent resolution images using fewer photons. This can be an important advantage for studying radiation-sensitive biological and soft matter specimens. PMID:19654762

  18. Advanced study of video signal processing in low signal to noise environments

    NASA Technical Reports Server (NTRS)

    Carden, F.

    1973-01-01

    Conventional analytical techniques used to determine and optimize phase-lock loop (PLL) characteristics are most often based on a model which is valid only if the intermediate frequency (IF) filter bandwidth is large compared to the PLL bandwidth and the phase error is small. An improved model (called the quasi-linear model) is developed which takes into account small IF filter bandwidths and nonlinear effects associated with large phase errors. By comparison of theoretical and experimental results it is demonstrated that the quasi-linear model accurately predicts PLL characteristics. This is true even for small IF filter bandwidths and large phase errors where the conventional model is invalid. The theoretical and experimental results are used to draw conclusions concerning threshold, multiplier output variance, phase error variance, output signal-to-noise ratio, and signal distortion. The relationship between these characteristics and IF filter bandwidth, modulating signal spectrum, and rms deviation is also determined.

  19. Signal-to-noise and radiation exposure considerations in conventional and diffraction x-ray microscopy

    PubMed Central

    Huang, Xiaojing; Miao, Huijie; Steinbrener, Jan; Nelson, Johanna; Shapiro, David; Stewart, Andrew; Turner, Joshua; Jacobsen, Chris

    2010-01-01

    Using a signal-to-noise ratio estimation based on correlations between multiple simulated images, we compare the dose efficiency of two soft x-ray imaging systems: incoherent brightfield imaging using zone plate optics in a transmission x-ray microscope (TXM), and x-ray diffraction microscopy (XDM) where an image is reconstructed from the far-field coherent diffraction pattern. In XDM one must computationally phase weak diffraction signals; in TXM one suffers signal losses due to the finite numerical aperture and efficiency of the optics. In simulations with objects representing isolated cells such as yeast, we find that XDM has the potential for delivering equivalent resolution images using fewer photons. This can be an important advantage for studying radiation-sensitive biological and soft matter specimens. PMID:19654762

  20. Signal-to-noise and radiation exposure considerations in conventional and diffraction x-ray microscopy

    DOE PAGESBeta

    Huang, Xiaojing; Miao, Huijie; Steinbrener, Jan; Nelson, Johanna; Shapiro, David; Stewart, Andrew; Turner, Joshua; Jacobsen, Chris

    2009-01-01

    Using a signal-to-noise ratio estimation based on correlations between multiple simulated images, we compare the dose efficiency of two soft x-ray imaging systems: incoherent brightfield imaging using zone plate optics in a transmission x-ray microscope (TXM), and x-ray diffraction microscopy (XDM) where an image is reconstructed from the far-field coherent diffraction pattern. In XDM one must computationally phase weak diffraction signals; in TXM one suffers signal losses due to the finite numerical aperture and efficiency of the optics. In simulations with objects representing isolated cells such as yeast, we find that XDM has the potential for delivering equivalent resolution imagesmore » using fewer photons. As a result, this can be an important advantage for studying radiation-sensitive biological and soft matter specimens.« less

  1. Signal-to-noise and radiation exposure considerations in conventional and diffraction x-ray microscopy

    SciTech Connect

    Huang, Xiaojing; Miao, Huijie; Steinbrener, Jan; Nelson, Johanna; Shapiro, David; Stewart, Andrew; Turner, Joshua; Jacobsen, Chris

    2009-01-01

    Using a signal-to-noise ratio estimation based on correlations between multiple simulated images, we compare the dose efficiency of two soft x-ray imaging systems: incoherent brightfield imaging using zone plate optics in a transmission x-ray microscope (TXM), and x-ray diffraction microscopy (XDM) where an image is reconstructed from the far-field coherent diffraction pattern. In XDM one must computationally phase weak diffraction signals; in TXM one suffers signal losses due to the finite numerical aperture and efficiency of the optics. In simulations with objects representing isolated cells such as yeast, we find that XDM has the potential for delivering equivalent resolution images using fewer photons. As a result, this can be an important advantage for studying radiation-sensitive biological and soft matter specimens.

  2. Ultrasonic correlator versus signal averager as a signal to noise enhancement instrument

    NASA Technical Reports Server (NTRS)

    Kishoni, Doron; Pietsch, Benjamin E.

    1990-01-01

    Ultrasonic inspection of thick and attenuating materials is hampered by the reduce amplitudes of the propagated waves to a degree that the noise is too high to enable meaningful interpretation of the data. In order to overcome the low signal to noise ratio (S/N), a correlation technique has been developed. In this method, a continuous pseudo-random pattern generated digitally is transmitted and detected by piezoelectric transducers. A correlation is performed in the instrument between the received signal and a variable delayed image of the transmitted one. The result is shown to be proportional to the impulse response of the investigated material, analogous to a signal received from a pulsed system, with an improved S/N ratio. The degree of S/N enhancement depends on the sweep rate. The correlator is described, and it is compared to the method of enhancing S/N ratio by averaging the signals. The similarities and differences between the two are highlighted and the potential advantage of the correlator system is explained.

  3. Spatial resolution, signal-to-noise and information capacity of linear imaging systems.

    PubMed

    Gureyev, Timur; Nesterets, Yakov; de Hoog, Frank

    2016-07-25

    A simple model for image formation in linear shift-invariant systems is considered, in which both the detected signal and the noise variance are varying slowly compared to the point-spread function of the system. It is shown that within the constraints of this model, the square of the signal-to-noise ratio is always proportional to the "volume" of the spatial resolution unit. In the case of Poisson statistics, the ratio of these two quantities divided by the incident density of the imaging particles (e.g. photons) represents a dimensionless invariant of the imaging system, which was previously termed the intrinsic imaging quality. The relationship of this invariant to the notion of information capacity of communication and imaging systems, which was previously considered by Shannon, Gabor and others, is investigated. The results are then applied to a simple generic model of quantitative imaging of weakly scattering objects, leading to an estimate of the upper limit for the amount of information about the sample that can be obtained in such experiments. It is shown that this limit depends only on the total number of imaging particles incident on the sample, the average scattering coefficient, the size of the sample and the number of spatial resolution units. PMID:27464167

  4. Fault Reactivation Analysis Using Microearthquake Clustering Based on Signal-to-Noise Weighted Waveform Similarity

    NASA Astrophysics Data System (ADS)

    Grund, Michael; Groos, Jörn C.; Ritter, Joachim R. R.

    2016-04-01

    The cluster formation of about 2000 induced microearthquakes (mostly M L < 2) is studied using a waveform similarity technique based on cross-correlation and a subsequent equivalence class approach. All events were detected within two separated but neighbouring seismic volumes close to the geothermal powerplants near Landau and Insheim in the Upper Rhine Graben, SW Germany between 2006 and 2013. Besides different sensors, sampling rates and individual data gaps, mainly low signal-to-noise ratios (SNR) of the recordings at most station sites provide a complication for the determination of a precise waveform similarity analysis of the microseismic events in this area. To include a large number of events for such an analysis, a newly developed weighting approach was implemented in the waveform similarity analysis which directly considers the individual SNRs across the whole seismic network. The application to both seismic volumes leads to event clusters with high waveform similarities within short (seconds to hours) and long (months to years) time periods covering two magnitude ranges. The estimated relative hypocenter locations are spatially concentrated for each single cluster and mirror the orientations of mapped faults as well as interpreted rupture planes determined from fault plane solutions. Depending on the waveform cross-correlation coefficient threshold, clusters can be resolved in space to as little as one dominant wavelength. The interpretation of these observations implies recurring fault reactivations by fluid injection with very similar faulting mechanisms during different time periods between 2006 and 2013.

  5. Fault Reactivation Analysis Using Microearthquake Clustering Based on Signal-to-Noise Weighted Waveform Similarity

    NASA Astrophysics Data System (ADS)

    Grund, Michael; Groos, Jörn C.; Ritter, Joachim R. R.

    2016-07-01

    The cluster formation of about 2000 induced microearthquakes (mostly M L < 2) is studied using a waveform similarity technique based on cross-correlation and a subsequent equivalence class approach. All events were detected within two separated but neighbouring seismic volumes close to the geothermal powerplants near Landau and Insheim in the Upper Rhine Graben, SW Germany between 2006 and 2013. Besides different sensors, sampling rates and individual data gaps, mainly low signal-to-noise ratios (SNR) of the recordings at most station sites provide a complication for the determination of a precise waveform similarity analysis of the microseismic events in this area. To include a large number of events for such an analysis, a newly developed weighting approach was implemented in the waveform similarity analysis which directly considers the individual SNRs across the whole seismic network. The application to both seismic volumes leads to event clusters with high waveform similarities within short (seconds to hours) and long (months to years) time periods covering two magnitude ranges. The estimated relative hypocenter locations are spatially concentrated for each single cluster and mirror the orientations of mapped faults as well as interpreted rupture planes determined from fault plane solutions. Depending on the waveform cross-correlation coefficient threshold, clusters can be resolved in space to as little as one dominant wavelength. The interpretation of these observations implies recurring fault reactivations by fluid injection with very similar faulting mechanisms during different time periods between 2006 and 2013.

  6. Signal-to-noise based local decorrelation compensation for speckle interferometry applications

    SciTech Connect

    Molimard, Jerome; Cordero, Raul; Vautrin, Alain

    2008-07-01

    Speckle-based interferometric techniques allow assessing the whole-field deformation induced on a specimen due to the application of load. These high sensitivity optical techniques yield fringe images generated by subtracting speckle patterns captured while the specimen undergoes deformation. The quality of the fringes, and in turn the accuracy of the deformation measurements, strongly depends on the speckle correlation. Specimen rigid body motion leads to speckle decorrelation that, in general, cannot be effectively counteracted by applying a global translation to the involved speckle patterns. In this paper, we propose a recorrelation procedure based on the application of locally evaluated translations. The proposed procedure implies dividing the field into several regions, applying a local translation, and calculating, in every region, the signal-to-noise ratio (SNR). Since the latter is a correlation indicator (the noise increases with the decorrelation) we argue that the proper translation is that which maximizes the locally evaluated SNR. The search of the proper local translations is, of course, an interactive process that can be facilitated by using a SNR optimization algorithm. The performance of the proposed recorrelation procedure was tested on two examples. First, the SNR optimization algorithm was applied to fringe images obtained by subtracting simulated speckle patterns. Next, it was applied to fringe images obtained by using a shearography optical setup from a specimen subjected to mechanical deformation. Our results show that the proposed SNR optimization method can significantly improve the reliability of measurements performed by using speckle-based techniques.

  7. Direct Signal-to-Noise Quality Comparison between an Electronic and Conventional Stethoscope aboard the International Space Station

    NASA Technical Reports Server (NTRS)

    Marshburn, Thomas; Cole, Richard; Ebert, Doug; Bauer, Pete

    2014-01-01

    Introduction: Evaluation of heart, lung, and bowel sounds is routinely performed with the use of a stethoscope to help detect a broad range of medical conditions. Stethoscope acquired information is even more valuable in a resource limited environments such as the International Space Station (ISS) where additional testing is not available. The high ambient noise level aboard the ISS poses a specific challenge to auscultation by stethoscope. An electronic stethoscope's ambient noise-reduction, greater sound amplification, recording capabilities, and sound visualization software may be an advantage to a conventional stethoscope in this environment. Methods: A single operator rated signal-to-noise quality from a conventional stethoscope (Littman 2218BE) and an electronic stethoscope (Litmann 3200). Borborygmi, pulmonic, and cardiac sound quality was ranked with both stethoscopes. Signal-to-noise rankings were preformed on a 1 to 10 subjective scale with 1 being inaudible, 6 the expected quality in an emergency department, 8 the expected quality in a clinic, and 10 the clearest possible quality. Testing took place in the Japanese Pressurized Module (JPM), Unity (Node 2), Destiny (US Lab), Tranquility (Node 3), and the Cupola of the International Space Station. All examinations were conducted at a single point in time. Results: The electronic stethoscope's performance ranked higher than the conventional stethoscope for each body sound in all modules tested. The electronic stethoscope's sound quality was rated between 7 and 10 in all modules tested. In comparison, the traditional stethoscope's sound quality was rated between 4 and 7. The signal to noise ratio of borborygmi showed the biggest difference between stethoscopes. In the modules tested, the auscultation of borborygmi was rated between 5 and 7 by the conventional stethoscope and consistently 10 by the electronic stethoscope. Discussion: This stethoscope comparison was limited to a single operator. However, we

  8. Improved ASTM G72 Test Method for Ensuring Adequate Fuel-to-Oxidizer Ratios

    NASA Technical Reports Server (NTRS)

    Juarez, Alfredo; Harper, Susana A.

    2016-01-01

    The ASTM G72/G72M-15 Standard Test Method for Autogenous Ignition Temperature of Liquids and Solids in a High-Pressure Oxygen-Enriched Environment is currently used to evaluate materials for the ignition susceptibility driven by exposure to external heat in an enriched oxygen environment. Testing performed on highly volatile liquids such as cleaning solvents has proven problematic due to inconsistent test results (non-ignitions). Non-ignition results can be misinterpreted as favorable oxygen compatibility, although they are more likely associated with inadequate fuel-to-oxidizer ratios. Forced evaporation during purging and inadequate sample size were identified as two potential causes for inadequate available sample material during testing. In an effort to maintain adequate fuel-to-oxidizer ratios within the reaction vessel during test, several parameters were considered, including sample size, pretest sample chilling, pretest purging, and test pressure. Tests on a variety of solvents exhibiting a range of volatilities are presented in this paper. A proposed improvement to the standard test protocol as a result of this evaluation is also presented. Execution of the final proposed improved test protocol outlines an incremental step method of determining optimal conditions using increased sample sizes while considering test system safety limits. The proposed improved test method increases confidence in results obtained by utilizing the ASTM G72 autogenous ignition temperature test method and can aid in the oxygen compatibility assessment of highly volatile liquids and other conditions that may lead to false non-ignition results.

  9. Regionalization and calibration of seismic discriminants, path effects and signal-to-noise for station ABKT (Alibek, Turkmenistan)

    SciTech Connect

    Rodgers, A.J.; Walter, W.R.

    1997-07-01

    We report measurements and analysis of regional seismic phase amplitude ratios and signal-to-noise for earthquakes observed at the International Monitoring System primary station ABKT (Alibek, Turkmenistan). We measured noise and phase amplitudes of the regional phases Pn, Pg, Sn, and Lg in four frequency bands between 0.75-9.0 Hz. Measurements were made in both the time and frequency domains. The spatial variation of amplitude ratios (e.g., Pn/Lg, Pg/Lg, Pn/Sn, Pg/Sn) and signal-to-noise (phase/noise) reveal significant path effect differences between the Hindu Kush, Kazahk Platform, Iranian Plateau and Caspian Sea. In order to represent this behavior, we have investigated several techniques for characterizing the data. These techniques are: 1) correlation with along-path distance and waveguide properties; 2) sector analysis; and 3) spatial averaging. Along-path waveguide properties, such as mean elevation and rms topographic slope are found to be the strongest factors related to Pg/Lg amplitude ratios at the lowest frequencies (<3.0 Hz). Other path properties such as mean crustal thickness and basement depth are not strongly correlated with Pg/Lg ratios. For sector analysis we divided the data into four (4) azimuthal sectors and characterized the data within each sector by a distance trend. Sectors were chosen based on the behavior of Pn/Lg, Pg/Lg and Pn/Sn amplitude ratios as well as topographic and tectonic character. Results reveal significant reduction (up to a factor of two) in the scatter of the Pn/Lg and Pg/Lg amplitude ratios for the sectorized data compared to the entire data set from all azimuths. Spatial averaging involves smoothing and interpolation for the ratios projected at the event location. Methods such as cap averaging and kriging will be presented at the meeting. 7 refs., 6 figs.

  10. Laboratory Study of the Noticeability and Annoyance of Sounds of Low Signal-to-Noise Ratio

    NASA Technical Reports Server (NTRS)

    Sneddon, Matthew; Howe, Richard; Pearsons, Karl; Fidell, Sanford

    1996-01-01

    This report describes a study of the noticeability and annoyance of intruding noises to test participants who were engaged in a distracting foreground task. Ten test participants read material of their own choosing while seated individually in front of a loudspeaker in an anechoic chamber. One of three specially constructed masking noise environments with limited dynamic range was heard at all times. A laboratory computer produced sounds of aircraft and ground vehicles as heard at varying distances at unpredictable intervals and carefully controlled levels. Test participants were instructed to click a computer mouse at any time that a noise distinct from the background noise environment came to their attention, and then to indicate their degree of annoyance with the noise that they had noticed. The results confirmed that both the noticeability of noise intrusions and their annoyance were closely related to their audibility.

  11. Visual Motherese? Signal-to-Noise Ratios in Toddler-Directed Television

    ERIC Educational Resources Information Center

    Wass, Sam V.; Smith, Tim J.

    2015-01-01

    Younger brains are noisier information processing systems; this means that information for younger individuals has to allow clearer differentiation between those aspects that are required for the processing task in hand (the "signal") and those that are not (the "noise"). We compared toddler-directed and adult-directed TV…

  12. Dependence of Signal-to-Noise Ratio on Operating Voltage in Photomultipliers.

    PubMed

    Jonas, M; Alon, Y

    1971-11-01

    The dependence of SNR on operating voltage at low light intensities was investigated in PM's of box-and-grid and venetian-blind structure, utilizing both the photon-counting and the dc methods of detection. SNR was found to be reasonably constant at both tube types in the tested range of operating voltages with the dc method of detection. In the photon-counting mode at a constant discriminating bias, SNR improved with rising operating voltage in the box-and-grid structure tube, but changed little in the venetian-blind structure tube. PMID:20111351

  13. Visual motherese? Signal-to-noise ratios in toddler-directed television.

    PubMed

    Wass, Sam V; Smith, Tim J

    2015-01-01

    Younger brains are noisier information processing systems; this means that information for younger individuals has to allow clearer differentiation between those aspects that are required for the processing task in hand (the 'signal') and those that are not (the 'noise'). We compared toddler-directed and adult-directed TV programmes (TotTV/ATV). We examined how low-level visual features (that previous research has suggested influence gaze allocation) relate to semantic information, namely the location of the character speaking in each frame. We show that this relationship differs between TotTV and ATV. First, we conducted Receiver Operator Characteristics analyses and found that feature congestion predicted speaking character location in TotTV but not ATV. Second, we used multiple analytical strategies to show that luminance differentials (flicker) predict face location more strongly in TotTV than ATV. Our results suggest that TotTV designers have intuited techniques for controlling toddler attention using low-level visual cues. The implications of these findings for structuring childhood learning experiences away from a screen are discussed. PMID:24702791

  14. Signal to Noise Ratio Characterization of Coherent Doppler Lidar Backscattered Signals

    NASA Astrophysics Data System (ADS)

    Abdelazim, Sameh; Santoro, David; Arend, Mark; Moshary, Fred; Ahmed, Sam

    2016-06-01

    An eye-safe coherent Doppler Lidar (CDL) system for wind measurement was developed and tested at the Remote Sensing Laboratory of the City College of New York (CCNY). The system employs a 1542 nm fiber laser to leverage components' availability and affordability of the telecommunication industry. A balanced detector with a bandwidth extending from dc to 125 MHz is used to eliminate the common mode relative intensity noise (RIN). The system is shot noise limited i.e., the dominant component of received signals' noise is the shot noise. Wind velocity can be measured under nominal aerosol loading and atmospheric turbulence conditions for ranges up to 3 km while pointing vertically with 0.08 m/s precision.

  15. Visual motherese? Signal-to-noise ratios in toddler-directed television

    PubMed Central

    Wass, Sam V; Smith, Tim J

    2015-01-01

    Younger brains are noisier information processing systems; this means that information for younger individuals has to allow clearer differentiation between those aspects that are required for the processing task in hand (the ‘signal’) and those that are not (the ‘noise’). We compared toddler-directed and adult-directed TV programmes (TotTV/ATV). We examined how low-level visual features (that previous research has suggested influence gaze allocation) relate to semantic information, namely the location of the character speaking in each frame. We show that this relationship differs between TotTV and ATV. First, we conducted Receiver Operator Characteristics analyses and found that feature congestion predicted speaking character location in TotTV but not ATV. Second, we used multiple analytical strategies to show that luminance differentials (flicker) predict face location more strongly in TotTV than ATV. Our results suggest that TotTV designers have intuited techniques for controlling toddler attention using low-level visual cues. The implications of these findings for structuring childhood learning experiences away from a screen are discussed. PMID:24702791

  16. Improving signal-to-noise ratio of structured light microscopy based on photon reassignment

    PubMed Central

    Singh, Vijay Raj; Choi, Heejin; Yew, Elijah Y. S.; Bhattacharya, Dipanjan; Yuan, Luo; Sheppard, Colin J. R.; Rajapakse, Jagath C.; Barbastathis, George; So, Peter T. C.

    2011-01-01

    In this paper, we report a method for 3D visualization of a biological specimen utilizing a structured light wide-field microscopic imaging system. This method improves on existing structured light imaging modalities by reassigning fluorescence photons generated from off-focal plane excitation, improving in-focus signal strength. Utilizing a maximum likelihood approach, we identify the most likely fluorophore distribution in 3D that will produce the observed image stacks under structured and uniform illumination using an iterative maximization algorithm. Our results show the optical sectioning capability of tissue specimens while mostly preserving image stack photon count, which is usually not achievable with other existing structured light imaging methods. PMID:22254180

  17. Improving signal-to-noise in the direct imaging of exoplanets and circumstellar disks with MLOCI

    NASA Astrophysics Data System (ADS)

    Wahhaj, Zahed; Cieza, Lucas A.; Mawet, Dimitri; Yang, Bin; Canovas, Hector; de Boer, Jozua; Casassus, Simon; Ménard, François; Schreiber, Matthias R.; Liu, Michael C.; Biller, Beth A.; Nielsen, Eric L.; Hayward, Thomas L.

    2015-09-01

    We present a new algorithm designed to improve the signal-to-noise ratio (S/N) of point and extended source detections around bright stars in direct imaging data.One of our innovations is that we insert simulated point sources into the science images, which we then try to recover with maximum S/N. This improves the S/N of real point sources elsewhere in the field. The algorithm, based on the locally optimized combination of images (LOCI) method, is called Matched LOCI or MLOCI. We show with Gemini Planet Imager (GPI) data on HD 135344 B and Near-Infrared Coronagraphic Imager (NICI) data on several stars that the new algorithm can improve the S/N of point source detections by 30-400% over past methods. We also find no increase in false detections rates. No prior knowledge of candidate companion locations is required to use MLOCI. On the other hand, while non-blind applications may yield linear combinations of science images that seem to increase the S/N of true sources by a factor >2, they can also yield false detections at high rates. This is a potential pitfall when trying to confirm marginal detections or to redetect point sources found in previous epochs. These findings are relevant to any method where the coefficients of the linear combination are considered tunable, e.g., LOCI and principal component analysis (PCA). Thus we recommend that false detection rates be analyzed when using these techniques. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (USA), the Science and Technology Facilities Council (UK), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

  18. Analyzing low signal-to-noise FUSE spectra. Confirmation of Lyman continuum escape from Haro 11

    NASA Astrophysics Data System (ADS)

    Leitet, E.; Bergvall, N.; Piskunov, N.; Andersson, B.-G.

    2011-08-01

    Context. Galaxies are believed to be the main providers of Lyman continuum (LyC) photons during the early phases of the cosmic reionization. Little is known however, when it comes to escape fractions and the mechanisms behind the leakage. To learn more, one may look at local objects, but so far only one low-z galaxy has shown any signs of emitting LyC radiation. With data from the Far Ultraviolet Spectroscopic Explorer (FUSE), we previously found an absolute escape fraction of ionizing photons (fesc) of 4-10% for the blue compact galaxy Haro 11. However, using a revised version of the reduction pipeline on the same data set, Grimes and collaborators were unable to confirm this and derived an upper limit of fesc ≲ 2% . Aims: We attempt to determine whether Haro 11 is emitting ionizing radiation to a significant level or not. We also investigate the performance of the reduction pipeline for faint targets such as Haro 11, and introduce a new approach to the background subtraction. Methods: The final version of the reduction pipeline, CalFUSE v3.2, was applied to the same Haro 11 data set as the two previous authors used. At these faint flux levels, both FUSE and CalFUSE are pushed to their limits, and a detailed analysis was undertaken to monitor the performance of the pipeline. We show that non-simultaneous background estimates are insuffient when working with data of low signal-to-noise ratio (S/N), and a new background model was developed based on a direct fit to the detector response. Results: We find that one has to be very careful when using CalFUSE v3.2 on low S/N data, and especially when dealing with sources where signal might originate from off-center regions. Applying the new background fit, a significant signal is detected in the LyC in both detector segments covering these wavelengths. Thus, the leakage is confirmed with a flux density of f900 = 4.0 × 10-15 erg s-1 cm-2 Å-1 (S/N = 4.6), measured on the airglow free regions in the LyC for the night

  19. Bootstrap Signal-to-Noise Confidence Intervals: An Objective Method for Subject Exclusion and Quality Control in ERP Studies

    PubMed Central

    Parks, Nathan A.; Gannon, Matthew A.; Long, Stephanie M.; Young, Madeleine E.

    2016-01-01

    Analysis of event-related potential (ERP) data includes several steps to ensure that ERPs meet an appropriate level of signal quality. One such step, subject exclusion, rejects subject data if ERP waveforms fail to meet an appropriate level of signal quality. Subject exclusion is an important quality control step in the ERP analysis pipeline as it ensures that statistical inference is based only upon those subjects exhibiting clear evoked brain responses. This critical quality control step is most often performed simply through visual inspection of subject-level ERPs by investigators. Such an approach is qualitative, subjective, and susceptible to investigator bias, as there are no standards as to what constitutes an ERP of sufficient signal quality. Here, we describe a standardized and objective method for quantifying waveform quality in individual subjects and establishing criteria for subject exclusion. The approach uses bootstrap resampling of ERP waveforms (from a pool of all available trials) to compute a signal-to-noise ratio confidence interval (SNR-CI) for individual subject waveforms. The lower bound of this SNR-CI (SNRLB) yields an effective and objective measure of signal quality as it ensures that ERP waveforms statistically exceed a desired signal-to-noise criterion. SNRLB provides a quantifiable metric of individual subject ERP quality and eliminates the need for subjective evaluation of waveform quality by the investigator. We detail the SNR-CI methodology, establish the efficacy of employing this approach with Monte Carlo simulations, and demonstrate its utility in practice when applied to ERP datasets. PMID:26903849

  20. Improving signal-to-noise performance for DNA translocation in solid-state nanopores at MHz bandwidths.

    PubMed

    Balan, Adrian; Machielse, Bartholomeus; Niedzwiecki, David; Lin, Jianxun; Ong, Peijie; Engelke, Rebecca; Shepard, Kenneth L; Drndić, Marija

    2014-12-10

    DNA sequencing using solid-state nanopores is, in part, impeded by the relatively high noise and low bandwidth of the current state-of-the-art translocation measurements. In this Letter, we measure the ion current noise through sub 10 nm thick Si3N4 nanopores at bandwidths up to 1 MHz. At these bandwidths, the input-referred current noise is dominated by the amplifier's voltage noise acting across the total capacitance at the amplifier input. By reducing the nanopore chip capacitance to the 1-5 pF range by adding thick insulating layers to the chip surface, we are able to transition to a regime in which input-referred current noise (∼ 117-150 pArms at 1 MHz in 1 M KCl solution) is dominated by the effects of the input capacitance of the amplifier itself. The signal-to-noise ratios (SNRs) reported here range from 15 to 20 at 1 MHz for dsDNA translocations through nanopores with diameters from 4 to 8 nm with applied voltages from 200 to 800 mV. Further advances in bandwidth and SNR will require new amplifier designs that reduce both input capacitance and input-referred amplifier noise. PMID:25418589

  1. C IV LINE-WIDTH ANOMALIES: THE PERILS OF LOW SIGNAL-TO-NOISE SPECTRA

    SciTech Connect

    Denney, K. D.; Vestergaard, M.; Pogge, R. W.; Kochanek, C. S.; Peterson, B. M.; Assef, R. J.

    2013-09-20

    Comparison of six high-redshift quasar spectra obtained with the Large Binocular Telescope with previous observations from the Sloan Digital Sky Survey shows that failure to correctly identify absorption and other problems with accurate characterization of the C IV λ1549 emission line profile in low signal-to-noise (S/N) data can severely limit the reliability of single-epoch mass estimates based on the C IV emission line. We combine the analysis of these new high-quality data with a reanalysis of three other samples based on high-S/N spectra of the C IV emission line region. We find that a large scatter between the Hβ- and C IV-based masses remains even for this high-S/N sample when using the FWHM to characterize the broad-line region velocity dispersion and the standard virial assumption to calculate the mass. However, we demonstrate that using high-quality data and the line dispersion to characterize the C IV line width leads to a high level of consistency between C IV- and Hβ-based masses, with <0.3 dex of observed scatter and an estimated ∼0.2 dex intrinsic scatter, in the mass residuals.

  2. The flat fielding and achievable signal-to-noise of the MAMA detectors

    NASA Technical Reports Server (NTRS)

    Kaiser, Mary Elizabeth; Lindler, Don J.; Bohlin, Ralph C.

    1997-01-01

    The Space Telescope Imaging Spectrograph (STIS) was designed to achieve a signal-to-noise (S/N) of at least 100:1 per resolution element. Multi-Anode Microchannel Arrays (MAMA) observations during Servicing Mission Orbital Verification (SMOV) confirm that this specification can be met. From analysis of a single spectrum of GD153, with counting statistics of approximately 165 a S/N of approximately 125 is achieved per spectral resolution element in the far ultraviolet (FUV) over the spectral range of 1280A to 1455A. Co-adding spectra of GRW+7OD5824 to increase the counting statistics to approximately 300 yields a S/N of approximately 190 per spectral resolution element over the region extending from 1347A to 1480A in the FUV. In the near ultraviolet (NUV), a single spectrum of GRW+7OD5824 with counting statistics of approximately 200 yields a S/N of approximately 150 per spectral resolution element over the spectral region extending from 2167 to 2520A. Details of the flat field construction, the spectral extraction, and the definition of a spectral resolution element will be described in the text.

  3. Integrated spectra extraction based on signal-to-noise optimization using integral field spectroscopy

    NASA Astrophysics Data System (ADS)

    Rosales-Ortega, F. F.; Arribas, S.; Colina, L.

    2012-03-01

    Aims: We explore the potential of a method to extract high signal-to-noise (S/N) integrated spectra of particular physical and/or morphological regions of a two-dimensional field using integral field spectroscopy (IFS) observations by applying an optimization procedure based on either continuum (stellar) or line (nebular) emission features. Methods: The optimization method is applied to a set of IFS VLT-VIMOS observations of (U)LIRG galaxies. We describe the advantages of the optimization by comparing the results with a fixed-aperture, single-spectrum case, and by implementing some statistical tests. Results: We demonstrate that the S/N of the IFS optimized integrated spectra is significantly higher than for the single-aperture unprocessed case. In some cases, the optimization based on the emission lines allows to characterize some of the source properties more reliably than with standard integration methods. We are able to clearly retrieve the weak continuum features, hence more precisely constrain the properties of the unresolved stellar population. The most suitable method for integrating spectra over (part of) the field-of-view ultimately depends on the science case, and may involve a trade off among the different variables (e.g. S/N, probe area, spatial resolution, etc.). we therefore provide an iterative user-friendly and versatile IDL algorithm that, in addition to the above-mentioned method, allows the user to spatially integrate spectra following more standard procedures. Our procedure is made available to the community as part of the PINGSoft IFS software package.

