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Sample records for including attenuation due

  1. ALPHA ATTENUATION DUE TO DUST LOADING

    SciTech Connect

    Dailey, A; Dennis Hadlock, D

    2007-08-09

    Previous studies had been done in order to show the attenuation of alpha particles in filter media. These studies provided an accurate correction for this attenuation, but there had not yet been a study with sufficient results to properly correct for attenuation due to dust loading on the filters. At the Savannah River Site, filter samples are corrected for attenuation due to dust loading at 20%. Depending on the facility the filter comes from and the duration of the sampling period, the proper correction factor may vary. The objective of this study was to determine self-absorption curves for each of three counting instruments. Prior work indicated significant decreases in alpha count rate (as much as 38%) due to dust loading, especially on filters from facilities where sampling takes place over long intervals. The alpha count rate decreased because of a decrease in the energy of the alpha. The study performed resulted in a set of alpha absorption curves for each of three detectors. This study also took into account the affects of the geometry differences in the different counting equipment used.

  2. Attenuation of ground vibrations due to different technical sources

    NASA Astrophysics Data System (ADS)

    Auersch, L.; Said, S.

    2010-09-01

    The attenuation of technically induced surface waves is studied theoretically and experimentally. In this paper, nineteen measurements of ground vibrations induced by eight different technical sources including road and rail traffic, vibratory and impulsive construction work or pile driving, explosions, hammer impulses and mass drops are described, and it is shown that the technically induced ground vibrations exhibit a power-law attenuation v ˜ r - q where the exponents q are in the range of 0.5 to 2.0 and depend on the source types. Comparisons performed demonstrate that the measured exponents are considerably higher than theoretically expected. Some potential effects on ground vibration attenuation are theoretically analyzed. The most important effect is due to the material or scattering damping. Each frequency component is attenuated exponentially as exp(- kr), but for a broad-band excitation, the sum of the exponential laws also yields a power law but with a high exponent. Additional effects are discussed, for example the dispersion of the Rayleigh wave due to soil layering, which yields an additional exponent of 0.5 in cases of impulsive loading.

  3. Seismic attenuation due to wave-induced flow

    SciTech Connect

    Pride, S; Berryman, J; Harris, J

    2003-10-17

    Analytical expressions for three P-wave attenuation mechanisms in sedimentary rocks are given a unified theoretical framework. Two of the models concern wave-induced flow due to heterogeneity in the elastic moduli at ''mesoscopic'' scales (scales greater than grain sizes but smaller than wavelengths). In the first model, the heterogeneity is due to lithological variations (e.g., mixtures of sands and clays) with a single fluid saturating all the pores. In the second model, a single uniform lithology is saturated in mesoscopic ''patches'' by two immiscible fluids (e.g., air and water). In the third model, the heterogeneity is at ''microscopic'' grain scales (broken grain contacts and/or micro-cracks in the grains) and the associated fluid response corresponds to ''squirt flow''. The model of squirt flow derived here reduces to proper limits as any of the fluid bulk modulus, crack porosity, and/or frequency is reduced to zero. It is shown that squirt flow is incapable of explaining the measured level of loss (10{sup -2} < Q{sup -1} < 10{sup -1}) within the seismic band of frequencies (1 to 10{sup 4} Hz); however, either of the two mesoscopic scale models easily produce enough attenuation to explain field data.

  4. Seismic attenuation due to wave-induced flow

    SciTech Connect

    Pride, S.R.; Berryman, J.G.; Harris, J.M.

    2003-10-09

    Analytical expressions for three P-wave attenuation mechanisms in sedimentary rocks are given a unified theoretical framework. Two of the models concern wave-induced flow due to heterogeneity in the elastic moduli at mesoscopic scales (scales greater than grain sizes but smaller than wavelengths). In the first model, the heterogeneity is due to lithological variations (e.g., mixtures of sands and clays) with a single fluid saturating all the pores. In the second model, a single uniform lithology is saturated in mesoscopic ''patches'' by two immiscible fluids (e.g., air and water). In the third model, the heterogeneity is at ''microscopic'' grain scales (broken grain contacts and/or micro-cracks in the grains) and the associated fluid response corresponds to ''squirt flow''. The model of squirt flow derived here reduces to proper limits as any of the fluid bulk modulus, crack porosity, and/or frequency is reduced to zero. It is shown that squirt flow is incapable of explaining the measured level of loss (10{sup -2} < Q{sup -1} < 10{sup -1}) within the seismic band of frequencies (1 to 10{sup 4} Hz); however, either of the two mesoscopic scale models easily produce enough attenuation to explain the field data.

  5. Is amplitude loss of sonic waveforms due to intrinsic attenuation or source coupling to the medium?

    USGS Publications Warehouse

    Lee, Myung W.

    2006-01-01

    Sonic waveforms acquired in gas-hydrate-bearing sediments indicate strong amplitude loss associated with an increase in sonic velocity. Because the gas hydrate increases sonic velocities, the amplitude loss has been interpreted as due to intrinsic attenuation caused by the gas hydrate in the pore space, which apparently contradicts conventional wave propagation theory. For a sonic source in a fluid-filled borehole, the signal amplitude transmitted into the formation depends on the physical properties of the formation, including any pore contents, in the immediate vicinity of the source. A signal in acoustically fast material, such as gas-hydrate-bearing sediments, has a smaller amplitude than a signal in acoustically slower material. Therefore, it is reasonable to interpret the amplitude loss in the gas-hydrate-bearing sediments in terms of source coupling to the surrounding medium as well as intrinsic attenuation. An analysis of sonic waveforms measured at the Mallik 5L-38 well, Northwest Territories, Canada, indicates that a significant part of the sonic waveform's amplitude loss is due to a source-coupling effect. All amplitude analyses of sonic waveforms should include the effect of source coupling in order to accurately characterize the formation's intrinsic attenuation.

  6. Correlation Attenuation Due to Measurement Error: A New Approach Using the Bootstrap Procedure

    ERIC Educational Resources Information Center

    Padilla, Miguel A.; Veprinsky, Anna

    2012-01-01

    Issues with correlation attenuation due to measurement error are well documented. More than a century ago, Spearman proposed a correction for attenuation. However, this correction has seen very little use since it can potentially inflate the true correlation beyond one. In addition, very little confidence interval (CI) research has been done for…

  7. Growth Attenuation and Due Process: "A Response to Gunther and Diekema (2006)"

    ERIC Educational Resources Information Center

    Turnbull, Rud; Wehmeyer, Michael; Turnbull, Ann; Stowe, Matt

    2006-01-01

    This article presents the authors' response to Gunther and Diekema's argument about growth attenuation and due process. As a case study, growth attenuation raises complicated issues. The authors address some issues that have not been sufficiently addressed. Those involve family support, assistive technology, constitutional rights to "self," the…

  8. World-wide link availability for geostationary and critically inclined orbits including rain attenuation effects

    NASA Astrophysics Data System (ADS)

    Schwab, L. M.

    1981-01-01

    Link availability for constellations of satellites in geostationary and critically inclined orbits is computed using a predictor model based on the Crane 8 region worldwide rain attenuation model. The results are contrasted to percent Earth visibility computations which do not include rain attenuation. For geostationary satellite constellations, the quantitative relationship for Earth coverage vs link margin vs availability vs number of satellites is described by a set of parametric curves.

  9. Time-domain simulation of constitutive relations for nonlinear acoustics including relaxation for frequency power law attenuation media modeling

    NASA Astrophysics Data System (ADS)

    Jiménez, Noé; Camarena, Francisco; Redondo, Javier; Sánchez-Morcillo, Víctor; Konofagou, Elisa E.

    2015-10-01

    We report a numerical method for solving the constitutive relations of nonlinear acoustics, where multiple relaxation processes are included in a generalized formulation that allows the time-domain numerical solution by an explicit finite differences scheme. Thus, the proposed physical model overcomes the limitations of the one-way Khokhlov-Zabolotskaya-Kuznetsov (KZK) type models and, due to the Lagrangian density is implicitly included in the calculation, the proposed method also overcomes the limitations of Westervelt equation in complex configurations for medical ultrasound. In order to model frequency power law attenuation and dispersion, such as observed in biological media, the relaxation parameters are fitted to both exact frequency power law attenuation/dispersion media and also empirically measured attenuation of a variety of tissues that does not fit an exact power law. Finally, a computational technique based on artificial relaxation is included to correct the non-negligible numerical dispersion of the finite difference scheme, and, on the other hand, improve stability trough artificial attenuation when shock waves are present. This technique avoids the use of high-order finite-differences schemes leading to fast calculations. The present algorithm is especially suited for practical configuration where spatial discontinuities are present in the domain (e.g. axisymmetric domains or zero normal velocity boundary conditions in general). The accuracy of the method is discussed by comparing the proposed simulation solutions to one dimensional analytical and k-space numerical solutions.

  10. Effects of fracture contact areas on seismic attenuation due to wave-induced fluid flow

    NASA Astrophysics Data System (ADS)

    Germán Rubino, J.; Müller, Tobias M.; Milani, Marco; Holliger, Klaus

    2014-05-01

    Wave-induced fluid flow (WIFF) between fractures and the embedding matrix is considered to be a predominant seismic attenuation mechanism in fractured rocks. That is, due to the strong compressibility contrast between fractures and embedding matrix, seismic waves induce strong fluid pressure gradients, followed by local fluid flow between such regions, which in turn produces significant energy dissipation. Natural fractures can be conceptualized as two surfaces in partial contact, containing very soft and highly permeable material in the inner region. It is known that the characteristics of the fracture contact areas control the mechanical properties of the rock sample, since as the contact area increases, the fracture becomes stiffer. Correspondingly, the detailed characteristics of the contact area of fractures are expected to play a major role in WIFF-related attenuation. To study this topic, we consider a simple model consisting of a horizontal fracture located at the center of a porous rock sample and represented by a number of rectangular cracks of constant height separated by contact areas. The cracks are modelled as highly compliant, porous, and permeable heterogeneities, which are hydraulically connected to the background material. We include a number of rectangular regions of background material separating the cracks, which represent the presence of contact areas of the fracture. In order to estimate the WIFF effects, we apply numerical oscillatory relaxation tests based on the quasi-static poro-elastic equations. The equivalent undrained, complex plane-wave modulus, which allows to estimate seismic attenuation and velocity dispersion for the vertical direction of propagation, is expressed in terms of the imposed displacement and the resulting average vertical stress at the top boundary. In order to explore the effects of the presence of fracture contact areas on WIFF effects, we perform an exhaustive sensitivity analysis considering different

  11. Attenuation in a shock tube due to unsteady-boundary-layer action

    NASA Technical Reports Server (NTRS)

    Mirels, Harold

    1957-01-01

    A method is presented for obtaining the attenuation of a shock wave in a shock tube due to the unsteady boundary layer along the shock-tube walls. It is assumed that the boundary layer is thin relative to the tube diameter and induces one-dimensional longitudinal pressure waves whose strength is proportional to the vertical velocity at the edge of the boundary layer. The contributions of the various regions in a shock tube to shock attenuation are indicated. The method is shown to be in reasonably good agreement with existing experimental data.

  12. Experimental and Numerical Investigation of Pressure Wave Attenuation due to Bubbly Layers

    NASA Astrophysics Data System (ADS)

    Jayaprakash, Arvind; Fourmeau, Tiffany; Hsiao, Chao-Tsung; Chahine, Georges; Dynaflow Inc. Team

    2013-03-01

    In this work, the effects of dispersed microbubbles on a steep pressure wave and its attenuation are investigated both numerically and experimentally. Numerical simulations were carried out using a compressible Euler equation solver, where the liquid-gas mixture was modeled using direct numerical simulations involving discrete deforming bubbles. To reduce computational costs a 1D configuration is used and the bubbles are assumed distributed in layers and the initial pressure profile is selected similar to that of a one-dimensional shock tube problem. Experimentally, the pressure pulse was generated using a submerged spark electric discharge, which generates a large vapor bubble, while the microbubbles in the bubbly layer are generated using electrolysis. High speed movies were recorded in tandem with high fidelity pressure measurements. The dependence of pressure wave attenuation on the bubble radii, the void fraction, and the bubbly layer thickness were parametrically studied. It has been found that the pressure wave attenuation can be seen as due to waves reflecting and dispersing in the inter-bubble regions, with the energy absorbed by bubble volume oscillations and re-radiation. Layer thickness and small bubble sizes were also seen as having a strong effect on the attenuation with enhanced attenuation as the bubble size is reduced for the same void fraction. This study was supported by the Department of Energy, under SBIR Phase II Contract DE-FG02-07ER84839.

  13. Measured backscatter and attenuation properties, including polarization effects, of various dispersions at 0.9 micron

    NASA Technical Reports Server (NTRS)

    Kohl, R. H.; Flaherty, M. I.; Partin, R. L.

    1977-01-01

    The optical properties of a wide variety of atmospheric dispersions were studied using a 0.9-micron lidar system which included a GaAs laser stack transmitter emitting a horizontally polarized beam of 4 milliradians vertical divergence and 1.5 milliradians horizontal divergence. A principal means for assessing optical properties was the polarization ratio, that is, the backscattered radiation power perpendicular to the transmitter beam divided by the backscattered radiation power parallel to the beam polarization. The ratio of the backscattered fraction to the attenuation coefficient was also determined. Data on the dispersion properties of black carbon smoke, road dust, fog, fair-weather cumulus clouds, snow and rain were obtained; the adverse effects of sunlight-induced background noise on the readings is also discussed.

  14. 20 CFR 410.450 - Death due to pneumoconiosis, including statutory presumption.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 2 2010-04-01 2010-04-01 false Death due to pneumoconiosis, including... Death Due to Pneumoconiosis § 410.450 Death due to pneumoconiosis, including statutory presumption... at the time of his death, or whose death is determined to have been due to pneumoconiosis....

  15. 20 CFR 410.450 - Death due to pneumoconiosis, including statutory presumption.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 20 Employees' Benefits 2 2011-04-01 2011-04-01 false Death due to pneumoconiosis, including... Death Due to Pneumoconiosis § 410.450 Death due to pneumoconiosis, including statutory presumption... at the time of his death, or whose death is determined to have been due to pneumoconiosis....

  16. Attenuation of Elastic Waves due to Scattering from Spherical Cavities and Elastic Inclusions.

    NASA Astrophysics Data System (ADS)

    Hinders, Mark Karl

    1990-01-01

    The attenuation of elastic waves due to scattering from a spherical inclusion of arbitrary size in an infinitely extended medium is investigated. The spherical scatterer and the exterior medium are isotropic, homogeneous, and linearly elastic, but of arbitrarily differing material parameters, with compressional and shear waves supported in both media. Exact expressions for scattered and transmitted fields caused by an incident plane compressional or shear wave of unit amplitude are calculated analytically and general expressions for extinction and scattering cross -sections are derived for both lossy and lossless scattering. Application to ultrasonic determination of porosity in cast aluminum is investigated.

  17. Quantifying the Attenuation Due to Geometry Interactions in Waveform Lidar Signals

    NASA Astrophysics Data System (ADS)

    Romanczyk, P.; van Aardt, J. A.; Cawse-Nicholson, K.; Kelbe, D.; Strahler, A. H.; Schaaf, C.; Krause, K.; Ramond, T.

    2013-12-01

    As a lidar pulse propagates through a forest canopy, it interacts with various components of the forest e.g., leaves, branches, ground, etc. At each interaction, the number of photons available for subsequent interactions is reduced due to a combination of reflection, transmission, absorption, and scattering events. In addition, the number of photons per unit area decreases with range due to the divergence of the laser pulse. These factors combine to produce a waveform signal with lower amplitude than would be observed for identical structure without the previous canopy structure interactions. Currently, our limited understanding of attenuation means that the inversion of the waveform to biophysical structure becomes difficult in terms of object representation within the canopy. Knowledge of the mechanics of the attenuation may reduce the uncertainty in inferring the structure from a waveform signal, e.g., leaf area index (LAI), sub-canopy gaps, and understory biomass. We present an experiment to quantify this waveform attenuation at various interactions. For this experiment we used two datasets: (i) The Dual Wavelength Echidna Lidar (DWEL) was used to scan tree branches, spaced at measured distances, to simulate a forest canopy. Branches were selectively removed/reordered from this simulated canopy to record waveform lidar signals with and without preceding canopy interactions. (ii) Additionally, the Digital Imaging and Remote Sensing Image Generation (DIRSIG) model was used to simulate the same forest structure at different locations in the canopy. This allowed precise simulation of our experimental setup, with the ability to control forest structure geometry and evaluate the effects on the observed lidar signal. For both data sets, we evaluated the signal attenuation by performing Gaussian decomposition on the waveform signal and comparing the parameters of the resultant Gaussians. This was done for various levels of canopy structure complexity, in terms of LAI

  18. Attenuation due to hysteretic damage in the free vibration of a beam

    SciTech Connect

    Mendelsohn, Daniel A.; Pecorari, Claudio

    2014-02-18

    We present an asymptotic analysis of nonlinear free vibration of a beam with a damage plane represented by nonlinear hysteretic bending and shear springs. The perturbation parameter is the product of the ratio of the nonlinear to linear parts of the stiffness times the amplitude of the free vibration. The loss of energy and ensuing attenuation due to hysteresis is accounted for by reducing the amplitude of vibration after each cycle by an amount such that the loss in total system energy equals the work done to traverse the hysteresis loop. A new Fourier representation for each cycle of the hysteresis and the deflection solution is used for this purpose and leads to higher harmonics, an evolving complex stiffness and corrected natural frequency that are linked to the attenuation. The frequency increases to its linear value from an initially reduced value. The damage parameter, frequency shift and fundamental amplitudes are presented as functions of the initial damage parameter and time (cycles of vibration). The amplitudes of several of the higher harmonics are also presented as functions of time. Many of the results exhibit sufficient sensitivity with respect to the damage parameter that they should be able to be used to characterize the damage.

  19. Uplift of the Colorado Plateau due to lithosphere attenuation during Laramide low-angle subduction

    USGS Publications Warehouse

    Spencer, J.E.

    1996-01-01

    The Colorado Plateau is blanketed by Phanerozoic marine and nonmarine strata as young as Cretaceous that are now exposed at elevations of about 2 km. Crustal thickening due to magmatism and horizontal crustal shortening was far less than necessary to cause this uplift, which is commonly attributed to the consequences of mantle lithosphere thinning and heating. The Colorado Plateau and the midcontinent region around Iowa consist of Precambrian bedrock overlain by a similar amount of Paleozoic platformal strata, and thus both regions once had similar lithospheric buoyancy. Mesozoic sedimentation increased the crustal thickness and lithospheric buoyancy of the Colorado Plateau relative to the midcontinent region. Backstripping calculations yield elevation without these sediments and lead to a calculated elevation difference between the two areas of about 1200 m, which represents unexplained plateau uplift. Review of constraints on uplift timing finds little support for a late Cenozoic uplift age and allows early to middle Cenozoic uplift, which is consistent with uplift mechanisms related to low-angle subduction that ended in the middle Cenozoic. Finite element heat flow calculations of low-angle subduction and lithosphere attenuation, using a range of initial lithosphere thicknesses and degree of attenuation, indicate that required uplift can result from tectonic removal of about 120 km of mantle lithosphere from an initially 200-km-thick lithosphere. This allows for partial preservation of North American mantle lithosphere with its distinctive isotopic signature in some late Cenozoic volcanic rocks and is consistent with normal Pn velocities in the uppermost mantle beneath the plateau.

  20. 20 CFR 410.410 - Total disability due to pneumoconiosis, including statutory presumption.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 2 2010-04-01 2010-04-01 false Total disability due to pneumoconiosis... Death Due to Pneumoconiosis § 410.410 Total disability due to pneumoconiosis, including statutory... pneumoconiosis arising out of employment in one or more of the Nation's coal mines,” and to the...

  1. Functions of cumulative distribution of attenuation due to rain on an interval from 9.5 Km A to 17.8 GHz

    NASA Technical Reports Server (NTRS)

    Fedi, F.; Migliorini, P.

    1981-01-01

    Measurement results of attenuation due to rain are reported. Cumulative distribution functions of the attenuation found in three connections are described. Differences between the distribution functions and different polarization frequencies are demonstrated. The possibilty of establishing a bond between the statistics of annual attenuation and worst month attenuation is explored.

  2. Acoustic attenuation due to transformation twins in CaCl2: Analogue behaviour for stishovite

    NASA Astrophysics Data System (ADS)

    Zhang, Zhiying; Schranz, Wilfried; Carpenter, Michael A.

    2012-09-01

    CaCl2 undergoes a tetragonal (P42/mnm) to orthorhombic (Pnnm) transition as a function of temperature which is essentially the same as occurs in stishovite at high pressures. It can therefore be used as a convenient analogue material for experimental studies. In order to investigate variations in elastic properties associated with the transition and possible anelastic loss behaviour related to the mobility of ferroelastic twin walls in the orthorhombic phase, the transition in polycrystalline CaCl2 has been examined using resonant ultrasound spectroscopy (RUS) at high frequencies (0.1-1.5 MHz) in the temperature interval 7-626 K, and dynamic mechanical analysis (DMA) at low frequencies (0.1-50 Hz) in the temperature interval 378-771 K. RUS data show steep softening of the shear modulus as the transition temperature is approached from above and substantial acoustic dissipation in the stability field of the orthorhombic structure. DMA data show softening of the storage modulus, which continues through to a minimum ˜20 K below the transition point and is followed by stiffening with further lowering of temperature. There is no obvious acoustic dissipation associated with the transition, as measured by tan δ, however. The elastic softening and stiffening matches the pattern expected for a pseudoproper ferroelastic transition as predicted elsewhere. Acoustic loss behaviour at high frequencies fits with the pattern of behaviour expected for a twin wall loss mechanism but with relaxation times in the vicinity of ˜10-6 s. With such short relaxation times, the shear modulus of CaCl2 at frequencies corresponding to seismic frequencies would include relaxations of the twin walls and is therefore likely to be significantly lower than the intrinsic shear modulus. If these characteristics apply also to twin wall mobility in stishovite, the seismic signature of the orthorhombic phase should be an unusually soft shear modulus but with no increase in attenuation.

  3. SU-E-J-215: Onboard Split PET Including the Effects of Attenuation, Scatter, and Random Events

    SciTech Connect

    Darwish, N; Kao, C; Thomadsen, B; Mackie, T

    2014-06-01

    Purpose: Positron emission tomography (PET) using split PET geometry was investigated as an on-board system for functional imaging and PET marker tracking, specifically with tomotherapy. The open dual ring PET would allow measurement of both inter and intra-fractional variation, improving the delineation of tumor volume at any stage in the radiation treatment delivery process. We present results from data obtained using Monte Carlo simulations including the effects of attenuation, random events, and scatter. Methods: PET design was accomplished via Monte Carlo simulations with GATE, the Geant4 Application for Emission Tomography. Images were reconstructed using Software for Image Reconstruction (STIR) with a fully 3D ordered subset expectation maximization (OSEM) image reconstruction technique. Results: Monte Carlo simulations of the split PET geometry indicate that including physical factors that degrade image quality such as attenuation, random events, and scatter still prove the feasibility of near real-time PET for both inter and intra-fractional radiation delivery. The image quality of scan times under 1 minute reveals that it is possible to utilize PET scanning and reconstruction during the treatment session intrafractionally. GATE also simulates the depth information but does not correct obliqueness of the path of line of response so the data is much more realistic than the data obtained with ray tracing. Conclusion: Onboard split PET with TomoTherapy can generate quality images under 1 minute scan times without the need to correct for attenuation, scatter, random events, or depth information of the interaction.

  4. Determination of modal attenuation due to external and internal fluids in pipes

    NASA Astrophysics Data System (ADS)

    Predoi, M. V.; Petre, C. C.; Boiangiu, M.; Craifaleanu, A.; Vasile, O.

    2015-11-01

    The ultrasonic nondestructive evaluation of structural integrity of pipes in high risk industries such as chemical or nuclear, represents a domain of highest importance. The inspection of kilometers of piping in rough conditions is a difficult if not an impossible task. Guided ultrasonic waves can propagate however along tens of meters in pipes and bring by the reflected signal, important information concerning the presence of flaws. There are three classes of guided modes in a pipe: longitudinal, torsional and flexural. The longitudinal modes have an axial symmetry of the radial and axial displacements. These waves prove to be most sensitive to partly circumferential flaws. These waves are dispersive, the wave velocity strongly depending on the frequency. The torsional modes are less dispersive, especially the fundamental SH0 mode. Moreover, the radial displacements are negligible, reducing the interaction with the surrounding fluids and thus reducing the attenuation. The interaction of these waves with axial flaws is more pronounced. The flexural modes are highly dispersive and attenuated. However, if the symmetry of the emitting transducer is not perfect, these modes can propagate in the pipe and their properties must be understood. The presence of fluid inside and in some cases outside the inspected pipe represents a challenging problem of computing the guided modes dispersion curves. The various guided modes velocities and attenuations are determined for several fluids which might be filling and surrounding the common size steel pipes. A dedicated software package developed by our team is used for this purpose. These dispersion curves are used for optimal numerical simulation, using the Finite Elements Method (FEM), in order to verify the attenuation mechanism. The obtained results allow a motivated selection of the least attenuated mode, from the three classes explained before, at a given inspection frequency and for a typical steel pipe, filled with various

  5. Attenuation and phase dispersion in the atmosphere due to the microwave spectrum of oxygen

    NASA Technical Reports Server (NTRS)

    Liebe, H. J.; Welch, W. M.

    1973-01-01

    Radio wave propagation in the 40- to 140-GHz band through the earth's atmosphere is strongly influenced by the behavior of the O2 microwave spectrum. This behavior causes the transfer function to depend critically upon altitude. The spectroscopic properties of O2 are discussed and reduced to engineering formulas expressing attenuation and phase dispersion rates in terms of frequency and meteorological parameters. The theory is supported on several accounts by reliable spectroscopic measurements. Pressure scanning spectroscopy is used to investigate the O2 microwave spectrum under simulated atmospheric conditions. The application of spectroscopic information to analytical treatments of transfer properties for inhomogeneous slant paths is demonstrated. Attenuation and phase dispersion between 49 and 72 GHz are evaluated for zenith and tangential paths.

  6. Analysis of a generalized model for influenza including differential susceptibility due to immunosuppression

    NASA Astrophysics Data System (ADS)

    Hincapié, Doracelly; Ospina, Juan

    2014-06-01

    Recently, a mathematical model of pandemic influenza was proposed including typical control strategies such as antivirals, vaccination and school closure; and considering explicitly the effects of immunity acquired from the early outbreaks on the ulterior outbreaks of the disease. In such model the algebraic expression for the basic reproduction number (without control strategies) and the effective reproduction number (with control strategies) were derived and numerically estimated. A drawback of this model of pandemic influenza is that it ignores the effects of the differential susceptibility due to immunosuppression and the effects of the complexity of the actual contact networks between individuals. We have developed a generalized model which includes such effects of heterogeneity. Specifically we consider the influence of the air network connectivity in the spread of pandemic influenza and the influence of the immunosuppresion when the population is divided in two immune classes. We use an algebraic expression, namely the Tutte polynomial, to characterize the complexity of the contact network. Until now, The influence of the air network connectivity in the spread of pandemic influenza has been studied numerically, but not algebraic expressions have been used to summarize the level of network complexity. The generalized model proposed here includes the typical control strategies previously mentioned (antivirals, vaccination and school closure) combined with restrictions on travel. For the generalized model the corresponding reproduction numbers will be algebraically computed and the effect of the contact network will be established in terms of the Tutte polynomial of the network.

  7. Accurate and efficient modeling of global seismic wave propagation for an attenuative Earth model including the center

    NASA Astrophysics Data System (ADS)

    Toyokuni, Genti; Takenaka, Hiroshi

    2012-06-01

    We propose a method for modeling global seismic wave propagation through an attenuative Earth model including the center. This method enables accurate and efficient computations since it is based on the 2.5-D approach, which solves wave equations only on a 2-D cross section of the whole Earth and can correctly model 3-D geometrical spreading. We extend a numerical scheme for the elastic waves in spherical coordinates using the finite-difference method (FDM), to solve the viscoelastodynamic equation. For computation of realistic seismic wave propagation, incorporation of anelastic attenuation is crucial. Since the nature of Earth material is both elastic solid and viscous fluid, we should solve stress-strain relations of viscoelastic material, including attenuative structures. These relations represent the stress as a convolution integral in time, which has had difficulty treating viscoelasticity in time-domain computation such as the FDM. However, we now have a method using so-called memory variables, invented in the 1980s, followed by improvements in Cartesian coordinates. Arbitrary values of the quality factor (Q) can be incorporated into the wave equation via an array of Zener bodies. We also introduce the multi-domain, an FD grid of several layers with different grid spacings, into our FDM scheme. This allows wider lateral grid spacings with depth, so as not to perturb the FD stability criterion around the Earth center. In addition, we propose a technique to avoid the singularity problem of the wave equation in spherical coordinates at the Earth center. We develop a scheme to calculate wavefield variables on this point, based on linear interpolation for the velocity-stress, staggered-grid FDM. This scheme is validated through a comparison of synthetic seismograms with those obtained by the Direct Solution Method for a spherically symmetric Earth model, showing excellent accuracy for our FDM scheme. As a numerical example, we apply the method to simulate seismic

  8. Cerebrolysin attenuates cerebral and hepatic injury due to lipopolysaccharide in rats.

    PubMed

    Abdel-Salam, O M E; Omara, E A; Mohammed, N A; Youness, E R; Khadrawy, Y A; Sleem, A A

    2013-12-01

    This study aimed to investigate the effect of cerebrolysin on oxidative stress in the brain and liver during systemic inflammation. Rats were intraperitoneally challenged with a single subseptic dose of lipopolysaccharide (LPS; 300 μg/kg) without or with cerebrolysin at doses of 21.5, 43 or 86 mg/kg. After 4 h, rats were euthanized and the brain and liver tissues were subjected to biochemical and histopathological analyses. Cerebrolysin revealed inhibitory effects on the elevation of lipid peroxidation and nitric oxide induced by LPS. In contrast, the decrease in reduced glutathione level and paraoxonase activity induced by LPS was attenuated by an injection of cerebrolysin in a dose-dependent manner. Moreover, cerebrolysin reduced LPS-induced activation of brain NF-κB and reversed LPS-induced decline of brain butyrylcholinesterase and acetylcholinesterase activities in a dose-dependent manner. Histopathological analyses revealed that neuronal damage and liver necrosis induced by LPS were ameliorated by cerebrolysin dose-dependently. Cerebrolysin treatment dose-dependently attenuated LPS-induced expressions in cyclooxygenase 2, inducible nitric oxide synthase, and caspase-3 in the cortex or striatum as well as the liver. These results suggest that cerebrolysin treatment might have beneficial therapeutic effects in cerebral inflammation. Cerebrolysin might also prove of value in liver disease and this possibility requires further exploration. PMID:24423658

  9. 25 CFR 162.546 - What requirements for due diligence must a WSR lease include?

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... WATER LEASES AND PERMITS Wind and Solar Resource Leases Wsr Leases § 162.546 What requirements for due... lessee to: (1) Commence installation of energy facilities within 2 years after the effective date of...

  10. 25 CFR 162.546 - What requirements for due diligence must a WSR lease include?

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... WATER LEASES AND PERMITS Wind and Solar Resource Leases Wsr Leases § 162.546 What requirements for due... lessee to: (1) Commence installation of energy facilities within 2 years after the effective date of...

  11. 25 CFR 162.517 - What requirements for due diligence must a WEEL include?

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... LEASES AND PERMITS Wind and Solar Resource Leases Weels § 162.517 What requirements for due diligence....592; and (2) Application of the requirement that the lessee transfer ownership of energy...

  12. 25 CFR 162.517 - What requirements for due diligence must a WEEL include?

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... LEASES AND PERMITS Wind and Solar Resource Leases Weels § 162.517 What requirements for due diligence....592; and (2) Application of the requirement that the lessee transfer ownership of energy...

  13. Angiotensin-(1-7) Attenuates Kidney Injury Due to Obstructive Nephropathy in Rats

    PubMed Central

    Kim, Chang Seong; Kim, In Jin; Bae, Eun Hui; Ma, Seong Kwon; Lee, JongUn; Kim, Soo Wan

    2015-01-01

    Background Angiotensin-(1–7) [Ang-(1–7)] counteracts many actions of the renin-angiotensin-aldosterone system. Despite its renoprotective effects, extensive controversy exists regarding the role of Ang-(1–7) in obstructive nephropathy, which is characterized by renal tubulointerstitial fibrosis and apoptosis. Methods To examine the effects of Ang-(1–7) in unilateral ureteral obstruction (UUO), male Sprague-Dawley rats were divided into three groups: control, UUO, and Ang-(1–7)-treated UUO rats. Ang-(1–7) was continuously infused (24 μg/[kg·h]) using osmotic pumps. We also treated NRK-52E cells in vitro with Ang II (1 μM) in the presence or absence of Ang-(1–7) (1 μM), Mas receptor antagonist A779 (1 μM), and Mas receptor siRNA (50 nM) to examine the effects of Ang-(1–7) treatment on Ang II-stimulated renal injury via Mas receptor. Results Angiotensin II (Ang II) and angiotensin type 1 receptor (AT1R) protein expression was higher in UUO kidneys than in controls. Ang-(1–7) treatment also decreased proapoptotic protein expression in UUO kidneys. Ang-(1–7) also significantly ameliorated TUNEL positive cells in UUO kidneys. Additionally, Ang-(1–7) reduced profibrotic protein expression and decreased the increased tumor growth factor (TGF)-β1/Smad signaling present in UUO kidneys. In NRK-52E cells, Ang II induced the expression of TGF-β1/Smad signaling effectors and proapoptotic and fibrotic proteins, as well as cell cycle arrest, which were attenuated by Ang-(1–7) pretreatment. However, treatment with A779 and Mas receptor siRNA enhanced Ang II-induced apoptosis and fibrosis. Moreover, Ang II increased tumor necrosis factor-α converting enzyme (TACE) and decreased angiotensin-converting enzyme 2 (ACE2) expression in NRK-52E cells, while pretreatment with Ang-(1–7) or A779 significantly inhibited or enhanced these effects, respectively. Conclusion Ang-(1–7) prevents obstructive nephropathy by suppressing renal apoptosis and fibrosis

  14. Recurrent and Sporadic Listeria monocytogenes Contamination in Alheiras Represents Considerable Diversity, Including Virulence-Attenuated Isolates▿ †

    PubMed Central

    Felício, M. T. S.; Hogg, T.; Gibbs, P.; Teixeira, P.; Wiedmann, M.