  4. Comparison of three tissue composition measurement techniques using digital mammograms--a signal-to-noise study.

    PubMed

    Breitenstein, D S; Shaw, C C

    1998-08-01

    Tissue composition measurement may provide a quantitatively and physically meaningful method to objectively determine the "mammographic density" linked to breast cancer risk. A single energy hybrid (SEH) techniques is described for measuring the tissue composition on a pixel-by-pixel basis with a single digital mammogram. Theoretical models were derived and used to compute signal-to-noise ratios (SNRs) in tissue composition measurement using the SEH method. The results were compared with those computed for measurements using the dual kVp and dual screen methods. SNRs were theoretically related to the pixel area, total unattenuated detector exposure and fluence spectra of the incident X-rays. SNRs were computed for measurement of the adipose tissue thickness for a 6 cm thick breast, consisting of 50% of adipose tissue and 50% of glandular tissue. Effects of kVp and prepatient filtration were studied by computing the SNRs for various kVps and filters and optimal kVps and filters are determined. The results showed that the SNRs obtained with the SEH method is an order of magnitude better than the dual kVp method, which, in turn, is an order of magnitude better than the dual screen method. When using the optimal kVp's and no prepatient filtration, the SNRs were computed to be 84.2, 13.2, and 2.0 for the SEH, dual kVp, and dual screen methods, respectively. Prepatient filtration can improve the SNR by as much as 35% for the dual kVp and dual screen techniques with reasonable tube loading factors (8-10). PMID:9718504

  5. High signal-to-noise acoustic sensor using phase-shifted gratings interrogated by the Pound-Drever-Hall technique

    NASA Astrophysics Data System (ADS)

    Kung, Peter; Comanici, Maria I.

    2014-11-01

    Optical fiber is made of glass, an insulator, and thus it is immune to strong electromagnetic interference. Therefore, fiber optics is a technology ideally suitable for sensing of partial discharge (PD) both in transformers and generators. Extensive efforts have been used to develop a cost effective solution for detecting partial discharge, which generates acoustic emission, with signals ranging from 30 kHz to 200 kHz. The requirement is similar to fiber optics Hydro Phone, but at higher frequencies. There are several keys to success: there must be at least 60 dB signal-to-noise ratio (SNR) performance, which will ensure not only PD detection but later on provide diagnostics and also the ability to locate the origin of the events. Defects that are stationary would gradually degrade the insulation and result in total breakdown. Transformers currently need urgent attention: most of them are oil filled and are at least 30 to 50 years old, close to the end of life. In this context, an issue to be addressed is the safety of the personnel working close to the assets and collateral damage that could be caused by a tank explosion (with fire spilling over the whole facility). This paper will describe the latest achievement in fiber optics PD sensor technology: the use of phase shifted-fiber gratings with a very high speed interrogation method that uses the Pound-Drever-Hall technique. More importantly, this is based on a technology that could be automated, easy to install, and, eventually, available at affordable prices.

  6. A MARKOV CHAIN MONTE CARLO ALGORITHM FOR ANALYSIS OF LOW SIGNAL-TO-NOISE COSMIC MICROWAVE BACKGROUND DATA

    SciTech Connect

    Jewell, J. B.; O'Dwyer, I. J.; Huey, Greg; Gorski, K. M.; Eriksen, H. K.; Wandelt, B. D. E-mail: h.k.k.eriksen@astro.uio.no

    2009-05-20

    We present a new Markov Chain Monte Carlo (MCMC) algorithm for cosmic microwave background (CMB) analysis in the low signal-to-noise regime. This method builds on and complements the previously described CMB Gibbs sampler, and effectively solves the low signal-to-noise inefficiency problem of the direct Gibbs sampler. The new algorithm is a simple Metropolis-Hastings sampler with a general proposal rule for the power spectrum, C {sub l}, followed by a particular deterministic rescaling operation of the sky signal, s. The acceptance probability for this joint move depends on the sky map only through the difference of {chi}{sup 2} between the original and proposed sky sample, which is close to unity in the low signal-to-noise regime. The algorithm is completed by alternating this move with a standard Gibbs move. Together, these two proposals constitute a computationally efficient algorithm for mapping out the full joint CMB posterior, both in the high and low signal-to-noise regimes.

  7. High Resolution and High Signal-to-Noise Measurements in the 0310 ← 0110 Q-Branch of N2O at 1160 cm-1

    NASA Astrophysics Data System (ADS)

    Vitcu, A.; Wehr, R.; Ciurylo, R.; Drummond, J. R.; May, A. D.

    2002-12-01

    High-resolution measurements of the Π ← Π Q-branch of pure N2O near 1160 cm-1 were made using a difference-frequency spectrometer with resolution of 5 × 10-5 cm-1 and a signal-to-noise ratio of 2000:1. Lines Q18F through Q12E have been recorded in a single scan, at room temperature and at pressures ranging from 1 to 130 torr. The spectra are analyzed up to 23 torr on a line-by-line basis using a hard collision profile including Dicke narrowing and line mixing. Since the separation of the central lines of this double-sided Q-branch is of the same order of magnitude with the collisional broadening, line mixing is considered in the analysis even at 1 torr and its dependence with pressure is studied.

  8. Systematic analysis of signal-to-noise ratio in bipartite ghost imaging with classical and quantum light

    SciTech Connect

    Brida, G.; Fornaro, G. A.; Genovese, M.; Berchera, I. Ruo; Chekhova, M. V.; Lopaeva, E. D.

    2011-06-15

    We present a complete and exhaustive theory of signal-to-noiseratio in bipartite ghost imaging with classical (thermal) and quantum (twin beams) light. The theory is compared with experiment for both twin beams and thermal light in a certain regime of interest.

  9. Real-time in Situ Signal-to-noise Ratio Estimation for the Assessment of Operational Communications Links

    NASA Technical Reports Server (NTRS)

    Manning, Robert M.

    2002-01-01

    The work presented here formulates the rigorous statistical basis for the correct estimation of communication link SNR of a BPSK, QPSK, and for that matter, any M-ary phase-modulated digital signal from what is known about its statistical behavior at the output of the receiver demodulator. Many methods to accomplish this have been proposed and implemented in the past but all of them are based on tacit and unwarranted assumptions and are thus defective. However, the basic idea is well founded, i.e., the signal at the output of a communications demodulator has convolved within it the prevailing SNR characteristic of the link. The acquisition of the SNR characteristic is of the utmost importance to a communications system that must remain reliable in adverse propagation conditions. This work provides a correct and consistent mathematical basis for the proper statistical 'deconvolution' of the output of a demodulator to yield a measure of the SNR. The use of such techniques will alleviate the need and expense for a separate propagation link to assess the propagation conditions prevailing on the communications link. Furthermore, they are applicable for every situation involving the digital transmission of data over planetary and space communications links.

  10. MagArray Biochips for Protein and DNA Detection with Magnetic Nanotags: Design, Experiment, and Signal-to-Noise Ratio

    NASA Astrophysics Data System (ADS)

    Osterfeld, Sebastian J.; Wang, Shan X.

    MagArray™ chips contain arrays of magnetic sensors, which can be used to detect surface binding reactions of biological molecules that have been labeled with 10 to 100 nm sized magnetic particles. Although MagArray chips are in some ways similar to fluorescence-based DNA array chips, the use of magnetic labeling tags leads to many distinct advantages, such as better background rejection, no label bleaching, inexpensive chip readers, potentially higher sensitivity, ability to measure multiple binding reactions in homogeneous assays simultaneously and in real-time, and seamless integration with magnetic separation techniques. So far, the technology of MagArray chips has been successfully used to perform quantitative analytic bioassays of both protein and nucleic acid targets. The potential of this technology, especially for point-of-care testing (POCT) and portable molecular diagnostics, appears promising, and it is likely that this technology will see significant further performance gains in the near future.

  11. Methods for voltage-sensitive dye imaging of rat cortical activity with high signal-to-noise ratio

    PubMed Central

    Lippert, Michael; Takagaki, Kentaroh; Xu, Weifeng; Huang, Xiaoying; Wu, Jian-Young

    2010-01-01

    We describe methods to achieve high sensitivity in voltage-sensitive dye (VSD) imaging from rat barrel and visual cortices in vivo with the use of a blue dye RH1691 and a high dynamic range imaging device (photodiode array). With an improved staining protocol and an off-line procedure to remove pulsation artifact, the sensitivity of VSD recording is comparable to that of local field potential recording from the same location. With this sensitivity, one can record from ~500 individual detectors, each covering an area of cortical tissue 160 μm in diameter (total imaging field ~4 mm in diameter) and a temporal resolution of 1,600 frames/s, without multiple-trial averaging. We can record 80 to 100 trials of intermittent 10 s trials from each imaging field before the VSD signal reduces to one half of its initial amplitude due to bleaching and wash-out. Taken together, the methods described in this report provide a useful tool for visualizing evoked and spontaneous waves from rodent cortex. PMID:17493915

  12. Self-Consistent Signal-to-Noise Analysis of CDMA Multiuser Detection with M-Ary Phase-Shift Keying

    NASA Astrophysics Data System (ADS)

    Kato, Hiroyuki; Okada, Masato; Miyoshi, Seiji

    2013-02-01

    We present a theory of the performance of parallel interference cancellation (PIC) for code division multiple access (CDMA) multiuser detection with M-ary phase-shift keying (M-ary PSK) in the large-system limit. The behavior of PIC is essentially the same as that of the associative memory model. Therefore, we analyze the PIC for CDMA using self-consistent signal-to-noise analysis (SCSNA), which was developed to describe the behavior of the associative memory model. We obtain a quantitative description of the performance of PIC.

  13. Data reduction, radial velocities and stellar parameters from spectra in the very low signal-to-noise domain

    NASA Astrophysics Data System (ADS)

    Malavolta, Luca

    2013-10-01

    Large astronomical facilities usually provide data reduction pipeline designed to deliver ready-to-use scientific data, and too often as- tronomers are relying on this to avoid the most difficult part of an astronomer job Standard data reduction pipelines however are usu- ally designed and tested to have good performance on data with av- erage Signal to Noise Ratio (SNR) data, and the issues that are related with the reduction of data in the very low SNR domain are not taken int account properly. As a result, informations in data with low SNR are not optimally exploited. During the last decade our group has collected thousands of spec- tra using the GIRAFFE spectrograph at Very Large Telescope (Chile) of the European Southern Observatory (ESO) to determine the ge- ometrical distance and dynamical state of several Galactic Globular Clusters but ultimately the analysis has been hampered by system- atics in data reduction, calibration and radial velocity measurements. Moreover these data has never been exploited to get other informa- tions like temperature and metallicity of stars, because considered too noisy for these kind of analyses. In this thesis we focus our attention on data reduction and analysis of spectra with very low SNR. The dataset we analyze in this thesis comprises 7250 spectra for 2771 stars of the Globular Cluster M 4 (NGC 6121) in the wavelength region 5145-5360Å obtained with GIRAFFE. Stars from the upper Red Giant Branch down to the Main Sequence have been observed in very different conditions, including nights close to full moon, and reaching SNR - 10 for many spectra in the dataset. We will first review the basic steps of data reduction and spec- tral extraction, adapting techniques well tested in other field (like photometry) but still under-developed in spectroscopy. We improve the wavelength dispersion solution and the correction of radial veloc- ity shift between day-time calibrations and science observations by following a completely

  14. Training sensory signal-to-noise resolution in children with ADHD in a global mental health setting.

    PubMed

    Mishra, J; Sagar, R; Joseph, A A; Gazzaley, A; Merzenich, M M

    2016-01-01

    Children with attention deficit/hyperactivity disorder (ADHD) have impaired focus on goal-relevant signals and fail to suppress goal-irrelevant distractions. To address both these issues, we developed a novel neuroplasticity-based training program that adaptively trains the resolution of challenging sensory signals and the suppression of progressively more challenging distractions. We evaluated this sensory signal-to-noise resolution training in a small sample, global mental health study in Indian children with ADHD. The children trained for 30 h over 6 months in a double-blind, randomized controlled trial. Training completers showed steady and significant improvements in ADHD-associated behaviors from baseline to post training relative to controls, and benefits sustained in a 6-month follow-up. Post-training cognitive assessments showed significant positive results for response inhibition and Stroop interference tests in training completers vs controls, while measures of sustained attention and short-term memory showed nonsignificant improvement trends. Further, training-driven improvements in distractor suppression correlated with the improved ADHD symptoms. This initial study suggests utility of signal-to-noise resolution training for children with ADHD; it emphasizes the need for further research on this intervention and substantially informs the design of a larger trial. PMID:27070409

  15. Training sensory signal-to-noise resolution in children with ADHD in a global mental health setting

    PubMed Central

    Mishra, J; Sagar, R; Joseph, A A; Gazzaley, A; Merzenich, M M

    2016-01-01

    Children with attention deficit/hyperactivity disorder (ADHD) have impaired focus on goal-relevant signals and fail to suppress goal-irrelevant distractions. To address both these issues, we developed a novel neuroplasticity-based training program that adaptively trains the resolution of challenging sensory signals and the suppression of progressively more challenging distractions. We evaluated this sensory signal-to-noise resolution training in a small sample, global mental health study in Indian children with ADHD. The children trained for 30 h over 6 months in a double-blind, randomized controlled trial. Training completers showed steady and significant improvements in ADHD-associated behaviors from baseline to post training relative to controls, and benefits sustained in a 6-month follow-up. Post-training cognitive assessments showed significant positive results for response inhibition and Stroop interference tests in training completers vs controls, while measures of sustained attention and short-term memory showed nonsignificant improvement trends. Further, training-driven improvements in distractor suppression correlated with the improved ADHD symptoms. This initial study suggests utility of signal-to-noise resolution training for children with ADHD; it emphasizes the need for further research on this intervention and substantially informs the design of a larger trial. PMID:27070409

  16. Technical note: signal-to-noise performance evaluation of a new 12-bit digitizer on time-of-flight mass spectrometer.

    PubMed

    Hondo, Toshinobu; Kawai, Yousuke; Toyoda, Michisato

    2015-01-01

    Rapid acquisition of time-of-flight (TOF) spectra from fewer acquisitions on average was investigated using the newly introduced 12-bit digitizer, Keysight model U5303A. This is expected to achieve a spectrum acquisition 32 times faster than the commonly used 8-bit digitizer for an equal signal-to-noise (S/N) ratio. Averaging fewer pulses improves the detection speed and chromatographic separation performance. However, increasing the analog-to-digital converter bit resolution for a high-frequency signal, such as a TOF spectrum, increases the system noise and requires the timing jitter (aperture error) to be minimized. We studied the relationship between the S/N ratio and the average number of acquisitions using U5303A and compared this with an 8-bit digitizer. The results show that the noise, measured as root-mean-square, decreases linearly to the square root of the average number of acquisitions without background subtraction, which means that almost no systematic noise existed in our signal bandwidth of interest (a few hundreds megahertz). In comparison, 8-bit digitizers that are commonly used in the market require 32 times more pulses with background subtraction. PMID:25906030

  17. Using Subsurface CO2 Concentrations and Isotopologues to Identify CO2 Seepage from CCS/CO2-EOR Projects: A Signal-to-Noise Based Analysis

    NASA Astrophysics Data System (ADS)

    Nickerson, N. R.; Risk, D. A.

    2012-12-01

    In order to fulfill a role in demonstrating containment, surface monitoring for Carbon Capture and Geologic Storage (CCS) sites must be able to clearly discriminate between natural, and leakage-source CO2. The CCS community lacks a clear metric for quantifying the degree of discrimination, for successful inter-comparison of monitoring approaches. This study illustrates the utility of Signal-to-Noise Ratio (SNR) to compare the relative performance of three commonly used soil gas monitoring approaches, including bulk CO2, δ13CO2, and Δ14CO2. For inter-comparisons, we used a simulated northern temperate landscape similar to that of Weyburn, Saskatchewan (home of the IEAGHG Weyburn-Midale CO2 Monitoring and Storage Project), in which realistic spatial and temporal CO2 and isotopic variation is simulated for periods of one year or more. Results indicate, that, for this particular ecosystem, Δ14C signatures have the best overall SNR at all simulated seepage rates, and for all points across the synthetic landscape. We then apply this same SNR based approach to data collected during a 6-month sampling campaign at three locations on the Weyburn oil field. This study emphasizes both the importance of developing clear metrics for monitoring performance, and the benefit of modeling for decision support in CCS monitoring design.

  18. Determination of in-flight AVIRIS spectral, radiometric, spatial and signal-to-noise characteristics using atmospheric and surface measurements from the vicinity of the rare-earth-bearing carbonatite at Mountain Pass, California

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Vane, Gregg; Conel, James E.

    1988-01-01

    An assessment of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) performance was made for a flight over Mountain Pass, California, July 30, 1987. The flight data were reduced to reflectance using an empirical algorithm which compensates for solar, atmospheric and instrument factors. AVIRIS data in conjunction with surface and atmospheric measurements acquired concurrently were used to develop an improved spectral calibration. An accurate in-flight radiometric calibration was also performed using the LOWTRAN 7 radiative transfer code together with measured surface reflectance and atmospheric optical depths. A direct comparison with coincident Thematic Mapper imagery of Mountain Pass was used to demonstrate the high spatial resolution and good geometric performance of AVIRIS. The in-flight instrument noise was independently determined with two methods which showed good agreement. A signal-to-noise ratio was calculated using data from a uniform playa. This ratio was scaled to the AVIRIS reference radiance model, which provided a basis for comparison with laboratory and other in-flight signal-to-noise determinations.

  19. A High Signal-To-Noise Ultraviolet Spectrum of NGC 7469: New Support for Reprocessing of Continuum Radiation

    NASA Technical Reports Server (NTRS)

    Kriss, Gerard A.; Peterson, Bradley M.; Crenshaw, D. Michael; Zheng, Wei

    2000-01-01

    From 1996 June 10 to 1996 July 29, the International AGN Watch monitored the Seyfert 1 galaxy NGC 7469 using the International Ultraviolet Explorer, the Rossi X-Ray Timing Explorer, and a network of ground-based observatories. On 1996 June 18, in the midst of this intensive monitoring period, we obtained a high signal-to-noise snapshot of the UV spectrum from 1150 to 3300 A, using the Faint Object Spectrograph (FOS) on the Hubble Space Telescope. This spectrum allows us to disentangle the UV continuum more accurately from the broad wings of the emission lines, to identify clean continuum windows free of contaminating emission and absorption, and to deblend line complexes such as Ly(alpha) + N V, C IV + He II + O III], Si III] + C III], and Mg II + Fe II. Using the FOS spectrum as a template, we have fitted and extracted line and continuum fluxes from the IUE monitoring data. The cleaner continuum extractions c o n h the discovery of time delays between the different UV continuum bands by Wanders et al. Our new measurements show delays increasing with wavelength for continuum bands centered at 1485, 1740, and 1825 A, relative to 1315 A with delays of 0.09, 0.28, and 0.36 days, respectively. Like many other Seyfert I galaxies, the UV spectrum of NGC 7469 shows intrinsic, blue-shifted absorption in Ly(alpha), N V, and C IV. Soft X-ray absorption is also visible in archival ASCA X-ray spectra. The strength of the UV absorption, however, is not compatible with a single-zone model in which the same material absorbs both the UV and X-ray light. Similar to other Seyfert galaxies, such as NGC 3516, the UV-absorbing gas in NGC 7469 has a lower ionization parameter and column density than the X-ray-absorbing material. While the UV and X-ray absorption does not arise in the same material, the frequent occurrence of both associated UV absorption and X-ray warm absorbers in the same galaxies suggests that the gas supply for each has a common origin.

  20. Signal-to-noise analysis for propagation of laser radiation through a tissue-like medium by diffuse photon-density waves

    NASA Astrophysics Data System (ADS)

    Netz, U. J.; Hielscher, A. H.; Scheel, A. K.; Beuthan, J.

    2007-04-01

    Biomedical optical imaging in the near-infrared (NIR) region provides the possibility to detect and determine pathological and functional changes in human tissue without the drawback of ionizing radiation. Of special promise is the application of this technology for the detection of joint diseases, such as rheumatoid arthritis (RA). It has been shown that optical changes in the synovial fluid and the vasculature surrounding the joints can be detected with optical methods. Applying optical tomographic methods one should be able to localize and quantify these changes for detection of the onset of RA. The first studies have been limited to continuous wave imaging. However, it is well known that enhanced resolution and better separation between absorption and scattering properties of tissue can be achieved using intensity modulated light sources. Intensity modulation of laser light in the MHz region leads to propagation of so-called diffuse photon density waves (PDW) through the tissue In this study we report on basic experimental results to determine performance and sensitivity of PDW-transillumination of tissue like phantoms. We used a vector network analyzer to generate and analyze intensity modulation from 100 MHz up to 1 GHz via a diode laser and an avalanche photo diode. Scans were performed across phantoms containing a layer with different absorbing and scattering properties bounded by an edge. The thickness of the phantoms was chosen similar to human fingers to gain information for optimization of tomographic imaging of finger joints. We experimentally determined the signal-to-noise ratio (SNR) of the system and compared the results to theoretical predictions. Noise and SNR of amplitude and phase depend on frequency of modulation. While the amplitude SNR decreases with frequency, phase SNR increases to assume a maximum value. We found that the inserted layer can be better characterized using phase information, which becomes more valuable as the source

  1. High Signal-to-Noise Echelle Spectroscopy of Quasar Absorption-Line Systems in the Direction of HS 1946+7658

    NASA Astrophysics Data System (ADS)

    Tripp, Todd M.; Lu, Limin; Savage, Blair D.

    1996-02-01

    We have obtained a high signal-to-noise (40 <= S/N <= 80) high- resolution (FWHM = 20 km s^-1^) spectrum of the radio-quiet QSO HS 1946+7658 (z_em_ = 3.051) with the echelle spectrograph on the KPNO 4 m telescope. We detect 11 metal systems in the direction of this QSO, including two Mg II systems, five C IV systems, two damped Lyα systems, and two associated systems. We use the apparent column density technique and profile fitting to measure the heavy element column densities and to assess the effects of absorption-line saturation. Profile fitting indicates that three of the C IV systems are narrow with b < 8 km s^-1^. This implies that T < 50,000 K, and therefore these systems are probably photoionized. The abundance patterns in the damped Lyα systems are strikingly similar to those observed in low- metallicity Milky Way stars and suggest that these absorption lines are due to galaxies in early stages of chemical enrichment (see Lu et al.). The prominent associated system at z_abs_ = 3.0496,3.0504 is detected in H I, C II, CIV, SiII, Si III, Si IV, A1 II, Al III, and N V. The high ion column density ratios in this associated system imply that the gas is more highly ionized than the Galactic halo. The high degree of ionization is not surprising given the extraordinary luminosity of the QSO (Hagen et al.). To study ionization and abundances in this associated system, we compare the observed column densities to a series of CLOUDY models in which photoionization by the QSO is the dominant ionization mechanism. For the input radiation field, we have used the various spectral energy distributions of HS 1946+7658 observed by Kuhn et al. The model that best fits the observed column densities of singly and doubly ionized species has solar relative and absolute abundances, but models with absolute metallicities a few times greater than solar fit comparably well. None of the models produce enough Si IV and C IV, but the QSO flux near the ionization potentials of these

  2. Improving Signal to Noise in Labeled Biological Specimens using Energy-Filtered TEM of sections with a Drift Correction Strategy and a Direct Detection Device

    PubMed Central

    Ramachandra, Ranjan; Bouwer, James C.; Mackey, Mason R.; Bushong, Eric; Peltier, Steven T.; Xuong, Nguyen-Huu; Ellisman, Mark H.

    2014-01-01

    Energy filtered transmission electron microscopy techniques are regularly used to build elemental maps of spatially distributed nanoparticles in materials and biological specimens. When working with thick biological sections, EELS techniques involving core-loss electrons often require exposures exceeding several minutes to provide sufficient signal to noise. Image quality with these long exposures is often compromised by specimen drift, which results in blurring and reduced resolution. To mitigate drift artifacts, a series of short exposure images can be acquired, aligned, and merged to form a single image. For samples where the target elements have extremely low signal yields, the use of CCD based detectors for this purpose can be problematic. At short acquisition times, the images produced by CCDs can be noisy and may contain fixed pattern artifacts that impact subsequent correlative alignment. Here we report on the use of direct electron detection devices (DDD’s) to increase the signal to noise as compared to CCD’s. A 3x improvement in signal is reported with a DDD vs. a comparably formatted CCD, with equivalent dose on each detector. With the fast rolling-readout design of the DDD, the duty cycle provides a major benefit, as there is no dead time between successive frames. PMID:24641915

  3. Kea: A New Tool to Obtain Stellar Parameters from Low to Moderate Signal-to-noise and High-resolution Echelle Spectra

    NASA Astrophysics Data System (ADS)

    Endl, Michael; Cochran, William D.

    2016-09-01

    In this paper, we describe Kea a new spectroscopic fitting method to derive stellar parameters from moderate to low signal-to-noise, high-resolution spectra. We developed this new tool to analyze the massive data set of the Kepler mission reconnaissance spectra that we have obtained at McDonald Observatory. We use Kea to determine effective temperatures (T eff), metallicity ([Fe/H]), surface gravity (log g), and projected rotational velocity (v{sin}i). Kea compares the observations to a large library of synthetic spectra that covers a wide range of different T eff, [Fe/H], and log g values. We calibrated Kea on observations of well-characterized standard stars (the Kepler field “platinum” sample) that range in T eff from 5000 to 6500 K, in [Fe/H] from ‑0.5 to +0.4 dex, and in log g from 3.2 to 4.6 dex. We then compared the Kea results from reconnaissance spectra of 45 Kepler objects of interest (KOIs) to stellar parameters derived from higher signal-to-noise spectra obtained with Keck/HIRES. We find typical uncertainties of 100 K in T eff, 0.12 dex in [Fe/H], and 0.18 dex in log g. Named after Nestor notabilis an alpine parrot native to New Zealand.

  4. Simultaneous unbalanced shared local oscillator heterodyne interferometry for high signal-to-noise-ratio, minimally destructive dispersive detection of time-dependent atomic spins

    NASA Astrophysics Data System (ADS)

    Locke, Mary; Fertig, Chad

    2013-09-01

    We demonstrate "Simultaneous Unbalanced Shared Local Oscillator Heterodyne Interferometry (SUSHI)," a new method for minimally destructive, high SNR dispersive detection of atomic spins. In SUSHI a dual-frequency probe laser interacts with atoms in one arm of a Mach-Zehnder interferometer, then beats against a bright local oscillator beam traversing the other arm, resulting in two simultaneous, independent heterodyne measurements of the atom-induced phase shift. Measurement noise due to mechanical disturbances of beam paths is strongly rejected by the technique of \\emph{active subtraction} in which anti-noise is actively written onto the local oscillator beam via an optical phase-locked-loop. In SUSHI, technical noise due to phase, amplitude, and frequency fluctuations of the various laser fields is strongly rejected (i) for any mean phase bias between the interferometer arms, (ii) without the use of piezo actuated mirrors, and (iii) without signal balancing. We experimentally demonstrate an ultra-low technical noise limited sensitivity of 51 nrad$/\\sqrt{\\R{Hz}}$ over a measurement bandwidth of 60 Hz to 8 kHz using a 230 $\\mu$W probe, and stay within $\\sim$3 dB of the standard quantum limit as probe power is reduced by more than 5 orders of magnitude to as low as 650 pW. SUSHI is therefore well suited to performing QND measurements for preparing spin squeezed states and for high SNR, truly continuous observations of ground-state Rabi flopping in cold atom ensembles.

  5. Airborne ultraviolet imaging system for oil slick surveillance: oil-seawater contrast, imaging concept, signal-to-noise ratio, optical design, and optomechanical model.

    PubMed

    Shi, Zhenhua; Yu, Lei; Cao, Diansheng; Wu, Qingwen; Yu, Xiangyang; Lin, Guanyu

    2015-09-01

    The airborne ultraviolet imaging system, which assesses oil slick areas better than visible and infrared optical systems, was designed to monitor and track oil slicks in coastal regions. A model was built to achieve the upwelling radiance distribution of oil-covered sea and clean seawater, based on the radiance transfer software. With this model, the oil-seawater contrast, which affects the detection of oil-covered coastal areas, was obtained. The oil-seawater contrast, fundamental imaging concept, analog calculation of SNR, optical design, and optomechanical configuration of the airborne ultraviolet imaging system are illustrated in this paper. The study of an airborne ultraviolet imaging system with F-number 3.4 and a 40° field of view (FOV) in near ultraviolet channel (0.32-0.38 μm) was illustrated and better imaging quality was achieved. The ground sample distance (GSD) is from 0.35 to 0.7 m with flight height ranges from 0.5 to 1 km. Comparisons of detailed characteristics of the airborne ultraviolet imaging system with the corresponding characteristics of previous ultraviolet systems were tabulated, and these comparisons showed that this system can achieve a wide FOV and a relative high SNR. A virtual mechanical prototype and tolerances analysis are illustrated in this paper to verify the performance of fabrication and assembly of the ultraviolet system. PMID:26368888

  6. Attenuation of mirror image and enhancement of the signal-to-noise ratio in a Talbot bands optical coherence tomography system

    NASA Astrophysics Data System (ADS)

    Bradu, Adrian; Podoleanu, Adrian Gh.

    2011-07-01

    A Fourier domain optical coherence tomography setup is presented built around an optical configuration that exhibits Talbot bands. A low astigmatism spectrometer is used, employing a spherical mirror and a cylindrical lens between a diffraction grating and a linear CCD camera. To produce Talbot bands, the two interferometer beams--object and reference--are laterally shifted in respect to each other in their way toward the diffraction grating. This allows attenuation of mirror terms and optimization of the sensitivity profile. We evaluate the optimization of the sensitivity profile with depth, in respect to its overall strength and its position peak, which can be shifted toward a larger optical path difference in the interferometer. We demonstrate the efficiency of such a configuration at large depths by imaging a thick phantom and human skin in vivo for different values of the lateral distance between the two beams.

  7. Content-aware video quality assessment: predicting human perception of quality using peak signal to noise ratio and spatial/temporal activity

    NASA Astrophysics Data System (ADS)

    Ortiz-Jaramillo, B.; Niño-Castañeda, J.; Platiša, L.; Philips, W.

    2015-03-01

    Since the end-user of video-based systems is often a human observer, prediction of human perception of quality (HPoQ) is an important task for increasing the user satisfaction. Despite the large variety of objective video quality measures, one problem is the lack of generalizability. This is mainly due to the strong dependency between HPoQ and video content. Although this problem is well-known, few existing methods directly account for the influence of video content on HPoQ. This paper propose a new method to predict HPoQ by using simple distortion measures and introducing video content features in their computation. Our methodology is based on analyzing the level of spatio-temporal activity and combining HPoQ content related parameters with simple distortion measures. Our results show that even very simple distortion measures such as PSNR and simple spatio-temporal activity measures lead to good results. Results over four different public video quality databases show that the proposed methodology, while faster and simpler, is competitive with current state-of-the-art methods, i.e., correlations between objective and subjective assessment higher than 80% and it is only two times slower than PSNR.