    2007-01-01

    Microbiological characterization of alheiras, traditional smoked meat sausages produced in northern Portugal, had previously shown that more than 60% of the lots analyzed were contaminated with Listeria monocytogenes at levels higher than 100 CFU/g. In order to better understand L. monocytogenes contamination patterns in alheiras, we characterized 128 L. monocytogenes isolates from alheiras using a variety of subtyping techniques (i.e., molecular serotyping; arsenic, cadmium, and tetracycline resistance typing; and pulsed-field gel electrophoresis [PFGE]). Subtyping of isolates from products collected on two separate dates provided evidence for the persistence of specific L. monocytogenes PFGE types in the production and distribution chains of alheiras from four different processors. A subset of 21 isolates was further characterized using ribotyping and Caco-2 cell invasion assays to evaluate the pathogenic potential of L. monocytogenes present in alheiras. Caco-2 invasion assays revealed seven isolates with invasion efficiencies that were less than 20% of that of the control strain 10403S. All seven isolates had premature stop codons in inlA that represented three distinct mutations, which had previously been observed in isolates from the United States or France. Our findings indicate the need for a comprehensive approach to control L. monocytogenes in alheiras, including strategies to reduce persistence. The presence of considerable diversity in invasion phenotypes among L. monocytogenes strains present in alheiras, including the presence of subtypes likely to be virulence attenuated, may provide an opportunity to initially focus control strategies on the subtypes most likely to cause human disease. PMID:17449681

  15. Twin-arginine translocation system (tat) mutants of Salmonella are attenuated due to envelope defects, not respiratory defects.

    PubMed

    Craig, Maureen; Sadik, Adam Y; Golubeva, Yekaterina A; Tidhar, Avital; Slauch, James M

    2013-09-01

    The twin-arginine translocation system (Tat) transports folded proteins across the cytoplasmic membrane and is critical to virulence in Salmonella and other pathogens. Experimental and bioinformatic data indicate that 30 proteins are exported via Tat in Salmonella Typhimurium. However, there are no data linking specific Tat substrates with virulence. We inactivated every Tat-exported protein and determined the virulence phenotype of mutant strains. Although a tat mutant is highly attenuated, no single Tat-exported substrate accounts for this virulence phenotype. Rather, the attenuation is due primarily to envelope defects caused by failure to translocate three Tat substrates, the N-acetylmuramoyl-l-alanine amidases, AmiA and AmiC, and the cell division protein, SufI. Strikingly, neither the amiA amiC nor the sufI mutations alone conferred any virulence defect. Although AmiC and SufI have previously been localized to the divisome, the synthetic phenotypes observed are the first to suggest functional overlap. Many Tat substrates are involved in anaerobic respiration, but we show that a mutant completely deficient in anaerobic respiration retains full virulence in both the oral and systemic phases of infection. Similarly, an obligately aerobic mutant is fully virulent. These results suggest that in the classic mouse model of infection, S. Typhimurium is replicating only in aerobic environments. PMID:23822642

  16. Twin-arginine Translocation System (tat) Mutants of Salmonella are Attenuated Due to Envelope Defects, not Respiratory Defects

    PubMed Central

    Craig, Maureen; Sadik, Adam Y.; Golubeva, Yekaterina A.; Tidhar, Avital; Slauch, James M.

    2013-01-01

    Summary The twin-arginine translocation system (Tat) transports folded proteins across the cytoplasmic membrane and is critical to virulence in Salmonella and other pathogens. Experimental and bioinformatic data indicate that 30 proteins are exported via Tat in Salmonella Typhimurium. However, there are no data linking specific Tat substrates with virulence. We inactivated every Tat-exported protein and determined the virulence phenotype of mutant strains. Though a tat mutant is highly attenuated, no single Tat-exported substrate accounts for this virulence phenotype. Rather, the attenuation is due primarily to envelope defects caused by failure to translocate three Tat substrates, the N-acetylmuramoyl-L-alanine amidases, AmiA and AmiC, and the cell division protein, SufI. Strikingly, neither the amiA amiC nor the sufI mutations alone conferred any virulence defect. Although AmiC and SufI have previously been localized to the divisome, the synthetic phenotypes observed are the first to suggest functional overlap. Many Tat substrates are involved in anaerobic respiration, but we show that a mutant completely deficient in anaerobic respiration retains full virulence in both the oral and systemic phases of infection. Similarly, an obligately aerobic mutant is fully virulent. These results suggest that in the classic mouse model of infection, S. Typhimurium is replicating only in aerobic environments. PMID:23822642

  17. 25 CFR 42.7 - What does due process in a formal disciplinary proceeding include?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... include? 42.7 Section 42.7 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR EDUCATION STUDENT... must give the student written notice of charges within a reasonable time before the hearing required by...; and (4) Information regarding those parts of the student's record that the school will consider...

  18. Long-Term Change of Sound Wave Propagation Attenuation Due to the Effects of Ocean Acidification

    NASA Astrophysics Data System (ADS)

    Gotoh, S.; Tsuchiya, T.; Hiyoshi, Y.

    2014-12-01

    In recent years, the concentration of carbon dioxide in the atmosphere is increasing due to global warming. And, the ocean acidification advances because this melts into seawater, pH decrease in seawater are concerned. The sound wave to propagate seawater, pH is known to affect absorption loss (α) by chemical buffer effects of the seawater. However, conventionally, α has not been investigated much in the calculation of pH. Therefore, when calculating the propagation distance in the sonar equation, pH =8~8.1 (Weak alkaline) are used empirically. Therefore we used an actual value of pH of 30 years from 1984 in the sea near the Japan, and investigated change over the years of absorption loss (α) at some frequency. As a result, we found that α value decreases gradually in the past 30 years, as high-latitude decreases. Further, the future, assuming that ocean acidification is more advanced, and to simulate a change of the absorption loss and propagation loss in end of this century using the pH value reported from the "Intergovernmental Panel on Climate Change" (IPCC). As a result, it was just suggested that α decreased more in the end of this century and affected the submarine detection. In addition, in recent years, we examined the effects of noise that offshore wind power construction proceeds in each country emits gives to the underwater sound. As a result, in the end of this century, an underwater noise increases about 17%, and underwater sound environmental degradation of the sea is concerned.

  19. Attenuation of urban agricultural production potential and crop water footprint due to shading from buildings and trees

    NASA Astrophysics Data System (ADS)

    Johnson, Mark S.; Lathuillière, Michael J.; Tooke, Thoreau R.; Coops, Nicholas C.

    2015-06-01

    Urban agriculture requires local water to replace ‘hydrologic externalities’ associated with food produced outside of the local area, with an accompanying shift of the water footprint (WF) for agricultural production from rural to urban areas. Water requirements of urban agriculture have been difficult to estimate due to the heterogeneity of shading from trees and buildings within urban areas. We developed CityCrop, a plant growth and evapotranspiration (ET) model that couples a 3D model of tree canopies and buildings derived from LiDAR with a ray-casting approach to estimate spatially-explicit solar inputs in combination with local climate data. Evaluating CityCrop over a 1 km2 mixed use, residential neighborhood of Vancouver Canada, we estimated median light attenuation to result in 12% reductions in both reference ET (ETo) and crop ET (ETc). However, median crop yields were reduced by only 3.5% relative to potential yield modeled without any light attenuation, while the median crop WF was 9% less than the WF for areas unimpeded by shading. Over the 75 day cropping cycle, median crop water requirements as ETc were 17% less than that required for a well-watered grass (as ETo). If all lawns in our modeled area were replaced with crops, we estimate that about 37% of the resident population could obtain the vegetable portion of their diet from within the local area over a 150 day growing season. However doing so would result in augmented water demand if watering restrictions apply to lawns only. The CityCrop model can therefore be useful to evaluate trade-offs related to urban agriculture and to inform municipal water policy development.

  20. Monte Carlo simulation of peak-acceleration attenuation using a finite-fault uniform-patch model including isochrone and extremal characteristics

    USGS Publications Warehouse

    Rogers, A.M.; Perkins, D.M.

    1996-01-01

    A finite-fault statistical model of the earthquake source is used to confirm observed magnitude and distance saturation scaling in a large peak-acceleration data set. This model allows us to determine the form of peak-acceleration attenuation curves without a priori assumptions about their shape or scaling properties. The source is composed of patches having uniform size and statistical properties. The primary source parameters are the patch peak-acceleration distribution mean, the distribution standard deviation, the patch size, and patch-rupture duration. Although our model assumes no scaling of peak acceleration with magnitude at the patch, the peak-acceleration attenuation curves, nevertheless, strongly scale with magnitude (dap/dM) ??? 0, and the scaling is distance dependent (dap/dM) ??? f(r). The distance-dependent magnitude scaling arises from two principal sources in the model. For a propagating rupture, loci exist on the fault from which radiated energy arrives at a particular station at the same time. These loci are referred to as isochrones. As fault size increases, the length of the isochrones and, hence, the number of additive pulses increase. Thus, peak accelerations increase with magnitude. The second effect, which arises in a completely different manner, is due to extreme-value properties. That is, as the fault size increases, the number of patches on the fault and the number of peak values at the station increase. Because these attenuated pulses are produced by a statistical distribution at the patch, the largest value will depend on the total number of peak values available on the seismogram. We refer to this result as the extremal effect, because it is predicted by the theory of extreme values. Both the extremal and isochrone effects are moderated by attenuation and distance to the fault, leading to magnitude- and distance-dependent peak-acceleration scaling. Remarkably, the scaling produced by both effects is very similar, although the

  1. Seismic wave attenuation and dispersion due to wave-induced fluid flow in rocks with strong permeability fluctuations.

    PubMed

    Germán Rubino, J; Monachesi, Leonardo B; Müller, Tobias M; Guarracino, Luis; Holliger, Klaus

    2013-12-01

    Oscillatory fluid movements in heterogeneous porous rocks induced by seismic waves cause dissipation of wave field energy. The resulting seismic signature depends not only on the rock compressibility distribution, but also on a statistically averaged permeability. This so-called equivalent seismic permeability does not, however, coincide with the respective equivalent flow permeability. While this issue has been analyzed for one-dimensional (1D) media, the corresponding two-dimensional (2D) and three-dimensional (3D) cases remain unexplored. In this work, this topic is analyzed for 2D random medium realizations having strong permeability fluctuations. With this objective, oscillatory compressibility simulations based on the quasi-static poroelasticity equations are performed. Numerical analysis shows that strong permeability fluctuations diminish the magnitude of attenuation and velocity dispersion due to fluid flow, while the frequency range where these effects are significant gets broader. By comparing the acoustic responses obtained using different permeability averages, it is also shown that at very low frequencies the equivalent seismic permeability is similar to the equivalent flow permeability, while for very high frequencies this parameter approaches the arithmetic average of the permeability field. These seemingly generic findings have potentially important implications with regard to the estimation of equivalent flow permeability from seismic data. PMID:25669286

  2. Ocean waves across the Arctic: Attenuation due to dissipation dominates over scattering for periods longer than 19 s

    NASA Astrophysics Data System (ADS)

    Ardhuin, Fabrice; Sutherland, Peter; Doble, Martin; Wadhams, Peter

    2016-06-01

    The poorly understood attenuation of surface waves in sea ice is generally attributed to the combination of scattering and dissipation. Scattering and dissipation have very different effects on the directional and temporal distribution of wave energy, making it possible to better understand their relative importance by analysis of swell directional spreading and arrival times. Here we compare results of a spectral wave model—using adjustable scattering and dissipation attenuation formulations—with wave measurements far inside the ice pack. In this case, scattering plays a negligible role in the attenuation of long swells. Specifically, scattering-dominated attenuation would produce directional wave spectra much broader than the ones recorded, and swell events arriving later and lasting much longer than observed. Details of the dissipation process remain uncertain. Average dissipation rates are consistent with creep effects but are 12 times those expected for a laminar boundary layer under a smooth solid ice plate.

  3. Calculation of the attenuation and phase displacement per unit of length due to rain composed of ellipsoidal drops

    NASA Technical Reports Server (NTRS)

    Maggiori, D.

    1981-01-01

    All of the phenomena which influence the propagation of radiowaves at frequencies above 10 GHz (attenuation, depolarization, scintillation) can by intensified by parameters directly derived from a solution of individual scatter, naturally in addition to be meteorological elements which characterize the physical medium. The diffusion caused by rainy precipitation was studied using Mie's algorithm for rain composed of spherical drops, and Oguchi's algorithm for rain composed of drops in an ellipsoidal form with axes of rotational symmetry arrange along the vertical line of a generic reference point. Specific phase displacement and attenuation along the principal planes, propagation of radiowaves in generic polarization, and propagation with inclined axes are also considered.

  4. Improvement of surface functionalities, including allergenicity attenuation, of whole buckwheat protein fraction by maillard-type glycation with dextran.

    PubMed

    Tazawa, Shigeru; Katayama, Shigeru; Hirabayashi, Masahiro; Yamaguchi, Daiki; Nakamura, Soichiro

    2014-12-01

    The purpose of the current study was to determine the effects of the introduction of polysaccharide chains onto the molecular surface of buckwheat proteins on buckwheat protein surface functionality. The whole buckwheat protein fraction (WBP) was prepared using 50 mM phosphate buffer (pH 7.5) containing 0.5 M NaCl and covalently linked with 6 kDa, 17.5 kDa, 40 kDa, 70 kDa, or 200 kDa dextran by Maillard-type glycation through controlled dry-heating at 60°C and 79% relative humidity for two weeks. Conjugation with 40 kDa dextran improved the water solubility and emulsifying properties of WBP without causing a serious loss of available lysine; 84.9% of the free amino groups were conserved. In addition, we found that the introduction of dextran chains onto the molecular surfaces of WBP attenuated the antigenicity of WBP. PMID:25580398

  5. Microwave attenuation and brightness temperature due to the gaseous atmosphere: A comparison of JPL and CCIR values

    NASA Technical Reports Server (NTRS)

    Smith, E. K.; Waters, J. W.

    1981-01-01

    A sophisticated but flexible radiative transfer program designed to assure internal consistency was used to produce brightness temperature (sky noise temperature in a given direction) and gaseous attenuation curves. The curves, derived from atmospheric models, were compared and a new set was derived for a specified frequency range.

  6. Acute hemolytic transfusion reactions due to multiple alloantibodies including anti-E, anti-c and anti-Jkb.

    PubMed

    Park, Tae Sung; Kim, Ki Uk; Jeong, Woo Jin; Kim, Hyung Hoi; Chang, Chulhun L; Chung, Joo Seop; Cho, Goon Jae; Lee, Eun Yup; Son, Han Chul

    2003-12-01

    We report a case of two consecutive episodes of acute hemolytic transfusion reactions (HTRs) due to multiple alloantibodies in a 34-yr-old man who suffered from avascular necrosis of left femoral head. He received five units of packed red blood cells (RBCs) during surgery. Then the transfusion of packed RBCs was required nine days after the surgery because of the unexplained drop in hemoglobin level. The transfusion of the first two units resulted in fever and brown-colored urine, but he received the transfusion of another packed RBCs the next day. He experienced even more severe symptoms during the transfusion of the first unit. We performed antibody screening test, and it showed positive results. Multiple alloantibodies including anti-E, anti-c and anti-Jkb were detected by antibody identification study. Acute HTRs due to multiple alloantibodies were diagnosed, and the supportive cares were done for 6 days. We suggest the antibody screening test should be included in the panel of pretransfusion tests for safer transfusion, and it is particularly mandatory for the patients with multiple transfusions, pregnant women, and preoperative patients. PMID:14676451

  7. Attenuation of Weather Radar Signals Due to Wetting of the Radome by Rainwater or Incomplete Filling of the Beam Volume

    NASA Technical Reports Server (NTRS)

    Merceret, Francis J.; Ward, Jennifer G.

    2000-01-01

    A search of scientific literature, both printed and electronic, was undertaken to provide quantitative estimates of attenuation effects of rainfall on weather radar radomes. The emphasis was on C-band (5 cm) and S-Band (10 cm) wavelengths. An empirical model was developed to estimate two-way wet radome losses as a function of frequency and rainfall rate for both standard and hydrophobic radomes. The model fits most of the published data within +/- 1 dB at both target wavelengths for rain rates from less than ten to more than 200 mm/hr. Rainfall attenuation effects remain under 1 dB at both frequencies regardless of radome type for rainfall rates up to 10 mm/hr. S-Band losses with a hydrophobic radome such as that on the WSR-88D remain under 1 dB up to 100 mm/hr. C-Band losses on standard radomes such as that on the Patrick AFB (Air Force Base) WSR-74C can reach as much as 5 dB at 50 mm/hr. In addition, calculations were performed to determine the reduction in effective reflectivity, Z, when a radar target is smaller than the sampling volume of the radar. Results are presented for both the Patrick Air Force Base WSR-74C and the WSR-88D as a function of target size and range.

  8. Whole-Body PET/MR Imaging: Quantitative Evaluation of a Novel Model-Based MR Attenuation Correction Method Including Bone

    PubMed Central

    Paulus, Daniel H.; Quick, Harald H.; Geppert, Christian; Fenchel, Matthias; Zhan, Yiqiang; Hermosillo, Gerardo; Faul, David; Boada, Fernando; Friedman, Kent P.; Koesters, Thomas

    2016-01-01

    In routine whole-body PET/MR hybrid imaging, attenuation correction (AC) is usually performed by segmentation methods based on a Dixon MR sequence providing up to 4 different tissue classes. Because of the lack of bone information with the Dixon-based MR sequence, bone is currently considered as soft tissue. Thus, the aim of this study was to evaluate a novel model-based AC method that considers bone in whole-body PET/MR imaging. Methods The new method (“Model”) is based on a regular 4-compartment segmentation from a Dixon sequence (“Dixon”). Bone information is added using a model-based bone segmentation algorithm, which includes a set of prealigned MR image and bone mask pairs for each major body bone individually. Model was quantitatively evaluated on 20 patients who underwent whole-body PET/MR imaging. As a standard of reference, CT-based μ-maps were generated for each patient individually by nonrigid registration to the MR images based on PET/CT data. This step allowed for a quantitative comparison of all μ-maps based on a single PET emission raw dataset of the PET/MR system. Volumes of interest were drawn on normal tissue, soft-tissue lesions, and bone lesions; standardized uptake values were quantitatively compared. Results In soft-tissue regions with background uptake, the average bias of SUVs in background volumes of interest was 2.4% ± 2.5% and 2.7% ± 2.7% for Dixon and Model, respectively, compared with CT-based AC. For bony tissue, the −25.5% ± 7.9% underestimation observed with Dixon was reduced to −4.9% ± 6.7% with Model. In bone lesions, the average underestimation was −7.4% ± 5.3% and −2.9% ± 5.8% for Dixon and Model, respectively. For soft-tissue lesions, the biases were 5.1% ± 5.1% for Dixon and 5.2% ± 5.2% for Model. Conclusion The novel MR-based AC method for whole-body PET/MR imaging, combining Dixon-based soft-tissue segmentation and model-based bone estimation, improves PET quantification in whole-body hybrid PET

  9. An attenuated Salmonella enterica serovar Typhimurium strain reduces disease severity, fecal shedding, and gastrointestinal colonization in swine due to virulent S. Typhimurium challenge

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background: Salmonella serovars frequently colonize swine without causing overt disease. Pathogen interventions are needed to limit Salmonella colonization in swine. Vaccination with an attenuated Salmonella strain may reduce pathogen carriage in swine and enhance food safety. Methods: Swine study ...

  10. Hepatic glutathione contributes to attenuation of thioacetamide-induced hepatic necrosis due to suppression of oxidative stress in diet-induced obese mice.

    PubMed

    Shirai, Makoto; Matsuoka, Miho; Makino, Toshihiko; Kai, Kiyonori; Teranishi, Munehiro; Takasaki, Wataru

    2015-08-01

    We previously reported that hepatic necrosis induced by thioacetamide (TA), a hepatotoxicant, was attenuated in mice fed a high-fat diet (HFD mice) in comparison with mice fed a normal rodent diet (ND mice). In this study, we focused on investigation of the mechanism of the attenuation. Hepatic content of thiobarbituric acid reactive substances (TBARS), an oxidative stress marker, significantly increased in ND mice at 24 and 48 hr after TA administration in comparison to that in vehicle-treated ND mice. At these time points, severe hepatic necrosis was observed in ND mice. Treatment with an established antioxidant, butylated hydroxyanisole, attenuated the TA-induced hepatic necrosis in ND mice. In contrast, in HFD mice, hepatic TBARS content did not increase, and hepatic necrosis was attenuated in comparison with ND mice at 24 and 48 hr after TA dosing. Metabolomics analysis regarding hepatic glutathione, a biological antioxidant, revealed decreased glutathione and changes in the amount of glutathione metabolism-related metabolites, such as increased ophtalmate and decreased cysteine, and this indicated activation of glutathione synthesis and usage in HFD mice. Finally, after treatment with L-buthionine-S,R-sulfoxinine, an inhibitor of glutathione synthesis, TA-induced hepatic necrosis was enhanced and hepatic TBARS contents increased after TA dosing in HFD mice. These results suggested that activated synthesis and usage of hepatic GSH, which suppresses hepatic oxidative stress, is one of the factors that attenuate TA-induced hepatic necrosis in HFD mice. PMID:26165648

  11. Serological response of swine to an attenuated Salmonella enterica serovar Typhimurium strain that reduces gastrointestinal colonization, fecal shedding and disease due to virulent Salmonella Typhimurium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Swine are often asymptomatic carriers of Salmonella spp. Interventions are needed to limit Salmonella colonization of swine to enhance food safety. An attenuated Salmonella enterica serovar Typhimurium mutant strain (BBS 202) was tested in swine to determine whether vaccination could provide protect...

  12. An rfaH mutant of Salmonella enterica serovar typhimurium is attenuated in swine and reduces intestinal colonization, fecal shedding, and disease severity due to virulent Salmonella Typhimurium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Swine are often asymptomatic carriers of Salmonella spp., and interventions are needed to limit colonization of swine to enhance food safety and reduce environmental contamination. We evaluated the attenuation and potential vaccine use in pigs of a Salmonella enterica serovar Typhimurium mutant of r...

  13. A model for attenuation of backscatter due to sediment accumulations and its application to determine sediment thicknesses with GLORIA sidescan sonar

    NASA Astrophysics Data System (ADS)

    Mitchell, Neil C.

    1993-12-01

    Where the seafloor consists of a highly backscattering surface covered with a drape of fine-grained sediment, and where the sediment does not contribute significantly to the backscattered signal, the sediment thickness can potentially be inferred from the amount of signal attenuation in the sediment layer. A first-order acoustical model is proposed in which the signal strength is reduced by an amount proportional to the sediment thickness and attenuation rate in the sediments. Data collected with Geological Long-Range Inclined Azdic (GLORIA) are used to develop and test this model. I explore the various sources of error in estimating sediment thickness using this technique and propose a model for nonuniform sediment drapes (the first-order model assumes a uniform thickness at the subfootprint scale).

  14. Valuation of green walls and green roofs as soundscape measures: including monetised amenity values together with noise-attenuation values in a cost-benefit analysis of a green wall affecting courtyards.

    PubMed

    Veisten, Knut; Smyrnova, Yuliya; Klæboe, Ronny; Hornikx, Maarten; Mosslemi, Marjan; Kang, Jian

    2012-11-01

    Economic unit values of soundscape/acoustic effects have been based on changes in the number of annoyed persons or on decibel changes. The normal procedure has been the application of these unit values to noise-attenuation measures affecting the noisier façade of a dwelling. Novel modular vegetation-based soundscape measures, so-called green walls, might be relevant for both noisy and quieter areas. Moreover, their benefits will comprise noise attenuation as well as non-acoustic amenity effects. One challenge is to integrate the results of some decades of non-acoustic research on the amenity value of urban greenery into design of the urban sound environment, and incorporate these non-acoustic properties in the overall economic assessment of noise control and overall sound environment improvement measures. Monetised unit values for green walls have been included in two alternative cases, or demonstration projects, of covering the entrances to blocks of flats with a green wall. Since these measures improve the noise environment on the quiet side of the dwellings and courtyards, not the most exposed façade, adjustment factors to the nominal quiet side decibel reductions to arrive at an estimate of the equivalent overall acoustic improvement have been applied. A cost-benefit analysis of the green wall case indicates that this measure is economically promising, when valuing the noise attenuation in the quieter area and adding the amenity/aesthetic value of the green wall. PMID:23202816

  15. Valuation of Green Walls and Green Roofs as Soundscape Measures: Including Monetised Amenity Values Together with Noise-attenuation Values in a Cost-benefit Analysis of a Green Wall Affecting Courtyards

    PubMed Central

    Veisten, Knut; Smyrnova, Yuliya; Klæboe, Ronny; Hornikx, Maarten; Mosslemi, Marjan; Kang, Jian

    2012-01-01

    Economic unit values of soundscape/acoustic effects have been based on changes in the number of annoyed persons or on decibel changes. The normal procedure has been the application of these unit values to noise-attenuation measures affecting the noisier façade of a dwelling. Novel modular vegetation-based soundscape measures, so-called green walls, might be relevant for both noisy and quieter areas. Moreover, their benefits will comprise noise attenuation as well as non-acoustic amenity effects. One challenge is to integrate the results of some decades of non-acoustic research on the amenity value of urban greenery into design of the urban sound environment, and incorporate these non-acoustic properties in the overall economic assessment of noise control and overall sound environment improvement measures. Monetised unit values for green walls have been included in two alternative cases, or demonstration projects, of covering the entrances to blocks of flats with a green wall. Since these measures improve the noise environment on the quiet side of the dwellings and courtyards, not the most exposed façade, adjustment factors to the nominal quiet side decibel reductions to arrive at an estimate of the equivalent overall acoustic improvement have been applied. A cost-benefit analysis of the green wall case indicates that this measure is economically promising, when valuing the noise attenuation in the quieter area and adding the amenity/aesthetic value of the green wall. PMID:23202816

  16. IDEA Special Education Due Process Complaints/Hearing Requests: Including Expedited Hearing Requests. A Guide for Parents of Children & Youth (Ages 3-21)

    ERIC Educational Resources Information Center

    Center for Appropriate Dispute Resolution in Special Education (CADRE), 2014

    2014-01-01

    A due process complaint is a written document used to request a due process hearing related to the identification, evaluation, or educational placement of a child with a disability, or the provision of a free, appropriate public education (FAPE) to the child. This publication describes Due Process Complaints/Hearing Requests generally for Part B…

  17. [Evaluation of the quality of drinking water in Senigallia (Italy), including the presence of asbestos fibres, and of morbidity and mortality due to gastrointestinal tumours].

    PubMed

    Fiorenzuolo, Giovanni; Moroni, Vania; Cerrone, Tiziana; Bartolucci, Elena; Rossetti, Siro; Tarsi, Riccardo

    2013-01-01

    The aim was to evaluate the organoleptic quality of drinking water conducted in asbestos cement piping, in eleven towns in the Marche region (Italy) and the presence of asbestos fibres. A descriptive survey was also conducted to assess possible health effects in the population, in particular morbidity and mortality due to gastrointestinal (GI) cancer. Study results show a very low concentration of free asbestos fibres in water samples examined. No differences in mortality and morbidity due to GI cancers were detected compared to the national population. PMID:23903037

  18. A simulation study to determine the attenuation and bias in health risk estimates due to exposure measurement error in bi-pollutant models

    EPA Science Inventory

    To understand the combined health effects of exposure to ambient air pollutant mixtures, it is becoming more common to include multiple pollutants in epidemiologic models. However, the complex spatial and temporal pattern of ambient pollutant concentrations and related exposures ...

  19. [Evaluation of ten fish species to be included as part of renal diet, due to their protein, phosphorus and fatty acids content].

    PubMed

    Castro-González, Maria Isabel; Maafs-Rodríguez, Ana Gabriela; Pérez-Gil Romo, Fernando

    2012-06-01

    Because renal disease is highly complex, its nutritional treatment is complicated and many foods are restricted, including fish because its phosphorus content. The aim of the present study was to analyze ten fillet fish species, commonly consumed in Mexico (Cyprinus carpio carpio, Ophichthus rex, Symphurus elongatus, Eucinostomus entomelas, Chirostoma patzcuaro, Bairdiella chrysoura, Salmo salar Oreochromis urolepis hornorum, Sphyraena guachancho, Istiophorus albicans), to determine their phosphorus (P), protein (Pr), cholesterol, sodium, potassium, vitamins D3 and E, and n-3 PUFA (EPA+DHA) according to the AOAC techniques, in order to identify which species could be included in renal diet; particularly because of their risk:benefit relations (calculated with those results). Protein values ranged from 16.5 to 33.5g/100 g of fillet; the specie with the highest phosphorus contest was Salmo salar, and with the lowest, Symphurus elongatus. EPA+DHA quantity ranged from 79.64 mg/100 g to 1,381.53 mg/100 g. Considering de P/Pr relation recommended to renal patients, all analyzed species (except Salmo salar, Ophichthus rex and Istiophorus albicans) could be included in their diet. As for the P/EPA+DHA relation, the species most recommended to renal patients are Symphurus elongatus, Bairdiella chrysoura and Sphyraena guachancho. PMID:23610899

  20. Estimation of torque on mechanical heart valves due to magnetic resonance imaging including an estimation of the significance of the Lenz effect using a computational model

    NASA Astrophysics Data System (ADS)

    Robertson, Neil M.; Diaz-Gomez, Manuel; Condon, Barrie

    2000-12-01

    Mitral and aortic valve replacement is a procedure which is common in cardiac surgery. Some of these replacement valves are mechanical and contain moving metal parts. Should the patient in whom such a valve has been implanted be involved in magnetic resonance imaging, there is a possible dangerous interaction between the moving metal parts and the static magnetic field due to the Lenz effect. Mathematical models of two relatively common forms of single-leaflet valves have been derived and the magnitude of the torque which opposes the motion of the valve leaflet has been calculated for a valve disc of solid metal. In addition, a differential model of a ring-strengthener valve type has been considered to determine the likely significance of the Lenz effect in the context of the human heart. For common magnetic field strengths at present, i.e. 1 to 2 T, the effect is not particularly significant. However, there is a marked increase in back pressure as static magnetic field strength increases. There are concerns that, since field strengths in the range 3 to 4 T are increasingly being used, the Lenz effect could become significant. At 5 to 10 T the malfunction of the mechanical heart valve could cause the heart to behave as though it is diseased. For unhealthy or old patients this could possibly prove fatal.

  1. Mild phenotype due to inverse duplication 4p16.3 - P15.3 including the Wolf-Hirschhorn critical region.

    PubMed

    Tschernigg, M; Petek, E; Wagner, K; Kroisel, P M

    2002-01-01

    Duplication of distal 4p results in a recognizable clinical phenotype. We report here on a 3 year old girl with a de novo inverse duplication of the chromosome segment 4p16.3-p15.3. The symptoms in this patient are milder than those of previously described patients with 4p duplication syndrome and include a deep hairline, deep-set eyes, short pug nose, full cheeks, simian crease, clinodactily of the fifth digit, no speech development and a moderate psychomotor retardation. Fluorescence in situ hybridization (FISH) using a chromosome 4 painting probe confirmed that the extra material is of chromosome 4 origin. Further analysis with the Wolf-Hirschhorn critical region probe demonstrated the duplication of this region. The lysosomal hydrolase alpha-L-iduronidase (IDUA) gene which is mutated in mucopolysaccaridosis type I (MPS I) and mapped to 4p16.3 might be responsible for some of the MPS like facial features. A phenotype-genotype correlation analysis in combination with literature review was undertaken to allow a further delineation of partial trisomy 4p syndromes. PMID:12017235

  2. Fiber Optic Attenuators

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Mike Buzzetti designed a fiber optic attenuator while working at Jet Propulsion Laboratory, intended for use in NASA's Deep Space Network. Buzzetti subsequently patented and received an exclusive license to commercialize the device, and founded Nanometer Technologies to produce it. The attenuator functions without introducing measurable back-reflection or insertion loss, and is relatively insensitive to vibration and changes in temperature. Applications include cable television, telephone networks, other signal distribution networks, and laboratory instrumentation.

  3. Scaling of Newtonian and non-Newtonian fluid dynamics without inertia for quantitative modelling of rock flow due to gravity (including the concept of rheological similarity)

    NASA Astrophysics Data System (ADS)

    Weijermars, Ruud; Schmeling, Harro

    1986-09-01

    Scale model theory for constructing dynamically scaled analogue models of rock flowing in the solid state has until now assumed that the natural and model flows were both viscous. In viscous flows, at the very low Reynolds numbers ( Re ≪ 1) common in solid rocks, geometrical similarity is sufficient to achieve dynamic similarity between a homogeneous material (scale) model and its natural prototype. However, experiments on the rheology of natural rocks suggest that they flow predominantly as non-Newtonian strain rate softening materials at the characteristic geological strain rate 10 -14 s -1. Non-dimensionalisation of both the equation of motion and the constitutive flow law of non-Newtonian flows is carried out to investigate what criteria are required to achieve dynamic similarity. It is shown that dynamic similarity of non-Newtonian flows at low inertia (e.g., a rock with Re ≪ 1 and its model analogue) can only be attained if the steady-state flow curves of the model materials and the various rocks in the prototype have mutually similar shapes and slopes, and if these flows operate on similar parts of their respective flow curves. We term this the requirement of rheological similarity. Dynamic similarity of low inertia flows ( Re ≪ 1) in non-Newtonian continua is achieved if they are rheologically and geometrically similar. Additional criteria for dynamic similarity of low inertia flows in inhomogeneous media (with Newtonian or non-Newtonian subregions, or both) are formulated in section 5. Scaling of thermal properties is not included. Steady-state flow curves of common rocks are compiled in log stress-log strain rate space together with analogue materials suitable for modelling of solid state rock deformation. This compilation aids the selection of model materials with flow curves geometrically similar to those of rocks in the prototype. Laboratory scale models of rock flow should generally be constructed of materials which strain rate soften during

  4. Orbit determination modelling analysis using GPS including perturbations due to geopotential coefficients of high degree and order, solar radiation pressure and luni-solar attraction

    NASA Astrophysics Data System (ADS)

    Vilhena de Moraes, Rodolpho; Cristiane Pardal, Paula; Koiti Kuga, Helio

    has been done, using such GPS data, for orbit determination of the Topex/Poseidon satellite, whose accurate ephemerides are freely available at Internet. It is shown that from a poor but acceptable modeling up to all effects included, the accuracy can vary from about 30m to 8m. Test results for short period (2 hours) and for long period (24 hours) are also shown.

  5. Attenuator And Conditioner

    DOEpatents

    Anderson, Gene R.; Armendariz, Marcelino G.; Carson, Richard F.; Bryan, Robert P.; Duckett, III, Edwin B.; Kemme, Shanalyn Adair; McCormick, Frederick B.; Peterson, David W.

    2006-04-04

    An apparatus and method of attenuating and/or conditioning optical energy for an optical transmitter, receiver or transceiver module is disclosed. An apparatus for attenuating the optical output of an optoelectronic connector including: a mounting surface; an array of optoelectronic devices having at least a first end; an array of optical elements having at least a first end; the first end of the array of optical elements optically aligned with the first end of the array of optoelectronic devices; an optical path extending from the first end of the array of optoelectronic devices and ending at a second end of the array of optical elements; and an attenuator in the optical path for attenuating the optical energy emitted from the array of optoelectronic devices. Alternatively, a conditioner may be adapted in the optical path for conditioning the optical energy emitted from the array of optoelectronic devices.

  6. Radiofrequency attenuator and method

    DOEpatents

    Warner, Benjamin P.; McCleskey, T. Mark; Burrell, Anthony K.; Agrawal, Anoop; Hall, Simon B.