  8. Signal-to-noise ratio evaluation with draw tower fibre Bragg gratings (DTGs) for dynamic strain sensing at elevated temperatures and corrosive environment

    NASA Astrophysics Data System (ADS)

    De Pauw, B.; Lamberti, A.; Vanlanduit, S.; Van Tichelen, K.; Geernaert, T.; Berghmans, F.

    2014-05-01

    Measuring strain at the surface of a structure can help to estimate the dynamical properties of the structure under test. Such a structure can be a fuel assembly of a nuclear reactor consisting of fuel pins. In this paper we demonstrate a method to integrate draw tower gratings (DTGs) in a fuel pin and we subject this pin to conditions close to those encountered in a heavy liquid metal (HLM) reactor. More specifically, we report on the performance of DTGs used as a strain sensor when immersed in HLM during thermal cycles (up to 300_C) for up to 700 hours.

  9. An Iterative Information-Reduced Quadriphase-Shift-Keyed Carrier Synchronization Scheme Using Decision Feedback for Low Signal-to-Noise Ratio Applications

    NASA Technical Reports Server (NTRS)

    Simon, M.; Tkacenko, A.

    2006-01-01

    In a previous publication [1], an iterative closed-loop carrier synchronization scheme for binary phase-shift keyed (BPSK) modulation was proposed that was based on feeding back data decisions to the input of the loop, the purpose being to remove the modulation prior to carrier synchronization as opposed to the more conventional decision-feedback schemes that incorporate such feedback inside the loop. The idea there was that, with sufficient independence between the received data and the decisions on it that are fed back (as would occur in an error-correction coding environment with sufficient decoding delay), a pure tone in the presence of noise would ultimately be produced (after sufficient iteration and low enough error probability) and thus could be tracked without any squaring loss. This article demonstrates that, with some modification, the same idea of iterative information reduction through decision feedback can be applied to quadrature phase-shift keyed (QPSK) modulation, something that was mentioned in the previous publication but never pursued.

  10. High Signal-to-Noise Echelle Spectroscopy of Quasar Absorption Line Systems with Metals in the Direction of HS 1700+6416

    NASA Astrophysics Data System (ADS)

    Tripp, Todd M.; Lu, Limin; Savage, Blair D.

    We have obtained a high signal-to-noise (30 <= S/N <= 70), high-resolution (FWHM = 20 km s-1) spectrum of the radio-quiet QSO HS 1700+6416 (zem = 2.72) with the echelle spectrograph on the Kitt Peak National Observatory 4 m telescope. We detect 13 metal systems in the optical spectrum of this QSO, including six systems with associated optically thin Lyman limit absorption in the HST spectrum obtained by Reimers et al. We use the apparent column density technique and profile fitting to measure the heavy-element column densities and to evaluate the impact of unresolved absorption saturation. Profile fitting indicates that four of the C IV systems are narrow, with b < 8 km s-1, which implies that these absorbers are relatively cool and are probably photoionized. The dense cluster of C IV doublets at 2.432 < zabs < 2.441 shows the weak line of one C IV absorber apparently aligned with the strong line of a different C IV doublet, i.e., line locked, for two pairs of C IV absorbers. Line locking has been detected previously in zabs ~ zem absorbers, where radiation pressure is likely to play a role, but is surprising in this case since this C IV complex is displaced by ~24,000 km s-1 from the QSO emission redshift. This may be the remnant (or precursor) of a broad absorption line (BAL) outflow. However, it is possible that these alignments are chance alignments rather than true line locking. The high-ion column density ratios in the multicomponent Lyman limit absorber at zabs = 2.3150 suggest that the ionization conditions in this absorber differ significantly from the conditions in the gaseous halo of the Milky Way. From photoionization models we derive [Si/H] >= -0.95 and [Al/H] >= -0.96 for the strongest component of this absorber. These are conservative lower limits derived from lower ionization stages only; photoionization models in agreement with the observed low and high ionization stages require [M/H] ~ -0.45. In contrast, Vogel & Reimers derived [N/H] < -1.04 and

  11. Real-time dynamic range and signal to noise enhancement in beam-scanning microscopy by integration of sensor characteristics, data acquisition hardware, and statistical methods.

    PubMed

    Kissick, David J; Muir, Ryan D; Sullivan, Shane Z; Oglesbee, Robert A; Simpson, Garth J

    2013-02-14

    Despite the ubiquitous use of multi-photon and confocal microscopy measurements in biology, the core techniques typically suffer from fundamental compromises between signal to noise (S/N) and linear dynamic range (LDR). In this study, direct synchronous digitization of voltage transients coupled with statistical analysis is shown to allow S/N approaching the theoretical maximum throughout an LDR spanning more than 8 decades, limited only by the dark counts of the detector on the low end and by the intrinsic nonlinearities of the photomultiplier tube (PMT) detector on the high end. Synchronous digitization of each voltage transient represents a fundamental departure from established methods in confocal/multi-photon imaging, which are currently based on either photon counting or signal averaging. High information-density data acquisition (up to 3.2 GB/s of raw data) enables the smooth transition between the two modalities on a pixel-by-pixel basis and the ultimate writing of much smaller files (few kB/s). Modeling of the PMT response allows extraction of key sensor parameters from the histogram of voltage peak-heights. Applications in second harmonic generation (SHG) microscopy are described demonstrating S/N approaching the shot-noise limit of the detector over large dynamic ranges. PMID:24817799

  12. Real-time dynamic range and signal to noise enhancement in beam-scanning microscopy by integration of sensor characteristics, data acquisition hardware, and statistical methods

    NASA Astrophysics Data System (ADS)

    Kissick, David J.; Muir, Ryan D.; Sullivan, Shane Z.; Oglesbee, Robert A.; Simpson, Garth J.

    2013-02-01

    Despite the ubiquitous use of multi-photon and confocal microscopy measurements in biology, the core techniques typically suffer from fundamental compromises between signal to noise (S/N) and linear dynamic range (LDR). In this study, direct synchronous digitization of voltage transients coupled with statistical analysis is shown to allow S/N approaching the theoretical maximum throughout an LDR spanning more than 8 decades, limited only by the dark counts of the detector on the low end and by the intrinsic nonlinearities of the photomultiplier tube (PMT) detector on the high end. Synchronous digitization of each voltage transient represents a fundamental departure from established methods in confocal/multi-photon imaging, which are currently based on either photon counting or signal averaging. High information-density data acquisition (up to 3.2 GB/s of raw data) enables the smooth transition between the two modalities on a pixel-by-pixel basis and the ultimate writing of much smaller files (few kB/s). Modeling of the PMT response allows extraction of key sensor parameters from the histogram of voltage peak-heights. Applications in second harmonic generation (SHG) microscopy are described demonstrating S/N approaching the shot-noise limit of the detector over large dynamic ranges.

  13. On signals faint and sparse: The ACICA algorithm for blind de-trending of exoplanetary transits with low signal-to-noise

    SciTech Connect

    Waldmann, I. P.

    2014-01-01

    Independent component analysis (ICA) has recently been shown to be a promising new path in data analysis and de-trending of exoplanetary time series signals. Such approaches do not require or assume any prior or auxiliary knowledge about the data or instrument in order to de-convolve the astrophysical light curve signal from instrument or stellar systematic noise. These methods are often known as 'blind-source separation' (BSS) algorithms. Unfortunately, all BSS methods suffer from an amplitude and sign ambiguity of their de-convolved components, which severely limits these methods in low signal-to-noise (S/N) observations where their scalings cannot be determined otherwise. Here we present a novel approach to calibrate ICA using sparse wavelet calibrators. The Amplitude Calibrated Independent Component Analysis (ACICA) allows for the direct retrieval of the independent components' scalings and the robust de-trending of low S/N data. Such an approach gives us an unique and unprecedented insight in the underlying morphology of a data set, which makes this method a powerful tool for exoplanetary data de-trending and signal diagnostics.

  14. Standardised mortality ratio based on the sum of age and percentage total body surface area burned is an adequate quality indicator in burn care: An exploratory review.

    PubMed

    Steinvall, Ingrid; Elmasry, Moustafa; Fredrikson, Mats; Sjoberg, Folke

    2016-02-01

    Standardised Mortality Ratio (SMR) based on generic mortality predicting models is an established quality indicator in critical care. Burn-specific mortality models are preferred for the comparison among patients with burns as their predictive value is better. The aim was to assess whether the sum of age (years) and percentage total body surface area burned (which constitutes the Baux score) is acceptable in comparison to other more complex models, and to find out if data collected from a separate burn centre are sufficient for SMR based quality assessment. The predictive value of nine burn-specific models was tested by comparing values from the area under the receiver-operating characteristic curve (AUC) and a non-inferiority analysis using 1% as the limit (delta). SMR was analysed by comparing data from seven reference sources, including the North American National Burn Repository (NBR), with the observed mortality (years 1993-2012, n=1613, 80 deaths). The AUC values ranged between 0.934 and 0.976. The AUC 0.970 (95% CI 0.96-0.98) for the Baux score was non-inferior to the other models. SMR was 0.52 (95% CI 0.28-0.88) for the most recent five-year period compared with NBR based data. The analysis suggests that SMR based on the Baux score is eligible as an indicator of quality for setting standards of mortality in burn care. More advanced modelling only marginally improves the predictive value. The SMR can detect mortality differences in data from a single centre. PMID:26700877

  15. Spectral identification of minerals using imaging spectrometry data: Evaluating the effects of signal to noise and spectral resolution using the tricorder algorithm

    NASA Technical Reports Server (NTRS)

    Swayze, Gregg A.; Clark, Roger N.

    1995-01-01

    The rapid development of sophisticated imaging spectrometers and resulting flood of imaging spectrometry data has prompted a rapid parallel development of spectral-information extraction technology. Even though these extraction techniques have evolved along different lines (band-shape fitting, endmember unmixing, near-infrared analysis, neural-network fitting, and expert systems to name a few), all are limited by the spectrometer's signal to noise (S/N) and spectral resolution in producing useful information. This study grew from a need to quantitatively determine what effects these parameters have on our ability to differentiate between mineral absorption features using a band-shape fitting algorithm. We chose to evaluate the AVIRIS, HYDICE, MIVIS, GERIS, VIMS, NIMS, and ASTER instruments because they collect data over wide S/N and spectral-resolution ranges. The study evaluates the performance of the Tricorder algorithm, in differentiating between mineral spectra in the 0.4-2.5 micrometer spectral region. The strength of the Tricorder algorithm is in its ability to produce an easily understood comparison of band shape that can concentrate on small relevant portions of the spectra, giving it an advantage over most unmixing schemes, and in that it need not spend large amounts of time reoptimizing each time a new mineral component is added to its reference library, as is the case with neural-network schemes. We believe the flexibility of the Tricorder algorithm is unparalleled among spectral-extraction techniques and that the results from this study, although dealing with minerals, will have direct applications to spectral identification in other disciplines.

  16. MEASUREMENT OF THE RADIUS OF NEUTRON STARS WITH HIGH SIGNAL-TO-NOISE QUIESCENT LOW-MASS X-RAY BINARIES IN GLOBULAR CLUSTERS

    SciTech Connect

    Guillot, Sebastien; Rutledge, Robert E.; Servillat, Mathieu; Webb, Natalie A. E-mail: rutledge@physics.mcgill.ca

    2013-07-20

    This paper presents the measurement of the neutron star (NS) radius using the thermal spectra from quiescent low-mass X-ray binaries (qLMXBs) inside globular clusters (GCs). Recent observations of NSs have presented evidence that cold ultra dense matter-present in the core of NSs-is best described by ''normal matter'' equations of state (EoSs). Such EoSs predict that the radii of NSs, R{sub NS}, are quasi-constant (within measurement errors, of {approx}10%) for astrophysically relevant masses (M{sub NS}>0.5 M{sub Sun }). The present work adopts this theoretical prediction as an assumption, and uses it to constrain a single R{sub NS} value from five qLMXB targets with available high signal-to-noise X-ray spectroscopic data. Employing a Markov chain Monte-Carlo approach, we produce the marginalized posterior distribution for R{sub NS}, constrained to be the same value for all five NSs in the sample. An effort was made to include all quantifiable sources of uncertainty into the uncertainty of the quoted radius measurement. These include the uncertainties in the distances to the GCs, the uncertainties due to the Galactic absorption in the direction of the GCs, and the possibility of a hard power-law spectral component for count excesses at high photon energy, which are observed in some qLMXBs in the Galactic plane. Using conservative assumptions, we found that the radius, common to the five qLMXBs and constant for a wide range of masses, lies in the low range of possible NS radii, R{sub NS}=9.1{sup +1.3}{sub -1.5} km (90%-confidence). Such a value is consistent with low-R{sub NS} equations of state. We compare this result with previous radius measurements of NSs from various analyses of different types of systems. In addition, we compare the spectral analyses of individual qLMXBs to previous works.

  17. Self-consistent signal-to-noise analysis of the statistical behavior of analog neural networks and enhancement of the storage capacity

    NASA Astrophysics Data System (ADS)

    Shiino, Masatoshi; Fukai, Tomoki

    1993-08-01

    Based on the self-consistent signal-to-noise analysis (SCSNA) capable of dealing with analog neural networks with a wide class of transfer functions, enhancement of the storage capacity of associative memory and the related statistical properties of neural networks are studied for random memory patterns. Two types of transfer functions with the threshold parameter θ are considered, which are derived from the sigmoidal one to represent the output of three-state neurons. Neural networks having a monotonically increasing transfer function FM, FM(u)=sgnu (||u||>θ), FM(u)=0 (||u||<=θ), are shown to make it impossible for the spin-glass state to coexist with retrieval states in a certain parameter region of θ and α (loading rate of memory patterns), implying the reduction of the number of spurious states. The behavior of the storage capacity with changing θ is qualitatively the same as that of the Ising spin neural networks with varying temperature. On the other hand, the nonmonotonic transfer function FNM, FNM(u)=sgnu (||u||<θ), FNM(u)=0 (||u||>=θ) gives rise to remarkable features in several respects. First, it yields a large enhancement of the storage capacity compared with the Amit-Gutfreund-Sompolinsky (AGS) value: with decreasing θ from θ=∞, the storage capacity αc of such a network is increased from the AGS value (~=0.14) to attain its maximum value of ~=0.42 at θ~=0.7 and afterwards is decreased to vanish at θ=0. Whereas for θ>~1 the storage capacity αc coincides with the value αc~ determined by the SCSNA as the upper bound of α ensuring the existence of retrieval solutions, for θ<~1 the αc is shown to differ from the αc~ with the result that the retrieval solutions claimed by the SCSNA are unstable for αc<α<αc~. Second, in the case of θ<1 the network can exhibit a new type of phase which appears as a result of a phase transition with respect to the non-Gaussian distribution of the local fields of neurons: the standard type of retrieval

  18. Beam-splitting ratio impact on the SNR for the balanced heterodyne

    NASA Astrophysics Data System (ADS)

    Jin, Lumei; Zhu, YongGuo

    2016-05-01

    Considered the beam-splitting ratio, the mathematical model of balanced heterodyne receiver is established, and the mathematical expression of the relationship between the signal-to-noise ratio and the beam-splitting ratio is obtained. Based on the experiment, we got the best range of beam-splitting ratio which is 0.159-0.5. The experiment results show that, in the framework of the best beam-splitting ratio, the balanced heterodyne receiver has better signal-to-noise ratio than the common heterodyne receiver.

  19. Ratio

    NASA Astrophysics Data System (ADS)

    Webster, Nathan A. S.; Pownceby, Mark I.; Madsen, Ian C.; Studer, Andrew J.; Manuel, James R.; Kimpton, Justin A.

    2014-12-01

    Effects of basicity, B (CaO:SiO2 ratio) on the thermal range, concentration, and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA) and SFCA-I iron ore sinter bonding phases have been investigated using an in situ synchrotron X-ray diffraction-based methodology with subsequent Rietveld refinement-based quantitative phase analysis. SFCA and SFCA-I phases are the key bonding materials in iron ore sinter, and improved understanding of the effects of processing parameters such as basicity on their formation and decomposition may assist in improving efficiency of industrial iron ore sintering operations. Increasing basicity significantly increased the thermal range of SFCA-I, from 1363 K to 1533 K (1090 °C to 1260 °C) for a mixture with B = 2.48, to ~1339 K to 1535 K (1066 °C to 1262 °C) for a mixture with B = 3.96, and to ~1323 K to 1593 K (1050 °C to 1320 °C) at B = 4.94. Increasing basicity also increased the amount of SFCA-I formed, from 18 wt pct for the mixture with B = 2.48 to 25 wt pct for the B = 4.94 mixture. Higher basicity of the starting sinter mixture will, therefore, increase the amount of SFCA-I, considered to be more desirable of the two phases. Basicity did not appear to significantly influence the formation mechanism of SFCA-I. It did, however, affect the formation mechanism of SFCA, with the decomposition of SFCA-I coinciding with the formation of a significant amount of additional SFCA in the B = 2.48 and 3.96 mixtures but only a minor amount in the highest basicity mixture. In situ neutron diffraction enabled characterization of the behavior of magnetite after melting of SFCA produced a magnetite plus melt phase assemblage.

  20. Improvement of signal-to-noise ratio of optoacoustic signals from double-walled carbon nanotubes by using an array of dual-wavelength high-power diode lasers

    NASA Astrophysics Data System (ADS)

    Leggio, Luca; de Varona, Omar E.; Escudero, Pedro; Carpintero del Barrio, Guillermo; Osiński, Marek; Lamela Rivera, Horacio

    2015-07-01

    Optoacoustic (OA) imaging is a rising biomedical technique that has attracted much interest over the last 15 years. This technique permits to visualize the internal soft tissues in depth by using short laser pulses, able to generate ultrasonic signals in a large frequency range. It combines the high contrast of optical imaging with the high resolution of ultrasound systems. The OA signals detected from the whole surface of the body serve to reconstruct in detail the image of the internal tissues, where the absorbed optical energy distribution outlines the regions of interest. In fact, the use of contrast agents could improve the detection of growing anomalies in soft tissues, such as carcinomas. This work proposes the use of double-walled carbon nanotubes (DWCNTs) as a potential nontoxic biodegradable contrast agent applicable in OA to reveal the presence of malignant in-depth tissues in near infrared (NIR) wavelength range (0.75-1.4 μm), where the biological tissues are fairly transparent to optical radiation. A dual-wavelength (870 and 905 nm) OA system is presented, based on arrays of high power diode lasers (HPDLs) that generate ultrasound signals from a DWCNT solution embedded within a biological phantom. The OA signals generated by DWCNTs are compared with those obtained using black ink, considered to be a very good absorber at these wavelengths. The experiments prove that DWCNTs are a potential contrast agent for optoacoustic spectroscopy (OAS).

  1. Funding the Formula Adequately in Oklahoma

    ERIC Educational Resources Information Center

    Hancock, Kenneth

    2015-01-01

    This report is a longevity, simulational study that looks at how the ratio of state support to local support effects the number of school districts that breaks the common school's funding formula which in turns effects the equity of distribution to the common schools. After nearly two decades of adequately supporting the funding formula, Oklahoma…

  2. 21 CFR 1404.900 - Adequate evidence.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Adequate evidence. 1404.900 Section 1404.900 Food and Drugs OFFICE OF NATIONAL DRUG CONTROL POLICY GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 1404.900 Adequate evidence. Adequate evidence means information sufficient to support the reasonable belief that a particular...

  3. 29 CFR 98.900 - Adequate evidence.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 1 2010-07-01 2010-07-01 true Adequate evidence. 98.900 Section 98.900 Labor Office of the Secretary of Labor GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 98.900 Adequate evidence. Adequate evidence means information sufficient to support the reasonable belief that a...

  4. 34 CFR 85.900 - Adequate evidence.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) Definitions § 85.900 Adequate evidence. Adequate evidence means information sufficient to support the reasonable belief that a particular act or omission has occurred. Authority: E.O. 12549 (3 CFR, 1986 Comp., p. 189); E.O 12689 (3 CFR, 1989 Comp., p. 235); 20 U.S.C. 1082, 1094, 1221e-3 and 3474; and Sec....

  5. 29 CFR 452.110 - Adequate safeguards.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 2 2010-07-01 2010-07-01 false Adequate safeguards. 452.110 Section 452.110 Labor... DISCLOSURE ACT OF 1959 Election Procedures; Rights of Members § 452.110 Adequate safeguards. (a) In addition to the election safeguards discussed in this part, the Act contains a general mandate in section...

  6. 29 CFR 452.110 - Adequate safeguards.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 2 2011-07-01 2011-07-01 false Adequate safeguards. 452.110 Section 452.110 Labor... DISCLOSURE ACT OF 1959 Election Procedures; Rights of Members § 452.110 Adequate safeguards. (a) In addition to the election safeguards discussed in this part, the Act contains a general mandate in section...

  7. Americans Getting Adequate Water Daily, CDC Finds

    MedlinePlus

    ... medlineplus/news/fullstory_158510.html Americans Getting Adequate Water Daily, CDC Finds Men take in an average ... new government report finds most are getting enough water each day. The data, from the U.S. National ...

  8. Americans Getting Adequate Water Daily, CDC Finds

    MedlinePlus

    ... gov/news/fullstory_158510.html Americans Getting Adequate Water Daily, CDC Finds Men take in an average ... new government report finds most are getting enough water each day. The data, from the U.S. National ...

  9. COS FUV Flat Fields and Signal-to-Noise Characteristics

    NASA Astrophysics Data System (ADS)

    Ake, Thomas B.; Massa, D.; Beland, S.; France, K.; Penton, S. V.; Sahnow, D.; McPhate, J.

    2010-07-01

    The COS FUV channel employs a detector comprised of two microchannel plate (MCP) segments with cross delay line anodes. The detector shows several types of non-uniformities due to the hexagonal and moire patterns in the MCPs, dead spots, gain variations, and shadows from the wire grid installed in front of the MCPs to increase quantum efficiency. These features induce fixed-pattern noise in FUV spectra. The effects of these artifacts can be reduced by dividing the data by a flat field and combining exposures taken at different grating settings. A spectral iterative technique, similar to that used for GHRS and FOS, shows that S/N > 100 can be achieved in extracted spectra. Although flat field observations were obtained during SMOV using white dwarfs, a two dimensional flat field of sufficient quality for standard CALCOS processing was not achieved. Other methodologies are being explored for flat field correction and are expected to be installed in CALCOS to improve the S/N of data incrementally. As an initial step, CALCOS currently ignores grid wire regions when creating a summed spectrum from exposures taken at different FP-POS positions. Average one-dimensional flats generated through spectral iteration have been investigated to correct individual exposures and show promise as an alternate flat fielding methodology. These may require separate flat fields for different cross-dispersion locations. An important result is that the flat fields and flux calibrations used by CALCOS are dependent on each other and should be derived together.

  10. Signal-to-noise limitations in white light holography

    NASA Technical Reports Server (NTRS)

    Ribak, Erez; Breckinridge, James B.; Roddier, Claude; Roddier, Francois

    1988-01-01

    A simple derivation is given for the SNR in images reconstructed from incoherent holograms. Dependence is shown to be on the hologram SNR, object complexity, and the number of pixels in the detector. Reconstruction of involved objects becomes possible with high-dynamic-range detectors such as CCDs. White-light holograms have been produced by means of a rotational shear interferometer combined with a chromatic corrector. A digital inverse transform recreated the object.

  11. Asbestos/NESHAP adequately wet guidance

    SciTech Connect

    Shafer, R.; Throwe, S.; Salgado, O.; Garlow, C.; Hoerath, E.

    1990-12-01

    The Asbestos NESHAP requires facility owners and/or operators involved in demolition and renovation activities to control emissions of particulate asbestos to the outside air because no safe concentration of airborne asbestos has ever been established. The primary method used to control asbestos emissions is to adequately wet the Asbestos Containing Material (ACM) with a wetting agent prior to, during and after demolition/renovation activities. The purpose of the document is to provide guidance to asbestos inspectors and the regulated community on how to determine if friable ACM is adequately wet as required by the Asbestos NESHAP.

  12. Adequate supervision for children and adolescents.

    PubMed

    Anderst, James; Moffatt, Mary

    2014-11-01

    Primary care providers (PCPs) have the opportunity to improve child health and well-being by addressing supervision issues before an injury or exposure has occurred and/or after an injury or exposure has occurred. Appropriate anticipatory guidance on supervision at well-child visits can improve supervision of children, and may prevent future harm. Adequate supervision varies based on the child's development and maturity, and the risks in the child's environment. Consideration should be given to issues as wide ranging as swimming pools, falls, dating violence, and social media. By considering the likelihood of harm and the severity of the potential harm, caregivers may provide adequate supervision by minimizing risks to the child while still allowing the child to take "small" risks as needed for healthy development. Caregivers should initially focus on direct (visual, auditory, and proximity) supervision of the young child. Gradually, supervision needs to be adjusted as the child develops, emphasizing a safe environment and safe social interactions, with graduated independence. PCPs may foster adequate supervision by providing concrete guidance to caregivers. In addition to preventing injury, supervision includes fostering a safe, stable, and nurturing relationship with every child. PCPs should be familiar with age/developmentally based supervision risks, adequate supervision based on those risks, characteristics of neglectful supervision based on age/development, and ways to encourage appropriate supervision throughout childhood. PMID:25369578

  13. Small Rural Schools CAN Have Adequate Curriculums.

    ERIC Educational Resources Information Center

    Loustaunau, Martha

    The small rural school's foremost and largest problem is providing an adequate curriculum for students in a changing world. Often the small district cannot or is not willing to pay the per-pupil cost of curriculum specialists, specialized courses using expensive equipment no more than one period a day, and remodeled rooms to accommodate new…

  14. A declaration of independence for Mg/Si. [Al/Si intensity ratio predictive usefulness for Mg/Si intensity ratio in lunar X-ray fluorescence

    NASA Technical Reports Server (NTRS)

    Hubbard, N.; Keith, J. E.

    1978-01-01

    The weak covariation that exists between Al/Si and Mg/Si for large areas of the lunar surface is little, if any, stronger than that forced on a random set of numbers that are subject to closure. The Mg and Al variations implied by the Mg/Si and Al/Si intensity ratio data are qualitatively like those seen in lunar soil sample data. Two petrogenetic provinces are suggested for terra materials; one appears to have 50% higher Mg values than the other. Using the improved data, Mg/Si variations can be studied at a signal-to-noise ratio greater than 5/1.

  15. CALIPSO lidar ratio retrieval over the ocean.

    PubMed

    Josset, Damien; Rogers, Raymond; Pelon, Jacques; Hu, Yongxiang; Liu, Zhaoyan; Omar, Ali; Zhai, Peng-Wang

    2011-09-12

    We are demonstrating on a few cases the capability of CALIPSO to retrieve the 532 nm lidar ratio over the ocean when CloudSat surface scattering cross section is used as a constraint. We are presenting the algorithm used and comparisons with the column lidar ratio retrieved by the NASA airborne high spectral resolution lidar. For the three cases presented here, the agreement is fairly good. The average CALIPSO 532 nm column lidar ratio bias is 13.7% relative to HSRL, and the relative standard deviation is 13.6%. Considering the natural variability of aerosol microphysical properties, this level of accuracy is significant since the lidar ratio is a good indicator of aerosol types. We are discussing dependencies of the accuracy of retrieved aerosol lidar ratio on atmospheric aerosol homogeneity, lidar signal to noise ratio, and errors in the optical depth retrievals. We are obtaining the best result (bias 7% and standard deviation around 6%) for a nighttime case with a relatively constant lidar ratio (in the vertical) indicative of homogeneous aerosol type. PMID:21935239

  16. CALIPSO Lidar Ratio Retrieval Over the Ocean

    NASA Technical Reports Server (NTRS)

    Josset, Damien B.; Rogers, Raymond R.; Pelon, Jacques; Hu, Yongxiang; Liu, Zhaoyan; Omar, Ali H.; Zhai, Peng-Wang

    2011-01-01

    We are demonstrating on a few cases the capability of CALIPSO to retrieve the 532 nm lidar ratio over the ocean when CloudSat surface scattering cross section is used as a constraint. We are presenting the algorithm used and comparisons with the column lidar ratio retrieved by the NASA airborne high spectral resolution lidar. For the three cases presented here, the agreement is fairly good. The average CALIPSO 532 nm column lidar ratio bias is 13.7% relative to HSRL, and the relative standard deviation is 13.6%. Considering the natural variability of aerosol microphysical properties, this level of accuracy is significant since the lidar ratio is a good indicator of aerosol types. We are discussing dependencies of the accuracy of retrieved aerosol lidar ratio on atmospheric aerosol homogeneity, lidar signal to noise ratio, and errors in the optical depth retrievals. We are obtaining the best result (bias 7% and standard deviation around 6%) for a nighttime case with a relatively constant lidar ratio (in the vertical) indicative of homogeneous aerosol type

  17. Multicanonical Determination of the Symbol Error Ratio of WDM Polarization Multiplexed QPSK Systems

    NASA Astrophysics Data System (ADS)

    Soliman, George; Yevick, David

    2014-12-01

    The multicanonical method is applied to the calculation of the symbol error ratio (SER) as a function of the optical signal to noise ratio (OSNR) at the receiver for a polarization multiplexed quadrature phase shift keying (PM-QPSK) wavelength division multiplexed (WDM) system. We improve upon previous calculations by including polarization mode dispersion (PMD) and subsequently verifying the numerical accuracy of our calculations. Our numerical studies demonstrate that acceptable accuracy can be achieved even when advancing the polarization through the fiber with relatively large propagation step lengths.

  18. Is a vegetarian diet adequate for children.

    PubMed

    Hackett, A; Nathan, I; Burgess, L

    1998-01-01

    The number of people who avoid eating meat is growing, especially among young people. Benefits to health from a vegetarian diet have been reported in adults but it is not clear to what extent these benefits are due to diet or to other aspects of lifestyles. In children concern has been expressed concerning the adequacy of vegetarian diets especially with regard to growth. The risks/benefits seem to be related to the degree of restriction of he diet; anaemia is probably both the main and the most serious risk but this also applies to omnivores. Vegan diets are more likely to be associated with malnutrition, especially if the diets are the result of authoritarian dogma. Overall, lacto-ovo-vegetarian children consume diets closer to recommendations than omnivores and their pre-pubertal growth is at least as good. The simplest strategy when becoming vegetarian may involve reliance on vegetarian convenience foods which are not necessarily superior in nutritional composition. The vegetarian sector of the food industry could do more to produce foods closer to recommendations. Vegetarian diets can be, but are not necessarily, adequate for children, providing vigilance is maintained, particularly to ensure variety. Identical comments apply to omnivorous diets. Three threats to the diet of children are too much reliance on convenience foods, lack of variety and lack of exercise. PMID:9670174

  19. 21 CFR 201.5 - Drugs; adequate directions for use.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 4 2010-04-01 2010-04-01 false Drugs; adequate directions for use. 201.5 Section...) DRUGS: GENERAL LABELING General Labeling Provisions § 201.5 Drugs; adequate directions for use. Adequate directions for use means directions under which the layman can use a drug safely and for the purposes...

  20. 21 CFR 201.5 - Drugs; adequate directions for use.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 4 2011-04-01 2011-04-01 false Drugs; adequate directions for use. 201.5 Section...) DRUGS: GENERAL LABELING General Labeling Provisions § 201.5 Drugs; adequate directions for use. Adequate directions for use means directions under which the layman can use a drug safely and for the purposes...

  1. 4 CFR 200.14 - Responsibility for maintaining adequate safeguards.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 4 Accounts 1 2010-01-01 2010-01-01 false Responsibility for maintaining adequate safeguards. 200.14 Section 200.14 Accounts RECOVERY ACCOUNTABILITY AND TRANSPARENCY BOARD PRIVACY ACT OF 1974 § 200.14 Responsibility for maintaining adequate safeguards. The Board has the responsibility for maintaining adequate technical, physical, and...

  2. 10 CFR 1304.114 - Responsibility for maintaining adequate safeguards.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Responsibility for maintaining adequate safeguards. 1304.114 Section 1304.114 Energy NUCLEAR WASTE TECHNICAL REVIEW BOARD PRIVACY ACT OF 1974 § 1304.114 Responsibility for maintaining adequate safeguards. The Board has the responsibility for maintaining adequate technical, physical, and security...

  3. 10 CFR 1304.114 - Responsibility for maintaining adequate safeguards.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Responsibility for maintaining adequate safeguards. 1304.114 Section 1304.114 Energy NUCLEAR WASTE TECHNICAL REVIEW BOARD PRIVACY ACT OF 1974 § 1304.114 Responsibility for maintaining adequate safeguards. The Board has the responsibility for maintaining adequate technical, physical, and security...

  4. 4 CFR 200.14 - Responsibility for maintaining adequate safeguards.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 4 Accounts 1 2011-01-01 2011-01-01 false Responsibility for maintaining adequate safeguards. 200....14 Responsibility for maintaining adequate safeguards. The Board has the responsibility for maintaining adequate technical, physical, and security safeguards to prevent unauthorized disclosure...

  5. MR Scanner Systems Should Be Adequately Characterized in Diffusion-MRI of the Breast

    PubMed Central

    Giannelli, Marco; Sghedoni, Roberto; Iacconi, Chiara; Iori, Mauro; Traino, Antonio Claudio; Guerrisi, Maria; Mascalchi, Mario; Toschi, Nicola; Diciotti, Stefano

    2014-01-01

    Breast imaging represents a relatively recent and promising field of application of quantitative diffusion-MRI techniques. In view of the importance of guaranteeing and assessing its reliability in clinical as well as research settings, the aim of this study was to specifically characterize how the main MR scanner system-related factors affect quantitative measurements in diffusion-MRI of the breast. In particular, phantom acquisitions were performed on three 1.5 T MR scanner systems by different manufacturers, all equipped with a dedicated multi-channel breast coil as well as acquisition sequences for diffusion-MRI of the breast. We assessed the accuracy, inter-scan and inter-scanner reproducibility of the mean apparent diffusion coefficient measured along the main orthogonal directions () as well as of diffusion-tensor imaging (DTI)-derived mean diffusivity (MD) measurements. Additionally, we estimated spatial non-uniformity of (NU) and MD (NUMD) maps. We showed that the signal-to-noise ratio as well as overall calibration of high strength diffusion gradients system in typical acquisition sequences for diffusion-MRI of the breast varied across MR scanner systems, introducing systematic bias in the measurements of diffusion indices. While and MD values were not appreciably different from each other, they substantially varied across MR scanner systems. The mean of the accuracies of measured and MD was in the range [−2.3%,11.9%], and the mean of the coefficients of variation for and MD measurements across MR scanner systems was 6.8%. The coefficient of variation for repeated measurements of both and MD was < 1%, while NU and NUMD values were <4%. Our results highlight that MR scanner system-related factors can substantially affect quantitative diffusion-MRI of the breast. Therefore, a specific quality control program for assessing and monitoring the performance of MR scanner systems for diffusion-MRI of the breast is

  6. Estimates of Adequate School Spending by State Based on National Average Service Levels.

    ERIC Educational Resources Information Center

    Miner, Jerry

    1983-01-01

    Proposes a method for estimating expenditures per student needed to provide educational adequacy in each state. Illustrates the method using U.S., Arkansas, New York, Texas, and Washington State data, covering instruction, special needs, operations and maintenance, administration, and other costs. Estimates ratios of "adequate" to actual spending…

  7. 7 CFR 4290.200 - Adequate capital for RBICs.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 15 2011-01-01 2011-01-01 false Adequate capital for RBICs. 4290.200 Section 4290.200 Agriculture Regulations of the Department of Agriculture (Continued) RURAL BUSINESS-COOPERATIVE SERVICE AND... Qualifications for the RBIC Program Capitalizing A Rbic § 4290.200 Adequate capital for RBICs. You must meet...

  8. 13 CFR 107.200 - Adequate capital for Licensees.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 13 Business Credit and Assistance 1 2011-01-01 2011-01-01 false Adequate capital for Licensees... INVESTMENT COMPANIES Qualifying for an SBIC License Capitalizing An Sbic § 107.200 Adequate capital for... Licensee, and to receive Leverage. (a) You must have enough Regulatory Capital to provide...

  9. 13 CFR 107.200 - Adequate capital for Licensees.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Adequate capital for Licensees... INVESTMENT COMPANIES Qualifying for an SBIC License Capitalizing An Sbic § 107.200 Adequate capital for... Licensee, and to receive Leverage. (a) You must have enough Regulatory Capital to provide...

  10. 7 CFR 4290.200 - Adequate capital for RBICs.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Adequate capital for RBICs. 4290.200 Section 4290.200 Agriculture Regulations of the Department of Agriculture (Continued) RURAL BUSINESS-COOPERATIVE SERVICE AND... Qualifications for the RBIC Program Capitalizing A Rbic § 4290.200 Adequate capital for RBICs. You must meet...

  11. 10 CFR 1304.114 - Responsibility for maintaining adequate safeguards.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 4 2011-01-01 2011-01-01 false Responsibility for maintaining adequate safeguards. 1304.114 Section 1304.114 Energy NUCLEAR WASTE TECHNICAL REVIEW BOARD PRIVACY ACT OF 1974 § 1304.114 Responsibility for maintaining adequate safeguards. The Board has the responsibility for maintaining...

  12. 40 CFR 716.25 - Adequate file search.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Adequate file search. 716.25 Section 716.25 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT HEALTH AND SAFETY DATA REPORTING General Provisions § 716.25 Adequate file search. The scope of...

  13. 40 CFR 51.354 - Adequate tools and resources.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 2 2011-07-01 2011-07-01 false Adequate tools and resources. 51.354... Requirements § 51.354 Adequate tools and resources. (a) Administrative resources. The program shall maintain the administrative resources necessary to perform all of the program functions including...

  14. 40 CFR 51.354 - Adequate tools and resources.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 2 2012-07-01 2012-07-01 false Adequate tools and resources. 51.354... Requirements § 51.354 Adequate tools and resources. (a) Administrative resources. The program shall maintain the administrative resources necessary to perform all of the program functions including...

  15. 40 CFR 51.354 - Adequate tools and resources.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 2 2014-07-01 2014-07-01 false Adequate tools and resources. 51.354... Requirements § 51.354 Adequate tools and resources. (a) Administrative resources. The program shall maintain the administrative resources necessary to perform all of the program functions including...

  16. 40 CFR 51.354 - Adequate tools and resources.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 2 2013-07-01 2013-07-01 false Adequate tools and resources. 51.354... Requirements § 51.354 Adequate tools and resources. (a) Administrative resources. The program shall maintain the administrative resources necessary to perform all of the program functions including...

  17. 40 CFR 716.25 - Adequate file search.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Adequate file search. 716.25 Section... ACT HEALTH AND SAFETY DATA REPORTING General Provisions § 716.25 Adequate file search. The scope of a person's responsibility to search records is limited to records in the location(s) where the...

  18. 40 CFR 716.25 - Adequate file search.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Adequate file search. 716.25 Section... ACT HEALTH AND SAFETY DATA REPORTING General Provisions § 716.25 Adequate file search. The scope of a person's responsibility to search records is limited to records in the location(s) where the...

  19. 40 CFR 716.25 - Adequate file search.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Adequate file search. 716.25 Section... ACT HEALTH AND SAFETY DATA REPORTING General Provisions § 716.25 Adequate file search. The scope of a person's responsibility to search records is limited to records in the location(s) where the...

  20. 40 CFR 716.25 - Adequate file search.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Adequate file search. 716.25 Section... ACT HEALTH AND SAFETY DATA REPORTING General Provisions § 716.25 Adequate file search. The scope of a person's responsibility to search records is limited to records in the location(s) where the...

  1. 10 CFR 1304.114 - Responsibility for maintaining adequate safeguards.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 4 2014-01-01 2014-01-01 false Responsibility for maintaining adequate safeguards. 1304.114 Section 1304.114 Energy NUCLEAR WASTE TECHNICAL REVIEW BOARD PRIVACY ACT OF 1974 § 1304.114 Responsibility for maintaining adequate safeguards. The Board has the responsibility for maintaining...

  2. 10 CFR 1304.114 - Responsibility for maintaining adequate safeguards.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 4 2013-01-01 2013-01-01 false Responsibility for maintaining adequate safeguards. 1304.114 Section 1304.114 Energy NUCLEAR WASTE TECHNICAL REVIEW BOARD PRIVACY ACT OF 1974 § 1304.114 Responsibility for maintaining adequate safeguards. The Board has the responsibility for maintaining...

  3. 10 CFR 503.35 - Inability to obtain adequate capital.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Inability to obtain adequate capital. 503.35 Section 503.35 Energy DEPARTMENT OF ENERGY (CONTINUED) ALTERNATE FUELS NEW FACILITIES Permanent Exemptions for New Facilities § 503.35 Inability to obtain adequate capital. (a) Eligibility. Section 212(a)(1)(D)...

  4. 10 CFR 503.35 - Inability to obtain adequate capital.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 4 2011-01-01 2011-01-01 false Inability to obtain adequate capital. 503.35 Section 503.35 Energy DEPARTMENT OF ENERGY (CONTINUED) ALTERNATE FUELS NEW FACILITIES Permanent Exemptions for New Facilities § 503.35 Inability to obtain adequate capital. (a) Eligibility. Section 212(a)(1)(D)...

  5. 15 CFR 970.404 - Adequate exploration plan.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... ENVIRONMENTAL DATA SERVICE DEEP SEABED MINING REGULATIONS FOR EXPLORATION LICENSES Certification of Applications § 970.404 Adequate exploration plan. Before he may certify an application, the Administrator must find... 15 Commerce and Foreign Trade 3 2011-01-01 2011-01-01 false Adequate exploration plan....

  6. 15 CFR 970.404 - Adequate exploration plan.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... ENVIRONMENTAL DATA SERVICE DEEP SEABED MINING REGULATIONS FOR EXPLORATION LICENSES Certification of Applications § 970.404 Adequate exploration plan. Before he may certify an application, the Administrator must find... 15 Commerce and Foreign Trade 3 2010-01-01 2010-01-01 false Adequate exploration plan....

  7. "Something Adequate"? In Memoriam Seamus Heaney, Sister Quinlan, Nirbhaya

    ERIC Educational Resources Information Center

    Parker, Jan

    2014-01-01

    Seamus Heaney talked of poetry's responsibility to represent the "bloody miracle", the "terrible beauty" of atrocity; to create "something adequate". This article asks, what is adequate to the burning and eating of a nun and the murderous gang rape and evisceration of a medical student? It considers Njabulo…

  8. Noise caused by a finite extinction ratio of the light modulator in CW cavity ring-down spectroscopy

    NASA Astrophysics Data System (ADS)

    Huang, H.; Lehmann, K. K.

    2009-02-01

    A model is presented for the effect of a finite extinction ratio of the light modulator used in continuous wave cavity ring-down spectroscopy (CW-CRDS) experiments. We present a simple analytical expression for the minimum isolation required to prevent a significant increase in the fluctuations of the cavity decay rate, which determine the sensitivity of the method. We also present systematic measurements of the signal to noise in CW-CRDS as a function of the effective isolation of the light modulator, and excellent agreement with the model is found.

  9. Optimized Signal-To Ratio with Shot Noise Limited Detection in Stimulated Raman Scattering Microscopy

    NASA Astrophysics Data System (ADS)

    Moester, M. J. B.; Ariese, F.; de Boer, J. F.

    2015-04-01

    We describe our set-up for Stimulated Raman Scattering (SRS) microscopy with shot noise limited detection for a broad window of biologically relevant laser powers. This set-up is used to demonstrate that the highest signal-to-noise ratio (SNR) in SRS with shot noise limited detection is achieved with a time-averaged laser power ratio of 1:2 of the unmodulated and modulated beam. In SRS, two different coloured laser beams are incident on a sample. If the energy difference between them matches a molecular vibration of a molecule, energy can be transferred from one beam to the other. By applying amplitude modulation to one of the beams, the modulation transfer to the other beam can be measured. The efficiency of this process is a direct measure for the number of molecules of interest in the focal volume. Combined with laser scanning microscopy, this technique allows for fast and sensitive imaging with sub-micrometre resolution. Recent technological advances have resulted in an improvement of the sensitivity of SRS applications, but few show shot noise limited detection. The dominant noise source in this SRS microscope is the shot noise of the unmodulated, detected beam. Under the assumption that photodamage is linear with the total laser power, the optimal SNR shifts away from equal beam powers, where the most signal is generated, to a 1:2 power ratio. Under these conditions the SNR is maximized and the total laser power that could induce photodamage is minimized. Compared to using a 1:1 laser power ratio, we show improved image quality and a signal-to-noise ratio improvement of 8 % in polystyrene beads and C. Elegans worms. Including a non-linear damage mechanism in the analysis, we find that the optimal power ratio converges to a 1:1 ratio with increasing order of the non-linear damage mechanism.

  10. Computed Tomography Image Compressibility and Limitations of Compression Ratio-Based Guidelines.

    PubMed

    Pambrun, Jean-François; Noumeir, Rita

    2015-12-01

    Finding optimal compression levels for diagnostic imaging is not an easy task. Significant compressibility variations exist between modalities, but little is known about compressibility variations within modalities. Moreover, compressibility is affected by acquisition parameters. In this study, we evaluate the compressibility of thousands of computed tomography (CT) slices acquired with different slice thicknesses, exposures, reconstruction filters, slice collimations, and pitches. We demonstrate that exposure, slice thickness, and reconstruction filters have a significant impact on image compressibility due to an increased high frequency content and a lower acquisition signal-to-noise ratio. We also show that compression ratio is not a good fidelity measure. Therefore, guidelines based on compression ratio should ideally be replaced with other compression measures better correlated with image fidelity. Value-of-interest (VOI) transformations also affect the perception of quality. We have studied the effect of value-of-interest transformation and found significant masking of artifacts when window is widened. PMID:25804842

  11. Arabidopsis: An Adequate Model for Dicot Root Systems?

    PubMed

    Zobel, Richard W

    2016-01-01

    The Arabidopsis root system is frequently considered to have only three classes of root: primary, lateral, and adventitious. Research with other plant species has suggested up to eight different developmental/functional classes of root for a given plant root system. If Arabidopsis has only three classes of root, it may not be an adequate model for eudicot plant root systems. Recent research, however, can be interpreted to suggest that pre-flowering Arabidopsis does have at least five (5) of these classes of root. This then suggests that Arabidopsis root research can be considered an adequate model for dicot plant root systems. PMID:26904040

  12. A High Aspect Ratio Microelectrode Array for Mapping Neural Activity in-vitro

    PubMed Central

    Kibler, Andrew B.; Jamieson, Brian G.; Durand, Dominique M.

    2011-01-01

    A novel high-aspect-ratio penetrating microelectrode array was designed and fabricated for the purpose of recording neural activity. The array allows two dimensional recording of 64 sites in vitro with high aspect ratio penetrating electrodes. Traditional surface electrode arrays, although easy to fabricate, do not penetrate to the viable tissue such as central hippocampus slices and thus have a lower signal/noise ratio and lower selectivity than a penetrating array. In the unfolded hippocampus preparation, the CA1–CA3 pyramidal cell layer in the whole unfolded rodent hippocampus preparation is encased by the alveus on one side and the Schaffer tract on the other and requires penetrating electrodes for high signal to noise ratio recording. An array of 64 electrode spikes, each with a target height of 200 μm and diameter of 20μm, was fabricated in silicon on a transparent glass substrate. The impedance of the individual electrodes was measured to be approximately 1.5MΩ± 497kΩ. The signal to noise ratio was measured and found to be 19.4 ± 3 dB compared to 3.9 ± 0.8 dB S/N for signals obtained with voltage sensitive dye RH414. A mouse unfolded hippocampus preparation was bathed in solution containing 50 micro-molar 4-Amino Pyridine and a complex two dimensional wave of activity was recorded using the array. These results indicate that this novel penetrating electrode array is able to obtain data superior to that of voltage sensitive dye techniques for broad field two-dimensional neuronal activity recording. When used with the unfolded hippocampus preparation, the combination forms a uniquely capable tool for imaging hippocampal network activity in the entire hippocampus. PMID:22179041

  13. Is the Marketing Concept Adequate for Continuing Education?

    ERIC Educational Resources Information Center

    Rittenburg, Terri L.

    1984-01-01

    Because educators have a social responsibility to those they teach, the marketing concept may not be adequate as a philosophy for continuing education. In attempting to broaden the audience for continuing education, educators should consider a societal marketing concept to meet the needs of the educationally disadvantaged. (SK)

  14. Comparability and Reliability Considerations of Adequate Yearly Progress

    ERIC Educational Resources Information Center

    Maier, Kimberly S.; Maiti, Tapabrata; Dass, Sarat C.; Lim, Chae Young

    2012-01-01

    The purpose of this study is to develop an estimate of Adequate Yearly Progress (AYP) that will allow for reliable and valid comparisons among student subgroups, schools, and districts. A shrinkage-type estimator of AYP using the Bayesian framework is described. Using simulated data, the performance of the Bayes estimator will be compared to…

  15. 9 CFR 305.3 - Sanitation and adequate facilities.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Sanitation and adequate facilities. 305.3 Section 305.3 Animals and Animal Products FOOD SAFETY AND INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE AGENCY ORGANIZATION AND TERMINOLOGY; MANDATORY MEAT AND POULTRY PRODUCTS INSPECTION AND VOLUNTARY INSPECTION AND CERTIFICATION...

  16. Understanding Your Adequate Yearly Progress (AYP), 2011-2012

    ERIC Educational Resources Information Center

    Missouri Department of Elementary and Secondary Education, 2011

    2011-01-01

    The "No Child Left Behind Act (NCLB) of 2001" requires all schools, districts/local education agencies (LEAs) and states to show that students are making Adequate Yearly Progress (AYP). NCLB requires states to establish targets in the following ways: (1) Annual Proficiency Target; (2) Attendance/Graduation Rates; and (3) Participation Rates.…

  17. Assessing Juvenile Sex Offenders to Determine Adequate Levels of Supervision.

    ERIC Educational Resources Information Center

    Gerdes, Karen E.; And Others

    1995-01-01

    This study analyzed the internal consistency of four inventories used by Utah probation officers to determine adequate and efficacious supervision levels and placement for juvenile sex offenders. Three factors accounted for 41.2 percent of variance (custodian's and juvenile's attitude toward intervention, offense characteristics, and historical…

  18. 34 CFR 200.13 - Adequate yearly progress in general.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 34 Education 1 2011-07-01 2011-07-01 false Adequate yearly progress in general. 200.13 Section 200.13 Education Regulations of the Offices of the Department of Education OFFICE OF ELEMENTARY AND SECONDARY EDUCATION, DEPARTMENT OF EDUCATION TITLE I-IMPROVING THE ACADEMIC ACHIEVEMENT OF THE...

  19. 34 CFR 200.20 - Making adequate yearly progress.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 34 Education 1 2011-07-01 2011-07-01 false Making adequate yearly progress. 200.20 Section 200.20 Education Regulations of the Offices of the Department of Education OFFICE OF ELEMENTARY AND SECONDARY EDUCATION, DEPARTMENT OF EDUCATION TITLE I-IMPROVING THE ACADEMIC ACHIEVEMENT OF THE DISADVANTAGED...

  20. Do Beginning Teachers Receive Adequate Support from Their Headteachers?

    ERIC Educational Resources Information Center

    Menon, Maria Eliophotou

    2012-01-01

    The article examines the problems faced by beginning teachers in Cyprus and the extent to which headteachers are considered to provide adequate guidance and support to them. Data were collected through interviews with 25 school teachers in Cyprus, who had recently entered teaching (within 1-5 years) in public primary schools. According to the…

  1. Separation of sources in radiofrequency measurements of partial discharges using time-power ratio maps.

    PubMed

    Albarracin, R; Robles, G; Martinez-Tarifa, J M; Ardila-Rey, J

    2015-09-01

    Partial discharges measurement is one of the most useful tools for condition monitoring of high-voltage (HV) equipment. These phenomena can be measured on-line in radiofrequency (RF) with sensors such as the Vivaldi antenna, used in this paper, which improves the signal-to-noise ratio by rejecting FM and low-frequency TV bands. Additionally, the power ratios (PR), a signal-processing technique based on the power distribution of the incoming signals in frequency bands, are used to characterize different sources of PD and electromagnetic noise (EMN). The calculation of the time length of the pulses is introduced to separate signals where the PR alone do not give a conclusive solution. Thus, if several EM sources could be previously calibrated, it is possible to detect pulses corresponding to PD activity. PMID:25997372

  2. Trilinearity deviation ratio: a new metric for chemometric analysis of comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry data.

    PubMed

    Pinkerton, David K; Parsons, Brendon A; Anderson, Todd J; Synovec, Robert E

    2015-04-29

    Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) is a well-established instrumental platform for complex samples. However, chemometric data analysis is often required to fully extract useful information from the data. We demonstrate that retention time shifting from one modulation to the next, Δ(2)tR, is not sufficient alone to quantitatively describe the trilinearity of a single GC×GC-TOFMS run for the purpose of predicting the performance of the chemometric method parallel factor analysis (PARAFAC). We hypothesize that analyte peak width on second dimension separations, (2)Wb, also impacts trilinearity, along with Δ(2)tR. The term trilinearity deviation ratio, TDR, which is Δ(2)tR normalized by (2)Wb, is introduced as a quantitative metric to assess accuracy for PARAFAC of a GC×GC-TOFMS data cube. We explore how modulation ratio, MR, modulation period, PM, temperature programming rate, Tramp, sampling phase (in-phase and out-of-phase), and signal-to-noise ratio, S/N, all play a role in PARAFAC performance in the context of TDR. Use of a PM in the 1-2 s range provides an optimized peak capacity for the first dimension separation (500-600) for a 30 min run, with an adequate peak capacity for the second dimension separation (12-15), concurrent with an optimized two-dimensional peak capacity (6000-7500), combined with sufficiently low TDR values (0-0.05) to facilitate low quantitative errors with PARAFAC (0-0.5%). In contrast, use of a PM in the 5s or greater range provides a higher peak capacity on the second dimension (30-35), concurrent with a lower peak capacity on the first dimension (100-150) for a 30 min run, and a slightly reduced two-dimensional peak capacity (3000-4500), and furthermore, the data are not sufficiently trilinear for the more retained second dimension peaks in order to directly use PARAFAC with confidence. PMID:25847163

  3. Maintaining adequate hydration and nutrition in adult enteral tube feeding.

    PubMed

    Dunn, Sasha

    2015-01-01

    Predicting the nutritional and fluid requirements of enterally-fed patients can be challenging and the practicalities of ensuring adequate delivery must be taken into consideration. Patients who are enterally fed can be more reliant on clinicians, family members and carers to meet their nutrition and hydration needs and identify any deficiencies, excesses or problems with delivery. Estimating a patient's requirements can be challenging due to the limitations of using predictive equations in the clinical setting. Close monitoring by all those involved in the patient's care, as well as regular review by a dietitian, is therefore required to balance the delivery of adequate feed and fluids to meet each patient's individual needs and prevent the complications of malnutrition and dehydration. Increasing the awareness of the signs of malnutrition and dehydration in patients receiving enteral tube feeding among those involved in a patient's care will help any deficiencies to be detected early on and rectified before complications occur. PMID:26087203

  4. Assessing juvenile sex offenders to determine adequate levels of supervision.

    PubMed

    Gerdes, K E; Gourley, M M; Cash, M C

    1995-08-01

    The present study analyzed the internal consistency of four inventories currently being used by probation officers in the state of Utah to determine adequate and efficacious supervision levels and placement for juvenile sex offenders. The internal consistency or reliability of the inventories ranged from moderate to good. Factor analysis was utilized to significantly increase the reliability of the four inventories by collapsing them into the following three factors: (a) Custodian's and Juvenile's Attitude Toward Intervention; (b) Offense Characteristics; and (c) Historical Risk Factors. These three inventories/factors explained 41.2% of the variance in the combined inventories' scores. Suggestions are made regarding the creation of an additional inventory. "Characteristics of the Victim" to account for more of the variance. In addition, suggestions as to how these inventories can be used by probation officers to make objective and consistent decisions about adequate supervision levels and placement for juvenile sex offenders are discussed. PMID:7583754

  5. High Resolution Double-Focusing Isotope Ratio Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Radke, J.; Deerberg, M.; Hilkert, A.; Schlüter, H.-J.; Schwieters, J.

    2012-04-01

    In recent years isotope ratio mass spectrometry has extended to the capability of quantifying very small isotope signatures related with low abundances and simultaneously detecting molecular masses such as isotopomers and isotopologues containing clumped isotopes. Some of those applications are limited by molecular interferences like different gas molecules with the same nominal mass, e.g. Ar/O2, adducts of the same molecule or of different molecules, and very small isotope abundances. The Thermo Scientific MAT 253 ULTRA is the next generation of high precision gas isotope ratio mass spectrometry, which combines a 10 KV gas ionization source (Thermo Scientific MAT 253) with a double focusing multi-collector mass analyzer (Thermo Scientific Neptune) and reduces those limitations by measuring isotope ratios on a larger dynamic range with high precision. Small ion beam requirements and high sensitivity are achieved by signal-to-noise improvements through enhanced ion beam amplification in faraday cups and ion counters. Interfering backgrounds, e.g. interfering isotopologues or isobaric ions of contaminants, are dramatically decreased by a dynamic range increase combined with high evacuation leading to undisturbed ion transmission through the double-focusing analyser. Furthermore, automated gain calibration for mathematical baseline corrections, switchable detector arrays, ion source control, analyser focusing and full data export is controlled under Isodat data control. New reference/sample strategies are under investigation besides incorporation of the continuous-flow technique and its versatile inlet devices. We are presenting first results and applications of the MAT 253 Ultra.

  6. Adequation of mini satellites to oceanic altimetry missions

    NASA Astrophysics Data System (ADS)

    Bellaieche, G.; Aguttes, J. P.

    1993-01-01

    Association of the mini satellite concept and oceanic altimetry missions is discussed. Mission definition and most constraining requirements (mesoscale for example) demonstrate mini satellites to be quite adequate for such missions. Progress in altimeter characteristics, orbit determination, and position reporting allow consideration of oceanic altimetry missions using low Earth orbit satellites. Satellite constellation, trace keeping and orbital period, and required payload characteristics are exposed. The mission requirements covering Sun synchronous orbit, service area, ground system, and launcher characteristics as well as constellation maintenance strategy are specified. Two options for the satellite, orbital mechanics, propulsion, onboard power and stabilizing subsystems, onboard management, satellite ground linkings, mechanical and thermal subsystems, budgets, and planning are discussed.

  7. Quantifying dose to the reconstructed breast: Can we adequately treat?

    SciTech Connect

    Chung, Eugene; Marsh, Robin B.; Griffith, Kent A.; Moran, Jean M.; Pierce, Lori J.

    2013-04-01

    To evaluate how immediate reconstruction (IR) impacts postmastectomy radiotherapy (PMRT) dose distributions to the reconstructed breast (RB), internal mammary nodes (IMN), heart, and lungs using quantifiable dosimetric end points. 3D conformal plans were developed for 20 IR patients, 10 autologous reconstruction (AR), and 10 expander-implant (EI) reconstruction. For each reconstruction type, 5 right- and 5 left-sided reconstructions were selected. Two plans were created for each patient, 1 with RB coverage alone and 1 with RB + IMN coverage. Left-sided EI plans without IMN coverage had higher heart Dmean than left-sided AR plans (2.97 and 0.84 Gy, p = 0.03). Otherwise, results did not vary by reconstruction type and all remaining metrics were evaluated using a combined AR and EI dataset. RB coverage was adequate regardless of laterality or IMN coverage (Dmean 50.61 Gy, D95 45.76 Gy). When included, IMN Dmean and D95 were 49.57 and 40.96 Gy, respectively. Mean heart doses increased with left-sided treatment plans and IMN inclusion. Right-sided treatment plans and IMN inclusion increased mean lung V{sub 20}. Using standard field arrangements and 3D planning, we observed excellent coverage of the RB and IMN, regardless of laterality or reconstruction type. Our results demonstrate that adequate doses can be delivered to the RB with or without IMN coverage.

  8. Purchasing a cycle helmet: are retailers providing adequate advice?

    PubMed Central

    Plumridge, E.; McCool, J.; Chetwynd, J.; Langley, J. D.

    1996-01-01

    OBJECTIVES: The aim of this study was to examine the selling of cycle helmets in retail stores with particular reference to the adequacy of advice offered about the fit and securing of helmets. METHODS: All 55 retail outlets selling cycle helmets in Christchurch, New Zealand were studied by participant observation. A research entered each store as a prospective customer and requested assistance to purchase a helmet. She took detailed field notes of the ensuing encounter and these were subsequently transcribed, coded, and analysed. RESULTS: Adequate advice for helmet purchase was given in less than half of the stores. In general the sales assistants in specialist cycle shops were better informed and gave more adequate advice than those in department stores. Those who have good advice also tended to be more good advice also tended to be more active in helping with fitting the helmet. Knowledge about safety standards was apparent in one third of sales assistants. Few stores displayed information for customers about the correct fit of cycle helmets. CONCLUSIONS: These findings suggest that the advice and assistance being given to ensure that cycle helmets fit properly is often inadequate and thus the helmets may fail to fulfil their purpose in preventing injury. Consultation between retailers and policy makers is a necessary first step to improving this situation. PMID:9346053

  9. Adequate drainage system design for heap leaching structures.

    PubMed

    Majdi, Abbas; Amini, Mehdi; Nasab, Saeed Karimi

    2007-08-17

    The paper describes an optimum design of a drainage system for a heap leaching structure which has positive impacts on both mine environment and mine economics. In order to properly design a drainage system the causes of an increase in the acid level of the heap which in turn produces severe problems in the hydrometallurgy processes must be evaluated. One of the most significant negative impacts induced by an increase in the acid level within a heap structure is the increase of pore acid pressure which in turn increases the potential of a heap-slide that may endanger the mine environment. In this paper, initially the thickness of gravelly drainage layer is determined via existing empirical equations. Then by assuming that the calculated thickness is constant throughout the heap structure, an approach has been proposed to calculate the required internal diameter of the slotted polyethylene pipes which are used for auxiliary drainage purposes. In order to adequately design this diameter, the pipe's cross-sectional deformation due to stepped heap structure overburden pressure is taken into account. Finally, a design of an adequate drainage system for the heap structure 2 at Sarcheshmeh copper mine is presented and the results are compared with those calculated by exiting equations. PMID:17321044

  10. Are PPS payments adequate? Issues for updating and assessing rates

    PubMed Central

    Sheingold, Steven H.; Richter, Elizabeth

    1992-01-01

    Declining operating margins under Medicare's prospective payment system (PPS) have focused attention on the adequacy of payment rates. The question of whether annual updates to the rates have been too low or cost increases too high has become important. In this article we discuss issues relevant to updating PPS rates and judging their adequacy. We describe a modification to the current framework for recommending annual update factors. This framework is then used to retrospectively assess PPS payment and cost growth since 1985. The preliminary results suggest that current rates are more than adequate to support the cost of efficient care. Also discussed are why using financial margins to evaluate rates is problematic and alternative methods that might be employed. PMID:10127450

  11. Signal-to-Noise Behavior for Matches to Gradient Direction Models of Corners in Images

    SciTech Connect

    Paglieroni, D W; Manay, S

    2007-02-09

    Gradient direction models for corners of prescribed acuteness, leg length, and leg thickness are constructed by generating fields of unit vectors emanating from leg pixels that point normal to the edges. A novel FFT-based algorithm that quickly matches models of corners at all possible positions and orientations in the image to fields of gradient directions for image pixels is described. The signal strength of a corner is discussed in terms of the number of pixels along the edges of a corner in an image, while noise is characterized by the coherence of gradient directions along those edges. The detection-false alarm rate behavior of our corner detector is evaluated empirically by manually constructing maps of corner locations in typical overhead images, and then generating different ROC curves for matches to models of corners with different leg lengths and thicknesses. We then demonstrate how corners found with our detector can be used to quickly and automatically find families of polygons of arbitrary position, size and orientation in overhead images.