    2009-01-20

    Radiofrequency attenuator and method. The attenuator includes a pair of transparent windows. A chamber between the windows is filled with molten salt. Preferred molten salts include quarternary ammonium cations and fluorine-containing anions such as tetrafluoroborate (BF.sub.4.sup.-), hexafluorophosphate (PF.sub.6.sup.-), hexafluoroarsenate (AsF.sub.6.sup.-), trifluoromethylsulfonate (CF.sub.3SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3SO.sub.2).sub.2N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3CF.sub.2SO.sub.2).sub.2N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3SO.sub.2).sub.3C.sup.-). Radicals or radical cations may be added to or electrochemically generated in the molten salt to enhance the RF attenuation.

  7. Radiofrequency attenuator and method

    DOEpatents

    Warner, Benjamin P.; McCleskey, T. Mark; Burrell, Anthony K.; Agrawal, Anoop; Hall, Simon B.

    2009-11-10

    Radiofrequency attenuator and method. The attenuator includes a pair of transparent windows. A chamber between the windows is filled with molten salt. Preferred molten salts include quarternary ammonium cations and fluorine-containing anions such as tetrafluoroborate (BF.sub.4.sup.-), hexafluorophosphate (PF.sub.6.sup.-), hexafluoroarsenate (AsF.sub.6.sup.-), trifluoromethylsulfonate (CF.sub.3SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3SO.sub.2).sub.2N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3CF.sub.2SO.sub.2).sub.2N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3SO.sub.2).sub.3 C.sup.-). Radicals or radical cations may be added to or electrochemically generated in the molten salt to enhance the RF attenuation.

  8. Adjustable Optical-Fiber Attenuator

    NASA Technical Reports Server (NTRS)

    Buzzetti, Mike F.

    1994-01-01

    Adjustable fiber-optic attenuator utilizes bending loss to reduce strength of light transmitted along it. Attenuator functions without introducing measurable back-reflection or insertion loss. Relatively insensitive to vibration and changes in temperature. Potential applications include cable television, telephone networks, other signal-distribution networks, and laboratory instrumentation.

  9. Amplitude loss of sonic waveform due to source coupling to the medium

    USGS Publications Warehouse

    Lee, Myung W.; Waite, William F.

    2007-01-01

    In contrast to hydrate-free sediments, sonic waveforms acquired in gas hydrate-bearing sediments indicate strong amplitude attenuation associated with a sonic velocity increase. The amplitude attenuation increase has been used to quantify pore-space hydrate content by attributing observed attenuation to the hydrate-bearing sediment's intrinsic attenuation. A second attenuation mechanism must be considered, however. Theoretically, energy radiation from sources inside fluid-filled boreholes strongly depends on the elastic parameters of materials surrounding the borehole. It is therefore plausible to interpret amplitude loss in terms of source coupling to the surrounding medium as well as to intrinsic attenuation. Analyses of sonic waveforms from the Mallik 5L-38 well, Northwest Territories, Canada, indicate a significant component of sonic waveform amplitude loss is due to source coupling. Accordingly, all sonic waveform amplitude analyses should include the effect of source coupling to accurately characterize a formation's intrinsic attenuation.

  10. GPR measurements of attenuation in concrete

    SciTech Connect

    Eisenmann, David Margetan, Frank J. Pavel, Brittney

    2015-03-31

    Ground-penetrating radar (GPR) signals from concrete structures are affected by several phenomenon, including: (1) transmission and reflection coefficients at interfaces; (2) the radiation patterns of the antenna(s) being used; and (3) the material properties of concrete and any embedded objects. In this paper we investigate different schemes for determining the electromagnetic (EM) attenuation of concrete from measured signals obtained using commercially-available GPR equipment. We adapt procedures commonly used in ultrasonic inspections where one compares the relative strengths of two or more signals having different travel paths through the material of interest. After correcting for beam spread (i.e., diffraction), interface phenomena, and equipment amplification settings, any remaining signal differences are assumed to be due to attenuation thus allowing the attenuation coefficient (say, in dB of loss per inch of travel) to be estimated. We begin with a brief overview of our approach, and then discuss how diffraction corrections were determined for our two 1.6 GHz GPR antennas. We then present results of attenuation measurements for two types of concrete using both pulse/echo and pitch/catch measurement setups.

  11. Rotary antenna attenuator

    NASA Technical Reports Server (NTRS)

    Dickinson, R. M.; Hardy, J. C.

    1969-01-01

    Radio frequency attenuator, having negligible insertion loss at minimum attenuation, can be used for making precise antenna gain measurements. It is small in size compared to a rotary-vane attenuator.

  12. Downhole pressure attenuation apparatus

    SciTech Connect

    Ricles, T.D.; Barton, J.A.

    1992-02-18

    This patent describes a process for preventing damage to tool strings and other downhole equipment in a well caused by pressures produced during detonation of one or more downhole explosive devices. It comprises adding to a tool string at least one pressure attenuating apparatus for attenuating the peak pressure wave and quasi-static pressure pulse produced by the explosive devices, the pressure attenuating apparatus including an initially closed relief vent including tubing means supporting a plurality of charge port assemblies each including an explosive filled shaped charge and a prestressed disc, the shaped charges interconnected by a detonating cord, the amount of explosive in each shaped charge being sufficient to rupture its associated disc without damaging surrounding tubular bodies in the well, and a vent chamber defined by the tubing means and providing a liquid free volume, and opening the relief vent substantially contemporaneously with downhole explosive device detonation by detonating the shaped charges to rupture the discs of the charge port assemblies.

  13. Digitally Controlled Beam Attenuator

    NASA Astrophysics Data System (ADS)

    Peppler, W. W.; Kudva, B.; Dobbins, J. T.; Lee, C. S.; Van Lysel, M. S.; Hasegawa, B. H.; Mistretta, C. A.

    1982-12-01

    In digital fluorographic techniques the video camera must accommodate a wide dynamic range due to the large variation in the subject thickness within the field of view. Typically exposure factors and the optical aperture are selected such that the maximum video signal is obtained in the most transmissive region of the subject. Consequently, it has been shown that the signal-to-noise ratio is severely reduced in the dark regions. We have developed a prototype digital beam attenuator (DBA) which will alleviate this and some related problems in digital fluorography. The prototype DBA consists of a 6x6 array of pistons which are individually controlled. A membrane containing an attenuating solu-tion of (CeC13) in water and the piston matrix are placed between the x-ray tube and the subject. Under digital control the pistons are moved into the attenuating material in order to adjust the beam intensity over each of the 36 cells. The DBA control unit which digitizes the image during patient positioning will direct the pistons under hydraulic control to produce a uniform x-ray field exiting the subject. The pistons were designed to produce very little structural background in the image. In subtraction studies any structure would be cancelled. For non-subtraction studies such as cine-cardiology we are considering higher cell densities (eg. 64x64). Due to the narrow range of transmission provided by the DBA, in such studies ultra-high contrast films could be used to produce a high resolution quasi-subtraction display. Additional benefits of the DBA are: 1) reduced dose to the bright image areas when the dark areas are properly exposed. 2) improved scatter and glare to primary ratios, leading to improved contrast in the dark areas.

  14. DC attenuation meter

    DOEpatents

    Hargrove, Douglas L.

    2004-09-14

    A portable, hand-held meter used to measure direct current (DC) attenuation in low impedance electrical signal cables and signal attenuators. A DC voltage is applied to the signal input of the cable and feedback to the control circuit through the signal cable and attenuators. The control circuit adjusts the applied voltage to the cable until the feedback voltage equals the reference voltage. The "units" of applied voltage required at the cable input is the system attenuation value of the cable and attenuators, which makes this meter unique. The meter may be used to calibrate data signal cables, attenuators, and cable-attenuator assemblies.

  15. Imaging Rayleigh wave attenuation with USArray

    NASA Astrophysics Data System (ADS)

    Bao, Xueyang; Dalton, Colleen A.; Jin, Ge; Gaherty, James B.; Shen, Yang

    2016-07-01

    The EarthScope USArray provides an opportunity to obtain detailed images of the continental upper mantle at an unprecedented scale. The majority of mantle models derived from USArray data to date contain spatial variations in seismic-wave speed; however, in many cases these data sets do not by themselves allow a non-unique interpretation. Joint interpretation of seismic attenuation and velocity models can improve upon the interpretations based only on velocity and provide important constraints on the temperature, composition, melt content, and volatile content of the mantle. The surface wave amplitudes that constrain upper-mantle attenuation are sensitive to factors in addition to attenuation, including the earthquake source excitation, focusing and defocusing by elastic structure, and local site amplification. Because of the difficulty of isolating attenuation from these other factors, little is known about the attenuation structure of the North American upper mantle. In this study, Rayleigh wave traveltime and amplitude in the period range 25-100 s are measured using an interstation cross-correlation technique, which takes advantage of waveform similarity at nearby stations. Several estimates of Rayleigh wave attenuation and site amplification are generated at each period, using different approaches to separate the effects of attenuation and local site amplification on amplitude. It is assumed that focusing and defocusing effects can be described by the Laplacian of the traveltime field. All approaches identify the same large-scale patterns in attenuation, including areas where the attenuation values are likely contaminated by unmodelled focusing and defocusing effects. Regionally averaged attenuation maps are constructed after removal of the contaminated attenuation values, and the variations in intrinsic shear attenuation that are suggested by these Rayleigh wave attenuation maps are explored.

  16. Imaging Rayleigh wave attenuation with USArray

    NASA Astrophysics Data System (ADS)

    Bao, Xueyang; Dalton, Colleen A.; Jin, Ge; Gaherty, James B.; Shen, Yang

    2016-04-01

    The EarthScope USArray provides an opportunity to obtain detailed images of the continental upper mantle at an unprecedented scale. The majority of mantle models derived from USArray data to date contain spatial variations in seismic-wave speed; however, in many cases these data sets do not by themselves allow a non-unique interpretation. Joint interpretation of seismic attenuation and velocity models can improve upon the interpretations based only on velocity and provide important constraints on the temperature, composition, melt content, and volatile content of the mantle. The surface-wave amplitudes that constrain upper-mantle attenuation are sensitive to factors in addition to attenuation, including the earthquake source excitation, focusing and defocusing by elastic structure, and local site amplification. Because of the difficulty of isolating attenuation from these other factors, little is known about the attenuation structure of the North American upper mantle. In this study, Rayleigh wave travel time and amplitude in the period range 25-100 s are measured using an interstation cross-correlation technique, which takes advantage of waveform similarity at nearby stations. Several estimates of Rayleigh wave attenuation and site amplification are generated at each period, using different approaches to separate the effects of attenuation and local site amplification on amplitude. It is assumed that focusing and defocusing effects can be described by the Laplacian of the travel-time field. All approaches identify the same large-scale patterns in attenuation, including areas where the attenuation values are likely contaminated by unmodelled focusing and defocusing effects. Regionally averaged attenuation maps are constructed after removal of the contaminated attenuation values, and the variations in intrinsic shear attenuation that are suggested by these Rayleigh wave attenuation maps are explored.

  17. Pressure surge attenuator

    DOEpatents

    Christie, Alan M.; Snyder, Kurt I.

    1985-01-01

    A pressure surge attenuation system for pipes having a fluted region opposite crushable metal foam. As adapted for nuclear reactor vessels and heads, crushable metal foam is disposed to attenuate pressure surges.

  18. Tracer attenuation in groundwater

    NASA Astrophysics Data System (ADS)

    Cvetkovic, Vladimir

    2011-12-01

    The self-purifying capacity of aquifers strongly depends on the attenuation of waterborne contaminants, i.e., irreversible loss of contaminant mass on a given scale as a result of coupled transport and transformation processes. A general formulation of tracer attenuation in groundwater is presented. Basic sensitivities of attenuation to macrodispersion and retention are illustrated for a few typical retention mechanisms. Tracer recovery is suggested as an experimental proxy for attenuation. Unique experimental data of tracer recovery in crystalline rock compare favorably with the theoretical model that is based on diffusion-controlled retention. Non-Fickian hydrodynamic transport has potentially a large impact on field-scale attenuation of dissolved contaminants.

  19. Underwing Compression Vortex-Attenuation Device

    NASA Technical Reports Server (NTRS)

    Patterson, James C., Jr.

    1994-01-01

    Underwing compression vortex-attenuation device designed to provide method for attenuating lift-induced vortex generated by wings of airplane. Includes compression panel attached to lower surface of wing, facing perpendicular to streamwise airflow. Concept effective on all types of aircraft. Causes increase in wing lift rather than reduction when deployed. Device of interest to aircraft designers and enhances air safety in general.

  20. Attenuation of seismic waves obtained by coda waves analysis in the West Bohemia earthquake swarm region

    NASA Astrophysics Data System (ADS)

    Bachura, Martin; Fischer, Tomas

    2014-05-01

    Seismic waves are attenuated by number of factors, including geometrical spreading, scattering on heterogeneities and intrinsic loss due the anelasticity of medium. Contribution of the latter two processes can be derived from the tail part of the seismogram - coda (strictly speaking S-wave coda), as these factors influence the shape and amplitudes of coda. Numerous methods have been developed for estimation of attenuation properties from the decay rate of coda amplitudes. Most of them work with the S-wave coda, some are designed for the P-wave coda (only on teleseismic distances) or for the whole waveforms. We used methods to estimate the 1/Qc - attenuation of coda waves, methods to separate scattering and intrinsic loss - 1/Qsc, Qi and methods to estimate attenuation of direct P and S wave - 1/Qp, 1/Qs. In this study, we analyzed the S-wave coda of local earthquake data recorded in the West Bohemia/Vogtland area. This region is well known thanks to the repeated occurrence of earthquake swarms. We worked with data from the 2011 earthquake swarm, which started late August and lasted with decreasing intensity for another 4 months. During the first week of swarm thousands of events were detected with maximum magnitudes ML = 3.6. Amount of high quality data (including continuous datasets and catalogues with an abundance of well-located events) is available due to installation of WEBNET seismic network (13 permanent and 9 temporary stations) monitoring seismic activity in the area. Results of the single-scattering model show seismic attenuations decreasing with frequency, what is in agreement with observations worldwide. We also found decrease of attenuation with increasing hypocentral distance and increasing lapse time, which was interpreted as a decrease of attenuation with depth (coda waves on later lapse times are generated in bigger depths - in our case in upper lithosphere, where attenuations are small). We also noticed a decrease of frequency dependence of 1/Qc

  1. Fiber optic attenuator

    NASA Technical Reports Server (NTRS)

    Buzzetti, Mike F. (Inventor)

    1994-01-01

    A fiber optic attenuator of the invention is a mandrel structure through which a bundle of optical fibers is wrapped around in a complete circle. The mandrel structure includes a flexible cylindrical sheath through which the bundle passes. A set screw on the mandrel structure impacts one side of the sheath against two posts on the opposite side of the sheath. By rotating the screw, the sheath is deformed to extend partially between the two posts, bending the fiber optic bundle to a small radius controlled by rotating the set screw. Bending the fiber optic bundle to a small radius causes light in each optical fiber to be lost in the cladding, the amount depending upon the radius about which the bundle is bent.

  2. Attenuation assessment of medical protective eyewear: the AVEN experience.

    PubMed

    Bertolini, M; Benecchi, G; Amici, M; Piola, A; Piccagli, V; Giordano, C; Nocetti, L

    2016-06-01

    The goal of this paper is to test the attenuation capability of seven models of protective eyewear used in routine clinical practice. Scattered radiation from a standard patient was simulated by using a water tank located over the treatment couch of a GE Innova 3100 x-ray angiography system. Seven protective eyewear models were tested using an anthropomorphic phantom mimicking the first operator. At each test, 4 thermoluminiscent dosimeters were placed on the phantom (respectively in front of the protective eyewear, under the eyewear, on the left earpiece and at chest level) in order to have an eyewear-independent reference. A test session without glasses was also acquired. Each model was tested with standard posterior-anterior (PA) projections and the two most common protective eyewear were tested using LAO90° and LAO45°CRA30° projections. A worst-case scenario was created to be sure of having an upper limit for the assessment of eyewear attenuation in routine clinical practice. In PA projections, the absolute attenuation value ranged between 71% and 81%, while relative attenuation between dose measured at eye lens and that measured at eyewear earpiece ranged from 67% to 85%. The slightly wider range was probably due to scatter radiation variability; anyway, differences are still included in the variable uncertainty of experimental measurements. It is worth noting that #3 eyewear model (the one without lateral protection) allows an attenuation similar to that of #5 eyewear model (with 0.5 mm lead lateral protection) in LAO90° and LAO45°CRA30° projections. Despite the experimental limitations, a description of the radiation properties of protective eyewear concerning radiation attenuation can be useful to rely on protection devices which can be used in routine clinical practice. PMID:27122122

  3. Variable laser attenuator

    DOEpatents

    Foltyn, Stephen R.

    1988-01-01

    The disclosure relates to low loss, high power variable attenuators comprng one or more transmissive and/or reflective multilayer dielectric filters. The attenuator is particularly suitable to use with unpolarized lasers such as excimer lasers. Beam attenuation is a function of beam polarization and the angle of incidence between the beam and the filter and is controlled by adjusting the angle of incidence the beam makes to the filter or filters. Filters are selected in accordance with beam wavelength.

  4. Variable laser attenuator

    DOEpatents

    Foltyn, S.R.

    1987-05-29

    The disclosure relates to low loss, high power variable attenuators comprising one or more transmissive and/or reflective multilayer dielectric filters. The attenuator is particularly suitable to use with unpolarized lasers such as excimer lasers. Beam attenuation is a function of beam polarization and the angle of incidence between the beam and the filter and is controlled by adjusting the angle of incidence the beam makes to the filter or filters. Filters are selected in accordance with beam wavelength. 9 figs.

  5. Evolution of Natural Attenuation Evaluation Protocols

    EPA Science Inventory

    Traditionally the evaluation of the efficacy of natural attenuation was based on changes in contaminant concentrations and mass reduction. Statistical tools and models such as Bioscreen provided evaluation protocols which now are being approached via other vehicles including m...

  6. Seismic Attenuation Inversion with t* Using tstarTomog.

    SciTech Connect

    Preston, Leiph

    2014-09-01

    Seismic attenuation is defined as the loss of the seismic wave amplitude as the wave propagates excluding losses strictly due to geometric spreading. Information gleaned from seismic waves can be utilized to solve for the attenuation properties of the earth. One method of solving for earth attenuation properties is called t*. This report will start by introducing the basic theory behind t* and delve into inverse theory as it pertains to how the algorithm called tstarTomog inverts for attenuation properties using t* observations. This report also describes how to use the tstarTomog package to go from observed data to a 3-D model of attenuation structure in the earth.

  7. Chlorine signal attenuation in concrete.

    PubMed

    Naqvi, A A; Maslehuddin, M; ur-Rehman, Khateeb; Al-Amoudi, O S B

    2015-11-01

    The intensity of prompt gamma-ray was measured at various depths from chlorine-contaminated silica fume (SF) concrete slab concrete specimens using portable neutron generator-based prompt gamma-ray setup. The intensity of 6.11MeV chloride gamma-rays was measured from the chloride contaminated slab at distance of 15.25, 20.25, 25.25, 30.25 and 35.25cm from neutron target in a SF cement concrete slab specimens. Due to attenuation of thermal neutron flux and emitted gamma-ray intensity in SF cement concrete at various depths, the measured intensity of chlorine gamma-rays decreases non-linearly with increasing depth in concrete. A good agreement was noted between the experimental results and the results of Monte Carlo simulation. This study has provided useful experimental data for evaluating the chloride contamination in the SF concrete utilizing gamma-ray attenuation method. PMID:26218450

  8. Attenuation coefficients for water quality trading.

    PubMed

    Keller, Arturo A; Chen, Xiaoli; Fox, Jessica; Fulda, Matt; Dorsey, Rebecca; Seapy, Briana; Glenday, Julia; Bray, Erin

    2014-06-17

    Water quality trading has been proposed as a cost-effective approach for reducing nutrient loads through credit generation from agricultural or point source reductions sold to buyers facing costly options. We present a systematic approach to determine attenuation coefficients and their uncertainty. Using a process-based model, we determine attenuation with safety margins at many watersheds for total nitrogen (TN) and total phosphorus (TP) loads as they transport from point of load reduction to the credit buyer. TN and TP in-stream attenuation generally increases with decreasing mean river flow; smaller rivers in the modeled region of the Ohio River Basin had TN attenuation factors per km, including safety margins, of 0.19-1.6%, medium rivers of 0.14-1.2%, large rivers of 0.13-1.1%, and very large rivers of 0.04-0.42%. Attenuation in ditches transporting nutrients from farms to receiving rivers is 0.4%/km for TN, while for TP attenuation in ditches can be up to 2%/km. A 95 percentile safety margin of 30-40% for TN and 6-10% for TP, applied to the attenuation per km factors, was determined from the in-stream sensitivity of load reductions to watershed model parameters. For perspective, over 50 km a 1% per km factor would result in 50% attenuation = 2:1 trading ratio. PMID:24866482

  9. Attenuation Tomography of the Upper Mantle

    NASA Astrophysics Data System (ADS)

    Adenis, A.; Debayle, E.; Ricard, Y. R.

    2014-12-01

    We present a 3-D model of surface wave attenuation in the upper mantle. The model is constrained by a large data set of fundamental and higher Rayleigh mode observations. This data set consists of about 1,800,000 attenuation curves measured in the period range 50-300s by Debayle and Ricard (2012). A careful selection allows us to reject data for which measurements are likely biased by the poor knowledge of the scalar seismic moment or by a ray propagation too close to a node of the source radiation pattern. For each epicenter-station path, elastic focusing effects due to seismic heterogeneities are corrected using DR2012 and the data are turned into log(1/Q). The selected data are then combined in a tomographic inversion using the non-linear least square formalism of Tarantola and Valette (1982). The obtained attenuation maps are in agreement with the surface tectonic for periods and modes sensitive to the top 200km of the upper mantle. Low attenuation regions correlate with continental shields while high attenuation regions are located beneath young oceanic regions. The attenuation pattern becomes more homogeneous at depths greater than 200 km and the maps are dominated by a high quality factor signature beneath slabs. We will discuss the similarities and differences between the tomographies of seismic velocities and of attenuations.

  10. [Anaphylaxis due to peach with negative ImmunoCAP result to peach allergens, including rPru p 1, rPru p 3, AND rPru p 4: a report of two cases].

    PubMed

    Maeda, Nobuko; Inomata, Naoko; Morita, Akiko; Kirino, Mio; Moriyama, Tatsuya; Ikezawa, Zenro

    2009-02-01

    We report two cases of anaphylactic reactions to peach with negative result of ImmunoCAP to peach. Case 1 is a 35-year-old man, who felt an itch in his oral cavity immediately after ingesting a whole fresh peach. He rapidly developed generalized urticaria, dyspnea, vomiting, and loss of consciousness. He recovered after treatment at a local hospital, thereafter he was referred to our hospital because ImmunoCAP conducted for screening allergens revealed a negative test result to peach and the cause of anaphylaxis remained unclear. He had a history of pollinosis. He reported that he previously felt an itch on his oral cavity after ingesting melon, watermelon, apple, and strawberry. Serum total IgE was 436 IU/ml. CAP-RAST revealed negative results to peach, strawberry and kiwi. Skin prick tests (SPTs) with raw peach pulp, canned peach pulp, strawberry and kiwi were positive. Case 2 is a 30-year-old woman who felt an itch on her oral cavity accompanied by blepharedema, rhinorrhea, generalized urticaria, nausea, abdominal pain and diarrhea after eating peach. She had a history of pollinosis. She reported that she previously developed urticaria after ingesting an apple. Serum total IgE was 85 IU/ml. ImmunoCAP revealed negative results to peach and apple. SPTs with canned yellow peach, strawberry and apple were positive. Consequently, the two patients were diagnosed with anaphylaxis due to peach, and allergic symptoms have never recurred since they avoided ingesting peach. Furthermore, in two patients ImmunoCAP to rPru p 1, rPru p 3, and rPru p 4 were negative. However, in IgE-immunoblotting of peach, serum IgE antibodies of two patients were bound to approximately 10 kDa proteins. Meanwhile, the cross-reactivity between Rosaceae fruits, such as peach, apple, apricot, and plum, has been reported. These results suggest that in patients, who are suspected of having peach anaphylaxis and show a negative ImmunoCAP result to peach, the additional testing, such as SPT with

  11. Stormwater Attenuation by Green Roofs

    NASA Astrophysics Data System (ADS)

    Sims, A.; O'Carroll, D. M.; Robinson, C. E.; Smart, C. C.

    2014-12-01

    Innovative municipal stormwater management technologies are urgently required in urban centers. Inadequate stormwater management can lead to excessive flooding, channel erosion, decreased stream baseflows, and degraded water quality. A major source of urban stormwater is unused roof space. Green roofs can be used as a stormwater management tool to reduce roof generated stormwater and generally improve the quality of runoff. With recent legislation in some North American cities, including Toronto, requiring the installation of green roofs on large buildings, research on the effectiveness of green roofs for stormwater management is important. This study aims to assess the hydrologic response of an extensive sedum green roof in London, Ontario, with emphasis on the response to large precipitation events that stress municipal stormwater infrastructure. A green roof rapidly reaches field capacity during large storm events and can show significantly different behavior before and after field capacity. At field capacity a green roof has no capillary storage left for retention of stormwater, but may still be an effective tool to attenuate peak runoff rates by transport through the green roof substrate. The attenuation of green roofs after field capacity is linked to gravity storage, where gravity storage is the water that is temporarily stored and can drain freely over time after field capacity has been established. Stormwater attenuation of a modular experimental green roof is determined from water balance calculations at 1-minute intervals. Data is used to evaluate green roof attenuation and the impact of field capacity on peak flow rates and gravity storage. In addition, a numerical model is used to simulate event based stormwater attenuation. This model is based off of the Richards equation and supporting theory of multiphase flow through porous media.

  12. Landing gear noise attenuation

    NASA Technical Reports Server (NTRS)

    Moe, Jeffrey W. (Inventor); Whitmire, Julia (Inventor); Kwan, Hwa-Wan (Inventor); Abeysinghe, Amal (Inventor)

    2011-01-01

    A landing gear noise attenuator mitigates noise generated by airframe deployable landing gear. The noise attenuator can have a first position when the landing gear is in its deployed or down position, and a second position when the landing gear is in its up or stowed position. The noise attenuator may be an inflatable fairing that does not compromise limited space constraints associated with landing gear retraction and stowage. A truck fairing mounted under a truck beam can have a compliant edge to allow for non-destructive impingement of a deflected fire during certain conditions.

  13. RADIO FREQUENCY ATTENUATOR

    DOEpatents

    Giordano, S.

    1963-11-12

    A high peak power level r-f attenuator that is readily and easily insertable along a coaxial cable having an inner conductor and an outer annular conductor without breaking the ends thereof is presented. Spaced first and second flares in the outer conductor face each other with a slidable cylindrical outer conductor portion therebetween. Dielectric means, such as water, contact the cable between the flares to attenuate the radio-frequency energy received thereby. The cylindrical outer conductor portion is slidable to adjust the voltage standing wave ratio to a low level, and one of the flares is slidable to adjust the attenuation level. An integral dielectric container is also provided. (AFC)

  14. Natural attenuation general data guide. Final report

    SciTech Connect

    Kram, M.L.; Goetz, F.

    1999-02-01

    This guide is a decision-making tool to help remedial project managers (RPMs) determine whether natural attenuation can be used as a remedial option at contaminant release sites. Data requirements and methodology to evaluate the potential for using natural attenuation are presented. For sites where the natural attenuation remedial option is implemented, tables of commonly measured parameters, general data collection rationale, and interpretation guidance are included. This format allows the RPM to recognize data gaps, interpret data, construct a conceptual site model, and develop a sampling and analysis plan for evaluation and monitoring purposes.

  15. Wave-induced fluid flow in random porous media: attenuation and dispersion of elastic waves.

    PubMed

    Müller, Tobias M; Gurevich, Boris

    2005-05-01

    A detailed analysis of the relationship between elastic waves in inhomogeneous, porous media and the effect of wave-induced fluid flow is presented. Based on the results of the poroelastic first-order statistical smoothing approximation applied to Biot's equations of poroelasticity, a model for elastic wave attenuation and dispersion due to wave-induced fluid flow in 3-D randomly inhomogeneous poroelastic media is developed. Attenuation and dispersion depend on linear combinations of the spatial correlations of the fluctuating poroelastic parameters. The observed frequency dependence is typical for a relaxation phenomenon. Further, the analytic properties of attenuation and dispersion are analyzed. It is shown that the low-frequency asymptote of the attenuation coefficient of a plane compressional wave is proportional to the square of frequency. At high frequencies the attenuation coefficient becomes proportional to the square root of frequency. A comparison with the 1-D theory shows that attenuation is of the same order but slightly larger in 3-D random media. Several modeling choices of the approach including the effect of cross correlations between fluid and solid phase properties are demonstrated. The potential application of the results to real porous materials is discussed. PMID:15957744

  16. Improving the quantitative accuracy of optical-emission computed tomography by incorporating an attenuation correction: application to HIF1 imaging

    NASA Astrophysics Data System (ADS)

    Kim, E.; Bowsher, J.; Thomas, A. S.; Sakhalkar, H.; Dewhirst, M.; Oldham, M.

    2008-10-01

    Optical computed tomography (optical-CT) and optical-emission computed tomography (optical-ECT) are new techniques for imaging the 3D structure and function (including gene expression) of whole unsectioned tissue samples. This work presents a method of improving the quantitative accuracy of optical-ECT by correcting for the 'self'-attenuation of photons emitted within the sample. The correction is analogous to a method commonly applied in single-photon-emission computed tomography reconstruction. The performance of the correction method was investigated by application to a transparent cylindrical gelatin phantom, containing a known distribution of attenuation (a central ink-doped gelatine core) and a known distribution of fluorescing fibres. Attenuation corrected and uncorrected optical-ECT images were reconstructed on the phantom to enable an evaluation of the effectiveness of the correction. Significant attenuation artefacts were observed in the uncorrected images where the central fibre appeared ~24% less intense due to greater attenuation from the surrounding ink-doped gelatin. This artefact was almost completely removed in the attenuation-corrected image, where the central fibre was within ~4% of the others. The successful phantom test enabled application of attenuation correction to optical-ECT images of an unsectioned human breast xenograft tumour grown subcutaneously on the hind leg of a nude mouse. This tumour cell line had been genetically labelled (pre-implantation) with fluorescent reporter genes such that all viable tumour cells expressed constitutive red fluorescent protein and hypoxia-inducible factor 1 transcription-produced green fluorescent protein. In addition to the fluorescent reporter labelling of gene expression, the tumour microvasculature was labelled by a light-absorbing vasculature contrast agent delivered in vivo by tail-vein injection. Optical-CT transmission images yielded high-resolution 3D images of the absorbing contrast agent, and

  17. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Joel Walls; M.T. Taner; Gary Mavko; Jack Dvorkin

    2002-01-01

    In Section 1 of this first report we will describe the work we are doing to collect and analyze rock physics data for the purpose of modeling seismic attenuation from other measurable quantities such as porosity, water saturation, clay content and net stress. This work and other empirical methods to be presented later, will form the basis for ''Q pseudo-well modeling'' that is a key part of this project. In Section 2 of this report, we will show the fundamentals of a new method to extract Q, dispersion, and attenuation from field seismic data. The method is called Gabor-Morlet time-frequency decomposition. This technique has a number of advantages including greater stability and better time resolution than spectral ratio methods.

  18. Approximate inverse and Sobolev estimates for the attenuated Radon transform

    NASA Astrophysics Data System (ADS)

    Rigaud, G.; Lakhal, A.

    2015-10-01

    The ill-posedness of the attenuated Radon transform is a challenging issue in practice due to the Poisson noise and the high level of attenuation. The investigation of the smoothing properties of the underlying operator is essential for developing a stable inversion. In this paper, we consider the framework of Sobolev spaces and derive analytically a reconstruction algorithm based on the method of the approximate inverse. The derived method inherits the efficiency and stability of the approximate inverse and supplies a method of extraction of contours. These algorithms appear to be efficient for an attenuation of human body type. However, for higher attenuations the ill-posedness increases exponentially what deteriorates accordingly the quality of reconstructions. Nevertheless, a high attenuation map affects less the contour extraction of a high contrast function and so can be neglected. This leads to simplifying the proposed method and circumvents in this case the artifacts due to the attenuation as attested by simulation results.

  19. Examination of the Lateral Attenuation of Aircraft Noise

    NASA Technical Reports Server (NTRS)

    Plotkin, Kenneth J.; Hobbs, Christopher M.; Bradley, Kevin A.; Shepherd, Kevin P. (Technical Monitor)

    2000-01-01

    Measurements of the lateral attenuation of noise from aircraft operations at Denver International Airport were made at distances up to 2000 feet and elevation angles up to 27 degrees. Attenuation Calculated from modem ground impedance theory agrees well with average measured attenuation. The large variability between measured and predicted levels observed at small elevation angles is demonstrated to be due to refraction by wind and temperature gradients.

  20. Cement-based materials' characterization using ultrasonic attenuation

    NASA Astrophysics Data System (ADS)

    Punurai, Wonsiri

    The quantitative nondestructive evaluation (NDE) of cement-based materials is a critical area of research that is leading to advances in the health monitoring and condition assessment of the civil infrastructure. Ultrasonic NDE has been implemented with varying levels of success to characterize cement-based materials with complex microstructure and damage. A major issue with the application of ultrasonic techniques to characterize cement-based materials is their inherent inhomogeneity at multiple length scales. Ultrasonic waves propagating in these materials exhibit a high degree of attenuation losses, making quantitative interpretations difficult. Physically, these attenuation losses are a combination of internal friction in a viscoelastic material (ultrasonic absorption), and the scattering losses due to the material heterogeneity. The objective of this research is to use ultrasonic attenuation to characterize the microstructure of heterogeneous cement-based materials. The study considers a real, but simplified cement-based material, cement paste---a common bonding matrix of all cement-based composites. Cement paste consists of Portland cement and water but does not include aggregates. First, this research presents the findings of a theoretical study that uses a set of existing acoustics models to quantify the scattered ultrasonic wavefield from a known distribution of entrained air voids. These attenuation results are then coupled with experimental measurements to develop an inversion procedure that directly predicts the size and volume fraction of entrained air voids in a cement paste specimen. Optical studies verify the accuracy of the proposed inversion scheme. These results demonstrate the effectiveness of using attenuation to measure the average size, volume fraction of entrained air voids and the existence of additional larger entrapped air voids in hardened cement paste. Finally, coherent and diffuse ultrasonic waves are used to develop a direct

  1. Live attenuated vaccines for invasive Salmonella infections.

    PubMed

    Tennant, Sharon M; Levine, Myron M

    2015-06-19

    Salmonella enterica serovar Typhi produces significant morbidity and mortality worldwide despite the fact that there are licensed Salmonella Typhi vaccines available. This is primarily due to the fact that these vaccines are not used in the countries that most need them. There is growing recognition that an effective invasive Salmonella vaccine formulation must also prevent infection due to other Salmonella serovars. We anticipate that a multivalent vaccine that targets the following serovars will be needed to control invasive Salmonella infections worldwide: Salmonella Typhi, Salmonella Paratyphi A, Salmonella Paratyphi B (currently uncommon but may become dominant again), Salmonella Typhimurium, Salmonella Enteritidis and Salmonella Choleraesuis (as well as other Group C Salmonella). Live attenuated vaccines are an attractive vaccine formulation for use in developing as well as developed countries. Here, we describe the methods of attenuation that have been used to date to create live attenuated Salmonella vaccines and provide an update on the progress that has been made on these vaccines. PMID:25902362

  2. Attenuation of serum inducibility of immediate early genes by oncoproteins in tyrosine kinase signaling pathways.

    PubMed Central

    Yu, C L; Prochownik, E V; Imperiale, M J; Jove, R

    1993-01-01

    Immediate early genes involved in controlling cell proliferation are rapidly and transiently induced following stimulation of susceptible cells with serum. To study how oncoproteins regulate immediate early genes, we examined serum inducibility of these genes in cells transformed by various oncoproteins. We found that induction of the immediate early gene, c-fos, by serum stimulation was markedly attenuated in four independent cell lines stably transformed by the v-Src tyrosine kinase. Cells chronically transformed by other oncoproteins implicated in tyrosine kinase signaling pathways, including v-Sis, v-Ras, and v-Raf, showed the same pattern of attenuation. In contrast, serum inducibility of c-fos was not attenuated in cells transformed by simian virus 40, which is thought to transform cells through a different pathway. Cell cycle analyses showed that proliferation of these transformed cell lines could be arrested effectively in 0.1% serum, demonstrating that the attenuation was not simply due to continuous cycling of transformed cells after serum deprivation. Moreover, serum inducibility of other immediate early genes, including c-jun, junB, egr-1, and NGFI-B, also was strikingly attenuated by these same oncoproteins. Nuclear run-on transcription assays established that this attenuation of serum inducibility occurred at the transcriptional level. Finally, flow cytometric analysis demonstrated that serum-starved v-Src-transformed cells were viable and able to progress into S phase of the cell cycle after serum stimulation, even though the induction of immediate early genes was greatly attenuated in these cells. Our results suggest that activation of immediate early genes is repressed by chronic stimulation of tyrosine kinase signaling pathways in transformed cells. Images PMID:8384301

  3. Seismic attenuation in Florida

    SciTech Connect

    Bellini, J.J.; Bartolini, T.J.; Lord, K.M.; Smith, D.L. . Dept. of Geology)

    1993-03-01

    Seismic signals recorded by the expanded distribution of earthquake seismograph stations throughout Florida and data from a comprehensive review of record archives from stations GAI contribute to an initial seismic attenuation model for the Florida Plateau. Based on calculations of surface particle velocity, a pattern of attenuation exists that appears to deviate from that established for the remainder of the southeastern US. Most values suggest greater seismic attenuation within the Florida Plateau. However, a separate pattern may exist for those signals arising from the Gulf of Mexico. These results have important implications for seismic hazard assessments in Florida and may be indicative of the unique lithospheric identity of the Florida basement as an exotic terrane.

  4. Postage Due?

    ERIC Educational Resources Information Center

    McNamee, Mike

    1990-01-01

    The Postal Service is auditing and trying to collect back postage from nonprofit organizations, including alumni associations. Although the post office initially accepted the materials in question for mailing, it now says alumni associations illegally loaned their permits to commercial firms such as travel agencies. (MSE)

  5. Fuselage panel noise attenuation by piezoelectric switching control

    NASA Astrophysics Data System (ADS)

    Makihara, Kanjuro; Miyakawa, Takeya; Onoda, Junjiro; Minesugi, Kenji

    2010-08-01

    This paper describes a problem that we encountered in our noise attenuation project and our solution for it. We intend to attenuate low-frequency noise that transmits through aircraft fuselage panels. Our method of noise attenuation is implemented with a piezoelectric semi-active system having a selective switch instead of an active energy-supply system. The semi-active controller is based on the predicted sound pressure distribution obtained from acoustic emission analysis. Experiments and numerical simulations demonstrate that the semi-active method attenuates acoustic levels of not only the simple monochromatic noise but also of broadband noise. We reveal that tuning the electrical parameters in the circuit is the key to effective noise attenuation, to overcome the acoustic excitation problem due to sharp switching actions, as well as to control chattering problems. The results obtained from this investigation provide meaningful insights into designing noise attenuation systems for comfortable aircraft cabin environments.

  6. A depolarization and attenuation experiment using the COMSTAR and CTS satellites

    NASA Technical Reports Server (NTRS)

    Bostian, C. W.; Manus, E. A.; Marshall, R. E.; Overstreet, W. P.; Persinger, R. R.; Powell, J. D.; Santago, P.; Stutzman, W. L.; Wiley, P. H.

    1978-01-01

    Monthly statistical data are presented on ground rainfall rate and attenuation of satellite downlinks at 11.7 GHz, 19.04 GHz, and 28.56 GHz and on cross-polarization isolation at 11.7 GHz. Regression equations for relating isolation to attenuation, attenuation to rain rate, and attenuation at one frequency to attenuation at another frequency are also included. Longer-term statistics are also presented and discussed.

  7. Tritium Attenuation by Distillation

    SciTech Connect

    Wittman, N.E.

    2001-07-31

    The objective of this study was to determine how a 100 Area distillation system could be used to reduce to a satisfactory low value the tritium content of the dilute moderator produced in the 100 Area stills, and whether such a tritium attenuator would have sufficient capacity to process all this material before it is sent to the 400 Area for reprocessing.

  8. Yellowstone Attenuation Tomography from Ambient Seismic Noise

    NASA Astrophysics Data System (ADS)

    Doungkaew, N.; Seats, K.; Lawrence, J. F.

    2013-12-01

    The goal of this study is to create a tomographic attenuation image for the Yellowstone region by analyzing ambient seismic noise. An attenuation image generated from ambient noise should provide more information about the structure and properties beneath Yellowstone, especially the caldera, which is known to be active. I applied the method of Lawrence & Prieto [2011] to examine lateral variations in the attenuation structure of Yellowstone. Ambient noise data were collected from broadband seismic stations located around Yellowstone National Park from 1999-2013. Noise correlation functions derived from cross correlations of the ambient noise at two stations were used to calculate a distance dependent decay (an attenuation coefficient) at each period and distance. An inversion was then performed to isolate and localize the spatial attenuation coefficients within the study area. I observe high amplitude decay of the ambient noise at the Yellowstone caldera, most likely due to elevated temperature and crustal melts caused by volcanism, geothermal heat flow, and hydrothermal activity such as geysers.

  9. Is there seismic attenuation in the mantle?

    NASA Astrophysics Data System (ADS)

    Ricard, Y.; Durand, S.; Montagner, J.-P.; Chambat, F.

    2014-02-01

    The small scale heterogeneity of the mantle is mostly due to the mixing of petrological heterogeneities by a smooth but chaotic convection and should consist in a laminated structure (marble cake) with a power spectrum S(k) varying as 1/k, where k is the wavenumber of the anomalies. This distribution of heterogeneities during convective stirring with negligible diffusion, called Batchelor regime is documented by fluid dynamic experiments and corresponds to what can be inferred from geochemistry and seismic tomography. This laminated structure imposes density, seismic velocity and potentially, anisotropic heterogeneities with similar 1/k spectra. A seismic wave of wavenumber k0 crossing such a medium is partly reflected by the heterogeneities and we show that the scattered energy is proportional to k0S(2k0). The reduction of energy for the propagating wave appears therefore equivalent to a quality factor 1/Q∝k0S(2k0). With the specific 1/k spectrum of the mantle, the resulting apparent attenuation should therefore be frequency independent. We show that the total contribution of 6-9% RMS density, velocity and anisotropy would explain the observed S and P attenuation of the mantle. Although these values are large, they are not unreasonable and we discuss how they depend on the range of frequencies over which the attenuation is explained. If such a level of heterogeneity were present, most of the attenuation of the Earth would be due to small scale scattering by laminations, not by intrinsic dissipation. Intrinsic dissipation must certainly exist but might correspond to a larger, yet unobserved Q. This provocative result would explain the very weak frequency dependence of the attenuation, and the fact that bulk attenuation seems negligible, two observations that have been difficult to explain for 50 years.

  10. Arsenic Cycling in Hydrocarbon Plumes: Secondary Effects of Natural Attenuation.

    PubMed

    Cozzarelli, Isabelle M; Schreiber, Madeline E; Erickson, Melinda L; Ziegler, Brady A

    2016-01-01

    Monitored natural attenuation is widely applied as a remediation strategy at hydrocarbon spill sites. Natural attenuation relies on biodegradation of hydrocarbons coupled with reduction of electron acceptors, including solid phase ferric iron (Fe(III)). Because arsenic (As) adsorbs to Fe-hydroxides, a potential secondary effect of natural attenuation of hydrocarbons coupled with Fe(III) reduction is a release of naturally occurring As to groundwater. At a crude-oil-contaminated aquifer near Bemidji, Minnesota, anaerobic biodegradation of hydrocarbons coupled to Fe(III) reduction has been well documented. We collected groundwater samples at the site annually from 2009 to 2013 to examine if As is released to groundwater and, if so, to document relationships between As and Fe inside and outside of the dissolved hydrocarbon plume. Arsenic concentrations in groundwater in the plume reached 230 µg/L, whereas groundwater outside the plume contained less than 5 µg/L As. Combined with previous data from the Bemidji site, our results suggest that (1) naturally occurring As is associated with Fe-hydroxides present in the glacially derived aquifer sediments; (2) introduction of hydrocarbons results in reduction of Fe-hydroxides, releasing As and Fe to groundwater; (3) at the leading edge of the plume, As and Fe are removed from groundwater and retained on sediments; and (4) downgradient from the plume, patterns of As and Fe in groundwater are similar to background. We develop a conceptual model of secondary As release due to natural attenuation of hydrocarbons that can be applied to other sites where an influx of biodegradable organic carbon promotes Fe(III) reduction. PMID:25612004

  11. Arsenic cycling in hydrocarbon plumes: secondary effects of natural attenuation

    USGS Publications Warehouse

    Cozzarelli, Isabelle M.; Schreiber, Madeline E.; Erickson, Melinda L.; Ziegler, Brady A.

    2016-01-01

    Monitored natural attenuation is widely applied as a remediation strategy at hydrocarbon spill sites. Natural attenuation relies on biodegradation of hydrocarbons coupled with reduction of electron acceptors, including solid phase ferric iron (Fe(III)). Because arsenic (As) adsorbs to Fe-hydroxides, a potential secondary effect of natural attenuation of hydrocarbons coupled with Fe(III) reduction is a release of naturally occurring As to groundwater. At a crude-oil-contaminated aquifer near Bemidji, Minnesota, anaerobic biodegradation of hydrocarbons coupled to Fe(III) reduction has been well documented. We collected groundwater samples at the site annually from 2009 to 2013 to examine if As is released to groundwater and, if so, to document relationships between As and Fe inside and outside of the dissolved hydrocarbon plume. Arsenic concentrations in groundwater in the plume reached 230 µg/L, whereas groundwater outside the plume contained less than 5 µg/L As. Combined with previous data from the Bemidji site, our results suggest that (1) naturally occurring As is associated with Fe-hydroxides present in the glacially derived aquifer sediments; (2) introduction of hydrocarbons results in reduction of Fe-hydroxides, releasing As and Fe to groundwater; (3) at the leading edge of the plume, As and Fe are removed from groundwater and retained on sediments; and (4) downgradient from the plume, patterns of As and Fe in groundwater are similar to background. We develop a conceptual model of secondary As release due to natural attenuation of hydrocarbons that can be applied to other sites where an influx of biodegradable organic carbon promotes Fe(III) reduction.

  12. A compact rotary vane attenuator

    NASA Technical Reports Server (NTRS)

    Nixon, D. L.; Otosh, T. Y.; Stelzried, C. T.

    1969-01-01

    Rotary vane attenuator, when used as a front end attenuator, introduces an insertion loss that is proportional to the angle of rotation. New technique allows the construction of a shortened compact unit suitable for most installations.

  13. Fluid dynamic bowtie attenuators

    NASA Astrophysics Data System (ADS)

    Szczykutowicz, Timothy P.; Hermus, James

    2015-03-01

    Fluence field modulated CT allows for improvements in image quality and dose reduction. To date, only 1-D modulators have been proposed, the extension to 2-D modulation is difficult with solid-metal attenuation-based modulators. This work proposes to use liquids and gas to attenuate the x-ray beam which can be arrayed allowing for 2-D fluence modulation. The thickness of liquid and the pressure for a given path length of gas were determined that provided the same attenuation as 30 cm of soft tissue at 80, 100, 120, and 140 kV. Gaseous Xenon and liquid Iodine, Zinc Chloride, and Cerium Chloride were studied. Additionally, we performed some proof-of-concept experiments in which (1) a single cell of liquid was connected to a reservoir which allowed the liquid thickness to be modulated and (2) a 96 cell array was constructed in which the liquid thickness in each cell was adjusted manually. Liquid thickness varied as a function of kV and chemical composition, with Zinc Chloride allowing for the smallest thickness; 1.8, 2.25, 3, and 3.6 cm compensated for 30 cm of soft tissue at 80, 100, 120, and 140 kV respectively. The 96 cell Iodine attenuator allowed for a reduction in both dynamic range to the detector and scatter to primary ratio. Successful modulation of a single cell was performed at 0, 90, and 130 degrees using a simple piston/actuator. The thickness of liquids and the Xenon gas pressure seem logistically implementable within the constraints of CBCT and diagnostic CT systems.

  14. Flexible graphene based microwave attenuators.

    PubMed

    Byun, Kisik; Ju Park, Yong; Ahn, Jong-Hyun; Min, Byung-Wook

    2015-02-01

    We demonstrate flexible 3 dB and 6 dB microwave attenuators using multilayer graphene grown by the chemical vapor deposition method. On the basis of the characterized results of multilayer graphene and graphene-Au ohmic contacts, the graphene attenuators are designed and measured. The flexible graphene-based attenuators have 3 dB and 6 dB attenuation with a return loss of less than -15 dB at higher than 5 GHz. The devices have shown durability in a bending cycling test of 100 times. The circuit model of the attenuator based on the characterized results matches the experimental results well. PMID:25590144

  15. Control algorithms for dynamic attenuators

    SciTech Connect

    Hsieh, Scott S.; Pelc, Norbert J.

    2014-06-15

    Purpose: The authors describe algorithms to control dynamic attenuators in CT and compare their performance using simulated scans. Dynamic attenuators are prepatient beam shaping filters that modulate the distribution of x-ray fluence incident on the patient on a view-by-view basis. These attenuators can reduce dose while improving key image quality metrics such as peak or mean variance. In each view, the attenuator presents several degrees of freedom which may be individually adjusted. The total number of degrees of freedom across all views is very large, making many optimization techniques impractical. The authors develop a theory for optimally controlling these attenuators. Special attention is paid to a theoretically perfect attenuator which controls the fluence for each ray individually, but the authors also investigate and compare three other, practical attenuator designs which have been previously proposed: the piecewise-linear attenuator, the translating attenuator, and the double wedge attenuator. Methods: The authors pose and solve the optimization problems of minimizing the mean and peak variance subject to a fixed dose limit. For a perfect attenuator and mean variance minimization, this problem can be solved in simple, closed form. For other attenuator designs, the problem can be decomposed into separate problems for each view to greatly reduce the computational complexity. Peak variance minimization can be approximately solved using iterated, weighted mean variance (WMV) minimization. Also, the authors develop heuristics for the perfect and piecewise-linear attenuators which do not requirea priori knowledge of the patient anatomy. The authors compare these control algorithms on different types of dynamic attenuators using simulated raw data from forward projected DICOM files of a thorax and an abdomen. Results: The translating and double wedge attenuators reduce dose by an average of 30% relative to current techniques (bowtie filter with tube current

  16. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Joel Walls; M.T. Taner; Naum Derzhi; Gary Mavko; Jack Dvorkin

    2003-12-01

    We have developed and tested technology for a new type of direct hydrocarbon detection. The method uses inelastic rock properties to greatly enhance the sensitivity of surface seismic methods to the presence of oil and gas saturation. These methods include use of energy absorption, dispersion, and attenuation (Q) along with traditional seismic attributes like velocity, impedance, and AVO. Our approach is to combine three elements: (1) a synthesis of the latest rock physics understanding of how rock inelasticity is related to rock type, pore fluid types, and pore microstructure, (2) synthetic seismic modeling that will help identify the relative contributions of scattering and intrinsic inelasticity to apparent Q attributes, and (3) robust algorithms that extract relative wave attenuation attributes from seismic data. This project provides: (1) Additional petrophysical insight from acquired data; (2) Increased understanding of rock and fluid properties; (3) New techniques to measure reservoir properties that are not currently available; and (4) Provide tools to more accurately describe the reservoir and predict oil location and volumes. These methodologies will improve the industry's ability to predict and quantify oil and gas saturation distribution, and to apply this information through geologic models to enhance reservoir simulation. We have applied for two separate patents relating to work that was completed as part of this project.

  17. Ultrasonic attenuation in pearlitic steel.

    PubMed

    Du, Hualong; Turner, Joseph A

    2014-03-01

    Expressions for the attenuation coefficients of longitudinal and transverse ultrasonic waves are developed for steel with pearlitic microstructure. This type of lamellar duplex microstructure influences attenuation because of the lamellar spacing. In addition, longitudinal attenuation measurements were conducted using an unfocused transducer with 10 MHz central frequency on the cross section of a quenched railroad wheel sample. The dependence of longitudinal attenuation on the pearlite microstructure is observed from the changes of longitudinal attenuation from the quenched tread surface to deeper locations. The results show that the attenuation value is lowest and relatively constant within the quench depth, then increases linearly. The experimental results demonstrate a reasonable agreement with results from the theoretical model. Ultrasonic attenuation provides an important non-destructive method to evaluate duplex microstructure within grains which can be implemented for quality control in conjunction with other manufacturing processes. PMID:24268679

  18. Enabling photon counting detectors with dynamic attenuators

    NASA Astrophysics Data System (ADS)

    Hsieh, Scott S.; Pelc, Norbert J.

    2014-03-01

    Photon-counting x-ray detectors (PCXDs) are being investigated as a replacement for conventional x-ray detectors because they promise several advantages, including better dose efficiency, higher resolution and spectral imaging. However, many of these advantages disappear when the x-ray flux incident on the detector is too high. We recently proposed a dynamic, piecewise-linear attenuator (or beam shaping filter) that can control the flux incident on the detector. This can restrict the operating range of the PCXD to keep the incident count rate below a given limit. We simulated a system with the piecewise-linear attenuator and a PCXD using raw data generated from forward projected DICOM files. We investigated the classic paralyzable and nonparalyzable PCXD as well as a weighted average of the two, with the weights chosen to mimic an existing PCXD (Taguchi et al, Med Phys 2011). The dynamic attenuator has small synergistic benefits with the nonparalyzable detector and large synergistic benefits with the paralyzable detector. Real PCXDs operate somewhere between these models, and the weighted average model still shows large benefits from the dynamic attenuator. We conclude that dynamic attenuators can reduce the count rate performance necessary for adopting PCXDs.

  19. Traffic Noise Ground Attenuation Algorithm Evaluation

    NASA Astrophysics Data System (ADS)

    Herman, Lloyd Allen

    The Federal Highway Administration traffic noise prediction program, STAMINA 2.0, was evaluated for its accuracy. In addition, the ground attenuation algorithm used in the Ontario ORNAMENT method was evaluated to determine its potential to improve these predictions. Field measurements of sound levels were made at 41 sites on I-440 in Nashville, Tennessee in order to both study noise barrier effectiveness and to evaluate STAMINA 2.0 and the performance of the ORNAMENT ground attenuation algorithm. The measurement sites, which contain large variations in terrain, included several cross sections. Further, all sites contain some type of barrier, natural or constructed, which could more fully expose the strength and weaknesses of the ground attenuation algorithms. The noise barrier evaluation was accomplished in accordance with American National Standard Methods for Determination of Insertion Loss of Outdoor Noise Barriers which resulted in an evaluation of this standard. The entire 7.2 mile length of I-440 was modeled using STAMINA 2.0. A multiple run procedure was developed to emulate the results that would be obtained if the ORNAMENT algorithm was incorporated into STAMINA 2.0. Finally, the predicted noise levels based on STAMINA 2.0 and STAMINA with the ORNAMENT ground attenuation algorithm were compared with each other and with the field measurements. It was found that STAMINA 2.0 overpredicted noise levels by an average of over 2 dB for the receivers on I-440, whereas, the STAMINA with ORNAMENT ground attenuation algorithm overpredicted noise levels by an average of less than 0.5 dB. The mean errors for the two predictions were found to be statistically different from each other, and the mean error for the prediction with the ORNAMENT ground attenuation algorithm was not found to be statistically different from zero. The STAMINA 2.0 program predicts little, if any, ground attenuation for receivers at typical first-row distances from highways where noise barriers

  20. Natural attenuation of pharmaceuticals and alkylphenol polyethoxylate metabolites during river transport: photochemical and biological transformation.

    PubMed

    Lin, Angela Yu-Chen; Plumlee, Megan H; Reinhard, Martin

    2006-06-01

    The capacity of rivers to naturally attenuate trace organic compounds is an important but poorly understood process because the many factors that control attenuation are interrelated and difficult to study in isolation. To better understand the relative importance of chemical (photolysis and sorption) and biological attenuation processes, contaminant removal along a 12-km stretch of the Santa Ana River (SAR) was determined as a function of travel time, distance, and irradiance. Target contaminants included three pharmaceuticals (gemfibrozil, ibuprofen, and naproxen) and their metabolites, and the metabolites of alkylphenol polyethoxylates (APEMs). The APEMs included alkylphenols (APs), short-chain alkylphenol polyethoxylates (APEOs), alkylphenol polyethoxycarboxylates (APECs), and carboxyalkylphenol polyethoxycarboxylates (CAPECs). Overall removals ranged from 50% for APs to 100% for naproxen and increased with distance and time, in many cases following first-order kinetics. For naproxen, which is photolabile, average removals were 20 to 30% more during the day than at night; the nighttime and daytime half-lives were 3 h and 1.7 to 1.9 h, respectively. Comparison of field and laboratory data suggests that approximately 40% of the daytime naproxen removal can be attributed to photolysis with the remainder due to other processes, most likely sorption. For ibuprofen and gemfibrozil, half-lives were 5.4 and 2.7 h, respectively, and laboratory data suggest that biotransformation is the principal attenuating process. The APEM attenuation might be due to sorption and biotransformation; phototransformation may also play a minor role. These data demonstrate that travel times on the order of hours can significantly mitigate the impact of effluent discharge on the water quality of shallow rivers. PMID:16764462

  1. Radiation Imaging and Attenuation

    NASA Astrophysics Data System (ADS)

    Davison, Candace; Yocum, Douglas

    2008-03-01

    X-ray and neutron images are used to demonstrate materials' different radiation attenuation properties. This leads to discussion of applications in medicine, industry and research. The Penn State Radiation Science and Engineering Center (RSEC) uses neutron radioscopy to image the inside of a working hydrogen fuel cell. This is one of the many educational activities that are conducted when students visit the RSEC. To encourage pre-college students to apply these principles and learn more about nuclear technology, we are sponsoring a design competition. For more information visit www.rsec.psu.edu

  2. Dose reduction technique using a combination of a region of interest (ROI) material x-ray attenuator and spatially different temporal filtering for fluoroscopic interventions

    NASA Astrophysics Data System (ADS)

    Swetadri Vasan, S. N.; Panse, A.; Jain, A.; Sharma, P.; Ionita, Ciprian N.; Titus, A. H.; Cartwright, A. N.; Bednarek, D. R.; Rudin, S.

    2012-03-01

    We demonstrate a novel approach for achieving patient dose savings during image-guided neurovascular interventions, involving a combination of a material x-ray region of interest (ROI) attenuator and a spatially different ROI temporal filtering technique. The part of the image under the attenuator is reduced in dose but noisy and less bright due to fewer x-ray quanta reaching the detector, as compared to the non-attenuating (or less attenuating) region. First the brightness is equalized throughout the image by post processing and then a temporal filter with higher weights is applied to the high attenuating region to reduce the noise, at the cost of increased lag; however, in the regions where less attenuation is present, a lower temporal weight is needed and is applied to preserve temporal resolution. A simulation of the technique is first presented on an actual image sequence obtained from an endovascular image guided interventional (EIGI) procedure. Then the actual implementation of the technique with a physical ROI attenuator is presented. Quantitative analysis including noise analysis and integral dose calculations are presented to validate the proposed technique.

  3. Dose Reduction Technique Using a Combination of a Region of Interest (ROI) Material X-Ray Attenuator and Spatially Different Temporal Filtering for Fluoroscopic Interventions

    PubMed Central

    Vasan, S.N Swetadri; Panse, A.; Jain, A.; Sharma, P.; Ionita, Ciprian N.; Titus, A.H.; Cartwright, A.N.; Bednarek, D.R; Rudin, S.

    2012-01-01

    We demonstrate a novel approach for achieving patient dose savings during image-guided neurovascular interventions, involving a combination of a material x-ray region of interest (ROI) attenuator and a spatially different ROI temporal filtering technique. The part of the image under the attenuator is reduced in dose but noisy and less bright due to fewer x-ray quanta reaching the detector, as compared to the non-attenuating (or less attenuating) region. First the brightness is equalized throughout the image by post processing and then a temporal filter with higher weights is applied to the high attenuating region to reduce the noise, at the cost of increased lag; however, in the regions where less attenuation is present, a lower temporal weight is needed and is applied to preserve temporal resolution. A simulation of the technique is first presented on an actual image sequence obtained from an endovascular image guided interventional (EIGI) procedure. Then the actual implementation of the technique with a physical ROI attenuator is presented. Quantitative analysis including noise analysis and integral dose calculations are presented to validate the proposed technique. PMID:24027617

  4. Attenuation of sound waves in drill strings

    SciTech Connect

    Drumheller, D.S. )

    1993-10-01

    During drilling of deep wells, digital data are often transmitted from sensors located near the drill bit to the surface. Development of a new communication system with increased data capacity is of paramount importance to the drilling industry. Since steel drill strings are used, transmission of these data by elastic carrier waves traveling within the drill pipe is possible, but the potential communication range is uncertain. The problem is complicated by the presence of heavy-threaded tool joints every 10 m, which form a periodic structure and produce classical patterns of passbands and stop bands in the wave spectra. In this article, field measurements of the attenuation characteristics of a drill string in the Long Valley Scientific Well in Mammoth Lakes, California are presented. Wave propagation distances approach 2 km. A theoretical model is discussed which predicts the location, width, and attenuation of the passbands. Mode conversion between extensional and bending waves, and spurious reflections due to deviations in the periodic spacings of the tool joints are believed to be the sources of this attenuation. It is estimated that attenuation levels can be dramatically reduced by rearranging the individual pipes in the drill string according to length. 7 refs., 20 figs., 4 tabs.

  5. Flux attenuation at NREL's High-Flux Solar Furnace

    NASA Astrophysics Data System (ADS)

    Bingham, Carl E.; Scholl, Kent L.; Lewandowski, Allan A.

    1994-10-01

    The High-Flux Solar Furnace (HFSF) at the National Renewable Energy Laboratory (NREL) has a faceted primary concentrator and a long focal-length-to-diameter ratio (due to its off-axis design). Each primary facet can be aimed individually to produce different flux distributions at the target plane. Two different types of attenuators are used depending on the flux distribution. A sliding-plate attenuator is used primarily when the facets are aimed at the same target point. The alternate attenuator resembles a venetian blind. Both attenuators are located between the concentrator and the focal point. The venetian-blind attenuator is primarily used to control the levels of sunlight failing on a target when the primary concentrators are not focused to a single point. This paper will demonstrate the problem of using the sliding-plate attenuator with a faceted concentrator when the facets are not aimed at the same target point. We will show that although the alternate attenuator necessarily blocks a certain amount of incoming sunlight, even when fully open, it provides a more even attenuation of the flux for alternate aiming strategies.

  6. Seismic attenuation in fractured porous media: insights from a hybrid numerical and analytical model

    NASA Astrophysics Data System (ADS)

    Ekanem, A. M.; Li, X. Y.; Chapman, M.; Main, I. G.

    2015-04-01

    Seismic attenuation in fluid-saturated porous rocks can occur by geometric spreading, wave scattering or the internal dissipation of energy, most likely due to the squirt-flow mechanism. In principle, the pattern of seismic attenuation recorded on an array of sensors contains information about the medium, in terms of material heterogeneity and anisotropy, as well as material properties such as porosity, crack density, and pore-fluid composition and mobility. In practice, this inverse problem is challenging. Here we provide some insights into the effects of internal dissipation by analysing synthetic data produced by a hybrid numerical and analytical model for seismic wave propagation in a fractured medium embedded within a layered geological structure. The model is made up of one anisotropic and three isotropic horizontal layers. The anisotropic layer consists of a porous, fluid-saturated material containing vertically aligned inclusions representing a set of fractures. This combination allows squirt-flow to occur between the pores in the matrix and the model fractures. Our results show that the fluid mobility and the associated relaxation time of the fluid-pressure gradient control the frequency range over which attenuation occurs. This induced attenuation increases with incidence angle and azimuth away from the fracture strike-direction. Azimuthal variations in the induced attenuation are elliptical allowing the fracture orientations to be obtained from the axes of the ellipse. These observations hold out the potential of using seismic attenuation as an additional diagnostic in the characterisation of rock formations for a variety of applications including hydrocarbon exploration and production, subsurface storage of CO2, and geothermal energy extraction.

  7. 34 CFR 303.15 - Include; including.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 34 Education 2 2010-07-01 2010-07-01 false Include; including. 303.15 Section 303.15 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF SPECIAL EDUCATION AND REHABILITATIVE SERVICES, DEPARTMENT OF EDUCATION EARLY INTERVENTION PROGRAM FOR INFANTS AND TODDLERS...

  8. The velocity and attenuation anisotropy of shale at ultrasonic frequency

    NASA Astrophysics Data System (ADS)

    Deng, Jixin; Wang, Shangxu; Han, De-hua

    2009-09-01

    The velocity and attenuation anisotropy of dry and oil-saturated shale were measured at laboratory ultrasonic frequency by using the transmission technique. Our purpose is to find the variation rules of wave velocity and attenuation in different directions as a function of effective pressure in dry and oil-saturated situations, and those intrinsic factors that result in such anisotropy. Using x-ray diffraction techniques and a scanning electron microscope, the causative factors for the velocity anisotropy are found to be mainly due to the alignment of clay mineral and microcracks. The attenuation of P- and S-waves also shows apparent directional dependence, but different from that of velocities. Attenuation anisotropy can be interpreted in terms of grain and pore geometry. For dry shale samples, the dominant attenuation mechanism is phase hysteresis due to static friction. On one hand, the Biot flow plays a key role in causing wave attenuation for the P-wave propagating parallel to bedding for fluid-saturated samples. On the other hand, the fluid-related attenuation is mainly attributed to the mechanisms of squirt flow for the P-wave propagating vertical to bedding.

  9. Chopping-Wheel Optical Attenuator

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    1988-01-01

    Star-shaped rotating chopping wheel provides adjustable time-averaged attenuation of narrow beam of light without changing length of optical path or spectral distribution of light. Duty cycle or attenuation factor of chopped beam controlled by adjusting radius at which beam intersects wheel. Attenuation factor independent of wavelength. Useful in systems in which chopping frequency above frequency-response limits of photodetectors receiving chopped light. Used in systems using synchronous detection with lock-in amplifiers.

  10. Ultrasonic Attenuation in Zircaloy-4

    SciTech Connect

    Gomez, M.P.; Banchik, A.D.; Lopez Pumarega, M.I.; Ruzzante, J.E.

    2005-04-09

    In this work the relationship between Zircaloy-4 grain size and ultrasonic attenuation behavior was studied for longitudinal waves in the frequency range of 10-90 MHz. The attenuation was analyzed as a function of frequency for samples with different mechanical and heat treatments having recrystallized and Widmanstatten structures with different grain size. The attenuation behavior was analyzed by different scattering models, depending on grain size, wavelength and frequency.

  11. LINE-ABOVE-GROUND ATTENUATOR

    DOEpatents

    Wilds, R.B.; Ames, J.R.

    1957-09-24

    The line-above-ground attenuator provides a continuously variable microwave attenuator for a coaxial line that is capable of high attenuation and low insertion loss. The device consists of a short section of the line-above- ground plane type transmission lime, a pair of identical rectangular slabs of lossy material like polytron, whose longitudinal axes are parallel to and indentically spaced away from either side of the line, and a geared mechanism to adjust amd maintain this spaced relationship. This device permits optimum fineness and accuracy of attenuator control which heretofore has been difficult to achieve.

  12. Extraordinary views of ordinary galaxies: Multiwavelength measures of star formation and attenuation

    NASA Astrophysics Data System (ADS)

    Johnson, Benjamin D.

    2008-01-01

    The meaningful comparison of models of galaxy evolution to observations is critically dependent on the accurate treatment of dust attenuation. To investigate dust absorption and emission in galaxies we have assembled a sample of ~1000 galaxies from the ultrviolet (UV) through the Infrared (IR) by the GALEX, SDSS, and Spitzer observatories. The ratio of IR to UV emission (IRX) is used to constrain the dust attenuation in galaxies. We consider this measure in optically red galaxies making several simplfying assumptions we estimate the fraction of IR emission due to the heating of by old stars to be as much as 99%. We use the 4000Å break as a robust and useful, though coarse, indicator of star formation history (SFH). Dust attenuation and star formation history (SFH) are the dominant factors affecting the color of galaxies. We explore the empirical relation between SFH, attenuation, and color (especially the UV color) for a wide range of galaxies, including early types. This relation is compared to models that separately predict the effects of dust and SFH on color. We perform fits to the relation between SFH, attenuation, and color, which links the production of starlight and its absorption by dust to the subsequent reemmision of the absorbed light in the IR. Galaxy models that self-consistently treat dust absorption and emission as well as stellar populations will need to reproduce these fitted relations in the low-redshift universe. We construct estimates of dust attenuation and star formation rate (SFR) from the UV and IR photmetry and compare them to optical indicators, including the SFR b of Brinchmann et al. (2004). We find that there is a significant trend of the ratio of SFR b to the IR+UV luminosity with D n (4000) that cannot be explained as due to the additional IR emission from dust heatred by old stars. We find that the dust attenuation inferred from the ratio of optical emission lines is ~ 2-3 times higher than that inferred from IRX for a wide range

  13. P- and S-wave seismic attenuation for deep natural gas exploration and development

    SciTech Connect

    Walls, Joel; Uden, Richard; Singleton, Scott; Shu, Rone; Mavko, Gary

    2005-04-12

    Using current methods, oil and gas in the subsurface cannot be reliably predicted from seismic data. This causes domestic oil and gas fields to go undiscovered and unexploited, thereby increasing the need to import energy.The general objective of this study was to demonstrate a simple and effective methodology for estimating reservoir properties (gas saturation in particular, but also including lithology, net to gross ratios, and porosity) from seismic attenuation and other attributes using P- and S-waves. Phase I specific technical objectives: Develop Empirical or Theoretical Rock Physics Relations for Qp and Qs; Create P-wave and S-wave Synthetic Seismic Modeling Algorithms with Q; and, Compute P-wave and S-wave Q Attributes from Multi-component Seismic Data. All objectives defined in the Phase I proposal were accomplished. During the course of this project, a new class of seismic analysis was developed based on compressional and shear wave inelastic rock properties (attenuation). This method provides a better link between seismic data and the presence of hydrocarbons. The technique employs both P and S-wave data to better discriminate between attenuation due to hydrocarbons versus energy loss due to other factors such as scattering and geometric spreading. It was demonstrated that P and S attenuation can be computed from well log data and used to generate synthetic seismograms. Rock physics models for P and S attenuation were tested on a well from the Gulf of Mexico. The P- and S-wave Q attributes were computed on multi-component 2D seismic data intersecting this well. These methods generated reasonable results, and most importantly, the Q attributes indicated gas saturation.