  12. Lineshape spectroscopy with a very high resolution, very high signal-to-noise crystal spectrometer

    NASA Astrophysics Data System (ADS)

    Beiersdorfer, P.; Magee, E. W.; Brown, G. V.; Chen, H.; Emig, J.; Hell, N.; Bitter, M.; Hill, K. W.; Allan, P.; Brown, C. R. D.; Hill, M. P.; Hoarty, D. J.; Hobbs, L. M. R.; James, S. F.

    2016-06-01

    We have developed a high-resolution x-ray spectrometer for measuring the shapes of spectral lines produced from laser-irradiated targets on the Orion laser facility. The instrument utilizes a spherically bent crystal geometry to spatially focus and spectrally analyze photons from foil or microdot targets. The high photon collection efficiency resulting from its imaging properties allows the instrument to be mounted outside the Orion chamber, where it is far less sensitive to particles, hard x-rays, or electromagnetic pulses than instruments housed close to the target chamber center in ten-inch manipulators. Moreover, Bragg angles above 50° are possible, which provide greatly improved spectral resolution compared to radially viewing, near grazing-incidence crystal spectrometers. These properties make the new instrument an ideal lineshape diagnostic for determining plasma temperature and density. We describe its calibration on the Livermore electron beam ion trap facility and present spectral data of the K-shell emission from highly charged sulfur produced by long-pulse as well as short-pulse beams on the Orion laser in the United Kingdom.

  13. An abundance study of IC 418 using high-resolution, signal-to-noise emission spectra

    NASA Astrophysics Data System (ADS)

    Sharpee, Brian David

    2003-11-01

    An on-going problem in astrophysics involves the large and varying disagreement between abundances measurements made in planetary nebulae (PNe), determined from the strengths of emission lines arising from the same source ion, but excited by differing mechanisms (recombination and collisional excitation) in planetary nebulae (PNe). We investigate the extent of this problem in IC 418, a PN chosen for its great surface brightness and perceived visually uncomplicated geometry, through the use of high resolution (R ≈ 30000 = 10 km sec-1 at 6500Å) echelle emission spectroscopy in the optical regime (3500 9850Å). These observations allow us to construct the most detailed list of atomic emission lines ever compiled for IC 418, and among the most detailed from among all PNe. Ionic abundances are calculated from the fluxes of numerous weak (1 × 10-5 Hβ) atomic emission lines from the ions of C,N,O, and Ne, using the most recent and accurate atomic transition information presently available. The high resolution of these spectra provides well-defined line profiles, which, coupled with the perceived simplicity of the object's expansion velocity distribution, allows us to better determine where in the nebula lines are formed, and where the ions that produce them are concentrated. Evidence for “non-conventional” line excitation mechanisms, such as continuum fluorescence from the ground state or enhanced dielectronic recombination, is sought in the profile morphologies and relative line strengths. Non-conventional excitation processes may influence the strengths of lines enough to significantly alter abundances calculated from them. Our calculations show that recombination line-derived abundances exceed those derived from collisionally excited lines, for those ions for which we observed lines of both types: O+, O+2, and Ne +2 by real and varying amounts. We find that both continuum fluorescence and dielectronic recombination excites numerous lines in IC 418, but that there is no evidence in our data that either process is responsible for the observed overabundances in all recombination lines as opposed to their collisionally excited counterparts. The calculated levels of temperature fluctuations in the zones in which these ion reside are dubious, and significantly exceed model predicted values. In summary, no satisfactory, single universally applicable answer to the abundance discrepancy problem shown to exist by us in IC 418, is revealed by our observations. We developed several new techniques to analyze these data. Of particular interest is EMILI (Emission Line Identifier), a public-domain program that utilizes a comprehensive atomic transition list and a set of simple tests and criteria, to quickly provide its user with a list of rank ordered IDs for unidentified emission lines found in deep, high resolution spectra. Presented here are the results of applying EMILI to the identification of weak emission lines in the spectra of IC 418 and other PNe.

  14. FIP, FIT or MAD? Analysis of High Signal-to-Noise ASCA Spectra of Coronal Stars

    NASA Technical Reports Server (NTRS)

    Simon, Theodore

    2002-01-01

    ASCA (Advanced Satellite for Cosmology and Astrophysics) and EUVE (Extreme Ultraviolet Explorer) spectra of active late-type stars imply that Fe and other medium-Z elements may be 2-10 times less abundant in the coronae of these stars than in their photo-spheres (the MAD effect). These deficiencies may be related to the solar FIP (First Ionization Potential) effect, in which Fe and other low First Ionization Potential elements appear enriched in the solar corona over their photospheric values. The FIP effect is time variable. As part of this proposal, the K0-2 III star, 29 Draconis, was observed in X rays with the ASCA spacecraft in order to measure the coronal abundances of this star at three different stellar longitudes over its 31-day rotation cycle. The goal of the observations was to learn whether coronal abundances, and hence coronal magnetic structure, vary across the surface of 29 Draconis in phase with the motion of dark star-spots across its disk. A second task included in this project was a systematic reanalysis of 18-20 deep exposures of active coronal stars, which were extracted from the ASCA public archives. New thermal models were computed for each spectrum in order to derive coronal metal abundances for each star. The goal of this survey was to search for possible trends in coronal abundance with various stellar parameters such as rotation, chromospheric activity levels at ultraviolet and optical wavelengths, or evolutionary stage.

  15. Lineshape spectroscopy with a very high resolution, very high signal-to-noise crystal spectrometer.

    PubMed

    Beiersdorfer, P; Magee, E W; Brown, G V; Chen, H; Emig, J; Hell, N; Bitter, M; Hill, K W; Allan, P; Brown, C R D; Hill, M P; Hoarty, D J; Hobbs, L M R; James, S F

    2016-06-01

    We have developed a high-resolution x-ray spectrometer for measuring the shapes of spectral lines produced from laser-irradiated targets on the Orion laser facility. The instrument utilizes a spherically bent crystal geometry to spatially focus and spectrally analyze photons from foil or microdot targets. The high photon collection efficiency resulting from its imaging properties allows the instrument to be mounted outside the Orion chamber, where it is far less sensitive to particles, hard x-rays, or electromagnetic pulses than instruments housed close to the target chamber center in ten-inch manipulators. Moreover, Bragg angles above 50° are possible, which provide greatly improved spectral resolution compared to radially viewing, near grazing-incidence crystal spectrometers. These properties make the new instrument an ideal lineshape diagnostic for determining plasma temperature and density. We describe its calibration on the Livermore electron beam ion trap facility and present spectral data of the K-shell emission from highly charged sulfur produced by long-pulse as well as short-pulse beams on the Orion laser in the United Kingdom. PMID:27370448

  16. Attention Enhances Synaptic Efficacy and Signal-to-Noise in Neural Circuits

    PubMed Central

    Briggs, Farran; Mangun, George R.; Usrey, W. Martin

    2013-01-01

    Summary Attention is a critical component of perception. However, the mechanisms by which attention modulates neuronal communication to guide behavior are poorly understood. To elucidate the synaptic mechanisms of attention, we developed a sensitive assay of attentional modulation of neuronal communication. In alert monkeys performing a visual spatial attention task, we probed thalamocortical communication by electrically stimulating neurons in the lateral geniculate nucleus of the thalamus while simultaneously recording shock-evoked responses from monosynaptically connected neurons in primary visual cortex. We found that attention enhances neuronal communication by (1) increasing the efficacy of presynaptic input in driving postsynaptic responses, (2) increasing synchronous responses among ensembles of postsynaptic neurons receiving independent input, and (3) decreasing redundant signals between postsynaptic neurons receiving common input. These results demonstrate that attention finely tunes neuronal communication at the synaptic level by selectively altering synaptic weights, enabling enhanced detection of salient events in the noisy sensory milieu. PMID:23803766

  17. Utility of Ion Mobility Mass Spectrometry for Drug-to-Antibody Ratio Measurements in Antibody-Drug Conjugates

    NASA Astrophysics Data System (ADS)

    Huang, Richard Y.-C.; Deyanova, Ekaterina G.; Passmore, David; Rangan, Vangipuram; Deshpande, Shrikant; Tymiak, Adrienne A.; Chen, Guodong

    2015-06-01

    Antibody-drug conjugates (ADCs) are emerging modalities in the pharmaceutical industry. Characterization of ADC's drug-to-antibody ratio (DAR) becomes a key assessment because of its importance in ADC efficacy and safety. DAR characterization by conventional intact protein MS analysis, however, is challenging because of high heterogeneity of ADC samples. The analysis often requires protein deglycosylation, disulfide-bond reduction, or partial fragmentation. In this study, we illustrate the practical utility of ion mobility mass spectrometry (IM-MS) in a routine LC/MS workflow for DAR measurements. This strategy allows analyte "cleanup" in the gas phase, providing significant improvement of signal-to-noise ratios of ADC intact mass spectra for accurate DAR measurements. In addition, protein drift time analysis offers a new dimension in monitoring the changes of DAR in lot-to-lot analysis.

  18. Dose Limits for Man do not Adequately Protect the Ecosystem

    SciTech Connect

    Higley, Kathryn A.; Alexakhin, Rudolf M.; McDonald, Joseph C.

    2004-08-01

    It has been known for quite some time that different organisms display differing degrees of sensitivity to the effects of ionizing radiations. Some microorganisms such as the bacterium Micrococcus radiodurans, along with many species of invertebrates, are extremely radio-resistant. Humans might be categorized as being relatively sensitive to radiation, and are a bit more resistant than some pine trees. Therefore, it could be argued that maintaining the dose limits necessary to protect humans will also result in the protection of most other species of flora and fauna. This concept is usually referred to as the anthropocentric approach. In other words, if man is protected then the environment is also adequately protected. The ecocentric approach might be stated as; the health of humans is effectively protected only when the environment is not unduly exposed to radiation. The ICRP is working on new recommendations dealing with the protection of the environment, and this debate should help to highlight a number of relevant issues concerning that topic.

  19. ENSURING ADEQUATE SAFETY WHEN USING HYDROGEN AS A FUEL

    SciTech Connect

    Coutts, D

    2007-01-22

    Demonstration projects using hydrogen as a fuel are becoming very common. Often these projects rely on project-specific risk evaluations to support project safety decisions. This is necessary because regulations, codes, and standards (hereafter referred to as standards) are just being developed. This paper will review some of the approaches being used in these evolving standards, and techniques which demonstration projects can implement to bridge the gap between current requirements and stakeholder desires. Many of the evolving standards for hydrogen-fuel use performance-based language, which establishes minimum performance and safety objectives, as compared with prescriptive-based language that prescribes specific design solutions. This is being done for several reasons including: (1) concern that establishing specific design solutions too early will stifle invention, (2) sparse performance data necessary to support selection of design approaches, and (3) a risk-adverse public which is unwilling to accept losses that were incurred in developing previous prescriptive design standards. The evolving standards often contain words such as: ''The manufacturer shall implement the measures and provide the information necessary to minimize the risk of endangering a person's safety or health''. This typically implies that the manufacturer or project manager must produce and document an acceptable level of risk. If accomplished using comprehensive and systematic process the demonstration project risk assessment can ease the transition to widespread commercialization. An approach to adequately evaluate and document the safety risk will be presented.

  20. Adequate peritoneal dialysis: theoretical model and patient treatment.

    PubMed

    Tast, C

    1998-01-01

    The objective of this study was to evaluate the relationship between adequate PD with sufficient weekly Kt/V (2.0) and Creatinine clearance (CCR) (60l) and necessary daily dialysate volume. This recommended parameter was the result of a recent multi-centre study (CANUSA). For this there were 40 patients in our hospital examined and compared in 1996, who carried out PD for at least 8 weeks and up to 6 years. These goals (CANUSA) are easily attainable in the early treatment of many individuals with a low body surface area (BSA). With higher BSA or missing RRF (Residual Renal Function) the daily dose of dialysis must be adjusted. We found it difficult to obtain the recommended parameters and tried to find a solution to this problem. The simplest method is to increase the volume or exchange rate. The most expensive method is to change from CAPD to APD with the possibility of higher volume or exchange rates. Selection of therapy must take into consideration: 1. patient preference, 2. body mass, 3. peritoneal transport rates, 4. ability to perform therapy, 5. cost of therapy and 6. risk of peritonitis. With this information in mind, an individual prescription can be formulated and matched to the appropriate modality of PD. PMID:10392062

  1. DARHT - an `adequate` EIS: A NEPA case study

    SciTech Connect

    Webb, M.D.

    1997-08-01

    The Dual Axis Radiographic Hydrodynamic Test (DARHT) Facility Environmental Impact Statement (EIS) provides a case study that is interesting for many reasons. The EIS was prepared quickly, in the face of a lawsuit, for a project with unforeseen environmental impacts, for a facility that was deemed urgently essential to national security. Following judicial review the EIS was deemed to be {open_quotes}adequate.{close_quotes} DARHT is a facility now being built at Los Alamos National Laboratory (LANL) as part of the Department of Energy (DOE) nuclear weapons stockpile stewardship program. DARHT will be used to evaluate the safety and reliability of nuclear weapons, evaluate conventional munitions and study high-velocity impact phenomena. DARHT will be equipped with two accelerator-driven, high-intensity X-ray machines to record images of materials driven by high explosives. DARHT will be used for a variety of hydrodynamic tests, and DOE plans to conduct some dynamic experiments using plutonium at DARHT as well.

  2. On Adequate Comparisons of Antenna Phase Center Variations

    NASA Astrophysics Data System (ADS)

    Schoen, S.; Kersten, T.

    2013-12-01

    One important part for ensuring the high quality of the International GNSS Service's (IGS) products is the collection and publication of receiver - and satellite antenna phase center variations (PCV). The PCV are crucial for global and regional networks, since they introduce a global scale factor of up to 16ppb or changes in the height component with an amount of up to 10cm, respectively. Furthermore, antenna phase center variations are also important for precise orbit determination, navigation and positioning of mobile platforms, like e.g. the GOCE and GRACE gravity missions, or for the accurate Precise Point Positioning (PPP) processing. Using the EUREF Permanent Network (EPN), Baire et al. (2012) showed that individual PCV values have a significant impact on the geodetic positioning. The statements are further supported by studies of Steigenberger et al. (2013) where the impact of PCV for local-ties are analysed. Currently, there are five calibration institutions including the Institut für Erdmessung (IfE) contributing to the IGS PCV file. Different approaches like field calibrations and anechoic chamber measurements are in use. Additionally, the computation and parameterization of the PCV are completely different within the methods. Therefore, every new approach has to pass a benchmark test in order to ensure that variations of PCV values of an identical antenna obtained from different methods are as consistent as possible. Since the number of approaches to obtain these PCV values rises with the number of calibration institutions, there is the necessity for an adequate comparison concept, taking into account not only the numerical values but also stochastic information and computational issues of the determined PCVs. This is of special importance, since the majority of calibrated receiver antennas published by the IGS origin from absolute field calibrations based on the Hannover Concept, Wübbena et al. (2000). In this contribution, a concept for the adequate

  3. Improving access to adequate pain management in Taiwan.

    PubMed

    Scholten, Willem

    2015-06-01

    There is a global crisis in access to pain management in the world. WHO estimates that 4.65 billion people live in countries where medical opioid consumption is near to zero. For 2010, WHO considered a per capita consumption of 216.7 mg morphine equivalents adequate, while Taiwan had a per capita consumption of 0.05 mg morphine equivalents in 2007. In Asia, the use of opioids is sensitive because of the Opium Wars in the 19th century and for this reason, the focus of controlled substances policies has been on the prevention of diversion and dependence. However, an optimal public health outcome requires that also the beneficial aspects of these substances are acknowledged. Therefore, WHO recommends a policy based on the Principle of Balance: ensuring access for medical and scientific purposes while preventing diversion, harmful use and dependence. Furthermore, international law requires that countries ensure access to opioid analgesics for medical and scientific purposes. There is evidence that opioid analgesics for chronic pain are not associated with a major risk for developing dependence. Barriers for access can be classified in the categories of overly restrictive laws and regulations; insufficient medical training on pain management and problems related to assessment of medical needs; attitudes like an excessive fear for dependence or diversion; and economic and logistical problems. The GOPI project found many examples of such barriers in Asia. Access to opioid medicines in Taiwan can be improved by analysing the national situation and drafting a plan. The WHO policy guidelines Ensuring Balance in National Policies on Controlled Substances can be helpful for achieving this purpose, as well as international guidelines for pain treatment. PMID:26068436

  4. Noise-induced systematic errors in ratio imaging: serious artefacts and correction with multi-resolution denoising.

    PubMed

    Wang, Yu-Li

    2007-11-01

    Ratio imaging is playing an increasingly important role in modern cell biology. Combined with ratiometric dyes or fluorescence resonance energy transfer (FRET) biosensors, the approach allows the detection of conformational changes and molecular interactions in living cells. However, the approach is conducted increasingly under limited signal-to-noise ratio (SNR), where noise from multiple images can easily accumulate and lead to substantial uncertainty in ratio values. This study demonstrates that a far more serious concern is systematic errors that generate artificially high ratio values at low SNR. Thus, uneven SNR alone may lead to significant variations in ratios among different regions of a cell. Although correct average ratios may be obtained by applying conventional noise reduction filters, such as a Gaussian filter before calculating the ratio, these filters have a limited performance at low SNR and are prone to artefacts such as generating discrete domains not found in the correct ratio image. Much more reliable restoration may be achieved with multi-resolution denoising filters that take into account the actual noise characteristics of the detector. These filters are also capable of restoring structural details and photometric accuracy, and may serve as a general tool for retrieving reliable information from low-light live cell images. PMID:17970912

  5. Study of Site Response in the Seattle and Tacoma Basins, Washington, Using Spectral Ratio Methods

    NASA Astrophysics Data System (ADS)

    Keshvardoost, R.; Wolf, L. W.

    2014-12-01

    Sedimentary basins are known to have a pronounced influence on earthquake-generated ground motions, affecting both predominant frequencies and wave amplification. These site characteristics are important elements in estimating ground shaking and seismic hazard. In this study, we use three-component broadband and strong motion seismic data from three recent earthquakes to determine site response characteristics in the Seattle and Tacoma basins, Washington. Resonant frequencies and relative amplification of ground motions were determined using Fourier spectral ratios of velocity and acceleration records from the 2012 Mw 6.1 Vancouver Island earthquake, the 2012 Mw 7.8 Queen Charlotte Island earthquake, and the 2014 Mw 6.6 Vancouver Island earthquake. Recordings from sites within and adjacent to the Seattle and Tacoma basins were selected for the study based on their signal to noise ratios. Both the Standard Spectral Ratio (SSR) and the Horizontal-to-Vertical Spectral Ratio (HVSR) methods were used in the analysis, and results from each were compared to examine their agreement and their relation to local geology. Although 57% of the sites (27 out of 48) exhibited consistent results between the two methods, other sites varied considerably. In addition, we use data from the Seattle Liquefaction Array (SLA) to evaluate the site response at 4 different depths. Results indicate that resonant frequencies remain the same at different depths but amplification decreases significantly over the top 50 m.

  6. A 10-bit ratio-independent cyclic ADC with offset canceling for a CMOS image sensor

    NASA Astrophysics Data System (ADS)

    Kaiming, Nie; Suying, Yao; Jiangtao, Xu; Zhaorui, Jiang

    2014-03-01

    A 10-bit ratio-independent switch-capacitor (SC) cyclic analog-to-digital converter (ADC) with offset canceling for a CMOS image sensor is presented. The proposed ADC completes an N-bit conversion in 1.5N clock cycles with one operational amplifier. Combining ratio-independent and polarity swapping techniques, the conversion characteristic of the proposed cyclic ADC is inherently insensitive both to capacitor ratio and to amplifier offset voltage. Therefore, the circuit can be realized in a small die area and it is suitable to serve as the column-parallel ADC in CMOS image sensors. A prototype ADC is fabricated in 0.18-μm one-poly four-metal CMOS technology. The measured results indicate that the ADC has a signal-to-noise and distortion ratio (SNDR) of 53.6 dB and a DNL of +0:12/-0:14 LSB at a conversion rate of 600 kS/s. The standard deviation of the offset variation of the ADC is reduced from 2.5 LSB to 0.5 LSB. Its power dissipation is 250 μW with a 1.8 V supply, and its area is 0.03 × 0.8 mm2.

  7. Acoustic Feature Optimization Based on F-Ratio for Robust Speech Recognition

    NASA Astrophysics Data System (ADS)

    Sun, Yanqing; Zhou, Yu; Zhao, Qingwei; Yan, Yonghong

    This paper focuses on the problem of performance degradation in mismatched speech recognition. The F-Ratio analysis method is utilized to analyze the significance of different frequency bands for speech unit classification, and we find that frequencies around 1kHz and 3kHz, which are the upper bounds of the first and the second formants for most of the vowels, should be emphasized in comparison to the Mel-frequency cepstral coefficients (MFCC). The analysis result is further observed to be stable in several typical mismatched situations. Similar to the Mel-Frequency scale, another frequency scale called the F-Ratio-scale is thus proposed to optimize the filter bank design for the MFCC features, and make each subband contains equal significance for speech unit classification. Under comparable conditions, with the modified features we get a relative 43.20% decrease compared with the MFCC in sentence error rate for the emotion affected speech recognition, 35.54%, 23.03% for the noisy speech recognition at 15dB and 0dB SNR (signal to noise ratio) respectively, and 64.50% for the three years' 863 test data. The application of the F-Ratio analysis on the clean training set of the Aurora2 database demonstrates its robustness over languages, texts and sampling rates.

  8. Percentage of Adults with High Blood Pressure Whose Hypertension Is Adequately Controlled

    MedlinePlus

    ... is Adequately Controlled Percentage of Adults with High Blood Pressure Whose Hypertension is Adequately Controlled Heart disease ... Survey. Age Group Percentage of People with High Blood Pressure that is Controlled by Age Group f94q- ...

  9. 21 CFR 514.117 - Adequate and well-controlled studies.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... production performance, or biased observation. One or more adequate and well-controlled studies are required... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Adequate and well-controlled studies. 514.117... Applications § 514.117 Adequate and well-controlled studies. (a) Purpose. The primary purpose of...

  10. 21 CFR 514.117 - Adequate and well-controlled studies.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... production performance, or biased observation. One or more adequate and well-controlled studies are required... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Adequate and well-controlled studies. 514.117... Applications § 514.117 Adequate and well-controlled studies. (a) Purpose. The primary purpose of...

  11. 21 CFR 514.117 - Adequate and well-controlled studies.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... production performance, or biased observation. One or more adequate and well-controlled studies are required... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Adequate and well-controlled studies. 514.117... Applications § 514.117 Adequate and well-controlled studies. (a) Purpose. The primary purpose of...

  12. 21 CFR 514.117 - Adequate and well-controlled studies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... production performance, or biased observation. One or more adequate and well-controlled studies are required... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Adequate and well-controlled studies. 514.117... Applications § 514.117 Adequate and well-controlled studies. (a) Purpose. The primary purpose of...

  13. 21 CFR 514.117 - Adequate and well-controlled studies.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... production performance, or biased observation. One or more adequate and well-controlled studies are required... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Adequate and well-controlled studies. 514.117... Applications § 514.117 Adequate and well-controlled studies. (a) Purpose. The primary purpose of...

  14. 21 CFR 801.5 - Medical devices; adequate directions for use.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Medical devices; adequate directions for use. 801... (CONTINUED) MEDICAL DEVICES LABELING General Labeling Provisions § 801.5 Medical devices; adequate directions for use. Adequate directions for use means directions under which the layman can use a device...

  15. 21 CFR 801.5 - Medical devices; adequate directions for use.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Medical devices; adequate directions for use. 801... (CONTINUED) MEDICAL DEVICES LABELING General Labeling Provisions § 801.5 Medical devices; adequate directions for use. Adequate directions for use means directions under which the layman can use a device...

  16. 21 CFR 801.5 - Medical devices; adequate directions for use.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Medical devices; adequate directions for use. 801... (CONTINUED) MEDICAL DEVICES LABELING General Labeling Provisions § 801.5 Medical devices; adequate directions for use. Adequate directions for use means directions under which the layman can use a device...

  17. 21 CFR 801.5 - Medical devices; adequate directions for use.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Medical devices; adequate directions for use. 801... (CONTINUED) MEDICAL DEVICES LABELING General Labeling Provisions § 801.5 Medical devices; adequate directions for use. Adequate directions for use means directions under which the layman can use a device...

  18. 21 CFR 801.5 - Medical devices; adequate directions for use.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Medical devices; adequate directions for use. 801... (CONTINUED) MEDICAL DEVICES LABELING General Labeling Provisions § 801.5 Medical devices; adequate directions for use. Adequate directions for use means directions under which the layman can use a device...

  19. 76 FR 51041 - Hemoglobin Standards and Maintaining Adequate Iron Stores in Blood Donors; Public Workshop

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-17

    ... HUMAN SERVICES Food and Drug Administration Hemoglobin Standards and Maintaining Adequate Iron Stores in... Standards and Maintaining Adequate Iron Stores in Blood Donors.'' The purpose of this public workshop is to... donor safety and blood availability, and potential measures to maintain adequate iron stores in...

  20. 36 CFR 13.960 - Who determines when there is adequate snow cover?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... adequate snow cover? 13.960 Section 13.960 Parks, Forests, and Public Property NATIONAL PARK SERVICE... Preserve Snowmachine (snowmobile) Operations § 13.960 Who determines when there is adequate snow cover? The superintendent will determine when snow cover is adequate for snowmachine use. The superintendent will follow...

  1. 36 CFR 13.960 - Who determines when there is adequate snow cover?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... adequate snow cover? 13.960 Section 13.960 Parks, Forests, and Public Property NATIONAL PARK SERVICE... Preserve Snowmachine (snowmobile) Operations § 13.960 Who determines when there is adequate snow cover? The superintendent will determine when snow cover is adequate for snowmachine use. The superintendent will follow...

  2. 36 CFR 13.960 - Who determines when there is adequate snow cover?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... adequate snow cover? 13.960 Section 13.960 Parks, Forests, and Public Property NATIONAL PARK SERVICE... Preserve Snowmachine (snowmobile) Operations § 13.960 Who determines when there is adequate snow cover? The superintendent will determine when snow cover is adequate for snowmachine use. The superintendent will follow...

  3. 36 CFR 13.960 - Who determines when there is adequate snow cover?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... adequate snow cover? 13.960 Section 13.960 Parks, Forests, and Public Property NATIONAL PARK SERVICE... Preserve Snowmachine (snowmobile) Operations § 13.960 Who determines when there is adequate snow cover? The superintendent will determine when snow cover is adequate for snowmachine use. The superintendent will follow...

  4. 36 CFR 13.960 - Who determines when there is adequate snow cover?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... adequate snow cover? 13.960 Section 13.960 Parks, Forests, and Public Property NATIONAL PARK SERVICE... Preserve Snowmachine (snowmobile) Operations § 13.960 Who determines when there is adequate snow cover? The superintendent will determine when snow cover is adequate for snowmachine use. The superintendent will follow...

  5. EMPIRICAL DETERMINATION OF EINSTEIN A-COEFFICIENT RATIOS OF BRIGHT [Fe II] LINES

    SciTech Connect

    Giannini, T.; Antoniucci, S.; Nisini, B.; Lorenzetti, D.; Alcalá, J. M.; Bacciotti, F.; Podio, L.; Bonito, R.; Stelzer, B.

    2015-01-01

    The Einstein spontaneous rates (A-coefficients) of Fe{sup +} lines have been computed by several authors with results that differ from each other by up to 40%. Consequently, models for line emissivities suffer from uncertainties that in turn affect the determination of the physical conditions at the base of line excitation. We provide an empirical determination of the A-coefficient ratios of bright [Fe II] lines that would represent both a valid benchmark for theoretical computations and a reference for the physical interpretation of the observed lines. With the ESO-Very Large Telescope X-shooter instrument between 3000 Å and 24700 Å, we obtained a spectrum of the bright Herbig-Haro object HH 1. We detect around 100 [Fe II] lines, some of which with a signal-to-noise ratios ≥100. Among these latter lines, we selected those emitted by the same level, whose dereddened intensity ratios are direct functions of the Einstein A-coefficient ratios. From the same X-shooter spectrum, we got an accurate estimate of the extinction toward HH 1 through intensity ratios of atomic species, H I  recombination lines and H{sub 2} ro-vibrational transitions. We provide seven reliable A-coefficient ratios between bright [Fe II] lines, which are compared with the literature determinations. In particular, the A-coefficient ratios involving the brightest near-infrared lines (λ12570/λ16440 and λ13209/λ16440) are in better agreement with the predictions by the Quinet et al. relativistic Hartree-Fock model. However, none of the theoretical models predict A-coefficient ratios in agreement with all of our determinations. We also show that literature data of near-infrared intensity ratios better agree with our determinations than with theoretical expectations.