  14. An attenuated philosophical gentleman.

    PubMed

    Christie, John R R

    2014-06-20

    Dr. Joseph Black had at one time, a house near us to the west. He was a striking and beautiful person; tall, very thin, and cadaverously pale; his hair carefully powdered, though there was little of it except what was collected in a long thin queue; his eyes dark, clear and large, like deep pools of pure water. He wore black speckless clothes, silk stockings, silver buckles, and either a slim green umbrella, or a genteel brown cane. The general frame and air were feeble and slender. The wildest boy respected Black. No lad could be irreverent toward a man so pale, so gentle, so elegant and so illustrious. So he glided, like a spirit, through our rather mischievous sportiveness, unharmed. He died seated, with a bowl of milk upon his knee, of which his ceasing to be did not spill a drop; a departure which it seemed, after the event, might have been foretold of this attenuated philosophical gentleman. PMID:24921110

  15. Transport and reaction processes affecting the attenuation of landfill gas in cover soils.

    PubMed

    Molins, S; Mayer, K U; Scheutz, C; Kjeldsen, P

    2008-01-01

    Methane and trace organic gases produced in landfill waste are partly oxidized in the top 40 cm of landfill cover soils under aerobic conditions. The balance between the oxidation of landfill gases and the ingress of atmospheric oxygen into the soil cover determines the attenuation of emissions of methane, chlorofluorocarbons, and hydrochlorofluorocarbons to the atmosphere. This study was conducted to investigate the effect of oxidation reactions on the overall gas transport regime and to evaluate the contributions of various gas transport processes on methane attenuation in landfill cover soils. For this purpose, a reactive transport model that includes advection and the Dusty Gas Model for simulation of multicomponent gas diffusion was used. The simulations are constrained by data from a series of counter-gradient laboratory experiments. Diffusion typically accounts for over 99% of methane emission to the atmosphere. Oxygen supply into the soil column is driven exclusively by diffusion, whereas advection outward offsets part of the diffusive contribution. In the reaction zone, methane consumption reduces the pressure gradient, further decreasing the significance of advection near the top of the column. Simulations suggest that production of water or accumulation of exopolymeric substances due to microbially mediated methane oxidation can significantly reduce diffusive fluxes. Assuming a constant rate of methane production within a landfill, reduction of the diffusive transport properties, primarily due to exopolymeric substance production, may result in reduced methane attenuation due to limited O(2) -ingress. PMID:18268309

  16. Peritoneal fluid causing inferior attenuation on SPECT thallium-201 myocardial imaging in women

    SciTech Connect

    Rab, S.T.; Alazraki, N.P.; Guertler-Krawczynska, E.

    1988-11-01

    On SPECT thallium images, myocardial left ventricular (LV) anterior wall attenuation due to breast tissue is common in women. In contrast, in men, inferior wall counts are normally decreased compared to anterior counts. The purpose of this report is to describe cases of inferior wall attenuation of counts in women caused by peritoneal fluid, not myocardial disease. Twelve consecutive SPECT thallium myocardial studies performed in women on peritoneal dialysis, being evaluated for kidney transplant, were included in this study. For all studies, 3.5 mCi 201Tl were injected intravenously. Thirty-two images were acquired over 180 degrees (45 degrees RAO progressing to 45 degrees LPO) at 40 sec per stop. SPECT images were reviewed in short axis, horizontal long and vertical long axes. Data were also displayed in bullseye format with quantitative comparison to gender-matched normal files. Ten of 12 female patients studied had inferior wall defects on images, confirmed by bullseye display. All patients had approximately 2 liters of peritoneal fluid. Review of planar rotational views showed diaphragm elevation and fluid margin attenuations affecting left ventricular inferior wall. Thus, peritoneal fluid is a cause of inferior attenuation on 201Tl cardiac imaging.

  17. Semi-empirical inversion technique for retrieval of quantitative attenuation profiles with underwater scanning lidar systems

    NASA Astrophysics Data System (ADS)

    Vuorenkoski, Anni K.; Dalgleish, Fraser R.; Twardowski, Michael S.; Ouyang, Bing; Trees, Charles C.

    2015-05-01

    A fine structure underwater imaging LiDAR (FSUIL) has recently been developed and initial field trials have been conducted. The instrument, which rapidly scans an array of closely spaced, narrow, collimated laser pulses into the water column produces two-dimensional arrays of backscatter profiles, with fine spatial and temporal resolution. In this paper a novel method to derive attenuation profiles is introduced. This approach is particularly attractive in applications where primary on-board processing is required, and other applications where conventional model-based approaches are not feasible due to a limited computational capacity or lack of a priori knowledge of model input parameters. The paper also includes design details regarding the new FSUIL instrument are given, with field results taken in clear to moderately turbid water being presented to illustrate the various effects and considerations in the analysis of the system data. LiDAR waveforms and LiDAR derived attenuation coefficients are analyzed and compared to calibrated beam attenuation, particulate scattering and absorption coefficients. The system was field tested during the NATO Ligurian Sea LIDAR & Optical Measurements Experiment (LLOMEx) cruise in March 2013, during the spring bloom conditions. Throughout a wide range of environmental conditions, the FSUIL was deployed on an in situ profiler obtaining thousands of three-dimensional LiDAR scans from the near surface down to the lower thermocline. Deployed concurrent to the FSUIL was a range of commercially available off-the-shelf instruments providing side-by-side in-situ attenuation measurement.

  18. Sn Attenuation in the Middle-East

    NASA Astrophysics Data System (ADS)

    Ku, W.; Kaviani, A.; Bao, X.; Sandvol, E. A.

    2015-12-01

    The Turkish-Iranian Plateau and Zagros Mountains, a dominant tectonic feature in the Middle-East, were formed as a result of the continental collision (between Arabian plate and Eurasia plates). In order to better understand the nature of the lithosphere mantle and origin of the measure seismic velocity anomalies we have made detailed measurements of the uppermost mantle attenuation using the high frequency regional phase Sn. In order to measure Sn attenuation. We have collected a large data set consisting of 18 years (1995-2012) of waveforms recorded by 305 permanent and temporary stations. We used a bandpass filter (0.1-0.5Hz) to identify efficient longer period Sn phases. In order to determine Sn Q we applied a Two Station Method (TSM) and Reverse Two Station Method (RTM) to eliminate the source effects. We have used the LSQR algorithm to tomographically map Sn attenuation tomography across the Middle-East. We also determined the Sn propagation efficiencies visually and tomographically map qualitatively assigned Sn propagation efficiencies across the Middle-East. The Sn Attenuation Tomography show moderately low Q values beneath the Turkish-Iranian Plateau (~250) and high Q values beneath the south Caspian sea (~400) and Arabian shield (~400). We also observe high Q values beneath the Zagros mountains (~450) that is consistent with the Arabian plate underthrusting beneath the Eurasia plate. The Sn Efficiency Tomography shows high attenuation within the Turkish-Iranian Plateau and low attenuation in the Arabian Plate and across the Caspian Sea. This is consistent with prior studies that suggest a hot and thin lithosphere beneath the Turkish-Iranian Plateau and it also suggests that intrinsic attenuation is the dominant component in Sn Q across the Turkish-Iranian Plateau. Due to the signal-to-noise criterion to select amplitudes and the efficiency criterion to select two-station and reverse-two-station paths for the inversion, the data are left-censored and the

  19. Attenuation as a function of the canal length of custom-molded earplugs: a pilot study.

    PubMed

    Tufts, Jennifer B; Chen, Siyuan; Marshall, Lynne

    2013-06-01

    Custom-molded earplugs (CMEPs) whose canal segments extend beyond the second bend of the ear canal can provide excellent attenuation but can sometimes be uncomfortable. Attenuation was measured for CMEPs whose canal segments were shortened in 2-mm increments. The within-subjects design permitted illustration of the form of the function relating attenuation to canal segment length for individuals. Reduction of attenuation due to canal segment shortening was generally more pronounced for frequencies ≤1000 Hz. Some regions of the canal segments were more critical than others in maintaining attenuation. The relationship between comfort and canal segment length was not straightforward. PMID:23742438

  20. A two-component rain model for the prediction of attenuation statistics

    NASA Technical Reports Server (NTRS)

    Crane, R. K.

    1982-01-01

    A two-component rain model has been developed for calculating attenuation statistics. In contrast to most other attenuation prediction models, the two-component model calculates the occurrence probability for volume cells or debris attenuation events. The model performed significantly better than the International Radio Consultative Committee model when used for predictions on earth-satellite paths. It is expected that the model will have applications in modeling the joint statistics required for space diversity system design, the statistics of interference due to rain scatter at attenuating frequencies, and the duration statistics for attenuation events.

  1. Range Restriction and Attenuation Corrections.

    ERIC Educational Resources Information Center

    Mumford, Michael D.; Mendoza, Jorge L.

    The present paper reviews the techniques commonly used to correct an observed correlation coefficient for the simultaneous influence of attenuation and range restriction effects. It is noted that the procedure which is currently in use may be somewhat biased because it treats range restriction and attenuation as independent restrictive influences.…

  2. Suicide Risk: Amplifiers and Attenuators.

    ERIC Educational Resources Information Center

    Plutchik, Robert; Van Praag, Herman M.

    1994-01-01

    Attempts to integrate findings on correlates of suicide and violent risk in terms of a theory called a two-stage model of countervailing forces, which assumes that the strength of aggressive impulses is modified by amplifiers and attenuators. The vectorial interaction of amplifiers and attenuators creates an unstable equilibrium making prediction…

  3. Evolutionary history and attenuation of myxoma virus on two continents.

    PubMed

    Kerr, Peter J; Ghedin, Elodie; DePasse, Jay V; Fitch, Adam; Cattadori, Isabella M; Hudson, Peter J; Tscharke, David C; Read, Andrew F; Holmes, Edward C

    2012-01-01

    The attenuation of myxoma virus (MYXV) following its introduction as a biological control into the European rabbit populations of Australia and Europe is the canonical study of the evolution of virulence. However, the evolutionary genetics of this profound change in host-pathogen relationship is unknown. We describe the genome-scale evolution of MYXV covering a range of virulence grades sampled over 49 years from the parallel Australian and European epidemics, including the high-virulence progenitor strains released in the early 1950s. MYXV evolved rapidly over the sampling period, exhibiting one of the highest nucleotide substitution rates ever reported for a double-stranded DNA virus, and indicative of a relatively high mutation rate and/or a continually changing selective environment. Our comparative sequence data reveal that changes in virulence involved multiple genes, likely losses of gene function due to insertion-deletion events, and no mutations common to specific virulence grades. Hence, despite the similarity in selection pressures there are multiple genetic routes to attain either highly virulent or attenuated phenotypes in MYXV, resulting in convergence for phenotype but not genotype. PMID:23055928

  4. Attenuation of Vaccinia Virus.

    PubMed

    Yakubitskiy, S N; Kolosova, I V; Maksyutov, R A; Shchelkunov, S N

    2015-01-01

    Since 1980, in the post-smallpox vaccination era the human population has become increasingly susceptible compared to a generation ago to not only the variola (smallpox) virus, but also other zoonotic orthopoxviruses. The need for safer vaccines against orthopoxviruses is even greater now. The Lister vaccine strain (LIVP) of vaccinia virus was used as a parental virus for generating a recombinant 1421ABJCN clone defective in five virulence genes encoding hemagglutinin (A56R), the IFN-γ-binding protein (B8R), thymidine kinase (J2R), the complement-binding protein (C3L), and the Bcl-2-like inhibitor of apoptosis (N1L). We found that disruption of these loci does not affect replication in mammalian cell cultures. The isogenic recombinant strain 1421ABJCN exhibits a reduced inflammatory response and attenuated neurovirulence relative to LIVP. Virus titers of 1421ABJCN were 3 lg lower versus the parent VACV LIVP when administered by the intracerebral route in new-born mice. In a subcutaneous mouse model, 1421ABJCN displayed levels of VACV-neutralizing antibodies comparable to those of LIVP and conferred protective immunity against lethal challenge by the ectromelia virus. The VACV mutant holds promise as a safe live vaccine strain for preventing smallpox and other orthopoxvirus infections. PMID:26798498

  5. Motion recovery in light-attenuating media from image-shading variations.

    PubMed

    Yu, C H; Negahdaripour, S

    1992-07-01

    One of the requirements for providing some autonomy in the operation of robotic vehicles is an accurate knowledge of position, orientation, and motion relative to nearby objects and the environment. Passive-vision sensing provides a useful tool for extracting such information from the images of the scene. Some applications, including the operation of undersea vehicles, involve working under artificial lighting in an attenuating medium. The extraction of motion, position, and orientation information requires models of image brightness that incorporate the effects that are due to the illumination attenuation and the illumination variation resulting from the motion of the light source. We investigate the problem of motion recovery from image-shading variations for a configuration common in many undersea applications. On the basis of the image model developed earlier [J. Opt. Soc. Am. A 8, 217 (1991)], we show that the motion of a vehicle can be determined in closed form by using three Lambertian planar surfaces as optical beacons. PMID:1634966

  6. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Joel Walls; M.T. Taner; Gary Mavko; Jack Dvorkin

    2002-04-01

    Wave-induced variations of pore pressure in a partially-saturated reservoir result in oscillatory liquid flow. The viscous losses during this flow are responsible for wave attenuation. The same viscous effects determine the changes in the dynamic bulk modulus of the system versus frequency. These changes are necessarily linked to attenuation via the causality condition. We analytically quantify the frequency dependence of the bulk modulus of a partially saturated rock by assuming that saturation is patchy and then link these changes to the inverse quality factor. As a result, the P-wave attenuation is quantitatively linked to saturation and thus can serve as a saturation indicator.

  7. Seismic attenuation: Laboratory measurements in fluid saturated rocks

    NASA Astrophysics Data System (ADS)

    Subramaniyan, Shankar; Madonna, Claudio; Tisato, Nicola; Saenger, Erik; Quintal, Beatriz

    2014-05-01

    Seismic wave attenuation could be used as an indicator of reservoir fluids due to its dependence on rock and fluid properties. Over the past 30 years, many laboratory methodologies to study attenuation in rocks have been employed, such as ultrasonic (MHz), resonant bar (kHz) and forced oscillation methods in the low frequency range (0.01-100Hz) (Tisato & Madonna 2012; Madonna & Tisato 2013). Forced oscillation methods have gained prominence over time as the frequency range of measurements correspond to that of field seismic data acquired for oil/gas exploration. These experiments measure attenuation as the phase shift between the applied stress (sinusoidal) and measured strain. Since the magnitudes of measured phase shifts are quite low (Q-1 ~0.01-0.1) and the amplitudes of strain applied to the rock samples are of the order ~10-6 (i.e., similar orders of magnitude to seismic waves), it is challenging. A comparison of such forced oscillation setups will be presented to provide an overview of the various possibilities of design and implementation for future setups. In general, there is a lack of laboratory data and most of the published data are for sandstones. Currently, attenuation measurements are being carried out on carbonate and sandstone samples. We employ the Seismic Wave Attenuation Module (SWAM, Madonna & Tisato 2013) to measure seismic attenuation in these samples for different saturation degrees (90% and 100% water) and under three different confining pressures (5, 10 and 15MPa). Preliminary results from these investigations will be discussed. REFERENCES Madonna, C. & Tisato, N. 2013: A new seismic wave attenuation module to experimentally measure low-frequency attenuation in extensional mode. Geophysical Prospecting, doi: 10.1111/1365-2478.12015. Tisato, N. & Madonna, C. 2012: Attenuation at low seismic frequencies in partially saturated rocks: Measurements and description of a new apparatus. Journal of Applied Geophysics, 86, 44-53.

  8. Effect of Non-Alignment/Alignment of Attenuation Map Without/With Emission Motion Correction in Cardiac SPECT/CT

    PubMed Central

    Dey, Joyoni; Segars, W. Paul; Pretorius, P. Hendrik; King, Michael A.

    2015-01-01

    Purpose We investigate the differences without/with respiratory motion correction in apparent imaging agent localization induced in reconstructed emission images when the attenuation maps used for attenuation correction (from CT) are misaligned with the patient anatomy during emission imaging due to differences in respiratory state. Methods We investigated use of attenuation maps acquired at different states of a 2 cm amplitude respiratory cycle (at end-expiration, at end-inspiration, the center map, the average transmission map, and a large breath-hold beyond range of respiration during emission imaging) to correct for attenuation in MLEM reconstruction for several anatomical variants of the NCAT phantom which included both with and without non-rigid motion between heart and sub-diaphragmatic regions (such as liver, kidneys etc). We tested these cases with and without emission motion correction and attenuation map alignment/non-alignment. Results For the NCAT default male anatomy the false count-reduction due to breathing was largely removed upon emission motion correction for the large majority of the cases. Exceptions (for the default male) were for the cases when using the large-breathhold end-inspiration map (TI_EXT), when we used the end-expiration (TE) map, and to a smaller extent, the end-inspiration map (TI). However moving the attenuation maps rigidly to align the heart region, reduced the remaining count-reduction artifacts. For the female patient count-reduction remained post motion correction using rigid map-alignment due to the breast soft-tissue misalignment. Quantitatively, after the transmission (rigid) alignment correction, the polar-map 17-segment RMS error with respect to the reference (motion-less case) reduced by 46.5% on average for the extreme breathhold case. The reductions were 40.8% for end-expiration map and 31.9% for end-inspiration cases on the average, comparable to the semi-ideal case where each state uses its own attenuation map for

  9. Waves in fragmented geomaterials with impact attenuation

    NASA Astrophysics Data System (ADS)

    Dyskin, Arcady; Pasternak, Elena

    2016-04-01

    Attenuation of waves in geomaterials, such as seismic waves is usually attributed to energy dissipation due to the presence of viscous fluid and/or viscous cement between the constituents. In fragmented geomaterials such as blocky rock mass there is another possible source of energy dissipation - impacting between the fragments. This can be characterised by the coefficient of restitution, which is the ratio between the rotational velocities after and before the impact. In particular, this manifests itself in the process of mutual rotations of the fragments/blocks, whereby in the process of oscillation different ends of the contacting faces of the fragments are impacting. During the rotational oscillations the energy dissipation is concentrated in the neutral position that is the one in which the relative rotation between two fragments is zero. We show that in a simple system of two fragments this dissipation is equivalent, in a long run, to the presence of viscous damper between the fragments (the Voigt model of visco-elasticity). Generalisation of this concept to the material consisting of many fragments leads to a Voigt model of wave propagation where the attenuation coefficient is proportional to the logarithm of restitution coefficient. The waves in such a medium show slight dispersion caused by damping and strong dependence of the attenuation on the wave frequency.

  10. Natural attenuation of perchlorate in denitrified groundwater.

    PubMed

    Robertson, William D; Roy, James W; Brown, Susan J; Van Stempvoort, Dale R; Bickerton, Greg

    2014-01-01

    Monitoring of a well-defined septic system groundwater plume and groundwater discharging to two urban streams located in southern Ontario, Canada, provided evidence of natural attenuation of background low level (ng/L) perchlorate (ClO4⁻) under denitrifying conditions in the field. The septic system site at Long Point contains ClO4⁻ from a mix of waste water, atmospheric deposition, and periodic use of fireworks, while the nitrate plume indicates active denitrification. Plume nitrate (NO3⁻ -N) concentrations of up to 103 mg/L declined with depth and downgradient of the tile bed due to denitrification and anammox activity, and the plume was almost completely denitrified beyond 35 m from the tile bed. The ClO4⁻ natural attenuation occurs at the site only when NO3⁻ -N concentrations are <0.3 mg/L, after which ClO4⁻ concentrations decline abruptly from 187 ± 202 to 11 ± 15 ng/L. A similar pattern between NO3⁻ -N and ClO4⁻ was found in groundwater discharging to the two urban streams. These findings suggest that natural attenuation (i.e., biodegradation) of ClO4⁻ may be commonplace in denitrified aquifers with appropriate electron donors present, and thus, should be considered as a remediation option for ClO4⁻ contaminated groundwater. PMID:23448242

  11. Attenuation compensation in TC-99M SPECT brain imaging: Use of attenuation maps derived from tranmission versus emission data

    SciTech Connect

    Pan, T.S.; Licho, R.; Penney, B.C.

    1994-05-01

    This study compares reconstructions of Tc-99m brain SPECT studies made using two methods of estimating the attenuation map: (1) transmission scanning, and (2) segmenting reconstructions of emission data and assigning attenuation coefficient values. A three-head SPECT system with fan beam collimators was used. Transmission scanning was performed using a line source at the focal line of a fan beam collimator right after the regular emission scan. The higher attenuation of the skull and the lower attenuation in the sinus cavities were identifiable despite the noise in the reconstructed transmission data due to: (1) the contamination of the transmission data by emission photons, (2) the maximum acquisition count rate imposed by the SPECT system, and (3) the clinical scanning time. Emission data were recorded using both photopeak and Compton scatter energy windows. Outlines of the head and the maxillary sinus could be obtained using only the Compton scatter reconstructions, whereas identifying the skull regions and the frontal sinus required the photopeak data as well. We placed appropriate linear attenuation coefficients in the soft tissue, bone, sinus and air regions (0.15,. 0.22, 0, and 0 cm{sup -1}) and blurred this attenuation map with a Gaussian kernel of about 0.2 cm standard deviation to obtain the attenuation map based on the emission data. Reconstructions were computed using the maximum likelihood expectation maximization algorithm with Siddon`s ray-tracing algorithm. Reconstructions based on the two attenuation maps were compared quantitatively on the patient data. The differences noted were quite small. These results imply that attenuation correction based on emission data alone may be adequate for Tc-99m SPECT brain imaging.

  12. Total Reducing Capacity in Aquifer Minerals and Sediments: Quantifying the Potential to Attenuate Cr(VI) in Groundwater

    SciTech Connect

    Sisman, S. Lara

    2015-07-20

    Hexavalent chromium, Cr(VI), is present in the environment as a byproduct of industrial processes. Due to its mobility and toxicity, it is crucial to attenuate or remove Cr(VI) from the environment. The objective of this investigation was to quantify potential natural attenuation, or reduction capacity, of reactive minerals and aquifer sediments. Samples of reduced-iron containing minerals such as ilmenite, as well as Puye Formation sediments representing a contaminated aquifer in New Mexico, were reacted with chromate. The change in Cr(VI) during the reaction was used to calculate reduction capacity. This study found that minerals that contain reduced iron, such as ilmenite, have high reducing capacities. The data indicated that sample history may impact reduction capacity tests due to surface passivation. Further, this investigation identified areas for future research including: a) refining the relationships between iron content, magnetic susceptibility and reduction capacity, and b) long term kinetic testing using fresh aquifer sediments.

  13. Live-Attenuated Bacterial Vectors: Tools for Vaccine and Therapeutic Agent Delivery

    PubMed Central

    Lin, Ivan Y. C.; Van, Thi Thu Hao; Smooker, Peter M.

    2015-01-01

    Genetically attenuated microorganisms, including pathogenic and commensal bacteria, can be engineered to carry and deliver heterologous antigens to elicit host immunity against both the vector as well as the pathogen from which the donor gene is derived. These live attenuated bacterial vectors have been given much attention due to their capacity to induce a broad range of immune responses including localized mucosal, as well as systemic humoral and/or cell-mediated immunity. In addition, the unique tumor-homing characteristics of these bacterial vectors has also been exploited for alternative anti-tumor vaccines and therapies. In such approach, tumor-associated antigen, immunostimulatory molecules, anti-tumor drugs, or nucleotides (DNA or RNA) are delivered. Different potential vectors are appropriate for specific applications, depending on their pathogenic routes. In this review, we survey and summarize the main features of the different types of live bacterial vectors and discussed the clinical applications in the field of vaccinology. In addition, different approaches for using live attenuated bacterial vectors for anti-cancer therapy is discussed, and some promising pre-clinical and clinical studies in this field are outlined. PMID:26569321

  14. Wave velocity dispersion and attenuation in media exhibiting internal oscillations

    NASA Astrophysics Data System (ADS)

    Frehner, Marcel; Steeb, Holger; Schmalholz, Stefan M.

    2010-05-01

    an arbitrary number of oscillators with different resonance frequencies. Exemplarily, we show a log-normal distribution of resonance frequencies. Such a distribution changes the acoustic properties significantly compared to the case with only one resonance frequency. The dispersion and attenuation resulting from our model agree well with the dispersion and attenuation (1) derived with a more exact mathematical treatment and (2) measured in laboratory experiments. (2) Three-phase model for residually saturated porous media We present a three-phase model describing wave propagation phenomena in residually saturated porous media. The model consists of a continuous non-wetting phase and a discontinuous wetting phase and is an extension of classical biphasic (Biot-type) models. The model includes resonance effects of single liquid bridges or liquid clusters with miscellaneous eigenfrequencies taking into account a visco-elastic restoring force (pinned oscillations and/or sliding motion of the contact line). In the present investigation, our aim is to study attenuation due to fluid oscillations and due to wave-induced flow with a macroscopic three-phase continuum model, i.e. a mixture consisting of one solid constituent building the elastic skeleton and two immiscible fluid constituents. Furthermore, we study monochromatic waves in transversal and longitudinal direction and discuss the resulting dispersion relations for a typical reservoir sandstone equivalent (Berea sandstone).

  15. Modeling future scenarios of light attenuation and potential seagrass success in a eutrophic estuary

    USGS Publications Warehouse

    del Barrio, Pilar; Ganju, Neil K.; Aretxabaleta, Alfredo L.; Hayn, Melanie; García, Andrés; Howarth, Robert W.

    2014-01-01

    Estuarine eutrophication has led to numerous ecological changes, including loss of seagrass beds. One potential cause of these losses is a reduction in light availability due to increased attenuation by phytoplankton. Future sea level rise will also tend to reduce light penetration and modify seagrass habitat. In the present study, we integrate a spectral irradiance model into a biogeochemical model coupled to the Regional Ocean Model System (ROMS). It is linked to a bio-optical seagrass model to assess potential seagrass habitat in a eutrophic estuary under future nitrate loading and sea-level rise scenarios. The model was applied to West Falmouth Harbor, a shallow estuary located on Cape Cod (Massachusetts) where nitrate from groundwater has led to eutrophication and seagrass loss in landward portions of the estuary. Measurements of chlorophyll, turbidity, light attenuation, and seagrass coverage were used to assess the model accuracy. Mean chlorophyll based on uncalibrated in-situ fluorometry varied from 28 μg L−1 at the landward-most site to 6.5 μg L−1 at the seaward site, while light attenuation ranged from 0.86 to 0.45 m-1. The model reproduced the spatial variability in chlorophyll and light attenuation with RMS errors of 3.72 μg L−1 and 0.07 m-1 respectively. Scenarios of future nitrate reduction and sea-level rise suggest an improvement in light climate in the landward basin with a 75% reduction in nitrate loading. This coupled model may be useful to assess habitat availability changes due to eutrophication and sediment resuspension and fully considers spatial variability on the tidal timescale.

  16. The Violent Content in Attenuated Psychotic Symptoms.

    PubMed

    Marshall, Catherine; Deighton, Stephanie; Cadenhead, Kristin S; Cannon, Tyrone D; Cornblatt, Barbara A; McGlashan, Thomas H; Perkins, Diana O; Seidman, Larry J; Tsuang, Ming T; Walker, Elaine F; Woods, Scott W; Bearden, Carrie E; Mathalon, Daniel; Addington, Jean

    2016-08-30

    The relationship between psychosis and violence has typically focused on factors likely to predict who will commit violent acts. One unexplored area is violence in the content of subthreshold positive symptoms. The current aim was to conduct an exploratory analysis of violent content in the attenuated psychotic symptoms (APS) of those at clinical high risk of psychosis (CHR) who met criteria for attenuated psychotic symptom syndrome (APSS). The APS of 442 CHR individuals, determined by the Structured Interview for Prodromal Syndromes, were described in comprehensive vignettes. The content of these symptoms were coded using the Content of Attenuated Positive Symptoms Codebook. Other measures included clinical symptoms, functioning, beliefs and trauma. Individuals with violent content had significantly higher APS, greater negative beliefs about the self and others, and increased bullying. The same findings and higher ratings on anxiety symptoms were present when participants with self-directed violence were compared to participants with no violent content. Individuals reporting violent content differ in their clinical presentation compared to those who do not experience violent content. Adverse life events, like bullying, may impact the presence of violent content in APS symptoms. Future studies should explore violent content in relation to actual behavior. PMID:27259137

  17. Evaluation of natural attenuation rate at a gasoline spill site.

    PubMed

    Kao, C M; Prosser, J

    2001-04-20

    Contamination of groundwater by gasoline and other petroleum-derived hydrocarbons released from underground storage tanks (USTs) is a serious and widespread environmental problem. Natural attenuation is a passive remedial approach that depends upon natural processes to degrade and dissipate contaminants in soil and groundwater. Currently, in situ column technique, microcosm, and computer modeling have been applied for the natural attenuation rate calculation. However, the subsurface heterogeneity reduces the applicability of these techniques. In this study, a mass flux approach was used to calculate the contaminant mass reduction and field-scale decay rate at a gasoline spill site. The mass flux technique is a simplified mass balance procedure, which is accomplished using the differences in total contaminant mass flux across two cross-sections of the contaminant plume. The mass flux calculation shows that up to 87% of the dissolved total benzene, toluene, ethylbenzene, and xylene (BTEX) isomers removal was observed via natural attenuation at this site. The efficiency of natural biodegradation was evaluated by the in situ tracer method, and the first-order decay model was applied for the natural attenuation/biodegradation rate calculation. Results reveal that natural biodegradation was the major cause of the BTEX mass reduction among the natural attenuation processes, and approximately 88% of the BTEX removal was due to the natural biodegradation process. The calculated total BTEX first-order attenuation and biodegradation rates were 0.036 and 0.025% per day, respectively. Results suggest that the natural attenuation mechanisms can effectively contain the plume, and the mass flux method is useful in assessing the occurrence and efficiency of the natural attenuation process. PMID:11240068

  18. Frequency-domain ultrasound waveform tomography breast attenuation imaging

    NASA Astrophysics Data System (ADS)

    Sandhu, Gursharan Yash Singh; Li, Cuiping; Roy, Olivier; West, Erik; Montgomery, Katelyn; Boone, Michael; Duric, Neb

    2016-04-01

    Ultrasound waveform tomography techniques have shown promising results for the visualization and characterization of breast disease. By using frequency-domain waveform tomography techniques and a gradient descent algorithm, we have previously reconstructed the sound speed distributions of breasts of varying densities with different types of breast disease including benign and malignant lesions. By allowing the sound speed to have an imaginary component, we can model the intrinsic attenuation of a medium. We can similarly recover the imaginary component of the velocity and thus the attenuation. In this paper, we will briefly review ultrasound waveform tomography techniques, discuss attenuation and its relations to the imaginary component of the sound speed, and provide both numerical and ex vivo examples of waveform tomography attenuation reconstructions.

  19. Pump apparatus including deconsolidator

    DOEpatents

    Sonwane, Chandrashekhar; Saunders, Timothy; Fitzsimmons, Mark Andrew

    2014-10-07

    A pump apparatus includes a particulate pump that defines a passage that extends from an inlet to an outlet. A duct is in flow communication with the outlet. The duct includes a deconsolidator configured to fragment particle agglomerates received from the passage.

  20. DNA-launched live-attenuated vaccines for biodefense applications.

    PubMed

    Pushko, Peter; Lukashevich, Igor S; Weaver, Scott C; Tretyakova, Irina

    2016-09-01

    A novel vaccine platform uses DNA immunization to launch live-attenuated virus vaccines in vivo. This technology has been applied for vaccine development against positive-strand RNA viruses with global public health impact including alphaviruses and flaviviruses. The DNA-launched vaccine represents the recombinant plasmid that encodes the full-length genomic RNA of live-attenuated virus downstream from a eukaryotic promoter. When administered in vivo, the genomic RNA of live-attenuated virus is transcribed. The RNA initiates limited replication of a genetically defined, live-attenuated vaccine virus in the tissues of the vaccine recipient, thereby inducing a protective immune response. This platform combines the strengths of reverse genetics, DNA immunization and the advantages of live-attenuated vaccines, resulting in a reduced chance of genetic reversions, increased safety, and improved immunization. With this vaccine technology, the field of DNA vaccines is expanded from those that express subunit antigens to include a novel type of DNA vaccines that launch live-attenuated viruses. PMID:27055100

  1. Improved Inlet Noise Attenuation by Alteration of Boundary Layer Profiles

    NASA Technical Reports Server (NTRS)

    Mani, Ramani; Luedke, Jon; Jones, Michael G.; Nark, Douglas M.

    2004-01-01

    Acoustic liners are an essential component of technology used to reduce aircraft engine noise. Flow affects attenuation due to the liner in several ways, one of which is that boundary layers adjacent to the liner refract the sound. In the case of inlet noise, the boundary layer causes sound to be refracted away from the liner, thus degrading attenuation. A concept to improve attenuation by the liner by alteration of inlet boundary layer profiles is presented. The alteration of profiles is achieved by inlet blowing. Computational fluid dynamics and duct mode propagation theory for ducts carrying a parallel sheared flow have been used to design experiments to explore such a possibility in the NASA Langley Research Center Grazing Incidence Tube using an inlet blowing scheme developed at General Electric Global Research. The effects of inlet blowing on two liner configurations were evaluated. Calculated results will be shown for blowing ratios (injected flow/duct flow) of approximately 12% and frequencies up to 3 kHz. These results emphasize changes of attenuation achieved by blowing for the two liners. Experimental results of measured flow profiles (with and without blowing) in the Grazing Incidence Tube, and of corresponding changes in attenuation by the liner due to blowing will be presented.

  2. Optical modulator including grapene

    DOEpatents

    Liu, Ming; Yin, Xiaobo; Zhang, Xiang

    2016-06-07

    The present invention provides for a one or more layer graphene optical modulator. In a first exemplary embodiment the optical modulator includes an optical waveguide, a nanoscale oxide spacer adjacent to a working region of the waveguide, and a monolayer graphene sheet adjacent to the spacer. In a second exemplary embodiment, the optical modulator includes at least one pair of active media, where the pair includes an oxide spacer, a first monolayer graphene sheet adjacent to a first side of the spacer, and a second monolayer graphene sheet adjacent to a second side of the spacer, and at least one optical waveguide adjacent to the pair.

  3. Sound attenuation in magnetorheological fluids

    NASA Astrophysics Data System (ADS)

    Rodríguez-López, J.; Elvira, L.; Resa, P.; Montero de Espinosa, F.