  6. Effective-one-body model for black-hole binaries with generic mass ratios and spins

    NASA Astrophysics Data System (ADS)

    Taracchini, Andrea; Buonanno, Alessandra; Pan, Yi; Hinderer, Tanja; Boyle, Michael; Hemberger, Daniel A.; Kidder, Lawrence E.; Lovelace, Geoffrey; Mroué, Abdul H.; Pfeiffer, Harald P.; Scheel, Mark A.; Szilágyi, Béla; Taylor, Nicholas W.; Zenginoglu, Anil

    2014-03-01

    Gravitational waves emitted by black-hole binary systems have the highest signal-to-noise ratio in LIGO and Virgo detectors when black-hole spins are aligned with the orbital angular momentum and extremal. For such systems, we extend the effective-one-body inspiral-merger-ringdown waveforms to generic mass ratios and spins calibrating them to 38 numerical-relativity nonprecessing waveforms produced by the SXS Collaboration. The numerical-relativity simulations span mass ratios from 1 to 8, spin magnitudes up to 98% of extremality, and last for 40 to 60 gravitational-wave cycles. When the total mass of the binary is between 20 and 200M⊙, the effective-one-body nonprecessing (dominant mode) waveforms have overlap above 99% (using the advanced-LIGO design noise spectral density) with all of the 38 nonprecessing numerical waveforms, when maximizing only on initial phase and time. This implies a negligible loss in event rate due to modeling. We also show that—without further calibration— the precessing effective-one-body (dominant mode) waveforms have overlap above 97% with two very long, strongly precessing numerical-relativity waveforms, when maximizing only on the initial phase and time.

  7. Amount-ratio determinations of water isotopologues by dual-laser absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Castrillo, Antonio; Dinesan, Hemanth; Casa, Giovanni; Galzerano, Gianluca; Laporta, Paolo; Gianfrani, Livio

    2012-11-01

    We propose a method for the measurements of the 17O/16O isotope amount ratio in water, based upon the use of a pair of offset-frequency locked extended-cavity diode lasers at 1.39 μm. This method enables one to acquire absorption spectra with an extremely high fidelity, exploiting the highly accurate, absolute, and repeatable frequency axis. One of the two lasers, namely the so-called slave laser, is continuously scanned across a pair of H216O and H217O lines at 7183.5 cm-1 and it interacts with a water vapor sample inside a multiple reflections cell, thus producing absorption spectra with a signal-to-noise ratio of the order of 4000 for a detection bandwidth of 1 kHz. The determination of the isotope amount ratio is performed through a careful analysis of the acquired spectra, by using semiclassical line profiles. In this respect, the influence of the choice of the line shape model is investigated. The experimental reproducibility of the spectrometer has been carefully assessed by means of an Allan variance analysis. Finally, the application of the Kalman filtering technique has shown that a precision of 0.6‰ can be achieved, from repeated spectral acquisitions over a time span of 6000 s.

  8. Meteor spectroscopy during the 2015 Quadrantids

    NASA Astrophysics Data System (ADS)

    Ward, Bill

    2015-08-01

    Spectroscopic video observations during the Quadrantid meteor shower 2015 were made with Watec low light level video cameras fitted with 12 mm f/0.8 lenses carrying 50 mm square diffraction gratings. Four spectra with adequate signal to noise ratios were captured and the results analysed and discussed.

  9. Isotopic Ratio, Isotonic Ratio, Isobaric Ratio and Shannon Information Uncertainty

    NASA Astrophysics Data System (ADS)

    Ma, Chun-Wang; Wei, Hui-Ling

    2014-11-01

    The isoscaling and the isobaric yield ratio difference (IBD) probes, both of which are constructed by yield ratio of fragment, provide cancelation of parameters. The information entropy theory is introduced to explain the physical meaning of the isoscaling and IBD probes. The similarity between the isoscaling and IBD results is found, i.e., the information uncertainty determined by the IBD method equals to β - α determined by the isoscaling (α (β) is the parameter fitted from the isotopic (isotonic) yield ratio).

  10. Determination of the ortho to para ratio of H2Cl+ and H2O+ from submillimeter observations.

    PubMed

    Gerin, Maryvonne; de Luca, Massimo; Lis, Dariusz C; Kramer, Carsten; Navarro, Santiago; Neufeld, David; Indriolo, Nick; Godard, Benjamin; Le Petit, Franck; Peng, Ruisheng; Phillips, Thomas G; Roueff, Evelyne

    2013-10-01

    The opening of the submillimeter sky with the Herschel Space Observatory has led to the detection of new interstellar molecular ions, H2O(+), H2Cl(+), and HCl(+), which are important intermediates in the synthesis of water vapor and hydrogen chloride. In this paper, we report new observations of H2O(+) and H2Cl(+) performed with both Herschel and ground-based telescopes, to determine the abundances of their ortho and para forms separately and derive the ortho-to-para ratio. At the achieved signal-to-noise ratio, the observations are consistent with an ortho-to-para ratios of 3 for both H2O(+) and H2Cl(+), in all velocity components detected along the lines-of-sight to the massive star-forming regions W31C and W49N. We discuss the mechanisms that contribute to establishing the observed ortho-to-para ratio and point to the need for a better understanding of chemical reactions, which are important for establishing the H2O(+) and H2Cl(+) ortho-to-para ratios. PMID:23869910

  11. IMPROVEMENTS IN ELASTOGRAPHIC CONTRAST-TO-NOISE RATIO USING SPATIAL-ANGULAR COMPOUNDING

    PubMed Central

    Techavipoo, Udomchai; Varghese, Tomy

    2005-01-01

    Spatial-angular compounding is a new technique developed for improving the signal-to-noise ratio (SNR) in elastography. Under this method, elastograms of a region-of-interest (ROI) are obtained from a spatially weighted average of local strain estimated along different insonification angles. In this article, we investigate the improvements in the strain contrast and contrast-to-noise ratio (CNR) of the spatially compounded elastograms. Spatial angular compounding is also applied and evaluated in conjunction with global temporal stretching. Quantitative experimental results obtained using a single-inclusion tissue-mimicking phantom demonstrate that the strain contrast reduces slightly but the CNR improves by around 8 to 13 dB. We also present experimental spatial angular compounding results obtained from an in vitro thermal lesion in canine liver tissue embedded in a gelatin phantom that demonstrate the improved visual characteristics (due to the improved CNR) of the compound elastogram. The experimental results provide guidelines for the practical range of maximum insonification angles and estimates of the optimum angular increment. (E-mail: tvarghese@wisc.edu) PMID:15831331

  12. Auditory masking in three pinnipeds: aerial critical ratios and direct critical bandwidth measurements.

    PubMed

    Southall, Brandon L; Schusterman, Ronald J; Kastak, David

    2003-09-01

    This study expands the limited understanding of pinniped aerial auditory masking and includes measurements at some of the relatively low frequencies predominant in many pinniped vocalizations. Behavioral techniques were used to obtain aerial critical ratios (CRs) within a hemianechoic chamber for a northern elephant seal (Mirounga angustirostris), a harbor seal (Phoca vitulina), and a California sea lion (Zalophus californianus). Simultaneous, octave-band noise maskers centered at seven test frequencies (0.2-8.0 kHz) were used to determine aerial CRs. Narrower and variable bandwidth masking noise was also used in order to obtain direct critical bandwidths (CBWs). The aerial CRs are very similar in magnitude and in frequency-specific differences (increasing gradually with test frequency) to underwater CRs for these subjects, demonstrating that pinniped cochlear processes are similar both in air and water. While, like most mammals, these pinniped subjects apparently lack specialization for enhanced detection of specific frequencies over masking noise, they consistently detect signals across a wide range of frequencies at relatively low signal-to-noise ratios. Direct CBWs are 3.2 to 14.2 times wider than estimated based on aerial CRs. The combined masking data are significant in terms of assessing aerial anthropogenic noise impacts, effective aerial communicative ranges, and amphibious aspects of pinniped cochlear mechanics. PMID:14514219

  13. Auditory masking in three pinnipeds: Aerial critical ratios and direct critical bandwidth measurements

    NASA Astrophysics Data System (ADS)

    Southall, Brandon L.; Schusterman, Ronald J.; Kastak, David

    2003-09-01

    This study expands the limited understanding of pinniped aerial auditory masking and includes measurements at some of the relatively low frequencies predominant in many pinniped vocalizations. Behavioral techniques were used to obtain aerial critical ratios (CRs) within a hemianechoic chamber for a northern elephant seal (Mirounga angustirostris), a harbor seal (Phoca vitulina), and a California sea lion (Zalophus californianus). Simultaneous, octave-band noise maskers centered at seven test frequencies (0.2-8.0 kHz) were used to determine aerial CRs. Narrower and variable bandwidth masking noise was also used in order to obtain direct critical bandwidths (CBWs). The aerial CRs are very similar in magnitude and in frequency-specific differences (increasing gradually with test frequency) to underwater CRs for these subjects, demonstrating that pinniped cochlear processes are similar both in air and water. While, like most mammals, these pinniped subjects apparently lack specialization for enhanced detection of specific frequencies over masking noise, they consistently detect signals across a wide range of frequencies at relatively low signal-to-noise ratios. Direct CBWs are 3.2 to 14.2 times wider than estimated based on aerial CRs. The combined masking data are significant in terms of assessing aerial anthropogenic noise impacts, effective aerial communicative ranges, and amphibious aspects of pinniped cochlear mechanics.

  14. A method of measuring the [α/Fe] ratios from the spectra of the LAMOST survey

    NASA Astrophysics Data System (ADS)

    Li, Ji; Han, Chen; Xiang, Mao-Sheng; Shi, Jian-Rong; Zhao, Jing-Kun; Liu, Xiao-Wei; Zhang, Hua-Wei; Yuan, Hai-Bo; Ci, Xuan; Zhang, Xiao-Feng; Wang, Yue-Xiang; Huang, Yang; Zhang, Yong; Hou, Yong-Hui; Wang, Yue-Fei; Cao, Zi-Huang

    2016-07-01

    The [α/Fe] ratios in stars are good tracers to probe the formation history of stellar populations and the chemical evolution of the Galaxy. The spectroscopic survey of LAMOST provides a good opportunity to determine [α/Fe] of millions of stars in the Galaxy. We present a method of measuring the [α/Fe] ratios from LAMOST spectra using the template-matching technique of the LSP3 pipeline. We use three test samples of stars selected from the ELODIE and MILES libraries, as well as the LEGUE survey to validate our method. Based on the test results, we conclude that our method is valid for measuring [α/Fe] from low-resolution spectra acquired by the LAMOST survey. Within the range of the stellar parameters T eff = [5000, 7500] K, log g = [1.0, 5.0] dex and [Fe/H]= [-1.5, +0.5] dex, our [α/Fe] measurements are consistent with values derived from high-resolution spectra, and the accuracy of our [α/Fe] measurements from LAMOST spectra is better than 0.1 dex with spectral signal-to-noise higher than 20.

  15. SPICE evaluation of the S/N ratio for Si microstrip detectors

    SciTech Connect

    Candelori, A.; Paccagnella, A.; Nardi, F.; Bacchetta, N.; Bisello, D.

    1999-10-01

    SPICE simulations of ac-coupled single-sided Si microstrip detectors connected to the PreShape 32 read-out chip have been performed in order to determine the geometrical characteristics (i.e., the strip pitch p and width w) which maximize the signal-to-noise ratio. All of the resistive and capacitive elements of the detector have been determined as a function of the w/p ratio by considering experimental and simulated data available in literature. The SPICE model the authors propose in this work takes into account all the main noise sources in the detector and read-out electronics. The minimum ionizing particle current signal shape has been introduced in the simulations. Two read-out configurations (every strip or every second strip) have been investigated for 6.4- and 12.8-cm-long detectors. The equivalent noise charge as determined by the simulations has been compared with analytical calculations, in order to determine the limits and the corrections to a simplified analytical noise model. Finally, general guidelines for the detector design have been proposed, based on the simulation results.

  16. Effect of Brain-to-Skull Conductivity Ratio on EEG Source Localization Accuracy

    PubMed Central

    Ren, Doutian

    2013-01-01

    The goal of this study was to investigate the influence of the brain-to-skull conductivity ratio (BSCR) on EEG source localization accuracy. In this study, we evaluated four BSCRs: 15, 20, 25, and 80, which were mainly discussed according to the literature. The scalp EEG signals were generated by BSCR-related forward computation for each cortical dipole source. Then, for each scalp EEG measurement, the source reconstruction was performed to identify the estimated dipole sources by the actual BSCR and the misspecified BSCRs. The estimated dipole sources were compared with the simulated dipole sources to evaluate EEG source localization accuracy. In the case of considering noise-free EEG measurements, the mean localization errors were approximately equal to zero when using actual BSCR. The misspecified BSCRs resulted in substantial localization errors which ranged from 2 to 16 mm. When considering noise-contaminated EEG measurements, the mean localization errors ranged from 8 to 18 mm despite the BSCRs used in the inverse calculation. The present results suggest that the localization accuracy is sensitive to the BSCR in EEG source reconstruction, and the source activity can be accurately localized when the actual BSCR and the EEG scalp signals with high signal-to-noise ratio (SNR) are used. PMID:23691502

  17. 21 CFR 314.126 - Adequate and well-controlled studies.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...-evident (general anesthetics, drug metabolism). (3) The method of selection of subjects provides adequate... respect to pertinent variables such as age, sex, severity of disease, duration of disease, and use of... 21 Food and Drugs 5 2011-04-01 2011-04-01 false Adequate and well-controlled studies....

  18. 40 CFR 152.20 - Exemptions for pesticides adequately regulated by another Federal agency.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Exemptions for pesticides adequately... PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS PESTICIDE REGISTRATION AND CLASSIFICATION PROCEDURES Exemptions § 152.20 Exemptions for pesticides adequately regulated by another Federal agency. The...

  19. 40 CFR 152.20 - Exemptions for pesticides adequately regulated by another Federal agency.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 24 2014-07-01 2014-07-01 false Exemptions for pesticides adequately... PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS PESTICIDE REGISTRATION AND CLASSIFICATION PROCEDURES Exemptions § 152.20 Exemptions for pesticides adequately regulated by another Federal agency. The...

  20. Calculation of the Cost of an Adequate Education in Kentucky: A Professional Judgment Approach

    ERIC Educational Resources Information Center

    Verstegen, Deborah A.

    2004-01-01

    What is an adequate education and how much does it cost? In 1989, Kentucky's State Supreme Court found the entire system of education unconstitutional--"all of its parts and parcels". The Court called for all children to have access to an adequate education, one that is uniform and has as its goal the development of seven capacities, including:…

  1. 9 CFR 2.33 - Attending veterinarian and adequate veterinary care.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 1 2012-01-01 2012-01-01 false Attending veterinarian and adequate veterinary care. 2.33 Section 2.33 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE ANIMAL WELFARE REGULATIONS Research Facilities § 2.33 Attending veterinarian and adequate veterinary care. (a)...

  2. 9 CFR 2.40 - Attending veterinarian and adequate veterinary care (dealers and exhibitors).

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 9 Animals and Animal Products 1 2012-01-01 2012-01-01 false Attending veterinarian and adequate veterinary care (dealers and exhibitors). 2.40 Section 2.40 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE ANIMAL WELFARE REGULATIONS Attending Veterinarian and Adequate Veterinary Care §...

  3. 75 FR 69648 - Safety Analysis Requirements for Defining Adequate Protection for the Public and the Workers

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-15

    ... SAFETY BOARD Safety Analysis Requirements for Defining Adequate Protection for the Public and the Workers... TO THE SECRETARY OF ENERGY Safety Analysis Requirements for Defining Adequate Protection for the... safety analysis, or DSA, is to be prepared for every DOE nuclear facility. This DSA, once approved by...

  4. 42 CFR 417.568 - Adequate financial records, statistical data, and cost finding.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 3 2012-10-01 2012-10-01 false Adequate financial records, statistical data, and....568 Adequate financial records, statistical data, and cost finding. (a) Maintenance of records. (1) An HMO or CMP must maintain sufficient financial records and statistical data for proper determination...

  5. 42 CFR 417.568 - Adequate financial records, statistical data, and cost finding.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 3 2013-10-01 2013-10-01 false Adequate financial records, statistical data, and....568 Adequate financial records, statistical data, and cost finding. (a) Maintenance of records. (1) An HMO or CMP must maintain sufficient financial records and statistical data for proper determination...

  6. 42 CFR 417.568 - Adequate financial records, statistical data, and cost finding.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 3 2014-10-01 2014-10-01 false Adequate financial records, statistical data, and....568 Adequate financial records, statistical data, and cost finding. (a) Maintenance of records. (1) An HMO or CMP must maintain sufficient financial records and statistical data for proper determination...

  7. Bovine hemoglobin as the sole source of dietary iron does not support adequate iron status in copper-adequate or copper-deficient rats

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This experiment was designed to determine whether hemoglobin as the sole source of dietary iron (Fe) could sustain normal Fe status in growing rats. Because adequate copper (Cu) status is required for efficient Fe absorption in the rat, we also determined the effects of Cu deficiency on Fe status of...

  8. Resolution of five-component mixture using mean centering ratio and inverse least squares chemometrics

    PubMed Central

    2013-01-01

    Background A comparative study of the use of mean centering of ratio spectra and inverse least squares for the resolution of paracetamol, methylparaben, propylparaben, chlorpheniramine maleate and pseudoephedrine hydrochloride has been achieved showing that the two chemometric methods provide a good example of the high resolving power of these techniques. Method (I) is the mean centering of ratio spectra which depends on using the mean centered ratio spectra in four successive steps that eliminates the derivative steps and therefore the signal to noise ratio is improved. The absorption spectra of prepared solutions were measured in the range of 220–280 nm. Method (II) is based on the inverse least squares that depend on updating developed multivariate calibration model. The absorption spectra of the prepared mixtures in the range 230–270 nm were recorded. Results The linear concentration ranges were 0–25.6, 0–15.0, 0–15.0, 0–45.0 and 0–100.0 μg mL-1 for paracetamol, methylparaben, propylparaben, chlorpheniramine maleate and pseudoephedrine hydrochloride, respectively. The mean recoveries for simultaneous determination were between 99.9-101.3% for the two methods. The two developed methods have been successfully used for prediction of five-component mixture in Decamol Flu syrup with good selectivity, high sensitivity and extremely low detection limit. Conclusion No published method has been reported for simultaneous determination of the five components of this mixture so that the results of the mean centering of ratio spectra method were compared with those of the proposed inverse least squares method. Statistical comparison was performed using t-test and F-ratio at P = 0.05. There was no significant difference between the results. PMID:24028626

  9. The probability distribution functions of emission line flux measurements and their ratios

    NASA Astrophysics Data System (ADS)

    Wesson, R.; Stock, D. J.; Scicluna, P.

    2016-04-01

    Many physical parameters in astrophysics are derived using the ratios of two observed quantities. If the relative uncertainties on measurements are small enough, uncertainties can be propagated analytically using simplifying assumptions, but for large normally distributed uncertainties, the probability distribution of the ratio become skewed, with a modal value offset from that expected in Gaussian uncertainty propagation. Furthermore, the most likely value of a ratio A/B is not equal to the reciprocal of the most likely value of B/A. The effect is most pronounced when the uncertainty on the denominator is larger than that on the numerator. We show that this effect is seen in an analysis of 12,126 spectra from the Sloan Digital Sky Survey. The intrinsically fixed ratio of the [O III] lines at 4959 and 5007Å is conventionally expressed as the ratio of the stronger line to the weaker line. Thus, the uncertainty on the denominator is larger, and non-Gaussian probability distributions result. By taking this effect into account, we derive an improved estimate of the intrinsic 5007/4959 ratio. We obtain a value of 3.012±0.008, which is slightly but statistically significantly higher than the theoretical value of 2.98. We further investigate the suggestion that fluxes measured from emission lines at low signal to noise are strongly biased upwards. We were unable to detect this effect in the SDSS line flux measurements, and we could not reproduce the results of Rola and Pelat who first described this bias. We suggest that the magnitude of this effect may depend strongly on the specific fitting algorithm used.

  10. Accurate quantitative 13C NMR spectroscopy: repeatability over time of site-specific 13C isotope ratio determination.

    PubMed

    Caytan, Elsa; Botosoa, Eliot P; Silvestre, Virginie; Robins, Richard J; Akoka, Serge; Remaud, Gérald S

    2007-11-01

    The stability over time (repeatability) for the determination of site-specific 13C/12C ratios at natural abundance by quantitative 13C NMR spectroscopy has been tested on three probes: enriched bilabeled [1,2-13C2]ethanol; ethanol at natural abundance; and vanillin at natural abundance. It is shown in all three cases that the standard deviation for a series of measurements taken every 2-3 months over periods between 9 and 13 months is equal to or smaller than the standard deviation calculated from 5-10 replicate measurements made on a single sample. The precision which can be achieved using the present analytical 13C NMR protocol is higher than the prerequisite value of 1-2 per thousand for the determination of site-specific 13C/12C ratios at natural abundance (13C-SNIF-NMR). Hence, this technique permits the discrimination of very small variations in 13C/12C ratios between carbon positions, as found in biogenic natural products. This observed stability over time in 13C NMR spectroscopy indicates that further improvements in precision will depend primarily on improved signal-to-noise ratio. PMID:17900175

  11. 45 CFR 1159.15 - Who has the responsibility for maintaining adequate technical, physical, and security safeguards...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... adequate technical, physical, and security safeguards to prevent unauthorized disclosure or destruction of... adequate technical, physical, and security safeguards to prevent unauthorized disclosure or destruction of... of maintaining adequate technical, physical, and security safeguards to prevent...

  12. Combining double difference and amplitude ratio approaches for Q estimates at the NW Bohemia earthquake swarm region

    NASA Astrophysics Data System (ADS)

    Kriegerowski, Marius; Cesca, Simone; Krüger, Frank; Dahm, Torsten; Horálek, Josef

    2016-04-01

    Aside from the propagation velocity of seismic waves, their attenuation can provide a direct measure of rock properties in the sampled subspace. We present a new attenuation tomography approach exploiting relative amplitude spectral ratios of earthquake pairs. We focus our investigation on North West Bohemia - a region characterized by intense earthquake swarm activity in a confined source region. The inter-event distances are small compared to the epicentral distances to the receivers meeting a fundamental requirement of the method. Due to the similar event locations also the ray paths are very similar. Consequently, the relative spectral ratio is affected mostly by rock properties along the path of the vector distance and thus representative of the focal region. In order to exclude effects of the seismic source spectra, only the high frequency content beyond the corner frequency is taken into consideration. This requires high quality as well as high sampling records. Future improvements in that respect can be expected from the ICDP proposal "Eger rift", which includes plans to install borehole monitoring in the investigated region. 1D and 3D synthetic tests show the feasibility of the presented method. Furthermore, we demonstrate influences of perturbations in source locations and travel time estimates on the determination of Q. Errors in Q scale linearly with errors in the differential travel times. These sources of errors can be attributed to the complex velocity structure of the investigated region. A critical aspect is the signal-to-noise ratio, which imposes a strong limitation and emphasizes the demand for high quality recordings. Hence, the presented method is expected to benefit from bore hole installations. Since we focus our analysis on the NW Bohemia case study example, a synthetic earthquake catalog incorporating source characteristics deduced from preceding moment tensor inversions coupled with a realistic velocity model provides us with a realistic

  13. Inferential Processing among Adequate and Struggling Adolescent Comprehenders and Relations to Reading Comprehension

    PubMed Central

    Barth, Amy E.; Barnes, Marcia; Francis, David J.; Vaughn, Sharon; York, Mary

    2015-01-01

    Separate mixed model analyses of variance (ANOVA) were conducted to examine the effect of textual distance on the accuracy and speed of text consistency judgments among adequate and struggling comprehenders across grades 6–12 (n = 1203). Multiple regressions examined whether accuracy in text consistency judgments uniquely accounted for variance in comprehension. Results suggest that there is considerable growth across the middle and high school years, particularly for adequate comprehenders in those text integration processes that maintain local coherence. Accuracy in text consistency judgments accounted for significant unique variance for passage-level, but not sentence-level comprehension, particularly for adequate comprehenders. PMID:26166946

  14. An Ultra-high-Resolution Survey of the Interstellar 7Li/6Li Isotope Ratio in the Solar Neighborhood

    NASA Astrophysics Data System (ADS)

    Knauth, David C.; Federman, S. R.; Lambert, David L.

    2003-03-01

    In an effort to probe the extent of variations in the interstellar 7Li/6Li ratio seen previously, ultra-high-resolution (R~360,000), high signal-to-noise spectra of stars in the Perseus OB2 and Scorpius OB2 associations were obtained. These measurements confirm our earlier findings of an interstellar 7Li/6Li ratio of about 2 toward ο Per, the value predicted from models of Galactic cosmic-ray spallation reactions. Observations of other nearby stars yield limits consistent with the isotopic ratio of ~12 seen in carbonaceous chondrite meteorites. If this ratio originally represented the gas toward ο Per, then to decrease the original isotope ratio to its current value an order of magnitude increase in the Li abundance is expected, but it is not seen. The elemental K/Li ratio is not unusual, although Li and K are formed via different nucleosynthetic pathways. Several proposals to account for the low 7Li/6Li ratio were considered, but none seems satisfactory. Analysis of the Li and K abundances from our survey highlighted two sight lines where depletion effects are prevalent. There is evidence for enhanced depletion toward X Per, since both abundances are lower by a factor of 4 when compared to other sight lines. Moreover, a smaller Li/H abundance is observed toward 20 Aql, but the K/H abundance is normal, suggesting enhanced Li depletion (relative to K) in this direction. Our results suggest that the 7Li/6Li ratio has not changed significantly during the last 4.5 billion years and that a ratio of ~12 represents most gas in the solar neighborhood. In addition, there appears to be a constant stellar contribution of 7Li, indicating that one or two processes dominate its production in the Galaxy.

  15. A multiple model SNR/RCS likelihood ratio score for radar-based feature-aided tracking

    NASA Astrophysics Data System (ADS)

    Slocumb, Benjamin J.; Klusman, Michael E., III

    2005-09-01

    Most approaches to data association in target tracking use a likelihood-ratio based score for measurement-to-track and track-to-track matching. The classical approach uses a likelihood ratio based on kinematic data. Feature-aided tracking uses non-kinematic data to produce an "auxiliary score" that augments the kinematic score. This paper develops a nonkinematic likelihood ratio score based on statistical models for the signal-to-noise (SNR) and radar cross section (RCS) for use in narrowband radar tracking. The formulation requires an estimate of the target mean RCS, and a key challenge is the tracking of the mean RCS through significant "jumps" due to aspect dependencies. A novel multiple model approach is used track through the RCS jumps. Three solution are developed: one based on an α-filter, a second based on the median filter, and the third based on an IMM filter with a median pre-filter. Simulation results are presented that show the effectiveness of the multiple model approach for tracking through RCS transitions due to aspect-angle changes.

  16. Is serum or sputum eosinophil cationic protein level adequate for diagnosis of mild asthma?

    PubMed

    Khakzad, Mohammad Reza; Mirsadraee, Majid; Sankian, Mojtaba; Varasteh, Abdolreza; Meshkat, Mojtaba

    2009-09-01

    Spirometry has been used as a common diagnostic test in asthma. Most of the patients with a mild asthma have a FEV1 within normal range. Hence, other diagnostic methods are usually used. The aim of this study was to evaluate whether eosinophil Cationic Protein (ECP) could be an accurate diagnostic marker of mild asthma. In this study diagnosis of asthma was made according to internationally accepted criteria. Asthma severity was evaluated according to frequency of symptoms and FEV1.Adequate sputum samples were obtained in 50 untreated subjects. A control group of 12 normal subjects that showed PC20 more than 8 mg/dl was also examined. Sputum was induced by inhalation of hypertonic saline. Inflammatory cells in sputum smears were assessed semi-quantitatively. ECP and IgE concentrations, eosinophil (EO) percentage and ECP/EO ratio in serum and sputum were also determined. The results revealed that Cough and dyspnea were the most frequent clinical findings. Dyspnea and wheezing were the symptoms that correlated with staging of asthma. FEV1 was within normal range (more than 80% of predicted) in 22 (44%) subjects.Asthmatic patients showed significantly higher numbers of blood eosinophils (4.5+/- 3.1% vs. 1.2+/-0.2%, P=0.009), and higher levels of serum ECP than control group (3.1+/- 2.6 % and 22.6+/- 15.8 ng/ml, respectively). Sputum ECP level in asthmatics was significantly higher than non- asthmatics (55.3+/-29.8ng/mL vs. 25.0+/-24.7ng/mL, P=0.045). Regression analysis showed no significant correlation between spirometric parameters and biomarkers, the only exception was significant correlation between FEF(25-75) and serum ECP (r= 0.28, P 0.041). Regarding clinical symptoms, wheezing was significantly correlated with elevation of most of biomarkers. Since, serum and sputum ECP levels are elevated in untreated asthmatics, the ECP level could be used for accurate diagnosis of mild form of asthma in which spirometry is unremarkable. PMID:20124607

  17. A new method for determining the 3He/4He ratio in the local interstellar medium

    NASA Astrophysics Data System (ADS)

    Lemoine, M.; Vidal-Madjar, A.; Ferlet, R.

    1993-06-01

    We propose here an original method for estimating the 3He/4 Heratio in the local diffuse interstellar medium at a low cost from an observational point of view. The main idea is to measure the shift in radial velocity of the 4He λ537Å and λ584Å lines due to the presence of 3He in the red wing of these lines, and to compare the observed shift to the shifts obtained through numerical simulations for different 3He/4He ratios. We performed such simulations in order to reveal the efficiency of this method, using typical astrophysical conditions and instrumental parameters corresponding to the Lyman-FUSE mission. We find that this method should yield the 3He/4He ratio with a 1 σ uncertainty ˜50% at a spectral resolving power R=30 000 and a signal-to-noise ratio S/N=50. This method thus appears more adapted to a forehand estimation of the interstellar 3He/4He ratio than the standard profile fitting method, which should yield a 1 σ uncertainty of 10% at R=30 000 and S/N ≃ 290 (Hurwitz & Bowyer, t985). Finally, our method should be able to settle the evolutionary status of 3He if 3He has been significantly enhanced or depleted in the last 4.6 Gyr. Combined with the measurement of the deuterium abundance on the same line of sight (already programmed on HST), this might yield very important constraint on Big-Bang nucleosynthesis consistency.

  18. The Golden Ratio

    ERIC Educational Resources Information Center

    Hyde, Hartley

    2004-01-01

    The Golden Ratio is sometimes called the "Golden Section" or the "Divine Proportion", in which three points: A, B, and C, divide a line in this proportion if AC/AB = AB/BC. "Donald in Mathmagicland" includes a section about the Golden Ratio and the ratios within a five-pointed star or pentagram. This article presents two computing exercises that…

  19. A method for determining adequate resistance form of complete cast crown preparations.

    PubMed

    Weed, R M; Baez, R J

    1984-09-01

    A diagram with various degrees of occlusal convergence, which takes into consideration the length and diameter of complete crown preparations, was designed as a guide to assist the dentist to obtain adequate resistance form. To test the validity of the diagram, five groups of complete cast crown stainless steel dies were prepared (3.5 mm long, occlusal convergence 10, 13, 16, 19, and 22 degrees). Gold copings were cast for each of the 50 preparations. Displacement force was applied to the casting perpendicularly to a simulated 30-degree cuspal incline until the casting was displaced. Castings were deformed at margins except for the 22-degree group. Castings from this group were displaced without deformation, and it was concluded that there was a lack of adequate resistance form as predicted by the diagram. The hypothesis that the diagram could be used to predict adequate or inadequate resistance form was confirmed by this study. PMID:6384470

  20. Performance evaluation of optically-preamplified hybrid QPSK M-ary PPM systems with finite extinction ratios

    NASA Astrophysics Data System (ADS)

    Landolsi, Taha; Hassan, Mohamed S.; Elrefaie, Aly F.; Hamid, Sanaa

    2015-10-01

    In this paper, we investigate the impact of finite extinction ratios on the error performance of optically-preamplified homodyne hybrid PDM-QPSK M-ary PPM (PQ-mPPM) systems. The study is carried for symbol sizes M ∈ { 2, 4, …, 1024 } and extinction ratios r ∈ { 10, 15, 20, 25, 30 }dB for probabilities of bit error down to Pb =3-9 , which covers systems with or without forward error correction (FEC). We demonstrate that the probability of slot correct location within a symbol in a PQ-mPPM homodyne system with finite extinction ratios is equal to the probability of symbol correct detection in a direct-detection system with dual polarized noise, with the same extinction ratio and symbol size M. This result is leveraged to compute the probabilities of bit error for the homodyne system using an accurate numerical approach. We show that when the extinction ratio is finite, the probability of slot correct location is decreased which not only increases the probability of bit error in the PPM demodulator subsystem but also leads to an increased probability of bit error in the QPSK demodulator. This results in a situation where systems with higher values of M lose their advantage. For example, at Pb =10-4 , M = 128 and M = 16 require the least signal to noise ratio for the case of r = 30 dB and 20 dB, respectively. The power penalty due to a finite extinction ratio depends on the symbol size M. For instance, at Pb =10-9 , M = 1024, and r = 20 dB, the penalty is δ = 10.6dB . It increases drastically to 22.1 dB for r = 10 dB. For M = 16, it is 0.6 dB and 5 dB for r = 20 dB and r = 10 dB, respectively.

  1. Comparison of four standards for determining adequate water intake of nursing home residents.

    PubMed

    Gaspar, Phyllis M

    2011-01-01

    Adequate hydration for nursing home residents is problematic. The purpose of this study was to compare four standards used to determine a recommended water intake among nursing home residents. Inconsistencies in the amount of water intake recommended based on the standards compared were identified. The standard based on height and weight provides the most individualized recommendation. An individualized recommendation would facilitate goal setting for the care plan of each older person and assist in the prevention of dehydration. It is essential that a cost-effective and clinically feasible approach to determine adequate water intake be determined for this population to prevent the adverse outcomes associated with dehydration. PMID:21469538

  2. Effect of Compression, Digital Noise Reduction and Directionality on Envelope Difference Index, Log-Likelihood Ratio and Perceived Quality.

    PubMed

    Geetha, Chinnaraj; Manjula, Puttabasappa

    2014-03-01

    The aim of the present study was to evaluate the use of the envelope difference index (EDI) and log-likelihood ratio (LLR) to quantify the independent and interactive effects of wide dynamic range compression, digital noise reduction and directionality, and to carry out self-rated quality measures. A recorded sentence embedded in speech spectrum noise at +5 dB signal to noise ratio was presented to a four channel digital hearing aid and the output was recorded with different combinations of algorithms at 30, 45 and 70 dB HL levels of presentation through a 2 cc coupler. EDI and LLR were obtained in comparison with the original signal using MATLAB software. In addition, thirty participants with normal hearing sensitivity rated the output on the loudness and clarity parameters of quality. The results revealed that the temporal changes happening at the output is independent of the number of algorithms activated together in a hearing aid. However, at a higher level of presentation, temporal cues are better preserved if all of these algorithms are deactivated. The spectral components speech tend to get affected by the presentation level. The results also indicate the importance of quality rating as this helps in considering whether the spectral and/or temporal deviations created in the hearing aid are desirable or not. PMID:26557357

  3. Peak-to-average power ratio reduction in all-optical orthogonal frequency division multiplexing system using rotated constellation approach

    NASA Astrophysics Data System (ADS)

    Hmood, Jassim K.; Noordin, Kamarul A.; Arof, Hamzah; Harun, Sulaiman W.

    2015-10-01

    In this paper, a new approach for reducing peak-to-average power ratio (PAPR) based on modulated half subcarriers in all-optical OFDM systems with rotated QAM constellation is presented. To reduce the PAPR, the odd subcarriers are modulated with rotated QAM constellation, while the even subcarriers are modulated with standard QAM constellation. The impact of the rotation angle on the PAPR is mathematically modeled. The effect of PAPR reduction on the system performance is investigated by simulating the all-optical OFDM system, which uses optical coupler-based inverse fast Fourier transform (IFFT)/fast Fourier transform (FFT). The all-optical system is numerically demonstrated with 29 subcarriers. Each subcarrier is modulated by a QAM modulator at a symbol rate of 25 Gsymbol/s. The results reveal that PAPR is reduced with increasing the angle of rotation. The PAPR reduction can reach about 0.8 dB when the complementary cumulative distribution function (CCDF) is 1 × 10-3. Furthermore, both the nonlinear phase noise and the optical signal-to-noise ratio (OSNR) of the system are improved in comparison with the original all-optical OFDM without PAPR reduction.

  4. Effect of Compression, Digital Noise Reduction and Directionality on Envelope Difference Index, Log-Likelihood Ratio and Perceived Quality

    PubMed Central

    Geetha, Chinnaraj; Manjula, Puttabasappa

    2014-01-01

    The aim of the present study was to evaluate the use of the envelope difference index (EDI) and log-likelihood ratio (LLR) to quantify the independent and interactive effects of wide dynamic range compression, digital noise reduction and directionality, and to carry out self-rated quality measures. A recorded sentence embedded in speech spectrum noise at +5 dB signal to noise ratio was presented to a four channel digital hearing aid and the output was recorded with different combinations of algorithms at 30, 45 and 70 dB HL levels of presentation through a 2 cc coupler. EDI and LLR were obtained in comparison with the original signal using MATLAB software. In addition, thirty participants with normal hearing sensitivity rated the output on the loudness and clarity parameters of quality. The results revealed that the temporal changes happening at the output is independent of the number of algorithms activated together in a hearing aid. However, at a higher level of presentation, temporal cues are better preserved if all of these algorithms are deactivated. The spectral components speech tend to get affected by the presentation level. The results also indicate the importance of quality rating as this helps in considering whether the spectral and/or temporal deviations created in the hearing aid are desirable or not. PMID:26557357

  5. 1 Tbit/inch2 Recording in Angular-Multiplexing Holographic Memory with Constant Signal-to-Scatter Ratio Schedule

    NASA Astrophysics Data System (ADS)

    Hosaka, Makoto; Ishii, Toshiki; Tanaka, Asato; Koga, Shogo; Hoshizawa, Taku

    2013-09-01

    We developed an iterative method for optimizing the exposure schedule to obtain a constant signal-to-scatter ratio (SSR) to accommodate various recording conditions and achieve high-density recording. 192 binary images were recorded in the same location of a medium in approximately 300×300 µm2 using an experimental system embedded with a blue laser diode with a 405 nm wavelength and an objective lens with a 0.85 numerical aperture. The recording density of this multiplexing corresponds to 1 Tbit/in.2. The recording exposure time was optimized through the iteration of a three-step sequence consisting of total reproduced intensity measurement, target signal calculation, and recording energy density calculation. The SSR of pages recorded with this method was almost constant throughout the entire range of the reference beam angle. The signal-to-noise ratio of the sampled pages was over 2.9 dB, which is higher than the reproducible limit of 1.5 dB in our experimental system.

  6. Highly photostable, reversibly photoswitchable fluorescent protein with high contrast ratio for live-cell superresolution microscopy.

    PubMed

    Zhang, Xi; Zhang, Mingshu; Li, Dong; He, Wenting; Peng, Jianxin; Betzig, Eric; Xu, Pingyong

    2016-09-13

    Two long-standing problems for superresolution (SR) fluorescence microscopy are high illumination intensity and long acquisition time, which significantly hamper its application for live-cell imaging. Reversibly photoswitchable fluorescent proteins (RSFPs) have made it possible to dramatically lower the illumination intensities in saturated depletion-based SR techniques, such as saturated depletion nonlinear structured illumination microscopy (NL-SIM) and reversible saturable optical fluorescence transition microscopy. The characteristics of RSFPs most critical for SR live-cell imaging include, first, the integrated fluorescence signal across each switching cycle, which depends upon the absorption cross-section, effective quantum yield, and characteristic switching time from the fluorescent "on" to "off" state; second, the fluorescence contrast ratio of on/off states; and third, the photostability under excitation and depletion. Up to now, the RSFPs of the Dronpa and rsEGFP (reversibly switchable EGFP) families have been exploited for SR imaging. However, their limited number of switching cycles, relatively low fluorescence signal, and poor contrast ratio under physiological conditions ultimately restrict their utility in time-lapse live-cell imaging and their ability to reach the desired resolution at a reasonable signal-to-noise ratio. Here, we present a truly monomeric RSFP, Skylan-NS, whose properties are optimized for the recently developed patterned activation NL-SIM, which enables low-intensity (∼100 W/cm(2)) live-cell SR imaging at ∼60-nm resolution at subsecond acquisition times for tens of time points over broad field of view. PMID:27562163

  7. The Relationship between Parental Involvement and Adequate Yearly Progress among Urban, Suburban, and Rural Schools

    ERIC Educational Resources Information Center

    Ma, Xin; Shen, Jianping; Krenn, Huilan Y.

    2014-01-01

    Using national data from the 2007-08 School and Staffing Survey, we compared the relationships between parental involvement and school outcomes related to adequate yearly progress (AYP) in urban, suburban, and rural schools. Parent-initiated parental involvement demonstrated significantly positive relationships with both making AYP and staying off…

  8. Influenza 2005-2006: vaccine supplies adequate, but bird flu looms.

    PubMed

    Mossad, Sherif B

    2005-11-01

    Influenza vaccine supplies appear to be adequate for the 2005-2006 season, though delivery has been somewhat delayed. However, in the event of a pandemic of avian flu-considered inevitable by most experts, although no one knows when it will happen-the United States would be woefully unprepared. PMID:16315443

  9. Calculating and Reducing Errors Associated with the Evaluation of Adequate Yearly Progress.

    ERIC Educational Resources Information Center

    Hill, Richard

    In the Spring, 1996, issue of "CRESST Line," E. Baker and R. Linn commented that, in efforts to measure the progress of schools, "the fluctuations due to differences in the students themselves could conceal differences in instructional effects." This is particularly true in the context of the evaluation of adequate yearly progress required by…

  10. How Much and What Kind? Identifying an Adequate Technology Infrastructure for Early Childhood Education. Policy Brief

    ERIC Educational Resources Information Center

    Daugherty, Lindsay; Dossani, Rafiq; Johnson, Erin-Elizabeth; Wright, Cameron

    2014-01-01

    To realize the potential benefits of technology use in early childhood education (ECE), and to ensure that technology can help to address the digital divide, providers, families of young children, and young children themselves must have access to an adequate technology infrastructure. The goals for technology use in ECE that a technology…

  11. Prenatal zinc supplementation of zinc-adequate rats adversely affects immunity in offspring

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We previously showed that zinc (Zn) supplementation of Zn-adequate dams induced immunosuppressive effects that persist in the offspring after weaning. We investigated whether the immunosuppressive effects were due to in utero exposure and/or mediated via milk using a cross-fostering design. Pregnant...

  12. 75 FR 5893 - Suspension of Community Eligibility for Failure To Maintain Adequate Floodplain Management...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-05

    ... FR 51735. Executive Order 13132, Federalism. This rule involves no policies that have ] federalism....C. 4001 et seq., Reorganization Plan No. 3 of 1978, 3 CFR, 1978 Comp., p. 329; E.O. 12127, 44 FR... To Maintain Adequate Floodplain Management Regulations AGENCY: Federal Emergency Management...

  13. 26 CFR 1.467-2 - Rent accrual for section 467 rental agreements without adequate interest.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... provide for a variable rate of interest. For purposes of the adequate interest test under paragraph (b)(1) of this section, if a section 467 rental agreement provides for variable interest, the rental... date as the issue date) for the variable rates called for by the rental agreement. For purposes of...

  14. The Unequal Effect of Adequate Yearly Progress: Evidence from School Visits

    ERIC Educational Resources Information Center

    Brown, Abigail B.; Clift, Jack W.

    2010-01-01

    The authors report insights, based on annual site visits to elementary and middle schools in three states from 2004 to 2006, into the incentive effect of the No Child Left Behind Act's requirement that increasing percentages of students make Adequate Yearly Progress (AYP) in every public school. They develop a framework, drawing on the physics…

  15. 9 CFR 2.33 - Attending veterinarian and adequate veterinary care.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 9 Animals and Animal Products 1 2011-01-01 2011-01-01 false Attending veterinarian and adequate veterinary care. 2.33 Section 2.33 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE ANIMAL WELFARE REGULATIONS Research Facilities § 2.33 Attending veterinarian...

  16. 9 CFR 2.33 - Attending veterinarian and adequate veterinary care.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Attending veterinarian and adequate veterinary care. 2.33 Section 2.33 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE ANIMAL WELFARE REGULATIONS Research Facilities § 2.33 Attending veterinarian...

  17. Perceptions of Teachers in Their First Year of School Restructuring: Failure to Make Adequate Yearly Progress

    ERIC Educational Resources Information Center

    Moser, Sharon

    2010-01-01

    The 2007-2008 school year marked the first year Florida's Title I schools that did not made Adequate Yearly Progress (AYP) for five consecutive years entered into restructuring as mandated by the "No Child Left Behind Act" of 2001. My study examines the perceptions of teacher entering into their first year of school restructuring due to failure to…

  18. A Model for Touch Technique and Computation of Adequate Cane Length.

    ERIC Educational Resources Information Center

    Plain-Switzer, Karen

    1993-01-01

    This article presents a model for the motion of a long-cane executing the touch technique and presents formulas for the projected length of a cane adequate to protect an individual with blindness against wall-type and pole-type hazards. The paper concludes that the long-cane should reach from the floor to the user's armpit. (JDD)

  19. Towards Defining Adequate Lithium Trials for Individuals with Mental Retardation and Mental Illness.

    ERIC Educational Resources Information Center

    Pary, Robert J.

    1991-01-01

    Use of lithium with mentally retarded individuals with psychiatric conditions and/or behavior disturbances is discussed. The paper describes components of an adequate clinical trial and reviews case studies and double-blind cases. The paper concludes that aggression is the best indicator for lithium use, and reviews treatment parameters and…

  20. 9 CFR 2.33 - Attending veterinarian and adequate veterinary care.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... animal health, behavior, and well-being is conveyed to the attending veterinarian; (4) Guidance to... 9 Animals and Animal Products 1 2014-01-01 2014-01-01 false Attending veterinarian and adequate veterinary care. 2.33 Section 2.33 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION...

  1. 9 CFR 2.40 - Attending veterinarian and adequate veterinary care (dealers and exhibitors).

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... on problems of animal health, behavior, and well-being is conveyed to the attending veterinarian; (4... 9 Animals and Animal Products 1 2013-01-01 2013-01-01 false Attending veterinarian and adequate veterinary care (dealers and exhibitors). 2.40 Section 2.40 Animals and Animal Products ANIMAL AND...

  2. 9 CFR 2.40 - Attending veterinarian and adequate veterinary care (dealers and exhibitors).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... on problems of animal health, behavior, and well-being is conveyed to the attending veterinarian; (4... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Attending veterinarian and adequate veterinary care (dealers and exhibitors). 2.40 Section 2.40 Animals and Animal Products ANIMAL AND...

  3. 9 CFR 2.40 - Attending veterinarian and adequate veterinary care (dealers and exhibitors).

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... on problems of animal health, behavior, and well-being is conveyed to the attending veterinarian; (4... 9 Animals and Animal Products 1 2011-01-01 2011-01-01 false Attending veterinarian and adequate veterinary care (dealers and exhibitors). 2.40 Section 2.40 Animals and Animal Products ANIMAL AND...

  4. 9 CFR 2.33 - Attending veterinarian and adequate veterinary care.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... animal health, behavior, and well-being is conveyed to the attending veterinarian; (4) Guidance to... 9 Animals and Animal Products 1 2013-01-01 2013-01-01 false Attending veterinarian and adequate veterinary care. 2.33 Section 2.33 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION...

  5. 9 CFR 2.40 - Attending veterinarian and adequate veterinary care (dealers and exhibitors).

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... on problems of animal health, behavior, and well-being is conveyed to the attending veterinarian; (4... 9 Animals and Animal Products 1 2014-01-01 2014-01-01 false Attending veterinarian and adequate veterinary care (dealers and exhibitors). 2.40 Section 2.40 Animals and Animal Products ANIMAL AND...

  6. Special or Not so Special: Special Education Background Experiences of Principals and Adequate Yearly Progress

    ERIC Educational Resources Information Center

    Wilcox, Jennifer E.

    2011-01-01

    This mixed-methods study researched the special education background experience of principals and the effect on students in the subgroup of Students with Disabilities in making Adequate Yearly Progress (AYP). In the state of Ohio, schools and districts are expected to make AYP as a whole and additionally make AYP for each subgroup (various…

  7. Inferential Processing among Adequate and Struggling Adolescent Comprehenders and Relations to Reading Comprehension

    ERIC Educational Resources Information Center

    Barth, Amy E.; Barnes, Marcia; Francis, David; Vaughn, Sharon; York, Mary

    2015-01-01

    Separate mixed model analyses of variance were conducted to examine the effect of textual distance on the accuracy and speed of text consistency judgments among adequate and struggling comprehenders across grades 6-12 (n = 1,203). Multiple regressions examined whether accuracy in text consistency judgments uniquely accounted for variance in…

  8. 42 CFR 438.207 - Assurances of adequate capacity and services.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... with the State's requirements for availability of services, as set forth in § 438.206. (e) CMS' right... HUMAN SERVICES (CONTINUED) MEDICAL ASSISTANCE PROGRAMS MANAGED CARE Quality Assessment and Performance... 42 Public Health 4 2010-10-01 2010-10-01 false Assurances of adequate capacity and services....

  9. 42 CFR 438.207 - Assurances of adequate capacity and services.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... requirements: (1) Offers an appropriate range of preventive, primary care, and specialty services that is adequate for the anticipated number of enrollees for the service area. (2) Maintains a network of providers... enrollment in its service area in accordance with the State's standards for access to care under this...

  10. 42 CFR 438.207 - Assurances of adequate capacity and services.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... requirements: (1) Offers an appropriate range of preventive, primary care, and specialty services that is adequate for the anticipated number of enrollees for the service area. (2) Maintains a network of providers... enrollment in its service area in accordance with the State's standards for access to care under this...

  11. 42 CFR 438.207 - Assurances of adequate capacity and services.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... requirements: (1) Offers an appropriate range of preventive, primary care, and specialty services that is adequate for the anticipated number of enrollees for the service area. (2) Maintains a network of providers... enrollment in its service area in accordance with the State's standards for access to care under this...

  12. Effect of tranquilizers on animal resistance to the adequate stimuli of the vestibular apparatus

    NASA Technical Reports Server (NTRS)

    Maksimovich, Y. B.; Khinchikashvili, N. V.

    1980-01-01

    The effect of tranquilizers on vestibulospinal reflexes and motor activity was studied in 900 centrifuged albino mice. Actometric studies have shown that the tranquilizers have a group capacity for increasing animal resistance to the action of adequate stimuli to the vestibular apparatus.

  13. 21 CFR 314.126 - Adequate and well-controlled studies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... conducting clinical investigations of a drug is to distinguish the effect of a drug from other influences... recognized by the scientific community as the essentials of an adequate and well-controlled clinical... randomization and blinding of patients or investigators, or both. If the intent of the trial is to...

  14. Final 2004 Report on Adequate Yearly Progress in the Montgomery County Public Schools

    ERIC Educational Resources Information Center

    Stevenson, Jose W.

    2005-01-01

    The vast majority of Montgomery County public schools made sufficient progress on state testing and accountability standards in 2004 to comply with the adequate yearly progress (AYP) requirements under the "No Child Left Behind (NCLB) Act of 2001." Information released by the Maryland State Department of Education (MSDE) in October 2004 shows that…

  15. 42 CFR 417.568 - Adequate financial records, statistical data, and cost finding.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 3 2011-10-01 2011-10-01 false Adequate financial records, statistical data, and... financial records, statistical data, and cost finding. (a) Maintenance of records. (1) An HMO or CMP must maintain sufficient financial records and statistical data for proper determination of costs payable by...

  16. 42 CFR 417.568 - Adequate financial records, statistical data, and cost finding.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 3 2010-10-01 2010-10-01 false Adequate financial records, statistical data, and... financial records, statistical data, and cost finding. (a) Maintenance of records. (1) An HMO or CMP must maintain sufficient financial records and statistical data for proper determination of costs payable by...

  17. Leadership Style and Adequate Yearly Progress: A Correlational Study of Effective Principal Leadership

    ERIC Educational Resources Information Center

    Leapley-Portscheller, Claudia Iris

    2008-01-01

    Principals are responsible for leading efforts to reach increasingly higher levels of student academic proficiency in schools associated with adequate yearly progress (AYP) requirements. The purpose of this quantitative, correlational study was to identify the degree to which perceptions of principal transformational, transactional, and…

  18. Percentage of Adults with High Cholesterol Whose LDL Cholesterol Levels Are Adequately Controlled

    MedlinePlus

    ... of Adults with High Cholesterol Whose LDL Cholesterol Levels are Adequately Controlled High cholesterol can double a ... with High Cholesterol that is Controlled by Education Level 8k4c-k22f Download these data » Click on legends ...

  19. 42 CFR 413.24 - Adequate cost data and cost finding.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 2 2010-10-01 2010-10-01 false Adequate cost data and cost finding. 413.24 Section 413.24 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES MEDICARE PROGRAM PRINCIPLES OF REASONABLE COST REIMBURSEMENT; PAYMENT FOR END-STAGE RENAL DISEASE SERVICES; OPTIONAL PROSPECTIVELY...

  20. Principals' Perceptions of Effective Strategies in Meeting Adequate Yearly Progress in Special Education

    ERIC Educational Resources Information Center

    Meyer, Jadie K.

    2012-01-01

    The purpose of this study was to examine the perceptions of principals who have met Adequate Yearly Progress (AYP) with the special education subgroup. This was a qualitative study, utilizing interviews to answer the research questions. The first three research questions analyzed the areas of assessment, building-level leadership, and curriculum…

  1. Human milk feeding supports adequate growth in infants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Despite current nutritional strategies, premature infants remain at high risk for extrauterine growth restriction. The use of an exclusive human milk-based diet is associated with decreased incidence of necrotizing enterocolitis (NEC), but concerns exist about infants achieving adequate growth. The ...

  2. 75 FR 74022 - Safety Analysis Requirements for Defining Adequate Protection for the Public and the Workers

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-30

    ... November 15, 2010 (75 FR 69648). The corrected text of the recommendation approved by the Board is below... or telephone number (202) 694-7000. Correction: In the Federal Register of November 15, 2010 (75 FR... SAFETY BOARD Safety Analysis Requirements for Defining Adequate Protection for the Public and the...

  3. Evaluating Rural Progress in Mathematics Achievement: Threats to the Validity of "Adequate Yearly Progress"

    ERIC Educational Resources Information Center

    Lee, Jaekyung

    2003-01-01

    This article examines major threats to the validity of Adequate Yearly Progress (AYP) in the context of rural schools. Although rural students and their schools made significant academic progress in the past on national and state assessments, the current goal of AYP turns out to be highly unrealistic for them unless states set far lower…

  4. 40 CFR 152.20 - Exemptions for pesticides adequately regulated by another Federal agency.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Exemptions for pesticides adequately regulated by another Federal agency. 152.20 Section 152.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS PESTICIDE REGISTRATION AND CLASSIFICATION...

  5. 40 CFR 152.20 - Exemptions for pesticides adequately regulated by another Federal agency.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 25 2013-07-01 2013-07-01 false Exemptions for pesticides adequately regulated by another Federal agency. 152.20 Section 152.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS PESTICIDE REGISTRATION AND CLASSIFICATION...

  6. 40 CFR 152.20 - Exemptions for pesticides adequately regulated by another Federal agency.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 25 2012-07-01 2012-07-01 false Exemptions for pesticides adequately regulated by another Federal agency. 152.20 Section 152.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS PESTICIDE REGISTRATION AND CLASSIFICATION...

  7. What Is the Cost of an Adequate Vermont High School Education?

    ERIC Educational Resources Information Center

    Rucker, Frank D.

    2010-01-01

    Access to an adequate education has been widely considered an undeniable right since Chief Justice Warren stated in his landmark decision that "Today, education is perhaps the most important function of state and local governments...it is doubtful that any child may reasonably be expected to succeed in life if he is denied the opportunity of an…

  8. Detecting isotopic ratio outliers

    SciTech Connect

    Bayne, C.K.; Smith, D.H.

    1985-01-01

    An alternative method is proposed for improving isotopic ratio estimates. This method mathematically models pulse-count data and uses iterative reweighted Poisson regression to estimate model parameters to calculate the isotopic ratios. This computer-oriented approach provides theoretically better methods than conventional techniques to establish error limits and to identify outliers. 6 refs., 3 figs., 3 tabs.

  9. The concept of adequate causation and Max Weber's comparative sociology of religion.

    PubMed

    Buss, A

    1999-06-01

    Max Weber's The Protestant Ethic and the Spirit of Capitalism, studied in isolation, shows mainly an elective affinity or an adequacy on the level of meaning between the Protestant ethic and the 'spirit' of capitalism. Here it is suggested that Weber's subsequent essays on 'The Economic Ethics of World Religions' are the result of his opinion that adequacy on the level of meaning needs and can be verified by causal adequacy. After some introductory remarks, particularly on elective affinity, the paper tries to develop the concept of adequate causation and the related concept of objective possibility on the basis of the work of v. Kries on whom Weber heavily relied. In the second part, this concept is used to show how the study of the economic ethics of India, China, Rome and orthodox Russia can support the thesis that the 'spirit' of capitalism, although it may not have been caused by the Protestant ethic, was perhaps adequately caused by it. PMID:15260028

  10. A novel strategy to overcome resistance in stent placement at lesion site after adequate predilatation.

    PubMed

    Jain, D; Tolg, R; Katus, H A; Richardt, G

    2000-12-01

    Resistance was encountered in passing a 3 x 18 mm stent across a lesion in the proximal left anterior descending coronary artery. Successive changes in stent with repeated balloon dilatations did not succeed. Finally, a 9 mm stent was passed across the lesion and deployed at the site of maximal resistance. The 18 mm stent was then placed through this stent. A novel strategy to overcome resistance in the stent passage through the lesion after an adequate balloon predilatation is reported. PMID:11103034

  11. Myth 19: Is Advanced Placement an Adequate Program for Gifted Students?

    ERIC Educational Resources Information Center

    Gallagher, Shelagh A.

    2009-01-01

    Is it a myth that Advanced Placement (AP) is an adequate program for gifted students? AP is so covered with myths and assumptions that it is hard to get a clear view of the issues. In this article, the author finds the answer about AP by looking at current realties. First, AP is hard for gifted students to avoid. Second, AP never was a program…

  12. STELLAR MASS-TO-LIGHT RATIOS FROM GALAXY SPECTRA: HOW ACCURATE CAN THEY BE?

    SciTech Connect

    Gallazzi, Anna; Bell, Eric F. E-mail: ericbell@umich.edu

    2009-12-01

    Stellar masses play a crucial role in the exploration of galaxy properties and the evolution of the galaxy population. In this paper, we explore the minimum possible uncertainties in stellar mass-to-light ratios (M {sub *}/L) from the assumed star formation history (SFH) and metallicity distribution, with the goals of providing a minimum set of requirements for observational studies. We use a large Monte Carlo library of SFHs to study as a function of galaxy spectral type and signal-to-noise ratio (S/N) the statistical uncertainties of M {sub *}/L values using either absorption-line data or broadband colors. The accuracy of M {sub *}/L estimates can be significantly improved by using metal-sensitive indices in combination with age-sensitive indices, in particular for galaxies with intermediate-age or young stellar populations. While M {sub *}/L accuracy clearly depends on the spectral S/N, there is no significant gain in improving the S/N much above 50 pixel{sup -1} and limiting uncertainties of {approx}0.03 dex are reached. Assuming that dust is accurately corrected or absent and that the redshift is known, color-based M {sub *}/L estimates are only slightly more uncertain than spectroscopic estimates (at comparable spectroscopic and photometric quality), but are more easily affected by systematic biases. This is the case in particular for galaxies with bursty SFHs (high H{delta} {sub A} at fixed D4000 {sub n}), the M {sub *}/L of which cannot be constrained any better than {approx}0.15 dex with any indicators explored here. Finally, we explore the effects of the assumed prior distribution in SFHs and metallicity, finding them to be higher for color-based estimates.

  13. The stability and calibration of water vapor isotope ratio measurements during long-term deployments

    NASA Astrophysics Data System (ADS)

    Bailey, A.; Noone, D.; Berkelhammer, M.; Steen-Larsen, H. C.; Sato, P.