    2013-02-01

    In this work, the attenuation of ultrasonic elastic waves propagating through magnetorheological (MR) fluids is analysed as a function of the particle volume fraction and the magnetic field intensity. Non-commercial MR fluids made with iron ferromagnetic particles and two different solvents (an olive oil based solution and an Araldite-epoxy) were used. Particle volume fractions of up to 0.25 were analysed. It is shown that the attenuation of sound depends strongly on the solvent used and the volume fraction. The influence of a magnetic field up to 212 mT was studied and it was found that the sound attenuation increases with the magnetic intensity until saturation is reached. A hysteretic effect is evident once the magnetic field is removed.

  4. Application of non-attenuating frequency radars for prediction of rain attenuation and space diversity performance

    NASA Technical Reports Server (NTRS)

    Goldhirsh, J.

    1979-01-01

    In order to establish transmitter power and receiver sensitivity levels at frequencies above 10 GHz, the designers of earth-satellite telecommunication systems are interested in cumulative rain fade statistics at variable path orientations, elevation angles, climatological regions, and frequencies. They are also interested in establishing optimum space diversity performance parameters. In this work are examined the many elements involved in the employment of single non-attenuating frequency radars for arriving at the desired information. The elements examined include radar techniques and requirements, phenomenological assumptions, path attenation formulations and procedures, as well as error budgeting and calibration analysis. Included are the pertinent results of previous investigators who have used radar for rain attenuation modeling. Suggestions are made for improving present methods.

  5. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Joel Walls; M.T. Taner; Naum Derzhi; Gary Mavko; Jack Dvorkin

    2003-04-01

    In this report we will show results of seismic and well log derived attenuation attributes from a deep water Gulf of Mexico data set. This data was contributed by Burlington Resources and Seitel Inc. The data consists of ten square kilometers of 3D seismic data and three well penetrations. We have computed anomalous seismic absorption attributes on the seismic data and have computed Q from the well log curves. The results show a good correlation between the anomalous absorption (attenuation) attributes and the presence of gas as indicated by well logs.

  6. Influence of attenuation on acoustic emission signals in carbon fiber reinforced polymer panels.

    PubMed

    Asamene, Kassahun; Hudson, Larry; Sundaresan, Mannur

    2015-05-01

    Influence of attenuation on acoustic emission (AE) signals in Carbon Fiber Reinforced Polymer (CFRP) crossply and quasi-isotropic panels is examined in this paper. Attenuation coefficients of the fundamental antisymmetric (A0) and symmetric (S0) wave modes were determined experimentally along different directions for the two types of CFRP panels. In the frequency range from 100 kHz to 500 kHz, the A0 mode undergoes significantly greater changes due to material related attenuation compared to the S0 mode. Moderate to strong changes in the attenuation levels were noted with propagation directions. Such mode and frequency dependent attenuation introduces major changes in the characteristics of AE signals depending on the position of the AE sensor relative to the source. Results from finite element simulations of a microscopic damage event in the composite laminates are used to illustrate attenuation related changes in modal and frequency components of AE signals. PMID:25682294

  7. Properties of sound attenuation around a two-dimensional underwater vehicle with a large cavitation number

    NASA Astrophysics Data System (ADS)

    Ye, Peng-Cheng; Pan, Guang

    2015-06-01

    Due to the high speed of underwater vehicles, cavitation is generated inevitably along with the sound attenuation when the sound signal traverses through the cavity region around the underwater vehicle. The linear wave propagation is studied to obtain the influence of bubbly liquid on the acoustic wave propagation in the cavity region. The sound attenuation coefficient and the sound speed formula of the bubbly liquid are presented. Based on the sound attenuation coefficients with various vapor volume fractions, the attenuation of sound intensity is calculated under large cavitation number conditions. The result shows that the sound intensity attenuation is fairly small in a certain condition. Consequently, the intensity attenuation can be neglected in engineering. Project supported by the National Natural Science Foundation of China (Grant Nos. 51279165 and 51479170) and the National Defense Basic Scientific Research Program of China (Grant No. B2720133014).

  8. Attenuation of near-IR light through dentin at wavelengths from 1300-1650-nm.

    PubMed

    Chan, Andrew C; Darling, Cynthia L; Chan, Kenneth H; Fried, Daniel

    2014-02-18

    Light scattering in dental enamel decreases markedly from the UV to the near-IR and recent studies employing near-IR transillumination and reflectance imaging including optical coherence tomography indicate that this wavelength region is ideally suited for imaging dental caries due to the high transparency of enamel. The opacity of dentin is an important factor in optimizing the contrast of demineralization in reflectance measurements. It also influences the contrast of occlusal lesions in transillumination. Light scattering in dentin is an order of magnitude larger than in enamel, it is highly anisotropic and has a different spectral light scattering dependence than enamel. The objective of this study was to measure the optical attenuation of near-IR light through dentin at near-IR wavelengths from 1300-1650-nm. In this study the collimated transmission of near-IR light through polished thin sections of dentin of 0.05 to 0.6 mm thickness was measured. Beer-Lambert plots show that the attenuation coefficients range in magnitude from 20 to 40 cm(-1). Attenuation increased significantly with increasing wavelength and the increases were not entirely consistent with increased water absorption. PMID:24839373

  9. Attenuation of near-IR light through dentin at wavelengths from 1300-1650-nm

    NASA Astrophysics Data System (ADS)

    Chan, Andrew C.; Darling, Cynthia L.; Chan, Kenneth H.; Fried, Daniel

    2014-02-01

    Light scattering in dental enamel decreases markedly from the UV to the near-IR and recent studies employing near-IR transillumination and reflectance imaging including optical coherence tomography indicate that this wavelength region is ideally suited for imaging dental caries due to the high transparency of enamel. The opacity of dentin is an important factor in optimizing the contrast of demineralization in reflectance measurements. It also influences the contrast of occlusal lesions in transillumination. Light scattering in dentin is an order of magnitude larger than in enamel, it is highly anisotropic and has a different spectral light scattering dependence than enamel. The objective of this study was to measure the optical attenuation of near-IR light through dentin at near-IR wavelengths from 1300-1650-nm. In this study the collimated transmission of near-IR light through polished thin sections of dentin of 0.05 to 0.6 mm thickness was measured. Beer-Lambert plots show that the attenuation coefficients range in magnitude from 20 to 40 cm-1. Attenuation increased significantly with increasing wavelength and the increases were not entirely consistent with increased water absorption.

  10. Rain induced attenuation studies for V-band satellite communication in tropical region

    NASA Astrophysics Data System (ADS)

    Badron, Khairayu; Ismail, Ahmad Fadzil; Din, Jafri; Tharek, Abd. Rahman

    2011-04-01

    Satellite communications operating at 10 GHz and above in the tropics suffer severe signal degradation due to rain. Attenuation due to rain at 38 GHz had been measured for a period of 20 months in Malaysia. Analyses carried out include seasonal variations, diurnal effects and the annual cumulative distributions. Obtained results were compared with several established prediction models including the ITU-R. The rain fade characteristics were also investigated in determining the levels of signal loss and fading. In addition, the studies highlight several potential fade mitigation techniques that can be embarked. These fundamental aprehensions are very critical for future earth space communication link design and can be exploited as preliminary groundwork plan for the researchers as well as engineers.

  11. High power radio frequency attenuation device

    DOEpatents

    Kerns, Quentin A.; Miller, Harold W.

    1984-01-01

    A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling are provided for the inner heat conducting portions of each fin. Also disclosed is a resistor device to selectively alternate unwanted radio frequency energy in a resonant cavity.

  12. Seismic velocity, attenuation and rheology of the upper mantle

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.; Minster, J. B.

    1980-01-01

    Seismic and rheological properties of the upper mantle in the vicinity of the low-velocity zone are expressed in terms of relaxation by dislocation glide. Dislocation bowing in the glide plane explains seismic velocities and attenuation. Climbing at higher stresses for longer periods of time give the observed viscosity, and explain the low velocity and high temperature attenuation found at seismic frequencies. Due to differing parameters, separate terms for thermal, seismic and rheological lithospheres are proposed. All three lithospheres, however, are related and are functions of temperature, and must be specified by parameters such as period, stress, and stress duration.

  13. Optical attenuation coefficient in individual ZnO nanowires.

    PubMed

    Little, Anree; Hoffman, Abigail; Haegel, Nancy M

    2013-03-11

    Attenuation coefficient measurements for the propagation of bandedge luminescence are made on individual ZnO nanowires by combining the localized excitation capability of a scanning electron microscope (SEM) with near-field scanning optical microscopy (NSOM) to record the distribution and intensity of wave-guided emission. Measurements were made for individual nanostructures with triangular cross-sections ranging in diameter from 680 to 2300 nm. The effective attenuation coefficient shows an inverse dependence on nanowire diameter (d(-1)), indicating scattering losses due to non-ideal waveguiding behavior. PMID:23482201

  14. Significant Attenuation of Lightly Damped Resonances Using Particle Dampers

    NASA Technical Reports Server (NTRS)

    Smith, Andrew; LaVerde, Bruce; Hunt, Ron; Knight, Joseph Brent

    2015-01-01

    When equipment designs must perform in a broad band vibration environment it can be difficult to avoid resonances that affect life and performance. This is especially true when an organization seeks to employ an asset from a heritage design in a new, more demanding vibration environment. Particle dampers may be used to provide significant attenuation of lightly damped resonances to assist with such a deployment of assets by including only a very minor set of modifications. This solution may be easier to implement than more traditional attenuation schemes. Furthermore, the cost in additional weight to the equipment can be very small. Complexity may also be kept to a minimum, because the particle dampers do not require tuning. Attenuating the vibratory response with particle dampers may therefore be simpler (in a set it and forget it kind of way) than tuned mass dampers. The paper will illustrate the use of an "equivalent resonance test jig" that can assist designers in verifying the potential resonance attenuation that may be available to them during the early trade stages of the design. An approach is suggested for transforming observed attenuation in the jig to estimated performance in the actual service design. KEY WORDS: Particle Damper, Performance in Vibration Environment, Damping, Resonance, Attenuation, Mitigation of Vibration Response, Response Estimate, Response Verification.

  15. Earth-Space Link Attenuation Estimation via Ground Radar Kdp

    NASA Technical Reports Server (NTRS)

    Bolen, Steven M.; Benjamin, Andrew L.; Chandrasekar, V.

    2003-01-01

    A method of predicting attenuation on microwave Earth/spacecraft communication links, over wide areas and under various atmospheric conditions, has been developed. In the area around the ground station locations, a nearly horizontally aimed polarimetric S-band ground radar measures the specific differential phase (Kdp) along the Earth-space path. The specific attenuation along a path of interest is then computed by use of a theoretical model of the relationship between the measured S-band specific differential phase and the specific attenuation at the frequency to be used on the communication link. The model includes effects of rain, wet ice, and other forms of precipitation. The attenuation on the path of interest is then computed by integrating the specific attenuation over the length of the path. This method can be used to determine statistics of signal degradation on Earth/spacecraft communication links. It can also be used to obtain real-time estimates of attenuation along multiple Earth/spacecraft links that are parts of a communication network operating within the radar coverage area, thereby enabling better management of the network through appropriate dynamic routing along the best combination of links.

  16. Experimental assessment of snow-induced attenuation on an Earth-space link operating at Ka-band

    NASA Astrophysics Data System (ADS)

    Amaya, César; García-Rubia, José-Miguel; Bouchard, Pierre; Nguyen, Tu

    2014-10-01

    This investigation assesses the attenuation induced by snowfall on an experimental slant-path link that monitors the 20.199 GHz beacon signal of the Anik F2 satellite. Beacon data collected at Communications Research Centre Canada (CRC) in Ottawa over 2 years, including the winters of 2010-2011 and 2011-2012, were analyzed as part of this study. The antenna of one of the two receivers used in the propagation campaign with Anik F2 was shielded, the first year under a tent and the second year under the roof of a building, in order to prevent degradations on the measured beacon signal due to snow or ice accumulation on the parabolic reflector surface. One of the main challenges of the study was the unambiguous identification of snow events. Information provided by several weather sensors, a profiling radiometer, and meteorological reports were used to help identify the type of precipitation. Events of wet and dry snow along with freezing rain are presented and discussed. Radiometric measurements of sky noise temperature were particularly useful to detect light snowfall events and to estimate event durations. Statistics of snow attenuation were derived for the winter months of the study. It is found that snow attenuation is modest at 20.2 GHz; however, modest attenuation may be important for small-margin communication systems.

  17. Evaluation of Moisture-Related Attenuation Coefficient and Water Diffusion Velocity in Human Skin Using Optical Coherence Tomography

    PubMed Central

    Lee, Cheng-Kuang; Tsai, Meng-Tsan; Chang, Feng-Yu; Yang, Chih-Hsun; Shen, Su-Chin; Yuan, Ouyang; Yang, Chih-He

    2013-01-01

    In this study, time-resolved optical coherence tomography (OCT) scanning images of the process of water diffusion in the skin that illustrate the enhancement in the backscattered intensities due to the increased water concentration are presented. In our experiments, the water concentration in the skin was increased by soaking the hand in water, and the same region of the skin was scanned and measured with the OCT system and a commercial moisture monitor every three minutes. To quantitatively analyze the moisture-related optical properties and the velocity of water diffusion in human skin, the attenuation coefficients of the skin, including the epidermis and dermis layers, were evaluated. Furthermore, the evaluated attenuation coefficients were compared with the measurements made using the commercial moisture monitor. The results demonstrate that the attenuation coefficient increases as the water concentration increases. Furthermore, by evaluating the positions of center-of mass of the backscattered intensities from OCT images, the diffusion velocity can be estimated. In contrast to the commercial moisture monitor, OCT can provide three-dimensional structural images of the skin and characterize its optical property, which together can be used to observe morphological changes and quantitatively evaluate the moisture-related attenuation coefficients in different skin layers. PMID:23529149

  18. Dose reduction using a dynamic, piecewise-linear attenuator

    SciTech Connect

    Hsieh, Scott S.; Fleischmann, Dominik; Pelc, Norbert J.

    2014-02-15

    Purpose: The authors recently proposed a dynamic, prepatient x-ray attenuator capable of producing a piecewise-linear attenuation profile customized to each patient and viewing angle. This attenuator was intended to reduce scatter-to-primary ratio (SPR), dynamic range, and dose by redistributing flux. In this work the authors tested the ability of the attenuator to reduce dose and SPR in simulations. Methods: The authors selected four clinical applications, including routine full field-of-view scans of the thorax and abdomen, and targeted reconstruction tasks for an abdominal aortic aneurysm and the pancreas. Raw data were estimated by forward projection of the image volume datasets. The dynamic attenuator was controlled to reduce dose while maintaining peak variance by solving a convex optimization problem, assuminga priori knowledge of the patient anatomy. In targeted reconstruction tasks, the noise in specific regions was given increased weighting. A system with a standard attenuator (or “bowtie filter”) was used as a reference, and used either convex optimized tube current modulation (TCM) or a standard TCM heuristic. The noise of the scan was determined analytically while the dose was estimated using Monte Carlo simulations. Scatter was also estimated using Monte Carlo simulations. The sensitivity of the dynamic attenuator to patient centering was also examined by shifting the abdomen in 2 cm intervals. Results: Compared to a reference system with optimized TCM, use of the dynamic attenuator reduced dose by about 30% in routine scans and 50% in targeted scans. Compared to the TCM heuristics which are typically used withouta priori knowledge, the dose reduction is about 50% for routine scans. The dynamic attenuator gives the ability to redistribute noise and variance and produces more uniform noise profiles than systems with a conventional bowtie filter. The SPR was also modestly reduced by 10% in the thorax and 24% in the abdomen. Imaging with the dynamic

  19. Dose reduction using a dynamic, piecewise-linear attenuator

    PubMed Central

    Hsieh, Scott S.; Fleischmann, Dominik; Pelc, Norbert J.

    2014-01-01

    Purpose: The authors recently proposed a dynamic, prepatient x-ray attenuator capable of producing a piecewise-linear attenuation profile customized to each patient and viewing angle. This attenuator was intended to reduce scatter-to-primary ratio (SPR), dynamic range, and dose by redistributing flux. In this work the authors tested the ability of the attenuator to reduce dose and SPR in simulations. Methods: The authors selected four clinical applications, including routine full field-of-view scans of the thorax and abdomen, and targeted reconstruction tasks for an abdominal aortic aneurysm and the pancreas. Raw data were estimated by forward projection of the image volume datasets. The dynamic attenuator was controlled to reduce dose while maintaining peak variance by solving a convex optimization problem, assuming a priori knowledge of the patient anatomy. In targeted reconstruction tasks, the noise in specific regions was given increased weighting. A system with a standard attenuator (or “bowtie filter”) was used as a reference, and used either convex optimized tube current modulation (TCM) or a standard TCM heuristic. The noise of the scan was determined analytically while the dose was estimated using Monte Carlo simulations. Scatter was also estimated using Monte Carlo simulations. The sensitivity of the dynamic attenuator to patient centering was also examined by shifting the abdomen in 2 cm intervals. Results: Compared to a reference system with optimized TCM, use of the dynamic attenuator reduced dose by about 30% in routine scans and 50% in targeted scans. Compared to the TCM heuristics which are typically used without a priori knowledge, the dose reduction is about 50% for routine scans. The dynamic attenuator gives the ability to redistribute noise and variance and produces more uniform noise profiles than systems with a conventional bowtie filter. The SPR was also modestly reduced by 10% in the thorax and 24% in the abdomen. Imaging with the

  20. NATURAL ATTENUATION OF CHLORINATED SOLVENTS

    EPA Science Inventory

    The protocol will simply describe in detail, with references and illustrations, the approach currently used by staff of the SPRD to evaluate natural attenuation of chlorinated solvents in ground water. Staff of SPRD, and staff of the Air Force Center for environmental excellence...

  1. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Joel Walls; M.T. Taner; Gary Mavko; Jack Dvorkin

    2002-07-01

    In fully-saturated rock and at ultrasonic frequencies, the microscopic squirt flow induced between the stiff and soft parts of the pore space by an elastic wave is responsible for velocity-frequency dispersion and attenuation. In the seismic frequency range, it is the macroscopic cross-flow between the stiffer and softer parts of the rock. We use the latter hypothesis to introduce simple approximate equations for velocity-frequency dispersion and attenuation in a fully water saturated reservoir. The equations are based on the assumption that in heterogeneous rock and at a very low frequency, the effective elastic modulus of the fully-saturated rock can be estimated by applying a fluid substitution procedure to the averaged (upscaled) dry frame whose effective porosity is the mean porosity and the effective elastic modulus is the Backus-average (geometric mean) of the individual dry-frame elastic moduli of parts of the rock. At a higher frequency, the effective elastic modulus of the saturated rock is the Backus-average of the individual fully-saturated-rock elastic moduli of parts of the rock. The difference between the effective elastic modulus calculated separately by these two methods determines the velocity-frequency dispersion. The corresponding attenuation is calculated from this dispersion by using (e.g.) the standard linear solid attenuation model.

  2. Effects of Wave Nonlinearity on Wave Attenuation by Vegetation

    NASA Astrophysics Data System (ADS)

    Wu, W. C.; Cox, D. T.

    2014-12-01

    The need to explore sustainable approaches to maintain coastal ecological systems has been widely recognized for decades and is increasingly important due to global climate change and patterns in coastal population growth. Submerged aquatic vegetation and emergent vegetation in estuaries and shorelines can provide ecosystem services, including wave-energy reduction and erosion control. Idealized models of wave-vegetation interaction often assume rigid, vertically uniform vegetation under the action of waves described by linear wave theory. A physical model experiment was conducted to investigate the effects of wave nonlinearity on the attenuation of random waves propagating through a stand of uniform, emergent vegetation in constant water depth. The experimental conditions spanned a relative water depth from near shallow to near deep water waves (0.45 < kh <1.49) and wave steepness from linear to nonlinear conditions (0.03 < ak < 0.18). The wave height to water depth ratios were in the range 0.12 < Hs/h < 0.34, and the Ursell parameter was in the range 2 < Ur < 68. Frictional losses from the side wall and friction were measured and removed from the wave attenuation in the vegetated cases to isolate the impact of vegetation. The normalized wave height attenuation decay for each case was fit to the decay equation of Dalrymple et al. (1984) to determine the damping factor, which was then used to calculate the bulk drag coefficients CD. This paper shows that the damping factor is dependent on the wave steepness ak across the range of relative water depths from shallow to deep water and that the damping factor can increase by a factor of two when the value of ak approximately doubles. In turn, this causes the drag coefficient CD to decrease on average by 23%. The drag coefficient can be modeled using the Keulegan-Carpenter number using the horizontal orbital wave velocity estimate from linear wave theory as the characteristic velocity scale. Alternatively, the Ursell

  3. Absorbed Dose in the Uterus of a Three Months Pregnant Woman Due to 131I

    NASA Astrophysics Data System (ADS)

    Vega-Carrillo, Héctor René; Manzanares-Acuña, Eduardo; Hernández-Dávila, Víctor Martín; Arcos-Pichardo, Areli; Barquero, Raquel; Iñiguez, M. Pilar

    2006-09-01

    The use of 131I is widely used in diagnostic and treatment of patients. If the patient is pregnant the 131I presence in the thyroid it becomes a source of constant exposition to other organs and the fetus. In this study the absorbed dose in the uterus of a 3 months pregnant woman with 131I in her thyroid gland has been calculated. The dose was determined using Monte Carlo methods in which a detailed model of the woman has been developed. The dose was also calculated using a simple procedure that was refined including the photons' attenuation in the woman organs and body. To verify these results an experiment was carried out using a neck phantom with 131I. Comparing the results it was found that the simple calculation tend to overestimate the absorbed dose, by doing the corrections due to body and organs photon attenuation the dose is 0.14 times the Monte Carlo estimation.

  4. Absorbed Dose in the Uterus of a Three Months Pregnant Woman Due to 131I

    SciTech Connect

    Vega-Carrillo, Hector Rene; Manzanares-Acuna, Eduardo; Hernandez-Davila, Victor Martin; Arcos-Pichardo, Areli; Barquero, Raquel; Iniguez, M. Pilar

    2006-09-08

    The use of 131I is widely used in diagnostic and treatment of patients. If the patient is pregnant the 131I presence in the thyroid it becomes a source of constant exposition to other organs and the fetus. In this study the absorbed dose in the uterus of a 3 months pregnant woman with 131I in her thyroid gland has been calculated. The dose was determined using Monte Carlo methods in which a detailed model of the woman has been developed. The dose was also calculated using a simple procedure that was refined including the photons' attenuation in the woman organs and body. To verify these results an experiment was carried out using a neck phantom with 131I. Comparing the results it was found that the simple calculation tend to overestimate the absorbed dose, by doing the corrections due to body and organs photon attenuation the dose is 0.14 times the Monte Carlo estimation.

  5. Simulation of attenuation regularity of detonation wave in PMMA

    NASA Astrophysics Data System (ADS)

    Lan, Wei; Xiaomian, Hu

    2011-06-01

    Polymethyl methacrylate (PMMA) is often used as clapboard or protective medium in the parameter measurement of detonation wave propagation, due to its similar shock impedance with the explosive. Theoretical and experimental research show that the pressure of shock wave in condensed material has the regularity of exponential attenuation with the distance of propagation. Simulation of detonation wave propagation in PMMA is conducted using a two-dimensional Lagrangian computational fluid dynamics program, and results are compared with the experimental data. Different charge diameters and different angles between the direction of detonation wave propagation and the normal direction of confined boundary are considered during the calculation. Results show that the detonation wave propagation in PMMA accords with the exponential regularity of shock wave attenuation in condensed material, and several factors are relevant to the attenuation coefficient, such as charge diameter and interface angle.

  6. Backscatter and attenuation properties of mammalian brain tissues

    NASA Astrophysics Data System (ADS)

    Wijekularatne, Pushpani Vihara

    Traumatic Brain Injury (TBI) is a common category of brain injuries, which contributes to a substantial number of deaths and permanent disability all over the world. Ultrasound technology plays a major role in tissue characterization due to its low cost and portability that could be used to bridge a wide gap in the TBI diagnostic process. This research addresses the ultrasonic properties of mammalian brain tissues focusing on backscatter and attenuation. Orientation dependence and spatial averaging of data were analyzed using the same method resulting from insertion of tissue sample between a transducer and a reference reflector. Apparent backscatter transfer function (ABTF) at 1 to 10 MHz, attenuation coefficient and backscatter coefficient (BSC) at 1 to 5 MHz frequency ranges were measured on ovine brain tissue samples. The resulting ABTF was a monotonically decreasing function of frequency and the attenuation coefficient and BSC generally were increasing functions of frequency, results consistent with other soft tissues such as liver, blood and heart.

  7. Extension of depth-resolved reconstruction of attenuation coefficients in optical coherence tomography for slim samples

    NASA Astrophysics Data System (ADS)

    Hohmann, Martin; Lengenfelder, B.; Kanawade, R.; Klämpfl, F.; Schmidt, Michael

    2015-12-01

    Coherent light propagating through turbid media is attenuated due to scattering and absorption. The decrease of the intensity of the coherent light is described by the attenuation coefficient. The measured decay of the coherent light through turbid media with optical coherence tomography (OCT) can be used to reconstruct the attenuation coefficient. Since most of the OCT systems work in the near-infrared region, they are the optical window from 800-1400 nm in tissue. Hence, the most part of the attenuation coefficient is caused due to the scattering. Therefore, deriving the attenuation coefficient is one way to get an approximation of the scattering coefficient which is difficult to access even up to day. Moreover, OCT measurements are one of the few possibilities to derive physical properties with micrometre resolution of the media under investigation.

  8. Principles underlying rational design of live attenuated influenza vaccines

    PubMed Central

    Jang, Yo Han

    2012-01-01

    Despite recent innovative advances in molecular virology and the developments of vaccines, influenza virus remains a serious burden for human health. Vaccination has been considered a primary countermeasure for prevention of influenza infection. Live attenuated influenza vaccines (LAIVs) are particularly attracting attention as an effective strategy due to several advantages over inactivated vaccines. Cold-adaptation, as a classical means for attenuating viral virulence, has been successfully used for generating safe and effective donor strains of LAIVs against seasonal epidemics and occasional pandemics. Recently, the advent of reverse genetics technique expedited a variety of rational strategies to broaden the pool of LAIVs. Considering the breadth of antigenic diversity of influenza virus, the pool of LAIVs is likely to equip us with better options for controlling influenza pandemics. With a brief reflection on classical attenuating strategies used at the initial stage of development of LAIVs, especially on the principles underlying the development of cold-adapted LAIVs, we further discuss and outline other attenuation strategies especially with respect to the rationales for attenuation, and their practicality for mass production. Finally, we propose important considerations for a rational vaccine design, which will provide us with practical guidelines for improving the safety and effectiveness of LAIVs. PMID:23596576

  9. Mid frequency shallow water fine-grained sediment attenuation measurements.

    PubMed

    Holland, Charles W; Dosso, Stan E

    2013-07-01

    Attenuation is perhaps the most difficult sediment acoustic property to measure, but arguably one of the most important for predicting passive and active sonar performance. Measurement techniques can be separated into "direct" measurements (e.g., via sediment probes, sediment cores, and laboratory studies on "ideal" sediments) which are typically at high frequencies, O(10(4)-10(5)) Hz, and "indirect" measurements where attenuation is inferred from long-range propagation or reflection data, generally O(10(2)-10(3)) Hz. A frequency gap in measurements exists in the 600-4000 Hz band and also a general acknowledgement that much of the historical measurements on fine-grained sediments have been biased due to a non-negligible silt and sand component. A shallow water measurement technique using long range reverberation is critically explored. An approximate solution derived using energy flux theory shows that the reverberation is very sensitive to depth-integrated attenuation in a fine-grained sediment layer and separable from most other unknown geoacoustic parameters. Simulation using Bayesian methods confirms the theory. Reverberation measurements across a 10 m fine-grained sediment layer yield an attenuation of 0.009 dB/m/kHz with 95% confidence bounds of 0.006-0.013 dB/m/kHz. This is among the lowest values for sediment attenuation reported in shallow water. PMID:23862792

  10. Measurement and Modeling of Ultrasonic Attenuation in Aluminum Rolled Plate

    SciTech Connect

    Li, Anxiang; Kim, Hak-Joon; Margetan, Frank; Thompson, R. B.

    2006-03-06

    When fabricating a new set of calibration blocks for Aluminum 7075 plate inspections, it is advantageous that the new blocks have similar ultrasonic attenuation to existing block sets. This allows the new set to qualify under the same ASTM procedures used for older sets. In the course of surveying candidate materials for possible use as calibration blocks, some interesting attenuation results were observed. When a candidate block was cut from a thick section of rolled plate, measured back-wall attenuation values in the rolling or transverse direction were quite sensitive to position in the plate-normal direction. Such variations are presumably tied to microstructural variations within the plate, as revealed by metallography. Some measured attenuation values were found to be in good agreement with predictions of the Stanke-Kino model, while others were not. The measurements and modeling work are reviewed, and additional experiments conducted to clarify certain issues are discussed. Those additional experiments suggest that beam distortion effects, due to microstructure variations within the beam cross-section, are primarily responsible for differences between measured and predicted attenuation values.

  11. Low-dose interpolated average CT for attenuation correction in cardiac PET/CT

    NASA Astrophysics Data System (ADS)

    Wu, Tung-Hsin; Zhang, Geoffrey; Wang, Shyh-Jen; Chen, Chih-Hao; Yang, Bang-Hung; Wu, Nien-Yun; Huang, Tzung-Chi

    2010-07-01

    Because of the advantages in the use of high photon flux and thus the short scan times of CT imaging, the traditional 68Ge scans for positron emission tomography (PET) image attenuation correction have been replaced by CT scans in the modern PET/CT technology. The combination of fast CT scan and slow PET scan often causes image misalignment between the PET and CT images due to respiration motion. Use of the average CT derived from cine CT images is reported to reduce such misalignment. However, the radiation dose to patients is higher with cine CT scans. This study introduces a method that uses breath-hold CT images and their interpolations to generate the average CT for PET image attenuation correction. Breath-hold CT sets are taken at end-inspiration and end-expiration. Deformable image registration is applied to generate a voxel-to-voxel motion matrix between the two CT sets. The motion is equally divided into 5 steps from inspiration to expiration and 5 steps from expiration to inspiration, generating a total of 8 phases of interpolated CT sets. An average CT image is generated from all the 10 phase CT images, including original inhale/exhale CT and 8 interpolated CT sets. Quantitative comparison shows that the reduction of image misalignment artifacts using the average CT from the interpolation technique for PET attenuation correction is at a similar level as that using cine average CT, while the dose to the patient from the CT scans is reduced significantly. The interpolated average CT method hence provides a low dose alternative to cine CT scans for PET attenuation correction.

  12. Antiaging Gene Klotho Attenuates Pancreatic β-Cell Apoptosis in Type 1 Diabetes.

    PubMed

    Lin, Yi; Sun, Zhongjie

    2015-12-01

    Apoptosis is the major cause of death of insulin-producing β-cells in type 1 diabetes mellitus (T1DM). Klotho is a recently discovered antiaging gene. We found that the Klotho gene is expressed in pancreatic β-cells. Interestingly, halplodeficiency of Klotho (KL(+/-)) exacerbated streptozotocin (STZ)-induced diabetes (a model of T1DM), including hyperglycemia, glucose intolerance, diminished islet insulin storage, and increased apoptotic β-cells. Conversely, in vivo β-cell-specific expression of mouse Klotho gene (mKL) attenuated β-cell apoptosis and prevented STZ-induced diabetes. mKL promoted cell adhesion to collagen IV, increased FAK and Akt phosphorylation, and inhibited caspase 3 cleavage in cultured MIN6 β-cells. mKL abolished STZ- and TNFα-induced inhibition of FAK and Akt phosphorylation, caspase 3 cleavage, and β-cell apoptosis. These promoting effects of Klotho can be abolished by blocking integrin β1. Therefore, these cell-based studies indicated that Klotho protected β-cells by inhibiting β-cell apoptosis through activation of the integrin β1-FAK/Akt pathway, leading to inhibition of caspase 3 cleavage. In an autoimmune T1DM model (NOD), we showed that in vivo β-cell-specific expression of mKL improved glucose tolerance, attenuated β-cell apoptosis, enhanced insulin storage in β-cells, and increased plasma insulin levels. The beneficial effect of Klotho gene delivery is likely due to attenuation of T-cell infiltration in pancreatic islets in NOD mice. Overall, our results demonstrate for the first time that Klotho protected β-cells in T1DM via attenuating apoptosis. PMID:26340932

  13. Ferrite attenuator modulation improves antenna performance

    NASA Technical Reports Server (NTRS)

    Hooks, J. C.; Larson, S. G.; Shorkley, F. H.; Williams, B. T.

    1970-01-01

    Ferrite attenuator inserted into appropriate waveguide reduces the gain of the antenna element which is causing interference. Modulating the ferrite attenuator to change the antenna gain at the receive frequency permits ground tracking until the antenna is no longer needed.

  14. Nonsilicon micro-machined variable optical attenuator

    NASA Astrophysics Data System (ADS)

    Zhou, Hai-lin; Dai, Xu-han; Ding, Gui-fu; Zhao, Xiaolin

    2011-08-01

    Optical power equalization between wavelength-path slots in wavelength division multiplexing (WDM) networks is an increasingly concerning issue in all-optical networks, and this made variable optical attenuators (VOAs) play an increasingly important role in fiber optic transmission systems. Various types of optical attenuators have been realized, but conventional available mechanical VOAs are bulky, costly, and slow. MOEMS technology provides new approaches to improve the characteristic mentioned above. Previous attempts to realize MEMS variable optical attenuators include the use of a micro-driven shutter, a mechanical antireflection switch (MARS) modulator, a micro-machined tilted mirror, and a micro-machined membrane-type waveguide. In this paper, we report the design and fabrication of two types of electromagnetically actuated variable optical attenuator (VOA). They are both driven by a similar construction containing of a plane coil and a FeNi armature. The first one adjusts the attenuation by moving a shutter between the two fibers, the second one by moving one of the fibers directly. The first one is fabricated by nonsilicon surface micromachining technology. In which a copper layer was used as the sacrificial layer, and the electroplated FeNi as the structure layer. This scheme provides another way to fabricate the optical microstructure. According to the experiment results, it has insertion loss less than 3 dB at 1550-nm wavelength, dynamic range greater than 40 dB, 0.2-dB repeatability, and return loss better than 40 dB, driving voltage less than 20 V. For the second one, it included the silicon platform for adjustment of optical coupling between two optical fibers. The main fabrication process of the silicon platform is was the KOH antistrophic wet chemical etching of <100> silicon wafers. The silicon wafer is further selectively etched from the bottom side to subtract the thickness of the silicon elastic platform. In addition, two V grooves were

  15. Development of a human live attenuated West Nile infectious DNA vaccine: Suitability of attenuating mutations found in SA14-14-2 for WN vaccine design.