    2015-10-01

    With the recent advent of commercial laser absorption spectrometers, field studies measuring stable isotope ratios of hydrogen and oxygen in water vapor have proliferated. These pioneering analyses have provided invaluable feedback about best strategies for optimizing instrumental accuracy, yet questions still remain about instrument performance and calibration approaches for multi-year field deployments. With clear scientific potential for using these instruments to carry out monitoring of the hydrological cycle, this study examines the long-term stability of the isotopic biases associated with three cavity-enhanced laser absorption spectrometers - calibrated with different systems and approaches - at two remote field sites: Mauna Loa Observatory, Hawaii, USA, and Greenland Environmental Observatory, Summit, Greenland. The analysis pays particular attention to the stability of measurement dependencies on water vapor concentration and also evaluates whether these so-called concentration dependences are sensitive to statistical curve-fitting choices or measurement hysteresis. The results suggest evidence of monthly-to-seasonal concentration-dependence variability - which likely stems from low signal-to-noise at the humidity-range extremes - but no long-term directional drift. At Mauna Loa, where the isotopic analyzer is calibrated by injection of liquid water standards into a vaporizer, the largest source of inaccuracy in characterizing the concentration dependence stems from an insufficient density of calibration points at low water vapor volume mixing ratios. In comparison, at Summit, the largest source of inaccuracy is measurement hysteresis associated with interactions between the reference vapor, generated by a custom dew point generator, and the sample tubing. Nevertheless, prediction errors associated with correcting the concentration dependence are small compared to total measurement uncertainty. At both sites, changes in measurement repeatability that are

  14. Quantitative visually lossless compression ratio determination of JPEG2000 in digitized mammograms.

    PubMed

    Georgiev, Verislav T; Karahaliou, Anna N; Skiadopoulos, Spyros G; Arikidis, Nikos S; Kazantzi, Alexandra D; Panayiotakis, George S; Costaridou, Lena I

    2013-06-01

    The current study presents a quantitative approach towards visually lossless compression ratio (CR) threshold determination of JPEG2000 in digitized mammograms. This is achieved by identifying quantitative image quality metrics that reflect radiologists' visual perception in distinguishing between original and wavelet-compressed mammographic regions of interest containing microcalcification clusters (MCs) and normal parenchyma, originating from 68 images from the Digital Database for Screening Mammography. Specifically, image quality of wavelet-compressed mammograms (CRs, 10:1, 25:1, 40:1, 70:1, 100:1) is evaluated quantitatively by means of eight image quality metrics of different computational principles and qualitatively by three radiologists employing a five-point rating scale. The accuracy of the objective metrics is investigated in terms of (1) their correlation (r) with qualitative assessment and (2) ROC analysis (A z index), employing pooled radiologists' rating scores as ground truth. The quantitative metrics mean square error, mean absolute error, peak signal-to-noise ratio, and structural similarity demonstrated strong correlation with pooled radiologists' ratings (r, 0.825, 0.823, -0.825, and -0.826, respectively) and the highest area under ROC curve (A z , 0.922, 0.920, 0.922, and 0.922, respectively). For each quantitative metric, the highest accuracy values of corresponding ROC curves were used to define metric cut-off values. The metrics cut-off values were subsequently used to suggest a visually lossless CR threshold, estimated to be between 25:1 and 40:1 for the dataset analyzed. Results indicate the potential of the quantitative metrics approach in predicting visually lossless CRs in case of MCs in mammography. PMID:23065144

  15. Deterrence and arrest ratios.

    PubMed

    Carmichael, Stephanie E; Piquero, Alex R

    2006-02-01

    In the limited research on the origins of sanction threat perceptions, researchers have focused on either the effects of actively engaging in crime or the effects of formal sanctioning but rarely on both (i.e., the arrest ratio or the number of arrests relative to the number of crimes committed). This article extends this line of research by using a sample of Colorado inmates and measures arrest ratios and sanction perceptions for eight different crime types. Analyses reveal that the offenders report both significant experiential and arrest ratio effects. Theoretical and policy implications, limitations, and directions for future research are outlined. PMID:16397123

  16. Global risk assessment of aflatoxins in maize and peanuts: are regulatory standards adequately protective?

    PubMed

    Wu, Felicia; Stacy, Shaina L; Kensler, Thomas W

    2013-09-01

    The aflatoxins are a group of fungal metabolites that contaminate a variety of staple crops, including maize and peanuts, and cause an array of acute and chronic human health effects. Aflatoxin B1 in particular is a potent liver carcinogen, and hepatocellular carcinoma (HCC) risk is multiplicatively higher for individuals exposed to both aflatoxin and chronic infection with hepatitis B virus (HBV). In this work, we sought to answer the question: do current aflatoxin regulatory standards around the world adequately protect human health? Depending upon the level of protection desired, the answer to this question varies. Currently, most nations have a maximum tolerable level of total aflatoxins in maize and peanuts ranging from 4 to 20ng/g. If the level of protection desired is that aflatoxin exposures would not increase lifetime HCC risk by more than 1 in 100,000 cases in the population, then most current regulatory standards are not adequately protective even if enforced, especially in low-income countries where large amounts of maize and peanuts are consumed and HBV prevalence is high. At the protection level of 1 in 10,000 lifetime HCC cases in the population, however, almost all aflatoxin regulations worldwide are adequately protective, with the exception of several nations in Africa and Latin America. PMID:23761295

  17. Global Risk Assessment of Aflatoxins in Maize and Peanuts: Are Regulatory Standards Adequately Protective?

    PubMed Central

    Wu, Felicia

    2013-01-01

    The aflatoxins are a group of fungal metabolites that contaminate a variety of staple crops, including maize and peanuts, and cause an array of acute and chronic human health effects. Aflatoxin B1 in particular is a potent liver carcinogen, and hepatocellular carcinoma (HCC) risk is multiplicatively higher for individuals exposed to both aflatoxin and chronic infection with hepatitis B virus (HBV). In this work, we sought to answer the question: do current aflatoxin regulatory standards around the world adequately protect human health? Depending upon the level of protection desired, the answer to this question varies. Currently, most nations have a maximum tolerable level of total aflatoxins in maize and peanuts ranging from 4 to 20ng/g. If the level of protection desired is that aflatoxin exposures would not increase lifetime HCC risk by more than 1 in 100,000 cases in the population, then most current regulatory standards are not adequately protective even if enforced, especially in low-income countries where large amounts of maize and peanuts are consumed and HBV prevalence is high. At the protection level of 1 in 10,000 lifetime HCC cases in the population, however, almost all aflatoxin regulations worldwide are adequately protective, with the exception of several nations in Africa and Latin America. PMID:23761295

  18. Self-esteem, social support, and satisfaction differences in women with adequate and inadequate prenatal care.

    PubMed

    Higgins, P; Murray, M L; Williams, E M

    1994-03-01

    This descriptive, retrospective study examined levels of self-esteem, social support, and satisfaction with prenatal care in 193 low-risk postpartal women who obtained adequate and inadequate care. The participants were drawn from a regional medical center and university teaching hospital in New Mexico. A demographic questionnaire, the Coopersmith self-esteem inventory, the personal resource questionnaire part 2, and the prenatal care satisfaction inventory were used for data collection. Significant differences were found in the level of education, income, insurance, and ethnicity between women who received adequate prenatal care and those who received inadequate care. Women who were likely to seek either adequate or inadequate prenatal care were those whose total family income was $10,000 to $19,999 per year and high school graduates. Statistically significant differences were found in self-esteem, social support, and satisfaction between the two groups of women. Strategies to enhance self-esteem and social support have to be developed to reach women at risk for receiving inadequate prenatal care. PMID:8155221

  19. Simplifying Likelihood Ratios

    PubMed Central

    McGee, Steven

    2002-01-01

    Likelihood ratios are one of the best measures of diagnostic accuracy, although they are seldom used, because interpreting them requires a calculator to convert back and forth between “probability” and “odds” of disease. This article describes a simpler method of interpreting likelihood ratios, one that avoids calculators, nomograms, and conversions to “odds” of disease. Several examples illustrate how the clinician can use this method to refine diagnostic decisions at the bedside.

  20. High Aspect Ratio Wrinkles

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Cheng; Crosby, Alfred

    2015-03-01

    Buckling-induced surface undulations are widely found in living creatures, for instance, gut villi and the surface of flower petal cells. These undulations provide unique functionalities with their extremely high aspect ratios. For the synthetic systems, sinusoidal wrinkles that are induced by buckling a thin film attached on a soft substrate have been proposed to many applications. However, the impact of the synthetic wrinkles have been restricted by limited aspect ratios, ranging from 0 to 0.35. Within this range, wrinkle aspect ratio is known to increase with increasing compressive strain until a critical strain is reached, at which point wrinkles transition to localizations, such as folds or period doublings. Inspired by the living creatures, we propose that wrinkles can be stabilized in high aspect ratio by manipulating the strain energy in the substrate. We experimentally demonstrate this idea by forming a secondary crosslinking network in the wrinkled surface and successfully achieve aspect ratio as large as 0.8. This work not only provides insights for the mechanism of high aspect ratio structures seen in living creatures, but also demonstrates significant promise for future wrinkle-based applications.

  1. Constraining lowermost mantle structure with PcP/P amplitude ratios from large aperture arrays

    NASA Astrophysics Data System (ADS)

    Ventosa, S.; Romanowicz, B. A.

    2015-12-01

    Observations of weak short-period teleseismic body waves help to resolve lowermost mantle structure at short wavelengths, which is essential for understanding mantle dynamics and the interactions between the mantle and core. Their limited amount and uneven distribution are however major obstacles to solve for volumetric structure of the D" region, topography of the core-mantle boundary (CMB) and D" discontinuity, and the trade-offs among them. While PcP-P differential travel times provide important information, there are trade-offs between velocity structure and core-mantle boundary topography, which PcP/P amplitude ratios can help resolve, as long as lateral variations in attenuation and biases due to focusing are small or can be corrected for. Dense broadband seismic networks help to improve signal-to-noise ratio (SNR) of the target phases and signal-to-interference ratio (SIR) of other mantle phases when the slowness difference is large enough. To improve SIR and SNR of teleseismic PcP data, we have introduced the slant-stacklet transform to define coherent-guided filters able to separate and enhance signals according to their slowness, time of arrival and frequency content. We thus obtain optimal PcP/P amplitude ratios in the least-square sense using two short sliding windows to match the P signal with a candidate PcP signal. This method allows us to dramatically increase the amount of high-quality observations of short-period PcP/P amplitude ratios by allowing for smaller events and wider epicentral distance and depth ranges.We present the results of measurement of PcP/P amplitude ratios, sampling regions around the Pacific using dense arrays in North America and Japan. We observe that short-period P waves traveling through slabs are strongly affected by focusing, in agreement with the bias we have observed and corrected for due to mantle heterogeneities on PcP-P travel time differences. In Central America, this bias is by far the stronger anomaly we observe

  2. 13CO2/12CO2 isotope ratio analysis in human breath using a 2 μm diode laser

    NASA Astrophysics Data System (ADS)

    Sun, Mingguo; Cao, Zhensong; Liu, Kun; Wang, Guishi; Tan, Tu; Gao, Xiaoming; Chen, Weidong; Yinbo, Huang; Ruizhong, Rao

    2015-04-01

    The bacterium H. pylori is believed to cause peptic ulcer. H. pylori infection in the human stomach can be diagnosed through a CO2 isotope ratio measure in exhaled breath. A laser spectrometer based on a distributed-feedback semiconductor diode laser at 2 μm is developed to measure the changes of 13CO2/12CO2 isotope ratio in exhaled breath sample with the CO2 concentration of ~4%. It is characterized by a simplified optical layout, in which a single detector and associated electronics are used to probe CO2 spectrum. A new type multi-passes cell with 12 cm long base length , 29 m optical path length in total and 280 cm3 volume is used in this work. The temperature and pressure are well controlled at 301.15 K and 6.66 kPa with fluctuation amplitude of 25 mK and 6.7 Pa, respectively. The best 13δ precision of 0.06o was achieved by using wavelet denoising and Kalman filter. The application of denoising and Kalman filter not only improved the signal to noise ratio, but also shorten the system response time.

  3. First constraint on cosmological variation of the proton-to-electron mass ratio from two independent telescopes.

    PubMed

    van Weerdenburg, F; Murphy, M T; Malec, A L; Kaper, L; Ubachs, W

    2011-05-01

    A high signal-to-noise spectrum covering the largest number of hydrogen lines (90 H(2) lines and 6 HD lines) in a high-redshift object was analyzed from an observation along the sight line to the bright quasar source J2123-005 with the Ultraviolet and Visual Echelle Spectrograph on the European Southern Observatory Very Large Telescope (Paranal, Chile). This delivers a constraint on a possible variation of the proton-to-electron mass ratio of Δμ/μ=(8.5 ± 3.6(stat) ± 2.2(syst))×10(-6) at redshift z(abs) = 2.059, which agrees well with a recently published result on the same system observed at the Keck telescope yielding Δμ/μ=(5.6 ± 5.5(stat) ± 2.9(syst))×10(-6). Both analyses used the same robust absorption line fitting procedures with detailed consideration of systematic errors. PMID:21635080

  4. First Look at the Upper Tropospheric Ozone Mixing Ratio from OMI Estimated using the Cloud Slicing Technique

    NASA Technical Reports Server (NTRS)

    Bhartia, Pawan K.; Ziemke, Jerry; Chandra, Sushil; Joiner, Joanna; Vassilkov, Alexandra; Taylor, Steven; Yang, Kai; Ahn, Chang-Woo

    2004-01-01

    The Cloud Slicing technique has emerged as a powerful tool for the study of ozone in the upper troposphere. In this technique one looks at the variation with cloud height of the above-cloud column ozone derived from the backscattered ultraviolet instruments, such as TOMS, to determine the ozone mixing ratio. For this technique to work properly one needs an instrument with relatively good horizontal resolution with very good signal to noise in measuring above-cloud column ozone. In addition, one needs the (radiatively) effective cloud pressure rather than the cloud-top pressure, for the ultraviolet photons received by a satellite instrument are scattered from inside the cloud rather than from the top. For this study we use data from the OMI sensor, which was recently launched on the EOS Aura satellite. OMI is a W-Visible backscattering instrument with a nadir pixel size of 13 x 24 km. The effective cloud pressure is derived from a new algorithm based on Rotational Raman Scattering and O2-O2, absorption in the 340-400 nm band of OMI.

  5. Adequate Iodine Status in New Zealand School Children Post-Fortification of Bread with Iodised Salt

    PubMed Central

    Jones, Emma; McLean, Rachael; Davies, Briar; Hawkins, Rochelle; Meiklejohn, Eva; Ma, Zheng Feei; Skeaff, Sheila

    2016-01-01

    Iodine deficiency re-emerged in New Zealand in the 1990s, prompting the mandatory fortification of bread with iodised salt from 2009. This study aimed to determine the iodine status of New Zealand children when the fortification of bread was well established. A cross-sectional survey of children aged 8–10 years was conducted in the cities of Auckland and Christchurch, New Zealand, from March to May 2015. Children provided a spot urine sample for the determination of urinary iodine concentration (UIC), a fingerpick blood sample for Thyroglobulin (Tg) concentration, and completed a questionnaire ascertaining socio-demographic information that also included an iodine-specific food frequency questionnaire (FFQ). The FFQ was used to estimate iodine intake from all main food sources including bread and iodised salt. The median UIC for all children (n = 415) was 116 μg/L (females 106 μg/L, males 131 μg/L) indicative of adequate iodine status according to the World Health Organisation (WHO, i.e., median UIC of 100–199 μg/L). The median Tg concentration was 8.7 μg/L, which was <10 μg/L confirming adequate iodine status. There was a significant difference in UIC by sex (p = 0.001) and ethnicity (p = 0.006). The mean iodine intake from the food-only model was 65 μg/day. Bread contributed 51% of total iodine intake in the food-only model, providing a mean iodine intake of 35 μg/day. The mean iodine intake from the food-plus-iodised salt model was 101 μg/day. In conclusion, the results of this study confirm that the iodine status in New Zealand school children is now adequate. PMID:27196925

  6. Adequate Iodine Status in New Zealand School Children Post-Fortification of Bread with Iodised Salt.

    PubMed

    Jones, Emma; McLean, Rachael; Davies, Briar; Hawkins, Rochelle; Meiklejohn, Eva; Ma, Zheng Feei; Skeaff, Sheila

    2016-01-01

    Iodine deficiency re-emerged in New Zealand in the 1990s, prompting the mandatory fortification of bread with iodised salt from 2009. This study aimed to determine the iodine status of New Zealand children when the fortification of bread was well established. A cross-sectional survey of children aged 8-10 years was conducted in the cities of Auckland and Christchurch, New Zealand, from March to May 2015. Children provided a spot urine sample for the determination of urinary iodine concentration (UIC), a fingerpick blood sample for Thyroglobulin (Tg) concentration, and completed a questionnaire ascertaining socio-demographic information that also included an iodine-specific food frequency questionnaire (FFQ). The FFQ was used to estimate iodine intake from all main food sources including bread and iodised salt. The median UIC for all children (n = 415) was 116 μg/L (females 106 μg/L, males 131 μg/L) indicative of adequate iodine status according to the World Health Organisation (WHO, i.e., median UIC of 100-199 μg/L). The median Tg concentration was 8.7 μg/L, which was <10 μg/L confirming adequate iodine status. There was a significant difference in UIC by sex (p = 0.001) and ethnicity (p = 0.006). The mean iodine intake from the food-only model was 65 μg/day. Bread contributed 51% of total iodine intake in the food-only model, providing a mean iodine intake of 35 μg/day. The mean iodine intake from the food-plus-iodised salt model was 101 μg/day. In conclusion, the results of this study confirm that the iodine status in New Zealand school children is now adequate. PMID:27196925

  7. Imaging the crustal structure of the valley of Mexico and higher mode identification using H/V spectral ratio

    NASA Astrophysics Data System (ADS)

    Rivet, D.; Campillo, M.; Sanchez-Sesma, F.; Singh, S. K.

    2012-04-01

    We reconstruct Rayleigh and Love waves from cross-correlations of ambient seismic noise recorded at 19 broad-band stations of the MesoAmerica Seismic Experiment (MASE) and Valley of Mexico Experiment (VMEX). The cross-correlations are computed over 2 years of noise records for the 8 MASE stations and over 1 year for the 11 VMEX stations. We use surface waves with sufficient signal-to-noise ratio to measure group velocity dispersion curves at period of 0.5 to 3 seconds. For paths within the soft quaternary sediments basin, the maximum energy is observed at velocity higher than expected for the fundamental mode. This observation suggests the importance of higher modes as the main vectors of energy in such complex structures. To perform a reliable inversion of the velocity structure beneath the valley, an identification of these dominants modes is required. To identify the modes of surface waves we use the spectral ratio of the horizontal components over the vertical component (H/V) measured on seismic coda. We compare the observed values with the theoretical H/V for the velocity model deduced from surface wave dispersion when assuming a particular mode. H/V ratio in the coda is computed under the hypothesis of equipartition of a diffuse field in a layered medium following Margerin et al. [2009] and Sánchez-Sesma et al. [2011]. We processed several events to ensure that the observed H/V is stable. The comparison of the modelled dispersion and H/V ratio allows for mode identification, and consequently to recover the velocity model of the structure. We conclude on the predominance of higher modes in our observations. The excitation of higher modes is key element of explanation for the long duration and amplification of the seismic signals observed in the Valley of Mexico.

  8. Chronic leg ulcer: does a patient always get a correct diagnosis and adequate treatment?

    PubMed

    Mooij, Michael C; Huisman, Laurens C

    2016-03-01

    Patients with chronic leg ulcers have severely impaired quality of life and account for a high percentage of annual healthcare costs. To establish the cause of a chronic leg ulcer, referral to a center with a multidisciplinary team of professionals is often necessary. Treating the underlying cause diminishes healing time and reduces costs. In venous leg ulcers adequate compression therapy is still a problem. It can be improved by training the professionals with pressure measuring devices. A perfect fitting of elastic stockings is important to prevent venous leg ulcer recurrence. In most cases, custom-made stockings are the best choice for this purpose. PMID:26916772

  9. Determining Adequate Margins in Head and Neck Cancers: Practice and Continued Challenges.

    PubMed

    Williams, Michelle D

    2016-09-01

    Margin assessment remains a critical component of oncologic care for head and neck cancer patients. As an integrated team, both surgeons and pathologists work together to assess margins in these complex patients. Differences in method of margin sampling can impact obtainable information and effect outcomes. Additionally, what distance is an "adequate or clear" margin for patient care continues to be debated. Ultimately, future studies and potentially secondary modalities to augment pathologic assessment of margin assessment (i.e., in situ imaging or molecular assessment) may enhance local control in head and neck cancer patients. PMID:27469263

  10. Family Structure Types and Adequate Utilization of Antenatal Care in Kenya.

    PubMed

    Owili, Patrick Opiyo; Muga, Miriam Adoyo; Chou, Yiing-Jenq; Hsu, Yi-Hsin Elsa; Huang, Nicole; Chien, Li-Yin

    2016-01-01

    Features of the health care delivery system may not be the only expounding factors of adequate utilization of antenatal care among women. Other social factors such as the family structure and its environment contribute toward pregnant women's utilization of antenatal care. An understanding of how women in different family structure types and social groups use basic maternal health services is important toward developing and implementing maternal health care policy in the post-Millennium Development Goal era, especially in the sub-Saharan Africa where maternal mortality still remains high. PMID:27214674

  11. Working group on the “adequate minimum” V=volcanic observatory

    USGS Publications Warehouse

    Tilling, R.I.

    1982-01-01

    A working group consisting of R. I. Tilling (United States, Chairman), M. Espendola (Mexico), E. Malavassi (Costa Rica), L. Villari (Italy), and J.P Viode (France) met on the island of Guadeloupe on February 20, 1981, to discuss informally the requirements for a "Minimum" volcano observatory, one which would have the essential monitoring equipment and staff to provide reliable information on the state of an active volcno. Given the premise that any monitoring of a volcano is better than none at all, the owrking group then proceeded to consider the concept of an "adequate minimum" observatory. 

  12. Maintaining Adequate CO2 Washout for an Advanced EMU via a New Rapid Cycle Amine Technology

    NASA Technical Reports Server (NTRS)

    Chullen, Cinda; Conger, Bruce

    2012-01-01

    Over the past several years, NASA has realized tremendous progress in Extravehicular Activity (EVA) technology development. This has been evidenced by the progressive development of a new Rapid Cycle Amine (RCA) system for the Advanced Extravehicular Mobility Unit (AEMU) Portable Life Support Subsystem (PLSS). The PLSS is responsible for the life support of the crew member in the spacesuit. The RCA technology is responsible for carbon dioxide (CO2) and humidity control. Another aspect of the RCA is that it is on-back vacuum-regenerable, efficient, and reliable. The RCA also simplifies the PLSS schematic by eliminating the need for a condensing heat exchanger for humidity control in the current EMU. As development progresses on the RCA, it is important that the sizing be optimized so that the demand on the PLSS battery is minimized. As well, maintaining the CO2 washout at adequate levels during an EVA is an absolute requirement of the RCA and associated ventilation system. Testing has been underway in-house at NASA Johnson Space Center and analysis has been initiated to evaluate whether the technology provides exemplary performance in ensuring that the CO2 is removed sufficiently and the ventilation flow is adequate for maintaining CO2 washout in the AEMU spacesuit helmet of the crew member during an EVA. This paper will review the recent developments of the RCA unit, testing planned in-house with a spacesuit simulator, and the associated analytical work along with insights from the medical aspect on the testing. 1

  13. Adequately-Sized Nanocarriers Allow Sustained Targeted Drug Delivery to Neointimal Lesions in Rat Arteries.

    PubMed

    Taniguchi, Ryosuke; Miura, Yutaka; Koyama, Hiroyuki; Chida, Tsukasa; Anraku, Yasutaka; Kishimura, Akihiro; Shigematsu, Kunihiro; Kataoka, Kazunori; Watanabe, Toshiaki

    2016-06-01

    In atherosclerotic lesions, the endothelial barrier against the bloodstream can become compromised, resulting in the exposure of the extracellular matrix (ECM) and intimal cells beneath. In theory, this allows adequately sized nanocarriers in circulation to infiltrate into the intimal lesion intravascularly. We sought to evaluate this possibility using rat carotid arteries with induced neointima. Cy5-labeled polyethylene glycol-conjugated polyion complex (PIC) micelles and vesicles, with diameters of 40, 100, or 200 nm (PICs-40, PICs-100, and PICs-200, respectively) were intravenously administered to rats after injury to the carotid artery using a balloon catheter. High accumulation and long retention of PICs-40 in the induced neointima was confirmed by in vivo imaging, while the accumulation of PICs-100 and PICs-200 was limited, indicating that the size of nanocarriers is a crucial factor for efficient delivery. Furthermore, epirubicin-incorporated polymeric micelles with a diameter similar to that of PICs-40 showed significant curative effects in rats with induced neointima, in terms of lesion size and cell number. Specific and effective drug delivery to pre-existing neointimal lesions was demonstrated with adequate size control of the nanocarriers. We consider that this nanocarrier-based drug delivery system could be utilized for the treatment of atherosclerosis. PMID:27183493

  14. Adequate Systemic Perfusion Maintained by a CentriMag during Acute Heart Failure

    PubMed Central

    Favaloro, Roberto R.; Bertolotti, Alejandro; Diez, Mirta; Favaloro, Liliana; Gomez, Carmen; Peradejordi, Margarita; Trentadue, Julio; Hellman, Lorena; Arzani, Yanina; Otero, Pilar Varela

    2008-01-01

    Mechanical circulatory support during severe acute heart failure presents options for myocardial recovery or cardiac replacement. Short-term circulatory support with the newest generation of magnetically levitated centrifugal-flow pumps affords several potential advantages. Herein, we present our experience with such a pump—the CentriMag® (Levitronix LLC; Waltham, Mass) centrifugal-flow ventricular assist device—in 4 critically ill patients who were in cardiogenic shock. From November 2007 through March 2008, 3 patients were supported after cardiac surgery, and 1 after chronic heart failure worsened. Two patients were bridged to heart transplantation, and 2 died during support. Perfusion during support was evaluated in terms of serum lactic acid levels and oxygenation values. In all of the patients, the CentriMag's pump flow was adequate, and continuous mechanical ventilation support was provided. Lactic acid levels substantially improved with CentriMag support and were maintained at near-normal levels throughout. At the same time, arterial pH, PO2, and carbon dioxide levels remained within acceptable ranges. No thromboembolic events or mechanical failures occurred. Our experience indicates that short-term use of the CentriMag ventricular assist device during acute heart failure can restore and adequately support circulation until recovery or until the application of definitive therapy. PMID:18941648

  15. A Recipe for Ratio

    ERIC Educational Resources Information Center

    Moffett, Pamela

    2012-01-01

    Many learners still struggled to appreciate, and understand the difference between, the concepts of fractions and ratio. This is not just a UK phenomenon, which is demonstrated here by the use of a resource developed by the Wisconsin Centre for Education, in association with the Freudenthal Institute of the University of Utrecht, with a group of…

  16. The stability and calibration of water vapor isotope ratio measurements during long-term deployments

    NASA Astrophysics Data System (ADS)

    Bailey, A.; Noone, D.; Berkelhammer, M.; Steen-Larsen, H. C.; Sato, P.

    2015-05-01

    With the recent advent of commercial laser absorption spectrometers, field studies measuring stable isotope ratios of hydrogen and oxygen in water vapor have proliferated. These pioneering analyses have provided invaluable feedback about best strategies for optimizing instrumental accuracy, yet questions still remain about instrument performance and calibration approaches for multi-year field deployments. With clear scientific potential for using these instruments to carry out long-term monitoring of the hydrological cycle, this study examines the long-term stability of the isotopic biases associated with three cavity-enhanced laser absorption spectrometers - calibrated with different systems and approaches - at two remote field sites: Mauna Loa Observatory, Hawaii, USA, and Greenland Environmental Observatory, Summit, Greenland. The analysis pays particular attention to the stability of measurement dependencies on water vapor concentration and also evaluates whether these so-called concentration-dependences are sensitive to statistical curve-fitting choices or measurement hysteresis. The results suggest evidence of monthly-to-seasonal concentration-dependence variability - which likely stems from low signal-to-noise at the humidity-range extremes - but no long-term directional drift. At Mauna Loa, where the isotopic analyzer is calibrated by injection of liquid water standards into a vaporizer, the largest source of inaccuracy in characterizing the concentration-dependence stems from an insufficient density of calibration points at low humidity. In comparison, at Greenland, the largest source of inaccuracy is measurement hysteresis associated with interactions between the reference vapor, generated by a custom dew point generator (DPG), and the sample tubing. Nevertheless, prediction errors associated with correcting the concentration-dependence are small compared to total measurement uncertainty. At both sites, a dominant source of uncertainty is instrumental

  17. Change in Seismic Attenuation of the Nojima Fault Zone Measured Using Spectral Ratios from Borehole Seismometers

    NASA Astrophysics Data System (ADS)

    Kano, Y.; Tadokoro, K.; Nishigami, K.; Mori, J.

    2006-12-01

    We measured the seismic attenuation of the rock mass surrounding the Nojima fault, Japan, by estimating the P-wave quality factor, Qp, using spectral ratios derived from a multi-depth (800 m and 1800 m) seismometer array. We detected an increase of Qp in 2003-2006 compared to 1999-2000. Following the 1995 Kobe earthquake, the project "Fault Zone Probe" drilled three boreholes to depths of 500 m, 800 m, 1800 m, in Toshima, along the southern part of the Nojima fault. The 1800-m borehole was reported to reach the fault surface. One seismometer (TOS1) was installed at the bottom of the 800-m borehole in 1996 and another (TOS2) at the bottom of 1800-m borehole in 1997. The sampling rate of the seismometers is 100 Hz. The slope of the spectral ratios for the two stations plotted on a linear-log plot is -π t^{*}, where t^{*} is the travel time divided by the Qp for the path difference between the stations. For the estimation of Qp, we used events recorded by both TOS1 and TOS2 for periods of 1999-2000 and 2003-2006. To improve the signal-to-noise ratio of the spectral ratios, we first calculated spectra ratios between TOS1 and TOS2 for each event and averaged the values over the earthquakes for each period. We used the events that occurred within 10 km from TOS2, and the numbers of events are 74 for 1999-2000 and 105 for 2003-2006. Magnitudes of the events range from M0.5 to M3.1. The average value of Qp for 1999-2000 increased significantly compared to 2003-2006. The attenuation of rock mass surrounding the fault in 2003-2006 is smaller than that in 1999-2000, which suggests that the fault zone became stiffer after the earthquake. At the Nojima fault, permeability measured by repeated pumping tests decreased with time from the Kobe earthquake, infering the closure of cracks and a fault healing process occurred The increase of Qp is another piece of evidence for the healing process of the Nojima fault zone. u.ac.jp/~kano/

  18. Tremor Depth and Vp/Vs Ratio from Moho Reflected Phases

    NASA Astrophysics Data System (ADS)

    Klaus, A. J.; Creager, K. C.; Ghosh, A.; Vidale, J. E.

    2010-12-01

    stacking techniques to enhance the signal-to-noise ratio. Promising signals at the predicted times of P-PmP, P-SmP and S-P have been found in a small aperture, 80-station array that recorded the 2008 episodic tremor and slip (ETS) event. Furthermore, we have recorded the ongoing 2010 ETS event on the Array of Arrays, a set of eight small-aperture arrays on the northern Olympic Peninsula.

  19. Constraint on a varying proton-to-electron mass ratio from molecular hydrogen absorption towards quasar SDSS J123714.60+064759.5

    NASA Astrophysics Data System (ADS)

    Daprà, M.; Bagdonaite, J.; Murphy, M. T.; Ubachs, W.

    2015-11-01

    Molecular hydrogen transitions in the sub-damped Lyman α absorber at redshift zabs ≃ 2.69, towards the background quasar SDSS J123714.60+064759.5, were analysed in order to search for a possible variation of the proton-to-electron mass ratio μ over a cosmological time-scale. The system is composed of three absorbing clouds where 137 H2 and HD absorption features were detected. The observations were taken with the Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph with a signal-to-noise ratio of 32 per 2.5 km s-1 pixel, covering the wavelengths from 356.6 to 409.5 nm. A comprehensive fitting method was used to fit all the absorption features at once. Systematic effects of distortions to the wavelength calibrations were analysed in detail from measurements of asteroid and `solar twin' spectra, and were corrected for. The final constraint on the relative variation in μ between the absorber and the current laboratory value is Δμ/μ = (-5.4 ± 6.3stat ± 4.0syst) × 10-6, consistent with no variation over a look-back time of 11.4 Gyr.

  20. Do measures commonly used in body image research perform adequately with African American college women?

    PubMed

    Kashubeck-West, Susan; Coker, Angela D; Awad, Germine H; Stinson, Rebecca D; Bledman, Rashanta; Mintz, Laurie

    2013-07-01

    This study examines reliability and validity estimates for 3 widely used measures in body image research in a sample of African American college women (N = 278). Internal consistency estimates were adequate (α coefficients above .70) for all measures, and evidence of convergent and discriminant validity was found. Confirmatory factor analyses failed to replicate the hypothesized factor structures of these measures. Exploratory factor analyses indicated that 4 factors found for the Sociocultural Attitudes Toward Appearance Questionnaire were similar to the hypothesized subscales, with fewer items. The factors found for the Multidimensional Body-Self Relations Questionnaire-Appearance Scales and the Body Dissatisfaction subscale of the Eating Disorders Inventory-3 were not similar to the subscales developed by the scale authors. Validity and reliability evidence is discussed for the new factors. PMID:23731233