    PubMed

    Yamshchikov, Vladimir; Manuvakhova, Marina; Rodriguez, Efrain

    2016-01-01

    Direct attenuation of West Nile (WN) virus strain NY99 for the purpose of vaccine development is not feasible due to its high virulence and pathogenicity. Instead, we created highly attenuated chimeric virus W1806 with the serological identity of NY99. To further attenuate W1806, we investigated effects of mutations found in Japanese encephalitis virus vaccine SA14-14-2. WN viruses carrying all attenuating mutations lost infectivity in mammalian, but not in mosquito cells. No single reversion restored infectivity in mammalian cells, although increased infectivity in mosquito cells was observed. To identify a subset of mutations suitable for further attenuation of W1806, we analyzed effects of E138K and K279M changes on virulence, growth properties, and immunogenicity of derivatized W956, from which chimeric W1806 inherited its biological properties and attenuation profile. Despite strong dominant attenuating effect, introduction of only two mutations was not sufficient for attenuating W1806 to the safety level acceptable for human use. PMID:26545140

  16. Effect of electrical resistivity on ultrasonic attenuation in NpTe

    NASA Astrophysics Data System (ADS)

    Singh, Devraj; Yadawa, Pramod K.; Sahu, Saurabh K.

    2010-08-01

    Ultrasonic attenuation due to electron-phonon interaction (EPI) has been computed in semimetallic single crystal neptunium telluride (NpTe) in low temperatures 5-80 K. For the same evaluation, we have also evaluated ultrasonic velocity, electronic viscosity and second order elastic constants (SOEC). The SOEC of NpTe have been evaluated using the Born model of ionic solid. The behaviour of ultrasonic attenuation is quite similar to its inverse resistivity. The ultrasonic attenuation due to EPI is most significant at 40 K. Computed results of ultrasonic parameter have been compared and discussed.

  17. ENHANCEMENTS TO NATURAL ATTENUATION: SELECTED CASE STUDIES

    SciTech Connect

    Vangelas, K; W. H. Albright, W; E. S. Becvar, E; C. H. Benson, C; T. O. Early, T; E. Hood, E; P. M. Jardine, P; M. Lorah, M; E. Majche, E; D. Major, D; W. J. Waugh, W; G. Wein, G; O. R. West, O

    2007-05-15

    In 2003 the US Department of Energy (DOE) embarked on a project to explore an innovative approach to remediation of subsurface contaminant plumes that focused on introducing mechanisms for augmenting natural attenuation to achieve site closure. Termed enhanced attenuation (EA), this approach has drawn its inspiration from the concept of monitored natural attenuation (MNA).

  18. Repetition priming results in sensitivity attenuation

    PubMed Central

    Allenmark, Fredrik; Hsu, Yi-Fang; Roussel, Cedric; Waszak, Florian

    2015-01-01

    Repetition priming refers to the change in the ability to perform a task on a stimulus as a consequence of a former encounter with that very same item. Usually, repetition results in faster and more accurate performance. In the present study, we used a contrast discrimination protocol to assess perceptual sensitivity and response bias of Gabor gratings that are either repeated (same orientation) or alternated (different orientation). We observed that contrast discrimination performance is worse, not better, for repeated than for alternated stimuli. In a second experiment, we varied the probability of stimulus repetition, thus testing whether the repetition effect is due to bottom-up or top-down factors. We found that it is top-down expectation that determines the effect. We discuss the implication of these findings for repetition priming and related phenomena as sensory attenuation. This article is part of a Special Issue entitled SI: Prediction and Attention. PMID:25819554

  19. A rack-mounted precision waveguide-below-cutoff attenuator with an absolute electronic readout

    NASA Technical Reports Server (NTRS)

    Cook, C. C.

    1974-01-01

    A coaxial precision waveguide-below-cutoff attenuator is described which uses an absolute (unambiguous) electronic digital readout of displacement in inches in addition to the usual gear driven mechanical counter-dial readout in decibels. The attenuator is rack-mountable and has the input and output RF connectors in a fixed position. The attenuation rate for 55, 50, and 30 MHz operation is given along with a discussion of sources of errors. In addition, information is included to aid the user in making adjustments on the attenuator should it be damaged or disassembled for any reason.

  20. Measured and calculated acoustic attenuation rates of tuned resonator arrays for two surface impedance distribution models with flow

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Abrahamson, A. Louis; Jones, Michael G.

    1988-01-01

    An experiment was performed to validate two analytical models for predicting low frequency attenuation of duct liner configurations built from an array of seven resonators that could be individually tuned via adjustable cavity depths. These analytical models had previously been developed for high frequency aero-engine inlet duct liner design. In the low frequency application, the liner surface impedance distribution is unavoidably spatially varying by virtue of available fabrication techniques. The characteristic length of this spatial variation may be a significant fraction of the acoustic wavelength. Comparison of measured and predicted attenuation rates and transmission losses for both modal decomposition and finite element propagation models were in good to excellent agreement for a test frequency range that included the first and second cavity resonance frequencies. This was true for either of two surface impedance distribution modeling procedures used to simplify the impedance boundary conditions. In the presence of mean flow, measurements revealed a fine scale structure of acoustic hot spots in the attenuation and phase profiles. These details were accurately predicted by the finite element model. Since no impedance changes due to mean flow were assumed, it is concluded that this fine scale structure was due to convective effects of the mean flow interacting with the surface impedance nonuniformities.

  1. Gas sensor with attenuated drift characteristic

    DOEpatents

    Chen, Ing-Shin [Danbury, CT; Chen, Philip S. H. [Bethel, CT; Neuner, Jeffrey W [Bethel, CT; Welch, James [Fairfield, CT; Hendrix, Bryan [Danbury, CT; Dimeo, Jr., Frank [Danbury, CT

    2008-05-13

    A sensor with an attenuated drift characteristic, including a layer structure in which a sensing layer has a layer of diffusional barrier material on at least one of its faces. The sensor may for example be constituted as a hydrogen gas sensor including a palladium/yttrium layer structure formed on a micro-hotplate base, with a chromium barrier layer between the yttrium layer and the micro-hotplate, and with a tantalum barrier layer between the yttrium layer and an overlying palladium protective layer. The gas sensor is useful for detection of a target gas in environments susceptible to generation or incursion of such gas, and achieves substantial (e.g., >90%) reduction of signal drift from the gas sensor in extended operation, relative to a corresponding gas sensor lacking the diffusional barrier structure of the invention

  2. Natural attenuation processes during in situ capping.

    PubMed

    Himmelheber, David W; Pennell, Kurt D; Hughes, Joseph B

    2007-08-01

    Chlorinated solvents are common groundwater contaminants that threaten surface water quality and benthic health when present in groundwater seeps. Aquatic sediments can act as natural biobarriers to detoxify chlorinated solvent plumes via reductive dechlorination. In situ sediment capping, a remedial technique in which clean material is placed at the sediment-water interface, may alter sedimentary natural attenuation processes. This research explores the potential of Anacostia River sediment to naturally attenuate chlorinated solvents under simulated capping conditions. Results of microcosm studies demonstrated that intrinsic dechlorination of dissolved-phase PCE to ethene was possible, with electron donor availability controlling microbial activity. A diverse microbial community was present in the sediment, including multiple Dehalococcoides strains indicated by the amplification of the reductive dehalogenases tceA, vcrA, and bvcA. An upflow column simulating a capped sediment bed subject to PCE-contaminated groundwater seepage lost dechlorination activity with time and only achieved complete dechlorination when microorganisms present in the sediment were provided electron donor. Increases in effluent chloroethene concentrations during the period of biostimulation were attributed to biologically enhanced desorption and the formation of less sorptive dechlorination products. These findings suggest that in situ caps should be designed to account for reductions in natural biobarrier reactivity and for the potential breakthrough of groundwater contaminants. PMID:17822095

  3. [ATTENUATED PSYCHOSIS SYNDROME: A LITERATURE REVIEW].

    PubMed

    Szmulewicz, Alejandro; Smith, José M; Valerio, Marina P

    2015-01-01

    Despite recent findings on the treatment of schizophrenia, it is an illness still associated with high morbidity and incapacity in social and work domains. There is a growing interest in examining the phases prior to the development of the illness so as to make early interventions that would potentially change its devastating course. The attenuated psychosis syndrome was included in the section III of the last version of the Diagnostic and Statistical Manual of Mental Disorders as a condition in which a patient exhibits mild psychotic symptoms, an intact reality testing and certain degree of social or occupational impairment. The present work is a review of the available literature on this subject. The main findings were: the risk of conversion to a psychotic disorder is relatively low and there are some variables (social withdrawal, negative symptoms, neurocognitive impairment, poor global functioning and certain neuroimaging findings) that increase this risk. Those people diagnosed with attenuated psychosis syndrome had one or more other current psychiatric comorbid conditions and these are the main reason to warrant medical attention. Regarding to the treatment of this condition, there are available evidence on atypical antipsychotics, cognitive-behavioral therapy and omega 3 fatty acid. PMID:26650554

  4. Natural and enhanced attenuation of metals

    SciTech Connect

    Rouse, J.V.; Pyrih, R.Z.

    1996-12-31

    The ability of natural earthen materials to attenuate the movement of contamination can be quantified in relatively simple geochemical experiments. In addition, the ability of subsurface material to attenuate potential contaminants can be enhanced through modifications to geochemical parameters such as pH or redox conditions. Such enhanced geochemical attenuation has been demonstrated at a number of sites to be a cost-effective alternative to conventional pump and treat operations. This paper describes the natural attenuation reactions which occur in the subsurface, and the way to quantify such attenuation. It also introduces the concept of enhanced geochemical attenuation, wherein naturally-occurring geochemical reactions can be used to achieve in situ fixation. The paper presents examples where such natural and enhanced attenuation have been implemented as a part of an overall remedy.

  5. Attenuated vaccines can recombine to form virulent field viruses.

    PubMed

    Lee, Sang-Won; Markham, Philip F; Coppo, Mauricio J C; Legione, Alistair R; Markham, John F; Noormohammadi, Amir H; Browning, Glenn F; Ficorilli, Nino; Hartley, Carol A; Devlin, Joanne M

    2012-07-13

    Recombination between herpesviruses has been seen in vitro and in vivo under experimental conditions. This has raised safety concerns about using attenuated herpesvirus vaccines in human and veterinary medicine and adds to other known concerns associated with their use, including reversion to virulence and disease arising from recurrent reactivation of lifelong chronic infection. We used high-throughput sequencing to investigate relationships between emergent field strains and vaccine strains of infectious laryngotracheitis virus (ILTV, gallid herpesvirus 1). We show that independent recombination events between distinct attenuated vaccine strains resulted in virulent recombinant viruses that became the dominant strains responsible for widespread disease in Australian commercial poultry flocks. These findings highlight the risks of using multiple different attenuated herpesvirus vaccines, or vectors, in the same populations. PMID:22798607

  6. Coriolis attenuation in the A congruent 130--150 region

    SciTech Connect

    Saha, M.; Goswami, A.; Bhattacharya, S.; Sen, S. )

    1990-10-01

    The particle-rotor model has been applied to calculate the band structure in a number of highly neutron deficient odd-{ital A} rare-earth nuclei in the {ital A}{congruent}130--150 region. Several transitional nuclei are also included in the study. The only adjustable parameter, used in the calculation, is the Coriolis attenuation coefficient. However, it is seen that the observed band structures in these nuclei can be reproduced practically without any {ital ad} {ital hoc} reduction of the Coriolis matrix elements. The systematics of the Coriolis attenuation in the neutron-deficient, transitional, and well-deformed rare-earth nuclei are discussed in the light of the present work and several theoretical studies, made earlier. The importance of the pairing interaction in the Coriolis attenuation study is emphasized.

  7. Pulse transducer with artifact signal attenuator. [heart rate sensors

    NASA Technical Reports Server (NTRS)

    Cash, W. H., Jr.; Polhemus, J. T. (Inventor)

    1980-01-01

    An artifact signal attenuator for a pulse rate sensor is described. The circuit for attenuating background noise signals is connected with a pulse rate transducer which has a light source and a detector for light reflected from blood vessels of a living body. The heart signal provided consists of a modulated dc signal voltage indicative of pulse rate. The artifact signal resulting from light reflected from the skin of the body comprises both a constant dc signal voltage and a modulated dc signal voltage. The amplitude of the artifact signal is greater and the frequency less than that of the heart signal. The signal attenuator circuit includes an operational amplifier for canceling the artifact signal from the output signal of the transducer and has the capability of meeting packaging requirements for wrist-watch-size packages.

  8. ATTENUATION OF REFLECTED WAVES IN MAN DURING RETROGRADE PROPAGATION FROM FEMORAL ARTERY TO PROXIMAL AORTA

    PubMed Central

    Baksi, A John; Davies, Justin E; Hadjiloizou, Nearchos; Baruah, Resham; Unsworth, Beth; Foale, Rodney A; Korolkova, Olga; Siggers, Jennifer H; Francis, Darrel P; Mayet, Jamil; Parker, Kim H; Hughes, Alun D

    2015-01-01

    Background Wave reflection may be an important influence on blood pressure, but the extent to which reflections undergo attenuation during retrograde propagation has not been studied. We quantified retrograde transmission of a reflected wave created by occlusion of the left femoral artery in man. Methods 20 subjects (age 31-83 y; 14 male) underwent invasive measurement of pressure and flow velocity with a sensor-tipped intra-arterial wire at multiple locations distal to the proximal aorta before, during and following occlusion of the left femoral artery by thigh cuff inflation. A numerical model of the circulation was also used to predict reflected wave transmission. Wave reflection was measured as the ratio of backward to forward wave energy (WRI) and the ratio of peak backward to forward pressure (Pb/Pf). Results Cuff inflation caused a marked reflection which was largest 5-10cm from the cuff (change (Δ) in WRI = 0.50 (95% CI 0.38, 0.62); p<0.001, ΔPb/Pf = 0.23 (0.18 - 0.29); p<0.001). The magnitude of the cuff-induced reflection decreased progressively at more proximal locations and was barely discernible at sites >40cm from the cuff including in the proximal aorta. Numerical modelling gave similar predictions to those observed experimentally. Conclusions Reflections due to femoral artery occlusion are markedly attenuated by the time they reach the proximal aorta. This is due to impedance mismatches of bifurcations traversed in the backward direction. This degree of attenuation is inconsistent with the idea of a large discrete reflected wave arising from the lower limb and propagating back into the aorta. PMID:26436672

  9. Benzene dispersion and natural attenuation in an alluvial aquifer with strong interactions with surface water

    NASA Astrophysics Data System (ADS)

    Batlle-Aguilar, Jordi; Brouyère, Serge; Dassargues, Alain; Morasch, Barbara; Hunkeler, Daniel; Höhener, Patrick; Diels, Ludo; Vanbroekhoven, Karolien; Seuntjens, Piet; Halen, Henri

    2009-05-01

    SummaryField and laboratory investigations have been conducted at a former coke plant, in order to assess pollutant attenuation in a contaminated alluvial aquifer, discharging to an adjacent river. Various organic (BTEX, PAHs, mineral oils) and inorganic (As, Zn, Cd) compounds were found in the aquifer in concentrations exceeding regulatory values. Due to redox conditions of the aquifer, heavy metals were almost immobile, thus not posing a major risk of dispersion off-site the brownfield. Field and laboratory investigations demonstrated that benzene, among organic pollutants, presented the major worry for off-site dispersion, mainly due to its mobility and high concentration, i.e. up to 750 mg L -1 in the source zone. However, benzene could never be detected near the river which is about 160 m downgradient the main source. Redox conditions together with benzene concentrations determined in the aquifer have suggested that degradation mainly occurred within 100 m distance from the contaminant source under anoxic conditions, and most probably with sulphate as main oxidant. A numerical groundwater flow and transport model, calibrated under transient conditions, was used to simulate benzene attenuation in the alluvial aquifer towards the Meuse River. The mean benzene degradation rate used in the model was quantified in situ along the groundwater flow path using compound-specific carbon isotope analysis (CSIA). The results of the solute transport simulations confirmed that benzene concentrations decreased almost five orders of magnitude 70 m downgradient the source. Simulated concentrations have been found to be below the detection limit in the zone adjacent to the river and consistent with the absence of benzene in downgradient piezometers located close to the river reported in groundwater sampling campaigns. In a transient model scenario including groundwater-surface water dynamics, benzene concentrations were observed to be inversely correlated to the river water

  10. A web-based tutorial for ultrasonic attenuation measurement

    NASA Astrophysics Data System (ADS)

    Margetan, Frank J.; Barnard, Dan; Orman, David; Feygin, Alex; Pavel, Brittney

    2014-02-01

    An ultrasonic attenuation-versus-frequency curve can serve as an "ultrasonic signature" which may be correlated with microstructural properties of interest such as grain size in metals or porosity level in composites. Attenuation also plays a role in ultrasonic inspections and is consequently a key input into many inspection simulation models. A web-based self-tutorial on practical attenuation measurements is under development. The focus is on pulse/echo immersion measurements made using a broadband transducer to deduce attenuation within the transducer's useable bandwidth. Two approaches are considered: one using a calibration specimen having a known attenuation curve, and one without. In the first approach a back-wall (BW) echo in the calibration specimen is compared with a BW echo in the test specimen. In the second approach various BW reverberation echoes in the test specimen are compared with one another or with a front-wall echo. The web-based tutorial incorporates three classes of materials. The first includes written documentation and videos describing the measurement setups, the data-acquisition and analysis procedures, and the underlying models use to analyze the raw UT data. Secondly, general purpose "stand-alone" data-analysis software is supplied that is designed to be used with any ultrasonic inspection system that can output A-scan data as a text file. This includes both FORTRAN software and Excel spreadsheet calculators that accept A-scan text data as inputs. Thirdly, we supply demonstration software where the data acquisition and analysis procedures are integrated with a specific class of commercial ultrasonic test instruments, namely those running UTEX Winpect control software. This paper provides an overview of the measurement methods and tutorial materials. We also present early results from round-robin trials in which selected metal and composite specimens are being sent to participating partners for attenuation measurement.

  11. Design and Simulation of Microwave Attenuators for Superconducting Quantum Devices

    NASA Astrophysics Data System (ADS)

    Lefebvre, Jay; Yeh, Jen-Hao; Wellstood, Frederick; Palmer, Benjamin

    We have found that dephasing times for quantum superconducting transmons operating nominally at T = 20 mK can be limited by thermal photons in the read-out cavity due to non-equilibrium noise on our input microwave line. In an effort to reduce this noise, we have used finite-element simulations to design attenuators that provide better thermalization of the input microwave signals being delivered to our devices. Our thermal simulations incorporate both electron-phonon decoupling effects due to dissipated power in each element of the attenuator as well as phonon thermal conduction and Kapitza boundary effects. We combine the resulting thermal map with a thermal noise model of each dissipative element of the filter to estimate the effective noise temperature of our filter design.

  12. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Joel Walls; M.T. Taner; Naum Derzhi; Gary Mavko; Jack Dvorkin

    2003-04-01

    In this report we will show some new Q related seismic attributes on the Burlington-Seitel data set. One example will be called Energy Absorption Attribute (EAA) and is based on a spectral analysis. The EAA algorithm is designed to detect a sudden increase in the rate of exponential decay in the relatively higher frequency portion of the spectrum. In addition we will show results from a hybrid attribute that combines attenuation with relative acoustic impedance to give a better indication of commercial gas saturation.

  13. A broadband DC to 20 GHz 3-bit MEMS digital attenuator

    NASA Astrophysics Data System (ADS)

    Sun, Junfeng; Zhu, Jian; Jiang, Lili; Yu, Yuanwei; Li, Zhiqun

    2016-05-01

    A 3-bit microelectromechanical system (MEMS) digital attenuator is designed with 0–20 GHz bandwidth. The attenuation ranges from 0 to 35 dB with 5 dB step. The attenuator, with the coplanar waveguide (CPW), is implemented by surface sacrificial layer technology. The DC-contact MEMS switches with three contact dimples are symmetrically placed around the T type resistor network, making the switches minimum in number and the structure compact. Through the lumped parameter method, the attenuator has good terminal matches in different attenuation states. The test results show that eight different attenuation states are realized within 0–20 GHz. The attenuation deviation is less than  ±5%, the insertion loss is less than 1.7 dB and the voltage standing wave rations is less than 1.4 under most of the attenuation states. With the MEMS switches and CPW being adopted, the attenuator has the advantages of higher linearity, lower insertion loss and power consumption. The chip size is about 3.2 mm2 including the pad. This work was supported by the International Science & Technology Cooperation Program of China (2013DFB10300).

  14. Identification of the attenuation potential of a karst aquifer by an artificial dualtracer experiment with caffeine.

    PubMed

    Hillebrand, Olav; Nödler, Karsten; Licha, Tobias; Sauter, Martin; Geyer, Tobias

    2012-10-15

    Little is known with respect to the attenuation capacity of karst aquifers. Even less is known about the risk posed by emerging micropollutants in these systems. In order to identify the attenuation potential of karst aquifers in-situ and to estimate the risk posed by micropollutants, a dualtracer test was conducted in this study in order to investigate differential transport in the subsurface: The reactive compound caffeine was used as a tracer to indicate the attenuation capacity within the aquifer in-situ. Due to the low limit of quantification, only small amounts of caffeine needed to be injected. To calibrate a model and to visualize the attenuation of caffeine a conservative reference tracer (uranine) is injected simultaneously. The methodology is tested in a well-characterised karst system in southwest Germany. The results indicate a significantly higher attenuation rate than was expected for karst aquifers. The attenuation is decribed as a first-order process. The corresponding half-life is 104 h. This low half-life suggests that a generally assumed low natural attenuation capacity of karst aquifers is unjustified. The observed mass loss of caffeine illustrates the potential of caffeine to be used as reactive tracer for indicating in-situ attenuation capacity within highly hydraulically conductive systems, such as karst aquifers. Due to the high attenuation rate of caffeine it does not pose a threat as a long-time contaminant. In combination with a conservative reference tracer an economical and environmentally benign method is presented in this manuscript for the in-situ determination of the attenuation capacity of highly conductive aquifer systems. PMID:22877878

  15. Evidence of oxidative attenuation of auxin signalling.

    PubMed

    Peer, Wendy Ann; Cheng, Yan; Murphy, Angus S

    2013-06-01

    Indole-3-acetic acid (IAA) is the principle auxin in Arabidopsis and is synthesized primarily in meristems and nodes. Auxin is transported to distal parts of the plant in response to developmental programming or environmental stimuli to activate cell-specific responses. As with any signalling event, the signal must be attenuated to allow the system to reset. Local auxin accumulations are thus reduced by conjugation or catabolism when downstream responses have reached their optima. In most cell types, localized auxin accumulation increases both reactive oxygen species (ROS) and an irreversible catabolic product 2-oxindole-3-acid acid (oxIAA). oxIAA is inactive and does not induce expression of the auxin-responsive reporters DR5 or 2XD0. Here it is shown that oxIAA is not transported from cell to cell, although it appears to be a substrate for the ATP-binding cassette subfamily G (ABCG) transporters that are positioned primarily on the outer lateral surface of the root epidermis. However, oxIAA and oxIAA-Glc levels are higher in ABCB mutants that accumulate auxin due to defective cellular export. Auxin-induced ROS production appears to be at least partially mediated by the NAD(P)H oxidase RbohD. oxIAA levels are higher in mutants that lack ROS-scavenging flavonoids (tt4) and are lower in mutants that accumulate excess flavonols (tt3). These data suggest a model where IAA signalling is attenuated by IAA catabolism to oxIAA. Flavonoids appear to buffer ROS accumulations that occur with localized increases in IAA. This buffering of IAA oxidation would explain some growth responses observed in flavonoid-deficient mutants that cannot be explained by their established role in partially inhibiting auxin transport. PMID:23709674

  16. Attenuation of experimental colitis in glutathione peroxidase 1 and catalase double knockout mice through enhancing regulatory T cell function.

    PubMed

    Kim, Hyung-Ran; Lee, Anbok; Choi, Eun-Jeong; Kie, Jeong-Hae; Lim, Woosung; Lee, Hyeon Kook; Moon, Byung-In; Seoh, Ju-Young

    2014-01-01

    Reactive oxygen species (ROS) have been implicated in the progression of inflammatory diseases including inflammatory bowel diseases (IBD). Meanwhile, several studies suggested the protective role of ROS in immune-mediated inflammatory diseases, and it was recently reported that dextran sodium sulfate (DSS)-induced colitis was attenuated in mice with an elevated level of ROS due to deficiency of peroxiredoxin II. Regulatory T cells (Tregs) are critical in the prevention of IBD and Treg function was reported to be closely associated with ROS level, but it has been investigated only in lowered levels of ROS so far. In the present study, in order to clarify the relationship between ROS level and Treg function, and their role in the pathogenesis of IBD, we investigated mice with an elevated level of ROS due to deficiency of both glutathione peroxidase (GPx)-1 and catalase (Cat) for the susceptibility of DSS-induced colitis in association with Treg function. The results showed that DSS-induced colitis was attenuated and Tregs were hyperfunctional in GPx1-/- × Cat-/- mice. In vivo administration of N-acetylcysteine (NAC) aggravated DSS-induced colitis and decreased Treg function to the level comparable to WT mice. Attenuated Th17 cell differentiation from naïve CD4+ cells as well as impaired production of IL-6 and IL-17A by splenocytes upon stimulation suggested anti-inflammatory tendency of GPx1-/- × Cat-/- mice. Suppression of Stat3 activation in association with enhancement of indoleamine 2,3-dioxygenase and FoxP3 expression might be involved in the immunosuppressive mechanism of GPx1-/- × Cat-/- mice. Taken together, it is implied that ROS level is critical in the regulation of Treg function, and IBD may be attenuated in appropriately elevated levels of ROS. PMID:24743300

  17. Computing the Seismic Attenuation in Complex Porous Materials

    NASA Astrophysics Data System (ADS)

    Masson, Yder Jean

    The present work analyzes seismic attenuation due to wave-induced flow in complex poroelastic materials containing an arbitrary amount of heterogeneity and fully or partially saturated with a mixture of fluids. In the first part, two distinct finite-difference (FDTD) numerical schemes for solving Biot's poroelastic set of equations are introduced. The first algorithm is designed to be used in the seismic band of frequencies; i.e., when the permeability of the medium doesn't depend on frequency. The second algorithm accounts for viscous boundary layers that appear in the pores at high frequencies (in this case, the permeability depends on frequency) and can be used across the entire band of frequencies. An innovative numerical method is presented in the second part allowing computation of seismic attenuation due to wave-induced flow for any poroelastic material. This method is applied to study the attenuation associated with different classes of materials saturated with a single fluid (water). For a material having a self-affine (fractal) distribution of elastic properties, it is demonstrated that frequency dependence in the attenuation is controlled by a single parameter that is directly related to the fractal dimension of the material. For anisotropic materials, a relation is established between the attenuation levels associated with waves propagating in different directions and the geometrical aspect ratio of the heterogeneities present within the material. The third part concerns the study of attenuation associated with materials having a homogeneous solid skeleton saturated with a mixture of immiscible fluids. The special case where the distribution of fluids is the result of an invasion-percolation process is treated in detail. Finally, the last part presents a novel experimental setup designed to measure fluctuations of the elastic properties in real rock samples. This device performs automated micro-indentation tests at the surface of rock samples and

  18. Estuarine wetland evolution including sea-level rise and infrastructure effects.

    NASA Astrophysics Data System (ADS)

    Rodriguez, Jose Fernando; Trivisonno, Franco; Rojas, Steven Sandi; Riccardi, Gerardo; Stenta, Hernan; Saco, Patricia Mabel

    2015-04-01

    Estuarine wetlands are an extremely valuable resource in terms of biotic diversity, flood attenuation, storm surge protection, groundwater recharge, filtering of surface flows and carbon sequestration. On a large scale the survival of these systems depends on the slope of the land and a balance between the rates of accretion and sea-level rise, but local man-made flow disturbances can have comparable effects. Climate change predictions for most of Australia include an accelerated sea level rise, which may challenge the survival of estuarine wetlands. Furthermore, coastal infrastructure poses an additional constraint on the adaptive capacity of these ecosystems. Numerical models are increasingly being used to assess wetland dynamics and to help manage some of these situations. We present results of a wetland evolution model that is based on computed values of hydroperiod and tidal range that drive vegetation preference. Our first application simulates the long term evolution of an Australian wetland heavily constricted by infrastructure that is undergoing the effects of predicted accelerated sea level rise. The wetland presents a vegetation zonation sequence mudflats - mangrove - saltmarsh from the seaward margin and up the topographic gradient but is also affected by compartmentalization due to internal road embankments and culverts that effectively attenuates tidal input to the upstream compartments. For this reason, the evolution model includes a 2D hydrodynamic module which is able to handle man-made flow controls and spatially varying roughness. It continually simulates tidal inputs into the wetland and computes annual values of hydroperiod and tidal range to update vegetation distribution based on preference to hydrodynamic conditions of the different vegetation types. It also computes soil accretion rates and updates roughness coefficient values according to evolving vegetation types. In order to explore in more detail the magnitude of flow attenuation due to

  19. Gust response of commercial jet aircraft including effects of autopilot operation

    NASA Technical Reports Server (NTRS)

    Goldberg, J. H.

    1982-01-01

    A simplified theory of aircraft vertical acceleration gust response based on a model including pitch, vertical displacement and control motions due to autopilot operation is presented. High-order autopilot transfer functions are utilized for improved accuracy in the determination of the overall response characteristics. Four representative commercial jet aircraft were studied over a wide range of operating conditions and comparisons of individual responses are given. It is shown that autopilot operation relative to the controls fixed case causes response attenuation of from 10 percent to approximately 25 percent depending on flight condition and increases in crossing number up to 30 percent, with variations between aircraft of from 5 percent to 10 percent, in general, reflecting the differences in autopilot design. A detailed computer program description and listing of the calculation procedure suitable for the general application of the theory to any airplane autopilot combination is also included.

  20. Attenuation of shock waves propagating through nano-structured porous materials

    NASA Astrophysics Data System (ADS)

    Al-Qananwah, Ahmad K.; Koplik, Joel; Andreopoulos, Yiannis

    2013-07-01

    Porous materials have long been known to be effective in energy absorption and shock wave attenuation. These properties make them attractive in blast mitigation strategies. Nano-structured materials have an even greater potential for blast mitigation because of their high surface-to-volume ratio, a geometric parameter which substantially attenuates shock wave propagation. A molecular dynamics approach was used to explore the effects of this remarkable property on the behavior of traveling shocks impacting on solid materials. The computational setup included a moving piston, a gas region and a target solid wall with and without a porous structure. The gas and porous solid were modeled by Lennard-Jones-like and effective atom potentials, respectively. The shock wave is resolved in space and time and its reflection from a solid wall is gradual, due to the wave's finite thickness, and entails a self-interaction as the reflected wave travels through the incoming incident wave. Cases investigated include a free standing porous structure, a porous structure attached to a wall and porous structures with graded porosity. The effects of pore shape and orientation have been also documented. The results indicate that placing a nano-porous material layer in front of the target wall reduced the stress magnitude and the energy deposited inside the solid by about 30 percent, while at the same time substantially decreasing the loading rate.

  1. Two-dimensional acoustic attenuation mapping of high-temperature interstitial ultrasound lesions

    NASA Astrophysics Data System (ADS)

    Tyréus, Per Daniel; Diederich, Chris

    2004-02-01

    Acoustic attenuation change in biological tissues with temperature and time is a critical parameter for interstitial ultrasound thermal therapy treatment planning and applicator design. Earlier studies have not fully explored the effects on attenuation of temperatures (75-95 °C) and times (5-15 min) common in interstitial ultrasound treatments. A scanning transmission ultrasound attenuation measurement system was devised and used to measure attenuation changes due to these types of thermal exposures. To validate the approach and to loosely define expected values, attenuation changes in degassed ex vivo bovine liver, bovine brain and chicken muscle were measured after 10 min exposures in a water bath to temperatures up to 90 °C. Maximum attenuation increases of approximately seven, four and two times the values at 37 °C were measured for the three tissue models at 5 MHz. By using the system to scan over lesions produced using interstitial ultrasound applicators, 2D contour maps of attenuation were produced. Attenuation profiles measured through the centrelines of lesions showed that attenuation was highest close to the applicator and decreased with radial distance, as expected with decreasing thermal exposure. Attenuation values measured in profiles through lesions were also shown to decrease with reduced power to the applicator. Attenuation increases in 2D maps of interstitial ultrasound lesions in ex vivo chicken breast, bovine liver and bovine brain were correlated with visible tissue coagulation. While regions of visible coagulation corresponded well to contours of attenuation increase in liver and chicken, no lesion was visible under the same experimental conditions in brain, due primarily to the heterogeneity of the tissue. Acoustic and biothermal simulations were employed to show that attenuation models taking into account these attenuation changes at higher temperatures and longer times were better able to fit experimental data than previous models. These

  2. Flux attenuation at NREL`s High-Flux Solar Furnace

    SciTech Connect

    Bingham, C E; Scholl, K L; Lewandowski, A A

    1994-10-01

    The High-Flux Solar Furnace (HFSF) at the National Renewable Energy Laboratory (NREL) has a faceted primary concentrator and a long focal-length-to-diameter ratio (due to its off-axis design). Each primary facet can be aimed individually to produce different flux distributions at the target plane. Two different types of attenuators are used depending on the flux distribution. A sliding-plate attenuator is used primarily when the facets are aimed at the same target point. The alternate attenuator resembles a venetian blind. Both attenuators are located between the concentrator and the focal point. The venetian-blind attenuator is primarily used to control the levels of sunlight failing on a target when the primary concentrators are not focused to a single point. This paper will demonstrate the problem of using the sliding-plate attenuator with a faceted concentrator when the facets are not aimed at the same target point. We will show that although the alternate attenuator necessarily blocks a certain amount of incoming sunlight, even when fully open, it provides a more even attenuation of the flux for alternate aiming strategies.

  3. Occurrence and in-stream attenuation of wastewater-derived pharmaceuticals in Iberian rivers.

    PubMed

    Acuña, Vicenç; von Schiller, Daniel; García-Galán, Maria Jesús; Rodríguez-Mozaz, Sara; Corominas, Lluís; Petrovic, Mira; Poch, Manel; Barceló, Damià; Sabater, Sergi

    2015-01-15

    A multitude of pharmaceuticals enter surface waters via discharges of wastewater treatment plants (WWTPs), and many raise environmental and health concerns. Chemical fate models predict their concentrations using estimates of mass loading, dilution and in-stream attenuation. However, current comprehension of the attenuation rates remains a limiting factor for predictive models. We assessed in-stream attenuation of 75 pharmaceuticals in 4 river segments, aiming to characterize in-stream attenuation variability among different pharmaceutical compounds, as well as among river segments differing in environmental conditions. Our study revealed that in-stream attenuation was highly variable among pharmaceuticals and river segments and that none of the considered pharmaceutical physicochemical and molecular properties proved to be relevant in determining the mean attenuation rates. Instead, the octanol-water partition coefficient (Kow) influenced the variability of rates among river segments, likely due to its effect on sorption to sediments and suspended particles, and therefore influencing the balance between the different attenuation mechanisms (biotransformation, photolysis, sorption, and volatilization). The magnitude of the measured attenuation rates urges scientists to consider them as important as dilution when aiming to predict concentrations in freshwater ecosystems. PMID:24908335

  4. [Attenuation of photosynthetically available radiation (PAR) in Meiliang Bay under different winds and waves].

    PubMed

    Zhang, Yunlin; Qin, Boqiang; Chen, Weimin; Hu, Weiping; Gao, Guang; Zhu, Guangwei; Luo, Liancong

    2005-06-01

    Based on the successive underwater irradiance measurement in situ from Jul. 12 to 17 in 2003, the attenuation of photosynthetically available radiation (PAR) and euphotic depth in Meiliang Bay were analyzed under different winds and waves. The results showed that the downward PAR attenuation coefficients ranged from 2.63 to 4.7 m(-1), with an average of 3.63 +/- 0.47 x m(-1), and the corresponding euphotic depth ranged from 0.98 to 1.75 m, with an average of 1.29 +/- 0.18 m, which demonstrated that phytoplankton and macrophyte could not grow below 1.5 m due to the lack of adequate solar radiation. The total suspended solids resulted from wind and wave increased the attenuation of light, with the downward attenuation coefficients of PAR being 2.63, 3.72 and 4.37 x m(-1) under small, medium and large wind and wave, respectively. Significant linear correlations were found between transparence, PAR attenuation coefficient, euphotic depth and total suspended solid, especially inorganic suspended solid, while chlorophyll a was the most nonsignificant light attenuator. Multiple stepwise linear regressions showed that inorganic suspended solid was the most important light attenuator dominating the light attenuation in wind-exposed Meiliang Bay. PMID:16180769

  5. Calculation Of Pneumatic Attenuation In Pressure Sensors

    NASA Technical Reports Server (NTRS)

    Whitmore, Stephen A.

    1991-01-01

    Errors caused by attenuation of air-pressure waves in narrow tubes calculated by method based on fundamental equations of flow. Changes in ambient pressure transmitted along narrow tube to sensor. Attenuation of high-frequency components of pressure wave calculated from wave equation derived from Navier-Stokes equations of viscous flow in tube. Developed to understand and compensate for frictional attenuation in narrow tubes used to connect aircraft pressure sensors with pressure taps on affected surfaces.

  6. General relationships between ultrasonic attenuation and dispersion

    NASA Technical Reports Server (NTRS)

    Odonnell, M.; Jaynes, E. T.; Miller, J. G.

    1978-01-01

    General relationships between the ultrasonic attenuation and dispersion are presented. The validity of these nonlocal relationships hinges only on the properties of causality and linearity, and does not depend upon details of the mechanism responsible for the attenuation and dispersion. Approximate, nearly local relationships are presented and are demonstrated to predict accurately the ultrasonic dispersion in solutions of hemoglobin from the results of attenuation measurements.

  7. Global Attenuation Model of the Upper Mantle

    NASA Astrophysics Data System (ADS)

    Adenis, A.; Debayle, E.; Ricard, Y. R.

    2015-12-01

    We present a three-dimensional shear attenuation model based on a massive surface wave data-set (372,629 Rayleigh waveforms analysed in the period range 50-300s by Debayle and Ricard, 2012). For each seismogram, this approach yields depth-dependent path average models of shear velocity and quality factor, and a set of fundamental and higher-mode dispersion and attenuation curves. We combine these attenuation measurements in a tomographic inversion after a careful rejection of the noisy data. We first remove data likely to be biased by a poor knowledge of the source. Then we assume that waves corresponding to events having close epicenters and recorded at the same station sample the same elastic and anelastic structure, we cluster the corresponding rays and average the attenuation measurements. Logarithms of the attenuations are regionalized using the non-linear east square formalism of Tarantola and Valette (1982), resulting in attenuation tomographic maps between 50s and 300s. After a first inversion, outlyers are rejected and a second inversion yields a moderate variance reduction of about 20%. We correct the attenuation curves for focusing effect using the linearized ray theory of Woodhouse and Wong (1986). Accounting for focussing effects allows building tomographic maps with variance reductions reaching 40%. In the period range 120-200s, the root mean square of the model perturbations increases from about 5% to 20%. Our 3-D attenuation models present strong agreement with surface tectonics at period lower than 200s. Areas of low attenuation are located under continents and areas of high attenuation are associated with oceans. Surprisingly, although mid oceanic ridges are located in attenuating regions, their signature, even if enhanced by focusing corrections, remains weaker than in the shear velocity models. Synthetic tests suggests that regularisation contributes to damp the attenuation signature of ridges, which could therefore be underestimated.

  8. Mosaic Attenuation: Etiology, Methods of Differentiation, and Pitfalls.

    PubMed

    Kligerman, Seth J; Henry, Travis; Lin, Cheng T; Franks, Teri J; Galvin, Jeffrey R

    2015-01-01

    Mosaic attenuation is a commonly encountered pattern on computed tomography that is defined as heterogeneous areas of differing lung attenuation. This heterogeneous pattern of attenuation is the result of diverse causes that include diseases of the small airways, pulmonary vasculature, alveoli, and interstitium, alone or in combination. Small airways disease can be a primary disorder, such as respiratory bronchiolitis or constrictive bronchiolitis, or be part of parenchymal lung disease, such as hypersensitivity pneumonitis, or large airways disease, such as bronchiectasis and asthma. Vascular causes resulting in mosaic attenuation are typically chronic thromboembolic pulmonary hypertension, which is characterized by organizing thrombi in the elastic pulmonary arteries, or pulmonary arterial hypertension, a heterogeneous group of diseases affecting the distal pulmonary arterioles. Diffuse ground-glass opacity can result in a mosaic pattern related to a number of processes in acute (eg, infection, pulmonary edema), subacute (eg, organizing pneumonia), or chronic (eg, fibrotic diseases) settings. Imaging clues that can assist the radiologist in pinpointing a diagnosis include evidence of large airway involvement, cardiovascular abnormalities, septal thickening, signs of fibrosis, and demonstration of airtrapping at expiratory imaging. PMID:26274445

  9. Differential dust attenuation in CALIFA galaxies

    NASA Astrophysics Data System (ADS)

    Vale Asari, N.; Cid Fernandes, R.; Amorim, A. L.; Lacerda, E. A. D.; Schlickmann, M.; Wild, V.; Kennicutt, R. C.

    2016-06-01

    Dust attenuation has long been treated as a simple parameter in SED fitting. Real galaxies are, however, much more complicated: The measured dust attenuation is not a simple function of the dust optical depth, but depends strongly on galaxy inclination and the relative distribution of stars and dust. We study the nebular and stellar dust attenuation in CALIFA galaxies, and propose some empirical recipes to make the dust treatment more realistic in spectral synthesis codes. By adding optical recombination emission lines, we find better constraints for differential attenuation. Those recipes can be applied to unresolved galaxy spectra, and lead to better recovered star formation rates.

  10. Atmospheric attenuation calibrations of surface weather observations

    NASA Technical Reports Server (NTRS)

    Sanii, Babak

    2001-01-01

    A correlation between near-IR atmospheric attenuation measurements made by the Atmospheric Visibility Monitor (AVM) at the Table Mountain Facility and airport surface weather observations at Edwards Air Force Base has been performed. High correlations (over 0.93) exist between the simultaneous Edwards observed sky cover and the average AVM measured attenuations over the course of the 10 months analyzed. The statistical relationship between the data-sets allows the determination of coarse attenuation statistics from the surface observations, suggesting that such statistics may be extrapolated from any surface weather observation site, Furthermore, a superior technique for converting AVM images to attenuation values by way of MODTRAN predictions has been demonstrated.

  11. Seismic attenuation in upper ocean crust at Hole 504B

    NASA Astrophysics Data System (ADS)

    Swift, Stephen A.; Lizarralde, D.; Stephen, Ralph A.; Hoskins, Hartley

    1998-11-01

    Seismic attenuation and its relationship to borehole stratigraphy in the upper 1.8 km of ocean basement at Hole 504B are determined from analysis of vertical seismic profile (VSP) data. VSP data provide unambiguous measurements of seismic amplitude decay along a vertical propagation path through the crust, and ancillary borehole measurements enable detailed modeling of the relative contributions from geometrical spreading, scattering, and intrinsic loss mechanisms to this decay. About 60% of the total observed amplitude decay occurs in the pillow basalt section and is due mostly to geometrical spreading and scattering from impedance contrasts. The remaining amplitude decrease is concentrated in two layers, at 500-650 and 800-900 meters below seafloor (mbsf) (225-375 and 525-625 m below basement), across which amplitude rapidly decays and the frequency characteristics of the downgoing wave field are significantly and permanently modified. Attenuation in these layers is not due to scattering but rather to an intrinsic mechanism that can be characterized by Q of 10 and 8, respectively. It is likely that the Q structure of both of these intervals is formed with the crust near the ridge and thus related to fundamental ocean crust forming processes. The shallow interval coincides with a change in alteration mineralogy deposited by late-stage fluid flow and may separate lower lavas that were emplaced within the rift zone from upper lavas that were emplaced by off-axis flow through large lava tubes. Intrinsic attenuation in the deeper horizon is probably due to an increase in porosity and cracking associated with either intracrustal deformation or subhorizontal faulting. There is negligible attenuation of seismic frequencies in the dikes below 1000 mbsf (˜725 m subbasement).

  12. Enhanced Attenuation Technologies: Passive Soil Vapor Extraction

    SciTech Connect

    Vangelas, K.; Looney, B.; Kamath, R.; Adamson, D.; Newell, C.

    2010-03-15

    Passive soil vapor extraction (PSVE) is an enhanced attenuation (EA) approach that removes volatile contaminants from soil. The extraction is driven by natural pressure gradients between the subsurface and atmosphere (Barometric Pumping), or by renewable sources of energy such as wind or solar power (Assisted PSVE). The technology is applicable for remediating sites with low levels of contamination and for transitioning sites from active source technologies such as active soil vapor extraction (ASVE) to natural attenuation. PSVE systems are simple to design and operate and are more cost effective than active systems in many scenarios. Thus, PSVE is often appropriate as an interim-remedial or polishing strategy. Over the past decade, PSVE has been demonstrated in the U.S. and in Europe. These demonstrations provide practical information to assist in selecting, designing and implementing the technology. These demonstrations indicate that the technology can be effective in achieving remedial objectives in a timely fashion. The keys to success include: (1) Application at sites where the residual source quantities, and associated fluxes to groundwater, are relatively low; (2) Selection of the appropriate passive energy source - barometric pumping in cases with a deep vadose zone and barrier (e.g., clay) layers that separate the subsurface from the atmosphere and renewable energy assisted PSVE in other settings and where higher flow rates are required. (3) Provision of sufficient access to the contaminated vadose zones through the spacing and number of extraction wells. This PSVE technology report provides a summary of the relevant technical background, real-world case study performance, key design and cost considerations, and a scenario-based cost evaluation. The key design and cost considerations are organized into a flowchart that dovetails with the Enhanced Attenuation: Chlorinated Organics Guidance of the Interstate Technology and Regulatory Council (ITRC). The PSVE

  13. Low consumption power variable optical attenuator with sol-gel derived organic/inorganic hybrid materials

    NASA Astrophysics Data System (ADS)

    Li, Dongxiao; Zhang, Yanwu; Liu, Liying; Xu, Lei

    2006-06-01

    An integrated optical waveguide variable optical attenuator (VOA) made of organic/inorganic hybrid materials was fabricated. At 1550 nm, the VOA showed a very low activation power of about 13 mW, due to the large thermo-optic coefficients of the hybrid materials. The optical power attenuations achieved were more than 25 dB for both TE and TM polarization. The response time of the device was less than 4.7 ms.

  14. Papilledema Due to Mirtazapine

    PubMed Central

    Ceylan, Mehmet Emin; Evrensel, Alper; Cömert, Gökçe

    2016-01-01

    Background: Mirtazapine is a tetracyclic antidepressant that enhances both noradrenergic and serotonergic transmission. The most common cause of papilledema is increased intracranial pressure due to brain tumor. Also it may occur as a result of idiopathic intracranial hypertension (IIH, pseudo tumor cerebri). Moreover, papilledema may also develop due to retinitis, vasculitis, Graves’ disease, hypertension, leukemia, lymphoma, diabetes mellitus and radiation. Case Report: In this article, a patient who developed papilledema while under treatment with mirtazapine (30 mg/day) for two years and recovered with termination of mirtazapine treatment was discussed to draw the attention of clinicians to this side effect of mirtazapine. Conclusion: Idiopathic intracranial hypertension and papilledema due to psychotropic drugs has been reported in the literature. Mirtazapine may rarely cause peripheral edema. However, papilledema due to mirtazapine has not been previously reported. Although papilledema is a very rare side effect of an antidepressant treatment, fundoscopic examinations of patients must be performed regularly. PMID:27308085

  15. Simultaneous reconstruction of emission activity and attenuation coefficient distribution from TOF data, acquired with external transmission source

    NASA Astrophysics Data System (ADS)

    Panin, V. Y.; Aykac, M.; Casey, M. E.

    2013-06-01

    The simultaneous PET data reconstruction of emission activity and attenuation coefficient distribution is presented, where the attenuation image is constrained by exploiting an external transmission source. Data are acquired in time-of-flight (TOF) mode, allowing in principle for separation of emission and transmission data. Nevertheless, here all data are reconstructed at once, eliminating the need to trace the position of the transmission source in sinogram space. Contamination of emission data by the transmission source and vice versa is naturally modeled. Attenuated emission activity data also provide additional information about object attenuation coefficient values. The algorithm alternates between attenuation and emission activity image updates. We also proposed a method of estimation of spatial scatter distribution from the transmission source by incorporating knowledge about the expected range of attenuation map values. The reconstruction of experimental data from the Siemens mCT scanner suggests that simultaneous reconstruction improves attenuation map image quality, as compared to when data are separated. In the presented example, the attenuation map image noise was reduced and non-uniformity artifacts that occurred due to scatter estimation were suppressed. On the other hand, the use of transmission data stabilizes attenuation coefficient distribution reconstruction from TOF emission data alone. The example of improving emission images by refining a CT-based patient attenuation map is presented, revealing potential benefits of simultaneous CT and PET data reconstruction.

  16. Simultaneous reconstruction of emission activity and attenuation coefficient distribution from TOF data, acquired with external transmission source.

    PubMed

    Panin, V Y; Aykac, M; Casey, M E

    2013-06-01

    The simultaneous PET data reconstruction of emission activity and attenuation coefficient distribution is presented, where the attenuation image is constrained by exploiting an external transmission source. Data are acquired in time-of-flight (TOF) mode, allowing in principle for separation of emission and transmission data. Nevertheless, here all data are reconstructed at once, eliminating the need to trace the position of the transmission source in sinogram space. Contamination of emission data by the transmission source and vice versa is naturally modeled. Attenuated emission activity data also provide additional information about object attenuation coefficient values. The algorithm alternates between attenuation and emission activity image updates. We also proposed a method of estimation of spatial scatter distribution from the transmission source by incorporating knowledge about the expected range of attenuation map values. The reconstruction of experimental data from the Siemens mCT scanner suggests that simultaneous reconstruction improves attenuation map image quality, as compared to when data are separated. In the presented example, the attenuation map image noise was reduced and non-uniformity artifacts that occurred due to scatter estimation were suppressed. On the other hand, the use of transmission data stabilizes attenuation coefficient distribution reconstruction from TOF emission data alone. The example of improving emission images by refining a CT-based patient attenuation map is presented, revealing potential benefits of simultaneous CT and PET data reconstruction. PMID:23648397

  17. Underwing compression vortex attenuation device

    NASA Technical Reports Server (NTRS)

    Patterson, James C., Jr. (Inventor)

    1993-01-01

    A vortex attenuation device is presented which dissipates a lift-induced vortex generated by a lifting aircraft wing. The device consists of a positive pressure gradient producing means in the form of a compression panel attached to the lower surface of the wing and facing perpendicular to the airflow across the wing. The panel is located between the midpoint of the local wing cord and the trailing edge in the chord-wise direction and at a point which is approximately 55 percent of the wing span as measured from the fuselage center line in the spanwise direction. When deployed in flight, this panel produces a positive pressure gradient aligned with the final roll-up of the total vortex system which interrupts the axial flow in the vortex core and causes the vortex to collapse.

  18. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Joel Walls; M.T. Taner; Naum Derzhi; Gary Mavko; Jack Dvorkin

    2002-10-01

    RSI has access to two synthetic seismic programs: Osiris seismic modeling system provided by Odegaard (Osiris) and synthetic seismic program, developed by SRB, implementing the Kennett method for normal incidence. Achieving virtually identical synthetic seismic traces from these different programs serves as cross-validation for both. The subsequent experiments have been performed with the Kennett normal incidence code because: We have access to the source code, which allowed us to easily control computational parameters and integrate the synthetics computations with our graphical and I/O systems. This code allows to perform computations and displays on a PC in MatLab or Octave environment, which is faster and more convenient. The normal incidence model allows us to exclude from the synthetic traces some of the physical effects that take place in 3-D models (like inhomogeneous waves) but have no relevance to the topic of our investigation, which is attenuation effects on seismic reflection and transmission.

  19. A scattering model for seismic attenuation and its global applications

    NASA Astrophysics Data System (ADS)

    Padhy, Simanchal

    2005-01-01

    The attenuation characteristics of Indian lithosphere and its comparison with different tectonic settings in the world are determined from the observations of the Q for Lg( QLg)-, and S( QS)-waves in the 1-30 Hz frequency range. The scattering is approximated with a Gaussian distribution of spherical scatterers. To approximate single scattering, we use Dainty's [Geophy. Res. Lett. 8 (11) (1981) 1126] model that attenuation is given by 1/ Q( ω) = 1/ Qi + g( ω) v/ ω, where Qi is intrinsic Q due to anelastic attenuation, v is shear wave velocity, ω is angular frequency, g = ∫ n( a) σ d a is the total scattering coefficient for S-to- S scattering, n( a) d a is the number of scattering spheres of radius a per unit volume, and σ is the scattering cross-section for the sphere. We find that if n( a) is described by a simple two parameter ( a0 and c) Gaussian of amplitude c and standard deviation and mean a0, the attenuation data for different regions of the world are well approximated over the frequency band of seismic observations. Our major findings are: (1) the maximum effect of scattering on attenuation occurs at 0.84 Hz or a wavelength of 4.16 km; (2) the values of g are frequency dependent. Values of g are of the order of 10 -3 km -1 at 1-30 Hz, varying from 0.0031 to 0.01 and 0.001 to 0.0083 km -1 for tectonically active and stable regions, respectively; (3) regions of active tectonics and seismicity generally have lower Qi values (1000) than that in stable regions (2000); and (4) regions of high Qi value exhibit low intensity of scattering.

  20. A Multiphase Approach to Determine Attenuation Structure of the Lithosphere and its Use in Earthquake-Explosion Discrimination

    NASA Astrophysics Data System (ADS)

    Pasyanos, M. E.; Walter, W. R.; Matzel, E.; Ford, S. R.; Rodgers, A. J.

    2009-12-01

    We have developed a new methodology that uses amplitudes of the four primary regional phases (Pn, Pg, Sn, and Lg) to determine the attenuation structure of the lithosphere. The amplitudes are inverted simultaneously for Qp and Qs of the crust, Qp and Qs of the upper mantle, event source terms, and station site terms, which ensures that parameters, such as seismic moment and apparent stress, are consistent among the various phases. We have applied this technique to several regions, including the Middle East and the Yellow Sea - Korean Peninsula region. Portions of these regions are particularly challenging because of the presence of areas (e.g. Sea of Japan, Black Sea) where some phases like Lg are completely or partially blocked. The attenuation models have utility for nuclear explosion monitoring applications. While regional P/S amplitudes have been recognized as an effective discriminant between earthquakes and explosions, path effects due to attenuation can greatly distort observed amplitudes. By correcting all sources for amplitudes of an expected earthquake, we can look for sources which do not fit the expected amplitude ratios of earthquakes. We find that the variance of the earthquake distribution is reduced significantly, and that we increase the separation of the earthquake and explosion populations, greatly improving our discrimination power. This technique also has similar potential value for predicting ground motions for seismic hazard studies, or for estimating the seismic moment (and corresponding moment magnitude) using regional amplitudes.

  1. Effect of alumina composition and surface integrity in alumina/epoxy composites on the ultrasonic attenuation properties.

    PubMed

    Cho, Eikhyun; Park, Gwanwoo; Lee, Jae-Wan; Cho, Sung-Min; Kim, Taekyung; Kim, Joongeok; Choi, Wonjoon; Ohm, Won-Suk; Kang, Shinill

    2016-03-01

    We report a method of fabricating backing blocks for ultrasonic imaging transducers, using alumina/epoxy composites. Backing blocks contain scatterers such as alumina particles interspersed in the epoxy matrix for the effective scattering and attenuation of ultrasound. Here, the surface integrity can be an issue, where the composite material may be damaged during machining because of differences in strength, hardness and brittleness of the hard alumina particles and the soft epoxy matrix. Poor surface integrity results in the formation of air cavities between the backing block and the piezoelectric element upon assembly, hence the increased reflection off the backing block and the eventual degradation in image quality. Furthermore, with an issue of poor surface integrity due to machining, it is difficult to increase alumina as scatterers more than a specific mass fraction ratio. In this study, we increased the portion of alumina within epoxy matrix by obtaining an enhanced surface integrity using a net shape fabrication method, and verified that this method could allow us to achieve higher ultrasonic attenuation. Backing blocks were net-shaped with various mass fractions of alumina to characterize the formability and the mechanical properties, including hardness, surface roughness and the internal micro-structure, which were compared with those of machined backing blocks. The ultrasonic attenuation property of the backing blocks was also measured. PMID:26585217

  2. Subduction zone guided waves: 3D modelling and attenuation effects

    NASA Astrophysics Data System (ADS)

    Garth, T.; Rietbrock, A.

    2013-12-01

    Waveform modelling is an important tool for understanding complex seismic structures such as subduction zone waveguides. These structures are often simplified to 2D structures for modelling purposes to reduce computational costs. In the case of subduction zone waveguide affects, 2D models have shown that dispersed arrivals are caused by a low velocity waveguide, inferred to be subducted oceanic crust and/or hydrated outer rise normal faults. However, due to the 2D modelling limitations the inferred seismic properties such as velocity contrast and waveguide thickness are still debated. Here we test these limitations with full 3D waveform modelling. For waveguide effects to be observable the waveform must be accurately modelled to relatively high frequencies (> 2 Hz). This requires a small grid spacing due to the high seismic velocities present in subduction zones. A large area must be modelled as well due to the long propagation distances (400 - 600 km) of waves interacting with subduction zone waveguides. The combination of the large model area and small grid spacing required means that these simulations require a large amount of computational resources, only available at high performance computational centres like the UK National super computer HECTOR (used in this study). To minimize the cost of modelling for such a large area, the width of the model area perpendicular to the subduction trench (the y-direction) is made as small as possible. This reduces the overall volume of the 3D model domain. Therefore the wave field is simulated in a model ';corridor' of the subduction zone velocity structure. This introduces new potential sources of error particularly from grazing wave side reflections in the y-direction. Various dampening methods are explored to reduce these grazing side reflections, including perfectly matched layers (PML) and more traditional exponential dampening layers. Defining a corridor model allows waveguide affects to be modelled up to at least 2

  3. Disulfiram attenuates osteoclast differentiation in vitro: a potential antiresorptive agent.

    PubMed

    Ying, Hua; Qin, An; Cheng, Tak S; Pavlos, Nathan J; Rea, Sarah; Dai, Kerong; Zheng, Ming H

    2015-01-01

    Disulfiram (DSF), a cysteine modifying compound, has long been clinically employed for the treatment of alcohol addiction. Mechanistically, DSF acts as a modulator of MAPK and NF-κB pathways signaling pathways. While these pathways are crucial for osteoclast (OC) differentiation, the potential influence of DSF on OC formation and function has not been directly assessed. Here, we explore the pharmacological effects of DSF on OC differentiation, activity and the modulation of osteoclastogenic signaling cascades. We first analyzed cytotoxicity of DSF on bone marrow monocytes isolated from C57BL/6J mice. Upon the establishment of optimal dosage, we conducted osteoclastogenesis and bone resorption assays in the presence or absence of DSF treatment. Luciferase assays in RAW264.7 cells were used to examine the effects of DSF on major transcription factors activation. Western blot, reverse transcription polymerase chain reaction, intracellular acidification and proton influx assays were employed to further dissect the underlying mechanism. DSF treatment dose-dependently inhibited both mouse and human osteoclastogenesis, especially at early stages of differentiation. This inhibition correlated with a decrease in the expression of key osteoclastic marker genes including CtsK, TRAP, DC-STAMP and Atp6v0d2 as well as a reduction in bone resorption in vitro. Suppression of OC differentiation was found to be due, at least in part, to the blockade of several key receptor activators of nuclear factor kappa-B ligand (RANKL)-signaling pathways including ERK, NF-κB and NFATc1. On the other hand, DSF failed to suppress intracellular acidification and proton influx in mouse and human osteoclasts using acridine orange quenching and microsome-based proton transport assays. Our findings indicate that DSF attenuates OC differentiation via the collective suppression of several key RANKL-mediated signaling cascades, thus making it an attractive agent for the treatment of OC

  4. Disulfiram Attenuates Osteoclast Differentiation In Vitro: A Potential Antiresorptive Agent

    PubMed Central

    Cheng, Tak S.; Pavlos, Nathan J.; Rea, Sarah; Dai, Kerong; Zheng, Ming H.

    2015-01-01

    Disulfiram (DSF), a cysteine modifying compound, has long been clinically employed for the treatment of alcohol addiction. Mechanistically, DSF acts as a modulator of MAPK and NF-κB pathways signaling pathways. While these pathways are crucial for osteoclast (OC) differentiation, the potential influence of DSF on OC formation and function has not been directly assessed. Here, we explore the pharmacological effects of DSF on OC differentiation, activity and the modulation of osteoclastogenic signaling cascades. We first analyzed cytotoxicity of DSF on bone marrow monocytes isolated from C57BL/6J mice. Upon the establishment of optimal dosage, we conducted osteoclastogenesis and bone resorption assays in the presence or absence of DSF treatment. Luciferase assays in RAW264.7 cells were used to examine the effects of DSF on major transcription factors activation. Western blot, reverse transcription polymerase chain reaction, intracellular acidification and proton influx assays were employed to further dissect the underlying mechanism. DSF treatment dose-dependently inhibited both mouse and human osteoclastogenesis, especially at early stages of differentiation. This inhibition correlated with a decrease in the expression of key osteoclastic marker genes including CtsK, TRAP, DC-STAMP and Atp6v0d2 as well as a reduction in bone resorption in vitro. Suppression of OC differentiation was found to be due, at least in part, to the blockade of several key receptor activators of nuclear factor kappa-B ligand (RANKL)-signaling pathways including ERK, NF-κB and NFATc1. On the other hand, DSF failed to suppress intracellular acidification and proton influx in mouse and human osteoclasts using acridine orange quenching and microsome-based proton transport assays. Our findings indicate that DSF attenuates OC differentiation via the collective suppression of several key RANKL-mediated signaling cascades, thus making it an attractive agent for the treatment of OC

  5. Markerless attenuation correction for carotid MRI surface receiver coils in combined PET/MR imaging.

    PubMed

    Eldib, Mootaz; Bini, Jason; Robson, Philip M; Calcagno, Claudia; Faul, David D; Tsoumpas, Charalampos; Fayad, Zahi A

    2015-06-21

    The purpose of the study was to evaluate the effect of attenuation of MR coils on quantitative carotid PET/MR exams. Additionally, an automated attenuation correction method for flexible carotid MR coils was developed and evaluated. The attenuation of the carotid coil was measured by imaging a uniform water phantom injected with 37 MBq of 18F-FDG in a combined PET/MR scanner for 24 min with and without the coil. In the same session, an ultra-short echo time (UTE) image of the coil on top of the phantom was acquired. Using a combination of rigid and non-rigid registration, a CT-based attenuation map was registered to the UTE image of the coil for attenuation and scatter correction. After phantom validation, the effect of the carotid coil attenuation and the attenuation correction method were evaluated in five subjects. Phantom studies indicated that the overall loss of PET counts due to the coil was 6.3% with local region-of-interest (ROI) errors reaching up to 18.8%. Our registration method to correct for attenuation from the coil decreased the global error and local error (ROI) to 0.8% and 3.8%, respectively. The proposed registration method accurately captured the location and shape of the coil with a maximum spatial error of 2.6 mm. Quantitative analysis in human studies correlated with the phantom findings, but was dependent on the size of the ROI used in the analysis. MR coils result in significant error in PET quantification and thus attenuation correction is needed. The proposed strategy provides an operator-free method for attenuation and scatter correction for a flexible MRI carotid surface coil for routine clinical use. PMID:26020273

  6. Markerless attenuation correction for carotid MRI surface receiver coils in combined PET/MR imaging

    NASA Astrophysics Data System (ADS)

    Eldib, Mootaz; Bini, Jason; Robson, Philip M.; Calcagno, Claudia; Faul, David D.; Tsoumpas, Charalampos; Fayad, Zahi A.

    2015-06-01

    The purpose of the study was to evaluate the effect of attenuation of MR coils on quantitative carotid PET/MR exams. Additionally, an automated attenuation correction method for flexible carotid MR coils was developed and evaluated. The attenuation of the carotid coil was measured by imaging a uniform water phantom injected with 37 MBq of 18F-FDG in a combined PET/MR scanner for 24 min with and without the coil. In the same session, an ultra-short echo time (UTE) image of the coil on top of the phantom was acquired. Using a combination of rigid and non-rigid registration, a CT-based attenuation map was registered to the UTE image of the coil for attenuation and scatter correction. After phantom validation, the effect of the carotid coil attenuation and the attenuation correction method were evaluated in five subjects. Phantom studies indicated that the overall loss of PET counts due to the coil was 6.3% with local region-of-interest (ROI) errors reaching up to 18.8%. Our registration method to correct for attenuation from the coil decreased the global error and local error (ROI) to 0.8% and 3.8%, respectively. The proposed registration method accurately captured the location and shape of the coil with a maximum spatial error of 2.6 mm. Quantitative analysis in human studies correlated with the phantom findings, but was dependent on the size of the ROI used in the analysis. MR coils result in significant error in PET quantification and thus attenuation correction is needed. The proposed strategy provides an operator-free method for attenuation and scatter correction for a flexible MRI carotid surface coil for routine clinical use.

  7. Low seismic velocities below mid-ocean ridges: Attenuation versus melt retention

    NASA Astrophysics Data System (ADS)

    Goes, Saskia; Armitage, John; Harmon, Nick; Smith, Hannah; Huismans, Ritske

    2012-12-01

    The first comprehensive seismic experiment sampling subridge mantle revealed a pronounced low-velocity zone between 40 and 100 km depth below the East Pacific Rise (EPR) that has been attributed to substantial retained melt fractions of 0.3-2%. Such high melt fractions are at odds with low melt productivity and high melt mobility inferred from petrology and geochemistry. Here, we evaluate whether seismic attenuation can reconcile subridge seismic structure with low melt fractions. We start from a dynamic spreading model which includes melt generation and migration and is converted into seismic structure, accounting for temperature-, pressure-, composition-, phase-, and melt-dependent anharmonicity, and temperature-, pressure-, frequency- and hydration-dependent anelasticity. Our models predict a double low-velocity zone: a shallow—approximately triangular—region due to dry melting, and a low-velocity channel between 60 and 150 km depth dominantly controlled by solid state high-temperature seismic attenuation in a damp mantle, with only a minor contribution of (<0.1%) melt. We test how tomographic inversion influences the imaging of our modeled shear velocity features. The EPR experiment revealed a double low-velocity zone, but most tomographic studies would only resolve the deeper velocity minimum. Experimentally constrained anelasticity formulations produce VSas low as observed and can explain lateral variations in near-ridge asthenospheric VS with ±100 K temperature variations and/or zero to high water content. Furthermore, such QS formulations also reproduce low asthenospheric VS below older oceans and continents from basic lithospheric cooling models. Although these structures are compatible with global QS images, they are more attenuating than permitted by EPR data.

  8. Detailed Study of Seismic Wave Attenuation in Carbonate Rocks: Application on Abu Dhabi Oil Fields

    NASA Astrophysics Data System (ADS)

    Bouchaala, F.; Ali, M. Y.; Matsushima, J.

    2015-12-01

    Seismic wave attenuation is a promising attribute for the petroleum exploration, thanks to its high sensitivity to physical properties of subsurface. It can be used to enhance the seismic imaging and improve the geophysical interpretation which is crucial for reservoir characterization. However getting an accurate attenuation profile is not an easy task, this is due to complex mechanism of this parameter, although that many studies were carried out to understand it. The degree of difficulty increases for the media composed of carbonate rocks, known to be highly heterogeneous and with complex lithology. That is why few attenuation studies were done successfully in carbonate rocks. The main objectives of this study are, Getting an accurate and high resolution attenuation profiles from several oil fields. The resolution is very important target for us, because many reservoirs in Abu Dhabi oil fields are tight.Separation between different modes of wave attenuation (scattering and intrinsic attenuations).Correlation between the attenuation profiles and other logs (Porosity, resistivity, oil saturation…), in order to establish a relationship which can be used to detect the reservoir properties from the attenuation profiles.Comparison of attenuation estimated from VSP and sonic waveforms. Provide spatial distribution of attenuation in Abu Dhabi oil fields.To reach these objectives we implemented a robust processing flow and new methodology to estimate the attenuation from the downgoing waves of the compressional VSP data and waveforms acquired from several wells drilled in Abu Dhabi. The subsurface geology of this area is primarily composed of carbonate rocks and it is known to be highly fractured which complicates more the situation, then we separated successfully the intrinsic attenuation from the scattering. The results show that the scattering is significant and cannot be ignored. We found also a very interesting correlation between the attenuation profiles and the

  9. Docking-mechanism attenuator with electromechanical damper

    NASA Technical Reports Server (NTRS)

    Syromyatnikov, V. S.

    1971-01-01

    Theoretical and practical problems involved in the application of electromechanical damping for spacecraft docking-mechanism attenuation are discussed. Some drawbacks of hydraulic dampers used for the purpose are pointed out. The basic scheme of the attenuator with the electromechanical damper is given.

  10. Relating P-wave attenuation to permeability

    SciTech Connect

    Akbar, N.; Dvorkin, J.; Nur, A. . Dept. of Geophysics)

    1993-01-01

    To relate P-wave attenuation to permeability, the authors examine a three-dimensional (3-D) theoretical model of a cylindrical pore filled with viscous fluid and embedded in an infinite isotropic elastic medium. They calculate both attenuation and permeability as functions of the direction of wave propagation. Attenuation estimates are based on the squirt flow mechanism; permeability is calculated using the Kozeny-Carmen relation. They find that in the case when a plane P-wave propagates parallel to this orientation (Q[sup [minus]1][delta] = 90[degree]), attenuation is always higher than when a wave propagates parallel to this orientation (Q[sup [minus]1][delta] = 0[degree]). The ratio of these two attenuation values Q[sup [minus]1][delta] = 90[degree]/Q[sup [minus]1] = 0[degree] increases with an increasing pore radius and decreasing frequency and saturation. By changing permeability, varying the radius of the pore, they find that the permeability-attenuation relation is characterized by a peak that shifts toward lower permeabilities as frequency decreases. Therefore, the attenuation of a low-frequency wave decreases with increasing permeability. They observe a similar trend on relations between attenuation and permeability experimentally obtained on sandstone samples.